FORMING-LIMIT DIAGRAMS FOR AL-2124 AND AL-LI-8090 THROUGH FRACTURE-MECHANICS AND PERTURBATION ANALYSIS

A parallel comparative 'fracture mechanics and perturbation analysis' study for the construction of 'forming-limit diagrams' is presented in this work. The first is based on the notions of a recently introduced generalization of the T-criterion of fracture for the case of uncrack ed specimens. According to this generalization the failure of a materi al is described by a set of two material constants, i.e. its maximum a bility to absorb dilatational and/or distortional strain energy. On th e other hand the perturbation analysis is based on the introduction of a disturbance added to the homogeneous solution satisfying the set of governing differential equations of the problem. Both approaches are applied for the case of two conventional alloys, i.e. Al 2124 and AI-L i 8090, and their predictions are then compared with each other and al so with the experimental results obtained from a series of in-plane an d out-of-plane metal-forming processes.