Application of Ultrasonic Frequency Domain Synthetic Aperture Focusing Technique in Defect Inspection for Spindle

In this paper, taking the steel spindle as the research object, a linear ultrasonic array transducer was placed on the end of the spindle to collect the ultrasonic array signals. The phase shift migration (PSM) imaging algorithm was used to perform Fourier transform on the collected ultrasonic array signal, and the frequency domain wave field was reconstructed by using the angular spectrum equation. Finally, the entire imaging area can be focused by the inverse Fourier transform. The imaging results show that the frequency domain SAFT can effectively improve the defect resolution of the image. For surface groove with 0.5 mm width and 1 mm depth, the half lateral width of defect were reduced from 23~29 mm to 19~22 mm, and the resolution can be increased by at least 17%~24%. It also proves that this algorithm has high computational efficiency and fully satisfices real-time imaging requirements in the application.