Research Of Car-body Conceptual Design Method Based On Stiffness Chain

Conceptual design is a key part in car-body design process,it finished the design of enveloping space,sections and joints which are hardly modified in detailed design phase.BIW(Body In White)stiffness is important criterion to evaluate vehicle reliability and safety.BIW bending and torsion stiffness analysis is an imperative step in auto development.The study is significant in improving body structure,promoting body stiffness and hardness characteristic and enhancing vehicle reliability and safety.Therefore car-body stiffness is a critical technical issue to be solved.The study on car-body stiffness distribution and key structures design in conceptual design phase has an important significance for improving vehicle performance and shortening design cycle.The research is around the issue of car-body stiffness distribution in conceptual design phase.A top-down conceptual design process was proposed based on the research of several key techniques in car-body conceptual design phase.A modeling method of simplified car-body model was put forward to realize rapid design in conceptual design phase.According to the feature that the car-body structural topology is closely related to and mutually influences with stiffness distribution,a method of car-body stiffness chain was proposed using frame structure theory,beam element concept and transfer matrix method.A simplified car-body wireframe model was established and 18 main sections were defined and the mathematic model of car-body stiffness chain with main sections as nodes was built.Stiffness optimum distribution was studied based on car-body stiffness chain and the mathematic model of car-body stiffness optimum distribution was built and then solved by genetic algorithm to obtain the material distribution in each main section.The rationality of stiffness optimum distribution and the availability of car-body stiffness chain were verified by comparing with the CAE analysis of approximate benchmarking car.Finally,this paper has studied the concept of body structure design and analysis software system according to the characteristics of car-body structure concept design,and the designer can complete the whole process of body structure concept design on the same platform,this system realize the integration of CAD data and the CAE data,which greatly improves the design efficiency and provides a new design tool for car body design personnel.This study provides valuable reference for the domestic automotive enterprises to carry out the top-down conceptual design,and discuss a new idea to improve the independent research and development level of domestic auto industry.