Nondestructive Measurement of Stress and Material Properties using Electromagnetic Fields

本研究的主要目的是发展研究者提出的磁声弹性学，实现更实用的应力评估无损技术和非磁性材料的新技术。 1．非线性电磁弹性本构方程的建立及验证提出了含磁滞的非线性铁磁材料的本构方程，并从理论上分析了磁滞对超声波传播的影响。我们还提出了塑性铁磁材料的本构方程，并证明我们可以分离塑性变形和磁弹性耦合对超声波速度变化的影响。从结果来看，可以将磁声弹性应用于承受较大应力的材料。为了考虑到更广泛的材料和变形，我们提出了磁本构方程，它可以描述磁率和各向异性的影响。2．磁场下应力和材料性能的无损评估我们表明，根据磁场下超声波的速度变化，可以分离织构和应力各向异性，并评估传统技术难以实现的更准确的应力。我们进一步研究了通过对样本施加磁场，可以通过测量一种超声波的速度变化来评估平面应力。我们研究了烧结材料的材料密度或弹性常数的分布可以通过波速的分布来获得。 3．磁声弹性的扩展我们利用压电或电致伸缩效应将磁声弹性推广到非磁性材料。理论研究的实验验证尚未完成，留待以后的课题进行。

The main purpose of the research was to develop magnetoacoustoelasticity proposed by the investigators, and to achieve more practical nondestructive techniques of stress evaluation and a new technique available for nonmagnetic materials.1. Establishment of nonlinear electromagnetoelastic constitutive equations and their verificationWe proposed the constitutive equations of nonlinear ferromagnetic materials with hysteresis and theoretically analyzed the effects of magnetic hysteresis on the propagation of ultrasonic waves. We also proposed the constitutive equations of plastic ferromagnetic materials and proved that we can separate the effects of the plastic deformation and the magnetoelastic couplings on the speed shift of ultrasonic waves. From the result, it becomes possible to apply the magnetoacoutoelasticity to materials subjected to larger stresses. In order to take into account wider classes of materials and deformations, we proposed the magnetic constitutive equations which can describe the effects of magnetic rate and anisotropy.2. Nondestructive evaluation of stress and material property under magnetic fieldWe showed that from the speed shift of ultrasonic waves under the magnetic field, it becomes possible to separate the texture and the stress anisotropies and to evaluate more accurate stress which has been difficult by conventional techniques. We further examined that by applying the magnetic fields to the specimen, the plane stress can be evaluated by measuring the speed shift of one kind of ultrasonic wave. We examined that the distribution of the material density or the elastic constants can be obtained from that of the wave speed for sintered materials.3. Extension of magnetoacoutoelasticityWe generalized magnetoacoutoelasticity to noumagnetic materials by using the piezoelectric or electrostrictive effects. Verification of the theoretical study by experiments has not been done and left for the future subject.