Energy-Coupling Mechanisms Revealed through Simultaneous Keyhole Depth and Absorptance Measurements during Laser-Metal Processing
Energy-Coupling Mechanisms Revealed through Simultaneous Keyhole Depth and Absorptance Measurements during Laser-Metal Processing
复制标题
激光金属加工过程中钥匙孔深度和吸光度测量揭示的能量耦合机制
DOI：
10.1103/physrevapplied.13.064070
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发表时间：
2020-06-29
影响因子：
4.6
通讯作者：
Simonds, Brian J.
中科院分区：
文献类型：
--
作者：
Allen, Troy R.;Huang, Wenkang;Simonds, Brian J.
高亮度光与熔融金属之间的相互作用是一种复杂的多物理现象，它支撑着基于激光的添加剂制造、焊接和切割等工业过程。需要仔细注意的一个方面是熔融金属中蒸汽凹陷或锁孔的形成和演化。这些凹陷的动态行为可以极大地改变激光反射的次数，因此与耦合到系统中的瞬时能量内在地联系在一起。尽管它很重要，但严重缺乏这种关系的直接现场实验证据，这给那些致力于模拟或控制基于激光的制造过程的人带来了挑战。在这项工作中，我们结合了两种同时最先进的实时测量技术(在线相干成像和积分球辐射测量)来证实和探索高动态蒸气压抑几何结构与激光能量吸收之间的明确正相关。对于导致水汽抑制形成的辐射(>；=0.49 mW/cm(2))，我们观察到瞬时深度(最小到800微米)和吸收率(最高0.92)之间的良好相关性(0.86)，直接证明了它们之间的相互依赖关系。在作为添加剂制造的重要区域的过渡模式中，我们观察到伴随着吸收率从0.34到0.53的伴随变化的暂时性蒸气抑制的形成。在较高的辐照度下，随着小孔深度的平稳增加，吸收的激光功率逐渐增加，这是对激光-金属加工过程中多次反射影响的实时实验观察。利用射线跟踪模拟，给出了同时测量深度和吸收的预测模型验证的价值，该模拟还证实了通过增加反射计数来增强吸收。这项工作提供了对基于激光的金属制造的基本物理的洞察，这对确定性建模和实时过程控制有用。
The interaction between high-irradiance light and molten metal is the complex multiphysics phenomenon that underpins industrial processes such as laser-based additive manufacturing, welding, and cutting. One aspect that requires careful attention is the formation and evolution of vapor depressions, or keyholes, within the molten metal. The dynamic behavior of these depressions can dramatically change the number of laser-beam reflections and is therefore intrinsically linked to the instantaneous energy coupled into the system. Despite its importance, there is a severe lack of direct in situ, experimental evidence of this relationship, which creates challenges for those who aim to model or control laser-based manufacturing processes. In this work, we combine two simultaneous state-of-the-art real-time measurement techniques (inline coherent imaging and integrating-sphere radiometry) to confirm and explore the definite positive correlation between the highly dynamic vapor-depression geometry and laser energy absorptance. For irradiances resulting in vapor-depression formation (>= 0.49MW/cm(2)), we observe excellent correlation (0.86) between the instantaneous depth (down to 800 mu m) and the absorptance (up to 0.92), directly demonstrating their interdependence. In the transition mode, an important regime for additive manufacturing, we observe temporary vapor-depression formation with concomitant changes in absorptance from 0.34 to 0.53. At higher irradiances, we detect stepwise increases in the absorbed laser power with a smoothly increasing keyhole depth, which is a real-time experimental observation of the effect of multiple reflections during laser-metal processing. The value of simultaneous depth and absorption measurements for predictive model validation is presented using ray-tracing simulations, which also confirm the absorption enhancement via incremental increases in the reflection count. This work provides insight into the underlying physics of laser-based metal manufacturing that is useful toward deterministic modeling and real-time process control.