In general, fatigue cracks of metallic materials are initiated at the surface defects such as inclusions, fine flaws, slip bands in individual grains and grain boundaries, and the final failure is caused through the propagation process of these cracks under subsequent cyclic loading. By introducing the probabilistic distribution of the surface defects, the fatigue life distribution of the metallic materials is theoretically derived in this study. Theoretical results obtained here are in good agreement with the trends of the experimental results on the fatigue life distributions in a wide range of the applied stresses.

View full abstract

The plane stress problem of an infinite plate with a circular hole containing a rigid disk under uniaxial tension or compression is numerically solved. Effect of friction on the contact surface between the hole and the disk is considered. A general form of a stress function expressed in the polar coordinates is used and unknown coefficients of the stress function are adjusted successively so that the stress function satisfies boundary conditions. Distributions of stresses and displacements around the hole are shown in figures. Effects of friction on the distributions are discussed.

View full abstract

Contact stresses in two elastic slabs and a sandwiched solid-metal flat gasket are studied to discuss the sealing behabior of the gasket. Assuming that the gasket is an elastic body, the three dimensional theory of elasticity is used to analyse the contact stresses and the deformations in the case where both sides of three laminated plates are compressed axisymmetrically under a local uniform pressure. By neglecting shearing stresses on the contact surfaces, an exact solution satisfying the remaining boundary conditions is obtained. Numerical calculations are carried out for various rigidities and thicknesses of the plates and the loading conditions. In order to investigate the usefulness of the theoretical analysis, the contact stress is measured experimentally by using pressure-sensitive pins attached to a circular plate. It is confirmed that the theoretical results agree well with the experimental ones.

View full abstract

When a circular rigid punch is pressed aslant to the surface of an elastic half-space, a portion of the punch separates from the surface of the half-space and the contact region varies with the depth of the indentation. Such a partial contact problem has not been analyzed theoretically until now. In the present paper, we show a method of numerical analysis for the above partial contact problem and obtain the contact area, the surface displacements and the contact pressure. Moreover, we make sure that the numerical results are coincident with the experimental ones with respect to the contact area and the surface displacements.

View full abstract

Expanding the methods of both an orthotropic plate and a multilayered isotropic plate, the authors propose a new method to measure principal residual stresses in a multilayered anisotropic plate laminated of plural orthotropic plates. The principal residual stresses are derived from Volterra's integral equations. Thin layers are successively removed from a front surface of a laminated anisotropic plate and the resultant strain in the back surface of the remaining plate is measured with strain gauges ; and then the principal residual stresses are calculated numerically as the solutions of the integral equations. The method is also applicable to multilayered anisotropic plates laminated of orthotropic plates of special elastic constants.

View full abstract

The former X-ray methods of residual stress distribution measurement in a plate is to measure the surface stress by X-ray on one surface, removed surface or nonremoved one, after successive thin layer removal from one surface. The authors propose in this paper new methods to obtain the residual stress distribution in a plate from the surface stresses measured by X-ray on both surfaces during the single surface removal or the both surface removal and show an example of the new methods applied to a quenched and tempered alloy steel plate of SKS 5.

View full abstract

Effects of the wake behind a cylindrical stay upon internal flows and performances of rectangular cross-sectional diffusers were examined. When a stay of a moderate diameter is set at an appropriate position in the passage, the flow separation is controlled effectively. This seems to be mainly attributable to the blockage effect of the stay, the displacement effect of the wake flow and the increment of the turbulent energy. As the result, the performance of the diffuser with a fairly large divergent angle is improved. The flow pattern and pressure recovery are also discussed theoretically in this paper.

View full abstract

Experimental investigations on the effect of boundary layer suction for a circular cylinder with a two-dimensional slit placed along a diameter have been carried out. Flow characteristics around the cylinder for cases of intermittent boundary layer suction (Pattern I), alternate boundary layer suction and blowing (Pattern II) and transition regions were clarified. Particularly, the mechanism of the boundary layer suction, fluid flows in the slit and rear surface of the cylinder and the mechanism of the vortex formation in the wake were clarified.

View full abstract

A free oscillating flow of a viscous fluid in a U-shaped tube is considered. For the case of laminar flow, an analytical representation for wall shear stress T_w which includes an acceleration term is adopted and the momentum integral equation is solved analytically. By comparing the present results with previous theoretical and experimental ones, it becomes evident that the solution obtained here agrees well with those of Biery and Yasukawa, et al., and that the solutions derived from any other approximate representations for wall shear stress are attributted to a special case of the present one. For the flow in which transition from laminar to turbulent occurs, the turbulent quasi-steady representation for T_w is used and the momentum integral equation is numerically solved by means of Runge-Kutta method. The agreement between the present numerical and experimental results is fairly good. Further, the limits between laminar, transitional, and turbulent regions are determined on the basis of the present experiments.

View full abstract

The phenomena of air penetration into the fabric coverings over a cylinder placed in a uniform cross flow have been examined theoretically and experimentally. It is found that the air penetrating from upstream side of fabric mostly flows downstream through a thin layer between the fabric and the cylinder, which is called a 'contact layer'. This thin contact layer is more permeable than the bulk of fabric because of the surface fuzz. The fluid-dynamical property of this layer is described by a characteristic number α^*, which is determined for each condition of fitting the material for the cylinder : 0.75 for the felt close around the cylinder, 0.25 for the felt stuck with adhesive tape, and 0.0 for the elastic bandage stuck with paste. The penetration flow is shown to be a function of α^*, dynamic pressure of incident flow, and intrinsic properties of the material (thickness and permeability).

View full abstract

Two dimensional free convective heat transfer within a parallelogram shaped enclosure has been investigated. Numerical calculations are carried out under the condition chat the infinite number of enclosures of the same shape are piled up vertically and every parting plate has no thickness. Parameter values are : Prandtle number 0.72, aspect ratios 0.25 to 2, oblique angles -π/3 to π/3 and Rayleigh numbers 1 to about 10⁶. Heat transfer coefficients on the hot wall are measured for air under the condition that 5 enclosures of the same shape are piled up vertically and very thin films are used for the parting plates. Experimental results are compared with numerical ones.

View full abstract

As the previous report has indicated, the main cause of the disagreement between calculated and experimental values is the effect of the radiation. In this report, the effect of the radiation on the convective heat transfer is investigated numerically. The same physical situation as the 2nd report is used for the calculation. Calculations are carried out by using the conditions of the experiments of the 2nd report and results are closely coincident with the experimental values. Calculations are also performed for aspect ratios 0.5 and 1, oblique angle π/3, distance between the hot and cold walls 0.01 to 0.04 m. The effects of the radiation on the convective heat transfer and the radiative heat transfer rate are made clear.

View full abstract

In order to measure the thermal diffusivity and thermal conductivity of a cylindrical or hollow cylindrical solid sample, the Laplace transform method is developed. In the general principle, a cylindrical sample is tightly enclosed in a hollow cylindrical sample and the temperature responses are detected at four sites in both samples which are heated from the periphery or central part. The principal systems for measuring the thermal diffusivity of cylindrical, hollow cylindrical and infinitely large samples are shown. The practical systems for simultaneous measurement are also shown. The method is examined by a numerical test and the measuring errors are evaluated. The respective test section and test appratus used in the thermal diffusivity measurement on stainless steel bar and simultaneous measurement on alumina and solidified-molten salt are shown.

View full abstract

This paper is concerned with an investigation of free vibrations of a truncated conical shell by means of the improved theory of shells. The equations of vibration and the boundary conditions are in general forms developed from stationary conditions of Lagrangian of a conical shell. These equations are solved in the conical shell with linearly varied thickness along axis add the effects of boundary conditions, number of nodal generators, thickness and semi-vertex angle on frequencies are discussed.

View full abstract

We have considered from a point of view of the control engineering how the pressure wave propagates with a strain under the influence of the relative position of a cylindrical choke in pneumatic conduit systems. We have treated the pneumatic conduit systems as a lossless fluid line. When the position or a cylindrical choke locates on both sides also at the center of the conduit systems, the transfer function of the systems is expressed in the first type, that is, G(s)=1/(A cosh Ts+Bsinh Ts) and when the position locates at a distance of 1/4 or 3/4 from the in-put-end, the transfer function of the systems is expressed in the second type, that is, G(s)=1/{A cosn Ts+B(sinh Ts±sinhT/2s)}. As B is a function of the position of the choke in the conduit systems, the transfer function of the first type explains well the experimental results, also the case of an arbitrary position of the choke. Finally, we have shown that the shape of the pressure wave is obtained easily by a graphical method, that is, the figure of the reflection or transmission of the wave to the cylindrical choke.

View full abstract

An externally pressurized gas-lubricated thrust bearing with surface-restriction compensation is analyzed theoretically for the hydrodynamic bearing characteristics such as the dynamic stiffness and the damping coefficient applying two kinds of gas flow models ; one considers an equivalent recessed thrust bearing neglecting the circumferential flow in the bearing clearance, and the other takes into account the effect of the circumferential flow by a simple evaluation of it. The theoretical results are discussed by comparing with the experimental ones. The design criterion of the bearing with the surface-restriction compensation is also discussed from the results of theoretical calculations.

View full abstract

The lubricating mechanism of a crosshead-pin bearing in a two-stroke cycle diesel engine has been analyzed theoretically and some influencing factors on the bearing performance have been investigated. The calculation method in the present work has been compared with a simplified calculation method suggested by Wakuri. As a result, the following conclusions are obtained. (1) In the clearance bearing, the peak pressure of oil-film in the central pad is very high but those in the other pads are too low to carry the load. (2) A bearing composed of pads which have a large ratio of the oscillating angle to the oil groove pitch angle loses the hydrodynamic load carrying capacity. (3) The maximum value of the oil-film pressure decreases with an increase of the oil viscosity, though its influence is comparatively small. (4) The fitted bearing is suitable for the crosshead-pin bearing since the oil-film pressures are uniform throughout all pads. (5) Wakuri's simplified calculation method overestimates the load carrying capacity.

View full abstract

Plastic gears are used when steel gears have problems in noise and lubrication. But as there are not actual result data on plastic gears, the plastic gears are little used. when nylon gears were run for power transmission an abrasion a deformation of tooth form and a life were investigated. In this investigation, changes in noise and transmission efficiency have been investigated when the tooth form of nylon gear is deformed in the course of running.

View full abstract

Measurements of the gear noise and the dynamic load acting on the meshing teeth of the gears with profile modification and without profile modification which are shifted by different amounts of addendum modification were carried out using power-circulating gear test rigs until a surface failure caused by scoring was observed. According to the experimental results of the gear noise and the dynamic load it is clear that the dynamic load acting on the meshing teeth decreases due to profile modification and that the gear noise of the gears with profile modification is lower about 5 dB than that of the gears without tooth profile modification. Further, the sound pressure levels at all the pass frequencies, the mesh frequency and the 2nd harmonic of the mesh frequency of the gears decrease at the incipient stage of scoring.

View full abstract