LAUSR

Abstract Hot stamping of 22MnB5 sheets by partition heating may represent an effective method to produce parts of the car body-in-white with improved collision performances thanks to proper tailored microstructural characteristics. In accordance with the heating and forming thermo-mechanical features of hot stamping using partition heating, uniaxial tensile tests at varying temperature and strain rate were carried out on a Gleeble™ 3500 thermo-mechanical simulator applying different heating temperatures ranging from 700 °C to 900 °C. The effect of the heating temperature, deformation temperature, and strain rate on the flow stress was analysed, showing that the peak flow stress increased at increasing volume fraction of austenite. An improved unified viscoplastic constitutive model taking into account the austenitization degree was developed and the related material constants identified making use of a genetic algorithm-based optimization tool. The established constitutive model was implemented into the FE-based software Abaqus™ to simulate the hot stamping process of a cup-shaped part using partition heating. The comparison between the numerical and experimental outcomes in terms of thickness distribution proved the accuracy of the 22MnB5 constitutive model taking into account the austenitization degree.