1.1 这些测试方法旨在根据临界应力强度因子表征塑料的韧性， K Ic公司 以及每单位面积裂纹表面的能量或临界应变能量释放率， G Ic公司 ，在断裂开始时。 1.2 这些测试方法涵盖了两种测试几何形状:单边缺口弯曲（SENB）和紧凑拉伸（CT）。 1.3 所使用的方案假定了裂纹试样的线弹性行为，因此对载荷-位移图的线性施加了一定的限制。 1.4 需要裂纹尖端的平面应变状态。试样厚度必须足以确保该应力状态。 1.5 裂纹必须足够尖锐，以确保获得最小的韧性值。 1.6 这些试验方法的重要性和许多试验条件与试验方法相同 电子399 ，因此，在大多数情况下，与金属标准有许多相似之处。但是，试验方法中未涵盖的某些条件和规范 电子399 ，但对塑料很重要。 1.7 本协议包括确定 G Ic公司 这对于塑料也是特别重要的。 1.8 这些试验方法提供了有关以下要求的一般信息: K Ic公司 和 G Ic公司 测试。与试验方法相同 电子399 ，提供了两个附件，给出了SENB和CT几何形状测试的具体要求。 1.9 通过这些测试方法获得的测试数据是相关的，适用于工程设计。 1.10 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建立适当的安全、健康和环境实践，并确定监管限制的适用性。 注1: 本标准和ISO 13586涉及相同的主题，但技术内容不同。 1.11 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》中确立的国际公认标准化原则制定的。 =====意义和用途====== 5.1 财产 K Ic公司 ( G Ic公司 )通过这些测试方法确定的材料在中性环境中在严重拉伸约束下存在尖锐裂纹时的断裂抗力，与约束方向上的裂纹尺寸和试样尺寸相比，裂纹尖端塑性（或非线性粘弹性）区域较小。 A. K Ic公司 该值被认为代表断裂韧性的下限值。该值已用于估计在役材料的失效应力和缺陷尺寸之间的关系，其中预期会出现上述高约束条件。参考文献 ( 1- 5. ) . 3. 5.1.1 这个 K Ic公司 ( G Ic公司 )给定材料的值是测试速度和温度的函数。此外，已发现循环载荷会导致裂纹扩展 K 值小于 K Ic公司 ( G Ic公司 ). 腐蚀性环境的存在会增加循环或持续载荷下的裂纹扩展。因此 K Ic公司 ( G Ic公司 )在设计服务部件时，应考虑实验室测试和现场条件之间可能存在的差异。 5.1.2 平面应变断裂韧性测试是不寻常的，因为有时没有预先保证 K Ic公司 ( G Ic公司 )将在特定测试中确定。因此，如本文所述，必须仔细考虑所有关于结果有效性的标准。 5.1.3 显然，无法确定 K Ic公司 ( G Ic公司 )如果材料的可用库存的任何尺寸不足以提供所需尺寸的样品。 5.2 由于塑料的断裂韧性通常取决于试样工艺历史，即注射成型、挤压成型、压缩成型等，因此应在报告表中注明相对于任何加工方向的试样裂纹方向（平行或垂直） 10.1 . 5.3 在进行本试验方法之前，应参考被测材料的规范。 相关ASTM材料规范中涵盖的任何试样制备、调节、尺寸或试验参数或其组合应优先于本试验方法中提及的那些。如果没有相关的ASTM材料规范，则默认条件适用。

1.1 These test methods are designed to characterize the toughness of plastics in terms of the critical-stress-intensity factor, K Ic , and the energy per unit area of crack surface or critical strain energy release rate, G Ic , at fracture initiation. 1.2 Two testing geometries are covered by these test methods, single-edge-notch bending (SENB) and compact tension (CT). 1.3 The scheme used assumes linear elastic behavior of the cracked specimen, so certain restrictions on linearity of the load-displacement diagram are imposed. 1.4 A state-of-plane strain at the crack tip is required. Specimen thickness must be sufficient to ensure this stress state. 1.5 The crack must be sufficiently sharp to ensure that a minimum value of toughness is obtained. 1.6 The significance of these test methods and many conditions of testing are identical to those of Test Method E399 , and, therefore, in most cases, appear here with many similarities to the metals standard. However, certain conditions and specifications not covered in Test Method E399 , but important for plastics, are included. 1.7 This protocol covers the determination of G Ic as well, which is of particular importance for plastics. 1.8 These test methods give general information concerning the requirements for K Ic and G Ic testing. As with Test Method E399 , two annexes are provided which give the specific requirements for testing of the SENB and CT geometries. 1.9 Test data obtained by these test methods are relevant and appropriate for use in engineering design. 1.10 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. Note 1: This standard and ISO 13586 address the same subject matter, but differ in technical content. 1.11 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 The property K Ic ( G Ic ) determined by these test methods characterizes the resistance of a material to fracture in a neutral environment in the presence of a sharp crack under severe tensile constraint, such that the state of stress near the crack front approaches plane strain, and the crack-tip plastic (or non-linear viscoelastic) region is small compared with the crack size and specimen dimensions in the constraint direction. A K Ic value is believed to represent a lower limiting value of fracture toughness. This value has been used to estimate the relation between failure stress and defect size for a material in service wherein the conditions of high constraint described above would be expected. Background information concerning the basis for development of these test methods in terms of linear elastic fracture mechanics can be found in Refs ( 1- 5 ) . 3 5.1.1 The K Ic ( G Ic ) value of a given material is a function of testing speed and temperature. Furthermore, cyclic loads have been found to cause crack extension at K values less than K Ic ( G Ic ). Crack extension under cyclic or sustained load will be increased by the presence of an aggressive environment. Therefore, application of K Ic ( G Ic ) in the design of service components should be made considering differences that may exist between laboratory tests and field conditions. 5.1.2 Plane-strain fracture toughness testing is unusual in that sometimes there is no advance assurance that a valid K Ic ( G Ic ) will be determined in a particular test. Therefore it is essential that all of the criteria concerning validity of results be carefully considered as described herein. 5.1.3 Clearly, it will not be possible to determine K Ic ( G Ic ) if any dimension of the available stock of a material is insufficient to provide a specimen of the required size. 5.2 Inasmuch as the fracture toughness of plastics is often dependent on specimen process history, that is, injection molded, extruded, compression molded, etc., the specimen crack orientation (parallel or perpendicular) relative to any processing direction shall be noted on the report form discussed in 10.1 . 5.3 Before proceeding with this test method, reference should be made to the specification of the material being tested. Any test specimen preparation, conditioning, dimensions, or testing parameters, or combination thereof, covered in the relevant ASTM materials specification shall take precedence over those mentioned in this test method. If there are no relevant ASTM material specifications, then the default conditions apply.