PSI - Issue 42

Miloslav Kepka et al. / Procedia Structural Integrity 42 (2022) 687–693 Author name / Structural Integrity Procedia 00 (2019) 000 – 000 7 Bilinear S-N curves (S-N lines) were considered in fatigue damage calculations. The exponent for the lower part of S-N line was set as = 2 − 1 , where w is the experimentally determined exponent of the upper part. The threshold stress amplitude for the calculation of fatigue damage was considered as ℎ = 0.5 , where σ c is the so-called fatigue limit of the investigated structural node (stress amplitude at the knee point of the bilinear S-N curve). The critical (limit) value of fatigue damage was taken as = 0.5 . This value is recommended for such cases where a weldment is being evaluated subjected to loads with variable amplitude. For example, the recommendation of International Institute of Welding, Hobbacher (2016). The stress spectra were evaluated from the strain gauge measurement when driving an empty and fully loaded bus on real city tracks. The total length of the recorded sections represented 100 km of driving with an empty vehicle and 100 km of driving with a fully loaded vehicle. With the manufacturer's consent, specific data can already be published in a professional journal. Acknowledgements The authors prepared this paper with the support of the Ministry of Industry and Trade of the Czech Republic, the project FV40260 “On -line measurement and analysis of the operational loading of structures with adaptive virtual models”. References Kepka, M., Rehor, P., 1992. Methodology of experimental research into operating strength and fatigue life of bus and trolleybus bodywork. International Journal of Vehicle Design, 1992, 13 (3), pp. 242-250. Spirk, S., Kepka, M., 2015. Tests and computer simulations of electric buses. 6th International Conference on Mechanics and Materials in Design: Recent advances in mechanics and materials, Ponta Delgada, Portugal, pp. 211-212. Kepka, M., Polach, P., Kepka jr., M., 2020. From Dynamic Models of Buses to Reliable Estimation of the Fatigue Life of Their Bodyworks. 7th International Conference Integrity-Reliability-Failure, Funchal, Portugal, pp. 419-430, Paper ref.: 17200. Palmgren A.Z., 1924. Die Lebensdauer von Kugellagern. Z. Ver. Deutsch. Ing., 68:339. Miner, M.A., 1945. Cumulative damage in fatigue. Transactions of the ASME, Series E. J. Appl. Mech.,12:159–64. Haibach E., 1970. Modified Linear Damage Accumulation Hypothesis Accounting for a Decreasing Fatigue Strength During the Increasing Fatigue Damage. LBF, Darmstadt, Germany, TM Nr. 50. Kepka, M., Kepka jr., M., 2021. Consideration of random loading processes and scatter of fatigue properties for assessing the service life of welded bus bodyworks. International Journal of Fatigue, 151, 106324, https://doi.org/10.1016/j.ijfatigue.2021.106324. Minich, R., Kepka jr., M., 2020. Laboratory fatigue tests of bodywork welded joints of SOR articulated electric bus: preliminary FEM analysis and design of test stands. University of West Bohemia, Pilsen, Czech Republic, Research report. Minich, R., Kepka jr., M., Tittel, J., 2021. Laboratory fatigue tests of bodywork welded joints of SOR articulated electric bus. University of West Bohemia, Pilsen, Czech Republic, Research report. Kepka, M., Kepka jr., M., 2018. Using design s-n curves and design stress spectra for probabilistic fatigue life assessment of vehicle components. 6th International Conference Integrity-Reliability-Failure, Porto, Portugal, pp. 373-384. Hultgren, G., Khurshid, M., Haglund, P., Barsoum, Z., 2021. Mapping of scatter in fatigue life assessment of welded structures - a round-robin study. Welding in the World 65, pp. 1841 – 1855. Hobbacher, A.F., 2016. Recommendations for Fatigue Design of Welded Joints and Components (2nd ed.). Publisher: Springer IIW225915. 693