Modern concepts of the theory of fracture in metal forming and its application for cold rolling of pipes. Report 1. An overview of modern theories of fracture

The problem of metal deformability without fracture is actual for metal pressure treatment processes since one of the main technical requirements for metal products is the absence of cracks, tears and similar defects in continuity. For some responsible types of products, the formation of even micro-pores is unacceptable, which may lead to degradation of the performance characteristics of the finished product. The article discusses some of the fracture criteria proposed on the basis of deformable solid mechanics and physical concepts. The criteria of S. I. Gubkin, G. A. Smirnov-Alyaev, V. L. Kolmogorov, V. A. Ogorodnikov, and A. A. Bogatov were analyzed in the first group of criteria, in the second group – criteria of B. E. Khaikin, M. V. Popov and her staff. Attention is paid to plasticity diagrams and kinetic equations of damage accumulation. As a result of the analysis, it is concluded that at present the most workable criterion of deformability for the case of cold plastic deformation is the criterion of A. A. Bogatov. Examples of the use of this criterion for predicting fracture during pipes and rods drawing are given