Research On The Body Structure Lightweight Based On Stiffness Characteristics

Lightweight technology, which is of great significance to energy saving and emission reduction, has now become one of the hotspot research areas in the automobile industry. Structure optimization, as one of the three major channels of vehicle lightweight design together with the use of lightweight materials and application of new technology, has been widely studied and extensively used to achieve the lightweight of vehicles without raising costs. In this paper, based on stiffness characteristics, three key techniques of the body structure lightweight design are studied, which includes topology optimization, sensitivity analysis and six sigma robustness optimization. This paper will focus on the following aspects:First, lightweight research based on topology optimization of the whole body. Traditional topology optimization, which usually concentrates on the optimization of the position and size of lightening hole, neglects the space topology optimization of the overall structure of the body. So in this paper, at the conceptual design phase, topology optimization technique will be applied into the design of overall body structure, in the hope of achieving the optimal body bearing skeleton and thus providing some guidance on the lightweight of body at the detailed design phase. Second, lightweight research based on stiffness sensitivity analysis of BIW.Traditional sensitivity analysis is often targeted at only certain components and thus is unable to give a reasonable evaluation to the degree of sensitivity. Therefore, the method of using sensitivity analysis to optimize the size of components often fails to achieve satisfactory results. In this paper, having analyzed the sensitivity of all parts of BIW, sensitivity indexes, including relative sensitivity and average relative sensitivity, will be put forward; the thicknesses of large panels of BIW, whose relative sensitivities are lower than the average, will be optimized and a lightweight design of BIW will be achieved.Third, lightweight research based on the six sigma robustness optimization of vehicle door. Current researches on vehicle structure lightweight often center on different approaches to lightweight; while neglecting the performance robustness of light-weighted vehicles. In fact, there are many uncertainties in the manufacture and use of vehicles. Even the slightest change in design variables may lead to the results that vehicle performance indexes go beyond control boundaries or that responses to design variables are extremely sensitive, then resulting in lower quality of the vehicle. Taking one specific door of TWB as examples, using the thicknesses of the plates and the position of welding line as variables, and through the methods of DOE(design of experiment), response surface method, optimization algorithms and Monte Carlo simulation, this paper manages to find an approach to lightweight based on six sigma robustness, which not only achieves a lightweight design of the door, but also greatly improves the robustness of the performance of the vehicle door.