【作者】 辜磊；

【导师】 刘建华；

【作者基本信息】 华中科技大学 ， 材料加工工程， 2006， 硕士

【摘要】 铝合金比重轻、强度高、塑性好、耐腐蚀性能好、无磁性、易于加工成形、无低温脆性转变,被广泛应用于各种焊接结构中,但是铝合金的焊接一直是个难点。激光-电弧复合焊接具有“1+1﹥2”的协同效应,可以提高激光能量的利用率,减少或消除焊接缺陷,获得单独激光、电弧焊接难以达到的效果,为铝合金的焊接提供了一种新的途径。论文进行了YAG-MIG复合焊工艺试验研究,在国内首次建立了铝合金复合焊接专用系统,得到了2mm薄板和8mm厚板ZL114铸造铝合金复合焊工艺参数;使用该系列参数成功的实现了环缝焊接,以期用于大批量工业生产。焊接本身就是个传质、传热、冶金和力学的复杂过程;复合焊接更为复杂,还涉及到光学物理、电弧物理等。单纯的依靠理论研究,很难解决工业生产的实际问题;单纯的工业实验成本昂贵,也很盲目。传统的焊接技术研究是以“理论-实验-生产”模式来发展,然而实验成本和耗时是一直难以解决的问题。随着计算机技术的发展,“理论-数值模拟-生产”的生产研究模式正在兴起。采用虚拟模拟技术,配合一定的工业实验,建立数值分析模型,可以减少成本、节省时间,是目前焊接工程领域的一个研究热点。文章从D.罗申赛尔(Rosenthal)、雷卡林院士提出的点、线、面的解析模型出发,分析了近年来体热源解析模型研究成果,结合当前N.T. NGUYEN等人推导体热源温度场模型的方法和吴甦等人提出的旋转高斯曲面体热源模型,建立了旋转高斯曲面体温度场解析模型,采用MATLAB计算得到了与实际的焊接测量值相当一致的解析解。并提出了一种求解温度场模型的简化算法和一种新的焊接热源模型:“集层高斯体热源模型”。解析模型难以求解或者求解简化会带来巨大的精度损失,采用了数值积分、有限差分、有限元等数值方法可以避免解析模型的缺点,然而该类方法理论基础深奥、计算量大。计算机技术的飞速发展,众多数值模拟软件弥补了数值方法中的计算问题,同时屏蔽掉了复杂难懂的基础理论,起到“黑匣子”的作用,给用户提供了一个简单易学的操作界面。ANSYS有限元软件是其中的佼佼者之一,具有结构、流体、热、电磁及其耦合分析功能,在工业领域和研究中得到广泛的应用。本文分析了基于ANSYS软件进行焊接温度场数值模拟的理论基础,对薄板铝合金进行了单道焊接温度场数值模拟,对厚板的铝合金进行了单/双道焊接温度场数值模拟。分析了采用不同热源得到的温度场数值模拟结果,并与实验结果进行比较,论证了旋转高斯曲面体热源在铝合金中、厚板复合焊接温度场数值模拟中的适应性。同时也为不同焊接工艺条件下铝合金中、厚板激光-电弧复合焊接焊缝形状和尺寸预测提供了一种有效的途径。更多还原

【Abstract】 Aluminium alloys are widely applied as weldments in industry for their light specific weight, high strength, good ductility, superior corrosion resistance, non-magnetism, easy workability, and no low temperature embrittleness transition etc, but their welding always is a problem. The laser-arc hybrid welding is a novel technique which has a synergic effect of“1+1﹥2”. It doesn’t only improve the efficiency of the laser, but also reduces or eliminates welding defects.YAG-MIG hybrid welding system for Aluminum alloy was built for the first time in China. Paramters were got for welding different gauges (2mm/8mm) of plates, and they were proved to go quite well in the cylinder butt welding with a V groove. The same or better qualities of welds are expected in the factory.Welding is a complicated process which relates to mass and heat transfer, metallurgy, mechanics; and more knowledge in the field of optics and arc physics are needed to be well understood in the hybrid welding.It is hard to put it into the industry application by mere reseach on theory, or the cost-consuming experiments that sometimes result in vain.The tranditional welding developing mode“theoty-experiment-production”was changed to“theoty-simulation-production”with the rapid development of computer technology in order to solve the time and cost consuming problems.A new analytical temperature field mode was reduced base on the Revolving Gause heat source given by Wu Su by the way presented by N.T. NGUYEN after retrospecting the theory of D. Rosenthal and Rykalin and anlyzed the recent reseach on body heat source, and calculated results using MATLAB shows great agreement with measured results. A simple way for calculating temperature field was developed and a new heat source model was suggested which named“Layered Gauss Body Heat Source Model”.Analytical solution is difficult or even cann’t be solved without great lose in accuracy. Numerical solutions such as numerical integration, finite difference, FEA (finite element analysis) can solve the problem through numerous calculations which can be done by a high speed computer. One of the best FEA software is ANSYS which can simulate structure, fluid, heat, magnetism, and their coupled field with an easy handling user-computer interface. Basic theory and techniques in temprature field simulation were discussed, and the simulations of different gauges of welds in single and double were investgated based on ANSYS.A Revolving Gause heat source was proved the best heat source model for mid/ thick aluminium alloy plate hybrid welding by comparing the results between the simulations and the experiments. It also provids an efficient way to predict the shape, penetration and width of weldments for the mid and thick Aluminum alloy plate in different welding parameters.更多还原