Computer modeling of the stress stress-strain state of thin thin-walled tubular structural elements for predicting the limiting state

Abstract

If a thin-walled pipe loaded with internal pressure and axial tension allows the appearance of plastic strains, 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 paper proposes the implementation of the methodology of predicting the limit values of true stresses in the pipe at different ratios of internal pressure and axial tension values through the development of an algorithm for its computer modelling. Unlike existing, the methodology takes into account the physical and mechanical properties of the material, the type of stress state and the change in the actual dimensions of the loaded pipe. The algorithm is based on analytical dependences, established by the authors.For two grades of steels (carbon steel 45 and alloy steel 10MnH2MoV), 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 numerical 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 developed computing modelling algorithm for finding the limit 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.