Micromechanical modeling of fracture initiation in 7050 aluminum

• Published in: Engineering fracture mechanics 2002-12, Vol.69 (18), p.2163-2186
• Main Authors: Hill, Michael R, Panontin, Tina L
• Format: Article
• Language: English
• Subjects: Aluminum; Constraint; Fracture; Micromechanical modeling
• ISSN: 0013-7944; 1873-7315
• DOI: 10.1016/S0013-7944(01)00148-5

Mechanical testing and finite element calculations have been carried out to characterize the fracture initiation behavior of the high-strength aluminum alloy 7050-T7451. Results show that fracture initiation is well predicted for two specimen types of differing constraint using the stress-modified, critical plastic strain micromechanical model. The relation between stress triaxiality and critical plastic strain was found from a series of notched tensile specimens. Data from these tests are interpreted using both companion finite element modeling and common, semi-empirical relations, and these two approaches are compared. Multiple, interrupted tests of standard, highly constrained single edge notched bend specimens are used to obtain the J– R curve in 7050 for small amounts of tearing to experimentally identify initiation. Companion modeling and the stress-modified, critical plastic strain relation are used to find the length scale for fracture, l ∗ , needed for initiation predictions. The calibrated stress-modified, critical plastic strain relation and length scale are then used to predict fracture initiation of a low-constraint specimen. The prediction is within 5% of the experimental measurements. Finally, various aspects of the procedure followed in the present work are compared to previous efforts using similar approaches.