Interaction of SH guided waves with wall thinning

Abstract

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Circumferential SH Wave Piezoelectric Transducer System for Monitoring Corrosion-Like Defect in Large-Diameter Pipes

“…In laboratory studies, SH modes in plates are often used as an approximation of CSH waves in pipes [22], since numerical model and experiments in the plate are much simpler. The interaction of SH 0 wave with wall thinning defects is highly influenced by the thinning geometry and the operating frequency range [23]. When the operating frequency is below the first cutoff frequency, the SH 0 wave will not convert to higher order SH modes when encountering defects, so the reflection and transmission behaviors of SH 0 wave across thinning defects are relatively simple.…”

“…The simulations conducted by Luo et al [22] show that, when the operating frequency is above the CSH 1 wave cutoff frequency, the CSH 0 wave's reflection and transmission characteristics from a notch in a pipe are quite different from those of SH 0 wave from a notch in a plate, even for a thin pipe with a low thickness-to-diameter ratio. Therefore, although there are some investigations which focus on the interaction of SH 0 wave with corrosion-like defects in the high frequency-thickness regime [14,23,[29][30][31], these conclusions obtained from SH 0 wave in the high frequency-thickness regime cannot be extended to CSH 0 wave in the pipe straightforwardly.…”

Towards Guided Wave Robotic NDT Inspection: EMAT Size Matters

“…At these excitation frequencies, the SH0 mode is also generated. The SH0 mode is non-dispersive and is not affected by wall thinning [2,7], hence it is a convenient reference, especially where there are any variations in amplitude or arrival time related to liftoff or transducer positioning that otherwise could be misinterpreted as defects.…”

“…Ultrasonic guided waves are promising for fast screening of large areas. In particular, shear horizontal wavemodes are suitable for inspection of wall thinning in plates and pipes, with generation of this wavemode possible using electromagnetic acoustic transducers (EMATs) [1,2]. EMATs are well suited for generating guided waves in conducting samples, and their noncontact nature is promising in robotic inspection applications as they remove the need for couplant.…”

“…Wall thinning can additionally be identified through identifying the cut-off frequency for higher order SH modes [8]. A combination of inspection using cut-off frequency, changes in arrival time, mode conversions, and transmitted or reflected wave amplitudes is the most promising way forward for fast wall loss screening [2]. To implement this and to access the highly dispersive regime of the SH1 mode, a large wavelength must be chosen.…”