An improved analytical model of the magnetostriction-based EMAT of SH0 mode guided wave in a ferromagnetic plate.

The accuracy of electro-acoustic energy transfer efficiency (EAETE) model directly determines the optimization results of an electromagnetic acoustic transducer (EMAT). In this study, the EMAT model of SH0 mode generation based on magnetostriction mechanism is re-examined. In the existing magnetostriction-based EMAT (MEMAT) analytical model, an approximate method of dynamic magnetic field was employed. Thus the effects of the tested ferromagnetic materials on the dynamic magnetic field in the air is ignored and the boundary condition between air and material is not exact. As a result, the calculated dynamic magnetic field inside the tested ferromagnetic materials is incorrect, thus leading to the calculation errors of magnetostriction body force and the final EAETE of MEMAT. The rigorous analytical solutions for calculating the dynamic magnetic field are derived based on Maxwell equations and boundary conditions in this study. The prediction results of improved analytical model were consistent with previously reported experimental results. Compared with existing analytical models, the improved model showed the higher prediction accuracy of several parameters, including dynamic magnetic field, magnetostriction force and the EAETE.