Characterization of Wear Debris Generated in Accelerated Rolling-Element Fatigue Tests

摘要

A Ferrographic analysis was used to determine the types and quantities of wear debris generated during accelerated rolling contact fatigue tests. The NASA five-ball rolling contact fatigue tester was used. Ball specimens were made of AMS 5749, a corrosion resistant, high-temperature bearing steel. The lubricant was a superrefined naphthenic mineral oil. Conditions included a maximum Hertz stress of 5.52×10 9 pascals and a shaft speed of 10 000 rpm. Four types of debris were observed - normal rubbing wear particles, fatigue microspall particles, spheres, and friction polymer deposits. For about half of the tests, the fatigue spall particle rating and the number of spherical particles reached a maximum during the last one-third of the test durations. The number of spheres observed in these accelerated fatigue tests was much less than others have reported during long duration testing under lower loads. Laminar particles, sometimes associated with rolling contact fatigue, were not observed in this study. The characterization of wear debris as a function of time was of limited use in predicting fatigue failures in these accelerated tests.