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，对钣金部件的质量要求越来越高，其中，变形控制起着重要的作用。目前尚未充分解决的一个问题是，由于上游生产过程中释放的残余应力，在后处理过程中厚板金属部件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，这只能通过昂贵且耗时的进一步后处理步骤（如热处理）来补偿。以机械加工后的厚金属板成形为例，应该表明，即使没有昂贵的返工工艺，也可以实现尺寸稳定的几何形状，以尽量减少变形。在本研究项目的范围内，首先对成形过程中引入的内应力进行模拟，并通过适当的测量方法对参考部件进行模拟，然后在加工过程中考虑内应力，以尽量减少部件的变形。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当前的残余应力状态。因此，后加工策略必须适应当前的残余应力状态。基于数值和实验结果，研究了成形速度、摩擦、去除策略、进给速度和浸泡深度等工艺参数对零件残余应力及其分布的影响。借助接收到的数据库，分析了各因素之间的因果关系，并推导出了减小构件畸变的适当措施。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，通常有效的度量是在参考组件的基础上推导出来的。同样，研究了成形过程的工艺参数对残余应力状态的影响，以便通过参数的选择，获得最适合后续加工的残余应力状态。与以前应用的方法相反，这些方法主要基于基于经验的方法，这种新方法旨在扩大对工艺的理解，从而系统地生产尺寸稳定的加工厚板金属部件。因此，研究结果为提高加工厚钢板部件的生产效率提供了一种创新的方法。

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.