Fracture stability

In addition to their successful applications to fracture stability problems, the stress intensity factors have been widely used as correlation parameters in analyzing the subcritical crack growth rates da/dn (in fatigue) and dafdt (in corrosion), n and t referring to the number of... 

Rinne, M. Shen, B. Lee, H-S. 2003. Aspb Pillar Stability Experiment. Modelling of fracture stability by FRACOD. SKB, IPR-03-05. 

Rinne M, Shen B, Lee H-S, 2003. Aspo pillar stability experiment. Part I Modelling of fracture stability by FRACOD. Part II Modelling Fracture Initiation and Acoustic Emission. Part III Reconstruction of Stress Field Using an Inverse Technique. International Progress Report, IPR-03-05. Swedish Nuclear Fuel and Waste Management Company, Stockholm, 2003. 

Jacob, E., et al., 1993. Evaluation of biodegradable cefazolin sodium microspheres for the prevention of infection in rabbits with experimental open tibial fractures stabilized with internal-fixation. Journal of Orthopaedic Research 11 (3), 404—411. 

R.F. Cook, D.R. Clarke, Fracture stability, R-curves and strength variability, Acta Mater., 36 [3] 555-62 (1988)... 

Fig. 9.4a,b. Femoral shaft fracture stabilized with Nancy nails. Lateral nail inserted through tip of greater trochanter to improve proximal stability, a both nails appear to be within the medullary canal on AP. b lateral view reveals that the medial nail has pierced the cortex in the calcar region... 

Torode and Zeig classification of pelvic fractures. Type I avulsion injuries. Type II Iliac wing fractures (stability of the ligament complex). 

Finnbogason et al. (1995) utilised plain radiographs to determine fracture stability ... 

Finnbogason T, Karlsson G, Lindberg L, Mortensson W (1995) Nondisplaced and minimally displaced fractures of the lateral humeral condyle in children a prospective radiographic investigation of fracture stability. J Pediatr Orthop 15 422-425... 

The current development towards thinner and larger wafers already shows that the fracture stability is a limiting factor. Sawing conditions that reduce the surface... 

Sohd materials, such as gilsonite and asphalt, and partially soluble sulfonated asphalt may also be added to plug small fractures in exposed shale surfaces and thereby limit water entry into the formation (105,124). The asphalts are oxidized or treated to impart partial solubiUty. These materials may be softened by the downhole temperature, causing them to deform and squeeze into small openings exposed to the borehole. Laboratory tests designed to evaluate shale-stabilizing muds have confirmed the beneficial action of these materials (125) (see also Soil STABILIZATION). 

At still higher true stress, do/de, the rate of work-hardening decreases further, becoming insufficient to maintain stability - the extra stress in the neck can no longer be accommodated by the work-hardening produced by making the neck, and the neck grows faster and faster, until final fracture takes place. 

Rider and Amott were able to produce notable improvements in bond durability in comparison with simple abrasion pre-treatments. In some cases, the pretreatment improved joint durability to the level observed with the phosphoric acid anodizing process. The development of aluminum platelet structure in the outer film region combined with the hydrolytic stability of adhesive bonds made to the epoxy silane appear to be critical in developing the bond durability observed. XPS was particularly useful in determining the composition of fracture surfaces after failure as a function of boiling-water treatment time. A key feature of the treatment is that the adherend surface prepared in the boiling water be treated by the silane solution directly afterwards. Given the adherend is still wet before immersion in silane solution, the potential for atmospheric contamination is avoided. Rider and Amott have previously shown that such exposure is detrimental to bond durability. 

Often, the immobilized product has a structural strength sufficient to prevent fracturing over time. Solidification accomplishes the objective by changing a non-solid waste material into a solid, monolithic structure that ideally will not permit liquids to percolate into or leach materials out of the mass. Stabilization, on the other hand, binds the hazardous constituents into an insoluble matrix or changes the hazardous constituent to an insoluble form. Other objectives of solidiflcation/stabilization processes are to improve handling of the waste and pri uce a stable solid (no free liquid) for subsequent use as a construction material or for landfilling. 

The acknowledged father of fracture mechanics is A. A. Griffith [6-13]. His principal contribution is an analysis of crack stability based on energy equilibrium. If a crack is in equilibrium, the decrease of strain energy U must be equal to the increase of surface energy S due to crack extension, that is, ... 

Cone angles and throat depth dictate the bit best suited for stabilization. Cone angles are steep (60° to 70°), medium (80° to 90°), flat (100° to 120°), best suited for highly stable, stable and for fracturing formation, respectively. 

Structured laundry liquids are currently available in Europe and were recently introduced in the United States [50,51]. These products typically contain high levels of surfactants and builder salts, as well as enzymes and other additives. In the presence of high ionic strength, the combination of certain anionic and nonionic surfactants form lamellar liquid crystals. Under the microscope (electron microscope, freeze fracturing) these appear as round droplets with an onion-like, multilayered structure. Formation of these droplets or sperulites permits the incorporation of high levels of surfactants and builders in a pourable liquid form. Stability of the dispersion is enhanced by the addition of polymers that absorb onto the droplet surface to reduce aggregation. 

In the matrix of PLA/ polycaprilactone (PCL)/OMMT nano-composites, the silicate layers of the organoclay were intercalated and randomly distributed (Zhenyang et at, 2007). The PLA/PCL blend significantly improved the tensile and other mechanical properties by addition of OMMT. Thermal stability of PLA/PCL blends was also explicitly improved when the OMMT content is less than 5%wt. Preparation of PLA/thermoplastic starch/MMT nano-composites have been investigated and the products have been characterized using X-Ray diffraction, transmission electron microscopy and tensile measurements. The results show improvement in the tensile and modulus, and reduction in fracture toughness (Arroyo et ah, 2010). 

Additives that assist the creation of a fracture include viscosifiers, such as polymers and crosslinking agents temperature stabilizers pH control agents and fluid loss control materials. Formation damage is reduced by such additives as gel breakers, biocides, surfactants, clay stabilizers, and gases. 

However, it has been established that an intense control of certain variables may improve the execution of a hydraulic fracturing job and the success of a stimulation. Therefore an intense quality control is recommended [552,553]. Such a program includes monitoring the breaker performance at low temperatures and measuring the sensitivity of fracturing fluids to variations in crosslinker loading, temperature stabilizers, and other additives at higher temperatures. 

Boron-crosslinked galactomannan fracturing fluids have an increased temperature stability. The temperature stability of fracturing fluids containing galactomannan polymers is increased by adding a sparingly soluble borate with... 

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