In succession to previous dynamical analysis, numerical calculations for static stresses around cavities in an infinite medium under uniform tension, were carried out by means of the integral equation method, and especially for multiply connected domains, usefulness of this technique was made clear. And further, interference effects of auxiliary holes for reducing the stress concentration around a given central circular hole in a uni-axially loaded infinite medium were systematically analyzed using the integral equation method, that is, the optimisations were carried out to determine the optimum sizes and locations for auxiliary holes for a given central hole, and the results were compared with photoelastic results.

View full abstract

The stress problems have been treated already for the case of the infinite elastic plane with a circular inclusion, which is subjected to a concentrated force or a uniform tension. In the present paper, the author analyzes the stresses for the cases of a uniformly distributed load acting on the infinite plane with a circular inclusion or on this circular inclusion. The solutions of this problem are composed of the terms in closed forms and the Fourier series, but the stress components are managed to be nearly presented with the values in closed forms by making the values of the series less than those in closed forms.

View full abstract

Crack energy density is a parameter which was proposed as one of the most important fracture parameters by one of the authors and enables us to make a unified smooth description of fracture mechanics from linear to non-linear problems. In this paper, the crack energy density concept is extended to an arbitrary direction except self-similar direction, the relations between the newly defined parameter ε_φ and well-known fracture parameters ( J_φ -integral, stress intensity factor) are obtained, and the availability of ε_φ as fracture criterion to mixed mode crack problems is demonstrated. It is also shown that crack energy density becomes equal to energy release rate in case of elastic problems, therefore, it can be said that the energy release rate to non-self-similar crack growth which has not been solved yet is given by the expression of ε_φ in terms of stress intensity factors obtained.

View full abstract

In designing a bolted joint, it is important to discuss the sealing performance and to estimate the force ratio, that is the ratio of an increment of bolt axial force to a load. Up to now, in order to improve the sealing performance raised faces of interface have been used. But the uses of these interfaces depend on experiences and the theoretical grounds are not clear. In the present paper, in the case of T-flanges having raised faces the sealing performance is analyzed by two dimensional theory of elasticity and point matching method. Then, the force ratio is analyzed. Moreover, with the application of the load a bending moment is produced in bolts and the stress is caused by this bending moment. The bending moment is also analyzed. In order to verify these analyses experiments are carried out. Analytical results are in a fairly good agreement with experimental ones.

View full abstract

Cause of flecking occurring on the surface of Cu electro-plating subjected to cyclic stress was investigated. It was known that two types of flecks occur, one caused by slip bands and the other by chemical change on the surface, and the number of flecks caused by slip bands is much more than that of ones by chemical change. Relation between the rate of increase in the density of grown grains generated in the plating layer and the number of cyclic stressings was also investigated. This relation is expressed by the same equation as the one between the rate of recrystallization of the cold-rolled pure copper and the heating time. Therefore, it is presumed that the mechanisms of grain growth and recrystallization may be identical. And it was also clarified that the relation between the density of grown grains, r, and the cycles of stress, N, is expressed by the equation, r=l-exp(-BN⁴), approximately.

View full abstract

The numerical analysis on the motion of the capsules are surveyed for the condition that the same capsules of 20kg in mass are pneumatically transported at a constant loading time interval in a horizontal and straight pipeline of 0.2m I.D. and 500m length under a constant inlet pressure. The results show that the mean capsule velocity is decreased a decreased loading cycle and that when there is air leakage through the clearance between the capsule and the pipe wall the capsule velocity is also decreased but the transport becomes smooth.

View full abstract

The velocity distribution and pressure drop in a spiral tube with three-shaped groove tube walls, were experimentally studied over the range from laminar to turbulent flow. From the results of flow visualization and velocity distribution, it was proved that fluids near the tube wall in the laminar flow range, flow in accordance with the groove, and the mixing effect of turbulent flow range is caused by the swirling flow in the tube. The equation of the friction factor for the laminar flow range which agrees well with the experimental values, was obtained by a approximate analysis. For the turbulent flow range, it was experimentally obtained by considering the effects of the groove depth and pitch of the spiral tube on the pressure drop.

View full abstract

An evaluation method for the dynamic pressure caused by steam condensation in such a large scale system as a BWR pressure suppression system has been developed. The pressure field obtained analytically in the pool has been coupled with that obtained in the vent pipes supposing the sources at the vent pipe exits. Both pressure fields in the vent pipes and in the pool are excited by applying the sources of impulsive nature to the vent pipe exits. The full scale test results performed at Japan Atomic Energy Research Institute have been simulated by the proposed method and agreement between experimental and calculated results is good. The so called multi-vent effects for the resultant dynamic pressure have been examined and the reduction effects for the dynamic pressure have been clarified. The dynamic pressure decreases in inverse proportion to an increase in the pool surface area.

View full abstract

Effects of a yaw angle on the vortex shedding frequency from a fixed circular cylinder were examined using a wind tunnel. Then, oscillations of an elastically supported cylinder whose motion was confined normal to its axis and the flow were investigated. The cosine law was confirmed to be applicable to the larger value of Reynolds number and/or the yaw angle for the vortex shedding frequency fro ma fixed cylinder. For an elastically supported cylinder a purely translational mode oscillation was observed at a low velocity. However, a rotaional mode oscillation was often superposed for higher velocities. The frequencies of these two modes of an oscillation were equal to their natural frequencies f_nz and f_nθ irrespective of the vortex shedding frequency f_vm. The translation mode oscillation had two resonance peaks at f<vm>/f_nz=1 and 2.6, whereas the rotation mode had only one peak at f_vm/f_nθ=2.8. A yaw angle made the vortex shedding irregular, making the resonance phenomena unclear for both the translation and the rotation modes.

View full abstract

The present report describes a measurement technique for the determination of bubble size distribution in a bubbly flow. Electrical proves with two electrodes A and B located at a distance d₁ in the flow direction, or at right angles to the flow direction are used to detect the void signal A ∩ B when both electrodes A and B touch a bubble. The measurement is carried out in the case of air bubbles being ejected from void generators made of sintered metal element with multi-nozzles. The result shows that the bubble size distribution and mean bubble size data agree well with the data obtained by a photographic method.

View full abstract

The Chebyshev polynomial expansion of the source function is presented to analyze the combined conductive and radiative heat transfer in an optically thick porous body. Better agreement between the theory and the experiment is shown concerning the temperature profiles and the heat transfer characteristics of cordierite porous bodies. This analytical method is also applied to the examination of the Rosseland approximation to radiative transfer in an isotropically scattering medium, and consequently it is revealed that the Rosseland approximation is valid in the range of optical thicknesses greater than 200. Moreover, it is suggested that in the case of ceramic porous bodies possessing a three-dimensional netted structure an increase in the equivalent extinction coefficient and a decrease in the tortousity-discontinuity factor are much conducive to improvement of their thermal performance as thermal insulators.

View full abstract

Two dimensional free convection and radiation in parallelogram shaped enclosures which are piled up infinitely, have been studied. in the computation, the thickness of the parting plates and the heat conduction in them are taken into account. The nondimensional thickness of the parting plates ranges from 5×10^-3 to 0.5, the nondimensional conductivity of the parting plate ranges from 1 to 500, the aspect ratios of the enclosure are 0.5 to 1, and the oblique angle of the parting plate is ω/3. In addition, using several kinds of parting plates of different thicknesses and different conductivities, the heat transfer by the convection was measured. The results are compared with the computations.

View full abstract

A special experimental system in which a surface of stationary molten tin is cooled by flowing water is employed, and the trigger mechanism of vapor explosion is investigated by measuring the transient tin temperature and by observing the aspects of phenomena with cinecamera. Tests are repeated varying water temperature as well as initial tin temperature over a wide range. In the cooling process of molten tin, four characteristic tin temperatures are detected which are associated with four peculiar phenomena: splashing, quenching, swelling and vapor explosion. The vapor explosion takes place only when the tin temperature is in the range limited from upper side by the so-called quench temperature and from lower side by the spontaneous nucleation temperature of water. From these results, some of the characteristics of small-scale vapor explosion in a previous paper can be explained well.

View full abstract

To study HC-NO_x type photochemical air pollution, a simple advection model in which polluted air was enclosed in boxes at uniform concentrations and transported in one direction was proposed. Changes in pollutant concentration at any arbitrarily selected points along the advection trajectory path were obtained from the calculation using this model. The calculated results were compared with the environmental survey results to clarify the significance of the model. The concentration changes in pollutants during a day were found to well conform to the representative pollutant concentration changes in the actual environment, verifying the usefulness of the suggested method in studying pollution-influencing factors. Based on the calculation experiments, seven factors considered useful in explaining the pollution episodes in the environment were pointed out. The influence of these factors, especially, the influence on the ozone concentration change along the advection path was clarified through comparison with the environmental pollution conditions.

View full abstract

The stoichiometry of methylnitrite formation in exhaust gases issued from a methanol fueled 4-stroke cycle S.I. engine was investigated. A part of exhaust gas was sampled and introduced into a reactor tube kept at a temperature ranging 20-200°C. Changes in unburned methanol, NO, NO₂ and methylnitrite concentrations were measured. With an increasing reacting time, methylnitrite increased in both NO_x and O₂ rich sample gases. The amount of increase in the concentration of methylnitrite was found to be close to the amount of decrease in the concentration of methanol for any reactor conditions. These observations suggest that methylnitrite is formed by the reaction between unburned methanol and nitrogen dioxide with the same moles of each. Furthermore, in the case of diluting the sampled gas by air to one fifth and one hundredth, a considerable formation of methylnitrite was also observed.

View full abstract

The fully-developed flow of an incompressible fluid through curved pipes with elliptic cross sections is investigated analytically and experimentally. The velocity profile of the primary flow and the flow pattern of the secondary flow are determined by numerical analysis. Also, studies are conducted on the effect of the shape of the cross section upon the friction coefficient which is necessary for the industrial engineering. The experimental results on the pressure drop are compared with the analytical results. An approximate expression for the friction coefficient, taking into account the effect of the aspect ratio and the helical tube pitch, is derived on the basis of the analytical and experimental results.

View full abstract

Studies have been made to compare and discuss the analytical solutions obtained by the method of characteristics with the experimental results on the water hammer. The measurements have been carried out using a 1/6 scale model of the primary coolant system of the experimental fast breeder reactor "JOYO" belonging to the Power Reactor and Nuclear Fuel Development Corporation. The water hammer has been taken place at flow velocities 0.5 and 1.0 m/s, caused by closing slowly the flow control clap valve in the time ranges 4.5∼9.6 seconds and 4.6∼11.2 seconds respectively. Qualitative agreement was found between the analytical and experimental results. And the calculation gave the safety value at the peak pressure. Therefore the calculation models and idea used in this paper have sufficient practical value.

View full abstract

In order to clarify fundamental aspects of the optimum valve operation to suppress pressure rises in waterhammer, two typical ploblems are studied for a single pipe line system without energy loss. One is closing a valve to minimize the maximum pressure in a specified valve closing time, and another is minimizing the valve closing time for a specified maximum pressure. The problems are solved by a graphical method based on the characteristics theory. From the results of the above two problems, the optimum valve movements and simple stepwise relations between valve closing time and the maximum pressure are derived. In addition the solution is improved for a similar problem proposed by Streeter, that is one of valve stroking.

View full abstract

The restoring force of an elastic shaft supported by ball bearings has nonlinear spring characteristics. In such a rotating shaft system, various kinds of forces due to the unbalance of a rotor, irregularity of balls, and so on, work and consequently combination tones occur. In this paper, we shall discuss the characteristics of all kinds of combination tones experimentally and theoretically. Especially, with attention to nonlinear components represented by polar coordinates, the possibility of occurrence and the shapes of resonance curves are investigated.

View full abstract

A method of calculating the natural frequencies of the axial vibrations of steam turbine blades and thick disks is presented, and the natural frequencies of blades are calculated and compared with the measured values. It is found that the difference between the calculated and measured values is within 10 per cent. The natural frequencies become higher at about 30 per cent depending on the defaults of the rotary inertia and the shear deformation. The effect of rotary inertia is small, while that of shear deformation is large. The relationship between the number of nodal diameters and natural frequencies is made clear by calculation.

View full abstract

We studied on the mechanisms of the generation of the wheel/rail noise and its transmission to the vehicle in high speed operation on an almost straight track like that of SHINKANSEN. Tests were carried out on the SHINKANSEN test track and the results were examined by narrow band frequency analysis. It was concluded that the contribution of the noise due to the vibration of a wheel and a bogie frame to the train noise is small, their damping is not effective and the internal noise is mostly due to the contribution of the air-borne noise transmitted through the floor.

View full abstract

Synchronization between visual information and auditory information plays an important part in smoothly exchanging information in man-machine interface. In this paper, as a fundamental study on the correlation between visual information and auditory information, sensory evaluation of foot-step (electronic sound signal) together with human walking animation image computer-produced by means of the analysis by synthesis method is selected as an object to be studied, and the image-sound synchronization is evaluated quantitatively. Furthermore, in order to grasp the internal state of the subjects, ECG (electrocardiogram) is measured, and the relation between ECG variability and results of sensory evaluation is discussed. Consequently, it is made clear that ECG (variance of R-R interval (cardiac cycle)) is useful as one of the indices for the working control.

View full abstract

A self-excited vibration induced in an externally pressurized, recessed-type gas bearing is applicable to a pneumatic vibrator. An orifice and a chamber connected to a recess produce a self-excited vibration describing a limit cycle, the amplitude and frequency of which vary with the area of the orifice and the volume of the chamber. In this paper, it is proposed, utilizing such a phenomenon, to provide the recess with an orifice of variable area and a chamber of variable volume as a powerful method to control the amplitude and frequency of the vibration, in addition to the conventional method of changing the supply pressure and the load, and the controlling ability of the proposed method is discussed theoretically and experimentally.

View full abstract

This paper presents a study on the influence of a centrifugal force on the performance characteristics of thermo-hydrodynamic turbulent thrust bearings. By applying a lubrication equation and an energy equation considering the combined effects of turbulence, centrifugal force and temperature rise in the film to plane inclined, sector shaped thrust bearings, the performance characteristics such as the film pressure, the minimum film thickness and the load carrying capacity are evaluated. The analysis shows that the centrifugal force affects significantly the film pressure and the load carrying capacity but insignificantly the friction torque and the temperature rise. The analytical results are compared with the experimental ones measured on the thrust bearing of 150 mm diameter with four sector shaped pads lubricated with spindle oil and water. The analytical results agree well with the experimental ones.

View full abstract

In recent years, the reinforced plastics (GFRP, CFRP and others) are used in a wide field of manufacturing industry. With an increase of the demand for such composite materials, the need to drill these products is increasing rapidly. This paper deals with drilling of GFRP and CFRP, using high speed steel (SKH9) and cemented carbode (KOl. PlO and ultra-fine grain) drills. Comparison of four drills is done by investigating tool wear pattern, flank wear width and cutting forces. A new type of tool wear which should be referred to as "combing wear" was found in drilling of CFRP. In addition, it was found that KOl has the highest wear resistance, FG shows the second highest and the wear of high speed steel drill is remarkably larger than that of carbide drills.

View full abstract

The present paper deals with the infiltration length of molten aluminum to a continuous glass fiber bundle for various squeeze conditions. The results show that the infiltrated length is proportional to the squeeze pressure, increases exponentially with an increase in the fiber temperature and does not depend on the ram speed. The empirical infiltration length was in good agreement with the calculated one, based on Darcy's law and a newly proposed infiltration model : molten aluminum infiltrates through the gap accompanied with the formation of a solidified layer on the fiber surface, and finally stops to solidify immediately when the heat quantity of the molten aluminum front is balanced to the released heat to fiber ahead of the front. Thus, a method to predict the infiltrated length for the practical squeeze casting is proposed.

View full abstract

This paper deals with the backward stability of a truck crane the carrier of which is supported by outriggers during crane working. Assuming the carrier to be supported elastically by four outriggers on the ground and the carrier frame to be deformed elastically, the behaviour of the truck crane overturning in the backward direction while in the unloaded condition has been theoretically analyzed. Further, an equation of motion of one degree of freedom has been made for a simplified model of the truck crane, and an approximate solution has been obtained. Thus the minimum acceptable backward stability of a truck crane can be easily determined for any carrier dimension and specification.

View full abstract

In this paper, the nonlinear torsional vibrations of a rotating shaft system having a disk and a magnet coupling consisting of rare-earth magnets are investigated analytically. The driver of the magnet coupling is excited by sinusoidal motion, and the disk is subjected to constant load torque. The transmission torque of the magnet coupling is represented by a sine function of relative angle between the driver and the follower. The governing partial equations are solved by the harmonic balance method. Besides the harmonic vibration, the one-second order and the one-third order subharmonic vibrations are obtained. Numerical calculations are carried out by the Newton-Rapson method, and the influences of the load torque on the nonlinear torsional vibrations are investigated.

View full abstract

In a self-excited vibration system with the restoring force expressed as the product of a non-linear function of deflection and a periodically variable coefficient, parametric resonances and subharmonic vibrations occur. In the present paper the influence of cubic non-linearity which is considered to induce subharmonic vibrations on such a system is investigated in detail. Approximate solutions of a system with the non-linear restoring force expressed as a cubic function are determined by the previously reported method. Consideration of that system without a self-excitation suggests the occurrence regions of a subharmonic resonance of order 1/2 and parametric resonances of first and second orders. In some numerical examples conforming to the suggestion, the system dealt with in the previous report is also considered in detail.

View full abstract

We developed a dynamic model for curving of four axle rail vehicles with conventional two axle bogies, and derived equations of their motion. Then some digital simulations were made to obtain time history of rail-wheel vertical and lateral forces during curving. In the case of an ordinary truck, it is shown that it runs on curved tracks with its outer wheel of the front axle slipping between the flange and the rail, as is well known. However, slipless curving is achieved by a proper selection of parameters. This simulation was also applied to those cases where dynamic coupler forces were applied, and there was a lateral rail irregularity.

View full abstract

Assuming that both a periodic exciting force (e.g., due to an unbalancing force) and a constant force (e.g., due to gravity) are acting on a nonlinear vibrating system, the 1/2-th subharmonic vibrations of the system with a hard Duffing type characteristic are investigated by making use of an averaging procedure. Furthermore, it is shown that the 1/2-th subharmonic oscillations can take place in the same system, even if there is only a periodic force as the driving force. Analytical results are compared with the results obtained by numerical integration from the same system, carried out by the Runge-Kutta-Gill method. As a result, it appears that the present theory gives relatively satisfactory results in calculating these vibrations.

View full abstract

The authors propose 'Multiple Component Mode Synthesis Method' for analyzing the vibration of complex mechanical structures. This method is carried out as follows. A structure is divided into some first divided components. Each first divided component is subdivided into some second divided ones. Repeating this process n times, the structure is divided into n-th divided components at last. The natural mode of each (n-1)-th divide component is analyzed using the natural modes of the n-th divided ones by the technique of the ordinary component mode synthesis method. Next, the natural modes of each (n-2)-th divided component is analyzed with the natural modes of the (n-1)-th divided ones. After repeating this process, the vibration of a total structure is analyzed. By the present method, a structure can be analyzed with less memory size of computer than either the ordinary component mode synthesis method or the finite element method. As a numerical example a plate is analyzed by the present method and the results are compared with those by experiment and by the finite element method.

View full abstract

The authors proposed a component mod synthesis method (CMS in brief) and a multiple component mode synthesis method (MCMS in brief) in the former papers on their study for analyzing the vibration of complex mechanical structures. In the present report, CPU time and accuracy of calculation by CMS and MCMS are compared with those with MSC-NASTRAN concerning the natural frequencies and the dynamic responses of two model structures. It has been made clear that the vibration of these structures can be analyzed by both CMS and MCMS with much less CPU time than by MSC-NASTRAN and with the same accuracy.

View full abstract

An estimation technique whereby the first excursion probability of the mechanical appendage system subjected to the nonstationary seismic excitation can be conventionally calculated is proposed. The first excursion probability of the appendage system is estimated by using this method and the following results are obtained. (1) The probability from this technique is more convervative than that from a simulation technique taking artificial time histories compatible to the design spectrum as input excitation. (2) The first excursion probability is practically independent of the natural period of the appendage system when the tolerable barrier level is normalized by the response amplification factor given by the design spectrum. (3) The first excursion probability decreases as the damping ratio of the appendage system increases. It also decreases as the mass ratio of the appendage system to the supporting system increases. (4) For the inelastic appendage system, the first excursion probability is reduced, if an appropriate elongation is permitted.

View full abstract

This paper proposes a new design concept of a self-optimizing support system for a rotating shaft. The purpose of this support system is to provide the self-tuning for the support stiffness such that the vibration of a rotating shaft usually occurs at the near antiresonance with changes of a rotating speed. The optimal tuning values of support stiffness are obtained by the on-line estimations of rotating angular velocities of a rotating shaft. The effect of the self-optimizing support system is proved by the tests of nonstationary responses for a fundamental rotor-shaft system.

View full abstract