Delayed fracture characteristic evaluation method and program

A non-transitory computer-readable medium storing a computer program thereon, the program configured to perform a delayed fracture characteristic evaluation method comprising:

• a test step of receiving test data obtained from applying a deformation to a test piece containing a metal sheet, and evaluating a generation status of a crack generated in the test piece by placing the deformed test piece in a hydrogen entry environment,
• a first step of inputting information about the deformation determined to have a delayed fracture by the evaluation, calculating a maximum residual stress generated in the test piece after the deformation by applying the deformation to the test piece by a forming analysis under first analysis conditions by a computer, and determining, from the calculated maximum residual stress, a reference stress for determining whether the delayed fracture occurs in a formed article of the metal sheet in a hydrogen environment;
• a second step of determining a residual stress generated in the formed article by forming the metal sheet into an intended formed article by a forming analysis under second analysis conditions by the computer;
• a third step of determining, from a correlation between a first stress calculated by the forming analysis under the first analysis conditions and a second stress calculated by the forming analysis under the second analysis conditions when press forming is performed under a same forming condition, a conversion factor for bringing the stress calculated by the forming analysis under the first analysis conditions closer to the stress calculated by the forming analysis under the second analysis conditions;
• and
• an evaluation step of evaluating the delayed fracture characteristics of the intended formed article from a comparison between the residual stress determined in the second step and a stress after converting the reference stress by the conversion factor,
• the program causing the computer to realize the first step and the third step.