Journal articles on the topic 'Normal stress continuity'
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Khattatov, Eldar, and Ivan Yotov. "Domain decomposition and multiscale mortar mixed finite element methods for linear elasticity with weak stress symmetry." ESAIM: Mathematical Modelling and Numerical Analysis 53, no. 6 (November 2019): 2081–108. http://dx.doi.org/10.1051/m2an/2019057.
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Two non-overlapping domain decomposition methods are presented for the mixed finite element formulation of linear elasticity with weakly enforced stress symmetry. The methods utilize either displacement or normal stress Lagrange multiplier to impose interface continuity of normal stress or displacement, respectively. By eliminating the interior subdomain variables, the global problem is reduced to an interface problem, which is then solved by an iterative procedure. The condition number of the resulting algebraic interface problem is analyzed for both methods. A multiscale mortar mixed finite element method for the problem of interest on non-matching multiblock grids is also studied. It uses a coarse scale mortar finite element space on the non-matching interfaces to approximate the trace of the displacement and impose weakly the continuity of normal stress. A priori error analysis is performed. It is shown that, with appropriate choice of the mortar space, optimal convergence on the fine scale is obtained for the stress, displacement, and rotation, as well as some superconvergence for the displacement. Computational results are presented in confirmation of the theory of all proposed methods.
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Blanco, Pablo J., Simone Deparis, and A. Cristiano I. Malossi. "On the continuity of mean total normal stress in geometrical multiscale cardiovascular problems." Journal of Computational Physics 251 (October 2013): 136–55. http://dx.doi.org/10.1016/j.jcp.2013.05.037.
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Yu, Kai Qin, Yin Fei Yang, Liang Li, Ning He, Bo Chen, and Xue Feng Zhang. "Residual Stresses Measurement Base on Three Reference Points Theory Using Contour Method." Materials Science Forum 800-801 (July 2014): 726–30. http://dx.doi.org/10.4028/www.scientific.net/msf.800-801.726.
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The objective of this work is to measure the residual stress normal to the cut plane which has a large size using contour method. Translations and rotations are applied to the second point cloud to assure the continuity of the contour. There is still the same work on the opposing cut plane, align and combine the two contour datasets, perform the interpolation and then integrate with a finite element modelling package to apply many thousands of different boundary conditions. The finite element result shows a good continuity indicating the success of transformation means applied on the point cloud. The result gets the stress distribution normal to the cut plane. Beam forming is simulated to study the residual stress distribution of the stretch-wrap bend forming, the residual stress from contour method and forming simulation present the same trend.
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Carrera, E. "A Reissner’s Mixed Variational Theorem Applied to Vibration Analysis of Multilayered Shell." Journal of Applied Mechanics 66, no. 1 (March 1, 1999): 69–78. http://dx.doi.org/10.1115/1.2789171.
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A comprehensive model of anisotropic multilayered double curved shells fulfilling a priori the interlaminar continuity requirements for the transverse shear and transverse normal stress as well as the static conditions on the bounding surfaces of the shell is developed in this paper. To this end, Reissner’s mixed variational theorem is employed to derive the equations governing the dynamic equilibrium and compatibility of each layer, while the interlaminar continuity conditions are used to drive the equations at the multilayered level. No assumptions have been made concerning the terms of type thickness to radii shell ratio h/R. Classical displacement formulations and related equivalent single layer equations have been derived for comparison purposes. Comparison of frequency predictions based upon the presented structural model with a number of results spread throughout the specialized literature and obtained via other models reveals that this advanced model provides results in excellent agreement with the ones based on three-dimensional elasticity theory, and better as compared to the ones violating the interlaminar stress continuity requirements and/or transverse normal stress and related effects.
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Abo-Dahab, S. M. "Propagation of p-, T-, and SV-waves at the interface between two solid–liquid media with magnetic field and initial stress in the context of two thermoelastic theories." Canadian Journal of Physics 93, no. 7 (July 2015): 807–23. http://dx.doi.org/10.1139/cjp-2014-0193.
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In this paper, we study the effects of magnetic field and initial stress on p-, T-, and SV-waves propagation. We investigated the problem of reflection and refraction of thermoelastic waves at a magnetized solid–liquid interface in the presence of initial stress. In the context of classical theory and Green–Lindsay theory of thermoelasticity, the problem has been solved. The boundary conditions applied at the interface are: (i) displacement continuity; (ii) vanishing tangential displacement; (iii) continuity of normal force per unit initial area; (iv) tangential force per unit initial area must vanish; and (v) continuity of temperature. The amplitudes ratios for the incident p-, T-, and SV-waves have been obtained. The reflection and transmittion coefficients from the incident waves are computed numerically, considering the initial stress and magnetic field effect and the results obtained have been presented graphically.
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Wang, X., and G. Shi. "A simple and accurate sandwich plate theory accounting for transverse normal strain and interfacial stress continuity." Composite Structures 107 (January 2014): 620–28. http://dx.doi.org/10.1016/j.compstruct.2013.08.033.
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Brown, L. M. "Indentation Size Effect and the Hall-Petch ‘Law’." Materials Science Forum 662 (November 2010): 13–26. http://dx.doi.org/10.4028/www.scientific.net/msf.662.13.
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The flow of material out from under regions in compression must occur by the operation of many slip systems, which together produce rotational flow. Such flow requires the accumulation of geometrically necessary dislocations, and leads to the indentation size effect: smaller indents produce higher hardness, a component of the hardness being inversely proportional to the square-root of the indenter size. A pattern of flow in polycrystals which satisfies both continuity of normal stress and continuity of matter at boundaries can be achieved by rotational flow, and it leads to a grain-size effect. Under most circumstances, the flow stress has a component which is inversely proportional to the square-root of the grain size, the Hall-Petch law. The flow is accompanied by the build-up of internal stress which can be relieved by intercrystalline cracking, thereby limiting the cohesive strength of polycrystals. The relationship between these ideas and traditional views is briefly explained, and an analysis is given of recent experimental results.
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Yin, W. L. "Free-Edge Effects in Anisotropic Laminates Under Extension, Bending and Twisting, Part I: A Stress-Function-Based Variational Approach." Journal of Applied Mechanics 61, no. 2 (June 1, 1994): 410–15. http://dx.doi.org/10.1115/1.2901459.
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A variational method involving Lekhnitskii’s stress functions is used to determine the interlaminar stresses in a multilayered strip of laminate subjected to arbitrary combinations of axial extension, bending, and twisting loads. The stress functions in each layer are approximated by polynomial functions of the thickness coordinate. The equilibrium equations, the traction-free boundary conditions, and the continuity conditions of the interlaminar stresses are exactly satisfied in the present analysis, while the compatibility equations and the continuity of the displacements across the interfaces are enforced in an averaged sense by applying the principle of complementary virtual work. This yields an eigenvalue problem for the interfacial values of the stress functions and their normal derivatives. Interlaminar stresses for all three distinct loading cases may be obtained, in a single solution process, by combining the eigenfunctions with appropriate particular solutions (peculiar to each loading case) so as to ensure satisfaction of the traction-free boundary condition at the free edge.
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Saad, E. I. "Axisymmetric motion of a spherical porous particle perpendicular to two parallel plates with slip surfaces." Canadian Journal of Physics 93, no. 7 (July 2015): 784–95. http://dx.doi.org/10.1139/cjp-2014-0549.
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A combined analytical–numerical approach to the problem of the low Reynolds number motion of a porous sphere normal to one of two infinite parallel plates at an arbitrary position between them in a viscous fluid is investigated. The clear fluid motion governed by the Stokes equation and the Darcy–Brinkman equation is used to model the flow inside the porous material. The motion in each of the homogeneous regions is coupled with the continuity of the velocity components, the continuity of the normal stress, and the tangential stress jump condition. The fluid is allowed to slip at the surface of the walls. A general solution for the field equations in the clear region is constructed from the superposition of the fundamental solutions in both cylindrical and spherical coordinate systems. The collocation solutions for the hydrodynamic interactions between the porous sphere and the walls are calculated with good convergence for various values of the slip coefficient of the walls, the separation between the porous sphere and the walls, the stress jump coefficient, and a coefficient that is proportional to the permeability. For the special cases of a solid sphere, our drag results show excellent agreement with the available solutions in the literature for all relative particle-to-wall spacing.
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Banks, J. W., and B. Sjögreen. "A Normal Mode Stability Analysis of Numerical Interface Conditions for Fluid/Structure Interaction." Communications in Computational Physics 10, no. 2 (August 2011): 279–304. http://dx.doi.org/10.4208/cicp.060210.300910a.
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AbstractIn multi physics computations where a compressible fluid is coupled with a linearly elastic solid, it is standard to enforce continuity of the normal velocities and of the normal stresses at the interface between the fluid and the solid. In a numerical scheme, there are many ways that velocity- and stress-continuity can be enforced in the discrete approximation. This paper performs a normal mode stability analysis of the linearized problem to investigate the stability of different numerical interface conditions for a model problem approximated by upwind type finite difference schemes. The analysis shows that depending on the ratio of densities between the solid and the fluid, some numerical interface conditions are stable up to the maximal CFL-limit, while other numerical interface conditions suffer from a severe reduction of the stable CFL-limit. The paper also presents a new interface condition, obtained as a simplified characteristic boundary condition, that is proved to not suffer from any reduction of the stable CFL-limit. Numerical experiments in one space dimension show that the new interface condition is stable also for computations with the non-linear Euler equations of compressible fluid flow coupled with a linearly elastic solid.
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Ruas, V., and J. H. Carneiro de Araujo. "Primal finite element solution of second order problems in three-dimension space with normal stress/flux continuity." ZAMM 87, no. 7 (July 25, 2007): 480–85. http://dx.doi.org/10.1002/zamm.200510330.
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Prakash, Jai, and Chirala Satyanarayana. "Axisymmetric Slow Motion of a Porous Spherical Particle in a Viscous Fluid Using Time Fractional Navier–Stokes Equation." Colloids and Interfaces 5, no. 2 (April 13, 2021): 24. http://dx.doi.org/10.3390/colloids5020024.
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In this paper, we present the unsteady translational motion of a porous spherical particle in an incompressible viscous fluid. In this case, the modified Navier–Stokes equation with fractional order time derivative is used for conservation of momentum external to the particle whereas modified Brinkman equation with fractional order time derivative is used internal to the particle to govern the fluid flow. Stress jump condition for the tangential stress along with continuity of normal stress and continuity of velocity vectors is used at the porous–liquid interface. The integral Laplace transform technique is employed to solve the governing equations in fluid and porous regions. Numerical inversion code in MATLAB is used to obtain the solution of the problem in the physical domain. Drag force experienced by the particle is obtained. The numerical results have been discussed with the aid of graphs for some specific flows, namely damping oscillation, sine oscillation and sudden motion. Our result shows a significant contribution of the jump coefficient and the fractional order parameter to the drag force.
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Zayman, Esra, and Bircan Simsek. "THE EFFECT OF PSYCHODRAMA ON ANXIETY LEVELS AND STRESS COPING STYLES IN ACADEMICIANS." Medicine Science | International Medical Journal 12, no. 1 (2023): 253. http://dx.doi.org/10.5455/medscience.2022.12.261.
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This study aimed to investigate the effects of psychodrama on stress and coping with stress in people working as medical doctors and nurses academicians. This study confirmed whether psychodrama could be effective on stress and coping mechanisms for nurses and medical doctors academicians. Individuals were evaluated by the state and continuity anxiety scale, the stress coping style scale, the Hamilton anxiety scale, and the Hamilton depression scale. The Statistical Program for Social Sciences-SPSS for Windows, version 22.0, was used for statistical analysis (SPSS Inc., Chicago, IL, USA).Data are given as mean (standard deviation) and number (percentage). To test the normal distribution compliance of the data, the Kolmogorov Smirnov test, T test for independent groups in normally distributed data with two groups, ANOVA test for data with more than two groups with normal distribution, and Mann Whitney U test for data with normal distribution was used. A statistically significant difference was found in the pre-test and post-test average scores of the applied scales. Practice Implications It is recommended that this study be performed with a more homogeneous patient group. It was found that psychodrama significantly affected stress and stress coping styles in individuals who work as academicians. It was found that psychodrama significantly affected stress and stress-coping styles in individuals. The most important limitation of our study was that the participants were in the same academic community.
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Xiaoyu, Jiang. "3-D Vibration Analysis of Fiber Reinforced Composite Laminated Cylindrical Shells." Journal of Vibration and Acoustics 119, no. 1 (January 1, 1997): 46–51. http://dx.doi.org/10.1115/1.2889686.
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In this paper, 3-D solutions of free vibrations are presented for isotropic and composite laminated cylindrical shells. The perturbation method and a variational principle are used to obtain the solutions which satisfy the 3-D differential equations of motion, the strain-displacement relations, the stress-strain relations, the boundary conditions and the continuity conditions at layer interfaces. The distributions of displacements and stresses in the shells are shown in figures. The free vibration frequencies are listed in tables. In the thickness direction of the shells, continuous displacements and stresses are obtained. And the importance of transverse shear stresses and transverse normal stress is analyzed.
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Sarkar, Priya, and Krishna Prasad Madasu. "Parallel and perpendicular flows of a couple stress fluid past a solid cylinder in cell model: Slip condition." Physics of Fluids 35, no. 3 (March 2023): 033101. http://dx.doi.org/10.1063/5.0135866.
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The axisymmetric steady flow of a couple stress fluid between two concentric cylinders with a slip effect is investigated with the help of the cell model technique. Here, the inner cylinder is rigid, and the outer cylinder is fictitious. The tangential slip, vanishing of normal velocity, and zero couple stress conditions are applied on the inner cylindrical surface. In addition, zero shear stress (Happel's model), continuity of normal velocity component, and zero couple stress conditions are used on the outer cylindrical surface. We consider two flow problems: the first is the parallel flow, and the second is the perpendicular flow to the cylinder in the cell model. Also, we have discussed the random case. For all the cases, the Kozeny constant is calculated. We described some special cases and compared them with well-known results. The effects of slip and couple stress parameters on the Kozeny constant with fixed value of couple stress viscosity parameter are presented graphically. The influence of the couple stress viscosity parameter on the Kozeny constant with fixed values of couple stress, and slip parameters for parallel flow are expressed graphically. The numerical values for the Kozeny constant for different values of fractional void volume are tabulated. We also obtained the results of the consistent couple stress theory as a special case.
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Liu, Shuhong, Jiajun Duan, Jinlu Fan, and Yongquan Zhu. "Stress and Displacement of Deep-Buried Composite Lining Tunnel under Different Contact Conditions." Mathematical Problems in Engineering 2023 (January 23, 2023): 1–11. http://dx.doi.org/10.1155/2023/7467290.
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Stress and displacement of the composite lining are important factors to be considered during tunnel design. By the complex variable method, analytical solutions for stress and displacement of surrounding rock, primary support and secondary lining satisfying the interface continuity and boundary conditions under far-field stresses are derived. Taking the railway composite lining tunnel as an example, the analytical distributions of stress and displacement along boundaries are given, which was in good agreement with the numerical solution calculated by finite element software. The results show that the maximum normal stress ratio (load sharing ratio) of the outer boundary between the secondary lining and the primary support is 0.74. The radial displacement of the inner boundary of surrounding rock, primary support, and secondary lining change consistently. The maximum settlement and uplift occur at the vault and bottom, respectively. The tangential stress of secondary lining is compressive stress, while the tangential stress of primary support is tensile stress and compressive stress. The maximum tangential stress of primary support and secondary lining is smaller than the allowable stress of concrete.
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MIKELIĆ, ANDRO, and MARY F. WHEELER. "ON THE INTERFACE LAW BETWEEN A DEFORMABLE POROUS MEDIUM CONTAINING A VISCOUS FLUID AND AN ELASTIC BODY." Mathematical Models and Methods in Applied Sciences 22, no. 11 (September 10, 2012): 1250031. http://dx.doi.org/10.1142/s0218202512500315.
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In this paper we undertake a rigorous derivation of the interface conditions between a poroelastic medium (the pay zone) and an elastic body (the non-pay zone). We assume that the poroelastic medium contains a pore structure of the characteristic size ε and that the fluid/structure interaction regime corresponds to diphasic Biot's law. The question is challenging because the Biot's equations for the poroelastic part contain one unknown more than the Navier equations for the non-pay zone. The solid part of the pay zone (the matrix) is elastic and the pores contain a viscous fluid. The fluid is assumed viscous and slightly compressible. We study the case when the contrast of property is of order ε2, i.e. the normal stress of the elastic matrix is of the same order as the fluid pressure. We assume a periodic matrix and obtain the a priori estimates. Then we let the characteristic size of the inhomogeneities tend to zero and pass to the limit in the sense of the two-scale convergence. The obtained effective equations represent a two-scale system for three displacements and two pressures, coupled through the interface conditions with the Navier equations for the elastic displacement in the non-pay zone. We prove that the appropriate interface conditions at the interface between an elastic and a poroelastic medium are: (i) the effective displacement continuity, (ii) the effective normal stress continuity and (iii) the normal Darcy velocity zero from the poroelastic side. In addition we determine the effective boundary conditions for the contact between a poroelastic body and a rigid obstacle, giving us the effective outer boundary conditions.
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Dai, Jiahui, Chao Liu, Minghui Li, and Zhenlong Song. "Influence of principal stress effect on deformation and permeability of coal containing beddings under true triaxial stress conditions." Royal Society Open Science 6, no. 2 (February 2019): 181438. http://dx.doi.org/10.1098/rsos.181438.
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In situ stress is generally an anisotropic/true triaxial stress ( σ 1 > σ 2 > σ 3 ). Bedding weakens the continuity and integrity of coal. It is critical to understand the mechanical behaviour and gas migration of coal under true triaxial stress conditions. We performed experiments of cubic coal samples to investigate the permeability evolution and mechanical behaviour of coal under true triaxial stress conditions by using newly developed true triaxial geophysical apparatus. We analysed the effect of principal stresses on deformation and permeability characteristics of coal containing bedding planes. The results show that volumetric strain, stress states and bedding directions determine the permeability comprehensively. The variable quantity of strain was the largest in the direction normal to the bedding plane. The expansion or compression degree was characterized by the difference between the major and minor principal strain ( ɛ 1 − ɛ 3 ). Essentially, this represents the difficulty degree with regard to coal being compressed at the initial stress state and the deformation degree in ɛ 1 and ɛ 3 direction. The variation of ( ɛ 1 − ɛ 3 ) was consistent with that of permeability. Under an identical true triaxial stress condition, permeability was smaller when larger stress was applied in the direction normal to the bedding plane. Additionally, stress level in the direction parallel to the bedding planes and the directions between stresses in the direction parallel to the bedding planes and the flow direction also affect the permeability and strain. By solving lateral expansion coefficient, coal also exhibited anisotropic properties.
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Carrera, E. "Layer-Wise Mixed Models for Accurate Vibrations Analysis of Multilayered Plates." Journal of Applied Mechanics 65, no. 4 (December 1, 1998): 820–28. http://dx.doi.org/10.1115/1.2791917.
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This paper presents the dynamic analysis of multilayered plates using layer-wise mixed theories. With respect to existing two-dimensional theories at the displacement formulated, the proposed models a priori fulfill the continuity of transverse shear and normal stress components at each interface between two adjacent layers. A Reissner’s mixed variational equation is employed to derive the differential equations, in terms of the introduced stress and displacement variables, that govern the dynamic equilibrium and compatibility of each layer. The continuity conditions at the interfaces are used to write corresponding equations at multilayered level. Related standard displacement formulations, based on the principle of virtual displacements, are given for comparison purposes. Numerical results are presented for the free-vibration response (fundamental and higher order frequencies are calculated) of symmetrically and unsymmetrically laminated cross-ply plates. Several comparisons to three-dimensional elasticity analysis and to some available results, related to both layer-wise and equivalent single-layer theories, have shown that the presented mixed models: (1) match the exact three-dimensional results very well and (2) lead to a better description in comparison to results related to other available analysis.
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Hamzah, Khairum Bin, and Nik Mohd Asri Nik Long. "Mode Stresses for the Interaction between Two Inclined Cracks in Bonded Two Half Planes." Key Engineering Materials 861 (September 2020): 524–28. http://dx.doi.org/10.4028/www.scientific.net/kem.861.524.
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The various mode of stresses for the interaction between two inclined cracks in the upper part of bonded two half planes which are normal stress (Mode I), shear stress (Mode II), tearing stress (Mode III) and mixed stress was studied. For this problem, the modified complex potentials (MCPs) method was used to develop the new system of hypersingular integral equations (HSIEs) by applying the conditions for continuity of resultant force and displacement functions with the unknown variable of crack opening displacement (COD) function and the right hand terms are the tractions along the crack. The curve length coordinate method and Gauss quadrature rules were used to solve numerically the obtained HSIEs to compute the stress intensity factors (SIFs) in order to determine the strength of the materials containing cracks. Numerical solutions presented the characteristic of nondimensional SIFs at the cracks tips. It is obtained that the various stresses and the elastic constants ratio are influences to the value of nondimensional SIFs at the crack tips.
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Wu, Xianlong, Gang Wang, Genxiao Li, Wei Han, Shangqu Sun, Shubo Zhang, and Wangliang Bi. "Research on Shear Behavior and Crack Evolution of Symmetrical Discontinuous Rock Joints Based on FEM-CZM." Symmetry 12, no. 8 (August 6, 2020): 1314. http://dx.doi.org/10.3390/sym12081314.
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The discontinuous joints are an essential type of natural joints. The normal force, joint persistency, and distribution exert great influences on the shear resistance of the rock joints. By simulating the uniaxial compression experiment and Brazilian test, the material parameters and the basic size standard for meshing were determined. The symmetrical discontinuous joint distribution of three types were established, the cohesive elements were inserted between the solid elements, and the numerical simulation of the shear test was conducted. The effects of joint distribution, joint continuity, and normal stress on the shear resistance of joint rock were investigated, and the law of crack evolution was analyzed. The results showed that the shear process of discontinuous joints can be divided into four stages: elastic stage, strengthening stage, plastic stage, and residual stress stage. For the scattered joint distribution, the rock bridge can provide more reinforcement for the joints, which enhances the shear resistance of the joints, the stress concentration point at the end of the joint is easy to accumulate more fracture energy, which induces the initiation of the cracks, and under the influence of unbalanced torque, the both-sided joint distribution is more likely to produce tension damage.
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Dong, Liang, Zuyue Wang, Chenhuai Tang, Yi Chen, Zhuanggen Tong, and Shantao Xiao. "Cause Analysis and Stress State Study of Corrosion Case of Shell and Tube Heat Exchanger." Highlights in Science, Engineering and Technology 21 (December 4, 2022): 332–37. http://dx.doi.org/10.54097/hset.v21i.3188.
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Shell and tube heat exchanger is an important equipment in nuclear power, chemical industry and other industries. The working conditions of such equipment are sometimes complex, and the use temperature, fluid state and flow may affect the normal operation of the equipment. In addition, there are many connecting pipes on the shell and tube head of the shell and tube heat exchanger connected with other equipment, which has an impact on the continuity of the equipment structure. Reasons for the corrosion of the shell and tube heat exchanger tube box head in a chemical plant was analyzed in this paper. Finite element method was used to model the corroded tube box head, studies of the stress distribution after corrosion. Some suggestions was given to avoid this kind of corrosion.
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Shirazi-Adl, A. "Finite Element Stress Analysis of a Push-Out Test Part 1: Fixed Interface Using Stress Compatible Elements." Journal of Biomechanical Engineering 114, no. 1 (February 1, 1992): 111–18. http://dx.doi.org/10.1115/1.2895434.
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In this first part of a two-part paper, interelement stress compatible finite elements are developed and used to perform the stress analysis of a push-out test with a fixed interface. In the formulation, the required continuity of some of the stresses along either a specific interface or all interelement interfaces is enforced by a penalty procedure. The model is axisymmetric and consists of two cylinders attached to each other through the interface. Various relative material properties and boundary conditions are simulated in order to examine their effects on the interface stresses. Both loadings of axial compression force and axial torque are considered. The predicted results exhibit identical interelement stresses and displacements even when highly dissimilar materials are used. They also exhibit a complex state of interface stresses which depend on the geometry, material arrangement, boundary conditions, and loading. The variation of the shear stress is often highly nonuniform and the radial normal stresses are likely to be large. The present results, therefore, disagree with the common assumptions made in the pull-out tests in the orthopaedic applications. Finally, stress analysis of a number of possible testing configurations could lead to the design of an optimal pull-out test which maximizes the usefulness of the measured results in terms of the interface bond strength and factors affecting it.
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Angelides, M., A. Shirazi-Adl, S. C. Shrivastava, and A. M. Ahmed. "A Stress Compatible Finite Element for Implant/Cement Interface Analyses." Journal of Biomechanical Engineering 110, no. 1 (February 1, 1988): 42–49. http://dx.doi.org/10.1115/1.3108404.
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A new finite element has been developed to enforce normal and shear stress continuity at bimaterial interface points in order to alleviate the problem of high stress discontinuity predictions by the conventional displacement finite element method. The proposed element is based on a five node isoparametric quadrilateral element where the fifth node is located at the interface boundary of the element. A series of validation tests have been carried out to assess the correctness of the stress distribution obtained by the new element at interfaces of highly dissimilar materials. The results of the tests are compared to analytical solutions and to results from convergence studies performed by the conventional finite element method (SAP-IV). Overall, the proposed element has been demonstrated to have a very satisfactory degree of reliability, especially in view of the observed inability of the conventional method to yield interpretable interface stress values for most cases analyzed. Finally, the new interface element has been applied to the analysis of an axisymmetric model of the knee tibial implant. The superiority of the proposed element over the conventional one has been demonstrated in this case by a convergence study.
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Low, Hong Tong, Xiao Bing Chen, Peng Yu, and Sony Winoto. "Mass Transport in a Microchannel Bioreactor with a Porous Wall." Applied Mechanics and Materials 110-116 (October 2011): 3489–94. http://dx.doi.org/10.4028/www.scientific.net/amm.110-116.3489.
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A two-dimensional flow model, incorporating mass transport, has been developed to simulate flow in a microchannel bioreactor with a porous wall. A two-domain method was implemented which was based on finite volume method. For the porous-fluid interface, a stress jump condition was used with continuity of normal stress; and the mass interfacial conditions were continuities of mass and mass flux. Two parameters are defined to characterize the mass transports in the fluid and porous regions. The porous Damkohler number is the ratio of consumption to diffusion of the substrates in the porous medium. The fluid Damkohler number is the ratio of substrate consumption in the porous medium to substrate convection in the fluid region. The concentration results are found to be well correlated by the use of a reaction-convection distance parameter which incorporates the effects of axial distance, substrate consumption and convection.
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Achata-Espinoza, Miguel, Carmen Rosa Muñoz-Dueñas, Sarai Cabrejos-Llontop, and Carlos Jesus Toro-Huamanchumo. "Spare the rod, spoil the child: Bullying during medical internship in three Peruvian hospitals." Revista de la Facultad de Medicina 65, no. 1 (January 1, 2017): 169–70. http://dx.doi.org/10.15446/revfacmed.v65n1.62752.
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Dear Editor,Bullying has traditionally been considered normal during health professional training (1). However, it is now recognized as harmful to both academic traiwning and mental and emotional health, with negative consequences such as low career satisfaction, depression, burnout syndrome, and post-traumatic stress symptoms (2,3).The hierarchy observed in the different stages of the medical career facilitates power abuse and makes medical students vulnerable. Likewise, frequently undervaluing abuse leads to less willingness to report bullying cases, and in the continuity of this behavior over time (1,4). During medical internships, students are also considered as workers, which increases the chances of being bullied; in addition, the training environment differs from what they experienced early in their career (3).
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Galybin, AN. "Integral equations in direct and inverse problems of elastostatics for crack detection in layered structures." Mathematics and Mechanics of Solids 25, no. 5 (February 20, 2020): 1140–54. http://dx.doi.org/10.1177/1081286520903436.
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This study deals with both direct and inverse problems for interfacial crack identification in laminates. The main focus is given to the case of an elastic substrate coated by a film made of a different elastic material. It is assumed that delamination can be developed on the interface between these materials. It is modelled as a combined open-sliding interface crack or by a pure sliding crack (slip). Its position may not be specified. The boundary conditions on the interface assume continuity of the stress vector across the whole interface and continuity of the displacements outside the crack. In the case of the slip the normal displacements are assumed to be continuous. The inverse boundary value considered is of the Cauchy type; it assumes that both stress and displacement vectors are known on the external boundary of the structure. In the case of the slip the problem is overdetermined on a part of the boundary, where three conditions are imposed, and undetermined on its remainder where just one condition is imposed. It is further referred to as a semi-inverse formulation. Therefore, these problems are ill-posed with the specified boundary conditions. Inverse, semi-inverse and direct problems are reduced to integral equations derived from basic properties of holomorphic functions followed by applications of Fourier transforms. Analytical solutions are found for the formulations considered and difficulties of numerical implementation are discussed in brief.
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Glovnea, Marilena, and Emanuel Diaconescu. "Improvement of Punch Profiles for Elastic Circular Contacts." Journal of Tribology 128, no. 3 (March 21, 2006): 486–92. http://dx.doi.org/10.1115/1.2197522.
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Machine design and electrical contacts involve frequently elastic circular contacts subjected to normal loads. Depending on geometry, these may be Hertzian or surface contacts. Both possess highly nonuniform pressure distributions which diminish contact load carrying capacity. The achievement of a uniform pressure distribution would be ideal to improve the situation, but this violates stress continuity. Instead, the generation of a uniform pressure over most of contact area can be sought. Generally, equivalent punch profile which generates this pressure is found by numerical evaluation of double integrals. This paper simplifies the derivation of punch profile by using an existing correspondence between a polynomial punch surface and elastically generated pressure. First, an improved pressure profile is proposed seeking to avoid high Huber-Mises-Hencky stresses near contact surface. Then, this is approximated by the product between typical Hertz square root and an even polynomial, which yields directly the punch profile. Formulas for normal approach and central pressure are derived.
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Iandiorio, C., and P. Salvini. "On the Formulation of an Elastic-Plastic Beam Model: the Pre-Integration Idea." IOP Conference Series: Materials Science and Engineering 1214, no. 1 (January 1, 2022): 012026. http://dx.doi.org/10.1088/1757-899x/1214/1/012026.
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Abstract This paper provides a formulation of an elastic-plastic beam model. The constitutive behaviour of material after elasticity limit is considered perfect plastic. Although this is not a general plastic behaviour, it allows to minimize mathematical difficulties to fulfil the idea: pre-integration trough the thickness extended to material non-linearity. Three types of deformation mechanisms are found: fully elastic, plasticization over only one side or both of sides. The complete kinematic set of equations are obtained, together with the analytical stress trends. Yield stress-continuity equations are used to separate the elastic and plastic domains. These domains define a quasi-state diagram; Allowing to associate the normal force and bending moment acting on the section to the elastic-plastic state within the section. Note that in the case of a rectangular section, the solution is given in a fully analytical form, otherwise the domains are solved numerical solutions. But these last, may be obtained once for all, for any one-symmetrical section.
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Qi, Hui, Yang Zhang, Fuqing Chu, and Jing Guo. "Scattering of SH Waves by a Partially Debonded Cylindrical Inclusion in the Covering Layer." Mathematical Problems in Engineering 2020 (May 30, 2020): 1–13. http://dx.doi.org/10.1155/2020/2614574.
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This article presents analytical solutions to the problem of dynamic stress concentration and the surface displacement of a partially debonded cylindrical inclusion in the covering layer under the action of a steady-state horizontally polarized shear wave (SH wave); these solutions are using the complex function method and wave function expansion method. By applying the large-arc assumption method, the straight line boundary of the half-space covering layer is transformed into a curved boundary. The wave field of the debonded inclusion is constructed utilizing a Fourier series and boundary conditions of continuity. The impact of debonding upon the dynamic stress concentration and surface displacement around the cylindrical concrete or steel inclusion is analyzed through numerical examples of the SH waves that are incident at normal angles, from a harder medium to a softer medium and from a softer medium to a harder medium. The examples show that various factors (including the medium parameters of the soil layers and the inclusion, the frequency of the incident waves, and the debonding situations) jointly affect the dynamic stress concentration factor and the surface displacement around the structure.
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Hamzah, Khairum Bin, Nik Mohd Asri Nik Long, Norazak Senu, and Zainidin K. Eshkuvatov. "Numerical Solution for Crack Phenomenon in Dissimilar Materials under Various Mechanical Loadings." Symmetry 13, no. 2 (January 31, 2021): 235. http://dx.doi.org/10.3390/sym13020235.
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A new mathematical model is developed for the analytical study of two cracks in the upper plane of dissimilar materials under various mechanical loadings, i.e., shear, normal, tearing and mixed stresses with different geometry conditions. This problem is developed into a new mathematical model of hypersingular integral equations (HSIEs) by using the modified complex potentials (MCPs) function and the continuity conditions of the resultant force and displacement with the crack opening displacement (COD) function as the unknown. The newly obtained mathematical model of HSIEs are solved numerically by utilizing the appropriate quadrature formulas. Numerical computations and graphical demonstrations are carried out to observe the profound effect of the elastic constants ratio, mode of stresses and geometry conditions on the dimensionless stress intensity factors (SIFs) at the crack tips.
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Guo, Qifeng, Jiliang Pan, Meifeng Cai, and Ying Zhang. "Investigating the Effect of Rock Bridge on the Stability of Locked Section Slopes by the Direct Shear Test and Acoustic Emission Technique." Sensors 20, no. 3 (January 23, 2020): 638. http://dx.doi.org/10.3390/s20030638.
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As a portion of intact rock separating joint surfaces, rock bridge plays a significant role in the stability of rock slopes. This paper aims to investigate the effect of different rock bridges on the mechanical properties and failure mode of rock slope by means of the direct shear test and acoustic emission technique. Field conditions were simulated in direct shear tests which were carried out on specimens with rock bridges at different continuity rates, normal stress, arrangements, and joint angles. Experimental results indicate that the strength of specimens is controlled by the rock bridge and the structural plane. The rock bridge contributes to the strength of the specimen, while the through plane weakens the strength of the specimen. The increase of normal stress can weaken the stress concentration near the tip of the rock bridge and improve the shear resistance of the specimen. The different arrangement of rock bridge has little effect on the normal displacement of the specimen, and has a great influence on the shear strength. The shear capacity of the specimen is related to the angle of the crack, and the angle of the crack is approximately proportional to the peak shear strength. For the specimens with different joint occurrence, the mode of crack propagation at the initial stage is basically the same, and the specimen is finally damaged due to the generation of through cracks in the core area of rock bridge. The instantaneous release of the huge energy generated during the experiment along the shear direction is the root cause of the sudden failure of the rock bridge. The formation, aggregation, and transfixion process of rock bridge is of concern and has been experimentally investigated in this paper for the prevention and control of the locked section rock slope with sudden disasters.
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Shelbourne, K. Donald, Marc S. Haro, and Tinker Gray. "Knee Dislocation with Lateral Side Injury." American Journal of Sports Medicine 35, no. 7 (July 2007): 1105–16. http://dx.doi.org/10.1177/0363546507299444.
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Background Knee dislocations with lateral side injury are rare and disabling if not treated. Hypothesis An en masse surgical technique to repair the lateral side will provide good stability, and the posterior cruciate ligament will heal when left in situ. Study Design Case series; Level of evidence, 4. Methods Twenty-three patients underwent an en masse lateral side repair after knee dislocation injury; all but 1 patient had anterior cruciate ligament reconstruction. Physical examination included the International Knee Documentation Committee score, isokinetic strength testing, KT-2000 arthrometer testing, radiography (including varus stress), and magnetic resonance imaging scan. Patients were evaluated subjectively with several surveys. Results Mean objective evaluation occurred for 17 patients at 4.6 years postoperatively, and 21 subjective evaluations occurred for 21 patients at 5.6 years postoperatively. The objective overall grade was normal for 10 patients and nearly normal for 7 patients. Lateral laxity was graded as normal in 15 patients and 1+ in 2 patients. The posterior drawer was normal in all but 3 patients, who had 1+ posterior laxity. The postoperative varus stress radiography demonstrated a mean increase of 1.1 ± 1.7 mm (range, —1.2-4.7) between knees. Magnetic resonance scans showed that the lateral side was thickened but intact in all patients. The posterior cruciate ligament was viewed as healed or intact in all patients but was sometimes seen as elongated or buckled. The mean subjective total scores were 91.3 points for the IKDC survey, 93.0 for the modified Noyes survey, and 8.0 for an activity score, but scores were higher for patients who underwent surgery within 4 weeks from the injury. Conclusions The en masse surgical technique to repair the lateral side combined with an anterior cruciate ligament reconstruction after knee dislocation provides excellent long-term stability. The repaired lateral side and untreated posterior cruciate ligament heal with continuity. Patients can return to high levels of activity.
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Lukashevich, A., N. Lukashevich, and E. Kobelev. "Finite elements for problems of the elasticity theory with the discontinuous stress approximation." E3S Web of Conferences 224 (2020): 02012. http://dx.doi.org/10.1051/e3sconf/202022402012.
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The paper deals with the development of the finite element models on the basis of stress approximation. At present, the displacementbased finite element method is mainly used for engineering calculations. Finite element formulations in stresses are not so widely spread, but in some cases these formulations can be more effective in particular with respect to the calculating stresses and also obtaining a two-sided estimate of the exact solution of the problem. The finite element models based on the approximation of discontinuous stress fields and the use of the penalty function method to satisfy the equilibrium equations are considered. It is shown that the continuity of both normal and tangential stresses only on the adjacent sides of the finite elements contributes to the expansion of the class of statically admissible stress fields. At the same time, the consistent approximation is provided, both of the main part of the functional of additional energy, and its penalty part. The necessary matrix relations for rectangular and triangular finite elements are obtained. The effectiveness of the developed models is illustrated by numerical studies. The calculation results were compared with the solution on the FEM in displacements, as well as with the results obtained using other schemes of approximating the stresses in the finite element. It is shown that the model of discontinuous stress approximations gives the bottom convergence of the solution, both in stresses and in displacements. At the same time, the accuracy on the stresses here is much higher than in the displacement-based FEM or when using conventional stress approximation schemes.
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BERTUZZI, ALESSANDRO, ANTONIO FASANO, ALBERTO GANDOLFI, and CARMELA SINISGALLI. "MODELING THE EVOLUTION OF A TUMORAL MULTICELLULAR SPHEROID AS A TWO-FLUID BINGHAM-LIKE SYSTEM." Mathematical Models and Methods in Applied Sciences 23, no. 14 (October 10, 2013): 2561–602. http://dx.doi.org/10.1142/s0218202513500401.
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In this paper we propose a model for the evolution of a tumor spheroid assuming a structure in which the central necrotic region contains an inner liquid core surrounded by dead cells that keep some mechanical integrity. This partition is a consequence of assuming that a finite delay is required for the degradation of dead cells into liquid. The phenomenological assumption of constant local volume fraction of cells is also made. The above structure is coupled with a mechanical two-phase model that views the cell component as a Bingham-like fluid and the extracellular liquid as an inviscid fluid. By imposing the continuity of the normal stress throughout the whole spheroid, we can describe the spheroid evolution and characterize the possible steady state. Depending on the values of mechanical parameters, the model predicts either an evolution toward the steady state or an unbounded growth. An existence and uniqueness result has been proved under suitable assumptions, along with some qualitative properties of the solution.
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Kheirikhah, Mohammad Mahdi, and Seyyed Mohammad Reza Khalili. "Bending Analysis of Composite Sandwich Plates with Flexible Core Using 3D Finite Element Method." Applied Mechanics and Materials 110-116 (October 2011): 1229–36. http://dx.doi.org/10.4028/www.scientific.net/amm.110-116.1229.
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Sandwich plates have been extensively used in many engineering applications such as automotive and aerospace. In the present paper, an accurate finite element model is presented for bending analysis of soft-core rectangular sandwich plates. The sandwich plate is composed of three layers: top and bottom skins and core layer. The core is assumed as a soft orthotropic material and skins are assumed generally unequal laminated composites. Finite element model of the problem has been constructed in the ANSYS 11.0 standard code area. Continuity conditions of transverse shear stresses at the interfaces are satisfied as well as the conditions of zero transverse shear stresses on the upper and lower surfaces of plate. Also transverse flexibility and transverse normal strain and stress of core are considered. The effect of geometrical parameters of the sandwich plate are studied. Comparison of the present results with those of plate theories confirms the accuracy of the proposed model.
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Shan, Renliang, Weijun Liu, Gengzhao Li, Chen Liang, Shuguo Shi, Ye Chen, and Shupeng Zhang. "Experimental Study on the Shear Mechanical Properties of Anchor Cable with C-Shaped Tube." Sustainability 14, no. 15 (August 4, 2022): 9616. http://dx.doi.org/10.3390/su14159616.
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Faced with serious tensile–shear fracturing of anchor bolts and cables in deep roadways, it is of great significance to investigate Anchor Cable with C-shaped tube (ACC), a combined structure of a C-shaped tube and an anchor cable with high strength and shear resistance. The shear mechanical properties of the anchor cable and ACC are systematically investigated using the technical means of theoretical analysis and double-shear tests. The improved equipment for a double-shear test not only considers the initial normal stress but also ensures the continuity of the anchor cable’s axial force transmission while considering the influence of the inclination angle on the shear performance of supporting components. The research indicates that the C-shaped tube inhibits the occurrence of stress concentration near the joint surface and improves the stress state of the anchor cable, transforming its failure mode from tensile–shear failure to tensile failure. Compared with the anchor cable, ACC has a higher shear capacity, greater shear stiffness and better ductility in the shear direction. The shear capacity of ACC is higher when it is perpendicular to the joint plane than when inclined to 80°, and the shear capacity of the joint plane is linear with the initial normal stress. Two methods were proposed to contrast the shear capacity between the anchor cable and ACC, including the shear capacity of supporting components and the shear capacity of the joint surface. The former is to evaluate the shear capability of the anchor cable and ACC, while the latter is to evaluate the ability of the anchor cable and ACC to control the shear deformation of the joint surface. The tests results show that the average shear capacity of ACC is 279 kN higher than the anchor cable, with an average increase of 34.9%. The average shear capacity of the joint surface anchored by ACC is 306 kN higher than the anchor cable, with an average increase of 25.2%. ACC can effectively improve the shear capacity of the anchor cable in the free section and has wide application prospects.
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Nayfeh, Adnan H., and Wael G. Abdelrahman. "Vibration Characteristics of Fibrous Composites with Damage." Journal of Vibration and Control 9, no. 6 (June 2003): 709–29. http://dx.doi.org/10.1177/1077546303009006005.
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A micromechanical model is developed in order to study the vibration characteristics of fibrous composites with damage. Damage is taken in the form of either a broken fiber or a matrix crack normal to the fiber direction. The unidirectionally reinforced periodic composite, when vibrating in the longitudinal (fiber) direction, is modeled as a concentric cylindrical system subjected at its outer boundaries to vanishing radial displacement and shear stress. Guided by the symmetry and the fiber-matrix interface continuity conditions, an approximate radial dependence of some of the field variables is first assumed. The two-dimensional field equations that hold in both the fiber and the matrix, together with their interface conditions, are then reduced to a quasi-one-dimensional system which automatically satisfies all interface and boundary conditions. The simplified model is applied to the study of the vibration characteristics of the composite with and without damage. The cases of broken fibers and cracked matrix are treated by invoking stress-free conditions at the crack faces. The dependence of the resonance frequencies and mode shapes on the nature and location of the damage is exploited. Significant reduction in the values of resonance frequencies can be realized for damage located close to the center of the composite system.
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PERRY, A. E., IVAN MARUSIC, and M. B. JONES. "On the streamwise evolution of turbulent boundary layers in arbitrary pressure gradients." Journal of Fluid Mechanics 461 (June 25, 2002): 61–91. http://dx.doi.org/10.1017/s002211200200825x.
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A new approach to the classic closure problem for turbulent boundary layers is presented. This involves, first, using the well-known mean-flow scaling laws such as the log law of the wall and the law of the wake of Coles (1956) together with the mean continuity and the mean momentum differential and integral equations. The important parameters governing the flow in the general non-equilibrium case are identified and are used for establishing a framework for closure. Initially closure is achieved here empirically and the potential for achieving closure in the future using the wall-wake attached eddy model of Perry & Marusic (1995) is outlined. Comparisons are made with experiments covering adverse-pressure-gradient flows in relaxing and developing states and flows approaching equilibrium sink flow. Mean velocity profiles, total shear stress and Reynolds stress profiles can be computed for different streamwise stations, given an initial upstream mean velocity profile and the streamwise variation of free-stream velocity. The attached eddy model of Perry & Marusic (1995) can then be utilized, with some refinement, to compute the remaining unknown quantities such as Reynolds normal stresses and associated spectra and cross-power spectra in the fully turbulent part of the flow.
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Nur Farahalya Razhali, Ishkrizat Taib, Nurul Fitriah Nasir, Ahmad Mubarak Tajul Arifin, Nor Adrian Nor Salim, Shahrul Azmir Osman, Nofrizal Idris Darlis, and A. K. Kareem. "Analysis of Hemodynamic Effect on Different Stent Strut Configuration in Femoral Popliteal Artery during the Physical and Physiological Conditions." Journal of Advanced Research in Applied Sciences and Engineering Technology 29, no. 1 (December 31, 2022): 223–36. http://dx.doi.org/10.37934/araset.29.1.223236.
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Peripheral arterial disease (PAD) is a narrowing of the peripheral arteries that might result in blockage if not immediately treated. Normally, an invasive technique called stenting is used at the stenosed arterial region to restore normal blood flow. Thus, it promotes the formation of thrombosis on the stented artery due to the presenting flow recirculation. However, the rate of thrombosis growth was reported to be different for both genders. This is due to an increase in body surface area, body mass index, and weight of the body. Thus, this study aims to investigate the effect of the physiological and physical conditions of men and women with different hemodynamic parameters on the strut configuration in FPA. Five different stent strut configurations were modelled and inserted into the FPA. The computational fluid dynamic (CFD) method was implemented to solve the continuity and N-S equations. The hemodynamic performance of the stent was analyzed based on hemodynamic parameters consisting of time- averaged wall shear stress (TAWSS), time-averaged wall shear stress gradient (TAWSSG), oscillatory shear index (OSI), and relative residence time (RRT). According to the observations, the distal region of the stented FPA had more dominant flow re-circulation than the proximal region. The high void area contributed to less growth of the thrombosis.
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RÄTY, M., R. HORN, and K. RASA. "Compressive behaviour of the soil in buffer zones under different management practices in Finland." Agricultural and Food Science 19, no. 2 (December 4, 2008): 160. http://dx.doi.org/10.2137/145960610791542370.
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Soil structure that favours infiltration is essential for successful functioning of vegetated buffer zones. We measured bulk density, air permeability and precompression stress in a clay soil (Vertic Cambisol) and a sandy loam (Haplic Regosol) in Finland, to identify management-related changes in the physical and mechanical properties in the surface soil of buffer zones. In addition, the impact of texture on these properties was studied at depths down to 180?200 cm. Soil cores (240 cm3) were sampled from a cultivated field, from buffer zones harvested by grazing (only in a clay soil) or by cutting and removing the vegetation, and from buffer zones covered with natural grass vegetation. The samples were equilibrated at a matric potential of -6 kPa and compressed at a normal stress range of 20-400 kPa (7 h), followed by stress removal (1 h). Generally, the clay soil was more compressible than the sandy loam. Due to trampling by cattle, the young grazed buffer zone (0-3 cm) had the largest bulk density and the smallest total porosity. For the grazed sites, reduced air permeability (2.7-5.1 × 10-5 m s-1) was found, compared with that of the buffer zone under natural vegetation (15-22 × 10-5 m s-1), indicating decreased pore continuity. Although the old grazed site was easily compressed, compared with the younger site, it showed a greater resilience capacity due to the protective cover of organic residues accumulated on the soil surface.
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Malvandi, Amir, Saeed Heysiattalab, Amirmahdi Ghasemi, D. D. Ganji, and Ioan Pop. "Nanoparticle migration effects at film boiling of nanofluids over a vertical plate." International Journal of Numerical Methods for Heat & Fluid Flow 27, no. 2 (February 6, 2017): 471–85. http://dx.doi.org/10.1108/hff-01-2016-0007.
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Purpose The purpose of this paper is to theoretically investigate the effects of nanoparticle migration on the heat transfer enhancement at film boiling of nanofluids. The modified Buongiorno model is used for modeling the nanofluids to observe the effects of nanoparticle migration. Design/methodology/approach The governing partial differential equations including continuity, momentum, energy and nanoparticle continuity are transformed to ordinary ones and solved numerically. For nanoparticle distribution, an analytical expression has been found. The results have been obtained for different parameters, including the Brownian motion to thermophoretic diffusion NBT, saturation nanoparticle volume fraction ϕsat and normal temperature difference. Findings A closed-form expression for nanoparticle distribution is obtained, and it is indicated that nanoparticle migration significantly affects the flow fields and thermophysical properties of nanofluids. It was shown that temperature gradient at heated wall grows as the migration of nanoparticles increases, which has positive effects on the heat transfer rate. However, decrement of thermal conductivity at heated wall because of nanoparticle depletion plays a negative role in heat transfer enhancement. In fact, there is a tradeoff between thermal conductivity reduction and an increment in temperature gradient at the wall, which determines the net enhancement/deterioration of the heat transfer rate. Research limitations/implications Flow has been assumed to be laminar, and the vapor temperature is constant such that boiling is the only heat transfer mechanism between the liquid-vapor interface. Also, the shear stress at the liquid-vapor interface is assumed to be negligible. The film thickness is small relative to the plate length to justify the boundary layer assumptions. Inertia forces are neglected relative to shear stress forces. Practical implications Outcomes of the present study are suitable for several heat exchange purposes such as evaporation and condensation in heat pipes, immersion, microchannel cooling of microelectronics and crystal growth. Originality/value The novelty of this paper has three aspects: modeling the film boiling of nanofluids considering the effects of nanoparticle migration; how it influences the cooling performance; and an analytical expression for the nanoparticle distribution at film boiling of nanofluids.
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SHEU, TONY W. H., S. C. CHEN, C. F. CHEN, T. P. CHIANG, and DING LEE. "A SPACE MARCHING SCHEME FOR UNDERWATER ACOUSTIC WAVE PROPAGATION IN FLUID-ELASTIC MEDIA." Journal of Computational Acoustics 07, no. 03 (September 1999): 185–206. http://dx.doi.org/10.1142/s0218396x99000138.
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We present in this paper partial differential equations which govern three-dimensional acoustic wave propagation in fluid-elastic media. Working equations are parabolized so as to allow the analysis to be conducted in a plane-by-plane fashion. This simplification, while permitting only outgoing wave propagation, facilitates the analysis and cuts down on computing time and disk storage. To couple working equations in fluid and elastic layers, we impose physically relevant conditions on the interface. On the horizontal interface we demand continuity of the normal displacement and normal stress. In addition, physical reasoning requires that shear stresses vanish on the interface for the present analysis, which is formulated under the inviscid flow assumption. We approximate spatial derivatives with respect to θ and z using the second-order accurate centered scheme. The resulting ordinary differential equation is solved using the implicit scheme to render also second-order prediction accuracy in r. With a numerical scheme, it is highly desirable to be able to check its prediction against suitable test problems, preferably ones for which an exact solution is available. In this three-dimensional study, test problems were chosen to demonstrate the applicability of the code to the individual fluid and elastic layer. We have also verified that the code is applicable to analysis of wave propagation in water and elastic layers, across which there is an interface.
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Hasheminejad, S. M., and M. Komeili. "Dynamic response of a thick functionally graded material tube under a moving load." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 221, no. 12 (December 1, 2007): 1545–54. http://dx.doi.org/10.1243/09544062jmes732.
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An analysis for axisymmetric steady-state response of an arbitrarily thick, isotropic, and functionally graded circular cylindrical shell of infinite length subjected to an axially moving normal ring load is presented. The mechanical properties of the graded shell are assumed to vary smoothly and continuously with the change of volume concentrations of the constituting materials across the thickness of the shell according to a power law distribution. The problem solution is derived by using Fourier transformation with respect to a moving reference frame in conjunction with the T-matrix solution technique that involves a system global transfer matrix, formed by applying continuity of the displacement and stress components at the interfaces of neighbouring layers. The analytical results are illustrated with numerical examples in which a metal-ceramic functionally graded material (FGM) pipe, composed of aluminium and zirconia, is subjected to a normal ring load travelling along the tube at constant speed. Four types of pipes are configured, i.e. a ceramic-rich composition with the ceramic at the inner (or outer) interface, and also a metal-rich composition with the metal at the inner (or outer) interface of the pipe. The presented model is used to determine the critical velocity of the moving load as a function of shell thickness for the selected material compositional gradient profiles. The effects of load velocity and shell thickness on the basic dynamic field quantities such as the mid-plane radial displacement and hoop stress amplitude along the pipe axis are also evaluated and discussed. Moreover, the response curves for the FGM shells are compared with those of equivalent bi-laminate shells containing comparable total volume fractions of constituent materials. Limiting cases are considered and good agreements with the solutions available in the literature are obtained.
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Patil, Amit, Arne Nordmark, and Anders Eriksson. "Free and constrained inflation of a pre-stretched cylindrical membrane." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 470, no. 2169 (September 8, 2014): 20140282. http://dx.doi.org/10.1098/rspa.2014.0282.
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This paper presents the free and constrained inflation of a pre-stretched hyperelastic cylindrical membrane and a subsequent constrained deflation. The membrane material is assumed as a homogeneous and isotropic Mooney–Rivlin solid. The constraining soft cylindrical substrate is assumed to be a distributed linear stiffness normal to the undeformed surface. Both frictionless and adhesive contact are modelled during the inflation as an interaction between the dry surfaces of the membrane and the substrate. An adhesive contact is modelled during deflation. The free and constrained inflation yields governing equations and boundary conditions, which are solved by a finite difference method in combination with a fictitious time integration method. Continuity in the principal stretches and stresses at the contact boundary is dependent on the contact conditions and inflation–deflation phase. The pre-stretch has a counterintuitive softening effect on free and constrained inflation. The variation of limit point pressures with pre-stretch and the occurrence of a cusp point is shown. Interesting trends are observed in the stretch and stress distributions after the interaction of the membrane with soft substrate, which underlines the effect of material parameters, pre-stretch and constraining properties.
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Teixeira, M. A. C., and C. B. da Silva. "Turbulence dynamics near a turbulent/non-turbulent interface." Journal of Fluid Mechanics 695 (February 13, 2012): 257–87. http://dx.doi.org/10.1017/jfm.2012.17.
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AbstractThe characteristics of the boundary layer separating a turbulence region from an irrotational (or non-turbulent) flow region are investigated using rapid distortion theory (RDT). The turbulence region is approximated as homogeneous and isotropic far away from the bounding turbulent/non-turbulent (T/NT) interface, which is assumed to remain approximately flat. Inviscid effects resulting from the continuity of the normal velocity and pressure at the interface, in addition to viscous effects resulting from the continuity of the tangential velocity and shear stress, are taken into account by considering a sudden insertion of the T/NT interface, in the absence of mean shear. Profiles of the velocity variances, turbulent kinetic energy (TKE), viscous dissipation rate ($\varepsilon $), turbulence length scales, and pressure statistics are derived, showing an excellent agreement with results from direct numerical simulations (DNS). Interestingly, the normalized inviscid flow statistics at the T/NT interface do not depend on the form of the assumed TKE spectrum. Outside the turbulent region, where the flow is irrotational (except inside a thin viscous boundary layer),$\varepsilon $decays as${z}^{\ensuremath{-} 6} $, where$z$is the distance from the T/NT interface. The mean pressure distribution is calculated using RDT, and exhibits a decrease towards the turbulence region due to the associated velocity fluctuations, consistent with the generation of a mean entrainment velocity. The vorticity variance and$\varepsilon $display large maxima at the T/NT interface due to the inviscid discontinuities of the tangential velocity variances existing there, and these maxima are quantitatively related to the thickness$\delta $of the viscous boundary layer (VBL). For an equilibrium VBL, the RDT analysis suggests that$\delta \ensuremath{\sim} \eta $(where$\eta $is the Kolmogorov microscale), which is consistent with the scaling law identified in a very recent DNS study for shear-free T/NT interfaces.
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El-Sayed, Mohamed Fahmy, and Agaeb Mahal Alanzi. "Electrohydrodynamic Liquid Sheet Instability of Moving Viscoelastic Couple-Stress Dielectric Fluid Surrounded by an Inviscid Gas through Porous Medium." Fluids 7, no. 7 (July 18, 2022): 247. http://dx.doi.org/10.3390/fluids7070247.
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Viscoelastic liquid sheet of couple-stress type streaming with relative motion into an inviscid gas through porous molium is studied theoretically and quantitatively in this project. To derive the differential equations that describe liquids, gases, and the electric field, we linearized the governing equations of motion and continuity, Maxwell’s equations in quasi-static approximation, and the appropriate boundary conditions at the two interfaces. Then we used the normal mode method. It was demonstrated analytically that the solutions to these differential equations can be found for both symmetric and antisymmetric disturbances, respectively. We could not obtain an explicit form of the growth rates since we could not solve the dispersion relations for both situations because they were obtained in highly complex forms. The Mathematica program is used to solve the dimensionless forms of the dispersion relations numerically using Gaster’s theorem. Various influences on the stability analysis of the considered system have been studied in detail, and it is determined that the system in the presence of a porous material is more unstable than it would be otherwise. In a two-dimensional system, the antisymmetric disturbance case is found to be more unstable than the corresponding symmetric disturbance situation. Some characteristics, such as Wabe number, Ohnesorge number, and electric field, have destabilizing effects, whereas others, such as porosity, medium permeability, viscoelasticity parameter, gas-to-liquid viscosity ratio, and dielachic constants, have stabilizing effects. Finally, it is discovered that the gas-to-liquid velocity ratio plays a dual role in the stability condition depending on whether the gas-to-liquid velocity ratio U ≶ 1. In the past, we have only found evidence of very few previous studies.
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Käser, Martin, and Michael Dumbser. "A highly accurate discontinuous Galerkin method for complex interfaces between solids and moving fluids." GEOPHYSICS 73, no. 3 (May 2008): T23—T35. http://dx.doi.org/10.1190/1.2870081.
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We have extended a new highly accurate numerical scheme for unstructured 2D and 3D meshes based on the discontinuous Galerkin approach to simulate seismic wave propagation in heterogeneous media containing fluid-solid interfaces. Because of the formulation of the wave equations as a unified first-order hyperbolic system in velocity stress, the fluid can be in movement along the interface. The governing equations within the moving fluid are derived from well-known first principles in fluid mechanics. The discontinuous Galerkin approach allows for jumps of the material parameters and the solution across element interfaces, which are handled by Riemann solvers or numerical fluxes. The use of Riemann solvers at the element interfaces makesthe treatment of the fluid particularly simple bysetting the shearmodulus in the fluid region to zero. No additional compatibility relations, such as vanishing shear stress or continuity of normal stresses, are necessary to couple the solid and fluid along an interface. The Riemann solver automatically recognizes the jump of the material coefficients at the interface and provides the correct numerical fluxes for fluid-solid contacts. Therefore, wave propagation in the entire computational domain containing heterogeneous media, namely moving fluids and elastic solids, can be described by a uniform set of acoustic and elastic wave equations. The accuracy of the proposed scheme is confirmed by comparing numerical results against analytic solutions. The potential of the new method was demonstrated in a 3D model problem typical for marine seismic exploration with a fluid-solid interface determined by a complicated bathymetry.
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Wang, Yujuan, Shudong Wang, Shengtian Yang, Yuling Zhao, Mingcheng Wang, and Banghui Yang. "Application of FY-2 precipitation data in meteorological drought monitoring of the Weihe river basin." World Journal of Engineering 11, no. 5 (November 1, 2014): 487–94. http://dx.doi.org/10.1260/1708-5284.11.5.487.
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The remote sensing data have become the irreplaceable source of data for the regions with little or without rainfall data, but these data also require scientific analysis, correction and application. This paper uses FY-2 rainfall data and the case studies of the droughts occurred in the Weihe River Basin from 2006 to 2009 to monitor the spatial and temporal evolution of climatic droughts. The monitoring results indicate that: (1) Except for 2008 which was a dry year, the other years in the Weihe River Basin had normal dry/wet conditions; (2) From October 2008 to January 2009, the rainfall was significantly reduced across the Weihe River Basin, and the continual rainfall was even less than 1 mm for December and January with a precipitation anomaly percentage lower than -80%, a sign of severe climatic drought. But the rainfall has improved since February 2009, when the precipitation reached 17.8 mm and Pa exceeded 100%, which helped to relieve the stress from drought resistance. A heavy precipitation continued for four months from June to September 2008, with the Pa exceeding 50%; (3) Due to the better temporal and spatial continuity than the ground-based meteorological observation, FY-2 precipitation data have good application prospects in the meteorological drought monitoring at a national or regional macro-scale.
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Malakooti, S., N. Mohammadi, M. J. Mahjoob, and K. Mohammadi. "Identification of Adhesive Bond in A Multi-Layered Structure Via Sound Insulation Characterestics." Journal of Mechanics 26, no. 3 (September 2010): 363–72. http://dx.doi.org/10.1017/s1727719100003920.
Full textAbstract:
AbstractIn this paper, adhesive bonds in multi-layered plates are identified based on experimental values of their sound insulation characteristics. An exact model based on two-dimensional elasticity theory is formulated. The problem is a time harmonic plane acoustic progressive wave interaction with an isotropic multi-layered infinite elastic plate with interlaminar bonding imperfections. The T-matrix solution technique, which involves a system global transfer matrix, is formed as the product of individual transfer matrices. This is accomplished by applying continuity of the displacement and stress components at the interfaces of neighboring layers along with the relevant boundary conditions at the left and right interfaces of the plate with the surrounding acoustic fluid (air). The resulting equations are then solved for the unknown plane wave reflection and transmission coefficients. The experimental values of sound transmission loss (TL) are measured by a modified B&K impedance tube. Results are presented for a double-layered (lead-steel) plate while the layers are bonded together with metal glue. The normal and transverse adhesive spring constants of the metal glue are then identified in an inverse manner. The agreement of experiments with the analytical TL values predicted for a new triple-layered plate (based on the identified bond properties) confirms the validity of the method.