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Tsuneo HIRAI, Shin TSUKUMA, Taichi FUJII, Tsuneo AZUMA
1978 Volume 21 Issue 162 Pages
1669-1676
Published: 1978
Released on J-STAGE: February 15, 2008
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The lateral fracture in a cold-forging die appears to be caused by the stress concentration at the internal corner fillet of the die. An investigation on the stress concentration factor for an axisymmetrical die with a circular arc fillet and with or without an ejector hole is reported. A theoretical analysis is carried out two-dimensionally by assuming a mirror pattern of the vertical section of the die. The value of the stress concentration is calculated on the case of the die without an ejector hole loaded by a uniformly distributed internal pressure and with an ejector hole applied by a partially distributed load substituting for the effect of the ejector hole. The validity of the analysis is comfirmed by the experimental results using the three-dimensional photoelasticity. The value of the stress concentration factor depends largely on the diameter of the ejector hole as well as the fillet radius.
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Toshio YAMAMOTO, Kimihiko YASUDA, Masayoshi KATO
1978 Volume 21 Issue 162 Pages
1677-1684
Published: 1978
Released on J-STAGE: February 15, 2008
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Free and forced vibrations of a string with time-variable length are treated theoretically under the assumption that the variation rate of the length is small. The solutions are obtained n the form of a power series of a small parameter which prescribes the variation rate of the length. The theoretical analysis shows that the free vibration has a nature of a travelling wave. As to the forced vibration occurring during a transition through the fundamental resonance point, the analysis shows that the amplitude becomes maximum slightly later than the moment when the "natural frequency" of the system coincides with the frequency of the external force. An experimental analysis is performed for the forced vibration. The comparison of the results of the theoretical analysis with those of the experimental analysis shows a fairly good agreement.
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Katsuyoshi SUZUKI, Hideo AIDA, Shin TAKAHASHI
1978 Volume 21 Issue 162 Pages
1685-1695
Published: 1978
Released on J-STAGE: February 15, 2008
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We have researched the out-of-plane vibrations of curved bars with uniform cross section, of which center lines are some plane curves. Two general methods for solving the problems are presented: one is to use a variable, of which the relation to arc length represents the curvature and the other is to use the curvature expressed by arc length. As numerical examples, the frequencies and the mode shapes are shown in graphs for symmetric arc bars with clamped ends having the center lines in the form of ellipses, sines, catenaries, hyperbolas, parabolas and cycloids. And from the results, a general tendency in the out-of plane vibrations of curved bars is found.
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Toshihiro IRIE, Gen YAMADA, Yoshihiro NARITA
1978 Volume 21 Issue 162 Pages
1696-1702
Published: 1978
Released on J-STAGE: February 15, 2008
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This paper presents an analytical method to study free vibration of polygonal plates clamped at the edges. A polygonal plate is formed by setting some rigid line supports on a simply supported rectangular plate. Regarding the reaction force and moment acting on all edges of the polygonal plate as unknown harmonic exciting loads, the stationary response of the plate to these loads is obtained. The force and moment distributed along the edges are expanded into a Fourier sine series with unknown coefficients, and homogeneous linear equations are derived with use of restraint conditions at the edges. The natural frequencies and the mode shapes of the polygonal plate are determined by calculating the eigenvalues and eigenvectors of the equations. From the numerical calculation carried out on an equilateral triangular through a regular octagonal plate, it was clarified that the mode shapes of clamped polygonal plates can be classified into several groups of various types.
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Toshihiro IRIE, Gen YAMADA
1978 Volume 21 Issue 162 Pages
1703-1709
Published: 1978
Released on J-STAGE: February 15, 2008
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Recently, thermally induced vibrations have assumed increased practical importance in many industrial fields, and some methods of analysis were developed to study the vibrations of beams and rectangular plates induced by external heating. However, only a limited number of papers are available on circular plates. This paper studies the thermally induced vibration of a circular plate and an annular plate. The plate is subjected to a sinusoidally varying heat flux on one surface, while the other surface is thermally insulated. The temperature distribution due to the heat input was analyzed by the Fourier heat conduction equation. The thermal moment due to the temperature was calculated and the stationary deflection and stresses of the plate induced by the thermal moment were analyzed theoretically. Some interesting phenomena were revealed as the result of the numerical calculation carried out by the application of the theory.
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Hisao KONDO
1978 Volume 21 Issue 162 Pages
1710-1716
Published: 1978
Released on J-STAGE: February 15, 2008
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Coupled oscillations of a liquid and a floating roof in a circular cylindrical tank are studied for small motions. The liquid is assumed as a perfect fluid, both floating roof and bottom plate of the tank are treated as thin plates, and the side wall is assumed rigid. The Fourier-Bessel expansion is used to obtain frequency equations. Numerical examples for the axisymmetric case are given to illustrate the effect of coupling, showing that a floating roof of small bending rigidity will oscillate approximately in sloshing (free surface oscillation) modes for lower natural frequencies, and that a bottom plate spring-supported on the foundation behaves actually as a rigid body.
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Seizo FUJII, Hideo FUJIMOTO, Takeshi NAGAO
1978 Volume 21 Issue 162 Pages
1717-1724
Published: 1978
Released on J-STAGE: February 15, 2008
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The purpose of this paper is to present a numerical method for the optimal control problems with inequality constraints. The ordinary Lagrange function method is in general limited to the problems with convex objective function and constraints, and the penalty method may suffer from numerical difficulties. Transformation method of an exponential function type with two correcting parameters is proposed to circumvent such difficulties. In this paper the algorithm and theoretical discussions are given. The efficiency and the accuracy of this method are investigated on a problem with nonconvex state constraint, and comparisons are made with other transformation methods.
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Junichi KUROKAWA, Tomitaro TOYOKURA, Masaaki SHINJO, Kazuyoshi MATSUO
1978 Volume 21 Issue 162 Pages
1725-1732
Published: 1978
Released on J-STAGE: February 15, 2008
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Roughness effects on the three-dimensional boundary layer flow along an enclosed rotating disk have been studied theoretically and experimentally as well as the admissible roughness. The results show that an increase of roughness of the rotating disk results in an increase of core rotation and then in a considerable increase of pressure drop toward the disk centre, that an increase of roughness of the chamber wall has reverse effects, and that the equal roughness of both walls makes the flow almost same as one along smooth surfaces. The theoretical results based on the logarithmic velocity distributions show good agreement with the measurements. The well-known formula of admissible roughness in the two-dimensional flow is confirmed to be effective even in the three-dimensional boundary layer flow, because the secondary flow has little effect on the flow in the immediate vicinity of the wall and then the viscous sublayer is not influenced so much.
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Shoji SUZUKI
1978 Volume 21 Issue 162 Pages
1733-1740
Published: 1978
Released on J-STAGE: February 15, 2008
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Study on noise reduction of the axial-flow fans was carried out, varying principal assumed parameters such as the chord length of the blade, the camber of the airfoil, the position of maximum camber, and the surface pressure distribution of the airfoil. A separated flow on the surface of the tow-dimensional airfoil was observed with use of the Schlieren divice, and measurements were made of the strength of turbulence with use of a hot wire probe so as to determine their correlation with fan noise. The airfoil profile was determined by calculation using an optimum pressure distribution. As a result, the relations between the parameters and fan noise reduction have been clarified.
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Hideki OHBA, Yukitoshi NAKASHIMA, Kazuaki SHIRAMOTO, Kazumasa SHIRAMOT ...
1978 Volume 21 Issue 162 Pages
1741-1749
Published: 1978
Released on J-STAGE: February 15, 2008
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A vortex pump having a large chamber in front of the recessed impeller is suited for pumping the liquids with suspended solids. The flow behaviours in the chamber and impeller have been observed by the surface flow pattern technique of the impeller and casing for the purpose of establishment of the fundamental flow model in vortex pump. On the basis of these observations, a simplified flow model has been proposed. On the other hand, a theoretical analysis using the equations of continuity, motion and the performances. Predicted values by the theory were compared with the experimental results, and fairly good agreement was obtained. In Addition, the effects of the casing and impeller geometries on the performance of pump were investigated experimentally.
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Shimpei MIYAKAWA
1978 Volume 21 Issue 162 Pages
1750-1756
Published: 1978
Released on J-STAGE: February 15, 2008
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The stability of a hydraulic circuit is studied in the most fundamental circuit consisting of a hydraulic motor and a counter-balance valve. By using linearized equations of the system, the effects of the flow rate of the hydraulic pump, spring constant and taper angle of the spool valve, and cylindrical choke in the pilot line on the stability of the system and the characteristics of self-excited vibration are clarified. As a result, fundamental data for preventing unstable phenomena are obtained.
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Kotohiko SEKOGUCHI, Tohru FUKANO, Akiharu OUSAKA, Kazumi ISHIDA
1978 Volume 21 Issue 162 Pages
1757-1764
Published: 1978
Released on J-STAGE: February 15, 2008
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An orifice-couple consisting of two segmental or eccentric orifices installed in series in the direction of flow was devised for component flow rate measurements in horizontal gas-liquid two-phase flow. One of the orifices takes its opening at the lower side of the tube cross section and the other at the upper side. Because the phase distribution in horizontal two-phase flow is, generally, asymmetric to the tube axis, the flow passing through the orifice-couple generates such two pressure differences as governed by the independent relationships between flow rate and pressure difference. The new device was applied to froth, separate and annular flow in the test tube of 26.0 mm in inner diameter. The experimental results show that the orifice-couple is effectively used to measure the component flow rate in every flow pattern tested, and that a suitable orifice is one of segmental opening with area ratio of 0.4∼0.6.
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Masahiko MIZOMOTO, Hiroyasu HAYANO, Shigeru IKAI
1978 Volume 21 Issue 162 Pages
1765-1771
Published: 1978
Released on J-STAGE: February 15, 2008
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This paper concerns the evaporation process of a single droplet of n-cetane and n-heptane on a hot surface. The initial diameter of the droplet is approximately 2 mm and the hot surface is made of stainless steel and the range of its surface temperatures is between 300°C and 600°C which involves the maximum evaporation rate point and the Leidenfrost point. From results of this experimental study, the effects on the evaporation life time of the gas temperature around the droplet and of the surface roughness are clarified. Furthermore, by the observation of the evaporation process through a high speed camera, the evaporation life time curve is divided into 6 regions according to the mode of evaporation of the droplet. Especially, the evaporation process in the transition region can be interpreted by the successive change of the modes of evaporation, that is from the contact evaporation to the spheroidal evaporation.
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Masahiko MIZOMOTO, Shigeru IKAI
1978 Volume 21 Issue 162 Pages
1772-1779
Published: 1978
Released on J-STAGE: February 15, 2008
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The ignition process of a single fuel droplet (n-centane, initial diameter approximately 2 mm) on a hot surface has been investigated. The mass evaporated in the very short duration soon after the initiation of contact with the hot surface has been measured. The following conclusions could be obtained. (1) The ignition delay time curve concerning the wall temperature has a maximum and a minimum point as in the case of the evaporation life time. But these critical values in each of them do not coincide with each other, because the evaporation rate in the ignition delay time (τi), directly controlling τi, differs so much from that in time of total evaporation. (2) The ignition delay time is controlled by the chemical reaction rate when the hot surface temperature (t
w) is lower than the Leidenfrost point, and by the physical process when t
w is higher than that.
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Toshimi TOBE, Masana KATO, Haruki OBARA
1978 Volume 21 Issue 162 Pages
1780-1786
Published: 1978
Released on J-STAGE: February 15, 2008
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Current and voltage across underwater gap where fine copper wires are exploded electrically are measured and the energy consumed there is calculated. Discharge efficiency, which is the ratio of energy consumed at the gap to the initial energy stored at capacitor bank, is evaluated under various charging voltages up to 63 kV, charging energies up to 2.6 kJ and natural frequencies of discharge circuit ranging from 10 kHz to 50 kHz. The maximum discharge efficiency reaches more than 80%, which is attained under the optimum wire dimensions given as S
w*=1.9×10
-3 (C
oV
o)
1.3f
o0.65, l
w*=4.3V
of
o-2/3 where S
w*(mm
2), l
w*(mm) are optimum cross sectional area and length of copper wire respectively, V
o(V), C
o(F) are charging voltage and capacitance of capacitor bank and f
o(Hz) is natural frequency of the circuit.
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