Experimental and numerical analysis of local and global plastic behaviour in fretting wear
Résumé
Fretting wear tests with a cylinder/plate contact geometry and the titanium alloy Ti6Al4V are conducted. After up to 1000 cycles the specimens are analysed by SE microscopy and 2D profilometry. A corresponding FE computation is developed whereby an emphasis is laid on a faithfull material description. A classical material model for cyclic plasticity and a more refined model which is capable of describing strain ratchetting are comparatively used in computations. A comparison of experimental and computational results reveals the subordinate importance of more refined material models in FE modelling of fretting wear tests in the gross slip regime. The fretting tests and an FE computation with the contact morphology of the 100th cycle allow nevertheless to shed some light into the mechanisms that cause the evolution of the experimental fretting log. The FE computations reveal the susceptibility of fretting contacts to strain ratchetting. It is shown that ratchetting leads to stress redistribution, geometry change and the formation of residual stress fields. The refined material model is consequently proposed for lifetime prediction in the fretting fatigue regime in partial slip. For this the Dang Van high cycle fatigue parameter should be computed after shakedown of strain ratchetting.