The Research Of Thin Steel Plate Electromagnetic Ultrasonic Wave Detection

Electromagnetic ultrasonic nondestructive testing technique is based on the principle of electromagnetic induction of new detection technology, the testing process, it does not require coupling medium can be achieved at high temperature, high pressure and other conditions of the testing work, so highly valued in the field of nondestructive testing. Ultrasound can also refine the electromagnetic electromagnetic ultrasonic plate wave, surface waves, longitudinal waves, shear waves in several forms, which are different in the non-destructive testing applications. In this paper, electromagnetic ultrasonic plate wave theory, based on a thin metal plate, especially the thin plate of NDT techniques were studied.This paper first electromagnetic ultrasonic nondestructive testing techniques for the development and application of the history of the introduction, analysis of the background and significance of the research topics discussed at this stage of the thin steel plate in the presence of some non-destructive testing deficiencies and urgent problems. Electromagnetic ultrasonic plate wave theory testing technology has been studied, and on this basis, using ANSYS finite element analysis software, the testing system for simulation analysis. EMAT established the 3D finite element model of the back to fold a square-shaped coils and permanent magnets form a combined simulation analysis to study the form inspired by the alternating magnetic field induction, eddy current and Lorentz force situation. The magnetization for ferromagnetic and magnetostrictive properties, analysis based on the magnetostrictive EMAT under the pressure of the magnetic mechanism of the matrix and inverse piezomagnetic matrix, derived force and magnetostriction magnetostrictive current density formula. To piezomagnetic - piezoelectric analogy, simulation and analysis of the magnetostriction mechanism of EMAT transducers process, displacement curve of the specimen internal particle and defect-fluctuations. Designed an electromagnetic ultrasonic plate wave flaw detection device, as an incentive to the carrier pulse train excitation signal, defect detection aluminum and steel plate with artificial defects,After testing and simulation analysis to verify the square-shaped permanent magnet and coil combination of back off, horseshoe-shaped permanent magnet and coil combination can be folded back, respectively, in the non-magnetic and ferromagnetic thin plate in the excitation of electromagnetic ultrasonic plate wave. Analysis of test data available, to determine defects by ultrasonic echo location and internal plate wave propagation velocity in the plate, you can achieve the positioning of the defect. Meanwhile, the plate wave dispersion characteristics and the presence of multi-mode, low-frequency thickness product cases, a single mode of electromagnetic ultrasonic plate wave is easier to achieve defect recognition. Hardware circuit, good and bad effects of the factors that affect the testing of all parameters except EMAT, the transmitting circuit impedance matching is particularly important.