Description of the deformation properties of materials in low-cycle fatigue calculations

The issues of reliability of the results of calculations of the structures durability operating under conditions of cyclic inelastic deformation are considered. The limited available experimental information and the specifics of computational technologies are taken into account. It is shown that division of the operation process into stages (running-in, stable operation, pre-fracture) and evident identification of the types of cyclic inelastic deformation (alternating flow, one-sided accumulation of deformations, their combination) allow to indicate which of the results of limited calculations, possible in today's conditions, are reliable and which are certainly not. Without such a division, it is impossible to substantiate the reliability of the results, at least at present time, while physical “ab initio” models of materials are too complex for use in structural calculations, and the empirical ones cannot be built due to the lack of data. An example of a calculation, demonstrating both the non-standard use of the means existing in the FEM packages for a more complete description of the material properties, and a significant difference in the results depending on the method of accounting for the effects under consideration is given.