«Equipment and technologies for oil and gas complex»

Physical modeling of the stress-strain state of the pipe under the impact of external radial concentrated load

UDC: 621.643.053
DOI: -

Authors:

¹ Ukhta State Technical University, Ukhta, Russia

Keywords: deformation theory of plasticity, quantitative criterion of a pipeline strength, safety factor, criterion of plasticity, principle of superposition, difficult engineering geocryological conditions, theory of thick-walled cylindrical shell, physical modeling of the stress-strain state of the object under loads

Annotation:

Main pipelines are subjected to a complex of forces during operation. The pipeline structure may be subjected to external radial non-axisymmetric forces in difficult geocryological engineering conditions. An actual problem is the assessment of the stress-strain state of the pipe wall under this type of loading. The mathematical apparatus describing strain-stresses and deformations in a cylindrical shell under radial non-axisymmetric load is very lengthy and includes systems of high-order differential equations. This mathematical apparatus is not applicable for technical calculations. The beam bending theory widely used in engineering strength calculations of pipelines is not entirely correct, since the design scheme of the pipe, strictly speaking, is a cylindrical shell, not a beam. Therefore, for a reliable assessment of pipe stresses under the action of an external radial concentrated (a special case of non-axisymmetric) load, physical experiments were performed on a laboratory stand. Plots of hoop and longitudinal stresses as well as intensity of stresses of pipe’s various cross sections under the action of the specified radial load are obtained. The case of the combined effect of radial load and internal pressure is also considered. The internal pressure stresses were determined according to the theory of a thick-walled cylindrical shell. The total stresses from the combination of loads were calculated in accordance with the principle of superposition. Local maximum and minimum stresses are found on the stress plots. Positive and negative zones of hoop and longitudinal stresses are determined. Zones of elastic-plastic deformation have been revealed. The limiting stress is calculated and the strength of the pipe is estimated. The data of physical and computer modeling of the pipe stress-strain state under load are compared. The methods of experimental and computational assessment of a pipeline strength considered in the article can be used, when performing physical modeling in the testing laboratory or an industrial testing area, as well as in the process of monitoring the pipelines technical state.

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