Effects of surface roughness and lubrication on the early stages of fretting of mechanical lap joints

This paper examines the effects of surface roughness and lubrication on the early stages of fretting response of aluminum and steel lap joint samples. Qualitative and quantitative changes in fretting loops due to changes in loading; roughness characteristics, and contact conditions are analyzed. Roughness is found to influence friction force, tangential joint stiffness, partial slip displacements, and energy dissipation per fretting cycle. Moreover, despite growing weaker, the influence of roughness is shown to prevail under boundary or starved lubrication using a synthetic polyol ester lubricant. Furthermore, galling is shown to complicate the fretting response of the aluminum joints under heavy preloading conditions.