Validating texture and lattice strain evolution models via in-situ neutron diffraction and shear tests

Abstract

Validating micromechanical models under different loadings is challenging due to limited availability of experimental setups that can probe complex stress states. In this work, we perform in situ neutron diffraction experiments during shear loading to study the evolution of crystallographic texture and lattice strains that develop in different grain families. The experiments are conducted on 316 stainless steel samples, having a flat shear sample geometry suitable for testing in uniaxial rigs. The complex stress state in the gauge volume is estimated using an elasto-plastic finite element (FE) simulation, which is validated via experimentally measured gauge strains. The FE simulation reveals the generation of non-negligible in-plane normal stress components together with the in-plane shear stress component. The predicted macroscopic stresses are used as boundary conditions to drive an elasto-viscoplastic fast Fourier transform (EVP-FFT) based crystal plasticity model, which predicts lattice strain evolution. In addition, the evolution of the diffraction intensity is simulated using the Taylor model. The predictions of both models match very well with the experimental results. The experiments reveal that the {220} and {311} grain families have higher lattice strains than the {200} family. This surprising result is explained with the help of simulations.