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Optimal welding condition in resistance spot welding of 7075-T6 aluminum alloy sheets with the thickness of 0.4mm was investigated by the tensile-shear strength tests and Taguchi method in experimental design with changing various welding conditions respectively. The tensile-shear tests were carried out at cross-head speeds of 0.1mm/min in accordance with the KS B0851. Design methods were systematically performed using an L₂₇(39) orthogonal array table. In the experimental design, three control factors of resistance spot welding conditions were electrode force, welding current and welding time. Electrode force conditions were 882N, 1323N and 1764N, and welding current were 13.5kA, 14kA and 14.5kA, and welding time were 3cycle, 4cycle and 5cycle.

A numerical modeling of the welding arc and weld pool is studied for moving GTA welding to investigate the effect of the surface active element oxygen and the plasma drag force on the weld shape. Based on the 2D axisymmetric numerical modeling of the argon arc, the heat flux, current density and plasma drag force are obtained under different welding currents. Numerical calculations to the weld pool development are carried out for moving GTA welding on SUS304 stainless steel with different oxygen contents 30 ppm and 220 ppm, respectively. The results show that the plasma drag force is another dominating driving force affecting the liquid pool flow pattern, except for the Marangoni force. The different welding currents will change the temperature distribution and plasma drag force on the pool surface, and affect the strength of Marangoni convection and the weld shape. The weld D/W ratio initially increases, followed by a constant value around 0.5 with the increasing welding current under high oxygen content. The weld D/W ratio under the low oxygen content slightly decreases with the increasing welding current. The predicted weld shape by simulation agrees well with experimental results.

A three-dimensional numerical model of double-arc in tandem gas metal arc welding (GMAW) was established based on the theory of arc physics, momentum equation, energy equation, continuous equation and Maxwell equations. The effects of different welding current on temperature field, velocity field and pressure field on the surface of workpieces were investigated. The results showed that the maximum values of arc temperature, arc plasma velocity and arc pressure on workpieces surface were increased with the increasing welding current. These maximum values occurred at the tip of double-wire. The current density and axial deflection angle of coupling arc were increased following the increasing welding current.

Gas tungsten arc welding (GTAW), also known as tungsten inert gas welding, is now widely used in the manufacturing industry. In GTAW, the weld size, especially the weld depth, is one of the important parameters of the weld. Many studies demonstrated that the weld depth significantly affects the quality of the weld joint and is greatly influenced by the welding current. Thus, estimating the welding current value for the desired weld depth is necessary. This paper presents a method to estimate the welding current in the GTAW process with a specified width penetration for AISI 304 stainless steel with 0.8mm thickness. The welding current determination of the GTAW process is performed by using the inverse method. In this work, the inverse method utilized is the Levenberg–Marquardt (LM) method. The advantage of the method is that the algorithm is simple, easy to apply, and has a high convergence rate. Two examples are considered to demonstrate the proposed method. The relative error between the desired width penetration of the weld value and the estimated width penetration of the weld by the LM method is very small (0.2% for case 1 and 0.08% for case 2). The results show that the proposed method efficiently estimates the welding current for a specified width penetration in the GTAW process.

The arc in the vicinity of the molten pool in the process of CO₂ welding has a complex distribution. Changes of the arc limit the development of seam tracking technology based on vision seriously. Therefore, exploring and studying the image's gray distribution, which is captured by the CCD camera in the vicinity of the molten pool, can provide the basic conditions for the selection of suitable welding current and the irradiated area, thus preparing for getting a clear picture. Firstly, image acquisition system which can be flexibly adjusted is established. Secondly, the numerical model of gray value in the area near the welding pool under different welding currents is built with the toolbox called cftool in Matlab. Experimental results show that: with the increase of welding current, the gray value of the image, which is captured by the CCD camera near the weld pool, is increased slightly; with the increase of distance, the gray value of the image, which is captured by the CCD camera near the weld pool, is reduced. When the distance between torch and the area is less than 10mm, the gray value decreased sharply. When the distance between torch and the area is more than 10mm, the gray value decreased slowly. The fitting results conform to the objective laws. It lays the foundation for the welding seam automatic tracking technology.