AN INVESTIGATION INTO THE MECHANISMS OF CLOSED 3-BODY ABRASIVE WEAR

Contacting components frequently fail by abrasion caused by solid cont aminants in the lubricant. This process can be classified as a closed three-body abrasive wear process. The mechanisms by which trapped part icles cause material removal are not fully understood. This paper desc ribes tests using model elastohydrodynamic contacts to study these mec hanisms. An optical elastohydrodynamic lubrication rig has been used t o study the deformation and fracture of ductile and brittle lubricant- borne debris. A ball-on-disk machine was used to study the behaviour o f the particles in partially sliding contacts. Small diamond particles were used as abrasives since these were thought not to break down in the contact; wear could then be directly related to particles of a kno wn size. The particles were found to embed in the softer surface and t o scratch the harder. The mass of material worn from the ball surface was approximately proportional to the particle sliding distance and ab rasive concentration. Small particles tumbled through the contact, whi lst larger particles ploughed. Mass loss was found to increase with ab rasive particle size. Individual abrasion scratches have been measured and related to the abrading particle. A simple model of the abrasive process has been developed and compared with experimental data. The di screpancies are thought to be the result of the uncertainty about the entrainment of particles into the contact.