An analytical study of the yield condition of bcc metal was carried out based on the Sachs model of polycrystalline aggregates. The yield stress ratio τ/σ of torsion to tension was calculated averaging the orientation factors among all grains. The resultant value of τ/σ was 0.57₃ for the uniform distribution of orientations, which is in good agreement with the value 0.577 obtained from von Mises' law and also with the experimental data. It turned out that the preferred orientation <110> or <100> resulting from uniaxial tension or rolling of bcc polycrystalline metals makes the value τ/σ larger than that of the uniform distribution of orientation. Discussions were made on the physical meaning of von Mises' law.

View full abstract

In this paper, the design formulas and charts indicating the relation between displacement and maximum stress values of U-shaped bellows for the case of axial loading are given, and simple and practical design formulas are derived from the design charts in the 2nd report. Also the simple design formulas and charts for C-and Ω-shaped bellows are presented. On the other hand authors' results, part of which have been already published, are compared with M. W. Kellogg's formulas which are nowadays widely employed for practical design.

View full abstract

Under the longitudinal compressive impact of steel bars, a single pulse stress wave which is most fundamental for the investigation of impact failure of materials was obtained. Making such a stress wave repeatedly pass through a cylindrical specimen of 0.04% carbon steel, we determined some experimental relations between the amplitude of stress and its duration, and residual strains measured with resistance wire strain gages bonded on the specimen. The experiments were carried out under the stress wave of which the amplitude was varied from static yield point to twice that, duration from 200 μsec to 600 μsec and the number of repetitions was less than 100. Residual strains are influenced by the amplitude of stress and its duration. The larger is the amplitude and also the longer the duration, the larger become the residual strains. They increase as the number of repetitions rises, but at certain number they increase radically. This phenomenon is due to the spread of plastic deformation from both ends of the specimen.

View full abstract

The residual deflection of large sleeved back-up rolls of a four-high cold strip-mill is dealt with in the present paper. First, effects of load sequence, shrink-fit allowance, condition at shrink-fit interface, shape of roll etc. upon the deflection as well as the mechanism of the deflection were made clear experimentally using model rolls 156 mm in diameter and 980 mm in total length. Next, residual stresses of model sleeved rolls were measured by the boring-out method. Then, with the aid of the results obtained the mechanism of the deflection was examined theoretically, and an approximate solution for the calculation of the deflection was derived. As the final stage of this study, field data on actual rolls were confirmed to which some techniques of preventing the residual deflection, found thus far in the course of basic study, had been applied.

View full abstract

In this paper the problem of self-synchronization of mechanical vibrators is treated. The influence of the initial conditions for the steady-state motion of the mechanism whereby a small roller may be kept in rotation by an oscillating motion of a hollow drum is studied by using cylindrical phase surface. Moreover, the rolling friction and viscous damping of the roller in rotation are obtained by making measurement of a definite phase relationship between the respective oscillations and the rotations. Furthermore, the stability of the motions of an automatic balancer for the equilibrating of rotating rotors is analyzed in detail and an experiment is made to verify the results of the above theory.

View full abstract

An analysis of static stiffness of a ball bearing which contains three and/or four balls is made as an extension of the former report. Though the bearing is far from being useful, it provides us with one of the most important models in examining the spring property inherent in this mechanism. All the effects due to the irregularity usually arising in the course of manufacturing and assembling are taken up for consideration, while the exciting forms of oscillation, as suggested in the former report, are actually represented by this ball bearing which is the most simple practical one. The excitation in the direction of rotor axis is motivated variously : (a) by simple force due to inner ring rotation, (b) by displacement due to rotation of inner ring and balls, (c) by parametric as a Mathieu system due to ball rotation and (d) by variable clearance due to inner ring rotation. Correspondence of exciting form to its cause was disclosed clearly by means of an approximated analytical expression. For instance, it is possible that a mounting error, e.g. an obliqueness of rings, constitutes an important origin of oscillation, especially in the direction of rotor axis, i.e. the so-called abnormal vibration.

View full abstract

The statics of granular systems of nearly spherical particles without adhesive forces was studied and a general theory applicable to many kinds of granular materials was obtained.

View full abstract

This paper makes an experimental investigation into cavitation phenomena and its damage by the magnetostrictive vibratory method. Photographs were taken with a flashlight to facilitate the observation of the phenomena, and the different reproducibilities of the results of these experiments were compared with each other in terms of the weight Ioss in the specimens made of Cu. From a consideration of the results the most suitable shape of specimen for the testing is reported.

View full abstract

In this report, the self-sustained oscillation due to the interaction between the spool motion and the oil column dynamics is studied, from the analytical and experimental view points. Here the simple valving system, in which a piston-type valve is connected to one end of a straight conduit being terminated at its upstream end by a large reservoir, is treated. And through analysis, a method of evaluating the stability of the system is derived and the frequncies of sustained oscillation are obtained by examination of a characteristic equation of the system. Furthermore the features of the sustained oscillations (limit cycles, or periodic solutions) are derived by manipulating a set of fundamental equations of the system. These theoretical results are checked by the experiments. And the phenomena are fairly clarified.

View full abstract

An experimental study has been made to determine the effect of vibration on the rate of heat transfer in natural convection from a horizontal fine wire to various fluids (air, water and ethylene glycol). Frequencies from 0 to 20 c/sec amplitudes from 0.5 to 35 mm and diameters of wire from 0.031 to 0.203 mm were employed. The effect of vibrating motion may be considered in terms of a vibrating Reynolds number R_e, based on the mean velocity of a wire. Nusselt number may be predicted by the general experimental formula N_u=0.57R_e^1/2 where, R_e is an equivalent vibrating Reynolds number defined by R_e=3.20 (G_rP_r)^1/3+R_eP_r^2/3 and P_r is Prandtl number and G_r is Grashof number. Also, three modes in heat transfer were decided by the criterion that the coefficient of heat transfer deviates 5% from the one in pure natural and forced convection. The boundaries of three modes may be controlled on the relative magnitudes of vibrating Reynolds and Grashof number and expressed by a dimensionless parameter X.

View full abstract

Heat transfer in pool boiling is much better than that in usual monophase fluid flow. It is said that its mechanism is based on turbulency of boiling bubbles. But a fine point of the mechanism is not very clear. Then author has investigated about the heat transfer in the contact area of a bubble on the heating surface, and has found that its area is the most important part in boiling heat transfer. Therefore it is now necessary to investigate the coefficient of heat transfer in pool boiling in the whole range of heating load. From this standpoint, author analyticaly investigated various mechanisms of heat transfer in pool boiling, especially in saturation, and has found that under high heat load the contact area of bubbles on the heating surface is the main part in boiling heat transfer, and that under low heat load natural convection by bubbles rising from the heating surface is so.

View full abstract

This paper is mainly concerned with explaining the mechanism of the reduction in drag of a burning fuel droplet. The research was carried out with the following results : Cylinder with a flame : (1) The drag of such a cylinder with a wake flame is about 0.8 times as small as that of a similar cylinder without a flame, and it varies proportionally to the square of the velocity of the air stream. (2) The reduction in drag measured directly is in fairly good agreement with that calculated according to the momentum theory. (3) In the range 1300<R_e<5000, this cylinder with a flame makes noise. This noise arises from the vibration of the flame. Sphere with a flame : The variations of drag with R_e are qualitatively the same as in the case of the cylinder. The drag of such a sphere with a flame is about 0.7 times as small as that of a similar sphere without a flame.

View full abstract

According to the previous investigation on a swirl chamber type diesel engine, an earlier outflow of the fuel into the cylinder brings about favorable combustion. However, there appears a flameless region in the midst of the swirl chamber when the injection nozzle is so directed as to ensure the outflow action. In this paper, a better utilization of the air of this flameless area was aimed by controlling the air motion. Through comparison of engine performance together with observations of flow pattern and flame development, the following results were obtained : In the presence of a strong air swirl, the combustion is retarded owing to a poor mixture formation. A rather weakened swirl, which is realized by a proper selection of direction of the connecting passage or by slightly obstructing the stream, causes a better fuel distribution which assists the flaming in the central part of the chamber, thus resulting in an improvement in the engine performance.

View full abstract

Some theoretical analyses and experimental investigations are performed to give a solution to the separation of tooth meshing, which is accompanied with alarming noise or occasionally abnormal noise. Tooth separation occurs at the specific speed defined by the amount of transmission error and tangential load. The more transmission errors are or the less the supplied load is, the lower the speed, at which separation occurs, may become. The largest dynamic load and the highest sound intensity level are presented immediately after the separation occurs. Noise spectra are elucidated in comparison with tooth behaviours. It is considered that an unusual subharmonic noise would be caused by abnormal meshing of every second tooth or every third tooth.

View full abstract