Defined adjustment of the residual stress distribution in strip and sheet material via roller levelling

由于带材和薄板生产线自动化的持续趋势，在寻找无干扰的生产过程时，有必要确保材料的稳定条件。带材和板材的基本特征是平整度和材料内部残余应力的分布。尽管带材和板材具有一定的平整度，但其残余应力的分布可能是不利的，并可能导致材料切割后的平整度缺陷。为了提供所需的平整度以及有益的残余应力分布，在生产过程的初始阶段使用滚轮矫直机。这种矫直机能够同时针对平整度和残余应力分布。这些整平机的最佳调整取决于各种参数。到目前为止，还不可能测量过程中的残余应力分布，因此不可能将应力分布作为过程控制的参考值。因此，本研究计划旨在开发一个数值模型，使工艺布局尊重平面和残余应力分布。在与工业伙伴合作的情况下，将对先前dfg项目的现有数值模型进行改进，以考虑残余应力分布。首先，利用数值模型研究了矫直机的调整与残余应力分布之间的关系。通过与工业合作伙伴开发的工艺模型的计算进行比较，可以对描述反向循环弯曲载荷下行为的所用材料数据进行一致性检查。此外，工业合作伙伴还根据相关应用提供了残余应力分布的优化标准。这些优化标准将被转移到数值模型，其中包括一个虚拟反馈控制。该数值模型包含反馈控制，可以计算矫直机的调整，从而同时优化平面度和残余应力分布。通过衍射方法对残余应力分布进行实验测量，可以验证和优化数值模型。因此，一个数值模型是可用的，能够确定调整辊矫直机，导致平面和优化残余应力分布。此外，该模型还提供了通过弯曲过程影响残余应力分布的可能性的信息。

Due to the ongoing trend for automation in strip and sheet production lines, it is necessary to ensure steady conditions in the material when looking for a disturbance-free production process. Essential characteristics of strips and sheets are both flatness and the distribution of residual stresses within the material. Despite the flatness of strips and sheets the distribution of the residual stresses might be disadvantageous and could lead to flatness defects after cutting of the material.In order to provide the desired flatness as well as a beneficial residual stress distribution roller levelling machines are used at the initial stage of the production process. Such levelling machines are able to target both on flatness and the residual stress distribution. The optimum adjustment of these levelling machines depends on various parameters. Up to now it is not possible to measure the residual stress distribution during the process and it is thereby not possible to use the stress distribution as a reference value for a process control. Therefore, this research proposal aims on the development of a numerical model that enables for a process layout respecting both flatness and residual stress distribution. In collaboration with an industrial partner an existing numerical model from a previous DFG-project is to be enhanced regarding the consideration of the residual stress distribution. At first, the dependence between the adjustment of the levelling machine and the residual stress distribution will be investigated using the numerical model. A comparison to calculations from process models developed by the industrial partner allows particularly for a consistency check regarding the used material data describing the behaviour under reversed cyclic bending load. Furthermore, the industrial partner provides optimisation criteria for the residual stress distribution based on relevant applications. These optimisation criteria will be transferred to numerical model which includes a virtual feedback-control.This numerical model including a feedback-control can calculate the adjustment of the levelling machine leading to simultaneously optimised flatness and residual stress distribution. An experimental measurement of the residual stress distribution via diffractometric methods enables for a validation and optimisation of the numerical model. Thus, a numerical model is available capable of determining the adjustment of roller levelling machines that lead both to flatness and an optimised residual stress distribution. Additionally, this model provides information about the possibility to influence the residual stress distribution through bending processes.