Issue 51

Y. Dubyk et alii, Frattura ed Integrità Strutturale, 51 (2020) 459-466; DOI: 10.3221/IGF-ESIS.51.34 459 Stress-strain assessment of plain dents in gas pipelines Yaroslav Dubyk IPP-Centre LLC, Ukraine dubykir@gmail.com , http://orcid.org/0000-0002-4327-412X Iryna Seliverstova G. S. Pysarenko Institute for Problem of Strength, National Academy of Sciences of Ukraine, Ukraine seliverstovairyna24@gmail.com, http://orcid.org/0000-0003-1166-792X A BSTRACT . This paper presents the analytical solution of the stress-strain state for a dented pipeline, based on the method of equivalent loads. Firstly, a solution for a harmonic imperfection was found, then using Fourier series expansion a semi-analytical procedure was proposed to assess a single dent. A comparison between analytical and numerical results for the axial force and pressure load were given. The influence of the dent dimensions, shell radius to thickness ratio and initial loading to stress concentration factor were discussed. K EYWORDS . Cylindrical shell; Plane dent; Approximate solution; Citation: Dubyk Y., Seliverstova I., Stress- strain assessment of plain dents in gas pipelines, Frattura ed Integrità Strutturale, 51 (2020) 459-466. Received: 11.11.2019 Accepted: 06.12.2019 Published: 01.01.2020 Copyright: © 2020 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION runk pipelines are one of the most common means used in the transportation of various kinds of energy resources. Ensuring trouble-free operation of pipelines is a pledge of both the environmental and energy security of the country through which they pass. The most common cause of accidents on trunk pipelines is the presence of mechanical damage (dents and gauges) and corrosion [1]. Therefore, the key point in the study of the technical condition and the extension of the life of trunk pipelines is the determination of their stress state, taking into account these local damages. Dents are one of the most common types of defects arising due to external interaction – damage by heavy machinery (excavators, tractors, pipe layers), falling stones on top of a pipeline or resting on supports [2]. Local imperfections like dents on pipelines are quite complicated for engineering analysis. To assess this problem, contact mechanics and nonlinearities in both material and geometry have to be considered in all phases of the dent life cycle. Recently these problems are addressed using FEA only [3, 4]. Finite Element method is the most largely used method for solving problems of engineering but since it is a numerical study it does not give the total accurate understanding of the problem. To investigate dent problems, it would be best to develop a closed-form analytical model would be the wisest choice to investigate dent problems but it is almost impossible due to the complicated geometry and it doesn't give considerable advantages comparing to FEM analysis. Instead a semi-analytical numerical procedure is proposed in the current study based on the equivalent load method. T