Dislocation-Microstructure Interaction at a Crack Tip - In Search of a Driving Force for Short Crack Growth

裂纹尖端的位错-微观结构相互作用 - 寻找短裂纹扩展的驱动力

• 批准号: EP/M000966/1
• 负责人: Liguo Zhao
• 金额: $ 51.18万
• 依托单位: Loughborough University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2014
• 资助国家: 英国
• 起止时间: 2014 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FM000966%2F1
• 关键词: Dislocation; Microstructure; Interaction; Crack; Tip

Nickel-based superalloys are particularly used in applications involving high temperatures and stresses, such as the critical gas-turbine blades and discs in aerospace and power-generation industries. The behaviour of short cracks in nickel superalloys is of particular importance for component design and life prediction, as a large proportion of service life is spent in the growth of small cracks before final failure. Due to the strong influence of local microstructure and heterogeneous stress/strain fields, short cracks are known to grow anomalously under fatigue and tend to exhibit high, irregular and scattered growth rates. The physical driving force for short crack growth is still not well understood yet despite intensive research effort, mainly due to the limited understanding of crack-tip behaviour.This proposal aims to investigate the fundamental deformation mechanism at the tip of a short crack for nickel-based superalloys under fatigue at a range of temperatures. The research will focus on the influence of evolving local plasticity, induced by dislocation dynamics at the crack tip, on short crack growth. The interaction between dislocation and material microstructure is the major source for heterogeneous plasticity and internal stress concentration, leading to initiation and growth of short cracks. Short crack growth testing in a controlled environment will be carried out to study the anomalous behaviour of short crack growth in these alloys under fatigue, which is the expertise of UoS. Temperature will be varied in order to observe the critical effect of temperature change on the slip behaviour near the crack tip. Following crack growth tests, post-mortem transmission-electron-microscopy analyses of crack-tip zone will be performed to reveal the detailed mechanisms for nucleation and multiplication of dislocations, pile-up and penetration of dislocations at phase/grain boundaries and the influence of grain misorientations on dislocation behaviour. In particular, match-stick samples will be extracted from the crack-tip fracture process zone of fatigue-tested specimens to allow in-situ measurements of crack tip deformation under fatigue, which are the established techniques at UoM. In this case, high resolution digital image correlation, with the assistance of grain orientation mapping and scanning-electron-microscopy imaging of gold remodelled surfaces, will be used to quantify shear strain in slip traces formed near the crack tip during fatigue loading. In addition, high energy synchrotron X-ray diffraction studies will be carried out to measure the elastic strain response and load transfer between different phases around the crack tip, which will provide insight regarding the penetration of dislocations into the gamma-prime precipitates.To physically simulate the material plasticity behaviour, a three-dimensional discrete-dislocation-dynamics (DDD) approach will be developed to model the interaction between dislocations and material microstructures, which is the strength of LU, based on experimental results. The DDD model will be interfaced with viscoplasticity and crystal plasticity models, and further applied to investigate the role of dislocation dynamics in depicting short crack growth. A multi-scale finite element method will be established for the crack-tip deformation analyses, which aims to identify a micromechanics-based driving force for short crack growth. Computational simulations will be thoroughly validated against local strain measurements (at both mesoscale and microscale), in-situ and post-mortem measurements as well as X-ray tomography of extracted match-stick samples. The ultimate goal is to deliver an efficient finite element procedure to predict short crack growth, with full validation against the experimental data, for end users.

基于镍的超合金量特别用于涉及高温和压力的应用，例如航空航天和发电行业中的关键气盘叶片和光盘。镍超合金中短裂纹的行为对于组件设计和寿命预测特别重要，因为在最终失败之前，在小裂缝的生长中花费了很大一部分的使用寿命。由于局部微观结构和异质应力/应变场的强烈影响，已知短裂纹在疲劳下异常生长，并且往往表现出高，不规则和散射的生长速率。尽管进行了深入的研究工作，主要是由于对裂纹尖端行为的理解有限，但仍尚不清楚短裂纹生长的物理驱动力。该提案旨在调查镍 - 短裂缝的基本变形机制在一系列温度下，基于疲劳下的超合金。该研究将重点关注裂纹尖端的脱位动力学对短裂纹生长所引起的局部可塑性的影响。位错和材料微观结构之间的相互作用是异质塑性和内部应力浓度的主要来源，导致短裂纹的起始和生长。将在受控环境中进行短裂纹生长测试，以研究疲劳下这些合金的短裂纹生长的异常行为，这是UOS的专业知识。温度将变化，以观察温度变化对裂纹尖端附近的滑动行为的关键作用。经过裂纹生长测试，将对裂纹尖端区域的验尸传播 - 电子显微镜分析进行分析，以揭示对位错的成核和繁殖的详细机制谷物对错位行为的不良对立。特别是，将从疲劳测试标本的裂纹尖端断裂过程区域中提取匹配样品，以允许在疲劳下的裂纹尖端变形的原位测量，这是UOM的既定技术。在这种情况下，高分辨率的数字图像相关性在晶粒方向映射和金重塑表面的扫描 - 电子 - 微观镜检查中，将用于在疲劳载荷期间在裂纹尖端附近形成的滑动痕迹中定量剪切应变。此外，将进行高能同步X射线衍射研究，以测量围绕裂纹尖端的不同阶段之间的弹性应变响应和载荷转移，这将提供有关脱位渗透到伽马 - p-Prime沉淀物的洞察力。模拟材料可塑性行为，将开发出三维离散脱位 - 动力学（DDD）方法，以模拟基于实验结果的位错和材料微观结构之间的相互作用，这是LU的强度。 DDD模型将与粘塑性和晶体可塑性模型相连，并进一步应用用于描述脱位动力学在描述短裂纹生长中的作用。将建立一种用于裂纹尖端变形分析的多尺度有限元方法，该方法旨在确定基于微力学的驱动力以进行短裂纹生长。计算模拟将在局部应变测量值（在中尺度和微观尺度上），原位和验尸测量以及提取的匹配键样样品的X射线层析成像进行彻底验证。最终目标是提供有效的有限元程序，以预测最终用户的实验数据的全面验证，以预测短期裂纹的增长。

项目成果

Coupling of phase field and viscoplasticity for modelling cyclic softening and crack growth under fatigue

• DOI: 10.1016/j.euromechsol.2021.104472
• 发表时间: 2022
• 期刊: European Journal of Mechanics - A/Solids
• 作者: J. Song;L.G. Zhao;H. Qi;S. Li;D. Shi;J. Huang;Y. Su;K. Zhang

Low cycle fatigue of a directionally solidified nickel-based superalloy: Testing, characterisation and modelling

• DOI: 10.1016/j.msea.2017.10.024
• 发表时间: 2017-12-21
• 期刊: MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
• 影响因子: 6.4
• 作者: Kashinga, R. J.;Zhao, L. G.;McColvin, G.
• 通讯作者: McColvin, G.

Computational modelling of full interaction between crystal plasticity and oxygen diffusion at a crack tip

晶体塑性与裂纹尖端氧扩散之间完全相互作用的计算模型

• DOI: 10.1016/j.tafmec.2017.10.010
• 发表时间: 2018
• 期刊: Theoretical and Applied Fracture Mechanics
• 影响因子: 5.3
• 作者: Farukh F

Modelling plastic deformation in a single-crystal nickel-based superalloy using discrete dislocation dynamics

• DOI: 10.1186/s40759-016-0012-y
• 发表时间: 2016-11
• 期刊: Mechanics of Advanced Materials and Modern Processes
• 作者: B. Lin;Minsheng Huang;F. Farukh;A. Roy;V. Silberschmidt;Liguo Zhao

Oxygen Diffusion and Its Coupling with Crystal Plasticity in a Nickel-Based Superalloy

镍基高温合金中氧扩散及其与晶体塑性的耦合

• 发表时间: 2016
• 作者: Liguo Zhao