Influence of absorption mechanisms on the temperature distribution on the keyhole wall during laser deep penetration welding

输入到小孔的能量决定了小孔的性质，特别是壁温，以及缺陷的发生。由于缺乏直接评估小孔壁温的方法，目前还不清楚不同的吸收机制对能量输入和温度分布的影响。工艺缺陷与小孔壁温之间的关系也不清楚。因此，该项目的目的是定性地描述激光能量输入与小孔内温度分布之间的关系，以打开形成稳定小孔的可能性，从而减少气孔的形成。焊接过程中温度分布的实验确定将通过在位于基材孔洞中的钽管中进行几次热学测量来完成。因此，可以局部测量熔池中的温度与小孔壁上的温度之比。吸收模型能够根据吸收机理来描述温度分布。比较测量的和模拟的温度场，可以评估吸收机制对总能量吸收的贡献比例。此外，还观察了工艺气孔演化过程中的温度分布，以表征气孔的形成过程。

The energy input into the keyhole determines the keyhole properties, especially the wall temperatures, and also the occurrence of defects. Due to a lack of methods for directly evaluating the keyhole wall temperatures, it is not clear how the different absorption mechanisms contribute to the energy input and the temperature distribution. It is also not understood how process defects correlate to the keyhole wall temperature.Therefore, the aim of the project is to qualitatively describe the correlations between the laser energy input and the temperature distribution in the keyhole to open a possibility of forming a stable keyhole and thereby reduce pore formation. The experimental determination of the temperature distribution during welding will be done with several pyrometric measurements in tantalum tubes positioned in holes in the base material. Thus, the temperatures in the melt pool to the temperature on the keyhole wall can be locally measured. An absorption model is able to describe the temperature distribution depending on the absorption mechanisms. Comparing the measured and the modelled temperature fields the proportion of the absorption mechanisms contributing to the overall energy absorption can be evaluated. In addition, the temperature distribution during the evolution of process pores is observed to characterize the pore formation process.