NVH Performance Analysis And Structural Optimization Of A MPV Body

Consumers can feel the noise and vibration of the vehicle directly,they pay special attention to the vehicle NVH performance,many countries have presented stricter relevant laws and regulations,so the vehicle NVH performance will be one of the major factors which influence competitiveness and quality.The white body is the core of the car,the automobile manufacturers pay close attention to the NVH performance of the body structure throughout the vehicle NVH performance development process.The thesis takes a MPV developed by a certain enterprise as the research object,the static and dynamic performance of the body structure is analyzed,and the vehicle NVH performance is optimized.The main research contents of this thesis include:Firstly,the simulation method of welding,gluing and other connecting modes of the body is described,the white body finite element model is established by this method.The conditions of modal analysis and static stiffness analysis are expounded,the model and static stiffness of BIP are analyzed by finite element method,and the modal identification method is adopted to find white body first-order bending and torsional mode,and the results of the body mode and stiffness analysis are evaluated.The dotted dynamic stiffness of key points like mount and suspension are analyzed by using modal frequency response method,calculated the dotted dynamic stiffness curve and equivalent dynamic stiffness,preliminary understanding the dynamic characteristic of each key point.Then,the finite element model of TB,cavity are established,and the mode of TB and cavity are analyzed,the key order modes of body structure,closures,steering system and cavity are identified.The results of TB modal analysis and TB body mode distribution table show that the mode of each system of TB body meets the requirement of avoiding frequency.And the NTF and VTF of the car have been analyzed by using modal frequency response method,with different stimulations the peaks of sound pressure and vibration have been get.Finally,through sensitivity analysis selected 30 design variables which have a greater influence on the mass,modal and stiffness of BIP,and design of experiment are carried out by using Hammersley sampling.The HyperKriging approximation model is established based on the experimental results,and multi-objective genetic algorithm was adopted to optimize the body structure.Finally,the NVH performance of the optimized body is verified,the results show that modal and stiffness performance have some improvement while the mass of BIP is reducing,and the modal performance has reached the design requirements,meanwhile the thesis studies the impact of mass,modal and stiffness' s change on the mode of TB,the dotted dynamic stiffness,NTF and VTF.This paper makes a summary of the simulation method of welding,gluing and other connecting modes in the vehicle NVH performance analysis,and the scientificity of the selected element is explained.The finite element model of car body structure which is applicabile to NVH analysis is established by this method,and this method has considerable value in engineering application.