A Fatigue Life Approach for Additively Manufactured Structures

The relevance of the additive manufacturing technology is steadily growing, especially for metallic structures. In order to exploit the lightweight design potential for cyclically loaded safety parts in industrial applications, tools and methods are required to describe the fatigue behavior and the impact of the different exposure strategies on the cyclic properties as well as on the endurance. Furthermore, a fatigue approach has to secure the transfer of the cyclic behavior derived by the use of specimens to arbitrary structures and loading conditions. Therefore, the nominal stress concept and the local strain-based notch concept will be reviewed in order to check their applicability for additively manufactured structures. At the end, a modified fatigue approach, which takes into account the main influences on the fatigue and fulfills the industrial requirements with respect to an optimized computation time and validity of the fatigue approach, will be derived. The use of the Incremental Step Test to derive the cyclic stress-strain behavior and the Fatigue Life Curve enables to consider the influence of the load time histories at different maximum stress amplitudes, as well as a continuous fatigue approach from the Low Cycle Fatigue up to the Very High Cycle Fatigue regime.