Elastic-Plastic Spherical Contact Under Combined Normal and Tangential Loading

The behavior of an elastic-plastic contact of a deformable sphere and a rigid flat under combined normal and tangential loading with full stick contact condition is investigated theoretically. This allows static friction modeling under highly adhesive conditions. Combined loading begins with a normal preload that produces an initial contact area and causes elastic or elastic-plastic deformations in the contact zone. The full stick contact condition leads to a junction between the contacting bodies which can bear tangential loading. On the second stage of the loading process, the tangential load is being applied gradually, while the normal load remains constant. The maximum tangential load that can be supported by the junction prior to sliding inception is determined as the static friction. The effect of normal load on this static friction is investigated. The evolution of the contact area during the tangential loading revealed an essential “junction growth” mainly just before sliding inception.