Fatigue life prediction of film-cooling Hole specimens with initial damage

IF 7.1 1区 工程技术 Q1 ENGINEERING, MECHANICAL
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Abstract

This study investigates a Nickel-based single crystal (SX) superalloy with femtosecond laser-drilled film-cooling holes (FCHs) under varying temperatures (room temperature, 850 °C, and 980 °C), employing a novel framework for predicting fatigue life based on initial manufacturing damage quantification. For all tested anisotropic SX superalloy specimens (including smooth and FCH specimens), the initial damage state is characterized as an equivalent initial flaw size (EIFS), and an EIFS calculation model considering stress concentration is established. Subsequently, the fatigue crack paths and microstructural characteristics of the FCH specimens at different temperatures are analyzed, elucidating crack initiation mechanisms and propagation patterns. A novel incremental plasticity J-integral driving force for fatigue crack propagation is introduced. By incorporating the closure effect of small crack propagation and employing Markov Chain Monte Carlo simulations for determining crack growth rate probabilities, a more accurate expression for the crack growth rate in relation to ΔJfat − ΔJth is derived. This expression comprehensively captures crack patterns on crystallographic planes and Type I mixed mode behavior. Finally, the total fatigue life of the FCH structures, featuring a threefold dispersion zone in both room and high-temperature environments, is predicted through experimental observations and description of crack growth rates. The predicted outcomes significantly outperform those of the conventional life prediction models reliant on crystal plasticity theory.

Abstract Image

具有初始损伤的薄膜冷却孔试样的疲劳寿命预测
本研究调查了在不同温度(室温、850 °C和980 °C)下具有飞秒激光钻孔薄膜冷却孔(FCH)的镍基单晶(SX)超级合金,采用了一种基于初始制造损伤量化预测疲劳寿命的新型框架。对于所有测试的各向异性 SX 超级合金试样(包括光滑试样和 FCH 试样),初始损伤状态被表征为等效初始缺陷尺寸(EIFS),并建立了考虑应力集中的 EIFS 计算模型。随后,分析了 FCH 试样在不同温度下的疲劳裂纹路径和微观结构特征,阐明了裂纹的起始机制和扩展模式。引入了一种新的疲劳裂纹扩展增量塑性 J 积分驱动力。通过纳入小裂纹扩展的闭合效应,并采用马尔科夫链蒙特卡罗模拟确定裂纹生长率概率,得出了与 ΔJfat - ΔJth 相关的更精确的裂纹生长率表达式。该表达式全面反映了晶体平面上的裂纹模式和 I 型混合模式行为。最后,通过实验观察和对裂纹生长率的描述,预测了 FCH 结构在室温和高温环境下的总疲劳寿命,该结构具有三倍分散区。预测结果明显优于依赖晶体塑性理论的传统寿命预测模型。
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来源期刊
International Journal of Mechanical Sciences
International Journal of Mechanical Sciences 工程技术-工程:机械
CiteScore
12.80
自引率
17.80%
发文量
769
审稿时长
19 days
期刊介绍: The International Journal of Mechanical Sciences (IJMS) serves as a global platform for the publication and dissemination of original research that contributes to a deeper scientific understanding of the fundamental disciplines within mechanical, civil, and material engineering. The primary focus of IJMS is to showcase innovative and ground-breaking work that utilizes analytical and computational modeling techniques, such as Finite Element Method (FEM), Boundary Element Method (BEM), and mesh-free methods, among others. These modeling methods are applied to diverse fields including rigid-body mechanics (e.g., dynamics, vibration, stability), structural mechanics, metal forming, advanced materials (e.g., metals, composites, cellular, smart) behavior and applications, impact mechanics, strain localization, and other nonlinear effects (e.g., large deflections, plasticity, fracture). Additionally, IJMS covers the realms of fluid mechanics (both external and internal flows), tribology, thermodynamics, and materials processing. These subjects collectively form the core of the journal's content. In summary, IJMS provides a prestigious platform for researchers to present their original contributions, shedding light on analytical and computational modeling methods in various areas of mechanical engineering, as well as exploring the behavior and application of advanced materials, fluid mechanics, thermodynamics, and materials processing.
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