Phase-Field Description of Ductile Fracture in Structural Steel under Cyclic Loading

Abstract

This paper presents analysis of fracture in structural steel subjected to cyclic loads, which is of paramount importance for evaluating the safety of steel buildings exposed to extreme events such as strong earthquakes. The analysis relies on the phase-field concept to describe the formation and propagation of cracks in a solid body, in conjunction with a large-deformation description of the motion and an elastoplastic constitutive law having nonlinear isotropic and kinematic hardening to account for the material hysteretic response. The evolution of the phase-field is driven by a low-cycle fatigue criterion, aimed to phenomenologically describe the effect of irreversible processes ultimately leading to ductile fracture. The proposed modeling scheme is used in the simulation of experimental tests on circumferentially notched steel coupons tested by the authors, and its capability to capture fracture occurrence, as well as cyclic crack opening and closing, is demonstrated.