根据当前制造业对高效、优质、低耗焊接技术的迫切要求，研发出低成本的高速电弧焊接新工艺DE-GMAW。该工艺在常规GMAW焊接设备的基础上，通过附加GTAW焊枪构成旁路电弧，分流了一部分通过焊丝的焊接电流，在施加于焊丝的电流较大的情况下（保证了熔敷率），减小了作用于母材的热输入，解决了高速焊接面临的矛盾，实现了高速电弧焊接。建立了适用于DE-GMAW焊接工艺的有限元模型，并对该工艺条件下的温度场和应力变形进行了数值模拟。结果表明：计算出的DE-GMAW焊缝横断面形状尺寸与实验结果吻合良好；在通过焊丝的总电流相同时，DE-GMAW焊接时焊缝尺寸、热影响区宽度、应力、应变及变形均小于常规GMAW焊时的结果。这为DE-GMAW焊接工艺参数优化提供了基础数据。

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.

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.

Establishing the correlation between transient behaviors of surface deformation of weld pools and workpiece penetration information, and quantitatively analyzing the surface deformation at top and bottom surfaces at the moment when the pool is penetrated and their dynamic responses to welding process parameters will provide many basic data for the realization of topside vision-based penetration control in gas tungsten arc welding (GTAW). A transient numerical model is developed to investigate the dynamic behaviors of full-penetrated GTAW weld pools in this paper. A whole and comprehensive scheme is used in which many factors such as moving arc, 3-D fluid and heat flow fields, transient state, full-penetrated weld pool and surface deformation at both top and bottom surfaces are considered. The transient developments of 3-D surface deformation and shape of weld pool during the period from partial penetration to full penetration are predicted. The simulated results show that the curves of ratios of the maximum depression to the length and width at top surface of weld pool at different times clearly indicate the basic information of penetration. So the relation of the ratios versus time can be used as an indicator to judge whether the weld pool is penetrated.

It is a key issue to establish an appropriate model of the heat source in the simulation of the keyhole plasma arc welding (PAW). It requires that the model account for the keyhole effect and have the characteristic of volumetric distribution along the direction of the plate thickness. For available heat source models, neither Gaussian nor double ellipsoidal modes of heat source is applicable to keyhole PAW process. With considering the force of the high speed plasma jet and the associated strong momentum, a modified three-dimensional conical heat source model is proposed as the basis for the numerical analysis of temperature fields in keyhole PAW process. Further, a new heat source model for quasi-steady state temperature field in keyhole PAW is developed to consider the “bugle-like” configuration of keyhole and the decay of heat intensity distribution of the plasma arc along the direction of the workpiece thickness. Based on this heat source model, finite-element analysis of temperature profile in keyhole PAW is conducted and the weld geometry is determined. The results show that the predicted location and locus of the melt-line in the PAW weld cross section are in good agreement with experimental measurements.