1.1 本试验方法包括通过恒定应力速率矩形梁弯曲试验、环对环双轴圆盘弯曲试验或直接拉伸强度来测定高级陶瓷的缓慢裂纹扩展（SCG）参数，其中强度是在环境温度下给定环境中施加应力速率的函数。在特定环境中，随着施加应力速率的降低而表现出的强度退化是该试验方法的基础，该方法能够评估材料的缓慢裂纹扩展参数。 注1: 该试验方法通常被称为“动态疲劳”试验 ( 1- 3. ) 2. 其中术语“疲劳”与术语“缓慢裂纹扩展”互换使用避免与术语中定义的仅在循环载荷下发生的材料“疲劳”现象混淆 E1823 ，该试验方法使用术语“恒定应力速率试验”而不是“动态疲劳”试验。 注2: 在玻璃和陶瓷技术中，相当长时间的静态试验称为“静态疲劳”试验，这是一种指定为应力断裂的试验（见术语 E1823 ). 1.2 本试验方法中表示的数值符合国际单位制（SI）和 IEEE/ASTM SI 10 . 1.3 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。 1.4 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》中确立的国际公认标准化原则制定的。 ====意义和用途====== 4.1 对于使用中的许多结构陶瓷部件，其使用寿命通常受到SCG工艺控制的限制。该试验方法为评估陶瓷材料在特定环境下的相对SCG敏感性提供了经验参数。此外，该试验方法可以确定加工变量和成分对SCG的影响以及对新开发或现有材料强度行为的影响，从而允许裁剪和优化材料加工以进行进一步修改。 总之，该试验方法可用于材料开发、质量控制、表征和有限设计数据生成目的。恒定应力速率测试的传统分析基于许多关键假设，其中最重要的假设将在下一段中列出。 4.2 矩形梁试样或等双轴圆盘弯曲试样的弯曲应力计算基于简单梁理论，假设材料是各向同性和均匀的，拉伸和压缩弹性模量相同，并且材料是线性弹性的。 平均晶粒度不应大于梁厚度的五十分之一。 4.3 矩形梁试样的试样尺寸和夹具应符合试验方法 C1161 ，它在实际配置和产生的误差之间提供了平衡，如参考文献中所述 ( 4. , 5. ) . 本试验方法仅允许四点试验配置用于矩形梁试样。不允许使用三点测试配置。应根据试验方法选择在环对环弯曲中测试的圆盘试样的试样尺寸和夹具 C1499 . 应根据试验方法选择直接抗拉强度试验的试样 C1273 . 4.4 SCG参数( n 和 D )通过将测量的实验数据拟合到强度和施加应力速率logσ之间的数学关系来确定 f = 1/( n +1） 日志 σ ˙ +日志 D . 推导该关系的基本假设是，SCG由经验幂律裂纹速度控制， v=A [ K 我 / K 集成电路 ] n （参见 附录X1 ). 注3: 还有各种其他形式的裂纹速度定律，通常在数学上更复杂或不太方便，或两者兼有，但在物理上可能更现实 ( 6. ) . 人们普遍认为，实际数据无法可靠地区分各种公式。因此，本试验方法中的数学分析不包括此类替代裂纹速度公式。 4.5 基于慢裂纹扩展参数至少为的假设，推导了强度和应力速率之间的数学关系 n ≥ 5. ( 1. , 7. , 8. ) . 因此，如果一种材料对SCG表现出非常高的敏感性，即， n <5，在解释结果时应特别小心。 4.6 根据中的方法对测试结果进行数学分析 4.4 假设材质不显示上升 R -曲线行为。应注意的是，这种行为的存在无法通过该试验方法确定。 4.7 暴露在应力腐蚀性气体或液体环境中的陶瓷材料的缓慢裂纹扩展行为可能随着机械、材料和电化学变量的变化而变化。因此，测试结果准确反映研究中特定变量的影响至关重要。只有这样，才能在有效的基础上将一项调查的数据与另一项调查的数据进行比较，或将其作为表征材料和评估结构行为的有效基础。 4.8 高级陶瓷的强度本质上是概率的。因此，由陶瓷材料强度确定的SCG也是一种概率现象。因此，统计再现性和设计需要适当的施加应力速率范围和数量以及每个施加应力速率下适当数量的试样 ( 2. ) . 本试验方法中提供了指南。 注4: 对于给定的陶瓷材料/环境系统，SCG参数 n 尽管其再现性取决于中提到的变量，但无论样本大小，其均为常数 4.8 . 相比之下，SCG参数 D 很大程度上取决于强度，因此取决于试样尺寸（参见 等式X1.6 在里面 附录X1 ). 4.9 给定试样和测试夹具配置的陶瓷材料的强度取决于其固有的抗断裂能力、缺陷的存在和环境影响。尽管不在本试验方法的范围内，但强烈建议对断口进行分析，尤其是为了验证与故障相关的机制（参考实践） C1322 ). 4.10 恒定应力速率试验的传统分析基于一个关键假设，即应力在整个试件中是均匀的。 这在直接拉伸试样中最容易实现。仅应使用在四点测试中内部量规部分断裂的试样。不得使用三点弯曲。外部和内部夹具接触点之间的断裂应予以考虑。同样的要求适用于双轴圆盘强度测试。只能使用内加载循环中发生的断裂。此外，假设断裂起源靠近拉伸表面，并且相对于矩形梁弯曲或圆盘强度试样的厚度不会增长很大。 4.11 恒定应力速率试验的传统分析也基于一个关键假设，即相同类型的缺陷控制所有加载速率下所有试样的强度。如果缺陷分布是多模态的，则本标准中的常规分析可能会产生错误的缓慢裂纹扩展参数估计。

1.1 This test method covers the determination of slow crack growth (SCG) parameters of advanced ceramics by using constant stress rate rectangular beam flexural testing, ring-on-ring biaxial disk flexural testing, or direct tensile strength, in which strength is determined as a function of applied stress rate in a given environment at ambient temperature. The strength degradation exhibited with decreasing applied stress rate in a specified environment is the basis of this test method which enables the evaluation of slow crack growth parameters of a material. Note 1: This test method is frequently referred to as “dynamic fatigue” testing ( 1- 3 ) 2 in which the term “fatigue” is used interchangeably with the term “slow crack growth.” To avoid possible confusion with the “fatigue” phenomenon of a material which occurs exclusively under cyclic loading, as defined in Terminology E1823 , this test method uses the term “constant stress rate testing” rather than “dynamic fatigue” testing. Note 2: In glass and ceramics technology, static tests of considerable duration are called “static fatigue” tests, a type of test designated as stress rupture (See Terminology E1823 ). 1.2 Values expressed in this test method are in accordance with the International System of Units (SI) and IEEE/ASTM SI 10 . 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 ====== 4.1 For many structural ceramic components in service, their use is often limited by lifetimes that are controlled by a process of SCG. This test method provides the empirical parameters for appraising the relative SCG susceptibility of ceramic materials under specified environments. Furthermore, this test method may establish the influences of processing variables and composition on SCG as well as on strength behavior of newly developed or existing materials, thus allowing tailoring and optimizing material processing for further modification. In summary, this test method may be used for material development, quality control, characterization, and limited design data generation purposes. The conventional analysis of constant stress rate testing is based on a number of critical assumptions, the most important of which are listed in the next paragraphs. 4.2 The flexural stress computation for the rectangular beam test specimens or the equibiaxial disk flexure test specimens is based on simple beam theory, with the assumptions that the material is isotropic and homogeneous, the moduli of elasticity in tension and compression are identical, and the material is linearly elastic. The average grain size should be no greater than one-fiftieth of the beam thickness. 4.3 The test specimen sizes and fixtures for rectangular beam test specimens should be in accordance with Test Method C1161 , which provides a balance between practical configurations and resulting errors, as discussed in Refs ( 4 , 5 ) . Only four-point test configuration is allowed in this test method for rectangular beam specimens. Three-point test configurations are not permitted. The test specimen sizes and fixtures for disk test specimens tested in ring-on-ring flexure should be chosen in accordance with Test Method C1499 . The test specimens for direct tension strength testing should be chosen in accordance with Test Method C1273 . 4.4 The SCG parameters ( n and D ) are determined by fitting the measured experimental data to a mathematical relationship between strength and applied stress rate, log σ f = 1/( n +1) log σ ˙ + log D . The basic underlying assumption on the derivation of this relationship is that SCG is governed by an empirical power-law crack velocity, v = A [ K I / K IC ] n (see Appendix X1 ). Note 3: There are various other forms of crack velocity laws which are usually more complex or less convenient mathematically, or both, but may be physically more realistic ( 6 ) . It is generally accepted that actual data cannot reliably distinguish between the various formulations. Therefore, the mathematical analysis in this test method does not cover such alternative crack velocity formulations. 4.5 The mathematical relationship between strength and stress rate was derived based on the assumption that the slow crack growth parameter is at least n ≥ 5 ( 1 , 7 , 8 ) . Therefore, if a material exhibits a very high susceptibility to SCG, that is, n < 5, special care should be taken when interpreting the results. 4.6 The mathematical analysis of test results in accordance with the method in 4.4 assumes that the material displays no rising R -curve behavior. It should be noted that the existence of such behavior cannot be determined from this test method. 4.7 Slow crack growth behavior of ceramic materials exposed to stress-corrosive gases or liquid environments can vary as a function of mechanical, material, and electrochemical variables. Therefore, it is essential that test results accurately reflect the effects of specific variables under study. Only then can data be compared from one investigation to another on a valid basis or serve as a valid basis for characterizing materials and assessing structural behavior. 4.8 The strength of advanced ceramics is probabilistic in nature. Therefore, SCG that is determined from the strengths of a ceramic material is also a probabilistic phenomenon. Hence, a proper range and number of applied stress rates in conjunction with an appropriate number of specimens at each applied stress rate are required for statistical reproducibility and design ( 2 ) . Guidelines are provided in this test method. Note 4: For a given ceramic material/environment system, the SCG parameter n is constant regardless of specimen size although its reproducibility is dependent on the variables mentioned in 4.8 . By contrast, the SCG parameter D depends significantly on strength and thus on specimen size (see Eq X1.6 in Appendix X1 ). 4.9 The strength of a ceramic material for a given specimen and test fixture configuration is dependent on its inherent resistance to fracture, the presence of flaws, and environmental effects. Analysis of a fracture surface, fractography, though beyond the scope of this test method, is highly recommended for all purposes, especially to verify the mechanism(s) associated with failure (refer to Practice C1322 ). 4.10 The conventional analysis of constant stress rate testing is based on a critical assumption that stress is uniform throughout the test piece. This is most easily achieved in direct tension test specimens. Only test specimens that fracture in the inner gauge section in four-point testing should be used. Three-point flexure shall not be used. Breakages between the outer and inner fixture contact points should be discounted. The same requirement applies to biaxial disk strength testing. Only fractures which occur in the inner loading circle should be used. Furthermore, it is assumed that the fracture origins are near to the tensile surface and do not grow very large relative to the thickness of rectangular beam flexure or disk strength test specimens. 4.11 The conventional analysis of constant stress rate testing is also based on a critical assumption that the same type flaw controls strength in all specimens at all loading rates. If the flaw distribution is multimodal, then the conventional analysis in this standard may produce erroneous slow crack growth parameter estimates.