The effect of deformation of the outer contour of a thick-walled tube on the example of two problems of steady-state creep theory

In this article the comparison of solutions by the perturbation method up to and including the second approximation of two nonlinear steady-state creep problems of a thick-walled tube under the action of internal pressure is carried out. Two types of disturbances of the tube’s outer boundary are considered: in the form of inconsistency of the outer and inner diameters, and as an elliptical shape. Using two materials with different nonlinearity properties, the model tube example shows that the non-linearity properties of the material have no significant influence on the growth of stresses, However, the shape of the change in the external profile of the tube affects the stress in the dangerous section of the tube more significantly. The analysis of the small parameter value, corresponding to the allowed deviations in the standard (GOST) for differences and corresponding growth of stresses, has been conducted.