PSI - Issue 42

Nikola Milovanovic et al. / Procedia Structural Integrity 42 (2022) 362–367 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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After all adopted approximations explained above, numerical simulation of the shaft was performed. After several iterations, crack growth results showed to be in compliance with the crack growth propagation in real shaft. Fatigue crack growth through the critical shaft cross section can be seen in Fig. 6.

Fig. 6 Fatigue crack growth through the critical cross section of the shaft.

4. Discussion and Conclusions First shaft model had finer FE mesh around the crack (i.e., the FE size around the crack were much smaller than on the rest of the shaft), which did not provide satisfactory crack growth results. A revision of the first model was made, thus second model was obtained. In the second model, the adopted FE size in the vicinity of the crack was with the same or slightly smaller dimensions compared to the FE size in the remaining part of the shaft. New FE mesh was adopted after several revisions. This series of simulation attempts had shown that there is no need for excessively mesh refining, especially in the case of this type of analysis. This practice was replaced with vice-versa one – FE size around the crack and on rest of the model were similar. Calculation itself has been significantly improved in terms of efficiency, accuracy and feasibility. It has been proven that a finer mesh in critical location of working machine (such as turbine shaft) does not mean that obtained results will be satisfactory and realistic. Acknowledgements This work is supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia (Contract No. 451-03-68/2022-14/200135 and. 451-03-68/2022-14/200213). References [1] Sedmak, S., Grabulov, V., Momčilović, D., 2009, Chronology of lost structural integrity initiated from manufacturing defects in welded structures, Structural Integrity and Life, Vol. 9(1), pp.39-50. [2] Milovanović, A.M., Mijatović, T., Diković , Lj., Trumbulović, Lj., Drndarević , B., 2021, Structural Integrity Analysis of a Cracked Pressure Vessel, Structural Integrity and Life, Vol.21, No.3, pp. 285 – 289 [3] Sedmak, A., Burzić, Z., Perković, S., Jovičić, R., Aranđelović, M., Radović, Lj., Ilić , N., 2019, Influence of welded joint microstructures on fatigue behaviour of specimens with a notch in the heat affected zone, Engineering Failure Analysis, Vol.106, 104162. [4] Djordjevic, B., Sedmak, A., Petrovski, B., Dimic, A., 2021, Probability Distribution on Cleavage Fracture in Function of J c for Reactor Ferritic Steel in Transition Temperature Region, Engineering Failure Analysis, Vol. 125, 105392. [5] Mastilovic, S., Djordjevic, B., Sedmak, A., 2022, A Scaling Approach to Size Effect Modeling of J c CDF for 20MnMoNi55 Reactor Steel in Transition Temperature Region, Engineering Failure Analysis, Vol. 131, 105838. [6] Jeremić, L., Đorđević, B., Šapić, I., Sedmak, S.A., Milovanović , N., 2020, Manufacturing and Integrity of Ammonia Storage Tanks, Structural Integrity and Life, ISSN 1451-3749, Vol.20, No.2, pp. 123 – 129. [7] Aranđelović, M., Jeremić, L., Đorđević, B., Sedmak, S. A., Opačić M., 2021, Integrity Assessment of Ammonia Storage Tank by Non Destructive Testing, Structural integrity and life, Vol.21, No.3, pp. 295 – 300. [8] Aranđelović, M., Sedmak, S., Jovičić, R., Perković, S., Burzić, Z., Đorđević, B., Radaković Z., 2021, Numerical Simulation of Welded Joint with Multiple Various Defects, Structural integrity and life, Vol.21, No.1, pp. 103 – 107.