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Sample records for crack morphology parameters

  1. Determination of crack morphology parameters from service failures for leak-rate analyses

    Energy Technology Data Exchange (ETDEWEB)

    Wilkowski, G.; Ghadiali, N.; Paul, D. [Battelle Memorial Institute, Columbus, OH (United States)] [and others

    1997-04-01

    In leak-rate analyses described in the literature, the crack morphology parameters are typically not well agreed upon by different investigators. This paper presents results on a review of crack morphology parameters determined from examination of service induced cracks. Service induced cracks were found to have a much more tortuous flow path than laboratory induced cracks due to crack branching associated with the service induced cracks. Several new parameters such as local and global surface roughnesses, as well as local and global number of turns were identified. The effect of each of these parameters are dependent on the crack-opening displacement. Additionally, the crack path is typically assumed to be straight through the pipe thickness, but the service data show that the flow path can be longer due to the crack following a fusion line, and/or the number of turns, where the number of turns in the past were included as a pressure drop term due to the turns, but not the longer flow path length. These parameters were statistically evaluated for fatigue cracks in air, corrosion-fatigue, IGSCC, and thermal fatigue cracks. A refined version of the SQUIRT leak-rate code was developed to account for these variables. Sample calculations are provided in this paper that show how the crack size can vary for a given leak rate and the statistical variation of the crack morphology parameters.

  2. Quantity effect of radial cracks on the cracking propagation behavior and the crack morphology.

    Directory of Open Access Journals (Sweden)

    Jingjing Chen

    Full Text Available In this letter, the quantity effect of radial cracks on the cracking propagation behavior as well as the circular crack generation on the impacted glass plate within the sandwiched glass sheets are experimentally investigated via high-speed photography system. Results show that the radial crack velocity on the backing glass layer decreases with the crack number under the same impact conditions during large quantities of repeated experiments. Thus, the "energy conversion factor" is suggested to elucidate the physical relation between the cracking number and the crack propagation speed. Besides, the number of radial crack also takes the determinative effect in the crack morphology of the impacted glass plate. This study may shed lights on understanding the cracking and propagation mechanism in laminated glass structures and provide useful tool to explore the impact information on the cracking debris.

  3. Influence of Crack Morphology on Leak Before Break Margins

    Energy Technology Data Exchange (ETDEWEB)

    Weilin Zang (Inspecta Technology AB, Stockholm (SE))

    2007-11-15

    The purpose of the project is to evaluate the deterministic LBB-margins for different pipe systems in a Swedish PWR-plant and using different crack morphology parameters. Results: - The influence of crack morphology on Leak Before Break (LBB) margins is studied. The subject of the report is a number of LBB-submittals to SKI where deterministic LBB-margins are reported. These submittals typically uses a surface roughness of 0.0762 mm (300 microinch) and number of turns equal to zero and an in-house code for the leak rate evaluations. The present report has shown that these conditions give the largest LBB-margins both in terms of the quotient between the critical crack length and the leakage crack size and for the leak rate margin. - Crack morphology parameters have a strong influence on the leak rate evaluations. Using the SQUIRT code and more recent recommendations for crack morphology parameters, it is shown that in many cases the evaluated margins, using 1 gpm as the reference leak rate detection limit, are below the safety factor of 2 on crack size and 10 on leak rate, which is generally required for LBB approval. - The effect of including weld residual stresses on the LBB margins is also investigated. It is shown that for the two examples studied, weld residual stresses were important for the small diameter thin wall pipe whereas it was negligible for the large diameter thick wall pipe which had a self-balanced weld residual stress distribution

  4. Wettability Induced Crack Dynamics and Morphology

    CERN Document Server

    Ghosh, Udita Uday; Bhandari, Aditya Bikram; Chakraborty, Suman; DasGupta, Sunando

    2014-01-01

    Substrate wettability alteration induced control over crack formation process in thin colloidal films has been addressed in the present study. Colloidal nanosuspension (53nm, mean particle diameter) droplets have been subjected to natural drying to outline the effects of substrate surface energies over the dry-out characteristics with emphasis on crack dynamics, crack morphology and underlying particle arrangements. Experimental findings indicate that number of cracks formed decreases with increase in substrate hydrophobicity. These physical phenomena have been explained based on the magnitude of stress dissipation incurred by the substrate. DLVO predictions are also found to be in tune with the reported experimental investigations.

  5. SHORT FATIGUE CRACK PARAMETER BASED ON THE TOTAL CRACK AREA

    Institute of Scientific and Technical Information of China (English)

    Z.X.Wu; X.C.Wu

    2001-01-01

    The progressive fatigue damage of a material is closely related to the whole populationof cracks on the surface of an un-notched specimen.In order to understand whichparameter is a more useful indicator of fatigue damage,rotatory bending fatigue testswere carried out using smooth specimens of medium-carbon steel.The behavior ofshort crack propagation during fatigue was examined and a new parameter "totalcrack area" was suggested.The aim of this paper is to extend the research on fatiguedamage in the already studied steel and to study how these damage parameters arecorrelated with the process of fatigue damage in order to evaluate the effectiveness ofdamage detection methods.

  6. Crack Tip Parameters for Growing Cracks in Linear Viscoelastic Materials

    DEFF Research Database (Denmark)

    Brincker, Rune

    intensity factors. In the special case of a constant Poisson ratio only 2 deformation intensity factors are needed. Closed form solutions are given both for a slowly growing crack and for a crack that is suddenly arrested at a point at the crack extension path. Two examples are studied; a stress boundary...... value problem, and a displacement boundary value problem. The results show that the stress intensity factors and the displacement intensity factors do not depend explicitly upon the velocity of the crack tip....

  7. Theoretical and numerical studies on morphological transitions in crack growth

    CERN Document Server

    Mühle, V

    1999-01-01

    This paper investigates the formation of crack patterns in stationary and transient temperature fields analytically with linear elastic fracture mechanics and numerically with the finite elements method (FEM). In particular, we consider the experimental situation of a narrow thin strip of hot glass slowly lowered into cold water, with temperature difference and velocity as variable parameters. The parameter regions of no crack, one straight crack and one oscillating crack are determined. The type of phase transition related to the borderline between straight and oscillating crack is characterized. The theoretical results are compared with those of other Similar investigations and comparisons are done for the propagation of multiple cracks. Quenching of a wide thin strip leads to a hierarchy of cracks whose scaling properties are analyzed. Without any fitting, theory and experiment agree surprisingly well.

  8. Biological Dimensions of Crack Morphology in Dryland Soils

    Science.gov (United States)

    DeCarlo, K. F.; Spiegel, M.; Caylor, K. K.

    2014-12-01

    Macropores and cracks have an integral role in soil hydrology, and the physicochemical factors that induce them have been the subject of much laboratory research. How these processes translate to field soils, however, is often obfuscated by the biological elements present that complicate its formation and dynamics. In this study, we investigated the biological influence of herbivores and vegetation on 3D crack morphology in a dryland swelling soil (black cotton/vertisol). Fieldwork was conducted at and near the Kenya Long-Term Exclosure Experiment (KLEE) plots in Mpala, central Kenya, where three different soil regions were identified: highly vegetated areas, animal trails, and termite mounds. Crack networks were physically characterized by pouring liquid resin into the soil and excavating them when dry, after which they were imaged and quantified using medical magnetic resonance imaging (MRI). Cracking intensity of each cast was corrected via soil moisture and bulk density measurements at 5 cm intervals over 30 cm. 3D characterization of the soil system shows that mechanical compaction is a major influence in the formation of extensive and deep cracks in animal trails, with megaherbivores (e.g. elephants) inducing the most extreme cracks. Bioturbation is seen as a major influence in the formation of shallower cracks in termite mounds, as termites loosen and aerate the soil and reduce the soil's cohesive properties. Highly vegetated soils show a large degree of variability: small, disconnected soil patches induced by vegetative cover and a larger root network results in smaller and shallower cracks, but full vegetative cover induces deep and irregular cracks, possibly due to diverted rainfall. Our results highlight the intricate connections between the biology and physics that dictate soil processes in a complex soil system at the field scale.

  9. Relationship among Parameters Evaluating Stress Corrosion Cracking

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    @@The threshold stress, σc, for sulfide stress corrosion cracking (SCC) of seven pipeline steels and five other steels, the critical stress, SC, for seven pipeline steels and two drill rod steels with various strengths and the susceptibility to SCC, IRA or σf(SCC)/σf, for four pipeline steels, two drill rod steels and five other steels were measured. The results showed that there are no definite elationships among σc, SC and IRA or σf(SCC)/σf. The threshold stress for hydrogen induced cracking (HIC) during charging with loading in the H2SO4 solution, σc(H), decreased linearly with logarithm of the concentration of diffusible hydrogen c0, i.e., σC(H)=A-B Inc0 for four pipeline steels. σc(H) obtained with a special cathodic current ic, which was corresponding to the diffusible hydrogen concentration during immersing in the H2S solution, were consistent with σc for sulfide SCC for four pipeline steels.Therefore, σc for sulfide SCC can be measured using dynamically charging in the H2SO4 solution with the special cathodic current ic.

  10. Prediction of air leakage and aerosol transport through concrete cracks with a fractal based crack morphology model

    Energy Technology Data Exchange (ETDEWEB)

    Bishnoi, L.R., E-mail: lrbishnoi@aerb.gov.in [Siting and Structural Engineering Division, Atomic Energy Regulatory Board, Mumbai 400 094 (India); Vedula, R.P., E-mail: rpv@iitb.ac.in [Mechanical Engineering Department, Indian Institute of Technology, Mumbai 400 076 (India)

    2013-12-15

    Highlights: • A fractal based numerical concrete crack morphology model is presented. • Computational studies conducted for airflow and aerosol transport through cracks. • Results are compared with experimental data and other empirical relations. • Comparative studies demonstrate model effectiveness and versatility of application. - Abstract: Cracks may appear in pressurized concrete containment of a nuclear power plant during a severe accident and provide leak paths for release of radioactive aerosols dispersed in the contained air. In this paper, a fractal based crack morphology model is presented for prediction of air leakage and aerosol transport through cracks in concrete. Airflow field generated in air leakage studies is used for aerosol transport studies with the Lagrangian discrete phase model using CFD code FLUENT. Computational studies conducted with the fractal based model are compared with the experimental data as well as the predictions from empirical relations available in open literature. The comparative studies demonstrate effectiveness of the proposed fractal based model and its versatility for practical applications.

  11. Complete Tangent Stiffness for eXtended Finite Element Method by including crack growth parameters

    DEFF Research Database (Denmark)

    Mougaard, J.F.; Poulsen, P.N.; Nielsen, L.O.

    2013-01-01

    The eXtended Finite Element Method (XFEM) is a useful tool for modeling the growth of discrete cracks in structures made of concrete and other quasi‐brittle and brittle materials. However, in a standard application of XFEM, the tangent stiffness is not complete. This is a result of not including...... the crack geometry parameters, such as the crack length and the crack direction directly in the virtual work formulation. For efficiency, it is essential to obtain a complete tangent stiffness. A new method in this work is presented to include an incremental form the crack growth parameters on equal terms...

  12. Automation of Optimized Gabor Filter Parameter Selection for Road Cracks Detection

    Directory of Open Access Journals (Sweden)

    Haris Ahmad Khan

    2016-03-01

    Full Text Available Automated systems for road crack detection are extremely important in road maintenance for vehicle safety and traveler’s comfort. Emerging cracks in roads need to be detected and accordingly repaired as early as possible to avoid further damage thus reducing rehabilitation cost. In this paper, a robust method for Gabor filter parameters optimization for automatic road crack detection is discussed. Gabor filter has been used in previous literature for similar applications. However, there is a need for automatic selection of optimized Gabor filter parameters due to variation in texture of roads and cracks. The problem of change of background, which in fact is road texture, is addressed through a learning process by using synthetic road crack generation for Gabor filter parameter tuning. Tuned parameters are then tested on real cracks and a thorough quantitative analysis is performed for performance evaluation.

  13. A NOVEL PARAMETER FOR EVALUATING THE FATIGUE CRACK GROWTH RATE IN CARBON STEELS

    Institute of Scientific and Technical Information of China (English)

    X.S.Wang; S.Q.Zhu; N.Kawagoishi; H.Nisitani

    2001-01-01

    A novel parameter is suggested for evaluating the fatigue crack growth rate in carbonsteels.Fatigue crack propagation tests of an annealed 0.42% carbon steel were carriedout under different conditions to investigate the relationship between this dominatingparameter and the crack opening displacement (COD).A new equation of fatiguecrack growth rate is formulated in terms of the suggested parameter.The physicalmeanings of the material parameters in this equation are explored experimentally.Considering the relation of crack growth and deformation properties,a simple andapplicable method is proposed to evaluate the fatigue crack growth rate.It is alsoobserved that the material parameters in the fatigue crack growth rate equation ofcarbon steels are related linearly to the material strength.The results are in a goodagreement with experimental results.

  14. Evaluation of Fracture Parameters for Cracks in Coupled Thermoelasticity for Functionally Graded Materials

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    Repka M.

    2015-11-01

    Full Text Available The finite element method (FEM is developed for coupled thermoelastic crack problems if material properties are continuously varying. The weak form is utilized to derive the FEM equations. In conventional fracture theories the state of stress and strain at the crack tip vicinity is characterized by a single fracture parameter, namely the stress intensity factor or its equivalent, J-integral. In the present paper it is considered also the second fracture parameter called as the T-stress. For evaluation of both fracture parameters the quarter-point crack tip element is developed. Simple formulas for both fracture parameters are derived comparing the variation of displacements in the quarter-point element with asymptotic expression of displacement at the crack tip vicinity. The leading terms of the asymptotic expansions of fields in the crack-tip vicinity in a functionally graded material (FGM are the same as in a homogeneous one with material coefficients taken at the crack tip.

  15. A Study on Crack Detection with Modal Parameters of A Jacket Platform

    Institute of Scientific and Technical Information of China (English)

    张兆德; 王德禹

    2004-01-01

    Crack detection procedures by different modal parameters are analyzed for identifying a crack and its location and magnitude in a jacket platform. The first ten natural frequencies and modal shapes of the jacket models are obtained by numerical experiments based on NASTRAN Code. A crack at different locations and of different magnitudes is imposed in the model at the underwater beams. Then, the modal evaluation parameters are calculated numerically, to illustrate the evaluation of modal parameter criteria used in jacket crack detection. The sensitivities of different modal parameters to different cracks are analyzed. A new technique is presented for predicting the approximate location of a breakage in the absence of the data of an intact model. This method can be used to detect a crack in underwater members by use of in complete mode shapes of the top members of the jacket.

  16. Homotopy Iteration Algorithm for Crack Parameters Identification with Composite Element Method

    Directory of Open Access Journals (Sweden)

    Ling Huang

    2013-01-01

    Full Text Available An approach based on homotopy iteration algorithm is proposed to identify the crack parameters in beam structures. In the forward problem, a fully open crack model with the composite element method is employed for the vibration analysis. The dynamic responses of the cracked beam in time domain are obtained from the Newmark direct integration method. In the inverse analysis, an identification approach based on homotopy iteration algorithm is studied to identify the location and the depth of a cracked beam. The identification equation is derived by minimizing the error between the calculated acceleration response and the simulated measured one. Newton iterative method with the homotopy equation is employed to track the correct path and improve the convergence of the crack parameters. Two numerical examples are conducted to illustrate the correctness and efficiency of the proposed method. And the effects of the influencing parameters, such as measurement time duration, measurement points, division of the homotopy parameter and measurement noise, are studied.

  17. Ultrasonic Analysis of Cracking Propagation Morphology in the Fusion Zone of High Strength Steel

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Cracking morphology in the fusion zone of HQ130 high strength steel was researched by "the y-slit test" and "three-point bend test", ultrasonic test and microscope. HQ130 and Q J63 high strength steel was welded by Ar+CO2 gasshielded arc welding under the condition without preheating. Experimental results indicated that welding cracks wereproduced in the partially melted zone of the weld root of HQ130 steel side and propagated parallel to the fusionzone. The cracks were developed alternatively between the weld and the partially melted zone, and are not strictlyruptured at W/F (weld metal/fusion zone) boundary surface. Controlling weld heat input (E) about 16 k J/cm couldmake the cracking rate lowest and satisfy the performance requirement of welded joint zone.

  18. MODELLING AND PARAMETER ESTIMATION IN REACTIVE CONTINUOUS MIXTURES: THE CATALYTIC CRACKING OF ALKANES. PART I

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    PEIXOTO F. C.

    1999-01-01

    Full Text Available Fragmentation kinetics is employed to model a continuous reactive mixture. An explicit solution is found and experimental data on the catalytic cracking of a mixture of alkanes are used for deactivation and kinetic parameter estimation.

  19. Evaluation of parameters affecting reflection cracking in geogrid-reinforced overlay

    Institute of Scientific and Technical Information of China (English)

    Shahab Fallah; Ali Khodaii

    2015-01-01

    The influence of the most important parameters on the service life of reinforced asphalt overlay with geogrid materials in bending mode was examined by employing the Taguchi method and analysis of variance techniques. The objectives of this experiment was to investigate the effects of grid stiffness, tensile strength, coating type, amount of tack coat, overlay thickness, crack width and stiffnesses of asphalt overlay and existing asphalt concrete on propagation of the reflection cracking. Results indicate that the stiffnesses of cracked layer and overlay are the main significant factors that can directly improve the service life of an overlay against the reflection cracking. Generally, glass grid is more effective in reinforced overlay than polyester grid. Effect of crack width of the existing layer is significant when its magnitude increases from 6 to 9 mm.

  20. A methodology for computing nonlinear fracture parameters for a bulging crack in a pressurised aircraft fuselage

    Science.gov (United States)

    Shenoy, V. B.; Potyondy, D. O.; Atluri, S. N.

    1994-09-01

    A computational methodology for obtaining nonlinear fracture parameters which account for the effects of plasticity at the tips of a bulging crack in a pressurised aircraft fuselage is developed. The methodology involves a hierarchical three stage analysis (global, intermediate, and local) of the cracked fuselage, with the crack incorporated into the model at each stage. The global analysis is performed using a linear elastic shell finite element model in which the stiffeners are treated as beam elements. The geometrically nonlinear nature of the bulging phenomenon is emulated in the intermediate analysis using a geometrically nonlinear shell finite element model. The local analysis is a three-dimensional solid finite element model of the cracked skin using a hypoelastic-plastic rate formulation. Kinematic boundary conditions for each stage are obtained from the preceding stage in the hierarchy using a general mesh independent mechanism. The T *integral, which accounts for both large deformations and plasticity, is taken to be the fracture parameter characterising the severity of the conditions at the crack tip, and is evaluated from the local analysis using the Equivalent Domain Integral (EDI) method. The implementation of the EDI technique for finite deformations in shell space is also outlined. The methodology is applied to a number of example problems for which correction factors relating the nonlinear T * values to those obtained from a linear elastic stiffened shell analysis are computed. The issue of flapping is addressed by investigating the behaviour of the longitudinal stress parallel to the crack for various cases.

  1. Mathematical and computational analyses of cracking formation fracture morphology and its evolution in engineering materials and structures

    CERN Document Server

    Sumi, Yoichi

    2014-01-01

    This book is about the pattern formation and the evolution of crack propagation in engineering materials and structures, bridging mathematical analyses of cracks based on singular integral equations, to computational simulation of engineering design. The first two parts of this book focus on elasticity and fracture and provide the basis for discussions on fracture morphology and its numerical simulation, which may lead to a simulation-based fracture control in engineering structures. Several design concepts are discussed for the prevention of fatigue and fracture in engineering structures, including safe-life design, fail-safe design, damage tolerant design. After starting with basic elasticity and fracture theories in parts one and two, this book focuses on the fracture morphology that develops due to the propagation of brittle cracks or fatigue cracks.   In part three, the mathematical analysis of a curved crack is precisely described, based on the perturbation method. The stability theory of interactive ...

  2. High activity in catalytic cracking of large molecules over micro-mesoporous silicoaluminophosphate with controlled morphology

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A novel micro-mesoporous silicoaluminophosphate(MUS-5) with controlled morphology has been first synthesized in a two-step route.The physical properties of the silicoaluminophosphate were characterized using XRD,SEM,TEM,nitrogen adsorption-desorption and NH3-TPD techniques.When the pH value of the solution system was varied in the range from 2.0 to 5.0,three different morphologies of silicoaluminophosphate including chain-like,flower-like and barrel-like morphology were obtained.Catalytic tests showed that the silicoaluminophosphate exhibited higher catalytic activity compared with the conventional microporous SAPO-5 under the same conditions for catalytic cracking of 1,3,5-triisopropylbenzene heavy aromatics.The remarkable catalytic reactivity was mainly attributed to the presence of the hierarchical porosity in the silicoaluminophosphate catalyst.

  3. Morphological Uniformity and the Null Subject Parameter in Adult SLA.

    Science.gov (United States)

    Davies, William D.

    1996-01-01

    Focuses on the application of the Null Subject Parameter. Data reveals that some second-language learners exhibit knowledge that English is morphologically nonuniform yet still accept English null subject sentences. Findings disprove the Morphological Uniformity Hypothesis, indicating that any reformulation of the Null Subject Parameter must…

  4. Evolution of residual stress and crack morphologies during 3D FIB tomographic analysis of alumina.

    Science.gov (United States)

    Elfallagh, F; Inkson, B J

    2008-05-01

    Three-dimensional focused ion beam (FIB) tomography is increasingly being used for 3D characterization of microstructures in the 50 nm-20 microm range. FIB tomography is a destructive, invasive process, and microstructural changes may potentially occur during the analysis process. Here residual stress and crack morphologies in single-crystal sapphire samples have been concurrently analyzed using Cr3+ fluorescence spectroscopy and FIB tomography. Specifically, maps of surface residual stress have been obtained from optically polished single-crystal alumina [surface orientation (1 ī 0 2)], from FIB milled surface trenches, from Vickers micro-indentation sites (loads 50 g-300 g), and from Vickers micro-indentation sites during FIB serial sectioning. The residual stress maps clearly show that FIB sputtering generates residual stress changes. For the case of the Vickers micro-indentations, FIB sputtering causes significant changes in residual stress during the FIB tomographic serial sectioning. 3D reconstruction of the crack distribution around micro-indentation sites shows that the cracks observed are influenced by the location of the FIB milled surface trenches due to localized stress changes.

  5. Protection Parameters against the Cracks by the Method of Volume Compensation Dam

    Directory of Open Access Journals (Sweden)

    Bulatov Georgiy

    2016-01-01

    Full Text Available This article provides estimates the parameters of protection from cracking dam due to volume compensation method. This article discusses the method of compensation dam volume. This method allows calculating the settings of security causing cracks the dam. Presents graphs of horizontal deformations of elongation calculated surface along the length of the construction and in time. Showing horizontal stress distribution diagram in the ground around the pile in plan and in section. Given all the necessary formulas for the method of compensation of the dam volume.

  6. Early shell crack detection technique using acoustic emission energy parameter blast furnaces

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dong Hyun; Lee, Sang Bum [RECTUSON Co.,Ltd., Changwon (Korea, Republic of); Bae, Dong Myung; Yang, Bo Suk [Pukyong National University, Busan (Korea, Republic of)

    2016-02-15

    Blast furnaces are crucial equipment for steel production. A typical furnace risks unexpected accidents caused by contraction and expansion of the walls under an environment of high temperature and pressure. In this study, an acoustic emission (AE) monitoring system was tested for evaluating the large-scale structural health of a blast furnace. Based on the growth of shell cracks with the emission of high energy levels, severe damage can be detected by monitoring increases in the AE energy parameter. Using this monitoring system, steel mill operators can establish a maintenance period, in which actual shell cracks can be verified by cross-checking the UT. From this study, we expect that AE systems permit early fault detection for structural health monitoring by establishing evaluation criteria based on the severity of shell cracking.

  7. Selection of finite-element mesh parameters in modeling the growth of hydraulic fracturing cracks

    Science.gov (United States)

    Kurguzov, V. D.

    2016-12-01

    The effect of the mesh geometry on the accuracy of solutions obtained by the finite-element method for problems of linear fracture mechanics is investigated. The guidelines have been formulated for constructing an optimum mesh for several routine problems involving elements with linear and quadratic approximation of displacements. The accuracy of finite-element solutions is estimated based on the degree of the difference between the calculated stress-intensity factor (SIF) and its value obtained analytically. In problems of hydrofracturing of oil-bearing formation, the pump-in pressure of injected water produces a distributed load on crack flanks as opposed to standard fracture mechanics problems that have analytical solutions, where a load is applied to the external boundaries of the computational region and the cracks themselves are kept free from stresses. Some model pressure profiles, as well as pressure profiles taken from real hydrodynamic computations, have been considered. Computer models of cracks with allowance for the pre-stressed state, fracture toughness, and elastic properties of materials are developed in the MSC.Marc 2012 finite-element analysis software. The Irwin force criterion is used as a criterion of brittle fracture and the SIFs are computed using the Cherepanov-Rice invariant J-integral. The process of crack propagation in a linearly elastic isotropic body is described in terms of the elastic energy release rate G and modeled using the VCCT (Virtual Crack Closure Technique) approach. It has been found that the solution accuracy is sensitive to the mesh configuration. Several parameters that are decisive in constructing effective finite-element meshes, namely, the minimum element size, the distance between mesh nodes in the vicinity of a crack tip, and the ratio of the height of an element to its length, have been established. It has been shown that a mesh that consists of only small elements does not improve the accuracy of the solution.

  8. Influence of temperature and exploitation period on fatigue crack growth parameters in different regions of welded joints

    Directory of Open Access Journals (Sweden)

    Ivica Camagic

    2016-03-01

    Full Text Available The influence of exploitation period and temperature on the fatigue crack growth parameters indifferent regions of a welded joint is analysed for new and exploited low-alloyed Cr-Mo steel A-387 Gr. B. The parent metal is a part of a reactor mantle which was exploited for over 40 years, and recently replaced with new material. Fatigue crack growth parameters, threshold value Kth, coefficient C and exponent m, have been determined, both at room and exploitation temperature. Based on testing results, fatigue crack growth resistance in different regions of welded joint is analysed in order to justify the selected welding procedure specification.

  9. Effect of softening function on the cohesive crack fracture parameters of concrete CT specimen

    Indian Academy of Sciences (India)

    Shailendra Kumar; S V Barai

    2009-12-01

    The paper presents numerical study on the fracture parameters of concrete compact tension test specimens of different sizes using cohesive crack model. As softening function is the main ingredient of the cohesive crack model, seven numbers of widely used softening functions are incorporated in the model based on enhanced algorithm. It is found that the difference between the highest and the lowest peak loads obtained using various softening functions (except linear) is less than about 9%. The peak load predicted by the linear softening curve is about 16% larger than that of mean peak load predicted by other softening functions. The cohesive crack model with linear softening yields the fracture process zones lower by approximately 30–50% than those obtained by using the other softening relations for specimen size range 200–600 mm. The numerical results are further compared with a reference test result available in the literature. It is observed that some of softening relations (except linear) predict the experimentally obtained peak load up to 6% of accuracy whereas the linear softening curve overestimates it by about 30%. The numerically gained softening branch of load-displacement curves compare well with the experimental observation.

  10. Effects of Cracking Test Conditions on Estimation Uncertainty for Weibull Parameters Considering Time-Dependent Censoring Interval

    Directory of Open Access Journals (Sweden)

    Jae Phil Park

    2016-12-01

    Full Text Available It is extremely difficult to predict the initiation time of cracking due to a large time spread in most cracking experiments. Thus, probabilistic models, such as the Weibull distribution, are usually employed to model the initiation time of cracking. Therefore, the parameters of the Weibull distribution are estimated from data collected from a cracking test. However, although the development of a reliable cracking model under ideal experimental conditions (e.g., a large number of specimens and narrow censoring intervals could be achieved in principle, it is not straightforward to quantitatively assess the effects of the ideal experimental conditions on model estimation uncertainty. The present study investigated the effects of key experimental conditions, including the time-dependent effect of the censoring interval length, on the estimation uncertainties of the Weibull parameters through Monte Carlo simulations. The simulation results provided quantified estimation uncertainties of Weibull parameters in various cracking test conditions. Hence, it is expected that the results of this study can offer some insight for experimenters developing a probabilistic crack initiation model by performing experiments.

  11. Electrospinning of nickel oxide nanofibers: Process parameters and morphology control

    Energy Technology Data Exchange (ETDEWEB)

    Khalil, Abdullah, E-mail: akhalil@masdar.ac.ae; Hashaikeh, Raed, E-mail: rhashaikeh@masdar.ac.ae

    2014-09-15

    In the present work, nickel oxide nanofibers with varying morphology (diameter and roughness) were fabricated via electrospinning technique using a precursor composed of nickel acetate and polyvinyl alcohol. It was found that the diameter and surface roughness of individual nickel oxide nanofibers are strongly dependent upon nickel acetate concentration in the precursor. With increasing nickel acetate concentration, the diameter of nanofibers increased and the roughness decreased. An optimum concentration of nickel acetate in the precursor resulted in the formation of smooth and continuous nickel oxide nanofibers whose diameter can be further controlled via electrospinning voltage. Beyond an optimum concentration of nickel acetate, the resulting nanofibers were found to be ‘flattened’ and ‘wavy’ with occasional cracking across their length. Transmission electron microscopy analysis revealed that the obtained nanofibers are polycrystalline in nature. These nickel oxide nanofibers with varying morphology have potential applications in various engineering domains. - Highlights: • Nickel oxide nanofibers were synthesized via electrospinning. • Fiber diameter and roughness depend on nickel acetate concentration used. • With increasing nickel acetate concentration the roughness of nanofibers decreased. • XRD and TEM revealed a polycrystalline structure of the nanofibers.

  12. The Aerodynamics of Hovering Insect Flight. II. Morphological Parameters

    Science.gov (United States)

    Ellington, C. P.

    1984-02-01

    Morphological parameters are presented for a variety of insects that have been filmed in free flight. The nature of the parameters is such that they can be divided into two distinct groups: gross parameters and shape parameters. The gross parameters provide a very crude, first-order description of the morphology of a flying animal: its mass, body length, wing length, wing area and wing mass. Another gross parameter of the wings is their virtual mass, or added mass, which is the mass of air accelerated and decelerated together with the wing at either end of the wingbeat. The wing motion during these accelerations is almost perpendicular to the wing surface, and the virtual mass is approximately given by the mass of air contained in an imaginary cylinder around the wing with the chord as its diameter. The virtual mass ranges from 0.3 to 1.3 times the actual wing mass, indicating that the total mass accelerated by the flight muscles can be more than twice the wing mass itself. Over the limited size range of insects in this study, the interspecific variation of non-dimensional forms of the gross parameters is much greater than any systematic allometric variation, and no interspecific correlations can be found. The new shape parameters provide quite a surprise, however: intraspecific coefficients of variation are very low, often only 1%, and interspecific allometric relations are extremely strong. Mechanical aspects of flight depend not only on the magnitude of gross morphological quantities, but also on their distributions. Non-dimensional radii are derived from the non-dimensional moments of the distributions; for example, the first radius of wing mass about the wing base gives the position of the centre of mass, and the second radius corresponds to the radius of gyration. The radii are called `shape parameters' since they are functions only of the normalized shape of the distributions, and they provide a second-order description of the animal morphology. The various

  13. Investigating the Effects of Lead Forming Parameters on Intermetallic Layer Crack Using the Finite-Element Method

    Science.gov (United States)

    Chin, J. W. C.; Kok, C. K.; Rajmohan, M. M.; Yeo, V. S. H.; Said, M. R.

    2012-04-01

    The lead trim-and-form process is important in the manufacturing of programmable logic devices, microprocessors, and memories. Normally, inspection of a chip package is performed in a lead inspection machine after the lead forming process to detect defects on the leads. One such defect is the lead intermetallic compound (IMC) crack, exhibiting itself as plating crack. In this study, IMC crack of package leads, which causes loose connection between the copper lead and the tin plating, was analyzed using the finite-element method. The simulation results were verified by matching the simulated and actual formed lead profile. Simulation results showed a strong correlation between IMC crack after forming and aging and high residual tensile strain induced during lead forming. A proposal was made to resolve the crack issue by performing design of experiment (DOE) to reduce the residual tensile strain of the lead upon forming. Three optimization parameters were chosen, namely the forming angle, the shank angle, and the pre-forming angle. It is shown that, with the optimized parameter setting, a reduction of the residual strain can be achieved, thus minimizing the risk of IMC crack.

  14. Detection and Quantification of Crack in Composite Mono Leaf Spring by Vibration Parameters

    Science.gov (United States)

    Jamadar, Nagendra Iranna; Kivade, Sangshetty Bheemanna; Pedada, Sudhakara Rao

    2016-06-01

    Automobile industries focus for the components alternative to conventional materials with composites. There is high demand for enhanced performance and light weight. The emphasis is given for composite mono leaf spring as potential item as it is made up of glass fibre reinforced plastics despite they are sensitive to damages such as crack, delamination, de-bonding etc., occurred during either manufacturing or in service condition. These damages grow in progression and results in catastrophic failure. This work aims to deal with structural health monitoring to study and analyse the damage levels in composite mono leaf spring such as detection, location and quantification of damage. An experimental investigation has been carried out to evaluate presence and severity of damage by vibration parameters and validated with simulation.

  15. MORPHOLOGICAL FEATURES AND MORPHOMETRIC PARAMETERS OF HUMAN FETAL THYMUS GLANDS

    Directory of Open Access Journals (Sweden)

    S. Havila Hasini

    2014-03-01

    Full Text Available Introduction: Thymus is one of the central lymphoid organs. It plays an important role in the differentiation, selection and maturation of T-lymphocytes. In the recent years morphology and morphometry of the thymus gland in the newborn is gaining significance as it demonstrates great variability between individual infants and in the same infant at different times. Materials and methods: In the present study 45 thymus specimens from aborted human fetuses of 16 to 40 weeks gestational age and both sexes were studied by autopsy for morphological and morphometric features. The morphometric parameters were measured using pachymeter. Results: The thymus gland was located in the superior mediastinum. 60% (27/45 specimens showed cervical extensions. Brachiocephalic vein anterior to thymus was observed in 3 cases which is an important anomaly to be observed in thymectomy procedure. Thymuses were greyish pink to greyish brown in colour. Variations were also observed in the number of lobes of glands in which one is single lobed, most of the glands are bilobed and few are trilobed. There is progressive increase in all morphometric dimensions of the thymus in relation to gestational age. Most of the specimens were less than 4cm in length. Half of the specimens were below 2cm in width and other half were 2.0 to 5.0 cm in width. For 90% of the specimens thickness of the organ was less than 0.5cm. The thymus gland was 0.2% of fetal body weight. Conclusion: The morphological observations of thymus gland shows great variations which has to be considered in thymectomy. In addition to anthropometric parameters of fetus, morphometric parameters of thymus glands present significant relation to the gestational age of fetuses. It is possible to determine the thymic morphometric parameters in relation to gestational age.

  16. Characterization of the Q parameter for evaluating creep crack growth rate for type 316LN stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Ekaputra, I. M. W.; Park, Jae Young; Kim, Seon Jin [Pukyong National University, Busan (Korea, Republic of); Kim, Woo Gon; Kim, Eung Seon [KAERI, Daejeon (Korea, Republic of)

    2016-07-15

    In this study, the Q parameter was characterized to evaluate the Creep crack growth rate (CCGR) of type 316LN stainless steel. Creep crack growth (CCG) data were obtained by CCG tests under different applied loads at 600 .deg. C. An additional CCG test was conducted at 550 .deg. C to investigate the possible temperature dependence of the stress intensity factor. An equation using the Q parameter for evaluating CCGR was proposed, and this parameter was characterized and compared with the typical C fracture parameter, which is commonly used. The Q parameter exhibited good linearity of the data, exhibiting no nonlinearity-induced dual value at the early stage. The Q parameter was suitable for characterizing the CCGR regardless of different applied loads and types of steels. In addition, fracture microstructures near the crack revealed a typical intergranular fracture mode, and this fracture was dominantly propagated along the grain boundary. The cracks were developed by the growth and interlinking of cavities, which were attributed to the precipitates forming along the grain boundary.

  17. Model of parameters controlling resistance of pipeline steels to hydrogen-induced cracking

    KAUST Repository

    Traidia, Abderrazak

    2014-01-01

    NACE MR0175/ISO 15156-2 standard provides test conditions and acceptance criteria to evaluate the resistance of carbon and low-alloy steels to hydrogen-induced cracking (HIC). The second option proposed by this standard offers a large flexibility on the choice of test parameters (pH, H2S partial pressure, and test duration), with zero tolerance to HIC initiation as an acceptance condition. The present modeling work is a contribution for a better understanding on how the test parameters and inclusion size can influence HIC initiation, and is therefore of potential interest for both steel makers and endusers. A model able to link the test operating parameters (pH, partial pressure of H2S, and temperature) to the maximum hydrogen pressure generated in the microstructural defects is proposed. The model results are then used to back calculate the minimum fracture toughness below which HIC extends. A minimum fracture toughness of 400 MPa√mm, at the segregation zone, prevents HIC occurrence and leads to successfully pass the HIC qualification test, even under extreme test conditions. The computed results show that the maximum generated pressure can reach up to 1,500 MPa. The results emphasize that the H2S partial pressure and test temperature can both have a strong influence on the final test results, whereas the influence of the pH of the test solution is less significant. © 2014, NACE International.

  18. Effect of Microstructural Parameters on Fatigue Crack Propagation in an API X65 Pipeline Steel

    Science.gov (United States)

    Mohtadi-Bonab, M. A.; Eskandari, M.; Ghaednia, H.; Das, S.

    2016-11-01

    In the current research, we investigate fatigue crack growth in an API X65 pipeline steel by using an Instron fatigue testing machine. To this, first the microstructure of steel was accurately investigated using scanning electron microscope. Since nonmetallic inclusions play a key role during crack propagation, the type and distribution of such inclusions were studied through the thickness of as-received X65 steel using energy-dispersive spectroscopy technique. It was found that the accumulation of such defects at the center of thickness of the pipe body was higher than in other regions. Our results showed that there were very fine oxide inclusions (1-2 µm in length) appeared throughout the cross section of X65 steel. Such inclusions were observed not at the fatigue crack path nor on both sides of the fatigue crack. However, we found that large manganese sulfide inclusions (around 20 µm in length) were associated with fatigue crack propagation. Fatigue experiments on CT specimens showed that the crack nucleated when the number of fatigue cycles was higher than 340 × 103. On fracture surfaces, crack propagation also occurred by joining the microcracks at tip of the main crack.

  19. Creep crack growth analysis using C{sub t}-parameter for internal circumferential and external axial surface cracks in a pressurized cylinder

    Energy Technology Data Exchange (ETDEWEB)

    Tun, Nwe Ni; Yang, Hee Seung; Yu, Jong Min; Yoon, Kee Bong [Dept. of Mechanical Engineering, Chung Ang University, Seoul (Korea, Republic of)

    2016-12-15

    Creep crack growth at elevated temperatures is a critical consideration in estimating the remaining life of high temperature structural components and in deciding their inspection interval. In this study, creep crack growth analyses for external radial-axial and internal radial-circumferential surface cracks in a pressurized cylinder were conducted by an analytical method. The effect of crack depth and crack length on the variations in Ct and remaining life predictions were investigated for surface cracks with various initial aspect ratios. It was observed that the remaining life of an internal radial-circumferential surface crack was approximately 53 times longer than that of an external radial-axial surface crack for the same crack size and loading conditions with 316 stainless steel material. It was also observed that the variations in remaining life, crack propagations, and the Ct values were considerably sensitive to the crack location and crack depth. Convergence of crack aspect ratio was not observed when the crack depth ratio was increased. Since the method is independent of material properties and location of the crack geometries, it can be extended to various material properties and various locations of the surface crack geometries.

  20. Finite element modeling of the effect of welding parameters on solidification cracking of Austenitic Stainless Steel 310

    Directory of Open Access Journals (Sweden)

    Eslam Ranjbarnodeh

    2016-12-01

    Full Text Available A transient thermo-mechanical model is employed to study the effects of welding parameters on the occurrence of solidification cracking. A finite element program, ANSYS, is employed to solve the thermal and mechanical equations while the different variables such as welding current, speed and sequence are considered in the simulation. The studied geometry was butt joint of two stainless steel plates with the thickness of 2 mm. Then, the samples were welded by TIG method without filler. To verify the numerical results, the model outputs were checked with the experimental observations and good agreement was observed. It was found that the increasing of welding current from 70 A to 100 A resulted in the increase in transverse tensile strain from 1.2 to 2.1 which can facilitate the occurrence of solidification cracking. Furthermore, the application of symmetric welding layout is an effective method to prevent solidification cracking.

  1. Unsaturated Seepage Analysis of Cracked Soil including Development Process of Cracks

    Directory of Open Access Journals (Sweden)

    Ling Cao

    2016-01-01

    Full Text Available Cracks in soil provide preferential pathways for water flow and their morphological parameters significantly affect the hydraulic conductivity of the soil. To study the hydraulic properties of cracks, the dynamic development of cracks in the expansive soil during drying and wetting has been measured in the laboratory. The test results enable the development of the relationships between the cracks morphological parameters and the water content. In this study, the fractal model has been used to predict the soil-water characteristic curve (SWCC of the cracked soil, including the developmental process of the cracks. The cracked expansive soil has been considered as a crack-pore medium. A dual media flow model has been developed to simulate the seepage characteristics of the cracked expansive soil. The variations in pore water pressure at different part of the model are quite different due to the impact of the cracks. This study proves that seepage characteristics can be better predicted if the impact of cracks is taken into account.

  2. Hydride morphology and striation formation during delayed hydride cracking in Zr-2.5% Nb

    Energy Technology Data Exchange (ETDEWEB)

    Shek, G.K. [Ontario Hydro Technol., Ont. (Canada). Mater. Technol. Unit; Jovanovic, M.T. [Alberta Univ., Edmonton, AB (Canada). Dept. of Mining, Metallurgical and Petroleum Engineering; Seahra, H. [Ontario Hydro Technol., Ont. (Canada). Mater. Technol. Unit; Ma, Y. [Alberta Univ., Edmonton, AB (Canada). Dept. of Mining, Metallurgical and Petroleum Engineering; Li, D. [Alberta Univ., Edmonton, AB (Canada). Dept. of Mining, Metallurgical and Petroleum Engineering; Eadie, R.L. [Alberta Univ., Edmonton, AB (Canada). Dept. of Mining, Metallurgical and Petroleum Engineering

    1996-08-01

    These experiments were designed to study hydride formation at the crack tip, acoustic emission (AE), potential drop (PD) and striation formation during DHC (delayed hydride cracking) in Zr-2.5% Nb. The test material was taken from an especially extruded pressure tube, which showed similar strength properties to normal pressure tube material but somewhat coarser microstructure. In testing at K{sub I} below 12 MPa {radical}m at both 200 and 250 C very large striations (>40 {mu}m at 200 and >50 {mu}m at 250 C) were produced. In simultaneous monitoring with acoustic emission and potential drop, both AE and PD jumps were shown to be monolithic. The number of striations on the fracture surface corresponded to the number of monolithic AE/PD jumps. Tapered shaped hydrides with the thick end adjacent to the crack tip were observed. These hydrides grew in size during the incubation period until they reached the striation length and then fractured monolithically. However, when K{sub I} was increased beyond about 12 MPa {radical}m for these same specimens, the striation spacing decreased below 30 {mu}m, the monolithic jumping dissolved into more continuous changes in signals, although the smaller striations were still visible on the fracture surface. (orig.).

  3. Hydride morphology and striation formation during delayed hydride cracking in Zr-2.5% Nb

    Science.gov (United States)

    Shek, G. K.; Jovanoviċ, M. T.; Seahra, H.; Ma, Y.; Li, D.; Eadie, R. L.

    1996-08-01

    These experiments were designed to study hydride formation at the crack tip, acoustic emission (AE), potential drop (PD) and striation formation during DHC (delayed hydride cracking) in Zr-2.5% Nb. The test material was taken from an especially extrude pressure tube, which showed similar strength properties to normal pressure tube material but somewhat coarser microstructure. In testing at KI below 12 MPa √m at both 200 and 250°C very large striations (> 40 μ at 200 and >50 μm at 250°C) were produced. In simultaneous monitoring with acoustic emission and potential drop, both AE and PD jumps were shown to be monolithic. The number of striations on the fracture surface corresponded to the number of monolithic AE/PD jumps. Tapered shaped hydrides with the thick end adjacent to the crack tip were observed. These hydrides grew in size during the incubation period until they reached the striation length and then fractured monolithically. However, when KI was increased beyond about 12 MPa √m for these same specimens, the striation spacing decreased below 30 μ, the monolithic jumping dissolved into more continuous changes in signals, although the smaller striations were still visible on the fracture surface.

  4. Parameters influencing the transgranular stress corrosion cracking behaviour of austenitic stainless steels in systems conveying reactor coolant

    Energy Technology Data Exchange (ETDEWEB)

    Kilian, R.; Wesseling, U. [Framatome ANP (Germany); Wachter, O. [E.ON Kernkraft (Germany); Widera, M. [RWE Power (Germany); Brummer, G. [HEW - (Germany); Ilg, U. [EnBW - (Germany)

    2002-07-01

    During replacement of an auxiliary system in the German PWR KKS (NPP Stade) a damage was detected in a valve housing and in the connected piping both made from stabilised austenitic stainless steel. During operation stagnant conditions are present in this area. Based on the failure analysis chloride induced stress corrosion cracking (SCC) was found as the dominating root cause. In the open literature many cases of corrosion observed in the water/steam interface in valve components as well as in adjacent portions of auxiliary circuits made of un-stabilized stainless steels are mentioned. A common feature of the reported cases is that transgranular cracking was found. Extensive laboratory investigations revealed that non-stabilised austenitic stainless steels are also sensitive to transgranular cracking in boric acid solutions particularly in concentrated solutions. Often these solutions are contaminated with chlorides and/or oxygen is present. Taking into account the literature data the question could arise whether the above mentioned cracking may be also caused by boric acid attack. Thus, for stabilised stainless steels laboratory exposure tests at 80 C in saturated aerated boric acid solution and at 300 C in (at 100 C) saturated, oxygen free boric acid solution have been performed. Double-U-bend specimens and wedge loaded 1T-CT specimens made of Ti- and Nb-stabilised austenitic stainless steels were used. The results revealed no evidence of crack initiation and crack growth. Based on the laboratory results and the literature data an attempt is undertaken to separate parameters influencing chloride induced SCC from the effect of boric acid. (authors)

  5. Characteristics of Morphological Parameters of Donkeys in the Czech Republic

    Directory of Open Access Journals (Sweden)

    Martina Kosťuková

    2015-01-01

    Full Text Available The donkey population in Central Europe and Czech Republic is very variation, which is a consequence of the donkeys originating from various areas of Europe. This has been proved to affect their body conformation. In this work, we are focusing on the population of donkeys in the Czech Republic and its analysis.The main aim of our work was to determine the values morphological parameters in the donkey population in the Czech Republic. Altogether, 23 body dimensions were taken and further processed to calculate 6 hippo metric indexes. The sample group we analyzed consisted by a total of 70 individuals, out of there were 23 stallions and 47 mares. The results were then processed using the methods of general linear model (GLM and multiple comparisons.We managed to prove a statistically significant influence of the sex factor for the following body measurements: shin length of the front limbs, chest width, withers height measured by tape, shin circumference on both front and pelvic limbs and also for weight index. Also, we have found a statistically significant difference in the scapula length when considering the age factor.

  6. Assessing reliability of fatigue indicator parameters for small crack growth via a probabilistic framework

    Science.gov (United States)

    Rovinelli, Andrea; Guilhem, Yoann; Proudhon, Henry; Lebensohn, Ricardo A.; Ludwig, Wolfgang; Sangid, Michael D.

    2017-06-01

    Microstructurally small cracks exhibit large variability in their fatigue crack growth rate. It is accepted that the inherent variability in microstructural features is related to the uncertainty in the growth rate. However, due to (i) the lack of cycle-by-cycle experimental data, (ii) the complexity of the short crack growth phenomenon, and (iii) the incomplete physics of constitutive relationships, only empirical damage metrics have been postulated to describe the short crack driving force metric (SCDFM) at the mesoscale level. The identification of the SCDFM of polycrystalline engineering alloys is a critical need, in order to achieve more reliable fatigue life prediction and improve material design. In this work, the first steps in the development of a general probabilistic framework are presented, which uses experimental result as an input, retrieves missing experimental data through crystal plasticity (CP) simulations, and extracts correlations utilizing machine learning and Bayesian networks (BNs). More precisely, experimental results representing cycle-by-cycle data of a short crack growing through a beta-metastable titanium alloy, VST-55531, have been acquired via phase and diffraction contrast tomography. These results serve as an input for FFT-based CP simulations, which provide the micromechanical fields influenced by the presence of the crack, complementing the information available from the experiment. In order to assess the correlation between postulated SCDFM and experimental observations, the data is mined and analyzed utilizing BNs. Results show the ability of the framework to autonomously capture relevant correlations and the equivalence in the prediction capability of different postulated SCDFMs for the high cycle fatigue regime.

  7. Single borehole test sensitivity towards crack and rock parameter. Lesson Hortberg; Einbohrlochtracertestsensitivitaet gegenueber Riss und Gesteinsparametern. Lektion Horstberg

    Energy Technology Data Exchange (ETDEWEB)

    Ghergut, Iulia; Behrens, Horst; Sauter, Martin [Goettingen Univ. (Germany). Angewandte Geologie

    2012-10-16

    The novel experiments of the GeoZentrum Hanover (Hanover, Federal Republic of Germany) on geothermal energy at the well bore Horstberg in the south heath also motivated the accompanying tracertest-mindset to move away from the tracer job stereotypes. For some possible designs at the tracertest at this drilling (forced-gradient divergent push by water fracking of Detfurth perforation, single-screen push-pull at Solling perforation, single-screen push-pull at Detfurth perforation, and so forth) the analysis shows how and why the controlling parameter do not comply with the mental basic pattern of the expectations at the tracertests ('tracertest by crack {yields} characterization of the crack', 'tracer residence time {yields} prognosis of the thermal lifetime').

  8. Analysis of Dynamic Fracture Parameters in Functionally Graded Material Plates with Cracks by Graded Finite Element Method and Virtual Crack Closure Technique

    Directory of Open Access Journals (Sweden)

    Li Ming Zhou

    2016-01-01

    Full Text Available Based on the finite element software ABAQUS and graded element method, we developed a dummy node fracture element, wrote the user subroutines UMAT and UEL, and solved the energy release rate component of functionally graded material (FGM plates with cracks. An interface element tailored for the virtual crack closure technique (VCCT was applied. Fixed cracks and moving cracks under dynamic loads were simulated. The results were compared to other VCCT-based analyses. With the implementation of a crack speed function within the element, it can be easily expanded to the cases of varying crack velocities, without convergence difficulty for all cases. Neither singular element nor collapsed element was required. Therefore, due to its simplicity, the VCCT interface element is a potential tool for engineers to conduct dynamic fracture analysis in conjunction with commercial finite element analysis codes.

  9. Identifiability of altimetry-based rating curve parameters in function of river morphological parameters

    Science.gov (United States)

    Paris, Adrien; André Garambois, Pierre; Calmant, Stéphane; Paiva, Rodrigo; Walter, Collischonn; Santos da Silva, Joecila; Medeiros Moreira, Daniel; Bonnet, Marie-Paule; Seyler, Frédérique; Monnier, Jérôme

    2016-04-01

    elevation Z0is systematically well identified with relative errors on the order of a few %. Eventually, these altimetry-based rating curves provide morphological parameters of river reaches that can be used as inputs into hydraulic models and a priori information that could be useful for SWOT inversion algorithms.

  10. Prediction of fracture parameters of circumferential through-wall cracks in the interface between an elbow and a pipe under internal pressure

    Energy Technology Data Exchange (ETDEWEB)

    Jang, Youn Young; Huh, Nam Su [Dept. of Mechanical System Design Engineering, Seoul National Univ. of Science and Technology, Seoul (Korea, Republic of); Jeong, Jae Uk [Doosan Heavy Industries and Construction, Changwon (Korea, Republic of)

    2016-09-15

    This paper provides plastic influence functions of GE/EPRI method for calculating J and Crack opening displacement (COD) of pipes with a circumferential Through-wall crack (TWC) in the interface between an elbow and a straight pipe by using 3-dimensional (3-D) elastic-plastic finite element analyses for Ramberg-Osgood (R-O) materials, in which internal pressure was considered as a loading condition. The proposed plastic influence functions are tabulated as a function of the pipe geometries, crack length and strain hardening exponent. In order to provide sufficient confidence for the proposed plastic influence functions, the estimation scheme using the proposed plastic influence functions for J and COD of cracked elbows was validated against FE results using R-O parameters for the SA312 TP316 stainless steel. Moreover, the predicted J and COD for elbows with a TWC in the interface between an elbow and a pipe by the proposed scheme were compared with those for cracked straight pipes to investigate the effect of the elbow geometries on crack behavior of elbows. One important point is that crack behaviors in the interface between an elbow and a straight pipe can be significantly different with those in straight pipes according to pipe thickness, crack length and bend radius of elbows. Thus, the proposed plastic influence functions can be useful to predict accurate J and COD for cracked elbows.

  11. Modelling and parameter estimation in reactive continuous mixtures: the catalytic cracking of alkanes - part II

    Directory of Open Access Journals (Sweden)

    F. C. PEIXOTO

    1999-09-01

    Full Text Available Fragmentation kinetics is employed to model a continuous reactive mixture of alkanes under catalytic cracking conditions. Standard moment analysis techniques are employed, and a dynamic system for the time evolution of moments of the mixture's dimensionless concentration distribution function (DCDF is found. The time behavior of the DCDF is recovered with successive estimations of scaled gamma distributions using the moments time data.

  12. 土壤表面干缩裂隙形态定量分析及其数值模拟%Morphological quantity analysis of soil surface shrinkage crack and its numerical simulation

    Institute of Scientific and Technical Information of China (English)

    朱磊; 陈玖泓; 刘德东

    2016-01-01

    Soil cracking is a common phenomenon in nature, which has great influence on soil properties, plant growth and soil moisture transfer. This study aimed to reveal the development law and formation mechanism of dry shrinkage cracks on the soil surface. Soil crack evolution test was carried out in 1-m2 soil in Yellow River irrigation area (105°40′E, 37°28′N) of Ningxia Zhongning County. Soil was irrigated to saturate condition, and dried under sunlight to form cracks. A Canon digital camera was used to take crack pictures every 2 h for 3 days. The picture was processed through binarization, noise removal and edge extraction of fracture for extraction of morphological properties. Minkowski area, length and Euler number were to quantify crackers. The cracker evolution was simulated through morphological dilation and erosion operation. The model assumed that the soil critical strain field followed normal distribution. Friction was taken as soil static adhesion force, and grid structure contraction frequency represented soil moisture evaporation intensity in hexagonal network structure composed of nodes. In the simulation, vertical interaction between layers of the soil was ignored, and the clay was considered as elastic material. The distance between each node in hexagonal structural network was reduced gradually on behalf of the soil evaporation. The reducing of distance between each node could cause the changing of force between network nodes, which resulted in soil cracking. The model was solved using program written by C++ language under the CodeLite platform and generated Tiff image as output. By comparison of crack area, crack length, euler number density that calculated by analyzing experiment pictures and images the program produced, it could be drawn that crack morphology could be described by Minkowski area, length, euler number density effectively; each parameter had its own variation as morphological analysis results did, among which area density

  13. Effect of processing parameters on the electromagnetic radiation emission during plastic deformation and crack propagation in copper-zinc alloys

    Institute of Scientific and Technical Information of China (English)

    KUMAR Rajeev; MISRA Ashok

    2006-01-01

    This paper presents some investigations on the effect of processing parameters on the emission of electromagnetic radiation (EMR) during plastic deformation and crack propagation in copper-zinc alloys. Timing of the EMR emissions, maximum stress during crack instability, stress-intensity factor, elastic strain energy release rate, maximum EMR amplitude, RMS value of EMR amplitude, EMR frequency and electromagnetic energy release rate were analysed for the effect of rolling directions at different percentage of zinc content in Cu-Zn alloy specimens. The same parameters were also analysed for 68-32 Cu-Zn alloy specimens at different annealing temperatures and at different angles θ, to the rolling direction. EMR emissions are observed to be highly anisotropic in nature. At θ=45° to 60°, marked changes in mechanical and electromagnetic parameters were observed.Specimens annealed at 500 °C, just above the recrystallization temperature, and at 700 °C, when grain-size growth is rapid, EMR responses have been found to have well-defined patterns.

  14. Pyrolysis of Pinus pinaster in a two-stage gasifier: Influence of processing parameters and thermal cracking of tar

    Energy Technology Data Exchange (ETDEWEB)

    Fassinou, Wanignon Ferdinand; Toure, Siaka [Laboratoire d' Energie Solaire-UFR-S.S.M.T. Universite de Cocody, 22BP582 Abidjan 22 (Ivory Coast); Van de Steene, Laurent; Volle, Ghislaine; Girard, Philippe [CIRAD-Foret, TA 10/16, 73, avenue J.-F. Breton, 34398 Montpellier, Cedex 5 (France)

    2009-01-15

    A new two-stage gasifier with fixed-bed has recently been installed on CIRAD facilities in Montpellier. The pyrolysis and the gasifier units are removable. In order to characterise the pyrolysis products before their gasification, experiments were carried out, for the first time only with the pyrolysis unit and this paper deals with the results obtained. The biomass used is Pinus pinaster. The parameters investigated are: temperature, residence time and biomass flow rate. It has been found that increasing temperature and residence time improve the cracking of tars, gas production and char quality (fixed carbon rate more than 90%, volatile matter rate less than 4%). The increase of biomass flow rate leads to a bad char quality. The efficiency of tar cracking, the quality and the heating value of the charcoal and the gases, indicate that: temperature between 650 C and 750 C, residence time of 30 min, biomass flow rate between 10 and 15 kg/h should be the most convenient experimental conditions to get better results from the experimental device and from the biomass pyrolysis process. The kinetic study of charcoal generation shows that the pyrolysis process, in experimental conditions, is a first-order reaction. The kinetic parameters calculated are comparable with those found by other researchers. (author)

  15. Parameters critical to the morphology of fluidization craters

    Science.gov (United States)

    Siegal, B. S.; Gold, D. P.

    1973-01-01

    In order to study further the role of fluidization on the moon, a laboratory investigation was undertaken on two particulate material size fractions to determine the effect of variables, such as, duration of gas streaming, gas pressure, and 'regolith' thickness on the morphology of fluidization craters. A 3.175-mm cylindrical vent was used to simulate a gas streaming conduit. Details of the fluidization chamber are discussed together with questions of experimental control, aspects of nomenclature, crater measurements, and the effect of variables.

  16. Significance of combined nutritional and morphological precaecal parameters for feed evaluations in non-ruminants

    OpenAIRE

    2002-01-01

    In this thesis the hypothesis is tested that the nutritional evaluation of dietary formulations in non-ruminants requires both functional-nutritional and functional-morphological parameters. The functional-nutritional parameters provide data on the outcome of the digestive process. Additionally, the functional-morphological parameters provide information about the effects of feed components on the small intestinal mucosa.Part I (chapters 2 - 4) considers the apparent digestibility as a functi...

  17. URBAN MORPHOLOGY AND AIR QUALITY IN DENSE RESIDENTIAL ENVIRONMENTS: CORRELATIONS BETWEEN MORPHOLOGICAL PARAMETERS AND AIR POLLUTION AT STREET-LEVEL

    Directory of Open Access Journals (Sweden)

    PRIYANTHA EDUSSURIYA

    2014-02-01

    Full Text Available This study is the second part of the series that identifies whether site-specific urban morphological parameters are correlated with air quality. This study aims to identify the most important urban morphological parameters that affects air quality at street level that affect air quality in metropolis like Hong Kong through field measurements and statistical analyses. The study considers 20 urban residential areas in five major districts of Hong Kong and real-time street level air pollutant and microclimatic data are collected from these areas. 21 morphological variables are identified and calculated based on the geometry of the urban fabric. Using principal component analyses, it is shown that out of the many urban morphological factors, only five morphological variables (plan area density, occlusivity, aerodynamic roughness height, mean built volume, compactness factor and four land development factors (aspect ratio, distance between building, mean building height and standard deviation of building height correlate with particulate matter. Besides mineralisation factor, contiguity and canyon ratio marginally correlate with particulate matter. On the other hand, nine variables (plan area density, compactness factor, occlusivity, aerodynamic roughness height, average size of building volume, aspect ratio, distance between buildings, mean building height and standard deviations of building heights correlate with NOx. All others play insignificant roles in street-level pollution effect. Moreover statistical analyses show little correlation between CO and ozone with urban morphological parameters. It is also established that the key microclimatic variables that connects PM and NOx with the urban morphological factors are northerly wind, relative humidity and temperature, which in turn translates to affecting the street-level air pollution.

  18. Correlation of morphological and molecular parameters for colon cancer

    Science.gov (United States)

    Yuan, Shuai; Roney, Celeste A.; Li, Qian; Jiang, James; Cable, Alex; Summers, Ronald M.; Chen, Yu

    2010-02-01

    Colorectal cancer (CRC) is the second leading cause of cancer death in the United States. There is great interest in studying the relationship among microstructures and molecular processes of colorectal cancer during its progression at early stages. In this study, we use our multi-modality optical system that could obtain co-registered optical coherence tomography (OCT) and fluorescence molecular imaging (FMI) images simultaneously to study CRC. The overexpressed carbohydrate α-L-fucose on the surfaces of polyps facilitates the bond of adenomatous polyps with UEA-1 and is used as biomarker. Tissue scattering coefficient derived from OCT axial scan is used as quantitative value of structural information. Both structural images from OCT and molecular images show spatial heterogeneity of tumors. Correlations between those values are analyzed and demonstrate that scattering coefficients are positively correlated with FMI signals in conjugated. In UEA-1 conjugated samples (8 polyps and 8 control regions), the correlation coefficient is ranged from 0.45 to 0.99. These findings indicate that the microstructure of polyps is changed gradually during cancer progression and the change is well correlated with certain molecular process. Our study demonstrated that multi-parametric imaging is able to simultaneously detect morphology and molecular information and it can enable spatially and temporally correlated studies of structure-function relationships during tumor progression.

  19. Comparison of biohumoral and morphological parameters in acute pancreatitis

    Directory of Open Access Journals (Sweden)

    Tasić Tomislav

    2014-01-01

    Full Text Available Introduction. Acute pancreatitis occurs as a result of autodigestive activation of pancreatic proenzymes, within the parenchyma of the glands. Objective. The goal of the work was to establish possible connection of etiology and severity of the acute pancreatitis and biohumoral parameters, ultrasound and CT. Methods. The study included 273 patients with pancreatitis, classified by Ranson’s score, according to degree of severity and etiology, whose biohumoral parameters were correlated with each other, and with the ultrasound and CT findings. Results. The values of amylase and ALT were significantly higher in the severe form of pancreatitis and biliary etiology compared to etilic (p<0.05. The ratio of AST/ALT was significantly higher in the group of etilic compared to biliary etiology (p<0.05. LDH was significantly higher in the severe form group compared to moderate form of pancreatitis (p<0.01. Cholesterol was significantly higher in the group of biliary compared to the group of etilic pancreatitis (p<0.05. There was a negative low correlation between the value of calcium ions in the plasma and CT analysis (p=0.05. Low degree negative correlation between the value of calcium ions and ultrasound analysis was established (p=0.0001. Conclusion. There was a negative correlation between the level of ionized calcium in the blood and the degree of the acute pancreatitis by the Balthazar score. Mean value of alpha amylase, total value of cholesterol and ALT were significantly higher in the group of biliary compared to the group of etilic acute pancreatitis. The average values of the alpha amylase, LDH and ALT were significantly higher in the group of severe form of the acute pancreatitis compared to the group of moderate form. The ratio AST/ALT was significantly higher in the group of etilic than in the group of biliary pancreatitis.

  20. The effect of crack cocaine addiction on the microstructure and morphology of the human striatum and thalamus using novel shape analysis and fast diffusion kurtosis imaging

    DEFF Research Database (Denmark)

    Garza-Villarreal, Eduardo A.; Mallar, Chakravarty; Hansen, Brian

    2016-01-01

    The striatum and thalamus are subcortical structures intimately involved in addiction, and the morphology and microstructure of these has been studied in murine models of cocaine addiction. However, human studies using non-invasive MRI has shown inconsistencies in morphology using volumetric...... analysis. In our study, we used MRI-based volumetric and novel shape analysis, as well as a novel fast diffusion kurtosis imaging sequence to study the morphology and microstructure of striatum and thalamus in crack cocaine addiction (CA) compared to matched healthy controls (HC). We did not find....... Our findings suggest that the use of finer methods and sequences is needed to characterize morphological and microstructural changes in cocaine addiction, and that brain changes in cocaine addiction are related to age....

  1. Morphologies in Solvent-Annealed Clotrimazole Thin Films Explained by Hansen-Solubility Parameters.

    Science.gov (United States)

    Ehmann, Heike M A; Zimmer, Andreas; Roblegg, Eva; Werzer, Oliver

    2014-03-05

    The induction of different crystal morphologies is of crucial importance for many applications. In this work, the preparation of various crystal morphologies within clotrimazole films on glass substrates is demonstrated. Amorphous clotrimazole thin films were transformed via vapor annealing into crystalline structures; highly monodisperse/multidisperse crystallites, spherulite, or dendritic structures were obtained as the solvent was exchanged. X-ray diffraction experiments reveal that the same polymorph is present for all samples but with varying texture. The achieved morphologies are explained in terms of Hansen-solubility parameters and vapor pressures; thus, the different morphologies and crystal orientations can be explained by solvent-solid interaction strengths within the thin film samples.

  2. Significance of combined nutritional and morphological precaecal parameters for feed evaluations in non-ruminants

    NARCIS (Netherlands)

    Leeuwen, van P.

    2002-01-01

    In this thesis the hypothesis is tested that the nutritional evaluation of dietary formulations in non-ruminants requires both functional-nutritional and functional-morphological parameters. The functional-nutritional parameters provide data on the outcome of the digestive process. A

  3. Crack Characterisation for In-service Inspection Planning - An Update

    Energy Technology Data Exchange (ETDEWEB)

    Waale, Jan [lnspecta Technology AB, Stockholm (Sweden)

    2006-05-15

    One important factor to optimize the NDT equipment and NDT procedure is to know the characteristics of the specific defects being sought for in each case. Thus, access is necessary to reliable morphology data of defects from all possible degradation mechanisms in all existing materials of the components that are subject to the NDT. In 1994 the Swedish Nuclear Power Inspectorate (SKI) initiated a project for compiling crack morphology data based on systematic studies of cracks that have been observed in different plants (nuclear and non-nuclear) in order to determine typical as well as more extreme values of e.g. orientation, width and surface roughness. Although, a large number of identified cracking incidents was covered by the work it was recognised that further studies were needed to increase the data base, and thereby getting more confidence in the use of different crack characteristic data for NDT development and qualification purposes. That is the major reason why the present work was initiated. A thorough review of the SKI archives was performed aiming to find useful material from the time period between 1994 and today to compile complementary data and produce an update. Furthermore, older material was collected and evaluated. Thus, the data cover cracking found within the time period 1977-2003. In addition, useful material was supplied by the Swedish nuclear power plants. The evaluation and presentation of the results are similar to the 1994 study, with a few exceptions. The base for the evaluation is failure analysis reports, where the crack morphology parameters were measured from photos on cracked surfaces or cross sections through cracks. The resulting data were divided into seven groups depending on the cracking mechanism/material group combination. The data groups are: IGSCC in austenitic stainless steels; IGSCC in nickel base alloys; IDSCC in nickel base weld metal; TGSCC in austenitic stainless steels Thermal fatigue in austenitic stainless steels

  4. Small-crack test methods

    Science.gov (United States)

    Larsen, James M.; Allison, John E.

    This book contains chapters on fracture mechanics parameters for small fatigue cracks, monitoring small-crack growth by the replication method, measurement of small cracks by photomicroscopy (experiments and analysis), and experimental mechanics of microcracks. Other topics discussed are the real-time measurement of small-crack-opening behavior using an interferometric strain/displacement gage; direct current electrical potential measurement of the growth of small cracks; an ultrasonic method for the measurement of the size and opening behavior of small fatigue cracks; and the simulation of short crack and other low closure loading conditions, utilizing constant K(max) Delta-K-decreasing fatigue crack growth procedures.

  5. Investigation of Key Parameters of Rock Cracking Using the Expansion of Vermiculite Materia

    Directory of Open Access Journals (Sweden)

    Chi-Hyung Ahn

    2015-10-01

    Full Text Available The demand for the development of underground spaces has been sharply increased in lieu of saturated ground spaces because the residents of cities have steadily increased since the 1980s. The traditional widely used excavation methods (i.e., explosion and shield have caused many problems, such as noise, vibration, extended schedule, and increased costs. The vibration-free (and explosion-free excavation method has currently attracted attention in the construction site because of the advantage of definitively solving these issues. For such reason, a new excavation method that utilizes the expansion of vermiculite with relatively fewer defects is proposed in this study. In general, vermiculite materials are rapidly expanded in volume when they receive thermal energy. Expansion pressure can be produced by thermal expansion of vermiculite in a steel tube, and measured by laboratory tests. The experimental tests are performed with various influencing parameters in an effort to seek the optimal condition to effectively increase expansion pressure at the same temperature. Then, calibrated expansion pressure is estimated, and compared to each model. After analyzing test results for expansion pressure, it is verified that vermiculite expanded by heat can provide enough internal pressure to break hard rock during tunneling work.

  6. Investigation of Key Parameters of Rock Cracking Using the Expansion of Vermiculite Materials

    Science.gov (United States)

    Ahn, Chi-Hyung; Hu, Jong Wan

    2015-01-01

    The demand for the development of underground spaces has been sharply increased in lieu of saturated ground spaces because the residents of cities have steadily increased since the 1980s. The traditional widely used excavation methods (i.e., explosion and shield) have caused many problems, such as noise, vibration, extended schedule, and increased costs. The vibration-free (and explosion-free) excavation method has currently attracted attention in the construction site because of the advantage of definitively solving these issues. For such reason, a new excavation method that utilizes the expansion of vermiculite with relatively fewer defects is proposed in this study. In general, vermiculite materials are rapidly expanded in volume when they receive thermal energy. Expansion pressure can be produced by thermal expansion of vermiculite in a steel tube, and measured by laboratory tests. The experimental tests are performed with various influencing parameters in an effort to seek the optimal condition to effectively increase expansion pressure at the same temperature. Then, calibrated expansion pressure is estimated, and compared to each model. After analyzing test results for expansion pressure, it is verified that vermiculite expanded by heat can provide enough internal pressure to break hard rock during tunneling work. PMID:28793610

  7. Effect of Gas Tungsten Arc Welding Parameters on Hydrogen-Assisted Cracking of Type 321 Stainless Steel

    Science.gov (United States)

    Rozenak, Paul; Unigovski, Yaakov; Shneck, Roni

    2016-05-01

    The susceptibility of AISI type 321 stainless steel welded by the gas tungsten arc welding (GTAW) process to hydrogen-assisted cracking (HAC) was studied in a tensile test combined with in situ cathodic charging. Specimen charging causes a decrease in ductility of both the as-received and welded specimens. The mechanical properties of welds depend on welding parameters. For example, the ultimate tensile strength and ductility increase with growing shielding gas (argon) rate. More severe decrease in the ductility was obtained after post-weld heat treatment (PWHT). In welded steels, in addition to discontinuous grain boundary carbides (M23C6) and dense distribution of metal carbides MC ((Ti, Nb)C) precipitated in the matrix, the appearance of delta-ferrite phase was observed. The fracture of sensitized specimens was predominantly intergranular, whereas the as-welded specimens exhibited mainly transgranular regions. High-dislocation density regions and stacking faults were found in delta-ferrite formed after welding. Besides, thin stacking fault plates and epsilon-martensite were found in the austenitic matrix after the cathodic charging.

  8. The effect of heat treatment and test parameters on the aqueous stress corrosion cracking of D6AC steel

    Science.gov (United States)

    Gilbreath, W. P.; Adamson, M. J.

    1974-01-01

    The crack growth behavior of D6AC steel as a function of stress intensity, stress and corrosion history and test technique, under sustained load in natural seawater, 3.3 percent NaCl solution, distilled water, and high humidity air was investigated. Reported investigations of D6AC were considered with emphasis on thermal treatment, specimen configuration, fracture toughness, crack-growth rates, initiation period, threshold, and the extension of corrosion fatigue data to sustained load conditions. Stress history effects were found to be most important in that they controlled incubation period, initial crack growth rates, and apparent threshold.

  9. Morphological and Functional Parameters in Patients with Tooth Wear before and after Treatment

    OpenAIRE

    Sierpinska, Teresa; Kuc, Joanna; Golebiewska, Maria

    2013-01-01

    Advanced tooth wear often results in lost vertical dimension and impacts facial aesthetics. Complex restorative treatment can replace the lost tooth structure and improve functional occlusal and facial skeleton parameters. Purpose: The aim of the study is to assess changes in the morphological and functional occlusal parameters of the facial skeleton after prosthetic rehabilitation that increased lost occlusal vertical dimension. Material and Methodology: 50 patients with advanced tooth wear ...

  10. Cellular morphological parameters of the human urinary bladder (malignant and normal).

    Science.gov (United States)

    Keshtkar, Ahmad; Keshtkar, Asghar; Lawford, Pat

    2007-06-01

    The normal and malignant cellular morphological parameters (intra- and extracellular spaces of the human urinary bladder) were obtained from analysis of digital images of bladder histology sections. Then these cellular morphological parameters were compared with the same parameters obtained from the literature for the bladder tissue. However, the limited quantitative data about these parameters available in the literature for bladder cell sizes and other geometrical parameters such as extra-cellular space does not provide a scientific basis to construct accurate structural models of normal and malignant bladder tissue. Therefore, there is usually no quantitative discussion of cell sizes in literature but the measured data in this work can provide a reasonable estimation of expected morphological parameter changes of bladder tissue with pathology. To produce this quantitative information, and also, to build a suitable models in another study using electrical properties of the tissue, 10 digital images of histological sections of normal, and six sections from malignant areas of the human urinary bladder, were chosen randomly (ex vivo). Finally, the measured data showed that there is a significant difference between the cell dimensions (in basal and intermediate layers) of normal and malignant bladder tissues.

  11. Controlling Morphological Parameters of Anodized Titania Nanotubes for Optimized Solar Energy Applications

    Directory of Open Access Journals (Sweden)

    Michael Hu

    2012-10-01

    Full Text Available Anodized TiO2 nanotubes have received much attention for their use in solar energy applications including water oxidation cells and hybrid solar cells [dye-sensitized solar cells (DSSCs and bulk heterojuntion solar cells (BHJs]. High surface area allows for increased dye-adsorption and photon absorption. Titania nanotubes grown by anodization of titanium in fluoride-containing electrolytes are aligned perpendicular to the substrate surface, reducing the electron diffusion path to the external circuit in solar cells. The nanotube morphology can be optimized for the various applications by adjusting the anodization parameters but the optimum crystallinity of the nanotube arrays remains to be realized. In addition to morphology and crystallinity, the method of device fabrication significantly affects photon and electron dynamics and its energy conversion efficiency. This paper provides the state-of-the-art knowledge to achieve experimental tailoring of morphological parameters including nanotube diameter, length, wall thickness, array surface smoothness, and annealing of nanotube arrays.

  12. Morphologic,mechanical and functional sonographic parameters of arteries in autosomal dominant polycystic kidney disease

    Institute of Scientific and Technical Information of China (English)

    戎殳

    2006-01-01

    Objective To investigate whether the risk factors of cardiovascular disease exist in early stage of ADPKD patients with normal renal function. Methods Morphologic , mechanical and functional sonographic parameters of arteries were examined by high-frequency ultrasonography in 32 hypertensive and 28 normotensive ADPKD patients with preserved renal function, 25 patients with es-

  13. Morphological parameters of a Spitzer survey of stellar structure in galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Holwerda, B. W. [ESTEC, Keplerlaan 1, 2200-AG Noordwijk (Netherlands); Muñoz-Mateos, J.-C.; Sheth, K.; Kim, T. [National Radio Astronomfy Observatory/NAASC, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Comerón, S.; Laurikainen, E.; Salo, H.; Laine, J. [Astronomy Division, Department of Physical Sciences, FI-90014 University of Oulu, P.O. Box 3000, Oulu (Finland); Meidt, S.; Mizusawa, T. [Max-Planck-Institut für Astronomie/Königstühl 17, D-69117 Heidelberg (Germany); Laine, S. [Spitzer Science Center, Mail Stop 220-6, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Hinz, J. L.; Zaritsky, D. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Regan, M. W. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Gil de Paz, A. [Departamento de Astrofísica, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Menéndez-Delmestre, K.; Seibert, M.; Ho, L. C. [The Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Gadotti, D. A. [European Southern Observatory, Casilla 19001, Santiago 19 (Chile); Erroz-Ferrer, S., E-mail: benne.holwerda@esa.int, E-mail: benne.holwerda@gmail.com [Instituto de Astrofísica de Canarias, Vía Láctea s/n E-38205 La Laguna (Spain); and others

    2014-01-20

    The morphology of galaxies can be quantified to some degree using a set of scale-invariant parameters. Concentration (C), asymmetry (A), smoothness (S), the Gini index (G), the relative contribution of the brightest pixels to the second-order moment of the flux (M {sub 20}), ellipticity (E), and the Gini index of the second-order moment (G{sub M} ) have all been applied to morphologically classify galaxies at various wavelengths. Here, we present a catalog of these parameters for the Spitzer Survey of stellar structure in Galaxies, a volume-limited, near-infrared (NIR) imaging survey of nearby galaxies using the 3.6 and 4.5 μm channels of the Infrared Array Camera on board the Spitzer Space Telescope. Our goal is to provide a reference catalog of NIR quantified morphology for high-redshift studies and galaxy evolution models with enough detail to resolve stellar mass morphology. We explore where normal, non-interacting galaxies—those typically found on the Hubble tuning fork—lie in this parameter space and show that there is a tight relation between concentration (C {sub 82}) and M {sub 20} for normal galaxies. M {sub 20} can be used to classify galaxies into earlier and later types (i.e., to separate spirals from irregulars). Several criteria using these parameters exist to select systems with a disturbed morphology, i.e., those that appear to be undergoing a tidal interaction. We examine the applicability of these criteria to Spitzer NIR imaging. We find that four relations, based on the parameters A and S, G and M {sub 20}, G{sub M} , C, and M {sub 20}, respectively, select outliers in morphological parameter space, but each selects different subsets of galaxies. Two criteria (G{sub M} > 0.6, G > –0.115 × M {sub 20} + 0.384) seem most appropriate to identify possible mergers and the merger fraction in NIR surveys. We find no strong relation between lopsidedness and most of these morphological parameters, except for a weak dependence of lopsidedness on

  14. MORPHOLOGICAL FEATURES AND MORPHOMETRIC PARAMETERS OF HUMAN FETAL VERMIFORM APPENDIX AT DIFFERENT GESTATIONAL

    Directory of Open Access Journals (Sweden)

    Reshma.Mohammad

    2013-09-01

    Full Text Available Background:Vermiform appendix is a vestigial organ of variable position in the abdomen. Its location, size andshape are subject to alterations with the race of the population and limited information is available on devel-opmental morphology and morphometry of fetal appendix.Materials and Methods:In the present study 60appendix specimens from aborted human fetuses of 17-40 weeks gestational age and both sexes were studiedby dissection method for age related morphological features and morphometric parameters. The morphologi-cal parameters observed include its location in relation to abdominal region, caecum and ileum, clock position,position of base in relation to caecal wall and direction of tip of appendix. The morphometric parameters oflength, diameter and distance between ileo-caecal orifice and appendicular orifice were measured.Results:The location of appendix in relation to abdominal region presented higher incidence of sub-hepatic position inless than 30 weeks fetuses and right iliac fossa location in more than 30 weeks fetuses.Discussion: in comparisionwith the literature available on adult vermiform appendix the observations in the present study arein favor ofinfluence of developmental processes on the localization of appendix including its base, ileo-caecalorifice,direction of tip, distance from McBurney’s point.Conclusion:Results of this work suggests variability in local-ization of appendix during prenatal development and the influence of gestational age, sex, size, growth ofcaecum and gut on its final position and was different from that of adults. There is increase in themorphomet-ric parameters of appendix with increase in gestational age. Both morphological and morphometric param-eters were different between sexes.

  15. Effect of crack surface geometry on fatigue crack closure

    Energy Technology Data Exchange (ETDEWEB)

    Drury, W.J. [P and L Technologies, Inc., Atlanta, GA (United States); Gokhale, A.M. [Georgia Inst. of Tech., Atlanta, GA (United States). School of Materials Science and Engineering; Antolovich, S.D. [Washington State Univ., Pullman, WA (United States). School of Mechanical and Materials Engineering

    1995-10-01

    The geometry of crack faces often plays a critical role in reducing crack extension forces when crack closure occurs during fatigue crack growth. Most previous studies of fatigue crack closure are concerned with mechanical measure of closure as related to the crack growth rate; very little attention has been given to the geometry of the crack surfaces. The objective is to identify those aspects of crack surface geometry that are important in the closure process, to develop quantitative fractographic techniques to estimate such attributes in a statistically significant and robust manner, and to correlate them to the physical process of crack closure. For this purpose, fatigue crack propagation experiments were performed on a Ni-base superalloy and crack growth rates and crack closure loads were measured. Digital image profilometry and software-based analysis techniques were used for statistically reliable and detailed quantitative characterization of fatigue crack profiles. It is shown that the dimensionless, scale-independent attributes, such a height-to-width ratio of asperities, fractal dimensions, dimensionless roughness parameters, etc., do not represent the aspects of crack geometry that are of primary importance in the crack closure phenomena. Furthermore, it is shown that the scale-dependent characteristics, such as average asperity height, do represent the aspects of crack geometry that play an interactive role in the closure process. These observations have implications concerning the validity of geometry-dependent, closure-based models for fatigue crack growth.

  16. Morphological Parameters of Spitzer Survey of Stellar Structure in Galaxies (S4G)

    CERN Document Server

    Holwerda, B W; Comeron, S; Meidt, S; Sheth, K; Laine, S; Hinz, J L; Regan, M W; Gil-de-Paz, A; Menendez-Delmestre, K; Seibert, M; Kim, T; Mizusawa, T; Laurikainen, E; Salo, H; Laine, J; Gadotti, D A; Zaritsky, D; Erroz-Ferrer, S; Ho, L C; Knapen, J H; Athanassoula, E; Bosma, A; Pirzkal, N

    2013-01-01

    The morphology of galaxies can be quantified to some degree using a set of scale-invariant parameters. Concentration (C), Asymmetry (A), Smoothness (S), the Gini index (G), relative contribution of the brightest pixels to the second order moment of the flux (M20), ellipticity (E), and the Gini index of the second order moment (GM) have all been applied to morphologically classify galaxies at various wavelengths. Here we present a catalog of these parameters for the Spitzer Survey of Stellar Structure in Galaxies (S4G), a volume-limited near-infrared imaging survey of nearby galaxies using the 3.6 and 4.5 micron channels of the IRAC camera. Our goal is to provide a reference catalog of near-infrared quantified morphology for high-redshift studies and galaxy evolution models with enough detail to resolve stellar mass morphology. We explore where normal, non-interacting galaxies -those typically found on the Hubble tuning fork- lie in this parameter space and show that there is a tight relation between Concentra...

  17. Growth patterns and dynamics of mud cracks at different diagenetic stages and its geological significance

    Institute of Scientific and Technical Information of China (English)

    Zhen-yu ZHAO; Yan-ru GUO; Yan WANG; Hong LIU; Qing ZHANG

    2014-01-01

    This paper discusses the growth stages, spatial structures, quantitative fitting relationships among various parameters, growth patterns and influencing factors of mud cracks by field survey, core observation and SEM analysis. The study shows that:(1) Mud crack growth can go through three stages, i.e. the syndiagenetic stage, the burial diagenetic stage (including early diagenetic stage, middle-late diagenetic stage) and the epidiagenetic stage. (2) Quantitative fitting relationships among various parameters allow a great significance to describe the spatial structure, the regional distribution and the growth environment of mud cracks. (3) Mud crack growth has three models, such as the unilateral growth model including the linear growth pattern, the curvilinear growth pattern and the bifurcation growth pattern, the multilateral growth model including the intersectional growth pattern, the join growth pattern and the dispersed growth pattern, and the mixed growth model including the combination of any patterns listed above. (4) Modern mud crack growth usually undergoes four stages. Sand beds in sand-mud rhythmic strata can play a lubricative role on crack growth and provide enough sandy deposits for filling cracks. (5) Mud crack growth usually produces bifurcation and bifurcation angles which are mostly 120° or 90° that are related to sediment heterogeneity and released energy. (6) Factors affecting mud crack growth cover many aspects: clay content and salinity can control the number of mud cracks in different areas;terrain can control mud crack morphology;and different sedimentary cycles can control the growth patterns and filling models of mud cracks.

  18. Effect of electrolysis parameters on the morphologies of copper powder obtained at high current densities

    Directory of Open Access Journals (Sweden)

    Orhan Gökhan

    2012-01-01

    Full Text Available The effects of copper ion concentrations and electrolyte temperature on the morphologies and on the apparent densities of electrolytic copper powders at high current densities under galvanostatic regime were examined. These parameters were evaluated by the current efficiency of hydrogen evolution. In addition, scanning electron microscopy was used for analyzing the morphology of the copper powders. It was found that the morphology was dependent over the copper ion concentration and electrolyte temperature under same current density (CD conditions. At 150 mA cm-2 and the potential of 1000±20 mV (vs. SCE, porous and disperse copper powders were obtained at low concentrations of Cu ions (0.120 M Cu2+ in 0.50 M H2SO4. Under this condition, high rate of hydrogen evolution reaction took place parallel to copper electrodeposition. The morphology was changed from porous, disperse and cauliflower-like to coral-like, shrub-like and stalk-stock like morphology with the increasing of Cu ion concentrations towards 0.120 M, 0.155 M, 0.315 M, 0.475 M and 0.630 M Cu2+ in 0.5 M H2SO4 respectively at the same CD. Similarly, as the temperature was increased, powder morphology and apparent density were observed to be changed. The apparent density values of copper powders were found to be suitable for many of the powder metallurgy applications.

  19. Effect of Substrate Temperature on Structural and Morphological Parameters Of ZnTe Thin Films

    Directory of Open Access Journals (Sweden)

    K.D. Patel

    2011-01-01

    Full Text Available Vacuum evaporated thin films of Zinc Telluride (ZnTe of 5000 Å thickness have been deposited on glass substrates at different substrate temperatures (303 K, 373 K, 448 K. Structural parameters were obtained using XRD analysis. Atomic Force Microscope (AFM in non-contact mode has been used to study the surface morphological properties of the deposited thin films. The results obtained from structural and surface morphological studies have been correlated and it is found that the films deposited at higher substrate temperatures possess increasingly good crystallinity and smoother surfaces.

  20. Irradiation effects of CO2 laser parameters on surface morphology of fused silica

    Institute of Scientific and Technical Information of China (English)

    Xiang Xia; Zheng Wan-Guo; Yuan Xiao-Dong; Dai Wei; Juang Yong; Li Xi-Bin; Wang Hai-Jun; Lü Hai-Bing; Zu Xiao-Tao

    2011-01-01

    To understand the surface morphology evolution of fused silica induced by 10.6-prn CO2 laser irradiation atdifferent parameters, this paper reports that optical microscopy, profilometry, and hydrophilicity tests are utilized to characterize the surface structure and roughness of the laser irradiated area. The results show that three typical surface morphologies and two typical by drophilicity test images are observed at different laser powers and pulse durations. Thecorrelations between surface temperature and surface morphology as well as hydrophilicity behaviours are presented.The different hydrophilicity behaviours are related to surface structures of the laser-induced crater and thermal diffusion area. The thermal diffusion length monotonously increases with increasing laser power and pulse duration. The crater width is almost determined by the laser beam size. The crater depth is more sensitive to the laser power and pulse duration than the crater width.

  1. The imprint of pulsar parameters on the morphology of Pulsar Wind Nebulae

    Science.gov (United States)

    Bühler, Rolf; Giomi, Matteo

    2016-11-01

    The morphology of young Pulsar Wind Nebulae (PWN) is largely determined by the properties of the wind injected by the pulsar. We have used a recent parametrization of the wind obtained from force-free electrodynamics simulations of pulsar magnetospheres to simulate nebulae for different sets of pulsar parameters. We performed axisymmetric relativistic magnetohydrodynamics simulations to test the morphology dependence of the nebula on the obliquity of the pulsar and on the magnetization of the pulsar wind. We compare these simulations to the morphology of the Vela and Crab PWN. We find that the morphology of Vela can be reproduced qualitatively if the pulsar obliquity angle is α ≈ 45° and the magnetization of the wind is high (σ0 ≈ 3.0). A morphology similar to the one of the Crab nebula is only obtained for low-magnetization simulations with α ≳ 45°. Interestingly, we find that Kelvin-Helmholtz instabilities produce small-scale turbulences downstream of the reverse shock of the pulsar wind.

  2. The imprint of pulsar parameters on the morphology of Pulsar Wind Nebulae

    CERN Document Server

    Buehler, Rolf

    2016-01-01

    The morphology of young Pulsar Wind Nebulae (PWN) is largely determined by the properties of the wind injected by the pulsar. We have used a recent parametrization of the wind obtained from Force Free Electrodynamics simulations of pulsar magnetospheres to simulate nebulae for different sets of pulsar parameters. We performed axisymmetric Relativistic Magnetohydrodynamics simulations to test the morphology dependence of the nebula on the obliquity of the pulsar and on the magnetization of the pulsar wind. We compare these simulations to the morphology of the Vela and Crab PWN. We find that the morphology of Vela can be reproduced qualitatively if the pulsar obliquity angle is alpha ~45deg and the magnetization of the wind is high (sigma_0 ~ 3.0). A morphology similar to the one of the Crab Nebula is only obtained for low magnetization simulations with alpha >~ 45deg. Interestingly, we find that Kelvin-Helmholtz instabilities produce small scale turbulences downstream of the reverse shock of the pulsar wind.

  3. The Parameter of Fatigue Damage Based on Characteristics of Short Cracks%基于短裂纹特性的疲劳损伤参数

    Institute of Scientific and Technical Information of China (English)

    赵毅红; 陈荣发

    2000-01-01

    In order to understand which parameter, such as the number of cracks and the total crack length, is a useful indicator of fatigue damage, rotatory bending fatigue tests are carried out using smooth specimens of medium-carbon steel. The behavior of short fatigue propagation and the evolution of surface cracks during fatigue life are examined. The aim of this paper is to study how these damage parameters are correlated with the process of fatigue damage in order to evaluate the effectiveness of damage detection methods.%通过对中碳钢光滑试样的疲劳实验,研究了疲劳过程中短裂纹的扩展和演化行为,分析了基于短裂纹群体行为的疲劳损伤参数来描述疲劳损伤的有效性。通过研究裂纹总数和裂纹总长这两个参数在疲劳损伤过程中的动态变化,对基于短裂纹群体行为的疲劳损伤检测方法进行了评价

  4. Embrittlement and anodic process in stress corrosion cracking: study of the influent micro-mechanical parameters; Fragilisation et processus anodiques en corrosion sous contrainte: etude des parametres micro-mecaniques influents

    Energy Technology Data Exchange (ETDEWEB)

    Tinnes, J.Ph

    2006-11-15

    We study the influence of local mechanical parameters on crack propagation in Stress Corrosion Cracking, at the scale of the microstructure. Two systems are compared: the CuAl{sub 9}Ni{sub 3}Fe{sub 2} copper-aluminium alloy in synthetic sea water under cathodic polarization, where the crack propagation mechanism is related to strain-assisted anodic dissolution, and the 316L austenitic stainless steel in MgCl{sub 2} solution, where embrittlement mechanisms related to hydrogen effects prevail. We use micro-notched tensile specimen that allow to study isolated short cracks. These experiments are modelled by means of finite elements calculations, and further characterized by Electron Back scattered Diffraction (EBSD) in the case of the 316L alloy. In terms of the local mechanical parameters that control propagation, fundamental differences are outlined between the two systems. They are discussed from the viewpoint of the available models of Stress Corrosion Cracking. (author)

  5. The Effects of Annealing Parameters on the Crystallization and Morphology of Cu(In,GaSe2 Absorber Layers Prepared by Annealing Stacked Metallic Precursors

    Directory of Open Access Journals (Sweden)

    Chia-Ho Huang

    2014-01-01

    Full Text Available CIGS films are prepared by single-stage annealing of the solid Se-coated In/Cu-Ga bilayer precursor. The annealing processes were performed using various Ar pressures, heating rates, and soaking times. A higher Ar pressure is needed to fabricate highly crystalline CIGS films, as no extra Se-vapor source is supplied. As the heating rate increases, the surface morphologies of the CIGS films become looser and some cracks are observed. However, the influence of soaking time is insignificant and the selenization process only requires a short time when the precursors are selenized at a higher temperature with a lower heating rate and a higher Ar pressure. In this study, a dense chalcopyrite CIGS film with a thickness of about 1.5-1.6 μm, with large grains (~1.2 μm and no cracking or peeling is obtained after selenizing at a temperature of 550°C, an Ar pressure of 300 Torr, a heating rate of 60°C/min, and a soaking time of 20 min. By adequate design of the stacked precursor and controlling the annealing parameters, single-stage annealing of the solid Se-coated In/Cu-Ga bilayer precursor is simplified for the fabrication of a fully crystallized chalcopyrite CIGS absorber layers with good crystallization and large grains.

  6. Charcoal Morphometry for Paleoecological Analysis: The Effects of Fuel Type and Transportation on Morphological Parameters

    Directory of Open Access Journals (Sweden)

    Alastair J. Crawford

    2014-08-01

    Full Text Available Premise of the study: Charcoal particles preserved in sediments are used as indicators of paleowildfire. Most research focuses on abundance as an indicator of fire frequency, but charcoals also convey information about the vegetation from which they are derived. One potential source of information is their morphology, which is influenced by the parent material, the nature of the fire, and subsequent transportation and burial. Methods: We charcoalified 26 materials from a range of plant taxa, and subjected them to simulated fluvial transport by tumbling them with water and gravel. We photographed the resulting particles, and used image analysis software to measure morphological parameters. Results: Leaf charcoal displayed a logarithmic decrease in area, and a logarithmic increase in circularity, with transportation time. Trends were less clear for stem or wood charcoal. Grass charcoal displayed significantly higher aspect ratios than other charcoal types. Conclusions: Leaf charcoal displays more easily definable relationships between morphological parameters and degree of breakdown than stem or wood charcoal. The aspect ratios of fossil mesocharcoal can indicate the broad botanical source of an assemblage. Coupled to estimates of charcoal abundance, this will improve understanding of the variation in flammability of ancient ecosystems.

  7. INFLUENCE OF SYNTHESIS PARAMETERS ON MORPHOLOGICAL PROPERTIES OF ALUMINUM(III-PILLARED BENTONITES

    Directory of Open Access Journals (Sweden)

    ANA-MARIA GEORGESCU

    2016-10-01

    Full Text Available Al-pillared interlayered clays (Al-PILCs have been prepared from Romanian natural calcium bentonite (Orasu Nou deposit and the effect of some parameters on the morphological properties has been investigated. The synthesis of Al-pillared bentonite consists in the following five steps: bentonite purification, ionic exchange of bentonite with Cu(II ions, preparation of pillaring agent, intercalation of ionic exchanged bentonite with pillaring agent and calcination. The pillared clays present a rigid structure, a high thermal stability given by the oxido-metallic pillars formed after calcination. The raw material and the obtained nanomaterials were characterized by scanning electron microscopy (SEM coupled with energy-dispersive X-ray spectroscopy (EDX and transmission electron microscopy (TEM. The intercalation of the Al-polyhydroxocations into the interlayer of montmorillonite strongly modified the morphology of the Al-PILCs. The material with the best characteristics will be chosen in the aim of its using in liquid effluents remediation.

  8. Crack layer theory

    Science.gov (United States)

    Chudnovsky, A.

    1984-01-01

    A damage parameter is introduced in addition to conventional parameters of continuum mechanics and consider a crack surrounded by an array of microdefects within the continuum mechanics framework. A system consisting of the main crack and surrounding damage is called crack layer (CL). Crack layer propagation is an irreversible process. The general framework of the thermodynamics of irreversible processes are employed to identify the driving forces (causes) and to derive the constitutive equation of CL propagation, that is, the relationship between the rates of the crack growth and damage dissemination from one side and the conjugated thermodynamic forces from another. The proposed law of CL propagation is in good agreement with the experimental data on fatigue CL propagation in various materials. The theory also elaborates material toughness characterization.

  9. Effect of ascorbic acid on morphological and biochemical parameters in tomato seedling exposure to salt stress

    Directory of Open Access Journals (Sweden)

    Krupa-Małkiewicz Marcelina

    2015-06-01

    Full Text Available The aim of this study is to determine the effect of both NaCl and KCl alone and in comparison to AsA on the morphological and some biochemical parameters of Oxheart and Vilma cultivars of tomato under laboratory and field conditions. A combination of salt applied in the laboratory experiment caused a significant effect on seed germination and root and shoot length and a significant reduction of Chl a, Chl b and Car contents in 14-day-old tomato seedlings. However, seedlings of cultivar Vilma were characterised by higher tolerance to applied salt stress.

  10. Numerical Simulation of Solidification Microstructure and Effects of Phase-field Parameters on Grain Growth Morphologies

    Institute of Scientific and Technical Information of China (English)

    Jingfeng LIU; Ruixiang LIU; Liliang CHEN

    2005-01-01

    By a simple phase field model, a series of numerical simulations of solidification microstructure was performed to show a rich variety of dendritic patterns. At the same time, the relation between the morphology of grain growth and some parameters including the strength of anisotropy, dimensionless latent heat and the size of initial solid zone was studied. It is for the first time that patterns of grain growth were associated with the size of initial solid zone,which is an interesting issue. The possible reason for this may be that variation in the size of initial solid zone may bring about fluctuation of the interface energy, making the interface unstable.

  11. Influence of electromagnetic field parameters on the morphology of graphite in grey cast iron

    Directory of Open Access Journals (Sweden)

    J. Szajnar

    2009-01-01

    Full Text Available One way to improve the unification of the casting structure may be the application of forced convection of liquid metal during thecrystallization in the form or continuous casting mould. This paper presents the results describing the influence of selected parameters of rotating electromagnetic field enforcing the movement of liquid metal in the form on the morphology of graphite in grey cast iron. The results were fragmented graphite flakes in conditions of regulating the rate of cooling in the range of temperature TZAL

  12. Effect of process parameters on crystal size and morphology of lactose in ultrasound-assisted crystallization

    Energy Technology Data Exchange (ETDEWEB)

    Patel, S.R.; Murthy, Z.V.P. [Chemical Engineering Department, S.V. National Institute of Technology, Surat - 395 007, Gujarat (India)

    2011-03-15

    {alpha}-lactose monohydrate is widely used as a pharmaceutical excipient. Drug delivery system requires the excipient to be of narrow particle size distribution with regular particle shape. Application of ultrasound is known to increase or decrease the growth rate of certain crystal faces and controls the crystal size distribution. In the present paper, effect of process parameters such as sonication time, anti-solvent concentration, initial lactose concentration and initial pH of sample on lactose crystal size, shape and thermal transition temperature was studied. The parameters were set according to the L{sub 9}-orthogonal array method at three levels and recovered lactose from whey by sonocrystallization. The recovered lactose was analyzed by particle size analyzer, scanning electron microscopy and differential scanning calorimeter. It was found that the morphology of lactose crystal was rod/needle like shape. Crystal size distribution of lactose was observed to be influenced by different process parameters. From the results of analysis of variance, the sonication time interval was found to be the most significant parameter affecting the volume median diameter of lactose with the highest percentage contribution (74.28%) among other parameters. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. Morphological divergence rate tests for natural selection: uncertainty of parameter estimation and robustness of results

    Directory of Open Access Journals (Sweden)

    Leandro R. Monteiro

    2005-01-01

    Full Text Available In this study, we used a combination of geometric morphometric and evolutionary genetics methods for the inference of possible mechanisms of evolutionary divergence. A sensitivity analysis for the constant-heritability rate test results regarding variation in genetic and demographic parameters was performed, in order to assess the relative influence of uncertainty of parameter estimation on the robustness of test results. As an application, we present a study on body shape variation among populations of the poeciliine fish Poecilia vivipara inhabiting lagoons of the quaternary plains in northern Rio de Janeiro State, Brazil. The sensitivity analysis showed that, in general, the most important parameters are heritability, effective population size and number of generations since divergence. For this specific example, using a conservatively wide range of parameters, the neutral model of genetic drift could not be accepted as a sole cause for the observed magnitude of morphological divergence among populations. A mechanism of directional selection is suggested as the main cause of variation among populations in different habitats and lagoons. The implications of parameter estimation and biological assumptions and consequences are discussed.

  14. Physiological description of multivariate interdependencies between process parameters, morphology and physiology during fed-batch penicillin production.

    Science.gov (United States)

    Posch, Andreas E; Herwig, Christoph

    2014-01-01

    Optimization of productivity and economics of industrial bioprocesses requires characterization of interdependencies between process parameters and process performance. In the case of penicillin production, as in other processes, process performance is often closely interlinked with the physiology and morphology of the organism used for production. This study presents a systematic approach to efficiently characterize the physiological effects of multivariate interdependencies between bioprocess design parameters (spore inoculum concentration, pO2 control level and substrate feed rate), morphology, and physiology. Method development and application was performed using the industrial model process of penicillin production. Applying traditional, statistical bioprocess analysis, multivariate correlations of raw bioprocess design parameters (high spore inoculum concentration, low pO2 control as well as reduced glucose feeding) and pellet morphology were identified. A major drawback of raw design parameter correlation models; however, is the lack of transferability across different process scales and regimes. In this context, morphological and physiological bioprocess modeling based on scalable physiological parameters is introduced. In this study, raw parameter effects on pellet morphology were efficiently summarized by the physiological parameter of the biomass yield per substrate. Finally, for the first time to our knowledge, the specific growth rate per spore was described as time-independent determinant for switching from pellet to disperse growth during penicillin production and thus introduced as a novel, scalable key process parameter for pellet morphology and process performance.

  15. Morphological classification and structural parameters for early-type galaxies in the Coma cluster

    CERN Document Server

    Andreon, S; Michard, R; Nieto, J L; Poulain, P

    1995-01-01

    We present the results of an isophotal shape analysis of three samples of galaxies in the Coma cluster. Quantitative morphology, together with structural and photometric parameters, is given for each galaxy. Special emphasis has been placed on the detailed classification of early-type galaxies. The three samples are: i) a sample of 97 early-type galaxies brighter than m_B = 17.00 falling within one degree from the center of the Coma cluster; these galaxies were observed with CCD cameras, mostly in good to excellent resolution conditions; ii) a magnitude complete sample of 107 galaxies of all morphological types down to m_B = 17.00 falling in a circular region of 50 arcmin diameter, slightly offcentered to the North-West of the cluster center; the images for this and the next sample come from digitized photographic plates; iii) a complete comparison sample of 26 galaxies of all morphological types down to m_R = 16.05 (or m_B \\simeq 17.5), also in a region of 50 arcmin diameter, but centered 2.6 degrees West of...

  16. A COMPARATIVE STUDY OF PLANT GROWTH REGULATORS ON MORPHOLOGICAL, SEED YIELD AND QUALITY PARAMETERS OF GREENGRAM

    Directory of Open Access Journals (Sweden)

    K Rajesh

    2014-09-01

    Full Text Available A field experiment was conducted to study the different growth regulating compounds on morphological, quality and yield parameters in greengram at Acharya N.G Ranga Agricultural University, Hyderabad during rabi 2009- 10. The basic material for the present investigation consists of Greengram cv WGG-37 and two growth promoting (NAA and Brassinosteroid and growth retarding substances (Chlormequat chloride and Mepiquat chloride. These growth regulators were sprayed at flower initiation stage. The morphological traits viz., plant height, number of branches per plant, number of trifoliates per plant and days to 50% flowering and maturity were significantly increased by NAA @ 20 ppm, whereas total dry matter production (TDM over growth regulator treatments at all stages NAA (20 ppm and brassinosteroid (20ppm recorded significantly higher values. Among the quality parameters highest seed protein content (% and highest nitrogen harvest index values were recorded with growth retarding substance chlormequat chloride (187.5 g a.i ha-1 in greengram. The seed yield increased significantly with NAA (20 ppm followed by mepiquat chloride 5% AS, brassinosteroid (20 ppm, chlormequat chloride (137.5.5 a.i/ha.

  17. [Study on molecular chain morphology and chain parameters of konjac glucomannan].

    Science.gov (United States)

    Li, Bin; Xie, Bi-jun

    2003-11-01

    To study the molecular chain morphology and chain parameters of konjac glucomannan (KGM). Solution behavior was studied by using light scattering(LS), gel permeation chromatograph (GPC) and method of viscosity. The molecular morphology was observed directly by atom force microscope (AFM) and transmission electron microscope (TEM). The average molecular weight (Mw), root-mean-square ratio of gyration(1/2), second Viral coefficients (A2) and multi-disperse coefficients (Mw/Mn) are 1.04 x 10(6), 105.0 +/- 0.9 nm, (-1.59 +/- 0.28) x 10(-3) mol.mL.g-2 and (1.020 +/- 0.003) respectively; Mark-Houwink equation was established as [eta] = 5.96 x 10(-2) Mw0.73, the molecular chain parameters were as follows: ML = 982.82 nm-1, q = 27.93 nm, d = 0.74 nm, h = 0.26 nm, L = 1,054.11 nm. Both the result showed by direct observation and the deduction drawn by solution behavior confirmed that the KGM molecular is stentering semi-flexible linear chain without branch.

  18. Optimization of Process Parameters for Cracking Prevention of UHSS in Hot Stamping Based on Hammersley Sequence Sampling and Back Propagation Neural Network-Genetic Algorithm Mixed Methods

    Institute of Scientific and Technical Information of China (English)

    Menghan Wang∗,Zongmin Yue; Lie Meng

    2016-01-01

    In order to prevent cracking appeared in the work⁃piece during the hot stamping operation, this paper proposes a hybrid optimization method based on Hammersley sequence sampling ( HSS) , finite analysis, back⁃propagation ( BP ) neural network and genetic algorithm ( GA ) . The mechanical properties of high strength boron steel are characterized on the basis of uniaxial tensile test at elevated temperatures. The samples of process parameters are chosen via the HSS that encourages the exploration throughout the design space and hence achieves better discovery of possible global optimum in the solution space. Meanwhile, numerical simulation is carried out to predict the forming quality for the optimized design. A BP neural network model is developed to obtain the mathematical relationship between optimization goal and design variables, and genetic algorithm is used to optimize the process parameters. Finally, the results of numerical simulation are compared with those of production experiment to demonstrate that the optimization strategy proposed in the paper is feasible.

  19. C/C复合材料SiC涂层裂纹形貌及分布的研究%Crack Morphology and Distribution of SiC Coating on Carbon/Carbon Composites

    Institute of Scientific and Technical Information of China (English)

    祝俊良; 史小红; 陈梓山; 李贺军

    2012-01-01

    Due to the mismatch of the thermal expansion coefficient between the coating and carbon/carbon composites, coating cracks inevitably appeared when the coating was cooled from the production temperature to the ambient temperature. To study the coating crack configuration, single-layer and double-layer SiC coatings on carbon-felt C/C composite and intertexture C/C composite were prepared, and the crack morphology and distribution were investigated. The optical microscope and scanning electron microscope were used to discuss the crack morphology and distribution, to explain the relationship of the coating cracks with the thermal stress on the coating and substrate defects. The XRD method was conducted to analyze the ingredient of single-layer and double-layer SiC coating, to describe the relationship of different types of SiC coating structure with the coating cracks. The results showed that the crack distribution and spacing were related to the fiber direction of substrate. With the increase of coating thickness, the number of cracks decreased. The intrinsic defects on the substrate would cause through-the-thickness cracks in the coating.%由于涂层与C/C复合材料之间热膨胀系数不匹配,当冷却至室温时在高温下制备的抗氧化涂层会产生裂纹,为分析涂层裂纹的组态,通过在碳毡和真空穿刺两种C/C复合材料基体上制备单层、双层SiC涂层来研究涂层裂纹的形貌及分布.利用金相显微镜和扫描电镜观察两种涂层裂纹的形貌和分布,解释了裂纹与涂层所受热应力及基体原有缺陷的关系,利用XRD分析了单层和双层涂层的成分,说明了不同类型SiC结构与涂层裂纹之间的联系.结果表明涂层裂纹分布及裂纹宽度与基体纤维方向有关;随着涂层厚度增大,微裂纹数量减少;基体原有缺陷会导致涂层产生穿透性裂纹.

  20. Morphological characterisation and agronomical parameters of different species of Salvia sp. (Lamiaceae

    Directory of Open Access Journals (Sweden)

    AJ Mossi

    Full Text Available The aim of this work is to assess the morphological characteristics and parameters of biomass production, such as fresh and dry matter weight (FMW and DMW, g/plant, yield of dry matter (YDM in terms of ton/ha, essential oil content (EOC, mL/100 g and yield of essential oils (YEO expressed as L/ha of the following plants Salvia verbenaca, Salvia argentea, Salvia lavandulifolia, Salvia pratensis, Salvia sclarea, Salvia triloba and Salvia officinalis. Except for Salvia argentea (S2 all other species have adapted to the south Brazilian climate conditions, with morphological differences among the species evaluated. In terms of DMW and YDM, S. officinalis was found to be the most productive species with 445.83 g/plant and 11.14 ton/ha. The higher essential oil content and yield was observed for S. officinalis, affording 1.99 mL/100 g and 221.74 L/ha, respectively. Chemical characterisation of the essential oils obtained from hydrodistillation was performed through GC and GC/MSD analyses, which revealed for most of the species studied, α e β-thujone, camphor and 1,8-cineole as major compounds, apart from S. sclarea, for which linalool, linalyl acetate and α-terpineol were the major components.

  1. Effect of synthesis parameters on morphology of polyaniline (PANI) and field emission investigation of PANI nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Bankar, Prashant K.; More, Mahendra A., E-mail: mam@physics.unipune.ac.in [Center for Advanced Studies in Materials Science and Condensed Matter Physics, Department of Physics, University of Pune, Pune-411007 (India); Patil, Sandip S. [Department of Physics, Modern College of Arts, Science and Commerce, Shivajinagar, Pune-411005. India (India)

    2015-06-24

    Polyaniline (PANI) nanostructures have been synthesized by simple chemical oxidation route at different monomer concentration along with variation in synthesis temperature. The effect of variation of synthesis parameters has been revealed using different characterization techniques. The structural and morphological characterization of the synthesized PANI nanostructures was carried out by scanning electron microscopy (SEM), transmission electron microscopy (TEM), whereas Fourier Transform Infrared spectroscopy (FTIR) has been used to reveal the chemical properties. With the variation in the synthesis temperature and monomer concentration, various morphologies characterized by formation of PANI nanoparticles, nanofibres, nanotubes and nanospheres, are revealed from the SEM analysis. The FTIR analysis reveals the formation of conducting state of PANI under prevailing experimental conditions. The field emission investigation of the conducting PANI nanotubes was performed in all metal UHV system at base pressure of 1x10{sup −8} mbar. The turn on field required to draw emission of 1 nA current was observed to be ∼ 2.2 V/μm and threshold field (corresponding to emission current density of 1 µA/cm2) was found to be 3.2 V/μm. The emission current was observed to be stable for more than three hours at a preset value 1 µA. The simple synthesis route and good field emission characteristics indicate potential of PANI nanofibres as a promising emitter for field emission based micro/nano devices.

  2. Morphological characterisation and agronomical parameters of different species of Salvia sp. (Lamiaceae).

    Science.gov (United States)

    Mossi, A J; Cansian, R L; Paroul, N; Toniazzo, G; Oliveira, J V; Pierozan, M K; Pauletti, G; Rota, L; Santos, A C A; Serafini, L A

    2011-02-01

    The aim of this work is to assess the morphological characteristics and parameters of biomass production, such as fresh and dry matter weight (FMW and DMW, g/plant), yield of dry matter (YDM) in terms of ton/ha, essential oil content (EOC, mL/100 g) and yield of essential oils (YEO) expressed as L/ha of the following plants Salvia verbenaca, Salvia argentea, Salvia lavandulifolia, Salvia pratensis, Salvia sclarea, Salvia triloba and Salvia officinalis. Except for Salvia argentea (S2) all other species have adapted to the south Brazilian climate conditions, with morphological differences among the species evaluated. In terms of DMW and YDM, S. officinalis was found to be the most productive species with 445.83 g/plant and 11.14 ton/ha. The higher essential oil content and yield was observed for S. officinalis, affording 1.99 mL/100 g and 221.74 L/ha, respectively. Chemical characterisation of the essential oils obtained from hydrodistillation was performed through GC and GC/MSD analyses, which revealed for most of the species studied, α e β-thujone, camphor and 1,8-cineole as major compounds, apart from S. sclarea, for which linalool, linalyl acetate and α-terpineol were the major components.

  3. Morphological parameters of the norway maple small undergrowthin forests of the Novgorod-Sivers’k Polissia

    Directory of Open Access Journals (Sweden)

    V. G. Skliar

    2012-02-01

    Full Text Available The size characteristics of the Norway maple small undergrowth in different association groups of the forests of Novgorod-Sivers’k Polissia are аnalyzed. As the trophicity of soil increases the values of static metric and dynamic morphoparameters of the undergrowth upsurge. And on the contrary, the values reduced with the growth of the forest overstory density and the projective cover of the herb-shrub layer. It is shown that in different plant communities the Norway maple undergrowth is characterised by specific morphological structure. The communal habitat of the group of Querceta convallariosa associations conforms with the parameters of ecocoenotical optimum, which conditions are most favourable for successful growth of the maple young generation.

  4. Solute transport modeling using morphological parameters of step-pool reaches

    Science.gov (United States)

    JiméNez, Mario A.; Wohl, Ellen

    2013-03-01

    Step-pool systems have been widely studied during the past few years, resulting in enhanced knowledge of mechanisms for sediment transport, energy dissipation and patterns of self-organization. We use rhodamine tracer data collected in nine step-pool reaches during high, intermediate and low flows to explore scaling of solute transport processes. Using the scaling patterns found, we propose an extension of the Aggregated Dead Zone (ADZ) approach for solute transport modeling based on the morphological features of step-pool units and their corresponding inherent variability within a stream reach. In addition to discharge, the reach-average bankfull width, mean step height, and the ratio of pool length to step-to-step length can be used as explanatory variables for the dispersion process within the studied reaches. These variables appeared to be sufficient for estimating ADZ model parameters and simulating solute transport in predictive mode for applications in reaches lacking tracer data.

  5. MORPHOLOGICAL PARAMETERS OF COMMON CARP (Cyprinus carpio carpio L. POPULATIONS IN REPUBLIC OF CROATIA

    Directory of Open Access Journals (Sweden)

    Tea Tomljanović

    2011-10-01

    Full Text Available In this study common carp populations from Croatian fish ponds (Draganići, Končanica, Našička Breznica, Orahovica (Grudnjak and Poljana, and three carp populations from open waters (Sava and Danube rivers and Vransko lake were analyzed, with total of 295 specimens. All populations were checked for 20 morphometric and 13 meristic parameters. The analysis was conducted using Principal component analysis (PCA and Constrained linear analysis of canonical redundancy (RDA. According to the number gill rakers the most distinguished are carps from Sava river and Vransko lake, and some individuals from the Danube river, while the fish pond populations do not emphasize by this parameter. Fish pond populationes Grudnjak, Draganići, Končanica and Našice are overlapping. The Danube population is divided into two groups: one group is closely associated with fish pond populations, while another group is closely link with populations of carp in open waters. Specimens of carp from the Danube, which are morphologically similar to fish pond carps are considered to have recently entered into open water and still have the external characteristics of domestic carps. By this research a significant separation of domestic and open waters carp was revealed which has proven Monte Carlo test (F=347.191; p=0.002, however, a clear separation of domestic strains of common carps is not noticeable.

  6. Determination of Structural and Morphological Parameters of Human Bulbar Conjunctiva from Optical Diffuse Reflectance Spectra

    Science.gov (United States)

    Lisenko, S. A.; Firago, V. A.; Kugeiko, M. M.; Kubarko, A. I.

    2016-09-01

    We have developed a method for on-the-fl y retrieval of the volume concentration of blood vessels, the average diameter of the blood vessels, the blood oxygenation level, and the molar concentrations of chromophores in the bulbar conjunctiva from its diffuse reflectance spectra, measured when the radiation delivery and detection channels are spatially separated. The relationship between the diffuse reflectance spectrum of the conjunctiva and its unknown parameters is described in terms of an analytical model, constructed on the basis of a highly accurate approximation analog of the Monte Carlo method. We have studied the effect of localization of hemoglobin in erythrocytes and localization of erythrocytes in the blood vessels on the power of the retrieval of structural and morphological parameters for the conjunctiva. We developed a device for obtaining video images of the conjunctiva and contactless measurements of its diffuse reflectance spectrum. By comparing simulated diffuse reflectance spectra of the conjunctiva with the experimental measurements, we established a set of chromophores which must be taken into account in the model for reproducing the experimental data within the measurement error. We observed absorption bands for neuroglobin in the experimental spectra, and provided a theoretical basis for the possibility of determining its absolute concentrations in the conjunctiva. We have shown that our method can detect low bilirubin concentrations in blood.

  7. [Bibliometric indexes of the editions, publishing the articles on the problems of morphology, and some bibliometric parameters of the authors of morphological publications].

    Science.gov (United States)

    Shevliuk, N N

    2013-01-01

    The article presents a comparative assessment of some bibliometric parameters of national journals, publishing the articles on the problems of morphological scientific disciplines, and concise analysis of the publication activity of morphologists. The data are given on the application of bibliometric indexes for the evaluation of the scientific contribution of national researchers to the field of morphology. The information contained in the national database-- Russian Index of Scientific Citation, and that collected by means of selected overview of the national and foreign medical and biological journals, publishing the articles on various problems of morphological sciences during the last 20 years, served as the basis for the analysis. It is noted that the authors should consider the bibliometric indexes of the journals to which they submit their articles.

  8. A Multi-Year Study on Rice Morphological Parameter Estimation with X-Band Polsar Data

    Directory of Open Access Journals (Sweden)

    Onur Yuzugullu

    2017-06-01

    Full Text Available Rice fields have been monitored with spaceborne Synthetic Aperture Radar (SAR systems for decades. SAR is an essential source of data and allows for the estimation of plant properties such as canopy height, leaf area index, phenological phase, and yield. However, the information on detailed plant morphology in meter-scale resolution is necessary for the development of better management practices. This letter presents the results of the procedure that estimates the stalk height, leaf length and leaf width of rice fields from a copolar X-band TerraSAR-X time series data based on a priori phenological phase. The methodology includes a computationally efficient stochastic inversion algorithm of a metamodel that mimics a radiative transfer theory-driven electromagnetic scattering (EM model. The EM model and its metamodel are employed to simulate the backscattering intensities from flooded rice fields based on their simplified physical structures. The results of the inversion procedure are found to be accurate for cultivation seasons from 2013 to 2015 with root mean square errors less than 13.5 cm for stalk height, 7 cm for leaf length, and 4 mm for leaf width parameters. The results of this research provided new perspectives on the use of EM models and computationally efficient metamodels for agriculture management practices.

  9. Physiological, morphological, and immunochemical parameters used for the characterization of clinical and environmental isolates of Acanthamoeba.

    Science.gov (United States)

    Becker-Finco, A; Costa, A O; Silva, S K; Ramada, J S; Furst, C; Stinghen, A E; De Figueiredo, B C; De Moura, J; Alvarenga, L M

    2013-03-01

    The factors that characterize Acanthamoeba strains as harmless or potentially pathogenic have not been elucidated. Analysing the in vitro and in vivo parameters of Acanthamoeba samples, including heat tolerance at temperatures close to that of the human body, cytopathic effects, and their ability to cause infections in animals, has been proposed to identify their pathogenic potential. Another promising criterion for differentiating strains is the analysis of their biochemical and immunochemical properties. In this study, a comparative evaluation between clinical and environmental Acanthamoeba isolates was performed on the basis of physiological, morphological, and immunochemical criteria. Crude antigens were used to characterize the protein profiles by electrophoresis and immunize mice to produce polyclonal and monoclonal antibodies. The antibodies were characterized using ELISA, Western blotting, and immunofluorescence techniques. The results obtained with polyclonal antibodies suggest the presence of specific proteins for each studied isolate and co-reactive immunochemical profiles among conserved components. Ten monoclonal antibody clones were obtained; mAb3 recognized 3 out of 4 samples studied. The results of this study may help standardize criteria for identifying and characterizing Acanthamoeba strains. Taken together, our results support the view that a set of features may help differentiate Acanthamoeba species and isolates.

  10. Influence of morphological parameters on the development of gingival recession in class III malocclusion.

    Science.gov (United States)

    Warmuz, Justyna; Jagielak, Maciej; Botzenhart, Ute; Seeliger, Julia; Gedrange, Tomasz; Dominiak, Marzena

    2016-07-01

    Cephalometric analysis, including both basic cranio- and gnathometric measurements and detailed evaluation of the construction of skeletal, muscular and mucosal systems combined with estimation of the risk of recession's occurrence, can be used to determine the direction of therapy and ensure appropriate aesthetic-functional effects of treatment. The objective of the present study was to compare the influence of the chosen morphologic parameters on the development of gingival recession in the front part of the jaw in patients with Angle class III. The research material was based on the medical documentation of 1800 patients. Sixty generally healthy patients qualified for the research with prognathism. On the basis of the side-head cephalograms, measurements were carried out to describe the bone structure in the front section of the lower jaw. The lower incisor teeth set-up was also analyzed. Gum recession of the lower incisor teeth was assessed on the basis of the inside-mouth photos of the patients with class III malocclusion. The occurrence of recession in a further 4 patients resulted from such a positioning of the lower teeth. In patients in the first group, treated with complex ortho-surgical treatment, the lower incisor teeth were adjusted much more vertically in the alveola and, thus, recession occurred only in one patient. Complex orthodontic-surgical therapy contributes to recession development to a lesser degree than the sham treatment and makes it a safe alternative therapy in patients with high diathesis for occurrence or progression of an existing recession.

  11. Morphological parameters to be used as biomarkers in ecotoxicology. Natural and induced variability; Morphologische Parameter als Biomarker in der Oekotoxikologie. Natuerliche und schadstoffinduzierte Variabilitaet

    Energy Technology Data Exchange (ETDEWEB)

    Segner, Helmut [Zentrum fuer Fisch- und Wildtiermedizin, Univ. Bern (Switzerland)

    2009-04-15

    Background: Ecotoxicology utilizes alterations of biological parameters of organisms as biomarkers of toxic exposure or effects. In environmental monitoring, biomarkers function as sensitive indicators of chemical pollution or as early warning signal of late effects. Aim: The pre-requisite for using a biological parameter as biomarker is the ability to unequivocally distinguish between the natural or normal and the induced or abnormal expression of the marker. This article discusses problems in discriminating between the normal and induce state, using morphological biomarkers as an example. Results and Discussion: Morphological and/or anatomical parameters are intuitively considered to be rather invariable. This article shows for the example of gonad morphology of fish that this expectation is not always correct, but that morphological markers may display pronounced baseline variability. The reasons for this variability are often not understood. This is limiting the utility and interpretation of the biomarker response, in particular when organisms are not only exposed to chemical but to multiple stressors. Outlook: The problem of discriminating between natural and induced variability of biomarkers is of particular relevance in low dose exposure scenarios, when stressors other than toxic chemicals may confound the toxicant-induced changes of the biomarker status. To better handle this problem and to be able to distinguish between adaptive and adverse changes, ecotoxicology has to set out for improved understanding of the phenotypic plasticity of organisms and genotypes. (orig.)

  12. Deep-sea pennatulaceans (sea pens) - recent discoveries, morphological adaptations, and responses to benthic oceanographic parameters

    Science.gov (United States)

    Williams, G. C.

    2015-12-01

    Pennatulaceans are sessile, benthic marine organisms that are bathymetrically wide-ranging, from the intertidal to approximately 6300 m in depth, and are conspicuous constituents of deep-sea environments. The vast majority of species are adapted for anchoring in soft sediments by the cylindrical peduncle - a muscular hydrostatic skeleton. However, in the past decade a few species ("Rockpens") have been discovered and described that can attach to hard substratum such as exposed rocky outcrops at depths between 669 and 1969 m, by a plunger-like adaptation of the base of the peduncle. Of the thirty-six known genera, eleven (or 30%) have been recorded from depths greater than 1000 m. The pennatulacean depth record holders are an unidentified species of Umbellula from 6260 m in the Peru-Chile Trench and a recently-discovered and described genus and species, Porcupinella profunda, from 5300 m the Porcupine Abyssal Plain of the northeastern Atlantic. A morphologically-differentiated type of polyp (acrozooid) have recently been discovered and described in two genera of shallow-water coral reef sea pens. Acrozooids apparently represent asexual buds and presumably can detach from the adult to start clonal colonies through asexual budding. Acrozooids are to be expected in deep-sea pennatulaceans, but so far have not been observed below 24 m in depth. Morphological responses at depths greater than 1000 m in deep-sea pennatulaceas include: fewer polyps, larger polyps, elongated stalks, and clustering of polyps along the rachis. Responses to deep-ocean physical parameters and anthropogenic changes that could affect the abundance and distribution of deep-sea pennatulaceans include changes in bottom current flow and food availability, changes in seawater temperature and pH, habitat destruction by fish trawling, and sunken refuse pollution. No evidence of the effects of ocean acidification or other effects of anthropogenic climate change in sea pens of the deep-sea has been

  13. Postnatal development of quantitative morphological parameters in the lateral geniculate nucleus of the marmoset monkey.

    Science.gov (United States)

    Fritschy, J M; Garey, L J

    1986-12-01

    Quantitative morphological parameters were studied in the lateral geniculate nucleus (LGN) of the marmoset monkey (Callithrix jacchus) during development, using a series of 14 animals, at ages from birth to adulthood. They include the volume of the LGN and of its layers and interlaminar zones, their neuronal content expressed as numerical density and total number, and the density and number of glial cells in the nucleus as a whole. The volume of the LGN increases rapidly after birth, reaches a maximum at 6 months of age, and then decreases to its adult value of about 11 mm3. Neuronal density follows a reciprocal curve, reaching an adult value of about 41,000 neurons/mm3, so that the total number of about 440,000 neurons per LGN remains constant throughout life although large interindividual variations, especially in juveniles, do not allow unequivocal statements about total neuronal number to be made. Parvocellular layers occupy most of the geniculate volume, and contain about 74% of its neurons in the adult. We found no difference in their development pattern compared with the magnocellular component. The 'superficial' layers and interlaminar zones contain more than 15% of the geniculate neurons, and they could therefore play an important functional role in the primary visual pathway of New World primates. The number of glial cells nearly triples during the first 6 weeks and stabilizes around 800,000 in the LGN of one hemisphere. As the same brains were used as in a previous study on the area 17 of the marmoset (Dev. Brain Res., 29 (1986) 173-188) direct comparisons of the development of cortex and thalamus can be made. Their development is parallel in time, and in both cases the adult values for volume, neuronal density and glial numbers are reached several months postnatally.

  14. Stress-corrosion cracking of titanium alloys.

    Science.gov (United States)

    Blackburn, M. J.; Feeney, J. A.; Beck, T. R.

    1973-01-01

    In the light of research material published up to May 1970, the current understanding of the experimental variables involved in the stress-corrosion cracking (SCC) behavior of titanium and its alloys is reviewed. Following a brief summary of the metallurgy and electrochemistry of titanium alloys, the mechanical, electrochemical, and metallurgical parameters influencing SCC behavior are explored with emphasis on crack growth kinetics. Macro- and microfeatures of fractures are examined, and it is shown that many transgranular SCC failures exhibit morphological and crystallographic features similar to mechanical cleavage failures. Current SCC models are reviewed with respect to their ability to explain the observed SCC behavior of titanium and its alloys. Possible methods for eliminating or minimizing stress corrosion hazards in titanium or titanium alloy components are described.

  15. Comparison of different morphological parameters with duration of obstruction created experimentally in unilateral upper ureters: An animal model

    Directory of Open Access Journals (Sweden)

    Shasanka Shekhar Panda

    2014-01-01

    Full Text Available Background: The objective of the following study is to determine and to compare the different morphological parameters with duration of obstruction created experimentally in unilateral upper ureters of rats. Materials and Methods: Unilateral upper ureteric obstruction was created in 60 adult Wistar rats that were reversed after predetermined intervals. Rats were sacrificed and ipsilateral kidneys were subjected for analysis of morphological parameters such as renal height, cranio-caudal diameter, antero-posterior diameter, lateral diameter, volume of the pelvis and average cortical thickness: Renal height. Results: Renal height and cranio-caudal diameter of renal pelvis after ipsilateral upper ureteric obstruction started rising as early as 7 days of creating obstruction and were affected earlier than antero-posterior and lateral diameter and also were reversed earlier than other parameters after reversal of obstruction. Renal cortical thickness and volume of the pelvis were affected after prolonged obstruction (> 3 weeks and were the late parameters to be reversed after reversal of obstruction. Conclusions: Cranio-caudal diameter and renal height were the early morphological parameters to be affected and reversed after reversal of obstruction in experimentally created ipsilateral upper ureteric obstruction.

  16. HYDROGEN TRANSFER IN CATALYTIC CRACKING

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Hydrogen transfer is an important secondary reaction of catalytic cracking reactions, which affects product yield distribution and product quality. It is an exothermic reaction with low activation energy around 43.3 kJ/mol. Catalyst properties and operation parameters in catalytic cracking greatly influence the hydrogen transfer reaction. Satisfactory results are expected through careful selection of proper catalysts and operation conditions.

  17. Knuckle Cracking

    Science.gov (United States)

    ... Ask The Expert Ask a Question Physician Corner Rheumatology Conference Rheumatology Rounds Case Rounds Radiology Rounds Pathophysiology of the ... Appointment Information Contact Us Our Faculty Our Staff Rheumatology Specialty Centers Knuckle Cracking Q & A September 10, ...

  18. PMMA/PS coaxial electrospinning: core–shell fiber morphology as a function of material parameters

    Science.gov (United States)

    Rahmani, Shahrzad; Arefazar, Ahmad; Latifi, Masoud

    2017-03-01

    Core–shell fibers of polymethyl methacrylate (PMMA) and polystyrene (PS) have been successfully electrospun by coaxial electrospinning. To evaluate the influence of the solvent on the final fiber morphology, four types of organic solvents were used in the shell solution while the core solvent was preserved. Morphological observations with scanning electron microscopy, transmission electron microscopy and optical microscopy revealed that both core and shell solvent properties were involved in the final fiber morphology. To explain this involvement, alongside a discussion of the Bagley solubility graph of PS and PMMA, a novel criterion based on solvent physical properties was introduced. A theoretical model based on the momentum conservation principle was developed and applied for describing the dependence of the core and shell diameters to their solvent combinations. Different concentrations of core and shell were also investigated in the coaxial electrospinning of PMMA/PS. The core–shell fiber morphologies with different core and shell concentrations were compared with their single electrospun fibers.

  19. Multiaxial mixed-mode cracking - small crack initiation and propagation

    Energy Technology Data Exchange (ETDEWEB)

    Freitas, M. de; Reis, L.; Li Bin [Lisbon Univ. (Portugal). ICEMS - Inst. of Material and Surface Science and Engineering

    2006-07-01

    Both the fatigue crack path and fatigue life of CK45 steel and 42CrMo4 steel under various multiaxial loading paths are studied in this paper. The replica method was applied to monitor the crack initiation and small crack growth, the fractographic analyses were carried out on the fracture surface and the crack initiation angle was measured. The effects of non-proportional loading on both the crack path and fatigue life were studied, and the flattening of asperities on the crack surface due to compressive normal stress was also observed. An improved model is proposed based on correcting the strain range parameter of the ASME code approach, taking into account the additional hardening caused by the non-proportional loading path, which can improve the predictions of the fatigue lives for various non-proportional loading paths and provide an easy way to overcome the drawbacks of the current ASME code approach for non-proportional fatigue. Based on these corrected strain range parameters, a strain intensity factor range is used to correlate with the experimental results of small crack growth rates. It is concluded that the orientation of the early crack growth can be predicted well by the critical damage plane, but the fatigue life can not be predicted accurately using only the parameters on the critical plane, since the damage on all the planes contributes to fatigue damage as stated by the integral approaches. (orig.)

  20. Morphologies in Solvent-Annealed Clotrimazole Thin Films Explained by Hansen-Solubility Parameters

    OpenAIRE

    Ehmann, Heike M. A.; Zimmer, Andreas; Roblegg, Eva; Werzer, Oliver

    2014-01-01

    The induction of different crystal morphologies is of crucial importance for many applications. In this work, the preparation of various crystal morphologies within clotrimazole films on glass substrates is demonstrated. Amorphous clotrimazole thin films were transformed via vapor annealing into crystalline structures; highly monodisperse/multidisperse crystallites, spherulite, or dendritic structures were obtained as the solvent was exchanged. X-ray diffraction experiments reveal that the sa...

  1. Interacting Cracks in an Environmentally Assisted Fracture

    Science.gov (United States)

    Levandovsky, Artem; Balazs, Anna

    2006-03-01

    We perform the study of environmentally assisted fracture within the framework of a lattice model. Formation of an ensemble of environmentally assisted microcracks, their coalescence and formation of crack ``avalanches'' lead to a very rich dynamical picture. Under specific condition crack healing can occur due to cohesive forces, which hold material together and tend to pull atoms together even if they are separated by a crack over several lattice units. We investigate the dynamical interplay between crack formation, arrest, healing and re-cracking. The goal here is to provide an understanding of the conditions leading to the phenomena of crack healing that happens along with the crack formation. We study the morphology of crack patterns with the intentions to establish a way to enhance the healing property of a material sample.

  2. Fatigue Crack Closure Analysis Using Digital Image Correlation

    Science.gov (United States)

    Leser, William P.; Newman, John A.; Johnston, William M.

    2010-01-01

    Fatigue crack closure during crack growth testing is analyzed in order to evaluate the critieria of ASTM Standard E647 for measurement of fatigue crack growth rates. Of specific concern is remote closure, which occurs away from the crack tip and is a product of the load history during crack-driving-force-reduction fatigue crack growth testing. Crack closure behavior is characterized using relative displacements determined from a series of high-magnification digital images acquired as the crack is loaded. Changes in the relative displacements of features on opposite sides of the crack are used to generate crack closure data as a function of crack wake position. For the results presented in this paper, remote closure did not affect fatigue crack growth rate measurements when ASTM Standard E647 was strictly followed and only became a problem when testing parameters (e.g., load shed rate, initial crack driving force, etc.) greatly exceeded the guidelines of the accepted standard.

  3. Estimation of leak rate through circumferential cracks in pipes in nuclear power plants

    Directory of Open Access Journals (Sweden)

    Jai Hak Park

    2015-04-01

    Full Text Available The leak before break (LBB concept is widely used in designing pipe lines in nuclear power plants. According to the concept, the amount of leaking liquid from a pipe should be more than the minimum detectable leak rate of a leak detection system before catastrophic failure occurs. Therefore, accurate estimation of the leak rate is important to evaluate the validity of the LBB concept in pipe line design. In this paper, a program was developed to estimate the leak rate through circumferential cracks in pipes in nuclear power plants using the Henry–Fauske flow model and modified Henry–Fauske flow model. By using the developed program, the leak rate was calculated for a circumferential crack in a sample pipe, and the effect of the flow model on the leak rate was examined. Treating the crack morphology parameters as random variables, the statistical behavior of the leak rate was also examined. As a result, it was found that the crack morphology parameters have a strong effect on the leak rate and the statistical behavior of the leak rate can be simulated using normally distributed crack morphology parameters.

  4. Influence of growth parameters on the surface morphology and crystallinity of InSb epilayers grown by liquid phase epitaxy

    Indian Academy of Sciences (India)

    N K Udayashankar; H L Bhat

    2003-12-01

    Unintentionally doped homoepitaxial InSb films have been grown by liquid phase epitaxy employing ramp cooling and step cooling growth modes. The effect of growth temperature, degree of supercooling and growth duration on the surface morphology and crystallinity were investigated. The major surface features of the grown film like terracing, inclusions, meniscus lines, etc are presented step-by-step and a variety of methods devised to overcome such undesirable features are described in sufficient detail. The optimization of growth parameters have led to the growth of smooth and continuous films. From the detailed morphological, X-ray diffraction, scanning electron microscopic and Raman studies, a correlation between the surface morphology and crystallinity has been established.

  5. Morphology and physical properties of soil material in cryogenic cracks of permafrost-affected meadow-chernozemic soils of the Trans-Baikal Region

    Science.gov (United States)

    Tsybenov, Yu. B.; Chimitdorzhieva, G. D.; Chimitdorzhieva, E. O.; Egorova, R. A.; Mil'kheev, E. Yu.; Davydova, T. V.; Korsunova, Ts. D.-Ts.

    2016-08-01

    Meadow-chernozemic soils (Turbic Chernozems Molliglossic) in the western Trans-Baikal Region are dissected by large cryogenic cracks penetrating to the depth of 100-120 cm and filled with humified material. The depth of humus pockets is 50-80 cm, and their width in the upper part is 50-90 cm. The lower boundary of most of the humus pockets lies at the depth of 60-70 cm. The development of cryogenic cracks proceeded due to their penetration into the frozen ground, which is evidenced by their sharply narrowing lower part. The fraction of physical clay (humus content in this material. The contents of humus and adsorbed bases sharply decrease down through the soil profile in the soil mass between the cracks and remain relatively stable in the material filling the cracks. The soil mass in humus pockets is less compact that that in the background soil mass at the same depth, which is explained by the higher humus content in the pockets. Humified soil material in the pockets is also characterized by a higher porosity and, hence, higher water permeability than the surrounding soil mass.

  6. Effect of Irradiation Parameters on Morphology of Polishing DF2 (AISI-O1 Surface by Nd:YAG Laser

    Directory of Open Access Journals (Sweden)

    Wei Guo

    2007-01-01

    Full Text Available Pulse Nd:YAG laser was used to polish DF2 cold work steel. Influence of irradiation parameters on the 3D surface morphology was studied by 3D profilometer, scanning electron microscopy (SEM, and atomic force microscope (AFM. Results among the tests showed when DF2 specimens were irradiated with parameters of (i laser input energy P=1 J, (ii pulse feedrate=300 mm/min, (iii pulse duration (PD =3 milliseconds, and (iv pulse frequency f=20∼25 Hz, laser polishing of DF2 cold work steel seemed to be successful.

  7. HISTORICAL GIS DATA AND CHANGES IN URBAN MORPHOLOGICAL PARAMETERS FOR THE ANALYSIS OF URBAN HEAT ISLANDS IN HONG KONG

    Directory of Open Access Journals (Sweden)

    F. Peng

    2016-06-01

    Full Text Available Rapid urban development between the 1960 and 2010 decades have changed the urban landscape and pattern in the Kowloon Peninsula of Hong Kong. This paper aims to study the changes of urban morphological parameters between the 1985 and 2010 and explore their influences on the urban heat island (UHI effect. This study applied a mono-window algorithm to retrieve the land surface temperature (LST using Landsat Thematic Mapper (TM images from 1987 to 2009. In order to estimate the effects of local urban morphological parameters to LST, the global surface temperature anomaly was analysed. Historical 3D building model was developed based on aerial photogrammetry technique using aerial photographs from 1964 to 2010, in which the urban digital surface models (DSMs including elevations of infrastructures and buildings have been generated. Then, urban morphological parameters (i.e. frontal area index (FAI, sky view factor (SVF, vegetation fractional cover (VFC, global solar radiation (GSR, Normalized Difference Built-Up Index (NDBI, wind speed were derived. Finally, a linear regression method in Waikato Environment for Knowledge Analysis (WEKA was used to build prediction model for revealing LST spatial patterns. Results show that the final apparent surface temperature have uncertainties less than 1 degree Celsius. The comparison between the simulated and actual spatial pattern of LST in 2009 showed that the correlation coefficient is 0.65, mean absolute error (MAE is 1.24 degree Celsius, and root mean square error (RMSE is 1.51 degree Celsius of 22,429 pixels.

  8. Historical GIS Data and Changes in Urban Morphological Parameters for the Analysis of Urban Heat Islands in Hong Kong

    Science.gov (United States)

    Peng, F.; Wong, M. S.; Nichol, J. E.; Chan, P. W.

    2016-06-01

    Rapid urban development between the 1960 and 2010 decades have changed the urban landscape and pattern in the Kowloon Peninsula of Hong Kong. This paper aims to study the changes of urban morphological parameters between the 1985 and 2010 and explore their influences on the urban heat island (UHI) effect. This study applied a mono-window algorithm to retrieve the land surface temperature (LST) using Landsat Thematic Mapper (TM) images from 1987 to 2009. In order to estimate the effects of local urban morphological parameters to LST, the global surface temperature anomaly was analysed. Historical 3D building model was developed based on aerial photogrammetry technique using aerial photographs from 1964 to 2010, in which the urban digital surface models (DSMs) including elevations of infrastructures and buildings have been generated. Then, urban morphological parameters (i.e. frontal area index (FAI), sky view factor (SVF)), vegetation fractional cover (VFC), global solar radiation (GSR), Normalized Difference Built-Up Index (NDBI), wind speed were derived. Finally, a linear regression method in Waikato Environment for Knowledge Analysis (WEKA) was used to build prediction model for revealing LST spatial patterns. Results show that the final apparent surface temperature have uncertainties less than 1 degree Celsius. The comparison between the simulated and actual spatial pattern of LST in 2009 showed that the correlation coefficient is 0.65, mean absolute error (MAE) is 1.24 degree Celsius, and root mean square error (RMSE) is 1.51 degree Celsius of 22,429 pixels.

  9. DISCRIMINATIVE ANALYSIS OF MORPHOLOGIC AND MOTORIC PARAMETER TO JUDO AND KARATE SPORTIEST BOYS

    Directory of Open Access Journals (Sweden)

    Lulzim Ibri

    2013-07-01

    Full Text Available In sample from 160 boys from secondary schools of Prizren 16-17 age, separated in two groups were implicated 18 tests, from them 10 test for valuation morphologic characteristic and 8 test, for valuation motoric abilities. Group (A is component from 80 judo athletes’ boys and group (B from 80 karate athletes’ boys. Purpose of this investigation is to verify changes between judo and karate athletes’ boys in morphologic characteristic and motoric abilities. The problem of investigation was to investigate if there are changes between judo and karate athletes’ boys in morphologic characteristic that represent longitudinal dimensionality, body measure and adipose tissue, and in motoric abilities (used is eurofit battery tests. For global analysis of dimension to some changes and variable system (which contribute in changes between judo and karate athletes’ boys were implicated t-test for small independent sample and, canonic discriminative analysis. The results of this study show that judo and karate athletes significantly differ among themselves in motoric abilities, judo athletes are better in the tests: long jump from place (LOJU, squeeze palm (SQPA and support the knuckle (SUKN, while the karate athletes are better in the tests: taping for hands (TAHE, reach sitting down position (RSDP and run there-hire 10x5 meters (R10x5M, but these changes were not noticed and morphological variables.

  10. Analysis of Two-Parameter (△K and Kmax) Fatigue Crack Propagation Models%包含△K和Kmax二参数的疲劳裂纹扩展模型

    Institute of Scientific and Technical Information of China (English)

    钱怡; 崔维成

    2011-01-01

    除了材料自身特性和环境因素外,疲劳裂纹扩展的方式取决于裂纹尖端附近的应力场.而该应力场由外加应力和残余应力组成,受到引起循环塑性区的应力强度因子变化幅度△K和产生单调塑性区的最大应力强度因子Kmax的共同影响.因此,驱动裂纹扩展的外部驱动力应该是△K和Kmax.通过比较Vasudevan和Sadananda,Kuiawski、张嘉振等人提出的3种典型的二参数疲劳裂纹扩展模型的特点,提出了一个兼顾内、外应力,适合变幅载荷下疲劳裂纹扩展的新模型.%The fatigue crack growth is dominated by stress field around the crack-tip except for the material characteristics and the effect of environment. The stress around the crack-tip is the superimposition of the residual stress and the externally applied stress, which are affected by maximum stress intensity factor, Kmax, and stress intensity factor range, △K. The former can be associated with the monotonic plastic zone, while the latter with the cyclic plastic zone. Therefore, the fatigue crack driving force should include two parameters △K and Kmax. After comparing three kinds of fatigue crack growth rate models, which were derived by Vasudevan and Sadananda, Kujawski, and Zhang, a new fatigue crack growth rate model is proposed. The model can deal with the variable amplitude loading cases, and will take into account the residual stress and the externally applied stress.

  11. Rare earth metals influence on morphology of non-metallic inclusions and mechanism of GP240GH and G17CrMo5-5cast steel cracking

    Directory of Open Access Journals (Sweden)

    M. Gajewski

    2009-10-01

    Full Text Available This paper presents results of research carried out in order to specify the influence of the rare earth metals on the morphology of the occuring non-metallic inclusions as well as on the cracking mechanism of GP240GH cast carbon steel and G17CrMo5-5 (0.18%C, 1.2%Cr, 0.53%Mo high temperature cast steel. The tests have been performed on successive industrial melts adding rare earth metals to the ladle during tapping of heat melt from the furnace. It was found that ball-shaped non-metalic inclusions occuring as a result of the rare earth metals influence are heterogenic and they significantly influence the cracking mechanism of Charpy specimens and the impact strength. The morphology of the specimens fracture surface has been substantially changed as a result of the rare earth metals modification. The impact strength of the tested cast carbon steel increased from 100 J/cm2 to ca 155 J/cm2, and the high-temperature cast steel from 30 J/cm2 to ca 100 J/cm2.

  12. Cluster Galaxy Morphologies: The Relationship among Structural Parameters, Activity and the Environment

    CERN Document Server

    Añorve, Christopher; Ibarra-Medel, Hector; León-Tavares, Jonathan

    2010-01-01

    We use an approach to estimate galaxy morphologies based on an ellipticity (e) vs. Bulge-to-Total ratio (B/T) plane. We have calibrated this plane by comparing with Dressler's classifications. With the aid of our calibration, we have classified 635 galaxies in 18 Abell clusters (0.02 < z < 0.08). Our approach allowed us to recover the Kormendy's relation. We found that ellipticals and Spirals are slightly brighter than S0 in R band. As S0 bulges are brighter than spirals bulges, we believe that ram pressure is not the main mechanism to generate S0s. In our sample, cluster radio galaxies morphologies cover the range S0-E-cD and their bulges have absolutes magnitudes distributed within -21 mag < M < -24.5 mag. If we believe Ferrarese & Merrit's relation, these radio sources have 10^8-10^9 M black hole mass.

  13. Experimental investigation of crack initiation and propagation in high- and gigacycle fatigue in titanium alloys by study of morphology of fracture

    Directory of Open Access Journals (Sweden)

    M.V. Bannikov

    2016-01-01

    Full Text Available Fatigue (high- and gigacycle crack initiation and its propagation in titanium alloys with coarse and fine grain structure are studied by fractography analysis of fracture surface. Fractured specimens were analyzed by interferometer microscope and electronic microscope to improve methods of monitoring of damage accumulation during fatigue test and verify the models for fatigue crack kinetics. Fatigue strength was estimated for high cycle fatigue (HCF regime using the Luong method [1] by “in-situ” infrared scanning of the sample surface for the step-wise loading history for different grain size metals. Fine grain alloys demonstrated higher fatigue resistance for both HCF and gigacycle fatigue regimes. Fracture surface analysis for cylindrical samples was carried out using optical and electronic microscopy method. High resolution profilometry (interferometerprofiler New View 5010 data of fracture surface roughness allowed us to estimate scale invariance (the Hurst exponent and to establish the existence of two characteristic areas of damage localization (different values of the Hurst exponent. Area 1 with diameter ~300 μm has the pronounced roughness and is associated with damage localization hotspot. Area 2 shows less amplitude roughness, occupies the rest fracture surface and considered as the trace of the fatigue crack path corresponding to the Paris kinetics

  14. Uncertainty in the use of MAMA software to measure particle morphological parameters from SEM images

    Energy Technology Data Exchange (ETDEWEB)

    Schwartz, Daniel S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Tandon, Lav [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-06-05

    The MAMA software package developed at LANL is designed to make morphological measurements on a wide variety of digital images of objects. At LANL, we have focused on using MAMA to measure scanning electron microscope (SEM) images of particles, as this is a critical part of our forensic analysis of interdicted radiologic materials. In order to successfully use MAMA to make such measurements, we must understand the level of uncertainty involved in the process, so that we can rigorously support our quantitative conclusions.

  15. Dynamic changes in optic disc morphology, choroidal thickness, anterior chamber parameters, and intraocular pressure during Valsalva maneuver

    Directory of Open Access Journals (Sweden)

    Alper Mete

    Full Text Available ABSTRACT Purpose: To investigate the effects of the Valsalva maneuver (VM on optic disc morphology, choroidal thickness, and anterior chamber parameters. Methods: This prospective observational study included 60 eyes of 60 healthy subjects. The anterior chamber parameters, including central corneal thickness (CCT, anterior chamber depth (ACD, anterior chamber angle (ACA, anterior chamber volume (ACV, pupil diameter (PD, axial length (AL, subfoveal and peripapillary choroidal thickness, optic disc parameters, and intraocular pressure (IOP, were measured at rest and during VM. Results: VM did not have any significant influence on AL, subfoveal and peripapillary choroidal thickness, optic disc area, rim area, cup area, cup-to-disc area ratio, vertical cup-to-disc ratio, rim volume, cup volume, and nerve head volume measurements (for all; p >0.05. IOP and PD significantly increased during VM (for both; p <0.001. VM significantly decreased CCT, ACD, ACA, and ACV values (for all; p <0.001. Moreover, the optic nerve cup volume decreased and the horizontal cup-to-disc ratio significantly increased during VM (for both; p <0.05. Conclusions: VM may cause transient changes in IOP, optic disc morphology, and anterior chamber parameters.

  16. Unilateral cleft lip and palate. Relationship between morphology of the dentition and functional parameters of the tongue.

    Science.gov (United States)

    Opitz, C; Hochmuth, M; Rabe, H; Subklew, D

    1997-01-01

    The relationship between orthodontic and logopedic findings was evaluated with statistical contingency analysis. The investigation was focused on selected dentomorphologic parameters and oral function/malfunction of 100 patients between 3 and 7 years of age with unilateral cleft lip and palate. For further classification into contingency tables "normal" and "abnormal" attributes were defined. Interdependencies between observed findings and their probable frequencies were calculated and represented in diagrams by means of statistical parameters such as the contingency coefficient. Scatterplots of the calculated coefficients showed a characteristic pattern corresponding to clinical experience. While overjet and transversal occlusion are strongly associated with oral functions, overbite tends not to be associated with oral functions. The contingency coefficient calculated from sagittal and transversal orthodontically relevant conditions of occlusion and incorrect tongue position as well as incorrect swallowing tends to be stronger than that of "abnormal" morphologic parameters and an incorrect tongue position during speech. The longitudinal study of lip position and the 3 investigated morphologic parameters revealed strongly associated contingency coefficients.

  17. Influence of electrospinning parameters on the structural morphology and diameter of electrospun nanofibers

    CSIR Research Space (South Africa)

    Jacobs, V

    2009-11-01

    Full Text Available Electrospinning is a simple method of producing nanofibers by introducing electric field into the polymer solutions. We report an experimental investigation on the influence of processing parameters and solution properties on the structural...

  18. Effects of Nitrogen and Shading on Root Morphologies, Nutrient Accumulation, and Photosynthetic Parameters in Different Rice Genotypes.

    Science.gov (United States)

    Pan, Shenggang; Liu, Haidong; Mo, Zhaowen; Patterson, Bob; Duan, Meiyang; Tian, Hua; Hu, Shuijing; Tang, Xiangru

    2016-08-25

    Nitrogen availability and illumination intensity are two key factors which affect rice growth. However, their influences on total nitrogen accumulation, photosynthetic rate, root morphologies, and yields are not fully understood. We conducted two field experiments to (1) evaluate the effects of shading under different N treatments on photosynthetic parameters, root morphologies, total nutrient accumulation, and grain yields of rice; and (2) elucidate the relationship between total nutrient accumulation and root morphologies under different shading conditions and nitrogen treatments. Three nitrogen rates, three shading treatments, and three different rice cultivars were used in two field experiments. Double shading during the grain-filling stage decreased total nutrient accumulation, altered root morphological characteristics, and decreased yields in rice. There were also significant interaction effects between nitrogen and shading on photosynthetic rate, transpiration rate, and total root length, root superficial area, and root volume. Significant interactions were found among cultivars and shading for photosynthetic rate and transpiration rate. Correlation analysis revealed that total nitrogen accumulation (TNA) and potassium accumulation (TKA) were significantly positively correlated with total root length, root superficial area, and root volume. N application could alleviate the detrimental effects of shading on total nutrient accumulation and grain yield in rice.

  19. Effect of Spindle Parameters of Woodworking Band Saw on the AE Value of Crack Band Saw Blade in Compound Material Processing (1)

    Science.gov (United States)

    Gao, Jin-gui; Jiang, Zhao-fang; Luo, Lai-peng

    2017-04-01

    Taking the MJ3210A motion band saw as the research object, the AE value of the band saw blade vibration was obtained by analyzing the VIBSYS vibration signal acquisition and analysis software system in Beijing, and the change of the AE value of the band saw and the crack was found out. The experimental results show that in the MJ3210A sports car sawing machine, the band saw blade with width of 130 mm is used, and the AE value of the cracked band saw blade is well in the high band saw blade AE value. Under the best working condition of the band saw, the band saw blade AE If the value exceeds 104.7 dB (A) above, it means that the band saw blade has at least one crack length greater than 1.38 mm for the crack defect and the need to replace the band saw blade in time. Different species with saw blade of the AE value is different, white pine wood minimum, the largest oak wood; according to a variety of wood processing AE instrument value to determine the band saw blade crack to the situation; so as to fully rational use of band saw blade, The failure and the degree of development to find a new method.

  20. FRACTAL KINEMATICS OF CRACK PROPAGATION IN GEOMATERIALS

    Institute of Scientific and Technical Information of China (English)

    谢和平

    1995-01-01

    Experimental results indicate that propagation paths of cracks in geomaterials are often irregular, producing rough fracture surfaces which are fractal. A formula is derived for the fractal kinematics of crack propagation in geomaterials. The formula correlates the dynamic and static fracture toughnesses with crack velocity, crack length and a microstructural parameter, and allows the fractal dimension to be obtained. From the equations for estimating crack velocity and fractal dimension it can be shown that the measured crack velocity, Vo , should be much smaller than the fractal crack velocity, V. It can also be shown that the fractal dimension of the crack propagation path can be calculated directly from Vo and from the fracture toughness.

  1. On multiple crack detection in beam structures

    Energy Technology Data Exchange (ETDEWEB)

    Moradi, Shapour; Kargozarfard, Mohammad [Shahid Chamran University, Ahvaz (Iran, Islamic Republic of)

    2013-01-15

    This study presents an inverse procedure to identify multiple cracks in beams using an evolutionary algorithm. By considering the crack detection procedure as an optimization problem, an objective function can be constructed based on the change of the eigenfrequencies and some strain energy parameters. Each crack is modeled by a rotational spring. The changes in natural frequencies due to the presence of the cracks are related to a damage index vector. Then, the bees algorithm, a swarm-based evolutionary optimization technique, is used to optimize the objective function and find the damage index vector, whose positive components show the number and position of the cracks. A second objective function is also optimized to find the crack depths. Several experimental studies on cracked cantilever beams are conducted to ensure the integrity of the proposed method. The results show that the number of cracks as well as their sizes and locations can be predicted well through this method.

  2. Influence of electrical parameters on morphology of nanostructured TiO2 layers developed by electrochemical anodization

    Directory of Open Access Journals (Sweden)

    Strnad Gabriela

    2017-01-01

    Full Text Available Ti6Al4V alloy micro rough surfaces with TiO2 self-organized nanostructured layers were synthesized using electrochemical anodization in phosphate/fluoride electrolyte, at different end potentials (5V, 10V, 15V, and 20 V. The current – time characteristics were recorded, and the link between current evolution and the morphology of developing oxide layers was investigated. On flat surfaces of Ti6Al4V alloy we developed TiO2 layers with different morphologies (random pores, nanopores of 25…50 nm, and highly organized nanotubes of 50…100 nm in diameter depending on electrical parameters of anodization process. In our anodization cell, in optimized conditions, we are able to superimpose nanostructured oxide layers (nanotubular or nanoporous over micro structured surfaces of titanium based materials used for biomedical implants.

  3. Mathematical Model of the Cupula-Endolymph System with Morphological Parameters for the Axolotl (Ambystoma tigrinum) Semicircular Canals.

    Science.gov (United States)

    Vega, Rosario; Alexandrov, Vladimir V; Alexandrova, Tamara B; Soto, Enrique

    2008-08-26

    By combining mathematical methods with the morphological analysis of the semicircular canals of the axolotl (Ambystoma tigrinum), a system of differential equations describing the mechanical coupling in the semicircular canals was obtained. The coefficients of this system have an explicit physiological meaning that allows for the introduction of morphological and dynamical parameters directly into the differential equations. The cupula of the semicircular canals was modeled both as a piston and as a membrane (diaphragm like), and the duct canals as toroids with two main regions: i) the semicircular canal duct and, ii) a larger diameter region corresponding to the ampulla and the utricle. The endolymph motion was described by the Navier-Stokes equations. The analysis of the model demonstrated that cupular behavior dynamics under periodic stimulation is equivalent in both the piston and the membrane cupular models, thus a general model in which the detailed cupular structure is not relevant was derived.

  4. Effects of penicillin G on morphology and certain physiological parameters of Lactobacillus acidophilus ATCC 4356.

    Science.gov (United States)

    Khaleghi, M; Kasra Kermanshahi, R; Zarkesh-Esfahani, S H

    2011-08-01

    Evidence shows that probiotic bacteria can undergo substantial structural and morphological changes in response to environmental stresses, including antibiotics. Therefore, this study investigated the effects of penicillin G (0.015, 0.03, and 0.06 mg/l) on the morphology and adhesion of Lactobacillus acidophilus ATCC 4356, including the colony morphotype, biofilm production, hydrophobicity, H₂O₂ formation, S-layer structure, and slpA gene expression. Whereas only smooth colonies grew in the presence of penicillin, rough and smooth colony types were observed in the control group. L. acidophilus ATCC 4356 was found to be hydrophobic under normal conditions, yet its hydrophobicity decreased in the presence of the antibiotic. No biofilm was produced by the bacterium, despite testing a variety of different culture conditions; however, treatment with penicillin G (0.015-0.06 mg/l) significantly decreased its production of H₂O₂ formation and altered the S-layer protein structure and slpA gene expression. The S-protein expression decreased with 0.015 mg/l penicillin G, yet increased with 0.03 and 0.06 mg/l penicillin G. In addition, the slpA gene expression decreased in the presence of 0.015 mg/l of the antibiotic. In conclusion, penicillin G was able to alter the S-layer protein production, slpA gene expression, and certain physicochemical properties of Lactobacillus acidophilus ATCC 4356.

  5. Effects of the isostretching method on morphological parameters and on a set of motor tests in the elderly

    Directory of Open Access Journals (Sweden)

    Christina Cruz Cepeda

    2013-07-01

    Full Text Available Moderate intensity resistance training seems to be effective in providing significant improvements on strength, balance and function in the elderly. This study aimed to analyze the effect of a 12-week isostretching training on functional capacity and muscle architecture in elderly women. The sample included 25 volunteers (n = 25 divided into a control group (CG, n = 11, 62.3 ± 1.9 years old, 1.58 ± 0.06 m, 73.4 ± 1.4 kg that followed their physical activity habits and an experimental group (EG, n = 14, 64.2 ± 4.3 years, 1.56 ± 0.05 m, 74.2 ± 1.6 kg that was submitted to an isostretching program. The following assessments were used: Timed Up and Go-TUGT, Tinetti balance test and evaluation of morphological parameters through ultrasound imaging technique. The results showed that the EG improved (p <0.05 in both TUGT and Tinetti. In the morphologic parameters of the vastus lateralis muscle in the EG, we observed the following: mean increase of 3.6 mm in length issue relaxation (p <0.05, ES = 1.15; increase of 4.9 mm in isometric contraction (p <0.05; ES = 1.94; increase of 16% in the pennation angle in the relaxed condition (p <0.05; ES = 0.70; increase of 12% in isometric contraction (p <0.05; ES = 0.50; increase of 8% in thickness in the relaxed condition (p <0.05, EF = 0.52; and increase of 9% in isometric contraction (p <0.05, EF = 0.43. The GC did not show any significant changes. The isometric training through the isostretching method promoted changes in the morphological and muscle parameters and also improved the functional abilities in elderly women.

  6. Quantitative correlation between air induced changes of electronic parameters and morphological features of copper phthalocyanine thin film surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Grządziel, L., E-mail: Lucyna.Grzadziel@polsl.pl; Krzywiecki, M.

    2015-01-15

    In this work, utilizing fine-resolved photoemission yield spectroscopy (PYS) method, the set of electronic parameters of the space charge layer of 16 nm-copper phthalocyanine (CuPc) thin films deposited on n-type Si(111) substrate covered with modified SiO{sub 2} was determined after long term air exposure. The PYS investigation revealed that work function and surface band bending increased upon gas adsorption by 0.64 eV and 0.32 eV respectively for organic layer and surface dipole effect appeared as the shift in electron affinity of 0.32 eV. Obtained results were compared with photoemission data received for corresponding CuPc films on different types of silicon Si(111) substrate. Collected parameters were correlated with the morphological features of the CuPc's surfaces measured applying atomic force microscopy (AFM) ability. Results of compiled PYS and AFM studies indicated particular electronic tendency for oxidation processes for certain shapes of phthalocyanine crystallites. It may suggest that by manipulation of the initial films' morphology it would be possible to control the air stability of the CuPc-based electronic devices and their vulnerability to degradation processes. - Highlights: • PYS study of 16 nm-CuPc/RCA-SiO{sub 2}/n-Si(111) electronic properties after air exposure. • eV{sub s}, χ{sub s}, φ changes due to oxidation process compared to the other CuPc results. • Electronic parameters shift correlated with morphological features obtained by AFM.

  7. [Intercorrelation of psychopathological, morphologic, neurophysiologic an psychometric parameters in schizophrenic patients].

    Science.gov (United States)

    Pester, U; Schwarz, A; Lerche, J; Brosz, M; Kropf, S; Ulrich, S; Bogerts, B; Wurthmann, C

    1997-07-01

    The present study was designed to determine the intercorrelation between schizophrenic symptoms, brain morphology, electrophysiological and neuropsychological variables. 44 patients, who met ICD-10 criteria for schizophrenic disorder, were included. At baseline, after 3 and 6 weeks BPRS, CGI, psychometric measurements and QEEG/ERP were performed. A CT scan was performed only at the beginning of the study. Data were evaluated by a multivariate test for data with an inherent structure. One of the most interesting findings is a correlation between BPRS total score and theta EEG power at baseline as well as under treatment. In conclusion, the study suggests the usefulness of multimethodological approaches in order to optimise diagnostic procedures in schizophrenia.

  8. Influence of brazing parameters and alloy composition on interface morphology of brazed diamond

    Energy Technology Data Exchange (ETDEWEB)

    Klotz, Ulrich E. [Empa, Swiss Federal Laboratories for Materials Testing and Research, Laboratory for Joining and Interface Technology, Uberlandstrasse 129, CH-8600 Duebendorf (Switzerland)], E-mail: klotz@fem-online.de; Liu Chunlei [Empa, Swiss Federal Laboratories for Materials Testing and Research, Laboratory for Joining and Interface Technology, Uberlandstrasse 129, CH-8600 Duebendorf (Switzerland); Khalid, Fazal A. [Faculty of Metallurgy and Materials Engineering, GIK Institute, Topi, NWFP (Pakistan); Elsener, Hans-Rudolf [Empa, Swiss Federal Laboratories for Materials Testing and Research, Laboratory for Joining and Interface Technology, Uberlandstrasse 129, CH-8600 Duebendorf (Switzerland)

    2008-11-15

    Active brazing is an effective technique for joining diamond or cBN grit to metallic substrates. This technique is currently used to manufacture superabrasive, high-performance tools. The investigation of interface reactions between diamond and active brazing alloys plays an important role in understanding and improving the brazing process and the resultant tool performance. Focused ion beam (FIB) milling enabled the high resolution investigation of these extremely difficult to prepare metal-diamond joints. The interfacial nanostructure is characterized by the formation of two layers of TiC with different morphologies. First a cuboidal layer forms directly on the diamond and reaches a thickness of approximately 70 nm. Then a second layer with columnar TiC crystals grows on the first layer into the brazing filler metal by a diffusion-controlled process. The combined thickness of both TiC layers varies between 50 nm and 600 nm depending on the brazing temperature and holding time.

  9. Floating basaltic lava balloons - constrains on the eruptive process based on morphologic parameters

    Science.gov (United States)

    Pacheco, J. M.; Zanon, V.; Kueppers, U.

    2011-12-01

    characteristics are indicative that the outer surface of the balloon quenched as it was being extruded and preserved the scars of a squeeze-up process. On this outer surface, several superficial expansion cracks reveal that after its generation the balloon endured some expansion before reaching the sea surface, most likely due to hydrostatic decompression during its rise. The entire shell of the balloons shows bends and folds resulting from large ductile deformations, also suggesting an origin as an effusive process of squeezing-up a large vesicle through a fissure in a thin lava crust, similarly to the extrusion of a gas filled lava toe. Actually, the volume of the lava shell is not enough to produce all the gas in the balloons interior. More likely, at an earlier stage, degassing of magma as an open system allowed gas to segregate and accumulate to form large vesicles. The development of very large vesicles would be favored by a ponding system such as a lava lake.

  10. MORPHOLOGICAL PARAMETERS OF FIVE POPULATIONS FROM THE UPPER FLOW OF THE SAVA RIVER

    Directory of Open Access Journals (Sweden)

    Željko Domitrović

    2004-09-01

    Full Text Available Out of 514 specimens of caught and analyzed fish, there were 250 specimens of chub, 94 specimens of spirlin, 78 specimens of stream barbel, 57 specimens of bleak, 35 specimens of barbel. All populations were checked for 9 morphometric and 5 meristic parameters. Although analyzed morphometric parameters showed constant values in accordance with the literature used, all 5 meristic values of chub, barbel and stream barbel were different from freshwater fish species determination key that is valid for this part of Europe. Some specimens of spirlin had deviation in the number of scales above and below the lateral line, while bleak had different number of unforked and forked rays in dorsal fin. This indicates that further investigation is necessary in order to introduce additional values to the existing key.

  11. Mode Ⅰ Plane Crack Interacting with an Interfacial Crack Along a Circular Inhomogeneity

    Institute of Scientific and Technical Information of China (English)

    WANG Rui; MA Jian-jun; LIU Zheng-guang

    2006-01-01

    The elastic interaction of the mode Ⅰ plane crack with an interfacial crack along a circular inhomogeneity is dealt with. The dislocation density and the stress intensity factors (SIFs) of the mode I plane crack are obtained numerically. A new kind of dislocation equilibrium equation about the plane crack is applied. The influence of some material parameters on the dislocation density and SIFs are analyzed.

  12. Effects of noise and filtering on SVD-based morphological parameters of the T wave in the ECG.

    Science.gov (United States)

    Lehtola, L; Karsikas, M; Koskinen, M; Huikuri, H; Seppanen, T

    2008-01-01

    Singular value decomposition (SVD) based electrocardiogram (ECG) morphology analysis is a novel method in the assessment of subtle abnormalities in the T wave morphology of 12-lead ECG. As various types of noise contaminate the ECG signal and create a bias for the morphological analyses, this study was designed to estimate the effects of noise on the SVD method in an experimental setup. Ideal signals were generated by filtering real ECG signals several times with the Savitzky-Golay filter. Random and real noise samples were superimposed on the ideal signals. The noisy signals were filtered with a power line interference filter combined with the Savitzky-Golay or the wavelet filter. Results show that noise increased both the dipolar and non-dipolar components significantly unless filtering was applied. R-TWR (relative T wave residuum) and A-TWR (absolute T wave residuum) were four to eight times higher in noisy signals. The experiments with patient data demonstrated that certain types of noise may even lead to erroneous classification of patients. Filtering brings the median values closer to the correct ones and decreases significantly the variance of the values of parameters.

  13. ECG spectral and morphological parameters reviewed and updated to detect adult and paediatric life-threatening arrhythmia.

    Science.gov (United States)

    Aramendi, E; Irusta, U; Pastor, E; Bodegas, A; Benito, F

    2010-06-01

    Since the International Liaison Committee on Resuscitation approved the use of automated external defibrillators (AEDs) in children, efforts have been made to adapt AED algorithms designed for adult patients to detect paediatric ventricular arrhythmias accurately. In this study, we assess the performance of two spectral (A(2) and VFleak) and two morphological parameters (TCI and CM) for the detection of lethal ventricular arrhythmias using an American Heart Association (AHA) compliant database that includes adult and paediatric arrhythmias. Our objective was to evaluate how those parameters can be optimally adjusted to discriminate shockable from nonshockable rhythms in adult and paediatric patients. A total of 1473 records were analysed: 751 from 387 paediatric patients ( 0.01) between the adult and paediatric patients for the shockable records; the differences for nonshockable records however were significant. Still, these parameters maintained the discrimination power when paediatric rhythms were included. A single threshold could be adjusted to obtain sensitivities and specificities above the AHA goals for the complete database. The sensitivities for ventricular fibrillation (VF) and ventricular tachycardia (VT) were 91.1% and 96.6% for VFleak, and 90.3% and 99.3% for A(2). The specificities for normal sinus rhythm (NSR) and other nonshockable rhythms were 99.5% and 96.3% for VFleak, and 99.0% and 97.7% for A(2). On the other hand, the morphological parameters showed significant differences between the adult and paediatric patients, particularly for the nonshockable records, because of the faster heart rates of the paediatric rhythms. Their performance clearly degraded with paediatric rhythms. Using a single threshold, the sensitivities and specificities were below the AHA goals, particularly VT sensitivity (60.4% for TCI and 65.8% for CM) and the specificity for other nonshockable rhythms (51.7% for TCI and 34.5% for CM). The specificities, particularly for

  14. Effect of process parameters on the morphology and adsorption properties of nanocrystalline boehmite

    Directory of Open Access Journals (Sweden)

    Obrenović Zoran

    2014-01-01

    Full Text Available In the last decade, exploration of transition alumina phases with good adsorption properties has attracted a great research interest from both a fundamental and a practical point of view. The transition phases of alumina are metastable polymorphs of aluminum oxide formed through the thermal dehydration of aluminum trihydroxide and aluminum oxyhydroxide. Powder X-ray diffraction (XRD, Fourier-transformed infrared spectroscopy (FT-IR, scanning electron microscopy (SEM and low-temperature nitrogen absorption studies were employed to trace the formation of the transition phases of alumina. In this work transition alumina powders were synthesized starting from sodium aluminate solution prepared from Bayer liquor. The neutralization of sodium aluminate solution was performed with the use of sulphuric acid, while glucose was added in the starting solution. In this way, the single phase nanocrystalline boehmite was obtained. As-synthesized boehmite powders have high surface area (above 360 m2/g and the average crystallite size less than 5 nm. The results showed that the properties of the powders (structure, morphology are strongly influenced by the initial pH value of sodium aluminate solution, as well as by the duration of neutralization step. [Projekat Ministarstva nauke Republike Srbije, br. III 45021

  15. [The effect of vegetarian diet on selected biochemical and blood morphology parameters].

    Science.gov (United States)

    Nazarewicz, Rafał

    2007-01-01

    The objective was to examine whether vegetarian diet influence biochemical parameters of blood and plasma urea in selective vegetarian group. The investigation covered 41 subject, 22 of them had been applying vegetarian diet and 19 were omnivorous. The study shows statistically significant lower values of white blood cells, % and amounts of neutrocytes and insignificant lower level of red blood cells, hemoglobine, hematocrit and platelet in vegetarian group. Significant lower plasma urea level was observed in that group. These changes indicate that high quality deficiency protein was due to vegetarian diet.

  16. Research on pavement crack recognition methods based on image processing

    Science.gov (United States)

    Cai, Yingchun; Zhang, Yamin

    2011-06-01

    In order to overview and analysis briefly pavement crack recognition methods , then find the current existing problems in pavement crack image processing, the popular methods of crack image processing such as neural network method, morphology method, fuzzy logic method and traditional image processing .etc. are discussed, and some effective solutions to those problems are presented.

  17. Morphological and hormonal parameters in two species of macaques: impact of seasonal breeding.

    Science.gov (United States)

    Muehlenbein, Michael P; Campbell, Benjamin C; Murchison, Mark A; Phillippi, Kathrine M

    2002-03-01

    To compare physiological and developmental differences between two cogeneric species that differ by seasonal vs. aseasonal breeding, values for morphological measurements, testicular volume, serum testosterone, estradiol, and dehydroepiandrosterone-sulfate levels were obtained from 53 rhesus during the early breeding season, as well as 41 pig-tailed macaque males maintained at the Tulane Primate Center. The two species exhibited similar body size, testosterone, and estradiol levels, but differed substantially in testicular volume (3.00 +/- 1.7 vs. 1.72 +/- 1.3 cc), abdominal skinfold measures (15.7 +/- 9.2 vs. 9.0 +/- 7.7 mm), and DHEA-S levels (18.0 +/- 11.7 vs. 7.6 +/- 5.4 microg/dl). Significant interaction effects for species by age group were found for weight, tricep circumference, length, and estradiol level. In addition, length was more closely related to testicular volume among rhesus compared to pig-tailed macaques, suggesting different developmental patterns between the species. Predictors of hormonal levels differed between the two species. In the rhesus, estradiol levels were related to testicular volume and testosterone levels while there were no anthropometric predictors of testosterone or DHEA-S. For the pig-tailed macaques, testicular volume was related to tricep circumference, testosterone to triceps skinfold and testicular volume, and estradiol to weight. It is argued that rhesus have larger testes for body size and more abdominal fat deposits during the early breeding season relative to pig-tailed macaques reflecting the increased demands of sperm competition in a seasonally breeding species. Hormonal differences associated with the difference in breeding system appear to be primarily related to adrenal rather than testicular activity.

  18. Efficient three-dimensional reconstruction of aquatic vegetation geometry: Estimating morphological parameters influencing hydrodynamic drag

    Science.gov (United States)

    Liénard, Jean; Lynn, Kendra; Strigul, Nikolay; Norris, Benjamin K.; Gatziolis, Demetrios; Mullarney, Julia C.; Bryan, Karin, R.; Henderson, Stephen M.

    2016-09-01

    Aquatic vegetation can shelter coastlines from energetic waves and tidal currents, sometimes enabling accretion of fine sediments. Simulation of flow and sediment transport within submerged canopies requires quantification of vegetation geometry. However, field surveys used to determine vegetation geometry can be limited by the time required to obtain conventional caliper and ruler measurements. Building on recent progress in photogrammetry and computer vision, we present a method for reconstructing three-dimensional canopy geometry. The method was used to survey a dense canopy of aerial mangrove roots, called pneumatophores, in Vietnam's Mekong River Delta. Photogrammetric estimation of geometry required 1) taking numerous photographs at low tide from multiple viewpoints around 1 m2 quadrats, 2) computing relative camera locations and orientations by triangulation of key features present in multiple images and reconstructing a dense 3D point cloud, and 3) extracting pneumatophore locations and diameters from the point cloud data. Step 3) was accomplished by a new 'sector-slice' algorithm, yielding geometric parameters every 5 mm along a vertical profile. Photogrammetric analysis was compared with manual caliper measurements. In all 5 quadrats considered, agreement was found between manual and photogrammetric estimates of stem number, and of number × mean diameter, which is a key parameter appearing in hydrodynamic models. In two quadrats, pneumatophores were encrusted with numerous barnacles, generating a complex geometry not resolved by hand measurements. In remaining cases, moderate agreement between manual and photogrammetric estimates of stem diameter and solid volume fraction was found. By substantially reducing measurement time in the field while capturing in greater detail the 3D structure, photogrammetry has potential to improve input to hydrodynamic models, particularly for simulations of flow through large-scale, heterogenous canopies.

  19. Coconut oil on biochemical and morphological parameters in rats submitted to normolipidic and hyperlipidic diets

    Directory of Open Access Journals (Sweden)

    Bianca de Oliveira Schumacher

    Full Text Available ABSTRACT: This study aimed to evaluate the influence of replacing soybean oil with extra virgin coconut oil in normolipidic and hyperlipidic diets, on the lipid metabolism of Wistar rats. In the first stage of the experiment (30 days, 36 rats were divided into 2 groups and fed with a control or a hyperlipidic diet. Six animals from each group were then killed, and the remaining rats were redistributed into 4 new groups: 2 groups remained on the control and hyperlipidic diets, and in the diets of the other 2 groups, the soybean oil was replaced with coconut oil (30 days. At the end of the assay, the biological models were decapitated for blood collection and removal of organs and peritoneal fat. Although the diet intake differed among groups during both stages of the experiment, no differences were noted with regard to weight gain and peritoneal fat. Replacing soybean oil with coconut oil in the rat diet lowered triglyceride and low-density lipoprotein serum concentrations in both groups. Liver parameters, namely, total cholesterol and triacylglycerols, increased with the substitution of soybean oil by coconut oil in the normolipidic diet and decreased in the hyperlipidic diet. Thus, replacing soybean oil by coconut oil may improve serum and liver lipid levels in Wistar rats.

  20. Estimation of genetic parameters for morphological and functional traits in a Menorca horse population

    Directory of Open Access Journals (Sweden)

    Marina Solé

    2014-01-01

    Full Text Available Functional conformation and performance in Classic and Menorca Dressage are the main selection criteria in the Menorca Horse breeding program. Menorca Dressage is an alternative Classical Dressage discipline which is exclusive of the Menorca Island, but including a series of movements that the animals perform in the traditional festivities called “Jaleo Menorquín”. One of these movements involves the horse raising its forelimbs and standing or walking on its hindlimbs, which is called “el bot”. To make the Menorca horse breed more competitive in the equestrian market, it is necessary to understand the genetic background that characterizes the aptitude for Menorca Dressage and its relationship with conformation traits. The analysed data consisted of 15 conformation traits from 347 Menorca horses (200 males and 147 females, with 1,550 performance records in Menorca Dressage competitions. Genetic parameters were estimated using linear and threshold animal models. The heritabilities for heights and lengths were high (0.45-0.76, those for angulations and binary conformation traits were low to moderate (0.10-0.36 as were the scores for dressage performance (0.13-0.21. The results suggest that the analyzed traits could be used as an efficient tool for selecting breeding horses.

  1. Estimation of genetic parameters for morphological and functional traits in a Menorca horse population

    Energy Technology Data Exchange (ETDEWEB)

    Sole, M.; Cervantes, I.; Gutierrez, J. P.; Gomez, M. D.; Valera, M.

    2014-06-01

    Functional conformation and performance in Classic and Menorca Dressage are the main selection criteria in the Menorca Horse breeding program. Menorca Dressage is an alternative Classical Dressage discipline which is exclusive of the Menorca Island, but including a series of movements that the animals perform in the traditional festivities called Jaleo Menorquin. One of these movements involves the horse raising its forelimbs and standing or walking on its hindlimbs, which is called el bot. To make the Menorca horse breed more competitive in the equestrian market, it is necessary to understand the genetic background that characterizes the aptitude for Menorca Dressage and its relationship with conformation traits. The analysed data consisted of 15 conformation traits from 347 Menorca horses (200 males and 147 females), with 1,550 performance records in Menorca Dressage competitions. Genetic parameters were estimated using linear and threshold animal models. The heritabilities for heights and lengths were high (0.45-0.76), those for angulations and binary conformation traits were low to moderate (0.10-0.36) as were the scores for dressage performance (0.13-0.21). The results suggest that the analyzed traits could be used as an efficient tool for selecting breeding horses. (Author)

  2. THE INFLUENCE OF POLYMERIC GROWTH REGULATORS ON MORPHOLOGICAL AND PHYSIOLOGICAL PARAMETERS OF RICE IN SALINE CONDITIONS

    Directory of Open Access Journals (Sweden)

    Tretyakova O. I.

    2016-04-01

    Full Text Available The article studies the influence of polymeric in the form of formers and growth regulators on the growth and development of rice plants when grown in saline conditions. We controlled the effect of salinity on grows regulators and vigor, seed germination, root and shoot weight, the content of photosynthetic pigments parameters, induction curves of delayed fluorescence, the indicators of structure of harvest, grain yield. It was found, that pre-sowing seed soaking in solutions of polymer grows regulators has a stimulating effect on the growth and development of rice plants in the early stages: we significantly increased germination and emergence, dry weight of root and shoot compared to control. At different stages of ontogeny rice, the absolute content of pigments in the leaves and the relationship between the individual variants change. The absolute content of pigments in leaves and their relationship between experiences at different stages of ontogeny change. In the period of intensive vegetative growth from seedling stage the content of total chlorophyll is maximum, and by the end of the growing season it decreases. It can be assumed that the salinity of the substrate significantly reduces the productivity of photosynthesis in young plants, possibly due to imbalance of ions in the cell, the older it gets – the weaker the phenomenon is and even becomes reversed. The second maximum IR ZF increases during the growing season from germination to flowering, then decreases to the beginning of ripening in all embodiments. The same dynamics is characteristic of the magnitude of the proton gradient in the membranes of chloroplasts tylakoids. Salt protection effect of growth regulators on grain yield is significant on both backgrounds of mineral nutrition

  3. [High resolution peripheral quantitative computed tomography for the assessment of morphological and mechanical bone parameters].

    Science.gov (United States)

    Fuller, Henrique; Fuller, Ricardo; Pereira, Rosa Maria R

    2015-01-01

    High resolution peripheral quantitative computed tomography (HR-pQCT) is a new technology commercially available for less than 10 years that allows performing in vivo assessment of bone parameters. HR-pQCT assesses the trabecular thickness, trabecular separation, trabecular number and connectivity density and, in addition, cortical bone density and thickness and total bone volume and density in high-definition mode, which additionally allows obtaining digital constructs of bone microarchitecture. The application of mathematics to captured data, a method called finite element analysis (FEA), allows the estimation of the physical properties of the tissue, simulating supported loads in a non-invasive way. Thus, HR-pQCT simultaneously acquires data previously provided separately by dual energy x-ray absorptiometry (DXA), magnetic resonance imaging and histomorphometry, aggregating biomechanical estimates previously only possible in extracted tissues. This method has a satisfactory reproducibility, with coefficients of variation rarely exceeding 3%. Regarding accuracy, the method shows a fair to good agreement (r(2) = 0.37-0.97). The main clinical application of this method is in the quantification and monitoring of metabolic bone disorders, more fully evaluating bone strength and fracture risk. In rheumatoid arthritis patients, this allows gauging the number and size of erosions and cysts, in addition to joint space. In osteoarthritis, it is possible to characterize the bone marrow edema-like areas that show a correlation with cartilage breakdown. Given its high cost, HR-pQCT is still a research tool, but the high resolution and efficiency of this method reveal advantages over the methods currently used for bone assessment, with a potential to become an important tool in clinical practice. Copyright © 2014 Elsevier Editora Ltda. All rights reserved.

  4. Chronic toxicity of verapamil on juvenile rainbow trout (Oncorhynchus mykiss): effects on morphological indices, hematological parameters and antioxidant responses.

    Science.gov (United States)

    Li, Zhi-Hua; Velisek, Josef; Zlabek, Vladimir; Grabic, Roman; Machova, Jana; Kolarova, Jitka; Li, Ping; Randak, Tomas

    2011-01-30

    In this study, the toxic effects of verapamil (VRP) were studied on juvenile rainbow trout, Oncorhynchus mykiss, by chronic semi-static bioassay. Fish were exposed to sublethal concentrations of VRP (0.5, 27 and 270 μg/L) for 0, 21 and 42 d. Multiple biomarkers were measured, including morphological indices, hematological parameters and antioxidant responses of different tissues (brain, gill, liver, muscle and intestine). Based on the results, there was no significant change in all parameters measured in fish exposed to VRP at environmental related concentration, but VRP-induced stress in fish exposed to higher concentrations reflected the significant changes of physiological and biochemical responses. Through principal component analysis and integrated biomarker response assessment, effects induced by VRP-stress in each test group were distinguished. Additionally, all parameters measured in this study displayed various dependent patterns to VRP concentrations and exposure time using two-way ANOVA statistic analysis. In short, the multiple responses in fish indicated that VRP induced physiological stress and could be used as potential biomarkers for monitoring residual VRP in aquatic environment; but molecular and genetic mechanisms of these physiological responses in fish are not clear and need to be further studied. Copyright © 2010 Elsevier B.V. All rights reserved.

  5. Determination of Morphological Parameters of Supported Gold Nanoparticles: Comparison of AFM Combined with Optical Spectroscopy and Theoretical Modeling versus TEM

    Directory of Open Access Journals (Sweden)

    Frank Hubenthal

    2012-07-01

    Full Text Available The morphology of small gold particles prepared by Volmer–Weber growth on sapphire substrates have been investigated by two different characterization techniques. First, by non-extensive atomic force microscopy (AFM in combination with optical spectroscopy and modeling of the optical properties using a theoretical model, recently developed in our group. Second, by extensive transmission electron microscopy (TEM. Comparing the results obtained with both techniques demonstrate that for small gold nanoparticles within the quasistatic limit, the morphological properties can be precisely determined by an appropriate theoretical modeling of the optical properties in combination with simple AFM measurements. The apparent mean axial ratio of the nanoparticles, i.e., the axial ratio that corresponds to the center frequency of the ensemble plasmon resonance, is obtained easily from the extinction spectrum. The mean size is determined by the nanoparticle number density and the amount of deposited material, measured by AFM and a quartz micro balance, respectively. To extract the most probable axial ratio of the nanoparticle ensemble, i.e., the axial ratio that corresponds to the most probable nanoparticle size in the ensemble, we apply the new theoretical model, which allows to extract the functional dependence of the nanoparticle shape on its size. The morphological parameters obtained with this procedure will be afterwards compared to extensive TEM measurements. The results obtained with both techniques yield excellent agreement. For example, the lateral dimensions of the nanoparticles after deposition of 15.2 × 1015 atoms/cm2 of gold has been compared. While a mean lateral diameter of (13 ± 2 nm has been extracted from AFM, optical spectroscopy and modeling, a value of (12 ± 2 nm is derived from TEM. The consistency of the results demonstrate the precision of our new model. Moreover, since our theoretical model allows to extract the functional

  6. Virtual restoration of cracks in digitized image of paintings

    Energy Technology Data Exchange (ETDEWEB)

    Spagnolo, G Schirripa; Somma, F

    2010-11-01

    An integrated methodology for the detection and removal of cracks on digitized image is presented in this paper. Crack-like pattern detection have been a matter of high concern among researchers mostly for its useful contribution to a variety of applications. The results presented here regard the craquelure of old paintings, however, the same methodology can be used for a much wider set of application. Many images contain similar patterns: crack in protective coating for polymers and other surfaces; fatigue crack in MEMS/NEMS; crack in epoxies used for underfill and encapsulation microelectronics components; etc. In this paper the cracks are detected by thresholding the output of the morphological top-hat transform. Afterwards, the thin dark brush strokes which have been misidentified as cracks are removed using automatic procedure. Finally, crack filling using texture synthesis algorithms. The methodology has been shown to perform very well on digitized images suffering from cracks.

  7. An optimal selection method for morphological filter's parameters and its application in bearing fault diagnosis

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Aijun; Xiang, Ling [North China Electric Power University, Hebei (China)

    2016-03-15

    The Mathematical morphological filter (MMF) is widely applied in vibration signal processing for fault diagnosis. The Structure element (SE) and the cutoff frequency of filter have important impacts on the filtering effect, but there is no selection principle of these parameters for vibration signal processing in fault diagnosis. In this paper, the working mechanism of the MMF is studied, and a novel technique with filter characteristics and selection criterion of the MMF is proposed. The filter characteristics of morphological filter are described through frequency response analysis. The relationship between the SE length and the cutoff frequency of MMF is put forward, and the quantitative selection method of SE in engineering is proposed to effectively remove the noise and detect the impulses. The method is evaluated using both simulated signal and experimental bearing vibration signal. The results show that quantized selection method can make MMF have the better filtering effect, and can reliably extract impulsive features for bearing defect diagnosis. The study provides a theoretical basis for the application of MMF in vibration signal processing.

  8. Influence of charge carrier mobility and morphology on solar cell parameters in devices of mono- and bis-fullerene adducts

    Science.gov (United States)

    Muth, Mathis-Andreas; Mitchell, William; Tierney, Steven; Lada, Thomas A.; Xue, Xiang; Richter, Henning; Carrasco-Orozco, Miguel; Thelakkat, Mukundan

    2013-12-01

    Herein, we analyze charge carrier mobility and morphology of the active blend layer in thin film organic solar cells and correlate them with device parameters. A low band gap donor-acceptor copolymer in combination with phenyl-C61-butyric acid methyl ester (PCBM) or two bis-adduct fullerenes, bis-PCBM and bis-o-quino-dimethane C60 (bis-oQDMC), is investigated. We study the charge transport of polymer:fullerene blends in hole- and electron-only devices using the space-charge limited current method. Lower electron mobilities are observed in both bis-adduct fullerene blends. Hole mobility, however, is decreased only in the blend containing bis-oQDMC. Both bis-adduct fullerene blends show very high open circuit voltage in solar cell devices, but poor photocurrent compared to the standard PCBM blend for an active layer thickness of 200 nm. Therefore, a higher short circuit current is feasible for the polymer:bis-PCBM blend by reducing the active layer thickness in order to compensate for the low electron mobility, which results in a PCE of 4.3%. For the polymer:bis-oQDMC blend, no such improvement is achieved due to an unfavorable morphology in this particular blend system. The results are supported by external quantum efficiency measurements, atomic force microscopy, transmission electron microscopy and UV/vis spectroscopy. Based on these results, the investigations presented herein give a more scientific basis for the optimization of solar cells.

  9. Metallurgical phenomena in laser finishing: Interdependences between solidification morphologies and hot cracking in laser welding of mostly austenitic materials. Final reportc; Metallkundliche Phaenomene der Laserstrahlmaterialbearbeitung. Teilvorhaben: Zusammenhaenge zwischen Erstarrungsmorphologien und Heissrissentstehung beim Laserschweissen von vornehmlich austenitischen Werkstoffen. Abschlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Schobbert, H.

    2000-06-01

    Austentic stainless steels are widely used in safety relevant applications such as chemical plant industry or off-shore industry. Due to the rapid development of laser welding processes, the economical efficiency increases and leads to a growing interest in industry for the production of, for example, straight bead welded pipes. A specific problem of laser welding is the economically desirable high welding speed, which leads in austenitic stainless steels to a change of solidification mode and thus, to a restricted hot cracking resistance. Thus, the solidification morphologies of austenitic stainless steels near the eutectic trough during laser welding were investigated. Thereby, the main aspect was the evaluation of a short-term metallurgical kinetic effects under rapid solidification conditions. It was proven that three widely used stainless steels (1.4828, 1.4306, and 1.4404) show a transition of primary solidifcation mode from primary ferritic to primary austenitic solidification depending on the solidification rate. The approximate value of the critical soldification rate can be determined using a newly developed model by analyzing the geometric structures of solidification. The critical solidification rate for the transition of the solidification mode depends on the chemical composition of the base metal. It was shown that austenitic stainless steels have a critical solidification rate of approximately 1 m/min. As a main result, it was proven that a transition of the solidification mode to primary austenitic solidification promotes the predicted susceptibiliyy of hot cracking. For this, a hot cracking test assembly has been developed in order to determine the hot cracking behavior under laser beam conditions. In contrast to existing hot crack tests, a critical strain rate for hot crack initiation could be measured. A classification of the materials with respect to their hot cracking susceptibility under the solidification conditions during laser welding can

  10. Influence of orlistat therapy on serum insulin level and morphological and functional parameters of peripheral arterial circulation in obese patients

    Directory of Open Access Journals (Sweden)

    Hajduković Zoran

    2005-01-01

    Full Text Available Background/Aim. Insulin resistance is related to accelerated atherosclerosis, whereas weight loss is associated with the increasing insulin sensitivity, the improvement of functional and the morphological parameters of arterial circulation, and the reduction of cardiovascular morbidity and mortality. The aim of our study was to evaluate the influence of orlistat treatment on serum insulin level and functional and morphologic parameters of peripheral arterial circulation. Methods. We conducted a prospective, randomized, double − blind, placebo − controlled study. Thirty patients with body mass index over 30 kg/m2 normotensive, nonsmokers, without clinically manifested cardiovascular disease or diabetes were randomly assigned either orlistat (120 mg, 3 times daily; n = 20 or placebo (n = 10 in a double − blind manner. All of the patients were on individually calculated hypocaloric diet. The follow-up period was 24 weeks. Arterial pressure, fasting serum glucose and insulin level, triglycerides, total cholesterol and low density lipoprotein-cholesterol were determined at the beginning, following 3 and 6 months. Also, the intima − media thickness of right superficial femoral artery and the mean blood flow velocity were determined with ultrasonography. Results. Inside the period of 3 and 6 months, there were the greater reductions of body mass index, arterial pressure, fasting glucose and insulin level, total cholesterol, low density lipoproteins, as well as the greater reductions of mean velocity blood flow and peripheral pulse pressure in the orlistat group vs the placebo group (p < 0.01. Greater reductions in the waist circumference and intima − media thickness were registered following 6 months in the orlistat vs the placebo group (p < 0.01. Conclusion. In the group of obese patients orlistat therapy reduced risk factors, serum insulin level and improved early arterial functional changes as assessed with the reductions of the mean

  11. Vascular Endothelial Growth Factor Is Associated with the Morphologic and Functional Parameters in Patients with Hypertrophic Cardiomyopathy

    Directory of Open Access Journals (Sweden)

    Radek Pudil

    2015-01-01

    Full Text Available Background. Hypertrophic cardiomyopathy (HCM is mostly autosomal dominant disease of the myocardium, which is characterized by myocardial hypertrophy. Vascular endothelial growth factor (VEGF is involved in myocyte function, growth, and survival. The aim of study was to analyze the clinical significance of VEGF in structural and functional changes in patient with HCM. Methods. In a group of 21 patients with nonobstructive HCM, we assessed serum VEGF and analyzed its association with morphological and functional parameters. Compared to healthy controls, serum VEGF was increased: 199 (IQR: 120.4–260.8 ng/L versus 20 (IQR: 14.8–37.7 ng/L, P<0.001. VEGF levels were associated with left atrium diameter (r=0.51, P=0.01, left ventricle ejection fraction (r=-0.56, P=0.01, fractional shortening (r=-0.54, P=0.02, left ventricular mass (r=0.61, P=0.03, LV mass index (r=0.46, P=0.04, vena cava inferior diameter (r=0.65, P=0.01, and peak gradient of tricuspid regurgitation (r=0.46, P=0.03. Conclusions. Increased VEGF level is associated with structural and functional parameters in patients with HCM and serves as a potential tool for diagnostic process of these patients.

  12. Effects of nitrogen nutritional stress on the morphological and yield parameters of tomato (Solanum lycopersicumL.)

    Institute of Scientific and Technical Information of China (English)

    Gideon O. Okunlola; Olusanya A. Olatunji; Akinjide M. Afolabi; Kolade K. Gbadegesin

    2015-01-01

    This investigation was carried out to better understand the effects of nitrogen stress on the growth and yield of tomato (Solanum lycopersiconL.). Seeds ofS. lycopersicon (Ife No. 1 variety) were collected from the Osun–State Ministry of Agriculture, Oshogbo, Nigeria and planted in analyzed top soil. The plants were grown for a period of five weeks within which they were supplied with water and kept under optimum environmental conditions that enhanced normal growth. After this period, the plants were subjected to different levels of nitrogen stress which include: plants supplied with dis-tilled water only (n), plants supplied with complete nutrient solution (N), plants supplied with nutrient solution in which nitrogen concentration sources was increased by a factor of 5 (N5), and plants supplied with nutrient solution in which nitrogen concentration sources was increased by a factor of 10 (N10). Analysis of Variance (ANOVA) results shows that there is no significant effect of stress on the growth and morphological parameters of tomato plants. However, there was a significant effect of nitrogen stress on the yield parameters. Nitrogen stress also caused an increase in the number and size of fruits produced in plants subjected with high nitrogen concentration.

  13. A new computational approach to cracks quantification from 2D image analysis: Application to micro-cracks description in rocks

    Science.gov (United States)

    Arena, Alessio; Delle Piane, Claudio; Sarout, Joel

    2014-05-01

    In this paper we propose a crack quantification method based on 2D image analysis. This technique is applied to a gray level Scanning Electron Microscope (SEM) images, segmented and converted in Black and White (B/W) images using the Trainable Segmentation plugin of Fiji. Resulting images are processed using a novel Matlab script composed of three different algorithms: the separation algorithm, the filtering and quantification algorithm and the orientation one. Initially the input image is enhanced via 5 morphological processes. The resulting lattice is “cut” into single cracks using 1 pixel-wide bisector lines originated from every node. Cracks are labeled using the connected-component method, then the script computes geometrical parameters, such as width, length, area, aspect ratio and orientation. A filtering is performed using a user-defined value of aspect ratio, followed by a statistical analysis of remaining cracks. In the last part of this paper we discuss about the efficiency of this script, introducing an example of analysis of two datasets with different dimension and resolution; these analyses are performed using a notebook and a high-end professional desktop solution, in order to simulate different working environments.

  14. DAMAGE MORPHOLOGICAL PARAMETERS

    Directory of Open Access Journals (Sweden)

    Jean-Louis Chermant

    2011-05-01

    Full Text Available This paper shows how it is possible to characterize and quantify the damages in materials using classical tools of automatic image analysis. Examples presented concern ceramic matrix composites, i.e. high tech materials. It gives important information to support the deformation and rupture mechanism of materials under mechanical solicitations.

  15. New and Improved T-wave Morphology Parameters to Differentiate Healthy Individuals from those with Cardiomyopathy and Coronary Artery Disease

    Science.gov (United States)

    Greco, E. C.; Schlegel, T. T.; Arenare, B.; DePalma, J. L.; Starc, V.; Rahman, M. A.; Delgado, R.

    2007-01-01

    We investigated the ability of several known as well as new ECG repolarization parameters to differentiate healthy individuals from patients with obstructive coronary artery disease (CAD) and cardiomyopathy (CM). Advanced high-fidelity 12-lead ECG tests (approx. 5-min supine) were first performed on a "training set" of 99 individuals: 33 with ischemic or dilated CM and low ejection fraction (EF less than 40%); 33 with catheterization-proven obstructive CAD but normal EF; and 33 age-/gender-matched healthy controls. The following multiple parameters of T-wave morphology (TWM) were derived via signal averaging and singular value decomposition (SVD, which yields 8 eigenvalues, rho(sub 1) greater than rho(sub 2)...greater than rho(sub 8) and studied for their retrospective accuracy in detecting underlying disease: 1) Principal component analysis ratio of the T wave (T-PCA) = 100*rho(sub 2)/rho(sub 1); 2) Relative T-wave residuum (rTWR) = 100* SIGMA (rho(sub 4)(sup 2) +...+ rho(sub 8)(sup 2)); 3) Modified complexity ratio of the T wave (T-mCR) = 100*SIGMA(rho(sub 3)(sup 2) +...+rho(sb 8) (sup 2)); and 4) Normalized 3-dimensional volume of the T wave (nTV) = 100*(rho(sub 2)*rho(sub 3)/rho(sub 1)(sup 2). All TWM parameters significantly differentiated CAD from controls (p less than 0.0001), and also CM from controls (p less than 0.0001). Retrospective areas under the ROC curve were 0.77, 0.81, 0.82, and 0.83 (CAD vs. controls) and 0.93, 0.89, 0.95 and 0.96 (CM vs. controls) for T-PCA, rTWR, T-mCR and nTV respectively. The newer TWM parameters (T-mCR and nTV) thus outperformed the more established parameters (T-PCA and rTWR), presumably by putting a greater emphasis on the third T-wave eigenvalue, which in most healthy subjects has little energy compared to the first two eigenvalues. Subsequent prospective analyses have also yielded similar results, such that we conclude that diagnostic differentiation of pathology from non-pathology may be especially aided by detecting

  16. Effect of spirulina food supplement on blood morphological parameters, biochemical composition and on the immune function of sportsmen

    Directory of Open Access Journals (Sweden)

    K Milasius

    2009-07-01

    Full Text Available Of highest biological value are natural concentrates of optimally combined substances produced by nature. One of food supplements of this kind is dietary Spirulina produced by the Tianshi firm (China. It is a most rationally balanced food supplement of a high biological value; it satisfies the needs of the whole body, including its immune system. The aim of the current work was to assess the effect of the multicomponent natural food supplement Spirulina on the physical development, blood morphological, biochemical picture and immune function of sportsmen. Materials and Methods: The study cohort comprised 12 high performance sportsmen (age 20-22 years. They were using tablets of Spirulina, a dietary product for 14 days. Physical development was determined with the aid of standard methods. The general blood picture was analyzed with the aid of a Micros-60 hematological analyzer (company ABX DIAGNOSTICS, France. Lymphocytes and their subsets were analysed by flow cytometery (FACSCalibur, Becton Dickinson Immunocytometry Systems (BDIS, USA and the absolute and percentage values were calculated. To evaluate immune function lymphocyte blasttransformation response to mitogens was studied. Results: Investigations carried out on endurance-training sportsmen showed that a 14-d administration of Spirulina exerted a positive effect on blood morphological composition indices and its biochemical changes. The results of our study confirm the positive effect of Spirulina food supplement on the quantitative parameters of immune system. Part of the study cohort after weeks showed a tendency of normalizing CD3 , CD3 CD4 lympocite count: positive changes were still present two weeks following the interruption of Spirulina intake

  17. Fatigue crack growth detect, assess, avoid

    CERN Document Server

    Richard, Hans Albert

    2016-01-01

    This book offers a concise introduction to fatigue crack growth, based on practical examples. It discusses the essential concepts of fracture mechanics, fatigue crack growth under constant and variable amplitude loading and the determination of the fracture-mechanical material parameters. The book also introduces the analytical and numerical simulation of fatigue crack growth as well as crack initiation. It concludes with a detailed description of several practical case studies and some exercises. The target group includes graduate students, researchers at universities and practicing engineers.

  18. Investigations of Low Temperature Time Dependent Cracking

    Energy Technology Data Exchange (ETDEWEB)

    Van der Sluys, W A; Robitz, E S; Young, B A; Bloom, J

    2002-09-30

    The objective of this project was to investigate metallurgical and mechanical phenomena associated with time dependent cracking of cold bent carbon steel piping at temperatures between 327 C and 360 C. Boiler piping failures have demonstrated that understanding the fundamental metallurgical and mechanical parameters controlling these failures is insufficient to eliminate it from the field. The results of the project consisted of the development of a testing methodology to reproduce low temperature time dependent cracking in laboratory specimens. This methodology was used to evaluate the cracking resistance of candidate heats in order to identify the factors that enhance cracking sensitivity. The resultant data was integrated into current available life prediction tools.

  19. Crack problem in a long cylindrical superconductor

    Science.gov (United States)

    Yong, Hua-Dong; Zhou, You-He; Zeng, Jun

    2008-12-01

    In this work, the general problem of a center crack in a long cylindrical superconductor is studied. The dependence of the stress intensity factor on the parameters, including the crack length and the applied field, is investigated. We presented a simple model in which the effect of the crack on the critical current is taken into account. It is assumed that the crack forms a perfect barrier to the flow of current. The Bean model and the Kim model are considered for the critical state. Based on the complex potential and boundary collocation methods, the stress intensity factor under the magnetic field is obtained for a long cylindrical superconductor containing a central crack. The results show that the crack length and the applied field have significant effects on the fracture behavior of the superconductor.

  20. Numerical Study of Corrosion Crack Opening

    DEFF Research Database (Denmark)

    Thoft-Christensen, Palle; Frandsen, Henrik Lund; Svensson, Staffan

    2008-01-01

    for the corrosion crack opening. Experiments and theoretical analysis by a numerical method, FEM, support that the relation between the reduction of the reinforcement bar diameter due to corrosion and the corresponding increase in crack width for a given time interval, measured on the surface of a concrete specimen...... is proportional. More recently, the constant of proportionality, the so-called crack-corrosion index, has been studied further with respect to its dependence on the diameter of the reinforcement and the concrete cover. In the present paper the above-mentioned work is presented and extended with more realistic 3D......-models of the cracked concrete beam. The crack-corrosion index is evaluated for a variation of different parameters, i.e. bar diameter, concrete cover, crack length and type of corrosion product. This paper is an extended version of a paper by Thoft-Christensen et al. (2005) presented at the IFIP WG 7.5 Conference...

  1. Crack Growth in Concrete Gravity Dams Based on Discrete Crack Method

    Directory of Open Access Journals (Sweden)

    A. R. Lohrasbi

    2008-01-01

    Full Text Available Seepage is the most parameter in water management safety and in stable agricultural. This seepage is passed through the cracks that are present to some degree in hydraulic structures. They may exist as basic defects in the constituent materials or may be induced in construction or during service life. To avoid such failure in concrete dams, safety would be an important factor. Over-design carries heavy penalty in terms of excess weight. So the fracture mechanics theory is a principal necessity of evaluating the stability of such crack propagation. For the process of crack propagation analysis in concrete structures, there are two general models: discrete crack and smeared crack. This study surveys the crack propagation in concrete gravity dams based on discrete crack methods. Moreover, we use a program provided specifically for this purpose.

  2. On Cracking of Charged Anisotropic Polytropes

    CERN Document Server

    Azam, M

    2016-01-01

    Recently in \\cite{34}, the role of electromagnetic field on the cracking of spherical polytropes has been investigated without perturbing charge parameter explicitly. In this study, we have examined the occurrence of cracking of anisotropic spherical polytropes through perturbing parameters like anisotropic pressure, energy density and charge. We consider two different types of polytropes in this study. We discuss the occurrence of cracking in two different ways $(i)$ by perturbing polytropic constant, anisotropy and charge parameter $(ii)$ by perturbing polytropic index, anisotropy and charge parameter for each case. We conclude that cracking appears for a wide range of parameters in both cases. Also, our results are reduced to \\cite{33} in the absence of charge.

  3. Detection of Cracking Levels in Brittle Rocks by Parametric Analysis of the Acoustic Emission Signals

    Science.gov (United States)

    Moradian, Zabihallah; Einstein, Herbert H.; Ballivy, Gerard

    2016-03-01

    Determination of the cracking levels during the crack propagation is one of the key challenges in the field of fracture mechanics of rocks. Acoustic emission (AE) is a technique that has been used to detect cracks as they occur across the specimen. Parametric analysis of AE signals and correlating these parameters (e.g., hits and energy) to stress-strain plots of rocks let us detect cracking levels properly. The number of AE hits is related to the number of cracks, and the AE energy is related to magnitude of the cracking event. For a full understanding of the fracture process in brittle rocks, prismatic specimens of granite containing pre-existing flaws have been tested in uniaxial compression tests, and their cracking process was monitored with both AE and high-speed video imaging. In this paper, the characteristics of the AE parameters and the evolution of cracking sequences are analyzed for every cracking level. Based on micro- and macro-crack damage, a classification of cracking levels is introduced. This classification contains eight stages (1) crack closure, (2) linear elastic deformation, (3) micro-crack initiation (white patch initiation), (4) micro-crack growth (stable crack growth), (5) micro-crack coalescence (macro-crack initiation), (6) macro-crack growth (unstable crack growth), (7) macro-crack coalescence and (8) failure.

  4. CMEs from AR 10365: Morphology and Physical Parameters of the Ejections and of the Associated Current Sheet

    Science.gov (United States)

    Schettino, G.; Poletto, G.; Romoli, M.

    2010-01-01

    We study the evolution and physical parameters of three consecutive coronal mass ejections (CMEs) that occurred at the west limb of the Sun on 2003 June 2 at 00:30, 08:54, 16:08 UT, respectively. The Large Angle and Spectrometric Coronagraph Experiment (LASCO) CME catalog shows that the CMEs entered the C2 field of view with position angles within a 5° interval. This suggests a common origin for the ejections, to be identified with the magnetic system associated with the active region that lies below the CMEs. The close proximity in time and source location of the events prompted us to analyze LASCO white light data and Ultraviolet Coronagraph Spectrometer (UVCS) spectra with the aim of identifying similarities and differences among the three CMEs. It turns out that two of them display the typical three-part structure, while no conclusion can be drawn about the morphology of the third ejection. The CMEs plasma is "cool," i.e., electron temperatures in the CMEs front are of the order of 2 × 105 K, with no significant variation between different events. However, ejection speeds vary by a factor of ~1.5 between consecutive events and electron densities (more precisely emission measures) by a factor of ~6 between the first CME and the second and third CMEs. In the aftermath of all events, we found evidence of current sheets (CSs) both in LASCO and UVCS. We give here the CS physical parameters (electron temperature, density, and kinetic temperature) and follow, in one of the events, their temporal evolution over a 6 hr time interval. A discussion of our results, in the framework of previous findings, concludes the paper.

  5. Study on the applicability of structural and morphological parameters of selected uranium compounds for nuclear forensic purposes

    Energy Technology Data Exchange (ETDEWEB)

    Ho Mer Lin, Doris

    2015-03-13

    Nuclear forensic science or nuclear forensics, is a relatively young discipline which evolved due to the need of analysing interdicted nuclear or radioactive material, necessary for determining its origin. Fundamentally, nuclear forensic science makes use of measurable material properties, referred to as ''signatures'', which provide hints on the history of the material. As part of the advancement in this multi-faceted field, new signatures are constantly sought after and as well as analytical techniques to efficiently and accurately determine the signatures. The work carried out in this study is part of this fulfilment to investigate new structural and morphological parameters as possible new nuclear forensic signatures for selected uranium compounds. The scientific goals have been oriented into three parts for investigations in this study. Firstly, five different compositions of uranium ore concentrates (UOCs) were prepared in the laboratory under well-defined conditions. These materials were subsequently characterized by several techniques such as X-ray diffraction, thermogravimetry/differential thermal analysis, Infrared and Raman spectroscopy, mass spectrometry, scanning electron microscopy etc. Such materials were pivotal for comparison with the industrial samples. Secondly, several uranium compounds, mainly UOCs were measured using Raman spectroscopy. At least three different Raman spectrometers were used and a comparison made in their performance and suitability for nuclear forensics. Raman spectra of industrial uranium materials were interpreted with regard to compound identification and to determination of (anionic) impurities. Anionic impurities that were present were identified and they could provide clues to the processing history of the samples. Statistical techniques such as principal component analysis (PCA) and partial least square-discriminant analysis (PLS-DA) were applied to several Raman spectra. The analysis showed that

  6. Crack initiation and propagation behavior of WC particles reinforced Fe-based metal matrix composite produced by laser melting deposition

    Science.gov (United States)

    Wang, Jiandong; Li, Liqun; Tao, Wang

    2016-08-01

    It is generally believed that cracks in metal matrix composites (MMC) parts manufacturing are crucial to the reliable material properties, especially for the reinforcement particles with high volume fraction. In this paper, WC particles (WCp) reinforced Fe-based metal matrix composites (WCp/Fe) were manufactured by laser melting deposition (LMD) technology to investigate the characteristics of cracks formation. The section morphology of composites were analyzed by optical microscope (OM), and microstructure of WCp, matrix and interface were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), in order to study the crack initiation and propagation behavior under different laser process conditions. The temperature of materials during the laser melting deposition was detected by the infrared thermometer. The results showed that the cracks often appeared after five layers laser deposition in this experiment. The cracks crossed through WC particles rather than the interface, so the strength of interface obtained by the LMD was relatively large. When the thermal stress induced by high temperature gradient during LMD and the coefficient of thermal expansion mismatch between WC and matrix was larger than yield strength of WC, the cracks would initiate inside WC particle. Cracks mostly propagated along the eutectic phases whose brittleness was very large. The obtained thin interface was beneficial to transmitting the stress from particle to matrix. The influence of volume fraction of particles, laser power and scanning speed on cracks were investigated. This paper investigated the influence of WC particles size on cracks systematically, and the smallest size of cracked WC in different laser processing parameters was also researched.

  7. Anodization parameters influencing the morphology and electrical properties of TiO2 nanotubes for living cell interfacing and investigations.

    Science.gov (United States)

    Khudhair, D; Bhatti, A; Li, Y; Hamedani, H Amani; Garmestani, H; Hodgson, P; Nahavandi, S

    2016-02-01

    Nanotube structures have attracted tremendous attention in recent years in many applications. Among such nanotube structures, titania nanotubes (TiO2) have received paramount attention in the medical domain due to their unique properties, represented by high corrosion resistance, good mechanical properties, high specific surface area, as well as great cell proliferation, adhesion and mineralization. Although lot of research has been reported in developing optimized titanium nanotube structures for different medical applications, however there is a lack of unified literature source that could provide information about the key parameters and experimental conditions required to develop such optimized structure. This paper addresses this gap, by focussing on the fabrication of TiO2 nanotubes through anodization process on both pure titanium and titanium alloys substrates to exploit the biocompatibility and electrical conductivity aspects, critical factors for many medical applications from implants to in-vivo and in-vitro living cell studies. It is shown that the morphology of TiO2 directly impacts the biocompatibility aspects of the titanium in terms of cell proliferation, adhesion and mineralization. Similarly, TiO2 nanotube wall thickness of 30-40nm has shown to exhibit improved electrical behaviour, a critical factor in brain mapping and behaviour investigations if such nanotubes are employed as micro-nano-electrodes.

  8. VALIDATION OF CRACK INTERACTION LIMIT MODEL FOR PARALLEL EDGE CRACKS USING TWO-DIMENSIONAL FINITE ELEMENT ANALYSIS

    Directory of Open Access Journals (Sweden)

    R. Daud

    2013-06-01

    Full Text Available Shielding interaction effects of two parallel edge cracks in finite thickness plates subjected to remote tension load is analyzed using a developed finite element analysis program. In the present study, the crack interaction limit is evaluated based on the fitness of service (FFS code, and focus is given to the weak crack interaction region as the crack interval exceeds the length of cracks (b > a. Crack interaction factors are evaluated based on stress intensity factors (SIFs for Mode I SIFs using a displacement extrapolation technique. Parametric studies involved a wide range of crack-to-width (0.05 ≤ a/W ≤ 0.5 and crack interval ratios (b/a > 1. For validation, crack interaction factors are compared with single edge crack SIFs as a state of zero interaction. Within the considered range of parameters, the proposed numerical evaluation used to predict the crack interaction factor reduces the error of existing analytical solution from 1.92% to 0.97% at higher a/W. In reference to FFS codes, the small discrepancy in the prediction of the crack interaction factor validates the reliability of the numerical model to predict crack interaction limits under shielding interaction effects. In conclusion, the numerical model gave a successful prediction in estimating the crack interaction limit, which can be used as a reference for the shielding orientation of other cracks.

  9. Phase-field study of grain boundary tracking behavior in crack-seal microstructures

    CERN Document Server

    Ankit, Kumar; Selzer, Michael; Reichardt, Mathias

    2012-01-01

    In order to address the vein-growth problem in geology, a multi-phase-field model is used to capture the dynamics of crystals precipitating from a super-saturated solution. To gain a complete understanding, we investigate the influence of various boundary conditions on crystal growth (free-growth and crack-sealing) that result in formation of vein microstructures. To begin with, we consider the anisotropy in surface energy to simulate crystals (with flat facets and sharp corners) possessing different orientations and study the resulting growth competition to deduce a consistent orientation selection rule in the free-growth regime. Next, from crack-sealing simulations, we co-relate the grain boundary tracking behavior and the relative rates of crack opening and trajectory, initial grain size and wall roughness. Further, we illustrate how these parameters induce the microstructural transition between blocky (crystals growing anisotropically) to fibrous morphology (isotropic) and formation of grain boundaries. T...

  10. Catalytic cracking of lignites

    Energy Technology Data Exchange (ETDEWEB)

    Seitz, M.; Nowak, S.; Naegler, T.; Zimmermann, J. [Hochschule Merseburg (Germany); Welscher, J.; Schwieger, W. [Erlangen-Nuernberg Univ. (Germany); Hahn, T. [Halle-Wittenberg Univ., Halle (Germany)

    2013-11-01

    A most important factor for the chemical industry is the availability of cheap raw materials. As the oil price of crude oil is rising alternative feedstocks like coal are coming into focus. This work, the catalytic cracking of lignite is part of the alliance ibi (innovative Braunkohlenintegration) to use lignite as a raw material to produce chemicals. With this new one step process without an input of external hydrogen, mostly propylene, butenes and aromatics and char are formed. The product yield depends on manifold process parameters. The use of acid catalysts (zeolites like MFI) shows the highest amount of the desired products. Hydrogen rich lignites with a molar H/C ratio of > 1 are to be favoured. Due to primary cracking and secondary reactions the ratio between catalyst and lignite, temperature and residence time are the most important parameter to control the product distribution. Experiments at 500 C in a discontinuous rotary kiln reactor show yields up to 32 wt-% of hydrocarbons per lignite (maf - moisture and ash free) and 43 wt-% char, which can be gasified. Particularly, the yields of propylene and butenes as main products can be enhanced four times to about 8 wt-% by the use of catalysts while the tar yield decreases. In order to develop this innovative process catalyst systems fixed on beads were developed for an easy separation and regeneration of the used catalyst from the formed char. (orig.)

  11. Gear Crack Propagation Investigation

    Science.gov (United States)

    1995-01-01

    Reduced weight is a major design goal in aircraft power transmissions. Some gear designs incorporate thin rims to help meet this goal. Thin rims, however, may lead to bending fatigue cracks. These cracks may propagate through a gear tooth or into the gear rim. A crack that propagates through a tooth would probably not be catastrophic, and ample warning of a failure could be possible. On the other hand, a crack that propagates through the rim would be catastrophic. Such cracks could lead to disengagement of a rotor or propeller from an engine, loss of an aircraft, and fatalities. To help create and validate tools for the gear designer, the NASA Lewis Research Center performed in-house analytical and experimental studies to investigate the effect of rim thickness on gear-tooth crack propagation. Our goal was to determine whether cracks grew through gear teeth (benign failure mode) or through gear rims (catastrophic failure mode) for various rim thicknesses. In addition, we investigated the effect of rim thickness on crack propagation life. A finite-element-based computer program simulated gear-tooth crack propagation. The analysis used principles of linear elastic fracture mechanics, and quarter-point, triangular elements were used at the crack tip to represent the stress singularity. The program had an automated crack propagation option in which cracks were grown numerically via an automated remeshing scheme. Crack-tip stress-intensity factors were estimated to determine crack-propagation direction. Also, various fatigue crack growth models were used to estimate crack-propagation life. Experiments were performed in Lewis' Spur Gear Fatigue Rig to validate predicted crack propagation results. Gears with various backup ratios were tested to validate crack-path predictions. Also, test gears were installed with special crack-propagation gages in the tooth fillet region to measure bending-fatigue crack growth. From both predictions and tests, gears with backup ratios

  12. Morphology and parameters of crystallization the blend PE/Epoxy/PE-co-PEG; Morfologia e parametros de cristalizacao da blenda PE/epoxi/PE-co-PEG

    Energy Technology Data Exchange (ETDEWEB)

    Becker, Daniela; Coelho, Luiz Antonio Ferreira; Nack, Fernanda; Silva, Bruna Louise, E-mail: dep2db@joinville.udesc.br [Universidade do Estado de Santa Catarina (UDESC), Joinville, SC (Brazil). Centro de Ciencias Tecnologicas

    2014-07-01

    This study aims to evaluate the morphology and crystallization parameters of high density polyethylene (HDPE) with different concentrations of epoxy (DGEBA / OTBG), and the compatibility of this system was used and the copolymer polyethylene-block-poly (ethylene glycol) (PEG-co-PE). The blends were obtained by mechanical mixing on a torque rheometer (Haake). Determined the crystallization parameters of the test matrix differential scanning calorimetry (DSC) and by X-ray diffraction (XRD). The morphology of the system was analyzed by transmission electron microscopy (TEM). It was observed by XRD analysis that the addition of compatibilizer and epoxy resins do not interfere with the crystal structure of HDPE, indicating that the increase in crystallinity associated with the crystallization kinetics. It was observed that the compatibilizing helped the adhesion, reducing the size of the dispersed phase becomes a more stable morphology and obtaining a distribution of the dispersed epoxy phase. (author)

  13. Automatic quantification of crack patterns by image processing

    Science.gov (United States)

    Liu, Chun; Tang, Chao-Sheng; Shi, Bin; Suo, Wen-Bin

    2013-08-01

    Image processing technologies are proposed to quantify crack patterns. On the basis of the technologies, a software "Crack Image Analysis System" (CIAS) has been developed. An image of soil crack network is used as an example to illustrate the image processing technologies and the operations of the CIAS. The quantification of the crack image involves the following three steps: image segmentation, crack identification and measurement. First, the image is converted to a binary image using a cluster analysis method; noise in the binary image is removed; and crack spaces are fused. Then, the medial axis of the crack network is extracted from the binary image, with which nodes and crack segments can be identified. Finally, various geometric parameters of the crack network can be calculated automatically, such as node number, crack number, clod area, clod perimeter, crack area, width, length, and direction. The thresholds used in the operations are specified by cluster analysis and other innovative methods. As a result, the objects (nodes, cracks and clods) in the crack network can be quantified automatically. The software may be used to study the generation and development of soil crack patterns and rock fractures.

  14. Effect of monochromatic and combined light colour on performance, blood parameters, ovarian morphology and reproductive hormones in laying hens

    Directory of Open Access Journals (Sweden)

    Md. Rakibul Hassan

    2013-07-01

    Full Text Available We evaluated the effect of monochromatic and combined light emitting diode (LED light colour on performance, ovarian morphology, and reproductive hormone and biochemical blood parameters in laying hens. A total of 600 Hy-line Brown pullets, 12 weeks of age, were divided (25×4×6 = birds × replications × treatments as follows: red (R, green (G, blue (B, and combinations of R→G and R→G→B treatments. Fluorescent white light (W was the control. The results showed that higher egg production was found under the monochromatic R and combination R→G treatments, and that heavier eggs were laid by the B and G treatments (P<0.05. Consequently, better feed conversion ratio was attained in the R→G treatment. Serum follicle stimulating hormone and 17β-estradiol levels were significantly higher in the R and R→G treatments. B treated birds came into production 15 days later than those treated with R light. Organ weight (ovary and stroma and ovarian follicle numbers (1-3 and 4-6 mm were significantly higher in R treated birds, as well as serum glucose and triglyceride contents. Serum IgG concentrations and the heterophil to lymphocyte ratio were not influenced by light colour. In these laying hens, 14 h R with 2 h G light in the later part of the day increased reproductive hormone levels, ovarian weight, and follicle number and hence increased egg production. Thus, these results suggest that a combination of R→G light may be comparable with monochromatic R light to enhance egg production in laying hens.

  15. Effects of crack depth and specimen size on ductile crack growth of SENT and SENB specimens for fracture mechanics evaluation of pipeline steels

    Energy Technology Data Exchange (ETDEWEB)

    Xu, J. [Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Richard Birkelands vei 1a, N-7491 Trondheim (Norway); School of Materials Science and Engineering, University of Science and Technology Beijing (USTB), 100083 Beijing (China); Zhang, Z.L., E-mail: zhiliang.zhang@ntnu.n [Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Richard Birkelands vei 1a, N-7491 Trondheim (Norway); Ostby, E.; Nyhus, B. [SINTEF, Materials and Chemistry, N-7465 Trondheim (Norway); Sun, D.B. [School of Materials Science and Engineering, University of Science and Technology Beijing (USTB), 100083 Beijing (China)

    2009-12-15

    A strong geometry dependence of ductile crack growth resistance emerges under large scale yielding. The geometry dependence is associated with different levels of crack tip constraint conditions. However, in a recent attempt to identify appropriate fracture mechanics specimens for pipeline steels, an 'independent' relationship between the crack growth resistance curves and crack depths for SENT specimens has been observed experimentally. In this paper, we use the complete Gurson model to study the effects of crack depth and specimen size on ductile crack growth behavior. Crack growth resistance curves for plane strain, mode I crack growth under large scale yielding conditions have been computed. SENB and SENT specimens with three different specimen sizes, each specimen size with three different crack depths, have been selected. It has been found that crack tip constraint (Q-parameter) has a weak dependence on the crack depth for specimens in the low constraint regime.

  16. Identification of cracks in thick beams with a cracked beam element model

    Science.gov (United States)

    Hou, Chuanchuan; Lu, Yong

    2016-12-01

    The effect of a crack on the vibration of a beam is a classical problem, and various models have been proposed, ranging from the basic stiffness reduction method to the more sophisticated model involving formulation based on the additional flexibility due to a crack. However, in the damage identification or finite element model updating applications, it is still common practice to employ a simple stiffness reduction factor to represent a crack in the identification process, whereas the use of a more realistic crack model is rather limited. In this paper, the issues with the simple stiffness reduction method, particularly concerning thick beams, are highlighted along with a review of several other crack models. A robust finite element model updating procedure is then presented for the detection of cracks in beams. The description of the crack parameters is based on the cracked beam flexibility formulated by means of the fracture mechanics, and it takes into consideration of shear deformation and coupling between translational and longitudinal vibrations, and thus is particularly suitable for thick beams. The identification procedure employs a global searching technique using Genetic Algorithms, and there is no restriction on the location, severity and the number of cracks to be identified. The procedure is verified to yield satisfactory identification for practically any configurations of cracks in a beam.

  17. Probabilistic analysis of linear elastic cracked structures

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    This paper presents a probabilistic methodology for linear fracture mechanics analysis of cracked structures. The main focus is on probabilistic aspect related to the nature of crack in material. The methodology involves finite element analysis; statistical models for uncertainty in material properties, crack size, fracture toughness and loads; and standard reliability methods for evaluating probabilistic characteristics of linear elastic fracture parameter. The uncertainty in the crack size can have a significant effect on the probability of failure, particularly when the crack size has a large coefficient of variation. Numerical example is presented to show that probabilistic methodology based on Monte Carlo simulation provides accurate estimates of failure probability for use in linear elastic fracture mechanics.

  18. Strain rate effects in stress corrosion cracking

    Energy Technology Data Exchange (ETDEWEB)

    Parkins, R.N. (Newcastle upon Tyne Univ. (UK). Dept. of Metallurgy and Engineering Materials)

    1990-03-01

    Slow strain rate testing (SSRT) was initially developed as a rapid, ad hoc laboratory method for assessing the propensity for metals an environments to promote stress corrosion cracking. It is now clear, however, that there are good theoretical reasons why strain rate, as opposed to stress per se, will often be the controlling parameter in determining whether or not cracks are nucleated and, if so, are propagated. The synergistic effects of the time dependence of corrosion-related reactions and microplastic strain provide the basis for mechanistic understanding of stress corrosion cracking in high-pressure pipelines and other structures. However, while this may be readily comprehended in the context of laboratory slow strain tests, its extension to service situations may be less apparent. Laboratory work involving realistic stressing conditions, including low-frequency cyclic loading, shows that strain or creep rates give good correlation with thresholds for cracking and with crack growth kinetics.

  19. Acoustic emission assessment of interface cracking in thermal barrier coatings

    Science.gov (United States)

    Yang, Li; Zhong, Zhi-Chun; Zhou, Yi-Chun; Zhu, Wang; Zhang, Zhi-Biao; Cai, Can-Ying; Lu, Chun-Sheng

    2016-04-01

    In this paper, acoustic emission (AE) and digital image correlation methods were applied to monitor interface cracking in thermal barrier coatings under compression. The interface failure process can be identified via its AE features, including buckling, delamination incubation and spallation. According to the Fourier transformation of AE signals, there are four different failure modes: surface vertical cracks, opening and sliding interface cracks, and substrate deformation. The characteristic frequency of AE signals from surface vertical cracks is 0.21 MHz, whilst that of the two types of interface cracks are 0.43 and 0.29 MHz, respectively. The energy released of the two types of interface cracks are 0.43 and 0.29 MHz, respectively. Based on the energy released from cracking and the AE signals, a relationship is established between the interface crack length and AE parameters, which is in good agreement with experimental results.

  20. A Parametric Study of Crack Propagation During Sonic IR Inspection

    Science.gov (United States)

    Chen, J. C.; Kephart, J.; Riddell, W. T.

    2006-03-01

    We have developed an experiment to study the propagation of synthetic cracks under various controlled conditions during sonic IR inspection. The experiment provides for good repeatability in testing. The parameters of interest include the initial crack length, load history (stress intensity and load ratio) during crack generation, geometry of the crack, material, and also the various conditions involving the ultrasonic source. In general, we find that under typical sonic IR inspection conditions, the initial crack will propagate when subjected to sonic IR testing. The crack growth after each inspection event varies and exhibits a distribution in length of propagation. The results show that the average crack propagation decreases with increasing initial crack length and increasing stress intensity.

  1. Modified Dugdale cracks and Fictitious cracks

    DEFF Research Database (Denmark)

    Nielsen, Lauge Fuglsang

    1998-01-01

    (displacement) respectively of material considered. The practical applicability of the two models is limited such that predicted strength sigma_CR must be less than sigma_L/3, which corresponds to an assumption that fictitious cracks are much smaller than real crack lengths considered. The reason......A number of theories are presented in the literature on crack mechanics by which the strength of damaged materials can be predicted. Among these are theories based on the well-known Dugdale model of a crack prevented from spreading by self-created constant cohesive flow stressed acting in local...... Dugdale crack is the same as if it has been weakened by the well-known Griffith crack, namely sigma_CR = (EG_CR/phi)^1/2 where E and 1 are Young's modulus and crack half-length respectively, and G_CR is the so-called critical energy release rate. The physical significance of G_CR, however, is different...

  2. Uncertainty Quantification in Fatigue Crack Growth Prognosis

    Directory of Open Access Journals (Sweden)

    Shankar Sankararaman

    2011-01-01

    Full Text Available This paper presents a methodology to quantify the uncertainty in fatigue crack growth prognosis, applied to structures with complicated geometry and subjected to variable amplitude multi-axial loading. Finite element analysis is used to address the complicated geometry and calculate the stress intensity factors. Multi-modal stress intensity factors due to multi-axial loading are combined to calculate an equivalent stress intensity factor using a characteristic plane approach. Crack growth under variable amplitude loading is modeled using a modified Paris law that includes retardation effects. During cycle-by-cycle integration of the crack growth law, a Gaussian process surrogate model is used to replace the expensive finite element analysis. The effect of different types of uncertainty – physical variability, data uncertainty and modeling errors – on crack growth prediction is investigated. The various sources of uncertainty include, but not limited to, variability in loading conditions, material parameters, experimental data, model uncertainty, etc. Three different types of modeling errors – crack growth model error, discretization error and surrogate model error – are included in analysis. The different types of uncertainty are incorporated into the crack growth prediction methodology to predict the probability distribution of crack size as a function of number of load cycles. The proposed method is illustrated using an application problem, surface cracking in a cylindrical structure.

  3. Cracks Detection Using Active Modal Damping and Piezoelectric Components

    Directory of Open Access Journals (Sweden)

    B. Chomette

    2013-01-01

    Full Text Available The dynamics of a system and its safety can be considerably affected by the presence of cracks. Health monitoring strategies attract so a great deal of interest from industry. Cracks detection methods based on modal parameters variation are particularly efficient in the case of large cracks but are difficult to implement in the case of small cracks due to measurement difficulties in the case of small parameters variation. Therefore the present study proposes a new method to detect small cracks based on active modal damping and piezoelectric components. This method uses the active damping variation identificated with the Rational Fraction Polynomial algorithm as an indicator of cracks detection. The efficiency of the proposed method is demonstrated through numerical simulations corresponding to different crack depth and locations in the case of a finite element model of a clamped-clamped beam including four piezoelectric transducers.

  4. Modeling Delamination of Interfacial Corner Cracks in Multilayered Structures

    DEFF Research Database (Denmark)

    Veluri, Badrinath (Badri); Jensen, Henrik Myhre

    2013-01-01

    for steady-state propagation has been developed. The crack propagation is investigated by estimating the fracture mechanics parameters that include the strain energy release rate, crack front profiles and the three-dimensional mode-mixity along the crack front. The developed numerical approach...... for the calculation of fracture mechanical properties has been validated with threedimensional models for varying crack front shapes. A custom quantitative approach was formulated based on the finite element method with iterative adjustment of the crack front to estimate the critical delaminatio stress as a function...

  5. Mitigation strategies for autogenous shrinkage cracking

    DEFF Research Database (Denmark)

    Bentz, Dale P.; Jensen, Ole Mejlhede

    2004-01-01

    , the fundamental parameters contributing to the autogenous shrinkage and resultant early-age cracking of concrete are presented. Basic characteristics of the cement paste that contribute to or control the autogenous shrinkage response include the surface tension of the pore solution, the geometry of the pore...... of early-age cracking due to autogenous shrinkage. Mitigation strategies discussed in this paper include: the addition of shrinkage-reducing admixtures more commonly used to control drying shrinkage, control of the cement particle size distribution, modification of the mineralogical composition......, it should be possible to minimize cracking due to autogenous shrinkage via some combination of the presented approaches....

  6. Impact of dielectric parameters on the reflectivity of 3C–SiC wafers with a rough surface morphology in the reststrahlen region

    Energy Technology Data Exchange (ETDEWEB)

    Engelbrecht, J.A.A., E-mail: Japie.Engelbrecht@nmmu.ac.za [Physics Department, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031 (South Africa); Janzén, E.; Henry, A. [Department of Physics, Chemistry and Biology, Linköping University, SE-581 83 Linköping (Sweden); Rooyen, I.J. van [Fuel Performance and Design Department, Idaho National Laboratory, PO Box 1625, Idaho Falls, ID 83415-6188 (United States)

    2014-04-15

    A layer-on-substrate model is used to obtain the infrared reflectance for 3C–SiC with a rough surface morphology. The effect of varying dielectric parameters of the “damaged layer” on the observed reflectivity of the 3C–SiC in the reststrahlen region is assessed. Different simulated reflectance spectra are obtained to those if the dielectric parameters of the “substrate” were varied. Most notable changes in the shape of the simulated reststrahlen peak are observed for changes in the high frequency dielectric constant, the phonon damping constant, the phonon frequencies and “thickness” of damaged surface layer.

  7. Crack growth time dependence analysis of granite under compressive-shear stresses state

    Institute of Scientific and Technical Information of China (English)

    LI Jiang-teng; CAO Ping; Gu De-sheng; Wu Chao

    2008-01-01

    The curves of crack relative length //b and crack growth time t of granite were gained under compressive stresses state according to subcritical crack growth parameters and crack stability growth equation by double-torsion constant displacement load relaxa-tion method. The relations between crack relative length and the crack growth time were discussed under different stresses and different crack lengths. The results show that there is a turning point on curve of crack relative length //b and crack growth time of granite. The slope of curve is small when crack relative length is less than the vertical coordinate of the point, and crack grows stably in this case. Cracks grow, encounter and integrate catastro-phically when crack relative length is more than the vertical coordinate of the point, and there is not a gradual stage from crack stability growth to crack instability growth, i.e. rock mass instability is sudden. The curves of crack relative length //b and crack growth time t of granite move to right with decrease of stress σ1 or crack length a, which implies that limit time increases consequently. The results correspond to practicality.

  8. Burst pressure predictions of pipelines with longitudinal cracks

    Energy Technology Data Exchange (ETDEWEB)

    Dotta, Fernando; Riggieri, Claudio [Sao Paulo Univ., SP (Brazil). Dept. de Engenharia Naval e Oceanica

    2003-07-01

    This study extends a micro mechanics approach based upon the computational cell methodology to model ductile crack extension of longitudinal crack-like defects in a high strength pipeline steel. Laboratory testing of an API 5L X60 steel at room temperature using standard, deep crack C(T) specimens provides the data needed to measure the crack growth resistance curve for the material. In the computational cell model, ductile crack extension occurs through void growth and coalescence (by cell extinction) within a thin layer of material ahead of crack tip. A simple scheme to calibrate material-specific parameters for the cells is also described. A central focus of the paper is the application of the cell methodology to predict experimentally measured burst pressures for pre-cracked pipe specimens with different crack sizes. The experimental program includes longitudinally pre cracked 20'' (508 mm) O.D. pipe specimens with 15.8 mm thickness and varying crack geometries. Plane-strain computations are conducted on detailed finite element models for the pipe specimens to describe crack extension with increased pressure. The numerical simulations demonstrate the effectiveness of the cell approach to describe crack growth response and to predict the burst pressure for the tested pipes. (author)

  9. Investigation of parameters highlighting drug induced small changes of the T-wave's morphology for drug safety studies.

    Science.gov (United States)

    Baas, Tobias; Gräfe, Ksenija; Khawaja, Antoun; Dössel, Olaf

    2011-01-01

    In guideline E14, the American Food and Drug Administration (FDA) requests for clinical studies to investigate the prolongation of the heart rate corrected QT-interval (QTc) of the ECG. As drug induced QT-prolongation can be caused by changes in the repolarisation of the ventricles, it is so far a thorough ECG biomarker of risk for ventricular tachyarrhythmias and Torsade de Pointes (TdP). Ventricular repolarisation changes not only change QT but also influence the morphology of the T-wave. In a (400 mg single dose) Moxifloxacin positive control study both, QTc and several descriptors describing the T-wave morphology have been measured. Moxifloxacin is changing two shape dependent descriptors significantly (P<0.05) about 3 to 4 hours after a 400 mg oral single dose of Moxifloxacin.

  10. Effect of high shear mixing parameters and degassing temperature on the morphology of epoxy-clay nanocomposites

    KAUST Repository

    Al-Qadhi, Muneer

    2013-01-01

    Epoxy-clay nanocomposites were prepared by high shear mixing method using Nanomer I.30E nanoclay as nano-reinforcement in diglycidyl ether of bisphenol A (DGEBA). The effect of mixing speed and time on the nature and degree of clay dispersion were investigated by varying the mixing speed in the range of 500-8000 RPM and mixing time in the range of 15-90 minutes. The effect of degassing temperature on the morphology of the resultant nanocomposites was also studied. Scanning and transmission microscopy (SEM and TEM) along with x-ray diffraction (XRD) have been used to characterize the effect of shear mixing speed, mixing time and degassing temperature on the structure of the resultant nanocomposites. The SEM, TEM and XRD examinations demonstrated that the degree of clay dispersion was improved with increasing the high shear mixing speed and mixing time. The results showed that the optimum high shear mixing speed and mixing time were 6000 rpm and 60 min, respectively. It was observed that the structure of the nanocomposites that have been degassed at 65°C was dominated by ordered intercalated morphology while disordered intercalated with some exfoliated morphology was found for the sample degassed at 100°C for the first 2 hours of the degassing process. © (2013) Trans Tech Publications, Switzerland.

  11. Impact of growth parameters on the morphology and microstructure of epitaxial GaAs nanowires grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Z.Y. [National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yu Tian Road, Shanghai 200083 (China); Chen, P.P., E-mail: ppchen@mail.sitp.ac.cn [National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yu Tian Road, Shanghai 200083 (China); Liao, Z.M. [Materials Engineering, University of Queensland, St. Lucia, QLD 4072 (Australia); Shi, S.X.; Sun, Y.; Li, T.X.; Zhang, Y.H. [National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yu Tian Road, Shanghai 200083 (China); Zou, J. [Materials Engineering, University of Queensland, St. Lucia, QLD 4072 (Australia); Center for Microscopy and Microanalysis, University of Queensland, St. Lucia, QLD 4072 (Australia); Lu, W. [National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yu Tian Road, Shanghai 200083 (China)

    2013-12-15

    Highlights: •Defect-free wurtzite GaAs nanowires were obtained by MBE at low growth temperature. •Some GaAs nanowires grown at low temperature show the morphology of two shoulders. •High growth temperature favors the formation of nanowires with uniform diameter. •Low V/III flux ratio causes many kinked GaAs nanowires. •A phase separation of the catalyst is observed under very Ga-rich condition. -- Abstract: The effect of the growth temperature and V/III flux ratio on the morphology and microstructure of GaAs nanowires grown on GaAs (1 1 1){sub B} substrates by Au-assisted molecular beam epitaxy with solid As{sub 4} source was investigated. It has been found that a low growth temperature of 400 °C can result in defect-free wurtzite structured nanowire with syringe-like morphology, while nanowires with more homogeneous diameter can be obtained at high temperatures (500 °C and 550 °C) with many stacking faults. It was also found that, at a low V/III flux ratio, GaAs nanowires had a shrinking neck section, while a high V/III flux ratio may result in disappearance of the shrinking necking section. For the Ga very rich condition, a phase separation of the catalysts can be observed, leaving a small Au–Ga droplet covered by the outer pure Ga droplet.

  12. Hydrogen cracking and stress corrosion of pipeline steels. Contribution of the cracking mechanisms study to the understanding of the in-service damage and to the definition of a ranking test; Fissuration assistee par l'hydrogene et corrosion sous contrainte des aciers de pipelines. Apports de l'etude des mecanismes de fissuration a la comprehension de l'endommagement de service et a la definition d'un test de classification

    Energy Technology Data Exchange (ETDEWEB)

    Le Friant, D.

    2000-12-19

    This work is based on the study of the cracking of a French oil transmission pipeline protected by a cathodic protection system. The objective is to identify field parameters, which contribute to the cracks propagation, and to assess changes in the operating conditions, which could lead to a mitigation of the phenomenon. We have focused on the study of the micro-mechanisms by means of slow strain rate tests. Then, cyclic loading tests were carried out to investigate cracks propagation mechanisms. Smooth and pre-notched specimens were tested at free and cathodic potential. Hydrogen is responsible for crack advance through changes in the local steels properties. Such effects take place when two phenomenons occur: favourable conditions for hydrogen entry and, a localisation of hydrogen and its effects. In particular, we have shown the essential role of a dynamic loading in promoting hydrogen entry into the steel (especially at the very crack tip). At cathodic potential, hydrogen-related effects are exacerbated by the presence of MnS inclusions which leads to the initiation of internal cracks (HIC) and to a SOHIC-like crack morphology. At free potential, the lesser amount of available hydrogen give localisation-related effects a greater importance. Cracking is then related to a hydrogen-induced SCC mechanism. Three parameters are involved in the field cracking: operating pressure variations, period of over-protection and a sensitive steels microstructure (MnS). Cathodic protection appears to be the most efficient field parameter to mitigate the phenomenon: it requires a better control of the polarisation level. Finally, a ranking test is outlined from the study of the cracking mechanisms. (author)

  13. The Effects of Agave fourcroydes Powder as a Dietary Supplement on Growth Performance, Gut Morphology, Concentration of IgG, and Hematology Parameters in Broiler Rabbits

    Science.gov (United States)

    Iser, Maidelys; Martínez, Yordan; Jiang, Hongmei; Valdivié Navarro, Manuel; Wu, Xiaosong; Al-Dhabi, Naif Abdullah; Rosales, Manuel; Duraipandiyan, Veeramuthu

    2016-01-01

    This study was conducted to determine the effects of Agave fourcroydes powder as a dietary supplement on the growth performance, gut morphology, serum concentration of IgG, and the hematology parameters of broiler rabbits. A total of 32 rabbits [New Zealand × Californian] were weaned at 35 days. They were randomly selected for two dietary treatments (eight repetitions per treatment), which consisted of a basal diet and a basal diet supplemented with 1.5% dried-stem powder of A. fourcroydes. On day 60 from the initiation of treatment, gut histomorphology (duodenum and cecum), serum concentration of IgG, and hematology parameters were all measured. The results showed that A. fourcroydes powder supplementation improved (P < 0.05) the ADFI, ADG, and final BW. Correspondingly, this treatment increased (P < 0.05) the muscle and mucosa thickness and height and width of villi. However, duodenum crypts depth was lower (P < 0.05) when rabbits were fed with this natural product, compared with the basal diet treatment. Results also indicated that the A. fourcroydes powder increased (P < 0.05) the serum concentration of IgG but did not change the hematology parameters. This data indicates that A. fourcroydes powder, as a supplement, had beneficial effects on increasing the growth performance and serum concentration of IgG, as well as improving the gut morphology without affecting the hematology parameters in broiler rabbits. PMID:27777945

  14. The Effects of Agave fourcroydes Powder as a Dietary Supplement on Growth Performance, Gut Morphology, Concentration of IgG, and Hematology Parameters in Broiler Rabbits.

    Science.gov (United States)

    Iser, Maidelys; Martínez, Yordan; Ni, Hengjia; Jiang, Hongmei; Valdivié Navarro, Manuel; Wu, Xiaosong; Al-Dhabi, Naif Abdullah; Rosales, Manuel; Duraipandiyan, Veeramuthu; Fang, Jun

    2016-01-01

    This study was conducted to determine the effects of Agave fourcroydes powder as a dietary supplement on the growth performance, gut morphology, serum concentration of IgG, and the hematology parameters of broiler rabbits. A total of 32 rabbits [New Zealand × Californian] were weaned at 35 days. They were randomly selected for two dietary treatments (eight repetitions per treatment), which consisted of a basal diet and a basal diet supplemented with 1.5% dried-stem powder of A. fourcroydes. On day 60 from the initiation of treatment, gut histomorphology (duodenum and cecum), serum concentration of IgG, and hematology parameters were all measured. The results showed that A. fourcroydes powder supplementation improved (P < 0.05) the ADFI, ADG, and final BW. Correspondingly, this treatment increased (P < 0.05) the muscle and mucosa thickness and height and width of villi. However, duodenum crypts depth was lower (P < 0.05) when rabbits were fed with this natural product, compared with the basal diet treatment. Results also indicated that the A. fourcroydes powder increased (P < 0.05) the serum concentration of IgG but did not change the hematology parameters. This data indicates that A. fourcroydes powder, as a supplement, had beneficial effects on increasing the growth performance and serum concentration of IgG, as well as improving the gut morphology without affecting the hematology parameters in broiler rabbits.

  15. The Effects of Agave fourcroydes Powder as a Dietary Supplement on Growth Performance, Gut Morphology, Concentration of IgG, and Hematology Parameters in Broiler Rabbits

    Directory of Open Access Journals (Sweden)

    Maidelys Iser

    2016-01-01

    Full Text Available This study was conducted to determine the effects of Agave fourcroydes powder as a dietary supplement on the growth performance, gut morphology, serum concentration of IgG, and the hematology parameters of broiler rabbits. A total of 32 rabbits [New Zealand × Californian] were weaned at 35 days. They were randomly selected for two dietary treatments (eight repetitions per treatment, which consisted of a basal diet and a basal diet supplemented with 1.5% dried-stem powder of A. fourcroydes. On day 60 from the initiation of treatment, gut histomorphology (duodenum and cecum, serum concentration of IgG, and hematology parameters were all measured. The results showed that A. fourcroydes powder supplementation improved (P<0.05 the ADFI, ADG, and final BW. Correspondingly, this treatment increased (P<0.05 the muscle and mucosa thickness and height and width of villi. However, duodenum crypts depth was lower (P<0.05 when rabbits were fed with this natural product, compared with the basal diet treatment. Results also indicated that the A. fourcroydes powder increased (P<0.05 the serum concentration of IgG but did not change the hematology parameters. This data indicates that A. fourcroydes powder, as a supplement, had beneficial effects on increasing the growth performance and serum concentration of IgG, as well as improving the gut morphology without affecting the hematology parameters in broiler rabbits.

  16. Effects of Crack on Vibration Characteristics of Mistuned Rotated Blades

    Directory of Open Access Journals (Sweden)

    Hailong Xu

    2017-01-01

    Full Text Available Rotated blades are key mechanical components in turbine and high cycle fatigues often induce blade cracks. Meanwhile, mistuning is inevitable in rotated blades, which often makes it much difficult to detect cracks. In order to solve this problem, it is important and necessary to study effects of crack on vibration characteristics of mistuned rotated blades (MRBs. Firstly, a lumped-parameter model is established based on coupled multiple blades, where mistuned stiffness with normal distribution is introduced. Next, a breathing crack model is adopted and eigenvalue analysis is used in coupled lumped-parameter model. Then, numerical analysis is done and effects of depths and positions of a crack on natural frequency, vibration amplitude, and vibration localization parameters are studied. The results show that a crack causes natural frequency decease and vibration amplitude increase of cracked blade. Bifurcations will occur due to a breathing crack. Furthermore, based on natural frequencies and vibration amplitudes, variational factors are defined to detect a crack in MRBs, which are validated by numerical simulations. Thus, the proposed method provides theoretical guidance for crack detection in MRBs.

  17. Cooling-dominated cracking in thermally stressed volcanic rocks

    Science.gov (United States)

    Browning, John; Meredith, Philip; Gudmundsson, Agust

    2016-08-01

    Most studies of thermally induced cracking in rocks have focused on the generation of cracks formed during heating and thermal expansion. Both the nature and the mechanism of crack formation during cooling are hypothesized to be different from those formed during heating. We present in situ acoustic emission data recorded as a proxy for crack damage evolution in a series of heating and cooling experiments on samples of basalt and dacite. Results show that both the rate and the energy of acoustic emission are consistently much higher during cooling than during heating. Seismic velocity comparisons and crack morphology analysis of our heated and cooled samples support the contemporaneous acoustic emission data and also indicate that thermal cracking is largely isotropic. These new data are important for assessing the contribution of cooling-induced damage within volcanic structures and layers such as dikes, sills, and lava flows.

  18. A New Method of Retarding Fatigue Crack Growth on Pressure Vessels

    Institute of Scientific and Technical Information of China (English)

    Jianzhong YIN; Yanyan WANG; Xinwei DING

    2001-01-01

    An artificial wedge to retard fatigue crack growth in tension has been investigated. The results show that an artificial wedge can reduce the growth rate of fatigue crack on Surface fatigue crack and, the fatigue crack growth behavior is essentially similar in-depth and width directions. Based on a theoretical analysis, a model for the effective crack growth parameter △Keff is presented. It is shown that the relationships between the calculated △Keff value and crack speed are almost the same as those of cracked specimens without a wedge. Therefore this model can be applied to estimate retardation behavior.

  19. Effect of Supragingival Irrigation with Aerosolized 0.5% Hydrogen Peroxide on Clinical Periodontal Parameters, Markers of Systemic Inflammation, and Morphology of Gingival Tissues in Patients with Periodontitis

    Science.gov (United States)

    Žekonis, Gediminas; Žekonis, Jonas; Gleiznys, Alvydas; Noreikienė, Viktorija; Balnytė, Ingrida; Šadzevičienė, Renata; Narbutaitė, Julija

    2016-01-01

    Background Various studies have shown that non-surgical periodontal treatment is correlated with reduction in clinical parameters and plasma levels of inflammatory markers. The aim of this study was to evaluate the effect of long-term weekly supragingival irrigations with aerosolized 0.5% hydrogen peroxide as maintenance therapy followed by non-surgical periodontal treatment on clinical parameters, plasma levels of inflammatory markers, and morphological changes in gingival tissues of patients with periodontitis. Material/Methods In total, 43 patients with chronic periodontitis were randomly allocated to long-term maintenance therapy. The patients’ periodontal status was assessed using clinical parameters of approximal plaque index, modified gingival index, bleeding index, pocket probing depth, and plasma levels of inflammatory markers (high-sensitivity C-reactive protein and white blood cell count) at baseline and after 1, 2, and 3 years. The morphological status of gingival tissues (immediately after supragingival irrigation) was assessed microscopically. Results Complete data were obtained on 34 patients. A highly statistically significant and consistent reduction was observed in all long-term clinical parameters and plasma levels of inflammatory markers. Morphological data showed abundant spherical bubbles in gingival tissues. Conclusions 1. The present study showed that non-surgical periodontal treatment with long-term weekly supragingival irrigations with aerosolized 0.5% hydrogen peroxide improved clinical periodontal status and plasma levels of inflammatory markers and may be a promising method in periodontology. 2. We found that supragingival irrigation with aerosolized 0.5% hydrogen peroxide created large numbers of spherical bubbles in gingival tissues. PMID:27743448

  20. The horizontal branch morphology of M31 globular clusters. Extreme second parameter effect in outer halo clusters

    CERN Document Server

    Perina, S; Buzzoni, A; Cacciari, C; Federici, L; Pecci, F Fusi; Galleti, S

    2012-01-01

    We use deep, high quality colour magnitude diagrams obtained with the Hubble Space Telescope to compute a simplified version of the Mironov index [SMI; B/(B+R)] to parametrize the horizontal branch (HB) morphology for 23 globular clusters in the M31 galaxy (Sample-A), all located in the outer halo at projected distances between 10 kpc and 100 kpc. This allows us to compare them with their Galactic counterparts, for which we estimated the SMI exactly in the same way, in the SMI vs. [Fe/H] plane. We find that the majority of the considered M31 clusters lie in a significantly different locus, in this plane, with respect to Galactic clusters lying at any distance from the center of the Milky Way. In particular they have redder HB morphologies at a given metallicity, or, in other words, clusters with the same SMI value are ~0.4 dex more metal rich in the Milky Way than in M31. We discuss the possible origin of this difference and we conclude that the most likely explanation is that many globular clusters in the ou...

  1. Role of particle shape anisotropy on crack formation in drying of colloidal suspension

    Science.gov (United States)

    Dugyala, Venkateshwar Rao; Lama, Hisay; Satapathy, Dillip K.; Basavaraj, Madivala G.

    2016-08-01

    Cracks in a colloidal film formed by evaporation induced drying can be controlled by changing drying conditions. We show, for the first time that the crack morphologies in colloidal films are dependent on shape of constituting particles apart from the microstructure and particle assembly. In order to investigate the particle shape effect on crack patterns, monodispered spherical and ellipsoidal particles are used in sessile drop experiments. On observing the dried sessile drop we found cracks along the radial direction for spherical particle dispersions and circular crack patterns for ellipsoidal particle dispersions. The change in crack pattern is a result of self assembly of shape anisotropic particles and their ordering. The ordering of particles dictate the crack direction and the cracks follow the path of least resistance to release the excess stress stored in the particle film. Ellipsoids having different aspect ratio (~3 to 7) are used and circular crack patterns are repeatedly observed in all experiments.

  2. Creep, Fatigue and Environmental Interactions and Their Effect on Crack Growth in Superalloys

    Science.gov (United States)

    Telesman, J.; Gabb, T. P.; Ghosn, L. J.; Smith, T.

    2017-01-01

    Complex interactions of creep/fatigue/environment control dwell fatigue crack growth (DFCG) in superalloys. Crack tip stress relaxation during dwells significantly changes the crack driving force and influence DFCG. Linear Elastic Fracture Mechanics, Kmax, parameter unsuitable for correlating DFCG behavior due to extensive visco-plastic deformation. Magnitude of remaining crack tip axial stresses controls DFCG resistance due to the brittle-intergranular nature of the crack growth process. Proposed a new empirical parameter, Ksrf, which incorporates visco-plastic evolution of the magnitude of remaining crack tip stresses. Previous work performed at 704C, extend the work to 760C.

  3. Effect of a phytogenic feed additive on performance, ovarian morphology, serum lipid parameters and egg sensory quality in laying hen.

    Science.gov (United States)

    Saki, Ali Asghar; Aliarabi, Hassan; Hosseini Siyar, Sayed Ali; Salari, Jalal; Hashemi, Mahdi

    2014-01-01

    This present study was conducted to evaluate the effects of dietary inclusion of 4, 8 and 12 g kg(-1) phytogenic feed additives mixture on performance, egg quality, ovary parameters, serum biochemical parameters and yolk trimethylamine level in laying hens. The results of experiment have shown that egg weight was increased by supplementation of 12 g kg(-1) feed additive whereas egg production, feed intake and feed conversion ratio (FCR) were not significantly affected. There were no significant differences in egg quality parameters by supplementation of phytogenic feed additive, whereas yolk trimethylamine level was decreased as the feed additive level increased. The sensory evaluation parameters did not differ significantly. No significant differences were found in serum cholesterol and triglyceride levels between the treatments but low- and high-density lipoprotein were significantly increased. Number of small follicles and ovary weight were significantly increased by supplementation of 12 g kg(-1) feed additive. Overall, dietary supplementation of polyherbal additive increased egg weigh, improved ovary characteristics and declined yolk trimethylamine level.

  4. Initiation and growth of thermal fatigue crack networks in an AISI 304 L type austenitic stainless steel (X2 CrNi18-09); Amorcage et propagation de reseaux de fissures de fatigue thermique dans un acier inoxydable austenitique de type X2 CrNi18-09 (AISI 304 L)

    Energy Technology Data Exchange (ETDEWEB)

    Maillot, V

    2004-07-01

    We studied the behaviour of a 304 L type austenitic stainless steel submitted to thermal fatigue. Using the SPLASH equipment of CEA/SRMA we tested parallelepipedal specimens on two sides: the specimens are continuously heated by Joule effect, while two opposites faces are cyclically. cooled by a mixed spray of distilled water and compressed air. This device allows the reproduction and the study of crack networks similar to those observed in nuclear power plants, on the inner side of circuits fatigued by mixed pressurized water flows at different temperatures. The crack initiation and the network constitution at the surface were observed under different thermal conditions (Tmax = 320 deg C, {delta}T between 125 and 200 deg C). The experiment produced a stress gradient in the specimen, and due to this gradient, the in-depth growth of the cracks finally stopped. The obtained crack networks were studied quantitatively by image analysis, and different parameters were studied: at the surface during the cycling, and post mortem by step-by-step layer removal by grinding. The maximal depth obtained experimentally, 2.5 mm, is relatively coherent with the finite element modelling of the SPLASH test, in which compressive stresses appear at a depth of 2 mm. Some of the crack networks obtained by thermal fatigue were also tested in isothermal fatigue crack growth under 4-point bending, at imposed load. The mechanisms of the crack selection, and the appearance of the dominating crack are described. Compared to the propagation of a single crack, the crack networks delay the propagation, depending on the severity of the crack competition for domination. The dominating crack can be at the network periphery, in that case it is not as shielded by its neighbours as a crack located in the center of the network. It can also be a straight crack surrounded by more sinuous neighbours. Indeed, on sinuous cracks, the loading is not the same all along the crack path, leading to some

  5. In-situ crack repair by laser cladding

    CSIR Research Space (South Africa)

    Van Rooyen, C

    2010-09-01

    Full Text Available sealing is achieved, an overlay layer of typically 1 mm thickness is cladded for improved pitting corrosion resistance. Crack sealing is considered to be a temporary repair technique. In-situ repair requires that the equipment should be mobile... 10 2 3 9 10 deg 10 deg 10 deg Table 1: Typical process parameters for crack sealing 2.2 Overlay cladding Overlay cladding of the sealed cracks is required to improve pitting corrosion...

  6. C-erb-B2 and Bcl-xl protein expression in Barrett's oesophagus in correlation with morphological parameters.

    Science.gov (United States)

    Barwijuk-Machała, M; Reszeć, J; Kemona, A; Sobaniec-Lotowska, M

    2004-01-01

    The aim of the study was to evaluate the correlation of c-erb-b2 and Bcl-xl expression in biopsy specimens of Barrett's oesophagus from 44 patients with morphological features. The examined group was subdivided into: negative for dysplasia, indefinite for dysplasia, positive for dysplasia-low grade, and adenocarcinoma with high grade dysplasia. Positive c-erb-B2 staining was found in 34.1% and Bcl-xl protein expression was observed in 96.9% of BE. The results showed increased c-erb-B2 and Bcl-xl protein expressions with progressive grades of dysplasia to adenocarcinoma. In conclusion, an evaluation of c-erb-B2 and Bcl-xl expression can be useful for the histopatologic diagnosis of BE and correct interpretation of dysplasia.

  7. Studies in the Relationship between Some Morphological Characters and Jumping Parameters in Sport Horses (Part I - Vertical Fence

    Directory of Open Access Journals (Sweden)

    Flavia Bochiş

    2010-05-01

    Full Text Available The multiliniar regression model introduced the variables control and estimated the contribution of every independent variable in the explication of the dependent variable variance, in a standard situation, when all independent had constant values. The taken into study independent variables were 12 morphological characters. The dependent value was represented by the entire length of the jump over the vertical fence and the bar-limbs distance in the same obstacle. The obtained value, for the multiple determination coefficients, nearby 1.00, in most of the cases in the high performance levels (B and C showed the efficiency of the model and a good selection for the included factors. The obtained result focusing on the ensemble reports, in fact a result which can lead us to think that this kind of modeling can be applied freely to the horse height.

  8. Effects of Locally Applied Glycerol and Xylitol on the Hydration, Barrier Function and Morphological Parameters of the Skin.

    Science.gov (United States)

    Korponyai, Csilla; Szél, Edit; Behány, Zoltán; Varga, Erika; Mohos, Gábor; Dura, Ágnes; Dikstein, Shabtay; Kemény, Lajos; Erős, Gábor

    2017-02-08

    Glycerol and xylitol hydrate the skin and improve its barrier function over a short period. We studied the effects of glycerol and xylitol on the physiological properties and morphology of the skin after longer-term application. Twelve volunteers with dry skin were examined. Three areas on the arms were determined. Area 1 served as untreated control. The vehicle was applied to area 2, while area 3 was treated twice daily with a formulation containing glycerol (5%) and xylitol (5%) for 14 days. Transepidermal water loss (TEWL), hydration and biomechanical properties of the skin were monitored. Biopsies were taken for routine histology and immunohistochemistry for filaggrin and matrix metalloproteinase-1 (MMP-1). The polyols increased the skin hydration and protein quantity of filaggrin, elevated the interdigitation index, decreased the TEWL and improved the biomechanical properties of the skin, but did not change the protein expression of MMP-1. A combination of glycerol and xylitol can be useful additional therapy for dry skin.

  9. Effect of crack propagation on crack tip fields

    Directory of Open Access Journals (Sweden)

    F.V. Antunes

    2013-07-01

    Full Text Available Crack closure influences fatigue crack growth rate and must be included in the design of components. Plasticity induced crack closure is intimately linked with the crack tip plastic deformation, which becomes residual as the crack propagates. The objective here is to study numerically the effect of crack propagation on crack tip fields. The transient effect observed at the beginning of crack propagation is linked to the hardening behavior of material. The effect of mesh refinement is studied, and a singular behavior is evident, which is explained by the sharp crack associated with mesh topology, composed of a regular pattern of square elements. The plastic zone size measured perpendicularly to crack flank in the residual plastic wake is quantified and compared with literature models. Finally, the removal of material at the first node behind crack tip with load cycling was observed for plane strain state and some hardening models in plane stress state.

  10. Dynamic stress intensity factor KⅢ and dynamic crack propagation characteristics of anisotropic materials

    Institute of Scientific and Technical Information of China (English)

    GAO Xin; WANG Han-gong; KANG Xing-wu

    2008-01-01

    Based on the mechanics of anisotropic materials,the dynamic propagation problem of a mode Ⅲ crack in an infinite anisotropic body is investigated.Stress,strain and displacement around the crack tip are expressed as an analytical complex function,which can be represented in power series.Constant coefficients of series are determined by boundary conditions.Expressions of dynamic stress intensity factors for a mode Ⅲ crack are obtained.Components of dynamic stress,dynamic strain and dynamic displacement around the crack tip are derived.Crack propagation characteristics are represented by the mechanical properties of the anisotropic materials,i.e.,crack propagation velocity M and the parameter α.The faster the crack velocity is,the greater the maximums of stress components and dynamic displacement components around the crack tip are.In particular,the parameter α affects stress and dynamic displacement around the crack tip.

  11. MORPHOLOGIC PARAMETERS AND LENGTH-MASS RELATIONSHIP OF THREE ROACH (Rutilus rutilus (L., 1758 POPULATIONS FROM NORTHWESTERN CROATIA

    Directory of Open Access Journals (Sweden)

    Nikica Šprem

    2001-09-01

    Full Text Available Three populations of roach from northwestern Croatia were checked for 24 morphometric and 7 meristic parameters, as well as for length-mass relationship. Some meristic characters expressed the values beyond those mentioned in the key for freshwater fish species determination in southeastern Europe. Length-mass relationship and condition factor (CF were the highest in the river Kupa and somewhat lower in the eutrophic stagnant water (3 rd Maksimir lake. On the other hand, these parameters were significantly lower at roach from oligotrophic stagnant water (Mrtvica. This indicates that roach is similarly well adapted to the stagnant as well as running waters and that its condition and morphometry is primarily influenced by the quantity of the food offered.

  12. Land use and urban morphology parameters for Vienna required for initialisation of the urban canopy model TEB derived via the concept of "local climate zones"

    Science.gov (United States)

    Trimmel, Heidelinde; Weihs, Philipp; Oswald, Sandro M.; Masson, Valéry; Schoetter, Robert

    2017-04-01

    Urban settlements are generally known for their high fractions of impermeable surfaces, large heat capacity and low humidity compared to rural areas which results in the well known phenomena of urban heat islands. The urbanized areas are growing which can amplify the intensity and frequency of situations with heat stress. The distribution of the urban heat island is not uniform though, because the urban environment is highly diverse regarding its morphology as building heights, building contiguity and configuration of open spaces and trees vary, which cause changes in the aerodynamic resistance for heat transfers and drag coefficients for momentum. Furthermore cities are characterized by highly variable physical surface properties as albedo, emissivity, heat capacity and thermal conductivity. The distribution of the urban heat island is influenced by these morphological and physical parameters as well as the distribution of unsealed soil and vegetation. These aspects influence the urban climate on micro- and mesoscale. For larger Vienna high resolution vector and raster geodatasets were processed to derive land use surface fractions and building morphology parameters on block scale following the methodology of Cordeau (2016). A dataset of building age and typology was cross checked and extended using satellite visual and thermal bands and linked to a database joining building age and typology with typical physical building parameters obtained from different studies (Berger et al. 2012 and Amtmann M and Altmann-Mavaddat N (2014)) and the OIB (Österreichisches Institut für Bautechnik). Using dominant parameters obtained using this high resolution mainly ground based data sets (building height, built area fraction, unsealed fraction, sky view factor) a local climate zone classification was produced using an algorithm. The threshold values were chosen according to Stewart and Oke (2012). This approach is compared to results obtained with the methodology of Bechtel et

  13. Influence of High Strength Steel Microstructure on Fatigue Crack Growth Rate

    Directory of Open Access Journals (Sweden)

    Enefola S. Ameh

    2016-07-01

    Full Text Available This study examines the effect of high strength steel microstructure morphology on fatigue crack growth rate (FCGR. To achieve this aim, three different heat treatment methods (normalizing, austempering quenching and tempering were considered and all the steel specimens were initially heated to 9500C austenization temperature for ninety minutes and then processed via the different heat treatment methods before viewing the resultant microstructures under light optical microscope (LOM. Fatigue crack growth rate tests were conducted on the resultant microstructures with compact tension specimens at room temperature as prescribed by American standard testing method E647. Results of FCGR tests showed normalized microstructure has the lowest FCGR (6.2698E-06, followed by quenched and tempered (7.9519E-06, asreceived (8.15E-06 and austempered (9.6667E-06 microstructure considering a low stress intensity factor range. The trend of results showed insignificant effect of microstructure over the Paris regime growth indicating fatigue crack growth rate is not a reliable parameter for correlating rate of crack propagation to microstructure

  14. Influence of five-month preparatory period on changes of morphological and performance parameters in the Czech junior representatives in whitewater slalom

    Directory of Open Access Journals (Sweden)

    Sigmund Martin

    2014-01-01

    Full Text Available BACKGROUND: Reaching the highest levels of performance in top-level sport relates to an assumption of optimal development of somatic parameters that form an important part of the sport performance. OBJECTIVE: The aim of this study is to capture the dynamics of the morphological changes and performance parameters of the current Czech junior representatives in whitewater slalom with regard to a five-month preparatory period. METHODS: The survey was carried out at the beginning of the preparatory period and after its termination (5 months. 21 representatives of the Czech Republic from the Junior Slalom category on whitewater participated in this research. Of the total studied probands were 14 men with a mean age of 16.03 ±0.56 years. There were 7 women with a mean age of 16.20 ±1.12 years. The anthropometric methods and bioelectrical impedance method (BIA were used. Performance indicators evaluated the development of muscle power capabilities of the upper extremities, abdominal muscle development and aerobic ability. The research data was processed by the appropriate procedures in the program Antrop vers. 2000.1. Statistical analysis was performed in Statistica vers.10.0. RESULTS: Changes in morphological parameters with respect to a fivemonth preparatory period are reflected especially at the level of body composition and individual fractions. In a group of male and female athletes in slalom there was a reduction in the absolute values of body fat with simultaneous increase in muscle fraction and the total increase in lean body mass. In both groups there was an overall segmental reduction in the percentage of body fat, however changes are not significant. Changes in somatotype with regard to a five-month preparatory period are insignificant in both groups. Changes in selected performance parameters typically show a significant and positive difference in both monitored groups. CONCLUSION: The observed changes of morphological and performance

  15. The horizontal branch morphology of M 31 globular clusters. Extreme second parameter effect in outer halo clusters

    Science.gov (United States)

    Perina, S.; Bellazzini, M.; Buzzoni, A.; Cacciari, C.; Federici, L.; Fusi Pecci, F.; Galleti, S.

    2012-10-01

    We use deep, high quality color magnitude diagrams obtained with the Hubble Space Telescope to compute a simplified version of the Mironov index (SMI; B/(B+R)) to parametrize the horizontal branch (HB) morphology for 23 globular clusters in the M 31 galaxy (Sample A), all located in the outer halo at projected distances between 10 kpc and 100 kpc. This allows us to compare them with their Galactic counterparts, for which we estimated the SMI exactly in the same way, in the SMI vs. [Fe/H] plane. We find that the majority of the considered M 31 clusters lie in a significantly different locus, in this plane, with respect to Galactic clusters lying at any distance from the center of the Milky Way. In particular they have redder HB morphologies at a given metallicity, or, in other words, clusters with the same SMI value are ≈ 0.4 dex more metal rich in the Milky Way than in M 31. We discuss the possible origin of this difference and we conclude that the most likely explanation is that many globular clusters in the outer halo of M 31 formed ≈1-2 Gyr later than their counterparts in the outer halo of the Milky Way, while differences in the cluster-to-cluster distribution of He abundance of individual stars may also play a role. The analysis of another sample of 25 bright M 31 clusters (eighteen of them with MV ≤ -9.0, Sample B), whose SMI estimates are much more uncertain as they are computed on shallow color magnitude diagrams, suggests that extended blue HB tails can be relatively frequent among the most massive M 31 globular clusters, possibly hinting at the presence of multiple populations. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Hubble Legacy Archive, which is a collaboration between the Space Telescope Science Institute (STScI/NASA), the Space Telescope European Coordinating Facility (ST-ECF/ESA) and the Canadian Astronomy Data Centre (CADC/NRC/CSA). STScI is operated by the Association of Universities for

  16. Application of the cracked pipe element to creep crack growth prediction

    Energy Technology Data Exchange (ETDEWEB)

    Brochard, J.; Charras, T.

    1997-04-01

    The modification of a computer code for leak before break analysis is very briefly described. The CASTEM2000 code was developed for ductile fracture assessment of piping systems with postulated circumferential through-wall cracks under static or dynamic loading. The modification extends the capabilities of the cracked pipe element to the determination of fracture parameters under creep conditions (C*, {phi}c and {Delta}c). The model has the advantage of evaluating significant secondary effects, such as those from thermal loading.

  17. Effect of Mobile Phone Radiations on Morphological and Biochemical Parameters of Mung Bean (Vigna radiata and Wheat (Triticum aestivum Seedlings

    Directory of Open Access Journals (Sweden)

    Mobin Afzal

    2012-03-01

    Full Text Available Over the last two decades an enormous escalation in wireless equipments has been made our lives easy. The uses of wireless accessories including mobile phone have been enabled instant our communication resources advance and fast, on the other hand along with their advantages there is great increase in radiations, an unprecedented type of pollution, in our environment. Current study was an attempt to observe the morphological and biochemical changes induced by cell phone radiations on Mung bean (Vigna radiata and Wheat (Triticum aestivum seedlings. The effect of cell phone Electromagnetic Radiations (EMR were determined by measuring membrane damage in terms of melondialdehyde [MDA] contents and changes in the levels of antioxidant enzymes like Guaiacol Peroxidase (GPX, Ascorbate Peroxidase (APX, and Catalase (CAT. Our results showed that cell phone EMR caused significant reduction in growth, fresh weight, dry weight, and relative water contents. Where as MDA contents and antioxidant enzymes were increased in stressed seedlings as compared to unstressed seedlings. We concluded that radiations emitted by mobile phone can induce oxidative stress which results in reduced growth and increase in the activity of antioxidant enzymes in mung bean and wheat seedlings.

  18. AFM Calculated Parameters of Morphology Investigation of Spin Coated MZO (M = Al, Sn, Cd, Co Layers

    Directory of Open Access Journals (Sweden)

    M. Benhaliliba

    2015-12-01

    Full Text Available This paper reports on the deposition and surface properties of the pure and doped zinc oxide layers produced by spin coating route. Pure and metallic (Al, Sn, Cd, Co doped ZnO films are characterized by mean of atomic force microscopy (AFM. Based on atomic force microscope observation, some parameters such as grain size, height, orientation of angle and histogram are determined. The AFM scanned 2D and 3D-views permit us to discover the roughness, the average height and the skewness of clusters or grains.

  19. Dynamic behaviour of a rotating cracked beam

    Science.gov (United States)

    Yashar, Ahmed; Ghandchi-Tehrani, Maryam; Ferguson, Neil

    2016-09-01

    This paper presents a new approach to investigate and analyse the vibrational behaviour of cracked rotating cantilever beams, which can for example represent helicopter or wind turbine blades. The analytical Hamiltonian method is used in modelling the rotating beam and two numerical methods, the Rayleigh-Ritz and FEM, are used to study the natural frequencies and the mode shapes of the intact rotating beams. Subsequently, a crack is introduced into the FE model and simulations are performed to identify the modal characteristics for an open cracked rotating beam. The effect of various parameters such as non-dimensional rotating speed, hub ratio and slenderness ratio are investigated for both the intact and the cracked rotating beam, and in both directions of chordwise and flapwise motion. The veering phenomena in the natural frequencies as a function of the rotational speed and the buckling speed are considered with respect to the slenderness ratio. In addition, the mode shapes obtained for the flapwise vibration are compared using the modal assurance criterion (MAC). Finally, a new three dimensional design chart is produced, showing the effect of crack location and depth on the natural frequencies of the rotating beam. This chart will be subsequently important in identifying crack defects in rotating blades.

  20. Protection of brittle film against cracking

    Science.gov (United States)

    Musil, J.; Sklenka, J.; Čerstvý, R.

    2016-05-01

    This article reports on the protection of the brittle Zrsbnd Sisbnd O film against cracking in bending by the highly elastic top film (over-layer). In experiments the Zrsbnd Sisbnd O films with different elemental composition and structure were used. Both the brittle and highly elastic films were prepared by magnetron sputtering using a dual magnetron. The brittle film easily cracks in bending. On the other hand, the highly elastic film exhibits enhanced resistance to cracking in bending. Main characteristic parameters of both the brittle and highly elastic films are given. Special attention is devoted to the effect of the structure (crystalline, amorphous) of both the brittle and highly elastic top film on the resistance of cracking of the brittle film. It was found that (1) both the X-ray amorphous and crystalline brittle films easily crack in bending, (2) the highly elastic film can have either X-ray amorphous or crystalline structure and (3) both the X-ray amorphous and crystalline, highly elastic top films perfectly protect the brittle films against cracking in bending. The structure, mechanical properties and optical transparency of the brittle and highly elastic sputtered Zrsbnd Sisbnd O films are described in detail. At the end of this article, the principle of the low-temperature formation of the highly elastic films is also explained.

  1. Modelling the root system architecture of Poaceae. Can we simulate integrated traits from morphological parameters of growth and branching?

    Science.gov (United States)

    Pagès, Loïc; Picon-Cochard, Catherine

    2014-10-01

    Our objective was to calibrate a model of the root system architecture on several Poaceae species and to assess its value to simulate several 'integrated' traits measured at the root system level: specific root length (SRL), maximum root depth and root mass. We used the model ArchiSimple, made up of sub-models that represent and combine the basic developmental processes, and an experiment on 13 perennial grassland Poaceae species grown in 1.5-m-deep containers and sampled at two different dates after planting (80 and 120 d). Model parameters were estimated almost independently using small samples of the root systems taken at both dates. The relationships obtained for calibration validated the sub-models, and showed species effects on the parameter values. The simulations of integrated traits were relatively correct for SRL and were good for root depth and root mass at the two dates. We obtained some systematic discrepancies that were related to the slight decline of root growth in the last period of the experiment. Because the model allowed correct predictions on a large set of Poaceae species without global fitting, we consider that it is a suitable tool for linking root traits at different organisation levels. © 2014 INRA. New Phytologist © 2014 New Phytologist Trust.

  2. Growth of inclined fatigue cracks using the biaxial CJP model

    Directory of Open Access Journals (Sweden)

    G. Laboviciute

    2015-07-01

    Full Text Available The CJP model of crack tip stresses is a modified version of the Williams crack tip stress field which takes account of simplified stress distributions that arise from the presence of a zone of plastic deformation associated with the crack flanks and crack tip, and that act on the elastic field responsible for driving crack growth. The elastic stress field responsible for crack growth is therefore controlled by the applied loading and by the induced boundary stresses at the interface with the plastic zone. This meso-scale model of crack tip stresses leads to a modified set of crack tip stress intensity factors that include the resultant influence of plastic wake-induced crack tip shielding, and which therefore have the potential to help resolve some longstanding controversies associated with plasticity-induced closure. A full-field approach has now been developed for stress using photoelasticity and also for displacement using digital image correlation. This paper considers the characterisation of crack growth rate data with the biaxial CJP model, using compact tension specimens that contain inclined cracks at the notch tip with initial angles of 30°, 45° and 60° to the horizontal axis. Significant experimental difficulties are experienced in growing cracks in a biaxial field under uniaxial tensile loading, as the natural tendency of the crack is to turn so that it becomes perpendicular to the maximum principal stress direction. However, crack angle is not an issue in the CJP model which calculates the stress field parallel with, and perpendicular to, the crack plane. These stress components can be rotated into directions comparable with the usual KI and KII directions and used to calculate stress intensity parameters that should be directly comparable with the standard stress intensity formulations. Another difficulty arises, however, in finding published expressions for KI and KII for CT specimens with curved or kinked cracks. The CJP model

  3. Extended FEM modeling of crack paths near inclusions

    DEFF Research Database (Denmark)

    Nielsen, Chris Valentin; Legarth, Brian Nyvang; Niordson, Christian Frithiof

    2012-01-01

    The extended FEM is applied to model crack growth near inclusions. A procedure to handle different propagation rates at different crack tips is presented. The examples considered investigate uniform tension as well as equibiaxial tension under plane strain conditions. A parameter study analyzes...

  4. A circumferential crack in a cylindrical shell under tension.

    Science.gov (United States)

    Duncan-Fama, M. E.; Sanders, J. L., Jr.

    1972-01-01

    A closed cylindrical shell under uniform internal pressure has a slit around a portion of its circumference. Linear shallow shell theory predicts inverse square-root-type singularities in certain of the stresses at the crack tips. This paper reports the computed strength of these singularities for different values of a dimensionless parameter based on crack length, shell radius and shell thickness.

  5. Steady-state propagation of interface corner crack

    DEFF Research Database (Denmark)

    Veluri, Badrinath; Jensen, Henrik Myhre

    2013-01-01

    by estimating the fracture mechanics parameters that includes the strain energy release rate, crack front profiles and the three-dimensional mode-mixity along the interface crack front. A numerical approach was then applied for coupling the far field solutions based on the Finite Element Method to the near...... field (crack tip) solutions based on the J-integral. The adopted two-dimensional numerical approach for the calculation of fracture mechanical properties was compared with three-dimensional models for quarter-circular and straight sided crack front shapes. A quantitative approach was formulated based...

  6. Pavement crack identification based on automatic threshold iterative method

    Science.gov (United States)

    Lu, Guofeng; Zhao, Qiancheng; Liao, Jianguo; He, Yongbiao

    2017-01-01

    Crack detection is an important issue in concrete infrastructure. Firstly, the accuracy of crack geometry parameters measurement is directly affected by the extraction accuracy, the same as the accuracy of the detection system. Due to the properties of unpredictability, randomness and irregularity, it is difficult to establish recognition model of crack. Secondly, various image noise, caused by irregular lighting conditions, dark spots, freckles and bump, exerts an influence on the crack detection accuracy. Peak threshold selection method is improved in this paper, and the processing of enhancement, smoothing and denoising is conducted before iterative threshold selection, which can complete the automatic selection of the threshold value in real time and stability.

  7. NONLINEAR DYNAMICS OF A CRACKED ROTOR IN A MANEUVERING AIRCRAFT

    Institute of Scientific and Technical Information of China (English)

    LIN Fu-sheng 林富生; MENG Guang 孟光; Eric Hahn

    2004-01-01

    The nonlinear dynamics of a cracked rotor system in an aircraft maneuvering with constant velocity or acceleration was investigated. The influence of the aircraft climbing angle on the cracked rotor system response is of particular interest and the results show that the climbing angle can markedly affect the parameter range for bifurcation, for quasi-periodic response and for chaotic response as well as for system stability. Aircraft acceleration is also shown to significantly affect the nonlinear behavior of the cracked rotor system, illustrating the possibility for on-line rotor crack fault diagnosis.

  8. Effect of cadmium on selected physiological and morphological parameters in metallicolous and non-metallicolous populations of Echium vulgare L.

    Science.gov (United States)

    Dresler, Sławomir; Bednarek, Wiesław; Wójcik, Małgorzata

    2014-06-01

    Cadmium tolerance of three populations of Echium vulgare L., naturally occurring on two Zn-Pb waste deposits (metallicolous populations M1, M2) and on an uncontaminated site (non-metallicolous population, NM) was investigated. The plants were cultivated in hydroponics at 0, 5, 15, 30, or 50μM Cd for 14 days. Although Cd reduced the content of photosynthetic pigments indifferently in the three populations, plant growth parameters and root viability analyses confirmed different Cd tolerances decreasing in the order M1>M2>NM in the populations studied. Organic acids (tartrate, malate, citrate, succinate) were not responsible for the elevated Cd tolerance of the metallicolous populations, although malate and citrate might participate in Cd detoxification in the roots of the M1 and M2. Phytochelatin concentrations were higher in the roots of M1 and M2 populations of E. vulgare, suggesting their role in Cd detoxification and different Cd tolerances.

  9. Mode I stress intensity factors of slanted cracks in plates

    Science.gov (United States)

    Ismail, Al Emran; Ghazali, Mohd Zubir Mohd; Nor, Nik Hisyamudin Muhd

    2017-01-01

    This paper presents the roles of slanted cracks on the stress intensity factors (SIF) under mode I tension and bending loading. Based on the literature survey, lack of solution of SIFs of slanted cracks in plain strain plates are available. In this work, the cracks are modelled numerically using ANSYS finite element program. There are two important parameters such as slanted angles and relative crack length. SIFs at the crack tips are calculated according to domain integral method. Before the model is further used, it is validated with the existing model. It is found that the present model is well agreed with the previous model. According to finite element analysis, there are not only mode I SIFs produced but also mode II. As expected the SIFs increased as the relative crack length increased. However, when slanted angles are introduced (slightly higher than normal crack), the SIFs increased. Once the angles are further increased, the SIFs decreased gradually however they are still higher than the SIFs of normal cracks. For mode II SIFs, higher the slanted angels higher the SIFs. This is due to the fact that when the cracks are slanted, the cracked plates are not only failed due to mode I but a combination between both modes I and II.

  10. An evaluation of the advantages and limitations in simulating indentation cracking with cohesive zone finite elements

    Science.gov (United States)

    Johanns, K. E.; Lee, J. H.; Gao, Y. F.; Pharr, G. M.

    2014-01-01

    A cohesive zone model is applied to a finite element (FE) scheme to simulate indentation cracking in brittle materials. Limitations of using the cohesive zone model to study indentation cracking are determined from simulations of a standard fracture toughness specimen and a two-dimensional indentation cracking problem wherein the morphology of the crack and the geometry of the indenter are simplified. It is found that the principles of linear-elastic fracture mechanics can be applied when indentation cracks are long in comparison to the size of the cohesive zone. Vickers and Berkovich pyramidal indentation crack morphologies (3D) are also investigated and found to be controlled by the ratio of elastic modulus to yield strength (E/Y), with median type cracking dominating at low ratios (e.g. E/Y = 10) and Palmqvist type cracking at higher ratios (e.g. E/Y = 100). The results show that cohesive FE simulations of indentation cracking can indeed be used to critically examine the complex relationships between crack morphology, material properties, indenter geometry, and indentation test measurements, provided the crack length is long in comparison to the cohesive zone size.

  11. Study on Kinetic Parameters of Crude Oil Cracking Gas and Its Application%原油裂解成气动力学参数及其应用研究

    Institute of Scientific and Technical Information of China (English)

    李贤庆; 仰云峰; 田辉; 肖贤明; 黄孝波; 王萌; 杨朝世

    2012-01-01

    The thermal simulation experiment of Yaha and Hade crude oil samples in Tarim Basin was carried out, by using the gold tube confined system. The yield characteristics and kinetic parameters of cracking gases from Yaha and Hade oil samples were studied. The results demonstrate that the Yaha and Hade oil samples have high total gas yields (738.87 ml/g, 598.98 ml/g) and C2_5 yields (256.85 ml/g, 188.63 ml/g). Differences are existed in the kinetic parameters of cracking gases in the Yaha and Hade oils. The activation energy distributions of methane, ethane and propane generated from the Yaha oil sample are in the range of (66 -83 ) × 4. 186kJ/mol, (59 -72) × 4. 186kJ/ mol, and (59 -65)×4. 186kJ/mol. Their frequency factors from the Yaha oil sample are 2.07 ×10^16s^-1, 1.0 ×10^14s^-1 , and 1.0 ×10^14s^-1 , respectively. The activation energy distributions of methane, ethane and propane from the Hade oil sample are in the range of (63 -84)×4. 186 kJ/mol, (57 ~63) ×4. 186 kJ/mol, and (58 ~70) ×4. 186 kJ/mol. Their frequency factors from the Hade oil sample are 1.42 ×10^16s^-1, 1 .0 ×10^14s^-1, and 1.0 ×10^14s^-1 , re- spectively. The Mandong 1 gas pool in the eastern Tarim Basin was taken as an example and its kinetic modeling of gas generation was studied. It is suggested that gas source of the Mandong 1 gas pool was resulted from a large number of crude oil cracking.%采用黄金管限定体系,对塔里木盆地牙哈、哈得原油样品进行了热模拟实验,研究了原油样品热裂解生成气态烃的产率特征及其动力学参数。结果表明,牙哈、哈得原油样品裂解具有高的C1-5产率(738.87ml/g、598.98ml/g)和C2-5产率(256.85ml/g、188.63ml/g)。牙哈、哈得原油样品裂解成气动力学参数存在差异:牙哈原油样品裂解气甲烷、乙烷、丙烷生成的活化能范围分别为(66—83)×4.186kJ/mol、(59~72)×4.186kJ/mol、(59—65)×4.186k

  12. Bioaccumulation of cadmium by spring barley (Hordeum vulgare L. and its effect on selected physiological and morphological parameters

    Directory of Open Access Journals (Sweden)

    Miriama Kopernická

    2016-01-01

    Full Text Available Heavy metals and other toxic elements in the environment, mainly located in soil and groundwater, have a significant effect on plant and its productivity that has a huge attention in recent years. Accumulation of heavy metals in soil cause toxicity to plants, and contaminate the food chain. The industrial areas, as well as developing countries have been contaminated with high concentration of heavy metals. Main sources of contamination are mining and other industrial processes, as well as military and or lanfills, sludge dumps or waste disposal sites. The heavy metals are very dangerous to environment and pose serious danger to public health by entering throught the food chain or into drinking water. Phytoextraction is one way how to remove the contaminants from soil by plants. Phytoextraction of heavy metals is a technology that has been studied for several years. It is more ecological and cheaper way how to clean our environment.Several plant species are known becauce they hyperaccumulate a high contents of metals from the soil. The accumulators are mainly herbaceous species, crops and nowadays angiosperm trees with a high growth such as poplars or willows. We have focused on the determination of some morphological (lenght and weight of roots and biomass and physiological (contents of dry mass and number of lief stomata characteristics and the determination of the bioaccumulation factor and the translocation factor of cadmium by spring barley (Hordeum vulgare L.. Imprints of leaves were evaluated using an optical microscope Axiostar Plus, Carl Zeiss, lens CP Achromat 40x/0.65, eyepiece PI 10x / 18, Canon Utilities Software Zoom Browser EX 4.6 and hardware Acer Travel Mate 4600, Canon Power Shot A95. The density of stomata was evaluated on an area of 1 mm2. Samples of the dried plants (leaves and roots were mineralized by acid digestion using microwave digestion device MARS X - press 5. The end of determination to obtain the cadmium content was

  13. A Finite Element Method for Cracked Components of Structures

    Institute of Scientific and Technical Information of China (English)

    刘立名; 段梦兰; 秦太验; 刘玉标; 柳春图; 余建星

    2003-01-01

    In this paper, a method is developed for determining the effective stiffness of the cracked component. The stiffness matrix of the cracked component is integrated into the global stiffness matrix of the finite element model of the global platform for the FE calculation of the structure in any environmental conditions. The stiffness matrix equation of the cracked component is derived by use of the finite variation principle and fracture mechanics. The equivalent parameters defining the element that simulates the cracked component are mathematically presented, and can be easily used for the FE calculation of large scale cracked structures together with any finite element program. The theories developed are validated by both lab tests and numerical calculations, and applied to the evaluation of crack effect on the strength of a fixed platform and a self-elevating drilling rig.

  14. Engineering Solution for the Uniform Strength of Partially Cracked Concrete

    DEFF Research Database (Denmark)

    Hansen, Elin A.; Hansen, Will; Brincker, Rune

    2005-01-01

    Significant computational resources are required to predict the remaining strength from numerical fracture analysis of a jointed plain concrete pavement that contains a partial depth crack. It is, therefore, advantageous when the failure strength can be adequately predicted with an engineering...... solution. Current engineering or closed-form solutions are based on the elastic effective crack approach with the fracture parameters toughness and critical crack tip opening of concrete. The solutions do not directly consider the effect of the distance to the boundary conditions (restrained slab length......) and the cracking process caused by stress softening across the crack. A proposed engineering solution methodology includes these latter variables. The application of the solution is demonstrated on a slab containing a partial depth midslab crack and subjected to in-plane tension. The solution captures the effects...

  15. Analytical Solutions for Corrosion-Induced Cohesive Concrete Cracking

    Directory of Open Access Journals (Sweden)

    Hua-Peng Chen

    2012-01-01

    Full Text Available The paper presents a new analytical model to study the evolution of radial cracking around a corroding steel reinforcement bar embedded in concrete. The concrete cover for the corroding rebar is modelled as a thick-walled cylinder subject to axisymmetrical displacement constraint at the internal boundary generated by expansive corrosion products. A bilinear softening curve reflecting realistic concrete property, together with the crack band theory for concrete fracture, is applied to model the residual tensile stress in the cracked concrete. A governing equation for directly solving the crack width in cover concrete is established for the proposed analytical model. Closed-form solutions for crack width are then obtained at various stages during the evolution of cracking in cover concrete. The propagation of crack front with corrosion progress is studied, and the time to cracking on concrete cover surface is predicted. Mechanical parameters of the model including residual tensile strength, reduced tensile stiffness, and radial pressure at the bond interface are investigated during the evolution of cover concrete cracking. Finally, the analytical predictions are examined by comparing with the published experimental data, and mechanical parameters are analysed with the progress of reinforcement corrosion and through the concrete cover.

  16. Production of steam cracking feedstocks by mild cracking of plastic wastes

    Energy Technology Data Exchange (ETDEWEB)

    Angyal, Andras; Miskolczi, Norbert; Bartha, Laszlo; Tungler, Antal; Nagy, Lajos; Vida, Laszlo; Nagy, Gabor

    2010-11-15

    In this work the utility of new possible petrochemical feedstocks obtained by plastic waste cracking has been studied. The cracking process of polyethylene (PE), polyethylene-polypropylene (PEPP) and polyethylene-polystyrene (PEPS) has been carried out in a pilot scale tubular reactor. In this process mild reaction parameters has been applied, with the temperature of 530 C and the residence time of 15 min. The produced hydrocarbon fractions as light- and middle distillates were tested by using a laboratory steam cracking unit. It was concluded that the products of the mild cracking of plastic wastes could be applied as petrochemical feedstocks. Based on the analytical data it was determined that these liquid products contained in significant concentration (25-50 wt.%) of olefin hydrocarbons. Moreover the cracking of polystyrene containing raw material resulted in liquid products with significant amounts of aromatic hydrocarbons too. The steam cracking experiments proved that the products obtained by PE and PEPP cracking resulted in similar or better ethylene and propylene yields than the reference samples, however the aromatic content of PEPS products reduced the ethylene and propylene yields. (author)

  17. Modelling of Corrosion Cracks

    DEFF Research Database (Denmark)

    Thoft-Christensen, Palle

    Modelling of corrosion cracking of reinforced concrete structures is complicated as a great number of uncertain factors are involved. To get a reliable modelling a physical and mechanical understanding of the process behind corrosion in needed.......Modelling of corrosion cracking of reinforced concrete structures is complicated as a great number of uncertain factors are involved. To get a reliable modelling a physical and mechanical understanding of the process behind corrosion in needed....

  18. Comparative analysis of morphological and topometric parameters of lumbar spine in normal state and in degenerative-dystrophic changes

    Directory of Open Access Journals (Sweden)

    Anisimova Е.А.

    2015-12-01

    Full Text Available Objective: to carry out comparative analysis and identify patterns of topographic variation patterns of lumbar spine in normal and degenerative changes. Material and methods. CT- and MRT-grams for men and women I (M1-22-35 years; W — 21-35 years and II (M2-36-60 years; W2-36-55 years periods of mature age with no signs of trauma, scoliosis and systemic diseases of the spine (n=140 and CT- and MRT-grams in patients with revealed degenerative changes in the lumbar spine degree II-III (n=120. The pictures with digital PACS system measure the height of the vertebral body, intervertebral disc height, vertical, horizontal diameter and the area of intervertebral foramen. Results. The height of the lumbar vertebral bodies normally increased from27,90±0,38mmatthe level of L, to 29,93±0,33 mm Lm, and then decreased to 24,35±0,27 mm at level L^, in osteochondrosis it is statistically significantly lower at all levels on average by 20%. The height of the intervertebral disc with osteochondrosis below at all levels by an average of 25% of its value in the range 5,27±0,19 to 6,13±0,17mm, while the normal disc height varies from 6,88±030 to 9,36±0,28mm. The area of intervertebral holes normally ranging from 103,29±5,78 to 127,99±5,92mm2, with osteochondrosis aperture area is reduced to a greater extent by decreasing the vertical diameter in comparison with the horizontal. Conclusion. For the studied parameters characteristic topographic variability has been determined. The maximum values parameters are marked at the top of the lumbar lordosis, at chest height, lumbar and lumbosacral junctions sizes are reduced. In osteochondrosis the intervertebral disc height and the height of lumbar vertebral bodies are reduced; intervertebral foramina area is also reduced to a greater extent by reducing the vertical diameter than the horizontal one.

  19. Imaging Cracks by Laser Excited Thermography

    Science.gov (United States)

    Schlichting, J.; Kervalishvili, G. N.; Maierhofer, Ch.; Kreutzbruck, M.

    2010-02-01

    During the last years active thermography is increasingly used in a number of NDT problems in production and maintenance. In this work we focus on the detection of vertical cracks starting at the surface, which is an important indication of structural failure. By using local thermal excitation it is possible to image anisotropies in the lateral diffusivity by recording the temporal temperature data with an infrared camera. The regional transient behaviour of temperature distribution then can provide quantitative information of the crack parameter. In doing so, we present an advanced technique for the determination of the crack depth. The experimental set-up is based on an Nd:YAG laser. The beam is focused on the test sample by using an optical scanner to create the required lateral heat flow. The time resolved temperature distribution is recorded with an infrared camera (InSb FPA, 3 to 5 μm) providing a frame rate of up to 500 Hz. In addition we report on numerical simulation to investigate the concept of local heat excitation for a quantitative estimation of crack parameters. The modeling also includes the influence of surface to surface radiation inside the crack. We obtained a good consistency between experimental and theoretical data.

  20. Stability analysis of cracks propagating in three dimensional solids

    Energy Technology Data Exchange (ETDEWEB)

    Larralde, H.; Al-Falou, A.A.; Ball, R.C. [Cavendish Lab., Cambridge (United Kingdom)

    1996-12-01

    The authors present a theory for the morphology of the fracture surface left behind by slowly propagating cracks in linear, isotropic and homogeneous three dimensional solids. The results are based on first order perturbation theory of the equations of elasticity for cracks whose shape is slightly perturbed from planar. For cracks propagating under pure type 1 loading they find that all perturbation modes are linearly stable, from which they can predict the roughness of the fracture surface induced by fluctuations in the material. The authors compare their results with the classical results for cracks propagating in two dimensional systems, and discuss the effects in the three dimensional analysis which result from taking into account contributions from non-singular terms of the stress field, as well as the effects arising from finite speeds of crack propagation.

  1. Effects of osmolality on sperm morphology, motility and flagellar wave parameters in Northern pike (Esox lucius L.).

    Science.gov (United States)

    Alavi, S M Hadi; Rodina, Marek; Viveiros, Ana T M; Cosson, Jacky; Gela, David; Boryshpolets, Sergei; Linhart, Otomar

    2009-07-01

    Northern pike (Esox lucius L.) spermatozoa are uniflagellated cells differentiated into a head without acrosome, a midpiece and a flagellar tail region flanked by a fin structure. Total, flagellar, head and midpiece lengths of spermatozoa were measured and show mean values of 34.5, 32.0, 1.32, 1.17 microm, respectively, with anterior and posterior widths of the midpiece measuring 0.8 and 0.6 microm, respectively. The osmolality of seminal plasma ranged from 228 to 350 mOsmol kg(-1) (average: 283.88+/-33.05). After triggering of sperm motility in very low osmolality medium (distilled water), blebs appeared along the flagellum. At later periods in the motility phase, the tip of the flagellum became curled into a loop shape which resulted in a shortening of the flagellum and a restriction of wave development to the proximal part (close to head). Spermatozoa velocity and percentage of motile spermatozoa decreased rapidly as a function of time postactivation and depended on the osmolality of activation media (Ppike is inhibited due to high osmolality in the seminal plasma. Osmolality of activation medium affects the percentage of motile sperm and spermatozoa velocity due to changes in flagellar wave parameters.

  2. Blood parameter analysis and morphological alterations as biomarkers on the health of Hoplias malabaricus and Geophagus brasiliensis

    Directory of Open Access Journals (Sweden)

    Silvia Romão

    2006-05-01

    Full Text Available This study aimed to assess the influence of the environment on fish health. Samples of Hoplias malabaricus and Geophagus brasiliensis, were collected from three different environments: area I was urban and areas II and III were rural. Analyses of red blood cell count, microhematocrit, hemoglobin concentration, white blood cell count and differential white cell count in blood smear were carried out. Mean corpuscular volume and mean corpuscular hemoglobin concentration were calculated. To analyze morphological alterations, gills, liver, kidney and gonads were submitted to routine histological processing. Individuals collected from area III had slightly lower blood indices than collected from area I . Severe kidney changes, degeneration of and crystallization within kidney tubules were observed. In area I, crystallization was observed in 92% of the specimens of G. brasiliensis. These results suggested that such alterations were related with poor water circulation in the place.Este trabalho teve como objetivo avaliar a influência do ambiente sobre a higidez dos peixes. Animais, das espécies Hoplias malabaricus e Geophagus brasiliensis foram coletados em três ambientes distintos, sendo ambiente I região urbana e ambientes II e III em região rural. Foram realizadas análises do número total de eritrócitos por microlitro de sangue, microhematócrito, taxa de hemoglobina, porcentagem de leucócito e contagem diferencial de leucócitos em extensão sanguínea. Calcularam-se os índices hematimétricos absolutos: volume corpuscular médio e concentração de hemoglobina corpuscular média. Para análises das alterações morfológicas, brânquias, fígado, gônadas e rim seguiram processamento histológico de rotina. Foram observados índices hematológicos ligeiramente menores em indivíduos coletados no ambiente III em relação aos animais coletados no ambiente I. As análises histológicas de brânquias, fígado e gônadas das espécies G

  3. Monitoring of solidification crack propagation mechanism in pulsed laser welding of 6082 aluminum

    Science.gov (United States)

    von Witzendorff, P.; Kaierle, S.; Suttmann, O.; Overmeyer, L.

    2016-03-01

    Pulsed laser sources with pulse durations in the millisecond regime can be used for spot welding and seam welding of aluminum. Seam welds are generally produced with several overlapping spot welds. Hot cracking has its origin in the solidification process of individual spot welds which determines the cracking morphology along the seam welding. This study used a monitoring unit to capture the crack geometry within individual spot welds during seam welding to investigate the conditions for initiation, propagation and healing (re-melting) of solidification cracking within overlapping pulsed laser welds. The results suggest that small crack radii and high crack angles with respect to welding direction are favorable conditions for crack healing which leads to crack-free seam welds. Optimized pulse shapes were used to produce butt welds of 0.5 mm thick 6082 aluminum alloys. Tensile tests were performed to investigate the mechanical strength in the as-welded condition.

  4. Effects of crack tip geometry on dislocation emission and cleavage A possible path to enhanced ductility

    CERN Document Server

    Schiøtz, J; Carlsson, A E

    1997-01-01

    We present a systematic study of the effect of crack blunting on subsequent crack propagation and dislocation emission. We show that the stress intensity factor required to propagate the crack is increased as the crack is blunted by up to thirteen atomic layers, but only by a relatively modest amount for a crack with a sharp 60$^\\circ$ corner. The effect of the blunting is far less than would be expected from a smoothly blunted crack; the sharp corners preserve the stress concentration, reducing the effect of the blunting. However, for some material parameters blunting changes the preferred deformation mode from brittle cleavage to dislocation emission. In such materials, the absorption of preexisting dislocations by the crack tip can cause the crack tip to be locally arrested, causing a significant increase in the microscopic toughness of the crack tip. Continuum plasticity models have shown that even a moderate increase in the microscopic toughness can lead to an increase in the macroscopic fracture toughne...

  5. Automatic Detection and Evaluation of Solar Cell Micro-Cracks in Electroluminescence Images Using Matched Filters

    Energy Technology Data Exchange (ETDEWEB)

    Spataru, Sergiu; Hacke, Peter; Sera, Dezso

    2016-11-21

    A method for detecting micro-cracks in solar cells using two dimensional matched filters was developed, derived from the electroluminescence intensity profile of typical micro-cracks. We describe the image processing steps to obtain a binary map with the location of the micro-cracks. Finally, we show how to automatically estimate the total length of each micro-crack from these maps, and propose a method to identify severe types of micro-cracks, such as parallel, dendritic, and cracks with multiple orientations. With an optimized threshold parameter, the technique detects over 90 % of cracks larger than 3 cm in length. The method shows great potential for quantifying micro-crack damage after manufacturing or module transportation for the determination of a module quality criterion for cell cracking in photovoltaic modules.

  6. Liver morphology and morphometry and plasma biochemical parameters of Wistar rats that received leaf infusion of Rudgea viburnoides Benth. (Rubiaceae

    Directory of Open Access Journals (Sweden)

    Juliana Castro Monteiro

    2009-04-01

    Full Text Available Rudgea viburnoides leaves are widely used in popular Brazilian medicine as a diuretic, antirheumatic, hypotensive and blood depurative tea. The present study was carried out to investigate the effects of this infusion on the liver and on the plasma biochemical parameters of Wistar rats. Two groups received the R. viburnoides leaf infusion at a daily dose of 10 or 20g dry-leaves/L water, during 40 days. The histopathological analysis did not show degenerated areas or infiltration of leucocytes. Hepatic morphometry showed accumulation of fat in the hepatocytes of the treated groups. There was no significant change in the plasma levels of urea, creatinin, uric acid, direct bilirubin, cholesterol, total proteins, albumin, gamma glutamyl tranferase (gamma-GT, alanine transaminase (ALT, aspartate transaminase (AST, chlorine, phosphate and calcium. A significant reduction in the plasma levels of triacylglycerol (TAG occurred in the group that received the higher dose.As folhas de Rudgea viburnoides Benth. são utilizadas na medicina popular como diuréticas, hipotensoras, anti-reumáticas, depurativas do sangue e em regimes de emagrecimento. O presente estudo foi delineado para avaliar o efeito da infusão das folhas de R. viburnoides nos parâmetros bioquímicos plasmáticos e na morfologia e morfometria hepática de ratos Wistar adultos. Dois grupos receberam a infusão das folhas, diariamente, nas dosagens de 10 e 20 g de folhas secas/L de água, durante 40 dias. O grupo controle recebeu a mesma quantidade de água. As análises histopatológicas não mostraram áreas degeneradas e infiltrados inflamatórios. A morfometria hepática mostrou acúmulo significativo de gordura nos hepatócitos dos animais tratados, principalmente no grupo que recebeu a maior dose da infusão (8,75% de gotículas lipídicas, comparado com 0,25% delas encontradas nos animais controles. Não foram observadas alterações nos níveis plasmáticos de uréia, creatinina,

  7. CRACK2. Modelling calcium carbonate deposition from bicarbonate solutions in cracks in concrete

    DEFF Research Database (Denmark)

    Brodersen, Knud Erik

    2003-01-01

    The numerical CRACK2 model simulates precipitation of calcite from calcium bicarbonate solution (e.g. groundwater) passing through cracks in concrete or other cementitious materials. A summary of experimental work is followed by a detailed description ofthe model. Hydroxyl ions are transported...... by diffusion in pore systems in columns of cementitious materials. The hydroxyl is precipitating calcite from a flow of bicarbonate solution in a crack connecting the ends of a row of such columns. Thecementitious material is simulated as calcium hydroxide mixed with inert material but with sodium hydroxide...... dissolved in the pore solution. Diffusive migration of cesium as radioactive isotope is also considered. Electrical interaction of the migratingions is taken into account. Example calculations demonstrate effects of parameter variations on distribution of precipitated calcite in the crack...

  8. Assessment of the influence of the inflammatory process on the activation of blood platelets and morphological parameters in patients with ulcerative colitis (colitis ulcerosa

    Directory of Open Access Journals (Sweden)

    Beata Polińska

    2011-04-01

    Full Text Available Ulcerative colitis (colitis ulcerosa is a non-specific inflammatory bowel disease of unknown etiology. Thesymptoms which are observed in the course of ulcerative colitis are: an increase in the number of leukocytes andblood platelets, an increase in the concentration of IL-6 and anemia. Blood platelets are the key element, linkingthe processes of hemostasis, inflammation and the repair of damaged tissues. Activation of blood platelets is connectedwith changes in their shape and the occurrence of the reaction of release. P-selectin appears on the surfacesof activated blood platelets and the concentration level of soluble P-selectin increases in the blood plasma. The aimof this study was to define whether the increased number of blood platelets in patients with ulcerative colitisaccompanies changes in their activation and morphology. A total of 16 subjects with ulcerative colitis and 32healthy subjects were studied. Mean platelet count, morphological parameters of platelets and MPC were measuredusing an ADVIA 120 hematology analyzer. Concentrations of sP-selectin and IL-6 in serum were marked byimmunoassay (ELISA. MPC, concentration of sP-selectin and IL-6 were significantly higher in subjects with ulcerativecolitis compared to those in the healthy group. There was a decrease of MPV in patients with ulcerativecolitis, which is statistically significant. Chronic inflammation in patients with ulcerative colitis causes an increase inthe number of blood platelets, a change in their morphology and activation. Decreased MPV value reflects activationand the role blood platelets play in the inflammatory process of the mucous membrane of the colon. A highconcentration of sP-selectin, which is a marker of blood platelet activation, demonstrates their part in the inflammatoryprocess. The increase in the concentration of sP-selectin correlated positively with the increase in concentrationof IL-6. This is why it may be a useful marker of the activity of

  9. Application of the physiological and morphological parameters of the brazilian population sample to the mathematical model of the human respiratory tract; Aplicacao dos parametros fisiologicos e morfologicos de uma amostra da populacao brasileira no modelo matematico do trato respiratorio humano

    Energy Technology Data Exchange (ETDEWEB)

    Reis, Arlene Alves dos

    2005-07-01

    The Human Respiratory Tract Model proposed by the ICRP Publication 66 accounts for the morphology and physiology of the respiratory tract. The characteristics of air drawn into the lungs and exhaled are greatly influenced by the morphology of the respiratory tract, which causes numerous changes in pressure, flow rate, direction and humidity as air moves into and out of the lungs. Concerning the respiratory physiological parameters the breathing characteristics influence the volume, the inhalation rate of air and the portion that enters through the nose and the mouth. These characteristics are important to determine the fractional deposition. The model uses morphological and physiological parameters from the Caucasian man to establish deposition fractions in the respiratory tract regions. It is known that the morphology and physiology are influenced by environmental, occupational and economic conditions. The ICRP recommends, for a reliable evaluation of the regional deposition, the use of parameters from a local population when information is available. The main purpose of this study is to verify the influence in using the morphology and physiology parameters representative of a sample of the Brazilian population on the deposition model of the ICRP Publication 66. The morphological and physiological data were obtained from the literature. The software EXCEL for Windows (version 2000) was used in order to implement the deposition model and also to allow the changes in parameters of interest. Initially, the implemented model was checked using the parameters defined by the ICRP and the results of the fraction deposition in the respiratory tract compartments were compared. Finally, morphological and physiological parameters from Brazilian adult male were applied and the fractional deposition calculated. The results suggest a significant variation in fractional deposition when Brazilian parameters are applied in the model. (author)

  10. A contrast stretching bilateral closing top-hat Otsu threshold technique for crack detection in images.

    Science.gov (United States)

    Sim, K S; Kho, Y Y; Tso, C P; Nia, M E; Ting, H Y

    2013-01-01

    Detection of cracks from stainless steel pipe images is done using contrast stretching technique. The technique is based on an image filter technique through mathematical morphology that can expose the cracks. The cracks are highlighted and noise removal is done efficiently while still retaining the edges. An automated crack detection system with a camera platform has been successfully implemented. We compare crack extraction in terms of quality measures with those of Otsu's threshold technique and the another technique (Iyer and Sinha, 2005). The algorithm shown is able to achieve good results and perform better than these other techniques.

  11. Influence of pulse electrodeposition parameters on microhardness, grain size and surface morphology of Ni–Co/SiO$_2$ nanocomposite coating

    Indian Academy of Sciences (India)

    SIAVASH IMANIAN GHAZANLOU; ALI SHOKUHFAR; SHIVA NAVAZANI; REZVAN YAVARI

    2016-09-01

    Ni–Co/SiO$_2$ nanocomposite coatings and Ni–Co alloy coatings were prepared on steel substrate using direct and pulse electrodeposition methods. X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), X-raymap and energy dispersive X-ray spectroscopy (EDX) were employed to investigate the phase structure, surface morphology, and elemental analysis of coatings, respectively. In high discharge rates, the surface morphology was rough, disordered and gross globular; on the contrary, in the low rates, it was smoother, more ordered and fine globular. Also, effect of electrodeposition parameters such as average current density, pulse frequency and duty cycle on the microhardness and grain size of nanocomposite coatings that produced through the pulse current electrodeposition method have been investigated. By amplifying both duty cycles up to 50% and average currentdensity from 2 to 6 A dm$^{−2}$, microhardness increased, while the grain size decreased. But when duty cycle mounted on more than 50% and the average current density went up to 8 A dm$^{−2}$, microhardness lessened, while the grain size rose. The optimum value for pulse frequency was about 25 Hz. Results showed that microhardness of nanocomposite coatings which were produced by pulse current method was higher than that of produced by direct currentmethod.

  12. Determination of age-related changes in the morphological structure (sagging) of the human cheek using a photonumeric scale and three-dimensional surface parameters.

    Science.gov (United States)

    Tsukahara, K; Takema, Y; Fujimura, T; Moriwaki, S; Kitahara, T; Imokawa, G

    2000-08-01

    The usefulness of the photo standard for evaluating skin sagging in the face, especially in the cheeks, was evaluated. A six-stage photo standard was prepared using photos of women aged 17-83-years-old at three magnification rates (136-188 women in each group). Based on this photo standard, scoring was performed using a six-grade scoring system by two specialists to obtain the consensus score. Scoring was also performed in parallel by five general observers. The degree of agreement between the two scores was evaluated by calculating the Kappa value. In each group, the Kappa value was 0.452-0.563, indicating moderate agreement. Thus, the photo standard may be useful for evaluating sagging. Based on the photo standard, a score of 2, at which sagging becomes detectable appeared at the age of 40 years. In parallel, 3D analysis of replicas around the cheek was performed to morphologically analyse age-related changes in sagging. When the depth parameter was compared between the nasolabial groove and the mouth corners, a higher value was observed in the nasolabial groove until the age of 40 years, but higher values were seen in the mouth corners thereafter. This may have been because sagging in the cheeks descends to the area around the mouth, resulting in reversion in the sWv value. These findings indicated that sagging in the cheeks becomes morphologically distinct in women in their forties.

  13. Morphological parameters and genetic diversity of progenies from seed production areas and unimproved stands of teak (Tectona grandis L.f.) in India

    Institute of Scientific and Technical Information of China (English)

    N. Lyngdoh; Geeta Joshi; G. Ravikanth; R. Vasudeva; R. Uma Shaanker

    2013-01-01

    We compared morphological and genetic attributes of prog-eny obtained from three seed production areas (SPAs) and three corre-sponding unimproved stands (UIS) of teak (Tectona grandis L.f) at three broad teak growing regions in the state of Karnataka, India. In general, seed morphological parameters such as seed weight, seed size and seed emptiness were significantly superior in SPAs compared to UISs. Seed germination percentage was also higher in seeds from SPAs. Seedling performance measured at two monthly intervals for six months was ob-served to be superior in SPAs at two of the three regions compared. Although the genetic diversity of progeny of SPAs was lower than UIS at all regions, the values were moderately high. Germination percent was positively correlated with fruit weight and kernel weight per seed, while diversity indices were negatively correlated with fruit weight, fruit di-ameter and kernel weight per seed. SPAs proved important as a source of moderately improved planting material with no severe threat to the ge-netic diversity of future plantations.

  14. The effects of dietary xylooligosaccharide on mucosal parameters, intestinal microbiota and morphology and growth performance of Caspian white fish (Rutilus frisii kutum) fry.

    Science.gov (United States)

    Hoseinifar, Seyed Hossein; Sharifian, Maryam; Vesaghi, Mohammad Javad; Khalili, Mohsen; Esteban, M Ángeles

    2014-08-01

    The present study investigates the effects of different levels of dietary xylooligosaccharide (XOS) on skin mucus bactericidal activity and protein content, intestinal microbiota and morphology as well as growth performance of Caspian white fish (Rutilus frisii kutum) fry. The specimens (1.54 ± 0.03 g) were fed experimental diets supplemented with different levels of XOS [0% (control), 1%, 2% and 3%] for 8 weeks. The results revealed that feeding on XOS significantly increased skin mucus antibacterial activity and protein levels (P 0.05). These results demonstrate beneficial effects of dietary XOS on different parameters of mucosal immunity (both skin mucus and intestinal microbiota) and encourage further studies regards various aspect of XOS administration in early life stages of fish.

  15. Synthesis, structure and properties of nickel-iron-tungsten alloy electrodeposits - part I: Effect of synthesis parameters on chemical composition, microstructure and morphology

    Directory of Open Access Journals (Sweden)

    Ćirović N.

    2015-01-01

    Full Text Available Kinetic and operational electrolysis parameters determine the polarization characteristics, electrodeposition current efficiency, morphology, chemical composition and microstructure of nickel/iron/tungsten alloy deposits. The alloys electrodeposited at a current density of 50 mAcm-2 to 1000 mAcm-2 contain an amorphous phase and nanocrystals of an FCC solid solution of iron and tungsten in nickel. During annealing at temperatures above 500ºC, amorphous phase crystallization, crystalline grain growth of the FCC phase and a reduction in both internal microstrain and minimum density of chaotically distributed dislocations take place in the alloy. Milling the spongy deposit of the alloy causes amorphous phase crystallization, FCC-phase crystalline grain growth, and size reduction and rounding of powder particles. [Projekat Ministarstva nauke Republike Srbije, br. 172057

  16. Fracture Assessment of Strengthened Cracked Metallic Components Using FRP Stiffeners

    Science.gov (United States)

    Ahmed, W. K.; Mourad, A.-H. I.

    2015-07-01

    The present study focuses on applying the fracture mechanics approach to the fracture assessment of a cracked member/component strengthened with fiber-reinforced polymer composite stiffeners. The parameters of linear elastic fracture mechanics (LEFM) — the stress intensity factor and the crack opening displacement — are estimated using a finite-element analysis. A metallic plate with an edge crack repaired with fiber-reinforced polymer composite stiffeners is considered in the study. The effects of crack length, debonding length, and adhesive stiffness on the LEFM parameters are examined. Two different loading conditions are considered — axial tension and bending. The results obtained show that fiber-reinforced polymer composite stiffeners are very useful in repairing cracked metallic components.

  17. Assessment of circumferential cracks in hypereutectic Al-Si clutch housings

    Directory of Open Access Journals (Sweden)

    M. Haghshenas

    2017-04-01

    Full Text Available As in situ natural composites with silicon phase acting as the reinforcing phase, Al-Si alloys are among most commonly used aluminum alloys in automotive applications (i.e. engine component. Silicon contributes to the strength of Al-Si alloys through load transfer from the Al matrix to the hard (rigid Si phase in the microstructure (load-carrying capacity. Casting parameters (i.e. solidification rate, elemental segregation, secondary dendrite spacing… as well as the size and distribution of the microstructural constituents in Al-Si alloys (i.e. morphology of Si particles, intermetallic compounds, secondary dendrite spacing contribute directly to the mechanical response and failure (or fracture behavior of the alloy within the service. In hyper-eutectic Al-Si alloys (i.e. B390.0, distribution of coarse pre-eutectic Si particle mainly contribute to stress concentration, crack initiation and propagation during the actual service condition. In the present paper, the parameters contribution to the formation of the circumferential cracks in clutch housings made of die cast hyper-eutectics B390.0 Al-Si alloys are assessed through optical microscopy and scanning electron microscopy. Casting variable, cooling rate, their effect on the cracks as well some of the possible causes are also discussed in detail.

  18. Environmentally assisted cracking in light water reactors.

    Energy Technology Data Exchange (ETDEWEB)

    Chopra, O. K.; Chung, H. M.; Clark, R. W.; Gruber, E. E.; Shack, W. J.; Soppet, W. K.; Strain, R. V.

    2007-11-06

    This report summarizes work performed by Argonne National Laboratory on fatigue and environmentally assisted cracking (EAC) in light water reactors (LWRs) from January to December 2002. Topics that have been investigated include: (a) environmental effects on fatigue crack initiation in carbon and low-alloy steels and austenitic stainless steels (SSs), (b) irradiation-assisted stress corrosion cracking (IASCC) of austenitic SSs in BWRs, (c) evaluation of causes and mechanisms of irradiation-assisted cracking of austenitic SS in PWRs, and (d) cracking in Ni-alloys and welds. A critical review of the ASME Code fatigue design margins and an assessment of the conservation in the current choice of design margins are presented. The existing fatigue {var_epsilon}-N data have been evaluated to define the effects of key material, loading, and environmental parameters on the fatigue lives of carbon and low-alloy steels and austenitic SSs. Experimental data are presented on the effects of surface roughness on fatigue crack initiation in these materials in air and LWR environments. Crack growth tests were performed in BWR environments on SSs irradiated to 0.9 and 2.0 x 10{sup 21} n x cm{sup -2}. The crack growth rates (CGRs) of the irradiated steels are a factor of {approx}5 higher than the disposition curve proposed in NUREG-0313 for thermally sensitized materials. The CGRs decreased by an order of magnitude in low-dissolved oxygen (DO) environments. Slow-strain-rate tensile (SSRT) tests were conducted in high-purity 289 C water on steels irradiated to {approx}3 dpa. The bulk S content correlated well with the susceptibility to intergranular SCC in 289 C water. The IASCC susceptibility of SSs that contain >0.003 wt. % S increased drastically. bend tests in inert environments at 23 C were conducted on broken pieces of SSRT specimens and on unirradiated specimens of the same materials after hydrogen charging. The results of the tests and a review of other data in the literature

  19. Crack propagation modeling using Peridynamic theory

    Science.gov (United States)

    Hafezi, M. H.; Alebrahim, R.; Kundu, T.

    2016-04-01

    Crack propagation and branching are modeled using nonlocal peridynamic theory. One major advantage of this nonlocal theory based analysis tool is the unifying approach towards material behavior modeling - irrespective of whether the crack is formed in the material or not. No separate damage law is needed for crack initiation and propagation. This theory overcomes the weaknesses of existing continuum mechanics based numerical tools (e.g. FEM, XFEM etc.) for identifying fracture modes and does not require any simplifying assumptions. Cracks grow autonomously and not necessarily along a prescribed path. However, in some special situations such as in case of ductile fracture, the damage evolution and failure depend on parameters characterizing the local stress state instead of peridynamic damage modeling technique developed for brittle fracture. For brittle fracture modeling the bond is simply broken when the failure criterion is satisfied. This simulation helps us to design more reliable modeling tool for crack propagation and branching in both brittle and ductile materials. Peridynamic analysis has been found to be very demanding computationally, particularly for real-world structures (e.g. vehicles, aircrafts, etc.). It also requires a very expensive visualization process. The goal of this paper is to bring awareness to researchers the impact of this cutting-edge simulation tool for a better understanding of the cracked material response. A computer code has been developed to implement the peridynamic theory based modeling tool for two-dimensional analysis. A good agreement between our predictions and previously published results is observed. Some interesting new results that have not been reported earlier by others are also obtained and presented in this paper. The final objective of this investigation is to increase the mechanics knowledge of self-similar and self-affine cracks.

  20. ENDOFEM INTEGRATED METHODOLOGY FOR FATIGUE CRACK GROWTH

    Institute of Scientific and Technical Information of China (English)

    C.F.Lee; L.T.Hsiao

    2002-01-01

    In this paper, the FEM with the incremental endochronic cyclic plasticity (EndoFEM) and the rc controlled node-released strategy are employed to study the fatigue crack opened/closed load (Pop) of A1 2024-T3 CCT specimens provided by Mageed and Pandey under several crack lengths and the constant amplitude with various load ratio (R). After statisfactory results are achieved by comparisons of computed Pop values and cited experimental data, the simulations will be extended to the crack lengths with significant bending effect due to short ligaments or high peak (Pmax) or high positive or very low negative R cyclic loads. Through these simulations, the complete map of Pop/Pmax vs. Kmax and R can be constructed and thereafter its correspondant empirical formulae can be proposed. Using these formulae and selecting the traditional fatigue crack growth parameter ΔKeff, the A1 2024-T3 fatigue crack growth rate da/dN vs. ΔK and R data, provided by Hiroshi and Schijve, can be employed to proposed empirical formulae of da/dN vs. ΔKeff and R. After integration, fatigue-crack-growth length a vs. N curves computed by EndoFEM can be obtained. The results are agreed very well with the existing experimental curves. According to the above procedures of simulation and steps of comparions with experiment, this paper may provides an integrate methodology of numerical simulation in the studies of fatigue crack growth for academic and industrial researches and design analysis.

  1. Slow Crack Growth of Brittle Materials With Exponential Crack-Velocity Formulation. Part 1; Analysis

    Science.gov (United States)

    Choi, Sung R.; Nemeth, Noel N.; Gyekenyesi, John P.

    2002-01-01

    Extensive slow-crack-growth (SCG) analysis was made using a primary exponential crack-velocity formulation under three widely used load configurations: constant stress rate, constant stress, and cyclic stress. Although the use of the exponential formulation in determining SCG parameters of a material requires somewhat inconvenient numerical procedures, the resulting solutions presented gave almost the same degree of simplicity in both data analysis and experiments as did the power-law formulation. However, the fact that the inert strength of a material should be known in advance to determine the corresponding SCG parameters was a major drawback of the exponential formulation as compared with the power-law formulation.

  2. Sensitivity analysis of longitudinal cracking on asphalt pavement using MEPDG in permafrost region

    OpenAIRE

    Chen Zhang; Hainian Wang; Zhanping You; Biao Ma

    2015-01-01

    Longitudinal cracking is one of the most important distresses of asphalt pavement in permafrost regions. The sensitivity analysis of design parameters for asphalt pavement can be used to study the influence of every parameter on longitudinal cracking, which can help optimizing the design of the pavement structure. In this study, 20 test sections of Qinghai–Tibet Highway were selected to conduct the sensitivity analysis of longitudinal cracking on material parameter based on Mechanistic-Empiri...

  3. Detailed investigation of the influence of the process parameters on the nano-morphology of Ag deposited on SiC by radio-frequency sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Ruffino, F.; Grimaldi, M. G. [Dipartimento di Fisica e Astronomia Universita di Catania and MATIS IMM-CNR, via S. Sofia 64, I-95123 Catania (Italy)

    2011-08-15

    In this work, a detailed study of the influence of the synthesis parameters (deposition time t and emission current I) on the morphological properties of Ag nanoparticles sputter-deposited on silicon carbide is carried out. Using the atomic force microscopy technique, we analyzed the evolution of several structural characteristics as a function both of t and I: the length and width of the Ag nanoparticles, the number of nanoparticles per unit area, the nanoparticles' fraction of the covered area, and the roughness of the resulting Ag film. Using consolidated theoretical frameworks and fitting approaches, the relations between such quantities and the process parameters t and I were established. In particular, the application of the interrupted coalescence model allowed us to evaluate the critical mean island diameter for the partial coalescence process; the dynamic scaling theories of growing interfaces lead, instead, to the determination of the dynamic scaling, growth, and roughness exponents (the values of which suggest a conservative growth process of the islands in which the atomic surface diffusion plays a key role). Finally, the Avrami approach to the study of the evolution of the fraction of area covered by the Ag islands allowed us to evaluate the Avrami exponent.

  4. Changes in blood morphology and chosen biochemical parameters in ultra-marathon runners during a 100-km run in relation to the age and speed of runners

    Directory of Open Access Journals (Sweden)

    Zbigniew Jastrzębski

    2016-10-01

    Full Text Available Objectives: The objective of the study was to reveal morphology, electrolyte and chosen biochemical parameters in terms of health risk in runners in reference to their age and running speed in the case of running a distance of 100 km, which occur after 12 h or 24 h of recovery. Material and Methods: Fourteen experienced, male, amateur, ultra-marathon runners, divided into two age and two speed groups took part in the 100-km run. Blood samples for analyses indexes were collected from the ulnar vein just before the run, after 25 km, 50 km, 75 km and 100 km, as well as 12 h and 24 h after termination of the run. Results: The sustained ultramarathon run along with the distance covered (p < 0.05 caused an increase in myoglobin (max 90-fold, bilirubin (max 2.8-fold and total antioxidant status (max 1.15-fold, which also continued during the recovery. Significant changes in the number of white blood cells were observed with each sequential course and could be associated with muscle damage. The electrolyte showed changes towards slight hyperkalemia, but no changes in natrium and calcium concentrations. There were no significant differences between the age and speed groups for all the parameters after completing the 100-km run as well as after 12 h and 24 h of recovery. Conclusions: Considering changes in blood morphology and chosen biochemical parameters in ultra-marathon runners during a 100-km run it can be stated that such an exhausting effort may be dangerous for human health due to metabolic changes and large damage to the organs. Negative metabolic changes are independent of age of an ultramarathon runner and occur both in younger (32±5.33 years and older participants (50.56±9.7 years. It can be concluded that organ damage and negative metabolic changes during a 100-km run occur similarly in participants less experienced as well as in well trained runners. Int J Occup Med Environ Health 2016;29(5:801–814

  5. Functional and morphological parameters with tissue characterization of cardiovascular magnetic imaging in clinically verified ''infarct-like myocarditis''

    Energy Technology Data Exchange (ETDEWEB)

    Schwab, Johannes [Paracelsus Medical Univ., General Hospital Nuremberg (Germany). Dept. of Cardiology and Radiology; Rogg, H.J.; Pauschinger, M.; Fessele, K. [Paracelsus Medical Univ., General Hospital Nuremberg (Germany). Dept. of Cardiology; Bareiter, T.; Baer, I. [Paracelsus Medical Univ., General Hospital Nuremberg (Germany). Dept. of Cardiology and Neuroradiology; Loose, R. [Paracelsus Medical Univ., General Hospital Nuremberg (Germany). Dept. of Radiology

    2016-04-15

    Cardiac magnetic resonance (CMR) has increasingly proved to be a valuable diagnostic tool for evaluating patients with suspected myocarditis. The objective of this study was to evaluate the diagnostic value of functional and morphological parameters including tissue characterization in patients with ''infarct-like myocarditis''. 43 patients with clinically verified cases of ''infarct-like myocarditis'' (median time to MRI scanning after admission for acute symptoms 3 days) and 35 control patients matched by age and sex were included in this retrospective case control study. In this study we used a 1.5 T MRI scanner conducting steady-state-free-precession sequences, T2-weighted imaging, T1-weighted imaging before and after contrast administration and late gadolinium enhancement sequences. According to the recommendations for CMR diagnosis of myocarditis (Lake Louise consensus criteria), a scan was positive for acute myocarditis if 2 of 3 CMR criteria were present. 30 % of the patients with ''infarct-like myocarditis'' had a reduced left ventricular ejection fraction, 11 % had an increased LV end-diastolic volume index and 35 % had an increased LV mass index. The sensitivity of wall motion abnormalities was 63 % with a regional distribution in 49 %. In 47 % of cases regional wall motion abnormalities were present in the lateral left ventricular segments. Pericardial effusions were discovered in 65 % of cases with a circular appearance in 21 % and focal manifestation in 44 %. The diagnostic sensitivity, specificity, and accuracy of CMR in patients with ''infarct-like myocarditis'' were 67 %, 100 % and 82 %, respectively. The LGE alone was the most sensitive test parameter with 86 %, providing a specificity of 100 % and accuracy of 92 %. Our study results can be applied to the subgroup of patients with ''infarct-like myocarditis'', where we found that LGE alone was the

  6. Hypervelocity impact on brittle materials of semi-infinite thickness: fracture morphology related to projectile diameter

    Science.gov (United States)

    Taylor, Emma A.; Kay, Laurie; Shrine, Nick R. G.

    Hypervelocity impact on brittle materials produces features not observed on ductile targets. Low fracture toughness and high yield strength produce a range of fracture morphologies including cracking, spallation and shatter. For sub-mm diameter projectiles, impact features are characterised by petaloid spallation separated by radial cracks. The conchoidal or spallation diameter is a parameter in current cratering equations. An alternative method for interpreting hypervelocity impacts on glass targets of semi-infinite thickness is tested against impact data produced using the Light Gas Gun (LGG) facility at the University of Kent at Canterbury (UKC), U.K. Spherical projectiles of glass and other materials with diameters 30-300 μm were fired at ~5 km s^-1 at a glass target of semi-infinite thickness. The data is used to test a power law relationship between projectile diameter and crack length. The results of this work are compared with published cratering/spallation equations for brittle materials.

  7. CRACK2 - Modelling calcium carbonate deposition from bicarbonate solution in cracks in concrete

    Energy Technology Data Exchange (ETDEWEB)

    Brodersen, K

    2003-03-01

    The numerical CRACK2 model simulates precipitation of calcite from calcium bicarbonate solution (e.g. groundwater) passing through cracks in concrete or other cementitious materials. A summary of experimental work is followed by a detailed description of the model. Hydroxyl ions are transported by diffusion in pore systems in columns of cementitious materials. The hydroxyl is precipitating calcite from a flow of bicarbonate solution in a crack connecting the ends of a row of such columns. The cementitious material is simulated as calcium hydroxide mixed with inert material but with sodium hydroxide dissolved in the pore solution. Diffusive migration of cesium as radioactive isotope is also considered. Electrical interaction of the migrating ions is taken into account. Example calculations demonstrate effects of parameter variations on distribution of precipitated calcite in the crack and on the composition of the outflowing solution, which can be compared directly with experimental results. Leaching behavior of sodium can be used to tune the model to experimental observations. The calcite is mostly precipitated on top of the original crack surface and may under certain circumstances fill the crack. The produced thin layers of low porosity calcite act as a diffusion barrier limiting contact between cement and solution. Pore closure mechanisms in such layers are discussed. Implications for safety assessment of radioactive waste disposal are shortly mentioned. The model is also relevant for conventional uses of concrete. (au)

  8. Finite-Element Analysis of Crack Arrest Properties of Fiber Reinforced Composites Application in Semi-Elliptical Cracked Pipelines

    Science.gov (United States)

    Wang, Linyuan; Song, Shulei; Deng, Hongbo; Zhong, Kai

    2017-07-01

    In nowadays, repair method using fiber reinforced composites as the mainstream pipe repair technology, it can provide security for X100 high-grade steel energy long-distance pipelines in engineering. In this paper, analysis of cracked X100 high-grade steel pipe was conducted, simulation analysis was made on structure of pipes and crack arresters (CAs) to obtain the J-integral value in virtue of ANSYS Workbench finite element software and evaluation on crack arrest effects was done through measured elastic-plastic fracture mechanics parameter J-integral and the crack arrest coefficient K, in a bid to summarize effect laws of composite CAs and size of pipes and cracks for repairing CAs. The results indicate that the K value is correlated with laying angle λ, laying length L2/D1, laying thickness T1/T2of CAs, crack depth c/T1 and crack length a/c, and calculate recommended parameters for repairing fiber reinforced composite CAs in terms of two different crack forms.

  9. Controlling Foam Morphology of Poly(methyl methacrylate via Surface Chemistry and Concentration of Silica Nanoparticles and Supercritical Carbon Dioxide Process Parameters

    Directory of Open Access Journals (Sweden)

    Deniz Rende

    2013-01-01

    Full Text Available Polymer nanocomposite foams have received considerable attention because of their potential use in advanced applications such as bone scaffolds, food packaging, and transportation materials due to their low density and enhanced mechanical, thermal, and electrical properties compared to traditional polymer foams. In this study, silica nanofillers were used as nucleating agents and supercritical carbon dioxide as the foaming agent. The use of nanofillers provides an interface upon which CO2 nucleates and leads to remarkably low average cell sizes while improving cell density (number of cells per unit volume. In this study, the effect of concentration, the extent of surface modification of silica nanofillers with CO2-philic chemical groups, and supercritical carbon dioxide process conditions on the foam morphology of poly(methyl methacrylate, PMMA, were systematically investigated to shed light on the relative importance of material and process parameters. The silica nanoparticles were chemically modified with tridecafluoro-1,1,2,2-tetrahydrooctyl triethoxysilane leading to three different surface chemistries. The silica concentration was varied from 0.85 to 3.2% (by weight. The supercritical CO2 foaming was performed at four different temperatures (40, 65, 75, and 85°C and between 8.97 and 17.93 MPa. By altering the surface chemistry of the silica nanofiller and manipulating the process conditions, the average cell diameter was decreased from 9.62±5.22 to 1.06±0.32 μm, whereas, the cell density was increased from 7.5±0.5×108 to 4.8±0.3×1011 cells/cm3. Our findings indicate that surface modification of silica nanoparticles with CO2-philic surfactants has the strongest effect on foam morphology.

  10. Defining a relationship between incident wave parameters and morphologic evolution of shoals on ebb tidal deltas using long term X-band radar observation from RIOS

    Science.gov (United States)

    Humberston, J. L.; McNinch, J.; Lippmann, T. C.

    2016-12-01

    The morphology of tidal inlet ebb-shoals varies dynamically over time, particularly in response to large wave events. Understanding which wave qualities most influence shoals' evolution would support advancements in sediment bypassing models as well as targeted maintenance dredging for hydrographic purposes. Unfortunately, shallow and rapidly changing bathymetry, turbid waters and ambiguous wave speeds resulting from multiple shoaling and de-shoaling areas limits many traditional surveying techniques from obtaining the spatial and temporal resolution necessary to effectively characterize shoal development. The Radar Inlet Observing System (RIOS) is a uniquely designed mobile X-band radar system that can be deployed to inlet environments and, using roof-mounted solar panels and an automatically triggered highly efficient diesel generator, run automated hourly collections and wirelessly stream data for up to several months at a time in nearly all weather and water conditions. During 2015 and early 2016, RIOS was deployed to St. Augustine Inlet, FL., New River Inlet, N.C., and Oregon Inlet, N.C. for periods of one to six months to allow for measureable shoal evolution. During deployments, ten minute collections (at 1 Hz) were conducted every hour and the data gridded to a 5m alongshore/cross-shore grid. Raw intensity returns were time-averaged and analyzed to define three metrics of shoal evolution: movement direction, movement velocity and inferred bathymetry. For each location and time period, wave frequencies, wave directions and significant wave heights were collected from the nearest wave-buoy. Time lapse videos of shoal positions were inspected and used in concert with cross-correlations values from each pair of shoal and wave parameters to determine the incident wave qualities most strongly relating to shoal evolution. Preliminary results suggest wave height, more than frequency, controls shoal movement. Wave direction and size collaboratively appear to direct

  11. Assessment of the influence of the inflammatory process on the activation of blood platelets and morphological parameters in patients with ulcerative colitis (colitis ulcerosa

    Directory of Open Access Journals (Sweden)

    Halina Kemona

    2011-04-01

    Full Text Available Ulcerative colitis (colitis ulcerosa is a non-specific inflammatory bowel disease of unknown etiology. The symptoms which are observed in the course of ulcerative colitis are: an increase in the number of leukocytes and blood platelets, an increase in the concentration of IL-6 and anemia. Blood platelets are the key element, linking the processes of hemostasis, inflammation and the repair of damaged tissues. Activation of blood platelets is connected with changes in their shape and the occurrence of the reaction of release. P-selectin appears on the surfaces of activated blood platelets and the concentration level of soluble P-selectin increases in the blood plasma. The aim of this study was to define whether the increased number of blood platelets in patients with ulcerative colitis accompanies changes in their activation and morphology. A total of 16 subjects with ulcerative colitis and 32 healthy subjects were studied. Mean platelet count, morphological parameters of platelets and MPC were measured using an ADVIA 120 hematology analyzer. Concentrations of sP-selectin and IL-6 in serum were marked by immunoassay (ELISA. MPC, concentration of sP-selectin and IL-6 were significantly higher in subjects with ulcerative colitis compared to those in the healthy group. There was a decrease of MPV in patients with ulcerative colitis, which is statistically significant. Chronic inflammation in patients with ulcerative colitis causes an increase in the number of blood platelets, a change in their morphology and activation. Decreased MPV value reflects activation and the role blood platelets play in the inflammatory process of the mucous membrane of the colon. A high concentration of sP-selectin, which is a marker of blood platelet activation, demonstrates their part in the inflammatory process. The increase in the concentration of sP-selectin correlated positively with the increase in concentration of IL-6. This is why it may be a useful marker

  12. Measure the Parameters of Morphology of Pathology by Image Processing Toolbox%图像处理工具箱测定卵泡的形态参数

    Institute of Scientific and Technical Information of China (English)

    李惠梅; 鲍立峰

    2009-01-01

    目的:数字图像处理被广泛的应用在生物医学领域,并取得一些成果,但对卵泡形态参数进行测量的系统报道不多.本文研究利用计算机图像处理技术,对促排卵治疗患者的卵泡形态参数进行测量,在生殖医学的临床诊断方面有重要的现实意义和广阔的应用前景.方法:使用The MathWorks公司的MATLAB软件中的图像处理工具箱(image pro-eessing toolbox)编写程序.先将获取的原始卵泡图像先进行四步预处理:一、提取原始图像,二、估计背景亮度,三、调整背景,四、调整对比度;然后再进行四步图像分割:一、提取图片,二、图像二值化,三、面积围封,四、确定边界.最后对得到所需样本.测量卵泡面积、周长、最大直径、等效圆直径、似圆度五个形态参数.结果:测出比较理想的卵泡的面积、周长、最大直径、等效圆直径、似圆度五个形态参数.结论:应用图像处理工具箱(image processing toolbox)可对卵泡形态参数的实现简便的测量.%Objective: Digital images processing is widely applied in the fields of biology and medicine, and some achievements have been gained by this technique. But there is few reports on measure the parameters of morphology of pathology from the patients which were threated by ovulation induction, by computer processing techniques. The work shows it has significant value in clinical diagnosis and reproductive medicine at present and in the future. Methods: Write the programmeces by Image Processing Toolbox in MATLAB. The original pathology images are preprocessed by 4 steps: step 1: read imagejstep 2: imopen the curve background brightness; step 3: adjust the background; step 4: adjust the contrast. Then segmentation image by 4 steps; step 1: read image; step 2: estimation the image; step 3: remove the noise; step 4: find the boundaries. The end, measure the parameters of morphology. Results: The pathology was studied percase for their

  13. Metallurgical and mechanical parameters controlling alloy 718 stress corrosion cracking resistance in PWR primary water; Facteurs metallurgiques et mecaniques controlant l'amorcage de defauts de corrosion sous contrainte dans l'alliage 718 en milieu primaire des reacteurs a eau sous pression

    Energy Technology Data Exchange (ETDEWEB)

    Deleume, J

    2007-11-15

    Improving the performance and reliability of the fuel assemblies of the pressurized water reactors requires having a perfect knowledge of the operating margins of both the components and the materials. The choice of alloy 718 as reference material for this study is justified by the industrial will to identify the first order parameters controlling the excellent resistance of this alloy to Stress Corrosion Cracking (SCC). For this purpose, a specific slow strain rate (SSR) crack initiation test using tensile specimen with a V-shaped hump in the middle of the gauge length was developed and modeled. The selectivity of such SSR tests in simulated PWR primary water at 350 C was clearly established by characterizing the SCC resistance of nine alloy 718 thin strip heats. Regardless of their origin and in spite of a similar thermo-mechanical history, they did not exhibit the same susceptibility to SCC crack initiation. All the characterized alloy 718 heats develop oxide scale of similar nature for various exposure times to PWR primary medium in the temperature range [320 C - 360 C]. {delta} phase precipitation has no impact on alloy 718 SCC initiation behavior when exposed to PWR primary water, contrary to interstitial contents and the triggering of plastic instabilities (PLC phenomenon). (author)

  14. Crack Detection for Aerospace Quality Spur Gears

    Science.gov (United States)

    Decker, Harry J.

    2002-01-01

    Health and Usage Monitoring System research and development involves analysis of the vibration signals produced by a gearbox throughout its life. There are two major advantages of knowing the actual lifetime of a gearbox component: safety and cost. In this report, a technique is proposed to help extract the critical data and present it in a manner that can be easy to understand. The key feature of the technique is to make it independent of speed, torque and prior history for localized, single tooth damage such as gear cracks. This extraction technique is demonstrated on two sets of digitized vibration data from cracked spur gears. Standard vibration diagnostic parameters are calculated and presented for comparison. Several new detection algorithms are also presented. The results of this study indicate that crack detection methods examined are not robust or repeatable. The proposed techniques provide a limited improvement to existing diagnostic parameters. Current techniques show that the cracks progressed at a much faster rate than anticipated which reduced available time for detection.

  15. Estimating crack growth in temperature damaged concrete

    Science.gov (United States)

    Recalde, Juan Jose

    2009-12-01

    Evaluation of the structural condition of deteriorated concrete infrastructure and evaluation of new sustainable cementitious materials require an understanding of how the material will respond to applied loads and environmental exposures. A fundamental understanding of how microstructural changes in these materials relate to changes in mechanical properties and changes in fluid penetrability is needed. The ability to provide rapid, inexpensive assessment of material characteristics and relevant engineering properties is valuable for decision making and asset management purposes. In this investigation, the effects of changes in dynamic elastic properties with water content and fluid penetrability properties before and after a 300°C exposure were investigated based on estimates of the crack density parameter from dry and saturated cracked media. The experimental and analytical techniques described in this dissertation allow calculation of a value for the crack density parameter using nondestructive determination of wet and dry dynamic shear modulus of relatively thin disks. The techniques were used to compare a conventional concrete mixture to several mixtures with enhanced sustainability characteristics. The three enhanced sustainable materials investigated were a very high fly ash mixture, a magnesium phosphate cement based mortar, and a magnesium phosphate cement based concrete, and were compared to a conventional concrete mixture. The analysis provided both quantitative assessment of changes with high temperature damage and autogenous healing, and estimates of changes in mean crack trace lengths. The results showed that water interaction, deterioration due to damage, and autogenous healing recovery were different for the magnesium phosphate cement based mixtures than the portland cement based concrete mixtures. A strong correlation was found between log-transformed Air Permeability Index, dynamic shear modulus, and crack density parameter. The findings imply

  16. Simulation of Interfacial Corner Cracks in Bimaterial Systems

    DEFF Research Database (Denmark)

    Veluri, Badrinath; Jensen, Henrik Myhre

    2012-01-01

    . The crack propagation is investigated by estimating the fracture mechanics parameters that include the strain energy release rate, crack front profiles and the three-dimensional mode-mixity along the crack front. A numerical approach is then applied for coupling the far field solutions utilizing......, a custom quantitative approach was formulated based on the finite element method with iterative adjustment of the crack front to estimate the critical delamination stress as a function of the fracture criterion and corner angles. The implication of the results on the delamination is discussed in terms...... of crack front profiles and the critical stresses, which can then be used as the framework for modeling reliability of advanced interconnects system....

  17. Determination of fatigue cracking direction in composite laminates

    Institute of Scientific and Technical Information of China (English)

    DAI Yao; HAO Gui-xiang; LI Yong-dong; HE Jia-wen; CUI Jian-guo; LI Nian; FU Yong-hui; SUN Jun

    2005-01-01

    The interface plays the central role in the failure analysis of composite laminates, therefore, the interface material properties are taken as the independent parameters. A simple, universal and practicable criterion, i.e. a ratio criterion of strain energy release rate, is proposed to determine the growing direction of a fatigue crack in the composite laminates. The method of arbitrary lines, which is very effective to solve the problems with high gradient feature, is used to analyze the experimental results at the key moments when a crack kinks, turns into the interface,or bifurcates. An approximate method of computing the energy release rate is given. The fatigue fracture tests of composite laminates are carried out, and the numerical predictions of crack growing directions agree well with the experimental results. It is concluded that the methods suggested in this paper are effective to obtain the cracking history and the growing path of a fatigue crack in composite laminates.

  18. Evaluation of Surface Cracks Using Magnetic Flux Leakage Testing

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The magnetic field distribution characteristics of surface cracks with various widths are discussed based on finite element (FEM) results. The crack depth was 0.20 mm, the width range was from 0.02 to 1.00 mm. The results showed that crack width and lift-off (the distance between surface and sensor) will influence signals. Discussed in this paper is the influence of various lift-off parameters on the peak to peak values of the normal component in magnetic flux leakage testing. The effects can be applied to evaluate surface breaking cracks of different widths and depths.An idea is presented to smooth narrow, sharp crack tips using alternating current (AC) field magnetization.

  19. A fracture mechanics analysis of bonded repaired skin/stiffener structures with inclined central crack

    Energy Technology Data Exchange (ETDEWEB)

    Chung, Ki Hyun; Yang, Won Ho; Kim, Cheol; Heo, Sung Pil [Sungkyunkwan Univ., Seoul (Korea, Republic of); Ko, Myung Hoon [Daelim College, Anyang (Korea, Republic of)

    2001-07-01

    Composite patch repair of cracked aircraft structures has been accepted as one of improving fatigue life and attaining better structural integrity. Analysis for the stress intensity factor at the skin/stiffener structure with inclined central crack repaired by composite stiffened panels are developed. A numerical investigation was conducted to characterize the fracture behavior and crack growth behavior. In order to investigate the crack growth direction, Maximum Tangential Stress(MTS) criteria is used. The main objective of this research is the validation of the inclined crack patching design. In this paper, the reduction of stresses intensity factors at the crack-tip and prediction of crack growth direction are determined to evaluate the effects of various non-dimensional design parameter including; composite patch thickness and stiffener distance. The research on cracked structure subjected to mixed mode loading is accomplished and it is evident that more work using different approaches is necessary.

  20. Influence factors of morphological development of soil cracks in degraded slopes in Yuanmou dry-hot valley region%元谋干热河谷区退化坡地土壤裂缝形态发育的影响因子

    Institute of Scientific and Technical Information of China (English)

    熊东红; 杨丹; 李佳佳; 苏正安; 董一帆; 翟娟

    2013-01-01

      土壤开裂影响土体内水分散失、溶质运移及土体结构,是元谋干热河谷坡地退化的一个重要过程及特征。该文通过对元谋干热河谷退化坡地典型土壤裂缝样方的实地调查及数据的室内分析,系统分析了土壤理化属性对裂缝发育程度的影响。研究结果表明:1)土壤裂缝发育程度与土壤黏粒含量、土壤胀缩度、土壤容重呈正相关,与土壤有机质含量、土壤总孔隙度呈较弱的负相关;2)土壤裂缝发育程度的首要影响因子是土壤结构性因子(土壤容重、总孔隙度和黏粒含量),其次为土壤胀缩度,然后是土壤有机质。该研究可为进一步研究土壤开裂导致的土地退化过程奠定基础,为制定开裂土体的改良措施提供参考。%Soil cracking is an important process and feature of the slope degradation in Yuanmou Dry-hot Valley Region, which influences water evaporation, solutes transport and soil structure. In this paper, 25 soil crack quads were investigated by using the photography method to describe the morphology of soil cracks, and meanwhile, soil samples were also obtained at soil depth 0-30 cm and >30-60 cm in the same quad. The crack area density (Dc) was obtained by ArcGIS 9.0. The values for soil physico-chemical properties were also obtained by laboratory analysis. And then, the influences of soil physico-chemical properties on the development degrees of soil cracks were analyzed by application of statistical analysis methods. The Results indicate that: (1) The development degrees of soil cracks have a positive correlation with clay content, swell-shrink property and bulk density, and are negatively correlated to organic content and soil porosity. Dc, which is the quantitative indicator for the development degrees of soil cracks has been found to have a significant strong correlation with clay content, their coefficients were 0.97 and 0.95 for 0-30 cm layer and for >30-60 cm

  1. Crack tip fracture toughness of base glasses for dental restoration glass-ceramics using crack opening displacements.

    Science.gov (United States)

    Deubener, J; Höland, M; Höland, W; Janakiraman, N; Rheinberger, V M

    2011-10-01

    The critical stress intensity factor, also known as the crack tip toughness K(tip), was determined for three base glasses, which are used in the manufacture of glass-ceramics. The glasses included the base glass for a lithium disilicate glass-ceramic, the base glass for a fluoroapatite glass-ceramic and the base glass for a leucite glass-ceramic. These glass-ceramic are extensively used in the form of biomaterials in restorative dental medicine. The crack tip toughness was established by using crack opening displacement profiles under experimental conditions. The crack was produced by Vickers indentation. The crack tip toughness parameters determined for the three glass-ceramics differed quite significantly. The crack tip parameters of the lithium disilicate base glass and the leucite base glass were higher than that of the fluoroapatite base glass. This last material showed glass-in-glass phase separation. The discussion of the results clearly shows that the droplet glass phase is softer than the glass matrix. Therefore, the authors conclude that a direct relationship exists between the chemical nature of the glasses and the crack tip parameter.

  2. Localization and characterization of fatigue cracks around fastener holes using spherically focused ultrasonic probes

    Science.gov (United States)

    Hopkins, Deborah; Datuin, Marvin; Aldrin, John; Warchol, Mark; Warchol, Lyudmila; Forsyth, David

    2017-02-01

    Results are presented from laboratory experiments and simulations that demonstrate the ability to localize fatigue cracks around fastener holes using spherically focused ultrasonic probes for shear-wave inspections. For the experiments, fatigue cracks were created in aluminum plates in a testing frame under cyclic loading. With the exceptions of one specimen with a mid-bore crack and another with a "through" crack, the remaining specimens contain surface-breaking cracks. All of the specimens were inspected for the cracks intersecting the back wall, and some were flipped over and re-inspected with the crack intersecting the front surface. Parameter and variable sensitivity studies were performed using CIVA Simulation Software. In contrast to C-scans where detection and localization of small cracks can be very difficult, modeling and initial experimental results demonstrate that cracks can be accurately located in "True" B-scans (B-scans projected in the part along the beam path). Initial results show that small-amplitude diffracted/scattered signals from the crack tips and edges are essential in obtaining clear crack traces in the True B-scans. It is important therefore that experimental data be acquired with sufficient gain to capture the diffracted/scattered signals. In all of the cases studied here, saturating the high-amplitude specular reflections from the fastener hole and crack enhanced the crack trace in the True B-scans.

  3. Mitochondrial Morphology and Fundamental Parameters of the Mitochondrial Respiratory Chain Are Altered in Caenorhabditis elegans Strains Deficient in Mitochondrial Dynamics and Homeostasis Processes.

    Science.gov (United States)

    Luz, Anthony L; Rooney, John P; Kubik, Laura L; Gonzalez, Claudia P; Song, Dong Hoon; Meyer, Joel N

    2015-01-01

    Mitochondrial dysfunction has been linked to myriad human diseases and toxicant exposures, highlighting the need for assays capable of rapidly assessing mitochondrial health in vivo. Here, using the Seahorse XFe24 Analyzer and the pharmacological inhibitors dicyclohexylcarbodiimide and oligomycin (ATP-synthase inhibitors), carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (mitochondrial uncoupler) and sodium azide (cytochrome c oxidase inhibitor), we measured the fundamental parameters of mitochondrial respiratory chain function: basal oxygen consumption, ATP-linked respiration, maximal respiratory capacity, spare respiratory capacity and proton leak in the model organism Caenhorhabditis elegans. Since mutations in mitochondrial homeostasis genes cause mitochondrial dysfunction and have been linked to human disease, we measured mitochondrial respiratory function in mitochondrial fission (drp-1)-, fusion (fzo-1)-, mitophagy (pdr-1, pink-1)-, and electron transport chain complex III (isp-1)-deficient C. elegans. All showed altered function, but the nature of the alterations varied between the tested strains. We report increased basal oxygen consumption in drp-1; reduced maximal respiration in drp-1, fzo-1, and isp-1; reduced spare respiratory capacity in drp-1 and fzo-1; reduced proton leak in fzo-1 and isp-1; and increased proton leak in pink-1 nematodes. As mitochondrial morphology can play a role in mitochondrial energetics, we also quantified the mitochondrial aspect ratio for each mutant strain using a novel method, and for the first time report increased aspect ratios in pdr-1- and pink-1-deficient nematodes.

  4. [Effects of exogenous Ca2+ on morphological and photosynthetic characteristics and chlorophyll fluorescent parameters of squash seedlings under high temperature and strong light stress].

    Science.gov (United States)

    Qin, Shu-hao; Li, Ling-ling; Chen, Na-na

    2010-11-01

    Taking squash (Cucurbita pepo L.) variety Alan as test object, this paper studied the effects of exogenous Ca2+ on the morphological and photosynthetic characteristics and chlorophyll fluorescent parameters of squash seedlings under the cross-stress of high temperature and strong light. Under the stress, applying 5-20 mmol x L(-1) of Ca2+ increased the plant height, leaf area, chlorophyll and carotenoid contents, photosynthetic rate (Pn), stoma conductance (Gs), transpiration rate (Tr), maximal PS II efficiency (Fv/Fm), actual PS II efficiency (phi(PS II)), and photochemical queching coefficient (q(P)), and decreased the intercellular CO2 concentration (Ci) and non-photochemical fluorescence quenching coefficient (NPQ), suggesting that this application of exogenous Ca2+ could effectively mitigate the damage of high temperature and strong light stress on the squash seedlings leaf, and make it keep more rapid photosynthetic electron transfer rate and higher PS II electron transfer activity. Among the treatments of applying Ca2+, 10 mmol Ca2+ x L(-1) had the best effect. When the Ca2+ application rate exceeded 40 mmol x L(1), no mitigation effect was observed on the high temperature and strong light stress.

  5. Solidification crack susceptibility of aluminum alloy weld metals

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The susceptibilities of the three aluminum alloys to solidification crack were studied with trans-varestraint tests and tensile tests at elevated temperature. Their metallurgical characteristics, morphologies of the fractured surface and dynamic cracking behaviors at elevated temperature were analyzed with a series of micro-analysis methods. The results show that dynamic cracking models can be classified into three types. The first model has the healing effect which is called type A. The second is the one with deformation and breaking down of metal bridge, called type B. The last one is with the separation of liquid film along grain boundary, called type C.Moreover, the strain rate has different effects on crack susceptibility of aluminum alloys with different cracking models. ZL101 and 5083 alloys belong to type A and type C cracking model respectively, in which strain rate has greater effect on eutectic healing and plastic deformation of metal bridge. 6082 alloy is type B cracking model in which the strain rate has little effect on the deformation ability of the liquid film.

  6. Stress analysis of fracture of atherosclerotic plaques: crack propagation modeling.

    Science.gov (United States)

    Rezvani-Sharif, Alireza; Tafazzoli-Shadpour, Mohammad; Kazemi-Saleh, Davood; Sotoudeh-Anvari, Maryam

    2016-12-09

    Traditionally, the degree of luminal obstruction has been used to assess the vulnerability of atherosclerotic plaques. However, recent studies have revealed that other factors such as plaque morphology, material properties of lesion components and blood pressure may contribute to the fracture of atherosclerotic plaques. The aim of this study was to investigate the mechanism of fracture of atherosclerotic plaques based on the mechanical stress distribution and fatigue analysis by means of numerical simulation. Realistic models of type V plaques were reconstructed based on histological images. Finite element method was used to determine mechanical stress distribution within the plaque. Assuming that crack propagation initiated at the sites of stress concentration, crack propagation due to pulsatile blood pressure was modeled. Results showed that crack propagation considerably changed the stress field within the plaque and in some cases led to initiation of secondary cracks. The lipid pool stiffness affected the location of crack formation and the rate and direction of crack propagation. Moreover, increasing the mean or pulse pressure decreased the number of cycles to rupture. It is suggested that crack propagation analysis can lead to a better recognition of factors involved in plaque rupture and more accurate determination of vulnerable plaques.

  7. Hot-crack test for aluminium alloys welds using TIG process

    Directory of Open Access Journals (Sweden)

    Deschaux-beaume F.

    2010-06-01

    Full Text Available Hot cracking is a critical defect frequently observed during welding of aluminium alloys. In order to better understand the interaction between cracking phenomenon, process parameters, mechanical factors and microstructures resulting from solidification after welding, an original hot-cracking test during welding is developed. According to in-situ observations and post mortem analyses, hot cracking mechanisms are investigated, taking into account the interaction between microstructural parameters, depending on the thermal cycles, and mechanical parameters, depending on geometry and clamping conditions of the samples and on the thermal field on the sample. Finally, a process map indicating the limit between cracking and non-cracking zones according to welding parameters is presented.

  8. Simulating Fatigue Crack Growth in Spiral Bevel Gears

    Science.gov (United States)

    Spievak, Lisa E.; Wawrzynek, Paul A.; Ingraffea, Anthony R.

    2000-01-01

    The majority of helicopter transmission systems utilize spiral bevel gears to convert the horizontal power from the engine into vertical power for the rotor. Due to the cyclical loading on a gear's tooth, fatigue crack propagation can occur. In rotorcraft applications, a crack's trajectory determines whether the gear failure will be benign or catastrophic for the aircraft. As a result, the capability to predict crack growth in gears is significant. A spiral bevel gear's complex shape requires a three dimensional model of the geometry and cracks. The boundary element method in conjunction with linear elastic fracture mechanics theories is used to predict arbitrarily shaped three dimensional fatigue crack trajectories in a spiral bevel pinion under moving load conditions. The predictions are validated by comparison to experimental results. The sensitivity of the predictions to variations in loading conditions and crack growth rate model parameters is explored. Critical areas that must be understood in greater detail prior to predicting more accurate crack trajectories and crack growth rates in three dimensions are identified.

  9. Stress intensity factors of eccentric cracks in bi-materials plate under mode I loading

    Energy Technology Data Exchange (ETDEWEB)

    Ismail, A. E. [Faculty of Mechanical and Manufacturing Engineering, Universiti Tun Hussein Onn Malaysia, 86400 Batu Pahat, Johor (Malaysia)

    2015-05-15

    Bi-material plates were generally used to joint electronic devices or mechanical components requiring dissimilar materials to be attached. During services, mechanical failure can be occurred due to the formation of cracks at the interfacial joint or away from the centre. Generally, linear elastic fracture mechanics approach is used to characterize these cracks based on stress intensity factors (SIF). Based on the literature survey, the SIFs for the central cracks were easily available. However, the SIFs for eccentric cracks were difficult to obtain. Therefore, this paper presented the SIFs for eccentric cracks subjected to mode I tension loading. Three important parameters were used such as relative crack depth, a/L, relative offset distance, b/L and elastic mismatch, E{sub 1}/E{sub 2} or α. It was found that such parameters significantly affected the characteristic of SIFs and it was depend on the location of cracks.

  10. Assessment of Reinforced Concrete Surface Breaking Crack Using Rayleigh Wave Measurement.

    Science.gov (United States)

    Lee, Foo Wei; Chai, Hwa Kian; Lim, Kok Sing

    2016-03-05

    An improved single sided Rayleigh wave (R-wave) measurement was suggested to characterize surface breaking crack in steel reinforced concrete structures. Numerical simulations were performed to clarify the behavior of R-waves interacting with surface breaking crack with different depths and degrees of inclinations. Through analysis of simulation results, correlations between R-wave parameters of interest and crack characteristics (depth and degree of inclination) were obtained, which were then validated by experimental measurement of concrete specimens instigated with vertical and inclined artificial cracks of different depths. Wave parameters including velocity and amplitude attenuation for each case were studied. The correlations allowed us to estimate the depth and inclination of cracks measured experimentally with acceptable discrepancies, particularly for cracks which are relatively shallow and when the crack depth is smaller than the wavelength.

  11. Experimental study on kinetic parameters of thermal cracking of biomass tar%生物质焦油热裂解动力学参数实验研究

    Institute of Scientific and Technical Information of China (English)

    黎柴佐; 冉景煜

    2012-01-01

    For the reason of the unstable evaporation in the tar sampling process and the difficulty of measuring and controlling reaction temperature,a moving bed as the tar sample introduction system was designed. A sample tray carrying tar was moved into the furnace with linear temperature distribution of the entrance zone. The movement of the tray instead of that of the tar,makes the tar sample introduction process more stable and the temperature easer to control. On this basis,tar cracking process and kinetic characteristics with the different sample introduction rate were studied. The results indicate the tar cracking rate is accelerated with increasing temperature at 573 ~ 1 123 K. The tar cracking rate reaches 58% at 1 123 K. The tar thermal cracking reaction is a first order reaction. On average,the activation energy is 39. 5 kJ/mol and the pre-exponential factor is 1. 58 min-1.%基于进样过程中焦油蒸发的不稳定性以及反应温度的测定和控制难度,设计了移动床焦油进样系统,使用样品槽携带焦油进入具有线性温度分布的炉膛空间,以样品槽的运动进样代替焦油流动进样,以获得稳定的焦油蒸发进样和更容易控制的反应温度.在此基础上,研究了不同进样速率下的焦油热裂解及其动力学特性.结果表明,在573 ~1 123 K,焦油的裂解率随温度的升高而加速升高,并在1 123 K时达到58%的裂解率;焦油热裂解遵循一级动力学反应,其平均活化能为39.5 kJ/mol,指前因子为1.58 min-1.

  12. Application of the cracked pipe element to creep crack growth prediction

    Energy Technology Data Exchange (ETDEWEB)

    Brochard, J.; Charras, T. [C.E.A.-C.E.-Saclay DRN/DMT, Gif Sur Yvette (France); Ghoudi, M. [C.E.A.-C.E.-Saclay, Gif Sur Yvette (France)

    1997-04-01

    Modifications to a computer code for ductile fracture assessment of piping systems with postulated circumferential through-wall cracks under static or dynamic loading are very briefly described. The modifications extend the capabilities of the CASTEM2000 code to the determination of fracture parameters under creep conditions. The main advantage of the approach is that thermal loads can be evaluated as secondary stresses. The code is applicable to piping systems for which crack propagation predictions differ significantly depending on whether thermal stresses are considered as primary or secondary stresses.

  13. Fatigue Crack Topography.

    Science.gov (United States)

    1984-01-01

    evaluating ciack initiation time and crack propagation, prgram I was used for performing the major fatigue test with the aircraft structure. In...advantage to begin with the end of the fracture, this is especially so in the case of the quantitative evaluation of striations. The overload fracture...Select the Measuring Line for Quantitative Evaluation Actually, the fatigue fracture should be inspected completely from the point of origin to the

  14. Cracking in desiccating soils

    OpenAIRE

    Ledesma Alberto

    2016-01-01

    Soil shrinkage is produced typically under desiccating conditions. Eventually shrinkage may generate cracks in the soil mass, a phenomenon that is being studied by several researchers, because its prediction is far from being a routine in Soil Mechanics. Within this context, Unsaturated Soil Mechanics provides a promising framework to understand the mechanisms involved. In addition to that, physical modelling of desiccating soils constitutes a good tool to explore the nature of this problem. ...

  15. Utopia Cracks and Polygons

    Science.gov (United States)

    2003-01-01

    MGS MOC Release No. MOC2-339, 23 April 2003This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a pattern of polygonal cracks and aligned, elliptical pits in western Utopia Planitia. The picture covers an area about 3 km (about 1.9 mi) wide near 44.9oN, 274.7oW. Sunlight illuminates the scene from the left.

  16. Fracture resistance enhancement of layered structures by multiple cracks

    DEFF Research Database (Denmark)

    Goutianos, Stergios; Sørensen, Bent F.

    2016-01-01

    A theoretical model is developed to test if the fracture resistance of a layered structure can be increased by introducing weak layers changing the cracking mechanism. An analytical model, based on the J integral, predicts a linear dependency between the number of cracks and the steady state...... fracture resistance. A finite element cohesive zone model, containing two cracking planes for simplicity, is used to check the theoretical model and its predictions. It is shown that for a wide range of cohesive law parameters, the numerical predictions agree well quantitatively with the theoretical model....... Thus, it is possible to enhance considerably the fracture resistance of a structure by adding weak layers....

  17. Cracking susceptibility of aluminum alloys during laser welding

    Directory of Open Access Journals (Sweden)

    Lara Abbaschian

    2003-06-01

    Full Text Available The influence of laser parameters in welding aluminum alloys was studied in order to reduce hot cracking. The extension of cracks at the welding surface was used as a cracking susceptibility (CS index. It has been shown that the CS changes with changing welding velocity for binary Al-Cu alloys. In general, the CS index increased until a maximum velocity and then dropped to zero, generating a typical lambda-curve. This curve is due to two different mechanisms: 1 the refinement of porosities with increasing velocity and 2 the changes in the liquid fraction due to decreasing microsegregation with increasing velocities.

  18. Slow Crack Growth of Brittle Materials With Exponential Crack-Velocity Formulation. Part 2; Constant Stress Rate Experiments

    Science.gov (United States)

    Choi, Sung R.; Nemeth, Noel N.; Gyekenyesi, John P.

    2002-01-01

    The previously determined life prediction analysis based on an exponential crack-velocity formulation was examined using a variety of experimental data on glass and advanced structural ceramics in constant stress rate and preload testing at ambient and elevated temperatures. The data fit to the relation of strength versus the log of the stress rate was very reasonable for most of the materials. Also, the preloading technique was determined equally applicable to the case of slow-crack-growth (SCG) parameter n greater than 30 for both the power-law and exponential formulations. The major limitation in the exponential crack-velocity formulation, however, was that the inert strength of a material must be known a priori to evaluate the important SCG parameter n, a significant drawback as compared with the conventional power-law crack-velocity formulation.

  19. Simulation Research on Stress Intensity Factors of Different Crack Aspect Ratios on Hollow Axles

    Institute of Scientific and Technical Information of China (English)

    ZHOU Suxia; XIE Jilong

    2009-01-01

    Because of the wicked service environment of the high speed train, it is possible that the hollow axle of the train may encounter the foreign object damage and form a sharp notch. Under the fatigue loading a crack can initiate from the notch and propagate to failure. It is noted that the stress intensity factor is the control parameter of the crack propagating, for the purpose of getting the more exact propagation characteristics, the stress intensity factor is studied mainly. The service loads of hollow axles are defined, and the stress distribution of hollow axles is obtained according to the load spectrum. The semi-ellipse crack configuration is defined with three parameters:the aspect ratio, the relative depth and the relative location along the crack front. Quarter point 20-node isoparametric degenerate singular elements are used for the region near the crack tip. The finite element model of crack extension of hollow axle is created, and the crack front is dispersed which can realize orthogonal extension. Based on this the stress intensity factors of crack front were calculated, and the distribution rules of the stress intensity factors of different initial crack shapes are obtained. The conclusions are compared with that of the analytic method and they agree with each other very well, and the calculating results show that there is a close relationship between the stress intensity factor and the initial crack shape. For a round crack the stress intensity factor at the surface point increases faster than the one at the center point with the crack propagation. However, for a narrow crack, the results are in contrast with that of a round one. So, all the cracks with different shapes propagate toward to a similar shape, and they grow at this shape to end. The study may contribute to the crack propagate characteristics research.

  20. Seismic Radiation from Crack Coalescence Model and Reconstruction of Seismically Equivalent Single Crack Model

    Science.gov (United States)

    Kame, N.; Uchida, K.

    2006-12-01

    We simulate dynamic rupture propagation in which two mode II cracks coalesce on a planar fault using a boundary integral equation method. Our main interests are in the rupture complexity and resultant seismic radiation due to coalescence and in the reconstruction of seismically equivalent another dynamic model that could be inferred only from the waveforms. First we analyze crack coalescence model (CCM) with homogeneous source parameters except on two pre- slipped regions. In CCM, a main crack nucleates, propagates and coalesces with a nucleating subsidiary crack. Our analysis shows that local high slip-rate pulse is generated by coalescence and a secondary Rayleigh slip pulse subsequently begins to propagate trailing the rupture front. Second we reconstruct a single crack model (SCM) with heterogeneous source parameters that can reproduce the same slip-rate history in CCM, that is, both models are seismically equivalent. In SCM we found singular increase in the stress drop and sudden decrease in the strength excess corresponding to the coalescence pulse region, which means that these two inhomogeneities appeared in SCM originally resulted from the stress interaction between approaching crack tips in CCM. Third we synthesize seismic radiation from CCM and successfully identify distinct phases associated with two pulses: the coalescence pulse phase shows seismic radiation similar to the stopping phase that has a typical ω-2 behavior at high frequency, which is also consistent with theoretically predicted radiation by the singular stress drop in SCM. Rayleigh slip-pulse phase appears dominantly in transverse component with strong forward directivity similar to rupture front phase although disappears in parallel component except very near the fault.

  1. Tomato fruit continues growing while ripening, affecting cuticle properties and cracking.

    Science.gov (United States)

    Domínguez, Eva; Fernández, María Dolores; Hernández, Juan Carlos López; Parra, Jerónimo Pérez; España, Laura; Heredia, Antonio; Cuartero, Jesús

    2012-12-01

    Fruit cuticle composition and their mechanical performance have a special role during ripening because internal pressure is no longer sustained by the degraded cell walls of the pericarp but is directly transmitted to epidermis and cuticle which could eventually crack. We have studied fruit growth, cuticle modifications and its biomechanics, and fruit cracking in tomato; tomato has been considered a model system for studying fleshy fruit growth and ripening. Tomato fruit cracking is a major disorder that causes severe economic losses and, in cherry tomato, crack appearance is limited to the ripening process. As environmental conditions play a crucial role in fruit growing, ripening and cracking, we grow two cherry tomato cultivars in four conditions of radiation and relative humidity (RH). High RH and low radiation decreased the amount of cuticle and cuticle components accumulated. No effect of RH in cuticle biomechanics was detected. However, cracked fruits had a significantly less deformable (lower maximum strain) cuticle than non-cracked fruits. A significant and continuous fruit growth from mature green to overripe has been detected with special displacement sensors. This growth rate varied among genotypes, with cracking-sensitive genotypes showing higher growth rates than cracking-resistant ones. Environmental conditions modified this growth rate during ripening, with higher growing rates under high RH and radiation. These conditions corresponded to those that favored fruit cracking. Fruit growth rate during ripening, probably sustained by an internal turgor pressure, is a key parameter in fruit cracking, because fruits that ripened detached from the vine did not crack.

  2. Study on the identification of the direction of the crack with vector total focusing method in ultrasonic phased arrays and the influence parameters%超声阵列矢量全聚焦裂纹识别及影响参数研究

    Institute of Scientific and Technical Information of China (English)

    焦敬品; 常予; 孙欣蓉; 何存富; 吴斌

    2015-01-01

    In view of the problem of localization and orientation identification of the crack in the industrial structure,a new vector total focusing method based on ultrasonic array technology is developed.On the basis of the corrected total focusing method,a method for recognizing the direction of the defect is proposed,which uses the vector direction of the sub array element at the focusing point,and is applied to identification of different direction of cracks.The full matrix data that collected from the CIVA simulation model is imaged by vector total focusing method.Respectively,the parameters of the sub array element have different effects on the identification of the direction of cracks.Therefore,the optimal combination of sub array parameters is proposed,which can be applied to the localization and orientation identification of multi-crack specimen.%针对工业结构中裂纹缺陷的定位和方向识别问题,发展了一种基于超声阵列技术的矢量全聚焦成像方法。在修正的全聚焦成像基础上,提出了一种利用子阵列在聚焦点处矢量方向判断缺陷方向的方法,并将其应用于不同角度裂纹的方向识别。对单裂纹 CIVA 仿真模型进行了全矩阵数据采集和矢量全聚焦成像,研究发现,子阵列检测参数对裂纹方向识别具有不同程度的影响。因此,提出了子阵列检测参数的最优组合,可同时应用于多裂纹试块的缺陷定位和方向识别。

  3. Modal Analysis for Crack Detection in Small Wind Turbine Blades

    DEFF Research Database (Denmark)

    Ulriksen, Martin Dalgaard; Skov, Jonas falk; Dickow, Kristoffer Ahrens

    2013-01-01

    The aim of the present paper is to evaluate structural health monitoring (SHM) techniques based on modal analysis for crack detection in small wind turbine blades. A finite element (FE) model calibrated to measured modal parameters will be introduced to cracks with different sizes along one edge...... of the blade. Changes in modal parameters from the FE model are compared with data obtained from experimental tests. These comparisons will be used to validate the FE model and subsequently discuss the usability of SHM techniques based on modal parameters for condition monitoring of wind turbine blades....

  4. Subcritical crack growth under mode I, II, and III loading for Coconino sandstone

    Science.gov (United States)

    Ko, Tae Young

    In systems subjected to long-term loading, subcritical crack growth is the principal mechanism causing the time-dependent deformation and failure of rocks. Subcritical crack growth is environmentally-assisted crack growth, which can allow cracks to grow over a long period of time at stresses far smaller than their failure strength and at tectonic strain rates. The characteristics of subcritical crack growth can be described by a relationship between the stress intensity factor and the crack velocity. This study presents the results of studies conducted to validate the constant stress-rate test for determining subcritical crack growth parameters in Coconino sandstone, compared with the conventional testing method, the double torsion test. The results of the constant stress-rate test are in good agreement with the results of double torsion test. More importantly, the stress-rate tests can determine the parameter A with a much smaller standard deviation than the double torsion test. Thus the constant stress-rate test seems to be both a valid and preferred test method for determining the subcritical crack growth parameters in rocks. We investigated statistical aspects of the constant stress-rate test. The effects of the number of tests conducted on the subcritical crack growth parameters were examined and minimum specimen numbers were determined. The mean and standard deviation of the subcritical crack growth parameters were obtained by randomly selecting subsets from the original strength data. In addition, the distribution form of the subcritical crack growth parameters and the relation between the parameter n and A were determined. We extended the constant stress-rate test technique to modes II and III subcritical crack growth in rocks. The experimental results of the modes I, II and III tests show that the values of the subcritical crack growth parameters are similar to each other. The subcritical crack growth parameter n value for Coconino sandstone has the range

  5. Dynamics of crack penetration vs. branching at a weak interface: An experimental study

    Science.gov (United States)

    Sundaram, Balamurugan M.; Tippur, Hareesh V.

    2016-11-01

    In this paper, the dynamic crack-interface interactions and the related mechanics of crack penetration vs. branching at a weak interface are studied experimentally. The interface is oriented perpendicular to the incoming mode-I crack in an otherwise homogeneous bilayer. The focus of this investigation is on the effect of interface location and the associated crack-tip parameters within the bilayer on the mechanics of the ensuing fracture behavior based on the optical methodologies laid down in Ref. Sundaram and Tippur (2016). Time-resolved optical measurement of crack-tip deformations, velocity and stress intensity factor histories in different bilayer configurations is performed using Digital Gradient Sensing (DGS) technique in conjunction with high-speed photography. The results show that the crack path selection at the interface and subsequently the second layer are greatly affected by the location of the interface within the geometry. Using optically measured fracture parameters, the mechanics of crack penetration and branching are explained. Counter to the intuition, a dynamically growing mode-I approaching a weak interface at a lower velocity and stress intensity factor penetrates the interface whereas a higher velocity and stress intensity factor counterpart gets trapped by the interface producing branched daughter cracks until they kink out into the next layer. An interesting empirical observation based on measured crack-tip parameters for crack penetration and branching is also made.

  6. Adaptive Road Crack Detection System by Pavement Classification

    Directory of Open Access Journals (Sweden)

    Alejandro Amírola

    2011-10-01

    Full Text Available This paper presents a road distress detection system involving the phases needed to properly deal with fully automatic road distress assessment. A vehicle equipped with line scan cameras, laser illumination and acquisition HW-SW is used to storage the digital images that will be further processed to identify road cracks. Pre-processing is firstly carried out to both smooth the texture and enhance the linear features. Non-crack features detection is then applied to mask areas of the images with joints, sealed cracks and white painting, that usually generate false positive cracking. A seed-based approach is proposed to deal with road crack detection, combining Multiple Directional Non-Minimum Suppression (MDNMS with a symmetry check. Seeds are linked by computing the paths with the lowest cost that meet the symmetry restrictions. The whole detection process involves the use of several parameters. A correct setting becomes essential to get optimal results without manual intervention. A fully automatic approach by means of a linear SVM-based classifier ensemble able to distinguish between up to 10 different types of pavement that appear in the Spanish roads is proposed. The optimal feature vector includes different texture-based features. The parameters are then tuned depending on the output provided by the classifier. Regarding non-crack features detection, results show that the introduction of such module reduces the impact of false positives due to non-crack features up to a factor of 2. In addition, the observed performance of the crack detection system is significantly boosted by adapting the parameters to the type of pavement.

  7. Adaptive Road Crack Detection System by Pavement Classification

    Science.gov (United States)

    Gavilán, Miguel; Balcones, David; Marcos, Oscar; Llorca, David F.; Sotelo, Miguel A.; Parra, Ignacio; Ocaña, Manuel; Aliseda, Pedro; Yarza, Pedro; Amírola, Alejandro

    2011-01-01

    This paper presents a road distress detection system involving the phases needed to properly deal with fully automatic road distress assessment. A vehicle equipped with line scan cameras, laser illumination and acquisition HW-SW is used to storage the digital images that will be further processed to identify road cracks. Pre-processing is firstly carried out to both smooth the texture and enhance the linear features. Non-crack features detection is then applied to mask areas of the images with joints, sealed cracks and white painting, that usually generate false positive cracking. A seed-based approach is proposed to deal with road crack detection, combining Multiple Directional Non-Minimum Suppression (MDNMS) with a symmetry check. Seeds are linked by computing the paths with the lowest cost that meet the symmetry restrictions. The whole detection process involves the use of several parameters. A correct setting becomes essential to get optimal results without manual intervention. A fully automatic approach by means of a linear SVM-based classifier ensemble able to distinguish between up to 10 different types of pavement that appear in the Spanish roads is proposed. The optimal feature vector includes different texture-based features. The parameters are then tuned depending on the output provided by the classifier. Regarding non-crack features detection, results show that the introduction of such module reduces the impact of false positives due to non-crack features up to a factor of 2. In addition, the observed performance of the crack detection system is significantly boosted by adapting the parameters to the type of pavement. PMID:22163717

  8. Cryptography cracking codes

    CERN Document Server

    2014-01-01

    While cracking a code might seem like something few of us would encounter in our daily lives, it is actually far more prevalent than we may realize. Anyone who has had personal information taken because of a hacked email account can understand the need for cryptography and the importance of encryption-essentially the need to code information to keep it safe. This detailed volume examines the logic and science behind various ciphers, their real world uses, how codes can be broken, and the use of technology in this oft-overlooked field.

  9. Detection of cracks in shafts with the Approximated Entropy algorithm

    Science.gov (United States)

    Sampaio, Diego Luchesi; Nicoletti, Rodrigo

    2016-05-01

    The Approximate Entropy is a statistical calculus used primarily in the fields of Medicine, Biology, and Telecommunication for classifying and identifying complex signal data. In this work, an Approximate Entropy algorithm is used to detect cracks in a rotating shaft. The signals of the cracked shaft are obtained from numerical simulations of a de Laval rotor with breathing cracks modelled by the Fracture Mechanics. In this case, one analysed the vertical displacements of the rotor during run-up transients. The results show the feasibility of detecting cracks from 5% depth, irrespective of the unbalance of the rotating system and crack orientation in the shaft. The results also show that the algorithm can differentiate the occurrence of crack only, misalignment only, and crack + misalignment in the system. However, the algorithm is sensitive to intrinsic parameters p (number of data points in a sample vector) and f (fraction of the standard deviation that defines the minimum distance between two sample vectors), and good results are only obtained by appropriately choosing their values according to the sampling rate of the signal.

  10. Simultaneous Measurements of Harmonic Waves at Fatigue-Cracked Interfaces

    Institute of Scientific and Technical Information of China (English)

    Hyunjo Jeong; Dan Barnard

    2011-01-01

    @@ Nonlinear harmonic waves generated at cracked interfaces are investigated theoretically and experimentally.A compact tension specimen is fabricated and the amplitude of the transmitted wave is analyzed as a function of position along the fatigued crack surface.In order to measure as many nonlinear harmonic components as possible, broadband lithium niobate (LiNbO3) transducers are employed together with a calibration technique for making absolute amplitude measurements with fluid-coupled receiving transducers.Cracked interfaces are shown to generate high acoustic nonlinearities, which are manifested as harmonics in the power spectrum of the received signal.The first subharmonic f/2 and the second harmonic 2f waves are found to be dominant nonlinear components for an incident toneburst signal of frequency f .To explain the observed nonlinear behavior,a partially closed crack is modeled by planar half interfaces that can account for crack parameters, such as crack opening displacement and crack surface conditions.The simulation results show reasonable agreement with the experimental results

  11. Combined mode I stress intensity factors of slanted cracks

    Science.gov (United States)

    Ismail, A. E.; Rahman, M. Q. Abdul; Ghazali, M. Z. Mohd; Zulafif Rahim, M.; Rasidi Ibrahim, M.; Fahrul Hassan, Mohd; Nor, Nik Hisyamudin Muhd; Ariffin, A. M. T.; Zaini Yunos, Muhamad

    2017-08-01

    The solutions of stress intensity factors (SIFs) for slanted cracks in plain strain plate are hard to find in open literature. There are some previous solutions of SIFs available, however the studies are not completed except for the case of plain stress. The slanted cracks are modelled numerically using ANSYS finite element program. There are ten slanted angles and seven relative crack depths are used and the plate contains cracks which is assumed to fulfil the plain strain condition. The plate is then stressed under tension and bending loading and the SIFs are determined according to the displacement extrapolation method. Based on the numerical analysis, both slanted angles and relative crack length, a/L played an important role in determining the modes I and II SIFs. As expected the SIFs increased when a/L is increased. Under tension force, the introduction of slanted angles increased the SIFs. Further increment of angles reduced the SIFs however they are still higher than the SIFs obtained using normal cracks. Under bending moment, the present of slanted angles are significantly reduced the SIFs compared with the normal cracks. Under similar loading, mode II SIFs increased as function of a/L and slanted angles where increasing such parameters increasing the mode II SIFs.

  12. Painting cracks: A way to investigate the pictorial matter

    Science.gov (United States)

    Giorgiutti-Dauphiné, Frédérique; Pauchard, Ludovic

    2016-08-01

    An old painting generally exhibits a wide variety of crack patterns. From a strictly aesthetic point of view, cracks are undesirable; nevertheless, they can be seen as the fingerprints of the painting and provide valuable knowledge about the art piece. Precisely, the morphology of crack patterns can be related to the mechanical properties of the pictorial matter or they can reveal information about the methods used by the artist or the conditions of conservation. In the present paper, we show how drying dispersions of colloidal particles in a volatile solvent on a non-porous substrate provides a good candidate to study crack formation in a solid layer. We recover the crack patterns observed in paintings, and we investigate the role of the substrate, e.g., the sub-layer, and of the thickness of the layer in the crack spacing. We show how to deduce mechanical properties of a sub-layer, provided the thickness and the elastic modulus of the layer are known. These experiments aim to propose a potentially non-invasive method to deduce quantitative information about mechanical properties of a pictorial matter which could be of great interest for cultural heritage.

  13. Perfect elastic-viscoplastic field at mode Ⅰ dynamic propagating crack-tip

    Institute of Scientific and Technical Information of China (English)

    WANG Zhen-qing; LIANG Wen-yan; ZHOU Bo; SU Juan

    2007-01-01

    The viscosity of material is considered at propagating crack-tip. Under the assumption that the artificial viscosity coefficient is in inverse proportion to power law of the plastic strain rate, an elastic-viscoplastic asymptotic analysis is carried out for moving crack-tip fields in power-hardening materials under plane-strain condition. A continuous solution is obtained containing no discontinuities. The variations of numerical solution are discussed for mode Ⅰ crack according to each parameter. It is shown that stress and strain both possess exponential singularity. The elasticity, plasticity and viscosity of material at crack-tip only can be matched reasonably under linear-hardening condition. And the tip field contains no elastic unloading zone for mode Ⅰ crack. It approaches the limiting case, crack-tip is under ultra-viscose situation and energy accumulates, crack-tip begins to propagate under different compression situations.

  14. Investigation on the Thermal Crack Evolution and Oxidation Effect of Compacted Graphite Iron Under Thermal Shock

    Science.gov (United States)

    Wang, Xiaosong; Zhang, Weizheng; Guo, Bingbin

    2015-09-01

    For a better understanding of the thermal fatigue behavior in compacted graphite cast iron (CGI), the cyclic thermal shock test is carried out through alternating induction heating and water quenching. The optical and scanning electron microscopy observations are used to examine the cracks and oxidation behavior on the cross section and heating surface of the material specimen, respectively. The results show that the thermal cracks in CGI initiate at the graphite phases mostly, and the multi-sourced thermal cracks would result in stable cracks morphology finally through crack shielding effect. In the oxidation analysis, it is found that the oxidation of graphite is selective, and the graphite is the potential channels for oxygen diffusion from the outside into the matrix, resulting in local oxidation of matrix around graphite and continuous oxygen diffusion paths in the microstructure. Thermal cracks nucleate from the oxidation holes at graphite caused by decarburization, and they prefer to propagate and coalesce by penetrating the oxide bridges.

  15. Crack-tip field on mode Ⅱ interface crack of double dissimilar orthotropic composite materials

    Institute of Scientific and Technical Information of China (English)

    Xue-xia ZHANG; Xiao-chao CUI; Wei-yang YANG; Jun-lin LI

    2009-01-01

    Two systems of non-homogeneous linear equations with 8 unknowns are obtained. This is done by introducing two stress functions containing 16 undetermined coefficients and two real stress singularity exponents with the help of boundary conditions. By solving the above systems of non-homogeneous linear equations, the two real stress singularity exponents can be determined when the double material parameters meet certain conditions. The expression of the stress function and all coefficients are obtained based on the uniqueness theorem of limit. By substituting these parameters into the corresponding mechanics equations, theoretical solutions to the stress intensity factor, the stress field and the displacement field near the crack tip of each material can be obtained when both discriminants of the characteristic equations are less than zero. Stress and displacement near the crack tip show mixed crack characteristics without stress oscillation and crack surface overlapping. As an example, when the two orthotropic materials are the same, the stress singularity exponent, the stress intensity factor, and expressions for the stress and the displacement fields of the orthotropic single materials can be derived.

  16. Population Genetic Structure and Marker Trait Associations Using Morphological, Phytochemical and Molecular Parameters in Habenaria edgeworthii-a Threatened Medicinal Orchid of West Himalaya, India.

    Science.gov (United States)

    Giri, Lalit; Jugran, Arun Kumar; Bahukhandi, Amit; Dhyani, Praveen; Bhatt, Indra D; Rawal, Ranbeer Singh; Nandi, Shyamal Kumar; Dhar, Uppeandra

    2017-01-01

    Habenaria edgeworthii Hook. f. ex Collett is an important terrestrial orchid used in different Ayurvedic formulations. In the present study, variations among morphological, phytochemical and molecular markers were assessed. A significant difference was observed among populations using morphological traits. Inter-simple sequence repeat (ISSR) data revealed lower genetic diversity at population level (He = 0.207) as compared to species level (He = 0.334). Analysis of molecular variance (AMOVA) indicates 74 % variation among populations and 26 % within population. Tuber extracts showed significantly (p morphological and phytochemical attributes were studied using multiple regression analysis (MRA). Several ISSR fragments were associated with some morphological and phytochemical traits. These ISSR fragments can be useful for breeding programme of the species when no other genetic information, such as linkage maps and quantitative trait loci, is available.

  17. Fatigue Crack Growth Analysis Under Spectrum Loading in Various Environmental Conditions

    Science.gov (United States)

    Mikheevskiy, S.; Glinka, G.; Lee, E.

    2013-03-01

    The fatigue process consists, from the engineering point of view, of three stages: crack initiation, fatigue crack growth, and the final failure. It is also known that the fatigue process near notches and cracks is governed by local strains and stresses in the regions of maximum stress and strain concentrations. Therefore, the fatigue crack growth can be considered as a process of successive crack increments, and the fatigue crack initiation and subsequent growth can be modeled as one repetitive process. The assumptions mentioned above were used to derive a fatigue crack growth model based, called later as the UniGrow model, on the analysis of cyclic elastic-plastic stresses-strains near the crack tip. The fatigue crack growth rate was determined by simulating the cyclic stress-strain response in the material volume adjacent to the crack tip and calculating the accumulated fatigue damage in a manner similar to fatigue analysis of stationary notches. The fatigue crack growth driving force was derived on the basis of the stress and strain history at the crack tip and the Smith-Watson-Topper (SWT) fatigue damage parameter, D = σmaxΔɛ/2. It was subsequently found that the fatigue crack growth was controlled by a two-parameter driving force in the form of a weighted product of the stress intensity range and the maximum stress intensity factor, Δ K p K {max/1- p }. The effect of the internal (residual) stress induced by the reversed cyclic plasticity has been accounted for and therefore the two-parameter driving force made it possible to predict the effect of the mean stress including the influence of the applied compressive stress, tensile overloads, and variable amplitude spectrum loading. It allows estimating the fatigue life under variable amplitude loading without using crack closure concepts. Several experimental fatigue crack growth datasets obtained for the Al 7075 aluminum alloy were used for the verification of the proposed unified fatigue crack growth

  18. Stress intensity factors and crack opening areas for axial through cracks in hollow cylinders under internal pressure loading

    Energy Technology Data Exchange (ETDEWEB)

    Ehlers, R.

    1986-01-01

    For a linear-elastic cylinder with an axial through crack subject to internal pressure loading, stress intensity factors and crack opening areas were calculated by the finite element method. Wall thickness and crack length were varied for constant mean radius of the cylinder, thus varying the shell parameter lambda with 2.5 cracks. The range of validity of these solutions is discussed. Starting from the observation that the energy release rate for a semi-infinite crack is finite, a simple interpolation formula is given that retains the proper asymptotic behaviour for very long and very short cracks. Crack opening areas are given and compared to an approximate analytical formula from the literature. Some general limitations of the validity of the present results, particularly the required minimum lengths of the cylinder, are discussed.

  19. Subcritical crack growth in fibrous materials

    CERN Document Server

    Santucci, Stéphane; Deschanel, Stéphanie; Vanel, Loic; Ciliberto, Sergio

    2006-01-01

    We present experiments on the slow growth of a single crack in a fax paper sheet submitted to a constant force $F$. We find that statistically averaged crack growth curves can be described by only two parameters : the mean rupture time $\\tau$ and a characteristic growth length $\\zeta$. We propose a model based on a thermally activated rupture process that takes into account the microstructure of cellulose fibers. The model is able to reproduce the shape of the growth curve, the dependence of $\\zeta$ on $F$ as well as the effect of temperature on the rupture time $\\tau$. We find that the length scale at which rupture occurs in this model is consistently close to the diameter of cellulose microfibrils.

  20. A study on fatigue crack growth in dual phase martensitic steel in air environment

    Indian Academy of Sciences (India)

    K V Sudhakar; E S Dwarakadasa

    2000-06-01

    Dual phase (DP) steel was intercritically annealed at different temperatures from fully martensitic state to achieve martensite plus ferrite, microstructures with martensite contents in the range of 32 to 76%. Fatigue crack growth (FCG) and fracture toughness tests were carried out as per ASTM standards E 647 and E 399, respectively to evaluate the potential of DP steels. The crack growth rates (/) at different stress intensity ranges ( ) were determined to obtain the threshold value of stress intensity range ( th). Crack path morphology was studied to determine the influence of microstructure on crack growth characteristics. After the examination of crack tortuosity, the compact tension (CT) specimens were pulled in static mode to determine fracture toughness values. FCG rates decreased and threshold values increased with increase in vol.% martensite in the DP steel. This is attributed to the lower carbon content in the martensite formed at higher intercritical annealing (ICA) temperatures, causing retardation of crack growth rate by crack tip blunting and/or deflection. Roughness induced crack closure was also found to contribute to the improved crack growth resistance at higher levels of martensite content. Scanning electron fractography of DP steel in the near threshold region revealed transgranular cleavage fracture with secondary cracking. Results indicate the possibility that the DP steels may be treated to obtain an excellent combination of strength and fatigue properties.

  1. Mussel adhesive protein coating: A potential therapeutic method for self-healing of cracked teeth

    Directory of Open Access Journals (Sweden)

    Li Bo-Lin

    2015-01-01

    Full Text Available Introduction: Nowadays, cracked tooth syndrome is the third main cause of tooth extraction, following caries and periodontal diseases, done in almost all the dental clinics. Nevertheless, the diagnosis and treatment of this condition remain controversial. All candidate therapeutics, such as occlusal adjustment, preventive filling, root canal therapy (RCT, and crown restoration, provide unpredictable outcomes. As such, methods to prevent further crack development and to induce crack self-healing must be developed. The Hypothesis: Mussels secreting adhesive foot protein (Mafp can attach to various surfaces under aqueous conditions. In nature, mussels adhere to stones and deposit layer by layer through mineralization, thereby forming mussel-stone composites with excellent mechanical property. Given the natural process of mussel-stone complex formation, we hypothesize that application of Mafp coating at the crack interface may mineralize the cracks by capturing calcium and phosphate ions from the saliva. This process consequently leads to crack self-healing and complete restoration of the tooth structure. Evaluation of the Hypothesis: To test our hypothesis, we need to develop a model in vivo. Cracked teeth disks are adhered together using Mafp solution. Then, the tooth disks are sutured on the interior side of the cheeks. After regular intervals, the disks are removed and characterized. Scanning electron microscopy is performed to evaluate the morphology of the crack interface. Microhardness and shear bond strength are used to evaluate the mechanical property of the healing cracked zone. Transmission electron microscopy is also conducted to evaluate the crystallinity of the crack interface.

  2. Salinity effects on the dynamics and patterns of desiccation cracks

    Science.gov (United States)

    Shokri, N.; Zhou, P.

    2012-12-01

    Cracking arising from desiccation is a ubiquitous phenomenon encountered in various industrial and geo-environmental applications including drying of clayey soil, cement, ceramics, gels, and many more colloidal suspensions. Presence of cracks in muddy sediments modifies the characteristics of the medium such as pore structure, porosity, and permeability which in turn influence various flow and transport processes. Thus it remains a topic of great interest in many disciplines to describe the dynamics of desiccation cracking under various boundary conditions. To this end, we conducted a comprehensive study to investigate effects of NaCl concentrations on cracking dynamics and patterns during desiccation of Bentonite. Mixtures of Bentonite and NaCl solutions were prepared with NaCl concentration varying from 2 to 10 percent in 0.5 percent increment (totally 17 configurations). The slurry was placed in a Petri dish mounted on a digital balance to record the evaporation dynamics. The atmospheric conditions were kept constant using an environmental chamber. An automatic camera was used to record the dynamics of macro-cracks (mm scale) at the surface of desiccating clay each minute. The obtained results illustrate the significant effects of salt concentration on the initiation, propagation, morphology and general dynamics of macro-cracks. We found that higher salt concentrations results in larger macro cracks' lengths attributed to the effects of NaCl on compressing the electric double layer of particles at increasing electrolyte concentrations which reduce considerably the repulsive forces among the particles and causing instability of the slurry and flocculation of the colloidal particles. Rheological measurements by means of a stress controlled rheometer revealed that the yield stress of the slurry decreases as NaCl concentration increases which may indicate aggregation of larger units in the slurry as a result of flocculation causing larger cracks' lengths due to

  3. Amplitude Distribution of Emission Wave for Cracking Process

    Directory of Open Access Journals (Sweden)

    Shahidan Shahiron

    2016-01-01

    Full Text Available Acoustic emission technique is a method of assessment for structural health monitoring system. This technique is an effective tool for the evaluation of any system without destroying the material conditions. It enables early crack detections and has very high sensitivity to crack growth. The crack patterns in concrete beam have been identified according to the type of cracking process and the crack classifications using the AE data parameters are mainly based on the AE amplitude, rise time, and average frequency. These data parameters have been analysed using statistical methods of b-value analysis. This research paper will mainly focus on the utilization of statistical b-value analysis in evaluating the emission amplitude distribution of concrete beams. The beam specimens (150 × 250 × 1900 mm were prepared in the laboratory system and tested with the four point bending test using cyclic loading together with acoustic emission monitoring system. The results showed that this statistical analysis is promising in determining the cracking process in concrete beams.

  4. Heat-affected zone liquation crack on resistance spot welded TWIP steels

    Energy Technology Data Exchange (ETDEWEB)

    Saha, Dulal Chandra [Department of Advanced Materials Engineering, Dong-Eui University, 995 Eomgwangno, Busanjin-gu, Busan 614-714 (Korea, Republic of); Chang, InSung [Automotive Production Development Division, Hyundai Motor Company (Korea, Republic of); Park, Yeong-Do, E-mail: ypark@deu.ac.kr [Department of Advanced Materials Engineering, Dong-Eui University, 995 Eomgwangno, Busanjin-gu, Busan 614-714 (Korea, Republic of)

    2014-07-01

    In this study, the heat affected zone (HAZ) liquation crack and segregation behavior of the resistance spot welded twinning induced plasticity (TWIP) steel have been reported. Cracks appeared in the post-welded joints that originated at the partially melted zone (PMZ) and propagated from the PMZ through the heat affected zone (HAZ) to the base metal (BM). The crack length and crack opening widths were observed increasing with heat input; and the welding current was identified to be the most influencing parameter for crack formation. Cracks appeared at the PMZ when nugget diameter reached at 4.50 mm or above; and the liquation cracks were found to occur along two sides of the notch tip in the sheet direction rather than in the electrode direction. Cracks were backfilled with the liquid films which has lamellar structure and supposed to be the eutectic constituent. Co-segregation of alloy elements such as, C and Mn were detected on the liquid films by electron-probe microanalysis (EPMA) line scanning and element map which suggests that the liquid film was enrich of Mn and C. The eutectic constituent was identified by analyzing the calculated phase diagram along with thermal temperature history of finite element simulation. Preliminary experimental results showed that cracks have less/no significant effect on the static cross-tensile strength (CTS) and the tensile-shear strength (TSS). In addition, possible ways to avoid cracking were discussed. - Highlights: • The HAZ liquation crack during resistance spot welding of TWIP steel was examined. • Cracks were completely backfilled and healed with divorced eutectic secondary phase. • Co-segregation of C and Mn was detected in the cracked zone. • Heat input was the most influencing factor to initiate liquation crack. • Cracks have less/no significant effect on static tensile properties.

  5. Constitutive Mixed Mode Behavior of Cracks in Concrete

    DEFF Research Database (Denmark)

    Jacobsen, Jonas Sejersbøl

    interpretation of the crack behavior. A stiff biaxial test set-up is applied to the mixed mode measurements. The relative opening and sliding of the crack is used as the control signals in a new enhanced closed control loop. The opening and the sliding of the crack are measured by clip gauges using a pair...... may open in mixed mode, i.e. a combination of opening and sliding. To get a thorough description of the structural consequences it is important to include the stress transferring effects related to the mixed mode opening. The existing constitutive mixed mode models either have a rather extensive model...... in a double notch specimen, the crack is exposed to mixed mode opening. The experiments may be used in a direct interpretation of the mixed mode behavior. The elliptic yield surface in the associated elasto-plastic material model is controlled by two hardening parameters, which represent the actual...

  6. Constitutive mixed mode model for cracks in concrete

    DEFF Research Database (Denmark)

    Jacobsen, J.S.; Poulsen, P.N.; Olesen, J.F.;

    2013-01-01

    The scope of the paper is to set up a constitutive mixed mode model for cracks in concrete. The model is formulated at macro level and includes the most important micro scale effects. An associated plasticity model inspired by the modified Cam clay model is established. The hardening parameters...... is determined from the topographic information and the constitutive model is thereby purely mechanically based. Using the actual topographic description the model is validated against experimental results for mixed mode crack openings....... are based on the standard Mode I tensile softening response and the response for Mode I crushing. The roughness of the crack is included through a topographic description of the crack surface. The constitutive behavior is based on the integration of local contributions. The local mixed mode ratio...

  7. Understanding the edge crack phenomenon in ceramic laminates

    Directory of Open Access Journals (Sweden)

    O. Ševeček

    2015-10-01

    Full Text Available Layered ceramic materials (also referred to as “ceramic laminates” are becoming one of the most promising areas of materials technology aiming to improve the brittle behavior of bulk ceramics. The utilization of tailored compressive residual stresses acting as physical barriers to crack propagation has already succeeded in many ceramic systems. Relatively thick compressive layers located below the surface have proven very effective to enhance the fracture resistance and provide a minimum strength for the material. However, internal compressive stresses result in out-of plane stresses at the free surfaces, what can cause cracking of the compressive layer, forming the so-called edge cracks. Experimental observations have shown that edge cracking may be associated with the magnitude of the compressive stresses and with the thickness of the compressive layer. However, an understanding of the parameters related to the onset and extension of such edge cracks in the compressive layers is still lacking. In this work, a 2D parametric finite element model has been developed to predict the onset and propagation of an edge crack in ceramic laminates using a coupled stress-energy criterion. This approach states that a crack is originated when both stress and energy criteria are fulfilled simultaneously. Several designs with different residual stresses and a given thickness in the compressive layers have been computed. The results predict the existence of a lower bound, below no edge crack will be observed, and an upper bound, beyond which the onset of an edge crack would lead to the complete fracture of the layer

  8. Determination of Concrete Fracture Parameters from a Three-Point Bending Test

    Institute of Scientific and Technical Information of China (English)

    张君; 刘骞

    2003-01-01

    The mechanical behavior within the processing zone of concrete material can be well described by the crack bridging performance. The material properties related to the crack bridging are cracking strength, tensile strength, and the stress-crack width relationship. In general, the cracking strength is lower than the tensile strength of concrete. Crack propagation is governed by the cracking strength. This paper presents a method to determine the above material parameters from a three-point bending test. In the experiment, a pre-notched beam is used. Corresponding values of load, crack mouth opening displacement, and load point displacement are simultaneously recorded. From experimentally determined load-crack mouth opening displacement curves, the above-mentioned crack bridging parameters are deduced by a numerical procedure. The method can be used to evaluate the influence of coarse aggregate and cementitious matrix strength on the stress-crack width relationship, tensile strength, and fracture energy of concrete.

  9. Experiences on IGSCC crack manufacturing

    Energy Technology Data Exchange (ETDEWEB)

    Veron, P. [Equipos Nucleares, S.A., Maliano (Spain)

    1997-02-01

    The author presents his experience in manufacturing IGSCC realistic defects, mainly in INCONEL 600 MA Steam Generator Tubes. From that experience he extracts some knowledge about this cracking (influence of chemistry in the environment, stress state, crack growth rate, and occurrence in laboratory condition of break before leak).

  10. Nonlocal modeling and buckling features of cracked nanobeams with von Karman nonlinearity

    Science.gov (United States)

    Akbarzadeh Khorshidi, Majid; Shaat, Mohamed; Abdelkefi, Abdessattar; Shariati, Mahmoud

    2017-01-01

    Buckling and postbuckling behaviors of cracked nanobeams made of single-crystalline nanomaterials are investigated. The nonlocal elasticity theory is used to model the nonlocal interatomic effects on the beam's performance accounting for the beam's axial stretching via von Karman nonlinear theory. The crack is then represented as torsional spring where the crack severity factor is derived accounting for the nonlocal features of the beam. By converting the beam into an equivalent infinite long plate with an edge crack subjected to a tensile stress at the far field, the crack energy release rate, intensity factor, and severity factor are derived according to the nonlocal elasticity theory. An analytical solution for the buckling and the postbuckling responses of cracked nonlocal nanobeams accounting for the beam axial stretching according to von Karman nonlinear theory of kinematics is derived. The impacts of the nonlocal parameter on the critical buckling loads and the static nonlinear postbuckling responses of cracked nonlocal nanobeams are studied. The results indicate that the buckling and postbuckling behaviors of cracked nanobeams are strongly affected by the crack location, crack depth, nonlocal parameter, and length-to-thickness ratio.

  11. Slow Crack Growth of Brittle Materials With Exponential Crack-Velocity Formulation. Part 3; Constant Stress and Cyclic Stress Experiments

    Science.gov (United States)

    Choi, Sung R.; Nemeth, Noel N.; Gyekenyesi, John P.

    2002-01-01

    The previously determined life prediction analysis based on an exponential crack-velocity formulation was examined using a variety of experimental data on advanced structural ceramics tested under constant stress and cyclic stress loading at ambient and elevated temperatures. The data fit to the relation between the time to failure and applied stress (or maximum applied stress in cyclic loading) was very reasonable for most of the materials studied. It was also found that life prediction for cyclic stress loading from data of constant stress loading in the exponential formulation was in good agreement with the experimental data, resulting in a similar degree of accuracy as compared with the power-law formulation. The major limitation in the exponential crack-velocity formulation, however, was that the inert strength of a material must be known a priori to evaluate the important slow-crack-growth (SCG) parameter n, a significant drawback as compared with the conventional power-law crack-velocity formulation.

  12. Numerical solutions of singular integral equations for planar rectangular interfacial crack in three dimensional bimaterials

    Institute of Scientific and Technical Information of China (English)

    XU Chun-hui; QIN Tai-yan; Nao-Aki Noda

    2007-01-01

    Stress intensity factors for a three dimensional rectangular interfacial crack were considered using the body force method. In the numerical calculations, unknown body force densities were approximated by the products of the fundamental densities and power series; here the fundamental densities are chosen to express singular stress fields due to an interface crack exactly. The calculation shows that the numerical results are satisfied. The stress intensity factors for a rectangular interface crack were indicated accurately with the varying aspect ratio, and bimaterial parameter.

  13. Effect of Sensitization on Corrosion-Fatigue Cracking in Al 5083 Alloy

    Science.gov (United States)

    2015-01-21

    1% NaCl solution, the observed environmental effects on fatigue crack growth can be explained by the hydrogen embrittlement mechanism and are...using a superposition model and a two-parameter approach to environment- assisted cracking . The superposition model is essentially a summation of...Metall. Trans. A. Vol. 11A, 1980, pp. 151-158. 15. A. Bonakdar, F. Wang, J.J. Williams, and N. Chawla, “ Environmental Effects on Fatigue Crack

  14. Theory for laminated plates with a through-the-thickeness crack

    Energy Technology Data Exchange (ETDEWEB)

    Chen, E. P.

    1980-01-01

    The flexural response of a laminated plate with a through-the-thickness crack was considered in this investigation. A laminated plate theory of the Reissner type has been developed to treat this problem. For demonstration purposes, the theory was applied to a balanced symmetric laminate which contains a through-the-thickness central crack. The stress intensity factor for the crack was determined and the influences of the various material and geremetric parameters on the stress intensity factor were discussed.

  15. Stress Corrosion Cracking Behavior of Multipass TIG-Welded AA2219 Aluminum Alloy in 3.5 wt pct NaCl Solution

    Science.gov (United States)

    Venugopal, A.; Sreekumar, K.; Raja, V. S.

    2012-09-01

    The stress corrosion cracking (SCC) behavior of the AA2219 aluminum alloy in the single-pass (SP) and multipass (MP) welded conditions was examined and compared with that of the base metal (BM) in 3.5 wt pct NaCl solution using a slow-strain-rate technique (SSRT). The reduction in ductility was used as a parameter to evaluate the SCC susceptibility of both the BM and welded joints. The results showed that the ductility ratio ( ɛ NaCl/( ɛ air) was 0.97 and 0.96, respectively, for the BM and MP welded joint, and the same was marginally reduced to 0.9 for the SP welded joint. The fractographic examination of the failed samples revealed a typical ductile cracking morphology for all the base and welded joints, indicating the good environmental cracking resistance of this alloy under all welded conditions. To understand the decrease in the ductility of the SP welded joint, preexposure SSRT followed by microstructural observations were made, which showed that the decrease in ductility ratio of the SP welded joint was caused by the electrochemical pitting that assisted the nucleation of cracks in the form of corrosion induced mechanical cracking rather than true SCC failure of the alloy. The microstructural examination and polarization tests demonstrated a clear grain boundary (GB) sensitization of the PMZ, resulting in severe galvanic corrosion of the SP weld joint, which initiated the necessary conditions for the localized corrosion and cracking along the PMZ. The absence of PMZ and a refined fusion zone (FZ) structure because of the lesser heat input and postweld heating effect improved the galvanic corrosion resistance of the MP welded joint greatly, and thus, failure occurred along the FZ.

  16. Chloride ion erosion experiment research in cracked concrete

    Science.gov (United States)

    Ting, Shu; Yang, Li

    2017-08-01

    For the study of chloride ion erosion in cracked concrete, this essay tries to take advantages of relevant trails to build up concrete chloride ion diffusion model based on the Fick’s second law. The parameter of this model is easy to be set, and many factors such as the effect of cracks are taken into consideration in this experiment. The concept of “chloride ion diffusion coefficient of equivalent apparent” is introduced to simplify the calculation. It can help simplify the calculation process, and get a more accurate test result, as well as facilitating the practical application of this parameter.

  17. Subcritical crack growth in oxide and non-oxide ceramics using the Constant Stress Rate Test

    Directory of Open Access Journals (Sweden)

    Agnieszka Wojteczko

    2015-12-01

    Full Text Available Fracture toughness is one of the most important parameters for ceramics description. In some cases, material failure occurs at lower stresses than described by KIc parameter. In these terms, determination of fracture toughness only, proves to be insufficient. This may be due to environmental factors, such as humidity, which might cause subcritical crack propagation in a material. Therefore, it is very important to estimate crack growth velocities to predict lifetime of ceramics used under specific conditions. Constant Stress Rate Test is an indirect method of subcritical crack growth parameters estimation. Calculations are made by using strength data, thus avoiding crack measurement. The expansion of flaws causes reduction of material strength. If subcritical crack growth phenomenon occurs, critical value of crack lengths increases with decreasing stress rate due to longer time for flaw to grow before the critical crack propagation at KIc takes place. Subcritical crack growth phenomenon is particularly dangerous for oxide ceramics due to chemical interactions occurring as a result of exposure to humidity. This paper presents results of Constant Stress Rate Test performed for alumina, zirconia, silicon carbide and silicon nitride in order to demonstrate the differences in subcritical crack propagation phenomenon course.

  18. A consistent partly cracked XFEM element for cohesive crack growth

    DEFF Research Database (Denmark)

    Asferg, Jesper L.; Poulsen, Peter Noe; Nielsen, Leif Otto

    2007-01-01

    capable of modelling variations in the discontinuous displacement field on both sides of the crack and hence also capable of modelling the case where equal stresses are present on each side of the crack. The enrichment was implemented for the 3-node constant strain triangle (CST) and a standard algorithm...... was used to solve the non-linear equations. The performance of the element is illustrated by modelling fracture mechanical benchmark tests. Investigations were carried out on the performance of the element for different crack lengths within one element. The results are compared with previously obtained...

  19. Basic solutions of multiple parallel symmetric mode-III cracks in functionally graded piezoelectric/piezomagnetic material plane

    Institute of Scientific and Technical Information of China (English)

    泮世东; 周振功; 吴林志

    2013-01-01

    The Schmidt method is adopted to investigate the fracture problem of mul-tiple parallel symmetric and permeable finite length mode-III cracks in a functionally graded piezoelectric/piezomagnetic material plane. This problem is formulated into dual integral equations, in which the unknown variables are the displacement jumps across the crack surfaces. In order to obtain the dual integral equations, the displacement jumps across the crack surfaces are directly expanded as a series of Jacobi polynomials. The results show that the stress, the electric displacement, and the magnetic flux intensity factors of cracks depend on the crack length, the functionally graded parameter, and the distance among the multiple parallel cracks. The crack shielding effect is also obviously presented in a functionally graded piezoelectric/piezomagnetic material plane with mul-tiple parallel symmetric mode-III cracks.

  20. Fatigue crack propagation behavior of a single crystalline superalloy

    Science.gov (United States)

    Lerch, B. A.; Antolovich, Stephen D.

    1990-01-01

    Crack propagation mechanisms occurring at various temperatures in a single crystalline Ni-base alloy, Rene N4, were investigated. The rates of crack growth at 21, 704, 927, 1038, and 1093 C were measured in specimens with 001-line and 110-line directions parallel to the load axis and the machined notch, respectively, using a pulsed dc potential drop apparatus, and the fracture surfaces at each temperature were examined using SEM. Crack growth rates (CGRs) for specimens tested at or below 927 C were similar, while at two higher temperatures, the CGRs were about an order of magnitude higher than at the lower temperatures. Results of SEM observations showed that surface morphologies depended on temperature.

  1. Edge Effect on Crack Patterns in Thermally Sprayed Ceramic Splats

    Science.gov (United States)

    Chen, Lin; Yang, Guan-Jun; Li, Cheng-Xin; Li, Chang-Jiu

    2017-02-01

    To explore the edge effect on intrasplat cracking of thermally sprayed ceramic splats, crack patterns of splats were experimentally observed and investigated through mechanical analysis. Both the polycrystalline splats and single-crystal splats showed obvious edge effects, i.e., preferential cracking orientation and differences in domain size between center fragments and edge fragments. In addition, substrate/interface delamination on the periphery was clearly observed for single-crystal splats. Mechanical analysis of edge effect was also carried out, and it was found that both singular normal stress in the substrate and huge peeling stress and shear stress at the interface were induced. Moreover, effective relief of tensile stress in splats is discussed. The good correspondence between experimental observations and mechanical analysis is elaborated. The edge effect can be used to tailor the pattern morphology and shed further light on coating structure design and optimization.

  2. Electrowinning of Nickel from ammonical sulphate bath and effect of acetone on morphology of nickel deposit and its correlation with kinetic parameters

    Directory of Open Access Journals (Sweden)

    Borikar, D. K.

    2006-01-01

    Full Text Available The electrodeposition of nickel from nickel sulphate bath was studied in ammonia medium. The electrolytic conditions for nickel deposition was optimized at room temperature. The effect of acetone on current efficiency, morphology, stability and particle size of deposited nickel powder was studied. The effect of organic additive Tribenzyl ammonium chloride (TBAC on the morphology of nickel powder was also studied. The kinetics of electrodeposition was studied and the results were utilized in developing mathematical model. During electrodeposition the current efficiency was found to increase with increase in acetone concentration up to 15% V/V in bath solution. On further increase of acetone concentration in bath solution current efficiency decreases. The stability of the electrowon deposited nickel powder was found to be in the range of 85 to 89 %. Powder morphology was found to be dentritic, porous and irregular. The morphology was also found to be underdeveloped dentritic to rounded aggregate as the concentration of organic additive TBAC increases. The average particle size of the deposited powder was found to be decreasing as the concentration of the acetone increases. The average size of the particle is in the range of 13-16 m.

  3. Determination of the correlation relationship of pedagogical tests of general physical training with a set of parameters describing the morphological features and canoeists.

    Directory of Open Access Journals (Sweden)

    Flerchuk Viktor Viktorovich

    2011-09-01

    Full Text Available Correlation connections of tests are certain to on general physical preparation with indexes morphological possibilities of sportsmen. 15 sportsmen took part in research. Propensity of sportsmen is set to certain distances in competition activity. Directions of selection and orientation of sportsmen are recommended to work of different orientation.

  4. Initiation of environmentally-assisted cracking in low-alloy steels

    Energy Technology Data Exchange (ETDEWEB)

    Wire, G.L.; Li, Y.Y.

    1996-06-01

    Environmentally-Assisted Cracking (EAC) in low alloy steels is activated by a critical level of sulfide ions at the crack tip, which is produced from dissolution of sulfide inclusions (MnS, FeS, etc.) in the steel following exposure by a growing crack. EAC of concern herein is the increase of fatigue crack growth rate of up to 40 to 100 times the rate in air that occurs at 240--300 C in high temperature LWR or boiler water environments. The initiation of EAC is the onset of the higher fatigue crack growth rates in fully developed cracks already presumed to be present due to fatigue, stress corrosion cracking, or induced by fabrication. Initiation of EAC is induced by a change in loading parameters causing the fatigue crack growth rate to increase from a small multiple (2--4) to 40--100 times the air rate. A steady state theory developed by Combrade, suggests that EAC will initiate only above a critical crack velocity and cease below this same velocity. However, more recent tests show that EAC can persist down to much lower velocities (100 times lower) in low oxygen water at slightly lower temperatures. A special set of experiments on high sulfur plate material demonstrate that EAC will not initiate from surface cracks with low sulfide inventories at low crack tip velocities. Transient diffusion calculations show that a finite crack extension at a high crack tip velocity is necessary to initiate EAC, providing a possible explanation for the lack of high crack growth observations reported in low alloy steels in structural applications involving low oxygen environments.

  5. Aging behavior and fatigue crack propagation of high Zn-containing Al-Zn-Mg-Cu alloys with zinc variation

    Directory of Open Access Journals (Sweden)

    Kai Wen

    2017-04-01

    Full Text Available In the present work, the influence of two-step aging treatments on hardness, electrical conductivity and mechanical properties of two high Zn-containing Al-Zn-Mg-Cu alloys with zinc content variation was investigated and the detailed T76 aging parameters were proposed. The microstructure of the precipitates were studied by transmission electron microscopy (TEM and high-resolution transmission electron microscopy (HREM and then quantitatively investigated with the aid of an image analysis. The fatigue performances were researched by the fatigue crack propagation (FCP rate test and fracture morphology was observed with scanning electron microscopy (SEM. The results show that the matrix precipitate size distributions of both alloys had significant difference, so as to fatigue crack propagation rates and fracture appearance. The shear and bypass mechanisms of dislocation-precipitate interactions were employed to explain the difference. Among the shearable precipitates, the proportion of larger size precipitates for the higher zinc content alloy is bigger than that for the lower zinc content alloy. The coarse shearable precipitates hinder the propagation of the fatigue cracks, leading to inferior FCP rate. For both alloys, the shear mechanism possesses the dominant factor, finally causing a preponderance in the FCP resistance for the higher zinc content alloy than the lower one.

  6. Sharp contact corners, fretting and cracks

    Directory of Open Access Journals (Sweden)

    D. A. Hills

    2013-07-01

    Full Text Available Contacts with sharp edges subject to oscillatory loading are likely to nucleate cracks from the corners, if the loading is sufficiently severe. To a first approximation, the corners behave like notches, where the local elastic behaviour is relieved by plasticity, and which in turn causes irreversibilities that give rise to crack nucleation, but also by frictional slip. One question we aim to answer here is; when is the frictional slip enveloped by plastic slip, so that the corner is effectively a notch in a monolithic material? We do this by employing the classical Williams asymptotic solution to model the contact corner, and, in doing so, we render the solution completely general in the sense that it is independent of the overall geometry of the components. We then re-define the independent parameters describing the properties of the Williams solution by using the inherent length scale, a procedure that was described at the first IJFatigue and FFEMS joint workshop [1]. By proceeding in this way, we can provide a self-contained solution that can be ‘pasted in’ to any complete contact problem, and hence the likelihood of crack nucleation, and the circumstances under which it might occur, can be classified. Further, this reformulation of Williams' solution provides a clear means of obtaining the strength (defined by crack nucleation conditions of a material pair with a particular contact angle. This means that the results from a test carried out using a laboratory specimen may easily be carried over to any complicated contact problem found in engineering practice, and a mechanical test of the prototypical geometry, which may often be quite difficult, is avoided.

  7. Oil cracking to gases: Kinetic modeling and geological significance

    Institute of Scientific and Technical Information of China (English)

    TIAN Hui; WANG Zhaoming; XIAO Zhongyao; LI Xianqing; XIAO Xianming

    2006-01-01

    ATriassic oil sample from LN14 of Tarim Basin was pyrolyzed using the sealed gold tubes at 200-620℃ under a constant pressure of 50 MPa.The gaseous and residual soluble hydrocarbons were analyzed. The results show that the cracking of oil to gas can be divided into two distinct stages: the primary generation of total C1-5 gases from liquid oil characterized by the dominance of C2-5 hydrocarbons and the secondary or further cracking of C2-5gases to methane and carbon-rich matters leading to the progressive dryness of gases. Based on the experimental data, the kinetic parameters were determined for the primary generation and secondary cracking of oil cracking gases and extrapolated to geological conditions to predict the thermal stability and cracking extent of crude oil. Finally, an evolution model for the thermal destruction of crude oil was proposed and its implications to the migration and accumulation of oil cracking gases were discussed.

  8. BEHAVIOR OF CRACKED EGGS AT NON – DESTRUCTIVE IMPACT

    Directory of Open Access Journals (Sweden)

    Jana Strnková

    2014-02-01

    Full Text Available The influence of cracks on the dynamical frequency response of eggshells was studied. The non-destructive impact tests of the intact and cracked eggs were performed. Record of impact force time history was enabled by experimental device. Response of eggshell to the impact was described by the surface displacement of the eggshell. This response was measured by the laser interferometry. The force and response were also expressed in the frequency domain using of the fast Fourier transform. Both time and frequency response were affected by the presence of cracks. It was shown that the influence of cracks on the eggshell response was more effectively described in the frequency domain. The frequency response was relatively very sensitive to the position and orientation of cracks. The frequency response function was characterized by many peaks. Five excitation resonant frequency characteristic of signals were extracted based on the difference of frequency domain response signals. Distinction between intact and cracked eggs was enabled by these parameters. Even if some main problems were solved some of them remained unsolved. One of them was the effect of the impacting body r shape. This problem could be effectively solved namely using of numerical methods. In order to describe the response of eggshell response to the non-destructive impact using of the numerical simulation exact description of eggshell shape was performed. This numerical simulation will be subject of forthcoming paper.

  9. Probabilistic Analysis of Crack Width

    Directory of Open Access Journals (Sweden)

    J. Marková

    2000-01-01

    Full Text Available Probabilistic analysis of crack width of a reinforced concrete element is based on the formulas accepted in Eurocode 2 and European Model Code 90. Obtained values of reliability index b seem to be satisfactory for the reinforced concrete slab that fulfils requirements for the crack width specified in Eurocode 2. However, the reliability of the slab seems to be insufficient when the European Model Code 90 is considered; reliability index is less than recommended value 1.5 for serviceability limit states indicated in Eurocode 1. Analysis of sensitivity factors of basic variables enables to find out variables significantly affecting the total crack width.

  10. Analysis of Crack Arrest Toughness.

    Science.gov (United States)

    1988-01-15

    vload(m) vp tn(m) Vertical Source Load (kN) on wedge HY80 Finite Element 0.0122 0.0099 3.81x10 -4 144 Steel Calculations Experiment 0.0122 --- 3.74x10-4...curve, are bona fide measures of the fracture arrest capability of tough ductile steels . The second is that the J-values represent the crack driving...fibrous mode of crack extension. (b) A new test method for studying fast fracture and arrest in tough steels . (c) Measurements of fast fracture and crack

  11. Accelerated Stress Corrosion Crack Initiation of Alloys 600 and 690 in Hydrogenated Supercritical Water

    Science.gov (United States)

    Moss, Tyler; Was, Gary S.

    2017-04-01

    The objective of this study is to determine whether stress corrosion crack initiation of Alloys 600 and 690 occurs by the same mechanism in subcritical and supercritical water. Tensile bars of Alloys 690 and 600 were strained in constant extension rate tensile experiments in hydrogenated subcritical and supercritical water from 593 K to 723 K (320 °C to 450 °C), and the crack initiation behavior was characterized by high-resolution electron microscopy. Intergranular cracking was observed across the entire temperature range, and the morphology, structure, composition, and temperature dependence of initiated cracks in Alloy 690 were consistent between hydrogenated subcritical and supercritical water. Crack initiation of Alloy 600 followed an Arrhenius relationship and did not exhibit a discontinuity or change in slope after crossing the critical temperature. The measured activation energy was 121 ± 13 kJ/mol. Stress corrosion crack initiation in Alloy 690 was fit with a single activation energy of 92 ± 12 kJ/mol across the entire temperature range. Cracks were observed to propagate along grain boundaries adjacent to chromium-depleted metal, with Cr2O3 observed ahead of crack tips. All measures of the SCC behavior indicate that the mechanism for stress corrosion crack initiation of Alloy 600 and Alloy 690 is consistent between hydrogenated subcritical and supercritical water.

  12. Crack propagation and the material removal mechanism of glass-ceramics by the scratch test.

    Science.gov (United States)

    Qiu, Zhongjun; Liu, Congcong; Wang, Haorong; Yang, Xue; Fang, Fengzhou; Tang, Junjie

    2016-12-01

    To eliminate the negative effects of surface flaws and subsurface damage of glass-ceramics on clinical effectiveness, crack propagation and the material removal mechanism of glass-ceramics were studied by single and double scratch experiments conducted using an ultra-precision machine. A self-manufactured pyramid shaped single-grit tool with a small tip radius was used as the scratch tool. The surface and subsurface crack propagations and interactions, surface morphology and material removal mechanism were investigated. The experimental results showed that the propagation of lateral cracks to the surface and the interaction between the lateral cracks and radial cracks are the two main types of material peeling, and the increase of the scratch depth increases the propagation angle of the radial cracks and the interaction between the cracks. In the case of a double scratch, the propagation of lateral cracks and radial cracks between paired scratches results in material peeling. The interaction between adjacent scratches depends on the scratch depth and separation distance. There is a critical separation distance where the normalized material removal volume reaches its peak. These findings can help reduce surface flaws and subsurface damage induced by the grinding process and improve the clinical effectiveness of glass-ceramics used as biological substitute and repair materials. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. Accelerated Stress Corrosion Crack Initiation of Alloys 600 and 690 in Hydrogenated Supercritical Water

    Science.gov (United States)

    Moss, Tyler; Was, Gary S.

    2017-01-01

    The objective of this study is to determine whether stress corrosion crack initiation of Alloys 600 and 690 occurs by the same mechanism in subcritical and supercritical water. Tensile bars of Alloys 690 and 600 were strained in constant extension rate tensile experiments in hydrogenated subcritical and supercritical water from 593 K to 723 K (320 °C to 450 °C), and the crack initiation behavior was characterized by high-resolution electron microscopy. Intergranular cracking was observed across the entire temperature range, and the morphology, structure, composition, and temperature dependence of initiated cracks in Alloy 690 were consistent between hydrogenated subcritical and supercritical water. Crack initiation of Alloy 600 followed an Arrhenius relationship and did not exhibit a discontinuity or change in slope after crossing the critical temperature. The measured activation energy was 121 ± 13 kJ/mol. Stress corrosion crack initiation in Alloy 690 was fit with a single activation energy of 92 ± 12 kJ/mol across the entire temperature range. Cracks were observed to propagate along grain boundaries adjacent to chromium-depleted metal, with Cr2O3 observed ahead of crack tips. All measures of the SCC behavior indicate that the mechanism for stress corrosion crack initiation of Alloy 600 and Alloy 690 is consistent between hydrogenated subcritical and supercritical water.

  14. A computational algorithm for crack determination: The multiple crack case

    Science.gov (United States)

    Bryan, Kurt; Vogelius, Michael

    1992-01-01

    An algorithm for recovering a collection of linear cracks in a homogeneous electrical conductor from boundary measurements of voltages induced by specified current fluxes is developed. The technique is a variation of Newton's method and is based on taking weighted averages of the boundary data. The method also adaptively changes the applied current flux at each iteration to maintain maximum sensitivity to the estimated locations of the cracks.

  15. Three-dimensional fatigue crack growth behavior in an aluminum alloy investigated with in situ high-resolution synchrotron X-ray microtomography

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, H., E-mail: huizhang@sp-mac4.pse.tut.ac.jp [Department of Production Systems Engineering, Toyohashi University of Technology, 1-1, Hibarigaoka, Tempaku, Toyohashi, Aichi 441-8580 (Japan); Toda, H.; Qu, P.C.; Sakaguchi, Y.; Kobayashi, M. [Department of Production Systems Engineering, Toyohashi University of Technology, 1-1, Hibarigaoka, Tempaku, Toyohashi, Aichi 441-8580 (Japan); Uesugi, K.; Suzuki, Y. [Japan Synchrotron Radiation Research Institute, 1-1-1, Kouto, Mikazuki-cho, Sayo-gun, Hyogo 679-5198 (Japan)

    2009-06-15

    The fatigue crack propagation process in an Al-Mg-Si alloy was investigated using in situ high-resolution synchrotron radiation X-ray microtomography. Tomography datasets were obtained at periodic intervals throughout the 120,000 fatigue cycles. Three-dimensional rendering of the through-thickness crack shape indicates that in a number of regions the adjacent sides of two branched cracks tend to overlap with fatigue cycling and form a crack overlapping region. Measured crack growth rates in each tomographic slice show that crack growth retardation generally occurs in these crack overlapping regions. The through-thickness variation in crack tip opening displacement was also measured and was used to account for the observed crack propagation behavior. Crack morphologies were observed at different load levels in a fatigue cycle. The crack closure level varied for two selected regions comprising different overlapping cracks. The correlation of the crack growth rate with both crack opening and closure levels was discussed and interpreted.

  16. Performance of various modified binders in road trials and under simulated crack movement in the laboratory

    CSIR Research Space (South Africa)

    Rust, FC

    1989-06-01

    Full Text Available crack movement from a knowledge of block sizes and structural parameters such as basin of deflection and an example of this is shown. It is also shown that these models can be used to predict the decrease in crack movement due to the overlaying of a...

  17. Direct assessment of tensile stress-crack opening behavior of Strain Hardening Cementitious Composites (SHCC)

    DEFF Research Database (Denmark)

    Pereira, Eduardo B.; Fischer, Gregor; Barros, Joaquim A.O.

    2012-01-01

    at the level of a single crack. The derived tensile stress-crack opening behavior is utilized to analyze and compare the influence of various composite parameters on the resulting tensile behavior. The deformations occurring during tensile loading are furthermore examined using a digital image...

  18. The Dugdale solution for two unequal straight cracks weakening in an infinite plate

    Indian Academy of Sciences (India)

    R R Bhargava; Shehzad Hasan

    2010-02-01

    A crack arrest model is proposed for an infinite elastic perfectly-plastic plate weakened by two unequal, quasi-static, collinear straight cracks. The Dugdale model solution is obtained for the above problem when the developed plastic zones are subjected to normal cohesive quadratically varying yield point stress. Employing complex variable technique and the superposition principle the desired solution is obtained. A qualitative study of load required to arrest the plastic zones opening with respect to affecting parameters viz. inter-crack distance, plastic zone and crack length is carried out. The results obtained are presented graphically.

  19. Thermo-elastic extended meshfree method for fracture without crack tip enrichment

    Institute of Scientific and Technical Information of China (English)

    A. ASADPOUR

    2015-01-01

    This is the first manuscript presenting an extended meshfree method for thermo- elastic fracture which does not exploit a crack tip enrichment. The crack is modeled by partition of unity enrichment of the displacement and temperature field. Only a step function is employed that facilitates the implementation. To ensure that crack tip is at the correct position, a Lagrange multiplier field ahead of the crack tip is introduced along a line. The Lagrange multiplier nodal parameters are discretised with the available meshfree functions. Two benchmark examples illustrate the efficiency of the method.

  20. Investigations about Starting Cracks in DC Casting of 6063 Type Billets. Part I: Experimental Results

    Science.gov (United States)

    Schneider, W.; Jensen, E. K.

    Influence on starting crack tendency (hot cracks in billet center) of varying a number of casting parameters was studied by experiments (Part I) and by model calculations (Part II). Effects of varying the following factors were examined in detail: casting conditions, starting block material, insulating various parts of the starting block, starting block shape. Both experiments and calculations pointed to starting block shape as a most important single factor controlling starting cracks. By using the in experiments determined and calculated depth of the liquid sump as a criterion, a proper shape was found that practically eliminates the starting crack problems in billets of the AA 606 3 type alloys.

  1. Investigation on Dynamic Propagation Characteristics of In-Plane Cracks in PVB Laminated Glass Plates

    Directory of Open Access Journals (Sweden)

    Xiaoqing Xu

    2016-01-01

    Full Text Available Polyvinyl butyral (PVB laminated glass has been widely used as an important component of mechanical and construction materials. Cracks on PVB laminated glass are rich in impact information, which contribute to its impact resistance design. In this paper, a three-dimensional (3D numerical simulation model describing PVB laminated glass under impact loading is firstly established and validated qualitatively and quantitatively compared with the corresponding experimental results recorded by the high-speed photography system. In the meantime, the extended finite element method (XFEM is introduced to analyze the crack propagation mechanism of laminated glass based on dynamic stress intensity factors (DSIFs and propagations of stress waves. Parametric studies are then carried out to investigate the influence of five critical parameters, that is, plate dimension, crack length, impact energy, glass properties, and PVB properties, on crack propagation characteristics of laminated glass. Results show that the interaction between crack tip and stress waves as well as the propagations of stress waves corresponds to the fluctuations of DSIFs at crack tip. Both the structure and material variables are proven to play a very important role in glass cracking DSIFs and thus govern the crack propagation behavior. Results may provide fundamental explanation to the basic crack propagation mechanism on radial cracks in PVB laminated glass under impact loading conditions, thus to instruct its impact design improvement.

  2. Fatigue Crack Propagation Under Variable Amplitude Loading Analyses Based on Plastic Energy Approach

    Directory of Open Access Journals (Sweden)

    Sofiane Maachou

    2014-04-01

    Full Text Available Plasticity effects at the crack tip had been recognized as “motor” of crack propagation, the growth of cracks is related to the existence of a crack tip plastic zone, whose formation and intensification is accompanied by energy dissipation. In the actual state of knowledge fatigue crack propagation is modeled using crack closure concept. The fatigue crack growth behavior under constant amplitude and variable amplitude loading of the aluminum alloy 2024 T351 are analyzed using in terms energy parameters. In the case of VAL (variable amplitude loading tests, the evolution of the hysteretic energy dissipated per block is shown similar with that observed under constant amplitude loading. A linear relationship between the crack growth rate and the hysteretic energy dissipated per block is obtained at high growth rates. For lower growth rates values, the relationship between crack growth rate and hysteretic energy dissipated per block can represented by a power law. In this paper, an analysis of fatigue crack propagation under variable amplitude loading based on energetic approach is proposed.

  3. Cracks in Utopia

    Science.gov (United States)

    1999-01-01

    Many of the craters found on the northern plains of Mars have been partly filled or buried by some material (possibly sediment). The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image presented here (MOC2-136b, above left) shows a high-resolution view of a tiny portion of the floor of one of these northern plains craters. The crater, located in Utopia Planitia at 44oN, 258oW, is shown on the right (MOC2-136a)with a small white box to indicate the location of the MOC image. The MOC image reveals that the material covering the floor of this crater is cracked and pitted. The origin and source of material that has been deposited in this crater is unknown.The MOC image was acquired in June 1999 and covers an area only 1.1 kilometers (0.7 miles) wide at a resolution of 1.8 meters (6 feet) per pixel. The context picture is a mosaic of Viking 2 orbiter images 010B53 and 010B55, taken in 1976. Both images are illuminated from the left. Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.

  4. Peridynamic model for fatigue cracking.

    Energy Technology Data Exchange (ETDEWEB)

    Silling, Stewart Andrew; Abe Askari (Boeing)

    2014-10-01

    The peridynamic theory is an extension of traditional solid mechanics in which the field equations can be applied on discontinuities, such as growing cracks. This paper proposes a bond damage model within peridynamics to treat the nucleation and growth of cracks due to cyclic loading. Bond damage occurs according to the evolution of a variable called the "remaining life" of each bond that changes over time according to the cyclic strain in the bond. It is shown that the model reproduces the main features of S-N data for typical materials and also reproduces the Paris law for fatigue crack growth. Extensions of the model account for the effects of loading spectrum, fatigue limit, and variable load ratio. A three-dimensional example illustrates the nucleation and growth of a helical fatigue crack in the torsion of an aluminum alloy rod.

  5. Study on stress intensity factors for crack on involute spur gear tooth

    Directory of Open Access Journals (Sweden)

    Jian Cai

    2015-03-01

    Full Text Available Investigating the stress intensity factors has a great importance to predict the fatigue damage for the involute spur gears. The aim of this article is to reveal the variation laws of stress intensity factors for crack on the involute spur gear tooth. For this purpose, a three-dimensional finite element model for calculating the stress intensity factors of the involute spur gear containing a surface crack is established using the finite element code ABAQUS. Based on the established three-dimensional finite element model, the influences of several parameters, such as torque, friction coefficient, crack depth, crack initial location, and crack size, on mode I, mode II, and mode III stress intensity factors are investigated numerically. The results of the study provide valuable guidelines for enhanced understanding of stress intensity factors for the crack on the involute spur gear tooth.

  6. Characterisation of crack tip fields under non-uniform fatigue loading

    Directory of Open Access Journals (Sweden)

    D. Nowell, M.E. Kartal

    2013-07-01

    Full Text Available The paper analyses previously reported work, which uses digital image correlation to measure fatigue crack closure. As well as determining crack opening loads, the information on crack shape may be used to estimate the stress intensity factor, as well as other parameters in more complex models of crack tip fields. A number of specimens were subjected to single overload cycles, which produced a significant retardation in crack growth rate. The method previously applied to the analysis of constant amplitude loading is here used to analyse the single overload case. The stress intensity factor history is found to be very different in the two cases and the consequences of this observation for analysis of fatigue crack propagation are discussed.

  7. Computational two-dimensional modeling of the stress intensity factor in a cracked metallic material

    Science.gov (United States)

    Rolón, J. E.; Cendales, E. D.; Cruz, I. M.

    2016-02-01

    Cracking of metallic engineering materials is of great importance due cost of replacing mechanical elements cracked and the danger of sudden structural failure of these elements. One of the most important parameters during consideration of the mechanical behavior of machine elements having cracking and that are subject to various stress conditions is the stress intensity factor near the crack tip called factor Kic. In this paper a computational model is developed for the direct assessment of stress concentration factor near to the crack tip and compared with the results obtained in the literature in which other models have been established, which consider continuity of the displacement of the crack tip (XBEM). Based on this numerical approximation can be establish that computational XBEM method has greater accuracy in Kic values obtained than the model implemented by the method of finite elements for the virtual nodal displacement through plateau function.

  8. Influence of Mineral Admixtures on the Electro-deposition Healing Effect of Concrete Cracks

    Institute of Scientific and Technical Information of China (English)

    CHU Hongqiang; JIANG Linhua; YOU Lushen; XU Ning; SONG Zijian; ZHANG Yan

    2014-01-01

    Two types of solutions (ZnSO4, MgSO4) were selected to study the influence of mineral admixtures on the electro-deposition healing effect of concrete cracks. Four parameters (i e, rates of weight gain, surface coating, crack closure and crack filling depth) were measured. The mineral composition of electro-deposits in the cracks was analyzed. The study shows that the healing effect of mortar specimens with 10%fly ash is the worst, while the healing effect of mortar specimens with 20%fly ash is better than that of the specimens without fly ash. The rates of weight gain, surface coating, crack closure and crack filling depth decrease with increasing content of the ground granulated blast-furnace slag(GGBS). The mineral admixtures have no influence on the composition of deposits.

  9. 21 CFR 137.190 - Cracked wheat.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 2 2010-04-01 2010-04-01 false Cracked wheat. 137.190 Section 137.190 Food and... Related Products § 137.190 Cracked wheat. Cracked wheat is the food prepared by so cracking or cutting into angular fragments cleaned wheat other than durum wheat and red durum wheat that, when tested by...

  10. The crack growth mechanism in asphaltic mixes

    NARCIS (Netherlands)

    Jacobs, .M.M.J.; Hopman, P.C.; Molenaar, A.A.A.

    1995-01-01

    The crack growth mechanism in asphalt concrete (Ac) mixes is studied. In cyclic tests on several asphaltic mixes crack growth is measured, both with crack foils and with cOD-gauges. It is found that crack growth in asphaltic mixes is described by three processes which are parallel in time: cohesive

  11. Standard test method for measurement of creep crack growth times in metals

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2007-01-01

    1.1 This test method covers the determination of creep crack growth (CCG) in metals at elevated temperatures using pre-cracked specimens subjected to static or quasi-static loading conditions. The time (CCI), t0.2 to an initial crack extension δai = 0.2 mm from the onset of first applied force and creep crack growth rate, ˙a or da/dt is expressed in terms of the magnitude of creep crack growth relating parameters, C* or K. With C* defined as the steady state determination of the crack tip stresses derived in principal from C*(t) and Ct (1-14). The crack growth derived in this manner is identified as a material property which can be used in modeling and life assessment methods (15-25). 1.1.1 The choice of the crack growth correlating parameter C*, C*(t), Ct, or K depends on the material creep properties, geometry and size of the specimen. Two types of material behavior are generally observed during creep crack growth tests; creep-ductile (1-14) and creep-brittle (26-37). In creep ductile materials, where cr...

  12. Elastic-viscoplastic field at mixed-mode interface crack-tip under compression and shear

    Institute of Scientific and Technical Information of China (English)

    梁文彦; 王振清; 刘方; 刘晓铎

    2014-01-01

    For a compression-shear mixed mode interface crack, it is difficult to solve the stress and strain fields considering the material viscosity, the crack-tip singularity, the frictional effect, and the mixed loading level. In this paper, a mechanical model of the dynamic propagation interface crack for the compression-shear mixed mode is proposed using an elastic-viscoplastic constitutive model. The governing equations of propagation crack interface at the crack-tip are given. The numerical analysis is performed for the interface crack of the compression-shear mixed mode by introducing a displacement function and some boundary conditions. The distributed regularities of stress field of the interface crack-tip are discussed with several special parameters. The final results show that the viscosity effect and the frictional contact effect on the crack surface and the mixed-load parameter are important factors in studying the mixed mode interface crack-tip fields. These fields are controlled by the viscosity coefficient, the Mach number, and the singularity exponent.

  13. Fiber Sensing of Micro -Crack

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Optical fiber sensors are used for sensing micro-cracking in composite and metal materials in aerospace applications. The sensing mechanism is based on the detection of acoustic emission signals, which are known to emanate from micro-cracks when they grow under further loading. The sensor head consists of a fiber Bragg grating that is capable of detecting acoustic emission signals generated by pencil lead breaking, of frequencies up to 200 kHz.

  14. Analysis of initial crack path in fretting fatigue

    Directory of Open Access Journals (Sweden)

    J. Vázquez

    2016-07-01

    Full Text Available The initial crack path is analysed in a fretting fatigue test with cylindrical contact, where there is a stress gradient and a multiaxial and non-proportional stress state. For this, a cylindrical pad is pressed, with a constant normal load, N, against a dog-bone type fatigue test specimen. Then, the test specimen is subjected to a cyclic axial stress, σ. Due to the cyclical axial stress, the assembly used and the friction between the contact pair, a tangential cyclic load Q is generated. In these tests, both components are made of Al7075-T651 alloy. The crack initiation path along the fracture surface is optically measured using a focus variation technique. The contact stress/strain fields obtained analytically, in junction with the Fatemi-Socie (FS and Smith-Watson- Topper (SWT multiaxial fatigue parameters, allow us to determine the controlling parameters of the crack initiation process observed in the tests and to estimate the crack path during the early stage of the crack growth.

  15. The mechanisms of cracks formation of silver-based contact materials under arc and making pressure

    Institute of Scientific and Technical Information of China (English)

    GUO Feng-yi(郭凤仪); CHEN Zhong-hua(陈忠华); ZHANG Ling-ling(张玲玲); ZHANG Ji-hua(张继华); FW Leuschner

    2004-01-01

    The arc erosion experiments on five kinds of silver-based contact materials, AgZnO (10), AgSnO2 (8.5) In2O3 (4), AgCdO (12), AgNi(10), AgWC(12)C(3) were carried out according to different breaking times, breaking currents, and making pressures. Then based on the theoretical analysis and the photographs taken by scanning electronic microscope with EDAX analyzer, the crack morphology was studied scientifically. Three types of cracks, which are cavity cracks, grain boundaries (or phase boundaries) slipping cracks, and thermal stress cracks, were put forward under arc and making pressure through establishing their physical models and discussing their formation mechanisms.

  16. Fabrication of imitative cracks by 3D printing for electromagnetic nondestructive testing and evaluations

    Directory of Open Access Journals (Sweden)

    Noritaka Yusa

    2016-05-01

    Full Text Available This study demonstrates that 3D printing technology offers a simple, easy, and cost-effective method to fabricate artificial flaws simulating real cracks from the viewpoint of eddy current testing. The method does not attempt to produce a flaw whose morphology mirrors that of a real crack but instead produces a relatively simple artificial flaw. The parameters of this flaw that have dominant effects on eddy current signals can be quantitatively controlled. Three artificial flaws in type 316L austenitic stainless steel plates were fabricated using a powderbed-based laser metal additive manufacturing machine. The three artificial flaws were designed to have the same length, depth, and opening but different branching and electrical contacts between flaw surfaces. The flaws were measured by eddy current testing using an absolute type pancake probe. The signals due to the three flaws clearly differed from each other although the flaws had the same length and depth. These results were supported by subsequent destructive tests and finite element analyses.

  17. Application of 3D wavelet transforms for crack detection in rotor systems

    Indian Academy of Sciences (India)

    C Nagaraju; K Narayana Rao; K Mallikarjuna Rao

    2009-06-01

    The dynamics and diagnostics of a cracked rotor have been gaining importance in recent years. The early detection of faults like fatigue cracks in rotor shafts are very important to prevent catastrophic failure of the rotor system. Vibration monitoring during start up or shut-down is as important as during steady state operation to detect cracks especially for machines such as aircraft engines which start and stop quite frequently and run at high speeds. So, the transient data of the cracked rotor has been transformed using the wavelet transforms for crack detection. Most of the works quoted in the literature used 1D wavelets or 2D wavelets (Continuous Wavelet Transform-CWT) for crack detection. The crack detectors in the signals are both time as well as frequency dependent. So, the use of 2D wavelets is also not enough to detect the crack. In the present work a 3D wavelet (CWT) has been utilized which clearly indicates both the time and frequency features of the crack. The presence of sub-criticals in the CWT may be a best crack indicator but it is not always reliable. The addition of noise to the signal may sometimes lead to inaccurate results. So, there is a need to identify a parameter in addition to the sub-criticals. The phase angle between the two signals (cracked and un-cracked) or two transverse vibrations can be a better crack indicator because it is very less sensitive to noise disturbance. So, to extract the above phase angle a new transform has been applied called Cross Wavelet Transform (XWT). The XWT is exploited for the first time to a rotor fault detection system in the present work. Some interesting results have been obtained using the same. The advantage of the XWT is that both, the phase angles between the transverse signals and also the amplitudes of sub-criticals are viewed in a single plot. Parametric analysis is also carried out by varying crack depth and crack position for diagnostic purposes. The inverse problem of crack identi

  18. On crack initiation in notched, cross-plied polymer matrix composites

    Science.gov (United States)

    Yang, Q. D.; Schesser, D.; Niess, M.; Wright, P.; Mavrogordato, M. N.; Sinclair, I.; Spearing, S. M.; Cox, B. N.

    2015-05-01

    The physics of crack initiation in a polymer matrix composite are investigated by varying the modeling choices made in simulations and comparing the resulting predictions with high-resolution in situ images of cracks. Experimental data were acquired using synchrotron-radiation computed tomography (SRCT) at a resolution on the order of 1 μm, which provides detailed measurement of the location, shape, and size of small cracks, as well as the crack opening and shear displacements. These data prove sufficient to discriminate among competing physical descriptions of crack initiation. Simulations are executed with a high-fidelity formulation, the augmented finite element method (A-FEM), which permits consideration of coupled damage mechanisms, including both discrete cracks and fine-scale continuum damage. The discrete cracks are assumed to be nonlinear fracture events, governed by reasonably general mixed-mode cohesive laws. Crack initiation is described in terms of strength parameters within the cohesive laws, so that the cohesive law provides a unified model for crack initiation and growth. Whereas the cracks investigated are typically 1 mm or less in length, the fine-scale continuum damage refers to irreversible matrix deformation occurring over gauge lengths extending down to the fiber diameter (0.007 mm). We find that the location and far-field stress for crack initiation are predicted accurately only if the variations of local stress within plies and in the presence of stress concentrators (notches, etc.) are explicitly computed and used in initiation criteria; stress redistribution due to matrix nonlinearity that occurs prior to crack initiation is accounted for; and a mixed-mode criterion is used for crack initiation. If these factors are not all considered, which is the case for commonly used failure criteria, predictions of the location and far-field stress for initiation are not accurate.

  19. A computational study of the time dependent crack growth process

    Energy Technology Data Exchange (ETDEWEB)

    Brust, F.W.; Krishnaswamy, P.

    1992-01-01

    Universal studies of creep crack growth for (1) constant load and (2) variable load cases are presented. Results of the constant load cases is compared to experiment. The behavior of displacements and integral creep for fracture parameters are discussed for both load cases. The need for using a constitutive law which can handle cyclic creep is discussed.

  20. Measures of struggle against appearance of cracks in earth dams

    Directory of Open Access Journals (Sweden)

    Ibraeva Yulia

    2016-01-01

    Full Text Available The article describes a method calculation of the basic parameters of the transverse rows of pile of simple printed or precast dam. As well, in this article have been shown all the necessary formulas for this calculation and have been proposed solutions to prevent cracking in the dams.

  1. Effects of Different Levels of Raw and Processed Oak Acorn (Quercus castaneifolia on Performance, Small Intestine Morphology, Ileal Digestibility of Nutrients, Carcass Characteristics and Some Blood Parameters in Broiler Chickens

    Directory of Open Access Journals (Sweden)

    Rezaie M

    2016-12-01

    Full Text Available This study was conducted to determine the effect of oak acorn (Quercus castaneifolia on performance, small intestine morphology, ileal digestibility of nutrient, carcass and some blood parameters in broiler chicks. A total of fifty hundred four one-d old male chickens (Ross308 strain with seven treatments and four replicates in each treatment were used. Experimental diets were: control (corn-soybean meal diet, raw oak acorn at the levels of 10 and 20 percent, soaked oak acorn diet containing 10 and 20 percent oak acorn soaked in water for 24h., diets contain 10 and 20 percent of soaked oak acorn soaked in water for 48h with twice water substitution. Experiment lasted from 1 to 42 day of ages. Results showed that body weight, weight gain, feed intake, feed conversion ratio, ileal dry matter and protein digestibility, and small intestine morphology was significantly (P

  2. Effect of Nano-TiC Dispersed Particles and Electro-Codeposition Parameters on Morphology and Structure of Hybrid Ni/TiC Nanocomposite Layers

    Directory of Open Access Journals (Sweden)

    Lidia Benea

    2016-04-01

    Full Text Available This research work describes the effect of dispersed titanium carbide (TiC nanoparticles into nickel plating bath on Ni/TiC nanostructured composite layers obtained by electro-codeposition. The surface morphology of Ni/TiC nanostructured composite layers was characterized by scanning electron microscopy (SEM. The composition of coatings and the incorporation percentage of TiC nanoparticles into Ni matrix were studied and estimated by using energy dispersive X-ray analysis (EDX. X-ray diffractometer (XRD has been applied in order to investigate the phase structure as well as the corresponding relative texture coefficients of the composite layers. The results show that the concentration of nano-TiC particles added in the nickel electrolyte affects the inclusion percentage of TiC into Ni/TiC nano strucured layers, as well as the corresponding morphology, relative texture coefficients and thickness indicating an increasing tendency with the increasing concentration of nano-TiC concentration. By increasing the amount of TiC nanoparticles in the electrolyte, their incorporation into nickel matrix also increases. The hybrid Ni/nano-TiC composite layers obtained revealed a higher roughness and higher hardness; therefore, these layers are promising superhydrophobic surfaces for special application and could be more resistant to wear than the pure Ni layers.

  3. New model of propagation rates of long crack due to structure fatigue

    Institute of Scientific and Technical Information of China (English)

    Jian-tao LIU; Ping-an DU; Ming-jing HUANG; Qing ZHOU

    2009-01-01

    By comparison of the characteristics of existing models for long fatigue crack propagation rates,a new model,called the generalized passivation-lancet model for long fatigue crack propagation rates (GPLFCPR),and a general formula for characterizing the process of crack growth rates are proposed based on the passivation-lancet theory.The GPLFCPR model overcomes disadvantages of the existing models and can describe the rules of the entire fatiguc crack growth process from the cracking threshold to the critical fracturing point effectively with explicit physical meaning. It also reflects the influence of material characteristics,such as strength parameters,fracture parameters and heat treatment. Experimental results obtained by testing LZ50 steel,AlZnMgCu0.5,0.5Cr0.5Mo0.25V steel,etc.,show good consistency with the new model. The GPLFCPR model is valuable in theoretical research and practical applications.

  4. Nominally brittle cracks in inhomogeneous solids: From microstructural disorder to continuum-level scale

    Directory of Open Access Journals (Sweden)

    Jonathan eBarés

    2014-11-01

    Full Text Available We analyze the intermittent dynamics of cracks in heterogeneous brittle materials and the roughness of the resulting fracture surfaces by investigating theoretically and numerically crack propagation in an elastic solid of spatially-distributed toughness. The crack motion split up into discrete jumps, avalanches, displaying scale-free statistical features characterized by universal exponents. Conversely, the ranges of scales are non-universal and the mean avalanche size and duration depend on the loading microstructure and specimen parameters according to scaling laws which are uncovered. The crack surfaces are found to be logarithmically rough. Their selection by the fracture parameters is formulated in term of scaling laws on the structure functions measured on one-dimensional roughness profiles taken parallel and perpendicular to the direction of crack growth.

  5. Fatigue reliability of cracked engineering structures

    Science.gov (United States)

    Lanning, David Bruce, Jr.

    1997-12-01

    This study investigates the reliability of engineering structures containing fatigue cracks. Stress concentrations and welded joints are probable locations for the initiation and propagation of fatigue cracks. Due to the many unknowns of loading, materials properties, crack sizes and crack shapes present at these locations, a statistics-based reliability analysis is valuable in the careful consideration of these many different random factors involved in a fatigue life analysis, several of which are expanded upon in this study. The basic problem of a crack near a stress concentration is first considered. A formulation for the aspect ratio (a/c) of a propagating semi-elliptical fatigue crack located at the toe of a welded T-joint is developed using Newman and Raju's stress intensity factor for a cracked flat plate with a weld magnification factor and compared to that of a cracked flat plate, and the reliability in terms of fatigue lifetime is calculated with the aid of Paris' crack propagation equation for membrane and bending loadings. Crack closure effects are then introduced in the consideration of short crack effects, where crack growth rates typically may exceed those found using traditional linear elastic fracture mechanics solutions for long cracks. The probability of a very small, microstructurally influenced crack growing to a size influenced by local plastic conditions is calculated utilizing the probability of a crack continuing to grow past an obstacle, such as a grain boundary. The result is then combined with the probability for failure defined using the crack closure-modified Paris equation to find an overall reliability for the structure. Last, the probability of fracture is determined when a crack front encounters regions of non-uniform toughness, such as typical in the heat affected zone of a welded joint. An expression for the effective crack lengths of the dissimilar regions is derived, and used in a weakest-link fracture model in the evaluation

  6. Influence of Solution Properties and Process Parameters on the Formation and Morphology of YSZ and NiO Ceramic Nanofibers by Electrospinning

    NARCIS (Netherlands)

    Cadafalch Gazquez, G.; Smulders, V.; Veldhuis, S.A.; Wieringa, P.; Moroni, L.; Boukamp, B.A.; Elshof, ten J.E.

    2017-01-01

    The fabrication process of ceramic yttria-stabilized zirconia (YSZ) and nickel oxide nanofibers by electrospinning is reported. The preparation of hollow YSZ nanofibers and aligned nanofiber arrays is also demonstrated. The influence of the process parameters of the electrospinning process, the phys

  7. The nonlocal solution of two parallel cracks in functionally graded materials subjected to harmonic anti-plane shear waves

    Institute of Scientific and Technical Information of China (English)

    Jun Liang; Shiping Wu; Shanyi Du

    2007-01-01

    In this paper, the dynamic interaction of two parallel cracks in functionally graded materials (FGMs) is investigated by means of the non-local theory. To make the analysis tractable, the shear modulus and the material den-sity are assumed to vary exponentially with the coordinate vertical to the crack. To reduce mathematical difficulties, a one-dimensional non-local kemel is used instead of a two-dimensional one for the dynamic problem to obtain stress fields near the crack tips. By use of the Fourier transform,the problem can be solved with the help of two pairs of dual integral equations, in which the unknown variables are the jumps of displacements across the crack surfaces. To solve the dual integral equations, the jumps of displace-ments across the crack surfaces are expanded in a series of Jacobi polynomials. Unlike the classical elasticity solu-tions, it is found that no stress singularity is present at the crack tips. The non-local elastic solutions yield a finite hoop stress at the crack tips. The present result provides theoret-ical references helpful for evaluating relevant strength and preventing material failure of FGMs with initial cracks. The magnitude of the finite stress field depends on relevant param-eters, such as the crack length, the distance between two parallel cracks, the parameter describing the FGMs, the fre-quency of the incident waves and the lattice parameter of materials.

  8. Health aspects of power transmission. [Effects of 60 Hz electric field on biochemical, morphological, and physiological parameters in mice and rats

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, R. D.

    1979-03-01

    Exposure of rats and mice to 60-Hz electric fields at 100 kV/m for up to 120 days had no statistically significant, reproducible effects on a number of measures of metabolic status and growth, bone growth and structure, reproduction, hematology and serum chemistry, endocrinology, cardiovascular function, nerve function, or organ and tissue morphology. An effect on cell-mediated immunity was detected and is being evaluated further in additional experiments. Exposure of rats in utero (day 0 of gestation to 8 days of age) had a transient effect at 14 days of age on motile behavior and development of the righting reflex. Significant effects were observed in synaptic transmission and behavior. Exposure to 60-Hz electric fields may increase the excitability of the nervous system of rats. Experiments are in progress to obtain a better understanding of these effects and their potential consequences.

  9. Injury rates in martial art athletes: anthropometric parameters and training volume, but not foot morphology indexes, are predictive risk factors for lower limb injuries.

    Science.gov (United States)

    Vitale, Jacopo A; Bassani, Tito; Galbusera, Fabio; Bianchi, Alberto; Martinelli, Nicolò

    2017-09-22

    Previous studies attempted to identify possible risk factors for acute and overuse injuries in several sports disciplines such as running, gymnastics or team sports. Given the lack of scientific works focused on risk factors for lower limb injuries in martial arts, the present study was aimed to investigate foot anatomy, anthropometric measures, and other background information as possible risk factors of injury in barefoot athletes practicing judo, karate, kung fu, thai boxe, or aikido. In addition, the injury rates were evaluated in relation with the different martial art styles. One group of 130 martial artists was retrospectively evaluated. Data of three foot morphological variables were collected: navicular height (NH), navicular drop (ND) and the rear foot (RF). In addition, each participant filled an interview questionnaire providing the following information: age, sex, body weight, height, BMI, hours of training per week, the kind of injury occurred to the lower limbs in the preceding year. Of 130 subjects, 70 (53.8%) did not sustain injuries, 35 (27.0%) suffered an acute injury and the remaining 25 (19.2%) reported an overuse injury. No significant differences were observed in the injury rates in relation to style and kind of martial art. Age, training volume and BMI were found as significant predictors of injury, while NH, ND and RF were not able to predict acute or overuse injury at lower limbs. The injury rates were similar in karate, judo, kung fu, aikido, and thai boxe. The foot morphology variables were not related with the presence or absence of acute and overuse injuries. Conversely, older and heavier martial artists, performing more hours of barefoot training, are at higher risk of acute and overuse injury. Athletic trainers should strongly take into account the present information in order to develop more accurate and specific injury prevention programs for martial artists.

  10. Evaluation of cracking in feedwater piping adjacent to the steam generators in Nine Pressurized Water Reactor Plants

    Energy Technology Data Exchange (ETDEWEB)

    Goldberg, A.; Streit, R.D.; Scott, R.G.

    1980-06-25

    Cracking in ASTM A106-B and A106-C feedwater piping was detected near the inlet to the steam generators in a number of pressurized water reactor plants. We received sections with cracks from nine of the plants with the objective of identifying the cracking mechanism and assessing various factors that might contribute to this cracking. Variations were observed in piping surface irregularities, corrosion-product, pit, and crack morphology, surface elmental and crystal structure analyses, and steel microstructures and mechanical properties. However, with but two exceptions, namely, arrest bands and major surface irregularities, we were unable to relate the extent of cracking to any of these factors. Tensile and fracture toughness (J/sub Ic/ and tearing modulus) properties were measured over a range of temperatures and strain rates. No unusual properties or microstructures were observed that could be related to the cracking problem. All crack surfaces contained thick oxide deposits and showed evidence of cyclic events in the form of arrest bands. Transmission electron microscopy revealed fatigue striations on replicas of cleaned crack surfaces from one plant and possibly from three others. Calculations based on the observed striation spacings gave a value of ..delta..sigma = 150 MPa (22 ksi) for one of the major cracks. The direction of crack propagation was invariably related to the piping surface and not to the piping axis. These two factors are consistent with the proposed concept of thermally induced, cyclic, tensile surface stresses. Although surface irregularities and corrosion pits were sources for crack initiation and corrosion may have contributed to crack propagation, it is proposed that the overriding factor in the cracking problem is the presence of unforeseen cyclic loads.

  11. Effect of wetting-drying cycles on soil desiccation cracking behaviour

    Directory of Open Access Journals (Sweden)

    Tang Chao-Sheng

    2016-01-01

    Full Text Available Better understanding the desiccation cracking process is essential in analysing drought effects on soil hydraulic and mechanical properties through consideration of the atmosphere-ground interaction. Laboratory tests were conducted to investigate the consequence of wetting-drying cycles on the initiation and propagation characteristics of desiccation cracks on soil surface. Initially saturated slurry specimens were prepared and subjected to five subsequent wetting-drying cycles. Image processing technique was employed to quantitatively analyze the morphology characteristics of crack patterns formed during each drying path. The results show that the desiccation cracking behaviour of soil is significantly affected by the wetting-drying cycles. Before the third wetting-drying cycle is reached, the surface crack ratio and the average crack width increases while the average clod area decreases with increasing the number of wetting-drying cycles. The number of intersections and crack segments per unit area reaches the peak values after the second wetting-drying cycle. After the third wetting-drying cycle is reached, the effect of increasing wetting-drying cycles on crack patterns is insignificant. Moreover, it is observed that the applied wetting-drying cycles are accompanied by a continual reconstruction of soil structure. The initial homogenous slurry structure is completely replaced with aggregated structure after the third cycles, and a significant increase in the inter-aggregate porosity can be observed.

  12. Influence of chemical liquids on the fatigue crack growth of the AZ31 magnesium alloy

    Science.gov (United States)

    Wang, Zhang-Zhong; He, Xian-Cong; Bai, Yun-Qiang; Ba, Zhi-Xin; Dai, Yu-Ming; Zhou, Heng-Zhi

    2012-03-01

    The fatigue crack growth behavior of an AZ31 magnesium alloy was investigated by comparing the effect of zirconate and phosphate chemical liquids. The morphology, components, and phase compositions of the chemical depositions at the fatigue crack tip were analyzed by employing scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD), respectively. For samples with and without the chemical liquids, their stress-intensity factor values at the fatigue crack tip were compared by using a stress-strain gauge. The results demonstrated that a zirconate film (Zr x O y ·Zn x O y ) and a phosphate film (Zn3(PO4)2·4H2O and MgZnP2O7) could be formed on the fatigue crack-surface at the fatigue crack tip. The stress distribution was changed because of the chemical depositions and the causticity of the chemical liquids. This could decrease the stress-intensity factor value and thus effectively cause fatigue crack closure, which reduces the fatigue crack growth rate. Moreover, it was found that the fatigue crack closure effect of zirconates was more positive than that of phosphates.

  13. The mechanism of hot crack formation in Ti-6Al-4V during cold crucible continuous casting

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    Hot crack is one of common defects in castings, which often results in failure of castings. This work studies the formation of hot crack during cold crucible continuous casting by means of experiments and theoretical analysis. The results show that hot crack occurs on the surface and in the circumference of ingots, where the solidified shell and the solidification front meet each other. The tendency of hot cracking decreases with the increase of withdrawal velocities in some extent.The hot crack is caused mainly by the friction force between the shell and the crucible inner wall, and it takes place when the stress resulting from friction exceeds the tensile strength of the shell. The factors of μm, ht, hs and hm, affecting hot cracks are analyzed and verified. In order to decrease the tendency of hot cracks, technical parameters should be optimized by decreasingμm, ht, hs and hm.

  14. Effect of Hot Deformation on Formation and Growth of Thermal Fatigue Crack in Chromium Wear Resistant Cast Iron

    Institute of Scientific and Technical Information of China (English)

    CHANG Li-min; LIU Jian-hua

    2006-01-01

    The formation and growth of thermal fatigue crack in chromium wear resistant cast iron was investigated, and the effect of hot deformation on the crack was analyzed by means of optical microscope and scanning electron microscope and high frequency induction thermal fatigue tester. The results show that eutectic carbide is the main location and passage for initiation and extension of thermal fatigue cracks, hot deformation can improve the eutectic carbide′s morphology and distribution, inhibit the generation and propagation of thermal fatigue cracks. In the experiment, the propagation rate of thermal fatigue crack reduces with the quantity of hot deformation increasing, which was analyzed in the point view of the activation energy of crack propagation.

  15. Cracking in autoclaved aerated concrete: Experimental investigation and XFEM modeling

    Energy Technology Data Exchange (ETDEWEB)

    Ferretti, D., E-mail: daniele.ferretti@unipr.it [Department of Civil, Environmental, Land Management Engineering and Architecture, University of Parma, P.co Area delle Scienze 181/A, 43124 Parma (Italy); Michelini, E. [Department of Civil, Environmental, Land Management Engineering and Architecture, University of Parma, P.co Area delle Scienze 181/A, 43124 Parma (Italy); Rosati, G. [Department of Civil and Environmental Engineering, Politecnico di Milano, Piazza L. Da Vinci 32, 20133 Milano (Italy)

    2015-01-15

    The paper aims to investigate and model cracking development in beams and deep-beams made of autoclaved aerated concrete (AAC). Fracture mechanics of AAC has been first studied by performing three-point bending tests on beams, similar to those commonly used for ordinary concrete elements. In some of these tests, crack growth has been also monitored by using ESPI laser technique. In this way, it has been possible to calibrate the main parameters of a proper cohesive law by means of extended finite element inverse analysis. Subsequently, cracking tests have been also performed on deep-beams, whose behavior is more representative of full scale walls. To validate the proposed cohesive law, deep-beam experimental behavior has been finally simulated through XFEM.

  16. WEIGHT FUNCTIONS FOR INTERFACE CRACKS IN DISSIMILAR ANISOTROPIC MATERIALS

    Institute of Scientific and Technical Information of China (English)

    MA Lifeng; CHEN Yiheng

    2004-01-01

    Bueckner's work conjugate integral customarily adopted for linear elastic materials is established for an interface crack in dissimilar anisotropic materials. The difficulties in separating Stroh's six complex arguments involved in the integral for the dissimilar materials are overcome and then the explicit function representations of the integral are given and studied in detail. It is found that the pseudo-orthogonal properties of the eigenfunction expansion form (EEF) for a crack presented previously in isotropic elastic cases, in isotopic bimaterial cases, and in orthotropic cases are also valid in the present dissimilar arbitrary anisotropic cases. The relation between Bueckner's work conjugate integral and the J-integral in these cases is obtained by introducing a complementary stressdisplacement state. Finally, some useful path-independent integrals and weight functions are proposed for calculating the crack tip parameters such as the stress intensity factors.

  17. Assessment of histological response of paediatric bone sarcomas using FDG PET in comparison to morphological volume measurement and standardized MRI parameters

    Energy Technology Data Exchange (ETDEWEB)

    Denecke, Timm; Misch, Daniel; Steffen, Ingo G.; Plotkin, Michail; Stoever, Brigitte [Charite - Universitaetsmedizin Berlin, Klinik fuer Strahlenheilkunde, Campus Virchow-Klinikum, Berlin (Germany); Hundsdoerfer, Patrick; Henze, Guenter [Charite - Universitaetsmedizin Berlin, Klinik fuer Paediatrie m.S. Onkologie und Haematologie, Otto-Heubner-Zentrum, Campus Virchow-Klinikum, Berlin (Germany); Schoenberger, Stefan [Universitaetsklinikum der Heinrich-Heine-Universitaet Duesseldorf, Klinik fuer Kinder-Onkologie, -Haematologie und -Immunologie, Duesseldorf (Germany); Furth, Christian; Ruf, Juri [Otto-von-Guericke-Universitaet Magdeburg, Klinik fuer Radiologie und Nuklearmedizin, Universitaetsklinikum Magdeburg A.oe.R., Magdeburg (Germany); Hautzel, Hubertus [Universitaetsklinikum der Heinrich Heine Universitaet Duesseldorf, Nuklearmedizinische Klinik, Duesseldorf (Germany); Kluge, Regine [Universitaetsklinikum Leipzig A.oe.R., Klinik und Poliklinik fuer Nuklearmedizin, Leipzig (Germany); Bierbach, Uta [Universitaetsklinikum Leipzig A.oe.R., Abteilung fuer Kinder-Haematologie, -Onkologie und -Haemostaseologie, Leipzig (Germany); Otto, Sylke [Universitaetsklinikum Greifswald, Institut fuer Diagnostische Radiologie und Neuroradiologie, Greifswald (Germany); Beck, James F. [Universitaetsklinikum Greifswald, Abteilung fuer Paediatrische Haematologie und Onkologie, Greifswald (Germany); Franzius, Christiane [MR- und PET/CT-Zentrum, Bremen-Mitte (Germany); Universitaetsklinikum Muenster, Klinik und Poliklinik fuer Nuklearmedizin, Muenster (Germany); Amthauer, Holger [Charite - Universitaetsmedizin Berlin, Klinik fuer Strahlenheilkunde, Campus Virchow-Klinikum, Berlin (Germany); Otto-von-Guericke-Universitaet Magdeburg, Klinik fuer Radiologie und Nuklearmedizin, Universitaetsklinikum Magdeburg A.oe.R., Magdeburg (Germany)

    2010-10-15

    The objective of this study was to evaluate positron emission tomography (PET) using {sup 18}F-fluoro-2-deoxy-D-glucose (FDG) in comparison to volumetry and standardized magnetic resonance imaging (MRI) parameters for the assessment of histological response in paediatric bone sarcoma patients. FDG PET and local MRI were performed in 27 paediatric sarcoma patients [Ewing sarcoma family of tumours (EWS), n = 16; osteosarcoma (OS), n = 11] prior to and after neoadjuvant chemotherapy before local tumour resection. Several parameters for assessment of response of the primary tumour to therapy by FDG PET and MRI were evaluated and compared with histopathological regression of the resected tumour as defined by Salzer-Kuntschik. FDG PET significantly discriminated responders from non-responders using the standardized uptake value (SUV) reduction and the absolute post-therapeutic SUV (SUV2) in the entire patient population ({nabla}SUV, p = 0.005; SUV2, p = 0.011) as well as in the subgroup of OS patients ({nabla}SUV, p = 0.009; SUV2, p = 0.028), but not in the EWS subgroup. The volume reduction measured by MRI/CT did not significantly discriminate responders from non-responders either in the entire population (p = 0.170) or in both subgroups (EWS, p = 0.950; OS, p = 1.000). The other MRI parameters alone or in combination were unreliable and did not improve the results. Comparing diagnostic parameters of FDG PET and local MRI, metabolic imaging showed high superiority in the subgroup of OS patients, while similar results were observed in the population of EWS. FDG PET appears to be a useful tool for non-invasive response assessment in the group of OS patients and is superior to MRI. In EWS patients, however, neither FDG PET nor volumetry or standardized MRI criteria enabled a reliable response assessment to be made after neoadjuvant treatment. (orig.)

  18. Assessment and prediction of drying shrinkage cracking in bonded mortar overlays

    Energy Technology Data Exchange (ETDEWEB)

    Beushausen, Hans, E-mail: hans.beushausen@uct.ac.za; Chilwesa, Masuzyo

    2013-11-15

    Restrained drying shrinkage cracking was investigated on composite beams consisting of substrate concrete and bonded mortar overlays, and compared to the performance of the same mortars when subjected to the ring test. Stress development and cracking in the composite specimens were analytically modeled and predicted based on the measurement of relevant time-dependent material properties such as drying shrinkage, elastic modulus, tensile relaxation and tensile strength. Overlay cracking in the composite beams could be very well predicted with the analytical model. The ring test provided a useful qualitative comparison of the cracking performance of the mortars. The duration of curing was found to only have a minor influence on crack development. This was ascribed to the fact that prolonged curing has a beneficial effect on tensile strength at the onset of stress development, but is in the same time not beneficial to the values of tensile relaxation and elastic modulus. -- Highlights: •Parameter study on material characteristics influencing overlay cracking. •Analytical model gives good quantitative indication of overlay cracking. •Ring test presents good qualitative indication of overlay cracking. •Curing duration has little effect on overlay cracking.

  19. Finite Element Simulation on Crack Analysis of a Thick-Tube

    Directory of Open Access Journals (Sweden)

    A.M. Ahmad Zaidi

    2009-09-01

    Full Text Available Most engineering failure began with cracks. Crack may caused by material defect, discontinuities in geometry or damage in service. Thus, Fracture Mechanics is introduced as a method for predicting failure of a surface containing a crack. This project is focusing on pre-existing crack with assumption that no microscopic defects are presents. Linear Elastic Fracture Mechanics (LEFM is used to evaluate the Stress Intensity Factor (SIF of the specimen. Further analysis is done by incorporating Elastic Plastic Fracture Mechanics (EPFM to understand the crack growth over period of time. In this study, the important parameters in fracture mechanics such as Stress Intensity Factor (SIF, Crack Mouth Opening Displacement (CMOD, J Integral and stable crack growth are been investigated. A complex loading simulation of NKS-3 specimen is done using finite element modeling. The NKS-3 is a thick-tube used in Pressurized Water Reactor (PWR which has a circumferential flaw on its inner surface. The cylinder is loaded with axial tensile load and internal pressure combined with thermal shock. A 2-Dimensional Axysimmetric-4 nodes element with focused mesh at the crack tip is employed in the simulation. Several analyses have been done using hardening data at different temperature. A comparison of solution is made for simulation with and without thermal load history. Further analysis showed that the stable crack growth is estimated to be around 3.0mm.

  20. Generation mechanism of nonlinear ultrasonic Lamb waves in thin plates with randomly distributed micro-cracks.

    Science.gov (United States)

    Zhao, Youxuan; Li, Feilong; Cao, Peng; Liu, Yaolu; Zhang, Jianyu; Fu, Shaoyun; Zhang, Jun; Hu, Ning

    2017-08-01

    Since the identification of micro-cracks in engineering materials is very valuable in understanding the initial and slight changes in mechanical properties of materials under complex working environments, numerical simulations on the propagation of the low frequency S0 Lamb wave in thin plates with randomly distributed micro-cracks were performed to study the behavior of nonlinear Lamb waves. The results showed that while the influence of the randomly distributed micro-cracks on the phase velocity of the low frequency S0 fundamental waves could be neglected, significant ultrasonic nonlinear effects caused by the randomly distributed micro-cracks was discovered, which mainly presented as a second harmonic generation. By using a Monte Carlo simulation method, we found that the acoustic nonlinear parameter increased linearly with the micro-crack density and the size of micro-crack zone, and it was also related to the excitation frequency and friction coefficient of the micro-crack surfaces. In addition, it was found that the nonlinear effect of waves reflected by the micro-cracks was more noticeable than that of the transmitted waves. This study theoretically reveals that the low frequency S0 mode of Lamb waves can be used as the fundamental waves to quantitatively identify micro-cracks in thin plates. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Experimental assessment of an RFID-based crack sensor for steel structures

    Science.gov (United States)

    E Martínez-Castro, R.; Jang, S.; Nicholas, J.; Bansal, R.

    2017-08-01

    The use of welded steel cover plates had been a common design practice to increase beam section capacity in regions of high moment for decades. Many steel girder bridges with cover plates are still in service. Steel girder bridges are subject to cyclic loading, which can initiate crack formation at the toe of the weld and reduce beam capacity. Thus, timely detection of fatigue cracks is of utmost importance in steel girder bridge monitoring. To date, crack monitoring methods using in-house radio frequency identification (RFID)-based sensors have been developed to complement visual inspection and provide quantitative information of damage level. Offering similar properties at a reduced cost, commercial ultra-high frequency (UHF) passive RFID tags have been identified as a more financially viable option for pervasive crack monitoring using a dense array of sensors. This paper presents a study on damage sensitivity of low-cost commercial UHF RFID tags for crack detection and monitoring on metallic structures. Using backscatter power as a parameter for damage identification, a crack sensing system has been developed for single and multiple tag configurations for increased sensing pervasiveness. The effect on backscatter power of the existence and stage of crack propagation has been successfully characterized. For further automation of crack detection, a damage index based on the variation of backscatter power has also been established. The tested commercial RFID-based crack sensor contributes to the usage of this technology on steel girder bridges.

  2. Chemical and metallurgical aspects of environmentally assisted fatigue crack growth in 7075-T651 aluminum alloy

    Science.gov (United States)

    Gao, Ming; Wei, R. P.; Pao, P. S.

    1988-07-01

    A comprehensive study has been carried out on a 7075-T651 alloy to examine the influence of water vapor on fatigue crack growth. The kinetics of fatigue crack growth were determined as a function of water vapor pressure at room temperature and at 353 K. Detailed fractographic analyses and surface chemistry studies were carried out to identify the micromechanisms and to quantify the chemical interactions for corrosion fatigue crack growth in this alloy. Experiments were also carried out in ultra-high vacuum and in oxygen to provide for comparisons. Two regions of fatigue crack growth response were identified. In the low pressure region (below 67 Pa at 5 Hz), crack growth is controlled by the rate of transport of water vapor to the crack tip, and the response can be described by a model for transport controlled crack growth. At pressures above 67 Pa, additional increases in crack growth rate occurred, which are attributed to the further reactions of water vapor with segregated magnesium in this alloy. Different micromechanisms for crack growth have been identified for vacuum, oxygen, and water vapor. These micromechanisms are considered in relation to the environmental parameters through a modified superposition model for corrosion fatigue.

  3. The Effects of Salt Water on the Slow Crack Growth of Soda Lime Silicate Glass

    Science.gov (United States)

    Hausmann, Bronson D.; Salem, Jonathan A.

    2016-01-01

    The slow crack growth parameters of soda-lime silicate were measured in distilled and salt water of various concentrations in order to determine if stress corrosion susceptibility is affected by the presence of salt and the contaminate formation of a weak sodium film. Past research indicates that solvents effect the rate of crack growth, however, the effects of salt have not been studied. The results indicate a small but statistically significant effect on the slow crack growth parameters A and n. However, for typical engineering purposes, the effect can be ignored.

  4. Crack Repair in Aerospace Aluminum Alloy Panels by Cold Spray

    Science.gov (United States)

    Cavaliere, P.; Silvello, A.

    2017-02-01

    The cold-spray process has recently been recognized as a very useful tool for repairing metallic sheets, achieving desired adhesion strengths when employing optimal combinations of material process parameters. We present herein the possibility of repairing cracks in aluminum sheets by cold spray. A 2099 aluminum alloy panel with a surface 30° V notch was repaired by cold spraying of 2198 and 7075 aluminum alloy powders. The crack behavior of V-notched sheets subjected to bending loading was studied by finite-element modeling (FEM) and mechanical experiments. The simulations and mechanical results showed good agreement, revealing a remarkable K factor reduction, and a consequent reduction in crack nucleation and growth velocity. The results enable prediction of the failure initiation locus in the case of repaired panels subjected to bending loading and deformation. The stress concentration was quantified to show how the residual stress field and failure are affected by the mechanical properties of the sprayed materials and by the geometrical and mechanical properties of the interface. It was demonstrated that the crack resistance increases more than sevenfold in the case of repair using AA2198 and that cold-spray repair can contribute to increased global fatigue life of cracked structures.

  5. Development of Efficient Finite Element Software of Crack Propagation Simulation using Adaptive Mesh Strategy

    Directory of Open Access Journals (Sweden)

    Abdulnaser M. Alshoaibi

    2009-01-01

    Full Text Available The purpose of this study is on the determination of 2D crack paths and surfaces as well as on the evaluation of the stress intensity factors as a part of the damage tolerant assessment. Problem statement: The evaluation of SIFs and crack tip singular stresses for arbitrary fracture structure are a challenging problem, involving the calculation of the crack path and the crack propagation rates at each step especially under mixed mode loading. Approach: This study was provided a finite element code which produces results comparable to the current available commercial software. Throughout the simulation of crack propagation an automatic adaptive mesh was carried out in the vicinity of the crack front nodes and in the elements which represent the higher stresses distribution. The finite element mesh was generated using the advancing front method. The adaptive remising process carried out based on the posteriori stress error norm scheme to obtain an optimal mesh. The onset criterion of crack propagation was based on the stress intensity factors which provide as the most important parameter that must be accurately estimated. Facilitated by the singular elements, the displacement extrapolation technique is employed to calculate the stress intensity factor. Crack direction is predicted using the maximum circumferential stress theory. The fracture was modeled by the splitting node approach and the trajectory follows the successive linear extensions of each crack increment. The propagation process is driven by Linear Elastic Fracture Mechanics (LEFM approach with minimum user interaction. Results: In evaluating the accuracy of the estimated stress intensity factors and the crack path predictions, the results were compared with sets of experimental data, benchmark analytical solutions as well as numerical results of other researchers. Conclusion/Recommendations: The assessment indicated that the program was highly reliable to evaluate the stress intensity

  6. Assessment of cracks in lateral supports of the magnet system of Wendelstein 7-X

    Energy Technology Data Exchange (ETDEWEB)

    Fellinger, Joris, E-mail: joris.fellinger@ipp.mpg.de [Max Planck Institute for Plasma Physics, EURATOM Association, Wendelsteinstr. 1, 17491 Greifswald (Germany); Bykov, Victor; Schauer, Felix [Max Planck Institute for Plasma Physics, EURATOM Association, Wendelsteinstr. 1, 17491 Greifswald (Germany)

    2013-10-15

    Highlights: ► Stress intensity factor comparison between analytical, FEM, XFEM and BEM methods. ► Evaluation of fatigue crack growth rate test data at 7 K on welded cast steel. ► Operational limits for Wendelstein 7-X w.r.t. crack growth in welded magnet system. -- Abstract: The superconducting coils of the magnet system of Wendelstein 7-X (W7-X) are bolted onto a central support ring and interconnected with five so-called lateral support elements (LSEs) per half module. After welding of the LSE hollow boxes to the coil cases cracks were found in the vicinity of the welds that could potentially limit the allowed number N of electromagnetic (EM) load cycles of the machine. In response to the appearance of first cracks during assembly, the stress intensity factor (SIF) of theoretical cracks of various sizes in potentially critical position and orientation were predicted in a fast approach. For each crack size, N was based on the SIF, derived from beam theory, and on Paris’ law parameters determined in fatigue crack growth rate (FCGR) tests, thus leading to tolerable maximal crack sizes and distances between cracks. It was proved that the actual crack dimensions remained below these values or turned out to be only superficial. Afterwards, (extended) finite element method (XFEM and FEM) and boundary element method (BEM) models were developed to project the SIF of most critical tolerated cracks, considering new FCGR tests and the local stress state in more detail. N appeared highly sensitive to the assumptions which were therefore critically reviewed. Finally, the limit for load combinations of different amplitudes was determined using Miner's rule. As a result it was shown that the predefined number of W7-X operation cycles is not jeopardized by any of the detected cracks.

  7. IDENTIFICATION OF CRACKED ROTOR BY WAVELET TRANSFORM

    Institute of Scientific and Technical Information of China (English)

    邹剑; 陈进; 蒲亚鹏

    2002-01-01

    The dynamic equation of cracked rotor in rotational frame was modelled, the numerical simulation solutions of the cracked rotor and the uncracked rotor were obtained. By the wavelet transform, the time-frequency properties of the cracked rotor and the uncracked rotor were discussed, the difference of the time-frequency properties between the cracked rotor and the uncracked rotor was compared. A new detection algorithm using wavelet transform to identify crack was proposed. The experiments verify the availability and validity of the wavelet transform in identification of crack.

  8. Fracture problem for an external circumferential crack in a functionally graded superconducting cylinder subjected to a parallel magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Z. [Department of Engineering Mechanics, Shijiazhuang Tiedao University, Shijiazhuang 050043 (China); Gao, S.W. [College of Civil Engineering, Hebei Institute of Architecture and Civil Engineering, Zhangjiakou 075000 (China); Feng, W.J., E-mail: wjfeng9999@126.com [Department of Engineering Mechanics, Shijiazhuang Tiedao University, Shijiazhuang 050043 (China)

    2016-02-15

    Highlights: • External circumferential crack problem of superconducting cylinder is investigated. • A functionally graded superconducting cylinder is analyzed. • The magnetically impermeable crack surface condition is applied. • The generalized Irie-Yamafuji critical state model outside the crack region is adopted. - Abstract: In this study, the multiple isoparametric finite element method (MIFEM) is used to investigate external circumferential crack problem of a functionally graded superconducting cylinder subjected to electromagnetic forces. The superconducting cylinder is composed by Bi2223/Ag composite with material parameters varying. A crack reference region is defined to reflect the effects of crack on flux and current densities, and the magnetically impermeable crack surface condition and the generalized Irie–Yamafuji critical state model outside the crack region are adopted. The distributions of magnetic flux density in the superconducting cylinder are obtained analytically for both the zero-field cooling (ZFC) and the field cooling (FC) activation processes. Based on the MIFEM, the stress intensity factors (SIFs) at crack fronts in the process of field ascent and/or descent are then numerically calculated. It is interesting to note from numerical results that for the present crack model in the ZFC activation process, the crack is easily propagate and grow with the applied field increases, and that in the field descent process of either the ZFC case or FC case, the crack generally does not propagate. In addition, in the field ascent process of the ZFC case, the SIFs depend on not only the crack depths and model parameters but also the applied field. The present study should be helpful to the design and application of high-temperature superconductors with external edge cracks.

  9. Brittle-tough transitions during crack growth in toughened adhesives

    Science.gov (United States)

    Thoules, Michael

    2008-03-01

    The use of structural adhesives in automotive applications relies on an effective understanding of their performance under crash conditions. In particular, there is considerable potential for mechanics-based modeling of the interaction between an adhesive layer and the adherends, to replace current empirical approaches to design. Since energy dissipation during a crash, mediated by plastic deformation of the structure, is a primary consideration for automotive applications, traditional approaches of fracture mechanics are not appropriate. Cohesive-zone models that use two fracture parameters - cohesive strength and toughness - have been shown to provide a method for quantitative mechanics analysis. Combined numerical and experimental techniques have been developed to deduce the toughness and strength parameters of adhesive layers, allowing qualitative modeling of the performance of adhesive joints. These techniques have been used to study the failure of joints, formed from a toughened adhesive and sheet metal, over a wide range of loading rates. Two fracture modes are observed: quasi-static crack growth and dynamic crack growth. The quasi-static crack growth is associated with a toughened mode of failure; the dynamic crack growth is associated with a more brittle mode of failure. The results of the experiments and analyses indicate that the fracture parameters for quasi-static crack growth in this toughened system are essentially rate independent, and that quasi-static crack growth can occur even at the highest crack velocities. Effects of rate appear to be limited to the ease with which a transition to dynamic fracture could be triggered. This transition appears to be stochastic in nature, and it does not appear to be associated with the attainment of any critical value for crack velocity or loading rate. Fracture-mechanics models exist in the literature for brittle-ductile transitions in rate-dependent polymers, which rely on rate dependent values of toughness

  10. Improvement of the extended finite element method for ductile crack growth

    Energy Technology Data Exchange (ETDEWEB)

    Pourmodheji, R. [Department of Mechanical Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Mashayekhi, M., E-mail: mashayekhi@cc.iut.ac.ir [Department of Mechanical Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of)

    2012-08-15

    The continuum damage mechanics (CDM) model is added to the extended finite element method (XFEM) to provide a model of ductile crack growth. In this model, the criterion for crack growth in the evaluation of ductile materials is the critical damage parameter obtained from continuum damage mechanics. Numerical implementation of the CDM-XFEM model was used to simulate crack growth modeling in comparison with experimental results, and the results are presented in this paper. The CDM-XFEM model was experimentally validated by the ductile damage evolution measured in A533B1 steel through three-point bending and compact tension tests. The identification of damage parameters was performed under various conditions. The critical load at crack growth initiation, the ductile behavior of cracks and the fracture toughness, J{sub Ic}, were also predicted with the CDM-XFEM model simulations. The results confirm the potential of the CDM-XFEM model for predicting crack growth in ductile materials. Using the proposed model, crack propagation has been simulated within two examples; center inclined crack and single edged notched beam for A533B1 steel.

  11. The nonlocal theory solution of a Mode-I crack in functionally graded materials

    Institute of Scientific and Technical Information of China (English)

    LIANG Jun

    2009-01-01

    The behavior of a Mode-I finite crack in functionally graded materials is investigated using the non-local theory. To make the analysis tractable, it is assumed that the shear modulus varies exponentially with coordinate vertical to the crack. The problem in this paper can be solved through the Fourier transform with the help of two pairs of dual integral equations, in which the unknown variables are jumps of displacements across crack surfaces. To solve dual integral equations, the jumps of displacements across crack surfaces are directly expanded in a series of Jacobi polynomials. Unlike the classical elasticity solutions, it is found that no stress singularities are present at crack tips. The non-local elastic solutions yield a finite stress at crack tips, thus allowing us to use the maximum stress as a fracture criterion. Numerical examples are provided to show the effects of the crack length, the parameter describing the functionally graded materials, the lattice parameter of materials and the materials constants upon the stress fields near crack tips.

  12. The nonlocal theory solution of a Mode-I crack in functionally graded materials

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The behavior of a Mode-I finite crack in functionally graded materials is investigated using the non-local theory. To make the analysis tractable, it is assumed that the shear modulus varies exponentially with coordinate vertical to the crack. The problem in this paper can be solved through the Fourier transform with the help of two pairs of dual integral equations, in which the unknown variables are jumps of dis- placements across crack surfaces. To solve dual integral equations, the jumps of displacements across crack surfaces are directly expanded in a series of Jacobi polynomials. Unlike the classical elasticity solutions, it is found that no stress singularities are present at crack tips. The non-local elastic solu- tions yield a finite stress at crack tips, thus allowing us to use the maximum stress as a fracture crite- rion. Numerical examples are provided to show the effects of the crack length, the parameter describ- ing the functionally graded materials, the lattice parameter of materials and the materials constants upon the stress fields near crack tips.

  13. An approach to reconstruction of a natural crack using signals of eddy current testing. 1. Reconstruction of an idealized natural crack

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Zhenmao [Japan Nuclear Cycle Development Inst., Oarai, Ibaraki (Japan). Oarai Engineering Center

    1998-12-01

    In this paper, an approach to the reconstruction of an idealized natural crack of non-vanishing conductivity is proposed with use of signals of eddy current testing. Two numerical models are introduced at first for modeling a Stress Corrosion Crack (SCC) in order it possibly to be represented by a set of crack parameters. A method for rapid prediction of the eddy current testing signals arisen from these idealized cracks is given then by extending a knowledge based fast forward solver developed by authors to the case of a non-vanishing conductivity. On the other hand, the inverse algorithm of conjugate gradient method is improved to reconstruct the crack parameters and is implemented with the pick-up signals and gradients calculated by using the rapid forward solver. Several examples are presented finally for validating the proposed strategy. The results verified that both of the models can give reasonable reconstruction results in case of a low noise level. The model concerning the touch of crack surfaces with a conducting band region surrounded by the crack edge, however, is proved more efficient that the model using a conductivity distribution from the point of view of both reconstruction speed and accuracy. (author)

  14. Review of Environmentally Assisted Cracking

    Science.gov (United States)

    Sadananda, K.; Vasudevan, A. K.

    2011-02-01

    Many efforts have been made in the past by several researchers to arrive at some unifying principles governing the embrittlement phenomena. An inescapable conclusion reached by all these efforts was that the behavior is very complex. Hence, recognizing the complexity of material/environment behavior, we focus our attention here only in extracting some similarities in the experimental trends to arrive at some generic principles of behavior. Crack nucleation and growth are examined under static load in the presence of internal and external environments. Stress concentration, either pre-existing or in-situ generated, appears to be a requirement for embrittlement. A chemical stress concentration factor is defined for a given material/environment system as the ratio of failure stress with and without the damaging chemical environment. All factors that affect the buildup of the required stress concentration, such as planarity of slip, stacking fault energy, etc., also affect the stress-corrosion behavior. The chemical stress concentration factor is coupled with the mechanical stress concentration factor. In addition, generic features for all systems appear to be (a) an existence of a threshold stress as a function of concentration of the damaging environment and flow properties of the material, and (b) an existence of a limiting threshold as a function of concentration, indicative of a damage saturation for that environment. Kinetics of crack growth also depends on concentration and the mode of crack growth. In general, environment appears to enhance crack tip ductility on one side by the reduction of energy for dislocation nucleation and glide, and to reduce cohesive energy for cleavage, on the other. These two opposing factors are coupled to provide environmentally induced crack nucleation and growth. The relative ratio of these two opposing factors depends on concentration and flow properties, thereby affecting limiting thresholds. The limiting concentration or

  15. Multiparametric MRI in the assessment of response of rectal cancer to neoadjuvant chemoradiotherapy: A comparison of morphological, volumetric and functional MRI parameters

    Energy Technology Data Exchange (ETDEWEB)

    Hoetker, Andreas M. [Memorial Sloan Kettering Cancer Center, Department of Radiology, New York, NY (United States); Universitaetsmedizin Mainz, Department of Diagnostic and Interventional Radiology, Mainz (Germany); Tarlinton, Lisa; Gollub, Marc J. [Memorial Sloan Kettering Cancer Center, Department of Radiology, New York, NY (United States); Mazaheri, Yousef [Memorial Sloan Kettering Cancer Center, Department of Medical Physics, New York, NY (United States); Woo, Kaitlin M.; Goenen, Mithat [Memorial Sloan Kettering Cancer Center, Department of Epidemiology and Biostatistics, New York, NY (United States); Saltz, Leonard B. [Memorial Sloan Kettering Cancer Center, Department of Medicine, Gastrointestinal Oncology Service, New York, NY (United States); Goodman, Karyn A. [Memorial Sloan Kettering Cancer Center, Department of Radiation Oncology, New York, NY (United States); Garcia-Aguilar, Julio [Memorial Sloan Kettering Cancer Center, Department of Surgery, New York, NY (United States)

    2016-12-15

    To compare morphological and functional MRI metrics and determine which ones perform best in assessing response to neoadjuvant chemoradiotherapy (CRT) in rectal cancer. This retrospective study included 24 uniformly-treated patients with biopsy-proven rectal adenocarcinoma who underwent MRI, including diffusion-weighted (DW) and dynamic contrast-enhanced (DCE) sequences, before and after completion of CRT. On all MRI exams, two experienced readers independently measured longest and perpendicular tumour diameters, tumour volume, tumour regression grade (TRG) and tumour signal intensity ratio on T2-weighted imaging, as well as tumour volume and apparent diffusion coefficient on DW-MRI and tumour volume and transfer constant K{sup trans} on DCE-MRI. These metrics were correlated with histopathological percent tumour regression in the resected specimen (%TR). Inter-reader agreement was assessed using the concordance correlation coefficient (CCC). For both readers, post-treatment DW-MRI and DCE-MRI volumetric tumour assessments were significantly associated with %TR; DCE-MRI volumetry showed better inter-reader agreement (CCC=0.700) than DW-MRI volumetry (CCC=0.292). For one reader, mrTRG, post-treatment T2 tumour volumetry and assessments of volume change made with T2, DW-MRI and DCE-MRI were also significantly associated with %TR. Tumour volumetry on post-treatment DCE-MRI and DW-MRI correlated well with %TR, with DCE-MRI volumetry demonstrating better inter-reader agreement. (orig.)

  16. Effect of electrical parameters on morphology, chemical composition, and photoactivity of the nano-porous titania layers synthesized by pulse-microarc oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Bayati, M.R., E-mail: bayati@iust.ac.i [School of Metallurgy and Materials Engineering, Iran University of Science and Technology, P.O. Box: 16845-161, Tehran (Iran, Islamic Republic of); Center of Excellence for Advanced Materials, Iran University of Science and Technology, P.O. Box: 16845-195, Tehran (Iran, Islamic Republic of); Moshfegh, A.Z. [Department of Physics, Sharif University of Technology, P.O. Box: 11155-9161, Tehran (Iran, Islamic Republic of); Institute for Nanoscience and Nanotechnology, Sharif University of Technology, P.O. Box 14588-89694, Tehran (Iran, Islamic Republic of); Golestani-Fard, F. [School of Metallurgy and Materials Engineering, Iran University of Science and Technology, P.O. Box: 16845-161, Tehran (Iran, Islamic Republic of); Center of Excellence for Advanced Materials, Iran University of Science and Technology, P.O. Box: 16845-195, Tehran (Iran, Islamic Republic of)

    2010-03-01

    TiO{sub 2} layers were grown via pulse type microarc oxidation process under different applied voltages, frequencies, and duty cycles. Surface chemical composition and phase structure of the synthesized layers were studied utilizing X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Furthermore, scanning electron microscope (SEM) and atomic force microscope (AFM) were employed to investigate surface morphology and topography of the layers. It was revealed that the layers had a porous structure with both anatase and rutile phases. The anatase relative content in the layers increased with the applied frequency; meanwhile, it decreased with duty cycle at low applied voltages, but increased with duty cycle at high applied voltages. The topographical evaluations showed that the surface of the layers is rough with an average roughness of about 1.8-9.9 nm. It was also found that the pore size decreased with the current frequency and increased with duty cycle at a fixed applied voltage. Photocatalytic performance of the layers was also examined by measuring the decomposition rate of methylene blue solution under ultraviolet irradiation of the surface. It was also found that about 94% of methylene blue solution was decomposed on the synthesized catalysts after 160 min UV irradiation of the surface.

  17. Investigation of the morphology and Wait's parameter variations of the low-latitude D region ionosphere using the multiple harmonics of tweeks

    Science.gov (United States)

    Tan, Le Minh

    2016-06-01

    Recording the tweeks with a maximum up to eight harmonics using the receiver installed at Tay Nguyen University (12.65° N, 108.02° E) during 2013-2014, we investigated the morphology of the nighttime D-region ionosphere. Tweeks were recorded on 5 quiet nights per month. The results show that the mean reflection height in 2014 (Rz = 79.3) is lower by 3.3 km than that in 2013 (Rz = 64.9). The reflection height at low latitudes is higher than that at high latitudes. The mean reference height h‧ in 2013 is higher about 0.9 km than that in 2014 and the mean sharpness factor β in 2013 is higher by 0.07 km-1 than that in 2014. The short-term variation of reflection heights for tweeks with harmonics m = 1-3 and sunspot number have the negative correlation coefficients. However, the correlations between them are not clear. On some nights, from 19:00-21:00 LT, the reflection height temporal variability shows a moderate to strong negative correlation with the tweek occurrence. This suggests that the reflection height variation may be caused by QE fields generated by lightning discharges. The variations of tweek reflection heights observed during 2013-2014, at low latitudes could be significantly caused by the ionization effect by Lyman- α and Lyman- β coming from geocorona, variation of neutral density, particle precipitations, and by direct energy coupling between lightning and lower ionosphere.

  18. Cracking and corrosion recovery boiler

    Energy Technology Data Exchange (ETDEWEB)

    Suik, H. [Tallinn Technical University, Horizon Pulp and Paper, Tallinn (Estonia)

    1998-12-31

    The corrosion of heat surfaces and the cracking the drums are the main problems of the recovery boiler. These phenomena have been appeared during long-term operation of boiler `Mitsubishi - 315` erected at 1964. Depth of the crack is depending on the number of shutdowns and on operation time. Corrosion intensity of different heat surfaces is varying depend on the metal temperature and the conditions at place of positioning of tube. The lowest intensity of corrosion is on the bank tubes and the greatest is on the tubes of the second stage superheater and on the tubes at the openings of air ports. (orig.) 5 refs.

  19. [Correlations between placental morphological and functional parameters and neonatal status after normal full-term, prolonged pregnancy, and truly protracted pregnancy].

    Science.gov (United States)

    Milovanov, A P; Fedorova, M V

    2011-01-01

    To solve the problem of differentiating protracted pregnancy, a special morphometric study was undertaken to examine three placental groups: 1) after normal full-term pregnancy (n = 35); 2) after prolonged pregnancy (n = 40); 3) after truly protracted pregnancy with partial or complete Clifford's syndrome (n = 30). A semiquantitative score (14 most important placental indicators), placenta and birth weights, Apgar scores, the infant's weight and height at the end of the first year of life were used so as to estimate the mild, moderate, and severe degree at 0.5, 1.5, and 3 points, respectively. One hundred and twenty-six possible pairs of structural and functional parameters were made up in all the groups. Pearson's correlation coefficient (r > 0.4) was applied to graphically display the pairs. Normal full-term pregnancy was characterized by few positive correlations mainly between the terminal villi and weight-height indices without associations with the Apgar scale. Prolonged pregnancy with the multiple placental tissue structural parameters along with organometric indices being involved was intermediate. The total scores permitted grades 1 and 2 chronic placental insufficiency (CPI) to be diagnosed in 27.5 and 2.5%, respectively. The severest form was truly protracted pregnancy that was distinguished by the maximum positive and negative correlations between all the parameters and the highest rate of diagnosis of CPI of grades 1 (45%) and 2 (15%). The findings strongly suggest that it is essential to identify prolonged and truly protracted pregnancy as important risk factors, by following up the infants for a year.

  20. Severity assessment of pulmonary embolism using dual energy CT - correlation of a pulmonary perfusion defect score with clinical and morphological parameters of blood oxygenation and right ventricular failure

    Energy Technology Data Exchange (ETDEWEB)

    Thieme, Sven F. [Ludwig-Maximilians-Universitaet, Department of Clinical Radiology, Muenchen (Germany); Institut fuer Klinische Radiologie der LMU Muenchen, Muenchen (Germany); Ashoori, Nima; Bamberg, Fabian; Sommer, Wieland H.; Johnson, Thorsten R.C.; Maxien, Daniel; Helck, Andreas D.; Reiser, Maximilian F.; Nikolaou, Konstantin [Ludwig-Maximilians-Universitaet, Department of Clinical Radiology, Muenchen (Germany); Leuchte, Hanno; Becker, Alexander [Ludwig-Maximilians-Universitaet, Department of Medicine I, Muenchen (Germany); Behr, Juergen [Ludwig-Maximilians-Universitaet, Department of Medicine I, Muenchen (Germany); Berufsgenossenschaftliches Universitaetsklinikum Bergmannsheil GmbH Ruhr-Universitaet Bochum, Department of Medicine III, Bochum (Germany)

    2012-02-15

    To correlate a Dual Energy (DE)-based visual perfusion defect scoring system with established CT-based and clinical parameters of pulmonary embolism (PE) severity. In 63 PE patients, DE perfusion maps were visually scored for perfusion defects (P-score). Vascular obstruction was quantified using the Mastora score. Both scores were correlated with short-axis diameters of the right and left ventricle, their ratio (RV/LV ratio), width of the pulmonary trunk, a number of clinical parameters and each other. Univariate and multivariate analyses were performed. Times to generate both scores were recorded. After univariate and multivariate analysis, a significant (p < 0.05) correlation with the P-score was shown for the Mastora score (r = 0.65), RV/LV ratio (r = 0.47), width of the pulmonary trunk (r = 0.26), troponin I (r = 0.43) and PaO{sub 2} (r = -0.50). For the left ventricular diameter, only univariate analysis showed a significant correlation. Mastora score correlated significantly with RV/LV ratio (r = 0.36), width of the pulmonary trunk (r = 0.27), PaO{sub 2} (r = -0.41) and troponin I (r = 0.37). Mean time for generating the P-score was significantly shorter than for the Mastora score. A DE-based P-score correlates with a number of parameters of PE severity. It might be easier and faster to perform than some traditional CT scoring methods for vascular obstruction. (orig.)

  1. Severity assessment of pulmonary embolism using dual energy CT - correlation of a pulmonary perfusion defect score with clinical and morphological parameters of blood oxygenation and right ventricular failure.

    Science.gov (United States)

    Thieme, Sven F; Ashoori, Nima; Bamberg, Fabian; Sommer, Wieland H; Johnson, Thorsten R C; Leuchte, Hanno; Becker, Alexander; Maxien, Daniel; Helck, Andreas D; Behr, Jürgen; Reiser, Maximilian F; Nikolaou, Konstantin

    2012-02-01

    To correlate a Dual Energy (DE)-based visual perfusion defect scoring system with established CT-based and clinical parameters of pulmonary embolism (PE) severity. In 63 PE patients, DE perfusion maps were visually scored for perfusion defects (P-score). Vascular obstruction was quantified using the Mastora score. Both scores were correlated with short-axis diameters of the right and left ventricle, their ratio (RV/LV ratio), width of the pulmonary trunk, a number of clinical parameters and each other. Univariate and multivariate analyses were performed. Times to generate both scores were recorded. After univariate and multivariate analysis, a significant (p < 0.05) correlation with the P-score was shown for the Mastora score (r = 0.65), RV/LV ratio (r = 0.47), width of the pulmonary trunk (r = 0.26), troponin I (r = 0.43) and PaO(2) (r = -0.50). For the left ventricular diameter, only univariate analysis showed a significant correlation. Mastora score correlated significantly with RV/LV ratio (r = 0.36), width of the pulmonary trunk (r = 0.27), PaO(2) (r = -0.41) and troponin I (r = 0.37). Mean time for generating the P-score was significantly shorter than for the Mastora score. A DE-based P-score correlates with a number of parameters of PE severity. It might be easier and faster to perform than some traditional CT scoring methods for vascular obstruction.

  2. Behavior of two parallel symmetry permeable cracks in functionally graded piezoelectric materials subjected to an anti-plane shear loading

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The behavior of two parallel symmetry permeable cracks in functionally graded piezoelectric materials subjected to an anti-plane shear loading was investigated. To make the analysis tractable, it was assumed that the material properties varied exponentially with coordinate vertical to the crack. By using the Fourier transform, the problem could be solved with the help of two pairs of dual integral equations, in which the unknown variables were the jumps of the displacements across the crack surfaces. To solve the dual integral equations, the displacement on the crack surfaces expanded in a series of Jacobi polynomials. The normalized stress and electrical displacement intensity factors were determined for different geometric and property parameters for permeable electric boundary conditions. Numerical examples were provided to show the effect of the geometry of the interacting cracks and the functionally graded material parameter upon the stress intensity factors of cracks.

  3. Modified Dugdale crack models - some easy crack relations

    DEFF Research Database (Denmark)

    Nielsen, Lauge Fuglsang

    1997-01-01

    are assumed to be self created by local materials flow. The strength sigma_CR predictid by the Dugdale model is sigma_CR =(E Gamma_CR/phi1)^½ where E and 1 are Young’s modulus and crack half-length respectively of the material considered. The so-called critical strain energy rate is Gamma_CR = sigma......_Ldelta_CR where sigma_L is strength, and at the same time constant flow stress, of the uncracked material while delta_CR is flow limit (displacement).Obviously predictions by the Dugdale model are most reliable for materials with stress-strain relations where flow can actually be described (or well approximated......) by a constant flow stress (sigma_L). A number of materials, however, do not at all exhibit this kind of flow. Such materials are considered in this paper by Modified Dugdale crack models which apply for any cohesive stress distribution in crack front areas. Formally modified Dugdale crack models exhibit...

  4. Subaqueous shrinkage cracks in the Sheepbed mudstone: Implications for early fluid diagenesis, Gale crater, Mars

    Science.gov (United States)

    Siebach, K. L.; Grotzinger, J. P.; Kah, L. C.; Stack, K. M.; Malin, M.; Léveillé, R.; Sumner, D. Y.

    2014-07-01

    The Sheepbed mudstone, Yellowknife Bay formation, Gale crater, represents an ancient lakebed now exhumed and exposed on the Martian surface. The mudstone has four diagenetic textures, including a suite of early diagenetic nodules, hollow nodules, and raised ridges and later diagenetic light-toned veins that crosscut those features. In this study, we describe the distribution and characteristics of the raised ridges, a network of short spindle-shaped cracks that crosscut bedding, do not form polygonal networks, and contain two to four layers of isopachous, erosion-resistant cement. The cracks have a clustered distribution within the Sheepbed member and transition laterally into concentrations of nodules and hollow nodules, suggesting that these features formed penecontemporaneously. Because of the erosion-resistant nature of the crack fills, their three-dimensional structure can be observed. Cracks that transition from subvertical to subhorizontal orientations suggest that the cracks formed within the sediment rather than at the surface. This observation and comparison to terrestrial analogs indicate that these are syneresis cracks—cracks that formed subaqueously. Syneresis cracks form by salinity changes that cause sediment contraction, mechanical shaking of sediment, or gas production within the sediment. Examination of diagenetic features within the Sheepbed mudstone favors a gas production mechanism, which has been shown to create a variety of diagenetic morphologies comparable to the raised ridges and hollow nodules. The crack morphology and the isopachous, layered cement fill show that the cracks were filled in the phreatic zone and that the Sheepbed mudstone remained fluid saturated after deposition and through early burial and lithification.

  5. Single-Breathhold Four-Dimensional Assessment of Left Ventricular Morphological and Functional Parameters by Magnetic Resonance Imaging Using the VAST Technique.

    Science.gov (United States)

    Rochitte, Carlos Eduardo; Azevedo, Clerio F; Rosário, Miguel A; Siqueira, Maria H R; Monsão, Victor; Saranathan, Manoj; Foo, Thomas K; Kalil Filho, Roberto; Cerri, Giovanni G; Ramires, José A F

    2011-01-01

    The accurate and reproducible assessment of cardiac volumes, function, and mass is of paramount importance in cardiology. In the present study we sought to determine whether the 3D cine-magnetic resonance (MR) technique, using the variable asymmetric sampling in time (VAST) approach, provided an accurate assessment of LV functional parameters when compared with the conventional 2D cine-MR technique. A total of 43 consecutive patients referred for a CMR examination for clinical reasons and 14 healthy volunteers were included in the study. Cine images were acquired using a steady-state free precession pulse sequence. Two different multiphase acquisitions were performed: conventional 2D cine-MR and 3D cine-MR. The short-axis cine images acquired by both cine-MR techniques were used for the quantitative assessment of LV end-diastolic, end-systolic and stroke volumes, LV mass and ejection fraction. All CMR examinations were completed successfully, with both cine-MR imaging techniques yielding interpretable diagnostic results in all patients. Regarding the quantitative assessment, Bland-Altman analyses demonstrated a good agreement between the measurements of both cine-MR techniques for all LV parameters. In addition, the agreement between 2D and 3D cine-MR techniques for the qualitative assessment of LV global function was perfect (kappa = 1.0, Ptechnique provides an accurate and reproducible quantitative assessment of LV volumes, mass and function when compared with the conventional 2D cine-MR method.

  6. Origin of undesirable cracks during layer transfer

    CERN Document Server

    Ponson, Laurent; Atwater, Harry; Ravichandran, Guruswami; Bhattacharya, Kaushik

    2008-01-01

    We investigate the origin of undesirable transverse cracks often observed in thin films obtained by the layer transfer technique. During this process, two crystals bonded to each other containing a weak plan produced by ion implantation are heated to let a thin layer of one of the material on the other. The level of stress imposed on the film during the heating phase due to the mismatch of thermal expansion coefficients of the substrate and the film is shown to be the relevant parameter of the problem. In particular, it is shown that if the film is submitted to a tensile stress, the microcracks produced by ion implantation are not stable and deviate from their straight trajectory making the layer transfer process impossible. However, if the compressive stress exceeds a threshold value, after layer transfer, the film can buckle and delaminate, leading to transverse cracks induced by bending. As a result, we show that the imposed stress \\sigma_m - or equivalently the heating temperature - must be within the ran...

  7. Influence of Solution Properties and Process Parameters on the Formation and Morphology of YSZ and NiO Ceramic Nanofibers by Electrospinning.

    Science.gov (United States)

    Cadafalch Gazquez, Gerard; Smulders, Vera; Veldhuis, Sjoerd A; Wieringa, Paul; Moroni, Lorenzo; Boukamp, Bernard A; Ten Elshof, Johan E

    2017-01-13

    The fabrication process of ceramic yttria-stabilized zirconia (YSZ) and nickel oxide nanofibers by electrospinning is reported. The preparation of hollow YSZ nanofibers and aligned nanofiber arrays is also demonstrated. The influence of the process parameters of the electrospinning process, the physicochemical properties of the spinning solutions, and the thermal treatment procedure on spinnability and final microstructure of the ceramic fibers was determined. The fiber diameter can be varied from hundreds of nanometers to more than a micrometer by controlling the solution properties of the electrospinning process, while the grain size and surface roughness of the resulting fibers are mainly controlled via the final thermal annealing process. Although most observed phenomena are in qualitative agreement with previous studies on the electrospinning of polymeric nanofibers, one of the main differences is the high ionic strength of ceramic precursor solutions, which may hamper the spinnability. A strategy to control the effective ionic strength of precursor solutions is also presented.

  8. Influence of Solution Properties and Process Parameters on the Formation and Morphology of YSZ and NiO Ceramic Nanofibers by Electrospinning

    Directory of Open Access Journals (Sweden)

    Gerard Cadafalch Gazquez

    2017-01-01

    Full Text Available The fabrication process of ceramic yttria-stabilized zirconia (YSZ and nickel oxide nanofibers by electrospinning is reported. The preparation of hollow YSZ nanofibers and aligned nanofiber arrays is also demonstrated. The influence of the process parameters of the electrospinning process, the physicochemical properties of the spinning solutions, and the thermal treatment procedure on spinnability and final microstructure of the ceramic fibers was determined. The fiber diameter can be varied from hundreds of nanometers to more than a micrometer by controlling the solution properties of the electrospinning process, while the grain size and surface roughness of the resulting fibers are mainly controlled via the final thermal annealing process. Although most observed phenomena are in qualitative agreement with previous studies on the electrospinning of polymeric nanofibers, one of the main differences is the high ionic strength of ceramic precursor solutions, which may hamper the spinnability. A strategy to control the effective ionic strength of precursor solutions is also presented.

  9. Fracture resistance on aggregate bridging crack in concrete

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xiufang; XU Shilang

    2007-01-01

    Fracture toughening exhibited in quasi-brittle materials such as concrete is often mainly related to the action of aggregate bridging,which leads to the presence of a fracture process zone ahead of stress-free cracks in such materials.In this investigation,the fracture resistance induced by aggregate bridging,denoted by GI-bridging,is the primary focus.In order to quantitatively determine it,a general analytical formula is firstly developed,based on the definition of fracture energy by Hillerborg.After this,we further present the calculated procedures of determining this fracture resistance from the recorded load vs.crack opening displacement curve.Then,both numerical simulations and fracture experiments are performed on concrete three-point bending beams.Utilizing the obtained load against crack opening displacement curve,the value of GI-bridging at any crack extension as well as the change of GI-bridging with the crack extension is examined.It is found that GI-bridging will firstly increase with the development of crack and then stay constant once the initial crack tip opening displacement reaches the characteristic crack opening displacement w0.The effects of material strength and specimen depth on this fracture resistance are also investigated.The results reveal that the values of GI-bridging of different specimens at any crack propagation are strongly associated with the values of fracture energy of specimens.If the values of fracture energy between different specimens are comparable,the differences between GI-bridging are ignored.Instead,if values of fracture energy are different,the GI-bridging will be different.This shows that for specimens with different strengths,GI-bridging will change greatly whereas for specimens that are different in depth,whether GI-bridging exhibits size effect depends on whether the fracture energy of specimens considered in the calculation of GI-bridging is assumed to be a size-dependent material parameter.

  10. Investigation about crack propagation paths in thin rim gears

    Directory of Open Access Journals (Sweden)

    F. Curà

    2014-10-01

    Full Text Available Crack propagation in gears is a problem related not only to the life of the components, but also to the concept of failsafe design. Fail safe design means to design a component in order that, if a failure occurs, this may cause a “safe failure”. This aspect is very important above all in aerospace industry. As a matter of fact, in aerospace application, the need of reducing weight brings to produce gears with very thick rim and web. Considering thin rim gears, when a crack is nucleated near the tooth root, it may propagate through the tooth (causing the loss of the entire tooth or a portion of it or the propagation may follow a path across the wheel diameter (causing the projection of big parts of the gear that may break the gearbox and may cause serious damage to the aircraft. The first failure mode is define as “failsafe failure” and the second one as “catastrophic failure” and of course has to be avoided. Designers need to have robust design criteria in order to predict crack propagation paths and to avoid catastrophic failures. In literature, few works are present concerning this topic, in particular related to the effect of geometrical parameters that may affect the crack propagation. In this work a numerical analysis about crack propagation in gears with respect to the backup ratio (ratio between tooth height and rim thickness, initial crack position and shape has been done by means of the Extended FEM (XFEM technique, realizing 3D models. XFEM 3D is a relatively new technique consisting in enriching traditional finite elements with more complex shape functions; in this way it is possible to propagate crack also between mesh nodes and to have mesh independent results. Aim of this paper is to highlight the crack propagation path in order to give to designers an high confident design criterion, related to the gear geometry. In particular, the effect of both rim thickness and orientation of the initial crack have been considered

  11. Uncertainty Evaluation of Weibull Estimators through Monte Carlo Simulation: Applications for Crack Initiation Testing

    Directory of Open Access Journals (Sweden)

    Jae Phil Park

    2016-06-01

    Full Text Available The typical experimental procedure for testing stress corrosion cracking initiation involves an interval-censored reliability test. Based on these test results, the parameters of a Weibull distribution, which is a widely accepted crack initiation model, can be estimated using maximum likelihood estimation or median rank regression. However, it is difficult to determine the appropriate number of test specimens and censoring intervals required to obtain sufficiently accurate Weibull estimators. In this study, we compare maximum likelihood estimation and median rank regression using a Monte Carlo simulation to examine the effects of the total number of specimens, test duration, censoring interval, and shape parameters of the true Weibull distribution on the estimator uncertainty. Finally, we provide the quantitative uncertainties of both Weibull estimators, compare them with the true Weibull parameters, and suggest proper experimental conditions for developing a probabilistic crack initiation model through crack initiation tests.

  12. Crack and flip phacoemulsification technique.

    Science.gov (United States)

    Fine, I H; Maloney, W F; Dillman, D M

    1993-11-01

    The crack and flip phacoemulsification technique combines the advantages of circumferential division of the nucleus and nucleofactis techniques. As such, it adds safety and control to the procedure. We describe each of the surgical maneuvers, including machine settings, and explain the rationale for maneuvers and machine settings.

  13. China Cracks Down Internet Piracy

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

      National Copyright Administration of China carried out a special operation to crack down on behaviors involving network infringement and piracy from September to December in 2005 ,according to the speech of Yan Xiaohong,Deputy Commissioner of National Copyright Administration on the Press Conference of the State Council.Now the relevant conditions are as follows:……

  14. China Cracks Down Internet Piracy

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    @@ National Copyright Administration of China carried out a special operation to crack down on behaviors involving network infringement and piracy from September to December in 2005 ,according to the speech of Yan Xiaohong,Deputy Commissioner of National Copyright Administration on the Press Conference of the State Council.Now the relevant conditions are as follows:

  15. HYDROTHERMAL CRACKING OF RESIDUAL OILS

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The hydrothermal cracking of heavy oils, such as Canadian oil sand bitumen and Arabian heavy vacuum residue, as well as their model compound were performed over sulfided Ni/Al2O3 and NiMo/Al2O3 catalysts under 663~703 K and 6.0~8.0 MPa of hydrogen pressure in a batch autoclave reactor. According to the reaction mechanism of hydrothermal cracking, a small amount of free redical initiators, such as di-tert-peroxide, sulfur, etc., was added into the feed to generate free redicals at lower temperature, and obviously showed promotional effect on the conversion of hydrocarbons. The reaction mechanisms of hydrothermal cracking as well as the enhancing effect of initiators were studied by a probe reaction with 1-phenyldodecane as a model compound. The hydrothermal cracking of hydrocarbon proceeded via free redical mechanism and hydrogenating quench. The initiators might easily generate free redicals under reaction temperature, these redicals might abstract H from hydrocarbon molecule and reasonably initiate the chain reactions, therefore, promote the conversion of hydrocarbon even at lower reaction temperature.

  16. Confining crack propagation in defective graphene.

    Science.gov (United States)

    López-Polín, Guillermo; Gómez-Herrero, Julio; Gómez-Navarro, Cristina

    2015-03-11

    Crack propagation in graphene is essential to understand mechanical failure in 2D materials. We report a systematic study of crack propagation in graphene as a function of defect content. Nanoindentations and subsequent images of graphene membranes with controlled induced defects show that while tears in pristine graphene span microns length, crack propagation is strongly reduced in the presence of defects. Accordingly, graphene oxide exhibits minor crack propagation. Our work suggests controlled defect creation as an approach to avoid catastrophic failure in graphene.

  17. Small changes in environmental parameters lead to alterations in antibiotic resistance, cell morphology and membrane fatty acid composition in Staphylococcus lugdunensis.

    Directory of Open Access Journals (Sweden)

    Marcus J Crompton

    , growth rates and morphology to achieve optimal adaptations for survival in changing environments.

  18. Correction to the crack extension direction in numerical modelling of mixed mode crack paths

    DEFF Research Database (Denmark)

    Lucht, Tore; Aliabadi, M.H.

    2007-01-01

    In order to avoid introduction of an error when a local crack-growth criterion is used in an incremental crack growth formulation, each straight crack extension would have to be infinitesimal or have its direction corrected. In this paper a new procedure to correct the crack extension direction i...

  19. Mesh sensitivity effects on fatigue crack growth by crack-tip blunting and re-sharpening

    DEFF Research Database (Denmark)

    Tvergaard, Viggo

    2007-01-01

    Crack-tip blunting under tensile loads and re-sharpening of the crack-tip during unloading is one of the basic mechanisms for fatigue crack growth in ductile metals. Based on an elastic–perfectly plastic material model, crack growth computations have been continued up to 700 full cycles by using...

  20. Fatigue crack growth from a cracked elastic particle into a ductile matrix

    NARCIS (Netherlands)

    Groh, S.; Olarnrithinun, S.; Curtin, W. A.; Needleman, A.; Deshpande, V. S.; Van der Giessen, E.

    2008-01-01

    The monotonic and cyclic crack growth rate of cracks is strongly influenced by the microstructure. Here, the growth of cracks emanating from pre-cracked micron-scale elastic particles and growing into single crystals is investigated, with a focus on the effects of (i) plastic confinement due to the

  1. Modeling of Biomass-Based Leaf Morphological Parameters on Main Stem for Rapeseed (Brassica napus L.)%基于生物量的油菜主茎叶片形态参数模拟研究

    Institute of Scientific and Technical Information of China (English)

    张文宇; 张伟欣; 葛道阔; 曹宏鑫; 刘岩; 宣守丽; 傅坤亚; 冯春焕; 陈魏涛

    2015-01-01

    为了定量油菜主茎叶片形态参数与生物量间的关系,本研究基于2011—2012年和2012—2013年不同品种、移栽密度及施肥水平油菜田间试验,通过观测不同品种和处理油菜叶片长、最大叶宽和叶柄长等形态参数,并分析了上述参数与叶片生物量的关系,构建了基于生物量的油菜叶长、最大叶宽和叶柄长模型。结果表明,在全生育期,不同品种和处理下油菜主茎叶长和最大叶宽均与叶片生物量的平方根成正比,而叶柄长与叶长成正比。所建模型利用截距为0的线性函数描述叶长和最大叶宽随生物量平方根的变化,用直线式描述叶柄长随叶长的变化。经独立试验资料检验,除宁油16叶柄长模型误差较大外,所建模型对其余形态参数均具有较好预测性,为通过生物量将油菜生长模型与形态结构模型结合提供了机理性较强的方法,为建立油菜功能-结构模型奠定了基础。%To quantify the relationships between main stem leaf morphological parameters for rapeseed and the corresponding leaf biomass, we conducted field experiments on varieties, transplanting densities, and fertilizer in 2011 to 2012, and 2012 to 2013 seasons. The biomass-based leaf morphological parameter models for rapeseed on main stem were constructed through observing leaf length, maximum leaf width, and leaf petiole length under various treatments, and analyzing the relationships between leaf morphological parameters and the corresponding leaf biomass. Because both of the leaf length and leaf width were positively proportional to the square root of the corresponding leaf biomass, meanwhile the leaf petiole length was positively proportional to the corresponding leaf length, the changes in the leaf length, the maximum leaf width, and the leaf petiole length with the changed of square root of the corresponding leaf biomass for different treatments could be described with linear

  2. Influence of Anion Types on the Electrodeposition Healing Effect of Concrete Cracks

    Institute of Scientific and Technical Information of China (English)

    CHU Hongqiang; JIANG Linhua; XU Ning; XIONG Chuansheng

    2012-01-01

    With the zinc salt and magnesium salt solutions,the influence of anion types on the electrodeposition healing effect of concrete cracks was investigated,four parameters such as rate of weight gain,surface coating,crack closure,and crack filling depth were measured,and the mineral composition and appearance of electrodeposits in the cracks were analyzed.The experimental results demonstrate that the electrodeposition healing effect is the best by adopting ZnSO4 and MgSO4 solutions.The mineral composition of electrodeposits in the cracks does not change with the anion types.The most particles of ZnO crystal appear as fusiform by using zinc salt solutions.If we selected MgSO4 solution,the Mg(OH)2 crystal was porous honeycomb.The electrodeposits present as flake structure while the other magnesium salt solutions were adopted.

  3. Process Optimization for Suppressing Cracks in Laser Engineered Net Shaping of Al2O3 Ceramics

    Science.gov (United States)

    Niu, F. Y.; Wu, D. J.; Yan, S.; Ma, G. Y.; Zhang, B.

    2017-03-01

    Direct additive manufacturing of ceramics (DAMC) without binders is a promising technique for rapidly fabricating high-purity components with good performance. Nevertheless, cracks are easily generated during fabrication as a result of the high intrinsic brittleness of ceramics and the great temperature gradients. Therefore, optimizing the DAMC process is a challenge. In this study, direct fabrication of Al2O3 single-bead wall structures are conducted with a laser engineered net shaping (LENS) system. A new process optimization method for suppressing cracks is proposed based on analytical models, and then the influence of process parameters on crack number is discussed experimentally. The results indicate that the crack number decreases obviously with the increase of scanning speed. Single-bead wall specimens without cracks are successfully fabricated by the optimized process.

  4. SCC crack growth rate of cold-worked austenitic stainless steels in PWR primary water conditions

    Energy Technology Data Exchange (ETDEWEB)

    Guerre, C.; Raquet, O.; Herms, E. [Commissariat a l' Energie Atomique (CEA), DEN/DPC/SCCME/LECA, Gif-sur-Yvette Cedex (France); Marie, S. [Commissariat a l' Energie Atomique (CEA), DEN/DM2S/SEMT/LISN, Gif-sur-Yvette Cedex (France); Le Calvar, M. [Inst. for Radiological Protection and Nuclear Safety (IRSN), DSR/SAMS, Fontenay-aux-Roses Cedex (France)

    2007-07-01

    Stress corrosion cracking (SCC) of stainless steels (SS) is a significant cause of failure in the pressurized water reactors (PWR). Most of the reported case history failures of SS in PWR can be attributed to pollutants (chloride, sulphate) and / or locally oxygenated environments, even to sensitisation of the SS. However, some failures have been attributed to heavy cold work (CW) of SS. In laboratory tests, SCC initiation of cold-worked SS has been obtained using slow strain rate tests (SSRT) in nominal PWR environment. This paper describes constant load and cyclic crack growth rate (CGR) tests on cold-worked SS, on CT specimens. 304L and 316L have been tested with a CW up to 60 %. CW 316L is more prone to cracking than 304L. Over 30 % of CW, 316L is susceptible to crack propagation under constant load. CW is the main controlling parameter for cracking. (author))

  5. Analysis of Cracking Mode of Anchor Structure of Underground Engineering Induced by Reinforcement Corrosion

    Directory of Open Access Journals (Sweden)

    Wantao Ding

    2014-02-01

    Full Text Available Based on elastic theory and assumption of maximum tensile-stress failure criterion, together with construction process of anchor structure and rust expansion critical process, this study proposed a simplified reinforcement rust expansion mechanical model of anchor structure system. Elastic criterion of different initial cracking mode was rewarded under different stress ratios. According to analysis of critical cracking mode of different medium, cracking order of mortar and surrounding rock depended on their material parameters, in-situ stress and thickness of mortar cover. Critical cracking conditions of different medium without effect of in-situ stress was the same as that of considering in-situ stress while k is equal to 3 or 1/3. And engineering example shows that three different cracking modes exist under different stress ratios. The result provides a useful reference for analysis of mechanical deterioration mechanism of anchor structure and design of support structure of underground engineering.

  6. Influence of Cracks on the Lifetime of Semi-Rigid Pavements

    Science.gov (United States)

    Kazimierowicz-Frankowska, Krystyna

    2016-12-01

    This paper focuses on a better understanding of the process of reflective cracking propagation through the pavement structure. A series of finite element numerical simulations were conducted to investigate the initial stress and strain states in typical semi-rigid pavements with and without reflective cracks under traffic loading. It was assumed that reflective-cracks propagate from the base layer to the pavement surface. The influence of selected parameters, such as the load position, overlay thickness, and subgrade quality on stress and strain concentrations was investigated. The behaviour of the pavement structure under repeated traffic loading was analyzed in terms of ground compaction. The original theoretical model proposed by Prof. Andrzej Sawicki was used to predict the deformation of a pavement subgrade subjected to traffic loading. The damaging effect of cracks appearing in the pavement structure was investigated. It was found that even a single crack in the pavement structure may significantly reduce the pavement lifetime.

  7. Twisting cracks in Bouligand structures.

    Science.gov (United States)

    Suksangpanya, Nobphadon; Yaraghi, Nicholas A; Kisailus, David; Zavattieri, Pablo

    2017-06-10

    The Bouligand structure, which is found in many biological materials, is a hierarchical architecture that features uniaxial fiber layers assembled periodically into a helicoidal pattern. Many studies have highlighted the high damage-resistant performance of natural and biomimetic Bouligand structures. One particular species that utilizes the Bouligand structure to achieve outstanding mechanical performance is the smashing Mantis Shrimp, Odontodactylus Scyllarus (or stomatopod). The mantis shrimp generates high speed, high acceleration blows using its raptorial appendage to defeat highly armored preys. The load-bearing part of this appendage, the dactyl club, contains an interior region [16] that consists of a Bouligand structure. This region is capable of developing a significant amount of nested twisting microcracks without exhibiting catastrophic failure. The development and propagation of these microcracks are a source of energy dissipation and stress relaxation that ultimately contributes to the remarkable damage tolerance properties of the dactyl club. We develop a theoretical model to provide additional insights into the local stress intensity factors at the crack front of twisting cracks formed within the Bouligand structure. Our results reveal that changes in the local fracture mode at the crack front leads to a reduction of the local strain energy release rate, hence, increasing the necessary applied energy release rate to propagate the crack, which is quantified by the local toughening factor. Ancillary 3D simulations of the asymptotic crack front field were carried out using a J-integral to validate the theoretical values of the energy release rate and the local stress intensity factors. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Fatigue crack growth simulations of 3-D linear elastic cracks under thermal load by XFEM

    Institute of Scientific and Technical Information of China (English)

    Himanshu PATHAK[1; Akhilendra SINGH[2; I.V. SINGH[3; S. K. YADAV[3

    2015-01-01

    This paper deals with the fatigue crack growth simulations of three-dimensional linear elastic cracks by XFEM under cyclic thermal load. Both temperature and displacement approximations are extrinsically enriched by Heaviside and crack front enrichment functions. Crack growth is modelled by successive linear extensions, and the end points of these linear extensions are joined by cubic spline segments to obtain a modified crack front. Different crack geometries such as planer, non-planer and arbitrary spline shape cracks are simulated under thermal shock, adiabatic and isothermal loads to reveal the sturdiness and versatility of the XFEM approach.

  9. Effect of BaSO4 on the fatigue crack propagation rate of PMMA bone cement.

    Science.gov (United States)

    Molino, L N; Topoleski, L D

    1996-05-01

    To determine the effect of BaSO4 on the fatigue crack growth rate, da/dN = C(delta K)n, of poly(methyl methacrylate) (PMMA) bone cement, radiopaque bone cement, radiolucent bone cement, and commercial PMMA (Plexiglas) were tested using a methodology based on ASTM E647. The crack growth rate of radiopaque bone cement was one order of magnitude less than that of radiolucent. Fractographic analysis showed that the regions of rapid catastrophic fracture were smooth for all materials tested. The radiopaque fatigue surface was rough and characterized by ragged-edged stacked plateaus, a morphology consistent with the model of crack propagation through the interbead matrix. Voids were visible in the interbead matrix on the order of the size of BaSO4 particles. The fatigue surface of radiolucent bone cement was relatively smooth, a morphology consistent with crack propagation through both the PMMA beads and interbead matrix. Fatigue striations were visible, and their spacing correlated well with crack propagation rates. The striations indicated an increased crack growth rate through the PMMA beads.

  10. Effects of Melatonin on Morphological and Functional Parameters of the Pineal Gland and Organs of Immune System in Rats During Natural Light Cycle and Constant Illumination.

    Science.gov (United States)

    Litvinenko, G I; Shurlygina, A V; Gritsyk, O B; Mel'nikova, E V; Tenditnik, M V; Avrorov, P A; Trufakin, V A

    2015-10-01

    We studied the response of the pineal gland and organs of the immune system to melatonin treatment in Wistar rats kept under conditions of abnormal illumination regimen. The animals were kept under natural light regimen or continuous illumination for 14 days and then received daily injections of melatonin (once a day in the evening) for 7 days. Administration of melatonin to rats kept at natural light cycle was followed by a decrease in percent ratio of CD4+8+ splenocytes and CD4-8+ thymocytes. In 24-h light with the following melatonin injections were accompanied by an increase in percent rate and absolute amount of CD4+8+ cells in the spleen, and a decrease in percent rate of CD11b/c and CD4-8+ splenocytes. In the thymus amount of CD4-8+ cells increased, and absolute number of CD4+25+ cells reduced. Melatonin significantly decreased lipofuscin concentration in the pineal gland during continuous light. Direction and intensity of effects of melatonin on parameters of cell immunity and state of the pineal gland were different under normal and continuous light conditions. It should be taken into account during using of this hormone for correction of immune and endocrine impairments developing during change in light/dark rhythm.

  11. Non-linear vibrations of cracked structures: application to turbine rotors; Vibrations non-lineaires des structures fissurees: application aux rotors de turbines

    Energy Technology Data Exchange (ETDEWEB)

    El Arem, S.

    2006-01-15

    The aim of this work is to study the dynamic response of a cracked rotor to establish some possibilities for early on line crack detection. First, a review on experimental, numerical and analytical works on the dynamics of cracked rotors is given. Then, an original method of calculating the behavior of a cracked beam section in bending with shearing effects is presented. The nonlinear behavior relations are derived from a three-dimensional model taking into account the unilateral contact conditions on the crack's lips. Based on an energy formulation, this method could be applied to any geometry of crack. The exploration by different numerical integration methods of the vibratory response of some models of cracked rotors is presented in the third chapter of this thesis. The un-cracked parts of a rotor are represented by elements of bar or beam type, and the cracked section by a nonlinear spring taking into account the breathing mechanism of the cracks. At the end of this part, an original method of construction of a finite element of a cracked beam is presented. The final chapter is devoted to the analytical study of the system with 2 degrees of freedom. The breathing mechanism of the crack is taken into account by considering specific periodic variation of the global stiffness of the system. The differential equations system is solved using the harmonic balance method. The linear stability of the periodic solutions is studied by the Floquet theory. Some vibratory parameters are proposed as crack indicators. (author)

  12. Effect of process parameters on surface morphology and characterization of PE-ALD SnO{sub 2} thin films for gas sensing

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Gwangpyo [JAMIC, Sunchun, Jeonnam 540-856 (Korea, Republic of); Satyanarayana, L. [Research Institute of Energy Resources Technology, Chosun University, Gwangju 501-759 (Korea, Republic of); Park, Jinseong [Department of Advanced Materials Engineering, Chosun University, Gwangju 501-759 (Korea, Republic of)]. E-mail: jsepark@chosun.ac.kr

    2006-09-15

    Tin dioxide (SnO{sub 2}) thin films were deposited by plasma enhanced-atomic layer deposition (PE-ALD) on Si(1 0 0) substrate using dibutyl tin diacetate (DBTA) ((CH{sub 3}CO{sub 2}){sub 2}Sn[(CH{sub 2}){sub 3}-CH{sub 3}]{sub 2}) as precursor. The process parameters were optimized as a function of substrate temperature, source temperature and purging time. It is observed that the surface phenomenon of the thin films was changed with film thickness. Atomic force microscopy (AFM) images and X-ray diffraction (XRD) pattern were used to observe the texture and crystallanity of the films. The films deposited for 100, 200 and 400 cycles were characterized by XPS to determine the chemical bonding properties. XPS results reveal that the surface dominant oxygen species for 100, 200 and 400 cycles deposited films are O{sub 2} {sup -}, O{sup -} and O{sup 2-}, respectively. The 200 cycles film has exhibited highest concentration of oxygen (O{sup -}) species before and after annealing. Conductivity studies revel that this film has best adsorption strength to the oxygen ions forming on the surface. The sensor with 200 cycles SnO{sub 2} thin film has shown highest sensitivity to CO gas than other films. A correlation between the characteristics of Sn3d{sub 5/2} and O1s XPS spectra before and after annealing and the electrical behavior of the SnO{sub 2} thin films is established.

  13. Effect of differently structured and processed feedstuffs on diverse parameters of ethology and digestibility of growing rabbits and their influence on morphological structures in small intestine.

    Science.gov (United States)

    Lang, Caroline; Hinchliffe, David; Brendle, Julia; Weirichl, Carmen; Hoy, Steffen

    2016-01-01

    The influence of different feedstuffs on parameters of digestion and ethology in growing rabbits (duration and number of feed intake, needed masticatory movements, pH value in stomach and small intestine, dry matter content of stomach chyme, level of destruction of cell structures in small intestine) was analysed. 384 five weeks old rabbits were fed with one of three feedstuffs: pellets (mean fibre length = 3 mm), fibre blocks (mean fibre length = 40 mm) and hay-oat-beat-ration (length of hay fibre ≥ 70 mm). The masticatory movements and duration for uptake 0.1 g of feedstuffs were measured in a special observation box. Rabbits in group cages were observed by 24 h video recording and duration and numbers of feed intakes were documented. After 8 weeks rabbits were slaughtered and pH values measured in stomach chyme (and dry matter content) and small intestine. Samples of them were taken and histologically examined (total length of villi and crypts, width of villi and degree of destruction determined by scores from 0 [= no destruction] to 3 [= severe destruction of villi]). Pellets lead to a faster feed intake with a lower number of masticatory movements. This equates a minor feeding time per feed intake and a higher amount of feedstuff in a shorter time. The dry matter content in stomach chyme increases and pH value was significantly higher there, but lower in duodenum. They also showed a significantly higher degree of destruction of villi, a shorter length and a larger width of villi than others.

  14. Magnetic-field-driven crack formation in an evaporated anisotropic colloidal assembly

    Science.gov (United States)

    Lama, Hisay; Dugyala, Venkateshwar Rao; Basavaraj, Madivala G.; Satapathy, Dillip K.

    2016-07-01

    We report the effect of applied magnetic field on the morphology of cracks formed after evaporation of a colloidal suspension consisting of shape-anisotropic ellipsoidal particles on a glass substrate. The evaporation experiments are performed in sessile drop configuration, which usually leads to accumulation of particles at the drop boundaries, commonly known as the "coffee-ring effect." The coffee-ring-like deposits that accompany cracks are formed in the presence as well as in the absence of magnetic field. However, the crack patterns formed in both cases are found to differ markedly. The direction of cracks in the presence of the magnetic field is found to be governed by the orientation of particles and not solely by the magnetic field direction. Our experimental results show that at the vicinity of cracks the particles are ordered and oriented with their long-axis parallel to crack direction. In addition, we observe that the crack spacing in general increases with the height of the particulate film.

  15. Efifciency of Concrete Crack-healing based on Biological Carbonate Precipitation

    Institute of Scientific and Technical Information of China (English)

    LUO Mian; QIAN Chunxiang; LI Ruiyang; RONG Hui

    2015-01-01

    The aim of this study was to improve the capacity for crack-repair in concrete by developing a new way. The self-healing agent based on biological carbonate precipitation was developed. Crack-healing capacity of the cement paste specimens with this biochemical agent was researched. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the precipitation in cracks. The healing efficiency was evaluated by measuring the water permeability after crack healing as well.The experimental results show that the applied biochemical agent can successfully improve the self-healing capacity of the cement paste specimens as larger cracks can be healed. The cracks with a width of 0.48 mm in the specimens with the biochemical agent are nearly fully healed by the precipitation after 80d repair. SEM and XRD analysis results demonstrate that the white precipitation in cracks is calcium carbonate, which displays spherical crystal morphology. Meanwhile, the water permeability test result shows that the biochemical agent can significantly decrease the water permeability of the cement paste specimens, the water permeability of specimens with the biochemical agent respectively decreases by 84%and 96%after 7 d and 28 d immersion in water, however the control specimens only respectively decrease by 41%and 60%, which indicates that the bacteria-based concrete appears to be a promising approach to increase concrete durability.

  16. Photoelastic studies of crack propagation and crack arrest. [Homalite 100

    Energy Technology Data Exchange (ETDEWEB)

    Irwin, G.R.; Dally, J.W.; Kobayashi, T.; Fourney, W.L.; Etheridge, J.M.

    1977-09-01

    This report describes the third year effort on research programs dealing with the characterization of dynamic aspects of fracture. The results included in this report are (1) verification of the BCL one-dimensional computer code; (2) determination of a-dot--K relationship from modified compact-tension specimen of Homalite 100; (3) verification of the MRL procedure for K/sub Ia/ measurement with machine-loaded C-DCB specimen of Homalite 100; (4) influence of adhesive toughness, adhesive thickness, and toughness of the arrest section on crack behavior in duplex specimens of both the M-CT and R-DCB types; (5) crack propagation in a thermally stressed ring specimen; and (6) development of a two-dimensional finite-difference code to predict fracture behavior in specimens of rectangular geometry under various a-dot vs K relationships. 118 figures, 53 tables.

  17. Structure Defects Interrelation of Heat-resistant Nickel Alloy Obtained by Selective Laser Melting Method and Strategy and Scanning Parameters

    Directory of Open Access Journals (Sweden)

    O. A. Bytsenko

    2016-01-01

    Full Text Available The objective was to conduct a study of the surface morphology and a chemical composition analysis of the powder of different fractional composition of a heat-resistant Ni-Co-Cr-AlTi-W-Mo-Nb alloy, and to define the patterns of change in the quantitative parameters of the structure of samples obtained by selective laser melting (SLM method with different parameters of power, laser speed, and a type of hatching (staggered, island diagonal, and solid diagonal.To study the surface morphology of the microstructure was used optical, laser-confocal and scanning electron microscopy. The elemental and local phase composition was performed by X-ray and miсro-X-ray spectrum analysis.The initial powder morphology study has found that the powder granules have a generally spherical shape, and the number of structural defects increases with increasing granule size. The microstructure of all granules has a dendritic structure. The superficial defects have a form of satellites, shapeless shield, round gas pores, and pores located in the inter-dendritic regions because of the shrinkage process.The study of the microstructure of the samples has been defined that dimensions of the structural components, pores, and micro-cracks depend on the parameters of the SLM process. With raising laser power within 160 - 190 W there is an increase in a fraction of pores and their average diameter. With further increase in laser power the volume fraction of pores is slightly reduced while their average size is, essentially, unchanged.It has been found that at the constant laser power and variable scanning speed the volume fraction of pores depends on the type of hatching. For staggered and solid diagonal hatching, at the constant laser power of 180 W with increasing scanning speed the volume fraction, at first, falls and then again grows, and for island diagonal hatching remains unchanged.When changing the laser power values within a range from 160 to 170 W for samples with

  18. Inhibiting Corrosion Cracking: Crack Tip Chemistry and Physics.

    Science.gov (United States)

    1986-03-14

    5 5. Swuzary 113 Rferences 114 wl NO 4L iv . List of Figuring 1. Microipette pulling machine . 29 2. Anodic polarization of 7075-T6 Al alloy in dilute...environment has a strong effect on microplastic behavior at the tip of a fatigue crack. Stolz and Pelloux suggest that nitrate ion competes with chloride...Crystalline Na2 N 20 29H20 precipitates when the filtrate is placed in a vacunm desiccator over sulfuric acid. The filtered precipitate is washed

  19. An effective finite element model for the prediction of hydrogen induced cracking in steel pipelines

    KAUST Repository

    Traidia, Abderrazak

    2012-11-01

    This paper presents a comprehensive finite element model for the numerical simulation of Hydrogen Induced Cracking (HIC) in steel pipelines exposed to sulphurous compounds, such as hydrogen sulphide (H2S). The model is able to mimic the pressure build-up mechanism related to the recombination of atomic hydrogen into hydrogen gas within the crack cavity. In addition, the strong couplings between non-Fickian hydrogen diffusion, pressure build-up and crack extension are accounted for. In order to enhance the predictive capabilities of the proposed model, problem boundary conditions are based on actual in-field operating parameters, such as pH and partial pressure of H 2S. The computational results reported herein show that, during the extension phase, the propagating crack behaves like a trap attracting more hydrogen, and that the hydrostatic stress field at the crack tip speed-up HIC related crack initiation and growth. In addition, HIC is reduced when the pH increases and the partial pressure of H2S decreases. Furthermore, the relation between the crack growth rate and (i) the initial crack radius and position, (ii) the pipe wall thickness and (iii) the fracture toughness, is also evaluated. Numerical results agree well with experimental data retrieved from the literature. Copyright © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

  20. Standard test method for determination of resistance to stable crack extension under low-constraint conditions

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2006-01-01

    1.1 This standard covers the determination of the resistance to stable crack extension in metallic materials in terms of the critical crack-tip-opening angle (CTOAc), ψc and/or the crack-opening displacement (COD), δ5 resistance curve (1). This method applies specifically to fatigue pre-cracked specimens that exhibit low constraint (crack-length-to-thickness and un-cracked ligament-to-thickness ratios greater than or equal to 4) and that are tested under slowly increasing remote applied displacement. The recommended specimens are the compact-tension, C(T), and middle-crack-tension, M(T), specimens. The fracture resistance determined in accordance with this standard is measured as ψc (critical CTOA value) and/or δ5 (critical COD resistance curve) as a function of crack extension. Both fracture resistance parameters are characterized using either a single-specimen or multiple-specimen procedures. These fracture quantities are determined under the opening mode (Mode I) of loading. Influences of environment a...

  1. Time domain analysis of nonlinear frequency mixing in a slender beam for localizing a breathing crack

    Science.gov (United States)

    Joglekar, D. M.; Mitra, Mira

    2017-02-01

    The nonlinear interaction of a dual frequency flexural wave with a breathing crack generates a peculiar frequency mixing phenomena, which is manifested in form of the side bands or peaks at combinations frequencies in frequency spectrum of the response. Although these peaks have been proven useful in ascertaining the presence of crack, they barely carry any information about the crack location. In this regards, the present article analyzes the time domain representation of the response obtained by employing a wavelet spectral finite element method. The study reveals that the combination tones generated at the crack location travel with dissimilar speeds along the waveguide, owing to its dispersive nature. The separation between the lobes corresponding to these combination tones therefore, depends on the distance that they have travelled. This observation is then used to formulate a method to predict the crack location with respect to the sensor. A brief parametric study shows marginal errors in predicting the crack location, which ascertains the validity of the method. This article also studies the frequency spectrum of the response. The peaks at combination tones are quantified in terms of a modulate parameter which depends on the severity of the crack. The inferences drawn from the time and the frequency domain study can be instrumental in designing a robust strategy for detecting location and severity of the crack.

  2. Crack branching in carbon steel. Fracture mechanisms

    Science.gov (United States)

    Syromyatnikova, A. S.; Alekseev, A. A.; Levin, A. I.; Lyglaev, A. V.

    2010-04-01

    The fracture surfaces of pressure vessels made of carbon steel that form during crack branching propagation are examined by fractography. Crack branching is found to occur at a crack velocity higher than a certain critical value V > V c . In this case, the material volume that is involved in fracture and depends on the elastoplastic properties of the material and the sample width has no time to dissipate the energy released upon crack motion via the damage mechanisms intrinsic in the material under given deformation conditions (in our case, via cracking according to intragranular cleavage).

  3. Strength of Cracked Reinforced Concrete Disks

    DEFF Research Database (Denmark)

    Hoang, Cao Linh; Nielsen, Mogens Peter

    1999-01-01

    The paper deals with models, based on the theory of plasticity, to be used in strength assessments of reinforced concrete disks suffering from different kinds of cracking. Based on the assumption that the sliding strength of concrete is reduced in sections where cracks are located, solutions...... for the shear strength of disks with initial cracks and disks suffering from isotropic cracking are presented. Furthermore, in the case of isotropicly cracked disks subjected to arbitrary in-plane loading, a general yield condition is derived....

  4. CRACK REASON ANALYSIS OF DAMAGED CARBONITRIDED PART

    Directory of Open Access Journals (Sweden)

    Karin Kocúrová

    2010-03-01

    Full Text Available The article deals with the analysis of a damaged part, which was designed for use in a mechanical clutch of a car. The crack in the part was found during the production inspection. The aim of metallographic and fractography analyses of the fracture surfaces was to discover the reasons for the crack. The reason for creating the crack was the formation of smaller cracks in the production during pressing process of the semiproduct. These cracks even grew after the following thermochemical treatment. The fracture was initiated during the straightening process of quenched part.

  5. Study on the propagation characteristic of the Thermal Fatigue Crack by cyclic thermal load in the STS 304 tube

    Energy Technology Data Exchange (ETDEWEB)

    An, Dae-Hwan; Hwang, Woong-Ki; Kim, Jae-Seong; Lee, Sang-Yul; Lee, Bo-Young [Korea Aerospace University, Goyang (Korea, Republic of)

    2008-05-15

    Thermal fatigue crack is one of the life-limiting mechanisms in nuclear power plant conditions. During the operation of a power plant thermal fatigue cracks can initiate and grow in various components (straight pipe sections, valve bodies, pipe elbows, and collector head screw holes). Causes for this are mixing, striping or stratification of hot and cold water. A typical component, where thermal fatigue cracking occurs, is a T-joint where hot and cold fluids meet and mix. The turbulent mixing of fluids with different temperatures induces rapid temperature changes to the pipe wall. The resulting uneven temperature distribution prevents thermal expansion and gives rise to thermal stresses. The successive thermal transients cause varying, cyclic thermal stresses. These cyclic thermal stresses cause fatigue crack initiation and growth similar to cyclic mechanical stresses. In order to fabricate thermal fatigue crack similar to realistic crack, successive thermal transients were applied to the specimen. In this study, in order to identify propagation characteristic of thermal fatigue crack, thermal fatigue crack specimens of 4000cycle, 6000cycle, 9000cycle were fabricated. Thermal transient cycles were combined with heating (60sec) and cooling cycle (30sec). Destructive testing and scanning electron microscopy were carried out to identify the crack propagation characteristic and fracture surface morphology.

  6. Prediction of Crack for Drilling Process on Alumina Using Neural Network and Taguchi Method

    Directory of Open Access Journals (Sweden)

    Kingsun Lee

    2015-01-01

    Full Text Available This study analyzes a variety of significant drilling conditions on aluminum oxide (with L18 orthogonal array using a diamond drill. The drilling parameters evaluated are spindle speed, feed rate, depth of cut, and diamond abrasive size. An orthogonal array, signal-to-noise (S/N ratio, and analysis of variance (ANOVA are employed to analyze the effects of these drilling parameters. The results were confirmed by experiments, which indicated that the selected drilling parameters effectively reduce the crack. The neural network is applied to establish a model based on the relationship between input parameters (spindle speed, feed rate, depth of cut, and diamond abrasive size and output parameter (cracking area percentage. The neural network can predict individual crack in terms of input parameters, which provides faster and more automated model synthesis. Accurate prediction of crack ensures that poor drilling parameters are not suitable for machining products, avoiding the fabrication of poor-quality products. Confirmation experiments showed that neural network precisely predicted the cracking area percentage in drilling of alumina.

  7. Alternating grain orientation and weld solidification cracking

    Science.gov (United States)

    Kou, S.; Le, Y.

    1985-10-01

    A new mechanism for reducing weld solidification cracking was proposed, based on the concept of the crack path and resistance to crack propagation, and its effectiveness was verified in magnetically oscillated GTA welds of a rather crack susceptible material 2014 aluminum alloy. This mechanism, i.e., alternating grain orientation, was most pronounced in welds made with transverse arc oscillation of low frequency and high amplitude, and solidification cracking was dramatically reduced in these welds. The effect of the arc oscillation pattern, amplitude, and frequency on the formation of alternating columnar grains and the reduction of solidification cracking in GTA welds of 2014 aluminum alloy was examined and explained. The present study demonstrated for the first time that columnar grains can, in fact, be very effective in reducing solidification cracking, provided that they are oriented favorably.

  8. Nondestructive evaluation of notched cracks in mortars by nonlinear ultrasonic technique

    Science.gov (United States)

    Chen, Jun; Ren, Jun; Yin, Tingyuan

    2016-04-01

    In this paper, a nonlinear ultrasonic technique is used to nondestructively characterise concentrated defects in cement-based materials. Cracks are artificially notched in mortar samples and five different crack widths are used to simulate increased damage of samples. The relative ratio of second harmonic amplitude to the square of fundamental ultrasonic signal amplitude is defined as the damage indicator of the nonlinear ultrasonic technique, which is measured for mortar samples in conjunction with a typical linear nondestructive evaluation parameter - ultrasonic pulse velocity. It is found that both linear and nonlinear damage parameters have a good correlation with the change of crack width, while the nonlinearity parameter shows a better sensitivity to the width increase. In addition, the nonlinearity parameter presents an exponential increase with the crack growth, indicating an accelerating nonlinear ultrasonic response of materials to increased internal damage in the late phase. The results demonstrate that the nonlinear ultrasonic technique based on the second harmonic principle keeps the high sensitivity to the isolated cracks in cement-based materials, similarly to the case of distributed cracks in previous studies. The developed technique could thus be a useful experimental tool for the assessment of concentrated damage of concrete structures.

  9. The phenomenological mechanochemistry of damage and radial cracking

    Science.gov (United States)

    Grinfeld, Michael

    2017-01-01

    Traditional damage theory deals with distributed microcracks rather than with individual cracks. In its simplest form, this theory adds just one additional parameter to the set of classical thermodynamic parameters of deformable solids like strain and temperature. Basically, the traditional damage theory reflects only one experimental observation: The elastic moduli become smaller with growing damage. Contrary to the traditional damage theory, the Phenomenological Mechanochemistry of Damage (PMD) uses an energetic approach; it includes, in addition to the bulk elastic energy, the energy associated with braking/recovery of chemical bonds. Therefore, in addition to the elasticity equations, it includes the equation describing evolution/dynamics of chemical bonds. With the minimum amount of physically transparent assumptions, it allows the reproduction of radial cracking patterns that are often observed in experiments and nature. In this paper, we review some earlier results and present the novel ones with emphasis on the electro- or magnetostatics ponderomotive forces.