Forming limit test method and forming limit test apparatus for metal sheet

摘要

PROBLEM TO BE SOLVED: To provide metal sheet testing equipment capable of testing a molding limit by using a test piece with a diameter of less than 100 mm even when the test piece is a high-strength metal sheet with a small pressing force of a blank holder.SOLUTION: When a molding limit of a test piece is tested by press-molding the center of the test piece under pressing with the convex-curved tip of a punch which passes through the center hole of a toric blank holder to be inserted into a molding test part in the center hole of the die while a blank in the periphery of a test piece with a diameter of less than 100 mm made of a metal sheet is being clamped with a toric die and the blank holder, a resistance to the fluidization of the blank is given with a wire bead projected in the die or the blank holder so as to encircle the molding test part, thereby suppressing an inflow of the blank into the molding test part.SELECTED DRAWING: Figure 3