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亚音速气流下不同空间位置激光烧蚀行为

Laser ablation behavior subjected to subsonic airflow at different spatial positions

  • 摘要: 为研究激光烧蚀过程中激光能量、表面气流、空间位置和金属材料之间的相互作用,提出了一个考虑亚音速切向气流和工件所处空间位置联合诱导熔体去除的流固耦合激光烧蚀模型,并通过与高速图像相比,验证了模型的合理性.在不同空间位置下,研究了表面气流与大尺度熔池的相互作用过程及熔体的剥离行为.研究发现,在气流和所处空间位置的联合作用下,一方面熔体被推出熔池后形成倾斜液柱,液柱熔体被加速至1.6 m/s甚至更高,为剥离熔池提供了高动量,另一方面液柱被拉伸至仅0.45 mm厚,易于克服表面张力,进而导致熔体剥离熔池形成飞溅.调整金属所处的空间位置,使得 \alpha 从90°减小至30°,重力沿金属受激光辐照表面的分量随之减少,液柱中熔体的流动速度由1.6 m/s减慢至1.4 m/s,熔体剥离所形成熔坑的尺寸逐渐减小,熔池剥离程度和金属质量损失显著降低.

     

    Abstract: In order to study the interaction between laser energy, surface airflow, spatial position and metal materials in the process of laser ablation, a fluid-structure coupled laser ablation model considering the combined action of subsonic tangential flow and spatial position of workpiece to induce melt removal is proposed, and compared with the high-speed image, the rationality of the model is verified.The interaction process between surface airflow and large-scale molten pool and melt peeling off behavior are studied at different spatial positions.It is found that induced by the combined action of airflow and spatial position, on one hand, the melt is pushed out of molten pool to form a tilted liquid column and accelerated to 1.6 m/s or even higher, providing high momentum for the melt to peel away from molten pool, on the other hand, the liquid column is elongated slender to be only 0.45 mm thick, which is easy to overcome the melt surface tension, this cause the melt to peel off and form spatter. Adjusting the metal spatial position and reducing \alpha from 90° to 30°, the component of gravity along the metal surface irradiated by laser is accordingly reduced. The melt flow velocity in the liquid column slows from 1.6 m/s to 1.4 m/s. The size of ablation crater formed by melt peeling off decreased gradually, and the peeling-off degree of molten pool and the metal mass loss are reduced significantly.

     

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