The present paper deals with elastic contact problems of a half-space loaded by a rigid cylindrical punch of elliptical cross-section in the cases of (a ) indentation, (b) bending and (c) torsion. In each case, the contact region of punch is mapped onto the unit circle. In the image plane, it is assumed that the distribution of contact stress on the stamp is of the same form as that for a rigid circular stamp, and the surface displacements of the half-space are obtained. It is shown that the results are the solutions of the elastic contact problems of the half-space loaded by a rigid elliptical punch.

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The present paper deals with mixed boundary value problems for an infinite solid containing a flat elliptical crack under internal pressure and bending. In each case, the author maps conformally the crack region onto the unit circle. In the image plane, he shows that the deformation of the crack surface is of the same form as that for a circular crack in the use of the variables of the plane, and obtains a rigorous solution of the problem in the closed form.

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Methods of photographing orthographic projections of a grating and a contour on a curved surface were proposed. In photographing a contour, a sheet of light is projected on an object intermittently and the object is moved so that its surface may be swept by the sheet, while a camera is focused at the sheet. The contour obtained in this way corresponds to what would be observed from direction of movement of the object. In photographing a grating, a sheet of light is projected continuously. These methods can be applied to any object regardless of its size, whereas in the usual methods using the tele-centric system, spread of region to be photographed is restricted by the aperture of the field lens. Some related methods of measuring shape using Young's interference fringes were modified in similar way. Further, a procedure of measurement of strain in the three dimensional deformation of sheet bulging was shown.

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A formal solution for travelling waves in isotropic linear elastic bars of rectangular cross section which have traction-free lateral surfaces is presented. The solution is obtained by crosswise superposition of two single series, each term of which gives zero shearing stresses on the lateral surfaces. Frequency equations, which define the dispersion relations of elastic waves, are given by infinite determinants. Based on the approximate frequency equations, dispersion relations for a longitudinal mode, a torsional mode, and bending modes were calculated with the aid of a digital computer. Numerical results were compared with those given by other authers.

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A method is presented to calculate the unbalance vibration behaviours using transfer matrix method in which such factors related to the vibration are covered as the interaction characteristics of load displacement between horizontal and vertical directions at oil film bearings, the dynamic stiffness of bearing support structures, etc. In case of the rotor systems with multi-spans, the numerical accuracy is occasionally deteriorated when number of sections, number of bearings and rotating speed exceed a certain boundary as far as the conventional method is applied. The authors developed a method to suppress the propagation of the error by modifying the procedure of matrix operations and solving the simultaneous linear equations at the last step of the computation works.

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This paper concerns theoretically and experimentally self-excited oscillations caused by solid friction in a system with rolling contact. A cylinder rolling without slippage on a curved surface of a rotating disc is connected to a spring and can oscillate around the axis of the disc under the application of spring force and solid friction between rolling contact surfaces. Theoretically it is pointed out that self-excited oscillations can occur in such a system when rolling friction is expressed as a function of relative rolling velocities between two solid bodies. Also in the experiment, rolling friction is observed to vary with the relative rolling velocities and it is ascertained that oscillations obtained in surfaces of the dry friction state are self-excited oscillations caused by rolling friction. Moreover, experimental results on the behavior of the cylinder under the lubricated surfaces are shown in several figures.

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This paper presents some experimental and analytical studies on a new repulsive type dynamic vibration absorber consisting of three permanent magnets of thick disk type^(1)∼(2). These magnets are so arranged in a non-magnetic conductive or non-conductive cylinder that one magnet can move freely between the two fixed ones. The result showed that: (1) Repulsive force⁽³⁾ interacting between the two magnets may be assumed to be inversely proportional to the nth power of the center distance between the magnets. This assumption makes the analysis easier, and the results of the experiment show considerable coincidence with those of the analysis. (2) The new absorber may be able to control the resonant amplitude of the vibrating body which weighs several dozen times the free magnet. Further merits of the absorber are an eddy current damping generated in the conductive cylinder and arbitrary choice of the vibration direction as well as the frequency adjustability.

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A method is proposed to calculate resonant amplitudes of pressure pulsation in the pipelines connected to reciprocating compressor delivery systems, in which nonlinear damping forces proportional to the square of velocity are used and the energy balance between excitation and dissipation are taken into consideration. Calculated values are compared with experimental values. As the result, it is confirmed that by the method proposed here resonant pressure amplitudes are estimated with sufficient accuracy for practice in case of a single sinusoidal flow input.

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Many Tainter-gates are being used with increased frequencies also in Japan, in order to control the water level of reservoirs. In this type of gate system, the effect of mechanical frictions is much less than in the type of vertical-lift gates, therefore providing a small hoisting load and a smooth operation of the gate. Though Tainter-gates have such great advantages, these facilities of the mechanism yield a fear that Tainter-gates may oscillate owing to some fluid-induced structural load, i.e. the operation of Tainter-gates may tend to become unstable. In this study, the stability of an idealized Tainter-gate system without damping effects, which is caused by surface waves on the back water of dam, was theoretically analyzed, but the analysis was restricted to the case that the resultant of the hydraulic pressure exerted on the weir plate passes under the trunnion pin. It was concluded as follows : Tainter-gates fundamentally possess the property of a self-excited oscillation.

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Computational calculations and experiments for laminar coaxial annular jets in a circular tube were carried out. From computational calculations using the method developed by Enzo O. Macagno, two flow patterns were obtained under the same boundary conditions. In one of them, the jet curved and attached to the side wall. In the other, the jet curved to the center line, and did not attach to the side wall. Experiments showed that two flow patterns similar to the results of calculations were obtainable. The results mentioned above are thought to be phenomena analogous to the Coanda effects.

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Digital simulation of a discontinuous diffusing flow with particular reference to the Coanda effects is carried out. We give an initial flow pattern arbitrarily and modify it step by step so that it satisfies the Navier-Stokes equations of motion. Reynolds number is assumed to be low enough to keep the flow within the laminar region. A symmetrical initial pattern results in a symmetrical solution anyway in all cases but it is supposedly an unstable flow pattern for Reynolds numbers higher than a critical value. We suppose so because: (1) an unsymmetrical initial pattern results in an unsymmetrical solution is deformed by a small disturbance imposed and eventually settles in the above mentioned unsymmetrical pattern, only for a Reynolds number higher than the critical value. It may thus be said that the Coanda effects occur also in the laminar region and, when they occur, solution of the Navier-Stokes equations is not unique.

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The purpose of this paper is to consider by the method of small perturbations how an external magnetic field suppresses the onset of a secondary vortex flow in a two-dimensional, incompressible, electrically conducting viscous flow in a curved channel. The magnetic field is applied in the direction perpendicular to the channel walls. The results show: (1) the critical Dean number K_C begins to increase as the Hartmann number H_a becomes larger than about 2, and in the limit H_a → ∞ the Dean number K_C tends to a relation proportinal to H_a^3/2; (2) the associated dimensionless wavenumber σ_C of the vortices also increases with H_a, and the location of the vortex center comes closer to the outer concave wall. In addition the effect of electrical conductivity of the wall material on the present stability problem is discussed.

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The flow characteristics of air-solids mixture in a horizontal pipeline for pneumatic conveyance with a contraction or an enlargement are obtained experimentally. The behavior of particles passing through a varying cross-section is analyzed in consideration of a change in the drag coefficient corresponding to an instantaneous particle velocity. The additional pressure loss of a contraction increases in proportion to a solid loading ratio and the proportional constant is severely affected by the area ratio and the cone angle of the contraction. Except for a few cases of small loading ratios for an enlargement, the agreement of a pressure loss obtained from calculation with an experimental one is quite favorable. It is shown that additional pressure losses of air-solids mixture with varying cross-sections can be represented in universal forms by the initial velocity ratio in a downstream pipeline.

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Characteristics of water waves and structural loads induced by a forced and periodical change of discharge from a sluice-gate were theoretically analyzed, as the first approach for making clear dynamical characteristics of Tainter-gates which are being used with increased frequencies in order to control the water level of dam. It was concluded as follows: A basic parameter characterizing water waves and structural loads is the modified Froude number F₀=√(d₀/g)·ω(d₀: the depth of the gate-opening, g: the gravitational acceleration, ω: the frequency of an oscillatory discharge). Characteristics of water waves are very analogous to the resonance characteristics of the forced oscillatory system consisting of a mass, a spring and a viscous damper. When F₀ is equal to about 0.8, wave motions fall into a resonance state. Characteristics of fluid-induced structural loads suggest a possibility that Tainter-gates fall into a self-excited oscillatory state. These theoretically obtained results were proved by experiments.

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In case where the overall heat transfer coefficient K varies with positions on the heat exchanger surface or fluid temperature in the cross-flow exchanger, the relations between the number of heat transfer units and the temperature efficiency ε are obtained analytically or numerically, assuming that K = 1+mxⁿ or K = 1+mθⁿ in the nondimensional form referred to the standard value K₀. The effects of parameters m and n are shown quantitatively, arranging the calculated results by the ratio of the efficiency change (ε-ε₀)/ε₀, where ε₀ is the temperature efficiency for K = K₀ and by the single overall coefficient signifying "true mean overall coefficient". Further, it is shown that there is considerable difference among flow arrangements and that conventional methods are not sufficient for large value of m.

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Experimental studies were made of the combustion characteristics, the flame structure and the combustion gas composition of a diffusion flame matrix burner which consists of a bundle of air tubes arranged in a regular matrix through a porous plate for fuel exit. For appropriate flow rates of air and fuel, a very short connected mat of flame is stabilized at a few millimeters above the porous surface. The stability limits and the temperature and stable-species concentration profiles were measured in detail for methane flames at atmospheric pressure. Results show that, although the stable flame appears to be almost flat as a whole, the local cross-sectional shape of the luminous flame zone and accordingly the combustion gas composition change mainly with the air ejection velocity. In order to burn the ejected fuel completely, it is necessary to suppress the air ejection velocity.

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An experimental study has been made on electrostatic probe measurements in flames propagating through a stoichiometric propane-air mixture in a tube in the initial pressure range from 200 to 500 mm Hg. The ion current records obtained by an electrostatic probe were examined in detail and were compared with the flame behavior recorded on the schlieren photographs taken with a high-speed camera. The results show that the flame behavior inferred from the ion current records coincides well with that observed on schlieren photographs. The maximum ion current was found to increase with the increase of the gas velocity in the high ion density region near the propagating flame front. The phenomena near the turbulent flame front could be understood to some extent from the ion current records.

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In this paper, it was tried to analyze theoretically the ignition lag in the diesel engine with a divided chamber. At first, four influential factors on the ignition lag, namely the compression ratio, the volume ratio of divided chamber, engine revolution and a factor K (=fμ/FC), were clarified. And the ignition lag characteristics were obtained in relation to these factors. Further, the optimum factor K, namely Kopt, with which the ignition lag showed the shortest value, was obtained. On the other hand, the behavior of the ignition lag in the case when the sectional area of connecting passage to the divided chamber was varied, was made clear.

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This paper reports an investigation into the effect of the material properties and geometry of cusps upon the elastic and plastic components of deflection of model surface asperities. An analysis of the relationships of the parameters is developed and the results of tests are shown to give close agreements with this analysis

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Distortions of gear tooth caused by hardening decrease gear accuracies, and residual stresses due to hradening influence considerably the bending fatigue strength of gear tooth. But few papers are concerned with distortions and residual stresses of gears. In this report as the first step to studying the distortions and the residual stresses of gears caused by hardening, those of a cylinder caused by water quenching are studied theoretically and experimentally. Coefficient of thermal expansion during martensite transformation and heat transfer coefficient of water during cooling for the cylinders with various diameters, were obtained experimentally. The yield stresses of a cylinder during the martensite transformation were assumed from some of authors' measurements. The residual stresses were calculated applying these data by the elastic-plastic finite element method, and they were also measured experimentally by Sachs' method. Results of the numerical calculations and experiments showed good coincidence qualitatively and quantitatively. Consequently, availability of calculation was confirmed.

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