Procedure for Torsional-Vibration Calculations in Ice

Abstract The safety of navigation at sea is closely connected to the reasonable operation of the marine power transmission system of a vessel. The propulsion unit inside a ship is considered as one of the most significant on-board systems that is mostly subjected to dynamic loading. The dynamic behaviour can cause various vibrations along the propulsion line that will substantially affect the propulsion shaft’s reliability and efficiency. One vital factor that can influence the shafting design is the shafting vibration behaviour, particularly the torsional vibration behaviour. This paper focuses on developing a FEM based Torsional Vibration Calculation (TVC) method to identify and examine the vibratory stresses arising in the propulsion shaft line of a container vessel with a new design approach of TVC analysis in ice conditions. The aim is to model the ice-based response of the propulsion system for different loading conditions and obtain the results in time-domain. Therefore, it has to be a completely numerical based approach. The developed method gives the dynamic response of the shafting system subjected to torsional vibrations for different engine operation conditions that are based on the Finnish-Swedish Ice Class Rules (FSICR).