An elastoplastic analysis of fretting crack nucleation: Correlation between critical distance and grain size

This study investigates the influence of microstructural size and stress gradients on crack nucleation in ferrite-pearlite steel under cylinder/plane fretting conditions. An experimental and numerical approach establishes a critical distance that correlates with grain size, revealing a significant distinction between elastic and elastoplastic behaviour. The results indicate that the optimal critical distance l approximates the grain size, highlighting that an internal stress exceeding the fatigue limit σ_(d,-1) is needed to nucleate. The findings emphasize the necessity of elastoplastic modelling for accurately describing the mechanisms of crack nucleation under high stress gradients, as previous elastic-only analyses may yield misleading interpretations.