Transitioning rate sensitivities across multiple length scales in crystal plasticity

Abstract eng:
A finite-element based plasticity model is developed for polycrytals deforming at high-strain—rates. The model is multi-scale, covering from thermally activated dislocation motion on a specific crystallographic slip system, to single crystal plasticity, to polycrystalline plasticity, and ultimately heterogeneous deformation of the macro-scale sample. Within the model, the rate dependence in macro-scale response arises solely from the characteristic stress to activate dislocation motion. This is accomplished by introduction of a novel methodology, used at the intermediate length scales, to remove any extraneous rate dependencies occurring as a result of the visco-plastic rate sensitive flow rule, commonly associated with crystal plasticity formulations. Simulation results are presented for the deformation of high-purity zirconium in a Taylor impact cylinder test. The variation in sample shape changes, texture evolution, and deformation twin fraction after the test are experimentally measured. These same quantities are calculated using the model and good agreement is achieved in all aspects.

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