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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. Influence of Crack Morphology on Leak Before Break Margins

    International Nuclear Information System (INIS)

    Weilin Zang

    2007-11-01

    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

  3. Crack layer morphology and toughness characterization in steels

    Science.gov (United States)

    Chudnovsky, A.; Bessendorf, M.

    1983-01-01

    Both the macro studies of crack layer propagation are presented. The crack extension resistance parameter R sub 1 based on the morphological study of microdefects is introduced. Experimental study of the history dependent nature of G sub c supports the representation of G sub c as a product of specific enthalpy of damage (material constant) and R sub 1. The latter accounts for the history dependence. The observation of nonmonotonic crack growth under monotonic changes of J as well as statistical features of the critical energy release rate (variance of G sub c) indicate the validity of the proposed damage characterization.

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

    DEFF Research Database (Denmark)

    Brincker, Rune

    In this paper the problem of describing the asymptotic fields around a slowly growing crack in a linearly viscoelastic material is considered. It is shown that for plane mixed mode problems the asymptotic fields must be described by 6 parameters: 2 stress intensity factors and 4 deformation...... 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....

  5. Severity parameters for steam cracking

    NARCIS (Netherlands)

    Golombok, M.; Bijl, J.L.M.; Kornegoor, M.

    2001-01-01

    There are several ways to measure severity in steam cracking which are all a function of residence time, temperature, and pressure. Many measures of severity are not practicable for experimental purposes. Our experimental study shows that methane make is the best measure of severity because it is an

  6. A numerical study of non-linear crack tip parameters

    Directory of Open Access Journals (Sweden)

    F.V. Antunes

    2015-07-01

    Full Text Available Crack closure concept has been widely used to explain different issues of fatigue crack propagation. However, different authors have questioned the relevance of crack closure and have proposed alternative concepts. The main objective here is to check the effectiveness of crack closure concept by linking the contact of crack flanks with non-linear crack tip parameters. Accordingly, 3D-FE numerical models with and without contact were developed for a wide range of loading scenarios and the crack tip parameters usually linked to fatigue crack growth, namely range of cyclic plastic strain, crack tip opening displacement, size of reversed plastic zone and total plastic dissipation per cycle, were investigated. It was demonstrated that: i LEFM concepts are applicable to the problem under study; ii the crack closure phenomenon has a great influence on crack tip parameters decreasing their values; iii the Keff concept is able to explain the variations of crack tip parameters produced by the contact of crack flanks; iv the analysis of remote compliance is the best numerical parameter to quantify the crack opening level; v without contact there is no effect of stress ratio on crack tip parameters. Therefore it is proved that the crack closure concept is valid.

  7. Crack classification in concrete beams using AE parameters

    Science.gov (United States)

    Bahari, N. A. A. S.; Shahidan, S.; Abdullah, S. R.; Ali, N.; Zuki, S. S. Mohd; Ibrahim, M. H. W.; Rahim, M. A.

    2017-11-01

    The acoustic emission (AE) technique is an effective tool for the evaluation of crack growth. The aim of this study is to evaluate crack classification in reinforced concrete beams using statistical analysis. AE has been applied for the early monitoring of reinforced concrete structures using AE parameters such as average frequency, rise time, amplitude counts and duration. This experimental study focuses on the utilisation of this method in evaluating reinforced concrete beams. Beam specimens measuring 150 mm × 250 mm × 1200 mm were tested using a three-point load flexural test using Universal Testing Machines (UTM) together with an AE monitoring system. The results indicated that RA value can be used to determine the relationship between tensile crack and shear movement in reinforced concrete beams.

  8. Stress corrosion cracking of Alloy 82 in hydrogenated steam at 400 C: influence of microstructural and mechanical parameters on initiation of SCC cracks

    International Nuclear Information System (INIS)

    Chaumun, Elizabeth

    2016-01-01

    In Pressurize Water Reactors (PWR), Stress Corrosion Cracking (SCC) is the mean degradation mode of components pieced together by welding. Nickel based alloys are, among others, used in dissimilar metal welding (DMW). International report showed only 3 cracking cases in Alloy 82 out of 300 cracking cases concerned on nickel based alloys DMW in primary water circuit. The aim of this study is to identify which microstructural and local mechanism parameters at microstructure scale provide the initiation of SCC cracks. Characterizations performed on specimen surface to identify those parameters are composed of chemical composition analysis and EBSD analysis (Electron Back-Scattered Diffraction) to know the morphology and the crystallography of grains for microstructure features on one hand, and experimental strain fields measured by Digital Imaging Correlation (DIC) of gold micro-grids deposed by electronic lithography on U-bend specimen surface and stress fields calculated along grains boundaries by finite element for local mechanical features on the other hand. The correlation between those characterizations and localization of initiation sites of SCC cracks, obtained on U-bend specimens tested in autoclave in hydrogen steam water at 400 C and 188 bar for 3500 hours, confirmed the susceptibility of the Alloy 82 in SCC conditions with intergranular SCC cracks. The perpendicular position to the loading direction (mode I) is the worst conditions for grains boundary in SCC. The others points concern the chemical composition (precipitation, impurities) around grain boundary and the grain boundary type which is more susceptible when it is a High Angle Grain Boundary. It is following by the mechanical characterization (stress and strain gradient) along grain boundary. This methodology can be used to other material and helped to define which microstructural and mechanical parameter can be define the initiation of SCC cracks. (author) [fr

  9. Crack diffusion coefficient - A candidate fracture toughness parameter for short fiber composites

    Science.gov (United States)

    Mull, M. A.; Chudnovsky, A.; Moet, A.

    1987-01-01

    In brittle matrix composites, crack propagation occurs along random trajectories reflecting the heterogeneous nature of the strength field. Considering the crack trajectory as a diffusive process, the 'crack diffusion coefficient' is introduced. From fatigue crack propagation experiments on a set of identical SEN polyester composite specimens, the variance of the crack tip position along the loading axis is found to be a linear function of the effective 'time'. The latter is taken as the effective crack length. The coefficient of proportionality between variance of the crack trajectory and the effective crack length defines the crack diffusion coefficient D which is found in the present study to be 0.165 mm. This parameter reflects the ability of the composite to deviate the crack from the energetically most efficient path and thus links fracture toughness to the microstructure.

  10. 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 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......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...... with the degrees of freedom in the FEM‐equations. The complete tangential stiffness matrix is based on the virtual work together with the constitutive conditions at the crack tip. Introducing the crack growth parameters as direct unknowns, both equilibrium equations and the crack tip criterion can be handled...

  11. Correlation of fracture parameters during onset of crack in middle tension specimen

    Directory of Open Access Journals (Sweden)

    M.S. Starvin

    2017-07-01

    Full Text Available The present study addresses the implementation of finite element analysis and the prediction of fracture parameters in a middle tension (MT specimen that was fabricated using AISI 4140 steel. The correlation of fracture parameters with external loads and crack sizes was investigated. A Finite Element code was developed to simulate the fracture model. The contour integral method was applied in the calculation of stress intensity factor and J-integral in the cracked specimen. The ASTM standard empirical formula was used to calculate the stress intensity factor (SIF and the numerical predictions were validated. A standard laboratory experiment was also carried out using the MT specimen to calculate the crack growth rate in this specific material. The SIF values were almost linear with external load but it was decreasing as the crack size increases. The crack requires minimum load for crack propagation as the crack size increases. Similarly the J-integral was accelerated with increase in crack size.

  12. Statistical analysis of process parameters to eliminate hot cracking of fiber laser welded aluminum alloy

    Science.gov (United States)

    Wang, Jin; Wang, Hui-Ping; Wang, Xiaojie; Cui, Haichao; Lu, Fenggui

    2015-03-01

    This paper investigates hot cracking rate in Al fiber laser welding under various process conditions and performs corresponding process optimization. First, effects of welding process parameters such as distance between welding center line and its closest trim edge, laser power and welding speed on hot cracking rate were investigated experimentally with response surface methodology (RSM). The hot cracking rate in the paper is defined as ratio of hot cracking length over the total weld seam length. Based on the experimental results following Box-Behnken design, a prediction model for the hot cracking rate was developed using a second order polynomial function considering only two factor interaction. The initial prediction result indicated that the established model could predict the hot cracking rate adequately within the range of welding parameters being used. The model was then used to optimize welding parameters to achieve cracking-free welds.

  13. Crack

    Science.gov (United States)

    ... spending time in a rehab facility or getting cognitive-behavioral therapy or other treatments. Right now, there are no medicines to treat a crack addiction. If you smoke crack, talking with a counselor ...

  14. Crack propagation direction in a mixed mode geometry estimated via multi-parameter fracture criteria

    Czech Academy of Sciences Publication Activity Database

    Malíková, L.; Veselý, V.; Seitl, Stanislav

    2016-01-01

    Roč. 89, AUG (2016), s. 99-107 ISSN 0142-1123. [International Conference on Characterisation of Crack Tip Fields /3./. Urbino, 20.04.2015-22.04.2015] Institutional support: RVO:68081723 Keywords : Near-crack-tip fields * Mixed mode * Crack propagation direction * Multi-parameter fracture criteria * Finite element analysis Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 2.899, year: 2016

  15. The relationship between observed stress corrosion cracking fracture morphology and microstructure in Alloy 600

    International Nuclear Information System (INIS)

    Symons, D.M.; Burke, M.G.; Foster, J.P.

    1997-01-01

    Microstructure is known to influence the stress corrosion cracking (SCC) behavior of Alloy 600 in both hydrogenated water and steam environments. This study evaluated the relative SCC response of a single heat of Alloy 600 as a function of microstructure in a hydrogenated doped-steam environment. The 400 C doped-steam environment was selected for the SCC tests to accelerate cracking. The material was evaluated in three conditions: (1) as-received (2) as-annealed, and (3) as-annealed + 26% deformation. Microstructural characterization was performed using analytical electron microscopy (AEM) techniques for the evaluation of carbide type and morphology, and general structure. Constant displacement (bolt-loaded) compact tension specimens were used to induce SCC. The as-annealed and as-annealed plus cold worked samples had two fracture morphologies: a rough intergranular SCC fracture morphology and a smooth intergranular fracture morphology. The SCC fracture in the as-received specimens was characterized by a classic intergranular morphology at low magnification, consistent with the microstructural evaluation of cross-sectional metallographic samples. More detailed examination revealed a pseudo-intergranular fracture morphology. This pseudo-intergranular morphology appears to be comprised of very fine cleavage-like microfacets. These observations may assist in understanding the difference in SCC fracture morphologies as reported in the open literature

  16. Crack under biaxial loading: Two-parameter description and prediction of crack growth direction

    Czech Academy of Sciences Publication Activity Database

    Seitl, Stanislav

    2014-01-01

    Roč. 31, APR (2014), s. 44-49 ISSN 0213-3725 R&D Projects: GA MŠk(CZ) 7AMB14AT012 Institutional support: RVO:68081723 Keywords : Concrete * T-stress * cracks growth prediction * numerical calculation * biaxial loading Subject RIV: JL - Materials Fatigue, Friction Mechanics

  17. Assessment of morphological and hydrological parameters of Oyun ...

    African Journals Online (AJOL)

    The study involves evaluation of basin area, slopes, shape of the basin as morphological parameters and analysis of flow frequencies for flood and low flows, developing unit hydrograph and analysis of rainfall intensity distribution in the study area as hydrological parameters. The morphological analysis of the basin yielded ...

  18. Analysis of parameters effects on crack breathing and propagation in shaft of rotor dynamic systems

    Directory of Open Access Journals (Sweden)

    M. Serier

    2013-01-01

    Full Text Available In this paper the design of experiment method is used to investigate and explain the effects of the rotor parameters on crack breathing and propagation in the shaft. Three factors are considered which have an influence on the behavior and the propagation of the crack: the rotational speed, the length of the rotor and the diameter of the shaft. The elaborated mathematical model allows determining the effects and interaction of speed, diameter and length on crack breathing mechanism.The model also determines the optimal values of the parameters to achieve high performance.

  19. Analysis on the Initial Cracking Parameters of Cross-Measure Hydraulic Fracture in Underground Coal Mines

    Directory of Open Access Journals (Sweden)

    Yiyu Lu

    2015-07-01

    Full Text Available Initial cracking pressure and locations are important parameters in conducting cross-measure hydraulic fracturing to enhance coal seam permeability in underground coalmines, which are significantly influenced by in-situ stress and occurrence of coal seam. In this study, stress state around cross-measure fracturing boreholes was analyzed using in-situ stress coordinate transformation, then a mathematical model was developed to evaluate initial cracking parameters of borehole assuming the maximum tensile stress criterion. Subsequently, the influences of in-situ stress and occurrence of coal seams on initial cracking pressure and locations in underground coalmines were analyzed using the proposed model. Finally, the proposed model was verified with field test data. The results suggest that the initial cracking pressure increases with the depth cover and coal seam dip angle. However, it decreases with the increase in azimuth of major principle stress. The results also indicate that the initial cracking locations concentrated in the second and fourth quadrant in polar coordinate, and shifted direction to the strike of coal seam as coal seam dip angle and azimuth of maximum principle stress increase. Field investigation revealed consistent rule with the developed model that the initial cracking pressure increases with the coal seam dip angle. Therefore, the proposed mathematical model provides theoretical insight to analyze the initial cracking parameters during cross-measure hydraulic fracturing for underground coalmines.

  20. 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 ...

  1. Determination of fracture parameters for interface cracks in transverse isotropic magnetoelectroelastic composites

    Directory of Open Access Journals (Sweden)

    Lei Jun

    2015-01-01

    Full Text Available To determine fracture parameters of interfacial cracks in transverse isotropic magnetoelectroelastic composites, a displacement extrapolation formula was derived. The matrix-form formula can be applicable for both material components with arbitrary poling directions. The corresponding explicit expression of this formula was obtained for each poling direction normal to the crack plane. This displacement extrapolation formula is only related to the boundary quantities of the extended crack opening displacements across crack faces, which is convenient for numerical applications, especially for BEM. Meantime, an alternative extrapolation formula based on the path-independent J-integral and displacement ratios was presented which may be more adaptable for any domain-based numerical techniques like FEM. A numerical example was presented to show the correctness of these formulae.

  2. Effects of Chemistry Parameters of Primary Water affecting Leakage of Steam Generator Tube Cracks

    Energy Technology Data Exchange (ETDEWEB)

    Shin, D. M.; Cho, N. C.; Kang, Y. S.; Lee, K. H. [KHNP CRI, Daejeon (Korea, Republic of)

    2016-10-15

    Degradation of steam generator (SG) tubes can affect pressure boundary tightness. As a defense-in-depth measure, primary to secondary leak monitoring program for steam generators is implemented, and operation is allowed under leakage limits in nuclear power plants. Chemistry parameters that affect steam generator tube leakage due to primary water stress corrosion cracking (PWSCC) are investigated in this study. Tube sleeves were installed to inhibit leakage and improve tube integrity as a part of maintenance methods. Steam generators occurred small leak during operation have been replaced with new steam generators according to plant maintenance strategies. The correlations between steam generator leakage and chemistry parameters are presented. Effects of primary water chemistry parameters on leakage from tube cracks were investigated for the steam generators experiencing small leak. Unit A experienced small leakage from steam generator tubes in the end of operation cycle. It was concluded that increased solubility of oxides due to high pHT could make leakage paths, and low boron concentration lead to less blockage in cracks. Increased dissolved hydrogen may retard crack propagations, but it did not reduce leak rate of the leaking steam generator. In order to inhibit and reduce leakage, pH{sub T} was controlled by servicing cation bed operation. The test results of decreasing pHT indicate low pHT can reduce leak rate of PWSCC cracks in the end of cycle.

  3. Effects of Chemistry Parameters of Primary Water affecting Leakage of Steam Generator Tube Cracks

    International Nuclear Information System (INIS)

    Shin, D. M.; Cho, N. C.; Kang, Y. S.; Lee, K. H.

    2016-01-01

    Degradation of steam generator (SG) tubes can affect pressure boundary tightness. As a defense-in-depth measure, primary to secondary leak monitoring program for steam generators is implemented, and operation is allowed under leakage limits in nuclear power plants. Chemistry parameters that affect steam generator tube leakage due to primary water stress corrosion cracking (PWSCC) are investigated in this study. Tube sleeves were installed to inhibit leakage and improve tube integrity as a part of maintenance methods. Steam generators occurred small leak during operation have been replaced with new steam generators according to plant maintenance strategies. The correlations between steam generator leakage and chemistry parameters are presented. Effects of primary water chemistry parameters on leakage from tube cracks were investigated for the steam generators experiencing small leak. Unit A experienced small leakage from steam generator tubes in the end of operation cycle. It was concluded that increased solubility of oxides due to high pHT could make leakage paths, and low boron concentration lead to less blockage in cracks. Increased dissolved hydrogen may retard crack propagations, but it did not reduce leak rate of the leaking steam generator. In order to inhibit and reduce leakage, pH_T was controlled by servicing cation bed operation. The test results of decreasing pHT indicate low pHT can reduce leak rate of PWSCC cracks in the end of cycle

  4. Morphology parameters for intracranial aneurysm rupture risk assessment.

    Science.gov (United States)

    Dhar, Sujan; Tremmel, Markus; Mocco, J; Kim, Minsuok; Yamamoto, Junichi; Siddiqui, Adnan H; Hopkins, L Nelson; Meng, Hui

    2008-08-01

    The aim of this study is to identify image-based morphological parameters that correlate with human intracranial aneurysm (IA) rupture. For 45 patients with terminal or sidewall saccular IAs (25 unruptured, 20 ruptured), three-dimensional geometries were evaluated for a range of morphological parameters. In addition to five previously studied parameters (aspect ratio, aneurysm size, ellipticity index, nonsphericity index, and undulation index), we defined three novel parameters incorporating the parent vessel geometry (vessel angle, aneurysm [inclination] angle, and [aneurysm-to-vessel] size ratio) and explored their correlation with aneurysm rupture. Parameters were analyzed with a two-tailed independent Student's t test for significance; significant parameters (P 41; 95% confidence interval, 1.03-1.92) and undulation index (odds ratio, 1.51; 95% confidence interval, 1.08-2.11) had the strongest independent correlation with ruptured IA. From the receiver operating characteristic analysis, size ratio and aneurysm angle had the highest area under the curve values of 0.83 and 0.85, respectively. Size ratio and aneurysm angle are promising new morphological metrics for IA rupture risk assessment. Because these parameters account for vessel geometry, they may bridge the gap between morphological studies and more qualitative location-based studies.

  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. Parameters of straining-induced corrosion cracking in low-alloy steels in high temperature water

    International Nuclear Information System (INIS)

    Lenz, E.; Liebert, A.; Stellwag, B.; Wieling, N.

    Tensile tests with slow deformation speed determine parameters of corrosion cracking at low strain rates of low-alloy steels in high-temperature water. Besides the strain rate the temperature and oxygen content of the water prove to be important for the deformation behaviour of the investigated steels 17MnMoV64, 20 MnMoNi55 and 15NiCuMoNb 5. Temperatures about 240 0 C, increased oxygen contents in the water and low strain rates cause a decrease of the material ductility as against the behaviour in air. Tests on the number of stress cycles until incipient cracking show that the parameters important for corrosion cracking at low strain velocities apply also to low-frequency cyclic loads with high strain amplitude. In knowledge of these influencing parameters the strain-induced corrosion cracking is counteracted by concerted measures taken in design, construction and operation of nuclear power stations. Essential aims in this matter are to avoid as far as possible inelastic strains and to fix and control suitable media conditions. (orig.) [de

  7. Affection mechanism research of initiation crack pressure of perforation parameters of horizontal well

    Directory of Open Access Journals (Sweden)

    Hua Tong

    2016-09-01

    Full Text Available Horizontal wells show better affect and higher success rate in low water ratio cement, complex fracture zone, crevice and heavy oil blocks, it is the main measures to expand control area of a single well. Hydraulic fracturing technology is the most financial way to improve the penetration of the reservoir to increase the production. However, compare with the vertical wells, the fracture of Horizontal wells are more complex, and lead to the initiation crack pressure is much higher than vertical wells. In this paper, defined the crack judging basis, and established the finite element model which could compute the initial crack pressure, to research the affection mechanism of perforation azimuth angle, density, diameter and depth, to provide references of perforation project's design and optimize. The research of this paper has significances on further understanding the affection mechanism of perforation parameters.

  8. On the inter relationship between fatigue crack growth parameters in Paris regime

    International Nuclear Information System (INIS)

    Sasikala, G.

    2016-01-01

    Studies on fatigue crack growth behaviour of several steels and their welds for nuclear applications have been characterized in the author's laboratory in the past decade as a part of (i) creating the required database for integrity assessment of components, (ii) providing inputs for materials development, and (iii) understanding the crack growth behaviour in the light of basic mechanisms of cyclic deformation and damage. These include, effects of test variables (such as temperature, load ratio R) and material conditions (such as base and weld materials in as received, as welded or after subjecting to different ageing conditions). Different steels investigated include the ferritic grades modified 9Cr-1Mo steel (P91) and reduced activation ferritic martensitic steel, and austenitic grade SS 316L(N) and its weld. A common observation in the FCG literature is the inverse relationship between the Paris constant (log C) and exponent m, which has attracted considerable attention of the researchers in the field. The present paper attempts a fresh look at the inter relationship between Paris parameters obtained in the FCG studies on the above materials including the effect of crack closure and crack tip shielding. Further, some observed deviations from the inter relationship will be discussed in the light of changes in material properties and crack growth mechanisms. (author)

  9. Crack characterization for in-service inspection planning

    International Nuclear Information System (INIS)

    Waale, J.; Ekstroem, P.

    1995-12-01

    During in-service inspection by non destructive testing the reliability is highly dependent on how the equipment is adjusted to the specific object and to the anticipated crack feature.The crack feature and morphology vary widely between different cracking mechanisms and between material types in which the cracks appear. The major objective of this study was to characterize a number of morphology parameters for common crack mechanism and structure material combinations. Critical morphology parameters are crack orientation, shape, width, surface roughness and branching. The crack parameters were evaluated from failure analyses reported from the nuclear and non-nuclear industry. In addition, a literature review was carried out on crack parameter reports and on failure analysis reports, which were further evaluated. The evaluated crack parameters were plotted and statistically processed in data groups with respect to crack mechanism and material type. The fatigue crack mechanism were classified as mechanical, thermal or corrosion fatigue and stress corrosion crack mechanism as intergranular, transgranular or inter dendritic stress corrosion cracking. Furthermore, some common weld defects were characterized for comparison. The materials were divided into three broad groups, ferritic low alloy steels, stainless steels and nickel base alloys. The results indicate significant differences between crack parameters when comparing data from different crack mechanism/material type combinations. Typical parameter values and scatter were derived for several combinations where the data was sufficient for statistical significance. 10 refs, 105 figs, 14 tabs

  10. Crack characterization for in-service inspection planning

    Energy Technology Data Exchange (ETDEWEB)

    Waale, J [SAQ Inspection Ltd, Stockholm (Sweden); Ekstroem, P [ABB Atom AB, Vaesteraas (Sweden)

    1995-12-01

    During in-service inspection by non destructive testing the reliability is highly dependent on how the equipment is adjusted to the specific object and to the anticipated crack feature.The crack feature and morphology vary widely between different cracking mechanisms and between material types in which the cracks appear. The major objective of this study was to characterize a number of morphology parameters for common crack mechanism and structure material combinations. Critical morphology parameters are crack orientation, shape, width, surface roughness and branching. The crack parameters were evaluated from failure analyses reported from the nuclear and non-nuclear industry. In addition, a literature review was carried out on crack parameter reports and on failure analysis reports, which were further evaluated. The evaluated crack parameters were plotted and statistically processed in data groups with respect to crack mechanism and material type. The fatigue crack mechanism were classified as mechanical, thermal or corrosion fatigue and stress corrosion crack mechanism as intergranular, transgranular or inter dendritic stress corrosion cracking. Furthermore, some common weld defects were characterized for comparison. The materials were divided into three broad groups, ferritic low alloy steels, stainless steels and nickel base alloys. The results indicate significant differences between crack parameters when comparing data from different crack mechanism/material type combinations. Typical parameter values and scatter were derived for several combinations where the data was sufficient for statistical significance. 10 refs, 105 figs, 14 tabs.

  11. Multi-parameter approximation of the stress field in a cracked body in the more distant surroundings of the crack tip

    Czech Academy of Sciences Publication Activity Database

    Veselý, V.; Sobek, J.; Frantík, P.; Seitl, Stanislav

    2016-01-01

    Roč. 89, AUG (2016), s. 20-35 ISSN 0142-1123. [International Conference on Characterisation of Crack Tip Fields /3./. Urbino, 20.04.2015-22.04.2015] Institutional support: RVO:68081723 Keywords : Crack-tip fields * Williams power series * Higher order terms * Stress field reconstruction * Multi-parameter approximation accuracy Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 2.899, year: 2016

  12. Modified stress intensity factor as a crack growth parameter applicable under large scale yielding conditions

    International Nuclear Information System (INIS)

    Yasuoka, Tetsuo; Mizutani, Yoshihiro; Todoroki, Akira

    2014-01-01

    High-temperature water stress corrosion cracking has high tensile stress sensitivity, and its growth rate has been evaluated using the stress intensity factor, which is a linear fracture mechanics parameter. Stress corrosion cracking mainly occurs and propagates around welded metals or heat-affected zones. These regions have complex residual stress distributions and yield strength distributions because of input heat effects. The authors previously reported that the stress intensity factor becomes inapplicable when steep residual stress distributions or yield strength distributions occur along the crack propagation path, because small-scale yielding conditions deviate around those distributions. Here, when the stress intensity factor is modified by considering these distributions, the modified stress intensity factor may be used for crack growth evaluation for large-scale yielding. The authors previously proposed a modified stress intensity factor incorporating the stress distribution or yield strength distribution in front of the crack using the rate of change of stress intensity factor and yield strength. However, the applicable range of modified stress intensity factor for large-scale yielding was not clarified. In this study, the range was analytically investigated by comparison with the J-integral solution. A three-point bending specimen with parallel surface crack was adopted as the analytical model and the stress intensity factor, modified stress intensity factor and equivalent stress intensity factor derived from the J-integral were calculated and compared under large-scale yielding conditions. The modified stress intensity was closer to the equivalent stress intensity factor when compared with the stress intensity factor. If deviation from the J-integral solution is acceptable up to 2%, the modified stress intensity factor is applicable up to 30% of the J-integral limit, while the stress intensity factor is applicable up to 10%. These results showed that

  13. Influences of image resolution on herbaceous root morphological parameters

    Directory of Open Access Journals (Sweden)

    ZHANG Zeyou

    2014-06-01

    Full Text Available Root images of four herbaceous species (including Plantago virginica,Solidago canadensis,Conyza canadensis and Erigeron philadelphicus were obtained by using EPSON V7000 scanner with different resolutions.Root morphological parameters including root length,diameter,volume and area were determined by using a WinRhizo root analyzing software.The results show a distinct influence of image resolution on root morphological parameter.For different herbaceous species,the optimal resolutions of root images,which would produce an acceptable precision with relative short time,vary with different species.For example,a resolution of 200 dpi was recommended for the root images of Plantago virginica and S.Canadensis, while 400 dpi for Conyza canadensis and Erigeron philadelphicus.

  14. A linear least squares approach for evaluation of crack tip stress field parameters using DIC

    Science.gov (United States)

    Harilal, R.; Vyasarayani, C. P.; Ramji, M.

    2015-12-01

    In the present work, an experimental study is carried out to estimate the mixed-mode stress intensity factors (SIF) for different cracked specimen configurations using digital image correlation (DIC) technique. For the estimation of mixed-mode SIF's using DIC, a new algorithm is proposed for the extraction of crack tip location and coefficients in the multi-parameter displacement field equations. From those estimated coefficients, SIF could be extracted. The required displacement data surrounding the crack tip has been obtained using 2D-DIC technique. An open source 2D DIC software Ncorr is used for the displacement field extraction. The presented methodology has been used to extract mixed-mode SIF's for specimen configurations like single edge notch (SEN) specimen and centre slant crack (CSC) specimens made out of Al 2014-T6 alloy. The experimental results have been compared with the analytical values and they are found to be in good agreement, thereby confirming the accuracy of the algorithm being proposed.

  15. Estimation of the crack propagation direction in a mixed-mode geometry via multi-parameter fracture criteria

    Czech Academy of Sciences Publication Activity Database

    Malíková, L.; Veselý, V.; Seitl, Stanislav

    2015-01-01

    Roč. 9, č. 33 (2015), s. 25-32 ISSN 1971-8993 Institutional support: RVO:68081723 Keywords : Near-crack-tip fields * Williams expansion * Crack propagation direction * Multi-parameter fracture criteria * Finite element analysis Subject RIV: JL - Materials Fatigue, Friction Mechanics

  16. Morphological parameters associated with ruptured posterior communicating aneurysms.

    Science.gov (United States)

    Ho, Allen; Lin, Ning; Charoenvimolphan, Nareerat; Stanley, Mary; Frerichs, Kai U; Day, Arthur L; Du, Rose

    2014-01-01

    The rupture risk of unruptured intracranial aneurysms is known to be dependent on the size of the aneurysm. However, the association of morphological characteristics with ruptured aneurysms has not been established in a systematic and location specific manner for the most common aneurysm locations. We evaluated posterior communicating artery (PCoA) aneurysms for morphological parameters associated with aneurysm rupture in that location. CT angiograms were evaluated to generate 3-D models of the aneurysms and surrounding vasculature. Univariate and multivariate analyses were performed to evaluate morphological parameters including aneurysm volume, aspect ratio, size ratio, distance to ICA bifurcation, aneurysm angle, vessel angles, flow angles, and vessel-to-vessel angles. From 2005-2012, 148 PCoA aneurysms were treated in a single institution. Preoperative CTAs from 63 patients (40 ruptured, 23 unruptured) were available and analyzed. Multivariate logistic regression revealed that smaller volume (p = 0.011), larger aneurysm neck diameter (0.048), and shorter ICA bifurcation to aneurysm distance (p = 0.005) were the most strongly associated with aneurysm rupture after adjusting for all other clinical and morphological variables. Multivariate subgroup analysis for patients with visualized PCoA demonstrated that larger neck diameter (p = 0.018) and shorter ICA bifurcation to aneurysm distance (p = 0.011) were significantly associated with rupture. Intracerebral hemorrhage was associated with smaller volume, larger maximum height, and smaller aneurysm angle, in addition to lateral projection, male sex, and lack of hypertension. We found that shorter ICA bifurcation to aneurysm distance is significantly associated with PCoA aneurysm rupture. This is a new physically intuitive parameter that can be measured easily and therefore be readily applied in clinical practice to aid in the evaluation of patients with PCoA aneurysms.

  17. Investigation on crack growth parameters in the elastic plastic region (interim report)

    International Nuclear Information System (INIS)

    Prij, J.

    1982-03-01

    Some theoretical as well as numerical results are presented with respect to the 2D and 3D application of linear elastic fracture mechanics. The application of the finite element method to calculate the stress and strain field in cracked bodies has been discussed with special attention to: singularity representation, parameter extraction and mesh refinement. Detailed 3D stress analyses of fracture mechanics test specimen are presented showing that: the stress intensity concept cannot be extended simply into a 3D concept, the energy release concept is more promising within this aspect and the plastic region along the crackfront will not have a dogbone shape. The 3D elastic fracture mechanics concept is applied to evaluate the consequences of the thermal stresses due to γ-heating in an in-pile crack growth experiment

  18. Linear least squares approach for evaluating crack tip fracture parameters using isochromatic and isoclinic data from digital photoelasticity

    Science.gov (United States)

    Patil, Prataprao; Vyasarayani, C. P.; Ramji, M.

    2017-06-01

    In this work, digital photoelasticity technique is used to estimate the crack tip fracture parameters for different crack configurations. Conventionally, only isochromatic data surrounding the crack tip is used for SIF estimation, but with the advent of digital photoelasticity, pixel-wise availability of both isoclinic and isochromatic data could be exploited for SIF estimation in a novel way. A linear least square approach is proposed to estimate the mixed-mode crack tip fracture parameters by solving the multi-parameter stress field equation. The stress intensity factor (SIF) is extracted from those estimated fracture parameters. The isochromatic and isoclinic data around the crack tip is estimated using the ten-step phase shifting technique. To get the unwrapped data, the adaptive quality guided phase unwrapping algorithm (AQGPU) has been used. The mixed mode fracture parameters, especially SIF are estimated for specimen configurations like single edge notch (SEN), center crack and straight crack ahead of inclusion using the proposed algorithm. The experimental SIF values estimated using the proposed method are compared with analytical/finite element analysis (FEA) results, and are found to be in good agreement.

  19. Development of nuclear methods for determining fluid-dynamic parameters in fluid catalyst cracking reactors

    International Nuclear Information System (INIS)

    Santos, V.A. dos; Dantas, C.C.

    1986-01-01

    Flow parameters of circulating fluidized bed in a simulated Fluid Catalyst Cracking reactor were determined by means of nuclear methods. The parameters were: residence time, density, inventory, circulation rate and radial distribution, for the catalyst; residence time for the gaseous phase. The nuclear methods where the gamma attenuation and the radiotracer. Two tracer techniques were developed, one for tagging of the catalyst by the 59 Fe as intrinsic tracer and another for tagging of the gaseous phase by the CH 3 82 Br as tracer. A detailed description of each measuring technique for all the investigated parameters is included. To carry out the determination for some of parameters a combination of the two methods was also applied. The results and the nuclear data are given in a table. (Author) [pt

  20. Metallurgical and mechanical parameters controlling alloy 718 stress corrosion cracking resistance in PWR primary water

    International Nuclear Information System (INIS)

    Deleume, J.

    2007-11-01

    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]. δ 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)

  1. Reliability analysis of stainless steel piping using a single stress corrosion cracking damage parameter

    International Nuclear Information System (INIS)

    Guedri, A.

    2013-01-01

    This article presents the results of an investigation that combines standard methods of fracture mechanics, empirical correlations of stress-corrosion cracking, and probabilistic methods to provide an assessment of Intergranular Stress Corrosion Cracking (IGSCC) of stainless steel piping. This is done by simulating the cracking of stainless steel piping under IGSCC conditions using the general methodology recommended in the modified computer program Piping Reliability Analysis Including Seismic Events, and by characterizing IGSCC using a single damage parameter. Good correlation between the pipe end-life probability of leak and the damage values were found. These correlations were later used to generalize this probabilistic fracture model. Also, the probability of detection curves and the benefits of in-service inspection in order to reduce the probability of leak for nuclear piping systems subjected to IGSCC were discussed for several pipe sizes. It was found that greater benefits could be gained from inspections for the large pipe as compared to the small pipe sizes. Also, the results indicate that the use of a better inspection procedure can be more effective than a tenfold increase in the number of inspections of inferior quality. -- Highlights: • We simulate the pipe probability of failure under different level of SCC damages. • The residual stresses are adjusted to calibrate the model. • Good correlations between 40-year cumulative leak probabilities and D σ are found. • These correlations were used to generalize this probabilistic fracture model. • We assess the effect of inspection procedures and scenarios on leak probabilities

  2. The generalized fracture criteria based on the multi-parameter representation of the crack tip stress field

    Science.gov (United States)

    Stepanova, L. V.

    2017-12-01

    The paper is devoted to the multi-parameter asymptotic description of the stress field near the crack tip of a finite crack in an infinite isotropic elastic plane medium subject to 1) tensile stress; 2) in-plane shear; 3) mixed mode loading for a wide range of mode-mixity situations (Mode I and Mode II). The multi-parameter series expansion of stress tensor components containing higher-order terms is obtained. All the coefficients of the multiparameter series expansion of the stress field are given. The main focus is on the discussion of the influence of considering the higher-order terms of the Williams expansion. The analysis of the higher-order terms in the stress field is performed. It is shown that the larger the distance from the crack tip, the more terms it is necessary to keep in the asymptotic series expansion. Therefore, it can be concluded that several more higher-order terms of the Williams expansion should be used for the stress field description when the distance from the crack tip is not small enough. The crack propagation direction angle is calculated. Two fracture criteria, the maximum tangential stress criterion and the strain energy density criterion, are used. The multi-parameter form of the two commonly used fracture criteria is introduced and tested. Thirty and more terms of the Williams series expansion for the near-crack-tip stress field enable the angle to be calculated more precisely.

  3. Two Parameter Fracture Mechanics: Fatigue Crack Behavior under Mixed Mode Conditions

    Czech Academy of Sciences Publication Activity Database

    Seitl, Stanislav; Knésl, Zdeněk

    2008-01-01

    Roč. 75, č. 3-4 (2008), s. 857-865 ISSN 0013-7944. [Crack Paths 2006. Parma, 14.09.2006-16.09.2006] R&D Projects: GA ČR GP101/04/P001 Institutional research plan: CEZ:AV0Z20410507 Keywords : Constraint * Mixed-mode loading * Fatigue crack * Crack growth * Crack path Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 1.713, year: 2008

  4. Determination of rock fracture parameters from crack models for failure in compression

    International Nuclear Information System (INIS)

    Kemeny, J.M.; Cook, N.G.W.

    1987-01-01

    Micromechanical models for axial splitting and for shear faulting are used to investigate parameters associated with rock fracture under compressive stresses. The fracture energies to create splitting fractures and shear faults are calculated using laboratory triaxial data. These energies are compared with the fracture energies for the propagation of microcracks that coalesce to form the larger scale fractures. It is found that for Westerly granite, the energies to create splitting fractures and shear faults are about three orders of magnitude greater than the energy needed to drive the tensile microcracks, due to the large amount of subsidiary crack surface area created in forming the larger scale fractures. A similar scale effect can be expected when extrapolating the laboratory results to field scale problems

  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. 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.

  7. On the controlling parameters for fatigue-crack threshold at low homologous temperatures

    International Nuclear Information System (INIS)

    Yu, W.; Gerberich, W.W.

    1983-01-01

    Fatigue crack propagation phenomena near the threshold stress intensity level ΔK /SUB TH/ , has been a vigorously studied topic in recent years. Near threshold the crack propagates rather slowly, thus giving enough time for various physical and chemical reactions to take place. Room air, which is the most commonly encountered environment, can still supply various ingredients such as oxygen, water vapor (and thus hydrogen) to support these reactions. Much effort had been directed toward the environmental aspects of near threshold fatigue crack growth. By conducting tests under vacuum, Suresh and coworkers found that the crack propagation rate in a 2-1/4 Cr-1Mo steel was higher in vacuum than in air. An oxide induced closure, which served to reduce the effective stress intensity at the crack tip, seems to furnish a good explanation. Neumann and coworkers proposed that during the fatigue process, extrusion-intrusion pairs can develop as a consequence of reversed slip around the crack tip when the crack was propagated near threshold stress intensity. Beevers demonstrated that fatigue fracture surfaces contact each other during unloading even under tension-tension cycling. Kanninen and Atkinson also reached the conclusion that the compressive stress acting at the crack tip due to residual plasticity can induce closure. Microstructural effects have also been cited as important factors in near threshold crack growth. It is generally accepted that coarser grains have a beneficial effect on the resistance to the near threshold crack propagation

  8. 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.

  9. Determination of Fracture Parameters for Multiple Cracks of Laminated Composite Finite Plate

    Science.gov (United States)

    Srivastava, Amit Kumar; Arora, P. K.; Srivastava, Sharad Chandra; Kumar, Harish; Lohumi, M. K.

    2018-04-01

    A predictive method for estimation of stress state at zone of crack tip and assessment of remaining component lifetime depend on the stress intensity factor (SIF). This paper discusses the numerical approach for prediction of first ply failure load (FL), progressive failure load, SIF and critical SIF for multiple cracks configurations of laminated composite finite plate using finite element method (FEM). The Hashin and Chang failure criterion are incorporated in ABAQUS using subroutine approach user defined field variables (USDFLD) for prediction of progressive fracture response of laminated composite finite plate, which is not directly available in the software. A tensile experiment on laminated composite finite plate with stress concentration is performed to validate the numerically predicted subroutine results, shows excellent agreement. The typical results are presented to examine effect of changing the crack tip distance (S), crack offset distance (H), and stacking fiber angle (θ) on FL, and SIF .

  10. Effect of some structural parameters on high-temperature crack resistance of tungsten

    International Nuclear Information System (INIS)

    Babak, A.V.; Uskov, E.I.

    1984-01-01

    The paper presents results of physicomechanical studied in high-temperature crack resistance of tungsten produced by powder metallurgy methods. It is shown that at high temperatures (>2000 deg C) a structure is formed in the material and fails at stresses independent of temperature. It is found that high-temperature tungsten crack resistance is affected neighter by changes in the effictive grain size, nor by appearance of grain-boundary microcraks in the material under high-temperature action

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Stress corrosion cracking of alloy 600 in water at high temperature: contribution to a phenomenological approach to the understanding of mechanisms

    International Nuclear Information System (INIS)

    Abadie, Pascale

    1998-01-01

    This research thesis aims at being a contribution to the understanding of mechanisms of stress corrosion cracking of an alloy 600 in water at high temperature. More precisely, it aimed at determining, by using quantitative data characterizing cracking phenomenology, which mechanism(s) is (are) able to explain crack initiation and crack growth. These data concern quantitative characterization of crack initiation, of crack growth and of the influence of two cracking parameters (strain rate, medium hydrogen content). They have been obtained by quantifying cracking through the application of a morphological model. More precisely, these data are: evolution of crack density during a tensile test at slow rate, value of initial crack width with respect to grain boundary length, and relationship between crack density and medium hydrogen content. It appears that hydrogen absorption seems to be involved in the crack initiation mechanism. Crack growth mechanisms and crack growth rates are also discussed [fr

  16. Avalanche weak layer shear fracture parameters from the cohesive crack model

    Science.gov (United States)

    McClung, David

    2014-05-01

    Dry slab avalanches release by mode II shear fracture within thin weak layers under cohesive snow slabs. The important fracture parameters include: nominal shear strength, mode II fracture toughness and mode II fracture energy. Alpine snow is not an elastic material unless the rate of deformation is very high. For natural avalanche release, it would not be possible that the fracture parameters can be considered as from classical fracture mechanics from an elastic framework. The strong rate dependence of alpine snow implies that it is a quasi-brittle material (Bažant et al., 2003) with an important size effect on nominal shear strength. Further, the rate of deformation for release of an avalanche is unknown, so it is not possible to calculate the fracture parameters for avalanche release from any model which requires the effective elastic modulus. The cohesive crack model does not require the modulus to be known to estimate the fracture energy. In this paper, the cohesive crack model was used to calculate the mode II fracture energy as a function of a brittleness number and nominal shear strength values calculated from slab avalanche fracture line data (60 with natural triggers; 191 with a mix of triggers). The brittleness number models the ratio of the approximate peak value of shear strength to nominal shear strength. A high brittleness number (> 10) represents large size relative to fracture process zone (FPZ) size and the implications of LEFM (Linear Elastic Fracture Mechanics). A low brittleness number (e.g. 0.1) represents small sample size and primarily plastic response. An intermediate value (e.g. 5) implies non-linear fracture mechanics with intermediate relative size. The calculations also implied effective values for the modulus and the critical shear fracture toughness as functions of the brittleness number. The results showed that the effective mode II fracture energy may vary by two orders of magnitude for alpine snow with median values ranging from 0

  17. Aerodynamic Parameters of a UK City Derived from Morphological Data

    Science.gov (United States)

    Millward-Hopkins, J. T.; Tomlin, A. S.; Ma, L.; Ingham, D. B.; Pourkashanian, M.

    2013-03-01

    Detailed three-dimensional building data and a morphometric model are used to estimate the aerodynamic roughness length z 0 and displacement height d over a major UK city (Leeds). Firstly, using an adaptive grid, the city is divided into neighbourhood regions that are each of a relatively consistent geometry throughout. Secondly, for each neighbourhood, a number of geometric parameters are calculated. Finally, these are used as input into a morphometric model that considers the influence of height variability to predict aerodynamic roughness length and displacement height. Predictions are compared with estimations made using standard tables of aerodynamic parameters. The comparison suggests that the accuracy of plan-area-density based tables is likely to be limited, and that height-based tables of aerodynamic parameters may be more accurate for UK cities. The displacement heights in the standard tables are shown to be lower than the current predictions. The importance of geometric details in determining z 0 and d is then explored. Height variability is observed to greatly increase the predicted values. However, building footprint shape only has a significant influence upon the predictions when height variability is not considered. Finally, we develop simple relations to quantify the influence of height variation upon predicted z 0 and d via the standard deviation of building heights. The difference in these predictions compared to the more complex approach highlights the importance of considering the specific shape of the building-height distributions. Collectively, these results suggest that to accurately predict aerodynamic parameters of real urban areas, height variability must be considered in detail, but it may be acceptable to make simple assumptions about building layout and footprint shape.

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

    KAUST Repository

    Traidia, Abderrazak; El-Sherik, A. M.; Duval, Sé bastien; Lubineau, Gilles; El Yagoubi, Jalal

    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

  19. 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').

  20. 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').

  1. 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.

  2. 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.

  3. 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.

  4. 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.

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

    International Nuclear Information System (INIS)

    Jang, Youn Young; Huh, Nam Su; Jeong, Jae Uk

    2016-01-01

    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

  6. 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

  7. 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)

  8. Characterization of Some Morphological Parameters of Orbicularis Oculi Motor Neurons in the Monkey

    OpenAIRE

    McNeal, DW; Ge, J; Herrick, JL; Stilwell-Morecraft, KS; Morecraft, RJ

    2007-01-01

    The primate facial nucleus is a prominent brainstem structure that is composed of cell bodies giving rise to axons forming the facial nerve. It is musculotopically organized, but we know little about the morphological features of its motor neurons. Using the Lucifer yellow intracellular filling method, we examined 17 morphological parameters of motor neurons innervating the monkey orbicularis oculi (OO) muscle, which plays an important role in eye lid closure and voluntary and emotional facia...

  9. 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....

  10. Suitable parameter choice on quantitative morphology of A549 cell in epithelial–mesenchymal transition

    Science.gov (United States)

    Ren, Zhou-Xin; Yu, Hai-Bin; Li, Jian-Sheng; Shen, Jun-Ling; Du, Wen-Sen

    2015-01-01

    Evaluation of morphological changes in cells is an integral part of study on epithelial to mesenchymal transition (EMT), however, only a few papers reported the changes in quantitative parameters and no article compared different parameters for demanding better parameters. In the study, the purpose was to investigate suitable parameters for quantitative evaluation of EMT morphological changes. A549 human lung adenocarcinoma cell line was selected for the study. Some cells were stimulated by transforming growth factor-β1 (TGF-β1) for EMT, and other cells were as control without TGF-β1 stimulation. Subsequently, cells were placed in phase contrast microscope and three arbitrary fields were captured and saved with a personal computer. Using the tools of Photoshop software, some cells in an image were selected, segmented out and exchanged into unique hue, and other part in the image was shifted into another unique hue. The cells were calculated with 29 morphological parameters by Image Pro Plus software. A parameter between cells with or without TGF-β1 stimulation was compared statistically and nine parameters were significantly different between them. Receiver operating characteristic curve (ROC curve) of a parameter was described with SPSS software and F-test was used to compare two areas under the curves (AUCs) in Excel. Among them, roundness and radius ratio were the most AUCs and were significant higher than the other parameters. The results provided a new method with quantitative assessment of cell morphology during EMT, and found out two parameters, roundness and radius ratio, as suitable for quantification. PMID:26182364

  11. A proposal for evaluation method of crack growth due to cyclic overload for piping materials based on an elastic-plastic fracture mechanics parameter

    International Nuclear Information System (INIS)

    Yamaguchi, Yoshihito; Katsuyama, Jinya; Onizawa, Kunio; Li, Yinsheng; Sugino, Hideharu

    2011-01-01

    The magnitude of Niigata-ken Chuetsu-Oki earthquake in 2007 was beyond the assumed one provided in seismic design. Therefore it becomes an important issue to evaluate the crack growth behaviors due to the cyclic overload like large earthquake. Fatigue crack growth is usually evaluated by Paris's law using the range of stress intensity factor (ΔK). However, ΔK is inappropriate in a loading condition beyond small scale yielding. In this study, the crack growth behaviors for piping materials were investigated based on an elastic-plastic fracture mechanics parameter, J-integral. It was indicated that the crack growth due to the cyclic overload beyond small scale yielding could be the sum of fatigue and ductile crack growth. The retardation effect of excessive loading on the crack growth was observed after the loading. The modified Wheeler model using J-integral has been proposed for the prediction of retardation effect. Finally, an evaluation method for crack growth behaviors due to the cyclic overload is suggested. (author)

  12. Global and nonglobal parameters of horizontal-branch morphology of globular clusters

    International Nuclear Information System (INIS)

    Milone, A. P.; Marino, A. F.; Dotter, A.; Norris, J. E.; Jerjen, H.; Asplund, M.

    2014-01-01

    The horizontal-branch (HB) morphology of globular clusters (GCs) is mainly determined by metallicity. However, the fact that GCs with almost the same metallicity exhibit different HB morphologies demonstrates that at least one more parameter is needed to explain the HB morphology. It has been suggested that one of these should be a global parameter that varies from GC to GC and the other a nonglobal parameter that varies within the GC. In this study we provide empirical evidence corroborating this idea. We used the photometric catalogs obtained with the Advanced Camera for Surveys of the Hubble Space Telescope and analyze the color-magnitude diagrams of 74 GCs. The HB morphology of our sample of GCs has been investigated on the basis of the two new parameters L1 and L2 that measure the distance between the red giant branch and the coolest part of the HB and the color extension of the HB, respectively. We find that L1 correlates with both metallicity and age, whereas L2 most strongly correlates with the mass of the hosting GC. The range of helium abundance among the stars in a GC, characterized by ΔY and associated with the presence of multiple stellar populations, has been estimated in a few GCs to date. In these GCs we find a close relationship among ΔY, GC mass, and L2. We conclude that age and metallicity are the main global parameters, while the range of helium abundance within a GC is the main nonglobal parameter defining the HB morphology of Galactic GCs.

  13. Morphology and parameters of crystallization the blend PE/Epoxy/PE-co-PEG

    International Nuclear Information System (INIS)

    Becker, Daniela; Coelho, Luiz Antonio Ferreira; Nack, Fernanda; Silva, Bruna Louise

    2014-01-01

    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)

  14. 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.

  15. Correlation of radiographic and MRI parameters to morphological and biochemical assessment of intervertebral disc degeneration

    OpenAIRE

    Benneker, Lorin M.; Heini, Paul F.; Anderson, Suzanne E.; Alini, Mauro; Ito, Keita

    2004-01-01

    Degenerative disc disease (DDD) is a common finding in MRI scans and X-rays. However, their correlation to morphological and biochemical changes is not well established. In this study, radiological and MRI parameters of DDD were assessed and compared with morphological and biochemical findings of disc degeneration. Thirty-nine human lumbar discs (L1–S1), age 19–86 years, were harvested from eight cadavers. Within 48 h postmortem, MRIs in various spin-echo sequences and biplanar radiographs of...

  16. 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

  17. 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.

  18. Analysis of accuracy of Williams series approximation of stress field in cracked body – influence of area of interest around crack-tip on multi-parameter regression performance

    Directory of Open Access Journals (Sweden)

    J. Sobek

    2017-01-01

    Full Text Available A study on the accuracy of an approximation of the stress field in a cracked body is presented. Crack-tip stress tensor is expressed using the linear elastic fracture mechanics (LEFM theory in this work, more precisely via its multi-parameter formulation, i.e. by Williams power series (WPS. Determination of coefficients of terms of this series is performed using a least squares-based regression technique known as over-deterministic method (ODM for which results from finite element (FE method computation are usually taken as inputs. Main attention is paid to a detailed analysis of a suitable selection of FE nodes whose results serve as the inputs to the employed method. Two different ways of FE nodal selection are compared – nodes selected from the crack tip vicinity lying at a ring of a certain radius versus nodes selected more or less uniformly from a specified part of the test specimen body. Comparison of these approaches is made with the help of procedures developed by the authors which enable both the determination of the coefficients of terms of the analytical WPS approximation of the stress field based on the FE results and the backward reconstruction of the field (again using WPS from those determined terms’ coefficients/functions. The wedge-splitting test (WST specimen with a crack is taken as example for the study.

  19. Multi-parameter approximation of stress field in a cracked specimen using purpose-built Java applications

    Czech Academy of Sciences Publication Activity Database

    Veselý, V.; Sopek, J.; Tesař, D.; Frantík, P.; Pail, T.; Seitl, Stanislav

    2015-01-01

    Roč. 9, č. 33 (2015), s. 120-133 ISSN 1971-8993 Institutional support: RVO:68081723 Keywords : Cracked specimen * Near-crack-tip fields * Williams expansion * Higher order terms * Stress field reconstruction * Finite element analysis * Java application Subject RIV: JL - Materials Fatigue, Friction Mechanics

  20. Morphology of the boron-rich phase along columnar grain boundary and its effect on the compression crack of Fe-6.5Si-0.05B alloy

    International Nuclear Information System (INIS)

    Fu Huadong; Zhang Zhihao; Yang Qiang; Xie Jianxin

    2011-01-01

    Research highlights: → Three morphologies of alloy phases were observed under different conditions. → Three different morphologies were thick-strip, fish-bone like and thin-strip. → These phases were all with enrichment of boron and dilution of silicon. → Three morphologies of alloy phases had different influences on mechanical property. - Abstract: The morphology of precipitated phases along Fe-6.5Si-0.05B columnar grain boundary and its effect on the initiation and propagation of compression cracks were investigated. Under the present experimental condition, alloy phases along the grain boundary exhibited three different morphologies, i.e., thick-strip, fish-bone like and thin-strip. These phases were all with enrichment of boron and dilution of silicon. The grain boundary with dendrite growth mode was apt to generate the thick-strip and fish-bone like phases, while the boundary with cellular growth mode was easy to form the thin-strip phase. The thick-strip phase was favorable to form 'weak plane' containing numerous micropores, which ultimately led to intergranular cracks. The fish-bone like phase was one of the main crack sources under the compression processing and easily caused transgranular cracks. The thin-strip phase enhanced the bond strength of the grain boundary and detained the crack propagation.

  1. Differences in morphological parameters of judo athletes of different age groups and performance level

    Directory of Open Access Journals (Sweden)

    Miloš Štefanovský

    2017-12-01

    Full Text Available Background: Some studies have pointed out the influence of morphological parameters on judo performance, however the relationship between morphological variables and performance status have not yet been confirmed. In addition, there is a lack of studies focused on morphological comparison of different age categories. Objective: The aim of this study was to assess differences in the morphological parameters of judo athletes of different age and performance level. Methods: The research sample was composed of 47 male judokas (age 19.15 ± 2.93 years; body weight 77.16 ± 11.39 kg; height 178.91 ± 6.39 cm; sport age 11.47 ± 2.74 years. It was divided by: (1 age, into cadets (15-17 years, n = 19, juniors (18-20 years, n = 15, and seniors (21+ years, n = 13 category and (2 performance status (elite, n = 10; non-elite, n = 37. In all participants, body fat, and the circumference measurement of wrist, forearm, flexed arm, and calf were observed. A personal interview was used to gain information about the athlete's performance status. Results: We found out that there are significant differences in arm circumference between cadets and seniors, cadets and juniors, juniors and seniors; and in the circumference of forearm between cadets and seniors; cadets and juniors, as well. According to the performance status, we have discovered significantly higher circumference of forearm and wrist in the elite group compared to the non-elite group. Conclusion: Forearm and wrist circumference is a reliable discriminative factor and should be taken into consideration, especially when selecting judo athletes into elite teams. However, we did not confirm that subcutaneous fat is a parameter able to distinguish between judo athletes of different performance status across various age categories.

  2. 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

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

    International Nuclear Information System (INIS)

    Waale, Jan

    2006-05-01

    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. 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.

  5. Influence of anodization parameters on the morphology of TiO 2 nanotube arrays

    Science.gov (United States)

    Omidvar, Hamid; Goodarzi, Saba; Seif, Ahmad; Azadmehr, Amir R.

    2011-07-01

    TiO 2 nanotube arrays can be fabricated by electrochemical anodization in organic and inorganic electrolytes. Morphology of these nanotube arrays changes when anodization parameters such as applied voltage, type of electrolyte, time and temperature are varied. Nanotube arrays fabricated by anodization of commercial titanium in electrolytes containing NH 4F solution and either sulfuric or phosphoric acid were studied at room temperature; time of anodization was kept constant. Applied voltage, fluoride ion concentration, and acid concentrations were varied and their influences on TiO 2 nanotubes were investigated. The current density of anodizing was recorded by computer controlled digital multimeter. The surface morphology (top-view) of nanotube arrays were observed by SEM. The nanotube arrays in this study have inner diameters in range of 40-80 nm.

  6. THE ACS SURVEY OF GALACTIC GLOBULAR CLUSTERS. IX. HORIZONTAL BRANCH MORPHOLOGY AND THE SECOND PARAMETER PHENOMENON

    International Nuclear Information System (INIS)

    Dotter, Aaron; Sarajedini, Ata; Anderson, Jay; Bedin, Luigi R.; Paust, Nathaniel; Reid, I. Neill; Aparicio, Antonio; MarIn-Franch, A.; Rosenberg, Alfred; Chaboyer, Brian; Majewski, Steven; Milone, Antonino; Piotto, Giampaolo; Siegel, Michael

    2010-01-01

    The horizontal branch (HB) morphology of globular clusters (GCs) is most strongly influenced by metallicity. The second parameter phenomenon, first described in the 1960s, acknowledges that metallicity alone is not enough to describe the HB morphology of all GCs. In particular, astronomers noticed that the outer Galactic halo contains GCs with redder HBs at a given metallicity than are found inside the solar circle. Thus, at least a second parameter was required to characterize HB morphology. While the term 'second parameter' has since come to be used in a broader context, its identity with respect to the original problem has not been conclusively determined. Here we analyze the median color difference between the HB and the red giant branch, hereafter denoted as Δ(V - I), measured from Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) photometry of 60 GCs within ∼20 kpc of the Galactic center. Analysis of this homogeneous data set reveals that, after the influence of metallicity has been removed from the data, the correlation between Δ(V - I) and age is stronger than that of any other parameter considered. Expanding the sample to include HST ACS and Wide Field Planetary Camera 2 photometry of the six most distant Galactic GCs lends additional support to the correlation between Δ(V - I) and age. This result is robust with respect to the adopted metallicity scale and the method of age determination, but must bear the caveat that high-quality, detailed abundance information is not available for a significant fraction of the sample. Furthermore, when a subset of GCs with similar metallicities and ages is considered, a correlation between Δ(V - I) and central luminosity density is exposed. With respect to the existence of GCs with anomalously red HBs at a given metallicity, we conclude that age is the second parameter and central density is most likely the third. Important problems related to HB morphology in GCs, notably multi-modal distributions

  7. 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.

  8. Misonidazole neurotoxicity in the mouse: evaluation of functional, pharmacokinetic, electrophysiologic and morphologic parameters

    International Nuclear Information System (INIS)

    Conroy, P.J.; Von Burg, R.; Passalacqua, W.; Penney, D.P.; Sutherland, R.M.

    1979-01-01

    The neurotoxic effects of chronic administration of misonidazole (0.3 mg/g/day, 5 times weekly) were investigated in Balb/cKa mice over 12 weeks; a variety of measurements were used, including functional and clinical performance, morphologic, electrophysiologic and pharmacokinetic parameters. The half life of drug for a single dose was greater in brain (3 hrs) compared to serum (1.2 hrs); these values decreased to 1.9 hrs and 1.0 hrs respectively after 3 weeks. Misonidazole induced a peripheral lesion after three weeks with a total administered dose of 13.5 g/m 2 or exposure dose of 57 to 75 mM X hrs, which is similar to the doses that cause neuropathy in humans. There was some suggestion of a central neurological deficit related to locomotor control and balance; however, no gross morphological damage was found in the brain. The sequence of effects demonstrated began at 3 to 4 weeks and included: 1) morphologic damage to peripheral nerves; 2) hyperactivity and listlessness; 3) a decrease in rotarod retention time which reached a value 50% of that of saline injected control mice at 8 to 10 weeks; 4) walking on tip-toes with a slightly hunched back (4 to 6 weeks); and 5) an increase in hind foot splay (6 to 7 weeks). The morphologic damage primarily involved the more distal portions of the nerves supplying the interosseous muscles and footpads of the hind limbs. The damage was more severe and progressed more rapidly with time in these distal areas compared to the more proximal regions of the nerves. No marked changes were found in nerve conduction velocity although neuropathy produced by acrylamide produced significant decreases. The changes in neurological parameters reported here may be useful in the further evaluation of hypoxic cell radiosensitizers

  9. Morphological and Metabolic Parameters of Red Blood Cells after Their Treatment with Ozone

    Directory of Open Access Journals (Sweden)

    Anna V. Deryugina

    2018-01-01

    Full Text Available The purpose of the study was to assess the morphology of red blood cells (RBC and the association of morphological parameters with lipid peroxidation processes and the content of organic phosphates in RBC when treating packed red blood cells with the ozonized saline solution (with an ozone concentration of 2 mg/l after different storage periods.Materials and methods. The morphology of human RBC, the concentration of malonic dialdehyde (MDA in RBC, the catalase activity, the concentration of ATP and 2,3-diphosphoglycerate (2,3-DPG were studied before and after treatment of RBC with the ozonized saline (with the ozone concentration of 2 mg/l after 7, 14, 21 and 30 days of storage.Results. The effect of ozone (2 ng/l in vitro on the packed red blood cells after 7–21 days of storage contributed to the recovery of RBC shape, increased the concentration of ATP and 2,3-DPG, and optimized the lipid peroxidation. Ozone did not demonstrate a pronounced positive effect on these parameters when the packed RBCs were stored for 30 days.Conclusion. The treatment of the packed RBCs with the ozonized saline solution (with the ozone concentration of 2 mg/l contributed to the recovery of the discocyte count due to optimization of lipid peroxidation processes in cell membranes and enhanced the synthesis of organic phosphates in cells due to the activation of glycolysis and the pentose phosphate pathway. This can be used to improve the morphological and metabolic status of the packed RBCs before their transfusion. 

  10. Estimation of the crack growth mechanism in the coking process. ; Behavior of fracture mechanics parameter. Cokes sonai kiretsu shinten ni kansuru ichikosatsu. ; Hakai rikigaku parameter no kyodo ni tsuite

    Energy Technology Data Exchange (ETDEWEB)

    Yoshino, H; Sato, H; Nogami, H; Miura, T [Tohoku University, Sendai (Japan). Faculty of Engineering

    1991-07-10

    Cracks generated in coke layers during a coking furnace operation are an important factor not only to decide quality of the product, but also govern the energy consumption affecting the heat transfer and material transfer. This paper describes estimations of thermal stress and observations to fracture mechanics parameters, applying the incremental theory to surface cracks seen in the initial stage of carbonization. As a result of calculations using the crack tip opening displacement (CTOD) as a parameter to evaluate displacement in the vicinity of crack tips, the values increased with the increasing heating rate, and agreed qualitatively with the trend found in the experiments. The CTOD relates closely to the temperature dependence of the contraction coefficient, and varies largely at the transition point from the first maximum point to the second maximum point, from which the surface cracks are predicted to have been generated in this temperature region. Also, an estimation was made on the stress expansion coefficient from the stress distribution, and a result that can explain the experimental resultswas obtained. 10 refs., 11 figs.

  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. Determination of the hydrodynamic and morphological parameters of the Luyano River using radiotracer techniques

    International Nuclear Information System (INIS)

    Valcarcel, Lino; Alberro, Nancy; Rodriguez, Maydel; Herrero, Zahily; Borroto, Jorge; Hernandez, Anel; Dominguez, Judith; Derivet, Milagros; Flores, Pedro; Cuesta, Jaime; Griffith, Jose

    2011-01-01

    The hydrodynamic and morphological parameters (the times of travel, velocities and flowrates of the waters, and the average widths, cross sections and depths) in the middle segment of the river Luyano were determined combining the employment of sodium pertechnectate (Na 99m TcO 4 ) as radiotracer with other conventional techniques. The results were used for the calibration of the expanded Streeter and Phelps model of the river. In the work, the methodology and the main results obtained during the journey realized between the second fortnight of March and the first of April 2009 are presented. (Author)

  13. 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.

  14. Morphology, crystallography, and crack paths of tempered lath martensite in a medium-carbon low-alloy steel

    International Nuclear Information System (INIS)

    Wang, Chengduo; Qiu, Hai; Kimura, Yuuji; Inoue, Tadanobu

    2016-01-01

    The tempered lath martensite and its crack propagation have significant influence on the ductility and toughness of the warm tempformed medium-carbon steel. The martensitic microstructures of these medium-carbon steels are transformed from twinned austenite and the orientation relationship of lath martensite (α′) with prior austenite (γ) is distinctive. In the present paper we investigate the microstructure and fracture mode of a quenched and tempered 0.4%C-2%Si-1%Cr-1%Mo steel using electron backscatter diffraction technique. The results showed that the orientation relationship between γ and α′ is Greninger-Troiano (G-T) relationship. A single γ grain was divided into 4 packets and each packet was subdivided into 3 blocks. The misorientation angles between adjacent blocks were ~54.3° or ~60.0° in a packet. Most γ grains were twins sharing a {111} γ plane. There were 7 packets in a twinned γ grain and the twin boundaries were in a special packet. Besides the common packet, there were three packets in each twin. Being different from the cleavage fracture along the {001} planes in conventional martensitic steels, both cleavage and intergranular cracks were present in our medium-carbon steel. The former was in the larger blocks and it propagated along the {001}, {011}, and {112} planes. The latter propagated along the block, packet, or prior austenite boundaries. The intergranular cracks were generally in the fine block region. These results suggested that the block size is the key factor in controlling the brittle fracture mode of lath martensitic steel.

  15. 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.

  16. 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.)

  17. Systematic study of influence of growth parameters on island morphology during molecular beam epitaxy growth: A Monte Carlo study

    International Nuclear Information System (INIS)

    Shankar Prasad Shrestha; Park, C.-Y.

    2006-05-01

    We have made a systematic study of influence of diffusion flux ratio (D/F), diffusional anisotropy (DA) and sticking anisotropy (SA) on island morphology to show the influence of each growth parameter on island morphology in presence of the other growth parameters. Our results show that the influence of D/F ratio and DA on island morphology depends on the sticking anisotropy of the adatoms. At the intermediate anisotropic case, increase in D/F ratio results in transition of the island morphology from 1d nature to 2 d nature. In anisotropic diffusion case, D/F ratio can change the growth direction of the island morphology. We also find that only sticking anisotropy is not sufficient to produce elongated islands, low D/F ratio is also essential. (author)

  18. 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.

  19. 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.

  20. 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.

  1. A Study on the Effect of Electrodeposition Parameters on the Morphology of Porous Nickel Electrodeposits

    Science.gov (United States)

    Sengupta, Srijan; Patra, Arghya; Jena, Sambedan; Das, Karabi; Das, Siddhartha

    2018-03-01

    In this study, the electrodeposition of nickel foam by dynamic hydrogen bubble-template method is optimized, and the effects of key deposition parameters (applied voltage and deposition time) and bath composition (concentration of Ni2+, pH of the bath, and roles of Cl- and SO4 2- ions) on pore size, distribution, and morphology and crystal structure are studied. Nickel deposit from 0.1 M NiCl2 bath concentration is able to produce the honeycomb-like structure with regular-sized holes. Honeycomb-like structure with cauliflower morphology is deposited at higher applied voltages of 7, 8, and 9 V; and a critical time (>3 minutes) is required for the development of the foamy structure. Compressive residual stresses are developed in the porous electrodeposits after 30 seconds of deposition time (-189.0 MPa), and the nature of the residual stress remains compressive upto 10 minutes of deposition time (-1098.6 MPa). Effect of pH is more pronounced in a chloride bath compared with a sulfate bath. The increasing nature of pore size in nickel electrodeposits plated from a chloride bath (varying from 21 to 48 μm), and the constant pore size (in the range of 22 to 24 μm) in deposits plated from a sulfate bath, can be ascribed to the striking difference in the magnitude of the corresponding current-time profiles.

  2. Towards the prediction of the growth of crack networks: influence of microstructural parameters on scattering at initiation

    International Nuclear Information System (INIS)

    Osterstock, St.

    2008-10-01

    This research thesis aims at understanding the importance of microstructure in the scattering of mechanical fields and of its potential influence on fatigue crack initiation, at studying the grains in which equi-biaxial fatigue cracks are appearing, and at proposing a coalescence model based on the discrete dislocation dynamics (DDD). After an overview of fatigue, the author describes the tests developed by EDF or the CEA to study thermal fatigue. Then, he presents the equi-biaxial fatigue test which allows the first stages of initiation of thermal fatigue cracks to be studied. Maps of cracked areas are obtained by Electron Back Scattered Diffraction, and results are discussed with respect to results obtained in dislocation dynamics. Polycrystalline computations are implemented. They allow a better understanding of the importance of the material microstructure for the scattering of the surface grain mechanical fields. Finally, a coalescence model is presented, based on experimental results obtained during the equi-biaxial fatigue testing. Coalescence criteria are proposed

  3. Effect of physical and chemical mutagens on morphological parameters in garlic

    International Nuclear Information System (INIS)

    Choudhary, A.D.; Dnyansagar, V.R.

    1980-01-01

    Cloves of garlic (Allium sativum Linn.) were treated with various doses of gamma rays and different concentrations of ethylmethane sulphonate, diethyl sulphate and ethyleneimine. The effect of mutagens was studied in respect of morphological parameters such as sprouting, survival, sprout height, plant height, number and size of leaves, number of cloves and weight of bulb. In case of mutagen treatment the percentage of sprouting and survival as well as sprout height were found to be decreased with an increase in the dose/concentration of the mutagen. The effect of mutagen on leaf size and number was inhibitory. However, the number of cloves and weight of bulb were found to be increased at lower dose concentration of mutagens. (author)

  4. Effect of fabrication parameters on morphological and optical properties of highly doped p-porous silicon

    Energy Technology Data Exchange (ETDEWEB)

    Zare, Maryam, E-mail: mar.zare@gmail.com [Young Researchers Club, Khomeinishahr Branch, Islamic Azad University, Khomeinishahr (Iran, Islamic Republic of); Shokrollahi, Abbas [Young Researchers Club, Khomeinishahr Branch, Islamic Azad University, Khomeinishahr (Iran, Islamic Republic of); Seraji, Faramarz E. [Optical Communication Group, Iran Telecom Research Center, Tehran (Iran, Islamic Republic of)

    2011-09-01

    Porous silicon (PS) layers were fabricated by anodization of low resistive (highly doped) p-type silicon in HF/ethanol solution, by varying current density, etching time and HF concentration. Atomic force microscopy (AFM) and field emission scanning electron microscope (FESEM) analyses were used to investigate the physical properties and reflection spectrum was used to investigate the optical behavior of PS layers in different fabrication conditions. Vertically aligned mesoporous morphology is observed in fabricated films and with HF concentration higher than 20%. The dependence of porosity, layer thickness and rms roughness of the PS layer on current density, etching time and composition of electrolyte is also observed in obtained results. Correlation between reflectivity and fabrication parameters was also explored. Thermal oxidation was performed on some mesoporous layers that resulted in changes of surface roughness, mean height and reflectivity of the layers.

  5. 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.

  6. Morphological parameters for implantation of the screwless spring loop dynamic posterior spinous process stabilizing system.

    Science.gov (United States)

    Song, Geun Soo; Lee, Yeon Soo

    2015-07-01

    This study aimed to quantify morphological characteristics of the posterior lumbar spinous process, which may affect stable implantation of screwless wire spring loops. Virtual implantations of a screwless wire spring loop onto pairs of lumbar spinous processes were performed for computed tomography (CT)-derived three-dimensional vertebral models of 40 Korean subjects. Morphological parameters of lumbar vertebrae 1 through 5 (L1-L5) were measured with regard to bone-implant interference. In males, the transspinous process fixation lengths decreased from 57.8±3.0mm to 48.8±3.2mm as the lumbar joints descend from L1-L2 to L4-L5, with those in females about 4.1±0.4mm shorter (pprocess and the greatest (8.1±2.2mm) for the L4 upper spinous process; this was 1.0±10.3mm less than that for males at corresponding levels (p>0.05). The ratio of the spinous process clenched thickness to the transspinous fixation length increased from 0.133±0.016 to 0.196±0.076 for the upper spinous processes as the lumbar joints descend. The ratio of the spinous process clenched thickness to the transspinous fixation length varies, depending on gender and whether the clenched level is the upper or lower spinous process. These parameters related to the clenching fixation stability should be considered in development and implantations of the screwless wire spring loop. Copyright © 2015 Elsevier GmbH. All rights reserved.

  7. Morphological and agronomical characterization and estimates of genetic parameters of sesbania Scop. (Leguminosae accessions

    Directory of Open Access Journals (Sweden)

    Veasey E.A.

    1999-01-01

    Full Text Available Twenty-two accessions of seven Sesbania (Leguminosae species: S. emerus, S. rostrata, S. tetraptera, S. exasperata (annuals, S. grandiflora, S. sesban and S. virgata (perennials, used for ruminant fodder, firewood, wood products, soil improvement, and human food, were investigated, with the aim of characterizing both inter- and intraspecific genetic variability, estimating genetic parameters for the characters evaluated and appraising the forage potential of the accessions. These were planted at the Instituto de Zootecnia, Nova Odessa, SP, Brazil, in a randomized complete block design with 22 treatments and four replications. Seventeen morphological and 17 agronomic characters were evaluated. Genetic parameters coefficient of intraspecific genetic diversity (bi and coefficient of intraspecific genetic variation (CVgi were obtained for the species represented by more than one accession. Highly significant differences were observed among as well as within species for most characters, showing considerable genetic variability. S. exasperata showed intraspecific genetic variability for the largest number of morphological characters. The same was observed for S. sesban for the agronomic characters. Most of the characters gave high bi values, above 0.80, indicating the possibility of selecting superior genotypes. The CVgi values, on the other hand, which indicate the magnitude of the existing genetic variability relative to the character mean, varied according to the species and character evaluated. Differences between annual and perennial species were observed, with higher biomass yields presented by the annuals at the first cut and by the perennials after the second cut, reaching the highest yield at the third cut. The annual species had higher seed production. Accession NO 934 of S. sesban gave the highest biomass yields and regrowth vigor, showing promise as a forage legume plant.

  8. Application of morphological and physiological parameters representative of a sample Brazilian population in the human respiratory tract model

    International Nuclear Information System (INIS)

    Reis, A.A.; Cardoso, J.C.S.; Lourenco, M.C.

    2005-01-01

    Full text: The Human Respiratory Tract Model (HRTM) proposed in ICRP Publication 66 account 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. These changing characteristics can influence the rates and the sites of deposition. 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 HRTM model uses morphological and physiological parameters from the Caucasian man to establish deposition fractions in the respiratory tract regions. lt 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 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 in 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 respiratory values at different levels of activity for ages varying from

  9. 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)

  10. Crack Resistance of Welded Joints of Pipe Steels of Strength Class K60 of Different Alloying Systems

    Science.gov (United States)

    Tabatchikova, T. I.; Tereshchenko, N. A.; Yakovleva, I. L.; Makovetskii, A. N.; Shander, S. V.

    2018-03-01

    The crack resistance of welded joints of pipe steels of strength class K60 and different alloying systems is studied. The parameter of the crack tip opening displacement (CTOD) is shown to be dependent on the size of the austenite grains and on the morphology of bainite in the superheated region of the heat-affected zone of the weld. The crack resistance is shown to be controllable due to optimization of the alloying system.

  11. Multi-parameter crack tip stress state description for estimation of fracture process zone extent in silicate composite WST specimens

    Czech Academy of Sciences Publication Activity Database

    Veselý, V.; Sobek, J.; Šestáková, L.; Frantík, P.; Seitl, Stanislav

    2013-01-01

    Roč. 7, č. 25 (2013), s. 69-78 ISSN 1971-8993 R&D Projects: GA ČR(CZ) GAP104/11/0833; GA ČR(CZ) GAP105/11/1551 Institutional support: RVO:68081723 Keywords : Near-crack tip fields * Williams series * higher-order terms * stress field approximation * wedge splitting test * fracture process zone Subject RIV: JL - Materials Fatigue, Friction Mechanics

  12. Study of new heat treatment parameters for increasing mechanical strength and stress corrosion cracking resistance of 7075 Aluminium alloy

    OpenAIRE

    Silva, G.; Rivolta, B.; Gerosa, R.; Derudi, U.

    2013-01-01

    For many years 7075 Aluminum alloys have been widely used especially in those applications for which highmechanical performances are required. It is well known that the alloy in the T6 condition is characterized bythe highest ultimate and yield strengths, but, at the same time, by poor stress corrosion cracking (SCC)resistance. For this reason, in the aeronautic applications, new heat treatments have been introduced toproduce T7X conditions, which are characterized by lower mechanical strengt...

  13. Application of morphological and physiological parameters representative of a Brazilian population sample in the respiratory tract model

    International Nuclear Information System (INIS)

    Dos Reis, A. A.; Cardoso, J. C. S.; Lourenco, M. C.

    2007-01-01

    The human respiratory tract model (HRTM) adopted by ICRP in its 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. These characteristics are important to determine the fractional deposition. 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 wherever such information is available. The main purpose of this study is to verify the influence of using the morphology and physiology parameters representative of a sample of the Brazilian population on the deposition model of the ICRP Publication 66 model. (authors)

  14. Process Parameters on the Crystallization and Morphology of Hydroxyapatite Powders Prepared by a Hydrolysis Method

    Science.gov (United States)

    Wang, Moo-Chin; Hon, Min-Hsiung; Chen, Hui-Ting; Yen, Feng-Lin; Hung, I.-Ming; Ko, Horng-Huey; Shih, Wei-Jen

    2013-07-01

    The effects of process parameters on the crystallization and morphology of hydroxyapatite (Ca10(PO4)6(OH)2, HA) powders synthesized from dicalcium phosphate dihydrate (CaHPO4·2H2O, DCPD) using a hydrolysis method have been investigated. X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectra, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED) were used to characterize the synthesized powders. When DCPD underwent hydrolysis in 2.5 NaOH solution (Na(aq)) at 303 K to 348 K (30 °C to 75 °C) for 1 hour, the XRD results revealed that HA was obtained for all the as-dried samples. The SEM morphology of the HA powders for DCPD hydrolysis produced at 348 K (75 °C) shows regular alignment and a short rod shape with a size of 200 nm in length and 50 nm in width. With DCPD hydrolysis in 2.5 M NaOH(aq) holding at 348 K (75 °C) for 1 to 24 hours, XRD results demonstrated that all samples were HA and no other phases could be detected. Moreover, the XRD results also show that all the as-dried powders still maintained the HA structure when DCPD underwent hydrolysis in 0.1 to 5 M NaOH(aq) at 348 K (75 °C) for 1 hour. Otherwise, the full transformation from HA to octa-calcium phosphate (OCP, Ca8H2(PO4)6·5H2O) occurred when hydrolysis happened in 10 M NaOH(aq). FT-IR spectra analysis revealed that some carbonated HA (Ca10(PO4)6(CO3), CHA) had formed. The SEM morphology results show that the 60 to 65 nm width of the uniformly long rods with regular alignment formed in the HA powder aggregates when DCPD underwent hydrolysis in 2.5 M NaOH(aq) at 348 K (75 °C) for 1 hour.

  15. Search for morphological parameters influential for prediction of the mechanical characteristics of an austeno-ferritic duplex stainless steel

    International Nuclear Information System (INIS)

    Messiaen, L.

    1997-01-01

    Duplex stainless steels are commonly used (among others in nuclear industry) for their good properties. However these steels may 'age' in service condition at high temperatures. As their mechanical properties (Charpy impact toughness, resistance to ductile tearing) are often very scattered and tend to decrease after ageing, it has become essential to predict them with high precision. For this, we propose to explain a part of the scattering of the mechanical properties with measurable parameters in relation with the particularly complicated two-phase morphology. The two-phase and bi-percolated morphology of the ferrite and austenite phases is first characterised from the observation of 2D images and from the reconstitution of a 3D image. At the same time we precise the genesis of the formation's mechanisms of the structure (germination and growth of the austenitic phase in the solidified ferri tic one) in relation with the literature. The morphological characteristics so observed corresponding with classical notions of mathematical morphology, - size, covariance, connexity -, we use morphological operators to measure morphological variables by image analysis. We establish then a link between toughness and a parameter measuring fineness of the morphology. The lack of data for very aged steels prevent us from proposing a model of toughness which could take this parameter into consideration at these ageing states, for which it is properly the more crucial to obtain specially precise predictions. A mathematical mo del of the 3D structure of the steel is finally proposed. We choose an homogeneous Markov chain of 3D spatial processes, whose evolution in time mimes the solidification. The morphology of the microstructure is so summarised with 8 parameters. This model is liable to be coupled with a model of toughness, for which it would so enlarge the possibilities of prediction. It could also be used to simulate subsequently the damage and the rupture of two

  16. Influence of deposition parameters on morphological properties of biomedical calcium phosphate coatings prepared using electrostatic spray deposition

    International Nuclear Information System (INIS)

    Leeuwenburgh, S.C.G.; Wolke, J.G.C.; Schoonman, J.; Jansen, J.A.

    2005-01-01

    In order to deposit biomedical calcium phosphate (CaP) coatings with a defined surface morphology, the electrostatic spray deposition (ESD) technique was used since this technique offers the possibility to deposit ceramic coatings with a variety of surface morphologies. A scanning electron microscopical study was performed in order to investigate the influence of several deposition parameters on the final morphology of the deposited coatings. The chemical characteristics of the coatings were studied by means of X-ray diffraction and Fourier-transform infrared spectroscopy. Regarding the chemical coating properties, the results showed that the coatings can be described as crystalline carbonate apatite coatings, a crystal phase which is similar to the mineral phase of bone and teeth. The morphology of CaP coatings, deposited using the ESD technique, was strongly dependent on the deposition parameters. By changing the nozzle-to-substrate distance, the precursor liquid flow rate and the deposition temperature, coating morphologies were deposited, which varied from dense to highly porous, reticular morphologies. The formation of various morphologies was the result of an equilibrium between the relative rates of CaP solute precipitation/reaction, solvent evaporation and droplet spreading onto the substrate surface

  17. 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.

  18. 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

  19. Corrosion cracking

    International Nuclear Information System (INIS)

    Goel, V.S.

    1985-01-01

    This book presents the papers given at a conference on alloy corrosion cracking. Topics considered at the conference included the effect of niobium addition on intergranular stress corrosion cracking, corrosion-fatigue cracking in fossil-fueled-boilers, fracture toughness, fracture modes, hydrogen-induced thresholds, electrochemical and hydrogen permeation studies, the effect of seawater on fatigue crack propagation of wells for offshore structures, the corrosion fatigue of carbon steels in seawater, and stress corrosion cracking and the mechanical strength of alloy 600

  20. The Effect of Field Dodder (Cuscuta campestris Yunck. on Morphological and Fluorescence Parameters of Giant Ragweed (Ambrosia trifida L.

    Directory of Open Access Journals (Sweden)

    Sava Vrbničanin

    2013-01-01

    Full Text Available The effect of the parasitic flowering plant known as field dodder (Cuscuta campestrisYunck. on morphological and fluorescence parameters of infested giant ragweed(Ambrosia trifida L. plants was examined under controlled conditions. The parameters ofchlorophyll fluorescence (Fo, Fv/Fm, ΦPSII, Fv, Fm, ETR and IF were measured on infested (Iand non-infested (N A. trifida plants over a period of seven days, beginning with the day ofinfestation. Morphological parameters (plant height, dry and fresh weight were measuredon the last day of fluorescence measurements. C. campestris was found to affect the height,fresh and dry weight of the infested A. trifida plants, causing significant reduction in plantheight and dry weight. Field dodder also affected several parameters of chlorophyll fluorescence(Fo, Fv/Fm, ΦPSII and Fv in infested A. trifida plants.

  1. Fracture Surface Morphology Under Ductile Tearing of Metal Plates

    DEFF Research Database (Denmark)

    Kacar, Muhammet F.; Tekoglu, Cihan; Nielsen, Kim Lau

    2017-01-01

    The present work takes as offset the hypothesis that microstructural parameters, related to particle size and distribution, govern the transition between crack surface morphologies observed in experiments. The key question is; why does tearing of a given metal plate leave a specific morphology...

  2. Study on effect of process parameters and mixing on morphology of ammonium diuranate

    International Nuclear Information System (INIS)

    Subhankar Manna; Chandrabhanu Basak; Thakkar, U.R.; Shital Thakur; Roy, S.B.; Joshi, J.B.; Institute of Chemical Technology, Matunga, Mumbai

    2016-01-01

    Ammonium diuranate (ADU) is an important intermediate for the production of uranium base fuel. Controlling morphology of crystalline ADU powders is very important as it is retained by its subsequent products. Because of the high level of supersaturation, the involved mechanisms of precipitation like primary nucleation, crystal growth, aggregation and breakage occur simultaneously and they control the morphology. Effects of concentration of uranyl nitrate solution, temperature and the mixing intensity have been investigated on the morphology, crystal structure and the other physical properties of ADU. Effect of temperature is found to be more dominant for controlling morphology. (author)

  3. Crack layer theory

    Science.gov (United States)

    Chudnovsky, A.

    1987-01-01

    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.

  4. Evaluation of crack interaction effect for in-plane surface cracks using elastic finite element analyses

    International Nuclear Information System (INIS)

    Huh, Nam Su; Choi, Suhn; Park, Keun Bae; Kim, Jong Min; Choi, Jae Boong; Kim, Young Jin

    2008-01-01

    The crack-tip stress fields and fracture mechanics assessment parameters, such as the elastic stress intensity factor and the elastic-plastic J-integral, for a surface crack can be significantly affected by adjacent cracks. Such a crack interaction effect due to multiple cracks can magnify the fracture mechanics assessment parameters. There are many factors to be considered, for instance the relative distance between adjacent cracks, crack shape and loading condition, to quantify a crack interaction effect on the fracture mechanics assessment parameters. Thus, the current guidance on a crack interaction effect (crack combination rule), including ASME Sec. XI, BS7910, British Energy R6 and API RP579, provide different rules for combining multiple surface cracks into a single surface crack. The present paper investigates a crack interaction effect by evaluating the elastic stress intensity factor of adjacent surface cracks in a plate along the crack front through detailed 3-dimensional elastic finite element analyses. The effects of the geometric parameters, the relative distance between cracks and the crack shape, on the stress intensity factor are systematically investigated. As for the loading condition, only axial tension is considered. Based on the elastic finite element results, the acceptability of the crack combination rules provided in the existing guidance was investigated, and the relevant recommendations on a crack interaction for in-plane surface cracks in a plate were discussed

  5. Evaluation of J and CTOD (Crack Tip Opening Displacement) fracture parameters for pipeline steels using Single Edge Notch Tension SE(T) specimens

    Energy Technology Data Exchange (ETDEWEB)

    Paredes Tobar, Lenin Marcelo; Ruggieri, Claudio [Universidade de Sao Paulo (USP), SP (Brazil). Escola Politecnica. Dept. de Engenharia Naval e Oceanica

    2009-12-19

    This work presents an evaluation procedure to determine the elastic-plastic J-integral and CTOD for pin-loaded and clamped single edge notch tension (SE(T)) specimens based upon the eta-method. The primary objective is to derive estimation equations applicable to determine J and CTOD fracture parameters for a wide range of a/W-ratios and material flow properties. Very detailed non-linear finite element analyses for plane-strain and full-thickness, 3-D models provide the evolution of load with increased crack mouth opening displacement which is required for the estimation procedure. The present analyses, when taken together with previous studies provide a fairly extensive body of results which serve to determine parameters J and CTOD for different materials using tension specimens with varying geometries. (author)

  6. A fully automated cell segmentation and morphometric parameter system for quantifying corneal endothelial cell morphology.

    Science.gov (United States)

    Al-Fahdawi, Shumoos; Qahwaji, Rami; Al-Waisy, Alaa S; Ipson, Stanley; Ferdousi, Maryam; Malik, Rayaz A; Brahma, Arun

    2018-07-01

    Corneal endothelial cell abnormalities may be associated with a number of corneal and systemic diseases. Damage to the endothelial cells can significantly affect corneal transparency by altering hydration of the corneal stroma, which can lead to irreversible endothelial cell pathology requiring corneal transplantation. To date, quantitative analysis of endothelial cell abnormalities has been manually performed by ophthalmologists using time consuming and highly subjective semi-automatic tools, which require an operator interaction. We developed and applied a fully-automated and real-time system, termed the Corneal Endothelium Analysis System (CEAS) for the segmentation and computation of endothelial cells in images of the human cornea obtained by in vivo corneal confocal microscopy. First, a Fast Fourier Transform (FFT) Band-pass filter is applied to reduce noise and enhance the image quality to make the cells more visible. Secondly, endothelial cell boundaries are detected using watershed transformations and Voronoi tessellations to accurately quantify the morphological parameters of the human corneal endothelial cells. The performance of the automated segmentation system was tested against manually traced ground-truth images based on a database consisting of 40 corneal confocal endothelial cell images in terms of segmentation accuracy and obtained clinical features. In addition, the robustness and efficiency of the proposed CEAS system were compared with manually obtained cell densities using a separate database of 40 images from controls (n = 11), obese subjects (n = 16) and patients with diabetes (n = 13). The Pearson correlation coefficient between automated and manual endothelial cell densities is 0.9 (p system, and the possibility of utilizing it in a real world clinical setting to enable rapid diagnosis and for patient follow-up, with an execution time of only 6 seconds per image. Copyright © 2018 Elsevier B.V. All rights reserved.

  7. Analysis of short and long crack behavior and single overload effect by crack opening stress

    International Nuclear Information System (INIS)

    Song, Sam Hong; Lee, Kyeong Ro

    1999-01-01

    The study analyzed the behaviors of short and long crack as well as the effect of single tensile overload on the crack behaviors by using fatigue crack opening behavior. Crack opening stress is measured by an elastic compliance method which may precisely and continuously provide many data using strain gages during experiment. The unusual growth behaviors of short crack and crack after the single tensile overload applied, was explained by the variations of crack opening stress. In addition, fatigue crack growth rate was expressed as a linear form for short crack as for long crack by using effective stress intensity factor range as fracture mechanical parameter, which is based on crack closure concept. And investigation is performed with respect to the relation between plastic zone size formed at the crack tip and crack retardation, crack length and the number of cycles promoted or retarded, and the overload effect on the fatigue life

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

    Science.gov (United States)

    Panda, Shasanka Shekhar; Bajpai, Minu; Mallick, Saumyaranjan; Sharma, Mehar C

    2014-01-01

    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. 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. 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. 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.

  9. 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.

  10. Crack Growth Behaviour of P92 Steel Under Creep-fatigue Interaction Conditions

    Directory of Open Access Journals (Sweden)

    JING Hong-yang

    2017-05-01

    Full Text Available Creep-fatigue interaction tests of P92 steel at 630℃ under stress-controlled were carried out, and the crack propagation behaviour of P92 steel was studied. The fracture mechanism of crack growth under creep-fatigue interaction and the transition points in a-N curves were analyzed based on the fracture morphology. The results show that the fracture of P92 steel under creep-fatigue interaction is creep ductile fracture and the (Ctavg parameter is employed to demonstrate the crack growth behaviour; in addition, the fracture morphology shows that the crack growth for P92 steel under creep-fatigue interaction is mainly caused by the nucleation and growth of the creep voids and micro-cracks. Furthermore, the transition point of a-lg(Ni/Nf curve corresponds to the turning point of initial crack growth changed into steady crack growth while the transition point of (da/dN-N curve exhibits the turning point of steady creep crack growth changed into the accelerated crack growth.

  11. The crack layer approach to toughness characterization in steel

    Science.gov (United States)

    Bessendorff, M.; Chudnovsky, A.

    1986-01-01

    In a study of the laws of crack propagation and toughness characterization, it is feasible to employ two alternative approaches, including the fracture mechanics approach and the material science approach. The crack layer (CL) theory discussed by Khandogin and Chudnovsky (1978) and Chudnovsky (1980) considers the crack together with the surrounding defects as one system which has several degrees of freedom. It is pointed out that the CL theory defines the relationship between the parameters of fracture mechanics and the characteristics of microstructural changes which are the subject of material science. Experiments are described, taking into account a toughness characterization test and microscopic studies. Attention is given to a phenomenological study of toughness characterization, the morphology of crack layer, and the evaluation of energy stored in the dislocation network.

  12. Detecting differences in some elite wheat lines for salt tolerance through multi parameters evaluation i. morphological and yield parameters

    International Nuclear Information System (INIS)

    Akram, M.; Afzal, M.; Ashraf, M.

    2011-01-01

    Salt tolerance potential of a newly developed wheat genotype (N-9760: V3) was assessed by comparing it with a known salt tolerant line (N-1073:V2) and a commercial cultivar (Inqlab: V1) using various growth parameters measured at the vegetative and maturity stages, The objectives were to know qualitative and quantitative tolerance status and possible utilization of the new genotype as well as to examine as to whether the parameters used to assess the tolerance at vegetative and maturity stages are affected differentially by various salinity levels. The experiment was conducted in pots using four salinity levels (EC 1.5, 5, 10 and 15 dS m/sup -1/). Root and shoot length, root and shoot fresh and dry weight, number of leaves and leaf area were recorded at the vegetative stage, while plant height, number of tillers, spike length and grain yield plant/sup -1/ were recorded at the maturity stage. Fresh weight of shoots, fresh and dry weights of roots, plant height, number of productive tillers and grain yield were least affected in V3 while shoot length, shoot fresh weight, number of leaves, leaf area and spike length were least affected in V2 by EC 15 dS m/sup -1/. Both genotypes appeared tolerant but all the parameters studied at both stages were affected differentially by salinity levels and genotypes hence, testing of every new genotype appeared essential. (author)

  13. Free vibration analysis of a cracked shear deformable beam on a two-parameter elastic foundation using a lattice spring model

    Science.gov (United States)

    Attar, M.; Karrech, A.; Regenauer-Lieb, K.

    2014-05-01

    The free vibration of a shear deformable beam with multiple open edge cracks is studied using a lattice spring model (LSM). The beam is supported by a so-called two-parameter elastic foundation, where normal and shear foundation stiffnesses are considered. Through application of Timoshenko beam theory, the effects of transverse shear deformation and rotary inertia are taken into account. In the LSM, the beam is discretised into a one-dimensional assembly of segments interacting via rotational and shear springs. These springs represent the flexural and shear stiffnesses of the beam. The supporting action of the elastic foundation is described also by means of normal and shear springs acting on the centres of the segments. The relationship between stiffnesses of the springs and the elastic properties of the one-dimensional structure are identified by comparing the homogenised equations of motion of the discrete system and Timoshenko beam theory.

  14. Biomechanical and morphological multi-parameter photoacoustic endoscope for identification of early esophageal disease

    Science.gov (United States)

    Jin, Dayang; Yang, Fen; Chen, Zhongjiang; Yang, Sihua; Xing, Da

    2017-09-01

    The combination of phase-sensitive photoacoustic (PA) imaging of tissue viscoelasticity with the esophagus-adaptive PA endoscope (PAE) technique allows the characterization of the biomechanical and morphological changes in the early stage of esophageal disease with high accuracy. In this system, the tissue biomechanics and morphology are obtained by detecting the PA phase and PA amplitude information, respectively. The PAE has a transverse resolution of approximately 37 μm and an outer diameter of 1.2 mm, which is suitable for detecting rabbit esophagus. Here, an in-situ biomechanical and morphological study of normal and diseased rabbit esophagus (tumors of esophagus and reflux esophagitis) was performed. The in-situ findings were highly consistent with those observed by histology. In summary, we demonstrated the potential application of PAE for early clinical detection of esophageal diseases.

  15. Effect of WOW process parameters on morphology and burst release of FITC-dextran loaded PLGA microspheres.

    Science.gov (United States)

    Mao, Shirui; Xu, Jing; Cai, Cuifang; Germershaus, Oliver; Schaper, Andreas; Kissel, Thomas

    2007-04-04

    Using fluorescein isothiocyanate labeled dextran (FITC-dextran 40, FD40) as a hydrophilic model compound, microspheres were prepared by a WOW double emulsion technique. Influence of process parameters on microsphere morphology and burst release of FD40 from PLGA microspheres was studied. Internal morphology of microspheres was investigated by stereological method via cryo-cutting technique and scanning electron microscopy (SEM). Drug distribution in microspheres was observed with confocal laser scanning microscopy (CLSM). Polymer nature (RG503 and RG503H) had significant influence on the micro-morphology of microspheres. Increase in continuous water phase volume (W2) led to increased surface porosity but decreased internal porosity. By increasing PVA concentration in the continuous phase from 0.1 to 1%, particle size changed marginally but burst release decreased from 12.2 to 5.9%. Internal porosity of microspheres decreased considerably with increasing polymer concentration. Increase in homogenization speed during the primary emulsion preparation led to decreased internal porosity. Burst release decreased with increasing drug loading but increased with drug molecular weight. Drug distribution in microspheres depended on preparation method. The porosity of microspheres decreased with time in the diffusion stage, but internal morphology had no influence on the release behavior in the bioerosion stage. In summary, surface porosity and internal morphology play a significant role in the release of hydrophilic macromolecules from biodegradable microspheres in the initial release phase characterized by pore diffusion.

  16. Cracking of anisotropic cylindrical polytropes

    Energy Technology Data Exchange (ETDEWEB)

    Mardan, S.A. [University of the Management and Technology, Department of Mathematics, Lahore (Pakistan); Azam, M. [University of Education, Division of Science and Technology, Lahore (Pakistan)

    2017-06-15

    We study the appearance of cracking in charged anisotropic cylindrical polytropes with generalized polytropic equation. We investigate the existence of cracking in two different kinds of polytropes existing in the literature through two different assumptions: (a) local density perturbation with conformally flat condition, and (b) perturbing polytropic index, charge and anisotropy parameters. We conclude that cracking appears in both kinds of polytropes for a specific range of density and model parameters. (orig.)

  17. Improvement of elastic-plastic fatigue crack growth evaluation method. 2. Crack opening behavior

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Yukio [Central Research Inst. of Electric Power Industry, Tokyo (Japan)

    2001-05-01

    Evaluation of crack growth behavior under cyclic loading is often required in the structural integrity assessment of cracked components. Closing and re-opening of the crack give large influence on crack growth rate through the change of fracture mechanics parameters. Based on the finite element analysis for a center-cracked plate, dependency of crack opening ratio on applied stress range and mean stress was examined. Simple formulae for representing the results were derived for plane stress and plane strain conditions. (author)

  18. 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.

  19. Linear viscoelastic and morphological description of multiphase systems affected by processing parameters

    Czech Academy of Sciences Publication Activity Database

    Kuthanová, V.; Hausnerová, B.; Kitano, T.; Lapčíková, Monika; Sáha, P.

    2011-01-01

    Roč. 119, č. 2 (2011), s. 989-999 ISSN 0021-8995 Institutional research plan: CEZ:AV0Z40500505 Keywords : polymer composites * injection molded compression * morphology Subject RIV: JI - Composite Materials Impact factor: 1.289, year: 2011

  20. 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.

  1. Sperm motility and morphology as changing parameters linked to sperm count variations.

    OpenAIRE

    Dua A; Vaidya S

    1996-01-01

    Variations in semen analyses of 177 males over a 1 year period were assessed. The average means of total counts, motility, morphology, total motile count and non-motile % were determined for 5 classes of patients ranging from azoospermic to normospermic. Positive relationships between a falling sperm count, a decrease in motility and total motile counts were seen. Also, increasingly, abnormal forms were found with lower sperm counts.

  2. Sperm motility and morphology as changing parameters linked to sperm count variations.

    Directory of Open Access Journals (Sweden)

    Dua A

    1996-10-01

    Full Text Available Variations in semen analyses of 177 males over a 1 year period were assessed. The average means of total counts, motility, morphology, total motile count and non-motile % were determined for 5 classes of patients ranging from azoospermic to normospermic. Positive relationships between a falling sperm count, a decrease in motility and total motile counts were seen. Also, increasingly, abnormal forms were found with lower sperm counts.

  3. 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.

  4. A morphogram with the optimal selection of parameters used in morphological analysis for enhancing the ability in bearing fault diagnosis

    International Nuclear Information System (INIS)

    Wang, Dong; Tse, Peter W; Tse, Yiu L

    2012-01-01

    Morphological analysis is a signal processing method that extracts the local morphological features of a signal by intersecting it with a structuring element (SE). When a bearing suffers from a localized fault, an impulse-type cyclic signal is generated. The amplitude and the cyclic time interval of impacts could reflect the health status of the inspected bearing and the cause of defects, respectively. In this paper, an enhanced morphological analysis called ‘morphogram’ is presented for extracting the cyclic impacts caused by a certain bearing fault. Based on the theory of morphology, the morphogram is realized by simple mathematical operators, including Minkowski addition and subtraction. The morphogram is able to detect all possible fault intervals. The most likely fault-interval-based construction index (CI) is maximized to establish the optimal range of the flat SE for the extraction of bearing fault cyclic features so that the type and cause of bearing faults can be easily determined in a time domain. The morphogram has been validated by simulated bearing fault signals, real bearing faulty signals collected from a laboratorial rotary machine and an industrial bearing fault signal. The results show that the morphogram is able to detect all possible bearing fault intervals. Based on the most likely bearing fault interval shown on the morphogram, the CI is effective in determining the optimal parameters of the flat SE for the extraction of bearing fault cyclic features for bearing fault diagnosis. (paper)

  5. Natural zeolite bitumen cracking

    Energy Technology Data Exchange (ETDEWEB)

    Kuznicki, S.M.; McCaffrey, W.C.; Bian, J.; Wangen, E.; Koenig, A. [Alberta Univ., Edmonton, AB (Canada). Dept. of Chemical and Materials Engineering

    2006-07-01

    A study was conducted to demonstrate how low cost heavy oil upgrading in the field could reduce the need for diluents while lowering the cost for pipelining. Low cost field upgrading could also contribute to lowering contaminant levels. The performance of visbreaking processes could be improved by using disposable cracking agents. In turn, the economics of field upgrading of in-situ derived bitumen would be improved. However, in order to be viable, such agents would have to be far less expensive than current commercial cracking catalysts. A platy natural zeolite was selected for modification and testing due to its unique chemical and morphological properties. A catalyst-bearing oil sand was then heat-treated for 1 hour at 400 degrees C in a sealed microreactor. Under these mild cracking conditions, the catalyst-bearing oil sand produced extractable products of much lower viscosity. The products also contained considerably more gas oil and middle distillates than raw oil sand processed under the same conditions as thermal cracking alone. According to model cracking studies using hexadecane, these modified mineral zeolites may be more active cracking agents than undiluted premium commercial FCC catalyst. These materials hold promise for partial upgrading schemes to reduce solvent requirements in the field. tabs., figs.

  6. Treadmill based reference running data for healthy subjects is dependent on speed and morphological parameters.

    Science.gov (United States)

    Schulze, Stephan; Schwesig, René; Edel, Melanie; Fieseler, Georg; Delank, Karl-Stefan; Hermassi, Souhail; Laudner, Kevin G

    2017-10-01

    To obtain spatiotemporal and dynamic running parameters of healthy participants and to identify relationships between running parameters, speed, and physical characteristics. A dynamometric treadmill was used to collect running data among 417 asymptomatic subjects during speeds ranging from 10 to 24km/h. Spatiotemporal and dynamic running parameters were calculated and measured. Results of the analyses showed that assessing running parameters is dependent on running speed. Body height correlated with stride length (r=0.5), cadence (r=-0.5) and plantar forefoot force (r=0.6). Body mass also had a strong relationship to plantar forefoot forces at 14 and 24km/h and plantar midfoot forces at 14 and 24km/h. This reference data base can be used in the kinematic and kinetic evaluation of running under a wide range of speeds. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. 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...

  8. 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.

  9. Effect of Physical Property and Surface Morphology of Copper Foil at Electrodeposition Parameter

    Energy Technology Data Exchange (ETDEWEB)

    Woo, Tae Gyu; Park, Il Song; Lee, Man Hyung; Seol, Kyeong Won [Chonbuk National University, Jeonju (Korea, Republic of)

    2014-06-15

    The effect of additives, current density and plated temperature on the surface morphology and physical property, during copper electrodeposition on polyimide (PI) film was investigated. Two kinds of additives, Cl and leveler (additive B), were used in this study. Electrochemical experiments were performed in conjunction with SEM, XRD and four-point probe to characterize the morphology and mechanical characteristics of copper electrodeposited in the presence of the additives. The surface roughness, crystal growth orientation and resistivity was controlled by the concentration of additive B. High resistivity and lower peel strength were observed on the surface of the copper layer electroplated in the electrolyte without additive B. However, a uniform surface, lower resistivity and high flexibility were obtained with a combination of 20 ppm Cl and 100 ppm additive B. Large particles were observed on the surface of the copper layer electroplated using a current density of 25 mA/cm{sup 2}, but a uniform surface and lower resistivity were obtained using a current density of 10 mA/cm{sup 2}. One of the required important properties of FCCL is flexibility of the copper foil. High flexibility of FCCL was obtained at a low current density, rather than a high current density. Moreover, a reasonable current density is 20 mA/cm{sup 2}, considering the productivity and mechanical properties of copper foil.

  10. Effect of morphological and functional changes in the secundines on biometric parameters of newborns from dichorionic twin pregnancies.

    Science.gov (United States)

    Waszak, Małgorzata; Cieślik, Krystyna; Pietryga, Marek; Lewandowski, Jacek; Chuchracki, Marek; Nowak-Markwitz, Ewa; Bręborowicz, Grzegorz

    2016-01-01

    The aim of the study was to determine if, and to what extent, structural and functional changes of the secundines influence biometric parameters of neonates from dichorionic twin pregnancies. The study included neonates from dichorionic, diamniotic twin pregnancies, along with their secundines. Based on histopathological examination of the secundines, the mass and dimensions of the placenta, length and condition of the umbilical cord, chorionicity, focal lesions, and microscopic placental abnormalities were determined for 445 pairs of twins. Morphological development of examined twins was characterized on the basis of their six somatic traits, while birth status of the newborns was assessed based on their Apgar scores. Statistical analysis included Student t-tests, Snedecor's F-tests, post-hoc tests, non-parametric chi-squared Pearson's tests, and determination of Spearman coefficients of rank correlation. The lowest values of analyzed somatic traits were observed in twins who had placentas with velamentous or marginal cord insertion. Inflammatory lesions in the placenta and placental abruption turned out to have the greatest impact of all analyzed abnormalities of the secundines. Inflammatory lesions in the placenta were associated with lower values of biometric parameters and a greater likelihood of preterm birth. Neonates with a history of placental abruption were characterized by significantly lower birth weight and smaller chest circumference. Morphological changes in the secundines have a limited impact on biometric parameters of neonates from dichorionic twin pregnancies. In turn, functional changes exert a significant effect and more often contribute to impaired fetal development.

  11. Process parameter and surface morphology of pineapple leaf electrospun nanofibers (PALF)

    Science.gov (United States)

    Surip, S. N.; Aziz, F. M. A.; Bonnia, N. N.; Sekak, K. A.; Zakaria, M. N.

    2017-09-01

    In recent times, nanofibers have attracted the attention of researchers due to their pronounced micro and nano structural characteristics that enable the development of advanced materials that have sophisticated applications. The production of nanofibers by the electrospinning process is influenced both by the electrostatic forces and the viscoelastic behavior of the polymer. Process parameters, like solution feed rate, applied voltage, nozzle-collector distance, and spinning environment, and material properties, like solution concentration, viscosity, surface tension, conductivity, and solvent vapor pressure, influence the structure and properties of electrospun nanofibers. Significant work has been done to characterize the properties of PALF nanofibers as a function of process and material parameters.

  12. 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.

  13. InGaN quantum well epilayers morphological evolution under a wide range of MOCVD growth parameter sets

    Energy Technology Data Exchange (ETDEWEB)

    Florescu, D.I.; Ting, S.M.; Merai, V.N.; Parekh, A.; Lee, D.S.; Armour, E.A.; Quinn, W.E. [Veeco TurboDisc Operations, 394 Elizabeth Avenue, Somerset, NJ 08873 (United States)

    2006-06-15

    This study exemplifies the use of TappingMode trademark atomic force microscopy (AFM) surface morphology imaging to investigate and optimise the metalorganic chemical vapour deposition (MOCVD) growth conditions and post-growth stability of thin (<40 Aa) InGaN layers with direct implications to the structural and optical properties of blue (460 nm) and green (520 nm) LEDs. InGaN epilayers less than 40 Aa thick of {proportional_to}20% solid phase indium were produced on thick (3-4 {mu}m) 2{sup ''} GaN templates grown on (0001) c-plane sapphire substrates. The morphological evolution of the InGaN material was studied utilising a DI3100 AFM tool. Surface morphology and its correlation with photoluminescence and X-ray diffraction results are discussed for every set of conditions employed. More specifically, the post-growth ambient exposure and thermal stability of the uncapped InGaN epilayers were investigated. In addition, the initial stage of subsequent GaN growth, which is an essential step towards the manufacture of LED active regions, was examined. Based on the above findings, a flexible MOCVD growth parameter space and improved LED constituent layer sequencing techniques have been established leading to more efficient and stable LED devices. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. InGaN quantum well epilayers morphological evolution under a wide range of MOCVD growth parameter sets

    International Nuclear Information System (INIS)

    Florescu, D.I.; Ting, S.M.; Merai, V.N.; Parekh, A.; Lee, D.S.; Armour, E.A.; Quinn, W.E.

    2006-01-01

    This study exemplifies the use of TappingMode trademark atomic force microscopy (AFM) surface morphology imaging to investigate and optimise the metalorganic chemical vapour deposition (MOCVD) growth conditions and post-growth stability of thin ( '' GaN templates grown on (0001) c-plane sapphire substrates. The morphological evolution of the InGaN material was studied utilising a DI3100 AFM tool. Surface morphology and its correlation with photoluminescence and X-ray diffraction results are discussed for every set of conditions employed. More specifically, the post-growth ambient exposure and thermal stability of the uncapped InGaN epilayers were investigated. In addition, the initial stage of subsequent GaN growth, which is an essential step towards the manufacture of LED active regions, was examined. Based on the above findings, a flexible MOCVD growth parameter space and improved LED constituent layer sequencing techniques have been established leading to more efficient and stable LED devices. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. French RSE-M and RCC-MR code appendices for flaw analysis: Presentation of the fracture parameters calculation-Part IV: Cracked elbows

    International Nuclear Information System (INIS)

    Marie, S.; Chapuliot, S.; Kayser, Y.; Lacire, M.H.; Drubay, B.; Barthelet, B.; Le Delliou, P.; Rougier, V.; Naudin, C.; Gilles, P.; Triay, M.

    2007-01-01

    Two French nuclear codes include flaw assessment procedures: the RSE-M Code 'Rules for In-service Inspection of Nuclear Power Plant Components' and the RCC-MR code 'Design and Construction rules for mechanical components of FBR nuclear islands and high temperature applications'. Development of analytical methods has been made for the last 10 years through a collaboration between CEA, EDF and AREVA-NP, and through R and D actions involving CEA and IRSN. These activities have led to unification of the common methods of the two codes. The calculation of fracture mechanics parameters, and in particular the stress intensity factor K I and the J integral, has been widely developed for industrial configurations. All the developments have been integrated in the 2005 edition of RSE-M and in 2007 edition of RCC-MR. This series of papers is composed of five parts: the first presents an overview of the methods proposed in the RCC-MR and RSE-M codes. Parts II-IV provide compendia for specific components. The geometries are plates (part II), pipes (part III) and elbows (part IV). Part V presents validation of the methods, with details on their accuracy. This paper presents the stress intensity factor and J calculation for cracked elbows. General data applicable for all defect geometries are first presented, and then, compendia for K I and σ ref calculations are provided for the available defect geometries

  16. Crack retardation by load reduction during fatigue crack propagation

    International Nuclear Information System (INIS)

    Kim, Hyun Soo; Nam, Ki Woo; Ahn, Seok Hwan; Do, Jae Yoon

    2003-01-01

    Fracture life and crack retardation behavior were examined experimentally using CT specimens of aluminum alloy 5083. Crack retardation life and fracture life were a wide difference between 0.8 and 0.6 in proportion to ratio of load reduction. The wheeler model retardation parameter was used successfully to predict crack growth behavior. By using a crack propagation rule, prediction of fracture life can be evaluated quantitatively. A statistical approach based on Weibull distribution was applied to the test data to evaluate the dispersion in the retardation life and fracture life by the change of load reduction

  17. Morphological Parameters in Relation to the Electromagnetic Properties of Microcellular Thermoplastic Polyurethane Foam in X-Band Frequency Ranges

    Directory of Open Access Journals (Sweden)

    Mohammad Hassan Moeini

    2017-04-01

    Full Text Available Microcellular thermoplastic polyurethane foams are examined as absorbing materials in the X-band (8.2-12.4 GHz frequency range by means of experiment. In this work, we aim to establish relationships between foam morphology including cell size and air volume fraction and electromagnetic properties including absorption, transmission and reflection quality. Nanocomposites based on thermoplastic polyurethane containing carbon black were prepared by coagulation method. In this procedure 15 wt% carbon black-containing nanocomposite was converted to microcellular foams using batch foaming process and supercritical carbon dioxide as physical foaming agent. The morphology of the foams was evaluated by scanning electron microscopy. S-parameters of the samples were measured by a vector network analyzer (VNA and the effect of morphological parameters such as cell size and air volume fraction on the absorbing properties was investigated. We also established structure/properties relationships which were essential for further optimizations of the materials used in the construction of radar absorbing composites. Foaming reduced the percolation threshold of the nanocomposites due to the reduction in the average distance between nanoparticles. Foaming and dielectric constant reduction dropped the reflection percentage significantly. The increase in air volume fraction in the foam increased absorption per its weight, because of multiple scattering in composite media. The sensitivity of electromagnetic wave toward the variation of cell size is strongly weaker than that toward the variation of air volume fraction. Electromagnetic properties of the microcellular foams deviated a little from effective medium theories (EMTs. Air volume fraction of the cells was a function of cell size and smaller cells showed higher absorption.

  18. 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.

  19. Crack tip stress and strain

    International Nuclear Information System (INIS)

    Francois, D.

    1975-01-01

    The study of potential energy variations in a loaded elastic solid containing a crack leads to determination of the crack driving force G. Generalization of this concept to cases other than linear elasticity leads to definition of the integral J. In a linear solid, the crack tip stress field is characterized by a single parameter: the stress-intensity factor K. When the crack tip plastic zone size is confined to the elastic singularity J=G, it is possible to establish relationship between these parameters and plastic strain (and in particular the crack tip opening displacement delta). The stress increases because of the triaxiality effect. This overload rises with increasing strain hardening. When the plastic zone size expands, using certain hypotheses, delta can be calculated. The plastic strain intensity is exclusively dependent on parameter J [fr

  20. Estimation of Genetic and Phenotypic Parameters for Udder Morphology Traits in Different Dairy Sheep Genotypes

    Directory of Open Access Journals (Sweden)

    Pavol Makovický

    2017-01-01

    Full Text Available Knowledge of genetic parameters is the basis of sound livestock improvement programmes. Genetic parameters have been estimated for linear udder traits: Udder depth (UD, Cistern depth (CD, Teat position (TP, Teat size (TS and external udder measurements: Rear udder depth (RUD, Cistern depth (CDe, Teat length (TL and Teat angle (TA – 1275 linear assessments (381 ewes and 1185 external udder measurements (355 ewes were included in the analysis for each character of 9 genotypes. Nine breeds and genotypes were included in these experiments: purebred Improved Valachian (IV, Tsigai (T, Lacaune (LC ewes, and IV and T crosses with genetic portion of Lacaune and East Friesian (EF – 25 %, 50 % and 75 %. Primary data were processed using restricted maximum likelihood (REML methodology and the multiple‑trait animal model, using programs REMLF90 and VCE 4.0. High genetic correlations were found between UD and RUD (0.86, CD and CD(e (0.93, TP and TA (0.90, TS and TL (0.94. The highest heritabilities were estimated for exact measurements of TL and CD (0.35–0.39 and subjectively assessed TA and TS (0.32 – 0.33.

  1. The Impact of Ventricular Assist Device Prior to Transplantation on Morphological Parameters in Cardiac Allografts

    DEFF Research Database (Denmark)

    Wassilew, Katharina

    2017-01-01

    . The Cochran-Mantel-Haenzsel test was applied to assess significance of the differences in interactions between groups. To evaluate the impact of bridge- to- transplant mechanical circulatory support on development on transplant vasculopathy in cardiac allografts, the intramyocardial terminal arterial network...... allograft dysfunction, as MCS patients show a higher frequency of antibody-mediated rejection (AMR) episodes. We aimed to analyze the effects of MCS on cardiac AMR with regards to capillary C3d and C4d depositions. Regarding the functional parameters, both acute cellular rejection (ACR) and an increase...... of interstitial fibrosis (IF) often correlate with impaired ventricular function. The innate immune system, in particular macrophages, plays an important role in the resorptive process of ACR and is, on the other hand, known to promote IF. In this study we aimed to analyze the effect of ACR and specifically...

  2. 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.

  3. 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.

  4. Cardiac MRI in pulmonary artery hypertension: correlations between morphological and functional parameters and invasive measurements

    Energy Technology Data Exchange (ETDEWEB)

    Alunni, Jean-Philippe; Otal, Philippe; Rousseau, Herve; Chabbert, Valerie [CHU Rangueil, Department of Radiology, Toulouse (France); Degano, Bruno; Tetu, Laurent; Didier, Alain [CHU Larrey, Department of Pneumology, Toulouse (France); Arnaud, Catherine [CHU Rangueil, Department of Methods in Clinical Research, Toulouse (France); Blot-Souletie, Nathalie [CHU Rangueil, Department of Cardiology, Toulouse (France)

    2010-05-15

    To compare cardiac MRI with right heart catheterisation in patients with pulmonary hypertension (PH) and to evaluate its ability to assess PH severity. Forty patients were included. MRI included cine and phase-contrast sequences, study of ventricular function, cardiac cavity areas and ratios, position of the interventricular septum (IVS) in systole and diastole, and flow measurements. We defined four groups according to the severity of PH and three groups according to IVS position: A, normal position; B, abnormal in diastole; C, abnormal in diastole and systole. IVS position was correlated with pulmonary artery pressures and PVR (pulmonary vascular resistance). Median pulmonary artery pressures and resistance were significantly higher in patients with an abnormal septal position compared with those with a normal position. Correlations were good between the right ventricular ejection fraction and PVR, right ventricular end-systolic volume and PAP, percentage of right ventricular area change and PVR, and diastolic and systolic ventricular area ratio and PVR. These parameters were significantly associated with PH severity. Cardiac MRI can help to assess the severity of PH. (orig.)

  5. 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)

  6. On cracking of charged anisotropic polytropes

    Energy Technology Data Exchange (ETDEWEB)

    Azam, M. [Division of Science and Technology, University of Education, Township Campus, Lahore-54590 (Pakistan); Mardan, S.A., E-mail: azam.math@ue.edu.pk, E-mail: syedalimardanazmi@yahoo.com [Department of Mathematics, University of the Management and Technology, C-II, Johar Town, Lahore-54590 (Pakistan)

    2017-01-01

    Recently in [1], 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 [2] in the absence of charge.

  7. 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

  8. French RSE-M and RCC-MR code appendices for flaw analysis: Presentation of the fracture parameters calculation-Part II: Cracked plates

    International Nuclear Information System (INIS)

    Marie, S.; Chapuliot, S.; Kayser, Y.; Lacire, M.H.; Drubay, B.; Barthelet, B.; Le Delliou, P.; Rougier, V.; Naudin, C.; Gilles, P.; Triay, M.

    2007-01-01

    French nuclear codes include flaw assessment procedures: the RSE-M Code 'Rules for In-service Inspection of Nuclear Power Plant Components' and the RCC-MR code 'Design and Construction rules for mechanical components of FBR nuclear islands and high temperature applications'. An important effort of development of these analytical methods has been made for the last 10 years in the frame of a collaboration between CEA, EDF and AREVA-NP, and in the frame of R and D actions involving CEA and IRSN. These activities have led to a unification of the common methods of the two codes. The calculation of fracture mechanics parameters, and in particular the stress intensity factor K I and the J integral, has been widely developed for industrial configurations. All the developments have been integrated in the 2005 edition of RSE-M and in the 2007 edition of RCC-MR. This series of articles is composed of 5 parts: the first part presents an overview of the methods proposed in the RCC-MR and RSE-M codes. Parts II-IV provide compendia for specific components. The geometries are plates (part II), pipes (part III) and elbows (part IV). Finally, part V presents the validation elements of the methods, with details on the process followed for the development and evaluation of the accuracy of the proposed analytical methods. This second article in the series presents all details for the stress intensity factor and J calculations for cracked plates. General data applicable for all defect geometries are first presented, and then, available defect geometries where compendia for K I and σ ref calculation are provided are given

  9. Application of the physiological and morphological parameters of the brazilian population sample to the mathematical model of the human respiratory tract

    International Nuclear Information System (INIS)

    Reis, Arlene Alves dos

    2005-01-01

    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. Dynamic ductile fracture of a central crack

    Science.gov (United States)

    Tsai, Y. M.

    1976-01-01

    A central crack, symmetrically growing at a constant speed in a two dimensional ductile material subject to uniform tension at infinity, is investigated using the integral transform methods. The crack is assumed to be the Dugdale crack, and the finite stress condition at the crack tip is satisfied during the propagation of the crack. Exact expressions of solution are obtained for the finite stress condition at the crack tip, the crack shape, the crack opening displacement, and the energy release rate. All those expressions are written as the product of explicit dimensional quantities and a nondimensional dynamic correction function. The expressions reduce to the associated static results when the crack speed tends to zero, and the nondimensional dynamic correction functions were calculated for various values of the parameter involved.

  11. Quantifying morphological parameters of the terminal branching units in a mouse lung by phase contrast synchrotron radiation computed tomography.

    Directory of Open Access Journals (Sweden)

    Jeongeun Hwang

    Full Text Available An effective technique of phase contrast synchrotron radiation computed tomography was established for the quantitative analysis of the microstructures in the respiratory zone of a mouse lung. Heitzman's method was adopted for the whole-lung sample preparation, and Canny's edge detector was used for locating the air-tissue boundaries. This technique revealed detailed morphology of the respiratory zone components, including terminal bronchioles and alveolar sacs, with sufficiently high resolution of 1.74 µm isotropic voxel size. The technique enabled visual inspection of the respiratory zone components and comprehension of their relative positions in three dimensions. To check the method's feasibility for quantitative imaging, morphological parameters such as diameter, surface area and volume were measured and analyzed for sixteen randomly selected terminal branching units, each consisting of a terminal bronchiole and a pair of succeeding alveolar sacs. The four types of asymmetry ratios concerning alveolar sac mouth diameter, alveolar sac surface area, and alveolar sac volume are measured. This is the first ever finding of the asymmetry ratio for the terminal bronchioles and alveolar sacs, and it is noteworthy that an appreciable degree of branching asymmetry was observed among the alveolar sacs at the terminal end of the airway tree, despite the number of samples was small yet. The series of efficient techniques developed and confirmed in this study, from sample preparation to quantification, is expected to contribute to a wider and exacter application of phase contrast synchrotron radiation computed tomography to a variety of studies.

  12. STUDIES ON THE RELATIONSHIP BETWEEN SOME MORPHOLOGICAL CHARACTERS AND JUMPING PARAMETERS OVER A VERTICAL FENCE IN SPORT HORSES

    Directory of Open Access Journals (Sweden)

    FLAVIA BOCHIŞ

    2009-10-01

    Full Text Available Looking for the form-function principle, the present study proposed to analyze the morphological traits of the equine athletes and the jumping over obstacles parameters. The intension was to focuses some guide lines in selecting the future potential champion. Indeed, this is only a basic item, not a guarantee, in a future career, where a lot of aspects take part. Even that, if a horse had a good rider and an excellent trainer, if it is not described by some basic biometrical and biomechanical reports (Duel, 1987, Lewczuk, 2002, it is impossible to reach very good results. In most of cases, when horses refused some exercising elements, we think about temperament, but in the same time, the aspect could be generated by a pain, or effectively by them incapacity due to an equilibrium fault (Lagarde, 2005.

  13. Ductile crack growth simulation from near crack tip dissipated energy

    International Nuclear Information System (INIS)

    Marie, S.; Chapuliot, S.

    2000-01-01

    A method to calculate ductile tearing in both small scale fracture mechanics specimens and cracked components is presented. This method is based on an estimation of the dissipated energy calculated near the crack tip. Firstly, the method is presented. It is shown that a characteristic parameter G fr can be obtained, relevant to the dissipated energy in the fracture process. The application of the method to the calculation of side grooved crack tip (CT) specimens of different sizes is examined. The value of G fr is identified by comparing the calculated and experimental load line displacement versus crack extension curve for the smallest CT specimen. With this identified value, it is possible to calculate the global behaviour of the largest specimen. The method is then applied to the calculation of a pipe containing a through-wall thickness crack subjected to a bending moment. This pipe is made of the same material as the CT specimens. It is shown that it is possible to simulate the global behaviour of the structure including the prediction of up to 90-mm crack extension. Local terms such as the equivalent stress or the crack tip opening angle are found to be constant during the crack extension process. This supports the view that G fr controls the fields in the vicinity near the crack tip. (orig.)

  14. 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

  15. 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.

  16. Age-Specific And Sexual Variability Of Morphological And Biomechanical Parameters Of Anterior Cerebral Artery Of Adults

    Directory of Open Access Journals (Sweden)

    I.V. Kirillova

    2009-12-01

    Full Text Available In the experiment on monoaxonic longitudinal distension by tensile-testing machine Tira Test 28005 (Germany with loading unit - 100 N the general rigidity, breaking point and relative lengthening of anterior cerebral artery (АСА of adult people have been under study. Under the microscope on transverse sections the external diameter of the artery, its wall thickness have been measured and diameter of lumen have been calculated. In total 228 АСА (132 - from corpses of men, 92-from corpses of women have been investigated. They have been received in 16 hours after autopsy of adult people whose cause of death has not been connected with vascular cerebral pathology. It has been revealed that right АСА is longer and narrower than left one. ACA's wall length and thickness predominate in men in comparison with women in average of 5,4 - 13,0%. With years АСА lengthens, its external diameter increases. Biomechanical parameters of ACA's wall do not have any authentic sexual differences, they don't depend on the side of the arterial ring. With years the rigidity of АСА decreases, especially in middle age. In old age its general rigidity increases. It is connected with the increase of ACA's wall thickness. The ability of АСА to lengthening doesn't depend upon age. Experimental findings may be used as criteria of age standard of morphological and biomechanical parameters of АСА

  17. 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.

  18. Surface and subsurface cracks characteristics of single crystal SiC wafer in surface machining

    Energy Technology Data Exchange (ETDEWEB)

    Qiusheng, Y., E-mail: qsyan@gdut.edu.cn; Senkai, C., E-mail: senkite@sina.com; Jisheng, P., E-mail: panjisheng@gdut.edu.cn [School of Electromechanical Engineering, Guangdong University of Technology, Guangzhou, 510006 (China)

    2015-03-30

    Different machining processes were used in the single crystal SiC wafer machining. SEM was used to observe the surface morphology and a cross-sectional cleavages microscopy method was used for subsurface cracks detection. Surface and subsurface cracks characteristics of single crystal SiC wafer in abrasive machining were analysed. The results show that the surface and subsurface cracks system of single crystal SiC wafer in abrasive machining including radial crack, lateral crack and the median crack. In lapping process, material removal is dominated by brittle removal. Lots of chipping pits were found on the lapping surface. With the particle size becomes smaller, the surface roughness and subsurface crack depth decreases. When the particle size was changed to 1.5µm, the surface roughness Ra was reduced to 24.0nm and the maximum subsurface crack was 1.2µm. The efficiency of grinding is higher than lapping. Plastic removal can be achieved by changing the process parameters. Material removal was mostly in brittle fracture when grinding with 325# diamond wheel. Plow scratches and chipping pits were found on the ground surface. The surface roughness Ra was 17.7nm and maximum subsurface crack depth was 5.8 µm. When grinding with 8000# diamond wheel, the material removal was in plastic flow. Plastic scratches were found on the surface. A smooth surface of roughness Ra 2.5nm without any subsurface cracks was obtained. Atomic scale removal was possible in cluster magnetorheological finishing with diamond abrasive size of 0.5 µm. A super smooth surface eventually obtained with a roughness of Ra 0.4nm without any subsurface crack.

  19. Study of initiation and growth of stress corrosion cracks. Quantitative characterization and modeling

    International Nuclear Information System (INIS)

    Peyrat, Christine

    1997-01-01

    A phenomenological study of Stress Corrosion Cracking (SCC) cracks initiation and growth was carried out on a Z 2 CN 18.10 stainless steel in a boiling aqueous magnesium chloride solution at 153 deg. C. The characterization method exploits the morphological information (cracks shape and size distribution) available on a specimen after SCC test. This method, independent of any mechanistic hypothesis, led to the analytical representation of the growth rate of a given crack as a function of its depth and of the density of deeper cracks. The presence of this last parameter could be the expression of a 'shielding effect' of mechanical origin, exerted by the cracks of large size. A 'true initiation' rate was calculated by an extrapolation based on the analytical expression of the growth rate. This analytical representation of cracks initiation and growth accounts for the saturation observed in the experimental determination of the 'apparent initiation'. As time goes, the number of cracks deeper than a given threshold depth tends towards a limit which depends very strongly on the chosen threshold. This saturation effect can be interpreted as exclusively due to the way the small cracks propagate, as the 'true initiation' rate can be expressed versus time by a simple power law. In the case of slow strain rate tests, it is shown that the kinetic parameters characteristic of initiation and growth depend on the applied elongation rate. In particular, the initial crack growth rate increases with elongation rate. The validity domains of the proposed expressions have been specified by means of SCC tests carried out under different types of mechanical loading. (author) [fr

  20. Tensile cracks in creeping solids

    International Nuclear Information System (INIS)

    Riedel, H.; Rice, J.R.

    1979-02-01

    The loading parameter determining the stress and strain fields near a crack tip, and thereby the growth of the crack, under creep conditions is discussed. Relevant loading parameters considered are the stress intensity factor K/sub I/, the path-independent integral C*, and the net section stress sigma/sub net/. The material behavior is modelled as elastic-nonlinear viscous where the nonlinear term describes power law creep. At the time t = 0 load is applied to the cracked specimen, and in the first instant the stress distribution is elastic. Subsequently, creep deformation relaxes the initial stress concentration at the crack tip, and creep strains develop rapidly near the crack tip. These processes may be analytically described by self-similar solutions for short times t. Small scale yielding may be defined. In creep problems, this means that elastic strains dominate almost everywhere except in a small creep zone which grows around the crack tip. If crack growth ensues while the creep zone is still small compared with the crack length and the specimen size, the stress intensity factor governs crack growth behavior. If the calculated creep zone becomes larger than the specimen size, the stresses become finally time-independent and the elastic strain rates can be neglected. In this case, the stress field is the same as in the fully-plastic limit of power law hardening plasticity. The loading parameter which determines the near tip fields uniquely is then the path-independent integral C*.K/sub I/ and C* characterize opposite limiting cases. The case applied in a given situation is decided by comparing the creep zone size with the specimen size and the crack length. Besides several methods of estimating the creep zone size, a convenient expression for a characteristic time is derived, which characterizes the transition from small scale yielding to extensive creep of the whole specimen

  1. Assessment of cracking in dissimilar metal welds

    International Nuclear Information System (INIS)

    Jenssen, Anders; Norrgaard, K.; Lagerstroem, J.; Embring, G.; Tice, D.R.

    2001-08-01

    During the refueling in 2000, indications were observed by non-destructive testing at four locations in the reactor pressure vessel (RPV) nozzle to safe end weld in Ringhals 4. All indications were confined to the outlet nozzle (hotleg) oriented at 25 deg, a nozzle with documented repair welding. Six boat samples were removed from the four locations, and the samples were subsequently subjected to a metallographic examination. The objectives were to establish the fracture morphology, and if possible the root cause for cracking. The examination revealed that cracks were present at all four boat sample locations and that they all were confined to the weld metal, alloy 182. Cracking extended in the axial direction of the safe-end. There was no evidence of any cracks extending into the RPV-steel, or the stainless steel safe-end. All cracking was interdendritic and significantly branched. Among others, these observations strongly suggested crack propagation mainly was caused by interdendritic stress corrosion cracking. In addition, crack type defects and isolated areas on the fracture surfaces suggested the presence of hot cracking, which would have been formed during fabrication. The reason for crack initiation could not be established based on the boat samples examined. However, increased stress levels due to repair welding, cold work from grinding, and defects produced during fabrication, e. g. hot cracks, may alone or in combination have contributed to crack initiation

  2. 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

  3. 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

  4. Finite element simulation for creep crack growth

    International Nuclear Information System (INIS)

    Miyazaki, Noriyuki; Sasaki, Toru; Nakagaki, Michihiko; Brust, F.W.

    1992-01-01

    A finite element method was applied to a generation phase simulation of creep crack growth. Experimental data on creep crack growth in a 1Cr-1Mo-1/4V steel compact tension specimen were numerically simulated using a node-release technique and the variations of various fracture mechanics parameters such as CTOA, J, C * and T * during creep crack growth were calculated. The path-dependencies of the integral parameters J, C * and T * were also obtained to examine whether or not they could characterize the stress field near the tip of a crack propagating under creep condition. The following conclusions were obtained from the present analysis. (1) The J integral shows strong path-dependency during creep crack growth, so that it is does not characterize creep crack growth. (2) The C * integral shows path-dependency to some extent during creep crack growth even in the case of Norton type steady state creep law. Strictly speaking, we cannot use it as a fracture mechanics parameter characterizing creep crack growth. It is, however, useful from the practical viewpoint because it correlates well the rate of creep crack growth. (3) The T * integral shows good path-independency during creep crack growth. Therefore, it is a candidate for a fracture mechanics parameter characterizing creep crack growth. (author)

  5. Fatigue crack growth and fracture behavior of bainitic rail steels.

    Science.gov (United States)

    2011-09-01

    "The microstructuremechanical properties relationships, fracture toughness, fatigue crack growth and fracture surface morphology of J6 bainitic, manganese, and pearlitic rail steels were studied. Microstructuremechanical properties correlation ...

  6. 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.

  7. Recent advances in modelling creep crack growth

    International Nuclear Information System (INIS)

    Riedel, H.

    1988-08-01

    At the time of the previous International Conference on Fracture, the C* integral had long been recognized as a promising load parameter for correlating crack growth rates in creep-ductile materials. The measured crack growth rates as a function of C* and of the temperature could be understood on the basis of micromechanical models. The distinction between C*-controlled and K I -controlled creep crack growth had been clarified and first attempts had been made to describe creep crack growth in the transient regime between elastic behavior and steady-state creep. This paper describes the progress in describing transient crack growth including the effect of primary creep. The effect of crack-tip geometry changes by blunting and by crack growth on the crack-tip fields and on the validity of C* is analyzed by idealizing the growing-crack geometry by a sharp notch and using recent solutions for the notch-tip fields. A few new three-dimensional calculations of C* are cited and important theoretical points are emphasized regarding the three-dimensional fields at crack tips. Finally, creep crack growth is described by continuum-damage models for which similarity solutions can be obtained. Crack growth under small-scale creep conditions turns out to be difficult to understand. Slightly different models yield very different crack growth rates. (orig.) With 4 figs

  8. 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

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

    International Nuclear Information System (INIS)

    Ho Mer Lin, Doris

    2015-01-01

    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

  10. Age-Specific and Sexual Variability of Morphological and Biomechanical Parameters of the Basilar Artery of Adult People

    Directory of Open Access Journals (Sweden)

    V.N. Nicolenko

    2009-06-01

    Full Text Available For the purpose of studying of morphological and biomechanical parameters of the basilar artery in an experiment on monoaxonic distension by tensile-testing machine Tira Test 28005 (Germany with a loading cell — 100 N we determined general solidity, breaking point, maximum and relative deformation of the artery. Preliminary under a microscope on cross-section cuts we measured the external diameter of the artery, its wall thickness and calculated the diameter of the lumen. In total, 114 basilar arteries (66 — from corpses of men, 48 — from corpses of women have been investigated. They were received not later than 16 hours after autopsy of adult people, whose cause of death has not been connected with a sharp vascular cerebral pathology. The statistically authentic prevalence of the size of wall thickness and general solidity of the men’s artery wall was revealed. In age aspect the external diameter, the lumen diameter and the wall thickness of the basilar artery increase. At the same time the solidity of the wall decreases and its ability to prolongation increases.

  11. On crack interaction effects of in-plane surface cracks using elastic and elastic-plastic finite element analyses

    International Nuclear Information System (INIS)

    Kim, Jong Min; Huh, Nam Su

    2010-01-01

    The crack-tip stress fields and fracture mechanics assessment parameters for a surface crack, such as the elastic stress intensity factor or the elastic-plastic J-integral, can be affected significantly by the adjacent cracks. Such a crack interaction effect due to multiple cracks can alter the fracture mechanics assessment parameters significantly. There are many factors to be considered, for instance the relative distance between adjacent cracks, the crack shape, and the loading condition, to quantify the crack interaction effect on the fracture mechanics assessment parameters. Thus, the current assessment codes on crack interaction effects (crack combination rules), including ASME Sec. XI, BS7910, British Energy R6 and API 579-1/ASME FFS-1, provide different rules for combining multiple surface cracks into a single surface crack. The present paper investigates crack interaction effects by evaluating the elastic stress intensity factor and the elastic-plastic J-integral of adjacent in-plane surface cracks in a plate through detailed 3-dimensional elastic and elastic-plastic finite element analyses. The effects on the fracture mechanics assessment parameters of the geometric parameters, the relative distance between two cracks, and the crack shape are investigated systematically. As for the loading condition, an axial tension is considered. Based on the finite element results, the acceptability of the crack combination rules provided in the existing guidance was investigated, and the relevant recommendations on a crack interaction for in-plane surface cracks are discussed. The present results can be used to develop more concrete guidance on crack interaction effects for crack shape characterization to evaluate the integrity of defective components

  12. 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

  13. Multi-parameter crack tip stress state description for evaluation of nonlinear zone width in silicate composite specimens in component splitting/bending test geometry

    Czech Academy of Sciences Publication Activity Database

    Veselý, V.; Frantík, P.; Sopek, J.; Malíková, L.; Seitl, Stanislav

    2015-01-01

    Roč. 38, č. 2 (2015), s. 200-214 ISSN 8756-758X R&D Projects: GA ČR(CZ) GAP104/11/0833 Institutional support: RVO:68081723 Keywords : near-crack tip fields * Williams series * higher-order terms * stress field * failure criterion * nonlinear zone * quasi-brittle fracture * splitting-bending geometry Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 1.838, year: 2015

  14. Estimation of Leak Rate Through Cracks in Bimaterial Pipes in Nuclear Power Plants

    Directory of Open Access Journals (Sweden)

    Jai Hak Park

    2016-10-01

    Full Text Available The accurate estimation of leak rate through cracks is crucial in applying the leak before break (LBB concept to pipeline design in nuclear power plants. Because of its importance, several programs were developed based on the several proposed flow models, and used in nuclear power industries. As the flow models were developed for a homogeneous pipe material, however, some difficulties were encountered in estimating leak rates for bimaterial pipes. In this paper, a flow model is proposed to estimate leak rate in bimaterial pipes based on the modified Henry–Fauske flow model. In the new flow model, different crack morphology parameters can be considered in two parts of a flow path. In addition, based on the proposed flow model, a program was developed to estimate leak rate for a crack with linearly varying cross-sectional area. Using the program, leak rates were calculated for through-thickness cracks with constant or linearly varying cross-sectional areas in a bimaterial pipe. The leak rate results were then compared and discussed in comparison with the results for a homogeneous pipe. The effects of the crack morphology parameters and the variation in cross-sectional area on the leak rate were examined and discussed.

  15. Password cracking

    OpenAIRE

    Χριστοφάκης, Μιχαήλ Κ.

    2014-01-01

    Information security is the next big thing in computers society because of the rapidly growing security incidents and the outcomes of those. Hacking and cracking existed even from the start of the eighties decade when there was the first step of the interconnection through the internet between humans. From then and ever after there was a big explosion of such incidents mostly because of the worldwide web which was introduced in the early nineties. Following the huge steps forward of computers...

  16. 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)

  17. A Voxel-Based Method for Automated Identification and Morphological Parameters Estimation of Individual Street Trees from Mobile Laser Scanning Data

    Directory of Open Access Journals (Sweden)

    Hongxing Liu

    2013-01-01

    Full Text Available As an important component of urban vegetation, street trees play an important role in maintenance of environmental quality, aesthetic beauty of urban landscape, and social service for inhabitants. Acquiring accurate and up-to-date inventory information for street trees is required for urban horticultural planning, and municipal urban forest management. This paper presents a new Voxel-based Marked Neighborhood Searching (VMNS method for efficiently identifying street trees and deriving their morphological parameters from Mobile Laser Scanning (MLS point cloud data. The VMNS method consists of six technical components: voxelization, calculating values of voxels, searching and marking neighborhoods, extracting potential trees, deriving morphological parameters, and eliminating pole-like objects other than trees. The method is validated and evaluated through two case studies. The evaluation results show that the completeness and correctness of our method for street tree detection are over 98%. The derived morphological parameters, including tree height, crown diameter, diameter at breast height (DBH, and crown base height (CBH, are in a good agreement with the field measurements. Our method provides an effective tool for extracting various morphological parameters for individual street trees from MLS point cloud data.

  18. Dependence of N-polar GaN rod morphology on growth parameters during selective area growth by MOVPE

    Science.gov (United States)

    Li, Shunfeng; Wang, Xue; Mohajerani, Matin Sadat; Fündling, Sönke; Erenburg, Milena; Wei, Jiandong; Wehmann, Hergo-Heinrich; Waag, Andreas; Mandl, Martin; Bergbauer, Werner; Strassburg, Martin

    2013-02-01

    Selective area growth of GaN rods by metalorganic vapor phase epitaxy has attracted great interest due to its novel applications in optoelectronic and photonics. In this work, we will present the dependence of GaN rod morphology on various growth parameters i.e. growth temperature, H2/N2 carrier gas concentration, V/III ratio, total carrier gas flow and reactor pressure. It is found that higher growth temperature helps to increase the aspect ratio of the rods, but reduces the height homogeneity. Furthermore, H2/N2 carrier gas concentration is found to be a critical factor to obtain vertical rod growth. Pure nitrogen carrier gas leads to irregular growth of GaN structure, while an increase of hydrogen carrier gas results in vertical GaN rod growth. Higher hydrogen carrier gas concentration also reduces the diameter and enhances the aspect of the GaN rods. Besides, increase of V/III ratio causes reduction of the aspect ratio of N-polar GaN rods, which could be explained by the relatively lower growth rate on (000-1) N-polar top surface when supplying more ammonia. In addition, an increase of the total carrier gas flow leads to a decrease in the diameter and the average volume of GaN rods. These phenomena are tentatively explained by the change of partial pressure of the source materials and boundary layer thickness in the reactor. Finally, it is shown that the average volume of the N-polar GaN rods keeps a similar value for a reactor pressure PR of 66 and 125 mbar, while an incomplete filling of the pattern opening is observed with PR of 250 mbar. Room temperature photoluminescence spectrum of the rods is also briefly discussed.

  19. Influence of structure on static cracking resistance and fracture of welded joints of pipe steels of strength class K60

    Science.gov (United States)

    Tereshchenko, N. A.; Tabatchikova, T. I.; Yakovleva, I. L.; Makovetskii, A. N.; Shander, S. V.

    2017-07-01

    The static cracking resistance of a number of welded joints made from pipe steels of K60 strength class has been determined. It has been established that the deformation parameter CTOD varies significantly at identical parameters of weldability of steels. The character of fracture has been investigated and the zone of local brittleness of welded joints has been studied. It has been shown that the ability of a metal to resist cracking is determined by the austenite grain size and by the bainite morphology in the region of overheating in the heat-affected zone of a welded joint.

  20. On applicability of crack shape characterization rules for multiple in-plane surface cracks

    International Nuclear Information System (INIS)

    Kim, Jong Min; Choi, Suhn; Park, Keun Bae; Choi, Jae Boong; Huh, Nam Su

    2009-01-01

    The fracture mechanics assessment parameters, such as the elastic stress intensity factor and the elastic-plastic J-integral, for a surface crack can be significantly affected by adjacent cracks. Regarding such an interaction effect, the relative distance between adjacent cracks, crack aspect ratio and loading condition were known to be important factors for multiple cracks, which affects the fracture mechanics assessment parameters. Although several guidance (ASME Sec. XI, BS7910, British Energy R6 and API RP579) on a crack interaction effect (crack combination rule) have been proposed and used for assessing the interaction effect, each guidance provides different rules for combining multiple surface cracks into a single surface crack. Based on the systematic elastic and elastic-plastic finite element analyses, the present study investigated the acceptability of the crack combination rules provided in the existing guidance, and the relevant recommendations on a crack interaction for in-plane surface cracks in a plate were discussed. To quantify the interaction effect, the elastic stress intensity factor and elastic-plastic J-integral along the crack front were used. As for the loading condition, only axial tension was considered. As a result, BS7910 seems to provide the most relevant crack combination rule for in-plane dual surface cracks, whereas API RP579 provides the most conservative results. In particular, ASME Sec. XI still seems to have some room for a revision to shorten the critical distance between two adjacent cracks for a crack combination. The overall tendency of the elastic-plastic analyses results is identical to that of the elastic analyses results.

  1. Torsion of cracked nanorods using a nonlocal elasticity model

    International Nuclear Information System (INIS)

    Loya, J A; Aranda-Ruiz, J; Fernández-Sáez, J

    2014-01-01

    This paper presents a nonlocal cracked-rod model from which we have analysed the torsional vibrations of a carbon nanotube with a circumferential crack. Several types of boundary conditions, including the consideration of a buckyball at the end of the nanotube, have been studied. The nonlocal Eringen elasticity theory is used to formulate the problem. The cracked rod is modelled by dividing the cracked element into two segments connected by a torsional linear spring whose stiffness is related to the crack severity. The effect of the nonlocal small-scale parameter, crack severity, cracked section position, different boundary conditions and attached mass are examined in this work. (paper)

  2. Cracking hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Forwood, G F; Lane, M; Taplay, J G

    1921-10-07

    In cracking and hydrogenating hydrocarbon oils by passing their vapors together with steam over heated carbon derived from shale, wood, peat or other vegetable or animal matter, the gases from the condenser are freed from sulfuretted hydrogen, and preferably also from carbon dioxide, and passed together with oil vapors and steam through the retort. Carbon dioxide may be removed by passage through slaked lime, and sulfuretted hydrogen by means of hydrated oxide of iron. Vapors from high-boiling oils and those from low-boiling oils are passed alternately through the retort, so that carbon deposited from the high-boiling oils is used up during treatment of low-boiling oils.

  3. Initiation and growth of thermal fatigue crack networks in an AISI 304 L type austenitic stainless steel (X2 CrNi18-09)

    International Nuclear Information System (INIS)

    Maillot, V.

    2004-01-01

    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, ΔT 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 morphological

  4. Choked flow through cracks

    International Nuclear Information System (INIS)

    Feburie, V.; Giot, M.; Granger, S.; Seynhaeve, J.M.

    1992-06-01

    The leaks through steam-generator cracks are the subject of a research carried out in cooperation between EDF and UCL. A software called ECREVISSE to predict the mass flow rate has been developed and has been successfully validated. The purpose of the paper is to present the mathematical model used in ECREVISSE as well as some comparison between the results and the presently available data. The model takes into account the persistence of some metastable liquid in the crack and the special flow pattern which appears in such particular geometry. Although the model involves the use of several correlations (friction, heat transfer), no adjustment of parameters against the data has been needed, neither in the single-phase part of the flow, or in the two-phase part. (authors). 8 figs., 1 tab., 20 refs

  5. Cystic fibrosis transmembrane conductance regulator is correlated closely with sperm progressive motility and normal morphology in healthy and fertile men with normal sperm parameters.

    Science.gov (United States)

    Jiang, L-Y; Shan, J-J; Tong, X-M; Zhu, H-Y; Yang, L-Y; Zheng, Q; Luo, Y; Shi, Q-X; Zhang, S-Y

    2014-10-01

    Cystic fibrosis transmembrane conductance regulator (CFTR) has been demonstrated to be expressed in mature spermatozoa and correlated with sperm quality. Sperm CFTR expression in fertile men is higher than that in infertile men suffering from teratospermia, asthenoteratospermia, asthenospermia and oligospermia, but it is unknown whether CFTR is correlated with sperm parameters when sperm parameters are normal. In this study, 282 healthy and fertile men with normal semen parameters were classified into three age groups, group (I): age group of 20-29 years (98 cases, 27.1 ± 6.2), group (II): age group of 30-39 years (142 cases, 33.7 ± 2.6) and group (III): age group of more than or equal to 40 years (42 cases, 44.1 ± 4.6). Sperm concentration, total count and progressive motility were analysed by computer-assisted sperm analysis. Sperm morphology was analysed by modified Papanicolaou staining. Sperm CFTR expression was conducted by indirect immunofluorescence staining. There was a significant positive correlation (P sperm progressive motility (r = 0.221) and normal morphology (r = 0.202), but there were no correlations between sperm CFTR expression and semen volume, sperm concentration, sperm total count as well as male age (P > 0.05). Our findings show that CFTR expression is associated with sperm progressive motility and normal morphology in healthy and fertile men with normal sperm parameters, but not associated with the number of spermatozoa and male age. © 2013 Blackwell Verlag GmbH.

  6. A study on the evolution of crack networks under thermal fatigue loading

    International Nuclear Information System (INIS)

    Kamaya, Masayuki; Taheri, Said

    2008-01-01

    The crack network is a typical cracking morphology caused by thermal fatigue loading. It was pointed out that the crack network appeared under relatively small temperature fluctuations and did not grow deeply. In this study, the mechanism of evolution of crack network and its influence on crack growth was examined by numerical calculation. First, the stress field near two interacting cracks was investigated. It was shown that there are stress-concentration and stress-shielding zones around interacting cracks, and that cracks can form a network under the bi-axial stress condition. Secondly, a Monte Carlo simulation was developed in order to simulate the initiation and growth of cracks under thermal fatigue loading and the evolution of the crack network. The local stress field formed by pre-existing cracks was evaluated by the body force method and its role in the initiation and growth of cracks was considered. The simulation could simulate the evolution of the crack network and change in number of cracks observed in the experiments. It was revealed that reduction in the stress intensity factor due to stress feature in the depth direction under high cycle thermal fatigue loading plays an important role in the evolution of the crack network and that mechanical interaction between cracks in the network affects initiation rather than growth of cracks. The crack network appears only when the crack growth in the depth direction is interrupted. It was concluded that the emergence of the crack network is preferable for the structural integrity of cracked components

  7. Stress corrosion cracking of duplex stainless steels in caustic solutions

    Science.gov (United States)

    Bhattacharya, Ananya

    Duplex stainless steels (DSS) with roughly equal amount of austenite and ferrite phases are being used in industries such as petrochemical, nuclear, pulp and paper mills, de-salination plants, marine environments, and others. However, many DSS grades have been reported to undergo corrosion and stress corrosion cracking in some aggressive environments such as chlorides and sulfide-containing caustic solutions. Although stress corrosion cracking of duplex stainless steels in chloride solution has been investigated and well documented in the literature but the SCC mechanisms for DSS in caustic solutions were not known. Microstructural changes during fabrication processes affect the overall SCC susceptibility of these steels in caustic solutions. Other environmental factors, like pH of the solution, temperature, and resulting electrochemical potential also influence the SCC susceptibility of duplex stainless steels. In this study, the role of material and environmental parameters on corrosion and stress corrosion cracking of duplex stainless steels in caustic solutions were investigated. Changes in the DSS microstructure by different annealing and aging treatments were characterized in terms of changes in the ratio of austenite and ferrite phases, phase morphology and intermetallic precipitation using optical micrography, SEM, EDS, XRD, nano-indentation and microhardness methods. These samples were then tested for general and localized corrosion susceptibility and SCC to understand the underlying mechanisms of crack initiation and propagation in DSS in the above-mentioned environments. Results showed that the austenite phase in the DSS is more susceptible to crack initiation and propagation in caustic solutions, which is different from that in the low pH chloride environment where the ferrite phase is the more susceptible phase. This study also showed that microstructural changes in duplex stainless steels due to different heat treatments could affect their SCC

  8. Hydride effect on crack instability of Zircaloy cladding

    Energy Technology Data Exchange (ETDEWEB)

    Tseng, Che-Chung, E-mail: cctseng@iner.gov.tw [Institute of Nuclear Energy Research, No. 1000, Wunhua Road, Jiaan Village, Lungtan, Township, Taoyuan County 32546, Taiwan (China); Sun, Ming-Hung [Institute of Nuclear Energy Research, No. 1000, Wunhua Road, Jiaan Village, Lungtan, Township, Taoyuan County 32546, Taiwan (China); Chao, Ching-Kong [Department of Mechanical Engineering, National Taiwan University of Science and Technology, 43 Keelung Road, Section 4, Taipei 106, Taiwan (China)

    2014-04-01

    Highlights: • Radial hydrides near the crack tip had a significant effect on crack propagation. • For radial hydrides off the crack line vertically, the effect on crack propagation was notably reduced. • The longer hydride platelet resulted in a remarkable effect on crack propagation. • A long split in the radial hydride precipitate would enhance crack propagation. • The presence of circumferential hydride among radial hydrides may play an important role in crack propagation. - Abstract: A methodology was proposed to investigate the effect of hydride on the crack propagation in fuel cladding. The analysis was modeled based on an outside-in crack with radial hydrides located near its crack tip. The finite element method was used in the calculation; both stress intensity factor K{sub I} and J integral were applied to evaluate the crack stability. The parameters employed in the analysis included the location of radial hydride, hydride dimensions, number of hydrides, and the presence of circumferential hydride, etc. According to our study, the effective distance between a radial hydride and the assumed cladding surface crack for the enhancement of crack propagation proved to be no greater than 0.06 mm. For a hydride not on the crack line, it would induce a relatively minor effect on crack propagation if the vertical distance was beyond 0.05 mm. However, a longer hydride precipitate as well as double radial hydrides could have a remarkable effect on crack propagation. A combined effect of radial and circumferential hydrides was also discussed.

  9. Automatic Crack Detection and Classification Method for Subway Tunnel Safety Monitoring

    Directory of Open Access Journals (Sweden)

    Wenyu Zhang

    2014-10-01

    Full Text Available Cracks are an important indicator reflecting the safety status of infrastructures. This paper presents an automatic crack detection and classification methodology for subway tunnel safety monitoring. With the application of high-speed complementary metal-oxide-semiconductor (CMOS industrial cameras, the tunnel surface can be captured and stored in digital images. In a next step, the local dark regions with potential crack defects are segmented from the original gray-scale images by utilizing morphological image processing techniques and thresholding operations. In the feature extraction process, we present a distance histogram based shape descriptor that effectively describes the spatial shape difference between cracks and other irrelevant objects. Along with other features, the classification results successfully remove over 90% misidentified objects. Also, compared with the original gray-scale images, over 90% of the crack length is preserved in the last output binary images. The proposed approach was tested on the safety monitoring for Beijing Subway Line 1. The experimental results revealed the rules of parameter settings and also proved that the proposed approach is effective and efficient for automatic crack detection and classification.

  10. Automatic crack detection and classification method for subway tunnel safety monitoring.

    Science.gov (United States)

    Zhang, Wenyu; Zhang, Zhenjiang; Qi, Dapeng; Liu, Yun

    2014-10-16

    Cracks are an important indicator reflecting the safety status of infrastructures. This paper presents an automatic crack detection and classification methodology for subway tunnel safety monitoring. With the application of high-speed complementary metal-oxide-semiconductor (CMOS) industrial cameras, the tunnel surface can be captured and stored in digital images. In a next step, the local dark regions with potential crack defects are segmented from the original gray-scale images by utilizing morphological image processing techniques and thresholding operations. In the feature extraction process, we present a distance histogram based shape descriptor that effectively describes the spatial shape difference between cracks and other irrelevant objects. Along with other features, the classification results successfully remove over 90% misidentified objects. Also, compared with the original gray-scale images, over 90% of the crack length is preserved in the last output binary images. The proposed approach was tested on the safety monitoring for Beijing Subway Line 1. The experimental results revealed the rules of parameter settings and also proved that the proposed approach is effective and efficient for automatic crack detection and classification.

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

    International Nuclear Information System (INIS)

    Engelbrecht, J.A.A.; Janzén, E.; Henry, A.; Rooyen, I.J. van

    2014-01-01

    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.

  12. 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.

  13. Stem characteristics of two forage maize (Zea mays L.) cultivars varying in whole plant digestibility. I. Relevant morphological parameters

    NARCIS (Netherlands)

    Boon, E.J.M.C.; Engels, F.M.; Struik, P.C.; Cone, J.W.

    2005-01-01

    The morphology and rumen fermentation kinetics of the maize cultivars (Zea mays L.) Vitaro and Volens were investigated in detail throughout their growing period as a first step towards understanding the relation between plant characteristics and cell wall fermentability of forage maize. Vitaro is

  14. Stress corrosion and corrosion fatigue crack growth monitoring in metals

    International Nuclear Information System (INIS)

    Senadheera, T.; Shipilov, S.A.

    2003-01-01

    Environmentally assisted cracking (including stress corrosion cracking and corrosion fatigue) is one of the major causes for materials failure in a wide variety of industries. It is extremely important to understand the mechanism(s) of environmentally assisted crack propagation in structural materials so as to choose correctly from among the various possibilities-alloying elements, heat treatment of steels, parameters of cathodic protection, and inhibitors-to prevent in-service failures due to stress corrosion cracking and corrosion fatigue. An important step towards understanding the mechanism of environmentally assisted crack propagation is designing a testing machine for crack growth monitoring and that simultaneously provides measurement of electrochemical parameters. In the present paper, a direct current (DC) potential drop method for monitoring crack propagation in metals and a testing machine that uses this method and allows for measuring electrochemical parameters during stress corrosion and corrosion fatigue crack growth are described. (author)

  15. Cracking on anisotropic neutron stars

    Science.gov (United States)

    Setiawan, A. M.; Sulaksono, A.

    2017-07-01

    We study the effect of cracking of a local anisotropic neutron star (NS) due to small density fluctuations. It is assumed that the neutron star core consists of leptons, nucleons and hyperons. The relativistic mean field model is used to describe the core of equation of state (EOS). For the crust, we use the EOS introduced by Miyatsu et al. [1]. Furthermore, two models are used to describe pressure anisotropic in neutron star matter. One is proposed by Doneva-Yazadjiev (DY) [2] and the other is proposed by Herrera-Barreto (HB) [3]. The anisotropic parameter of DY and HB models are adjusted in order the predicted maximum mass compatible to the mass of PSR J1614-2230 [4] and PSR J0348+0432 [5]. We have found that cracking can potentially present in the region close to the neutron star surface. The instability due cracking is quite sensitive to the NS mass and anisotropic parameter used.

  16. 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.

  17. Applied model of through-wall crack of coolant vessels of WWER-type reactors

    International Nuclear Information System (INIS)

    Petrosyan, V.; Hovakimyan, T.; Vardanyan, M.; Khachatryan, A.; Minasyan, K.

    2010-01-01

    We propose an applied-model of Through-Wall Crack (TWC) for WWER-type units primary vessels. The model allows to simulate the main morphological parameters of real TWC, i.e. length, area of inlet and outlet openings, channel depth and small and large size unevenness of the crack surface. The model can be used for developing and improving the coolant-leak detectors for the primary circuit vessels of WWER-units. Also, it can be used for research of the coolant two-phase leakage phenomenon through narrow cracks/channels and thermo-physical processes in heat-insulation layer of the Main Coolant Piping (MCP) during the leak

  18. Numerical Study of Corrosion Crack Opening

    DEFF Research Database (Denmark)

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

    2008-01-01

    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...... 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...

  19. High speed cinematography of cracks spreading under failure of amorphous metallic alloys

    Energy Technology Data Exchange (ETDEWEB)

    Tabachnikova, E.D.; Golovin, Y.I.; Makarov, M.V. [AN Ukrainskoj SSR, Kharkov (Ukraine). Fiziko-Tekhnicheskij Inst. Nizkikh Temperatur; Shibkov, A.A.

    1997-08-01

    The results of experimental investigation of crack propagation velocity in amorphous alloys are presented. It is shown that there exists some correlation between crack velocity and fracture mode and morphology (orig.). 4 refs.

  20. High speed cinematography of cracks spreading under failure of amorphous metallic alloys

    International Nuclear Information System (INIS)

    Tabachnikova, E.D.; Golovin, Y.I.; Makarov, M.V.; Shibkov, A.A.

    1997-01-01

    The results of experimental investigation of crack propagation velocity in amorphous alloys are presented. It is shown that there exists some correlation between crack velocity and fracture mode and morphology (orig.)

  1. Compressive failure with interacting cracks

    International Nuclear Information System (INIS)

    Yang Guoping; Liu Xila

    1993-01-01

    The failure processes in concrete and other brittle materials are just the results of the propagation, coalescence and interaction of many preexisting microcracks or voids. To understand the real behaviour of the brittle materials, it is necessary to bridge the gap from the relatively matured one crack behaviour to the stochastically distributed imperfections, that is, to concern the crack propagation and interaction of microscopic mechanism with macroscopic parameters of brittle materials. Brittle failure in compression has been studied theoretically by Horii and Nemat-Nasser (1986), in which a closed solution was obtained for a preexisting flaw or some special regular flaws. Zaitsev and Wittmann (1981) published a paper on crack propagation in compression, which is so-called numerical concrete, but they did not take account of the interaction among the microcracks. As for the modelling of the influence of crack interaction on fracture parameters, many studies have also been reported. Up till now, some researcher are working on crack interaction considering the ratios of SIFs with and without consideration of the interaction influences, there exist amplifying or shielding effects of crack interaction which are depending on the relative positions of these microcracks. The present paper attempts to simulate the whole failure process of brittle specimen in compression, which includes the complicated coupling effects between the interaction and propagation of randomly distributed or other typical microcrack configurations step by step. The lengths, orientations and positions of microcracks are all taken as random variables. The crack interaction among many preexisting random microcracks is evaluated with the help of a simple interaction matrix (Yang and Liu, 1991). For the subcritically stable propagation of microcracks in mixed mode fracture, fairly known maximum hoop stress criterion is adopted to compute branching lengths and directions at each tip of the crack

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

    KAUST Repository

    Al-Qadhi, Muneer; Merah, N.; Mezghani, Khaled S.; Khan, Zafarullah; Gasem, Zuhair Mattoug Asad; Sougrat, Rachid

    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.

  3. 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.

  4. 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.

  5. 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.

  6. Crack turning in integrally stiffened aircraft structures

    Science.gov (United States)

    Pettit, Richard Glen

    resistance orthotropy---a second-order linear elastic method with a characteristic length parameter to incorporate T-stress/process-zone effects, and an elastic-plastic method that uses the Crack Tip Opening Displacement (CTOD) to determine the failure response. Together with a novel method for obtaining enhanced accuracy T-stress calculations, these methods are incorporated into an adaptive-mesh, finite-element fracture simulation code. A total of 43 fracture tests using symmetrically and asymmetrically loaded double cantilever beam specimens were run to develop crack turning parameters and compare predicted and observed crack paths.

  7. Surface morphology of laser tracks used for forming the non-smooth biomimetic unit of 3Cr2W8V steel under different processing parameters

    International Nuclear Information System (INIS)

    Zhang Zhihui; Zhou Hong; Ren Luquan; Tong Xin; Shan Hongyu; Li Xianzhou

    2008-01-01

    Aiming to form the high quality of non-smooth biomimetic unit, the influence of laser processing parameters (pulse energy, pulse duration, frequency and scanning speed in the present work) on the surface morphology of scanned tracks was studied based on the 3Cr2W8V die steel. The evolution of the surface morphology was explained according to the degree of melting and vaporization of surface material, and the trend of mean surface roughness and maximum peak-to-valley height. Cross-section morphology revealed the significant microstructural characteristic of the laser-treated zone used for forming the functional zone on the biomimetic surface. Results showed that the combination of pulse energy and pulse duration plays a major role in determining the local height difference on the irradiated surface and the occurrence of melting or vaporization. While frequency and scanning speed have a minor effect on the change of the surface morphology, acting mainly by the different overlapping amount and overlapping mode. The mechanisms behind these influences were discussed, and schematic drawings were introduced to describe the mechanisms

  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. 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.)

  10. Path stability of a crack with an eigenstrain

    International Nuclear Information System (INIS)

    Beom, Hyeon Gyu; Kim, Yu Hwan; Cho, Chong Du; Kim, Chang Boo

    2006-01-01

    A slightly curved crack with an eigenstrain is considered. Solutions for a slightly curved crack in a linear isotropic material under asymptotic loading as well as for a slightly curved crack in a linear isotropic material with a concentrated force are obtained from perturbation analyses, which are accurate to the first order of the parameter representing the non-straightness. Stress intensity factors for a slightly curved crack with an eigenstrain are obtained from the perturbation solutions by using a body force analogy. Particular attention is given to the crack path stability under mode I loading. A new parameter of crack path stability is proposed for a crack with an eigenstrain. The path stability of a crack with steady state growth in a transforming material and a ferroelectric material is examined

  11. Dynamic experiments on cracked pipes

    International Nuclear Information System (INIS)

    Petit, M.; Brunet, G.; Buland, P.

    1991-01-01

    In order to apply the leak before break concept to piping systems, the behavior of cracked pipes under dynamic, and especially seismic loading must be studied. In a first phase, an experimental program on cracked stainless steel pipes under quasi-static monotonic loading has been conducted. In this paper, the dynamic tests on the same pipe geometry are described. These tests have been performed on a shaking table with a mono frequency input signal. The main parameter of the tests is the frequency of excitation versus the frequency of the system

  12. Quenching cracks - formation and possible causes

    International Nuclear Information System (INIS)

    Macherauch, E.; Mueller, H.; Voehringer, O.

    1976-01-01

    The most important principles controlling the martensitic hardening of steels containing carbon are presented, and their effects on the cracks formed by tempering are discussed. Micro-crack formation, influenced by any increase in the carbon content, is dependent on the variations of martensitic morphology; this factor is of decisive importance. Apart from micro residual stresses, macro residual stresses become increasingly involved in the crack development. This is dependent on the given content of carbon and increase in the dimensions of the samples. Based on the empirical values gained from experience about cracks formed by tempering and using a schematic diagram, the constructive influences on the propensity to cracks formed by tempering, with regard to materials and processing, are evaluated. Also the effects of thermic, mechanical and chemical after-treatments upon the propensity to tempering cracks are discussed. In conclusion, the problem of the formation of cracks in hardened parts, i.e. the elongation of the cracks under static stress, is treated briefly. (orig.) [de

  13. Comparison of morphological and kinetic parameters in distinction of benign and malignant breast lesions in dynamic contrast enhanced magnetic resonance imaging

    Directory of Open Access Journals (Sweden)

    Direnç Özlem Aksoy

    2013-12-01

    Full Text Available Objective: To evaluate the value of qualitative morphologicaland kinetic data and quantitative kinetic data indistinction of malignancy in dynamic contrast enhancedmagnetic resonance imaging (DCE-MRI of the breast.Methods: DCE-MRIs of 49 subjects were evaluated.Morphological and contrast enhancement parameters of95 lesions were recorded in these subjects. Post-contrastkinetic behavior of these lesions were also investigated.Among the quantitative parameters, relative enhancements(E1, E2, Epeak, time-to-peak (Tpeak, slope ofcurve (Slope, signal enhancement ratio (SER, and maximumintensity time ratio (MITR were calculated. Theseresults were compared with the pathological diagnosis.Results: Spiculated contour (100%, rim enhancement(97.87%, irregular shape (95.74%, and irregular margin(91.49% were the most specific morphological featuresof malignancy in mass lesions. In non-mass lesions, focalzone (91.49% was the most specific feature of malignancy.74.5% of the benign lesions showed type 1, 77.1%of the malignant lesions showed type 2 and 3 curves accordingto the kinetic curve evaluation. All quantitativeparameters except Epeak were found to be statisticallysignificant in distinction of malignancy.Conclusion: None of the morphological features of thebenign lesions were found to be significantly specific.More specific features can be described for malignantlesions. Early behavior of the kinetic curve is not usefulfor diagnosis of malignancy but the intermediate and latebehavior gives useful information. Quantitative data involvedin this study might be promising.Key words: Morphological, kinetic, breast lesions, magnetic resonance imaging, dynamic

  14. Comparison of Selected Morphological, Rheological and Biochemical Parameters of Winter Swimmers' Blood at the End of One Winter Swimming Season and at the Beginning of Another.

    Science.gov (United States)

    Teległów, Aneta; Marchewka, Jakub; Tabarowski, Zbigniew; Rembiasz, Konrad; Głodzik, Jacek; Scisłowska-Czarnecka, Anna

    2015-01-01

    The aim of the study was to examine potential differences in the morphological, rheological and biochemical blood parameters of winter swimmers who remained physically active during the period between the end of one winter swimming season and the beginning of another. The study included a group of healthy winter swimmers (n = 17, all between 30 and 60 years of age). Six months following the end of winter season, the levels of mean corpuscular hemoglobin concentration and mean corpuscular hemoglobin turned out to be significantly higher, while erythrocyte count and hematocrit level significantly lower than at the baseline. Moreover, the break in winter swimming was reflected by a significant increase in median erythrocyte elongation index at all shear stress levels ≥ 1.13 Pa. The only significant changes in biochemical parameters of the blood pertained to an increase in the concentration of transferrin and to a decrease in the total protein, albumin and beta-1 globulin concentrations. Seasonal effort of winter swimmers between the end of one winter swimming season and the beginning of another has a positive influence on morphological, rheological and biochemical blood parameters.

  15. Growth of different phases and morphological features of MnS thin films by chemical bath deposition: Effect of deposition parameters and annealing

    Energy Technology Data Exchange (ETDEWEB)

    Hannachi, Amira, E-mail: amira.hannachi88@gmail.com; Maghraoui-Meherzi, Hager

    2017-03-15

    Manganese sulfide thin films have been deposited on glass slides by chemical bath deposition (CBD) method. The effects of preparative parameters such as deposition time, bath temperature, concentration of precursors, multi-layer deposition, different source of manganese, different complexing agent and thermal annealing on structural and morphological film properties have been investigated. The prepared thin films have been characterized using the X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). It exhibit the metastable forms of MnS, the hexagonal γ-MnS wurtzite phase with preferential orientation in the (002) plane or the cubic β-MnS zinc blende with preferential orientation in the (200) plane. Microstructural studies revealed the formation of MnS crystals with different morphologies, such as hexagons, spheres, cubes or flowers like. - Graphical Abstract: We report the preparation of different phases of manganese sulfide thin films (γ, β and α-MnS) by chemical bath deposition method. The effects of deposition parameters such as deposition time and temperature, concentrations of precursors and multi-layer deposition on MnS thin films structure and morphology were investigated. The influence of thermal annealing under nitrogen atmosphere at different temperature on MnS properties was also studied. Different manganese precursors as well as different complexing agent were also used. - Highlights: • γ and β-MnS films were deposited on substrate using the chemical bath deposition. • The effect of deposition parameters on MnS film properties has been investigated. • Multi-layer deposition was also studied to increase film thickness. • The effect of annealing under N{sub 2} at different temperature was investigated.

  16. Crack Growth Properties of Sealing Glasses

    Science.gov (United States)

    Salem, Jonathan A.; Tandon, R.

    2008-01-01

    The crack growth properties of several sealing glasses were measured using constant stress rate testing in 2% and 95% RH (relative humidity). Crack growth parameters measured in high humidity are systematically smaller (n and B) than those measured in low humidity, and velocities for dry environments are approx. 100x lower than for wet environments. The crack velocity is very sensitivity to small changes in RH at low RH. Confidence intervals on parameters that were estimated from propagation of errors were comparable to those from Monte Carlo simulation.

  17. Modified Dugdale cracks and Fictitious cracks

    DEFF Research Database (Denmark)

    Nielsen, Lauge Fuglsang

    1998-01-01

    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...... areas, so-called fictitious cracks, in front of the crack.The Modified Dugdale theory presented in this paper is also based on the concept of Dugdale cracks. Any cohesive stress distribution, however, can be considered in front of the crack. Formally the strength of a material weakened by a modified...... 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...

  18. 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.

  19. Dislocation structures around crack tips of fatigued polycrystalline copper

    International Nuclear Information System (INIS)

    Kaneko, Yoshihisa; Ishikawa, Masao; Hashimoto, Satoshi

    2005-01-01

    Dislocation structures near fatigue cracks of polycrystalline copper specimens were analyzed using the electron channelling contrast imaging (ECCI) technique. Prior to the ECCI observations, optical microscopy was conducted to classify the fatigue crack morphologies into several kinds. It was found that the dislocation structures were correlated with the slip morphologies observed using the optical microscope. The cell structure almost corresponded to the severely deformed plastic zone where the individual slip bands could not be identified. The labyrinth dislocation structure was detected at the double-slip region. Ladder-like dislocation structure was detected ahead of the Stage I type fatigue crack. Hence, it can be said that the persistent slip band (PSB) was a favorable crack path. However, the microscopic route of the crack growth was not along the PSB but along the cell structure, which was developed locally in the vicinity of the crack tip

  20. Comparison of cryopreserved human sperm in vapor and liquid phases of liquid nitrogen: effect on motility parameters, morphology, and sperm function.

    Science.gov (United States)

    Punyatanasakchai, Piyaphan; Sophonsritsuk, Areephan; Weerakiet, Sawaek; Wansumrit, Surapee; Chompurat, Deonthip

    2008-11-01

    To compare the effects of cryopreserved sperm in vapor and liquid phases of liquid nitrogen on sperm motility, morphology, and sperm function. Experimental study. Andrology laboratory at Ramathibodi Hospital, Thailand. Thirty-eight semen samples with normal motility and sperm count were collected from 38 men who were either patients of an infertility clinic or had donated sperm for research. Each semen sample was divided into two aliquots. Samples were frozen with static-phase vapor cooling. One aliquot was plunged into liquid nitrogen (-196 degrees C), and the other was stored in vapor-phase nitrogen (-179 degrees C) for 3 days. Thawing was performed at room temperature. Motility was determined by using computer-assisted semen analysis, sperm morphology was determined by using eosin-methylene blue staining, and sperm function was determined by using a hemizona binding test. Most of the motility parameters of sperm stored in the vapor phase were not significantly different from those stored in the liquid phase of liquid nitrogen, except in amplitude of lateral head displacement. The percentages of normal sperm morphology in both vapor and liquid phases also were not significantly different. There was no significant difference in the number of bound sperm in hemizona between sperm cryopreserved in both vapor and liquid phases of liquid nitrogen. Cryopreservation of human sperm in a vapor phase of liquid nitrogen was comparable to cryopreservation in a liquid phase of liquid nitrogen.

  1. Nucleation and growth of fatigue cracks in magnesium alloys of different structure

    International Nuclear Information System (INIS)

    Grinberg, N.M.; Serdyuk, V.A.; Malinkina, T.I.; Kamyshkov, A.S.

    1982-01-01

    Duration of the fatigue crack nucleation and growth rate have been in a wide range of stress intensity factor variations for MA2-1, MA2-1 hp (higher purity), MA12, (T2, T6 and T8), MA15, IMB6, MA21 magnesium alloys of different composition and structural state. The threshold and criti- cal values of stress intensity factors, Ksub(th) and Ksub(fc) are determined for those alloys, and morphology of fracture is studied at different stages of crack growth. Duration of the nucleation stage of a fatigue crack, the rate and micromechanisms of its growth are found to depedend on alloying and structural state of magnesium alloys. The best crack resistance characteristics has the MA2-1 alloy, the poorest - MA12 (T2) alloy. It is stated that thermal treatment by hardening and ageing increases the resistance of the MA12 alloy to fatigue fracture and the MA2-1 alloy of higher purity gives poorer parameters of crack resistance [ru

  2. The Role of Large-Format Histopathology in Assessing Subgross Morphological Prognostic Parameters: A Single Institution Report of 1000 Consecutive Breast Cancer Cases

    Directory of Open Access Journals (Sweden)

    Tibor Tot

    2012-01-01

    Full Text Available Breast cancer subgross morphological parameters (disease extent, lesion distribution, and tumor size provide significant prognostic information and guide therapeutic decisions. Modern multimodality radiological imaging can determine these parameters with increasing accuracy in most patients. Large-format histopathology preserves the spatial relationship of the tumor components and their relationship to the resection margins and has clear advantages over traditional routine pathology techniques. We report a series of 1000 consecutive breast cancer cases worked up with large-format histology with detailed radiological-pathological correlation. We confirmed that breast carcinomas often exhibit complex subgross morphology in both early and advanced stages. Half of the cases were extensive tumors and occupied a tissue space ≥40 mm in its largest dimension. Because both in situ and invasive tumor components may exhibit unifocal, multifocal, and diffuse lesion distribution, 17 different breast cancer growth patterns can be observed. Combining in situ and invasive tumor components, most cases fall into three aggregate growth patterns: unifocal (36%, multifocal (35%, and diffuse (28%. Large-format histology categories of tumor size and disease extent were concordant with radiological measurements in approximately 80% of the cases. Noncalcified, low-grade in situ foci, and invasive tumor foci <5 mm were the most frequent causes of discrepant findings.

  3. Anodization parameters influencing the morphology and electrical properties of TiO{sub 2} nanotubes for living cell interfacing and investigations

    Energy Technology Data Exchange (ETDEWEB)

    Khudhair, D. [Deakin University, Waurn Ponds Campus, Vic 3216 (Australia); Bhatti, A., E-mail: asim.bhatti@deakin.edu.au [Deakin University, Waurn Ponds Campus, Vic 3216 (Australia); Li, Y. [RMIT University, Bundoora, Victoria 3083 (Australia); Hamedani, H. Amani; Garmestani, H. [Georgia Institute of Technology, GA 30332 (United States); Hodgson, P.; Nahavandi, S. [Deakin University, Waurn Ponds Campus, Vic 3216 (Australia)

    2016-02-01

    Nanotube structures have attracted tremendous attention in recent years in many applications. Among such nanotube structures, titania nanotubes (TiO{sub 2}) 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 TiO{sub 2} 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 TiO{sub 2} directly impacts the biocompatibility aspects of the titanium in terms of cell proliferation, adhesion and mineralization. Similarly, TiO{sub 2} nanotube wall thickness of 30–40 nm 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. - Highlights: • We spotlight on the importance of TiO{sub 2} nanotubes in medical applications. • The influence of nanotubes morphology on the electrical conductivity and biocompatibility properties • Influence of key anodizing parameters on the nanotube morphology • Methods to improve the electrical conductivity of TiO{sub 2} nanotubes • Potential of employment of TiO{sub 2} nanotubes as micro–nano-electrodes.

  4. Cocaine (Coke, Crack) Facts

    Science.gov (United States)

    ... That People Abuse » Cocaine (Coke, Crack) Facts Cocaine (Coke, Crack) Facts Listen Cocaine is a white ... 69 KB) "My life was built around getting cocaine and getting high." ©istock.com/ Marjot Stacey is ...

  5. 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.

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

    Science.gov (United States)

    Niel, A.; Deschaux-Beaume, F.; Bordreuil, C.; Fras, G.

    2010-06-01

    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.

  7. Pulsed electrodeposition of cobalt nanoparticles on copper: influence of the operating parameters on size distribution and morphology

    International Nuclear Information System (INIS)

    Pagnanelli, Francesca; Altimari, Pietro; Bellagamba, Marco; Granata, Giuseppe; Moscardini, Emanuela; Schiavi, Pier Giorgio; Toro, Luigi

    2015-01-01

    Cobalt nanoparticles were synthesized by pulsed electrodeposition on copper substrate. Scanning electron microscopy and image analysis were used to determine morphology and particle size distribution of nanoparticle populations obtained in different operating conditions. After preliminary tests, t on and t off were set at 50 and 300 ms respectively to obtain distinct nanoparticles and avoid dendritic structures. Experimental tests were performed according to two partially superimposed factorial designs with two factors at two levels. First factorial design investigated the effect of current density (I = 10 and 50 mA/cm 2 ) and discharged cobalt (Q = 2.5 × 10 −3 and 1.0 × 10 −2 C); second factorial design investigated the effect of cobalt concentration (C 0 = 0.01 and 0.1 M) for the same two levels of Q. For optimized value of t on /t off , square and hexagonal shaped nanoparticles were obtained. Statistical analysis evidenced that, for C 0 = 0.1 mol/L, current density is the most influencing factor on mean size: increasing I from 10 to 50 mA/cm 2 determined a diminution of mean size of 240 nm. For the same cobalt concentration, increasing the deposition time (Q) determined an increase of mean size of 60 nm. Diminishing the initial cobalt concentration from 0.1 to 0.01 mol/L determined an increase of mean size from 10 nm to 36 nm. For C 0 = 0.01 mol/L nanoparticles grow reaching an optimal size (36 nm) and then, increasing the time of deposition, optimal sized subunits tend to aggregate. As for polydispersity of nanoparticles, statistical tests denoted that increasing I determined significant reduction of variance, while increasing the time of deposition determined a significant increase of variance

  8. 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.

  9. Continuum damage mechanics analysis of crack tip zone

    International Nuclear Information System (INIS)

    Yinchu, L.; Jianping, Z.

    1989-01-01

    The crack tip field and its intensity factor play an important role in fracture mechanics. Generally, the damage such as microcracks, microvoids etc. will initiate and grow in materials as the cracked body is subjected to external loadings, especially in the crack tip zone. The damage evolution will load to the crack tip damage field and the change of the stress, strain and displacement fields of cracks tip zone. In this paper, on the basis of continuum damage mechanics, the authors have derived the equations which the crack tip field and its intensity factor must satisfy in a loading process, calculated the angle distribution curves of stress, strain and displacement fields in a crack tip zone and have compared them with the corresponding curves of HRR field and linear elastic field in undamaged materials. The equations of crack tip field intensity factors have been solved and its solutions give the variation of the field intensity factors with the loading parameter

  10. High temperature cracking of steels: effect of geometry on creep crack growth laws

    International Nuclear Information System (INIS)

    Kabiri, M.R.

    2003-12-01

    This study was performed at Centre des Materiaux de l'Ecole des Mines de Paris. It deals with identification and transferability of high temperature creep cracking laws of steels. A global approach, based on C * and J non-linear fracture mechanics parameters has been used to characterize creep crack initiation and propagation. The studied materials are: the ferritic steels 1Cr-1Mo-1/4V (hot and cold parts working at 540 and 250 C) used in the thermal power stations and the austenitic stainless steel 316 L(N) used in the nuclear power stations. During this thesis a data base was setting up, it regroups several tests of fatigue, creep, creep-fatigue, and relaxation. Its particularity is to contain several creep tests (27 tests), achieved at various temperatures (550 to 650 C) and using three different geometries. The relevance of the C * parameter to describe the creep crack propagation was analysed by a means of systematic study of elasto-viscoplastic stress singularities under several conditions (different stress triaxiality). It has been shown that, besides the C * parameter, a second non singular term, denoted here as Q * , is necessary to describe the local variables in the vicinity of the crack tip. Values of this constraint parameter are always negative. Consequently, application of typical creep crack growth laws linking the creep crack growth rate to the C * parameter (da/dt - C * ), will be conservative for industrial applications. Furthermore, we showed that for ferritic steels, crack incubation period is important, therefore a correlation of Ti - C * type has been kept to predict crack initiation time Ti. For the austenitic stainless steel, the relevant stage is the one of the crack propagation, so that a master curve (da/dt - C * ), using a new data analysis method, was established. Finally, the propagation of cracks has been simulated numerically using the node release technique, allowing to validate analytical expressions utilised for the experimental

  11. Effects of gamma rays on rat testis tissue according to the morphological parameters and immunohistochemistry: radioprotective role of silymarin.

    Science.gov (United States)

    Marzban, Mohsen; Anjamshoa, Maryam; Jafari, Parnia; Masoumi, Hossien; Ahadi, Reza; Fatehi, Daryoush

    2017-06-01

    To determine the radioprotective effects of Silymarin in adult male Sprague-Dawley rats irradiated with γ-rays. The present experimental study was performed in Tehran University of Medical Sciences, Tehran, Iran from December 2009 to March 2010. The study was performed on 40 rats, which were randomly and equally divided into four groups: 1) control group: neither received Silymarin nor irradiated with γ-rays; 2) γ-irradiation group: testis region exposed to 2Gy of γ-rays; 3) Silymarin & γ-irradiation: rats received 100 mg/kg of Silymarin 24hrs before exposure to 2Gy of γ-rays; 4) Silymarin & γ-irradiation: rats received 200 mg/kg of Silymarin 24hrs before exposure to 2Gy of γ-rays. After animal experiments and preparing the tissue sections, different histological and histomorphological parameters of seminiferous tubules and the biological characteristics of Leydig cells were evaluated applying quantitative assessment, Johnson scoring, and Leydig cell apoptosis assay by TUNEL method. The data were analyzed applying ANOVA and Tukey's post hoc test, using SPSS software (V.19). Irradiation of 2 Gy γ-rays to the testis of the rats significantly affected the frequency of spermatogonia, primary spermatocyte, round spermatid, spermatozoa, seminiferous tube and lumen diameters, thickness of the epithelium, Leydig cell nuclear diameter and volume, epithelium height, and apoptotic cells (p<0.05). However, administration of Silymarin improved the mentioned parameters specifically in 200 mg/kg of dosage. Silymarin could act as a potent radioprotector and it can be used in modulation as well as improvement to radiation therapy to prevent male reproductive function, specifically seminiferous tubules in an animal model; however, its molecular mechanism is still not clear and needs more molecular researches.

  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. Crack initiation under generalized plane strain conditions

    International Nuclear Information System (INIS)

    Shum, D.K.M.; Merkle, J.G.

    1991-01-01

    A method for estimating the decrease in crack-initiation toughness, from a reference plane strain value, due to positive straining along the crack front of a circumferential flaw in a reactor pressure vessel is presented in this study. This method relates crack initiation under generalized plane strain conditions with material failure at points within a distance of a few crack-tip-opening displacements ahead of a crack front, and involves the formulation of a micromechanical crack-initiation model. While this study is intended to address concerns regarding the effects of positive out-of- plane straining on ductile crack initiation, the approach adopted in this work can be extended in a straightforward fashion to examine conditions of macroscopic cleavage crack initiation. Provided single- parameter dominance of near-tip fields exists in the flawed structure, results from this study could be used to examine the appropriateness of applying plane strain fracture toughness to the evaluation of circumferential flaws, in particular to those in ring-forged vessels which have no longitudinal welds. In addition, results from this study could also be applied toward the analysis of the effects of thermal streaming on the fracture resistance of circumferentially oriented flaws in a pressure vessel. 37 refs., 8 figs., 1 tab

  14. 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.

  15. 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

  16. Crack propagation and fracture in silicon carbide

    International Nuclear Information System (INIS)

    Evans, A.G.; Lange, F.F.

    1975-01-01

    Fracture mechanics and strength studies performed on two silicon carbides - a hot-pressed material (with alumina) and a sintered material (with boron) - have shown that both materials exhibit slow crack growth at room temperature in water, but only the hot-pressed material exhibits significant high temperature slow crack growth (1000 to 1400 0 C). A good correlation of the observed fracture behaviour with the crack growth predicted from the fracture mechanics parameters shows that effective failure predictions for this material can be achieved using macro-fracture mechanics data. (author)

  17. 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)

  18. Developments in delayed hydride cracking in zirconium alloys

    International Nuclear Information System (INIS)

    Puls, Manfred P.

    2008-01-01

    Delayed hydride cracking (DHC) is a process of diffusion assisted localized hydride embrittlement at flaws or regions of high stress. Models of DHC propagation and initiation have been developed that capture the essential elements of this phenomenon in terms of parameters describing processes occurring at the micro-scale. The models and their predictions of experimental results applied to Zr alloys are assessed. The propagation model allows rationalization of the effect of direction of approach to temperature and of the effect of the state and morphology of the beta phase in Zr-2.5Nb on DHC velocity. The K I dependence of the DHC velocity can only be approximately rationalized by the propagation models. This is thought to be because these models approximate the DHC velocity by a constant and shape-invariant rate of growth of the hydride at the flaw and have not incorporated a coupling between the applied stress field due to the flaw alone and the precipitated hydrides that would result in a variation of the shape and density of the hydrided region with K I . Separately, models have been developed for DHC initiation at cracks and blunt flaws. Expressions are obtained for the threshold stress intensity factor, K IH , for DHC initiation at a crack. A model for K IH has been used to rationalize the experimental result that DHC initiation is not possible above a certain temperature, even when hydrides can form at the crack tip. For blunt flaws with root radii in the μm range, and engineering process zone procedure has been derived to determine the initiation conditions requiring that both a critical stress and a critical flaw tip displacement must be achieved for hydride fracture. The engineering process zone procedure takes account of the dependence of DHC initiation on the flaw's root radius. Although all of the foregoing models are capable of describing the essential features of DHC, they are highly idealized and in need of further refinement. (author)

  19. 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,

  20. Cadmium, lead and mercury concentrations and their influence on morphological parameters in blood donors from different age groups from southern Poland.

    Science.gov (United States)

    Janicka, Monika; Binkowski, Łukasz J; Błaszczyk, Martyna; Paluch, Joanna; Wojtaś, Włodzimierz; Massanyi, Peter; Stawarz, Robert

    2015-01-01

    Due to industrial development, environmental contamination with metals increases which leads to higher human exposure via air, water and food. In order to evaluate the level of the present exposition, the concentrations of metals can be measured in such biological materials as human blood. In this study, we assessed the concentrations of cadmium (Cd), mercury (Hg) and lead (Pb) in blood samples from male blood donors from southern Poland (Europe) born in 1994 (n=30) and between 1947 and 1955 (n=30). Higher levels of Pb were seen in the group of older men (4.48 vs 2.48μg/L), whereas the Hg levels were lower (1.78 vs 4.28μg/L). Cd concentrations did not differ between age groups (0.56μg/L). The levels of Cd and Pb in older donors were significantly correlated (Spearman R 0.5135). We also observed a positive correlation between the number of red blood cells (RBC) and Hg concentrations in the older group (Spearman R 0.4271). Additionally, we noted numerous correlations among morphological parameters. Based on our results, we can state that metals influence the blood morphology and their concentrations in blood vary among age groups. Copyright © 2014 Elsevier GmbH. All rights reserved.

  1. Influence of Thermal Parameters, Microstructure, and Morphology of Si on Machinability of an Al–7.0 wt.% Si Alloy Directionally Solidified

    Directory of Open Access Journals (Sweden)

    Cássio A. P. Silva

    2018-01-01

    Full Text Available This study aims to correlate the influence of thermal and microstructural parameters such as growth rate and cooling rate (VL and TR and secondary dendrite spacing (λ2, respectively, in the machining cutting temperature and tool wear on the necking process of the Al–7 wt.% Si alloy solidified in a horizontal directional device using a high-speed steel with a tungsten tool. The dependence of λ2 on VL and TR and dependence of the maximum cutting temperature and maximum flank wear on λ2 were determined by power experimental laws given by λ2 = constant (VL and TRn and TMAX, VBMAX = constant (λ2n, respectively. The maximum cutting temperature increased with increasing of λ2. The opposite occurred with the maximum flank wear. The role of Si alloying element on the aforementioned results has also been analyzed. A morphological change of Si along the solidified ingot length has been observed, that is, the morphology of Si in the eutectic matrix has indicated a transition from particles to fibers along the casting together with an increase of the particle diameters with the position from the metal/mold interface.

  2. Refinement and evaluation of crack-opening-area analyses for circumferential through-wall cracks in pipes

    International Nuclear Information System (INIS)

    Rahman, S.; Brust, F.; Ghadiali, N.; Krishnaswamy, P.; Wilkowski, G.; Choi, Y.H.; Moberg, F.; Brickstad, B.

    1995-04-01

    Leak-before-break (LBB) analyses for circumferentially cracked pipes are currently being conducted in the nuclear industry to justify elimination of pipe whip restraints and jet impingement shields which are present because of the expected dynamic effects from pipe rupture. The application of the LBB methodology frequently requires calculation of leak rates. These leak rates depend on the crack-opening area of a through-wall crack in the pipe. In addition to LBB analyses, which assume a hypothetical flaw size, there is also interest in the integrity of actual leaking cracks corresponding to current leakage detection requirements in NRC Regulatory Guide 1.45, or for assessing temporary repair of Class 2 and 3 pipes that have leaks as are being evaluated in ASME Section 11. This study was requested by the NRC to review, evaluate, and refine current analytical models for crack-opening-area analyses of pipes with circumferential through-wall cracks. Twenty-five pipe experiments were analyzed to determine the accuracy of the predictive models. Several practical aspects of crack-opening such as; crack-face pressure, off-center cracks, restraint of pressure-induced bending, cracks in thickness transition regions, weld residual stresses, crack-morphology models, and thermal-hydraulic analysis, were also investigated. 140 refs., 105 figs., 41 tabs

  3. 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)

  4. Influence of MSD crack pattern on the residual strength of flat stiffened sheets

    Science.gov (United States)

    Nilsson, K.-F.

    A parameter study of the residual strength for a multiple site damaged (MSD) stiffened sheet is presented. The analysis is based on an elastic-plastic fracture analysis using the yield-strip model for interaction between a lead crack and the smaller MSD cracks. Two crack growth criteria, one with a pronounced crack growth resistance and one with no crack growth resistance and five different MSD crack patterns, are analysed for different sizes of the lead crack and the smaller MSD cracks. The analysis indicates that the residual strength reduction depends on all these parameters and that MSD may totally erode the crack arrest capability of a tear strap. Another important outcome is that for certain combinations also very small MSD cracks may induce a significant residual strength reduction.

  5. Investigation of Helicopter Longeron Cracks

    Science.gov (United States)

    Newman, John A.; Baughman, James; Wallace, Terryl A.

    2009-01-01

    Four cracked longerons, containing a total of eight cracks, were provided for study. Cracked regions were cut from the longerons. Load was applied to open the cracks, enabling crack surface examination. Examination revealed that crack propagation was driven by fatigue loading in all eight cases. Fatigue crack initiation appears to have occurred on the top edge of the longerons near geometric changes that affect component bending stiffness. Additionally, metallurgical analysis has revealed a local depletion in alloying elements in the crack initiation regions that may be a contributing factor. Fatigue crack propagation appeared to be initially driven by opening-mode loading, but at a crack length of approximately 0.5 inches (12.7 mm), there is evidence of mixed-mode crack loading. For the longest cracks studied, shear-mode displacements destroyed crack-surface features of interest over significant portions of the crack surfaces.

  6. Crack detecting method

    International Nuclear Information System (INIS)

    Narita, Michiko; Aida, Shigekazu

    1998-01-01

    A penetration liquid or a slow drying penetration liquid prepared by mixing a penetration liquid and a slow drying liquid is filled to the inside of an artificial crack formed to a member to be detected such as of boiler power generation facilities and nuclear power facilities. A developing liquid is applied to the periphery of the artificial crack on the surface of a member to be detected. As the slow-drying liquid, an oil having a viscosity of 56 is preferably used. Loads are applied repeatedly to the member to be detected, and when a crack is caused to the artificial crack, the permeation liquid penetrates into the crack. The penetration liquid penetrated into the crack is developed by the developing liquid previously coated to the periphery of the artificial crack of the surface of the member to be detected. When a crack is caused, since the crack is developed clearly even if it is a small opening, the crack can be recognized visually reliably. (I.N.)

  7. The elastic-plastic failure assessment diagram of surface cracked structure

    International Nuclear Information System (INIS)

    Ning, J.; Gao, Q.

    1987-01-01

    The simplified NLSM is able to calculate the EPFM parameters and failure assessment curve for the surface cracked structure correctly and conveniently. The elastic-plastic failure assessment curve of surface crack is relevant to crack geometry, loading form and material deformation behaviour. It is necessary to construct the EPFM failure assessment curve of the surface crack for the failure assessment of surface cracked structure. (orig./HP)

  8. Fracture resistance of welded panel specimen with perpendicular crack in tensile

    International Nuclear Information System (INIS)

    Gochev, Todor; Adziev, Todor

    1998-01-01

    Defects caused by natural crack in welded joints of high-strength low-alloy (HSLA) steels are very often. Perpendicular crack in welded joints and its heat treatment after the welding has also an influence on the fracture resistance. The fracture resistance of welded joints by crack in tense panel specimens was investigated by crack mouse opening displesment (CMOD), the parameter of fracture mechanic. Crack propagation was analysed by using a metallographic analysis of fractured specimens after the test. (Author)

  9. 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

  10. Curvilinear crack layer propagation

    Science.gov (United States)

    Chudnovsky, Alexander; Chaoui, Kamel; Moet, Abdelsamie

    1987-01-01

    An account is given of an experiment designed to allow observation of the effect of damage orientation on the direction of crack growth in the case of crack layer propagation, using polystyrene as the model material. The direction of crack advance under a given loading condition is noted to be determined by a competition between the tendency of the crack to maintain its current direction and the tendency to follow the orientation of the crazes at its tip. The orientation of the crazes is, on the other hand, determined by the stress field due to the interaction of the crack, the crazes, and the hole. The changes in craze rotation relative to the crack define the active zone rotation.

  11. Delayed hydride cracking: theoretical model testing to predict cracking velocity

    International Nuclear Information System (INIS)

    Mieza, Juan I.; Vigna, Gustavo L.; Domizzi, Gladys

    2009-01-01

    Pressure tubes from Candu nuclear reactors as any other component manufactured with Zr alloys are prone to delayed hydride cracking. That is why it is important to be able to predict the cracking velocity during the component lifetime from parameters easy to be measured, such as: hydrogen concentration, mechanical and microstructural properties. Two of the theoretical models reported in literature to calculate the DHC velocity were chosen and combined, and using the appropriate variables allowed a comparison with experimental results of samples from Zr-2.5 Nb tubes with different mechanical and structural properties. In addition, velocities measured by other authors in irradiated materials could be reproduced using the model described above. (author)

  12. 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

  13. 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

  14. Stress corrosion cracking experience in steam generators at Bruce NGS

    International Nuclear Information System (INIS)

    King, P.J.; Gonzalez, F.; Brown, J.

    1993-01-01

    In late 1990 and through 1991, units 1 and 2 at the Bruce A Nuclear Generating Station (BNGS-A) experienced a number of steam generator tube leaks. Tube failures were identified by eddy current to be circumferential cracks at U-bend supports on the hot-leg side of the boilers. In late 1991, tubes were removed from these units for failure characterization. Two active failure modes were found: corrosion fatigue in both units 1 and 2 and stress corrosion cracking (SCC) in unit 2. In unit 2, lead was found in deposits, on tubes, and in cracks, and the cracking was mixed-mode: transgranular and intergranular. This convincingly indicated the involvement of lead in the stress corrosion cracking failures. A program of inspection and tube removals was carried out to investigate more fully the extent of the problem. This program found significant cracking only in lead-affected boilers in unit 2, and also revealed a limited extent of non-lead-related intergranular stress corrosion cracking in other boilers and units. Various aspects of the failures and tube examinations are presented in this paper. Included is discussion of the cracking morphology, measured crack size distributions, and chemical analysis of tube surfaces, crack faces, and deposits -- with particular emphasis on lead

  15. 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

  16. 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.

  17. A unified model of hydride cracking based on elasto-plastic energy release rate over a finite crack extension

    International Nuclear Information System (INIS)

    Zheng, X.J.; Metzger, D.R.; Sauve, R.G.

    1995-01-01

    A fracture criterion based on energy balance is proposed for elasto-plastic cracking at hydrides in zirconium, assuming a finite length of crack advance. The proposed elasto-plastic energy release rate is applied to the crack initiation at hydrides in smooth and notched surfaces, as well as the subsequent delayed hydride cracking (DHC) considering limited crack-tip plasticity. For a smooth or notched surface of an elastic body, the fracture parameter is related to the stress intensity factor for the initiated crack. For DHC, a unique curve relates the non-dimensionalized elasto-plastic energy release rate with the length of crack extension relative to the plastic zone size. This fracture criterion explains experimental observations concerning DHC in a qualitative manner. Quantitative comparison with experiments is made for fracture toughness and DHC tests on specimens containing certain hydride structures; very good agreement is obtained. ((orig.))

  18. Crack imaging by pulsed laser spot thermography

    International Nuclear Information System (INIS)

    Li, T; Almond, D P; Rees, D A S; Weekes, B

    2010-01-01

    A surface crack close to a spot heated by a laser beam impedes lateral heat flow and produces alterations to the shape of the thermal image of the spot that can be monitored by thermography. A full 3D simulation has been developed to simulate heat flow from a laser heated spot in the proximity of a crack. The modelling provided an understanding of the ways that different parameters affect the thermal images of laser heated spots. It also assisted in the development of an efficient image processing strategy for extracting the scanned cracks. Experimental results show that scanning pulsed laser spot thermography has considerable potential as a remote, non-contact crack imaging technique.

  19. Crack identification by artificial neural network

    Energy Technology Data Exchange (ETDEWEB)

    Hwu, C.B.; Liang, Y.C. [National Cheng Kung Univ., Tainan (Taiwan, Province of China). Inst. of Aeronaut. and Astronaut.

    1998-04-01

    In this paper, a most popular artificial neural network called the back propagation neural network (BPN) is employed to achieve an ideal on-line identification of the crack embedded in a composite plate. Different from the usual dynamic estimate, the parameters used for the present crack identification are the strains of static deformation. It is known that the crack effects are localized which may not be clearly reflected from the boundary information especially when the data is from static deformation only. To remedy this, we use data from multiple-loading modes in which the loading modes may include the opening, shearing and tearing modes. The results show that our method for crack identification is always stable and accurate no matter how far-away of the test data from its training set. (orig.) 8 refs.

  20. Strip yielding model for calculation of COD in spheres with short cracks

    International Nuclear Information System (INIS)

    Miller, A.G.

    1981-08-01

    The crack opening displacement at the centre of a crack in a sphere with internal pressure has been calculated, using a strip yielding model. The results have been displayed for a range of geometrical parameters and loads. (author)

  1. Detection of a fatigue crack in a rotor system using full-spectrum ...

    Indian Academy of Sciences (India)

    parameters identified are the additive stiffness due to crack, disc eccentricity due to unbalance, and system viscous damping. ... to increase in direct proportion to the crack size, accord- ... come defects in traditional methods of vibration signal.

  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. Bursting pressure of autofrettaged cylinders with inclined external cracks

    International Nuclear Information System (INIS)

    Seifi, Rahman; Babalhavaeji, Majid

    2012-01-01

    Autofrettaging a pressure vessel improves its pressure capacity. This is reliable if there isn’t any crack or other type of flaws. In this paper, the effects of external surface cracks on bursting pressure of autofrettaged cylinders are studied. It is observed that bursting pressure decreases considerably (up to 30%) due to external cracks in the cylinders without autofrettage. This reduction increases for high levels of the applied autofrettage. External axial cracks have more effects than inclined cracks. Comparing experimental and numerical results show that the numerical methods can acceptably predict the bursting pressure of the autofrettaged cracked cylinders. These predictions are valid when the fracture parameter (J-Integral) is calculated from the modified equation that takes into account the effects of residual stresses. - Highlights: ► Modified J-Integral can be used for study of autofrettaged cracked cylinders. ► External axial cracks reduce considerably the pressure capacity of cylinders. ► External circumferential cracks have not considerable effects on bursting pressure. ► Autofrettage has contrary effects on external crack in compared with internal crack.

  4. Bursting pressure of autofrettaged cylinders with inclined external cracks

    Energy Technology Data Exchange (ETDEWEB)

    Seifi, Rahman, E-mail: rseifi@basu.ac.ir [Mechanical Engineering Department, Faculty of Engineering, Bu-Ali Sina University, Hamedan (Iran, Islamic Republic of); Babalhavaeji, Majid [Mechanical Engineering Department, Faculty of Engineering, Bu-Ali Sina University, Hamedan (Iran, Islamic Republic of)

    2012-01-15

    Autofrettaging a pressure vessel improves its pressure capacity. This is reliable if there isn't any crack or other type of flaws. In this paper, the effects of external surface cracks on bursting pressure of autofrettaged cylinders are studied. It is observed that bursting pressure decreases considerably (up to 30%) due to external cracks in the cylinders without autofrettage. This reduction increases for high levels of the applied autofrettage. External axial cracks have more effects than inclined cracks. Comparing experimental and numerical results show that the numerical methods can acceptably predict the bursting pressure of the autofrettaged cracked cylinders. These predictions are valid when the fracture parameter (J-Integral) is calculated from the modified equation that takes into account the effects of residual stresses. - Highlights: Black-Right-Pointing-Pointer Modified J-Integral can be used for study of autofrettaged cracked cylinders. Black-Right-Pointing-Pointer External axial cracks reduce considerably the pressure capacity of cylinders. Black-Right-Pointing-Pointer External circumferential cracks have not considerable effects on bursting pressure. Black-Right-Pointing-Pointer Autofrettage has contrary effects on external crack in compared with internal crack.

  5. Crack propagation under conditions of low cycle fatigue

    International Nuclear Information System (INIS)

    Hellmann, D.

    1988-01-01

    A literature review is given of convenient concepts describing the mechanical behaviour of a cracked body under cyclic loading. Only the range of high growth rates is considered. However, caused by large scale yielding in this range, the application of linear elastic fracture mechanics is no longer possible. Mechanical parameters which control fatigue crack growth are a modified stress intensity factor, the J-integral, the crack tip opening displacement and a suitable strain amplitude. (orig.) With 20 figs [de

  6. Atomistics of crack propagation

    International Nuclear Information System (INIS)

    Sieradzki, K.; Dienes, G.J.; Paskin, A.; Massoumzadeh, B.

    1988-01-01

    The molecular dynamic technique is used to investigate static and dynamic aspects of crack extension. The material chosen for this study was the 2D triangular solid with atoms interacting via the Johnson potential. The 2D Johnson solid was chosen for this study since a sharp crack in this material remains stable against dislocation emission up to the critical Griffith load. This behavior allows for a meaningful comparison between the simulation results and continuum energy theorems for crack extension by appropriately defining an effective modulus which accounts for sample size effects and the non-linear elastic behavior of the Johnson solid. Simulation results are presented for the stress fields of moving cracks and these dynamic results are discussed in terms of the dynamic crack propagation theories, of Mott, Eshelby, and Freund

  7. Fatigue crack propagation behavior of stainless steel welds

    Science.gov (United States)

    Kusko, Chad S.

    The fatigue crack propagation behavior of austenitic and duplex stainless steel base and weld metals has been investigated using various fatigue crack growth test procedures, ferrite measurement techniques, light optical microscopy, stereomicroscopy, scanning electron microscopy, and optical profilometry. The compliance offset method has been incorporated to measure crack closure during testing in order to determine a stress ratio at which such closure is overcome. Based on this method, an empirically determined stress ratio of 0.60 has been shown to be very successful in overcoming crack closure for all da/dN for gas metal arc and laser welds. This empirically-determined stress ratio of 0.60 has been applied to testing of stainless steel base metal and weld metal to understand the influence of microstructure. Regarding the base metal investigation, for 316L and AL6XN base metals, grain size and grain plus twin size have been shown to influence resulting crack growth behavior. The cyclic plastic zone size model has been applied to accurately model crack growth behavior for austenitic stainless steels when the average grain plus twin size is considered. Additionally, the effect of the tortuous crack paths observed for the larger grain size base metals can be explained by a literature model for crack deflection. Constant Delta K testing has been used to characterize the crack growth behavior across various regions of the gas metal arc and laser welds at the empirically determined stress ratio of 0.60. Despite an extensive range of stainless steel weld metal FN and delta-ferrite morphologies, neither delta-ferrite morphology significantly influence the room temperature crack growth behavior. However, variations in weld metal da/dN can be explained by local surface roughness resulting from large columnar grains and tortuous crack paths in the weld metal.

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

    Directory of Open Access Journals (Sweden)

    Anthony L Luz

    Full Text Available 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.

  9. 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.

  10. Hydrogen-induced cracking: 2

    International Nuclear Information System (INIS)

    Puls, M.P.

    1984-12-01

    There is a strong motivation for understanding the factors controlling zirconium hydride reorientation under stress because of the important role this plays in hydrogen-induced crack growth and/or crack initiation in zirconium and its alloys, particularly under thermal cycling conditions. Following an approach developed by Sauthoff, an analysis of the orienting effect of external stress on the nucleation, growth and coarsening of γ- and delta-zirconium hydride precipitates in zirconium and its alloys is presented. The analysis is based on a previous theoretical study of some of the factors affecting hydride solubility in stressed and unstressed solids. Expressions are derived for the effect of stress on nucleation, growth and coarsening. We conclude, on the basis of these that the preferential orientation of hydride precipitates under stress is most efficient during the nucleation stage. The reason for this is that the overall driving force for nucleation, for the chosen parameters and the usual experimental conditions, is fairly small. Therefore, the driving force for orientating under stress can be a substantial fraction of the overall driving force. The analysis shows that hydride growth is unlikely to play a role in preferential orientation, but coarsening could be important under carefully chosen experimental conditions, which may be relevant to the hydride-cracking process

  11. Cracked gas generator

    Energy Technology Data Exchange (ETDEWEB)

    Abthoff, J; Schuster, H D; Gabler, R

    1976-11-17

    A small cracked-gas generator in a vehicle driven, in particular, by an air combustion engine has been proposed for the economic production of the gases necessary for low toxicity combustion from diesel fuel. This proceeds via catalytic crack-gasification and exploitation of residual heat from exhaust gases. This patent application foresees the insertion of one of the catalysts supporting the cracked-gas reaction in a container through which the reacting mixture for cracked-gas production flows in longitudinal direction. Further, air ducts are embedded in the catalyst through which exhaust gases and fresh air flow in counter direction to the cracked gas flow in the catalyst. The air vents are connected through heat conduction to the catalyst. A cracked gas constituting H/sub 2//CO/CO/sub 2//CH/sub 4/ and H/sub 2/O can be produced from the air-fuel mixture using appropriate catalysts. By the addition of 5 to 25% of cracked gas to the volume of air drawn in by the combustion engine, a more favourable combustion can be achieved compared to that obtained under normal combustion conditions.

  12. In-situ crack repair by laser cladding

    CSIR Research Space (South Africa)

    Van Rooyen, C

    2010-09-01

    Full Text Available Laser cladding crack repair of austenitic stainless steel vessels subjected to internal water pressure was evaluated. The purpose of this investigation was to develop process parameters for in-situ repair of through-wall cracks in components...

  13. Laser cladding crack repair of austenitic stainless steel

    CSIR Research Space (South Africa)

    Van Rooyen, C

    2009-06-01

    Full Text Available Laser cladding crack repair of austenitic stainless steel vessels subjected to internal water pressure was evaluated. The purpose of this investigation was to develop process parameters for in-situ repair of through-wall cracks in components...

  14. Prevention of delayed hydride cracking in zirconium alloys

    International Nuclear Information System (INIS)

    Cheadle, B.A.; Coleman, C.E.; Ambler, J.F.R.

    1987-01-01

    Zirconium alloys are susceptible to a mechanism for crack initiation and propagation called delayed hydride cracking. From a review of component failures and experimental results, we have developed the requirements for preventing this cracking. The important parameters for cracking are hydrogen concentration, flaws, and stress; each should be minimized. At the design and construction stages hydrogen pickup has to be controlled, quality assurance needs to be at a high enough level to ensure the absence of flaws, and residual stresses must be eliminated by careful fabrication and heat treatment

  15. Numerical approach of memory effect on crack closure phenomenon

    International Nuclear Information System (INIS)

    Billardon, R.; Brunet, M.; Lemaitre, J.

    1981-01-01

    In the case of variable amplitude loading, it is necessary to introduce in the fatigue crack propagation law a parameter accounting for the threshold value of strain energy release rate. In order to relate this threshold to crack closure or crack opening, a finite element procedure has been developed based upon anisotropic elastoplastic constitutive equations (Marquis). This finite element procedure is used for the cyclic elastoplastic analysis of fatigue bending crack tests carried on 2024 aluminium alloy, 2 millimeters thick. The influence of the hardening rule used is studied for the case of one single overload on constant amplitude (0, +) loading. (orig./HP)

  16. Investigation of hot cracking resistance of 2205 duplex steel

    Energy Technology Data Exchange (ETDEWEB)

    Adamiec, J; Scibisz, B, E-mail: janusz.adamiec@polsl.pl [Silesian University of Technology, Faculty of Materials Science and Metallurgy, ul. Krasinskiego 8, PL-40019 Katowice (Poland)

    2010-02-15

    Austenitic duplex steel of the brand 2205 according to Avesta Sheffield is used for welded constructions (pipelines, tanks) in the petrol industry, chemical industry and food industry. It is important to know the range of high-temperature brittleness in designing welding technology for constructions made of this steel type. There is no data in literature concerning this issue. High-temperature brittleness tests using the simulator of heat flow device Gleeble 3800 were performed. The tests results allowed the evaluation of the characteristic temperatures in the brittleness temperature range during the joining of duplex steels, specifically the nil-strength temperature (NST) and nil-ductility temperatures (NDT) during heating, the strength and ductility recovery temperatures (DRT) during cooling, the R{sub f}parameter (R{sub f} = (T{sub liquidus} - NDT)/NDT) describing the duplex steel inclination for hot cracking, and the brittleness temperature range (BTR). It has been stated that, for the examined steel, this range is wide and amounts to ca. 90 deg. C. The joining of duplex steels with the help of welding techniques creates a significant risk of hot cracks. After analysis of the DTA curves a liquidus temperature of T{sub L} = 1465 deg. C and a solidus temperature of T{sub S} = 1454 deg. C were observed. For NST a mean value was assumed, in which the cracks appeared for six samples; the temperature was 1381 deg. C. As the value of the NDT temperature 1367 deg. C was applied while for DRT the assumed temperature was 1375 deg. C. The microstructure of the fractures was observed using a Hitachi S-3400N scanning electron microscope (SEM). The analyses of the chemical composition were performed using an energy-dispersive X-ray spectrometer (EDS), Noran System Six of Thermo Fisher Scientific. Essential differences of fracture morphology type over the brittle temperature range were observed and described.

  17. Investigation of hot cracking resistance of 2205 duplex steel

    International Nuclear Information System (INIS)

    Adamiec, J; Scibisz, B

    2010-01-01

    Austenitic duplex steel of the brand 2205 according to Avesta Sheffield is used for welded constructions (pipelines, tanks) in the petrol industry, chemical industry and food industry. It is important to know the range of high-temperature brittleness in designing welding technology for constructions made of this steel type. There is no data in literature concerning this issue. High-temperature brittleness tests using the simulator of heat flow device Gleeble 3800 were performed. The tests results allowed the evaluation of the characteristic temperatures in the brittleness temperature range during the joining of duplex steels, specifically the nil-strength temperature (NST) and nil-ductility temperatures (NDT) during heating, the strength and ductility recovery temperatures (DRT) during cooling, the R f parameter (R f = (T liquidus - NDT)/NDT) describing the duplex steel inclination for hot cracking, and the brittleness temperature range (BTR). It has been stated that, for the examined steel, this range is wide and amounts to ca. 90 deg. C. The joining of duplex steels with the help of welding techniques creates a significant risk of hot cracks. After analysis of the DTA curves a liquidus temperature of T L = 1465 deg. C and a solidus temperature of T S = 1454 deg. C were observed. For NST a mean value was assumed, in which the cracks appeared for six samples; the temperature was 1381 deg. C. As the value of the NDT temperature 1367 deg. C was applied while for DRT the assumed temperature was 1375 deg. C. The microstructure of the fractures was observed using a Hitachi S-3400N scanning electron microscope (SEM). The analyses of the chemical composition were performed using an energy-dispersive X-ray spectrometer (EDS), Noran System Six of Thermo Fisher Scientific. Essential differences of fracture morphology type over the brittle temperature range were observed and described.

  18. Dynamic Characteristics of Electrostatically Actuated Microbeams with Slant Crack

    Directory of Open Access Journals (Sweden)

    Han Zhou

    2015-01-01

    Full Text Available An improved model of the slant crack on a microbeam is presented. Based on fracture mechanics, the rotation coefficient for the slant crack is derived as a massless rotational spring accounting for the additional stress intensity factors generated by the orientation of the crack compared to the transverse crack. Comparisons between microbeams with a slant crack of different geometry parameters (slant angle, depth ratio, and crack position are investigated with regard to the dynamic mechanical behaviors and nonlinear response. By presenting a mathematical modeling, the effects of the slant crack and the electric actuation of an electrostatically actuated fixed-fixed microbeam on the dynamic characteristics are examined in detail. It is shown that the crack position has more significant influence on the pull-in voltage value than the slant angle or the depth ratio. Approaching the slant crack to the fixed end or enlarging the external incentives amplifies the nonlinearity of the microbeam system, while the effects of depth ratio and slant angle are dependent on the crack position. The resonance frequency and the resonance amplitude are affected as well.

  19. Automatic Pavement Crack Recognition Based on BP Neural Network

    Directory of Open Access Journals (Sweden)

    Li Li

    2014-02-01

    Full Text Available A feasible pavement crack detection system plays an important role in evaluating the road condition and providing the necessary road maintenance. In this paper, a back propagation neural network (BPNN is used to recognize pavement cracks from images. To improve the recognition accuracy of the BPNN, a complete framework of image processing is proposed including image preprocessing and crack information extraction. In this framework, the redundant image information is reduced as much as possible and two sets of feature parameters are constructed to classify the crack images. Then a BPNN is adopted to distinguish pavement images between linear and alligator cracks to acquire high recognition accuracy. Besides, the linear cracks can be further classified into transversal and longitudinal cracks according to the direction angle. Finally, the proposed method is evaluated on the data of 400 pavement images obtained by the Automatic Road Analyzer (ARAN in Northern China and the results show that the proposed method seems to be a powerful tool for pavement crack recognition. The rates of correct classification for alligator, transversal and longitudinal cracks are 97.5%, 100% and 88.0%, respectively. Compared to some previous studies, the method proposed in this paper is effective for all three kinds of cracks and the results are also acceptable for engineering application.

  20. Effect of temperature on crack initiation in gas formed structures

    Energy Technology Data Exchange (ETDEWEB)

    Gohari, S.; Vrcelj, Z.; Sharifi, S.; Sharifishourabi, G.; Abadi, R. [Universiti Teknlogi Malaysia, Skudai (Malaysia)

    2013-12-15

    In the gas forming process, the work piece is formed by applying gas pressure. However, the gas pressure and the accompanying gas temperature can result in crack initiation and unstable crack growth. Thus, it is vital to determine the critical values of applied gas pressure and temperature to avoid crack and fracture failure. We studied the mechanism of fracture using an experimental approach and finite element simulations of a perfect aluminum sheet containing no inclusions and voids. The definition of crack was based on ductile damage mechanics. For inspection of initiation of crack and rupture in gas-metal forming, the ABAQUS/EXPLICIT simulation was used. In gas forming, the applied load is the pressure applied rather than the punching force. The results obtained from both the experimental approach and finite element simulations were compared. The effects of various parameters, such as temperature and gas pressure value on crack initiation, were taken into account.

  1. 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.

  2. 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)

  3. Inspecting cracks in foam insulation

    Science.gov (United States)

    Cambell, L. W.; Jung, G. K.

    1979-01-01

    Dye solution indicates extent of cracking by penetrating crack and showing original crack depth clearly. Solution comprised of methylene blue in denatured ethyl alcohol penetrates cracks completely and evaporates quickly and is suitable technique for usage in environmental or structural tests.

  4. 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....

  5. Cracking the Gender Codes

    DEFF Research Database (Denmark)

    Rennison, Betina Wolfgang

    2016-01-01

    extensive work to raise the proportion of women. This has helped slightly, but women remain underrepresented at the corporate top. Why is this so? What can be done to solve it? This article presents five different types of answers relating to five discursive codes: nature, talent, business, exclusion...... in leadership management, we must become more aware and take advantage of this complexity. We must crack the codes in order to crack the curve....

  6. SSRI Facilitated Crack Dancing

    Directory of Open Access Journals (Sweden)

    Ravi Doobay

    2017-01-01

    Full Text Available Choreoathetoid movement secondary to cocaine use is a well-documented phenomenon better known as “crack dancing.” It consists of uncontrolled writhing movements secondary to excess dopamine from cocaine use. We present a 32-year-old male who had been using cocaine for many years and was recently started on paroxetine, a selective serotonin reuptake inhibitor (SSRI for worsening depression four weeks before presentation. He had been doing cocaine every 2 weeks for the last three years and had never “crack danced” before this episode. The authors have conducted a thorough literature review and cited studies that suggest “crack dancing” is associated with excess dopamine. There has never been a documented case report of an SSRI being linked with “crack dancing.” The authors propose that the excess dopaminergic effect of the SSRI lowered the dopamine threshold for “crack dancing.” There is a communication with the Raphe Nucleus and the Substantia Nigra, which explains how the SSRI increases dopamine levels. This is the first documented case of an SSRI facilitating the “crack dance.”

  7. Ultrasonic sizing of fatigue cracks

    International Nuclear Information System (INIS)

    Burns, D.J.

    1983-12-01

    Surface and buried fatigue cracks in steel plates have been sized using immersion probes as transmitters-receivers, angled to produce shear waves in the steel. Sizes have been estimated by identifying the ultrasonic waves diffracted from the crack tip and by measuring the time taken for a signal to travel to and from the crack tip. The effects of compression normal to a fatigue crack and of crack front curvature are discussed. Another diffraction technique, developed by UKAEA, Harwell, is reviewed

  8. 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.

  9. Distinguishing oil and water layers in a cracked porous medium using pulsed neutron logging data based on Hudson's crack theory

    Science.gov (United States)

    Zhang, Xueang; Yang, Zhichao; Tang, Bin; Wang, Renbo; Wei, Xiong

    2018-05-01

    During geophysical surveys, water layers may interfere with the detection of oil layers. In order to distinguish between oil and water layers in porous cracked media, research on the properties of the cracks, the oil and water layers, and their relation to pulsed neutron logging characteristics is essential. Using Hudson's crack theory, we simulated oil and water layers in a cracked porous medium with different crack parameters corresponding to the well log responses. We found that, in a cracked medium with medium-angle (40°-50°) cracks, the thermal neutron count peak value is higher and more sensitive than those in low-angle and high-angle crack environments; in addition, the thermal neutron density distribution shows more minimum values than in other cases. Further, the thermal neutron count and the rate of change for the oil layer are greater than those of the water layer, and the time spectrum count peak value for the water layer in middle-high-angle (40°-70°) cracked environments is higher than that of the oil layer. The thermal neutron density distribution sensitivity is higher in the water layer with a range of small crack angles (0°-30°) than in the oil layer with the same range of angles. In comparing the thermal neutron density distribution, thermal neutron count peak, thermal neutron density distribution sensitivity, and time spectrum maximum in the oil and water layers, we find that neutrons in medium-angle (40°-50°) cracked reservoirs are more sensitive to deceleration and absorption than those in water layers; neutrons in approximately horizontal (0°-30°) cracked water layers are more sensitive to deceleration than those in reservoirs. These results can guide future work in the cracked media neutron logging field.

  10. Facts and views on the role of anionic impurities, crack tip chemistry and oxide films in environmentally assisted cracking

    International Nuclear Information System (INIS)

    Aaltonen, P.; Bojinov, M.; Helin, M.

    2002-01-01

    The aim of this literature study has been to evaluate the level of understanding of the role of anionic impurities in environmentally assisted cracking (EAC) of iron- and nickel-based alloys in the coolant conditions of a boiling water reactor (BWR) - type nuclear power plant, mainly under normal water chemistry (NWC). The study has been motivated by a need to find the most relevant experimental approaches that can be applied when looking for correlations between crack growth rate and measurable electrochemical and chemical parameters. Special crack tip chemistry conditions are established, when trace amounts are present in the BWR coolant and become enriched within a crack. Anions may influence both the conductivity and the pH of the coolant within the crack. In addition, they may influence the composition, structure and properties of the oxide films formed on crack walls either directly via adsorption or incorporation or indirectly via the effect of changes in pH within the crack. Based on the proposed mechanisms for EAC, oxide films formed on crack wall surfaces are likely to play a key role in determing the crack growth rate of structural materials. The prediction of the influence of anionic impurities is thus likely to be facilitated by means of understanding their effect on the films on crack walls. One of the most promising approaches to experimentally clarify this influence is based on investigating the electrochemical behaviour of oxide films Fe- and Ni-based materials in high-temperature conditions simulating the special chemistry within a stress corrosion crack. Results from such studies should be compared and combined with ex situ analytical results obtained using modern electron microscopic techniques. In addition to crack growth, currently available electro-chemical techniques should also be applied to find out whether crack initiation can be explained and modelled on the basis of the electrochemical behaviour of oxide films. (orig.)

  11. 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

    Present extended finite element method (XFEM) elements for cohesive crack growth may often not be able to model equal stresses on both sides of the discontinuity when acting as a crack-tip element. The authors have developed a new partly cracked XFEM element for cohesive crack growth with extra...... enrichments to the cracked elements. The extra enrichments are element side local and were developed by superposition of the standard nodal shape functions for the element and standard nodal shape functions for a sub-triangle of the cracked element. With the extra enrichments, the crack-tip element becomes...... 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...

  12. A crack growth evaluation method for interacting multiple cracks

    International Nuclear Information System (INIS)

    Kamaya, Masayuki

    2003-01-01

    When stress corrosion cracking or corrosion fatigue occurs, multiple cracks are frequently initiated in the same area. According to section XI of the ASME Boiler and Pressure Vessel Code, multiple cracks are considered as a single combined crack in crack growth analysis, if the specified conditions are satisfied. In crack growth processes, however, no prescription for the interference between multiple cracks is given in this code. The JSME Post-Construction Code, issued in May 2000, prescribes the conditions of crack coalescence in the crack growth process. This study aimed to extend this prescription to more general cases. A simulation model was applied, to simulate the crack growth process, taking into account the interference between two cracks. This model made it possible to analyze multiple crack growth behaviors for many cases (e.g. different relative position and length) that could not be studied by experiment only. Based on these analyses, a new crack growth analysis method was suggested for taking into account the interference between multiple cracks. (author)

  13. Crack-tip constraint analyses and constraint-dependent LBB curves for circumferential through-wall cracked pipes

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Y.L.; Wang, G.Z., E-mail: gzwang@ecust.edu.cn; Xuan, F.Z.; Tu, S.T.

    2015-04-15

    Highlights: • Solution of constraint parameter τ* for through-wall cracked pipes has been obtained. • Constraint increases with increasing crack length and radius–thickness ratio of pipes. • Constraint-dependent LBB curve for through-wall cracked pipes has been constructed. • For increasing accuracy of LBB assessments, constraint effect should be considered. - Abstract: The leak-before-break (LBB) concept has been widely applied in the structural integrity assessments of pressured pipes in nuclear power plants. However, the crack-tip constraint effects in LBB analyses and designs cannot be incorporated. In this paper, by using three-dimensional finite element calculations, the modified load-independent T-stress constraint parameter τ* for circumferential through-wall cracked pipes with different geometries and crack sizes has been analyzed under different loading conditions, and the solutions of the crack-tip constraint parameter τ* have been obtained. Based on the τ* solutions and constraint-dependent J–R curves of a steel, the constraint-dependent LBB (leak-before-break) curves have been constructed. The results show that the constraint τ* increases with increasing crack length θ, mean radius R{sub m} and radius–thickness ratio R{sub m}/t of the pipes. In LBB analyses, the critical crack length calculated by the J–R curve of the standard high constraint specimen for pipes with shorter cracks is over-conservative, and the degree of conservatism increases with decreasing crack length θ, R{sub m} and R{sub m}/t. Therefore, the constraint-dependent LBB curves should be constructed to modify the over-conservatism and increase accuracy of LBB assessments.

  14. Inclusion of live yeast and mannan-oligosaccharides in high grain-based diets for sheep: Ruminal parameters, inflammatory response and rumen morphology.

    Directory of Open Access Journals (Sweden)

    Tatiana Garcia Diaz

    Full Text Available The objective of this study was to evaluate the effects of dietary supplementation with live yeast (Saccharomyces cerevisiae, mannan-oligosaccharides and the combination of these additives on the inflammatory response, ruminal parameters and rumen morphology of sheep fed a high grain-based diet. Thirty-Two Dorper x Santa Ines crossbred lambs with an average weight of 24±2 kg were distributed in a completely randomized design. The animals were housed in individual stalls and fed ad libitum. Diet treatments were: Control (without additive; LY (2 g/kg DM of live yeast, Saccharomyces cerevisiae, MOS (2 g/kg DM of mannan-oligosaccharides and LY+MOS (2 g/kg DM of LY + 2 g/kg DM of MOS. The experiment lasted 42 days. The supplementation with MOS alone and the additives combination resulted in increased ruminal pH (P<0.01, while the total concentrations of short chain fatty acids (SCFA in the rumen were higher (P<0.05 only in the diets with LY and MOS. Ammonia (NH3 concentration in the rumen decreased (P<0.04 with the additives usage. Diets with LY, MOS and with additives combination reduced (P<0.01 the levels of lipopolysaccharides (LPS in the plasma with values of 0.46; 0.44 and 0.04 EU/mL, respectively when compared to the control (0.93 EU/mL. MOS and LY+MOS treatments had reduced stratum corneum thickness (P<0.01 in comparison to the control treatment. The total thickness of ruminal epithelium was lower with the addition of MOS in the diet (P<0.03 than with LY additive. The incidence and severity of hepatic abscesses in animals whose diet was supplemented with LY and LY+MOS was lower (P<0.05 than in animals fed the control diet. The use of LY, MOS and LY+MOS in the high-concentrate diets for sheep reduced NH3 concentrations and LPS translocation into the bloodstream. Diets containing MOS and LY+MOS enhanced the health of the ruminal epithelium by reducing the thickness of the stratum corneum, and diets containing LY and LY+MOS decreased the

  15. Nonlinear crack mechanics

    International Nuclear Information System (INIS)

    Khoroshun, L.P.

    1995-01-01

    The characteristic features of the deformation and failure of actual materials in the vicinity of a crack tip are due to their physical nonlinearity in the stress-concentration zone, which is a result of plasticity, microfailure, or a nonlinear dependence of the interatomic forces on the distance. Therefore, adequate models of the failure mechanics must be nonlinear, in principle, although linear failure mechanics is applicable if the zone of nonlinear deformation is small in comparison with the crack length. Models of crack mechanics are based on analytical solutions of the problem of the stress-strain state in the vicinity of the crack. On account of the complexity of the problem, nonlinear models are bason on approximate schematic solutions. In the Leonov-Panasyuk-Dugdale nonlinear model, one of the best known, the actual two-dimensional plastic zone (the nonlinearity zone) is replaced by a narrow one-dimensional zone, which is then modeled by extending the crack with a specified normal load equal to the yield point. The condition of finite stress is applied here, and hence the length of the plastic zone is determined. As a result of this approximation, the displacement in the plastic zone at the abscissa is nonzero

  16. Mitigation strategies for autogenous shrinkage cracking

    DEFF Research Database (Denmark)

    Bentz, Dale P.; Jensen, Ole Mejlhede

    2004-01-01

    As the use of high-performance concrete has increased, problems with early-age cracking have become prominent. The reduction in water-to-cement ratio, the incorporation of silica fume, and the increase in binder content of high-performance concretes all contribute to this problem. In this paper......, 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...

  17. Numerical treatment of creep crack growth

    International Nuclear Information System (INIS)

    Kienzler, R.; Hollstein, T.

    1990-06-01

    To accomplish the safety analysis and to predict the lifetime of high-termpature components with flaws, several concepts have been proposed to correlate creep-crack initiation and growth with fracture mechanics parameters. The concepts of stress-intensity factor K, reference stress σ ref , line integral C * , and others will be discussed. Among them, the C * -integral concept seems to have the widest range of applicability, if large creep zones develop and steady state creep conditions can be assumed. The numerical evaluation of C * by the virtual crack extension method is described. The methods are demonstrated by two- and three-dimensional finite element simulations including creep crack growth. As for ductile fracture experiments, plane stress and plane strain simulations are bounds to the three-dimensional simulations which agree well with corresponding experiments. (orig.)

  18. Fatigue crack closure in submicron-thick freestanding copper films

    International Nuclear Information System (INIS)

    Kondo, Toshiyuki; Ishii, Takaki; Hirakata, Hiroyuki; Minoshima, Kohji

    2015-01-01

    The fatigue crack closure in approximately 500-nm-thick freestanding copper films were investigated by in situ field emission scanning electron microscope (FESEM) observations of the fatigue crack opening/closing behavior at three stress ratios of R=0.1, 0.5, and 0.8 in the low–K max (maximum stress intensity factor) region of K max <4.5 MPam 1/2 . The direct observation of fatigue cracks clarified that crack closure occurred at R=0.1 and 0.5, while the fatigue crack was always open at R=0.8. Changes in the gage distance across the fatigue crack during a fatigue cycle were measured from the FESEM images, and the crack opening stress intensity factor K op was evaluated on the basis of the stress intensity factor K vs. the gage distance relationship. The effective stress intensity factor range ΔK eff =K max −K op was then evaluated. The R-dependence of the da/dN vs. ΔK eff relationship was smaller than that of the da/dN vs. ΔK relationship. This suggests that ΔK eff is a dominating parameter rather than ΔK in the fatigue crack propagation in the films. This paper is the first report on the presence of the fatigue crack closure in submicron-thick freestanding metallic films

  19. 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)

  20. Evaluation of strength and failure of brittle rock containing initial cracks under lithospheric conditions

    Science.gov (United States)

    Li, Xiaozhao; Qi, Chengzhi; Shao, Zhushan; Ma, Chao

    2018-02-01

    Natural brittle rock contains numerous randomly distributed microcracks. Crack initiation, growth, and coalescence play a predominant role in evaluation for the strength and failure of brittle rocks. A new analytical method is proposed to predict the strength and failure of brittle rocks containing initial microcracks. The formulation of this method is based on an improved wing crack model and a suggested micro-macro relation. In this improved wing crack model, the parameter of crack angle is especially introduced as a variable, and the analytical stress-crack relation considering crack angle effect is obtained. Coupling the proposed stress-crack relation and the suggested micro-macro relation describing the relation between crack growth and axial strain, the stress-strain constitutive relation is obtained to predict the rock strength and failure. Considering different initial microcrack sizes, friction coefficients and confining pressures, effects of crack angle on tensile wedge force acting on initial crack interface are studied, and effects of crack angle on stress-strain constitutive relation of rocks are also analyzed. The strength and crack initiation stress under different crack angles are discussed, and the value of most disadvantaged angle triggering crack initiation and rock failure is founded. The analytical results are similar to the published study results. Rationality of this proposed analytical method is verified.

  1. Crack initiation and growth in welded structures

    International Nuclear Information System (INIS)

    Assire, A.

    2000-01-01

    This work concerns the remaining life assessment of a structure containing initial defects of manufacturing. High temperature crack initiation and growth are studied for austenitic stainless steels, and defect assessment methods are improved in order to take into account welded structures. For these one, the probability to have a defect is significant. Two kinds of approaches are commonly used for defect assessment analysis. Fracture mechanics global approach with an energetic criterion, and local approach with a model taking into account the physical damage mechanism. For both approaches mechanical fields (stress and strain) have to be computed everywhere within the structure. Then, Finite Element computation is needed. The first part of the thesis concerns the identification of non linear kinematic and isotropic constitutive models. A pseudo-analytical method is proposed for a 'Two Inelastic Strain' model. This method provides a strategy of identification with a mechanical meaning, and this enables to associate each parameter to a physical phenomenon. Existing identifications are improved for cyclic plasticity and creep on a large range of stress levels. The second part concerns high temperature crack initiation and growth in welded structures. Finite Element analysis on plate and tube experimental configuration enable to understand the phenomenons of interaction between base metal and weld metal under mechanical and thermal loading. Concerning global approach, criteria based on C* parameter (Rice integral for visco-plasticity) are used. Finite Element computations underline the fact that for a defect located in the weld metal, C* values strongly depend on the base metal creep strain rate, because widespread visco-plasticity is located in both metals. A simplified method, based on the reference stress approach, is proposed and validated with Finite Element results. Creep crack growth simplified assessment is a quite good validation of the experimental results

  2. Realistic and efficient 2D crack simulation

    Science.gov (United States)

    Yadegar, Jacob; Liu, Xiaoqing; Singh, Abhishek

    2010-04-01

    Although numerical algorithms for 2D crack simulation have been studied in Modeling and Simulation (M&S) and computer graphics for decades, realism and computational efficiency are still major challenges. In this paper, we introduce a high-fidelity, scalable, adaptive and efficient/runtime 2D crack/fracture simulation system by applying the mathematically elegant Peano-Cesaro triangular meshing/remeshing technique to model the generation of shards/fragments. The recursive fractal sweep associated with the Peano-Cesaro triangulation provides efficient local multi-resolution refinement to any level-of-detail. The generated binary decomposition tree also provides efficient neighbor retrieval mechanism used for mesh element splitting and merging with minimal memory requirements essential for realistic 2D fragment formation. Upon load impact/contact/penetration, a number of factors including impact angle, impact energy, and material properties are all taken into account to produce the criteria of crack initialization, propagation, and termination leading to realistic fractal-like rubble/fragments formation. The aforementioned parameters are used as variables of probabilistic models of cracks/shards formation, making the proposed solution highly adaptive by allowing machine learning mechanisms learn the optimal values for the variables/parameters based on prior benchmark data generated by off-line physics based simulation solutions that produce accurate fractures/shards though at highly non-real time paste. Crack/fracture simulation has been conducted on various load impacts with different initial locations at various impulse scales. The simulation results demonstrate that the proposed system has the capability to realistically and efficiently simulate 2D crack phenomena (such as window shattering and shards generation) with diverse potentials in military and civil M&S applications such as training and mission planning.

  3. Statistical crack mechanics

    International Nuclear Information System (INIS)

    Dienes, J.K.

    1993-01-01

    Although it is possible to simulate the ground blast from a single explosive shot with a simple computer algorithm and appropriate constants, the most commonly used modelling methods do not account for major changes in geology or shot energy because mechanical features such as tectonic stresses, fault structure, microcracking, brittle-ductile transition, and water content are not represented in significant detail. An alternative approach for modelling called Statistical Crack Mechanics is presented in this paper. This method, developed in the seventies as a part of the oil shale program, accounts for crack opening, shear, growth, and coalescence. Numerous photographs and micrographs show that shocked materials tend to involve arrays of planar cracks. The approach described here provides a way to account for microstructure and give a representation of the physical behavior of a material at the microscopic level that can account for phenomena such as permeability, fragmentation, shear banding, and hot-spot formation in explosives

  4. Cracking the Cipher Challenge

    CERN Document Server

    CERN. Geneva. Audiovisual Unit; Singh, Simon

    2002-01-01

    In the back of 'The Code Book', a history of cryptography, Simon Singh included a series of 10 encoded messages, each from a different period of history. The first person to crack all 10 messages would win a prize of £10,000. Now that the prize has been won, Simon can reveal the story behind the Cipher Challenge. Along the way he will show how mathematics can be used to crack codes, the role it played in World War Two and how it helps to guarantee security in the Information Age.

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

    International Nuclear Information System (INIS)

    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)

  6. 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

    2018-04-01

    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.

  7. Influence of sample geometry and microstructure on the hydrogen induced cracking characteristics under uniaxial load

    Energy Technology Data Exchange (ETDEWEB)

    Laureys, A., E-mail: aurelie.laureys@ugent.be [Department of Materials, Textiles and Chemical Engineering, Ghent University (UGent), Tech Lane Ghent Science Park - Campus A, Technologie park 903, B-9052 Gent (Belgium); Depover, T., E-mail: tom.depover@ugent.be [Department of Materials, Textiles and Chemical Engineering, Ghent University (UGent), Tech Lane Ghent Science Park - Campus A, Technologie park 903, B-9052 Gent (Belgium); Petrov, R., E-mail: roumen.petrov@ugent.be [Department of Materials, Textiles and Chemical Engineering, Ghent University (UGent), Tech Lane Ghent Science Park - Campus A, Technologie park 903, B-9052 Gent (Belgium); Department of Materials Science and Engineering, Delft University of Technology, Mekelweg 2, 2628 CD Delft (Netherlands); Verbeken, K., E-mail: kim.verbeken@ugent.be [Department of Materials, Textiles and Chemical Engineering, Ghent University (UGent), Tech Lane Ghent Science Park - Campus A, Technologie park 903, B-9052 Gent (Belgium)

    2017-04-06

    The present work evaluates hydrogen induced cracking in a TRIP (transformation induced plasticity) assisted steel and pure iron. The goal of this work is to understand the effect of the macroscopic stress distribution in the material on the hydrogen induced cracking phenomenon. Additionally, the effect of a complex multiphase microstructure on the characteristics of hydrogen induced cracking was investigated by comparing results for TRIP-assisted steel and pure iron as reference material. Tensile tests on notched and unnotched samples combined with in-situ electrochemical hydrogen charging were conducted. Tests were performed until the tensile strength was reached and until fracture. The resulting hydrogen induced cracks were studied by optical microscopy and scanning electron microscopy (SEM). Hydrogen induced cracks showed a typical S-shape and crack propagation was mainly transgranular, independently of the presence of a notch or the material's microstructure. This was also the case for the V-shaped secondary crack network and resulting stepped crack morphology characteristic for hydrogen induced damage. These observations indicate that the stress state surrounding the crack tip has a very large impact on the hydrogen induced cracking characteristics. The use of a notch or the presence of a different microstructure did not influence the overall hydrogen induced cracking features, but did change the kinetics of the hydrogen induced cracking process.

  8. Influence of sample geometry and microstructure on the hydrogen induced cracking characteristics under uniaxial load

    International Nuclear Information System (INIS)

    Laureys, A.; Depover, T.; Petrov, R.; Verbeken, K.

    2017-01-01

    The present work evaluates hydrogen induced cracking in a TRIP (transformation induced plasticity) assisted steel and pure iron. The goal of this work is to understand the effect of the macroscopic stress distribution in the material on the hydrogen induced cracking phenomenon. Additionally, the effect of a complex multiphase microstructure on the characteristics of hydrogen induced cracking was investigated by comparing results for TRIP-assisted steel and pure iron as reference material. Tensile tests on notched and unnotched samples combined with in-situ electrochemical hydrogen charging were conducted. Tests were performed until the tensile strength was reached and until fracture. The resulting hydrogen induced cracks were studied by optical microscopy and scanning electron microscopy (SEM). Hydrogen induced cracks showed a typical S-shape and crack propagation was mainly transgranular, independently of the presence of a notch or the material's microstructure. This was also the case for the V-shaped secondary crack network and resulting stepped crack morphology characteristic for hydrogen induced damage. These observations indicate that the stress state surrounding the crack tip has a very large impact on the hydrogen induced cracking characteristics. The use of a notch or the presence of a different microstructure did not influence the overall hydrogen induced cracking features, but did change the kinetics of the hydrogen induced cracking process.

  9. Fatigue crack propagation under elastic plastic medium at elevated temperature

    International Nuclear Information System (INIS)

    Asada, Y.; Yuuki, R.; Sakon, T.; Sunamoto, D.; Tokimasa, K.; Makino, Y.; Kitagawa, M; Shingai, K.

    1980-01-01

    The purposes of the present study are to establish the testing method to obtain compatible data on the low cycle fatigue crack propagation at elevated temperature, and to investigate the parameter controlling the crack propagation rate. In the present study, the preliminary experiments have been carried out on low cycle fatigue crack propagation behaviour in type 304 stainless steel in air at 550 0 C, using two types of specimen with a through thickness notch. Both strain controlled and stress controlled fatigue tests have been done under a fully reversed strain or stress cycling. The data obtained are correlated with some fracture mechanics parameters and are discussed with the appropriate parameter for evaluating the low cycle fatigue crack propagation behaviour at elevated temperature. (author)

  10. Microstructural modelling of creep crack growth from a blunted crack

    NARCIS (Netherlands)

    Onck, P.R.; Giessen, E. van der

    1998-01-01

    The effect of crack tip blunting on the initial stages of creep crack growth is investigated by means of a planar microstructural model in which grains are represented discretely. The actual linking-up process of discrete microcracks with the macroscopic crack is simulated, with full account of the

  11. Detection of cracks on concrete surfaces by hyperspectral image processing

    Science.gov (United States)

    Santos, Bruno O.; Valença, Jonatas; Júlio, Eduardo

    2017-06-01

    All large infrastructures worldwide must have a suitable monitoring and maintenance plan, aiming to evaluate their behaviour and predict timely interventions. In the particular case of concrete infrastructures, the detection and characterization of crack patterns is a major indicator of their structural response. In this scope, methods based on image processing have been applied and presented. Usually, methods focus on image binarization followed by applications of mathematical morphology to identify cracks on concrete surface. In most cases, publications are focused on restricted areas of concrete surfaces and in a single crack. On-site, the methods and algorithms have to deal with several factors that interfere with the results, namely dirt and biological colonization. Thus, the automation of a procedure for on-site characterization of crack patterns is of great interest. This advance may result in an effective tool to support maintenance strategies and interventions planning. This paper presents a research based on the analysis and processing of hyper-spectral images for detection and classification of cracks on concrete structures. The objective of the study is to evaluate the applicability of several wavelengths of the electromagnetic spectrum for classification of cracks in concrete surfaces. An image survey considering highly discretized wavelengths between 425 nm and 950 nm was performed on concrete specimens, with bandwidths of 25 nm. The concrete specimens were produced with a crack pattern induced by applying a load with displacement control. The tests were conducted to simulate usual on-site drawbacks. In this context, the surface of the specimen was subjected to biological colonization (leaves and moss). To evaluate the results and enhance crack patterns a clustering method, namely k-means algorithm, is being applied. The research conducted allows to define the suitability of using clustering k-means algorithm combined with hyper-spectral images highly

  12. Comparative study of direct and inverse problems of cracked beams

    Directory of Open Access Journals (Sweden)

    Mahieddine Chettah

    2018-01-01

    Full Text Available In recent decades, the analysis and evaluation of the cracked structures were hot spots in several engineering fields and has been the subject of great interest with important and comprehensive surveys covering various methodologies and applications, in order to obtain reliable and effective methods to maintain the safety and performance of structures on a proactive basis. The presence of a crack, not only causes a local variation in the structural parameters (e.g., the stiffness of a beam at its location, but it also has a global effect which affects the overall dynamic behavior of the structure (such as the natural frequencies. For this reason, the dynamic characterization of the cracked structures can be used to detect damage from non-destructive testing. The objective of this paper is to compare the accuracy and ability of two methods to correctly predict the results for both direct problem to find natural frequencies and inverse problem to find crack’s locations and depths of a cracked simply supported beam. Several cases of crack depths and crack locations are investigated. The crack is supposed to remain open. The Euler–Bernoulli beam theory is employed to model the cracked beam and the crack is represented as a rotational spring with a sectional flexibility. In the first method, the transfer matrix method is used; the cracked beam is modeled as two uniform sub-segments connected by a rotational spring located at the cracked section. In the second method which is based on the Rayleigh’s method, the mode shape of the cracked beam is constructed by adding a cubic polynomial function to that of the undamaged beam. By applying the compatibility conditions at crack’s location and the corresponding boundary conditions, the general forms of characteristic equations for this cracked system are obtained. The two methods are then utilized to determine the locations and depths by using any two natural frequencies of a cracked simply

  13. Linear Cracking in Bridge Decks

    Science.gov (United States)

    2018-03-01

    Concrete cracking in bridge decks remains an important issue relative to deck durability. Cracks can allow increased penetration of chlorides, which can result in premature corrosion of the reinforcing steel and subsequent spalling of the concrete de...

  14. 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.

  15. Crack detection '86

    International Nuclear Information System (INIS)

    1986-01-01

    The participants of the conference heard 36 papers of which 13 were incorporated in INIS. The incorporated papers deal with the quality control of the equipment of nuclear power plants, with technical specifications and possibilities of diverse crack detection devices, as well as with personnel training for nondestructive materials testing. (E.S.)

  16. Mode Shape Analysis of Multiple Cracked Functionally Graded Timoshenko Beams

    Directory of Open Access Journals (Sweden)

    Tran Van Lien

    Full Text Available Abstract The present paper addresses free vibration of multiple cracked Timoshenko beams made of Functionally Graded Material (FGM. Cracks are modeled by rotational spring of stiffness calculated from the crack depth and material properties vary according to the power law throughout the beam thickness. Governing equations for free vibration of the beam are formulated with taking into account actual position of the neutral plane. The obtained frequency equation and mode shapes are used for analysis of the beam mode shapes in dependence on the material and crack parameters. Numerical results validate usefulness of the proposed herein theory and show that mode shapes are good indication for detecting multiple cracks in Timoshenko FGM beams.

  17. Nonlinear ultrasonic fatigue crack detection using a single piezoelectric transducer

    Science.gov (United States)

    An, Yun-Kyu; Lee, Dong Jun

    2016-04-01

    This paper proposes a new nonlinear ultrasonic technique for fatigue crack detection using a single piezoelectric transducer (PZT). The proposed technique identifies a fatigue crack using linear (α) and nonlinear (β) parameters obtained from only a single PZT mounted on a target structure. Based on the different physical characteristics of α and β, a fatigue crack-induced feature is able to be effectively isolated from the inherent nonlinearity of a target structure and data acquisition system. The proposed technique requires much simpler test setup and less processing costs than the existing nonlinear ultrasonic techniques, but fast and powerful. To validate the proposed technique, a real fatigue crack is created in an aluminum plate, and then false positive and negative tests are carried out under varying temperature conditions. The experimental results reveal that the fatigue crack is successfully detected, and no positive false alarm is indicated.

  18. The effect of inflation on the morphology-derived rheological parameters of lava flows and its implications for interpreting remote sensing data - A case study on the 2014/2015 eruption at Holuhraun, Iceland

    Science.gov (United States)

    Kolzenburg, S.; Jaenicke, J.; Münzer, U.; Dingwell, D. B.

    2018-05-01

    Morphology-derived lava flow rheology is a frequently used tool in volcanology and planetary science to determine rheological parameters and deduce the composition of lavas on terrestrial planets and their moons. These calculations are usually based on physical equations incorporating 1) lava flow driving forces: gravity, slope and flow-rate and 2) morphological data such as lava flow geometry: flow-width, -height or shape of the flow outline. All available methods assume that no geometrical changes occur after emplacement and that the measured flow geometry reflects the lava's apparent viscosity and/or yield strength during emplacement. It is however well-established from terrestrial examples that lava flows may inflate significantly after the cessation of flow advance. This inflation affects, in turn, the width-to-height ratio upon which the rheological estimates are based and thus must result in uncertainties in the determination of flow rheology, as the flow height is one of the key parameters in the morphology-based deduction of flow properties. Previous studies have recognized this issue but, to date, no assessment of the magnitude of this error has been presented. This is likely due to a lack of digital elevation models (DEMs) at sufficiently high spatial and temporal resolution. The 2014/15 Holuhraun eruption in central Iceland represents one of the best monitored large volume (1.5 km3) lava flow fields (85 km2) to date. An abundance of scientific field and remote sensing data were collected during its emplacement. Moreover, inflation plays a key role in the emplacement dynamics of the late stage of the lava field. Here, we use a time series of high resolution DEMs acquired by the TanDEM-X satellite mission prior, during and after the eruption to evaluate the error associated with the most common methods of deriving lava flow rheology from morphological parameters used in planetary science. We can distinguish two dominant processes as sources of error in

  19. Ultrasonic testing of fatigue cracks under various conditions

    International Nuclear Information System (INIS)

    Jessop, T.J.; Cameron, A.G.B.

    1983-01-01

    Reliable detection of the fatigue cracks was possible under all conditions studied. Applied load affected the ultrasonic response in a variety of ways but never more than by 20dB and generally considerably less. Material variations affected the response under applied load by up to 20dB. Oxide in the crack and crack morphology affected the response by up to 9dB (12dB under load). Crack size variations and presence of water had little effect. Sizing accuracy was generally within 2mm although there was a tendency to undersize. The time of flight sizing technique gave the best accuracy if a tensile load was applied

  20. Technique to eliminate helium induced weld cracking in stainless steels

    International Nuclear Information System (INIS)

    Chin-An Wang; Chin, B.A.

    1992-01-01

    Experiments have shown that Type 316 stainless steel is susceptible to heat-affected-zone (HAZ) cracking upon cooling when welded using the gas tungsten arc (GTA) process under lateral constraint. The cracking has been hypothesized to be caused by stress-assisted helium bubble growth and rupture at grain boundaries. This study utilized an experimental welding setup which enabled different compressive stresses to be applied to the plates during welding. Autogenous GTA welds were produced in Type 316 stainless steel doped with 256 appm helium. The application of a compressive stress, 55 Mpa, during welding suppressed the previously observed catastrophic cracking. Detailed examinations conducted after welding showed a dramatic change in helium bubble morphology. Grain boundary bubble growth along directions parallel to the weld was suppressed. Results suggest that stress-modified welding techniques may be used to suppress or eliminate helium-induced cracking during joining of irradiated materials

  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. Copyright © 2011 Elsevier Ltd. All rights reserved.

  2. Comparison of experiment and theory for elastic-plastic plane strain crack growth

    International Nuclear Information System (INIS)

    Hermann, L.; Rice, J.R.

    1980-02-01

    Recent theoretical results on elastic-plastic plane strain crack growth, and experimental results for crack growth in a 4140 steel in terms of the theoretical concepts are reviewed. The theory is based on a recent asymptotic analysis of crack surface opening and strain distributions at a quasi-statically advancing crack tip in an ideally-plastic solid. The analysis is incomplete in that some of the parameters which appear in it are known only approximately, especially at large scale yielding. Nevertheless, it suffices to derive a relation between the imposed loading and amount of crack growth, prior to general yielding, based on the assumption that a geometrically similar near-tip crack profile is maintained during growth. The resulting predictions for the variation of J with crack growth are found to fit well to the experimental results obtained on deeply cracked compact specimens

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

    International Nuclear Information System (INIS)

    Chung, Ki Hyun; Yang, Won Ho; Kim, Cheol; Heo, Sung Pil; Ko, Myung Hoon

    2001-01-01

    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

  4. Crack closure, a literature study

    Science.gov (United States)

    Holmgren, M.

    1993-08-01

    In this report crack closure is treated. The state of the art is reviewed. Different empirical formulas for determining the crack closure are compared with each other, and their benefits are discussed. Experimental techniques for determining the crack closure stress are discussed, and some results from fatigue tests are also reported. Experimental data from the literature are reported.

  5. 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.

  6. Test Method Variability in Slow Crack Growth Properties of Sealing Glasses

    Science.gov (United States)

    Salem, J. A.; Tandon, R.

    2010-01-01

    The crack growth properties of several sealing glasses were measured by using constant stress rate testing in 2 and 95 percent RH (relative humidity). Crack growth parameters measured in high humidity are systematically smaller (n and B) than those measured in low humidity, and crack velocities for dry environments are 100x lower than for wet environments. The crack velocity is very sensitive to small changes in RH at low RH. Biaxial and uniaxial stress states produced similar parameters. Confidence intervals on crack growth parameters that were estimated from propagation of errors solutions were comparable to those from Monte Carlo simulation. Use of scratch-like and indentation flaws produced similar crack growth parameters when residual stresses were considered.

  7. Crack propagation and arrest simulation of X90 gas pipe

    International Nuclear Information System (INIS)

    Yang, Fengping; Huo, Chunyong; Luo, Jinheng; Li, He; Li, Yang

    2017-01-01

    To determine whether X90 steel pipe has enough crack arrest toughness or not, a damage model was suggested as crack arrest criterion with material parameters of plastic uniform percentage elongation and damage strain energy per volume. Fracture characteristic length which characterizes fracture zone size was suggested to be the largest mesh size on expected cracking path. Plastic uniform percentage elongation, damage strain energy per volume and fracture characteristic length of X90 were obtained by five kinds of tensile tests. Based on this criterion, a length of 24 m, Φ1219 × 16.3 mm pipe segment model with 12 MPa internal gas pressure was built and computed with fluid-structure coupling method in ABAQUS. Ideal gas state equation was used to describe lean gas behavior. Euler grid was used to mesh gas zone inside the pipe while Lagrangian shell element was used to mesh pipe. Crack propagation speed and gas decompression speed were got after computation. The result shows that, when plastic uniform percentage elongation is equal to 0.054 and damage strain energy per volume is equal to 0.64 J/mm"3, crack propagation speed is less than gas decompression speed, which means the simulated X90 gas pipe with 12 MPa internal pressure can arrest cracking itself. - Highlights: • A damage model was suggested as crack arrest criterion. • Plastic uniform elongation and damage strain energy density are material parameters. • Fracture characteristic length is suggested to be largest mesh size in cracking path. • Crack propagating simulation with coupling of pipe and gas was realized in ABAQUS. • A Chinese X90 steel pipe with 12 MPa internal pressure can arrest cracking itself.

  8. Diffraction-based study of fatigue crack initiation and propagation in aerospace aluminum alloys

    Science.gov (United States)

    Gupta, Vipul K.

    The crack initiation sites and microstructure-sensitive growth of small fatigue cracks are experimentally characterized in two precipitation-hardened aluminum alloys, 7075-T651 and 7050-T7451, stressed in ambient temperature moist-air (warm-humid) and -50°C dry N2 (cold-dry) environmental conditions. Backscattered electron imaging (BSE) and energy dispersive spectroscopy (EDS) of the fracture surfaces showed that Fe-Cu rich constituent particle clusters are the most common initiation sites within both alloys stressed in either environment. The crack growth within each alloy, on average, was observed to be slowed in the cold-dry environment than in the warm-humid environment, but only at longer crack lengths. Although no overwhelming effects of grain boundaries and grain orientations on small-crack growth were observed, crack growth data showed local fluctuations within individual grains. These observations are understood as crack propagation through the underlying substructure at the crack surface and frequent interaction with low/high-angle grain and subgrain boundaries, during cyclic loading, and, are further attributed to periodic changes in crack propagation path and multiple occurrences of crack-branching observed in the current study. SEM-based stereology in combination with electron backscattered diffraction (EBSD) established fatigue crack surface crystallography within the region from ˜1 to 50 mum of crack initiating particle clusters. Fatigue crack facets were parallel to a wide variety of crystallographic planes, with pole orientations distributed broadly across the irreducible stereographic triangle between the {001} and {101}-poles within both warm-humid and cold-dry environments. The results indicate environmentally affected fatigue cracking in both cases, given the similarity between the observed morphology and crystallography with that of a variety of aerospace aluminum alloys cracked in the presence of moist-air. There was no evidence of

  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. Separating the Influence of Environment from Stress Relaxation Effects on Dwell Fatigue Crack Growth

    Science.gov (United States)

    Telesman, Jack; Gabb, Tim; Ghosn, Louis J.

    2016-01-01

    Seven different microstructural variations of LSHR were produced by controlling the cooling rate and the subsequent aging and thermal exposure heat treatments. Through cyclic fatigue crack growth testing performed both in air and vacuum, it was established that four out of the seven LSHR heat treatments evaluated, possessed similar intrinsic environmental resistance to cyclic crack growth. For these four heat treatments, it was further shown that the large differences in dwell crack growth behavior which still persisted, were related to their measured stress relaxation behavior. The apparent differences in their dwell crack growth resistance were attributed to the inability of the standard linear elastic fracture mechanics (LEFM) stress intensity parameter to account for visco-plastic behavior. Crack tip stress relaxation controls the magnitude of the remaining local tensile stresses which are directly related to the measured dwell crack growth rates. It was hypothesized that the environmentally weakened grain boundary crack tip regions fail during the dwells when their strength is exceeded by the remaining local crack tip tensile stresses. It was shown that the classical creep crack growth mechanisms such as grain boundary sliding did not contribute to crack growth, but the local visco-plastic behavior still plays a very significant role by determining the crack tip tensile stress field which controls the dwell crack growth behavior. To account for the influence of the visco-plastic behavior on the crack tip stress field, an empirical modification to the LEFM stress intensity parameter, Kmax, was developed by incorporating into the formulation the remaining stress level concept as measured by simple stress relaxation tests. The newly proposed parameter, Ksrf, did an excellent job in correlating the dwell crack growth rates for the four heat treatments which were shown to have similar intrinsic environmental cyclic fatigue crack growth resistance.

  11. Evaluation Model for Restraint Effect of Pressure Induced Bending on the Plastic Crack Opening of Circumferential Through-Wall-Crack

    International Nuclear Information System (INIS)

    Kim, Jin-Weon

    2006-01-01

    Most of the pipe crack evaluation procedures, including leak-before-break (LBB) analysis, assume that the cracked pipe subjected to remote bending or internal pressure is free to rotate. In this case, the pressure induced bending (PIB) enhances crack opening of a through-wall-crack (TWC) in a pipe. In a real piping system, however, the PIB will be restrained because the ends of the pipe are constrained by the rest of the piping system. Hence, the amount of restraint affects the crack opening of a TWC in a pipe, and the restraint effect on crack opening directly affects the results of LBB evaluation. Therefore, it is necessary to investigate the restraint effect of PIB on crack opening displacement (COD) to quantify the uncertainties in current analysis procedures and to ensure the application of LBB concepts to nuclear piping systems. Recently, several researches were conducted to investigate the restraint effect of PIB on COD, and they proposed a simplified model to evaluate COD under restrained conditions. However, these results are quite limited because the restraint effect was evaluated only in terms of linear-elastic crack opening. In practice, the TWC in a pipe behaves plastically under normal operating loads, and the current LBB analysis methodologies require elastic-plastic crack opening evaluation. Therefore, this study evaluates the restraint effect of PIB on the plastic crack opening of a TWC in a pipe using finite element analysis under various influencing parameters. Based on these results, a closed-from model to be able to estimate the restraint effect of PIB on plastic crack opening is proposed

  12. Crack growth in an austenitic stainless steel at high temperature

    International Nuclear Information System (INIS)

    Polvora, J.P.

    1998-01-01

    This study deals with crack propagation at 650 deg C on an austenitic stainless steel referenced by Z2 CND 17-12 (316L(NN)). It is based on an experimental work concerning two different cracked specimens: CT specimens tested at 650 deg C in fatigue, creep and creep-fatigue with load controlled conditions (27 tests), tube specimens containing an internal circumferential crack tested in four points bending with displacement controlled conditions (10 tests). Using the fracture mechanics tools (K, J and C* parameters), the purpose here is to construct a methodology of calculation in order to predict the evolution of a crack with time for each loading condition using a fracture mechanics global approach. For both specimen types, crack growth is monitored by using a specific potential drop technique. In continuous fatigue, a material Paris law at 650 deg C is used to correlate crack growth rate with the stress intensity factor range corrected with a factor U(R) in order to take into account the effects of crack closure and loading ratio R. In pure creep on CT specimens, crack growth rate is correlated to the evolution of the C* parameter (evaluated experimentally) which can be estimated numerically with FEM calculations and analytically by using a simplified method based on a reference stress approach. A modeling of creep fatigue growth rate is obtained from a simple summation of the fatigue contribution and the creep contribution to the total crack growth. Good results are obtained when C* parameter is evaluated from the simplified expression C* s . Concerning the tube specimens tested in 4 point bending conditions, a simulation based on the actual A 16 French guide procedure proposed at CEA. (authors)

  13. Crack growth simulation for plural crack using hexahedral mesh generation technique

    International Nuclear Information System (INIS)

    Orita, Y; Wada, Y; Kikuchi, M

    2010-01-01

    This paper describes a surface crack growth simulation using a new mesh generation technique. The generated mesh is constituted of all hexahedral elements. Hexahedral elements are suitable for an analysis of fracture mechanics parameters, i.e. stress intensity factor. The advantage of a hexahedral mesh is good accuracy of an analysis and less number of degrees of freedoms than a tetrahedral mesh. In this study, a plural crack growth simulation is computed using the hexahedral mesh and its distribution of stress intensity factor is investigated.

  14. 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.

  15. A numerical analysis of crack growth in brittle microcracking composites

    International Nuclear Information System (INIS)

    Biner, S.B.

    1993-01-01

    A set of numerical analyses of crack growth was performed to elucidate the mechanism of microcracking on the observed fracture behavior of brittle solids and composites. The random nucleation, orientation and size effects of discrete microcracks and resulting interactions are fully accounted for in a hybrid finite element model. The results indicate that the energy expenditure due the microcrack nucleation seems not to contribute significantly to the resistance to crack growth. The main controlling parameter appears to be elastic interaction of the microcracks with the main crack in the absence of a reinforcing phase; therefore, the microcrack density plays an important role. In the case of the composites, the interaction of the main crack with the stress fields of the reinforcing phase, rather than interaction of microcracks, is the controlling parameter for the resistance to the crack growth even in the presence of a large population of microcracks. It will be also shown that the crack branching and crack kinking can readily develop as a result of microcracking

  16. A study on the fractures of iodine induced stress corrosion cracking of new zirconium alloys

    International Nuclear Information System (INIS)

    Peng Qian; Zhao Wenjin; Li Weijun; Tang Zhenghua; Heng Xuemei

    2005-10-01

    The morphology and chemical compositions of I-SCC fractures of new zirconium alloys were investigated by SEM and EDXA. The feature on fracture surface for I-SCC samples, such as corrosion products, the secondary cracking, intergranular cracking and pseudo-cleavage transgranular cracking, have been observed. And the fluting, the typical characteristic of I-SCC also has been found. Intergranular cracking is visible at crack initiation stage and transgranular cracking is distinguished at crack propagation stage. The corrosion products are mainly composed of Zr and O; and I can be detected on the local pseudocleavage zone. The most of grooves on the fractures of relieved-stress annealing samples are parallel with the roll plane. The intergranular cracking in relieved-stress annealing samples is not obvious. When the test temperature increases, the activity of iodine increases and the stress on crack tip is easier to be released, thus the corrosion products on fracture also increase and intergranular cracking is visible. The partial pressure of iodine influents the thickness of corrosion products, and intergranular cracking is easier to be found when iodine partial pressure is high enough. (authors)

  17. Instability analysis of a fully plastic center-cracked strip of a power hardening material

    International Nuclear Information System (INIS)

    Zahoor, A.; Paris, P.C.

    1978-01-01

    An approach for predicting unstable crack growth in a power hardening material is discussed. A fully plastic center-cracked strip of finite width under plane strain conditions, which involves J-controlled crack growth, is analyzed. The conditions for unstable crack growth are identified in terms of a non-dimensional parameter, the Tearing Modulus, T, which incorporates the effect of elastic system compliance on the cracked structure as well as the influence of hardening. Numerical results also illustrate the strong influences on stability of both the strain hardening characteristics of the material and certain geometrical proportions which greatly influence the system compliance. (author)

  18. Study on crack generation at root of socket welds

    International Nuclear Information System (INIS)

    Iida, K.; Matsuda, F.; Sato, M.; Nayama, M.; Akitomo, N.

    1994-01-01

    A program to investigate the fatigue strength of the socket welded joint has been carried out by the Japan Power Engineering and Inspection Corporation (JAPEIC) under contract with the Ministry of International Trade and Industry (MITI). In this program, many types of socket welded joints were prepared with parameters varied, and the small cracks were observed at root sections of some welded joints. This study has been carried out to make clear the factors on crack generation at the root sections of the socket welded joints and to understand the cause and mechanism of crack generation. (orig.)

  19. 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.

  20. Cracking of charged polytropes with generalized polytropic equation of state

    Energy Technology Data Exchange (ETDEWEB)

    Azam, M. [University of Education, Division of Science and Technology, Lahore (Pakistan); Mardan, S.A. [University of the Management and Technology, Department of Mathematics, Lahore (Pakistan)

    2017-02-15

    We discuss the occurrence of cracking in charged anisotropic polytropes with generalized polytropic equation of state through two different assumptions; (i) by carrying out local density perturbations under a conformally flat condition (ii) by perturbing anisotropy, polytropic index and charge parameters. For this purpose, we consider two different definitions of polytropes that exist in literature. We conclude that under local density perturbations scheme cracking does not appear in both types of polytropes and stable configuration is observed, while with the second type of perturbation cracking appears in both types of polytropes under certain conditions. (orig.)

  1. 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....

  2. Delayed hydride cracking: alternative pre-cracking method

    International Nuclear Information System (INIS)

    Mieza, Juan I.; Ponzoni, Lucio M.E.; Vigna, Gustavo L.; Domizzi, Gladys

    2009-01-01

    The internal components of nuclear reactors built-in Zr alloys are prone to a failure mechanism known as Delayed Hydride Cracking (DHC). This situation has triggered numerous scientific studies in order to measure the crack propagation velocity and the threshold stress intensity factor associated to DHC. Tests are carried out on fatigued pre-crack samples to ensure similar test conditions and comparable results. Due to difficulties in implementing the fatigue pre-crack method it would be desirable to replace it with a pre-crack produced by the same process of DHC, for which is necessary to demonstrate equivalence of this two methods. In this work tests on samples extracted from two Zr-2.5 Nb tubes were conducted. Some of the samples were heat treated to obtain a range in their metallurgical properties as well as different DHC velocities. A comparison between velocities measured in test samples pre-cracked by fatigue and RDIH is done, demonstrating that the pre-cracking method does not affect the measured velocity value. In addition, the incubation (t inc ), which is the time between the application of the load and the first signal of crack propagation, in samples pre-cracked by RDIH, was measured. It was found that these times are sufficiently short, even in the worst cases (lower speed) and similar to the ones of fatigued pre-cracked samples. (author)

  3. Morphology and fracture of enamel.

    Science.gov (United States)

    Myoung, Sangwon; Lee, James; Constantino, Paul; Lucas, Peter; Chai, Herzl; Lawn, Brian

    2009-08-25

    This study examines the inter-relation between enamel morphology and crack resistance by sectioning extracted human molars after loading to fracture. Cracks appear to initiate from tufts, hypocalcified defects at the enamel-dentin junction, and grow longitudinally around the enamel coat to produce failure. Microindentation corner cracks placed next to the tufts in the sections deflect along the tuft interfaces and occasionally penetrate into the adjacent enamel. Although they constitute weak interfaces, the tufts are nevertheless filled with organic matter, and appear to be stabilized against easy extension by self-healing, as well as by mutual stress-shielding and decussation, accounting at least in part for the capacity of tooth enamel to survive high functional forces.

  4. Effect of dynamic strain ageing on the environmentally assisted cracking of low-alloy steels oxygenated high-temperature water

    International Nuclear Information System (INIS)

    Devrient, B.; Roth, A.; Kuester, K.; Ilg, U.; Widera, M.

    2007-01-01

    The plastic deformation behavior of low-alloy steels (LAS) is significantly influenced by their individual susceptibility to dynamic strain ageing (DSA). Interstitial atoms of nitrogen (N) or carbon (C) in the steel matrix can change the mechanical properties like ductility and strength by interaction with moving dislocations during plastic deformation. The degree of DSA is depending on temperature and strain rate during plastic deformation. Under critical parameter combinations strength increases while ductility decreases. Furthermore, the interaction of dislocations and interstitial atoms can lead to a localization of plastic deformation, which results in planar gliding processes. Shear bands in LAS types with a high susceptibility to DSA show significantly higher slip steps during plastic deformation as compared to heats with low susceptibility to DSA. Since the basic mechanism of environmentally-assisted cracking (EAC) of LAS in high-temperature water (HTW) environment is slip-step-dissolution, slip behavior is of crucial nature for the kinetics of crack initiation and crack growth. Therefore, a program concerning deformation behavior, slip characterization regarding distribution and size, and behavior in oxygenated HTW environment was performed. Analysis of slip steps by advanced techniques for surface morphology investigation showed that the maximum height of slip steps is in the range of freshly formed magnetite layers on LAS in oxygenated HTW environment. This supports the active effect of localized deformation on EAC in LAS types of high susceptibility to DSA. The exposure to oxygenated HTW environment with additional mechanical loading under critical combinations of temperature and strain rate of different LAS types with high, intermediate and low susceptibility to DSA in Slow Strain Rate Tensile-tests (SSRT) showed preferential crack initiation in the areas of coarse shear bands due to localized deformation. Furthermore, a continuous transition of the

  5. Fatigue Crack Topography.

    Science.gov (United States)

    1984-01-01

    alloys (2). [--I Fig. 6. Fatigue fracture in Nitrile- butadien rubber ( NBR ). Fig. 7. The characteristic features of fatigue fracture in press moulded...in plastics and even in rubber . It follows therefore, that fatigue fractures must also occur in the mineral layers of our earth or in the rock on...effective until the weakest point yields and forms a crack. To get a feeling for this process, you can imagine that the stressed article is made of rubber

  6. Distributed password cracking

    OpenAIRE

    Crumpacker, John R.

    2009-01-01

    Approved for public release, distribution unlimited Password cracking requires significant processing power, which in today's world is located at a workstation or home in the form of a desktop computer. Berkeley Open Infrastructure for Network Computing (BOINC) is the conduit to this significant source of processing power and John the Ripper is the key. BOINC is a distributed data processing system that incorporates client-server relationships to generically process data. The BOINC structu...

  7. 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.

  8. Cracking hydrocarbons. [British patent

    Energy Technology Data Exchange (ETDEWEB)

    Heyl, G E

    1926-05-06

    The vapors from a still in which oils, coal tar, pitch, creosote, and c. or solid carbonaccous material such as coal or shale are cracked by being heated to 600/sup 0/ to 1000/sup 0/C. are passed through a fractionating column to remove high-boiling constituents which are passed into a second cracking still. The vapors from this still are treated to separate high-boiling fractions which are passed into a third still. The sills preferably contain removable troughs or liners, which are freed from carbon deposits either after removal from the still or by a scraping disc which is rotated in and moved along the trough. Oil to be cracked is forced by a pump through a preheater to a still. Vapours pass through a carbon separator and dephlegmator to a condenser. The reflux from the dephlegmator is forced by a pump to a still, the vapors from which pass through a carbon separator and a dephlegmator, the reflux from which is passed into a third still fitted with a separate carbon separator, dephlegmator and final condenser.

  9. Methods of forecasting crack growth rate under creep conditions

    International Nuclear Information System (INIS)

    Ol'kin, S.I.

    1979-01-01

    Using construction aluminium alloy application possibility of linear mechanics of the destruction for quantitative description of crack development process under creepage conditions is investigated. It is shown, that the grade dependence between the stress intensity coefficient and the crack growth rate takes place only at certain combination of the sample geometry and creepage parameters, and consequently, its applicability in every given case must necessarily be tested experimentally

  10. Experimental study of the crack depth ratio threshold to analyze the slow crack growth by creep of high density polyethylene pipes

    International Nuclear Information System (INIS)

    Laiarinandrasana, Lucien; Devilliers, Clémence; Lucatelli, Jean Marc; Gaudichet-Maurin, Emmanuelle; Brossard, Jean Michel

    2014-01-01

    To assess the durability of drinking water connection pipes subjected to oxidation and slow crack growth, a comprehensive database was constructed on a novel specimen geometry: the pre-cracked NOL ring. 135 tests were carried out consisting of initial crack depth ratio ranging from 0.08 to 0.6; single or double longitudinal cracks: tensile with steady strain rate and creep loading. A threshold value of the crack depth ratio of 0.2, induced by the oxidation was determined by analyzing several mechanical parameters. This threshold value was shown to be independent on the strain rate effects, single or double crack configuration and the kind of loading: tensile or creep. Creep test results with crack depth ratio larger than 0.2 were then utilized to establish a failure assessment diagram. A methodology allowing the prediction of residual lifetime of in-service pipes was proposed, using this diagram. - Highlights: • Experimental data on pre-cracked rings featuring a longitudinally cracked HDPE pipe. • Crack depth ratio threshold for slow crack growth study consecutive to oxidation. • Investigation of the effects of the single/double notch(es) and of the strain rate. • Original results obtained from tests performed with tensile and creep loadings. • Correlation between creep initiation time and C* with DENT and ring specimens

  11. Studies on the behavior of part-through circumferential crack at intrados in elbows under in-plane bending moment

    International Nuclear Information System (INIS)

    Srivastava, A.; Prabhakaran, K.M.; Ghosh, A.K.

    2011-01-01

    Highlights: → Behavior of cracked elbows with part-through crack at intrados under bending moment is studied. → Some part of crack always opens and some part gets closed irrespective of mode of applied moment. → Fraction of the crack that opens basically decides the weakening effect of the cracked elbow. → Results will be useful for fracture studies and limit load estimation especially for LBB. - Abstract: This paper presents the behavior of part-through circumferential crack at intrados in elbows under in-plane bending moment. This is based on detailed non-linear (both material and geometric) finite element analysis performed on various sizes of elbows (generally used in piping industry), having different crack sizes. It is observed that some part of the crack always opens and some part gets closed irrespective of the mode of applied bending moment (opening/closing). The fraction of the crack that opens basically decides the weakening effect of the cracked elbow. It is observed that there is a threshold value of crack length and crack depth, before which no crack opening is observed under opening mode. Also as elbow becomes thinner, the threshold value of above two parameters increases. Quite interestingly, the part of crack which closes in opening mode opens under closing mode. The above mentioned study on the behavior of crack will be useful for fracture studies and limit load estimation especially when leak before break concept is to be employed.

  12. Thermal fatigue crack growth on a thick wall tube containing a semi elliptical circumferential crack

    International Nuclear Information System (INIS)

    Deschanels, H.; Wakai, T.; Lacire, M.H.; Michel, B.

    2001-01-01

    In order to check the ability of the simplified assessment procedure (A16 guide) to predict fatigue crack growth, a benchmark problem was conducted. This work is carried out under the project ''agreement on the Exchange of Information and Collaboration in the field of Research and Development of Fast Breeder Reactor (FBR) between Europe (EU) and Japan''. Experimental work is conducted by PNC using Air cooled Thermal transient Test Facility (ATTF). Specimen is a thick wall tube containing a semi elliptical (3-D) circumferential crack and subjected to cyclic thermal transients. The constitutive material is the 304 austenitic stainless steel type SUS304. Due to thermal shock (650 C-300 C) the stress distribution through the wall is non-linear and well approximated using a 3 rd order polynomial. When comparing computations and tests data we observe a good agreement for the crack propagation in length. In crack depth, accurate results are obtained in the first part of the test, but on the later stage of the experiment the computations slightly underestimate the propagation (deep crack). In addition, we notice the importance of good evaluation of fracture mechanics parameters for non-linear stress distribution through the wall. At present A16 guide handbook gives stress intensity factor solutions for non-linear stress distribution through the wall. (author)

  13. Effect of Nano-TiC Dispersed Particles and Electro-Codeposition Parameters on Morphology and Structure of Hybrid Ni/TiC Nanocomposite Layers.

    Science.gov (United States)

    Benea, Lidia; Celis, Jean-Pierre

    2016-04-06

    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.

  14. Chalcone Synthase (CHS) Gene Suppression in Flax Leads to Changes in Wall Synthesis and Sensing Genes, Cell Wall Chemistry and Stem Morphology Parameters

    Science.gov (United States)

    Zuk, Magdalena; Działo, Magdalena; Richter, Dorota; Dymińska, Lucyna; Matuła, Jan; Kotecki, Andrzej; Hanuza, Jerzy; Szopa, Jan

    2016-01-01

    The chalcone synthase (CHS) gene controls the first step in the flavonoid biosynthesis. In flax, CHS down-regulation resulted in tannin accumulation and reduction in lignin synthesis, but plant growth was not affected. This suggests that lignin content and thus cell wall characteristics might be modulated through CHS activity. This study investigated the possibility that CHS affects cell wall sensing as well as polymer content and arrangement. CHS-suppressed and thus lignin-reduced plants showed significant changes in expression of genes involved in both synthesis of components and cell wall sensing. This was accompanied by increased levels of cellulose and hemicellulose. CHS-reduced flax also showed significant changes in morphology and arrangement of the cell wall. The stem tissue layers were enlarged averagely twofold compared to the control, and the number of fiber cells more than doubled. The stem morphology changes were accompanied by reduction of the crystallinity index of the cell wall. CHS silencing induces a signal transduction cascade that leads to modification of plant metabolism in a wide range and thus cell wall structure. PMID:27446124

  15. 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.

  16. A reliability index for assessment of crack profile reconstructed from ECT signals using a neural-network approach

    International Nuclear Information System (INIS)

    Yusa, Noritaka; Chen, Zhenmao; Miya, Kenzo; Cheng, Weiying

    2002-01-01

    This paper proposes a reliability parameter to enhance an version scheme developed by authors. The scheme is based upon an artificial neural network that simulates mapping between eddy current signals and crack profiles. One of the biggest advantages of the scheme is that it can deal with conductive cracks, which is necessary to reconstruct natural cracks. However, it has one significant disadvantage: the reliability of reconstructed profiles was unknown. The parameter provides an index for assessment of the crack profile and overcomes this disadvantage. After the parameter is validated by reconstruction of simulated cracks, it is applied to reconstruction of natural cracks that occurred in steam generator tubes of a pressurized water reactor. It is revealed that the parameter is applicable to not only simulated cracks but also natural ones. (author)

  17. Investigation of Cracks Found in Helicopter Longerons

    Science.gov (United States)

    Newman, John A.; Baughman, James M.; Wallace, Terryl A.

    2009-01-01

    Four cracked longerons, containing a total of eight cracks, were provided for study. Cracked regions were cut from the longerons. Load was applied to open the cracks, enabling crack surface examination. Examination revealed that crack propagation was driven by fatigue loading in all eight cases. Fatigue crack initiation appears to have occurred on the top edge of the longerons near geometric changes that affect component bending stiffness. Additionally, metallurigical analysis has revealed a local depletion in alloying elements in the crack initiation regions that may be a contributing factor. Fatigue crack propagation appeared to be initially driven by opening-mode loading, but at a crack length of approximately 0.5 inches (12.7 mm), there is evidence of mixed-mode crack loading. For the longest cracks studied, shear-mode displacements destroyed crack-surface features of interest over significant portions of the crack surfaces.

  18. Modified Dugdale crack models - some easy crack relations

    DEFF Research Database (Denmark)

    Nielsen, Lauge Fuglsang

    1997-01-01

    the same strength as a plain Dugdale model. The critical energy release rates Gamma_CR, however, become different. Expressions (with easy computer algorithms) are presented in the paper which relate critical energy release rates and crack geometry to arbitrary cohesive stress distributions.For future...... lifetime analysis of viscoelastic materials strain energy release rates, crack geometries, and cohesive stress distributions are considered as related to sub-critical loads sigma stress-deformation tests......The Dugdale crack model is widely used in materials science to predict strength of defective (cracked) materials. A stable Dugdale crack in an elasto-plastic material is prevented from spreading by uniformly distributed cohesive stresses acting in narrow areas at the crack tips. These stresses...

  19. Creep crack growth in phosphorus alloyed oxygen free copper

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Rui; Seitisleam, Facredin (Swerea KIMAB (Sweden)); Sandstroem, Rolf; Jin, Lai-Zhe (Materials Science and Engineering, Royal Inst. of Technology (Sweden))

    2011-01-15

    Using standard compact tension (CT) specimens taken from a pierce and draw cylinder, creep crack growth (CCG) has been studied in phosphorus-alloyed oxygen-free copper (Cu-OFP) parent metal at 22, 75, 175, and 215 deg C. Pre- and post-test metallography are performed. At higher temperatures the rupture time of CCG is shorter by a factor up of 65 than that of uniaxial at same stress/reference stress. At 175 and 215 deg C, crack does grow by creep about 10 mm before final instantaneous failure. In contrast, there is hardly any visible crack growth at 22 and 75 deg C. The tests were interrupted after 5000 to 13000 hours. For ruptured tests at 175 and 215 deg C, strongly elongated and deformed grains are observed adjacent to crack. Extensive and intergranular creep cavities and microcracks are found several mm around crack. For interrupted tests at 22 and 75 deg C, strongly elongated and deformed grains, creep cavities, as well as microcracks are observed close to crack tip. Surface cracks from both sides have initiated and grown about 45 deg to the load direction towards inside. For the interrupted tests, hardness adjacent to crack tip has more than doubled because of work hardening, or heavy deformation. This is consistent with large crack tip opening. The true strain at the crack tip is estimated to 10 and 4 for the tests at 22 and 75 deg C, respectively. The stress state behind the crack tip has been modelled with FEM. Stress relaxation after loading has also been taken into account. A model for the creep damage based on the creep strain rate has been formulated that can describe the uniaxial creep rupture data without fitting parameters. Based on the formulation for the creep damage, a model for the crack propagation has been set up. When the creep damage has reached the value unity in front of the crack tip, the crack is assumed to propagate. Taking multiaxial effects into account the observed life times of the CT specimens can be well described. The multiaxial

  20. Creep crack growth in phosphorus alloyed oxygen free copper

    International Nuclear Information System (INIS)

    Wu, Rui; Seitisleam, Facredin; Sandstroem, Rolf; Jin, Lai-Zhe

    2011-01-01

    Using standard compact tension (CT) specimens taken from a pierce and draw cylinder, creep crack growth (CCG) has been studied in phosphorus-alloyed oxygen-free copper (Cu-OFP) parent metal at 22, 75, 175, and 215 deg C. Pre- and post-test metallography are performed. At higher temperatures the rupture time of CCG is shorter by a factor up of 65 than that of uniaxial at same stress/reference stress. At 175 and 215 deg C, crack does grow by creep about 10 mm before final instantaneous failure. In contrast, there is hardly any visible crack growth at 22 and 75 deg C. The tests were interrupted after 5000 to 13000 hours. For ruptured tests at 175 and 215 deg C, strongly elongated and deformed grains are observed adjacent to crack. Extensive and intergranular creep cavities and microcracks are found several mm around crack. For interrupted tests at 22 and 75 deg C, strongly elongated and deformed grains, creep cavities, as well as microcracks are observed close to crack tip. Surface cracks from both sides have initiated and grown about 45 deg to the load direction towards inside. For the interrupted tests, hardness adjacent to crack tip has more than doubled because of work hardening, or heavy deformation. This is consistent with large crack tip opening. The true strain at the crack tip is estimated to 10 and 4 for the tests at 22 and 75 deg C, respectively. The stress state behind the crack tip has been modelled with FEM. Stress relaxation after loading has also been taken into account. A model for the creep damage based on the creep strain rate has been formulated that can describe the uniaxial creep rupture data without fitting parameters. Based on the formulation for the creep damage, a model for the crack propagation has been set up. When the creep damage has reached the value unity in front of the crack tip, the crack is assumed to propagate. Taking multiaxial effects into account the observed life times of the CT specimens can be well described. The multiaxial

  1. Mechanism of crack initiation and crack growth under thermal and mechanical fatigue loading

    International Nuclear Information System (INIS)

    Utz, S.; Soppa, E.; Silcher, H.; Kohler, C.

    2013-01-01

    measurements the deformation induced transformation of an fcc-austenite into a bcc α'-martensite was observed in different stages of the specimen lifetime. Plastic zones develop at the crack tips, in which stress and strain amplitudes are much higher than the nominal loading, and enable martensitic transformation in the surrounding of the crack tip. The consequence of this is that cracks grow in the ''martensitic tunnels''. The short and long crack growth behaviours of the steel X6CrNiNb18-10 under mechanical loading at room temperature and T = 288 C were studied for different loading parameters. Moreover, the R-ratio was modified in order to study the effect of crack closure at the crack tip for long cracks. Several FE models of specimens with different geometries and microstructures were created and cyclically loaded according to the experimental boundary conditions. A plastic constitutive law based on a Chaboche type model was implemented as a user subroutine in the FE software ABAQUS. The corresponding material parameters were identified using uniaxial LCF tests of X6CrNiNb18-10 with different strain amplitudes and at different temperatures. These calculations delivered the estimation of stress and strain distributions in the critical areas in which the crack initiation was expected.

  2. Mechanism of crack initiation and crack growth under thermal and mechanical fatigue loading

    Energy Technology Data Exchange (ETDEWEB)

    Utz, S.; Soppa, E.; Silcher, H.; Kohler, C. [Stuttgart Univ. (Germany). Materials Testing Inst.

    2013-07-01

    measurements the deformation induced transformation of an fcc-austenite into a bcc α'-martensite was observed in different stages of the specimen lifetime. Plastic zones develop at the crack tips, in which stress and strain amplitudes are much higher than the nominal loading, and enable martensitic transformation in the surrounding of the crack tip. The consequence of this is that cracks grow in the ''martensitic tunnels''. The short and long crack growth behaviours of the steel X6CrNiNb18-10 under mechanical loading at room temperature and T = 288 C were studied for different loading parameters. Moreover, the R-ratio was modified in order to study the effect of crack closure at the crack tip for long cracks. Several FE models of specimens with different geometries and microstructures were created and cyclically loaded according to the experimental boundary conditions. A plastic constitutive law based on a Chaboche type model was implemented as a user subroutine in the FE software ABAQUS. The corresponding material parameters were identified using uniaxial LCF tests of X6CrNiNb18-10 with different strain amplitudes and at different temperatures. These calculations delivered the estimation of stress and strain distributions in the critical areas in which the crack initiation was expected.

  3. 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.

  4. Fatigue-crack propagation behavior of Inconel 600

    International Nuclear Information System (INIS)

    James, L.A.

    1976-05-01

    The techniques of linear-elastic fracture mechanics were employed to characterize the effects of several parameters upon the fatigue-crack propagation behavior of Inconel 600. The parameters studied included temperature, cyclic frequency, stress ratio, thermal aging, and a limited amount of testing in a liquid sodium environment

  5. 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.

  6. 3-D analysis of fatigue crack behaviour in a shot peened steam turbine blade material

    Energy Technology Data Exchange (ETDEWEB)

    He, B.Y., E-mail: Binyan.he@soton.ac.uk [Engineering Materials, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ (United Kingdom); Katsamenis, O.L. [muVIS X-ray Imaging Centre, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ (United Kingdom); Mellor, B.G.; Reed, P.A.S. [Engineering Materials, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ (United Kingdom)

    2015-08-26

    Serial mechanical sectioning and high resolution X-ray tomography have been used to study the three-dimensional morphology of small fatigue cracks growing in a 12 Cr tempered martensitic steam turbine blade material. A range of surface conditions has been studied, namely polished and shot peened (with varying levels of intensity). In the polished (unpeened) condition, inclusions (alumina and manganese sulphide) played an important role in initiating and controlling early fatigue crack behaviour. When fatigue cracks initiated from an alumina stringer, the crack morphology was normally dominated by single stringers, which were always in the centre of the fatigue crack, indicating its primary role in initiation. Manganese sulphide inclusion groups however seemed to dominate and affect the crack path along both the surface and depth crack growth directions. The more intensely shot peened condition did not however evidence inclusion or stringer affected fatigue crack initiation or growth behaviour; sub-surface crack coalescence being clearly observed by both serial sectioning and computed tomography (CT) imaging techniques at a depth of about 150–180 μm. These sub-surface crack coalescences can be linked to both the extent of the compressive residual stress as well as the depth of the plastic deformation arising from the intense shot peening process. Shot peening appears to provide a different defect population that initiates fatigue cracks and competes with the underlying metallurgical defect populations. The most beneficial shot peening process would in this case appear to “deactivate” the original metallurgical defect population and substitute a known defect distribution from the shot peening process from which fatigue cracks grow rather slowly in the strain hardened surface layer which also contains compressive residual stresses. A benefit to fatigue life in bending, even under Low Cycle Fatigue (LCF) conditions, has been observed in these tests if a

  7. 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.

  8. Crack width monitoring of concrete structures based on smart film

    International Nuclear Information System (INIS)

    Zhang, Benniu; Wang, Shuliang; Li, Xingxing; Zhang, Xu; Yang, Guang; Qiu, Minfeng

    2014-01-01

    Due to its direct link to structural security, crack width is thought to be one of the most important parameters reflecting damage conditions of concrete structures. However, the width problem is difficult to solve with the existing structural health monitoring methods. In this paper, crack width monitoring by means of adhering enameled copper wires with different ultimate strains on the surface of structures is proposed, based on smart film crack monitoring put forward by the present authors. The basic idea of the proposed method is related to a proportional relationship between the crack width and ultimate strain of the broken wire. Namely, when a certain width of crack passes through the wire, some low ultimate strain wires will be broken and higher ultimate strain wires may stay non-broken until the crack extends to a larger scale. Detection of the copper wire condition as broken or non-broken may indicate the width of the structural crack. Thereafter, a multi-layered stress transfer model and specimen experiment are performed to quantify the relationship. A practical smart film is then redesigned with this idea and applied to Chongqing Jiangjin Yangtze River Bridge. (paper)

  9. Crack width monitoring of concrete structures based on smart film

    Science.gov (United States)

    Zhang, Benniu; Wang, Shuliang; Li, Xingxing; Zhang, Xu; Yang, Guang; Qiu, Minfeng

    2014-04-01

    Due to its direct link to structural security, crack width is thought to be one of the most important parameters reflecting damage conditions of concrete structures. However, the width problem is difficult to solve with the existing structural health monitoring methods. In this paper, crack width monitoring by means of adhering enameled copper wires with different ultimate strains on the surface of structures is proposed, based on smart film crack monitoring put forward by the present authors. The basic idea of the proposed method is related to a proportional relationship between the crack width and ultimate strain of the broken wire. Namely, when a certain width of crack passes through the wire, some low ultimate strain wires will be broken and higher ultimate strain wires may stay non-broken until the crack extends to a larger scale. Detection of the copper wire condition as broken or non-broken may indicate the width of the structural crack. Thereafter, a multi-layered stress transfer model and specimen experiment are performed to quantify the relationship. A practical smart film is then redesigned with this idea and applied to Chongqing Jiangjin Yangtze River Bridge.

  10. A theoretical evaluation of the oxygen concentration in a corrosion-fatigue crack

    International Nuclear Information System (INIS)

    Turnbull, A.

    1981-01-01

    The oxygen concentration in a corrosion-fatigue crack has been evaluated theoretically by assuming that oxygen was consumed by cathodic reduction on the walls of the crack and mass transport occurred by diffusion and advection (forced convection), with the latter resulting from the sinusoidal variation of the displacement of the crack walls. By using parameters relevant to a compact tension specimen, the time-dependent distribution of the oxygen concentration in the crack was calculated as a function of ΔK (the range of the stress intensity factor), R-value (minimum load/maximum load), frequency, crack length, and electrode potential. The influence of advection was to significantly enhance the mass transport of oxygen in the crack compared with ''diffusion-only'' even at low frequencies and low ΔK. Regions in the crack were identified in which advection dominance or diffusion dominance of the mass transport of oxygen occurred

  11. Workshop on initiation of stress corrosion cracking under LWR conditions: Proceedings

    International Nuclear Information System (INIS)

    Nelson, J.L.; Cubicciotti, D.; Licina, G.J.

    1988-05-01

    A workshop titled ''Initiation of Stress Corrosion Cracking under LWR Conditions'' was held in Palo Alto, California on November 13, 1986, hosted by the Electric Power Research Institute. Participants were experts on the topic from nuclear steam supply and component manufacturers, public and private research laboratories, and university environments. Presentations included discussions on the definition of crack initiation, the effects of environmental and electrochemical variables on cracking susceptibility, and detection methods for the determination of crack initiation events and measurement of critical environmental and stress parameters. Examination of the questions related to crack initiation and its relative importance to the overall question of cracking of LWR materials from these perspectives provided inputs to EPRI project managers on the future direction of research efforts designed to prevent and control cracking. Thirteen reports have been cataloged separately

  12. Effect of plastic prestrain on the crack tip constraint of pipeline steels

    International Nuclear Information System (INIS)

    Eikrem, P.A.; Zhang, Z.L.; Nyhus, B.

    2007-01-01

    Before and during operation, pipelines may suffer from plastic pre-deformation due to accidental loading, cold bending and ground movement. Plastic prestrain not only modifies steel's yield and flow properties but also influences its fracture performance. This paper focuses on the effect of prestrain history on crack driving force and crack tip constraint. A single-edge notched tension specimen has been selected for the study and the crack is assumed to exist before a prestrain history was applied. The results show that prestrain history has a strong effect on the crack tip stress field. A new parameter has been proposed to characterize the prestrain-induced crack tip constraint. For the same crack tip opening displacement level, prestrain history will elevate the crack tip stress field. The prestrain-induced constraint decreases with the increase of loading

  13. 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.

  14. Stress corrosion cracking

    International Nuclear Information System (INIS)

    Dietzel, W.; Turnbull, A.

    2007-01-01

    Comprehensive Structural Integrity is a reference work which covers all activities involved in the assurance of structural integrity. It provides engineers and scientists with an unparalleled depth of knowledge in the disciplines involved. The new online Volume 11 is dedicated to the mechanical characteristics of materials. This paper contains the chapter 11.03 and is structured as follows: General aspects of SCC testing; Non-precracked specimens; Precracked specimens - the fracture mechanics approach to SCC; Crack growth measurement; Limitations of the LEFM approach to SCC; The use of SCC data; Guide to selection of mechanical scc test method

  15. Cutting of metal components by intergranular cracking

    International Nuclear Information System (INIS)

    Chavand, J.; Gauthier, A.; Lopez, J.J.; Tanis, G.

    1985-01-01

    The objective of this contract was to study a new steel-sheet cutting technique for dismantling nuclear installations without in principle producing secondary waste. This technique is based on intergranular cracking of steel induced by the combined action of penetration of molten metal into the steel and application of a mechanical load. Cutting has been achieved for stainless-steel sheets with thicknesses ranging from a few mm to 50 mm and for carbon-steel plates with thicknesses between 20 and 60 mm. For carbon steel is seems possible that components as thick as 100 mm can be cut. The tests have permitted selection of the heating methods and determination of the cracking parameters for the materials and range of thickness studied. In the case of thin sheets, results were obtained for cutting in varied positions suited to the techniques of dismantling in hot cells. A temperature-measuring system using an infrared camera has been developed to determine the variation of the temperature field established in the component. In association with the three-dimensional computation code COCO developed by the CEA, this system permits prediction of the changes in stresses in the cracked zone when the cutting parameters are modified. 34 figs

  16. 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

  17. Effects of dietary Astragalus polysaccharides (APS) on growth performance, immunological parameters, digestive enzymes, and intestinal morphology of Nile tilapia (Oreochromis niloticus).

    Science.gov (United States)

    Zahran, Eman; Risha, Engy; Abdelhamid, Fatma; Mahgoub, Hebata Allah; Ibrahim, Tarek

    2014-05-01

    This work investigated the potential immunomodulatory and growth-promoting effects of Astragalus polysaccharides (APS) in Nile tilapia (Oreochromis niloticus). The dietary supplementation with APS (1500 mg/kg of diet) caused a significant increase in growth parameters (initial and final weight, weight gain (WG), specific growth rate (SGR), feed conversion ratio (FCR) and feed intake (FI), when compared to non-supplemented control basal diet. In addition, APS upregulated the phagocytic activity, the respiratory burst activity, plasma lysozyme, the bactericidal activity, superoxide dismutase (SOD), glutathione peroxidase (GPx), and amylase activity. However, it had no effect on serum nitric oxide (NO) or Malondialdehyde (MDA) levels. While APS had no effect of intestinal histology, a slight increase in the villi length was recorded. Collectively, our results indicate that dietary APS supplementation could improve the growth performance and the immune parameters of cultured tilapia fish. Copyright © 2014 Elsevier Ltd. All rights reserved.

  18. 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.)

  19. Fracture of longitudinally cracked ductile tubes

    International Nuclear Information System (INIS)

    Larsson, H.; Bernard, J.

    1978-01-01

    Various bulging factor and plasticity correction factor formulations are discussed and a new plasticity correction factor leading to a simple failure law is proposed. Failure stresses predicted by the usual Linear Elastic Fracture Mechanics formula corrected for plasticity are shown to be identical with the Dowling and Townley two-criteria approach if the relevant parameters are chosen in a suitable manner. Burst tests on AISI 304 stainless steel tubes performed at the Joint Research Centre, Ispra are described. The strengthening effect of the sealing patch was taken into account by replacing the Folias bulging factor by a smaller empirical factor determined by Bernard and Henry from fatigue crack growth tests. A flow stress sigma and a toughness Ksub(c) were derived which apply to the prediction of the onset of stable crack growth in 304 stainless steel tubes at room temperature. For other ductile materials and temperatures tentative formulae are proposed. (author)

  20. Multiscale model of short cracks in a random polycrystalline aggregate

    International Nuclear Information System (INIS)

    Simonovski, I.; Cizelj, L.; Petric, Z.

    2006-01-01

    A plane-strain finite element crystal plasticity model of microstructurally small stationary crack emanating at a surface grain in a 316L stainless steel is proposed. The model consisting of 212 randomly shaped, sized and oriented grains is loaded monotonically in uniaxial tension to a maximum load of 1.12Rp0.2 (280MPa). The influence that a random grain structure imposes on a Stage I crack is assessed by calculating the crack tip opening (CTOD) and sliding displacements (CTSD) for single crystal as well as for polycrystal models, considering also different crystallographic orientations. In the single crystal case the CTOD and CTSD may differ by more than one order of magnitude. Near the crack tip slip is activated on all the slip planes whereby only two are active in the rest of the model. The maximum CTOD is directly related to the maximal Schmid factors. For the more complex polycrystal cases it is shown that certain crystallographic orientations result in a cluster of soft grains around the crack-containing grain. In these cases the crack tip can become a part of the localized strain, resulting in a large CTOD value. This effect, resulting from the overall grain orientations and sizes, can have a greater impact on the CTOD than the local grain orientation. On the other hand, when a localized soft response is formed away from the crack, the localized strain does not affect the crack tip directly, resulting in a small CTOD value. The resulting difference in CTOD can be up to a factor of 4, depending upon the crystallographic set. Grains as far as 6 times the value of crack length significantly influence that crack tip parameters. It was also found that a larger crack containing grain tends to increase the CTOD. Finally, smaller than expected drop in the CTOD (12.7%) was obtained as the crack approached the grain boundary. This could be due to the assumption of the unchanged crack direction, only monotonic loading and simplified grain boundary modelling. (author)

  1. Multiparametric MRI in the assessment of response of rectal cancer to neoadjuvant chemoradiotherapy: A comparison of morphological, volumetric and functional MRI parameters

    International Nuclear Information System (INIS)

    Hoetker, Andreas M.; Tarlinton, Lisa; Gollub, Marc J.; Mazaheri, Yousef; Woo, Kaitlin M.; Goenen, Mithat; Saltz, Leonard B.; Goodman, Karyn A.; Garcia-Aguilar, Julio

    2016-01-01

    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"t"r"a"n"s 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.)

  2. 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.)

  3. 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.

  4. Induction Thermography for Surface Crack Detection and Depth Determination

    Directory of Open Access Journals (Sweden)

    Beate Oswald-Tranta

    2018-02-01

    Full Text Available In the last few years, induction thermography has been established as a non-destructive testing method for localizing surface cracks in metals. The sample to be inspected is heated with a short induced electrical current pulse, and the infrared camera records—during and after the heating pulse—the temperature distribution at the surface. Transforming the temporal temperature development for each pixel to phase information makes not only highly reliable detection of the cracks possible but also allows an estimation of its depth. Finite element simulations were carried out to investigate how the phase contrast depends on parameters such as excitation frequency, pulse duration, material parameters, crack depth, and inclination angle of the crack. From these results, generalized functions for the dependency of the phase difference on all these parameters were derived. These functions can be used as an excellent guideline as to how measurement parameters should be optimized for a given material to be able to detect cracks and estimate their depth. Several experiments on different samples were also carried out, and the results compared with the simulations showed very good agreement.

  5. Crack closure and growth behavior of short fatigue cracks under random loading (part I : details of crack closure behavior)

    International Nuclear Information System (INIS)

    Lee, Shin Young; Song, Ji Ho

    2000-01-01

    Crack closure and growth behavior of physically short fatigue cracks under random loading are investigated by performing narrow-and wide-band random loading tests for various stress ratios. Artificially prepared two-dimensional, short through-thickness cracks are used. The closure behavior of short cracks under random loading is discussed, comparing with that of short cracks under constant-amplitude loading and also that of long cracks under random loading. Irrespective of random loading spectrum or block length, the crack opening load of short cracks is much lower under random loading than under constant-amplitude loading corresponding to the largest load cycle in a random load history, contrary to the behavior of long cracks that the crack opening load under random loading is nearly the same as or slightly higher than constant-amplitude results. This result indicates that the largest load cycle in a random load history has an effect to enhance crack opening of short cracks

  6. Fully plastic solutions of semi-elliptical surface cracks

    International Nuclear Information System (INIS)

    Yagawa, Genki; Yoshimura, Shinobu; Kitajima, Yasumi; Ueda, Hiroyoshi.

    1990-01-01

    Nonlinear finite element analyses of semi-elliptical surface cracks are performed under the fully plastic condition. The power-law hardening materials and the deformation theory of plasticity are assumed. Either the penalty function method or the Uzawa's algorithm is utilized to treat the incompressibility of plastic strains. The local and global J-integral values are obtained using a virtual crack extension technique for plates and cylinders with semi-elliptical surface cracks subjected to uniform tensions. The fully plastic solutions for surface cracked plates are given in the form of polynominals with geometric parameters a/t, a/c and the strain hardening exponent (n). In addition, the effects of curvature on fully plastic solutions are discussed through the comparison between the results of plates and cylinders. (author)

  7. Investigation of the susceptibility to solidification cracking in copper alloys

    Energy Technology Data Exchange (ETDEWEB)

    Warren, Richard [Avesta Sheffield R and D, Avesta (Sweden)

    2000-04-01

    A test procedure has been developed at LuTH for investigating the susceptibility to cracking at high temperatures in weldments. It has been proposed to adapt this testing procedure to investigate the cracking susceptibility at high temperatures during strip casting of certain copper alloys. Six different materials were selected for investigation - OFHC copper, tellurium containing copper, 4% tin bronze, 6% tin bronze, 30% zinc brass and 35% zinc brass. The aim of the investigation was to characterize the cracking susceptibility of the candidate materials so as to be able to rank and compare them in a quantitative manner. A further aim of the work was to study the suitability of using the data on the cracking indices generated in the present work in thermomechanical models of the casting process to optimize the casting parameters for each of the materials.

  8. The assessment of creep-fatigue initiation and crack growth

    International Nuclear Information System (INIS)

    Priest, R.H.; Miller, D.A.

    1991-01-01

    An outline of Nuclear Electric's Assessment Procedure for the High Temperature Response of Structures ('R5') for creep-fatigue initiation and crack growth is given. A unified approach is adopted for both regimes. For initiation, total damage is described in terms of separate creep and fatigue components. Ductility exhaustion is used for estimating creep damage whilst continuous cycling endurance data are used to evaluate the fatigue damage term. Evidence supporting this approach is given through the successful prediction of creep-fatigue endurances for a range of materials, cycle types, dwell period times, etc. Creep-fatigue crack growth is similarly described in terms of separated creep and fatigue components. Crack growth rates for each component are characterised in terms of fracture mechanics parameters. It is shown that creep crack growth rates can be rationalised on a ductility basis. Creep-fatigue interactions are accommodated in the cyclic growth component through the use of materials coefficients which depend on dwell time. (orig.)

  9. Modification of the FRI crack growth model formulation from a mathematical viewpoint

    International Nuclear Information System (INIS)

    Hashimoto, Tsuneyuki; Koshiishi, Masato

    2009-01-01

    The FRI model of crack growth, which incorporates mechanical properties into the slip oxidation mechanism of crack advance, is an extension of the well-known Ford-Andresen model. When the exponent of the oxidation current decay curve is set close to 1, however, the FRI model gives an infinite crack growth rate. Here, the oxidation decay curve integral is revised to eliminate this divergence, and modified crack growth rate equations are derived. Also presented here is a procedure for determining the oxidation current parameters from the curve-fitting to measurements of crack growth rate. Parameter value determination and crack growth calculations are illustrated for cold-worked Type 316L stainless steel. (author)

  10. 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.

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

    International Nuclear Information System (INIS)

    Saha, Dulal Chandra; Chang, InSung; Park, Yeong-Do

    2014-01-01

    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

  12. 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

  13. Data-Science Analysis of the Macro-scale Features Governing the Corrosion to Crack Transition in AA7050-T7451

    Science.gov (United States)

    Co, Noelle Easter C.; Brown, Donald E.; Burns, James T.

    2018-05-01

    This study applies data science approaches (random forest and logistic regression) to determine the extent to which macro-scale corrosion damage features govern the crack formation behavior in AA7050-T7451. Each corrosion morphology has a set of corresponding predictor variables (pit depth, volume, area, diameter, pit density, total fissure length, surface roughness metrics, etc.) describing the shape of the corrosion damage. The values of the predictor variables are obtained from white light interferometry, x-ray tomography, and scanning electron microscope imaging of the corrosion damage. A permutation test is employed to assess the significance of the logistic and random forest model predictions. Results indicate minimal relationship between the macro-scale corrosion feature predictor variables and fatigue crack initiation. These findings suggest that the macro-scale corrosion features and their interactions do not solely govern the crack formation behavior. While these results do not imply that the macro-features have no impact, they do suggest that additional parameters must be considered to rigorously inform the crack formation location.

  14. Effects of dietary Bacillus licheniformis on growth performance, immunological parameters, intestinal morphology and resistance of juvenile Nile tilapia (Oreochromis niloticus) to challenge infections.

    Science.gov (United States)

    Han, Biao; Long, Wei-Qing; He, Ju-Yun; Liu, Yong-Jian; Si, Yu-Qi; Tian, Li-Xia

    2015-10-01

    The effects of oral administration of Bacillus licheniformis on growth performance, immunity, intestinal morphology and disease resistance of juvenile tilapia were investigated. Six experimental diets supplemented with different concentrations of B. licheniformis (0%, 0.02%, 0.04%, 0.06%, 0.08% and 0.1% of AlCare(®), containing live germ 2 × 10(10) CFU/g) were formulated, viz. control, T1, T2, T3, T4 and T5. Each diet was randomly assigned to triplicate groups of 30 fishes (3.83 ± 0.03 g). After 10 weeks of feeding trial, weight gain (WG), final body wet weight (FBW) and specific growth rate (SGR) increased significantly in groups T2, T3, T4 and T5 compared with control and T1 (p 0.05). Compared with control, dietary B. licheniformis supplementation increased the content of complement C3 in serum significantly (P licheniformis supplementation (P > 0.05). When tilapia were challenged against Streptococcus iniae, survival rate improved significantly when tilapia fed with T2, T3, T4 and T5 (P licheniformis (T2, T3, T4, T5) tended to be regularly arranged and exhibited less exfoliation, twist and fusion. These results indicated that dietary supplementation of B. licheniformis not only increased the growth, immune response and disease resistance of juvenile tilapia, but also influenced anterior intestinal development and integrity. Furthermore, in our study, the optimal concentration of B. licheniformis in diets for tilapia was greater than or equal to 4.4 × 10(6) CFU/g. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. Numerical modeling of heat-transfer and the influence of process parameters on tailoring the grain morphology of IN718 in electron beam additive manufacturing

    International Nuclear Information System (INIS)

    Raghavan, Narendran; Dehoff, Ryan; Pannala, Sreekanth; Simunovic, Srdjan; Kirka, Michael; Turner, John; Carlson, Neil; Babu, Sudarsanam S.

    2016-01-01

    The fabrication of 3-D parts from CAD models by additive manufacturing (AM) is a disruptive technology that is transforming the metal manufacturing industry. The correlation between solidification microstructure and mechanical properties has been well understood in the casting and welding processes over the years. This paper focuses on extending these principles to additive manufacturing to understand the transient phenomena of repeated melting and solidification during electron beam powder melting process to achieve site-specific microstructure control within a fabricated component. In this paper, we have developed a novel melt scan strategy for electron beam melting of nickel-base superalloy (Inconel 718) and also analyzed 3-D heat transfer conditions using a parallel numerical solidification code (Truchas) developed at Los Alamos National Laboratory. The spatial and temporal variations of temperature gradient (G) and growth velocity (R) at the liquid-solid interface of the melt pool were calculated as a function of electron beam parameters. By manipulating the relative number of voxels that lie in the columnar or equiaxed region, the crystallographic texture of the components can be controlled to an extent. The analysis of the parameters provided optimum processing conditions that will result in columnar to equiaxed transition (CET) during the solidification. The results from the numerical simulations were validated by experimental processing and characterization thereby proving the potential of additive manufacturing process to achieve site-specific crystallographic texture control within a fabricated component.

  16. Theoretical and experimental studies on the electric impedance of active piezoelectric sensors bonded on cracked beams

    International Nuclear Information System (INIS)

    Kuang, Y D; Chen, C Y; Shi, S Q; Chan, P K L; He, X Q

    2010-01-01

    The electric impedance of symmetrically surface-bonded piezoelectric sensors on a cracked beam is studied. To investigate the effect of the crack on the electric impedance in a convenient fashion, an analytical expression is derived that is correlated to the physical parameters of the crack and the host beam. The beam segment covered with piezoelectric patches and the cracked region are regarded as a bimorph segment and an equivalent spring, respectively, and the entire beam system is then represented by three elastic beam segments and a bimorph segment together with the spring. Electric impedance experiments are also conducted for uncracked beams and for cracked beams with single-edge or double-edge cracks. The experimental results agree with those generated by the analytical expression. The crack depth has little effect on the corresponding mode frequency for cracks located at the mode node of a beam. For cracks located away from the mode node, the corresponding mode frequency decreases as the crack depth increases. Moreover, the closer the crack to the anti-node of the mode, the greater the decrease in the corresponding mode frequency. The mechanism of these changes is discussed. The findings should prove helpful for structural health monitoring using active piezoelectric sensors

  17. Microstructure modeling and crystal plasticity simulations for the evaluation of fatigue crack initiation in α-iron specimen including an elliptic defect

    Energy Technology Data Exchange (ETDEWEB)

    Briffod, Fabien, E-mail: briffod@rme.mm.t.u-tokyo.ac.jp; Shiraiwa, Takayuki; Enoki, Manabu

    2017-05-17

    In this study, fatigue crack initiation in pure α-iron is investigated through a microstructure-sensitive framework. At first, synthetic microstructures are modeled based on an anisotropic tessellation that accounts for the information of the grains morphology extracted from electron backscatter diffraction (EBSD) analysis. Low-cycle fatigue experiments under strain-controlled conditions are conducted in order to calibrate a crystal plasticity model and a J{sub 2} model including isotropic and kinematic hardening. A critical plane fatigue indicator parameter (FIP) based on the Tanaka-Mura model is then presented to evaluate the location and quantify the driving force for the formation of a crack. The FIP is averaged over several potential crack paths within each grain defined by the intersection between a given slip plane and the plane of the model thus accounting for both the lattice orientation and morphology of the grain. Several fatigue simulations at various stress amplitudes are conducted using a sub-modeling technique for the attribution of boundary conditions on the polycrystalline aggregate models including an elliptic defect. The influence of the microstructure attributes and stress level on the location and amplitude of the FIP are then quantified and discussed.

  18. 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.

  19. Cracking in Drying Colloidal Films

    Science.gov (United States)

    Singh, Karnail B.; Tirumkudulu, Mahesh S.

    2007-05-01

    It has long been known that thick films of colloidal dispersions such as wet clays, paints, and coatings crack under drying. Although capillary stresses generated during drying have been recently identified as the cause for cracking, the existence of a maximum crack-free film thickness that depends on particle size, rigidity, and packing has not been understood. Here, we identify two distinct regimes for crack-free films based on the magnitude of compressive strain at the maximum attainable capillary pressure and show remarkable agreement of measurements with our theory. We anticipate our results to not only form the basis for design of coating formulations for the paints, coatings, and ceramics industry but also assist in the production of crack-free photonic band gap crystals.

  20. 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.

  1. 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.

  2. Prediction of Crack Growth Aqueous Environments.

    Science.gov (United States)

    1983-06-01

    ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT. PROJECT. TASK AREA & WORK UNIT NUMBERS SRI International 333 Ravenswood Avenue Menlo Park, CA 94025 II...34no crack" has at least a vestigial rupture, associated with cyclic loading of the oxide film at the crack tip. The curve labeled "crack" was obtained...be an effect of crack opening. For the data set labeled "crack", the vestigial crack, although short, is very tight and the impedance is large. Under

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

    DEFF Research Database (Denmark)

    Brodersen, Knud Erik

    2003-01-01

    . The produced thin layers of low porositycalcite 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 forconventional uses...... 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...

  4. Buckling Analysis of Edge Cracked Sandwich Plate

    Directory of Open Access Journals (Sweden)

    Rasha Mohammed Hussein

    2016-07-01

    Full Text Available This work presents mainly the buckling load of sandwich plates with or without crack for different cases. The buckling loads are analyzed experimentally and numerically by using ANSYS 15. The experimental investigation was to fabricate the cracked sandwich plate from stainless steel and PVC to find mechanical properties of stainless steel and PVC such as young modulus. The buckling load for different aspect ratio, crack length, cracked location and plate without crack found. The experimental results were compared with that found from ANSYS program. Present of crack is decreased the buckling load and that depends on crack size, crack location and aspect ratio.

  5. Repair welding of cracked steam turbine blades

    International Nuclear Information System (INIS)

    Bhaduri, A.K.; Gill, T.P.S.; Albert, S.K.; Shanmugam, K.; Iyer, D.R.

    1999-01-01

    The procedure for repair welding of cracked steam turbine blades made of martensitic stainless steels has been developed using the gas tungsten arc welding process. Weld repair procedures were developed using both ER316L austenitic stainless steel filler wire and ER410 martensitic stainless steel filler wire. The repair welding procedure with austenitic filler wire was developed to avoid preheating of the blade as also hydrogen induced cold cracking, and involved evaluation of three different austenitic filler wires, viz. ER309L, ER316L and ERNiCr-3. The overall development of the repair welding procedure included selection of welding consumables (for austenitic filler metal), optimisation of post weld heat treatment parameters, selection of suitable method for local pre-heating and post-weld heat treatment (PWHT) of the blades, determination of mechanical properties of weldments in as-welded and PWHT conditions, and microstructural examination. After various trials using different procedures, the procedure of local PWHT using electrical resistance heating on the top surface of the weldment and monitoring the temperature by placing a thermocouple at the bottom of the weld, was found to give the most satisfactory results. A similar procedure was used for preheating while using ER410 filler metal. Mechanical testing of weldments before and after PWHT involved tensile tests at room temperature, face and root bend tests, and microhardness measurements across the fusion line and heat affected zone. During procedure qualification, mock-ups and actual repair welding, dye penetrant testing was used at different stages and where ever possible radiography was carried out. These procedures were developed for repair welding of cracked blades in the low-pressure (LP) steam turbines of Indian nuclear power plants. The procedure with ER316 L filler wire has so far been applied for repair welding of 2 cracked blades (made of AISI 410 SS) of LP steam turbines, while the procedure

  6. Crack propagation behaviour in stainless steel AISI 316L at elevated temperatures under static and cyclic loading

    International Nuclear Information System (INIS)

    Lange, H.

    1991-01-01

    Experimental investigations of crack growth under creep and creep-fatigue conditions are presented. The experiments were performed with the austenitic steel AISI 316L, that will be used in fast breeder reactors. A comparison of crack propagation behaviour at temperatures of T = 550deg C and T = 700deg C in common through-thickness cracked specimens and in plates containing surface cracks is carried out by application of several fracture mechanics parameters. The quantitative description of crack initiation times and crack velocities is persued particularly. The propagation rate of one-dimensional cracks under cyclic loading conditions at T = 550deg C is also treated with fracture mechanical methods. The influence of the hold periods on crack speed is discussed. (orig.) [de

  7. Comparison of theory and experiment for elastic-plastic plane-strain crack growth. [AISI 4140 steel

    Energy Technology Data Exchange (ETDEWEB)

    Hermann, L.; Rice, J.R.

    1980-08-01

    Recent theoretical results on elastic-plastic plane-strain crack growth are reviewed and experimental results for crack growth in a 4140 steel are discussed in terms of the theoretical concepts. The theory is based on a recent asymptotic analysis of crack surface opening and strain distributions at a quasistatically advancing crack tip in an ideally plastic solid. The analysis is incomplete in that some of the parameters which appear in it are known only approximately, especially at large-scale yielding. Nevertheless, it is sufficient for the derivation of a relation between the imposed loading and amount of crack growth prior to general yielding, based on the assumption that a geometrically similar near-tip crack profile is maintained during growth. The resulting predictions for the variation of J with crack growth are found to fit well to the experimental results obtained on deeply cracked compact specimens.

  8. Microstructure and mechanical properties of internal crack healing in a low carbon steel

    Energy Technology Data Exchange (ETDEWEB)

    Xin, Ruishan [Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); Key Laboratory for Advanced Materials Processing Technology of Ministry of Education, Tsinghua University, Beijing 100084 (China); Ma, Qingxian, E-mail: maqxdme@mail.tsinghua.edu.cn [Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); Key Laboratory for Advanced Materials Processing Technology of Ministry of Education, Tsinghua University, Beijing 100084 (China); Li, Weiqi [Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); Key Laboratory for Advanced Materials Processing Technology of Ministry of Education, Tsinghua University, Beijing 100084 (China)

    2016-04-26

    The behavior of internal crack healing in a low carbon steel at elevated temperatures was investigated. The internal cracks were introduced into low carbon steel samples via the drilling and compression method. The microstructure of crack healing zone was observed using optical microscopy and scanning electron microscopy. The mechanical properties of crack healing zone at room temperature were tested. The results show that there are two mechanisms of crack healing in the low carbon steel. Crack healing is caused by atomic diffusion at lower temperatures, and mainly depends on recrystallization and grain growth at higher temperatures. The microstructural evolution of crack healing zone can be divided into four stages, and the fracture morphology of crack healing zone can be classified into five stages. At the initial healing stage, the fracture exhibits brittle or low ductile dimple fracture. The ultimate fracture mode is dimple and quasi-cleavage mixed fracture. Fine grain microstructures improve the ultimate tensile strength of crack healing zone, which is even higher than that of the matrix. The strength recovery rate is higher than that of the plasticity.

  9. Structural sensitivity of cyclic crack resistance of rotor steel in gaseous hydrogen

    International Nuclear Information System (INIS)

    Romaniv, O.N.; Nikiforchin, G.N.; Kozak, L.Yu.

    1984-01-01

    Comparative evaluation of cyclic crack resistance of hardened rotor set steel 35KhN3MFA in different cstructural states during tesis in agea geseous hydrogen, in the air and in vacuum, has been mde made. It is shown, that structural sensitivity of near-threshold crack resistance of the studied rotor steel in gaseous hydrogen is to a high extent determined by the closing and morphology of fatigue crack. The decrease in crack closing (CC) observed during tests in hydrogen in low-strenght and crack branching in high-strength steels results in the fact, that in contrast to well-known notions on a higher sensitivity to hydrogen embrittlement of high-strenght alloys the negative effect of hydrogen on the near-threshold cyclic crack resistance is manifested only in steel in low-strenght state. The considered regularities in crack growth in low-alloyed steel under the effect of gaseous hydrogen are just only for high-frequency loading. In all probability in the case of fatigue crack growth (GCG) at low frequencies of loading not only the medium activity, but also the role o, closing and crack geometty in the kinetics of fatigue fracture, the clarifying of which requires further studieds, will change

  10. 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.

  11. FASTRAN II - FATIGUE CRACK GROWTH STRUCTURAL ANALYSIS (UNIX VERSION)

    Science.gov (United States)

    Newman, J. C.

    1994-01-01

    Predictions of fatigue crack growth behavior can be made with the Fatigue Crack Growth Structural Analysis (FASTRAN II) computer program. As cyclic loads are applied to a selected crack configuration with an initial crack size, FASTRAN II predicts crack growth as a function of cyclic load history until either a desired crack size is reached or failure occurs. FASTRAN II is based on plasticity-induced crack-closure behavior of cracks in metallic materials and accounts for load-interaction effects, such as retardation and acceleration, under variable-amplitude loading. The closure model is based on the Dugdale model with modifications to allow plastically deformed material to be left along the crack surfaces as the crack grows. Plane stress and plane strain conditions, as well as conditions between these two, can be simulated in FASTRAN II by using a constraint factor on tensile yielding at the crack front to approximately account for three-dimensional stress states. FASTRAN II contains seventeen predefined crack configurations (standard laboratory fatigue crack growth rate specimens and many common crack configurations found in structures); and the user can define one additional crack configuration. The baseline crack growth rate properties (effective stress-intensity factor against crack growth rate) may be given in either equation or tabular form. For three-dimensional crack configurations, such as surface cracks or corner cracks at holes or notches, the fatigue crack growth rate properties may be different in the crack depth and crack length directions. Final failure of the cracked structure can be modelled with fracture toughness properties using either linear-elastic fracture mechanics (brittle materials), a two-parameter fracture criterion (brittle to ductile materials), or plastic collapse (extremely ductile materials). The crack configurations in FASTRAN II can be subjected to either constant-amplitude, variable-amplitude or spectrum loading. The applied

  12. FASTRAN II - FATIGUE CRACK GROWTH STRUCTURAL ANALYSIS (IBM PC VERSION)

    Science.gov (United States)

    Newman, J. C.

    1994-01-01

    Predictions of fatigue crack growth behavior can be made with the Fatigue Crack Growth Structural Analysis (FASTRAN II) computer program. As cyclic loads are applied to a selected crack configuration with an initial crack size, FASTRAN II predicts crack growth as a function of cyclic load history until either a desired crack size is reached or failure occurs. FASTRAN II is based on plasticity-induced crack-closure behavior of cracks in metallic materials and accounts for load-interaction effects, such as retardation and acceleration, under variable-amplitude loading. The closure model is based on the Dugdale model with modifications to allow plastically deformed material to be left along the crack surfaces as the crack grows. Plane stress and plane strain conditions, as well as conditions between these two, can be simulated in FASTRAN II by using a constraint factor on tensile yielding at the crack front to approximately account for three-dimensional stress states. FASTRAN II contains seventeen predefined crack configurations (standard laboratory fatigue crack growth rate specimens and many common crack configurations found in structures); and the user can define one additional crack configuration. The baseline crack growth rate properties (effective stress-intensity factor against crack growth rate) may be given in either equation or tabular form. For three-dimensional crack configurations, such as surface cracks or corner cracks at holes or notches, the fatigue crack growth rate properties may be different in the crack depth and crack length directions. Final failure of the cracked structure can be modelled with fracture toughness properties using either linear-elastic fracture mechanics (brittle materials), a two-parameter fracture criterion (brittle to ductile materials), or plastic collapse (extremely ductile materials). The crack configurations in FASTRAN II can be subjected to either constant-amplitude, variable-amplitude or spectrum loading. The applied

  13. Stress-dependent permeability and wave dispersion in tight cracked rocks: Experimental validation of simple effective medium models

    Science.gov (United States)

    Sarout, Joel; Cazes, Emilie; Delle Piane, Claudio; Arena, Alessio; Esteban, Lionel

    2017-08-01

    We experimentally assess the impact of microstructure, pore fluid, and frequency on wave velocity, wave dispersion, and permeability in thermally cracked Carrara marble under effective pressure up to 50 MPa. The cracked rock is isotropic, and we observe that (1) P and S wave velocities at 500 kHz and the low-strain (S waves and 9% for P waves at 1 MPa, and (4) wave dispersion virtually vanishes above 30 MPa. Assuming no interactions between the cracks, effective medium theory is used to model the rock's elastic response and its permeability. P and S wave velocity data are jointly inverted to recover the crack density and effective aspect ratio. The permeability data are inverted to recover the cracks' effective radius. These parameters lead to a good agreement between predicted and measured wave velocities, dispersion and permeability up to 50 MPa, and up to a crack density of 0.5. The evolution of the crack parameters suggests that three deformation regimes exist: (1) contact between cracks' surface asperities up to 10 MPa, (2) progressive crack closure between 10 and 30 MPa, and (3) crack closure effectively complete above 30 MPa. The derived crack parameters differ significantly from those obtained by analysis of 2-D electron microscope images of thin sections or 3-D X-ray microtomographic images of millimeter-size specimens.

  14. An analytical method for free vibration analysis of Timoshenko beam theory applied to cracked nanobeams using a nonlocal elasticity model

    International Nuclear Information System (INIS)

    Torabi, K.; Nafar Dastgerdi, J.

    2012-01-01

    This paper is concerned with the free transverse vibration of cracked nanobeams modeled after Eringen's nonlocal elasticity theory and Timoshenko beam theory. The cracked beam is modeled as two segments connected by a rotational spring located at the cracked section. This model promotes discontinuities in rotational displacement due to bending which is proportional to bending moment transmitted by the cracked section. The governing equations of cracked nanobeams with two symmetric and asymmetric boundary conditions are derived; then these equations are solved analytically based on concerning basic standard trigonometric and hyperbolic functions. Besides, the frequency parameters and the vibration modes of cracked nanobeams for variant crack positions, crack ratio, and small scale effect parameters are calculated. The vibration solutions obtained provide a better representation of the vibration behavior of short, stubby, micro/nanobeams where the effects of small scale, transverse shear deformation and rotary inertia are significant. - Highlights: ► The free vibration analysis of cracked nanobeams is investigated. ► This study is based on the theory of nonlocal elasticity and Timoshenko beam theory. ► The small scale effect parameter greatly affects the value of natural frequencies. ► Crack reduces the natural frequencies, causes a discontinuity in the cracked section.

  15. An analytical method for free vibration analysis of Timoshenko beam theory applied to cracked nanobeams using a nonlocal elasticity model

    Energy Technology Data Exchange (ETDEWEB)

    Torabi, K., E-mail: kvntrb@KashanU.ac.ir; Nafar Dastgerdi, J., E-mail: J.nafardastgerdi@me.iut.ac.ir

    2012-08-31

    This paper is concerned with the free transverse vibration of cracked nanobeams modeled after Eringen's nonlocal elasticity theory and Timoshenko beam theory. The cracked beam is modeled as two segments connected by a rotational spring located at the cracked section. This model promotes discontinuities in rotational displacement due to bending which is proportional to bending moment transmitted by the cracked section. The governing equations of cracked nanobeams with two symmetric and asymmetric boundary conditions are derived; then these equations are solved analytically based on concerning basic standard trigonometric and hyperbolic functions. Besides, the frequency parameters and the vibration modes of cracked nanobeams for variant crack positions, crack ratio, and small scale effect parameters are calculated. The vibration solutions obtained provide a better representation of the vibration behavior of short, stubby, micro/nanobeams where the effects of small scale, transverse shear deformation and rotary inertia are significant. - Highlights: Black-Right-Pointing-Pointer The free vibration analysis of cracked nanobeams is investigated. Black-Right-Pointing-Pointer This study is based on the theory of nonlocal elasticity and Timoshenko beam theory. Black-Right-Pointing-Pointer The small scale effect parameter greatly affects the value of natural frequencies. Black-Right-Pointing-Pointer Crack reduces the natural frequencies, causes a discontinuity in the cracked section.

  16. The stress corrosion cracking of copper nuclear waste containers

    International Nuclear Information System (INIS)

    King, F.; Litke, C.D.; Ikeda, B.M.

    1999-01-01

    The extent of stress corrosion cracking (SCC) of copper nuclear waste containers is being predicted on the basis of a 'limited propagation' argument. In this argument, it is accepted that crack initiation may occur, but it is argued that the environmental conditions and material properties required for a through-wall crack to propagate will not be present. In this paper, the effect of one environmental parameter, the supply of oxidant (J ox ), on the crack growth rate is examined. Experiments have been conducted on two grades of Cu in NANO 2 environments using two loading techniques. The supply of oxidant has been varied either electrochemically in bulk solution using different applied current densities or by embedding the loaded test specimens in compacted buffer material containing O 2 as the oxidant. Measured and theoretical crack growth rates as a function of J ox are compared with the predicted oxidant flux to the containers in a disposal vault and an estimate of the maximum crack depth on a container obtained. (author)

  17. The stress corrosion cracking of copper nuclear waste containers

    International Nuclear Information System (INIS)

    King, F.; Litke, C.D.; Ikeda, B.M.

    1999-01-01

    The extent of stress corrosion cracking (SCC) of copper nuclear waste containers is being predicted on the basis of a limited propagation argument. In this argument, it is accepted that crack initiation may occur, but it is argued that the environmental conditions and material properties required for a through-wall crack to propagate will not be present. In this paper, the effect of one environmental parameter, the supply of oxidant (J OX ), on the crack growth rate is examined. Experiments have been conducted on two grades of Cu in NaNO 2 environments using two loading techniques. The supply of oxidant has been varied either electrochemically in bulk solution using different applied current densities or by embedding the loaded test specimens in compacted buffer material containing O 2 as the oxidant. Measured and theoretical crack growth rates as a function of J OX are compared with the predicted oxidant flux to the containers in a disposal vault and an estimate of the maximum crack depth on a container obtained

  18. Weibull modeling of particle cracking in metal matrix composites

    International Nuclear Information System (INIS)

    Lewis, C.A.; Withers, P.J.

    1995-01-01

    An investigation into the occurrence of reinforcement cracking within a particulate ZrO 2 /2618 Al alloy metal matrix composite under tensile plastic straining has been carried out, special attention being paid to the dependence of fracture on particle size and shape. The probability of particle cracking has been modeled using a Weibull approach, giving good agreement with the experimental data. Values for the Weibull modulus and the stress required to crack the particles were found to be within the range expected for the cracking of ceramic particles. Additional information regarding the fracture behavior of the particles was provided by in-situ neutron diffraction monitoring of the internal strains, measurement of the variation in the composite Young's modulus with straining and by direct observation of the cracked particles. The values of the particle stress required for the initiation of particle cracking deduced from these supplementary experiments were found to be in good agreement with each other and with the results from the Weibull analysis. Further, it is shown that while both the current experiments, as well as the previous work of others, can be well described by the Weibull approach, the exact values of the Weibull parameters do deduced are very sensitive to the approximations and the assumptions made in constructing the model

  19. Stress corrosion cracking of nickel base alloys characterization and prediction

    International Nuclear Information System (INIS)

    Santarini, G.; Pinard-Legry, G.

    1988-01-01

    For many years, studies have been carried out in several laboratories to characterize the IGSCC (Intergranular Stress Corrosion Cracking) behaviour of nickel base alloys in aqueous environments. For their relative shortness, CERTs (Constant Extension Rate Tests) have been extensively used, especially at the Corrosion Department of the CEA. However, up to recently, the results obtained with this method remained qualitative. This paper presents a first approach to a quantitative interpretation of CERT results. The basic datum used is the crack trace depth distribution determined on a specimen section at the end of a CERT. It is shown that this information can be used for the calculation of initiation and growth parameters which quantitatively characterize IGSCC phenomenon. Moreover, the rationale proposed should lead to the determination of intrinsic cracking parameters, and so, to in-service behaviour prediction

  20. 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.

  1. A Mesopore-Dependent Catalytic Cracking of n-Hexane Over Mesoporous Nanostructured ZSM-5.

    Science.gov (United States)

    Qamar, M; Ahmed, M I; Qamaruddin, M; Asif, M; Sanhoob, M; Muraza, O; Khan, M Y

    2018-08-01

    Herein, pore size, crystalinity, and Si/Al ratio of mesoporous ZSM-5 (MFI) nanocrystals was controlled by synthesis parameters, such as surfactant concentration ([3-(trimethoxysilyl)propyl] hexa-decyl dimethyl ammonium chloride), sodium hydroxide concentrations, synthesis temperature and time. The morphology, surface structure and composition of the MFI particles was systematically investigated. More notably, the mesopore-dependent catalytic activity of ZSM-5 was evaluated by studying the cracking of n-hexane. The findings suggest the porosity has pronounced impact on the catalytic activity, selectivity and stability of ZSM-5 nanocrystals. Critical surface attributes such as nature of acid sites (Brønsted and Lewis), concentration, and strength are obtained by the infrared study of adsorbed probe molecules (pyridine) and the temperature programmed desorption. In spite of being weaker in Si/Al ratio or acidic strength, mesoporous catalysts showed more stable and efficient cracking of n-hexane suggesting that acidity seems not the predominant factor operative in the activity, selectivity and stability.

  2. 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.

  3. Multispecimen fatigue crack propagation testing

    International Nuclear Information System (INIS)

    Ermi, A.M.; Bauer, R.E.; Chin, B.A.; Straalsund, J.L.

    1981-01-01

    Chains of miniature center-cracked-tension specimens were tested on a conventional testing machine and on a prototypic in-reactor fatigue machine as part of the fusion reactor materials alloy development program. Annealed and 20 percent cold-worked 316 stainless steel specimens were cycled under various conditions of temperature, frequency, stress ratio and chain length. Crack growth rates determined from multispecimen visual measurements and from an electrical potential technique were consistent with those obtained by conventional test methods. Results demonstrate that multispecimen chain testing is a valid method of obtaining fatigue crack propagation information for alloy development. 8 refs

  4. Monitoring crack growth using thermography

    International Nuclear Information System (INIS)

    Djedjiga, Ait Aouita; Abdeldjalil, Ouahabi

    2008-01-01

    The purpose of this work is to present a novel strategy for real-time monitoring crack growth of materials. The process is based on the use of thermal data extracted along the horizontal axis of symmetry of single edge notch tension (SENT) specimens, during fatigue tests. These data are exploited using an implemented program to detect in situ the growth of fatigue crack, with the critical size and propagation speed of the crack. This technique has the advantage to be applicable to a wide range of materials regardless of their electrical conductivity and their surface texture. (authors)

  5. Password Cracking Using Sony Playstations

    Science.gov (United States)

    Kleinhans, Hugo; Butts, Jonathan; Shenoi, Sujeet

    Law enforcement agencies frequently encounter encrypted digital evidence for which the cryptographic keys are unknown or unavailable. Password cracking - whether it employs brute force or sophisticated cryptanalytic techniques - requires massive computational resources. This paper evaluates the benefits of using the Sony PlayStation 3 (PS3) to crack passwords. The PS3 offers massive computational power at relatively low cost. Moreover, multiple PS3 systems can be introduced easily to expand parallel processing when additional power is needed. This paper also describes a distributed framework designed to enable law enforcement agents to crack encrypted archives and applications in an efficient and cost-effective manner.

  6. Crack Tip Flipping under Mode I Tearing: Investigated by X-Ray Tomography

    DEFF Research Database (Denmark)

    Nielsen, Kim Lau; Gundlach, Carsten

    2017-01-01

    The fracture surface morphology that results from mode I tearing of ductile plate metals depends heavily on both the elastic-plastic material properties and the microstructure. Severe tunneling of the advancing crack tip (resulting in cup-cup, or bath-tub like fracture surfaces) can take place...... in a range of materials, often of low strength, while tearing of high strength metals typically progress by the shear band failure mechanism (slanting). In reality, however, most fracture surfaces display a mixture of morphologies. For example, slant crack propagation can be accompanied by large shear lips...... near the outer free plate surface or a complete shear band switch - seemingly distributed randomly on the fracture surface. The occasionally observed shear band switch of mode I slant cracks, related to ductile plate tearing, is far from random as the crack can flip systematically from one side...

  7. Creep crack growth behaviour of an AISI 316 steel plate for fast reactor structures

    International Nuclear Information System (INIS)

    D'Angelo, D.; Regis, V.

    1985-01-01

    The paper presents and analyses creep crack growth data obtained at 550, 600 and 650 0 C in air with SENT and CT specimens on type 316 stainless steel plate for LMFBR applications. Crack initiation and crack growth are tentatively correlated to K, sigmasub(net) and J* taking into account the constraint conditions due to specimen geometry. The validity of these parameters is discussed following the concept of transition time from small scale creep at the crack tip to extensive creep within the ligament. Post exposure microstructural and fractographic investigations do evidence that grain deformation processes are mainly responsible for cavity evolution. (orig.)

  8. Steam generator tubes rupture probability estimation - study of the axially cracked tube case

    International Nuclear Information System (INIS)

    Mavko, B.; Cizelj, L.; Roussel, G.

    1992-01-01

    The objective of the present study is to estimate the probability of a steam generator tube rupture due to the unstable propagation of axial through-wall cracks during a hypothetical accident. For this purpose the probabilistic fracture mechanics model was developed taking into account statistical distributions of influencing parameters. A numerical example considering a typical steam generator seriously affected by axial stress corrosion cracking in the roll transition area, is presented; it indicates the change of rupture probability with different assumptions focusing mostly on tubesheet reinforcing factor, crack propagation rate and crack detection probability. 8 refs., 4 figs., 4 tabs

  9. Evaluation of stress corrosion crack growth in BWR piping systems

    International Nuclear Information System (INIS)

    Kassir, M.; Sharma, S.; Reich, M.; Chang, M.T.

    1985-05-01

    This report presents the results of a study conducted to evaluate the effects of stress intensity factor and environment on the growth behavior of intergranular stress corrosion cracks in type 304 stainless steel piping systems. Most of the detected cracks are known to be circumferential in shape, and initially started at the inside surface in the heat affected zone near girth welds. These cracks grow both radially in-depth and circumferentially in length and, in extreme cases, may cause leakage in the installation. The propagation of the crack is essentially due to the influence of the following simultaneous factors: (1) the action of applied and residual stress; (2) sensitization of the base metal in the heat affected zone adjacent to girth weld; and (3) the continuous exposure of the material to an aggressive environment of high temperature water containing dissolved oxygen and some levels of impurities. Each of these factors and their effects on the piping systems is discussed in detail in the report. The report also evaluates the time required for hypothetical cracks in BWR pipes to propagate to their critical size. The pertinent times are computed and displayed graphically. Finally, parametric study is performed in order to assess the relative influence and sensitivity of the various input parameters (residual stress, crack growth law, diameter of pipe, initial size of defect, etc.) which have bearing on the growth behavior of the intergranular stress corrosion cracks in type 304 stainless steel. Cracks in large-diameter as well as in small-diameter pipes are considered and analyzed. 27 refs., 25 figs., 10 tabs

  10. Zircaloy-4 stress corrosion by iodine: crack kinetics and influence of irradiation on the crack initiation

    International Nuclear Information System (INIS)

    Serres, A.

    2008-01-01

    During the PWR power transients, iodine-induced stress corrosion cracking (I-SCC) is one of the potential failure modes of Zircaloy-4 fuel claddings under Pellet-Cladding Interaction conditions. The primary objective of this study is to distinguish the parameters that contribute to the I-SCC phenomenon in iodized methanol solutions at ambient temperature, on notched tensile specimens, using crack growth rate measurements provided by Direct Current Potential Drop. The results show that for a KI lower than 20 MPa.m 1/2 , the IG and mixed IG/TG velocity of propagation is a linear function of KI, regardless of the propagation mode. Between 20 and 25 MPa.m 1/2 , the TG crack growth rate also depends linearly on KI, but increases at a faster rate with respect to KI than during the IG and mixed IG/TG propagation steps. The crack propagation direction and plane (LT and TL) have an impact on the propagation modes, but no impact on the kinetics. The increase of iodine content induces an increase of the crack growth rate for a given KI, and a decrease of the KI, threshold, allowing the crack propagation. This work enables us to quantify the effect of iodine content and of KI on the crack propagation step, propose a propagation law taking into accounts these parameters, and improve the I-SCC description for models. During operation, a zirconium cladding is neutron-irradiated, modifying its microstructure and deformation modes. The second objective of the study is therefore to investigate the impact of these modifications on I-SCC. For that purpose, smooth specimens in recrystallized Zircaloy-4 are proton-irradiated to 2 dpa at 305 C, the microstructure and deformation modes of unirradiated and irradiated Zircaloy-4 are characterized by TEM and SEM, and the influence of these radiation-induced modifications on the I-SCC susceptibility is studied. The Laves phases precipitates are slightly modified by irradiation. The formation of P -type dislocation loops correlated with

  11. Quantitative characterization of initiation and propagation in stress corrosion cracking. An approach of a phenomenological model

    International Nuclear Information System (INIS)

    Raquet, O.

    1994-01-01

    A purely phenomenological study of stress corrosion cracking was performed using the couple Z2CN 18.10 (304L) austenitic stainless steel/boiling MgCl 2 aqueous solution. The exploitation of the morphological information (shape of the cracks and size distribution) available after constant elongation rate tests led to the proposal of an analytical expression of the crack initiation and growth rates. This representation allowed to quantitatively characterize the influence of the applied strain rate as well as the effect of corrosion inhibitors on the crack initiation and propagation phases. It can be used in the search for the stress corrosion cracking mechanisms as a 'riddle' for the determination of the rate controlling steps. As a matter of fact, no mechanistic hypothesis has been used for its development. (author)

  12. Mechanism of fatigue crack initiation in austenitic stainless steels in light water reactor environments

    International Nuclear Information System (INIS)

    Chopra, O.K.; Shack, W.J.; Muscara, J.

    2003-01-01

    This paper examines the mechanism of fatigue crack initiation in austenitic stainless steels (SSs) in light water reactor (LWR) coolant environments. The effects of key material and loading variables on the fatigue lives of wrought and cast austenitic SSs in air and LWR environments have been evaluated. The influence of reactor coolant environments on the formation and growth of fatigue cracks in polished smooth SS specimens is discussed. The results indicate that the fatigue lives of these steels are decreased primarily by the effects of the environment on the growth of cracks <200 μm and, to a lesser extent, on enhanced growth rates of longer cracks. The fracture morphology in the specimens has been characterized. Exploratory fatigue tests were conducted to study the effects of surface micropits or minor differences in the surface oxide on fatigue crack initiation. (author)

  13. Evaluation of the inner wall axial cracks of steam generator tubes by eddy current test

    International Nuclear Information System (INIS)

    Hur, Do Haeng; Choi, Myung Sik; Lee, Doek Hyun; Han, Jung Ho

    2001-01-01

    For the enhancement of ECT reliability on the primary water stress corrosion cracks of nuclear steam generator tubes, it is important to comprehend the signal characteristics on crack morphology and to select an appropriate probe type. In this paper, the sizing accuracy and the detectability for the inner wall axial cracks of tubes were quantitatively evaluated using the electric discharge machined notches and the corrosion cracks which were developed on the operating steam generator tubes. The difference of eddy current signal characteristics between pancake and axial coil were also investigated. The results obtained from this study provide a useful information for more precise evaluation on the inner wall axial cracks of steam generator tubes.

  14. Fractographic Observations on the Mechanism of Fatigue Crack Growth in Aluminium Alloys

    Science.gov (United States)

    Alderliesten, R. C.; Schijve, J.; Krkoska, M.

    Special load histories are adopted to obtain information about the behavior of the moving crack tip during the increasing and decreasing part of a load cycle. It is associated with the crack opening and closure of the crack tip. Secondly, modern SEM techniques are applied for observations on the morphology of the fractures surfaces of a fatigue crack. Information about the cross section profiles of striations are obtained. Corresponding locations of the upper and the lower fracture surface are also explored in view of the crack extension mechanism. Most experiments are carried out on sheet specimens of aluminum alloys 2024-T3, but 7050-T7451 specimens are also tested in view of a different ductility of the two alloys.

  15. Subsurface metals fatigue cracking without and with crack tip

    Directory of Open Access Journals (Sweden)

    Andrey Shanyavskiy

    2013-07-01

    Full Text Available Very-High-Cycle-Fatigue regime for metals was considered and mechanisms of the subsurface crack origination were introduced. In many metals first step of crack origination takes place with specific area formation because of material pressing and rotation that directed to transition in any volume to material ultra-high-plasticity with nano-structure appearing. Then by the border of the nano-structure takes place volume rotation and fracture surface creates with spherical particles which usually named Fine-Granular-Area. In another case there takes place First-Smooth-Facet occurring in area of origin due to whirls appearing by the one of the slip systems under discussed the same stress-state conditions. Around Fine-Granular-Area or First-Smooth-Facet there plastic zone appeared and, then, subsurface cracking develops by the same manner as for through cracks. In was discussed quantum-mechanical nature of fatigue crack growth in accordance with Yang’s modulus quantization for low level of deformations. New simply equation was considered for describing subsurface cracking in metals out of Fine-Granular-Area or Fist-Smooth-Facet.

  16. 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.

  17. Finite element limit analysis based plastic limit pressure solutions for cracked pipes

    International Nuclear Information System (INIS)

    Shim, Do Jun; Huh, Nam Su; Kim, Yun Jae; Kim, Young Jin

    2002-01-01

    Based on detailed FE limit analyses, the present paper provides tractable approximations for plastic limit pressure solutions for axial through-wall cracked pipe; axial (inner) surface cracked pipe; circumferential through-wall cracked pipe; and circumferential (inner) surface cracked pipe. Comparisons with existing analytical and empirical solutions show a large discrepancy in circumferential short through-wall cracks and in surface cracks (both axial and circumferential). Being based on detailed 3-D FE limit analysis, the present solutions are believed to be the most accurate, and thus to be valuable information not only for plastic collapse analysis of pressurised piping but also for estimating non-linear fracture mechanics parameters based on the reference stress approach

  18. Prediction of Fatigue Crack Growth in Gas Turbine Engine Blades Using Acoustic Emission.

    Science.gov (United States)

    Zhang, Zhiheng; Yang, Guoan; Hu, Kun

    2018-04-25

    Fatigue failure is the main type of failure that occurs in gas turbine engine blades and an online monitoring method for detecting fatigue cracks in blades is urgently needed. Therefore, in this present study, we propose the use of acoustic emission (AE) monitoring for the online identification of the blade status. Experiments on fatigue crack propagation based on the AE monitoring of gas turbine engine blades and TC11 titanium alloy plates were conducted. The relationship between the cumulative AE hits and the fatigue crack length was established, before a method of using the AE parameters to determine the crack propagation stage was proposed. A method for predicting the degree of crack propagation and residual fatigue life based on the AE energy was obtained. The results provide a new method for the online monitoring of cracks in the gas turbine engine blade.

  19. Steady-state, elastic-plastic growth of slanted cracks in symmetrically loaded plates

    DEFF Research Database (Denmark)

    Nielsen, Kim Lau; Hutchinson, J. W.

    2017-01-01

    parameter through the plate in the plastic zone at the crack tip. The distribution of the mode I and mode III stress intensity factors along the crack front are obtained for the elastic problem. The out-of-plane bending constraint imposed on the plate significantly influences the mixed mode behavior along......Elastic and elastic-plastic results are obtained for a semi-infinite slanted through-crack propagating in a symmetrically loaded plate strip with the aim of providing theoretical background to commonly observed plate tearing behavior. Were it is not for the slant of the crack through the thickness...... of the plate, the problem would be mode I, but due to the slant the local conditions along the crack front are a combination of mode I and mode III. A three-dimensional formulation for steady-state crack propagation is employed to generate distributions of effective stress, stress triaxiality and Lode...

  20. Stress intensity factors of three parallel edge cracks under bending moments

    International Nuclear Information System (INIS)

    Ismail, A E

    2013-01-01

    This paper reports the study of stress intensity factors (SIF) of three edge cracks in a finite plate under bending moments. The goal of this paper was to analyze the three edge crack interactions under such loading. Several studies can be found in literature discussing on mode I SIF. However, most of these studies obtained the SIFs using tensile force. Lack of SIF reported discussing on the SIFs obtained under bending moments. ANSYS finite element program was used to develop the finite element model where singular elements were used to model the cracks. Different crack geometries and parameters were utilized in order to characterize the SIFs. According to the present results, crack geometries played a significant role in determining the SIFs and consequently induced the crack interaction mechanisms

  1. 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...

  2. Surface crack growth in cylindrical hollow specimen subject to tension and torsion

    Directory of Open Access Journals (Sweden)

    V. Shlyannikov

    2015-07-01

    Full Text Available The subject for studies is an aluminium cylindrical hollow specimen with external axial and part circumferential semi-elliptical surface crack undergoing fatigue loads. Both the optical microscope measurements and the crack opening displacement (COD method are used to monitor and calculate both crack depth and crack length during the tests. The variation of crack growth behaviour is studied under cyclic axial tension, pure torsion and combined tension+torsion fatigue loading. For the particular surface flaw geometries considered, the elastic and plastic in-plane and out-of-plane constraint parameters, as well as the governing parameter for stress fields in the form of In-integral and plastic stress intensity factor, are obtained as a function of the aspect ratio, dimensionless crack length and crack depth. The combined effect of tension and torsion loading and initial surface flaw orientation on the crack growth for two type of aluminium alloys is made explicit. The experimental and numerical results of the present study provided the opportunity to explore the suggestion that fatigue crack propagation may be governed more strongly by the plastic stress intensity factor rather than the magnitude of the elastic SIFs alone. One advantage of the plastic SIF is its sensitivity to combined loading due to accounting for the plastic properties of the material.

  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. Super oil cracking update

    International Nuclear Information System (INIS)

    Mulraney, D.

    1997-01-01

    The conversion of residual fuel oil to usable middle distillates was discussed. The residue conversion processing paths are usually based on separation, carbon rejection, or hydrogen addition principles. Super Oil Cracking (SOC) uses a slurry catalyst system in a new, tubular reactor to achieve high levels of hydrothermal conversion. SOC can upgrade a variety of heavy, high metals residue feedstocks with high yields of middle distillates. The SOC products can also be further treated into feedstocks for FCC or hydrocracking. The SOC process can be incorporated easily into a refinery to obtain incremental residue conversion directly. It can also be integrated with other residue processes, acting as a demetallization and decarbonization step which results in enhanced overall conversion. The relative rate of coke formation and its handling are distinguishing characteristics between residue upgrading technologies. The SOC process operates at higher temperatures that other residue hydrocracking processes resulting in higher rates of thermal decomposition, thus preventing coke formation. SOC process can operate as a stand-alone upgrader or can be integrated with other bottoms processing steps to extend the refiner's range of options for increasing bottoms conversion.3 tabs., 14 figs

  5. Metallurgy of stress corrosion cracking

    International Nuclear Information System (INIS)

    Donovan, J.A.

    1973-01-01

    The susceptibility of metals and alloys to stress corrosion is discussed in terms of the relationship between structural characteristics (crystal structure, grains, and second phases) and defects (vacancies, dislocations, and cracks) that exist in metals and alloys. (U.S.)

  6. 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.

  7. Shapes formed by interacting cracks

    Science.gov (United States)

    Daniels, Karen

    2012-02-01

    Brittle failure through multiple cracks occurs in a wide variety of contexts, from microscopic failures in dental enamel and cleaved silicon to geological faults and planetary ice crusts. In each of these situations, with complicated stress geometries and different microscopic mechanisms, pairwise interactions between approaching cracks nonetheless produce characteristically curved fracture paths. We investigate the origins of this widely observed ``en passant'' crack pattern by fracturing a rectangular slab which is notched on each long side and subjected to quasi-static uniaxial strain from the short side. The two cracks propagate along approximately straight paths until they pass each other, after which they curve and release a lens-shaped fragment. We find that, for materials with diverse mechanical properties, each curve has an approximately square-root shape, and that the length of each fragment is twice its width. We are able to explain the origins of this universal shape with a simple geometrical model.

  8. Stress intensity factors and constant stress terms for interface cracks

    International Nuclear Information System (INIS)

    Fett, T.; Rizzi, G.

    2004-01-01

    In bi-material joints cracks can propagate along the interface or kink into one of the two materials. Whereas the energy release rate can be applied for interface cracks in the same way as usual for homogeneous materials, the computation of stresses in the vicinity of the crack tip is significantly more complicated. In order to assess crack kinking, it is necessary to know the mixed-mode stress intensity factor contributions K I and K II as well as the constant stress terms in the two materials. Whereas the stress intensity factors are available for a large number of infinite and semi-infinite bodies, there is experimental interest in practically used test specimens. This especially holds for the constant x-stress terms. Finite element computations are performed for the special case of a disappearing second Dundurs parameter, i.e. β=0. The fracture mechanics parameters K I , K II , σ 0 for the interface crack are reported in the form of diagrams and approximate relations. (orig.)

  9. 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

  10. Dynamic Crack Branching - A Photoelastic Evaluation,

    Science.gov (United States)

    1982-05-01

    0.41 mPai and a 0.18 MPa, and predicted a theoretical kinking angle of 84°whichagreed well with experimentally measured angle. After crack kinking...Consistent crack branching’at KIb = 2.04 MPaI -i- and r = 1.3 mm verified this crack branching criterion. The crack branching angle predicted by--.’ DD

  11. 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...

  12. Crack propagation in dynamic thermoelasticity

    International Nuclear Information System (INIS)

    Bui, H.D.

    1980-01-01

    We study the singular thermoelastic fields near the crack tip, in the linear strain assumption. The equations are coupled and non linear. The asymptotic expansions of the displacement and the temperature are given for the first and the second order. It is shown that the temperature is singular when the crack propagates. However, this field does not change the dominant singularity of the mechanical field which is the same as that obtained in the theory of isothermal elasticity [fr

  13. Modelling of stress corrosion cracking in zirconium alloys

    International Nuclear Information System (INIS)

    Fandeur, O.; Rouillon, L.; Pilvin, P.; Jacques, P.; Rebeyrolle, V.

    2001-01-01

    During normal and incidental operating conditions, PWR power plants must comply with the first safety requirement, which is to ensure that the cladding wall is sound. Indeed some severe power transients potentially induce Stress Corrosion Cracking (SCC) of the zirconium alloy clad, due to strong Pellet Cladding Interaction (PCI). Since, at present, the prevention of this risk has some consequences on the French reactors manoeuvrability, a better understanding and forecast of the clad damage related to SCC/PCI is needed. With this aim, power ramp tests are performed in experimental reactors to assess the fuel rod behaviour and evaluate PCI failure risks. To study in detail SCC mechanisms, additional laboratory experiments are carried out on non-irradiated and irradiated cladding tubes. Numerical simulations of these tests have been developed aiming, on the one hand, to evaluate mechanical state variables and, on the other hand, to study consistent mechanical parameters for describing stress corrosion clad failure. The main result of this simulation is the determination of the validity ranges of the stress intensity factor, which is frequently used to model SCC. This parameter appears to be valid only at the onset of crack growth, when crack length remains short. In addition, the role of plastic strain rate and plastic strain as controlling parameters of the SCC process has been analysed in detail using the above mechanical description of the crack tip mechanical fields. Finally, the numerical determination of the first-order parameter(s) in the crack propagation rate law is completed by the development of laboratory tests focused on these parameters. These tests aim to support experimentally the results of the FE simulation. (author)

  14. 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.

  15. Importance and role of grain size in free surface cracking prediction of heavy forgings

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zhenhua [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Key Laboratory of Advanced Forging & Stamping Technology and Science, Yanshan University, Ministry of Education of China, Qinhuangdao 066004 (China); Sun, Shuhua; Wang, Bo [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Shi, Zhongping [Key Laboratory of Advanced Forging & Stamping Technology and Science, Yanshan University, Ministry of Education of China, Qinhuangdao 066004 (China); Fu, Wantang, E-mail: wtfu@ysu.edu.cn [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China)

    2015-02-11

    The importance and role of grain size in predicting surface cracking of heavy forgings were investigated. 18Mn18Cr0.5N steel specimens with four different grain sizes were tensioned between 900 and 1100 °C at a strain rate of 0.1 s{sup −1}. The nucleation sites and crack morphology were analyzed through electron backscatter diffraction analysis, and the fracture morphology was examined using scanning electron microscopy. The nucleation sites were independent of the grain size, and cracks primarily formed at grain boundaries and triple junctions between grains with high Taylor factors. Grains with lower Taylor factors inhibited crack propagation. Strain was found to mainly concentrate near the grain boundaries; thus, a material with a larger grain size cracks more easily because there are fewer grain boundaries. Fine grains can be easily rotated to a lower Taylor factor to further inhibit cracking. The fracture morphology transformed from a brittle to ductile type with a lowering of grain size. At lower temperature, small dimples on the fracture surfaces of specimens with smaller grain sizes were left by single parent grains and the dimple edge was the grain edge. At higher temperature, dimples formed through void coalescence and the dimple edge was the tearing edge. Finally, the relationship between the reduction in area, grain size, and deformation temperature was obtained.

  16. 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.

  17. Numerical investigations on applicability of permanent magnet method to crack detection in HTS film

    Energy Technology Data Exchange (ETDEWEB)

    Kamitani, A., E-mail: kamitani@yz.yamagata-u.ac.jp [Yamagata University, 4-3-16, Johnan, Yonezawa, Yamagata 992-8510 (Japan); Takayama, T. [Yamagata University, 4-3-16, Johnan, Yonezawa, Yamagata 992-8510 (Japan); Saitoh, A. [University of Hyogo, 2167, Shosha, Himeji, Hyogo 671-2280 (Japan)

    2014-09-15

    Highlights: • The defect parameter is defined for characterizing a crack position. • The defect parameter shows a remarkable change only near a crack. • A crack detection method is proposed on the basis of the permanent-magnet method. • The high-speed rough detection can be achieved by means of the proposed method. - Abstract: The scanning permanent-magnet (PM) method was originally developed for determining the spatial distribution of the critical current density in a high-temperature superconducting (HTS) film. In the present study, its applicability to the crack detection in an HTS film is investigated numerically. To this end, a defect parameter is defined for characterizing a crack position and it is calculated along various scanning lines. The results of computations show that, only when the scanning position is near a crack, the defect parameter shows a violent change. On the basis of the behavior of the defect parameter, the method for roughly identifying a crack is also proposed.

  18. Numerical investigations on applicability of permanent magnet method to crack detection in HTS film

    International Nuclear Information System (INIS)

    Kamitani, A.; Takayama, T.; Saitoh, A.

    2014-01-01

    Highlights: • The defect parameter is defined for characterizing a crack position. • The defect parameter shows a remarkable change only near a crack. • A crack detection method is proposed on the basis of the permanent-magnet method. • The high-speed rough detection can be achieved by means of the proposed method. - Abstract: The scanning permanent-magnet (PM) method was originally developed for determining the spatial distribution of the critical current density in a high-temperature superconducting (HTS) film. In the present study, its applicability to the crack detection in an HTS film is investigated numerically. To this end, a defect parameter is defined for characterizing a crack position and it is calculated along various scanning lines. The results of computations show that, only when the scanning position is near a crack, the defect parameter shows a violent change. On the basis of the behavior of the defect parameter, the method for roughly identifying a crack is also proposed

  19. 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.

  20. Microbial corrosion and cracking in steel. A concept for evaluation of hydrogen-assisted stress corrosion cracking in cathodically protected high-pressure gas transmission pipelines

    DEFF Research Database (Denmark)

    Nielsen, Lars Vendelbo

    An effort has been undertaken in order to develop a concept for evaluation of the risk of hydrogen-assisted cracking in cathodically protected gas transmission pipelines. The effort was divided into the following subtasks: A. Establish a correlation between the fracture mechanical properties...... crack propagation. This resulted in threshold curves that can be used for assessment of the risk of hydrogen-assisted cracking as a function of operating pressure and hydrogen content - having the flaw size as discrete parameter. The results are to be used mainly on a conceptual basis......, but it was indicated that the requirements for crack propagation include an overprotective CP-condition, a severe sulphate-reducing environment, as well as a large flaw (8 mm or a leak in the present case). A 1 mm flaw (which may be the maximum realistic flaw size) is believed to be unable to provoke crack propagation...

  1. Morphological demosaicking

    Science.gov (United States)

    Quan, Shuxue

    2009-02-01

    Bayer patterns, in which a single value of red, green or blue is available for each pixel, are widely used in digital color cameras. The reconstruction of the full color image is often referred to as demosaicking. This paper introduced a new approach - morphological demosaicking. The approach is based on strong edge directionality selection and interpolation, followed by morphological operations to refine edge directionality selection and reduce color aliasing. Finally performance evaluation and examples of color artifacts reduction are shown.

  2. Monitoring micro-crack healing in an engineered cementitious composite using the environmental scanning electron microscope

    Energy Technology Data Exchange (ETDEWEB)

    Suryanto, B., E-mail: b.suryanto@hw.ac.uk; Buckman, J.O.; Thompson, P.; Bolbol, M.; McCarter, W.J.

    2016-09-15

    Environmental Scanning Electron Microscopy (ESEM) is used to study the origin of micro-crack healing in an Engineered Cementitious Composite (ECC). ESEM images were acquired from ECC specimens cut from pre-cracked, dog-bone samples which then subjected to submerged curing followed by exposure to the natural environment. The mineralogical and chemical compositions of the healing products were determined using the EDX facility in the ESEM. It is shown that the precipitation of calcium carbonate is the main contributor to micro-crack healing at the crack mouth. The healing products initially appeared in an angular rhombohedral morphology which then underwent a discernable transformation in size, shape and surface texture, from relatively flat and smooth to irregular and rough, resembling the texture of the original surface areas surrounding the micro-cracks. It is also shown that exposure to the natural environment, involving intermittent wetting/drying cycles, promotes additional crystal growth, which indicates enhanced self-healing capability in this environment. - Highlights: •ESEM with EDX used to characterize the origin of micro-crack healing in an ECC •Evolution of healing precipitates studied at three specific locations over four weeks •Specimens exposed to laboratory environment, followed by the natural environment •Calcium carbonate is the main contributor to crack healing at the crack mouth. •Outdoor exposure involving intermittent rain promotes additional crystal growth.

  3. An energy analysis of crack-initiation and arrest in epoxy

    Science.gov (United States)

    Chudnovsky, A.; Kim, A.; Bosnyak, C. P.

    1992-01-01

    The objective of this work is to study fracture processes such as crack initiation and arrest in epoxy. A compact tension specimen with displacement-controlled loading is employed to observe multiple crack initiations and arrests. The energy release rate at crack initiation is significantly higher than that at crack arrest, as has been observed elsewhere. In this study, the difference between these energy release rates is found to depend on specimen size (scale effect), and is quantitatively related to the fracture surface morphology. The scale effect, similar to that in strength theory, is conventionally attributed to the statistics of defects which control the fracture process. Triangular shaped ripples, deltoids, are formed on the fracture surface of the epoxy during the slow sub-critical crack growth, prior to the smooth mirrorlike surface characteristic of fast cracks. The deltoids are complimentary on the two crack faces which excludes any inelastic deformation from consideration. The deltoids are analogous to the ripples created on a river surface downstream from a small obstacle. However, in spite of the expectation based on this analogy and the observed scale effect, there are no 'defects' at the apex of the deltoids detectable down to the 0.1 micron level. This suggests that the formation of deltoids during the slow process of subcritical crack growth is an intrinsic feature of the fracture process itself, triggered by inhomogeneity of material on a submicron scale. This inhomogeneity may be related to a fluctuation in the cross-link density of the epoxy.

  4. 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.

  5. The effect of aqueous environments upon the initiation and propagation of fatigue cracks in low-alloy steels

    International Nuclear Information System (INIS)

    James, L.A.

    1996-01-01

    The effect of elevated temperature aqueous environments upon the initiation and propagation of fatigue cracks in low-alloy steels is discussed in terms of the several parameters which influence such behavior. These parameters include water chemistry, impurities within the steels themselves, as well as factors such as the water flow rate, loading waveform and loading rates. Some of these parameters have similar effects upon both crack initiation and propagation, while others exhibit different effects in the two stages of cracking. In the case of environmentally-assisted crack (EAC) growth, the most important impurities within the steel are metallurgical sulfide inclusions which dissolve upon contact with the water. A ''critical'' concentration of sulfide ions at the crack tip can then induce environmentally-assisted cracking which proceeds at significantly increased crack growth rates over those observed in air. The occurrence, or non-occurrence, of EAC is governed by the mass-transport of sulfide ions to and from the crack-tip region, and the mass-transport is discussed in terms of diffusion, ion migration, and convection induced within the crack enclave. Examples are given of convective mass-transport within the crack enclave resulting from external free stream flow. The initiation of fatigue cracks in elevated temperature aqueous environments, as measured by the S-N fatigue lifetimes, is also strongly influenced by the parameters identified above. The influence of sulfide inclusions does not appear to be as strong on the crack initiation process as it is on crack propagation. The oxygen content of the environment appears to be the dominant factor, although loading frequency (strain rate) and temperature are also important factors

  6. Applications of energy-release-rate techniques to part-through cracks in plates and cylinders. Volume 2. ORVIRT: a finite element program for energy release rate calculations for 2-dimensional and 3-dimensional crack models

    International Nuclear Information System (INIS)

    Bass, B.R.; Bryson, J.W.

    1983-02-01

    Certain studies of fracture phenomena, such as pressurized-thermal-shock of cracked structures, require that crack tip parameters be determined for combined thermal and mechanical loads. A method is proposed here that modifies the isothermal formulation of deLorenzi to account for thermal strains in cracked bodies. The formulation has been implemented in the virtual-crack-extension program ORVIRT (Oak Ridge VIRTual-Crack-Extension). Program ORVIRT performs energy release rate calculations for both 2- and 3-dimensional nonlinear models of crack configurations in engineering structures. Two applications of the ORVIRT program are described. In the first, semielliptical surface cracks in an experimental test vessel are analyzed under elastic-plastic conditions using the finite element method. The second application is a thick-walled test vessel subjected to combined pressure and thermal shock loading

  7. Effect of the delta ferrite solidification morphology of austenitic steels weld metal on the joint properties

    International Nuclear Information System (INIS)

    Bilmes, P.; Gonzalez, A.; Llorente, C.; Solari, M.

    1996-01-01

    The properties of austenitic stainless steel weld metals are largely influenced by the appearance in the microstructure of delta ferrite of a given morphology. The susceptibility to hot cracks and low temperature toughness are deeply conditioned by the mixed complex austenitic-ferritic structures which depending on the steel chemical composition and on the cooling rate may be developed. The latest research on this issue points out the importance of the sodification mode as regards to the influence in the appearance of delta ferrite of a certain morphology. In fact, it is very important to understand the solidification sequences, the primary solidification modes which are possible and the subsequent solid state transformations to correlate the structural elements of the weld metal with the parameters of the welding process on the one had, and the weld joint properties on the other. (Author) 19 refs

  8. The Relation Between Alloy Chemistry and Hot-Cracking

    Science.gov (United States)

    Nunes, A. C., Jr.; Talia, J. E.

    2000-01-01

    Hot cracking is a problem in welding 2195 aluminum-lithium alloy. Weld wire additives seem to reduce the problem. This study proposes a model intended to clarify the way alloying elements affect hot-cracking. The brittle temperature range of an alloy extends wherever the tensile stress required to move the meniscus of the liquid film at the grain/dendrite boundaries is less than the bulks flow stress Sigma(sub B) of the grains: 2gamma/delta alloys outgas.) If the above condition is not met, the grains deform under stress and the liquid film remains in place. Curves of 2gamma/delta and sigma(sub B) vs. temperature in the range just below the melting temperature determine the hot cracking susceptibility of an alloy. Both are zero at onset of solidification. sigma(sub B) rises as the thermal activation of the slip mechanism is reduced. 2gamma/delta rises as the film thickness delta which can be estimated from the Scheil equation, drops. But, given an embrittled alloy, whether the alloy actually cracks is determined by the strain imposed upon it in the embrittled condition. A critical strain is estimated, Epsilon(sub C) on the order of Epsilon(sub C) is approximately delta/l where L = grain size and where the the volume increment due to the strain, concentrated at the liquid film, is on the order of the liquid film volume. In the early 80's an empirical critical strain cracking envelope Epsilon(sub C)(T) was incorporated into a damage criterion to estimate the effect of welding parameters on the formation of microfissures in a superalloy with good results. These concepts, liquid film decoherence vs. grain bulk deformation and critical strain, form the key elements of a quantitative theory of hot-cracking applicable for assessing the effect of alloying elements on hot-cracking during welding.

  9. Thermally-Induced Crack Evaluation in H13 Tool Steel

    Directory of Open Access Journals (Sweden)

    Hassan Abdulrssoul Abdulhadi

    2017-11-01

    Full Text Available This study reported the effect of thermal wear on cylindrical tool steel (AISI H13 under aluminum die-casting conditions. The AISIH13 steels were immersed in the molten aluminum alloy at 700 °C before water-quenching at room temperature. The process involved an alternating heating and cooling of each sample for a period of 24 s. The design of the immersion test apparatus stylistically simulated aluminum alloy dies casting conditions. The testing phase was performed at 1850, 3000, and 5000 cycles. The samples were subjected to visual inspection after each phase of testing, before being examined for metallographic studies, surface crack measurement, and hardness characteristics. Furthermore, the samples were segmented and examined under optical and Scanning Electron Microscopy (SEM. The areas around the crack zones were additionally examined under Energy Dispersive X-ray Spectroscopy (EDXS. The crack’s maximum length and Vickers hardness profiles were obtained; and from the metallographic study, an increase in the number of cycles during the testing phase resulted in an increase in the surface crack formation; suggesting an increase in the thermal stress at higher cycle numbers. The crack length of Region I (spherically shaped was about 47 to 127 µm, with a high oxygen content that was analyzed within 140 µm from the surface of the sample. At 700 °C, there is a formation of aluminum oxides, which was in contact with the surface of the H13 sample. These stresses propagate the thermal wear crack length into the tool material of spherically shaped Region I and cylindrically shape Region II, while hardness parameters presented a different observation. The crack length of Region I was about 32% higher than the crack length of Region II.

  10. The mechanism of hot crack formation in Ti-6A1-4V during cold crucible continuous casting

    Directory of Open Access Journals (Sweden)

    Hongsheng DING

    2004-08-01

    Full Text Available Hot crack is one of common defects in castings, which often results in failure of castings. This work studies the formation of hot cracks during cold crucible continous casting by means of experiments and thoretical analysis. The results show that the hot crack occurs on the surface and in the circumference of ingots, where the solidified shell and 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 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 affecting the hot cracks are analyzed and verified. In order to decrease the tendency of hot cracks, technical parameters should be optimized.

  11. Cracking in Flexural Reinforced Concrete Members