Experimental and Theoretical Analysis of Deep Penetration Welding Processes with Low-Power Laser-Assisted Plasma Arcs

本研究项目旨在进一步提高我们目前对激光辅助等离子弧焊接工艺的认识，特别考虑到在低激光束强度和低电弧电流下实验验证的深熔深效应。首先，通过针对不同类型的金属（例如铁、铝、镁、钛或其合金）的板上焊道焊接试验来确定加工条件。其次，它的目的是揭示最相关的相互作用机制负责转移到深熔焊接制度的特定的实验和理论方法。第一次，新的研究假设，关于激光辅助等离子弧焊过程中的能量传递效率和热和流体-机械相互作用的可能变化，将得到验证。这涉及深熔焊接条件下的光束吸收、电弧根形成和预热效应的研究。此外，在环境压力分布和局部流场的变化的影响，引起的电弧流与激光诱导蒸发过程的相互作用，对深穿透效果的特点。自行研制的激光束和等离子弧同轴布置，引导激光束通过薄空心钨阴极，将应用于激光辅助等离子弧焊接试验。此外，不同的实验装置被设计用于详细调查可能的相互作用现象。经过调整的数值模拟模型支持对无法通过实验方法直接观察到的影响进行评估。因此，在激光辅助等离子弧焊接中最重要的相互作用机制将被确定。随着对工艺的进一步了解，可以根据被焊接材料的特定特性，得出激光辅助等离子弧焊接的最佳参数设置指南。

This research project aims at the further improvement of our current knowledge about laser-assisted plasma arc welding processes with particular consideration of the experimentally verified deep penetration effect at low laser beam intensities and low arc currents. Firstly, the processing conditions are to be identified by means of bead-on-plate welding trials for different types of metals such as iron, aluminum, magnesium, titanium or their alloys. Secondly, it is intended to reveal the most relevant interaction mechanisms being responsible for the transfer into the deep penetration welding regime by particular experimental and theoretical approaches. For the first time, new research hypotheses, concerning possible changes of the energy transfer efficiency and of thermal and fluid-mechanical interactions during laser-assisted plasma arc welding, will be verified. This involves investigations of beam absorption, arc root formation and preheating effects under conditions of deep penetration welding. Furthermore, the impact of changes in ambient pressure distribution and local flow fields, induced by the arc flow in interaction with laser-induced evaporation processes, on the deep penetration effect are to be characterized. A self-developed coaxial arrangement of the laser beam and the plasma arc, which directs the laser beam through a thin hollow tungsten cathode, will be applied for the laser-assisted plasma arc welding trials. In addition, different experimental setups are designed for detailed investigations of possible interaction phenomena. Adapted numerical simulation models support the evaluation of effects that cannot be directly observed by experimental methods. As a result, the most important interaction mechanisms in laser-assisted plasma arc welding will be identified. With the improved process understanding, guidelines for optimal parameter settings for laser-assisted plasma arc welding can be derived, depending on the particular properties of the material being welded.