Method for identifying variation factor portion of springback amount

A method for identifying a variation factor portion of a springback amount, the method identifying a portion in a press formed part that is a factor for variation in a springback amount when variation occurs in the springback amount in the press formed part due to scattering in press forming conditions, and comprising:

• press forming a first press formed part under first press forming conditions in advance;
• creating a first press formed part model from three-dimensional shape measurement data obtained by measuring a surface shape of the first press formed part after die release;
• performing mechanical analysis in a state in which the first press formed part model is sandwiched by a tool-of-press-forming model until reaching a press forming bottom dead center;
• acquiring residual stress distribution in the first press formed part at the press forming bottom dead center under the first press forming conditions;
• press forming a second press formed part under second press forming conditions different from the first press forming conditions within a range of the scattering in press forming conditions in advance;
• creating a second press formed part model from three-dimensional shape measurement data obtained by measuring a surface shape of the second press formed part after die release;
• performing mechanical analysis in a state in which the second press formed part model is sandwiched by the tool-of-press-forming model until reaching the press forming bottom dead center;
• acquiring residual stress distribution in the second press formed part at the press forming bottom dead center under the second press forming conditions;
• performing springback analysis on the first press formed part for which the acquired residual stress distribution in the first press formed part has been set, and calculating a first springback amount;
• replacing a value of residual stress in a partial area of the acquired residual stress distribution in the first press formed part with a value of residual stress in an area corresponding to the partial area of the acquired residual stress distribution in the second press formed part;
• performing springback analysis on the first press formed part for which the value of the residual stress has been replaced, and calculating a second springback amount;
• obtaining a difference between the second springback amount and the first springback amount;
• and
• identifying a portion in the first press formed part that is a factor for variation in springback amount of the first press formed part based on the obtained difference.