Damage accumulation below the worn surfaces during the sliding wear of copper.

Damage accumulation below the contact surfaces constitutes an important form of delamination wear in ductile materials. In this study, metallographic techniques were used to determine the extent of plastic deformation and strain localization events during the sliding wear of commercially pure copper samples. Tests were performed using a block-on-ring type wear machine on specimens in annealed condition and after 50% deformation by rolling. Strain and microhardness gradients were measured as a function of sliding distance and the strain hardening behavior of deformed subsurface layer was determined. It was observed that both the magnitude of strain gradients and the depths of plastically deformed layer increased with the sliding distance. Wear proceeded with the removal of flakelike debris formed as a result of subsurface fracture through a shear band decohesion mechanism. It was found that the location of maximum damage was not at the contact surface but at a certain distance below it. This critical depth was determined by the relative intensities of shear and hydrostatic stress gradients. A model based on Rice and Tracy analysis of void growth was proposed to account for the experimental observations. The stress and strain distributions adjacent to the wear surface were sensitive to the degree of prior cold working. In addition, the wear rate of the 50% rolled specimens was higher than that of annealed specimens when tested at loads higher than 1000 g. This was related to the different strain hardening behavior and the smaller thickness of plastically deformed layer for rolled Cu below the worn surface.Dept. of Mechanical, Automotive, and Materials Engineering. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1991 .H856. Source: Masters Abstracts International, Volume: 31-01, page: 0412. Supervisor: Ahmet T. Alpas. Thesis (M.A.Sc.)--University of Windsor (Canada), 1991