Research On Vibro-acoustic Characteristics Of Vehicle Body Structure-cavity Coupling System

Vibration and noise characteristics of body structure-acoustic cavity coupling system are important research contents of vehicle NVH.With the continuous improvement of people’s requirements for car ride comfort,the problem of vehicle noise and vibration has become a concern of many manufacturers and customers.The whole vehicle is developing towards green,high-end and intelligent electrification.Precision instruments and related circuits,such as automobile interior,cost a lot.Noise problems in high-frequency band can change the sound field environment in the vehicle by using acoustic materials.Noise produced by low-frequency vibration always interferes with the core components,and no effective solution has yet been found.By constructing the car body acoustic vibration coupling model,modeling and solving,the solution of the modal vibration mode and modal frequency of the structure acoustic cavity coupling model is affected by the structure and acoustic cavity.The situation that the underbody wall panel is easy to deform still exists in the coupling state.In practice,the body structure is connected with the whole vehicle structure by welding,and the increase of welding points and bolt holes improves the problem that the large-area wall panel is easy to vibrate.In order to improve the peak pressure and the frequency density of the sound pressure level,we need to build sound absorbing materials in the sound field of the car,simulate the sound absorption characteristics of different materials through the parameters of flow resistance and impedance characteristics.At present,melamine foam cotton is applied in higher industrial application.The foam has different angles of incidence wave,and the frequency reaches 10 k Hz after the frequency.At present,through the analysis,it can be seen that although the sound field optimization in the medium and high frequency band has been improved,and the optimization of the sound field is effective,it should also be considered from the perspective of lightweight and economy.The vibration and noise from the medium and low frequency also needs to be improved from the structure.In the next research,the concept of "phononic crystal" is proposed to solve the problem of medium and low frequency vibration and noise.Secondly,the single-layer panel sound insulation finite element model and the double-layer panel sound insulation model are constructed.The sound transmission loss curve is solved by the energy method,and the sound insulation curve is solved by the finite element software for comparison,so as to prove the correctness of the finite element simulation process.In practical engineering,most wall panels choose the firewall between the automobile engine compartment and the cockpit as the main research object,and consider the influence of sound insulation characteristics from the aspect of thickness,It also analyzes the sound insulation performance of automobile windshield glass,with glass and PVB as the main materials,through different combinations of material characteristics,slightly incident space formed by incident waves at different angles,and analyzes the transmission characteristics of stiffness control area,quality control area and resistance control area on the sound insulation curve.In order to make the sound insulation of the material move towards the low-frequency area and the sound insulation interval as wide as possible,acoustic metamaterial,a periodically arranged material for medium and low-frequency sound insulation,is introduced.It is not a natural material,but an artificial material designed and manufactured by people and contains two or more elastic modulus or density.Due to its periodic arrangement characteristics,there is a band gap in the propagation process of elastic wave,The wave in the band gap can hardly propagate through this area,which is widely used in the problem of sound insulation and noise reduction.In this paper,COMSOL multiphysics is used to solve the eigenvalue based on the finite element theory,with the built-in flouqut periodic boundary conditions.The models in the literature are selected for comparison to verify the accuracy.At the same time,the scatterers,matrix and other parts are deformed to explore the methods affecting the band gap characteristics.In this paper,the finite element model of car body structure acoustics is established,and the model of relevant structural parts of car body is taken as the research object.After appropriate simplification and treatment,under the condition of meeting the design requirements of safety and quality,taking into account the factors such as lightweight and economy,the follow-up research is carried out to provide some reference ideas for the experiment and the development of acoustic materials.