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Based on the hypothesis that uniform friction stir weld quality can be produced by maintaining a constant weld zone temperature, an investigation was conducted to develop a feedback strategy and a closed-loop control algorithm to maintain constant temperature. A 3D transient heat transfer simulation was used to relate the surface temperature measured by a pyrometer to the average weld zone temperature, and a 0D analytical heat transfer model was employed to predict changes in average stir zone temperature as a function of feed rate and heat input. Bead on plate friction stir welding experiments were conducted on 6061-T6 and 5083-H111 aluminium alloy specimens. Use of two backing plates of different thermal diffusivity was shown to alter the heat flow in the weld zone. A simple controller was designed.

7th International Symposium, 20-22 May 2008, 6A: Process/Control 2, Paper 01