Fretting Fatigue Behavior and Contact Load Evolution in Commercially Pure Titanium

The process known as fretting fatigue occurs at the contact surface between two components pressed together by a static load and is related to the simultaneous occurrence of wear, corrosion and fatigue damage. A small-amplitude oscillatory movement leads to friction stresses and surface wear. The oxidation of small fragments of metal (in normal atmospheric conditions) produces oxide debris. A cyclic external load applied to one or both the components gives rise to the early initiation of fatigue cracks. In this paper, the fretting fatigue behavior of commercially pure titanium flat samples (1.5 mm thick) is evaluated. In order to carry out the experimental work, a fretting device composed by a frame, load cell and screw-mounted fretting pads was built and mounted in a servo-hydraulic testing machine. The fatigue tests were conducted under load control and stress ratio R = 0.1 for the following values of initial contact load applied to the fretting pads: 100, 300, 500 and 900 N. Additional test were performed: i)using a Teflon ® fretting pad and ii) in argon atmosphere. The contact load evolution was recorded during the tests. The fretting scars were analyzed via scanning electron microscopy. The fatigue life was modeled by the two-parameter Weibull distribution. The results were evaluated in terms of the influence of the fretting phenomenon on the fatigue life of the material, as well as the effects of fretting conditions on the contact load evolution and wear debris formation