The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
J. H. Chang - One of the best experts on this subject based on the ideXlab platform.
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CALCULATION OF NEAR-TIP NON-SINGULAR STRESSES UNDER MIXED-MODE Crack Surface TRACTIONS
International Journal of Fracture, 2013Co-Authors: J. H. Chang, J. W. JengAbstract:When the Crack Surfaces are subjected to nonuniform mixed-mode Surface tractions, there exist at the tip additional constant stress components other than the T-stress and the influence from the higher order non-singular stress terms may become more significant. In this work, an effective numerical approach is proposed to calculate the corresponding non-singular stresses. By introducing the concept of mixed-mode auxiliary stress fields, a de-singularized loading system is established for the calculation. The proposed scheme is applicable for 2-D problems subjected to arbitrarily distributed nonuniform Crack Surface tractions.
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Using M-integral for multi-Cracked problems subjected to nonconservative and nonuniform Crack Surface tractions
International Journal of Solids and Structures, 2011Co-Authors: J. H. ChangAbstract:Abstract In this paper, an energy parameter based on the concept of the M -integral is proposed for describing the fracture behavior of a multi-Cracked solid subjected to nonconservative and nonuniform Crack Surface tractions. By using the M -integral with a suitably chosen closed contour, one can evaluate the ‘Surface creation energy’ (SCE) required for creation of the stressed Cracks. Also, it is demonstrated that the property of path-independence holds even under the action of Crack Surface tractions. Therefore, the singular stress field in the near-tip areas is not directly involved in the calculation so that a complicated finite element model around the Crack tips is not required in evaluation of the M -integral.
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FE calculation of contour integrals in plane anisotropic elastic media with Crack Surface tractions
Finite Elements in Analysis and Design, 2001Co-Authors: J. H. ChangAbstract:Abstract The application of the Jk, M, and L integrals is extended for fracture analysis with consideration of Crack Surface tractions. The study is considered to be feasible for problems with generally linearly anisotropic elastic materials. With the presence of Crack Surface tractions in anisotropic fields, the concept of path independence of these contour integrals needs to be modified by additionally including extra domain and line integrals, where the near-tip region is inevitably included in their evaluations. A numerical procedure, based on the finite element solutions, is therefore presented for calculation of these integrals, with special attention addressed to modeling of the portion of integration around the near-tip area, where singular mechanical behavior dominates. No particular singular elements are used in the study.
Frank Dehn - One of the best experts on this subject based on the ideXlab platform.
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Effect of steel fiber on the Crack permeability evolution and Crack Surface topography of concrete subjected to freeze-thaw damage
Cement and Concrete Research, 2020Co-Authors: Wei Zeng, Yining Ding, Yulin Zhang, Frank DehnAbstract:Abstract This paper describes the steel fiber effect on the Crack permeability and Crack Surface topography of concrete subjected to freeze-thaw damage. The sequential Crack permeability of steel fiber reinforced concrete are investigated by a vacuum permeability set-up. The topographical analysis is applied on the Crack Surface by an invented 3-D laser scanning equipment. The results show that the Crack permeability of concrete is less than the value predicted by the Poiseuille flow model and their difference decreases gradually with the Crack widening. With increment of steel fiber dosage and freeze-thaw damage level, the effect of steel fiber on reducing the Crack permeability becomes strong. Topographical analysis illustrates that both steel fiber and freeze-thaw damage enhance the roughness of concrete Crack Surface. The relationship between roughness number of Crack Surface and material permeability parameter α follows an exponential function, which can be employed to quickly estimate the Crack permeability of concrete.
G. S. Wang - One of the best experts on this subject based on the ideXlab platform.
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A generalised solution for the Crack Surface displacement of mode I two-dimensional part-elliptical Crack
International Journal of Fracture, 1993Co-Authors: G. S. WangAbstract:A generalised approximate Crack Surface displacement solution for the two-dimensional part-elliptical mode I Crack was developed. This solution includes the Surface Crack, corner Crack and embedded Crack, which is subjected to the arbitrary Crack Surface pressure. The Crack Surface displacement is derived from stress intensity factor solution and corresponding Crack Surface pressure distribution. Comparisons of the solution with accurate solutions showed that rather high accuracy has been achieved with the developed solution for various Surface, embedded and corner Crack problems. This solution can be used to derive three-dimensional weight functions as long as the stress intensity factor and the corresponding Crack Surface pressure are available for arbitrary mode I problems.
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Weight functions and stress intensity factors for mode I Cracks in arbitrary 2D geometries under general Crack Surface loading
Engineering Fracture Mechanics, 1993Co-Authors: G. S. Wang, A.f. BlomAbstract:Abstract Stress intensity factors for Mode I Cracks in arbitrary two-dimensional geometries under general Crack Surface loading are derived in closed form by boundary element calculations and approximate weight functions. The boundary element method was developed previously to deal with arbitrary two-dimensional Crack problems involving uniform Crack Surface pressure. Reference stress intensity factors calculated by the boundary element method are used to derive stress intensity factors for the same Crack under arbitrary Crack Surface loading with weight functions based on an improved Petroski-Achenbach Crack Surface displacement approximation. Various Crack problems are studied and limitations of the method are discussed. The investigation shows that a self-consistency examination will effectively reveal the accuracy of the derived weight functions and the associated stress intensity factors.
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A solution for SIFs of part-elliptical Cracks based on approximate Crack Surface displacement and energy method
International Journal of Fracture, 1992Co-Authors: G. S. WangAbstract:A procedure has been developed to derive stress intensity factors (SIFs) for part-elliptical Cracks based on an approximate Crack Surface displacement mode assumption for general configurations. The Crack Surface displacement mode is composed of available 2D Crack Surface displacement modes at intersections of the Crack Surface and boundaries, or in symmetry planes. Along with the obtained Crack Surface displacement mode, SIFs are determined by the magnitude of the Crack Surface displacement derived from energy release rate for virtual Crack increments. The procedure was analytically verified with the exact solution for an embedded Crack in an infinite body subjected to uniform Crack Surface pressure. Several examples show the obtained results in acceptable agreements with available solutions.
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SIFs of part-through mode I Cracks for uniform Crack Surface pressure
Engineering Fracture Mechanics, 1992Co-Authors: G. S. WangAbstract:Abstract A procedure has been developed to derive the stress intensity factors (SIFs) for part-elliptical Cracks subjected to uniform Crack Surface pressure based on an approximate Crack Surface displacement mode assumption. The Crack Surface displacement mode is composed of 2D Crack Surface displacement modes at intersections of the Crack Surface and boundaries, or at symmetry planes, which are determined by a line-spring method. Along with the obtained Crack Surface displacement, SIFs can be determined by the magnitude of the Crack Surface displacement derived from the energy release relations for virtual Crack growths. The procedure was verified with the exact SIF result for an embedded Crack in an infinite body subjected to uniform Crack Surface pressure. Examples show that the obtained results are in good agreement with available solutions.
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Crack Surface displacements for mode i one dimensional Cracks in general two dimensional geometry
Engineering Fracture Mechanics, 1991Co-Authors: G. S. WangAbstract:Abstract A Crack Surface displacement solution for Mode I one-dimensional Cracks under arbitrary Crack Surface loads in general two-dimensional geometry is presented. The solution is based on the stress intensity factors computed with the boundary element method [G. S. Wang and A. F. Blom, FFA TN 1990-10, Aeronautical Research Institute of Sweden (1990)], and the corresponding approximate weight functions [G. S. Wang and A. F. Blom, FFA TN 1996-17, Aeronautical Research Institute of Sweden (1990)]. Comparisons have been, made between the present solution, exact solutions and acceptable solutions. It has been shown that the present solution gives the Crack Surface displacements with excellent accuracy.
Wei Zeng - One of the best experts on this subject based on the ideXlab platform.
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Effect of steel fiber on the Crack permeability evolution and Crack Surface topography of concrete subjected to freeze-thaw damage
Cement and Concrete Research, 2020Co-Authors: Wei Zeng, Yining Ding, Yulin Zhang, Frank DehnAbstract:Abstract This paper describes the steel fiber effect on the Crack permeability and Crack Surface topography of concrete subjected to freeze-thaw damage. The sequential Crack permeability of steel fiber reinforced concrete are investigated by a vacuum permeability set-up. The topographical analysis is applied on the Crack Surface by an invented 3-D laser scanning equipment. The results show that the Crack permeability of concrete is less than the value predicted by the Poiseuille flow model and their difference decreases gradually with the Crack widening. With increment of steel fiber dosage and freeze-thaw damage level, the effect of steel fiber on reducing the Crack permeability becomes strong. Topographical analysis illustrates that both steel fiber and freeze-thaw damage enhance the roughness of concrete Crack Surface. The relationship between roughness number of Crack Surface and material permeability parameter α follows an exponential function, which can be employed to quickly estimate the Crack permeability of concrete.
Xiangmin Jiao - One of the best experts on this subject based on the ideXlab platform.
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hp generalized fem and Crack Surface representation for non planar 3 d Cracks
International Journal for Numerical Methods in Engineering, 2009Co-Authors: J P Pereira, C A Duarte, Damrong Guoy, Xiangmin JiaoAbstract:A high-order generalized finite element method (GFEM) for non-planar three-dimensional Crack Surfaces is presented. Discontinuous p-hierarchical enrichment functions are applied to strongly graded tetrahedral meshes automatically created around Crack fronts. The GFEM is able to model a Crack arbitrarily located within a finite element (FE) mesh and thus the proposed method allows fully automated fracture analysis using an existing FE discretization without Cracks. We also propose a Crack Surface representation that is independent of the underlying GFEM discretization and controlled only by the physics of the problem. The representation preserves continuity of the Crack Surface while being able to represent non-planar, non-smooth, Crack Surfaces inside of elements of any size. The proposed representation also provides support for the implementation of accurate, robust, and computationally efficient numerical integration of the weak form over elements cut by the Crack Surface. Numerical simulations using the proposed GFEM show high convergence rates of extracted stress intensity factors along non-planar curved Crack fronts and the robustness of the method. Copyright © 2008 John Wiley & Sons, Ltd.
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hp‐Generalized FEM and Crack Surface representation for non‐planar 3‐D Cracks
International Journal for Numerical Methods in Engineering, 2009Co-Authors: J P Pereira, C A Duarte, Damrong Guoy, Xiangmin JiaoAbstract:A high-order generalized finite element method (GFEM) for non-planar three-dimensional Crack Surfaces is presented. Discontinuous p-hierarchical enrichment functions are applied to strongly graded tetrahedral meshes automatically created around Crack fronts. The GFEM is able to model a Crack arbitrarily located within a finite element (FE) mesh and thus the proposed method allows fully automated fracture analysis using an existing FE discretization without Cracks. We also propose a Crack Surface representation that is independent of the underlying GFEM discretization and controlled only by the physics of the problem. The representation preserves continuity of the Crack Surface while being able to represent non-planar, non-smooth, Crack Surfaces inside of elements of any size. The proposed representation also provides support for the implementation of accurate, robust, and computationally efficient numerical integration of the weak form over elements cut by the Crack Surface. Numerical simulations using the proposed GFEM show high convergence rates of extracted stress intensity factors along non-planar curved Crack fronts and the robustness of the method. Copyright © 2008 John Wiley & Sons, Ltd.