Helical Probe Structure for Durable Friction Stir Welding

The patent applies the dynamics principle by making the thread groove structure variable rather than fixed. The pitch of the thread groove is changed along the axial direction of the probe, with the pitch being different in different axial sections. This dynamic variation in pitch allows the thread groove to adapt to different material flow conditions at different depths, thereby improving the stirring force while still maintaining manufacturability through a systematic gradient design.

The patent applies parameter changes by systematically varying the pitch parameter of the thread groove along the axial direction. The pitch is designed to be larger in the upper section and smaller in the lower section, creating a gradient structure that optimizes both the material stirring effect (improving joint efficiency) and the stress distribution (improving durability). This parameter optimization allows the tool to maintain high performance while reducing wear and extending service life.

The patent applies local quality by creating different thread groove characteristics at different locations along the probe. The variable pitch design ensures that each axial section has optimized groove parameters suitable for its specific function: the upper section with larger pitch handles material transport, while the lower section with smaller pitch provides intensive stirring. This localized optimization reduces overall tool wear while maintaining high-speed welding capability.