Journal
SMART MATERIALS AND STRUCTURES
Volume 24, Issue 6, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/0964-1726/24/6/065036
Keywords
nonlinear wave modulation; noncontact laser ultrasonics; state space attractor; baseline-free damage diagnosis; damage visualization
Funding
- Climate Change Research Hub of KAIST [N01150138]
- Ministry of Science, ICT & Future Planning, Republic of Korea [N01150138] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
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Damage often causes a structural system to exhibit severe nonlinear behaviors, and the resulting nonlinear features are often much more sensitive to the damage than their linear counterparts. This study develops a laser nonlinear wave modulation spectroscopy (LNWMS) so that certain types of damage can be detected without any sensor placement. The proposed LNWMS utilizes a pulse laser to generate ultrasonic waves and a laser vibrometer for ultrasonic measurement. Under the broadband excitation of the pulse laser, a nonlinear source generates modulations at various frequency values due to interactions among various input frequency components. State space attractors are reconstructed from the ultrasonic responses measured by LNWMS, and a damage feature called Bhattacharyya distance (BD) is computed from the state space attractors to quantify the degree of damage-induced nonlinearity. By computing the BD values over the entire target surface using laser scanning, damage can be localized and visualized without relying on the baseline data obtained from the pristine condition of a target structure. The proposed technique has been successfully used for visualizing fatigue crack in an aluminum plate and delamination and debonding in a glass fiber reinforced polymer wind turbine blade.
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