Crack growth resistance in metallic alloys: the role of isotropic versus kinematic hardening

TL;DR

This study compares how isotropic and kinematic hardening influence crack growth resistance in metallic alloys, revealing that kinematic hardening enhances resistance and affects crack extension needed for steady state.

Contribution

It provides a detailed analysis of the effects of isotropic versus kinematic hardening on crack growth resistance using cohesive zone modeling.

Findings

Kinematic hardening increases crack growth resistance compared to isotropic hardening.

Kinematic hardening requires greater crack extension to reach steady state.

The differences are due to non-proportional loading near the crack tip.

Abstract

The sensitivity of crack growth resistance to the choice of isotropic or kinematic hardening is investigated. Monotonic mode I crack advance under small scale yielding conditions is modelled via a cohesive zone formulation endowed with a traction-separation law. R-curves are computed for materials that exhibit linear or power law hardening. Kinematic hardening leads to an enhanced crack growth resistance relative to isotropic hardening. Moreover, kinematic hardening requires greater crack extension to achieve the steady state. These differences are traced to the non-proportional loading of material elements near the crack tip as the crack advances. The sensitivity of the R-curve to the cohesive zone properties and to the level of material strain hardening is explored for both isotropic and kinematic hardening.