Quantitative detection of internal defects in thick wall structure of spherical tank based on ultrasonic phased array diffraction imaging

Ultrasonic phased array detection technology is suitable for nondestructive testing of internal defects in thick-walled structures. However, the traditional −6 dB amplitude method is often used for quantification of the phased array, which is difficult to improve the quantitative accuracy of planar defects. Based on this, a quantitative method of diffraction wave time difference at the end of planar defects was proposed, which combined the advantages of phased array sound field control. Firstly, the numerical model of the detection process was established, and the excitation mechanism of the diffraction wave at the defect end under the phased array sound field was analyzed. Secondly, the diffraction wave signal of the defect end of the thick-walled sample was extracted, and the location and quantitative detection were carried out accordingly. Finally, the quantitative detection ability of ultrasonic phased array diffraction wave quantitative method and −6 dB amplitude method was compared and analyzed. The experimental results showed that the diffraction wave signals at the end of the defect could be effectively received by adjusting the position of the probe in the fan-shaped scanning sound field of the phased array, and the positioning and quantitative accuracy based on the diffraction wave signals at the end of the defect was higher than that of the −6 dB amplitude method, and the diffraction wave detection was more suitable for the detection of planar defects.