Effects of Electric Fields on Slow Crack Growth in Glass

Electrical de fields applied through electrodes on either side of a slow-running crack in soda-lime-silica glass resulted in a deviation of the crack plane and in delayed deceleration, arrest, and healing. In some cases crack closure occurred while still under load. Resumption of propagation resumed gradually upon removal of the field. It is suggested that the effects involve displacement of the dilated negatively charged zone at the crack tip, while healing is effected by reformation of bonds between the crack surfaces.