Journal of Japan Institute of Light Metals
Online ISSN : 1880-8018
Print ISSN : 0451-5994
ISSN-L : 0451-5994
Volume 57, Issue 6
Displaying 1-6 of 6 articles from this issue
RESEARCH REPORT
  • Nobuo HATTORI, Masaki TANIGAWA, Masazumi OKIDO
    2007 Volume 57 Issue 6 Pages 228-233
    Published: 2007
    Released on J-STAGE: July 30, 2007
    JOURNAL FREE ACCESS
    Pre-coated aluminum sheets are superior in cost performance and productivity compared to aluminum sheets coated after press forming. Functional pre-coated aluminum sheets, with superior surface characteristics such as lubricity and corrosion resistance as well as aluminum's inherent lightness and excellent heat conductivity, have been increasingly used in electrical and other industrial fields. The serious problems that result from the forming of pre-coated aluminum sheets, namely peeling and whitening, can be attributed to the properties of the coating film. These problems have to be defined in terms of the properties of the coating film and then solved to create top quality products that are not characterized by peeling and whitening. Using aluminum sheets coated with polyester films at various glass transition temperatures, whitening in drawing of pre-coated aluminum sheet was investigated in this study. The effect of the application of lubricants on whitening behavior based on the stretching test was also investigated. Results showed that the degree of whitening was directly affected by the kind of lubricants used. Whitening was only caused in areas where lubricants were applied, and micro-cracks were only observed in the areas where whitening occurred. In addition, whitening was observed only in films with high glass transition temperatures. Based on these results, it was clear that whitening is attributable to the occurring of micro-cracks. As films with high glass transition temperatures are hard, excessive internal stress (cause of cracks) tend to concentrate on local area. It is considered that the adsorbed lubricant on the polyester films acts to decrease the mechanical strength of the films. As a result of the lubricant adsorption, the film can not withstand internal stress in stress-concentrated regions, which in turn causes micro-cracks to develop.
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  • Hiroki TAKANO, Kimiyoshi KITAZAWA, Hikaru YAMAMOTO, Nae MARUTANI
    2007 Volume 57 Issue 6 Pages 234-239
    Published: 2007
    Released on J-STAGE: July 30, 2007
    JOURNAL FREE ACCESS
    Conventionally, sheet metal wastes with bend corners, such as automotive body panels and electric household appliance cases have been recycled through the smelting process. The smelting process has a recycling problem in which a large amount of CO2 emissions arises. To overcome this problem, without the smelting process, sheet metal wastes with bend corners are required to be unbent to flat sheet. Although these sheet metal wastes can be unbent to flat sheets, the thickness of the unbent sheet decreases along the bend line. Here, we propose an incremental flatting process in which the bent sheet can be thickened with flatting. For the purpose of clarifying adequacy of this proposed method, thickening behavior of 1050 aluminum sheets during the flatting was experimentally investigated. Experimental results suggested that bent sheets were flatted and, simultaneously, sheets thickness were increased. Farther, it was found that the thickening phenomenon was affected by blank holding conditions.
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  • Nobuhiro KOGA, Masayoshi ASAKA, Kunlachart JUNLAPEN
    2007 Volume 57 Issue 6 Pages 240-244
    Published: 2007
    Released on J-STAGE: July 30, 2007
    JOURNAL FREE ACCESS
    Recently, high-torque AC servomotors have been developed, and NC servo press machines equipped with these servomotors have become commercially available in Japan. The NC servo press machine has a programmable function for fully controlling the position and velocity of the slide on the machine, as well as for setting its motion such that the slide descends while it is vertically vibrating. In this study, we carried out forming experiments on a 1050 aluminum sheet by vibratory deep-drawing and vibratory ironing using the low-frequency vibration motion of the slide, and experimentally examined the improvement effects of vibration load on the forming limit during each machining process. As results, when the NC servo press machine was used in conventional die machining, (1) the limiting drawing ratio increased by 0.15 during vibratory deep-drawing and (2) the limiting ironing rate increased by approximately 10% during vibratory ironing, without using a special vibration machine. For deep-drawing, the occurrence of wrinkles was prevented when vibration was applied.
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  • Osamu HASEGAWA, Ken-ichi MANABE, Hisashi NISHIMURA
    2007 Volume 57 Issue 6 Pages 245-249
    Published: 2007
    Released on J-STAGE: July 30, 2007
    JOURNAL FREE ACCESS
    In this study, the effect of wing-type dies, which has an advantage to fit the workpiece to a punch in press bending of extruded shape, is investigated. From geometrical analysis and experiment, it is clarified that the sliding direction of shape on the die is varied with the position of wing rotational center. A successful forming avoiding collapse, one kind of buckling, is achieved through the experiment of press bending using A6063-T5 alloy shape with high supported wing-type dies. The theoretical results are in good agreement of experimental results that the friction acts in the direction of axial tension for the shape under press bending with high supported dies. It is clarified that, the high supported wing-type dies is effective method as press bending of shape. Furthermore, we found it is possible to restrict galling on shape under bending with the high supported wing-type dies.
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