Effects of Edge Heating and Strain Gradient on Stretch Flange Deformation Limit of Steel Sheet

To improve the stretch flange deformation limit of ultrahigh-strength steels, a partial edge heating method was investigated. The effect strain gradient on when applied investigated by hole expansion test and FEM analysis. formability improved application because recovery shearing microstructure reduction hardness difference microstructure. It found that improvement for with depends region. In low region, margin small. On other hand, in high markedly compared without heating. confirmed direction perpendicular to maximum principal could be used prediction also determination fracture analysis actual parts even under conditions.