Study of Extension for Forming Limit of Sheet Metal at High Temperature

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A prototype bulging machine which was used at high temperature salt bath liquid as pressure substance was made. The efforts for temperature of the liquid, materials and thicknesses of the sheet metal were experimentally examined for the pressure of the liquid, the forming limit, the bulging profiles and the strain distribution. The bulging mechanism could become clear by numerical simulation using finite element method. The temperature of is changed from 200ﾟC to 450ﾟC. The pressure of liquid, the height of bulging and strain distribution were measured at various temperature of the liquid. As the temperature of liquid was higher, the pressure decreases. The pressure value at 450ﾟC became 10% of the value at room temperature. When the bulge height is equal to 20mm, the bulge profiles and distribution made little difference at various temperatures. As the bulging height were higher, the deformation was caused at the vicinity of the bulging top. The bulging limit could be extended by the bulging method.