工程陶瓷引弧微爆炸加工中等离子体射流的光学特征

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Micro-detonation of striking arc machining is a newly developed special machining technology for engineering ceramics and its energy output is by plasma jet.For there are intense light and heat while machining,it is very difficult to observe the plasma jet.By means of high speed photography and spectroscopic diagnosis,the external morphology and internal physical state of plasma jet are studied.The external appearance of plasma jet and material removal process of Si3N4 and Al2O3 are observed by using high speed photography.The observation finds that the diameter of jet increases with the increase of electric current and the diameter of ablation pit in single pulse machining expands gradually with machining time.The shape of ablation pit seems like a spherical cap.Combined with the propertiesy of materials,it can be inferred that the Si3N4 decomposes and Al2O3 melts during machining.For spectral analysis of the plasma jet,hydrogen atomic tracing method is employed and Hα spectral line is chosen.Results of analysis show that the electron density of plasma,which is obtained by Stark broadening method,is in the range of 1016 to 1017 cm?3 and reaches the condition of local thermodynamics balance.The influence regularity of machining parameters to electron density is analyzed.引弧微爆炸加工是一种新型工程陶瓷特种加工技术,其能量通过等离子体射流输出,由于加工过程伴随着强烈的光和热,直接测试十分困难。通过高速摄像技术和光谱分析技术,综合对等离子射流的外部形态和内部物理状态进行研究。利用高速摄像,观察射流的外观以及氮化硅和氧化铝两种陶瓷材料加工时的材料去除过程。观察发现,射流直径随电流值的增大而增大,单脉冲加工时蚀坑直径随着加工时间逐渐扩展,蚀坑形状近似为球冠形;结合材料性质,推断出氮化硅陶瓷加工时分解,氧化铝陶瓷加工时直接熔化。对等离子体射流的光谱分析,采用氢原子示踪法,选择Hα谱线进行。分析结果显示,采用斯塔克展宽法获得的等离子体的电子密度在1016～1017cm?3范围内,满足局部热力学平衡状态,并分析了加工参数对电子密度的影响规律。