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Sample records for edge crack torsion

  1. Observation of Intralaminar Cracking in the Edge Crack Torsion Specimen

    Science.gov (United States)

    Czabaj, Michael W.; Ratcliffe, James G.; Davidson, Barry D.

    2013-01-01

    The edge crack torsion (ECT) test is evaluated to determine its suitability for measuring fracture toughness associated with mode III delamination growth onset. A series of ECT specimens with preimplanted inserts with different lengths is tested and examined using nondestructive and destructive techniques. Ultrasonic inspection of all tested specimens reveals that delamination growth occurs at one interface ply beneath the intended midplane interface. Sectioning and optical microscopy suggest that the observed delamination growth results from coalescence of angled intralaminar matrix cracks that form and extend across the midplane plies. The relative orientation of these cracks is approximately 45 deg with respect to the midplane, suggesting their formation is caused by resolved principal tensile stresses arising due to the global mode-III shear loading. Examination of ECT specimens tested to loads below the level corresponding to delamination growth onset reveals that initiation of intralaminar cracking approximately coincides with the onset of nonlinearity in the specimen's force-displacement response. The existence of intralaminar cracking prior to delamination growth onset and the resulting delamination extension at an unintended interface render the ECT test, in its current form, unsuitable for characterization of mode III delamination growth onset. The broader implications of the mechanisms observed in this study are also discussed with respect to the current understanding of shear-driven delamination in tape-laminate composites.

  2. A Modified Edge Crack Torsion Test for Measurement of Mode III Fracture Toughness of Laminated Tape Composites

    Science.gov (United States)

    Czabaj, Michael W.; Davidson, Barry D.; Ratcliffe, James G.

    2016-01-01

    Modifications to the edge crack torsion (ECT) test are studied to improve the reliability of this test for measuring the mode-III fracture toughness, G (sub IIIc), of laminated tape fiber-reinforced polymeric (FRP) composites. First, the data reduction methods currently used in the ECT test are evaluated and deficiencies in their accuracy are discussed. An alternative data reduction technique, which uses a polynomial form to represent ECT specimen compliance solution, is evaluated and compared to FEA (finite element analysis) results. Second, seven batches of ECT specimens are tested, each batch containing specimens with a preimplanted midplane edge delamination and midplane plies with orientations of plus theta divided by minus theta, with theta ranging from 0 degrees to 90 degrees in 15-degree increments. Tests on these specimens show that intralaminar cracking occurs in specimens from all batches except for which theta = 15 degrees and 30 degrees. Tests on specimens of these two batches are shown to result in mode-III delamination growth at the intended ply interface. The findings from this study are encouraging steps towards the use of the ECT test as a standardized method for measuring G (sub IIIc), although further modification to the data reduction method is required to make it suitable for use as part of a standardized test method.

  3. Evaluation of the Edge Crack Torsion (ECT) Test for Mode 3 Interlaminar Fracture Toughness of Laminated Composites

    Science.gov (United States)

    Li, Jian; Lee, Edward W.; OBrien, T. Kevin; Lee, Shaw Ming

    1996-01-01

    An analytical and experimental investigation was carried out on G40-800/R6376 graphite epoxy laminates to evaluate the Edge Crack Torsion (ECT) test as a candidate for a standard Mode 3 interlaminar fracture toughness test for laminated composites. The ECT test consists of a (90/(+/- 45)(sub 3)/(+/- 45)(sub 3)/90))(sub s) laminate with a delamination introduced by a non-adhesive film at the mid-plane along one edge and loaded in a special fixture to create torsion along the length of the laminate. Dye penetrate enhanced X-radiograph of failed specimens revealed that the delamination initiated at the middle of the specimen length and propagated in a self similar manner along the laminate mid-plane. A three-dimensional finite element analysis was performed that indicated that a pure Mode 3 delamination exists at the middle of specimen length away from both ends. At the ends near the loading point a small Mode 2 component exists. However, the magnitude of this Mode 2 strain energy release rate at the loading point is small compared to the magnitude of Mode 3 component in the mid-section of the specimen. Hence, the ECT test yielded the desired Mode 3 delamination. The Mode 3 fracture toughness was obtained from a compliance calibration method and was in good agreement with the finite element results. Mode 2 End-Notched Flexure (ENF) tests and Mode 1 Double Cantilever Beam (DCB) tests were also performed for the same composite material. The Mode 1 fracture toughness was much smaller than both the Mode 2 and Mode 3 fracture toughness. The Mode 2 fracture toughness was found to be 75% of the Mode 3 fracture toughness.

  4. Characterization of the Edge Crack Torsion (ECT) Test for Mode III Fracture Toughness Measurement of Laminated Composites

    Science.gov (United States)

    Ratcliffe, James G.

    2004-01-01

    The edge crack torsion (ECT) test is designed to initiate mode III delamination growth in composite laminates. The test has undergone several design changes during its development. The objective of this paper was to determine the suitability of the current ECT test design a mode III fracture test. To this end, ECT tests were conducted on specimens manufactured from IM7/8552 and S2/8552 tape laminates. Three-dimensional finite element analyses were performed. The analysis results were used to calculate the distribution of mode I, mode II, and mode III strain energy release rate along the delamination front. The results indicated that mode IIIdominated delamination growth would be initiated from the specimen center. However, in specimens of both material types, the measured values of GIIIc exhibited significant dependence on delamination length. Load-displacement response of the specimens exhibited significant deviation from linearity before specimen failure. X-radiographs of a sample of specimens revealed that damage was initiated in the specimens prior to failure. Further inspection of the failure surfaces is required to identify the damage and determine that mode III delamination is initiated in the specimens.

  5. Study of coupling between bending and torsional vibration of cracked rotor system supported by radial active magnetic bearings

    OpenAIRE

    Ferfecki P.

    2007-01-01

    The coupling of bending and torsional vibration due to the presence of transverse fatigue crack in a rotor system supported by radial active magnetic bearings (AMB) is investigated. For this purpose the modified stiffness matrix with six degrees of freedom per node is used and takes into account all the coupling phenomena that exists in a cracked rotor. The partial opening and closing of crack is considered by means of status of stress intensity factor along the crack edge. The equation of mo...

  6. Stress intensity and crack displacement for small edge cracks

    Science.gov (United States)

    Orange, Thomas W.

    1988-01-01

    The weight function method was used to derive stress intensity factors and crack mouth displacement coefficients for small edge cracks (less than 20 percent of the specimen width) in common fracture specimen configurations. Contact stresses due to point application of loads were found to be small but significant for three-point bending and insignificant for four-point bending. The results are compared with available equations and numerical solutions from the literature and with unpublished boundary collocation results.

  7. Study of coupling between bending and torsional vibration of cracked rotor system supported by radial active magnetic bearings

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    Ferfecki P.

    2007-11-01

    Full Text Available The coupling of bending and torsional vibration due to the presence of transverse fatigue crack in a rotor system supported by radial active magnetic bearings (AMB is investigated. For this purpose the modified stiffness matrix with six degrees of freedom per node is used and takes into account all the coupling phenomena that exists in a cracked rotor. The partial opening and closing of crack is considered by means of status of stress intensity factor along the crack edge. The equation of motion of rotor system is nonlinear due to response dependent non-linear breathing crack model and nonlinear force coupling introduced by AMB. A response of the rotor system is obtained by direct integration of nonlinear equation of motion. When the torsional harmonic excitation is applied to the rotor system with the crack then the sum and difference of torsional frequency around a bending natural frequency is observed in the lateral vibration spectrum. Influence of different values of crack parametersfor two different speeds of rotor is investigated with help of frequency spectra.

  8. Edge delamination of composite laminates subject to combined tension and torsional loading

    Science.gov (United States)

    Hooper, Steven J.

    1990-01-01

    Delamination is a common failure mode of laminated composite materials. Edge delamination is important since it results in reduced stiffness and strength of the laminate. The tension/torsion load condition is of particular significance to the structural integrity of composite helicopter rotor systems. Material coupons can easily be tested under this type of loading in servo-hydraulic tension/torsion test stands using techniques very similar to those used for the Edge Delamination Tensile Test (EDT) delamination specimen. Edge delamination of specimens loaded in tension was successfully analyzed by several investigators using both classical laminate theory and quasi-three dimensional (Q3D) finite element techniques. The former analysis technique can be used to predict the total strain energy release rate, while the latter technique enables the calculation of the mixed-mode strain energy release rates. The Q3D analysis is very efficient since it produces a three-dimensional solution to a two-dimensional domain. A computer program was developed which generates PATRAN commands to generate the finite element model. PATRAN is a pre- and post-processor which is commonly used with a variety of finite element programs such as MCS/NASTRAN. The program creates a sufficiently dense mesh at the delamination crack tips to support a mixed-mode fracture mechanics analysis. The program creates a coarse mesh in those regions where the gradients in the stress field are low (away from the delamination regions). A transition mesh is defined between these regions. This program is capable of generating a mesh for an arbitrarily oriented matrix crack. This program significantly reduces the modeling time required to generate these finite element meshes, thus providing a realistic tool with which to investigate the tension torsion problem.

  9. Influence of Torsional Excitation on Dynamic Responses of Rotors with a Breathing Slant Crack

    Science.gov (United States)

    Lu, Zhiwen; Hua, Chunrong; Dong, Dawei; Yan, Bing; Fan, Kang

    2017-05-01

    Focusing on a rotor-bearing system with a breathing slant crack in the power transmission machine, influence of torsional excitations on the coupled nonlinear responses of the system is studied in this work. The slant crack element stiffness matrix is derived based on energy principal and the crack breathing phenomenon is simulated by the Crack Closure Line Position (CCLP) model; and the time-varying coupled dynamic equation of a rotor with a slant breathing crack considering the eccentricity of static unbalance is established using the finite element method and is solved by the NEWMARK method; then the influences of static torque and periodic torsional excitations on rotor dynamic responses in transverse and torsional directions are discussed. Results show that with the increment of static torque, cracks will become open gradually and the nonlinearity degree of rotors will increase firstly and then decrease. For periodic torsional excitation, the torsional excitation frequency and its rotating frequency combination can be found in transverse vibration response, and the larger is the amplitude of excitation, the larger are the combinational frequency components. Then a crack monitoring method for power transmission machines can be suggested by monitoring the coupled response characteristics and their variation from transverse responses of rotors before and after the loads change.

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

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    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.

  11. Selective Formation of Zigzag Edges in Graphene Cracks.

    Science.gov (United States)

    Fujihara, Miho; Inoue, Ryosuke; Kurita, Rei; Taniuchi, Toshiyuki; Motoyui, Yoshihito; Shin, Shik; Komori, Fumio; Maniwa, Yutaka; Shinohara, Hisanori; Miyata, Yasumitsu

    2015-09-22

    We report the thermally induced unconventional cracking of graphene to generate zigzag edges. This crystallography-selective cracking was observed for as-grown graphene films immediately following the cooling process subsequent to chemical vapor deposition (CVD) on Cu foil. Results from Raman spectroscopy show that the crack-derived edges have smoother zigzag edges than the chemically formed grain edges of CVD graphene. Using these cracks as nanogaps, we were also able to demonstrate the carrier tuning of graphene through the electric field effect. Statistical analysis of visual observations indicated that the crack formation results from uniaxial tension imparted by the Cu substrates together with the stress concentration at notches in the polycrystalline graphene films. On the basis of simulation results using a simplified thermal shrinkage model, we propose that the cooling-induced tension is derived from the transient lattice expansion of narrow Cu grains imparted by the thermal shrinkage of adjacent Cu grains.

  12. Dynamic fracture mechanics analysis for an edge delamination crack

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    Rizzi, Stephen A.; Doyle, James F.

    1994-01-01

    A global/local analysis is applied to the problem of a panel with an edge delamination crack subject to an impulse loading to ascertain the dynamic J integral. The approach uses the spectral element method to obtain the global dynamic response and local resultants to obtain the J integral. The variation of J integral along the crack front is shown. The crack behavior is mixed mode (Mode 2 and Mode 3), but is dominated by the Mode 2 behavior.

  13. Nonlinear vibration of edge cracked functionally graded Timoshenko beams

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    Kitipornchai, S.; Ke, L. L.; Yang, J.; Xiang, Y.

    2009-07-01

    Nonlinear vibration of beams made of functionally graded materials (FGMs) containing an open edge crack is studied in this paper based on Timoshenko beam theory and von Kármán geometric nonlinearity. The cracked section is modeled by a massless elastic rotational spring. It is assumed that material properties follow exponential distributions through beam thickness. The Ritz method is employed to derive the governing eigenvalue equation which is then solved by a direct iterative method to obtain the nonlinear vibration frequencies of cracked FGM beams with different end supports. A detailed parametric study is conducted to study the influences of crack depth, crack location, material property gradient, slenderness ratio, and end supports on the nonlinear free vibration characteristics of cracked FGM beams. It is found that unlike isotropic homogeneous beams, both intact and cracked FGM beams show different vibration behavior at positive and negative amplitudes due to the presence of bending-extension coupling in FGM beams.

  14. Understanding the edge crack phenomenon in ceramic laminates

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    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

  15. Damage, crack growth and fracture characteristics of nuclear grade graphite using the Double Torsion technique

    Energy Technology Data Exchange (ETDEWEB)

    Becker, T.H., E-mail: thorsten.becker@uct.ac.za [University of Cape Town, The University of Manchester, Materials Performance Centre, School of Materials, Manchester M13 9PL (United Kingdom); Marrow, T.J., E-mail: james.marrow@materials.ox.ac.uk [Department of Materials, University of Oxford (United Kingdom); Tait, R.B., E-mail: robert.tait@uct.ac.za [Department of Mechanical Engineering, University of Cape Town, Cape Town (South Africa)

    2011-07-01

    The crack initiation and propagation characteristics of two medium grained polygranular graphites, nuclear block graphite (NBG10) and Gilsocarbon (GCMB grade) graphite, have been studied using the Double Torsion (DT) technique. The DT technique allows stable crack propagation and easy crack tip observation of such brittle materials. The linear elastic fracture mechanics (LEFM) methodology of the DT technique was adapted for elastic-plastic fracture mechanics (EPFM) in conjunction with a methodology for directly calculating the J-integral from in-plane displacement fields (JMAN) to account for the non-linearity of graphite deformation. The full field surface displacement measurement techniques of electronic speckle pattern interferometry (ESPI) and digital image correlation (DIC) were used to observe and measure crack initiation and propagation. Significant micro-cracking in the fracture process zone (FPZ) was observed as well as crack bridging in the wake of the crack tip. The R-curve behaviour was measured to determine the critical J-integral for crack propagation in both materials. Micro-cracks tended to nucleate at pores, causing deflection of the crack path. Rising R-curve behaviour was observed, which is attributed to the formation of the FPZ, while crack bridging and distributed micro-cracks are responsible for the increase in fracture resistance. Each contributes around 50% of the irreversible energy dissipation in both graphites.

  16. Ductile crack growth simulation and effects of crack growth on single-edge notched bend specimens

    Science.gov (United States)

    Shimada, Keito; Komiya, Shinji; Iwashita, Tsutomu

    2017-10-01

    This paper describes the testing of single-edge notched bend (SENB) specimens, which are used for fracture toughness tests, and the ductile crack initiation from the notch tip of the specimens. All of the specimens exhibited brittle fracture with relatively large ductile crack growth (from 1.0 to 4.8 mm). The paper also shows the ductile crack growth simulation using a damage model (Bonora model) for finite element analysis (FEA). FEA reproduced ductile crack growth observed in the SENB tests and the analysis results showed the effects of the ductile crack growth rate on stress distribution around the crack tips. In addition, the value of the Weibull stress was calculated in the paper, and the Weibull stress slightly decreased if the model had a higher ductile crack growth rate as compared with the model that had a lower ductile crack growth rate.

  17. Surface strain gradient effects in the torsion of a circular bar with radial cracks

    Science.gov (United States)

    Xu, Yang; Wang, Xu

    2016-12-01

    We study the contribution of surface strain gradient elasticity to the Saint-Venant torsion problem of a circular cylinder containing a radial crack. The surface strain gradient elasticity is incorporated by using an enriched version of the continuum-based surface/interface model of Gurtin and Murdoch. By using Green's function method, the original boundary value problem is reduced to a Cauchy singular integro-differential equation which can be numerically solved by using the Gauss-Chebyshev integration formula, the Chebyshev polynomials and the collocation method. Due to the presence of surface strain gradient elasticity on the crack faces, the stresses are bounded at the crack tips. The torsion problem of a circular cylinder containing two symmetric collinear radial cracks of equal length with surface strain gradient elasticity is also solved by using a similar method. Numerical results indicate that the surface strain gradient effect exerts a significant influence on the torsional rigidity and the jump in warping function. In particular, the jump in warping function forms a cusp shape with zero enclosed angle at the crack tips.

  18. Ultrasonic Monitoring of Ply Crack and Delamination Formation in Composite Tube Under Torsion Load

    Science.gov (United States)

    Johnston, P. H.; Wright, C. W.; Zalameda, J. N.; Seebo, J. P.

    2010-01-01

    As a simple model of a rotor spar, a circular graphite-epoxy composite laminate cylinder was subjected to cyclic torsional load. The test section of the cylindrical specimen varied from four to six plies of plus or minus 45 degree fibers, due to intentional ply overlaps and gaps. A layer of 13-micrometer Teflon film was inserted between plies at three locations to serve as delamination initiators. A commercial X-Y scanner was mounted to the load frame to enable ultrasonic inspection without removing the specimen. A focused immersion probe was mounted in a captive water column with a rugged Nitrile membrane tip, which was coupled to the cylinder using a mist of soapy water. The transducer was aligned normal to the cylinder surface using the X-axis. Scanning was performed along the length of the specimen with the Y-axis and the specimen was incrementally rotated by the torsion head of the load frame. After 350k cycles of torsion, several linear 45 degree diagonal indications appeared as 5-40% attenuation of the back wall echo, with no apparent echoes from the interior of the composite, suggesting through-ply cracks in the innermost ply. Crack indications grew and new cracks appeared as torsion cycling continued. Internal reflections from delaminations associated with the growing ply cracks appeared after 500k cycles. Three areas of extensive multi-layer delaminations appeared after 1150k cycles. Failure of the specimen occurred at 1600k cycles. The observed progressive damage was not associated with the Teflon inclusions. Concurrent thermographic measurements provided lower resolution confirmation of the damage observed.

  19. Analytical approach to calculate bending, longitudinal and torsional local stiffness of an asymmetric circumferential crack with contact condition

    Science.gov (United States)

    Sharafi, Mojtaba Meidan; Nikravesh, Majid Yadavar; Safarpour, Pedram

    2017-09-01

    In this paper, bending, longitudinal and torsional stiffness of an eccentric circumferential crack is investigated with taking into account contact condition on the crack surfaces based on fracture mechanics. Although several researches have analyzed stress intensity factors of symmetric circumferential crack, the stiffness of an asymmetric circumferential crack in different directions (along and perpendicular to eccentricity) regarding contact condition has not been studied by an analytical method until now. In this paper we aim to describe behavior of eccentric circumferential crack under axial loading and establish a relation between axial force and the resulting displacement vector. The twisting angle of asymmetric circumferential crack due to torsional loading is also calculated and compared to twisting angle of a symmetric crack. In order to simulate the local bending stiffness in the contact condition, nonlinear governing equations of bending stiffness associated to cracked beam section is developed by dividing it to strip elements and utilizing stiffness equations related to noncontact condition. It is validated by 3D finite element (FE) nonlinear model. Results show a significant compatibility between presented analytical and 3D FE methods. Moreover results of simulations show that without taking into account contact condition, axial, torsional and bending stiffness of symmetric and asymmetric circumferential crack are equal and radius of un-cracked area is the only influential factor.

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

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    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.

  1. An analytical and experimental investigation of edge delamination in laminates subjected to tension, bending, and torsion

    Science.gov (United States)

    Chan, Wen S.

    1989-01-01

    An integrated two-dimensional finite element was developed to calculate interlaminar stresses and strain energy release rates for the study of delamination in composite laminates subjected to uniaxial tension, bending, and torsion loads. Addressed are the formulation, implementation, and verification of the model. Parametric studies were conducted on the effect of Poisson's ratio mismatch between plies and the stacking sequence on interlaminar stress, and on the effect of delamination opening height and delamination length, due to bending, on strain energy release rate for various laminates. A comparison of strain energy release rates in all-graphite and graphite/glass hybrid laminates is included. The preliminary results of laminates subjected to torsion are also included. Fatigue tension tests were conducted on Mode 1 and mixed mode edge-delamination coupons to establish the relationship between fatigue load vs. onset of delamination cycle. The effect on the fatigue delamination onset of different frequencies (1 and 5 Hz) was investigated for glass, graphite,and their hybrid laminates. Although a 20 percent increase in the static onset-of-delamination strength and a 10 percent increase in ultimate strength resulted from hybridizing the all-graphite laminate with a 90 deg glass ply, the fatigue onset is lower in the hybrid laminate than in the all-graphite laminate.

  2. Averaged strain energy density-based synthesis of crack initiation life in notched steel bars under torsional fatigue

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    Filippo Berto

    2016-10-01

    Full Text Available The torsional fatigue behaviour of circumferentially notched specimens made of austenitic stainless steel, SUS316L, and carbon steel, SGV410, characterized by different notch root radii has been recently investigated by Tanaka. In that contribution, it was observed that the total fatigue life of the austenitic stainless steel increases with increasing stress concentration factor for a given applied nominal shear stress amplitude. By using the electrical potential drop method, Tanaka observed that the crack nucleation life was reduced with increasing stress concentration, on the other hand the crack propagation life increased. The experimental fatigue results, originally expressed in terms of nominal shear stress amplitude, have been reanalysed by means of the local strain energy density (SED averaged over a control volume having radius R0 surrounding the notch tip. To exclude all extrinsic effects acting during the fatigue crack propagation phase, such as sliding contact and/or friction between fracture surfaces, crack initiation life has been considered in the present work. In the original paper, initiation life was defined in correspondence of a 0.1÷0.4-mm-deep crack. The control radius R0 for fatigue strength assessment of notched components, thought of as a material property, has been estimated by imposing the constancy of the averaged SED for both smooth and cracked specimens at NA = 2 million loading cycles

  3. The Effect of Geometric Configurations on the Elastic Behavior of an Edge-Cracked Bonded Strip

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    Xin Lan

    2017-01-01

    Full Text Available Interface cracks often initiate around the bonding free-edge corner due to the high-stress concentration. In this research, the elastic behavior of an edge-cracked dissimilar bonded strip subjected to remote tensile load is investigated using the proportional crack tip opening displacement method based on FE analysis for arbitrary material combinations. The stress intensity factor, energy release rate, and mode mixity are computed and compared systematically with varying geometrical configurations and material combinations. Then, the combined effects of the relative height of the bonded component and material combination are discussed for the typical engineering materials.

  4. Crack edge collocation for the direct computation of stress intensity factors using the displacement discontinuity method

    CSIR Research Space (South Africa)

    Napier, JAL

    2002-09-01

    Full Text Available intensity factors to be solved directly at the crack edges. This is achieved by employing an enhanced edge collocation procedure. The limiting interpretation of the governing integral equations is discussed and two simple examples are presented to illustrate...

  5. Nonlinear vibration of edged cracked FGM beams using differential quadrature method

    Science.gov (United States)

    Ke, LiaoLiang; Wang, YueSheng; Yang, Jie; Kitipornchai, Sritawat; Alam, Firoz

    2012-11-01

    This paper investigated the nonlinear vibration of functionally graded beams containing an open edge crack based on Timoshenko beam theory. The cracked section is modeled by a massless elastic rotational spring. It is assumed that material properties follow exponential distributions through the beam thickness. The differential quadrature (DQ) method is employed to discretize the nonlinear governing equations which are then solved by a direct iterative method to obtain the nonlinear vibration frequencies of beams with different boundary conditions. The effects of the material gradient, crack depth and boundary conditions on nonlinear free vibration characteristics of the cracked FGM beams are studied in detail.

  6. Developing Fatigue Pre-crack Procedure to Evaluate Fracture Toughness of Pipeline Steels Using Spiral Notch Torsion Test

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jy-An John [ORNL; Tan, Ting [ORNL; Jiang, Hao [ORNL; Zhang, Wei [ORNL; Feng, Zhili [ORNL

    2012-10-01

    The spiral notch torsion test (SNTT) has been utilized to investigate the crack growth behavior of X52 steel base and welded materials used for hydrogen infrastructures. The X52 steel materials are received from a welded pipe using friction stir welding techniques. Finite element models were established to study the crack growth behavior of steel SNTT steel samples, which were assumed to be isotropic material. A series SNTT models were set up to cover various crack penetration cases, of which the ratios between crack depth to diameter (a/D ratio) ranging from 0.10 to 0.45. The evolution of compliance and energy release rates in the SNTT method have been investigated with different cases, including different geometries and materials. Indices of characteristic compliance and energy release rates have been proposed. Good agreement has been achieved between predictions from different cases in the same trend. These work shed lights on a successful protocol for SNTT application in wide range of structural materials. The further effort needed for compliance function development is to extend the current developed compliance function to the deep crack penetration arena, in the range of 0.55 to 0.85 to effectively determine fracture toughness for extremely tough materials.

  7. Propagation of a Dugdale crack at the edge of a half plane

    Science.gov (United States)

    Ferdjani, Hicheme; Abdelmoula, Radhi

    2018-01-01

    This work deals with the propagation of a Dugdale crack at the edge of a half plane. The corresponding singular integral equation is solved semi-analytically. The expressions of the stress intensity factor and of the crack gap are deduced. A propagation criterion deduced from the revisited Griffith theory (Ferdjani and Marigo in Eur J Mech A Solids 53:1-9, 2015) is applied. The length of the process zone is calculated and compared with the literature results. The presented results show the evolution of the applied load with the crack length for different values of the ratio of the critical length of the Dugdale model to the initial crack length. The shape of the crack gap is also presented. Finally, a comparison between the Griffith and Dugdale models is performed.

  8. Assessing edge cracking resistance in AHSS automotive parts by the Essential Work of Fracture methodology

    Science.gov (United States)

    Frómeta, D.; Tedesco, M.; Calvo, J.; Lara, A.; Molas, S.; Casellas, D.

    2017-09-01

    Lightweight designs and demanding safety requirements in automotive industry are increasingly promoting the use of Advanced High Strength Steel (AHSS) sheets. Such steels present higher strength (above 800 MPa) but lower ductility than conventional steels. Their great properties allow the reduction of the thickness of automobile structural components without compromising the safety, but also introduce new challenges to parts manufacturers. The fabrication of most cold formed components starts from shear cut blanks and, due to the lower ductility of AHSS, edge cracking problems can appear during forming operations, forcing the stop of the production and slowing down the industrial process. Forming Limit Diagrams (FLD) and FEM simulations are very useful tools to predict fracture problems in zones with high localized strain, but they are not able to predict edge cracking. It has been observed that the fracture toughness, measured through the Essential Work of Fracture (EWF) methodology, is a good indicator of the stretch flangeability in AHSS and can help to foresee this type of fractures. In this work, a serial production automotive component has been studied. The component showed cracks in some flanged edges when using a dual phase steel. It is shown that the conventional approach to explain formability, based on tensile tests and FLD, fails in the prediction of edge cracking. A new approach, based on fracture mechanics, help to solve the problem by selecting steel grades with higher fracture toughness, measured by means of EWF. Results confirmed that fracture toughness, in terms of EWF, can be readily used as a material parameter to rationalize cracking related problems and select AHSS with improved edge cracking resistance.

  9. Geometrically Nonlinear Static Analysis of Edge Cracked Timoshenko Beams Composed of Functionally Graded Material

    Directory of Open Access Journals (Sweden)

    Şeref Doğuşcan Akbaş

    2013-01-01

    Full Text Available Geometrically nonlinear static analysis of edge cracked cantilever Timoshenko beams composed of functionally graded material (FGM subjected to a nonfollower transversal point load at the free end of the beam is studied with large displacements and large rotations. Material properties of the beam change in the height direction according to exponential distributions. The cracked beam is modeled as an assembly of two subbeams connected through a massless elastic rotational spring. In the study, the finite element of the beam is constructed by using the total Lagrangian Timoshenko beam element approximation. The nonlinear problem is solved by using incremental displacement-based finite element method in conjunction with Newton-Raphson iteration method. The convergence study is performed for various numbers of finite elements. In the study, the effects of the location of crack, the depth of the crack, and various material distributions on the nonlinear static response of the FGM beam are investigated in detail. Also, the difference between the geometrically linear and nonlinear analysis of edge cracked FGM beam is investigated in detail.

  10. Edge waves in a fluid under ice cover with a crack

    Science.gov (United States)

    Tkacheva, L. A.

    2017-04-01

    An analytical solution of the problem on oscillations of ice cover with a rectilinear crack under the action of a local time-periodic load has been obtained. For plates with equal thicknesses, the solution has been obtained in explicit form. It has been found that the contact of plates with different thicknesses is accompanied by the appearance of directions of predominant wave propagation at an angle to the crack in the far field. In the case of a contact of identical plates with free edges and free overlapping, the waveguide mode is excited. The waveguide mode manifests itself especially strongly when the plate has contact with a hard vertical wall.

  11. Edge cracks in nickel and aluminium single crystals: A molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Chandra, Sagar, E-mail: sagarc@barc.gov.in; Chavan, V. M.; Patel, R. J. [Refueling Technology Division, Bhabha Atomic Research Centre, Mumbai-400085 (India); Samal, M. K. [Reactor Safety Division, Bhabha Atomic Research Centre, Mumbai-400085 (India)

    2016-05-23

    A molecular dynamics study of edge cracks in Ni and Al single crystals under mode-I loading conditions is presented. Simulations are performed using embedded-atom method potentials for Ni and Al at a temperature of 0.5 K. The results reveal that Ni and Al show different fracture mechanisms. Overall failure behavior of Ni is brittle, while fracture in Al proceeds through void nucleation and coalescence with a zig-zag pattern of crack growth. The qualitative nature of results is discussed in the context of vacancy-formation energies and surface energies of the two FCC metals.

  12. Wave propagation analysis of edge cracked circular beams under impact force.

    Directory of Open Access Journals (Sweden)

    Şeref Doğuşcan Akbaş

    Full Text Available This paper presents responses of an edge circular cantilever beam under the effect of an impact force. The beam is excited by a transverse triangular force impulse modulated by a harmonic motion. The Kelvin-Voigt model for the material of the beam is used. The cracked beam is modelled as an assembly of two sub-beams connected through a massless elastic rotational spring. The considered problem is investigated within the Bernoulli-Euler beam theory by using energy based finite element method. The system of equations of motion is derived by using Lagrange's equations. The obtained system of linear differential equations is reduced to a linear algebraic equation system and solved in the time domain by using Newmark average acceleration method. In the study, the effects of the location of crack, the depth of the crack, on the characteristics of the reflected waves are investigated in detail. Also, the positions of the cracks are calculated by using reflected waves.

  13. J and CTOD estimation equations for shallow cracks in single edge notch bend specimens

    Science.gov (United States)

    Kirk, Mark T.; Dodds, Robert H., Jr.

    1993-07-01

    Results from 2D plane strain finite element analyses are used to develop J and CTOD estimation strategies appropriate for application to both shallow and deep crack single edge notch bend (Se(B)) specimens. Ramberg-Osgood strain hardening exponents (n) between 4 and 50 are employed to model crack depth to specimen width ratios. The estimation formulas divide J and CTOD into small-scale-yielding (SSY) and large-scale-yielding (LSY) components. For each case, the SSY component is determined by the linear elastic stress intensity factor. The formulas differ in evaluation of the LSY component. A formula is derived within 9 percent of which the finite element results for all investigated conditions fall.

  14. Fracture analysis of transverse crack-tip and free-edge delamination in laminated composites

    Science.gov (United States)

    Armanios, Erian A.; Sriram, P.; Badir, Ashraf M.

    1991-01-01

    A shear deformation model including hygrothermal effects is developed for the analysis of local delaminations originating from transverse cracks in 90-deg plies located in and around the laminate midplane. A sublaminate approach is used and the model is applied to (+/- 25/90n)s T300/934 graphite/epoxy laminates for n values between 0.5 and 8, along with previously developed edge-delamination shear-deformation models. Critical loads and delamination modes are identified and compared with experimental results. Hygrothermal effects are included in all the models to make the comparisons realistic.

  15. Creep analysis and torsional vibration analysis of cable-stayed bridges with two edge composite girders; Nishuketa gosei kozo shachokyo no creep kaiseki to nejiri shindo kaiseki

    Energy Technology Data Exchange (ETDEWEB)

    Hoshino, M. [Nihon University, Tokyo (Japan). College of Science and Technology

    1996-07-21

    This paper describes the creep analysis and torsional vibration analysis of cable-stayed bridges with two edge composite girders. The girder is composed of the concrete slab and the steel girder. I-girders are placed at both edges of the profile. Such a type of bridge was investigated. As the stress migrates by the creep of concrete slab, it is necessary to evaluate the influence of this creep precisely in designing. In the analysis, the composite girder was expressed not by the single member, but by the binary member consisting of concrete member and steel member. Two methods were employed, i.e., method A in which both members are connected by the rigid body beam and method B in which the profile of concrete is converted into the profile of steel. The method A provided better accuracy, but the method B was often sufficient. Torsional rigidity of the open profile structure was much smaller than that of the box profile. As the torsional natural frequency was low, proper torsional vibration analysis was indispensable especially from the viewpoint of wind resistance. Two methods were employed, which utilize the vibration analysis method for general space frame structures. Results of both methods were agreed mutually, but the second method provided better calculation efficiency. 10 refs., 9 figs., 6 tabs.

  16. Flexural edge waves generated by steady-state propagation of a loaded rectilinear crack in an elastically supported thin plate.

    Science.gov (United States)

    Nobili, Andrea; Radi, Enrico; Lanzoni, Luca

    2017-08-01

    The problem of a rectilinear crack propagating at constant speed in an elastically supported thin plate and acted upon by an equally moving load is considered. The full-field solution is obtained and the spotlight is set on flexural edge wave generation. Below the critical speed for the appearance of travelling waves, a threshold speed is met which marks the transformation of decaying edge waves into edge waves propagating along the crack and dying away from it. Yet, besides these, and for any propagation speed, a pair of localized edge waves, which rapidly decay behind the crack tip, is also shown to exist. These waves are characterized by a novel dispersion relation and fade off from the crack line in an oscillatory manner, whence they play an important role in the far field behaviour. Dynamic stress intensity factors are obtained and, for speed close to the critical speed, they show a resonant behaviour which expresses the most efficient way to channel external work into the crack. Indeed, this behaviour is justified through energy considerations regarding the work of the applied load and the energy release rate. Results might be useful in a wide array of applications, ranging from fracturing and machining to acoustic emission and defect detection.

  17. Flexural edge waves generated by steady-state propagation of a loaded rectilinear crack in an elastically supported thin plate

    Science.gov (United States)

    Nobili, Andrea; Radi, Enrico; Lanzoni, Luca

    2017-08-01

    The problem of a rectilinear crack propagating at constant speed in an elastically supported thin plate and acted upon by an equally moving load is considered. The full-field solution is obtained and the spotlight is set on flexural edge wave generation. Below the critical speed for the appearance of travelling waves, a threshold speed is met which marks the transformation of decaying edge waves into edge waves propagating along the crack and dying away from it. Yet, besides these, and for any propagation speed, a pair of localized edge waves, which rapidly decay behind the crack tip, is also shown to exist. These waves are characterized by a novel dispersion relation and fade off from the crack line in an oscillatory manner, whence they play an important role in the far field behaviour. Dynamic stress intensity factors are obtained and, for speed close to the critical speed, they show a resonant behaviour which expresses the most efficient way to channel external work into the crack. Indeed, this behaviour is justified through energy considerations regarding the work of the applied load and the energy release rate. Results might be useful in a wide array of applications, ranging from fracturing and machining to acoustic emission and defect detection.

  18. Design and conceptualization of a cutting tool to investigate the influence of the shear cutting process on edge crack sensitivity

    Science.gov (United States)

    Feistle, M.; Krinninger, M.; Paetzold, I.; Stahl, J.; Golle, R.; Volk, W.

    2017-09-01

    High-strength and ultra-high-strength sheet materials are becoming increasingly integrated in the automotive and commercial vehicle industries. Consequently, their edge crack sensitivity requires particular attention, starting with the component design. In addition to the only standardized testing method, the hole expansion test according to ISO 16630, various testing procedures characterize the occurrence of edge cracks. However, neither the ISO standard nor any other published experimental setup focuses on the design of the cutting tool used to generate the cutting surfaces, which is fundamental in order to produce conclusive results with low variance. This paper presents the constructive design and choice of materials with regard to a cutting tool for the Edge-Fracture-Tensile-Test as well as a punching tool for the hole expansion test. The modular concept allows an evaluation of the influence of the following parameters on the edge crack sensitivity: single-stage or multi-stage shear cutting process, open or closed cutting line, die clearance, cutting edge geometry.

  19. Structures and properties of molecular torsion balances to decipher the nature of substituent effects on the aromatic edge-to-face interaction.

    Science.gov (United States)

    Gardarsson, Haraldur; Schweizer, W Bernd; Trapp, Nils; Diederich, François

    2014-04-14

    Various recent computational studies initiated this systematic re-investigation of substituent effects on aromatic edge-to-face interactions. Five series of Tröger base derived molecular torsion balances (MTBs), initially introduced by Wilcox and co-workers, showing an aromatic edge-to-face interaction in the folded, but not in the unfolded form, were synthesized. A fluorine atom or a trifluoromethyl group was introduced onto the edge ring in ortho-, meta-, and para-positions to the C-H group interacting with the face component. The substituents on the face component were varied from electron-donating to electron-withdrawing. Extensive X-ray crystallographic data allowed for a discussion on the conformational behavior of the torsional balances in the solid state. While most systems adopt the folded conformation, some were found to form supramolecular intercalative dimers, lacking the intramolecular edge-to-face interaction, which is compensated by the gain of aromatic π-stacking interactions between four aryl rings of the two molecular components. This dimerization does not take place in solution. The folding free enthalpy ΔG(fold) of all torsion balances was determined by (1)H NMR measurements by using 10 mM solutions of samples in CDCl3 and C6D6. Only the ΔG(fold) values of balances bearing an edge-ring substituent in ortho-position to the interacting C-H show a steep linear correlation with the Hammett parameter (σ(meta)) of the face-component substituent. Thermodynamic analysis using van't Hoff plots revealed that the interaction is enthalpy-driven. The ΔG(fold) values of the balances, in addition to partial charge calculations, suggest that increasing the polarization of the interacting C-H group makes a favorable contribution to the edge-to-face interaction. The largest contribution, however, seems to originate from local direct interactions between the substituent in ortho-position to the edge-ring C-H and the substituted face ring. © 2014 WILEY

  20. Crack

    Science.gov (United States)

    ... make people edgy and irritable. They may have panic attacks and full-blown psychosis where they hear ... die. It's extremely hard to kick a crack addiction. Even after people have been off the drug ...

  1. Dynamical torsion and torsion potential

    OpenAIRE

    Xie, Hong-Jun; Shirafuji, Takeshi

    1996-01-01

    We introduce a generalized tetrad which plays the role of a potential for torsion and makes torsion dynamic. Starting from the Einstein-Cartan action with torsion, we get two field equations, the Einstein equation and the torsion field equation by using the metric tensor and the torsion potential as independent variables; in the former equation the torsion potential plays the role of a matter field. We also discuss properties of local linear transformations of the torsion potential and give a...

  2. An analytical method for free vibration analysis of functionally graded beams with edge cracks

    Science.gov (United States)

    Wei, Dong; Liu, Yinghua; Xiang, Zhihai

    2012-03-01

    In this paper, an analytical method is proposed for solving the free vibration of cracked functionally graded material (FGM) beams with axial loading, rotary inertia and shear deformation. The governing differential equations of motion for an FGM beam are established and the corresponding solutions are found first. The discontinuity of rotation caused by the cracks is simulated by means of the rotational spring model. Based on the transfer matrix method, then the recurrence formula is developed to get the eigenvalue equations of free vibration of FGM beams. The main advantage of the proposed method is that the eigenvalue equation for vibrating beams with an arbitrary number of cracks can be conveniently determined from a third-order determinant. Due to the decrease in the determinant order as compared with previous methods, the developed method is simpler and more convenient to analytically solve the free vibration problem of cracked FGM beams. Moreover, free vibration analyses of the Euler-Bernoulli and Timoshenko beams with any number of cracks can be conducted using the unified procedure based on the developed method. These advantages of the proposed procedure would be more remarkable as the increase of the number of cracks. A comprehensive analysis is conducted to investigate the influences of the location and total number of cracks, material properties, axial load, inertia and end supports on the natural frequencies and vibration mode shapes of FGM beams. The present work may be useful for the design and control of damaged structures.

  3. Eddy current testing for blade edge micro cracks of aircraft engine

    Science.gov (United States)

    Zhang, Wei-min; Xu, Min-dong; Gao, Xuan-yi; Jin, Xin; Qin, Feng

    2017-10-01

    Based on the problems of low detection efficiency in the micro cracks detection of aircraft engine blades, a differential excitation eddy current testing system was designed and developed. The function and the working principle of the system were described, the problems which contained the manufacture method of simulated cracks, signal generating, signal processing and the signal display method were described. The detection test was carried out by taking a certain model aircraft engine blade with simulated cracks as a tested specimen. The test data was processed by digital low-pass filter in the computer and the crack signals of time domain display and Lissajous figure display were acquired. By comparing the test results, it is verified that Lissajous figure display shows better performance compared to time domain display when the crack angle is small. The test results show that the eddy current testing system designed in this paper is feasible to detect the micro cracks on the aeroengine blade and can effectively improve the detection efficiency of micro cracks in the practical detection work.

  4. Stress and strain field singularities, micro-cracks, and their role in failure initiation at the composite laminate free-edge

    Science.gov (United States)

    Dustin, Joshua S.

    A state-of-the-art multi-scale analysis was performed to predict failure initiation at the free-edge of an angle-ply laminate using the Strain Invariant Failure Theory (SIFT), and multiple improvements to this analysis methodology were proposed and implemented. Application of this analysis and theory led to the conclusion that point-wise failure criteria which ignore the singular stress and strain fields from a homogenized analysis and the presence of free-edge damage in the form of micro-cracking, may do so at the expense of failure prediction capability. The main contributions of this work then are made in the study of the laminate free-edge singularity and in the effects of micro-cracking at the composite laminate free-edge. Study of both classical elasticity and finite element solutions of the laminate free-edge stress field based upon the assumption of homogenized lamina properties reveal that the order of the free-edge singularity is sufficiently small such that the domain of dominance of this term away from the laminate free-edge is much smaller than the relevant dimensions of the microstructure. In comparison to a crack-tip field, these free-edge singularities generate stress and strain fields which are half as intense as those at the crack-tip, leading to the conclusion that existing flaws at the free-edge in the form of micro-cracks would be more prone to the initiation of free-edge failure than the existence of a singularity in the free-edge elasticity solutions. A methodical experiment was performed on a family of [±25°/90°] s laminates made of IM7/8552 carbon/epoxy composite, to both characterize micro-cracks present at the laminate free-edge and to study their behavior under the application of a uniform extensional load. The majority of these micro-cracks were of length on the order of a few fiber diameters, though larger micro-cracks as long as 100 fiber diameters were observed in thicker laminates. A strong correlation between the application of

  5. Experimental and Computational Studies on the Scattering of an Edge-Guided Wave by a Hidden Crack on a Racecourse Shaped Hole

    Directory of Open Access Journals (Sweden)

    Benjamin Steven Vien

    2017-07-01

    Full Text Available Reliable and quantitative non-destructive evaluation for small fatigue cracks, in particular those in hard-to-inspect locations, is a challenging problem. Guided waves are advantageous for structural health monitoring due to their slow geometrical decay of amplitude with propagating distance, which is ideal for rapid wide-area inspection. This paper presents a 3D laser vibrometry experimental and finite element analysis of the interaction between an edge-guided wave and a small through-thickness hidden edge crack on a racecourse shaped hole that occurs, in practice, as a fuel vent hole. A piezoelectric transducer is bonded on the straight edge of the hole to generate the incident wave. The excitation signal consists of a 5.5 cycle Hann-windowed tone burst of centre frequency 220 kHz, which is below the cut-off frequency for the first order Lamb wave modes (SH1. Two-dimensional fast Fourier transformation (2D FFT is applied to the incident and scattered wave field along radial lines emanating from the crack mouth, so as to identify the wave modes and determine their angular variation and amplitude. It is shown experimentally and computationally that mid-plane symmetric edge waves can travel around the hole’s edge to detect a hidden crack. Furthermore, the scattered wave field due to a small crack length, a, (compared to the wavelength λ of the incident wave is shown to be equivalent to a point source consisting of a particular combination of body-force doublets. It is found that the amplitude of the scattered field increases quadratically as a function of a/λ, whereas the scattered wave pattern is independent of crack length for small cracks a << λ. This study of the forward scattering problem from a known crack size provides a useful guide for the inverse problem of hidden crack detection and sizing.

  6. Elastic and Plastic Analysis of a Single Edge Cracked Tension Specimen with Clamped Ends

    National Research Council Canada - National Science Library

    Mercier, Gerald

    1998-01-01

    ... (compliance and elastic stress intensity) and the plastic response (J-plastic, Eta(pl)) of the clamped end model were determined at ratios of height-to-width of 6, 8 and 10 and crack length to width ratios between 0.1 and 0.6...

  7. Hot Rolling Scrap Reduction through Edge Cracking and Surface Defects Control

    Energy Technology Data Exchange (ETDEWEB)

    Beaudoin, Armand [Univ. of Illinois, Urbana-Champaign, IL (United States)

    2016-05-29

    The design of future aircraft must address the combined demands for fuel efficiency, reduced emissions and lower operating costs. One contribution to these goals is weight savings through the development of new alloys and design techniques for airframe structures. This research contributes to the light-weighting through fabrication of monolithic components from advanced aluminum alloys by making a link between alloy processing history and in-service performance. Specifically, this research demonstrates the link between growing cracks with features of the alloy microstructure that follow from thermo-mechanical processing. This is achieved through a computer model of crack deviation. The model is validated against experimental data from production scale aluminum alloy plate, and demonstration of the effect of changes in processing history on crack growth is made. The model is cast in the open-source finite element code WARP3D, which is freely downloadable and well documented. This project provides benefit along several avenues. First, the technical contribution of the computer model offers the materials engineer a critical means of providing guidance both upstream, to process tuning to achieve optimal properties, and downstream, to enhance fault tolerance. Beyond the fuel savings and emissions reduction inherent in the light-weighting of aircraft structures, improved fault tolerance addresses demands for longer inspection intervals over baseline, and a lower life cycle cost.

  8. Appendicular Torsion

    Directory of Open Access Journals (Sweden)

    Siddharth Pramod Dubhashi

    2016-01-01

    Full Text Available Torsion of the vermiform appendix is a rare condition detectable only at operation. It can be primary or secondary. This is a case report of 52-year-old female with 180° anti-clockwise rotation of the appendix. Torsion can further leads to strangulation and infarction of the organ. Appendicular torsion could be included in the differential diagnosis of pain in right iliac fossa.

  9. Structural health monitoring method for wind turbine trailing edge: Crack growth detection using Fibre Bragg Grating sensor embedded in composite materials

    DEFF Research Database (Denmark)

    Pereira, Gilmar Ferreira; Mikkelsen, Lars Pilgaard; McGugan, Malcolm

    2015-01-01

    In this article a novel method to assess a crack growing/damage event in composite material using Fibre Bragg Grating (FBG) sensors embedded in a host material and its application into a composite material structure, Wind Turbine Trailing Edge, is presented. A Structure-Material-FBG model...... was developed, which simulates the FBG sensor output response, when embedded in a host material, during a crack growing/damage event. This Structure-Material-FBG model provides a tool to analyse the application of this monitoring technique in other locations/structures, by predicting the sensor output...... adhesive, were instrumented with one array of FBG sensors embedded into the host material, and digital image correlation technique was used to determine the presence of the specific phenomena caused by the crack, and to correlate with the FBG sensor....

  10. Appendicular Torsion

    African Journals Online (AJOL)

    [4] It can be primary or subsequent to other pathological conditions like faecolith, mucocele, carcinoid tumor or ... KEYWORDS: Anti‑clockwise, appendix, primary, secondary, torsion. This is an open access article ... Valenciano‑Fuentes B. Torsion of vermiform appendix: Value of ultrasonographic findings. Eur J Pediatr Surg ...

  11. Testicular Torsion

    Science.gov (United States)

    ... Campbell-Walsh Urology. 10th ed. Philadelphia, Pa.: Saunders Elsevier; 2012. http://www.clinicalkey.com. Accessed Feb. 13, 2015. Somani BK, et al. Testicular torsion. BMJ. 2010;341:c3213. Cubillos J, et al. Familial testicular torsion. Journal of Urology. 2011;185:2469. Hittelman AB. Neonatal ...

  12. TESTICULAR TORSION:

    African Journals Online (AJOL)

    TESTICULAR TORSION: EXPERIENCE IN THE MIDDLE BELT OF NIGERIA. S.A. KURANGA AND G.A. RAHMAN. Department of Surgery, University of l/orin Teaching Hospital, Ilorin, Nigeria. Objective To determine the fate of the testis affected by testicular torsion (TT) in relation to the duration of the symptoms and to.

  13. Effect of Steel Fibers on the Behavior of Over-Reinforced Beams Subjected to Pure Torsion

    National Research Council Canada - National Science Library

    Warnitchai P; Rama Seshu D; Gunneswara Rao T.D

    2010-01-01

    .... Torsion tests on the 15 reinforced steel fiber reinforced concrete beams revealed that, fiber has noticeable effect on the cracking torque and very little effect on the ultimate torsional strength of the member...

  14. Testicular torsion

    DEFF Research Database (Denmark)

    Brasso, K; Andersen, L; Kay, L

    1993-01-01

    Thirty-five patients were examined 6-11 years after operation for torsion of the testis. Loss of testicular tissue was significantly associated with long preoperative duration of symptoms and with low postoperative sperm counts. The sex hormones were normal in the majority of patients but there w......Thirty-five patients were examined 6-11 years after operation for torsion of the testis. Loss of testicular tissue was significantly associated with long preoperative duration of symptoms and with low postoperative sperm counts. The sex hormones were normal in the majority of patients...

  15. Sample geometry and the brittle-ductile behavior of edge cracks in 3D atomistic simulations by molecular dynamics

    Czech Academy of Sciences Publication Activity Database

    Pelikán, Vladimír; Hora, Petr; Machová, Anna; Kolman, Radek; Uhnáková, Alena

    2017-01-01

    Roč. 258 (2017), s. 45-48, č. článku 188189. ISSN 1662-9779 R&D Projects: GA ČR(CZ) GA15-20666S Institutional support: RVO:61388998 Keywords : BCC iron * crack growth * dislocation emission * twins Subject RIV: BM - Solid Matter Physics ; Magnetism https://www.scientific.net/SSP.258.45

  16. Appendicular Torsion

    African Journals Online (AJOL)

    A‑2/103, Shivranjan Towers, Someshwarwadi, Pashan, Pune ‑ 411 008,. Maharashtra, India. E‑mail: spdubhashi@gmail.com. INTRODUCTION. Acute appendicitis presents with pain in right iliac fossa. Torsion of the vermiform appendix, though rare, also presents in a similar fashion, and it is detectable only at operation.[1].

  17. Model Verification and Validation Concepts for a Probabilistic Fracture Assessment Model to Predict Cracking of Knife Edge Seals in the Space Shuttle Main Engine High Pressure Oxidizer

    Science.gov (United States)

    Pai, Shantaram S.; Riha, David S.

    2013-01-01

    Physics-based models are routinely used to predict the performance of engineered systems to make decisions such as when to retire system components, how to extend the life of an aging system, or if a new design will be safe or available. Model verification and validation (V&V) is a process to establish credibility in model predictions. Ideally, carefully controlled validation experiments will be designed and performed to validate models or submodels. In reality, time and cost constraints limit experiments and even model development. This paper describes elements of model V&V during the development and application of a probabilistic fracture assessment model to predict cracking in space shuttle main engine high-pressure oxidizer turbopump knife-edge seals. The objective of this effort was to assess the probability of initiating and growing a crack to a specified failure length in specific flight units for different usage and inspection scenarios. The probabilistic fracture assessment model developed in this investigation combined a series of submodels describing the usage, temperature history, flutter tendencies, tooth stresses and numbers of cycles, fatigue cracking, nondestructive inspection, and finally the probability of failure. The analysis accounted for unit-to-unit variations in temperature, flutter limit state, flutter stress magnitude, and fatigue life properties. The investigation focused on the calculation of relative risk rather than absolute risk between the usage scenarios. Verification predictions were first performed for three units with known usage and cracking histories to establish credibility in the model predictions. Then, numerous predictions were performed for an assortment of operating units that had flown recently or that were projected for future flights. Calculations were performed using two NASA-developed software tools: NESSUS(Registered Trademark) for the probabilistic analysis, and NASGRO(Registered Trademark) for the fracture

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

    Science.gov (United States)

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

    2017-01-01

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

  19. 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)

  20. Growth of 3D edge cracks in mode I and T-stress on the atomistic level

    Czech Academy of Sciences Publication Activity Database

    Machová, Anna; Uhnáková, Alena; Hora, Petr

    2017-01-01

    Roč. 138, October (2017), s. 315-322 ISSN 0927-0256 R&D Projects: GA MŠk(CZ) EF15_003/0000493; GA ČR(CZ) GA15-20666S; GA ČR GA17-12925S Institutional support: RVO:61388998 Keywords : bcc iron * crack growth * dislocation emission * twins * atomic stress Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.292, year: 2016 https://ac.els-cdn.com/S092702561730349X/1-s2.0-S092702561730349X-main.pdf?_tid=8f83cc00-ae60-11e7-b591-00000aacb35f&acdnat=1507711721_680aea8fb4017419ccde42f653cfad33

  1. An evaluation of substituent effects on aromatic edge-to-face interactions and CF-π versus CH-π interactions using an imino torsion balance model.

    Science.gov (United States)

    Jennings, W Brian; O'Connell, Niamh; Malone, John F; Boyd, Derek R

    2013-08-28

    A selection of imines derived from phenyl t-butyl ketones and substituted 2-phenylethylamines or phenylalanine exhibit slow rotation around the aryl–imino bond at ambient temperature, resulting in a large non-equivalence of the ortho hydrogens in the 1H NMR spectra. This facilitates assessment of aryl substituent effects on the face tilted-T CH–π interaction between a phenyl ring (A) on the imino carbon proximate to the terminal phenyl ring (B). Analysis of the marked temperature dependence of the chemical shift of the interacting ortho hydrogen affords estimates of the opposing enthalpic and entropic factors involved in the rapid equilibrium between the closed edge-to-face conformation and alternative open conformations devoid of a CH–π interaction while in solution. Above ca. 80 °C the entropy term (TΔS) cancels out the enthalpy (ΔH) favouring the closed conformation and open conformations are preferred. Accordingly, commonly reported binding free energies may not be a good measure of the energetic strength of intramolecular aromatic interactions. Investigation of an ortho fluoro substituted compound indicates that a CF–π interaction is at least 1.0 kcal mol−1 weaker in enthalpy than the CH–π interaction. Several X-ray crystal structures depicting an intramolecular edge-to-face interaction are presented.

  2. Probabilistic Model Updating for Sizing of Hole-Edge Crack Using Fiber Bragg Grating Sensors and the High-Order Extended Finite Element Method

    Directory of Open Access Journals (Sweden)

    Jingjing He

    2016-11-01

    Full Text Available This paper presents a novel framework for probabilistic crack size quantification using fiber Bragg grating (FBG sensors. The key idea is to use a high-order extended finite element method (XFEM together with a transfer (T-matrix method to analyze the reflection intensity spectra of FBG sensors, for various crack sizes. Compared with the standard FEM, the XFEM offers two superior capabilities: (i a more accurate representation of fields in the vicinity of the crack tip singularity and (ii alleviation of the need for costly re-meshing as the crack size changes. Apart from the classical four-term asymptotic enrichment functions in XFEM, we also propose to incorporate higher-order functions, aiming to further improve the accuracy of strain fields upon which the reflection intensity spectra are based. The wavelength of the reflection intensity spectra is extracted as a damage sensitive quantity, and a baseline model with five parameters is established to quantify its correlation with the crack size. In order to test the feasibility of the predictive model, we design FBG sensor-based experiments to detect fatigue crack growth in structures. Furthermore, a Bayesian method is proposed to update the parameters of the baseline model using only a few available experimental data points (wavelength versus crack size measured by one of the FBG sensors and an optical microscope, respectively. Given the remaining data points of wavelengths, even measured by FBG sensors at different positions, the updated model is shown to give crack size predictions that match well with the experimental observations.

  3. Torsional Strengthening of RC Beams Using GFRP Composites

    Science.gov (United States)

    Patel, Paresh V.; Jariwala, Vishnu H.; Purohit, Sharadkumar P.

    2016-09-01

    Fiber reinforced polymer as an external reinforcement is used extensively for axial, flexural and shear strengthening in structural systems. The strengthening of members subjected to torsion is recently being explored. The loading mechanism of beams located at the perimeter of buildings which carry loads from slabs, joists and beams from one side of the member generates torsion that are transferred from the beams to the columns. In this work an experimental investigation on the improvement of the torsional resistance of reinforced concrete beams using Glass Fiber Reinforced Polymer (GFRP) is presented. Total 24 RC beams have been cast in this work. Ten beams of dimension 150 mm × 150 mm × 1300 mm are subjected to pure torsion while fourteen beams of 150 mm × 150 mm × 1700 mm are subjected to combined torsion and bending. Two beams in each category are designated as control specimen and remaining beams are strengthened by GFRP wrapping of different configurations. Pure torsion on specimens is applied using specially fabricated support mechanism and universal testing machine. For applying combined torsion and bending a loading frame and test set up are fabricated. Measurements of angle of twist at regular interval of torque, torsion at first crack, and ultimate torque, are obtained for all specimens. Results of different wrapping configurations are compared for control and strengthened beams to suggest effective GFRP wrapping configuration.

  4. Postcesarean Splenic Torsion

    Directory of Open Access Journals (Sweden)

    Yu-Hui Huang

    2006-09-01

    Conclusion: Splenic torsion is a rare cause of acute abdominal pain during pregnancy or postpartum, and the symptoms vary depending on the degree of torsion. Early involvement of many complementary specialty services enabled early recognition of this rare entity and timely definitive treatment.

  5. Intermittent Testicular Torsion

    African Journals Online (AJOL)

    2017-12-05

    Dec 5, 2017 ... Objective: The aim of this study is to highlight the clinical characteristics of patients with intermittent testicular torsion and draw attention to this underreported condition. Methods: Clinical and demographic data of all patients treated for intermittent testicular torsion from January 2007 to June 2015 were ...

  6. Gallbladder torsion. Case report

    DEFF Research Database (Denmark)

    Brasso, K; Rasmussen, O V

    1991-01-01

    Gallbladder torsion is a rare surgical emergency occurring primarily in elderly women. The anatomical background is a variation in the attachment of the gallbladder to the inferior margin of the liver. Increasing life span will probably lead to an increasing number of cases, and gallbladder torsion...

  7. Multiscale modeling and simulation of nanotube-based torsional oscillators

    Directory of Open Access Journals (Sweden)

    Xiao Shaoping

    2006-01-01

    Full Text Available AbstractIn this paper, we propose the first numerical study of nanotube-based torsional oscillators via developing a new multiscale model. The edge-to-edge technique was employed in this multiscale method to couple the molecular model, i.e., nanotubes, and the continuum model, i.e., the metal paddle. Without losing accuracy, the metal paddle was treated as the rigid body in the continuum model. Torsional oscillators containing (10,0 nanotubes were mainly studied. We considered various initial angles of twist to depict linear/nonlinear characteristics of torsional oscillators. Furthermore, effects of vacancy defects and temperature on mechanisms of nanotube-based torsional oscillators were discussed.

  8. Extended FEM modeling of crack paths near inclusions

    DEFF Research Database (Denmark)

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

    2012-01-01

    the effects on the crack path when changing the relative stiffness between inclusion and matrix material, the relative distance between initial crack and inclusion, and the size of the inclusion. Both edge cracks and internal cracks are studied. An example with an internal crack near an inclusion is presented...

  9. Torsional stress and resistance of concrte member. Concrete buzai no nejiri oryoku to tairyoku

    Energy Technology Data Exchange (ETDEWEB)

    Saeki, N. (Hokkaido University, Sapporo (Japan). Faculty of Engineering)

    1991-09-01

    Torsional stress and resistance are discussed for designing concrete members. A hypothesis was given that, in the simple torsion elasticity theory, the axial displacement is freely variable and no stress is created. In spherical and cylindrical cross section, no axial deformation will occur, but a displacement can occur in rectangular cross section. The general torsion elasticity theory can be applied also to a case where an axial stress is created. A discussion was also given to the plasticity theory in which shear stress enters the plastic region. A plain concrete is destructed at the same time as cracks develop, hence it reaches its resistance limit when the calculated value for a tensile stress caused from a torsional stress exceeds its tensile strength. Torsional resistance of a reinforced concrete after cracks have developed is calculated generally by the space truss theory, wherein the torsional load is thought shared in the lateral reinforcing bars, axial reinforcing bars, and diagonal concrete members. The pure torsion or torsion-pure bending resistance may be calculated theoretically, but the combined torsion-bending resistance is sought generally based on correlative curves derived from experiments. 25 refs., 14 figs., 2 tabs.

  10. Testicular torsion repair

    Science.gov (United States)

    ... male growth, sex life, and fertility. Patient Instructions Surgical wound care - open Images Male reproductive anatomy Testicular torsion repair - series References ... of the testes and scrotum and their surgical management. In: Wein AJ, ed. Campbell-Walsh Urology . ...

  11. Torsion pendulum revisited

    Energy Technology Data Exchange (ETDEWEB)

    Bassan, Massimo [Dipartimento di Fisica, Università di Roma Tor Vergata, and INFN, Sezione di Roma Tor Vergata, I-00133 Roma (Italy); De Marchi, Fabrizio, E-mail: fabrizio.demarchi@roma2.infn.it [Dipartimento di Fisica, Università di Roma Tor Vergata, and INFN, Sezione di Roma Tor Vergata, I-00133 Roma (Italy); Marconi, Lorenzo [Dipartimento di Fisica ed Astronomia, Università degli Studi di Firenze, and INFN, Sezione di Firenze (Italy); Pucacco, Giuseppe [Dipartimento di Fisica, Università di Roma Tor Vergata, and INFN, Sezione di Roma Tor Vergata, I-00133 Roma (Italy); Stanga, Ruggero [Dipartimento di Fisica ed Astronomia, Università degli Studi di Firenze, and INFN, Sezione di Firenze (Italy); Visco, Massimo [IAPS-INAF, and INFN, Sezione di Roma Tor Vergata, I-00133 Roma (Italy)

    2013-10-01

    We present an analysis of the motion of a simple torsion pendulum and we describe how, with straightforward extensions to the usual basic dynamical model, we succeed in explaining some unexpected features we found in our data, like the modulation of the torsion mode at a higher frequency and the frequency splitting of the swinging motion. Comparison with observed values yields estimates for the misalignment angles and other parameters of the model.

  12. 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.

  13. Heterogeneous flow during high-pressure torsion

    Directory of Open Access Journals (Sweden)

    Roberto B. Figueiredo

    2013-06-01

    Full Text Available High-Pressure Torsion (HPT has attracted significant attention in recent years as an effective technique to process ultrafine and nanostructured materials. The hydrostatic pressure developed during processing prevents the occurrence of cracks and the low thickness to diameter ratio provides the opportunity for developing high strains at low numbers of rotations. The present work analyses the plastic flow during HPT. Experimental results and computer modeling are used to describe heterogeneous plastic flow. It is shown that variations in structure, hardness and in the distribution of strain are observed along the disc thickness. The sources of these heterogeneities are discussed.

  14. Catastrophic failure of nacre under pure shear stresses of torsion.

    Science.gov (United States)

    Alghamdi, Saleh; Tan, Ting; Hale-Sills, Christopher; Vilmont, Floyd; Xia, Tian; Yang, Jie; Huston, Dryver; Dewoolkar, Mandar

    2017-10-13

    Nacre, a composite made from biogenic aragonite and proteins, exhibits excellent strength and toughness. Here, we show that nacreous sections can exhibit complete brittle fracture along the tablet interfaces at the proportional limit under pure shear stresses of torsion. We quantitatively separate the initial tablet sliding primarily resisted by nanoscale aragonite pillars from the following sliding resisted by various microscale toughening mechanisms. We postulate that the ductility of nacre can be limited by eliminating tablet interactions during crack propagations. Our findings should help pursuing further insights of layered materials by using torsion.

  15. Fracture Toughness of Thin Plates by the Double-Torsion Test Method

    Science.gov (United States)

    Salem, Jonathan A.; Radovic, Miladin; Lara-Curzio, Edgar; Nelson, George

    2006-01-01

    Double torsion testing can produce fracture toughness values without crack length measurement that are comparable to those measured via standardized techniques such as the chevron-notch, surface-crack-in-flexure and precracked beam if the appropriate geometry is employed, and the material does not exhibit increasing crack growth resistance. Results to date indicate that 8 2 are required if crack length is not considered in stress intensity calculations. At L/W = 2, the normalized crack length should be 0.35 80) nonlinear effects were encountered.

  16. Higher Franz-Reidemeister torsion

    CERN Document Server

    Igusa, Kiyoshi

    2002-01-01

    The book is devoted to the theory of topological higher Franz-Reidemeister torsion in K-theory. The author defines the higher Franz-Reidemeister torsion based on Volodin's K-theory and Borel's regulator map. He describes its properties and generalizations and studies the relation between the higher Franz-Reidemeister torsion and other torsions used in K-theory: Whitehead torsion and Ray-Singer torsion. He also presents methods of computing higher Franz-Reidemeister torsion, illustrates them with numerous examples, and describes various applications of higher Franz-Reidemeister torsion, particularly for the study of homology of mapping class groups. Packed with up-to-date information, the book provides a unique research and reference tool for specialists working in algebraic topology and K-theory.

  17. Isolated Fallopian Tube Torsion

    Directory of Open Access Journals (Sweden)

    S. Kardakis

    2013-01-01

    Full Text Available Isolated torsion of the Fallopian tube is a rare gynecological cause of acute lower abdominal pain, and diagnosis is difficult. There are no pathognomonic symptoms; clinical, imaging, or laboratory findings. A preoperative ultrasound showing tubular adnexal masses of heterogeneous echogenicity with cystic component is often present. Diagnosis can rarely be made before operation, and laparoscopy is necessary to establish the diagnosis. Unfortunately, surgery often is performed too late for tube conservation. Isolated Fallopian tube torsion should be suspected in case of acute pelvic pain, and prompt intervention is necessary.

  18. Torsional vibration analysis of bars including secondary torsional shear deformation effect by the boundary element method

    Science.gov (United States)

    Sapountzakis, E. J.; Tsipiras, V. J.; Argyridi, A. K.

    2015-10-01

    In this paper a boundary element method (BEM) is developed for the torsional vibration problem of bars of arbitrary doubly symmetric constant cross section, taking into account the nonuniform warping and secondary torsional shear deformation effects (STSDE). The bar is subjected to arbitrarily distributed or concentrated dynamic torsional loading along its length, while its edges are subjected to the most general torsional and warping boundary conditions. Apart from the angle of twist, the primary angle of twist per unit length is considered as an additional 1-D degree of freedom in order to account for the STSDE in the equations of motion of the bar. The warping shear stress distribution and the pertinent secondary torsional rigidity are computed by satisfying local equilibrium considerations under dynamic conditions without adhering to assumptions of Thin Tube Theory (TTT). By employing a distributed mass model system accounting for rotatory and warping inertia, an initial boundary value and two boundary value problems with respect to the variable along the bar time-dependent 1-D kinematical components, to the primary and secondary warping functions, respectively, are formulated. The latter are solved employing a pure BE method, requiring exclusively boundary discretization of the bar's cross section. The numerical solution of the aforementioned initial boundary value problem is performed through a BE method leading to a system of differential equations with displacement only unknowns, which is solved using an efficient direct time integration technique. Additionally, for the free vibrations case, a generalized eigenvalue problem is formulated through a similar BE technique. The accuracy and reliability of the results is assessed by FEM solutions employing solid or shell modelling. Both open- and closed-shaped cross section bars are examined and the necessity to include nonuniform torsional and STSD effects in the dynamic analysis of bars is demonstrated.

  19. Appearance of singularities of optical fields under torsion of crystals containing threefold symmetry axes.

    Science.gov (United States)

    Skab, Ihor; Vasylkiv, Yurij; Zapeka, Bohdan; Savaryn, Viktoriya; Vlokh, Rostyslav

    2011-07-01

    We present an analysis of the effect of torsion stresses on the spatial distribution of optical birefringence in crystals of different point symmetry groups. The symmetry requirements needed so that the optical beam carries dislocations of the phase front are evaluated for the case when the crystals are twisted and the beam closely corresponds to a plane wave. It is shown that the torsion stresses can produce screw-edge, pure screw, or pure edge dislocations of the phase front in the crystals belonging to cubic and trigonal systems. The conditions for appearance of canonical and noncanonical vortices in the conditions of crystal torsion are analyzed. © 2011 Optical Society of America

  20. Fault diagnosis of planetary gearboxes via torsional vibration signal analysis

    Science.gov (United States)

    Feng, Zhipeng; Zuo, Ming J.

    2013-04-01

    Torsional vibration signals are theoretically free from the amplitude modulation effect caused by time variant vibration transfer paths due to the rotation of planet carrier and sun gear, and therefore their spectral structure are simpler than transverse vibration signals. Thus, it is potentially easy and effective to diagnose planetary gearbox faults via torsional vibration signal analysis. We give explicit equations to model torsional vibration signals, considering both distributed gear faults (like manufacturing or assembly errors) and local gear faults (like pitting, crack or breakage of one tooth), and derive the characteristics of both the traditional Fourier spectrum and the proposed demodulated spectra of amplitude envelope and instantaneous frequency. These derivations are not only effective to diagnose single gear fault of planetary gearboxes, but can also be generalized to detect and locate multiple gear faults. We validate experimentally the signal models, as well as the Fourier spectral analysis and demodulation analysis methods.

  1. Triorchidism with Torsion

    African Journals Online (AJOL)

    are retractile and more mobility is at increased risk for torsion. An increased prevalence of carcinoma has also been reported.[1]. Case Report. A 72-year-old man presented with vague pain in the lower abdomen and scrotum. There was no history of trauma and he stated that the pain was severe in nature and had been ...

  2. Tumour, Torsion or Trauma?

    African Journals Online (AJOL)

    finally revealed testicular torsion. Remarkably, the testis was viable and the finding of a hematoma of the epididymis suggested a history of trauma which was not forthcoming from the patient. The acute scrotum demands expeditious attention and the clinician must aim to reach a definitive diagnosis in the shortest time ...

  3. Triorchidism with Torsion

    African Journals Online (AJOL)

    scrotal mass. Of the remaining cases, 20% of the testes are inguinal and 5% are retroperitoneal.[1,2] Supernumerary testes are retractile and more mobility is at increased risk for torsion. An increased prevalence of carcinoma has also been reported.[1]. Case Report. A 72-year-old man presented with vague pain in the ...

  4. Knuckle Cracking

    Science.gov (United States)

    ... people realize that cracking knuckles produces a funny noise and may repeat cracking just to produce the ... main areas of exercise are aerobic exercise and resistance News Categories Ankylosing Spondylitis News Fibromyalgia News Gout ...

  5. Tibiotalar torsion: bioengineering paradigm.

    Science.gov (United States)

    Michele, A A; Nielsen, P M

    1976-10-01

    1. Medial tibiotalar torsion is the most common disorder peculiar to mankind. 2. The pathogonomic findings are (a) an axial medially rotated and adducted distal third of the shaft of the tibia, (b) the plafond of the tibia with its mortise containing the "track-bound" talus, which is deflected strongly toward the tibial side, (c) an exaggerated midtarsal equinus, (d) ostensible restriction of dorsiflexion of the hindfoot against the tibia, (e) mild separation of the distal tibiofibular articulation, and (f) forward displacement of the gravitational axis to the naviculocunei-form joint. 3. Faulty leg crossing in utero resulting in an abnormal pelvofemoral-tibial design is discussed and its important consequences in the vulnerable 40 per cent of the population are emphasized. 4. The kinesiomechanics of the leg, ankle and foot is reviewed. 5. The radiographic parameters of medial tibiotalar torsion are presented, as well as the multiple facets of the clinical examination. 6. Methods of treatment depending on age and severity of the disorder are recommended. Surgery, detortional casts, and corrective footwear are discussed. Shoes presently available are inadequate for tibiotalar torsion and therefore engineering principles must be applied in the design and construction of all footwear, including sneakers and sportswear. This can be done only if the pathological biomechanics of this group of disorders is recognized. Biplane proximal tibial osteotomy is recommended in refractory cases, especially when tibiotalar torsion is demonstrated. 7. After 30 years of experience, the author finds that results with these patients have been uniformly good to excellent, depending on age and mode of treatment. 8. In medial tibiotalar torsion, the consequent adaptive changes are readily observed, but rarely are they recognized as the inevitable sequelae of medial tibiotalar torsion. 9. Adaptive compensating disorders are identified and their mechanism described. 10. The management of

  6. Management of adnexal torsion

    Directory of Open Access Journals (Sweden)

    Neslihan Erkal

    2014-03-01

    Full Text Available Objective: To evaluate clinical findings, operative reports, the pathological results of patients with diagnosis of adnexal torsion. Methods: Fourteen patients with diagnosis of adnexal torsion who presented to our clinic between January 2009 and March 2013 were included in this retrospective analysis. Data including clinical findings, operative reports, the pathological results were recorded. Results: The mean age of the patients was 28.1 ± 10.5 with a range of 16 to 52 years. All patients underwent ultrasonography, and a pelvic mass appearance was detected in all cases. The mean diameter of the mass was 8,04±2,96 cm. All of the patients had lower abdominal pain, nausea and vomiting. Six patients were operated laparoscopically, while eight patients had laparotomy. Detorsion and cystectomy was performed in 7 (50.0% of the patients. Two of patients were pregnant in operation time that treated by cystectomy and detorsion of the ovaries successfully in the first and third trimester (one by laparoscopy. There was one patient of isolated fallopian tube torsion due to hydrosalpinks treated by laparoscopic salpingectomy. Two of the patients had paratubal cyst and tubal torsion. Detorsion and cystectomy by laparoscopy and salpingectomy by laparotomy were performed for these patients respectively. The most common histopathology was serous cystadenoma (28,6%. Conclusion: Adnexal torsion is a rare gynecologic emergency of women and occur in reproductive ages mostly. Prompt diagnosis and conservative treatment is important for the safety of ovaries and fallopian tubes and future fertility. J Clin Exp Invest 2014; 5 (1: 7-11

  7. High cycle torsional fatigue properties of 17-4PH stainless steel

    Directory of Open Access Journals (Sweden)

    K. Yanase

    2016-07-01

    Full Text Available Sensitivity to small defects under torsional fatigue loading condition is examined in the high cycle fatigue regime. Fatigue crack initiation and small crack growth behaviors were observed during fatigue testing and fractographic investigations were performed. The results are compared to the data obtained in the uniaxial fatigue tests, which allows the effect of biaxial stresses on the surface of material to be discussed. Finally, an approach for predicting the fatigue limit of 17-4PH stainless steel under torsional and tension-compression fatigue loadings is presented.

  8. Nonlinear Hysteretic Torsional Waves.

    Science.gov (United States)

    Cabaret, J; Béquin, P; Theocharis, G; Andreev, V; Gusev, V E; Tournat, V

    2015-07-31

    We theoretically study and experimentally report the propagation of nonlinear hysteretic torsional pulses in a vertical granular chain made of cm-scale, self-hanged magnetic beads. As predicted by contact mechanics, the torsional coupling between two beads is found to be nonlinear hysteretic. This results in a nonlinear pulse distortion essentially different from the distortion predicted by classical nonlinearities and in a complex dynamic response depending on the history of the wave particle angular velocity. Both are consistent with the predictions of purely hysteretic nonlinear elasticity and the Preisach-Mayergoyz hysteresis model, providing the opportunity to study the phenomenon of nonlinear dynamic hysteresis in the absence of other types of material nonlinearities. The proposed configuration reveals a plethora of interesting phenomena including giant amplitude-dependent attenuation, short-term memory, as well as dispersive properties. Thus, it could find interesting applications in nonlinear wave control devices such as strong amplitude-dependent filters.

  9. Femtosecond torsional relaxation

    Science.gov (United States)

    Clark, J.; Nelson, T.; Tretiak, S.; Cirmi, G.; Lanzani, G.

    2012-03-01

    Molecular conformational reorganization following photon absorption is a fundamental process driving reactions such as the cis-trans isomerization at the heart of the primary step of vision and can be exploited for switching in artificial systems using photochromics. In general, conformational change occurs on a timescale defined by the energy of the main vibrational mode and the rate of energy dissipation. Typically, for a conformational change such as a twist around the backbone of a conjugated molecule, this occurs on the tens of picoseconds timescale. However, here we demonstrate experimentally that in certain circumstances the molecule, in this case an oligofluorene, can change conformation over two orders of magnitude faster (that is sub-100fs) in a manner analogous to inertial solvent reorganization demonstrated in the 1990s. Theoretical simulations demonstrate that non-adiabatic transitions during internal conversion can efficiently convert electronic potential energy into torsional kinetic energy, providing the `kick' that prompts sub-100fs torsional reorganization.

  10. Torsional Rigidity of Minimal Submanifolds

    DEFF Research Database (Denmark)

    Markvorsen, Steen; Palmer, Vicente

    2006-01-01

    We prove explicit upper bounds for the torsional rigidity of extrinsic domains of minimal submanifolds $P^m$ in ambient Riemannian manifolds $N^n$ with a pole $p$. The upper bounds are given in terms of the torsional rigidities of corresponding Schwarz symmetrizations of the domains in warped...... for the torsional rigidity are actually attained and give conditions under which the geometric average of the stochastic mean exit time for Brownian motion at infinity is finite....

  11. Stability in quadratic torsion theories

    Science.gov (United States)

    Vasilev, Teodor Borislavov; Cembranos, Jose A. R.; Valcarcel, Jorge Gigante; Martín-Moruno, Prado

    2017-11-01

    We revisit the definition and some of the characteristics of quadratic theories of gravity with torsion. We start from a Lagrangian density quadratic in the curvature and torsion tensors. By assuming that General Relativity should be recovered when the torsion vanishes and investigating the behaviour of the vector and pseudo-vector torsion fields in the weak-gravity regime, we present a set of necessary conditions for the stability of these theories. Moreover, we explicitly obtain the gravitational field equations using the Palatini variational principle with the metricity condition implemented via a Lagrange multiplier.

  12. Steady-state propagation of interface corner crack

    DEFF Research Database (Denmark)

    Veluri, Badrinath; Jensen, Henrik Myhre

    2013-01-01

    Steady-state propagation of interface cracks close to three-dimensional corners has been analyzed. Attention was focused on modeling the shape of the interface crack front and calculating the critical stress for steady-state propagation of the crack. The crack propagation was investigated...... field (crack tip) solutions based on the J-integral. The adopted two-dimensional numerical approach for the calculation of fracture mechanical properties was compared with three-dimensional models for quarter-circular and straight sided crack front shapes. A quantitative approach was formulated based...... for propagation and the angle of intersection of the crack front with the free edge....

  13. Testicular torsion: A surgical emergency

    Energy Technology Data Exchange (ETDEWEB)

    Prater, J.M.; Overdorf, B.S. (Surgical Residency Program at Yale University, New Haven, CT (USA))

    1991-09-01

    Testicular torsion is caused by twisting of the spermatic cord, which results in compromised testicular blood flow. The degree of ischemic injury is determined by the severity of arterial compression and the interval between the onset of symptoms and surgical intervention. Torsion usually occurs at puberty, and an anatomic defect known as bell-clapper deformity is usually present. Typical symptoms include acute scrotal pain with associated nausea and vomiting. Up to one-half of patients report previous similar episodes. On examination, the testis is high-riding, tender, swollen and firm. Testicular scan or Doppler ultrasound examination can be helpful in distinguishing torsion from acute epididymitis. Prompt surgical treatment is indicated to reduce the torsion, and bilateral orchiopexy is performed to prevent recurrence. Exocrine function, as determined by semen analysis, is often abnormal after unilateral torsion. 25 references.

  14. Torsion testing of bed joints

    DEFF Research Database (Denmark)

    Hansen, Klavs Feilberg; Pedersen, Carsten Mørk

    2008-01-01

    This paper describes a simple test method for determining the torsion strength of a single bed joint between two bricks and presents results from testing using this test method. The setup for the torsion test is well defined, require minimal preparation of the test specimen and the test can...... be carried out directly in a normal testing machine. The torsion strength is believed to be the most important parameter in out-of-plane resistance of masonry walls subjected to bending about an axis perpendicular to the bed joints. The paper also contains a few test results from bending of small walls about...... an axis perpendicular to the bed joints, which indicate the close connection between these results and results from torsion tests. These characteristics make the torsion strength well suited to act as substitute parameter for the bending strength of masonry about an axis perpendicular to the bed joints....

  15. Discrete dislocation plasticity modeling of short cracks in single crystals

    NARCIS (Netherlands)

    Deshpande, VS; Needleman, A; Van der Giessen, E

    2003-01-01

    The mode-I crack growth behavior of geometrically similar edge-cracked single crystal specimens of varying size subject to both monotonic and cyclic axial loading is analyzed using discrete dislocation dynamics. Plastic deformation is modeled through the motion of edge dislocations in an elastic

  16. Chiral edge fluctuations of colloidal membranes

    Science.gov (United States)

    Jia, Leroy; Zakhary, Mark; Dogic, Zvonimir; Pelcovits, Robert; Powers, Thomas

    Using experiments and theory we study chiral fluctuations of the edge of a nearly flat colloidal membrane, consisting of rod-like viruses held together by the depletion interaction. Our measurements show an anomalous peak in the power spectrum around 1 inverse micron. Using an effective theory to describe the liquid crystal degrees of freedom by geometric properties of the edge, such as length, geodesic torsion, and curvature, we calculate the spectrum of out-of-plane edge fluctuations. The peak arises for sufficiently strong chirality, and corresponds to the instability of a flat membrane to a shape with helical, rippled edges.

  17. Spin and torsion in gravitation

    CERN Document Server

    De Sabbata, Venzo

    1994-01-01

    This book gives an exposition of both the old and new results of spin and torsion effects on gravitational interactions with implications for particle physics, cosmology etc. Physical aspects are stressed and measurable effects in relation to other areas of physics are discussed.Among the topics discussed are: alternative ways of unifying gravity with electroweak and strong interactions by an energy dependent spin torsion coupling constant; the idea that all interactions can be understood as originating from spin curvature coupling; the possibility of cosmological models with torsion providing

  18. Hematosalpinx torsion in an adolescent

    Directory of Open Access Journals (Sweden)

    Inês Vaz

    2016-02-01

    Full Text Available Introduction: Isolated fallopian tube torsion is an uncommon cause of acute lower abdominal pain. Ectopic pregnancy, hydro or hematosalpinx, endometriosis, adnexal masses and other causes of adnexal disease are predisposing factors. The diagnosis is difficult and often delayed due to the lack of pathognomonic symptoms, characteristic physical signs, and specific imaging and laboratory studies. Defi nitive diagnosis requires a surgical approach. Case report: The authors present a case of hematosalpinx and its tubal torsion in a virgin teenager with no prior predisposing factors. Discussion: This rare case may highlight a new insight into pathophysiology of tubal torsion and recalls hematosalpinx as a differential diagnosis.

  19. Mechanisms of Subcritical Cracking in Calcite

    Science.gov (United States)

    Royne, A.; Dysthe, D. K.; Bisschop, J.

    2008-12-01

    microplasticity (pile-up of dislocations in the process zone around the crack tip). In our experiment, we study the subcritical growth of a cleavage crack through a single calcite crystal. We use the well documented Double Torsion method which allows for easy study of a tensile crack growing in the specimen. We find that the environmental conditions, and in particular the availability of water, has a significant influence on both the crack tip velocity at a given load, but also the behaviour of the crack movement. Based on our experimental data, we propose what mechanisms are dominant for subcritical crack growth in calcite at various load levels.

  20. Constraining spacetime torsion with LAGEOS

    Science.gov (United States)

    March, Riccardo; Bellettini, Giovanni; Tauraso, Roberto; Dell'Agnello, Simone

    2011-11-01

    We compute the corrections to the orbital Lense-Thirring effect (or frame-dragging) in the presence of spacetime torsion. We analyze the motion of a test body in the gravitational field of a rotating axisymmetric massive body, using the parametrized framework of Mao, Tegmark, Guth and Cabi. In the cases of autoparallel and extremal trajectories, we derive the specific approximate expression of the corresponding system of ordinary differential equations, which are then solved with methods of Celestial Mechanics. We calculate the secular variations of the longitudes of the node and of the pericenter. We also show how the LAser GEOdynamics Satellites (LAGEOS) can be used to constrain torsion parameters. We report the experimental constraints obtained using both the nodes and perigee measurements of the orbital Lense-Thirring effect. This makes LAGEOS and Gravity Probe B complementary frame-dragging and torsion experiments, since they constrain three different combinations of torsion parameters.

  1. A calculation method of cracking moment for the high strength ...

    Indian Academy of Sciences (India)

    Abstract. In this study, a method is given to calculate cracking moments of high strength reinforced concrete beams under the effect of pure torsion. To determine the method, both elastic and plastic theories were used. In this method, dimensions of beam cross-section were considered besides stirrup and longitudinal ...

  2. A calculation method of cracking moment for the high strength ...

    Indian Academy of Sciences (India)

    In this study, a method is given to calculate cracking moments of high strength reinforced concrete beams under the effect of pure torsion. To determine the method, both elastic and plastic theories were used. In this method, dimensions of beam cross-section were considered besides stirrup and longitudinal reinforcements.

  3. Harmonic structures and intrinsic torsion

    DEFF Research Database (Denmark)

    Conti, Diego; Madsen, Thomas Bruun

    We discuss the construction of 8-manifolds with harmonic Sp(2)Sp(1)-structures. In particular, we find 10 new examples of nilmanifolds that admit a closed 4-form Omega whose stabiliser is Sp(2)Sp(1). Our constructions entail the notion of SO(4)-structures on 7-manifolds. We present a thorough inv...... investigation of the intrinsic torsion of such structures; in addition to the construction of harmonic structures, this analysis leads to explicit Lie group examples with invariant intrinsic torsion....

  4. Harmonic structures and intrinsic torsion

    DEFF Research Database (Denmark)

    Conti, Diego; Madsen, Thomas Bruun

    2015-01-01

    We discuss the construction of Sp(2)Sp(1)-structures whose fundamental form is closed. In particular, we find 10 new examples of 8-dimensional nilmanifolds that admit an invariant closed 4-form with stabiliser Sp(2) Sp(1). Our constructions entail the notion of SO(4)-structures on 7-manifolds. We...... present a thorough investigation of the intrinsic torsion of such structures, leading to the construction of explicit Lie group examples with invariant intrinsic torsion....

  5. COD measurements at various positions along a crack

    Science.gov (United States)

    Sharpe, W. N., Jr.; Su, X.

    1988-01-01

    Load versus crack-opening-displacement (COD) was measured at various positions along the border of a fatigue crack as it grew from a small surface crack on the edge of an aluminum specimen into a through-the-thickness crack. Displacements were measured with a laser-based interferometric system with a gage length of 70 microns and a resolution of 0.01 micron. These load-COD curves can be used to determine opening loads and thereby investigate the effect of closure on the growth of small cracks. In general, the opening loads decrease as the crack grows.

  6. Improvement of torsional resistance from bond strength and reinforcement indexes in fibrous normal strength concrete beams

    Science.gov (United States)

    Karim, F. R.; Abu Bakar, B. H.; Kok Keong, Choong; Aziz, O. Q.

    2017-10-01

    This paper highlights the effect of tension stiffening index on the torsional resistance at the crack and peak loads in under-reinforced fibrous normal strength concrete beams under pure torsional loading. The different grades of steel reinforcements were used with different surface texture of the reinforcements. Four fibrous normal strength concrete beams were cast and tested under pure torsional loading. The beams were designed based on ACI 318, where the clear span to depth ratio and aspect ratio of the section were kept constant at 5.72 and 1.22, respectively. The test results verified that the torsional resistance of peak load was improved up to 12.91% due to the reduction of tension stiffening index, whereas the cracking torsional resistance and the value of twisting angle were slightly influenced. Moreover, due to the reduction of tension stiffening index up to 11.66%, the strain in transverse and longitudinal reinforcements were enhanced up to 91.8% and 73.6%, respectively.

  7. Effects of toughness anisotropy and combined tension, torsion, and bending loads on fracture behavior of ferritic nuclear pipe

    Energy Technology Data Exchange (ETDEWEB)

    Mohan, R.; Marshall, C.; Ghadiali, N.; Wilkowski, G. [Battelle, Columbus, OH (United States)

    1997-04-01

    This paper summarizes work on angled through-wall-crack initiation and combined loading effects on ferritic nuclear pipe performed as part of the Nuclear Regulatory Commission`s research program entitled {open_quotes}Short Cracks In Piping an Piping Welds{close_quotes}. The reader is referred to Reference 1 for details of the experiments and analyses conducted as part of this program. The major impetus for this work stemmed from the observation that initially circumferentially oriented cracks in carbon steel pipes exhibited a high tendency to grow at a different angle when the cracked pipes were subjected to bending or bending plus pressure loads. This failure mode was little understood, and the effect of angled crack grown from an initially circumferential crack raised questions about how cracks in a piping system subjected to combined loading with torsional stresses would behave. There were three major efforts undertaken in this study. The first involved a literature review to assess the causes of toughness anisotropy in ferritic pipes and to develop strength and toughness data as a function of angle from the circumferential plane. The second effort was an attempt to develop a screening criterion based on toughness anisotropy and to compare this screening criterion with experimental pipe fracture data. The third and more significant effort involved finite element analyses to examine why cracks grow at an angle and what is the effect of combined loads with torsional stresses on a circumferentially cracked pipe. These three efforts are summarized.

  8. A Two-Disk Extended Jeffcott Rotor Model Distinguishing a Shaft Crack from Other Rotating Asymmetries

    Directory of Open Access Journals (Sweden)

    Xi Wu

    2008-01-01

    Full Text Available A mathematical model of a cracked rotor and an asymmetric rotor with two disks representing a turbine and a generator is utilized to study the vibrations due to imbalance and side load. Nonlinearities typically related with a “breathing” crack are included using a Mayes steering function. Numerical simulations demonstrate how the variations of rotor parameters affect the vibration response and the effect of coupling between torsional and lateral modes. Bode, spectrum, and orbit plots are used to show the differences between the vibration signatures associated with cracked shafts versus asymmetric shafts. Results show how nonlinear lateral-torsional coupling shifts the resonance peaks in the torsional vibration response for cracked shafts and asymmetric rotors. The resonance peaks shift depending on the ratio of the lateral-to-torsional natural frequencies with the peak responses occurring at noninteger values of the lateral natural frequency. When the general nonlinear models used in this study are constrained to reduce to linear torsional vibration, the peak responses occur at commonly reported integer ratios. Full spectrum analyses of the X and Y vibrations reveal distinct vibration characteristics of both cracked and asymmetric rotors including reverse vibration components. Critical speeds and vibration orders predicted using the models presented herein include and extend diagnostic indicators commonly reported.

  9. Torsional Phacoemulsification and Tip Selection

    Directory of Open Access Journals (Sweden)

    Fırat Helvacıoğlu

    2014-10-01

    Full Text Available One of the recent advances in cataract surgery is torsional phacoemulsification. It was developed to increase the efficacy of ultrasonic emulsification. In torsional phacoemulsification, the torsional movement of the tip is translated to side-to-side cutting action with the aid of bent phaco tips. Lens material is cut in both directions, rather than only during a forward stroke. The efficiency of this technique is further enhanced by an improvement in followability provided by the inherent non-repulsive nature of the side-to-side motion. Tip selection is very important for the efficiency of torsional phacoemulsification. Theoretically, there are 2 ways to enhance the cutting efficiency of the tip. First is the stroke length; the 22-degree bent 30-degree Kelman mini-flared tip cuts longer than the 12-degree bent 30-degree mini-flared Kelman tip. Second is the angulation or bevel; the higher the degree (45 degrees, the better cutting efficiency. Retrospective analyses of the previously published clinical studies clearly demonstrated that the efficacy of the torsional phacoemulsification has positive correlation with both the aperture angles and neck angles of the tips. (Turk J Ophthalmol 2014; 44: 392-5

  10. Monitoring small-crack growth by the replication method

    Science.gov (United States)

    Swain, Mary H.

    1992-01-01

    The suitability of the acetate replication method for monitoring the growth of small cracks is discussed. Applications of this technique are shown for cracks growing at the notch root in semicircular-edge-notch specimens of a variety of aluminum alloys and one steel. The calculated crack growth rate versus Delta K relationship for small cracks was compared to that for large cracks obtained from middle-crack-tension specimens. The primary advantage of this techinque is that it provides an opportunity, at the completion of the test, to go backward in time towards the crack initiation event and 'zoom in' on areas of interest on the specimen surface with a resolution of about 0.1 micron. The primary disadvantage is the inability to automate the process. Also, for some materials, the replication process may alter the crack-tip chemistry or plastic zone, thereby affecting crack growth rates.

  11. Tibiofibular torsion in congenital clubfoot.

    Science.gov (United States)

    Farsetti, Pasquale; Dragoni, Massimiliano; Ippolito, Ernesto

    2012-01-01

    Tibiofibular torsion was measured by computed tomography in three series of patients affected by congenital clubfoot who were treated with different protocols. The normal leg of unilateral deformities served as the control. For the bilateral cases, only the right side was included in the study. The angle between the bicondylar axis of the tibia and the bimalleolar axis was the index of tibiofibular torsion. There were 34 clubfeet in the first series, treated with a posteromedial release, and 40 clubfeet in the second series, treated with a modified Ponseti method, whereas the third series included 16 clubfeet, treated with the original Ponseti method. All 90 clubfeet were graded at birth as group 3 according to the Manes classification. No patient had previous treatment. The patients of the first and the second series were followed up to maturity, whereas the patients of the third series were followed up to a maximum of 11 years of age. In the congenital clubfoot, the tibia and the fibula were externally rotated, in comparison with the normal leg; in fact, the average value of the angle of tibiofibular torsion was 32.2° in the first series, 23.9° in the second series, and 21.1° in the third series. In the normal tibiae, the average value of the angle of tibiofibular torsion was 21.4°. The difference between the first series and the normal controls was statistically significant, as was the difference between the first one and the other two series. The value of the tibiofibular torsion angle seems to be related to the manipulation technique used to treat clubfoot: when the manipulation does not allow a progressive eversion of the talus underneath the calcaneus, the external tibial torsion increases. At follow-up, an intoeing gait was present in seven treated clubfeet of the first series. In all of them except one, the highest value of the external tibial torsion angle was observed, with a low value of the Kite's angle and/or residual forefoot adduction. In the

  12. Painless Ovarian Torsion Mimicking a Uterine Myoma

    Directory of Open Access Journals (Sweden)

    Cheng-Kuo Lin

    2006-12-01

    Conclusion: Ovarian torsion is a significant cause of acute lower abdominal pain in women and is a gynecologic surgical emergency. Nevertheless, surgical strategies are usually impeded because of ambiguous warning signs. Clinicians may be misled by certain conditions such as silent ovarian torsion. Although there may be no specific indication, the diagnosis of ovarian torsion should be considered on finding a pelvic mass.

  13. Molecular dynamics simulation of propagating cracks

    Science.gov (United States)

    Mullins, M.

    1982-01-01

    Steady state crack propagation is investigated numerically using a model consisting of 236 free atoms in two (010) planes of bcc alpha iron. The continuum region is modeled using the finite element method with 175 nodes and 288 elements. The model shows clear (010) plane fracture to the edge of the discrete region at moderate loads. Analysis of the results obtained indicates that models of this type can provide realistic simulation of steady state crack propagation.

  14. Pancreatic torsion in a dog

    OpenAIRE

    Brabson, Tamera L.; Maki, Lynn C.; Newell, Susan M.; Ralphs, S. Christopher

    2015-01-01

    A 6-month-old male intact Cane Corso mastiff dog was presented for a recent history of vomiting, abdominal pain, and lethargy. A diagnosis of pancreatic torsion was made during abdominal exploratory surgery and was confirmed with histopathology. The dog underwent partial pancreatectomy and recovered with no complications.

  15. [Testicular torsion: A case report].

    Science.gov (United States)

    García-Fernández, Gustavo; Bravo-Hernández, Alberto; Bautista-Cruz, Raúl

    The acute scrotum is an emergency. Testicular torsion represents approximately 25% of the causes. The annual incidence of testicular torsion is approximately 1/4,000 persons under 25 years, with highest prevalence between 12 and 18 years old. It usually occurs without apparent cause, but it has been associated with anatomical, traumatic, and environmental factors, among others. A male 15 year-old male, with no history of importance, was seen in the Emergency Department, presenting with a sudden and continuous pain in the left testicle. It was accompanied by a pain that radiated to the abdomen and left inguinal area, with nausea and vomiting of more than 12h onset. Doppler ultrasound showed changes suggestive of testicular torsion. Surgery was performed that showed findings of a necrotic left testicle with rotation of the spermatic cord of 360°. A left orchiectomy was performed. Testicular torsion should always be considered one of the leading causes of acute scrotal pain. Delays in diagnosis should be avoided as this is directly related to the percentage of testicular salvage or loss. Copyright © 2016 Academia Mexicana de Cirugía A.C. Publicado por Masson Doyma México S.A. All rights reserved.

  16. Torsion and Open Book Decompositions

    OpenAIRE

    Etnyre, John B.; Vela-Vick, David Shea

    2009-01-01

    We show that if (B,\\pi) is an open book decomposition of a contact 3-manifold (Y,\\xi), then the complement of the binding B has no Giroux torsion. We also prove the sutured Heegaard-Floer c-bar invariant of the binding of an open book is non-zero.

  17. Torsion of a wandering spleen

    African Journals Online (AJOL)

    splenic ligaments, particularly the gastrosplenic and splenorenal ligaments. Wandering spleen may present in varying forms, from an incidentally detected radiological mass to an asymptomatic, mobile intra-abdominal mass or, as in our case, the more sinister presentation of severe pain secondary to torsion. Case report.

  18. Tunneling cracks in full scale wind turbine blade joints

    DEFF Research Database (Denmark)

    Jørgensen, Jeppe Bjørn; Sørensen, Bent F.; Kildegaard, C.

    2017-01-01

    A novel approach is presented and used in a generic tunneling crack tool for the prediction of crack growth rates for tunneling cracks propagating across a bond-line in a wind turbine blade under high cyclic loadings. In order to test and demonstrate the applicability of the tool, model predictions...... are compared with measured crack growth rates from a full scale blade fatigue test. The crack growth rates, measured for a several metre long section along the blade trailing-edge joint during the fatigue test, are found to be in-between the upper- and lower-bound predictions....

  19. Investigation method of torsional properties and damages of glass/epoxy composite pipes

    Directory of Open Access Journals (Sweden)

    Putić Slaviša S.

    2006-01-01

    Full Text Available Pipes made of composites glass fiber/epoxy resin are predominantly used in the chemical industry, construction, infrastructure and war technique. The pipes made for this purpose are in their use exposed to static and dynamic loading. Depending on the purpose, the pipes, especially those in complex structures, can be loaded by torsion. In that case, exceeding allowed tensions can cause damages such as cracking the fibers and matrix delamination. These damages can lead to the appearance of cracks on the pipes and in many cases to complete breakage of the pipe. Because of this, it is very important to evaluate composite pipes exposed to torsion and find out in which way the construction is weakened, what actually is the main goal of this paper.

  20. TORSION OF THE VERMIFORM APPENDIX: A CASE REPORT

    Directory of Open Access Journals (Sweden)

    Dr. Imtiaz Wani

    2009-07-01

    Full Text Available Torsion of the vermiform appendix is a rare condition with few cases reported in the literature. Various factors predispose to torsion. Various factors predispose to torsion. We report a case of primary torsion of the vermiform appendix. The clinical presentation was indistinguishable from acute appendicitis and the diagnosis was made at operation. Appendix was preileal in position and the direction of torsion was anticlockwise. There was intrinsic torsion with no obvious factor for torsion identified. Appendectomy was performed.

  1. Effect of Torsion on Externally Prestressed Segmental Concrete Bridge with Shear Key

    OpenAIRE

    M. A. Algorafi; A. A. A. Ali; Jaafar, M.S.; I. Othman; M. P. Anwar; Rashid, R

    2009-01-01

    Externally Prestressed Segmental (EPS) concrete box sections are widely used in the construction of bridge structures today. EPS concept has become an attractive tool for rehabilitation and strengthening of existing bridges which have insufficient strength and/or excessive deflection and cracking. Problem statement: EPS bridges are affected by combined stresses (bending, shear, normal, and torsional) at the joint interface between the segments. However, very limited researchers studied this t...

  2. Crack detection in a beam with an arbitrary number of transverse cracks using genetic algorithms

    Energy Technology Data Exchange (ETDEWEB)

    Khaji, N. [Tarbiat Modares University, Tehran (Iran, Islamic Republic of); Mehrjoo, M. [Islamic Azad University, Tehran (Iran, Islamic Republic of)

    2014-03-15

    In this paper, a crack detection approach is presented for detecting depth and location of cracks in beam-like structures. For this purpose, a new beam element with an arbitrary number of embedded transverse edge cracks, in arbitrary positions of beam element with any depth, is derived. The components of the stiffness matrix for the cracked element are computed using the conjugate beam concept and Betti's theorem, and finally represented in closed-form expressions. The proposed beam element is efficiently employed for solving forward problem (i.e., to gain precise natural frequencies and mode shapes of the beam knowing the cracks' characteristics). To validate the proposed element, results obtained by new element are compared with two-dimensional (2D) finite element results and available experimental measurements. Moreover, by knowing the natural frequencies and mode shapes, an inverse problem is established in which the location and depth of cracks are determined. In the inverse approach, an optimization problem based on the new finite element and genetic algorithms (GAs) is solved to search the solution. It is shown that the present algorithm is able to identify various crack configurations in a cracked beam. The proposed approach is verified through a cracked beam containing various cracks with different depths.

  3. Semiclassics of rotation and torsion.

    OpenAIRE

    Braun, Petr A.; Gerwinski, Peter; Haake, Fritz; Schomerus, Henning

    1996-01-01

    We discuss semiclassical approximations of the spectrum of the periodically kicked top, both by diagonalizing the semiclassically approximated Floquet matrix F and by employing periodic-orbit theory. In the regular case when F accounts only for a linear rotation periodic-orbit theory yields the exact spectrum. In the chaotic case the first method yields the quasienergies with an accuracy of better than 3% of the mean spacing. By working in the representation where the torsional part of the Fl...

  4. On the use of marker loads and replicas for measuring growth rates for small cracks

    Science.gov (United States)

    Swain, M. H.; Newman, J. C., Jr.

    1984-01-01

    The initiation and growth of small cracks (5-500 microns) from edge notches in 2024-T3 aluminum alloy sheets were studied under constant-amplitude loading. Two methods were used to measure crack shape and size. In the first method, striation marker bands were periodically formed along the crack front by interrupting the constant-amplitude loading by either an elevated R-ratio load sequence, or by an overload sequence. In each case the marker loading was selected so as to have minimal influence on the growth rate under the primary loading. In the second method, the surface crack length was monitored by taking surface replicas at regular intervals. The marker band techniques did not provide reliable crack length and crack shape information for cracks smaller than 2 mm. The replica technique provided accurate information for surface crack length at all crack lengths, and fracture tests on specimens with small cracks provided crack-shape information.

  5. Newton-Cartan gravity and torsion

    Science.gov (United States)

    Bergshoeff, Eric; Chatzistavrakidis, Athanasios; Romano, Luca; Rosseel, Jan

    2017-10-01

    We compare the gauging of the Bargmann algebra, for the case of arbitrary torsion, with the result that one obtains from a null-reduction of General Relativity. Whereas the two procedures lead to the same result for Newton-Cartan geometry with arbitrary torsion, the null-reduction of the Einstein equations necessarily leads to Newton-Cartan gravity with zero torsion. We show, for three space-time dimensions, how Newton-Cartan gravity with arbitrary torsion can be obtained by starting from a Schrödinger field theory with dynamical exponent z = 2 for a complex compensating scalar and next coupling this field theory to a z = 2 Schrödinger geometry with arbitrary torsion. The latter theory can be obtained from either a gauging of the Schrödinger algebra, for arbitrary torsion, or from a null-reduction of conformal gravity.

  6. Re-torsion of the ovaries

    DEFF Research Database (Denmark)

    Hyttel, Trine E W; Bak, Geske S; Larsen, Solveig B

    2015-01-01

    The increasing use of de-torsion of the ovaries may result in re-torsion. This review addresses risk of re-torsion and describes preventive strategies to avoid re-torsion in pre-menarcheal girls, and fertile and pregnant women. We clinically reviewed PubMed, Embase, Trip and Cochrane databases....... The main outcome measures were re-torsion and viability of ovary with fixation measures. A total of 38 publications including 71 girls, 363 fertile women, and 69 pregnant women were found to be relevant. All studies were case reports or case series, sometimes with non-randomized controls. The studies show...... considerable heterogeneity in design, population, management and outcome. Only four studies included more than 50 cases. In pregnancy the risk of re-torsion was as high as 19.5-37.5%; among fertile women it was 28.6%. Most articles concluded that fixation of the ovaries to the pelvic sidewall or plication...

  7. Effect of Microstructure on Torsional Fatigue Endurance of Martensitic Carbon Steel

    Science.gov (United States)

    Toyoda, Shunsuke; Ishiguro, Yasuhide; Kawabata, Yoshikazu; Sakata, Kei; Sato, Akio; Sakai, Jun'ichi

    The microstructural influence of martensitic carbon steel on torsional fatigue endurance was investigated, taking into consideration the application of high strength steel electric resistance welded (ERW) tubes to automotive structural parts. The chemical composition of the base steel alloy was 0.1-0.2%C-0.2-1.5%Si-1.3-1.9%Mn-0.01%P-0.001%S-(Cr, Mo, Ti, Nb, B). Laboratory vacuum-fused ingots were hot-rolled, heated to 1023 or 1223 K in a salt bath, and then water-quenched and tempered at 473 K. Consequently, three types of microstructure, martensite (M), martensite and ferrite (M+F), and ferrite and pearlite (F+P), were prepared. Fully reversed torsional fatigue testing was conducted with 6 mm diameter round bar specimens. Torsional fatigue endurance was found to monotonously increase with increases in the tensile strength of the specimen from 540 to 1380 MPa. The martensitic single structure and the M+F dual-phase structure showed a similar level of fatigue endurance at a tensile strength of approximately 950 MPa. However, fatigue micro-crack morphology varied slightly between them. At the surface of the M+F specimen, many small cracks were observed in addition to the main crack. Conversely, in the martensitic specimen, these small cracks were rarely observed. ΔK decreasing/increasing crack growth testing with compact tension (CT)-type specimens was also conducted. Based on these experimental results, the effect of microstructure and stress level on the initiation/propagation cycle ratio is discussed. In addition to fatigue properties, some practical properties, such as low-temperature toughness and hydrogen embrittlement resistance, were also evaluated in view of actual applications for automotive structural parts.

  8. Dirac operators and Killing spinors with torsion; Dirac-Operatoren und Killing-Spinoren mit Torsion

    Energy Technology Data Exchange (ETDEWEB)

    Becker-Bender, Julia

    2012-12-17

    On a Riemannian spin manifold with parallel skew torsion, we use the twistor operator to obtain an eigenvalue estimate for the Dirac operator with torsion. We consider the equality case in dimensions four and six. In odd dimensions we describe Sasaki manifolds on which equality in the estimate is realized by Killing spinors with torsion. In dimension five we characterize all Killing spinors with torsion and obtain certain naturally reductive spaces as exceptional cases.

  9. Intranatal Torsion of Polydactyly: A Rare Event.

    Science.gov (United States)

    Gupta, Priyanka; Neogi, Sujoy; Shukla, Amlin; Patwari, A K

    2016-01-01

    Polydactyly is one of the most common anomalies of hand and/or foot. Postnatal torsion of pedunculated polydactyly is a well known complication but intranatal torsion has been infrequently described in published literature. Here, we describe a case of pedunculated ulnar polydactyly which was gangrenous at birth due to intranatal torsion. Controversies surrounding the management of narrow pedicled pedunculated polydactyly by traditional method of suture ligation at base are also discussed.

  10. Tibial Torsion Among Filipinos: A Cadaveric Study

    Directory of Open Access Journals (Sweden)

    Villamin CAC

    2012-07-01

    Full Text Available Tibial torsion, the twisting of the tibia about its long axis, can affect rotational positioning in total knee replacement. This angle varies depending on the ethnicity of the subject. There are no published studies to date to determine the tibial torsion among Filipinos. In this study, 28 cadaveric limbs were examined. Our results show that the average tibial torsion among adult Filipinos is 28.9°.

  11. The odd side of torsion geometry

    DEFF Research Database (Denmark)

    Conti, Diego; Madsen, Thomas Bruun

    2014-01-01

    We introduce and study a notion of `Sasaki with torsion structure' (ST) as an odd-dimensional analogue of Kähler with torsion geometry (KT). These are normal almost contact metric manifolds that admit a unique compatible connection with 3-form torsion. Any odd-dimensional compact Lie group is shown......, we relate the ST structure to a KT structure on the space of leaves, and show that both the cylinder and the cone over an ST manifold are KT, although only the cylinder behaves well with respect to closedness of the torsion form. Finally, we introduce a notion of `G-moment map'. We provide criteria...

  12. Mechanical stability of roll-to-roll printed solar cells under cyclic bending and torsion

    DEFF Research Database (Denmark)

    Finn, Mickey; Martens, Christian James; Zaretski, Aliaksandr V.

    2018-01-01

    The ability of printed organic solar cells (OSCs) to survive repeated mechanical deformation is critical to large-scale implementation. This paper reports an investigation into the mechanical stability of OSCs through bending and torsion testing of whole printed modules. Two types of modules...... are used that differ slightly in thickness as well as on the basis of the electrode materials: silver nanowires or carbon-based inks. Each type of module is subjected to two different mechanical modes of deformation, bending and torsion, of several thousand cycles per module using a purpose-built robotic....... This crazing leads to eventual delamination due first to decohesion of the active layer at the edge of the modules and later to deadhesion between the PEDOT:PSS (electrode) and P3HT:PCBM (semiconductor) layers. The torsion mode imposes greater stresses than the bending mode and thus leads to failure at fewer...

  13. Effect of web openings on the structural behavior of RC beams subjected to pure torsion

    Directory of Open Access Journals (Sweden)

    Abdo Taha

    2017-01-01

    Full Text Available In the construction of modern buildings, the presence of openings became a necessity nowadays in order to accommodate the many pipes and ducts required for the different services. On the other hand, the presence of these openings in RC beams affects their structural behavior. One important behavior that needs further study would be torsion. Currently, there are no guide lines available to analyze or design RC beams with web openings under pure torsion. Thus, the main objective of this research is to investigate the behavior of simply supported RC beams with openings subjected to pure torsion. In the first part of this paper, an experimental study is conducted on seven beams subjected to pure torsion loading in order to investigate the effect of the number of openings, the spacing between stirrups, and beam depth. All beams have a constant clear span length of 1800 mm and a constant beam width of 150 mm. The beams have varying opening number and stirrups arrangement as well as varying beam depth in order to investigate the effect of these parameters on the behavior of the beams. Systematic measurements such as the cracking torque, the ultimate torque, the angle of rotation of the beam at cracking, and the angle of rotation of the beam at the ultimate load are conducted for further understanding of the beam behavior under torsion. In the second part of the paper, the experimental results are compared with the numerical results obtained using the non-linear finite element analysis program, ANSYS. Good agreement between the experimental and numerical results is found.

  14. Calculation of reinforced concrete ceilings with normal cracks accounting the Chebyshev approximation

    Directory of Open Access Journals (Sweden)

    Azizov Taljat

    2017-01-01

    Full Text Available The article shows the influence of torsional rigidity of reinforced concrete elements on the spatial work of bridges, overlappings, building frames and other complex statically indeterminate systems. It is shown that the determination of torsional stiffnesses by the existing methods assumes the obligatory presence of spatial spiral cracks, and torsional stiffness in the presence of normal cracks is not investigated. A method for determining the torsional rigidity of reinforced concrete elements is described in the presence of normal cracks in them. It is shown that this approach allows calculating the torsion of reinforced concrete elements of any cross-section and taking into account the nonlinear properties of concrete. The article also describes the use of approximation methods, in particular, the apparatus of the best Chebyshev approximation. In Table 2, the displacements obtained as a result of the approximation with the displacements obtained directly from the calculations using the Lira software using volumetric finite elements are compared. In column 6 of the table, the displacement values obtained by software package (Lira software and in column 7, the displacements obtained on the basis of approximation in the Matlab environment are given.

  15. Edge Bioinformatics

    Energy Technology Data Exchange (ETDEWEB)

    2015-08-03

    Edge Bioinformatics is a developmental bioinformatics and data management platform which seeks to supply laboratories with bioinformatics pipelines for analyzing data associated with common samples case goals. Edge Bioinformatics enables sequencing as a solution and forward-deployed situations where human-resources, space, bandwidth, and time are limited. The Edge bioinformatics pipeline was designed based on following USE CASES and specific to illumina sequencing reads. 1. Assay performance adjudication (PCR): Analysis of an existing PCR assay in a genomic context, and automated design of a new assay to resolve conflicting results; 2. Clinical presentation with extreme symptoms: Characterization of a known pathogen or co-infection with a. Novel emerging disease outbreak or b. Environmental surveillance

  16. Stress-intensity factor equations for cracks in three-dimensional finite bodies subjected to tension and bending loads

    Science.gov (United States)

    Newman, J. C., Jr.; Raju, I. S.

    1984-01-01

    Stress intensity factor equations are presented for an embedded elliptical crack, a semielliptical surface crack, a quarter elliptical corner crack, a semielliptical surface crack along the bore of a circular hole, and a quarter elliptical corner crack at the edge of a circular hole in finite plates. The plates were subjected to either remote tension or bending loads. The stress intensity factors used to develop these equations were obtained from previous three dimensional finite element analyses of these crack configurations. The equations give stress intensity factors as a function of parametric angle, crack depth, crack length, plate thickness, and, where applicable, hole radius. The ratio of crack depth to plate thickness ranged from 0 to 1, the ratio of crack depth to crack length ranged from 0.2 to 2, and the ratio of hole radius to plate thickness ranged from 0.5 to 2. The effects of plate width on stress intensity variation along the crack front were also included.

  17. Simultaneous acute appendicitis with right testicular torsion

    Directory of Open Access Journals (Sweden)

    Tanveer Akhtar

    2012-01-01

    Full Text Available We present a child with both acute appendicitis and torsion of the right testis presenting at the same time. Testicular torsion possibly occurring due to vomiting in acute appendicitis so far has not been reported in the literature.

  18. Torsional vibrations of infinite composite poroelastic cylinders

    African Journals Online (AJOL)

    user

    Abstract. A study of torsional vibrations of an infinite composite poroelastic circular solid cylinder made of two different materials is made. The frequency equation of such torsional vibrations is obtained following analytical model based on Biot's theory of wave propagation in liquid saturated porous media. Each dilatation of ...

  19. EXPERIMENTAL AND ANALYTICAL COMPARISON OF TORSION ...

    African Journals Online (AJOL)

    This study investigated the effect of combined actions of torsional moments, bending moments and shear forces in reinforced concrete beams with concrete compressive strength of 30N/mm2.The ultimate torsional moments, bending moments, and shear forces of the beams were determined experimentally, through a simple ...

  20. Misdiagnosed Adult Testicular Torsion: Case Report | Ndaguatha ...

    African Journals Online (AJOL)

    Adult testicular torsion is thought to be rare if not relatively unusual. The rarity could be an underestimation since there are many episodes of missed torsions and misdiagnosis with other conditions of acute scrotum despite the now widespread ultra sound availability that are being reported in the literature. Such a ...

  1. Teenage testicular torsion. | Onuigbo | International Journal of ...

    African Journals Online (AJOL)

    Aim: To study testicular torsion in teenagers in the Igbo community. Method: A retrospective study was carried out as regards requests for pathological examination of specimens received at a Regional Reference Laboratory based in Enugu. Results: Over a period of 30 years, 28 surgical specimens of testicular torsion in ...

  2. Appendicular Torsion | Dubhashi | Nigerian Journal of Surgery

    African Journals Online (AJOL)

    . It can be primary or secondary. This is a case report of 52-year-old female with 180° anti-clockwise rotation of the appendix. Torsion can further leads to strangulation and infarction of the organ. Appendicular torsion could be included in the ...

  3. Right paratesticular abscess mimicking neonatal testicular torsion ...

    African Journals Online (AJOL)

    U.O. Ezomike

    Abstract. The clinical presentation of neonatal paratesticular abscess may closely resemble that of, neonatal testicular torsion and the use of scrotal ultrasonography to differentiate the two has low, sensitivity. We propose early operative treatment of suspected neonatal testicular torsion to salvage, the testicle in cases of ...

  4. TESTICULAR TORSION: CASE REPORT R. T. KUREMU ...

    African Journals Online (AJOL)

    hi-tech

    2004-05-05

    May 5, 2004 ... Possible precipitating factors in testicular torsion include cold, exercise, sexual fore play, abnormal position during sleep or sitting, sudden closing of thighs, trauma, tight pants, coughing and defection(2). Early diagnosis remains a clinical challenge. Even though the clinical features of torsion are typical, the.

  5. Evaluating Pavement Cracks with Bidimensional Empirical Mode Decomposition

    Directory of Open Access Journals (Sweden)

    Nii Attoh-Okine

    2008-05-01

    Full Text Available Crack evaluation is essential for effective classification of pavement cracks. Digital images of pavement cracks have been analyzed using techniques such as fuzzy set theory and neural networks. Bidimensional empirical mode decomposition (BEMD, a new image analysis method recently developed, can potentially be used for pavement crack evaluation. BEMD is an extension of the empirical mode decomposition (EMD, which can decompose nonlinear and nonstationary signals into basis functions called intrinsic mode functions (IMFs. IMFs are monocomponent functions that have well-defined instantaneous frequencies. EMD is a sifting process that is nonparametric and data driven; it does not depend on an a priori basis set. It is able to remove noise from signals without complicated convolution processes. BEMD decomposes an image into two-dimensional IMFs. The present paper explores pavement crack detection using BEMD together with the Sobel edge detector. A number of images are filtered with BEMD to remove noise, and the residual image analyzed with the Sobel edge detector for crack detection. The results are compared with results from the Canny edge detector, which uses a Gaussian filter for image smoothing before performing edge detection. The objective is to qualitatively explore how well BEMD is able to smooth an image for more effective edge detection with the Sobel method.

  6. On the use of marker loads and replicas for measuring growth rates for small cracks

    Science.gov (United States)

    Swain, M. H.; Newman, J. C., Jr.

    1984-01-01

    The initiation and growth of small cracks (5-500 microns m) from edge notches in 2024-T3 aluminum alloy sheets were studied under constant amplitude loading. Two methods were used to measure crack shape and size. In the first method, striation marker bands were periodically formed along the crack front by interrupting the constant amplitude loading by either an elevated R-ratio load sequence, or by an overload sequence. In the second method, the surface crack length was monitored by taking surface replicas at regular intervals. The marker band techniques did not provide reliable crack length and crack shape information for cracks smaller than 2 mm. The replica technique provided accurate information for surface crack length at all crack lengths, and fracture tests on specimens with small cracks provided crack-shape information. Crack growth rates were plotted against the stress intensity factor ranges. The results exhibited the small crack effect, in that the small cracks grew faster than large cracks at the same stress-intensity factor range. A crack closure model was also used to analyze the growth of small cracks from small (inclusion) defects at the notch surface.

  7. The impact of clinical use on the torsional behavior of Reciproc and WaveOne instruments

    Directory of Open Access Journals (Sweden)

    Rafael Rodrigues Soares de MAGALHÃES

    Full Text Available ABSTRACT Torsional overload is a fracture representative parameter for instruments in single-file techniques. Objective The aim of this study was to assess the influence of clinical use, in vivo, on the torsional behavior of Reciproc and WaveOne instruments considering the possibility that they degraded with use. Material and Methods Diameter at each millimeter, pitch length, and area at 3 mm from the tip were determined for both types of instruments. Twenty-four instruments, size 25, 0.08 taper, of each system were divided into two groups (n=12 each: Control Group (CG, in which new Reciproc (RC and WaveOne Primary (WO instruments were tested in torsion until rupture based on ISO 3630-1; and Experimental Group (EG, in which each new instrument was clinically used to clean and shape the root canals of one molar. After clinical use, the instruments were analyzed using optical and scanning electron microscopy and subsequently tested in torsion until fracture. Data were analyzed using one-way analysis of variance at a=.05. Results WO instruments showed significantly higher mean values of cross-sectional area A3 (P=0.000 and smaller pitch lengths than RC instruments with no statistically significant differences in the diameter at D3 (P=0.521. No significant differences in torsional resistance between the RC and WO new instruments (P=0.134 were found. The clinical use resulted in a tendency of reduction in the maximum torque of the analyzed instruments but no statistically significant difference was observed between them (P=0.327. During the preparation of the root canals, two fractured RC instruments and longitudinal and transversal cracks in RC and WO instruments were observed through SEM analysis. Conclusion After clinical use, no statistically significant reduction in the torsional resistance was observed.

  8. 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...

  9. Effect of fluid salinity on subcritical crack propagation in calcite

    Science.gov (United States)

    Rostom, Fatma; Røyne, Anja; Dysthe, Dag Kristian; Renard, François

    2013-01-01

    The slow propagation of cracks, also called subcritical crack growth, is a mechanism of fracturing responsible for a ductile deformation of rocks under crustal conditions. In the present study, the double-torsion technique was used to measure the effect of fluid chemistry on the slow propagation of cracks in calcite single crystals at room temperature. Time-lapse images and measurements of force and load-point displacement allowed accurate characterization of crack velocities in a range of 10- 8 to 10- 4 m/s. Velocity curves as a function of energy-release rates were obtained for different fluid compositions, varying NH4Cl and NaCl concentrations. Our results show the presence of a threshold in fluid composition, separating two regimes: weakening conditions where the crack propagation is favored, and strengthening conditions where crack propagation slows down. We suggest that electrostatic surface forces that modify the repulsion forces between the two surfaces of the crack may be responsible for this behavior.

  10. Crack problem for a bulk superconductor with nonsuperconducting inclusions under an electromagnetic force

    Directory of Open Access Journals (Sweden)

    Feng Xue

    2015-04-01

    Full Text Available In this paper, the flux-pinning-induced elastic stress analysis considering the crack-inclusion interaction is carried out for a bulk superconductor in the magnetization process. A approximate model for the crack problem of a bulk superconductor with nonsuperconducting inclusions (particles dispersed in a superconducting matrix is described. The crack is simulated as a continuous distribution of edge dislocations in the solution procedure. The obtained results show that, the shear modulus, inclusion-crack size, inclusion-crack distance, and also the magnetic field have obvious effects on the stress intensity factors (SIFs at the crack tips of the superconductor.

  11. Thermoelastic damping in torsion microresonators with coupling effect between torsion and bending

    Science.gov (United States)

    Tai, Yongpeng; Li, Pu; Fang, Yuming

    2014-02-01

    Predicting thermoelastic damping (TED) is crucial in the design of high Q MEMS resonators. In the past, there have been few works on analytical modeling of thermoelastic damping in torsion microresonators. This could be related to the assumption of pure torsional mode for the supporting beams in the torsion devices. The pure torsional modes of rectangular supporting beams involve no local volume change, and therefore, they do not suffer any thermoelastic loss. However, the coupled motion of torsion and bending usually exists in the torsion microresonator when it is not excited by pure torque. The bending component of the coupled motion causes flexural vibrations of supporting beams which may result in significant thermoelastic damping for the microresonator. This paper presents an analytical model for thermoelastic damping in torsion microresonators with the coupling effect between torsion and bending. The theory derives a dynamic model for torsion microresonators considering the coupling effect, and approximates the thermoelastic damping by assuming the energy loss to occur only in supporting beams of flexural vibrations. The thermoelastic damping obtained by the present model is compared to the measured internal friction of single paddle oscillators. It is found that thermoelastic damping contributes significantly to internal friction for the case of the higher modes at room temperature. The present model is validated by comparing its results with the finite-element method (FEM) solutions. The effects of structural dimensions and other parameters on thermoelastic damping are investigated for the representative case of torsion microresonators.

  12. Improving Tensile and Compressive Properties of an Extruded AZ91 Rod by the Combined Use of Torsion Deformation and Aging Treatment.

    Science.gov (United States)

    Song, Bo; Wang, Chunpeng; Guo, Ning; Pan, Hucheng; Xin, Renlong

    2017-03-10

    In this study, AZ91 magnesium alloy rods were used to investigate the effects of torsion deformation on microstructure and subsequent aging behavior. Extruded AZ91 rod has a uniform microstructure and typical fiber texture. Torsion deformation can generate a gradient microstructure on the cross-section of the rod. After torsion, from the center to the edge in the cross-section of the rod, both stored dislocations and area fraction of {10-12} twins gradually increase, and the basal pole of the texture tends to rotate in the ED direction. Direct aging usually generates coarse discontinuous precipitates and fine continuous precipitates simultaneously. Both twin structures and dislocations via torsion deformation can be effective microstructures for the nucleation of continuous precipitates during subsequent aging. Thus, aging after torsion can promote continuous precipitation and generate gradient precipitation characteristics. Both aging treatment and torsion deformation can reduce yield asymmetry, and torsion deformation enhances the aging hardening effect by promoting continuous precipitation. Therefore, combined use of torsion deformation and aging treatment can effectively enhance the yield strength and almost eliminate the yield asymmetry of the present extruded AZ91 rod. Finally, the relevant mechanisms are discussed.

  13. Acute and intermittent testicular torsion: Analysis of presentation ...

    African Journals Online (AJOL)

    Background: Testicular torsion compromises the blood supply to the testes and may result in testicular loss or damage if not dealt with promptly. It can occur either as acute testicular torsion (ATT) or intermittent testicular torsion (ITT). This study examines the presentation, management, and outcome of adult testicular torsion.

  14. Torsion of the vermiform appendix: A case report | Wani | Internet ...

    African Journals Online (AJOL)

    Torsion of the vermiform appendix is a rare condition with few cases reported in the literature. Various factors predispose to torsion. Various factors predispose to torsion. We report a case of primary torsion of the vermiform appendix. The clinical presentation was indistinguishable from acute appendicitis and the diagnosis ...

  15. Environmental stress cracking of PVC and PVC-CPE - Part III Crack growth

    NARCIS (Netherlands)

    Breen, J.

    1995-01-01

    The fracture toughness of Polyvinylchloride (PVC) and PVC modified with 10% chlorinated polyethylene (PVC-CPE) was studied in vapour and in liquid environments by crack growth measurements on single-edge notch specimens under three-point bending at 23°C. In addition, some results obtained in air at

  16. Cocaine (Coke, Crack) Facts

    Science.gov (United States)

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

  17. Crack sealer fill characteristics.

    Science.gov (United States)

    2010-06-01

    Laboratory testing was conducted to determine the extent of crack fill for crack sealers composed of methyl methacrylate, : epoxy, urethane, and high molecular weight methacrylate. The test specimens consisted of eight-inch long concrete : cylinders ...

  18. Ultrasonographic diagnosis of adnexal torsion in pregnancy

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Eun Ju; Kim, Jai Keun [Ajou University School of Medicine, Suwon (Korea, Republic of)

    2002-06-15

    To evaluate the usefulness of ultrasonography (US) and color Doppler sonography (CDS) in the diagnosis of adnexal torsion in pregnancy.US and CDS findings of 31 patients with surgically proven adnexal torsion during pregnancy were retrospectively reviewed. On US, the presence of twisted vascular pedicle (TVP), ovary, or adnexal mass were evaluate while te presence of blood flow within the TVP and ovary or adnexal mass were evaluated on CDS. Adnexal torsion was diagnosed by the detection of TVP and absent flow to the ovary, and the diagnostic accuracy of US was assessed. TVP was detectable on US in 25 of 31 cases (80.7%) with adnexal torsion during pregnancy. In four cases, torsion of the ovary was seen as the multiple peripherally located in the enlarged ovary, and in one case, torsion of the hyperstimulated ovary appeared as multiple cysts measuring between 2 to 7 cm in diameter combined with swollen parenchyma. Ovarian mass was detected on the same side of the torsion in 27 cases, the diameter ranging from 3.5 to 22 cm (mean=8.4 cm); 15 of them were mostly cystic while nine masses with the mixture of cystic and solid portions and two masses consisted of solid portion were also observed on US. The blood flow was present in the twisted vessels on CDS in 13 of 25 cases with TVP, and flow within the ovary or an adnexal mass was seen in 12 cases. The remaining 12 cases showed no flow within TVP and the ovary. In six cases with no visible TVP, the blood flow of the ovary was present in five cases and absent in one case. Torsion was confidently diagnosed in 25 cases with the visible TVP and in one case with absent ovarian flow on US and CDS, showing the diagnostic accuracy of 83.9%. US and CDS can be useful diagnostic modalities in the diagnosis of adnexal torsion in pregnancy.

  19. Left-sided omental torsion: CT appearance

    Energy Technology Data Exchange (ETDEWEB)

    Aoun, N.; Haddad-Zebouni, S.; Slaba, S.; Ghossain, M. [Hotel-Dieu de France Hospital, Beirut (Lebanon). Dept. of Radiology; Noun, R. [Hotel-Dieu de France Hospital, Beirut (Lebanon). Dept. of General Surgery

    2001-01-01

    A 34-year-old male presented with exquisite left flank pain. Computed tomography showed a hyperdense vascular structure surrounded by whirling linear streaks situated in the greater omentum under the splenic flexure of the colon. Omental stranding extended caudally into the pelvis where part of the inflamed omentum entered a left inguinal hernia sac. Surgery revealed left-sided torsion of the greater omentum. Left-sided omental torsion is infrequent and pre-operative diagnosis is rarely established. The CT findings of an omental fatty mass with a whirling pattern is characteristic of omental torsion. Preoperative diagnosis is important because conservative management has been suggested. (orig.)

  20. Torsion and entropy driven denaturation of DNA

    Energy Technology Data Exchange (ETDEWEB)

    Roy, Subhamoy Singha, E-mail: ssroy.science@gmail.com [Department of Physics, JIS College of Engineering (Autonomous), West Bengal University of Technology, Kalyani, Nadia 741235 (India); Bandyopadhyay, Pratul, E-mail: b_pratul@yahoo.co.in [Physics and Applied Mathematics Unit, Indian Statistical Institute, 203 B.T. Road, Kolkata 700108 (India)

    2013-11-29

    A unified theory of the denaturation transition having torsion energy as the control parameter has been formulated here in the framework of the mapping of a DNA molecule onto a Heisenberg spin system. The torsion energy incorporates the torque, tension and temperature, the latter being associated with the twist angle. The denaturation transition can be mapped onto the quantum phase transition induced by a quench when the temperature effect is incorporated in the quench time and torsion takes the role of the external field. The denaturation transition occurs when the entanglement entropy of the spin system vanishes.

  1. Measurement of tibial torsion by computer tomography

    Energy Technology Data Exchange (ETDEWEB)

    Jend, H.H.; Heller, M.; Dallek, M.; Schoettle, H. (Hamburg Univ. (Germany, F.R.))

    1981-01-01

    A CT procedure for objective measurements of tibial torsion independent of axial rotation in the nearby joints is described. Transverse sections in defined planes of the tibia permit easy calculation of normal and abnormal congenital or posttraumatic angles of torsion. In 69 limbs normal tibial torsion was 40/sup 0/+-9/sup 0/. In a series of 42 limbs with complicated healing of a fracture of both bones of the leg it is shown that tibial maltorsion is a deformity which in most cases leads to arthrosis of the ankle joint.

  2. Effects of External Hydrogen on Hydrogen Transportation and Distribution Around the Fatigue Crack Tip in Type 304 Stainless Steel

    Science.gov (United States)

    Chen, Xingyang; Zhou, Chengshuang; Cai, Xiao; Zheng, Jinyang; Zhang, Lin

    2017-10-01

    The effects of external hydrogen on hydrogen transportation and distribution around the fatigue crack tip in type 304 stainless steel were investigated by using hydrogen microprint technique (HMT) and thermal desorption spectrometry. HMT results show that some silver particles induced by hydrogen release are located near the fatigue crack and more silver particles are concentrated around the crack tip, which indicates that hydrogen accumulates in the vicinity of the crack tip during the crack growth in hydrogen gas environment. Along with the crack propagation, strain-induced α' martensite forms around the crack tip and promotes hydrogen invasion into the matrix, which will cause the crack initiation and propagation at the austenite/ α' martensite interface. In addition, the hydrogen content in the vicinity of the crack tip is higher than that at the crack edge far away from the crack tip, which is related to the stress state and strain-induced α' martensite.

  3. Torsional behavior of reinforced concrete T-beams strengthened with CFRP strips

    Directory of Open Access Journals (Sweden)

    Rafid Saeed Atea

    2017-12-01

    This work aims at studying the strengthening of T beams in torsion by using carbon fiber reinforced polymer (CFRP. The CFRP laminates will be used for strengthening previous to loading. The experimental work includes investigation of twelve reinforced concrete T beams tested under pure torsion. The first beam was the reference beam, without CFRP. The second beam was a simple concrete beam. The remaining ten beams. Variables considered in the test program include; effect of flange strengthening, effect of fiber orientation (90° or 45° CFRP strips with respect to the longitudinal axis, effect of using additional longitudinal CFRP strips with transverse CFRP strips, effect of bolt anchoring CFRP strips in the web and flange and effect of continuous CFRP strips between web and flange (isolated T section. Test results were discussed based on torque – twist behavior, beam elongations, CFRP strain, concrete strain and influence of CFRP on cracking torque, ultimate torque and failure modes.

  4. Edge Detection,

    Science.gov (United States)

    1985-09-01

    PROJECT. T ASK0 Artificial Inteligence Laboratory AREA It WORK UNIT NUMBERS V 545 Technology Square ( Cambridge, HA 02139 I I* CONTOOL1LIN@4OFFICE NAME...ARD-A1t62 62 EDGE DETECTION(U) NASSACNUSETTS INST OF TECH CAMBRIDGE 1/1 ARTIFICIAL INTELLIGENCE LAB E C HILDRETH SEP 85 AI-M-8 N99SI4-8S-C-6595...used to carry out this analysis. cce~iO a N) ’.~" D LI’BL. P p ------------ Sj. t i MASSACHUSETTS INSTITUTE OF TECHNOLOGY i ARTIFICIAL INTELLIGENCE

  5. Torsion vehicle model test for automotive vehicle

    Science.gov (United States)

    Nor, M. K. Mohd; Ho, C. S.; Ma'at, N.

    2017-04-01

    Torsion vehicle model test of Simple Structural Surfaces (SSS) model for automotive vehicle sedan is proposed in this paper to demonstrate the importance of providing continuous load path within the vehicle structures. The proposed approach is relatively easy to understand as compared to Finite Element Method (FEM). The results prove that the proposed vehicle model test is capable to show that a satisfactory load paths can five a sufficient structural stiffness within the vehicle structure. It is clearly observed that the global torsion stiffness reduces significantly when only one panel is removed from the complete SSS model. The results also five a food agreement with respect to the theoretical hypothesis as the structure is less stiff in torsion in an open section condition. The SSS model and the corresponding torsion test is obviously useful to give an overview of vehicle structural integrity. It can be potentially integrated with FEM to speed up the design process of automotive vehicle.

  6. Torsion and geometrostasis in covariant superstrings

    Energy Technology Data Exchange (ETDEWEB)

    Zachos, C.

    1985-01-01

    The covariant action for freely propagating heterotic superstrings consists of a metric and a torsion term with a special relative strength. It is shown that the strength for which torsion flattens the underlying 10-dimensional superspace geometry is precisely that which yields free oscillators on the light cone. This is in complete analogy with the geometrostasis of two-dimensional sigma-models with Wess-Zumino interactions. 13 refs.

  7. The natural evolution of internal tibial torsion.

    Science.gov (United States)

    Weiner, D S; Weiner, S D

    1979-11-01

    Faced with a confusing body of literature concerning the necessity for treatment of internal tibial torsion, the authors conducted a retrospective review of 395 consecutive cases of manifest intoeing arising from internal tibial torsion. An additional Group of 200 uninvolved teenagers served as older controls. The conclusion drawn supports an attitude of patience and observation as spontaneous resolution is to be routinely expected by skeletal maturity. Copyright 2013, SLACK Incorporated.

  8. Vaidya-like exact solutions with torsion

    CERN Document Server

    Blagojević, M

    2015-01-01

    Starting from the Oliva-Tempo-Troncoso black hole, a solution of the Bergshoeff-Hohm-Townsend massive gravity, a new class of the Vaidya-like exact solutions with torsion is constructed in the three-dimensional Poincar\\'e gauge theory. A particular subclass of these solutions is shown to possess the asymptotic conformal symmetry. The related canonical energy contains a contribution stemming from torsion.

  9. Torsion of Wandering Gallbladder following Colonoscopy

    Directory of Open Access Journals (Sweden)

    Sean R. Warfe

    2013-01-01

    Full Text Available Torsion of the gallbladder is an uncommon condition that may present as an acute abdomen. Its preoperative diagnosis can often be challenging due to its variable presentation, with specific sonographic signs seen infrequently. We describe, to our knowledge, the first case of torsion of a wandering gallbladder following a colonoscopy in a 69-year-old female who presented with acute abdominal pain after procedure. This was discovered intraoperatively, and after a subsequent cholecystectomy, she had an uncomplicated recovery.

  10. Attentional Modulation of Eye Torsion Responses

    Science.gov (United States)

    Stevenson, Scott B.; Mahadevan, Madhumitha S.; Mulligan, Jeffrey B.

    2016-01-01

    Eye movements generally have both reflexive and voluntary aspects, but torsional eye movements are usually thought of as a reflexive response to image rotation around the line of sight (torsional OKN) or to head roll (torsional VOR). In this study we asked whether torsional responses could be modulated by attention in a case where two stimuli rotated independently, and whether attention would influence the latency of responses. The display consisted of rear-projected radial "pinwheel" gratings, with an inner annulus segment extending from the center to 22 degrees eccentricity, and an outer annulus segment extending from 22 degrees out to 45 degrees eccentricity. The two segments rotated around the center in independent random walks, stepping randomly 4 degrees clockwise or counterclockwise at 60 Hz. Subjects were asked to attend to one or the other while keeping fixation steady at the center of the display. To encourage attention on one or the other segment of the display, subjects were asked to move a joystick in synchrony with the back and forth rotations of one part of the image while ignoring the other. Eye torsion was recorded with the scleral search coil technique, sampled at 500 Hz. All four subjects showed roughly 50% stronger torsion responses to the attended compared to unattended segments. Latency varied from 100 to 150 msec across subjects and was unchanged by attention. These findings suggest that attention can influence eye movement responses that are not typically under voluntary control.

  11. Living edge

    DEFF Research Database (Denmark)

    Earon, Ofri

    2014-01-01

    was originally introduced to enhance indoor qualities including light and view. Throughout the paper, it is argued that these ecological motives have grown to architectural and urban dimensions. The paper analyzes the characteristics and potentials of these dimensions and their interconnections. The paper...... on the ground level, but there is a lack of recognition in the significance of communicative characters as well at the higher part of the edge. The city’s planning approach is “Consider urban life before urban space. Consider urban space before buildings” This urban strategy neglects the possible architectural...... contribution to the street atmosphere and its effect on urban life. Bay balcony has been a common architectural element in Copenhagen’s residential buildings, since the end of the twenties. It is a domestic border with an architectural thickness combining window, door, windowsill and balcony. The bay balcony...

  12. Torsional oscillations of strange stars

    Directory of Open Access Journals (Sweden)

    Mannarelli Massimo

    2014-01-01

    Full Text Available Strange stars are one of the hypothetical compact stellar objects that can be formed after a supernova explosion. The existence of these objects relies on the absolute stability of strange collapsed quark matter with respect to standard nuclear matter. We discuss simple models of strange stars with a bare quark matter surface, thus standard nuclear matter is completely absent. In these models an electric dipole layer a few hundreds Fermi thick should exist close to the star surface. Studying the torsional oscillations of the electrically charged layer we estimate the emitted power, finding that it is of the order of 1045 erg/s, meaning that these objects would be among the brightest compact sources in the heavens. The associated relaxation times are very uncertain, with values ranging between microseconds and minutes, depending on the crust thickness. Although part of the radiated power should be absorbed by the electrosphere surrounding the strange star, a sizable fraction of photons should escape and be detectable.

  13. Use of NDE to Evaluate Reflection Cracking in Airfield Pavements

    Science.gov (United States)

    1985-11-01

    formed at the crack, edge, or joint. This void is a zone of weakness. If remedial measures such as undersealing are not performed prior to overlaying...often appear in fabrics as they are being placed. These wrinkles should be remedied prior to overlay placement to prevent stress concentrations from...concluded that nonwoven polypropylene fabric was the best interlayer system for the prevention of reflection cracking in asphalt over- lays of

  14. Hydroxyl free radical production during torsional phacoemulsification.

    Science.gov (United States)

    Aust, Steven D; Hebdon, Thomas; Humbert, Jordan; Dimalanta, Ramon

    2010-12-01

    To quantitate free radical generation during phacoemulsification using an ultrasonic phacoemulsification device that includes a torsional mode and evaluate tip designs specific to the torsional mode. Chemistry and Biochemistry Department, Utah State University, Logan, Utah, USA. Experimental study. Experiments were performed using the Infiniti Vision System and OZil handpiece. Hydroxyl radical concentrations in the aspirated irrigation solution during torsional phacoemulsification were quantitated as nanomolar malondialdehyde (nM MDA) and determined spectrophotometrically using the deoxyribose assay. The mean free radical production during phacoemulsification with torsional modality at 100% amplitude was 30.1 nM MDA ± 5.1 (SD) using a 0.9 mm 45-degree Kelman tapered ABS tip. With other tip designs intended for use with the torsional modality, free radical production was further reduced when fitted with the 0.9 mm 45-degree Kelman mini-flared ABS tip (13.2 ± 5.6 nM MDA) or the 0.9 mm 45-degree OZil-12 mini-flared ABS tip (14.3 ± 6.7 nM MDA). Although the measurements resulting from the use of the latter 2 tips were not statistically significantly different (P ≈ .25), they were different from those of the tapered tip (P<.0001). The MDA concentration in the aspirated irrigation solution using the torsional modality was approximately one half that reported for the handpiece's longitudinal modality in a previous study using the same bent-tip design (Kelman tapered, P<.0001). The level of MDA was further reduced approximately one half with torsional-specific tips. Copyright © 2010 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  15. Eliminating cracking during drying.

    Science.gov (United States)

    Jin, Qiu; Tan, Peng; Schofield, Andrew B; Xu, Lei

    2013-03-01

    When colloidal suspensions dry, stresses build up and cracks often occur -a phenomenon undesirable for important industries such as paint and ceramics. We demonstrate an effective method which can completely eliminate cracking during drying: by adding emulsion droplets into colloidal suspensions, we can systematically decrease the amount of cracking, and eliminate it completely above a critical droplet concentration. Since the emulsion droplets eventually also evaporate, our technique achieves an effective function while making little changes to the component of final product, and may therefore serve as a promising approach for cracking elimination. Furthermore, adding droplets also varies the speed of air invasion and provides a powerful method to adjust drying rate. With the effective control over cracking and drying rate, our study may find important applications in many drying- and cracking-related industrial processes.

  16. A new torsion control mechanism induced by blood circulation in dragonfly wings.

    Science.gov (United States)

    Hou, Dan; Yin, Yajun; Zhong, Zheng; Zhao, Hongxiao

    2015-02-06

    A new mechanism to generate the torque of flapping dragonfly wings is disclosed in this paper. The concept is inspired by blood circulation in insect wings. The blood flowing in veins induces Coriolis forces in the flapping wings. The Coriolis forces acting on veins are of opposite directions when blood flows in and out. The opposite Coriolis forces generate torsional moment to the wing, especially in the leading-edge part. To estimate the time-varying torque induced by the blood circulation, a simplified U-tube model is designed. A three-dimensional finite element model of the wing is developed to analyze the dynamic behaviors under this torque. The dragonfly wing is in favor of torsional deformation because the corrugated structure is of high flexural rigidity in the spanwise direction but is of low torsional rigidity in the chordwise direction. In both the downstroke and upstroke, the twist of the leading-edge part causes the sections to camber spontaneously. Such a kind of deformation is found to be of great importance to improve aerodynamic efficiency. In addition, it also compensates for the disadvantageous bending deformation caused by air pressure in flapping flight. These results are important for better understanding of the multifunctional structures of dragonfly wings and may give some inspiration to the bionics of flapping-wing micro air vehicles (FMAVs).

  17. Ultimate Strength of Ship Hulls under Torsion

    DEFF Research Database (Denmark)

    Paik, Jeom Kee; Thayamballi, Anil K.; Pedersen, Preben Terndrup

    2001-01-01

    For a ship hull with large deck openings such as container vessels and some large bulk carriers, the analysis of warping stresses and hatch opening deformations is an essential part of ship structural analyses. It is thus of importance to better understand the ultimate torsional strength characte......For a ship hull with large deck openings such as container vessels and some large bulk carriers, the analysis of warping stresses and hatch opening deformations is an essential part of ship structural analyses. It is thus of importance to better understand the ultimate torsional strength...... characteristics of ships with large hatch openings. The primary aim of the present study is to investigate the ultimate strength characteristics of ship hulls with large hatch openings under torsion. Axial (warping) as well as shear stresses are normally developed for thin-walled beams with open cross sections...... subjected to torsion. A procedure for calculating these stresses is briefly described. As an illustrative example, the distribution and magnitude of warping and shear stresses for a typical container vessel hull cross section under unit torsion is calculated by the procedure. By theoretical and numerical...

  18. Crack propagation modeling using Peridynamic theory

    Science.gov (United States)

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

    2016-04-01

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

  19. Normal and abnormal torsional development in children.

    Science.gov (United States)

    Fabry, G; Cheng, L X; Molenaers, G

    1994-05-01

    This study presents findings in a series of 123 children with intoeing gait. The intoeing was caused by increased femoral anteversion (IFA) in 70% of the cases, and internal tibial torsion (ITT) in 30%. Rotation of the hips, thigh-foot angle, Q-angle, and computed tomography measured anteversion and tibial torsion divided the two groups very clearly. In the IFA group, 40.3% of the patients presented with an externally rotated tibia and 59.7% had an internally rotated tibia. In the ITT group, the anteversion was normal for age and the tibial torsion was significantly decreased. Eighty children who corrected their intoeing gait, and of whom 83.4% had IFA, were also reviewed: a decrease in anteversion was observed in 20.5% of the patients; 62.9% showed no decrease in anteversion.

  20. Torsional rigidity of submanifolds with controlled geometry

    DEFF Research Database (Denmark)

    Hurtado, Ana; Markvorsen, Steen; Palmer, Vicente

    2009-01-01

    We prove explicit upper and lower bounds for the torsional rigidity of extrinsic domains of submanifolds ^m$ with controlled radial mean curvature in ambient Riemannian manifolds ^n$ with a pole $ and with sectional curvatures bounded from above and from below, respectively. These bounds are given...... in terms of the torsional rigidities of corresponding Schwarz symmetrizations of the domains in warped product model spaces. Our main results are obtained using methods from previously established isoperimetric inequalities, as found in e.g. [MP4] and [MP5]. As in [MP4] we also characterize the geometry...... of those situations in which the bounds for the torsional rigidity are actually attained and study the behavior at infinity of the so-called geometric average of the mean exit time for Brownian motion....

  1. Torsional wave propagation in solar tornadoes

    Science.gov (United States)

    Vasheghani Farahani, S.; Ghanbari, E.; Ghaffari, G.; Safari, H.

    2017-03-01

    Aims: We investigate the propagation of torsional waves in coronal structures together with their collimation effects in the context of magnetohydrodynamic (MHD) theory. The interplay of the equilibrium twist and rotation of the structure, e.g. jet or tornado, together with the density contrast of its internal and external media is studied to shed light on the nature of torsional waves. Methods: We consider a rotating magnetic cylinder embedded in a plasma with a straight magnetic field. This resembles a solar tornado. In order to express the dispersion relations and phase speeds of the axisymmetric magnetohydrodynamic waves, the second-order thin flux tube approximation is implemented for the internal medium and the ideal MHD equations are implemented for the external medium. Results: The explicit expressions for the phase speed of the torsional wave show the modification of the torsional wave speed due to the equilibrium twist, rotation, and density contrast of the tornado. The speeds could be either sub-Alfvénic or ultra-Alfvénic depending on whether the equilibrium twist or rotation is dominant. The equilibrium twist increases the phase speed while the equilibrium rotation decreases it. The good agreement between the explicit versions for the phase speed and that obtained numerically proves adequate for the robustness of the model and method. The density ratio of the internal and external media also play a significant role in the speed and dispersion. Conclusions: The dispersion of the torsional wave is an indication of the compressibility of the oscillations. When the cylinder is rotating or twisted, in contrast to when it only possesses a straight magnetic field, the torsional wave is a collective mode. In this case its phase speed is determined by the Alfvén waves inside and outside the tornado.

  2. Crack and Kids.

    Science.gov (United States)

    Besharov, Douglas J.

    1990-01-01

    Reviews problems of crack-addicted babies. Suggests the following areas for grant support: (1) results of fetal exposure; (2) medical treatment and foster care for newborns; (3) research on behavioral changes resulting from crack use; (4) public awareness materials; (5) education for addicted mothers who keep their babies; and (6) removing babies…

  3. Updating a cracked database

    NARCIS (Netherlands)

    S. Idreos (Stratos); M.L. Kersten (Martin); S. Manegold (Stefan)

    2007-01-01

    textabstractA cracked database is a datastore continuously reorganized based on operations being executed. For each query, the data of interest is physically reclustered to speed-up future access to the same, overlapping or even disjoint data. This way, a cracking DBMS self-organizes and adapts

  4. Cracking behavior of tungsten armor under ELM-like thermal shock loads: A computational study

    National Research Council Canada - National Science Library

    Li, Muyuan; Werner, Ewald; You, Jeong-Ha

    2015-01-01

    In this work, the cracking behavior of tungsten under edge-localized mode (ELM)-like thermal shock loads was investigated on the basis of a rigorous computational fracture mechanical analysis combined with the finite element method...

  5. Spontaneous lung lobe torsion in two pugs.

    Science.gov (United States)

    Rooney, M B; Lanz, O; Monnet, E

    2001-01-01

    Two, young adult, male pugs presented for spontaneous left-cranial lung lobe torsions. Clinical signs associated with these two cases included increased weakness, increased respiratory effort, tachypnea, acute collapse, lethargy, anorexia, and cyanosis. The torsed lung lobes were excised using a thoracoabdominal stapling device without detorsing the lobes. Both dogs recovered uneventfully, and at least one year postoperatively, no clinical abnormalities were noted by their owners. Results of this report suggest that spontaneous lung lobe torsion in pugs occurs and should be a differential diagnosis for pugs with increased respiratory effort, tachypnea, nonproductive cough, acute collapse, cyanosis, and lethargy. Surgical excision may be curative.

  6. Torsional Performance of Wind Turbine Blades

    DEFF Research Database (Denmark)

    Branner, Kim; Berring, Peter; Berggreen, Christian

    2007-01-01

    The present work investigates how well different finite element modeling techniques can predict bending and torsion behavior of a wind turbine blade. Two shell models are investigated. One model has element offsets and the other has the elements at the mid-thickness surfaces of the model. The last...... two models investigated use a combination of shell and solid elements. The results from the numerical investigations are compared with measurements from testing of a section of a full-scale wind turbine blade. It is found that only the combined shell/solid models give reliable results in torsion. Both...

  7. Stress Intensity Factors of Slanted Cracks in Bi-Material Plates

    Science.gov (United States)

    Ismail, Al Emran; Azhar Kamarudin, Kamarul; Nor, Nik Hisyamudin Muhd

    2017-10-01

    In this study, the stress intensity factors (SIF) of slanted cracks in bi-material plates subjected to mode I loading is numerically solved. Based on the literature survey, tremendous amount of research works are available studying the normal cracks in both similar and dissimilar plates. However, lack of SIF behavior for slanted cracks especially when it is embedded in bi-material plates. The slanted cracks are then modelled numerically using ANSYS finite element program. Two plates of different in mechanical properties are firmly bonded obliquely and then slanted edge cracks are introduced at the lower inclined edge. Isoparametric singular element is used to model the crack tip and the SIF is determined which is based on the domain integral method. Three mechanical mismatched and four slanted angles are used to model the cracks. According to the present results, the effects of mechanical mismatch on the SIF for normal cracks are not significant. However, it is played an important role when slanted angles are introduced. It is suggested that higher SIF can be obtained when the cracks are inclined comparing with the normal cracks. Consequently, accelerating the crack growth at the interface between two distinct materials.

  8. Tussive syncope in a pug with lung-lobe torsion

    Science.gov (United States)

    Davies, John A.; Snead, Elisabeth C.R.; Pharr, John W.

    2011-01-01

    The most common presenting clinical signs of lung-lobe torsion include dyspnea, tachypnea, lethargy, and anorexia. Tussive syncope secondary to lung-lobe torsion has not been documented. This article describes the presentation, diagnosis, management, and outcome of a pug with tussive syncope secondary to lung-lobe torsion. PMID:22131584

  9. The relationship between torsional rigidity and bending strength ...

    African Journals Online (AJOL)

    The modulus of rigidity, G, and bending moment of elasticity, MOE, of SA pine are evaluated from a direct torsion test and bending tests. Specimens were subjected to a series of tests with the view to determining direct torsional rigidity, apparent bending modulus of elasticity and pure bending modulus of elasticity. Torsional ...

  10. Testicular torsion: case report | Kuremu | East African Medical Journal

    African Journals Online (AJOL)

    This is a report of bilateral testicular torsion. The objective of the report is to highlight the serious implications of misdiagnosis of testicular torsion. Other than loss of the testis due to necrosis in unilateral torsion, immunological damage of the opposite testis occurs. Early, accurate diagnosis, and institution of the appropriate ...

  11. Acute and intermittent testicular torsion: Analysis of presentation ...

    African Journals Online (AJOL)

    2015-11-18

    Nov 18, 2015 ... Background: Testicular torsion compromises the blood supply to the testes and may result in testicular loss or damage if not dealt with promptly. It can occur either as acute testicular torsion (ATT) or intermittent testicular torsion (ITT). This study examines the presentation, management, and outcome of adult ...

  12. Crack tip strain evolution and crack closure during overload of a growing fatigue crack

    Directory of Open Access Journals (Sweden)

    De-Qiang Wang

    2017-07-01

    Full Text Available It is generally accepted that fatigue crack growth is retarded after an overload, which has been explained either by plasticity-induced crack closure or near-tip residual stress. However, any interpretation of overload effect is insufficient if strain evolution in front of crack tip is not properly considered. The current understanding of overload-induced retardation lacks the clarification of the relationship between crack closure at crack wake and strain evolution at crack tip. In this work, a material with low work hardening coefficient was used to study the effect of overload on crack tip strain evolution and crack closure by in-situ SEM observation and digital image correlation technique. Crack opening displacement (COD and crack tip strain were measured before and after the overload. It was observed that the evolution of crack tip strain follows the crack opening behaviour behind the crack tip, indicating a smaller influence of overload on micro-mechanical behaviour of fatigue crack growth. After the overload, plastic strain accumulation was responsible for crack growth. The strain at a certain distance to crack tip was mapped, and it was found that the crack tip plastic zone size correlated well with crack growth rate during post-overload fatigue crack propagation.

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

    Science.gov (United States)

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

    2017-02-01

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

  14. Three-dimensional elastic stress and displacement analysis of tensile fracture specimens containing cracks

    Science.gov (United States)

    Gyekenyesi, J. P.; Mendelson, A.; Kring, J.

    1973-01-01

    A seminumerical method is presented for three-dimensional elastic analysis of finite geometry solids with traction-free cracks. Stress and displacement distributions are calculated for two rectangular bars which are loaded by a uniform surface stress distribution. The first bar contains a through-thickness central crack while the second bar has double-edge cracks. Stress intensity factors K sub I for both configurations are presented.

  15. Shot Peening Effect on Fatigue Crack Repaired Weldments

    Directory of Open Access Journals (Sweden)

    J. Efrain Rodriguez-Sanchez

    2017-01-01

    Full Text Available Fracture mechanics calculations are required to validate the safety level defined in design codes to prevent a fatigue failure. The periodic inspection-assessment cycle can lead to the implementation of a fatigue crack repair by crack removal. To improve the fatigue performance of the crack repair, residual compressive stresses induced by peening can be considered. This paper is in relation to the peening effect estimation on stress intensity factors in fatigue crack repaired weldments, since the stress intensity factor is a key parameter in fracture mechanics calculations. A set of T-butt specimens were experimentally fatigue tested and crack propagation data was gathered for the calculation of stress intensity factors. The experiments were designed to estimate the residual compressive stress depth layer and its effect on crack propagation inhibition. Experimental estimation of the peening effect on stress intensity factors in fatigue crack repaired weldments was validated by comparison against an analytical weight function solution. Experimental stress intensity factors determined from a set of fatigue tested T-butt specimens allowed estimating preliminarily that peening has a limited effect on fatigue crack propagation inhibition for edge repaired T-butt weldments subjected to bending loading.

  16. Fatigue-Life Prediction Methodology Using Small-Crack Theory

    Science.gov (United States)

    Newmann, James C., Jr.; Phillips, Edward P.; Swain, M. H.

    1997-01-01

    This paper reviews the capabilities of a plasticity-induced crack-closure model to predict fatigue lives of metallic materials using 'small-crack theory' for various materials and loading conditions. Crack-tip constraint factors, to account for three-dimensional state-of-stress effects, were selected to correlate large-crack growth rate data as a function of the effective-stress-intensity factor range (delta K(eff)) under constant-amplitude loading. Some modifications to the delta k(eff)-rate relations were needed in the near-threshold regime to fit measured small-crack growth rate behavior and fatigue endurance limits. The model was then used to calculate small- and large-crack growth rates, and to predict total fatigue lives, for notched and un-notched specimens made of two aluminum alloys and a steel under constant-amplitude and spectrum loading. Fatigue lives were calculated using the crack-growth relations and microstructural features like those that initiated cracks for the aluminum alloys and steel for edge-notched specimens. An equivalent-initial-flaw-size concept was used to calculate fatigue lives in other cases. Results from the tests and analyses agreed well.

  17. Near tip stress and strain fields for short elastic cracks

    Science.gov (United States)

    Soediono, A. H.; Kardomateas, G. A.; Carlson, R. L.

    1994-01-01

    Recent experimental fatigue crack growth studies have concluded an apparent anomalous behavior of short cracks. To investigate the reasons for this unexpected behavior, the present paper focuses on identifying the crack length circumstances under which the requirements for a single parameter (K(sub I) or delta K(sub I) if cyclic loading is considered) characterization are violated. Furthermore, an additional quantity, the T stress, as introduced by Rice, and the related biaxiality ratio, B, are calculated for several crack lengths and two configurations, the single-edge-cracked and the centrally-cracked specimen. It is postulated that a two-parameter characterization by K and T (or B) is needed for the adequate description of the stress and strain field around a short crack. To further verify the validity of this postulate, the influence of the third term of the Williams series on the stress, strain and displacement fields around the crack tip and in particular on the B parameter is also examined. It is found that the biaxiality ratio would be more negative if the third term effects are included in both geometries. The study is conducted using the finite element method with linearly elastic material and isoparametric elements and axial (mode I) loading. Moreover, it is clearly shown that it is not proper to postulate the crack size limits for 'short crack' behavior as a normalized ratio with the specimen width, a/w; it should instead be stated as an absolute, or normalized with respect to a small characteristic dimension such as the grain size. Finally, implications regarding the prediction of cyclic (fatigue) growth of short cracks are discussed.

  18. Vibration of Cracked Circular Plates at Resonance Frequencies

    Science.gov (United States)

    HUANG, CHI-HUNG; MA, CHIEN-CHING

    2000-09-01

    It is well known that the presence of cracks will affect the dynamic characteristics of the vibrating plate. Such a problem is complicated because it combines the field of vibration analysis and fracture mechanics. In this study, an optical system called the AF-ESPI method with the out-of-plane displacement measurement is employed to investigate the vibration characteristics of a free circular plate with a radial crack emanating from the edge. The boundary conditions along the circular edge are free. As compared with the film recording and optical reconstruction procedures used for holographic interferometry, the interferometric fringes of AF-ESPI are produced instantly by a video recording system. Based on the fact that clear fringe patterns will appear only at resonant frequencies, both resonant frequencies and corresponding mode shapes can be obtained experimentally at the same time by the proposed AF-ESPI method. Numerical finite element calculations are also performed and the results are compared with the experimental measurements. Good agreements are obtained for both results. The vibrating mode shapes obtained in this study can be classified into two types, symmetric and antisymmetric modes with respect to the crack line. The influence of crack length on resonant frequencies is also investigated in terms of the dimensionless frequency parameter (λ2) versus crack length ratio (a/D). We find that if the crack face displacement is out of phase, i.e., the antisymmetric type, a large value of stress intensity factor may be induced and the cracked circular plate will be dangerous, from the fracture mechanics point of view. However, there are some resonant frequencies for which the crack face displacements are completely in phase, i.e., the symmetric type, which yields a zero stress intensity factor and the cracked plate will be safe.

  19. Torsion of the gallbladder: a case report

    Directory of Open Access Journals (Sweden)

    Ijaz Samia

    2008-07-01

    Full Text Available Abstract Introduction Torsion of the gallbladder is a rare condition that most commonly affects the elderly. Pre-operative diagnosis is the exception rather than the rule. Any delay in treatment can be fatal as the gallbladder may rupture, leading to biliary peritonitis. Case presentation We present the case of an 80-year-old woman who was admitted with right upper quadrant pain initially thought to be secondary to acute cholecystitis. Subsequent ultrasound and computed tomography scans of the abdomen revealed signs suggestive of acute cholecystitis but neither modality detected any gallstones. As the patient's symptoms failed to resolve on conservative management, she was taken to theatre for an open cholecystectomy. Intra-operatively, the gallbladder had undergone complete torsion and appeared gangrenous. A routine cholecystectomy followed and she recovered from the operation without incident. Conclusion It is rare to diagnose torsion of the gallbladder pre-operatively despite advances in diagnostic imaging. However, this differential diagnosis should be borne in mind particularly in the elderly patient, without proven gallstones, who fails to improve on conservative management. An emergency cholecystectomy is indicated in the event of diagnosing torsion of the gallbladder to avert the potentially lethal sequelae of biliary peritonitis.

  20. Torsion of the gallbladder: a case report.

    Science.gov (United States)

    Ijaz, Samia; Sritharan, Kaji; Russell, Neil; Dar, Manzoor; Bhatti, Tahir; Ormiston, Michael

    2008-07-24

    Torsion of the gallbladder is a rare condition that most commonly affects the elderly. Pre-operative diagnosis is the exception rather than the rule. Any delay in treatment can be fatal as the gallbladder may rupture, leading to biliary peritonitis. We present the case of an 80-year-old woman who was admitted with right upper quadrant pain initially thought to be secondary to acute cholecystitis. Subsequent ultrasound and computed tomography scans of the abdomen revealed signs suggestive of acute cholecystitis but neither modality detected any gallstones. As the patient's symptoms failed to resolve on conservative management, she was taken to theatre for an open cholecystectomy. Intra-operatively, the gallbladder had undergone complete torsion and appeared gangrenous. A routine cholecystectomy followed and she recovered from the operation without incident. It is rare to diagnose torsion of the gallbladder pre-operatively despite advances in diagnostic imaging. However, this differential diagnosis should be borne in mind particularly in the elderly patient, without proven gallstones, who fails to improve on conservative management. An emergency cholecystectomy is indicated in the event of diagnosing torsion of the gallbladder to avert the potentially lethal sequelae of biliary peritonitis.

  1. Fermion Helicity Flip Induced by Torsion Field

    OpenAIRE

    Capozziello, S.; Iovane, G.; Lambiase, G.; Stornaiolo, C.

    1999-01-01

    We show that in theories of gravitation with torsion the helicity of fermion particles is not conserved and we calculate the probability of spin flip, which is related to the anti-symmetric part of affine connection. Some cosmological consequences are discussed.

  2. Plant-based torsional actuator with memory

    Science.gov (United States)

    Nayomi Plaza; Samuel L. Zelinka; Don S. Stone; Joseph E. Jakes

    2013-01-01

    A bundle of a few loblolly pine (Pinus taeda) cells are moisture-activated torsional actuators that twist multiple revolutions per cm length in direct proportion to moisture content. The bundles generate 10 N m kg􀀀1 specific torque during both twisting and untwisting, which is higher than an electric motor. Additionally, the bundles exhibit a moisture-...

  3. Regional assessment of left ventricular torsion by CMR tagging

    Directory of Open Access Journals (Sweden)

    Marcus J Tim

    2008-05-01

    Full Text Available Abstract Purpose To introduce a standardized method for calculation of left ventricular torsion by CMR tagging and to determine the accuracy of torsion analysis in regions using an analytical model. Methods Torsion between base and apex, base and mid, and mid and apex levels was calculated using CSPAMM tagging and Harmonic Phase tracking. The accuracy of torsion analysis on a regional basis (circumferential segments and transmural layers was analyzed using an analytical model of a deforming cylinder with a displaced axis of rotation (AoR. Regional peak torsion values from twelve healthy volunteers calculated by the described method were compared to literature. Results The deviation from the analytical torsion per % AoR-displacement (of the radius was 0.90 ± 0.44% for the circumferential segments and only 0.05% for the transmural layers. In the subjects, circumferentially, anterolateral torsion was larger than inferior (12.4 ± 3.9° vs. 5.0 ± 3.3°, N.S.. Transmurally, endocardial torsion was smaller than epicardial (7.5 ± 1.3° vs. 8.0 ± 1.5°, p Conclusion Variability in the position of the AoR causes a large variability in torsion in circumferential segments. This effect was negligible for global torsion, and torsion calculated in transmural layers. Results were documented for the healthy human heart and are in agreement with data from literature.

  4. Fatigue crack propagation and cyclic deformation at a crack tip

    Science.gov (United States)

    Kang, T. S.; Liu, H. W.

    1974-01-01

    The fatigue crack propagation relation da/dN = f(R) Delta K squared can be derived with three assumptions: small-scale yielding, material homogeneity, and that crack tip stresses and strains are not strongly affected by plate thickness. The function f(R) is a constant at a given stress ratio, R. The effects of plate thickness and stress ratio on crack tip deformation and fatigue crack growth in 2024-T351 aluminum alloy were studied. High Delta K level in a thin specimen causes crack tip necking. Necking is more pronounced at high stress ratio. Necking causes high maximum strain near a crack tip and fast crack growth rate.

  5. Inelastic Seismic Torsional Behaviour of Elevated Tanks

    Science.gov (United States)

    DUTTA, S. C.; JAIN, S. K.; MURTY, C. V. R.

    2001-04-01

    Torsional failure of elevated tanks has occurred in past earthquakes. The overall axisymmetric structural geometry and mass distribution of such structures may leave only a small accidental eccentricity between centre of stiffness and centre of mass. Such a small accidental eccentricity is not expected to cause a torsional failure. This paper studies the possibility of amplified torsional behaviour of elevated water tanks due to such small accidental eccentricity in inelastic range through detailed case studies; using two simple idealized systems with two coupled lateral-torsional degrees of freedom and, strength-deteriorating and elasto-plastic hysteresis models. The systems are capable of retaining the characteristics of two extreme categories of water tanks namely, (a) tanks on staging with less number of columns and panels and (b) tanks on staging with large number of columns and panels. The study shows that the presence of a small eccentricity may lead to localized unsymmetrical yielding in some of the reinforced concrete staging elements. This may lead to progressive strength deterioration through successive yieldings in same elements under cyclic loading during earthquakes. Such localized strength drop may increasingly develop large strength eccentricity resulting in large localized inelastic displacement and ductility demand, leading to failure. These observations are also verified for a real-life example elevated tank. The tanks supported on staging with fewer columns and panels are found to have greater torsional vulnerability. The tanks located near a fault are found to be vulnerable under near-fault pulses with a large duration compared to the lateral period of tank.

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

    Science.gov (United States)

    Chen, Jingjing; Xu, Jun; Liu, Bohan; Yao, Xuefeng; Li, Yibing

    2014-01-01

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

  7. Pattern recognition of concrete surface cracks and defects using integrated image processing algorithms

    Science.gov (United States)

    Balbin, Jessie R.; Hortinela, Carlos C.; Garcia, Ramon G.; Baylon, Sunnycille; Ignacio, Alexander Joshua; Rivera, Marco Antonio; Sebastian, Jaimie

    2017-06-01

    Pattern recognition of concrete surface crack defects is very important in determining stability of structure like building, roads or bridges. Surface crack is one of the subjects in inspection, diagnosis, and maintenance as well as life prediction for the safety of the structures. Traditionally determining defects and cracks on concrete surfaces are done manually by inspection. Moreover, any internal defects on the concrete would require destructive testing for detection. The researchers created an automated surface crack detection for concrete using image processing techniques including Hough transform, LoG weighted, Dilation, Grayscale, Canny Edge Detection and Haar Wavelet Transform. An automatic surface crack detection robot is designed to capture the concrete surface by sectoring method. Surface crack classification was done with the use of Haar trained cascade object detector that uses both positive samples and negative samples which proved that it is possible to effectively identify the surface crack defects.

  8. Analysis of cracked RC beams under vibration

    Science.gov (United States)

    Capozucca, R.; Magagnini, E.

    2017-05-01

    Among the methods of monitoring of integrity, vibration analysis is more convenient as non-destructive testing (NDT) method. Many aspects regarding the vibration monitoring of the structural integrity of damaged RC elements have not been completely analysed in literature. The correlation between the development of the crack pattern on concrete surface under bending loadings, as well as the width and depth of cracks, and the variation of dynamic parameters on a structural element is an important aspects that has to be more investigated. This paper deals with cracked RC beams controlled by NDT based on natural vibration, which may be correlated to damage degree due to cracking of concrete under severe state of loading. An experimental investigation on the assessment of RC beams in different scale under loading has been done through dynamic tests in different constraint conditions of edges measuring frequency values and frequency variation. Envelope of Frequency Response Functions (FRFs) are shown and the changes of natural frequency values are related to the damage degree of RC beams subjected to static tests. Finally, a comparison between data obtained by finite element analysis and experimental results is shown.

  9. 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....

  10. SSRI Facilitated Crack Dancing.

    Science.gov (United States)

    Doobay, Ravi; Sun, Lili; Shah, Amish; Masuta, Pardeep; Shepherd, Zachary

    2017-01-01

    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."

  11. 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.”

  12. Investigation of the torsional stiffness of flexible disc coupling

    Science.gov (United States)

    Buryy, A.; Simonovsky, V.; Obolonik, V.

    2017-08-01

    Calculation of flexible coupling torsional stiffness is required when analyzing the torsional vibrations of the reciprocating machinery train. While having the lowest torsional stiffness of all the elements of the train, flexible coupling has a significant influence on the natural frequencies of torsional vibration. However, considering structural complexity of coupling, precise definition of its torsional stiffness is quite a difficult task. The paper presents a method for calculating the torsional stiffness of flexible disc coupling based on the study of its finite element model response under the action of torque. The analysis of the basic parameters that quantitatively and qualitatively affect the coupling torsional stiffness has been also provided. The results of the calculation as well as model adequacy, sufficient for practical application, have been confirmed at the experimental measurement of flexible disc coupling torsional stiffness. The obtained elastic characteristics (dependences of applied torque and torsional stiffness versus twist angle) are nonlinear in the initial stage of loading. This feature should be taken into account when creating reliable mathematical models of torsional vibrations of reciprocating machinery trains containing flexible disc couplings.

  13. Cracking behavior of tungsten armor under ELM-like thermal shockloads II: A revised prediction for crack appearance map

    Directory of Open Access Journals (Sweden)

    Muyuan Li

    2016-12-01

    Full Text Available In this work, the surface cracking features of tungsten armor under thermal shock loads by edge-localized mode (ELM were investigated by means of computational fracture mechanics analysis. For the simulation it was assumed that a small crack was initiated at low temperature after the shut-off of thermal load in contrast to the previous studies where the presence of a crack before thermal loading was assumed. The threshold power density for surface cracking was predicted to range between 0.3 and 0.6GW/m2 while the threshold of base temperature lay between 200 and 400°C. The theoretically predicted damage map agreed well with the experimental data from electron beam irradiation tests. The current simulation model turned out to match better to the real experimental observation than the previous predictions where the threshold base temperature lies roughly between 400 and 600°C.

  14. Specimen edge effects on bending fatigue of carburized steel

    Science.gov (United States)

    Cohen, R. E.; Matlock, D. K.; Krauss, G.

    1992-10-01

    The effects of specimen geometry on the fatigue behavior of SAE 4320 steel carburized at 927 °C were evaluated with two sets of cantilever bend specimens, one set machined with square edges and one set machined with round edges. The specimens with square edges exhibited a 13% lower fatigue limit. In comparison to the rounded samples, the lower fatigue limit in the square-edged samples was attributed to the presence of a higher volume fraction of retained austenite in the sample corners and a lower surface residual compressive stress. As a result of the differences in residual stress, preferential crack initiation sites existed in the square-edged samples at a location approximately 200 to 900 ώm from the square edge. The implications of this study on laboratory analyses of the bending fatigue performance of carburized gear steels are discussed.

  15. Corrosion-fatigue crack propagation of aluminum alloys for high-speed trains

    Science.gov (United States)

    Shen, Lin; Chen, Hui; Che, Xiaoli; Xu, Lidong

    2017-07-01

    A modified single-edge notch tension (SENT) specimen exposed to saline environment was utilized to investigate the corrosion-fatigue crack growth behaviors of 5083, 6005 and 7N01 aluminum alloys. The fatigue crack propagation life, corrosion-fatigue crack rate (da/dN) were tested. The microstructures and fracture surfaces of specimens were examined by optical microscopy and scanning electron microscopy (SEM). The results showed that fatigue crack propagation rate of 7N01 in 3.5% NaCl was significantly higher than 6005 and 5083 alloys. The mechanisms of anodic dissolution and hydrogen embrittlement are used to explain the results.

  16. Machine Vision based Micro-crack Inspection in Thin-film Solar Cell Panel

    Directory of Open Access Journals (Sweden)

    Zhang Yinong

    2014-09-01

    Full Text Available Thin film solar cell consists of various layers so the surface of solar cell shows heterogeneous textures. Because of this property the visual inspection of micro-crack is very difficult. In this paper, we propose the machine vision-based micro-crack detection scheme for thin film solar cell panel. In the proposed method, the crack edge detection is based on the application of diagonal-kernel and cross-kernel in parallel. Experimental results show that the proposed method has better performance of micro-crack detection than conventional anisotropic model based methods on a cross- kernel.

  17. Torsion and transverse bending of cantilever plates

    Science.gov (United States)

    Reissner, Eric; Stein, Manuel

    1951-01-01

    The problem of combined bending and torsion of cantilever plates of variable thickness, such as might be considered for solid thin high-speed airplane or missile wings, is considered in this paper. The deflections of the plate are assumed to vary linearly across the chord; minimization of the potential energy by means of the calculus of variations then leads to two ordinary linear differential equations for the bending deflections and the twist of the plate. Because the cantilever is analyzed as a plate rather than as a beam, the effect of constraint against axial warping in torsion is inherently included. The application of this method to specific problems involving static deflection, vibration, and buckling of cantilever plates is presented. In the static-deflection problems, taper and sweep are considered.

  18. Torsional Kinematic Model for Concentric Tube Robots.

    Science.gov (United States)

    Dupont, Pierre E; Lock, Jesse; Butler, Evan

    2009-05-12

    A recent approach to steerable needle design is based on combining pre-curved tubes concentrically. By rotating and extending the tubes with respect to each other, the position and orientation of the needle tip, as well as the shape of the inserted length, can be controlled. Prior models neglected torsional twisting in the curved portions of the tubes. This paper presents a mechanics model that includes torsion, applies to any number of tubes and allows curvature and stiffness to vary with arc length. While the general model is comprised of differential equations, an analytic solution is given for two tubes of constant curvature. This solution enables analytic prediction of "snap through" instability based on a single dimensionless parameter. Simulation and experiments are used to illustrate the results.

  19. Torsion of a giant mesenteric lipoma

    Energy Technology Data Exchange (ETDEWEB)

    Wolko, Jonathan D.; Rosenfeld, David L.; Lazar, Michael J.; Underberg-Davis, Sharon J. [Department of Radiology, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, P.O. Box 19, New Brunswick, NJ 08903-0019 (United States)

    2003-01-01

    Mesenteric lipoma is a rare benign neoplastic condition that can grow to be very large and mimic other midgut fatty tumors. These benign tumors can cause various gastrointestinal symptoms such as obstruction and abdominal pain. We report the case of a 9-year-old boy who presented with a small bowel obstruction caused by torsion of a large mesenteric lipoma. This is an important but unusual tumor and should be considered in the differential of fatty lesions within the mesentery. (orig.)

  20. Is Torsion a Fundamental Physical Field?

    CERN Document Server

    Lecian, Orchidea Maria; Montani, Giovanni

    2016-01-01

    The local Lorentz group is introduced in flat space-time, where the resulting Dirac and Yang-Mills equations are found, and then generalized to curved space-time: if matter is neglected, the Lorentz connection is identified with the contortion field, while, if matter is taken into account, both the Lorentz connection and the spinor axial current are illustrated to contribute to the torsion of space-time.

  1. Electrostatically actuated torsional resonant sensors and switches

    KAUST Repository

    Younis, Mohammad I.

    2016-12-29

    Embodiments in accordance of a torsional resonant sensor disclosure is configured to actuate a beam structure using electrostatic actuation with an AC harmonic load (e.g., AC and DC voltage sources) that is activated upon detecting a particular agent having a mass above a predefined level. In various embodiments, the beam structure may be different types of resonant structures that is at least partially coated or layered with a selective material.

  2. the Analysis of Coupled Lateral Torsional Vibrations

    Directory of Open Access Journals (Sweden)

    Tomasz Szolc

    2000-01-01

    Full Text Available In the paper, dynamic investigations of the rotor shaft systems are performed by means of the discrete-continuous mechanical models. In these models the rotor shaft segments are represented by the rotating cylindrical flexurally and torsionally deformable continuous viscoelastic elements. These elements are mutually connected according to the structure of the real system in the form of a stepped shaft which is suspended on concentrated inertial viscoelastic supports of linear or non-linear characteristics. At appropriate shaft crosssections, by means of massless membranes, there are attached rigid rings representing rotors, disks, gears, flywheels and others. The proposed model enables us to investigate coupled linear or non-linear lateral torsional Vibrations of the rotating systems in steady-state and transient operating conditions. As demonstrative examples, for the steam turbo-compressor under coupled lateral torsional vibrations, the transient response due to a blade falling out from the turbine rotor as well as the steady-state response in the form of parametric resonance caused by residual unbalances are presented.

  3. Perinatal testicular torsion and medicolegal considerations.

    Science.gov (United States)

    Massoni, F; Troili, G M; Pelosi, M; Ricci, S

    2014-06-01

    Perinatal testicular torsion (PTT) is a very complex condition because of rarity of presentation and diagnostic and therapeutic difficulties. In presence of perinatal testicular torsion, the involvement of contralateral testis can be present also in absence of other indications which suggest the bilateral involvement; therefore, occurrences supported by literature do not exclude the use of surgery to avoid the risk of omitted or delayed diagnosis. The data on possible recovery of these testicles are not satisfactory, and treatment consists of an observational approach ("wait-and-see") or an interventional approach. The hypothesis of randomized clinical trials seems impracticable because of rarity of disease. The authors present a case of PTT, analyzing injuries due to clinical and surgical management of these patients, according to medicolegal profile. The delayed diagnosis and the choice of an incorrect therapeutic approach can compromise the position of healthcare professionals, defective in terms of skill, prudence and diligence. Endocrine insufficiency is an unfortunate event. The analysis of literature seems to support, because of high risk, a surgical approach aimed not only at resolution of unilateral pathology or prevention of a relapse, but also at prevention of contralateral testicular torsion.

  4. Isolated Fallopian Tube Torsion in Adolescents

    Directory of Open Access Journals (Sweden)

    S. Rajaram

    2013-01-01

    Full Text Available Background. Fallopian tube torsion is a rare cause of acute abdomen, occurring commonly in females of reproductive age. It lacks pathognomonic symptoms, signs, or imaging features, thus causing delay in surgical intervention. Case. We report two cases of isolated fallopian tube torsion in adolescent girls. In the first case a 19-year-old patient presented with acute pain in the left iliac region associated with episodes of vomiting for one day and mild tenderness on examination. Laparoscopy revealed left sided twisted fallopian tube associated with hemorrhagic cyst of ovary. The tube was untwisted and salvaged. In another case an 18-year-old virgin girl presented with similar complaints since one week, associated with mild tenderness in the lower abdomen and tender cystic mass on per rectal examination. On laparoscopy right twisted fallopian tube associated with a paratubal cyst was found. Salpingectomy was done as the tube was gangrenous. Conclusion. Fallopian tube torsion, though rare, should be considered in women of reproductive age with unilateral pelvic pain. Early diagnostic laparoscopy is important for an accurate diagnosis and could salvage the tube.

  5. Nonlinear nonuniform torsional vibrations of bars by the boundary element method

    Science.gov (United States)

    Sapountzakis, E. J.; Tsipiras, V. J.

    2010-05-01

    In this paper a boundary element method is developed for the nonuniform torsional vibration problem of bars of arbitrary doubly symmetric constant cross-section taking into account the effect of geometrical nonlinearity. The bar is subjected to arbitrarily distributed or concentrated conservative dynamic twisting and warping moments along its length, while its edges are supported by the most general torsional boundary conditions. The transverse displacement components are expressed so as to be valid for large twisting rotations (finite displacement-small strain theory), thus the arising governing differential equations and boundary conditions are in general nonlinear. The resulting coupling effect between twisting and axial displacement components is considered and torsional vibration analysis is performed in both the torsional pre- or post-buckled state. A distributed mass model system is employed, taking into account the warping, rotatory and axial inertia, leading to the formulation of a coupled nonlinear initial boundary value problem with respect to the variable along the bar angle of twist and to an "average" axial displacement of the cross-section of the bar. The numerical solution of the aforementioned initial boundary value problem is performed using the analog equation method, a BEM based method, leading to a system of nonlinear differential-algebraic equations (DAE), which is solved using an efficient time discretization scheme. Additionally, for the free vibrations case, a nonlinear generalized eigenvalue problem is formulated with respect to the fundamental mode shape at the points of reversal of motion after ignoring the axial inertia to verify the accuracy of the proposed method. The problem is solved using the direct iteration technique (DIT), with a geometrically linear fundamental mode shape as a starting vector. The validity of negligible axial inertia assumption is examined for the problem at hand.

  6. Isolated Penile Torsion in Brothers: A Case Report

    Directory of Open Access Journals (Sweden)

    Metin Gunduz

    2012-04-01

    Full Text Available Penile torsion can be congenital and associated with hypospadias and chordee, or can be acquired after circumcision. The incidence of isolated neonatal penile torsion was 1.7 to 27% in the literature. The majority were between 10 and deg; and 20 and deg;. Generally, torsion was to the left in cases. The techniques for correction of penile torsion described in the literature are penile de-gloving and reattaching of skin, resection of Buck's fascia incising the base of the penis and removing angular ellipses of corporeal tissue with subsequent plication of tunica, and dorsal dartos flap rotation in severe cases. In conclusion, penile torsion may be familial. Therefore, brothers should be examined carefully. The degloving and realignment technique is successful in isolated penile torsion. [Arch Clin Exp Surg 2012; 1(2.000: 122-124

  7. Nonminimal couplings, gravitational waves, and torsion in Horndeski's theory

    Science.gov (United States)

    Barrientos, José; Cordonier-Tello, Fabrizio; Izaurieta, Fernando; Medina, Perla; Narbona, Daniela; Rodríguez, Eduardo; Valdivia, Omar

    2017-10-01

    The Horndeski Lagrangian brings together all possible interactions between gravity and a scalar field that yield second-order field equations in four-dimensional spacetime. As originally proposed, it only addresses phenomenology without torsion, which is a non-Riemannian feature of geometry. Since torsion can potentially affect interesting phenomena such as gravitational waves and early universe inflation, in this paper we allow torsion to exist and propagate within the Horndeski framework. To achieve this goal, we cast the Horndeski Lagrangian in Cartan's first-order formalism and introduce wave operators designed to act covariantly on p -form fields that carry Lorentz indices. We find that nonminimal couplings and second-order derivatives of the scalar field in the Lagrangian are indeed generic sources of torsion. Metric perturbations couple to the background torsion, and new torsional modes appear. These may be detected via gravitational waves but not through Yang-Mills gauge bosons.

  8. Severely deformed Cu by using compression with oscillatory torsion method

    OpenAIRE

    K. Rodak

    2007-01-01

    Purpose: The present study is aimed at a quantitative description of microstructural parameters as a misorientationangle of Cu deformed by using compression with oscillatory torsion.Design/methodology/approach: Cu samples were deformed at torsion frequency (f) changed from 0 Hz(compression only) to 1.8 Hz under a constant torsion angle (α) ≈ 8° and compression speed (v)=0.1mm/s.Structural investigations were conducted by using transmission electron microscopy (TEM). Local misorientationhave b...

  9. Design of a nonlinear torsional vibration absorber

    Science.gov (United States)

    Tahir, Ammaar Bin

    Tuned mass dampers (TMD) utilizing linear spring mechanisms to mitigate destructive vibrations are commonly used in practice. A TMD is usually tuned for a specific resonant frequency or an operating frequency of a system. Recently, nonlinear vibration absorbers attracted attention of researchers due to some potential advantages they possess over the TMDs. The nonlinear vibration absorber, or the nonlinear energy sink (NES), has an advantage of being effective over a broad range of excitation frequencies, which makes it more suitable for systems with several resonant frequencies, or for a system with varying excitation frequency. Vibration dissipation mechanism in an NES is passive and ensures that there is no energy backflow to the primary system. In this study, an experimental setup of a rotational system has been designed for validation of the concept of nonlinear torsional vibration absorber with geometrically induced cubic stiffness nonlinearity. Dimensions of the primary system have been optimized so as to get the first natural frequency of the system to be fairly low. This was done in order to excite the dynamic system for torsional vibration response by the available motor. Experiments have been performed to obtain the modal parameters of the system. Based on the obtained modal parameters, the design optimization of the nonlinear torsional vibration absorber was carried out using an equivalent 2-DOF modal model. The optimality criterion was chosen to be maximization of energy dissipation in the nonlinear absorber attached to the equivalent 2-DOF system. The optimized design parameters of the nonlinear absorber were tested on the original 5-DOF system numerically. A comparison was made between the performance of linear and nonlinear absorbers using the numerical models. The comparison showed the superiority of the nonlinear absorber over its linear counterpart for the given set of primary system parameters as the vibration energy dissipation in the former is

  10. Association of Torsion With Testicular Cancer: A Retrospective Study.

    Science.gov (United States)

    Uguz, Sami; Yilmaz, Sercan; Guragac, Ali; Topuz, Bahadır; Aydur, Emin

    2016-02-01

    Testicular torsion is a medical emergency that usually requires surgical exploration. However, testicular malignancy has been anecdotally reported with the association of torsion in surgical specimens, and the published data remain scant on the association of torsion with testicular tumors. By retrospective medical record review, we identified 32 patients who had been diagnosed with testicular torsion, 20 of whom had undergone orchiectomy. Of these 20 patients, 2 were diagnosed with a malignancy. Our study, the largest case series to date, has shown an association between testicular torsion and testicular cancer of 6.4%. Testicular torsion is a medical emergency that usually requires surgical exploration. However, testicular malignancy has been anecdotally reported in association with torsion in surgical specimens. However, the published data remain scant on the association between torsion and the presence of testicular tumors. The present retrospective study explored the association between torsion and testicular cancer in patients with testicular torsion undergoing orchiectomy during scrotal exploration. A medical record review was performed of patients who had had a diagnosis of testicular torsion from January 2003 to February 2015. The clinicopathologic characteristics of the patients were recorded. A total of 32 patients were identified. Their mean age was 21.1 years (range, 7-39 years). All the patients had unilateral testicular torsion, which affected the left side in 17 and the right side in 15. Manual detorsion was successful in 6 patients, and 26 patients underwent emergency surgery with testicular detorsion (6 fixation surgery and 20 orchiectomy). The type of incision was scrotal in 6, inguinal in 10, and unspecified in 4. Pathologic examination of the orchiectomy specimens showed malignancy in 2 cases (seminoma and malign mixed germ cell tumor). To the best of our knowledge, the present single-center case series is the largest case series to date of

  11. Secondary Torsion of Vermiform Appendix with Mucinous Cystadenoma

    Directory of Open Access Journals (Sweden)

    Maki Kitagawa

    2007-06-01

    Full Text Available Torsion of the vermiform appendix is a rare disorder, which causes abdominal symptoms indistinguishable from acute appendicitis. We report a case (a 34-year-old male of secondary torsion of the vermiform appendix with mucinous cystadenoma. This case was characterized by mild inflammatory responses, pentazocine-resistant abdominal pain, and appendiceal tumor, which was not enhanced by the contrast medium on computed tomography presumably because of reduced blood flow by the torsion. These findings may be helpful for the preoperative diagnosis of secondary appendiceal torsion.

  12. Nanoindentation near the edge

    Science.gov (United States)

    J.E. Jakes; C.R. Frihart; J.F. Beecher; R.J. Moon; P.J. Resto; Z.H. Melgarejo; O.M. Saurez; H. Baumgart; A.A. Elmustafa; D.S. Stone

    2009-01-01

    Whenever a nanoindent is placed near an edge, such as the free edge of the specimen or heterophase interface intersecting the surface, the elastic discontinuity associated with the edge produces artifacts in the load-depth data. Unless properly handled in the data analysis, the artifacts can produce spurious results that obscure any real trends in properties as...

  13. Cracking the Credit Hour

    Science.gov (United States)

    Laitinen, Amy

    2012-01-01

    The basic currency of higher education--the credit hour--represents the root of many problems plaguing America's higher education system: the practice of measuring time rather than learning. "Cracking the Credit Hour" traces the history of this time-based unit, from the days of Andrew Carnegie to recent federal efforts to define a credit…

  14. Cracking the Codes

    Science.gov (United States)

    Heathcote, Dorothy

    1978-01-01

    Prescribes an attitude that teachers can take to help students "crack the code" of a dramatic work, combining a flexible teaching strategy, the suspension of beliefs or preconceived notions about the work, focusing on the drams's text, and choosing a reading strategy appropriate to the dramatic work. (RL)

  15. Toward laboratory torsional spine magnetic reconnection

    Science.gov (United States)

    Chesny, David L.; Orange, N. Brice; Oluseyi, Hakeem M.; Valletta, David R.

    2017-12-01

    Magnetic reconnection is a fundamental energy conversion mechanism in nature. Major attempts to study this process in controlled settings on Earth have largely been limited to reproducing approximately two-dimensional (2-D) reconnection dynamics. Other experiments describing reconnection near three-dimensional null points are non-driven, and do not induce any of the 3-D modes of spine fan, torsional fan or torsional spine reconnection. In order to study these important 3-D modes observed in astrophysical plasmas (e.g. the solar atmosphere), laboratory set-ups must be designed to induce driven reconnection about an isolated magnetic null point. As such, we consider the limited range of fundamental resistive magnetohydrodynamic (MHD) and kinetic parameters of dynamic laboratory plasmas that are necessary to induce the torsional spine reconnection (TSR) mode characterized by a driven rotational slippage of field lines - a feature that has yet to be achieved in operational laboratory magnetic reconnection experiments. Leveraging existing reconnection models, we show that within a 3$ apparatus, TSR can be achieved in dense plasma regimes ( 24~\\text{m}-3$ ) in magnetic fields of -1~\\text{T}$ . We find that MHD and kinetic parameters predict reconnection in thin current sheets on time scales of . While these plasma regimes may not explicitly replicate the plasma parameters of observed astrophysical phenomena, studying the dynamics of the TSR mode within achievable set-ups signifies an important step in understanding the fundamentals of driven 3-D magnetic reconnection and the self-organization of current sheets. Explicit control of this reconnection mode may have implications for understanding particle acceleration in astrophysical environments, and may even have practical applications to fields such as spacecraft propulsion.

  16. Fracture Toughness and Slow Crack Growth Behavior of Ni-YSZ and YSZ as a Function of Porosity and Temperature.

    Energy Technology Data Exchange (ETDEWEB)

    Radovic, Miladin [ORNL; Lara-Curzio, Edgar [ORNL; Nelson, George [Georgia Institute of Technology

    2006-01-01

    In this paper we report on the fracture toughness of YSZ and Ni-YSZ and slow-crack growth behavior of Ni-YSZ at 20C and 800C. Results are presented for tests carried out in air for YSZ and in a gas mixture of 4%H2 and 96%Ar for Ni-YSZ containing various levels of porosity. The double-torsion test method was utilized to determine the fracture toughness from the peak load obtained during fast loading test specimens that had been precracked, while crack velocity versus stress intensity curves were obtained in the double torsion using hte load relaxation method. It was found that fracture toughness of these materials decreases with temperature and int he case of Ni-YSZ it also decreases with increasing porosity. The effect of temperature and microstructure, which was characterized by Scanning Electron Microscopy, on the fracture behavior of these materials, is discussed.

  17. Adnexal torsion in third trimester of pregnancy

    Science.gov (United States)

    Passarinho, Rita Marquez; Afonso, Énio; Reis, Luís; Santos Silva, Isabel

    2012-01-01

    The authors report an unusual case of adnexal torsion in a patient in the third trimester of pregnancy. A 32-year-old woman, gravida 1, para 0, in the 32nd week of gestation initially presented with clinical signs of acute appendicitis. On laparotomy, it was identified that a necrotic mass of the right adnexa and performed a unilateral salpingo-oophorectomy. The postoperative period was uneventful. In the 37th week of gestation, the labour was induced by fetal intrauterine growth restriction. She delivered vaginally, a healthy baby, with 2085 g and an Apgar score of 9 and 10 at the first and fifth minute, respectively. PMID:23109412

  18. Variable mode-mixity during fatigue cycles – crack tip parameters determined from displacement fields measured by digital image correlation

    Directory of Open Access Journals (Sweden)

    Michael Vormwald

    2017-07-01

    Full Text Available This paper focusses on discussing equivalent stress intensity factors and kink angles after a change of mode-mixity from one cycle to the next and when the mode-mixity changes continuously during the fatigue cycles. Thin-walled tubes with through-wall cracks have been loaded by proportional and non-proportional tension and torsion. In the experimental investigation, the region of fatigue crack growth was observed by applying the digital image correlation technique. Data on the variations of the displacement and strain fields during the cycles were acquired and used to determine mixed-mode variations of stress intensity factors associated with opening modes I, II and III. For each specific specimen the crack path was observed in order to relate its curvature – both kinks and continuously developing warped cracks – with the variations of the displacement field and associated stress intensity factors.

  19. Slow crack growth resistance and bridging stress determination in alumina-rich magnesium aluminate spinel/tungsten composites

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez-Suarez, T.; Lopez-Esteban, S.; Pecharroman, C. [Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Cientificas (CSIC), C/ Sor Juana Ines de la Cruz, 3, 28049 Cantoblanco, Madrid (Spain); Moya, J.S. [Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Cientificas (CSIC), C/ Sor Juana Ines de la Cruz, 3, 28049 Cantoblanco, Madrid (Spain)], E-mail: jsmoya@icmm.csic.es; El Attaoui, H.; Benaqqa, C.; Chevalier, J. [Universite de Lyon, INSA-Lyon, MATEIS, UMR CNRS 5510, 20 avenue Albert Einstein, Villeurbanne F-69621 (France)

    2009-04-15

    The slow crack growth (SCG) resistance (V-K{sub I} diagrams) of magnesium aluminate spinel and its tungsten composites with different metallic content (7, 10, 14 and 22 vol.%) is reported. It is found that tungsten plays a crucial role in the composite by increasing crack resistance: the higher the W content, the higher the stress intensity factor needed for crack extension at a given rate. The reinforcement is due to the bridging mechanism performed by metal particles, as it strongly affects the compliance of cracked specimens. Its magnitude is estimated by a compliance function {phi}(a) from a double torsion test. From the compliance function, R-curve behaviour is predicted for the composite with highest tungsten content. It explains the effect of metal particles on SCG curves. The W-MgAl{sub 2}O{sub 4} interface is believed to influence the reinforcement mechanism.

  20. A Patient Presenting with Concurrent Testis Torsion and Epididymal Leiomyoma

    Directory of Open Access Journals (Sweden)

    E. Arpali

    2013-01-01

    Full Text Available Leiomyomas are the second most common tumors of epididymis. Patients with leiomyomas are sometimes misdiagnosed with testicular tumors. A Case of a patient with a scrotal mass presenting with testicular torsion is reported. Concurrent occurrence of testicular torsion and epididymal leiomyoma is an extremely rare condition.

  1. CONSTRAINING SPACETIME TORSION WITH THE MOON, MERCURY AND LAGEOS

    Directory of Open Access Journals (Sweden)

    Riccardo March

    2013-12-01

    Full Text Available We consider an extension of Einstein General Relativity where, beside the Riemann curvature tensor, we suppose the presence of a torsion tensor. Using a parametrized theory based on symmetry arguments, we report on some results concerning the constraints that can be put on torsion parameters by studying the orbits of a test body in the solar system.

  2. Correlation of severity of penile torsion with type of hypospadias ...

    African Journals Online (AJOL)

    A. Bhat

    Abstract. Objective: This study was carried out to evaluate the correlation between the severity of penile torsion on the one hand and the degree of ventral penile curvature and the type of hypospadias on the other. We also assessed the effectiveness of correction of chordee and torsion by penile degloving and mobilization ...

  3. Mechanical origins of rightward torsion in early chick brain development

    Science.gov (United States)

    Chen, Zi; Guo, Qiaohang; Dai, Eric; Taber, Larry

    2015-03-01

    During early development, the neural tube of the chick embryo undergoes a combination of progressive ventral bending and rightward torsion. This torsional deformation is one of the major organ-level left-right asymmetry events in development. Previous studies suggested that bending is mainly due to differential growth, however, the mechanism for torsion remains poorly understood. Since the heart almost always loops rightwards that the brain twists, researchers have speculated that heart looping affects the direction of brain torsion. However, direct evidence is lacking, nor is the mechanical origin of such torsion understood. In our study, experimental perturbations show that the bending and torsional deformations in the brain are coupled and that the vitelline membrane applies an external load necessary for torsion to occur. Moreover, the asymmetry of the looping heart gives rise to the chirality of the twisted brain. A computational model and a 3D printed physical model are employed to help interpret these findings. Our work clarifies the mechanical origins of brain torsion and the associated left-right asymmetry, and further reveals that the asymmetric development in one organ can induce the asymmetry of another developing organ through mechanics, reminiscent of D'Arcy Thompson's view of biological form as ``diagram of forces''. Z.C. is supported by the Society in Science - Branco Weiss fellowship, administered by ETH Zurich. L.A.T acknowledges the support from NIH Grants R01 GM075200 and R01 NS070918.

  4. experimental and analytical comparison of torsion, bending moment

    African Journals Online (AJOL)

    HOD

    from the beam's principal axis at the mid-span, using. Computerized Universal Testing Machine TUE-C-100. BS 8110, Euro code 2 and ACI 318 were used to calculate the ... Less attention was paid in the past by reinforced concrete designers to these effects of torsion in reinforced concrete members. When torsion is.

  5. Quantum gravity effect in torsion driven inflation and CP violation

    Energy Technology Data Exchange (ETDEWEB)

    Choudhury, Sayantan [Department of Theoretical Physics, Tata Institute of Fundamental Research,Colaba, 1, Homi Bhabha Road, Mumbai 400005 (India); Pal, Barun Kumar [Inter-University Centre for Astronomy and Astrophysics,Ganeshkhind, Pune 411007 (India); Netaji Nagar College for Women,Regent Estate, Kolkata 700092 (India); Basu, Banasri; Bandyopadhyay, Pratul [Physics and Applied Mathematics Unit, Indian Statistical Institute,203 B.T. Road, Kolkata 700 108 (India)

    2015-10-28

    We have derived an effective potential for inflationary scenario from torsion and quantum gravity correction in terms of the scalar field hidden in torsion. A strict bound on the CP violating θ parameter, O(10{sup −10})<θ

  6. Lingular segment torsion following a left upper division segmentectomy.

    Science.gov (United States)

    Taira, Naohiro; Kawasaki, Hidenori; Takahara, Sayako; Furugen, Tomonori; Ichi, Takaharu; Kushi, Kazuaki; Yohena, Tomofumi; Kawabata, Tsutomu

    2017-01-01

    Numerous publications regarding lung torsion have reported lobar torsion after lobectomy. On the other hand, torsion of the remaining segment after segmentectomy is extremely rare. We herein report a rare case of lingular segment torsion following a left upper division segmentectomy. A 68-year old female underwent thoracoscopic segmentectomy of the left upper division. She underwent chest radiography immediately after the initial surgery, which revealed complete expansion on the operated side. Routine chest radiograph findings on postoperative day 1 demonstrated atelectasis on the operated side, although she did not have any symptoms. Chest computed tomography was conducted because a follow-up chest radiograph on postoperative day 5 showed no improvement, and she was diagnosed with torsion of the lingular segment. We performed an exploratory thoracotomy. Based on intraoperative findings, the lingular segment was found to have a 90° clockwise torsion along the pedicle axis, although the segment was viable. We straightened the kinked lingular segment and affixed the lingular segment to the left lower lobe. The postoperative course was uneventful. Although lobectomy is the most common cause of lung torsion, physicians should check for lung segment torsion when performing segmentectomy. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

  7. Correlation of severity of penile torsion with type of hypospadias ...

    African Journals Online (AJOL)

    Objective: This study was carried out to evaluate the correlation between the severity of penile torsion on the one hand and the degree of ventral penile curvature and the type of hypospadias on the other. We also assessed the effectiveness of correction of chordee and torsion by penile degloving and mobilization of the ...

  8. Primary omental torsion in children: case report | Khalid | Pan ...

    African Journals Online (AJOL)

    Primary omental torsion is a rare cause of acute abdominal pain, we report a case of 10-year-old boy admitted with crampy abdominal pain, routine laboratory tests and plain abdominal radiography was normal, the patient underwent surgical exploration with the initial diagnosis of appendicitis, primary omental torsion was ...

  9. Case series on testicular torsion: an educational emergency for sub ...

    African Journals Online (AJOL)

    305 records ... Testicular torsion remains a common surgical emergency of adolescent males presenting with sudden onset of intense scrotal pain in Africa. While the magnitude of testicular torsion is not known it has been identified as a cause of male infertility. Testicular loss in Africa is directly related to delay in surgery and ...

  10. Dismal salvage of testicular torsion: A call to action! | Maranya ...

    African Journals Online (AJOL)

    Background: Testicular ischaemia and infarction in cases of torsion depend on the duration and degree of twisting. Early evaluation and treatment are associated with high salvage reports. Objective: To determine the salvage rates of testicular torsion in selected hospitals at the Coast Province of Kenya Design: A ...

  11. Intermittent Testicular Torsion | Obi | Nigerian Journal of Clinical ...

    African Journals Online (AJOL)

    Objective: The aim of this study is to highlight the clinical characteristics of patients with intermittent testicular torsion and draw attention to this underreported condition. Methods: Clinical and demographic data of all patients treated for intermittent testicular torsion from January 2007 to June 2015 were prospectively collected ...

  12. Torsion of the Spermatic Cord: Is Bilateral Orchidopexy Really ...

    African Journals Online (AJOL)

    Aim: To evaluate the rationale for bilateral orchidopexy as treatment for unilateral torsion of the testis, by determining how frequently the contralateral testis shows an abnormal pathology in unilateral testicular torsion. Patients and Methods:This is a retrospective study using adult urology patients treated for both acute and ...

  13. Manual Detorsion of Testicular Torsion - A Primary Care Intervention ...

    African Journals Online (AJOL)

    Testicular torsion is one of the known acute urological emergencies that require prompt intervention. Salvage of the testis is only possible if derotation is performed within 6 hours of onset of symptoms. The objective of this paper is to report successful manual detorsion of the testes of patients with testicular torsion.

  14. Prediction of Torsional Strength for Very High Early Strength Geopolymer

    Directory of Open Access Journals (Sweden)

    Woraphot PRACHASAREE

    2017-11-01

    Full Text Available Very early high strength geopolymers are gaining acceptance as alternative repair materials for highways and other infrastructure. In this study, a very rapid geopolymer binder based on Metakaolin (MK and Parawood ash (PWA, developed by the authors, was experimentally tested and a prediction model for its torsional strength is proposed. The geopolymer samples were subjected to uniaxial compression, flexural beam, and torsion tests. The modulus of rupture and torsional strength in terms of compression strength were found to be well approximated by 0.7(f’c1/2 and 1/7(x2y (f’c1/2, respectively. Also an interaction relation to describe combined bending and torsion was developed in this study. In addition, the effects of aspect ratio (y/x were studied on both torsional strength and combined bending and torsion. It was found that an aspect ratio of y/x = 3 significantly reduced the torsional resistance, to about 50 % of the torsional strength of a square section.DOI: http://dx.doi.org/10.5755/j01.ms.23.4.17280

  15. Experimental and Simulation Studies of Strength and Fracture Behaviors of Wind Turbine Bearing Steel Processed by High Pressure Torsion

    Directory of Open Access Journals (Sweden)

    Ning Wang

    2016-12-01

    Full Text Available White structure flaking (WSF has been found to be one of the failure modes in bearing steels under rolling contacts through the formation of cracks associated with a microstructural change called white etching area (WEA. In the present research, the effects of the high-pressure torsion (HPT process on the microstructure and mechanical properties of an AISI 52100 alloy are studied. An annealed AISI 52100 was subjected to high-pressure torsion at room temperature under a pressure of up to ~6 GPa for up to three turns. Finite-element modeling (FEM was used to simulate the process under high-pressure torsion and quasi-constrained conditions to reveal the material property changes occurring in HPT. Scanning electron microscopy and microhardness testing after processing were used to investigate the microstructural and mechanical property evolution of the steel. Strain induced microstructural transformations occur and affect the mechanical properties in a similar way to the well-known white etching area (WEA found beneath the surface of wind turbine bearings. Here, HPT is used to study the feasibility of creating microstructural changes that are similar to WEA. This paper presents the preliminary results of using HPT to produce WEAs.

  16. Sharp contact corners, fretting and cracks

    Directory of Open Access Journals (Sweden)

    D. A. Hills

    2013-07-01

    Full Text Available Contacts with sharp edges subject to oscillatory loading are likely to nucleate cracks from the corners, if the loading is sufficiently severe. To a first approximation, the corners behave like notches, where the local elastic behaviour is relieved by plasticity, and which in turn causes irreversibilities that give rise to crack nucleation, but also by frictional slip. One question we aim to answer here is; when is the frictional slip enveloped by plastic slip, so that the corner is effectively a notch in a monolithic material? We do this by employing the classical Williams asymptotic solution to model the contact corner, and, in doing so, we render the solution completely general in the sense that it is independent of the overall geometry of the components. We then re-define the independent parameters describing the properties of the Williams solution by using the inherent length scale, a procedure that was described at the first IJFatigue and FFEMS joint workshop [1]. By proceeding in this way, we can provide a self-contained solution that can be ‘pasted in’ to any complete contact problem, and hence the likelihood of crack nucleation, and the circumstances under which it might occur, can be classified. Further, this reformulation of Williams' solution provides a clear means of obtaining the strength (defined by crack nucleation conditions of a material pair with a particular contact angle. This means that the results from a test carried out using a laboratory specimen may easily be carried over to any complicated contact problem found in engineering practice, and a mechanical test of the prototypical geometry, which may often be quite difficult, is avoided.

  17. Peculiar torsion dynamical response of spider dragline silk

    Science.gov (United States)

    Liu, Dabiao; Yu, Longteng; He, Yuming; Peng, Kai; Liu, Jie; Guan, Juan; Dunstan, D. J.

    2017-07-01

    The torsional properties of spider dragline silks from Nephila edulis and Nephila pilipes spiders are investigated by using a torsion pendulum technique. A permanent torsional deformation is observed after even small torsional strain. This behaviour is quite different from that of the other materials tested here, i.e., carbon fiber, thin metallic wires, Kevlar fiber, and human hair. The spider dragline thus displays a strong energy dissipation upon the initial excitation (around 75% for small strains and more for a larger strain), which correspondingly reduces the amplitude of subsequent oscillations around the new equilibrium position. The variation of torsional stiffness in relaxation dynamics of spider draglines for different excitations is also determined. The experimental result is interpreted in the light of the hierarchical structure of dragline silk.

  18. Krukenberg Tumor: A Rare Cause of Ovarian Torsion

    Directory of Open Access Journals (Sweden)

    Sameer Sandhu

    2012-01-01

    Full Text Available Ovarian torsion is the fifth most common gynecological surgical emergency. Ovarian torsion is usually associated with a cyst or a tumor, which is typically benign. The most common is mature cystic teratoma. We report the case of a 43-year-old woman who came to the Emergency Department with rare acute presentation of bilateral Krukenberg tumors, due to unilateral ovarian torsion. In this case report, we highlight the specific computed tomography (CT features of ovarian torsion and demonstrate the unique radiological findings on CT imaging. Metastasis to the ovary is not rare and 5 to 10% of all ovarian malignancies are metastatic. The stomach is the common primary site in most Krukenberg tumors (70%; an acute presentation of metastatic Krukenberg tumors with ovarian torsion is rare and not previously reported in radiology literature.

  19. Lung lobe torsion in seven juvenile dogs.

    Science.gov (United States)

    Latimer, Christian R; Lux, Cassie N; Sutton, Jessie S; Culp, William T N

    2017-12-15

    CASE DESCRIPTION 7 juvenile (< 12 months old) dogs with lung lobe torsion were evaluated. CLINICAL FINDINGS All patients were male; breeds included Pug (n = 5), Chinese Shar-Pei (1), and Bullmastiff (1). Dyspnea and lethargy were the most common initial complaints, with a duration of clinical signs ranging from 1 to 10 days. A CBC showed leukocytosis and neutrophilia in all dogs. Anemia was present in 6 dogs, 2 of which received packed RBC transfusions. The diagnosis was made on the basis of results of thoracic radiography, CT, ultrasonography, or a combination of modalities. The left cranial lung lobe was most commonly affected (n = 4), followed by the right middle lung lobe (2) and the right cranial lung lobe (1). TREATMENT AND OUTCOME A lateral intercostal thoracotomy with lobectomy of the affected lobe was performed in all patients. All dogs survived to be discharged between 1 and 2 days postoperatively. Six of 7 owners contacted for follow-up information 7 to 170 months after discharge reported satisfaction with the treatment and no apparent signs of recurrence of disease. CLINICAL RELEVANCE The juvenile patients of this report were successfully treated surgically with no apparent complications. Clinicians should be aware of the possibility of lung lobe torsion when evaluating young dogs with clinical signs related to the respiratory system, including those with vague signs, to avoid undue delays in treatment.

  20. Corrosion Product Film-Induced Stress Facilitates Stress Corrosion Cracking.

    Science.gov (United States)

    Wang, Wenwen; Zhang, Zhiliang; Ren, Xuechong; Guan, Yongjun; Su, Yanjing

    2015-06-11

    Finite element analyses were conducted to clarify the role of corrosion product films (CPFs) in stress corrosion cracking (SCC). Flat and U-shaped edge-notched specimens were investigated in terms of the CPF-induced stress in the metallic substrate and the stress in the CPF. For a U-shaped edge-notched specimen, the stress field in front of the notch tip is affected by the Young's modulus of the CPF and the CPF thickness and notch geometry. The CPF-induced tensile stress in the metallic substrate is superimposed on the applied load to increase the crack tip strain and facilitate localized plasticity deformation. In addition, the stress in the CPF surface contributes to the rupture of the CPFs. The results provide physical insights into the role of CPFs in SCC.

  1. 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

    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...... XFEM results applying fully cracked XFEM elements, with computational results achieved using standard cohesive interface elements in a commercial code, and with experimental results. The suggested element performed well in the tests....

  2. Merenje torzionih oscilacija pomoću mernih traka / Measurement of torsional vibrations by using strain gages

    Directory of Open Access Journals (Sweden)

    Dragan Trifković

    2005-05-01

    Full Text Available U ovom radu prikazan je metod merenja torzionih oscilacija mehaničkih sistema na osnovu merenja torzionog napona pomoću mernih traka. Ovaj metod naročito je pogodan za proveru nivoa naprezanja elemenata sistema, koji prenose promenljive obrtne momente i torziono osciluju. Osim toga, mogu se određivati i kritične brzine obrtanja elemenata sistema, pri kojima se javljaju rezonantna naprezanja i otkazi sistema, kao što su: pojačana buka, trošenje zupčanika, zamor materijala, oštećenja i lomovi vratila, spojnica i si. Predložen je merni lanac u kojem centralno mesto zauzima suvremeni mobilni merni sistem Spider 8, koji omogućava merenje, obradu i prikaz rezultata pomoću računara. / In this work the measuring method of torsion vibrations is presented according to the measurement of torsion stress using strain gages. This method is particularly suitable in checking the system elements strain level that transfers changeable torsion moments and oscillate torsionally. Besides that, the system elements critical velocity rotation can be estimated, folio-wed by the resonant strain and problems in the function of that system such as: amplified noise, -wearing-out of gears, fatigue crack, damage and break of shafts and junctions etc. The measuring chain is proposed in -which the central part is a contemporary mobile system Spider 8, -which enables measurement, processing and displays measured results on a computer.

  3. Fatigue Crack Propagation from Notched Specimens of 304 SS in elevated Temperature Aqueous Environment

    Energy Technology Data Exchange (ETDEWEB)

    Wire, G. L.; Mills, W. J.

    2002-08-01

    Fatigue crack propagation (FCP) rates for 304 stainless steel (304SS) were determined in 24 degree C and 288 degree C air and 288 degree C water using double-edged notch (DEN) specimens of 304 stainless steel (304 SS). Test performed at matched loading conditions in air and water at 288 degree C with 20-6- cc h[sub]2/kg h[sub]2O provided a direct comparison of the relative crack growth rates in air and water over a wide range of crack growth rates. The DEN crack extension ranged from short cracks (0.03-0.25 mm) to long cracks up to 4.06 mm, which are consistent with conventional deep crack tests. Crack growth rates of 304 SS in water were about 12 times the air rate. This 12X environmental enhancement persisted to crack extensions up to 4.06 mm, far outside the range associated with short crack effects. The large environmental degradation for 304 SS crack growth is consistent with the strong reduction of fatigue life in high hydrogen water. Further, very similar environmental effects w ere reported in fatigue crack growth tests in hydrogen water chemistry (HWC). Most literature data in high hydrogen water show only a mild environmental effect for 304 SS, of order 2.5 times air or less, but the tests were predominantly performed at high cyclic stress intensity or equivalently, high air rates. The environmental effect in low oxygen environments at low stress intensity depends strongly on both the stress ratio, R, and the load rise time, T[sub]r, as recently reported for austenitic stainless steel in BWR water. Fractography was performed for both tests in air and water. At 288 degree C in water, the fracture surfaces were crisply faceted with a crystallographic appearance, and showed striations under high magnification. The cleavage-like facets on the fracture surfaces suggest that hydrogen embrittlement is the primary cause of accelerated cracking.

  4. Torsion Des Courbes Elliptiques Sur Les Corps Cubiques. (torsion Of Elliptic Curves Over Cubic Fields)

    CERN Document Server

    Parent, P

    2000-01-01

    Given a number field $K$ and an elliptic curve $E$ defined over $K$, there exists only finitely many torsion points in $E(K)$; this is the theorem of L. Merel in [Zbl 936.11037]. How is the torsion subgroup of $E(K)$ made? Let $d$ be a positive integer, let $S(d)$ be the set of all the prime numbers $p$ such that there exists a number field $K$ of degree $d$ over ${\\Bbb Q}$ and an elliptic curve $E$ defined over $K$ with a rational point of order $p$, not equal to the origin of $E$. The set $S(d)$ is finite, and $S(1)=\\{2,3,5,7\\}$ (B. Mazur [Zbl 394.14008]), $S(2)=\\{2,3,5,7,11,13\\}$ (S. Kamienny [Zbl 832.14023]). More generally if $p\\in S(d)$ then $p\\leq(1+3^{d/2})^2$ if $d\

  5. Online Identification and Verification of the Elastic Coupling Torsional Stiffness

    Directory of Open Access Journals (Sweden)

    Wanyou Li

    2016-01-01

    Full Text Available To analyze the torsional vibration of a diesel engine shaft, the torsional stiffness of the flexible coupling is a key kinetic parameter. Since the material properties of the elastic element of the coupling might change after a long-time operation due to the severe working environment or improper use and the variation of such properties will change dynamic feature of the coupling, it will cause a relative large calculation error of torsional vibration to the shaft system. Moreover, the torsional stiffness of the elastic coupling is difficult to be determined, and it is inappropriate to measure this parameter by disassembling the power unit while it is under normal operation. To solve these problems, this paper comes up with a method which combines the torsional vibration test with the calculation of the diesel shafting and uses the inherent characteristics of shaft torsional vibration to identify the dynamic stiffness of the elastic coupling without disassembling the unit. Analysis results show that it is reasonable and feasible to identify the elastic coupling dynamic torsional stiffness with this method and the identified stiffness is accurate. Besides, this method provides a convenient and practical approach to examine the dynamic behavior of the long running elastic coupling.

  6. Humeral torsion and passive shoulder range in elite volleyball players.

    Science.gov (United States)

    Schwab, Laura M; Blanch, Peter

    2009-05-01

    To evaluate variations in humeral torsion in elite male volleyball players and determine whether these changes are related to training history, retrospective injury history and volleyball performance. Cross sectional design. Twenty-four elite male volleyball players. Humeral torsion, passive gleno-humeral rotation ranges and the available internal and external rotation from the humeral torsion neutral position of the dominant and non-dominant arm were measured. Training history and retrospective injury status were ascertained from a questionnaire. Performance was assessed by coach perceived spiking ability and peak serve velocity measures. Humeral torsion angles demonstrated the dominant arm to be on average 9.6 degrees more retroverted than the non-dominant arm (p=0.00). In the comparison of volleyball players with and without a history of overuse upper limb injury the most significant finding is on the non-dominant side, those with a history of injury had significantly decreased available external rotation from the humeral torsion neutral position (mean difference=-15.1, p=0.04). There was an unexpected negative weak relationship between age commenced and decreased humeral retroversion (r=-0.413, p=0.045). There did not appear to be any relationship between humeral torsion and performance measures. The dominant arm of elite male volleyball athletes is more retroverted. There was a tendency for stronger findings in the non-dominant arm in volleyball players with retrospective injury history. We were unable to find any significant correlation between humeral torsion angle and performance measures.

  7. Experimental investigation of torsional vibration isolation using Magneto Rheological Elastomer

    Directory of Open Access Journals (Sweden)

    Praveen Shenoy K

    2018-01-01

    Full Text Available Rotating systems suffer from lateral and torsional vibrations which have detrimental effect on the roto-dynamic performance. Many available technologies such as vibration isolators and vibration absorbers deal with the torsional vibrations to a certain extent, however passive isolators and absorbers find less application when the input conditions are dynamic. The present work discusses use of a smart material called as Magneto Rheological Elastomer (MRE, whose properties can be changed based on magnetic field input, as a potential isolator for torsional vibrations under dynamic loading conditions. Carbonyl Iron Particles (CIP of average size 5 μm were mixed with RTV Silicone rubber to form the MRE. The effect of magnetic field on the system parameters was comprehended under impulse loading conditions using a custom built in-house system. Series arrangement of accelerometers were used to differentiate between the torsional and the bending modes of vibration of the system. Impact hammer tests were carried out on the torsional system to study its response, in the presence and absence of magnetic field. The tests revealed a shift in torsional frequency in the presence of magnetic field which elucidates the ability of MRE to work as a potential vibration isolator for torsional systems.

  8. Uterine torsion in a Sprague Dawley rat (Rattus norvegicus

    Directory of Open Access Journals (Sweden)

    K. H. Erlwanger

    2011-04-01

    Full Text Available Uterine torsion is a twisting of the uterus or uterine horn perpendicular to its long axis.We report a case of uterine torsion in an adult breeding Sprague Dawley rat. The rat died a month after her last recorded delivery. Post mortem examination of the rat revealed 270° torsion of the right uterine horn. The uterus contained a single foetus. The liver was pale and enlarged. The rest of the viscera appeared normal. Histopathological examination showed acute hepatic necrosis and pulmonary congestion with mild lymphocytic infiltrates peribronchially. The acute hepatic necrosis may have been associated with septicaemia due to compromised blood vessels following the uterine torsion. The presence of a single foetus could have resulted in foeto-maternal disproportion with resultant uterine torsion. Torsion of the uterus can be accompanied by haemostatic and metabolic complications, which could have caused the death of the rat. Although uterine torsion is a rare condition in rats, it should be considered as a potential complication of gestation in animal breeding units.

  9. Clinical measurement of compensatory torsional eye movement during head tilt.

    Science.gov (United States)

    Lim, Han Woong; Kim, Ji Hong; Park, Seung Hun; Oh, Sei Yeul

    2017-03-01

    To measure the degree of compensatory torsional eye movement during head tilt using a fundus photography method. We enrolled 55 healthy subjects who were 20-66 years of age. Fundus photographs were obtained in the presumed baseline position and in stepwise head tilt positions to evaluate ocular torsion using a non-mydriatic fundus camera. Horizontal marks on the nose were photographed simultaneously to evaluate head tilt. Images were analysed using Photoshop to measure the degree of ocular torsion and head tilt. A consistent compensatory torsional eye movement was observed in all subjects during head tilt. The degree of compensatory torsional eye movement showed a positive correlation with the angle of head tilt. Ocular torsional disconjugacy was observed during head tilt, with larger excycloductional eye movement than incycloductional eye movement (4.88 ± 2.91° versus 4.50 ± 2.76°, p eye movement was significantly associated with the degree of head tilt (β = 0.191, p eye movement. Considering the availability of fundus photography in clinical ophthalmology practice, the proposed method can be used as a clinical tool to measure compensatory torsional eye movement. © 2016 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

  10. Torsion based universal MEMS logic device

    KAUST Repository

    Ilyas, Saad

    2015-10-28

    In this work we demonstrate torsion based complementary MEMS logic device, which is capable, of performing INVERTER, AND, NAND, NOR, and OR gates using one physical structure within an operating range of 0-10 volts. It can also perform XOR and XNOR with one access inverter using the same structure with different electrical interconnects. The paper presents modeling, fabrication and experimental calculations of various performance features of the device including lifetime, power consumption and resonance frequency. The fabricated device is 535 μm by 150 μm with a gap of 1.92 μm and a resonant frequency of 6.51 kHz. The device is capable of performing the switching operation with a frequency of 1 kHz.

  11. Ultrafine grained Cu processed by compression with oscillatory torsion

    OpenAIRE

    K. Rodak

    2007-01-01

    Purpose: The aim of this work is a study of Cu microstructure after severe plastic deformation process by usingcompression with oscillatory torsion test.Design/methodology/approach: Cu samples were deformed at torsion frequency (f) changed from 0 Hz(compression) to 1.8 Hz under a constant torsion angle (α) ≈8° and compression speed (v)=0.1mm/s. Structuralinvestigations were conducted by using light microscopy (LM) and transmission electron microscopy (TEM).Findings: The structural analysis ma...

  12. A new method for tibial torsion measurement by computerized tomography.

    Science.gov (United States)

    Madadi, Firooz; Madadi, Firoozeh; Maleki, Arash; Shamie, Arya Nick; Washington, Eleby Rudolph; Yazdanshenas, Hamed

    2016-03-01

    Computerized tomography (CT) is the gold standard technique for tibial torsion assessment. This study compared two methods of tibial torsion assessment and proposed a new method, which could be of value in cases of abnormal fibular changes. The CT-scanograms of 60 participants were assessed by using two different techniques, differed in determination of the distal tibial axis. The interobserver reliability was 0.861 and 0.863 in the first and second methods, respectively. The intraobserver reliability in both measurement methods was 0.868. We proposed a reliable method, independent of the fibular midpoint, in assessment of tibial torsion by CT.

  13. The Torsional Eccentricity of the Structures in Miscellaneous Design Codes

    Directory of Open Access Journals (Sweden)

    Ioana Olteanu

    2010-03-01

    Full Text Available Structures rarely achieve structural symmetry. Even in symmetric structures, the asymmetric position of the structural components tends to produce an effective asymmetric structure. Such an asymmetry even if is small, can produce a torsional response coupled with translational response. In the torsional analysis, the provisions of the seismic norms are based on determining the static eccentricity. In this paper is presented a general way of computing the eccentricity in torsional design. The purpose of this article is to make a comparison of the general rules used to determine the eccentricity and their values. Are taken into account the norms from: Romania, Europe, Japan, Germany and the United States of America.

  14. Camera image processing for automated crack detection of pressed panel products (Conference Presentation)

    Science.gov (United States)

    Moon, Hoyeon; Jung, Hwee Kwon; Lee, Changwon; Park, Gyuhae

    2017-04-01

    Crack detection on pressed panel during the press forming process is an important step to ensure the quality of panel products. Traditional crack detection technique has been generally performed by experienced human inspectors, which is subjective and expensive. Therefore, the implementation of automated and accurate crack detection is necessary during the press forming process. In this study, we performed an optimal camera positioning and automated crack detection using two image processing techniques with multi-view-camera system. The first technique is based on evaluation of the panel edge lines which are extracted from a percolated object image. This technique does not require a reference image for crack detection. Another technique is based on the comparison between a reference and a test image using the local image amplitude mapping. Before crack detection, multi-view images of a panel product are captured using multiple cameras and 3D shape information is reconstructed. Optimal camera positions are then determined based on the shape information. Afterwards, cracks are automatically detected using two crack detection techniques based on image processing. In order to demonstrate the capability of the proposed technique, experiments were performed in the laboratory and the actual manufacturing lines with the real panel products. Experimental results show that proposed techniques could effectively improve the crack detection rate with improved speed.

  15. 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.)

  16. Analytical model and stability analysis of the leading edge spar of a passively morphing ornithopter wing.

    Science.gov (United States)

    Wissa, Aimy; Calogero, Joseph; Wereley, Norman; Hubbard, James E; Frecker, Mary

    2015-10-26

    This paper presents the stability analysis of the leading edge spar of a flapping wing unmanned air vehicle with a compliant spine inserted in it. The compliant spine is a mechanism that was designed to be flexible during the upstroke and stiff during the downstroke. Inserting a variable stiffness mechanism into the leading edge spar affects its structural stability. The model for the spar-spine system was formulated in terms of the well-known Mathieu's equation, in which the compliant spine was modeled as a torsional spring with a sinusoidal stiffness function. Experimental data was used to validate the model and results show agreement within 11%. The structural stability of the leading edge spar-spine system was determined analytically and graphically using a phase plane plot and Strutt diagrams. Lastly, a torsional viscous damper was added to the leading edge spar-spine model to investigate the effect of damping on stability. Results show that for the un-damped case, the leading edge spar-spine response was stable and bounded; however, there were areas of instability that appear for a range of spine upstroke and downstroke stiffnesses. Results also show that there exist a damping ratio between 0.2 and 0.5, for which the leading edge spar-spine system was stable for all values of spine upstroke and downstroke stiffnesses.

  17. Influence of Shear Stiffness Degradation on Crack Paths in Uni-Directional Composite Laminates

    Science.gov (United States)

    Satyanarayana, Arunkumar; Bogert, Phil B.

    2017-01-01

    Influence of shear stiffness degradation in an element, due to damage, on crack paths in uni-directional laminates has been demonstrated. A new shear stiffness degradation approach to improve crack path prediction has been developed and implemented in an ABAQUS/Explicit frame work using VUMAT. Three progressive failure analysis models, built-in ABAQUS (TradeMark), original COmplete STress Reduction (COSTR) and the modified COSTR damage models have been utilized in this study to simulate crack paths in five unidirectional notched laminates, 15deg, 30deg, 45deg, 60deg and 75deg under uniaxial tension load. Results such as crack paths and load vs. edge displacement curves are documented in this report. Modified COSTR damage model shows better accuracy in predicting crack paths in all the uni-directional laminates compared to the ABAQUS (TradeMark) and the original COSTR damage models.

  18. Characterization of cracking in Strain-Hardening Cementitious Composites using the compact tension test

    DEFF Research Database (Denmark)

    Pereira, Eduardo B.; Fischer, Gregor; Barros, Joaquim A. O.

    The characterization of the tensile behavior of strain hardening cementitious composites (SHCC) is of significant importance to the material design. In a previous work the tensile stress-crack opening response of different types of SHCC was characterized using notched specimens tested in direct...... tension, where a single crack was obtained and mechanically characterized by performing Single Crack Tension Test (SCTT). In this study the tensile behavior of SHCC materials is characterized under eccentric tensile load using the Compact Tension Test (CTT). The long edge notch placed in the rectangular...... plate specimens and the eccentrically applied tensile load create the local conditions necessary to the initiation of a single crack at the tip of the notch. Further propagation and opening of the crack in Mode I allow the assessment of the tensile load-displacement relationship. The experimental...

  19. Effect of crack curvature on stress intensity factors for ASTM standard compact tension specimens

    Science.gov (United States)

    Alam, J.; Mendelson, A.

    1983-01-01

    The stress intensity factors (SIF) are calculated using the method of lines for the compact tension specimen in tensile and shear loading for curved crack fronts. For the purely elastic case, it was found that as the crack front curvature increases, the SIF value at the center of the specimen decreases while increasing at the surface. For the higher values of crack front curvatures, the maximum value of the SIF occurs at an interior point located adjacent to the surface. A thickness average SIF was computed for parabolically applied shear loading. These results were used to assess the requirements of ASTM standards E399-71 and E399-81 on the shape of crack fronts. The SIF is assumed to reflect the average stress environment near the crack edge.

  20. Crack Development in Cross-Ply Laminates Under Uniaxial Tension

    Science.gov (United States)

    Gyekenyesi, Andrew L.

    1996-01-01

    This study addresses matrix-dominated failures in carbon fiber/polymer matrix composite laminates in a cross-ply lay-up. The events of interest are interlaminar fracture in the form of transverse cracks in the 90' plies and longitudinal splitting in the 0 deg plies and interlaminar fracture in the form of 0/90 delamination. These events were observed using various nondestructive evaluation (NDE) techniques during static tensile tests. Acoustic emission (AE) x radiography, and edge view microscopy were the principal ones utilized in a real-time environment. A comparison of the NDE results with an analytical model based on the classical linear fracture mechanics concept of strain energy release rate as a criterion for crack growth was performed. The virtual crack closure theory was incorporated with a finite element model to generate strain energy release rate curves for the analytical case. Celion carbon fiber/polyimide matrix (G30-500/PMR-15) was the material tested with cross-ply lay-ups of (0(2)/90(6))s and (0(4)/90(4))s. The test specimens contained thermally induced cracks caused by the high-temperature processing. The analytical model was updated to compensate for the initial damage and to study further accumulation by taking into account the crack interactions. By correlating the experimental and analytical data, the critical energy release rates were found for the observable events of interest.

  1. Catalytic cracking with deasphalted oil

    Energy Technology Data Exchange (ETDEWEB)

    Beaton, W.I.; Taylor, J.L.; Peck, L.B.; Mosby, J.F.

    1990-07-10

    This patent describes a catalytic cracking process. It comprises: hydrotreating resid; thereafter deasphalting the hydrotreated resid to produce substantially deasphalted oil; catalytically cracking the hydrotreated oil in a catalytic cracking unit in the presence of a cracking catalyst to produce upgraded oil leaving coked catalyst; and regenerating the coked catalyst in the presence of a combustion-supporting gas comprising excess molecular oxygen in an amount greater than the stoichiometric amount required for substantially completely combusting the coke on the catalyst to carbon dioxide.

  2. Interface crack growth for anisotropic plasticity with non-normality effects

    DEFF Research Database (Denmark)

    Tvergaard, Viggo; Legarth, Brian Nyvang

    2007-01-01

    A plasticity model with a non-normality plastic flow rule is used to analyze crack growth along an interface between a solid with plastic anisotropy and an elastic substrate. The fracture process is represented in terms of a traction-separation law specified on the crack plane. A phenomenological...... an oscillating stress singularity, and with conditions of small scale yielding this solution is applied as boundary conditions on the outer edge of the region analyzed. Crack growth resistance curves are calculated numerically, and the effect of the near-tip mode mixity on the steady-state fracture toughness...

  3. Polygon-Cracked Plain

    Science.gov (United States)

    2005-01-01

    21 July 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a polygon-cracked plain in the south polar region of Mars. When this picture was acquired in April 2005, the surface was covered with seasonal carbon dioxide frost. Dark spots and streaks indicate areas where the frost had begun to change and sublime away. Location near: 86.8oS, 300.5oW Image width: width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Spring

  4. 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.

  5. Fatigue Crack Topography.

    Science.gov (United States)

    1984-01-01

    possibilities. 2. EXPERIMENTAL PROGRAM The materials under investigation were typical commetial aircraft alloys as the titanium alloy Ti6Al4V , aluminium alloys...the macroscopic crack growth rate da/dN is plotted vs. the stress intensity range K as a straight 15e for constant amplitude loading with the Ti6Al4V ...cyc- le, and the units on the ordinate give the amount of striation spacing r mm. For Ti6Al4V striations were detectable for stress intensity ranges

  6. Free Vibration Analysis for Cracked FGM Beams by Means of a Continuous Beam Model

    Directory of Open Access Journals (Sweden)

    E Chuan Yang

    2015-01-01

    Full Text Available Based on Euler-Bernoulli beam theory and a continuous stiffness beam model, the free vibration of rectangular-section beams made of functionally graded materials (FGMs containing open edge cracks is studied. Assuming the material gradients follow exponential distribution along beam thickness direction, the conversion relation between the vibration governing equations of a FGM beam and that of an isotropic homogenous beam is deduced. A continuous function is used to characterize the bending stiffness of an edge cracked FGM beam. Thus, the cracked FGM beam is treated as an intact beam with continuously varying bending stiffness along its longitudinal direction. The characteristic equations of beams with different boundary conditions are obtained by transfer matrix method. To verify the validity of the proposed method, natural frequencies for intact and cracked FGM beams are calculated and compared with those obtained by three-dimensional finite element method (3D FEM and available data in the literature. After that, further discussions are carried out to analyze the influences of crack depth, crack location, material property, and slenderness ratio on the natural frequencies of the cracked FGM beams.

  7. Fatigue and fracture assessment of cracks in steel elements using acoustic emission

    Science.gov (United States)

    Nemati, Navid; Metrovich, Brian; Nanni, Antonio

    2011-04-01

    Single edge notches provide a very well defined load and fatigue crack size and shape environment for estimation of the stress intensity factor K, which is not found in welded elements. ASTM SE(T) specimens do not appear to provide ideal boundary conditions for proper recording of acoustic wave propagation and crack growth behavior observed in steel bridges, but do provide standard fatigue crack growth rate data. A modified versions of the SE(T) specimen has been examined to provide small scale specimens with improved acoustic emission(AE) characteristics while still maintaining accuracy of fatigue crack growth rate (da/dN) versus stress intensity factor (ΔK). The specimens intend to represent a steel beam flange subjected to pure tension, with a surface crack growing transverse to a uniform stress field. Fatigue test is conducted at low R ratio. Analytical and numerical studies of stress intensity factor are developed for single edge notch test specimens consistent with the experimental program. ABAQUS finite element software is utilized for stress analysis of crack tips. Analytical, experimental and numerical analysis were compared to assess the abilities of AE to capture a growing crack.

  8. Edge delamination in angle-ply composite laminates, part 5

    Science.gov (United States)

    Wang, S. S.

    1981-01-01

    A theoretical method was developed for describing the edge delamination stress intensity characteristics in angle-ply composite laminates. The method is based on the theory of anisotropic elasticity. The edge delamination problem is formulated using Lekhnitskii's complex-variable stress potentials and an especially developed eigenfunction expansion method. The method predicts exact orders of the three-dimensional stress singularity in a delamination crack tip region. With the aid of boundary collocation, the method predicts the complete stress and displacement fields in a finite-dimensional, delaminated composite. Fracture mechanics parameters such as the mixed-mode stress intensity factors and associated energy release rates for edge delamination can be calculated explicity. Solutions are obtained for edge delaminated (theta/-theta theta/-theta) angle-ply composites under uniform axial extension. Effects of delamination lengths, fiber orientations, lamination and geometric variables are studied.

  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. Spin-torsion effects in the hyperfine structure of methanol

    Science.gov (United States)

    Coudert, L. H.; Gutlé, C.; Huet, T. R.; Grabow, J.-U.; Levshakov, S. A.

    2015-07-01

    The magnetic hyperfine structure of the non-rigid methanol molecule is investigated experimentally and theoretically. 12 hyperfine patterns are recorded using molecular beam microwave spectrometers. These patterns, along with previously recorded ones, are analyzed in an attempt to evidence the effects of the magnetic spin-torsion coupling due to the large amplitude internal rotation of the methyl group [J. E. M. Heuvel and A. Dymanus, J. Mol. Spectrosc. 47, 363 (1973)]. The theoretical approach setup to analyze the observed data accounts for this spin-torsion in addition to the familiar magnetic spin-rotation and spin-spin interactions. The theoretical approach relies on symmetry considerations to build a hyperfine coupling Hamiltonian and spin-rotation-torsion wavefunctions compatible with the Pauli exclusion principle. Although all experimental hyperfine patterns are not fully resolved, the line position analysis yields values for several parameters including one describing the spin-torsion coupling.

  11. Isolated adnexal torsion in a 20-week spontaneous twin pregnancy

    Directory of Open Access Journals (Sweden)

    Ilker Kahramanoglu

    2016-01-01

    Discussion: Adnexal torsion as a cause of acute abdomen may be kept in mind in pregnants, even if there is no predisposing factor. Laparoscopy may be performed safely in 2nd trimester for acute abdomen.

  12. Outcomes of Surgery for Posterior Polar Cataract Using Torsional Ultrasound

    Directory of Open Access Journals (Sweden)

    Selçuk Sızmaz

    2013-10-01

    Full Text Available Purpose: The aim of this study is to report outcomes of surgery for posterior polar cataract using torsional ultrasound. Material and Method: Medical records of 26 eyes of 21 consecutive patients with posterior polar cataract who had cataract surgery using the torsional phacoemulsification were evaluated retrospectively. The surgical procedure used, phacoemulsification parameters, intraoperative complications, and postoperative visual outcome were recorded. Results: Of the 26 eyes, 24 (92.3% had small to medium posterior polar opacity. Two eyes had large opacity. All surgeries were performed using the torsional handpiece. Posterior capsule rupture occurred in 4 (15.3% eyes. The mean visual acuity improved significantly after surgery (p<0.001. The postoperative visual acuity was worse than 20/20 in 5 eyes. The cause of the low acuity was amblyopia. Discussion: Successful surgical results and good visual outcome can be achieved with phacoemulsification using the torsional handpiece. (Turk J Ophthalmol 2013; 43: 345-7

  13. Evaluation of left ventricular torsion in children with hypertrophic cardiomyopathy.

    Science.gov (United States)

    Prinz, Christian; Faber, Lothar; Horstkotte, Dieter; Körperich, Hermann; Moysich, Axel; Haas, Nikolaus; Kececioglu, Deniz; Thorsten Laser, Kai

    2014-04-01

    To evaluate the role of torsion in hypertrophic cardiomyopathy in children. A total of 88 children with idiopathic hypertrophic cardiomyopathy (n = 24) and concentric hypertrophy (n = 20) were investigated with speckle-tracking echocardiography and compared with age- and gender-matched healthy controls (n = 44). In hypertrophic cardiomyopathy, we found increased torsion (2.8 ± 1.6 versus 1.9 ± 1.0°/cm [controls], p Hypertrophic cardiomyopathy patients demonstrated a negative correlation between left ventricular muscle mass and torsion (r = -0.7, p hypertrophic cardiomyopathy is characterised by predominantly enhanced systolic basal clockwise rotation. Diastolic untwisting is delayed in both groups. Torsion may be an interesting marker to guide patients with hypertrophic cardiomyopathy.

  14. Amplitude-temperature analysis of hard rubber by torsional vibration

    Czech Academy of Sciences Publication Activity Database

    Šulc, Petr; Pešek, Luděk; Bula, Vítězslav; Cibulka, Jan; Košina, Jan

    2016-01-01

    Roč. 821, č. 2016 (2016), s. 295-302 ISSN 1660-9336 Institutional support: RVO:61388998 Keywords : hard rubber * torsion vibration * finite deformation * parameter identification Subject RIV: BI - Acoustics

  15. Torsion of a wandering spleen | Carapinha | South African Journal of ...

    African Journals Online (AJOL)

    Abstract. Torsion of a wandering spleen is a rare and difficult diagnosis in the paediatric population, with death a possible outcome. In this paper we present our experience of a single case and discuss the embryology and management thereof.

  16. Perinatal testicular torsion: literature review and local experience

    African Journals Online (AJOL)

    IUTT) and postnatal testicular torsion (PTT). IUTT includes cases of vanished testis and testicular mass presenting at birth. Controversies exist regarding the need for urgent exploration and contralateral orchiopexy. The aim of this study is to ...

  17. Damping of Torsional Beam Vibrations by Control of Warping Displacement

    DEFF Research Database (Denmark)

    Høgsberg, Jan Becker; Hoffmeyer, David; Ejlersen, Christian

    2016-01-01

    Supplemental damping of torsional beam vibrations is considered by viscous bimoments acting on the axial warping displacement at the beam supports. The concept is illustrated by solving the governing eigenvalue problem for various support configurations with the applied bimoments represented...

  18. In vitro transcription of a torsionally constrained template

    DEFF Research Database (Denmark)

    Bentin, Thomas; Nielsen, Peter E

    2002-01-01

    of torsionally constrained DNA by free RNAP. We asked whether or not a newly synthesized RNA chain would limit transcription elongation. For this purpose we developed a method to immobilize covalently closed circular DNA to streptavidin-coated beads via a peptide nucleic acid (PNA)-biotin conjugate in principle...... mimicking a SAR/MAR attachment. We used this construct as a torsionally constrained template for transcription of the beta-lactamase gene by Escherichia coli RNAP and found that RNA synthesis displays similar characteristics in terms of rate of elongation whether or not the template is torsionally...... constrained. We conclude that transcription of a natural bacterial gene may proceed with high efficiency despite the fact that newly synthesized RNA is entangled around the template in the narrow confines of torsionally constrained supercoiled DNA....

  19. Axial Torsion of Gangrenous Meckel's Diverticulum Causing Small ...

    African Journals Online (AJOL)

    Axial Torsion of Gangrenous Meckel's Diverticulum Causing. Small Bowel Obstruction. K. Sasikumar, Ravinder Naik Noonavath, G. S. Sreenath, Nanda Kishore Maroju. INTRODUCTION. Meckel's diverticulum (MD) is a commonly encountered congenital anomaly of the small intestine. Autopsy studies estimate overall.

  20. Torsion of an undescended testis located in the inguinal canal.

    Science.gov (United States)

    Weiss, Andrew P; Van Heukelom, Jon

    2012-05-01

    Torsion of undescended testis located within the inguinal canal is a rare finding in the emergency department (ED). This diagnosis can present as undifferentiated abdominal or groin pain, and a full genitourinary examination is essential to making this diagnosis. We present this case to increase awareness among emergency physicians regarding torsion of undescended testis. A 5-year-old boy presented to the ED with abdominal pain and a mass in his right groin. Physical examination and Doppler ultrasound were used to diagnose torsion of undescended testis. In a patient with undescended testis, torsion must be considered as a cause of abdominal or groin pain. Full genitourinary examination is essential to making this diagnosis. Copyright © 2012 Elsevier Inc. All rights reserved.

  1. Perinatal testicular torsion: literature review and local experience ...

    African Journals Online (AJOL)

    IUTT) and postnatal testicular torsion (PTT). IUTT includes cases of vanished testis and testicular mass presenting at birth. Controversies exist regarding the need for urgent exploration and contralateral orchiopexy. The aim of this study is to ...

  2. Edge colouring by total labellings

    DEFF Research Database (Denmark)

    Brandt, Stephan; Rautenbach, D.; Stiebitz, M.

    2010-01-01

    We introduce the concept of an edge-colouring total k-labelling. This is a labelling of the vertices and the edges of a graph G with labels 1, 2, ..., k such that the weights of the edges define a proper edge colouring of G. Here the weight of an edge is the sum of its label and the labels of its...

  3. Adobe Edge Quickstart Guide

    CERN Document Server

    Labrecque, Joseph

    2012-01-01

    Adobe Edge Quickstart Guide is a practical guide on creating engaging content for the Web with Adobe's newest HTML5 tool. By taking a chapter-by-chapter look at each major aspect of Adobe Edge, the book lets you digest the available features in small, easily understandable chunks, allowing you to start using Adobe Edge for your web design needs immediately. If you are interested in creating engaging motion and interactive compositions using web standards with professional tooling, then this book is for you. Those with a background in Flash Professional wanting to get started quickly with Adobe

  4. Anthropometric study of angle of femoral torsion in Maharashtrian population

    Directory of Open Access Journals (Sweden)

    Anil Kumar Dwivedi

    2016-01-01

    Full Text Available Introduction: Angle of femoral torsion is a normal torsion or twist present in femur that plays an important role in stability and function of the hip joint. The angle of femoral torsion can be defined as the angle formed by femoral condyle′s plane (bicondylar plane and a plane passing through center of neck and femoral head. Abnormal angle of femoral torsion has been implicated in the etiology of hip osteoarthrosis and developmental dysplasia of hip joint. Materials and Methods: This study was carried out on unpaired 280, adult human femora devoid of any gross pathology, 139 male (65 right and 74 left, and 141 female (71 right and 70 left from bone banks of three medical colleges of Maharashtra. The gender of each specimen was determined by the established practice. Femora were evaluated by Kingsley Olmsted method, and data were tabulated and statistically analyzed. Results: The average angle of femoral torsion 13.39° and 11.23° on the right and left side respectively in male, 16.21° and 13.23° on the right and left side, respectively, in female. Statistical analysis using Student′s "t"-test revealed significant difference (P < 0.05, greater angle of femoral torsion in female and on the right side. Conclusion: Knowledge of angle of femoral torsion is becoming significant nowadays with an increase in demand for total hip replacement, as the angle of femoral torsion is crucial to attain a normal activity of the replaced joint.

  5. Torsion-induced optical rotation in isotropic glass media.

    Science.gov (United States)

    Vasylkiv, Yuriy; Adamenko, Dmitro; Kvasnyuk, Oleksiy; Smaga, Ihor; Skab, Ihor; Shopa, Yaroslav; Vlokh, Rostyslav

    2015-03-20

    We have revealed that torsion stresses produce an optical activity effect in initially isotropic glass media. The optical activity caused by spatially inhomogeneous mechanical stresses has been experimentally studied for a standard glass BK7 subjected to torques, using a single-beam polarimetry and a polarizer-sample-analyzer scheme. The torsion-gyration coefficient for the BK7 glass has been determined as (3.96±0.82)×10-17  m3/N.

  6. A fake plane via 2-adic uniformization with torsion

    OpenAIRE

    Allcock, Daniel; Kato, Fumiharu

    2014-01-01

    We adapt the theory of non-Archimedean uniformization to construct a smooth surface from a lattice in PGL3(Q2) that has nontrivial torsion. It turns out to be a fake projective plane, commensurable with Mumford's fake plane yet distinct from it and the other fake planes that arise from 2-adic uniformization by torsion-free groups. As part of the proof, and of independent interest, we compute the homotopy type of the Berkovich space of our plane.

  7. A Numerical Model for Torsion Analysis of Composite Ship Hulls

    Directory of Open Access Journals (Sweden)

    Ionel Chirica

    2012-01-01

    Full Text Available A new methodology based on a macroelement model proposed for torsional behaviour of the ship hull made of composite material is proposed in this paper. A computer program has been developed for the elastic analysis of linear torsion. The results are compared with the FEM-based licensed soft COSMOS/M results and measurements on the scale simplified model of a container ship, made of composite materials.

  8. Outcomes of Surgery for Posterior Polar Cataract Using Torsional Ultrasound

    OpenAIRE

    Selçuk Sızmaz; Aysel Pelit

    2013-01-01

    Purpose: The aim of this study is to report outcomes of surgery for posterior polar cataract using torsional ultrasound. Material and Method: Medical records of 26 eyes of 21 consecutive patients with posterior polar cataract who had cataract surgery using the torsional phacoemulsification were evaluated retrospectively. The surgical procedure used, phacoemulsification parameters, intraoperative complications, and postoperative visual outcome were recorded. Results: Of the 26 eyes...

  9. Torsional Moment Measurement on Bucket Wheel Shaft of Giant Machine

    Directory of Open Access Journals (Sweden)

    Jiří FRIES

    2011-06-01

    Full Text Available Bucket wheel loading at the present time (torsional moment on wheel shaft, peripheral cutting force is determined from electromotor incoming power or reaction force measured on gearbox hinge. Both methods together are weighted by steel construction absorption of driving units and by inertial forces of motor rotating parts. In the article is described direct method of the torsional moment measurement, which eliminates mentioned unfavourable impacts except absorption of steel construction of bucket wheel itself.

  10. Flap-lag-torsion aeroelastic stability of circulation-controlled rotors in hover

    Science.gov (United States)

    Chopra, I.; Johnson, W.

    1978-01-01

    The results of a theoretical investigation of the flap-lag-torsion stability of circulation controlled rotors in hover are presented. Stability boundaries are presented as a function of thrust and lag frequency, at several levels of blowing coefficient, for flap frequencies of 1.1/rev and 1.8/ rev. The effects of several parameters on the blade flap-lag stability are examined, including structural damping, structural coupling, pitch-lag and pitch-flap coupling, and the blade feathering motion. The trailing edge blowing can have a major impact on the blade aeroelastic stability, which should be considered in the rotor design. The implications of these results for the current CCR and X-Wing rotorcraft designs are considered.

  11. Experiences on IGSCC crack manufacturing

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-02-01

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

  12. Bicavitary effusion secondary to liver lobe torsion in a dog

    Directory of Open Access Journals (Sweden)

    Khan Z

    2016-04-01

    Full Text Available Zaheda Khan,1 Kathryn Gates,2 Stephen A Simpson,31Emergency and Critical Care, Animal Specialty and Emergency Center, Los Angeles, CA, 2Emergency and Critical Care, Advanced Critical Care, Emergency and Specialty Services, Culver City, CA 3Emergency and Critical Care, Southern California Veterinary Specialty Hospital, Irvine, CA, USA Abstract: We described the diagnosis and successful treatment of pleural and peritoneal effusion secondary to liver lobe torsion in a dog. A 12-year-old female spayed Borzoi dog was referred for heart failure. Emergency room thoracic and abdominal ultrasound showed a large volume of pleural effusion with mild peritoneal effusion and an abdominal mass. Pleural fluid analysis classified the effusion as exudative. A complete ultrasound revealed mild peritoneal effusion and decreased blood flow to the right liver lobe. Other causes of bicavitary effusion were ruled out based on blood work, ultrasound, echocardiogram, and computed tomography. The patient was taken to surgery and diagnosed with caudate liver lobe torsion and had a liver lobectomy. At the 2-week postoperative recheck, the patient was doing well and there was complete resolution of the pleural effusion. Liver lobe torsion is a rare occurrence in dogs and can be difficult to diagnose. Clinical signs are nonspecific for liver lobe torsion and patients may present in respiratory distress with significant pleural fluid accumulation. When assessing patients with pleural and peritoneal effusion, liver lobe torsion should be considered as a differential diagnosis.Keywords: pleural effusion, peritoneal effusion, hepatic torsion

  13. A new hybrid longitudinal-torsional magnetostrictive ultrasonic transducer

    Science.gov (United States)

    Karafi, Mohammad Reza; Hojjat, Yousef; Sassani, Farrokh

    2013-06-01

    In this paper, a novel hybrid longitudinal-torsional magnetostrictive ultrasonic transducer (HL-TMUT) is introduced. The transducer is composed of a magnetostrictive exponential horn and a stainless steel tail mass. In this transducer a spiral magnetic field made up of longitudinal and circumferential magnetic fields is applied to the magnetostrictive horn. As a result, the magnetostrictive horn oscillates simultaneously both longitudinally and torsionally in accordance with the Joule and Wiedemann effects. The magnetostrictive exponential horn is designed in such a manner that it has the same longitudinal and torsional resonant frequency. It is made up of ‘2V Permendur’, which has isotropic magnetic properties. The differential equations of the torsional and longitudinal vibration of the horn are derived, and a HL-TMUT is designed with a resonant frequency of 20 573 Hz. The natural frequency and mode shapes of the transducer are considered theoretically and numerically. The experimental results show that this transducer resonates torsionally and longitudinally with frequencies of 20 610 Hz and 20 830 Hz respectively. The maximum torsional displacement is 1.5 mrad m-1 and the maximum longitudinal displacement is 0.6 μm. These are promising features for industrial applications.

  14. Adobe Edge Preview 3

    CERN Document Server

    Grover, Chris

    2011-01-01

    Want to use an Adobe tool to design animated web graphics that work on iPhone and iPad? You've come to the right book. Adobe Edge Preview 3: The Missing Manual shows you how to build HTML5 graphics using simple visual tools. No programming experience? No problem. Adobe Edge writes the underlying code for you. With this eBook, you'll be designing great-looking web elements in no time. Get to know the workspace. Learn how Adobe Edge Preview 3 performs its magic.Create and import graphics. Make drawings with Edge's tools, or use art you designed in other programs.Work with text. Build menus, lab

  15. INFLUENCE OF TWIST TECHNOLOGY BY METHOD OF DOUBLE TORSION ON FORMATION OF RESIDUAL TORSIONS AND STRAIGHTNESS OF METAL CORD

    Directory of Open Access Journals (Sweden)

    V. P. Fetisov

    2012-01-01

    Full Text Available The purpose of the present work is research of influence of the technological factors, changing the elasticplastic state of twisted product, on stability within time of residual torsions and straightness of metal cord.

  16. Type IIIa cracking at 2CrMo welds in 1/2CrMoV pipework

    Energy Technology Data Exchange (ETDEWEB)

    Brett, S.J.; Smith, P.A. [National Power plc, Swindon (United Kingdom)

    1998-12-31

    The most common form of in-service defect found today on the welds of National Power`s 1/2CrMoV pipework systems is Type IV cracking which occurs in intercritically transformed material at the edge of the heat affected zone. However an alternate form of cracking, termed IIIa, which occurs close to the weld fusion line in fully grain refined heat affected zones, has also been observed. The incidence of Type IIIa cracking has increased in recent years and these defects now constitute a significant part of the total recorded crack population. This presentation describes Type IIIa cracking and compares and contrasts it with the better documented Type IV cracking. Particular reference is made to the role of carbon diffusion at the weld fusion line in promoting Type IIIa damage in preference to Type IV. (orig.) 5 refs.

  17. Edge Simulation Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Krasheninnikov, Sergei I. [Univ. of California, San Diego, CA (United States); Angus, Justin [Univ. of California, San Diego, CA (United States); Lee, Wonjae [Univ. of California, San Diego, CA (United States)

    2018-01-05

    The goal of the Edge Simulation Laboratory (ESL) multi-institutional project is to advance scientific understanding of the edge plasma region of magnetic fusion devices via a coordinated effort utilizing modern computing resources, advanced algorithms, and ongoing theoretical development. The UCSD team was involved in the development of the COGENT code for kinetic studies across a magnetic separatrix. This work included a kinetic treatment of electrons and multiple ion species (impurities) and accurate collision operators.

  18. Effectiveness of lycopene on experimental testicular torsion.

    Science.gov (United States)

    Güzel, Mahmut; Sönmez, Mehmet Fatih; Baştuğ, Osman; Aras, Necip Fazıl; Öztürk, Ayşe Betül; Küçükaydın, Mustafa; Turan, Cüneyt

    2016-07-01

    We aimed to demonstrate the long term effectiveness of lycopene, a precursor of vitamin A, on the testes for ischemia-reperfusion injury. Seventy male Wistar albino rats were used for this experiment. The rats were divided into seven groups. Group 1 served as the control group; group 2 was sham-operated; group 3 received 20mg/kg/day lycopene (intraperitoneally); in group 4, the right testes of rats were kept torted for 2hours and then were detorted and the animals lived for three days; in group 5, the right testes of rats were kept torted for 2hours and then were detorted and the animals lived for ten days; in group 6, the right testes of the rats were kept torted for 2hours and then detorted and the animals received 20mg/kg/day lycopene (intraperitoneally) for three days; in group 7, the right testes of the rats were kept torted for 2hours and then were detorted and the animals received 20mg/kg/day lycopene (intraperitoneally) for ten days. Lycopene was used intraperitoneally. Some of the testes tissues were used for biochemical analyses and the other tissues were used for histological procedures. The Johnsen's score was used for seminiferous tubule deterioration. The TUNEL method was utilized to show apoptosis of testicular tissue. Testosterone levels were measured from blood samples and SOD, MDA, TNF-α, IL-1β and IL-6 measurements were recorded from tissue samples. The results were analyzed statistically. In groups 1, 2 and 3 there was normal testicular structure. Rats in groups 4 and 5 had damaged testicular tissues. In groups 6 and 7, in which we used lycopene, the testes were not better than those in groups 4 and 5. The MSTD and JTBS values were better in group 6, but not in group 7 among the torsion groups. As a result, MDA, SOD, TNF-α and IL-1β were increased and serum testosterone and IL-6 levels were decreased in groups 4 and 5 compared to group 1. There was no improvement in the groups treated with lycopene for therapeutic purposes. It was shown that

  19. An assessment of the small-crack effect for 2024-T3 aluminum alloy

    Science.gov (United States)

    Newman, J. C., Jr.; Swain, M. H.; Phillips, E. P.

    1986-01-01

    Data on small-crack behavior were obtained for a single-edge-notched tensile specimen made of 2024-T3 Al alloy and used to evaluate the capability of a semiempirical crack-growth and closure model to predict the fatigue life of notched specimens. Fatigue tests were conducted under either constant-amplitude loading (with stress ratios of 0.5, 0, -1, and -2) or spectrum loading, using a replication technique to record growth. It was found that small cracks exhibited the 'small-crack' effect in that they grew faster than large cracks when subjected to the same stress intensity factor range. Experimental small-crack growth rates agreed well with the model predictions. For making predictions of fatigue life, an initial surface defect void size of 3 x 12 x 0.4 microns was used in all calculations; predicted fatigue lives agreed well with experimentally determined values obtained in all tests. The crack-closure model indicated that the 'small-crack' effect on fatigue life was greatest in tests involving significant compressive loads.

  20. Analysis of matrix cracking and local delamination in (0/theta/-theta)s graphite epoxy laminates under tensile load

    Science.gov (United States)

    Salpekar, S. A.; O'Brien, T. K.

    1993-01-01

    Three-dimensional element analyses of (0/theta/-theta)s graphite epoxy laminates, where theta = 15, 20, 25, 30, and 45 deg, subjected to axial tensile load, were performed. The interlaminar stresses in the theta/-theta interface were calculated with and without a matrix crack in the central -theta plies. The interlaminar normal stress changes from a small compressive stress when no matrix crack is present to a high tensile stress at the intersection of the matrix crack and the free edge. The analysis of local delamination from the -theta matrix crack indicates a high strain energy release rate and a localized Mode I component near the free edge, within one-ply distance from the matrix crack. To examine the stress state causing the matrix cracking, the maximum principal normal stress in a plane perpendicular to the fiber direction in the -theta ply was calculated in an uncracked laminate. The corresponding shear stress parallel to the fiber was also calculated. The principal normal stress at the laminate edge increased through the ply thickness and reached a very high tensile value at the theta/-theta interface indicating that the crack in the -theta ply may initiate at the theta/-theta interface.

  1. Influence of mistuning on blade torsional flutter

    Science.gov (United States)

    Srinivasan, A. V.

    1980-01-01

    An analytical technique for the prediction of fan blade flutter was evaluated by utilizing first stage fan flutter data from tests on an advanced high performance engine. The formulation includes both aerodynamic and mechanical coupling among all the blades of the assembly. Mistuning is accounted for in the analysis so that individual blade inertias, frequencies, or damping can be considered. Airfoil stability was predicted by calculating a flutter determinant, the eigenvalues of which indicate the extent of susceptibility to flutter. When blade to blade differences in frequencies are considered, a stable system is predicted for the test points examined. For a tuned system, it was found that torsional flutter can be predicted at a limited number of interblade phase angles. Examination of these phase angles indicated that they were "close" to the condition of acoustic resonance. For the range of Mach numbers and reduced frequencies considered, the so called subcritical flutter cannot be predicted. The essential influence of mechanical coupling among the blades is to change the frequencies of the system with little or no change in damping; however, aerodynamic coupling together with mechanical coupling could change not only frequencies, but also damping in the system, with a trend toward instability.

  2. Magnetic resonance imaging findings in adnexial torsion

    Directory of Open Access Journals (Sweden)

    Ronald Meira Castro Trindade

    2010-03-01

    Full Text Available Adnexial torsion is an unusual event, but a major cause of abdominal pain in women. It is often associated with ovarian tumor or cyst, but can occur in normal ovaries, especially in children. The twisting of adnexial structures may involve the ovary or tube, but frequently affects both. In most cases, it is unilateral, with slight predilection for the right side. In imaging findings, increased ovarian volume and adnexial masses are observed, with reduced or absent vascularization. In cases of undiagnosed or untreated complete twist, hemorrhagic necrosis may occur leading to complications; in that, peritonitis is the most frequent. Early diagnosis helps preventing irreversible damage with conservative treatment, thereby saving the ovary. Limitations in performing physical examination, possible inconclusive results in ultrasound and exposure to radiation in computed tomography makes magnetic resonance imaging a valuable tool in emergency assessment of gynecological diseases. The objective of this study was to report two confirmed cases of adnexial twist, emphasizing the contribution of magnetic resonance imaging in the diagnosis of this condition.

  3. Magnetic resonance imaging findings in adnexial torsion

    Energy Technology Data Exchange (ETDEWEB)

    Trindade, Ronald Meira Castro; Quadros, Marianne Siquara de [Hospital Albert Einstein, Sao Paulo, SP (Brazil). Instituto de Ensino e Pesquisa], e-mail: rtrindade@einstein.br; Baroni, Ronaldo Hueb; Rosemberg, Michelle; Racy, Marcelo de Castro Jorge; Tachibana, Adriano [Hospital Albert Einstein, Sao Paulo, SP (Brazil); Funari, Marcelo Buarque de Gusmao [Hospital Albert Einstein, Sao Paulo, SP (Brazil). Imaging Service

    2010-01-15

    Adnexial torsion is an unusual event, but a major cause of abdominal pain in women. It is often associated with ovarian tumor or cyst, but can occur in normal ovaries, especially in children. The twisting of adnexial structures may involve the ovary or tube, but frequently affects both. In most cases, it is unilateral, with slight predilection for the right size. In imaging findings, increased ovarian volume and adnexial masses are observed, with reduced or absent vascularisation. In cases of undiagnosed or untreated complete twist, hemorrhagic necrosis may occur leading to complications; in that, peritonitis is the most frequent. Early diagnosis helps preventing irreversible damage with conservative treatment, thereby saving the ovary. Limitations in performing physical examination, possible inconclusive results in ultrasound and exposure to radiation in computed tomography makes magnetic resonance imaging a valuable tool in emergency assessment of gynecological diseases. The objective of this study was to report two confirmed cases of adnexial twist, emphasizing the contribution of magnetic resonance imaging in the diagnosis of this condition. (author)

  4. The Edge supersonic transport

    Science.gov (United States)

    Agosta, Roxana; Bilbija, Dushan; Deutsch, Marc; Gallant, David; Rose, Don; Shreve, Gene; Smario, David; Suffredini, Brian

    1992-01-01

    As intercontinental business and tourism volumes continue their rapid expansion, the need to reduce travel times becomes increasingly acute. The Edge Supersonic Transport Aircraft is designed to meet this demand by the year 2015. With a maximum range of 5750 nm, a payload of 294 passengers and a cruising speed of M = 2.4, The Edge will cut current international flight durations in half, while maintaining competitive first class, business class, and economy class comfort levels. Moreover, this transport will render a minimal impact upon the environment, and will meet all Federal Aviation Administration Part 36, Stage III noise requirements. The cornerstone of The Edge's superior flight performance is its aerodynamically efficient, dual-configuration design incorporating variable-geometry wingtips. This arrangement combines the benefits of a high aspect ratio wing at takeoff and low cruising speeds with the high performance of an arrow-wing in supersonic cruise. And while the structural weight concerns relating to swinging wingtips are substantial, The Edge looks to ever-advancing material technologies to further increase its viability. Heeding well the lessons of the past, The Edge design holds economic feasibility as its primary focus. Therefore, in addition to its inherently superior aerodynamic performance, The Edge uses a lightweight, largely windowless configuration, relying on a synthetic vision system for outside viewing by both pilot and passengers. Additionally, a fly-by-light flight control system is incorporated to address aircraft supersonic cruise instability. The Edge will be produced at an estimated volume of 400 aircraft and will be offered to airlines in 2015 at $167 million per transport (1992 dollars).

  5. A generalized equation for the resonance frequencies of a fluid-filled crack

    Science.gov (United States)

    Maeda, Yuta; Kumagai, Hiroyuki

    2017-04-01

    Although a model of the resonance of a rectangular fluid-filled crack (crack model) is one of the most frequently used source models of long-period seismic events at volcanoes, there has been no analytical solution for the resonance frequencies. We previously proposed an empirical expression for the resonance frequencies as a mathematical function of the crack length, aperture, and properties of the fluid and the surrounding elastic medium. However, the expression contained an empirical constant that had to be investigated numerically for each crack aspect ratio and oscillation mode, a requirement that prevented widespread use of the expression. In the present study, we examined the theoretical basis for the expression. We assumed that the ratio of the crack wall displacement to the fluid pressure near each crack edge varied as the square root of the distance from the edge. Using this assumption, we showed theoretically that the previously proposed empirical analytical expression was a good approximation (difference ≤2 per cent) to another more complete expression. This theoretical expression is a closed form of a mathematical function of the crack model parameters and oscillation mode number; there are no empirical constants to be determined numerically. The expression thus enabled us to analytically compute the resonance frequencies for arbitrary rectangular cracks, and the results were in good agreement (difference ≤5 per cent) with numerical solutions. Resonance frequencies of cracks can be very easily predicted using this expression. This predictive ability may enhance our quantitative understanding of the processes that generate long-period events at volcanoes.

  6. 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.

  7. Effect of Water Environment on Subcritical Crack Growth of Machinable Ceramics; Kaisakusei seramikkusu no kiretsu shinten tokusei ni oyobosu mizu kankyo no eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Ikeda, K.; Kaizu, K.; Inotani, T. [Miyazaki Univ., Miyazaki (Japan); Yoshikawa, A.; Adachi, K.; Igaki, H. [Osaka Sangyo Univ., Osaka (Japan)

    1997-06-15

    The fatigue behavior of ceramics has been discussed on the basis of the relation between stress intensity facter (KI) and crack velocity (V). In this paper, the effect of environment on the relation between KI and V was studied on machinable ceramics (mica glass ceramics) and two kinds of glass ceramics with different grain sizes. The double torsion (DT) technique was used for the determination of the KI-V characteristics under different environments of air and ion-exchanged water. The characteristics of acoustic emission (AE) during stress corrosion cracking of mica glass ceramics was also examined. In water environment, the region II in the KI-V curve, in which crack velocity varies slowly with KI, disappeared. From this experimental fact, it was considered that at high KI, the crack velocity is encouraged by diffusion of the corrosive species to the crack and thus depended on the amount of water. SEM farc tography revealed that mica single crystals in the material caused crack arrest and deflection to occur. It is also found that AE event rate is quantitatively related to the crack velocity. AE measurement can be used in studying the crack propagation behavior of mica glass ceramics. 11 refs., 12 figs., 3 tabs.

  8. EdgeCentric: Anomaly Detection in Edge-Attributed Networks

    OpenAIRE

    Shah, Neil; Beutel, Alex; Hooi, Bryan; Akoglu, Leman; Gunnemann, Stephan; Makhija, Disha; Kumar, Mohit; Faloutsos, Christos

    2015-01-01

    Given a network with attributed edges, how can we identify anomalous behavior? Networks with edge attributes are commonplace in the real world. For example, edges in e-commerce networks often indicate how users rated products and services in terms of number of stars, and edges in online social and phonecall networks contain temporal information about when friendships were formed and when users communicated with each other -- in such cases, edge attributes capture information about how the adj...

  9. The rolling performance of Fe-6.5 wt.% Si sheets edged with stainless steel

    Science.gov (United States)

    Zhang, B.; Ye, F.; Liang, Y. F.; Shi, X. J.; Lin, J. P.

    2017-10-01

    Compared with common electrical steel, high silicon electrical steel (Fe-6.5 wt.% Si alloy) exhibits excellent soft magnetic properties and a wide application prospect in high frequency electromagnetic fields. In the process of cold rolling Fe-6.5 wt.% Si alloy, edge-crack often occurs on the sheets due to the inadequate ductility and limited formability. It was found that the Fe-6.5 wt.% Si alloy sheet edged with 304 stainless steel by laser welding show an improved rolling performance. The composite sheet could be cold rolled to a thickness of 0.07 mm without observed edge cracks. The mechanical property of the edging material should be in an appropriate window in reference to that of the Fe-6.5 wt.% Si alloy.

  10. A practical approach to fracture analysis at the trailing edge of wind turbine rotor blades

    DEFF Research Database (Denmark)

    Eder, Martin Alexander; Bitsche, Robert; Nielsen, Magda

    2014-01-01

    of the trailing edge joint is a common failure type, and information on specific reasons is scarce. This paper is concerned with the estimation of the strain energy release rates (SERRs) in trailing edges of wind turbine blades in order to gain insight into the driving failure mechanisms. A method based...... on the virtual crack closure technique (VCCT) is proposed, which can be used to identify critical areas in the adhesive joint of a trailing edge. The paper gives an overview of methods applicable for fracture cases comprising non-parallel crack faces in the realm of linear fracture mechanics. Furthermore......, the VCCT is discussed in detail and validated against numerical analyses in 2D and 3D. Finally, the SERR of a typical blade section subjected to various loading conditions is investigated and assessed in order to identify potential design drivers for trailing edge details. Analysis of the blade section...

  11. 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.

  12. Optical fiber accelerometer based on MEMS torsional micromirror

    Science.gov (United States)

    Zeng, Fanlin; Zhong, Shaolong; Xu, Jing; Wu, Yaming

    2008-03-01

    A novel structure of optical fiber accelerometer based on MEMS torsional micro-mirror is introduced, including MEMS torsional micro-mirror and optical signal detection. The micro-mirror is a non-symmetric one, which means that the torsional bar supporting the micro-mirror is not located in the axis where the center of the micro-mirror locates. The optical signal detection is composed of PIN diode and dual fiber collimator, which is very sensitive to the coupling angle between the input fiber and output fiber. The detection principle is that acceleration is first transformed into torsional angle of the micro-mirror, then, optical insertion loss of the dual fiber collimator caused by the angle can be received by PIN. So under the flow of acceleration to torsional angle to optical signal attenuation to optical power detection, the acceleration is detected. The theory about sensing and optical signal detect of the device are discussed in this paper. The sensitive structure parameters and performance parameters are calculated by MATLAB. To simulate the static and modal analysis, the finite element analysis, ANSYS, is employed. Based on the above calculation, several optimization methods and the final structure parameters are given. The micro-mirror is completed by using silicon-glass bonding and deep reactive ion etching (DRIE). In the experiment, the acceleration is simulated by electrostatic force and the test results show that the static acceleration detection agrees with the theory analysis very well.

  13. Torsion as a dark matter candidate from the Higgs portal

    Science.gov (United States)

    Belyaev, Alexander S.; Thomas, Marc C.; Shapiro, Ilya L.

    2017-05-01

    Torsion is a metric-independent component of gravitation, which may provide a more general geometry than the one taking place within general relativity. On the other hand, torsion could lead to interesting phenomenology in both particle physics and cosmology. In the present work it is shown that a torsion field interacting with the SM Higgs doublet and having a negligible coupling to standard model (SM) fermions is protected from decaying by a Z2 symmetry, and therefore becomes a promising dark matter (DM) candidate. This model provides a good motivation for Higgs portal vector DM scenario. We evaluate the DM relic density and explore direct DM detection and collider constraints on this model to understand its consistency with experimental data and establish the most up-to-date limits on its parameter space. We have found in the model when the Higgs boson is only partly responsible for the generation of torsion mass, there is a region of parameter space where torsion contributes 100% to the DM budget of the Universe. Furthermore, we present the first results on the potential of the LHC to probe the parameter space of minimal scenario with Higgs portal vector DM using mono-jet searches and have found that LHC at high luminosity will be sensitive to the substantial part of model parameter space which cannot be probed by other experiments.

  14. Prune belly syndrome, splenic torsion, and malrotation: a case report.

    Science.gov (United States)

    Tran, Sifrance; Grossman, Eric; Barsness, Katherine A

    2013-02-01

    An 18 year old male with a history of prune belly syndrome (PBS) presented with acute abdominal pain and palpable left upper quadrant mass. Computed tomography (CT) of the abdomen revealed a medialized spleen with a "whirl sign" in the splenic vessels, consistent with splenic torsion. Coincidentally, the small bowel was also noted to be on the right side of the abdomen, while the colon was located on the left, indicative of malrotation. Emergent diagnostic laparoscopy confirmed splenic torsion and intestinal malrotation. Successful laparoscopic reduction of the splenic torsion was achieved, however, conversion to an open procedure by a vertical midline incision was necessary owing to the patient's unique anatomy. Open splenopexy with a mesh sling and Ladd's procedure were subsequently performed. Malrotation and wandering spleen are known, rare associated anomalies in PBS; however, both have not been reported concurrently in a patient with PBS in the literature. In patients with PBS, acute abdominal pain, and an abdominal mass, high clinical suspicion for gastrointestinal malformations and prompt attention can result in spleen preservation and appropriate malrotation management. We present a case of a teenager who presented with a history of PBS, acute abdominal pain, and a palpable abdominal mass. The patient was found to have splenic torsion and intestinal malrotation. The clinical findings, diagnostic imaging, and surgical treatment options of splenic torsion are reviewed. Copyright © 2013 Elsevier Inc. All rights reserved.

  15. Malpractice Litigation and Testicular Torsion: A Legal Database Review.

    Science.gov (United States)

    Colaco, Marc; Heavner, Matthew; Sunaryo, Peter; Terlecki, Ryan

    2015-12-01

    The litigious nature of the American medical environment is a major concern for physicians, with an estimated annual cost of $10 billion. The purpose of this study is to identify causes of litigation in cases of testicular torsion and what factors contribute to verdicts or settlements resulting in indemnity payments. Publicly available jury verdict reports were retrieved from the Westlaw legal database (Thomson Reuters, New York, NY). In order to identify pertinent cases, we used the search terms "medical malpractice" and "testicular torsion" with date ranging from 2000 to 2013. Jury verdicts, depositions, and narrative summaries were evaluated for their medical basis, alleged malpractice, findings, and indemnity payment(s) (if any). Fifty-two cases were identified that were relevant to this study. Fifty-one percent of relevant cases were found in favor of the defendant physician, with the remaining 49% involving an indemnity payment (13% of which were settled). The most commonly sued medical providers were emergency physicians (48% of defendants), with urologists being second most common and making up 23% of the defendant pool. Emergency physicians were significantly more likely to make indemnity payments than urologists. Testicular torsion is a delicate condition and requires expertise in evaluation and treatment. When emergency physicians choose not to consult an urologist for possible torsion, they leave themselves open to litigation risk. When an urologist is involved in torsion litigation, they are rarely unsuccessful in their defense. Finally, ultrasound is no guarantee for success against litigation. Copyright © 2015 Elsevier Inc. All rights reserved.

  16. Computed tomographic determination of tibial torsion in the dog.

    Science.gov (United States)

    Aper, Rhonda; Kowaleski, Michael P; Apelt, Detlef; Drost, W Tod; Dyce, Jonathan

    2005-01-01

    The goal of this study was to develop a method for computed tomographic (CT) measurement of tibial torsion, and to compare this technique with direct anatomic measurement of tibial torsion in cadaveric canine tibiae. Paired hind limbs of 10 cadaveric dogs were mounted on a custom-designed limb holding apparatus. One-millimeter thick, contiguous, transverse CT slices were obtained from the distal femur to the proximal tibia and 2 mm CT slices were obtained from the distal tibia to the proximal tarsus. The tibiae were freed of soft tissues and digital photographic images of the proximal and distal articular surfaces were obtained with the camera lens aligned perpendicular to the long axis of the tibia. Multiple proximal and distal tibial axes were identified on the images; two proximal and two distal axes were found to be repeatable in all specimens in both the direct and CT methods. The torsion angle was calculated by determining the difference between the axis angles for each pair of proximal and distal axes. There was no significant difference in torsion angle identified between the direct photographic and CT method for any pair of proximal and distal axes. CT determination of tibial torsion is a rapid and accurate method, and warrants investigation in clinical patients.

  17. Autoparallel vs. Geodesic Trajectories in a Model of Torsion Gravity

    Directory of Open Access Journals (Sweden)

    Luis Acedo

    2015-11-01

    Full Text Available We consider a parametrized torsion gravity model for Riemann–Cartan geometry around a rotating axisymmetric massive body. In this model, the source of torsion is given by a circulating vector potential following the celestial parallels around the rotating object. Ours is a variant of the Mao, Tegmark, Guth and Cabi (MTGC model in which the total angular momentum is proposed as a source of torsion. We study the motion of bodies around the rotating object in terms of autoparallel trajectories and determine the leading perturbations of the orbital elements by using standard celestial mechanics techniques. We find that this torsion model implies new gravitational physical consequences in the Solar system and, in particular, secular variations of the semi-major axis of the planetary orbits. Perturbations on the longitude of the ascending node and the perihelion of the planets are already under discussion in the astronomical community, and if confirmed as truly non-zero effects at a statistically significant level, we might be at the dawn of an era of torsion phenomenology in the Solar system.

  18. Autoparallel vs. Geodesic Trajectories in a Model of Torsion Gravity

    Science.gov (United States)

    Acedo, Luis

    2015-11-01

    We consider a parametrized torsion gravity model for Riemann-Cartan geometry around a rotating axisymmetric massive body. In this model, the source of torsion is given by a circulating vector potential following the celestial parallels around the rotating object. Ours is a variant of the Mao, Tegmark, Guth and Cabi (MTGC model) in which the total angular momentum is proposed as a source of torsion. We study the motion of bodies around the rotating object in terms of autoparallel trajectories and determine the leading perturbations of the orbital elements by using standard celestial mechanics techniques. We find that this torsion model implies new gravitational physical consequences in the Solar system and, in particular, secular variations of the semi-major axis of the planetary orbits. Perturbations on the longitude of the ascending node and the perihelion of the planets are already under discussion in the astronomical community, and if confirmed as truly non-zero effects at a statistically significant level, we might be at the dawn of an era of torsion phenomenology in the Solar system.

  19. [Torsion of wandering spleen in a teenager: about a case].

    Science.gov (United States)

    Dème, Hamidou; Akpo, Léra Géraud; Fall, Seynabou; Badji, Nfally; Ka, Ibrahima; Guèye, Mohamadou Lamine; Touré, Mouhamed Hamine; Niang, El Hadj

    2016-01-01

    Wandering or migrating spleen is a rare anomaly which is usually described in children. Complications, which include pedicle torsion, are common and can be life-threatening. We report the case of a 17 year-old patient with a long past medical history of epigastric pain suffering from wandering spleen with chronic torsion of the pedicle. The clinical picture was marked by spontaneously painful epigastric mass, evolved over the past 48 hours. Abdominal ultrasound objectified heterogeneous hypertrophied ectopic spleen in epigastric position and a subcapsular hematoma. Doppler showed a torsion of splenic pedicle which was untwisted 2 turns and a small blood stream on the splenic artery. Abdominal CT scan with contrast injection showed a lack of parenchymal enhancement of large epigastric ectopic spleen and a subcapsular hematoma. The diagnosis of wandering spleen with chronic torsion of the pedicle complicated by necrosis and subcapsular hematoma was confirmed. The patient underwent splenectomy. The postoperative course was uneventful. We here discuss the contribution of ultrasound and CT scan in the diagnosis of wandering spleen with chronic torsion of the pedicle.

  20. Crackscope : automatic pavement cracking inspection system.

    Science.gov (United States)

    2008-08-01

    The CrackScope system is an automated pavement crack rating system consisting of a : digital line scan camera, laser-line illuminator, and proprietary crack detection and classification : software. CrackScope is able to perform real-time pavement ins...

  1. Uncontrolled concrete bridge parapet cracking.

    Science.gov (United States)

    2013-06-01

    The Ohio Department of Transportation has recently identified the problem of wide-spread premature cracking of concrete bridge : parapets throughout its District 12 region (Northeast Ohio). Many of the bridge decks that contain these prematurely crac...

  2. Premature asphalt concrete pavement cracking.

    Science.gov (United States)

    2015-06-01

    Recently, the Oregon Department of Transportation (ODOT) has identified hot mix asphalt concrete : (HMAC) pavements that have displayed top-down cracking within three years of construction. The objective of : the study was to evaluate the top-down cr...

  3. Initiation and propagation of small corner cracks

    Science.gov (United States)

    Ellyin, Ferdnand; Kujawski, Daniel; Craig, David F.

    1994-01-01

    The behaviour of small corner cracks, inclined or perpendicular to loading direction, is presented. There are two aspects to this investigation: initiation of small cracks and monitoring their subsequent growth. An initial pre-cracking procedure under cyclic compression is adopted to minimize the residual damage at the tip of the growing and self-arresting crack under cyclic compression. A final fatigue specimen, cut from the larger pre-cracked specimen, has two corner flaws. The opening load of corner flaw is monitored using a novel strain gauge approach. The behaviour of small corner cracks is described in terms of growth rate relative to the size of the crack and its shape.

  4. Multidimensional Seismic Control by Tuned Mass Damper with Poles and Torsional Pendulums

    National Research Council Canada - National Science Library

    Haoxiang He; Wentao Wang; Honggang Xu

    2017-01-01

    .... In order to simultaneously control the translational responses and the torsional angle of asymmetry structures, a new type of tuned mass damper with tuned mass blocks, orthogonal poles, and torsional pendulums (TMDPP) is proposed...

  5. Torsional wave propagation in multiwalled carbon nanotubes using nonlocal elasticity

    Science.gov (United States)

    Arda, Mustafa; Aydogdu, Metin

    2016-03-01

    Torsional wave propagation in multiwalled carbon nanotubes is studied in the present work. Governing equation of motion of multiwalled carbon nanotube is obtained using Eringen's nonlocal elasticity theory. The effect of van der Waals interaction coefficient is considered between inner and outer nanotubes. Dispersion relations are obtained and discussed in detail. Effect of nonlocal parameter and van der Waals interaction to the torsional wave propagation behavior of multiwalled carbon nanotubes is investigated. It is obtained that torsional van der Waals interaction between adjacent tubes can change the rotational direction of multiwalled carbon nanotube as in-phase or anti-phase. The group and escape velocity of the waves converge to a limit value in the nonlocal elasticity approach.

  6. Standing torsional waves in a fully saturated, porous, circular cylinder

    CERN Document Server

    Solorza, S; 10.1111/j.1365-246X.2004.02198.x

    2004-01-01

    For dynamic measurement of the elastic moduli of a porous material saturated with viscous fluid using the resonance-bar technique, one also observes attenuation. In this article we have carried out the solution of the boundary-value problem associated with standing torsional oscillations of a finite, poroelastic, circular cylinder cast in the framework of volume-averaged theory of poroelasticity. Analysing this solution by eigenvalue perturbation approach we are able to develop expressions for torsional resonance and temporal attenuation frequencies in which the dependence upon the material properties are transparent. It shows how the attenuation is controlled by the permeability and the fluid properties, and how the resonance frequency drops over its value for the dry solid-frame due to the drag effect of fluid mass. Based upon this work we have a firm basis to determine solid-frame shear modulus, permeability, and tortuosity factor from torsional oscillation experiments.

  7. Mechanical Design of AM Fabricated Prismatic Rods under Torsion

    Directory of Open Access Journals (Sweden)

    Manzhirov Alexander V.

    2017-01-01

    Full Text Available We study the stress-strain state of viscoelastic prismatic rods fabricated or repaired by additive manufacturing technologies under torsion. An adequate description of the processes involved is given by methods of a new scientific field, mechanics of growing solids. Three main stages of the deformation process (before the beginning of growth, in the course of growth, and after the termination of growth are studied. Two versions of statement of two problems are given: (i given the torque, find the stresses, displacements, and torsion; (ii given the torsion, find the stresses, displacements, and torque. Solution methods using techniques of complex analysis are presented. The results can be used in mechanical and instrument engineering.

  8. Abnormalities of Penile Curvature: Chordee and Penile Torsion

    Directory of Open Access Journals (Sweden)

    Sylvia Montag

    2011-01-01

    Full Text Available Congenital chordee and penile torsion are commonly observed in the presence of hypospadias, but can also be seen in boys with the meatus in its orthotopic position. Varying degrees of penile curvature are observed in 4–10% of males in the absence of hypospadias. Penile torsion can be observed at birth or in older boys who were circumcised at birth. Surgical management of congenital curvature without hypospadias can present a challenge to the pediatric urologist. The most widely used surgical techniques include penile degloving and dorsal plication. This paper will review the current theories for the etiology of penile curvature, discuss the spectrum of severity of congenital chordee and penile torsion, and present varying surgical techniques for the correction of penile curvature in the absence of hypospadias.

  9. Sonographic Finding of Extravaginal Testicular Torsion in a Neonate: A Case Report

    Energy Technology Data Exchange (ETDEWEB)

    Son, Jee Young; Kim, Young Jun; Park, Hee Sun; Jeon, Hae Jeong; Park, Hyoung Keun; Paick, Sung Hyun; Kim, Hyeong Gon; Lho, Yong Soo; Lim, So Dug; Jung, Sung Il [Konkuk University School of Medicine, Seoul (Korea, Republic of)

    2011-06-15

    Extravaginal testicular torsion is known to be the predominant mechanism of the torsion in fetuses and neonates. In this torsion, twisting of the spermatic cord occurs outside the sac of the tunica vaginalis in the scrotum. Herein, we describe the sonographic findings of an extravaginal testicular torsion in a newborn baby who presented with a hard scrotal mass. Gray-scale ultrasound (US) showed hypoechoic linear striations in the testis with a thick hyperechoic peritesticular rim. Surgical exploration revealed an extravaginally twisted testis

  10. Deep learning methods for protein torsion angle prediction.

    Science.gov (United States)

    Li, Haiou; Hou, Jie; Adhikari, Badri; Lyu, Qiang; Cheng, Jianlin

    2017-09-18

    Deep learning is one of the most powerful machine learning methods that has achieved the state-of-the-art performance in many domains. Since deep learning was introduced to the field of bioinformatics in 2012, it has achieved success in a number of areas such as protein residue-residue contact prediction, secondary structure prediction, and fold recognition. In this work, we developed deep learning methods to improve the prediction of torsion (dihedral) angles of proteins. We design four different deep learning architectures to predict protein torsion angles. The architectures including deep neural network (DNN) and deep restricted Boltzmann machine (DRBN), deep recurrent neural network (DRNN) and deep recurrent restricted Boltzmann machine (DReRBM) since the protein torsion angle prediction is a sequence related problem. In addition to existing protein features, two new features (predicted residue contact number and the error distribution of torsion angles extracted from sequence fragments) are used as input to each of the four deep learning architectures to predict phi and psi angles of protein backbone. The mean absolute error (MAE) of phi and psi angles predicted by DRNN, DReRBM, DRBM and DNN is about 20-21° and 29-30° on an independent dataset. The MAE of phi angle is comparable to the existing methods, but the MAE of psi angle is 29°, 2° lower than the existing methods. On the latest CASP12 targets, our methods also achieved the performance better than or comparable to a state-of-the art method. Our experiment demonstrates that deep learning is a valuable method for predicting protein torsion angles. The deep recurrent network architecture performs slightly better than deep feed-forward architecture, and the predicted residue contact number and the error distribution of torsion angles extracted from sequence fragments are useful features for improving prediction accuracy.

  11. Coupling a small torsional oscillator to large optical angular momentum

    Science.gov (United States)

    Shi, H.; Bhattacharya, M.

    2013-03-01

    We propose a new configuration for realizing torsional optomechanics: an optically trapped windmill-shaped dielectric interacting with Laguerre-Gaussian cavity modes containing both angular and radial nodes. In contrast to existing schemes, our method can couple mechanical oscillators smaller than the optical beam waist to the in-principle unlimited orbital angular momentum that can be carried by a single photon, and thus generate substantial optomechanical interactions. Combining the advantages of small mass, large coupling, and low clamping losses, our work conceptually opens the way for the observation of quantum effects in torsional optomechanics.

  12. Seasonal preponderance in testicular torsion: is it a myth?

    Science.gov (United States)

    Karakan, Tolga; Bagcioglu, Murat; Özcan, Serkan; Telli, Onur; Turgut, Hasan; Özkan, Mehmet; Germiyanoglu, Cancon

    2015-12-01

    In this study, we aimed to investigate the relation of testicular torsion and weather conditions, and to report results from Turkey, a country located between temperate and sub-tropical climate zones. A total of 56 patients that had surgery with the diagnosis of testicular torsion in Ankara Education and Research Hospital Urology Clinic between 2005 and 2014 were included in the study. Age of the patient, side of torsion, date and time at onset of pain, scrotal exploration time, ischemia duration, degree of cord torsion, the surgical procedure performed, and scrotal Doppler ultrasound (USG) findings at the time of diagnosis and 1 month after surgery were retrospectively analyzed. The web archives of Turkish Republic Meteorology General Directorate was used to determine the seasonal and mean temperatures at the time of diagnosis. The data were analyzed with SPSS v. 16 statistical package program using Chi-square, Mann- Whitney U and Wilcoxon tests. The mean age of 56 males included in the study was 18.88 ± 0.73 years. Right testicular torsion was seen in 23, and left testicular torsion was seen in 33 patients. Testicular arterial flow was absent in 37, arterial flow was moderately decreased in 12, and significantly decreased in 7 patients on Doppler USG. Detorsion procedure was performed in 46 patients while 10 patients had orchiectomy. Nine patients were admitted in summer, 14 in fall, 15 in winter, and 18 in spring. The mean air temperature at the time of admittance was 9.31 ± 1.05 °C. The prevalence of testicular torsion was not found different among the seasons (p=0.39). The analysis of air temperature at the time of admittance of the patients revealed that it was below 15 °C in 40 patients while it was above 15 °C in 16 patients, with a significant difference in between (p=0.002). The prevalence of testicular torsion did not change in relation with the seasons. However, it was determined that its prevalence was directly proportional to the air temperature

  13. A black hole with torsion in 5D Lovelock gravity

    Science.gov (United States)

    Cvetković, B.; Simić, D.

    2018-03-01

    We analyze static spherically symmetric solutions of five dimensional (5D) Lovelock gravity in the first order formulation. In the Riemannian sector, when torsion vanishes, the Boulware–Deser black hole represents a unique static spherically symmetric black hole solution for the generic choice of the Lagrangian parameters. We show that a special choice of the Lagrangian parameters, different from the Lovelock Chern–Simons gravity, leads to the existence of a static black hole solution with torsion, the metric of which is asymptotically anti-de Sitter (AdS). We calculate the conserved charges and thermodynamical quantities of this black hole solution.

  14. Primary decomposition of torsion R[X]-modules

    Directory of Open Access Journals (Sweden)

    William A. Adkins

    1994-01-01

    Full Text Available This paper is concerned with studying hereditary properties of primary decompositions of torsion R[X]-modules M which are torsion free as R-modules. Specifically, if an R[X]-submodule of M is pure as an R-submodule, then the primary decomposition of M determines a primary decomposition of the submodule. This is a generalization of the classical fact from linear algebra that a diagonalizable linear transformation on a vector space restricts to a diagonalizable linear transformation of any invariant subspace. Additionally, primary decompositions are considered under direct sums and tensor product.

  15. Pediatric ovarian malignancy presenting as ovarian torsion: incidence and relevance.

    Science.gov (United States)

    Oltmann, Sarah C; Fischer, Anne; Barber, Robert; Huang, Rong; Hicks, Barry; Garcia, Nilda

    2010-01-01

    With ovarian torsion, concern for underlying malignancy in the enlarged ovary has previously driven surgeons to resection. Detorsion alone has been recommended to allow for resolution of edema of the ovary with follow-up ultrasound surveillance to evaluate for a persistent mass, yet is not routine practice. However, the incidence of malignancies presenting as ovarian torsion is not documented. Does the risk of an underlying malignancy justify salpingoophorectomy and decreased fertility? After institutional review board exemption (IRB#-022008-095), a 15(1/2)-year retrospective review was conducted to identify cases of operative ovarian torsion in our medical center. Tumors with neoplastic pathology (malignant and benign) were analyzed and compared with all reported cases in the literature. A total of 114 patients (mean +/- SEM age, 10 years, 2 days to 19 years +/- 0.53) with operatively proven ovarian torsion were identified. Four malignancies (3.5%) and 26 benign neoplasms (23%) were present in this age group. Malignancies consisted of serous borderline tumors (2), juvenile granulosa cell tumor (1), and dysgerminoma (1). All were stage I: the former were stage IA and cured with resection alone, and 1 was a stage IB dysgerminoma, which required chemotherapy. The literature yielded a total of 593 cases of operative ovarian torsion with 9 (1.5%) malignancies and 193 (33%) benign neoplasms. The malignancies were juvenile granulosa cell tumor (n = 4), dysgerminoma (n = 2), serous borderline tumors (n = 2), and 1 undifferentiated adenocarcinoma. By combining our series with 13 in the literature, a 1.8% malignancy rate occurred in 707 patients with ovarian torsion, markedly less than the reported malignancy rate of 10% in children with ovarian masses. Thus, neither a pathologic nor malignant lead point should be assumed in cases of torsion. In our series, which represents the largest series of torsion in the pediatric literature, all malignancies presented as stage I

  16. Ultrasonographic diagnosis of torsion of testicular appendages; Diagnostico por ecografia de la torsion de los apendices testiculares

    Energy Technology Data Exchange (ETDEWEB)

    Esparza, J.; Gonzalez, A.; Cordero, J. L. [Hospital Virgen del Camino. Pamplona (Spain)

    2000-07-01

    To determine the efficacy of ultrasound in boys presenting torsion of a testicular appendage. A series of 30 boys with acute scrotal pain due to torsion of a testicular appendage was studied. Nine patients underwent surgery. The clinical findings and course in the remaining 21 suggested the presence of this abnormality. All of them underwent conventional and color Doppler ultrasound using a 7.5 MHz transducer. In 15 boys, ultrasound images depicted the affected appendage as a mass between the epididymal head and the testicle. In 13 cases, only signs of a inflammatory reaction, with enlargement of the epididymal head and tunicas presenting hyperflow and hydrocele, mimicking acute epididymities. In two cases, the images were normal. There is no definitive, distinguishing ultrasound image corresponding to testicular appendage torsion. Therefore, this diagnostic technique should be accompanied by clinical assessment. (Author) 14 refs.

  17. Corrosion fatigue crack propagation in metals

    Science.gov (United States)

    Gangloff, Richard P.

    1990-01-01

    This review assesses fracture mechanics data and mechanistic models for corrosion fatigue crack propagation in structural alloys exposed to ambient temperature gases and electrolytes. Extensive stress intensity-crack growth rate data exist for ferrous, aluminum and nickel based alloys in a variety of environments. Interactive variables (viz., stress intensity range, mean stress, alloy composition and microstructure, loading frequency, temperature, gas pressure and electrode potential) strongly affect crack growth kinetics and complicate fatigue control. Mechanistic models to predict crack growth rates were formulated by coupling crack tip mechanics with occluded crack chemistry, and from both the hydrogen embrittlement and anodic dissolution/film rupture perspectives. Research is required to better define: (1) environmental effects near threshold and on crack closure; (2) damage tolerant life prediction codes and the validity of similitude; (3) the behavior of microcrack; (4) probes and improved models of crack tip damage; and (5) the cracking performance of advanced alloys and composites.

  18. Cracking in Flexural Reinforced Concrete Members

    DEFF Research Database (Denmark)

    Rasmussen, Annette Beedholm; Fisker, Jakob; Hagsten, Lars German

    2017-01-01

    The system of cracks developing in reinforced concrete is in many aspects essential when modelling structures in both serviceability- and ultimate limit state. This paper discusses the behavior concerning crack development in flexural members observed from tests and associates it with two different...... existing models. From the investigations an approach is proposed on how to predict the crack pattern in flexural members involving two different crack systems; primary flexural cracks and local secondary cracks. The results of the approach is in overall good agreement with the observed tests and captures...... the pronounced size effect associated with flexural cracking in which the crack spacing and crack widths are approximately proportional to the depth of the member....

  19. Edge domination in grids

    DEFF Research Database (Denmark)

    Klostermeyer, William F.; Yeo, Anders

    2015-01-01

    It has been conjectured that the edge domination number of the m × n grid graph, denoted by γ′(Pm□Pn), is ⌊mn/3⌋, when m,n ≥ 2. Our main result gives support for this conjecture by proving that ⌊mn/3⌋ ≤ -γ′{Pm□Pn) ≤ mn/3 + n/12 + 1, when m,n ≥ 2. We furthermore show that the conjecture holds when...

  20. Off the edge

    OpenAIRE

    Stoneham, Luke

    2014-01-01

    This thesis was submitted for the degree of Doctor of Philosophy and was awarded by Brunel University London. Work which takes from elsewhere forms an important thread in European art music. There is a long tradition of music which variously borrows, thieves, pastiches, plagiarises, ironically ‘retakes’, hoaxes, impersonates and appropriates. The music I have written for Off the edge, while seeking to honour and add to this thread, also attempts to zoom in upon and make explicit the idea o...

  1. Simulation of Chloride Diffusion in Cracked Concrete with Different Crack Patterns

    Directory of Open Access Journals (Sweden)

    Xiao-Yong Wang

    2016-01-01

    Full Text Available Chloride-induced corrosion of steel rebar is one of the primary durability problems for reinforced concrete structures in marine environment. Furthermore, if the surfaces of concrete structures have cracks, additional chloride can penetrate into concrete through cracked zone. For chloride ingression into cracked concrete, former researches mainly focus on influence of crack width on chloride diffusion coefficients. Other crack characteristics, such as chloride depth, crack shape (equal-width crack or tapered crack, crack density, and spacing, are not studied in detail. To fill this gap, this paper presents a numerical procedure to simulate chloride ingression into cracked concrete with different crack geometry characteristics. Cracked concrete is divided into two parts, sound zone and cracked zone. For stress-free concrete, the diffusion coefficient of sound zone is approximately assumed to be the same as sound concrete, and the diffusion coefficient of cracked zone is expressed as a piecewise function of crack width. Two-dimensional finite element method is used to determine chloride concentration. It is found that, with the increasing of crack width, crack depth, and crack amount, chloride ingression will aggravate. The analysis results generally agree with experimental results.

  2. Failure analysis of a first stage IN738 gas turbine blade tip cracking in a thermal power plant

    OpenAIRE

    Rani, Sushila; Atul K. Agrawal; Rastogi, Vikas

    2017-01-01

    This research paper deals with the investigation of causes of failure of the first stage gas turbine blade of 30 MW gas turbine having tip cracks at the trailing as well as leading edge. This blade is made of nickel based super alloy IN738LC, having directional solidified grain structure and contains aluminide coating (Pt–Al2) by diffusion process. The main focus of the paper is evaluation of tip crack at the trailing edge and further degradation of blade coating. The investigations included ...

  3. Effects of torsion on intervertebral disc gene expression and biomechanics, using a rat tail model.

    Science.gov (United States)

    Barbir, Ana; Godburn, Karolyn E; Michalek, Arthur J; Lai, Alon; Monsey, Robert D; Iatridis, James C

    2011-04-15

    In vitro and in vivo rat tail model to assess effects of torsion on intervertebral disc biomechanics and gene expression. Investigate effects of torsion on promoting biosynthesis and producing injury in rat caudal intervertebral discs. Torsion is an important loading mode in the disc and increased torsional range of motion is associated with clinical symptoms from disc disruption. Altered elastin content is implicated in disc degeneration, but its effects on torsional loading are unknown. Although effects of compression have been studied, the effect of torsion on intervertebral disc gene expression is unknown. In vitro biomechanical tests were performed in torsion on rat tail motion segments subjected to 4 treatments: elastase, collagenase, genipin, control. In vivo tests were performed on rats with Ilizarov-type fixators implanted to caudal motion segments with five 90 minute loading groups: 1 Hz cyclic torsion to ± 5 ± 15° and ± 30°, static torsion to + 30°, and sham. Anulus and nucleus tissues were separately analyzed using qRT-PCR for gene expression of anabolic, catabolic, and proinflammatory cytokine markers. In vitro tests showed decreased torsional stiffness following elastase treatment and no changes in stiffness with frequency. In vivo tests showed no significant changes in dynamic stiffness with time. Cyclic torsion upregulated elastin expression in the anulus fibrosus. Up regulation of TNF-α and IL-1β was measured at ±30°. We conclude that strong differences in the disc response to cyclic torsion and compression are apparent with torsion increasing elastin expression and compression resulting in a more substantial increase in disc metabolism in the nucleus pulposus. Results highlight the importance of elastin in torsional loading and suggest that elastin remodels in response to shearing. Torsional loading can cause injury to the disc at excessive amplitudes that are detectable biologically before they are biomechanically.

  4. Quantum torsion with non-zero standard deviation: Non-perturbative approach for cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Dzhunushaliev, Vladimir, E-mail: v.dzhunushaliev@gmail.com [Dept. Theor. and Nucl. Phys., KazNU, Almaty, 010008 (Kazakhstan); Institute for Basic Research, Eurasian National University, Astana, 010008 (Kazakhstan); Institute of Physicotechnical Problems and Material Science of the NAS of the Kyrgyz Republic, 265 a, Chui Street, Bishkek, 720071 (Kyrgyzstan); Institut für Physik, Universität Oldenburg, Postfach 2503, D-26111 Oldenburg (Germany); Folomeev, Vladimir, E-mail: vfolomeev@mail.ru [Institute of Physicotechnical Problems and Material Science of the NAS of the Kyrgyz Republic, 265 a, Chui Street, Bishkek, 720071 (Kyrgyzstan); Institut für Physik, Universität Oldenburg, Postfach 2503, D-26111 Oldenburg (Germany); Kleihaus, Burkhard, E-mail: b.kleihaus@uni-oldenburg.de [Institut für Physik, Universität Oldenburg, Postfach 2503, D-26111 Oldenburg (Germany); Kunz, Jutta, E-mail: jutta.kunz@uni-oldenburg.de [Institut für Physik, Universität Oldenburg, Postfach 2503, D-26111 Oldenburg (Germany)

    2013-02-12

    Cosmology with non-perturbative quantum corrections resulting from torsion is considered. It is shown that the evolution of closed, open and flat Universes is changed because of the presence of a non-zero dispersion of quantum torsion. The evolution of a Universe with quantum torsion and with one type of average curvature can be similar to the evolution of a Universe without quantum torsion and with another type of average curvature. For the description of the non-perturbative quantum torsion, a vector field approximation is applied.

  5. Mechanics of quasi-static crack growth

    Energy Technology Data Exchange (ETDEWEB)

    Rice, J R

    1978-10-01

    Results on the mechanics of quasi-static crack growth are reviewed. These include recent studies on the geometry and stability of crack paths in elastic-brittle solids, and on the thermodynamics of Griffith cracking, including environmental effects. The relation of crack growth criteria to non-elastic rheological models is considered and paradoxes with energy balance approaches, based on singular crack models, are discussed for visco-elastic, diffuso-elastic, and elastic-plastic materials. Also, recent approaches to prediction of stable crack growth in ductile, elastic-plastic solids are discussed.

  6. Correlation of severity of penile torsion with type of hypospadias ...

    African Journals Online (AJOL)

    A. Bhat

    shaft (torsion) toward either side of the midline and ventral curvature was measured using a sterile small protractor around the penile shaft. ... ing with skin re-attachment [2,4,5], dorsal dartos wrap rotation [3], pubicperiostealstitch[6] ... the parents/patients was taken for data evaluation, photographs and inclusion in study.

  7. Torsion of the Spermatic Cord: An Exemplary Early Presentation ...

    African Journals Online (AJOL)

    Unfortunately, in many series, late presentation is still the norm. In the index patient, the presentation time was very short. In our environment, patients with torsion of the spermatic cord can present early and be operated promptly if we can provide public health education, mobile phones, commercial taxis, and good road ...

  8. Static balancing of an inverted pendulum with prestressed torsion bars

    NARCIS (Netherlands)

    Radaelli, G.; Buskermolen, R; Barents, R; Herder, J.L.

    2017-01-01

    This paper presents a method for the design of a statically balanced inverted pendulum. The non-linear moment-rotation characteristic of the pendulum's weight is approximated by a piecewise linear characteristic. Each transition is realized by engaging or disengaging one or more torsion bars, by

  9. Clinical characteristics of adnexal torsion in premenarchal patients.

    Science.gov (United States)

    Ganer Herman, Hadas; Shalev, Amir; Ginat, Shimon; Kerner, Ram; Keidar, Ran; Bar, Jacob; Sagiv, Ron

    2016-03-01

    To compare clinical characteristics of adnexal torsion in premenarchal patients as compared to postmenarchal ones. A retrospective 22-year cohort of all cases of surgically verified adnexal torsion in premenarchal and postmenarchal patients (excluding postmenopausal and pregnant patients). Data collected included symptoms, signs and imaging at presentation, surgical mode, and procedure and histology. 16 cases of adnexal torsion among premenarchal patients were compared to 302 cases among postmenarchal ones. Clinical presentation was similar, notable only for more nausea and vomiting among the premenarchal group. Ovarian cysts were more commonly demonstrated among postmenarchal patients (82.4 and 30.8%, p appearance on ultrasound, which was more common in premenarchal patients (69.3 vs. 17.2%, p trend for detorsion and cystectomy/fenestration, which were more common in postmenarchal surgeries (25 vs. 50.6%, p = 0.06). Histology was similar among both groups, with no cases of malignancy in premenarchal patients. Adnexal torsion in premenarchal patients is rare, presents similarly to older patients, but involves a normal adnexa in 69% of cases, therefore requiring a high index of suspicion in any premenarchal patient with acute onset abdominal pain.

  10. Influence of rigid boundary on the propagation of torsional surface ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 124; Issue 1. Influence of rigid boundary on the propagation of torsional ... rigid boundary, whereas it does at the free boundary. Graphical user interface (GUI) software has been developed using MATLAB 7.5 to generalize the effect of various parameter discussed.

  11. Determination of ocular torsion by means of automatic pattern recognition

    NARCIS (Netherlands)

    Groen, Eric; Bos, Jelte E.; Nacken, Peter F M; De Graaf, Bernd

    A new, automatic method for determination of human ocular torsion (OT) was developed based on the tracking of iris patterns in digitized video images. Instead of quantifying OT by means of cross-correlation of circular iris samples, a procedure commonly applied, this new method automatically selects

  12. Determination of ocular torsion by means of automatic pattern recognition

    NARCIS (Netherlands)

    Groen, E.L.; Bos, J.E.; Nacken, P.F.M.; Graaf, B. de

    1996-01-01

    A new, automatic method for determination of human ocular torsion (OT) was devel-oped based on the tracking of iris patterns in digitized video images. Instead of quanti-fying OT by means of cross-correlation of circular iris samples, a procedure commonly applied, this new method automatically

  13. Torsion of an Epiploic Appendix Pretending as Acute Appendicitis

    Directory of Open Access Journals (Sweden)

    Kamran Ahmad Malik

    2010-07-01

    Full Text Available Torsion of an epiploic appendix is a rare surgical entity. Its unusual symptomatology, wide variation in physical findings and the absence of helpful laboratory and radiological studies makes it very difficult to diagnose pre-operatively. This is a report of this rare entity found in a patient upon diagnostic laparoscopy performed for suspected acute appendicitis

  14. Penile torsion correction by diagonal corporal plication sutures

    Directory of Open Access Journals (Sweden)

    Brent W. Snow

    2009-02-01

    Full Text Available Penile torsion is commonly encountered. It can be caused by skin and dartos adherence or Buck’s fascia attachments. The authors suggest a new surgical approach to solve both problems. If Buck’s fascia involvement is demonstrated by artificial erection then a new diagonal corporal plication suture is described to effectively solve this problem.

  15. The dynamic characteristics of a torsionally flexible metal coupling

    Directory of Open Access Journals (Sweden)

    Krzysztof FILIPOWICZ

    2008-01-01

    Full Text Available At work a structure was presented to the new structural form of the metal coupling about the great torsion susceptibility and description of the research stands and methodology of determining its dynamic characteristics and also to get research findings determining exchanged characterizations which were presented.

  16. Torsional vibration of thin-walled elastic beams with doubly ...

    African Journals Online (AJOL)

    In this paper, the problem of analyzing the torsional vibration of thin-walled elastic beams, with open cross-sections that are doubly symmetric and traversed by moving concentrated masses at constant speeds is addressed. The mathematical model adopted accounts for both the gravitational and inertial effects of the ...

  17. Investigation of torsional vibrations in thick walled hollow poroelastic ...

    Indian Academy of Sciences (India)

    Abstract. This paper deals with the study of torsional vibrations of thick walled hollow poroelastic cylinder using Biot's extension theory. Considering the boundaries to be stress free, the frequency equation is obtained in the presence of dissipation which is transcendental and complex valued in nature. In the special case of ...

  18. Investigation of torsional vibrations in thick walled hollow poroelastic ...

    Indian Academy of Sciences (India)

    This paper deals with the study of torsional vibrations of thick walled hollow poroelastic cylinder using Biot's extension theory. Considering the boundaries to be stress free, the frequency equation is obtained in the presence of dissipation which is transcendental and complex valued in nature. In the special case of ...

  19. Torsional Newton-Cartan geometry and the Schrodinger algebra

    NARCIS (Netherlands)

    Bergshoeff, Eric A.; Hartong, Jelle; Rosseel, Jan

    2015-01-01

    We show that by gauging the Schrodinger algebra with critical exponent z and imposing suitable curvature constraints, that make diffeomorphisms equivalent to time and space translations, one obtains a geometric structure known as (twistless) torsional Newton-Cartan geometry (TTNC). This is a version

  20. Numerical Simulation of Gleeble Torsion Testing of HSLA-65 Steel

    Science.gov (United States)

    2008-04-01

    3800 Torsion machine on AISI 304L and HSLA-65 steels to simulate the friction stir welding of these materials. A photograph of the experimental setup...strain rate levels = 420 flow stress values provided in the dataset for DEFORM 3D. Because of lack of data as well as some inconsistencies between

  1. Can Ocular Torsion be Measured Using the Slitlamp Biomicroscope?

    Directory of Open Access Journals (Sweden)

    Kothari Mihir

    2005-03-01

    Full Text Available PURPOSE: To evaluate and compare a stereo-biomicroscopic technique of ocular torsion measurement with fundus photographic technique. METHODS: This prospective masked observational study included 72 eyes of 36 consecutive subjects with normal ocular motility. The disc-foveal angle was measured by two masked investigators using a slitlamp stereo-biomicroscopic and fundus photographic technique. RESULTS: The mean age was 13.7 years (6 - 44 years, and 15 (41.6% were males. The average torsion using the slitlamp technique was 5.5 3.3o and 6.1 4.3o with fundus photographic technique. Clinical agreement between the two techniques for 5o and 6o torsion was 81% and 90% respectively. The average difference between the two techniques was 3.0 2.6o. The mean inter-ocular difference was 3.3 2.7o (SD, 2.77 and 5.5 4.6o using the slitlamp and fundus photographic technique respectively. The Pearson correlation coefficient (r2 was 0.5 CONCLUSION: The fundus photographic technique remains the gold standard test for the measurement of ocular torsion. The slitlamp biomicroscopic method can be useful where a fundus camera is unavailable. Further studies are required to test the repeatability of these tests.

  2. Torsion of the appendix testis in an undescended testicle | Hajji ...

    African Journals Online (AJOL)

    Physical examination revealed a tender, swollen and painful undescended testis located in the inguinal area with an empty ipsilateral hemiscrotum. Men presenting with pain and undescended testis are more likely to have testicular torsion, malignancy, associated inguinal hernia or trauma. The extra-scrotal position of the ...

  3. Torsional vibrations of infinite composite poroelastic cylinders | Shah ...

    African Journals Online (AJOL)

    The displacements of second and third torsional modes are determined and presented graphically for the ratio of radius of composite poroelastic solid cylinder to the radius of the inner solid cylinder. Results of previous works are shown as special case of the present analysis. By ignoring liquid effects, the results of purely ...

  4. Algebraic deformations arising from orbifolds with discrete torsion

    OpenAIRE

    Căldăraru, Andrei; Giaquinto, Anthony; Witherspoon, Sarah

    2002-01-01

    We develop methods for computing Hochschild cohomology groups and deformations of crossed product rings. We use these methods to find deformations of a ring associated to a particular orbifold with discrete torsion, and give a presentation of the center of the resulting deformed ring. This connects with earlier calculations by Vafa and Witten of chiral numbers and deformations of a similar orbifold.

  5. Colonic stricture secondary to torsion of an ovarian cyst

    Energy Technology Data Exchange (ETDEWEB)

    Karmazyn, Boaz; Ziv, Nitza; Horev, Gadi [Department of Diagnostic Radiology, Schneider Children' s Medical Center of Israel, Petah Tiqva (Israel); Steinberg, Ran; Zer, Michael [Pediatric Surgery, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv (Israel)

    2002-01-01

    Intestinal obstruction in the newborn is a potentially life-threatening complication. The most common causes are meconium plug, meconium ileus, intestinal atresia, intestinal malrotation, and Hirschprung's disease. We present an unusual case of intestinal obstruction caused by torsion of an ovarian cyst. The left fimbria and ovary swirled around the sigmoid colon, causing colonic stricture. (orig.)

  6. Adnexal torsion: MR imaging findings of viable ovary

    Energy Technology Data Exchange (ETDEWEB)

    Haque, T.L.; Konishi, J. [Dept. of Nuclear Medicine, Hitachi Medical Corp., Kyoto (Japan); Togashi, K.; Kobayashi, H. [Dept. of Diagnostic and Interventional Imageology, Hitachi Medical Corp., Kyoto (Japan); Fujii, S. [Dept. of Gynecology and Obstetrics, Kyoto Univ. (Japan)

    2000-12-01

    We report a case of torsed ovarian cystic tumor, in which contrast-enhanced high-resolution MR images accurately contributed to the diagnosis of torsion despite the lack of symptoms and to the preoperative evaluation of viability of the edematous ovary. Accurate preoperative assessment by MR images and prompt conservative surgical approach succeeded in salvaging the involved ovary. (orig.)

  7. Penile Torsion: an Overlooked Anomaly with Distal Hypospadias

    African Journals Online (AJOL)

    HussamHassan

    Purpose: To identify the incidence of penile torsion among patients with hypospadias, while using a simple and objective method to measure the degree of rotation. Materials & Methods: From December 2007 to March 2009, all boys presenting to our department for hypospadias repair. (100 boys) were examined for ...

  8. Triorchidism with Torsion | Kumar | Annals of Medical and Health ...

    African Journals Online (AJOL)

    Polyorchidism is a rare anomaly; triorchidism is the commonest type and is frequently associated with cryptorchidism, inguinal hernia, and testicular torsion. It is also reported as an increased risk of testicular malignancy. We report a case of 72.year.old man with left supernumerary testes in the left hemiscrotum.

  9. Torsion Pendulum Experiment at the International Physics Olympiad

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 5; Issue 6. Torsion Pendulum Experiment at the International Physics Olympiad. Sandeep Bala. Classroom Volume 5 Issue 6 June 2000 pp 76-85. Fulltext. Click here to view fulltext PDF. Permanent link:

  10. Effect of irregularity on torsional surface waves in an initially ...

    Indian Academy of Sciences (India)

    The present paper is concerned with the propagation of torsional surface waves in an initially stressedanisotropic porous layer sandwiched between homogeneous and non-homogeneous half-space. We assumethe quadratic inhomogeneity in rigidity and density in the lower half-space and irregularity is taken inthe form of ...

  11. Spectral Action for Torsion with and without Boundaries

    DEFF Research Database (Denmark)

    Iochum, B.; Levy, Cyril Olivier; Vassilevich, D.

    2012-01-01

    We derive a commutative spectral triple and study the spectral action for a rather general geometric setting which includes the (skew-symmetric) torsion and the chiral bag conditions on the boundary. The spectral action splits into bulk and boundary parts. In the bulk, we clarify certain issues...

  12. Penile Torsion: an Overlooked Anomaly with Distal Hypospadias ...

    African Journals Online (AJOL)

    Purpose: To identify the incidence of penile torsion among patients with hypospadias, while using a simple and objective ethod to measure the degree of rotation. Materials & Methods: From December 2007 to March 2009, all boys presenting to our department for hypospadias repair (100 boys) were examined for ...

  13. Portal venous thrombosis developing after torsion of a wandering ...

    African Journals Online (AJOL)

    Torsion of a wandering spleen is a rare disease. The symptoms and signs of this condition are only present when the splenic pedicle torts. The etiological factors are the congenital absence of the ligaments that hold the spleen in its normal anatomic position, or the relaxation of these ligaments resulting from conditions like ...

  14. Torsion of the Spermatic Cord: An Exemplary Early Presentation

    African Journals Online (AJOL)

    2017-10-26

    Oct 26, 2017 ... How to cite this article: Oluyemi OY. Torsion of the spermatic cord: an exemplary early presentation. Niger J Clin Pract 2017;XX;000-000. This is an open access article distributed under the terms of the Creative Commons. Attribution-Non Commercial-Share Alike 3.0 License, which allows others to remix,.

  15. Revisiting the Zassenhaus conjecture on torsion units for the integral ...

    Indian Academy of Sciences (India)

    Abstract. In recent years several new restrictions on integral partial augmentations for torsion units of ZG have been introduced, which have improved the effectiveness of the Luthar–Passi method for checking the Zassenhaus conjecture for specific groups. G. In this note, we report that the Luthar–Passi method with the new ...

  16. Portal Venous Thrombosis Developing after Torsion of a Wandering ...

    African Journals Online (AJOL)

    2017-03-06

    Mar 6, 2017 ... Website: www.njcponline.com. DOI:10.4103/1119-3077.201431. Case Report. How to cite this article: Yilmaz Ö, Kiziltan R, Almali N, Aras A. Portal venous thrombosis developing after torsion of a wandering spleen. Niger J Clin. Pract 2017;20:394-6. This is an open access article distributed under the terms ...

  17. Torsion of bars with regular polygonal sections | Zongo | Global ...

    African Journals Online (AJOL)

    In this article, the study of the torsion of cylindrical bars using large singular finite elements method leads to the resolution of the system of linear equations using MATLAB software. Particularly, the numerical solution of the problem of beams with regular section shows clearly the precision of the method depending upon the ...

  18. Effect of irregularity on torsional surface waves in an initially ...

    Indian Academy of Sciences (India)

    The present paper is concerned with the propagation of torsional surface waves in an initially stressed anisotropic porous layer sandwiched between homogeneous and non-homogeneous half-space. We assume the quadratic inhomogeneity in rigidity and density in the lower half-space and irregularity is taken in the form ...

  19. Tumour, Torsion or Trauma? | Nduhiu | Annals of African Surgery

    African Journals Online (AJOL)

    We present a case of a 22 year old who was managed by various levels of clinicians for a 12 day period prior to testicular exploration which finally revealed testicular torsion. Remarkably, the testis was viable and the finding of a hematoma of the epididymis suggested a history of trauma which was not forthcoming from the ...

  20. Testicular torsion on the Jos Plateau | Ugwu | West African Journal ...

    African Journals Online (AJOL)

    In order to determine the pattern and the factors that influenced outcome, we retrospectively studied fifty-seven patients with torsion of the testis admitted to the Jos University Teaching hospital between August 1993 and July 2001. The age ranged from 2 to 55 years with a mean of 22.7 years. Majority (79%) of the patients ...

  1. Origin of methyl torsional potential barrier–An overview

    Indian Academy of Sciences (India)

    This paper presents the evolution of views on methyl internal rotation potential barrier. Various mechanisms proposed for the origin of torsional barrier in ethane have been reviewed. Inadequacy of one dimensional description of internal rotation has been highlighted in small methyl conjugated molecules in the light of its ...

  2. Influence of rigid boundary on the propagation of torsional surface ...

    Indian Academy of Sciences (India)

    The present work illustrates a theoretical study on the effect of rigid boundary for the propagation of torsional surface wave in an inhomogeneous crustal layer over an inhomogeneous half space. It is believed that the inhomogeneity in the half space arises due to hyperbolic variation in shear modulus and density whereas ...

  3. The Torsion-Extension Coupling in Pretwisted Elastic Beams

    DEFF Research Database (Denmark)

    Krenk, Steen

    1983-01-01

    An explicit asymptotic formula is derived for the untwist of a pretwisted elastic beam subjected to homogeneous extension or equivalently for the longitudinal contraction produced by a torsional moment. It is based on an asymptotic expansion of the three dimensional equations of linear elasticity...

  4. Testicular torsion: Needless testicular loss can be prevented | Njeze ...

    African Journals Online (AJOL)

    Background: The risk of losing the testis is an ever present threat in patients with testicular torsion, who delay before presenting to the surgeon. A retrospective study was carried out to audit patients with acute scrotal pain who came to the Trans Ekulu Hospital Enugu, the promptness of offering them surgical treatment and ...

  5. Timoshenko–Wagner–Kappus Torsion Bending Theory and Wind ...

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 7; Issue 10. Timoshenko–Wagner–Kappus Torsion Bending Theory and Wind Tunnel Balance Design. S P Govinda Raju K R Y Simha. General Article Volume 7 Issue 10 October 2002 pp 54-58 ...

  6. Getter materials for cracking ammonia

    Energy Technology Data Exchange (ETDEWEB)

    Boffito, Claudio; Baker, John D.

    1999-11-02

    A method is provided for cracking ammonia to produce hydrogen. The method includes the steps of passing ammonia over an ammonia-cracking catalyst which is an alloy including (1) alloys having the general formula Zr.sub.1-x Ti.sub.x M.sub.1 M.sub.2, wherein M.sub.1 and M.sub.2 are selected independently from the group consisting of Cr, Mn, Fe, Co, and Ni, and x is between about 0.0 and about 1.0 inclusive; and between about 20% and about 50% Al by weight. In another aspect, the method of the invention is used to provide methods for operating hydrogen-fueled internal combustion engines and hydrogen fuel cells. In still another aspect, the present invention provides a hydrogen-fueled internal combustion engine and a hydrogen fuel cell including the above-described ammonia-cracking catalyst.

  7. Edge Relaxation and Boundary Continuity.

    Science.gov (United States)

    1980-05-01

    V. Measures of Performance 94 1. Fixed Points, Entropy , and Consistency 94 2. Global Measures of Uncertainty, Drift, and Inconsistency 96 VI...operators have been applied. Marr EMARR763 uses a set of edge detectors of varying size to determine the appropriate width of an edge to be asserted in his...certain edges is a fixed point. The array of probabilities has zero entropy when the probability of each edge in the array is 0 or 1. The closed-loop

  8. Pairs Of Edges As Chords And As Cut-Edges

    Directory of Open Access Journals (Sweden)

    McKee Terry A.

    2014-11-01

    Full Text Available Several authors have studied the graphs for which every edge is a chord of a cycle; among 2-connected graphs, one characterization is that the deletion of one vertex never creates a cut-edge. Two new results: among 3-connected graphs with minimum degree at least 4, every two adjacent edges are chords of a common cycle if and only if deleting two vertices never creates two adjacent cut-edges; among 4-connected graphs, every two edges are always chords of a common cycle.

  9. Fatigue crack initiation from small defects under low stress ratios in SAE52100 bearing steel

    Science.gov (United States)

    Hino, Y.; Matsunaga, H.

    2010-03-01

    Axial-loading fatigue tests were carried out under low stress ratios, R = -∞ ~ -5.33, by use of a cylindrical specimen of SAE52100 bearing steel having drill holes of 50 ~ 200 μm in diameter. The maximum stresses, σmax = 0 ~ 300 MPa were combined with the minimum stresses, σmin of -1600 or -1800 MPa. Even at σmax = 0, fatigue cracks were initiated at hole edges by cyclic compressive stress of σmin = -1800 MPa, and the cracks finally became non-propagating. When σmax was positive, fatigue cracks were initiated even at σmin = -1600 MPa and they also became non-propagating. The length of non-propagating cracks increased with an increase in σmax. Those phenomena were considered to be related to the tensile residual stress that was induced by the plastic deformation in the vicinity of hole edges. The relationship between the length of non-propagating crack and the residual stress field was investigated in terms of elastic-plastic finite element analysis.

  10. Elastic compliance of single-edge-notched tension SE(T (or SENT specimens

    Directory of Open Access Journals (Sweden)

    B. Tyson

    2014-10-01

    Full Text Available There has been a trend recently to use specimen geometries for toughness measurement that are more representative of actual flaw geometries in service. A prominent example is the use of single-edge-notched tension specimens for assessment of surface flaws in pipelines. To obtain a resistance (R curve, i.e. J-integral or CTOD as a function of crack growth, it is necessary to monitor the crack size as a function of J or CTOD. To facilitate obtaining these data from a single specimen, the elastic CMOD unloading compliance C has been used in several testing programs to estimate crack size. C is a function of several variables in addition to crack size – notably, specimen constraint (plane stress or plane strain. In this paper, the dependence of C on these variables will be discussed.

  11. Preliminary results with a torsion microbalance indicate that carbon dioxide and exposed carbonic anhydrase in the organic matrix are the basis of calcification on the skeleton surface of living corals

    OpenAIRE

    Ian M. Sandeman

    2012-01-01

    Ocean acidification is altering the calcification of corals, but the mechanism is still unclear. To explore what controls calcification, small pieces from the edges of thin plates of Agaricia agaricites were suspended from a torsion microbalance into gently stirred, temperaturecontrolled, seawater. Net calcification rates were monitored while light, temperature and pH were manipulated singly. The living coral pieces were sensitive to changes in conditions, especially light, and calcification ...

  12. Cracking and corrosion recovery boiler

    Energy Technology Data Exchange (ETDEWEB)

    Suik, H. [Tallinn Technical University, Horizon Pulp and Paper, Tallinn (Estonia)

    1998-12-31

    The corrosion of heat surfaces and the cracking the drums are the main problems of the recovery boiler. These phenomena have been appeared during long-term operation of boiler `Mitsubishi - 315` erected at 1964. Depth of the crack is depending on the number of shutdowns and on operation time. Corrosion intensity of different heat surfaces is varying depend on the metal temperature and the conditions at place of positioning of tube. The lowest intensity of corrosion is on the bank tubes and the greatest is on the tubes of the second stage superheater and on the tubes at the openings of air ports. (orig.) 5 refs.

  13. Nonlinear structural crack growth monitoring

    Science.gov (United States)

    Welch, Donald E.; Hively, Lee M.; Holdaway, Ray F.

    2002-01-01

    A method and apparatus are provided for the detection, through nonlinear manipulation of data, of an indicator of imminent failure due to crack growth in structural elements. The method is a process of determining energy consumption due to crack growth and correlating the energy consumption with physical phenomena indicative of a failure event. The apparatus includes sensors for sensing physical data factors, processors or the like for computing a relationship between the physical data factors and phenomena indicative of the failure event, and apparatus for providing notification of the characteristics and extent of such phenomena.

  14. University of Florida Torsion Pendulum for Testing Key LISA Technology

    Science.gov (United States)

    Apple, Stephen; Chilton, Andrew; Olatunde, Taiwo Janet; Hillsberry, Daniel; Parry, Samantha; Ciani, Giacomo; Wass, Peter; Mueller, Guido; Conklin, John

    2018-01-01

    This presentation will describe the design and performance of a new torsion pendulum at the University of Florida used for testing inertial sensors and associated technologies for use in space – based gravitational wave observatories and geodesy missions. In particular this new torsion pendulum facility is testing inertial sensors and associated technology for the upcoming LISA (laser interferometer space antenna) space-based gravitational wave observatory mission. The torsion pendulum apparatus is comprised of a suspended cross bar assembly that has LISA test mass mockups at each of its ends. Two of the test mass mockups are enclosed by capacitive sensors which provide actuation and position sensing. The entire assembly is housed in a vacuum chamber. The pendulum cross-bar converts rotational motion of the test masses about the suspension fiber axis into translational motion. The 22 cm cross bar arm length along with the extremely small torsional spring constant of the suspension fiber results in a near free fall condition in the translational degree-of-freedom orthogonal to both the member and the suspension fiber. The test masses are electrically isolated from the pendulum assembly and their charge is controlled via photoemission using fiber coupled UV LEDS. Position of the test masses is measured using both capacitive and interferometric readout. The broadband sensitivity of the capacitive readout and laser interferometer readout is 30 nm/√Hz and 0.5 nm/√Hz respectively. The performance of the pendulum measured in equivalent acceleration noise acting on a LISA test mass is approximately 3 × 10-13 ms-2/√Hz at 2 mHz. This presentation will also discuss the design and fabrication of a flight-like gravitational reference sensor that will soon be integrated into the torsion pendulum facility. This flight-like GRS will allow for noise performance measurements in a more LISA-like configuration.

  15. Continuity of the torsionless limit as a selection rule for gravity theories with torsion

    CERN Document Server

    Fabbri, Luca

    2014-01-01

    While one can in principle augment gravity theory with torsion, it is generally thought that any such torsion affects would be too small to be of consequence. Here we show that this cannot in general be the case. We show that the limit of vanishing torsion is not necessarily a continuous one, with the theory obtained in the limit not necessarily coinciding with the theory in which torsion had never been present at all. However, for a standard torsion tensor that is antisymmetric in two of its indices we have found two cases in which the vanishing torsion limit is in fact continuous, namely Einstein gravity and conformal gravity. For other gravity theories of common interest to possess a continuous limit the torsion tensor would need to be antisymmetric in all three of its indices.

  16. The Reflective Cracking in Flexible Pavements

    Directory of Open Access Journals (Sweden)

    Pais Jorge

    2013-07-01

    Full Text Available Reflective cracking is a major concern for engineers facing the problem of road maintenance and rehabilitation. The problem appears due to the presence of cracks in the old pavement layers that propagate into the pavement overlay layer when traffic load passes over the cracks and due to the temperature variation. The stress concentration in the overlay just above the existing cracks is responsible for the appearance and crack propagation throughout the overlay. The analysis of the reflective cracking phenomenon is usually made by numerical modeling simulating the presence of cracks in the existing pavement and the stress concentration in the crack tip is assessed to predict either the cracking propagation rate or the expected fatigue life of the overlay. Numerical modeling to study reflective cracking is made by simulating one crack in the existing pavement and the loading is usually applied considering the shear mode of crack opening. Sometimes the simulation considers the mode I of crack opening, mainly when temperature effects are predominant.

  17. Farriery for hoof wall defects: quarter cracks and toe cracks.

    Science.gov (United States)

    Pleasant, R Scott; O'Grady, Stephen E; McKinlay, Ian

    2012-08-01

    Conditions that result in the loss of the structural integrity of the hoof wall, such as quarter and toe cracks, are not uncommon and usually manifest in lameness. The successful management of these problems involves identifying and addressing the underlying causes, stabilization of the foot, and committed follow-up. Copyright © 2012 Elsevier Inc. All rights reserved.

  18. Modified Dugdale crack models - some easy crack relations

    DEFF Research Database (Denmark)

    Nielsen, Lauge Fuglsang

    1997-01-01

    _Ldelta_CR where sigma_L is strength, and at the same time constant flow stress, of the uncracked material while delta_CR is flow limit (displacement).Obviously predictions by the Dugdale model are most reliable for materials with stress-strain relations where flow can actually be described (or well approximated...... are assumed to be self created by local materials flow. The strength sigma_CR predictid by the Dugdale model is sigma_CR =(E Gamma_CR/phi1)^½ where E and 1 are Young’s modulus and crack half-length respectively of the material considered. The so-called critical strain energy rate is Gamma_CR = sigma......) by a constant flow stress (sigma_L). A number of materials, however, do not at all exhibit this kind of flow. Such materials are considered in this paper by Modified Dugdale crack models which apply for any cohesive stress distribution in crack front areas. Formally modified Dugdale crack models exhibit...

  19. Long-crack growth rate data: Constant amplitude and FALSTAFF loading

    Science.gov (United States)

    Phillips, E. P.

    1988-01-01

    This annex describes test procedures and presents the results from the tests for conventional, long-crack growth rate data. These data were used for comparisons with the short-crack growth rate data. Data were generated in tests with constant stress ratio load sequences (R = -2, -1, 0, and 0.5) and with the FALSTAFF load sequence. Results for long-crack tests with the Gaussian load sequence are discussed. The constant stress ratio tests included decreasing, increasing, and constant load amplitude sequences. All cracks exceeded 6 mm in length when data were taken. All tests were conducted on center-cracked specimens of 2024-T3 aluminum alloy sheet taken from a large stock of this material held at the NASA Langley Research Center for fatigue research programs. The baseline long-crack growth rate data for this AGARD program were generated using 50 mm wide, center-cracked specimens which were cut from some of the same sheets that were used to make the edge-notched, short-crack specimens. At growth rates below about 10 to the -5 mm/cycle, the baseline data were supplemented by data generated using 76 mm wide specimens made from sheets other than those used for the short-crack program. At growth rates above about 10 to the -5 mm/cycle, the baseline data were supplemented by data generated using 305 mm wide specimens made from sheets other than those used for the other two specimen sizes. The results from the 305 mm specimens were published in 1969. All specimen configurations are shown.

  20. Fracture mechanics parameters for small fatigue cracks

    Science.gov (United States)

    Newman, J. C., Jr.

    1992-01-01

    This paper presents a review of some common small-crack test specimens, the underlying causes of the small-crack effect, and the fracture-mechanics parameters that have been used to correlate or predict their growth behavior. This review concentrates on continuum mechanics concepts and on the nonlinear behavior of small cracks. The paper reviews some stress-intensity factor solutions for small-crack test specimens and develops some simple elastic-plastic J integral and cyclic J integral expressions that include the influence of crack-closure. These parameters were applied to small-crack growth data on two aluminum alloys, and a fatigue life prediction methodology is demonstrated. For these materials, the crack-closure transient from the plastic wake was found to be the major factor in causing the small-crack effect.

  1. Cracking of SHCC due to reinforcement corrosion

    NARCIS (Netherlands)

    Savija, B.; Lukovic, M.; Pacheco Farias, J.; Schlangen, H.E.J.G.; Saouma, V.; Bolander, J.; Landis, E.

    2016-01-01

    Reinforcement corrosion is the most important deterioration mechanism affecting reinforced concrete infrastructures. After corrosion starts, expansive pressures are exerted onto the surrounding concrete, causing cracking and spalling of the cover concrete. The amount of cover cracking can possibly

  2. Effectiveness of two reflection crack attenuation techniques.

    Science.gov (United States)

    2015-09-01

    Asphalt overlays are one of the most common tools for rehabilitating existing asphalt and concrete pavements. : However, the performance of new overlays is often jeopardized by the cracking distress in the existing : pavement. This existing cracking ...

  3. Investigation of reflective cracking mitigation techniques : [summary].

    Science.gov (United States)

    2014-03-01

    When new asphalt is placed over concrete or : asphalt pavement, cracks or joints in the old : layer can appear in the new overlay; this is : called reflective cracking (RC). In current Florida : practice, an asphalt rubber membrane interlayer : (ARMI...

  4. Development of the crack sealant adhesion test.

    Science.gov (United States)

    2009-04-01

    Crack sealants are widely used in Texas to prevent water from entering into lower structural layers thereby : extending pavement life. However, most current crack sealants have been reported to have a very short life mainly due : to adhesive failures...

  5. Symmetric Problem of Elasticity Theory for a Half-Plane Weakened with a Round Opening and a Crack

    OpenAIRE

    Babloyan A.H.; Baghdasaryan A.V.

    2007-01-01

    The article presents the solution of a symmetric problem of elasticity theory for an elastic half-plane weakened by a round opening and a rectilinear crack, the latter being perpendicular to the edge of the half-plane. Symmetrically distributed normal loadings are given at the edges of the opening, the half-plane and banks of the split. On the infinity the half-plane spreads by equally distributed loadings with p intensity (fig.1).

  6. Symmetric Problem of Elasticity Theory for a Half-Plane Weakened with a Round Opening and an Internal Crack

    OpenAIRE

    A.H. Babloyan; A.V. Baghdasaryan

    2007-01-01

    The article presents the solution of a symmetric problem of elasticity theory for an elastic half-plane weakened by a round opening and a rectilinear internal crack, the latter being perpendicular to the edge of the half-plane. Symmetrically distributed normal loadings are given at the edges of the opening, the half-plane and banks of the split. On the infinity the half-plane spreads by equally distributed loadings with p intensity (fig.1).

  7. Junction formation during desiccation cracking.

    Science.gov (United States)

    Toga, K B; Alaca, B Erdem

    2006-08-01

    In order to provide a sound physical basis for the understanding of the formation of desiccation crack networks, an experimental study is presented addressing junction formation. Focusing on junctions, basic features of the network determining the final pattern, provides an elemental approach and imparts conceptual clarity to the rather complicated problem of the evolution of crack patterns. Using coffee-water mixtures a clear distinction between junction formation during nucleation and propagation is achieved. It is shown that for the same drying suspension, one can switch from the well-known symmetric triple junctions that are unique to the nucleation phase to propagation junctions that are purely dictated by the variations of the stress state. In the latter case, one can even manipulate the path of a propagating crack in a deterministic fashion by changing the stress state within the suspension. Clear microscopic evidence is provided for the formation of propagation junctions, and material inhomogeneity is observed to be reflected by a broad distribution of angles, in stark contrast to shrinkage cracks in homogeneous solid films.

  8. The debauchery that crack brings

    Directory of Open Access Journals (Sweden)

    Francisco Eudison da Silva Maia

    2015-09-01

    Full Text Available Among the substances with psychoactive effects, the most powerful and damaging is the crack, which acts directly on the central nervous system, producing various sensations of pleasure over the conventional. Currently, because of the debauchery that is causing, it is considered a problem of public health worldwide.

  9. Steam Hydrocarbon Cracking and Reforming

    Science.gov (United States)

    Golombok, Michael

    2004-01-01

    The interactive methods of steam hydrocarbon reforming and cracking of the oil and chemical industries are scrutinized, with special focus on their resemblance and variations. The two methods are illustrations of equilibrium-controlled and kinetically-controlled processes, the analysis of which involves theories, which overlap and balance each…

  10. Crack and seat concrete pavement

    Science.gov (United States)

    1987-09-01

    Prevention of reflective cracking in HMAC overlays placed over PCCP has been based on experience gained from trial and error methods of in-service pavements in many states. Arizona recently utilized this technique on a PCCP section of Interstate 40 b...

  11. The quest for intensified steam cracking process

    NARCIS (Netherlands)

    Van Goethem, M.W.M.; Verheijen, P.J.T.

    2005-01-01

    In this paper the results are presented on the quest for an intensified steam cracking process. The main focus is to improve the efficiency of the steam cracking process. The first part of the investigation is to examine which of the current available processes is close to the ideal steam cracking

  12. Twisting cracks in Bouligand structures.

    Science.gov (United States)

    Suksangpanya, Nobphadon; Yaraghi, Nicholas A; Kisailus, David; Zavattieri, Pablo

    2017-12-01

    The Bouligand structure, which is found in many biological materials, is a hierarchical architecture that features uniaxial fiber layers assembled periodically into a helicoidal pattern. Many studies have highlighted the high damage-resistant performance of natural and biomimetic Bouligand structures. One particular species that utilizes the Bouligand structure to achieve outstanding mechanical performance is the smashing Mantis Shrimp, Odontodactylus Scyllarus (or stomatopod). The mantis shrimp generates high speed, high acceleration blows using its raptorial appendage to defeat highly armored preys. The load-bearing part of this appendage, the dactyl club, contains an interior region [16] that consists of a Bouligand structure. This region is capable of developing a significant amount of nested twisting microcracks without exhibiting catastrophic failure. The development and propagation of these microcracks are a source of energy dissipation and stress relaxation that ultimately contributes to the remarkable damage tolerance properties of the dactyl club. We develop a theoretical model to provide additional insights into the local stress intensity factors at the crack front of twisting cracks formed within the Bouligand structure. Our results reveal that changes in the local fracture mode at the crack front leads to a reduction of the local strain energy release rate, hence, increasing the necessary applied energy release rate to propagate the crack, which is quantified by the local toughening factor. Ancillary 3D simulations of the asymptotic crack front field were carried out using a J-integral to validate the theoretical values of the energy release rate and the local stress intensity factors. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Application of Concrete Segment Panels for Reduction of Torsional Vibration Responses of Girder Bridges

    Directory of Open Access Journals (Sweden)

    Kwark Jong-Won

    2015-01-01

    Full Text Available The dynamic flexural behaviour of railway bridges is influenced by the torsional behaviour, and the flexural response tends to be amplified as the flexural natural frequency (the 1st vibrational mode and torsional frequency (the 2nd vibrational mode are adjoining. To avoid this phenomenon, the installation of concrete segment panels was considered for the reinforcement of torsional stiffness by connecting bottom flanges between girders. This alternative can increase the torsional stiffness by providing the restraint in torsional vibration and reduce the influence of torsional behaviour on the amplification of flexural responses. This study investigates the effect of the concrete segment panels on the control of torsional dynamic responses and on the increment of torsional frequency. The excitation tests on a full-size bridge specimen with 30 m span length were conducted with respect to the installation length of concrete panels up to 7 m from each ends. The results show that the installation of concrete segment panel augments the torsional frequency up to 22 % while the flexural frequency keeps its original value. It is concluded that the dynamic behaviour of girder bridges can be controlled by the adjustment of installation length of concrete panels, thereby reducing the torsional responses.

  14. Influence of humeral torsion on interpretation of posterior shoulder tightness measures in overhead athletes.

    Science.gov (United States)

    Myers, Joseph B; Oyama, Sakiko; Goerger, Benjamin M; Rucinski, Terri Jo; Blackburn, J Troy; Creighton, R Alexander

    2009-09-01

    To measure the influence of humeral torsion on interpretation of clinical indicators of posterior shoulder tightness in overhead athletes. Cross-sectional control group comparison. A university-based sports medicine research laboratory. Twenty-nine healthy intercollegiate baseball players and 25 college-aged control individuals with no history of participation in overhead athletics were enrolled. In all participants, bilateral humeral rotation and humeral horizontal adduction variables were measured with a digital inclinometry. Bilateral humeral torsion was measured with ultrasonography. Group and limb comparisons were made for clinical indicators of posterior shoulder tightness (humeral rotation and horizontal adduction variables) and humeral torsion variables. The relationship between humeral torsion and clinical indicators of posterior shoulder tightness were established. The dominant limb of the baseball players demonstrated greater humeral torsion, and less internal rotation and total rotation range of motion, compared with control participants and the nondominant limb in both groups. Once corrected for torsion, no group or limb differences in internal rotation were present. Statistically significant relationships existed between the amount of humeral torsion and measures of posterior shoulder tightness. Although limb differences in clinical indicators of posterior tightness exist in healthy overhead athletes, these measures appear to be influenced by humeral torsion rather than soft tissue tightness. Once torsion is accounted for, the limb differences observed clinically were minimal in healthy overhead athletes. When possible, accounting for humeral torsion when interpreting clinical measures of posterior shoulder tightness may aid in treatment decisions.

  15. The effect to bending fatigue strength of 65 mn under torsion strain-hardening

    Science.gov (United States)

    Zou, Guangping; Xue, Qichao; Li, Wei

    2010-03-01

    Bending Fatigue experiments for 65Mn are carried out to study the effects of torsion strain-hardening. Firstly bending fatigue specimens are pre-twisted for torsion strain-hardening by using torsion testing machine. And specimens are divided as 8 groups and each group has 8 specimens. A series of plastic shear strains are applied to each group. Then bending fatigue experiments are carried on to estimate torsion fatigue strength by fatigue bending machine. Finally micrograms of fatigue damage are taken by stereo microscope. The test results showed that torsion strain-hardening has a certain effects that when torsion plastic strain is small, bending fatigue strength is increased. Oppositely, when torsion plastic strain is large, bending fatigue strength are all decreased in a large rate compared with specimens without torsion strain-hardening. Comparing different test results and corresponding paragraphs obtained from stereo microscope, a reasonable explanation can be deduced by using metal micromechanics theory and crystal lattice dislocation theory. A possible reason is that when torsion plastic strain is small, there will be more dislocation in crystal lattice, which can raise the fatigue strength. And when torsion plastic strain is large, dislocations are piled up in some position which can bring flaws under loads, which reduce the fatigue strength of specimen.

  16. Testicular torsion and weather conditions: analysis of 21,289 cases in Brazil

    Directory of Open Access Journals (Sweden)

    Fernando Korkes

    2012-04-01

    Full Text Available PURPOSE: The hypothesis of association between testicular torsion and hyperactive cremasteric reflex, worsened by cold weather, has not been proved. Thirteen studies in the literature evaluated this issue, with inconclusive results. The aim of the present study was to evaluate the seasonality of testicular torsion in a large subset of patients surgically treated in Brazil, and additionally to estimate the incidence of testicular torsion. MATERIALS AND METHODS: Brazilian Public Health System Database was assessed from 1992-2010 to evaluate hospital admissions associated with treatment of testicular torsion. Average monthly temperature between 1992-2010 was calculated for each region. RESULTS: We identified 21,289 hospital admissions for treatment of testicular torsion. There was a higher number of testicular torsions during colder months (p = 0.002. To estimate the incidence of testicular torsion, we have related our findings to data from the last Brazilian census (2010. In 2010, testicular torsion occurred in 1.4:100,000 men in Brazil. CONCLUSIONS:Testicular torsion occurred at an annual incidence of approximately 1.4:100,000 men in Brazil in 2010. Seasonal variations do occur, with a significant increase of events during winter. Our findings support the theory of etiological role of cold weather to the occurrence of testicular torsion. Strategies to prevent these events can be based on these findings.

  17. Torsion of the fallopian the mimicking appendicitis in a pregnant woman; Torsion de la trompa de Falopio en una mujer gestante simulando apendicitis

    Energy Technology Data Exchange (ETDEWEB)

    Tapia-Vine, M.; Pedrosa, I.; Escribano, N. [Hospital Clinico San Carlos (Spain)

    2000-07-01

    Isolated torsion of the fallopian tube is an uncommon entity. Given the difficulties involved in the preoperative diagnosis, the ultrasound findings characteristic of this anomaly are not widely known. We present a case of tubal torsion associated with a cyst, describing the ultrasound images in our case and those reported in the literature. (Author) 18 refs.

  18. Clinical assessment of left ventricular systolic torsion: effects of myocardial infarction and ischemia.

    Science.gov (United States)

    Bansal, Manish; Leano, Rodel L; Marwick, Thomas H

    2008-08-01

    The helical arrangement of myocardial fibers leads to left ventricular (LV) torsion, a vital contributor to systolic and diastolic function. Rotation and torsion can now be measured; we sought to determine the utility of torsion as a marker of LV function at rest and after stress in patients with myocardial infarctions (MIs) and ischemia. Dobutamine echocardiography was performed in 125 patients. After the exclusion of 40 patients with suboptimal images, LV systolic rotation and torsion were measured offline using speckle-tracking echocardiography in 44 patients with and 41 without prior MIs. Hemodynamic findings and the extent of infarction and ischemia were correlated with length-corrected torsion measurements at baseline and at peak-dose dobutamine. Resting global and regional LV systolic torsion were significantly reduced in patients with compared with those without previous MIs (1.16 +/- 1.15 degrees /cm vs 3.16 +/- 1.3 degrees /cm, P anteroapical or inferoposterior infarcts (1.81 +/- 1.13 degrees /cm vs 2.27 +/- 1.18 degrees /cm, P = NS) and no differences in regional torsion. Torsion was most impaired in patients with multiple areas of infarction (1.03 +/- 0.89 degrees /cm, P < .001). However, dobutamine-induced ischemia (2.59 +/- 1.14 ischemic segments) had no effect on global and regional systolic torsion at peak dose or change in torsion from rest to peak dose. The influence of MI on LV systolic torsion appears to be related to infarct size rather than site, and torsion was an independent determinant of resting function. LV torsion was not significantly influenced by stress-induced myocardial ischemia.

  19. Comparison of thermal cracking and hydro-cracking yield distributions

    Energy Technology Data Exchange (ETDEWEB)

    Romero, S.; Sayles, S. [KBC Advanced Technologies Inc., Houston, TX (United States)

    2009-07-01

    Operators of bitumen upgraders are faced with the challenge of obtaining maximum performance from existing equipment whose performance is already pushed to the limits. The main constraint is the primary upgrader processes, notably coking and hydrocracking. Under the current economic conditions, funding for new equipment is difficult. However, changes can be made to optimize unit performance by better understanding the basic kinetics in thermal cracking and hydrocracking. This paper reviewed the yield distribution differences between thermal cracking and hydrocracking to provide insight into the basic components of operational changes. The objective was to compare yields, product quality distributions and the elemental balances. The opportunities to increase production and improve performance were then analyzed quantitatively within the existing unit equipment limits. tabs., figs.

  20. Effects of Friction and Anvil Design on Plastic Deformation during the Compression Stage of High-Pressure Torsion

    Energy Technology Data Exchange (ETDEWEB)

    Song, Yuepeng; Chen, Miaomiao; Xu, Baoyan; Guo, Jing; Xu, Lingfeng; Wang, Zheng [Mechanical and Electronic Engineering College, Tai’an (China); Gao, Dongsheng [Shandong Provincial Key Laboratory of Horticultural Machineries and Equipments, Tai’an (China); Kim, Hyoung Seop [Department of Materials Science and Engineering, Pohang (Korea, Republic of)

    2016-11-15

    Herein, we report the results of our investigation on the effect of friction and anvil design on the heterogeneous plastic-deformation characteristics of copper during the compressive stage of high-pressure torsion (HPT), using the finite element method. The results indicate that the friction and anvil geometry play important roles in the homogeneity of the deformation. These variables affect the heterogeneous level of strain in the HPT compressed disks, as well as the flash in the disk edge region. The heterogeneous plastic deformation of the disks becomes more severe with the increasing depth of the cavity, as anvil angle and friction coefficient increase. However, the homogeneity increases with increases in the wall angle. The length of flash and the area of the dead metal zone increase with the depth of the cavity, while they decrease at a wall angle of 180°.

  1. Edge-on!

    Science.gov (United States)

    2007-08-01

    Peering at Uranus's Rings as they Swing Edge-on to Earth for the First Time Since their Discovery in 1977 As Uranus coasts through a brief window of time when its rings are edge-on to Earth - a view of the planet we get only once every 42 years - astronomers peering at the rings with ESO's Very Large Telescope and other space or ground-based telescopes are getting an unprecedented view of the fine dust in the system, free from the glare of the bright rocky rings. They may even find a new moon or two. ESO PR Photo 37/07 ESO PR Photo 37/07 The Uranus System "ESO's VLT took data at the precise moment when the rings were edge-on to Earth," said Imke de Pater, of University of California, Berkeley who coordinated the worldwide campaign. She worked with two team members observing in Chile: Daphne Stam of the Technical University Delft in the Netherlands and Markus Hartung of ESO. The observations were done with NACO, one of the adaptive optics instruments installed at the VLT. With adaptive optics, it is possible to obtain images almost free from the blurring effect of the atmosphere. It is as if the 8.2-m telescope were observing from space. Observations were also done with the Keck telescope in Hawaii, the Hubble Space Telescope, and at the Palomar Observatory. "Using different telescopes around the world allows us to observe as much of the changes during the ring-plane crossing as possible: when Uranus sets as seen from the VLT, it can still be observed by the Keck," emphasised Stam. Uranus orbits the Sun in 84 years. Twice during a Uranian year, the rings appear edge-on to Earth for a brief period. The rings were discovered in 1977, so this is the first time for a Uranus ring-crossing to be observed from Earth. The advantage of observations at a ring-plane crossing is that it becomes possible to look at the rings from the shadowed or dark side. From that vantage point, the normally bright outer rings grow fainter because their centimetre- to metre-sized rocks obscure

  2. Cheating on the edge.

    Directory of Open Access Journals (Sweden)

    Lee Alan Dugatkin

    2008-07-01

    Full Text Available We present the results of an individual agent-based model of antibiotic resistance in bacteria. Our model examines antibiotic resistance when two strategies exist: "producers"--who secrete a substance that breaks down antibiotics--and nonproducers ("cheats" who do not secrete, or carry the machinery associated with secretion. The model allows for populations of up to 10,000, in which bacteria are affected by their nearest neighbors, and we assume cheaters die when there are no producers in their neighborhood. Each of 10,000 slots on our grid (a torus could be occupied by a producer or a nonproducer, or could (temporarily be unoccupied. The most surprising and dramatic result we uncovered is that when producers and nonproducers coexist at equilibrium, nonproducers are almost always found on the edges of clusters of producers.

  3. Edge remap for solids

    Energy Technology Data Exchange (ETDEWEB)

    Kamm, James R.; Love, Edward; Robinson, Allen C; Young, Joseph G.; Ridzal, Denis

    2013-12-01

    We review the edge element formulation for describing the kinematics of hyperelastic solids. This approach is used to frame the problem of remapping the inverse deformation gradient for Arbitrary Lagrangian-Eulerian (ALE) simulations of solid dynamics. For hyperelastic materials, the stress state is completely determined by the deformation gradient, so remapping this quantity effectively updates the stress state of the material. A method, inspired by the constrained transport remap in electromagnetics, is reviewed, according to which the zero-curl constraint on the inverse deformation gradient is implicitly satisfied. Open issues related to the accuracy of this approach are identified. An optimization-based approach is implemented to enforce positivity of the determinant of the deformation gradient. The efficacy of this approach is illustrated with numerical examples.

  4. CRACK REASON ANALYSIS OF DAMAGED CARBONITRIDED PART

    Directory of Open Access Journals (Sweden)

    Karin Kocúrová

    2010-03-01

    Full Text Available The article deals with the analysis of a damaged part, which was designed for use in a mechanical clutch of a car. The crack in the part was found during the production inspection. The aim of metallographic and fractography analyses of the fracture surfaces was to discover the reasons for the crack. The reason for creating the crack was the formation of smaller cracks in the production during pressing process of the semiproduct. These cracks even grew after the following thermochemical treatment. The fracture was initiated during the straightening process of quenched part.

  5. A torsional artificial muscle from twisted nitinol microwire

    Science.gov (United States)

    Mirvakili, Seyed M.; Hunter, Ian W.

    2017-04-01

    Nitinol microwires of 25 μm in diameter can have tensile actuation of up to 4.5% in less than 100 ms. A work density of up to 480 MPa can be achieved from these microwires. In the present work, we are showing that by twisting the microwires in form of closed-loop two-ply yarn we can create a torsional actuator. We achieved a revisable torsional stroke of 46°/mm with peak rotational speed of up to 10,000 rpm. We measured a gravimetric torque of up to 28.5 N•m/kg which is higher than the 3 - 6 N•m/kg for direct-drive commercial electric motors. These remarkable performance results are comparable to those of guest-infiltrated carbon nanotube twisted yarns.

  6. MR evaluation of femoral neck version and tibial torsion

    Energy Technology Data Exchange (ETDEWEB)

    Koenig, James Karl; Dwek, Jerry R. [University of California, San Diego, Children' s Hospital and Health Center, Department of Radiology, San Diego, CA (United States); Pring, Maya E. [Rady Children' s Hospital, Department of Pediatric Orthopedic Surgery, San Diego, CA (United States)

    2012-01-15

    Abnormalities of femoral neck version have been associated with a number of hip abnormalities in children, including slipped capital femoral epiphysis, proximal femoral focal deficiency, coxa vara, a deep acetabulum and, rarely, developmental dysplasia of the hip. Orthopedic surgeons also are interested in quantifying the femoral neck anteversion or retroversion in children especially to plan derotational osteotomies. Historically, the angle of femoral version and tibial torsion has been measured with the use of radiography and later by CT. Both methods carry with them the risks associated with ionizing radiation. Techniques that utilize MR are used less often because of the associated lengthy imaging times. This article describes a technique using MRI to determine femoral neck version and tibial torsion with total scan times of approximately 10 min. (orig.)

  7. Omental torsion in a captive polar bear (Ursus maritimus).

    Science.gov (United States)

    Mendez-Angulo, Jose L; Funes, Francisco J; Trent, Ava M; Willette, Michelle; Woodhouse, Kerry; Renier, Anna C

    2014-03-01

    This is the first case report of an omental torsion in a polar bear (Ursus maritimus). A captive, 23-yr-old, 250-kg, intact female polar bear presented to the University of Minnesota Veterinary Medical Center with a 2-day history of lethargy, depression, and vomiting. Abdominal ultrasound identified large amounts of hyperechoic free peritoneal fluid. Ultrasound-guided abdominocentesis was performed and yielded thick serosanguinous fluid compatible with a hemoabdomen. An exploratory laparotomy revealed a large amount of malodorous, serosanguineous fluid and multiple necrotic blood clots associated with a torsion of the greater omentum and rupture of a branch of the omental artery. A partial omentectomy was performed to remove the necrotic tissue and the abdomen was copiously lavaged. The polar bear recovered successfully and is reported to be clinically well 6 mo later. This condition should be considered as a differential in bears with clinical signs of intestinal obstruction and hemoabdomen.

  8. Symmetry of chiral nanotubes: Natural torsion and diffraction evidence

    Energy Technology Data Exchange (ETDEWEB)

    Vukovic, Tatjana; Lazic, Natasa; Milosevic, Ivanka; Damnjanovic, Milan [NanoLab, Faculty of Physics, University of Belgrade, Studentski trg 12, Belgrade 11001 (Serbia)

    2012-12-15

    Optimizations performed with geometrical, molecular mechanics, and density functional models show that chiral carbon nanotube configuration is slightly twisted with respect to the rolled-up geometry. The torsion angle is small, <1 Aa{sup -1} for ultrathin tubes, and decreases with tube diameter. The effect can be explained through breaking of local symmetry of the equally distant neighbors in graphene, which is diminished by the torsion. Although, the twist is small, still, we single out features in diffraction patterns which can distinguish between twisted and non-twisted configurations, at least for narrow single-walled carbon nanotubes. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. TORSIONAL DEFORMATION AND FATIGUE BEHAVIOUR OF 6061 ALUMINIUM ALLOY

    Directory of Open Access Journals (Sweden)

    marini marno

    2012-02-01

    Full Text Available Torsional deformation and fatigue behaviour of both solid and thin-walled tubular specimens were made from as-received and heat treated 6061 aluminium alloy were studied. 6061 aluminium alloy have been widely used as a candidate material in automobile, aerospace, aircraft and structural application because of their superior mechanical properties such as high strength to weight ratio, good ductility and others. The differences in cyclic deformation and fatigue behaviours between round and solid specimens where a stress gradient exist, and thin-walled tubular specimens where a uniform stress state is commonly assumed, are also discussed. Von Mises and Tresca criteria has been used to predict the monotonic and cyclic deformation curve and compared to the torsional data obtained from the experiment. The S-N curve was used to present and evaluate the fatigue life of the specimens. Through fractographic analysis, failure criteria of fracture surfaces were observed and discussed. 

  10. Structural plasticity of single chromatin fibers revealed by torsional manipulation

    CERN Document Server

    Bancaud, Aurelien; Barbi, Maria; Wagner, Gaudeline; Allemand, Jean-Francois; Mozziconacci, Julien; Lavelle, Christophe; Croquette, Vincent; Victor, Jean-Marc; Prunell, Ariel; Viovy, Jean-Louis

    2006-01-01

    Magnetic tweezers are used to study the mechanical response under torsion of single nucleosome arrays reconstituted on tandem repeats of 5S positioning sequences. Regular arrays are extremely resilient and can reversibly accommodate a large amount of supercoiling without much change in length. This behavior is quantitatively described by a molecular model of the chromatin 3-D architecture. In this model, we assume the existence of a dynamic equilibrium between three conformations of the nucleosome, which are determined by the crossing status of the entry/exit DNAs (positive, null or negative). Torsional strain, in displacing that equilibrium, extensively reorganizes the fiber architecture. The model explains a number of long-standing topological questions regarding DNA in chromatin, and may provide the ground to better understand the dynamic binding of most chromatin-associated proteins.

  11. Edge profiles and limiter tests in Extrap T2

    Science.gov (United States)

    Bergsåker, H.; Hedin, G.; Ilyinsky, L.; Larsson, D.; Möller, A.

    New edge profile measurements, including calorimetric measurements of the parallel heat flux, were made in Extrap T2. Test limiters of pure molybdenum and the TZM molybdenum alloy have been exposed in the edge plasma. The surface damage was studied, mainly by microscopy. Tungsten coated graphite probes were also exposed, and the surfaces were studied by microscopy, ion beam analysis and XPS. In this case cracking and mixing of carbon and tungsten at the interface was observed in the most heated areas, whereas carbide formation at the surface was seen in less heated areas. In these tests pure Mo generally fared better than TZM, and thin and cleaner coatings fared better than thicker and less clean.

  12. On Polya's inequality for torsional rigidity and first Dirichlet eigenvalue

    OpenAIRE

    Berg, M. van den; Ferone, V.; Nitsch, C.; Trombetti, C.

    2016-01-01

    Let $\\Omega$ be an open set in Euclidean space with finite Lebesgue measure $|\\Omega|$. We obtain some properties of the set function $F:\\Omega\\mapsto \\R^+$ defined by $$ F(\\Omega)=\\frac{T(\\Omega)\\lambda_1(\\Omega)}{|\\Omega|} ,$$ where $T(\\Omega)$ and $\\lambda_1(\\Omega)$ are the torsional rigidity and the first eigenvalue of the Dirichlet Laplacian respectively. We improve the classical P\\'olya bound $F(\\Omega)\\le 1,$ and show that $$F(\\Omega)\\le 1- \

  13. The Attenuation of Torsional Strain Wave in a PMMA Rod

    OpenAIRE

    田辺, 裕治; 前川, 一郎; 半田, 晋一; 原, 利昭; Tanabe, Yuji; Maekawa, Ichiro; Handa, Shinichi; Hara, Toshiaki

    1990-01-01

    In order to clarify the strain attenuation during shear wave propagation, impact torsion experiments are carried out using a PMMA rod specimen. The strain pulses measured by strain gages are complicated due to the superposition of many reflected and transmitted waves from the supported end of the specimen. To obtain data from such pulses for determining a viscoelastic model, a method which modifies the pulse form is developed taking into account wave propagation behavior in the experimental s...

  14. Effect of Axial Torsion on sp Carbon Atomic Wires

    OpenAIRE

    Ravagnan, L.; Manini, N.; Cinquanta, E.; Onida, G.; Motta, C.; Sangalli, D.; Bordoni, A; Devetta, M.; Piseri, P.; Milani, P.

    2009-01-01

    Ab-initio calculations within Density Functional Theory combined with experimental Raman spectra on cluster-beam deposited pure carbon films provide a consistent picture of sp-carbon chains stabilized by sp^3 or sp^2 terminations, the latter being sensitive to torsional strain. This unexplored effect promises many exciting applications since it allows one to modify the conductive states near the Fermi level and to switch on and off the on-chain pi-electron magnetism.

  15. Effect of axial torsion on sp carbon atomic wires.

    Science.gov (United States)

    Ravagnan, Luca; Manini, Nicola; Cinquanta, Eugenio; Onida, Giovanni; Sangalli, Davide; Motta, Carlo; Devetta, Michele; Bordoni, Andrea; Piseri, Paolo; Milani, Paolo

    2009-06-19

    Ab initio calculations within density-functional theory combined with experimental Raman spectra on cluster-beam deposited pure-carbon films provide a consistent picture of sp-carbon chains stabilized by sp;{3} or sp;{2} terminations, the latter being sensitive to torsional strain. This unexplored effect promises many exciting applications since it allows one to modify the conductive states near the Fermi level and to switch on and off the on-chain pi-electron magnetism.

  16. Metatarsal torsion in monkeys, apes, humans and australopiths.

    Science.gov (United States)

    Drapeau, Michelle S M; Harmon, Elizabeth H

    2013-01-01

    This paper presents an analysis of metatarsal torsion in apes, cercopithecoids and humans, compares australopiths with these species, and discusses their inferred foot morphology and function relative to prehensility, arboreality and the presence or absence of a longitudinal arch. Our results show that locomotor modes are reflected in metatarsal torsion values. Apes, which climb vertically with their foot inverted, have hallucal metatarsal heads that are turned toward the other toes and lateral toes that are inverted. Cercopithecoids, which tend to orient their feet in an axis more parallel to the line of motion, present signs of prehensility by having inverted 2nd metatarsals that oppose the hallux, while their two lateral-most metatarsals are strongly everted. Humans, with their rigid feet and longitudinal arches, have all toes that present their plantar surface toward the ground, resulting in hallucal and 2nd metatarsals that are relatively untwisted and the others that are strongly everted. Humans are different from all taxa only for the 2nd and 3rd metatarsal. It is hypothesized that the untwisted 2nd metatarsal reflects the lack of digit opposability of the medial foot and the strongly everted 3rd metatarsal reflects the longitudinal arch. Australopithecus afarensis was characterized by an everted lateral foot, the prerequisite for the development, but not necessarily an indicator, of a longitudinal arch. In Australopithecus africanus, torsion of fragmentary and complete 1st, 2nd, 3rd and 5th metatarsals suggest that the species did not have a foot with monkey- or ape-like prehensile capabilities and did not have a human-like longitudinal arch. In the Swartkrans remains, torsion is consistent with an unprehensile foot. The morphology of the fossils indicates that there was strong selection to orient the plantar surface of the toes facing the ground at the expense of a grasping foot and inversion ability. Copyright © 2012 Elsevier Ltd. All rights reserved.

  17. A measurement of G with a cryogenic torsion pendulum.

    Science.gov (United States)

    Newman, Riley; Bantel, Michael; Berg, Eric; Cross, William

    2014-10-13

    A measurement of Newton's gravitational constant G has been made with a cryogenic torsion pendulum operating below 4 K in a dynamic mode in which G is determined from the change in torsional period when a field source mass is moved between two orientations. The source mass was a pair of copper rings that produced an extremely uniform gravitational field gradient, whereas the pendulum was a thin fused silica plate, a combination that minimized the measurement's sensitivity to error in pendulum placement. The measurement was made using an as-drawn CuBe torsion fibre, a heat-treated CuBe fibre, and an as-drawn Al5056 fibre. The pendulum operated with a set of different large torsional amplitudes. The three fibres yielded high Q-values: 82 000, 120 000 and 164 000, minimizing experimental bias from fibre anelasticity. G-values found with the three fibres are, respectively: {6.67435(10),6.67408(15),6.67455(13)}×10(-11) m(3) kg(-1) s(-2), with corresponding uncertainties 14, 22 and 20 ppm. Relative to the CODATA2010 G-value, these are higher by 77, 37 and 107 ppm, respectively. The unweighted average of the three G-values, with the unweighted average of their uncertainties, is 6.67433(13)×10(-11) m(3) kg(-1) s(-2) (19 ppm). © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  18. Microstructural White Matter Changes in Primary Torsion Dystonia

    OpenAIRE

    Carbon, Maren; Kingsley, Peter B.; Tang, Chengke; Bressman, Susan; Eidelberg, David

    2008-01-01

    Primary torsion dystonia (PTD) has been conceptualized as a disorder of the basal ganglia. However, recent data suggest a widespread pathology involving motor control pathways. In this report, we explored whether PTD is associated with abnormal anatomical connectivity within motor control pathways. We used diffusion tensor magnetic resonance imaging (DT-MRI) to assess the microstructure of white matter. We found that fractional anisotropy, a measure of axonal integrity and coherence, was sign...

  19. Torsional Elastic Property Measurements of Selected Orthodontic Archwires.

    Science.gov (United States)

    1987-01-01

    Triple-Stranded Stainless Steel Wires - Evaluation of Mechanical Properties and Comparison with Titanium Alloy Alternatives. Angle Orthod 57:18-32...Greenberg AR: Effects of Composition and Cross-section on the Elastic Properties of Orthodontic Archwires. Angle Orthod 51:325-341, 1981. S11. Thurow, RC... Orthod 71:565-573, 1977. 14. Wagner JA, Nikolai RJ: Stiffness of Incisor Segments of Edgewise Arches in Torsion and Bending. Angle Orthod 55:37-50, 1985

  20. Quantitative software analysis of ultrasonographic textures in experimental testicular torsion.

    Science.gov (United States)

    Aslan, Mustafa; Kucukaslan, Ibrahim; Mulazimoglu, Serkan; Soyer, Tutku; Şenyücel, Mine; Çakmak, Murat; Scholbach, Jakob; Aslan, Selim

    2013-04-01

    Ultrasonography (US) has high diagnostic value in testicular torsion but is vulnerable to several potential errors, especially in the early period. Echotexture (ETX) analysis software provides a numerical expression of B-mode images and allows quantitative evaluation of blood flow due to ischemic damage using power Doppler US (PDUS) analysis. Our aim in this study was to determine the diagnostic value and effective parameters of EXT analysis software in the early period of torsion using B-mode and PDUS images. In this study, eight rats were used. Following anesthesia, the right testis was rotated to a 1080-degree counterclockwise position whereas the left testis was left in place to have a control group. B-mode and PDUS images of both sides were recorded with a portable US device immediately (0 hour) and 1 and 2 hours after torsion. The B-mode images were analyzed in terms of gradient, homogeneity, and contrast using the BS200pro software (BAB Digital Imaging System 2007, Ankara, Turkey). Intensity (I)-red and area (A)-red values were measured on PDUS images with the Pixelflux (Version 1.0, Chameleon-Software, Leipzig, Germany). The data were evaluated by the Mann-Whitney U and Wilcoxon tests. Data from B-mode US image EXT analysis showed no significant difference between the right and left testicles in 0 to 2 hours (p > 0.05). The values obtained from PDUS analysis (I-red and A-red) significantly decreased at the testicular torsion side at the end of the second hour (p 0.05) whereas the flow was significantly lower at 2 hours (p analysis. Georg Thieme Verlag KG Stuttgart · New York.

  1. Impact of intelligent phacoemulsification software on torsional phacoemulsification surgery

    OpenAIRE

    Canturk Ugurbas S; Caliskan S; Alpay A; Ugurbas SH

    2012-01-01

    Silay Canturk Ugurbas, Sinan Caliskan, Atilla Alpay, Suat Hayri UgurbasDepartment of Ophthalmology, Bulent Ecevit University School of Medicine, Zonguldak, TurkeyBackground: The purpose of this study was to compare phacoemulsification energy parameters during torsional phacoemulsification with or without the use of intelligent phacoemulsification (IP) software.Methods: One hundred and twenty-eight eyes with nuclear grades ranging from 1 to 5 were enrolled in this randomized prospective study....

  2. Calculation of characteristics of torsionally vibrating mechatronic system

    OpenAIRE

    A. Buchacz

    2007-01-01

    Purpose: of this paper is the application of the approximate method to solve the task of assigning the frequencymodalanalysis and characteristics of a mechatronic system.Design/methodology/approach: was the formulated and solved as a problem in the form of a set of differentialequations of motion and state equations of the considered mechatronic model of an object. To obtain thesolution, Galerkin’s method was used. The discussed torsionally vibrating mechanical system is a continuousbar of ci...

  3. Elasto-plastic torsion problem as an infinity Laplace's equation

    Directory of Open Access Journals (Sweden)

    Ahmed Addou

    2006-12-01

    Full Text Available In this paper, we study a perturbed infinity Laplace's equation, the perturbation corresponds to an Leray-Lions operator with no coercivity assumption. We consider the case where data are distributions or $L^{1}$ elements. We show that this problem has an unique solution which is the solution to the variational inequality arising in the elasto-plastic torsion problem, associated with an operator $A$.

  4. Factors affecting pediatric patient transfer in testicular torsion.

    Science.gov (United States)

    Lodwick, Daniel L; Cooper, Jennifer N; Minneci, Peter C; Deans, Katherine J; McLeod, Daryl

    2016-06-01

    Testicular torsion is a surgical emergency, and interhospital transfer could delay care and increase the risk of orchiectomy. This study identifies factors associated with transfer for pediatric testicular torsion. This retrospective cross-sectional study examined emergency department (ED) visits for testicular torsion by men aged 1-21 y in National Emergency Department Sample from 2006 to 2012. Freestanding children's hospitals were excluded. Analyses were weighted to produce nationally representative estimates. Patient- and institutional-level predictors of transfer were evaluated using Rao-Scott chi-square tests and multivariable logistic regression. There were 11,435 ED visits for testicular torsion resulting in admission or transfer. In multivariable regression, the probability of transfer decreased with increasing age but remained higher for patients aged 15-17 y than for those aged 18-21 y (odds ratio [OR] = 1.51, P patients living in zip codes in the highest income quartile (OR = 0.69 versus lowest, P = 0.003) or with listed comorbidities (OR = 0.55, P Transfer was less likely in the Northeast (OR = 0.28 versus Midwest, P Transfer was less common with increasing annual pediatric ED volume (OR = 0.95 per 1000 patients, P Transfer rates increased significantly over the study period (23.6%-38.8%, P transferred than young adults. Interhospital transfers in these patients may represent a potential target for improving care. Future work should focus on evaluating the effect of transfer on the risk for undergoing orchiectomy. Copyright © 2016 Elsevier Inc. All rights reserved.

  5. Effect of bilateral superior oblique split lengthening on torsion

    Directory of Open Access Journals (Sweden)

    Jitendra Jethani

    2015-01-01

    Full Text Available Introduction: Superior oblique split lengthening (SOSL is done for weakening of superior oblique. It corrects the superior oblique overaction (SOOA and A pattern. Its effect on the torsion of the eye is not known. We present our data on the effect of this particular procedure on torsion. Materials and Methods: We did a study of 16 patients (32 eyes who underwent bilateral SOSL and compared the disc foveal angle (DFA preoperatively and postoperatively. The split lengthening was done from 4 mm to 7 mm depending upon the overaction of superior oblique. Results: The mean age was 15.3 ± 8.4 years. Mean preoperative DFA in the right eye (RE was −3.9° and in the left eye (LE was −2.9°. Mean postoperative DFA in RE was 0.2° and in LE was 0.9°. The mean change in the DFA for RE was 4.1° ± 1.3° and for LE was 3.8° ± 1.2°. All the patients were aligned horizontally within 6 prism diopter and no pattern and no diplopia postoperatively. The A pattern was corrected in all the patient postsurgery. For each mm of surgery, an improvement of 0.8° was seen in the DFA. Conclusion: We report the effect of SOSL on torsion. The SOSL reduces intorsion postsurgery and is, therefore, a valuable procedure in SOOA where both pattern and in torsion needs to be corrected.

  6. Torsion of a wandering spleen: a case report.

    Science.gov (United States)

    Kaabar, Néjib; Ben Abdallah, Rabiaa; Yengui, Houssem; Hellal, Youssef; Ben Malek, Riadh; Bouthour, Habib; Sayed, Sadok

    2014-04-01

    Wandering spleen is a rare entity in child. It is generated by laxity or failure of development of spleen ligaments causing the migration of the spleen from its normal anatomical site to another abdominal or pelvic location. It can be congenital or acquired. The most dangerous complication is the occurrence of torsion of the spleen around its pedicle. aim: Report of a new observation and present the diagnostic, treatment and outcome aspects of torsion of ectopic spleen. We report the case of a 17 years old girl who was admitted for an acute abdomen pain and fever. Clinical examination revealed generalized abdominal defence and an under umbilical mass which was very painful on palpation. Ultrasound and CT scans have visualized the pelvic mass, which measured four inches long axis. The spleen wasn't on its normal seat. The patient was operated urgently. Surgical exploration showed that the mass corresponded to a wandering spleen in pelvic position, necrotic and twisted around its pedicle. A splenectomy was performed with simple sequences. torsion of the wandering spleen can progress to total necrosis of the spleen mass. This complication is feared in any ectopic and painful spleen.

  7. Diesel engine torsional vibration control coupling with speed control system

    Science.gov (United States)

    Guo, Yibin; Li, Wanyou; Yu, Shuwen; Han, Xiao; Yuan, Yunbo; Wang, Zhipeng; Ma, Xiuzhen

    2017-09-01

    The coupling problems between shafting torsional vibration and speed control system of diesel engine are very common. Neglecting the coupling problems sometimes lead to serious oscillation and vibration during the operation of engines. For example, during the propulsion shafting operation of a diesel engine, the oscillation of engine speed and the severe vibration of gear box occur which cause the engine is unable to operate. To find the cause of the malfunctions, a simulation model coupling the speed control system with the torsional vibration of deformable shafting is proposed and investigated. In the coupling model, the shafting is simplified to be a deformable one which consists of several inertias and shaft sections and with characteristics of torsional vibration. The results of instantaneous rotation speed from this proposed model agree with the test results very well and are successful in reflecting the real oscillation state of the engine operation. Furthermore, using the proposed model, the speed control parameters can be tuned up to predict the diesel engine a stable and safe running. The results from the tests on the diesel engine with a set of tuned control parameters are consistent with the simulation results very well.

  8. Torsional Buckling and Writhing Dynamics of Elastic Cables and DNA

    Energy Technology Data Exchange (ETDEWEB)

    Goyal, S; Perkins, N C; Lee, C L

    2003-02-14

    Marine cables under low tension and torsion on the sea floor can undergo a dynamic buckling process during which torsional strain energy is converted to bending strain energy. The resulting three-dimensional cable geometries can be highly contorted and include loops and tangles. Similar geometries are known to exist for supercoiled DNA and these also arise from the conversion of torsional strain energy to bending strain energy or, kinematically, a conversion of twist to writhe. A dynamic form of Kirchhoff rod theory is presented herein that captures these nonlinear dynamic processes. The resulting theory is discretized using the generalized-method for finite differencing in both space and time. The important kinematics of cross-section rotation are described using an incremental rotation ''vector'' as opposed to traditional Euler angles or Euler parameters. Numerical solutions are presented for an example system of a cable subjected to increasing twist at one end. The solutions show the dynamic evolution of the cable from an initially straight element, through a buckled element in the approximate form of a helix, and through the dynamic collapse of this helix through a looped form.

  9. Damage Evolution in Complex-Phase and Dual-Phase Steels during Edge Stretching.

    Science.gov (United States)

    Pathak, Nikky; Butcher, Cliff; Worswick, Michael James; Bellhouse, Erika; Gao, Jeff

    2017-03-27

    The role of microstructural damage in controlling the edge stretchability of Complex-Phase (CP) and Dual-Phase (DP) steels was evaluated using hole tension experiments. The experiments considered a tensile specimen with a hole at the center of specimen that is either sheared (sheared edge condition) or drilled and then reamed (reamed edge condition). The damage mechanism and accumulation in the CP and DP steels were systematically characterized by interrupting the hole tension tests at different strain levels using scanning electron microscope (SEM) analysis and optical microscopy. Martensite cracking and decohesion of ferrite-martensite interfaces are the dominant nucleation mechanisms in the DP780. The primary source of void nucleation in the CP800 is nucleation at TiN particles, with secondary void formation at martensite/bainite interfaces near the failure strain. The rate of damage evolution is considerably higher for the sheared edge in contrast with the reamed edge since the shearing process alters the microstructure in the shear affected zone (SAZ) by introducing work-hardening and initial damage behind the sheared edge. The CP microstructures were shown to be less prone to shear-induced damage than the DP materials resulting in much higher sheared edge formability. Microstructural damage in the CP and DP steels was characterized to understand the interaction between microstructure, damage evolution and edge formability during edge stretching. An analytical model for void evolution and coalescence was developed and applied to predict the damage rate in these rather diverse microstructures.

  10. Damage Evolution in Complex-Phase and Dual-Phase Steels during Edge Stretching

    Directory of Open Access Journals (Sweden)

    Nikky Pathak

    2017-03-01

    Full Text Available The role of microstructural damage in controlling the edge stretchability of Complex-Phase (CP and Dual-Phase (DP steels was evaluated using hole tension experiments. The experiments considered a tensile specimen with a hole at the center of specimen that is either sheared (sheared edge condition or drilled and then reamed (reamed edge condition. The damage mechanism and accumulation in the CP and DP steels were systematically characterized by interrupting the hole tension tests at different strain levels using scanning electron microscope (SEM analysis and optical microscopy. Martensite cracking and decohesion of ferrite-martensite interfaces are the dominant nucleation mechanisms in the DP780. The primary source of void nucleation in the CP800 is nucleation at TiN particles, with secondary void formation at martensite/bainite interfaces near the failure strain. The rate of damage evolution is considerably higher for the sheared edge in contrast with the reamed edge since the shearing process alters the microstructure in the shear affected zone (SAZ by introducing work-hardening and initial damage behind the sheared edge. The CP microstructures were shown to be less prone to shear-induced damage than the DP materials resulting in much higher sheared edge formability. Microstructural damage in the CP and DP steels was characterized to understand the interaction between microstructure, damage evolution and edge formability during edge stretching. An analytical model for void evolution and coalescence was developed and applied to predict the damage rate in these rather diverse microstructures.

  11. Edge conduction in vacuum glazing

    Energy Technology Data Exchange (ETDEWEB)

    Simko, T.M.; Collins, R.E. [Sydney Univ., NSW (Australia). Dept. of Applied Physics; Beck, F.A.; Arasteh, D. [Lawrence Berkeley Lab., CA (United States)

    1995-03-01

    Vacuum glazing is a form of low-conductance double glazing using in internal vacuum between the two glass sheets to eliminate heat transport by gas conduction and convection. An array of small support pillars separates the sheets; fused solder glass forms the edge seal. Heat transfer through the glazing occurs by radiation across the vacuum gap, conduction through the support pillars, and conduction through the bonded edge seal. Edge conduction is problematic because it affects stresses in the edge region, leading to possible failure of the glazing; in addition, excessive heat transfer because of thermal bridging in the edge region can lower overall window thermal performance and decrease resistance to condensation. Infrared thermography was used to analyze the thermal performance of prototype vacuum glazings, and, for comparison, atmospheric pressure superwindows. Research focused on mitigating the edge effects of vacuum glazings through the use of insulating trim, recessed edges, and framing materials. Experimentally validated finite-element and finite-difference modeling tools were used for thermal analysis of prototype vacuum glazing units and complete windows. Experimental measurements of edge conduction using infrared imaging were found to be in good agreement with finite-element modeling results for a given set of conditions. Finite-element modeling validates an analytic model developed for edge conduction.

  12. Edge Bundling in Information Visualization

    National Research Council Canada - National Science Library

    Hong Zhou Panpan Xu Xiaoru Yuan Huamin Qu

    2013-01-01

    The edge, which can encode relational data in graphs and multidimensional data in parallel coordinates plots, is an important visual primitive for encoding data in information visualization research...

  13. Polygon/Cracked Sedimentary Rock

    Science.gov (United States)

    2004-01-01

    4 December 2004 Exposures of sedimentary rock are quite common on the surface of Mars. Less common, but found in many craters in the regions north and northwest of the giant basin, Hellas, are sedimentary rocks with distinct polygonal cracks in them. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an example from the floor of an unnamed crater near 21.0oS, 311.9oW. Such cracks might have formed by desiccation as an ancient lake dried up, or they might be related to ground ice freeze/thaw cycles or some other stresses placed on the original sediment or the rock after it became lithified. The 300 meter scale bar is about 328 yards long. The scene is illuminated by sunlight from the upper left.

  14. Determination of interlaminar fracture toughness and fracture mode dependence of composites using the edge delamination test

    Science.gov (United States)

    Obrien, T. K.; Johnston, N. J.; Morris, D. H.; Simonds, R. A.

    1983-01-01

    Edge delamination testing has been conducted in order to determine the mixed mode interlaminar fracture toughness of unnotched (+, -35/0/90)s and (0/+, -35/90)s laminates with graphite fibers and epoxy matrices, with or without elastomer additives. Although the two stacking sequences were chosen so that the total strain energy release rates were equal, the percentages of crack opening and shear mode energy release rates were found to vary widely between the layups. Plots of interlaminar fracture toughness as a function of crack opening energy release rate percentage have been drawn to generate delamination failure criteria which reflect the observed fracture mode dependence.

  15. Nonlocal Peridynamic Modeling and Simulation on Crack Propagation in Concrete Structures

    Directory of Open Access Journals (Sweden)

    Dan Huang

    2015-01-01

    Full Text Available An extended peridynamic approach for crack propagation analysis in concrete structures was proposed. In the peridynamic constitutive model, concrete material was described as a series of interacting particles, and the short-range repulsive force and anisotropic behavior of concrete were taken into account in the expression of the interactive bonding force, which was given in terms of classical elastic constants and peridynamic horizon. The damage of material was defined locally at the level of pairwise bond, and the critical stretch of material bond was described as a function of fracture strength in the classical concrete failure theory. The efficiency and accuracy of the proposed model and algorithms were validated by simulating the propagation of mode I and I-II mixed mode cracks in concrete slabs. Furthermore, crack propagation in a double-edge notched concrete beam subjected to four-point load was simulated, in which the experimental observations are captured naturally as a consequence of the solution.

  16. Stress induced martensite at the crack tip in NiTi alloys during fatigue loading

    Directory of Open Access Journals (Sweden)

    E. Sgambitterra

    2014-10-01

    Full Text Available Crack tip stress-induced phase transformation mechanisms in nickel-titanium alloys (NiTi were analyzed by Digital Image Correlation (DIC, under fatigue loads. In particular, Single Edge Crack (SEC specimens, obtained from a commercial pseudoelastic NiTi sheet, and an ad-hoc experimental setup were used, for direct measurements of the near crack tip displacement field by the DIC technique. Furthermore, a fitting procedure was developed to calculate the mode I Stress Intensity Factor (SIF, starting from the measured displacement field. Finally, cyclic tensile tests were performed at different operating temperature, in the range 298-338 K, and the evolution of the SIF was studied, which revealed a marked temperature dependence.

  17. Molecular Dynamics Simulation of Crack Propagation in Single-Crystal Aluminum Plate with Central Cracks

    Directory of Open Access Journals (Sweden)

    Jun Ding

    2017-01-01

    Full Text Available The crack propagation process in single-crystal aluminum plate (SCAP with central cracks under tensile load was simulated by molecular dynamics method. Further, the effects of model size, crack length, temperature, and strain rate on strength of SCAP and crack growth were comprehensively investigated. The results showed that, with the increase of the model size, crack length, and strain rate, the plastic yield point of SCAP occurred in advance, the limit stress of plastic yield decreased, and the plastic deformability of material increased, but the temperature had less effect and sensitivity on the strength and crack propagation of SCAP. The model size affected the plastic deformation and crack growth of the material. Specifically, at small scale, the plastic deformation and crack propagation in SCAP are mainly affected through dislocation multiplication and slip. However, the plastic deformation and crack propagation are obviously affected by dislocation multiplication and twinning in larger scale.

  18. Fatigue cracks in Eurofer 97 steel: Part II. Comparison of small and long fatigue crack growth

    Science.gov (United States)

    Kruml, T.; Hutař, P.; Náhlík, L.; Seitl, S.; Polák, J.

    2011-05-01

    The fatigue crack growth rate in the Eurofer 97 steel at room temperature was measured by two different methodologies. Small crack growth data were obtained using cylindrical specimens with a shallow notch and no artificial crack starters. The growth of semicircular cracks of length between 10-2000 μm was followed in symmetrical cycling with constant strain amplitude ( R ɛ = -1). Long crack data were measured using standard CT specimen and ASTM methodology, i.e. R = 0.1. The growth of cracks having the length in the range of 10-30 mm was measured. It is shown that the crack growth rates of both types of cracks are in a very good agreement if J-integral representation is used and usual assumptions of the crack closure effects are taken into account.

  19. Cutting Edge Localisation in an Edge Profile Milling Head

    NARCIS (Netherlands)

    Fernandez Robles, Laura; Azzopardi, George; Alegre, Enrique; Petkov, Nicolai

    2015-01-01

    Wear evaluation of cutting tools is a key issue for prolonging their lifetime and ensuring high quality of products. In this paper, we present a method for the effective localisation of cutting edges of inserts in digital images of an edge profile milling head. We introduce a new image data set of

  20. Application of a boundary element method to the study of dynamical torsion of beams

    Science.gov (United States)

    Czekajski, C.; Laroze, S.; Gay, D.

    1982-01-01

    During dynamic torsion of beam elements, consideration of nonuniform warping effects involves a more general technical formulation then that of Saint-Venant. Nonclassical torsion constants appear in addition to the well known torsional rigidity. The adaptation of the boundary integral element method to the calculation of these constants for general section shapes is described. The suitability of the formulation is investigated with some examples of thick as well as thin walled cross sections.

  1. Appendiceal torsion associated with undescended caecum: a case report and review of the literature

    Science.gov (United States)

    Dimitriadis, Panagiotis A; Makar, Ragai R; Randall, Jon K; Ramus, James

    2012-01-01

    Torsion of the vermiform appendix is a rare disorder that causes symptoms similar to those of acute appendicitis. Primary and secondary causes of appendiceal torsion have been reported in the literature. Laparoscopy appears to be the most appropriate modality for diagnosis and treatment where the condition is suspected. To our knowledge this is the first case of appendiceal torsion in an adult causing right upper quadrant pain related to caecal malposition. PMID:23010467

  2. Deep brain stimulation and neuromodulation for torsion dystonia

    Directory of Open Access Journals (Sweden)

    Jing WANG

    2015-10-01

    Full Text Available Objective To discuss the curative effect and safety of deep brain stimulation (DBS and neuromodulation in the treatment of patients with torsion dystonia. Methods Ten patients with torsion dystonia underwent subthalamic nucleus DBS (STN-DBS and 3 patients with torsion dystonia underwent globus pallidus internus DBS (GPi-DBS. Regulate the stimulus parameters, evaluate the improvement of torsion dystonia by using Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS and record related adverse events. Results Among the 13 patients, 6 patients were improved by over 60% in 1-3 d and 3 patients one week after stimulation, and the improvement rate was > 75% in 6 months and > 85% in one year. Two patients showed improvement 2 months after stimulation, and the improvement rate was > 60% in 6 months and > 80% in one year. One patient showed slight improvement immediately after operation, and the improvement rate increased to 45% in 6 months and 75% in one year. One patient removed the stimulator. No adverse event related to the operation was found in all 13 patients. The stimulus parameters for STN-DBS were voltage 1.50-2.00 V, frequency 130-145 Hz, pulse width 60-90 μs at 6 months postoperatively, and were voltage 2.00-2.50 V, frequency 130-150 Hz, pulse width 60-90 μs at one year postoperatively. The stimulus parameters for GPi-DBS were voltage 2.50-2.80 V, frequency 130-160 Hz, pulse width 60-90 μs at 6 months postoperatively, and were voltage 2.50-4.00 V, frequency 145-170 Hz, pulse width 60-90 μs at one year postoperatively. Conclusions Both STN-DBS and GPi-DBS have good curative effect and safety in the treatment for torsion dystonia. Besides, patients should be treated with individual neuromodulation. DOI: 10.3969/j.issn.1672-6731.2015.10.007

  3. Left ventricular remodeling and torsion dynamics in hypertensive patients.

    Science.gov (United States)

    Cameli, Matteo; Lisi, Matteo; Righini, Francesca Maria; Massoni, Alberto; Mondillo, Sergio

    2013-01-01

    Left ventricular (LV) torsion is a fundamental component of wall motion and plays an important role to optimize ventricular ejection fraction. The aim of our study was to calculate by speckle tracking echocardiography LV twist angle in patients with hypertension and LV remodeling, analyzing torsional indices in all patterns of hypertrophy, in comparison to torsional dynamics of age-matched healthy subjects. Hypertensive patients (n = 202) were divided in three groups, patients with concentric remodeling (n = 70), concentric hypertrophy (n = 68) and eccentric hypertrophy (n = 64), in relation to the echocardiographic measurements of relative wall thickness and LV mass, analyzing their torsional patterns by speckle tracking in comparison to age-matched control group. Compared to healthy controls, LV twist angle was increased in patients with hypertension and concentric remodeling (15.2° ± 1.9° vs. 11.0° ± 1.6°; p < 0.001), reaching the highest value in patients with concentric hypertrophy (19.4° ± 2.6°); instead LV twist angle presented depressed in the group of patients that presented eccentric hypertrophy (5.0° ± 1.1°). Regarding LV untwisting rate, it was higher in the concentric remodeling and concentric hypertrophy groups (-123.1°/s ± 12.1°/s and -145.1°/s ± 15.5°/s, respectively) in comparison with the controls (-90.0°/s ± 10.1°/s; p < 0.0001 for both). Instead, lower values of LV untwisting rate were observed in the eccentric remodeling group (-81.6°/s ± 8.1°/s), not significantly different to controls' values (p = 0.09). Enhanced LV twist angle appears to be a compensatory mechanism in hypertensive patients during the earlier stages of concentric remodeling and concentric hypertrophy; this hyper-torsion is inevitably loss in the more advanced stage of eccentric hypertrophy.

  4. Nonsteady motion of a transverse-shear crack across the interface between elastic media

    Science.gov (United States)

    Simonov, I. V.

    1986-11-01

    This article examines the motion of a crack along the line joining two different elastic half-planes under the influence of variable shear stresses. Analogous to the case of a homogeneous medium [1 3], the law of motion of the edge is assumed to be known. Among the features of the physical situation being examined are the nonsymmetrical character of the solution with a symmetrical load distribution and the dependence of the number of Rayleigh wave which can be generated (two, one, none) on the ratios of the elastic parameters. The problem decomposes in the image space into a scalar problem of conjugating two functions reflecting the connection between the displacement discontinuity on the crack and the shear stress on the crack extension. The formula must then be inverted to represent the normal stress. The solution is constructed by the method of factorization, which was used in [2, 3] for a problem with a movable separation point for the boundary conditions. The properties of the Rayleigh boundary function for contacting elastic bodies are also studied. It is shown that the Holder continuity condition for the input functions is sufficient to determine the asymptotes at the edge of the crack, analogous to the case of steady crack movement [4]. With transformations of the convolutions, we used the methods of contour integration and applied the residue theorem. This made it possible to somewhat simplify the results [2]. The subject of crack starting is addressed in an examination of special types of loading. The solution of a similarity problem was given in [5].

  5. Free Vibration Analysis for Cracked FGM Beams by Means of a Continuous Beam Model

    OpenAIRE

    Yang, E Chuan; Zhao, Xiang; Li, Ying Hui

    2015-01-01

    Based on Euler-Bernoulli beam theory and a continuous stiffness beam model, the free vibration of rectangular-section beams made of functionally graded materials (FGMs) containing open edge cracks is studied. Assuming the material gradients follow exponential distribution along beam thickness direction, the conversion relation between the vibration governing equations of a FGM beam and that of an isotropic homogenous beam is deduced. A continuous function is used to characterize the bending s...

  6. Influence of precracked specimen configuration and starting stress intensity on the stress corrosion cracking of 4340 steel

    Science.gov (United States)

    Lisagor, W. B.

    1984-01-01

    Experimental results are presented from a study of the effects of precracked specimen configuration and initial starting stress intensity on crack growth rate and threshold stress intensity, for both onset of cracking and crack arrest. Attention is given to AISI 4340 steel in a 3.5-percent NaCl solution, for configurations of a single edge-cracked specimen tested in cantilever bending under constant load, and a modified compact specimen bolt loaded to a constant deflection. The threshold stress intensity value determined was independent of specimen configuration, if the stress intensity value associated with the compact specimen is taken where the discontinuous break occurs in the velocity-stress intensity curve.

  7. Adnexal Torsion with Dystrophic Calcifications in an Adolescent: A Chronic Entity?

    Directory of Open Access Journals (Sweden)

    Pinar Solmaz Hasdemir

    2013-01-01

    Full Text Available Intermittent pelvic pain caused by ovarian cysts in adolescence may be due to torsion or partial torsion of the ovary. We present a case of 18-year old adolescent with symptomatic left ovarian torsion with calcifications demonstrated by pelvic MRI and ultrasonography prior to surgery. The pathologic investigation demonstrated dystrophic calcifications. We speculated that the pattern of the intermittent pain in the story of the patient and the dystrophic calcifications in pathologic investigation which is thought that it might have been potentially developed as a result of chronic hypoxia due to intermittent partial torsions over a period of two years.

  8. Effect of Soil Structure Interaction on Torsional Response of Structure Supported by Asymmetric Soil Foundation System

    Directory of Open Access Journals (Sweden)

    Fangyuan Zhou

    2016-01-01

    Full Text Available The torsional response of a structure supported by asymmetric foundation was investigated in this study. Several types of the asymmetric soil foundation system were employed to analyze the effect of soil structure interaction on torsional response of the superstructure. It can be concluded from the study that torsional response would be generated for a structure supported by asymmetric soil foundation system under horizontal seismic excitation, and the generated torsional response of the superstructure changed with the degree of the asymmetry of the foundation.

  9. Torsional behavior of chiral single-walled and double-walled carbon nanotubes

    Science.gov (United States)

    Dian-Rong, Han; Lei, Zhu; Ya-Fei, Dai; Cheng-Lin, Luo

    2017-10-01

    The torsional behavior of the chiral single-walled carbon nanotubes (SWCNTs) and double-walled carbon nanotubes (DWCNTs) is investigated using molecular dynamics (MD) method. The results show that the torsional behavior of chiral DWCNTs presents a weaker direction dependent than that of SWCNTs. The critical buckling shear strain of DWCNT in the untwisting direction of the outer tube is always greater than that in the opposite direction. The torsional rigidities of the DWCNT and its outer tubes are approximately identical. However, torsional elastic range of the DWCNT is much higher than that of the outer tube. Moreover, the torsional direction dependency of incommensurate chiral (n 1  +  m 1, -m1)@ (n 2,m 2) tube is weaker than that of commensurate (n 1,m 1)@ (n 2,m 2) tube, which implies that if the chiral angles of the inner and the outer tube of a DWCNT are arranged in opposite directions, the torsional direction dependency of a DWCNT will be further reduced. Meanwhile, rotational inertia of the DWCNT remains nearly unchanged under torsion in a quite large torsional range. These conclusions will be helpful in designing torsional components of NEMS (nano-electromechanical system) using carbon tubes.

  10. An induction motor model for high-frequency torsional vibration analysis

    Science.gov (United States)

    Widdle, R. D.; Krousgrill, C. M.; Sudhoff, S. D.

    2006-03-01

    High-frequency torsional oscillations of a 50 horsepower (hp) induction motor are investigated up to approximately 30 kHz. It is experimentally determined that torsional oscillations, due to the switching harmonics of the motor drive, contribute significantly to the torsional oscillation of the output shaft. Two torsional vibration models are developed. One model assumes the rotor to be rigid, while the other has a compliant rotor. The compliant model allows for greater transmission of high-frequency oscillations, and a better prediction of the measured output shaft vibration.

  11. Effect of Microstructure on Torsional Fatigue Endurance of Martensitic Carbon Steel

    National Research Council Canada - National Science Library

    TOYODA, Shunsuke; ISHIGURO, Yasuhide; KAWABATA, Yoshikazu; SAKATA, Kei; SATO, Akio; SAKAI, Jun'ichi

    2009-01-01

    The microstructural influence of martensitic carbon steel on torsional fatigue endurance was investigated, taking into consideration the application of high strength steel electric resistance welded (ERW...

  12. A combined experimental and theoretical study on realizing and using laser controlled torsion of molecules

    DEFF Research Database (Denmark)

    Madsen, Christian Bruun; Madsen, Lars Bojer; Viftrup, Simon

    2009-01-01

    It is demonstrated that strong laser pulses can introduce torsional motion in the axially chiral molecule 3,5-difluoro-3',5'-dibromobiphenyl. A nanosecond laser pulse spatially aligns the stereogenic carbon-carbon (C–C) bond axis allowing a perpendicularly polarized, intense femtosecond pulse...... to initiate torsional motion accompanied by a rotation about the fixed axis. We monitor the induced motion by femtosecond time-resolved Coulomb explosion imaging. Our theoretical analysis corroborates the experimental findings and on the basis of these results we discuss future applications of laser......-induced torsion, viz., time-resolved studies of deracemization and laser controlled molecular junctions based on molecules with torsion....

  13. Unusual cause of acute abdominal pain in a postmenopausal woman: adnexal torsion

    Directory of Open Access Journals (Sweden)

    Alper Biler

    2016-03-01

    Full Text Available Adnexal torsion is an infrequent but significant cause of acute lower abdominal pain in women. While adnexal torsion is generally considered in premenopausal women presenting with acute abdominal pain and a pelvic mass, it is a rare cause of acute abdominal pain during postmenopausal period. The diagnosis of adnexal torsion is often challenging due to nonspesific clinical, laboratory and physical examination findings. Causes of adnexal torsion is also different in premenopausal and postmenopausal women. While a simple functional cyst is often the cause of torsion in premenopausal women, it is more rarely the cause in postmenopausal women. Adnexal torsion is a surgical emergency. The surgery of adnexal torsion is performed either via conventional exploratory laparotomy or laparoscopic surgery. Adnexal torsion in postmenopausal women should be considered not only in the setting of sudden onset pain, but also in long-term abdominal discomfort. In this article, we presented a case with adnexal torsion that rarely cause acute abdominal pain in postmenopausal women. [Cukurova Med J 2016; 41(1.000: 167-170

  14. Tibial torsion in non-arthritic Indian adults: A computer tomography study of 100 limbs

    Directory of Open Access Journals (Sweden)

    Mullaji Arun

    2008-01-01

    Full Text Available Background: Knowledge of normal tibial torsion is mandatory during total knee replacement (TKR, deformity correction and fracture management of tibia. Different values of tibial torsion have been found in different races due to biological and mechanical factors. Value of normal tibial torsion in Indian limbs is not known, hence this study to determine the norm of tibial torsional value in normal Indian population. Materials and Methods: Computer tomography (CT scans were performed in 100 non-arthritic limbs of 50 Indian adults (42 males, eight females; age 26-40 years. Value of tibial torsion was measured using dorsal tangent to tibial condyles proximally and bimalleolar axis distally. Results: Normal tibial torsion was found to be 21.6 ± 7.6 (range 4.8 to 39.5 with none of the values in internal rotation. Right tibia was externally rotated by 2 degrees as compared to the left side ( P 0.029. No significant difference was found in male and female subjects. Value of tibial torsion was less than in Caucasian limbs, but was comparable to Japanese limbs when studies using similar measurement technique were compared. Conclusions: Indian limbs have less tibial torsion than Caucasian limbs but the value of tibial torsion is comparable to Japanese limbs.

  15. The Robotic Edge Finishing Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Loucks, C.S.; Selleck, C.B.

    1990-08-01

    The Robotic Edge Finishing Laboratory at Sandia National Laboratories is developing four areas of technology required for automated deburring, chamfering, and blending of machined edges: (1) the automatic programming of robot trajectories and deburring processes using information derived from a CAD database, (2) the use of machine vision for locating the workpiece coupled with force control to ensure proper tool contact, (3) robotic deburring, blending, and machining of precision chamfered edges, and (4) in-process automated inspection of the formed edge. The Laboratory, its components, integration, and results from edge finishing experiments to date are described here. Also included is a discussion of the issues regarding implementation of the technology in a production environment. 24 refs., 17 figs.

  16. Edge instabilities of topological superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Hofmann, Johannes S. [Institut fuer Theoretische Physik und Astrophysik, Universitaet Wuerzburg (Germany); Max-Planck-Institut fuer Festkoerperforschung, Stuttgart (Germany); Assaad, Fakher F. [Institut fuer Theoretische Physik und Astrophysik, Universitaet Wuerzburg (Germany); Schnyder, Andreas P. [Max-Planck-Institut fuer Festkoerperforschung, Stuttgart (Germany)

    2016-07-01

    Nodal topological superconductors display zero-energy Majorana flat bands at generic edges. The flatness of these edge bands, which is protected by time-reversal and translation symmetry, gives rise to an extensive ground state degeneracy and a diverging density of states. Therefore, even arbitrarily weak interactions lead to an instability of the flat-band edge states towards time-reversal and translation-symmetry broken phases, which lift the ground-state degeneracy. Here, we employ Monte Carlo simulations combined with mean-field considerations to examine the instabilities of the flat-band edge states of d{sub xy}-wave superconductors. We find that attractive interactions induce a complex s-wave pairing instability together with a density wave instability. Repulsive interactions, on the other hand, lead to ferromagnetism mixed with spin-triplet pairing at the edge. We discuss the implications of our findings for experiments on cuprate high-temperature superconductors.

  17. Controlling fatigue crack paths for crack surface marking and growth investigations

    Directory of Open Access Journals (Sweden)

    S. Barter

    2016-01-01

    Full Text Available While it is well known that fatigue crack growth in metals that display confined slip, such as high strength aluminium alloys, develop crack paths that are responsive to the loading direction and the local microstructural orientation, it is less well known that such paths are also responsive to the loading history. In these materials, certain loading sequences can produce highly directional slip bands ahead of the crack tip and by adjusting the sequence of loads, distinct fracture surface features or progression marks, even at very small crack depths can result. Investigating the path a crack selects in fatigue testing when particular combinations of constant and variable amplitude load sequences are applied is providing insight into crack growth. Further, it is possible to design load sequences that allow very small amounts of crack growth to be measured, at very small crack sizes, well below the conventional crack growth threshold in the aluminium alloy discussed here. This paper reports on observations of the crack path phenomenon and a novel test loading method for measuring crack growth rates for very small crack depths in aluminium alloy 7050-T7451 (an important aircraft primary structural material. The aim of this work was to firstly generate short- crack constant amplitude growth data and secondly, through the careful manipulation of the applied loading, to achieve a greater understanding of the mechanisms of fatigue crack growth in the material being investigated. A particular focus of this work is the identification of the possible sources of crack growth retardation and closure in these small cracks. Interpreting these results suggests a possible mechanism for why small fatigue crack growth through this material under variable amplitude loading is faster than predicted from models based on constant amplitude data alone.

  18. Crack formation and prevention in colloidal drops

    Science.gov (United States)

    Kim, Jin Young; Cho, Kun; Ryu, Seul-A.; Kim, So Youn; Weon, Byung Mook

    2015-08-01

    Crack formation is a frequent result of residual stress release from colloidal films made by the evaporation of colloidal droplets containing nanoparticles. Crack prevention is a significant task in industrial applications such as painting and inkjet printing with colloidal nanoparticles. Here, we illustrate how colloidal drops evaporate and how crack generation is dependent on the particle size and initial volume fraction, through direct visualization of the individual colloids with confocal laser microscopy. To prevent crack formation, we suggest use of a versatile method to control the colloid-polymer interactions by mixing a nonadsorbing polymer with the colloidal suspension, which is known to drive gelation of the particles with short-range attraction. Gelation-driven crack prevention is a feasible and simple method to obtain crack-free, uniform coatings through drying-mediated assembly of colloidal nanoparticles.

  19. Closure measurements of naturally initiating small cracks

    Science.gov (United States)

    Sharpe, W. N., Jr.; Su, X.

    1988-01-01

    The initiation and growth of cracks in smooth 2024-T3 aluminum specimens have been investigated using acetate replicas. Crack opening displacements were measured as a function of load at several positions along the crack as it grew across the thickness of the specimen and became a through-the-thickness crack of a few millimeters in length. Tests run for R-ratios of 0.5, 0.0 and -1.0 showed that closure loads were well predicted by Newman's (1984) model. It is noted that small cracks grow slightly faster than would be predicted by long-crack data, and it is suggested that effects other than plasticity-induced closure must be taken into account.

  20. Numerical Study of Corrosion Crack Opening

    DEFF Research Database (Denmark)

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

    2008-01-01

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