Threshold and propagation of defects under RCF: an experimental approach

This study investigates the threshold and propagation behavior of artificial defects under rolling contact fatigue (RCF) through a combined experimental methodology. Multiaxial fatigue tests on gear steel specimens with ring-shaped EDM defects were used to evaluate Mode II and Mode III thresholds under out-of-phase axial-torsional loading. Complementary bidisc tests on crowned specimens assessed crack growth under lubricated conditions at varying Hertzian pressures. Crack propagation was monitored via high-resolution tomography and quantified using finite element models to compute stress intensity factors. Coplanar shear-driven growth was observed in both setups, with Mode II as the dominant mechanism. A predictive methodology integrating experimental crack growth data and numerical modeling showed strong agreement with fatigue lives, underscoring the relevance of combining multiaxial and RCF approaches in defect tolerance analysis.