Monitoring Circumferential Welds in Canisters with Helical Ultrasonic Guided Waves

Abstract

Welded regions in canisters that are used to store industrial chemicals, fuels, gases, spent nuclear fuels, etc., are susceptible to damage due to stress corrosion cracking and fatigue failure. Hence, monitoring their integrity over time is essential to prevent leaks. One way to monitor the canister welds’ integrity is through active SHM with helicalguided ultrasonic waves (HGUW). When HGUW interact with defects in welds, their signature is altered, and based on this, the regions of defects can be located and mapped. This work demonstrates the mapping of damaged regions in circumferential welds in canisters using HGUW. A canister cut section, made by circumferentially welding two rings, was used as the test structure to demonstrate the mapping methodology. Two circumferential PZT arrays, each one on the opposing side of the weld, provided a network of paths that enabled monitoring of the weld all around the circumference. The presence or absence of damage in any section of the weld can be determined by analyzing the wave propagating along a path passing through the specific region. By combining information from all such paths, a map indicating the location of damages was constructed. Accordingly, waveforms from all paths of the network were acquired, and the information from them was used to generate a map via the Reconstruction Algorithm for Probabilistic Inspection of Damage (RAPID) method to locate the damaged area. The successful mapping of the damaged region established this technique as a valid option for the long-term monitoring of circumferential welds.