Vibro-acoustic Properties Of Sandwich Plates With Constrained Viscoelastic Layer

Sandwich plates with constrained viscoelastic layer are widely used in aviation,aerospace and transportation industries,because of their high damping,great specific stiffness and specific strength.The power devices are gradually improved in the direction of high power and high load with the development of high-speed trains,automobiles,large airplanes and warships towards high-speed and lightweight,which results in increasingly serious structural vibration and noise problems.Therefore,it is of great significance to study the vibro-acoustic performances of viscoelastic constrained damping plate and to predict its sound transmission loss and radiation accurately for noise and vibration control in practical engineering applications.In this paper,the vibro-acoustic characteristics of viscoelastic constrained damping plate under diffusive sound field are discussed,and the acoustic radiation problems under point force excitation are preliminarily explored.The theoretical derivation,numerical analysis and experimental verification of the vibro-acoustic performances of sandwich plates with constrained viscoelastic layer are given.The main innovations and research contents can be summarized as follows:(1)Taking single-leaf and bending plates as examples,two commonly used numerical analysis methods,LMS Virtual.Lab acoustic simulation and modal superposition method,are used to calculate the sound transmission loss of plate structure,and the calculation characteristics of the two numerical methods are obtained by compared with the measured values.(2)Modal superposition method is extended to solve the vibro-acoustic response of viscoelastic constrained damping plates under diffusive acoustic field excitation.By substituting the vibration displacement of the mode superposition form into the vibration control differential equation of the constrained damper plate,the simplified cross-coupled modal equation is made by the standard orthogonality of the mode,and then the velocity distribution function of the plate is obtained.Finally,the theoretical model of the sound transmission loss of sandwich plates with constrained viscoelastic layer under the excitation of the diffusive sound field is obtained.The validity of the model is verified by compared the theoretical predicted value with the experimental values.The effects of structural damping,size,face sheet material,thickness and shear modulus of damping layer on the sound insulation performance of the restrained damping plate are further analyzed.(3)A simplified fourth-order theoretical model is presented for sandwich plates with soft damping layer.The model can be used to calculate the sound transmission loss of constrained damping plates quickly.It should be noted that the shear modulus of the damping layer is neglected in the model,and the equivalent composite loss factor is introduced to describe the damping characteristics of the constrained damping plate to compensate for the influence of the omitted shear modulus of the damping layer on the numerical calculation of sound transmission characteristics.(4)The formulas for calculating modal average acoustic radiation efficiency of viscoelastic constrained damping plate under point force excitation are deduced based on modal superposition method.The acoustic radiation characteristics of constrained damping plate and rectangular steel plate with the same mass are compared.The influence gauges of the thickness of damper layer,face sheet material and the position of the excitation force on the acoustic radiation of constrained damping plate are further analyzed.