Simulation of Semi-Solid Material Mechanical Behavior Using a Combined Discrete/Finite Element Method

Abstract

As a necessary step toward the quantitative prediction of hot tearing defects, a 3D stress-strain simulation based on a combined Finite Element (FE) / Discrete Element Method (DEM) has been developed that is capable of predicting the mechanical behavior of semi-solid metallic alloys during solidification. The solidification model used for generating the initial solid-liquid structure is based on a Voronoi tessellation of randomly distributed nucleation centers and a solute diffusion model for each element of this tessellation. At a given fraction of solid, deformation is then simulated with the solid grains being modeled using an elasto-viscoplastic constitutive law, while the remaining liquid layers at grain boundaries are approximated by flexible connectors, each consisting of a spring element and a damper element acting in parallel. The model predictions have been validated against Al-Cu alloy experimental data from the literature. The results show that a combined FE/DEM 2 approach is able to express the overall mechanical behavior of semi-solid alloys at the macro scale based on the morphology of the grain structure. For the first time, the localization of strain in the intergranular regions is taken into account. Thus, this approach constitutes an indispensible step towards the development of a comprehensive model of hot tearing.