In this paper, coupled thermoelastic wave problems are treated with approximate solutions based on the limit-value theorem and with a numerical inversion technique of the Laplace transform. The problems considered are those of a half-space under a sudden strain with constant temperature, or a constant velocity impact with adiabatic condition over the boundary plane. The numerical results show that the approximate solutions are applicable to solve these problems for short and also long times. Further, it is shown from the analyses of two particular cases that at the wave front the coupled thermoelastic waves subjected to a thermoelastic damping, approach asymptotically certain values determined from the boundary conditions. For the adiabatic boundary condition, the influence of coupled thermoelastic effect remains at all points of the body considered, but for the other case, it vanishes gradually at the points through which the wave front has already passed with heat conduction from the boundary.

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The elastic compression of a block with Coulomb friction on the tool-specimen interface is analysed, where the total stiffness matrix is rearranged according to the condition for nodes on frictional plane in Finite Element Method. As an example, the distribution of stresses in a block, the area of sticking on the contact surface, the distribution of displacement in the block, the pressure distribution and the mean pressure on the contact surface are calculated under plane strain condition. The effects of specimen shape, friction coefficient and Poisson's ratio on the calculated results are studied. The area of sticking on the contact surface increases with a decrease in block height, with an increase in friction coefficient and with a decrease in Poisson's ratio. The thinner the block is, the higher the pressure which is necessary for yielding becomes. Discussions are made on the calculated results as well as on the property of unsymmetric stiffness matrix in the analysis.

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In this paper, the instability problems of columns are analyzed by analytical and graphical methods for the cantilevered columns, which are subjected to axial and tangential rectangular periodic loads at the free ends. The effects of damping are also investigated on each system. The results are compared with those of columns under sinusoidal periodic loads in first and second modes. It is made clear that the instability regions of columns under rectangular loads are different from those under sinusoidal loads in two models (columns under axial load and tangential load).

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A varying-pitch helical compression spring is often used under high speed excitation, but its fundamental dynamic properties have not been elucidated. In this paper the dynamic properties of a varying-pitch spring subjected to a sinusoidal excitation are investigated theoretically and experimentally. The theoretical analysis is done by solving a one-dimensional wave equation with unknown boundary conditions varying with time. (1) The amplitude-frequency curve of a varying-pitch spring is similar to that of a single-degree of freedom system in which the spring control takes a nonlinear symmetrical form. (2) The theoretical results well coincide with the experimental ones. (3) The dynamic stress in a varying-pitch spring is lower than the one in the equal-pitch spring. The reason is considered that the dynamic energy is dispersed during the repetition of contact and separation of the adjacent coils of the varying-pitch spring.

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The paper analyzes theoretically the turbulent boundary layer on a rotating blade with consideration for the effects of its stagger angle and twist. The helical coordinate system was introduced to obtain the boundary layer equation in a general form. The equation, furthermore, was transformed into a momentum equation. The solution for the flow on the workless blade was derived by assuming the velocity distribution and the shearing stress on the wall surface based on 1/7-th-power law. The calculated results of the thickness of boundary layer and the radial flow in it agree pretty well with the experimental results. The effect of the stagger angle on the boundary layer thickness is also shown numerically.

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The theories have been developed on the flow with tangential injection of air on a surface of a cylinder, for the sake of which the jet was divided into two parts, namely, the boundary layer and the mixing region. There have been derived three kinds of systems of differential equations under various assumptions such that the first method ignores the curvature of the wall and assumes the conservation of momentum in the mixing region, the second method takes into account the curvature and the conservation of angular momentum and the third method assumes that 〓≠0 in addition to the assumptions in the second method. It is concluded from the comparison of calculation with experiment that the curvature of the wall should not be ignored and that the second or third method well predicts a separation point for adequate pressure gradient.

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The region behind the reflected shock in a shock tube is used as a reservoir of gas for a hypersonic tunnel and in chemical kinetics studies. In order to clarify the gas properties in this region, the interaction phenomenon of the reflected shock with the boundary layer must be made clear. Although many studies have been carried out about this interaction, they are not comprehensive. In this paper, this interaction was observed optically by schlieren method, and the growth rate of the bifurcation and the velocity of the reflected shock were clarified. Furhter, based on the present and previous experimental data, and modifying the previous flow models, a new flow model was presented on the interaction of the reflected shock with the boundary layer. The growth rate of the bifurcation and the velocity of the reflected shock calculated by this model are in fair by good agreement with experimental results.

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Entrained air in a centrifugal pump has undesirable effects on the pump operation and knowledges of the pump performance under air admitting conditions will be needed for actual purpose. In order to investigate the performance, a semi-open impeller pump with a transparent casing was employed and the behavior of the entrained air bubbles in the pump was observed. The impeller work and hydraulic loss of the pump, together with energy loss for air delivering are discussed. The total head of the pump is decreased by the air admission, but the head developed by the impeller remains substantially constant, The drop of the pump head is mainly caused by the energy consumption for air delivering within the range of q_s/Q≤0.02, and when q_s/Q is increased beyond this range the hydraulic loss due to the flow resistance of air bubbles increases its weight in the head drop. These relations are given in empirical formulas.

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Experiments on two supercavitating pumps, pumps A and B, were carried out to investigate the characteristics of supercavitating pumps. The two pumps were designed for the specific speed N_s of 3, 300 (in units m, m³/min, rpm) and the suction specific speed S of 2, 000. In the design of the impeller of pump A experimental data obtained by Wade and Acosta on supercavitating cascades of planoconvex hydrofoils were used. Wu's theory on supercavitating circular are hydrofoils was applied to design the impeller of pump B. Following results were obtained by experiments. The performance of pump A is N_s 3, 030, S 2, 320 and efficiency 59.4%, and that of pump B is N_s 3, 440, S 3, 260 and efficiency 51.8%, under supercavitating conditions. It was confirmed that specific speed and suction specific speed of supercavitating pumps were much higher than those of conventional axial flow pumps.

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In the present report, instability of a hydraulic driving system and a direct servosystem with a piston-type control valve is studied. The theoretical and experimental investigations are carried out on the system with underlapped valves, taking account of flow forces acting on a valve spool and the compressibility of oil in a cylinder. The results obtained are summarized as follows. (1) Oscillations occurring in the system are distinguished as two types, i.e., oscillations I and II, according to their characteristics. The oscillation I is of the type caused by the influence of the steady-state flow force acting on the valve, and the oscillation II is of the type caused by the compressibility of oil in the cylinder. (2) Both the oscillations I and II build up limit cycles. The limitation of the amplitude of the oscillation I or II is caused by the effect of the damping force acting on the valve spool, or by the effect of the valve which acts as a damping element, respectively. (3) The stability criteria of the system and some characteristics of the oscillations derived from theoretical analysis are compared with the results obtained from computations by an analog computer and experiments. Their agreement is good.

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The transient heat conduction problem in an anisotropic solid is difficult to solve analytically, and it seems most convenient to obtain the solution by numerical methods such as the finite difference method. In this paper, the following have been made clear. (1) Considering the accuracy of the solution and the stability of the finite difference equations, it is shown to be desirable to convert the anisotropic field into an isotropic one by enlarging the field along the principal axis, and then to apply the finite difference method. (2) The equation for modifying heat flux at the boundary, accompanied with the above conversion, is proposed, and the method to obtain the solution, which was reported in the former papers, is shown to be applicable to the anisotropic field. (3) The actual transient temperature change in two-dimensional multicrystalline carbon, which is regarded as orthotropic solid, agrees well with the finite difference solution by the method prescribed in this paper.

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An experimental and a theoretical study of the evaporation of a single droplet on a hot surface under the elevated ambient temperature and pressure (0∼50kg/cm²) were made in order to elucidate the evaporation phenomena of spray droplets on the walls in the combustion chambers of diesel engines. In the experimental work, the effects of ambient gas pressure, temperature and initial droplet temperature on the life time of a fuel droplet were investigated. The results show that life time curve shifts to the direction of higher plate temperature and the life time in spheroidal evaporation decreases with an increasing ambient gas pressure. Only the spheroidal evaporation is affected by the ambient gas temperature. In the analysis, different models were postulated for the film evaporation and the spheroidal evaporation, and the differential equations about the temperature and the diameter of a droplet were derived. The theoretical results show reasonable agreement with the experimental results.

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This paper describes a study of peculiar phenomena in fuel-rich oxy-acetylene detonations. The detonation wave and the accompanying soot-formation were observed by a high speed streak camera. The pressure and particle velocity changes in the expansion wave were measured and compared with theoretical predictions. The effect of an additive which is thought to accelerate the soot-formation was investigated. The following results were obtained. (1) In the fuel-rich region, fluctuations in wave velocities are observed, and the velocity switches from one theoretical value to another with the change in equivalence ratios. (2) A shock wave following the detonation is formed with the accumulation of the compression waves generated by the soot-formation. (3) The pressure and particle velocity changes in the expansion wave agree with the theory based on the assumption that the expansion wave is a centered simple wave. (4) With a small amount of benzene, fluctuations in velocities are no longer observed and the transition occurs at lower equivalence ratios.

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The paper presents the results of a study of the influence of load-difference in reciprocating stroke on lubricated wear of mild steel against hardened steel. Reciprocating friction machine used for the wear tests is designed to give differential load in reciprocating strokes. The load-difference in the strokes is expressed by the load amplitude (P₁-P₂)/2, where P₂ and P₂ are applied loads for each stroke. In the initial stage, a higher wear rate is obtained under reciprocating than under one-way friction, due to the more plastic flow of the surface. In the steady stage, the influence of load-difference is larger than that in the initial one, and the wear mechanism is explained as a phenomenon of surface fatigue by considering the relation between the load amplitude and the rate of pit formations.

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Using the two-dimensional drawing-type friction testing machine reported in the 2nd report, the experiments on aluminium sheets have been first carried out. The following have been concluded. (1) The frictional shear stress τ_f on the blank-holder surface is proportional to a real contact pressure Pr in every lubricant. This is similar to that obtained on the sheet metal drawing and the U-bending reported previously. After all it has been concluded that τ_f is not influenced by the plastic deformation but by Pr only, on the frictional surface where the apparent surface area does not increase. (2) The values of τ_f on the die surface are always larger than those on the blank-holder surface. It has been found newly that τ_f is influenced by an increase of the apparent surface area besides Pr, on the die surface. (3) Variations of τ_f on both the blank-holder and the die surface correspond consistently to variations of the appearance of the frictional surfaces. (4) Consequently, it has been concluded that the bulk plastic deformation influences mainly the frictional mechanism through an increase of apparent surface area.

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