To inspect oil and gas pipelines by using SH0 mode guided circumferential ultrasonic wave,a novel electromagnetic acoustic transducer（EMAT） for guided circumferential wave was designed.The EMAT has two structural features,a carbon steel sheet is on top of all the magnets and small nonmagnetic blocks are placed between adjacent magnets.To improve its transduction efficiency,ANSYS software was used to optimize some geometric parameters of EMAT.The optimal result is the carbon steel sheet should be thicker than 1 mm,and the wire spacing of the coil should be as small as possible.Experiments on a tube 200 mm in OD and 4 mm in wall thickness indicate that the EMAT optimized can excite the SH0 mode guided wave effectively.
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