Cryogenic fracturing

Fig. 39 SEM micrographs of the cryogenically fractured surfaces of different PTFE-EPDM composites, showing PTEE morphology and dispersion in EPDM...

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). 

Fig. 2. SEM micrograph of cryogenic fracture surfaces taken at T (upper) and P (lower) crack propagation. (o,6) PCIO, c,d) PC20 and (e,f) PC30.

Typical SEM micrographs of cryogenically fractured surfaces show an homogeneous distribution of the rubber particles for both DZ and NZ materials (Fig. 3). In Table I are reported the specific surface of the nylon/particle interface and the mean free path within the rubber phase. It appears that the rubber particles are by far finer in the NZ blend even though the number of particles is underestimated for this material due to the presence of very small particles and the poor contrast between the rubber and the nylon. 

Fig. 3 SEM micrographs of cryogenically fractured materials (a) DZ blend (b) NZ blend.

Figure 2. SEM image of a blend with 10% PS strained to fracture and then cryogenically fractured parallel to the direction of deformation. The parameters that describe the void geometry are defined in the schematic.

Figure 2. Scanning electron micrographs of a blend with 5% Kraton G—1652M that was drawn to fracture and cryogenically fractured lengthwise. The direction of stress is shown by the arrow.

Figure 9.13. SEM observation of the cryogenic fracture surface in a composite of plasticized starch reinforced with cellulose fibers (white line = 100 microns) [AVE 01b]...

Figure 4, Scanning electron micrograph of a cryogenic fracture surface of a PA 6/EPM 90/10 binary blend.

Fig. 14. SEM micrograph of cryogenic fracture surface of HDPE/iPP (25/75) extruded binary blend.

THE INFLUENCE OF PROCESSING AND HEAT TREATMENT ON THE CRYOGENIC FRACTURE MECHANICS PROPERTIES OF INCONEL 718 ... 

The resistance curves for base metal specimens of the TL orientation at three temperatures are shown in Fig. 3. The values of //c decreased from 255 to 120 to 50 kJ m, as test temperature was lowered from 295 to 76 to 4 K. The slopes of the resistance curves also decreased progressively as temperature was lowered. Therefore, less energy was required for both the initiation and propagation of cryogenic fractures. Despite the adverse temperature effects, unstable linear-elastic fractures were never observed in this study the Kic(J) data in Table II are estimates based on Eq. (3). 

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