Adaptive Ultrasonic Phased Array Imaging for Inspection of Uneven Polyethylene Electrofusion Joints

Ultrasonic testing is a critical non-destructive evaluation (NDE) technique used to assess the structural integrity of polyethylene (PE) pipelines, especially in industries such as gas transportation and water systems. However, significant challenges arise when applying phased array ultrasonic focusing to PE electrofusion joints with uneven surfaces. The uneven surface requires a specific thickness of couplant for effective coupling, and the differences in acoustic impedance and ultrasonic velocity between the couplant and PE material changes the sound propagation path at the interface, which in turn leads to image distortion, reduced resolution, and decreased sensitivity in phased array inspection images. To overcome these challenges, an adaptive ultrasonic phased array imaging technique was proposed. First, the surface geometry was reconstructed. Then, based on Fermat’s principle and the reconstructed surface geometry, the sound propagation path was iteratively calculated, and then the transmit and receive delays of the phased array were adjusted to achieve effective focusing. Finally, the performance of the adaptive imaging algorithm was evaluated using experimental data and compared to conventional phased array ultrasonic inspection results. The results show that the proposed adaptive technique can improve the resolution and signal-to-noise ratio of the imaging, and clearly reveal the internal structure of the electrofusion joint.