Research On Finite Element Modeling And Optimization Analysis For Coach-Body Frame

The FEA is an efficient tool of modem engineering. It would bring us dramatic effect inmany aspects, especially in optimizing bus structure shortening the cycle and reducing the cost of developing new models. Applying the finite element technique to analyze the structure, put forward better opinions to satisfy the body's requests in stiffness and strength, become the main part in body designing. Along with the technical development in computer, large software such as ANSYS, NASTRAN, PARTRAN and so on are developed now, the FEA can be applied in the static&dynamic analysis, also the mode analysis of body structure. It has been proved that using FEA in bus body analysis is efficient, the static&dynamic analysis can be proceeded, the bearing capability and vibration characteristic can be evaluated, the stiffness, strength and inherence vibration model can be recognized. It can be also know the possible stress and distortion of the bus body. The FEA has shown its advantages in the application in auto industries.In the thesis, take a bus as an example, on the basis of two-dimensional project drawings, firstly established a geometry model of the full scale bus skeleton utilizing ANSYS. By using beam element, the finite element model for strength analysis was setup and simplified. The FEA model also involves treatments of boundary conditions, simplified treatment of some skeleton parts and deals with the fixed weight and loading that is put on the structure. Considering four typical operation situation, such as the bus running with the uniform velocity; one of the wheels hang in the air when the bus running on an uneven road; the bus brakes suddenly and the bus steers quickly. The calculation of strength of bus body's structure is expatiated. Then the research calculates the free vibration modes of the bus skeleton. At last, calculate the stress response of it by inputting the road spectrum into the model of it, and attempt to improve the dynamic capability of it.Optimization analysis design is another aspect of this paper. Car-body frame Optimization analysis is propitious to reduce whole vehicle weight. Reduction of body weight can not only save materials, but also improve acceleration performance and fuel economy of the vehicle and reduce engine emission. The Optimization analysis scheme, discussed in this paper, is based upon the results of CAE analysis and static and dynamic test, and also based upon experience of related research and engineer practice, according to which, 273 Kg of the coach-body frame weight is reduced, which comes up to the goal of 5% weight to decrease, but stress distributing change little and the coach-body frame stiffness performance meets requirements.The calculating results prove that the finite element model established in the text is rational, the analysis is correct, and the results could directly help to evaluate and improve the design of the passenger car.