Modified Experimental Approach to Investigate Coefficient of Friction and Wear under Lubricated Fretting Condition by Utilizing SRV Test Machine 2018-01-0835

Fretting is an important phenomenon that happens in many mechanical parts. It is the main reason in deadly failures in automobiles, airliners, and turbine engines. The damage is noticed between two surfaces clamped together by bolts or rivets that are nominally at rest, but have a small amplitude oscillation because of vibration or local cyclic loading. Fretting damage can be divided into two types. The first type is the fretting fatigue damage where a crack would initiate and propagate at specific location at the interface of the mating surfaces. Cracks usually initiate in the material with lower strength because of the local cyclic loading conditions which eventually lead to full failure. The second type is the fretting wear damage because of external vibration. Researchers have investigated this phenomenon by theoretical modeling and experimental approaches. Although a lot of research has been done on fretting damage, some of the parameters have not been well studied. In this study, the fretting damage mechanism was simulated by utilizing SRV test machine to obtain the real time coefficient of friction (COF). A large spherical surface (about 34 mm in diameter) on flat setup was used to run the test under lubricated condition. The parameters that were investigated include load, oscillation amplitude, oscillation frequency, temperature, material, and surface profile. It was found that all the studied parameters had a moderate effect on the coefficient of friction except for the temperature, which had little effect. In terms of wear scar analysis, the study showed that increasing contact pressure, oscillation amplitude and oscillation frequency caused an increase in wear scar width and depth by 30% to 45% for most testes.