scholarly journals Development of a Nonlinear Dependence for Determining the Stress-Strain State of the Pipeline-Composite Bandage System

2021 ◽  
Vol 248 ◽  
pp. 04024
Author(s):  
Robert А. Ramazanov ◽  
Igor F. Kantemirov ◽  
Denis A. Gulin ◽  
Indira F. Makhmudova ◽  
Zulfiya F. Ismagilova
Keyword(s):  
Polymer Composite ◽  
Strain State ◽  
Polymeric Materials ◽  
Polymer Materials ◽  
Nonlinear Dependence ◽  
Technical Diagnostics ◽  
Stress Strain ◽  
Repair Work ◽  
Industrial Enterprises ◽  
Stress Strain State

The range of applications of polymeric materials in the oil and gas industries is expanding every year. For example, at present, a number of industrial enterprises are engaged in the production of various tape polymer composite structures that are used to repair pipelines. They are widely used due to the significant advantages of polymeric materials over steel such as low costs, low weight, corrosion resistance and strength. Moreover, most of the operated pipelines are about to reach their standard service life. In the course of technical diagnostics, a significant number of defects of mechanical origin from external influences are constantly revealed. Repair work on pipelines must fully restore the bearing capacity of the site. Therefore, the use of polymer materials for pipeline repair is an important task. Here, we propose to use polymer composite bandages, which will increase the overhaul period. However, a coherent methodology for choosing a material and calculating the required thickness of this structure is not available in the literature, and, therefore, the purpose of this work was to develop such a methodology, as well as to assess the stress-strain state of pipeline-bandage systems. The method presented in this work takes into account the possible anisotropy of the shroud material in the longitudinal and transverse directions and the possibility of plastic deformation of the pipeline material in the annular direction. This work is based on the following assumptions: (a) bilinear dependence of stress on deformation for steel; (b) plastic deformations of the band material are absent; and (3) absolute adhesion between the pipeline and the band. The paper presents the analysis of the market of polymeric materials for pipeline repair, their key properties, and the minimum thickness of the band made of these materials was calculated for various values of the stress concentration coefficient.

The Simulation of Ultra-High Molecular Weight Polyethylene Cryogenic Pipeline Stress-Strain State

2021 ◽  
Vol 1031 ◽  
pp. 132-140
Author(s):  
Ekaterina Karyakina ◽  
Ildar Shammazov ◽  
Vladimir Voronov ◽  
Aleksey Shalygin
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Strain State ◽  
Polymer Materials ◽  
Creep Process ◽  
Cryogenic Temperatures ◽  
Stress Strain ◽  
Stress Strain State ◽  
Cryogenic Pipeline ◽  
Ultra High Molecular Weight

At present the production of polymer materials is developing intensively, new materials, comparable with steels in their strength properties have recently appeared. In this connection, the analysis of polymer materials applied in the pipe industry has been carried out, and the use of ultra-high molecular weight polyethylene (UHMWPE) is proposed as a structural pipeline material, allowing pipes to operate at cryogenic temperatures. The focal point of the article is the consideration of the fracture mechanisms of those materials and the nature of the change in the mechanical properties of UHMWPE under cryogenic temperatures, also taking into account the creep process. The expression for determining the value of the creep modulus depending on the temperature and operating time was obtained. A method is proposed for conducting initial strength estimation. Moreover, the computer model of stress-strain state of an underground cryogenic polymer pipeline for liquefied natural gas transportation is obtained. The results of simulation depict the potential possibility of using of UHMWPE for the cryogenic pipeline construction

scholarly journals INVESTIGATION OF STRESS-STRAIN STATE OF CYLINDRICAL BODY OF MODIFIED HDPE

2019 ◽  
Vol 62 (7) ◽  
pp. 118-122
Author(s):  
Stepan V. Litvinov ◽  
Lyubov I. Lesniak ◽  
Serdar B. Yazyev ◽  
Ivan M. Zotov
Keyword(s):  
Ionizing Radiation ◽  
Strain State ◽  
Polymeric Materials ◽  
Cylindrical Body ◽  
Rheological Parameters ◽  
Scientific School ◽  
Mechanical Parameters ◽  
Principal Stresses ◽  
Stress Strain ◽  
Stress Strain State

The change in the stress-strain state over time in structures and their elements from polymeric materials can be quite substantial. This is due to the pronounced rheology of the polymers. One of the most accurate laws of stress-strain bond is generalized nonlinear Maxwell-Gurevich equation, which takes into account three rheological parameters: the modulus of elasticity, the velocity modulus and the coefficient of initial relaxation viscosity. A significant influence on the physico-mechanical parameters of the polymer is also exerted by various factors: the presence of a temperature field and ionizing radiation, the presence of additives in the polymer and so on. The paper presents the results of mathematical modeling of a disc made of high-density polyethylene (HDPE) in an axisymmetric setting under the influence of mechanical axial pressure. This model is chosen because of the most frequent use of HDPE irradiated and with additives in medicine, including for the manufacture of orthopedic prostheses. Different compositions of HDPE are considered: under the influence of ionizing radiation, with additives of hydroxyapatite and with their combined effect. All physico-mechanical parameters of HDPE (dose of ionizing radiation and the fraction of hydroxyapatite injected) are described by mathematical expressions obtained in the scientific school of Professor B.M. Yazyev on the basis of an analysis of the corresponding polymer relaxation curves. The results of the solution of the problem have shown that the basic stresses (radial, circumferential and axial) vary in the course of time in different ways. The growth of the value of the primary basic stresses can be 2-2.5 times. If the analysis is carried out on the main stresses, then their value increases by approximately 1.5 times. Also, the change in the principal stresses is observed even when it is not observed for the basic stresses.

Ensuring the strength and stability of the tank wall during repairs by installing rigid frames

2021 ◽  
pp. 152-165
Author(s):  
Артем Николаевич Задумин ◽  
Евгений Григорьевич Ильин ◽  
Михаил Владимирович Лиховцев ◽  
Алексей Александрович Катанов
Keyword(s):  
Computer Modeling ◽  
Strain State ◽  
Mutual Influence ◽  
Tank Wall ◽  
Stress Strain ◽  
Stability Calculation ◽  
Actual Structure ◽  
Repair Work ◽  
Stress Strain State ◽  
Cutting Out

Устранение дефектов металла и сварных швов стенок вертикальных цилиндрических резервуаров возможно методом вырезки и замены удаленных фрагментов ремонтными вставками с использованием рам жесткости. При этом в нормативных документах отсутствуют методики расчета таких усиливающих элементов и собственно конструкции стенки резервуара с данными элементами. С целью оценки прочности и устойчивости стенки резервуара и рамы жесткости во время проведения ремонтных работ выполнено компьютерное моделирование и проведены расчеты напряженно-деформированного состояния указанных металлоконструкций. В рамках исследования рассмотрены основные российские и зарубежные нормативные документы, регламентирующие нагрузки и методики расчета устойчивости стенки резервуара, проанализированы публикации, посвященные расчету устойчивости стенки резервуара с применением компьютерного моделирования. Приведены результаты компьютерного моделирования и расчетов на прочность и устойчивость в зависимости от снеговой и ветровой нагрузок. По итогам выполненных работ сделаны следующие выводы: 1) расчеты должны учитывать ветровую нагрузку, действующую под углом 40° к вырезаемому фрагменту; 2) допустимые размеры одной вставки не должны превышать габариты одного листа пояса резервуара; 3) не рекомендуется одновременная вырезка и замена более чем одного фрагмента; 4) при необходимости возможность одновременной вырезки проемов в двух и более местах должна определяться расчетом, учитывающим взаимное влияние количества, расположения и размеров проемов на напряженно-деформированное состояние стенки резервуара и рам жесткости. Elimination of metal defects and welds in the walls of vertical cylindrical tanks is possible by cutting out and replacing the removed fragments with repair inserts using stiffening frames. At the same time, there are no methods for calculating such reinforcing elements and the actual structure of the tank wall with these elements in the regulatory documents. In order to assess the strength and stability of the tank wall and the stiffening frame during the repair work, computer modeling was performed and the stress-strain state of these metal structures was calculated. Within the framework of the research the main Russian and foreign normative documents regulating the loads and methods of tank wall stability calculation are considered; the publications devoted to the tank wall stability calculation by means of computer modeling are analyzed. The results of computer modeling and calculations for strength and stability depending on snow and wind loads are presented. Results of the research performed were used to make the following conclusions: 1) calculations should take into account the wind load, acting at an angle of 40° to the section to be cut out; 2) the allowable dimensions of one insert should not exceed the dimensions of one sheet of the tank ring; 3) simultaneous cutting out and replacement of more than one section is not recommended; 4) if necessary simultaneous cutting of openings in two or more places should be determined by calculation, taking into account the mutual influence of the number, location and sizes of openings on the stress-strain state of the tank wall and stiffening frames.

scholarly journals Research of the endurance of epoxy composite materials under cyclic compression

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Boris Bondarev ◽  
Pavel Komarov ◽  
Anton Kosta ◽  
Oleg Korneev ◽  
Alexander Bondarev ◽  
...  
Keyword(s):  
Composite Materials ◽  
Cyclic Loading ◽  
Polymer Composite ◽  
Strain State ◽  
Epoxy Composite ◽  
Polymer Composite Materials ◽  
Careful Study ◽  
Stress Strain ◽  
Cyclic Action ◽  
Stress Strain State

The widespread use of polymer composite materials is largely constrained by the complexity of predicting the characteristics of their stress-strain state under cyclic types of loading. Due to the poor knowledge of the behavior of polymer composite materials under this kind of loading. At present, it is rather difficult to predict the durability of polymer composite materials under static types of loading, and the available methods for materials of a crystalline structure and polymers are not always applicable to them. Insufficient theoretical and experimental data on the assessment of the stress-strain state of polymer concretes under prolonged loading. Under long-term action of cyclic loads, changes in the structure of polymer composite materials occur due to local self-heating at the tops of growing submicrocracks and the associated change in the elastic-hesteretic properties of the material. In this case, the energy of fatigue manifests itself, when the simultaneous multifactorial cyclic action of natural and force stresses leads to an effect that exceeds the total action of certain types of stresses. And, if such processes have been sufficiently studied for wood, a natural polymer material, then for artificial conglomerates, such as polymer composites, these issues require careful study. Studies of the endurance of epoxy polymer concretes were carried out on samples of prisms 100x100x400 mm according to the method developed by the authors. The formula was used to determine the minimum number of samples required to build endurance lines. The value of the cycle asymmetry coefficient was taken equal to 0.6. The value of the maximum cyclic loading was taken from 0.62 Rв with a gradual decrease. The values of the endurance limit of an epoxy composite material under cyclic loading Rв,pul = 0.43 Rв or 93.72 MPa were obtained, which makes it possible to judge the sufficient durability of this material.

Sign in / Sign up

Export Citation Format

Share Document