Vibration Characteristics Research Of Typical Ship Structural Based On Travelling Wave Approach

Plate and beam are the basic structure of the ship,and there is great significance to do a research of vibration wave transfer characteristic on ship vibration control.The current travelling wave approach is generally used to study wave propagation of semi-infinite plate and beam.For the finite size structure with boundary,the objects of current wave method focus on only beam,plate and the L-shaped plate structure.The paper aims to extend the subject to multi plate coupling structure such as finite size T type,cross type,and beam plate coupling structure.Based on the reverberation matrix method,the dynamic response formula of beam and L-shaped plates were deceived.According to dual coordinates referred to reverberation ray matrix,the local dual coordinate system for travelling wave approach model was established.The structure in the ship structure acoustic conditions changing position was discrete,and the local dual coordinate system for each discrete plate was built.After dispersing amplitude coefficients of bending wave and in-plane wave and assembling state vectors of force and displacement for each discrete plate,the general expression of travelling wave approach was put forward.Transform the point driving forces into line driving forces.According to the current travelling wave approach,the steady state response of finite sized T-shaped,cross shaped plate and other structure under the point force was derived.Vibration power flow of the structure was calculated by MATLAB programming,and the convergence,efficiency and accuracy of traveling wave approach’s semi-analytical solution were verified by finite element numerical calculation.According to the coupled continuity hypothesis of plate and rib,four kinds of coupled model were built,which contain plate-Euler beam model,plate-plate-Euler beam model,plate-additional mass body model and plate-discrete mass model.Based on wave approach by MATLAB,the vibration power flow of coupled finite plate was calculated,and the influence of the structural stiffness and moment of inertia on the vibration power flow transmission was discussed.Some discrete mass points were arranged in the plate.The combined effects of many quality points can be regarded as a linear superposition of some line mass,and the effectiveness of a linear mass superposition can be verified by numerical solution of finite element method.The vibration control equation of classical Poisson-Kirchhoff theory and Mindlin theory was solved out by travelling wave approach.The results of vibration power flow show that both in-plane shear and rotation inertia have impacts on structural power flow in the whole frequency domain.When structural loss factor is zero,power flow is much smaller which can be ignored.When structural loss factor exists,in addition to the peak frequency region,active power flow increases with the loss factor.In the low-frequency range,the bending vibration power flow is significantly greater than the in-plane vibration power flow,and the in-plane vibration power flow can be ignored.In the process of structure acoustic design,the plate connection angle should try to be between 90°-150° to create the impedance mismatch,thus benefitting the attenuation of the vibration power flow.