Ultrasonic TOFD technique and image enhancement based on synthetin aperture rousing technique

An ultrasonic TOFD (time of flight diffraction) B-scan image was processed in order to accurately locate crack tip in heavy aluminum butt weld. SAFT (synthetic aperture focusing technique) was introduced for improving lateral resolution of the image. According to the geometric relation between the probes and crack tip, an algorithmic model for SAFT processing was founded and SAFT reconstructed image was obtained. Linearization was proposed in order to enhance time resolution of the image before SAFT processing, and a novel technique named as L-SAFT (linearization-SAFT) was developed for ultrasonic TOFD B-scan image reconstruction. The results show that the technique can enhance resolution of the image effectively. Both lateral and vertical location of the crack tip in the specimen can be measured rapidly and accurately with this technique, which contribute to precise locating and sizing of defect.