CAREER: Fundamental Studies of Contact Fatigue in Metallic Materials

技术：研究的目的是全面了解金属材料中的接触疲劳现象。通过建模与实验相结合的方法，为解释接触疲劳损伤的裂纹萌生、载荷作用下裂纹扩展、远场载荷作用下裂纹扩展和快速断裂四个阶段的框架奠定基础。将采用一种独特的基于黏附的分析模型，并结合基于有限元的数值模型，为裂纹萌生和寿命预测提供定量指导。通过对具有广泛不同微观结构的材料（单晶和多晶镍，双晶和片层钛铝化物）的实验，将获得接触疲劳裂纹萌生的关键见解。通过对单晶镍的研究，可以确定接触疲劳的微观结构特征，如位错结构的形成和/或导致裂纹成核的持续滑移带的形成。通过对多晶镍的研究，可以发现晶界在抑制或增强接触疲劳裂纹中的作用。相分布（即双相与片层形式）以及相对于接触几何形状的畴取向对接触疲劳裂纹萌生和扩展的影响将在钛铝化物体系中进行评估。非技术：研究将对飞机、汽车和生物医药行业产生科学和技术影响。科学的理解将有助于开发具有微结构的材料，为飞机结构和生物医学植入物的安全关键部件提供更高的抗接触疲劳能力。这些活动将加强路易斯安那州立大学在先进材料领域的研究基地和教育工作。这项研究将整合一个三层教育计划，包括通过杜兰大学科学学者计划向K-12学生提供外展项目；杜兰大学和泽维尔大学（一所历史上的黑人学院和大学）为本科生和研究生提供课堂和研究机会，并为研究生提供专门的研究培训。此外，近100名高中生、350名本科生、105名少数民族学生和25名研究生将在5年期间受益。此外，还将建立一个包含课程内容和讲座信息的在线档案，方便所有学生和教师通过系里的网站访问。这项拨款由DMR和EPSCoR的金属项目共同资助。

TECHNICAL: Research is directed towards obtaining a comprehensive understanding of the contact fatigue phenomenon in metallic materials. Through an approach that combines modeling and experimentation, the study will lay the foundation for a framework that explains the four stages of contact fatigue damage, namely, crack initiation, crack propagation under load, crack propagation under the influence of far-field loads, and fast fracture. A unique adhesion-based analytical model will be applied, which together with the formulation of a finite element based numerical model, would provide quantitative guidelines for crack initiation and life prediction. From experiment on materials (single crystalline- and polycrystalline-nickel, and duplex- and lamellar- titanium aluminide) with widely different microstructures, key insights on contact fatigue crack initiation will be obtained. Microstructure characteristic of contact fatigue such as the formation of dislocation structures and/or persistent slip bands preceding and contributing to crack nucleation will be identified through the study of single crystalline nickel. The role of grain-boundaries in inhibiting or enhancing contact fatigue cracking will be discerned through the study of polycrystalline nickel. The effects of phase distribution, i.e., duplex vs. lamellar forms, and domain orientations with respect to contact geometry, on contact fatigue crack initiation and propagation will be evaluated in the titanium aluminide system. NON-TECHNICAL: Research would have scientific and technological impact in the aircraft, automotive, and bio-medical industry. The scientific understanding would help in the development of materials with microstructures that provide enhanced resistance to contact fatigue in safety-critical components in aircraft structures and biomedical implants. The activities will enhance Louisiana State's research base and educational efforts in the field of advanced materials. The research would integrate a three-tier educational plan involving outreach programs addressing K-12 students through the Tulane Science Scholar Program; class-room and research opportunities for undergraduate and graduate students at Tulane and Xavier University (a Historically Black College and University) and dedicated research training for graduate students. Additionally, nearly 100 high school students, 350 undergraduates, 105 minorities, and 25 graduate students would benefit from the effort during the five-year period. An online archive incorporating information about course contents and lectures will also be created to provide easy access to all students and faculty through the department web site. This grant is being co-funded by the Metals Program in DMR and EPSCoR.