Roman Bishchak

Effect of Long Term Operation on Degradation of Material of Main Gas Pipelines

The mechanisms of metal damage in the pipe of the main pipeline are investigated, the main reasons for their appearance are found and analysed. The main results are obtained by joint use of metallography, indentation, method for processing and analysis of digital images.

Degradation of the main gas pipeline material and mechanisms of its fracture

AbstractThe effect of the in-service scattered damage in the pipe wall metal is evaluated, and the effect of hydrogen absorbed by metal on the variation of the structure and mechanical properties of the main gas pipeline after a long-term operation is found. The main regularities in the graded nature of the static deformation process and the effect of hydrogenation on the scattered damage and fracture accumulation are found.

Low temperature impact toughness of the main gas pipeline steel after long-term degradation

The correlation of microstructure, temperature and Charpy V-notch impact properties of a steel 17G1S pipeline steel was investigated in this study. Within the concept of physical mesomechanics, the dynamic failure of specimens is represented as a successive process of the loss of shear stability, which takes place at different structural/scale levels of the material. Characteristic stages are analyzed for various modes of failure, moreover, typical levels of loading and oscillation periods, etc. are determined. Relations between low temperature derived through this test, microstructures and Charpy (V-notch) toughness test results are also discussed in this paper.

Peculiarities of the static and dynamic failure mechanism of long-term exploited gas pipeline steel

Mechanical properties are substantiated, that are the most vulnerable to maintenance material deterioration of under prolonged operating time, accompanied by intense damage. The opposite behavior of relative elongation and contraction indicates the intensity of scattered damage of the operated metal. Reducing the percentage reduction indicates operational metal embrittlement, as a result of strain hardening, which can serve as confirmation of the increase in hardness and microhardness. Fractographic analysis of failure mechanisms of steel 17G1S cut in the length and breadth of the pipe is implemented.

Defectiveness of external and internal surfaces of the main oil and gas pipelines after long-term operation

AbstractDamage by pitting corrosion of the surface areas of the local oil and gas pipelines was identified and numerically analysed in this paper. Having used the methods of optical and scanning electron microscopy, the basic laws of structural and mechanical degradation were established. Based on the data of fractographic control, the shape of defects and substantiated morphological characteristics were examined. It was established that certain informative signs of the defects correspond to certain stages of operation. Having used methods of fractodiagnostics, the main reasons for the performance defects of main oil and gas pipelines were established, and the mechanisms of degradation as well as fracture of the materials they are made from were described. According to the findings, the cause of the decrease in the reliability of the main oil and gas pipeline networks is general and localised corrosion as well as technological defects in the pipeline metal. These studies are essential for the establishmen...

Structural and mechanical defects of materials of offshore andonshore main gas pipelines after long-term operation

Abstract The study has established the main regularities of a fatigue failure of offshore gas steel pipes installed using S-lay and J-lay methods.We have numerically analyzed the influence of preliminary deformation on the fatigue life of 09Mn2Si steel at different amplitudes of cyclic loading. The results have revealed the regularities of formation and development of a fatigue crack in 17Mn1Si steel after 40 years of underground operation. The quantitative analysis describes the regularities of occurrence and growth of fatigue cracks in the presence of a stress concentration.

Analysis of surface relief evolution of polycrystalline aluminum alloy under static deformation

The peculiarities of using the surface as a damage sensor of the A2024 aluminum alloy under significant plastic strains are analyzed. Physical and mechanical regularities in the spatial self-organization of the structural and mechanical defects are found, and their relationship with the pore formation and deformation processes inside the material is established. It is proved that the surface relief formation can be used as the engineering parameter of the A2024 aluminum alloy damage under static deformation.

Influence of in-service degradation on strain localization in steel of main gas pipelines

General regularities in the failure kinetics of steel of main gas pipelines (17GS) are established using the method of complete stress-strain curves, meanwhile in-service degradation of metals is taken into account. The influence of material degradation on material properties under static tensioning is considered using two independent approaches: the phenomenological model of damage accumulation in metals, and the fractographic analysis method. The accumulation of in-service damage is found to increase a degree of material opening and lead to partial “embrittlement” of the steel matrix due to the microdefects accumulation in the vicinity of metal cracking caused by hydrogenation.

Reasons for crack nucleation in welded joints of main gas-pipelines after a long-term operation

A crack of operational origin in the welded joint of the main gas pipeline is analyzed. The reasons for its nucleation and impact on technological microdefects that were formed earlier during the welding are found. Micromechanisms and stages of nucleation and propagation of the crack are investigated.