Data fusion of multi-view plane wave imaging for nozzle weld inspection

Ultrasonic non-destructive testing of nozzle-to-pipe welds has always been a challenge due to the complex saddle-shaped geometry of this junction. Inspection from the nozzle side can minimize geometry effects, however, conventional ultrasonic phased array methods suffer from artifacts and inadequate resolution. This paper proposes a novel nozzle-side inspection method based on the data fusion of multi-view plane wave imaging (PWI). A semi-analytic ultrasonic measurement model is derived, and a sensitivity mapping algorithm is presented for optimizing the inspection setup and enabling data fusion. Experiments were conducted on reference blocks and a nozzle specimen containing three embedded defects. Results demonstrate the capability of sensitivity mappings to not only optimize the inspection configuration, but also serve as filters to fuse multi-view images. Nozzle sidewalls were positioned in fusion images, evidencing the ability to deduce probe position around nozzle circumference without encoder feedback. A 10 dB amplitude difference was observed between the tip diffraction and specular reflection, enabling the defect characterization along with position and sizing accuracy within 0.59 mm and angle deviation below 9 degrees. Slag, crack and lack of penetration were also characterized in the nozzle specimen, validating the proposed method.