Fretting Fatigue Behavior of a Titanium Alloy Ti-6AL-4V at Elevated Temperature

Fretting fatigue crack initiation in titanium alloy, Ti-6Al-4V, at elevated temperature is investigated experimentally and analytically using finite element analysis. The temperature of this study is chosen to be 260 oC. Several specimens are tested at different stress levels to establish the life data (i.e. S-N relationship). The crack initiation location and the crack angle orientation along the contact surface are determined using scanning electron microscopy. Finite element analysis is used to obtain the stress states for the experimental conditions used during the fretting fatigue tests. These are then used to investigate several critical plane based multi-axial fatigue parameters. These parameters are evaluated based on their ability to predict the crack initiation location, crack orientation angle along the contact surface, and the number of cycles to fretting fatigue crack initiation. These predictions are compared with their experimental counterparts to characterize the role of normal and shear stresses on fretting fatigue crack initiation at elevated temperature. Also, plain and fretting fatigue data at room and elevated temperature are compared. From these comparisons, it can be concluded that 260 temperature does not have any detrimental effect on fretting fatigue crack initiation of Ti-6Al-4V when compared to that at room temperature. Further, fretting fatigue crack initiation mechanism in the tested titanium alloy appears to be governed by the shear stress on the critical plane. However, further work is needed to understand the role of both shear and normal stresses on the critical plane at elevated temperatures.