Nondestructive Estimation of Residual Stresses by Magnetoacoustoelasticity

点击翻译按钮获取中文摘要

The summary of the research in the term is the followings.1. We analyzed the magnetic anisotropy, induced by working such as rolling, of ferromagnetic materials like steel which are widely used as structural materials. It is shown that there is a possibility that higher order anisotropy is generated due to the nonlinearity in the magnetization curve, even in the case of rolling plates with orthotropic magnetic symmetry. The prediction is verified by the plane magnetization experiment of a carbon steel plate.2. For acoustoelastic stress estimation on ferromagnetic materials under the strong magnetic field, we considered the influences of the magnetic field on the propagation of ultrasonic waves. For soft ferromagnetic materials without magnetic hysteresis, we showed that a complicated relation between the magnetic field and the speed of the ultrasonic wave is well explained by a generalized theory of the conventional continuum model of magnetoelastic materials.3. For the purpose of more practical nondestructive measurements under the strong magnetic field, we studied the influences of the magnetic hysteresis on the propagation of ultrasonic waves. In a result, it is shown that from the magnetic hysteresis and the magnetoelastic effect, there occurs a hysteresis in the speed and the acoustoelastic constants with respect to the change of the magnetic field. The theoretical result is verified by the acoustoelastic experiment on low-carbon steel under a magnetic field.4. It is found that the distortion of the wave form and the attenuation of the wave are induced by the magnetic hysteresis and the magnetoelastic couplings. The development of a new technique utilizing the effect by wave form analysis for stress estimation is left as a future subject.