ANISOTROPY IN FRACTURE-BEHAVIOR OF THIN AL 7075-T651 PLATES

The objective of this study was to relate, if possible, the anisotropy in fracture resistance with the anisotropy in elastic properties of t hin (6.38 mm) plates of aluminum alloy 7075-T651. Fracture resistances , as characterized by fracture toughness K-Q associated with the plane -stress condition, were measured in L-T, L + 30, L + 60 and T-L orient ations. These tests revealed a significant anisotropy in K-Q values wi th the K-Q in the T-L orientation being 20.6% smaller than K-Q in the L-T orientation. Tension tests revealed anisotropy in the elastic prop erties (elastic modulus and Poisson's ratio) too, with the Poisson rat io in the longitudinal direction being 2.68% larger than in the transv erse direction. The Strain-Energy-Density (SED) and the Maximum=Tangen tial-Stress (MTS) criteria were used to correlate the anisotropy in el astic properties with fracture resistance. Calculations, based on the SED and MTS criteria, showed that the anisotropy in elastic properties was inadequate to explain the large anisotropy in K-Q values. Copyrig ht (C) 1996 Elsevier Science Ltd