自行车用无级变速器结构设计【8张CAD图纸+WORD毕业论文】【汽车车辆专业】

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目录
1 绪论 3
1.1 机械无级变速器的概述及应用 3
1.2 无级变速器的分类 3
1.3 机械无级变速器的发展 4
1.4 无级变速自行车研究现状 6
1.5 毕业论文设计内容和要求 7
2 钢球行星式无级变速器的总体方案选择 9
2.1 采用螺旋传动实现球架的左右移动 9
2.2 依靠左右推动实现球架的移动 10
2.3 两方案的选择与比较 10
3 钢球行星式无级变速器部分零件的设计计算 11
3.1 钢球的设计计算 11
3.2 钢球支轴转角的设计计算 12
3.3 轴槽的长度及卡盘的倾斜角的设计计算 13
3.4 轴的设计计算 14
3.4.1 轴的选材及最小直径的计算 14
3.4.2 轴的结构设计 15
3.4.3 轴的校核 16
3.5 滚动轴承的选择 18
3.6 自行车无级变速器的安装 19
4 钢球行星式无级变速器的变速原理论证 20
4.1 关于本文的无级变速器 20
4.2 无级变速的运动结构分析 20
4.2.1无级变速的运动 20
4.2.2 变速原理分析 22
5 结论 23
参考文献 24
致谢 25
外文翻译 26

自行车用无级变速器结构设计

专业:机械设计制造及其自动化
学生:朱杨华指导老师：聂松辉
摘要
无级变速器传动是指在某种控制的作用下，使机器的输出轴转速可在两个极值范围内连续变化的传动方式。而无级变速器是这样的一种装置，它具有主动和从动两根轴，并能通过传递转矩的中间介质（固体、流体、电磁流）把两根轴直接或间接地联系起来，以传递动力。当对主、从动轴的联系关系进行控制时，即可使两轴间的传动比发生变化（在两极值范围内连续而任意地变化）。本文在分析各种无级变速器和无级变速自行车的基础上，把钢球外锥式无级变速器进行部分改装，从而形成了自行车的无级变速装置。该装置通过八个钢球利用摩擦力将动力进行输入输出，用一对斜齿轮进行分度调速，从而使自行车在0.75～1.22之间进行无级调速。研究表明：无级变速器被用于自行车方面可以大大改善自行车的使用性能，方便广大消费者使用。
关键字: 无级变速自行车无级变速器调速

The design of the CVT on bicycle

Major:Mechanical design manufacturing and automation

Student: Zhu Yang Hua Supervisor:Nei Song Hui
Abstract
Have no the class gearbox spread to mean under the function that is a certain to control, make the exportation stalk of machine turn soon can at two pole is worth the continuous variety in the scope of spread a way.But have no class gearbox is such a kind of device, it has active with from move two stalks, and can pass to deliver the middle of turning the Ju to lie quality(the solid, fluid and electromagnetism flows) to contact two stalks directly or indirectly to deliver power.When to lord, from move an axial contact relation to carry on a control, can immediately make spreading of 2 compare occurrence variety.(be worth to change in a row but at will inside the scope in two poles).Based on the analysis of various CVT and CVT bikes,in this dissertation ,we change some parts of the Kopp-B CVT forming a new kind of CVT used to the bicycle .They are used to input or output the power through the friction and a pair of helical gears is also used to adjust the speed, so the speed can change between 0.75 and 1.22.This research shows that when the CVT are used in the bicycle ,they can significant improve the performance of bike so that all customers can use it convenient.
Keyword: CVT bike CVT Speed control.

1 绪论
1.1 机械无级变速器的概述及应用
机械无级变速器是一种传动装置，是在输入转速一定的情况下实现输出转速在一定范围内连续变化的一种运动和动力传递装置，由变速传动机构、调速机构及加压装置或输出机构组成。
机械无级变速器转速稳定、滑动率小、具有恒功率机械特性、传动效率较高，能更好地适应各种机械的工况要求及产品需要，易于实现整个系统的机械化、自动化，且结构简单，维修方便、价格相对便宜。机械无级变速器的适用范围广，有在驱动功率不变的情况下，因工作阻力变化而需要调节转速以产生相应的驱动力矩者（如化工行业中的搅拌机械，即需要随着搅拌物料的粘度、阻力增大而能相应减慢搅拌速度）；有根据工况要求需要调节速度者（如起重运输机械要求随物料及运行区段的变化而能相应改变提升或运行速度，食品机械中的烤干机或制药机械要求随着温度变化而调节转移速度）；有为获得恒定的工作速度或张力而需要调节速度者（如断面切削机床加工时需保持恒定的切削线速度，电工机械中的绕线机需保持恒定的卷绕速度，纺织机械中的浆纱机及轻工机械中的薄膜机皆需调节转速以保证恒定的张力等）；有为适应整个系统中各种工况、工位、工序或单元的不同要求而需协调运转速度以及需要配合自动控制者（如各种各样半自动或自动的生产、操作或装配流水线）；有为探求最佳效果而需变换速度者（如试验机械或离心机需调速以获得最佳分离效果）；有为节约能源而需进行调速者（如风机、水泵等）；此外，还有按各种规律的或不规律的变化而进行速度调节以及实现自动或程序控制等。
综上所述。可以看出采用无级变速器，尤其是配合减速传动时进一步扩大其变速范围与输出转矩，能更好的适应各种工况要求，使之效能最佳，在提高产品的产量和质量，适应产品变换需要，节约能源，实现整个系统的机械化、自动化等各方面皆具有显著的效果。故无级变速器目前已成为一种基本的通用传动形式，应用于纺织、轻工、食品、包装、化工、机床、电工、起重运输矿山冶金、工程、农业、国防及试验等各类机械。

1.2无级变速器的分类
机械无级变速器分为刚性式、行星式、链式、带式和脉动式四大类。
（1）摩擦式无级变速器由刚性传动元件组成，不调速时各传动件的回转轴线位置固定不变。它具有结构简单、形式多样的特点。它分为有中间滚轮与无中间滚轮两大类，前者有较大的调速比（Rb≤16～20），后者的Rb＜6。为提高功率体积比常采用多中间体的分汇流传传动方式。对于既升速又降速的变速装置一般需用两套加压装置。传动件接触区可设计成初始点或线接触的结构，前者承载能力稍差，但相对滑动较小，并能补偿受力变形及加工装配等误差；后者承载能力较高，但对制造和装配要求较高。
（2）行星式无级变速器具有作行星运动的中间滚动体，依靠滚动副间的牵引（摩擦）力，通过改变太阳轮或行星轮的工作半径来实现变速的无级变速器。其传动原理与一般锥齿轮行星轮系很相似，但没有轮齿因而工作半径在运动过程中可以调整。
由于上述传动原理的特点，使行星无级变速器的结构、性能与刚性式无级变速器不同。行星无级变速器的共同特点：1、变速范围较宽广；2、输出转速恒低于输入转速；3、输出特性好；4、采用多行星轮分汇流传动；5、结构紧凑，加压和调速操纵机构比较简单。
链式无级变速器通过两相对锥轮之间形成楔形夹槽，夹持着特殊结构的变速传动链，依靠压紧力使链和链轮形成力（或准形）封闭运动副，依靠摩擦力来传递动力，它属于钢质挠性变

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内容简介：: 湘潭大学兴湘学院毕业论文题目：自行车用无级变速器结构设计专业：机械设计制造及其自动化学号： 2010963142 姓名：朱杨华指导教师：聂松辉完成日期： 2014年5月29日湘潭大学兴湘学院毕业设计说明书题目：自行车用无级变速器结构设计专业：机械设计制造及其自动化学号： 2010963142 姓名：朱杨华指导教师：聂松辉完成日期： 2014年5月29日湘潭大学兴湘学院毕业论文（设计）任务书论文（设计）题目：自行车用无级变速器结构设计学号： 2010963142 姓名：朱杨华专业：机械设计制造及其自动化指导教师：聂松辉系主任：一、主要内容及基本要求 1、输入功率P=0.15kw、最低转速n=20rpm、调速范围R=8； 2、装配图A0#1张、零部件图总量不小于A0#1张； 3、设计说明书一份（含电子文档）； 4、英文文献翻译资料一份，不少于3000Words。二、重点研究的问题 1、机械式无级变速器的变速原理； 2、基于变速原理的传动结构实现。三、进度安排各阶段完成的内容起止时间1熟悉课题与基础资料第1周2调研、收集资料第2周3方案设计与论证第34周4无级变速器各零件三维模型设计第57周5无级变速器总装配图设计第8周6无级变速器工程图设计第9周7无级变速器关键部件运动仿真第10周8撰写设计说明书第11周9英文文献翻译答辩第12周四、应收集的资料及主要参考文献应收集的资料：自行车无级变速器的类型和无级变速自行车的研究现状，零件的设计与计算的方法，以及选型等。主要参考文献： 1 周有强. 机械无级变速器M. 成都:机械工业出版社,2001. 2 阮忠唐.机械无级变速器设计与选用指南M.北京:化学工业出版社，1999. 外文翻译半固态成型：竞争来自汽车复杂零件的锻造机Q. ZHU1, S. P. MIDSON21.英国康明斯涡轮增压技术有限公司，圣安得烈路，哈德斯菲尔德，Hd1 6RA S；2.美国铝复杂组分公司，科罗拉多州丹佛贾森街道2211南，80223， 2010年5月13日收到; 2010年6月25日接受摘要叶轮制造的最新技术被称为半固态成型（SSM）。它是康明斯涡轮增压技术有限公司与铝复合元件公司一起开发，SSM压缩机轮的一种方式。它能使铸造和加工固体之间（MFS）铝合金车轮，实现成本和耐久性的地方。实验结果表明，SSM材料具有优良的显微组织和力学性能，这些都高于MFS材料。测试包括耐久性的组分测试，使用加速的速度周期测试，证明SSM压缩机轮子比铸造的等值更耐用和接近MFS叶轮。为了使半固态处理进一步挑战of other complex components and other materials in automotive industry in terms of both cost and durability are also discussed.，对汽车行业中制造成本和其他成分复杂等材料的耐久性进行了讨论。关键词：铝合金; 半固体造型; 耐久性; 汽车复杂组分; 蒸气增压器压缩机轮子1引言柴油和汽油发动机是造成的排放和全球变暖的一个重要来源。为了提高燃油效率和减少排放，汽车轻量化是一种有效的方法.。半固态成型（SSM）已成功帮助，减轻汽车零部件的重量，明显改善的机械性能。所以，可以用小或更薄的壁零件。汽车零部件已成功用SSM。达斯古普塔 1 总结了最普遍的应用如下： 1) A357-T5,2)自动传输使换中档杠杆A357-T5， 3)发动机装配A357-T5， 4)引擎托架1 800 g A357-T5， 5)上部控制臂A356-T6， 6)悬浮A357-T5， 7)引擎托架720 g A357-T5， 8)引擎托架2400 g A357-T5和9)柴油引擎A356- T5泵体加油路轨。发动机技术发展的另一种有效的提高燃油效率和减少排放。增加气压比率到发动机方式能够进一步提高燃油效率和减少排放的目的。增加气压可以通过在一个涡轮增压器压缩机轮来实现。压缩机轮需要非常复杂的叶片，几何实现高压力比。应付250 C和重大温度差时，压缩机轮承受的旋转速度高达200 000转/分钟。除机械力量和温度能力的要求之外，由于在速度周期上的刀片的变化和振动，疲劳是一种典型的失效模式。这种组合的复杂的几何形状和坚韧操作条件,意味着调制解调器压缩机轮子要求最佳的物质技术。几十年来，压缩机的车轮含有铝，硅和铜的合金。要达到指定的耐久性目标，然而，制约他们的发行速度，即是必要的。由于铸造缺陷，在操作过程中减少了发动机的效率。因此，固体(MFS)或锻件压缩机轮子的开发，克服铸件瑕疵问题。在耐久性的改善也意味MFS轮子可能可靠地跑以更高的速度，增长的燃料效率和减少排放。缺点是MFS铸造比较昂贵。因此，半固态成形加工（SSM）应用开发的制造过程中，在铸造和MFS铝合金之间车轮，去实现成本和耐久性能。由于压缩机轮几何形状复杂，精度控制的要求和严格的操作条件，制造压缩机轮可能是SSM最困难的过程。在这项工作SSM应用的开发和结果在制造业压缩机轮子在复杂几何学汽车组分制造被提出，为例SSM应用。2 涡轮增压最近涡轮增压技术广泛用于柴油发动机和汽油发动机，直接喷射技术也一起发展。对于新汽车涡轮增压器的应用量（合适的）。如图1所示，在过去10年1999年-2004年稳定增长约10%和2004年-2009年约5%，平均年增长率约7%。在2004年-2009年较低的增长率，主要是由经济衰退引起的。自2008年以来，未来10年预计年增长率将有约8%。2007年蒸气增压器新车的世界总宽容量大约是20百万个单位，相当于6.8十亿USD。图1 全球涡轮增压发动机市场（首次适应卷）涡轮增压器可以通过压缩机轮子有效地增加气压，这是由通过废气涡轮轴排气。图2显示了一个典型的废气旁通增压器。压缩机轮子的转动速度可高达200 000 r/min。进一步增加的速度是提高效率和燃油经济性。然而，转动速度由压缩机和涡轮叶轮的材料物产生限制。涡轮增压器故障主要是由压缩机或涡轮机在高温条件下引起疲劳。图2典型的废气旁通增压器概述3 SMM制造涡轮增压器压缩机轮的挑战涡轮增压器压气机叶轮几何的设计是非常复杂，为了满足特定的效率和耐久性的要求。图3给出了一个典型的压缩机叶轮的设计。叶片长度与叶片厚度比约为25，这使得它在SSM难填补的叶片和中央集线器刀片的质量比可以达到80左右，同时这使得它很难获得满意的叶片和轮毂组织。此外，叶片的曲度在处理以后SSM模子难拆卸。因此，模具设计，浇注系统设计及模具温度控制和流道系统是达到一个成功的结果的关键参量2。另外，材料也必须经过仔细挑选，以满足在严格操作条件下符合压缩机轮子的耐久性的严密要求。图3概述（a）、剖面图（b）典型的压缩机w heel砂轮4 材料的选择材料的选择是决定开始的物理性能如热导率，热系数和合金密度保证当前组分设计有效性。认为3XX铸造铝合金可用于目前压缩机轮的设计。可用所有 3-33 数据的SSM的力学性能和铸铝合金比较后，319s合金被选择制造压缩机轮子。图4显示319s合金具有合理最好的和一致的拉伸强度和伸长率。从纯粹的拉伸性能的观点，SSM A201也显示了可喜的成果。因此，SSM A201试验，更好的实现了文学强度和延性比。然而，SSM A201没有市售的。所以用于制造压缩机轮仍然是SSM 319s合金。图4 SSM铝合金的拉伸性能比较永久模铸造的（PM）5 结果在表1中给出了SSM压缩机轮选择合金319s化学成分。图5显示SSM 319s压缩机轮有优越的抗拉伸强度和延展性。在2618锻造热处理T61的条件下用于压缩机轮的c355和目前354接近。单轴疲劳试验结果表明，试样从一个平行的方向锻造2618合金的金属流动具有优良的耐疲劳性，而在垂直方向有类似的疲劳性能抵抗熔铸355（6）。金属化流程样品的取向之间这个区别主要出现从粗第二个阶段微粒的对准线。改善疲劳在图6小应变中可以看到SSM 319s在铸造355的属性。如图7所示，已被证明组件的磁盘疲劳试验，是由单轴的压缩应力与R O在从压缩机轮子的后面面孔用机器制造的盘样品进行。在涡轮增压器组件测试中，检测的细胞受康明斯涡轮增压技术的限制，结果列于图8。图8显示了铸造c355，2618和SSM 319s相比的耐久性。SSM 319s和伪造2618压缩机轮之间，虽然他们都优越铸造c355的耐久性。SSM 319s和伪造的2618的这重大改善主要来自材料的改善和铸件瑕疵的排除，例如氧化物。除对材料的完整性，锻造和SSM的改进清洁。锻造2618和SSM 319s比铸造的C355和354.0的晶粒结构细化和显微组织是对压缩机轮子的耐久性改善的另一贡献(图9)。图5显示了SSM 319s铸造优越的抗拉性能C355, 354.0 and 319 while comparable with forged 2618c355，354和319，与锻造2618图6通过铸造SSM 319s显示出c355与锻造2618优越的耐疲劳性图7 SSM 319s显示出在铸造c355阻力优越的单轴疲劳resistance over cast C355图8 SSM 319s压缩机轮表现出在铸造c355压缩机轮与forged 2618锻造2618优越的耐久性图9晶粒结构的铸造c355（a），2618（b）和锻造SSM 319s (c), indicating comparable grain size between forgedSSM 319s（c），表明类似的晶粒尺寸之间锻造and SSM alloys, while both significant finer than cast alloy和SSM合金，而显著小于铸造合金。5 执行总结1）涡轮增压是实现大幅减排和燃油经济一个最成功的技术。涡轮增压发动机在过去10年已经取得大约7%的体积增加，并且未来10年预测增长8%。2）SSM已被成功地应用于生产极其复杂的几何涡轮增压器的压缩机车轮。3）SSM压缩机轮取得了拉伸，疲劳性能和部件的耐久性。所以，它接近2618锻造，优于铸造c355。6 未来的挑战虽然制造业的SSM汽车零部件已取得重大进展，研究人员努力开发新的合金和工艺，仍有需要更多的努力来满足工业要求。这些措施包括：1）更多选择的合金有汽车的工业应用不同要求，一些需要高强度，而有些人可能需要高的热性能，疲劳性，耐腐蚀性和耐磨性。这些都需要不同的合金系统满足一个或多个工业应用的要求。2）高熔点合金系统发展SSM是最大的努力过程历史上以相对较低的熔化点、合金如铝和镁合金。一些努力和成功取得了高熔点点合金如钢 34 ，但进一步的研究需要发展的材料系统的铸铁，钢镍基合金。这些材料具有显着的比铝和镁合金密度更高，所以有更大的潜在节省更多的重量汽车零部件，从而更多的燃油经济性，和提高质量和性能，耐久性在SSM过程改进的光比合金。3）复杂的几何部件一些汽车零部件的复杂几何，例如一个涡轮增压器压气机轮和发动机缸头，使得它很难实现严格的性能要求，在铸造锻坯加工效率/成本。因此，SSM几何组成有制造复杂的巨大潜力。非常低的剪切强度在半固态状态合金使它实现制造复杂的几何部件时浇注系统的合理设计与模具结构在低剪切强度达到可容纳相对较高的抗压强度。4）还原电流SSM元件成本在使用SSM加工过程中减少零件的制造成本实现锻坯。然而，由于成本高制造原料棒料，复杂性浇注系统和模具结构以及相对高成本，SSM组件的成本仍然显著高于铸造。因此，应作出努力，进一步达到降低成本棒料的原材料，设计和制造浇注系统和模具结构和工艺。致谢作者想表达他们的感谢，在康明斯涡轮增压迈克尔凤博士对批判性阅读和科技有限公司本文的评论。多亏了安得烈.杰克逊的铝成分复杂，开发工具和一般支持successfully manufacturing the SSM impelle成功地生产的SSM叶轮。参考文献 1 达斯古普塔R. 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Cummins Turbo Technologies Limited, together with Aluminum Complex Components Inc, developed SSM compressor wheels as a way of achieving cost and durability performance somewhere between that of cast and machined from solid (MFS) aluminium alloy wheels. Experimental results show SSM material has a superior microstructure and mechanical properties over cast and comparable to MFS materials. Component testing including durability testing, using accelerated speed cycle tests, proves SSM compressor wheels emerge as being significantly more durable than cast equivalents and approaching that of MFS impellers. Further challenges for semi-solid processing in manufacture of other complex components and other materials in automotive industry in terms of both cost and durability are also discussed. Key words: aluminum alloys; semi-solid moulding; durability; automotive complex component; turbocharger compressor wheel 1 Introduction Diesel and gasoline engines are one of the most important sources to cause emission and global warming. To increase fuel efficiency and to reduce emission, vehicle weight reduction is one of the effective ways. Semi-solid moulding (SSM) has successfully helped to reduce weight of automotive components due to the significant improvement of mechanical properties over cast, so, smaller or thinner wall parts can be used. Automotive components have been successfully manufactured by SSM. DASGUPTA1 has summarized the most popular applications as: 1) fuel rail of A357-T5, 2) automatic transmission gear shift lever of A357-T5, 3) engine mount of A357-T5, 4) engine bracket 1 800 g of A357-T5, 5) upper control arm of A356-T6, 6) suspension of A357-T5, 7) engine bracket 720 g of A357-T5, 8) engine bracket 2 400 g of A357-T5, and 9) diesel engine pump body of A356-T5. Engine technology development is another effective way increasing fuel efficiency and to reduce emission. Increasing the air pressure ratio to the engine is a way to achieve the objective of further improving fuel efficiency and reducing emission. One way to increase air pressure can be achieved by a compressor wheel in a turbocharger. The compressor wheel needs very complex blade geometry to achieve high pressure ratios. Compressor wheel withstands rotational speeds up to 200 000 r/min but must do so while coping with up to 250 C and a significant temperature gradient. In addition to the requirements of mechanical strength and temperature capability, fatigue is a typical failure mode of a compressor wheel in application due to changes in speed cycles and vibration of blades. This combination of sophisticated geometry and tough operating conditions means that the modern compressor wheels demand the best material technology. Compressor wheels for decades have been cast from alloys containing aluminum, silicon and copper. To achieve the specified durability targets, however, it is necessary to restrict their release speed, i.e. to reduce efficiency of an engine during operation due to cast defects. Therefore, the machined from solid (MFS) or forging compressor wheels have been developed to overcome the casting defect problem. The improvement in durability also means MFS wheel can run reliably at the higher speeds, increasing fuel efficiency and reducing emission. The downside is that MFS is significantly more expensive than casting. Therefore, semi-solid moulding (SSM) processing is applied to develop a manufacturing process that is a Corresponding author: Q. ZHU; +44-1484-832567; E-mail: Qiang.zhuC; Qiang.zhuTrans. Nonferrous Met. Soc. China 20(2010) s1042- -s1047 Q. ZHU, et al/Trans. Nonferrous Met. Soc. China 20(2010) s1042- -s1047 s1043way of achieving cost and durability performance somewhere between that of cast and MFS aluminum alloy wheels. Due to the complex geometry, precision control requirement and severe operation condition of a compressor wheel, manufacturing compressor wheel may be one of the most difficult processes for SSM. In this work, development and results of SSM application in manufacturing compressor wheels are presented, as an example of SSM application in manufacture of complex geometric automotive components. 2 Turbocharging Turbocharging technology is widely used for diesel engine and recently also for gasoline engine together with direct injection technology development. The volume of turbocharger application for new vehicles (first fit) has steadily increased by about 10% between 1999 and 2004 and 5% between 2004 and 2009, leading to about 7% average annual increase rate in the past 10 years (Fig.1). The lower increase rate between 2004 and 2009 has been mainly caused by the economic recession since 2008 and it is expected that annual increase rate in the next 10 years will be about 8%. The total world wide volume of turbochargers in 2007 was about 20 million units for new vehicles, which was equivalent to 6.8 billion USD. Fig.1 Global turbocharged engine market (first fit volume) Turbocharger can effectively increase air pressure ratio through a compressor wheel, which is driven by turbine wheel through a shaft by exhaust gas. Fig.2 shows a typical wastegated turbocharger. The speed of rotation of the compressor wheel can reach as high as 200 000 r/min. Further increasing speed is desirable for improved efficiency and fuel economy. However, the rotation speed is limited by materials properties of the compressor and turbine wheels. Failure of a turbocharger is mainly caused by fatigue of the compressor or turbine wheel operated at high temperatures. Fig.2 Overview of typical wastegated turbocharger 3 Challenges of manufacturing turbocharger compressor wheels by SSM The geometry of a turbocharger compressor wheel is designed to be very complex in order to meet specific efficiency and durability requirement. Fig.3 presents a typical design of a compressor wheel. The ratio of blade length to blade thickness is about 25, which makes it difficult to fill the blade during SSM process, and the ratio of mass at central hub to blade can be about 80, which makes it difficult to get satisfied microstructure for both blade and hub simultaneously. In addition, the curvature of the blades makes it difficult to disassemble the SSM die after processing. Therefore, die design, runner system design and temperature control of the die and runner system are the key parameters to achieve a successful result2. In addition, materials must be also selected very carefully to meet the stringent requirements of durability of a compressor wheel under the severe operation conditions. Fig.3 Overview (a) and section view (b) of typical compressor wheel Q. ZHU, et al/Trans. Nonferrous Met. Soc. China 20(2010) s1042- -s1047 s1044 4 Materials selection Materials selection was started from determining the physical properties such as thermal conductivity, thermal coefficient and alloy density to ensure the validity of current component design. It was recognized that all 3XX cast aluminum alloys can be applied for currently designed compressor wheels. After comparison of all available data3-33 of mechanical properties for SSM and cast aluminum alloys, the 319s alloy was selected to manufacture compressor wheels. Fig.4 shows that SSM 319s alloy has reasonably the best and consistent tensile strength and elongation. From purely tensile property point of view, SSM A201 also shows promising results and therefore, trials were also conducted. Better strength and comparable ductility of SSM A201 than those in literature was achieved. However, SSM A201 was not commercially available so SSM 319s was still the alloy used to manufacture compressor wheels. Fig.4 Tensile properties of SSM aluminum alloys compared with permanent mould (PM) cast ones 5 Results Chemical composition of the selected alloy 319s for SSM compressor wheel is given in Table 1. Fig.5 shows that the SSM 319s compressor wheel had superior tensile strength and ductility over cast C355 and 354.0 currently used on compressor wheels and approaching those of the forged 2618 under the condition of heat treatment T61. Uniaxial fatigue testing results showed that samples cut from forged 2618 alloy in a parallel direction to the metal flow had superior fatigue resistance whereas in the perpendicular direction it had similar fatigue resistance to cast 355 (Fig.6). This difference between orientations of sample to metal flow mainly arises from the alignment of coarse second phase particles. Improvement of fatigue property of SSM 319s over cast 355 can also be seen at Table 1 Chemical composition of 319s (mass fraction, %) Element Min. Max. Copper (Cu) 2.0 3.0 Magnesium (Mg) 0.25 0.35 Silicon (Si) 5.0 6.0 Iron (Fe) 0.15 Nickel (Ni) 0.03 Zinc (Zn) 0.05 Titanium (Ti) 0.20 Manganese (Mn) 0.03 Lead+Tin (Pb+Sn) 0.05 Strontium (Sr) 0.01 0.05 Others (Each) 0.03 Others (Total) 0.1 Aluminium (Al) Bal. Fig.5 SSM 319s showing superior tensile properties over cast C355, 354.0 and 319 while comparable with forged 2618 Fig.6 SSM 319s showing superior fatigue resistance over cast C355 while comparable with forged 2618 small strains in Fig.6. This has been proven by component disk fatigue test, where uniaxial compressive stress with R0 on the disk samples machined from back face of compressor wheel was performed, as shown in Fig.7. Component testing in a turbocharger was carried out on gas stand testing cells at Cummins Turbo Technologies Limited and the results are given in Fig.8. Q. ZHU, et al/Trans. Nonferrous Met. Soc. China 20(2010) s1042- -s1047 s1045Life comparison between cast C355, forged 2618 and SSM 319s in Fig.8 shows a comparable durability between SSM 319s and forged 2618 compressor wheels, while they both have superior durability over cast C355. This significant improvement of SSM 319s and forged 2618 arises mainly from improvement of material integrity and the elimination of casting defect such as oxides. In addition to the material integrity and cleanliness improvement by forging and SSM, refinement of grain structure and thus microstructure of forged 2618 and SSM 319s compared with cast C355 and 354.0 is another contribution to the durability improvement of compressor wheels (Fig.9). Fig.7 SSM 319s showing superior component uniaxial fatigue resistance over cast C355 Fig.8 SSM 319s compressor wheel showing superior durability over cast C355 compressor wheel while comparable with forged 2618 5 Executive summary 1) Turbocharging is one of the most successful technologies to achieve significant emission reduction and fuel economy. About 7% volume increase of turbocharged engines has been achieved in the past 10 years and 8% increase in the next 10 years is predicated. 2) SSM has been successfully applied to produce extremely complex geometric turbocharger compressor wheels. Fig.9 Grains structure of cast C355 (a), forged 2618 (b) and SSM 319s (c), indicating comparable grain size between forged and SSM alloys, while both significant finer than cast alloy 3) SSM compressor wheel has achieved tensile and fatigue properties, and so component durability, approaching forged 2618 and superior over cast C355. 6 Future challenges Although significant progress of manufacturing automotive components by SSM has been achieved and extensive efforts to develop new alloys and processes have been made by researchers, there are still needs for more efforts to satisfy requirements from the industry. These include: 1) More choices of alloys There are different requirements for automotive industrial applications, some need high strength, while some may need high thermal capability, fatigue resistance, corrosion resistance and/or wearing resistance. These need different alloy systems to meet one or more requirements for industrial applications. 2) High melting point alloy systems The greatest efforts of developing SSM processes historically are on alloys with relatively low melting Q. ZHU, et al/Trans. Nonferrous Met. Soc. China 20(2010) s1042- -s1047 s1046 points such as aluminum and magnesium alloys. Some efforts and success have been achieved on high melting point alloys such as steels34, but further studies are desirable to develop material systems of cast iron, steels and nickel base alloys. These materials have significant higher density than aluminum and magnesium alloys, so there is greater potential to save more weight of automotive components, and thus more fuel economy, and to improve durability by quality and property improvement in terms of SSM processes than for light alloys. 3) Complex geometric components Complex geometry of some automotive components, such as compressor wheels of a turbocharger and cylinder head in an engine, makes it difficult to achieve the stringent property requirements in cast and efficiency/cost in machining from forged billets. SSM has, therefore, great potential to manufacture complex geometric components. The very low shear strength of alloys at semi-solid status makes it achievable to manufacture complex geometric components when a proper design of runner system and die configuration can be achieved in accommodating the low shear strength but relatively high compressive strength. 4) Cost reduction of current SSM components Cost reduction of manufacturing components has been achieved using SSM process over machining from forged billets. However, due to the high cost of manufacturing raw material bar stock, complexity of runner system and die configuration as well as relatively high process costs, the costs of SSM components are still significantly higher than those of casting. Therefore, efforts should be made to further achieve cost reduction of raw material bar stock, of design and manufacture of runner system and die configuration and of processes. Acknowledgements The authors would express their acknowledgement to Dr. Michael VOONG of Cummins Turbo Technologies Limited for the critical reading and comments of this paper. Thanks also to Andrew P. JACKSON of Aluminum Complex Components Inc. for developing the tooling and general support for successfully manufacturing the SSM impellers. References 1 DASGUPTA R. C/ Proc of 8th Inter Conf on Semi-Solid Processing of Alloys and Composites. Cyprus, 2004. 2 ZHU Q, JACKSON A P. Method and apparatus of Manufacturing Turbine or Compressor WheelsP. WO2007/010181, 2007. 3 LIU D. D. Sheffield: University of Sheffield, 2003. 4 Metal Handbook. Properties and Selection: Nonferrous Alloys and Special Purpose MaterialsM. Vol.2, 10th Ed. Metal Park, OH: ASM, 1990. 5 WABUSSEG H, KAUFMANN H, UGGOWITZER P J. C/ CHIARMETTA G L, ROSSO M. Proc of 6th Inter Conf on Semi-Solid Processing of Alloys and Composites. Turin, Italy, 2000: 777-782. 6 BERGSMA S C, TOLLE M C, EVANGELISTA E. C/ BHASIN A K, MOORE J J, YOUNG K P, MIDSON S. Proc of 5th Inter Conf on Semi-Solid Processing of Alloys and Composites. Golden, Colorado, USA, 1998: 149-155. 7 ROSSO M, GIORDANO P, CHIARMETTA G L. C/ CHIARMETTA G L, ROSSO M. Proc of 6th Inter Conf on Semi-Solid Processing of Alloys and Composites. Turin, Italy, 2000: 325-330. 8 GARAT M, BLAIS S, PLUCHON C. C/ BHASIN A K, MOORE J J, YOUNG K P, MIDSON S P. Proc of 5th Inter Conf on Semi-Solid Processing of Alloys and Composites. Golden, Colorado, USA, 1998: xvii-xxxi. 9 EISEN P. C/ BHASIN A K, MOORE J J, YOUNG K P, MIDSON S P. Proc of 5th Inter Conf on Semi-Solid Processing of Alloys and Composites. Golden, Colorado, USA, 1998: ix-xvi. 10 NIU X P, HU B H, HAO S W. C/ BHASIN A K, MOORE J J, YOUNG K P, MIDSON S P. Proc of 5th Inter Conf on Semi-Solid Processing of Alloys and Composites. Golden, Colorado, USA, 1998: 141-148. 11 CHIARMETTA G. C/ KIRKWOOD D H, KAPRANOS P. 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