Investigation of the elastoplastic and fracture behavior of solid materials considering microstructural anisotropy: A discrete element modeling study

The discrete element method (DEM) has great advantages in expressing the deformation and fracture of materials at large scale compared to the molecular dynamics (MD) and the finite element method (FEM). However, its application is constrained by the fact that most of the existing models are limited to elastic-brittle homogeneous materials.

In this paper, a spring connected DEM model is proposed to describe the elastoplastic and fracture behavior of materials under quasi-static and dynamic loading conditions. In contrast to many other DEM models, the central element is connected to the surrounding double-layer elements with both short-range and long-range interactions.

The elastic parameters of the connecting components are derived from the conservation of strain energy density, and the distortion energy is expressed uniquely by the defined distortion coefficients. Based on the von-Mises yield criterion and isotropic hardening effect, the plastic behavior of the connecting component is derived.

Furthermore, the energy release rate and Voronoi tessellation method are used to characterize the failure process and the microstructures generation, respectively. The bilinear elastoplastic response under quasi-static cyclic loading as well as the elastic and plastic stress wave propagating in a one-dimensional bar and a two-dimensional plate subjected to impact loading are analyzed successfully with the proposed approach.

In addition, the simulations of mode-I and mode-II crack propagation are conducted and validated by the theoretical prediction and dynamic shearing impact experiment, respectively. The effects of short-range and long-range interactions on material quasi-static and dynamic behavior are also discussed, and it is concluded that their impact on the material dynamic behavior (e.g. wave speed and crack propagation) is greater than that on the quasi-static response (e.g. elastoplastic deformation).