镁合金双弧焊接过程数值模拟与应力分析

发布时间：2018-01-20 03:10

本文关键词： AZ31B镁合金 DE-GMAW 数值模拟应力分析　出处：《南昌大学》2017年硕士论文　论文类型：学位论文

【摘要】：双电极气体保护焊(Double Electrode Gas Metal Arc Welding,DE-GMAW)是一种高效经济的焊接方法,采用钨极惰性气体保护焊(Tungsten Inert Gas Arc Welding,TIG)与熔化极惰性气体保护电弧焊(Metal Inert Gas Arc Welding,MIG)相结合,利用旁路TIG的分流作用,解决了常规电弧焊在高速焊接时,为了提高熔敷率而增加焊接电流却导致母材热输入过大的问题。将此种焊接工艺应用到目前备受瞩目的镁合金材料中,可实现镁合金材料的高效连接,使镁合金加工技术满足更多领域的需求。本文基于ANSYS软件,针对2mm厚的AZ31B镁合金薄板DE-GMAW双弧表面堆焊进行了数值模拟,并结合DE-GMAW焊接实验,做了如下研究:(1)针对倾斜的TIG焊枪,通过空间坐标转换,推导出适用于倾斜电弧的热源模型,进而建立了适用于本文的双弧热源模型。采用模拟与实验相结合的方法,不断的改变旁路电弧的耦合效率,使模拟的熔池尺寸不断逼近实验值,最终确定旁路电弧的耦合效率。(2)将双弧热源加载至AZ31B镁合金焊件的有限元模型上进行求解,得到了焊接温度场的动态分布和热循环曲线,并且讨论了总电流和旁路电流对温度场的影响,以及旁路电弧对母材的热量输入和熔池尺寸的影响。模拟结果与实验结果相符,验证了双弧热源的正确性。(3)采用热-应力间接耦合的模拟方法获得了AZ31B镁合金DE-GMAW的焊接应力动态分布,以及沿焊缝方向和垂直焊缝方向上、焊缝及附近区域的残余应力,模拟结果与焊接结构学理论一致。(4)针对焊后的残余应力,采用小孔释放法进行了测量;并对焊后工件的整体变形进行了实验测量。测量的残余应力及整体变形结果与模拟值基本符合。通过模拟得到的温度场、应力和变形的结果,与焊接理论及实验测量结果相符,证明了采用本文建立的双弧焊接热源模型可以准确的反映焊接电弧的实际加热过程和焊接结果,能够为AZ31B镁合金DE-GMAW焊接工艺提供正确的理论数据。
[Abstract]:Double Electrode Gas Metal Arc welding (DE-GMAW) is an efficient and economical welding method. Tungsten Inert Gas Arc Welding was welded by tungsten inert gas. TIG) is combined with Metal Inert Gas Arc Welding (mig), and the shunt effect of TIG is utilized. It solves the problem that increasing welding current in order to increase deposition rate in conventional arc welding at high speed results in excessive heat input of base metal. This welding process is applied to magnesium alloy materials which are attracting much attention at present. Can realize the magnesium alloy material high efficiency connection, make the magnesium alloy processing technology to meet the needs of more fields. This paper is based on ANSYS software. The double arc surfacing welding of AZ31B magnesium alloy sheet with 2mm thickness was numerically simulated, and the experiment of DE-GMAW welding was carried out. The following research is done: 1) for the inclined TIG welding torch, the heat source model suitable for the inclined arc is derived through the spatial coordinate transformation. Furthermore, a two-arc heat source model suitable for this paper is established. By combining simulation and experiment, the coupling efficiency of by-pass arc is constantly changed, so that the size of the simulated molten pool is approaching the experimental value. Finally, the coupling efficiency of by-pass arc is determined. (2) the double arc heat source is loaded on the finite element model of AZ31B magnesium alloy welding, and the dynamic distribution of welding temperature field and thermal cycle curve are obtained. The effects of total current and bypass current on the temperature field, and the influence of bypass arc on the heat input of the base metal and the size of the molten pool are discussed. The simulation results are in agreement with the experimental results. The correctness of double-arc heat source is verified. (3) the dynamic distribution of welding stress of AZ31B magnesium alloy DE-GMAW is obtained by using the thermal-stress indirect coupling simulation method. And the residual stress of weld and its adjacent area along the direction of weld and vertical weld. The simulation results are consistent with the theory of welding structure. 4) the residual stress after welding is measured by small hole release method. The results of residual stress and global deformation are in good agreement with the simulated values. The temperature field, stress and deformation are obtained by simulation. It is proved that the heat source model established in this paper can accurately reflect the actual heating process and welding results of the welding arc. It can provide correct theoretical data for AZ31B magnesium alloy DE-GMAW welding process.
【学位授予单位】：南昌大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG457.19

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