【作者】 熊俊；

【导师】 张广军；

【作者基本信息】 哈尔滨工业大学 ， 材料加工工程， 2010， 硕士

【摘要】 双钨极耦合电弧是近年来发展起来的一种新兴的焊接热源,它是由双钨极氩弧焊焊枪产生的,焊枪内容纳了两个彼此绝缘的钨极,并由两台独立的电源供电。耦合电弧的形态已不再是轴对称的,它的物理特性也是未知的。研究耦合电弧的特性,如温度或电子密度等参数,可以更好的理解耦合电弧在焊接中的应用。目前,对耦合电弧的研究仍然比较少。因此,本文将利用光谱诊断的方法对耦合电弧温度场进行系统研究。以氩气保护定点耦合电弧为研究对象,建立了耦合电弧光谱图像采集系统,该系统包括高速摄像机、滤光片、中性减光片和透镜。为了获得不同方向的电弧图像,双钨极氩弧焊焊枪可以在0°到180°范围内绕其中心轴旋转。由于耦合电弧的非对称性,其发射系数不仅与径向位置有关,而且与方位角有关。因此,Abel逆变换将不再适用。本文开发了代数重建算法程序用于耦合电弧发射系数的恢复,同时通过一个偏置高斯模型研究了三种投影角度方案(4,8和10个角度)对重建质量的影响。结果表明,4个角度重建质量较差,10个角度由于投影角数多重建效果最好,且误差在1%到8%之间变化,特别是在电弧最为关键的中心部分,最大误差可以小于1%。采用代数重建算法恢复了钨极间距1mm、电流140A+140A、弧长4mm的耦合电弧发射系数,然后利用标准温度法计算其温度场。诊断结果表明,电弧的峰值温度约为18500K,且不再位于钨极下方而是在两钨极中间,电弧的温度分布形态已脱离了单弧的中心对称形态,其分布形态类似一个椭圆,这个椭圆的短轴与两钨极排列方向相同。研究了电流、钨极间距和弧长等焊接参数对耦合电弧温度场的影响,随着电流的增加,耦合电弧温度整体升高,电弧温度场更加扩展。随钨极间距的增大,电弧最高温度下降,由于本文研究的钨极间距较小,其对电弧温度场扩展的作用不是很明显,但仍在很大程度上影响了电弧体的整体温度。弧长一般不会影响耦合电弧的最高温度分布,只是随着弧长的增加,电弧温度场上下扩展。因此,弧长对电弧温度场的影响是有限的。更多还原

【Abstract】 The twin-electrode TIG coupling arc is a new type non-axisymmetric welding heat source developed in recent years, which is generated by a special welding torch that has two slanting tungsten electrodes insulated from each other. And two power supplies are separately connected to the two electrodes. The shape of the coupling arc is no longer axisymmetric. The physical properties of this coupling arc are unknown. Measurements of plasma properties, such as the temperatures or the densities of species, can greatly improve the understanding and performance of the coupling arc applications. To the present little research has been reported. In this paper, the temperature distribution of the coupling arc is systematically determined by spectroscopic technique.According to the study object of a stationary coupling arc between both slanting electrodes and a water-cooled copper plate, a monochromatic imaging system is capable of acquiring two-dimensional images with a high speed camera, a neutral, and a narrow-band filter and a lens. For the purpose of acquiring coupling arc images from different directions, the welding torch can rotate around its axis from 0°to 180°.Due to the asymmetry of the coupling arc, the emission coefficient of the non-axisymmetric plasma is not only related to radial location, but also related to azimuth. Thus, the Abel inversion is not applicable to it. In this investigation, the emission coefficient of the coupling arc was reconstructed on the basis of the algebraic reconstruction technique (ART) which was programmed by matlab language. The dependence of the reconstructed quality on three configurations (four, eight, ten projected views) were presented and discussed via a displaced gaussian model in order to define optimal scheme for good quality with limited views. The results show that the four-view configuration has a high reconstructed error. The minimum error is found for the ten-view configuration due to the largest number of views. For the ten-view configuration, the emission coefficient was reconstructed with error ranging between 1% and 8%. Furthermore, the results are more accurate and noise-resistant in the center area of the arc, which is one of the most critical parts to determine, the maximum error is less than 1%.The developed ART program was used to reconstruct the emission coefficient of a coupling arc with a current of 140 each, electrode distance 1 mm and arc length 4mm. The temperature distribution of the coupling arc was determined according to the normal temperature method. The results indicate that the maximum temperature in the high temperature region is approximately 18500 K. It is in the middle of both electrodes not below the electrodes. The distribution of temperature is different from centrosymmetric shape which is the conventional shape of a single arc. It is similar to an ellipse, and the short axis of the ellipse is in the direction that both electrodes are arranged along.The dependence of the welding parameters, such as the current, the electrode distance and arc length, were investigated. Increase of the arc current is associated with an increase of the arc temperature and the extension of the temperature distribution. The electrode distance ranging between 0.5 and 2 has no distinct affect on the temperature distribution because of the smallness of the electrode distance, but it has a significant effect on the bulk temperature,with the increase of the electrode distance, the bulk temperature decreases. Arc length seldom affects the distribution of the maximum temperatures, with the increase of the arc length, the extension of temperature distribution is larger. So the influence of the arc length on the temperatures of the coupling arc is limited.更多还原