A note on computing the growth of small cracks in AM Ti-6Al-4V

The certification requirements for additively manufactured (AM) replacement parts requires the ability to predict the growth of small sub mm cracks. To this end, it is shown that the Hartman-Schijve crack growth equation proposed in a prior paper for the growth of small cracks in AM Ti-6Al-4V manufactured specimens also accurately predicts the growth of small cracks in Laser Beam Powder Bed Fusion (LB-PBF) manufactured Ti-6Al-4V specimens. The specimens studied are built with two different LB-PBF machines with different processing parameters. Particular attention is given to the growth of crack from initial sizes that are of the same order of magnitude as the minimum equivalent initial damage size (EIDS) in the US Air Force (USAF) approach to the certification of an AM replacement part.