Length Scale Considerations in the Formation of Attachment Fatigue Cracks

Abstract

Abstract : Fretting fatigue is often the root cause of nucleation of high cycle fatigue (HCF) cracks in clamped components. Fretting fatigue damage accumulation occurs within depths of only a few grains at the interface between contacting components. Therefore, more accurate assumptions concerning length scale, damage volume, and material models are needed to establish a more solid physical foundation underlying fretting fatigue life prediction methods. In particular, the influence of crystallographic orientation distribution on the plastic deformation field is significant, as is size of grains or second phases. In this program, 2D and first generation 3D crystal plasticity models are developed for Ti alloys and used to simulate the fretting process. Experimental observations of fretting fatigue crack formation reinforces the results of predictions obtained using computational crystal plasticity models in fretting simulations. New experimental observations are reported regarding the evolution of crystallographic orientation, microhardness, composition, and grain size on duplex Ti-6AI-4V specimens subjected to a range of fretting loading conditions, over a range of cycles.