Rotating bending and torsional fatigue tests of plain and notched steel specimens with electropolished surfaces were carried out. The main results obtained are as follows. (1) The maximum shear stresses in the crack initiation limit of torsional fatigue are determined only by the stress gradient X independently of the notch depth as in the case of bending fatigue. (2) When the values of X are equal, the maximum shear stress in the crack initiation limit of torsional fatigue is about 1.2 times that of bending fatigue. (3) The surface states of notch roots after 10⁷ cycles of the limit stress for crack initiation in torsional fatigue are similar to each other irrespective of the maximum stress repeated on the notch root, as in the case of bending fatigue. The fatigue damages at the crack initiation limit under torsional stresses are severer than the ones under bending stresses. (4) The mechanism of non-propagation of a crack in torsional notched specimens is different from that in bending notched specimens.

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In the present paper, erosion tests are carried out by vibrating a disc at the free end of a magnetostrictive oscillator close to the surface of sintered metals in water or in oil. The damages are due to fatigue by the collapse pressure of cavitation bubbles under a thick liquid film and due to fatigue by the surface shearing of a squeezed film under a thin liquid film. The thickness of liquid film showing the maximum value of the weight loss which is due to cavitation erosion, is larger on the sintered metal of higher porosity, because the porous surface of the sintered metal is easily filled with cavitation bubbles. The resistance to the erosion damages of sintered iron is lower than that of mild steel, and increases with smaller porosity, being proportional to the square of Brinell hardness. The resistance to the erosion damage of sintered copper-lead alloy of low porosity is considerably higher than that of lining copper-lead alloy. The fall-off particles of the former are very small compared with those of the latter. The resistance of high porosity alloy is also higher than that of the lining alloy when the film thickness is small.

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Using the Lagrangian denoted in the previous paper, we have investigated the vibration of a cylindrical shell with built-in-free ends except the axisymmetric vibration. From the minimum conditions of the Lagrangian which is a quadratic form of the unknown boundary values, we show how to obtain the frequency equations and the relations of the boundary values. The frequencies of the two cylindrical shells with radius-thickness ratios of 0.2887×10³ are obtained. The experiments are carried out and their results are compared with the theoretical ones. The vibration of a cylindrical shell which resembles that of a bar with built-in-free ends is also shown and compard with the vibration of the bar and that of the shell in other modes.

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In this investigation experimental studies on the acoustic resonance are undertaken. In the first place the effect of the pitch of tubes on Strouhal number or the nondimensional acoustic resonance frequency is studied in a wind tunnel test using many model banks. According to the result the Strouhal number increases with a decreasing pitch of tubes. In the second place a two-dimensional model basin test is undertaken and putting together the theory on the single tube in a flow previously reported and the observation result on the model basin test, a self-iduced vibration theory for the acoustic resonance is proposed.

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The expression of the root locus by a self-conjugate equation is newly proposed as an analytical reprsentation of the root locus. The equation of the tangent at any point on the root locus is expressed in the simplest form by a self-conjugate equation. Thus both the condition for the breakaway point and the characteristic of the tangent at the breakaway point are made clear. Also the equation of the asymptote of the root locus is determined in a more detailed form than ever.

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The characteristics of the finite low-aspect-ratio wing in uniform shear flow is analized on the basis of the assumption that the disturbance velocities are small in comparison with the undisturbed flow velocity and that the width of the wing increases gradually in the chordwise direction. This assumption is analogous to that in the Jones' theory for the low-aspect-ratio wing in uniform potential flow. As the result, it is found that the aerodynamic forces acting on the wing are strongly influenced by the velocity gradient of the free shear flow; when the zero-velocity point of the free shear flow comes infinitely closer to the wing tip, the total lift and total drag coefficients become about 20 percent smaller than the values of the wing in uniform potential flow. If the free stream velocity gradient tends to zero (uniform velocity distribution), the present theory agrees perfectly with the Jones' one.

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In this paper, the flow mechanism of the steady bathtub vortex was studied by measuring velocity distributions on the free surface, and the critical depth of air-entrainment was discussed analytically and experimentally. On the other hand, the velocity distribution in the water tank was not measured in this experiment, so that a theoretical study was performed to know the flow there. The obtained results are mainly as follows : (1) The velocity distribution on the free surface was made clear. (2) To know the decline of peripheral velocity component due to viscosity, the parameter α was introduced, and its value was determined. (3) The critical depth for the origin of air-entraining vortex was given. (4) The flow in a viscous core was analysed and the effect of Reynolds number N on the velocity distribution was made clear.

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Pure natural heat convection fields in the entrance region of a heated vertical circular tube, in which the temperature and velocity profiles were developing simultaneously, were solved by a numerical method of finite difference. And then the characteristics of heat transfer were obtained. The analysis presented here was based on the assumption that the inlet velocity profile is uniform. It was verified analytically and numerically that, for the case of uniform wall temperature, the inlet velocity U₁ has an asymptotic value 1/8 as the tube length approaches infinity. As for the case of uniform heat flux at the wall, U₁ is directly proportional to √(L/p)_r over the range L>L_e, where L_e is the entrance length. The relationship between the dimensionless pipe length L and dimensionless suction velocity U₁ was also obtained, using P_r=0.72, for both the wall conditios. In the case that the pipe length is semi-infinite and the wall temperature is uniform, a relationship between P_r and thermal, as well as hydrodynamic, entrance length was obtained for P_r=0.01, 0.1, 0.72, 1.0, 10 and 100, and some interesting irregularities of developing velocity profiles were also observed except for the case P_r=1.0.

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As a clue to elucidating the combustion process in diesel engines, the burning characteristics of a fuel drop in heated and pressurized air stream was studied experimentally. Its pressure was varied from 0.4 to 16 ata, its temperature, from the room temperature to 600°C, and its velocity, up to the transition velocity where the flame shape changes from envelope type to wake type. The fuel drops were simulated by porous spheres transpired liquid fuel. As the fuel, methanol, n-butanol and kerosene were used. Under these conditions, the flame shape, the burning rate m, and the flame transition air velocity U_c were measured. Among the results of measurement, main ones concerning the influence of temperature and pressure are as follows. When the temperature is raised, U_c rapidly icnraeses, but m scarcely changes. When the pressure is raised with the velocity, m increases remarkably. And when the temperature and the pressure are raised, flame becomes long and the soot formation increases.

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A few empirical formulas describing the burning rate of a fuel drop have been published already. But their validity is restricted to the case of atmospheric pressure. Regarding the quantities which provide the flame shape, no attempt has been made to formulate them. In this report, the empirical formulas for the burning rate and the flame shape were derived respectively under the theoretical consideration. The derivation was carried out as follows. After finding out the dimensionless factors governing the phenomena by applying the law of similitude to the fundamental equations and boundary conditions, the functional relations between them were determined by using the experimental results of the 1st Report. Thus, the empirical formulas common to fuels of three kinds used were obtained. In addition, it was confirmed by comparing with the experimental results that these formulas would be available to the extent of fine droplet (∼100 microns in diameter).

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When the relative velocity between air stream and burning fuel droplet is raised, the flame shape changes suddenly from an envelope type to a wake type and the burning rate decreases remarkably at a specified velocity U_c. In this report, the experimental data on this flame transition air velocity, which were shown in the 1st Report, are summarized into a formula under the theoretical consideration. Although a few interpretations on the mechanism of flame transition have been proposed, they do not explain the experimental results so well. So the authors assume that the transition occurs when the rate of heat lost to the surroundings exceeds the rate of heat generated by chemical reaction in a region of frontal surface of flame. Under this assumption, the critical condition for transition is described quantitatively. Combining the governing factors, which are found from this condition, the empirical formula for U_c is set up such as to satisfy the experimental results.

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In the present paper, using a glow plug for a starting aid in the swirl chamber diesel engine, the authors observed the state of ignition at the starting by means of high-speed photography in order to determine the function of glow plug and to gain a key to its uses. As the result, the phenomena on starting with glow plug are able to be classified into the following three types, that is, (1) Ignition is mainly due to glow plug temperature. (2) First firing is dependent upon both glow plug and compressed air temperature. (3) Compressed air temperature most affects starting behavior.

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An experiment was made to study the relations of the air distributions to the combustion chamber performances and the combustion processes in a high intensity combustion chamber. The box-type combustion chamber used in the experiment can supply the primary-, the secondary- and the tertiary-air flow separately with desired rate. The combustion efficiencies, the flow patterns, the lean blow-off limits, the pressure losses adn the temperature distributions in the combustion chamber were emasured for various air distributions and liner-swirler combinations, and it was found that these factors depended on each air distribution and liner-swirler combination. According to the main result of the experiment, if the information on the primary combustion zone, for example, the air-fuel ratio in it and the length of the recirculation zone, are obtained, it is possible to explain the combustion chamber performances and the combustion processes in the combustion chamber reasonably.

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For leadscrews used on machine tools or length measuring instruments, requirement of grinding after hardening is increasing. Therefore, ground leadscrews of a higher pitch accuracy are required. Taking into account that one of the causes of pitch error in thread grinding is thermal deformation in the workpiece screw and the grinding machine, it is desirable that the pitch error compensation be performed according to the grinding condition of the workpiece screw. The purpose of this study is to improve the pitch accuracy of ground leadscrews by using the compensation of a numerical control system. The method is as follows : Initially thread grinding without compensation is performed. On the basis of the pitch error obtained in this case, a tape for compensation is punched, and a second thread grinding is performed with the operation of the numerically controlled compensation device. As the result of an experiment, in a ground leadscrew of 1m in thread length the accumulated pitch error in the whole length was reduced to about 5 μ by using this device.

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The purpose of this paper is to verify how the behavior of work-softening with a Pb-Sn alloy affects the cutting mechanism, applying experimental methods on the basis of slip line solutions. Also experiments are performed on conventional orthogonal cutting and in addition, on cutting with the chip-pulling technique and by high rake tools or by a double rake tool. As one of the results, it is considered that the free surface boundary condition for slip line solutions is fulfilled in the smooth cutting by using high rake tools, under the experimental conditions. The experimental results are applicable to the high speed cutting, when work-softening is expected to contribute to teh cutting mechanism.

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The surface roughness of metals finished by turning has been treated as a problem determined geometrically by the geometry of cutting tools composed of a nose radius and end- and side-cutting-edge angles and the rate of feed. It has also been regarded as being affected adversely by such factors as a build-up edge, the boundary wear at the end-cutting-edge and vibration in the system of the tool and work being machined. It is commonly known, however, that the surface roughness of low carbon steel depends on the depth of cut and the side-cutting-edge angle when it is machined by a cutting tool of a small nose radius. Another factor may have to be introduced to account for this phenomenon. In this paper, microphotographs of that part of work being machined from which chips are separated at the end-cutting-edge of a cutting tool were observed to examine the effect of the condition of chip separation on the surface roughness. It is expounded that the above-mentioned phenomenon can be accounted for by a new factor based on the chip formation mechanism which has an adverse effect on the surface roughness ; the factor being divided into four elements : (1) burrs on the work being machined at the end-cutting-edge of a tool, (2) burns on chips at the end-cutting-edge, (3) fluctuations of feed force and (4) the secondary contact between chips and the surface which has been just machined.

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This paper deals with the problem of the business management of workers using the control chart of flicker value. We define the range of flicker value for a day or two consecutive days. This measure is to reduce the personal difference of flicker value. The control chart of the quality control is modified to be suitable for the business management. This method is applied to the control of bus drivers in working hours. Then it is made clear that the range of flicker value of worker decreases as worker's years of experience increase and factors which disturb the controlled condition can be found from this chart. It is possible to carry out the business management numerically by this method.

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