船舶浮筏系统动力学特性的影响因素研究

Research on Influences on Dynamical Characteristics of Ship Floating Raft

在船舶浮筏隔振系统的动力学特性研究中 ,以往的刚体分析模型会在高频段造成很大误差。本文从基于有限元的弹性体模型出发 ,对隔振系统的多种方案进行了模拟激励下的响应分析 ,讨论了影响浮筏隔振性能的结构与材料因素 ,如隔振支承刚度与阻尼、筏体的刚度与阻尼、浮筏基座刚度与阻尼等。通过船模实验验证了所建立的动力学模型 。

In the research on the dynamical characteristics of the ship floating raft, the rigid model, which was commonly adopted in the analysis of double deck isolation system, will cause unaccepted errors especially in the high frequency band. To estimate the level of the noise produced by the ship engine, an elasticity model based on the FEM is put forward. Several influence factors on the isolation properties are investigated through the response analysis and transfer function analysis with various structural and material schemes when the excitation is simulated. These factors studied in this paper includes the supporting stiffness, the damping of the isolator, the Young's module and the damping of the raft material, the rigidity and the damping of the foundation of the floating raft, etc. The sensitivity analysis reveals the relation between the structural as well as the material parameters and the transmission efficiency of the mechanical vibration. It is proved for the floating raft system that the stiffness and the damping play a complicated rule in the transmission of the vibration and noise along the raft sturcture. Relying on the different frequency band and different position on the ship, the effect is sometimes positive or negative. Several curves, which describe the sensitivity, are given and the results are discussed. The theoretical results from the simulation are verified through the experiments on an actual ship model with different schemes of both structure and material. The coincidence is revealed through the comparison and then several conclusions are put forward in the reduction of the structural vibration and noise in ships. The data obtained from the experiments are valuable in the determination of the parameters in the theoretical model. The sensitivity analysis is proved significant to the design of the isolation system in ships.