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 for L-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 a cumulative 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 tolerance analysis 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.

Design and Qualification of an Additively Manufactured Manifold for Aircraft Landing Gears Applications

“…The life assessment of AM fatigue-critical aerospace parts has been addressed in [47]: Finite Element Analyses (FEA) results were used in the iterative design process to determine the life of a typical aerospace joint in titanium Ti-6Al-4V under cyclic loadings. The same alloy was analysed in [48] to achieve sufficient confidence and knowledge for predicting fatigue life and crack growth propagations. Airbus investigated the feasibility of replicating critical structural joints in titanium [49,50].…”

Wire arc additive manufacturing of aluminium alloys for aerospace and automotive applications: A review

“…High cycle fatigue is regarded as one of the major causes of turbine failures in military aircraft [45]. To avoid mechanical failure in an aeroengine, it is crucial to investigate the effect of fatigue crack initiation (FCI) and short crack growth (SCG) in the aeroengine spare parts produced with the use of additively manufactured aluminium alloys materials [118]. In WAAM techniques, process parameters (such as voltage, wire feed speed, current, inter-pass temperature, and shielding gas flow), material composition, environmental conditions (such as gas contamination) [77], and many other factors can significantly influence oxidation effects.…”