Experimental characterisation and numerical simulation of contact evolution effect on fretting crack nucleation for Ti–6Al–4V

Contact evolution effects during fretting can be divided into two categories, namely, change of contact geometry due to wear and near-surface damage. In this paper a study on the effect of contact evolution on fretting crack nucleation in Ti–6Al–4V is carried out, based on a cylinder-on-flat contact fretting wear configuration. The fretted surfaces are carefully profiled so that the evolution of the contact geometry around fretting-induced cracks is identified. The evolution of the near-surface microstructure is identified by scanning electron microscopy. According to the experimental results, a predictive framework is presented to capture the competition and interaction between the contact evolution and crack initiation. The modelling of fretting wear is central to this approach, since it predicts not only the extent of wear damage, but also the concomitant change in fatigue pertinent stresses. The analysis of fretting wear tests, including partial slip and gross sliding conditions, without the substrate fatigue loading of fretting fatigue tests, provides an opportunity to investigate the crack initiation and thus validate predictions. A multi-axial fatigue damage parameter is employed within a cumulative fatigue-damage methodology to predict the wear-induced crack nucleation behaviour under different slip regimes.