Numerical investigation of the lift-off effect on the cut-off frequency in the Rayleigh wave

The EMAT is a non-contact transducer, but it is sensitive to the lift off. To study the lift off effect on the feature cut off frequency in the Rayleigh wave, a finite element method (FEM) is used. Based on different hypotheses of the source current density, three formulations are realized with the simulation software COMSOL. Ignoring the skin and proximity effects will yield enormous errors. The results obtained with the complete formulation are relatively accurate. A two dimensions (2D) EMAT transmitting model is built upon the complete formulation. On the basis of the 2D model, the lift off effect on the feature cut off frequency is investigated in detail.