Dönges Benjamin, Syha Melanie, Hüsecken Anne K, Pietsch Ullrich, Ludwig Wolfgang, Krupp Ulrich, Christ Hans-Jürgen
Institut für Werkstofftechnik, Universität Siegen, D-57068 Siegen, Germany.
Institut für Angewandte Materialien, Karlsruher Institut für Technologie, D-76131 Karlsruhe, Germany.
Materials (Basel). 2021 Mar 22;14(6):1562. doi: 10.3390/ma14061562.
Diffraction and phase contrast tomography techniques were successfully applied to an austenitic-ferritic duplex stainless steel representing exemplarily a metallic material containing two phases with different crystal structures. The reconstructed volumes of both phases were discretized by finite elements. A crystal plasticity finite-element analysis was executed in order to simulate the development of the experimentally determined first and second order residual stresses, which built up due to the manufacturing process of the material. Cyclic deformation simulations showed the single-grain-resolved evolution of initial residual stresses in both phases and were found to be in good agreement with the experimental results. Solely in ferritic grains, residual stresses built up due to cyclic deformation, which promoted crack nucleation in this phase. Furthermore, phase contrast tomography was applied in order to analyze the mechanisms of fatigue crack nucleation and short fatigue crack propagation three-dimensionally and nondestructively. The results clearly showed the significance of microstructural barriers for short fatigue crack growth at the surface, as well as into the material. The investigation presented aims for a better understanding of the three-dimensional mechanisms governing short fatigue crack propagation and, in particular, the effect of residual stresses on these mechanisms. The final goal was to generate tailored microstructures for improved fatigue resistance and enhanced fatigue life.
衍射和相衬断层扫描技术成功应用于一种奥氏体-铁素体双相不锈钢，该材料典型地代表了一种包含两种具有不同晶体结构相的金属材料。通过有限元对两相的重建体积进行离散化。进行了晶体塑性有限元分析，以模拟实验测定的由于材料制造过程而产生的一阶和二阶残余应力的发展。循环变形模拟显示了两相中初始残余应力的单晶粒分辨演变，并且发现与实验结果吻合良好。仅在铁素体晶粒中，由于循环变形产生了残余应力，这促进了该相中的裂纹萌生。此外，应用相衬断层扫描技术对疲劳裂纹萌生和短疲劳裂纹扩展的机制进行三维无损分析。结果清楚地表明了微观结构障碍对表面以及材料内部短疲劳裂纹扩展的重要性。所提出的研究旨在更好地理解控制短疲劳裂纹扩展的三维机制，特别是残余应力对这些机制的影响。最终目标是生成定制的微观结构，以提高抗疲劳性并延长疲劳寿命。
