Measurement and prediction methods for forming limit strain of stretch bending deformation in sheet metal forming

Abstract In this study, a new test method using protruding punch was proposed, that can separate bending and stretching deformations. test, the blank makes simultaneous contact with head shoulder to ensure constant angle during test. After contact, increasing stroke increases amount of stretch deformation without changing deformation. addition, control inflow materials by controlling BHF, it is possible evaluate cracks even for low forming limits. This distribution strain through thickness. As result, measurable surface formation limit in higher than FLC uniform along It suggested because gradient thickness delayed timing necking occurrence. There linear relationship between maximum principal on sheet surface, which be applied prediction stretch-bending FEM analysis.