铝合金搅拌摩擦焊接力参量对缺陷的响应规律研究

The response of welding force to defect in aluminum alloy friction stir welding

  • 摘要: 力参量是铝合金搅拌摩擦焊接中缺陷演变的信息载体,在缺陷预测和识别中具有重要作用。本文利用测力平台实现了铝合金FSW过程前进阻力、侧向力和轴向压力的原位测量,分析了不同工艺参数下焊接力信号和焊缝成形的变化规律,研究了力参量特征对隧道和孔洞缺陷的响应机理。结果表明,在典型工艺参数下,三向力呈现先增加、后稳定、最后快速降低的变化趋势,力信号的变化较好地反映了搅拌头机械运动和焊缝材料热塑性状态变化。当旋转较低或焊接速度较高时,焊缝内部出现隧道缺陷,轴向力数值相对较低,侧向力数值相对较高。在恒定工艺参数下,轴向力的降低和侧向力的增加同样较好地反映焊缝隧道缺陷的形成。轴向力的降低是由于轴肩对焊缝材料的挤压作用减弱,焊缝材料难以被包裹并迁移至焊缝表面,从而导致隧道和沟槽缺陷产生;侧向力的增加是由于搅拌针驱动材料的能力减弱,导致搅拌针前方材料在焊缝后退侧堆积,加剧了搅拌针对后退侧材料的挤压,进而导致搅拌针后方材料回填困难,形成隧道缺陷。

     

    Abstract: Force components serve as the information carriers for defect evolution in aluminum alloy friction stir welding, playing a crucial role in defect prediction and identification. This paper utilizes a force measuring platform to facilitate in-situ measurement of the traverse force, lateral force, and plunge force throughout the welding process. The variations in force signals and defect sizes observed at different welding parameters are analyzed, and the responses of force components to defect evolution are examined. The results indicate that force signals initially increase, stabilize, and then rapidly decrease during the welding process, reflecting the mechanical movement of the stirring head and the changes in the thermoplastic state of the weld materials. When the rotation speed is low or the welding speed is high, tunnel defects emerge within the weld; in these cases, the plunge force is relatively low while the lateral force is comparatively high. Even with constant process parameters, a decrease in axial force and an increase in lateral force can indicate the formation of tunnel defects. Furthermore, the reduction in plunge force is attributed to the diminished extrusion effect of the shoulder on the weld material, making it difficult for the material to be wrapped and migrated to the weld surface, thereby leading to the formation of tunnel and groove defects. The increase in lateral force results from the reduced ability of the stirring pin to drive the material, causing a buildup of material in front of the stirring pin on the retreating side of the weld. This exacerbates the extrusion of materials on the retreating side by the stirring pin, making it challenging for the materials behind the stirring pin to backfill, which ultimately leads to the formation of tunnel defects.

     

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