Study On Key Techniques Of Vehicle Lightweight

Lightweight has become a crucial research topic in automotive technology. Structural optimization, size optimization, new materials and lightweight technology are all the ways of lightweight. Although there is much research on the ways to lightweight, the theoretical system of lightweight and the analysis procedure of lightweight means should also be further improved. In this dissertation, multi-objective optimization, multi-disciplinary optimization methods and other modern design methods combined with approximate model and a variety of numerical optimization methods(including the authors proposed hybid genetic algorithms) were adopted to reseach on all lightweight approaches. A detail research on overall size optimization of the white in body, structural optimization of parts, the type of materials and specifications optimiziation, and multi-disciplinary optimization in lightweight technology were carried out. This dissertation mainly carried out the following research:1. The overall size optimization based on multi-objective optimization method. The conventional size optimization methods focus on optimizing the size of components rather than the overall size of vehicles. In fact, a reasonable design of overall size of vehicles is best way of lightweight of vehicles. It develops a new car with similar structural, but with different length, height and width. The length, height and width of the whole car, thickness of the some panel are served as the optimal variables, and sampling points were obtained by using optimal Latin squares design of experimental method, at the meantime, the moving least-squares response surface approximate method are used to approximate the multi-objective system of the body-in-white NVH, body-in-white key area strength. The approximate model was optimized by using NSGA-â…¡(non-dominated sorting based genetic algorithm). It lightens the weight of the new body and searchs for additional space to maximize interior space which meeting the requirements of body-in-white NVH, strength.2. The lightweight design based on parts structure optimization. A new fusion algorithm is proposed based on genetic ant colony optimization strategy. The new algorithm employs Ant Colony system Algorithm (ACA) features and Genetic Algorithms (GA) crossover and mutation evolutionary strategy improves features of the global search. The performance of the door system, including the open comfort and open N V H, has been constructed by the Kring response surface approximate method. The shape of the three guide rails has been optimized by using fusion algorithm method to meet the sliding door open comfort and open NVH. Meantime, it lightens the weight of the sliding door. Based on South Korea's experience, open NVH has evaluated by the deviation of opening acceleration between average acceleration. The example shows the feasibility of this method.3. Extended the research on multi-objective and multi-material-multi-part specification composite construction. Conventional lightweight design is often optimized for the part thickness basis of the single-material and single-specifications. While in this dissertation, a multi-objective optimization method is proposes by combining a system of the type of material, parts specifications, parts thickness with an aim to minimize the weight and cost. And the mathematical model of such a multi-material-multi-part specification composite construction multi-objective optimization is also proposed. In the mathematical model, the type of material, rather than a number of properties of materials, parts specifications, rather than part geometry and the price properties, are defined as discrete variables, which greatly reducing the complexity of optimization problems. Then the the optimal Latin squares design of experimental method and least-squares response surface approximate method are also adopted to construct the objectives and constraints. The approximate model is optimized by using NSGA-â…¡. The proposed method is illustrated through a case of lightweight design of a steering wheel and a steering wheel compression test rig, and the results also show the feasibility of this method.4. The Multi-disciplinary optimization for lightweight technology. A detail research on tailor-welded bank and hot-forming bank has carried on by using multi-disciplinary optimization. In the application of tailor-welded bank:Sampling points were obtained by using uniform Latin squares design of experimental method, and the MDO(multidisciplinary design optimization) approximated system, including the door stiffness, strength and side crashworthiness, has been constructed by the moving least-squares response surface approximate method. The approximate model was then optimized by using sequential quadratic programming method. The performance of the door system, including the vertical stiffness, strength and side crashworthiness, has been improved by optimizing the positions of the welding line as well as thickness of each part. In addition, the weight of the door is also reduced. In the application of hot-forming bank:Sampling points were obtained by using optimal Latin squares design of experimental method. The MDO approximated system with the body-in-white stiffness, body-in-white key area strength, frontal crashworthiness has been constructed by means of moving least-squares response surface approximate method. The thickness of the hot-forming rail member and the reinforcement panel have been optimized by using sequential quadratic programming method to meet the stiffness of body-in-white, body-in-white key area strength and frontal crashworthiness. Meanwhile, the weight of the body frame is also reduced.