Study On Fast Algorithmof Shaft-Cabin Vibration And Separating Of Propeller-Shaft Response

Under the excitation of the host,shaft and propeller,ship stern is one of the most violent vibration part of the ship.With the increasingly stringent requirements of IMO and underwater vehicles for ship vibration and noise,ship stern shaft-paddle-hull coupled vibration analysis and control technology highlights and has become a hotspot.Considering the large size and complex structure,fast and accurate prediction of ship vibration has become one of difficulties in the industry.The separation of the vibration response under the stern excitation is the key to determine the main excitation source and reduce the vibration noise of the ship effectively.In this paper,the rapid calculation method of the vibration of the shaft-shell structure and the separation test method of thepropeller shaft vibration responseare carried out.This paper explores the method of calculating the vibration of the shaft system and shell structure by improving the local structure and the shaft system.And this paper analyzes to quickly separate the propeller and shaft vibration response without changing the propeller.The sub-structure FE model of the propulsion shaft and the test sub-structure model of the cabin are established on the base of theory/experiment combined modal synthesis method.And a simulation/experiment hybrid model of the shaft-cabin structure is built by the LMS Virtual Lab simulation platform,and the modal analysis of the hybrid model is carried out.Then,based on the sub-structure synthesis method of frequency response function(FRF),the vibration frequency responses of the hybrid model are analyzed.In this paper,the FE method is used to analyze the FRF between the shaft and the bearing connection point.The FRF of the bearing connection point to the shell response point is analyzed by experiment.Based on the FRF synthesis method of LMS Virtual Lab,the vibration response of the shaft-cabin coupling structure is analyzed.Finally,a new testing method of separation of the propeller shaft vibration response is proposed in this paper.The effects of propulsive perturbation excitation and propeller excitation on the propulsion shafting system were tested by field dynamic balance test,and the method has been verified on the propeller-shaft test bench.The vibration characteristics of the hybrid model are compared with the full finite element simulations and experimental tests.The results show that the hybrid modeling and simulation not only meets the accuracy but also greatly reduces the simulation time.The proposed hybrid method is superior to full FEM in studying the coupled vibration of the shafting and cabin system,especially in computational efficiency.It will provide a strong technical support for the vibration characteristics analysis of a complex structure in modification and optimization.