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  • 1
    facet.materialart.
    Unknown
    Acoustic fatigue characterization of carbon/carbon panels (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Data from a sonic fatigue test of a blade-stiffened carbon/carbon panel is analyzed to determine the progression of damage to failure. The reduction in stiffness, as observed from acceleration measurements taken during the test, is correlated with the physical damage. Damage was measured through visual inspection, thermographic measurements, and through the novel use of vibration data collected using a scanning laser vibrometer.
    Keywords: COMPOSITE MATERIALS
    Type: In: International Congress on Experimental Mechanics, 7th, Las Vegas, NV, June 8-11, 1992, Proceedings. Vol. 2 (A94-12901 02-39); p. 1348-1355.
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Unknown
    Operational military helicopter interior noise and vibration measurements with comparisons to ride quality criteria (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Balka (1981) has identified the attainment of a 'jet-smooth' ride as a primary goal of the helicopter industry for commercial and certain military helicopters. It was noted that criteria accounting for both multiple axis vibration and interior noise are needed. The present investigation has the objective to present a vibration and interior noise data base in a format suitable for direct evaluation of aircraft ride quality. The investigation is also concerned with an assessment of the measured environment against available criteria as an indication of the state-of-the-art for current machines. Interior noise and vibration measurements were obtained on eight military helicopters during routine operational flights. The data are presented in the form of a number of parameters.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: AIAA PAPER 83-2526
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Unknown
    Structureborne noise in aircraft (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: The amount of noise reaching an aircraft's interior by structureborne paths, when high levels of other noises are present, involves the measurement of transfer functions between vibrating levels on the wing and interior noise. The magnitude of the structureborne noise transfer function is established by exciting the aircraft with an electrodynamic shaker; a second transfer function is measured using the same sensor locations with the aircraft engines operating. Attention is given to the case of a twin-turboprop OV-10A aircraft; the resulting transfer function values at the discrete frequencies corresponding to the propeller blade passage frequency and its first four harmonics are tabulated and illustrated.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: Mechanical signature analysis - Machinery vibration, flow-induced vibration, and acoustic noise analysis; Sept. 27-30, 1987; Boston, MA; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Unknown
    A study of helicopter interior noise reduction (1975)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The interior noise levels of existing helicopters are discussed along with an ongoing experimental program directed towards reducing these levels. Results of several noise and vibration measurements on Langley Research Center's Civil Helicopter Research Aircraft are presented, including measurements taken before and after installation of an acoustically-treated cabin. The predominant noise source in this helicopter is the first stage planetary gear-clash in the main gear box, both before and after installation of the acoustically treated cabin. Noise reductions of up to 20 db in some octave bands may be required in order to obtain interior noise levels comparable to commercial jet transports.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-TM-X-72655 , L-10076 , Ann. Natl. Forum of the Amer. Helicopter Soc; May 01, 1975
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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