PSI - Issue 61

Rachid Azzi et al. / Procedia Structural Integrity 61 (2024) 241–251 Rachid Azzi and Farid Asma / Structural Integrity Procedia 00 (2023) 000 – 000

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The reduction of frequency is higher (1.5-2%) for the fourth mode shape because it presents more deformation in the defect positions. The defects located near the blade tip (S17) have less effect (less than 1%) on the three natural frequencies because the deformations at the blade tip are small. The two types of defects “I” and “V” induce approximately the same effect on the natural frequencies. The difference between the percentage frequency reduction of a fixed blade and a rotating blade at 2500 RPM is weak. Therefore, the rotation speed of 1500 RPM has no significant effect on the bending stiffness of the propeller blade. The mode shapes of the damaged blade did not undergo any substantial change with the presence of the defect. This could be because the mode shape presents less deformation in the zone of the defect or due to a local character of the defect. The responses of the damaged blades are completely different from those of a healthy blade in amplitude and phase, the vibration amplitude of a damaged blade is greater than that of a healthy blade. When the defect length increases, the amplitude of displacement of the blade tip increases, and when the defect approaches the blade root, the amplitude of vibration increases. The dynamic responses for different damage lengths and different positions are too small. This could be because the displacements are less sensible to the presence of the defect. Finally, the defect shape effect is not significant on the dynamic response of the blade tip. This parametric study improves the understanding of the influence of the defects on the dynamic behavior of a propeller in service. References Ino, Y., Tatara, Y., 1984. Failure analysis of propeller blade, NK Tech Bulletin, 58-65. Pantazopoulos, G. A., Toulfatzis, A. I., Tzompanakis, K. A., 2011. Failure Analysis of a Cast Mn-Bronze Propeller. Journal of Failure Analysis and Prevention, 11(3), 186–192. doi:10.1007/s11668-010-9428-6. Chang-Sup L., 2002. Analysis of the structural failure of marine propeller blades, Journal of Ship & ocean technology, Sotech 6(3), 37-45. Blednova Zh.M. Rusinov P.O.a, Dmitrenko D.V.a. 2016. Failure analysis of screw propellers and increase of fail safety by surface modification with multicomponent materials with shape memory effect. Procedia Structural Integrity 2 (2016) 1497–1505 Carlton, J., 2018. Marine Propellers and Propulsion, Fourth Edition, Butterworth-Heinemann, Elsevier. Saito, A., 2009. Nonlinear vibration analysis of cracked structures- application to turbomachinery rotors with cracked blades. PhD thesis, the University of Michigan. Epps, B.P., Kimball, R.W., 2013. OpenProp v3: Open-source software for the design and analysis of marine propellers and horizontal-axis turbines. url: http://engineering.dartmouth.edu/epps/openprop. Huang, Z., Xiong, Y., Yong, G., 2016. Composite propeller's strain modal and structural vibration performance. Chinese Journal of Ship Research, 11(2). doi:10.3969/j.issn.1673-3185.2016.02.013. Sinou, J.-J., and Lees, A. W., 2005. “Influence of cracks in rotating shafts”. Journal of Sound and Vibration, 285(4-5), p. 1015–1037. R. S. Mohan, A. Sarkar, A. S. Sekhar, 2014. Vibration analysis of a steam turbine blade. Inter.noise, Melbourne Australia 16-19 November 2014.