Physics of fracture and mechanics of self-affine cracks

The physics associated with self-affine crack formation and propagation is discussed. Some novel concepts are suggested for the mechanics of self-affine cracks. These concepts are employed to model the crack face morphology and, in turn, to solve various problems with self-affine cracks. It is shown that linear elastic fracture mechanics (LEFM) is a special case of self-affine crack mechanics and should be used only in length scales larger than the self-affine correlation length. The theoretical results are confirmed by available experimental data. It is emphasized that the ASTM standards for test pieces for fracture toughness measurements must be completed by the specification of absolute specimen sizes which should be larger than the self-affine correlation length for the fracture surface roughness.