Fatigue crack-growth behavior of materials in viscous fluid environments

The potent effect of the hydrodynamic pressure developed in the wake of a crack growing under cyclic loads in a viscous fluid environment is considered. While existing semi-analytical solutions provide an estimate of the hydrodynamic pressure effect, they are inherently restricted by the assumption of specific crack opening profiles. To correct this limitation and to extend the study to a complete range of materials and fluid environments, a fully consistent numerical approach was developed. A self-consistent fracture mechanics solution procedure is derived initially for atomistically sharp cracks in brittle materials, and then extended to include the effect of crack tip blunting in more ductile materials. Three important dimensionless parameters are identified through which effects of various physical properties on crack-growth behavior can be examined. These include specimen geometry, material properties, fluid viscosity and cyclic loading conditions. General plots are constructed spanning wide ranges of these dimensionless parameters so that the hydrodynamic pressure contribution to crack-growth rates can easily be estimated for a complete range of materials, fluid environments and loading parameters. (C) 1999 Elsevier Science Ltd. All rights reserved.