Numerical calculation of laser beam path influenced by high temperature gas above specimen during laser welding
Numerical calculation of laser beam path influenced by high temperature gas above specimen during laser welding
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激光焊接过程中试件上方高温气体对激光束路径影响的数值计算
DOI：
10.2351/1.5061617
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
S. Katayama
中科院分区：
文献类型：
--
作者：
M. Mizutani;S. Katayama
一般认为，波长在1 ~ 1.1 μm之间的光纤激光器、圆盘激光器和YAG激光器比波长为10.6 μm的CO2激光器对羽流和等离子体等介质的相互作用更小。然而，我们最近发现，在光纤激光远程焊接过程中，焊缝的形成受到气流状态、大气状态、试样上方的超细颗粒或等离子体羽流的很大影响。结果表明，在没有消除试样上方介质的情况下，激光束倾向于偏转或折射并聚焦在远端位置。为了理解激光束发生偏转的原因，本文采用温度梯度对假定折射率介质中的激光轨迹进行了数值计算。计算结果表明，焊接过程中试样上方陡峭的折射率梯度会降低光束质量，使焦点远移到原点之外。一般认为，波长在1 ~ 1.1 μm之间的光纤激光器、圆盘激光器和YAG激光器比波长为10.6 μm的CO2激光器对羽流和等离子体等介质的相互作用更小。然而，我们最近发现，在光纤激光远程焊接过程中，焊缝的形成受到气流状态、大气状态、试样上方的超细颗粒或等离子体羽流的很大影响。结果表明，在没有消除试样上方介质的情况下，激光束倾向于偏转或折射并聚焦在远端位置。为了理解激光束发生偏转的原因，本文采用温度梯度对假定折射率介质中的激光轨迹进行了数值计算。计算结果表明，焊接过程中试样上方陡峭的折射率梯度会降低光束质量，使焦点发生偏移。
It has been generally accepted that the laser beams of about 1 to 1.1 μm in wavelength, such as fiber, disk and YAG lasers have smaller interaction to the media such as plume and plasma between the optics system and the specimen than CO2 laser beam of 10.6 μm. However, we have recently found that weld bead formation is greatly affected by the state of the gas flow, the atmosphere, the ultrafine particles or the plasma plume above the specimen during fiber laser remote welding. The result showed that a laser beam tended to be deflected or refracted and focused on the far position without the positive elimination of the media above the specimen. In this paper, in order to understand why a laser beam is deflected, a numerical calculation about the laser trajectory in assumptive refractive index media by a temperature gradient was carried out. The calculation result suggested that the steep refractive index gradient above the specimen during welding should degrade the beam quality and shift the focal point far beyond the original position.It has been generally accepted that the laser beams of about 1 to 1.1 μm in wavelength, such as fiber, disk and YAG lasers have smaller interaction to the media such as plume and plasma between the optics system and the specimen than CO2 laser beam of 10.6 μm. However, we have recently found that weld bead formation is greatly affected by the state of the gas flow, the atmosphere, the ultrafine particles or the plasma plume above the specimen during fiber laser remote welding. The result showed that a laser beam tended to be deflected or refracted and focused on the far position without the positive elimination of the media above the specimen. In this paper, in order to understand why a laser beam is deflected, a numerical calculation about the laser trajectory in assumptive refractive index media by a temperature gradient was carried out. The calculation result suggested that the steep refractive index gradient above the specimen during welding should degrade the beam quality and shift the focal point fa...