Kinematics of slip-induced rotation for uniaxial shock or ramp compression

TL;DR

This paper investigates the lattice rotation in uniaxially compressed crystals, showing traditional models fail and proposing a new elastoplastic framework that accurately predicts rotation and slip activity.

Contribution

It introduces a novel elastoplastic decomposition model that better predicts lattice rotation in uniaxial shock or ramp compression scenarios.

Findings

Traditional Schmid and Taylor analyses are inadequate for uniaxial compression.

The proposed model accurately predicts lattice rotation in molecular dynamics simulations.

The framework can identify slip systems and activity levels in idealized compression cases.

Abstract

When a metallic specimen is plastically deformed, its underlying crystal structure must often rotate in order to comply with its macroscopic boundary conditions. There is growing interest within the dynamic compression community in exploiting x-ray diffraction measurements of lattice rotation to infer which combinations of plasticity mechanisms are operative in uniaxially shock- or ramp-compressed crystals, thus informing materials science at the greatest extremes of pressure and strain rate. However, it is not widely appreciated that several of the existing models linking rotation to slip activity are fundamentally inapplicable to a planar compression scenario. We present molecular dynamics simulations of single crystals suffering true uniaxial strain, and show that the Schmid and Taylor analyses used in traditional materials science fail to predict the ensuing lattice rotation. We propose a simple alternative framework based on the elastoplastic decomposition that successfully recovers the observed rotation for these single crystals, and can further be used to identify the operative slip systems and the amount of activity upon them in the idealized cases of single and double slip.