Four actuators fretting fatigue rig and tests with cyclic normal load for Ti-6Al-4V

Abstract

In the present paper, a new four actuators fretting fatigue rig is presented. This machine is capable of performing tests at high or room temperature. Further, it is possible to independently control all the loads involved in the fretting tests (bulk, normal and tangential loads) in a static and cyclic way. In order to evaluate the influence of cyclic normal load on the fretting case, a new set of fretting fatigue and coefficient of friction tests were carried out for the Ti-6Al-4V alloy. Also, a finite element model (considering and neglecting wear) was used in conjunction with a critical plane parameter (SWT) and a non-local stress averaging approach to estimate fretting life. The experimental results have shown that cyclic normal load has a beneficial effect on fretting life compared with those under constant normal load. Further, no significant difference was noticed for the coefficient of friction measured under static and cyclic normal load conditions. Concerning the life estimate approaches considered in this work, for the constant normal load case, both implemented methodologies, whether accounting or neglecting wear, provided satisfactory results, with the former being slightly more accurate. However, life estimates were more accurate for the cyclic normal load case when disregarding wear.