By the conventional method of the fatigue test, the accuracy of the endurance limit cannot be estimatd. On the other hand, the statistical methods represented by the probit method, the staircase method and so on require a large number of specimens. In this report the fatigue test by staircase method with small samples is presented. The step size of the staircase method should be chosen as close to the standard deviation σ of the endurance limit as possible. When σ is unknown, the following procedure is recommended. The conventional fatigue test is performed in the range where S-log N curve can be replaced by the straight line with a slope. The experimental results are plotted on the S-log N diagram. The linear regression analysis is applied to find σ. The assumptions included in this procedure are discussed. The methods of computing the confidence interval of the mean and the lower tolerance limit of the endurance limit were investigated. The lower tolerance limit of the endurance limit is a statistical concept and the conventional term "lower limit of the endurance limit" is defined from the statistical point of view. Finally these methods were applied to some experimental examples.

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The lengths of the cracks formed by the corrosion fatigue in saline are studied on the smooth specimens or a carbon steel, and the effect or corrosion fatigue on the low temperature brittleness is discussed. The cracks occur at the early stage of the fatigue life and the cyclic rates of their propagation dl/dN depend on the true stress σ_ck repeated at the root of the crack, where k represents the notch effect of corrosion pits increasing with time. The transition temperature T_r°C of the specimens having the cracks caused by corrosion fatigue and the rate or its change with cycle ΔT_r/ΔN rise with increasins of cyclic ratio. It also rises according to the increase of square root of crack length l^1/2, having no relation to the nominal stress σ_c of the corrosion fatigue.

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The atmospheric effect on the frequency effect was studied in the high temperature fatigue of a carbon steel by using dried town gas as an inert environment. At 550°C, the fatigue strength was higher in gas than in air in the long life test under low stress levels owing to the reduction of corrosion fatigue effects by high temperature oxidation. At 400°C, the effect of gas was hardly found on fatigue strengths. Considerations were made on the frequency effect in stress τ-rupture time t curves and in plastic strain amplitude γ_p-cycles to rupture N curves. The relation of γ_pN<0.44>=K was obtained under various cyclic frequencies and various temperatures, covering a wide range of N. The value of K was larger for lower frequency than for higher frequency, the effect of frequency increasing at higher temperature. The deviation was found after long time in the air, due to corrosion fatigue by high temperature oxidation.

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A special apparatus was constructed for tests of wear on plastics, the essential part of which is a metal rod vibrating at a high freqeuncy (18.3kc). Some experiments were carried out in the range from 140 to 560 g of the force of contact and from 25 to 75 μ of the amplitude of vibration. The amount of wear can be measured at any time of the duration of experiments. Polyethylene, Nylon-6 and Poly-vinyl-chloride were tested. Effects of force, amplitude, irradiation of γ-ray and other factors upon wear are investigated. Speculation on the mechanism of wear for the results is done with help of microscopic observation on rubbing surfaces.

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In this paper, firstly, the nonlinear characteristics in the axial direction of a ball bearing are analyzed and the analytical results have been found in good agreement with the experimental ones. Secondly, the amplitudes of the steady motion at the rotational angular velocities nearly equal to the natural circular frequency of the system are analyzed. The various typical response curves calculated from the analysis are compared with those obtained from the experiments. As a result, the nonlinear vibratory phenomena caused by a ball bearing have been clarified.

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A power series method of calculating the two-dimensional flow in the boundary layer of an incompressible fluid is presented. First, a general method of series solution, which is a generalization of H. Gortler's series and retains the desirable features of his method that the first term of the series satisfies the outer flow boundary condition, is given. Then a practical method of calculation, a particular case of the general method, in which the independent variables are geometrical coordinates, is explained in detail. Coefficients of the new series are universal functions and can be expressed in terms of the known universal functions of the Blasius' series or the Gort1er's series. Thus numerical calculation of the boundary layer by the present method is easy to perform. Skin friction on a circular cylinder in the stream is calculated by the writer's series and the rapidity of convergence is examined. It gives a good approximation to the solution even when only two terms of the series are used, thus proving it suitable for the use in practical calculations.

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In the centrifugal pump impeller, the fluid flows often on a circular cone surface inclining at a small angle with the plane perpendicular to the impeller axis. In this report, the author has treated such case by applying the method of series expansion, the method of generalised displacement flow mentioned in the 2nd Report, and the method of complex velocity functions presented in the 1st Report.

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In the centrifugal pump impeller, the fluid flows often on the curved surface slightly differing from the plane perpendicular to the impeller axis. In this report, the author has treated such cases by applying the method of series expansion, the method of generalised displacement flow, and the method of complex velocity functions.

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The aim of this report is to obtain the two-dimensional performance of compressor cascade with high stagger. The results are as follows : 1) The test method to obtain two-dimensional performance of compressor cascades has been determined. 2) The tests were carried out successfully and the performances of compressor cascades were obtained for 31 combinations of the pitch chord ratio S/C=0.7, 1.0, 1.2, and the stagger angle ξ=45°, 50°, 60°, 65°to each of the camber C_lo =0.0, 0.4, 0.8, 1.2. 3) The design points were selected and the design loading limits were derived from the cascade data.

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In this paper, the author represents the drag coefficients that are necessary when we design an axial-flow compressor. These drag coefficients are based on the data of the single-stage axial-flow blower, which is applied to the measurement of total pressure distribution on the relative flow field in down-stream of the rotating blades by a special technique. From this study, the author proposes new formulas of the drag coefficients as follows : 1) Profile drag coefficient [numerical formula] (Conventional formula) 2) Secondary-flow drag coefficient [numerical formula] 3) Annulus drag coefficient [numerical formula] 4) Tip clearance drag coefficient [numerical formula]

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In this paper, the resistance of a water flow through co-axial cylinders when the inner cylinder rotates, is studied experimentally. The resistances are measured for six gap sizes (s/r₁=0.0136∼0.115, s : gap, r₁ : radius of inner cylinder) and for various combinations of axial and rotational flows. Results obtained are as follows : 1. When the axial flow is laminar, the resistance of a flow is unaffected up to a certain rotating speed (R_ωc : critical rotating Reynolds number), but beyond this speed the flow resistance increases as the R_ω increases. 2. The value of critical Taylor number R_ωc(s/r₁)^1/2 increases as the axial Reynolds number (R_e=v_ms/ν) increases up to a certain value (R_e=600), beyond this value R_ωc(s/r₁)^1/2 decreases to zero with the increase of R_e. When the axial flow is turbulent, such a critical rotating Reynolds number cannot be recognized. 3. When R_ω>10 000, the resistance coefficient of a flow λ can be expressed by λ= 0.26 R_e^-0.24 ×{1+(7/8)²(R_ω/2Re)²}^0.38 even for small R_e.

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The problem of laminar free convection, which is accompanied by vapor transfer, on a flat plate placed vertically in humid air is treated on some assumptions. By means of the successive method, the equations of motion, energy and diffusion are solved. As practical examples, calculation is carried out under the conditions where the Prandtl number is a constant, 0.72, and the Schmidt number takes three respective values, 0.5, 0.6 and 0.72. Both θ'(0) and M'(0) are approximately proportional to [numerical formula]. Where θ'(0) and M'(0) are gradients of temperature and partia1 density of vapor at the wall, respectively, C_w the density of humid air at the wall, C_vs, C_vw the partial densities of vapor at an infinite distance and at the wall, respectively.

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Recently, the development of a homogeneous reactor which uses an aqueous slurry of uranium oxide or thorium oxide as a reactor fuel or a fertile material has been desired. In this case, the fluid is not a Newtonian fluid but rather a Bingham plastic, and the heat transfer of fluid flow with internal heat generation should be analyzed. This paper presents the analytic solutions of the fully-developed heat transfer of a Bingham plastic with a uniform heat source in a laminar flow through a circular tube with uniform wall heat transfer beyond the entrance region of velocity and temperature. From the results shown in figures, it is clarified that the fluid-temperature distribution, the mixed-mean fluid temperature and Nusselt number are affected heavily both by the ratio of the yield stress to shearing stress at wall and by the wall heat transfer.

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The dust collection efficiency of a cyclone type air-cleaner as applied to a single-cylinder internal combustion engine and the effect of this air-cleaner on the volumetric efficiency of the engine were researched in a series of engine motoring tests. The test results were compared with those obtained in a series of tests by using a blower. The performances of a paper filter were also tested by the same methods. The following results were obtained : 1. The maximum values of dust collection efficiency of both air-cleaners were lower by a few percent under pulsating air flow (engine test) than under steady air flow (blower test). 2. The efficiencies of the cyclone type air-cleaner obtained in blower tests gave always lower values than those of the paper filter, in the normal range of suction air flow rate. While in the tests with engine, the cyclone gave rather higher values in high speed range. Consequently, the effect of the engine speed on the cyclone efficiency was less than on that of the paper filter. Above results were considered theoretically.

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The paper deals with a new method of measuring the scavenging efficiency in a loop-scavenged two-stroke cycle diesel engine and its assessment on a test engine. The two valves installed on the cylinder head are to be timely opened by the overhead cam shaft driven at half an engine speed, and to extract the gases of the same cycle before and after the scavenging, giving the possibility of determining either the scavenging efficiency when the engine is operated as fourstroke cycle, or the trapping efficiency when done as two-stroke cycle. The experments employing this apparatus revealed a great deal of valuable information for improving the scavenging system, and also indicated that the scavenging efficiency in a well-designed cylinder could reach over 90% at a delivery ratio of 1.3∼1.4, which does not seem to be inferior to that obtained in the uniflow scavenged system.

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A series of studies on combustion mechanism in cold start of diesel engines conducted by means of chemical analysis, flame observation, measurements of compression pressure and motoring torque are presented in this paper. For the purpose of making the cold start easy, it is generally practiced to add some amount of liquid fuel, such as gasoline, into the intake air. Then such gasoline-air mixture makes a prereaction by compression heat, which increases the compression pressure and decreases the motoring torque as well. It was clarified by the analysis of the exhaust gas that peroxide and aldehyde were produced. In the intermediate products, peroxide promotes the ignition and formaldehyde acts as an inhibitor. Addition of methane or town gas to suction air inhibits the prereaction. In a start test with ordinary injection of fuel, addition of these gases strongly inhibits the ignition of the fuel. In starting, using only the injected fuel, the combustion is supposed to be the "low temperature mode".

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The load distribution along the width of a pinion in marine propulsion gears is treated in detail, divided into cases of spur, single helical and double helical pinions meshing with a gear or two. And in each case the effect of misalignment on tooth contact caused by cutting inaccuracies and average temperature difference between the pinion and the gear is treated, where it is concluded that the misalignment affects the load distribution rather severely than the pinion slenderness or tooth stiffness.

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In order to analyze the operating characteristics of the high speed rolling bearings, it is necessary to investigate the rolling friction at high speed. But the attempts to measure the rolling friction have hitherto been confined to low rolling speed. In this paper, a new method for measuring the rolling friction at high speed is discussed and some data of high speed rolling friction obtained are reported. And then, the theory for the high speed rolling friction is deduced.

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Dynamic loads on spur gear teeth are examined by a gear testing machine and a strain gauge apparatus. The ground pinion and gear are tested at the perithery velocity 80 m/sec and below. Some teeth of the gear have normal pitch errors of about 15μ which are given on purpose. The magnitude of the dynamic load increases at the critical speed at which the meshing frequency is equal to the natural frequency of the vibratory system consisting of the pinion, the gear and the combined tooth stiffness. At a speed over the critical one, a heavy dynamic load occurs on the tooth which has a protruded error. If there is a tooth which has an indented error, the tooth tends to carry no load, and a heavy dynamic load will occur after several teeth. The calculated results, which are analysed as a vibration problem, are nearly coincident with the measured results.

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The nominal coefficient of friction between the wire rope and the sheave lining was measured by an experimental device for Koepe winding. The angle of contact is 188 degrees in the device and nearly equal to that in actual winders. In the measurement the kind of lining and coating, surface pressure and slip velocity were changed variously. Examining the relation between the nominal coefficient of friction and the rope pull, we concluded that this measured value is applicable to the designing calculation of actual winders.

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