Melt dynamics in remote laser material processing

与传统的气体辅助切割工艺相比，远程融合切割（RFC）或前压切割由于其资源效率和工业上更灵活的可行性，在各种工业应用中具有很高的潜力。然而，稳定的流程布局对于利用这种潜力至关重要。目前，由于参数的变化，过程的行为通常不稳定，并且缺乏解释或解决这种行为所需的过程理解。因此，在拟议的项目中，将开发稳定工艺布局所需的工艺理解。为了全面了解这一过程，不仅研究了RFC的过程，还研究了其过程窗口的边界，即向焊接状态的过渡。在第一步，实验所需的分析算法和已经开发的仿真模型将适应过程，改进和验证。然后，该过程将通过实验和模拟来分析和理解材料去除的机制。更具体地说，相互作用区的拓扑结构、形状和大小将通过录像和模拟的方式进行研究，并将阐明这些特征如何影响RFC中的熔体流动和材料去除。此外，将主要模拟分析蒸发和相关蒸汽压力如何影响熔体流动，以及表面张力、蒸汽压力和流体动压在RFC和过渡到焊接中的表现。由于RFC对轨道几何形状变化的反应比焊接更敏感，这经常导致切割损失，因此将通过录像和模拟的方式研究轨道几何形状如何影响相互作用区的形状、熔体流动和材料去除。此外，还将研究激光功率如何以及在多大程度上影响最大进给速度和切割边缘的质量。由于本项目使用的是经过验证的流体动力学过程模型，如果在过程的某些区域实验和模拟之间存在差异，造成差异的原因可能限于实施模型中的错误或错误的材料特性。因此，通过与实验的比较和模型的迭代变化，可以建立对过程的理解。这一过程的理解将用于研究控制和稳定过程的可能性，例如通过调制激光功率或使用相位掩模修改强度分布。这些知识将被浓缩到用户规则中，以促进RFC的工业适用性。

Remote Fusion Cutting (RFC) or Front Pressure Cutting has high potential for various industrial applications compared to conventional gas-assisted cutting processes due to its resource efficiency and its more flexible feasibility in industry. Stable process layout, however, is crucial to make use of this potential. Currently, the process behaves often instable regarding changes of parameters and the process understanding needed to explain or resolve this behavior is lacking.Therefore, in the proposed project the process understanding necessary for stable process layout will be developed. In order to understand the process comprehensively, not only the process of RFC, but also the borders of its process window, i. e. the transitions to the welding regime will be investigated. In the first step, the analysis algorithms necessary for the experiments and the already developed simulation model will be adapted to the process, improved and verified. Then, the process will be examined experimentally and simulatively to analyze and understand the mechanisms of material removal. More specifically, topology, shape and size of the interaction zone will be investigated videgraphically and simulatively and it will be clarified how these characteristics influence melt flow and material removal in RFC. Furthermore, it will be analyzed, primarily simulatively, how evaporation and the associated vapor pressure influence melt flow and how surface tension, vapor pressure and hydrodynamic pressure behave in RFC and in the transitions to welding. Since RFC reacts to changes of track geometries way more sensitively than welding and this often leads to loss of cut, it will be investigated videographically and simulatively how the track geometry influences the shape of the interaction zone, the melt flow and the material removal. Additionally, it will be investigated how and how much the laser power influences the maximum feed rate and the quality of the cut edges.Due to the verified fluiddynamic process model used in the project, in case of differences between experiment and simulation in certain areas of the process, the cause of the differences can be limited to an error in the implemented model or to false material properties. Therefore, by comparisons with experiments and iterative changes of the model process understanding can be built. This process understanding will be used to investigate possibilities to control and stabilize the process, e. g. by modulation of the laser power or modifications of the intensity distributions using phase masks. This knowledge will be condensed in user rules to contribute to the industrial applicability of RFC.