Formalisation and experimental validation of a novel design methodology to estimate finite lifetime under fretting fatigue loading

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Fretting fatigue refers to the damage occurring at contact area between two materials and is associated with the simultaneous action of a small oscillatory motion and a remote cyclic force. In metallic materials undergoing in-service time-variable loading, given the features of the nominal load history, fretting leads to an increase of fatigue damage as compared with that in the absence of fretting. Fretting fatigue is always a matter of concern to structural engineers since it can remarkably reduce the in-service lifetime of important structural parts such as, for instance, threaded pipe connections, bladedisk attachments in gas/steam turbines, and aero-engine splined couplings. By making use of the "notch analogue" concept, the aim of this research is to formalise and validate a novel methodology specifically devised to estimate lifetime under variable amplitude (VA) fretting fatigue by directly assessing the local linear-elastic multiaxial stress fields damaging the materialin the vicinity of the contact region.