1.1 本指南提供了测量人造石墨和碳试样断裂功的一般教程信息和最佳实践。虽然适用于所有碳和石墨材料，但本指南专门针对核石墨所需的测量，其中试样的几何形状和/或体积可能有限制。 1.2 以SI单位表示的值将被视为标准值。SI单位后括号中给出的值仅供参考，不被视为标准值。 1.3 本标准并不旨在解决与其使用相关的所有安全性问题（如果有）。本标准的使用者有责任在使用前建立适当的安全、健康和环境实践并确定法规限制的适用性。1.4 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认的标准化原则制定的。 ======意义和用途====== 5.1 结构完整性评估通常使用强度和弹性模量值来预测石墨部件中的裂纹萌生，并且有一套ASTM标准（第 2 、试验方法 C651 , C695 , C747 , C749 , C769 ，和指南 D7775 ）以涵盖这些属性的测量。 5.2 裂纹萌生后石墨组分的行为取决于断裂力学参数，如断裂韧性和断裂功。试验方法 D7779 提供了基于线弹性应力分析测量石墨断裂韧性的规范和要求。此外，测试方法 D7779 适用于对样品尺寸以及适用的加工和样品制备技术没有限制的情况。 5.3 大多数多晶石墨是非线性弹性、非均匀、准脆性材料。对于此类材料，确定断裂特性的有效方法是分析与裂纹扩展相关的整体能量平衡，类似于Griffith的脆性断裂理论。这种方法没有非线性弹性断裂的数学复杂性，在实践中更容易实现。 5.4 断裂功γ f （焦耳/米 2 ），定义为形成裂纹所需的能量除以裂纹的横截面积。假设在裂纹扩展过程中单位面积的能量是恒定的。通常，与将裂纹扩展到全尺寸所需的功相比，具有到断裂点的过量应变能的部件会因快速断裂而失效。任何多余的能量都通过产生应力波的过程转化为动能。如果过量能量的量足够大，则应力波将具有大于材料强度的峰值幅度，导致可能导致部件碎裂的二次裂纹的萌生和扩展。 5.5 然而，一些在断裂点的应变能小于将裂纹扩展到全尺寸所需的功的构件以准脆性方式失效，并导致稳定裂纹、裂纹桥接和分布的微-开裂。石墨部件通常在其制造状态下进行测试，并且在这些极端之间的某处失效，表现出快速断裂，具有相对少量的二次破裂和很小的碎裂倾向。反应器环境中石墨组分的WoF和应变速率的变化对于评估组分的二次开裂和碎裂的趋势是重要的。

1.1 This guide provides general tutorial information and best practice for measuring the work of fracture on manufactured graphite and carbon specimens. Although applicable to all carbon and graphite materials, this guide is aimed specifically at measurements required on nuclear graphites, where there may be constraints on the geometry and/or volume of the test specimen. 1.2 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 5.1 Structural integrity assessments typically use values of strength and elastic modulus to predict crack initiation in graphite components and there is a suite of ASTM standards (Section 2 , Test Methods C651 , C695 , C747 , C749 , C769 , and Guide D7775 ) to cover the measurement of these properties. 5.2 The graphite component behavior after crack initiation depends on fracture mechanics parameters, such as fracture toughness and the work of fracture. Test Method D7779 provides the specification and requirements for measuring the fracture toughness of graphite based on linear-elastic stress analysis. Moreover, Test Method D7779 applies to cases where there are no restrictions on specimen size and on applicable machining and specimen preparation techniques. 5.3 Most polycrystalline graphites are non-linear elastic, non-uniform, quasi-brittle materials. For such materials, an effective approach for the determination of fracture properties is the analysis of the global energy balance associated with crack extension, similar to Griffith's theory of brittle fracture. This approach does not have the mathematical complexity of the non-linear elastic fracture and is easier to implement in practice. 5.4 Work of Fracture, γ f (J/m 2 ), is defined as the energy required to form a crack divided by the cross sectional area of the crack. It is assumed that the energy per unit area is constant during crack propagation. In general, components that have an excess of strain energy to the point of fracture, compared to the work needed to extend the crack to full dimension, fail by fast fracture. Any excess energy is converted into kinetic energy through a process that generates stress waves. If the amount of excess energy is sufficiently large, the stress waves will have peak magnitudes greater than the material strength, leading to the initiation and propagation of secondary cracks that could result in the fragmentation of the component. 5.5 However, some components that have less strain energy at the point of fracture than the work needed to extend the crack to full dimension, fail in a quasi-brittle manner and result in stable cracks, crack bridging and distributed micro-cracking. Graphite components are generally tested in their as-manufactured state and fail somewhere between these extremes showing fast fracture with relatively minor amounts of secondary cracking and little tendency to fragment. The change in the WoF and strain rate of graphite components in a reactor environment is important in assessing the component’s tendency for secondary cracking and fragmentation.