Fractographs

The representation of the results from slow strain-rate tests may be through the usual ductility parameters such as reduction in area, the maximum load achieved, the crack velocity or even the time to failure, although as with all tests, metallographic or fractographic examination, whilst not readily quantifiable, should also be involved. Since stress-corrosion failures are usually associated with relatively little plastic deformation, the ductility... 

Figure 20.15 SEM fractographs of the LCP/PEN blend fibers after Instron tensile tests (a) 10/90 (wt%) (b) 25/75 (wt%) [13]. From Kim, S. H., Hong, S. M., Hwang, S. S. and Yoo, H. O., J. Appl. Polym. Sci., 74, 2448-2456 (1999), Copyright (1999, John Wiley Sons, Inc.). This material is used by permission of John Wiley Sons, Inc...

C. D. Beachem, The Interpretation of Electron Microscope Fractographs, (1966), Naval Research Lab., Washington, DC. 

Poza, P., Perez-Rigueiro, J., Elices, M., and Llorca, J. "Fractographic analysis of silkworm and spider silk". Eng. Bract. Mech. 69(9), 1035-1048 (2002). 

After completion of DHC test specimen has been unloaded and cooled down in the furnace to the room temperature. Specimen then has been subjected to cyclic loading to outline the DHC crack and then fractured. After completion of DHC test actual crack length was measured from fractographs (Fig. 2). 

A crack in a ceramic material upon initiation may accelerate and interact with microstructure, stress field and the generated acoustic vibrations. These interactions may lead to some fractographic features such as fracture mirror, hackle or river patterns and Wallner lines. 

We conclude from our morphology observations and the properties listed in Table VI that at low bisphenol A content the system shows the same appearance and therefore the same properties as the CTBN-epoxy system. As the bisphenol A is increased to an optimum of 24 phr, the particles decrease in size, a two-particle size population develops, and multiple failure sites appear. An example of the bisphenol A modified system is shown in Figure 2 in which the fractograph shows one family of small particles < 0.1 pin diameter and another family of larger particles 1-5 pm diameter. Another feature shown in this micrograph are multiple... 

W.B. Steward, A Fractographic Irivestigation of Explosively Fragmented Silicon-Manganese Steels By Scanning Electron Microscopy , FA-M72-11-1 (1972) 50) J.W.S. Hearle,... 

Except for perfect crystals, the fracture surfaces in solids are never very smooth. In fact, it seems now to be established experimentally that for weakly disordered solids, the surfaces formed during fracture processes are very rough, and on a mesoscopic scale (which is much larger than the atomic scale but smaller than the macroscopic sample size) they are observed to have self-affine properties (Mandelbrot et al 1984, Bouchaud et al 1993 a,b, Roux 1994). These have recently been observed using various fractographic investigations. By self-affinity of the fracture surface, we mean that the surface coordinate in the direction perpendicular to the crack or fracture x — y) plane has the scaling property such that... 

Post-failure studies of the fracture surface morphology of bulk semi-crystalline polymers are more difficult than those of amorphous materials due to the more complex multiphase structure associated with semi-crystalline materials However, it was shown that some fractographic details point to the formation of a stress whitened region ahead of a notch prior to final fracture of the material. In particular, stress-whitened regions were easily visible in semi-crystalline polymers such as LDPE and HDPE The resulting, macroscopically apparently brittle fracture... 

Ffg. 4.16. SKM fractographs of RCG bands in different polymers. Crack propagation direction is indicated by urroH-s... 

Morphological and fractographic inspection of the materials were performed on cryogenic fractured surfaces taken from the central region of tested and untested DDENT specimens, using a Jeol JSM 6400 Scanning Electronic microscope (SEM). 

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