机械专业毕业论文（设计）外文翻译如何延长轴承寿命

1、毕业论文（设计）毕业论文（设计） 外外 文文 翻翻 译译 题题 目目： 如何延长轴承寿命 系部名称：系部名称： 专业班级：专业班级： 学生姓名：学生姓名： 学学 号：号： 指导教师：指导教师： 教师职称：教师职称： 如何延长轴承寿命如何延长轴承寿命 摘要摘要： 自然界苛刻的工作条件会导致轴承的失效，但是如果遵循一些简单的规则， 轴承正常运转的机会是能够被提高的。在轴承的使用过程当中，过分的忽视会导致轴 承的过热现象，也可能使轴承不能够再被使用，甚至完全的破坏。但是一个被损坏的 轴承，会留下它为什么被损坏的线索。通过一些细致的侦察工作，我们可以采取行动 来避免轴承的再次失效。 关键词关键词： 轴

2、承 失效 寿命 导致轴承失效的原因很多，但常见的是不正确的使用、污染、润滑剂使用不当、 装卸或搬运时的损伤及安装误差等。诊断失效的原因并不困难，因为根据轴承上留下 的痕迹可以确定轴承失效的原因。 然而，当事后的调查分析提供出宝贵的信息时，最好首先通过正确地选定轴承来 完全避免失效的发生。为了做到这一点，再考察一下制造厂商的尺寸定位指南和所选 轴承的使用特点是非常重要的。 1 1 轴承失效的原因轴承失效的原因 在球轴承的失效中约有 40%是由灰尘、脏物、碎屑的污染以及腐蚀造成的。污染 通常是由不正确的使用和不良的使用环境造成的，它还会引起扭矩和噪声的问题。由 环境和污染所产生的轴承失效是可以预防

3、的，而且通过简单的肉眼观察是可以确定产 生这类失效的原因。 通过失效后的分析可以得知对已经失效的或将要失效的轴承应该在哪些方面进行 查看。弄清诸如剥蚀和疲劳破坏一类失效的机理，有助于消除问题的根源。 只要使用和安装合理，轴承的剥蚀是容易避免的。剥蚀的特征是在轴承圈滚道上 留有由冲击载荷或不正确的安装产生的压痕。剥蚀通常是在载荷超过材料屈服极限时 发生的。如果安装不正确从而使某一载荷横穿轴承圈也会产生剥蚀。轴承圈上的压坑 还会产生噪声、振动和附加扭矩。 类似的一种缺陷是当轴承不旋转时由于滚珠在轴承圈间振动而产生的椭圆形压痕。 这种破坏称为低荷振蚀。这种破坏在运输中的设备和不工作时仍振动的设备中都

4、会产 生。此外，低荷振蚀产生的碎屑的作用就象磨粒一样，会进一步损害轴承。与剥蚀不 同，低荷振蚀的特征通常是由于微振磨损腐蚀在润滑剂中会产生淡红色。 消除振动源并保持良好的轴承润滑可以防止低荷振蚀。给设备加隔离垫或对底座 进行隔离可以减轻环境的振动。另外在轴承上加一个较小的预载荷不仅有助于滚珠和 轴承圈保持紧密的接触，并且对防止在设备运输中产生的低荷振蚀也有帮助。 造成轴承卡住的原因是缺少内隙、润滑不当和载荷过大。在卡住之前，过大的摩 擦和热量使轴承钢软化。过热的轴承通常会改变颜色，一般会变成蓝黑色或淡黄色。 摩擦还会使保持架受力，这会破坏支承架，并加速轴承的失效。 材料过早出现疲劳破坏是由重载

5、后过大的预载引起的。如果这些条件不可避免， 就应仔细计算轴承寿命，以制定一个维护计划。 另一个解决办法是更换材料。若标准的轴承材料不能保证足够的轴承寿命，就应 当采用特殊的材料。另外，如果这个问题是由于载荷过大造成的，就应该采用抗载能 力更强或其他结构的轴承。 蠕动不象过早疲劳那样普遍。轴承的蠕动是由于轴和内圈之间的间隙过大造成的。 蠕动的害处很大，它不仅损害轴承，也破坏其他零件。 蠕动的明显特征是划痕、擦痕或轴与内圈的颜色变化。为了防止蠕动，应该先用肉眼 检查一下轴承箱件和轴的配件。 蠕动与安装不正有关。如果轴承圈不正或翘起，滚珠将沿着一个非圆周轨道运动。 这个问题是由于安装不正确或公差不正

6、确或轴承安装现场的垂直度不够造成的。如果 偏斜超过 0.25，轴承就会过早地失效。 检查润滑剂的污染比检查装配不正或蠕动要困难得多。污染的特征是使轴承过早 的出现磨损。润滑剂中的固体杂质就象磨粒一样。如果滚珠和保持架之间润滑不良也 会磨损并削弱保持架。在这种情况下，润滑对于完全加工形式的保持架来说是至关重 要的。相比之下，带状或冠状保持架能较容易地使润滑剂到达全部表面。 锈是湿气污染的一种形式，它的出现常常表明材料选择不当。如果某一材料经检 验适合工作要求，那么防止生锈的最简单的方法是给轴承包装起来，直到安装使用时 才打开包装。 2 2 避免失效的方法避免失效的方法 解决轴承失效问题的最好办法

7、就是避免失效发生。这可以在选用过程中通过考虑 关键性能特征来实现。这些特征包括噪声、起动和运转扭矩、刚性、非重复性振摆以 及径向和轴向间隙。 扭矩要求是由润滑剂、保持架、轴承圈质量（弯曲部分的圆度和表面加工质量） 以及是否使用密封或遮护装置来决定。润滑剂的粘度必须认真加以选择，因为不适宜 的润滑剂会产生过大的扭矩，这在小型轴承中尤其如此。另外，不同的润滑剂的噪声 特性也不一样。举例来说，润滑脂产生的噪声比润滑油大一些。因此，要根据不同的 用途来选用润滑剂。 在轴承转动过程中，如果内圈和外圈之间存在一个随机的偏心距，就会产生与凸 轮运动非常相似的非重复性振摆（nrr） 。保持架的尺寸误差和轴承圈

8、与滚珠的偏心都 会引起 nrr。和重复性振摆不同的是，nrr 是没有办法进行补偿的。 在工业中一般是根据具体的应用来选择不同类型和精度等级的轴承。例如，当要 求振摆最小时，轴承的非重复性振摆不能超过 0.3 微米。同样，机床主轴只能容许最 小的振摆，以保证切削精度。因此在机床的应用中应该使用非重复性振摆较小的轴承。 在许多工业产品中，污染是不可避免的，因此常用密封或遮护装置来保护轴承， 使其免受灰尘或脏物的侵蚀。但是，由于轴承内外圈的运动，使轴承的密封不可能达 到完美的程度，因此润滑油的泄漏和污染始终是一个未能解决的问题。 一旦轴承受到污染，润滑剂就要变质，运行噪声也随之变大。如果轴承过热，它

9、 将会卡住。当污染物处于滚珠和轴承圈之间时，其作用和金属表面之间的磨粒一样， 会使轴承磨损。采用密封和遮护装置来挡开脏物是控制污染的一种方法。 噪声是反映轴承质量的一个指标。轴承的性能可以用不同的噪声等级来表示。 噪声的分析是用安德逊计进行的，该仪器在轴承生产中可用来控制质量，也可对 失效的轴承进行分析。将一传感器连接在轴承外圈上，而内圈在心轴以 1800r/min 的 转速旋转。测量噪声的单位为 anderon。即用 um/rad 表示的轴承位移。 根据经验，观察者可以根据声音辨别出微小的缺陷。例如，灰尘产生的是不规则 的劈啪声；滚珠划痕产生一种连续的爆破声，确定这种划痕最困难；内圈损伤通常

10、产 生连续的高频噪声，而外圈损伤则产生一种间歇的声音。 轴承缺陷可以通过其频率特性进一步加以鉴定。通常轴承缺陷被分为低、中、高 三个波段。缺陷还可以根据轴承每转动一周出现的不规则变化的次数加以鉴定。 低频噪声是长波段不规则变化的结果。轴承每转一周这种不规则变化可出现 1.610 次，它们是由各种干涉（例如 轴承圈滚道上的凹坑）引起的。可察觉的凹坑 是一种制造缺陷，它是在制造过程中由于多爪卡盘夹的太紧而形成的。 中频噪声的特征是轴承每旋转一周不规则变化出现 1060 次。这种缺陷是由在轴 承圈和滚珠的磨削加工中出现的振动引起的。轴承每旋转一周高频不规则变化出现 60300 次，它表明轴承上存在着

11、密集的振痕或大面积的粗糙不平。 利用轴承的噪声特性对轴承进行分类，用户除了可以确定大多数厂商所使用的abec标 准外，还可确定轴承的噪声等级。abec标准只定义了诸如孔、外径、振摆等尺寸公差。 随着abec级别的增加（从3增到9） ，公差逐渐变小。但abec等级并不能反映其他轴承 特性，如轴承圈质量、粗糙度、噪声等。因此，噪声等级的划分有助于工业标准的改 进。 （本文摘译自nasa technical memorandum 107440） extending bearing life abstract：nature works hard to destroy bearings, but the

12、ir chances of survival can be improved by following a few simple guidelines. extreme neglect in a bearing leads to overheating and possibly seizure or, at worst, an explosion. but even a failed bearing leaves clues as to what went wrong. after a little detective work, action can be taken to avoid a

13、repeat performance. keywords: bearings failures life bearings fail for a number of reasons，but the most common are misapplication，contamination，improper lubricant，shipping or handling damage，and misalignment. the problem is often not difficult to diagnose because a failed bearing usually leaves tell

14、tale signs about what went wrong however，while a postmortem yields good information，it is better to avoid the process altogether by specifying the bearing correctly in the first placeto do this，it is useful to review the manufacturers sizing guidelines and operating characteristics for the selected

15、bearing. equally critical is a study of requirements for noise, torque, and runout, as well as possible exposure to contaminants, hostile liquids, and temperature extremes. this can provide further clues as to whether a bearing is right for a job. 1 why bearings fail about 40% of ball bearing failur

16、es are caused by contamination from dust, dirt, shavings, and corrosion. contamination also causes torque and noise problems, and is often the result of improper handling or the application environmentfortunately, a bearing failure caused by environment or handling contamination is preventable，and a

17、 simple visual examination can easily identify the cause conducting a postmortem il1ustrates what to look for on a failed or failing bearingthen，understanding the mechanism behind the failure, such as brinelling or fatigue, helps eliminate the source of the problem. brinelling is one type of bearing

18、 failure easily avoided by proper handing and assembly. it is characterized by indentations in the bearing raceway caused by shock loadingsuch as when a bearing is dropped-or incorrect assembly. brinelling usually occurs when loads exceed the material yield point(350,000 psi in sae 52100 chrome stee

19、l)it may also be caused by improper assembly, which places a load across the racesraceway dents also produce noise，vibration，and increased torque. a similar defect is a pattern of elliptical dents caused by balls vibrating between raceways while the bearing is not turningthis problem is called false

20、 brinelling. it occurs on equipment in transit or that vibrates when not in operation. in addition, debris created by false brinelling acts like an abrasive, further contaminating the bearing. unlike brinelling, false binelling is often indicated by a reddish color from fretting corrosion in the lub

21、ricant. false brinelling is prevented by eliminating vibration sources and keeping the bearing well lubricated. isolation pads on the equipment or a separate foundation may be required to reduce environmental vibration. also a light preload on the bearing helps keep the balls and raceway in tight co

22、ntact. preloading also helps prevent false brinelling during transit. seizures can be caused by a lack of internal clearance, improper lubrication, or excessive loading. before seizing, excessive, friction and heat softens the bearing steel. overheated bearings often change color，usually to blue-bla

23、ck or straw coloredfriction also causes stress in the retainer，which can break and hasten bearing failure premature material fatigue is caused by a high load or excessive preloadwhen these conditions are unavoidable，bearing life should be carefully calculated so that a maintenance scheme can be work

24、ed out another solution for fighting premature fatigue is changing materialwhen standard bearing materials，such as 440c or sae 52100，do not guarantee sufficient life，specialty materials can be recommended. in addition，when the problem is traced back to excessive loading，a higher capacity bearing or

25、different configuration may be used creep is less common than premature fatiguein bearingsit is caused by excessive clearance between bore and shaft that allows the bore to rotate on the shaftcreep can be expensive because it causes damage to other components in addition to the bearing 0ther more li

26、kely creep indicators are scratches，scuff marks，or discoloration to shaft and boreto prevent creep damage，the bearing housing and shaft fittings should be visually checked misalignment is related to creep in that it is mounting relatedif races are misaligned or cockedthe balls track in a noncircumfe

27、rencial paththe problem is incorrect mounting or tolerancing，or insufficient squareness of the bearing mounting sitemisalignment of more than 1/4can cause an early failure contaminated lubricant is often more difficult to detect than misalignment or creepcontamination shows as premature wearsolid co

28、ntaminants become an abrasive in the lubricantin addition。insufficient lubrication between ball and retainer wears and weakens the retainerin this situation，lubrication is critical if the retainer is a fully machined typeribbon or crown retainers，in contrast，allow lubricants to more easily reach all

29、 surfaces rust is a form of moisture contamination and often indicates the wrong material for the applicationif the material checks out for the job，the easiest way to prevent rust is to keep bearings in their packaging，until just before installation 2 avoiding failures the best way to handle bearing

30、 failures is to avoid themthis can be done in the selection process by recognizing critical performance characteristicsthese include noise，starting and running torque，stiffness，nonrepetitive runout，and radial and axial playin some applications, these items are so critical that specifying an abec lev

31、el alone is not sufficient torque requirements are determined by the lubricant，retainer，raceway quality(roundness cross curvature and surface finish)，and whether seals or shields are usedlubricant viscosity must be selected carefully because inappropriate lubricant，especially in miniature bearings，c

32、auses excessive torquealso，different lubricants have varying noise characteristics that should be matched to the application. for example，greases produce more noise than oil nonrepetitive runout(nrr)occurs during rotation as a random eccentricity between the inner and outer races，much like a cam act

33、ionnrr can be caused by retainer tolerance or eccentricities of the raceways and ballsunlike repetitive runout, no compensation can be made for nrr. nrr is reflected in the cost of the bearingit is common in the industry to provide different bearing types and grades for specific applicationsfor exam

34、ple，a bearing with an nrr of less than 0.3um is used when minimal runout is needed，such as in diskdrive spindle motorssimilarly，machinetool spindles tolerate only minimal deflections to maintain precision cutsconsequently, bearings are manufactured with low nrr just for machine-tool applications con

35、tamination is unavoidable in many industrial products，and shields and seals are commonly used to protect bearings from dust and dirthowever，a perfect bearing seal is not possible because of the movement between inner and outer racesconsequently，lubrication migration and contamination are always prob

36、lems once a bearing is contaminated, its lubricant deteriorates and operation becomes noisierif it overheats，the bearing can seizeat the very least，contamination causes wear as it works between balls and the raceway，becoming imbedded in the races and acting as an abrasive between metal surfacesfendi

37、ng off dirt with seals and shields illustrates some methods for controlling contamination noise is as an indicator of bearing qualityvarious noise grades have been developed to classify bearing performance capabilities noise analysis is done with an anderonmeter, which is used for quality control in

38、 bearing production and also when failed bearings are returned for analysis. a transducer is attached to the outer ring and the inner race is turned at 1,800rpm on an air spindle. noise is measured in andirons, which represent ball displacement in m/rad. with experience, inspectors can identify the

39、smallest flaw from their sound. dust, for example, makes an irregular crackling. ball scratches make a consistent popping and are the most difficult to identify. inner-race damage is normally a constant high-pitched noise, while a damaged outer race makes an intermittent sound as it rotates. bearing defects are further identified by their frequenci