Wear

This chapter describes the various mechanisms of wear and types of particles present in wear debris, followed by representative data of wear of materials. Wear includes six principal, quite distinct phenomena that have only one thing in common: the removal of solid material from rubbing surfaces. These are: (1) adhesive; (2) abrasive; (3) fatigue; (4) impact by erosion and percussion; (5) chemical (or corrosive); and (6) electrical-arc-induced wear. Other commonly encountered wear types are fretting and fretting corrosion. Wear process is generally quantified by wear rate. Wear rate is defined as the volume or mass of material removed per unit time or per unit sliding distance. Other forms could be dimensionless, such as the depth of material per unit sliding distance, or the volume removed per apparent area of contact and per unit sliding distance. Polymers, which include plastics and elastomers, generally exhibit very low friction and moderate wear.