Fracture growth

The theoretieal fraeture parameters in (8.22) and (8.23), based on a model assuming an inherent power law fracture flaw distribution and a constant fracture growth velocity, can be determined with the strain rate dependent fracture data in Fig. 8.11 (Grady and Kipp, 1980). Using the fracture data for oil shale provides a value of m = 8 and a fracture stress dependence on strain... 

Yeo AL, Levy D, Martin FC, Sonksen P, Sturgess I, Wheeler MM, Young A. Frailty and the biochemical effects of recombinant human growth hormone in women after surgery for hip fracture. Growth Hormone IGF Res 2003 13 361-70. 

Dynamics of fracture scaling behaviour for fracture growth patterns and propagation... 

Fig. 3.17. Molecular dynamic simulation results for the onset of fracture growth instablity in a triangular lattice network with Lennard-Jones potential, having an initial crack at the left-side boundary, (a) Initial stages of growth, and (b) late stage unstable growth with large propagation velocities (Abraham et al 1994).

Fig. 3.18. Computer simulation results for fracture growth in perfect lattice. Transition from smoothly advancing crack to violent propagation and branching instabilities occurs with larger pulling stresses (from Marder and Fineberg 1996).

By analogy with what have been done with the conventional LEFM approach, the first solution seems to be the most appropriate. This point is, however, ambiguous two values of rp and therefore of Ketr could not have been determined with certainty those in the transition zone at 0.4 and 0.7 m/s as direct consequence of the unstable-stable transition occurring in each series. We have indeed noticed that for an a/W, where both macroscopic behaviours have been observed, the values of Fmax were 5 to 10% higher under unstable crack propagation than for stable fracture growth. Table 6 shows the different values of rp and Ketr obtained ... 

Friction pressures and viscosities are two important physical characteristics of well stimulation fluids. Friction pressures, fluid hydrostatics and fracturing gradients determine the minimum surface pumping pressure necessary to maintain fracture growth. Often friction pressure is the de-... 

Newly exposed shale shrinks, fostering fracture growth, thus the process is self-reinforcing. 

FRACOD is a two dimensional BEM/DDM code for fracturing analysis in rocks, (see Part 11 in Rinne, 2003). The code is based on the principles of linear elastic fracture mechanics and has been developed to track both fracture initiation and propagation. The initiation of fracturing can be specified using any criterion, but once initiated fracture growth is controlled by the fracture toughness. 

Figure 2. Predicted AE locations due to fracture sliding and fracture growth.

Pre-placed iiactures grows radially surrounding the boreholes but their growth is inhibited by the presence of already developed iiactures from previously blasted surrounding blastholes. Numerical difficulties prevented fracture growth in time and in directions. 

Numerical simulation of rock fracturing by blasting is approached by two broad methodologies, namely, continuum approach and discontinuum approach. The continuum approach assumes continuity with the fractures representation, while individual cracks are tracked in the discontinuum approach. The primary aim of the continuum approach is to estimate the extent of the weakening in the material around the source they do not characterize the very local fracture growths. 

Fig. 11.38. Event density in projection in projection to the three coordinate planes in five successive stages of fracture growth. The fracture plane from core inspection is indicated by dashed lines (Zang et al. 1998).

A significant difference between the appearance of fracture surfaces of fatigue specimens tested at 75 and -300 F at the same stress is that the specimens tested at -300 F show more "rubbing" action. It appears that the fracture growth is not as rapid as that in the case of the specimens tested at 75 F. The extent of fatigue damage on the specimen prior to fracture indicates the combined effects of a slower crack propagation rate and the increased tensile properties. 

Figure 3. Fracture growth in Kevlar 149 microoonposites. Two independent sites are involved, the darker zone between these undergoes virtually no...

Factors facilitating fracture growth are sharp edges of filler particles and the shape of the particles and their packing, mainly if they are localized in the zone... 

Williams, M.L. (1965) Initiation and growth of viscoelastic fracture. Int. J. Fract. Mech. 1, 292-310 Williams, M.L. (1967) Fatigue-fracture growth in linearly viscoelastic materials. J. Appl. Phys. 38, 4476-4480... 

Fracture Growth Resulting From Injecting a Viscous Fluid. 

Theoretical Underpinning of the Voight Relation Rock Mechanics, Fracture Growth, Damage, and Lava Dome Growth/Failure... 

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