Modelling the failure of dual phase steel sheets using a meso-scale finite element - cellular automata framework

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The weight of vehicle structures can be reduced by manufacturing sheet metal automotive body parts from advanced high strength steels (AHSS), such as dual phase steels. And the implementation of these AHSS can be accelerated if accurate material and damage models are adopted into numerical simulations of the stamping process. A comprehensive meso-scale material model has been developed in a finite element cellular automata (FE+CA) framework that is able to predict the forming behavior and the onset of fracture in dual phase steel components based on their mechanical properties and some microstructural characteristics. This model predicts the development of ductile damage in terms of void nucleation, growth and coalescence functions and, depending on the microstructural features of the steel, will ultimately determine the final proportions of brittle and ductile fracture. It is proposed to calibrate this meso-scale model to each of a series of Stelco's commercial grades of automotive cold-rolled dual phase steel (DP780, DP980 and DP1180) and to validate the model for the prediction of challenging forming processes. This work will involve the mechanical and microstructural characterization of each grade of dual phase steel, the fitting of material parameters in the advanced constitutive model and the simulation of specific forming processes. This hybrid FE+CA model will be validated by comparing the predicted outcomes with the experimental forming and fracture results.This work will provide Stelco with an advanced numerical model that can be used with LS-DYNA, the commercial finite element software they use to support their automotive customer base. With some experience, Stelco will be able to effectively use this meso-scale model to predict the forming and fracture behavior of dual phase steels, as well as other grades of AHSS such as multi-phase steels and complex phase steels. This first collaborative research project is expected to strengthen Stelco as a steel supplier of choice for automotive applications.