The equivalent stresses at calculation of creep rupture of metals under complex stress state (review)

The criteria of creep rupture of metals under complex stress state are based on conception of equivalent stress $\sigma_e$. The basic attention is gived to determination of dependence of equivalent stress from the main stresses $\sigma_1,\sigma_2,\sigma_3$ and to determination of dependence of rupture time from value $\sigma_e$.
The detailed review of dependencies $\sigma_e(\sigma_1,\sigma_2,\sigma_3)$ is described, which were proposed by domestic and foreign scientists. The equivalent stresses $\sigma_e$, which are depended only on main stresses, and $\sigma_e$, which are depended also on the additional constants, are considered separately. By using of statistical methods the formulas for $\sigma_e$ are obtained for various kinds of complex stress states.