laurent briottet - Academia.edu (original) (raw)
Papers by laurent briottet
International Hydrogen Conference (IHC 2016): Materials Performance in Hydrogen Environments, 2017
Calibration and validation of the LINGRA-N model were performed using herbage dry matter (DM) yie... more Calibration and validation of the LINGRA-N model were performed using herbage dry matter (DM) yield data from field studies conducted at three locations in Slovenia. Calibration was done by minimising root mean square error (RMSE) and validation by using RMSE and Willmott's index of agreement (dw). Calibration of LINGRA-N was not successful for the experiment conducted on permanent grassland in Ljubljana in the period 1974-1993 (RMSE% = 14%, dw = 0.37). Better results were obtained for grass monocultures in Jablje (J) and Rakičan (R) in the period 1998-2013, with the best fit for cocksfoot (Dactylis glomerata L.; RMSE% = 12%, dw = 0.84). Fifty-year simulations were performed for cocksfoot (J-DG) and timothy grass (Phleum pratense L.) in Jablje (J-PP) and perennial ryegrass (Lolium perenne L.) in Jablje (J-LP) and Rakičan. Outliers with very low simulated herbage DM yield were detected only in the second half of the study period and were associated with drought and/or high maximum air temperatures. A time series analysis of annual potential yield values showed a statistically significant (P=0.05) negative trend for J-LP (-24 kg DM ha-1 year-1) and J-PP (-29 kg DM ha-1 year-1). A change in the variability of the reduction factor for crop growth due to drought was already noticeable.
Mechanics - Microstructure - Corrosion Coupling, 2019
Abstract: The implementation of mechanical tests within controlled aggressive environments remain... more Abstract: The implementation of mechanical tests within controlled aggressive environments remains essential for the study of stress corrosion cracking (SCC), corrosion fatigue (CF), and hydrogen embrittlement (HE) phenomena insofar as the constant evolution of materials requires requalifying and reevaluating their sensitivity for each new grade and more generally for each new material/environment system.
Volume 6B: Materials and Fabrication, 2018
The European Union is intending to reduce their carbon emissions by up to 80–95% by 2050. This wi... more The European Union is intending to reduce their carbon emissions by up to 80–95% by 2050. This will imply the increase of electricity coming from variable renewable energy sources. Producing hydrogen from this electricity is one way to facilitate the integration of such intermittent sources. Currently, there is no consensus in the world on the allowed amount of hydrogen in the natural gas with the aim to use the natural gas existing transportation grid to transport such mixture. The object of the present study is to provide additional experimental data concerning the effect of the hydrogen content in a N2/H2 mixture on the toughness of an API X70 steel dedicated to gas transport. The toughness has been measured in terms of Crack Tip Opening Displacement under a total pressure of 85 bar. The mechanical results are compared to existing results. It is confirmed that 1% H2 induces a significant decrease of the material toughness. Moreover, the content of O2 impurity in the N2/H2 mixture...
Volume 6: Materials and Fabrication, 2020
The purpose of the present work is to study the effect of the hydrogen content in a H2-NG (Natura... more The purpose of the present work is to study the effect of the hydrogen content in a H2-NG (Natural Gas) blend on the mechanical behavior of a C-Mn low alloy steel L485-MB (NF EN ISO 3183) under monotonic loading. Different testing conditions were explored for the blend: 2% H2-NG, 25% H2-NG, 100% H2 and 100% NG at a total pressure of 8.5 MPa using two slow strain rates: 10−4 s−1 and 10−6 s−1. Tests in the blend were compared to those under pure hydrogen at the same partial pressures. Furthermore, two surface roughnesses have been explored, one corresponding to a mirror polish, the other as lathed. The embrittlement has been assessed by necking measurements and fracture analysis for the whole testing conditions. The results show a drop of ductility with the increase of partial pressure of hydrogen in NG. Besides, no significant effect of hydrogen were observed on flow stress. In addition, the L485-MB pipeline steel presents a shear type fracture mode in high partial pressure of hydrog...
International Hydrogen Conference (IHC 2016): Materials Performance in Hydrogen Environments, 2017
Mechanics - Microstructure - Corrosion Coupling, 2019
Mise en forme des métaux et fonderie, 2015
La ductilite est l'aptitude d'un materiau a subir une deformation irreversible sans se ro... more La ductilite est l'aptitude d'un materiau a subir une deformation irreversible sans se rompre. Ainsi, dans le contexte de la mise en forme des metaux, la ductilite est une propriete qu'il est tres important de connaitre, de controler et, eventuellement, de modifier. Dans la plupart des cas, comme par exemple en traction uniaxiale, la ductilite est limitee par deux facteurs pouvant combiner leurs effets : l'instabilite et l'endommagement. Le premier d'entre eux, qui peut revetir des formes tres diverses suivant la geometrie de l'echantillon et la sollicitation imposee (par exemple, striction diffuse ou localisee), joue un role predominant dans le cas des produits plats (emboutissage des toles). En revanche, l'endommagement est le principal facteur limitant la ductilite dans les produits massifs.
Materials Science and Engineering: A, 2021
Abstract CuCrZr is a precipitation hardening alloy, used for its good electrical and thermal prop... more Abstract CuCrZr is a precipitation hardening alloy, used for its good electrical and thermal properties combined to high mechanical properties. Using additive manufacturing technologies, and more specifically the laser powder bed fusion (L-PBF) process, allows designing highly complex parts such as compact and efficient CuCrZr heat exchangers. Additional understanding of the specific CuCrZr metallurgy during this manufacturing process is still needed to fully take advantages of these possibilities. This work aimed (i) to clarify the impact of the L-PBF process and post-fabrication heat treatments on the microstructure of L-PBF CuCrZr alloy, (ii) to determine the corresponding mechanical and electrical properties and (iii) to quantify the contributions of the different nano-scale strengthening mechanisms (nano-precipitation, dislocations, solid solution, grain size refinement) depending on the different heat treatments. The microstructures of the CuCrZr samples are carefully analyzed at different scales thanks to scanning electron and transmission electron microscopy, highlighting the effect of the different heat treatments. In all heat-treated samples, Cr nano-precipitates are uniformly dispersed in the Cu matrix; few Zr nano-precipitates are observed either at grain boundaries, next to Cr nano-precipitates, or inside the Cu matrix. Moreover, the mean grain size, dislocation density, mean radius and volume fraction of the Chromium nano-precipitates are measured. These data are introduced in the identified hardening mechanisms to estimate the yield strengths (YS) of the different analyzed CuCrZr microstructures. The results are compared to the experimental values, including those of a reference wrought heat-treated CuCrZr, and discussed. A good correlation is found between calculated and experimental values. For the first time, the main hardening mechanisms of L-PBF CuCrZr are quantified and the interest of the “L-PBF + Direct Age Hardening (DAH)” process route to get a high amount of Cr nano-precipitates is confirmed. The DAH applied to L-PBF materials provides high mechanical properties (184 HV1 hardness, YS = 527 MPa, UTS = 585MPa) while keeping a good elongation (14%) and electrical conductivity (42 MS. m−1). These results are due to a combination between (i) a high Cr nano-precipitates density, leading to a high precipitation hardening, and (ii) a high dislocation density associated to the presence of remaining solidification cells.
MATEC Web of Conferences, 2018
For several years, Inconel 718 made by Laser Beam Melting (LBM) has been used for components of t... more For several years, Inconel 718 made by Laser Beam Melting (LBM) has been used for components of the Ariane propulsion systems manufactured by ArianeGroup. In the aerospace field, many components of space engines are used under hydrogen environment. The risk of hydrogen embrittlement (HE) can be therefore a first order problem. Consequently, to improve the HE sensitivity of LBM Inconel 718, a systematic approach needs to be developed to characterize the microstructure at different scales and its interaction with hydrogen. This study addresses the impact of gaseous hydrogen on the material mechanical behavior under fatigue loadings. In a first step, the low cycle fatigue behavior under 300 bar of hydrogen gas has been evaluated with specimen loaded at a constant load ratio of R=0.1 and a frequency of 0.5 Hz. A reduction in the cycle number of fracture is shown. This reduction of fatigue life is a consequence of the impact of hydrogen damage processes. The impact of hydrogen is evaluated at the stages of crack initiation, crack propagation. These results are discussed in relation with the hydrogen embrittlement mechanisms and particularly in terms of hydrogen / plasticity interactions. To achieve this, the fracture surface morphology was first examined using scanning electron microscopy and second samples near the fracture surface were extracted using Focused-Ion Beam machining from regions containing striation. The main result observed is a reduction of the size of dislocation organization in relation with a decrease of the striation distance.
International Journal of Hydrogen Energy, 2017
Volume 6B: Materials and Fabrication, 2016
International Journal of Hydrogen Energy, 2015
Volume 6B: Materials and Fabrication, 2015
X4CrNiMo 16.5.1 steel (commercial name APX4) is a low carbon martensitic stainless steel known fo... more X4CrNiMo 16.5.1 steel (commercial name APX4) is a low carbon martensitic stainless steel known for its remarkable mechanical characteristics and its good resistance to corrosion. The use of APX4 in the manufacture of high pressure gas vessels requires a thorough understanding of its resistance to Hydrogen Embrittlement (HE) as the gas can contain traces of hydrogen, and martensitic steels, and their welds, are generally very sensitive to HE. This paper deals with the first part of this study, involving the characterization of the microstructure and the mechanical properties of each zone of the electron beam weld (melted zone and four different heat affected zones), and the investigation of their embrittlement in a hydrogen environment. For this purpose, tensile tests were performed in hydrogen gas at various pressures on both the base metal and the welded samples. In situ tensile tests with picture correlation analysis have been planned for the subsequent part of our study. These ex...
Volume 6B: Materials and Fabrication, 2015
The current international standards and codes dedicated to the design of pressure vessels do not ... more The current international standards and codes dedicated to the design of pressure vessels do not properly ensure fitness for service of vessels used for gaseous hydrogen storage and subjected to hydrogen enhanced fatigue. In this context, the European project MATHRYCE intends to propose an easy to implement vessel design methodology based on lab-scale tests and taking into account hydrogen enhanced fatigue.In the present document the lab-scale experimental developments and results are presented. The material considered was a commercially available Q&T low alloy Cr-Mo steel from a seamless pressure vessel. Due to the high hydrogen diffusion at room temperature in such steel, all the tests were performed under hydrogen pressure to avoid outgassing. Different types of lab-scale tests were developed and used in order to identify the most promising one for a design code. The effect of mechanical parameters, such as H2 pressure, frequency and ΔK, on fatigue crack initiation and propagation was analyzed. In particular, special attention was paid on the influence of H2 on the relative parts of initiation and propagation in the fatigue life of a component.The second part of the work was dedicated to cyclic hydraulic and hydrogen pressure tests on full scale vessels. Three artificial defects with different geometries per cylinder were machined in the inner wall of each tested cylinder. They were specifically designed in order to detect fatigue crack initiation and fatigue crack propagation with a single test.The final goal of this work is to propose a methodology to derive a “hydrogen safety factor” from lab-scale tests. The proposed method is compared to the full-scale results obtained, leading to recommendations on the design of pressure components operating under cyclic hydrogen pressure.Copyright © 2015 by ASME
International Journal of Hydrogen Energy, 2015
EPJ Web of Conferences, 2013
International Hydrogen Conference (IHC 2012)
Materials Science Forum, 2005
A two parameters rupture criterion for Ti-6Al-4V is proposed, based on cryogenic rupture tests. m... more A two parameters rupture criterion for Ti-6Al-4V is proposed, based on cryogenic rupture tests. microstructural observations and FEM analysis,. The damage mechanisms including the cavities nucleation process are analyzed. Moreover, the final steps of rupture are discussed with the help of the thermo-mechanical coupling mechanisms that are expected to operate at low temperatures.
Volume 6B: Materials and Fabrication, 2014
The current international standards and codes dedicated to the design of pressure vessels do not ... more The current international standards and codes dedicated to the design of pressure vessels do not properly ensure fitness for service of such vessel used for gaseous hydrogen storage and subjected to hydrogen enhanced fatigue. Yet, hydrogen can reduce the fatigue life in two ways: by decreasing the crack initiation period and by increasing the fatigue crack growth rate. The European project MATHRYCE aims are to propose an easy to implement vessel design methodology based on lab-scale tests and taking into account hydrogen enhanced fatigue.The study is focused on a low alloy Cr-Mo steel, exhibiting a tempered bainitic and martensitic microstructure, and classically used to store hydrogen gas up to 45 MPa. Due to hydrogen diffusion at room temperature in such steel, tests have to be performed under hydrogen pressure to avoid outgassing.In the present work, experimental procedures have been developed to study both crack initiation and crack growth. The specimens and tests instrumentation have been specifically designed to quantitatively measure in-situ these two stages under high hydrogen pressure. We developed and tested crack gages located close to a small drilled notch. This notch simulates the presence of steel nonmetallic inclusions and other microstructural features that can affect fatigue crack initiation and propagation. The experimental results addressing the effects of the testing conditions, such as stress ratio, frequency and hydrogen pressure will be compared to the local strain and stress fields obtained by Finite Element Method and correlated to the possible hydrogen enhanced fatigue mechanisms involved.Copyright © 2014 by ASME
International Hydrogen Conference (IHC 2016): Materials Performance in Hydrogen Environments, 2017
Calibration and validation of the LINGRA-N model were performed using herbage dry matter (DM) yie... more Calibration and validation of the LINGRA-N model were performed using herbage dry matter (DM) yield data from field studies conducted at three locations in Slovenia. Calibration was done by minimising root mean square error (RMSE) and validation by using RMSE and Willmott's index of agreement (dw). Calibration of LINGRA-N was not successful for the experiment conducted on permanent grassland in Ljubljana in the period 1974-1993 (RMSE% = 14%, dw = 0.37). Better results were obtained for grass monocultures in Jablje (J) and Rakičan (R) in the period 1998-2013, with the best fit for cocksfoot (Dactylis glomerata L.; RMSE% = 12%, dw = 0.84). Fifty-year simulations were performed for cocksfoot (J-DG) and timothy grass (Phleum pratense L.) in Jablje (J-PP) and perennial ryegrass (Lolium perenne L.) in Jablje (J-LP) and Rakičan. Outliers with very low simulated herbage DM yield were detected only in the second half of the study period and were associated with drought and/or high maximum air temperatures. A time series analysis of annual potential yield values showed a statistically significant (P=0.05) negative trend for J-LP (-24 kg DM ha-1 year-1) and J-PP (-29 kg DM ha-1 year-1). A change in the variability of the reduction factor for crop growth due to drought was already noticeable.
Mechanics - Microstructure - Corrosion Coupling, 2019
Abstract: The implementation of mechanical tests within controlled aggressive environments remain... more Abstract: The implementation of mechanical tests within controlled aggressive environments remains essential for the study of stress corrosion cracking (SCC), corrosion fatigue (CF), and hydrogen embrittlement (HE) phenomena insofar as the constant evolution of materials requires requalifying and reevaluating their sensitivity for each new grade and more generally for each new material/environment system.
Volume 6B: Materials and Fabrication, 2018
The European Union is intending to reduce their carbon emissions by up to 80–95% by 2050. This wi... more The European Union is intending to reduce their carbon emissions by up to 80–95% by 2050. This will imply the increase of electricity coming from variable renewable energy sources. Producing hydrogen from this electricity is one way to facilitate the integration of such intermittent sources. Currently, there is no consensus in the world on the allowed amount of hydrogen in the natural gas with the aim to use the natural gas existing transportation grid to transport such mixture. The object of the present study is to provide additional experimental data concerning the effect of the hydrogen content in a N2/H2 mixture on the toughness of an API X70 steel dedicated to gas transport. The toughness has been measured in terms of Crack Tip Opening Displacement under a total pressure of 85 bar. The mechanical results are compared to existing results. It is confirmed that 1% H2 induces a significant decrease of the material toughness. Moreover, the content of O2 impurity in the N2/H2 mixture...
Volume 6: Materials and Fabrication, 2020
The purpose of the present work is to study the effect of the hydrogen content in a H2-NG (Natura... more The purpose of the present work is to study the effect of the hydrogen content in a H2-NG (Natural Gas) blend on the mechanical behavior of a C-Mn low alloy steel L485-MB (NF EN ISO 3183) under monotonic loading. Different testing conditions were explored for the blend: 2% H2-NG, 25% H2-NG, 100% H2 and 100% NG at a total pressure of 8.5 MPa using two slow strain rates: 10−4 s−1 and 10−6 s−1. Tests in the blend were compared to those under pure hydrogen at the same partial pressures. Furthermore, two surface roughnesses have been explored, one corresponding to a mirror polish, the other as lathed. The embrittlement has been assessed by necking measurements and fracture analysis for the whole testing conditions. The results show a drop of ductility with the increase of partial pressure of hydrogen in NG. Besides, no significant effect of hydrogen were observed on flow stress. In addition, the L485-MB pipeline steel presents a shear type fracture mode in high partial pressure of hydrog...
International Hydrogen Conference (IHC 2016): Materials Performance in Hydrogen Environments, 2017
Mechanics - Microstructure - Corrosion Coupling, 2019
Mise en forme des métaux et fonderie, 2015
La ductilite est l'aptitude d'un materiau a subir une deformation irreversible sans se ro... more La ductilite est l'aptitude d'un materiau a subir une deformation irreversible sans se rompre. Ainsi, dans le contexte de la mise en forme des metaux, la ductilite est une propriete qu'il est tres important de connaitre, de controler et, eventuellement, de modifier. Dans la plupart des cas, comme par exemple en traction uniaxiale, la ductilite est limitee par deux facteurs pouvant combiner leurs effets : l'instabilite et l'endommagement. Le premier d'entre eux, qui peut revetir des formes tres diverses suivant la geometrie de l'echantillon et la sollicitation imposee (par exemple, striction diffuse ou localisee), joue un role predominant dans le cas des produits plats (emboutissage des toles). En revanche, l'endommagement est le principal facteur limitant la ductilite dans les produits massifs.
Materials Science and Engineering: A, 2021
Abstract CuCrZr is a precipitation hardening alloy, used for its good electrical and thermal prop... more Abstract CuCrZr is a precipitation hardening alloy, used for its good electrical and thermal properties combined to high mechanical properties. Using additive manufacturing technologies, and more specifically the laser powder bed fusion (L-PBF) process, allows designing highly complex parts such as compact and efficient CuCrZr heat exchangers. Additional understanding of the specific CuCrZr metallurgy during this manufacturing process is still needed to fully take advantages of these possibilities. This work aimed (i) to clarify the impact of the L-PBF process and post-fabrication heat treatments on the microstructure of L-PBF CuCrZr alloy, (ii) to determine the corresponding mechanical and electrical properties and (iii) to quantify the contributions of the different nano-scale strengthening mechanisms (nano-precipitation, dislocations, solid solution, grain size refinement) depending on the different heat treatments. The microstructures of the CuCrZr samples are carefully analyzed at different scales thanks to scanning electron and transmission electron microscopy, highlighting the effect of the different heat treatments. In all heat-treated samples, Cr nano-precipitates are uniformly dispersed in the Cu matrix; few Zr nano-precipitates are observed either at grain boundaries, next to Cr nano-precipitates, or inside the Cu matrix. Moreover, the mean grain size, dislocation density, mean radius and volume fraction of the Chromium nano-precipitates are measured. These data are introduced in the identified hardening mechanisms to estimate the yield strengths (YS) of the different analyzed CuCrZr microstructures. The results are compared to the experimental values, including those of a reference wrought heat-treated CuCrZr, and discussed. A good correlation is found between calculated and experimental values. For the first time, the main hardening mechanisms of L-PBF CuCrZr are quantified and the interest of the “L-PBF + Direct Age Hardening (DAH)” process route to get a high amount of Cr nano-precipitates is confirmed. The DAH applied to L-PBF materials provides high mechanical properties (184 HV1 hardness, YS = 527 MPa, UTS = 585MPa) while keeping a good elongation (14%) and electrical conductivity (42 MS. m−1). These results are due to a combination between (i) a high Cr nano-precipitates density, leading to a high precipitation hardening, and (ii) a high dislocation density associated to the presence of remaining solidification cells.
MATEC Web of Conferences, 2018
For several years, Inconel 718 made by Laser Beam Melting (LBM) has been used for components of t... more For several years, Inconel 718 made by Laser Beam Melting (LBM) has been used for components of the Ariane propulsion systems manufactured by ArianeGroup. In the aerospace field, many components of space engines are used under hydrogen environment. The risk of hydrogen embrittlement (HE) can be therefore a first order problem. Consequently, to improve the HE sensitivity of LBM Inconel 718, a systematic approach needs to be developed to characterize the microstructure at different scales and its interaction with hydrogen. This study addresses the impact of gaseous hydrogen on the material mechanical behavior under fatigue loadings. In a first step, the low cycle fatigue behavior under 300 bar of hydrogen gas has been evaluated with specimen loaded at a constant load ratio of R=0.1 and a frequency of 0.5 Hz. A reduction in the cycle number of fracture is shown. This reduction of fatigue life is a consequence of the impact of hydrogen damage processes. The impact of hydrogen is evaluated at the stages of crack initiation, crack propagation. These results are discussed in relation with the hydrogen embrittlement mechanisms and particularly in terms of hydrogen / plasticity interactions. To achieve this, the fracture surface morphology was first examined using scanning electron microscopy and second samples near the fracture surface were extracted using Focused-Ion Beam machining from regions containing striation. The main result observed is a reduction of the size of dislocation organization in relation with a decrease of the striation distance.
International Journal of Hydrogen Energy, 2017
Volume 6B: Materials and Fabrication, 2016
International Journal of Hydrogen Energy, 2015
Volume 6B: Materials and Fabrication, 2015
X4CrNiMo 16.5.1 steel (commercial name APX4) is a low carbon martensitic stainless steel known fo... more X4CrNiMo 16.5.1 steel (commercial name APX4) is a low carbon martensitic stainless steel known for its remarkable mechanical characteristics and its good resistance to corrosion. The use of APX4 in the manufacture of high pressure gas vessels requires a thorough understanding of its resistance to Hydrogen Embrittlement (HE) as the gas can contain traces of hydrogen, and martensitic steels, and their welds, are generally very sensitive to HE. This paper deals with the first part of this study, involving the characterization of the microstructure and the mechanical properties of each zone of the electron beam weld (melted zone and four different heat affected zones), and the investigation of their embrittlement in a hydrogen environment. For this purpose, tensile tests were performed in hydrogen gas at various pressures on both the base metal and the welded samples. In situ tensile tests with picture correlation analysis have been planned for the subsequent part of our study. These ex...
Volume 6B: Materials and Fabrication, 2015
The current international standards and codes dedicated to the design of pressure vessels do not ... more The current international standards and codes dedicated to the design of pressure vessels do not properly ensure fitness for service of vessels used for gaseous hydrogen storage and subjected to hydrogen enhanced fatigue. In this context, the European project MATHRYCE intends to propose an easy to implement vessel design methodology based on lab-scale tests and taking into account hydrogen enhanced fatigue.In the present document the lab-scale experimental developments and results are presented. The material considered was a commercially available Q&T low alloy Cr-Mo steel from a seamless pressure vessel. Due to the high hydrogen diffusion at room temperature in such steel, all the tests were performed under hydrogen pressure to avoid outgassing. Different types of lab-scale tests were developed and used in order to identify the most promising one for a design code. The effect of mechanical parameters, such as H2 pressure, frequency and ΔK, on fatigue crack initiation and propagation was analyzed. In particular, special attention was paid on the influence of H2 on the relative parts of initiation and propagation in the fatigue life of a component.The second part of the work was dedicated to cyclic hydraulic and hydrogen pressure tests on full scale vessels. Three artificial defects with different geometries per cylinder were machined in the inner wall of each tested cylinder. They were specifically designed in order to detect fatigue crack initiation and fatigue crack propagation with a single test.The final goal of this work is to propose a methodology to derive a “hydrogen safety factor” from lab-scale tests. The proposed method is compared to the full-scale results obtained, leading to recommendations on the design of pressure components operating under cyclic hydrogen pressure.Copyright © 2015 by ASME
International Journal of Hydrogen Energy, 2015
EPJ Web of Conferences, 2013
International Hydrogen Conference (IHC 2012)
Materials Science Forum, 2005
A two parameters rupture criterion for Ti-6Al-4V is proposed, based on cryogenic rupture tests. m... more A two parameters rupture criterion for Ti-6Al-4V is proposed, based on cryogenic rupture tests. microstructural observations and FEM analysis,. The damage mechanisms including the cavities nucleation process are analyzed. Moreover, the final steps of rupture are discussed with the help of the thermo-mechanical coupling mechanisms that are expected to operate at low temperatures.
Volume 6B: Materials and Fabrication, 2014
The current international standards and codes dedicated to the design of pressure vessels do not ... more The current international standards and codes dedicated to the design of pressure vessels do not properly ensure fitness for service of such vessel used for gaseous hydrogen storage and subjected to hydrogen enhanced fatigue. Yet, hydrogen can reduce the fatigue life in two ways: by decreasing the crack initiation period and by increasing the fatigue crack growth rate. The European project MATHRYCE aims are to propose an easy to implement vessel design methodology based on lab-scale tests and taking into account hydrogen enhanced fatigue.The study is focused on a low alloy Cr-Mo steel, exhibiting a tempered bainitic and martensitic microstructure, and classically used to store hydrogen gas up to 45 MPa. Due to hydrogen diffusion at room temperature in such steel, tests have to be performed under hydrogen pressure to avoid outgassing.In the present work, experimental procedures have been developed to study both crack initiation and crack growth. The specimens and tests instrumentation have been specifically designed to quantitatively measure in-situ these two stages under high hydrogen pressure. We developed and tested crack gages located close to a small drilled notch. This notch simulates the presence of steel nonmetallic inclusions and other microstructural features that can affect fatigue crack initiation and propagation. The experimental results addressing the effects of the testing conditions, such as stress ratio, frequency and hydrogen pressure will be compared to the local strain and stress fields obtained by Finite Element Method and correlated to the possible hydrogen enhanced fatigue mechanisms involved.Copyright © 2014 by ASME