Principles for the design of components exposed to pressurized hydrogen taking into account material-related damage mechanisms

氢作为未来能源和燃料的重要性日益增加，这一点随着资源的稀缺以及国际汽车工业的最新发展而凸显出来。氢的应用要求开发和鉴定新材料，并在暴露于氢的部件的设计过程中考虑氢的影响。钢在暴露于加压氢或电解负荷下的材料行为的基本表征已经成为众多研究的主题。计划中的研究项目侧重于设计暴露于加压氢气的循环加载组件，同时考虑材料特性。重点将放在应用程序的局部应变的概念，以及转移概念的循环数据，高应力材料的体积。最后提到的概念将加强有关氢渗透体积的应变幅度和局部应变分布的依赖性。局部概念基于这样的假设，即临界位置处的局部过程和材料行为是疲劳裂纹萌生的决定性因素，因此疲劳寿命也是决定性的。尽管假设在空气中应用时应力梯度和测试频率的影响较小，为了量化影响参数，将在空气中和50 bar压力下的加压氢气中，以不同的测试频率，对有缺口和无缺口试样进行应变和力控制疲劳测试。在选定的载荷水平下，静态和动态机械载荷对扩散和捕获行为的影响将在应变和力下进行表征。在电化学渗透测试中进行控制，并与未加载条件进行比较。此外，委员会认为，随着时间的推移，渗透电流密度的测定允许根据时间和施加的负载来评估氢活性。热载气抽取测量将在每个应变和力水平的疲劳和渗透试验完成后进行。研究的广泛意义根据研究结果，将指出局部概念和高应力材料体积的转移概念在氢暴露部件设计中的应用局限性，并指出这些概念和实验的必要适应性。参数的确定。

Scarcities of resources as well as latest developments in the international automotive industry underline a growing importance of hydrogen as a future energy source and fuel.Its application requires the development and qualification of new materials and consideration of the influence of hydrogen in the design process of components exposed to hydrogen.Basic characterisations of the material behaviour of steels under exposure to pressurized hydrogen or electrolytic loading have been subject of numerous studies. The planned research project focuses on the design of cyclically loaded components exposed to pressurized hydrogen taking into account material properties. Emphasis will be put on the application of local strain concepts as well as the transfer concept for cyclic data, the highly stressed material volume. Last mentioned concept will be enhanced regarding a hydrogen permeation volume in dependence of the strain amplitude and local strain distribution.The local concept bases on the assumption that local processes and material behaviour at critical locations are determinant for the initiation of fatigue cracks and therefore fatigue life, irrespective of the complexity of component geometry.While minor influences of stress gradients and testing frequencies are assumed for the application in air, they have to be expected for hydrogen exposure.In order to quantify influencing parameters strain- and force-controlled fatigue tests will be carried out in air and under pressurized hydrogen at 50 bar at different testing frequencies with notched and unnotched specimens.The influence of static and dynamic mechanical loading on the diffusion and trapping behaviour at selected load levels will be characterised under strain- and force-control in electrochemical permeation tests and be compared to the unloaded condition. Moreover, the determination of the permeation current density over time allows an assessment of hydrogen activity in dependence of time and applied load.In order to gain information regarding the potential threat of hydrogen embrittlement due the effective content of hydrogen TDS/hot carrier gas extraction measurements will be carried out after completion of the fatigue and permeation tests for each strain and force level.Extensive significance of the research results is ensured by the selection of two steels with austenitic and ferritic microstructure that reveal significant differences in their trapping and diffusion behaviour.Based on the research results application limitations of the local concept as well as the transfer concept of the highly stressed material volume for the design of components exposed to hydrogen will be pointed out and essential adaptations of the concepts as well as the experimental parameter determination be deduced.