激光深熔焊接小孔效应的理论和试验研究

本文采用理论和试验相结合的方法系统研究了激光深熔焊接GG17玻璃时的小孔效应。首先采用高速摄影的方法清晰、完整地观测到了激光深熔焊接GG17玻璃时小孔的形状,并通过实验研究了聚焦光斑尺寸、离焦量、焊接速度等焊接工艺参数对小孔尺寸和形状的影响。然后,论文根据实验得到的小孔形状,通过曲线拟合的方法得到小孔前后沿孔壁的曲线方程,再按照几何光学原理,分析了激光在小孔孔壁上的多次反射吸收情况,并由此计算出了小孔孔壁通过多次反射吸收的激光功率密度分布情况。最后,建立了一个分层圆柱体面热源传热模型,在综合考虑热传导和熔池对流换热的基础上,计算了小孔周围的温度场和流场,求出了小孔孔壁上的热流密度分布,并与小孔孔壁吸收的激光功率密度进行了比较。

A theoretical and experimental investigation on keyhole effects in deep penetration laser welding

The keyhole effects in deep - penetration laser welding of GG17 glass are theoretically and experimentally studied in this paper. First of all, a keyhole can be clearly observed by a high speed camera, then the effects of such parameters as focal spot, focal position and welding speed on the shape and size of the keyhole are investigated. Secondly, the equations of the front and rear wall of the keyhole can be obtained by the method of polynomial fitting, then the laser intensity absorbed by the keyhole wail through Fresnel absorption can be calculated. Finally, on the basis of considering conduction and convection in the welding pool, a model with a cylinder surface heat source has been developed to calculated the temperature field and the flow field around the keyhole, the heat flux on the keyhole wall can then be obtained and a comparison between the heat flux and the laser intensity absorbed by the keyhole wall has been made.