Method of preparing forming limit diagram in press forming, method for predicting crack and method of producing press parts

Abstract

A method of preparing a forming limit diagram in press forming includes obtaining a forming limit curve by subjecting a surface of a metal plate to be press-formed to marking at a distance between reference points of 0.5-1.0 mm, bulging the metal plate with a punch having a top minimum curvature radius of 3-10 mm and measuring a maximum principal strain and minimum principal strain at a time of generating cracks on the surface of the metal plate at a top portion of the punch from a change of the marking.

Dependencies are inferred from the claim text.