# Phase-field study of crack nucleation and propagation in elastic - perfectly plastic bodies

## TL;DR

This paper develops a phase-field model to study crack nucleation and propagation in elastic-perfectly plastic materials, revealing how plastic zones influence crack behavior and surface roughness.

## Contribution

It introduces a rate-independent phase-field formulation coupling elasticity, plasticity, and fracture, providing new insights into crack initiation and propagation in plastic bodies.

## Key findings

- Plastic zones blunt crack tips in plane strain, inhibiting crack growth.
- Crack propagation occurs intermittently with a rough surface in plane strain.
- Failure involves shear zones and incomplete fracture in plane stress.

## Abstract

Crack initiation and propagation in elastic - perfectly plastic bodies is studied in a phase-field or variational gradient damage formulation. A rate-independent formulation that naturally couples elasticity, perfect plasticity and fracture is presented, and used to study crack initiation in notched specimens and crack propagation using a surfing boundary condition. Both plane strain and plane stress are addressed. It is shown that in plane strain, a plastic zone blunts the notch or crack tip which in turn inhibits crack nucleation and propagation. Sufficient load causes the crack to nucleate or unpin, but the crack does so with a finite jump. Therefore the propagation is intermittent or jerky leaving behind a rough surface. In plane stress, failure proceeds with an intense shear zone ahead of the notch or crack tip and the fracture process is not complete.