A point source correlation technique for automatic discontinuity identification and sizing using time of flight diffraction

This paper proposes a technique for automatic discontinuity location and sizing using the ultrasonic time of flight diffraction technique. Here, the crack tips are modeled as point sources of diffracted waves in a homogenous, isotropic medium. The diffraction arcs are modeled using a ray based approach and the modeled arcs are correlated with the experimental B-scan data. The points of high correlation provide information about the location of the crack tips. A statistical echo separation procedure to isolate the diffraction arcs in the B-scan image is discussed. This paper also addresses the issue of application of this time of flight diffraction technique to a thin section (less than 12 mm [0.47 in.]), wherein the echoes from the various sources (lateral wave, back surface reflection, diffraction from crack tips and so on) interfere with each other, making it difficult to identify diffracted signals from the discontinuity tips.