QUBE: QUasi-Brittle fracture: a 3D Experimentally-validated approach

QUBE：准脆性断裂：一种经过 3D 实验验证的方法

• 批准号: EP/J019992/1
• 负责人: James Marrow
• 金额: $ 48.26万
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2012
• 资助国家: 英国
• 起止时间: 2012 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FJ019992%2F1
• 关键词: QUBE; QUasi; Brittle; fracture; 3D

Ductile materials, like metals and alloys, are widely used in engineering structures either by themselves or as reinforcement. They usually can sustain a lot of plastic damage before failing. Engineers understand quite well the ways that metals fail and how tolerant they are to damage, so efficient and less massive structures may be designed with well-defined margins of safety or reserve strength to cope with extreme events. By comparison, elastic brittle materials such as glasses and ceramics can fail without prior warning, so much larger safety margins are needed.Quasi-brittle materials are an important class of structural materials. They are brittle materials with some tolerance to damage and include concrete, polygranular graphite, ceramic-matrix composites, geological structures like rocks and bio-medical materials such as bone and bone replacements. Although their damage tolerance is much less than many metals and alloys, it can be quite significant compared to brittle materials such as ceramics and glasses. But this is not accounted for very well when engineers design with, or assess, quasi-brittle materials, as there is not an adequate understanding of the role on their damage tolerance of factors such as the microstructure of the material or the state of stress. Quasi-brittle materials are usually treated as fully brittle, taking little or no account of their damage tolerance, so assessments incorporate very significant safety margins, leading to designs that may be inefficient and unnecessarily bulky. Even when some assessment of damage tolerance is included, the microstructure can change as the material ages over time, and we need ways to measure the effects of this and to predict what it will do to the safety of the structure. This project aims to develop a method to predict the performance and evaluate the integrity of structures and components made from quasi-brittle materials. This will extend opportunities for their use in engineering applications, enabling more efficient design with greater confidence in safety.Quasi-brittleness is a property that emerges from the material's microstructure. A quasi-brittle material can be made from a connected network of very brittle parts (for instance, a porous ceramic). It exhibits a characteristic "graceful" failure as parts break locally when loaded sufficiently, which gives it damage tolerance. The "gracefulness" of the failure is affected by the random variations of strength and stiffness of the network and the form of the connections. Such networks represent a key part of the microstructure of the material, and to understand quasi-brittle fracture we need to construct models that properly describe the microstructure. There is a need to understand and define the mechanisms that control the fracture at the small and the large scale within these quasi-brittle materials. This will allow us to capture sensitivity to microstructure differences and degradation, and to produce general models that are suitable for the wide range of quasi-brittle materials and applications.Three-dimensional models that are faithful to the microstructure can be created using modern 3D microscopy methods, such as X-ray computed tomography. But these models are far too complex to simply scale up to structures very large relative to the microstructure. There is no computer than can do this, yet. We will develop modelling methods that sufficiently represent the complexity of quasi-brittle microstructures over a wide range of length scales, such as cellular automata finite elements. We will use advanced tomography and strain mapping techniques to observe how damage develops and to test and refine our models. We will then use this and the understanding that we gain to design new material tests and characterisation methods so that our methods may be used in a wide range of materials, from concretes to advanced nuclear composites, bone replacement biomaterials and geological materials.

延性材料（如金属和合金）本身或作为加固被广泛用于工程结构中。在失败之前，它们通常可以维持很多塑料损害。工程师很好地了解了金属失效的方式以及对破坏的耐受性，因此可以使用明确定义的安全性或储备强度来设计高效且较少的结构，以应对极端事件。相比之下，弹性脆性材料（例如眼镜和陶瓷）可能会在没有事先警告的情况下失败，需要更大的安全边缘。Quasi-brittle材料是重要的结构材料类。它们是易于损害的脆性材料，包括混凝土，多粒石墨，陶瓷 - 马trix复合材料，岩石和生物医学材料（例如骨骼和骨骼替代品）等地质结构。尽管它们的损伤耐受性远低于许多金属和合金，但与诸如陶瓷和眼镜之类的脆性材料相比，它可能非常重要。但是，当工程师设计或评估准脆性材料时，这并不能很好地解释，因为对材料的微观结构或压力状态等因素的损害耐受性没有足够的了解。准脆性材料通常被视为完全脆性，几乎没有考虑其损害耐受性，因此评估包含非常明显的安全边缘，导致设计可能效率低下且不必要地笨重。即使包括对损伤耐受性的某些评估，微结构随着时间的流逝会随着材料的年龄而改变，我们需要方法来衡量其影响并预测其对结构安全性的影响。该项目旨在开发一种方法来预测性能并评估由准脆性材料制成的结构和组件的完整性。这将扩大其在工程应用程序中使用的机会，使更有效的设计对安全性更有信心。quasi-brittless是一种从材料的微观结构中出现的属性。准脆性材料可以由非常脆的零件的连接网络（例如，多孔陶瓷）制成。它表现出特征性的“优雅”故障，因为在充分加载时，零件在本地破裂，从而赋予其损伤。失败的“优美性”受网络强度和刚度的随机变化以及连接形式的影响。这样的网络代表了材料的微观结构的关键部分，并且要了解准脆性断裂，我们需要构建正确描述微结构的模型。有必要理解并定义控制这些准脆性材料中小规模和大规模断裂的机制。这将使我们能够捕获对微观结构差异和退化的敏感性，并产生适合各种准脆性材料和应用的通用模型。可以使用现代3D显微镜创建忠于微观结构的三维模型方法，例如X射线计算机断层扫描。但是这些模型太复杂了，无法简单地扩展到相对于微观结构非常大的结构。还没有计算机可以做到这一点。我们将开发建模方法，以足够代表较宽的长度尺度（例如蜂窝自动机有限元元素）上准脆性微观结构的复杂性。我们将使用高级断层扫描和应变映射技术来观察损害如何发展以及测试和完善我们的模型。然后，我们将使用这一点，并理解我们可以设计新的材料测试和表征方法，以便我们的方法可用于各种材料，从混凝土到先进的核复合材料，骨骼替代生物材料和地质材料。

项目成果

3D Cellular Automata Finite Element Method with Explicit Microstructure: Modeling Quasi-brittle Fracture using Meshfree Damage Propagation

具有显式微观结构的 3D 元胞自动机有限元方法：使用无网格损伤传播模拟准脆性断裂

• DOI: 10.1016/j.mspro.2014.06.186
• 发表时间: 2014
• 期刊: Procedia Materials Science
• 作者: Saucedo-Mora L

Measurements of Stress Concentration Behaviour in AGR Nuclear Graphite

AGR 核石墨中应力集中行为的测量

• 发表时间: 2015
• 作者: Jordan M

Three-dimensional displacement mapping of diffused Pt thermal barrier coatings via synchrotron X-ray computed tomography and digital volume correlation

• DOI: 10.1016/j.scriptamat.2015.10.033
• 发表时间: 2016-04
• 期刊: Scripta Materialia
• 影响因子: 6
• 作者: D. Khoshkhou;M. Mostafavi;C. Reinhard;M. Taylor;D. Rickerby;I. Edmonds;H. Evans;J. Marrow;B. Connolly

In situ measurement of the strains within a mechanically loaded polygranular graphite

• DOI: 10.1016/j.carbon.2015.09.058
• 发表时间: 2016
• 期刊: Carbon
• 影响因子: 10.9
• 作者: T. Marrow;Dong Liu;S. Barhli;L. S. Mora;Yelena Vertyagina;D. Collins;C. Reinhard;S. Kabra

3D cellular automata finite element (CAFE) modelling and experimental observation of damage in quasi-brittle nuclear materials: Indentation of a SiC-SiCfibre ceramic matrix composite

准脆性核材料损伤的 3D 元胞自动机有限元 (CAFE) 建模和实验观察：SiC-SiC 纤维陶瓷基复合材料的压痕

• 发表时间: 2013
• 期刊: International Workshop on Structural Materials for Innovative Nuclear Systems
• 作者: Saucedo Mora L.