A study on fretting fatigue behaviors in 2024-T351 aluminum alloy

Fretting fatigue is an important fatigue failure mechanism in aircraft structures, such as mechanically fastened lap joint components. It is well known that multiple site fatigue cracking was originated from fretting damages especially in aging aircrafts and these premature crackings due to the fretting threaten aircraft safety which was certified by the damage tolerant fail safe concept. Fretting damages are related with partial microslip at contact surfaces which are nominally-clamped and subjected to oscillatory loads. In this investigation a series of experimental tests were carried out to observe the crack initiation and propagation behaviors and the effects of related fretting parameters on fatigue life in A12024-T351 plate. And elasto-plastic contact stress analyses were also performed to assess the stress and strain fields in the subsurface during fretting contact. Contact pressure and tangential force were revealed as important parameters in determining crack initiation and propagation life. The strain-life and Smith-Watson-Topper(SWT) models were evaluated to predict crack initiation life and to compare with test results. It turned out that the maximum strain amplitude at the contact interface was a predominant parameter for fretting crack initiation and the short crack propagation life became more important, when the contact pressure became higher.