静态偏置磁场强度对铁磁材料电磁超声换能机制的影响

The electromagnetic acoustic transduction mechanism of the Ferromagnetic material is complicated because of its magnetostrictive effect and nonlinear magnetization characteristic. It is helpful to improve the transduction efficiency and signal-to-noise ratio of electromagnetic acoustic transducer (EMAT) that analyzing the dominant factors of electromagnetic ultrasonic transducing mechanism in ferromagnetic materials under different magnetic field strength. In this paper, the simulation model of Lamb wave EMAT for ferromagnetic material was established. With the change of external magnetic field, the variation laws of Lorentz force, magnetostrictive force and magnetizing force were studied. The main factors influencing the transduction mechanism were analyzed by comparing the displacements under the Lorentz force, the magnetostrictive force and composition of the Lorentz force and the magnetostrictive force. The experimental results show that the displacement and velocity of Lamb wave are consistent with the simulation results. The study proves that: The magnetostrictive effect plays a dominant role in the field of weak magnetic, the Lorentz force increases and plays a major role when the ferromagnetic material is near magnetic saturation, the strain caused by the magnetostrictive effect is very small and barely changes at the magnetic saturation stage.