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首页> 外文期刊>Journal oflaser Applications >Visualization of refraction and attenuation of near-infrared laser beam due to laser-induced plume
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Visualization of refraction and attenuation of near-infrared laser beam due to laser-induced plume

机译：可视化激光诱导羽流引起的近红外光束的折射和衰减

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摘要

This study was performed to obtain a fundamental knowledge of the interaction between a near-infrared laser beam and an induced plume during welding. The plume was characterized by spectroscopy, and the effect and mechanism of the laser-induced plume on the refraction and/or attenuation were investigated by high-speed video observation of the plume and the probe laser, and power meter measurement of the fiber probe laser beam of 1090 nm wavelength which passed horizontally through the plume formed during bead-on-plate welding of an 8-mm-thick type 304 plate with a 1.5 kW yttrium-aluminum-garnet (YAG) laser beam. The plume induced by YAG laser at the focus position grew about 20 mm toward the incident laser beam and was identified to be nonionized metallic vapor of 3600 K in average temperature on the basis of the spectroscopic analyses. The high-speed observation images and the power measuring results revealed that the rapid movement and the low brightness of the probe laser beam, seen after the plume, were caused by refraction due to density difference between the plume and its environment and Rayleigh scattering due to ultrafine particles, respectively. The maximum refraction and attenuation were 1.2 mrad and 3%, which were much lower than the beam divergence and the same levels as power variation in the incident YAG laser beam under argon (Ar) shielding gas, respectively. Moreover, the YAG laser-induced plume hardly affected the reduction in weld penetration under the defocused conditions since the penetration of type 304 weld made without Ar shielding gas was deeper than that produced with Ar shielding gas although the former plume was longer than the latter one. This reason was interpreted in terms of the greater effect of surface tension-driven melt flows. Consequently, the wavelengths of near-infrared laser beams were desirable for laser welding in the case of the laser-induced plume of less than 20 mm height, owing to their weak optical interaction to the plume.
机译：进行这项研究是为了获得焊接过程中近红外激光束与感应羽流之间相互作用的基础知识。通过光谱学对烟羽进行表征，并通过高速视频观察烟羽和探针激光器，并通过功率计测量光纤探针激光器，研究了激光羽流对折射和/或衰减的影响和机理。波长为1090 nm的光束水平穿过1.5 mm钇铝石榴石（YAG）激光束对厚8毫米的304型板进行压焊时形成的羽流。 YAG激光在焦点位置感应出的烟流向入射激光束方向增长了约20 mm，并且根据光谱分析被确定为平均温度为3600 K的非离子化金属蒸气。高速观测图像和功率测量结果表明，羽流之后所观察到的探测激光束的快速运动和低亮度，是由于羽流与周围环境之间的密度差以及由于瑞利散射引起的折射而引起的。分别是超细颗粒。最大折射和衰减分别为1.2毫拉德和3％，远低于光束发散度，并且与在氩气（Ar）保护气体下入射YAG激光束的功率变化相同。此外，YAG激光诱导的烟流几乎不会影响散焦条件下焊缝熔深的降低，因为无氩气保护气体的304型焊缝的熔深比采用氩气保护气体产生的熔深，尽管前者的烟气长于后者。 。用表面张力驱动的熔体流动的更大影响来解释该原因。因此，在激光诱导的烟羽高度小于20 mm的情况下，由于近红外激光束的波长与烟羽之间的光学相互作用较弱，因此希望进行激光焊接。

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