| The main thrusts of this study are to investigate stable tearing aspects of the 2524T351 aluminum fracture process, and to derive an equation involving crack opening displacement and constraint. Specifically, the elastic-plastic finite element analysis code CRACK3D is utilized to develop a converged mesh and perform three-dimensional crack growth simulations of a compact tension specimen. Using a nodal release technique to progressively extend the crack along a known fracture surface with pre-defined crack fronts at known load levels, good agreement is demonstrated for simulated and experimentally measured global displacement.; The computed crack opening displacement (COD) at 0.50 mm behind the crack front indicates that (a) the critical COD is larger near the free surface than in the interior for both 2524-T351 and 2024-T3 LT, and (b) critical COD is larger for 2524-T351 than for 2024-T3 LT. The computed constraint integrated over a specified distance ahead of the crack front is (a) larger in the interior than near the free surface for both materials, and (b) larger for 2524-T351 as compared to 2024-T3 LT.; Using the COD and Am pairs obtained from the nodal release simulation, a COD-Am stable tearing equation is derived and shown to be similar to one previously derived for 2024-T3 LT. The 2524-T351 equation predicts higher critical COD values for the same constraint values, indicating a trend of increased fracture resistance for 2524-T351 relative to 2024-T3 LT. Using local re-meshing along a specified crack path to simulate the tunneled crack shape, the predicted crack tunneling response is shown to be in good agreement with experimental evidence, with perturbation in the specified crack path having some effect on the flaw shape during crack extension, but not on the overall trends. |
