Reflection of Torsional T (0, 1) Guided Waves from Pipeline Corrosion

Pang, Jing Sen (2019) Reflection of Torsional T (0, 1) Guided Waves from Pipeline Corrosion. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

The guided wave method can inspect pipelines very quickly. However, the reflection signals when the T (0, 1) wave mode incident on corrosion profiles were not well explored, hence this research investigated the response signals when torsional guided wave mode, T (0, 1) incident on defects. Numerical analysis was the primary focus in this experiment. A numerical model of 6 inch schedule 40 pipe was first developed and corrosion profile of various geometries were built on the outer surface of pipeline, through altering the depth and the circumferential length. The experiments were conducted using the finite element software, ANSYS to perform the numerical analysis solving wave propagation problem. A five cycle Hanning tone-burst signal with central frequency of 30k Hz was deployed throughout the study, the results showed the occurrence of mode conversion when the excited T (0, 1) incident on the defects which were generally non-symmetric. However, as the circumferential extent were increased, in which the defect tend to behave the characteristics of a symmetric feature, lesser mode conversion was observed. Thus, the existence of flexural mode F (1, m) can be a good indicator for the operator to differentiate between symmetric and non-symmetric features. It was noticed that as the depth of the defects were increased, the reflection coefficients were found to increase monotonically. Such behaviour were observed since the estimated cross-sectional area loss (ECL) were generally increased as the depth became deeper, hence a higher fraction of the transmission wave were reflected. The results collected from this experiment aims to serve as guidelines while the on-site inspections were performed by the inspectors. With known propagation speed of the guided wave, the location of single defect can be determined precisely with high accuracy.