Efficient Modelling of Chip Formation in Orthogonal Cutting Based on Isogeometric Analysis and Modern Methods for Material Characterization

该项目考虑了切屑形成的数值模拟及其在估计切割过程的工艺参数方面的潜力。同样在商业软件中，基于有限元方法的切屑形成的数值模拟是预测切削过程中复杂的热机械效应的常用方法；特别是在刀具刃口附近。然而，现有技术显示出局限性，即一方面实际的切屑形成模拟只允许表示非常短的工艺序列，另一方面它们的基本模型的有效性有限；特别是在诸如力、应力、应变、温度和切屑形状的工艺数值的定量预测方面。这些局限性部分是由于材料和摩擦模型不足造成的，然而，有明确的证据表明，所使用的有限元网格(细化、单元类型、单元变形和取向)不仅对数值结果的精度有很大影响，而且对可以捕捉到的一般现象也有很大影响。这尤其包括剪切带的发展。这些依赖关系旨在通过使用现代数值方法来解决，即等几何分析(IGA)和时空有限元。拟议项目的具体科学目标是开发一种基于等几何分析和已建立的计算流体力学中的变形空间域/稳定时空(DSD/SST)方法的现代切屑形成数值分析工具。新工具将在效率和精度方面进行评估，特别是在初级和次级剪切区以及工件表面区的影响方面。它必须得到现代材料表征方法的支持。在方法论方面，对IGA在用热力学耦合材料方程模拟动态接触问题时所呈现的行为的理解。特别是通过重新划分网格步骤引起的数值误差的显著减少，有望导致数值精度的提高。这是切屑形成模拟的重要一步，并将立即提高其适用性。

The proposed project considers the numerical simulation of chip formation and its potential to estimate process parameters for cutting processes. Also available in commercial software, the numerical simulation of chip formation based on the finite element method is a commonly used approach to predict the complex thermo-mechanical effects in cutting; in particular in the vicinity of the cutting edge. However, the state of the art shows limitations, i.e. on the one hand the actual chip formation simulations permit only the representation of very short process sequences and on the other hand their underlying models are of limited validity; in particular in terms of the quantitatively prediction of process values such as forces, stresses, strains, temperatures, and chip shapes. These limitations are partially due to insufficient material and friction models, however, there exists clear evidence that the utilized finite element meshes (refinement, element type, element deformation and orientation) have a strong influence not only on the accuracy of the numerical result, but also on the general phenomena that can be captured. This includes in especially the development of shear bands. These dependencies are intended to be resolved via the use of modern numerical methods, namely isogeometric analysis (IGA) and space-time finite elements.The specific scientific aim of the proposed project is to develop a modern numerical analysis tool for chip formation based on isogeometric analysis and the in computational fluid dynamics already established Deforming-Spatial-Domain/Stabilized Space-Time (DSD/SST) method. The new tool is to be assessed in terms of efficiency and accuracy, in particular regarding effects in the primary and secondary shear zone, but also the workpiece surface zone. It has to be supported by modern methods of material characterization. On the methodological side, an understanding of the behavior IGA presents when modeling dynamic contact problems with thermodynamically coupled material equations. Especially the significant reduction of numerical errors, which are induced through remeshing steps, are expected to lead to an increase in numerical accuracy. This constitutes an important step for chip formation simulation and will immediately improve its applicability.