Research On Optimal Design Of Joint In Vehicle Body In Concept Design Phase

With rapid development and fierce competition in the automobile industry, the demand for the stiffness, strength,durability and safety of the auto-body is higher and higher. T his trend requires us to adopt the efficient method to design the structure of the auto-body in the conceptual design phase, which could not only ensure the quality and performance of vehicles, but also shorten the designing cycle and reduce produ cing costs. In the stage of conceputual design, subjected to the types and the shapes of the vechiles, the layout and the size of the auto-body has little room to change, while the key section and joint structure of the auto-body has more room to do design. T herefore, it is imperative to do the durability design for the key structrues of the auto-body at the early stage, which will contribute to improving the efficiency of the auto-body design.At first, the design method used in conceputual design of vehicle body was introduced detailed in this paper, finite element method ?implicit parametric?analogy procedure of joint and the method of modeling of conceputual vehicle body were included, these methods were the basis to carry out the concept design of structure of vehicle body. By comparing their advantages, implicit parametric and its method of modeling was choosed suitably for this paper.Secondly, the rearch on structure of joint in concept design phase was carried out, First research on the structure of joint effect on the performance of the vehicle was conducted. Based on the parameterized model of the vehicle body, the position of key joint which sensitivity was highest was found by the analysis of sensitivity. In allusion to the control factors of joint structure: the shape and the thickness of cross section and the size of transition region, analysis of DOE was proceed to find out the effect on the performance of stiffness of the vehicle. Studies have shown that compared with traditional mechanical parameter value section of the simplified method, the research based on the concrete geometry have more practical significance. Second parameterized joint model was used to study the influence of the structure of joint to the stiffness of joint, T he inner relationship between the size of cross section ?Mechanical parameters of cross section ? the stiffness of joint and vehicle was found out, and according to the joint stiffness which extracted from the deformation of joint in the working condition of the vehicle, the idea of analyzing the specific issues was put forward, for a specific condition, targeted research on stiffness of joint.Finally, A process of concept development of the structure of joint based on the technology of implicit parametric was proposed. With the development of a new vehicle, the parameterized sub-model of joint was established, in order to simulate the stress status of joint i n the vehicle. Combined with the research results in this pape,appropriate goals and constraints was selected and the variable which meet the need of project of the shape ? thickness and the position of cross section was established. Using the software of Isight to integrate, genetic algorithm(NSGA-II) was adopted to realize the multi-objective optimization. T he research in this paper has shown that: T his method have solved the problem effectively of the design of the structure of joint can't carry out at the early concept design phase because detailed finite element model isn't established. T he shape of joint which meet the design objective and engineering demands can be confirmed at in concept d esign phase. The method not only can guide forward de sign of the joint, but also can greatly improve the efficiency of joint conceptual design.