METHOD FOR DETERMINING BENDING FRACTURE IN METAL PLATE, PROGRAM, AND STORAGE MEDIUM

摘要

A bending fracture limit stress à cr is calculated for each value of (bend radius R at sheet thickness center of a metal sheet)/(initial sheet thickness t0); a fracture limit curve L1 is calculated for a uniform deformation state in space of stresses under the assumption of static strain rate and a fracture limit stress à 1_pl is calculated under plane strain deformation, from work hardening characteristics obtained by uniaxial tensile testing of a material configuring the metal sheet; a ratio ³ is determined between the bending fracture limit stress à cr corresponding to R/t0 of an element subject to determination in the metal sheet, and the fracture limit stress à 1_pl under plane strain deformation in a uniform deformation state; and a fracture limit curve L2 corresponding to R/t0 is calculated by multiplying a stress component of the fracture limit curve L1 by the ratio ³. Then a corresponding major stress à OB cr is calculated from the major stress à OR of the element subject to determination and the fracture limit curve L2 corresponding to the bend amount R/t 0 in stress mode; a risk ratio à OR /à OB cr is calculated that is a risk ratio for stretch bending fracture, from the larger out of the stress à OR and the fracture limit stress à OB cr ; and fracture determination is performed for the element subject to determination based on the risk ratio à OR /à OB cr .