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論文

論文
中西, 康彦
出版情報: 日本機械学會論文集. A編.  70  pp.56-62,  2004-01-25.  日本機械学会
概要: application/pdf<br />Journal Article<br />In this paper, we propose a topology optimization method for two-dimensional structures. Virtual nodal forces are employed as design variables that are functions of parameters derived from boundary cycles in the homology theory. The density of material in each element is determined by the design variables so that the density of strain energy is equal to the prescribed value. The objective function is the volume of a plate, and it is minimized. The virtual nodal forces always satisfy the equilibrium at each node in the process of optimization without constraints on parameters, although all elastic equations are not satisfied until the process is completed. In other words, the finite element analysis and topology optimization progress simultaneously. This method does not require repeating finite element analysis. Although the optimum structures obtained by this method as numerical examples varied depending on values of constants in the optimization method or the size of elements, the conditions of the density of strain energy were almost satisfied. It can be said that the validity of the proposed method was proved. 続きを見る
2.

論文

論文
中西, 康彦
出版情報: 日本機械学會論文集. A編.  69  pp.1606-1612,  2003-11-25.  日本機械学会
概要: application/pdf<br />Journal Article<br />In the process of topology optimization, topology of a structure is, in general, changed in succession. In this paper, a method of inferring the change of topology is proposed. This method makes it possible to impose constraint conditions upon topology of the structure. Topological constraint conditions can be expressed by homology groups. As a numerical example, topology of a plate is optimized using an artificial model (the density approach) under topological constraint conditions that (I) the structure is not divided into pieces during the optimization process, and (II) the number of holes is less than or equal to the prescribed number. As a result, it was found that (1) topological constraints were correctly satisfied by the proposed method, (2) the least useful members tend to be removed by topological constraints, and other ones are reinforced, and (3) the strain energy of structures obtained under certain topological constraints is somewhat higher than that of ones without topological constraints 続きを見る
3.

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論文
中西, 康彦 ; 松原, 雅昭
出版情報: 日本機械学會論文集. A編.  68  pp.1018-1023,  2003-07-25.  日本機械学会
概要: application/pdf<br />Journal Article<br />In this paper, location, angle and size of plural defects in a structural component are identified by an elastodynamic boundary element method. Each defect is noncircular and represented by 5 parameters, a radius, an angle, x and y coordinates of the location and the degree of distortion of its shape. External force of harmonic excitation is applied to the component and the displacements at points on its boundary are chosen as additional information. The square sum of the differences in displacements between real values and inference from numerical solutions is minimized to identify the defects using the conjugate gradient method. Though the number of defects is assumed to be one in the beginning of the identification process, the assumed defect is divided into two parts when the value of the parameter representing its distortion satisfies a certain condition. To judge correctly whether it should be divided, it is assumed that defects are filled with imaginary material of which mass density and Young's modulus are considerably low in comparison with those of a structural component. 続きを見る
4.

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論文
中西, 康彦
出版情報: 日本機械学會論文集. A編.  68  pp.850-857,  2002-06-25.  日本機械学会
概要: application/pdf<br />Journal Article<br />When an element is removed from a ground structure or an initial shape by genetic algorithm, homogenization method and so forth in the process for optimizing topology of a structure, its topology is probably changed. In this paper, we propose a new method of inferring the change in topology of a structure before the elimination of each element. This method can show the relation between elements of a structure and invariant factors in homology groups representing topology of the structure. As a numerical example, the proposed method is utilized for imposing topological constraint conditions on a three-dimensional structure consisting of triangular elements. The number of elements and strain energy of the structure are minimized under the conditions. As a result, it was found that a topological constraint on a zero-dimensional homology group of which rank is equal to the number of connected components of the structure is the most important one to reduce the number of elements and strain energy. 続きを見る
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論文
MATSUE, Junji ; NAKAZATO, Takashi ; SHIRAI, Hiroyuki
出版情報: JSME international journal. Ser. B, Fluids and thermal engineering.  43  pp.518-525,  2000-08-15.  社団法人日本機械学会
概要: application/pdf<br />Journal Article<br />A dynamic analysis of a free piston Vuilleumier cycle heat pump was performed by a time-stepping integration method. The nonlinear relationship between displacement and force for pistons was taken into account for the motion of reciprocating components, in addition to the pressure change of working gas, nonlinear viscous dissipative force due to an oscillating flow and discontinuous damping force caused by solid friction. The displacement of pistons and pressure changes in the Vuilleumier cycle heat pump were integrated by an ideal isothermal thermodynamic relationship. It was assumed that the flow friction was proportional to the kinematic pressure of working gas, and that the solid friction at the seals was due to the functions of the working gas pressure and the tension of seal springs. In order to investigate the dependence of the characteristics of a machine on various dynamical parameters, some calculations were performed for a proposed case study machine and discussed. The roles of working gas pressure, the displacer piston rod and dissipative force due to flow and solid friction were clarified, and the proposed method was found to be very effective in predicting dynamic behavior of free piston Vuilleumier cycle heat pumps and in designing the machine components. 続きを見る
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論文
Nakanishi, Yasuhiko
出版情報: JSME international journal. Series A, Solid mechanics and material engineering.  43  pp.234-241,  2000-07-15.  社団法人日本機械学会
概要: application/pdf<br />Journal Article<br />Genetic algorithm (GA) is one of the most useful methods to optimize topology of structures. The performance of GA, however, deeply depends upon a rule of coding from a structure to a string (a chromosome), which must be decided before the execution of GA. An improper coding can cause a lot of unanalyzable structures to be generated in the process of optimization, which are separated into several pieces with no supporting or loading points. In this paper, a method to give such unanalyzable structures a fitness value based upon their topology using homology theory is proposed to raise the probability of obtaining the optimum structures. As numerical examples, topology of two-dimensional frames and three-dimensional structures consisting of triangular elements supported on a rigid wall and loaded vertically on a point distant from the wall are optimized under a constraint of constant weight. As a result, it was found that the proposed method increased the average fitness value and the number of optimum structures obtained in 100 trials of GA in comparison with other methods that considered unanalyzable structures to be useless. 続きを見る
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論文
舩津, 賢人 ; 糟谷, 紘一 ; 白井, 紘行
出版情報: 日本機械学會論文集. B編.  65  pp.4009-4014,  1999-12-25.  日本機械学会
概要: application/pdf<br />Journal Article<br />We calculated the flow-field and surface response condition of a planetary probe entering the Jupiter atmosphere, Within the region behind a detached shock wave, the blunt nose is heated to high temperature. So that, the numerical results were obtained under a viscous-shock-layer analysis. To protect the probe against high temperature condition and to reduce the heat flux, which includes convectional and radiative heat transfer, we used the ablation of C/C composite materials. This simulation included mass injection, radiative transfer, diffusion, and viscous effects. The radiations included were molecular bands, atomic lines, and continuum processes. It was found that carbon ablation materials were effective in reducing the radiative heat flux. 続きを見る
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論文
藤沢, 延行 ; 井上, 智 ; 横田, 正二 ; 田名網, 弘 ; 渡部, 功 ; 高野, 祐二
出版情報: 日本機械学會論文集. B編.  65  pp.48-53,  1999-01-25.  日本機械学会
概要: application/pdf<br />Journal Article<br />Air flows in a heater unit for automobiles are studied by flow visualization w ith tracer injection technique and the visualized images are analyzed by cross correlation method to obtain the velocity distributions in the unit at various mixdoor angles. The results indicate the variations of flow pattern in the heater unit with the mixdoor angles and the appearance of strong interaction between separated main flow and circulating heater flow at relatively large mixdoor angles, which promotes the flow mixing and simultaneously increases the pressure loss inside the unit. The flow fields in the heater unit are calculated numerically based on three dimensional momentum equations combined with κ-ε model of turbulence and with an experimental flow model of heater core. The numerical results reproduce well the experimental flow patterns in the heater unit, but there exits some deviations in the mean velocity and surface pressure distributions at large mixdoor angles. 続きを見る
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論文
天田, 重庚 ; 長瀬, 裕機人
出版情報: 日本機械学會論文集. A編.  62  pp.1672-1676,  1996-07-25.  日本機械学会
概要: application/pdf<br />Journal Article<br />Bamboo is a composite material reinforced by fibers called bundle sheaths. It also has functionally graded structures on macro-and micro-scales. Bamboo has a cylindrical structure with many nodes, and its diameter and thickness vary with height from the ground, which is called the macroscopic graded structure. The fibers are densely distributed in the outer region, which is called the microscopic graded structure. This report presents an analysis of the large-deflective behavior of bamboo based on large-deflection beam theory. The analysis takes gravity and wind load into consideration The beam is modeled using the measured data of the sample bamboo. The maximum surface stress of the bamboo culm keeps approximately a constant even if wind load increases. Unique and smart structural behavior of bamboo deflection is described with respect to the graded structures. 続きを見る
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論文
松栄, 準治 ; 白井, 紘行 ; 大竹, 雅久 ; 黒沢, 美暁
出版情報: 日本機械学會論文集. C編.  60  pp.3070-3075,  1994-09-25.  日本機械学会
概要: application/pdf<br />Journal Article<br />A dynamic analysis of free-piston Vuilleumier-cycle heat pumps has been carried out by a time-stepping integration technique. This technique allows application of a nonlinear relationship between displacements and working gas pressure variations in the equations of motion for reciprocating components. Although ideal isothermal thermodynamics was assumed for the Vuilleumier cycle, the present analysis provided more accurate information on its characteristics than the linearized dynamics. Some calculations for a case study were performed, including dissipative forces with a nonlinear relationship in the equations. It was found that the present method was very effective in predicting the dynamic behavior of free-piston Vuilleumier-cycle heat pumps and in designing the components of machines. 続きを見る