Energy utilisation and generation during friction stir spot welding

Energy utilisation during spot welding is investigated using a combination of calorimetry, peak temperature measurement and plunge testing. When a steel tool, clamp and anvil support is used, only 12.6% of the energy generated during the spot welding is transferred into the welded Al 6111 sheets. In contrast, when a mica clamp and anvil support are used, 50% of the energy generated during spot welding transfers into the welded Al 6111 sheets. Only a small percentage of the energy generated during the friction stir spot welding operation is required for stir zone formation. During plunge testing of 6.3 mm thick Al 6061-T6 material, less than 4.03% of the energy which is generated during friction stir spot welding is required for stir zone formation. The remainder of the energy generated dissipates into the tool assembly, clamp, anvil support and the aluminium sheets which are being welded. The rotating pin produces around 70% of the energy generated during spot welding of 6.3 mm thick Al-6061 material, with the remainder being contributed by the tool shoulder.