Analytical Approach to Failure Determination of Advanced High‐Strength Steel in Stretch‐Bending Mode

Experimental and analytical studies on the stretch‐bending characteristics of advanced high‐strength steel sheets, primarily used in the automotive industry, are conducted. Herein, the stretch‐bending test, in which a specimen fixed at both ends is bent at its center with sharp punches until failure occurs, is conducted. Assuming that the failure of the material occurred at the maximum tensile force, a relationship between applied force and forming height is derived. Nine steels including high‐strength low‐alloy, dual‐phase, and transformation‐induced plasticity steels are tested, and the calculated results are compared with experimental limit‐forming heights. Finally, a failure criterion based on process variables and tensile properties of the material is proposed based on the deformation in the sheet thickness direction.