Development Of Nondestructive Testing Probe Based On Magnetoacoustic Tomography With Magnetic Induction

Aluminium alloy plates with low density, high strength and corrosion resistance have been widely used in aerospace manufacturing, but the defects on the surface and subsurface is hadden and dangerous, which have caused a series of accidents and threaten our life and the environment. Currently the cracks are mainly detected by ECT (Eddy Current Testing) and the corrosions are mainly detected by ITWI (Infrared Thermal Wave Imaging).This paper proposed a new method that introducing the MAT-MI (Magnetoacoustic Tomography with Magnetic Induction) in medical imaging to the NDT (Non-Destructive Testing) field. Because the cracks change the conductivity distribution on the plate, by exciting the plate using pulsed magnetic field and then recieving the ultrasonic signals on its surface, we can reconstruct the conductivity distribution on the plate.Firstly, this paper established the MAT-MI forward problems analytical model for Alu-minium alloy plates, and calculated the static and the dynamic magnetic field contributions in excitation; then studied the magnetoacoustic signal propagation mechanism and deter-mined the wave pattern of the magnetoacoustic signal; Finally developed an probe equip-ment based on MAT-MI, which contains electromagnetic transducer and magnetoacoustic signal excitation and recieving circuit.Using the equipment designed above, a series of experiments are performed. Includ-ing exciting methods of the two modes of magnetoacoustic signals and the characters of magnetoacoustic signal based on SHO mode wave etc. At last, the equipment proved its effectiveness of detecting cracks of20mm long and2mm deep on the surface of the Alu-minium alloy plate.