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Martin Bohning - One of the best experts on this subject based on the ideXlab platform.

  • crack propagation in pe hd induced by environmental Stress Cracking esc analyzed by several imaging techniques
    Polymer Testing, 2018
    Co-Authors: Markus Schilling, Ingo Alig, Harald Oehler, Dirk Lellinger, Dietmar Meinel, Ute Niebergall, Martin Bohning
    Abstract:

    Abstract Different imaging techniques were employed to monitor Full Notch Creep Test (FNCT) experiments addressing environmental Stress Cracking in more detail. The FNCT is a well-established test method to assess slow crack growth and environmental Stress Cracking of polymer materials, especially polyethylene. The standard test procedure, as specified in ISO 16770, provides a simple comparative measure of the resistance to crack growth of a certain material based on the overall time to failure when loaded with a well-defined mechanical Stress and immersed in a liquid medium promoting crack propagation. Destructive techniques which require a direct view on the free fracture surface, such as light microscopy and laser scanning microscopy, are compared to non-destructive techniques, i.e. scanning acoustic microscopy and x-ray micro computed tomography. All methods allow the determination of an effective crack length. Based on a series of FNCT specimens progressively damaged for varied durations under standard test conditions, the estimation of crack propagation rates is also enabled. Despite systematic deviations related to the respective imaging techniques, this nevertheless provides a valuable tool for the detailed evaluation of the FNCT and its further development.

  • full notch creep test fnct of pe hd characterization and differentiation of brittle and ductile fracture behavior during environmental Stress Cracking esc
    Polymer Testing, 2017
    Co-Authors: Markus Schilling, Ute Niebergall, Martin Bohning
    Abstract:

    Abstract The damage mechanisms slow crack growth (SCG) and environmental Stress Cracking (ESC), relevant for PE-HD materials are characterized based on improved full notch creep testing (FNCT) of two selected typical PE-HD materials for container applications. In this context, a distinction of the failure mechanisms as well as a categorization of involved media is suggested. Employing a novel FNCT device, elongation data were obtained in addition to conventional time-to-failure results of Stress-dependent as well as temperature-dependent measurements. Changes in failure behavior, as determined by fracture surface analysis based on light microscopy (LM) and laser scanning microscopy (LSM), are correlated with FNCT results and used to introduce an additional possibility for the identification of brittle/ductile fracture behavior.

  • environmental Stress Cracking of polyethylene high density pe hd induced by liquid media validation and verification of the full notch creep test fnct
    Materialwissenschaft Und Werkstofftechnik, 2017
    Co-Authors: Markus Schilling, Ingo Alig, Harald Oehler, Martin Bohning, Ute Niebergall
    Abstract:

    The full-notch creep test (FNCT) is widely used to characterize the slow crack growth (SCG) behavior of polyolefin materials in “inert” media as well as effects of environmental Stress Cracking (ESC) in which the medium has decisive influence on damage mechanism and time to failure. The test is of greatest importance for pipe and blow molding types of polyethylene, high density (PE-HD). Usually the full-notch creep test is applied as a standardized testing method (ISO 16770) using a few universal liquid media, such as solutions of Arkopal N 100. In our study, selected relevant polyethylene, high density materials are investigated also in real media – practical formulations as well as representative pure chemicals – and influences of temperature and geometry of specimen and notch are explicitly addressed. Furthermore, the investigations comprise also the environmental Stress Cracking behavior of polyethylene, high density in media that are sorbed to a significant extent – examples are diesel and biodiesel – based on comparison with samples previously saturated with those media. Thus, also the underlying diffusion controlled sorption process has to be assessed before. The investigations were performed using a full-notch creep testing device with 12 individual sub-stations, each equipped with individual electronic Stress and temperature control and continuous online monitoring of the specimen elongation.

Markus Schilling - One of the best experts on this subject based on the ideXlab platform.

  • crack propagation in pe hd induced by environmental Stress Cracking esc analyzed by several imaging techniques
    Polymer Testing, 2018
    Co-Authors: Markus Schilling, Ingo Alig, Harald Oehler, Dirk Lellinger, Dietmar Meinel, Ute Niebergall, Martin Bohning
    Abstract:

    Abstract Different imaging techniques were employed to monitor Full Notch Creep Test (FNCT) experiments addressing environmental Stress Cracking in more detail. The FNCT is a well-established test method to assess slow crack growth and environmental Stress Cracking of polymer materials, especially polyethylene. The standard test procedure, as specified in ISO 16770, provides a simple comparative measure of the resistance to crack growth of a certain material based on the overall time to failure when loaded with a well-defined mechanical Stress and immersed in a liquid medium promoting crack propagation. Destructive techniques which require a direct view on the free fracture surface, such as light microscopy and laser scanning microscopy, are compared to non-destructive techniques, i.e. scanning acoustic microscopy and x-ray micro computed tomography. All methods allow the determination of an effective crack length. Based on a series of FNCT specimens progressively damaged for varied durations under standard test conditions, the estimation of crack propagation rates is also enabled. Despite systematic deviations related to the respective imaging techniques, this nevertheless provides a valuable tool for the detailed evaluation of the FNCT and its further development.

  • full notch creep test fnct of pe hd characterization and differentiation of brittle and ductile fracture behavior during environmental Stress Cracking esc
    Polymer Testing, 2017
    Co-Authors: Markus Schilling, Ute Niebergall, Martin Bohning
    Abstract:

    Abstract The damage mechanisms slow crack growth (SCG) and environmental Stress Cracking (ESC), relevant for PE-HD materials are characterized based on improved full notch creep testing (FNCT) of two selected typical PE-HD materials for container applications. In this context, a distinction of the failure mechanisms as well as a categorization of involved media is suggested. Employing a novel FNCT device, elongation data were obtained in addition to conventional time-to-failure results of Stress-dependent as well as temperature-dependent measurements. Changes in failure behavior, as determined by fracture surface analysis based on light microscopy (LM) and laser scanning microscopy (LSM), are correlated with FNCT results and used to introduce an additional possibility for the identification of brittle/ductile fracture behavior.

  • environmental Stress Cracking of polyethylene high density pe hd induced by liquid media validation and verification of the full notch creep test fnct
    Materialwissenschaft Und Werkstofftechnik, 2017
    Co-Authors: Markus Schilling, Ingo Alig, Harald Oehler, Martin Bohning, Ute Niebergall
    Abstract:

    The full-notch creep test (FNCT) is widely used to characterize the slow crack growth (SCG) behavior of polyolefin materials in “inert” media as well as effects of environmental Stress Cracking (ESC) in which the medium has decisive influence on damage mechanism and time to failure. The test is of greatest importance for pipe and blow molding types of polyethylene, high density (PE-HD). Usually the full-notch creep test is applied as a standardized testing method (ISO 16770) using a few universal liquid media, such as solutions of Arkopal N 100. In our study, selected relevant polyethylene, high density materials are investigated also in real media – practical formulations as well as representative pure chemicals – and influences of temperature and geometry of specimen and notch are explicitly addressed. Furthermore, the investigations comprise also the environmental Stress Cracking behavior of polyethylene, high density in media that are sorbed to a significant extent – examples are diesel and biodiesel – based on comparison with samples previously saturated with those media. Thus, also the underlying diffusion controlled sorption process has to be assessed before. The investigations were performed using a full-notch creep testing device with 12 individual sub-stations, each equipped with individual electronic Stress and temperature control and continuous online monitoring of the specimen elongation.

Ute Niebergall - One of the best experts on this subject based on the ideXlab platform.

  • crack propagation in pe hd induced by environmental Stress Cracking esc analyzed by several imaging techniques
    Polymer Testing, 2018
    Co-Authors: Markus Schilling, Ingo Alig, Harald Oehler, Dirk Lellinger, Dietmar Meinel, Ute Niebergall, Martin Bohning
    Abstract:

    Abstract Different imaging techniques were employed to monitor Full Notch Creep Test (FNCT) experiments addressing environmental Stress Cracking in more detail. The FNCT is a well-established test method to assess slow crack growth and environmental Stress Cracking of polymer materials, especially polyethylene. The standard test procedure, as specified in ISO 16770, provides a simple comparative measure of the resistance to crack growth of a certain material based on the overall time to failure when loaded with a well-defined mechanical Stress and immersed in a liquid medium promoting crack propagation. Destructive techniques which require a direct view on the free fracture surface, such as light microscopy and laser scanning microscopy, are compared to non-destructive techniques, i.e. scanning acoustic microscopy and x-ray micro computed tomography. All methods allow the determination of an effective crack length. Based on a series of FNCT specimens progressively damaged for varied durations under standard test conditions, the estimation of crack propagation rates is also enabled. Despite systematic deviations related to the respective imaging techniques, this nevertheless provides a valuable tool for the detailed evaluation of the FNCT and its further development.

  • full notch creep test fnct of pe hd characterization and differentiation of brittle and ductile fracture behavior during environmental Stress Cracking esc
    Polymer Testing, 2017
    Co-Authors: Markus Schilling, Ute Niebergall, Martin Bohning
    Abstract:

    Abstract The damage mechanisms slow crack growth (SCG) and environmental Stress Cracking (ESC), relevant for PE-HD materials are characterized based on improved full notch creep testing (FNCT) of two selected typical PE-HD materials for container applications. In this context, a distinction of the failure mechanisms as well as a categorization of involved media is suggested. Employing a novel FNCT device, elongation data were obtained in addition to conventional time-to-failure results of Stress-dependent as well as temperature-dependent measurements. Changes in failure behavior, as determined by fracture surface analysis based on light microscopy (LM) and laser scanning microscopy (LSM), are correlated with FNCT results and used to introduce an additional possibility for the identification of brittle/ductile fracture behavior.

  • environmental Stress Cracking of polyethylene high density pe hd induced by liquid media validation and verification of the full notch creep test fnct
    Materialwissenschaft Und Werkstofftechnik, 2017
    Co-Authors: Markus Schilling, Ingo Alig, Harald Oehler, Martin Bohning, Ute Niebergall
    Abstract:

    The full-notch creep test (FNCT) is widely used to characterize the slow crack growth (SCG) behavior of polyolefin materials in “inert” media as well as effects of environmental Stress Cracking (ESC) in which the medium has decisive influence on damage mechanism and time to failure. The test is of greatest importance for pipe and blow molding types of polyethylene, high density (PE-HD). Usually the full-notch creep test is applied as a standardized testing method (ISO 16770) using a few universal liquid media, such as solutions of Arkopal N 100. In our study, selected relevant polyethylene, high density materials are investigated also in real media – practical formulations as well as representative pure chemicals – and influences of temperature and geometry of specimen and notch are explicitly addressed. Furthermore, the investigations comprise also the environmental Stress Cracking behavior of polyethylene, high density in media that are sorbed to a significant extent – examples are diesel and biodiesel – based on comparison with samples previously saturated with those media. Thus, also the underlying diffusion controlled sorption process has to be assessed before. The investigations were performed using a full-notch creep testing device with 12 individual sub-stations, each equipped with individual electronic Stress and temperature control and continuous online monitoring of the specimen elongation.

P Morrissey - One of the best experts on this subject based on the ideXlab platform.

  • environmental Stress Cracking of poly vinylidene fluoride and welds in alkaline solutions
    Polymer Degradation and Stability, 2000
    Co-Authors: P Hinksman, David H Isaac, P Morrissey
    Abstract:

    Abstract A study has been carried out to investigate the resistance of poly(vinylidene fluoride) (PVDF) to high pH aqueous sodium hydroxide solutions. In addition to surveying the conditions that caused environmental Stress Cracking (ESC) in test samples machined from injection moulded plaques, interest centred on regions of formed components that might contain high residual Stresses, in particular vibration-welded samples. The first series of experiments involved subjecting standard test samples to fixed strains in three-point bend testing rigs and immersing them in highly alkaline environments. As expected, higher strains caused more problems for the material, with a cut off limit at about 5% strain, below which no measurable effects were observed in any environment within the timescale (63 days) of the experiments. Even above 5% strain, PVDF was found to be resistant to NaOH solutions of pH 12.5 and 13 although significant effects were seen as the pH was increased to 13.5, 14 and 14.39. Under these high strain, high pH conditions, the damage was manifest as discolouration of the samples due to dehydrofluorination. It was found that the time between immersion in the solution and the observation of initial discolouration was the most useful parameter for characterising the relative severity of environments. Tests on welded samples indicated that the flash from the welding process contained high residual strains (certainly >5%), but tensile residual Stresses in the bulk material at the weld line were relatively small. Weld strength was about 90% of that measured for the bulk material but failure at welds was relatively brittle.

  • environmental Stress Cracking of poly vinyl chloride in alkaline solutions
    Polymer Degradation and Stability, 2000
    Co-Authors: S Bishop, David H Isaac, P Hinksman, P Morrissey
    Abstract:

    Abstract The environmental Stress Cracking (ESC) effects on PVC of various high pH sodium hydroxide environments have been studied. The behaviour of PVC specimens in air and pH 12, 13, 13.5 and 14.39 sodium hydroxide solutions has been examined under three-point bend, tensile and creep conditions. Two parameters were used in three-point bend testing to determine the effect of an applied strain and high pH environment on the stability of PVC, namely time to craze initiation and width of crazing. It was found that, in general, crazing occurred sooner and to a greater degree with increasing strain and pH, although there was some evidence that craze growth was most rapid at pH 13.5. The results also indicated a critical strain value of ∼1.5–1.6%, below which crazing was not observed in any of these alkaline environments. Creep and tensile testing revealed that the time for which a PVC specimen was immersed in the environment was very important in determining the severity of the environmental effect. Creep tests at elevated temperatures showed that the time for the effects to be manifest decreased with increasing temperature. Creep rates were highest in pH 13.5 sodium hydroxide solution indicating that this was the most hostile of the environments considered.

Iannuzzi Mariano - One of the best experts on this subject based on the ideXlab platform.

  • Hydrogen-induced Stress Cracking of swaged super duplex stainless steel subsea components
    'NACE International', 2019
    Co-Authors: Hazarabedian M.s., Viereckl Andy, Quadir Z., Leadbeater G., Golovanevskiy Vladimir, Erdal S., Georgeson P., Iannuzzi Mariano
    Abstract:

    A recent subsea failure of two subsea connectors made of UNS S32760, a 25 wt% Cr super duplex stainless steel, led to an extensive root cause failure analysis. The components showed a single longitudinal crack along a swaged section, which arrested toward its thicker end. The brittle nature of the fracture surface, calcareous deposits on the component, and exposure to cathodic protection suggested hydrogen-induced Stress Cracking—a form of environmentally assisted Cracking—as a plausible failure mechanism. Thus, the three causative factors promoting hydrogen-induced Stress Cracking, namely, a susceptible microstructure, a hydrogen bearing environment, as well as sufficiently high applied and residual Stresses in the material were the focus of this investigation. This work details the material characterization work and presents a possible failure mechanism. The results showed that the failure developed from a combination of factors, typical for hydrogen-induced Stress Cracking. The measured hydrogen content in parts of the material exceeded 40 ppm, more than an order of magnitude higher than what is normally expected in super duplex stainless steels. Additionally, a highly anisotropic, coarse microstructure was observed, which in combination with the introduced cold-work from the swaging process and potential Stress raisers from design and machining could have facilitated crack initiation, ultimately leading to the failure of the component. This hypothesis was reinforced by the presence of secondary cracks along the main, brittle fracture surface. Furthermore, mechanical testing results showed a detrimental effect on the material’s properties due to the presence of residual hydrogen and the swaging operation

  • Hydrogen induced Stress Cracking of super duplex stainless steel UNS S32760 - A root cause failure investigation
    2019
    Co-Authors: Hazarabedian M.s., Iannuzzi Mariano, Viereckl Andy, Quadir Z., Leadbeater G., Golovanevskiy Vladimir, Georgeson P., Erdal S.
    Abstract:

    © 2019 by NACE International. A recent subsea failure of two coupling assembly flanges made of UNS S32760, a 25 wt% Cr super duplex stainless steel, lead to an extensive root cause failure analysis. The components showed a single longitudinal crack along the swaged ferrule, which arrested towards its thicker section. The brittle nature of the fracture surface, calcareous deposits on the ferrule and exposure to cathodic protection suggested hydrogen induced Stress Cracking-a form of environmentally assisted Cracking-as a plausible failure mechanism. Thus, the three causative factors promoting hydrogen induced Stress Cracking, namely, the microstructure, the environment and applied and residual Stresses in the material were the focus of this investigation. This paper discusses the material characterization work, which includes optical and scanning electron microscopy, X-ray spectroscopy, electron backscatter diffraction analysis, tensile testing, microhardness mapping, and corrosion examinations. The results have shown that the failure resulted from a combination of factors, typical for hydrogen induced Stress Cracking. The measured hydrogen content in parts of the material exceeded 40 ppm, more than an order of magnitude higher than what is normally expected in super duplex stainless steels. Additionally, a highly anisotropic, coarse microstructure was observed, which in combination with the introduced cold work from the swaging process and potential Stress raisers from the ferrule design and machining could have facilitated crack initiation, ultimately leading to the failure of the component. This hypothesis was reinforced by the presence of secondary cracks along the main, brittle fracture surface. Further, mechanical testing results showed a detrimental effect on the material's properties due to the presence of residual hydrogen and the swaging operation

  • Effect of nickel on the hydrogen Stress Cracking resistance of ferritic/pearlitic low alloy steels
    'NACE International', 2018
    Co-Authors: Husby H., Wagstaff P., Iannuzzi Mariano, Johnsen Roy, Kappes M.
    Abstract:

    Nickel additions to low alloy steels improve mechanical and technological properties. However, Part 2 of ISO Standard 15156 limits the nickel content to a maximum of 1 wt% in oil and gas environments containing H2S because of controversial concerns regarding sulfide Stress Cracking. The objective of this work was to investigate the effect of nickel in solid solution in the ferrite phase on hydrogen Stress Cracking resistance. Ferritic/pearlitic research-grade low alloy steels with nominal nickel contents of 0, 1, 2, and 3 wt% were tested by the slow strain rate test method with cathodic hydrogen charging to -1.05 VAg/AgCl and -2 VAg/AgCl. No difference in fracture mode or morphology was found between the alloys. However, the plastic elongation ratios and reduction in area ratios decreased with increasing nickel content when tested at -2 VAg/AgCl. The direct and indirect effects of nickel, such as the influence of an increasing fraction of pearlite with increasing nickel content, are discussed

  • Effect of nickel on the hydrogen Stress Cracking resistance of ferritic/pearlitic low alloy steels
    'NACE International', 2018
    Co-Authors: Husby Hans, Iannuzzi Mariano, Johnsen Roy, Wagstaff Philip, Kappes, Mariano Alberto
    Abstract:

    Nickel additions to low alloy steels improve mechanical and technological properties. However, Part 2 of ISO Standard 15156 limits the nickel content to a maximum of 1 wt% in oil and gas environments containing H2S because of controversial concerns regarding sulfide Stress Cracking. The objective of this work was to investigate the effect of nickel in solid solution in the ferrite phase on hydrogen Stress Cracking resistance. Ferritic/pearlitic research-grade low alloy steels with nominal nickel contents of 0, 1, 2, and 3 wt% were tested by the slow strain rate test method with cathodic hydrogen charging to -1.05 VAg/AgCl and -2 VAg/AgCl. No difference in fracture mode or morphology was found between the alloys. However, the plastic elongation ratios and reduction in area ratios decreased with increasing nickel content when tested at -2 VAg/AgCl. The direct and indirect effects of nickel, such as the influence of an increasing fraction of pearlite with increasing nickel content, are discussed.Fil: Husby, Hans. Norwegian University Of Science And Technology; NoruegaFil: Wagstaff, Philip. Norwegian University Of Science And Technology; NoruegaFil: Iannuzzi, Mariano. Norwegian University Of Science And Technology; Noruega. Curtin University; AustraliaFil: Johnsen, Roy. Norwegian University Of Science And Technology; NoruegaFil: Kappes, Mariano Alberto. Universidad Nacional de San Martín. Instituto Sabato; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

  • Sulfide Stress Cracking of nickel-containing low-alloy steels
    'Walter de Gruyter GmbH', 2014
    Co-Authors: Iannuzzi Mariano, Kappes M., Rebak R., Carranza R.
    Abstract:

    Low-alloy steels (LAS) are extensively used in oil and gas (O&G) production due to their good mechani- cal properties and low cost. Even though nickel improves mechanical properties and hardenability with low penalty on weldability, which is critical for large subsea compo- nents, nickel content cannot exceed 1-wt% when used in sour service applications. The ISO 15156-2 standard limits the nickel content in LAS on the assumption that nickel concentrations above 1-wt% negatively impact sulfide Stress Cracking (SSC) resistance. This restriction excludes a significant number of high-strength and high-toughness alloys, such as Ni-Cr-Mo (e.g., UNS G43200 and G43400), Ni-Mo (e.g., UNS G46200), and Ni-Cr-Mo-V grades, from sour service applications and can be used only if suc- cessfully qualified. However, the standard is based on controversial research conducted more than 40 years ago. Since then, researchers have suggested that it is the micro- structure that determines SSC resistance, regardless of Ni content. This review summarizes the advantages and dis- advantages of nickel-containing LAS in terms of strength, weldability, hardenability, potential weight savings, and cost reduction. Likewise, the state of knowledge on the effect of nickel on hydrogen absorption as well as SSC ini- tiation and propagation kinetics is critically reviewed