マルテンサイト組織化した鉄筋を用いて作った鉄筋コンクリート部材は, 鉄筋を焼きもどすことによりマルテンサイト組織が変化して鉄筋に収縮が生じてプレストレスコンクリートに変わる. このことを利用して, 実用性のあるプレストレスコンクリート製品をうる目的で少しばかり実験を行なった.
その結果, 炉中にて鉄筋を焼きもどすと加熱時間が長時間のためコンクリートが劣化してき裂を生じたり, 鉄筋にレラクゼーションが生じるためか充分な結果が得られないことがわかった. また, 高周波誘導加熱により鉄筋を焼きもどす場合, 鉄筋応力が約30kg/mm²でプレストレス応力を加えることができること, 高周波コイルは1重コイルより2重コイルのほうが良いこと, この加熱方法でもコンクリートにき裂が生じることなどが判明した.
また, 鉄筋の材質, 焼き入れ方法の研究により, 一層大きなプレストレスを与える可能性があることなどもわかった.

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The hardness of slow-cooled (at cooling rate 0.57°C/min) and water-quenched Cu-Al-Ni alloys (with 10.0-14.5% Al and 0.0-14.0% Ni) was measured, and the phase in the alloys was observed. And the interrelations of the hardness, the phase, the Aluminium and the Nickel content etc. were studied.
The main results obtained are as follows:
(1) On the slow-cooled specimens the maximum of hardness appears in alloys with 10.0-10.5% Al and about 10% Ni, and in those with above 11.2% Al and 0-2% Ni.
(2) On the water-quenched specimens the hardness of alloys with 10.0-10.5% Al lowers slightly according to the increase of Nickel content, and that of the alloys with above 11.2% Al reaches the maximum at a certain Nickel content. The maximum of alloys with 11.2-13.0% Al migrates to the side with more Nickel content according to the increase of Aluminium content.
(3) The α phase increases and the δ phase decreases according to the increase of Nickel content.
(4) The grain size of the α phase in alloys with below 12.0% Al and rich Nickel content and of the δ phase in those with above 12.0% Al and rich Nickel content become extremely small.

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In the previous papers, some of the present authors reported the test carried out of the repeated tension impact about unnotched specimens of some metals to find the impact fatigue curves for wider ranges of the number of repetitions, and clarified the discontinuity of their curves.
In this paper, we have performed similar tests about the specimens which had various circumferential notches made respectively of 0.17%C steel, 0.82%C steel and copper, covering the number of repetitions N=1∼10⁶ in order to study the effects of notch on impact fatigue curves.
The summary of the experimental results is as follows;
(1) Like the impact fatigue curves of unnotched specimens in the previous paper, the curves of notched specimens consists of two curves, one is plastic fatigue curve, the other is true fatigue curve, which are found to be discontinuous.
(2) The impact value at N=1 decreases when the radius ρ of notch becomes smaller. The plastic fatigue curves start from the impact value at N=1 for each type of the specimen, and at small number of repetitions they cross over each other as shown in Figs. 2, 12 and 16.
(3) The impact fatigue strength at N=10⁵∼10⁶ in the true fatigue region are estimated from the results of the experiments as shown in Tables IV. V and VI.

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The constant stress and the constant deflection test were carried out of the rotating and bending fatigue of Ni-Cr-Mo steel cantilever in the plastic range at the frequency of 62rpm and at different temperatures, respectively at room temperature, at 350°C and at 550°C. In the constant stress test, the change of vertical and horizontal deflection at the loading end of the test specimen was observed. In the constant deflection test, the change of stress was also observed. The test results were discussed and compared with those obtained on the 0.35% carbon steels reported in the previous issue.
The main conclusions of the results are as follows:
1) It has been found in the constant stress test that the fatigue life is longest at room temperature, and falls respectively at 350°C and at 550°C. In the constant deflection test the fatigue life is approximately equal both at room temperature and at 350°C but remarkably falls at 550°C.
2) The changes of deflection in the constant stress test and changes of stress in the constant deflection test have shown difference according to the temperature. On the whole they show opposite tendency.
3) These results in both the tests have been compared based on the static bending test. The constant deflection is found stronger than the constant stress both at room temperature and at 350°C, but reverse at 550°C.

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Considerable cavitation erosion has recently been observed in high-speed boats of a certain class on their propellers after a continuous high speed operation of only several hours.
Such cavitation erosion occurred within a small area of the propeller-blade roots.
The present study has been made with the object of finding effective means for the prevention of the cavitation erosion.
High Mn-Al bronze and high Ni-Al bronze propellers were prepared for this study. The high-speed boat was equipped with two propellers, and was operated for 4 hours at the rate of over 30 knots per hour.
The results obtained are as follows:
(1) It is confirmed that cavitation erosion resistance of high Mn-Al bronze propeller is more efficacious than that of high Ni-Al bronze.
(2) It is supposed that two materials better than Al bronze (AlBC3) about cavitation erosion resistance have been found.
(3) The tendency shown in the present operating test is the same as the result of the magnetostrictive cavitation test.

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Systematic measurements by differential thermal analysis have been made on glasses of the system PbO-B₂O₃, PbO-SiO₂, on commercial glasses, borax glass and B₂O₃ glass. And also the DTA methods have been used for the study of chemical reactions between glass-making materials on the system PbO-SiO₂. For all the commercial glasses DTA curves indicate that the transformation phenomena are characteristic and no crystallization takes place.
The transformation range on any glass estimated from the DTA curves coincides exactly with the range measured by the thermal expansion. For the B₂O₃-PbO and SiO₂-PbO glasses the exothermic peaks suggest the formation of borates or silicates, and the endothermic peaks at 600∼800°C suggest the melting of these compounds, and are followed by glass formation. The DTA curves for the batch materials of the system PbO-SiO₂ show the endothermic peaks at 720∼760°C or around. These endothermic effects are attributable for 30∼50mol parts PbO-70∼50mol parts SiO₂ to the formation of PbO-SiO₂, and for 70mol parts PbO-30mol parts SiO₂ to the formation of 2PbO-SiO₂, 4PbO-SiO₂ and the melting of these compounds.

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In the present study measurements have been made of the stress waves and strains in the cylindrical rock specimen caused by the detonator's attack, and thence some mechanical properties of rocks under such an impulsive loading have been analyzed and discussed.
The results of this investigation have been summarized as follows.
(1) To obtain the stress wave shape, it has been recognized that a method utilizing the displacement of the free end face of the rock specimen is simpler and more convenient than the conventional method developed by Dr. J.S. Rinehart.
(2) The method to obtain the dynamic tensile strength of rock based on the phenomenon known as spalling has been revised more suitably to practical ends.
(3) It has been found from the analysis of the data for the change in the propagation velocity of the stress wave with distance that even in the case of the detonator's attack a plastic wave or a shock wave seems to be generated in the region nearest the shot point.

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This paper summarizes the results of tests on two series of T-shaped structural parts reinforced with right-angled triangular ribs. Studies were made in these cases of the effect of various factors on the stress concentration at the reentrant corner formed by the ribs and their members by using the two-dimensional photoelastic method.
Some of the conclusions resulting from these studies are given below.
1. In the case where the member has a rectangular projection and subjected to pure bending:
(a) Neither the height nor the width of the projection affect the stress concentration factor.
(b) The stress concentration factor increases with the increase in the height of the member in a way of decreasing rate and finally approaches a certain value, but it increases drastically when the thickness of the member becomes larger than that of the rib.
(c) If the side of the rib attached to the projection is shortend, keeping the side attached to the member constant, the stress concentration factor at the reentrant corner in the member decreases, while the stress concentration factor in the projection increases. It is considered therefore that there might exist such geometry of a rib as the stress concentration factors at both reentrant corners become equal.
(d) When a structural part is reinforced with two ribs of similar geometry, the ribs of quite the same dimensions should be used so that the stress concentration factor in each reentrant corner is equal.
2. In the case where two members form the T-shaped structural part:
(a) In the case where the member 1 is supported at both ends and the other member 2 is subjected to tensile force, (see Fig. 5(a)), the stress concentration factor in the member 1 increases with the decreasing fillet radius, but it is neither influenced by the dimention of the rib nor by the magnitude of the shearing force.
(b) When both the members are subjected to bending, the stress concentration factor at the reentrant corner B is smaller than that at C (see Fig. 2 and Fig. 5(b)). The stress concentration factor at B decreases as the dimension of the ribs increases, but the stress concentration factor at C is not influenced by the dimension of the rib.

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