Deformation features of trunk pipelines with composite linings under static loads

Abstract

This paper considers the deformation process of a typical section of a steel trunk pipeline with a defective zone, strengthened with a carbon fiber composite lining, under the influence of stationary internal pressure. Defects in the form of thinning of the pipe thickness and cracks were investigated. The stressed-strained state of the structure at critical pressure was analyzed. The thickness of the composite lining was determined, at which the bandage compensates for the effect of internal pressure on the damaged section of the pipeline. Research was carried out numerically based on finite element modeling in the ANSYS software package. When studying the stressed-strained state of a pipe with a defect of an arbitrary complex shape under the influence of critical pressure, a compensating value was obtained. The result showed that a carbon fiber lining with a thickness of 17 % of the rated thickness of the pipe could completely compensate for the effects of internal pressure in the defect area. In this case, the stresses in the carbon fiber lining were close to minimal. When studying the stressed-strained state of a pipe with a large crack of arbitrary shape at critical pressure, a compensating value was also obtained. It has been established that to compensate for the concentration of internal pressure in the crack zone, the thickness of the composite lining should be at the level of 34 % of the rated thickness of the pipe. In this case, the deformation of the steel pipe in the area of the crack occurs in the elastic region. The exception is the crack tips, where plastic deformations are observed, and stresses arise up to 93 % of the ultimate strength of the pipe steel. At the same time, the stresses in the carbon fiber lining remain close to minimal. Thus, it is recommended to use carbon fiber linings with a thickness of 17 % or more of the rated pipe thickness to bandage damage constituting up to 75 % of the thickness of a steel pipe. To bandage cracks, it is recommended to use carbon fiber linings with a thickness of at least 34 % of the rated pipe thickness