Vibration Isolation Charactereristics Of Ship Anti-vibration Cave

The stern of a ship is the area with the most hull vibration problems,mainly due to the dense vibration sources at the stern,including main and auxiliary engines,propellers and their shafting.Among them,the stern vibration caused by the pulsating pressure of the propeller has always been the focus of ship vibration.One of the vibration reduction methods is to set an anti-vibration cave at the stern to reduce the transmission of excited vibration to the hull.The anti-vibration cave can be regarded as an elastic vibration isolation system between the propeller and the hull structure.At present,the research on the anti-vibration cave is mostly based on the modification test analysis of the specific ship type,lack of theoretical and numerical methods.In this paper,the finite element analysis method based on rubber hyperelasticity and air compressibility is used to analyze the structural design and vibration isolation characteristics of the anti-vibration cave.The research contents of this paper include:（1）The main design parameters of anti-vibration cave are given:length and width L×B,depth h,rubber plate thickness t,initial air pressure P₀,and reinforcement rebar layer parameters（including cross-sectional area A,spacing s,layout angleα）.The finite element modeling method of anti-vibration cave is described,including the selection of structural element and air element types and the definition of the coupling between them,the description of rubber hyperelastic material characteristics,and the determination of static and dynamic analysis steps.（2）The inflation process,free vibration,and frequency response under unit excitation are calculated by finite element method.The effects of parameters such as depth,plate thickness,initial air pressure,rebar cross-sectional area,rebar spacing,and layout angle on the inflation deformation,natural frequency,and vibration response of the anti-vibration cave were compared and analyzed.（3）Applying anti-vibration cave in a medium-sized cruise ship,and 3design solutions of anti-vibration cave are given according to different parameters.Based on the combined evaluation method of the overall insertion loss and the amplitude of the velocity response of the evaluation point,the stern vibration reduction effect of different design schemes for vibration isolation points was evaluated.