铝板的CO_2激光焊接等离子体二维温度分布的测量

Measurement of Two-dimensional Plasma Temperature Field of Al in CO_2 Laser Welding

利用两个严格同步触发的高速相机,拍摄获取纯铝在CO2激光焊接过程中的等离子体在同一个方向上的二维投影。每个高速相机镜头前均加载了一定规格的滤波片,分别能允许宽度为4 nm、中心线分别为670和589 nm的谱线通过。这两条谱线分别是Al元素的一级和二级电离特征谱线。结合相机标定的原理,对两个特征谱线的二维投影图片进行配准,根据等离子体的热力学方程,使用双谱线比较法,得到了等离子体的二维温度分布。与传统的光谱方法相比,本文的方法可以获得二维温度场,从而可以从更加丰富的角度去分析等离子体的温度与侧吹气体流量等焊接参数的关系。

Two strictly synchronous high-speed cameras were used to obtain the plasma image in the same location in the process of CO2 laser welding of pure Al. Each camera was equipped with a special prepared filter, which can only pass 2 nm wide spectral lines with the center wavelength of 670 nm and 589 nm. These two lines are primary and secondary ionization Al element characteristic line, respectively. Camera calibration was used to precisely fit the image position in the two projections gotten from the each camera. Then according thermodynamic equation of plasma, the relative intensity method of dual spectral line was adopted to get two dimensional temperature field of plasma. Compared with traditional methods, the research can provide new ideas to analyze the plasma temperature, as well as the relationship with the gas flow rate.