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Author: search.filters.author.Norasethasopon, S.

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    Finite-element simulation of inclusion size effects on copper shaped-wire drawing
    (2006-04-25)
    Norasethasopon, S.
    ;
    Yoshida, K.
    The effects of inclusion size on copper shaped-wire drawing were investigated. For this purpose, an experimental investigation for optimal die half-angle was conducted. Based on experimental data of optimal die half-angle, the deformation and the hydrostatic stress of the copper shaped-wire that contain an inclusion were calculated by two-dimensional finite element analysis. As the FEA results, while the leading edge of the inclusion passed through the die, the necking due to inclusion wire drawing occurred on some parts of the copper wire surface in front of and near the leading edge of the inclusion. The effects of inclusion size on drawing stress, tensile stress in front of inclusion and contact compressive stress while copper shaped-wire drawing were carried out. © 2006 Elsevier B.V. All rights reserved.
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    Influences of inclusion shape and size in drawing of copper shaped-wire
    (2006-03-10)
    Norasethasopon, S.
    ;
    Yoshida, K.
    The present paper shows how two of the inclusion parameters, the inclusion size and aspect ratio, influenced the drawing stress, maximum hydrostatic stress and maximum die pressure during drawing of the single filament copper shaped-wire. The optimum die angle was determined. It was found that the maximum drawing stress increased as inclusion size and aspect ratio increased. The inclusion location that the maximum drawing stress occurred in drawing wire was at s/L ratio, the ratio of distance from die entrance to distance between die entrance and exit, equal to 0.55. The necking due to inclusion wire drawing occurred on some parts of the copper wire surface in front of and nearby inclusion and increased in accordance with inclusion size increase as the inclusion passed through the die. The maximum hydrostatic tensile stress directly increased as inclusion aspect ratio increased for small and medium inclusion, but it inversely increased for large inclusion. It was mostly found where the leading edge of the inclusion was located in the drawn zone. The maximum die pressure was low and constant and not affected by inclusion size. However, it was very slightly influenced by inclusion aspect ratio where longitudinal inclusion size ratio was between 0.0 and 0.3. It rapidly increased as inclusion aspect ratio and inclusion size increased where longitudinal inclusion size ratio was 0.3 up. It was found where the leading edge of the inclusion was located in the drawn zone for longitudinal inclusion size ratio = 0.2, 0.3 and 0.8, in the reduction zone for longitudinal inclusion size ratio = 0.4 and 0.5, and mostly around the die exit for low inclusion aspect ratio. © 2005 Elsevier B.V. All rights reserved.
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    Surface quality improvement of multistage forged microparts for wristwatches
    (2003-12-20)
    Yoshida, K.
    ;
    Kuboki, I.
    ;
    Norasethasopon, S.
    The trial of a new production technique using multistage forging of watch parts called the "crown" has been investigated. In the conventional forging process, the flaws on the shearing surface of the mother wire remain in the final products. These surface defects present the most important problem in the manufacturing process of decorative watch parts. An analysis of the deformation behavior of the flaws during multistage forging using a finite-element (FE) simulation and experiments has been performed, and a new manufacturing process that yields better products is suggested. In the conventional process, small amounts of metal flow and plastic strain near the center of the sample during multistage forging were observed by FE simulation, and as a result, the flaws on the shearing surface of the mother wire remained on the surface of final products. The simulation results are compared and are in good agreement with experimental results on metal flow of the flaws. Carrying out additional forging with a conical punch in the conventional manufacturing process in order to accelerate the metal flow at the center of the sample is effective for obtaining improved final products. © 2003 Elsevier Science B.V. All rights reserved.