摘 要

运载火箭是由多级火箭组成的航天运输工具。它的用途是把人造地球卫星、载人飞船、航天站或空间探测器等有效载荷送入预定轨道。运载火箭已成为我们进行月球勘测、外太空空间站建设、深空作业等航天活动不可或缺的工具，同时又作为用来保卫祖国安全、维护国家权益和促进国民经济发展的重大战略装备，它的发展成为每个航天大国竞争的重点之一。这其中以“火箭王冠”著称的运载火箭燃料箱就成为了制约各个国家运载火箭的研发与制造的核心部件。运载火箭可灌注的燃料总量越多，火箭的承载能力便越强，而燃料的总量直接取决于运载火箭燃料箱的直径。但是过大的直径势必会增加其质量，已有研究结果表明运载火箭总体质量每减少1kg所能取得的经济效益接近十万美元。

因此，为了实现在满足给定的结构强度条件下尽可能减轻整体质量，本文把改进的重点放在了燃料箱底件的成形材料与结构优化上。轻质高强度合金凭借其低密度、高比强度、强抗腐蚀性能等优点，现已成为新一代运载火箭燃料贮箱的首选材料。然而，高强度合金材料的室温成形性能不佳，属于难成形的材料；火箭燃料贮箱箱底类大型薄壁曲面件结构刚度差，属于难成形的结构。如何提高轻质高强度合金薄壁曲面件成形性能并实现其精确成形制造已成为制约我国航空航天等领域发展的瓶颈问题。

本文主要介绍了目前用于航天航空领域的轻质高强度合金和当前国内外板材的成形技术现状。通过比较和分析得出以下结论：性能优异、来源广泛且价格便宜、可回收使用的轻质铝合金是目前燃料箱底件制造的首选材料。具有高度自动化和高生产效率的传统冲压成形在很长一段时间内仍然是板材成形的主要手段。

本文运用了Solidworks软件对运载火箭燃料箱底件进行了简化建模分析，以铝合金为材料并根据轻量化、节能化的原则对燃料箱底件进行了结构优化。提出了横筋和环筋两类优化方式，并得出了多种优化结构（一字筋、T字筋、十字筋、风车筋、单圆环筋、双圆环筋、十字环筋）。同时以十字环筋为最终结构优化方案进行了成形方案的设计，为运载火箭燃料箱底件的结构优化提供了新的方向。

本文还进一步分析了运载火箭燃料箱底件冲压成形时不同工艺参数对成形结果的影响，通过模拟仿真手段，比较了板料厚度与板料大小（可成形深度）两个工艺参数对冲压成形结果的影响。主要从冲压成形的成形深度偏差、应变和应变能三个方面进行了分析。结果表明：（1）厚度为4mm的板与厚度为2mm板的实际成形深度与理论成形深度偏差不大，但应变上厚度为4mm的板要比2mm板高出0.02，应变能则高出一倍。（2）直径为120mm的板（极限成形深度为30mm）与直径为200mm的板（极限成形深度为50mm）相比，直径为200mm的板实际成形深度与理论成形深度偏差为4%要大于直径为120mm的板成形深度偏差2%，应变上直径为120mm的板要比200mm的板高出0.01，应变能低出比例则为1.5%。

关键词：运载火箭燃料箱底件；成形方案；结构优化；加强筋；冲压成形

Abstract

Launch vehicle is a space vehicle composed of multi-stage rockets. Its purpose is to carry payloads such as artificial earth satellites, manned spacecraft, space stations or space probe into orbit. The launch vehicle has become an indispensable tool for us to carry out space activities such as Lunar Survey, construction of Outer Space Station and deep space operations, at the same time, as a major strategic equipment used to protect the security of the motherland, safeguard the rights and interests of the country and promote the development of the national economy, its development has become one of the key points of competition of every space power. Among these, the rocket fuel tank, known as the "Rocket Crown", has become the core component that restricts the research, development and manufacture of launch vehicles in various countries. The more fuel that can be injected into a launch vehicle, the greater its carrying capacity, and the amount of fuel directly depends on the diameter of the launch vehicle fuel tank. But too large a diameter is bound to increase its mass, and studies have shown that a reduction in the overall mass of a launch vehicle of 1 kg can yield economic benefits close to $100,000.

Therefore, in order to reduce the overall mass as much as possible to meet the given structural strength, we focus on the improvement of the fuel tank bottom materials and structure optimization. Light and high strength alloys have become the preferred materials for the fuel tanks of new generation launch vehicles because of their low density, high specific strength and strong corrosion resistance. However, the High Strength Alloy has poor formability at room temperature and is difficult to form, while the large thin-walled curved surface parts of the bottom of the rocket fuel tank have poor structural stiffness and are difficult to form. How to improve the formability of light-weight and high-strength alloy thin-walled curved surface parts and realize its precise manufacturing has become a bottleneck problem which restricts the development of aerospace and other fields in China.

In this paper, the present status of light-weight and high-strength alloys and sheet forming technology at home and abroad used in aerospace field are introduced. Through comparison and analysis, it is concluded that the light aluminum alloy with excellent performance, wide source and cheap price is the first choice for the manufacture of fuel tank bottom. Traditional sheet metal forming with high automation and high production efficiency is still the main means of sheet metal forming for a long time. In this paper, the fuel tank of launch vehicle is modeled and analyzed by using Solidworks software, and the structure of the fuel tank is optimized according to the principle of light weight and energy saving. In this paper, two kinds of optimization methods of transverse reinforcement and ring reinforcement are put forward, and many kinds of optimized structures are obtained, such as one-word reinforcement, t-word reinforcement, cross reinforcement, windmill reinforcement, single-circle reinforcement, double-circle reinforcement and cross reinforcement. At the same time, the forming scheme is designed with the Cross Ring Bar as the final structure optimization scheme, which provides a new direction for the structural optimization of the carrier rocket fuel tank bottom.

In this paper, the effects of different process parameters on the forming results of the bottom parts of the rocket fuel tank are analyzed, and the results are simulated. The effects of sheet thickness and sheet size (formable depth) on the forming results were compared. The forming depth deviation, strain and strain energy of stamping were analyzed. The results show that: (1) the difference between the actual and theoretical forming depths of the sheet with thickness of 4mm and 2mm is not significant, but the thickness of the sheet with thickness of 4mm in strain is 0.02 higher than that of the sheet with thickness of 2mm, and the strain energy is 54% higher. (2) a sheet with a diameter of 120 mm (limit forming depth 30 mm) is compared with a sheet with a diameter of 200 mm (limit forming depth 50 mm), the deviation of the actual and theoretical forming depths of 200 mm sheet metal is 4%, which is larger than that of 120 mm sheet metal. The deviation of the actual and theoretical forming depths of 120 mm sheet metal is 0.01 higher than that of 200 mm sheet metal, and the ratio of the lower strain energy is 1.5%.

Keywords：Bottom of carrier rocket fuel tank; Forming scheme; Structure optimization; Reinforcing rib；Stamping forming

目录

摘要 I

Abstract III