Nondestructive testing of pitting corrosion cracks in rivet of multilayer structures

This research proposes an ultrasonic testing method for inspecting pitting corrosion cracks in a rivet of multilayer structures. The system is a combination of a magnetic sensor array and an ultrasonic sensor. The magnetic sensor array is used to automatically measure the presence of a rivet and its center position. Then, the ultrasonic sensor is guided to the rivet center in order to inspect pitting corrosion cracks in the rivet. The magnetic sensor uses a 64-Hall sensor elements array with a 0.52-mm interval that can measure the rivet center position at a standard deviation of 0.27 mm and 0.42 mm in the scan and sensor directions, respectively. The ultrasonic signal is analyzed in the frequency domain using the short-time Fourier transform that helps better observe the presence of cracks compared with the conventional signal analysis in A-scan present.