Constitutive and fracture models of hot stamped parts with multiphase using digital image correlate technology

Abstract The hot stamping technology is widely used because of the good formability, lower forming force, less spring back and high strength parts obtained. However, with the consistently increasing requirements for safety performance improvement, the fully martensitic hot stamped parts cannot meet the new requires, which consist high strength and energy absorbing. The compatibility of mechanical properties and safety performance of vehicle parts such as b-pillar has been proposed that different mechanical properties are needed in different regions of the same parts, namely tailored properties. Microstructure of hot stamped parts with tailored properties consist of multiphase, so in this paper, experiments and simulation have been performed to study the constitutive and fracture models of hot stamped parts with multiphase. The digital image correlation (DIC) technology was used to measure the strain over the whole specimen and the elastoplasticity constitutive models of martensite, bainite and ferrite/pearlite have been obtained. By combining the experiments and numerical simulation, the parameters of fracture model have been optimized, which are very hardly to be determined using only experiments. The constitutive and fracture models of multiphase has been obtained using the liner-mixture rule.