Myroslava Hredil - Academia.edu (original) (raw)
Papers by Myroslava Hredil
Materials science, Jun 18, 2024
Engineering failure analysis, May 1, 2024
Materials science, Nov 1, 2023
Fracture and Structural Integrity, Dec 22, 2021
A methodology of experimental research on hydrogen embrittlement of pipe carbon steels due to the... more A methodology of experimental research on hydrogen embrittlement of pipe carbon steels due to the transportation of hydrogen or its mixture with natural gas by a long-term operated gas distribution network is presented. The importance of comparative assessments of the steel in the as-received and operated states basing on the properties that characterize plasticity, resistance to brittle fracture and hydrogen assisted cracking is accentuated. Two main methodological peculiarities are pointed out, (i) testing specimens should be cut out in the transverse direction relative to the pipe axis; (ii) strength and plasticity characteristics should be determined using flat tensile specimens with the smallest possible thickness of the working part. The determination of hydrogen concentration in metal, metallographic and fractographic analyses have been supplemented the study. The effectiveness of the proposed methodology has been illustrated by the example of the steel research after its 52-year operation.
International Journal of Fatigue, Oct 1, 2019
Novel method of fatigue crack growth arrest in structural steels based on artificial creation of ... more Novel method of fatigue crack growth arrest in structural steels based on artificial creation of crack closure effect is proposed. Special liquid technological environment is used which, falling into a crack cavity and interacting with crack surface metal, forms solid products there, which prevents crack surfaces contact during a period of unloading. This leads to crack arrest in a wide range of stress intensity factor ΔK. Crack growth retardation effect enhances with an increase of the active component concentration in a solution. Some technological aspects for practical application of the proposed method are considered.
Zeszyty Naukowe. Mechanika / Politechnika Opolska, 2011
Materials Science, Mar 1, 2017
The susceptibility to hydrogen-assisted cracking of cold-drawn pearlitic steel wires used as rein... more The susceptibility to hydrogen-assisted cracking of cold-drawn pearlitic steel wires used as reinforcement in concrete is studied in alkaline media modeling pore liquids in concrete. The prestressing steel is established to become susceptible to hydrogen embrittlement under potentials of-1.1 V (SCE). The maximum fracture load, as well as the elongation to fracture, decrease as the cathodic potential increases; the effect is more noticeable for slow strain rates. The fracture mechanism in aggressive media differs from the fracture mechanism in air. The role of surface defects in the environment-assisted cracking is discussed.
Materials Science, Mar 1, 2015
Cold drawing process is widely used for strengthening of wires made from pearlitic steels for rei... more Cold drawing process is widely used for strengthening of wires made from pearlitic steels for reinforsed concrete structures. Then the steels undergo plastic deformation and the amount of defects rises. It could worsen their corrosion resistance. In this work the effect of cold drawing on the electrochemical behaviour of a pearlitic steel in alkali and neutral environments is investigated. Under passivation conditions in the environment with рН 12.5 the changes in the steel properties are not fixed. The decrease in polarization resistance values and therefore corrosion acceleration as a result of the steel treatment is observed only in the vicinity of corrosion potential in 3% NaCl solution.
Strength of Materials, Sep 1, 2009
ABSTRACT The degradation of the mechanical and corrosion properties of grade 17G1S steel in gas m... more ABSTRACT The degradation of the mechanical and corrosion properties of grade 17G1S steel in gas main pipelines after their 28–40-year operation is studied. A simultaneous decrease in their strength and hardness on the one hand, and impact toughness, fracture toughness and resistance to hydrogeninduced cracking, on the other, is observed. The influence of damages to the steel on the degradation of its properties is analyzed.
Materials Science, May 1, 2022
Procedia structural integrity, 2019
The calculation model is developed to evaluate the residual lifetime of a pipe with a crack consi... more The calculation model is developed to evaluate the residual lifetime of a pipe with a crack considering in-service degradation of the pipeline steel and the effect of soil corrosion. The model is based on the first law of thermodynamics. The problem of determination of the period of subcritical crack growth in a pipe is reduced to the differential equation subjected to definite initial and final conditions. Obtained equation together with the boundary conditions are used for prediction of the residual lifetime of the pipe made of the X52 pipe steel. The pipe contains external surface semi-elliptical crack. The task consists in the determination of the time of crack propagation through the pipe wall till its decompression. According to the experimental data, cracks in the studied steel under long-term loading and soil corrosion propagate mainly at constant rate, which is different for the as-received pipeline steel and the steel after 30 years in service. Based on these data, the equation for approximate determination of the crack growth rate for arbitrary service time of the pipe made of the X52 steel is proposed. To evaluate the crack propagation time, the energy approach is employed. For a crack that remains semi-elliptical during propagation, the problem is reduced to the differential equation system that determines the variations of the crack semi-axes. The system solution under definite initial and final conditions renders the expression for the pipe residual lifetime. The dependences of pipe residual lifetime on initial crack depth and pipe operation time are derived. The strong influence of the time of steel previous service on the pipe residual lifetime is manifested.
Procedia structural integrity, 2019
Long-term service of steel structures causes a deterioration of the initial mechanical properties... more Long-term service of steel structures causes a deterioration of the initial mechanical properties of metal and, therefore, decreases their workability. Sea portal cranes are operated in the regime of intensive cyclic loading that leads to exhaustion of steels plasticity. Therefore, these structures undergo essential degradation which reveals itself firstly in a decrease of brittle fracture resistance. Some units of 33 year operated crane are investigated from the point of a possible loss by rolled steel its initial mechanical and corrosion properties. A level of operational stresses in different units of the real crane measured by the strain gauge method varied somewhere by a factor of three. A strong dependence between the assessed level of in-service stresses and a drop of impact strength determined by Charpy testing is established. This indicates a crucial role of the factor of operational stresses in a decrease in brittle fracture resistance of the operated metal. Comparison of the test results for the specimens cut in mutually perpendicular directions confirmed the known regularity: impact strength of the transverse specimens relative to the rolling direction is lower than the longitudinal ones. This difference is revealed to become more pronounced with the build-up of metal degradation and, respectively, with an increase of operational stresses. It is shown that the level of in-service degradation of the metal along rolling direction rises with a reduction of the rolling plate thickness. It is explained by the aggressive action of marine atmosphere which caused not only corrosion of marine structures but also serves as a factor of steel hydrogenation and a development of microdamaging in metal that facilitates delamination in fibrous structure steel. Polarization resistance is defined for the tested units as the electrochemical parameter most sensitive to materials in-service degradation. A clear correlation between the mechanical and electrochemical metal characteristics is shown: the metal with a lower brittle fracture resistance has a lower polarization resistance. This relationship is suggested to use for non-destructive examination of metal state of portal cranes in a course of their long term service.
Procedia structural integrity, 2020
Materials Science, Sep 1, 2007
We study the degradation of the mechanical and corrosion properties of 17G1S steel in gas mains a... more We study the degradation of the mechanical and corrosion properties of 17G1S steel in gas mains as a result of operation for 28-40 yr. We reveal the simultaneous decrease in its strength and hardness, on the one hand, and impact toughness and crack resistance, on the other hand. The indicated parameters prove to be most sensitive to the in-service degradation of the metal. The degradation of steel leads to the increase in the strain-hardening coefficient and the appearance of the yield plateau in the tensile stress-strain diagram and causes the appearance of sensitivity to hydrogen embrittlement increasing in the process of operation. We analyze the role of absorbed hydrogen affecting the mechanism of strain aging and responsible for the appearance of defects. It is shown that the polarization resistance can be used not only for monitoring of the corrosion state of gas pipelines but also for the prediction of changes in their mechanical properties in the process of operation.
Materials Science, Nov 1, 2013
ABSTRACT We describe the method and laboratory facilities for the investigation of reinforced-con... more ABSTRACT We describe the method and laboratory facilities for the investigation of reinforced-concrete specimens whose integrity is violated by the rapid corrosion of reinforcement. A cylindrical concrete specimen with central steel rod and an anodic potential applied to this rod is held in a corrosive environment. The corrosion rate of the rod is increased due to its polarization and the corrosion products wedge the concrete specimen from inside. As a result, after a certain period of time the specimen suffers cracking. The proposed method includes recording corrosion currents during the experiment, which enables us to estimate the intensity of corrosion.
Materials Science, 2016
The changes in the plasticity characteristics of prestressing steel wires in air and in hydrogena... more The changes in the plasticity characteristics of prestressing steel wires in air and in hydrogenating environments caused by the process of cold drawing are investigated on the basis of slow strain-rate tests on smooth specimens. The tested pearlitic steel is highly susceptible to hydrogen embrittlement in all stages of cold drawing. The inconsistency is revealed between the changes of two plasticity characteristics: reduction in area and uniform elongation. The obtained results are analyzed by distinguishing the contributions of resistance to crack initiation and crack propagation. The susceptibility to crack initiation increases as a result of cold drawing with simultaneous improvement of the crack propagation resistance.
Materials Science, Mar 1, 2013
The positive influence of microadmixtures of rare-earth metals on the strength, plasticity, impac... more The positive influence of microadmixtures of rare-earth metals on the strength, plasticity, impact toughness, and cyclic crack-growth resistance of 17G1S pipe steel is discovered. The decomposition of the impact toughness into the work of crack initiation ai{a_i}ai and the work of crack propagation ap{a_p}ap made it possible to discover the following specific features in the temperature dependences of ap{a_p}ap: at elevated testing temperatures guaranteeing the ductile fracture of steel, the positive effect of alloying by REM is preserved. At the same time, at lowered temperatures of brittle fracture, this effect becomes negative and the work ap{a_p}ap decreases. Distilled water somewhat decreases the cyclic crack-growth resistance of steel and the positive effect caused by the REM admixtures manifests itself only in the increase in the cyclic fracture toughness of steel.
Materials Science, Mar 1, 2011
Mechanical and electrochemical properties of individual zones of a welded joint of 17H1S pipe ste... more Mechanical and electrochemical properties of individual zones of a welded joint of 17H1S pipe steel are investigated. It is established that long operation causes decreases in the plasticity and impact toughness, especially of the metal of the heat-affected zone. For the operated metal, we observe a general regularity of the shift of the potential for all zones of the welded joint in the direction of negative values, which is the weakest for the base metal. With increase in the operation time of main pipelines, corrosion may be localized on the weld metal.
Materials science, Jun 18, 2024
Engineering failure analysis, May 1, 2024
Materials science, Nov 1, 2023
Fracture and Structural Integrity, Dec 22, 2021
A methodology of experimental research on hydrogen embrittlement of pipe carbon steels due to the... more A methodology of experimental research on hydrogen embrittlement of pipe carbon steels due to the transportation of hydrogen or its mixture with natural gas by a long-term operated gas distribution network is presented. The importance of comparative assessments of the steel in the as-received and operated states basing on the properties that characterize plasticity, resistance to brittle fracture and hydrogen assisted cracking is accentuated. Two main methodological peculiarities are pointed out, (i) testing specimens should be cut out in the transverse direction relative to the pipe axis; (ii) strength and plasticity characteristics should be determined using flat tensile specimens with the smallest possible thickness of the working part. The determination of hydrogen concentration in metal, metallographic and fractographic analyses have been supplemented the study. The effectiveness of the proposed methodology has been illustrated by the example of the steel research after its 52-year operation.
International Journal of Fatigue, Oct 1, 2019
Novel method of fatigue crack growth arrest in structural steels based on artificial creation of ... more Novel method of fatigue crack growth arrest in structural steels based on artificial creation of crack closure effect is proposed. Special liquid technological environment is used which, falling into a crack cavity and interacting with crack surface metal, forms solid products there, which prevents crack surfaces contact during a period of unloading. This leads to crack arrest in a wide range of stress intensity factor ΔK. Crack growth retardation effect enhances with an increase of the active component concentration in a solution. Some technological aspects for practical application of the proposed method are considered.
Zeszyty Naukowe. Mechanika / Politechnika Opolska, 2011
Materials Science, Mar 1, 2017
The susceptibility to hydrogen-assisted cracking of cold-drawn pearlitic steel wires used as rein... more The susceptibility to hydrogen-assisted cracking of cold-drawn pearlitic steel wires used as reinforcement in concrete is studied in alkaline media modeling pore liquids in concrete. The prestressing steel is established to become susceptible to hydrogen embrittlement under potentials of-1.1 V (SCE). The maximum fracture load, as well as the elongation to fracture, decrease as the cathodic potential increases; the effect is more noticeable for slow strain rates. The fracture mechanism in aggressive media differs from the fracture mechanism in air. The role of surface defects in the environment-assisted cracking is discussed.
Materials Science, Mar 1, 2015
Cold drawing process is widely used for strengthening of wires made from pearlitic steels for rei... more Cold drawing process is widely used for strengthening of wires made from pearlitic steels for reinforsed concrete structures. Then the steels undergo plastic deformation and the amount of defects rises. It could worsen their corrosion resistance. In this work the effect of cold drawing on the electrochemical behaviour of a pearlitic steel in alkali and neutral environments is investigated. Under passivation conditions in the environment with рН 12.5 the changes in the steel properties are not fixed. The decrease in polarization resistance values and therefore corrosion acceleration as a result of the steel treatment is observed only in the vicinity of corrosion potential in 3% NaCl solution.
Strength of Materials, Sep 1, 2009
ABSTRACT The degradation of the mechanical and corrosion properties of grade 17G1S steel in gas m... more ABSTRACT The degradation of the mechanical and corrosion properties of grade 17G1S steel in gas main pipelines after their 28–40-year operation is studied. A simultaneous decrease in their strength and hardness on the one hand, and impact toughness, fracture toughness and resistance to hydrogeninduced cracking, on the other, is observed. The influence of damages to the steel on the degradation of its properties is analyzed.
Materials Science, May 1, 2022
Procedia structural integrity, 2019
The calculation model is developed to evaluate the residual lifetime of a pipe with a crack consi... more The calculation model is developed to evaluate the residual lifetime of a pipe with a crack considering in-service degradation of the pipeline steel and the effect of soil corrosion. The model is based on the first law of thermodynamics. The problem of determination of the period of subcritical crack growth in a pipe is reduced to the differential equation subjected to definite initial and final conditions. Obtained equation together with the boundary conditions are used for prediction of the residual lifetime of the pipe made of the X52 pipe steel. The pipe contains external surface semi-elliptical crack. The task consists in the determination of the time of crack propagation through the pipe wall till its decompression. According to the experimental data, cracks in the studied steel under long-term loading and soil corrosion propagate mainly at constant rate, which is different for the as-received pipeline steel and the steel after 30 years in service. Based on these data, the equation for approximate determination of the crack growth rate for arbitrary service time of the pipe made of the X52 steel is proposed. To evaluate the crack propagation time, the energy approach is employed. For a crack that remains semi-elliptical during propagation, the problem is reduced to the differential equation system that determines the variations of the crack semi-axes. The system solution under definite initial and final conditions renders the expression for the pipe residual lifetime. The dependences of pipe residual lifetime on initial crack depth and pipe operation time are derived. The strong influence of the time of steel previous service on the pipe residual lifetime is manifested.
Procedia structural integrity, 2019
Long-term service of steel structures causes a deterioration of the initial mechanical properties... more Long-term service of steel structures causes a deterioration of the initial mechanical properties of metal and, therefore, decreases their workability. Sea portal cranes are operated in the regime of intensive cyclic loading that leads to exhaustion of steels plasticity. Therefore, these structures undergo essential degradation which reveals itself firstly in a decrease of brittle fracture resistance. Some units of 33 year operated crane are investigated from the point of a possible loss by rolled steel its initial mechanical and corrosion properties. A level of operational stresses in different units of the real crane measured by the strain gauge method varied somewhere by a factor of three. A strong dependence between the assessed level of in-service stresses and a drop of impact strength determined by Charpy testing is established. This indicates a crucial role of the factor of operational stresses in a decrease in brittle fracture resistance of the operated metal. Comparison of the test results for the specimens cut in mutually perpendicular directions confirmed the known regularity: impact strength of the transverse specimens relative to the rolling direction is lower than the longitudinal ones. This difference is revealed to become more pronounced with the build-up of metal degradation and, respectively, with an increase of operational stresses. It is shown that the level of in-service degradation of the metal along rolling direction rises with a reduction of the rolling plate thickness. It is explained by the aggressive action of marine atmosphere which caused not only corrosion of marine structures but also serves as a factor of steel hydrogenation and a development of microdamaging in metal that facilitates delamination in fibrous structure steel. Polarization resistance is defined for the tested units as the electrochemical parameter most sensitive to materials in-service degradation. A clear correlation between the mechanical and electrochemical metal characteristics is shown: the metal with a lower brittle fracture resistance has a lower polarization resistance. This relationship is suggested to use for non-destructive examination of metal state of portal cranes in a course of their long term service.
Procedia structural integrity, 2020
Materials Science, Sep 1, 2007
We study the degradation of the mechanical and corrosion properties of 17G1S steel in gas mains a... more We study the degradation of the mechanical and corrosion properties of 17G1S steel in gas mains as a result of operation for 28-40 yr. We reveal the simultaneous decrease in its strength and hardness, on the one hand, and impact toughness and crack resistance, on the other hand. The indicated parameters prove to be most sensitive to the in-service degradation of the metal. The degradation of steel leads to the increase in the strain-hardening coefficient and the appearance of the yield plateau in the tensile stress-strain diagram and causes the appearance of sensitivity to hydrogen embrittlement increasing in the process of operation. We analyze the role of absorbed hydrogen affecting the mechanism of strain aging and responsible for the appearance of defects. It is shown that the polarization resistance can be used not only for monitoring of the corrosion state of gas pipelines but also for the prediction of changes in their mechanical properties in the process of operation.
Materials Science, Nov 1, 2013
ABSTRACT We describe the method and laboratory facilities for the investigation of reinforced-con... more ABSTRACT We describe the method and laboratory facilities for the investigation of reinforced-concrete specimens whose integrity is violated by the rapid corrosion of reinforcement. A cylindrical concrete specimen with central steel rod and an anodic potential applied to this rod is held in a corrosive environment. The corrosion rate of the rod is increased due to its polarization and the corrosion products wedge the concrete specimen from inside. As a result, after a certain period of time the specimen suffers cracking. The proposed method includes recording corrosion currents during the experiment, which enables us to estimate the intensity of corrosion.
Materials Science, 2016
The changes in the plasticity characteristics of prestressing steel wires in air and in hydrogena... more The changes in the plasticity characteristics of prestressing steel wires in air and in hydrogenating environments caused by the process of cold drawing are investigated on the basis of slow strain-rate tests on smooth specimens. The tested pearlitic steel is highly susceptible to hydrogen embrittlement in all stages of cold drawing. The inconsistency is revealed between the changes of two plasticity characteristics: reduction in area and uniform elongation. The obtained results are analyzed by distinguishing the contributions of resistance to crack initiation and crack propagation. The susceptibility to crack initiation increases as a result of cold drawing with simultaneous improvement of the crack propagation resistance.
Materials Science, Mar 1, 2013
The positive influence of microadmixtures of rare-earth metals on the strength, plasticity, impac... more The positive influence of microadmixtures of rare-earth metals on the strength, plasticity, impact toughness, and cyclic crack-growth resistance of 17G1S pipe steel is discovered. The decomposition of the impact toughness into the work of crack initiation ai{a_i}ai and the work of crack propagation ap{a_p}ap made it possible to discover the following specific features in the temperature dependences of ap{a_p}ap: at elevated testing temperatures guaranteeing the ductile fracture of steel, the positive effect of alloying by REM is preserved. At the same time, at lowered temperatures of brittle fracture, this effect becomes negative and the work ap{a_p}ap decreases. Distilled water somewhat decreases the cyclic crack-growth resistance of steel and the positive effect caused by the REM admixtures manifests itself only in the increase in the cyclic fracture toughness of steel.
Materials Science, Mar 1, 2011
Mechanical and electrochemical properties of individual zones of a welded joint of 17H1S pipe ste... more Mechanical and electrochemical properties of individual zones of a welded joint of 17H1S pipe steel are investigated. It is established that long operation causes decreases in the plasticity and impact toughness, especially of the metal of the heat-affected zone. For the operated metal, we observe a general regularity of the shift of the potential for all zones of the welded joint in the direction of negative values, which is the weakest for the base metal. With increase in the operation time of main pipelines, corrosion may be localized on the weld metal.