ASTM C1678-10(2015)
陶瓷和玻璃中斷裂鏡面尺寸斷口分析的標準實施規程

Standard Practice for Fractographic Analysis of Fracture Mirror Sizes in Ceramics and Glasses

被代替

標準號

ASTM C1678-10(2015)

發布

2010年

發布單位

美國材料與試驗協會

替代標準

ASTM C1678-21

當前最新

ASTM C1678-21

 

 

引用標準

ASTM C1145 ASTM C1256 ASTM C1322

適用范圍

5.1 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.

σ   =   stress at the origin (MPa or ksi), R   =   fracture mirror radius (m or in), A   =   fracture mirror constant (MPa√m or ksi√in).

Eq 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 Refs8201;1 and 2.

5.5 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 calculat......

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