Workflow for fatigue life prediction of additive manufactured complex designs from powder bed fusion of Ti–6Al–4V

Abstract

Accurate fatigue life predictions of metal additive manufactured components are critical for design optimization and to leverage the advantages provided by additive manufacturing technology. As compared to conventional manufacturing processes, additive manufactured components have poor surface roughness and more internal porosities. Hot isostatic pressing has been shown to reduce porosities significantly whereas, surface improvement is not possible due to inaccessibility to the interior surfaces of complex shaped components. In the past, the fatigue prediction in presence of such surface defects has been explored using qualitative method such as ranking and quantitative method such as endurance limit prediction. A few fracture-based crack growth methods have been shown to validate with test for uniaxial coupon tests. The application of such methods for a complex shaped component with continuous variation of stress and roughness has not been explored. In this article, fatigue life prediction of thin-walled tubes manufactured using powder bed fusion of Ti–6Al–4V is documented. The Hartman-Schijve and Generalized Paris law equations are used with statistical variations of stress and surface roughness to predict the most probable life. The study shows a good correlation with physical test data. A detailed workflow for the process of fatigue life prediction is created.