Press-forming mold designing method and press-forming mold
AssigneeJfe Steel Corporation
InventorsYusuke Fujii, Toyohisa Shinmiya, Yuji Yamasaki, Kazuhiko Higai
Life of this patent
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Abstract
A prediction equation “R0/t≧(2R/t+(2R/t+1)εf)/2(1−(1+2R/t)εf)” is derived which predicts that bendability-dominated fracture will not occur when the critical surface strain εcritical is not exceeded by a strain on the metal sheet surface causing the occurrence of ductility-dominated fracture that is obtained from the minimum curvature radius R0 of a press-forming mold and the critical strain εf in a plane strain region in a forming limit diagram. The minimum curvature radius R0 of a mold required to prevent the occurrence of bendability-dominated fracture is estimated, and the mold is designed with a curvature radius that is not less than the curvature radius R0.
Claims8
A press-forming mold designing method comprising:
- providing a metal sheet workpiece having a sheet thickness t;
- determining a minimum curvature radius R0 of a press-forming mold surface, the minimum curvature radius R0 satisfying the following equation:
- R0/t≧(2R/t+(2R/t+1)εf)/2(1−(1+2R/t)εf)
- wherein:
- εf is a critical strain for the occurrence of fracture in a plane strain region of an outwardly bent side of the metal sheet workpiece, and
- R is a critical bending radius defined as a minimum bending radius allowing the metal sheet workpiece to be bent without the occurrence of fracture on an outwardly bent surface of the metal sheet workpiece;
- and
- fabricating a press-forming mold having a punch, wherein a surface of the punch that is configured to contact the metal sheet workpiece does not have any portion with a radius of curvature less than the minimum curvature radius R0.
Dependencies are inferred from the claim text.