A Study of Internal Defect Testing With the Laser-EMAT Ultrasonic Method

This paper studies the ultrasonic detection and evaluation of internal volume defects in metals using laser generation and electromagnetic acoustic transducer (EMAT) detection. A finite element model is developed to simulate the interaction of laser-generated ultrasonic waves with the defect in the material. Not only have the directly scattered shear waves been observed, but also the mode-converted creeping waves on the defect surface. A noncontact laser-EMAT ultrasonic testing experimental system was successfully applied to validate the observed phenomena in the simulation results. The defect can not only be detected and located by the directly scattered shear waves, but can also be quickly evaluated with a new method based on quantitative time-of-flight analysis of the directly scattered waves and the mode-converted waves on the defect surface.