J-evaluation on tensile testing (JETT) based fracture toughness assessment of Aluminium (6063) alloy using circumferentially notched round bar specimens

The J-evaluation on tensile testing (JETT) using circumferential notch round bar specimens has been proposed for rapid determination of fracture toughness of structural materials exhibiting substantial ductile mode fracture. However, very little has been reported on the effect of notch parameters (notch diameter and notch angle) on the JETT fracture toughness values determined. In this study, Al 6063 alloy was used as test material, and the dependence of the fracture properties on notch parameters, investigated. The Al6063 alloy samples were machined having a constant gauge length (D) of 10 mm, notch diameters (d) of 6, 7, and 8 mm, and notch angles of 45, 60, and 75°, and subjected to tensile loading to fracture. The results obtained showed that the notch strength of the alloy increased with decrease in notch diameter and increased slightly with increasing notch angle. The percent elongation of the notch samples increased with increase in notch diameter and slightly with increase in notch angle. The JETT-fracture toughness values were observed to be more convergent with ^D_d ratio within the range 1.25-1.7 and the use of notch angles of 60 and 75° with an average value of 328.33 ± 23.73 kJ/m² obtained. Notch angle of 45°, is not recommended for the JETT basis for evaluation of fracture toughness of Al 6063 alloy.