Torsion fatigue tests at -60°C are made to examine the understressing effect of the eutectoid steel, based on the assumption that the strain ageing occurring in the specimens during the fatigue tests is restrained at -60°C. The specimens tested are cooled by gasifying liquid nitorogen, in order to hold the designated temperature. It is found that the main cause of the understressing effect of the eutectoid steel is work hardening at -60°C against both work hardening and strain ageing at room temperature, and the fatigue life of eutectoid steel is mainly controlled by the hardness of the material before fatigue test at -60°C.

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Using plain specimens of annealed S50C carbon steel, fatigue tests were conducted under fully reversed sinusoidal axial stress and under repeated impact stress. Inelastic behavior of specimens was observed using strain gauges mounted on the specimens. Under the impact fatigue stress, fractures occurred at the stress levels lower than the ordinary fatigue limit and in the region of a larger number of stress cycles than 10⁷. The inelastic strains accompanied with a fracture were unexpectedly small comparing with those under sinusoidal stress. And the amount of hysteresis energy accumulated : in the specimen during the impact fatigue test was also less than the corresponding value under sinusoidal stress.

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Noncontact measurement was made of the surface temperatures of steel specimens subjected to rotating bending. The temperature variation was expressed as the sum of two exponential functions with due consideration for heat transmission. The thermal energy produced during one stress cycle could be regarded to be almost constant throughout the main fatigue process and its stress dependence was found to be expressible in an exponential function of the reciprocals of the stress amplitudes. A fatigue criterion has been obtained, which agrees with the results presented by others from the standpoint of hysteresis energy dissipation, and, being applied to the notched specimens, gives a means to determine the fatigue notch factors. The calculated values have been shown to agree satisfactorily with the data in the literature.

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This paper is concerned with a numerical analysis of visco-elastic shells of revolution under unsymmetrical loads. The numerical method of elastic analysis of shells of revolution developed by Budiansky is extended to deal with a wide range of visco-elastic problems of the quasistatic type. The visco-elastic behaviour of a material is represented by a 4-parameter model. As a numerical examples two problems of a cylindrical shell and a conical drum composed of multishells subjected to stepwise displacements with respect to time are analyzed.

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The stress strain relation and the subsequent yield surface in loading along the strain path with a corner are experimentally investigated in the deviatoric stress and strain space by subjecting thin-walled brass specimens to combined axial load, internal pressure and torsion. The change in direction of the stress vector can be uniquely associated with the length of strain path irrespective of the amount of prestrain and the corner angle of strain path, if the change in direction of the stress vector is represented by a nondimensional value divided by the corner angle. The minimum value of the magnitude of stress vector after turning the corner is independent of the amount of prestrain, if it is reduced to a nondimensional value divided by the magnitude of stress vector at the corner. The subsequent yield surface after preloading along the strain pat with a corner is not symmetric with respect to the direction of coresponding prestress. But, with an increase of prestrain, the symmetry of the yield surface is found and the shape is congruent with the subsequent yield surface after radial preloading to the same amount of prestrain.

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In this paper, a new analytical method in a stress space is suggested to solve the elasto-plastic plane problem that has not been treated analytically even with the total strain theory of plasticity. At first, a general formulation for the elasto-plastic plane theory is established for a compressible isotropic work-hardening material obeying a nonlinear stress-strain law. Then, the basic nonlinear differential equation in ordinary Cartesian coordinate system can be linearized in the system of the stress space, and a complex displacement function, which gives us the solution, can be written in the closed form. Provided that Ramberg-Osgood's law holds as the nonlinear stress-strain relation, the strain component and the corresponding coordinate can be obtained easily and the stress component can be evaluated by the numerical calculation.

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In this paper, the response of a hollow infinite circular cylinder (as a plane strain field) of a circular disk (as a plane stress field) is studied, which is subjected to a pair of impulsive line loads along its outer generators facing each other. First, the line loads are expanded in a Fourier series and represented as a sum of a uniformly distributed pressure and pressures in the form of trigonometric functions. By the use of this method of superposition, the dynamic stresses in the cylinder or the disk are analized based on the two dimensional dynamic theory of elasticity by using the stress functions and the Laplace transformation. As the result, it is shown that the maximum tensile stress is produced along the inner generators corresponding to the loaded ones and the value is about twice as large as the corresponding static result.

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It has been shown that, in a nonlinear vibratory system subjected to several harmonic excitations of frequencies Ω₁, Ω₂, …, Ω_M, so-called combination tone can be induced with frequency Ω=|m₁Ω₁+m₂Ω₂+…+m_MΩ_M| (m₁, m₂, …=±1, ±2, …), When Ω is close to the natural frequency of the system. Also in this system a more general type of oscillation can be expected to occur with frequency Ω=(1/N)|m₁Ω₁Ω₂+…+m_MΩ_M| (N=2, 3, 4, …; m₁, m₂, …=±1, ±2, …) When Ω is close to the natural frequency. Such oscillations, if they occur, may be termed "sub-combination tone." The present paper concerns the occurrence of such oscillations in a typical case in which a system with nonlinear spring characteristics of a cubic function of the displacement is subjected to two periodic forces of frequencies Ω₁ and Ω₂. The theoretical analysis shows that the sub-combination tones of frequencies Ω=(1/2) |Ω₁±Ω₂| can occur in the system. The theoretical analysis is checked by an analog-computer.

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The frequency response of cushion pressure to a small sinusoidal oscillation of hover-height is investigated for an air cushion system composed of a fan, a duct and a peripheral-jet-type cushion head both theoretically and experimentally. From comparison of the theory with the experimental results, it is concluded that the dynamic characteristics of the air cushion are well described within the limits of this experiment using the characteristic constants calculated with a quasisteady flow model for an unbalanced jet. Furthermore it is shown that the propagation of a low-frequency pressure pulsation in such a large-scale pipe line as an air cushion system is described in the same manner as in pneumatic transmission lines.

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In order to measure the local wall friction force exerted by a skewed turbulent boundary layer on a smooth surface, an improved Preston tube has been developed. A semi-circular shroud is applied to a conventional Preston tube to make it insensitive to direction of flow, just like a Kiel total-pressure probe. The improved Preston tube is used to measure the wall friction force on the flat end wall of a curved channel with 180 degree turning angle, and the results are compared with those deduced from the Clauser chart method.

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By using an apparatus in which a water column is accelerated by compressed air in a tube, the column velocities up to about 100m/sec are obtained. The liquid column motion in the tube is approximately analysed in order to determine the driving pressure and the apparatus dimensions such that the desired velocity of liquid flow can be obtained at the end of the tube. Magnitude and duration of impact pressure caused by the water column stopping at the closed end of the tube are calculated, considering the variation of compressibility of water with a change in pressure. Those results coincide with experimental data given by Rice and Walsh, and by Cook et al., and involve Heymann's formula as being the first approximation. Experimental results obtained in the constructed apparatus showed that the actual impact pressure were influenced by vacuum pressure in the tube before the impact.

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Based on an analysis of a free boundary potential jet impinging on a plane, a solution of a viscous free jet falling down on a rotating disk is obtained. In such a flow having a free boundary, two parameters must be adopted, one giving the condition of the free boundary and the other characterizing the rotating disk. For 272 combinations of these two parameters, numerical solutions have been obtained and some examples of their results have been illustrated in diagrams. This solutions of the boundary-layer obtained now is a generalized solution of H. Schlichting and E. Truckenbrodt's report.

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For the purpose of checking the accuracy of the analysis made in the 1 st Report, the theoretical values and the experimental results are compared as to the thickness of liquid film on the rotating disk. A change of the electrical reistance caused by the change of the thickness of liquid film is applied as a measuring principle. The measuring accuracy obtained is about ±0.02mm. In the experiments including a wide range of Reynolds' numbers R_〓0=200∼18000 and the parameters m=0∼0.8, experimental values agree well with the theoretical results at R_〓0≥1000. At R.₀=200∼500 several percent error is recognized soon after the boundary-layer develops up to the free surface.

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The convective heat transfer from a rotating disk with additional flow has recently been proved to give an effective cooling mechanism of rotating devices, such as memory storage disks in computers, or impeller disk for cryogenic fluid pumps. This problem in addition to withdrawal flow was theoretically solved by Sparrow & Gregg, Stuart and Mabuchi et al. The present paper reports the experiments on these themes which were made by using a rotating naphthalene disk with source flow. Authors measured heat and mass transfer characteristics of (I) a disk with source flow in an open environment and (II) a shrouded rotating disk with source flow in semi-closed space. Authors came to the conclusions as follows ; S_h∞=0.955R_〓r⁰.45+2.7×10^-9R_〓i².45R_〓r⁰.45 where Rei denotes the source flow Reynolds number and Rer the rotational Reynolds number S_hc=[1+0.047(vi/wc)⁰.74(1-2.183^-(d₁/d₀))]S_h∞ where Vi : mean velocity of a source flow, ω : angular velocity of a rotating disk, c : spacing between two disks, and d₁ and d₀ : diameters of a stationary and a rotating disk respectively. The above equation correlates about 95% of all measured data.

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The pressure dependences of carbon particle cloud radiation and of nunluminous gas radiation are examined individually in order to predictradiation from luminous flame of liquid fuel at high pressures. For carbon particle cloud radiation, the equation of carbon formation is determined in terms of pressure and excess air factor with reference to the experiments on the soot formation from vaporized fuel at low excess air factor and on the combustion of a single droplet of fuel in a large chamber. For nonluminous gas radiation, the expressions obtained by Edwards are adopted. A method is developed to calculate the luminous flame radiation at high pressures using the above expressions and the experimental results at an atmospheric pressure. The calculated results agree well with the measured values. The maximum, average and endzone absorption coefficients in the luminous flame can be easily calculated.

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In this study we have investigated more detailed behaviours of the horizontal stiffness and the micro-slip on a bolted joint. Horizontal displacements on bolted joints having various contact surface conditions have been measured during repeated tangential loadings and unloadings. From experimental results, it is known that the horizontal displacement is a direct sum of the elastic displacement and the micro-slip, and the tangential load-displacement curve shows a hysteresisloop under the repeated loading cycles. The hysteresisloops mentioned above may be classified as two typical types. First type of the hysteresisloop is an almost constant one having a small width or a large width and this can be found on ground joint surfaces made of mild steel or of brass. Second type is an advanced one having gradually decreasing width and this can be found on ground joint surfaces made of cast iron. The electrical contact resistance has been also measured in order to clarify the more detailed behaviours of the micro-slip on the bolted joint.

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In this report, various kinds of vibrations of a gearing, including those of bearings, are examined closely on their phase-relationship, vibrational mode and frequency spectrum, whose results are compared with the calculated ones based on the theory in the 6th report. Results obtained are as follows : The theory is useful not only for behaviours and the vibrational mode of the circumferential vibration and the radial one in spur gears but also for the vibrational mode of bearings, although the calculated value for the conversion ratio to radial vibration is a little smaller than the experimental one mainly because of the frequency characteristics of bearings being neglected. Regarding the generation mechanism of the axial vibration of spurgears, the vibration of a gear body as an elastic circular disc, which was not considered in the theory, can be predominant by a resonance under some definite condition.

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It is clarified that a neutral point exists on the contact surface between a polyurethane ring and a blank, which plays a similar role to no-slip points in rolling of sheets or upsetting of circular hollow disks. A neutral point moves radially inwards to the die opening as compression ratio of a ring increases. The direction of the frictional force acting on a blank reverses at a neutral point, and only the frictional force on the inner area of a neutral radius contributes to the deformation of a blank. A friction hill appears in the pressure distribution on the contact surface between a ring and a blank. It should be emphasized that the deformation of a blank can be advanced very much either by using powdered rosin only on the inside of a neutral radius or by using a blank with a smaller diameter than one of a polyurethane ring.

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