Research on influence of lorentz force mechanism on EMAT's transduction efficiency in steel plate

Electromagnetic acoustic technique shows great promise in defect detection and classification for being free of couplant, no requirement of surface preconditioning, and being able to excite pure surface acoustic wave, etc. However, the deficiency of designing theories of electromagnetic acoustic transducers (EMATs) makes its transduction efficiency poor. This paper makes improvement to EMAT design through modeling of the EMAT behavior in steel plate and analyzes the distribution regularity of the eddy current, magnetic field, and Lorentz force produced by a surface wave EMAT. The modeling study gives the influence of EMAT parameters on the energy density of surface wave and the relationship between main structural parameters of the EMAT and the transducer's transduction efficiency, which indicates that, decrease of lift-off distance, coil conductor's width, and magnet's bottom area, and increase of magnet's thickness could effectively improve the transduction efficiency of the EMAT. Finally, the validity and accuracy of the model is verified by experiment.