Ultrasonic testing methods and units for characterizing planar flaws in hard-to-inspect materials such as welded and cladded pipes containing intergranular stress corrosion cracks. The invention characterizes flaws with pitch-catch transducers positioned front to back on a single module. One module uses a bimodal transducer to transmit longitudinal and shear waves to produce, through surface wave mode conversion, reflection and diffraction, a triplet of associated longitudinal and shear wave signals received by another bimodal transducer. Other modules use pitch-catch transducers to produce a doublet of associated shear wave signals from diffraction of an incident longitudinal and/or shear waves at the upper and lower extremities of underclad fatigue cracks and buried cracks. The signals are enchanced by multiple one sided cross focusing on preselected target areas in the test specimen and are cognizable by pattern recognition. Flaw characterization results from the created linear relationship between signal separation and crack depth.
George J. Gruber