Nondestructive evaluation of advanced materials by use of electromagnetoacoustic interactions

作为本研究的基础，我们推导了具有磁弹性耦合的铁磁材料的各种磁力学行为。我们推广了松本提出的磁力学本构方程，将磁历史的依赖性作为更广泛类别的铁磁材料的内变量。将本构方程应用于典型的铁磁材料，可以很好地描述磁化曲线、磁致伸缩曲线，包括应力依赖性、磁滞和非线性。当磁场施加到铁磁材料上时，在磁化矢量方向上感应声各向异性。然后通过测量每个方向上极化的横波的速度来估计磁化矢量的方向。…的区别此外，最大速度和最小速度与声学各向异性有很强的相关性，因此也可以估计磁化矢量的大小。这种磁化强度的无损测量可以应用于电磁分析的验证，有助于更准确、更有效地设计电磁仪器。作为电磁声相互作用的另一种应用，我们使用电磁换能器(EMAT)通过超声检测来可视化内部缺陷。本文首先通过波形分析和电磁分析，对电磁兼容技术的发射和接收过程进行了仿真。通过扫描样品表面附近的EMAT可以获得缺陷的超声图像。以平滑、反卷积和衰减效应为波形分析，以SAFT-UT和ALOK技术为扫描方法，对超声图像的改善进行了研究。较少

As the foundation of the present research, we formulated various magnetomechanical behaviors of ferromagnetic materials with magnetoelastic couplings. We extended the magnetomechanical constitutive equation proposed by Matsumoto to include the dependence of magnetic histories as internal variables for wider classes of ferromagnetic materials. Applying the constitutive equations to typical ferromagnetic materials, we have shown that they can describe in good accuracy the magnetization curve, the magnetostriction curve including their stress dependence, hysteresis and nonlinearity.We next applied the magnetoacoustic effects to the nondestructive evaluation of the stress and the magnetization. When the magnetic field is applied to a ferromagnetic material, the acoustic anisotropy is induced in the direction of the magnetization vector. Then the direction of the magnetization vector can be estimated by measuring the speed of the transverse wave polarized in each direction. The difference o … More f the maximum and the minimum speeds has a strong correlation with the acoustic anisotropy, so that the magnitude of the magnetization vector can be also estimated. Such a nondestructive measurement of the magnetization can be applied to verification of the electromagnetic analysis, which contributes to more accurate and effective design of electromagnetic instruments. It is also shown that conventional acoustoelastic measurement enables us to evaluate plane stress if the magnetic field is applied.As another application of electromagnetoacoustic interactions, we visualized the internal defects by ultrasonic inspection using electromagnetic acoustic transducer (EMAT). We first simulated the transmitting and the receiving processes of EMAT by the wave analysis and the electromagnetic analysis. An ultrasonic image of defects can be obtained by scanning EMAT near the specimen surface. Improvement of the ultrasonic image was studied by employing smoothing, deconvolution and damping effect as waveform analysis, and SAFT-UT and ALOK techniques as scanning method. Less