FINITE-ELEMENT ANALYSIS OF FRETTING STRESSES

Clamped contacts subjected to vibratory loading undergo cyclic relativ e tangential motion or micro-slip near the edges of contact. This cycl ic micro-slip, known as fretting, leads to removal of material through a mechanism known as fretting wear and formation and growth of cracks through a mechanism known as fretting fatigue. In aircraft, fretting fatigue occurs at the rivet/hole interface leading to multisite damage which is a potential failure mechanism for aging aircraft. A finite e lement model of a current fretting fatigue experiment aimed at charact erizing fretting in riveted joints is detailed. A non-symmetric bulk t ension is applied to the specimen in addition to the loads transferred from the fretting pad. The model is verified through comparison to th e Mindlin solution for a reduced loading configuration, in which the b ulk tension is not applied. Results from the model with the bulk tensi on show that the distribution of micro-slip in the contact is not symm etric and that for some loads reversed micro-slip occurs. Finite eleme nt results are given for the effects that four different sets of loadi ng parameters have on the maximum tensile stress induced by fretting a t the trailing edge of contact It cart be shown using multiaxial fatig ue theory that this stress controls fretting fatigue crack formation. This maximum tensile stress is compared to that of the Mindlin solutio n for a symmetric distribution of micro-slip. This stress is also comp ared to that of a variation based on the Mindlin solution for the case s with a non-symmetric distribution of micro-slip. It is concluded tha t the solution based on the Mindlin variation and the fill finite elem ent solution lead to similar predictions of the maximum tensile stress , even when the shear traction solutions differ significantly.