【正文】 是缺少內(nèi)隙、潤(rùn)滑不當(dāng)和載荷過(guò)大。 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。 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。 另一個(gè)解決辦法是更換材料。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。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)的明顯特征是劃痕、擦痕或軸與內(nèi)圈的顏色變化。 蠕動(dòng)與安裝不正有關(guān)。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。軸承就會(huì)過(guò)早地失效。污染的特 征是使軸承過(guò)早的出現(xiàn)磨損。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。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。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(kāi)包裝。 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)。 扭矩要求是由潤(rùn)滑劑、保持架、軸承圈質(zhì)量（彎曲部分的圓度和表面加工質(zhì)量）以及是否使用密封或遮護(hù)裝置來(lái)決定。另外，不同的潤(rùn)滑劑的噪聲特性也不一樣。因此，要根據(jù)不同的用途來(lái)選用潤(rùn)滑劑。保持架的尺寸誤差和軸承圈與滾珠的偏心都會(huì)引起 NRR。 在工業(yè)中一般是根據(jù)具體的應(yīng)用來(lái)選擇不同類(lèi)型和精度等級(jí)的軸承。同樣，機(jī)床主軸只能容許最小的振擺，以保證切削精度。 在許多工業(yè)產(chǎn)品中，污染是不可避免的，因此常用密封或遮護(hù)裝置來(lái)保護(hù)軸承，使其免受灰塵或臟物的侵蝕。 一旦軸承受到污染，潤(rùn)滑劑就要變質(zhì)，運(yùn)行噪聲也隨之變大。當(dāng)污染物處于滾珠和軸承圈之間時(shí)，其作用和金屬表面之間的磨粒一樣，會(huì)使軸承磨損。 噪聲是反映軸承質(zhì)量的一個(gè)指標(biāo)。 噪聲的分析是用安德遜計(jì)進(jìn)行的，該儀器在軸承生產(chǎn)中可用來(lái)控制質(zhì)量，也可對(duì)失效的軸承進(jìn)行分析。測(cè)量噪聲的單位為 anderon。 根據(jù)經(jīng)驗(yàn)，觀察者可以根據(jù)聲音辨別出微小的缺陷。 17 軸承缺陷可以通過(guò)其頻率特性進(jìn)一步加以鑒定。缺陷還可以根據(jù)軸承每轉(zhuǎn)動(dòng)一周出現(xiàn)的不規(guī)則變化的次數(shù)加以鑒定。軸承每轉(zhuǎn)一周這種不規(guī)則變化可出現(xiàn)~10 次，它們是由各種干涉（例如 軸承圈滾道上的凹坑 ）引起的。 中頻噪聲的特征是軸承每旋轉(zhuǎn)一周不規(guī)則變化出現(xiàn) 10~60 次。軸承每旋轉(zhuǎn)一周高頻不規(guī)則變化出現(xiàn) 60~300次，它表明軸承上存在著密集的振痕或大面積的粗糙不平。 ABEC標(biāo)準(zhǔn)只定義了諸如孔、外徑、振擺等尺寸公差。但 ABEC 等級(jí)并不能反映其他軸承特性，如軸承圈質(zhì)量、粗糙度、噪聲等。 18 畢業(yè)設(shè)計(jì)（論文）外文翻譯原文 4 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 mon 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 place． To 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. 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 environment． Fortunately, 19 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 bearing． Then， 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 loading－ such as when a bearing is droppedor incorrect assembly. Brinelling usually 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 races． Raceway 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 turning． This 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 blueblack or straw colored． Friction also causes stress in the retainer， which can break and hasten bearing failure． Premature material fatigue is caused by a high load or excessive preload． When these conditions are unavoidable， bearing life should be carefully calculated so that a 20 maintenance scheme can be worked out． Another 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 remended. In addition， when the problem is traced back to excessive loading， a higher capacity bearing or different configuration may be used． Creep is less mon than premature fatigue． In bearings． it is caused by excessive clearance between bore and shaft that allows the bore to rotate on the shaft． Creep can be expensive because it causes damage to other ponents in addition to the bearing． 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 checked． Misalignment is related to creep in that it is mounting related． If races are misaligned or cocked． The balls track in a noncircumferencial path． The p