基于非线性接触本构的颗粒材料离散元数值模拟

在考虑颗粒间细观非线性接触关系的基础上,基于空隙胞元法,采用颗粒离散元法对二维颗粒体试样进行了平面应变数值模拟。颗粒间接触用广义弹簧单元表示,相邻颗粒接触点的塑性变形用非线性弹簧表示。在准静态、小变形条件下,研究了试样的微观织构变化和宏观力学行为。单个空隙胞元的变形通过周围颗粒的相对运动来计算,将离散系统中的变形与连续体中的相应变形联系起来,应用于颗粒离散元方法中平均应力的计算。文中给出了细观尺度上局部织构(通过空隙数,接触价键,配位数来表征)的变化过程,对比了不同情况下的应力–应变关系曲线,再现了试样的加卸载曲线。结果表明了颗粒介质之间的咬合作用对材料的宏观力学行为有比较明显的影响。

Simulation of mechanical behaviors of granular materials by discrete element method based on mesoscale nonlinear contact law

Numerical simulation of two-dimensional assembly of disks was carried out based on discrete element method(DEM) where the non-linear contact relationship between particles was considered.Each particle was located by a node at its centre and the plastic indentation of the contacts between neighboring particles was represented by a non-linear spring.The local fabric evolution(void number,the valence and the coordination number) and macroscopic mechanical behavior were investigated under quasi-static biaxial loading at small deformation.By making a link between the discrete force system and its continuum equivalent,macroscopic average stress in the granular assembly could be derived.The macrocosmic stress-strain relationships under different circumstances were presented and loading-unloading cycle could be reproduced by DEM.The effect of friction coefficient between particles on the intensity was compared and discussed.It was shown that the microscopic parameters of granular materials affected greatly the macroscopic response of the granular materials.