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- Duret-Thual, Claude, et al.
(författare)
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Assessment of the hydrogen induced stress cracking resistance of precipitation hardened nickel-based alloys using the slow strain rate tensile test method - Review of a three years test program
- 2019
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Ingår i: NACE - International Corrosion Conference SeriesVolume 2019-March, 2019, Article number 13284Corrosion Conference and Expo 2019; Nashville; United States; 24 March 2019 through 28 March 2019. - : National Assoc. of Corrosion Engineers International.
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Konferensbidrag (refereegranskat)abstract
- Precipitation Hardened (PH) Ni-based alloys have proved to be sensitive to Hydrogen Induced Stress Cracking (HISC), and HISC related failures in the Oil and Gas industry have been experienced in the case of UNS N07718, UNS N07725 and UNS N07716. Slow Strain Rate Tensile (SSRT) tests conducted under cathodic polarization gave encouraging results as a means to evaluate HISC resistance when applied to UNS N07718, enabling the discrimination of acceptable and unacceptable microstructures as according to API 6A CRA. As a consequence, an extensive test program was launched on several PH Ni grades, a program sponsored by several petroleum companies. The main objectives of this program were to develop a test method to allow for the evaluation of HISC resistance, in order to rank materials and possibly define acceptance criteria for each material, and also to better understand the relationship between microstructure and HISC resistance. Twenty-eight industrial heats of PH Ni Alloys of eight material grades were fully characterized (microstructure, mechanical properties) and evaluated using the SSRT test method under applied cathodic polarization. The yield strength of the materials tested was in the range 120 to 160 ksi. The quantitative susceptibility of the materials to HISC was established using the plastic elongation pCP and the plastic elongation ratio pCP/ pinert. Test results showed that some PH alloys that exhibited acceptable microstructures, in accordance with API 6ACRA, did not necessarily exhibit high plastic elongation ratios. The need to implement HISC related tests in the selection of PH Ni base alloys for Oil and Gas applications is indicated
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- Mitrovic, Darko, et al.
(författare)
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Reconstructing the transport cycle in the sugar porter superfamily using coevolution-powered machine learning
- 2023
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Ingår i: eLIFE. - : eLife Sciences Publications, Ltd. - 2050-084X. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Sugar porters (SPs) represent the largest group of secondary-active transporters. Some members, such as the glucose transporters (GLUTs), are well known for their role in maintaining blood glucose homeostasis in mammals, with their expression upregulated in many types of cancers. Because only a few sugar porter structures have been determined, mechanistic models have been constructed by piecing together structural states of distantly related proteins. Current GLUT transport models are predominantly descriptive and oversimplified. Here, we have combined coevolution analysis and comparative modeling, to predict structures of the entire sugar porter superfamily in each state of the transport cycle. We have analyzed the state-specific contacts inferred from coevolving residue pairs and shown how this information can be used to rapidly generate free-energy landscapes consistent with experimental estimates, as illustrated here for the mammalian fructose transporter GLUT5. By comparing many different sugar porter models and scrutinizing their sequence, we have been able to define the molecular determinants of the transport cycle, which are conserved throughout the sugar porter superfamily. We have also been able to highlight differences leading to the emergence of proton-coupling, validating, and extending the previously proposed latch mechanism. Our computational approach is transferable to any transporter, and to other protein families in general.
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| 4. |
- Salvatori, I., et al.
(författare)
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Assessment of the hydrogen induced stress cracking resistance of precipitation hardened nickel-based alloys using the slow strain rate tensile test method : Influence of microstructure
- 2019
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Ingår i: NACE - International Corrosion Conference SeriesVolume 2019-March, 2019, Article number 13365Corrosion Conference and Expo 2019; Nashville; United States; 24 March 2019 through 28 March 2019. - : National Assoc. of Corrosion Engineers International.
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Konferensbidrag (refereegranskat)abstract
- Within the framework of a Joint Industrial Project sponsored by several petroleum companies, the behavior of several Precipitation Hardened (PH) Ni-based alloys with respect to Hydrogen Induced Stress Cracking (HISC) resistance was studied, using the Slow Strain Rate Tensile (SSRT) test method conducted under hydrogen charging conditions (applying a constant cathodic current density throughout the test). Among the test materials, several industrial Heats of UNS N07718, UNS N09945/945X, UNS N09925, UNS N09935, UNS N07725 and UNS N07716 were evaluated. A detailed microstructural analysis was performed on each heat, at different levels, involving SEM and TEM examinations at high magnification on etched samples, to reveal the phases present at grain boundaries. Methodologies were developed to quantify the grain boundary coverage (length of precipitates at grain boundary divided by the total grain boundary length), and to study the distribution in size (equivalent diameter, surface, shape factor) of the grain boundary precipitates, and applied to the studied materials. Elemental chemical analysis of the precipitates was also conducted by Energy Dispersive X-ray spectrometry. The performance of the different alloys with respect to HISC resistance is discussed on the basis of the plastic elongation obtained in the SSRT tests under cathodic polarization, the microstructural features and the microstructural criteria given in the API 6A CRA standard.
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| 5. |
- Trillo, E., et al.
(författare)
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Assessment of the hydrogen induced stress cracking resistance of precipitation hardened nickel-based alloys using the slow strain rate tensile test method - Experimental parameters and related issues
- 2019
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Ingår i: NACE - International Corrosion Conference SeriesVolume 2019-March, 2019, Nashville; United States; 24 March 2019 through 28 March 2019. - : National Assoc. of Corrosion Engineers International.
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Konferensbidrag (refereegranskat)abstract
- Within the framework of a Joint Industrial Project (JIP) sponsored by several petroleum companies, the behavior of several Precipitation Hardened (PH) Ni-based alloys with respect to Hydrogen Induced Stress Cracking (HISC) resistance was studied using the Slow Strain Rate Tensile (SSRT) test method under hydrogen charging conditions. The experimental conditions included a 0.5M sulfuric acid solution at 5 mA/cm2 and at 40°C at a strain rate of 10-6 sec-1. A round robin was performed that highlighted the need to measure the effective strain rate of the specimen during the elastic part of the SSRT test, the cell configuration, the current density, the gas cap composition, were all studied to determine the effects on the results. Once the test conditions had been optimized, the study of different industrial heats was carried out on specimens sampled in three locations, 120 degrees apart and at mid radius. It was found that sampling different areas could lead to changes in the test results, resulting mainly from microstructural variances at different locations of the bar. The results generated in this program could then be studied by relating plastic elongation obtained under CP as well as cracking mode and microstructure compliance with the API 6A CRA standard.
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