METHOD OF CREATING FORMING LIMIT DIAGRAM IN PRESS FORMING, METHOD OF PREDICTING CRACK, AND METHOD OF MANUFACTURING PRESSED PART

摘要

PROBLEM TO BE SOLVED: To provide a method of creating a forming limit diagram FLD capable of accurately predicting occurrence of cracks in press forming, to provide a method of predicting occurrence of cracks using the FLD, and to provide a method of manufacturing a pressed part using the method of predicting cracks.SOLUTION: After marks are marked at a gage length of 0.5-1.0 mm on a surface of a metal plate to be press-formed, the metal plate is subjected to incremental forming using a punch of 3-10 mm of the minimum radius of curvature of the tip. The maximum principal strain and the minimum principal strain at a time point when cracks occur on the surface of the metal plate punched with the punch tip are measured from changes in the marks to create the forming limit diagram through obtainment of a forming limit line. The occurrence of cracks in press forming is predicted on the basis of the forming limit diagram, and press forming is performed in a condition that the cracks are not caused.