Car Body Dynamics Characteristics Test And Finite Element Analysis

As people living standard rise, the requirements of automobile comprehensive performance is increasing day by day. In order to reduce the vibration intensity, reduce the noise level, and improve the ride comfort, people must pay attention to the design optimization of car's structural dynamic characteristics. Body is one of cars'three assemblies, its structure decides the mechanics properties of the whole vehicle. Therefore, to analyze the dynamic characteristic of car body is especially important. The modal analysis technology is one of the important technologies to forecast, test and modify automobile structure dynamic characteristics.This article is combined with a new platform of car development project. This new platform car project based on the original model, and the body is new development.. Through its body modal analysis, to get the dynamic characteristics of the platform body, so as to evaluate the new platform vehicle body dynamic performance and optimize the dynamic characteristics of the body.This article uses the method of combining finite element modal analysis and experiment modal analysis to evaluate the dynamic characteristics of the new platform car body. Identify t?body structure of the natural vibration frequencies , modal and weak position of the body, and use Test.lab Modification Prediction module to do sensitivity analysis and determine the structure changed sensitive parts of the body.?Using finite element model body of sensitive position structure changed, and to the improvement of the body after in finite element modal analysis and modal test, validation of finite element analysis and the effectiveness of the structure changed, so as to improve the dynamic characteristics of the body.According to the modal analysis theory and finite element method, this article uses HyperMesh software, Nastran software to do finite element modal analysis. Use Test.lab to acquisitive data and analyze, then use Assurance Criterion (MAC) to evaluatethe dynamic characteristics of body, finally obtain the modal parameters of the body. Comparative the finite element modal analysis results and the measured modal parameters, to verify the validity of the finite element model.Using the module of Test.lab Structures analysis/Modification Prediction to do the sensitivity analysis of the BIW. According to the modal analysis results, find out that there is much vibration of center floor pan. Because in the normal driving conditions, engine vibration transfer to the car body from the floor, so need to improve the floor structure, and reduce the vibration of the floor. This article does the sensitivity analysis of vibration modes on center floor pan, and the structure of the modified sensitive position is center floor beam and rear floor. And adjustment of the center floor beam and rear floor can improve the local vibration frequency most effective.Using the finite element model to improve body structures. This article provides two modification projects.? The results show that increasing the floor channel to strengthen extension panel and rear floor reinforcement, finite element modal analysis to determine the body modal does not appear in the local mode vibration of floor, indicating an increase in floor channel to strengthen extension panel and rear floor reinforcement is effectively suppressed in the floor of the local vibration.Finally, conduct do modal test of the improved body to verify the finite element modal analysis results. The finite element modal analysis results are accurate.This article uses the method of combining finite element modal analysis and experiment modal analysis to identify body danger dynamic response value (or super index) causes, position and domain. Use the finite element model to improve the structure of dangerous position. Do modal test of the improved body to validate the results of finite element analysis, so as to achieve the purpose of car body structure optimization.In short, use the modal analysis technology in the new car development early to improve body structure and optimize design, can shorten the development cycle, reduce development costs.