Analysis And Optimization Of The Acoustic Performance Of The Honeycomb Floor Structure In Lightweight Metro Train

In the background of the lightweight requirements for metro train,Honeycomb floor structure has gradually become one of the most common metro train floor structure,with its high stiffness to weight ratio,excellent stability and heat insulation performance.However,the decreased weight of the floor structure will reduce its acoustic performance,deteriorate the vibration of train body,amplify interior noise and affect the passengers comfort.The Honeycomb floor structure used in the metro train in china is studied using experimental and the hybrid FE-SEA methods.Sound transmission loss and sound radiation characteristics of the structure are analyzed to get the best acoustic performance optimization without changing the mass of the structure.Specific contents are as follows:First of all,using sound insulation test method of reverberation chamber to reverberation chamber,on the premise of similar mass,the advantages and disadvantages on the acoustic performance of honeycomb floor structure relative to other typical metro train floor structure is studied.The results show that the acoustic performance of the aluminum honeycomb floor structure is often worse than laminate plate in the low-middle frequency.It is because that the aluminum honeycomb belongs to double plate structure with acoustic bridge,there are some resonance modes between the upper and lower panel and the acoustic energy can be transmitted through acoustic bridge.However,because of its special structure,aluminum honeycomb floor structure has large rigidity,there is none consistent appearance in the frequency range of focus when study the interior noise of metro transit.The sound insulation performance of the aluminum honeycomb has certain advantages in the high frequency.Then,the sound transmission loss prediction model and the sound radiation characteristics prediction model are developed with FE-SEA method in order to research the influence of skin-core mass distribution,the height,size and orientation of hexagonal honeycomb on the acoustical performance of the Honeycomb floor structure.Then the study is extend to different honeycomb shape and material of the Honeycomb floor structure.The results shows that the honeycomb floor structure has the best acoustic performance when choose the higher middle layer,the mass ratio "1:1:1" honeycomb vertical panel,with the material of high modulus and low density.Finally,the influence of the different position,different thickness and different forms of the damping layer on the acoustic performance of the honeycomb floor structure is discussed on the basis of structural optimization.It is suggested to use a 2mm damping material with a thickness of 0.5mm to 1mm aluminum foil as a constraint layer at the top of the panel in order to get a best damping efficiency.