Method of evaluating stretch-flangeability with small scale specimen without specimen size effects

摘要

According to the present invention, a specimen in a smaller scale relative to a measurement method of a stretch-flangeability established in the international standard is used for measuring the stretch-flangeability of plate shaped metal materials precisely without a small scale effect, and can be used for measuring the stretch-flangeability in a local area. The method according to the present invention comprises: (a) a step of determining the size of a shrank specimen piece by computer-simulating a predetermined shrank specimen by using valid element analysis; (b) a step of implementing a punching process provided in a standard test law by using the standard specimen piece made of an identical material with that of the determined shrank specimen piece; (c) a step of observing a distribution aspect of a shear defect of a hole surrounding portion of the specimen piece implemented with the punching process, and measuring a hole expandability ratio; (d) a step of comparing a distribution aspect of the shear defect of the shrank specimen piece and the standard specimen piece, and the hole expandability ratio, and verifying a measurement reliability in stretch-flangeability of the shrank specimen piece; and (e) a step of measuring the stretch flangeability by using the size of the shrank specimen piece verified with the measurement reliability.