Modeling and analysis of surface wave EMAT and its acoustic field

Surface wave is widely used to detect and locate the surface and sub-surface defects. A model has been developed for the calculation of surface wave generated by an electromagnetic acoustic transducer (EMAT) operating on the Lorentz principle by finite element method. We establish the displacement model of surface wave based on acoustic theory in elastic solids. The surface wave is measured by a Michelson laser interferometer, and good agreement is observed between the calculated and measured results, verifying the validity of the finite element model. It is concluded that Lorentz force contains two components which are excited by static and dynamic magnetic field respectively. And Lorentz force due to static magnetic field plays a dominate role in generating surface wave when the excitation current is lower than 793.9 A, while that due to dynamic one is dominate when the current exceeds 793.9 A.