Analysis of theoretical and experimental methods of determining Vibration parameters of ship propulsion systems

Torsional and bending vibrations of ship shafts, as well as crankshafts of engines are devoted to numerous studies by different authors, moreover, the parameters of torsional vibrations are standardized by Classification Bodies, but it should be recognized that the destruction of ship shafts is quite a frequent phenomenon at present, therefore, the problem remains relevant. A significant contribution to the development of the theory of natural and forced torsional vibrations of shafts was made by Professor V.P. Terskikh. Using his algorithm, a computer program was created, which was widely used in practical calculations in our country. The method of determination of natural frequencies and corresponding vibration forms proposed by V.P. Terskikh is approximate, and the authors are not aware of any works devoted to analyzing the accuracy of the method. For this purpose in the present article a comparative analysis of the results of calculation of torsional natural vibrations of the propulsion system of the hydrofoil vessel “Comet-120M” of the project 23160, obtained according to the method of V.P. Terskikh and with the help of the software complex “ANSYS” is carried out, which showed that for the first five tones there is a good coincidence, but for the higher tones the results are significantly different. Torsional oscillations are not the main cause of ship shafting failure, the influence of normal stresses caused by bending oscillations has a greater effect here. Bending vibrations of ship shafts depend on a number of factors that are difficult to quantitatively theoretically analyze. In this connection, experimental studies of the stress state of the shafting material during its operation as part of a ship propulsion system play an important role. The article presents the results of measurements of the stress state of one of the vessels.