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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4. Discussion With the help of the different non-destructive tests, a large data field could be determined, showing good possibilities for detecting the Dross with magnetic particle inspection, ultrasonic testing and, also, with the help of X ray analysis. The tests revealed that it is possible to determine the position and depth of Dross in the cast component quite well, especially from the opposite side from the Dross. In further steps in the research project, these data will be transferred to numerical analysis to perform a better and more precise calculation to estimate the component’s fatigue life. Therefore, the stored tomographic data from X-ray and ultrasonic measurements will be transferred into FEM. During the investigations on the virtual Young’s modulus and the density regression, a not very high coefficient of determination, R², was determined, although both values seem to correlate fairly well. This might originate in the method of determining the E f . To date, this was only done with the help of one extensometer. However, since the Dross is not homogeneously distributed in the specimens, it might be interesting to determine the elongation in the specimens during the fatigue tests with two extensometers and later average the values for the virtual Young’s modulus from each side. The metallographic investigations showed a large variety of Dross formations in the test blocks and specimens, but gave a good overview of the main elements in the different forms. In further work, this can be used to specify the fatigue strength of Dross and, also, might help to decide, in much more detail, how large the loss in fatigue strength will be. 5. Conclusion and Outlook During the investigations, it became obvious that Dross in nodular cast iron offers a wide range of possibilities for further investigations. Especially, a better correlation between the density and virtual Young’s modulus is of interest and will be investigated further by applying two extensometers during the forthcoming fatigue tests in the project. Moreover, more fatigue tests will be performed in the next stages of the projects to gather more data for establishing S-N curves, classified according to the stiffness or the density. Even should this lead to an improvement of fatigue assessment of Dross-affected components, it will be also interesting to set up an assessment concept to enable a proper and local fatigue assessment based on a measured density and a reference S-N curve, as was already done in Bleicher (2016) for shrinkages in nodular cast iron. Additionally, a classification concept for Dross will be provided, giving information on Dross form in relation to representative pictures for magnetic particle inspection, sulphur test and X-ray computer tomography for each form. This will enable a comparison of a found Dross in a component with an assumption for the allowable fatigue strength right at the component in the foundry. 6. Acknowledgements The results presented in this paper were derived during the research projects “unverDROSSen”. For the funding of this project, sincere thanks are given to the German Federal Ministry of Economic Affairs and Energy (BMWi). Furthermore, all project partners are thanked for their participation and support to complete this project successfully. 7. References Bartels, Ch., et. al., 2007. Gusseisen mit Kugelgraphit – Herstellung – Eigenschaften – Anwendung, Konstruieren + Gießen, no. 2, vol. 32, ZGV Basquin, O. H., 1910. The exponential law of endurance tests, American Society Test, Materials Proceedings, no. 10, p. 625–630 Best, K. J., Reifferscheid, K. J., 2002. Dross – warum? – Gußfehler bei der Herstellung von Gußeisen mit Kugelgraphit, GIESSEREI-PRAXIS, no. 5, p. 181–188 Blair, M., Monroe, R., Beckermann, Ch., Hardin, R., Carlson, K., Monroe, Ch., 2005. Predicting the Occurrence and Effects of Defects in Castings, JOM, Journal of the Minerals, Metals and Materials Society, p. 29–34 Bleicher, C.,2016. Ein Beitrag zur Beurteilung der Schwingfestigkeit von Gusseisen mit Kugelgraphit mit besonderer Berücksichtigung der Auswirkungen von Lunkern auf die Bauteillebensdauer, Fraunhofer Institute LBF, LBF report no. FB-246, 2016 Bouvet, P., Monat, T., 2012. Influence of oxide skins on the SG cast iron parts fatigue strengt, Fonderie magazine, no. 24, p. 17–27, 2012