620.171.3

large deformations, strength conditions, thin-walled cylinders, complex stress state.

Thin-walled cylindrical tubes are used not only as structural elements but also cause great scientific-practical interest for modeling the behavior of structural elements with different geometrical shapes under complex stress state. The prediction technique for thin-walled cylindrical tubular samples of metal isotropic materials loaded by internal pressure and axial tensile strength is proposed in this paper. The investigation was carried out within momentless theory for large residual deformation areas. The material was considered to be isotropic and incompressible. Elastic deformations were neglected. The realization of Kirchhoff-Love hypothesis of thin-walled shell theory is accepted. The equilibrium boundary conditions of plastic deformation were obtained analytically. In order to derive the boundary relationships between residual relative strains and real stresses Dorn-Nadai conditions of the beginning of deformation localization process were used. The influence of stressed state and thin-walled tube geometry on the boundary real stresses and residual deformations values is observed. The analysis of the obtained conditions showed the decrease of the material strength resource when the values of primary stresses ratios approach to 0.5 and 2. It is proved analytically that with the reduction of the tensile strength and approximation of stressed state to the «internal pressure» type the strength resource of the thin-walled cylindrical tube sharply decreases.  

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Thin-walled cylindrical tubes are used not only as structural elements but also cause great scientific-practical interest for modeling the behavior of structural elements with different geometrical shapes under complex stress state. The prediction technique for thin-walled cylindrical tubular samples of metal isotropic materials loaded by internal pressure and axial tensile strength is proposed in this paper. The investigation was carried out within momentless theory for large residual deformation areas. The material was considered to be isotropic and incompressible. Elastic deformations were neglected. The realization of Kirchhoff-Love hypothesis of thin-walled shell theory is accepted. The equilibrium boundary conditions of plastic deformation were obtained analytically. In order to derive the boundary relationships between residual relative strains and real stresses Dorn-Nadai conditions of the beginning of deformation localization process were used. The influence of stressed state and thin-walled tube geometry on the boundary real stresses and residual deformations values is observed. The analysis of the obtained conditions showed the decrease of the material strength resource when the values of primary stresses ratios approach to 0.5 and 2. It is proved analytically that with the reduction of the tensile strength and approximation of stressed state to the «internal pressure» type the strength resource of the thin-walled cylindrical tube sharply decreases.