PSI - Issue 19

Kai Schnabel et al. / Procedia Structural Integrity 19 (2019) 442–451 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Figure 4 Dependency of the highly stressed volume HBV, left: on the notch radius; right: on the notch opening angle

4. Fatigue assessment of the nominal and received ‘as - built’ geometries A fatigue assessment is based on assessment concepts. These are mostly based on a wide range of experimental data. This wide range of data is necessary to be able to consider all relevant influencing factors that lead to a change in fatigue life. In case of additively manufactured metallic components, this database has not yet been created. In addition, it is currently not conclusively clarified, which manufacturing parameters and factors has to be logged for the database and need to be considered in a fatigue assessment. Literature data shows that mainly the surface roughness, defects like pores and lack of fusion, all including not melted particles, are responsible for shortening the fatigue life, [ (Scurria, et al. 2019), (Siddique, et al. 2015), (Konecna, et al. 2017), (Bagehorn, Wehr und Maier 2017)]. These defects can be amplified by residual stresses and the local stress-strain behavior as a result of different microstructures, which are also responsible for an anisotropic stress-strain behavior, (Blinn, et al. 2018). As long as there are no guidelines available, which can take these fatigue life relevant factors in the design phase of AM components appropriately into account, guidelines for classical manufactured components have to be proven for their accuracy in the assessment of additively manufactured structures. In Germany, one of the guidelines for the fatigue assessment of mechanical engineering components is the FKM guideline “Analytical strength assessment of components” (Rennert, et al. 2013), which was introduced for the assessment of steel, cast iron and aluminum materials. The underlying database does not include AM specimen and components, thus a reliable fatigue life assessment is therefore not necessarily to be expected. However, the application of the assessment algorithm could be justified, if additive manufactured aluminum components behave like casted or wrought aluminum alloys. The difference between the nominal geometry, which is the input for the manufacturing process and the manufactured specimen, is assessed using the FKM guideline and the results are compared with the received ‘ as-built ’ specimens. Because the fatigue assessment of the FKM guideline is based on the tensile strength R m , tensile tests on nine stress relieve heat treated AlSi10Mg specimens built orthogonal to the building platform without support structure have been performed and evaluated, Figure 5. The tensile strength is determined to the average value of = 360 and used for further investigation.