FRACTURE TOUGHNESS AND FATIGUE CRACK GROWTH TESTS OF FRICTION STIR WELDED PLATES

Friction stir welding has been demonstrated as a viable replacement to conventional
fusion welding in various engineering applications. In most cases, the suitable
welding parameters were selected based primarily on the tensile tests performed on
welded test joints. In this project, a study on fracture toughness and fatigue crack
growth of friction stir welded aluminium plates was performed. Two types of tests
were conducted according to ASTM Standard Test Method £647-08 for fatigue crack
growth and £399-08 for fracture toughness. The objectives of the project were to
perform Fracture Toughness and Fatigue Crack Growth test on Friction Stir Welded
aluminium plates, determining the plane strain fracture toughness K1c, establishing the
rate of fatigue crack growth of the A6061 welded plates, and comparing those
properties with non-welded A6061 plates. Friction stir welding was conducted using
CNC milling machine with a tool pin of 8 mm length, pin diameter of 6 mm and
shoulder diameter of 12 mm at 1600 rpm tool rotational speed, 12 mmlmin weld
speed and 12s dwell time. The results indicated that the friction stir welded plates
exhibited lower fracture toughness and higher cracks propagation rate than nonwelded
plates.