METHOD FOR DETERMINING STRETCH FLANGE LIMIT STRAIN AND METHOD FOR ASSESSING PRESS FORMING FEASIBILITY

摘要

A method for specifying stretch flange limit strain according to the present invention includes specifying stretch flange limit strain so as to satisfy a relation in the following formula by using: strain gradient in an inward direction directed from an end portion of a metal sheet at a time a press load is applied; and strain gradient in a sheet thickness direction of the metal sheet intersecting the loading direction: µ ¸lim = A �¢ a ‹ ” �¢ µ ¸ / ”r + b ‹ ” �¢ µ ¸ / ”t + c where µ ¸lim represents the stretch flange limit strain (tangential direction of the sheet edge), ”µ ¸ /”r represents the strain gradient in the inward direction, ”µ ¸ /”t represents the strain gradient in the sheet thickness direction, A, a, and b represent influence coefficients, and c represents the limit strain at a time the strain gradient is zero.