MACROSCOPIC NATURE OF BRITTLE-FRACTURE

The different possible mechanisms of cleavage fracture initiation are rather well known. It has been recognized that the critical steps for cleavage fracture are: I Initiation of a microcrack eg. fracturing of a second phase particle. II Propagation of this microcrack into the su rrounding grains. III Further propagation of the propagating microcrac k into other adjacent grains. Depending on temperature, loading rate a nd material, different steps are more likely to be most critical. Beca use materials generally are not uniform on a microscale, cleavage frac ture initiation is a statistical event, which have implications upon t he macroscopic nature of brittle fracture. In this presentation the ma croscopic nature of brittle fracture will be examined and its impact u pon the application of fracture mechanical material parameters for str uctural integrity evaluations will be discussed.