Research On Vibration Characteristics Of Beam And Plate Combined Structure For Vibration Isolation Of Warship Equipment Pedestal

The gearbox will product great vibration and noise for the gear teeth impacting each other during the warship navigating.The vibration energy propagation through the gearbox pedestal and ship shell which will cause the underwater noise radiation.The vibration energy transmitted form the gearbox pedestal will obviously affect the warship acoustic stealth performance.So improveing the gearbox pedestal vibration isolation performance is important for warship acoustic stealth design.The gearbox pedestal the structure composed of beam and plate,which fixed on the deck.The pedestal web connect with the axis and rib plate of ship shell,which form the classic cross-shaped plate,T-shaped plate and L-shaped plate structure.The square steel beam and CLD(Constrained layer damp)added on the pedestal web for isolateing the vibration propergation through ship shell.The beam and plate conbined model is used to investigate the vibration supression of square beam on the classic plate connection sturcture,which can provide theoretical guide for gearbox pedestal square steel bean design.The square steel beam based on the gearbox pedestal connects with each other and forms the classic cross-shaped beam,T-shaped beam and L-shaped beam structure.Studying the vibration propagation through the square steel beam connection structure,this can provide the guidance for the square steel beam suppression design.However,the square steel beam cannot consume vibration energy,the CLD is added on the pedestal web for further improve the vibration isolation performace.The CLD will consume gearbox pedestal the vibration energy and the pedestal vibration also reduce.This will reduce the gearbox pedestal vibration and improve the acoustic stealth performance of warships.In the course of gearbox vibration,the plate consisting of the gearbox pedestal has bending vibration,in-plane vibration and the couple vibration of bending and in-plane.The square steel beam lying on the webs has the same vibration form..Therefore,sduding the influence of axial vibration and beam cross-section shear distortion and rotary inertia on the vibration propagation,and the influence laws of beam cross-section shear distortion and rotary inertia as the beam highness and frequency range changing.This will provide the theorital guidance for the square steel beam design.According to the vibration characteristics of gearbox pedestal,the influence of in-plane vibration on the vibration propagation through beam plate compose structure and the influence law of the in-plane vibration on the vibration energy as the bean and plate cross section dimension vary.The influence of beam and plate cross-section shear distortion and rotary inertia on the vibration propagation is also discussed.The influence of beam location,cross-section dimension on the vibration supression result of classic beam plate compose structure is discussed.This will guide the gearbox pedestal square steel beam design of warship.Researching the CLD vibration reduction result on the beam and plate structure of ship shell and gearbox pedestal,which can guide the CLD reduction conceptual design of gearbox pedestal.The influence of CLD pavement location,material parameters and geometric dimension on damping effect is investigated first.The CLD beam throry results and application effect are verified by contrast with the CLD cantilever beam test result.The CLD plate is an extension of CLD beam on the structure.The influence of partial CLD patch location,CLD material parameters,inclination angle and geometric dimension on damping effect is analyzed,which are used to guide the gearbox pedestal damping scheme design.The CLD plate theory results and application in the engineer structure by CLD cantilever plate test.The warship gearbox pedestal square steel beam and CLD vibration supression is design according to theory result,and the scheme is tested on the reduction box pedestal.The experimental results indicate that the amplitude of acceleration measuring point decreased more than 4d B after the web add square steel beam.The amplitude of acceleration measuring point decreased more than 9d B after the CLD pasting on the web.The tested results are applicated on the gearbox pedestal of a frigate.The calculation results indicate that the amplitude of acceleration measuring points decreased more than 5d B after the square steel beam added on the web,and the amplitude of acceleration measuring points decreased more than 13 dB after CLD pasted on the web.