The Experts below are selected from a list of 690 Experts worldwide ranked by ideXlab platform
W. J. Drugan - One of the best experts on this subject based on the ideXlab platform.
-
Asymptotic analysis of growing Crack stress/deformation fields in porous ductile metals and implications for stable Crack growth
International Journal of Fracture, 1995Co-Authors: Y. Miao, W. J. DruganAbstract:Asymptotic stress and deformation fields near a quasi-statically growing plane strain tensile Crack tip in porous elastic-ideally plastic material, characterized by the Gurson-Tvergaard yield condition and associated flow rule, are derived for small uniform porosity levels throughout the range 0 to 4.54 percent. The solution configuration resembles that for Crack growth in fully dense, elastically compressible, elastic-ideally plastic Huber-Mises material for this porosity range, except that the angular extents and border locations of near-tip solution sectors vary with porosity level, as do the stress and deformation fields within sectors. Increasing porosity is found to result in a dramatic reduction in maximum hydrostatic stress level, greater than that for a stationary Crack; it also causes a significant angular redistribution of stresses, particularly for a range of angles ahead of the Crack and adjacent to the Crack Flank. The near-tip deformation fields derived are employed to generalize a previously-developed, successful ductile Crack growth criterion. Our model predicts that for materials having the same initial slopes of their Crack growth resistance curves, but different levels of uniform porosity, higher porosity results in a substantially greater propensity for stable Crack growth.
-
asymptotic analysis of growing Crack stress deformation fields in porous ductile metals and implications for stable Crack growth
International Journal of Fracture, 1995Co-Authors: Y. Miao, W. J. DruganAbstract:Asymptotic stress and deformation fields near a quasi-statically growing plane strain tensile Crack tip in porous elastic-ideally plastic material, characterized by the Gurson-Tvergaard yield condition and associated flow rule, are derived for small uniform porosity levels throughout the range 0 to 4.54 percent. The solution configuration resembles that for Crack growth in fully dense, elastically compressible, elastic-ideally plastic Huber-Mises material for this porosity range, except that the angular extents and border locations of near-tip solution sectors vary with porosity level, as do the stress and deformation fields within sectors. Increasing porosity is found to result in a dramatic reduction in maximum hydrostatic stress level, greater than that for a stationary Crack; it also causes a significant angular redistribution of stresses, particularly for a range of angles ahead of the Crack and adjacent to the Crack Flank. The near-tip deformation fields derived are employed to generalize a previously-developed, successful ductile Crack growth criterion. Our model predicts that for materials having the same initial slopes of their Crack growth resistance curves, but different levels of uniform porosity, higher porosity results in a substantially greater propensity for stable Crack growth.
-
Influence of Porosity on Plane Strain Tensile Crack-Tip Stress Fields in Elastic-Plastic Materials: Part II
Journal of Applied Mechanics, 1993Co-Authors: Y. Miao, W. J. DruganAbstract:This paper continues the investigation of Drugan and Miao (1992). There we studied analytically the influence of a uniform porosity distribution on the stress field near a plane strain tensile Crack tip in ductile (elastic-ideally plastic) material, assuming that material very near the tip is at yield at all angles about the tip. Our solutions exhibited completely continuous stress fields for porosity f ≤ 0.02979, but for higher porosities they involved radial surfaces of radial normal stress jumps. Here we investigate whether, for this higher range of porosity, relaxing our assumption of yield at all angles about the tip will facilitate solutions exhibiting fully continuous stress fields. The answer to this is shown to be yes, with a single near-tip sector assembly providing such solutions for this entire higher porosity range. On either side of the Crack symmetry plane, this solution configuration consists of a leading plastic sector possessing radial stress characteristics (“generalized centered fan ”), followed by a plastic sector of constant Cartesian components of stress, followed finally by a sector of purely elastic material adjacent to the Crack Flank. The angular extents of these sectors vary substantially with porosity level. In regions of purely elastic response, we have accounted for the influence of porosity on the overall, or effective, elastic moduli. Among the interesting features of these new solutions are a significantly enlarged generalized centered fan sector as compared to that of the fully plastic Part I solutions for the same f values, and for f values just slightly above the 0.02979 level, a narrow elastic sector exists in which stresses vary so rapidly with angle that they appear to be nearly discontinuous. This rapid variation spreads out as the elastic sector enlarges with increasing f, and, in contrast to the fully plastic solutions, the radial normal component of stress becomes negative near the Crack Flank.
Y. Miao - One of the best experts on this subject based on the ideXlab platform.
-
Asymptotic analysis of growing Crack stress/deformation fields in porous ductile metals and implications for stable Crack growth
International Journal of Fracture, 1995Co-Authors: Y. Miao, W. J. DruganAbstract:Asymptotic stress and deformation fields near a quasi-statically growing plane strain tensile Crack tip in porous elastic-ideally plastic material, characterized by the Gurson-Tvergaard yield condition and associated flow rule, are derived for small uniform porosity levels throughout the range 0 to 4.54 percent. The solution configuration resembles that for Crack growth in fully dense, elastically compressible, elastic-ideally plastic Huber-Mises material for this porosity range, except that the angular extents and border locations of near-tip solution sectors vary with porosity level, as do the stress and deformation fields within sectors. Increasing porosity is found to result in a dramatic reduction in maximum hydrostatic stress level, greater than that for a stationary Crack; it also causes a significant angular redistribution of stresses, particularly for a range of angles ahead of the Crack and adjacent to the Crack Flank. The near-tip deformation fields derived are employed to generalize a previously-developed, successful ductile Crack growth criterion. Our model predicts that for materials having the same initial slopes of their Crack growth resistance curves, but different levels of uniform porosity, higher porosity results in a substantially greater propensity for stable Crack growth.
-
asymptotic analysis of growing Crack stress deformation fields in porous ductile metals and implications for stable Crack growth
International Journal of Fracture, 1995Co-Authors: Y. Miao, W. J. DruganAbstract:Asymptotic stress and deformation fields near a quasi-statically growing plane strain tensile Crack tip in porous elastic-ideally plastic material, characterized by the Gurson-Tvergaard yield condition and associated flow rule, are derived for small uniform porosity levels throughout the range 0 to 4.54 percent. The solution configuration resembles that for Crack growth in fully dense, elastically compressible, elastic-ideally plastic Huber-Mises material for this porosity range, except that the angular extents and border locations of near-tip solution sectors vary with porosity level, as do the stress and deformation fields within sectors. Increasing porosity is found to result in a dramatic reduction in maximum hydrostatic stress level, greater than that for a stationary Crack; it also causes a significant angular redistribution of stresses, particularly for a range of angles ahead of the Crack and adjacent to the Crack Flank. The near-tip deformation fields derived are employed to generalize a previously-developed, successful ductile Crack growth criterion. Our model predicts that for materials having the same initial slopes of their Crack growth resistance curves, but different levels of uniform porosity, higher porosity results in a substantially greater propensity for stable Crack growth.
-
Influence of Porosity on Plane Strain Tensile Crack-Tip Stress Fields in Elastic-Plastic Materials: Part II
Journal of Applied Mechanics, 1993Co-Authors: Y. Miao, W. J. DruganAbstract:This paper continues the investigation of Drugan and Miao (1992). There we studied analytically the influence of a uniform porosity distribution on the stress field near a plane strain tensile Crack tip in ductile (elastic-ideally plastic) material, assuming that material very near the tip is at yield at all angles about the tip. Our solutions exhibited completely continuous stress fields for porosity f ≤ 0.02979, but for higher porosities they involved radial surfaces of radial normal stress jumps. Here we investigate whether, for this higher range of porosity, relaxing our assumption of yield at all angles about the tip will facilitate solutions exhibiting fully continuous stress fields. The answer to this is shown to be yes, with a single near-tip sector assembly providing such solutions for this entire higher porosity range. On either side of the Crack symmetry plane, this solution configuration consists of a leading plastic sector possessing radial stress characteristics (“generalized centered fan ”), followed by a plastic sector of constant Cartesian components of stress, followed finally by a sector of purely elastic material adjacent to the Crack Flank. The angular extents of these sectors vary substantially with porosity level. In regions of purely elastic response, we have accounted for the influence of porosity on the overall, or effective, elastic moduli. Among the interesting features of these new solutions are a significantly enlarged generalized centered fan sector as compared to that of the fully plastic Part I solutions for the same f values, and for f values just slightly above the 0.02979 level, a narrow elastic sector exists in which stresses vary so rapidly with angle that they appear to be nearly discontinuous. This rapid variation spreads out as the elastic sector enlarges with increasing f, and, in contrast to the fully plastic solutions, the radial normal component of stress becomes negative near the Crack Flank.
Y J Chao - One of the best experts on this subject based on the ideXlab platform.
-
constraint effects on Crack tip fields in elastic perfectly plastic materials
Journal of The Mechanics and Physics of Solids, 2001Co-Authors: X K Zhu, Y J ChaoAbstract:Abstract Asymptotic Crack-tip stress fields accounting for constraint effects are developed for a stationary plane strain Crack under mode-I, mode-II or mixed-mode I/II loading. The mixed-mode loading is considered only within small-scale yielding. Materials are taken into account in incompressible, elastic-perfectly plastic materials, and plastic deformation of materials obeys von Mises yield criterion. This investigation is an extension of the solution obtained by Li and Hancock [Li, J., Hancock, J.W., 1999. Mode I and mixed mode fields with incomplete Crack tip plasticity. International Journal of Solids and Structures 36 (5), 711–725] with special attention on what constraint parameters existed in the elastic-plastic Crack-tip fields. Results indicate that the asymptotic Crack-tip field is a 4-sector solution for mode-I Cracks and a 6-sector solution for mixed-mode Cracks, and is comprised of plastic sectors and elastic sector(s), and contain two undetermined parameters Tp and Tπ which are hydrostatic stresses ahead of the Crack tip and on the Crack Flank, respectively. When Tp and Tπ vanish, the present elastic-plastic Crack-tip field reduces to the fully plastic Prandtl slip-line field. Comparison shows that the asymptotic Crack-tip stress fields can precisely match with elastic-plastic finite element results over all angles around a Crack tip for various fracture specimens with constraint levels from high to low. The magnitudes of Tp and Tπ determine the level of Crack-tip constraint in plastic sectors and in elastic sector, respectively, due to geometric and loading configurations or mode mixity. Thus the parameters Tp and Tπ can be used as constraint parameters to effectively characterize the entire Crack-tip field in elastic-perfectly plastic materials under the plane strain conditions.
Xiaomin Deng - One of the best experts on this subject based on the ideXlab platform.
-
Plane strain near-tip fields for elastic-plastic interface Cracks
International Journal of Solids and Structures, 1995Co-Authors: Xiaomin DengAbstract:Abstract The plane strain problem of a stationary interface Crack between two dissimilar ductile solids is studied asymptotically, where the ductile solids are assumed to be incompressible, elastic perfectly plastic, and obey the J 2 -flow theory of plasticity. Candidate asymptotic Crack-tip assemblies of plastic and elastic sectors are proposed, and all associated admissible near-tip fields are presented. It is found that when the Crack tip is fully surrounded by plastic sectors, then only isolated, mode 1 type solutions exist. When an elastic sector appears along the Crack Flank in one solid and all other sectors in the two solids are plastic, a two-parameter family of solutions exists, which produces Crack-tip stress variations similar to those of the mixed-mode as well as mode I slip-line fields for homogeneous ductile materials. When each of the two solids contains an elastic sector along the Crack Flank, the Crack-tip solutions are found to belong to a four-parameter family, which also resembles mixed-mode and mode I solutions for homogeneous solids. For completeness, the special case of ductile/rigid interfaces is also studied, and several one-parameter families of Crack-tip solutions are obtained, which are complementary to those already published in the literature.
-
A finite element investigation of quasi-static and dynamic asymptotic Crack-tip fields in hardening elastic-plastic solids under plane stress
International Journal of Fracture, 1992Co-Authors: Xiaomin Deng, Ares J. RosakisAbstract:The asymptotic structures of Crack-tip stress and deformation fields are investigated numerically for quasi-static and dynamic Crack growth in isotropic linear hardening elastic-plastic solids under mode I, plane stress, and small-scale yielding conditions. An Eulerian type finite element scheme is employed. The materials are assumed to obey the von Mises yield criterion and the associated flow rule. The ratio of the Crack-tip plastic zone size to that of the element nearest to the Crack tip is of the order of 1.6 × 10^4. The results of this study strongly suggest the existence of Crack-tip stress and strain singularities of the type r ^s ( s < 0) at r =0, where r is the distance to the Crack tip, which confirms the asymptotic solutions of variable-separable type by Amazigo and Hutchinson [1] and Ponte Castañeda [2] for quasi-static Crack growth, and by Achenbach, Kanninen and Popelar [3] for dynamic Crack propagation. Both the values of the parameter s and the angular stress and velocity field variations from the present full-field finite element analysis agree very well with those from the analytical solutions. It is found that the dominance zone of the r ^s-singularity is quite large compared to the size of the Crack-tip active plastic zone. The effects of hardening and inertia on the Crack-tip fields as well as on the shape and size of the Crack-tip active plastic zone are also studied in detail. It is discovered that as the level of hardening decreases and the Crack propagation speed increases, a secondary yield zone emerges along the Crack Flank, and kinks in stress and velocity angular variations begin to develop. This dynamic phenomenon observable only for rapid Crack growth and for low hardening materials may explain the numerical difficulties, in obtaining solutions for such cases, encountered by Achenbach et al. who, in their asymptotic analysis, neglected the existence of reverse yielding zones along the Crack surfaces.
W. Brocks - One of the best experts on this subject based on the ideXlab platform.
-
Notes on plastic reloading zone in the asymptotic analysis of elastic-plastic Crack extension
Archive of Applied Mechanics, 1991Co-Authors: H. Yuan, W. BrocksAbstract:The asymptotic structures of near-tip stress and deformation fields are studied for steady-state Crack extension in elastic-plastic solids. The condition for the existence of a plastic reloading zone is formulated. If a plastic reloading zone is to exist in hardening materials, the effective stress must become unbounded as the Crack Flank is approached. It is shown explicitly in the case of mode III that solutions with logarithmic singularity produce negative plastic dissipation in the plastic reloading sector.
-
Notes on plastic reloading zone in the asymptotic analysis of elastic-plastic Crack extension
Archive of Applied Mechanics, 1991Co-Authors: H. Yuan, W. BrocksAbstract:The asymptotic structures of near-tip stress and deformation fields are studied for steady-state Crack extension in elastic-plastic solids. The condition for the existence of a plastic reloading zone is formulated. If a plastic reloading zone is to exist in hardening materials, the effective stress must become unbounded as the Crack Flank is approached. It is shown explicitly in the case of mode III that solutions with logarithmic singularity produce negative plastic dissipation in the plastic reloading sector. Untersucht wird die asymptotische Form von rißspitzennahen Spannungs- und Verformungsfeldern bei der stationären Rißausbreitung in elastisch-plastischen Körpern. Die Bedingung für die Existenz einer rückplastizierten Zone wird formuliert. Wenn eine solche Zone bei verfestigendem Material vorhanden sein soll, muß die Vergleichsspannung bei Annäherung an die RißFlanke unendlich werden. Es wird gezeigt, daß bei Mode III die Lösungen mit logarithmischer Singularität negative Dissipation in der rückplastizierten Zone bedeuten würden.
