Formability of advanced high strength steels

Novel draw-bend tests of 3 dual-phase (DP) steels utilizing velocity control of both actuators revealed three patterns of failure depending on draw speed, draw speed ratio, and R/t ratio. Shear failure occurs preferentially for smaller R/t and higher deformation rates. During draw bend tests, the temperature rises are significant, up 100°C before necking, with consequent loss of strength in affected regions. A novel 1-D constitutive equation relating flow stress to strain, strain rate, and temperature was developed based on tensile tests. FE simulations using the measured constitutive response predicted the types of failures accurately, without introducing damage mechanics. The deformation-induced heating is a critical part of the failure process.