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Shock and Vibration
Volume 2017 (2017), Article ID 5164594, 11 pages
https://doi.org/10.1155/2017/5164594
Research Article

Nonpenetrating Damage Identification Using Hybrid Lamb Wave Modes from Hilbert-Huang Spectrum in Thin-Walled Structures

1Department of Dam Safety Management, Nanjing Hydraulic Research Institute, Nanjing 210029, China
2Department of Civil and Environmental Engineering and Composite Materials and Engineering Center, Washington State University, Pullman, WA 99164-2910, USA
3School of Mechanics and Materials, Hohai University, Nanjing 210098, China

Correspondence should be addressed to Zijian Wang

Received 12 June 2017; Revised 19 September 2017; Accepted 16 October 2017; Published 20 November 2017

Academic Editor: Sandris Ručevskis

Copyright © 2017 Zijian Wang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Lamb waves have shown promising advantages for damage identification in thin-walled structures. Multiple modes of Lamb wave provide diverse sensitivities to different types of damage. To sufficiently utilize damage-related wave features, damage indices were developed by using hybrid Lamb wave modes from Hilbert-Huang spectra. Damage indices were defined as surface integrals of Hilbert-Huang spectra on featured regions determined by time and frequency windowing. The time windowing was performed according to individual propagation velocity of different Lamb wave mode, while the frequency windowing was performed according to the frequency of excitation. By summing damage indices for all transmitter-receiver pairs, pixels were calculated to reconstruct a damage map to characterize the degree of damage at each location on structure. Both numerical and experimental validations were conducted to identify a nonpenetrating damage. The results demonstrated that the proposed damage indices using hybrid Lamb wave modes are more sensitive and robust than the one using single Lamb wave mode.