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| 1.
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山口, 誉夫 ; 永井, 健一 ; 丸山, 真一 ; 斉藤, 友明
概要:
application/pdf<br />Journal Article<br />This paper describes vibration analysis using finite element method for two viscoelastic blocks connected by a nonlinear concentrated spring. One of the blocks is supported by another linear
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concentrated spring. The restoring force of the nonlinear concentrated spring has cubic nonlinearity and linear hysteresis damping. Finite element for the nonlinear spring is expressed and is connected to the viscoelastic blocks modeled by linear solid finite elements in consideration with complex modulus of elasticity. Further, the discretized equations in physical coordinate are transformed into the nonlinear ordinary coupled equations using normal coordinate corresponding to linear natural modes. This transformation yields computation efficiency. Influences of share of dissipated energy on nonlinear frequency responses for the viscoelastic blocks are clarifi
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| 2.
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山口, 誉夫 ; 津川, 純一 ; 岡部, 雅哉 ; 榎本, 秀喜 ; 黒沢, 良夫
概要:
application/pdf<br />Journal Article<br />This paper deals with analysis for positioning of sound absorbing materials in a muffler having expansion chamber. Elements of absorber are modeled by 3D finite element, which having complex
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density and complex volume elasticity. By expanding the solution of complex eigenvalue problem with small parameter, equations of motion are derived using first order of asymptotic components. From the equations, contribution of damping elements on modal damping is derived in consideration of multiple modes. The sound absorber is arranged in muffler according to this contribution. It proposed a positioning method of sound absorbers within the limits of design feasible region and it applied to the expansion type muffler and availability of this method is verified.
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| 3.
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半谷, 禎彦 ; 高橋, 俊也 ; 北原, 総一郎
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application/pdf<br />Journal Article<br />Formation of porosity in the die casting process is unavoidable. The porosity has harmful influences on the mechanical properties, such as tensile strength and fracture toughness, of the
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products. We have introduced PRPC (Porosity Reducing Post Compression) process of ADC 12 aluminum alloy die castings to reduce inside porosity. In this study, influencing factor to reduction efficiency of porosity when applying PRPC process was investigated by quality engineering method. As a result, control factors of the PRPC process had a larger influence on reduction efficiency of porosity comparing to the influence of scatter due to each product.
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| 4.
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山口, 誉夫 ; 中原, 直人 ; 永井, 健一 ; 丸山, 真一 ; 藤井, 雄作
概要:
application/pdf<br />Journal Article<br />This paper describes vibration analysis using finite element method for elastic blocks connected by a nonlinear concentrated spring. The restoring force of the spring is assumed to be
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expressed by power series of the relative displacement between ends of the spring. Finite element for the nonlinear spring is expressed and is connected to the elastic blocks modeled by linear solid finite elements. Further, the discretized equations in physical coordinate are transformed into the nonlinear ordinary coupled equations using normal coordinate corresponding to linear natural modes. This transformation yields computation efficiency. Influences of Young's modulus on nonlinear frequency responses for the elastic block are clarified.
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山口, 誉夫 ; 中原, 直人 ; 永井, 健一
概要:
application/pdf<br />Journal Article<br />This paper describes vibration analysis using finite element method for an elastic block supported by a nonlinear concentrated spring. This block is connected to another block by a
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linear concentrated spring. The restoring force of the nonlinear spring has cubic nonlinearity. In this system, resonance responses mainly involve nonlinearity due to two vibration modes. Finite element for the nonlinear spring is expressed. Then the nonlinear spring element and linear spring element are combined to the elastic blocks modeled by linear solid finite elements. Further, the discretized equations in physical coordinate are transformed into the nonlinear ordinary coupled differential equations using normal coordinate corresponding to linear natural modes. This transformation yields computation efficiency. Influences of Young's modulus on frequency responses are clarifed.
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| 6.
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中西, 康彦
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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
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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.
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| 7.
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山口, 誉夫 ; 永井, 健一 ; 丸山, 真一 ; 油田, 知宏
概要:
application/pdf<br />Journal Article<br />This paper describes vibration analysis using finite element method for an elastic block supported by a nonlinear concentrated spring. The restoring force of the spring has cubic
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nonlinearity. Finite element for the nonlinear spring is expressed and is connected to the elastic block modeled by linear solid finite elements. Further, the discretized equations in physical coordinate are transformed into the nonlinear ordinary coupled equations using normal coordinate corresponding to linear natural modes. This transformation yields computation efficiency. Influences of Young's modulus on nonlinear frequency responses for the elastic block are clarified.
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| 8.
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中西, 康彦
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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
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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
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| 9.
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黒沢, 良夫 ; 山口, 誉夫 ; 榎本, 秀喜 ; 松村, 修二
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application/pdf<br />Journal Article<br />We have developed a technique for estimating vibrations of vehicle body struct
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ures with damping materials using large-scale finite element (FE) model, which will enable us to grasp and to reduce high-frequency road noise (200～500Hz). In the new technique, first order solutions for modal loss factors are derived applying asymptotic method. This method saves calculation time to estimate modal damping as a practical tool in the design stages of the body structures. Frequency responses were calculated using this technique and the results almost agreed with the test results. This technique can show the effect of damping materials on automotive body panels, and it enables the more efficient layout of the damping materials. Further, we clarified damping properties of car structures under coupled vibration between frames and panels with viscoelastic layers.
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| 10.
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秋山, 繁 ; 天田, 重庚 ; 千田, 哲也 ; 島田, 道男 ; 古谷, 典〓 ; 矢野, 不二夫
概要:
application/pdf<br />Journal Article<br />Nuclear power plants have the greatest potential for use in space ships, under
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water vehicles, and so on. Because the space and the weight for those plants have limitation, it is very important to develop new radiation shielding materials which have excellent mechanical strength and heat-resistant characteristics. Chromium carbide ceramics (Cr_3C_2) is the neutron absorber which is more excellent than titanium boride ceramics and has been investigated as a radiation shielding material. This report presents an evaluation of thermal shock strength by the laser irradiation technique for chromium carbide ceramics. Their temperature and thermal stress distributions are analyzed by the finite element method (FEM), and critical fracture curves, which can specify a critical power density for a given laser beam spot diameter, are obtained from the relationships between the spot diameter of the laser beam and the maximum tensile thermal stress. And furthermore, size effects to the fracture criterion of chromium carbide ceramics are examined, and the laser irradiation experiments are performed on chromium carbide ceramics using a CO_2 laser. Finally, theoretical results are compared with experimental ones, and the thermal shock strength P_L of Cr_3C_2 ceramics with laser irradiation is ～3.4 W/mm^2 for tension by the FEM analyses
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| 11.
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大橋, 隆弘 ; 本村, 貢
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application/pdf<br />Journal Article<br />The authors develop the expert system for process planning of combined cold forging sequence. Starting from the final product shape, the expert system designs a temporally pre-form shape and process
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by using case-based reasoning. Then, the temporally process is evaluated by the deformation analysis with using general purpose FEM code. When the result is not close to the post-form, temporary pre form shape is corrected by rules described on the cases with considering the result of the analysis. After then, corrected shape is analyzed by the FEM code again. The system repeats the above procedure until getting raw material and develops forging process plans. Thanks to this approach, the system designs forging sequences with using combined process, i. e. direct-indirect extrusion having different extrusion-ratio. A combined process requires lower energy and force than the ordinary in general, so the system is advantageous on developing the sequence design including combined process. The authors applied the system on actual forging example, and evaluate with experiment using plasticine. In the case, developed sequence design requires lower peak-manufacturing force than the ordinary sequence design including no combined process and only 62.5 [%] of the energy of the ordinary.
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| 12.
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Akiyama, Shigeru ; Amada, Shigeyasu ; Yoshii, Tokuharu
概要:
application/pdf<br />Journal Article<br />Various structural ceramics have been developed as heat-resistant materials. In some applications it is anticipated that they will be exposed to very-high-temperature environments of the order of
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thousands of degrees. Moreover, these ceramics are subjected to thermal loadings which change rapidly with time. Therefore, it is very important to investigate their thermal shock characteristics. In this report, the distributions of temperatures and thermal stresses of cylindrical-shaped Al_2O_3 ceramics under irradiation by laser beams are analyzed using the finite element method. Critical fracture curves are obtained from the relationships between spot diameters of laser beams and maximum values of thermal stresses for various power densities of laser beams. The irradiation experiments yield these critical fracture curves, and theoretical and experimental curves are in good agreement.
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| 13.
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笠井, 周 ; 久米原, 宏之 ; 阿久戸, 庸夫 ; 山上, 源作
概要:
application/pdf<br />Journal Article<br />In order to accurately measure axial tension in bolted joint at the initial tightening and to evaluate the change in the axial tension in the joint, it is important to clarify the strain
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distribution of the cylindrical part tightened initially. As a first step, the effects of form accuracy of the nut bearing surface on tightening performance were investigated by FEM analysis and experiments. The obtained results were as follows. Peripheral strain distribution on the internal surface of hollow-type bolted joint is affected by the form accuracy of the nut bearing surface. The strain distribution depends on the height and number of asperities as a model of the height of summit and the number of waviness on the nut bearing surface. The trends of analytical results by FEM approximately agree with those of the experimental results. The effect of form accuracy on the range of strain distribution can be classified into three regions due to the height of asperities. It is found that as a guide for the design of bolted joints, the methods with FEM and with correlation coefficient are useful for the classification of the form accuracy.
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| 14.
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秋山, 繁 ; 天田, 重庚
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application/pdf<br />Journal Article<br />Structural ceramics are attracting attention in the development of space ships, aircraft and nuclear fusion reactors because they have excellent wear-resistant and heat-resistant
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characteristics. However, in some applications it is anticipated that they will be exposed to very high temperatures of the order of thousands of degrees. Therefore, it is very important to investigate their thermal shock characteristics. In this report, the distributions of temperatures and thermal stresses of cylindrically shaped ceramics under laser beams are discussed using the finite element computer code (MARC) with arbitrary quadrilateral axisymmetric ring elements. The relationships between spot diameters of laser beams and maximum values of compressive thermal stresses are derived for various power densities. From these relationships, a critial fracture curve is obtained, and it is compared with the experimental result.
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| 15.
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小島, 宏行
概要:
application/pdf<br />Journal Article<br />In this paper, first, a finite element formulation method for a horizontal fle
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xible robot arm with two links is presented. In the analysis, the kinetic energy of the flexible arm is represented in brief compared with the previous method, and the matrix equation of motion in consideration of the nonlinear forces, such as the Coriolis force, is derived by the finite element method and the variational theorem. Then, the state equation of the mechatoronics system consisting of the flexible arm and the position control system is obtained. Second, the numerical simulations in the case of applying the path control based on the trapezoidal velocity curve are carried out by use of the Wilson-θ method, and the effects of the bending rigidity and the shape of the trapezoidal velocity curve on the dynamic characteristics of the mechatoronics system are demonstrated.
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| 16.
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小島, 宏行 ; 森平, 明宏 ; 根津, 紀久雄 ; 坂本, 賢治
概要:
application/pdf<br />Journal Article<br />In this report, the nonlinear forced vibration responses of a plate subjected to alternating electromagnetic attractive force are investigated theoretically and experimentally in
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consideration of the superharmonic and the subharmonic vibrations as well as the harmonic one. In the analysis, first, the electromagnetic attractive force is formulated by applying the least squares method to the experimental results. By the use of this formulation, the matrix equation of motion of the plate is obtained by applying the finite element method. Then, the nonlinear simultaneous equations, which decide the superharmonic and the subharmonic vibrations as well as the harmonic one, are derived by the harmonic balance method and the reduced impedence method. The numerical results carried out by the Newton-Raphson method agree well with the experimental results, and the validity of the present analysis is confirmed.
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| 17.
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小島, 宏行
概要:
application/pdf<br />Journal Article<br />When an alternating electromagnetic force is applied to the mechanical vibration system, nonlinear forced vibrations such as superharmonic and subharmonic vibrations are generated owing to the
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nonlinearity of the electromagnetic force. In this report, the analytical method by the finite element method and the harmonic balance method is presented to investigate the nonlinear vibrations of a beam subjected to the alternating electromagnetic force. In the analysis, the equations of motion of the beam are obtained by the finite element method, and the nonlinear matrix equations which decide the force vibration amplitudes are derived in consideration of the second order superharmonic and the one-second order subharmonic by applying the harmonic balance method. Then, the nonlinear matrix equations are reduced, and three simultaneous equations are derived. Furthermore, the numerical results by use of the Newton-Rapson method agree well with the previous numerical results, and the present analytical method is confirmed.
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神宮, 利夫 ; 根津, 紀久雄 ; 坂本, 賢治
概要:
application/pdf<br />Journal Article<br />When a stepped beam is impacted, time histories of bending strain are measured by strain gauges which are cemented at the fixed end and the corner of discontinuity in the beam. Although the
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variations of bending strain calculated by the finite element method based on Bernoulli-Euler beam theory also involve the high frequency modes, those by experiment consist of the basic frequency mode and a few low frequency modes. Since the fixed end of a canti-lever beam in an experiment is not perfectly rigid, the periodicity of vibration is affected by it. The time histories of bending strain on the shelf of discontinuity differ from the flexural motion by the simpler Bernoulli-Euler theory. However, observing the variations of bending strain at the other location, except for the high frequency modes, the vibration of both is in fair agreement.
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| 19.
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小島, 宏行 ; 根津, 紀久雄 ; 黒沢, 勝彦
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application/pdf<br />Journal Article<br />Dynamic characteristics of a beam structure with an active electromagnetic damper are investigated by the use of the finite element method and the Laplace transformation. A shock pulse is
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applied to a beam subjected to a camping force by the active electromagnetic damper. In the analysis, first, the governing matrix equations of the coupling system consisting of the beam and the active electromagnetic damper are obtained by the use of the finite element method. Then, the governing matrix equations are transformed into the complex domain by the Laplace transformation method, and the transient vibration responses of the coupling system are derived directly by the application of the residue theorem. Furthermore, numerical calculations are carried out for an exponentially decaying pulse and a half sinus one, and the numerical results agree well with the previous experimental ones.
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