CAPILLARY EFFECT ON SUBCRITICAL CRACK-GROWTH - A MODEL

A model of subcritical steady-state crack growth assisted by water vap or reacting with the material is studied. A water droplet is assumed t o be sucked in into the crack by capillary effect, so that a bubble of moist gas (air) is present between the droplet and the crack tip. The water vapor is assumed to be transported by diffusion to the crack ti p, where it is consumed by the reaction of rupture. The crack length i s assumed to be well in excess of the lengths of the droplet and the b ubble. A calculated example for glass is presented. It showed that the droplet in the crack can significantly affect the crack velocity unde r the conditions ensuring sufficiently large gas bubble length. This c an be of interest for rock mechanics applications, considering the gla ss as a model of brittle rocks.