Effect of the Characteristics of Low-Temperature Plastic Deformation of Metals with bcc Lattice on the Stress-Strain State at the Tip of a Macrocrack

Abstract

We present the results of application of a physical criterion of yield in the complex stress-strain state to the description of plastic deformation at the crack tip. Unlike the von Mises criterion, the proposed criterion enables one to take into account the characteristics of plastic deformation of bcc metals at low temperatures. We simulated the process of loading of a platelike specimen (400×1600 mm) containing a central crack under conditions of plane deformation. It is shown that the drop of shear resistance under the action of normal tensile stresses observed in the process of low-temperature plastic deformation of bcc metals and alloys strongly affects the parameters of the stress-strain state of the metal at the crack tip. Thus, it leads to the enlargement of the zone of local plastic strains, promotes an increase in the maximum level of plastic strains at the crack tip, and affects the relationship between the tangential and normal stresses in the plastic zone. It is demonstrated that the physical criterion of yield can be efficiently used for the numerical analysis of the stress-strain state at the crack tip in bcc metals and alloys at low temperatures by the finite-element method.