Modal Analysis Of BIW Construction & Optimization Design In Modal Parameters

With the development of the automobile industry, the FEA (finite element analysis) has been wildly used in automotive design. In order to improve the ability of automotive design and independent innovation, the modern automotive design method has been more and more applied in Chinese automobile companies.In this article, the finite element model of the body is established first, and then the modal characteristics of vehicles such as vibration mode and frequencies has been received through the calculation analysis of finite element model. According to the dynamical performance of the modal analysis of the BIW (body in-white), the relevant evaluation indexes and appraisal methods have been summarized. Furthermore the body's natural dynamic features and located some weakness of the structure are got.As an effective method in the structural design and optimization, Sensitivity analysis is accepted in many times. In this paper, to ascertain the change of the cover panel such as pshell's thickness of the car body to the influence of the first class frequencies, the sensitivity analysis was performed. Base on the sensitivity analysis we can get more rational design parameters in the following optimization analysis.Comply with the conclusion of above optimization analysis, the parts which have more influence to the low-order modal were selected, and the thickness of these parts were set as design parameters. In the optimization design, different object functions can be designed according to different purpose. Refer to the similar researches, in this paper two object functions were designed, which were the weight of Body-in-white and the frequency values of the low-order modal.In the following analysis, the evaluation on the vibration characteristics of the body structure is performed and requency response analysis is preferred. Finally, the optimization analysis on requency response carries out to validate the validity of construction modification.The subject was established for the dynamic analysis of BIW, which is "modal analysis-sensitivity analysis-optimization analysis ". The article can apply to any other similar research. The item accumulated some experience for some correlative research. The result provided a valuable consult for the further optimization of the whole body.