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Damage Identification of Metallic Structures Using A₀ Mode of Lamb Waves

Department of Engineering Mechanics, Chongqing University Chongqing 400011, P.R. China, hu{at}ssl.mech.tohoku.ac.jp, Department of Aerospace Engineering, Tohoku University, Aramaki-Aza-Aoba 6-6-01, Aoba-ku, Sendai 980-8579, Japan

Takahito Shimomukai

Department of Aerospace Engineering, Tohoku University, Aramaki-Aza-Aoba 6-6-01, Aoba-ku, Sendai 980-8579, Japan

Hisao Fukunaga

Department of Aerospace Engineering, Tohoku University, Aramaki-Aza-Aoba 6-6-01, Aoba-ku, Sendai 980-8579, Japan

Zhongqing Su

Department of Mechanical Engineering, The Hong Kong Polytechnic University Hong Kong SAR, China

A Lamb wave-based technique was developed for detecting damages in metallic structures, such as cracks and holes in metallic beams and plates. For metallic structures with transverse cracks and holes, A₀ mode of Lamb waves was employed due to its shorter wave length compared with S₀ mode, which leads to high sensitivity to small damages. Two kinds of excitation techniques for generating comparatively pure A₀ mode using piezoelectric lead zirconate titanate (PZT) actuators were realized experimentally. In one technique, two PZT actuators with applied out-of-phase voltages were attached on both sides of the structures. While in the other technique, a kind of grease lubricant was used between the bottom surface of one PZT actuator and the surface of the specimens. Both techniques were able to enhance the component of A₀ mode and reduce the component of S₀ mode effectively. Secondly, in terms of the arrival time of the A₀ wave mode reflected from damages obtained using the wavelet analysis, the positions of damages were identified accurately. The above two techniques were then validated by identifying the transverse cracks and holes in aluminum beams and plates, respectively. Numerical simulations using the finite element method (FEM) for the wave propagation in these structures with damages were carried out. The obtained experimental and numerical results demonstrate that it is possible to identify damage position very accurately by using only sensor data of defective structures without referring benchmark signals (sensor data of intact structures).

Key Words: Lamb wave • A0 mode • metallic structures • damage identification • FEM

This version was published on September 1, 2008

Structural Health Monitoring, Vol. 7, No. 3, 271-285 (2008)
DOI: 10.1177/1475921708090566


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