标题： 具有粘结强度的弹塑性球体的广义加载-卸载接触定律 显示英文标题

标题： Generalized loading-unloading contact laws for elasto-plastic spheres with bonding strength

摘要： 我们提出了具有粘结强度的弹塑性球体的广义加载-卸载接触定律。 所提出的机制接触定律通过一种正则化项在卸载开始时保持连续性，这种正则化项遵循粘聚区模型的精神，在颗粒间断裂条件中引入了一个小而可控的误差。 这种连续性特性与标准机制加载和卸载接触理论的行为形成鲜明对比，这些理论在颗粒在塑性变形过程中形成固态桥接时，在卸载开始时表现出不连续性。 该公式依赖于五个材料属性，即两个弹性属性（杨氏模量和泊松比）、两个塑性属性（塑性刚度和幂律硬化指数）以及一个断裂力学属性（断裂韧性），其预测结果与详细的有限元模拟一致。 通过进行三维颗粒力学静态计算，对粉末压制成型的三个最重要步骤——即压制、卸载和顶出过程中的微观结构演变进行计算，验证了所提出公式的数值鲁棒性和效率。 这些模拟揭示了微观结构特征、工艺变量和压块机械属性的演变，直至相对密度接近于一，这些结果在定量上与实验观察到的结果相似，并与文献中报道的（半）经验公式有显著的一致性。 显示英文摘要

摘要： We present generalized loading-unloading contact laws for elasto-plastic spheres with bonding strength. The proposed mechanistic contact laws are continuous at the onset of unloading by means of a regularization term, in the spirit of a cohesive zone model, that introduces a small and controllable error in the conditions for interparticle breakage. This continuity property is in sharp contrast with the behavior of standard mechanistic loading and unloading contact theories, which exhibit a discontinuity at the onset of unloading when particles form solid bridges during plastic deformation. The formulation depends on five material properties, namely two elastic properties (Young's modulus and Poisson's ratio), two plastic properties (a plastic stiffness and a power-law hardening exponent) and one fracture mechanics property (fracture toughness), and its predictions are in agreement with detailed finite-element simulations. The numerical robustness and efficiency of the proposed formulation are borne out by performing three-dimensional particle mechanics static calculations of microstructure evolution during the three most important steps of powder die-compaction, namely during compaction, unloading, and ejection. These simulations reveal the evolution, up to relative densities close to one, of microstructural features, process variables and compact mechanical attributes which are quantitatively similar to those experimentally observed and in remarkable agreement with the (semi-)empirical formulae reported in the literature.