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1、精选学习资料 - - - - - - - - - 毕业论文 设计）外 文 翻 译题 目：如何延长轴承寿命系部名称：专业班级：同学姓名：学 号：指导老师：老师职称：如何延长轴承寿命摘要 ： 自然界苛刻的工作条件会导致轴承的失效,但是假如遵循一些简洁的规就,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0 / 11 名师归纳总结 - - - - - - -第 1 页,共 11 页精选学习资料 - - - - - - - - - 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,我们可以实行
2、 行动来防止轴承的再次失效；关键词 ： 轴承 失效 寿命 导致轴承失效的缘由很多,但常见的是不正确的使用、污染、润滑剂使用不当、装卸或搬运时的损耗及安装误差等；诊断失效的缘由并不困难,由于依据轴承上留下 的痕迹可以确定轴承失效的缘由；然而,当事后的调查分析供应出珍贵的信息时,最好第一通过正确地选定轴承来 完全防止失效的发生；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 轴承的使用特点是特别重要的；1 轴承失效的缘由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,它仍会引起扭矩和噪声的问题；由 环境和污染所产生的轴承失
3、效是可以预防的,而且通过简洁的肉眼观看是可以确定产 生这类失效的缘由；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当在哪些方面进行 查看；弄清诸如剥蚀和疲惫破坏一类失效的机理,有助于排除问题的根源；只要使用和安装合理,轴承的剥蚀是简洁防止的；剥蚀的特点是在轴承圈滚道上 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；假如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 仍会产生噪声、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
4、备中都 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,低荷振蚀的特点通常是由于微振磨损腐蚀在润滑剂中会产生淡红色；排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忙；造成轴承卡住的缘由是缺少内隙、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；过热的轴承通常会转变颜色,一般会变成蓝黑色或淡黄色；1 / 11 名师归纳总结 - - - - - - -第 2 页,共 11 页精选学习
5、资料 - - - - - - - - - 摩擦仍会使保持架受力,这会破坏支承架,并加速轴承的失效；材料过早显现疲惫破坏是由重载后过大的预载引起的；假如这些条件不行防止,就应认真运算轴承寿命,以制定一个爱护方案；另一个解决方法是更换材料；如标准的轴承材料不能保证足够的轴承寿命,就应 当采纳特别的材料；另外,假如这个问题是由于载荷过大造成的,就应当采纳抗载能 力更强或其他结构的轴承；蠕动不象过早疲惫那样普遍；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；蠕动的明显特点是划痕、擦痕或轴与内圈的颜色变化；为了防止蠕动,应当先用肉眼 检查一下轴承箱件和轴
6、的配件；蠕动与安装不正有关；假如轴承圈不正或翘起,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确或轴承安装现场的垂直度不够造成的；假如偏斜超过 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；污染的特点是使轴承过早 的显现磨损；润滑剂中的固体杂质就象磨粒一样；假如滚珠和保持架之间润滑不良也 会磨损并减弱保持架；在这种情形下,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简洁地使润滑剂到达全部表面；锈是湿气污染的一种形式,它的显现经常说明材料挑选不当；假如某一材料经检 验适合工作要求,那么防止生锈的最简洁的方法
7、是给轴承包装起来,直到安装使用时 才打开包装；2 防止失效的方法 解决轴承失效问题的最好方法就是防止失效发生；这可以在选用过程中通过考虑 关键性能特点来实现；这些特点包括噪声、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打算；润滑剂的粘度必需认真加以挑选,由于不相宜 的润滑剂会产生过大的扭矩,这在小型轴承中特别如此；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,要依据不同的 用途来选用润滑剂；2 / 11 名师归纳总结 - - - - - - -
8、第 3 页,共 11 页精选学习资料 - - - - - - - - - 在轴承转动过程中,假如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特别相像的非重复性振摆NRR）；保持架的尺寸误差和轴承圈与滚珠的偏心都会引起 NRR；和重复性振摆不同的是,NRR是没有方法进行补偿的；在工业中一般是依据详细的应用来挑选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 M；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当使用非重复性振摆较小的轴 承；在很多工业产品中,污染是不行防止的,因此常用密封或遮护装置来爱护轴承,使其免受灰尘或脏
9、物的腐蚀；但是,由于轴承内外圈的运动,使轴承的密封不行能达 到完善的程度,因此润滑油的泄漏和污染始终是一个未能解决的问题；一旦轴承担到污染,润滑剂就要变质,运行噪声也随之变大；假如轴承过热,它 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；采纳密封和遮护装置来挡开脏物是掌握污染的一种方法；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掌握质量,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；
10、即用 um/rad 表示的轴承位移；依据体会,观看者可以依据声音辨别出微小的缺陷；例如,灰尘产生的是不规章 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；内圈损耗通常产 生连续的高频噪声,而外圈损耗就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；缺陷仍可以依据轴承每转动一周显现的不规章变化的次数加以鉴定；低频噪声是长波段不规章变化的结果；轴承每转一周这种不规章变化可显现 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
11、点是轴承每旋转一周不规章变化显现1060 次；这种缺陷是由在轴承圈和滚珠的磨削加工中显现的振动引起的；轴承每旋转一周高频不规章变化显现 60300次,它说明轴承上存在着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,仍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 3 / 11 名师归纳总结 - - - - - - -第 4 页,共 11 页精选学习资料 - - - - - - - - - 差；随着 ABEC级别的增加 从3增到9）,公差逐步变小；但 ABEC等级并不能反映其他轴承特性,如轴承圈质量、粗糙
12、度、噪声等；因此,噪声等级的划分有助于工业标准的改进； 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 turningTh
13、is problem is called false 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 fre
14、tting corrosion in the lubricant. 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 bal
15、ls and raceway in tight contact. 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
16、 color,usually to blue-black or straw colored Friction also causes stress in the retainer,which can break and hasten bearing failurePremature material fatigue is caused by a high load or excessive preloadWhen these conditions are unavoidable, bearing life should be carefully calculated so that a mai
17、ntenance scheme can be worked outAnother solution for fighting premature fatigue is changing material When 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
18、higher capacity bearing or different configuration may be usedCreep 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
19、 the bearing5 / 11 名师归纳总结 - - - - - - -第 6 页,共 11 页精选学习资料 - - - - - - - - - 0ther more likely creep indicators are scratches, scuff marks,or discoloration to shaft and bore To prevent creep damage, the bearing housing and shaft fittings should be visually checkedMisalignment is related to creep in t
20、hat it is mounting related If races are misaligned or cocked The balls track in a noncircumferencial path The problem is incorrect mounting or tolerancing , or insufficient squareness of the bearing mounting siteMisalignment of more than 1/4can cause an early failureContaminated lubricant is often m
21、ore difficult to detect than misalignment or creepContamination shows as premature wearSolid contaminants become an abrasive in the lubricant In addition ；insufficient lubrication between ball and retainer wears and weakens the retainer In this situation, lubrication is critical if the retainer is a
22、 fully machined typeRibbon or crown retainers,in contrast, allow lubricants to more easily reach all surfacesRust 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 i
23、n their packaging,until just before installation2 Avoiding failures The best way to handle bearing 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
24、radial and axial playIn some applications, these items are so critical that specifying an ABEC level alone is not sufficientTorque requirements are determined by the lubricant , retainer , raceway qualityroundness cross curvature and surface finish ,and whether seals or shields are used Lubricant vi
25、scosity must be selected carefully because inappropriate lubricant ,especially in miniature bearings,causes excessive torqueAlso,different lubricants have varying noise characteristics that should be matched to the application. For example,greases produce more noise than oilNonrepetitive runoutNRRoc
26、curs during rotation as a random eccentricity between the inner and outer races,much like a cam actionNRR can be caused by retainer tolerance or 6 / 11 名师归纳总结 - - - - - - -第 7 页,共 11 页精选学习资料 - - - - - - - - - eccentricities of the raceways and ballsUnlike repetitive runout, no compensation can be ma
27、de 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 example,a bearing with an NRR of less than 0.3um is used when minimal runout is needed,such as in diskdrive spindle motorsSimilarly ,machinet
28、ool spindles tolerate only minimal deflections to maintain precision cutsConsequently, bearings are manufactured with low NRR just for machine-tool applicationsContamination is unavoidable in many industrial products ,and shields and seals are commonly used to protect bearings from dust and dirtHowe
29、ver,a perfect bearing seal is not possible because of the movement between inner and outer racesConsequently,lubrication migration and contamination are always problemsOnce a bearing is contaminated, its lubricant deteriorates and operation becomes noisierIf it overheats,the bearing can seizeAt the
30、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 surfaces Fending off dirt with seals and shields illustrates some methods for controlling contaminationNoise is as an indicator of bearing qualityVari
31、ous noise grades have been developed to classify bearing performance capabilitiesNoise analysis is done with an Anderonmeter, which is used for quality control in bearing production and also when failed bearings are returned for analysis. A transducer is attached to the outer ring and the inner race
32、 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 smallest flaw from their sound. Dust, for example, makes an irregular crackling. Ball scratches make a consistent popping and are the most
33、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 frequencies. Generally, defects are separated into low, medium, and high wavelengths. Defects are
34、also referenced to the number of irregularities per revolution. Low-band noise is the effect of long-wavelength irregularities that occur about 1.6 to 10 7 / 11 名师归纳总结 - - - - - - -第 8 页,共 11 页精选学习资料 - - - - - - - - - times per revolution. These are caused by a variety of inconsistencies, such as po
35、ckets in the race. Detectable pockets are manufacturing flaws and result when the race is mounted too tightly in multiplejaw chucks. Medium-hand noise is characterized by irregularities that occur 10 to 60 times per revolution. It is caused by vibration in the grinding operation that produces balls
36、and raceways. High-hand irregularities occur at 60 to 300 times per revolution and indicate closely spaced chatter marks or widely spaced, rough irregularities. Classifying bearings by their noise characteristics allows users to specify a noise grade in addition to the ABEC standards used by most ma
37、nufacturers. ABEC defines physical tolerances such as bore, outer diameter, and runout. As the ABEC class number increase from 3 to 9, tolerances are tightened. ABEC class, however, does not specify other bearing characteristics such as raceway quality, finish, or noise. Hence, a noise classification helps improve on the industry standard.8 / 11 名师归纳总结 - - - - - - -第 9 页,共 11 页精选学习资料 - - - - - - - - - 老师评语老师签名：2022 年 03 月 12 日0 / 11 名师归纳总结 - - - - - - -第 10 页,共 11 页精选学习资料 - - - - - - - - - 1 / 11 名师归纳总结 - - - - - - -第 11 页,共 11 页