极性变换过程的电弧图像同步错时拍摄及其动态行为观测

Synchronous staggered shooting of electric arc images and arc dynamics during polarity commutation

对变极性钨极惰性气体(tungsten inert gas,TIG)保护焊电流换向过程中的电弧形态和电流变化信息进行同步采集及综合分析,有助于深入认识极性变换过程中电弧的动态变化机理。然而,变极性过程持续时间短,对电流信息和电弧图像的同步采集精度以及图像采集设备的采集频率和图像分辨率都提出了较高要求。该文综合运用数据采集卡的同步输入与输出功能及高速摄像的同步触发功能,实现了变极性过程的焊接电流和电弧图像的同步采集,同步误差可控制在2μs以内,同时,利用脉冲触发电压周期与变极性周期的差值,实现了以较低的采集频率和较高的图像分辨率而获得了近似连续变化的电弧图像,降低了对图像采集设备的性能要求。在此基础上,对焊接电弧动态行为随电流的变化规律进行初步分析,发现变极性过程中电弧形态变化滞后于电流变化,电流过零时刻及前后不会发生电弧熄灭现象,且电弧灰度最低时刻出现在极性变换后的电流恢复阶段,研究结果为进一步改善变极性TIG焊的电弧燃烧稳定性指明了方向。

The synchronous acquisition and analysis of information about arc shape and current variations during the polarity commutation process of variable polarity tungsten inert gas(VP-TIG)arc welding are helpful to understand the arc dynamics mechanism.However,the polarity commutation process is relatively short,which leads to higher accuracy requirements for synchronous acquisition of the current information and arc image,as well as the acquisition frequency and image resolution of the image acquisition equipment.In this paper,the synchronous input and output functions of a data acquisition board were related to the synchronous trigger of a high-speed camera to realize synchronization acquisition of the welding current and arc image during polarity commutation with the synchronization error controlled to within 2μs.In addition,use of the difference between the trigger voltage pulse and variable polarity periods enabled approximately continuous observation of the arc images with a lower acquisition frequency and higher image resolution,which reduces the camera speed requirement.The observations of the welding arc changes with the current showed that the arc shape variation lags behind the current change during the polarity commutation process and arc extinction does not occur at or around the time when the current value passes zero.In addition,the arc with the lowest gray level appears in the current recovery stage after the polarity commutation process.The results indicate directions for further improving the arc burning stability of VP-TIG arc welding.