側(cè)軸承杯加工工藝編制及夾具設(shè)計(jì)

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關(guān) 鍵詞：: 側(cè)軸承杯加工工藝編制及夾具設(shè)計(jì) 加工工藝編制及夾具設(shè)計(jì)

資源描述：: 側(cè)軸承杯加工工藝編制及夾具設(shè)計(jì),側(cè)軸承杯加工工藝編制及夾具設(shè)計(jì),加工工藝編制及夾具設(shè)計(jì)

內(nèi)容簡(jiǎn)介：: 畢業(yè)設(shè)計(jì)（論文）英文資料翻譯 Mechanical Design Theory 學(xué) 院：西北工業(yè)大學(xué)明德學(xué)院專業(yè)：機(jī)械設(shè)計(jì)制造及其自動(dòng)化班級(jí)： 161002 姓名：王冬堯學(xué) 號(hào)： 103324 指導(dǎo)老師：賀榮 2013 年 4 月 0 EXTENDING BEARING LIFE Abstract：Nature works hard to destroy bearings, but their 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 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 telltale 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 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 failures 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 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 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 1 occurs when loads exceed the material yield point(350,000 psi in SAE 52100 chrome steel)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 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 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 balls 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 color，usually to blue-black 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 worked 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 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 likely 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 2 Misalignment is related to creep in that it is mounting relatedIf races are misaligned or cockedThe balls track in a noncircumferencial 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 contaminants 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 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 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 level 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，causes 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 actionNRR 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 example，a bearing with an NRR of less than 0.3um is used when minimal runout is needed，such as in disk 3 drive spindle motorsSimilarly，machinetool spindles tolerate only minimal deflections to maintain precision cutsConsequently, bearings are manufactured with low NRR just for machine-tool applications Contamination 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 problems 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 surfacesFending 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 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 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 frequencies. Generally, defects are separated into low, medium, and high wavelengths. Defects are 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 times per revolution. These are caused by a variety of inconsistencies, such as pockets 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 and raceways. High-hand irregularities occur at 60 to 300 times per revolution and indicate closely spaced chatter marks or widely spaced, rough irregularities. 4 Classifying bearings by their noise characteristics allows users to specify a noise grade in addition to the ABEC standards used by most manufacturers. 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. 如如何何延延長(zhǎng)長(zhǎng)軸軸承承壽壽命命摘摘要要：自然界苛刻的工作條件會(huì)導(dǎo)致軸承的失效，但是如果遵循一些簡(jiǎn)單的規(guī)則，軸承正常運(yùn)轉(zhuǎn)的機(jī)會(huì)是能夠被提高的。在軸承的使用過(guò)程當(dāng)中，過(guò)分的忽視會(huì)導(dǎo)致軸承的過(guò)熱現(xiàn)象，也可能使軸承不能夠再被使用，甚至完全的破壞。但是一個(gè)被損壞的軸承，會(huì)留下它為什么被損壞的線索。通過(guò)一些細(xì)致的偵察工作，我們可以采取行動(dòng)來(lái)避免軸承的再次失效。關(guān)關(guān)鍵鍵詞詞：軸軸承承失失效效壽壽命命導(dǎo)致軸承失效的原因很多，但常見(jiàn)的是不正確的使用、污染、潤(rùn)滑劑使用不當(dāng)、裝卸或搬運(yùn)時(shí)的損傷及安裝誤差等。診斷失效的原因并不困難，因?yàn)楦鶕?jù)軸承上留下的痕跡可以確定軸承失效的原因。然而，當(dāng)事后的調(diào)查分析提供出寶貴的信息時(shí)，最好首先通過(guò)正確地選定軸承來(lái)完全避免失效的發(fā)生。為了做到這一點(diǎn)，再考察一下制造廠商的尺寸定位指南和所選軸承的使用特點(diǎn)是非常重要的。 1 1 軸軸承承失失效效的的原原因因在球軸承的失效中約有40%是由灰塵、臟物、碎屑的污染以及腐蝕造成的。污染通常是由不正確的使用和不良的使用環(huán)境造成的，它還會(huì)引起扭矩和噪聲的問(wèn)題。由環(huán)境和污染所產(chǎn)生的軸承失效是可以預(yù)防的，而且通過(guò)簡(jiǎn)單的肉眼觀察是可以確定產(chǎn)生這類失效的原因。通過(guò)失效后的分析可以得知對(duì)已經(jīng)失效的或?qū)⒁У妮S承應(yīng)該在哪些方面進(jìn)行查看。弄清諸如剝蝕和疲勞破壞一類失效的機(jī)理，有助于消除問(wèn)題的根源。只要使用和安裝合理，軸承的剝蝕是容易避免的。剝蝕的特征是在軸承圈滾道上留有由沖擊載荷或不正確的安裝產(chǎn)生的壓痕。剝蝕通常是在載荷超過(guò)材料屈服極限時(shí)發(fā)生的。如果安裝不正確從而使某一載荷橫穿軸承圈也會(huì)產(chǎn)生剝蝕。軸承圈上的壓坑還會(huì)產(chǎn)生噪聲、振動(dòng)和附加扭矩。 5 類似的一種缺陷是當(dāng)軸承不旋轉(zhuǎn)時(shí)由于滾珠在軸承圈間振動(dòng)而產(chǎn)生的橢圓形壓痕。這種破壞稱為低荷振蝕。這種破壞在運(yùn)輸中的設(shè)備和不工作時(shí)仍振動(dòng)的設(shè) 備中都會(huì)產(chǎn)生。此外，低荷振蝕產(chǎn)生的碎屑的作用就象磨粒一樣，會(huì)進(jìn)一步損害軸承。與剝蝕不同，低荷振蝕的特征通常是由于微振磨損腐蝕在潤(rùn)滑劑中會(huì)產(chǎn)生淡紅色。消除振動(dòng)源并保持良好的軸承潤(rùn)滑可以防止低荷振蝕。給設(shè)備加隔離墊或?qū)?底座進(jìn)行隔離可以減輕環(huán)境的振動(dòng)。另外在軸承上加一個(gè)較小的預(yù)載荷不僅有助于滾珠和軸承圈保持緊密的接觸，并且對(duì)防止在設(shè)備運(yùn)輸中產(chǎn)生的低荷振蝕也有幫助。造成軸承卡住的原因是缺少內(nèi)隙、潤(rùn)滑不當(dāng)和載荷過(guò)大。在卡住之前，過(guò)大的摩擦和熱量使軸承鋼軟化。過(guò)熱的軸承通常會(huì)改變顏色，一般會(huì)變成藍(lán)黑色或淡黃色。摩擦還會(huì)使保持架受力，這會(huì)破壞支承架，并加速軸承的失效。材料過(guò)早出現(xiàn)疲勞破壞是由重載后過(guò)大的預(yù)載引起的。如果這些條件不可避免，就應(yīng)仔細(xì)計(jì)算軸承壽命，以制定一個(gè)維護(hù)計(jì)劃。另一個(gè)解決辦法是更換材料。若標(biāo)準(zhǔn)的軸承材料不能保證足夠的軸承壽命，就應(yīng)當(dāng)采用特殊的材料。另外，如果這個(gè)問(wèn)題是由于載荷過(guò)大造成的，就應(yīng)該采用抗載能力更強(qiáng)或其他結(jié)構(gòu)的軸承。蠕動(dòng)不象過(guò)早疲勞那樣普遍。軸承的蠕動(dòng)是由于軸和內(nèi)圈之間的間隙過(guò)大造成的。蠕動(dòng)的害處很大，它不僅損害軸承，也破壞其他零件。蠕動(dòng)的明顯特征是劃痕、擦痕或軸與內(nèi)圈的顏色變化。為了防止蠕動(dòng)，應(yīng) 該先用肉眼檢查一下軸承箱件和軸的配件。蠕動(dòng)與安裝不正有關(guān)。如果軸承圈不正或翹起，滾珠將沿著一個(gè)非圓周軌道運(yùn)動(dòng)。這個(gè)問(wèn)題是由于安裝不正確或公差不正確或軸承安裝現(xiàn)場(chǎng)的垂直度不夠造成的。如果偏斜超過(guò)0.25，軸承就會(huì)過(guò)早地失效。檢查潤(rùn)滑劑的污染比檢查裝配不正或蠕動(dòng)要困難得多。污染的特征是使軸承過(guò)早的出現(xiàn)磨損。潤(rùn)滑劑中的固體雜質(zhì)就象磨粒一樣。如果滾珠和保持架之間潤(rùn) 滑不良也會(huì)磨損并削弱保持架。在這種情況下，潤(rùn)滑對(duì)于完全加工形式的保持架來(lái)說(shuō)是至關(guān)重要的。相比之下，帶狀或冠狀保持架能較容易地使?jié)櫥瑒┑竭_(dá)全部表面。銹是濕氣污染的一種形式，它的出現(xiàn)常常表明材料選擇不當(dāng)。如果某一材料經(jīng)檢驗(yàn)適合工作要求，那么防止生銹的最簡(jiǎn)單的方法是給軸承包裝起來(lái)，直到安裝使用時(shí)才打開包裝。 2 2 避避免免失失效效的的方方法法 6 解決軸承失效問(wèn)題的最好辦法就是避免失效發(fā)生。這可以在選用過(guò)程中通過(guò) 考慮關(guān)鍵性能特征來(lái)實(shí)現(xiàn)。這些特征包括噪聲、起動(dòng)和運(yùn)轉(zhuǎn)扭矩、剛性、非重復(fù) 性振擺以及徑向和軸向間隙。扭矩要求是由潤(rùn)滑劑、保持架、軸

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