Pavlo Maruschak

Fatigue and brittle fracture of carbon steel of gas and oil pipelines

The areas of low frequency and corrosion fatigue for basic metal and welding joints of oil and gas pipelines have been determined on the basis of corrosion-fatigue test results. The most dangerous diapasons of the operation loadings were also determined. The present work also proposes the methodical approaches to the survivability prediction.

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.

Self-Organisation of the Heat Resistant Steel Structure Following Dynamic Non-Equilibrium Processes

Using an original experimental methodology and software for contactless investigation into strains applying the method of digital image correlation, conditions for DNP realization in the test setup with pre-set rigidity have been found. Strain velocities have been determined to be equal to 2...10 s–1 in the processes of forming and developing a dissipative structure of heat resistant steel under the DNP (dynamic non-equilibrium process).

Enhancing plasticity of high-strength titanium alloys VT 22 under impact-oscillatory loading

Abstract The purpose of this paper is to provide new experimental data for high-strength VT 22 titanium α + β-type alloy under impact-oscillatory loading and dynamic non-equilibrium process. Based on the performed experimental studies, it was found that overall plastic deformation of this alloy can be increased by a factor 2.75 compared with its initial state without significant loss of strength. To achieve this goal, a new methodology to study the impact behaviour of materials under non-equilibrium process has been used. Physical research revealed that significant microstructural refinement of the alloy is observed after such type of loading, as the result of which the fine grains are formed with subgrain refinement which takes place within the basis of alloy.

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.

Experimental Study of the Surface of Steel 15Kh13MF after the Nanosecond Laser Shock Processing

The influence of processing parameters on the morphology of periodical structures on surface of steel 15Kh13MF after the nanosecond laser irradiation are discussed and analyzed. Modification of microstructure, surface morphology, and hardness by laser treatment is discussed

Fractographic Analysis of Surface and Failure Mechanisms of Nanotitanium after Laser Shock-Wave Treatment

In this work, the effect of the laser shock-wave treatment on the surface morphology and regularities in failure of nanotitanium is investigated. Based on the data of fractodiagnostics it is established that the shock-wave treatment changes the mechanism of failure from the brittle chipping to the mixed ductile-brittle one by the shear + separation scheme.

Structural levels of the nucleation and growth of fatigue crack in 17Mn1Si steel pipeline after long-term service

AbstractThe majority of modern gas pipelines in Ukraine, Lithuania and Russia have been operating for more than 30–40 years. The problem of forecasting residual life-time of materials comprising such gas pipelines calls for study of their degradation kinetics as well as requires to determine its relationship with the strain-force loading parameters. The aim of the paper is to study the kinetics of fracture in order to range mechanisms of cyclic deformation of 17Mn1Si steel at nucleation and growth of a fatigue crack. Flat specimens were cut out from a fragment of 17Mn1Si steel pipe after 40 years of service. Microstructures of specimens were examined. In the paper, an attempt was made to apply the combined approach to study of deformation and fracture based on the following research parameters from nonlinear fracture mechanics: physical mesomechanics and numerical fractography.