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有了本质的改进。这促进了激光焊接工艺的产业布局。结合光束传播，可以预期关于例如光束几何形状、偏振、波长和调制的进一步发展步骤。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，甚至阻止了激光的使用。新的调查结果导致的结论是，在毛细血管的前侧和突起的毛细血管的后侧的波形结构中起着决定性的作用，在生成过程中的孔隙和飞溅。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组件相结合，允许使用来自毛细管的光的偏振状态来重建毛细管的3D几何形状，已经为实现上述发现做出了贡献，并将在本项目中用于澄清过程。然而，由于这些技术也是有限的，在他们的可访问性和在本地和时间的分辨率，它将是必不可少的，以数字方法分析所确定的过程。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。对于这种应用，在大变形的表面必须预期，网格自由的方法有巨大的优势，计算网格不必重复计算。光滑粒子流体动力学（SPH）方法特别适合于这样的问题，因为连续介质的状态变量被离散在根据速度场移动的点上，因此不受网格的约束。SPH程序Pasimodo（其可在申请人的地点获得）必须用一些模块扩展并与射线追踪程序组合，该射线追踪程序也是可获得的并且计算光束在毛细管中的传播和能量传递到熔体层中的空间分布。必须开发另一个模块，该模块计算由蒸发和气体流动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端产生的波以及毛细管后侧的突起以及由此产生的过程，根据现有信息，这些过程导致孔隙生成和飞溅。应使用三种明显不同的材料（钢、铝和冰）研究物理机制。第二个项目阶段的目标是评估工艺参数的影响，并使用由此产生的模型优化激光焊接工艺，同时考虑其稳定性。