Study of the critical fracture stress of steel in uniaxial tension

Abstract

1. A necessary and sufficient condition for avalanche fracture of the tough microcleavage type at low temperature and with developed plastic strain in the neck is the attainment of the critical tensile stress σ1max during loading. This stress is equal to the microcleavage stress of the given structure and is the stress at which a nucleated submicrocrack becomes a Griffith crack and initiates fracture. 2. The resistance of microcleavage in the initial (undeformed) state is determined by structural parameters of the steel d and Kr. The change in this resistance during deformation depends on the strain-hardening parameters A and n. 3. The sharp drop in the true fracture stress Sk near the ductile-brittle transition temperature Tb and the strain dependence of the cold-shortness threshold are conditional upon the character of the change in the resistance of the steel to microcleavage with a change in strain. 4. The characteristic of avalanche tough fracture of steel Sk and parameters of the stress state in the neck j, L, and B can be used to determine the resistance of deformed steel to microcleavage Rmce without the attainment of the cold-shortness temperature in an experiment.