Adaptive space-time finite element model for oxidation-driven fracture

This paper presents an adaptive, space-time finite element model for oxidation-driven fracture. The model incorporates finite-deformation viscoplastic 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 system, with particular attention to stabilized discontinuous Galerkin formulations for the chemical diffusion and the material evolution equations. We describe a new computational approach for simulating fracture that uses space-time finite elements to track continuous crack-tip motion. This provides an accurate representation of the deformation history in ductile fracture, as is required for the reliable integration of the evolution equations for history-dependent materials. The space-time model supports both transient and direct steady-state calculations. It promotes efficient computations by eliminating the need for extensive mesh refinement away from the current crack-tip location and by exploiting the temporal coherence available in problems formulated in a moving crack-tip frame. A h-adaptive finite element procedure reveals the potential of the space-time model for controlling element distortion and maintaining solution accuracy. Numerical studies of mode-III fracture, plane-strain mode-I fracture and stress-enhanced diffusion illustrate the importance of stabilization and adaptivity for obtaining accurate and reliable solutions.National Aeronautics & Space Administration 96/11 NGT 70374 96/1