A new rotating bending fatigue testing machine which operates in a perfectly resonant condition under a new principle has been devised and constructed. The specimen is subjected to a rotating bending stress by the inertia force of an eccentric mass forcibly rotated, although the specimen is fixed to the frame of the machine and can't rotate. The amplitude of the vibration can be arbitrarily varied from zero to a maximum by the movable drive shaft which is especially devised, so that the starting of the test and the regulation of the amplitude are easy and exact. when the driving speed attains the resonance point, the motion of the inertia mass becomes exactly circular. Some fatigue tests were carried out on smooth and notched specimens, and the machine proved to be satisfactory in operation.

View full abstract

The fatigue strength of expansion joints of pressure vessels under the axial load is studied. The fatigue tests in the elastic and plastic ranges are carried out by the fatigue testing machine designed for this purpose and the experimental data are treated by the Mises equivalent stress calculated from an elastic shell theory. The results are compared with the fatigue strength of test pieces made of the same material as the expansion joints and the method for prediction of fatigue life of expansion joints is discussed. The formula for estimation of life of 18-8 stainless steel expansion joints is proposed and compared with Kellogg's which is commonly used nowadays.

View full abstract

The deflection of various shaped plates for which it is difficult to obtain the analytic solution is measured by an optical interference method. Several examples of application of the above analogy to thermal stress problems are illustrated, utilizing the analogy between the problems of the bending stresses in clamped plates and those of plane thermoelasticity.

View full abstract

The photoelastic stress-freezing and slicing method is applied to determine the stress distributions in a cylindrical pressure vessel with a flush type nozzle, under internal pressure. The nozzle is attached perpendicularly to the vessel. Test models made of an epoxy resin are fabricated by casting so as to make the nozzle and the main cylinder one body, using molds of curing silicone-rubber which are reinforced by this iron pipes. The experiment is performed on different sizes of the nozzle and various dimensions of the fillet radius on the outside surface at the junction between the nozzle and the main cylinder. The stress distributions along the outside and inside surfaces of the models are given in the region of the junction. Effects of nozzle sizes and fillet radii on the stress concentration are discussed in some detail.

View full abstract

Formerly, the photo-rheological stress analysis was applied for finding stress distributions in the roll and strip specimens in strip rolling. In the strip rolling, however, a method in which the strip is subjected to front tension with rolling torque has been applied for improving the process. In the present paper, the photo-rheological stress analysis is applied to analyse the effect of front tension on the stress distribution in the roll and strip specimens. As the result of analysis, the effect of front tension on the rolling appeared as follows: 1) on the roll specimen, the stress components in the specimen and the normal pressure on the contact surface decrease considerably with increase of the front tension. 2) on the strip specimen, though the effect of front tension does not appear so remarkably as in the roll, the residual stress after rolling fairly decreases with increase of the front tension.

View full abstract

The vibrational problem which occurs during passage through a critical speed has been investigated with regard to the maximum deflection of shaft. In this paper, we shall study the vibrational characteristics, such as the deflection of a shaft, the angular velocity of whirling motion and the phase angle between the unbalance and the whirling motion, under a uniform angular acceleration over the wide range of angular velocity of a shaft. From the numerical solutions and the experiments on a simple system with one disk, it is clarified that the amplitude of the whirling motion causes a beat after running through the critical speed and in case of acceleration the maximum (minimum) amplitude of beat occurs when the angular velocity of the whirling motion becomes maximum (minimum) and that the phase angle becomes nπ+π/2 radians when the angular velocity of whirling is equal to the angular frequency corresponding to the critical speed of the system.

View full abstract

Lateral vibration of a rotating shaft system with a rotating anisotropy is discussed in the present paper. Let the rotating speed of the shaft, the angular velocity of the anisotropy, the natural frequency of the system and the frequency of an external periodic force acting on the system be ω, λω, p and ω₀ respectively. A resonant phenomenon arises when ω₀≒2λω-p as well as when ω₀≒p in such a vibratory system. It can be concluded that forced vibration with the frequency ω₀ or ω'₀(=2λω-ω₀) arises when ω₀≒p or ω₀=p^^-(=2λω-p). Furthermore, a certain vibration the cause of which is relatively hard to under stand can be defined physically by referring to the above conclusion.

View full abstract

Pontryagin's maximum principle is only applicable when right hand side functions in a differential equation of a controlled system and an integrand in criterion function as well as their partial derivatives with respect to x are all continuous for both x and u. The optimal control problem in which any above condition is not satisfied is called a problem with discontinuity. In this case the state space is divided by boundary into some regions in which the maximum principle is applicable. In this paper one approach to find out the optimal control law for the problem is discussed. That is, d optimal backward time trajectories are sought in a whole state space by solving one after another the newly established optimal problem with the maximum principle for each region. Usually, costate vector experiences a jump at the discontinuity point but in our method it arises as the result of the solution and any account for jump condition is not required. The mechanism of jump, however, is also examined in this paper.

View full abstract

The effect of the tip clearance on the aerodynamic force is investigated theoretically about wings in an inviscid, incompressible, uniform flow. The present investigation is carried out by extending Bollay's analysis which was made along the lines suggested by Prandtl. From the author's experiments it is shown that Bollay's simplifying assumptions are also applied to the wing with the tip clearance. The assumptions are as follows: (1) the vortex strength is constant across the span, (2) the downwash along the span is constant and equal to the value at the center of the span. Bollay's method for evaluating integrals, however, can not be applied to calculate the induced velocities due to the vortex system formed by mirror images of the wing. The author makes clear successfully those integrals and obtains the force acting on the wing. The agreement in a force perpendicular to the wing surface between the present theory and the author's experiment for the wing of aspect ratio 1.43 is good for a small tip clearance and fair for a large one.

View full abstract

Many techniques have been developed for the visualization of fluid flows. Dye, smoke, A1 powder and tuft have been often used to visualize flow patter. But, each technique is intended for its qualitative use and not supposed to yield quantitative information. Especially, in case of high speed, transient and separated flows, they can provide no information. A new technique called "Hydrogen bubble method" provides very fine bubbles in the water flow as a tracer. These bubbles can thus illustrate the pattern of the water flows in considerable detail. In this paper, the uncertainty of the hydrogen bubble method by buoyancy, wakes and absorption is examined. This method can be used successfully to give a flow profile for the range up to the velocity 6m/sec. Finally, flow profiles for a transverse plate fin are presented as an illustration.

View full abstract

Some types of axial piston pumps and motors are equipped with an intermittent oil lubrication system for the sliding surfaces of cylinder block and distributor. Most of this system feeds pressurized oil to the outer side of the distributor intermittently and is an automatic regulating system tactfully utilizing the hydrostatic bearing in which the load capacity varies with the variation in oil film thickness and sharing the support of the load with the pressure distribution produced on the inner circumfential surface, maintains an approximate uniform oil film thickness on the sliding surface. Results of the analysis may be summarized as follows: (1) The characteristics of pumps and motors adopting the intermittent lubrication system can be grasped by considering the mean value of the equilibrium force, and the optimum oil film thickness and resistance coefficient of the throttle groove can be calculated. (2) Optimum oil film thickness varies with the size and operating condition of the pumps and motors. It is about (15-17)10^-4cm for a displacement equivalent to 100 cm³/rev.

View full abstract

Radial force of a centrifugal pump was measured, using a pump which had a device for measuring the radial force and a volute casing with an interchangeable tongue. The authors obtained some knowledge about the following items and discussed them: (1) The effect of the cross-sectional area and shape of volute tongue on the pump characteristic and radial force. (2) The characteristic of dynamic component of radial force. (3) The effect of cavitation on the radial force.

View full abstract

This paper deals with the relation between the operational ability of workers and the work load shown by the flicker value measurement. The subjects are assigned to operate a simulator of the motor-man's platform of the automobile under working conditions, in which subjects are obliged to watch one, two or three vigilance objects. The flicker value and the frequency of missing objects are measured in working hours and analysed by the statistical multivariate method. It is made clear that the work load of a subject increases as the number of objects increases. And the subject who directs his attention to a certain vigilance object can direct also his attention to other objects and his operational ability is very high but his work load is very heavy. Further the work load on the subject, whose operational ability to all vigilance objects is medium, is lightest. Therefore, it is possible to select workers who are fit for work by these results.

View full abstract

An investigation was carried out on a new technique of powder metallurgy which could produce an aluminium alloy competitive with SAP (Sintered Aluminium Products) produced at high temperature. Apparent density and hardness of the extruded material increased with increasing back pressure to reach constant maximum values. The effect of temperature on ductility is very small especially in the range from 300°C to 500°C. Tensile strength and hardness at elevated temperatures up to 500°C are significantly higher in the present extruded material than in conventional aluminium alloys. These mechanical properties are very similar to those of SAP, which leads to the conclusion that a dispersion strengthened aluminium alloy can be obtained even at room temperature. The estimated pressure during extrusion processes showed a good approximation to the condition required for pressure bonding of pure aluminium.

View full abstract