Numerical prediction of the strength of a thin-walled pipe loaded with internal pressure and axial tension taking into account its actual dimensions

Abstract

If a thin-walled pipe loaded with internal pressure and tension allows the appearance of plastic strains takes place, then the uniform plastic stability loss with the emergence of a local plastic deformation zone is considered the limit state, the corresponding stresses are considered as the limit ones. Correct prediction of the stress-strain state at the moment of strain localization requires taking into account the actual size of the loaded pipe and the calculation of true stresses. The article proposes the implementation of the method of predicting the limit values of true stresses that appear in the pipe at different ratios of internal pressure and axial tension. The physical and mechanical properties of the material, the type of stress state and the change in the actual dimensions of the loaded pipe are taken into account. For two grades of steels (carbon steel 45 and alloy steel 10MnН2MoV), an increase in the calculated strength threshold is shown with an insignificant additional load of a pipe loaded with pressure and axial tension. Analysis of the results showed that it is possible to establish a balance between the actual geometry of the element and the load, which will solve the problem of finding the optimal ratio of «weight-strength», important for practical applications in aircraft, rocket and mechanical engineering. The proposed method for finding the limiting values of actual stresses makes it possible to calculate a realistic safety factor and make improved engineering solutions at the design and operation stages of structural elements; to increase the efficiency and safety of using pipeline and shell-type saving systems.