PSI - Issue 18

Christoph Bleicher et al. / Procedia Structural Integrity 18 (2019) 46–62 Author name / Structural Integrity Procedia 00 (2019) 000–000

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emanate from cracks already present in the specimens, necessitating a fracture mechanical approach for the lifetime assessment of cast components having such critical Dross. A comparison of the test results of sound and Dross-affected material in the stress-strain regime shows that the Dross drastically reduces the Young’s modulus as well as the elongation of EN-GJS-400-15 parts. This is obvious, when taking into account that many test results did not fit onto the cyclic stress-strain curve of the sound material. To have a generally applicable fatigue assessment approach for cast components with Dross, the loss in material stiffness, and thus the virtual Young’s modulus, is evaluated for each fatigue specimen. This was conducted for all specimens with a fracture in the specimen test volume to enable a later correlation with the density in the test volume, according to the approach in Bleicher (2016). Furthermore, this is the volume, on which the strain was applied during the fatigue tests. As an example, Fig. 16 shows the results of three different specimens, for which the virtual Young’s modulus E f was determined. All in all, the different Dross formations in the specimens led to virtual Young’s modulus between 8 and 180 GPa, whereas the Young’s modulus of the sound material investigated is around 168 GPa. After the fatigue tests, all specimens with a rupture in the test volume were used to determine a correlation between the virtual Young’s modulus and the density. For this reason, the test volume (8 mm x 15 mm x 25 mm) was removed from all specimens on CNC-controlled milling machines ensuring a precise and repeatable cutting process, Fig. 17. The removed test volumes were weighed and the density determined.

Fig. 14. Stress-strain curve of sound material with results of the Dross-affected specimens

Fig. 15. Strain-life curve of sound material with results of the Dross-affected specimens