Dynamics of Fracture Propagation

Abstract

In discussing the fracture of solids under a single application of the load, generally one may differentiate three types of material response. The first is the so-called crystalline shatter of a defect-free crystal with an ideally uniform geometry and under ideally uniform external loads, or fragmentation of defect-free high strength brittle solids. In the case of perfect crystals the fracture may be a complete shatter of the material or the instantaneous rupture along a plane. In this case too the initial fracture may be followed by material fragmentation which will be discussed briefly later in this paper. The second type of response may arise in another ideal case in which the geometry and the microstructure of the medium and the external loads are such that the fracture nucleation and growth (i.e., the formation and propagation of microcracks) take place uniformly and simultaneously along a certain plane. In such a case the fracture propagation from each microcrack may have similar velocities. Even though these velocities may in themselves be somewhat limited, due to the multiplicity of fracture nuclei, the final phase of the fracture, i.e., the process of rapid crack propagation, may be of very short duration. A carefully grooved homogeneous thin sheet under uniform tension may come close to satisfying the conditions necessary for this type of fracture.