Numerical Simulation Research Of Electromagnetic Ultrasonic Transducer

Nowadays, with the the growing demand for electricity of China, the operation stablity of critical equipment in power plant is becoming more important. As one of nondestructive testing technology, Ultrasonic guided wave testing method can get rid of the limit of point by point scanning as conventional ultrasonic wave testing technology,which can detect the defects inside and outside the devices of power plant quickly and intuitively, is showing great potential.EMAT is a new type of ultrasonic emission receiver. Compared with traditional piezoelectric ultrasonic sensors, EMAT has outstanding advantages:Without the preprocessing and acoustic coupling agent on the surface when making detection, can produce various types of ultrasound. But, electromagnetic ultrasonic testing technology also has limitations, such as low efficiency, relying on good data acquisition and analysis system.This paper studied the physical fields coupling of the working process of the transducer by using the Finite element simulation method, chose several main parameters of the EMAT, analyzed the influence they could make to the ultrasonic guided wave exciting, while designed related experiment to verify the conclusion basing on the understanding of the research both at home and abroad, and then the transducer has been optimized.At the first, this paper made analysis of the working mechanism and structure of the EMAT. Validated the physical field models, which were related in the working process basing on the analysis of the working mechanism of the EMAT, the validated physical field models consist of static magnetic field produced by the magnet and the eddy current produced by alternating current in the coil.Then, designed and build up the model of EMAT which mainly aimed at So mode ultrasonic guided wave, and calculation the working process of the EMAT by simulation, the further research has been done is describe the transmission and the changing rule for the magnetic field, eddy current, lorentz force, volumetric strain.At last, transducer has been optimized from several aspects:the mating magnetic, the electric, and the coordination between magnetic and electric fields. Got the regular of EMAT efficiency by changing the parameters, including of the magnetic strength of the magnet, lift-off distance between aluminum plate and magnet, number of spiral circle, size of spiral circle, lift-off distance between aluminum plate and coil, coordination between coil and magnet, while design related experimental to validate the accuracy of the dates calculated by the finite element numerical simulation. The optimized EMAT has higher conversion efficiency and can make nondestructive testing more accurately.