Chapter 2 - Griffith Theory of Fracture

Abstract

The theoretical strength of a solid is usually understood as the applied stress that fractures a perfect crystal of the material by breaking the atomic bonds along the fractured surfaces. The theoretical strength is estimated using the interatomic bonding force versus the atomic separation relation. Failure of a solid is characterized by separation of the body. At the atomistic level, the fracture strength of a “perfect” material depends on the strength of its atomic bonds. In addition, Griffith postulated that all bulk glasses contain numerous minute flaws in the form of microcracks that act as stress concentration generators. This new concept accompanied by the energy release approach that he introduced started the era of modern fracture mechanics. The Griffith theory for fracture of perfectly brittle elastic solids is founded on the principle of energy conservation, that is, energy added to and released from the body must be the same as that dissipated during crack extension.