Hiroshi Hatafuku

Estimation of residual stresses in magnetic metals by using ultrasonic method

The residual stresses in deformed magnetic metal rods are estimated by measuring the electromotive force induced from a propagation of ultrasonic waves. When a longitudinal ultrasonic wave is transmitted to magnetic metals, a magnetic field with an ultrasonic wave frequency is generated in specimens by the inverse effect of magnetostriction. The magnetic field is detected as an electromotive force induced in a sensing coil. In this paper, it is shown that the amplitude of electromotive force due to ultrasonic waves depends on both the effective magnetic field and the residual stress in magnetic materials deformed. As a result, the residual strain of as-received specimens estimated is the same as a 10% deformed rod.

Magnetic domain structures of plastically deformed Ni/sub 3/Fe alloys

The magnetic domain structure of plastically deformed Ni/sub 3/Fe alloys has been observed in the ordered and disordered state. The magnetic properties of the plastically deformed Ni/sub 3/Fe alloys are influenced by two effects: the directional order in the antiphase boundary, and the strain field around dislocations. Domain patterns due to the directional order are observed in the fully ordered state, and those due to strain field in the disordered state.

Magnetocrystalline anisotropy in Ni3Fe alloys

Abstract The first magnetocrystalline anisotropy constant, K1, was measured in Ni-Fe alloys containing 67 to 80 wt% Ni. In the disordered state, the present study is in good agreement with Bozorths result. A remarkable difference between the two was found in the ordered state. This is attributed to the state of order due to annealing conditions.

The Effect of Ultrasonic Resonance on Impedance in Magnetic Rods

When an ultrasonic wave is applied to the end of a magnetic rod and a standing wave is generated, high frequency stress will be generated at the standing wave nodes according to the frequency of the ultrasonic wave. The change in magnetic moment generated by this high frequency stress can be easily observed with a detector coil. On the other hand, since stress is not generated at the positions of the antinodes, an induced electromotive force is not produced in the detector coil. Therefore, observation of the stress distribution in the sample rod with the detector coil is possible. Since this phenomenon is reversible, a standing wave may also be generated by applying high frequency voltage, using a detector coil as an excitation coil. In that case, the impedance of the excitation coil changes from the node to the antinode positions. Therefore, it is possible to measure the stress distribution in a sample using only an excitation coil. This paper is a report of research into the effect that the standing wave in a magnetic rod exerts on the impedance of an excitation coil.

Estimation of effective magnetic field in a nickel rod by the magnetoacoustic effect

The effective magnetic field in a nickel rod with an applied uniform external field is studied by transmitting ultrasonic waves. When the ultrasonic stationary wave is formed in a nickel rod, a high-frequency magnetic field is generated in the nodes by the reciprocal effect of magnetostriction. The strength of the effective magnetic field in the nickel rod is estimated by measuring the electromotive force induced by the high-frequency magnetic field.

Effect of annealing on magnetization process of Ni/sub 3/Fe alloy

The magnetocrystalline anisotropy, the magnetostriction, and the structure-sensitive properties in the magnetization process were studied in the ordered-disordered states of Ni/sub 3/Fe alloy. The single crystals were cooled very slowly at the rate of 1 degrees C/day to obtain the fully ordered state. Magnetization curves and hysteresis loops were measured using picture frame specimens. The magnetocrystalline anisotropy and the magnetostriction were also measured in disk specimens. The magnetic domain was also observed. The experimental results obtained in the ordered state are considerably different from those obtained by previous investigators. The difference is attributed to the degree of order-the magnetic properties obtained by previous investigators are those of a partially ordered state. >

Measurement of residual stress of magnetic substance by surface acoustic waves

In magnetic substances under oscillating stress due to the application of acoustic waves (such as ultrasonic waves), an oscillating anisotropic field may be generated by the inverse effect of magnetostriction. If this magnetic field oscillation can be detected, the stress state inside the magnetic substance can be determined. Based upon this principle, we have set up an apparatus for stress measurements, applied it to Ni plates with different residual stresses, and have obtained output signals corresponding to different stresses. This measuring technique makes it possible to know the stress state in structures before the formation of cracks, and hence offers a very promising nondestructive testing device.

Effect of annealing on magnetization process of Ni/sub 3-x/Fe/sub 1+x/ (-0.2<x<0.2) alloys

The magnetocrystalline anisotropy, the magnetostriction and the structure-sensitive properties in the magnetization process were studied in the ordered and disordered states of specimens between 70.1 wt% Ni and 79.7 wt% Ni. The single crystals were cooled at the rate of 1 K/day to obtain the fully ordered state. Magnetization curves and hysteresis loops were measured using picture frame specimens. The magnetocrystalline anisotropy and the magnetostriction were also measured in disc specimens. New experimental results obtained in the order state are considerably different from those obtained by previous investigators. The difference is attributed to the degree of order and the magnetic properties of the previous investigators are those of a partially ordered state. >

The influence of plastic deformation on magnetization processes in Ni 3 Fe

The measurement of hysteresis loops was made in the long range ordered Ni-24.7 at% Fe single crystal which had plastically deformed, in order to study the role of dislocations in the Bloch wall movement. By tensile deformation a remarkable change was observed in coercive force H c and maximum permeability μ m ; H c increases in proportion to the square root of plastic strain e and becomes five times as much as before plastic deformation by 1% strain and μ m decreases to be about one fifth by the same strain, respectively. The change of H c and μ m recovered by annealing near the transition temperature of order-disorder. It was concluded from these experimental results that the atomic disordering introduced by plastic deformation acts as an obstacle in the Bloch wall movement rather than the internal stresses around dislocations. The relationship of H c and e is explained quantitatively according to the modified slip induced directional order model.

Estimation of effective magnetic field in an iron bar by the ultrasonic resonance method

In this paper the strength of the effective field, H/sub eff/, is estimated along a rod specimen by transmitting ultrasonic waves to the specimen. The iron bar used in the study has a size 5/spl times/5 mm/sup 2/ in cross section and 100 mm in length. The effective field, H/sub eff/, is calculated from the magnetization curve and demagnetization factor of the specimen. The dependence of the electromotive force (emf) due to ultrasonic waves on H/sub eff/ at the center node of bar in the stationary state is presented. The magnetostriction measured at the center of the iron bar is also presented.