Fretting Fatigue Life Estimations Based on Critical Distance Theory

Fretting fatigue process have many features such as early stage crack initiation at contact edge, very slow crack propagation and fatigue failure after very long life operation. In this paper at first we present fretting fatigue model in high cycle region, which is considering the wear process near contact edge. And then we present fretting fatigue life estimation method in low cycle fatigue region using critical distance stress theory. Generally this critical distance theory was applied for the fatigue limit estimation using fatigue limit of smooth specimen σw0, and threshold stress intensity factor range ∆Kth. In this paper we estimated the low cycle fretting fatigue life based on new critical distance theory, which is modified for high stress region using ultimate tensile strength σB, and fracture toughness KIC. The critical distance for estimating low cycle fretting fatigue strength was calculated by interpolation of critical distance on fretting fatigue limit (estimated from σw0 and ∆Kth ) with critical distance on static strength (estimated from σB and KIC ). By unifying these low cycle fretting fatigue life estimation method with high cycle fretting fatigue life estimation method we can estimate the total fretting life easily. And to confirm the availability of this estimation method we perform the fretting fatigue test using Ni—Mo-V steel.