反应釜毕业设计外文翻译

1 Welding Simulation of Cast Aluminium A356 X T Pham P Gougeon and F O Gagnon Aluminium Technology Centre National Research Council Canada Chicoutimi Quebec Canada Abstract Welding of cast aluminium hollow parts is a new promising technical trend for structural assemblies However big gap between components weld porosity large distortion and risk for hot cracking need to be dealt with In this paper the MIG welding of aluminium A356 cast square tubes is studied The distortion of the welded tubes was predicted by numerical simulations A good agreement between experimental and numerical results was obtained Introduction Aluminium structures become more and more popular in industries thanks to their light weights especially in the automotive manufacturing industry Moreover welding of cast aluminium hollow parts is a new promising technical trend for structural assemblies 1 3 However it may be very challenging due to many problems such as big gap between components weld porosity large distortion and risk for hot cracking 4 5 Due to local heating complex thermal stresses occur during welding residual stress and distortion result after welding In this paper the aluminium A356 cast tube MIG welding is studied The software Sysweld 6 was used for welding simulations The objective is to validate the capability of this software in predicting the distortion of the welded tubes in the presence of large gaps In this work the porosity of welds was checked after welding using the X ray technique The heat source parameters were identified based on the weld cross sections and welding parameters Full 3D thermal metallurgical mechanical simulations were performed The distortions predicted by the numerical simulations were compared to experimental results measured after welding by a CMM machine Experiments Experimental setup Two square tubes are made of A356 by sand casting and then machined They are assembled by four MIG welds named W1 to W4 Their dimensions and the welding configuration are depicted in Figure 1 Both small inner and large outer tubes are well positioned on a fixture using v blocks as shown in Figure 2 The dimensions of the tubes make a peripheral gap of 1 mm between them This fixture is fixed on a positioner that allows the welding process to be carried out always in the horizontal position The length of each weld is of 35 mm The Fronius welding head which is mounted on a Motoman robot was used for the MIG welding process Table 1 indicates the parameters of the welding process for 2 this welding configuration Table 1 MIG welding parameters VoltageAmperageSpeedThick1Thick2Gap V A m min mm mm mm 232601 25441 a b Figure 1 Tube welding configuration a cross section view b tube dimensions 3 Figure 2 Experimental setup for tube welding Testing The porosity of welds was observed before and after welding using the X ray technique to check the quality of these welds according to the standard ASTM E155 The whole welded tubes were then tested by traction on a MTS testing machine The final dimensions of the welded tubes are measured on a CMM machine at many points on the tubes The distortion of the welded tubes is determined by comparing the final positions with the initial positions of the tubes Numerical analysis In Sysweld a welding analysis is performed based on a weak coupling formulation between the heat transfer and mechanical problems Only the thermal history will affect on the mechanical properties but not in reverse direction Therefore a thermal metallurgical mechanical analysis is divided into two steps The first step is a thermal metallurgical analysis in which the heat transferred from the welding source makes phase changes during the welding process The results of temperature and phase changes from the first step are then used as input for the second analysis It is a pure thermo elasto plastic simulation 6 Heat source model identification Before running a welding simulation it is necessary to determine the parameters of the heat source model This is called heat source fitting Actually it is a thermal simulation using this heat source model in the steady state which iscombined with an optimization tool to obtain the parameters of the heat source Figure 3 presents the form of a 3D conical heat source of which the energy distribution is described in Eq 1 as follows F Q0exp r r0 1 4 in which Q0 denotes the power density and r r0 are defined by r x x0 x x0 vt 2 and r0 re re ri ze z z0 ze zi 3 where x0 y0 z0 is the origin of the local coordinate system of the heat source re and ri the radius of the heat source at the positions ze and zi respectively v the welding speed and t the time In this study a metallographic cross section has been used to identify the heat source parameters as shown in Figure 4 The use of a 3D conical heat source fits very well the weld cross section The mesh size in the cross section is around 0 5 mm for this case The finer is the mesh the more accurate is the shape of the melting pool but the longer is the simulation Figure 3 3D conical heat source Sysweld 5 a b Figure 4 a Metallographic cross section b Melting pool cross section Analysis model The mesh of the tubes was created in Hypermesh 7 0 Sysweld 2007 has been used as solver and pre post processor A full 3D thermal metallurgical mechanical analysis with brick and prism elements Two welding sequences have been done such as W1 W2 W3 W4 and W1 W3 W2 W4 The tubes are clamped using four v blocks during the welding two for each tube In the simulations the positions where the tubes are in contact against the surfaces of the v blocks are considered as fixed conditions i e Ux Uy Uz 0 In the release phase the tubes are free from the v blocks Results The distortion of the welded tube is measured when it is released from the constraints The distortion is determined by measuring the displacement of the small tube on the top and lateral surfaces along the centre line of the tube These measures are relative to the large tube 6 Figures 5a b depict the distortion predicted by the numerical simulations of the sequence W1 W2 W3 W4 and W1 W3 2 W4 respectively Good agreements between experimental and numerical results were obtained in the two welding sequences as indicated in Tables 2 3 in both the distortion tendency and distortion range of the process variation a b Figure 5 Tube distortion Norm U a Sequence W1 W2 W3 W4 b Sequence W1 W3 W2 W4 Table 2 Distortion result comparison welding sequence W1 W2 W3 W4 Displacements mm 7 UyUz ExperimrntalFrom 0 4to 0 59From 0 35to 0 51 3D simulation 0 4 0 51 Table 3 Distortion result comparison welding sequence W1 W3 W2 W4 Displacements mm UyUz ExperimrntalFrom 0 07to 0 11From 0 12to 0 21 3D simulation 0 05 0 26 a b Figure 7 State of stresses Sxy a Clamped b Released Red positive Blue negative 8 a b Figure 8 State of stresses Sxz a Clamped b Released Red positive Blue negative Figures 6 8 shows the state of the stresses of the welded tubes at room temperature for the sequence W1 W2 W3 W4 after welding when clampled and released from constraints x is the direction along the axe of the welded tube To show how the welded tube is distorted positive negative values are used instead of the true values of stresses The distortion of the welded tube can be explained as the new equilibrium position due to the residual stresses when there is no external load It is remarked that in the presence of large gaps the distortion of the welded tube is very likely in the rotational mode around local welds 9 Conclusions The MIG welding is very good for assembling aluminium cast tubes hollow parts in the presence of large gaps The 3D thermal metallurgical mechanical simulation of the cast tube welding using Sysweld has been validated A very good agreement between numerical and experimental results was obtained for both the distortion tendency and distortion range The welding sequence has a major influence on the distortion of the welded structure It turns out that the optimization of the welding sequences for a reasonable distortion of a welded structure with a large number of welds becomes very important Acknowledgments The authors would like to thank gratefully Rio Tinto Alcan and General Motor for financial and technical supports particularly Martin Fortier and Pei Chung Wang Also the authors are grateful to Welding Team at ATC Audrey Boily Martin Larouche Fran ois Nadeau and Mario Patry for experimental works References 1 K H Von Zengen Aluminium in future cars A challenge for materials science Materials Science Forum 519 521 Part 2 1201 1208 2006 2 S Wiesner S M Rethmeier and H Wohlfart MIG and laser welding of aluminium alloy pressure die cast parts with wrought profiles Welding International 19 2 130 133 2005 3 R Akhter L Ivanchev C V Rooyen P Kazadi and H P Burger Laser welding of SSM Cast A356 aluminium alloy processed with CSIR Rheo technology Solid State Phenomena 116 117 173 176 2006 4 J F Lancaster Metallurgy of welding Abington Publishing 1999 5 Grong Metallurgical modelling of welding The institute of materials 1997 6 Sysweld Sysweld reference manual ESI Group 2005 10 译文 铸造A356铝合金的焊接模拟 X T Pham P Gougeon and F O Gagnon Aluminium Technology Centre National Research Council Canada Chicoutimi Quebec Canada 摘要 空心铝铸造件的焊接是一个很有前途的新结构组件技术的趋势 然而 组件之间 的差距较大 焊接孔隙度 大变形和热裂需要处理的风险 在这篇文章中 对铸造 A356 铝合金的方管的 MIG 焊接进行了研究 并对焊接管弯曲变形进行了数值模拟预测 实验结果和数值模拟结果的相似度很高 1 1 前言 前言 由于铝合金结构自身的重量轻 所以它变得越来越流行 尤其是在汽车制造业 此外 空心铝铸造件的焊接是一种新的有前途的结构组件技术的趋势 1 3 但是它可能 有很大的挑战 由于大的差距 例如组件之间 焊接孔隙度 大变形和热裂的危险等 很多问题 4 5 由于局部加热 复杂的热应力发生在焊接中 焊后会出现残余应力和变 形的结果 在这篇文章中 关于铸造 A356 铝合金的方管的 MIG 焊接进行了研究 Sysweld 软件 6 被用于焊接模拟 其目的是验证这个软件在大差距的焊接管扭曲变形 的预测中的能力 在这项工作中 在焊接后利用 X 射线技术来检查焊缝的孔隙率 在 热源参数的基础上 确定了焊缝截面和焊接参数 冶金力学的 3D 热量模拟已经被使用 用数值模拟所预测出来的扭曲值与焊后用 CCM 机器所测量的实验结果进行了比较 2 2 实验 实验 2 1 实验方案 两个成直角的管子是用 A356 通过砂型铸造然后在加工形成的 他们是由四个管 MIG 焊接组装而成 命名为 W1 至 W4 他们的尺寸和焊接配置描绘如图 1 不论小还 是大的管子都很好的定位在一个采用 V 形块的夹具上 如图 2 所示 管子的规模使它 们之间产生了一个 1 毫米厚的不主要的缝隙 这个夹具固定在一个定位上 使焊接过 程中总是保持水平位置 每个焊缝的长度是 35 毫米 被安装在 Motoman 机器人上的 Fronius 焊头是用于 MIG 焊过程中的 表 1 表明了这个焊接结构的焊接工艺参数 11 表 1 MIG 焊接参数 电压电流速度厚板1厚板2缝隙 V A m min mm mm mm 232601 25441 a 12 b 图1 钢管焊接配置 a 截面图 b 钢管尺寸 图2 管焊接实验装置 2 2 测试 焊接前后利用 X 射线技术观察焊缝气孔 按 ASTM E155 标准检查这些焊缝质量 13 然后整个焊接管子通过一个 MTS 试验机上的牵引来测试 焊接管最终的尺寸被定位在 管子上的多个点的 CMM 机器所测量 扭曲的焊接管的最终位置与初始位置的管子进 行比较 3 3 数值分析数值分析 在 Sysweld 软件中 焊接分析是基于热传导和力学问题之间的微弱链接而制定的 只有热学经历在相同方向上才将影响力学性能 因此 热学冶金力学分析分为两个步 骤 第一步是一种热学冶金分析 其中在焊接过程的相变过程中从焊接电源的热量被 转移 第一步温度和相变的结果将作为第二次的分析 它是一个纯热弹塑性模拟 6 4 4 热源模型的鉴定热源模型的鉴定 焊接模拟运行之前 有必要确定热源模型的参数 这就是所谓的热源配件 实际 上 它是一种热模拟中的稳定状态 在这种稳定状态中用一种优化工具来获得的热量 来源的参数 图3给出了一个三维锥形热源形式 它的能量分布在方程中描述 举例如 下 F Q0exp r r0 1 其中Q0 表示功率密度 r r0 被定义为 r x x0 x x0 vt 2 和 r0 re re ri ze z z0 ze zi 3 其中 x0 y0 z0 是局部坐标系原点热源 re和 ri 在位置 ze 和 zi 分别为半径热源 v 为 焊接速度 t 为时间 在这项研究中 金相截面已被用来确定热源 如图 4 所示的参数 一个三维锥形 热源使用非常适合的焊接横截面 在横截面的网状尺寸是这种情况下约为 0 5 毫米 越 细的网状 越是更准确的熔池形状 但不再是模拟 14 图3 三维锥形热源 Sysweld a 15 b 图4 a 金相截面 b 熔池截面 5 5 模型分析模型分析 在 Hypermesh7 0 上创建了管网 Sysweld2007 已被用来作为求解器和前后处理器 一个完整的三维热学冶金力学分析用砖和棱镜为元素 两种焊接序列已完成 如 W1 W2 W3 W4 和 W1 W3 W2 W4 在焊接过程中 夹住管子的过程中使用四个 V 形块 每个管子两个 在模拟中 管子的立场是反对接触的 V 形块的表面被认为是固定的条 件 如 Ux Uy Uz 0 在释放阶段 管子在 V 形块中是不受力的 6 6 结果结果 当焊接管子从束缚状态被释放时 它的变形被控制 失真是通过测量沿管子 的中心线从顶部到两侧面的小管的位移 这些措施是相对于大管的 图 5a b 的描述失 真通过数值模拟预测序列为 W1 W2 W3 W4 和 W1 W3 W2 W4 在数值计算结果和实 验中获得了良好的协议的两种焊接顺序如表 2 3 所示 在这两种倾向的扭曲和变形的 过程中变化的范围 16 a b 图 5 电子管失真 标准 U a 序列 W1 W2 W3 W4 b 序列 W1 W3 W2 W4 表 2 扭曲结果的比较 焊接顺序 W1 W2 W3 W4 位移 mm 17 UyUz 实验 0 4 至 0 59 0 35 至 0 51 三维模拟 0 4 0 51 表 2 畸变结果比较 焊接顺序 W1 W2 W3 W4 位移 mm UyUz 实验 0 07 至 0 11 0 12 至 0 21 三维模拟 0 05 0 26 a 18 b 图 6 规定压力 Sxx a 夹紧 b 放松 红 正 蓝 负 a 19 b 图 7 规定压力 Sxy a 夹紧 b 放松 红 正 蓝 负 a 20 b 图 8 规定压力 Sxz a 夹紧 b 放松 红 正 蓝 负 图 6