Papers
in JOURNAL OF THE JAPAN SOCIETY FOR TECHNOLOGY OF PLASTICITY
(vol.44 no.509
June 2003)
Strip Width Variation Behavior and its Mathematical Model
in Hot Strip Finishing Mills
Atsushi ISHII, Yasuyuki TAKAMACHI, Shigeru OGAWA,
Kenji YAMADA, Masayoshi AKETA and Nobuo FUKUI
(Received on April 4, 2002)
The behavior of the strip width variation in hot strip finishing mills is investigated by coupled analysis of the plastic deformation of the rolled material with the rigid plastic finite element method and the roll elastic deformation with the axially partitioned computation method. It is found that the strip width variation in the vicinity of the roll-bite is principally governed by the stress acting in the rolling direction near the strip width edge, which depends chiefly upon the entry and the delivery tension and change in the strip crown ratio during rolling. A series of tensile creep tests for a steel at elevated temperatures reveals that even in such a short time range within which the rolled material passes through the inter-stand distance, the transient creep phenomenon may yield a significant amount of width variation. These findings are utilized to develop a mathematical model capable of accurately estimating the strip width variation, and it is confirmed that the developed mathematical model can predict the width variation during finish rolling with an excellent accuracy in a commercial hot strip mill.
Key words: hot strip finishing mills, width variation behavior, finite element method, creep
A Method for One-Piece Press Forming of Rim and Disk
of Automobile Steel Wheel
Seijiro MAKI, Daisuke NAKAGAWARA and Ken-ichiro MORI
(Received on June 20, 2002)
A new forming method for automobile steel wheels based on one-piece press forming was proposed. To clarify the feasibility of the method, the forming performance of a model wheel in 1/8 scale with abstracted profile features of a real 13-inch-diameter-size steel wheel was experimentally investigated using aluminum and steel sheets as experimental materials. To further clarify the applicability of the method to a hot-rolled steel sheet, a ductility test based on bending, taking into consideration the deformation history of the portion, which would be subjected to the severest deformation, was conducted. The model forming method was successfully performed and the ductility test showed no crack development on the outside bent surface, though the surface slightly roughened. A conclusion that the newly devised method is highly feasible was drawn from the results of the experiments.
Key words: sheet metal forming, process design, automobile steel wheel, ferrous metal sheet
Analysis of Hydraulic Forming Process for Noncircular Tube
Shinji TANAKA, Takashi NAGANAWA, Yuuji YOSHITOMI,
Shouta IWAKURA and Toshimi SATOH
(Received on October 3, 2002)
A new hydraulic forming process is analytically investigated by rigid plastic FEM. We have developed some techniques for this method to simulate hydraulic bulging or tube bending. Using these techniques, the hydraulic forming process is investigated for the fabrication of a noncircular tube with a complicated shape from a circular one. This irregularly shaped tube has a circular cross section at both ends and a rectangular one at the center, and has different perimeters of each cross section in the lateral direction. This preformed tube is desired to be as uniform as possible in thickness for the following hydraulic bending process. We determine the optimal hydraulic schedule to fabricate the preformed tube from a circular tube. Consequently, thickness reduction becomes 8% which is half of that in the conventional bulging process. Moreover, the effects of upsetting and bending on the tube deformation in the cross section at the center are studied approximately as 2D problems. By analyzing these results, we find that a good product can be fabricated by modifying the die geometry.
Key words: rigid plastic FEM, tube forming, hydraulic forming, noncircular tube, preformed tube
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