AN ELASTOPLASTIC ANALYSIS OF THE CRACK-TIP FIELD IN A COMPACT TENSIONSPECIMEN

The computer-assisted moire technique and finite element computations were used to determine displacements, strains and stresses in the neig hborhood of a crack tip. The measurements were performed in an aluminu m 6061-T6 compact tension specimen. The experimentally determined stre sses were compared to the stresses obtained from the finite element ca lculations. Some important conclusions concerning the small scale yiel ding stress field can be obtained: (1) The presence of a HRR plastic h eld is not confirmed by experimental observations or numerical results , (2) A deep notch model fits the experimental observations better tha n the asymptotic singular solution, (3) The residual stresses generate d during the fatigue loading to produce a sharp crack have a strong in fluence on the crack tip stress distribution, (4) The crack tip blunti ng and the residual stresses displace the maximum tangential stresses away from the crack tip of a distance larger than the currently accept ed two crack opening displacements, (5) The experimental and numerical results support the view point that in small-scale yielding, the J-do minance is independent of the validity of the HRR solution. Copyright (C) 1996 Elsevier Science Ltd