Comparing local deformation measurements to predictions from crystal plasticity during reverse loading of an aerospace alloy

Abstract

Cyclic loading is of great importance in aerospace applications but the origins of the change in flow stress with load path are poorly understood and difficult to predict. Many crystal plasticity models are capable of modelling macroscopic flow behaviour during non-monotonic load paths, such as the Bauschinger effect often seen when reverse loading. Although these models represent the microstructure explicitly, it remains unclear whether they capture reversibility at the local microstructural scale, or simply fit the macroscopic hardening response better by using more fitting parameters. Here we present experimental surface deformation data acquired using high resolution digital image correlation (HR-DIC) during a reverse load cycle. With resolution greater than 200nm, these experiments reveal the discrete nature of deformation in the form of localised crystallographic slip bands. These results are then compared statistically, over many hundreds of grains, to crystal plasticity simulations of reverse loading. Simulation results are taken from both finite element method (CPFEM) and fast Fourier transform (CPFFT) encompassing the two popular numerical techniques for full-field crystal plasticity models.