Phase-field modeling of cyclic behavior in quasi-brittle materials: a micromechanics-based approach

TL;DR

This paper develops a phase-field model incorporating cyclic plasticity and ratcheting for quasi-brittle materials, enabling better simulation of fatigue failure through an energetic, thermodynamically consistent approach.

Contribution

It introduces a novel micromechanics-based phase-field framework that explicitly models ratcheting in cyclic plasticity within a thermodynamic formulation.

Findings

Model captures ratcheting strain accumulation over cycles

Numerical results show influence of ratcheting on failure behavior

Framework applicable to low-cycle fatigue analysis

Abstract

In this paper, we extend a micromechanics-based phase-field framework for fatigue fracture to incorporate cyclic plasticity with ratcheting. This mechanism is particularly relevant for low-cycle fatigue, where the accumulation of inelastic strains plays a critical role in the progression to final failure. An energetic formulation is proposed in which the ratcheting strain is explicitly incorporated into both the free energy and the dissipation potential. Ratcheting is modeled within a pressure-dependent, non-associative plasticity framework through the evolution of a ratcheting strain that progressively accumulates over loading cycles, capturing the characteristic inelastic strain growth of cyclic plasticity in a thermodynamically consistent manner. The plastic potential is formulated such that the deviatoric and volumetric components of ratcheting can be controlled independently. A staggered solution scheme is employed to solve for the internal variables, including the ratcheting strain. Numerical examples under monotonic and cyclic loading conditions are presented to evaluate the proposed model and to investigate the influence of ratcheting on the material response.