Health monitoring of complex curved structures using an ultrasonic wavefield propagation imaging system

Abstract

An ultrasonic wavefield propagation imaging system is introduced and then applied for ultrasonic wavefield imaging of complex curved surfaces. A Q-switched pulsed laser is utilized as a moving ultrasonic generator, and a PZT ultrasonic sensor is fixed during the laser beam scanning and detects the ultrasonic waves propagated from the points excited by the laser beam. The waveforms are allocated in the spatial domain of the scanned points and then manipulated in the form of a time versus wavefield movie. The visualized wavefields enable easy detection and interpretation of structural defects because anomalies during wavefield propagation can be visualized. Furthermore, this ultrasonic wavefield propagation imaging system enables reference-free inspection, complex curved surface scanning because it does not require control of focal length and incidence angle of the laser beam, and excellent adaptability with built-in structural health monitoring sensors, such as piezoelectric and fiber optic sensors. The system is demonstrated in the applications of wavefield visualization on a drill surface, detection of mass loss parts inside an elbow pipe joint, and detection and characterization of impact damage and stringer disbond in a composite skin–stringer structure.

NDE using laser generated ultrasound and integrated ultrasonic transducer receivers

“…Since IUTs are miniature in size and light weight and they may have sufficient high sensitivity similar to commercially available broad band UTs and are used only as receivers, operation in long life using battery and energy-harvested energy is expected. As both laser generation and IUT can be used for curved surfaces and high temperature operation, possibilities for NDE of large and complex structures in harsh conditions may be possible [12].…”

Non-contact and non-destructive Lamb wave generation using laser-induced plasma shock wave

“…Numerous studies on Lamb wave applications to detect damage in large structures such as airplanes, factories, and ships are underway. Lamb wave generation techniques can be divided into two main categories: those using a contact-type device (e.g., piezoelectric zirconate titanate) [8][9][10][11][12][13][14][15][16][17][18][19][20][21] and those using a non-contact type device [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] . Damage detection using a contact-type device seems inefficient, but inserting the device into a target structure can improve the efficiency.…”

Ultrasonic wavefield imaging: Research tool or emerging NDE method?

“…Numerous papers have been published on various methodologies for quantifying damage. Early efforts considered "snapshot" visualization [22] as well as accumulated energy plots [23]. Other approaches include standing wave analysis [6], wavenumber filtering [24], instantaneous wavenumber techniques [25][26][27], anomaly detection via dictionary learning [28], and a combined beamforming and wavenumber analysis technique [29], although this list is certainly not inclusive.…”