Analysis on the Surface Blind Area of Time of Flight Diffraction and the Technology and Application of Ultrasonic Creeping Wave Testing in Surface Blind Area

This paper researches on the blind area of the time of flight diffraction (TOFD) by theoretically analyzing the surface blind area and by the experiment on TOFD detection block, and it shows that one of major limitations of TOFD is the flaw top tip located in a blind area. Thus, other testing methods are needed to cover the blind area. Experiments and comparisons among three methods (Ultrasonic Pulse Echo, Magnetic Particle and Ultrasonic Creeping Wave testing) are carried out to get a decent detection performance. The results presented in this paper indicate that creeping wave testing technique can effectively detect overweight defect in the blind area of TOFD as a complemented method.