In metal additive manufacturing, process-induced defects are a prime source of failure under cyclic loading at the present time. In this work, X-ray Computed Tomography was used to characterise the defect population inside the gauge volume of near-net shape manufactured dog-bone samples. The result further corroborates that crack initiating defects are at the lower tail of a positive-skewed size distribution, but not necessarily correspond to the largest defect. Contrary to common assumption, defects were not randomly located, but a clear tendency towards the free surface was observed. Then, from these surface defects, fatigue crack growth rates were measured using the replica technique. Although measured cracks were relatively small, e.g. below 1 mm, a similitude to long crack growth rates was demonstrated, when pore size was added to measured crack lengths. Finally, the crack initiation life from porosity was observed to be at least 50% of the total fatigue life based on the first detectable surface crack on the replica. This should be taken into consideration when using fracture mechanics for fatigue life prediction in presence of defects, where it is common to assume crack initiation from the very first cycle.
Bibliographical noteNOTICE: this is the author’s version of a work that was accepted for publication in Engineering Fracture Mechanics. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Engineering Fracture Mechanics, 259 (2017)
© 2021, Elsevier. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/
- Additive manufacturing
ASJC Scopus subject areas
- Materials Science(all)
- Mechanics of Materials
- Mechanical Engineering