Parametric study to identify the cause of high torsional vibration of the propulsion shaft in the ship

Since torsional vibration can lead to fatigue failure of the propulsion shaft in a ship, it should be restricted from the first step of the design through calculation and verified at the sea trial test step through measurement. Considering that the torsional vibration of the shaft is a system characteristic, it is strongly related to the vibration modes at the natural frequencies of the shaft. Therefore, the actual torsional vibration problem can occur due to the variation of parameters such as those of the vibration system, including mass of inertia, damping, and stiffness, which differ from the design.In this research, the root cause analysis of the high torsional vibration which occurred in the actual ship is described through a parametric study performed using numerical analysis. Parameters that can increase the torsional vibration of the propulsion shaft are selected, including coupling stiffness, shaft stiffness, coupling damping, and shaft damping. Through the torsional vibration calculations with variations of these parameters, the extent of the effect of these parameters on the torsional vibration of the propulsion shaft is investigated and the cause of the increased torsional vibration is identified.