Abstract: In conjunction of the time-of-flight diffraction method and the pulse-echo method, and in-situ ultrasonic method for quantitative non-destructive evaluation of the welding crack’s position and zizing is presented. The deficiency of the time-of-flight diffraction method, the poor sensitivity for near-surface crack, is improved by pulse-echo method, and the demand of the x-axes scan can be omitted. The reason for the error, the factors which influence the resolution and accuracy of the method are analyzed. Using a pair of broadband longitudinal wave with 15MHz center frequency transducers, The position of a crack, with the size of 2mm of the steel welding plate can be charatanzed accurately.

Key words: Crack Time of flight diffraction (TOFD), Ultrasonic Q NDE, Welding