2024年6月19日、NIMSにて、Mines Paris-PSL, CNRSのDr. Jacques Bessonによるご講演が第155回構材ゼミとして開催されました。
Dr. Jacques Besson
(Mines Paris-PSL, Directeur de recherche au CNRS)
日時：2024年6月19日(水曜日)15:00～16:00
会場：先進構造材料研究棟 5階カンファレンスルーム
開催者：柴田曉伸（鉄鋼材料グループ）
第155回構材ゼミ 開催風景
Abstract：
Modelling hydrogen embrittlement of vintage and modern ferritic pipes and tubes
Jacques Besson
MinesParis, PSL, Centre des Matériaux, UMR CNRS 7633, France
jacques.besson@minesparis.psl.eu
The transportation of gaseous hydrogen through pipelines is crucial for its widespread application in a decarbonized energy landscape. However, the susceptibility of ferritic steels to Hydrogen Embrittlement (HE) poses a significant challenge, hindering progress in this field. This study focuses on simulating hydrogen embrittlement in steels for pipes and tubes to better understand the underlying mechanisms and develop strategies for mitigating its detrimental effects.
In this research, the Finite Element (FE) method is employed to simulate the complex interactions between hydrogen and ferritic steels at a macroscopic level. The model includes the description of diffusion in a stress field accounting for multiple trapping sites (described by a trap density and a trapping energy). In the case of trapping by dislocations, the associated density increases with increasing plastic strain. The model can account for a possible effect of hydrogen on the flow stress to represent Hydrogen-Enhanced Localized Plasticity (HELP). The presence of hydrogen in the material leads to specific damage mechanisms such as Hydrogen Enhanced Decohesion (HEDE) or Hydrogen Enhanced Strain-Induced Vacancy (HESIV). The proposed model focuses on the description of HEDE introducing a damage variable whose evolution depends on local hydrogen concentration, the principal stress, and accumulated plastic strain. As constitutive models considering damage suffer from mesh dependency, a nonlocal formulation is used based on an implicit gradient formulation. As materials retain some ductility, a large deformation formulation must be used. In addition, a mixed formulation is used to avoid spurious pressure fluctuations and obtain accurate stress fields. The problem is solved using a monolithic strategy in which the hydrogen lattice concentration, displacement, pressure, volume change fields, and nonlocal damage fields are simultaneously determined.
The proposed simulation strategy is applied in various case studies: (i) crack propagation under air and hydrogen, (ii) simulation of pressurized disk tests, (iii) simulation of hydrogen intake during tensile tests, (iv) simulation of protection using oxygen, (v) simulations of TDS cycles.
Acknowledgments: This work is funded by the ANR France Chair program MESSIAH (ANR-20- CHIN-0003).