PARTICLE BEHAVIOR IN 2-PHASED LUBRICATION

Emulsions and slurries are commonly encountered in tribology problems. The dispersed phase in the mixture plays an important role in lubrica tion or wear, but the mechanisms of particle capture by two surfaces h ave never been well understood, While no similar models have been prop osed for slurries, emulsions researchers have attributed lubrication m echanisms to a 'plate out' theory through which oil separates from the emulsion and coats the exposed metal surfaces, Observations of partic le behavior by Nakahara et al. (ASME J. Tribol., 110 (1988) 344-353) c ast doubt on this theory; particles very close to the tooling were rej ected and played no part in the lubrication process. Further, the beha vior of a particle depended greatly on its size, This paper offers a p otential explanation for this behavior through a computational fluid d ynamics model of a rigid particle in an inlet zone. A particle in such a flow field is found to cross streamlines to an equilibrium position a certain distance from the tooling or workpiece. This segregation lo cation is related to the particle size with the same trends of particl e penetration as observed by Nakahara et al. The theory applies to emu lsion lubrication, slurry lubrication and wear involving solid particl es suspended in a liquid. (C) 1997 Elsevier Science S.A.