CAREER: Quantitative Understanding of the Effects of Micro- and Macro-texture on Fatigue Crack Initiation and Early Growth in high Performance Alloys

职业：定量理解微观和宏观织构对高性能合金疲劳裂纹萌生和早期扩展的影响

• 批准号: 0645246
• 负责人: Tongguang Zhai
• 金额: $ 40万
• 依托单位: University of Kentucky Research Foundation
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-07-01 至 2013-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0645246&HistoricalAwards=false
• 关键词: CAREER; Quantitative; Understanding; Effects; Micro

TECHNICAL: This CAREER project addresses the resistance of grain boundaries to short fatigue crack growth and the effects of crystallographic texture and grain structure on the fatigue properties in high performance alloys. Currently, none of the existing models are able to take into account the 3-dimensional effects of microstructure in calculating short fatigue crack growth, and, therefore, their success is limited. This research is built on the PI's recent success in identifying the twist and tilt components of crack plane deflection at grain boundaries as the key factors that control the growth behavior of short cracks across the boundaries. In this research, a uniquely designed fatigue experiment on a single crystal alloy with a fine notch will be carried out in order to reveal the quantitative relation between crack plane deflection and the resistance to crack growth. The effects of texture on the fatigue properties will also be studied in details with electron backscatter diffraction in new generation high strength aluminum alloys that have different textures. The data obtained from all these experiments will be used to develop a 3-d model to quantify the growth behavior of short fatigue cracks by taking into account 3-d interaction between grain boundaries and the crack, and the effects of texture in the alloys. It is anticipated that the results derived from this project will 1) quantify the resistance of grain boundaries to short fatigue crack growth, 2) identify the optimum texture that leads to the more balanced mechanical properties, especially the fatigue properties, and 3) develop a 3D model for better simulation of short crack growth hence improving the methodology for life prediction of key engineering components. NON-TECHNICAL: Quantitative understanding of the interaction of a short fatigue crack with grain boundaries is critical to design of safer engineering structures such as airplanes and spacecrafts, and for more sustainable use of materials. In this project, the research work will be integrated into the PI's teaching activities, and the findings from this research project will also be utilized to promote materials education. A new course on crystallographic texture aimed at upper level undergraduate students and beginning graduate students will be developed to bridge the gap between extensive research and insufficient education in the field of texture. Currently, few universities offer such as a course in the U.S. In addition to graduate students, undergraduate students will also be trained in texture theory and research by participating in experimental and theoretical activities in this project. As an outreach activity in this project, the PI will also develop an on-line self-study course on texture in order to promote education on texture beyond the PI's university and help to train the technical personnel in materials industry about texture and the importance of its control during processing of metallic materials. Feedback about these courses will be actively sought and used to further improve the effectiveness of these courses.

技术支持：这个CAREER项目致力于解决晶界对短疲劳裂纹扩展的阻力以及晶体学织构和晶粒结构对高性能合金疲劳性能的影响。目前，没有一个现有的模型能够考虑到三维微观结构的影响，在计算短疲劳裂纹扩展，因此，他们的成功是有限的。这项研究是建立在PI的最近成功地识别的扭曲和倾斜成分的裂纹平面偏转在晶界的关键因素，控制跨越边界的短裂纹的生长行为。在这项研究中，一个独特的设计上的单晶合金与细切口的疲劳实验将进行，以揭示裂纹平面偏转和裂纹扩展阻力之间的定量关系。本文还将利用电子背散射衍射技术详细研究新一代高强度铝合金中不同织构对疲劳性能的影响。从所有这些实验中获得的数据将被用来开发一个三维模型，以量化短疲劳裂纹的增长行为，考虑到三维晶界和裂纹之间的相互作用，以及在合金中的织构的影响。预计该项目的结果将1）量化晶界对短疲劳裂纹扩展的抵抗力，2）确定导致更平衡的机械性能（特别是疲劳性能）的最佳织构，以及3）开发3D模型以更好地模拟短裂纹扩展，从而改进关键工程部件的寿命预测方法。非技术性：定量了解疲劳短裂纹与晶界的相互作用对于设计更安全的工程结构（如飞机和航天器）以及更可持续地使用材料至关重要。在这个项目中，研究工作将被纳入PI的教学活动，从这个研究项目的结果也将被用来促进材料教育。针对高层次本科生和研究生初期的学生，将开发一门新的晶体学织构课程，以弥补织构领域广泛研究和教育不足之间的差距。目前，在美国很少有大学提供这样的课程。除了研究生外，本科生也将通过参加本项目的实验和理论活动来进行纹理理论和研究的培训。作为该项目的一项推广活动，PI还将开发一个关于纹理的在线自学课程，以促进PI大学以外的纹理教育，并帮助培训材料行业的技术人员了解纹理及其在金属材料加工过程中控制的重要性。将积极征求对这些课程的反馈意见，并利用这些反馈意见进一步提高这些课程的实效。