AN ADAPTIVE SPACE-TIME FINITE-ELEMENT MODEL FOR OXIDATION-DRIVEN FRACTURE

This paper presents an adaptive, space-time finite element model for o xidation-driven fracture. The model incorporates finite-deformation vi scoplastic material behaviour, stress-enhanced diffusive transport of reactive chemical species and a cohesive interface fracture criterion. We describe in detail the variational formulation of the coupled syst em, with particular attention to stabilized discontinuous Galerkin for mulations for the chemical diffusion and the material evolution equati ons. We describe a new computational approach for simulating fracture that uses space-time finite elements to track continuous crack-tip mot ion. This provides an accurate representation of the deformation histo ry in ductile fracture, as is required for the reliable integration of the evolution equations for history-dependent materials. The space-ti me model supports both transient and direct steady-state calculations. It promotes efficient computations by eliminating the need for extens ive mesh refinement away from the current crack-tip location and by ex ploiting the temporal coherence available in problems formulated in a moving crack-tip frame. An h-adaptive finite element procedure reveals the potential of the space-time model for controlling element distort ion and maintaining solution accuracy. Numerical studies of mode-III f racture, plane-strain mode-I fracture and stress-enhanced diffusion il lustrate the importance of stabilization and adaptivity for obtaining accurate and reliable solutions. (C) 1998 Elsevier Science S.A.