Defect detection using the phased-array laser ultrasonic crack diffraction enhancement method

Abstract

The ultrasonic time-of-flight diffraction (TOFD) method has drawbacks such as blind areas on the upper and lower surfaces during detection, a low signal-to-noise ratio (SNR) for ultrasonic diffraction signals, and difficulty achieving accurate quantitative analysis. A phased-array laser ultrasonic method using a fiber picosecond laser and an ultra-high-speed rotating mirror has been developed for crack detection to address these problems. Moreover, the four factors that affect the performance of the phased-array laser ultrasonic method were analyzed using the finite element method, and the change rule of the diffraction signal is analyzed using two calculated indexes: SNR and node displacement. Furthermore, an experimental verification was conducted, and the numerical simulation is consistent with the experimental results. Based on the experimental and simulation results, the weights of the four factors were calculated using the entropy evaluation method.