Papers by Author: Taro Tokuda

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Authors: Taro Tokuda, Takeshi Uemori, Tetsuya Yoshida, Michihiro Takiguchi, Fusahito Yoshida
Abstract: In sheet metal industries, press-formed sheet elements are usually adhesively bonded together at the final stage of assembly. Instead of such a conventional process, the present authors proposed a new technique that first flat sheets are adhesively bonded together and then press-formed into the final products. In previous study, the problem of the die-bending (V-bending and hat-shaped bending) with symmetrical shape has studied. In this study, asymmetric-shaped bending of adhesively bonded sheet metals was investigated by experiments and FEM analysis method. In the case of asymmetric-shaped bending, it was found that the timing of contact from the die corner to the die hypotenuse is early in the press-forming process compared with symmetrical bending (V-bending and hat-shaped bending). For the FEM analysis results, the maximum shear strain in asymmetric-shaped bending was smaller than that in symmetric-shaped bending at the hat-shaped side. Thus, the shape of the die has a large influence on the die-bending of adhesively bonded sheet metals.
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Authors: Michihiro Takiguchi, Taro Tokuda, Tetsuya Yoshida, Takeshi Uemori, Fusahito Yoshida
Abstract: In this paper, the deformation behavior of adhesive layer in stretch-bending/unbending for adhesively bonded sheet metals was investigated by experiments and finite element method (FEM). We paid special attention to the cyclic shear deformation of the adhesive layers during the plastic working. Major results obtained are summarized as follows: (1) When the adhesively bonded sheet metals is bent and pulled out at a 90° angle, shear deformation due to bending of the adhesive layer starts shortly before reaching the die corner and unbending starts at the middle of the corner. (2) The die radius has a large influence on the bending behavior. (3) It is possible to suppress shear deformation of the adhesive layer by using a material with small tensile strength as one of the two adherends.
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Authors: Michihiro Takiguchi, Taro Tokuda, Tetsuya Yoshida, Takeshi Uemori, Fusahito Yoshida
Abstract: In this paper, the deformation behavior of adhesive layer in die-bending for adhesively bonded sheet metals was investigated by experiments and finite element method (FEM). We paid special attention to the bending/unbending shear deformation of the adhesive layer during the die-bending of adhesively bonded sheet metals by using highly ductile acrylic adhesive. Major results obtained are summarized as follows: (1) The bending/unbending shear deformation of the adhesive layer was observed during the die-bending. (2) The punch radius has a large influence on the die-bending in the adhesively bonded sheet metals. (3) It is desirable to perform die-bending at high speed as well as air-bending.
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Authors: Michihiro Takiguchi, Taro Tokuda, Tetsuya Yoshida, Mitsuo Funaki, Hiroshi Hamasaki, Fusahito Yoshida
Abstract: In this paper, the effect of material characteristics on plastic forming of adhesively bonded dissimilar sheet metals was investigated by experiments and finite element method (FEM). The acrylic adhesive employed in the experiments has visco-plasticity characteristics with high ductility and strong strain-rate and temperature sensitivity in strength. Major results obtained are summarized as follows: (1) In the adhesively bonded dissimilar sheet metals, the gull-wing bend and the shear deformation of the adhesive layer are suppressed by the combination of the sheet metals when a bending inside sheet has high-tensile strength. (2) The gull-wing bend is suppressed by high-speed forming at a lower temperature as well as the same kind of sheet metals. (3) The calculated results using MSC Marc2010 are relatively good agreement with the experimental results.
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