Structure diagram of the bulk wave EMAT.
Axisymmetric structures of EMATs in cylindrical coordinate system with (a) a delta function coil and (b) a spiral coil. The current densities of the currents are i 0.
Axisymmetric structure of the static magnetic field in cylindrical coordinate system with (a) a delta function current of k 0 and (b) a current loop of k. The current loop k is around the side face and along the circumferential direction of the permanent magnet.
Eddy-current along the r axis in the surface of sample when we consider the permanent magnet or not.
Lorentz forces along the r axis in the surface of sample: the forces generated by (a) static magnetic fields and (b) dynamic magnetic fields.
Multi-types of radiated wave field distribution radiated by the Lorentz forces generated by static magnetic fields, which are Fr , ω and Fr , ω .
Displacement ratios η at different liftoffs of magnet l 1, with respect to the ratios of the magnet radius to coil radius.
Multi-types of the radiated wave field distribution radiated by Lorentz forces generated by dynamic magnetic fields, which are Fr ,2 ω and Fr ,2 ω .
Comparisons of the displacements between the present model and FEM software. The displacements are provided by (a) Fr, ω and (b) Fz , ω at the frequency of 2 MHz.
Schematic diagram of the experiment system for measurement of the radiated wave distributions.
Comparisons between measured voltages and calculated displacements along the r axis for the EMATs (a) with permanent magnet and (b) without permanent magnet.
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