Extension flange crack evaluation method, metal plate selection method, press die design method, part shape design method, and press part manufacturing method

摘要

Provided is a technique for more easily evaluating the elongation flange crack of the sheared end face of the evaluation metal plate. A hole expansion test is performed on an arbitrarily selected second metal plate under predetermined molding conditions, and the hole expansion ratio is converted into a hole edge strain consisting of true strain. The hole edge strain and radius are obtained. There are two or more reference strain gradient information (10c), which is the relationship with the strain gradient along the direction, by changing the molding conditions. Perform hole expansion molding on the evaluation metal plate under the same molding conditions as each molding condition corresponding to at least two reference strain gradient information (10c), and set at least two limit hole expansion rates at the hole expansion limit of the evaluation metal plate. The formable region (ARA) of the evaluation metal plate is obtained from at least two reference strain gradient information (10c) and the limit hole expansion rate at the obtained at least two hole expansion limits. The stretchable flange crack at the shear end face of the evaluation metal plate is evaluated by the determined formable region (ARA).