Analysis of rolled edge cracking of ZK60 magnesium alloy based on shear modified GTN damage model

Abstract Edge cracking is a common defect during the hot rolling of magnesium alloy sheets, primarily due to the limited ductility associated with their hexagonal close-packed (HCP) structure. This study aims to elucidate the mechanisms of edge crack initiation and propagation in ZK60 alloy under hot rolling at 300 °C, based on a shear-modified Gurson-Tvergaard-Needleman (GTN) damage model. A shear-modified GTN model was developed and implemented into the ABAQUS/Explicit platform via a user-defined VUMAT subroutine. Model parameters were calibrated using high-temperature uniaxial tensile and pure shear tests. Rolling simulations were conducted and validated against experimental trials, with attention to crack morphology and initiation sites. Numerical simulations reproduced the experimentally observed edge crack patterns with high accuracy. Stress and damage analyses revealed that sheet edges are subjected to a combined tensile–shear stress state with moderate to low triaxiality, which promotes void growth and shear damage. A characteristic V-shaped damage distribution was obtained, consistent with fracture morphologies. Moreover, the simulated average crack length of 6.2 mm exhibits a good agreement with both the experimental measurement range (4.88–7.28 mm) and the average value (6.08 mm), validating the accuracy of the model. Crack initiation was found to be governed by porosity accumulation rather than equivalent plastic strain alone, highlighting the decisive role of stress-state-dependent damage evolution in edge crack formation.