Investigation Of Vibration And Shock Resistance Property Of A Large Engineering Ship Shafting

The vibration of ship propulsion shafting excited by unsteady forces from propeller and internal-combustion engine,via bearing pedestals,can transfer to other ship structures to produce noise and additional vibrations that deteriorate the living condition.Another threat to the safety of ship operation comes from shock forces on the shafting system,from propeller’s impingements caused by water currents as the ship navigates in bad weather of strong wind or wavy sea surface.To ensure the safety and comfort especially for big ship,these two aspects of harmful effects has to be adequately evaluated.The investigation of this thesis focuses on these two aspects for a type of large scale engineering ship with ample residential capacity.We establish the theoretical model for the longitudinal vibration of the shaft;then we obtain the first three modal frequencies and modal patterns with application of commercial software of finite element,which show no resonance at the specified rotations of propeller.We also obtain the inherent frequencies of the shafting’s whirling vibration under different eccentric rate of the bearings as well as the amplitudes of these vibrations through analysis and computation of the established dynamic model of the shafting’s whirling vibration.Applying finite element method,in the last part,we carry calculation for the responses of the shafting to the vertical and the horizontal shock of acceleration and get the maximum displacements and stresses at important positions of the shafting;these results confirm the strength requirement of the system design.All of the obtained results deliver valuable references for vibration property and safety checking of the propulsion shafting of the similar kind of large scale engineering ship.