Mirror region

When smooth specimens of PS are cycled at 26.7 Hz in a tensile mode at a maximum stress of 17.2 MPa discontinuous crack growth bands similar to those shown in Fig. 8 are seen in the mirror region near the fracture source. These bands are also similar in morphology to those observed in testing notched PS specimens at a minimum stress that is maintained at one-tenth the maximum stress However, DCG bands were not seen when tests are carried out under a fully reversed stress of 17.2 MPa at... 

Figure 15. Time evolution of local temperature of the last region (see right panel) the shock goes through in the downstream half of the right slab for /gap = 5, 10, and 20 A. We also show that time evolution of the local temperature of the corresponding (mirror) region in the perfect slab (black lines).

The microstructure of this type of material was studied as early as 1952 by Fischer and Isenbarth (1). These authors demonstrated by thin section transmission microscopy that a two-phase microstructure was present in a number of materials available commercially for restoring tooth structure. In 1955 Helmcke reported similar findings with electron microscopic studies of fracture replicas (2, 3). Then in 1958, Smith examined at low magnification fracture surfaces in materials made from denture base polymers attention centered on a system of ridges concentric with a mirror region (4). In retrospect, this phenomenon was similar to that observed in one-phase samples of poly (methyl methacrylate) (5). Subsequently, in 1961, Smith showed that the microstruc-... 

Figure 6. Fractograph of material III showing the fine features of a large particle in the mirror region...

Figure 8.75 Fracture surfaces in brittle materials generally show a smooth region that surrounds the failure origin (mirror region) but the surface increases in roughness as the crack accelerates (mist region) until crack branching occurs. The branched region contains ridges known as hackle. (Optical micrograph courtesy of Matt Chou.)...

Figure 9.7 Micrograph of fracture surface in giass showing the mirror region surrounded by mist and hackie. The iocation of the fracture origin is marked "O" and the boundaries of the mist and hackie regions are indicated, respectiveiy, by and R),.

Fig. 1.19. (a) Schematic of the vertical cavity surface emitting laser. (After Cho-quette (2002).) (b) TEM image of the optical cavity and the surrounding DBR mirror region which comprises alternating layers of high- and low-refractive index material. The thickness of the optical cavity is 250 nm. (Photograph courtesy of D. Mathes and R. Hull. Reproduced with permission.)... 

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