A Guided Wave Plate Experiment for a Pipe

Abstract

The plate approximation of a pipe is a topic discussed for decades. Rules have been established to make the comparisons. Presented here is a related topic, but one to answer the question of whether an easy-to-conduct plate experiment can be used to predict what happens in a pipe for ultrasonic guided wave. For longitudinal guided waves in a pipe, the approximation is valid clearly only over a very short distance or inordinate closeness to a defect for wave scattering analysis; but for circumferential guided waves, the validity is unclear and therefore it is worthwhile to study criteria on the approximation and simplification of a pipe experiment as a plate experiment by means of wave mechanics analysis and modeling computation. Circumferential shear horizontal (SH) waves in pipes and SH waves in plates were studied in this paper toward this goal and it was found that the wave frequency and wall thickness to radius ratio were the two key parameters with respect to the similarity. Dispersion curves and wave structures of the SH waves in plates and in pipes were compared to find the origin of the similarity. Experimental simulations and modeling with boundary element methods were also carried out for the reflection and transmission coefficients of the SH waves impinging into a defect, from which some criteria have been established for the plate model approximation. Although a pipe model is more accurate for pipe experiments, a plate model often gives a quick and reasonable solution especially when it is difficult to establish a pipe model.