A computational and experimental assessment of the pipeline stress state under bending load and internal pressure

Abstract

Main pipelines are subjected to a complex of loads during operation. Monitoring of the stress state of the pipeline wall is necessary for performing strength calculations and evaluating the pipeline reliability.The article is devoted to the method of computational and experimental study of the stress state of a pipe under a bending load and combined action of a bending load and internal pressure.The experiments have been carried out on a laboratory bench. The object of the study is a pipe that has the following characteristics: an outer diameter of 325 mm, a wall thickness of 8.5 mm and steel grade of "14XGS". Electrical resistance strain gages were used to measure the strain of the pipe wall. Formulas for calculating the stress state components of the pipe wall in the elastic-plastic deformation stage are proposed. It is given formulas for calculating the stress state components of the pipe wall in the elastic-plastic deformation stage. Plots of hoop and longitudinal stresses as well as von Mises stress are obtained for the case of bending load on the pipe and the case of combined loading under bending and internal pressure. The areas of maximum values of von Mises stress where the transition to the limiting state is most likely have been determined.When only the bending load is applied, the maximum von Mises stress zone is observed on the lower area of the pipe in its central region. When combined loading under bending and internal pressure, the maximum von Mises stress zone is observed on the lateral area of the pipe in its central region.