Energy dissipation in contact of rough metallic surfaces under normal loading

This paper describes an experimental study of energy dissipation at the normal contact of solids by plastic deformation of surface asperities and adhesion. Experiments were conducted in which ball and plate made of AISI440C were cyclically pressed against each other in helium, hydrogen gas and air. It was found that energy dissipation occurred with no evidence of adhesion, and the plastic deformation of surface asperities was a main factor of the energy dissipation. Energy dissipated in the first contact, and it continued in the subsequent contact cycles. This implied that the asperities did not shakedown in the first contact under macroscopically elastic contact. Larger energy dissipation in the first contact led to larger energy dissipation in the repeated contacts. It was concluded from these results that substantial energy dissipation occurred by plastic deformation of surface asperities under normal loads that exceeded the shakedown limit.