A novel time-of-flight difference determination method for ultrasonic thickness measurement with ultrasonic echo onset point detection

Determining the time-of-flight difference (TOFD) between adjacent echoes is essential for accurate ultrasonic thickness measurement. However, due to energy attenuation, time shift and frequency dispersion during the propagation process, the actual received ultrasonic signal will always have waveform changes and noise interference, and it is challenging to ensure satisfactory accuracy using traditional methods. Herein, A TOFD determination method based on ultrasonic echo onset point (UEOP) detection was proposed. The method combines the optimal main energy spectrum (ODES) and Akaike information criterion (AIC) to detect the UEOP of ultrasonic echo, and then determines the TOFD based on the UEOP of adjacent echoes. Numerical experiments were carried out to evaluate the detection performance of the proposed method under waveform change and different noise levels. Experimental validation of ultrasonic thickness measurement on aluminum alloy samples shows that the proposed method can obtain accurate thickness measurement results.