Advanced characterization techniques for fatigue life estimation of additively manufactured metal samples and complex geometriesTuesday (26.05.2020) 14:50 - 15:10
Additive manufacturing (AM) is an indispensable element for manufacturing of future light-weight and resource-saving components which are increasingly important for aerospace and energy applications. However, due to the high variability in AM techniques as well as corresponding process parameters many different material conditions can be created. Additionally, size and amount of specimens often limit a comprehensive scope of testing. Therefore, new characterization techniques have to be established in order to time-efficiently determine the cyclic material behavior of AM metals based on a small amount of samples.
Within this work, different specimens manufactured by laser (L-PBF) and electron beam powder bed fusion (E-PBF) were investigated. In particular, L-PBF manufactured steel 316L and E-PBF manufactured Inconel 718 were present as conventional specimens or as complex structures, respectively. As only a limited amount of samples was available, so-called multiple amplitude tests (MAT) on a servohydraulic testing system were conducted to estimate the fatigue behavior and strength of the investigated Fe and Ni alloys. Supplementary, mechanical, thermometric, electric and acoustic measurement techniques were introduced to detect specific material reactions. Based on this, it can be demonstrated that damage development leads to characteristic material reactions which were reliably detected by the aforementioned measurement techniques. In particular, thermometric and electric measurement techniques are highly recommended, since change in temperature or electrical resistance are sensitive for damage evolution, showing that continuous monitoring is applicable for AM samples and structures. Further on, first material reaction in MAT can be used to estimate the fatigue behavior time- and cost-efficiently, so that the influence of different process parameters or material conditions can be characterized in a reliable manner.