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The flight-by-flight stress sequences were applied to notched sheet specimens of Ti-8Al-1Mo-1V and Ti-6Al-4V titanium alloys. The effects of design mean stress, the stress range for ground-air-ground cycles, simulated thermal stress, the number of stress cycles in each flight, and salt corrosion were studied. In order to determine whether short-time tests were feasible, the results of accelerated tests (2 sec per flight) were compared with the results of real-time tests (96 min per flight).
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Possibilities for reducing fatigue-test time for supersonic-transport materials and structures were studied in tests with simulated flight-by-flight loading. Four types of wear particles were observed: normal rubbing wear particles, fatigue spall particles, spheres, and friction polymer.įatigue-test acceleration with flight-by-flight loading and heating to simulate supersonic-transport operation Conditions included a maximum Hertz stress of 5.52 billion Pa and a shaft speed of 10,000 rpm. The lubricant was a super-refined naphthenic mineral oil. Ball specimens were made of AMS 5749, a corrosion-resistant high-temperature bearing steel. The NASA five-ball rolling contact fatigue tester was used. The characterization of wear debris as a function of time was of limited use in predicting fatigue failures in these accelerated tests.įerrographic analysis of wear debris generated in accelerated rolling element fatigue testsįerrographic analysis was used to determine the types and quantities of wear particles generated during accelerated rolling contact fatigue tests. Four types of wear debris were observed: (1) normal rubbing wear particles, (2) fatigue microspall particles, (3) spheres, and (4) friction polymer deposits. Conditions included a maximum Hertz stress of 5.52 10 to the 9th power Pa and a shaft speed of 10,000 rpm. The lubricant was a superrefined naphthenic mineral oil. Ball specimens were made of a corrosion resistant, high-temperature bearing steel. The five-ball rolling contact fatigue tester was used. Characterization of wear debris generated in accelerated rolling-element fatigue testsĪ ferrographic analysis was used to determine the types and quantities of wear debris generated during accelerated rolling contact fatigue tests.