Fatigue Response of Nanostructured Metallic Materials

最近的研究表明，与传统的“微结构”材料相比，纳米结构材料在屈服强度、硬度和耐磨性等机械性能方面表现出显著的增强。然而，目前对纳米结构材料的疲劳和断裂行为还没有全面的了解。此外，通过创建纳米结构表面层/涂层来提高传统材料疲劳寿命的潜力还没有得到足够深入的探索。因此，该项目旨在获得纳米结构材料中疲劳现象的关键见解。通过对模型纳米结构金属系统（镍和铁）的分析建模、数值模拟和实验相结合的方法，本研究为：(1)对纳米结构材料的平面疲劳和疲劳裂纹扩展响应的基本理解奠定了基础；（ii）纳米结构材料接触疲劳响应的定量评估；（iii）在纳米结构材料的接触疲劳裂纹萌生预测中应用了一种新的粘附模型；(4)建立纳米结构材料接触疲劳寿命预测的简化数值模型。本研究在以下三个层面产生广泛影响：(i)研究：通过推进目前对纳米结构材料疲劳相关机制的理解，研究活动对摩擦学行业（包括飞机、汽车和生物医学、疲劳敏感应用）产生科学和技术影响。一个研究生接受全面的研究训练。由于路易斯安那州的研究投资明显低于其他州，项目活动也增强了该州在纳米技术领域的研究基础和教育努力。（ii）少数民族的教育经验：结合本研究项目，由PI开发的关于变形，疲劳和断裂的研究生/本科生课程得到加强，为课堂学习疲劳现象提供令人兴奋的动手实验部分。

Recent research efforts have demonstrated that nanostructured materials exhibit significant enhancements in mechanical properties such as yield strength, hardness and wear resistance, when compared to conventional 'microstructured' materials. However, a comprehensive understanding of the fatigue and fracture behavior of nanostructured materials is currently unavailable. Furthermore, the potential for enhancing the fatigue life of conventional materials through the creation of nanostructured surface layers/coatings has not been explored in sufficient depth. Hence, this project is directed towards obtaining key insights on the fatigue phenomenon in nanostructured materials. Through an approach that combines analytical modeling, numerical modeling, and experiments on model nanostructured metallic systems (nickel and iron), this study lays the foundation for: (i) a fundamental understanding of the plain fatigue and fatigue crack growth response of nanostructured materials; (ii) a quantitative assessment of the contact fatigue response of nanostructured materials; (iii) a unique application of a novel adhesion model for the prediction of contact fatigue crack initiation in nanostructured materials; and (iv) the development of a simplified numerical model for contact fatigue life prediction in nanostructured materials. The present study leads to broad impact at the following three levels: (i) Research: By advancing the current understanding of the mechanisms associated with fatigue of nanostructured materials, the research activities provide scientific and technological impact in the tribology industry (including aircraft, automotive, and bio-medical, fatigue-sensitive applications). Comprehensive research training is imparted to one graduate student. Because Louisiana's research investment has been significantly lower than in other states, the project activities also enhance the state's research base and educational efforts in the field of nanotechnology. (ii) Educational experience for minorities: In conjunction with this research project, a graduate/undergraduate course on Deformation, Fatigue and Fracture that has been developed by the PI, is enhanced to provide an exciting hands-on experimental component to the class-room learning experience about the fatigue phenomenon.