A rapid testing method for fatigue in metal additive manufacturing

Additive manufacturing (AM) technologies allow for achieving the objectives of lightweight designs with increased integrated functionality. They have the potential to reduce material waste and allow for a flexible geometric design. AM enables a faster development cycle, because the elimination of expensive tooling makes it possible to shorten the time between design, production, and testing. These advantages make AM especially interesting for applications in the aircraft industry. The layer by-layer production from powder results in the mechanical properties being generated only during the manufacturing process, causing the long-term behaviour of AM components to be not fully understood yet. Fatigue testing is one approach to achieve a better understanding, and therefore broader acceptance, for AM as a production technology. Since conventional fatigue testing methods are time consuming and additionally require a lot of material for specimen production, it is desirable to implement new testing methods for AM parts. Therefore, it was investigated whether a LUMiFrac centrifuge, which is usually used to determine the strength of adhesive bonds, can be utilized for testing the fatigue and tensile strength of AlSi7Mg0.6specimens, manufactured by laser beam melting (LBM).An adapted specimen geometry, considering the requirements made by the centrifuge and taking the specific characteristics of the AM process into account, was developed for this purpose. Testing of the specimen geometry with different surface modifications verified that it allows for testing material properties. It was shown that the centrifuge tensile testing method is suitable for determining the tensile strength of the developed specimens, because it delivers similar results as conventional tensile testing. Additionally, it has been successfully demonstrated that a specimen can be brought to failure in the centrifuge by dynamic tension-tension loading.