Paper: The Influence of Porosity on Fatigue Crack Initiation in Additively Manufactured (AM) Titanium Components

Publication: Scientific Reports

Authors: Sam Tammas-Williams, Postdoctoral Research Associate at MAPP, Philip Withers, MAPP Investigator, Iain Todd, MAPP Director, and Philip Prangnell, MAPP Investigator. 

Impact:  Fatigue life is a mechanical and scientific term that relates to how long an object or material will last before failing because of concentrated stresses. There are a number of different factors that can influence fatigue life including the type of material being used, its structure, its shape and temperature changes.

This paper shows a way fatigue life improvement may be achieved when using electron beam melting (EBM). 

Summary: The paper demonstrates the use of a new time-lapse x-ray computed tomography (CT) method to improve the understanding of the effect of pores on the fatigue life of components made using EBM by tracking fatigue crack initiation and growth in 3D. 

Effect of pore size on fatigue life - Effect of pore size on fatigue life - S-N curve showing only those samples that failed from porosity for samples tested in the z-direction

It confirms that the fatigue lives of samples manufactured by EBM are strongly influenced by the presence of retained porosity, with fatigue life proportional to pore size. A ranking technique is developed to predict which pores are the most detrimental to fatigue life. The analysis shows fatigue life improvement may be achieved by minor adjustment to the manufacturing process to avoid defects appearing in critical locations. 

Click  here to view the paper.