| The ride comfort of the driver and the passenger was directly affected by the NVH performance of the vehicle.With the continuous improvement of the ride comfort requirements for vehicle,the major automobile manufacturers have paid more and more attention to the development of this performance.The intra vehicle noise is an important indicator of NVH level.Reducing the noise effectively in the vehicle has become an important design goal in the development stage of the vehicle,and it is of great significance to the promotion of the market competitiveness of the automobile product.This paper took a certain type of SUV model as the research object,and the finite element method was used to study the modal parameters and acoustic characteristics of the car body.Combined with the acoustic solid coupling theory,a response model of point target noise was built,and the acoustic sensitivity analysis of the body panel was carried out on this basis.The sensitivity analysis results were combined with differential evolution algorithm,and then applied in the process of noise optimization design.The following is an introduction to the main work and conclusions of the paper.(1)The finite element model of vehicle body structure was established,and the modal parameters of vehicle body were obtained by free modal analysis.And the reliability of the finite element model was verified by comparing the calculated modes with the experimental modal results.Then the finite element model of sound field and the acoustic structure coupling model were established,then studied the acoustic mode and the vehicle interior acoustic response characteristics.Through applying harmonic excitation on the left point of engine mounting,the noise peak values and the corresponding frequencies were obtained in four target points of vehicle intra sound pressure.(2)The efficiency of finite element computation model are relatively low,to improve the efficiency of the follow-up analysis,the polynomial response surface model which was combined with the experimental design method,was applied to fit the RMS(root mean square)value of sound pressure level in target point,and the accuracy of the model was verified by calculating the relative error and doing the significance test.Based on response surface model,global sensitivity analysis and local sensitivity analysis were carried out for thickness parameters of body panels,from which the sensitivity of the thickness variation of each panel to the vehicle interior noise level was obtained,and the range of parameter thickness was also determined.(3)A mathematical optimization model of noise objective function was established based on the results of sensitivity analysis,in which the thickness of panels were design variables,the first order torsional modal frequency and the allowable variation range of panels thickness were the constraints.The peak sound pressure was reduced by 6.5dB(A)after optimizing the model with genetic algorithm,and the overall noise level had been significantly reduced.In order to improve the adaptive ability of the iterative process of the algorithm so that a better solution could be obtained,an improved differential evolution algorithm was introduced in which the sensitivity values of design variables were coupled with the algorithm iteration process,and it was applied to the optimization process of the noise objective function.Then the thickness values of the optimized panels were substituted into the acoustic structure coupling model to do the acoustic response analysis.The peak value of the sound pressure level in the target point was further reduced by 1.6dB(A)compared with the optimization results of genetic algorithm,which showed that the acoustic level in the car had been obviously improved. |
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