MODELING OF MICROFRACTURE-INDUCED WEAR AND WEAR TRANSITION IN SLIDINGOF POLYCRYSTALLINE ALUMINA CERAMICS

An equation has been proposed to describe sliding wear caused by micro fracture in polycrystalline alumina ceramics. The wear equation has be en simplified, and grain size dependence for dry sliding wear data by Wu et al. has been shown to agree with this equation. For lubricated s liding in a ball-on-flat configuration, modification of the equation i s necessary. A concept of equivalent ''real'' contact area for lubrica ted contacts is introduced to account for the different stresses at th e interface as the contact conditions change before and after a wear t ransition. Microfracture occurs when superimposed stress exceeds a cri tical threshold. The decrease in surface conformity due to surface rou ghening and trapping of pulled-out grains can significantly increase t he magnitude of the contact stresses, which leads to high wear rates. We incorporate the contact geometry effects into the microfracture wea r equation. This new wear equation provides a self-consistent data fit ting of load dependent wear transition in lubricated sliding of alumin a observed by Cho et al. The implications of this model are discussed.