摘要
Based on the proper assumptions and approximations, the coupling mechanism of the electromagnetic acoustic transducer (EMAT) for ultrasonic generation within ferromagnetic material was studied by analyzing the eddy current distribution, Lorentz force, magnetostriction force and magnetization force. Some useful numerical calculations are presented to explain the EMAT behavior with general geometric arrangements. It is indicated that for the ferromagnetic material the magnetostriction effect dominates the EMAT phenomenon for ultrasonic wave generation in low magnetic field intensity, while the material does not reach its magnetizing saturation. But, with the increase of the bias magnetic field and saturation, the magnetostrictive terms will make no contributions to the ultrasonic generation and the Lorentz force becomes the only exciting mechanism. It is important to determine both the Lorentz and magnetostriction forces and select the appropriate working manner for achieving an optimized design.
基于适当的假设和近似 ,通过分析电涡流的分布、洛伦兹力、磁致伸缩力和磁化力 ,研究了在铁磁材料中用电磁声换能器 (EMAT)的方法产生超声的耦合机理 ,并针对有实用意义的结构参数进行了数值计算以解释换能器的性能 .结果表明 :对于铁磁性材料 ,在磁场强度较低、材料磁化未达到饱和时 ,磁致伸缩效应在EMAT超声波的产生中起主导作用 ;但是 ,随着偏置磁场的逐渐增强而使材料达到磁化饱和时 ,磁致伸缩逐渐消失 ,对产生超声不再有贡献作用 ,洛伦兹力变成是激发超声的惟一原因 .因此 ,为获得优化的设计 ,计算洛伦兹力和磁致伸缩力以及选择合适的工作方式变得尤为重要 .
基金
TheNationalHighTechnologyResearchand DevelopmentProgramofChina (863Program) (No .2 0 0 1AA60 2 0 2 1) .
