Multi Field Simulation of Fracture

We present as areas of interest for multifield fracturing thermomechanical fracturing, fluid pressure induced isothermal and nonisothermal fracturing, fracturing due to radiation, drying, hydrogen embrittlement, and fractures induced by chemical effects. We discuss the most appropriate constitutive models for their simulation and choose the cohesive fracture model for quasi-brittle materials. Successively we show governing equations for a thermo-hydro-mechanical problem, which is representative for multifield problems. Possible extensions to more fields are addressed. Then methods for numerical modeling of multifield fracturing are presented and the most representative ones, i.e., interface and embedded discontinuity elements, X-FEM, thick level set and phase field models, and discrete crack approach with adaptive remeshing are discussed in some detail. After incorporating this last method in the governing equations, their numerical solution is shown together with the necessary adaptivity in time and space. This solution is validated. Successively applications to thermomechanical fracture; hydraulic fracturing in case of a pumped well and of 2D and 3D dams; fracturing of drying concrete and of a massive concrete beam and finally mechanical effects of chemical processes in concrete are shown. In the case of the pumped well with constant pumping rate, a comparison between an Extended Finite Element solution and that of the discrete crack approach with adaptive remeshing is made which allows for interesting considerations about the nature of hydraulic fracturing. The examples permit to conclude that with increasing complexity of the multifield problems that of the employed fracture models decreases, i.e., advanced fracture models have to date only been applied to problems with a limited number of fields, mainly displacement, thermal and/or pressure fields. There is hence plenty of room for improvement.