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基于流体力学方程组和麦克斯韦方程组, 在合理的边界条件下, 建立了双钨极耦合电弧三维准静态数学模型. 通过对方程组的迭代求解, 获得了不同钨极间距和电弧长度下耦合电弧的温度场、流场、电弧压力和电流密度分布等重要结果, 与已有的实验研究符合良好. 模拟结果表明: 与相同条件下的钨极惰性气体保护焊电弧相比, 双钨极耦合电弧的最高温度和最大等离子流速较低, 阳极表面电弧压力和电流密度峰值明显减小; 钨极间距和弧长对耦合电弧的温度场、流场、电流密度和电弧压力等都具有显著的影响, 且耦合电弧阳极的电弧压力和电流密度分布不能用高斯近似进行描述.
关键词:
耦合电弧
三维模型
数值模拟 相似文献
2.
Approximate entropy a new statistic to quantify arc and welding process stability in short-circuiting gas metal arc welding 下载免费PDF全文
Based on the phase state reconstruction of welding current in short-circuiting gas metal arc welding using carbon dioxide as shielding gas, the approximate entropy of welding current as well as its standard deviation has been calculated and analysed to investigate their relation with the stability of electric arc and welding process. The extensive experimental and calculated results show that the approximate entropy of welding current is significantly and positively correlated with arc and welding process stability, whereas its standard deviation is correlated with them negatively. A larger approximate entropy and a smaller standard deviation imply a more stable arc and welding process, and vice versa. As a result, the approximate entropy of welding current promises well in assessing and quantifying the stability of electric arc and welding process in short-circuiting gas metal arc welding. 相似文献
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Cherng-Yuh Su Hsuan-Ching Lin Tsung-Kun Yang Chung-Kwei Lin 《Journal of nanoparticle research》2010,12(5):1755-1763
With the use of a modified plasma arc gas condensation technique and control of the processing parameters, namely, plasma
current and chamber pressure, we synthesized tungsten oxide nanomaterials with aspect ratios ranging from 1.1 (for equiaxed
particles with the length and width of 48 nm and 44 nm, respectively) to 12.7 (for rods with the length and width of 266 nm
and 21 nm, respectively). The plasma current and chamber pressure, respectively, ranged from 70 to 90 A and from 200 to 600 Torr.
We then characterized the tungsten oxide nanomaterials by means of X-ray diffraction, high-resolution transmission electron
microscope, UV–visible spectroscope, and photoluminescence (PL) spectroscope. Experimental results show that equiaxed tungsten
oxide nanoparticles were produced at a relatively low plasma current of 70 A, whereas nanorods were produced when plasma currents
or chamber pressures were increased. All of the as-prepared tungsten oxide nanomaterials exhibited a WO2.8 phase. Compared to the nanoparticles, the nanorods exhibited unique properties, such as a redshift in the UV–visible spectrum,
a blue emission in PL spectrum, and a good performance in field emission. With respect to the field emission, the turn-on
voltage for WO2.8 nanorods was found to be as low as 1.7 V/μm. 相似文献
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基于局域热平衡状态假设并考虑金属蒸汽的作用, 建立了钨极惰性气体保护焊电弧与熔池交互作用的三维数学模型. 电弧等离子体的热力学参数和输运系数由温度和金属蒸汽浓度共同决定, 并使用第二黏度近似简化处理金属蒸汽在氩等离子中的输运过程. 在考虑熔池流动时, 主要考虑了浮力、电磁力、表面张力和等离子流拉力的作用. 通过对麦克斯韦方程组、连续性方程、动量守恒方程、能量守恒方程和组分输运方程的耦合求解, 得到了金属蒸汽在电弧中的空间分布、电弧和熔池的温度场、速度场和电流密度分布等重要结果. 通过与未考虑金属蒸汽的结果对比, 研究了熔池上表面产生的金属蒸汽对电弧等离子体行为的影响, 以及电弧等离子对熔池行为的影响. 结果表明, 金属蒸汽主要富集在熔池上表面附近; 金属蒸汽对电弧等离子体有明显的收缩作用, 而对等离子速度和电势影响较小; 金属蒸汽的出现对熔池上表面速度分布和剪切力分布以及熔池形貌并无明显影响. 求解结果与已有的实验结果和计算结果符合良好. 相似文献
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根据磁流体动力学方程组,建立了微束等离子电弧模型,使用有限元分析软件COMSOL进行模拟计算。结果表明,电弧中心温度分布从钨针至焊件整体呈"毛笔"状,其中,喷嘴下方电弧形态呈"钟罩"形,在焊件上温度分布符合高斯分布特征;电弧等离子体在喷嘴内部速度较大,离开喷嘴后,其方向由喷嘴内的竖直向下逐渐变为到达工件时的向四周扩散;电流由焊件表面流出,经过弧柱区域流入钨针下端面,在钨针下端面附近取得最大值;电弧磁通密度分布呈"肺叶"状。最后进行了相应的熔焊试验,试验过程中拍摄的电弧轮廓与仿真电弧形态基本一致。 相似文献
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In the present study, different amounts of graphene nanosheets (GNSs) were added to the 4043 aluminum alloy powders by using the mechanical alloying method to produce the composite filler wires. With each of the produced composite filler wires, one all-weld metal coupon was welded using the gas tungsten arc (GTA) welding process. The microstructure, mechanical properties and fracture surface morphology of the weld metals have been evaluated and the results are compared. As the amount of GNSs in the composition of filler wire is increased, the microstructure of weld metal was changed from the dendritic structure to fine equiaxed grains. Furthermore, the tensile strength and microhardness of weld metal was improved, and is attributed to the augmented nucleation and retarded growth. From the results, it was seen that the GNSs/Al composite filler wire can be used to improve the microstructure and mechanical properties of GTA weld metals of aluminum and its alloys. 相似文献
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When the output from a high power Nd:YAG laser irradiates a metallic surface, metal vapor is generated and changes into the plasma state, which is called a laser-induced plasma plume. If the high power laser is combined with an arc plasma, they mutually attract and influence each other. In this study, several analytic steps are introduced to analyze the laser-arc hybrid welding plasma. A conduction equation is first solved to obtain the temperature distribution on the metallic surface. Next, an analysis of the metal vapor is conducted to investigate the Ar–Fe mixture using a numerical method. As a result of the analysis, it is revealed that the plasma is concentrated in the vicinity of the laser-irradiation position and that the local temperature of the plasma is increased. Plasma flow and current density profiles are also affected by the laser irradiation. 相似文献
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建立了脉冲电流下自由燃烧的TIG电弧的二维轴对称数学模型,利用FLUENT软件,通过选择合适的边界条件和强烈耦合控制方程组对脉冲TIG电弧进行了数值模拟,得到了在焊接电流周期性变化下电弧形态、电弧温度场、电弧轴线方向上的温度和速度及焊接工件表面电弧压力的变化情况;针对电弧压力,得到了不同峰值电流、占空比、脉冲频率作用下的分布情况,并分析了它们在脉冲电流作用下的周期性变化规律.分析结果表明:当脉冲电流发生突变时,它们的变化滞后于脉冲电流的变化,且从基值电流向峰值电流变化时的响应速度更快,并最终达到一个相对稳
关键词:
脉冲TIG焊
电弧
数值模拟
FLUENT 相似文献
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Numerical computations of the electrical properties and temperature profiles of wall-stabilized arcs in sulphur hexafluoride, SF6, at 1 ata are presented. The voltage gradient vs. arc current characteristic curve has a minimum point at which the axial temperature is the same inherent value of the gas independent of the arc radius. Also, the radial temperature distributions up to several hundreds of amperes corresponding to the axial temperature of some 20000 °K have been computed. 相似文献
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In this paper a modifed continuous energy law was explored to investigate transport behavior in a gas metal arc welding(GMAW)system.The energy law equality at a discrete level for the GMAW system was derived by using the finite element scheme.The mass conservation and current density continuous equation with the penalty scheme was applied 10 improve the stability.According to the phase-field model coupled with the energy law preserving method,the GMAW model was discretized and a metal transfer process with a pulse current was simulated.It was found that the numerical solution agrees well with the data of the metal transfer process obtained by high-speed photography.Compared with the numerical solution of the volume of fuid model,which was widely studied in the GMAW system based on the finite element method Euler scheme,the energy law preserving method can provide better accuracy in predicting the shape evolution of the droplet and with a greater computing efficiency. 相似文献
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Haidar J. Lowke J.J. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1997,25(5):931-936
We have developed a unified arc electrode model that enables us to make predictions of the time development of molten drops from the welding wire in gas metal arc welding. The wire is taken as the positive electrode, and the effects of surface tension, magnetic pinch forces, and convection within the drop are taken into account to predict drop detachment for any given arc current. For pure argon, we have previously predicted the sharp transition that is observed experimentally at about 300 A between globular transfer at low current, when drop diameters are larger than the wire diameter, and spray transfer, for currents above 300 A, when drop diameters are smaller than the wire diameter. In this paper, we predict that addition of 25% of CO2 to the argon leads to an increase in the transition current to more than 325 A, also in agreement with published experimental results. For pure CO2, we find a significantly different drop behavior due to the more constricted arc. Both small and large drops are produced, with many very small drops being produced successively between each large drop 相似文献
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This research was done on the basis of prediction that there is a relationship between welding parameters and geometry of the back-bead in arc welding which is a gap. Multiple regression analysis and artificial neural network were used as methods for predicting the geometry of the back-bead. The multiple regression analysis and the artificial neural network were formed, and the analysis data or verification data which were used in the formation process of the multiple regression, and the training data or test data which were used in the formation process of the artificial neural network, were used to perform the prediction of the back-bead. Through this research, it was found that the error rate predicted by the artificial neural network was smaller than that predicted by the multiple regression analysis, in terms of the width and depth of the back-bead. It was also found that between the two predictions, the prediction of the width of the back-bead was superior to the prediction of the depth in both methods. 相似文献
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The vibrational excitation of hydrogen adsorbed on the low-index faces of tungsten have been investigated using electron energy-loss spectroscopy. The results indicate the same vibrational force constant in “on-top” sites independent of substrate-atom geometrical environment. 相似文献
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The possibility of measuring the hydrogen impurity concentration in dense gas mixtures by coherent anti-Stokes Raman scattering
(CARS) is studied. In this technique, biharmonic laser pumping based on stimulated Raman scattering (SRS) in compressed hydrogen
is used. Because of the interference between the coherent scattering components from buffer gas molecules and molecules of
the impurity to be detected, the signal recorded may depend on the hydrogen concentration by a parabolic law, which has a
minimum and makes the results uncertain. It is shown that this uncertainty can be removed if the frequency of the biharmonic
laser pump, which is produced by the SRS oscillator, somewhat differs from the frequency of molecular oscillations of hydrogen
in the test mixture. A sensitivity of 5 ppm is obtained as applied to the hydrogen-air mixture under normal pressure. The
coefficients of the nonresonance cubic hyperpolarizability of molecules and atoms are measured relative to nitrogen in a number
of gas media. 相似文献
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将等离子焊接(PAW)电弧和钨极氩弧焊(TIG)电弧串接,相对作用于工件的正反面形成双面电弧焊接(DSAW)系统,可以引导焊接电流沿工件厚度方向流过小孔,补偿等离子电弧穿透工件时消耗的能量,以有效地提高等离子弧的穿透能力.综合考虑影响双面电弧焊接正反面熔池几何形状的力学因素,建立了熔池表面变形的控制方程,以此为基础并采用帖体曲线坐标系建立了DSAW焊接传热的数学模型,分析了DSAW,PAW焊接传热的差异,从传热的角度解释了DSAW焊接熔深增加的原因.焊接工艺实验表明,计算结果与实测结果吻合良好.
关键词:
双面电弧焊接(DSAW)
传热模型
熔池表面变形模型 相似文献
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《Superlattices and Microstructures》1999,25(1-2):487-491
The morphology of carbon nanotubes synthesized by arc discharge in a CF4gas atmosphere was investigated by scanning electron microscopy and transmission electron microscopy. The electronic properties of these nanotubes were investigated by electron spin resonance. The synthesis conditions in CF4gas were then compared with those in CH4, H2and He based on these results. Furthermore, the mechanism of tube growth in CF4gas was discussed briefly. 相似文献
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Hydrogen trapping at specific111In-vacancy complexes in tungsten was studied by means of perturbed angular correlations. The hydrogen was either implanted
into the sample or diffused from the gas. We observed desorption of the trapped hydrogen in the temperature range 450–550
K. 相似文献