Investigation of the formability of ductile sheet materials under non-proportional loading with consideration of the anisotropic damage behaviour

板料成形性的确定是板料零件设计的重要环节。由于复杂构件具有非线性的变形历史，用线性极限形状变化曲线来描述是不够的，因为剩余的成形性和破坏模式在很大程度上取决于变形历史。在本研究项目的框架内，应能够预测随加载方向变化的非比例加载路径后的变形能力。为此，对两种材料AA6xxx和DP600进行了系统的研究，获得了它们在复杂变形历史后的成形能力和破坏模式。在数值模拟的帮助下，创建了一个损伤模型，旨在映射这些材料的变形和破坏行为，从而能够对材料行为进行数值分析。研究项目的主要目标包括：•确定成形历史，加载方向以及应力状态对所选材料的成形性和力学参数的影响。•系统的区分和检测方法，用于区分韧性破坏和剪切破坏，并适应时间依赖的评估方法。•获得预应变与载荷方向变化之间的临界比率，由此产生剪切破坏，而不是颈缩，从而导致成形性损失。确定在成形操作之间的减压步骤和相关的材料松弛对失效模式的影响。•非线性织构发育对微孔的形成有显著影响。这种影响尚未得到调查，将在本项目范围内进行更详细的研究。

The determination of the formability of sheet materials is an important step in the design of sheet metal components. Since complex components have a non-linear deformation history, a description by means of a linear limit shape change curve is not sufficient because the remaining formability as well as the failure mode significantly depend on the deformation history. Within the framework of this research project, it should be possible to predict the deformability after non-proportional loading paths with a change in the loading direction. For this purpose, two materials, AA6xxx and DP600, are systematically investigated in order to obtain their forming capability and the failure mode after a complex deformation history. With the help of numerical simulations, a damage model is created, which isintended to map the deformation and failure behavior of these materials and thus enables a numerical analysis of the materialbehavior. The main goals of the research project include: • Identification of the influence of the forming history, the loading direction as well as the stress state on the formability and themechanical parameters of the selected materials. • Systematic differentiation and detection method for distinguishing between ductile failure and shear failure with adaptation of the time-dependent evaluation method. • Deriving a critical ratio between the pre-strain and a load direction change, from which on a shear failure occurs instead of necking which leads to a consequent loss of formability. • Determining the influence of a relieving step and the associated relaxation of the material between the forming operations on thefailure pattern.• The non-linear texture development has a significant influence on the formation of micropores. This effect, which has not yet been investigated, is to be examined in more detail within the scope of this project.