Abstract
It is necessary to develop a transducer that can quickly detect the inner and outer wall defects of thick-walled pipes, in order to ensure the safety of such pipes. In this paper, a flexible broadband Rayleigh-waves comb transducer based on PZT (lead zirconate titanate) for defect detection of thick-walled pipes is studied. The multiple resonant coupling theory is used to expand the transducer broadband and the FEA (Finite Element Analysis) method is used to optimize transducer array element parameters. Optimization results show that the best array element parameters of the transducer are when the transducer array element length is 30 mm, the thickness is 1.2 mm, the width of one end of is 1.5 mm, and the other end is 3 mm. Based on the optimization results, such a transducer was fabricated and its performance was tested. The test results were consistent with the finite-element simulation results, and the −3 dB bandwidth of the transducer reached 417 kHz. Transducer directivity test results show that the Θ−3dB beam width was equal to 10 °, to meet the defect detection requirements. Finally, defects of thick-walled pipes were detected using the transducer. The results showed that the transducer could detect the inner and outer wall defects of thick-walled pipes within the bandwidth.
Highlights
As an important component that is subject to high temperatures and high pressures, thick-walled pipes have been widely used in the main steam pipelines of the electric power industry
A flexible broadband comb Rayleigh waves transducer with non-equidistant interval was designed using the finite element method combined with the multiple resonant coupling theory of piezoelectric ceramics
In the FEA orthogonal experiment, the optimal array element length and thickness are obtained by comparing the impedance values of array elements with different thickness and length
Summary
As an important component that is subject to high temperatures and high pressures, thick-walled pipes have been widely used in the main steam pipelines of the electric power industry. Thick-walled pipes are subject to random inspections using traditional nondestructive examinations, such as using magnetic particle testing, radiographic testing, and point-by-point ultrasonic testing, which are inefficient and have difficulty meeting the requirements of good engineering practices. Ultrasonic guided waves, used as a new nondestructive examination technique, can improve the detection efficiency for thick-walled pipes. As one of the guided waves, can propagate for a long distance on the smooth surface of workpieces without reflection. It is especially suitable for defect detection on workpiece surfaces with Rayleigh waves, and has received extensive attention from scholars. Hassan and Babich et al [1,2] studied the interaction between Rayleigh waves and semi-circular defects with a limited size on a workpiece
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