PSI - Issue 38

Boris Spak et al. / Procedia Structural Integrity 38 (2022) 572–580 Author name / Structural Integrity Procedia 00 (2021) 000 – 000

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assess the estimation capabilities of LSA for this clinched joint. Taking into account a greater neck thickness of variant 1.4 in comparison to variant 1.0, it is not unreasonable to assume a shorter fatigue life up to crack initiation while showing a higher number of cycles in crack growth. 5. Conclusions In this study, a fatigue life estimation based on LSA for two different clinched joints manufactured from the same aluminum alloy EN AW-6060 T66 was performed. Fatigue life estimation using the damage parameter P SWT is carried out. Experimentally obtained fatigue lives for the failure criteria crack initiation and fracture are compared to the fatigue life estimation. Based on the results, the following conclusions were reached: 1. Experimental results for both variants of clinched joint show similar fatigue lives for failure criterion fracture. Fatigue life assessment based on LSA estimates a lower number of cycles for variant 1.4 in comparison to variant 1.0. 2. The observed scatter range of experimental fatigue life results with respect to the failure criterion fracture, lead to the conclusion that further effects, such as friction in between sheets, may have an impact on the fatigue life of clinched joints. 3. Consideration of mean stress effects using damage parameter P SWT results in very conservative fatigue life estimation. Omitting of mean stresses provides an estimation closer to the experimentally obtained number of cycles to crack initiation. This is a major point of interest for further research to understand the evolution of mean stresses and possible interaction with cyclic hardening and softening as wells as the impact of residual stress on the fatigue life. 4. The change in cyclic material properties due to forming operation, i. e. cold forming and induced hardness increase that is observed in the neck of the joint, needs to be considered to improve the estimation capabilities of the LSA. Acknowledgements The research project was carried out in the framework of the industrial collective research programme (AiF-Nr. 20300BR). It was supported by the Federal Ministry for Economic Affairs and Energy (BMWi) through the AiF (German Federation of Industrial Research Associations eV) based on a decision taken by the German Bundestag. References DIN 50125, 2016. Testing of metallic materials - Tensile test pieces. DIN EN ISO 6892-1, 2020. Metallic materials - Tensile testing - Part 1: Method of test at room temperature (ISO 6892-1:2019). DVS-EFB 3480-1, 2007. Testing of properties of joints - Testing of properties of mechanical and hybrid (mechanical/bonded) joints. SEP 1240, 2006. Testing and Documentation Guideline for the Experimental Determination of Mechanical Properties of Steel Sheets for CAE Calculations. Bäumel, A. Jr., Seeger, T., 1990. Materials Data for Cyclic Loading. Supplement 1. Clormann, U. H., Seeger, T., 1986. HCM – Ein Zählverfahren für Betriebsfestigkeit auf werkstoffmechanischer Grundlage. Stahlbau 55. Ewenz, L., Kalich, J., Zimmermann, M., Füssel, U., 2021. Effect of Different Tool Geometries on the Mechanical Properties of Al-Al Clinch Joints. Key Engineering Materials 883, 65-72. Fiedler, M., Wächter, M., Varfolomeev, I., Vormwald, M., Esderts, A., 2019. FKM Richtlinie Nichtlinear - Rechnerischer Festigkeitsnachweis unter expliziter Erfassung nichtlinearen Werkstoffverformungsverhaltens für Bauteile aus Stahl, Stahlguss und Aluminiumknetlegierung. Gibmaier, J., Lin, R., Oden, M., Scholtes, B. 2002. Residual Stress Distributions around Clinched Joints. Materials Science Forum 404-407, 617 622. Kim, J-B., Kim, H-K., 2014. Fatigue behaviour of clinched joints in a steel sheet. Fatigue & Fracture of Engineering Materials & Structures. Masing, G., 1926. Proceedings of the 2 nd International Congress for Applied Mechanics, 332-335. Mori, K., Abe, Y., Kato, T., 2012. Mechanism of superiority of fatigue strength for aluminum alloy sheets joined by mechanical clinching and self pierce riveting. Journal of Materials Processing Technology 212, 1900-1905. Mucha, J., 2011. The analysis of lock forming mechanism in the clinching joint. Materials and Design 32, 4943-4954. Ramberg, W., Osgood, W. R., 1943. Description of stress-strain curves by three parameters. Sjöström, P., Johansson, S. A. H., 2005. Residual Stress Relaxation During fatigue of Clinched joints in Stainless Steels. Materials Science Forum 490-491, 404-408.