PSI - Issue 57

Cristian Bagni et al. / Procedia Structural Integrity 57 (2024) 859–871 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

871 13

standard spot welded/riveted joints fatigue analysis as described in the nCode DesignLife Theory Guide (Hottinger Brüel & Kjær (2023)). The first methodology has the disadvantage of potentially producing over-conservative fatigue estimations, but with the advantage of being significantly more economical from both a modelling and computational perspective. The second methodology, instead, would produce more realistic fatigue life estimations compared to the first methodology. However, it would require an additional FE and fatigue analysis with consequent higher modelling and computational efforts. The FE modelling strategy proposed for the first methodology (or the first step of the second methodology) was applied to model examples of both lap shear and coach peel specimen geometries, using ANSYS software and a convergence study was carried out. The results of the convergence study showed that wrapping the exposed faces of the solid elements, used to model the adhesive, with membrane shell elements is a valid solution to recover the peel stresses from the solid elements, with the advantage of making these stresses reasonably mesh insensitive. Finally, the process to derive bespoke fatigue parameters of the hybrid joints through physical testing was also described. Studying the stiffness evolution of the lap shear specimens during the tests highlighted that the failure of hybrid joints can be split into two stages: the first stage corresponds to the crack initiation and propagation in the adhesive layer, followed by a rapid stiffness decrease, associated to the failure of the adhesive, leading to the second stage, where only the mechanical joints carry the load and contribute to the fatigue life of the joint. A series of tests is currently underway at Hottinger Brüel & Kjær ’s ‘Advanced Materials Characterisation & Testing’ laboratory in the United Kingdom, in collaboration with an electric vehicle manufacturer, NIO Performance Engineering Ltd. The full set of results generated at the end of the testing programme will be used to further validate the proposed methodology. Furthermore, they will be used to generate the final SN curves, enhance the simulation capability, and therefore, ensure the structural integrity of NIO vehicle body architecture. Acknowledgements The Authors would like to thank NIO Performance Engineering Ltd for the collaboration. We also thank Alex Pierpoint and Jeffrey Mentley from Hottinger Bruel & Kjaer for their kind support on specimen preparation, testing, and valuable discussions on modelling methods. References Abdel Wahab, M.M., 2012. Fatigue in Adhesively Bonded Joints: A Review. ISRN Materials Science 2012, 1 – 25. Al-Samhan, A.M., 2005. Analysis of Adhesively Bonded Riveted Joints, Journal of King Saud University 18, 57 – 65. Al-Samhan, A., Darwish, S.M.H., 2003. Finite element modeling of weld-bonded joints, Journal of Materials Processing Technology 142, 587 – 598. Fricke, H., Vallée, T., 2016. Numerical modeling of hybrid-bonded joints. Journal of Adhesion 92, 652 – 664. Heyes, P., Björkman, G., Blows, A., Mumford, T., Briskham, P., 2012. A fracture mechanics approach to durability calculations for adhesive joints. SAE International Journal of Materials and Manufacturing 5, 215 – 225. Hottinger Brüel & Kjær, 2023. DesignLife Fatigue Theory Guide. Lai, W.J., Pan, J., 2015. Failure mode and fatigue behavior of weld-bonded lap-shear specimens of magnesium and steel sheets. International Journal of Fatigue 75, 184 – 197. Moroni, F., 2019. Fatigue behaviour of hybrid clinch-bonded and self-piercing rivet bonded joints. Journal of Adhesion 95, 577 – 594. Sadowski, T., Golewski, P., Zarzeka-Raczkowska, E., 2011. Damage and failure processes of hybrid joints: Adhesive bonded aluminium plates reinforced by rivets. Computational Materials Science 50, 1256 – 1262. Sadowski, T., Zarzeka-Raczkowska, E., 2012. Hybrid adhesive bonded and riveted joints - Influence of rivet geometrical layout on strength of joints. Archives of Metallurgy and Materials 57, 1127 – 1135. Sun, X., Stephens, E. V., Khaleel, M.A., 2007. Fatigue behaviors of self-piercing rivets joining similar and dissimilar sheet metals. International Journal of Fatigue 29, 370 – 386. Wu, G., Li, D., Lai, W.J., Shi, Y., Kang, H., Peng, Y., Su, X., 2021. Fatigue behaviors and mechanism-based life evaluation on SPR-bonded aluminum joint. International Journal of Fatigue 142, Article 105948. Yang, B., Shan, H., Liang, Y., Ma, Y., Niu, S., Zhu, X., Li, Y., 2022. Effect of adhesive application on friction self-piercing riveting (F-SPR) process of AA7075-T6 aluminum alloy. Journal of Materials Processing Technology 299, Article 117336.