Effect Of Defect Orientation In Pipe On Acoustic Wave Propagation

Mohammed Abbas, Saddam Hamood Ali (2017) Effect Of Defect Orientation In Pipe On Acoustic Wave Propagation. Project Report. UTeM, Melaka, Malaysia. (Submitted)

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Abstract

Guided wave in non-destructive testing (NDT) and structural health monitoring (SHM) is a technique to perform an inspection in large or long structures such as in pipes from single position of transducer. There are three types of guided wave modes in axial direction of the pipe, which are torsional T (0, n), Longitudinal L (0, n) modes, and flexural F (M, n) modes. In low frequency range, the guided wave can only propagate in modes of L (0, 1), L (0, 2) or T (0, 1) in pipe structures. L (0, 2) mode is a typical mode that use in inspection technique due to its fastest wave speed and small dispersion in low frequency range. Therefore, we decided to investigate its behavior on the orientations of defects, which placed at the similar location in two aluminum pipes. The study used two-angle beam transducers consist of piezoelectric of transducers and acrylic shoes to find the artificial defects with placed in perpendicular and oblique orientations, respectively. The two angle beam transducers is used on the top and bottom of pipe and measured at five different locations with distance of 14 mm between each location. The five signals are then used to enhance the defect echo, which obtained from the excitation of five cycles of tone burst signal generated at central frequencies of 80 kHz to 150 kHz. The location of perpendicular defect is successfully located approximately at the exact location of the defect while the location of oblique defect is not unsuccessfully identified by using the two-angle beam transducer. This indicated that the reflected wave from defect is affected by the orientations of defects in pipes.

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