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  • MECHANICAL ENGINEERING  (9)
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  • 1
    facet.materialart.
    Unknown
    Operating characteristics of a 0.87 kW-hr flywheel energy storage module (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Discussion is given of the design and loss characteristics of 0.87 kW-hr (peak) flywheel energy storage module suitable for aerospace and automotive applications. The maraging steel flywheel rotor, a 46-cm-(18-in-) diameter, 58-kg (128-lb) tapered disk, delivers 0.65 kW-hr of usable energy between operating speeds of 10,000 and 20,000 rpm. The rotor is supported by 20- and 25-mm bore diameter, deep-groove ball bearings, lubricated by a self-replenishing wick type lubrication system. To reduce aerodynamic losses, the rotor housing was evacuated to vacuum levels from 40 to 200 millitorr. Dynamic rotor instabilities uncovered during testing necessitated the use of an elastometric-bearing damper to limit shaft excursions. Spindown losses from bearing, seal, and aerodynamic drag at 50 millitorr typically ranged from 64 to 193 W at 10,000 and 20,000 rpm, respectively. Discharge efficiency of the flywheel system exceeded 96 percent at torque levels greater than 21 percent of rated torque.
    Keywords: MECHANICAL ENGINEERING
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
    facet.materialart.
    Unknown
    Effect of lubricant extreme-pressure additives on surface fatigue life of AISI 9310 spur gears (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Surface fatigue tests were conducted with AISI 9310 spur gears using a formulated synthetic tetraester oil (conforming to MIL-L-23699 specifications) as the lubricant containing either sulfur or phosphorus as the EP additive. Four groups of gears were tested. One group of gears tested without an additive in the lubricant acted as the reference oil. In the other three groups either a 0.1 wt % sulfur or phosphorus additive was added to the tetraester oil to enhance gear surface fatigue life. Test conditions included a gear temperature of 334 K (160 F), a maximum Hertz stress of 1.71 GPa (248 000 psi), and a speed of 10,000 rpm. The gears tested with a 0.1 wt % phosphorus additive showed pitting fatigue life 2.6 times the life of gears tested with the reference tetraester based oil. Although fatigue lives of two groups of gears tested with the sulfur additive in the oil showed improvement over the control group gear life, the results, unlike those obtained with the phosphorus oil, were not considered to be statistically significant.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TP-2408 , E-2042 , NAS 1.60:2408
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
    facet.materialart.
    Unknown
    Design and evaluation of a 3 million DN series-hybrid thrust bearing (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The design and experimental evaluation of a series-hybrid thrust bearing, consisting of a 150-mm ball bearing and a centrifugally actuated, conical, fluid-film bearing, is presented. Tests were conducted up to 16,000 rpm and at this speed an axial load of 15,600 N (3500 lb) was safely supported by the hybrid bearing system. Through the series-hybrid bearing principle, the effective ball bearing speed was reduced to approximately one-half of the shaft speed. A speed reduction of this magnitude would result in a tenfold increase in the ball bearing fatigue life. A successful evaluation of fluid-film bearing lubricant supply failure was performed repeatedly at an operating speed of 10,000 rpm. A complete and smooth changeover to full-scale ball bearing operation was effected when the oil supply to the fluid-film bearing was cut off. Reactivation of the fluid-film oil supply system produced a flawless return to the original mode of hybrid operation.
    Keywords: MECHANICAL ENGINEERING
    Type: ASME PAPER 76-LUBS-17 , Lubrication Symposium; May 24, 1976 - May 26, 1976; Atlanta, GA
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
    facet.materialart.
    Unknown
    An experimental evaluation of the stresses in drilled balls (1974)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Stresses in dimensionally similar large models of 40-, 50- and 60-percent mass reduction cylindrically hollow 'drilled' bearing balls were experimentally evaluated with flat strain gage rosettes. Dimensionless principal stress coefficients were calculated and were applied to estimate the bending stresses in the drilled balls of three series of full-scale bearing experiments. Stresses were highest when the applied load approached the edge of the hole, and ranged up to almost 620 million Newtons per sq m at the bore.
    Keywords: MECHANICAL ENGINEERING
    Type: ASME PAPER 74-LUB-17 , American Society of Mechanical Engineers and American Society of Lubrication Engineers, Joint Lubrication Conference; Oct 08, 1974 - Oct 10, 1974; Montreal; Canada
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    NASA TECHNICAL REPORTS
  • 5
    facet.materialart.
    Unknown
    Performance of 75-millimeter-bore bearings using electron-beam-welded hollow balls with a diameter ratio of 1.26 (1975)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An experimental investigation was performed to determine the rolling element fatigue life of electron beam-welded hollow balls with a diameter ratio (o.d./i.d.) of 1.26 and to determine the operating characteristics of bearings using these hollow balls. Similar bearings with solid balls were also tested and the data compared. The bearings were operated at shaft speeds up to 28,000 rpm with a thrust load of 2200 N (500 lb). Ball failures during the bearing tests were due to flexure fatigue. The solid and hollow ball bearings tested showed little difference in outer race temperatures and indicated the same bearing torque. The 17.5-mm (0.6875-in.) diameter balls were also tested in the five-ball fatigue tester and showed no significant difference in life when compared with the life of a solid ball.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TN-D-7869 , E-7961
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
    facet.materialart.
    Unknown
    Lubricant and additive effects on spur gear fatigue life (1985)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Spur gear endurance tests were conducted with six lubricants using a single lot of consumable-electrode vacuum melted (CVM) AISI 9310 spur gears. The sixth lubricant was divided into four batches each of which had a different additive content. Lubricants tested with a phosphorus-type load carrying additive showed a statistically significant improvement in life over lubricants without this type of additive. The presence of sulfur type antiwear additives in the lubricant did not appear to affect the surface fatigue life of the gears. No statistical difference in life was produced with those lubricants of different base stocks but with similar viscosity, pressure-viscosity coefficients and antiwear additives. Gears tested with a 0.1 wt % sulfur and 0.1 wt % phosphorus EP additives in the lubricant had reactive films that were 200 to 400 (0.8 to 1.6 microns) thick.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TM-87044 , E-2482 , NAS 1.15:87044 , 1985 Lubrication Conf.; Oct 08, 1985 - Oct 10, 1985; Atlanta, GA; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
    facet.materialart.
    Unknown
    Operating characteristics of a 0.87 kW-hr flywheel energy storage module (1985)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Discussion is given of the design and loss characteristics of 0.87 kW-hr (peak) flywheel energy storage module suitable for aerospace and automotive applications. The maraging steel flywheel rotor, a 46-cm- (18-in-) diameter, 58-kg (128-lb) tapered disk, delivers 0.65 kW-hr of usable energy between operating speeds of 10,000 and 20,000 rpm. The rotor is supported by 20- and 25-mm bore diameter, deep-groove ball bearings, lubricated by a self-replenishing wick type lubrication system. To reduce aerodynamic losses, the rotor housing was evacuated to vacuum levels from 40 to 200 millitorr. Dynamic rotor instabilities uncovered during testing necessitated the use of an elastometric-bearing damper to limit shaft excursions. Spindown losses from bearing, seal, and aerodynamic drag at 50 millitorr typically ranged from 64 to 193 W at 10,000 and 20,000 rpm, respectively. Discharge efficiency of the flywheel system exceeded 96 percent at torque levels greater than 21 percent of rated torque.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TM-87038 , E-2535 , NAS 1.15:87038 , Intersoc. Energy Conversion Eng. Conf. (IECEC); Aug 18, 1985 - Aug 23, 1985; Miami Beach, FL; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 8
    facet.materialart.
    Unknown
    Lubricant and additive effects on spur gear fatigue life (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Spur gear endurance tests were conducted with six lubricants using a single lot of consumable-electrode vacuum melted (CVM) AISI 9310 spur gears. The sixth lubricants was divided into four batches each of which had a different additive content. Lubricant tested with a phosphorus-type load carrying additive showed a statistically significant improvement in life over lubricants without this type of additive. The presence of sulfur type antiwear additives in the lubricant did not appear to affect the surface fatigue life of the gears. No statistical difference in life was produced with those lubricants of different base stocks but with similar viscosity, pressure-viscosity coefficients and antiwar additives. Gears tested with a 0.1 wt pct sulfur and 0.1 wt pct phosphorus EP additives in the lubricant had reactive films that were 200 to 400 (0.8 to 1.6 microns) thick.
    Keywords: MECHANICAL ENGINEERING
    Type: ASME PAPER 85-TRIB-14 , ASME, Transactions, Journal of Tribology (ISSN 0742-4787); 108; 468-475;
    Format: text
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    NASA TECHNICAL REPORTS
  • 9
    facet.materialart.
    Unknown
    Design and evaluation of a 3 million DN series-hybrid thrust bearing (1976)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The bearing, consisting of a 150-mm ball bearing and a centrifugally actuated, conical, fluid-film bearing, was fatigue tested. Test conditions were representative of a mainshaft ball bearing in a gas turbine engine operating at maximum thrust load to simulate aircraft takeoff conditions. Tests were conducted up to 16000 rpm and at this speed an axial load of 15568 newtons (3500 lb) was safely supported by the hybrid bearing system. Through the series-hybrid bearing principle, the effective ball bearing speed was reduced to approximately one-half of the shaft speed. It was concluded that a speed reduction of this magnitude results in a ten-fold increase in the ball bearing fatigue life. A successful evaluation of fluid-film bearing lubricant supply failure was performed repeatedly at an operating speed of 10,000 rpm. A complete and smooth changeover to full-scale ball bearing operation was effected when the oil supply to the fluid-film bearing was cut off. Reactivation of the fluid-film oil supply system resulted in a flawless return to the original mode of hybrid operation.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TM-X-71873 , E-8646 , Spring Lubrication Symp.; May 24, 1976 - May 26, 1976; Atlanta, GA; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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