Fractures types

Brittle fracture Ductile fracture Shear fracture 

All the fracture types shown schematically in Fig. 8.2 may also be observed experimentally (see for example Pelleg). However, only two of these are illustrated in Fig. 8.3 the (a) classic cup-and-cone-type and (b) brittle fracture obtained by tensile testing to fracture. No necking occurs in brittle fracture and the percentage of elongation and reduction of the area are nearly zero. In this type of tensile fracture, the yield and tensile strengths are essentially identical. 

Since most ceramics are predominantly brittle at RT, it is important to mention 

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The combination of residual or applied tensile stress above a threshold value in the metal, the solution s composition, temperature, metal composition, and metal structure all affect this brittle-fracture-type of cracking. Using steels with a high content of nickel can reduce its appearance. 

Figure I. Schematic drawings of Hearles classification of fiber fracture types. (Reproduced with permission from Ref. 8.)...

The modern silk sample not subjected to heat or light stress displayed fracture Types 2, 5, 7, and 11. The dominant fracture type exhibited by these fibers was Type 7 50 of the modern silk fractures were of this type. This finding indicates that surface flaws largely govern the fracture mechanism of modern silk. A smaller number of fracture Types 2, 5, and 11 were observed. This observation indicates that at least some of these fibers also exhibit ductility, a moderate loss of interfibrillar cohesion, and large internal voids, although their influence in fiber fracture is considerably less than that of surface flaws. 

Figure 9 Enhancement of tensile elongation and change of fracture type of NisAl (with 24 at. % Al) by small boron additions. (Ref. 43. Reproduced by kind permission of Springer Science Business Media)...

Figure 17 Generalized hydrogeological section of the SG-3 well testing ground. 1— Zones of negative temperature anomalies 2—zones of intensive Assuring 3—highly mineralized waters 4— reservoir rocks of fracture-vein and fracture types 5—zone of intensive micromovements 6—boundary between III and IV volcanogenic-sedimentary sheets 7—temperature, °C 8—wells (Borevsky et aL, 1984) (reproduced from The Superdeep Well of the Kola...

Planar fractures represent the most common fracture type in the investigated rocks of the Fuglen, Hekkingen and the Knurr Formations, and approximately 70-90% of the structures fall into this group. The planar fractures are commonly single structures, but are also found in clusters of 2-5, and as swarms of more than 5 closely spaced parallel or sub-parallel fractures. Based on morphology, the planar fractures are subdivided into four sub-types. 

Type Fill, wavy, heavily striated fractures, are not common, but have been recorded in a few cases. This fracture type seems to be more common in the more... 

Fracture types FI-FIII may be characterised by their striation frequencies (/j = striations/ m as measured transverse to the striation strike-line). Table 2 gives one example of results from striation countings from well 7321/9-1, illustrating that type FI and FII fractures have typical/j values in the range of 0.010-0.035, significantly different from type Fill which has typical values of 5.5-8.3 x 10 . ... 

Striation frequency (fg) correlated to fracture type. Example from well... 

The origin of type VI fractures is enigmatic, but it may be speculated that these are associated with volume reducing processes during burial. Since this fracture type is rare, no further steps have been taken to determine their origin. 

Distribution of different fracture types cap rocks of the southwestern Barents Sea (see Table 1)... 

Independent of the test methods applied and the respective results, a precise analysis of the failure source is required. Here, fracture-type time-diagrams are used in which an allocation of failure sources is made over the test period (adhesion fracture, cohesion fracture, adherend fracture, corrosion, q.v. Figure 7.8 and Figure 10.7). 

As a result of the toughening mechanism, the transition temperature, Tbt, at which the fracture type changes from brittle to tough shifts to lower values (from 60 °C for unmodified PA6 to about -30 °C). The dependence of TBX on rubber-particle content, particle diameter, and type of rubber has been extensively studied by Gaymans, Borggreve, and co-workers (6, 31, 33, 34). 

Fracture type Shear strength Residual shear strength Shear stiffness Normal stiffness... 

Earlier on, several authors studied some factors that influence oil yield from fracture-type reservoirs producing by dissolved gas drive [22,24]. In their models, they represented crude oil by mixtures of kerosene with Vaseline The viscosity of these mixures was considerably lower than that of the Miocene crudes of Krasnodar oil fields. 

Two types of reservoirs, each with different permeability, are found within the petroliferous bed of the fields in the Krasnodar Petroliferous Region. A number of laboratory models were therefore prepared to reproduce these permeability differences. Models using sand as porous medium (porosity-type models) simulated the reservoirs of the first type. The range of permeability of this medium corresponded to that of the actual reservoirs of the same type. Models characterized by fracture-type porosity (fracture-type models), were used to represent the second type of the reservoir. Again, the permeability characteristics of the medium used in the latter type models were similar to those of the real reservoirs. 

In experiments, the drainage and extraction of crude oil were studied separately for the fracture-type and for the porosity-type reservoirs. The corresponding types of models were used to study each of the two reservoir types. 

Five-millimeter wide strips of foil, 100 microns in thickness, were inserted between the inner walls of the tube and the glass strips. In this manner, the model formed a system of parallel strips, SO cm in length. The width of the fractures varied depending on their position along the cross section of the tube. The openings within these cracks were 100 microns wide, corresponding to the presumed size of fracture opening in the real reservoir of the fracture type. Fracture porosity of such models calculated by the method of material balance equation was 13.5%. 

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