Knowledge of the constitutive behavior of single crystals is essential for crystal plasticity modeling, yet experimental methodologies for obtaining such data remain limited. Conventional approaches typically rely on polycrystalline specimens which introduce averaging effects that obscure the single grain behavior. Single crystal experiments offer a more direct route to capture the fundamental deformation mechanisms, but are challenging due to complex specimen preparation and the difficulty of achieving large plastic strains beyond diffuse necking in conventional tensile tests. This thesis builds upon a recently developed experimental methodology which enables extraction of stress-strain response of single crystals beyond diffuse necking in tensile tests from in-situ simple shear tests. This work uses this existing framework and data to simulate the deformation response using the finite element method (FEM). The proposed sample geometry was designed and validated under an isotropic assumption, and is here extended to a crystal plasticity framework to assess its performance under anisotropic single crystal behavior. The objective is to determine whether the geometry maintains a near-simple shear state on introduction of crystallographic anisotropy. The material considered is AA6082 alloy in a naturally aged condition. The FEM solver Abaqus together with the OXFORD-UMAT subroutine was utilized to perform crystal plasticity simulations using a phenomenological power-law slip model and a Voce-type hardening law. This study investigates the effect of crystallographic orientation on deformation kinetics, kinematics, slip system activity of single crystals, and the global stress–strain response from the simple shear test. The simulations show that the geometry imposes a near-simple-shear strain state and the predicted strain fields and crystallographic orientation evolution are consistent with reported experimental measurements. However, the stress state deviates from that of ideal simple shear and is dependent on the crystal orientation. While qualitative trends in the global stress–strain response are captured, quantitative agreement remains limited, highlighting limitations in the test methodology for constitutive calibration using single crystals.
Ripudaman Singh (Thu,) studied this question.