Fretting fatigue characteristics with relating contact pressure and surface roughness of highly workable titanium alloy, Ti-4.5Al-3V-2Mo-2Fe

Abstract

The effects of contact pressure and surface roughness on fretting fatigue strength of Ti-4.5Al-3V-2Mo-2Fe conducted with annealing at 1123 K were investigated in this study. Fretting fatigue tests in low and high cycle fatigue life regions of the alloy were carried out at each contact pressure of 10, 15, 30, 45, 75, 105 and 153 MPa using relatively rough surface specimens with roughness number around 120∼140 nm. Furthermore, the fretting fatigue tests were also performed on the relatively smooth surface specimens with roughness number around 13.2∼32.2 nm at a selected contact pressure of 153 MPa. The fretting fatigue crack initiation mechanism is changed by contact pressure. At a contact pressure of 15 MPa, fretting fatigue life tends to be very low in each fatigue life region. The tangential force tends to increase with increasing contact pressure in each fatigue life region. Contrary to this trend, the tangential force coefficient tends to decrease with increasing contact pressure in each fatigue life region. The fretting fatigue life of the alloy with smooth surface is greater about 20% and 10% in low and high cycle fatigue life regions, respectively, than that of the alloy with relatively rough surface.