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Macroscopic mechanical response of metal polycrystal with mean grain diameter of 0.2 to 5 microns are simulated by a strain gradient crystal plasticity software code which incorporates some phenomenological models for dislocation accumulation and annihilation, as well as dislocation-grain boundary interactions. Obtained results of macroscopic stress-strain relation show significant increase of yield stress and strain hardening ratio for fine grained specimens.

Following Sih's approach to the rectilinearly anisotropic plane strain elasticity, the present work analytically studies the stress field, image force and shielding effect of an edge dislocation in the vicinity of an elliptical hole. The results show that the dislocation source plays a very important role in the interaction. The stress field and the image force are more pronounced for the edge dislocation emitted from the elliptical hole than that for the edge dislocation come elsewhere. Tungsten (W) single crystal is used to simulate an isotropically elastic material, and iron (Fe), copper (Cu) and zinc (Zn) to represent the anisotropic bcc, fee and hcp structures, respectively. The effects of anisotropy are the most pronounced on the stress component sigma(zz) among all stress components. When a dislocation is emitted from the hole and moves far away, the interaction between the dislocation and the hole behaves like that between the real dislocation and an image dislocation located at the center of the hole having the same Burgers vector but with an opposite sign as the real. However, there is no interaction at all between a dislocation and the hole if the dislocation come elsewhere is located far away from the hole. In general, the anisotropy produces an abnormal image force. When the dislocation is located on the x-axis and has a Burgers vector parallel to the x-axis, an abnormal image force is induced along the y-axis, while an abnormal image force is induced along the x-axis when the dislocation is located on the y-axis and has a Burgers vector parallel to the y-axis. The solution of an edge dislocation interacting with an elliptical hole in an infinite isotropic, elastic body is provided in an Appendix. (C) 1999 Elsevier Science Ltd. All rights reserved.

Following Sih's approach to the rectilinearly anisotropic plane strain elasticity, the present work analytically studies the stress field, image force and shielding effect of an edge dislocation in the vicinity of an elliptical hole. The results show that the dislocation source plays a very important role in the interaction. The stress field and the image force are more pronounced for the edge dislocation emitted from the elliptical hole than that for the edge dislocation come elsewhere. Tungsten (W) single crystal is used to simulate an isotropically elastic material, and iron (Fe), copper (Cu) and zinc (Zn) to represent the anisotropic bcc, fee and hcp structures, respectively. The effects of anisotropy are the most pronounced on the stress component sigma(zz) among all stress components. When a dislocation is emitted from the hole and moves far away, the interaction between the dislocation and the hole behaves like that between the real dislocation and an image dislocation located at the center of the hole having the same Burgers vector but with an opposite sign as the real. However, there is no interaction at all between a dislocation and the hole if the dislocation come elsewhere is located far away from the hole. In general, the anisotropy produces an abnormal image force. When the dislocation is located on the x-axis and has a Burgers vector parallel to the x-axis, an abnormal image force is induced along the y-axis, while an abnormal image force is induced along the x-axis when the dislocation is located on the y-axis and has a Burgers vector parallel to the y-axis. The solution of an edge dislocation interacting with an elliptical hole in an infinite isotropic, elastic body is provided in an Appendix. (C) 1999 Elsevier Science Ltd. All rights reserved.