铝合金LB-VPPA复合焊接残余应力场预测

针对双高能束激光-变极性等离子弧(LB-VPPA)复合焊接热源，基于SYSWELD软件热源模型二次开发功能，在理论分析LB-VPPA复合焊接热源电弧形态的基础上，建立了“双椭球体+三维锥体+圆柱体”热源模型，通过正、反极性不同特性热源模型的循环加载，准确计算出了LB-VPPA复合焊接温度场. 根据热弹塑性理论对相应节点应力的瞬时演变及焊后残余应力分布进行了数值计算，并通过实际焊接工艺试验获得的焊缝截面及残余应力的实际测量,验证了数值计算的准确性. 通过分析对比10 mm厚5A03铝合金VPPA焊和LB-VPPA复合焊接残余应力场发现，LB-VPPA复合焊由于能量更加集中，高温区更为密集，虽然最大纵向残余应力相对较大，但呈最大残余拉应力的区域面积较VPPA焊小. 研究结果对铝合金LB-VPPA复合焊接工艺的研究及实际应用具有一定的指导意义.

Numerical prediction of residual stress field in LB-VPPA hybrid welding of aluminum alloys

Based on theoretical analysis in LB-VPPA hybrid welding heat source arc shape, “double ellipsoid+3-D conical+cylindrical”heat source model was established for double high energy beam LB-VPPA hybrid welding heat source by secondary development of SYSWELD software heat source model. The temperature fields of LB-VPPA hybrid welding were accurately calculated by the cyclic loading of heat source models with different characteristics of positive and negative polarities in the SYSWELD software. According to the thermal elastoplastic theory, instantaneous evolution of the stress at corresponding node and residual stress distribution after welding were calculated, and the accuracy of numerical simulations was proved by the comparison of the weld cross section of the actual welding experiment and the simulation results and by the actual measurement of residual stress. Comparing the residual stress field of VPPA and LB-VPPA hybrid welding of 5A03 aluminum alloy with 10 mm thickness, it was found that the energy of LB-VPPA composite welding was more concentrated and the high-temperature area was more intensive. Although the maximum longitudinal residual stress was relatively larger, the area of tensile stress was smaller than the VPPA welding. The results of this study were helpful for the research and practical application of aluminum alloy LB-VPPA hybrid welding technology.