【作者】 熊进辉；

【导师】 樊丁； 余淑荣；

【作者基本信息】 兰州理工大学 ， 材料学， 2007， 硕士

【摘要】 焊接是一个涉及电弧物理、传热、冶金和力学的复杂过程。焊接现象包括焊接时的电磁、传热过程、金属的熔化和凝固、冷却时的相变、焊接应力和变形等。一旦能够实现对各种焊接现象的计算机模拟，我们就可以通过计算机系统来确定焊接各种结构和材料的最佳设计、最佳工艺方法和焊接参数。利用ANSYS软件对异厚度铝合金激光拼焊的温度场进行三维瞬态有限元分析。为了提高计算精度和效率，采用过渡网格划分形式划分网格以保证焊缝处网格足够细小。选取高斯函数分布的热源模型，利用ANSYS软件的APDL语言编写程序实现移动热源的加载。在模拟中既考虑一般激光焊接中材料热物理性能参数的温度相关性、熔化潜热、边界条件、等离子体、熔池对流、保护气体等对温度场的影响，又考虑异厚度铝合金激光拼焊的特性。利用高温热电偶检测异厚度铝合金激光拼焊过程中的温度场，将模拟值与实测值进行对比分析，结果表明模拟值与实测值吻合良好。采用间接法模拟应力应变场。定义弹性模量E，热膨胀系数α，泊松比μ等随温度变化的材料力学参数值。指定塑性分析选项为经典的双线性随动强化(BKIN)。边界条件约束焊件的自由度，以模拟夹具的作用。模拟结果显示，由于厚度不同，薄厚两板应力应变场存在差异，薄板焊缝附近的应力场范围较大，变形比厚板复杂且比厚板大。利用小孔释放法检测异厚度铝合金激光拼焊板的残余应力，将模拟值与实测值进行对比分析，结果显示模拟值与实测值吻合良好。对异厚度铝合金激光拼焊的熔化过程进行分析。选用三种不同的热源模型：高斯面热源、体热源、组合热源，利用ANSYS软件对异厚度铝合金激光拼焊的温度场进行三维瞬态有限元分析，观察三种热源模型形成的熔池形状(即焊缝形状)。结果表明：采用组合热源模型模拟的焊缝形状与实际拼焊的焊缝形状最为接近，证明分析的合理性。利用异厚度铝合金激光拼焊间隙填充模型，建立偏移量与间隙、工件厚度比、激光光束半径的定量关系式，关系式中偏移量与间隙、激光光束半径成正比，与工件厚度比成反比。在异厚度铝合金激光拼焊工艺实验中，选取不同的工件厚度比进行偏移定量关系式的验证实验。实验结果表明：理论计算值与工艺实验值基本吻合。理论计算值可以作为异厚度铝合金激光拼焊工艺实验的定量参考值。更多还原

【Abstract】 Welding is a complicated physicochemical process which involves in electromagnetism, heat transferring, metal melting and freezing, phase-change welding stress and deformation and so on. In order to get high quality welding structure, these factors have to be controlled. If welding process can be simulated with computer, the best design, procedure method and optimum welding parameter can be obtained.By using ANSYS soft, a 3D temperature field of aluminum alloy for different thickness with laser welding was simulated, In order to improve solution accuracy and efficiency, the transition mesh was used. Gauss function heat source model was chose. ANSYS’ APDL to compile program to apply load of moving heat source was used. The effects of temperature-dependence material parameters and potential heat, boundary conditions, plasma, melting pool convection and characteristics of different thickness are considered in the model. By using high-temperature thermocouple, the temperature was measured. It is shown that the simulation results are in accordance with the experimental results.The effects of temperature-dependence material parameters were considered in the model. The BKIN was established. Some proper restrictions of displacement were applied for simulating effect of clamps. The result of simulation indicates that, the stress-strain field in the thinner plate is larger than thicker one. Using hole-drilling technique, the residual-stress was measured. It is shown that the simulation results are in accordance with the experimental results.Melting characteristics of aluminum alloy for different thickness with laser welding were analyzed. In order to compare to welding line in different welding modes, Gauss function heat source model, body heat source model, and combination heat source model were chose, which stand for the three different welding modes in laser welding respectively. By using ANSYS soft, the 3D temperature field and shape of welding line of aluminum alloy of different thickness on laser welding are simulated. It is shown that the simulation results are in accordance with the combination heat source model.The model of gap-filling of different thickness tailored blanks in laser welding wasintroduced. The connection with offset and gap, thickness of work-piece, radial beam of laser was established. The different thickness of work-pieces which were used in laser welding of different thickness tailored blanks. It is shown that the calculative results are in accordance with the experimental results. The calculative results as reference would use in laser welding of different thickness tailored blanks.更多还原