Strain localization is often a precursor to the ductile failure of materials. This paper investigates plastic strain localization phenomena in the case of random microstructures, namely cubic cells made of an elastic-perfectly plastic matrix embedding distribution of identical non-overlapping spherical voids. The consideration of random microstructures allows for a better representation of the interaction between voids and greater diversity of failure modes than single-void (or unit) cells. The cells are simulated by means of the finite element (FE) method for proportional stress loading paths with controlled stress triaxiality and Lode parameters. Strain localization is detected by Rice’s criterion computed at the cell level. This criterion is shown to accurately capture the onset of localization and the type of failure mode, either extension or shear banding. Moreover, the influence of the loading orientation, i.e. the orientation of the principal axes of the applied stress tensor with respect to the microstructure cube, is systematically studied. Significant anisotropy of failure behavior is observed, especially in the case of single void unit cells, which can be attributed to the intrinsic anisotropy of the simulation cells. Finally minimal failure strain values at localization with respect to all loading orientations are found. A zone of reduced ductility is observed under generalized shear loading conditions.

应变局部化通常是材料延性破坏的前兆。本文研究了随机微观结构情况下的塑性应变局部化现象，即由相同非重叠球形空隙的弹性完全塑性基质嵌入分布制成的立方晶胞。与单孔（或单元）电池相比，考虑随机微结构可以更好地表示孔之间的相互作用和更多的失效模式。单元通过有限元 (FE) 方法模拟，用于具有受控应力三轴性和 Lode 参数的比例应力加载路径。应变定位由在细胞水平计算的 Rice 标准检测。该标准被证明可以准确地捕捉定位的开始和故障模式的类型，延伸或剪切带。此外，系统地研究了加载方向的影响，即施加的应力张量的主轴相对于微观结构立方体的方向。观察到失效行为的显着各向异性，特别是在单空隙单元的情况下，这可归因于模拟单元的固有各向异性。最后，找到了相对于所有加载方向的局部最小失效应变值。在广义剪切载荷条件下观察到延展性降低的区域。观察到失效行为的显着各向异性，特别是在单空隙单元的情况下，这可归因于模拟单元的固有各向异性。最后，找到了相对于所有加载方向的局部最小失效应变值。在广义剪切载荷条件下观察到延展性降低的区域。观察到失效行为的显着各向异性，特别是在单空隙单元的情况下，这可归因于模拟单元的固有各向异性。最后，找到了相对于所有加载方向的局部最小破坏应变值。在广义剪切载荷条件下观察到延展性降低的区域。