ASPERITY-ASPERITY FRICTION AS MEASURED BY A 2-BALL COLLISION APPARATUS

Wear of materials is controlled by the contact mechanics and the respo nse of material to stresses as influenced by the interfacial temperatu res. The contact mechanics describes the geometry and the way that asp erity-to-asperity collision takes place, It also describes the stresse s imposed by the asperities under sliding motion. Since the asperities are of uneven height, the stresses imposed by different pairs of aspe rities necessarily are unequal. When two surfaces come together, there is a distribution of the contact stresses. Therefore, in a wear exper iment, the authors measure friction by measuring the cumulative averag e of the frictional force at a particular moment, and the authors meas ure wear by measuring the cumulative sum of all the material removed b y the collision process over the duration of the experiment. The indiv idual asperity pair contact mechanics is important in the authors' und erstanding of the wear process. Critical data such as asperity frictio n when a single wear event takes place is lacking. The deformation pro cess of a single asperity pair under sliding motion is crucial in our effort to predict wear.This paper describes the design and constructio n of a two-ball asperity collision simulator and presents the data on asperity friction associated with a single wear event.