FATIGUE WEAR MECHANISM OF ALUMINA, SIMULATED BY SYNCHRONIZED BIAXIAL REPEATED INDENTATIONS

The role of fatigue as a prominent factor in alumina ceramic wear duri ng repeat pass sliding was investigated, a new experimental technique, consisting of synchronized biaxial (normal and tangential) repeated l oading of a sphere on a flat plate, was developed to impose the stress cycling conditions of repeat pass sliding with various equivalent lev els of friction. No large-scale material removal through macro-scale ( greater than apparent contact diameter or many-grain diameter) crack l inkage was observed. Material removal occurred by micro-scale (grain-s ize or smaller) fragmentation in a fatigue mode. Three different wear stages were seen, i.e. asperity-scale fragmentation, loosening of grai n at the crack opening edges, and grain break-out by bridging of the s eries cracks that form at the trailing edge of contact.