GOALI: Investigation by Ultrasonic Methods of the Very long Life Fatigue Behavior of Structural Aluminum and Magnesium Alloys

该项目研究了铸造铝和镁结构合金的长寿命疲劳行为，这些合金在汽车和其他需要轻质材料的技术中得到应用。研究的目的是建立精确的裂纹起裂和短裂纹扩展模型，用于预测疲劳寿命。使用频率约为20khz的超声疲劳循环载荷，可在实际时间框架内实现非常长的使用寿命。所提出的方法远比耗时的传统技术更具成本效益。该计划将研究导致这种重要合金存在或不存在耐久性限制的基本机制。一项重要的工作将集中在超声波疲劳技术的潜在用途上，作为更传统测试方法的可行替代或替代方法，特别是在临界疲劳寿命处于很长寿命状态的情况下。该GOALI计划将继续密歇根大学和福特汽车公司福特研究实验室（FRL）之间的成功合作。共同项目负责人将共同指导一名博士生。这项工作的教育影响在于研究生通过暑期实习与工业界的同行密切接触，以及来自福特的合作研究者的研究方向。该项目为研究生和大学人员提供了一个机会，与福特汽车公司的工业同行一起开发具有很长疲劳寿命的铸铝和镁合金。研究结果不仅有利于汽车工业，也有利于需要轻质抗疲劳金属合金的技术。该研究将建立表征超长疲劳寿命的新技术，利用学术界和工业界的专业知识和设备，找到许多实际应用。

This project investigates the long life fatigue behavior of cast aluminum and magnesium structural alloys that find application in automotive and other technologies where lightweight materials are required. An objective of the study is to develop accurate models of crack initiation and short crack growth that can be used for predicting fatigue life. Very long lifetimes will be achieved in a practical timeframe using ultrasonic fatigue in which cyclic loading is applied at frequencies of approximately 20 kHz. The proposed method is far more cost effective than the conventional techniques that are extremely time consuming. The proposed program will examine the fundamental mechanisms responsible for the presence or absence of endurance limits in this important set of alloys. A significant effort will be focused on the potential use of ultrasonic fatigue techniques as a viable alternative or replacement for more conventional testing methods, especially where critical fatigue lives are in the very long life regime. This proposed GOALI program would continue a successful collaboration between the University of Michigan and the Ford Research Laboratories (FRL) of Ford Motor Company. The co-PI will co-advise a PhD student on this project. The educational impact of this work lies in close contact of the graduate students with the industrial counterpart through summer internships as well as the research direction by the co-investigator from Ford.This project provides an opportunity to graduate research students and university personnel to work with industrial counterparts at the Ford Motor Company in developing cast aluminum and magnesium alloys with very long fatigue life. The results of the study will benefit not only automotive industry but also technologies that require lightweight fatigue resistant metallic alloys. The research will establish new techniques of characterizing very long fatigue lifetimes that find many practical applications by taking advantage of the expertise and facilities at the academia and industry.