机械英文翻译及其原文小齿轮和锥齿轮的失效分析

1、 河 北 科 技 大 学毕业设计(论文)外文资料翻译学 院： 机械电子工程学院 专 业： 机械设计制造及其自动化 姓 名： 周 亮 学 号： 030501222 (用外文写)外文出处： engineering failure analysis volume 13,issue 8,december 2006,pages 1285-1292 附 件： 1.外文资料翻译译文；2.外文原文。 指导教师评语： 本外文资料翻译通顺，格式和字数符合要求。 签名： 2007年 月 日附件1：外文资料翻译译文小齿轮和锥齿轮的失效分析a. benselya, s. stephen jayakumara, d. m

2、ohan lala, g. nagarajana and a. rajaduraib安娜大学机械工程学院和印度大学的教授tamil nadua. benselya, s. stephen jayakumara, d. mohan lala, g. nagarajana 和 a. rajaduraib的这篇论文在2005年9月14日发表，2005年10月31日被收录，并于2006年二月9日可在线使用。摘要锥齿轮和小齿轮是汽车传动装置的重要组成部件。这些部件的失效对车辆运动有着强烈的影响。并将逐步导致修理时间的增加。除了他的功能受到影响外，这些部件也会增加危险性。用标准的材料力学去分析齿轮断裂，以

3、此来研究齿轮失效的原因。分析得出的结论表明制造材料的组成成分是失效的原因，在材料中可以明显的发现含有大量锰而没有镍和钼。这导致材料核心的硬度很高，高硬度却会使车辆传递系统中的重要部件产生早期的失效。关键字：渗碳；锥齿轮；齿轮齿的失效；金属断面的显微镜研究法来研究失效；奥氏体；文章概要1介绍2加工工序3试验研究4检测5点蚀6化学分析7微硬度分析8微观结构9齿轮齿接触的研究10结论感言参考目录1介绍机械系统的平均寿命总是依赖系统的最重要部分1。 在动力传动系统中通常是齿轮。齿轮设计通常按高速重载的的条件来设计最小的尺寸和重量。被用于重型车辆的一个典型锥齿轮和小齿轮如图1 图1 图形的整体尺寸展示

4、他们是车辆的最重要的部分，因此要求抗磨损性好和抗接触疲劳强度高。理想的锥齿轮和小齿轮应该符合美国齿轮制造业协会（agma）的11项质量标准，即均匀和适宜的金属质地，极好的抗扭矩变形，极大的抗冲击力，耐磨性，最佳的传动效率，比较小的噪声，小的自由震动和齿轮几何学。气体深碳是达到这些标准的一个工序。他使得齿轮耐磨损性和韧性增大2。制造者应该通过一些制造业标准选择适当的材料和正确的热处理参数来使重要的部件持久和高效。en353（15ni cr 1 mo 12）和en207(20 mn cr 1)是用于制造这些重要部件比较多的细密纹理的钢材。当en207被广泛的用于按规定尺寸制作齿轮和轴时，en353

5、却用于重型齿轮，轴，小齿轮，凸轮轴，连接销，重型车辆的传动部件的制造3。这篇文章将介绍锥齿轮和小齿轮的失效研究。2加工工序锥齿轮和小齿轮是在热处理后从850-880等温条件下获得的均质材料制造的。锻造是计算机数字控制齿轮的外形几何尺寸的精密制造。它在900 - 930下进行渗碳处理来得到均匀的表面薄膜。渗碳能达到1.524到1.905毫米的深度。淬火是在780 - 820下进行的，为了避免扭曲变形，淬火后要在油中冷却。对小齿轮来说，选择淬火是尽力提高齿轮的抗磨损性。小齿轮的曲线被特别的处理，这是为了得到能抵抗更高的冲击力和由固定产生的扭转力矩。淬火后，锥齿轮和小齿轮还要降温到150 - 200

6、以此来消除内应力。最后，锥齿轮和小齿轮要做全面的检测以防止早期的失效，同时保证无噪音的产生。齿轮隙被保证在0.2 0.3 毫米内以使噪音和震动最小4。3试验研究图2显示的是目前被采用的研究方法轮。图2 失效研究的方法4检测被研究的失效锥齿轮和小齿轮来自于一辆中等类型的商业汽车。这辆车有一个120千瓦引擎，并能够负载13000千克。它是一辆比较稳定和理想的建筑工程用车。如果一个锥齿轮或小齿轮失效，那么通常要换一对这样的齿轮；否则整个的寿命将会降低。锥齿轮的齿数是变化的，从客车到重型汽车都不同。重型汽车齿轮的齿数比客车的少些，但是齿的厚度要比客车的厚些。从检测上发现锥齿轮和小齿轮的齿数分别是和。他

7、们的预期寿命大概在和公里路程之间。失效的锥齿轮和小齿轮的表面断裂显露出在齿边缘处存在烧伤痕迹（冷焊），个齿的齿根断裂，在齿外部边缘处齿的碎屑到处都有。更进一步研究发现齿轮齿中没有磨损的表面在前面或者在后面，这使得锥齿轮和小齿轮看上去相对较新。（见图3）图3 失效的锥齿轮啮合的齿轮（也就是小齿轮）显示齿轮表面的疲劳断裂是由一个微小的裂纹引起的。大的碎片也远离了齿。疲劳纹理标志能在图4中看到。表面的疲劳是由表面的比较硬的组织在压应力下造成的。然而，破裂形成的裂纹深度要比点蚀所形成的深，并且它的内力的作用与交替变化的应力有关系。这经常被当成至关重要的，但因为它导致了表面低碳部分的疲劳断裂，先前的命名

8、将被经常使用。5点蚀通常，齿轮失效是由几个机械装置失效引起，但是大多数是由齿轮的齿面点蚀导致。实际上，齿面点蚀是机械装置失效的主要原因。这些失效都是由滚动接触磨损和部件表面寿命在应用的负荷下的磨损造成5。因此，我们用一个立体显微镜来对失效的部件进行大量的研究以次来探索齿面磨损齿轮的齿面磨损的特点是由齿轮接触面上的凹坑的出现。如图4图4 失效的小齿轮表面磨损的过程可以看作是表面破损或裂缝，他们都是在长期的接触负载下产生。当裂缝变的足够大时不稳定的生长就发生，而这则会导致一部分表层材料的崩落。导致这些发生的就是凹坑。在两个部件中凹坑有效性很少。相对来说，在小齿轮上的凹坑数目要比差动齿轮的多，并且齿

9、轮变形量也要比差动齿轮的高。这说明事实上失效是因为齿轮的工艺不够而不是点蚀。6化学分析因为没有关于齿轮的化学组成和热处理条件可用信息，下面的任务就是对材料进行鉴定。如图3所示，一件小的样品是用磨削轮在差动轮的a点处进行切割，并用发光摄谱仪和显微照片来进行研究与分析。化学分析在两个不同的部分进行，一个是在部件表面，另一个在部件的核心部分。化学分析有助于确定那些选来准备加工成部件的原材料的基本成分，在炭化处理过程中的含碳量以及基本组成在由制造者加工过程中的中和 。en353和en207的成分分析的结果在表1中列出表1 化学成分 元素 化学成分 (wt%) en 353 en 207 失效的组成 表

10、面核心碳0.120.180.170.220.910.24铬0.751.251.01.31.461.44锰0.61.01.11.41.441.43镍1.01.50.010.01钼0.080.150.010.01硅0.10.350.4 (最大)0.240.26我们可以发现那些选来准备做齿轮的材料和en353或en207都不符合，但是它们和en207在某些组成元素的变化上更接近。en 353 和en207比起来更适合与重载的场合应用不过也是比较昂贵的。碳元素和锰元素的含量都超标。碳，锰，珞，镍和钼能够增加材料的可淬性，但是和其他的合金成分比较起来锰和镍起的作用更大3。硅的出现也稍微增加硬化度但是在回

11、火期间保有成份的坚硬。镍加强亚铁盐而且增加硬化能力,细化精粒, 用良好的延展性来增加柔性的界限和可拉长的程度。它也能改善由疲劳撞击引起的抗力。因此镍没有上面所说的特点，所以它在材料中很少。钼的较高的含量可以减少脆性，阻止晶粒边界。通常当它参与亚铁盐形成碳化物的时候，钼，镍和铬被合成。同时，它也能阻止晶粒的生长。然而, 如表 1 所见到. 钼的百分比也会引起淬火脆性和晶粒边界分离。为了要检查材料的硬化能力，材料的碳同等物 (ce) 被评估如下:(1)发现在不合格的材料中碳的同等物含量是077，然而，在en207和en353中的含量则分别是0713和077。化学分析确定了失效是由于选择了不耐蚀的材

12、料。不仅制造业者已经在材料的基本组成上通过增加锰的比例来中和，这样就可以用锰来替换教昂贵的镍了。碳的含量还是高。这造成材料核心硬度较高但是表面却失效6。7硬度分析作为渗碳材料的一种情况，硬度的倾向是从外至里，外部比内部的硬度大。因此，实行微硬度研究，并且结果在图 5 中显示。大体上, 为计算有效表面深度 (ecd) 所采取的表面压力值是 540 hv， 并且它的深度期望在 1.524 和 1.905 毫米之间。 在最初含炭量（硬度关于深度保持不变）所达到的深度叫做完全表面深度。因此，完全表面深度超过有效表面深度。在同一硬度中，完全表面深度和有效表面深度分别是 737 hv ， 1.4 和 1.

13、22 毫米。对于失效的部分，核心硬度在齿根的中心测量，其数值是458 hv。 通常，期望的核心硬度在 317 和 401hv 之间，最大值可达 430 hv,超过这个值零件可能会被破坏。这对重型机械的要求是非常高的，高硬度材料是因为含锰比较多。高的核心硬度造成附属表面疲累和抗挤压力的下降。这也是导致早期失效的原因。在这一项研究， ecd 只有 1.22 毫米,他不能充分确定表面深度。不够的表面深度造成了如图 4 所显示的小齿轮牙齿破碎状而且依次减少顶轮的耐久性。这是由于在渗碳期间温度过低或者由于碳供给不充足。图5 微硬度测试8微观结构虽然残留奥氏体对增加接触疲累强度有益,当奥氏体以行列的形式排

14、列时，对空间结构和表面的硬度有益。在操作期间，亚稳定奥氏体将会在压应力和拉应力下转变成马氏体,这将使体积变大。体积的增大可能产生扭曲变形，从而产生压力，这可经过欠稳定和噪音造成寿命减短。过多的残留奥氏体也将会降低材料硬度和早期的抗疲劳强度。基本上，除了避免不必要的马氏体转换产物，如调质珠光体，钢必须要有充足合适的合金元素的加入来使金属的表面光滑和核心硬度提高7。含碳量控制核心硬度，其他的合金元素帮助控制核心硬度和马氏体变化物的含量。马氏体的转化物如珠光体和贝氏体比马氏体的质地软，而且会使钢的抗疲劳强度降低。因此，这种情况应该被避免。添加的元素如碳，锰，镍，钼和铬会降低马氏体开始的温度，并且会增

15、加奥氏体的含量。一个来自失效部分的小样品进一步在光学显微镜下进行微观结构的研究。失效成份的表面和核心微观图像在图 6 被显示。图 6. 失败成份的微细构造。 (a) 表面微观图像; (b) 核心微观图像。 表面微观图像显示含有70%的马氏体和 20-25% 残奥氏体,还有少部分的铁素体。 然而核心微观图像显示带状的贝氏体周围分布着均匀的铁素体。取代生成好的珠光体，带状贝氏体的产生可能是因为锰的含量增加导致的, 核心硬度高达458hv就能够说明这点 。这与贝氏体(410 hv)的硬度大约是相等的。关于裂纹性质的重要信息能从裂纹表面的微观研究中获得8。断口金相检验使用电子显微镜扫描(sem)。 实

16、际表面的更深一步研究使得电子显微镜扫描成为分析失效的一个重要工具。使用电子显微镜扫描来研究断裂齿的图像在图7中。裂纹已经产生的模型是非常易碎的，这在一点是非常明显的。图7 失效样本的图形9齿接触研究用失效的零件来进行接触研究是为了知道其中的细节和失效的顺序。用小齿轮的前齿面在锥齿轮的后锥面上进行旋转试验来研究齿的接触。锥齿轮齿的失效指数是17,18,19,27,29,30,31,32和38，然而小齿轮的失效指数是3。当传动比是6.5时，每一次试验的小齿轮的失效齿数并没有增加，而是和下次的试验一样。依次旋转下，和小齿轮的失效齿（第三齿）配对的锥齿轮失效齿可以在表中看到。锥齿轮失效的齿依次是17,

17、31,38,18,32,29,30和27。从图表2中可以看到小齿轮的失效齿并没有影响与他配对的锥齿轮的齿。从中也可证实失效并没有在锥齿轮的一次旋转中发生。在首次失效后再旋转七倍的时间，全部的齿就会失效。失效会逐渐的发生，最后就会发生冷焊现象。这一点表明冷焊现象发生在锥齿轮和全部的零件上，当工作时间超过失效时间的6倍时。失效的试验品部分也发生齿根断裂。表2 锥齿轮和小齿轮接触的研究锥齿轮的旋转相同条件下,小齿轮和锥齿轮接触依次失效的齿131017 小的2431 中间38 中间45271421283542341118 中间2532 大的39418152229 小的3643551219 小的2633

18、406219162330 大的374476132027 cold weld3441 齿根全部有裂纹的锥齿轮齿接触研究是在有标记(黄色油漆)的小齿轮帮助下完成的。然后它在锥齿轮上进行旋转。标有标记的失效样品锥齿轮将与标准样品齿轮进行比较，结果可以从图8中看到。这证明小齿轮与锥齿轮只是部分的接触，可能是由于校正的不好。这会在接触的齿上产生高的接触应力，导致更大的负载作用在非常小的面积上。在图3上可以看到这种情况导致齿的破裂发生在齿的边上。图8齿接触的样品10结论这个不正确的选择导致材料内部硬度高 ，致使早期失效产生。硬度分析得出的结论是有效的表面深度没有达到要求的水平是因为在渗碳时温度不够或者是碳

19、元素不够。不正确的热处理会使奥氏体在表面残留过多（大概25%），这对工作的零件有害。失效首先发生在小齿轮上，不管失效的齿与锥齿轮是在哪接触的，这都引起锥齿轮的早期失效 。局部的倒根是锥齿轮失效的典型事件。因此，重要零件必须进行热处理，使其有最少的网状碳素体，少的含碳量，少的奥氏体，来避免在工作时发生破裂，减少齿的快速磨损，和防止工作时扭曲变形。奥氏体的存在能用常规的热处理替代低温处理的方法来减少9。淬火后马上低温处理，接着进行回火处理可以增强零件的耐磨损性和刚度。在将来可以生产更耐用的零件。感言作者对mr. jeyaprakash narayanan, ex-ashok leyland, se

20、nior manager在论文方面的指导表示衷心的感谢。同时也要对mr. i. jeyakrishnan, dgm technical and mr. k. sevugarajan, metallurgist of m/s. ip rings limited, maraimalainagar的帮助表示感谢。参考书目1 s. farfan, c. rubio-gonzlez, t. cervantes-hernndez and g. mesmacque, high cycle fatigue, low cycle fatigue and failure modes of a carburized

21、 steel, int j fatigue 26 (2004), pp. 673678. 2 h.s. avner, introduction to physical metallurgy, tata mcgraw-hill publishing company limited (2002). 3 s.n. bagchi and p. kuldip, industrial steel reference book, wiley eastern limited (1986). 4 comet 4x4. ashok leyland service manual, 1969. 5 k.j. abha

22、y and v. diwakar, metallurgical analysis of failed gear, eng fail anal 9 (2002), pp. 359365. 6 k.h. prabhudev, handbook of heat treatment of steels, tata mcgraw-hill publishing company limited (2000). 7 fatigue and failures. asm handbook, vol. 19, 2002. p. 698700. 8 failure analysis and prevention.

23、asm handbook, vol. 11, 2002. p. 70027. 9 r.f. barron, effect of cryogenic treatment on lathe tool wear, prog refrigeration sci technol 1 (1973), pp. 529533. 附件2：外文原文（复印件）failure investigation of crown wheel and pinion a. benselya, , , s. stephen jayakumara, d. mohan lala, g. nagarajana and a. rajadu

24、raib received 14 september 2005; accepted 31 october 2005. available online 9 february 2006. abstract the crown wheel and pinion are the critical components in the transmission system of an automobile. failure of these components has drastic effect on the vehicular movement. this in turn leads to in

25、creased downtime for repairs. the cost of these components adds to the criticality in addition to its function. a fractured gear was subjected to detailed analysis using standard metallurgical techniques to identify the cause for failure. the study concludes that the failure is due to the compromise

26、 made in raw material composition by the manufacturer, which is evident by the presence of high manganese content and non-existence of nickel and molybdenum. this resulted in high core hardness (458hv) leading to premature failure of the vital component of transmission system in a vehicle. keywords:

27、 carburization; crown wheel; gear-tooth failures; failure investigation fractography; retained austenite article outline 1. introduction 2. manufacturing process 3. experimental investigation 4. visual examination 5. pitting 6. chemical analysis 7. microhardness survey 8. microstructure 9. tooth con

28、tact studies 10. conclusions acknowledgements references1. introduction life expectancy of mechanical systems is always dependent on the most critical component of the system 1. in power transmission system this is usually the gear. gear design is commonly bounded by the requirements that gear shoul

29、d carry high loads at high speeds with minimal size and weight. a typical crown wheel and pinion used in heavy vehicles is shown in fig. 1. display full size version of this image (54k)fig. 1.crown wheel and pinion. they are the most stress prone parts of a vehicle and demands high wear resistance,

30、high contact fatigue strength. an ideal crown wheel and pinion should have uniform and optimum metallurgical quality, excellent heat distortion control, maximum impact strength, stiff wear resistance, optimal transmission efficiency, less noise, vibration-free operation and gear geometry in accordan

31、ce with american gear manufacturers association (agma) 11 qualities. gas carburizing is a process employed to achieve some of these properties. it produces a very high wear resistant case and a soft tough core 2. the manufacturer should make the critical components durable and efficient through accu

32、rate and consistent manufacturing standards by selecting appropriate material and correct heat treatment parameters. en 353 (15 ni cr 1 mo 12) and en 207 (20 mn cr 1) are the two widely used fine-grained steel billet materials used in manufacturing of these critical components. typical applications

33、of en 353 being heavy-duty gears, shaft, pinions, camshafts, gudgeon pins, heavy vehicles transmission components while en 207 being used widely for medium sized gear wheels and shafts 3. this paper deals with a failure investigation of a crown wheel and pinion. 2. manufacturing process crown wheel

34、and pinion are manufactured from forged blanks that are isothermally annealed at 850880c to obtain uniform properties after heat treatment. the forgings are precision machined by computer numerical control gear generators to high dimensional accuracy. it is followed by gas carburizing at 900930c to

35、have uniform case, which can vary from 1.5241.905mm in its depth. hardening is done at 780820c in controlled atmospheric temperature and press quenched in oil to avoid distortion. in the case of pinion, selective case hardening is done to impart maximum strength to the pinion to maximize wear resist

36、ance. the pinion thread is specially treated to soft conditions to withstand higher shock loading and yielding arising out of torque tightening. after hardening, the crown wheel and pinion are tempered at 150200c to remove thermal stresses. finally, the crown wheel and pinion are checked thoroughly

37、for hard spots to prevent premature failure and also to ensure noise-free operation. the backlash is kept within 0.20.3mm band to keep noise and vibration to a bare minimum 4. 3. experimental investigation the research methodology adopted in the present investigation is shown in fig. 2. display full

38、 size version of this image (26k)fig. 2.research methodology for failure investigation. 4. visual examination the failed crown wheel and pinion taken for the investigation is from a medium type commercial vehicle. this vehicle has a 120kw engine and can transmit a payload of 13,000kg. it is a more s

39、table and ideal vehicle for construction and off road applications. if a crown wheel or pinion fails, always it is necessary that both have to be replaced completely as a matching pair; otherwise the life of the unit will be greatly reduced. the number of teeth in the crown wheel varies from passeng

40、er vehicles to heavy vehicles. heavy vehicles have less number of teeth when compared to passenger vehicles and also the thickness of the teeth is larger than passenger vehicles teeth thickness. from the visual examination it was found that the number of teeth in the crown wheel and pinion is 45 and

41、 7, respectively. the expected normal life of the component will approximately range between 1,50,000 and 2,00,000km. the fractured surfaces of the failed crown wheel and pinion showed the presence of burn marks (cold weld) on the edge of a teeth, partial uprooting on 8 number of tooth and teeth chi

42、pping all along the outer edge of the crown wheel. it was further observed that the gear teeth had no worn-out surface either on the front or on the rear side indicating that the crown wheel and pinion are relatively new (see fig. 3). display full size version of this image (35k)fig. 3.crown wheel f

43、ailure. the companion gear (i.e. pinion) shows sub case fatigue fracture initiated by fine cracks. large fragments have spalled away from the tooth. fatigue beach marks can also be seen in fig. 4. sub case fatigue is fracture of case hardened components by the formation of crack below the contact su

44、rface within the hertzian stress field. however, the depth at which the crack forms is much greater than the macro pitting fatigue and it is a function of material strength in conjunction with the alternating hertzian shear stress. it is also sometimes referred as case crushing but since it results

45、from fatigue crack that initiates below the effective case depth or in the lower carbon portion of the case, the former nomenclature will be used frequently. thin case depth relative to radius of curvature is the factor that controls the occurrence of sub case fatigue. display full size version of t

46、his image (34k)fig. 4.pinion failure. 5. pitting generally, gears fail due to several mechanisms but most often due to surface pitting of gear teeth. surface pitting is in fact the principal mode of failure of mechanical elements that are subjected to rolling contacts and governs the surface life of

47、 a component under applied load 5. hence, the failed components were subjected to macro examination using a stereomicroscope for pitting failure. the pitting of gear teeth is characterized by the occurrence of small pits on the contact surfaces, as visible in fig. 4. the process of surface pitting c

48、an be visualized as formation of surface-breaking or sub surface initial cracks, which grow under repeated contact loading. eventually the crack becomes large enough for unstable growth to occur, which results in a part of the surface material layer breaking away. the resulting void is a pit. the av

49、ailability of pits in both the components was very less. relatively, the number of pits in pinion is larger as the number of revolutions of pinion is higher than crown wheel. this confirms to the fact that the failure is premature and not due to pitting. 6. chemical analysis as no information with r

50、espect to the chemical composition and the heat treatment condition of the pinion material was available, the next task in the failure analysis was the material identification. a small size specimen was cut using abrasive cut off wheel from location a of the crown wheel as shown in fig. 3 and subjec

51、ted for optical emission spectrometer studies and metallographic examination. chemical analysis was carried out at two different locations, one at the surface (case) and another at the central portion (core) of the component. the chemical analysis helps to identify the basic composition of the raw m

52、aterial selected for the component, carbon potential used for carburizing process and any compromise on the basic composition with respect to the component that made by the manufacturer. the results of the chemical analysis along with the nominal composition of en 353 and en 207 are given in the tab

53、le 1. table 1. chemical composition elements chemical composition (wt%) en 353 en 207 failed component casecorecarbon0.120.180.170.220.910.24chromium0.751.251.01.31.461.44manganese0.61.01.11.41.441.43nickel1.01.50.010.01molybdenum0.080.150.010.01silicon0.10.350.4 (max)0.240.26it was found that the m

54、aterial selected for the preparation of the crown wheel and pinion was not exactly matching with either en 353 or en 207, but it was nearer to en 207 with variation in the composition of certain elements. en 353 is a better material for heavy-duty application than en 207 and it is costlier. also ele

55、ments like c, and mn were found to be excess than the required level expected for heavy-duty applications. c, mn, cr, ni and mo increase hardenability but the influence is higher for manganese, and nickel on comparing with other alloying elements 3. the presence of si also increases hardenability a

56、little but retains hardness of the component during tempering. nickel strengthens ferrite and increases hardenability, refines the grain, increases elastic limit and tensile strength with no practical loss in ductility. it also improves the resistance to fatigue and impact. since nickel is almost nil in the failed material it is devoid of all the above said characteristics. a higher percentage of molybdenum inhi