## Reevaluation of the Stress-life Relation in Rolling-element BearingsFour groups of 12.7 millimeter diameter vacuum-degassed AISI 52100 balls were tested, each at a maximum Hertz stress in the range of 4.5 times 10 to 9th power to 6.0 times 10 to 9th power N/m2. Tests were run in the five-ball fatigue tester at a contact angle of 30 deg and a shaft speed of 10,000 rpm. The 10 percent fatigue lives at the four stress levels indicated that fatigue life is inversely proportional to maximum Hertz stress raised to the power of 12. This result agrees with a survey of the literature which suggests that a stress-life exponent of approximately 12 is typical of vacuum-processed bearing steels rather than the exponent of 9 which has been generally accepted by the bearing industry. |

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10-percent lives air-melted materials AISI e2100 AISI angle of 30 ball failures ball Four Ball Temperature balls were tested Bearing Fatigue bearing industry contact angle data ref diameter balls effect of stress effect of vacuum exponent of 9 exponent of approximately failure index Fatigue Results five-ball fatigue tester five-ball system groups of 12.7-millimeter heat of vacuum-degassed Hertz stress range higher stresses increased stress inverse cubic relation level of maximum Lewis Research Center load-life relation Lower ball lower test ball lower-ball failures Lubr LUBRICANT VISCOSITY maximum Hertz stress millions of upper-ball NASA outer race outer-race temperature Palmgren paraffinic mineral oil Performing Organization power of load reference 20 Roller Rolling Contact ROLLING-ELEMENT BEARINGS Rolling-element fatigue shaft speed stress-life exponent STRESS-LIFE RELATION table II(a Ten-percent Tests were run thermocouple Toroid typical of vacuum-processed upper test ball upper-ball stress cycles vacuum-degassed AISI 52100 vacuum-processed bearing steels vacuum-processed materials vacuum-processed steel Weibull Zaretsky