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  • 1990-1994  (6)
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  • 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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  • 2
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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
    Format: application/pdf
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  • 3
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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
    Format: application/pdf
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  • 4
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    Modal analysis of multistage gear systems coupled with gearbox vibrations (1991)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An analytical procedure to simulate vibrations in gear transmission systems is presented. This procedure couples the dynamics of the rotor-bearing gear system with the vibration in the gear box structure. The model synthesis method is used in solving the overall dynamics of the system, and a variable time-stepping integration scheme is used in evaluating the global transient vibration of the system. Locally each gear stage is modeled as a multimass rotor-bearing system using a discrete model. The modal characteristics are calculated using the matrix-transfer technique. The gearbox structure is represented by a finite element models, and modal parameters are solved by using NASTRAN. The rotor-gear stages are coupled through nonlinear compliance in the gear mesh while the gearbox structure is coupled through the bearing supports of the rotor system. Transient and steady state vibrations of the coupled system are examined in both time and frequency domains. A typical three-geared system is used as an example for demonstration of the developed procedure.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TM-103797 , E-6085 , NAS 1.15:103797 , AVSCOM-TR-90-C-033 , International Conference on Motion and Power Transmissions; Nov 24, 1991 - Nov 26, 1991; Hiroshima; Japan
    Format: application/pdf
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  • 5
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    Gear noise, vibration, and diagnostic studies at NASA Lewis Research Center (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The NASA Lewis Research Center and the U.S. Army Aviation Systems Command are involved in a joint research program to advance the technology of rotorcraft transmissions. This program consists of analytical as well as experimental efforts to achieve the overall goals of reducing weight, noise, and vibration, while increasing life and reliability. Recent analytical activities are highlighted in the areas of gear noise, vibration, and diagnostics performed in-house and through NASA and U.S. Army sponsored grants and contracts. These activities include studies of gear tooth profiles to reduce transmission error and vibration as well as gear housing and rotordynamic modeling to reduce structural vibration and transmission and noise radiation, and basic research into current gear failure diagnostic methodologies. Results of these activities are presented along with an overview of near-term research plans in the gear noise, vibration, and diagnostics area.
    Keywords: MECHANICAL ENGINEERING
    Type: IME International Conference; Apr 09, 1990 - Apr 11, 1990; Cambridge
    Format: text
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  • 6
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    Vibration Signature Analysis of a Faulted Gear Transmission System (1994)
    In:  CASI
    Details
    Publication Date: 2019-08-16
    Description: A comprehensive procedure in predicting faults in gear transmission systems under normal operating conditions is presented. Experimental data was obtained from a spiral bevel gear fatigue test rig at NASA Lewis Research Center. Time synchronous averaged vibration data was recorded throughout the test as the fault progressed from a small single pit to severe pitting over several teeth, and finally tooth fracture. A numerical procedure based on the Winger-Ville distribution was used to examine the time averaged vibration data. Results from the Wigner-Ville procedure are compared to results from a variety of signal analysis techniques which include time domain analysis methods and frequency analysis methods. Using photographs of the gear tooth at various stages of damage, the limitations and accuracy of the various techniques are compared and discussed. Conclusions are drawn from the comparison of the different approaches as well as the applicability of the Wigner-Ville method in predicting gear faults.
    Keywords: MECHANICAL ENGINEERING
    Type: AD-A290195 , ARL-TR-475 , E-8914 , NAS 1.15:106623 , NASA-TM-106623 , Joint Propulsion Conference; Jun 27, 1994 - Jun 29, 1994; Indianapolis, IN; United States
    Format: application/pdf
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