The fracture strength of GRP (Glassfiber Reinforced Plastics), which depends on the applied time of stress and the stress rate, was analyzed by using a time dependent probabilistic failure model. The fracture process was assumed to be a 1-step stochastic process and the transition probability of failure to be γS^δf(t) where S and t represent stress and time, respectively and γ and δare constants. The evaluation of the damage in the case when the stress varied was done by "the reduced time method" proposed in this paper. When f(t)=t^γ and S=at (γ, a; constants), the fracture stress S_c was calculated as follows. [numerical formula] where D_c is a constant. The constant a is stress rate and so the effect of stress rate on the fracture stress could be clearly presented. Static fatigue strength was also analyzed. The analytical results showed a good agreement with experimental results For glass plates and glassfiber composites, the constants γ and δ were found to be about -0.7 and 6.26, respectively. therefore, the traditional time independent probabilistic theory overestimates the effect of strain rate on the strength of materials.

View full abstract

In the previous paper, a plane stress problem of an infinite elastic plate with a rigid and smooth circular disk was considered. In this paper, the case of an elastic circular disk is considered, and the problem of uniaxial tension or compression of an infinite plate is treated. This problem is solved by the same method as in the previous paper, i.e. a numerical method using recurrently the general form of a stress function expressed in the polar coordinated, and the distributions of stresses and displacements along the boundary of the circular hole are elucidated.

View full abstract

Elastic deformation of inhomogeneous materials such as polycrystals or materials with inclusion under multi-axial stress is analysed. A general relation between constraint ratio proposed by the author and strain or stress concentration factor tensor proposed Hill is obtained, and its reduced forms for special cases are studied. The relation between constraint ratio and Eshelby's tensor S is studied for spheroidal inclusion imbedded in infinite matrix. Numerical values of constraint ratio, Hill's tensor and Eshelby's tensor are calculated for several models of inhomogeneous materials and compared with each other.

View full abstract

This paper includes a method showing how to use experimental, two-dimensional cascade data for a quasi-three-dimensional design of axial flow compressor blades. A theoretical analysis has been performed by a suitable transformation of stream surface into a two-dimensional plane. Two parameters, which can be obtained by a solution of through flow problem, are introduced to represent inclination of the stream surface and variation of axial velocity through a rotor. With these parameters, a camber and a stagger which are selected from the cascade data can be corrected easily for the stream surface inclination and the axial velocity variation.

View full abstract

An analysis is made of steady laminar flow in pipes with axially symmetric and non-symmetric wavy walls. Secondary flow patterns and friction factors are obtained for the case of small amplitude waviness. When kR_e (k: the pipe wall wave number, R_e: Reynolds number) is large, the adaptation of wall waviness to secondary flow is delayed due to the inertia forces of fluid and comes to be confined to a region near the pipe wall. When k is small, the friction factors depend on β, the number of helix starts, but not on R_e. When k is large, on the contrary, they are almost independent of β.

View full abstract

To clarify the effects of a longitudinal magnetic field on the ferromagnetic fluid low in a circular pipe, the pressure drop was measured in the range of Reynolds numbers Re=3008000 and the magnetic fields H=00.796×105(A/m) by using a ferricolloid W-35. It is clearly shown that the coefficient of frictional resistance increases with the magnetic field, but the increasing rate decreases with an increase of Re in laminar flow regime and remains at nearly constant values in turbulent flow regime. An approximate analysis of laminar flow is also developed by using the Shliomis basic equations. The results of the analysis explain the experimental results in the laminar flow regime qualitatively by correcting the effect of adhesion layer of the surfactant.

View full abstract

A new type of float-type variable area flowmeter (rotameter)using a straight outside tube and a tapered internal rod is invented and tested. The flow equation is determined with the aid of momentum theory. Fundamental considerations relating to design and production are also given. Results of trial manufacture and experiments for the newly designed rotameter showed very good stability of float. The discharge coefficient was fairly constant in a wide range of Reynolds numbers (up 50) and with variation of floats. This fact indicates that viscosity variation of fluid has little influence on flow measurement by this rotameter. The production of this rotameter is far easier than that of the conventional tapered tube rotameter. This rotameter is advantageous in that it can easily be produced with an appropriate measuring scale.

View full abstract

The experimental results of measuring the thermal conductivity of water and steam at high temperatures and pressures are rather limited and their accuracy is generally poor. In the present paper, for the accurate measurement of thermal conductivity of water and steam at high temperatures and pressures, a new experimental apparatus with a silver co-axial cylinder cell is constructed. Measurement of liquid water up to 200°C and 1470 bar is carried out with an accuracy better than 1.4% and it is proved that the results are well expressed by a simple equation of temperature and density. A comparison with the published data up to now shows that the present results agree well with those in the lower pressure region than 500 bar. However, the data by Amirkhanov et al. show a considerable deviation from the present results around 200°C in the higher pressure region than 1000 bar.

View full abstract

By using the same co-axial cylinder cell as in the previous report, measurement of thermal conductivity of water and steam is carried out in the temperature range from 104 to 420°C and in the pressure range from 98 to 1470 bar. The accuracy of the results is estimated to be better than 1.7% below 400°C and of the order of 2-2.5% above 400°C. The results are well expressed by a simple equation of temperature and density. A comparison with the published data up to now show that the present results agree well with the other data in the lower pressure region than 500 bar. A higher pressures than 1000 bar, the discrepancy between the data by Amirkhanov-Adamov and those of the present work is very large both in the water and steam region, and a large uncertainty of the former is suspected.

View full abstract

An equation for the thermal conductivity of water and steam is formulated in the temperature range from 0 to 800°C and in the pressure range from the triple point pressure to 1000 bar, including the critical region. For the formulation 43 references and more than 4000 experimental data are considered and tested for reliability. The agreement of the equation with the experimental data is satisfactory in the whole range of temperatures and pressures including the critical region, and the extent of the uncertainty of the equation is shown in various ranges of temperatures and pressures. The equation is also proved to be applicable to the higher pressure region than 1000 bar with reasonable accuracy.

View full abstract

The primary object of this study is to gain a better understanding of the heat transfer mechanism in the evaporator of a heat pipe. To evaluate the effects of working pressure, working fluid, pipe inclination and noncondensable gas on the heat transfer mechanism, sintered powders were used as the wick, and pure water and R113 as the working fluid. Experimental results for the heat transfer coefficient are compared with predicted values based on the mechanism proposed by authors. The results indicated the mechanism to be substantially correct.

View full abstract

For air-cooled heat exchangers of air-conditioners, it has become necessary to improve heat transfer coefficient in tubes in order to balance the other improvements, i.e. higher air-side heat transfer area. In the mean time the increase of pressure drop has been inherent in the increase of heat transfer coefficient in tubes. This paper shows that a new heat transfer tube can increase boiling heat transfer coefficient in tube to about twice that of a smooth tube, without an increase in pressure drop. For a horizontal tube about 11.2 mm I.D. with small internal spiral grooves using Refrigerant R-22, the optimum size of internal grooves ranges as follows, Depth of the groove 0.2mm Pitch of the groove 0.51.0mm Inclination of the groove 7° or 90°

View full abstract

The flowrate and size of entrained droplets were measured in upward annular flow of air and liquid. The rate of droplets entrained from the liquid film to the gas core was derived taking into account the rate of droplets transferred from the gas core onto the liquid film. The size distribution of the droplets in the gas core was approximated by a gamma distribution and empirical equations were proposed for the mean diameter of the droplets in terms of the conditions of gas flow and the surface tension.

View full abstract

The evaporation and ignition process of a single droplet of n-cetane on a hot surface has been investigated in detail in the range of the hot surface temperatures 300550°C, and of the initial droplet diameters approximately 0.73.3 mm. The modes of evaporation of droplet are observed through high speed cine-photography. It is found that the upper limit of a hot surface temperature, at which the mode of evaporation of droplet contacting with hot surface disappears, shifts to a lower temperature with decreasing the initial droplet diameter. The ignition delay time also increases abruptly at this surface temperature. Furthermore, the effects of the initial droplet diameter on the evaporation life time and the ignition delay time have been delineated from the observed results, and the critical diameter of the droplet below which the ignition does not occur has been determined experimentally.

View full abstract

Forced vibrations of a nonlinear two-degree-of freedom internally-resonanced system with the natural frequencies in the ratio 2:3 are treated. Theoretical analysis is carried out on the behavior of the system near the lower and higher resonance frequencies. The analysis shows that the system can take three different vibratory states depending on the initial condition. In the first state only a harmonic oscillation occurs and this state is similar to the ordinary resonance. In the second state an ultra-subharmonic oscillation of order 3/2 or order 2/3 occurs and in the third, an almost periodic motion occurs. The validity of the theoretical analysis is confirmed by an analog computer.

View full abstract

In this paper, the in-plane vibrations of a uniform curved bar of which the center line is a plane curve are investigated considering the bending, the extension, the shear deformation and the rotatory inertia of the bar. We obtain the Lagrangian of vibration of the curved bar in a period, and from the stationary condition of the Lagrangian, we determine the equations of vibration and the boundary conditions. As examples, we make calculations for elliptic arc bars with built-in ends and with simply supported ends, and obtain the frequencies and the mode shapes. The numerical results of the present analysis are compared with those by the classical theory and the effects of the shear deformation and the rotatory inertia are clarified.

View full abstract

A reduced impedance method is proposed in order to analyze vibrations of complex mechanical structures. Natural frequencies and modes of coupled vibrations between a disk and blades of an impeller can be analyzed using this method. In this method a total structure is considered as an assembly of some sub-structures, and reduced impedance matrices on combined regions in each sub-structure are calculated and are composed together to make dynamic equations of the total system. On the other hand, the natural frequencies of impellers are obtained experimentally with piezo electric elements and non-contacting type displacement meters. Natural modes of them are observed by the holographic technique with argon gas laser beams. The results of the theoretical analysis are in good agreement with the experimental ones.

View full abstract

A thyristor-controlled multiblade fan motor generates noise from fans when torsional vibrations in its shaft system resonate with the pulsation torque of the fan motor. The autors analyzed the conditions that are necessary for avoiding torsional resonance in a shaft system with multiblade fans at both ends of the shaft, and examined the effect of making a shaft system symmetrical on vibration reduction. It was found that the number of resonant frequencies of a shaft system could be reduced from six to two by this method. The applicability of this method of making a shaft system symmetrical was also investigated with respect to practical shaft systems.

View full abstract

In order to avoid torsional resonance in a fan motor shaft system with multiblade fans and plural planes of symmetry perpendicular to the shaft, a method of frequency control using correction weights was devised. In this method, the vibration characteristics of a shaft system are controlled by using the natural frequencies of the system. A least squares method which uses the influence coefficients is used to calculate the size of the correction weights. This method was applied to the shaft systems with asymmetrical mass distribution, and its effectiveness was investigated in numerical simulations. It was found that a very marked effect of vibration suppression can be obtained if the planes of symmetry are considered when the correction planes are selected.

View full abstract

Slip between paper and drum leads to drawing quality deterioration in a drum-type x-y plotter. From this view point, this paper presents a formulation for a paper feed control system consisting of a vacuum column and paper feed motors, the analytical paper position and paper tension variation in the vacuum column, and the comparison of numerical results with experimental data. It particularly explains that paper friction force in the vacuum column seriously influences the dynamic characteristics of the system and finally describes the critical velocity in thigh speed x-y plotters.

View full abstract

In this report, firstly a relationship between five parameters of a two-link mechanism with two degrees of freedom and three position variables of an arc fixed on its second link is derived in order to establish a method for calculating co-ordinates of the Burmester points with respect to five finitely separated spherical positions. Secondly it is shown that by using this relationship as a basic equation co-ordinates of the Burmester points can be determined by means of a simple procedure that consists in solving a set of five linear equations and a sixths order equation. The analytical method established in this report with the numerical results proves that the number of the Burmester points in spherical motion is generally zero, two, four, or six.

View full abstract

This paper presents a study of influence of lubricant inertia on performances of journal bearings in turbulent lubrication. Assuming that the profiles of velocity distribution and wall shear stresses are not strongly affected by the lubricant inertia, the research work, which is an extension of the turbulent lubrication theory developed in the first paper, has been made by an inertia perturbation method. The theory introduced in the paper is applied to finite width journal bearings, and the obtained results show the effect of the lubricant inertia on journal bearing performances such as film pressure, load capacity and attitude angle.

View full abstract

The "surface-restriction" compensation in an externally pressurized gas bearing is a type of hydrostatic step compensation, and is composed of many narrow grooves on the bearing surface instead of shallow recess to form a restricting step. In this paper, two kinds of flow models are introduced to analyze the hydrostatic performances of externally pressurized gas thrust bearing with this compensation yielding the theoretical pressure distribution, load capacity and bearing stiffness. The experimental results agreed well with theoretical ones for pressure distribution and load capacity, while they showed a little larger values than theory for bearing stiffness. A design criterion is also given for this type of the thrust bearing.

View full abstract