Modelling of microscopic crack initiation behaviour of fretting fatigue based on X-ray micro-computed tomography scan.

• The model is stablished on X-Ray micro-computed tomography technology (μCT), combing SWT damage theory and Theory of Critical Distance (TCD) technique. • Inclusions can affect the crack initiation direction of fretting fatigue and reduce the initiation lifetime. The closer it is to the surface, the more dangerous it is. • The difference between the properties of inclusions and matrix materials leads to local mechanical response mismatch and concentration. • The aggregation distribution of inclusions results in the merging and connection of local regions with high stress, strain, and damage concentration. Fretting fatigue is a particularly destructive form of fatigue failure that has drawn significant attention from researchers. This paper proposes a numerical modelling method based on tomography scan to investigate the impact of inclusions on fretting fatigue crack initiation behaviour. The results reveal that inclusions can affect the crack initiation direction and reduce the initiation lifetime. The difference between the properties of inclusions and matrix leads to local mechanical response mismatch, resulting in local stress, strain, and damage concentration. The mismatch in strain and damage follows a gradient distribution along the thickness as the distribution in these mechanical responses. These could explain why particles closer to the surface are more likely to cause damage. Additionally, the aggregation distribution of inclusions results in merging and connecting local regions with high stress, strain, and damage concentration, ultimately promoting fracture behaviour. Finally, the numerical models are validated with experimental data from fretting fatigue tests. Compared to the homogeneous model, the numerical model that considers inclusions from topography data can more accurately analyse the material damage and provide a more comprehensive understanding of fretting fatigue behaviour. [ABSTRACT FROM AUTHOR]