Effects of Shot-Peening on Fretting Fatigue Crack Growth Behavior in Ti-6Al-4V

The effects of shot-peening on fretting fatigue crack growth behaviour in titanium alloy, Ti-6Al-4V were investigated. Three shot-peening intensities: 4A, 7A and 10A were considered. The analysis involved the fracture mechanics and finite element sub-modelling technique to estimate crack propagation lives. These computations were supplemented with the experimentally measured total fretting fatigue lives of laboratory specimens to assess the crack initiation lives. Shot-peening has significant effect on the initiation/propagation phases of fretting fatigue cracks; however this effect depends upon the shot-peening intensity. The ratio of crack initiation and total life increased while the ratio of the crack propagation and total life decreased with an increase of shot-peening intensity. Effects of residual compressive stress from shot-peening on the crack growth behaviour were also investigated. The fretting fatigue crack propagation component of the total life with relaxation increased in comparison to its counterpart without relaxation in each shot-peened intensity case while the initiation component decreased. Improvement in the fretting fatigue life from the shot-peening and also with an increase in the shot-peening intensity appears to be not always due to increase in the crack initiation resistance from shot-peened induced residual compressive stress.