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我们根据电磁场辐照低电导率样本时电磁场和声波场之间的耦合关系,对脉冲磁激励的磁声效应和热声效应展开研究。本文基于电磁场理论和声波传播理论知识,推导了脉冲磁激励的声压波动方程;构建二维载流线圈和低电导率圆形薄片模型以模拟成像物理环境,利用有限元方法分析瞬态电磁场;并且根据电磁场仿真结果,进行磁声效应和热声效应所产生的声场仿真计算。仿真结果表明,微秒级高斯脉冲磁场激励下,低电导率样本中热声效应比磁声效应大,且起主要作用;微秒级高斯脉冲磁场和0.2 T静磁场激励下,低电导率样本中热声效应和磁声效应共存。该研究为感应式磁声成像和磁热声成像的进一步应用奠定了基础。
We study the magnetoacoustic and thermoacoustic effects of pulsed magnetic excitation based on the coupling between the electromagnetic field and the acoustic field when the electromagnetic field irradiates low conductivity samples. Based on the theory of electromagnetic field and the theory of acoustic wave propagation, the paper deduces the sound pressure fluctuation equation of pulsed magnetic excitation, constructs two-dimensional current-carrying coil and low-conductivity circular slice model to simulate the imaging physical environment and analyzes the transient electromagnetic field by finite element method. And according to the electromagnetic field simulation results, the acoustic field and the thermoacoustic effect generated by the sound field simulation. The simulation results show that the thermoacoustic effect in low conductivity samples is larger than magnetoacoustic effect and plays a major role under microsecond Gaussian pulsed magnetic field excitation. Under microsecond Gaussian pulsed magnetic field and 0.2 T static magnetic field excitation, low conductivity samples The thermoacoustic and magneto-acoustic effects coexist. The research laid the foundation for the further application of inductive magneto-acoustic imaging and magnetocaloric imaging.