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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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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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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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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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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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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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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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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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