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

利用先进的高强度钢（AHSS）（如双相钢）制造钣金汽车车身部件，可以减轻汽车结构的重量。在冲压过程的数值模拟中采用精确的材料模型和损伤模型可以加快AHSS的实施。在有限元元胞自动机（FE+CA）框架下建立了一个综合的细观尺度材料模型，该模型能够基于双相钢构件的力学性能和一些微观组织特征来预测其成形行为和断裂发生。该模型根据空洞成核、生长和聚结功能预测了延性损伤的发展，并根据钢的微观组织特征，最终确定了脆性和延性断裂的最终比例。建议将该中尺度模型校准到Stelco的一系列商业等级的汽车冷轧双相钢（DP780， DP980和DP1180），并验证该模型用于预测具有挑战性的成形过程。这项工作将涉及双相钢各等级的力学和微观结构表征，在先进的本构模型中拟合材料参数，以及具体成形过程的模拟。该混合FE+CA模型将通过将预测结果与实验成形和断裂结果进行比较来验证。这项工作将为Stelco提供一个先进的数值模型，可以与LS-DYNA一起使用，LS-DYNA是他们用来支持其汽车客户群的商业有限元软件。有了一定的经验，Stelco将能够有效地使用这种中尺度模型来预测双相钢的形成和断裂行为，以及其他等级的AHSS，如多相钢和复杂相钢。这首个合作研究项目有望加强Stelco作为汽车应用钢材供应商的选择。

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.