Experimentelle und modellmäßige Bewertung der dreidimensionalen Auswirkung mikrostruktureller Barrieren während der Rissinitiierungphase VHCF-beanspruchter Werkstoffe

即使在10亿次循环后，金属材料制成的部件也可能显示出塑性变形的痕迹，而不会失效。然而，相同的部件可能会在相同的载荷下断裂，但循环次数较少。本研究假设位错运动势垒的抗力决定疲劳损伤的发生，这一假设将用不同强度的铁素体和奥氏体相的双相钢来量化。此外，还将分析两相之间的同时塑性和残余应力分布，以及疲劳临界微结构团簇的随机排列等重要方面。环境效应对VHCF损伤的影响这一重要问题将通过在不同气氛下的实验来解决。采用了三种交互的现代实验和理论方法：(I)超声疲劳试验与原位分析技术相结合；(Ii)利用高能同步辐射进行三维组织重建和空间分辨衍射测量；(Iii)两相组织内弹性和塑性各向异性疲劳变形的有限元模拟，作为VHCF损伤容限寿命预测概念的基础，以及抗疲劳材料结构优化的可能性。

Even after one billion cycles, components made of metallic materials may show traces of plastic deformation without being failed. However, the same components can fracture at the same load but a lower number of cycles. The hypothesis of the present research that the resistance of microstructural barriers to dislocation motion decides about the occurrence of fatigue damage will be quantified by duplex steel of different strength of the ferrite and austenite phase. Furthermore, important aspects, such as the simultaneous plasticity and residual stress distribution between the two phases, as well as the stochastic arrangement of fatigue-critical microstructural clusters will be analyzed. The important question about the influence of environmental effects on the VHCFdamage is going to be addressed by experiments in different atmospheres. Three interacting modern experimental and theoretical approaches are used: (i) ultrasonic fatigue testing in combination with in-situ analysis techniques (ii) three-dimensional microstructural reconstruction and spatially-resolved diffraction measurements using high energy synchrotron radiation and (iii) finite element modeling of the elastic and plastic anisotropic fatigue deformation within the twophase microstructure as a base of a damage-tolerant life prediction concept for the VHCF regime as well as an possibility for structural optimization of fatigue-resistant materials.