Paper 14: Rolling Contact Failure Control through Lubrication

Abstract

Lubrication in rolling contacts serves primarily to control failure and must be engineered for that purpose.Four classes of failure are defined in rolling contact mechanisms: wear (mild wear and smearing, involving metal transfer); plastic flow (cold or due to overheating); fatigue (spalling and surface distress); and bulk failure modes occurring away from the contact areas.Generalized ‘stress fields’ leading to rolling contact failure are defined as mechanical, thermal and (possibly) chemical ‘stresses’. The severity parameters of these stress fields are developed and illustrated by typical relationships based on Hertzian assumptions and are progressively refined through the stepwise inclusion of tractive surface forces, plasticity, elastohydrodynamics, and of effects of surface micro-topography (boundary lubrication) and material inhomogeneities. Effects of lubrication on these severity parameters are identified.Experimental and theoretical findings on the detailed failure mechanism are used to derive failure criteria, including lubrication effects, for each failure mode. Methods are presented on this basis for the control of failures.