Mechanics of edge crack growth under transient pressure and temperature conditions

The propagation of an edge fracture under compression in a semi-infinite impermeable isotropic elastic solid, subject to suddenly applied internal fluid pressure and temperature change, is studied numerically. The process involves a strong coupling between the elastic deformation, heat conduction in solids and fluid transport in fractures. Fluid flow is described by the lubrication equation, while the fracture width and fluid front are affected by thermal stresses and fluid pressure. Numerical results are provided for the cases where the cooling-induced tensile stress can overcome the compressive stress across the crack to propagate it at a thermally controlled speed, which is larger than the speed for crack growth resulting only from applied pressure. The presence of the pressurized fluids can result in crack growth starting earlier and can produce a slow early time crack speed. As time increases, the crack motion is accelerated by the pressure acting in the fracture from the viscous fluid flow toward the crack tip. The crack growth rate varies over a wider range relative to a pure thermally driven crack growth case and a stable, rapid growth period occurs, during which the calculated crack speeds are consistent with experimental results. The crack growth curves are located in between two thermally controlled ones for the fracture with and without uniform pressure, respectively. In addition, the dimensionless factors controlling the hydrothermal crack growth are derived from a dimensional analysis. Numerical results demonstrate that viscous flow which leads to the fluid front lagging behind the crack tip can stabilize crack growth under a larger temperature change. (C) 2015 Elsevier Ltd. All rights reserved.