Necessary and sufficient criteria for brittle, ductile-brittle, and ductile fractures

On the basis of modeling processes of deformation and fracture of tensile precracked specimens, it is found to be possible to describe ductile, ductile-brittle, and brittle fractures within the framework of a single local mechanism using a single fracture criterion. Ultimate plasticity as a function of the three-dimensionality of the stressed state is chosen to be this criterion. Diagrams of the ultimate plasticity of three alloys are compared. The relation between the nature of the fracture and the type of the diagram of deformation and plasticity is shown. An algorithm for calculating the strength of a welded structure with defects is proposed.