TORSIONAL DEFORMATION AND FATIGUE BEHAVIOUR OF 6061 ALUMINIUM ALLOY

Torsional deformation and fatigue behaviour of both solid and thin-walled tubular specimens made from as-received and heat treated 6061 aluminium alloy were studied. 6061 aluminium alloy have been widely used as a candidate material in automobile, aerospace, aircraft and structural application because of their superior mechanical properties such as high strength to weight ratio, good ductility and others. The differences in cyclic deformation and fatigue behaviours between round and solid specimens where a stress gradient exist, and thin-walled tubular specimens where a uniform stress state is commonly assumed, are also discussed. Von Mises and Tresca criteria has been used to predict the monotonic and cyclic deformation curve and compared to the torsional data obtained from the experiment. Both Tresca and Von Mises fit the experimental curve but Tresca estimation shows a curve that fits the experimental curve better than the Von Mises Fatigue life of the specimens were recorded and presented in the S-N curve and shows that heat treated T6 alloy exhibit higher fatigue life and fatigue strength compared to the as-received alloy. Through fractographic analysis, failure criteria of fracture surfaces were observed and discussed.