The Experts below are selected from a list of 6399 Experts worldwide ranked by ideXlab platform
W.j. Feng - One of the best experts on this subject based on the ideXlab platform.
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Transient thermal fracture analysis of a penny-shaped magnetic and dielectric Crack in a magnetoelectroelastic cylinder
Journal of Thermal Stresses, 2016Co-Authors: L. L. Liu, W.j. Feng, J. X. LiuAbstract:ABSTRACTThe problem of penny-shaped magnetic and dielectric Crack in a magnetoelectroelastic cylinder is investigated under thermal shock load. The problem is reduced to solve three coupled Fredholm integral equations. The field intensity factors are derived. Numerical results of Crack opening displacement intensity factors are presented, and the effects of thermal shock time, Crack Configuration, and magnetoelectrical Crack surface conditions on Crack propagation and growth are evaluated. Among others, the larger cylinder's radius, the easier to propagate the Crack is. For a fixed Crack Configuration, magnetoelectrical Crack surface conditions have different effects on Crack propagation as well.
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Transient response of interface Cracks between dissimilar magneto-electro-elastic strips under out-of-plane mechanical and in-plane magneto-electrical impact loads
Composite Structures, 2007Co-Authors: W.j. Feng, J. LiuAbstract:Using the integral transform and the Cauchy singular integral equation methods, the problem of interface Cracks between dissimilar magneto-electro-elastic strips under out-of-plane mechanical and in-plane magneto-electrical impacts is investigated. The magneto-electric permeable boundary condition on the Crack surfaces is adopted. The number of the interface Cracks is arbitrary. The field intensity factors and energy release rates are derived and discussed. The effects of the Crack Configuration and the main constitutive parameters of the magneto-electro-elastic materials on the dynamic response are examined. Results show that the dynamic energy release rates (DERRs) as the Crack extension force are quite equivalent to the dynamic stress intensity factors (DSIFs) for magneto-electric permeable interface Cracks. The DERRs may be retarded or accelerated by specifying different combinations of material parameters. In addition, the parameters of the Crack Configuration, including the ratio of the strip width to the Crack length, the ratio of the widths for different strips, and the distances between two Cracks, exert a considerable influence on the DERRs. The results seem useful for design of the magneto-electro-elastic composite structures and devices of high performance.
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Dynamic internal Crack problem of a functionally graded magneto-electro-elastic strip
International Journal of Solids and Structures, 2006Co-Authors: W.j. FengAbstract:In this paper the dynamic anti-plane problem for a functionally graded magneto-electro-elastic strip containing an internal Crack perpendicular to the boundary is investigated. The Crack is assumed to be either magneto-electrically impermeable or permeable. Integral transforms and dislocation density functions are employed to reduce the problem to Cauchy singular integral equations. Numerical results show the effects of loading combination parameter, material gradient parameter and Crack Configuration on the dynamic response. With the magneto-electrically permeable assumption, both the magnetical and electrical impacts have no contribution to the Crack tip field singularity. However, with the impermeable assumption, both the applied magnetical loads and electrical loads play a dominant role in the dynamic fracture behavior of Crack tips. And for the two kinds of Crack surface conditions, increasing the graded index can all retard the Crack extension.
Xi-qiao Feng - One of the best experts on this subject based on the ideXlab platform.
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Transient response of an insulating Crack between dissimilar piezoelectric layers under mechanical and electrical impacts
Archive of Applied Mechanics (Ingenieur Archiv), 2002Co-Authors: Xi-qiao FengAbstract:The dynamic response of an interface Crack between two dissimilar piezoelectric layers subjected to mechanical and electrical impacts is investigated under the boundary condition of electrical insulation on the Crack surface by using the integral transform and the Cauchy singular integral equation methods. The dynamic stress intensity factors, the dynamic electrical displacement intensity factor, and the dynamic energy release rate (DERR) are determined. The numerical calculation of the mode-I plane problem indicates that the DERR is more liable to be the token of the Crack growth when an electrical load is applied. The dynamic response shows a significant dependence on the loading mode, the material combination parameters as well as the Crack Configuration. Under a given loading mode and a specified Crack Configuration, the DERR of an interface Crack between piezoelectric media may be decreased or increased by adjusting the material combination parameters. It is also found that the intrinsic mechanical-electrical coupling plays a more significant role in the dynamic fracture response of in-plane problems than that in anti-plane problems.
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Transient response of an interface Crack between dissimilar piezoelectric layers under mechanical impacts
International Journal of Solids and Structures, 2002Co-Authors: Xi-qiao FengAbstract:Using the integral transform and the Cauchy singular integral equation methods, the problem of an interface Crack between two dissimilar piezoelectric layers under mechanical impacts is investigated under the permeable electrical boundary condition on the Crack surface. The dynamic stress intensity factors (DSIFs) of both mode-I and II are determined. The effects of the Crack Configuration and the combinations of the constitutive parameters of the piezoelectric materials on the dynamic response are examined. The numerical calculation of the mode-I plane problem indicates that the DSIFs may be retarded or accelerated by specifying different combinations of material parameters. In addition, the parameters of the Crack Configuration, including the ratio of the Crack length to the layer width and the ratio between the widths of two layers, exert a considerable influence on the DSIFs. The results seem useful for design of the piezoelectric structures and devices of high performance.
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Elastic Wave Scattering by an Interface Crack Between a Piezoelectric Layer and an Elastic Substrate
Solid Mechanics and Its Applications, 1Co-Authors: Xi-qiao FengAbstract:The scattering problem of a plane elastic wave by an interface Crack between a piezoelectric layer and an elastic substrate is analyzed by means of the integral transform and the Cauchy singular integral equation methods. The effects of the Crack Configuration, the incident direction of the wave and the material combinations are examined.
N.k. Anifantis - One of the best experts on this subject based on the ideXlab platform.
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Performance of quarter-point boundary elements in analysing thermally stressed kinked and curved Cracks
Computer Methods in Applied Mechanics and Engineering, 1996Co-Authors: D.e. Katsareas, N.k. AnifantisAbstract:Abstract The performance of quarter-point and traction-singular quarter-point boundary elements, dealing with kinked and curved thermal Cracks, is investigated. These special Crack-tip elements simulate correctly the r 1 2 and r −1 2 near-tip behavior of temperature/displacement and heat flux/thermal stress fields, respectively. The well-known displacement and traction-based formulas are generalized for any Crack Configuration and used for the evaluation of heat flux and mixed-mode thermal stress intensity factors. The two-dimensional stationary thermoelasticity problem is solved via the boundary-only element method, through which volume discretization is completely eliminated. It is demonstrated by the conducted numerical experiments that present results converge to the exact ones, obtained from the literature, when the Crack-tip element size tends to zero. The accuracy of the proposed method is maintained at high levels for all Crack Configurations considered, without the need for a dense mesh. This conclusion stands even for Cracks nearly zero in size, thus rendering the method a potent tool for thermal Crack initiation and extension analysis.
Peter Wriggers - One of the best experts on this subject based on the ideXlab platform.
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3D ductile Crack propagation within a polycrystalline microstructure using XFEM
Computational Mechanics, 2018Co-Authors: Steffen Beese, Stefan Loehnert, Peter WriggersAbstract:In this contribution we present a gradient enhanced damage based method to simulate discrete Crack propagation in 3D polycrystalline microstructures. Discrete Cracks are represented using the eXtended finite element method. The Crack propagation criterion and the Crack propagation direction for each point along the Crack front line is based on the gradient enhanced damage variable. This approach requires the solution of a coupled problem for the balance of momentum and the additional global equation for the gradient enhanced damage field. To capture the discontinuity of the displacements as well as the gradient enhanced damage along the discrete Crack, both fields are enriched using the XFEM in combination with level sets. Knowing the Crack front velocity, level set methods are used to compute the updated Crack geometry after each Crack propagation step. The applied material model is a crystal plasticity model often used for polycrystalline microstructures of metals in combination with the gradient enhanced damage model. Due to the inelastic material behaviour after each discrete Crack propagation step a projection of the internal variables from the old to the new Crack Configuration is required. Since for arbitrary Crack geometries ill-conditioning of the equation system may occur due to (near) linear dependencies between standard and enriched degrees of freedom, an XFEM stabilisation technique based on a singular value decomposition of the element stiffness matrix is proposed. The performance of the presented methodology to capture Crack propagation in polycrystalline microstructures is demonstrated with a number of numerical examples.
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3D ductile Crack propagation within a polycrystalline microstructure using XFEM
Computational Mechanics, 2018Co-Authors: Steffen Beese, Stefan Loehnert, Peter WriggersAbstract:In this contribution we present a gradient enhanced damage based method to simulate discrete Crack propagation in 3D polycrystalline microstructures. Discrete Cracks are represented using the eXtended finite element method. The Crack propagation criterion and the Crack propagation direction for each point along the Crack front line is based on the gradient enhanced damage variable. This approach requires the solution of a coupled problem for the balance of momentum and the additional global equation for the gradient enhanced damage field. To capture the discontinuity of the displacements as well as the gradient enhanced damage along the discrete Crack, both fields are enriched using the XFEM in combination with level sets. Knowing the Crack front velocity, level set methods are used to compute the updated Crack geometry after each Crack propagation step. The applied material model is a crystal plasticity model often used for polycrystalline microstructures of metals in combination with the gradient enhanced damage model. Due to the inelastic material behaviour after each discrete Crack propagation step a projection of the internal variables from the old to the new Crack Configuration is required. Since for arbitrary Crack geometries ill-conditioning of the equation system may occur due to (near) linear dependencies between standard and enriched degrees of freedom, an XFEM stabilisation technique based on a singular value decomposition of the element stiffness matrix is proposed. The performance of the presented methodology to capture Crack propagation in polycrystalline microstructures is demonstrated with a number of numerical examples.
Baolin Wang - One of the best experts on this subject based on the ideXlab platform.
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Near-Tip Fields for Penny-Shaped Cracks in Magnetoelectroelastic Media
Key Engineering Materials, 2006Co-Authors: Baolin Wang, Yiu-wing MaiAbstract:This paper solves the penny-shaped Crack Configuration in transversely isotropic solids with coupled magneto-electro-elastic properties. The Crack plane is coincident with the plane of symmetry such that the resulting elastic, electric and magnetic fields are axially symmetric. The mechanical, electrical and magnetical loads are considered separately. Closed-form expressions for the stresses, electric displacements, and magnetic inductions near the Crack frontier are given.
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A penny-shaped Crack in a transversely isotropic piezoelectric layer
European Journal of Mechanics - A Solids, 2001Co-Authors: Baolin Wang, Naotake Noda, Jiecai HanAbstract:In this paper, we develop a model to treat penny-shaped Crack Configuration in a piezoelectric layer of finite thickness. The piezoelectric layer is subjected to axially symmetric mechanical and electrical loads. Hankel transform technique is used to reduce the problem to the solution of a system of integral equations. A numerical solution for the Crack tip fields is obtained for different Crack radius and Crack position.
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Fracture mechanics for multilayers with penny-shaped Cracks subjected to dynamic torsional loading
International Journal of Engineering Science, 2000Co-Authors: Baolin Wang, Jingyong HanAbstract:This paper provides a method for investigating the penny-shaped interface Crack Configuration in orthotropic multilayers under dynamic torsional loading. The multilayer is said to have finite height along the direction normal to the interfaces. By utilizing Laplace transform and Hankel transform technique, the general solution for each layer is derived. The Dual integral equations of the entire elastic region are then obtained through introducing the mechanical boundary and layer interface conditions. The stress intensity factors (SIFs) are computed by solving Dual integral equations numerically in Laplace transform domain. The solution in time domain is obtained by utilizing numerical Laplace inverse. Numerical example shows that the main advantage of the present model is its ability for treating multiple Crack Configurations in multilayers and the number of layers can be sufficiently large. The present model can also treat Crack problems for functionally graded materials (FGMs) with arbitrarily distributed and continuously varied material properties by subdividing the FGM into a number of thinner layers such that the elastic properties are constants within each individual layer, but they vary from layer to layer.
