Model-based description of bond formation, evolution and failure in multi-pass roll bonding processes

在前一个项目的背景下，开发了一个实验室实验来分析键的形成并随后表征键的强度。然后将实验室实验结果用于校准材料组合AA1050/AA2024的用户子程序（winter）。利用基于UINTER的建模方法对单辊粘合过程进行模拟，可以定性地证实在轧制过程中实验观察到的粘合分离。在这个项目中，下一步将是进一步发展表征和建模方法，以描述多道次辊粘合过程以及模型验证。研究了目前还不能在工业上加工但在汽车制造中很有应用价值的材料组合AA6016/AA8079。由AA6016制成的芯是标准的沉淀硬化铝合金，由AA8079制成的表面层是含有少量铁和硅的近纯铝合金。这导致了高成形性和耐腐蚀性。为了分析多道次轧制过程，特别是材料中的温度变化和轧制道次之间扩散的影响，必须在建模过程中加以表征和考虑。此外，较高的累积变形和轧制孔道间的间隔时间要求改进求解算法的数值稳定性。因此，本知识转移项目的目标是：1)表征一个参数场，以基于上一个项目中开发的实验室实验，校准所研究材料组合（AA6016/AA8079）的用户子程序（winter）。2)进一步发展多步骤实验室实验，以表征轧制孔道间扩散的影响，以详细描述结合强度的演变。3)改进过程和粘合模型，以描述和分析反转或连续多道次辊粘合过程。-关于粘接模型，这需要描述在成形过程中和在交叉时间内的粘接强度演变。关于工艺模型，必须考虑与周围环境和轧辊的热交换。另外，如果过程中的单道变形降低了网格，则需要将粘合强度转移到下一道的新网格中。4)将改进后的工艺和粘接模型与项目合作方实验室轧机的轧制试验结果进行对比，验证改进后的工艺和粘接模型。

In the context of the preceding project, a laboratory experiment to analyze the bond formation and to subsequently characterize the bond strength was developed. The results of the laboratory experiments were then used to calibrate a user-subroutine (UINTER) for the material combination AA1050/AA2024. Based on simulations of single roll bonding passes - using the UINTER based modelling approach - the experimentally observed separation of the bond during the rolling process could be qualitatively confirmed. Within this project the next step will be the further development of the characterization and modelling method towards a description of multi-pass roll bonding processes as well as the model validation. The material combination AA6016/AA8079 which cannot be processed industrial at the moment but is of great interest for usage in the automobile manufacturing is to be investigated. The core made of AA6016 is a standard precipitation-hardening aluminum alloy and the surface layer made of AA8079 is a nearly pure aluminum alloy with small quantities of iron and silicon. This results in a high formability and corrosion resistance. To analyze multi-pass roll bonding processes, in particular the temperature evolution in the material and the effect of diffusion in between the rolling passes has to be characterized and taken into account during the modelling. Furthermore, the higher accumulated deformation and the interpass times between the rolling passes require improvements in the numerical stability of the solution algorithm. Therefore, the objectives of the present knowledge transfer project are: 1) Characterization of a parameter field to calibrate the user-subroutine (UINTER) for the investigated material combination (AA6016/AA8079) based on the laboratory experiment developed in the previous project. 2) Additional development of a multi-step laboratory experiments to characterize the influence of diffusion in between the rolling passes, for a detailed description of the evolution of bond strength. 3) Improvement of the process- and bonding model to describe and analyze reversing or continues multi-pass roll bonding processes. - Regarding the bonding model this requires the description of the bond strength evolution during forming and in the interpass times. - Regarding the process model the heat exchange with the surrounding and the rolls has to be considered. Additional, if the single pass deformations in the process degradate the mesh the bond strength needs to be transferred to a new mesh for the next pass. 4) Validation of the improved process and bonding model by comparison of the results with rolling experiments conducted on the laboratory rolling mill of the project partner.