| The low-frequency structural noise radiated by the vehicle body is an important manifestation of the vehicle NVH,which directly affects the ride comfort.The structural noise characteristics of the body are mainly affected by the modal performance and the acoustic performance.The modal performance focuses on the first-order bending and the first-order torsion.The acoustic performance is generally expressed by the noise transfer function.Combining the finite element method and the test method to carry out comprehensive diagnosis and analysis on the structural noise problem of the vehicle body,carry out efficient and reasonable structural optimization design,and explore new optimization schemes to improve the structure noise performance of the vehicle body,which are of great significance to improve the market competitiveness of the product.In this paper,the finite element model of the SUV body-in-prime is built by Hypermesh,and the model precision is benchmarked by modal simulation analysis and experimental modal analysis.Based on the modal strain energy analysis method,the reason why the first-order torsional mode is not up to standard is diagnosed.By optimizing the welding points,the optimized BIP mode meets the set targets and the weight of the vehicle body remains at the same level.Then,based on the optimized BIP,the finite element model of the trimmed-body is established,and the structural noise characteristics of the trimmed-body are studied through modal analysis of the trimmed-body,acoustic modal analysis and analysis of the noise transfer function of the key contact points.The results show that there are 6 non-compliant NTF paths,and subsequent diagnosis and optimization are needed.Based on the source-transmission channel,six paths that do not meet the NTF target requirements are diagnosed and analyzed.The specific diagnostic analysis measures are dynamic stiffness analysis,operational deflection shape analysis and analysis of the participation factor grid.The results of the diagnostic analysis show that the main reason for the failure of the No.1 hanging X and Z direction to the four NTF paths is that the attached jog stiffness are insufficient.The reason why the two NTF paths in the right Z direction of the rear suspension and the tank installation point are not up to standard is the vibration of the dangerous plate on the transmission channel.By adding the reinforcing bracket and the support plate,the joint jog stiffness of the No.1 hanging X and Z directions are improved,and the sound pressure response of the No.1 hanging X and Z to the four non-compliant NTF paths are controlled.Through multi-objective optimization of dangerous plate on the transmission channel in HyperStudy,the problem of two NTF paths not up to standard in Z direction of rear mount and right Z direction of water tank installation point are solved.The optimization results show that the two non-compliant NTF paths of the rear mount and right of tank installation points in the Z direction meet the targets,and the weight of the TB remains at the same level.Finally,the dynamic stiffness optimization scheme and the plate thickness multi-objective optimization scheme are applied to the finite element model,and the structural noise performance of the TB concerned in this paper are fully simulated and verified,and their performances meet the requirements.It is verified that the process and optimization method of the body structural noise diagnosis proposed in this paper is effective. |
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