Stability behind the limit of elasticity

Generalization of the formula of Euler on not elastic area and definition of critical force in the compression member behind a limit of elasticity is considered in article. It is set an example of calculation in which comparison of the decisions received by methods of F.Engessera, T.Karmana and I.Tsurkova which involves laws deformation theories of plasticity is resulted. Ultimate stress which was determined on resulting module, gives superior limit of stress for load capacity of a design, on tangent module - limiting minimum, stress, on module Tsurkova it located between these solutions.