ANALYSIS OF TWO CREEP RUPTURE MODEL

Various invariants of the stress tensor (maximum normal stress, Mises equivalent stress, doubled maximum tangential stress) are considered, as well as their linear combinations with one material parameter, when approximating the experimental creep rupture data obtained under a complex stress state. The error of the total discrepancy between the experimental data and the approximating values is always less for linear combinations with the material parameter than for the basic invariants of the stress tensor. This determines the predominant practical use of these linear combinations with the parameter. In this paper, we consider two models for describing the creep-rupture process under a complex stress state. One is a linear combination of the Mises equivalent stress and the maximum normal stress. The other is a linear combination of the doubled maximum tangential stress and the maximum normal stress. The effect of each of the two maximum stresses on the rupture time is established from the analysis of the results of the statistical processing of experimental data obtained under tension and torsion of tubular specimens.