【正文】 次的畢業(yè)設(shè)計(jì)讓我明白了自己的不足，也讓我系統(tǒng)的回顧了大學(xué)期間所學(xué)的專業(yè)知識(shí)，溫故而知新，一定程度上也提高了我的個(gè)人能力。另外，也讓我明白學(xué)習(xí)如何通過有效途徑查找相關(guān)資料也是十分的重要。在畢業(yè)設(shè)計(jì)期間，我和其他同學(xué)相互交流，共同學(xué)習(xí)探討，不僅促進(jìn)了同學(xué)之間的感情，也在和睦的氛圍之中，相互學(xué)習(xí)，共同解決了一些設(shè)計(jì)上的難題，并且加深了對(duì)專業(yè)知識(shí)的理解。此時(shí)此刻，我要感謝黃嘉興、王啟廣兩位指導(dǎo)老師的悉心指導(dǎo)和幫助；感謝給我?guī)韼椭耐瑢W(xué)們。通過本次的畢業(yè)設(shè)計(jì)，鍛煉了我的個(gè)人能力，為我今后獨(dú)立工作樹立了信心。雖然，設(shè)計(jì)的過程十分艱辛，但我認(rèn)為這將是我人生之中一筆寶貴的財(cái)富。參考文獻(xiàn)[1] 王洪興、李、（1）.徐州：中國礦業(yè)大學(xué)出版社 2001[2] 陳飛、：中國礦業(yè)大學(xué)出版社 2007[3] 王洪興、：中國礦業(yè)大學(xué)出版社 2011[4] ：清華大學(xué)出版社 2008[5] 關(guān)慧貞、：機(jī)械工業(yè)出版社 2009[6] 程志紅、：東南大學(xué)出版社 2006[7] ：東南大學(xué)出版社 2006[8] ：機(jī)械工業(yè)出版社 2002[9] ：機(jī)械工業(yè)出版社 2002[10] 李慶余、. 北京：機(jī)械工業(yè)出版社 2003[11] 袁績乾. 機(jī)械制造技術(shù)基礎(chǔ) .北京：機(jī)械工業(yè)出版社 2001[12] 陳立德. . 北京：高等教育出版社出版 2007[13] 陳立德. . 北京：高等教育出版社 2007 [14] 楊慧英、[M]. 北京：清華大學(xué)出版社 2002.[15] 羅特軍. 理論力學(xué). 北京：高等教育出版社 2006[16] 任家隆. 機(jī)械制造基礎(chǔ)[M]. 北京：高等教育出版社 2003翻譯部分英文原文Failure investigation of a Taper Roller Bearing: A case studyBearing life refers to the total number of revolutions (or time period) a bearing performs satisfactorily under stated conditions before failure. In general, based on the operating conditions the scope of the bearing life is defined. In case of heavy machinery, small flaking or spalling on the bearing may not be considered as an immediate failure and its life can be prolonged with proper maintenance. On the other hand it may be a limiting factor where the application demands high precision control and sensitive even to very slight dimensional variation, noise or vibration..More monly, the life of a bearing is specified by L10 (or B10) life which is defined as the total number of revolutions in which 90 % of identical bearings will survive under the same operating and environmental conditions before failure by fatigue. The operating load and speed are the prime factors in estimating the L10 life which is given by,pLna= . (C /P) Where,Lna= Rated life in millions of revolution (10 )a1= Reliability adjustment factor a2= Material adjustment factora3= Operating condition adjustment factorC= Basic dynamic load rating in NewtonP= Equivalent dynamic load in Newtonp= 3 for ball bearings and 10/3 for roller bearing With the proper selection of bearing for a given application, the bearing fails predominantly by fatigue and can be estimated by the above equation [1,2]. There are several other parameters like improper selection of bearing for a given application, inadequate lubrication, improper installation, excessive loading/preloading, vibrations, impact loading, environmental factors like corrosive media, temperature, contaminated environment that can cause a bearing to fail before its predicted life time and are classified as premature failures. The failure modes of a bearing, besides fatigue, include plastic flow, fracture, wear, corrosion and electrical pitting. By gathering data on application of the bearing and operating conditions during running and at the time of failure, damage analysis can be made by studying the mode of failure and its most probable root cause for the premature failure can be established. If more than one parameter is involved in premature failure, it will increase the plexity of identifying the root cause [35].In the present study, damage analysis made on the prematurely failed front wheel outer tapered roller bearing is discussed. A schematic view of tractor is shown in and the location of front wheel outer bearing is highlighted in circles (in ).2. Experimental detailsA detailed study on the failed bearing was made including visual examination, chemical position, micro hardness, microstructure, retained austenite measurement, wear debris analysis and scanning electron microscope (SEM) studies. Visual examination was carried out using a stereo zoom microscope. The chemical position of the failed ponents was carried out using spark emission spectrometry. Bakelite mounted and polished cut sections were used for metallographic observation and microhardness measurements. The microstructure was studied after etching with 3% Nital. Retained austenite content was measured using Xray diffraction (XRD) technique, on the roller surface and cone raceway. The damaged cage was carefully cleaned using petroleum benzene and the wear debris collected after filtration of the solvent for particle size analysis using an image analyser.3. Results MaterialMaterial position was evaluated by spark emission spectrometer and the chemical position (in weight percentage) is shown in Table 1. Macroscopic analysisThe cone, rollers and cage in as received condition are shown in . Under low magnification using a stereo zoom microscope, one end of the rollers was found to be severely damaged than the other. This feature was seen in all the rollers. In the cone, deep grooves were noticed along with pit marks on the race way。 a crack was also observed on the inner surface of the cone aligned with the deep groove as shown in (a). SEM observation made on the cut section of the cone shows the deep groove and the crack originating from the groove and propagating towards the bore surface as shown in (b). Microstructural analysisLongitudinal cut sections of a roller and cone showed fine tempered martensite with uniform distribution of carbides free from carbide network or any detrimental feature. The origin of crack was also free from decarburization indicating that the heat treatment conditions were normal. Microstructure observed on roller specimen is shown in (a). Near the damaged side of the roller, cracks were observed propagating towards the centre of the roller as shown in (b) and (c). Hardness analysisHardness profiles taken along the cut section revealed that near the surface of roller and raceway surface of the cone, the hardness values were in the range of 6465 HRc and in the core it were in the range of 6163 HRc. Retained austenite measurementsRetained austenite measurements were carried out on roller surface, raceway of the cone using XRD. RA was about % on raceway and % on roller surface. Wea