Mechanism of Fracture of Glass and Similar Brittle Solids

A theory is proposed which connects the stress, f, required to break a brittle material in simple tension, with its duration of application, t. The slow process preceding fracture is shown to be the orientation of the atomic network contained in an elementary prism of length r=λ0E/f, where E is Young's modulus and λ0 is the critical elongation required for fracture. The rate‐controlling factor is the activation energy, Eα/f, for the orientation or rearrangement of the atomic network under the stress, f. Moisture on glass, and moisture plus oxygen on certain metals, are important catalytic or fatigue‐promoting factors because they reduce the unit activation energy, α. The theory leads to the equations t=(1/k0)eEα/fkT and logt=−logk0+(Eα/2.3kT)/f, where t is the time for fracture (duration of the stress), k is the Boltzmann constant, T the absolute temperature, and α and k0 are experimentally determined constants. The logarithmic expression has the same form as the Glathart‐Preston [J. App. Phys. 17, 189 (1...