Critical states of longitudinal seam pipes of large diameter under axial compression and internal pressure

We consider the conditions of loading of a thin-walled cylindrical shell containing a layer of less strong material along the generatrix, including a longitudinal seam pipe of a large diameter, under its axial compression and internal pressure. The base shell material and the layer material are elastoplastic and hardenable. The ultimate strengths and yield points of the layer are lower than that of the base material. We investigate critical states of the layer and shell arising from general or local plastic strains. The purpose of the article is to establish dependence of critical strains, stresses and pressures on the shell on its mechanical and geometric parameters and loading conditions. The method of the study is based on the application of the Swift — Marciniak criterion to lose the stability of the process of plastic strain of the layer material. We obtain explicit analytical expressions for the required quantities. The results allow to determine critical pressures under the given conditions of loading and wall thickness at a given operating pressure.