A method of solution is proposed to solve the problem of the theory of elasticity for a region containing more than two spherical cavities, extending the method utilized by A. E. Green for plates with circular holes. The method consists of the simple expression of harmonic function referred to a spherical coordinate by the sequences of those referred to another spherical coordinate. The solution is based upon the Boussinesq stress-function approach, and a series solution is obtained for the problem of elasticity for a region containing more than two spherical cavities whose centres lie on a straight line. Numerical evaluations are given for the stress distributions along the boundaries of cavities when the elastic body is under a uniform tension in the direction of a centre line.

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Ever since the so-called slip theory was proposed by Batdorf and Budiansky in 1949, it has become a subject of discussion and is not yet settled which of the theories should be valid, the slip theory or the incremental strain theory. In the present paper, the characteristic shear function introduced by them is computed for the two fundamental loading processes, tension and torsion of circular tubes, and accordingly it is shown that the function assumes different values in each case, consequently that the slip theory is invalid.

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The low-temperature-quenching (L. T. Q.) is greatly effective on the improvement of the mechanical properties, especially of the fatigue strength, of steel. The effect of the L. T. Q. on the increase of the fatigue strength is more remarkable in specimens with notch than in plain ones. The reason for this is as follows : (a) The strengthening of the ferrite by strain-aging during the repeated loading must be more remarkable owing to the sharp concentrated stress at the root of notch which accelerates the strain-aging. (b) Before the formation of fatigue crack at the root of notch, there appears a region which resists the formation of fatigue cracks. In the low-temperature-quenched specimen, this region is not only expands inward more and more by repeated loading but also strengthened. (c) When a fatigue crack is once formed, the resistance against its propergation is greater in notched specimens than in plain ones.

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Hitherto, the turbine blade of about ten centimeter long has been failed sometimes due to the fatigue caused by vibration. The cause of the failure is considered by the author to be the resonant vibration of the blade system excited by pulsating steam flow passing through the nozzle group. Turbine blades strengthened by the shroud at their periphery constitute a vibration system having normal vibrations of fixed free type and also a vibration system of fixed supported type. The latter type of vibration system has (n-1) kinds of normal mode with nearly same natural frequency. These natural frequencies coincide with each other when the stiffness of shroud is negligibly small. The first order of these vibration is apt to resonate with exciting force caused by the steam flow, when the ratio of interval of nozzles to that of blades are about two. Therefore, it is more important to avoid the resonance of fixed supported type normal vibration of the system with pulsating steam force than to avoid that of fixed free type.

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The dynamic bending stress and moment of an initially curved elastic bar subjected to an axial impact by a rigid mass are analyzed approximately and the results are applied to a rod of rock drill. The analytical results are fairly well in argreement with the experimental results qualitatively as well as quantitatively. It may be said that in the drilling rod the bending stress due to inital deflection is small, but the one due to the eccentric blow is rather large as compared with the longitudinal stress, the main one. These bending stresses increase linearly with the impact velocity and initial deflection or eccentricity of the blow. They are also affected by the mass of the striking body and the slenderness ratio of the rod. The peaks of the stress distribution stand near to the ends.

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It has been micro-structurally studied why the fatigue fracture of metals appears smooth and shelly ; white or black. The study has revealed that the fatigue fracture, initially rough, becomes smooth under repeated stress ; the metal dust produced is sintered, and in the case of high-carbon steel quench-hardened, under friction heat, into a very hard material. In this process, if air enters into the crack, the color of fracture surface will turn to black owing to the influence of friction heat ; otherwise, it would be white.

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The writers of this paper carried out theoretical and experimental investigations in order to ascertain precisely how the external pressure exerted on a hoisting drum by multi-layers of rope wound around it under tension increases as the number of rope layers is increased. Experiments were performed on model drums by winding ropes under constant tension and the circumferential strains produced inside the drum shells were measured. The number of layers was increased up to eight. As far as the research extended, the experimental results coincided well with the theory of the authors. The ratio between the increase in the external pressure on the hoisting drum and the number of rope layers grew the larger as the rigidity of the drum increased and the modulus of elasticity of the rope decreased. Conversely, the smaller the rigidity of the drum and the greater the modulus the smaller was the ratio. The ratios of Mr. Waters which have generally been adopted are smaller than those of the authors and are on the dangerous for the designing of hoisting drums.

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The results are presented for the following three experiments on the upward flow of airwater mixtures in a vertical tube having an inside diameter of 51 mm. (a) Visual observation of the flow patterns. (b) Measurement of the static pressures along the tube. From these results, the volume fraction of air in the tube and the relative velocity of air were calculated. A tentative correlation is presented about the drag coefficient of the force acting between air and water owing to the relative velocity. (c) Measurement of the tube wall temperature under a constant heat rate. The flow rates include the range of 200 to 5000 kg/h for water and 0 to 45 kg/h for air. It seems that the obstacles in tubes have particular effects on the flow of air-water mixtures. Then, some experiments were also performed to make qualitatively clear the effects of obstacles inserted into the vertical tube.

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In this paper, the author experimentally investigated the pressure drop due to friction for the flow of water containing bubbles in a non-heated downcomer. First, the pressure drop due to friction and dryness fraction for the parallel downward flow of the mixtures of air and water were measured in a vertical 1500 mm long and 19 mm inside diameter glass pipe. Next, the ratios of the coefficient of friction in high pressure regions were extensively computed from the results of the above experiment. Finally, in case we used nonheated downcomer, it was proposed that we might adopt 0.03 as an approximate value of the coefficient of friction.

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The combustion process, known as Texaco Combustion Process, eliminates the knock of a conventional gasoline engine by means of the swirling air and fuel injection. Furthermore, it enables the engine power to be controlled by variation of fuel quantity without air throttling. However, the existence of the stationary flame front, which contributes for the elimination of knock, is not yet confirmed. In this paper, the slow motion pictures of flame front in a combustion chamber with air-swirl were taken through the glass window. The result of the experiment reveals that a stationary flame front exists under a certain running condition.

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At present, the operation of blowers generally involves the decrease of overall operational efficiency or else it must adopt methods which are quite uneconomical owing to installation expenses etc. Recently, however, there is greater requirement for higher pressure and speed, furthermore as the tendency to automatic operation grows greater, the development and improvement of surging prevention method for safe operation becomes strongly requested. Recently, the author has made a study on surge prevention method of "two-valve operation" blower and has been able to obtain the aforementioned objectives, although not quite thoroughly. The result of this experiment clearly shows that this operating method is more useful and effective on the following matters than any published before ; 1) energy loss for eliminating surging is small, 2) this apparatus and operation are simple, 3) this method can be controlled in high stability.

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On the hypothesis that the collection characteristics of the hydrocyclone will depend upon the design of the unit and operating conditions, performance tests were carried out at this Institute using an experimental unit. This paper gives the results of the work, including some suggestions with respect to collection efficiency. The influence of the following factors on the collection efficiency η_c was investigated : (1) Feed inlet velocity ν_i, (2) Diameter of vortex finder D_o, underflow nozzle D_u and cylindrical portion D, (3) Dimension of inlet nozzle √(bh), (4) Effective height of cyclone H_e, (5) Inserted length of vortex finder S, (6) Types of feeding, (7) Pulp density δ_f and particle size of feed slurries d. In addition to the above, the author has shown the following two theoretical formulas : (1) Critical feed inlet velocity corresponding to the maximum collection efficiency η_{c (max)} may be expressed as Eq. (4.4), and (2) Collection efficiency η_c may be expressed as Eq. (4.7).

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The flow through radial impellers is, in general, of such a complex nature that an exact solution is not obtainable, even if it is assumed that the flow to be inviscid, incompressible and irrotational so that the methods of potential theory may be employed. For a particular outward-flow impeller whose blades are of logarithmic spiral shape and of constant height, an accurate velocity distribution along the blades has been computed, under the assumption of the two-dimensional potential flow, by making use of the author's rigorous method (1)† of solving the problem. In the same case, an approximate velocity distribution is obtained following the procedures of a new method, described in detail in this paper, and it agrees fairly well with the aforementioned accurate one. Deducing out of this fact that the two results agree fairly well for the special case, it is assumed that the usefulness of the new approximate method of obtaining the velocity distribution may be extended to any radial outward-flow impeller in which the blades are of any shape and of varying heights. From thus determined approximate velocity distribution, the pressure distribution along the blades, then the torque exerted by the impeller on the fluid, and further the slip factor of the radial impeller, can be derived. The application of this approximate method for two centrifugal pump impellers and test data are presented, and the agreement of the results of the approximate method and the experiment is satisfactory.

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Author performed a series of experiments with various Kaplan turbines to study cavitation phenomena against runaway speeds under various conditions and arrived at the following conclusions : (1) There are two different types of cavitation phenomena, the 1st and the 2nd types, each with its own aspect of cavitation bubbling and runawy speed. (2) In the case of the 1st type, there occurred the identical formation of cavitation bubbles on each of all blades of a runner, while in the 2nd type, the formation of bubbles on every other blades is identical, those on two adjacent blades are not alike. (3) Occurrence of the 1st type or the 2nd type of cavitation bubbles depends upon the value of cavitation co-efficient, number and angle of blades, guide-vane opening, etc., and in many cases the increase in number of blades results in the 2nd type formation of cavitation bubbles.

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Using conformal representation, the oil flow coefficient of the pressure-fed journal bearing with an axial oil groove is calculated. Though the graphical conformal mapping by Wilcock and Rosenblatt gives merely the data for particular forms of the groove, the coefficient for any value of l/L and b/L can be obtained by this analytical method where l and b are the length and width of the groove respectively, and L is the axial length of the bearing. And also the coefficient for nearly circular hole is simply calculated.

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The gearing motion of worm gears is characterized by sliding. To obtain worm gears of high performance, therfore, it is essential to make the actual contact area large enough by finishing them precisely, and exercise special care in the design, manufacture and assembling, in order that the lubricant may pervade evenly all over the contact area. The authors tested the performance of actual worm gears by means of the Power circulating Worm gear testing machine and made it clear that the entry gap and the running-in were very important. The authors also clarified that worm gears were in action under the condition of boundary lubrication.

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