Electromagnetic Ultrasonic Testing Technology Research And System Design

Electromagnetic ultrasonic testing technique which has the advantages of high efficiency, strong environment adaptability, safety, and light-duty, is widely applied to the field of industrial nondestructive testing. Recently, it has become a hot research area at home and abroad.First, The existing technology and its development trend in the field of industrial nondestructive testing at home and abroad is summarized in this paper, power exchanging mechanism deeply analyzed of electromagnetic ultrasonic mechanism based on the lorentz force mechanism and electromagnetic mechanism. Model has been established of EMAT for ferromagnetic materials. Using the model to solve the magnetic induction intensity, the eddy current density, the density of lorentz force, magnetostriction force density, and the coil impedance change rules of key parameters. The finite element simulation software are used to simulating the model.Secondly, successfully develops an electromagnetic ultrasonic detection system based on FPGA. Including Tone burst excitation signal synthetic circuit based on DDS technology; EMAT coil drivers circuit which pulse power outputs up to10kW;The coil impedance matches circuit; The receiving circuit designed in this paper has a strong ability of weak signal detection under a strong noise environment. USB communication circuit, high-speed data acquisition and gain control circuit are designed in the integration of digital systems.Finally, experiments of ferromagnetic materials and compare the echo signal strength under different excitation frequency, it is concluded that ultrasonic frequency characteristics; The echo signal of dealing with artificial defects is analyzed in order to make sure the position of crack; The coil impedance measured actually to validate the correctness of the simulation results which are obtained by the model. The validity of the model is proved by these experiments.