Variation, with Temperature, of the Cracking Velocity of Glass

The limiting velocity of fracture for a soda‐lime glass was measured as a function of temperature over the range of 80° and 475°K. The value of the fracture velocity was obtained by electronically measuring the time necessary for the crack to travel between two platinum lines fired into the surface of the glass specimen. The value of the fracture velocity for this glass was found to be 1485 m. per second at 300°K. with the velocity decreasing slightly with increasing temperature over the range studied. The results indicate a temperature coefficient on the order of –0.15 m. per second per °K.