Damage and fracture

Abstract

Micromechanical aspects, mechanisms and models of fracture are addressed, which have become increasingly topical since the 1990s though the basic ideas and perceptions date back to the early years of fracture mechanics. The characteristics of brittle and ductile damage on the micro-scale and the respective fractographic appearance are outlined and the implications on local criteria of fracture are specified. Two approaches for establishing constitutive equations of damage are distinguished, namely micro-mechanical models which aim at describing the physical processes of damage on the micro-scale following the concept of representative volume elements and phenomenological constitutive equations for stresses and strains describing macroscopically observable effects of degradation based on thermodynamical principles. Two particular models of major significance, the Gurson and the Rousselier yield function are described. A brief introduction to parameter identification ends the chapter.