In order to obtain some knowledge about the fatigue mechanism of high hardness materials, fatigue tests and microscopic observations were carried out of four kinds of induction hardened steels. It was found that a structural change took place on these specimens surfaces during the fatigue process, which was quite different from the slip as observed in ductile materials and was essentially unknown. It was established that this structural change was closely related to crack formation and the fatigue fracture of an induction hardened low carbon steel took place as a consequence of the propagation and joining up of the micro cracks induced by the structural change. In this report the mechanism of fatigue crack formation associated with the structural change is discussed by assuming that the structural change may occur as a result of carbide precipitation on the prior austenitic grain boundary, although the reason why the structural change takes place is not clear.

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There has been published a number of papers on the plastic behavior of metals under hydrostatic pressures but few investigation is reported on the elasto-plastic properties of metals, where high accuracy is required in measurements. In the conventional piston-cylinder type apparatus where the deformation of the specimen together with the hydrostatic pressure is produced by a movement of a piston, an error in stress-measurement is likely to be induced by a frictional force acting between piston and cylinder. A new apparatus using cylindrical specimens which are subjected to the internal and external pressures, has been developed in order to eliminate the error due to the frictional force. The strains and the difference in the internal and the external pressures were measured with high accuracy using wire strain gages. The effect of hydrostatic pressure up to 5 000kg/cm² has been studied on the deformation of aluminum and on the yield of low carbon steel. The strss-strain curve and the ultimate pressure of cylinders exhibited little change in aluminum but an increase in its ductility was observed. There was little change in the lower yield point of low carbon steel.

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In this report, instability to hydraulic servosystem with a piston-type control valve is studied.The investigation is carried out mainly on the system with underlapped valve. The effects of compressibility of oil on the system instability is examined, and then sustained oscillations caused by the compressibility are analyzed theoretically and experimentally. The results obtained are summarized as follows : 1. The system is completely stable under the assumption of incompressible oil flow, regardless of constant-pressure or constant-flow operation. And no sustained oscillation occurs in the system. 2. Compressibility of oil often makes the system unstable, and also sustained oscillations can occur. 3. The stability criteria of the system and some characteristics of sustained oscillations, both of which are derived by theoretical analysis, are compared with the results obtained from computations by analog computer and experiments. Their agreement is good.

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Thermal phenomena at the P-N junction of semiconductors are investigated, by experiments with Bithmus-Tellide, to verify the characteristic phenomena of semiconductors through which electric current and heat flow simultaneously. The limits of application of Onsager's reciprocal-relation to this phenomenon, the fundamental equations and the boundary conditions of the heat conduction problems of semiconductors are revealed. The effect of the above verified thermal phenomenon (Peltier effect) upon the temperature rise of P-N junctions of semiconductor devices is discussed and the characteristic value of the degree of stability of devices is obtained.

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Boiler-turbine response is of fundamental importance to optimal power distribution in modern electric network. The response is directly related to safety of plant operation during drastic load change of emergencies. For these reasons, the theoretical analyses were developed to make possible the prediction of dynamics for both Sulzer- and Benson-type boiler-turbine units. Several field tests were performed using three actual plants with Sulzer- and Benson-type boilers (The Kyushu Electric Power Co.). The analytical method proposed herein was verified by these test results.

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In the Diesel engine with an open combustion chamber, the utilization of gas motion produced in the chamber is important to improve engine performance. As the first step to finding the relation between the shape of combustion chamber and the formation process of squish, squish velocity has been measured with a velocity detector of solenoid type by motoring a model engine, and then investigated theoretically. The measured squish velocity is not much different from the ideal one calculated under the condition without any loss. Through theoretical considerations, it is confirmed that the decrease of velocity due to both the heat loss to the wall and the leakage of charged air through the piston rings is remarkable in the period after 20 deg. before t.d.c. and becomes maximum at top dead center. However, the absolute value of decrement seems to be too small to affect seriously the squish velocity.

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The present investigation evaluates the effect of the auxiliary fuel on the performances of a diesel engine by changing the shape of prechamber, and reveals the following points : (1) The maximum output of the engine with intake fuel addition rises almost to the same level independently of the prechamber types. (2) This increase of the output is caused by the improvement of overall thermal efficiency owing to rapid combustion in the main chamber, though the aspirated mixture gives no effect on the utilization of the oxygen contained in the cylinder. (3) The exhaust smoke is beneficially affected by the manifold introduction of auxiliary fuel. However, various unburned hydrocarbons can be detected in abundance.

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Gas turbine, generally, has comparatively low value of thermal efficiency and specific power, and the variations of these values are considerably large when the ambient temperature is varied. This paper is intended to present a solution to this problem by adopting a new cycle concept. To increase the temperature ratio of the cycle is one of the most effective ways to improve thermal efficiency and specific power. In this case, the low-temperature absorption-type refrigerating machine, which is operated by using the gas turbine wasted heat as a heating source to the generator, is introduced as one of the cooling devices to lower the intake air temperature to the compressor. The primary goal of our study is to investigate the general thermodynamic characteristics of this combined cycle. It has been made clear that the new cycle can achieve remarkably higher thermal efficiency and specific power thatn the gas turbine running alone. Furthermore, the cycle has a desirable merit of lessening the variation in these values, when the ambient temperature increases.

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On a heavy load high speed gear, it seems that the combination of surface pressure and high sliding velocity causes a failure of oil film which leads to a scoring. The pV formula, pVT formula and the surface temperature formula of tooth surface have been used for the determination of scoring limit. But a final formula of scoring limit hasn't been obtained. Using a four ball tester for the basic study of scoring under a pure sliding condition and an Amsler's metal abrasion tester for the study of scoring under a sliding-rolling condition, the authors examined the combined effect of the sliding velocity and sliding ratio on scoring limit. Authors obtained a general formula of surface temperature in the case of an elastic, perfectly plastic solid and compared the formula with the experimental results. Then, they obtained the following results : On a high chromium steel, when the surface temperature was raised to a constant value, a scoring took place. Therefore, it is reasonable to determine the scoring limit from the standpoint of the surface temperature.

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Bland and Ford's solution is used for calculating the roll force and torque in cold rolling of metal strip, and Sims' solution is used in hot rolling. The present paper deals with a theoretical solution which is applicable to rolling under any condition of friction, by making certain mathematical approximations to the fundamental equations derived by Orowan. This solution may be effective for explaining the rolling process in the range of mixed friction which would take place in warm rolling and hot rolling. Further the solution should be used for the cold rolling in the range of frictional coefficients larger than 0.1.

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The stability criterion for the grinding system has been analyzed by the help of frequency response method. However, this analysis shows only whether the system is stable or not in the steady state and so the experimental fact that the self-excited chatter vibration in grinding grows up gradually is not verified yet. In the present paper, it is shown first that even the system in an unstable region according to the old stability criterion is stable at the beginning of grinding until the primary waviness coincident with the chatter frequency is formed to a certain level by disturbance ; second, that the waviness growing up process revealed by translating the system from the frequency domain to the time domain can be described by a series of the rates of dynamic cutting residue ; and finally that the vibration is kept to a steady amplitude if it grows uo to the level where the regenerative effect decreases due to a non-contact of wheel with work.

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