Distributed Damage Processes in Fracture

Abstract

Fracture events in materials occur in a wide variety of ways, ways which differ in both macroscopic and microscopic characteristics. One class of such characteristics has come to be called “distributed damage”. The concept of distributed damage processes as part of a total fracture event implies multiple sites of cracking, void formation, or other damage phenomena, instead of a single crack which causes fracture by self-extension. An important consequence of the multiple damage concept has to do with fracture kinetics. The rates of damage formation at these multiple sites need not replicate the rate of crack motion, so that the familiar models of the crack tip as stationary in a field of moving material must become much more complex to represent varying damage rate phenomena Finally, even the concept of fracture by crack motion can be less relevant, even irrelevant, in the presence of multiple damage. It is in principle possible for a specimen which is undergoing distributed damage processes to exhibit fracture, for example by stable growth and impingement of microvoids, without ever containing a distinct crack. Thus description of distributed damage fractures typically requires greater complexity (or sophistication), both in experimental viewpoint and also in modeling, compared to self-extending cracks. In addition, they often are markedly sensitive to microstructural parameters, and thus are of particular interest to the metallurgist and materials scientist.