Investigating the Detectability of Surface Volumetric Defects in Ultrasonic Testing with the Use of Rayleigh Waves Generated by an Electromagnetic-Acoustic Transducer

Abstract—The paper presents the results of studying the detectability of surface volumetric defects by ultrasonic method of nondestructive testing. The possibility of using Rayleigh surface waves excited by an electromagnetic-acoustic transducer (EMAT) for these purposes is considered. Blind vertical drillings of various diameters and depths were used as artificial defects to simulate defects in low carbon steel samples. Based on the results of measurements, the dependence of the amplitude of the received signals on drilling parameters has been constructed. When statistically processing the results, the signal-to-noise ratio during the excitation of the Rayleigh wave with the help of the EMAT on defect-free areas of samples was taken into account. Optimal models of the distribution of signal amplitudes were determined to construct the curves of probability of detection (PoD) of a defect. Under the conditions of the experiments, based on the PoD curves constructed, conclusions have been drawn about the minimum dimensions of surface volumetric defects identified with 90% probability with allowance for the confidence interval of 90% and about the possibility of adjusting the parameters of ultrasonic testing by signals reflected from vertical drillings.