Research Papers

Effect of Planetary Gear Carrier-Plate Cracks on Vibration Spectrum

[+] Author and Article Information
Romano Patrick

GE Energy,
Advanced Technology Operations,
Atlanta, GA 30339-8402

Al Ferri

School of Mechanical Engineering,
Georgia Institute of Technology,
Atlanta, GA 30332-0405
e-mail: al.ferri@me.gatech.edu

George Vachtsevanos

School of Electrical and Computer Engineering,
Georgia Institute of Technology,
Atlanta, GA 30332-0250

Keller and Grabill refer to this number as the order of a sideband.

McNames calls all surviving sidebands “dominant”. McFadden calls one sideband “dominant” and the others “surviving.”

1Corresponding author.

Contributed by the Design Engineering Division of ASME for publication in the JOURNAL OF VIBRATION AND ACOUSTICS. Manuscript received November 12, 2009; final manuscript received December 13, 2011; published online September 10, 2012. Editor: Noel C. Perkins.

J. Vib. Acoust 134(6), 061001 (Sep 10, 2012) (12 pages) doi:10.1115/1.4006651 History: Received November 12, 2009; Revised December 13, 2011

This paper examines the problem of identifying cracks in planetary gear systems through the use of vibration sensors on the stationary gearbox housing. In particular, the effect of unequal spacing of planet gears relative to the rotating carrier plate on various frequency components in the vibration spectra is studied. The mathematical analysis is validated with experimental data comparing the vibration signature of helicopter transmissions operating either normally or with damage, leading to shifts in the planet gear positions. The theory presented is able to explain certain features and trends in the measured vibration signals of healthy and faulty transmissions. The characterization offered may serve as a means of detecting damage in planetary gear systems.

Copyright © 2012 by ASME
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Fig. 1

Representation of a planetary gear with the vibration sensor fixed on the annulus gear. Arrows represent the direction of motion. Here, θp is the angle (measured counterclockwise) from the sensor to the axis of rotation of planet gear number p.

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Fig. 2

Spectrum of nonepicyclic tooth meshing vibration as seen from a fixed point on the planetary carrier

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Fig. 3

Modulation function, showing the intensity of the meshing vibration signal of a single planet gear in translation, as perceived on a fixed point (vibration sensor) on the annulus gear

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Fig. 4

Spectrum of modulation signal

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Fig. 5

Vibration spectrum of a single planet gear. Only the right-hand side of the spectrum is shown.

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Fig. 6

Sidebands of equally spaced planetary gearbox with Np = 3 and Nt = 134

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Fig. 11

Comparison of sidebands in the spectra of an equally spaced planetary gearbox and a gearbox with planetary shifting

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Fig. 10

Effect of single-planet shift in the magnitude of dominant (or apparent) and nondominant sidebands; 3-planet case. Ordinate is scaled by the magnitude of a single planet’s contribution.

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Fig. 9

Phasor representation of the formation of planetary system sidebands through the addition of individual planet sidebands: (a) dominant and apparent sidebands, and (b) nondominant sidebands

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Fig. 8

Sideband phase change Δϕp,m,n of the dominant sideband (n = 0) as a function of the geometric angular shift δp of a planet gear for different tooth meshing harmonics. System represented has Np = 3 and Nt = 134.

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Fig. 7

Angular shift of planet gear number 3 in a system with Np = 3

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Fig. 12

Planetary gear carrier plate of a UH-60A Blackhawk helicopter: (a) top view of a healthy plate, and (b) view of a crack on one of the posts; the crack path is indicated by the arrows. (Original photographs published by Sahrmann [27]; reproduced with permission.)

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Fig. 17

Progression of sideband magnitudes for frequency components as a function of crack length at 40% engine torque

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Fig. 18

Progression of sideband magnitudes for frequency components as a function of crack length for 100% engine torque up to about 3.3 in. and 93% engine torque afterwards

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Fig. 13

Vibration spectrum for test cell gearboxes with Np = 5 planet gears and Nt = 228 teeth in the annulus gear

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Fig. 14

Vibration spectrum of the on-aircraft experimental data. Data legend is the same as in Fig. 13.

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Fig. 15

Representation of vibration snapshots taken for the crack growth experiment of a seeded crack in a planetary carrier plate

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Fig. 16

Categorization of planetary gear spectrum sidebands for a planetary gearbox with Np = 5 planet gears




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