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.

激光束源的开发使基于激光的处理是针对光束质量和功率的基本改进。这促进了激光焊接过程的工业分布。结合光束传播，可以预期有关例如光束几何，极化，波长和调制。然而，焊珠瑕疵是由飞溅，吹孔，孔，裂缝和驼峰引起的，限制了应用的范围，甚至阻止使用激光。研究的新结果得出的结论是，毛细管前部的波浪结构和毛细管后侧的突起在孔和飞溅物的发电过程中起决定性作用。新的诊断工具（例如在线X射线技术和高速记录系统）结合了新的光学元件组件，从而可以利用毛细管的光的极化状态来重建毛细管的3D几何形状，已经有助于获得上述发现，并应在该项目中使用该过程来阐明该过​​程。但是，由于这些技术的可访问性和局部和时间分辨率都受到限制，因此使用数值方法分析确定的过程是必不可少的。核心问题是模拟熔体流动，从而使气相的自由表面起着决定性作用。对于必须期望表面变形较大的应用，无网格的方法具有巨大的优势，即计算网格不得重复重新计算。平滑的颗粒流体动力学（SPH）方法特别适合此类问题，因为连续体的状态变量在点处被离散，根据速度场的移动，因此不与网格结合。 SPH程序Pasimodo在申请人站点可用，必须与一些模块一起扩展，并与射线追踪程序结合使用，该程序也可用，该程序还可以计算毛细管中的光束传播以及能量传递的空间分布到熔体层中。必须开发一个进一步的模块，该模块计算由蒸发和气流引起的熔体表面上的压力。最终工具应用于计算在毛细管前部产生的波，以及毛细管后侧的突起以及所得过程，根据目前的信息，这些过程引导到毛孔的产生和飞溅。物理机制应使用三种显着不同的材料，钢，铝和冰进行研究。第二个项目阶段的目的是评估过程参数的影响，并使用结果模型来优化激光焊接过程，这也与其稳定性有关。