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The effect of asperity flattening of a rough spherical contact during cyclic loading is investigated experimentally. Two types of surfaces are examined; the first is an “as-manufactured” isotropic surface and the second a smooth “laser-polished” surface. Both the surfaces exhibit a large amount of hysteresis of the load–displacement curve during the first load–unload cycles. This hysteresis is found to decrease as a function of the number of load cycles. A comparison of the experimental results with results obtained from a numerical model for a rough spherical contact shows good correlation. The model shows that for rough surfaces the total displacement is a function of the contacting asperities while for smooth surfaces the main contribution comes from the bulk displacement.

A finite-element analysis was used to investigate the elastic contact of a bilayered coated sphere compressed by a rigid flat, under the normal loading and “slip” contact condition. A bilayered coating consisting of a hard outer layer and a soft interlayer relative to the substrate was studied. An electrical analysis was performed on the deformed coated sphere to investigate the effect of the thickness of both the hard and soft coatings and their material properties on the electrical contact resistance (ECR). It was found that for any given load, under fully elastic contact, proper material and thickness of the soft interlayer can increase the contact area by up to 35% and reduce the electrical resistance by up to 75%, compared to a reference case without the soft interlayer. Increasing the outer hard coating thickness increases the ECR. The increase in the contact area was found to have a secondary effect on the reduction of the contact resistance compared to the effect of the material’s conductivity. [ABSTRACT FROM AUTHOR]

The Cattaneo--Mindlin concept of interfacial slip in tangentially loaded compliant bodies is revisited and its basic simplifying assumptions are critically examined. It is shown that these assumptions, which, in the absence of modern numerical techniques, were essential in 1949 to enable an elegant quantitative solution of the basic problem of presliding between contacting bodies, may be nonphysical. An alternative approach to the same problem that is based on treating sliding inception as a failure mode involving material plastic yield is discussed. This alternative approach was suggested even before 1949 but for the same lack of modern numerical techniques could only be promoted qualitatively. Some recent theoretical models, which are based on this earlier alternative approach, and in which the simplifying assumptions of the Cattaneo--Mindlin concept were completely relaxed, are described along with their experimental verification. It is shown that the presliding problem between contacting bodies can be accurately solved by these models using realistic physical assumptions and failure criterion. [ABSTRACT FROM AUTHOR]

A finite element (FE) model is presented for the evolution of fracture and friction in elastic-plastic adhesive spherical contact. The model is based on a realistic criterion of ductile fracture in a three-dimensional contact problem and the failed elements are deleted. Full stick contact condition is used at the contact interface to model a strong adhesion there. Fracture evolution is presented allowing the process of material removal in the form of a wear particle. The evolution of friction with increasing tangential loading as well as sliding inception are presented. Predicted wear coefficient and static and dynamic friction coefficients are compared with experimental results and possible reasons for discrepancies between the predicted and experimental results are discussed. • Adhesive wear and friction of three-dimensional spherical contact is studied. • A finite element model based on ductile fracture with element deletion is applied. • Volume of wear particle and static and dynamic friction coefficients are presented. • Model results are compared with published experimental results in the literature. [ABSTRACT FROM AUTHOR]