1.1 本规程涵盖了表面裂纹张力（SCT）试样的设计、制备和测试。它特别涉及在持续增加的力下进行的测试，不包括循环和持续载荷。确定的数量是一个表面上有半椭圆形或圆形疲劳裂纹的试样的残余强度。该值取决于裂纹尺寸、试样厚度以及材料特性。 1.2 可以测试的金属材料不受强度、厚度或韧性的限制。然而，对坚韧材料的厚试样进行测试可能需要一台容量极高的拉伸试验机。本规程对非金属材料的适用性尚未确定。 1.3 这种做法仅限于试验截面中具有均匀矩形横截面的试样。 试验段的宽度和长度必须大于裂纹长度。应选择适合试验最终目的的裂纹深度和长度。 1.4 残余强度可能在很大程度上取决于特定范围内的温度，这取决于材料的特性。这种做法适用于任何适当温度下的测试。 1.5 在常规拉伸试验中通常使用的范围内，残余强度被认为对加载速率相对不敏感。当预期使用中的装载率非常低或非常高时，应使用超出本规范范围的特殊程序来调查装载率的影响。 注1: 关于此类试验的背景和需求的更多信息，请参阅ASTM任务组E24.01.05关于零件贯穿裂纹试验的报告( 1. )。 2. 1.6 以国际单位制或英寸磅单位表示的数值应单独视为标准。每个系统中规定的值可能不是完全相等的；因此，每个系统应独立使用。将两个系统的值合并可能导致不符合标准。 1.7 本标准并不旨在解决与其使用相关的所有安全问题（如有）。本标准的使用者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。 1.8 本国际标准是根据世界贸易组织技术性贸易壁垒委员会发布的《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====== 4.1 表面裂纹张力（SCT）试验用于评估具有可能在使用中出现的缺陷类型的简单片状或板状结构构件的承载能力。该试验也用于研究目的，以研究在使用条件下裂纹的失效机制。 4.2 SCT试样的残余强度是裂纹深度和长度、试样厚度以及材料特性的函数。这种关系极其复杂，目前无法完全描述或描述。 4.2.1 只有当服务条件与测试条件完全平行时，SCT测试的结果才适合直接应用于设计。中建议了一些进一步分析的方法 附录X1 。 4.3 为了使SCT测试数据具有可比性和可重复性，并在实验室之间建立相关性，建立统一的SCT测试实践至关重要。 4.4 本规程中描述的试样配置、制备和仪器通常也适用于循环力或持续力测试。然而，这些测试中的每一个都有特定的约束条件。这些超出了本规程的范围，但在参考文献1中进行了讨论。 ( 1. )。

1.1 This practice covers the design, preparation, and testing of surface-crack tension (SCT) specimens. It relates specifically to testing under continuously increasing force and excludes cyclic and sustained loadings. The quantity determined is the residual strength of a specimen having a semielliptical or circular-segment fatigue crack in one surface. This value depends on the crack dimensions and the specimen thickness as well as the characteristics of the material. 1.2 Metallic materials that can be tested are not limited by strength, thickness, or toughness. However, tests of thick specimens of tough materials may require a tension test machine of extremely high capacity. The applicability of this practice to nonmetallic materials has not been determined. 1.3 This practice is limited to specimens having a uniform rectangular cross section in the test section. The test section width and length must be large with respect to the crack length. Crack depth and length should be chosen to suit the ultimate purpose of the test. 1.4 Residual strength may depend strongly upon temperature within a certain range depending upon the characteristics of the material. This practice is suitable for tests at any appropriate temperature. 1.5 Residual strength is believed to be relatively insensitive to loading rate within the range normally used in conventional tension tests. When very low or very high rates of loading are expected in service, the effect of loading rate should be investigated using special procedures that are beyond the scope of this practice. Note 1: Further information on background and need for this type of test is given in the report of ASTM Task Group E24.01.05 on Part-Through-Crack Testing ( 1 ). 2 1.6 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard. 1.7 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. 1.8 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 The surface-crack tension (SCT) test is used to estimate the load-carrying capacity of simple sheet- or plate-like structural components having a type of flaw likely to occur in service. The test is also used for research purposes to investigate failure mechanisms of cracks under service conditions. 4.2 The residual strength of an SCT specimen is a function of the crack depth and length and the specimen thickness as well as the characteristics of the material. This relationship is extremely complex and cannot be completely described or characterized at present. 4.2.1 The results of the SCT test are suitable for direct application to design only when the service conditions exactly parallel the test conditions. Some methods for further analysis are suggested in Appendix X1 . 4.3 In order that SCT test data can be comparable and reproducible and can be correlated among laboratories, it is essential that uniform SCT testing practices be established. 4.4 The specimen configuration, preparation, and instrumentation described in this practice are generally suitable for cyclic- or sustained-force testing as well. However, certain constraints are peculiar to each of these tests. These are beyond the scope of this practice but are discussed in Ref. ( 1 ).