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  • 1
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    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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  • 2
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    Large-bore tapered-roller bearing performance and endurance to 2.4 million DN (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The operating characteristics and experimental life estimates for 120.65 mm bore tapered roller bearings of two designs under combined radial and thrust loads were determined. A modified standard bearing design was tested at speeds up to 15,000 rpm. A computer optimized, high speed design was tested at speeds up to 20,000 rpm. Both designs were tested at a combined load of 26,700 N (6000 lb) radial load and and 53,400 N (12,000 lb) thrust load. Advanced helicopter transmissions which require the higher-speed capability of tapered-roller bearings also require higher temperature capability (ref. 2). Thus, materials with temperature capabilities higher than the conventional carburizing steels are required.
    Keywords: MECHANICAL ENGINEERING
    Type: Advanced Power Transmission Technol.; p 253-270
    Format: application/pdf
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  • 3
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    Present technology of rolling-element bearings (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The present technology of rolling-element bearings, the barriers and limits which currently exist, and some of the future requirements that will demand further advancements are identified.
    Keywords: MECHANICAL ENGINEERING
    Type: Advanced Power Transmission Technol.; p 35-47
    Format: application/pdf
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  • 4
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    Comparison of predicted and experimental thermal performance of angular-contact ball bearings (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Predicted bearing heat generation and bearing temperature were verified by experimental data for ball bearings over a range of sizes, shaft speeds, and lubricant flow rates. The computer program Shaberth requires, as input, a factor which describes the air-oil mixture in the bearing cavity for calculation of the ball drag contribution to bearing heat generation. An equation for this lubricant percent volume in the bearing cavity was derived and appears to be valid over the range of test conditions including bearing bore sizes from 35 to 167 mm and shaft speeds from 1.0 to 3.0 million DN.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TP-2275 , E-1751 , NAS 1.60:2275
    Format: application/pdf
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  • 5
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    Lubrication of optimized-design tapered-roller bearings to 2.4 million DN (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The performance of 120.65 mm (4.75 in.) bore high speed design, tapered roller bearings was investigated at shaft speeds to 20,000 rpm (2.4 million DN) under combined thrust and radial load. The test bearing design was computer optimized for high speed operation. Temperature distribution bearing heat generation were determined as a function of shaft speed, radial and thrust loads, lubricant flow rates, and lubricant inlet temperature. The high speed design, tapered roller bearing operated successfully at shaft speeds up to 20,000 rpm under heavy thrust and radial loads. Bearing temperatures and heat generation with the high speed design bearing were significantly less than those of a modified standard bearing tested previously. Cup cooling was effective in decreasing the high cup temperatures to levels equal to the cone temperature.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TP-1714 , E-270
    Format: application/pdf
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  • 6
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    Rolling-element fatigue life of AISI M-50 and 18-4-1 balls (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Rolling element fatigue studies were conducted with AISI M-50, EFR 18-4-1, and VAR 18-4-1. Groups of 12.7 mm (1/2-in) diameter balls of each material were tested in the five ball fatigue tester. Test conditions included a load of 1540 N (347 lbf) giving a maximum Hertz stress of 5520 MPa (800 000 psi), a shaft speed of 10,700 rpm, and a contact angle of 30 deg. Tests were run at a race temperature of 339 K (150 F) with a type 2 ester lubricant. The rolling element fatigue life of AISI M-50 was not significantly different from that of EFR 18-4-1 or VAR 18-4-1 based on a statistical comparison of the test results.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TP-1202 , E-9350
    Format: application/pdf
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  • 7
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    Characterization of wear debris generated in accelerated rolling-element fatigue tests (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A ferrographic analysis was used to determine the types and quantities of wear debris generated during accelerated rolling contact fatigue tests. The five-ball rolling contact fatigue tester was used. Ball specimens were made of 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 to the 9th power Pa and a shaft speed of 10,000 rpm. Four types of wear debris were observed: (1) normal rubbing wear particles, (2) fatigue microspall particles, (3) spheres, and (4) friction polymer deposits. The characterization of wear debris as a function of time was of limited use in predicting fatigue failures in these accelerated tests.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TP-1203 , E-9260
    Format: application/pdf
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  • 8
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    Effect of longitudinal surface finish on elastohydrodynamic lubrication (1975)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The effect of longitudinal-lay surface finish on the elastohydrodynamic film thickness and the percentage of film between rolling disks in contact were evaluated using a rolling disk apparatus. Film thickness was measured by transmitted X-rays, and percentage of film was monitored by an alternating-current continuity circuit. Disk finish was varied on both the crowned upper disk and the cylindrical lower disk. A type-2 ester and a synthetic paraffinic oil were used as lubricants. It was shown that the roughness with longitudinal lay has a deleterious effect on both film thickness and percentage of film. Measured film thicknesses for the two lubricants were comparable at equivalent test conditions. The percentage of film where a change in surface topography was observed was approximately 20 percent for the synthetic paraffinic oil and 10 percent for the type-2 ester.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TN-D-7967 , E-7971
    Format: application/pdf
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  • 9
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    Rolling-element fatigue life with two synthetic cycloaliphatic traction fluids (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The life potential of two synthetic cycloaliphatic hydrocarbon traction fluids in rolling element fatigue was evaluated in a five ball fatigue tester. Life comparisons with a MIL-L-23699 qualified tetraester oil showed that the traction test oils had good fatigue life performance, comparable to that of the tetraester oil. No statistically significant life differences between the traction fluids and the tetraester oil were exhibited under the accelerated fatigue test conditions. Erratic operating behavior was occasionally encountered during tests with the antiwear additive containing traction fluid for reasons thought to be related to excessive chemical activity under high contact pressure. This behavior occasionally resulted in premature test termination due to excessive surface distress and overheating.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TN-D-8124 , E-8457
    Format: application/pdf
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  • 10
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    Flexural fatigue of hollow rolling elements (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Hollow cylindrical bars were tested in the rolling-contact fatigue tester to determine the effects of material and outside diameter to inside diameter (OD/ID) ratios of 2.0, 1.6, 1.4, and 1.2 on fatigue failure mode and subsequent failure propagation. The range of applied loads with these OD/ID ratios resulted in maximum tangential tensile stresses ranging from 165 to 655 megapascals (24,000 to 95,000 psi) at the bore surface. Flexural failures of the hollow test bars occurred when this bore stress was 490 megapascals (71,000 psi) or greater with AISI 52100 hollow bars and 338 megapascals (49,000 psi) or greater with AISI M-50 hollow bars. Good correlation was obtained in relating the failures of these hollow bars with flexural failures of drilled balls from previously published full scale bearing tests.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TN-D-8313 , E-8621
    Format: application/pdf
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