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

由于带材和板材生产线的自动化趋势不断发展，因此在寻找无干扰的生产过程时，必须确保材料的稳定状态。带材和板材的基本特性是平整度和材料内的残余应力分布。尽管带材和板材具有平整度，但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辊式矫直机。这种整平机能够以平整度和残余应力分布为目标。这些整平机的最佳调整取决于各种参数。到目前为止，不可能在工艺过程中测量残余应力分布，因此不可能将应力分布用作工艺控制的参考值。因此，本研究建议旨在开发一个数值模型，使工艺布局尊重平面度和残余应力分布。在与工业合作伙伴的合作中，将对先前DFG项目中的现有数值模型进行增强，以考虑残余应力分布。首先，将使用数值模型研究矫直机的调节与残余应力分布之间的依赖关系。通过与工业合作伙伴开发的工艺模型的计算结果进行比较，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残余应力分布的优化标准。这些优化准则将被转换为包括虚拟反馈控制的数值模型，该包括反馈控制的数值模型可以计算矫直机的调节，从而同时优化平整度和残余应力分布。通过衍射方法的残余应力分布的实验测量，使验证和优化的数值模型。因此，一个数值模型是可用的，能够确定调整辊矫直机，导致平整度和优化的残余应力分布。此外，该模型还提供了有关通过弯曲工艺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.