Hybrid laser ultrasonic inspection based on optical fiber technique

Laser generation and electromagnetic acoustic transducer (EMAT) detection techniques are combined as a hybrid ultrasonic technique for the inspection of the defects in the steel. Laser transmits through the optical fiber and irradiates on the steel surface. In case of inspection, Rayleigh wave is generated to test the surface defects based on the principle of mode conversion. In order to improve the testing accuracy and signal-to-noise ratio, wavelet soft-threshold method is introduced in the present work. Experimental results show that errors of testing surface defect are less than 10%, which proves laser-EMAT technique to be suitable for nondestructive assessment of metallic materials.