In this paper, bars having a stringer of metal sheet in the central line, and semi-circular or V-notches on both sides are investigated photoelastically. The bars are made of epoxy resin and stringer of metal sheet (duralumin or copper), which are bonded together with Araldite 121. The bars are experimented under tension with the simple polariscope. The radii (or depths) of these notches of the bars are varied in several values. Consequently, several interesting results are obtained. And then the problem of reinforced bars having a reinforcement of different materials is studied.

View full abstract

In the present paper, the two-dimensional stress distribution in an orthogonally aeolotropic plate, bounded by two concentric circular contours, is treated by the perturbation method using the orthogonal co-ordinates, similar to that of the previous papers. Numerical examples are worked out for three kinds of material, oak, plywood and isotropic plate. The results show that considerably large stress concentration may occur in some aeolotropic plates even in the case of uniform inner pressure.

View full abstract

As to the plane stresses of orthotropic material, various studies have been worked out by many investigators, but the stresses in a plate bounded by lines asymmetric with respect to the elastic axes of the material, have been little studied yet. In this paper, some problems of this kind are treated by the use of Beltrami-Cayley's conformal mapping method. As examples, the stress distributions in (1) a semi-infinite plate, (2) an infinite plate with an elliptic hole, and (3) an elliptic plate, are calculated. The results obtained show significant differences from those in isotropic plate or in orthotropic plate with symmetrical boundary to the elastic axes of the plate.

View full abstract

In this report, the buckling problem of a simply supported triangular plate having inner angles of 30, 60 and 90 degrees under uniformly distributed compressive and shearing load is solved. In the case of uniform compression, the exact solution is obtained by combining the solutions for a simply supported rectangular plate. In the case of general loading condition, the solution is approximately obtained by the Galerkin's method. Numerical results obtained which give the buckling load are shown in graphical form and in a table.

View full abstract

In this report, the buckling problem of a simply supported equilateral triangular plate under uniformly distributed compressive and shearing load is solved by the same method as that described in the previous paper. In the case of uniform compression, the exact solution is obtained by the combined form of trigonometric functions. Further, it is shown that, though the lowest buckling load obtained here coincides with that obtained by Woinowsky-Krieger, their solution is not always correct. In the cases of general loading condition, the solution is approximately obtained by the Galerkin's method. Numerical results obtained are shown in graphical form and in a table.

View full abstract

For the purpose of finding the effect of initial out-of-roundness on the failure pressure of thin-walled cylinders whose lateral sides were subjected to uniform external pressure, failure experiments on 9 thin-walled cylinders were conducted. Those cylinders were of such dimensions that, if they were completely round, the computed values of yielding pressure would be smaller than those of elastic buckling pressure. Results were as follows : (1) The initial out-of-roundness of the machined cylinders used in the experiment need not be taken into consideration for the calculation of their failure pressures. (2) It is appropriate that the magnitudes of initial out-of-roundness of the cylinders such as the plate-worked ones are determined by a method similar to that proposed by Holt.

View full abstract

It has been noticed in the rotating bending fatigue test on 125φmm smooth surface specimens, described in part 1, that a shell pattern appeared on the fractured surface when a radical change of the stress was made on the specimen. The author has established a general relationship between stress and propagation speed of fatigue cracks from analytical studies on shapes of the shell pattern, which may be summarized as follows : 1. The shell pattern shows a definite shape, which is drawn as a family of curves depending upon arc length of th crack. 2. Assuming that the stress νσ_n (kg/mm²) on the edge line of the fractured surface was equal to the stress on a beam having a sectional shape same as that of the specimen having a reduced area by the fracture, νσ_n was computed on a number of samples of shell patterns, as a result of which it has been found that the relation between the propagation speed ν_c (μ/c) and νσ_n may be obtained from the following formula : [chemical formula] where : σ₀ is a critical value of νσ_n=11.5kg/mm². When νσ_n exceeds σ₀, the propagation of crack takes place. B is a constant depending upon the size of the specimen ; B=17 for 125φ mm specimen.

View full abstract

During alternating stressing of annealed steels in reversed bending, residual compressive stress is introduced near the surface of specimen, and its magnitude changes with the number of stress cycles. Residual stress appears from the very early period of stress repetitions, and the maximum value occurs at about 10⁵ stress cycles, thereafter it fades gradually. Residual stress was found to vanish approximately immediately before fracture. The higher the carbon content or the yield point of the steel, the larger is the residual stress produced. The change in hardness due to alternating stressing is quite similar to that in residual stress. In the case of ascending stressing, both residual stress and hardness were found to increase more than in the case of stressing at a primary stress amplitude. By numerical calculations, the contribution of residual stresses to the fatigue strength at a fixed stress amplitude was studied. On the basis of this ideal S-N curve, the role of residual stresses in the coaxing phenomenon was also made clear.

View full abstract

Mechanisms of work hardening and recovery following an abrupt change in stress were discussed on the basis of the behavior of dislocations. It was suggested that there would be a mechanism, which might act as a mechanism of recovery when the applied stress was suddenly decreased, while it might act as a mechanism of hardening when the applied stress was abruptly increased. The effect of this hardening and recovery was analytically expressed using the data of creep tests with sudden change in stress. It was shown that the behavior of mild steel after a sudden change in stress in primary or secondary stage of creep could be predicted well by the authors'theory, using the characteristic functions just and previously determined.

View full abstract

The author has found experimentally that sub-harmonic oscillations and "summed and differential harmonic"oscillations take place in a shaft system with non-linear spring characteristics and multiple degrees of freedom. In the present paper, these vibrations are treated mathematically and analytically. Conclusions arrived at may be summarized as follows : (1) The equation of response curves of sub-harmonic oscillations of order 1/2 has qualitatively the same construction as that of rectilinear vibratory system. The hard or soft spring characteristics result in response curves of both hard and soft spring types. (2) When two vibrations taking place at the critical speed of "summed and differential harmonic"oscillations are both forward or both backward precessional whirling motions, only the summed harmonic type can occur and the differential type does not take place. When "summed and differential harmonic"oscillation consists of forward and backward precessional motions, only differential type has possibility of occurrence.

View full abstract

For convenience'sake of designing the foundation and mounting of Hammer-Forging Machine, the author has introduced the vibration formulae based on impact force, in case its shape is rectangular and saw teeth. These formulae would solve the problem more accurately for actual phenomena than usual formulae which are introduced by the percussion theory on semi-rigid body. By strict consideration of physical meaning, some of these formulae are solved by conventional treatment and contain some approximate solution. But the author has found that the result of the foundation and mounting practically designed for the 1/2 ton steam hammer and 1 ton one by these formulae and the various data, reported, are more similar to actual phenomena. These formulae are considered convenient for service and also valuable for practical design.

View full abstract

In this paper, as a whole the following five items with respect to air hammer could be discussed and their necessity is proclaimed. i. Theory and numerical calculations about characteristics of the tup-motion. ii. Adequate selection of the principal speed of a crank shaft. iii. Measurement for the forging effect of an air hammer by Heim method using a test piece of lead cylinder, or by the final velocity of a single blow of tup. iv. Comparative discussion about the experimental data described in reference (2) and the theoretical analysis of the tup-motion by our study. v. Computation of the efficiency of an air hammer and the motor horse power required to drive it.

View full abstract

In this paper, it is first shown that the conception of the boundary layer, as in the case of the Newtonian fluid flow, may also be applicable to the non-Newtonian fluid flow at high Reynolds number in a wider sense R₆=(ρV^2-(1/n)L^1/n)/μ_psu^1/n(ρ : density, V : characteristic velocity, L : characteristic length, μ_psu : pseudo viscosity similar to the viscosity of Newtonian fluid, n : rheological constant) ; and the fundamental equations of motion for non-Newtonian fluid can be simplified by the approximations of the boundary layer equation. Then, the relation between the thickness of boundary layer δ and the Reynolds number R₆ can also be deduced as follows : [chemical formula] Moreover, as an example of the analytical treatment by the approximations of boundary layer equation, the flow state in the portion of inlet length of a circular pipe is also analysed by means of variational method. Thus, the respective relations between the inlet length x_l, the Hagenbach's correction ΔH of non-Newtonian flow and the rheological constant n have been found by the author's researches.

View full abstract

In the 4 th report we studied the relations between valve-lift, discharge, lifting-force and angle of issuing-jet for nine kinds of flat-seated valve, all of which discharge water freely in the air. From the experimental data thus obtained non-dimensional discharge q₀ and liftingforce p₀ are computed and expressed as functions of opening-ratio l/d₀ or diametral-ratio d/d₀, where l stands for valve-lift, d for valve-diameter and d₀ for valve-port diameter. These experimental formulae give fundamental values for discharge and lifting-force of disc valve and could be referred to as standard formulae in the research on disc valves of any kind.

View full abstract

The flow in an impeller is affected by the incidence angle. The impellers used in this experiment are of three types ; two of which have constant passage height, but one is with an inducer and another is without, and the other has a constant sectional area all the way from inlet to outlet, but without any inducer. The influence of incidence angle on the flow in the impeller has been measured by the kiel probe and the yaw-meter that rotate with the impeller. From this result, it has been recognized that the separation of the flow occurs at the triangle-area that is bounded by the trailing face of blade and the shroud. The pressure distribution on the blade face that has been measured in the experiments is compared with that of the two-dimensional theory. This theory is found to be in comparatively good agreement except for the region near the leading edges of the blades with the experimental results ; that is, the pressure on the blade face is influenced by the main flow only, and it is hardly affected by the secondary flows that complicate the flow through the impeller.

View full abstract

The present paper deals with some examinations on the kneading effect of thermoplastics by the screw extruder from a hydrodynamical point of view. Provided that the ratio between the rate of flow and drag flow K=Q/Q_d is known, the rate of shear D and its mean D in the direction of the channel depth can be determined. Consequently if the distribution of K along the screw length is known, the total amount of kneading can be guessed.

View full abstract

The present paper describes the experimental studies about the extrusion of Polyvinyl chloride, which has been conducted with a 30 mm diameter extruder. The experimental results have been treated with respect to the influence of the screw shape, its revolutions and resistance of the dies upon the kneading effects of the products.

View full abstract

Experiments were carried out on the saturated film boiling of water and sodium oleate solution, using three kinds of nichrome wire, 0.6, 0.8 and 1.0 mm in diameter and platinum wire, 0.5 mm in diameter. The bubble dynamics in stable film boiling was studied. The product of bubble diameter just leaving the vapor film and the frequecy of bubble formation takes constant value, if the radiation heat flux exceeds (1∼2) % of total heat flux, showing nearly the same numerical value as in case of nucleate boiling, but it decreases with the drop of radiation heat flux below the above-mentioned one. In other words, the behaviors of bubble generation in film boiling present different aspects according to the difference of emissivity of heating surface, even if the total heat fluxes remain the same. Though the results from the experimental values of heat transfer coefficient show fairly good agreement with Banchero's equation, the experimental points are somewhat lower than Banchero's equation below the heat flux in which the product of bubble diameter and frequency of bubble formation becomes constant. It will be, therefore, necessary to introduce a correlating equation, taking the vapor film stirring effect of generating bubbles into consideration.

View full abstract

Steam ejectors can have three basic kinds of performance characteristics according to the outside conditions of ejector-driving steam pressure, back pressure of diffuser and flow rate of entrained fluid. From the experimental studies on the flow state in ejectors, it has been shown that the three performance characteristics are closely connected with the types of the flow state, respectively, and the existing ranges of these characteristics can be simply expressed by the outside conditions of ejector. The results of experiment on the effects of the various dimensions of ejector are also presented.

View full abstract

The author has found a new theoretical way of calculating the emissivity of a gas which contains particles. The emissivity of a gas, which contains a group of particles, is calculated by the following equations. εG_a is the emissivity by the same gas when it does not contain particles. εG_a=1-e^<-(K_GLL)> εG_a'=1-e^<-(K_GLL)>'(K_GLL)'=(K_GLL) (1+γ) [chemical formula] where L is the thickness of gas layer. The particles are assumed to distribute uniformly and constitute spheres of equal diameter. A_P is the area of a sphere surface. Side planes of an imaginary cube, which corresponds to a sphere, are perfectly black and A_B is the area of a cube surface. As ΔL is the length of edge of a cube, A_B is 6 (ΔL)². (K_GΔLΔL) and (K_GLL) are factors corresponding to the thickness of gas layers ΔL and L for εG_a of a gas as in above equations. These are given by Hottel and others for non-luminous gases. The experiments by the author show that the results agree well with his theoretical analysis. The experimental results by Sherman, being analysed by author's methed, show no contradiction. The experimental formula by Lindmark and Wohlenberg are expressed as special cases of author's theory. For a gas, which contains two or more groups of particles calculation can be made by repeating the above method. From the calculation it is revealed that an emissivity of a gas, which contains a group of particles, is greater than that of a gas alone. In this case the temperature of particles is assumed to be not lower than that of a gas. The increment of emissivity is expressed by the above equations.

View full abstract

Bending rigidity of a crankcase of high speed internal combustion engines is usually smaller in the horizontal-transverse direction of the engine, because of its common hanger-bearing-type construction. For this reason, the elastic vibration appears mainly in the horizontal direction. In our research the bending deflection of a crankcase was measured under such conditions that the load was applied to the middle point of a crankcase in the horizontal-transverse direction being simply supported at the both end-bearing centres. In analysing the results of bending tests with several models of crankcase, the calculating equations for the bending deflection of a crankcase were induced from "Torsion Theory of Thin Sections"with some modifications. The results of bending tests on regular engines show that those equations are practically adequate to calculate the deflection of a crankcase.

View full abstract

The turbine roller bearings of a turbojet-engine operate under the severe condition of high speed, high temperature and heavy load. Therefore, there are many problems in practical use. The object of this experiment is to obtain the fundamental data on whether oil-mist lubrication is applicable in practical use or not. Experiments are carried out under various severe conditions of speeds, temperatures and loads. Performances by oil-mist lubrication are also compared with those by oil-jet lubrication. As the result of experiments, the rise of bearing temperature is found to be a function of rotating speed and air quantity, independent of oil quantity and load. It is understood that the air in oilmist lubrication acts an important role of cooling medium. The cooling effect by oil-mist lubrication is very large and in this point oil-mist lubrication is better than oil-jet lubrication.

View full abstract

The differential speed type thread rolling machine was invented by Yamamoto, and industrialized by Akashi. The investigations of the problems which were experienced in connection with the industrialization of this machine are summarized in this report. The first report describes the principle of this machine and the problems concerning the rolling pressure. On the differential speed type thread rolling machine, two cylindrical dies are used, their speeds being unequal. The blank is fed in the tangential direction by utilizing the speed difference. This machine is suitable for the mass production of the precision screws. The rolling pressure was measured on the industrialized machine, and the experimental values were compared with the calculated values according to Yamamoto's theory. Both values show good agreement. The method of calculating the center distance between two dies, in which the thread is formed completely and no excessive load is imposed on the machine, was established. For this purpose the deflection of the main spindle, the elastic deformation of the blank and so on were discussed.

View full abstract

In the second report the following problems of the differential speed type thread rolling machine are discussed : (1) the power required for thread rolling, (2) the axial movement of the blank during thread rolling, (3) the calculation of the outside diameter of the die. The tangential force acting on the die is the most important factor of the power required for thread rolling. Also the power consumed at the parts of the power transmission mechanism must be considered. The output of the main motor in the case where the screw thread is rolled by the differential speed type thread rolling machine was measured. The experimental values were compared with the values estimated on the basis of the rolling pressure and the tangential force. Both values show good agreement. It is desirable to make the axial movement of the blank during the thread rolling as small as possible. The amount of the axial movement of the blank on the industrialized machine was measured. The experimental values agree with the values calculated according to Yamamoto's theory. The method of calculating the outside diameter of the die, in which the amount of the axial movement of the blank is minimized and the effective working zones are uniformly distributed over the die surface, was established.

View full abstract

In this work, examining actual phenomena of wrinkling in deep drawing operations, the mechanism of prevention of wrinkling are clarified. In addition, formulas are induced theoretically to predict the critical conditions of wrinkling in both cases where a blank-holder is not used and where a blank-holder is used. As the first report, fundamentals of analytical method and results in case where a blankholder is not used are reported.

View full abstract

In this report, based on the equilibrium equation of moments induced in the first report, the critical conditions of wrinkling are considered and discussed for the case where a blankholder is used. In practice of deep drawing operation, we cannot but often allow arising of small wrinkles in a flange through various causes, but if the wave amplitude of wrinkles is lower than the allowable value, wrinkles do not practically remain in the product, since an effect of suppressing flange wrinkles exists in die radius. Thus, the allowable specific wave amplitude of flange wrinkles is deduced, and by introducing this into the equilibrium equation, a formula for prediction of the critical blank-holding pressure is induced.

View full abstract

In this report, the validity of the prediction formula is checked by experiments as much in detail as possible. Consequently, the formula has been found satisfactory to predict the critical blank-holding pressure necessary for obtaining a product in which "local wrinkles"remain. And also, it has been experimentally confirmed that the value of the allowable specific wave amplitude ω_cr to be introduced into the formula is a constant nearly equal to the specific wave amplitude of wrinkles which arise locally in the flange. To predict the critical blank-holding pressure necessary for obtaining a product in which"trace of wrinkles"remains or"no wrinkles"remain, a multiplier ω_B or ω_A should be applied to the formula instead of ω_cr.

View full abstract