Fretting Fatigue Modeling and Life Prediction

The US Navy is working towards providing more reliable estimates of fatigue life to reduce the risk of component failure during flight and to improve repair schedules while reducing costs. Fretting fatigue is seen as one of the controlling factors in the life of aircraft engine components where cyclic loading leads to contact and slip between mating parts. For instance, the disk/blade assemblies in turbine engines suffer fretting at the dovetail contacts. In the proposed analysis methodology, an analytical model of fretting fatigue crack nucleation based on the uncracked stresses in the contact region provides the component life up to the point of a measurable crack. A finite-element-based approach to model the discrete, arbitrary, 3D crack growth from the measurable, initial crack to the point of failure provides a stress intensity factor history and remaining life estimate. The marriage of the two approaches provides a cradle-to-grave analysis capability for modeling fretting fatigue. Fracture Analysis Consultants Inc. (FAC) along with Research Applications Inc. (RAI), in consultation with Pratt & Whitney, intend to develop and validate such a methodology starting from RAI’s analytical model of fretting fatigue crack nucleation and FAC’s finite-element-based fracture analysis software, Franc3D/NG.