1 Introduction
The key task for the automobile industry and its suppliers in future lies in speedily developing and implementing ecologically sound and economically justifiable mobility systems. Light metals such as aluminum and magnesium along with glass and carbon fiber reinforced materials, ceramics and composites have opened up the potential for considerable weight reduction and for "green" vehicle concepts which can be realized economically. Aluminum in particular can provide the impetus for new designs for the next millennium. Decades ago, the u of aluminum in auto construction was en as an "experiment"; Today it is a vital factor in reducing weight and thus lowering fuel consumption.
The average pasnger car today contains 60 to 70 kg of aluminum, and current developments point to a doubling of this amount in the next few years. Motor vehicles both now and in future must meet requirements for: greater performance, greater safety, comfort, low pollution. Lightweight construction is not just about reducing weight; it is a question of -striking the right balance between reduced weight and structural efficiency. In vehicle construction this normally means making the best u of the generally very tight space available for individual components so as to allow weight to be minimized while still meeting all stiffness, strength, natural frequency or acoustical requirements. To achieve this, stress must be distributed throughout the structure as evenly as possible. Modern numerical analysis
methods such as FEA allow a very detailed analysis of system behavior, provide cost-efficient support for the complex process of optimization and thus make a huge contribution to advances in lightweight construction. Packaging, safety considerations, reproducibility and price place restrictions on the degree of weight reduction achievable.
The broad range of experti available to Krupp Presta AG allows the company to analyze customer specifications for steering systems and provide appropriate solutions.
2 Requirements to be met by steering systems
The steering is an important part of the feel of a car. The steering system should make driving an enjoyable experience with no unpleasant vibration from the road surface while guaranteeing the required hand- sing. It is also important that high safety requirements be met, both under normal conditions and in crash situations. The key criteria for the steering system are thus as follows:rolling friction, torsional stiffness /strength, Damping, temperature, corrosion, durability / fatigue, weight. Crash kinematics and energy absorption steering column requirements:natural frequency / stiffness, mass, damping, space, strength (crash, misu), ergonomics, handling, acoustics, crash kinematics and energy absorption. Other basic conditions:interfaces with adjacent components, installation, joining techniques, price.
3 Materials
material light weighting can be achieved by using either stronger or lighter material. When stiffness or natural frequency are Important sizing criteria, low density materials with a high modulus of elasticity by quired. Non-exotic materials must be lected which are readily recyclable, low in price and display good durability.Further requirements are t by the manufacturing and joining process. Steel, aluminum, magnesium and a variety of plastics are the materials of choice for steering systems.
Low specific gravity, high corrosion resistance, low fabricating costs, high energy absorption and good recycle ability make aluminum a favored light weighting material. Owing to its high energy content, up to 90% of the aluminum ud in auto construction can be recycled (intelligent design / no mixing with other materials). The favorable energy balance of aluminum puts it at a great advantage over many other materials.In environmental terms aluminum scores highly. The large amounts of primary energy required to make raw aluminum are offt over the lifetime of the vehicle. Composites could also become a very attractive proposition on account of their extreme stiffness, low weight and energy absorption capabilities. At prent, howler, price is a problem, as are joining and quality assurance.
4 Reducing component weight
A focud strategy to reduce component weight requires a lightweight approach to design (force distribution, stress), material (material lection), specifications (modified, realistic specifications)
Key factors in lightweight design include [1]: force flows, material properties, ambient conditions ® safety requirements, reliability of joints, manufacture ability. Practical experience has shown that car makers' specifications bad on steel need to be revid for lightweighting. Requirements valid for a steel steering shaft, for example, can result in vere oversizing of an aluminum shaft. Reducing component weight requires material compatible designs combined with material- compatible specifications.
5 Lightweight components
As part of its development program Krupp Presta is replacing conventional steel steering components such as steering rods , shafts or forks with corresponding aluminum components produced by new process. Weight savings of 20-30% are achievable depending on the basic conditions stipulated by the customer. Aluminum and magnesium die castings are already being ud in steering columns , and further opportunities for weight reduction are being investigated. The
lightweight steering column (Fig. 1) produced by Krupp Presta for the Audi A6 is a good example. By using magnesium die castings it has been possible to limit the weight of the steering column to just 5kg, a reduction of 15-20% over conventional (steel) designs.
6 Steering column design
Experience has shown that it is possible to design steering columns for cars more or less on the basis of their natural frequency alone. Additional engineering work may be required to design critical parts which must not break in the ca of a crash or misu (e.g. theft). The main task when engineering a steering column is thus to achieve the highest possible natural frequencies while minimizing weight. Low-stiffness components are being analyzed and refined in an effort to achieve uniform loading of the structure. In solving this task, u is made of numerical methods such as FEA. The structure is divided into finite elements which are characterized by specific deformation assumptions. Using FE analysis it is possible to examine complex structures, analyze nsitivities and links, discuss variations or ways of making improvements and optimize the structure numerically. Topological optimization is carried out for the analysis of low-stress areas and for the basic design of ribs and beads. CAD geometry
data are procesd in an FE pre-processor. Correct modeling of the following is esntial, individual parts, stiffness, contact faces, kinematics mass. Modeling is followed by computation and evaluation of the data obtained. The deformation energy is a global measure for asssing stress. Normalizing the element deformation energy by the element mass provides information on the stress acting on the element relative to its mass. The kinetic energy is regarded as the influence of vibrating mass which have a negative effect on the natural frequency of the steering column. By evaluating stress and strain conditions, highly localized weak points or high-stress areas can be identified.
7 Conclusions
Existing technologies must be continuously adapted and improved in line with the requirements of the auto industry. Systematic weight reduction is a major challenge and requires clo cooperation between vehicle manufacturers and suppliers. Materials, fabricating and joining technologies must be further refined. One prerequisite for the continuing success of Krupp Presta is the flexibility to react to customer wishes and requirements.
Reference
[1] Klein, B.:
Leichtbau-Konstruktion. Berech- nungsgrundlagen und Gestaltung.
Braunschweig: Vieweg, 1997
一、简介一、简介 汽车工业及其供应商，在未来的关键任务在于迅速制定和实施无害生态和经济上合理流动系统。随着玻璃和碳纤维增强材料，陶瓷和复合材料的广泛应用，如铝、镁轻金属开辟了轻量化使具有发展潜力的“绿色”概念车得以投产。特别是铝可以为以后的新设计提供了动力。几十年前，铝在汽车建设中被视为“概念”，如今它是减轻重量，从而降低油耗的重要因素。如今的汽车一般含有60到70千克的铝，千克的铝，按照目前的发展趋势，按照目前的发展趋势，按照目前的发展趋势，在未来数年的这一数额将增加一倍。在未来数年的这一数额将增加一倍。在未来数年的这一数额将增加一倍。现在和将现在和将来的汽车必须符合以下要求：更高的性能、更安全、舒适、低污染。轻型结构不只是降低重量，它是一个很值得研究的课题，减轻重量和结构效率之间要达到相应平衡。在汽车制造中，这通常意味着充分利用有限空间可用于各个部件以使重量最小化，同时，还要求满足所有的刚度，强度，固有频率和声学要求。要实现这一要求，这一要求，强度必须在结构分布上尽可能均匀。强度必须在结构分布上尽可能均匀。强度必须在结构分布上尽可能均匀。现代数值分析方法，现代数值分析方法，现代数值分析方法，如有限元分如有限元分析允许一个非常详细的分析系统
途径，提供具有成本效益提供具有成本效益,，支持复杂的优化过程，从而在轻量化进步建设中做出巨大贡献。在安装，安全，装配，成本等方面的考虑，在一定程度上可以实现轻量化。在一定程度上可以实现轻量化。克虏伯公司提供的专业知识范围广泛，克虏伯公司提供的专业知识范围广泛，克虏伯公司提供的专业知识范围广泛，使该使该公司在分析转向系统，客户要求的规格上提供适当的解决办法。公司在分析转向系统，客户要求的规格上提供适当的解决办法。
二、需求得到的满足转向系统二、需求得到的满足转向系统
转向系统是车辆的一个重要的组成部分。转向系统使驱动有良好行驶过程，减轻来自路面的糟糕的振动，减轻来自路面的糟糕的振动，保证所需的转向手感。保证所需的转向手感。保证所需的转向手感。同样重要的是，同样重要的是，同样重要的是，无论在正常无论在正常情况还是在崩溃的情况下，情况还是在崩溃的情况下，高安全性的要求得到满足。高安全性的要求得到满足。高安全性的要求得到满足。因此，因此，因此，影响转向系统的主影响转向系统的主要因素如下：滚动摩擦、抗扭刚度要因素如下：滚动摩擦、抗扭刚度//强度、阻尼温度、耐腐蚀性、抗疲劳性能、重量等。影响碰撞冲击力和能量吸收转向柱因素：固有频率重量等。影响碰撞冲击力和能量吸收转向柱因素：固有频率//刚度性能、应用广泛、阻尼作用、占用空间、强度、人体工程学设计、处理、声学、碰撞冲击力和能量吸收等方面的满足要求。其他基本条件：接口与相邻元件可靠、拆装方便、连接可靠、成本低。连接可靠、成本低。
三、材料三、材料
通过材料轻量化可以实现保证强度下，减轻重量的目的。当刚度或固有频率有相对严格的管径标准时，需要具有高弹性模量的低密度材料。选材一般选择常用材料，一方面材料利用率大，价格低廉，良好的耐用性。另一方面的要求是由制造业和连接过程决定的。钢、铝、镁和复合材料是转向系统的首选材料。低比重，高耐腐蚀性，制造成本低，高能量吸收和良性循环的能力，使铝倍受青睐。由于其热能含量高，可达90%90%用于汽车建设铝可以回收（智能设计用于汽车建设铝可以回收（智能设计用于汽车建设铝可以回收（智能设计//没有与其他材料混合）。铝的回收利用率高，铝在环境方面优势超过许多其他材料。所需的原料铝的初级能源的大量抵消了车辆的使用寿命，复合材料也将非常有发展前景，它有极大的刚性，低重量和能量吸收能力强，然而，目前，由于造价成本高，只是作为局部零件来减轻重量。只是作为局部零件来减轻重量。
四、减少零件的重量四、减少零件的重量
采用集成方法以降低组件的重量，需要一个轻量化的方案。采用集成方法以降低组件的重量，需要一个轻量化的方案。
设计（力分布、应力）、材料（选材）、规格（可修改，现实的规格）。轻量化设计的关键因素包括：力流、材料特性、环境条件、安全要求、连接可靠、生产能力等。产能力等。实践经验表明，实
践经验表明，实践经验表明，对汽车制造商的规格需要轻量化修订。对汽车制造商的规格需要轻量化修订。对汽车制造商的规格需要轻量化修订。有效需求为钢有效需求为钢材转向轴，材转向轴，例如，例如，例如，可能会导致铝轴严重的偏大。可能会导致铝轴严重的偏大。可能会导致铝轴严重的偏大。减少零件重量要求材料设计结合减少零件重量要求材料设计结合材料相容规格。材料相容规格。
五、轻量级组件五、轻量级组件
作为其发展计划的克虏伯普雷斯塔是取代传统的钢转向部件，如转向杆转向部件，轴或轴叉相应的铝元件生产的新工艺。根据客户的需求，可实现减轻20-30%20-30%的重量。的重量。的重量。转向柱已被用于铝和镁压铸件，转向柱已被用于铝和镁压铸件，转向柱已被用于铝和镁压铸件，并正在研究进一步减轻重量。并正在研究进一步减轻重量。并正在研究进一步减轻重量。轻轻便的转向柱由克虏伯普雷斯塔生产的奥迪A6是一个很好的例子。通过使用镁合金压铸件有可能限制转向柱的重量为5公斤，减少15-20%15-20%常规（钢）设计。常规（钢）设计。常规（钢）设计。
六、转向柱设计六、转向柱设计
经验表明，它有可能或仅靠其固有频率的基础上设计汽车转向柱。可能需要额外的工作量设计关键部件，在崩溃或滥用（如盗窃）的情况下，不能突破。当转向柱在主要工作任务时，达到尽可能高的固
有频率，同时最大限度地减少重量。分析低刚度组件结构，实现均匀加载结构。在解决这个任务，使用数值方法，如有限元分析。这是由特定的变形假设为特征的有限元结构所决定的。利用有限元分析检测复杂结构，灵敏度分析以及存在联系，分析如何作出改善和优化结构的数值。拓扑优化进行了分析低应力区的基本设计。数值。拓扑优化进行了分析低应力区的基本设计。
CAD 几何数据处理在FE 预处理的基础上。以下是正确的建模需要考虑的方面。刚性、接触面、运动学、质量。其次是所获得的数据的计算和评估模型。变应力的评估是广泛强调采取的措施。晶粒细化，组织均匀，则应变能力好。振动影响着转向柱的固有频率。通过评估应变力的状况，可以确定应力集中区。着转向柱的固有频率。通过评估应变力的状况，可以确定应力集中区。
七、结论七、结论
现有技术必须不断调整和完善以符合推动汽车行业的发展。减轻转向系统重量是一个重大的挑战，一个重大的挑战，并需要汽车制造商和供应商之间的密切合作。并需要汽车制造商和供应商之间的密切合作。并需要汽车制造商和供应商之间的密切合作。材料，材料，材料，制造和连制造和连接技术，必须进一步完善。克虏伯公司持续成功的先决条件之一是不断创新完善以满足客户的愿望和需求。以满足客户的愿望和需求。
参考参考 [1][1]克莱因，克莱因，克莱因，B B ：
Leichtbau- Konstruktion 。 Berech nungsgrundlagen 和Gestaltung Gestaltung。不伦瑞。不伦瑞克：发表，克：发表，199719971997。。 论坛论坛 - Mitteilungen - Mitteilungen 蒂森克虏伯和技术蒂森克虏伯和技术
