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Research Papers

Crack Identification in a Rotating Shaft via the Reverse Directional Frequency Response Functions

[+] Author and Article Information
Yun-Ho Seo

Center for Noise and Vibration Control, Department of Mechanical Engineering, KAIST, Daejeon 305-701, Korea

Chong-Won Lee1

Center for Noise and Vibration Control, Department of Mechanical Engineering, KAIST, Daejeon 305-701, Koreacwlee@kaist.ac.kr

K. C. Park

Department of Aerospace Engineering and Sciences, University of Colorado at Boulder, Colorado, CO 80303

1

Corresponding author.

J. Vib. Acoust 131(1), 011012 (Jan 08, 2009) (12 pages) doi:10.1115/1.2981168 History: Received January 30, 2008; Revised May 31, 2008; Published January 08, 2009

A method is proposed for identifying the location of an open transverse crack in flexible rotor systems by modeling the crack as a localized element with rotating asymmetry. It exploits the strong correlations between the modal constants of the reverse directional frequency response functions (r-dFRFs) and the degree and location of asymmetry. A map of the modal constants of the r-dFRFs for all elements is constructed to identify the location of crack by comparing the identified modal constants to those of the reference map. This paper also addresses practical issues associated with measurement noises and limited number of sensors. The proposed crack identification method is finally applied to a flexible rotor system with an open transverse crack in order to demonstrate the identification procedure for detection of the crack location.

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Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

A characteristic model of an asymmetric rotor

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Figure 2

The r-dFRFs of the characteristic model: asymmetry at spring No. 1: (a) Hp1g̃1(jω) and (b) Hp2g̃1(jω); Δk∕k=0.001 (—), Δk∕k=0.01 (----), Δk∕k=0.1 (—)

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Figure 3

Modal constants for different locations of asymmetry: (a) Hp1g̃1(jω) and (b) Hp2g̃1(jω); Δk∕k=0.01, Δk1 (○), Δk2 (×), and Δk3 (+)

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Figure 4

Equivalent modeling of a rotor model with (a) a rectangular cross-sectioned beam element and (b) an open crack

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Figure 5

The r-dFRFs for (a) a rectangular cross-sectioned and (b) an open-cracked model

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Figure 6

Procedure for locating asymmetry

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Figure 7

Examples for a reference map of modal constants

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Figure 8

Schematic for obtaining an estimated height

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Figure 9

(a) A reference rotor model for a map of modal constants and (b) the target rotor model with an open crack

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Figure 10

Identified modal constants of a target rotor system (a) Sensor No. 1 (Hpg̃7,19(jω)), (b) Sensor No. 2 (Hpg̃19,19(jω)), and (c) Sensor No. 3 (Hpg̃31,19(jω)); (-◼-: no noise; -●-: 10% noise)

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Figure 11

Examples of obtaining estimated heights for identified modal constants in Hpg̃19,19(jω) (a) (Mri)32 and (b) (Mri)92

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Figure 12

Standard deviations of estimated height identifying the locations of a crack

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