Simulation of magnetoacoustic tomography with magnetic induction images of metal sheet with anisotropic conductivity

A method for numerically simulating MagnetoAcoustic Tomography with Magnetic Induction (MAT-MI) images of a metal sheet with anisotropic conductivity is proposed to provide image data for research and performance testing of Non-Destructive Testing (NDT) based on MAT-MI.A computer-simulated metal sheet with anisotropic conductivity is constructed and placed in a static magnetic field.A meander coil is placed over the metal sheet to stimulate an alternating excitation magnetic field.The induced eddy current and the acoustic source,i.e.,Lorentz force,generated by the static and alternating magnetic field are numerically simulated to obtain the gray-scale images of the surface wave displacement.The simulation results show that the defect on the metal sheet surface can be clearly identified and located from the images according to the characteristics of rapid attenuation of the surface wave at the defects.Ignoring the conductivity anisotropy of metal materials will reduce the imaging quality and lead to misjudgment of defects.The imaging quality can be improved through increasing the signal-to-noise ratio of the measured displacement signal of surface waves.The resolution to detect small and irregular defects can be improved by reducing the lift-off distance and increasing the excitation current frequency.