附 录
The skeleton of a wingspan van body is one of the most important components for a van. Its weight is about one third of the whole vehicle gross mass. The weight lightening of skeletons is of great importance to reduce the vehicle weight. This dissertation seeks feasible methods for the lightened skeleton of a van body through FEM (finite element method) analysis on the skeleton of a wingspan van’s body. FEA has become one of the most important tools in modern automobile design. Compared with traditional methods, its advantages lie in improving the quality of auto products, reducing the cost of product-developing and production, and increasing the competition of auto products in the market. In order to improve the level of van body designing and guarantee the competition of designed vehicles in the market, we must heighten the FEA technique of the van body to a strategic level.
Van, as a fuel-consuming vehicle, is attached great importance in regards to its fuel-saving level which is directly connected with the energy consumption of our whole country. Due to this great significance, van manufacturers all over the world try their best to lighten the weight of vans. The technique of weight-lightening design has become one of the hot techniques in the research field.
Since the exploitation condition of van is extremely bad, and stress condition is complex, the skeleton should have enough rigidity so as to keep the relative positions of some parts unchanged and the change of the van body shall be limited to a minimum degree while the van goes. There also should be enough intensity in the skeleton so as to ensure its reliability and life-span. The insufficient skeleton rigidity not only causes vibration and noise, but also makes the ease of driving, the stability of operation and the reliability of some parts decline too. Therefore, how to design light-weighted skeletons that meet consumers’ requirements becomes a challenging job. The skeleton of a wingspan van’s body is analyzed and studied by the ANSYS in this paper. The static intensity and rigidity of the skeleton is analyzed and studied in the instances of pure bending, coupled bending and torsion, braking condition and sharp-turning. The results indicate that the stress of the skeleton is less than the utmost intensity that the material being used has to resist. There is little displacement in the skeleton and it meets the demand of the design. This paper also deals with the dynamic analysis of van skeletons with mode analysis as a main part, which is the core of the dynamic configuration design. It overcomes the shortcoming of the static analysis and emphasized that the problem should be considered from the whole
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configuration. The local intensity can be learned through the vibration model and the responding frequency of the skeleton which are obtained from the model analysis.
Amelioration design can be done with various optimization methods. In the research, a conclusion is drawn that the optimization module of ANSYS is not applicable for the whole skeleton of van body, because the skeleton has too many stems and dimension. According to the characteristics of the skeleton, several schemes used to design lightened skeletons are proposed in this essay. Some components of little influence on the intensity and rigidity are subject to direct amelioration, and some sensitive components are to the repeated calculations under different conditions for the best optimizing design. This research had done a large number of calculations in different conditions for different stems. The final results show that this combined method is feasible. The weight of the skeleton of the designed van body is reduced by 95.8Kg.
Finally, with the statistic from the stems and the dimensions of the skeleton as variables for designing and with the whole volume of the skeleton as the goal, this essay makes a preliminary discussion of the weight-lightening of the structure of skeleton using ANSYS optimizing model.
Optimized results make the skeleton light, save raw materials, reduce the cost of manufacture, decrease the fuel consumption and do no destruction to the environment.
The research in the essay demonstrates that FEA and ANSYS offer excellent basic theories and methods for the skeleton structure, simulation of power characteristics and weight-lightening design.
They have very important project values in weight-lightening designing of the skeleton
structure.
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中文翻译：
翼展式厢式货车车厢骨架是重要的承载件，它的质量也占货车整车整备质量的三分之一左右。车厢骨架的轻量化设计对减轻汽车的质量有着非常重要的意义。本文就是通过对翼展式厢式货车车厢骨架有限元的分析计算，寻求切实可行的车厢骨架轻量化途径。
有限元法已经成为现代汽车设计的重要工具之一，与传统的设计方法相比，它的优势在于提高汽车产品的质量、降低产品开发与生产制造成本，提高汽车产品在市场上的竞争力。为了促进厢式货车车厢设计水平的提高，保证整车在市场上的竞争能力，必须将厢式货车车厢有限元分析技术提高到战略的高度上来。
厢式货车作为耗油大户，其节能与否已直接影响到我国整体的能源消耗水平，国家对此高度重视。由于汽车轻量化对节能增效的巨大意义，国际各大汽车生产商都在尽可能的情况下减轻车身质量。汽车的轻量化设计技术已经成为目前汽车研究领域的研究热点之一。
由于货车的使用条件十分恶劣，受力状况非常复杂。骨架应有足够的弯曲刚度，以使装在其上的有关机构之间的相对位置在汽车行驶过程中保持不变并使车身的变形最小；骨架也应有足够的强度，以保证其有足够的可靠性与寿命。骨架刚度不足会引起振动和噪声，也使得汽车的乘坐舒适性、操作稳定性及某些机件的可靠性下降。因此，如何设计出满足使用要求的轻量化骨架成了一项具有挑战性的工作。
本文利用有限元分析软件 ANSYS 对某翼展式厢式货车车厢骨架进行了分析和研究，讨论了该骨架静态时在纯弯曲工况、弯扭工况、制动工况和紧急转弯工况下的强度和刚度。分析结果表明，该车架的应力值小于材料的强度极限，满足设计的要求，骨架变形不是很大，也符合设计要求。
本文还进行了车架的动态分析，主要是模态分析，它是结构动态设计的核心，克服 了静态方法的局限性，强调从结构的整体考虑问题。通过对骨架进行模态分析，计算出骨架的模态振型与相应的固有频率，通过固有频率与振型从整体上考虑车架的局部强度问题。
改进设计可以使用各种方法，本课题在实际应用中发现，ANSYS 软件中自带的优化模块，用搜索可行域、进行循环计算的方法不适用于整个车厢骨架这种构件复杂、尺寸繁多对象的应用。根据该货车车厢骨架的特点，论文提出了几种方案对骨架进行了轻量化设计。一些对强度、刚度影响小的构件，直接进行改进，
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而一些重要构件则进行了不同工况水平下的多次计算，从中寻求轻量化设计方案。计算结果表明，这种方法切实可行， 具有明显效果。 通过对车厢骨架结构的分析计算， 最后使质量成功下降了 95.8Kg。 最后，以车架纵梁和横梁截面尺寸作为设计变量，以车架总体积为设计目标，运用ANSYS 优化模块对车架结构的轻量化设计进行初步的探讨。优化的结果使得骨架自身重量减少，节约了原材料，降低了生产的成本，提高了汽车的燃油经济性，并且有利于环保。
本文的研究说明有限元法和Ansys软件为骨架结构及动力特性的仿真以及轻量化设计提供了良好的基础理论及方法，借助于它们对骨架结构的轻量化设计研究具有非常重要的工程价值。
本文来自烟台大学王其光《翼展车厢有限元分析与轻量化设计》
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