Fatigue crack initiation simulation in pure iron polycrystalline aggregate

Abstract

A numerical study was conducted to evaluate the fatigue crack initiation stage in pure α-iron. A two-dimensional synthetic polycrystalline aggregate was generated with Voronoi tessellation to represent the microstructure. Low-cycle fatigue experiments under fully reversed strain-controlled loading were conducted for different strain amplitudes. The stable stress-strain hysteresis loops were used to calibrate a non-linear kinematic hardening model for metal plasticity suitable for cyclic simulations. An existing procedure based on the Tanaka-Mura model for fatigue crack initiation was extended to body-centered cubic lattice to account for two orthogonal slip systems as potential crack locations. This procedure was applied for fully reversed fatigue simulations with various stress amplitudes ranging from low-cycle to high-cycle fatigue regime. The effect of the stress level on the crack morphology and the fatigue crack initiation life was evaluated. Finally the applicability and limitations of the proposed procedure was discussed.