Abstract
To make clear the mode conversion behavior of S0-mode lamb wave and SH0-plate wave converting to the longitudinal mode guided wave and torsional mode guided wave in a pipe, respectively, the experiments were performed based on a previous built pipe inspection system. The pipe was wound with an L-shaped plate or a T-shaped plate as the waveguide, and the S0-wave and SH0-wave were excited separately in the waveguide. To carry out the objective, a meander-line coil electromagnetic acoustic transducer (EMAT) for S0-wave and a periodic permanent magnet (PPM) EMAT for SH0-wave were developed and optimized. Then, several comparison experiments were conducted to compare the efficiency of mode conversion. Experimental results showed that the T(0,1) mode, L(0,1) mode, and L(0,2) mode guided waves can be successfully detected when converted from the S0-wave or SH0-wave with different shaped waveguides. It can also be inferred that the S0-wave has a better ability to convert to the T(0,1) mode, while the SH0-wave is easier to convert to the L(0,1) mode and L(0,2) mode, and the L-shaped waveguide has a better efficiency than T-shaped waveguide.
Highlights
Online monitoring of pipes at high temperature for wall thickness and defects is a key to many industrial non-destructive evaluation (NDE) demands, such as the power generation and the nuclear industry
There are two techniques which are commonly employed for generating guided waves: the piezoelectric transducer and electromagnetic acoustic transducer (EMAT) [2]
Theoflongitudinal and torsional mode guided waveswaveguide have for different types defects duedue toto their different oscillation patterns, both of them are always employed for a comprehensive and torsional mode guided waves have different differentfor types of defects due their different oscillation both ofdetection them areabilities alwaysfor employed a comprehensive to their different oscillation patterns, in both of them are always employed a comprehensive pipe evaluation
Summary
Online monitoring of pipes at high temperature for wall thickness and defects is a key to many industrial non-destructive evaluation (NDE) demands, such as the power generation and the nuclear industry. EMAT has the ability to generate and detect ultrasonic waves without making a contact with the test object which makes it suitable to inspect high-temperature pipes with a large. A sensor system for high-temperature pipe inspection, which can transmit and receive ultrasonic guideda sensor waves using afor long waveguide, has been developed by Murayama [16]. Theoflongitudinal and torsional mode guided waveswaveguide have for different types defects duedue toto their different oscillation patterns, both of them are always employed for a comprehensive and torsional mode guided waves have different differentfor types of defects due their different oscillation both ofdetection them areabilities alwaysfor employed a comprehensive to their different oscillation patterns, in both of them are always employed a comprehensive pipe evaluation [6,16,17,18] Inthis this system, thetransformation transformation testing wavefrom fromthe pipe evaluation.
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