| With the development of modern automobile technology and the improvement of people’s living standards,consumers have higher requirements for the comfort of car rides.Automotive NVH performance has become an important indicator to measure automobile performance,and automakers improve vehicle NVH performance to improve consumer satisfaction and product competitiveness,so the research and analysis of automotive NVH performance and improvement are of great significance.In the NVH performance of automobiles,low-frequency roar noise is easy to cause discomfort to drivers and passengers,and has become a key issue for consumers when buying cars,while the causes of low-frequency noise are complex and there is no unified suppression method,which has become a key issue in the NVH development process of major automobile manufacturers in the world.This paper takes a prototype model as the research object,and studies the low-frequency vibration and noise in the NVH performance of the model based on the modal analysis method and the noise transfer function analysis method.Aiming at the low-frequency noise problem in the cab,the analysis is carried out in combination with the theory of plate contribution to determine the board to be optimized.Finally,optimization measures were taken to optimize it,so that the noise level in the car of the prototype model reached the target requirements.The detailed work and main conclusions of this paper are as follows:(1)The harm of poor in-cab noise to drivers and passengers is expounded,and the research development and current status of automotive NVH at home and abroad are summarized.The types,mechanisms and noise control methods of interior noise in automobiles are analyzed and studied,and the current analysis methods and related basic acoustic theories of in-cab noise are introduced.(2)Free mode analysis of body-in-white structure.In Hypermesh,finite element model construction is performed on the body-in-white model of passenger cars,material properties are assigned,and connection methods are set.The processed model is submitted for calculation,and the first 8-order modes are selected for analysis,and the results show that the structural vibration characteristics of the body-in-white are better.Finally,the free mode test of the body-in-white is carried out,and it is found that the natural frequency and mode shape distribution of the two are basically the same by comparing the test results with the simulation results,and the relative error of the natural frequency is up to 4.51%,which is controlled within 5%,which meets the actual requirements of the project and provides a model reference for the subsequent interior noise research.(3)Analysis of cab noise.The structure simplification model and TB body model are established in ACTRAN VI,on this basis,the cab sound cavity model is extracted,the sound cavity free mode calculation is carried out,and the distribution of seat system position in the cab is reasonable by analyzing the frequency and mode shape of the first 8modes of the sound cavity.Then,the sound-solid interaction model is established,and the left front and left rear suspension attachment points are selected for noise transfer function analysis,and it is found that the left front suspension attachment point is in the 130～133Hz frequency band,and the sound pressure at the driver’s right ear position exceeds the target requirements.Finally,the noise transfer function test is carried out,which verifies that the noise transfer function simulation results are consistent with the test results.(4)With the help of the cab plate contribution theory,aiming at the calculation of the noise transfer function of the left front suspension attachment point,the driver’s position exceeds the target requirements in the 130～133 Hz frequency band,the main panels of the cab are analyzed in ACTRAN VI,and it is concluded that the front apron,front floor and top cover are positive contribution to the larger plates,and the structural optimization of the relevant plates,the optimization of the thickness of the plates and the adoption of measures such as coating free damping materials are carried out.Finally,the noise transfer function of the optimized cab is calculated,and the sound pressure of the driver’s position in the frequency band of 130～133 Hz is significantly reduced,which meets the target requirement of 60 d B. |
