MINIMAL RESISTANCE OF ENGINEERING MATERIALS TO BRITTLE-FRACTURE AS PREDICTED BY LOCAL APPROACH

Two basic concepts of brittle fracture are considered: the first invol ving stage-by-stage interatomic bonds decohesion at the crack tip, the second - microcrack coalescence. Quantitative evaluation has been mad e of the material threshold and minimal fracture toughness values whic h correspond to the above concepts. The paper presents the analysis of methods for the experimental evaluation of two main structure paramet ers, which govern the material fracture, and discloses their physical meaning. These are the characteristic distance and cleavage stress. It also considers the methods of a priori express-evaluation of the mate rials fracture toughness from their conventional mechanical characteri stics.