In this work, the tensile-shear mechanical behaviors of friction stir spot weld and adhesive hybrid joint were performed from both numerical and experimental viewpoints. Weld through (WT) and flow in (FI) processes were studied in this research. The focus was to evaluate joint defects, tensile-shear failure load (TSFL), failure energy, failure mode and stress distribution of the joint. In FI joints, keyhole and hook defects appeared in the weld zone and the areas of material removed from the base metal were filled with adhesive. In the WT joints, the adhesive layer close to the weld zone was carbonized due to the welding heat. Meanwhile, under the rotating movement of welding tool, the adhesive impurities entered the stirring zone (SZ) and heat affected zone (HAZ) of the weld, which decreased mechanical performances of WT joints. Compared to the friction stir spot welding (FSSW) joint, the TSFL value, stiffness and failure energy of FI joint were increased by 2.7, 1.1 and 8.14 times, respectively. In order to study the stress distribution of the joints, a finite element (FE) model, which considered the weld structure and mechanical properties of weld regions, was implemented. Moreover, the adhesive layer was simplified by the cohesive zone model (CZM). FE results show that the FI process effectively decreases the stress concentration of the weld edge from 243.09 to 15.5 MPa, under the 2 kN tensile load. The weld can block the adhesive crack propagation, and the adhesive optimized the stress distribution of FI joints through a synergistic effect. So, the use of FI process for aluminum alloy connection is strongly recommended, especially in crucial structure areas.

中文翻译：

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搅拌摩擦点焊与胶粘混合接头的拉伸剪切力学行为：实验与数值研究

在这项工作中，从数值和实验的角度进行了搅拌摩擦点焊和粘合剂混合接头的拉伸剪切力学行为。在这项研究中研究了穿通（WT）和流入（FI）工艺。重点是评估接头缺陷，拉伸剪切破坏载荷（TSFL），破坏能量，破坏模式和接头的应力分布。在FI接头中，焊接区域出现了锁眼和弯钩缺陷，从母材上去除的材料区域被粘合剂填充。在WT接头中，由于焊接热，靠近焊接区域的粘合剂层碳化。同时，在焊接工具旋转运动下，胶粘剂杂质进入焊缝的搅拌区（SZ）和热影响区（HAZ），降低了焊缝的机械性能。与搅拌摩擦点焊（FSSW）接头相比，FI接头的TSFL值，刚度和破坏能量分别提高了2.7倍，1.1倍和8.14倍。为了研究接头的应力分布，建立了考虑焊接结构和焊接区域力学性能的有限元模型。此外，通过内聚区模型（CZM）简化了粘合层。有限元结果表明，在2 kN的拉伸载荷下，FI过程有效地将焊缝的应力集中从243.09降低到15.5 MPa。焊缝可以阻止胶粘剂裂纹的扩展，并且胶粘剂可以通过协同作用优化FI接头的应力分布。因此，强烈建议将FI工艺用于铝合金连接，特别是在关键结构区域。