1.1 本试验方法用于测定高级陶瓷材料棒状试样在环境温度下的弯曲强度。在许多情况下，最好测试圆形试样，而不是矩形弯曲试样，特别是当材料制成棒状时。这种方法允许测试机加工、拉伸或烧制的棒状试样。它允许在杆尺寸和横截面形状均匀性方面有一定的自由度。建议杆直径在1.5至8 mm之间，长度在25至85 mm之间，但允许使用其他尺寸。 四点- 1. / 4. -点，如所示 图1 是首选的测试配置。允许三点加载。本方法描述了仪器、试样要求、试验程序、计算和报告要求。该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。 图1 四点- 1. / 4. -点弯曲加载配置 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。本试验方法适用于强度为50 MPa（~7 ksi）或更高的陶瓷。试验方法也可用于玻璃试样，尽管试验方法 第158页 专门设计用于眼镜。该试验方法可用于机加工、拉伸、挤压和烧制的圆形试样。该试验方法可用于具有椭圆形横截面几何形状的试样。 4.2 弯曲强度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。平均粒度应不大于棒直径的五十分之一。标准中的均匀性和各向同性假设排除了对连续纤维增强陶瓷使用该试验的可能性。 4.3 一组试样的抗弯强度受与试验程序相关的几个参数的影响。 这些因素包括加载速率、试验环境、试样尺寸、试样制备和试验夹具 ( 1- 3. ) . 3. 该方法包括特定的试样夹具尺寸组合，但允许在规定范围内进行替代配置。这些组合被选择为实用的，以最小化实验误差，并允许容易地将圆柱杆强度与其他配置的数据进行比较。包括威布尔有效体积和威布尔有效表面的方程。 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材料中缺陷的大小和严重程度。 燃料棒中的缺陷本质上可能在整个体积上分布。这些缺陷中的一些可能位于外表面或附近。缺陷也可以是内在表面分布的，所有缺陷都位于试样外表面。磨削裂纹属于后一类。缺陷的变化会导致一组试样的强度自然分散。尽管断裂表面的断口分析超出了本标准的范围，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文献 ( 3- 5. ) 和实践 第1322页 和 第123页 . 4.5 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，更容易适应高温和断裂韧性测试，有时在威布尔统计研究中也很有用。它还使用较小的力来破坏试样。对于很短、很粗的样本，这也很方便，因为很难在四个样本中进行测试- 点加载。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 is for the determination of flexural strength of rod-shaped specimens of advanced ceramic materials at ambient temperature. In many instances it is preferable to test round specimens rather than rectangular bend specimens, especially if the material is fabricated in rod form. This method permits testing of machined, drawn, or as-fired rod-shaped specimens. It allows some latitude in the rod sizes and cross section shape uniformity. Rod diameters between 1.5 and 8 mm and lengths from 25 to 85 mm are recommended, but other sizes are permitted. Four-point- 1 / 4 -point as shown in Fig. 1 is the preferred testing configuration. Three-point loading is permitted. This method describes the apparatus, specimen requirements, test procedure, calculations, and reporting requirements. The 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. FIG. 1 Four-Point- 1 / 4 -Point Flexure Loading Configuration 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 strength is 50 MPa (~7 ksi) or greater. The test method may also be used with glass test specimens, although Test Methods C158 is specifically designed to be used for glasses. This test method may be used with machined, drawn, extruded, and as-fired round specimens. This test method may be used with specimens that have elliptical cross section geometries. 4.2 The flexure strength 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 one-fiftieth of the rod diameter. The homogeneity and isotropy assumptions in the standard rule out the use of this test for continuous fiber-reinforced ceramics. 4.3 Flexural strength of a group of test specimens is influenced by several parameters associated with the test procedure. Such factors include the loading rate, test environment, specimen size, specimen preparation, and test fixtures ( 1- 3 ) . 3 This method includes specific specimen-fixture size combinations, but permits alternative configurations within specified limits. These combinations were chosen to be practical, to minimize experimental error, and permit easy comparison of cylindrical rod strengths with data for other configurations. Equations for the Weibull effective volume and Weibull effective surface are included. 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 in the material. Flaws in rods may be intrinsically volume-distributed throughout the bulk. Some of these flaws by chance may be located at or near the outer surface. Flaws may alternatively be intrinsically surface-distributed with all flaws located on the outer specimen surface. Grinding cracks fit the latter category. Variations in the flaws cause a natural scatter in strengths for a set of test specimens. Fractographic analysis of fracture surfaces, although beyond the scope of this standard, is highly recommended for all purposes, especially if the data will be used for design as discussed in Refs ( 3- 5 ) and Practices C1322 and C1239 . 4.5 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 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 fracture toughness testing, and it is sometimes helpful in Weibull statistical studies. It also uses smaller force to break a specimen. It is also convenient for very short, stubby specimens which would be difficult to test in four-point loading. Nevertheless, four-point flexure is preferred and recommended for most characterization purposes.