An experimental study is made on the changes of residual stress in the rapid heat treated low carbon steel specimens under fatigue loading with special interest in the relationship between the slip bands formation observed by an optical microscope (×200 and ×400) and the fading out of residual stresses. Especially, authors take note of the magnitudes of residual stress before and after the fatal crack propagation into the martensite. Detailed microstructural observation through an optical microscope shows that at stress amplitudes below the yield stress (0.2% proof stress), when cracks are staying in the ferrite, the release of residual stresses is caused by the cumulative plastic deformation by slip bands in the retained ferrite. Then, they relieve more as the crack begins its propagation into the martensite. On the other hand, at the stress amplitudes above the yield stress a large amount of release of residual stresses could be caused by cumulative plastic deformations both in the retained ferrite and in the martensite.

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Numerical analysis of a simplified crack model has been conducted on the wedge action of the viscous fluid in the cracks subjected to the bending moment, and rotating bending fatigue tests have been carried out on carbon steel specimens in paraffin oils of high and low viscosity. The crack rate decreases when the product of the viscosity and the cycle frequency, ηf, is increased in agreement with the analysis. However, the crack rate increases when ηf is greater than about 10⁵ owing to the poor penetration of oil into the fissures. The protective effect of oil, which limits the access of oxygen to freshly created surfaces, is hardly found. Neither the effect of the viscosity nor that of the cycle frequency is observed in silicone oil. This may be due to the small pressure index and to the weaker adhesion to the crack wall of silicone oil, which is improved by activation with stearic acid.

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The Problem concerning an anisotropic hollow sphere subjected to impulsive pressure is analyzed based on the dynamic theory of elasticity. Applying Duhamel's integral to the results obtained for the pressure with step distribution in time, which are valid to predict the impact stresses on the conservative side in design of any structure or machine, the results for arbitrary impulsive pressure may be derived. The dynamic factor consisting in the concept of the factor of safety proposed by Cardullo is investigated theoretically based on the results obtained above. By using the approximate formula derived in this study, the effects of the anisotropy of the material and the thickness of the wall on the dynamic factor may be evaluated qualitatively. The result for the isotropic material is involved in the present results for a special case of elastic constants.

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In this paper, a dynamic buckling problem of elastoplastic columns axially loaded at one end by a moving rigid body is treated, and the experimental results are compared with those calculated from the theory in which a tangent modulus E_t is used both for compression and bending of the column up to the buckling load. When impact velocities of the rigid body are small, the theoretical values agree with the experimental ones. If the kinetic energy of the moving body is kept constant while its mass and velocity are varied, the results obtained from experiments and numerical calculations are as follows: In the case of low impact velocities with large masses, the column buckles more easily and the buckling load is smaller than that of high impact velocities with small masses. This difference appears distinctly when the impact velocity of the body is high but almost disappears when the impact velocity is low.

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When a hollow cylinder is compressed axially with rough plane tools, elastic-plastic deformation is disturbed by friction forces acting on the tool surfaces. This non-uniform deformation is analysed by the finite element method from elastic through partially plastic to fully plastic stages. Experimentally measured values of relative slip ratio introduced by the authors before are used as boundary conditions (namely in sticking, with no lubricant and with lubricants) instead of friction coefficient. Then, shape of bulge of inside and outside surfaces, load, distribution of pressure and of tangential stress on the contact surface between the tool and the cylinder, distribution of stress and strain, growth of plastic zones, etc. are calculated under various conditions. As the result, many new matters concerning them are made clear, for example, double bulge yields on the outside surface when h₀ (the ratio of height to outside diameter) is large, and the pressure on the contact surface decreases toward the outside when h₀ or a_r (the ratio of internal to external radius) is small but increases when h₀ or a_r is large.

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Central cracking of a brittle metal during cold-extrusion and its prevention by applying a hydrostatic back pressure are studied in relation to the fracture characteristics of the material. The fracture strain of magnesium is obtained experimentally as a function of hydrostatic component of stress. The critical back pressure to prevent cracking is obtained experimentally. The critical back pressure shows the maximum value at a certain extrusion ratio, which is dependent on die angle.

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This paper describes the critical back pressure which prevents the central cracking of a product during hydrostatic extrusion of magnesium in correlation between the experimental and analytical results. The strain and the hydrostatic component of stress at the center axis of the billet in extrusion are obtained by applying the slip line field analysis. The analytical estimation of the critical back pressure is in good coincidence with the experimental result reported previously.

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This paper deals with a vibrational problem which occurs during passage through a critical speed. An exact solution for the problem has been obtained assuming that the angular velocity of the external force increases linearly with time and the system has no damping. This solution, however, contains Fresnel integrals and these integrals prevent us from understanding characteristics of the transient vibration. In this paper, we derive approximate equations from the exact solution by using the series and the asymptotic expanssion for Fresnel integral. These approximate equations show that the transient vibration is divided into three domains of τ and also show characteristics of the amplitude, the phase angle and the angular velocity of vibration in each domain.

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Gas dynamic performance of a helium two stage shock tube which is designed for a simulator of an MHD power generator is studied theoretically and experimentally. To obtain adequate working fluids behind the shock waves, a two stage shock tube with a diameter of 130mm and a length of 13m is designed. As a buffer gas argon and helium are chosen and their effects on the performance are studied. When helium is used, the performance well agrees with the theory in which the reduction of the shock velocity in the buffer chamber is considered. Obtained shock velocity is 3800m/sec, which can produce shocked gas with 1atm. and 2000°K. This is considered to fulfil the working conditions of an MHD generator. When the tailoring interface operation is made, we can obtain uniform gases of the duration time of 2.2 msec, which is 60% of the ideal value.

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Streamwise components of turbulent velocity, microscale and velocity spectra were measured using hot wire secnsors. The experiment suggests that by additives of polymer large eddy structures in an adjacent wall region are increased and that small scale eddies are reduced. The wall regions both of a Newtonian fluid and a dilute polymer solution are studied theoretically based on Townsend's method. The analysis shows; 1) the velocity profile in the wall layer is determined by applying energy equilibrium hypothesis to an attached eddy; 2) the Toms effect is explained by a pair structure of attached eddies and an elongational viscosity of polymer solution:3) the thickness of viscous sublayer of polymer solution is determined by concentration, intrinsic viscosity, number of monomer units, relaxation time and friction velocity; and 4) the pipe friction coefficient in the saturated region of the phenomenon is predicted without experiments.

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Finite difference methods were developed to solve transient problems of nonlinear heat conduction with temperature dependent thermal properties, and the following steps were presented. (1) Finite difference equations of heat conduction and of boundary conditions were presented and the stability conditions of them were discussed. (2) The types of boundary conditions which could be treated by these finite difference equations were larified. (3) Difference equations of the explicit type were shown to be applicable to most nonlinear problems of heat conduction, and the sufficient conditions to obtain numerical solutions of required accuracies were discussed and presented. (4) Numerical results of temperature response in plastic plates were compared with experimental results and these were shown to agree with sufficient accuracies.

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The ion current to the forward stagnation region of a highly negative probe is analyzed by using the boundary-layer approximation. The ratio of the sheath thickness to the boundary-layer thickness is assumed in the range from a few tenths to 1. The effects of various parameters on the ion current are made clear. The dimensionless current-voltage characteristic which depends on the velocity profile, the ambipolar Schmidt number and the Prandtl number has been introduced. This relation is avbailable to calculate the ion number density from the measured current and applied probe potential. Numerical examples are shown for typical cases. It is shown that the ion current increases with the absolute value of the probe potential and a constant saturation current cannot be obtained.

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In this paper, the relation between the back pressure and the length of the exhaust pipe of small internal combustion engines was studied, and it was made clear that the value of the back pressure (i. e. the reading of the manometer) could be shown by a fluctuating curve of a definite pattern in accordance with the length of the exhaust pipe.

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In a diesel engine, the form of combustion chamber is considered to be important in designing a low compression ratio engine. In this paper, the optimum form of combustion chamber for the performances was found out and by using this chamber the reduction of the compression ratio approximately to 12 was attained without deterioration of performances, for example the maximum output and the specific fuel consumption. This seems to depend mainly on the increase of the degree of constant volume owing to shortened duration of combustion as the compression ratio decreases. To determine the form of combustion chamber, the air velocity into the combustion chamber with varied diameters of combustion chamber entrance was controlled and the relation between the aspect of combustion and the performances was obtained. As the air velocity increased, the degree of constant volume increased because of increased maximum rate of heat release and shortened duration of combustion and this worked effectively on the thermal efficiency, but in contrast, the cooling loss increased. Thus, this resulted in the optimum diameter of combustion chamber entrance especially at heavier load range. Besides, even when the diameter of combustion chamber entrance decreased, the throttling loss was considered to be negligible in the direct injection type engine.

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Rolling contact fatigue tests were conducted under lubricated conditions using rollers made of carbon steels and a grey cast iron having surface roughnesses ranging from 0.2 to 220μm R_max (peak-to-valley roughness) and form actors ranging from 0.6 to 0.9 Results obtained are as follows: (1) In the case of the equal hardness combination cf annealed carbon steels (160 H_B), no pitting occurred after 10⁷ rotations at a Hertzian stress of 0.71 H_B (113 kg/mm²) even when the sum of initial surface roughnesses (R_max1+R_max2) was greater than nine times the calculated oil film thickness (h<min>) based on elastohydrodynamic lubrication theory. (2) Also in the case of unequal hardness combinations, no pitting occurred on the softer rollers having an artificial V-shaped groove of 120μm in depth and a form factor of 0.9 at a Hertz Ian stress of 0.7 H_B if the surface roughness of harder roller was smaller than h_<min&gut;. (3) In the case of cast iron, many cracks arrested in the subsurface were observed in the rollers which were finished by turning and had feed marks of 0.18 mm in pitch. (4) Cast iron rollers finished by grinding or superfinishing were apt to pit rather than the ones finished by turning. This may be ascribed to the enclosement of lubricating oil at the contact band because the flaky graphite at the surface can be taken as the surface can be taken as cracks corresponding to the ones produced on the steel rollers. (5) From the author's experiments, it is estimated that in the case of materials having many inclusions and brittleness, putting cracks occur first at subsurface under a Hertzian stress smaller than the one which causes work hardening at the subsurface where the reversed shear stress is maximum.

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Contact of rough surfaces can be replaced by that between a rough surface and a rigid flat one, so that the methods of the 3rd report can be reapplied here. In this report, the factors of surface asperities (for example, slope and height of surface asperities in contact) were synthesized, and formulae for practical use on the elastic and the plastic deformation of rough surfaces in contact when the directions of surface asperities were parallel to each other were suggested. This report revealed that the variance of slope of surface asperities of surface asperities in contact is σ_θ1²+ σ_θ2², where σ_θ1², σ_θ2² are variances of slope of projections respectively. As a result, the relations between the elastic and the plastic deformations δ_E, δ_S yielded by the existence of surface asperities and the normal load are as follows. δ^^-_E=a_e{(P^^-+P^^-₀)^<0.09-P^^-₀^0.09}, δ^^-_S={P^^-+P^^-₀)^0.18-P^^-₀<0.18>} where, δ^^-_E=δ_E/σ, δ^^-_S=δ_S/σ, σ: standard deviation of surface asperity in contact, P^^-=P/Ap_m, A: nominal contact area, p_m : plastic flow pressure, a_e, a_s, P^^-₀ : constants. These constants were given in this research.

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This paper presents an analysis of the dynamic behavior of hydrostatic guideways. The linearized non-dimensional equations for the table motion and the coefficients of the equations are presented. This analysis by means of transfer functions clarifies the effects of the dimensions of the talbe and the oil feed line system, and can be applied to designing of hydrostatic guideways.

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Among spatial path-generating mechanisms some four-link mechanisms have been analyzed and synthesized. However these mechanisms have only several parameters which determine the coupler motion, and hardly generate complex motions. In order to generate complex motions, the methods of using the spatial multiple-link mechanisms which have pairs of multiple degrees of freedom and the ones which are composed of several planar mechanisms are suggested. In the present paper, the spatial motions with translations along three axes and rotations about two axes are classified. Taking such motions apart into several planar ones, a spatial multiple-link mechanism composed of the planar mechanisms which generate each planar motion is synthesized. Then making a mechanism as an example, theoretical and experimental analyses of the static and dynamic displacements are performed, and by use of these results, a dynamic synthesis is carried out.

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