Research on weak signal detection technique for electromagnetic ultrasonic inspection system

Electromagnetic acoustic transducers (EMATs) are very sensitive to surrounding noise while their transduction efficiency is rather poor. Consequently, ultrasonic signals received by EMATs are often contaminated by strong noise. To extract information of the received signals, a weak signal detection technique based on moving average, cross-correlation and self-correlation methods has been proposed. Crack signals obtained by an electromagnetic ultrasonic inspection system are processed by this cross-and-self-correlation detection technique. Feasibility and efficiency of the proposed technique are verified by experiment results with high reproducibility. By combining cross-correlation and self-correlation detection methods, this technique possesses a much stronger capability of weak signal detection than applying them individually.