A finite element methodology to incorporate kinematic activation of discrete deformation twins in a crystal plasticity framework

Abstract

A finite element framework is presented in which grains within a polycrystalline microstructure are pre-discretized into lamellar regions that become candidates to deform by twinning. This enables the mapping of the motion due to twinning on geometrically proper regions. At some point in the loading of the polycrystal, a twin is triggered, at which point the nodes within a twin region are rapidly mapped to their twinned location, the region’s crystal lattice is reoriented, and the remainder of the body deforms by means of crystallographic slip to enforce mechanical equilibrium. The framework allows for both the onset of twinning and twin growth, and is intended to serve as a test bed for investigating models proposed for these phenomena. In this paper, the framework is described and simulations are performed to demonstrate its ability to handle the large, fast deformation of twinning within a targeted grain of a polycrystalline aggregate. Various simulations are performed, where the initial twin width and the point of twin activation in the loading history are parameterized. Deformation fields in and around the twinned region are inspected after a twinning event, and changes in local stress states are discussed in light of global and local energetic metrics.