An experimental technique of fretting fatigue test was developed and fretting fatigue tests of Al-2024-T4 were conducted under several conditions. In the normal stress and frictional stress calibrations hole and cross type specimen were used. The calibrations resulted in good linearity and repeatability. In fretting fatigue experiment a plate type specimen to which tow bridge type pads were attached was used, and a C.C.D cmera and a P.C vision board was used to observe the crack behavior. The oblique cracks appeared at the early stage of crack growth and they became mode I cracks as the crack grows over about 1mm. This transition point was found to be longer when surface tractions are higher or bulk stress is lower. Before the crack become the mode I crack 'well point' was detected under every conditions.
The crack growth rate was found to be affected by surface tractions, pad contact area and bulk stress. It was also found that partial slip and stick is most detrimental condition for material life. Equivalent stress intensity factor was used to analyse the behavior of fretting fatigue crack and it was found to be valuable, but it needed some modification in the early stage of crack growth.