The authors analyzed the axial motion of a horizontal rotor supported by a ball bearing and a journal bearing. The results of analysis show that the ball bearing possesses a spring constant varying with the motion of the balls. So in some regions the motion becomes unstable and a subharmonic vibration of the order one-half may appear. Statical experiments in order to determine the stiffness of the ball bearing and dynamical experiments to measure the subharmonic vibrations of the order one-half have been carried out for two ball bearings having respectively three and six balls. The unstable regions where a subharmonic vibration appeared agreed with the analytical results. At the boundaries between the stable and the unstable regions, the subharmonic vibration and the forced vibration caused by the inclination of the groove of the inner ring composed a beat. The period and the phase of the beat agreed with the analytical results.

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In this paper, steady, forced vibrations in an unsymmetrical piecewise-linear system with one degree of freedom, whose characteristics of the restoring and damping force are composed of two distinct linear regions, are analysed by means of a new method utilizing appropriate perfect Fourier series expansion. Main features of this method consist in the following procedures : 1) Linearizing the original nonlinear equation of motion by presumedly expanding the nonlinear part of the restoring and damping force into a Fourier series with the same period as of the given exciting force. 2) Obtaining the formal solution of the thus linearized equation by deeming the above-mentioned nonlinear part as if it were an exciting force from without. This solution contains certain unknown coefficients of the Fourier expansion above assumed. 3) Determining these unknown coefficients from the conditions that the above obtained formal solution satisfies the given piecewise-linear characteristics of the system. A certain process of convergency improvement by means of series transformation may prove highly effective in this step.

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Results of analysis, by means of the Fourier series method introduced in the first report, of steady, forced vibrations in an unsymmetrical piecewise-linear system, whose characteristics are composed of two distinct linear regions in relation not only to the restoring force but also to the damping force, are compared with those of the analog-computer experiments performed for the above mentioned system with the help of the auxiliary apparatus composed of electronic limiters, a voltage comparator etc.

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By further developing the hitherto utilized dynamical model of the typical ultrasonic carving machine, we considered it as an unsymmetrical piecewise-linear system containing a solid horn as a continuous body. And by applying the analytical method introduced by the author in the 1 st report to the solving of the forced vibrations of this system, we deduced theoretically various working characteristics of the ultrasonic carving machine. Some of them explain the experimental results only qualitatively, but some do even quantitatively.

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In the present paper, the fatigue process is studied by observing the half-value breadth of the X-ray diffraction lines taken from (310) atomic plane with C₀-K_α radiation, which were obtained from the specimens of carbon steel wire, cast iron and cast steel stressed alternately in rotary bending. It is found that during the fatigue process the change of half-value breadth is directly related with the change in micro-stresses. Considering from the change of half-value breadth due to stress cycles, the authors think that the fatigue process consists of three sequent stages, namely the first stage of fatigue, secondary stage of fatigue, and tertiary stage of fatigue. At the end of the secondary stage of fatigue the half-value breadth has a constant value irrespective of the magnitude of applied stress. The relation between b/B and log n/N (b and B are the current and the initial value of half-value breadth, and n and N are the current and the ultimate number of stress cycles) is represented by a straight line irrespective of the magnitude of alternate applied stress. This relation supplies a possibility for the non-destructive prediction of the fatigue life.

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Dynamic creep and rupture tests were carried out with annealed specimens of a 0.15 percent carbon steel under the combined static and alternating stress with stress ratios (alternating stress/mean stress) of more than unity. The test temperature was 450°C. The results of the present study together with those obtained in the previous study for the stress ratios less than unity were analysed in the light of the authors'theory, which aims to relate the strength under dynamic stress to the static creep strength. The conclusion obtained is summarized as follows : 1. The forms of the dynamic creep curves are similar to those of the static creep curves even for the case of the stress ratio of more than unity. 2. The prediction of dynamic creep rupture strength from the static creep rupture data together with the fatigue data under reversed stress is established over the entire range of stress ratios from zero (static stress) to infinity (reversed stress). This is based on the idea that the damages of material under varying stress are composed both of the creep damage previously discussed and the fatigue damage caused by the dislocation oscillation under alternating stress. 3. The equivalent static stress, which was defined previously to predict the dynamic creep strength from the static creep data in the stage of transient creep, is applicable to the case of creep including the steady state component in addition to the transient component and also to the case of rupture. 4. The influence of the dislocation oscillation due to alternating stress on the dynamic creep was also discussed.

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Creep of mild steel was studied at a temperature of 450°C under unsymmetrical periodic stresses such that in a stress cycle the time under stresses higher than the mean stress was shorter than the time under stresses lower than the mean stress. It was found that in this case the mechanical equation of state in solid predicted a smaller deformation as compared with the one obtained by experiment, while it had been applicable without any appreciable error in the case of a symmetrical stress wave. It was also ascertained that the smaller the ratio of the loading time of the higher stress to that of the lower stress and the shorter the period of a stress cycle, the more the tendency was accentuated, although the lower stress affected little the total deformation under a given stress wave provided that the higher stress was constant.

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In the preceding paper, it was clarified that the deformation of mild steel subjected to an unsymmetrical stress wave could not be predicted by the mechanical equation of state in solid, which was often called the strain hardening theory, while the deformation under a symmetrical stress wave could be predicted by it. The purpose of this paper is to establish a method of predicting the deformation under unsymmetrical periodic stresses as well as the deformation under symmetrical periodic stresses. The deformation was predicted by the authors' theory of deformation, which explained the behavior of material at any instant from the viewpoint of the integrated effect of work hardening and recovery, which the material had experienced before. It is concluded that prediction by this method is considerably good in any case of rectangular stress wave.

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Elastische Hysteresis bedeutet hier die Abweichung von der ursprunglichen elastischen Geradlinie im Spannungs-Dehnungs-Diagramm. Unter Wechselbeanspruchungen einschlieΒend die Ermudungsgrenze tritt einige plastische Wechseldehnung in der Probe auf, und daraus erfolgt sogenannte elastische Hysteresisschleife. Solche plastische Wechseldehnung scheint fur den Dauerbruch des Werkstoffes eine wichtige Rolle zu spielen. Um den Mechanismus der Ermudungserscheinungen in Bezug auf die Hysteresisschleife oder diese plastische Wechseldehnung zu klaren, wurden bereits zahlreiche Untersuchungen veroffentlicht. Eine Schwierigkeit liegt aber daran, daΒ fur die Feststellung dieser sehr geringen Dehnung ein passendes FeinmeΒgerat entwickelt werden muΒ. Die hier durchgefuhrten Untersuchungen zielen auf die Entwicklung soiches FeinmeΒgerates und auch die Erklarung der einigen Verhalten der plastischen Wechseldehnung unter Wechselbeanspruchungen. Einige Betrachtungen fur die Versuchsergebnisse wurden in Bezug auf den Zusammenhang zwischen der plastischen Wechseldehnung und der Bruchlastspielzahl angestellt.

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In this paper the self-excited rolling motion occasionally seen in a vehicle suspended by air springs is treated. Analysis and discussion are made to see under what conditions this motion arises and how to design the control system of air springs so as to be able to prevent such motion. On an example of vehicles in which this motion has occurred, the amplitude and frequency of this motion are calculated.

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The frequency n of eddies generated behind a circular cylinder in fluid is expressed by the equation n=S(v/d), where v is the fluid velocity, d the diameter of circular cylinder and S Strouhal's number, which has been treated as the function of Reynold's number. Many inverstigators have experimented on the values of Strouhal's number between R₆≒3×10∼5×10⁵, but the values between. R₆≒2×10⁴∼1×10⁵ have not been obtained. The present authors have experimented on all of them between R₆≒6×10∼5×10⁵ by three devices with a high speed tunnel, a low speed tunnel and a water rotating vessel respectively and have made it clear that they take nearly a value of 0.18 between R₆=1×10⁴∼1×10⁵, suddenly increasing to 0.3∼0.6 at the point near the critical Reynold's number R_ec≒5×10⁵.

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This paper presents the results of experiments on flat-seated valves with broader seat-face, discharging water into the air under a constant head of about 194 cm. Five valves were used in all, of which the first four had diameter d smaller than seat-face diameter d₁ and the last one had d equal to d₁. When the lift of the vales with d<d₁ is gradually increased, the steam flowing out separates partially from the seat-face at a certain valve-lift, and then separates completely from the seat-face at a higher lift and becomes free jet. When the valve is closing the free jet finally clings to the seat-face at a very small valve-lift. These are represented by three special points on the characteristic curve of each valve. In case of the valve with d=d₁, there are one separating and one clinging point on the curve, just as the valves with d>d₁ on which the authors have already reported. They try to give some explanations for these phenomena hereunder.

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The essential object of this paper is to know the reasons for the conspicuous increase of the head and brake horse-power of an axial-flow pump at low flow rates. In this report, the characteristics of pump, the flows before and behind the impeller blades and the pressure distributions on the casing wall near the impeller and guide vanes were measured. The results obtained are mainly as follows : 1. When the discharge becomes less than that which begins the reverse flow on the suction side of impeller blades, the radial flow in the impeller increases suddenly, and the characteristics of pump change remarkably, too. 2. At that time, the casing wall gives an important effect upon the radial flow in the impeller and the angle between the rotational direction and the relative velocity of the fluid becomes larger than the discharge angle of runner blades near the casing on the delivery side of the impeller.

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In this paper, the flow in an axial-flow pump impeller at partial flow rates is studied by dividing it into two domains ; one is near the casing wall where the radial flow is seriously affected by the wall, another is far from it where the fluid flows along impeller blades and the effect of the wall is negligibly small. By considering about the flow in impeller blades in this way, it becomes possible to analyse an impeller action and to demonstrate the reason for the conspicuous increase of the head at partial quantities. The analytical method to find the relation between the discharge and the theoretical head is obtained. But the complexity of the flow makes it necessary to introduce some coefficients, which should be determined empirically.

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In order to obtain the data, which are necessary to find the values of coefficients introduced in the analytical solutions on the theoretical characteristics of axial flow pumps, and to find the head loss at impeller blades, the velocity and energy distributions before and behind impeller blades, the pump characteristics and the pressure distributions on the casing wall near impeller blades are measured on 9 in. vertical axial flow pumps with the impellers of several different types. The results obtained are as follows. 1. The effects of the number of vanes, vane setting and vane profil on the impeller performance are revealed. 2. The width of a clearance between the impeller tips and the casing wall has little effect on the impeller performance at low flow rates.

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In this paper, the values of some coefficients, which have been introduced in the theoretical analysis about the axial-flow pump performance shown in part 2 of this study, are determined by using the velocity distributions at the inlet and outlet from impeller blades obtained in part 3. These coefficients can be shown in comparatively simple forms, and an application of the theoretical solution to the actual problem becomes possible. In order to prove the accuracy of the theoretical solution, the flows before and behind the impeller blades and the theoretical head-flow characteristics of an axial-flow pump with impeller blades designed by the modified aerofoil theory are calculated by using these coefficients. The results coincide considerably well with the experimental ones.

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By using the experimental results shown in the previous reports, the writer treated the relation between the capacities and the theoretical heads, and discussed the effects due to the type of impeller. The results obtained are as follows : 1. The hydraulic loss in impeller blades becomes maximum at critical discharge q_c, and it has quite different tendencies before and behind q_c. 2. In the axial flow domain (capacities larger than q_c), the characteristics of an aerofoil section at the mean effective radius are derived for the mean flows at the inlet and outlet from impeller blades. It is found that the values of lift coefficients are in good agreement with the test data for the single airfoil for l/t&gne;0.8 (l : chord length, t : pitch), in spite of the change of setting angles and the number of blades. 3. In the centrifugal flow domain (capacities less than q_c), the energy losses in impeller blades can be shown fairly well in a comparatively simple form.

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In this paper, the following problems are discussed. 1. The discharge-head characteristics of an axial flow pump are analysed empirically, and the coefficients of energy losses in guide vanes, suction and delivery pipes are determined. 2. Experimental studies are performed about the circulating flows on the suction and delivery sides of impeller blades of several different types, which affect seriously the shaft horse-power performance at low flow rates. The coefficients of head loss and the velocity coefficients of the circulating flow are derived in the same relation respectively, regardless of the different types of impellers. 3. Types of an axial-flow pump impeller which should have an excellent performance at partial capacities are estimated.

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A fast response and sensitive resistance thermometer is studied which utilizes the "skineffect" and "resonance", on condition that a radio-frequency is used instead of direct-current as a power source. A fine platinum wire (0.08 mm diameter) fed with about 7 Mc r.f. current shows a character superior to the one which is obtained by the customary method with respect to the response and the sensitivity. Also this device has the advantage that it can be applied without decreasing the response and the sensitivity, even if a thick wire is used to obtain better mechanical strength. As a result, it will be useful for measuring the transient temperature change, for instance, a hot gas in the cylinders of internal combustion engines and other similar machines.

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Simple calculations on heat transfer by the theory of boundary layer in the case where free convection and laminar flow coexist at the same time in the velocity entry length of vertical double pipes with annular space heated from inner pipe are performed. In this paper, (I) the temperature distribution and velocity distribution are represented by Bessel functions, (2) f₀ (z) the temperature distribution of inner pipe wall is considered. (3) Gauss' method in the numerical integration is applied. These are very convenient in the numerical calculations for Tables of Bessel functions and Gauss' method with high accuracy can be utilized. The theoretical results coincide very well with the experimental results of water heated from the inner pipe.

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Ionization current flowing across the probe gap inserted in an engine combustion chamber is observed by means of an oscilloscope, and the effects on the current of operating conditions, type of fuel used, source voltage or resistance in the current circuit and others are studied. The current is found to be in response to the various states of combustion, and the validity of the ionization current method for indicating engine combustion processes is verified. Features distinguishing the knocking combustion are also studied in detail, and it is confirmed that the oscillation peculiar to knocking can be observed in the ionization current as well. A knockmeter of novel type which is very simple and applicable in commercial engines as well as test engines is developed, and it is ascertained to be quite satisfactory.

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To analyze the metal cutting mechanism in the transitional cutting stage after first contact between the cutting tool and the work material, the theory of pseudo-steady plastic flow was applied. Determining the relation between friction angle on tool face and cutting time by cutting test, the change of cutting mechanism during the transitional stage was analyzed theoretically. This was compared with the experimental result on lead. It was found that both theoretical and experimental results followed a similar trend.

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This investigation deals with the roughness and property of surface produced by ceramic tools in comparison with those produced by carbide tools. At first, we observed experimentally the effect of cutting conditions, tool geometries and flank wear on tools on the roughness of surfaces machined by ceramic and carbide tools. And the utililzation of the Surface Quality Meter which measures electrical contact resistance between graphite and machined surface, has revealed information concerning the effect of oxide layer on the lustre of machined surface. It is concluded from the results in this paper that in general the surface finish produced by ceramic tools is better than that produced by carbide tools.

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As the precision of balance depends largely upon the knife edge, the characteristics of the knife edge must be researched to improve the balance. Among researches on the knife edge only a few treat its precision. As the cause of the dispersions of equilibrium position was assumed either the rolling friction or the change of the location of the fulcrum caused by the roughness of the flat bearing. We assume that the dispersions are caused by the change of the stress distributions due to the roughness of the contact surface. An investigation was done. Standard deviation was calculated, and it was found that σ_△W was proportional to the breadth of surface in contact b, calculated by Hertz's formula, and found that the following relation existed, σ_△W=W/L·α·b

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For the purpose of finding radical preventive measures for the wear and damage of the geartooth surface, the present study was carried out. This paper describes some experiments with roller testing apparatus with which the frictional moment and the electrical resistance between the rollers were measured under various driving conditions of contact load P, rolling speed V_r, specific sliding S, oil viscosity η, relative radius of curvature ρ and roughness of contact surface H_max. Depending upon the dimensionless parameter ηV_r/P, the lubricating characteristics can be classified into three regions. And the empirical formula of the frictional coefficient in the region of semi-fluid lubrication is induced. The friction obtained under a sliding motion with rolling is very much larger than that under a pure rolling, and the maximum frictional coefficient is found for a comparatively small specific sliding. The relative radius of curvature and the roughness of contact surface have much influence upon the oil-film thickness.

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In this paper, a method promoting a fluid lubrication in the deep drawing of sheet metals is introduced. Possibilities of this method are proved by laboratory scale experiments on aluminium and reported. It is shown that the process brought about many encouraging results for the improvement of the drawing ratio. Some contributions are made to the practical developement of this process by clarifying fully the pressure characteristic of this method which is an important key to its success.

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The published literatures on the fatigue strength of the rolled threads have been surveyed by the author. One of the causes of the difference among the results of these investigations seems to be the thread rolling conditions. If the effect of the thread rolling conditions on the fatigue strength of the rolled threads is clarified, the rolling condition for the rolled threads of fatigue strength extremely higher than that of the cut threads may be obtained. The rolling conditions were analysed for the thread rolling processes used today. From this analysis it has been found that the rolling condition is expressed by the number of revolutions of the blank from the start to the end of rolling and the type of the rolling pressure curve. The rolling pressure curves are classified into 3 types ; namely the decreasing pressure type, the constant pressure type and the increasing pressure type. This analysis was confirmed by the experiments on the oil pressure type thread rolling machine with a special attachment.

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After the gear teeth have been separated because of the relative changes in velocity imparted to the gears by the action of the accelerating load, and have reached the position of maximum separation they will come together again with an impact. In the present paper, the dynamic loads on spur gear teeth caused by the impact phenomena are calculated theoretically. The fundamental equation of the dynamic load on teeth is the nonlinear Volterra integral equation, and the author solves this integral equation by the collocation method approximately. For the practical use, the numerical results of dynamic loads on teeth based on some assumptions are shown in the form of the design formula.

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Combustion of coal by gasification-transformation of coal into gas prior to combustion in a furnace-is an advantageous method of combustion especially for smoke-removal in cities and for utilization of low-quality coal, and can be applied for boilers, gas turbines and industrial furnaces. Gas producers for this purpose must have improved efficiencies and high capacities. Construction and test results of a continuously operating gas producer, which was test-built to verify this method, are described and it is shown that this producer can be operated at a gasification efficiency (hot gas base) 94% for a long period by employing an improved injection method of air and steam. And, experimental results and technical problems about combustion of low-quality coal by gasification method are also discussed.

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