Model-based minimization of distortion when machining post-processing of formed aluminum thick sheets

由于越来越复杂的几何形状和新材料的使用，对板材零件的质量要求越来越高，其中最重要的是变形的控制。目前尚未解决的一个问题是，由于上游生产过程中释放的残余应力，厚板零件在后处理过程中的固有应力引起的变形。由此产生的尺寸偏差是该行业的一个主要问题，只能通过昂贵且耗时的后处理步骤(如热处理)来补偿。以加工精加工的厚板成形为例，应该证明，即使没有昂贵的返工过程来最小化变形，尺寸稳定的几何形状也是可能的。在本研究项目的范围内，首先要模拟成形过程中引入的内应力，并在基准部件上采用适当的测量方法，然后在加工过程中将其考虑在内，以便将部件变形降至最低。在这种情况下，首先需要建立一个适合于成形和后续加工过程的仿真模型，并尽可能准确地反映普遍存在的残余应力状态。随后，加工后的策略必须适应当前的残余应力状态。在数值模拟和实验结果的基础上，研究了成形速度、摩擦、去除策略、进给速度和浸入深度等工艺参数对零件残余应力及其分布的影响。借助于接收到的数据库，随后对因果关系进行了分析，并得出了减小部件失真的适当措施。其目的是使加工后处理适应普遍存在的残余应力状态，并通过适当的工艺参数生产尺寸稳定的零件。在这种情况下，通常应根据参考分量导出有效的测量结果。同时，研究了成形工艺参数对残余应力状态的影响，以期通过对工艺参数的选择，获得最适合后续加工的残余应力状态。与以前应用的基于经验的方法不同，这种新的方法旨在扩大对工艺的理解，从而系统地生产尺寸稳定的机械加工厚板零件。研究结果为提高加工厚钢板零件的生产效率提供了一条创新的途径。

Due to more and more complex geometries and the use of new materials, the quality requirements for sheet metal components are increasing, whereby, above all, the control of distortions plays a major role. A currently insufficiently solved problem is the inherent stress-induced distortion of thick sheet metal components in the post-processing processes, due to released residual stresses from upstream production processes. The resulting dimensional deviations are a major problem for the industry, which can only be compensated by a costly and time-consuming further post-processing step like heat-treatment. Using the example of thick sheet metal forming with machining finishing, it should be shown that a dimensionally stable geometry is possible even without costly reworking processes to minimize distortion. Within the scope of this research project, the internal stresses introduced during the forming process are to be simulated first, as well as by suitable measuring methods on the reference component and then taken into account during machining in order to minimize component distortion. In this case, it is first necessary to build up a simulation model, which is suitable for the forming and for the subsequent machining process and reflects the prevailing residual stress state as accurately as possible. Subsequently, the strategy of the post-machining must be adapted to the current residual stress state. Based on numerical and experimental results, the influence of the process parameters, such as forming speed, friction, removal strategy, feed rate or immersion depth on the residual stresses and their distribution in the component is investigated. With the aid oft he received database, the causal relationships are subsequently analyzed and suitable measures for minimizing component distortion are derived. The aim is to adapt the machining post-processing to the prevailing residual stress state and to produce a dimensionally stable component by means of suitable process parameters. In this case, generally valid measures are to be derived on the basis of a reference component. Likewise, the influence of the process parameters of the forming process on the residual stress state is investigated in order to be able to achieve the most suitable residual stress state for the subsequent machining by selecting the parameters. In contrast to the previously applied approaches, which are mostly based on an experience-based approach, the novel approach aims to expand the understanding of the process and thereby systematically produce dimensionally stable machined thick sheet metal components. The research results thus offer an innovative way to increase the efficiency of the production of machined thick sheet steel components.