PSI - Issue 21

E.F. Akbulut Irmak et al. / Procedia Structural Integrity 21 (2019) 190–197 E. F. Akbulut Irmak et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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Borderline pores are the biggest defects in the specimens and they initiate cracks from the side towards the middle of the specimen, Figure 5.

a c Figure 5. Fracture surface of SLM-produced AlSi10Mg uniaxial tensile specimens in 0-degree a) left, b) center and C) right. b

Nevertheless, the presence of large pores on the fracture surface of a tensile specimen is a sign of high scatter in fracture strain-stress triaxiality diagram as well, Figure 6. The presence of such a wide range in values in the graph complicates the numerical estimation of the failure of the specimens. For this reason, GISSMO (Generalized Incremental Stress state Dependent Model) damage evolution was applied. The damage exponent was determined as n=2 whereas the fading exponent was used m=1. For detailed explanation, see Andrade et al. (2016).

Figure 6. Plot of fracture strain as a function of stress triaxiality.

SLM-produced specimens were cut from the undamaged area and the size and distribution of the void structures were investigated by microscope, Figure 7. Approximate diameter of voids was determined as 100 µm. Some of the small voids are seen to merge with another void nearby. According to the findings, it can be stated that the pores in structures are critical. In order to investigate the influence of pores, numerical specimens with randomly distributed pores were modeled and simulated.