Characterization, Modeling, and Prediction of Fatigue Damage Under Variable Amplitude Loading

疲劳是承受振动的结构系统中无处不在的问题，并可能导致灾难性的故障、伤害和生命损失。疲劳损伤的定量预测是工程实践中一个尚未解决的关键问题。该奖项支持建立材料疲劳和结构动力学之间联系的基础研究。这样的链接使疲劳损伤建模和预测，是有效的结构健康监测和基于状态的维护技术不可或缺的组成部分。项目目标的成功实现将提高关键基础设施和机械的安全性和性能，并将为美国经济和社会带来广泛的利益。该项目具有多学科性质，包括材料科学，动力系统建模，疲劳测试和非线性时间序列分析。研究方法和项目的结果也将丰富工程教育和扩大参与的代表性不足的群体在跨学科research.Current的疲劳机制在微观尺度上的理解是不足以提供适用于宏观尺度的疲劳寿命估计的信息。此外，现有的模型和受损结构的动态行为的分析不直接产生洞察疲劳机制或疲劳预测。该奖项将支持跨其不同阶段的疲劳演化研究，其与结构动力学和载荷的相互作用，以及载荷对疲劳动力学的影响。分析，数值和实验研究的组合将进行调查疲劳累积和结构振动之间的相互作用。研究结果将用于变幅载荷条件下的实际疲劳寿命预测。该项目将制定一个建模方法，允许利用非线性载荷特性进行疲劳寿命预测。由此产生的损伤模型和疲劳寿命预测方法-使用新的，物理上有意义的，易于估计的负载指标-将有助于设计抗疲劳，并实现有效的疲劳预测。

Fatigue is an omnipresent problem in structural systems subjected to vibrations, and can lead to catastrophic failures, injuries, and loss of life. Quantitative prognostication of fatigue damage is still a largely unresolved and critical problem of engineering practice. This award supports fundamental research establishing the connection between material fatigue and structural dynamics. Such a link enables fatigue damage modeling and prediction and is an indispensable component of effective structural health monitoring and condition-based maintenance technologies. Successful achievement of the project objectives will enhance safety and performance of critical infrastructure and machinery, and will provide wide-ranging benefits to the U.S. economy and society. The project has a multidisciplinary nature incorporating material science, dynamical systems modeling, fatigue testing, and nonlinear time series analysis. The research approach and the project findings will also enrich engineering education and broaden participation of underrepresented groups in cross-disciplinary research.Current understanding of fatigue mechanisms at the micro-scale is not sufficient to provide information applicable to macro-scale fatigue life estimation. Furthermore, existing models and analyses of the dynamic behavior of damaged structures do not directly yield insight into fatigue mechanisms or fatigue prediction. This award will support the study of fatigue evolution across its different stages, its interaction with structural dynamics and loads, and the effect of loads on fatigue dynamics. A combination of analytical, numerical, and experimental studies will be conducted to investigate the interaction between fatigue accumulation and structural oscillations. The findings will be employed for practical fatigue life prediction under variable amplitude loading conditions. The project will formulate a modeling approach that permits the exploitation of nonlinear load characteristics for fatigue life prediction. The resulting damage model and method for fatigue life prediction - using new, physically meaningful, and easy to estimate load metrics - will be instrumental in designing against fatigue, and enabling effective fatigue prognostication.