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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e.g. reduced Y OUNG ’ S moduli. This second mode is intended for FE modelled AM components in a calculation with locally ‘ smeared ’ material parameters. For regions with very similar above mentioned properties, the same structural element should be used. Depending on the needed accuracy, a different number of structural elements can be pre-calculated with the finite element method on simple local models in the first mode and used in the complex FE model in the second mode. The result is a toolbox of different structural elements, which can be divided in three different orders of structural elements (SE), Table 2. Depending on the order of the structural element, more than one microstructure can be included, because of the presence of different process parameters in different areas of one AM component.

Table 2 Description of the order of structural elements

Derivability of parameters for the stress-strain behavior or fatigue strength of the structural element Specimen of simple microstructure and free of defects, which is difficult to prepare, because of rare defect free area Prepared specimen including defects, e.g. with removed contour area

Schematic example

Description of the structural element

Figure 7 left

First order SE

Imperfection free, one single microstructure

Second order SE Third order SE

Including imperfections, but one single microstructure Including imperfection with more than one microstructure, e.g. one from the core material and one from the contour material

Figure 7 center

As-built specimen (netshape)

Figure 7 right

In particular, inside this toolbox, structural elements can represent all defects which will rise in AM structures like pores or rough surfaces or a combination of both. All structural elements are pre-calculated and include the above mentioned information. A FE representation of an AM component contains different structural elements, depending on the knowledge about the inner structure. The more information are available, the more accurate the results can be calculated. The toolbox can be reused for other models and only an allocation of the different structural elements has to be done.

Figure 7 Schematic images of structural elements, left: first order, center: second order, right: third order

6. Conclusion

Additively manufactured components need to be assessed in terms of fatigue strength, because they are on their way into safety relevant applications e.g. in the automotive and aviation industry. Process defects and imperfections like pores, lack of fusion or very rough surfaces, originated from support structures, are unavoidable. Reliable assessment