This paper is a description of the experiments and discussions on the lower yield point of mild steel under biaxial state of uniform stress. The specimens used in the experiments are thin-walled tubes machined from a mild steel bar, which is considered practically to be isotropic in the virgin state. In the experiments the stresses at the yield point and the strain figures due to yielding are observed respectively. We obtained from the experiments various information on the yield point of mild steel. The conclusions are as follows: -The shearing stresses at the lower yield point under uniform stress are constant for a given material. Therefore, hydrostatic pressure does not affect the yield point, and intermediate principal stress does neither.

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A new mechanical random fatigue testing machine was devised and manufactures which could give the random load to the specimen by using various sizes of steel balls mixed at an arbitrary ratio. The testing machine proved to be practical from a statistical point of view. Some kinds of random fatigue tests were carried out with this testing machine, and each random load-time history was analyzed by three different load count methods, namely the peak count method, the range count method and the full wave count method. Fatigue lives were estimated from these analytical results by applying Miner's law, and they were compared with the actual lives obtained empirically in order to discuss the propriety of the load count method for service loads. The evaluated lives by the full wave count method coincided to a considerable extent with the actual fatigue lives irrespective of the extent of the irregularity of the random load, which means that the full wave count method is most desirable for the random load counting.

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To reduce the weight of crane structures, service loads (impact factors, frequency distributions of stresses etc.) of seven cranes (ladle cranes, ordinary overhead traveling cranes and an unloader) were measured. Meanwhile, program fatigue tests were conducted in accordance with the frequency distributions of stresses in the crane structures. A new standard for designing crane structures has been proposed, using the results obtained. Its main features are as follows: (1) separate examinations of fatigue strength and static strength, (2) expression of the allowable stresses for fatigue using the stress amplitude instead of the maximum stress, (3) use of factors which have clear physical meanings.

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This report is related to the self-exciting whirling of a rotor that is suspended in the space without any mechanical contact by a servo-controlled magnetic force in the axial direction. How to fix a magnetic core to the apparatus greatly affects the character of whirling and whirling threshold speed, and there exists the optimum condition in order to obtain a stable high-speed rotation. Here a mathematical model is built considering the internal damping which is due to magnetic properties or control circuits, and it is solved by a perturbation method. Then the same model is simulated on an analog computer and its solutions obtained. Those results are compared with experiments. The experimental whirl behaviors are in good agreement with two solutions if a damping ratio(h) is limited. The analyses give good criteria in the design of the bearing.

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In the axial type fans and compressors, the velocity distribution relative to the blades is generally not uniform. Therefore, in the practical applications, it is important to find the characteristics of the wing in non-uniform flow. In this investigation, the characteristics of a finite large aspect ratio wing in uniform shear flow with the velocity varying in the spanwise direction are analyzed by the singularity method which is different from the method adopted by von Karman and Tsien. As the result, the characteristics of arbitrary wings are obtained concretely, and, at the same time, the physical difference between the characteristics of wings in uniform shear flow and those in uniform potential flow is clarified. Furthermore, the wing planform and its aerodynamic forces satisfying the condition of the minimum induced drag are given analytically.

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In this paper the frictional pressure drop, void fraction and flow pattern of an air-water two-phase flow in helically coiled tubes are presented. The coils are constructed of 9.92 mm I.D. copper tube and the ratios of inside diameter to coil diameter are 1/11 and 1/22.7, and the lengths are 4 m and 4.5 m respectively. The experiments were conducted in the range of superficial water velocity w_lo: 0.35∼1.16 m/sec and superficial air velocity w_go: 0∼5 m/sec. The frictional pressure drop of the two-phase flow in these coils is 1.1 to 1.5 times as much as that in a straight tube in the range of the experiment. Three types of empirical equations for the frictional pressure drop are proposed, and also the experimental data are correlated by a modified Lockhart-Martinelli method. The values of void fraction in the coils are approximately equal to those in a straight tube for the same water and air flow rates.

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Consideration is given to heat transfer for the problem of simultaneous development of velocity and temperature profiles in the case of a laminar flow in the entrance region between two flat plates. The duct consists of two diffuse, black, isothermal parallel surfaces separated by a finite distance. A medium filling the space between plates emits and absorbs thermal radiation. Numerical solutions are obtained for a slug flow (P_r=0), a flow of the inlet region (P_r=1) and a fully developed flow that was shown in the 2nd report, and show the influence of parameters such as the optical thickness, the ratio of conductive energy to radiative energy and Graetz number on the temperature variation across the duct and the heat transfer rates. The radiative heat transfer rate is scarcely affected but the convective one is much affected by flow patterns. An approximate method for the prediction of heat transfer rates in any flow patterns is shown and the results are in good agreement with the exact ones in the region of large optical thickness.

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Pressure distributions on the disk surface and along the axis through the stagnation point have been measured. The settling place of rotating disk, the measuring point of velocity, and the dimensions of the disk model have been decided to refer well to the condition assumed in theoretical analysis. The results are summarized as follows. (1) The generalized experimental formulas which contained the effect of natural convection were established for the heat transfer from a rotating disk in the quiescent fluid and a stationary disk in the axial flow. (2) Experimental results in the presence of both rotating and axial stream velocities revealed good agreement with theory (2nd Report). (3) For the rotation alone, our results agreed with Cobb-Saunders and for the axial flow alone due to separation at the edge of the disk, Sogin's experimental data are about 17% larger than our results and theory.

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A leadscrew which is used in an up-to-date machine tool, measuring machine and so on requires very high accuracy. In practical use, a leadscrew may thermally expand due to heat sources such as an oil tank or undoubtedly to frictional heat between the leadscrew and the mating nut. Thermal expansion of a leadscrew lowers the working accuracy of the machine, as if the latter has a pitch error. This paper treats experimental and theoretical analysis on the thermal expansion of leadscrews which are used in a thread grinder and a thread cutting lathe. As the result, the following are clarified. (1) Theoretical analysis of temperature-rise and thermal expansion due to frictional heat shows good agreement with the experimental results. (2) Thermal expansion of a leadscrew mounted on a thread grinding machine is much influenced by the heat sources such as an oil tank as well as the frictional heat. (3) Thermal expansion of a leadscrew mounted on a screw cutting lathe is exclusively influenced by the frictional heat.

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