Fatigue cracking in high-cycle- and very-high-cycle-fatigue areas of peened and unpeened Al-based alloys because of fretting damages

In-service fretting damage influenced the fatigue crack origination in materials under the damaged surface for the very-high-cycle fatigue. Specimens of BS L65 Al–Cu alloy with peened and unpeened surfaces tested under cyclic tension and static compression had the crack initiation on the surface because of fretting damage. The static compression was used to reproduce the fretting damage on the specimen surface. The special methodology was applied to the crack growth analysis in the case of the biaxial stress-state with R = −1.0 for the investigated material. The fretting influence on the fatigue crack propagation was estimated on the basis of the functional correction, F(fr), for the stress intensity factor, KI. The fretting damage influence on the fatigue crack growth was briefly discussed regarding the kinetic curves reproduced from the fractographic analysis. The bimodal S–N curve was introduced to describe the influence of fretting damages on the behaviour of materials in high- and very-high-cycle-fatigue areas.