1.1 本试验方法包括在高温下测定高级陶瓷的弯曲强度。 2. 四点- 1. / 4. -规定跨度的点荷载和三点荷载为标准荷载，如 图1 。规定横截面的矩形试样与规定的试样夹具组合中的规定特征一起使用。试样尺寸可为3×4×45至50 mm，在40 mm外跨四点或三点夹具上进行测试。或者，可以使用这些尺寸的一半或两倍的试样和夹具跨度。试验方法允许对机加工或烧制试样进行试验。加工准备的几个选项包括:应用匹配加工、常规程序或指定的标准程序。本试验方法描述了仪器、试样要求、试验程序、计算和报告要求。 本试验方法适用于单片或颗粒或晶须增强陶瓷。它也可以用于眼镜。它不适用于连续纤维增强陶瓷复合材料。 1.2 以国际单位制表示的数值应视为标准。括号中给出的值仅供参考。 1.3 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。 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《国际标准、指南和建议制定原则决定》中确立的国际公认标准化原则制定的。 =====意义和用途====== 4.1 该测试方法可用于材料开发、质量控制、表征和设计数据生成。本试验方法适用于弯曲强度为 ∼ 50兆帕( ∼ 7千磅/平方英寸）或更大。 4.2 弯曲应力是基于简单梁理论计算的，假设材料是各向同性和均质的，拉伸和压缩弹性模量相同，材料是线性弹性的。平均晶粒度不得大于 1. / 50 梁的厚度。试验方法中的均匀性和各向同性假设排除了将其用于连续纤维增强复合材料的可能性 第1341页 更合适。 4.3 一组试样的弯曲强度受与试验程序相关的几个参数的影响。 这些因素包括试验速率、试验环境、试样尺寸、试样制备和试验夹具。选择试样和夹具尺寸，以在实际配置和试验方法中讨论的结果误差之间提供平衡 第161页 、和参考 ( 1- 3. ) . 4. 指定了特定的夹具和样本配置，以便在不需要威布尔尺寸缩放的情况下对数据进行快速比较。 4.4 陶瓷材料的弯曲强度取决于其固有的抗断裂能力以及缺陷的大小和严重程度。这些变化会导致试样样本的测试结果自然分散。尽管断裂表面的断口分析超出了本试验方法的范围，但强烈建议对所有目的进行断口分析，特别是如果数据将用于参考 ( 4. ) 和实践 第1322页 和 第123页 . 4.5 该方法确定了在高温和环境条件下，以标称、中速测试速率的弯曲强度。这些条件下的弯曲强度可以是或不一定是惰性弯曲强度。高温下的弯曲强度可能强烈依赖于试验速率，这是蠕变、应力腐蚀或缓慢裂纹扩展的结果。如果测试的目的是测量惰性弯曲强度，则需要采取额外的预防措施，可能需要更快的测试速度。 注6: 许多陶瓷易受环境辅助的缓慢裂纹生长或热激活的缓慢裂纹增长的影响。氧化物陶瓷、玻璃、玻璃陶瓷和含有边界相玻璃的陶瓷特别容易发生缓慢的裂纹增长。通过使用惰性测试气氛（例如干燥氮气或真空），可将环境因素（例如空气中的水作为湿度）引起的时间依赖性影响降至最低。 或者，如果目标是测量惰性强度，则可以使用比本标准规定更快的测试速率。即使在惰性气氛中，高温下也可能发生热激活的缓慢裂纹扩展。如果目标是测量惰性弯曲强度，则应使用比本标准规定更快的测试速率。另一方面，许多陶瓷如碳化硼、碳化硅、氮化铝和许多氮化硅在室温或适度升高的温度下对缓慢的裂纹生长不敏感，对于这种材料，在实验室环境条件下以标称测试速率测得的弯曲强度为惰性弯曲强度。 4.6 三点试验配置仅使试样的一小部分暴露在最大应力下。因此，三点弯曲强度可能远大于四点- 点弯曲强度。三点弯曲有一些优点。它使用更简单的测试夹具，更容易适应高温，有时在威布尔统计研究中也很有用。然而，对于大多数表征目的，首选并推荐四点弯曲。 4.7 三点试验配置仅使试样的一小部分暴露在最大应力下。因此，三点弯曲强度可能远大于四点弯曲强度。三点弯曲有一些优点。它使用更简单的测试夹具，更容易适应高温，有时在威布尔统计研究中也很有用。然而，对于大多数表征目的，首选并推荐四点弯曲。

1.1 This test method covers determination of the flexural strength of advanced ceramics at elevated temperatures. 2 Four-point- 1 / 4 -point and three-point loadings with prescribed spans are the standard as shown in Fig. 1 . Rectangular specimens of prescribed cross-section are used with specified features in prescribed specimen-fixture combinations. Test specimens may be 3 by 4 by 45 to 50 mm in size that are tested on 40-mm outer span four-point or three-point fixtures. Alternatively, test specimens and fixture spans half or twice these sizes may be used. The test method permits testing of machined or as-fired test specimens. Several options for machining preparation are included: application matched machining, customary procedures, or a specified standard procedure. This test method describes the apparatus, specimen requirements, test procedure, calculations, and reporting requirements. The test method is applicable to monolithic or particulate- or whisker-reinforced ceramics. It may also be used for glasses. It is not applicable to continuous fiber-reinforced ceramic composites. 1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only. 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 This test method may be used for material development, quality control, characterization, and design data generation purposes. This test method is intended to be used with ceramics whose flexural strength is ∼ 50 MPa ( ∼ 7 ksi) or greater. 4.2 The flexure stress is computed based on simple beam theory, with 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 1 / 50 of the beam thickness. The homogeneity and isotropy assumptions in the test method rule out the use of it for continuous fiber-reinforced composites for which Test Method C1341 is more appropriate. 4.3 The flexural strength of a group of test specimens is influenced by several parameters associated with the test procedure. Such factors include the testing rate, test environment, specimen size, specimen preparation, and test fixtures. Specimen and fixture sizes were chosen to provide a balance between the practical configurations and resulting errors as discussed in Test Method C1161 , and Refs ( 1- 3 ) . 4 Specific fixture and specimen configurations were designated in order to permit the ready comparison of data without the need for Weibull size scaling. 4.4 The flexural strength of a ceramic material is dependent on both its inherent resistance to fracture and the size and severity of flaws. Variations in these cause a natural scatter in test results for a sample of test specimens. Fractographic analysis of fracture surfaces, although beyond the scope of this test method, is highly recommended for all purposes, especially if the data will be used for design as discussed in Ref ( 4 ) and Practices C1322 and C1239 . 4.5 This method determines the flexural strength at elevated temperature and ambient environmental conditions at a nominal, moderately fast testing rate. The flexural strength under these conditions may or may not necessarily be the inert flexural strength. Flexure strength at elevated temperature may be strongly dependent on testing rate, a consequence of creep, stress corrosion, or slow crack growth. If the purpose of the test is to measure the inert flexural strength, then extra precautions are required and faster testing rates may be necessary. Note 6: Many ceramics are susceptible to either environmentally assisted slow crack growth or thermally activated slow crack growth. Oxide ceramics, glasses, glass ceramics, and ceramics containing boundary phase glass are particularly susceptible to slow crack growth. Time-dependent effects that are caused by environmental factors (for example, water as humidity in air) may be minimized through the use of inert testing atmosphere such as dry nitrogen gas or vacuum. Alternatively, testing rates faster than specified in this standard may be used if the goal is to measure the inert strength. Thermally activated slow crack growth may occur at elevated temperature even in inert atmospheres. Testing rates faster than specified in this standard should be used if the goal is to measure the inert flexural strength. On the other hand, many ceramics such as boron carbide, silicon carbide, aluminum nitride, and many silicon nitrides have no sensitivity to slow crack growth at room or moderately elevated temperatures and for such materials, the flexural strength measured under laboratory ambient conditions at the nominal testing rate is the inert flexural strength. 4.6 The three-point test configuration exposes only a very small portion of the specimen to the maximum stress. Therefore, three-point flexural strengths are likely to be much greater than four-point flexural strengths. Three-point flexure has some advantages. It uses simpler test fixtures, it is easier to adapt to high temperature, and it is sometimes helpful in Weibull statistical studies. However, four-point flexure is preferred and recommended for most characterization purposes. 4.7 The three-point test configuration exposes only a very small portion of the specimen to the maximum stress. Therefore, three-point flexural strengths are likely to be much greater than four-point flexural strengths. Three-point flexure has some advantages. It uses simpler test fixtures, it is easier to adapt to high temperature, and it is sometimes helpful in Weibull statistical studies. However, four-point flexure is preferred and recommended for most characterization purposes.