Stress distribution and crack initiation for an elastic contact including friction

In a contact between a spherical indenter and the plane surface of a brittle solid, experimental studies show that circular cracks emanate outside the edge of the contact region, not at the contact edge as expected from the Hertz solution. In this paper different levels of approximation where friction is accounted for, are compared with the solution of the fully coupled contact problem. In particular, the maximum tensile principal stress and its location are computed. The location of the calculated maximum stress is compared with the radius of the ring crack found in indentation tests. It is shown that an uncoupled analysis with a stick and a slip zone gives accurate results for most practical material combinations. The coefficient of friction is experimentally measured by use of a leaning plane. Comparisons are made with experiments performed on ceramics and glass, which show that the use of the measured coefficients of friction will predict a smaller crack initiation radius than those found from experiments. Copyright 0 1996 Elsevier Science Ltd