A Multiscale Crack Iteration and Remeshing Model for Low-Cycle Crack Propagation Evaluation

A multiscale crack iteration and remeshing model was proposed and implemented to predict the low-cycle crack propagation behavior for steel. Crack propagation behavior was quantified by fatigue indicator parameters (FIPs) in the crystal plasticity model. Once the crack propagation rate and direction were determined in the grain, the crack seam was inserted into the model by remeshing in postprocessing. To further relax the fatigue driving force and reduce the impact of FIP variation, an iteration procedure, in which sufficient computational cycles were preselected and iterated during the simulation, was applied to the mesoscale model. Additionally, the boundary conditions of the mesoscale model were obtained from the macroscale model by the multiscale simulation method. A three-point bending fatigue test was carried out to validate the iteration and remeshing model. The experimental results showed two cracks generated from the upper and lower surfaces during the fatigue test, and the crack propagation rate increased as the crack grew toward the center region. Meanwhile, the numerical model, including two initiated cracks, was implemented corresponding to the central region in the experimental specimen. By applying the boundary condition from the macroscale simulation associated with the experiment, the two cracks grew during the iteration and remeshing. The simulation results showed two cracks growing gradually toward the region with a reasonable number of cycles. The zigzag pattern simulated from the mesoscale model also qualitatively correlates well with the observation from experimental results.