Metal sheets have good performance and have been widely used. Different kinds of defects can be generated during the preparation and service of metal plates, which will cause the structural performance of the metal plates to decline, thus requiring structural health monitoring (SHM). This study proposes an electromagnetic ultrasonic (EMUS) surface wave detection technique for metal sheet defects via simulation. The numerical results show that after the excitation parameters of the EMUS transducer are optimized through orthogonal experimental design, the amplitude of the EMUS signal generated is increased by about 80%. The power spectrum density (PSD) of the EMUS response signal is used to detect defects. Compared with the peak-to-peak detection, the accuracy is higher, and the reliability is better. The accuracy of the proposed “central zero-point” method for measuring the time delay of the EMUS signal wave packet is higher than that of the “peak-to-peak amplitude” method and the “vibration starting point” method and is close to the accuracy of the “cross-correlation” method.

Pipeline inspection has long been a major research topic in non-destructive testing (NDT). Conventional electromagnetic acoustic transducers (EMATs) generally generate bidirectional ultrasonic waves, which exhibit several inherent limitations in defect detection, including low signal amplitude, limited directivity, and incompatibility with pulse-echo inspection configurations. The use of unidirectional guided waves generated by EMATs offers a potential means of addressing these limitations in pipeline inspection. In this study, a method for pipeline defect imaging using electromagnetic ultrasonic unidirectional waves is investigated. First, the generation mechanism of unidirectional waves is theoretically analyzed based on the principle of wave superposition. Subsequently, finite element simulations are performed to investigate the effects of key transducer parameters on the amplitude of the generated unidirectional waves, and an optimal combination of excitation parameters is determined. Finally, defect imaging experiments are conducted on pipelines containing different types of defects. The simulation and experimental results show that the signal amplitude of the electromagnetic ultrasonic unidirectional waves increases by approximately 57.3% after optimization using an orthogonal experimental design. Experimental B-scan results show that the proposed bidirectional B-scan synthesis method provides a qualitative visualization and profile assessment of the defects.