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Tuesday, November 2, 2010

Vibration characteristics of car body structure and design optimization

Modern society, the car has become a very important means of transport, is closely related with people's basic necessities. Chinese passenger car sales in 2009 reached more than a thousand million, up 59% growth rate for the Chinese auto industry set a new milestone. Benefited from the government introduced financial incentives, the overall auto market last year sold over 1350 units world-first, 44% record high growth leader in the global automotive industry. Essential to modern society as a means of transport, the auto industry has been considerable development, a country's level of automobile manufacturing, to a large extent a reflection of its technological development. Although China's auto production and sales in 2009 ranked first in the world in one fell swoop, but we should see the domestic car in the automotive CAD / CAE technology and the huge gap between foreign countries. Assembly of the car body is one of the three, it is not only a beautiful shape and appearance, enough space, smooth curve shape is more important is to have superior performance. At present, the 3D digital-analog design using finite element method on a variety of car body to accurately predict performance, automotive technology is an important research focus.Body structure in the design stage of the mode, intensity and stiffness for accurate analysis, and to solve the problems in the digital-analog stage, thereby greatly reducing vehicle development time and reduce costs. This paper briefly describes the car system development and application of CAE technology, the inherent characteristics of the body structure of the basic concepts, basic theory of finite element method and application in the body structure, modal analysis and optimization theory. And thus provide a theoretical basis for the entire paper. With graduate student participation in the development of a 0.8L two mini-car, white body structure and the structure and function of sub-assembly made a detailed introduction. Use of the 3D micro-structure of the number of car body model, the first structure is simplified, including how to deal with a reasonable structure of flange, holes and strengthen the tendons and other local structures. The simplified model into ANSYS software to build the car body structure of the finite element model, select the appropriate unit type and size of the model grid by grid. In order to obtain the natural vibration characteristics of body structure, its modal analysis. Analysis of the data obtained, identify the problems and prepare for the optimal design stage. In structural optimization, take the first order bending, twisting sensitivity of some of the more sensitive pieces of sheet metal thickness as design variables, the model with white body and light weight as the goal to increase the frequency of low order modes optimized for the purpose of analysis. Vehicle body structure for the proposed improvement program, the ultimate goal is to spend the least cost and shortest time to design the most reasonable body structure. 

Key words: body structure; vibration characteristics; modal analysis; design optimization

 

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