Vibration Calculation Of Ship Propulsion Shafting

Ship propulsion shafting is an important part of a marine power plant, consistingof driving shafts, bearings, couplings and other shafting attachments. Ship propulsionshafting is utilized to connect the output flange of the Main Engine and the propeller.During the running of the shafting, various impact loadings and periodic excitationforces act on it. The duration time of impact loadings is short, and the vibrationresulting from them will rapidly decay since the various damping effects in the shaftstructure. However, the periodic excitation forces such as the diesel excitations andpropeller excitations will lead to steady propulsion shafting vibrations since they arecontinuous excitations. Such steady vibrations include torsional, longitudinal andwhirling vibrations. If the vibrations exceed the acceptable safety margins of the shaftstructures, various shaft failures, or serious engine vibrations and hull vibrations, etc.will affect the efficiency and the ship safety. Therefore it is of great importance toresearch the ship propulsion shafting vibration.Based on the shaft vibration theory, a shafting vibration calculation software byusing MATLAB language was firstly developed which aimed at calculating thetorsional, longitudinal and whirling vibrations of the shafting. The software wasvalidated by the data available in the open literature, and the software was utilizedto calculate the torsional, longitudinal and whirling vibrations of a shafting test bench.Secondly, according to the sizes of each part of the shafting test bench, a rigid-flexhybrid model for this shafting test bench was established by employing the3Dmodeling software SolidWorks, the multibody dynamics simulation softwareADAMS and finite element analysis software ANSYS. Then based on this model, thesimulation analysis for the torisonal vibration under various working conditions wasconducted, and obtain the angular velocity of the shaft and the torsional angulardisplacement curve were obtained. The spectral analysis of torsional angulardisplacement curve was also conducted. Next, a finite element model for calculatingthe whirling vibration of the shafting test bench was established by using ANSYS andSolidWorks, the modal analysis was conducted after imposing constraints on the model. The natural frequency and the vibration mode for whirling vibration werederived. Finally, the results of theoretical calculation and simulation were comparedto mutually validate the accuracy of the results, and demonstrate at the same time thefeasibility of using the multibody dynamics software and the finite elementcalculation software for calculating torsional and whirling vibrations, respectively.