Non-local plasticity effects on notch fracture mechanics

TL;DR

This paper explores how gradient-enhanced dislocation hardening affects notch failure mechanics, revealing the significant role of geometrically necessary dislocations across various notch geometries and conditions.

Contribution

It introduces a comprehensive finite element analysis using strain gradient plasticity to assess GND effects on notch fracture, covering a wide range of geometries and length scales.

Findings

Plastic strain gradients significantly influence crack initiation and propagation.

GND effects are most relevant in specific notch geometries and length scales.

The study provides guidelines for applying gradient plasticity in damage prediction.

Abstract

We investigate the influence of gradient-enhanced dislocation hardening on the mechanics of notch-induced failure. The role of geometrically necessary dislocations (GNDs) in enhancing cracking is assessed by means of a mechanism-based strain gradient plasticity theory. Both stationary and propagating cracks from notch-like defects are investigated through the finite element method. A cohesive zone formulation incorporating monotonic and cyclic damage contributions is employed to address both loading conditions. Computations are performed for a very wide range of length scale parameters and numerous geometries are addressed, covering the main types of notches. Results reveal a strong influence of the plastic strain gradients in all the scenarios considered. Transitional combinations of notch angle, radius and length scale parameter are identified that establish the regimes of GNDs-relevance, laying the foundations for the rational application of gradient plasticity models in damage assessment of notched components.