In the development of reciprocating engines, the objectives have included the simultaneous improvement of the power, fuel and lubricant economy, and engine durability. To achieve these objectives, many tribological problems have had to be solved with regard to pistons, piston rings and cylinders, which are particularly crucial and complicated. Some of these problems are reviewed, and their main points of concern are listed as follows: (1) temperatures of the piston and the cylinder and their influences, including methods to keep them below critical values, (2) relations between the piston-ring motion, blow-by gas and oil consumption, (3) piston friction loss and its characteristics, (4) effects of multi-grade oil and friction modifiers on friction of the piston and cam, and (5) capability of the two-ring package to reduce piston friction, piston weight and engine height.

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For the analysis and design of fluid systems, especially whose systems in which fluid transients in a pipe play an important role, numerical calculation by the method of characteristics is a very useful tool. Because the method of characteristics is suitable for computer programing, even fluid transients in complicated pipelines can be analyzed with less effort. Using this method, the surge pressure and transient flow rate in a pipeline can be accurately analyzed. Due to the reliance on computer simulations, it becomes more and more important and necessary to fully comprehend physical phenomena through experiments and to make use of the results of the design and control of fluid systems.

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Stresses around two symmetrically located interface cracks which lie in the composite materials constructed of two elastic half-planes bonded through an elastic layer are examined. To avoid the oscillatory stress singularities near the crack tips, the crack surface displacements are expanded in trigonometrical functions accompanied with the unknown coefficients. A modified version of the Schmidt method is used to determine these coefficients. Numerical calculations are carried out for the stress intensity factors.

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The plastic zone created at a crack tip is observed microscopically by using scanning electron microscope. CT specimens of 2017-T 4 and 7075-T 6 aluminum alloy are loaded onto or into the J_IC level and the crack tip regions are observed, so that the size of the process zone (PZ) and the fracture mechanism in it are estimated. The results are as follows: (1) In the process zone, the number of nucleated voids and their diameters decreased along the propagation direction of the crack. The size of PZ is about 100-130μm for 2017-T 4 and 50-150μm for 7075-T 6. (2) The diameter of the void which is nucleated at the inclusion in the process zone, increased with the increase in J value and became saturated just before separation; that is, at the nucleation of the dimple. (3) The coalescence of voids seems to occur in two ways. (4) For ductile fracture, as in 2017-T 4 and 7075-T 6, the crack tip is always blunted both on the blunting line and the R-curve.

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An efficient alternating method is developed for the analysis of a group of interacting multiple elliptical cracks in an infinite solid. In this alternating method, and analytical solution for an elliptical crack in an infinite solid is used. To save computational time, geometrical symmetries of crack shapes and locations are effectively utilized in conjunction with the symmetry of the analytical solution with respect to the Cartesian coordinate system. Parametric studies on the interaction behavior of multiple coplanar elliptical cracks are made for several examples of problems. The stress intensity factors for those problems are determined efficiently and accurate by the present alternating method.

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Cavitation, which causes erosion on metal surfaces, is regarded as harmful. But in this study, the phenomena of the cavitation were used positively for metal working, surface treatment and reviving "coined and shaved off" characters. In the experiments, cavitation was generated in the water by ultrasonic vibrations of 20 kHz. The main results are as follows. (1) "Coined and shaved off" characters on metal surface are revived by cavitation. (2) The fatigue limits of mild steels are increased by exposing the surface to the cavitation flow. (3) It is clarified that the erosion working by the radiation of cavitations is useful for cutting work. The relations among the shapes of terminal rods of a vibration system, the working conditions of the process and the erosion patterns are also clarified. (4) The vibration mode of the terminal rods that are specially designed for generating cavitation are analyzed by F. E. M..

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It is difficult to solve the problem of stress-strain distribution in plastic regions in comparison with elastic bodies. Thus, and attempt to expand and apply stress-strain analysis by photoelasticity, with regard to polycarbonate resin in plastic photoelasticity, has been promoted so far and many significant achievements have results therefrom. This study is an examination of the possibilities of the plastic strain freezing method in comparison with the elastic stress freezing method. First, we attempted to determine the best temperature for plastic strain freezing. Further, it became apparent from systematic experimental results that it is 'strain' and not 'stress' which is frozen in plastic regions. In other words, it was made clear that the Birefringence N in strain freezing was proportional to the difference in the principal strains (ε₁-ε₂).

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This paper presents the results of an experimental study on the deflection and reattachment of an axisymmetric radial turbulent wall jet (main jet) discharged from a cylindrical nozzle onto an adjacent disk plate, in the presence of a lateral control flow from and annular slit. The main content of this report concerns the effect of various control flow rates (ratio of the control flow rate to the main jet flow rate) on the flow structure in the region near the nozzle exit. Mean and turbulent velocities were measured with a hot-wire anemometer, while static pressure was measured by means of a Pitot-static tube and a pressure pick-up of a strain gauge type. The velocity profile, shape and length of a jet potential core, and the deflection of the jet's center axis depend mainly on the control flow rate and the wall effect.

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A computational marching procedure for two-phase flows which are dispersed, parabolic, and turbulent is outlined in detail. Convection, diffusion and viscous action as well as entrainment and volume fraction fluctuations are taken into account for both phases. Each phase is calculated in its own grid to reduce false diffusion to a minimum. The use of two independent grids requires formulae for the transfer of variables which are presented. A test case id examined to estimate the effect of false diffusion on the second d phase. A two-phase jet is calculated and the results are found to be in good agreement with experimental data.

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An equation of oscillation is obtained from both the pressure balance in a reservoir-capillary system and the momentum balance of a jet between the exit of the capillary and the downstream cross section where the velocity of the jet is uniform. Through and examination of this equation, the following results are found: (1) The critical shear rate of an unstable flow is the shear rate at which the (φ+Bξ) term of the first differential coefficient in the second order differential equation is zero. (2) When the (φξ+ηψ) term of the zero order differential coefficient in the equation becomes negative, the jet always exhibits unstable flow. (3) As has been proved by results obtained up to this time, the principal cause of unstable flow is irregular in the vicinity of the capillary entrance.

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A statistical pattern recognition method was applied to the analysis of the signals of a cross-sectional mean void fraction for discriminating gas-liquid two-phase flow regimes. The analysis and discrimination were carried out based on six key flow patterns: bubble, cap-bubble, plug, froth (F_I and F_II), and annular flow. For each flow condition, 100 void signals with a recording dimension of 1 second were used and transferred to discrete data, the sampling frequency of which was selected as 100 Hz by comparison with correct recognition rates obtained from different frequencies. The magnitude of the time-averaged void fraction was partly employed supplementary to the pattern recognition method. The boundaries between the six flow regimes were determined corresponding to a correct recognition rate of 80% and were drawn on a superficial gas-liquid velocities diagram. These flow boundaries were also compared with those available in the literature.

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The minimum-heat-flux (MHF) -point condition and film-boiling heat transfer in subcooled pool boiling of water were experimentally investigated by using a horizontal cylinder and a sphere. First, collapse behavior of vapor films was observed, and it was found that collapse modes can be classified into coherent and propagative collapses. Second, the relation between the MHF-point temperature and the propagation rate of film collapse was experimentally obtained, and the MHF-point temperature at which coherent collapse occurred was defined as its true value. The experimental data obtained show that the true MHF-point temperature is not strongly dependent on liquid subcooling and it does not exceed the liquid's maximum, metastable superheat temperature even at large subcoolings. Finally, using the experimental data of subcooled film-boiling heat transfer for various liquids, a prediction technique based on Hamill's correlation was developed.

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It is known that there exists a boiling condition of subcooled liquid at which many microbubbles are emitted from a heated surface in the transition boiling regime. We call this phenomenon "microbubble emission boiling" (MEB). MEB occurs easily in systems where the subcooled liquid removes the bubbles naturally, and not against their own motion from the surface soon after their generation. Consequently the subcooling and the velocity of the liquid should be very important factors concerning the occurrence of MEB. In this study, our purpose was to clarify the effects of the degree of liquid subcooling and its approaching velocity to the surface on the occurrence of MEB and the intensity of microbubble emission by measuring temperature fluctuations of the surface and pressure fluctuations in the liquid above the surface.

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Using the low density particles (polystyrene hollow spheres) described in the 1st report, mean heat transfer coefficients from a single row of horizontal cylindrical tubes immersed in floating particles were measured, with the aim of reducing pressure drop in a fluidized bed heat exchanger. In this study, furthermore, in order to make particles float stably around tubes, rectangular tubes (aspect ratio: 30/3) were used because the change in flow area between the tubes is small; that is, the change in flow velocity between the tubes is small compared with that of cylindrical tubes. The results show that: 1 L₀/L_h≥1, and the mean heat transfer coefficients are independent of both L₀ and L_h, in the same way as with cylindrical tubes. 2 Mean heat transfer coefficients decrease slightly more than those with cylindrical tubes. 3 However, since rectangular tubes can be arranged more densely than cylindrical tubes, their thermal performance under the same pumping power is improved to about three times that of cylindrical tubes.

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Turbulent structures of a diffusion flame formed in a flat plate boundary layer have been investigated experimentally. The flame is formed in the boundary layer with a 10 m/s free stream velocity, when a fuel (hydrogen/nitrogen mixture) is injected uniformly through a porous wall. Simultaneous measurements of two velocity components parallel and normal to a flat plate have been made, using a polarized four beam laser-Doppler velocimetry, and statistical properties up to third order cross correlations have been calculated. A mean density profile has also been obtained from temperature data measured by a thermocouple, and stable species concentration data measure by gas chromatograghy. From these data, statistical properties have been obtained, taking into account the effect of the mean density variation. Results obtained suggest that the turbulent production and transfer mechanism can be fundamentally identified with that of an isothermal shear flow even around the flame zone.

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Detailed digital simulations and eigenvalue analyses of self-excited vibration during slippage of parallel Cardan drives were made. The effects of the stiffness and damping of flexible couplings and gearbox suspension rubber springs were studied, and measures to suppress the self-excited vibration were clarified. Experiments involving two cases of a leaf spring coupling were made by varying the stiffness and damping of the coupling and the gear box suspension rubber spring. The results agreed well with theoretical results. Experiments for a third case with a gear coupling were also made. (average total tractive effort/total driving axle load) was measured for two cases with and without self-excited vibration, and it was shown that the latter case could attain a larger μ_a.

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By treating the positioning control problem of a cautilever-type arm rotating horizontally, the digital optimal control problem of an elastic structure system is theoretically and experimentally considered in this study. Especially, a method for examining the influence of spillover due to a finite dimensional approximation of the elastic structure and a calculation delay in the digital control is presented. By the practical development of control equipment and the various control experiments, the usefulness of the proposed design method is verified, and important information about this kind of control is obtained. Furthermore, the influence of the friction in the DC servo-motor is investigated, mainly by digital simulations.

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In the previous paper, experimental work was reported in which the crack generation during fretting in a vacuum was dependent on the slip amplitude and normal load. In this paper, the condition of the crack generation is considered. The tensile stress concentration at the trailing edge of the contact area depends on the tangential force coefficient and the contact pressure. The properties of the stress concentration against load and slip amplitude are very similar to those of the crack generation. The mechanism of crack initiation in low-cycle fatigue is applied to the crack generation in fretting; when the stress concentration causes local yielding at the edge, the accumulation of the local plastic strain occurs during the repetition of the fretting cycle, followed by the initiation of the crack. The reason why a crack is not generated during fretting in air is discussed.

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Many investigations into the problems of ball motion in ball bearings have been reported. However, studies of the influence of race failure on ball motion are few. Recently, utilizing the Hall effect, a new method for measuring three-dimensional ball motion was developed so that it is now possible to analyze the angular velocity components of ball motion from experimental data. The authors carried out a series of experiments on ball motion using damaged bearings. In this paper, the experimental results obtained under a shaft speed of N_i=12 rpm, 1000 rpm and a radial load of Pr=490 N are reported. The effect of shaft speed and the influence of a damaged race on ball motion are discussed, based on the analysis of the experimental data.

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In the previous paper, the synthesis of a planar adjustable 9-link mechanism was reported, as a practical example of an automatic conveying machine which generates an L-path. It has been found that the driving system of the above-mentioned machine, which is constructed of an analog computer, an induction motor, a magnetic power clutch and brake, is so complicated that the system made the response worse, and that positioning errors of the machine hand at the edge points of the path increase. In this paper, a 12-link adjustable mechanism is proposed, which is made by joining a 4-link mechanism to the input link of the above 9-link mechanism, for the purpose of making the crank motion uniform in one direction and simplifying the electric controller of the driving system. Moreover, an optimum distributed mass and moment of inertia of the input link is determined so as to minimize the input torque. The dynamic characteristics of the machine are also investigated theoretically and experimentally. As a result, the velocity response and the positioning accuracy of the machine hand at the edge points of the path can be greatly improved.

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