3D-printing for Aerospace : Fatigue Behaviour of Additively Manufactured Titanium

Abstract: Laser powder bed fusion (L-PBF) and electron beam powder bed fusion (E-PBF) are two of the most common additive manufacturing (AM) methods which both provide the engineer with a great freedom of design.This means that parts with light weight, multifunctional applications and improved performance could be achieved through innovative design solutions which have attracted a lot of interest from the aerospace industry.This PhD project has focused on the following fatigue related areas forL-PBF and E-PBF Ti6Al4V material which all need to be addressed before AM can be fully introduced to critical aerospace applications: effect of geometry, roughness and loading on fatigue life, improved fatigue life through post processing, fatigue crack growth behaviour and fatigue prediction methods.The results show that the rough as-built surface is the single most severe factor for fatigue but that the fatigue strength of at least L-PBF material can be improved to levels similar to conventionally manufactured material using surface post processing. Furthermore, the results verify that acumulative damage approach gives good accuracy in predicting fatigue life for variable amplitude loading and that fatigue crack growth rates using material data from standard specimens can be used for damage tolerancean alysis independent of part geometry and stress level.The conclusion is therefore that the fatigue properties can be improved to acceptable levels and predicted using conventional methods. There are still some challenges to solve, however, especially within non-destructive testing before AM can be introduced to critical aerospace applications.