In situ quantitative non-destructive evaluation of the welding crack using ultrasonic time of flight of diffraction-echo method

In conjunction of the time-of-flight diffraction method and the pulse-echo method, an in-situ ultrasonic method for quantitative non-destructive evaluation of the welding crack's position and sizing 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 15 MHz center frequency transducers. The position of a crack, with the size of 2 mm of the steel welding plate can be characterized accurately.