High-load fretting of Ti–6Al–4V interfaces in point contact

Abstract

The aim of this study is to characterize the baseline fretting behavior of Ti–6Al–4V on Ti–6Al–4V in point contact at relatively high pressure. The effect of the displacement amplitude on fretting damage is investigated. Two normal forces of 586 and 1485 N corresponding to 1.4 and 3.5, respectively, of the force for subsurface yield based on von Mises criterion are considered. Experiments are conducted at both room temperature and 260 °C. The range in displacement amplitudes span the partial slip, mixed fretting, and gross-slip regimes. The relationship between the displacement amplitude and the tangential force amplitude is determined by two methods: (1) a conventional constant displacement method using multiple specimens and (2) an incremental displacement method using a single specimen. Both methods give the same transition amplitude that separates partial and gross-slip conditions. However, the measured coefficient of friction for the latter method is greater. Surface cracks are observed when the displacement amplitude is near the transition between partial and gross slip. Significant fretting wear occurs in the gross-slip regime. The measured coefficient of friction under high-load fretting is independent of the normal load and is comparable the value measured in lightly loaded dry fretting contacts.