高能脉冲激励下的电磁超声响应特性

The transmitted and received ultrasonic intensities of conventional electromagnetic ultrasonic transducer (EMAT) has small amplitudes and low signal-to-noise ratios. A concept for a novel high - energy ultrasonic excitation system without static magnetic field is presented, and its core is high-energy pulse excitation power supply. The novel high-energy pulse excitation power supply applies a transient high voltage to the excitation coil by a LC oscillator circuit and generates thousands of amps of current in the excitation coil, which is much larger than the current in the conventional EMAT excitation coil. The intensity of ultrasonic signals can be greatly increased and the transducer volume can be effectively reduced. The mechanism of high-energy pulse excitation of ultrasonic waves was studied in this paper. The variation law of magnetic field, force field and sound field of the high-energy pulsed EMAT during the transduction process was then obtained. High-energy pulsed power supply excited the Lamb wave with A₀ mode as the main mode, and the electromagnetic ultrasound experiment under the excitation of high-energy pulse was performed. The experimental results show that when the lift-off distance is less than 2mm, the Lamb wave with A₀ mode as the main mode has high signal-to-noise ratio and can accurately locate the defect, which has more advantages in detecting micro-crack defects.