On the use of the Theory of Critical Distances and the Modified Wohler Curve Method to estimate fretting fatigue strength of cylindrical contacts

This paper summarises an attempt to propose a methodology suitable for estimating high-cycle fatigue strength of cylindrical contacts under a partial slip regime. In particular, Taylor's point method, usually applied to predict fatigue limits of notched components, was used in conjunction with the Modified Wohler Curve Method allowing us to formulate a novel fretting fatigue prediction methodology. The devised procedure takes as its starting point the idea that to correctly estimate fatigue damage under fretting fatigue two different aspects must be taken into account: stress gradients and degree of multiaxiality of the stress field damaging the fatigue process zone. The first problem was addressed by using the Theory of Critical Distances, whereas the latter by using an appropriate multiaxial fatigue criterion. In order to check the accuracy of the proposed methodology, a number of tests on cylindrical contacts were selected from the technical literature for two high strength alloys commonly used in the aerospace industry, namely Al4%Cu and Ti-6Al-4V. The performed analyses showed a sound agreement between estimations and experimental data. In particular, the proposed method correctly predicted failures in the medium-cycle fatigue regime, allowing the high-cycle fatigue estimations to fall within an error interval of about +/- 20%. This result is very interesting, especially by the light of the fact that such an approach is based on the use of linear-elastic stresses, making it suitable for being used in situations of practical interest by post-processing linear-elastic finite element results. (c) 2006 Elsevier Ltd. All rights reserved.