Evaluation of the two-parameter fracture criterion for various crack configurations made of 7075-T6 aluminium alloy using finite-element fracture simulations

摘要

For many years, a two-parameter fracture criterion (TPFC) has been used to correlate and predict failure loads on cracked metallic fracture specimens. The current study was conducted to evaluate the use of the TPFC on a high-strength aluminium alloy, using elastic-plastic finite-element (FE) analyses with the critical crack-tip-opening angle (CTOA) fracture criterion. In 1966, Forman generated fracture data on middle-crack tension, M(T), specimens made of thin-sheet 7075-T6 aluminium alloy, which is a quasi-brittle material. The fracture data included a wide range of specimen half-widths (w) ranging from 38 to 305 mm. A two-dimensional FE analysis code (ZIP2D) with a "plane-strain core" option was used to model the fracture process with a critical CTOA chosen to fit the M(T) test data. Fracture simulations were then conducted on other M(T), single-edge-crack tension, SE(T), and bend, SE(B), specimens over a wide range in widths (w = 19-610 mm). No test data were available on the SE-type specimens. The results supported the TPFC equation for net-section stresses less than the material proportional limit. However, some discrepancies in the FE fracture simulations results were observed among the numerical analyses made on the three specimen types. Thus, more research is needed to improve the transferability of the TPFC from the M(T) specimen to both the SE(T) and SE(B) specimens for quasi-brittle materials.