抄録
This study investigates the influence of tool shape on stirring performance and wear in Friction Stir Welding (FSW) of steel materials using particle-based numerical simulation. Two tool shapes were examined: a conventional cylindrical probe and a spherical probe, which is expected to maintain equivalent joint quality while minimizing the stirring area and potentially extending tool life. The simulation method, based on particle dynamics, was employed to analyze material behavior during FSW and evaluate the effects of tool rotation speed and welding speed on stirring performance and tool wear for both tool shapes. Stirring performance was assessed by quantifying material dispersion in the welded joint, while tool wear was evaluated based on the adhesive wear theory. Results showed that stirring intensity was higher on the advancing side (AS) than the retreating side (RS) for both tool shapes, consistent with experimental observations from previous studies. The probe tip shape was found to significantly affect stirring performance. Increasing rotation speed enhanced stirring, while increasing welding speed reduced it. Tool wear was most pronounced during the initial plunge phase. During quasi-steady state, wear was greater on the RS of the tool where flow stress is lower, and at the tool edges where relative speed is high and hardness decreases due to temperature rise. The spherical tool exhibited less wear compared to the cylindrical tool across all tested conditions. The effects of welding parameters on tool wear aligned well with trends reported in literature, with higher rotation speeds increasing wear and higher welding speeds decreasing it. The spherical tool consistently demonstrated lower wear, particularly in the probe region, suggesting its potential as a longer-lasting alternative to conventional cylindrical tools in FSW of steel materials.
