Since friction stir welding can be used to join sheet-to-sheet it seemed possible for it to be adapted for patch repair within sheet material. The problem was the hole created at the exit point.
The weld completion difficulty has been overcome by traversing the rotating tool up an artificially created ramp a few millimetres above the substrate. This ramp is then machined off once the weld is complete.
The process is expected to be ideal for repairing cracks in vessels or pipes. TWI's application uses a fixed programmable robot, but it is expected that the process will lend itself to being performed in the field.
The positive advantages are that the repair process can be operated in wet environments. The tooling is low force and can be used on portable FSW equipment. The rotating pin exit hole can be eliminated and the repair technique is programmable and repeatable.
For more information, please email contactus@twi.co.uk