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  • MACHINE ELEMENTS AND PROCESSES  (18)
  • 1970-1974  (18)
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  • 1
    Publication Date: 2019-06-27
    Description: An analysis was developed for the microasperity elastohydrodynamic lubrication of a ball spinning in a nonconforming groove. This analysis was compared to the conventional elastohydrodynamic analysis of a ball spinning in a nonconforming groove. Rheological models for a di-2-ethylhexyl sebacate, a super-refined naphthenic mineral oil, and a polyphenyl ether (5P4E) were constructed from spinning torque data by using both analyses. The value of the lubricant pressure-viscosity coefficient that makes the data fit the analyses of the fluids differs somewhat from published data. For all three lubricants, an exponential composite model best described the lubricant rheology. Good agreement existed with the experimental and analytical values of torque for both the conventional and microasperity elastohydrodynamic analysis for a spinning ball in a nonconforming groove.
    Keywords: MACHINE ELEMENTS AND PROCESSES
    Type: NASA-TN-D-6761 , E-6713
    Format: application/pdf
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  • 2
    Publication Date: 2019-06-27
    Description: Two groups of 3.50-in. pitch-diameter spur gears, without tip relief, made from consumable-electrode vacuum-melted (CVM) AISI M-50 steel and CVM super nitralloy (5Ni-2A1) were tested under conditions which produced fatigue pitting. The M-50 gears had fatigue lives approximately 50 percent longer than the super nitralloy gears. Both groups of gears failed by classical rolling-element fatigue at the pitch circle. When the gears were overrun past initial spall formation, the spalled M-50 gear teeth failed by fatigue fracture. The M-50 material had higher wear than the super nitralloy material. Differences in fatigue life and wear were not considered statistically significant.
    Keywords: MACHINE ELEMENTS AND PROCESSES
    Type: NASA-TN-D-7261 , E-7164
    Format: application/pdf
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  • 3
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    In:  CASI
    Publication Date: 2019-06-27
    Description: Lubrication considerations in design of gears
    Keywords: MACHINE ELEMENTS AND PROCESSES
    Type: NASA-TM-X-52942
    Format: application/pdf
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  • 4
    Publication Date: 2019-06-27
    Description: Effects of antiwear and extreme-pressure additives in synthetic paraffinic oil on ball spinning torque
    Keywords: MACHINE ELEMENTS AND PROCESSES
    Type: NASA-TN-D-5820
    Format: application/pdf
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  • 5
    Publication Date: 2019-07-13
    Description: Lubricant jet flow impingement and penetration depth into a gear tooth space were measured at 4920 and 2560 rpm using a 8.89 cm (3.5 inch) pitch diameter 8 pitch spur gear at oil pressures from 70,000 to 410,000 n/sqm (10 psi to 60 psi). A high speed motion picture camera was used with xenon and high speed stroboscopic lights to slow down and stop the motion of the oil jet. An analytical model was developed for the vectorial impingement dept and for the impingement depth with tooth space windage effects included. The windage effects for oil drop size greater than .0076 cm (.003 inches). The analytical impingement dept compared favorably with experimental results above an oil jet pressure of 70,000 n/sqm (10psi). There was further penetration into the tooth space after impingement, but much of this oil was thrown out of the tooth space without further contacting the gear teeth.
    Keywords: MACHINE ELEMENTS AND PROCESSES
    Type: NASA-TM-X-71572 , E-8012 , lubrication Conf.; Oct 08, 1974 - Oct 10, 1974; Montreal
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  • 6
    Publication Date: 2019-07-13
    Description: Tests were conducted at 170 F with groups of 3.5-in.-pitch-diameter spur gear with and without tip relief made of consumable-electrode vacuum melted (CVM) Spur Nitralloy (5Ni-2Al) and CVM AISI M-50 steel. The AISI M-50 gears without tip relief had lives approximately 50 percent longer than the Super Nitralloy gears without tip relief. However, the Super Nitralloy gears with tip relief had lives equal to the AISI M-50 gears without tip relief. The difference in lives were not statistically significant. All gears failed by classical pitting fatigue at the pitch circle. However, the AIAI M-50 gears with tip relief failed by tooth fracture. AISI M-50 gear sets without tip relief having a spalled gear tooth which were deliberately overrun after spalling had occurred, failed by tooth fracture.
    Keywords: MACHINE ELEMENTS AND PROCESSES
    Type: NASA-TM-X-68269 , E-7575 , Joint Lubrication Conf.; Oct 16, 1973 - Oct 18, 1973; Atlanta, GA; United States
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  • 7
    Publication Date: 2019-06-27
    Description: Test of rolling element fatigue life with fluorinated ether lubricant at cryogenic temperature using five ball fatigue tester
    Keywords: MACHINE ELEMENTS AND PROCESSES
    Type: NASA-TN-D-6367 , E-6045
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  • 8
    Publication Date: 2019-06-27
    Description: Tests were conducted with two groups of 8.89-centimeter (3.5-in.) pitch diameter spur gears with standard 20 deg involute profile with tip relief made of CVM Super-Nitralloy (5Ni-2Al) and CVM AISI M-50 at a temperature of 350 K (170 F). Super-Nitralloy gears with tip relief had a life 150 percent that of gears without tip relief. An increased scoring phenomenon was noted with the Super-Nitralloy gears with tip relief. Through-hardened AISI M-50 gears with tip relief failed due to tooth fracture. AISI M-50 gears without tip relief had a life approximately 40 times greater than the AISI M-50 gears with tip relief.
    Keywords: MACHINE ELEMENTS AND PROCESSES
    Type: NASA-TN-D-7535
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  • 9
    Publication Date: 2019-06-27
    Description: The NASA spinning torque apparatus was modified to measure the spinning torque on a cageless ball thrust bearing. Friction torque was measured for thrust loads varying from 44.5 to 403 newtons (10 to 90 lb) at speeds of 1000, 2000, and 3000 rpm. Tests were conducted with di-2-ethylhexyl sebacate and a synthetic paraffinic oil. These tests were run with either oil jet lubrication or with a thin surface film of lubricant only. An analytical model which included rolling resistance was developed and extended from previous models for spinning torque and lubricant rheology. The model was extended by the inclusion of rolling resistance. The computed values were in fair agreement with the experimental results and confirmed previous hypotheses that a thin lubricant film gives minimum bearing torque and an oil jet flow of a viscous lubricant will result in considerable rolling torque in addition to the torque due to ball spin.
    Keywords: MACHINE ELEMENTS AND PROCESSES
    Type: NASA-TN-D-7356 , E-7284
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  • 10
    Publication Date: 2019-06-27
    Description: The elastohydrodynamic theory for predicting the spinning friction of a ball in a nonconforming groove was modified to incorporate a rheological model. The rheological model is based on the exponential pressure viscosity relation for low shear stresses, but at high shear rates and pressures, the relation is altered to one in which the shear stress is porportional to the normal stress. The model was fitted to experimental spinning torques for four different lubricants: a synthetic paraffinic lubricant, di-2-ethylhexyl sebacate, a super-refined naphthenic mineral oil, and a polyphenyl ether (5P4E). Good agreement between the model and experiment was found.
    Keywords: MACHINE ELEMENTS AND PROCESSES
    Type: NASA-TN-D-7280 , E-7256
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