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  • 1
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    Modal simulation of gear box vibration with experimental correlation (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-12-09
    Keywords: MECHANICAL ENGINEERING
    Type: Journal of Propulsion and Power (ISSN 0748-4658); 9; 2; p. 301-306.
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Analytical and experimental study of vibrations in a gear transmission (1991)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: An analytical simulation of the dynamics of a gear transmission system is presented and compared to experimental results from a gear noise test rig at NASA Lewis. The analytical procedure developed couples the dynamic behaviors of the rotor-bearing-gear system with the response of the gearbox structure. Transient and steady-state vibrations of the gearbox system are presented in the time and frequency domains. The vibration characteristics of a simple single-mesh-gear noise test rig are modeled. The numerical simulations are compared to experimental data measured under typical operating conditions. The system natural frequencies, peak vibration amplitudes, and gear mesh frequencies are generally in good agreement.
    Keywords: MECHANICAL ENGINEERING
    Type: AIAA PAPER 91-2019
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  • 3
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    Testing of YUH-61A helicopter transmission in NASA Lewis 2240-kW (3000-hp facility (1986)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A helicopter transmission that was being considered for the Army's Utility Tactical Transport Attack System (UTTAS) was tested in the NASA Lewis 2240-kW (3000-hp) test facility to obtain the transmission's operational data. The results will form a vibration and efficiency data base for evaluation similar-class helicopter transmissions. The transmission's mechanical efficiency was determined to be 98.7 percent at its rated power level of 2080 kW (2792 hp). At power levels up to 113 percent of rated the transmission displayed 56 percent higher vibration acceleration levels on the right input than on the left input. Both vibration signature analysis and final visual inspection indicated that the right input spiral-bevel gear had poor contact patterns. The highest vibration meter level was 52 g's rms at the accessory gear, which had free-wheeling gearsets. At 113 percent power and 100 percent rated speed the vibration meter levels generally ranged from 3 to 25 g's rms.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TP-2538 , E-2801 , NAS 1.60:2538
    Format: application/pdf
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  • 4
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    Testing of UH-60A helicopter transmission in NASA Lewis 2240-kW (3000-hp) facility (1986)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The U.S. Army's UH-60A Black Hawk 2240-kW (3000-hp) class, twin-engine helicopter transmission was tested at the NASA Lewis Research Center. The vibration and efficiency test results will be used to enhance the data base for similar-class helicopters. Most of the data were obtained for a matrix of test conditions of 50 to 100 percent of rated rotor speed and 20 to 100 percent of rated input power. The transmission's mechanical efficiency at 100 percent of rated power was 97.3 and 97.5 percent with its inlet oil maintained at 355 and 372 K (180 and 210 F), respectively. The highest vibration reading was 72 g's rms at the upper housing side wall. Other vibration levels measured near the gear meshes are reported.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TP-2626 , E-2941 , NAS 1.60:2626
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  • 5
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    Computing Stresses In Spur Gears (1995)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Dynamic Analysis of Spur Gear Transmissions (DANST) developed as easy-to-use program for static and dynamic analysis of spur-gear systems. Used for parametric studies to predict effects of operating speed, torque, stiffness, damping, inertia, and tooth profile on dynamic loads and tooth-bending stresses in spur gears. Performs geometric modeling and dynamic analysis for low- or high-contact-ratio spur gears. Simulates gear systems with contact ratios ranging from one to three. Written in FORTRAN 77.
    Keywords: MECHANICS
    Type: LEW-15420 , NASA Tech Briefs (ISSN 0145-319X); 19; 12; P. 73
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  • 6
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    Profile modification to minimize spur gear dynamic loading (1989)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: An analytical computer simulation program for dynamic modeling of low-contact-ratio spur gear systems is presented. The procedure computes the static transmission error of the gears operating under load and uses a fast Fourier transform to generate the frequency spectrum of the static transmission error at various tooth profile modifications. The dynamic loading response of an unmodified (perfect involute) gear pair was compared with that of gears with various profile modifications. Correlations were found between various profile modifications and the resulting dynamic loads. An effective error, obtained from frequency domain analysis of the static transmission error of the gears, gave a very good indication of the optimum profile modification to reduce gear dynamic loading. Design curves generated by dynamic simulation at various profile modifications are given for gear systems operated at various loads. Optimum profile modifications can be determined from these design curves for improved gear design.
    Keywords: MECHANICAL ENGINEERING
    Type: 1989 International Power Transmission and Gearing Conference; Apr 25, 1989 - Apr 28, 1989; Chicago, IL; United States
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    NASA TECHNICAL REPORTS
  • 7
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    Vibration in Planetary Gear Systems with Unequal Planet Stiffnesses (1982)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An algorithm suitable for a minicomputer was developed for finding the natural frequencies and mode shapes of a planetary gear system which has unequal stiffnesses between the Sun/planet and planet/ring gear meshes. Mode shapes are represented in the form of graphical computer output that illustrates the lateral and rotational motion of the three coaxial gears and the planet gears. This procedure permits the analysis of gear trains utilizing nonuniform mesh conditions and user specified masses, stiffnesses, and boundary conditions. Numerical integration of the equations of motion for planetary gear systems indicates that this algorithm offers an efficient means of predicting operating speeds which may result in high dynamic tooth loads.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TM-83428 , E-1716 , NAS 1.15:83428 , Appl. Mech. Conf.; Sep 19, 1983 - Sep 21, 1983; St. Louis
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  • 8
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    Vibration and noise analysis of a gear transmission system (1993)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: This paper presents a comprehensive procedure to predict both the vibration and noise generated by a gear transmission system under normal operating conditions. The gearbox vibrations were obtained from both numerical simulation and experimental studies using a gear noise test rig. In addition, the noise generated by the gearbox vibrations was recorded during the experimental testing. A numerical method was used to develop linear relationships between the gearbox vibration and the generated noise. The hypercoherence function is introduced to correlate the nonlinear relationship between the fundamental noise frequency and its harmonics. A numerical procedure was developed using both the linear and nonlinear relationships generated from the experimental data to predict noise resulting from the gearbox vibrations. The application of this methodology is demonstrated by comparing the numerical and experimental results from the gear noise test rig.
    Keywords: MECHANICAL ENGINEERING
    Type: AIAA PAPER 93-2150 , ; 16 p.|AIAA, SAE, ASME, and ASEE, Joint Propulsion Conference and Exhibit; Jun 28, 1993 - Jun 30, 1993; Monterey, CA; United States
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  • 9
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    Vibration and noise analysis of a gear transmission system (1993)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This paper presents a comprehensive procedure to predict both the vibration and noise generated by a gear transmission system under normal operating conditions. The gearbox vibrations were obtained from both numerical simulation and experimental studies using a gear noise test rig. In addition, the noise generated by the gearbox vibrations was recorded during the experimental testing. A numerical method was used to develop linear relationships between the gearbox vibration and the generated noise. The hypercoherence function is introduced to correlate the nonlinear relationship between the fundamental noise frequency and its harmonics. A numerical procedure was developed using both the linear and nonlinear relationships generated from the experimental data to predict noise resulting from the gearbox vibrations. The application of this methodology is demonstrated by comparing the numerical and experimental results from the gear noise test rig.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TM-106162 , E-7859 , NAS 1.15:106162 , AIAA PAPER 93-2150 , ARL-MR-77 , Joint Propulsion Conference and Exhibit; Jun 28, 1993 - Jun 30, 1993; Monterey, CA; United States
    Format: application/pdf
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  • 10
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    Gear noise, vibration, and diagnostic studies at NASA Lewis Research Center (1990)
    In:  Other Sources
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    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
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