Friction Stir Welding

Selected Papers:

Friction stir welding (FSW) was invented at The Welding Institute (TWI) in the UK in 1991.  This relatively new, solid-state joining process differentiates itself from many other welding processes by not melting the workpiece.  As a result, the joining process generates excellent joint properties, is energy efficient, environment friendly, and versatile.  The basic concept of FSW can be described as follows: a non-consumable rotating FSW tool with a specially designed shoulder and probe is pressed against the base metal surface, while a vertical downward force is applied.  Due to friction between the rotating tool and the workpiece and plastic deformation of the workpiece, the temperature in the weld zone increases.  The generated heat is usually not sufficient to melt the material, however, the workpiece is softened in the area around the probe and the deformation resistance (i.e., yield strength) of the base material decreases.  The tool is traversed along the weld interface to mix the joining members in a forging action along the joining line to create a weld in the solid state.  Friction stir welding results in intense plastic deformation and temperature increase in the weld zone, which leads to a significant microstructural evolution without typically causing phase changes.

Friction Stir Welding - Detailed Schematic

Schematic of the Friction Stir Welding Process

While FSW is superior to other welding processes, such as gas-arc welding, significant challenges remain in regards to robust process control, weld defect detection, and field use (for repair or large structure manufacturing).  Our research has focused on solving these problems, primarily through the application of robotics and closed-loop process control and monitoring.

Friction Stir Welding - Closed Loop Control

Closed-Loop Control of Proces Temperature and Plunge Force for Improved Friction Stir Weld Quality

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We are grateful for the support of

  • National Science Foundation (NSF - CMMI program)
  • Office of Naval Research (ONR - STTR)
  • Wisconsin Innovation & Economic Development Research Program (IEDR)