Backscattered Transverse Wave Imaging of Cracked-Faces with Linear and Nonlinear Ultrasonics

Abstract

A new backscattered-wave imaging of a cracked-face itself is proposed. Different from the conventional TOFD and phased array techniques, the wave scattered on a rugged fatigue-cracked face and/or intergranular stress-corrosion-cracking, SCC, face is captured in this technique. By focusing ultrasonic beams at every peak on those faces with a point-focused transducer and a scanner and by mapping the scattered-wave amplitudes on the scanned plane, we make an image of the cracked face itself. For tight cracked faces of nm opening, the second and higher harmonic amplitudes, generated by clapping and/or rubbing such a face with finite amplitude burst waves, are mapped in the similar way. By comparing the linear and nonlinear images of cracked faces, we can classify the extent of the crack opening. Some images of fatigue cracked faces are shown.