In order to investigate the probability distributions of crack initiation lives N_l under stresses near the endurance limit, S50C specimens having two small transverse holes were tested under cantilever type rotating bending stress. Through the analysis of the data the following conclusions are obtained. (1) The growth of the fatigue crack under the stresses near the endurance limit is very slow, but the crack propagates even after 10⁸ cycles, repeating acceleration and deceleration. (2) The S-N_l curve, the relation between the stress σ and the crack initiation life N_l, is thought to be composed of three H^^--, F^^-- and S^^--curves, each of which represents the S-N_l relation resulting from a different crack initiation mechanism, where H^^--curve shows the S-N_l relation at stress levels well above the endurance limit σ_W, F^^--curve appears at stress levels near σ_W, and S^^--curve at still lower stress levels. The apparent scatter of N_l under stresses near σ_W can be explained as a result of the superposition of the respective distributions around these curves.

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Environmentally enhanced fatigue crack initiation and propagation characteristics of a high strength steel have been discussed in regard to the influences of stress cycle frequency and of tempering temperature. A small amount of moisture or an aqueous environment considerably decreases the fatigue strength of the steel tempered at a temperature lower than 400°C due to the increased sensitivity to hydrogen embrittlement (HE). The co-operative action of fatigue and HE due to the occluded hydrogen results in an enhanced crack growth characteristics can be well explained by the occulusion process of hydrogen. The facet area fraction by HE increases with an increase by hydrogen content, though striation-like secondary cracking is observable on almost whole surfaces in argon. A fruitful cathodic protection can not be expected for the corrosion fatigue of a high strength steel having a high hydrogen content.

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Following the previous paper on the forced vibration problem of a cylindrical shell, the stress response is discussed when a certain point on the cylinder surface is periodically excited by a concentrated force. The principal parts of the stress response may be represented by the closed terms, and the property of their singularities may be also examined briefly. The results of some computations are presented for the behavior of stress response between certain frequency regions, in which the effect of in-plane inertia on them and their correspondence with the deformation response may be examined.

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The hydroelastic instability of an infinitely long ferromagnetic plate exposed on one side to a high velocity flow of a heavy nonconducting fluid and placed in a uniform magnetic field normal to the plate is soft linear material. The analysis is based on the small deflection plate theory, a quasistatic model of the magnetoelastic interaction and the classical linearized potential flow theory. Assuming a plate deflection in the form of traveling waves, Galerkin's method and Fourier transforms are used to derive a characteristic equation, from which both the velocities of divergence and flutter are determined for a wide range of mass ratio and magnetic field. An increase in the transverse magnetic of mass ratio and magnetic field. An increase in the transverse magnetic field is found to decrease both the velocities of divergence and flutter.

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In the present paper, a simple method is presented for measuring dynamic stresses in a bar under impact loading. This method is based on the fact that in a bar under one-dimensional axial stress, there is a singular direction along which plastic strain vanishes, and by measuring the strain in this direction, the axial stress can be obtained. According to the present method, the stress and strain of the plastic wave along a bar with uniform cross section were observed separately. A difference of the mode between the stress and strain waves was clearly observed.

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This paper discusses the problem of in-plane vibrations of a viscoelastic circular rod under the consideration of rotatory inertia and shearing deformation. A three-element viscoelastic model is adopted in the analysis, and the solution for the viscoelastic rod is obtained from the correspondence principle by applying the Laplace transform to the constitutive equation for the viscoelastic materials and the equation of motion for the elastic rod developed from the improved theory. The results obtained are compared with those for the elementary theory which are obtained by neglecting the effects of the shear and the rotatory inertia in this study.

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In this paper an oscillatory system which has two stable oscillatory modes and is disturbed by random external force is considered. In the deterministic case, the state settles to a stable point which is determined by the initial condition. If the random input is applied to this system, an interesting statistical phenomenon is seen that the state moves between both modes. For the oscillatory systems the averaging method is useful. The stochastic differential equations in regard to the amplitude and phase are obtained and the system is analyzed on the basis of them. First the behaviour of the steady state is considered. Secondly the first passage time problem, namely the time which the state takes to make transition to another stable area leaving one stable area, is discussed. The analytic results are compared with those obtained by the digital simulation.

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The conveying mechanism is analyzed considering air flow resistance and re-arrangement of the granules that is explained by frictional model. Rice, gravel and Alundum are experimentally conveyed, and the acceleration, the loci, the landing phase and the conveying velocity are measured. (1) When the granular layer slides repeatedly, granules in shearing layer change their arrangement every time sliding direction changes. The re-arrangement decreases the conveying velocity. (2) The air flow resistance accelerates the landing phase of the layer and reduces the effect of vibration.

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In this paper, control characteristics of a shaking machine under the influences of an oscillatory test structure are discussed. In addition, it is shown that the influences of the oscillatory test structure can be compensated by feeding back the relative acceleration, velocity and displacement between the shaking table and the test structure with proper gain rate. The effect of this compensation method is confirmed experimentally with a shaking machine which has a one ton table.

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An exact solution in mathematical sense for the transient response of a second order relay servomechanism is obtained. By applying the succession function method, the condition for the system to have a cycle is given and the proof that this cycle is a limit cycle is established. Based on this proof an algorithm and a chart to calculate the period and the amplitude of the cycle are constructed. Moreover, the approximate periodic solution obtained by the describing function method is also studied.

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The performance and noise level of the high specific speed airfoil fan are affected by the structural factors of its casing. Of such factors the following two are thought to produce particularly pronounced effects : (1) clearance and shape of the tongue; and (2) clearance and lap of the suction cone and mouth ring. The work presented here is a study to determine the effects of such structural factors. For experimental purposes two types of tongues were developed: a skew type slanting in the direction parallel to the vane outlet width; and a modified type having a clearance changed in the same direction as above. A series of experiments was performed in single suction type airfoil fans in which these parameters were incorporated. As a result, their effects on the performance, noise level and noise spectrum of the fan were clarified, thus enabling us to obtain useful information for fan design optimization.

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Experiments of the fluctuating force acting on a cylinder placed in the downstream of a moving cylinder with constant velocity in a uniform airstream have been carried out. At first, the case where both cylinders are stationary is treated. Our experimental results and knowledge of the flow pattern around the cylinders enable us to form an idea that the separation point shifts downstream because of the turbulence arising from the upper cylinder. Owing to this interference, the lift and drag acting on the cylinder placed in the downstream are changed. When the upper cylinder moves with constant velocity in the direction normal to the airstream, the variation of fluctuating force with time differs for various values of the velocity of the cylinder, distance between both cylinders and diameter ratio of the cylinders. Causes for these variations are explained from the results of the flow measurements around the stationary cylinders.

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Secondary flows generated in curved ducts of rectangular cross-section are experimentally investigated. The velocity gradient of the uniform inlet shear flow and the duct width are taken as parameters to investigate their influences on the distortions of the velocity distribution, of the streamline, and of the kinetic energy distribution which are due to the secondary flow. When the inlet flow is uniform excluding thin wall boundary layers, a pair of secondary vortices is seen to roll up along the inner wall. As the inlet velocity gradient increases, the secondary motion due to this shear becomes apparent and the kinetic energy of the secondary flow increases. On the other hand, as the duct becomes wider, the rated at which the inlet kinetc energy is converted into that of the secondary flow increases. A rather simple solution for the channel theory is derived and comparisons with experimental results are made.

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Flow characteristics of air-solids mixture in a horizontal pipe-line with a single or double T-branches connected vertically to a main pipe are described. The pressure losses of a single T-branches and mutual interference effects of double T-branches are obtained experimentally and the behavior of solids in a pipeline and branches is analyzed using a one dimensional flow model. The branching loss of a main pipe with a single T-branch decreases as the solid loading ratio increases, and for double T-branches the upward branch has greater influence on the branching loss of the downward one far downstream that the case with air flow alone. When particles are decelerated in the flow direction, a distance necessary to reach the steady velocity is fare longer than when accelerated. Some attempts are made to explain the experimental results with a theoretical analysis.

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It is often experienced that a flow in practical pipe lines becomes a turbulent one under extraordinary low Reynolds number. In order to make clear the phenomena a flow in a circular pipe with a protrusion is examined by measuring fluid friction as a function of Reynolds number and by observing a streak line in it. And it is obviously concluded that a laminar flow through a circular straight pipe is locally disturbed by a protrusion set in the pipe and that Reynolds number when the turbulence begins is constant if the diameter and dimension and shape of the protrusion are determined, that is, a quasi-critical Reynolds number is effectively defined. And the relation between dimension and shape of a protrusion and the quasi-critical Reynolds number is investigated.

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In the mathematical model described in this paper, the following friction components are considered: (1) friction torque proportional to operating pressure, (2) viscous friction torque proportional to rotational speed and viscosity of fluid and (3) constant friction torque independent of operating conditions. The friction component which is proportional to operating pressure decreases with an increase of the rotational speed. This effect is also considered in this model. Therefore this mode can represent the whole torque performance from start to maximum speed.

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It is considered that transfer, control and measurement of molten metals by MHD devices are very important for automation in casting and metallurgical industries. From such a practical standpoint, investigations on MHD channel flows of liquid metals seem to be fully significant in engineering. However the experimental investigations on the unsteady MHD channel flows are few. This report deals with the experimental investigation on the transient flow of mercury in a rectangular channel. A constant magnetic field or constant magnetic and electric fields are suddenly applied in the direction perpendicular to the flow, being initially hydrodynamic, and the created electromagnetic effects modify the motion to give rise to a magnetohydrodynamically developed flow. Then the applied fields are suddenly removed from the magnetohydrodynamically developed flow. It is shown that the flow undergoes oscillations during the transition from hydrodynamic to magnetohydrodynamic conditions or from magnetohydrodynamic to hydrodynamic ones and that the time required for the transient flow to reach the steady state is longer in the region of transitional flow.

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In this report, the phenomena on an oil column separation resulting from a sudden decrease of the pressure or a flow at the end of various pipeline systems are reported. The main contents are as follows: (1) The theoretical solutions for the occurrence limits of the column separation are derived. Agreement between the calculated values and the experimental ones is good. (2) The photographs of cavities formed by the column separation are taken, and the cavity behaviours are explained. (3) The pressure surge resulting from a collapse of the cavity also is recorded.

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Nucleate and transition boiling within a space gap made by holding a ll-mm dia. glass disc in coaxial position above a heated ll-mm dia. horizontal, upward-facing copper disc has been studied experimentally for saturated water at atmospheric pressure. The distance between the glass disc and the heated surface s is changed within a range from s=∞ to s=0.1 mm, and high-speed photography is employed to record the behavior of liquid and vapor within the narrow space. It is clarified in the present study that, following the change of s, characteristic variations appear in the state of boiling, in the form of supply of liquid to the heated surface, and in the occurrence of burnout, respectively.

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Static and dynamic characteristics of pressure drop in supercritical pressure boilers were studied. In this paper, experimental results of static pressure drop of CO₂ at supercritical and relatively high subcritical pressures in a heated test tube were presented, and effects of various factors such as flow rate, heat flux, inlet temperature, and pressure were discussed. The calculated results by numerical integration using the friction coefficient of single phase flow agreed with the experimental results. The experimental results were well correlated by the dimensionless expression of pressure drop previously reported. This means that the results obtained by this CO₂ experiment will be also applicable to the case of working fluid of H₂O. Mean friction coefficients of supercritical fluid in the whole tube length were shown and an empirical equation of the coefficient for the heat flux was proposed.

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This paper presents a theoretical analysis of a hybrid plain journal bearing with many capillary-restrictors for high speed and heavy load. When solving the Reynolds equation for the bearing, a difficulty arises in prescribing the boundary condition at the feeding position, where the flow of a fluid is very complicated. In order to remove the difficulty, a row of the feeding holes is replaced by a band source distributed continuously in the circumferential direction, and the restricting effect is simply expressed by constructing flow models in the vicinity of a restrictor. Using these replacement and expression, the boundary condition is given in simple form to make the analysis easy. From the obtained solutions, the statics characteristics such as the load carrying capacity, the journal-center locus and the flow rate, and the dynamic ones such as the spring and damping coefficients and the whirl instability are clarified.

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Plane strain wedge indentation of the surface of a semi-infinite porous material with a non-workhardening matrix is analysed, using an approximate method based on the slip line field theory for porous materials in consideration of the change in density during deformation. Studies are made of the influences of the wedge angle, the initial density and the yield stress of the porous material on the indentation pressure, the change in density and the mean effective strain in the plastically deforming region.

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