Patent ID: 8393523

Claim:
A method of performing ultrasonic stir welding, comprising the steps of: providing a welding head assembly to include a plate and a rod passing through said plate wherein said rod is rotatable about a longitudinal axis thereof, said rod being in contact with a work piece to be welded; rotating said rod about said longitudinal axis thereof during a welding operation wherein said work piece is plasticized adjacent said rod with a first region of said work piece plasticized and in contact with said rod being forward of said rod and a second region of said work piece plasticized and in contact with said rod being aft of said rod; applying a series of on-off ultrasonic pulses to said rod as said rod rotates about said longitudinal axis thereof such that said on-off ultrasonic pulses propagate parallel to said longitudinal axis of said rod; and controlling at least a pulse rate associated with said on-off ultrasonic pulses during said step of rotating wherein said pulse rate is selected such that said first region of said work piece plasticized sticks to said rod and said second region of said work piece plasticized is released from said rod.