Investigation of the influence of reversing stroke profiles on the workpiece characteristics in deep drawing using servo press technology (ServoDrawing)

拉深成形是生产具有三维几何形状的板料零件的最重要的制造技术之一。由于经济和生态的原因，高强度轻质结构钢越来越多地用于车身零件的深冲压。更高的强度允许使用更薄的金属板，这导致部件重量的减少，同时保持部件的负载能力。与传统的深冲钢质量相比，这些高强度钢具有明显较低的可成形性。这导致屈曲增加和髋臼杯底座断裂的早期发生。此外，出现了显著更高的工艺力。因此，高强度轻质结构钢的使用产生了关于深冲压工艺边界的新挑战。由此产生了经济问题，因为高强度钢的降低的可成形性和较高的工艺力缩小了可通过深拉工艺生产的工件的范围。在深冲过程中对高强度钢的可成形性产生选择性影响的一种可能性是使用创新的伺服压力机技术。与传统的驱动器相比，伺服压力机技术可以在低输入速度和停止位置实现非常精确的压头定位和高扭矩。伺服压力机允许在物理限制范围内自由编程冲压位移过程时间特性。一个特殊的柱塞位移-过程时间特性是反向行程曲线。其特征在于在成形过程中撞锤运动方向的一次或多次反转。首先，研究活动表明，在深冲过程中的材料流动是积极的影响相比，传统的轮廓反向行程轮廓。这种影响的原因尚未研究，因此需要采取行动。科学问题在于解释反向行程轮廓对工件中的材料流动的影响以及接触区域内关于摩擦效应的摩擦学相互作用。该项目的目的是开发一个广泛的解释模型，用于解释高强度钢拉深过程中反向行程曲线与工件特性之间的因果关系。所期望的模型解释了屈曲效应，板薄，工艺力减少和刀具和工件之间的摩擦关系的经验相关性和基于有限元分析公式的机械活动原理。通过所获得的基本工艺知识，实现了具有反向行程轮廓的高强度钢拉深的基于理解的和面向目标的工艺设计。

Deep drawing is one of the most important manufacturing technologies for the production of sheet metal components with threedimensional geometry. High strength lightweight construction steels are more and more used for the deep drawing of car body parts, due to economic and ecological reasons. The higher strength allows the use of thinner sheet metals which leads to a decrease of part weight while maintaining the load capacity of the parts. In comparison to conventional deep drawing steel qualities these high strength steels possess a significantly lower formability. This leads to increased buckling and earlier occurrence of cup base fracture. Furthermore, significantly higher process forces arise. Thus, new challenges regarding the process boundaries of deep drawing arise out of the use of high strength lightweight construction steels. From this follows an economic problem, as the reduced formability of high strength steels and the higher process forces narrow down the range of workpieces producible by deep drawing processes. One possibility for a selective impact on formability of high strength steel during deep drawing is the use of innovative servo press technology. In contrast to conventional drives a very exact positioning of the ram and high torques also at low input speed as well as in stop position are possible with servo press technology. Servo presses allow the free programming of ram-displacement-process time-characteristics within the physical limits. A special ram displacement-process time characteristic is the reversing stroke profile. It is characterized by a single or multiple reversion of the ram moving direction during the forming process. First research activities reveal that the material flow during deep drawing is positively influenced by reversing stroke profiles in comparison to conventional profiles. The cause for this effect is not researched yet and thereby derives a need of action. The scientific problem consists in the explanation of the influences of reversing stroke profiles on material flow in the workpieces as well as the tribological interactions within the contact areas regarding friction effects. The aim of this project is the development of an extensive explanatory model for the cause and effect relationships between reversing stroke profiles and the resulting workpiece characteristics for the deep drawing of high strength steels. The aspired model explains the mechanical active principles on buckling effects, sheet thinning, process force reduction and tribologic relationships between tool and workpiece by empirical correlations and analytical formulations based on FEM. By the acquired fundamental process knowledge a comprehension based and target-oriented process design for the deep drawing of high strength steels with reversing stroke profiles is enabled.