Several Research On Model Modification Of Carbody Structure

Carbody is subject to torsion, bending, collision and so loads during using. Most modern carbody is integral body. Under these multiple loads, the rigidity of the body which reflects the relationship between loads and deformation plays an important role. If it is not rigid enough, the carriage will seal losing efficiency so as to leakage of rain or damage inner decorations. It may happen that the doorframe, window frame and luggage opening will deform too excessive to open the doors when crash happens. Also, an improper rigidity body design will affect the power response, NVH performance, ride characteristics, handling stability or even active safety.The aim of the research in modifying the body model is to enhance the rigidity of whole carbody rationally, to improve the performance of weakness and to insure the design request. Meanwhile, vibration characteristics can be improved by modifying the body components. And the problem of lightweight can be reduced.The main purpose in this paper is to investigate the mechanics characteristics of carbody so that it will be reasonable loaded and rigidity distributed properly. By FEM, research the relationship between the changes of components and carbody rigidity. According to the result of sensitivity analysis, modify the configuration and utilize the theory in design process so that it can also supply gist that can be checked. Ultimately, it can be sure that lightweight body, reduce cost and waste, improve fuel economy and unite the lightweight, economy and reliability during the design process.Firstly, introduce the basic ideas and theory of FEM briefly. Then elaborate on the approach of carbody configuration analysis using FEM and the commonly process of FEM modeling. And describe the model of carbody which will be used to calculate in this paper.Secondly, analyses the real sense of carbody vibration test. In view of type loads condition, simplify the vibration system of carbody. Introduce the characteristics of global mode, component mode analysis and board local mode. After that, briefly introduce the technology of carbody mode test.Following, according to practical loads and restrictions of carbody, finite element analysis on carbody static rigidity are taken. Meanwhile, as the GB regulations, take an experimentation of carbody under the same condition. Form a comparison between numerical simulation and experimentation; it can safely come to the conclusion that the finite element analysis model and its result are correct. Then aiming at performance requirement, strain energy density/mass sensitivity as called relative sensitivity analysis of BIW components are taken to provide reference to the modification. If the result data of components are larger, they would be added thickness. Whereas they must be reduced thickness.Finally, three modification projects about different aims are proposed: higher stiffness, lower mass and integrated project. The basic idea of modification is: with relative sensitivity analyses of carbody performance, it can select proper components to increase or decrease thickness. After the comparison between these plans, a preferable project: integrated project is gained.At the same time, in order to find a better measure to solve the problem of excessive amount of calculation, CA method and Improved CA method which belong to reanalysis method are studied and a numerical example is given to verification the efficiency and accuracy.