Numerical definition of an equivalent GTAW heat source

The aim of this paper is to present a new numerical heat source for gas tungsten arc welding (GTAW) simulation. This source is described as a homogeneous thermal flux which is defined by a power P distributed in a disk the radius of which is R: it enables the main dimensions of the weld bead and the evolution in temperature in the solid part to be predicted. The two parameters P and R relate to the process parameters, the arc length h and the current intensity I.Experimental tests were performed in order to study the weld bead dimensions in incomplete penetration and full penetration welds. For each test, the heat source parameters (P,R) which enable the experimental weld bead dimensions to be obtained were identified: a link between the heat source parameters (P,R) and the welding parameters (I,h) was established and thus a predictive heat source was produced.     

激光-电弧复合热源焊接

在激光热源的基础上复合电弧进行焊接，可以降低焊接成本，提高焊接效率。本文综述了激光—电弧复合热源焊接国内外研究的现状，对旁轴式和同轴式两种复合方式进行了分析比较，并展望了该技术的发展前景。     

Inverse resolution of the heat-transfer equation with internal heat source: Application to the quenching of steels with phase transformations

A method is described for calculating the time dependence of the temperature and heat flux (on heating and cooling) at the surface of a solid body. For a given ambient temperature and a known time-temperature function of an interior point, the surface heat flux is computed through an inverse conduction algorithm taking into account the nonlinear nature of the problem. Moreover, this algorithm includes the enthalpy of phase transformations. The influence of space and time steps on inverse calculations (precision, stability) is investigated. The method is then applied to thermal cases involving different transformations in steels.     

结合型分布带状分段移动热源模型

在数值模拟分析大型焊接结构的焊接残余应力和变形时,可以采用分段移动带状热源模型以便提高计算效率.为此,首先试验分析了不同焊接速度对焊接温度场带状特性的影响.并在已建立的结合型分布圆形热源模型的基础上,推导出了结合型分布带状分段移动热源模型的节点热流与加载时间的计算公式.结果表明,焊接速度大于4mm/s时,较长区段的温度场已经具有带状分布特点.此外,与高斯分布带状分段移动热源模型的节点热流与加载时间的计算公式相比,推导出的公式不但与总的热输入量有关,还与电弧和熔滴的热量分配比有密切的关系.     

铝合金变极性穿孔型等离子弧焊工艺的热源模型

选用包含面高斯热源和圆柱体热源模型的组合热源模型去模拟变极性穿孔型等离子弧焊工艺的温度场．通过大量的工艺试验,分析主要工艺参数对铝合金变极性穿孔型等离子弧焊成形的影响．借助有限元分析手段,在热源模型和实际工艺参数之间建立了联系,并通过线性回归分析的方法将这种联系用数学方式表达出来．结果表明,变极性穿孔型等离子弧焊除了电流和行走速度外,离子气流量、钨极内缩量和喷嘴末端到工件表面的距离都是十分重要的工艺参数,对焊缝形貌特征影响很大．     

Line Gauss heat source model: an efficient approach for numerical welding simulation

Abstract

In view of the characteristics of the welding heat source, a new heat source model based on an established Gauss model, termed the line Gauss heat source, is developed to improve calculation efficiency. A typical welding process is simulated using both Gauss and line Gauss source models. The results show that using the new model, analysis time can be reduced greatly while high precision is maintained, and this method renders three-dimensional simulation of some real welding structures containing long welds practical. The cutting processes for the side plate of a bridge crane beam are simulated using the line Gauss source model, and the results agree fairly well with real measurements.     

等离子加热中间罐流体流动和传热行为的物理模拟

采用水模在线加热研究等离体加热中间罐内流体温度的分布,实验结果表明,实行等离子加热,中间罐内流体温度分布不均,上表面温度高,底部温度低,采用不同的挡墙安放在不同位置对中间罐流体的温度影响较大。     

Surface hardening of steels by alloying with laser heating and subsequent chemical heat treatment

The necessity of providing a high set of operating properties has stimulated the development of combined technologies of surface hardening. A combination of laser alloying of low-carbon steels by nitride-forming elements (V, Cr, Mo, Al) with subsequent chemical heat treatment seems promising in this respect. Such a combined treatment provides a favorable distribution of residual stresses, elevates considerably the microhardness of the strengthened layers, and increases the wear resistance by a factor of 1.5–3 compared to nitrided nitralloys like steel 38Kh2MYuA. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 11–14, July, 1997.     

Finite element analysis of keyhole plasma arc welding based on an adaptive heat source mode

An adaptive heat source mode is proposed to account for the keyhole effect and the characteristics of volumetric distribution along the direction of the workpiece thickness. Finite element analysis of the temperature field in keyhole plasma arc welding is conducted and the weld geometry is obtained. The predicted results are in agreement with the measured ones.