Probabilistic reliability assessment of a component in the presence of internal defects

Abstract

Structural strength may degrade during the service life of an aircraft due to undetected material defects or accidental damages. Additively manufactured or welded structures are particularly susceptible to fatigue cracking due to stress concentration at the surface and internal material defects. Despite significant benefits provided by the laser-based manufacturing techniques, there is still a lack of understanding how these parts fail under cyclic loading. This study aims to investigate the effect of internal material defects on the high cycle fatigue (HCF) behaviour of Ti-6Al-4V. It is shown that internal fish-eye fatigue fracture is a dominant failure mode if a subsequent surface treatment technique is applied. A probabilistic lifetime assessment framework for predicting the joint durability and its scatter in the HCF regime is developed. A good agreement between the modelling results and experiments is demonstrated.