Finite element analysis of the phase transformation during a hot stamping process

A technology to manufacture highest-strength automotive components is hot stamping. This process combines forming and heat treatment of sheet metal material. During and after the hot stamping process phase transformations from austenite to other phases occur. For a realistic prediction of the resulting component properties by means of Finite Element Analysis it is essential to consider the complex effects of phase transformation. Experimental and numerical investigations of hot stamping of a cap profile are carried out. In respect of the numerical investigations, aspects of a developed material model are presented, that considers the transformation-induced stresses and the plastic anisotropy. The model is tested by comparison of experiment and simulation with respect to phase fractions and distortion. Due to the temperature history during the forming phase and the heat treatment phase marginal distortion of the hot-stamped cap profile occurs. The microstructure is characterized by a phase mixture of martensite and bainite. The results of the numerical simulation correspond with those of the experimental investigations. A significant influence of transformation-induced stresses on the calculated part distortion is detected.