Phase-field modeling of fatigue coupled to cyclic plasticity in an energetic formulation

TL;DR

This paper introduces a variational phase-field model coupling fatigue fracture and cyclic plasticity, capturing low- and high-cycle fatigue mechanisms and crack propagation in materials under cyclic loading.

Contribution

It develops a novel energetic formulation that integrates fatigue effects with cyclic plasticity, enabling comprehensive simulation of fatigue crack initiation and growth.

Findings

Model accurately predicts fatigue crack initiation and growth.

Captures both low-cycle and high-cycle fatigue behaviors.

Demonstrates effectiveness through numerical simulations.

Abstract

This paper presents a modeling framework to describe the driving mechanisms of cyclic failure in brittle and ductile materials, including cyclic plasticity and fatigue crack growth. A variational model is devised using the energetic formulation for rate-independent systems, coupling a phase-field description of fatigue fracture to a cyclic plasticity model that includes multi-surface kinematic hardening, gradient-enhanced isotropic hardening/softening and ratcheting. The coupled model embeds two distinctive fatigue effects. The first captures the characteristic features of low-cycle fatigue, driven by the accumulation of plastic strains, while the second accounts for high-cycle fatigue, driven by free energy accumulation. The interplay between these mechanisms allows to describe a wide range of cyclic responses under both force loading and displacement loading, as shown in several numerical simulations. Moreover, the phase-field approach to fracture accounts for the initiation and propagation of fatigue-induced cracks.