1.1本规程适用于脆性材料中断裂镜尺寸的分析和解释。断裂反射镜（图1）是脆性材料中围绕断裂起源的断裂标志。断裂镜像尺寸可与已知的断裂镜像常数一起使用，以估计断裂部件中的应力。或者，可以将断裂镜尺寸与试样中的已知应力结合使用，以计算断裂镜常数。本规程适用于玻璃和多晶陶瓷实验室试样以及断裂部件。 玻璃和陶瓷的分析和解释程序相似，但不完全相同。列出并描述了不同的光学显微镜检查技术，包括观察角度、照明方法、适当的放大倍数和测量协议。给出了计算断裂反射镜常数和解释圆形和非圆形反射镜的断裂反射镜尺寸和形状的指南，包括应力梯度、几何效应和/或残余应力。本规程提供了图形和显微照片，说明了玻璃和多晶陶瓷断裂镜中常见的不同类型特征和测量技术。 1.2以国际单位制表示的数值应视为标准值。本标准不包括其他计量单位。 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和健康实践，并确定监管限制的适用性。 ====意义和用途====== 断口镜尺寸分析是分析玻璃和陶瓷断口的有力工具。断裂反射镜是脆性材料中的断裂标志，如实践中所讨论的，围绕断裂起源 C1256 和 C1322 . 图1显示了识别关键特征的示意图。图2显示了玻璃中的示例。断裂反射镜区域非常平滑，在玻璃中具有高反射性，因此得名 “ 断裂反射镜。 ” 事实上，高倍显微镜显示，即使在玻璃的镜面区域内，随着裂纹远离原点，也有非常精细的特征和逐渐增加的粗糙度。这些是亚微米大小，因此无法用光学显微镜识别。早期的研究者将断裂镜解释为具有离散边界，包括 “ 镜雾 ” 边界和 “ 薄雾镰刀 ” 玻璃中的边界。这些也被称为 “ 内后视镜 ” 或 “ 外后视镜 ” 边界。现在已知，不存在对应于断口特征中特定变化的离散边界。表面粗糙度从断裂镜内部逐渐增加到明显边界之外。边界是一个解释、显微镜的分辨率和观察模式的问题。在非常弱的样本中，反射镜可能比样本或组件大，并且不会出现边界。 无花果。3-5展示陶瓷示例。在多晶陶瓷中，限定符 “ 相当地 ” 如中所示 “ 相对平稳 ” 必须使用，因为即使在原点周围的区域，微观结构也存在固有的粗糙度。在粗晶粒或多孔陶瓷中，可能无法识别镜像边界。在多晶陶瓷中，由于裂纹-微观结构相互作用产生的固有粗糙度，即使在反射镜内，也不太可能检测到镜雾边界。文字 “ 成体系的 ” 在定义中 “ 多晶陶瓷中的镜像哈克尔边界 ” 需要一些详细说明。镜像边界线是辐射裂纹达到终端速度后产生的速度线。然而，在某些情况下，在陶瓷破裂镜内可以很好地产生过早的孤立裂纹。在判断镜像边界时，应忽略它。来自镜子内部孤立障碍物（如大颗粒或团块）的尾波冲击可能会提前触发 “ 过早的 ” 梳理线条。划痕或磨削缺陷中的步骤可能会触发从原点本身发出的分叉线。 有时，多晶陶瓷的微观结构会在陶瓷基复合材料（颗粒、晶须或片状）或自增强陶瓷中产生严重的判断问题，其中细长和互锁的晶粒会带来更大的抗断裂性。镜子在低倍率下可能很明显，但很难准确评估其尺寸。镜像区域本身可能有点凹凸不平；因此，有必要对什么是镜像边界进行一些判断。 在某些载荷条件下，断裂反射镜是圆形的，例如具有内部原点的拉伸试样，或者对于拉伸试样中的表面原点，断裂反射镜几乎是半圆形的，或者如果反射镜在弯曲试样中很小。 如果断裂反射镜处于应力梯度中，其形状可能会发生变化，在某些方向上会拉长甚至不完整。如果断裂反射镜是从试样或部件的角起点形成的，则可能是四分之一圆。断裂反射镜仅在中等至高局部应力条件下形成。由于裂纹在试样范围内可能无法达到足够的速度，因此弱试样可能不会显示全部或部分镜像边界。 断裂镜子不仅带来一个 ’ s注意原点，但也提供有关导致断裂的原点应力大小及其分布的信息。 断裂镜尺寸和断裂处的应力通过公式1进行经验关联: 哪里: σ = 原点应力（MPa或ksi）， R = 断裂镜半径（m或in）， A. = 断裂镜像常数（MPa √ m或ksi √ 中）。 方程式1在下文中称为 “ 经验应力 – 断裂镜尺寸关系， ” 或 “ 应力镜尺寸关系 ” 简而言之。参考文献1和2中回顾了等式1的历史和一般的断裂镜分析。 A、 the “ 断裂镜像常数 ” （有时也称为 “ 镜像常数 ” )具有应力强度单位（MPa √ m或ksi √ 在）中，许多人认为这是一种物质属性。如图所示。1和2，可以在眼镜中辨别出单独的雾状和锯齿状区域以及它们之间的明显边界。每个都有一个对应的镜像常数a。最常见的表示法是将镜像雾边界称为内镜像边界，其镜像常数指定为a 一、 . 雾线边界称为外镜像边界，其镜像常数指定为A o . 在多晶陶瓷中，通常看不到镜雾边界。 通常，仅测量镜像黑客边界，并且仅测量A o 对于镜像，计算了哈克尔边界。比等式1更基本的关系可能基于应力强度因子（K 我 )在mirror mist或mist hackle边界处，但等式1更实用，使用更简单。 基于等式1和A值或应力强度因子的尺寸预测与拉伸试样中小反射镜的极限情况非常匹配。这也适用于以强弯曲试样中的表面缺陷为中心的小半圆镜。因此，至少对于一些特殊的反射镜情况，A应该与基于应力强度因子的更基本参数直接相关。 实验室试样断口中断口反射镜的尺寸可与已知的断口反射镜常数结合使用，以验证断口处的应力是否符合预期。实验室试样的断裂镜尺寸和已知应力也可用于计算断裂镜常数A。 部件中断裂反射镜的尺寸可与已知断裂反射镜常数结合使用，以估计部件在原点处的应力。实践 C1322 有各种陶瓷和玻璃的断裂镜常数的综合列表。

1.1 This practice pertains to the analysis and interpretation of fracture mirror sizes in brittle materials. Fracture mirrors (Fig. 1) are telltale fractographic markings that surround a fracture origin in brittle materials. The fracture mirror size may be used with known fracture mirror constants to estimate the stress in a fractured component. Alternatively, the fracture mirror size may be used in conjunction with known stresses in test specimens to calculate fracture mirror constants. The practice is applicable to glasses and polycrystalline ceramic laboratory test specimens as well as fractured components. The analysis and interpretation procedures for glasses and ceramics are similar, but they are not identical. Different optical microscopy examination techniques are listed and described, including observation angles, illumination methods, appropriate magnification, and measurement protocols. Guidance is given for calculating a fracture mirror constant and for interpreting the fracture mirror size and shape for both circular and noncircular mirrors including stress gradients, geometrical effects, and/or residual stresses. The practice provides figures and micrographs illustrating the different types of features commonly observed in and measurement techniques used for the fracture mirrors of glasses and polycrystalline ceramics. 1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 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 and health practices and determine the applicability of regulatory limitations prior to use. ====== Significance And Use ====== Fracture mirror size analysis is a powerful tool for analyzing glass and ceramic fractures. Fracture mirrors are telltale fractographic markings in brittle materials that surround a fracture origin as discussed in Practices C1256 and C1322 . Fig. 1 shows a schematic with key features identified. Fig. 2 shows an example in glass. The fracture mirror region is very smooth and highly reflective in glasses, hence the name “ fracture mirror. ” In fact, high magnification microscopy reveals that, even within the mirror region in glasses, there are very fine features and escalating roughness as the crack advances away from the origin. These are submicrometer in size and hence are not discernable with an optical microscope. Early investigators interpreted fracture mirrors as having discrete boundaries including a “ mirror-mist ” boundary and also a “ mist-hackle ” boundary in glasses. These were also termed “ inner mirror ” or “ outer mirror ” boundaries, respectively. It is now known that there are no discrete boundaries corresponding to specific changes in the fractographic features. Surface roughness increases gradually from well within the fracture mirror to beyond the apparent boundaries. The boundaries were a matter of interpretation, the resolving power of the microscope, and the mode of viewing. In very weak specimens, the mirror may be larger than the specimen or component and the boundaries will not be present. Figs. 3-5 show examples in ceramics. In polycrystalline ceramics, the qualifier “ relatively ” as in “ relatively smooth ” must be used, since there is an inherent roughness from the microstructure even in the area immediately surrounding the origin. In coarse-grained or porous ceramics, it may be impossible to identify a mirror boundary. In polycrystalline ceramics, it is highly unlikely that a mirror-mist boundary can be detected due to the inherent roughness created by the crack-microstructure interactions, even within the mirror. The word “ systematic ” in the definition for “ mirror-hackle boundary in polycrystalline ceramics ” requires some elaboration. Mirror boundary hackle lines are velocity hackle lines created after the radiating crack reaches terminal velocity. However, premature, isolated hackle can in some instances be generated well within a ceramic fracture mirror. It should be disregarded when judging the mirror boundary. Wake hackle from an isolated obstacle inside the mirror (such as a large grain or agglomerate) can trigger early “ premature ” hackle lines. Steps in scratches or grinding flaws can trigger hackle lines that emanate from the origin itself. Sometimes the microstructure of polycrystalline ceramics creates severe judgment problems in ceramic matrix composites (particulate, whisker, or platelet) or self-reinforced ceramics whereby elongated and interlocking grains impart greater fracture resistance. Mirrors may be plainly evident at low magnifications, but accurate assessment of their size can be difficult. The mirror region itself may be somewhat bumpy; therefore, some judgment as to what is a mirror boundary is necessary. Fracture mirrors are circular in some loading conditions such as tension specimens with internal origins, or they are nearly semicircular for surface origins in tensile specimens, or if the mirrors are small in bend specimens. Their shapes can vary and be elongated or even incomplete in some directions if the fracture mirrors are in stress gradients. Fracture mirrors may be quarter circles if they form from corner origins in a specimen or component. Fracture mirrors only form in moderate to high local stress conditions. Weak specimens may not exhibit full or even partial mirror boundaries, since the crack may not achieve sufficient velocity within the confines of the specimen. Fracture mirrors not only bring one ’ s attention to an origin, but also give information about the magnitude of the stress at the origin that caused fracture and their distribution. The fracture mirror size and the stress at fracture are empirically correlated by Eq 1: where: σ = stress at the origin (MPa or ksi), R = fracture mirror radius (m or in), A = fracture mirror constant (MPa √ m or ksi √ in). Equation 1 is hereafter referred to as the “ empirical stress – fracture mirror size relationship, ” or “ stress-mirror size relationship ” for short. A review of the history of Eq 1, and fracture mirror analysis in general, may be found in Refs 1 and 2. A, the “ fracture mirror constant ” (sometimes also known as the “ mirror constant ” ) has units of stress intensity (MPa √ m or ksi √ in) and is considered by many to be a material property. As shown in Figs. 1 and 2, it is possible to discern separate mist and hackle regions and the apparent boundaries between them in glasses. Each has a corresponding mirror constant, A. The most common notation is to refer to the mirror-mist boundary as the inner mirror boundary, and its mirror constant is designated A i . The mist-hackle boundary is referred to as the outer mirror boundary, and its mirror constant is designated A o . The mirror-mist boundary is usually not perceivable in polycrystalline ceramics. Usually, only the mirror-hackle boundary is measured and only an A o for the mirror-hackle boundary is calculated. A more fundamental relationship than Eq 1 may be based on the stress intensity factors (K I ) at the mirror-mist or mist-hackle boundaries, but Eq 1 is more practical and simpler to use. The size predictions based on Eq 1 and the A values, or alternatively stress intensity factors, match very closely for the limiting cases of small mirrors in tension specimens. This is also true for small semicircular mirrors centered on surface flaws in strong flexure specimens. So, at least for some special mirror cases, A should be directly related to a more fundamental parameter based on stress intensity factors. The size of the fracture mirrors in laboratory test specimen fractures may be used in conjunction with known fracture mirror constants to verify the stress at fracture was as expected. The fracture mirror sizes and known stresses from laboratory test specimens may also be used to compute fracture mirror constants, A. The size of the fracture mirrors in components may be used in conjunction with known fracture mirror constants to estimate the stress in the component at the origin. Practice C1322 has a comprehensive list of fracture mirror constants for a variety of ceramics and glasses.