Quantitative comparison between experimental measurements and CP-FEM predictions of plastic deformation in a tantalum oligocrystal

Quantitative comparisons of experimental measurements and model predictions are crucial to validate and improve material models as well as to understand underlying physical phenomena. In this work, we used a recently developed in situ technique combining high resolution digital image correlation (HR-DIC) and electron backscatter diffraction (EBSD) to obtain intergranular surface strain fields and crystal rotations. These measurements were compared to predictions from a crystal plasticity-finite element method (CP-FEM) simulation. To accurately reproduce the initial grain morphology in the CP-FEM simulation without assumptions regarding the sub-surface microstructure, a coarse columnar-grained tantalum specimen was used. Experimental data was projected onto the finite element mesh to compare measured and simulated data on a point-wise basis. It is shown that model predictions of both surface strain fields and crystal rotations agree reasonably well with HR-DIC and EBSD measurements at various applied strains. This procedure provides an objective and quantitative methodology to evaluate the model-experiment agreement and allows for testing of various model parameters to improve the model. (C) 2014 Elsevier Ltd. All rights reserved.