1.1 本试验方法涵盖了通过圆盘径向压缩测定石墨劈裂抗拉强度的试验装置、试样制备和试验程序。该小试样几何形状（试验方法 D7779 )专门用于辐照胶囊。提醒用户使用测试方法 C749 如果可能，用于测量石墨的抗拉强度特性。 1.2 以国际单位制表示的数值应视为标准值。国际单位制后括号中给出的值仅供参考，不被视为标准值。 1.3 所有尺寸、力测量和应力计算应符合实践中制定的有效数字和舍入准则 D6026 . 1.4 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 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》中确立的国际公认标准化原则制定的。 ====意义和用途====== 4.1 根据定义，制造石墨的抗拉强度是通过直接单轴拉伸试验（试验方法）获得的 C749 ). 这个 C749 拉伸试样相对较大，通常与可用的辐照容器体积或氧化装置不兼容（试验方法 D7542 ). 劈裂拉伸试验提供了一种替代方法，用于测试具有严重几何约束的试样的拉伸性能，否则无法满足试验方法规定的试验几何 C749 . 通过在压缩载荷下在边缘加载圆盘状试样，产生的横向于加载轴的拉伸应力提供了石墨抗拉强度特性的指示。为了获得一致且有意义的劈裂抗拉强度值，至关重要的是，断裂发生在圆盘的中心，而不是沿着边缘。该标准试验有助于确保圆盘试样由于垂直于加载轴的拉伸应力而沿加载直径发生径向断裂，并且断裂始于圆盘中心。 4.2 使用径向压缩试验确定的应力是在规定条件下加载时，圆盘中心的最大拉伸应力，断裂始于圆盘中心。应了解，该拉伸应力值是在复杂的双轴应力条件下通过试样获得的。当仔细且一致地进行试验时，这些拉伸应力值彼此具有可比性，但该试验的执行者应验证获得的值。将本标准值与使用试验方法获得的单轴拉伸应力值进行比较时的任何偏差 C749 应予以识别和报告。验证应在同一材料上进行，并且可能不适用于同一材料的其他状态（例如，氧化、辐照）。有关小样本测试的指南，请参阅指南 D7775 .

1.1 This test method covers testing apparatus, specimen preparation, and testing procedures for determining the splitting tensile strength of graphite by diametral line compression of a disk. This small specimen geometry (Test Method D7779 ) is specifically intended for irradiation capsule use. Users are cautioned to use Test Method C749 if possible for measuring tensile strength properties of graphite. 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 All dimension and force measurements and stress calculations shall conform to the guidelines for significant digits and rounding established in Practice D6026 . 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 ====== 4.1 By definition, the tensile strength of manufactured graphite is obtained by the direct uniaxial tensile test (Test Method C749 ). The C749 tensile test specimen is relatively large and is frequently incompatible with available irradiation capsule volumes, or oxidation apparatus (Test Method D7542 ). The splitting tensile test provides an alternate means of testing tensile properties on specimens that have severe geometric constraints and otherwise cannot meet the prescribed testing geometries of Test Method C749 . By loading a disc-shaped specimen, on edge, under a compressive load, the resulting tensile stresses transverse to the loading axis provide an indication of the tensile strength properties of graphite. To obtain consistent and meaningful values of a splitting tensile strength, it is vital that the fracture initiate in the center of the disk and not along an edge. This standard test helps to ensure that the disk specimens break diametrally along the loading diameter due to tensile stresses that are perpendicular to the loading axis and that the fracture initiates at the center of the disk. 4.2 The stress determined using the diametral compression test is the maximum tensile stress at the center of the disk when loaded under the prescribed conditions and the fracture initiates at the center of the disk. It should be understood that this tensile stress value is obtained with the specimen in a complex biaxial stress condition. When the test is performed carefully and consistently these tensile stress values are comparable to each other, but the performers of this test should validate the values obtained. Any bias when comparing values with this standard to the uniaxial tensile stress values obtained using Test Method C749 should be identified and reported. Validation shall be performed on the same material and may not be applicable to other states of the same material (for example, oxidized, irradiated). Guidance on small specimen testing can be found in Guide D7775 .