| In modern society vehicle has become a very important transport, and is closely related to people's basic necessities. China's passenger car sales in 2009 reached more than 1,000 units, up to 59%growth rate for China's auto industry setting a new milestone. Benefited from the government having introduced various fiscal incentives, the overall automotive market in China last year sold more than 1,350 units, up in the world, with 44%record high growth leader in the global automotive industry.As an essential means of transport to society, the automotive industry has been developing significantly. To a large extent, a country's automobile industry level reflects the level of its technological development. Although China's automobile production and sales in 2009 ranked first in the world in one fell swoop, but we should know the huge gap in the automotive CAD/CAE technology between the domestic car and foreign countries. Car body is one of the three assembly of the car, which not only has beautiful form and appearance, enough space and smooth shape curve, but also superior performance is more important. Currently, using finite element method to accurately predict the various performances of car body during the 3D digital-analog design is an important hot automotive technology research content. During the design stage modal body structure, accuraty analyse of strength and rigidity, etc., and solve the problem in the digital-analog stage, thereby greatly reduce vehicle development time and the cost..This paper briefly described the development and application of vehicle CAE technology in system, the basic concepts of the inherent characteristics of the body structure, basic theory of finite element method and application in the body structure, modal analysis and optimization design theory. And these provide a theoretical basis for the entire paper. Combination of graduate students take part in the development of a 0.8L two micro car, white body structure and the sub-assembly of the structure and function of a detailed introduction.Use of the 3D digital-analog of Mini car body structure, firstly simplify the structure, including how to deal with a reasonable structure including flange, holes and strengthen the tendons and other local structure. Then send the simplified model into AN SYS software, establish the finite element model of the vehicle body structure, select the appropriate unit type and size of the model grid meshing,In order to obtain the natural vibration characteristics of body structure, do its modal analysis, use the data and find the problems to provide preparation to optimize the design stage. In structural optimization, take the thickness of some of the more sensitive pieces of sheet metal of the first order bending, twisting sensitivity as design variables, to improve the low frequency modes and to reduce the weight of the white body as the goals of optimizing analysis, the ultimate goal is to spend the least cost and shortest time to design the most reasonable body structure.
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