The Influence of Thread Parameters on Ultrasonic Guided Wave Propagation in Threaded Circular Pipe Structures

Abstract Threaded pipe structures are critical components in equipment used in various fields. The threaded sections are prone to induce defects due to stress concentration, threatening the safe operation of the equipment. Consequently, the inspection of these structures is essential. While the ultrasonic guided wave (UGW) method has been applied to inspect threaded pipes, the influence of thread parameters on UGW propagation characteristics is yet to be examined. This study first analyzed the dispersion characteristics of UGWs. It reveals that the group velocity dispersion curve of the L(0,2) mode initially increases and then decreases over the frequency range of 60–140 kHz. The group velocity is higher in trapezoidal threads than in rectangular threads. Dispersion curves for different thread heights exhibit a crossover near 85 kHz. Dispersion curves for different pitches intersect around 83 kHz. Second, the effect of thread parameter variations on the reflection characteristics was investigated. It was found that the trapezoidal thread exhibits a higher reflection coefficient than the rectangular thread. The reflection coefficient increases with the thread height and decreases with pitch. Third, the influence of thread parameters on defect detection sensitivity was examined. Results demonstrate that the L(0,2) mode offers high sensitivity for defect detection in threaded pipes featuring trapezoidal threads, a thread height of 1 mm, and a pitch of 4.5 mm. Finally, the effectiveness of the L(0,2) mode in detecting defects of varying depths within threaded pipes was validated. This research provides a novel method for the inspection of threaded pipe structures.