機械類專業(yè)學習方法(編輯修改稿)
2024-10-25 10:35 本頁面
【文章內(nèi)容簡介】 n 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 is one type of bearing failure easily avoided by proper handing and is characterized by indentations in the bearing raceway caused by shock loading－such as when a bearing is droppedor incorrect 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 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 occurs on equipment in transit or that vibrates when not in addition, debris created by false brinelling acts like an abrasive, further contaminating the brinelling, false binelling is often indicated by a reddish color from fretting corrosion in the brinelling is prevented by eliminating vibration sources and keeping the bearing well pads on the equipment or a separate foundation may be required to reducerunning torque，stiffness，nonrepetitive runout，and radial and axial play．In 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 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 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 retainer tolerance or eccentricities of the raceways and balls．Unlike repetitive runout, no pensation can be made for 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．Conseque
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