Rotating bending fatigue tests were performed for SUS 304 stainless steel, which had various grain sizes. The fatigue limit of a plain specimen is much higher than the 0.2% proof stress, and the increase in the fatigue limit caused by the coaxing effect amounts to about 40% of that in the test under the condition of constant stress amplitude. The strain measured by using a slip ring shows that these results are due to a marked hardening produced during cyclic stressing. A non-propagating fatigue crack forms only at the elevated temperature in a notched specimen. The maximum depth of that crack is about 600μm independently of grain size. According to a detailed examination by the scanning electron microscope, a great number of carbide precipitates get together preferentially around the non-propagating fatigue crack. From this it is suggested that the formation of the non-propagating fatigue crack might be greatly controlled by such a metallurgical factor as well as a mechanical one.

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This paper concerns an analysis of torsional stresses in a two-part cylindrical rod. At the corner of the rod, the stresses have singularities with unknown order. Then, a stress analysis is carried out by the classical method without consideration of the stress singularity. The stress states of the rod are given numerically for some cases. The results show that the order of the stress singularity depends on the shear modulus of the rod only.

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The instability problem stated in the title is analyzed on the basis of Biot's mechanics of incremental deformations. The slab is reinforced by inextensible, completely flexible fibers in the direction of its axis. The analysis indicates that there exists a universal solution to this instability problem. It is found that the slab under compressive load becomes unstable with two distinct buckling patterns, antisymmetric and symmetric, while no buckling occurs under tensile load, as expected. When the slab buckles, the stress singularities represented by the Dirac delta distribution appear in the boundary fibers.

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In this paper, the most applicable diameter of specimen is searched for through the direct vibratory damage-experiments conducted with various frequencies and amplitudes.

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The potential theory has been used to analyze the flow characteristics of a swirl spray nozzle, but the theoretical results do not coincide with the experimental ones. One reason for this inconsistency is likely in the energy loss caused by a swirl flow in the vortex chamber. In order to investigate the energy loss, the energy distribution in swirl flow is studied and the flow characteristics of a swirl spray nozzle introducing this effect is analyzed, then the theoretical results are compared with the experimental ones. The results show that the energy loss in the cylindrical chamber is directly proportional to the difference in peripheral velocity head of the fluid, and the energy loss in the vortex chamber must be taken into account to evaluate the discharge coefficient of a swirl spray nozzle.

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Using a photoelastic apparatus or Schlieren interferometer, we experimentally studied the mechanism of the impulsive force generation by a spark-induced cavitation bubble, collapsing near the solid boundary. The experimental results indicate that the cause of the impulsive force is classified by the parameter l, where l= (maximum bubble center distance from the solid boundary) / (maximum bubble radius). In case of l&gnE;1.35, the shock waves are dominant and in case of l<1.35, the water microjet impingement is the main cause of the impulsive force. In a special case (l&lnE;1.24>), both the shock waves and the water microjet are supposed to impact against the solid boundary. Even when an asymmetrically collapsing bubble rebounds, the shock waves are observed.

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The performance of a supersonic air ejector was experimentally studied over a range of ejector-to-nozzle throat-area-ratios Ψ and primary nozzle Mach numbers M_lp. The investigations covered both straight-tube and second-throat ejector types. As the result, the effects of the ratio Ψ on the ejector performance were made clear. The performance curves were classified into five groups by the values of Ψ and a primary chamber-to-ambient pressure ratio p_op/p_a. For a fixed Ψ, an optimum p_op/p_a exists which realizes a maximum secondary flow rate and a minimum secondary chamber pressure. Also, for a fixed M_lp, the optimum p_op/p_a becomes minimum at a certain Ψ, which was defined as an optimum throat-area-ratio. The physical meanings of the optimum pressure ratio and the optimum throat-area-ratio were clarified using the results of pressure measurements and optical observations.

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Reciprocating oil flows through orifices are measured with the intention to verify the 'viscous end correction' theory developed in the previous paper. The impedance tube technique in acoustics can help detect varying-with-time flow rates. The transitional relation between the pressure drop across and flow rate through an orifice over one period is observed as a colsed hysteresis curve. These curves show such peculiar features as sharp tips, inflected distortions and eventual self-crossings according as the nonlinearity grows. Although obtained data are more or less subject to the nonlinear effects, the orifice resistance in the linear region is successfully evaluated from them by extrapolation. The results endorse the validity of the present theory, dismissing Sivian's attempt to apply Rayleigh's end correction tube to harmonic viscous flows. Another finding is that the nonlinear pressure loss in an oscillatory orifice flow falls below its steady-state conterpart.

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This report intends to experimentally reveal the fundamental differences between the steady and unsteady nonlinearities of orifice flows. The same measurements as in the foregoing paper are conducted in pulsating oil flows through orifices. Separating nonlinear components from total pressure drops and plotting them versus flow rates yields another hysteresis curve which represents the unsteady nonlinearity alone. It turns out that this curve invariably takes on similar inflection and counterclockwise hysteresis, and on the average lies below the steady-state loss. These findings lead to a hypothesis that eddies which bring about nonlinear energy dissipation in orifice flows tend to resist the change of magnitude, which is here called 'eddy inertia'. An idea of time lag inherent in the nonlinear loss helps embody this hypothesis as an empiric formula. This formula successfully explains the peculiar behaviors of hysteresis curves and Bolt's observation that the nonlinearity reduces the orifice reactances.

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A slipper bearing is one of the factors which affect significantly the performance of swash plate type axial piston machines. In this paper, considering all the oil-film parameters, that is, tilting angle, maximum tilting angle azimuth and mean clearance, a theoretical analysis on the characteristics of the slipper bearing is made from the standpoint of fluid film lubrication. As numerical examples, changes in the oil-film parameters due to a rectangular change of a supply pressure are shown. And also, the limit of fluid film lubrication is given in relation to the supply pressure and the rotational speed.

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The measurement of particle size distribution using a superimposed Fraunhofer diffraction pattern of moving particles on the focal plane was investigated. The following results were obtained. (1) Analysing the obscuration of diffracted light intensity of slits by obstacles behind the slits, the influence of particle numbers in a unit volume (cm³) on the diffracted light intensity was estimated. (2) At the mean particle size 60μm, it is found that this system can measure the correct particle size distribution for the particle numbers<6 × 10⁴ in a unit volume (cm³).

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With the aid of a derivative spectrophotometer, emission characteristics of formaldehyde from a methanol fueled S. I. engine were obtained. Formaldehyde and unburned methanol were measured at several distances along the exhaust tube for various air-fuel equivalence ratios and ignition timings. Experiments show that dominant oxidation of unburned methanol in exhaust system is obtained at temperatures above 400°C. However, formaldehyde levels were maintained during the exhaust movement for a fuel rich mixture. In fuel lean operation, formaldehyde increased in exhaust tube. This fact suggests that formaldehyde is formed by the oxidation of unburned methanol during the exhaust process, and the formation already begins in the cylinder. Careful experiments using a heated tube reactor set at engine exhaust port, and kept at a constant temperature range of 300-650°C probe that formaldehyde accumulation occurs in exhaust system at a temperature range of approximately 400-600°C.

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One of the promising engines may be a divided chamber spark ignition engine (a torch ignition engine) which can be operated with lean mixtures. In its chamber configuration, however, there are some components which affect the combustion process and the engine performance. Experiments were carried out with combustion chambers of various constructional parameters, and it was found that the combustion process was mainly affected by the character of the torch issueing from the prechamber. Among the parameters, dimensions of an orifice which divides the combustion space have an important effect on the combustion process. Because of the dominant effect of the torch, even a lean mixture can be rapidly burned.

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The operating data of Stirling engines are necessary in the process of developing or designing them, but they are not available enough. This paper describes the development of an accurate computer simulation model for predicting the performance of Stirling engines to complement those operating data. Though the model represents the working space by 43 successive control volumes, the method employed here can save its computing time. The model also takes into consideration the leakage of working gas through the piston ring which may affect the performance of Stirling engine to a large extent. The model was applied to a large marine Stirling engine and the calculated results show good agreement with the experimental ones.

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It is pointed out that the natural frequencies in the lateral vibration of a beam having a circular hole, irrespective of the modes and its support conditions, vary with the position of the hole. When the center of the hole is positioned near a point where the antinode of the normal mode would appear in the absence of a hole, the natural frequency assumes a local minimum. On the other hand, when the center of the hole is positioned near the inflectinoal point of the normal mode of the beam without a hole, the natural frequency assumes a local maximum. The natural frequencies were computed according to Rayleigh's method using the deflection curves obtained by modifying the normal functions for the beam without a hole, and the above mentioned property was verified analytically. The theoretical results were in good agreement with experimental results up to the first three natural frequencies.

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This paper deals with the motion of an unsymmetrical rotor possessing nonlinear spring characteristics, due to the angular clearance of a singlerow deep groove ball bearing, in the vicinity of the major critical speed. When this system is operated near the major critical speed, no unstable vibration occurs, but we obtain peculiar resonance curves of hard spring type which have three stable amplitudes at most against the rotating speed. The resonance curves are classified into two types. They are the cases where the jump phenomenon appears once or twice during deceleration of the rotating speed. It is clarified that the type of the resonance curve depends on the angular position of rotor unbalance.

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This paper presents a seismic response analysis of a cylindrical liquid storage tank on an elastic foundation subjected to a horizontal earthquake, which is based on the energy method considering the coupled effect between sloshing and bulging. The kinetic energy and the strain one of an empty tank shell are estimated by the finite element method for an axisymmetric shell. On the other hand, the kinetic energy and the potential one of the liquid in the tank are estimated analytically by superposing three types of velocity potentials as follows : (1) Velocity potential for the free surface oscillation ignoring the vibration of the tank side shell. (2) Velocity potential for the coupled vibration between the tank side shell and the liquid ignoring the free surface oscillation and the vibration of the tank bottom plate. (3) Velocity potential for the coupled vibration between the bottom plate and the liquid ignoring the free surface oscillation and the vibration of the tank side shell. Through numerical calculations, effects of the stiffness of the tank foundation and the thickness of the tank bottom plate on vibration characteristics and seismic response ones are investigated.

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The perfect model following (PMF) is an established technique in control system synthesis which has such a characteristic that the state variables of plant perfectly follow those of model. However, the condition for PMF to be able to synthesize is rather severe. In order to relax this condition and enable easy synthesis of PMF system, extended PMF (EPMF) is proposed. EPMF is a PMF where the output (not state variables) of plant perfectly follows that of model. A condition of EPMF and design procedure of EPMF are derived. Sensitivity reduction in EPMF is analyzed. Design examples for some systems and an aircraft control system are performed and simulated. Possibility of wide application and desirable characteristics of EPMF are shown.

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A computational method is presented for obtaining the steady-state temperature responses of parallel-flow and counterflow heat exchangers subject to sinusoidal flow rate changes of large amplitude. The method is based on the assumptions that the fluids pass through a series of lumped heat exchangers with lumped capacitances and that the steady-state responses are to be expressed by Fourier series, and it enables us to reduce the computation time remarkably. The frequency-and amplitude-dependent describing functions between the input sinusoidal flow rate changes and the fundamental component of the steady-state response of the outlet temperature of tube-side or shell-side fluid are also derived. Numerical examples are given to show the effects of the amplitude of the flow rate changes on the describing function plots. Finally the nonlinear behavior of the steady-state periodic responses computed by this method is confirmed by means of digital simulations.

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It is clarified theoretically and experimentally that, when an unsymmetrical shaft is supported by single-row deep groove ball bearings, an unstable vibration with frequency +2ω (ω : rotating speed of a shaft) appears at the secondary critical speed due to the coexistence of a stationary directional difference and a rotating directional difference of stiffness. The stationary directional difference is due to the directional difference of support condition by means of a single-row deep groove ball bearing which has angular clearance, and the rotating directional difference is due to the flatness of the shaft. The width of this unstable region depends on the assembly of the system. No unstable vibration appears at the secondary critical speed in the system where an unsymmetrical shaft is supported by self-aligning double-row ball bearings and in an unsymmetrical rotor system.

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This paper presents the theoretical results of a study on thermal characteristics of a journal bearing. Joint calculation is made of the temperature destribution across the oil film thickness and on the bearing bush inner surface, as well as, of the heat flow ratio as a function of the clearance ratio, eccentricity ratio, journal speed, rate of heat diffusion on the bearing bush outer surface, lubricant viscosity and supply temperature. The results show that the maximum temperature and the location vary markedly with a change in the clearance ratio. Moreover, the theory presented agrees with the experimental results of D. Dowson and others.

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It is becoming increasingly important to determine the dynamic characteristics of journal bearings precisely for recent high speed rotatory machines. In this paper, the oil film spring and damping coefficients are calculated taking the effect of oil film viscosity variation into consideration. The theoretical results make clear the influences of the journal speed and bearing clearance ratio on these coefficients. The measured spring and damping coefficients vary with the journal speed, even though Somerfelds Number is equal. This phenomenon is well accounted for by the theory which deals with the effect of viscosity variation in the oil film.

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In this paper, the authors investigated theoretically and experimentally the influence of the gas inertia forces generated within the stabilizing restictor on the dynamic characteristics of externally pressurized circular thrust gas bearings with a stabilizer. From comparison with the experiment, it may be concluded that the influence on the dynamic characteristics should be considerable, and that the presented analysis yields good predictions for both the bearing stiffness and the damping coefficient in a wide range of designing conditions.

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The surface-restriction compensated gas bearing with T-shaped grooves has the following advantages ; (1) good damping performance, and (2) manufacturing ease, because of a small number of grooves, compared with the I-shaped groove bearing, which is composed of many narrow linear grooves. This paper reports on dynamic characteristics of T-shaped groove bearing analyzed by the small perturbation method and results of an investigation by modified finite difference method, which can rationally express any bearing surface division, including both groove and land parts, by only one grid. Based on these calculated results, design criteria are given for a high performance bearing with high stiffness and high damping values. Furthermore, stability thresholds are also calculated.

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The profile of the pitch curve of external and internal noncircular gears, and the restricting conditions to avoid the interferences were analyzed, and the designing conditions of the mechanisms were decided. Then, the noncircular planetary gear mechanisms were synthesized as intermittent motion mechanisms, and the noncircular gear shaper was made by way of experiment and gears were cut. And then, the mechanisms were produced and the static characteristic was investigated.

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