Running-in of metallic surfaces in the boundary lubrication regime

During the running-in of surfaces a change in roughness takes place. The presented model predicts this change for concentrated contacts using an elasto-plastic contact model based on a semi-analytical-method recently developed. Combining this method with a local coefficient of friction, which is determined using a mechanical threshold on the protective nature of the lubricant, and a strain related failure to model the smoothening of surfaces protected by a lubricant, the surface topography can be calculated. Multiple examples using concentrated contacts are simulated using real engineering surfaces and realistic values for the properties of the chemical reaction layer as well as the nano crystalline layer present at and underneath the surface. The results obtained are realistic, indicating the usefulness of the developed method.

► The efficiency of the SAM contact code is increased by adapting the plasticity loop from a strain based to a stress based iteration.
► A soft ductile layer on top of the bulk material has a positive influence on the wear of materials.
► The use of a local coefficient of friction in wear modeling gives better results.
► The use of a plastic threshold for material removal is a realistic one.