Investigating fretting fatigue response of additively manufactured Ti-6Al-4V in dovetail joint connections

Abstract

Fretting generates surface damage at the contact interface of components under pressure subjected to small-magnitude, relative oscillatory motion. In the presence of bulk cyclic loading, fretting fatigue occurs, significantly reducing the lifetime of affected components, such as the dovetail joint connections in turbine blades. In this research, the fretting fatigue response of additively manufactured (AM) Ti-6Al-4V parts was studied, focusing on the dovetail geometry. A specialized test setup was developed to evaluate the resistance of the AM material to fretting fatigue conditions and compare its response to its conventionally manufactured counterpart. In parallel, a finite element (FE) model of the testing apparatus was created to provide deeper insights into the stress distribution at the contact interface. Results of the numerical simulations revealed that the most damaging mode of fretting fatigue, known as stick–slip, was achieved, closely resembling the conditions often observed in real-life industrial assemblies. The experimental results demonstrate that the tribomechanical fretting fatigue response of AM-Ti64 aligns with that of the conventionally manufactured material. While AM-Ti64 exhibits better crack propagation resistance, it is more prone to fretting damage. However, the AM material is hindered by near-surface internal defects, such as lack-of-fusion-induced voids and porosities, which form during the manufacturing process. These defects act as stress concentrators, leading to early failures outside the contact zone.