MIXED-MODE I/III FRACTURE-TOUGHNESS OF 2034 ALUMINUM-ALLOYS

A study of the mixed mode I and III fracture resistance of four 2034 aluminum alloys with varying manganese content is presented in this paper. The mixed mode fracture tests are carried out using modified compact tension specimens. As there is no standard test method for mixed mode fracture, special formulations of the J integral are used to characterize the mixed mode fracture resistance. The results indicate that the overall effect of mode III shear component is to lower the critical J-integral energy by enhancing the tendency for shear instability and early void formation. Manganese present in small amounts forms intermediate size dispersoids which increase the strength and work hardening ability without the loss of fracture toughness. In larger amounts, manganese forms large particles which lower the fracture toughness significantly. These micromechanisms and those of mixed mode fracture are discussed.