Phased array techniques for an optimized inspection of dissimilar welds

The inspection of austenitic stainless steel welds by ultrasonic techniques is disturbed by the heterogeneous and anisotropic structure of the weld. To make matters worse the specimen also consists of different areas of austenitic and ferritic steel. The disturbance may result from beam deviations, beam splitting, scattering or attenuation. For defect localization and size characterization the before mentioned disturbances induce uncertainties and unknowns and may not meet the inspection requirements in the first place. The development of more advanced phased array UT inspection techniques starts with the evaluation of the acoustic beam propagation required to determine the target flaw positions. By using the laser vibrometer it was possible to study the propagation of longitudinal and shear waves and their interaction with the weld in great detail and thus taking the results into account for the configuration of the novel system and the reconstruction of the ultrasonic data.