Improved process stability in three-dimensional paper forming due to numerical modeling of the material inhomogeneity

该研究项目的目的是通过考虑现有材料的不均匀性来改进纸张成形过程的设计和控制。为此，研究了局部不同性能对材料宏观力学行为的影响，并进行了数值模拟。德累斯顿工业大学（VM/VT）和达姆施塔特工业大学（PtU）的申请者正在这个项目上进行合作。迄今为止，他们一直专注于传统（VM/VT）和基于活动介质（PtU）的纸张成型工艺，从而受益于互补的专业知识。申请人的数值过程映射方法是基于微观力学模型（VM/VT）和将金属成型的既定模型转移到纸成型（PtU）。关于局部不均匀分布的材料特性（如密度）对整体力学特性的影响，目前的技术状况提供了不一致的信息。拟议项目中的工作旨在澄清材料性能的哪些波动对宏观行为有重大影响。为此，规划了不同的测量方法，如地层测量、数字图像相关和热成像。这些都集成到经典的材料表征方法，如拉伸试验，以观察局部力学行为。在施加不同的载荷场景时，还可以将弹塑性应变分量分开。在单元水平上对非均匀材料性能进行数值模拟和参数化是研究项目的第二部分。使用先前确定的数据，并在三个层次上开发了数值模型。除了将全局确定的特征值在单元水平上以非均匀分布覆盖外，还建立了一个分层和损伤（裂纹开始）的模型。通过与拉伸试验、膨胀试验等实例试验的对比，验证了三个模型水平的正确性。最后，将该模型集成到三维成形仿真中，研究材料和工艺参数对成形结果的影响。这里使用了来自纸张成型领域的申请人的互补经验。这使得有可能得出成型兼容纸生产的规范，稳健的工艺设计和工艺控制。在这个项目的范围内，澄清了材料的哪些性质波动是造成宏观特征值分散的原因。基于这些结果，数值方法有助于制定半成品和纸成型工艺的设计准则。

The aim of the research project is to improve the design and control of paper forming processes by taking into account the existing material inhomogeneity. To this end, the influence of the locally different properties on the macroscopic mechanical behavior of the material is to be investigated and numerically modeled. The applicants of TU Dresden (VM/VT) and TU Darmstadt (PtU) are cooperating on this project. They benefit from the complementary expertise, whereby they have focused on conventional (VM/VT) and active media-based (PtU) paper forming processes, so far. The applicants' approaches to numerical process mapping are based on micromechanical models (VM/VT) and the transfer of established models of metal forming to paper forming (PtU). The state of the art provides inconsistent information on the influence of locally inhomogeneously distributed material properties, such as density, on global mechanical properties. The work in the proposed project is intended to clarify which fluctuations in material properties have a significant influence on macroscopic behavior. For this purpose, different measurement methods such as formation measurement, digital image correlation and thermography are planned. These are integrated into classical material characterization methods such as the tensile test to observe the local mechanical behavior. When impressing different load scenarios, elastic and plastic strain components can also be separated from each other.The numerical modeling and parameterization of inhomogeneous material properties at element level represents the second part of the research project. The previously determined data is used and a numerical model is developed in three levels. In addition to the part that overlays the globally determined characteristic values with an inhomogeneous distribution at element level, a model for modeling delamination and damage (crack start) is developed. The three model levels are validated by comparison with example tests such as the tensile test and the bulge test. Finally, the model is integrated into three-dimensional, complete forming simulations to investigate the influence of material and process parameters on the forming result. The complementary experiences of the applicants from the fields of paper forming are used here. This makes it possible to derive specifications for forming-compatible paper production, robust process design and process control. Within the scope of this project, the question is clarified which property fluctuations in the material are responsible for the dispersion of the macroscopic characteristic values. Based on these results, numerical methods help to develop design guidelines for semi-finished products and paper forming processes.