Mechanical model for yield strength of nanocrystalline materials under high strain rate loading

Abstract

To understand the high strain rate deformation mechanism and determine the grain size, strain rate and porosity dependent yield strength of nanocrystalline materials, a new mechanical model based on the deformation mechanism of nanocrystalline materials under high strain rate loading was developed. As a first step of the research, the yield behavior of the nanocrystalline materials under high strain rate loading was mainly concerned in the model and uniform deformation was assumed for simplification. Nanocrystalline materials were treated as composites consisting of grain interior phase and grain boundary phase, and grain interior and grain boundary deformation mechanisms under high strain rate loading were analyzed, then Voigt model was applied to coupling grain boundary constitutive relation with mechanical model for grain interior phase to describe the overall yield mechanical behavior of nanocrystalline materials. The predictions by the developed model on the yield strength of nanocrysatlline materials at high strain rates show good agreements with various experimental data. Further discussion was presented for calculation results and relative experimental observations.