| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for evaluating hemming properties of an Al alloy panel material compatible with hemming of the panel material of an automobile and providing a highly reliable test results with high reproducibility. SOLUTION: A stripe test piece 6 of an objective panel material is fixed to a press and the side edge parts of the test piece are bent sequentially. At first, the side edge parts are bent into flanges of 90 deg. along the corner part of a die 8, the 90 deg. bent flange parts 6a, 6b are further bent into flanges of 45 deg., edge part of an inner material 10 is inserted into the inside of the 45 deg. bent flange parts 6a, 6b, and the 45 deg. bent flange parts 6a, 6b are further bent into 180 deg. bent flange parts while clamping the edge part of the inner material 10. When the hemming properties of the test piece is evaluated from the situation of crack in the surface of the 180 deg. bent flange parts 6a, 6b, each bending operation is performed by means of a punch 9 while pressing the test piece 6 against the surface of the die 8 and the opposite flange parts 6a, 6b of the test piece 6 are bent simultaneously in each bending operation.
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