A novel method for the analysis of fretting running regime under variable normal load conditions

Many fretting-related engineering failure cases are under varying normal load and bulk load conditions. This complex loading condition makes fretting running regime very complicated. Since the fretting running regime significantly influences the fretting-induced fatigue and wear, it is worth discussing the fretting running regime under these loading conditions, which is barely studied at present. Based on the kinetics analysis of the commonly used fretting structure, a Q- P curves analysis method was derived. Different loading conditions (proportional and non-proportional) and fretting running regimes (partial slip and gross slip) were carefully discussed. It reveals that the coefficient of friction, stiffness of the specimen and pad support sheets, and loading parameters of variable normal load and bulk load are the main factors which influence the fretting running regime. Due to the variable normal load, the Q- δ curves and the tangential force history become extremely intricate. While the proposed Q- P curves analysis method shows a satisfactory result for the illustration of the fretting running regime under these complex loading conditions. It provides a novel methodology for the fretting mechanism analysis under variable normal load conditions.