Fatigue tests have been carried out on carbon steel specimens in air, in dry air and in argon as an inert atmosphere to observe the effects of atmospheres on the rate of crack propagation. Eddy current method was applied to measure the propagation of fatigue cracks continuously, and the followings have been made clear. (1) Moisture and oxygen in air appear to have small deleterious effects on the crack initiation. In the crack propagation period the effect of adsorption of oxygen is the most significant and the rate of crack growth remarkably decreases in an inert atmosphere. This may be due to the smaller reduction of surface energy in argon than in air because no chemisorption occurs on the freshly created surfaces at the crack tip in an inert atmosphere. (2) Under the high-low two step stresses fatigue tests, the crack remains dormant after the transition to the lower stress level owing to the residual stresses at the crack tip produced by the previous higher stresses. Under the two step atmosphere tests of argon and air, similar phenomena are observed to those under the two step tests, and the effects of atmospheres on crack rate are made clear.

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The Sachs boring-out method is used for determining the axially symmetrical residual stresses in circular cylinders. However, when a specimen cut off from a long cylinder (solid or hollow) is too short, the above method will not be satisfactory, owing to the end effect of the specimen, to estimate the residual stresses in the original cylinder. Since it is usually accepted that dimensional changes caused by any relaxation of stresses are purely elastic, the present author analyzes the whole process of measurements on purely elastic theory and gives a method determining residual stresses in the original cylinder from the experimental data for a specimen with any arbitrary length.

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On the basis of the analysis of his previous report, the author evaluates deformations in various specimens cut off from a long cylinder in which a given longitudinal residual stress exists. According to the present results, it appears that if ξ>2∼2.25 (ξ is the ratio of length to diameter of a specimen), we can use the equations introduced by Sachs with safety for determining the residual stresses, and if ξ<2, the distributions of the residual stresses computed from the Sachs equations are somewhat different from those in the original cylinder except for its outer half portion. Furthermore, the author shows that the agreement between the calculated result and the experimental is good, and proposes a method for determining approximately the distributions of residual stresses in the original long cylinder from the data with a short specimen (ξ>1.25).

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Repeating plastic strain is an essential factor of fatigue phenomena. M. Kawamoto and K. Koibuchi have already reported "Hereditary method" concerning the estimation of fatigue lives under service load on the basis of plastic strain. Here, experiments of stress-strain curves under several variable stress sequences have been done and analysed by Hereditary method. And also, it has been tried to express these curves qualitatively, using a mechanical model consisting of springs and sliders.

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In this paper the fatigue strength of U-shaped bellows under axial loading is studied. Fatigue tests of bellows in the elastic and plastic ranges are carried out by using the fatigue testing machine designed for this research, and the results are compared with the fatigue strength of test pieces made of the same material as bellows. From experimental data a formula for estimation of the life of U-shaped bellows made of stainless steel is proposed, i.e. [numerical formula] where N is cycles to failure and σ is the maximum stress value calculated from the design formula or charts in the 1st or 2nd report. This formula is compared with M.W.Kellogg's formula which is nowadays usually employed.

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To the problem of deformation and stresses of flat-oval Bourdon tubes, a numerical difference method is applied, which was proposed by W.K. Sepetoski and others, and useful design charts and formulas for evaluating their sensitivity and stresses are obtained.

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The author has studied the vibration of a circular plate built-in around the inner boundary and having weights or a bar on the outer one. He obtains the Lagrangian in the vibration of a circular plate represented by the deflection and the slope around the inner and the outer boundaries. Minimizing the Lagrangian, he obtains the frequency and the mode. The theoretical and the experimental results are shown in graphs.

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It is difficult to observe the detail of motion of the Shore hammer, dropping and rebounding in the closed measuring tube of the Shore hardness tester in very short time, and the detail of motion of the hammer has not yet been observed. In this report, the behaviour of motion of the hammer, especially the distribution of frictional energy loss in the rebounding process, has been made clear by electronic measurement, using an experimental device similar to the present D-type Shore hardness tester. As the result, it has been found that the dropping motion is steady, accompanied with no energy loss, while the rebounding motion is unsteady accompanied with a considerably large energy loss, especially in a short range after impact. And also, difference in characteristics of the hardness scale between high hardness and low hardness has been pointed out and discussed here.

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As a first step to the elucidation of the unsteady boundary layer on the shock tube wall, the incompressible boundary layer on a semi-infinite flat plate which starts to move impulsively has been solved by adopting Meksyn's method for the steady boundary layer with pressure gradient. The approximate solution which varies smoothly from Rayleigh's unsteady solution to Blasius's steady solution has been obtained and also ascertained to agree considerably well with the reasonable numerical solution by Lam and Crocco.

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Theoretical and experimental investigation of"the flexure-torsion flutter of aerofoils in cascade"are presented. In this first report are shown a computational method and computed results of unsteady lift, drag and moment acting on the vibrating aerofoils in cascade, and some experimental results of these unsteady aerodynamic forces and moment. In computation are included the effects of stagger angle, solidity, attack angle (or steady circulation), inter-blade phase angle of vibration and camber of blade (or distribution of steady circulation). Each aerofoil constituting the cascade is considered to have two degrees of freedom of translational vibration (not necessarily normal to blade chord) and torsional vibration about elastic axis. Agreements between computational and experimental results are satisfactory. The effects of cascade parameters on critical flutter speed of binary flutter analyzed using the aerodynamic derivatives developed in this 1st report are shown in the 2nd report.

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The experiments are carried out using a flat plate which is partly heated under constant heat flux conditions. The plate is submerged in air and water flows. With the measured wall temperature distributions known, heat flux is calculated by employing the Rubesin's or the Seban's heat transfer cofficient and by the method of superimpositions of temperatures. As the result, it is known that the Prandtl number effect on the coefficient is close to P_r^1/3. However, sufficient accuracies of the calculation are still not obtained even by employing the Rubesin's formula which includes P_r^1/3 in it. The author proposes and develops a method in this report to utilize the Spalding function for the calculation of the superimposition. The experimental results prove that the proposed method is more accurate than the former.

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This paper describes an analytical procedure for getting the band emissivities of carbon dioxide and water vapour and also shows the results of calculations. The wavelength range is divided into four regions, where a strong band is included in one region respectively. The spectral absorption (or emission) coefficients of the bands are determined on the basis of total emissivities data of Hottel et al. coupled with the spectroscopic discussions about the location, width and contour of each band and the band emissivities are evaluated for both CO₂ and H₂O gases. The summations of the individual band emissivity correspond with the total emissivities of Hottel et al. throughout the parameters (temperature and optical length) of interest. Consequently these results are applicable to the problems of radiative heat transfer, taking into account the monochromatic distribution of energy, the evaluations of the emissivities of mixture gases, etc.

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This paper reports on experiments of slag-tap operations by a vertical-type test furnace using a bank of water-tubes with refractory-coating. A circular burner of pulverized-fuel-firing is placed on the center of the roof of the furnace and makes a down-ward flame. Mixtures of pulverized fuel and air from the burner are led across the tube bank, the surfaces of which are covered with slag film. The viscous slag film entraps incoming particles of fuel and holds them against the velocity of the air stream and thus high burning rates under high temperature are obtained. In the test furnace, rates of heat release of 3.90×10⁶∼9.18×10⁶ kcal/m³hr were realized and approximately 95% of fuel ash was recovered in the form of pebbles. A consideration about the critical value of heat release and the thickness of slag film is made.

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To ensure durability of an injector on a diesel engine, the lift of a needle itself and oil pressure around the needle, etc. are measured. As the result, it is found that the change in injection characteristics is not substantial in the range of the maximum needle height (h=0.25∼0.85 mm) ; the collision velocity of a needle with its seat increases, as the pressure-drop time rate on the pump side, the cam shaft speed, the height of needle stopper increase and the spring constant and the weight of movable parts decrease ; this collision velocity is almost independent of the fore-opening pressure ; and the oil pressure change rate dp/dt on the nozzle side may be proportional only to the cam shaft speed squared. Assuming the rate of pressure change dp/dt, a theoretical equation of collision velocity of a needle with its seat is introduced. The theoretical velocity generally agrees with the experimental one.

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