| Cavity structures are widely used in engineering fields,such as aircraft and automobile cabins.When subjected to external excitation,the vibration and noise generated by the cavity will greatly affect its comfort and safety.Constrained layer damping(CLD)structure can improve the energy dissipation efficiency of the damping material,which can suppress the structural vibration and reduce the noise radiation.By laying CLD on the cavity,the vibration and noise level of the cavity can be effectively reduced.Therefore,the research on the acoustic and vibration characteristics of the CLD cavity structure has wide engineering application background and important theoretical significance.Due to the complexity of the structure,CLD cavity is usually solved by the finite element method.However,the traditional finite element method requires a large number of mesh to ensure the simulation accuracy at high frequencies,so its computational efficiency is low,and its numerical simulation accuracy at high frequencies is poor for the influence of dispersion error.The edge-based smoothed finite element method(ES-FEM)can overcome the above shortcomings,soften the stiffness of the system,reduce the dispersion error,and make the numerical solution closer to the real solution.Therefore,an elastic cavity treated with constrained layer damping is taken as the research object in this paper,and the ES-FEM is adopted to model the acoustic field.The viscoelastic material is simulated by the GHM model.Considering the multi-field coupling between the elastic cavity,constrained layer damping and the sound field,a mathematical model of the elastic cavity treated with constrained layer damping is established,and the effects of the structural parameters of CLD structure and the laying method on the acoustic-vibration coupling characteristics of the CLD cavity are also discussed.The main research contents of this paper are as follows:(1)The research status of cavity structure and CLD structure at domestic and abroad,as well as the commonly used research methods are introduced,and the shortcomings of the traditional finite element method in the analysis of medium and high frequency sound field are also pointed out.To solve this problem,the edge-based smoothed finite element method is introduced into the sound field modeling of laying CLD cavities.(2)By using the GHM model to describe the constitutive relations of the viscoelastic materials,the numerical model of the 2D CLD elastic cavity is found by considering the continuity conditions between layers.In this model,the elastic wall element is the 2-node4-DOF beam elements,and the CLD structure element is 2-node 8-DOF beam elements.Using the ES-FEM to model the internal sound field,the structure-acoustic coupling governing equation of the 2D CLD cavity is derived by taking accounting the displacement continuity condition and the fluid-structure coupling effect.(3)Employing the same idea and method,the numerical model of the 3D CLD elastic cavity is found by using the ES-FEM.In this model,the elastic wall element is the 3-node9-DOF elastic plate element and the CLD plate element is the 3-node 21-DOF CLD plate element.(4)Numerical examples show that,the calculation accuracy of the edge-smooth finite element coupling model established in this paper is almost similar to that of the traditional finite element model in the low frequency range,but the calculation accuracy and stability of the present method is better than that of the traditional finite element model in the midhigh frequency band.(5)The study on the acoustic and vibration characteristics of the CLD cavity found that,laying a constrained layer damping can significantly improve the cavity’s vibration and noise level.However,the influence of factors such as the thickness of the viscoelastic layer,the thickness of the constrained layer,and the laying area on the acoustic and vibration characteristics of the CLD cavity is more complicated.Structural optimization can further improve the vibration and noise reduction efficiency of the constrained layer damping structure.The research methods and content of this article can provide a new method and certain theoretical support for the acoustic and vibration design and optimization of complex elastic cavities in the middle and high frequency range. |
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