アモルファス構造の金属ガラスナノワイヤを作成するために分子動力学法を用いて、B2構造のCu-Zr、Ni-Alナノワイヤを対象に溶融シミュレーションを行った。そしてこれらのナノワイヤに様々な温度で引張変形シミュレーションを行った。比較のためにB2構造のCu-Zr、Ni-Alナノワイヤ、もまた引張変形シミュレーションを行った。結果として、金属ガラスナノワイヤの引張強さがナノワイヤの引張強さの1/3～1/4倍になったことが明らかになった。 引張ひずみが増加するにつれ、B2構造のCu-Zrナノワイヤは2回構造変化を生じた。一方それに対して金属ガラスナノワイヤのみ局所的にナノワイヤの断面が減少し、くびれを生じた。

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In order to investigate the notch effect on the fatigue strength of 18-8 stainless steel at an elevated temperature, rotary bending fatigue tests were carried out at 450°C and room temperature, using specimens 12mm in diameter with V-type grooves of 60°, whose stress concentration factors α_k were between 2.5 and 4.0. A Wöhler type fatigue testing machine was operated at 1900rpm. The notch effect on coaxing was also investigated at 450°C.
After the tests, the microstructures and Vickers hardness of specimens not fractured after 10⁷ cycles of stresses at the respective endurance limit in each α_k were examined.
The test results were qualitatively discussed in connection with several phenomena, such as (a) the decrease of actual stresses due to yielding at the notch bottom region, (b) work hardening and (c) shortening of the distances between the slip lines accelerated by their developments and the preferential precipitations along these lines.
The main results obtained are as follows:
(1) At room temperature, the fatigue notch factor β increases as α_k increases, though β has comparatively low value close to 1. This tendency seems to be due to the decrease of actual stresses and work hardening.
(2) At 450°C, β decreases as α_k increases. This phenomenon seems to be due to the differences of the distances between the slip lines, besides the effects of actual stress decrement and work hardening.
(3) At 450°C, the pronounced increment of fatigue strength is brought about by coaxing. The upper limit seems to exist, however, concerning this increment of the endurance limit. These phenomena will be explained in the same way as in (2).

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We measured the micro-Vickers hardness of 0.26 %-carbon steel, which had been subjected to rotatory bending stress at a high temperature. The fatigue test was conducted at the room temperature, 300°C and 550°C mainly, and hardness testing was held under 1000 gram load. Summary of the results is as follows : (l) At 300°C, the increase of the hardness number is greater and the hardening layer is deeper than that at the room temperature. But at 550°C, the hardness change is little or nothing. (2) Moreover, this hardening layer is caused by the repeated stress above about 0.8 σ_ω at the room temperature, but about 0.65 σ_ω at 300°C, where σ_ω is the endurance limit at each temperature.

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In this report, the changes of structure in α+β brass by hot-working temperature and working reduction were investigated using plate specimens of 58.5%Cu, 59.0%Cu, 60.0%Cu, 60.5%Cu, 61.0%Cu, 61.5%Cu and 61.9%Cu brass, of the size of 30 mm×90 mm×180 mm, and the structure after forging for various holding times using specimens of the same contents 1 cm³ in size. The results obtained were as follows: (1) There was a suitable temperature zone for producing homogenous structure in α+β brass. (2) There was a suitable holding time correlated with the hot-working temperature and the size of the specimen. (3) Within temperature zone of adapted for producing homogenous structure, it grew finer in the case of larger working reduction at the beginning.

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Some of the important mechanical properties of a steel sheet or plate, such as the Lankford value, r, and the separation index, SI, show texture dependency. In this study, these two properties, r and SI, were related to the propagation-velocity of elastic waves in steel, which varies with its texture. SI is defined as the total separation length devided by the fractured surface area at the time when fracture occurs on a specimen in the impact test. Elastic waves were propagated in two modes: perpendicular or parallel to its surface.
The main results obtained are as follows:
(1) For elastic waves propagating perpendicularly to its surface, it was found that the square of the propagation-velocity of longitudinal waves, v_L², was proportional to the averaged Lankford value, r, but decreased linearly with increasing SI. The theoretical considerations made in this study revealed that v_L decreased monotonously with an increase in <100> axis-density parallel to the normal direction of the specimen, but increased monotonously with an increase in <111> axis-density parallel to the normal direction. The experimental results reported so far show that the <100> axis-density parallel to the normal direction is proportional to SI, and the <111> axis-density parallel to the normal direction is proportional to r. Thus, the combination of these theoretical and experimental results yield the behaviour obtained in the present experiments.
(2) For elastic waves propagating in parallel with its surface, it was found that the square of the propagation-velocity of surface waves, v_S², was proportional to the Lankford value in the direction parallel to the wave-propagation. Lamb waves may also be used for this kind of measurement because of its similarity to surface waves.
Since the propagation-velocity of elastic waves can be measured continuously while steel is being produced, the on-line evaluation of some mechanical properties such as the Lankford value or the separation index of steel seems possible.

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In order to study the possibility of calculating the Young's modulus, E, for a cold rolled mild steel sheet on the basis of its texture represented by the three-dimensional orientation distribution function, w(ψ, θ, φ), the E value calculated was compared with the experimental value. ψ, θ, and φ denote a set of Eulerian angles between the coordinate system of crystallite and the reference system of specimen. From the E value calculated, E(ψ, θ, φ), which was specified by means of Eulerian angles in the same definition as used in describing the orientation of a crystallite in a polycrystalline sheet, the E value for a polycrystalline sheet, E_cal, was computed by
E_cal=4/π²∫^π/2₀∫^π/2₀∫^π/2₀E(ψ, θ, φ)w(ψ', θ, φ) sin θdθdψ'dφ
where ψ'=ψ+ω and ω is an angle between the folling direction and stretching direction.
Experiments were made on rimmed steel, aluminium killed steel and decarburized rimmed steel, and their Young's modulus were measured by using the resonant vibration method.
The results obtained are summarized as follows:
(1) As for planar anisotropy of the calculated Young's modulus, E_cal at the transverse direction, E_T, was smaller than that making an angle of 45° with the rolling direction, E_D, and larger than that along the rolling direction, E_L. The planar anisotropy of the observed one, E_obs, showed the same tendency as that of E_cal for all samples.
(2) The observed Young's modulus E_obs, coincided with E_cal within the relative error of 1% for the sample having a strong preferred orientation. For the rimmed steel sample, which has the weakest preferred orientation, the ratio of E_obs and E_cal was 1.07. (where E=(E_L+E_T+2E_D)/4)
It was concluded from these results that the Young's modulus of a polycrystalline material can be, quantitatively, estimated from its texture analysed three-dimensionally.

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Tool steel (SK5) was ground with WA or CBN abrasive grains to determine the effect of grinding on the initiation of fatigue cracks. The grinding direction was parallel or perpendicular to the loading axis. The main results are as follows. (1) About 66% of fatigue cracks originated at grinding streaks or inclusions. In all cases, fatigue cracks originating at inclusions were observed. The major origin, however, of the specimens ground perpendicular to the loading axis, with WA abrasive grains was grinding streaks. (2) In every case, a large percent of fatigue life was spent to form fatigue cracks. (3) When ground with WA abrasive grains, spark-out does not raise the fatigue limit of the specimens ground parallel to the loading axis but raises that of specimens ground perpendicular to it. When ground with CBN abrasive grains, the fatigue limit does not depend upon the grinding direction. Spark-out raises the fatigue limit to a higher value than in the case of WA abrasive grains. Although there were some exceptions, the minimum hardness of the ground surfaces was proportional to the fatigue limit.

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It has been reported by the authors that the estimation of fatigue life of the materials under constant stress amplitude can be made using the liner relation of b/B-log n/N (where B and b are the initial and the current half-value breadth of diffraction line in fatigue and n/N is the cycle ratio). In the present paper, the following experiments were performed; the first, the experiments were made on the case of varying stress amplitude of two stress levels above fatigue limit and investigated the change of half-value breadth due to varying stress amplitude. The second, the half-value breadth was measured by using satisfactory method in physical meaning and compared with the conventional method which has been adopted in these series of investigations. Finally, discussed on a change of half-value breadth under varying stress amplitude and postulated a certain method for nondestructive estimation of fatigue life.

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