Fretting fatigue is a potential risk for serious and unexpected damage in modern machine components. A test device has been developed for evaluating fretting fatigue and wear in complete and almost complete contacts with asymptotic edge effects. The device developed also allows plain fatigue testing. The fretting loading can be fully reversing or may fluctuate and it can be adjusted continuously. Macroscopic crack nucleation and growth are followed using strain gauge measurements. A series of fretting fatigue tests and a reference series of plain fatigue tests were carried out with EN 10083-1-34CrNiMo6 þ QT steel. The fatigue life in the fretting series with a sharp, flat-ended pad was notably lower compared to the plain fatigue life, resulting in a strength reduction factor of 3.
Fretting is a consequence of small relative oscillatory movement between contacting parts and can cause serious damage to machine components. This paper describes the implementation of digital image correlation method to a fretting test device to measure the relative movement, i.e. slip, between the contacting parts. A complete contact fretting test device is used, in which two flat fretting pads are clamped against a cyclically loaded flat fretting specimen. The material used is quenched and tempered steel. Digital image correlation, equipped with a microscope, is employed to measure the local displacement field at the contact edge. The micrometer-level slip amplitude and the length of the slip region are determined at specific time intervals during a fretting fatigue test. Both of these quantities appear to decrease and stabilize during fretting fatigue testing. The slip decreases markedly during the initial cycles.
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