Defect characterization by ultrasonic diffraction techniques

Different ultrasonic diffraction techniques are described. Two diffraction techniques have been chosen for the experiments. Three steel blocks with notches of different sizes and orientations were tested with satellite-pulse-observation (SPOT) and peak-echo techniques (PE). The shear-wave mode was used in the experiments. The best results in sizing defects were achieved by using the peakecho technique with a 45° angle probe. The average error was -0.5 mm and the standard deviation ±1.3 mm. The corresponding values using the same technique and a 60° angle probe were 2.8 mm and ±2.1 mm. The average error was -0.5 mm and standard deviation ±2.3 mm by transit time differences in SPOT. The evaluation from the frequency content in sizing defects by SPOT gave an average error of -0.3 mm and a standard deviation of ±2.3 mm.