Adhesive debonding inspection with a small EMAT in resonant mode

In this paper, a noncontact ultrasonic testing method with using a small electromagnetic acoustic transducer (EMAT) in resonant mode is proposed for metal-based adhesive debonding inspection. The small EMAT with a new magnet configuration and a small coil is developed firstly to improve the spatial resolution and detecting ability for minute defects. Different from conventional pulse echo method using short pulse excitation for debonding inspection, a new method based on power spectrum estimation of the resonant ultrasonic signal with long burst excitation is applied to increase the signal-to-noise ratio (SNR) and detecting ability of the small EMAT. Finally, ultrasonic C-scan images of specimens with various adhesive bonding are obtained to demonstrate the capability of this technique.