| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for working a punched surface excellent in a fatigue strength. SOLUTION: When the punching work is applied to a metal plate by using a punch 2 and a die 3, this method for improving the fatigue strength on the punched surface is performed, with after punching out the metal plate by making a clearance between the punch and the die to 80-200% of the plate thickness, the indentation work is applied as 490-1,960 N/mm indentation amount per unit length at a hole edge by using the punch having not less than the punching hole diameter to the outer shape at least in the corner part on the back surface of the punching surface and 90-160°angle at the tip end part. COPYRIGHT: (C)2005,JPO&NCIPI
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