PSI - Issue 40

Vladlen Nazarov et al. / Procedia Structural Integrity 40 (2022) 348–353 Vladlen Nazarov / Structural Integrity Procedia 00 (2022) 000 – 000

352

5

1 eq

Complex equivalent stresses turned out to be a special case of basic equivalent stresses, where

mises    for

2 eq  

max for experimental data Nazarov (2014a). The minimum 2 eq  and took almost the same values for experimental data 

experimental data Kobayashi et al. (2017) and total errors of complex equivalent stresses 1

eq  and

Dyson et al. (1977) and Cane (1981), while these values are noticeably less than the minimum total errors for the basic equivalent stresses. In general, based on the analysis of all considered experimental data, it can be concluded that there is no common equivalent stress for describing both types of plane stress state. A visual representation of the result of the choice of the equivalent stress depending on the type of plane stress can be represented as a rectangular element exposed to the corresponding main stresses (Fig. 1).

Fig. 1. Choice of an equivalent stress to describe the creep rupture depending on the type of plane stress state.

In this paper, the question of choosing an equivalent stress has solved, which allows describing the creep rupture for two different plane stress states differing in the sign of one of the main stresses. Three basic and two complex equivalent stresses with a parameter have considered. The minimum total error of the difference between the experimental rupture time and theoretical rupture time have been taken as the criterion for selecting the equivalent stress. The analysis of the total errors showed that for each type of plane stress state, a specific complex equivalent stress with a parameter should be used. To describe the rupture time under conditions of biaxial tension, the sum of the maximum normal stress and the Mises stress should be used. To describe the creep rupture during simultaneous tension and compression of an elementary plane element in two mutually orthogonal directions, the sum of the maximum normal stress and the doubled maximum tangential stress as should be used. 5. Conclusion This work is devoted to the choice of the creep rupture criterion that empirically most accurately describes the creep rupture in accordance of experimental data for two schemes of a plane stress state. On the basis of minimizing the total error of the difference between the experimental rupture time and approximating rupture time, the justification have been given of the choice of the complex equivalent stress that most accurately describes the creep rupture for a specific scheme of the stress state for an isotropic material in accordance with experimental data have been carried out. The results of the work are of practical significance and can be used when performing calculations of the corresponding structural elements and machine parts operating under statistical loads at a plane stress state. Acknowledgements

This work was partially supported by the Russian Foundation for Basic Research (grant 20−08−00387).