On the Intrinsic Link between Gradient Strengthening and Passivation Onset in Single Crystal Plasticity

TL;DR

This paper develops a thermodynamically consistent gradient crystal plasticity model that links size-dependent strengthening with boundary effects, revealing how dissipative gradient effects influence the onset of plastic flow in single crystals.

Contribution

It introduces a novel finite-deformation gradient plasticity framework explicitly accounting for energetic and dissipative microstress contributions, connecting size effects with boundary conditions.

Findings

Gradient laws reproduce size-dependent strengthening at plastic flow onset.

Passivation boundary constraints lead to nearly elastic responses.

Dissipative gradient effects are crucial in boundary-driven mechanical responses.

Abstract

A finite-deformation framework for gradient crystal plasticity is developed within a thermodynamically consistent setting grounded in Gurtin's power-conjugate formulation. The model introduces a flow rule that accounts explicitly for both energetic and dissipative microstress contributions. Numerical simulations are performed to investigate the response of single crystals subjected to passivation-type boundary constraints. The results reveal that constitutive laws capable of reproducing size-dependent strengthening at the onset of plastic flow simultaneously generate a pronounced, nearly elastic-type response when passivation is imposed. These findings establish a fundamental connection between gradient-induced yield strengthening and boundary-driven elevation of the mechanical response, highlighting the essential influence of dissipative gradient effects.