The paper discusses from first principles all aspects relevant to the plasticity of porous materials. Emphasis is laid on unhomogeneous yielding, defined as the process of yielding and plastic flow under gradient-free macroscopically nonuniform deformation. The nonuniformity is represented by strain localization in one or more bands of finite thickness. A universal feature of all intrinsic yield criteria is their dependence upon the normal and shear tractions resolved on the band. When specialized to isotropy, a Mohr–Coulomb criterion and a Rankine–Tresca criterion emerge as two extremes. The latter is an ideal that typifies the yield behavior of porous materials under arbitrary loadings. The general theory stands for a finite number of bands or yield systems. Its overall structure bears some features of crystal plasticity, but with dependence upon the resolved normal stress. The evolution of microstructural parameters can be given in general terms, being solely based on the kinematic constraints of unhomogeneous yielding and matrix incompressibility. Throughout the paper, the competition with homogeneous yielding, heretofore taken for granted, is analyzed with or without strain and strain-rate hardening effects. We close by discussing the thermodynamic consistency of this new class of constitutive relations and a link to strain-gradient theories.

本文从第一性原理讨论了与多孔材料塑性相关的所有方面。重点放在非均匀屈服上，定义为在无梯度宏观非均匀变形下的屈服和塑性流动过程。不均匀性由一个或多个有限厚度带中的应变局部化表示。所有内在屈服标准的一个普遍特征是它们依赖于在带上解析的法向和剪切牵引力。当专用于各向同性时，Mohr-Coulomb 准则和 Rankine-Tresca 准则作为两个极端出现。后者是代表多孔材料在任意载荷下的屈服行为的理想值。一般理论代表有限数量的波段或产量系统。其整体结构具有一些晶体可塑性的特点，但依赖于解决的法向压力。微观结构参数的演变可以用一般术语给出，仅基于非均匀屈服和基体不可压缩性的运动学约束。在整篇论文中，在有或没有应变和应变率硬化效应的情况下，分析了迄今为止被认为是理所当然的均匀屈服竞争。最后，我们讨论了这一类新本构关系的热力学一致性以及与应变梯度理论的联系。在有或没有应变和应变率硬化效应的情况下进行分析。最后，我们讨论了这一类新本构关系的热力学一致性以及与应变梯度理论的联系。在有或没有应变和应变率硬化效应的情况下进行分析。最后，我们讨论了这一类新本构关系的热力学一致性以及与应变梯度理论的联系。