| 摘要 |
<p>A forming limit curve is obtained 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 principal maximum strain and principal minimum 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, from which a forming limit diagram is prepared and a crack generation is predicted in the press forming based on the forming limit diagram, and then the press forming is conducted under conditions not causing crack generation.</p> |
