機(jī)械畢業(yè)設(shè)計(jì)外文翻譯---如何延長(zhǎng)軸承壽命-其他專業(yè)-wenkub
2023-01-30 06:10:11 本頁(yè)面
【正文】 pplications, 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 used． Lubricant viscosity must be selected carefully because inappropriate lubricant， especially in miniature bearings， causes excessive torque． Also， 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 action． NRR can be caused by 畢業(yè)設(shè)計(jì)說(shuō)明書(shū)（論文） 8 retainer tolerance or eccentricities of the raceways and balls． Unlike repetitive runout, no pensation can be made for NRR. NRR is reflected in the cost of the bearing． It is mon in the industry to provide different bearing types and grades for specific applications． For example， a bearing with an NRR of less than is used when minimal runout is needed，such as in disk— drive spindle motors． Similarly， machine— tool spindles tolerate only minimal deflections to maintain precision cuts． Consequently, bearings are manufactured with low NRR just for machinetool applications． Contamination is unavoidable in many industrial products， and shields and seals are monly used to protect bearings from dust and dirt． However， a perfect bearing seal is not possible because of the movement between inner and outer races． Consequently， lubrication migration and contamination are always problems． Once a bearing is contaminated, its lubricant deteriorates and operation bees noisier． If it overheats， the bearing can seize． At the very least，contamination causes wear as it works between balls and the raceway， being imbedded in the races and acting as an abrasive between metal surfaces． Fending off dirt with seals and shields illustrates some methods for controlling contamination． Noise is as an indicator of bearing quality． Various 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 μm/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
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