A Finite element model is developed with a commercial code to investigate the keyhole dynamics and stability at keyhole threshold, a fusion regime characteristic to laser microwelding or to Laser Powder Bed Fusion. The model includes relevant physics to treat the hydrodynamic problems—surface tension, Marangoni stress, and recoil pressure—as well as a self-consistent ray-tracing algorithm to account for the “beam-trapping” effect. Implemented in both static and scanning laser configurations, the model successfully reproduces some key features that most recent x-ray images have exhibited. The dynamics of the liquid/gas interface is analyzed, in line with the distribution of the absorbed intensity as well as with the increase of the keyhole energy coupling. Based on these results, new elements are provided to discuss our current understanding of the keyhole formation and stability at threshold.

中文翻译：

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激光粉末床融合过程中阈值孔洞瞬态动力学和稳定性的有限元建模研究

用商业代码开发了有限元模型，以研究在锁孔阈值下的锁孔动力学和稳定性，这是激光微焊接或激光粉末床熔合的特征。该模型包括用于处理流体动力学问题（表面张力，Marangoni应力和反冲压力）的相关物理原理，以及用于解决“束阱”效应的自洽射线追踪算法。该模型以静态和扫描激光配置实施，成功地再现了最新X射线图像所展现的一些关键特征。根据吸收强度的分布以及锁孔能量耦合的增加，分析了液/气界面的动力学。根据这些结果，