QUASI-STATIC RATE-INDEPENDENT EVOLUTIONS: CHARACTERIZATION, EXISTENCE, APPROXIMATION AND APPLICATION TO FRACTURE MECHANICS

We characterize quasi-static rate-independent evolutions, by means of their graph parametrization, in terms of a couple of equations: the first gives stationarity while the second provides the energy balance. An abstract existence result is given for functionals F of class C-1 in reflexive separable Banach spaces. We provide a couple of constructive proofs of existence which share common features with the theory of minimizing movements for gradient flows. Moreover, considering a sequence of functionals F-n and its Gamma-limit F we provide, under suitable assumptions, a convergence result for the associated quasi-static evolutions. Finally, we apply this approach to a phase field model in brittle fracture.