Modelling of the capillary in laser beam penetration welding with the Smoothed Particle Hydrodynamics Method

使用平滑粒子流体动力学方法对激光束熔透焊接中的毛细管进行建模

• 批准号: 266218804
• 负责人: Professor Dr.-Ing. Peter Eberhard
• 金额: --
• 依托单位: Institut für Technische und Numerische Mechanik (ITM)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/266218804?language=en
• 关键词: Modelling; capillary; laser; beam; penetration

The development of laser beam sources led laser based processing to essential improvements regarding beam quality und power. This promoted the industrial distribution of the laser welding process. In combination with beam propagation, further development steps can be expected concerning e.g. beam geometry, polarization, wave length, and modulation. Nevertheless, weld bead imperfections caused by spattering, blow holes, pores, cracks, and humping restrict the scope of applications or even prevent the use of lasers. New results from investigations lead to the conclusion that wavy structures at the capillary front and protrusions at the rear side of the capillary play a decisive role in the generation process of pores and spatters. New diagnostic tools like the online X-Ray technique and high speed recording systems in combination with new optics components, which allow to use the polarization state of the light coming from the capillary to reconstruct the 3D geometry of the capillary, have already contributed to attain the above-mentioned findings and shall be used in this project to clarify the processes. Since, however, also these techniques are limited both in their accessibility and in the local and temporal resolution, it will be indispensable to analyse the identified processes with numerical methods. The core problem is the simulation of the melt flow, whereby the free surface to the gas phase plays a decisive role. For such applications, where large deformations of the surface have to be expected, grid-free methods have the huge advantage that calculation grids have not to be recalculated repeatedly. The Smoothed Particle Hydrodynamics (SPH) method is especially well suited for such problems, because the state variables of the continuum are discretized at points, which are moved according to the velocity field and are, therefore, not bound to a grid. The SPH program Pasimodo, which is available at the applicants site, has to be extended with some modules and combined with a ray-tracing program, which is also available and which calculates the beam propagation in the capillary and the spatial distribution of the energy transfer into the melt layer. A further module has to be developed, which calculates the pressure acting on the melt surface resulting from the evaporation and gas flow. The final tool shall be used to calculate waves generated at the capillary front as well as protrusions at the rear side of the capillary together with the resulting processes, which lead, according to present information, to pore generation and spattering. The physical mechanisms shall be investigated with three significantly different materials, steel, aluminum, and ice. The aim in a second project phase will be to evaluate the influence of the process parameters and to use the resulting model to optimize the laser welding process also concerning its stability.

激光束源的发展导致基于激光的加工在光束质量和功率方面得到了根本性的改进。这促进了激光焊接工艺的产业布局。与光束传播相结合，可以预期进一步的开发步骤，例如：光束几何形状、偏振、波长和调制。然而，由飞溅、气孔、气孔、裂纹和隆起引起的焊道缺陷限制了应用范围，甚至阻碍了激光的使用。新的研究结果得出这样的结论：毛细管前部的波状结构和毛细管后部的突起在孔隙和飞溅的产生过程中起着决定性的作用。新的诊断工具，如在线 X 射线技术和高速记录系统，与新的光学元件相结合，允许使用来自毛细管的光的偏振态来重建毛细管的 3D 几何形状，已经有助于实现上述调查结果应在本项目中使用以澄清流程。然而，由于这些技术在其可访问性以及局部和时间分辨率方面都受到限制，因此用数值方法分析所识别的过程是必不可少的。核心问题是熔体流动的模拟，其中气相的自由表面起着决定性的作用。对于此类需要预计表面会发生较大变形的应用，无网格方法具有无需重复重新计算计算网格的巨大优势。平滑粒子流体动力学 (SPH) 方法特别适合解决此类问题，因为连续体的状态变量在点上离散化，这些点根据速度场移动，因此不受网格限制。 SPH 程序 Pasimodo（可在申请人现场获得）必须扩展一些模块，并与射线追踪程序相结合，该程序也可用，可计算毛细管中的光束传播和能量转移的空间分布进入熔体层。必须开发另一个模块，用于计算蒸发和气流产生的作用在熔体表面上的压力。最终工具应用于计算毛细管前部产生的波以及毛细管后侧的突起以及由此产生的过程，根据目前的信息，这些过程导致孔隙生成和飞溅。应使用钢、铝和冰这三种显着不同的材料来研究物理机制。项目第二阶段的目标是评估工艺参数的影响，并使用所得模型来优化激光焊接工艺以及其稳定性。