1.1 本试验方法包括使用以下参数测定金属材料断裂韧性的程序和指南: K，J ，和 CTOD ( D ).韧性可以在 R -曲线格式或作为点值。根据本试验方法测定的断裂韧性是针对载荷的打开模式（模式I）。 附注1: 直到这个版本， K Ic 可以使用该测试方法以及使用测试方法进行评估 E399 为避免重复，评估 K Ic 已从该测试方法中删除，用户将参考测试方法 E399 . 1.2 推荐的试样是单刃弯曲，[SE（B）]，致密，[C（T）]，和盘形致密，[DC（T）]。所有样品都包含因疲劳裂纹而变尖的缺口。 1.2.1 试样尺寸（尺寸）要求根据所应用的断裂韧性分析而变化。该指南是通过考虑材料韧性、材料流动强度以及每个所寻求值的韧性值的单独鉴定要求而制定的。 附注2: 使用参数测定断裂韧性的其他标准方法 K，J 、和CTOD包含在测试方法中 E399 , E1290 ，和 E1921 开发该测试方法是为了提供从单个测试中确定所有适用的韧性参数的通用方法。 1.3 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。 1.4 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。1.5 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 假设存在预先存在的尖锐疲劳裂纹，通过本试验方法确定的材料断裂韧性值表征其对以下物质的抵抗力: (1) 静止裂纹的断裂， (2) 一些稳定撕裂后的骨折， (3) 稳定的撕裂发作，以及 (4) 持续稳定撕裂。当在测试前无法预测材料响应时，该测试方法特别有用。试验方法中规程的应用 E1921 推荐用于测试在韧性到脆性转变中经历解理断裂的铁素体钢。 5.1.1 这些断裂韧性值可以作为材料比较、选择和质量保证的基础。断裂韧性可用于对类似屈服强度范围内的材料进行分级。 5.1.2 这些断裂韧性值可以作为结构缺陷容限评估的基础。需要了解实验室测试和现场条件之间可能存在的差异，以进行适当的容错评估。 5.2 以下警告性声明基于一些观察。 5.2.1 在将与发生一些稳定撕裂后的断裂相关的断裂韧性值应用于结构缺陷容限评估时，必须特别小心。这种响应是铁素体钢在过渡状态下的特征。这种响应对材料不均匀性和可能由平面几何形状、厚度差异、加载模式和结构细节引起的约束变化特别敏感。 5.2.2 The J -R曲线（SE（B）、C（T）和DC（T））已被观察到相对于拉伸载荷配置的结果是保守的。 5.2.3 的价值 D c , D u , J c ，和 J u 可能会受到样本尺寸的影响。

1.1 This test method covers procedures and guidelines for the determination of fracture toughness of metallic materials using the following parameters: K, J , and CTOD ( δ ). Toughness can be measured in the R -curve format or as a point value. The fracture toughness determined in accordance with this test method is for the opening mode (Mode I) of loading. Note 1: Until this version, K Ic could be evaluated using this test method as well as by using Test Method E399 . To avoid duplication, the evaluation of K Ic has been removed from this test method and the user is referred to Test Method E399 . 1.2 The recommended specimens are single-edge bend, [SE(B)], compact, [C(T)], and disk-shaped compact, [DC(T)]. All specimens contain notches that are sharpened with fatigue cracks. 1.2.1 Specimen dimensional (size) requirements vary according to the fracture toughness analysis applied. The guidelines are established through consideration of material toughness, material flow strength, and the individual qualification requirements of the toughness value per values sought. Note 2: Other standard methods for the determination of fracture toughness using the parameters K, J , and CTOD are contained in Test Methods E399 , E1290 , and E1921 . This test method was developed to provide a common method for determining all applicable toughness parameters from a single test. 1.3 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. 1.4 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. 1.5 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 Assuming the presence of a preexisting, sharp, fatigue crack, the material fracture toughness values identified by this test method characterize its resistance to: (1) fracture of a stationary crack, (2) fracture after some stable tearing, (3) stable tearing onset, and (4) sustained stable tearing. This test method is particularly useful when the material response cannot be anticipated before the test. Application of procedures in Test Method E1921 is recommended for testing ferritic steels that undergo cleavage fracture in the ductile-to-brittle transition. 5.1.1 These fracture toughness values may serve as a basis for material comparison, selection, and quality assurance. Fracture toughness can be used to rank materials within a similar yield strength range. 5.1.2 These fracture toughness values may serve as a basis for structural flaw tolerance assessment. Awareness of differences that may exist between laboratory test and field conditions is required to make proper flaw tolerance assessment. 5.2 The following cautionary statements are based on some observations. 5.2.1 Particular care must be exercised in applying to structural flaw tolerance assessment the fracture toughness value associated with fracture after some stable tearing has occurred. This response is characteristic of ferritic steel in the transition regime. This response is especially sensitive to material inhomogeneity and to constraint variations that may be induced by planar geometry, thickness differences, mode of loading, and structural details. 5.2.2 The J -R curve from bend-type specimens recommended by this test method (SE(B), C(T), and DC(T)) has been observed to be conservative with respect to results from tensile loading configurations. 5.2.3 The values of δ c , δ u , J c , and J u may be affected by specimen dimensions.