MATHEMATICAL ANALYSIS OF CENTRAL COMPOSITE DESIGN ON TENSILE STRENGTH OF FRICTION STIR WELDED ALUMINUM ALLOY JOINTS

Aluminum alloy 6061 is a medium to high strength heat-treatable alloy. It has very good corrosion resistance and very good weld ability although reduced strength in the weld zone. It has medium fatigue strength. It has good cold formability in the temper T4, but limited formability in T6 temper. It is typically used for heavy duty structures in Rail coaches, Truck frames, Ship building, Bridges and Military bridges, Aerospace applications including helicopter rotor, skins, Tube, Pylons and Towers, Transport, Motorboats, Rivets. The structural application of aluminum alloy involves welding and joining, which are difficult to weld using conventional welding processes. In 1991 a solid state joining process named Friction Stir Welding was developed and this technique has attracted considerable interest from the aerospace and automotive industries, since it is able to produce defect free joints particularly for light metals i.e. aluminum alloy and magnesium alloy. This process uses a non-consumable tool to generate frictional heat in the abutting surfaces. The welding parameters such as tool rotational speed, welding speed and tool shoulder diameter play a major role in deciding the weld quality. In this research work an attempt has been made to understand the effect of tool rotational speed, welding speed and tool shoulder diameter on friction stir welding of AA6061 aluminum alloy. Statistical tools such as design of experiments, analysis of variance, and regression analysis are used to develop the relationships. The mathematical model has been developed to predict mechanical properties of friction stir welded aluminum alloy joints at the 95% confidence level.