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【期刊论文】Numerical simulation of dynamic development of keyhole in double-sided arc welding
武传松, CSWu, , J S Sun and Y M Zhang
Modelling Simul. Mater. Sci. Eng. 12(2004)423-442,-0001,():
-1年11月30日
Double-sided arc welding (DSAW) is a novel process for joining metals that is capable of achieving deep narrow penetration in a single pass with minimized distortion. Aclear understanding of the process fundamentals is critical in order to fully examine the potential of DSAW, to guide the further developments of the process, to direct the practicability study, and to design the process parameters. This paper aims at developing a numerical model for examining and simulating the dynamic keyhole establishment process, which will be a key in developing an effective control technology for DSAW. The model is used to determine the geometrical shape of the keyhole and the weld pool, and the temperature distribution in the workpiece. Quantitative information on the establishment of the keyhole in DSAW, such as the transient development of the keyhole and the weld pool, the increase rate of the depth of the surface depression, the time interval from full penetration to the keyhole establishment, the minimum span of the weld pool for describing the conditions required to complete the keyhole establishment, and variation of the overflow height of the weld pool surface on the plasma arc welding side, has been obtained through numerical analysis. The DSAWexperiments show that the predicted weld cross-section is in agreement with the measured one. The results lay a foundation for guiding the further development of the DSAW process and its effective control.
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武传松, P C Zhao, C S Wu and Y M Zhang
Modelling Simul. Mater. Sci. Eng. 12(2004)765-780,-0001,():
-1年11月30日
The gas tungsten arc welding process is an uncertain nonlinear multivariable system. In order to control the welding process, the nonlinear dynamic relationship between the weld pool geometry reflecting the weld quality and the welding parameters must be developed. A three-dimensional numerical model is developed to investigate the dynamic characteristics of the weld pool geometry when the welding current and welding speed undergo a step-change. Under the welding conditions employed in this research, the transformation periods are about 4s for a 20A down step-change of welding current, and about 2s for a 20mmmin−1 up step-change of welding speed, respectively. At the initial stage during the step-change of welding current and welding speed, the responses of weld pool geometry are quicker, but they slow down subsequently until the weld pool reaches a newquasi-steady state. Welding experiments were conducted to verify the simulation results. It was found that the predicted weld pool geometries agree with the measured ones.
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【期刊论文】Numerical analysis of temperature field during double-sided arc welding of thick materials
武传松, C.S. Wu *, J.S. Sun
Computational Materials Science 25(2002)457-468,-0001,():
-1年11月30日
Double-sided arc welding (DSAW) is a novel arc process developed at the University of Kentucky in which the workpiece is disconnected from the power supply and the two torches are used to establish two arcs on the both sides of the workpiece to close the current loop. As a result, the welding current is forced to flow through the workpiece along the thickness direction. This configuration and current flow direction improve the concentration of the arc energy distribution and provide a mechanism to guide the arc into the keyhole. Hence, DSAW process is capable of achieving deep narrow penetration and symmetrical welds. However, despite the progress in process development, there is a lack of a clear understanding of the physical processes and phenomena occurring in the weldment. In this study, a numerical model is developed to compute the temperature field and history in double-sided arc weldment. Using this numerical model, the temperature distributions and profiles at different cross-sections and along different lines of interest have been computed and compared with the results in regular plasma arc welding. It was found that DSAW process has advantages in obtaining deep narrow penetration, in producing symmetrical hour glass-shaped welds, in reducing the sensitization zone, in lowering the temperature gradient along the thickness, thus lowering the thermal distortion and residual stress, and in decreasing the sensitization duration.
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【期刊论文】Analysis of the heat flux distribution at the anode of a TIG welding arc
武传松, C.S. Wu *, J.Q. Gao
Computational Materials Science 24(2002)323-327,-0001,():
-1年11月30日
The correlation of the heat flux on the anode surface with the plasma properties at the free-fall edge was developed. By using the models of the tungsten inert gas (TIG) welding arc and the anode boundary layer, the heat transfer contributions to the anode heat flux in TIG welding were analyzed. The percentages of the electron flow contribution and the convection contribution were determined. The results show that the energy carried by the electrons constitutes most of the heat on the anode surface. 2001 Elsevier Science B.V. All rights reserved.
Analysis, Heat flux distribution, Anode, Welding arc
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【期刊论文】A Fuzzy Logic System for Process Monitoring and Quality Evaluation in GMAW
武传松, BY C. S. WU, T. POLTE AND D. REHFELDT
SUPPLEMENT TO THE WELDING JOURNAL, February 2001,-0001,():
-1年11月30日
This paper introduces a fuzzy logic system that is able to recognize common disturbances during automatic gas metal arc welding (GMAW) using measured welding voltage and current signals. A statistical method was employed to process the captured transient raw data, and the probability density distributions (PDDs) and the class frequency distributions (CFDs) were obtained. Based on the processed data (PDD values of welding voltage and current and CFD values of the short-circuiting time), the system automatically generates fuzzy rules and membership functions of linguistic variables, conducts inference and defuzzification, and completes the evaluation process without further expert knowledge.
Fuzzy Logic, Weld Process Monitoring, Weld Quality Monitoring, GMAW, Weld Process Control
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