PRESS-FORMING MOLD DESIGNING METHOD AND PRESS-FORMING MOLD

摘要

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.

主权项

1. A press-forming mold designing method wherein the minimum curvature radius R0 of a press-forming mold is controlled to satisfy the following equation:
R0/t≧(2R/t+(2R/t+1)εf)/2(1−(1+2R/t)εf) wherein R0 is the minimum curvature radius of the press-forming mold, εf is the critical strain for the occurrence of fracture in a plane strain region of a metal sheet workpiece, t is the sheet thickness of the metal sheet workpiece, and R is the minimum bending radius allowing the metal sheet workpiece to be bent without the occurrence of fracture on the surface.