A shear stress-based parameter for fretting fatigue crack initiation

The purpose of this study was to investigate the fretting fatigue crack ini tiation behaviour of titanium alloy, Ti-6Al-4V. Fretting contact conditions were varied by using different geometries of the fretting pad. Applied for ces were also varied to obtain fretting fatigue crack initiation lives in b oth the low- and high-cycle fatigue regimes. Fretting fatigue specimens wer e examined to determine the crack location and the crack angle orientation along the contact surface. Salient features of fretting fatigue experiments were modelled and analysed with finite element analysis. Computed results of the finite element analyses were used to formulate a shear stress-based parameter to predict the fretting fatigue crack initiation life, location a nd orientation. Comparison of the analytical and experimental results showe d that fretting fatigue crack initiation was governed by the maximum shear stress, and therefore a parameter involving the maximum shear stress range on the critical plane with the correction factor for the local mean stress or stress ratio effect was found to be effective in characterizing the fret ting fatigue crack initiation behaviour in titanium alloy, Ti-6Al-4V.