Non-local large-strain FFT-based formulation and its application to interface-dominated plasticity of nano-metallic laminates

This paper presents a novel formulation and its robust numerical implementation of strain-gradient (SG) crystal plasticity within a large-strain (LS) elasto-viscoplastic (EVP) fast Fourier transform (FFT)-based micromechanical model. The resulting non-local SG-LS-EVPFFT formulation is used to model and understand the process of kink band formation during layer-parallel compression of nano-metallic laminates (NMLs). NMLs are layered composites with nanoscale thicknesses, thus requiring consideration of the interaction between dislocations and interfaces within the micromechanical model. The length-scale parameter of the SG model is calibrated by simulating a double pile-up and comparing predictions to analytical solution. This required new expressions for the defect energy, resulting in more accurate double pile-up predictions. The calibrated SG-LS-EVPFFT model is then used to simulate layer-parallel compression of copper-niobium NML. Formation of kink bands is predicted, and the model is used to rationalize the microscopic mechanisms enabling the formation process. It is found that accumulation of dislocations at interfaces leads to activation of layer-parallel slip, which in turn leads to kink band formation.

Automated summary

This paper presents a new formulation and numerical implementation of a strain-gradient crystal plasticity model within a large-strain elasto-viscoplastic fast Fourier transform-based micromechanical model. The model is used to study the formation of kink bands during layer-parallel compression of nano-metallic laminates. The interaction between dislocations and interfaces is considered in the model to accurately simulate the behavior of the layered composites.