Fracture patterns

Some items and components may require examination that is more detailed. Specific techniques for data analysis are beyond the scope of this guidebook. Entire volumes have been written on specific issues such as the fracture patterns of alloys and the corresponding clues for determining the actual cause and mechanism for the failure. Known specific materials and alloys perform and fail in consistent and predictable ways. This area of expertise is normally supplied to the incident investigation team via the use of specialists, from either within the parent organization or from outside experts or labs engaged specifically for the task. 

The fracture patterns of noncrystalline or partly crystalline, partly amorphous materials are unpredictable. Conchoidal fracture is typical of glass and yields odd-shaped flakes of various sizes. 

The fracture patterns of fibrous materials may be distinctive, but inspection alone rarely provides sufficient information to identify a fiber or its source accurately. 

Also the character of fracture under the DF in corrosive medium is changed samples of steel Fe76.iCriiNiioMo2Tio.9 after HE with e < 5 have brittle intergranular fracture pattern with traces of plastic deformation at some grain boundaries. The initial (undeformed) state is typical of brittle fracture (trans- and intercrystalline one) with no indication of a plastic deformation. After HE with e >... 

Because the alumina composites show (ATc)exp/ (A< 1, which indicates that the thermal shock resistance is overestimated by equation 1, the fracture behavior of alumina-filled composites is examined in further detail. As shown in Figure 7, debonding of the interface is observed in the thermal-shock test specimen but not in the fracture-toughness test specimen Therefore, for the evaluation of thermal shock resistance by equation 1 without overestimation, KIc should be measured under the condition in which the same fracture pattern as that seen in the thermal shock test is obtained. 

Figure 2.7 Photograph of a cryptocrystalline magnesite nodule. Note the distinguishing conchoidal fracture pattern.

The fracture pattern is extremely dependent on existing tectonic stresses. 

A key uncertainty for modelling fracture patterns arises from the inference of the parameters of the power-law fracture length distribution. Several models have been fitted to the BVG data, each yielding different hydraulic results. The main geo-... 

Acoustic Emission evolution was modelled for each loading step. Most of the AE events occur in the vicinity of the central pillar walls. Figure 6. The propagation of major fractures creates intense AE events and they are active at the unconfmed borehole wall for all loading stages as inferred from fracturing pattern, see detail in Figure 6. 

Although magnalium is composed of two ductile metals, it is quite brittle. Note the whiskers and fracture patterns seen in the surfaces of these particles. 

A typical fracture pattern for the TGBA phase with a surface cut nearly parallel to the pitch direction is shown in Plate 3. The surface has a regular undulating texture similar to that observed for chiral nematic phase, which also agrees with the surface contours predicted by a simple model for the surface fracture of a chiral nematic. Measurement of the minimum undulating repeat distance gives a value of 0.25 to 0.30 pm, which corresponds to one half of the pitch. Thus, the pitch is about 0.5 to 0.6 pm, which is consistent with the value determined from the optical measurements described earlier. 

Plate 3. A typical fracture pattern for the TGBA phase with a surface cut nearly parallel to the pitch direction, the surface has a regular undulating texture similar to that observed for the chiral nematic phase... 

When the hair is dry and between 30 and 90% RH, the step fracture is the predominate fracture pattern (Figures 5-46 and 5-47). For the fiber depicted in Figure 5-46, the axial cleavage extends well beyond the step. However, for the fiber illustrated by Figure 5 7, it stops at the step. Long single-step fractures like these usually originate near the surface. When the... 

If the hair and its cuticle are in good condition (e.g., near the root end), a smooth break tends to occur see Figure 8-4. As the fiber becomes dryer, below 90% RH, step fractures are the most commonly observed fracture pattern. Fibrillation and splitting describe a distinct cortical fracturing pattern and tend to occur more with twisted or kinky fibers [15] or when the relative humidity is low, rather than when the fiber is wet. The reason for this effect is that the cortex is less extensible than the cuticle when the fiber is dry, below 90% RH [13]. See Chapter 5 for electron micrographs illustrating these different fracture patterns for hair fibers. 

Split ends can occur from breaking, if the cuticle is in poor condition. However, split ends can also occur from the more common fracture patterns such as the step fracture and fibrillation, through the subsequent abrasive actions of combing and brushing. 

Figure 8-3. Schematic depicting some of the more important fracture patterns for human hair.

Walsh, J. J. Watterson, J. 1993, Fractal analysis of fracture patterns using the standard box-counting technique valid and invalid methodologies. Journal of Structural Geology 15(12) 1509 1512... 

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