Modal Analysis And Experimental Study Of Trimmed Body

With the people’s pursuit of comfort and government’s supervision for noise pollution,The NVH performance of car has gradually become the focus of R & D and key of increasing the competitiveness.Body is the car’s infrastructure.Trimmed body is the whole vehicle without the powertrain and chassis system,whose structural characteristics directly affect the NVH performance of vehicle.Based on the actual needs of the project from school-enterprise cooperation,this paper uses the Trimmed Body as the research object.The Finite Element Analysis is used to analyze the modes of TB and the interior components according to the relevant theories.The Modal Synthesis technology is used to research the impact of the structure or constraints changing on inherent characteristics.This paper focuses on the modal test of the TB to explore the appropriate test scheme and the modal recognition methods,and compares results of test and analysis to verify the accuracy of the modeling analysis.According to the results of modal analysis,the body structure is optimized based on HyperStudy platform.Finally,based on the TB modes,the acoustic-cavity model and the acoustic-solid coupling model are used to analyze the acoustic performance of TB.The specific research contents are as follows:(1)The finite element modeling methods of BIW and TB are introduced,and on this basis,the modal analysis of BIW and TB is finished.The influence of the installation of inner and outer ornament components on the dynamic characteristics of body and the influence of the boundary condition of the inner and outer ornamental system on its own modes are studied with the BIW–TB relevance technology.(2)In order to ensure the accuracy of the modal test,the acceleration sensor used in the test is calibrated.(3)Based on the test of structural linearity,the frequency domain identification and the time domain identification are used to carry out the modal test of TB,In order to solve the problem that modes of TB are difficult to identify.This paper introduces the optimal test scheme and signal acquisition method for TB,and focuses on the comparison of the recognition methods.The random subspace method combined with the arrangement of measuring point on TB frame gets the good application and provides a new idea for the body mode test.(4)The program of TB structure optimization is made.The design variables are determined through the sensitivity analysis.Based on the optimal Latin HyperCube test design,the Kriging Fitting is used to establish the approximation model of responsing surface.The MOGA algorithm is used to solve the optimization.At last,the accuracy’s verification of the optimization results is finished.(5)The acoustic cavity model and acoustic-solid coupling model are established.Besides,the modal analysis of sound cavity and NTF of the driver’s ear are completed.According to the results,the analysis of sheet contribution in sound pressure peak frequency are carried out for noise control and optimization of body.