FRETTING FATIGUE PROBLEMS ASSOCIATED WITH ALMOST FLAT CONTACTS M.Ciavarella1, G.Demelio1 and D.A.Hills2

ABSTRACT: A fretting fatigue pad is simulated as a flat punch having rounded corners. The contact problem is solved under conditions of normal loading and a shearing force, less than that necessary to cause full sliding. Further, the interior stress state induced is found, and it is shown that, unless the corner radius becomes vanishingly mall, the stress field in the region of the pad corners is well defined. A crack is then inserted in the region of high tension, and a solution for the crack-tip stress intensity factor found, using the method of distributed dislocations. Thus, a complete solution in mechanics is generated for a nominally flat pad, most often used in fretting fatigue experiments, but having a slightly modified geometry. Finally, issues regarding design against fretting fatigue are discussed: it is concluded that the use of this geometry is generally highly recommended, as a optimum between the Hertzian, and the limit flat geometries. This advantage was not evident from a stress field analysis