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

资源的稀缺以及国际汽车工业的最新发展凸显了氢作为未来能源和燃料的重要性。它的应用需要新材料的开发和鉴定，并在暴露于氢的部件的设计过程中考虑氢的影响。暴露于加压氢气或电解载荷下的钢的材料行为的基本特征已成为许多研究的主题。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，同时考虑到材料特性。重点将放在局部应变概念的应用，以及循环数据，高应力材料体积的传递概念。最后提到的概念将加强关于氢渗透体积的应变幅值和局部应变分布的依赖。局部概念基于这样的假设，即局部工艺和关键位置的材料行为决定了疲劳裂纹的产生，从而决定了疲劳寿命，而与部件几何形状的复杂性无关。虽然假定在空气中应用时应力梯度和测试频率的影响较小，但对于氢气暴露，它们必须是预期的。为了量化影响参数，在不同的测试频率下，在空气和50bar的加压氢气条件下进行了有缺口和无缺口试样的应变和力控制疲劳试验。静态和动态机械载荷对选定载荷水平下扩散和捕获行为的影响将在电化学渗透测试中的应变和力控制下进行表征，并与卸载条件进行比较。此外，随着时间的推移，渗透电流密度的测定允许在依赖于时间和施加负载的氢活性的评估。为了获得关于氢的有效含量造成氢脆的潜在威胁的信息，将在完成每个应变和力水平的疲劳和渗透试验后进行TDS/热载气萃取测量。研究结果的广泛意义是通过选择两种具有奥氏体和铁素体微观结构的钢来保证的，这两种钢在捕获和扩散行为上存在显着差异。根据研究结果，指出局部概念和高应力材料体积传递概念在氢暴露部件设计中的应用局限性，并推导出这些概念的基本适应性和实验参数的确定。

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.