阴APP导航

Assembly using Friction Stir Welding (FSW) presents a tremendous capability in terms of light-weighting and mechanical performance gains over conventional assembly techniques for the manufacture of integrated structural elements. In this perspective, serial industrial robots have high potential to be a cost-effective and viable option for industrial application of FSW on the low-series, three dimensional components typical of elements of transportation structures. The definition of the FSW operational window through parametric optimization of the process variables should however consider the limitations inherent to this robot architecture.

In this work, robotic FSW of 3.18 mm thick aluminium alloy (AA) 6061 was investigated for the assembly of a large-scale single-curvature primary structure comprising skin-to-skin and stringer-to-skin joints, corresponding to butt and lap welds respectively. Weld trials were performed using a MTS ISTIR system to examine the influence of weld pitch on the welding defects, microstructure, hardness and bend performance. With increasing weld pitch, the occurrence of a zigzag oxide layer in the weld nugget of friction stir butt welded AA6061 was observed to become increasingly pronounced, though the impact on the bend performance of the weld was negligible. Weld trials performed in lap configuration at a weld pitch of 0.3 mm/rev revealed a well formed weld nugget, with the expected mechanical performance and minimized thinning in the sheet material. The maximum forge force recorded during FSW was 11.9 kN, a payload that can be rendered by a robotized work cell.

As the analysis of the recommended optimized process conditions indicated that the amplitude of process forces was typically more than 50% higher in the case of lap joints compared to those recorded in the butt configuration, the former was used in the second part of this paper as the main criterion for the synthesis of robotic FSW scenarios for the fabrication of integrated structural components with stringer-to-skin and skin-to-skin joints. The software approach used for this purpose is described and the synthesized work cell layouts for a candidate serial industrial robot are presented.