ON THE GRIFFITH CRITERION FOR 3-DIMENSIONAL CRACKS

The Griffith theory of brittle fracture is extended to three-dimensional cracks. A mathematical formulation of the theory encounters insurmountable difficulties since the shape into which the crack would grow is not known a priori. A physical hypothesis for the determination of the new crack shape which would allow the subsequent calculation of the critical loads is made. The case of an elliptical crack in an infinite plate subjected to a uniform uniaxial stress perpendicular to the crack plane is considered as an example.