Nonlinear evaluation of the long-term critical force

An evolution of a normal sections stiffness generated by a creep and corrosion of materials, changing its mechanical characteristics are taken into account. The aim of the paper is to refine the known estimates based on the concept of a statistical distribution of the disabilities links a combination of which constitutes an element. This concept allows us to derive non-linear rheological equations. The proposed generalization of the Boltzmann creep strains superposition principle is used. The destruction of a part of the links results in a redistribution of the forces to the links capable to resist. This generates a non-linear dependence of deformations on the calculated stresses obtained under the assumption of equality for all links durability. By solving it we obtain a structural stress. The product of its limit per an area of the normal element section is a long structural critical force. The significant decline of the critical force value is due to the degradation of the mechanical characteristics. Accounting for non-linearity assessment of the long-term critical force gives the values less than the well-known ones from the literature values. (paper)