3. Nature of micro-contacts and wear patterns

Under mixed or boundary lubrication and in dry contact, the parts are only in contact over an area A _r smaller than the nominal, or apparent, contact area A. The actual contact pressures p _r are therefore considerably higher than the macroscopic pressure p, and we therefore need to consider the nature of the deformations of the micro-contacts which condition p _r and the wear mechanisms: a microelastic regime is likely to limit damage and wear.