【正文】 y 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.譯文譯文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。參考文獻參考文獻[1] 張健 . 機械故障診斷技術 [M] . 北京：機械工業(yè)出版社，2008.[2] 沈標正 . 機電故障診斷技術 [M] . 北京：機械工業(yè)出版社，2001[3] 王江平 . 機械設備故障診斷技術及運用 [M] . 西安：西北工業(yè)大學出版社，2001[4] 王淑芳 . 機電驅動技術 [M] . 北京：科學出版社，2008[5] 孫桓，陳作模，葛文杰 . 機械原理 [M] . 北京：高等教育出版社，2006[6] 劉杰 . 機電一體化技術基礎與產品設計 [M] . 北京：冶金工業(yè)出版社，2010外文資料原文外文資料原文EXTENDING BEARING LIFEBearings 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.1. Why bearings failAbout 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, 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 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 problem is incorrect mounting or tolerancing，or insufficient squareness of the bearing mounting site．Misalignment of more than 1/4無論我成功與否，你們總以鼓勵的言語告訴我很棒，謝謝你們，我會繼續(xù)努力。最后要感謝的是我的父母和家人，我永遠都不會忘記你們的良苦用心和一如既往的支持與鼓勵。當然還有我的朋友與公司同事，在遇到困難的時候，都毫不猶豫的向我伸出援助之手。然后還要感謝所有在大學期間傳授我知識的老師，每一位老師的悉心教導都是我完成這篇論文的基礎。在不斷完善和修改的過程中，也讓我更加懂得“一分耕耘才有一分收獲”的道理。在這里還要深深的對您說上一句抱歉，因為我的懶散和懈怠，令您費盡苦心并且?guī)捉?。當我對論文的思路感到迷茫時，在您和系上領導的幫助下，我論文的課題改為公司實習的內容，不僅讓我鞏固了實習期間學到的內容，也讓我的畢業(yè)論文更有實際意義。論文得以順利完成，要感謝的人實在太多了。這篇論文所涉及的議題是和我的指導老師交流后定下的，在前期的實習積累經驗，到中期的修改和討論，及最后的反復斟酌，我希望能盡自己最大的努力，寫出一篇具有現實意義的論文。只有對設備的每一個部件及其功能有足夠的認識，才可以在最短的時間內對設備出現的錯誤與故障做出最快最準確的診斷，為公司創(chuàng)造最大的經濟效益，同時也為我國起步很晚的機械故障診斷技術貢獻自己的一份薄力。對自己以后工作所涉及到的設備LUL從設備結構到傳感器功能再到工作流程有了一個系統的認識。繁瑣的傳感器和復雜的驅動裝置幾乎讓從未接觸過這些先進設備的我窒息，但是有學校教給我的專業(yè)基礎知識作后盾，再加上公司安排的理論培訓和上線操作，一個個難題都在不知不覺中迎刃而解。通過查詢和請教同事，我慢慢克服了這方面的困難。首先，高水平的英語要求對我來說是一個很大的突破，尤其是英語在專業(yè)方面的難度體現得淋漓盡致。我在公司主要培訓對日本Hirata公司的LUL進行預防性維護和故障診斷。其中包括機械原理、機電驅動技術