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TECHNICAL PAPERS

Exploring Effective Methods for Simulating Damaged Structures With Geometric Variation: Toward Intelligent Failure Detection

[+] Author and Article Information
Daniel A. McAdams1

Department of Mechanical and Aerospace Engineering,  University of Missouri—Rolla, Rolla, MO 65409-0050dmcadams@umr.edu

David Comella

Department of Mechanical and Aerospace Engineering,  University of Missouri—Rolla, Rolla, MO 65409-0050

Irem Y. Tumer

Complex Systems Design Group, Intelligent Systems Division, NASA Ames Research Center, Moffett Field, CA 94035-1000itumer@mail.arc.nasa.gov

1

Author to whom correspondence should be addressed.

J. Appl. Mech 74(2), 191-202 (Jan 25, 2006) (12 pages) doi:10.1115/1.2188535 History: Received September 09, 2004; Revised January 25, 2006

Inaccuracies in the modeling assumptions about the distributional characteristics of the monitored signatures have been shown to cause frequent false positives in vehicle monitoring systems for high-risk aerospace applications. To enable the development of robust fault detection methods, this work explores the deterministic as well as variational characteristics of failure signatures. Specifically, we explore the combined impact of crack damage and manufacturing variation on the vibrational characteristics of beams. The transverse vibration and associated eigenfrequencies of the beams are considered. Two different approaches are used to model beam vibrations with and without crack damage. The first approach uses a finite difference approach to enable the inclusion of both cracks and manufacturing variation. The crack model used with both approaches is based on a localized decrease in the Young’s modulus. The second approach uses Myklestad’s method to evaluate the effects of cracks and manufacturing variation. Using both beam models, Monte Carlo simulations are used to explore the impacts of manufacturing variation on damaged and undamaged beams. Derivations are presented for both models. Conclusions are presented on the choice of modeling techniques to define crack damage, and its impact on the monitored signal, followed by conclusions about the distributional characteristics of the monitored signatures when exposed to random manufacturing variations.

Copyright © 2007 by American Society of Mechanical Engineers
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References

Figures

Grahic Jump Location
Figure 1

Histogram for the first natural frequency of the uncracked beam (finite difference method)

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Figure 2

Histogram for the second natural frequency of the uncracked beam (finite difference method)

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Figure 3

Histogram for the third natural frequency of the uncracked beam (finite difference method)

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Figure 4

Histogram for the fourth natural frequency of the uncracked beam (finite difference method)

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Figure 5

Histogram for the fifth natural frequency of the uncracked beam (finite difference method)

Grahic Jump Location
Figure 6

Histogram for the first natural frequency of the cracked beam (finite difference method)

Grahic Jump Location
Figure 7

Histogram for the second natural frequency of the cracked beam (finite difference method)

Grahic Jump Location
Figure 8

Histogram for the third natural frequency of the cracked beam (finite difference method)

Grahic Jump Location
Figure 9

Histogram for the fourth natural frequency of the cracked beam (finite difference method)

Grahic Jump Location
Figure 10

Histogram for the fifth natural frequency of the cracked beam (finite difference method)

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Figure 11

Lumped model for a pinned-pinned beam

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Figure 12

Free-body diagram for station I

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Figure 13

Free-body diagram for station I

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Figure 14

Histogram for the first natural frequency of the uncracked beam (Myklestad’s method)

Grahic Jump Location
Figure 15

Histogram for the second natural frequency of the uncracked beam (Myklestad’s method)

Grahic Jump Location
Figure 16

Histogram for the third natural frequency of the uncracked beam (Myklestad’s method)

Grahic Jump Location
Figure 17

Histogram for the fourth natural frequency of the uncracked beam (Myklestad’s method)

Grahic Jump Location
Figure 18

Histogram for the fifth natural frequency of the uncracked beam (Myklestad’s method)

Grahic Jump Location
Figure 19

Histogram for the first natural frequency of the cracked beam (Myklestad’s method)

Grahic Jump Location
Figure 20

Histogram for the second natural frequency of the cracked beam (Myklestad’s method)

Grahic Jump Location
Figure 21

Histogram for the third natural frequency of the cracked beam (Myklestad’s method)

Grahic Jump Location
Figure 22

Histogram for the fourth natural frequency of the cracked beam (Myklestad’s method)

Grahic Jump Location
Figure 23

Histogram for the fifth natural frequency of the cracked beam (Myklestad’s method)

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