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大橋, 隆弘 ; 本村, 貢
概要:
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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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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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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秋山, 繁 ; 天田, 重庚
概要:
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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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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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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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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小島, 宏行 ; 根津, 紀久雄 ; 黒沢, 勝彦
概要:
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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