MIXED-MODE-I/II FRACTURE-BEHAVIOR OF AN ALUMINUM-ALLOY

Mixed-mode fracture in aluminium 7075-T6 has been investigated by means of experimental and numerical considerations. Efforts were focused on incipient crack propagation where fractographical examinations revealed the presence of two different types of growth. In the near mode II range initiation occurred by straight, macroscopically stable, shear separation. For the remaining part, crack growth initiation took place in a similar way as in pure mode I where extensive shearing was observed to occur in a zig-zag pattern. The shift in initiation behaviour seemed to result in an increase of fracture toughness. In the numerical study where crack growth was assumed to occur as a consequence of expired work-hardening capacity, the location and orientation of incipient shear band development was investigated in a comparative manner, which indeed showed some resemblance to the experimentally observed features.