The behavior of fatigue cracks in plain specimens of eutectoid steel, in which the cracks are subjected to macroscopic tensile and shear stresses, is examined by both rotary bending and cyclic torsion tests. The size of slipped region at the crack tip and the micro-Vickers hardness in the region are examined. At the critical propagating stress, the following results are obtained. The size of slipped region is little affected by the crack length. The micro-Vickers hardness at the crack tip of tensile mode in cyclic torsion is different from that of shear mode in cyclic torsion, and the former is the same as that of tensile mode in rotary bending. That is, the hardness change is not dependent upon the load mode (rotary bending or cyclic torsion), but upon the stress mode generated at the crack tip.

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The rotating bending tests of specimens with a small hole were made on five materials. The main results obtained are as follows: (1) The life for crack propagation under the stress of (1+ζ) times the fatigue limit of plain specimens is greatly different for different materials (ζ: a positive constant). (2) When the crack length l is small, the rate of crack propagation dl/dN is nearly proportional to 6ⁿl (n: material constant). The values of n are 3∼8. The difference in the value of n is based on the difference in the crack closure behavior. (3) The relation between the crack length l and the relative number of cycles normalized by the life for crack propagation is independent of stress levels and materials. (4) When the crack lendth l is equal, the form of crack surface is also equal, irrespective of stress levels and materials. (5) The rotating bending fatigue test of specimens with a small hole is suitable for the estimation of crack propagating property of a material.

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From the tensile creep rupture tests for unnotched and round notched bar specimens of 1Cr-1Mo-1/4V steel at 600°C and the numerical calculation results by using finite element method, the following are concluded: (1) The material tested has the transition phenomena from notch-strengthening to notch-weakening at elapsed time of about 120 hrs. The rupture ductility of the material remarkably decreases after elapsed time of this transition. (2) In the region of notch-strengthening, the levels of the equivalent stress and the strain at the notch root of the notched specimen are lower than those of the notched specimen under the same nominal stress. This holds also in the case of hydrostatic stress at the notch root. On the contrary, the quantitative relation mentioned above is reversed in the notch-weakening. The former is one of the important factors determining the notch-strengthening, while the latter is a factor for the notch-weakening.

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This paper contains an exact solution for the stresses arising in an infinite elastic plate having a symmetrically located spherical cavity and subjected to uniaxial tension. The problem of stress analysis in a plate with a spherical cavity was investigated by several authors. But their solutions were all for the problems of plates subjected to the axisymmetrical loads. The present paper is aimed to present for the asymmetrical cavity problem of the plate. The solution obtained is in integral form and infinite series form, and is deduced with the aid of six harmonic stress functions. Numerical results are included for the stresses on the surface of a spherical cavity and along the z-axis, corresponding to several values of a cavity. The results obtained are compared with the axisymmetric solution.

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The theoretical prediction of plastic stress-strain relations of face-centered-cubic polycrystals subjected to proportional loadings is discussed on the basis of K. B.W model. This theory is applied to predict the stress-strain curve of thin-walled aluminium cylinders subjected to internal pressure loading by using the experimental curve of simple tension. A good agreement between the theoretical and experimental results is obtained. Furthermore it is found that Taylor's prediction based on the ratio of the yielding stress of a polycrystal to that of a single crystal gives almost the same results as the K. B. W. model prediction.

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The subsequent yield surfaces after proportional preloading are experimentally investigated for the materials whose stress-strain curves in the proportional loading are represented by the effective stress-strain relation of Tresca-type. The yield surfaces are obtained by subjecting thin-walled tubular specimens of aluminum alloy to combined axial load and internal pressure. These results are compared with those of combined axial load and torsion. For the Tresca-type materials, the shapes of the yield surfaces represented in the π-plane and in the deviatoric stress plane are found to depend on the direction of the prestress. A new stress plane modified from the deviatoric stress plane is proposed, in which the yield surfaces are given uniquely as a function of the length of the prestrain path.

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This paper is devoted to realization of the optimum vibration isolators for systems subjected to stationary random excitations. A systematic procedure expressing the optimum vibration isolating forces as functions of the state variables is proposed and illustrated by examples of a single- and a two-degree-of-freedom system.

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Bayonet-type heat exchangers are classified into four cases by the flow directions of shell- and tube-side fluids. The transfer functions, relating outlet temperature responses to changes in inlet temperatures of both tube- and shell-side fluids, are obtained for bayonet-type heat exchangers. Numerical examples are presented, and the effects of flow directions on the frequency response are examined. Experiments of frequency response are carried out, and the data are shown to be in good agreement with the theoretical results.

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The performance of pumps with semi-open impellers was tested under air admitting conditions and the effects of running clearance between the impeller vanes and the stationary casing were discussed. The results were compared with those of closed-impeller pumps. when the clearance reduces, the pump ability under no air admission increases continuously, but the performance is much decreased by air admission. When the clearance relative to the channel depth of impellers λ is increased beyond 0.1, the drop of pump head due to air admission is much weakened, and it tends to a definite value, regardless of impeller shape. When two pumps with a closed-impeller and with a semi-open impeller show the same performance under no air admission, both pumps develop nearly the same performance under air admitting condition. The clearance range of λ=0.033∼0.086 is suitable for the duty of delivering air-water mixture.

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In the present paper, the authors intend to discuss the applicability of the analytical method for a turbulent boundary layer having pressure gradients with injection or suction treated in the previous papers to the boundary layer on the cascaded blade surfaces with injection or suction all over them and to investigate the influence of the injection or the suction on the cascaded blade characteristics by the cascade tests. The following main results are obtained: (1) The analytical method for a turbulent boundary layer having pressure gradients with injection or suction treated in the previous papers is applicable to the boundary layer on the blade surfaces with injection or suction all over them. (2) Judging from the total pressure loss coefficient, though the optimum injection ratio must be determined after due consideration of the cooling characteristics of the blade, m the available injection ration in the fluid dynamic characteristics if ν₀/u₀≦0.004. And the effect of the suction all over the blade surfaces is found little for a high performance cascade (such as NACA A₃K₇).

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For the purpose of obtaining an accurate performance of a disk friction pump rotor, theories in a previous report are compared with experiments. The laminar flow theory with modification in the inlet region agrees well with the experimental results when a disk clearance of the rotor is narrow. The outlet end effect of disks is discussed. On the basis of the these results, formulae are made of the performances of the disk friction pump rotor, and optimum disk clearance and optimum radius of inner periphery of the rotor are given. Furthermore, whether a flow regime in the rotor is laminar or turbulent is experimentally analyzed. In the experiments, it has been confirmed that the flow regime is always laminar except for a small region near the inner and the outer periphery, and that two types of vortex rows can be observed in compliance with the flow rate change.

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This paper presents a theoretical study of the transient characteristics for a system consisting of hydraulic actuator, fluid pipe and operation valve. In this analysis fluid motion in pipe is treated as a two-dimensional unsteady laminar flow, and non-linear characteristics of the flow through a valve is considered exactly. The solution for pressure variations at arbitrary pipe section and actuator displacement are obtained in terms of convolution integral and their numerical results are presented. The effects of system parameters and operating parameters, especially, valve orifice shape, valve movement (e.g., instantaneous closure, partial closure, gradual closure, exponential gradual closure, etc.) on the transient response of the system are discussed. Two approximate solutions, one obtained by treating a fluid in pipe as a one-dimensional steady laminar flow, and the other obtained by considering only the compressibility of the fluid in pie are also presented and compared with an exact solution.

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This paper deals with transient characteristics of a valve-controled hydraulic driving system consisting of actuator, fluid pipe and operation valve, especially with pressure surge generation in a pipe due to sudden valve closure. Pressure variation was measured under various system and operating parameters, such as valve closure time, valve closure process, valve orifice shape, etc., and compared with theoretical results of the preceding paper. Consequently, the following matters became evident. (1) The theoretical results which were obtained by employing a wave equation of two-dimensional viscous flow for an unsteady pipe flow agree well with experimental results in any system parameters and valve closure process. (2) An approximate solution which was obtained by considering only the compressibility of fluid in pipe is accurate enough for practical usage in case of very slow valve closure. (3) Variation of discharge coefficient of valve depending on Reynolds number, saturation of valve flow at large opening and leakage flow through valve orifice after closure can not be disregarded in case of gradual valve closure.

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The formation of nitric oxide from small additions of ammonia in premixed methane/air and hydrogen/air flat burner flames was studied and the conversion ratio of ammonia to nitric oxide was compared with the ;model calculation proposed. Experimental results show that fuel-NO is formed promptly above the equilibrium concentration in and near the flame zone and that the conversion ratio becomes larger (i) at higher air ratio, (ii) for less fuel-N, and (iii) at higher flame temperature. These characteristics can be explained by the kinetic scheme based primarily on extended Zeldovich mechanism if an assumption is made that fuel-N decays finally into N atom.

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Problems in the formation mechanism of fuel-NO in diffusion flames are researched by adding ammonia or nitric oxide to fuel or combustion air. conversion ratios of ammonia to nitric oxide in diffusion flames are lower than those in premixed flames because added ammonia is decomposed in fuel-rich region near the inner flame surface. Conversion ratios are strongly affected by the amount of air included in fuel. Formation processes of fuel-NO in hydrogen diffusion flames can be explained by reaction scheme based on extended Zeldovich mechanism as well as in premixed flames if an assumption is made that fuel-N decays finally into N atom. Decomposition reaction of added NO plays a very important role in methane diffusion flames.

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In a two-stroke cycle gasoline engine, the limits of flame propagation were measured under various operating conditions, and the composition temperature and pressure of the cylinder gas at the limits were investigated. The adiabatic flame temperature in a lean or rich limit mixture was calculated on the basis of the cylinder gas state at the time of ignition. It is shown that, in the case where the engine speed and the ignition timing are fixed, the adiabatic flame temperature remains almost constant along both the lean and rich limits, regardless of the residual gas concentration or the mixture temperature.

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A rolling sliding contact fatigue test was conducted with the use of Ni-Cr-Mo-V steel discs (H=340H_B, S=250H_B) for marine main turbine's reduction gears and lubricating oil (No.200 turbine oil) at the soft-specimens slide-sweep ratio of -24% and 2100 rpm: and in the test, the X-ray diffraction techniques were used in obtaining the value of the residual stress on the contact surface where rolling fatigue pits were produced. The residual stresses closely related with; (a) the Herzian maximum pressure and the D-value (total surface roughness of the two discs/EHL minimum oil film thickness) under poorly lubricated conditions such as in D>1; (b) the repetition of contact at early stage of test. A change in the production of residual stress takes place with D=2 as boundary. In addition, the relation between pitting failure and the half breadth of distribution curve of diffraction strength is described.

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