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  • MACHINE ELEMENTS AND PROCESSES  (18)
  • MECHANICAL ENGINEERING  (7)
  • 1990-1994  (6)
  • 1970-1974  (19)
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Years
Year
  • 1
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    Effects of gear box vibration and mass imbalance on the dynamics of multistage gear transmission (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The dynamic behavior of multistage gear transmission system, with the effects of gear-box-induced vibrations and rotor mass-imbalances is analyzed. The model method, using undamped frequencies and planar mode shapes, is used to reduce the degree-of-freedom of the system. The various rotor-bearing stages as well as lateral and torsional vibrations of each individual stage are coupled through localized gear-mesh-tooth interactions. Gear-box vibrations are coupled to the gear stage dynamics through bearing support forces. Transient and steady state dynamics of lateral and torsional vibrations of the geared system are examined in both time and frequency domain. A typical three-staged geared system is used as an example. Effects of mass-imbalance and gear box vibrations on the system dynamic behavior are presented in terms of modal excitation functions for both lateral and torsional vibrations. Operational characteristics and conclusions are drawn from the results presented.
    Keywords: MECHANICAL ENGINEERING
    Type: ASME, Transactions, Journal of Vibration and Acoustics (ISSN 0739-3717); 113; 333-344
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Comparison of conventional and microasperity elastohydrodynamic lubrication of a ballspinning in a nonconforming groove (1972)
    In:  CASI
    Details
    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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    NASA TECHNICAL REPORTS
  • 3
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    Pitting fatigue characteristics of AISI M-50 and super nitralloy spur gears (1973)
    In:  CASI
    Details
    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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  • 4
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    Lubrication considerations in gear design (1970)
    In:  CASI
    Details
    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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  • 5
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    Effects of antiwear and extreme pressure additives in a synthetic paraffinic lubricant on ball spinning torque (1970)
    In:  CASI
    Details
    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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  • 6
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    Analytical and Experimental Vibration Analysis of a Faulty Gear System (1994)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A comprehensive analytical procedure was developed for predicting faults in gear transmission systems under normal operating conditions. A gear tooth fault model is developed to simulate the effects of pitting and wear on the vibration signal under normal operating conditions. The model uses changes in the gear mesh stiffness to simulate the effects of gear tooth faults. The overall dynamics of the gear transmission system is evaluated by coupling the dynamics of each individual gear-rotor system through gear mesh forces generated between each gear-rotor system and the bearing forces generated between the rotor and the gearbox structure. The predicted results were compared with experimental results obtained from a spiral bevel gear fatigue test rig at NASA Lewis Research Center. The Wigner-Ville distribution (WVD) was used to give a comprehensive comparison of the predicted and experimental results. The WVD method applied to the experimental results were also compared to other fault detection techniques to verify the WVD's ability to detect the pitting damage, and to determine its relative performance. Overall results show good correlation between the experimental vibration data of the damaged test gear and the predicted vibration from the model with simulated gear tooth pitting damage. Results also verified that the WVD method can successfully detect and locate gear tooth wear and pitting damage.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TM-106689 , E-9045 , NAS 1.15:106689 , ARL-TR-574 , 1994 Fall Technical Workshop; Oct 24, 1994 - Oct 26, 1994; St. Louis, MO; United States
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  • 7
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    Analysis of the Effects of Surface Pitting and Wear on the Vibrations of a Gear Transmission System (1994)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A comprehensive procedure to simulate and analyze the vibrations in a gear transmission system with surface pitting, 'wear' and partial tooth fracture of the gear teeth is presented. An analytical model was developed where the effects of surface pitting and wear of the gear tooth were simulated by phase and magnitude changes in the gear mesh stiffness. Changes in the gear mesh stiffness were incorporated into each gear-shaft model during the global dynamic simulation of the system. The overall dynamics of the system were evaluated by solving for the transient dynamics of each shaft system simultaneously with the vibration of the gearbox structure. In order to reduce the number of degrees-of-freedom in the system, a modal synthesis procedure was used in the global transient dynamic analysis of the overall transmission system. An FFT procedure was used to transform the averaged time signal into the frequency domain for signature analysis. In addition, the Wigner-Ville distribution was also introduced to examine the gear vibration in the joint time frequency domain for vibration pattern recognition. Experimental results obtained from a gear fatigue test rig at NASA Lewis Research Center were used to evaluate the analytical model.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TM-106678 , E-9014 , NAS 1.15:106678 , ARL-TR-520 , AUSTRIB 1994; Dec 05, 1994 - Dec 08, 1994; Perth; Australia
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  • 8
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    Study of lubricant jet flow phenomena in spur gears (1974)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Review of the results of lubrication tests conducted in the NASA-Lewis Research Center gear test apparatus modified for high speed photography of gear tooth lubrication. The experimental results are compared with an analytical model that includes windage effects. The resulting findings show that the analytical model provides good agreement with the experimental impingement depth and that small oil drops are affected by gear windage. For this reason, the best lubrication is provided when the oil jet is not atomized.
    Keywords: MECHANICAL ENGINEERING
    Type: ASME PAPER 74-LUB-3 , American Society of Mechanical Engineers and American Society of Lubrication Engineers, Joint Lubrication Conference; Oct 08, 1974 - Oct 10, 1974; Montreal; Canada
    Format: text
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    NASA TECHNICAL REPORTS
  • 9
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    Study of lubricant jet flow phenomena in spur gears (1974)
    In:  CASI
    Details
    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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  • 10
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    A life study of AISI M-50 and Super Nitralloy spur gears with and without tip relief (1973)
    In:  CASI
    Details
    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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