力学不均匀性对焊接接头拉伸性能的影响研究

为了研究焊接接头力学不均一性对单向拉伸性能的影响，本文采用数字散斑相关方法（DSCM）研究了纯铝激光-电弧复合焊焊接接头在拉伸过程中的局部变形行为，获得了母材、热影响区和焊缝区的应变分布情况，发现应力43.6MPa时熔合线附近的热影响区首先进入屈服阶段，并且随着荷载的增加，总应变迅速增大，热影响区真实应变远大于名义应变，并导致最终断裂。硬度测试结果显示热影响区出现明显的退火软化现象，硬度最低，使其成为焊接接头拉伸过程中最薄弱区域。基于能量法和硬度测试结果提出了纯铝焊接接头各区域屈服强度的预测模型，预测值与实验结果吻合良好。

Research on tensile properties of welded joint with mechanical heterogeneity

Tensile test was performed on laser-MIG hybrid welded joint to investigate the profiles of local deformation in Base Metal (BM), Heat Affected Zone (HAZ) and Weld Zone (WZ), with the help of Digital Speckle Correlation (DSCM) Method. It was found that HAZ entered the yield stage firstly at the nominal stress of 48.5MPa because of the mechanical heterogeneity in welded joint and the total strain in HAZ went up rapidly along with the increase of axial loading, which was much larger than the nominal strain, leading to the final fracture. The result of hardness measurement showed that soft annealing in HAZ was observed obviously, which led to that HAZ became the weakest part in the tensile test of welded joint. A new prediction model for yield strength of BM, HAZ and WZ was proposed based on energy method and hardness measurement. A good agreement was reached between the predicted value and experimental results.