SCIENCE AND TECHNOLOGY ENGLIAH FOR MECHANICAL ENGINEERING For plain ball bearings, radial load ratings in pounds(as given in catalogs) are based upon a given rpm and a given number of hours of life with 90% survival. The product rpm X 60 X hr life is then equal to 106. Round per minute Other manufacturers give rated loads on the basis of 106 revolutions instead of hours of life(again, 90% survival). In that case, the number of hours of life can be found by dividing10° by rpm×60. It will be clear from the foregoing that, for a given load, changes in rpm(within the design limits as given by the manufacturer) affect life in hours inversely, thus n,/n,=H,/H 6.5 where n=rpm and H=life (hr ) Changes in load, on the other hand, affect life in revolutions exponentially: thus
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING For plain ball bearings, radial load ratings in pounds (as given in catalogs) are based upon a given rpm and a given number of hours of life with 90% survival. The product rpm × 60 × hr life is then equal to 106 . Other manufacturers give rated loads on the basis of 106 revolutions instead of hours of life (again, 90% survival). In that case, the number of hours of life can be found by dividing 106 by rpm × 60. It will be clear from the foregoing that, for a given load, changes in rpm (within the design limits as given by the manufacturer) affect life in hours inversely; thus, n1 /n2 =H2 /H1 6.5 where n=rpm and H=life (hr.). Changes in load, on the other hand, affect life in revolutions exponentially; thus, Round per minute
SCIENCE AND TECHNOLOGY ENGLIAH FOR MECHANICAL ENGINEERING (F1/F2)=B2/B1 6.6 where F=load (b) and b= life(revolutions). Values of k range between 3 and 4(3 for ball bearings; 3.3 for most roller and needle bearings). Note that for k-3, doubling the load means reducing the life in revolutions by a factor of 8 The relation between B (life in revolutions) and H (life in hours), is as follows B=H×rpm×60 6.7
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING (F1 /F2 ) k = B2 /B1 6.6 where F= load (lb) and B= life (revolutions). Values of k range between 3 and 4 (3 for ball bearings; 3.3 for most roller and needle bearings). Note that for k=3, doubling the load means reducing the life in revolutions by a factor of 8. The relation between B (life in revolutions) and H (life in hours), is as follows: B = H × rpm × 60 6.7
SCIENCE AND TECHNOLOGY ENGLIAH FOR MECHANICAL ENGINEERING Other Factors Affecting Bearing Life The rated life of any bearing with rolling contact is based upon proper application conditions, such as adequate lubrication, good alignment alignment, and adherence to recommended 调整 inter ference fit values for the races, if applicable Any negative variance from these conditions adherence will affect fatigue life unfavorably 附着,坚持 On the other hand, life can be extended interference fit considerably by providing superior lubrication.过盈配合 Also. for the same size and materials. the manufacturer can produce a bearing with greater life expectancy by increasing the accuracy of manufacture i.e. by reducing manufacturing tolerances
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING On the other hand, life can be extended considerably by providing superior lubrication. Also, for the same size and materials, the manufacturer can produce a bearing with greater life expectancy by increasing the accuracy of manufacture i.e. by reducing manufacturing tolerances. Other Factors AffectingBearing Life The rated life of any bearing with rolling contact is based upon proper application conditions, such as adequate lubrication, good alignment, and adherence to recommended interference fit values for the races, if applicable. Any negative variance from these conditions will affect fatigue life unfavorably. alignment 调整 adherence 附着，坚持 interference fit 过盈配合