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Sample records for 12d3 fracture properties

  1. Subtask 12D3: Fracture properties of V-5Cr-5Ti Alloy

    SciTech Connect

    Li, H.; Hamilton, M.L.; Jones, R.H.

    1995-03-01

    The purpose of this research is to investigate the effect of heat treatment on microstructure and fracture toughness of a V-5Cr-5Ti alloy in the range -50-100{degrees}C. Fracture toughness and impact tests were performed on a V-5Cr-5Ti alloy. Specimens annealed at 1125{degrees}C for 1 h and furnace cooled in a vacuum of 1.33 x 10{sup -5} Pa were brittle at room temperature (RT) and experienced a mixture of intergranular and cleavage fracture. Fracture toughness (J{sub IQ}) at RT was 52 kJ/m{sup 2} and the impact fracture energy (IFE) was 6 J. The IFE at -100{degrees}C was only 1 J. While specimens exhibited high fracture toughness at 100{degrees}C (J{sub IQ} is 485 kj/m{sup 2}), fracture was a mixture of dimple and intergranular failure, with intergranular fracture making up 40% of the total fracture surface. The ductile to brittle transition temperature (DBTT) was estimated to be about 20{degrees}C. When some specimens were given an additional annealing at 890{degrees}C for 24 h, they became very ductile at RT and fractured by microvoid coalescence. The J{sub IQ} value increased from 52 kJ/m{sup 2} to {approximately}1100 kJ/m{sup 2}. The impact test failed to fracture specimens at RT due to a large amount of plastic deformation. 7 refs., 1 fig., 6 tabs.

  2. Sequence conservation of the 12D3 gene in Mexican isolates of Babesia bovis.

    PubMed

    Perez, J; Javier Perez, J; Vargas, P; Antonio Alvarez, J; Rojas, C; Figueroa, J V

    2010-04-01

    The 12D3 antigen present in Babesia bovis has been evaluated as a recombinant vaccine candidate and the 12d3 coding sequence has been reported for an Australian and an USA (Texas) isolate of B. bovis. However, no approach has been conducted to perform analysis of 12d3 sequence conservation on a larger number of B. bovis isolates. This could provide important information to determine whether a recombinant vaccine containing this antigen could be widely used. This study reports the cloning and sequencing analysis of the 12d3 coding region in 20 different B. bovis isolates collected from various geographical regions in the tropics and subtropics of Mexico. Comparative analysis of the consensus nucleotide sequences obtained for each isolate revealed a high degree of conservation (94-99% sequence identity) among the 12d3 alleles present in the Mexican isolates when compared with the 12d3 ORF sequences from the Texan (T2Bo) B. bovis isolate. Similarly, BLASTX sequence homology search showed a high percent identity (93-99%) of the deduced amino acid 12D3 sequence as compared with the T2Bo isolate sequence. The high level of sequence conservation in 12d3 among the 20 B. bovis isolates collected from geographically distant locations in Mexico suggests that there exists a minimal bovine-host immunological pressure which could be translated into antigenic diversity or variation, and most probably this is reflected in the non-inmunodominant characteristic of the 12D3 antigen as it has been previously described in the literature. 12D3 antigen can be considered as a viable candidate for inclusion in a recombinant vaccine for cattle babesiosis caused by B. bovis in Mexico.

  3. Fracture properties of lightweight concrete

    SciTech Connect

    Chang, T.P.; Shieh, M.M.

    1996-02-01

    This study presents the experimental results of fracture properties of concrete incorporating two kinds of domestic lightweight aggregate (LWA) manufactured through either a cold-bonding or a sintering process. The cold-bonded aggregates were mainly made of pulverized fly-ash through a cold-pelletization process at ambient temperature, while the sintered aggregates were made of clay and shale expanded by heat at a temperature near 1,200 C. Experimental results show that the 28-day compressive strengths of {phi} 100 x 200 mm cylindrical concrete specimen made of those LWAs range from 30.1 (sintered) to 33.9 MPa (cold-bonded). By means of size effect law, it is found that the fracture energies, G{sub f}, were 34.42 N/m (sintered) and 37.2 N/m (cold-bonded), respectively.

  4. Macroscopic properties of fractured porous media

    NASA Astrophysics Data System (ADS)

    Thovert, J.; Mourzenko, V. V.; Adler, P. M.

    2007-12-01

    The determination of the local fields in fractured porous media is a challenging problem, because of the multiple scales that are involved and of the possible nonlinearity of the governing equations. The purpose of this paper is to provide an overall view of the numerical technique which has been used to solve numerous problems. It is based on a three-dimensional discrete description of the fracture network and of the embedding matrix. Any fracture network geometry, any type of boundary condition, and any distribution of the fracture and matrix properties can be addressed, without simplifying approximations. The first step is to mesh the fracture network as it is by triangles of a controlled size. This meshing by an advancing front technique is done successively for each fracture and the intersections between fractures are taken into account. Then, the space in between the fractures is meshed by tetrahedra by the advancing front technique again. The faces of the tetrahedra which are in contact with fractures, coincide with the corresponding triangles in these fractures. The performances of these meshing codes will be illustrated by a few examples. The second step consists in discretizing the conservation equations by the finite volume technique. Specific properties are given to each fracture such as a surface permeability or a joint rigidity. This general technique has been applied to the basic and most important properties of fracture networks and of fractured porous media (1). These properties are single and two phase flows, wether they are accompagnied or not by dispersion of a solute and mechanical properties possibly coupled with flow. These applications will be briefly illustrated by some examples, including when possible comparison with real data. Ref: (1) P.M. Adler, V.V. Mourzenko, J.-F. Thovert, I. Bogdanov, in Dynamics of fluids and transport in fractured rock, ed. B. Faybishenko, Geophysical Monograph Series, 162, 33, 2005.

  5. The elastic properties of fractured rocks

    NASA Astrophysics Data System (ADS)

    Darcel, C.; Le Goc, R.; Davy, P.

    2013-12-01

    The consequences of fracturing on rock mass strength still remain an issue for rock engineering practices, including excavation or repository design, support design, slope stability and caving in mines. The difficulty is twice and concerns both the description of the fracturing pattern, and the relationship between fracture characteristics and rock mass mechanical properties. This is generally assessed by empirical knowledge but no complete quantitative and theoretical relations are yet established. To our knowledge, the only theoretical work was to found a relationship between the elastic strength and the percolation parameter (i.e. a normalized sum of the cube of fracture radius) for 3D frictionless fracture networks. The relationship has been demonstrated for Poissonian (randomly distributed) low-density (i.e. where fractures are not almost intersecting) networks, with a narrow range of fracture radius. By means of finite-element models and Green's function methods, we extend the analysis to fracture networks with geologically realistic geometry: i.e. non-Poissonian, relatively high densities, and power-law length distributions. The elastic strength of the fractured rock mass is still found to decrease exponentially with the percolation parameter on average. But large deviations from the mean exist for heavy tailed fracture length distribution, i.e. when the probability of having fractures of the order of the system size is no more negligible. We discuss the way to ameliorate the prediction by taking into account configuration details that are not described by statistical parameters.

  6. Physical Properties of Fractured Porous Media

    NASA Astrophysics Data System (ADS)

    Mohammed, T. E.; Schmitt, D. R.

    2015-12-01

    The effect of fractures on the physical properties of porous media is of considerable interest to oil and gas exploration as well as enhanced geothermal systems and carbon capture and storage. This work represents an attempt to study the effect fractures have on multiple physical properties of rocks. An experimental technique to make simultaneous electric and ultrasonic measurements on cylindrical core plugs is developed. Aluminum end caps are mounted with ultrasonic transducers to transmit pules along the axis of the cylinder while non-polarizing electrodes are mounted on the sides of the core to make complex conductivity measurements perpendicular to the cylinder axis. Electrical measurements are made by applying a sinusoidal voltage across the measurement circuit that consist of a resister and the sample in series. The magnitude and phase of the signal across the sample is recorded relative to the input signal across a range of frequencies. Synthetic rock analogs are constructed using sintered glass beads with fractures imbedded in them. The fracture location, size and orientation are controlled and each fractured specimen has an unfractured counterpart. Porosity, Permeability, electrical conductivity and ultrasonic velocity measurements are conducted on each sample with the complex electrical conductivities recorded at frequencies from 10hz to 1 Mhz. These measurements allow us to examine the changes induced by these mesoscale fractures on the embedding porous medium. Of particular interest is the effect of fracture orientation on electrical conductivity of the rock. Seismic anisotropy caused by fractures is a well understood phenomenon with many rock physics models dedicated to its understanding. The effect of fractures on electrical conductivity is less well understood with electrical anisotropy scarcely investigated in the literature. None the less, using electrical conductivity to characterize fractures can add an extra constraint to characterization based

  7. The radiation swelling effect on fracture properties and fracture mechanisms of irradiated austenitic steels. Part I. Ductility and fracture toughness

    NASA Astrophysics Data System (ADS)

    Margolin, B.; Sorokin, A.; Shvetsova, V.; Minkin, A.; Potapova, V.; Smirnov, V.

    2016-11-01

    The radiation swelling effect on the fracture properties of irradiated austenitic steels under static loading has been studied and analyzed from the mechanical and physical viewpoints. Experimental data on the stress-strain curves, fracture strain, fracture toughness and fracture mechanisms have been represented for austenitic steel of 18Cr-10Ni-Ti grade (Russian analog of AISI 321 steel) irradiated up to neutron dose of 150 dpa with various swelling. Some phenomena in mechanical behaviour of irradiated austenitic steels have been revealed and explained as follows: a sharp decrease of fracture toughness with swelling growth; untypical large increase of fracture toughness with decrease of the test temperature; some increase of fracture toughness after preliminary cyclic loading. Role of channel deformation and channel fracture has been clarified in the properties of irradiated austenitic steel and different tendencies to channel deformation have been shown and explained for the same austenitic steel irradiated at different temperatures and neutron doses.

  8. Properties of Flow Zones in Fractured Rock

    NASA Astrophysics Data System (ADS)

    Salve, R.

    2004-12-01

    Observations over the last 25 years from various field studies suggest that preferential flow is common in soils and rocks. Despite this realization, very little is known about the large-scale properties (e.g., structure, distribution, continuity) of such flow regimes. This information is important for predictive models, but it remains elusive, mainly because of the difficulties involved in characterizing flow that has substantial spatial (both vertical and horizontal) and temporal variability. To better understand preferential flow in fractured rock, we carried out an in situ field experiment in the Topopah Spring tuff found in Exploratory Studies Facility at Yucca Mountain, Nevada. This experiment involved the release of ~22 m3 of ponded water (at a pressure head of ~0.04 m) over a period of 7 months, directly onto a 12 m2 infiltration plot. As water was released, changes in moisture content were monitored along horizontal boreholes located in the formation ~19-22 m below. Distinct flow zones, with significant differences in flow velocity, size, and extent of lateral movement, intercepted the 6-9 m long monitoring boreholes. Further, in some flow zones saturation levels persisted for the time period in which water was released, while in others there were periodic fluctuations. There was also evidence of water being diverted above the ceiling of a cavity in the immediate vicinity of the monitoring boreholes. Observations from this field experiment suggested that inconsistencies exist in present conceptual models of flow in fractured rock. Particularly, these observations suggest that isolated conduits within the fractured rock formation encompass a large number of fractures to form preferential flow paths that persist if there is a continuous supply of water. It appears that in fractured welded tuffs, the propensity for vertical dispersion and fracture-matrix interactions may be significantly greater than suggested by existing conceptual models. These observations

  9. Disentangling scaling properties in anisotropic fracture.

    PubMed

    Bouchbinder, Eran; Procaccia, Itamar; Sela, Shani

    2005-12-16

    Structure functions of rough fracture surfaces in isotropic materials exhibit complicated scaling properties due to the broken isotropy in the fracture plane generated by a preferred propagation direction. Decomposing the structure functions into the even order irreducible representations of the SO(2) symmetry group indexed by (m = 0, 2, 4, . . .) results in a lucid and quickly convergent description. The scaling exponent of the isotropic sector (m = 0) dominates at small length scales. One can reconstruct the anisotropic structure functions using only the isotropic and the first nonvanishing anisotropic sector (m = 2) [or at most the next one (m = 4)]. The scaling exponent of the isotropic sector should be observed in a proposed, yet unperformed, experiment.

  10. Fracture properties of an acrylic bone cement.

    PubMed

    Bialoblocka-Juszczyk, E; Baleani, M; Cristofolini, L; Viceconti, M

    2008-01-01

    This study investigated experimentally the fracture properties, i.e., the fatigue strength, the resistance to crack propagation and the fracture toughness, of an acrylic bone cement (Cemex RX). The mean endurance limit was determined following the staircase method. The endurance limit was estimated at 9.2 MPa. The fatigue crack propagation rate was measured according to the ASTM E647 standard. The equation of the line fitting the crack growth per cycle (da/dN) versus the stress-intensity factor range (delta K), in a log-log graph, was used to calculate the empirical constants of Paris' law for the selected bone cement: da/dN (m/cycle) = 3.56 x 10(-7) x delta K (MPa x m1/2)5.79. This power-law relationship described well (R2 = 0.96) the growth rate in the stable crack growth region, i.e., in the mid delta K range. The fracture toughness K(IC) of the bone cement was determined according to the ASTM E399 standard. The K(IC) mean value was 1.38 MPa x m1/2. These experimental results provide the set of necessary inputs for numerical studies aimed to investigate the damage accumulation process in the mantle fixing cemented prostheses.

  11. When do fractured media become seismically anisotropic? Some implications on quantifying fracture properties

    NASA Astrophysics Data System (ADS)

    Yousef, B. M.; Angus, D. A.

    2016-06-01

    Fractures are pervasive features within the Earth's crust and they have a significant influence on the multi-physical response of the subsurface. The presence of coherent fracture sets often leads to observable seismic anisotropy enabling seismic techniques to remotely locate and characterise fracture systems. In this study, we confirm the general scale-dependence of seismic anisotropy and provide new results specific to shear-wave splitting (SWS). We find that SWS develops under conditions when the ratio of wavelength to fracture size (λS / d) is greater than 3, where Rayleigh scattering from coherent fractures leads to an effective anisotropy such that effective medium model (EMM) theory is qualitatively valid. When 1 <λS / d < 3 there is a transition from Rayleigh to Mie scattering, where no effective anisotropy develops and hence the SWS measurements are unstable. When λS / d < 1 we observe geometric scattering and begin to see behaviour similar to transverse isotropy. We find that seismic anisotropy is more sensitive to fracture density than fracture compliance ratio. More importantly, we observe that the transition from scattering to an effective anisotropic regime occurs over a propagation distance between 1 and 2 wavelengths depending on the fracture density and compliance ratio. The existence of a transition zone means that inversion of seismic anisotropy parameters based on EMM will be fundamentally biased. More importantly, we observe that linear slip EMM commonly used in inverting fracture properties is inconsistent with our results and leads to errors of approximately 400% in fracture spacing (equivalent to fracture density) and 60% in fracture compliance. Although EMM representations can yield reliable estimates of fracture orientation and spatial location, our results show that EMM representations will systematically fail in providing quantitatively accurate estimates of other physical fracture properties, such as fracture density and compliance

  12. Influence of Natural Fractures Cohesive Properties on Geometry of Hydraulic Fracture Networks

    NASA Astrophysics Data System (ADS)

    Gonzalez-Chavez, M. A.; Dahi Taleghani, A.; Puyang, P.

    2014-12-01

    An integrated modeling methodology is proposed to analyze hydraulic fracturing jobs in the presence of the natural fracture network in the formation. A propagating hydraulic fracture may arrest, cross, or diverts into a preexisting natural crack depending on fracture properties of rock and magnitude and direction of principal rock stresses. Opening of natural fractures during fracturing treatment could define the effectiveness of the stimulation technique. Here, we present an integrated methodology initiated with lab scale fracturing properties using Double Cantilever Beam tests (DCB) to determine cohesive properties of rock and natural fractures. We used cohesive finite element models to reproduce laboratory results to verify the numerical model for the interaction of the hydraulic fracture and individual cemented natural fractures. Based on the initial investigations, we found out that distribution of pre-existing natural fractures could play a significant role in the final geometry of the induced fracture network; however in practice, there is not much information about the distribution of natural fractures in the subsurface due to the limited access. Hence, we propose a special optimization scheme to generate natural fracture geometry from the location of microseismic events. Accordingly, the criteria of evaluating the fitness of natural fracture realizations is defined as the total minimum distance squares of all microseismic events, which is the sum of minimum square distance for all microseismic events. Moreover, an additional constraint in this problem is that we need to set a minimum distance between fracture grids. Using generated natural fracture realizations, forward field-scale simulations are implemented using cohesive finite element analysis to find the best match with the recorded bottomhole pressure. To show the robustness of the proposed workflow for real field problem, we implemented this technique on available data from several well Chicontepec

  13. Fracture properties of the human mandible.

    PubMed

    Unnewehr, M; Homann, C; Schmidt, P F; Sotony, P; Fischer, G; Brinkmann, B; Bajanowski, T; DuChesne, A

    2003-12-01

    A total of seven human mandibles were struck to breaking point under standardised conditions using a pendulum. The cortical deformation for two impact directions was measured with strain gauge strips located at eight defined sites. Fronto-median impacts led to mostly bilateral and always multiple fractures in the posterior area of the bone, especially in the collum and the condyle. The fracture threshold was between 2.5 and 3.1 kN. Lateral impact caused fractures near the impact area as direct fractures of the ipsilateral corpus. Mainly single and double fractures were observed. For lateral impact the fracture threshold was between 0.6 and 0.8 kN. PMID:13680253

  14. Estimation of hydrologic properties of an unsaturated, fractured rock mass

    SciTech Connect

    Klavetter, E.A.; Peters, R.R.

    1986-07-01

    In this document, two distinctly different approaches are used to develop continuum models to evaluate water movement in a fractured rock mass. Both models provide methods for estimating rock-mass hydrologic properties. Comparisons made over a range of different tuff properties show good qualitative and quantitative agreement between estimates of rock-mass hydrologic properties made by the two models. This document presents a general discussion of: (1) the hydrology of Yucca Mountain, and the conceptual hydrological model currently being used for the Yucca Mountain site, (2) the development of two models that may be used to estimate the hydrologic properties of a fractured, porous rock mass, and (3) a comparison of the hydrologic properties estimated by these two models. Although the models were developed in response to hydrologic characterization requirements at Yucca Mountain, they can be applied to water movement in any fractured rock mass that satisfies the given assumptions.

  15. Fracture properties evaluation of stainless steel piping for LBB applications

    SciTech Connect

    Kim, Y.J.; Seok, C.S.; Chang, Y.S.

    1997-04-01

    The objective of this paper is to evaluate the material properties of SA312 TP316 and SA312 TP304 stainless steels and their associated welds manufactured for shutdown cooling line and safety injection line of nuclear generating stations. A total of 82 tensile tests and 58 fracture toughness tests on specimens taken from actual pipes were performed and the effect of various parameters such as the pipe size, the specimen orientation, the test temperature and the welding procedure on the material properties are discussed. Test results show that the effect of the test temperature on the fracture toughness was significant while the effects of the pipe size and the specimen orientation on the fracture toughness were negligible. The material properties of the GTAW weld metal was in general higher than those of the base metal.

  16. Material properties and fracture mechanics in relation to ceramic machining

    SciTech Connect

    Griffith, L.V.

    1993-12-02

    Material removal rate, surface finish, and subsurface damage are largely governed by fracture mechanics and plastic deformation, when ceramics are machined using abrasive methods. A great deal of work was published on the fracture mechanics of ceramics in the late 1970s and early 1980s, although this work has never resulted in a comprehensive model of the fixed abrasive grinding process. However, a recently published model describes many of the most important features of the loose abrasive machining process, for example depth of damage, surface roughness, and material removal rate. Many of the relations in the loose abrasive machining model can be readily discerned from fracture mechanics models, in terms of material properties. By understanding the mechanisms of material removal, from a material properties perspective, we can better estimate how one material will machine in relation to another. Although the fracture mechanics models may have been developed for loose abrasive machining, the principles of crack initiation and propagation are equally valuable for fixed abrasive machining. This report provides a brief review of fracture in brittle materials, the stress distribution induced by abrasives, critical indenter loads, the extension of cracks, and the relation of the fracture process to material removal.

  17. Fracture Toughness Properties of Gd123 Superconducting Bulks

    NASA Astrophysics Data System (ADS)

    Fujimoto, H.; Murakami, A.

    Fracture toughness properties of melt growth GdBa2Cu3Ox (Gd123) large single domain superconducting bulks with Ag2O of 10 wt% and Pt of 0.5 wt%; 45 mm in diameter and 25 mm in thickness with low void density were evaluated at 77 K through flexural tests of specimens cut from the bulks, and compared to those of a conventional Gd123 with voids. The densified Gd123 bulks were prepared with a seeding and temperature gradient method; first melt processed in oxygen, then crystal growth in air; two-step regulated atmosphere heat treatment. The plane strain fracture toughness, KIC was obtained by the three point flexure test of the specimens with through precrack, referring to the single edge pre-cracked beam (SEPB) method, according to the JIS-R-1607, Testing Methods for Fracture Toughness of High Performance Ceramics. The results show that the fracture toughness of the densified Gd123 bulk with low void density was higher than that of the standard Gd123 bulk with voids, as well as the flexural strength previously reported. We also compared the fracture toughness of as-grown bulks with that of annealed bulks. The relation between the microstructure and the fracture toughness of the Gd123 bulk was clearly shown.

  18. Determining the frequency dependence of elastic properties of fractured rocks

    NASA Astrophysics Data System (ADS)

    Ahrens, Benedikt; Renner, Jörg

    2016-04-01

    In the brittle crust, rocks often contain joints or faults on various length scales that have a profound effect on fluid flow and heat transport, as well as on the elastic properties of rocks. Improving the understanding of the effect of fractures and the role of stress state and heterogeneity along the fractures on elastic properties of rocks is potentially important for the characterization of deep geothermal reservoirs. Seismic surveys, typically covering a frequency range of about 1 to 1000 Hz, are a valuable tool to investigate fractured rocks but the extraction of fracture properties remains difficult. The elementary frequency-dependent interaction between fractured rock matrix and viscous pore fluids and the resulting effects on wave propagation require well-founded dispersion analyses of heterogeneous rocks. In this laboratory study, we investigate the stress dependence of the effective elastic properties of fractured reservoir rocks over a broad frequency range. To assess the effect of faults on the effective elastic properties, we performed cyclic axial loading tests on intact and fractured samples of Solnhofen limestone and Padang granodiorite. The samples contained an idealized fault, which was created by stacking two sample discs on top of each other that experienced various surface treatments to vary their roughness. The dynamic loading tests were conducted with frequencies up to 10 Hz and amplitudes reaching 10% of the statically applied stress. Simultaneously, P- and S-wave measurements were performed in the ultrasonic frequency range (above 100 kHz) with a total of 16 sensors, whose positioning above and below the samples guarantees a wide range of transmission and reflection angles. Preliminary results of static and dynamic elastic properties of intact Padang granodiorite show a pronounced increase in Young's moduli and Poisson's ratio with increasing axial stress. Stress relaxation is accompanied by a decrease of the modulus and the Poisson

  19. Upscaling Fracture Properties in Support of Dual-Permeability Simulations

    NASA Astrophysics Data System (ADS)

    Reeves, D. M.; Parashar, R.

    2008-12-01

    Rainier Mesa (RM) is a tuffaceous, high elevation plateau on the Nevada Test Site (NTS) that has been subjected to numerous nuclear tests between 1957 and 1992. Unlike other tests on the NTS located within or just above the saturated zone, tests at the RM T-tunnel complex were conducted within a variably-saturated sequence of bedded and non-welded vitric and zeolitized tuff units, located approximately 500 m above the regional groundwater flow system. The low permeability and high porosity of the underlying zeolitized tuff units suggest the downward transport of radionuclides released from these tests are minimal through the tuff matrix. However, numerous faults observed to discharge water into tunnel drifts may serve as preferential pathways for radionuclide migration. Data collected from tunnel drifts indicate that faulting within the zeolitized tuff units are sparse with fractal clustering, and that connectivity between adjacent fault clusters is often weak to non-existent. The sparse fault density at RM, in conjunction with the extreme variability in the spatial distribution of faults, poses challenges not readily addressed by existing upscaling methods that upscale fracture properties as equivalent grid tensors. The unique fault statistics at RM has led to the development of a fracture continuum method designed to faithfully preserve flow and transport properties of the sparse fault networks. This method is based on selective mapping and upscaling of fault hydraulic and transport properties onto a continuum grid in support of dual-permeability simulations. Comparisons of global flow and random walk particle breakthrough between two-dimensional discrete fracture network and fracture continuum simulations demonstrate the utility of this method.

  20. The fracture properties and mechanical design of human fingernails.

    PubMed

    Farren, L; Shayler, S; Ennos, A R

    2004-02-01

    Fingernails are a characteristic feature of primates, and are composed of three layers of the fibrous composite keratin. This study examined the structure and fracture properties of human fingernails to determine how they resist bending forces while preventing fractures running longitudinally into the nail bed. Nail clippings were first torn manually to examine the preferred crack direction. Next, scissor cutting tests were carried out to compare the fracture toughness of central and outer areas in both the transverse and longitudinal direction. The fracture toughness of each of the three isolated layers was also measured in this way to determine their relative contributions to the toughness. Finally, the structure was examined by carrying out scanning electron microscopy of free fracture surfaces and polarized light microscopy of nail sections. When nails were torn, cracks were always diverted transversely, parallel to the free edge of the nail. Cutting tests showed that this occurred because the energy to cut nails transversely, at approximately 3 kJ m(-2), was about half that needed (approx. 6 kJ m(-2)) to cut them longitudinally. This anisotropy was imparted by the thick intermediate layer, which comprises long, narrow cells that are oriented transversely; the energy needed to cut this layer transversely was only a quarter of that needed to cut it longitudinally. In contrast the tile-like cells in the thinner dorsal and ventral layers showed isotropic behaviour. They probably act to increase the nail's bending strength, and as they wrap around the edge of the nail, they also help prevent cracks from forming. These results cast light on the mechanical behaviour and care of fingernails.

  1. Numerical evaluation of effective unsaturated hydraulic properties for fractured rocks

    SciTech Connect

    Lu, Zhiming; Kwicklis, Edward M

    2009-01-01

    To represent a heterogeneous unsaturated fractured rock by its homogeneous equivalent, Monte Carlo simulations are used to obtain upscaled (effective) flow properties. In this study, we present a numerical procedure for upscaling the van Genuchten parameters of unsaturated fractured rocks by conducting Monte Carlo simulations of the unsaturated flow in a domain under gravity-dominated regime. The simulation domain can be chosen as the scale of block size in the field-scale modeling. The effective conductivity is computed from the steady-state flux at the lower boundary and plotted as a function of the averaging pressure head or saturation over the domain. The scatter plot is then fitted using van Genuchten model and three parameters, i.e., the saturated conductivity K{sub s}, the air-entry parameter {alpha}, the pore-size distribution parameter n, corresponding to this model are considered as the effective K{sub s}, effective {alpha}, and effective n, respectively.

  2. HYDROGEN EFFECTS ON THE FRACTURE TOUGHNESS PROPERTIES OF FORGED STAINLESS STEELS

    SciTech Connect

    Morgan, M

    2008-03-28

    The effect of hydrogen on the fracture toughness properties of Types 304L, 316L and 21-6-9 forged stainless steels was investigated. Fracture toughness samples were fabricated from forward-extruded forgings. Samples were uniformly saturated with hydrogen after exposure to hydrogen gas at 34 MPa or 69 and 623 K prior to testing. The fracture toughness properties were characterized by measuring the J-R behavior at ambient temperature in air. The results show that the hydrogen-charged steels have fracture toughness values that were about 50-60% of the values measured for the unexposed steels. The reduction in fracture toughness was accompanied by a change in fracture appearance. Both uncharged and hydrogen-charged samples failed by microvoid nucleation and coalescence, but the fracture surfaces of the hydrogen-charged steels had smaller microvoids. Type 316L stainless steel had the highest fracture toughness properties and the greatest resistance to hydrogen degradation.

  3. Correlations among ultrasonic propagation factors and fracture toughness properties of metallic materials

    NASA Technical Reports Server (NTRS)

    Vary, A.

    1976-01-01

    Empirical evidence was developed to show that a close relation exists among fracture toughness, yield strength, and ultrasonic attenuation properties of metallic materials. The evidence was obtained by ultrasonic probing of specimens of two maraging steels and a titanium alloy. It was concluded that nondestructive ultrasonic methods can be used to indirectly evaluate fracture-related material properties. The results suggest that these nondestructive ultrasonic measurements can also serve as an adjunct to destructive testing, measurement, and analysis of fracture properties.

  4. Fracture properties of aged and post-processed dental composites.

    PubMed

    Drummond, J L; Botsis, J; Zhao, D; Samyn, J

    1998-04-01

    The purpose of this study was to determine the flexure strength (sigma f), Young's modulus (E), and fracture toughness (KIC) of five dental composites after aging in water and air. The composites were, by weight, 75% or 79% glass filler and 25% or 21% resin composed of 60% Bis-GMA and 40% TEG-DMA. The filler was either strontium glass (75Sr or 79Sr) or a combination, by weight, of 90% strontium glass and 10% colloidal silica (75Sr10 or 79Sr10). The specimens, 2 x 4 x 70 mm bars, were aged in either air or distilled water at 37 degrees C and were tested in their respective aging media at a loading rate of 1.22 mm/s. The sigma f and E were tested in four-point loading and the KIC in three-point loading. The addition of the fillers to the unfilled resin resulted in a statistically significant increase in the flexure strength, flexure modulus, and fracture toughness. Aging in air had minimal effect on these properties. However, testing and aging in water led to a significant decrease in the mechanical properties in the first 6 months, but had limited effect from 6 to 12 months.

  5. Flow Rate- and Fracture Property Dependence of Fracture-Matrix Ensemble Relative Permeability

    NASA Astrophysics Data System (ADS)

    Matthai, S. K.; Lang, P.; Bazrafkan, S.

    2012-12-01

    The grid-block scale ensemble relative permeability, kri of fractured porous rock with appreciable matrix permeability is of decisive interest to reservoir simulation and the prediction of production, injector-producer water breakthrough, and ultimate recovery. While the dynamic behaviour of naturally fractured reservoirs (NFR) already provides many clues about (pseudo) kri on the inter-well length scale, such data are difficult to interpret because, in the subsurface, the exact fracture geometry is unknown. Here we present numerical simulation results from discrete fracture and matrix (DFM) unstructured grid hybrid FEM-FVM simulation models, predicting the shape of fracture-matrix kri curves. In contrast to our earlier work, we also simulate capillary fracture matrix transfer (CFMT) and without relying the frequently made simplifying assumption that fracture saturation reflects fracture-matrix capillary pressure equilibrium. We also employ a novel discretization of saturation which permits jump discontinuities to develop across the fracture-matrix interface. This increased physical realism permits - for the first time - to test our earlier semi-analytical model of the flow rate dependence of relative permeability, ensuing from CFMT. The sensitivity analysis presented here constrains CMFT-related flow rate dependence of kri and illustrates how it manifests itself in two geometries of layer-restricted well-developed fracture patterns mapped in the field. We have also investigated the dependence of kri on fracture aperture as computed using discrete element analysis for plausible states of in situ stress. Our results indicate that fracture-matrix ensemble relative permeability can be matched with a new semi-analytic model taking into account the fracture-matrix flux ratio, the wetted fracture-matrix interface area as a function of saturation and the breakthrough saturation. However, we also detect a scale dependence of kri requiring a more elaborate treatment.

  6. Inferring the Properties of Fluid-Filled Fractures using Tube Waves

    NASA Astrophysics Data System (ADS)

    OReilly, O. J.; Dunham, E. M.; Moos, D.

    2014-12-01

    We present a methodology to infer the geometry of fluid-filled fractures (both aperture and length) using the interaction between tube waves in cylindrical fluid-filled conduits and trapped waves in fractures intersecting the conduit. This approach could be applied to study engineered fractures in oil and gas reservoirs as well as volcanic systems. We specifically investigate the reflection and transmission of tube waves, propagating along the cylindrical conduit, from fractures. Pressure changes carried by the tube wave can couple to resonant oscillations of the fractures, and the spectral properties of these oscillations carry information about fracture geometry. The fracture is coupled to the conduit at the fracture mouth by balancing pressure and conserving mass as fluid flows into or out of the fracture. In our linearized theory, the fracture response is quantified through a frequency-domain transfer function relating fluid pressure and velocity at the fracture mouth. For a given transfer function, tube wave seismograms can be obtained using a single, inverse fast Fourier transform. Fracture transfer functions are obtained from numerical simulations of wave propagation along fluid-filled cracks. These simulations rigorously couple an approximate version of the linearized Navier-Stokes equation for a viscous, compressible fluid to the elastic wave equation in the surrounding medium. To solve this problem, we have developed a two-dimensional high-order finite difference method capable of handling complex fracture geometries. Fracture resonance is associated with standing crack waves (also known as Krauklis waves) propagating along the fracture. We find that although details of fracture properties can be revealed by recorded pressure or seismic signals, reductions in aperture, as occur at crack tips, can reduce the amplitude of high frequency resonant modes through increased viscous dissipation.

  7. Fractures

    PubMed Central

    Hall, Michael C.

    1963-01-01

    Recent studies on the epidemiology and repair of fractures are reviewed. The type and severity of the fracture bears a relation to the age, sex and occupation of the patient. Bone tissue after fracture shows a process of inflammation and repair common to all members of the connective tissue family, but it repairs with specific tissue. Cartilage forms when the oxygen supply is outgrown. After a fracture, the vascular bed enlarges. The major blood supply to healing tissue is from medullary vessels and destruction of them will cause necrosis of the inner two-thirds of the cortex. Callus rapidly mineralizes, but full mineralization is achieved slowly; increased mineral metabolism lasts several years after fracture. PMID:13952119

  8. Dry fracture method for simultaneous measurement of in-situ stress state and material properties

    SciTech Connect

    Serata, S.; Oka, S.; Kikuchi, S.

    1996-04-01

    Based on the dry fracture principle, a computerized borehole probe has been developed to measure stress state and material properties, simultaneously. The probe is designed to obtain a series of measurements in a continuing sequence along a borehole length, without any interruptive measures, such as resetting packers, taking indentation of borehole wall, overcoming, etc. The new dry fracture probe for the single fracture method is designed to overcome the difficulties posed by its ancestor which was based on the double fracture method. The accuracy of the single fracture method is confirmed by a close agreement with the theory, FE modeling and laboratory testing.

  9. Fractures

    MedlinePlus

    ... commonly happen because of car accidents, falls, or sports injuries. Other causes are low bone density and osteoporosis, which cause weakening of the bones. Overuse can cause stress fractures, which are very small cracks in the ...

  10. Studies of Transport Properties of Fractures: Final Report

    SciTech Connect

    Stephen R. Brown

    2006-06-30

    We proposed to study several key factors controlling the character and evolution of fracture system permeability and transport processes. We suggest that due to surface roughness and the consequent channeling in single fractures and in fracture intersections, the tendency of a fracture system to plug up, remain permeable, or for permeability to increase due to chemical dissolution/precipitation conditions will depend strongly on the instantaneous flow channel geometry. This geometry will change as chemical interaction occurs, thus changing the permeability through time. To test this hypothesis and advance further understanding toward a predictive capability, we endeavored to physically model and analyze several configurations of flow and transport of inert and chemically active fluids through channels in single fractures and through fracture intersections. This was an integrated program utilizing quantitative observations of fractures and veins in drill core, quantitative and visual observations of flow and chemical dissolution and precipitation within replicas of real rough-walled fractures and fracture intersections, and numerical modeling via lattice Boltzmann methods.

  11. The Use of Shear-Thinning Fluids as "Smart" Tracers to Infer Fracture Network Properties

    NASA Astrophysics Data System (ADS)

    Roques, C.; Selker, J. S.; Le Borgne, T.; Meheust, Y.; Abou Najm, M.; Rochefort, W. E.; Davy, P.; Bour, O.; Loiseau, M.; Givens, S.; Herring, B. J.

    2015-12-01

    The identification of preferential flow paths, their connectivity and their hydraulic properties in fractured rocks is critical for fluid flow and solute transport. Classical hydraulic tests allow defining a mean effective aperture based on simplified fracture models. Here we study the potential of using shear-thinning fluids as "smart" tracers to infer the distribution of fracture hydraulic properties. The main hypothesis considers that the flow of a shear-thinning fluid will sample specific pathways of the network as the fluid presents more viscous-shear behaviors. The flow field distribution of shear-thinning fluids in a 2D parallel fracture is first investigated numerically by implementing a viscous-shear model on classical flow equations. The relationship between fracture aperture and the degree of the flow enhancement due to the thinning behavior is quantified - given by the ratio between the non-Newtonian fluid average velocity and its corresponding Newtonian fluid at viscosity. A dimensionless solution describing the flow enhancement with respect to fracture aperture is derived from the theory. We also examine the impact of multiple fracture setups on the flow field redistribution in radial flow condition. Two main fracture configurations that can be found in a real network are considered: fractures organized in series and in parallel. We describe different flow enhancement behaviors controlled by the power exponent of the fluid and the fracture geometry. In perspective, some first experimental results are introduced that will guide the development of an inverse modelling framework.

  12. Elastic properties and fracture strength of quasi-isotropic graphite/epoxy composites

    NASA Technical Reports Server (NTRS)

    Sullivan, T. L.

    1977-01-01

    The layups of the studied laminates are (0, + or - 60) sub s, (0, + or - 45, 90) sub s, (0, + or - 30, + or - 60, 90) sub s (0, + or - 22 1/2, + or - 45, + or - 67 1/2, 90) sub s. The properties determined were tensile modulus, Poisson's ratio, bending stiffness, fracture strength and fracture strain. Measured properties and properties predicted using laminate theory were found to be in reasonable agreement. Reasons for data scatter were determined.

  13. Characterization of hydraulic fractures and reservoir properties of shale using natural tracers

    NASA Astrophysics Data System (ADS)

    Heath, J. E.; Gardner, P.; Kuhlman, K. L.; Malama, B.

    2013-12-01

    Hydraulic fracturing plays a major role in the economic production of hydrocarbon from shale. Current fracture characterization techniques are limited in diagnosing the transport properties of the fractures on the near wellbore scale to that of the entire stimulated reservoir volume. Microseismic reveals information on fracture geometries, but not transport properties. Production analysis (e.g., rate transient analysis using produced fluids) estimates fracture and reservoir flow characteristics, but often relies on simplified models in terms of fracture geometries and fluid storage and transport. We present the approach and potential benefits of incorporating natural tracers with production data analysis for fracture and reservoir characterization. Hydraulic fracturing releases omnipresent natural tracers that accumulate in low permeability rocks over geologic time (e.g., radiogenic 4He and 40Ar). Key reservoir characteristics govern the tracer release, which include: the number, connectivity, and geometry of fractures; the distribution of fracture-surface-area to matrix-block-volume; and the nature of hydrocarbon phases within the reservoir (e.g., methane dissolved in groundwater or present as a separate gas phase). We explore natural tracer systematics using numerical techniques under relevant shale-reservoir conditions. We evaluate the impact on natural tracer transport due to a variety of conceptual models of reservoir-transport properties and boundary conditions. Favorable attributes for analysis of natural tracers include the following: tracer concentrations start with a well-defined initial condition (i.e., equilibrium between matrix and any natural fractures); there is a large suite of tracers that cover a range of at least 7x in diffusion coefficients; and diffusive mass-transfer out of the matrix into hydraulic fractures will cause elemental and isotopic fractionation. Sandia National Laboratories is a multi-program laboratory managed and operated by

  14. TRITIUM AGING EFFECTS ON THE FRACTURE TOUGHNESS PROPERTIES OF FORGED STAINLESS STEEL

    SciTech Connect

    Morgan, M

    2008-04-14

    The fracture toughness properties of Type 21-6-9 stainless steel were measured for forgings in the unexposed, hydrogen-exposed, and tritium-exposed-and-aged conditions. Fracture toughness samples were cut from conventionally-forged and high-energy-rate-forged forward-extruded cylinders and mechanically tested at room temperature using ASTM fracture-toughness testing procedures. Some of the samples were exposed to either hydrogen or tritium gas (340 MPa, 623 K) prior to testing. Tritium-exposed samples were aged for up to seven years and tested periodically in order to measure the effect on fracture toughness of {sup 3}He from radioactive tritium decay. The results show that hydrogen-exposed and tritium-exposed samples had lower fracture- toughness values than unexposed samples and that fracture toughness decreased with increasing decay {sup 3}He content. Forged steels were more resistant to the embrittling effects of tritium and decay {sup 3}He than annealed steels, although their fracture-toughness properties depended on the degree of sensitization that occurred during processing. The fracture process was dominated by microvoid nucleation, growth and coalescence; however, the size and spacing of microvoids on the fracture surfaces were affected by hydrogen and tritium with the lowest-toughness samples having the smallest microvoids and finest spacing.

  15. Modifications of Carbonate Fracture Hydrodynamic Properties by CO{sub 2}-Acidified Brine Flow

    SciTech Connect

    Deng, Hang; Ellis, Brian R.; Peters, Catherine A.; Fitts, Jeffrey P.; Crandall, Dustin; Bromhal, Grant S.

    2013-08-01

    Acidic reactive flow in fractures is relevant in subsurface activities such as CO{sub 2} geological storage and hydraulic fracturing. Understanding reaction-induced changes in fracture hydrodynamic properties is essential for predicting subsurface flows such as leakage, injectability, and fluid production. In this study, x-ray computed tomography scans of a fractured carbonate caprock were used to create three dimensional reconstructions of the fracture before and after reaction with CO{sub 2}-acidified brine (Ellis et al., 2011, Greenhouse Gases: Sci. Technol., 1:248-260). As expected, mechanical apertures were found to increase substantially, doubling and even tripling in some places. However, the surface geometry evolved in complex ways including ‘comb-tooth’ structures created from preferential dissolution of calcite in transverse sedimentary bands, and the creation of degraded zones, i.e. porous calcite-depleted areas on reacted fracture surfaces. These geometric alterations resulted in increased fracture roughness, as measured by surface Z{sub 2} parameters and fractal dimensions D{sub f}. Computational fluid dynamics (CFD) simulations were conducted to quantify the changes in hydraulic aperture, fracture transmissivity and permeability. The results show that the effective hydraulic apertures are smaller than the mechanical apertures, and the changes in hydraulic apertures are nonlinear. Overestimation of flow rate by a factor of two or more would be introduced if fracture hydrodynamic properties were based on mechanical apertures, or if hydraulic aperture is assumed to change proportionally with mechanical aperture. The differences can be attributed, in part, to the increase in roughness after reaction, and is likely affected by contiguous transverse sedimentary features. Hydraulic apertures estimated by the 1D statistical model and 2D local cubic law (LCL) model are consistently larger than those calculated from the CFD simulations. In addition, a novel

  16. Influence of age on mechanical properties of healing fractures and intact bones in rats.

    PubMed

    Ekeland, A; Engesoeter, L B; Langeland, N

    1982-08-01

    Mechanical properties of fractured and intact femora have been studied in young and adult, male rats. A standardized, closed, mid-diaphyseal fracture was produced in the left femur, the right femur serving as control. The fracture was left to heal without immobilization. At various intervals, both fractured and intact femora were loaded in torsion until failure. The fractured femora regained the mechanical properties of the contralateral, intact bones after about 4 weeks in young and after about 12 weeks in adult rats. For intact bones, both the ultimate torsional moment (strength) and the torsional stiffness increased with age of the animals, whereas the ultimate torsional angle remained unchanged. For bone as a material, however, the ultimate torsional stress (strength) and the modulus of rigidity (stiffness) increased with age only in young rats, being almost constant in the adult animals. The various biomechanical parameters of the healing fractures did not reach those of the contralateral, intact bones simultaneously. The torsional moment required to twist a healing femoral fracture 20 degrees (0.35 radians), a deformation close to what an intact femur can resist, proved to be a functional and simple measure of the degree of fracture repair in rats.

  17. Correlating laboratory observations of fracture mechanical properties to hydraulically-induced microseismicity in geothermal reservoirs.

    SciTech Connect

    Stephen L. Karner, Ph.D

    2006-02-01

    To date, microseismicity has provided an invaluable tool for delineating the fracture network produced by hydraulic stimulation of geothermal reservoirs. While the locations of microseismic events are of fundamental importance, there is a wealth of information that can be gleaned from the induced seismicity (e.g. fault plane solutions, seismic moment tensors, source characteristics). Closer scrutiny of the spatial and temporal evolution of seismic moment tensors can shed light on systematic characteristics of fractures in the geothermal reservoir. When related to observations from laboratory experiments, these systematic trends can be interpreted in terms of mechanical processes that most likely operate in the fracture network. This paper reports on mechanical properties that can be inferred from observations of microseismicity in geothermal systems. These properties lead to interpretations about fracture initiation, seismicity induced after hydraulic shut-in, spatial evolution of linked fractures, and temporal evolution of fracture strength. The correlations highlight the fact that a combination of temperature, stressing rate, time, and fluid-rock interactions can alter the mechanical and fluid transport properties of fractures in geothermal systems.

  18. Association of microstructural and mechanical properties of cancellous bone and their fracture risk assessment tool scores.

    PubMed

    Wu, Dengke; Li, Xin; Tao, Cheng; Dai, Ruchun; Ni, Jiangdong; Liao, Eryuan

    2015-01-01

    This study is to investigate the association between fracture probabilities determined by using the fracture risk assessment tool (FRAX) and the microstructure and mechanical properties of femoral bone trabecula in osteoporosis (OP) and osteoarthritis (OA) patients with hip replacements. By using FRAX, we evaluated fracture risks of the 102 patients with bone replacements. Using micro CT scanning, we obtained the analysis parameters of microstructural properties of cancellous bone. Through morphometric observations, fatigue tests and compression tests, we obtained parameters of mechanical properties of cancellous bones. Relevant Pearson analysis was performed to investigate the association between the fracture probability and the microstructure and mechanical properties of femoral bone trabecula in patients. Fifteen risk factors in FRAX were compared between OP and OA patients. FRAX hip fracture risk score and major osteoporotic in OP and OA patients were significantly different. FRAX was associated with tissue bone mineral density and volumetric bone mineral density. Our study suggests that the probabilities of major osteoporotic and hip fracture using FRAX is associated with bone mass but not with micro bone quality. PMID:26064297

  19. Local fracture properties and dissimilar weld integrity in nuclear power plants

    NASA Astrophysics Data System (ADS)

    Wang, Guozhen; Wang, Haitao; Xuan, Fuzhen; Tu, Shantung; Liu, Changjun

    2013-09-01

    In this paper, the local fracture properties in a Alloy52M dissimilar metal welded joint (DMWJ) between A508 ferritic steel and 316 L stainless steel in nuclear power plants were investigated by using the single-edge notched bend (SENB) specimens, and their use in integrity assessment of DMWJ structures was analyzed. The results show that the local fracture resistance in the DMWJ is determined by local fracture mechanism, and which is mainly related to the microstructures and local strength mismatches of materials at the crack locations. The initial cracks always grow towards the materials with lower strength, and the crack path deviation is mainly controlled by the local strength mismatch. If the local fracture properties could not be used for cracks in the heat affected zones (HAZs), interface and near interface zones, the use of the fracture properties ( J-resistance curves) of base metals or weld metals following present codes will unavoidably produce non-conservative (unsafe) or excessive conservative assessment results. In most cases, the assessment results will be potentially unsafe. Therefore, it is recommended to obtain and use local mechanical and fracture properties in the integrity assessment of DMWJs.

  20. Evaluation of regional fracture properties for groundwater development using hydrolithostructural domain approach in variably fractured hard rocks of Purulia district, West Bengal, India

    NASA Astrophysics Data System (ADS)

    Acharya, Tapas; Prasad, Rajesh; Chakrabarti, S.

    2014-04-01

    Estimation of geohydrologic properties of fractured aquifers in hard crystalline and/or metamorphosed country rocks is a challenge due to the complex nature of secondary porosity that is caused by differential fracturing. Hydrologic potentiality of such aquifers may be assessed if the geological controls governing the spatial distribution of these fracture systems are computed using a software-based model. As an exemplar, the Precambrian metamorphics exposed in and around the Balarampur town of Purulia district, West Bengal (India) were studied to find out the spatial pattern and consistency of such fracture systems. Surfer and Statistica softwares were used to characterize these rock masses in terms of hydrological, structural and lithological domains. The technique is based on the use of hydraulically significant fracture properties to generate representative modal and coefficient of variance ( Cν) of fracture datasets of each domain. The Cν is interpreted to obtain the spatial variability of hydraulically significant fracture properties that, in turn, define and identify the corresponding hydrolithostructural domains. The groundwater flow estimated from such a technique is verified with the routine hydrological studies to validate the procedure. It is suggested that the hydrolithostructural domain approach is a useful alternative for evaluation of fracture properties and aquifer potentiality, and development of a regional groundwater model thereof.

  1. Investigating flow properties of partially cemented fractures in Travis Peak Formation using image-based pore-scale modeling

    NASA Astrophysics Data System (ADS)

    Tokan-Lawal, Adenike; Prodanović, Maša.; Eichhubl, Peter

    2015-08-01

    Natural fractures can provide preferred flow pathways in otherwise low-permeability reservoirs. In deep subsurface reservoirs including tight oil and gas reservoirs, as well as in hydrothermal systems, fractures are frequently lined or completely filled with mineral cement that reduces or occludes fracture porosity and permeability. Fracture cement linings potentially reduce flow connectivity between the fracture and host rock and increase fracture wall roughness, which constricts flow. We combined image-based fracture space characterization, mercury injection capillary pressure and permeability experiments, and numerical simulations to evaluate the influence of fracture-lining cement on single-phase and multiphase flows along a natural fracture from the Travis Peak Formation, a tight gas reservoir sandstone in East Texas. Using X-ray computed microtomographic image analysis, we characterized fracture geometry and the connectivity and geometric tortuosity of the fracture pore space. Combining level set method-based progressive quasistatic and lattice Boltzmann simulations, we assessed the capillary-dominated displacement properties and the (relative) permeability of a cement-lined fracture. Published empirical correlations between aperture and permeability for barren fractures provide permeability estimates that vary among each other, and differ from our results, vary by several orders of magnitude. Compared to barren fractures, cement increases the geometric tortuosity, aperture variation of the pore space, and capillary pressure while reducing the single-phase permeability by up to 2 orders of magnitude. For multiphase displacement, relative permeability and fluid entrapment geometry resemble those of porous media and differ from those characteristic of barren fractures.

  2. Influence of mechanical rock properties and fracture healing rate on crustal fluid flow dynamics

    NASA Astrophysics Data System (ADS)

    Sachau, Till; Bons, Paul; Gomez-Rivas, Enrique; Koehn, Daniel; de Riese, Tamara

    2016-04-01

    Fluid flow in the Earth's crust is very slow over extended periods of time, during which it occurs within the connected pore space of rocks. If the fluid production rate exceeds a certain threshold, matrix permeability alone is insufficient to drain the fluid volume and fluid pressure builds up, thereby reducing the effective stress supported by the rock matrix. Hydraulic fractures form once the effective pressure exceeds the tensile strength of the rock matrix and act subsequently as highly effective fluid conduits. Once local fluid pressure is sufficiently low again, flow ceases and fractures begin to heal. Since fluid flow is controlled by the alternation of fracture permeability and matrix permeability, the flow rate in the system is strongly discontinuous and occurs in intermittent pulses. Resulting hydraulic fracture networks are largely self-organized: opening and subsequent healing of hydraulic fractures depends on the local fluid pressure and on the time-span between fluid pulses. We simulate this process with a computer model and describe the resulting dynamics statistically. Special interest is given to a) the spatially and temporally discontinuous formation and closure of fractures and fracture networks and b) the total flow rate over time. The computer model consists of a crustal-scale dual-porosity setup. Control parameters are the pressure- and time-dependent fracture healing rate, and the strength and the permeability of the intact rock. Statistical analysis involves determination of the multifractal properties and of the power spectral density of the temporal development of the total drainage rate and hydraulic fractures. References Bons, P. D. (2001). The formation of large quartz veins by rapid ascent of fluids in mobile hydrofractures. Tectonophysics, 336, 1-17. Miller, S. a., & Nur, A. (2000). Permeability as a toggle switch in fluid-controlled crustal processes. Earth and Planetary Science Letters, 183(1-2), 133-146. Sachau, T., Bons, P. D

  3. Macroscopic properties of isotropic and anisotropic fracture networks from the percolation threshold to very large densities

    NASA Astrophysics Data System (ADS)

    Adler, P. M.; Thovert, J.; Mourzenko, V.

    2011-12-01

    The main purpose of this review paper is to summarize some recent studies of fracture networks. Progress has been made possible thanks to a very versatile numerical technique based on a three-dimensional discrete description of the fracture networks. Any network geometry, any boundary condition, and any distribution of the fractures can be addressed. The first step is to mesh the fracture network as it is by triangles of a controlled size. The second step consists in the discretization of the conservation equations by the finite volume technique. Two important properties were systematically studied, namely the percolation threshold rho_c and the macroscopic permeability K_n of the fracture network. Dimensionless quantities are denoted by a prime. The numerical results are interpreted in a systematic way with the concept of excluded volume which enables us to define a dimensionless fracture density rho' equal in the average to the average number of intersections per fracture. 1. Isotropic networks of identical fractures The dimensionless percolation threshold rho'_c of such networks was systematically studied for fractures of various shapes. rho'_c was shown to be almost independent of the shape except when one has very elongated rectangles. A formula is proposed for rho'_c. The permeability of these networks was calculated for a wide range of fracture densities and shapes. K'_n(rho') is almost independent of the fracture shape; an empirical formula is proposed for any value of rho' between rho'_c and infinity. For large rho', K_n is well approximated by the Snow formula initially derived for infinite fractures. 2. Anisotropic networks of identical fractures The fracture orientations are supposed to follow a Fisher distribution characterized by the parameter kappa; when kappa=0, the fractures are isotropic; when kappa=infinity, the fractures are perpendicular to a given direction. rho'_c does not depend significantly on kappa and the general formula proposed in 1

  4. Permeability, porosity, and percolation properties of two-dimensional disordered fracture networks.

    PubMed

    Yazdi, Anoosheh; Hamzehpour, Hossein; Sahimi, Muhammad

    2011-10-01

    Using extensive Monte Carlo simulations, we study the effective permeability, porosity, and percolation properties of two-dimensional fracture networks in which the fractures are represented by rectangles of finite widths. The parameters of the study are the width of the fractures and their number density. For low and intermediate densities, the average porosity of the network follows a power-law relation with the density. The exponent of the power law itself depends on the fractures' width through a power law. For an intermediate range of the densities, the effective permeability scales with the fractures' width as a power law, with an exponent that depends on the density. For high densities the effective permeability also depends on the porosity through a power law, with an exponent that depends on the fractures' width. In agreement with the results, experimental data also indicate the existence of a power-law relationship between the effective permeability and porosity in consolidated sandstones and sedimentary rocks with a nonuniversal exponent. The percolation threshold or critical number density of the fractures depends on their width and is maximum if they are represented by squares, rather than rectangles. PMID:22181271

  5. Permeability, porosity, and percolation properties of two-dimensional disordered fracture networks.

    PubMed

    Yazdi, Anoosheh; Hamzehpour, Hossein; Sahimi, Muhammad

    2011-10-01

    Using extensive Monte Carlo simulations, we study the effective permeability, porosity, and percolation properties of two-dimensional fracture networks in which the fractures are represented by rectangles of finite widths. The parameters of the study are the width of the fractures and their number density. For low and intermediate densities, the average porosity of the network follows a power-law relation with the density. The exponent of the power law itself depends on the fractures' width through a power law. For an intermediate range of the densities, the effective permeability scales with the fractures' width as a power law, with an exponent that depends on the density. For high densities the effective permeability also depends on the porosity through a power law, with an exponent that depends on the fractures' width. In agreement with the results, experimental data also indicate the existence of a power-law relationship between the effective permeability and porosity in consolidated sandstones and sedimentary rocks with a nonuniversal exponent. The percolation threshold or critical number density of the fractures depends on their width and is maximum if they are represented by squares, rather than rectangles.

  6. Macroscopic properties of fracture networks from the percolation threshold to very large densities

    NASA Astrophysics Data System (ADS)

    Adler, P.; Thovert, J.-F.; Mourzenko, V. V.

    2012-04-01

    Progress has been made possible thanks to a very versatile numerical technique based on a three-dimensional discrete description of the fracture networks. Any network geometry, any boundary condition, and any distribution of the fractures can be addressed. The first step is to mesh the fracture network as it is by triangles of a controlled size. The second step consists in the discretization of the conservation equations by the finite volume technique. Two important properties were systematically studied, namely the percolation threshold rhoc and the macroscopic permeability Kn of the fracture network. Dimensionless quantities are denoted by a prime. The numerical results are interpreted in a systematic way with the concept of excluded volume which enables us to define a dimensionless fracture density rho' equal in the average to the average number of intersections per fracture. 1. Isotropic networks of identical fractures The dimensionless percolation threshold rho'c of such networks was systematically studied for fractures of various shapes. rho'c was shown to be almost independent of the shape except when one has very elongated rectangles. A formula is proposed for rho'_c. The permeability of these networks was calculated for a wide range of fracture densities and shapes. K'_n(rho') is almost independent of the fracture shape; an empirical formula is proposed for any value of rho' between rho'c and infinity. For large rho', Kn is well approximated by the Snow formula initially derived for infinite fractures. 2. Anisotropic networks of identical fractures The fracture orientations are supposed to follow a Fisher distribution characterized by the parameter kappa; when kappa=0, the fractures are isotropic; when kappa=infinity, the fractures are perpendicular to a given direction. rho'c does not depend significantly on kappa and the general formula proposed in 1 can be used as a first approximation. A considerable simplification occurs for permeability. The

  7. The Thermal Expansion, Elastic and Fracture Properties of Porous Cordierite at Elevated Temperatures

    SciTech Connect

    Shyam, Amit; Lara-Curzio, Edgar; Pandey, Amit; Watkins, Thomas R; More, Karren

    2012-01-01

    The properties that determine the thermal shock resistance in materials are reported for porous cordierite, a leading candidate material for the fabrication of diesel particulate filters. Fracture toughness and slow crack growth tests were performed on test specimens obtained from the walls of diesel particulate filter monolithic substrates using the double-torsion test method at temperatures between 20 C and 900 C. The thermal expansion and elastic properties were characterized between 20 C and 1000 C. The role of the microstructure of porous cordierite in determining its unusual thermal expansion and elevated temperature Young's modulus and fracture toughness are discussed.

  8. Hydraulic properties of two-dimensional random fracture networks following power law distributions of length and aperture

    NASA Astrophysics Data System (ADS)

    de Dreuzy, J.-R.; Davy, P.; Bour, O.

    2002-12-01

    Field observations have revealed that the diffusion properties of fractured materials are strongly influenced by the presence of fractures. Using power law fracture length and fracture permeability distributions currently observed on natural fractured networks, we model the equivalent permeability of two-dimensional (2D) discrete fracture networks by using numerical simulations and theoretical arguments. We first give the dependence of the network equivalent permeability, obtained at the scale of the network, on the characteristic power law exponents of the fracture length and fracture permeability distributions. We especially show that the equivalent permeability depends simply on the geometrical mean of the local fracture permeability distribution. Such networks are characterized by an increase of permeability with scale without limitations, provided that the fracture length and fracture permeability distributions are broad enough. Although a correlation length cannot be systematically defined, the flow structure is still characterized by simple properties. The flow is either extremely channeled in one dominant path or distributed in several separated structures. We show finally that the observed scale effects and flow structure are very different from the one obtained in the lognormal fracture permeability distribution case.

  9. Property Evolution of Fractured Wellbore Cement under Dynamic Flow Conditions Relevant to Geological Carbon Sequestration

    NASA Astrophysics Data System (ADS)

    Cao, P.; Karpyn, Z. T.; Li, L.

    2012-12-01

    Interaction between wellbore cement and injected CO2 is one of the main processes that can potentially alter cement properties. Wellbore cementing defects, such as cracks/fractures inside cement plugs or weak bonding between formation/cement, may form preferential leakage pathways due to cement alteration during geological carbon sequestration. This work investigates the evolution of cement properties under dynamic flow conditions. A cement casted sandstone core of 3.81cm diameter and 7.67cm long, with cracks in the central cemented region was made. The fractured cemented sandstone core was flooded continuously using CO2-saturated brine under pressure and temperature conditions relevant to carbon sequestration. Changes in fracture structure were visualized and quantified using X-ray Micro-CT imaging. Within an eight-day flow-through period, the cement zone experienced chemical alterations evident through color changes as well as changes in fracture volume, surface area, and structure while the host sandstone remained unaltered. A higher rate of cement degradation was observed in the early stage of CO2-saturated brine flooding. The rate of cement alteration varies spatially, such that fracture apertures located near the core inlet experienced more severe cement degradation than those closer to the core outlet, by a factor of two. Analysis of fracture growth rate relative to the fracture aperture field also showed larger initial fracture apertures correlated with preferential aperture growth. Fracture rims were observed to become smoother from CT images, which were confirmed by decreasing surface area to volume ratio over time. This may be due to carbonate calcium precipitation as a result of carbonation during the flow-through experiment. In addition, in-situ permeability of a fractured cement-casted sample was measured to increase by a factor of 24 over the eight days of continuous injection of CO2-saturated brine. This work provided mechanistic and quantitative

  10. Effects of hydrogen on mechanical properties and fracture mechanism of 8090 Al-Li alloy

    NASA Astrophysics Data System (ADS)

    Chen, Lian; Chen, Wenxiu; Liu, Zhonghao; Shao, Yuxia; Hu, Zhuangqi

    1993-06-01

    The effects of hydrogen and strain rate on the mechanical properties and fracture mechanism of 8090 Al-Li alloy under electrochemical charging conditions have been studied. Experimental results demonstrate that the tensile strength [ultimate tensile strength (UTS) and yield strength (YS)] and plasticity [reduction of area (RA) and elongation (EL)] drop linearly with the decrease of strain rate. The charged hydrogen increases the tensile strength but markedly impair the plasticity. The susceptibility of hydrogen embrittlement increases with the decreases of strain rate, and the susceptibility of the charged specimens was larger than that of the uncharged ones over the strain-rate range. Observation by scanning electron microscope (SEM) reveals that the charged hydrogen enhances intergranular delamination cracking on the fracture surface. The fracture model of charged specimens at low strain rates(dot \\varepsilon {text{< 3}}{text{.4 X 10}}^{{text{ - 4}}} /s) is grain boundary brittle fracture (GBBF), while that of other conditions is grain boundary ductile fracture (GBDF). Secondary ion mass spectroscopy (SIMS) study shows that the atomic binding energy of Al and Li in the alloy decreased after hydrogen charging, and the atomic binding energy drop of the former is more than the latter. In this article, the hydrogen transport through the mobile dislocation mechanism of hydrogen-induced fracture and the hydrogen effect on atomic binding energy were also discussed in detail.

  11. Characterization of Mode II Fracture Properties of Fiber Reinforced Insulation Systems for Superconducting Cables

    NASA Astrophysics Data System (ADS)

    Nikbin, K.; Nyilas, A.; Weiss, K.

    2006-03-01

    Within the framework of European fusion technology program works have been initiated towards characterization of fracture mechanical properties of insulation layers sandwiched between metallic components which contain cracks. The aim of these measurements is to develop a reliable and validated test technique for the determination of the fracture components based on mode I and II fracture toughness values of the cracked insulation material. Prior to the start of the mode II and mixed mode measurements the mode I fracture toughness of the insulation systems were measured at 295 K and at 7 K using different size compact tension (CT) specimens composed of stainless steel sandwiching reinforced epoxy insulation material. For the necessary pre-crack a fine Teflon paper of 0.035 mm thickness has been inserted inside the epoxy system. For the mode II fracture toughness tests specimens of type DLT (double lap tensile), DLC (double lap compression), SLC (single lap compression), ENF (end-notched flexure), and TENF (tapered end-notched flexure) have been investigated for their applicability. With extremely sensitive displacement measurements the compliances of the DLT, DLC, SLC, ENF, and TENF specimens could be recorded for the necessary computation of total fracture energy release rate G.

  12. Effect of cerium and impurities on fatigue and fracture properties of 8090 alloy sheets

    SciTech Connect

    Meng Liang; Zheng Xiulin

    1995-07-01

    The objective of the present study is to examine the effect of a rare earth addition, Ce, and some impurities, Fe, Si, Na and K, on the fatigue and fracture properties of 8090 Al-Li alloy sheet by means of the determinations for the fatigue life (N{sub f}) under a constant stress amplitude, fatigue crack propagation (FCP) rates and plane stress fracture toughness. Impurity Fe and Si in 8090 alloy sheets increase the fatigue crack propagation rates and impair the fracture properties although they could not bring about significant effect on the fatigue life under the test conditions maximum cyclic stress of 280 MPa, load ratio of 0.1 and Fe + Si content of 0.24%. Impurity Na and K in 8090 alloy sheets reduce the fracture properties and fatigue life. When the level stress intensity factor is higher, or {Delta} K>10{sup 1.1} Mpam{sup 1/2} in the test, Na and K markedly increase the fatigue crack propagation rates. Ce addition in 8090 alloy sheets containing a certain amount of Fe and Si impurities could suppress the effects of Na and K impurities on the fracture behavior. Adding about 0.28% Ce in 8090 alloy containing trace Fe and Si impurities improves the crack propagation resistance and plane stress fracture toughness. However, adding Ce from 0.10% to 0.29% is unprofitable to the fatigue life of 8090 alloy containing more impurities. There are more and coarser Ce-containing compound particles in the alloy sheets with high Ce content. These particles could produce a detrimental effect on the fatigue properties.

  13. Experimental Investigation of Seepage Properties of Fractured Rocks Under Different Confining Pressures

    NASA Astrophysics Data System (ADS)

    Ma, D.; Miao, X. X.; Chen, Z. Q.; Mao, X. B.

    2013-09-01

    The effectiveness of transmitting underground water in rock fractures is strongly influenced by the widths of the fractures and their interconnections. However, the geometries needed for water flow in fractured rock are also heavily controlled by the confining pressure conditions. This paper is intended to study the seepage properties of fractured rocks under different confining pressures. In order to do this, we designed and manufactured a water flow apparatus that can be connected to the electro-hydraulic servo-controlled test system MTS815.02, which provides loading and exhibits external pressures in the test. Using this apparatus, we tested fractured mudstone, limestone and sandstone specimens and obtained the relationship between seepage properties and variations in confining pressure. The calculation of the seepage properties based on the collection of water flow and confining pressure differences is specifically influenced by non-Darcy flow. The results show that: (1) The seepage properties of fractured rocks are related to confining pressure, i.e. with the increase of confining pressure, the permeability decreases and the absolute value of non-Darcy flow coefficient increases. (2) The sandstone coefficients and range from to m2 and to m-1, respectively, and exhibit a greater change compared to coefficients of mudstone and limestone. (3) From the regression analysis of experimental data, it is concluded that the polynomial function is a better fit than the power and logarithmic functions. The results obtained can provide an important reference for understanding the stability of rock surrounding roadways toward prevention of underground water gushing-out, and for developing underground resources (e.g. coal).

  14. The effect of humidity on the fracture properties of human fingernails.

    PubMed

    Farran, Laura; Ennos, A Roland; Eichhorn, Stephen J

    2008-12-01

    Fingernails are a characteristic anatomical feature of primates and their function is dictated by the environment in which they are utilised. The present study examined the mechanical properties of human fingernails as a function of relative humidity (RH) and the subsequent moisture content of the nail material. Nail clippings were stored at a range of RH values and then weighed in order to determine their moisture content. There was a non-linear relationship between the moisture content of nails and the RH of their local environment. The in vivo moisture content of nails, measured from 55% to 80% RH, was between 14% and 30%, similar to other keratinous materials such as claws, hooves and feathers. Cutting tests on the nail samples showed that the work of fracture was between 11 and 22 kJ m(-2), rising to a peak at 55% RH and falling at higher and lower humidities. At all RH values there was anisotropy within the nail between the proximal and lateral directions, the work of fracture being greater proximally. This anisotropy was greatest at 55% RH, at which point the proximal work of fracture was double the lateral value. These results suggest that the mechanical behaviour of human fingernails is optimised at in vivo conditions; they resist tearing most strongly under these conditions and particularly resist tearing into the nail bed. At more extreme humidity levels the fracture properties of the nail deteriorate; they are brittle when fully dry and fracture and split when wet.

  15. Relationship between microstructure, material distribution, and mechanical properties of sheep tibia during fracture healing process.

    PubMed

    Gao, Jiazi; Gong, He; Huang, Xing; Fang, Juan; Zhu, Dong; Fan, Yubo

    2013-01-01

    The aim of this study was to investigate the relationship between microstructural parameters, material distribution, and mechanical properties of sheep tibia at the apparent and tissue levels during the fracture healing process. Eighteen sheep underwent tibial osteotomy and were sacrificed at 4, 8, and 12 weeks. Radiographs and micro-computed tomography (micro-CT) scanning were taken for microstructural assessment, material distribution evaluation, and micro-finite element analysis. A displacement of 5% compressive strain on the longitudinal direction was applied to the micro-finite element model, and apparent and tissue-level mechanical properties were calculated. Principle component analysis and linear regression were used to establish the relationship between principle components (PCs) and mechanical parameters. Visible bony callus formation was observed throughout the healing process from radiographic assessment. Apparent mechanical property increased at 8 weeks, but tissue-level mechanical property did not increase significantly until 12 weeks. Three PCs were extracted from microstructural parameters and material distribution, which accounted for 87.592% of the total variation. The regression results showed a significant relationship between PCs and mechanical parameters (R>0.8, P<0.05). Results of this study show that microstructure and material distribution based on micro-CT imaging could efficiently predict bone strength and reflect the bone remodeling process during fracture healing, which provides a basis for exploring the fracture healing mechanism and may be used as an approach for fractured bone strength assessment.

  16. Properties of a pair of fracture networks produced by triaxial deformation experiments: insights on fluid flow using discrete fracture network models

    NASA Astrophysics Data System (ADS)

    Ghislain, Trullenque; Rishi, Parashar; Clément, Delcourt; Lucille, Collet; Pauline, Villard; Sébastien, Potel

    2016-09-01

    Results of a series of deformation experiments conducted on gabbro samples and numerical models for computation of flow are presented. Rocks were subjected to triaxial tests (σ1 > σ2 = σ3) under σ3 = 150 MPa confining pressure at room temperature, to generate fracture network patterns. These patterns were either produced by keeping a constant confining pressure and loading the sample up to failure (conventional test: CT), or by building up a high differential stress and suddenly releasing the confining pressure (confining pressure release test: CPR). The networks are similar in overall density but differ primarily in the orientation of smaller fractures. In the case of CT tests, a conjugate fracture set is observed with one dominant fracture zone running at about 20° from σ1. CPR tests do not show such a conjugate pattern and the mean fracture orientation is at around 35° from σ1. Discrete fracture network (DFN) methodology was used to determine the distribution of flow and hydraulic head for both fracture sets under simple boundary conditions and uniform transmissivity values. The fracture network generated by CT and CPR tests exhibit different patterns of flow field and hydraulic head configurations, but convey approximately the same amount of flow at all scales for which DFN models were simulated. The numerical modelling results help to develop understanding of qualitative differences in flow distribution that may arise in rocks of the same mineralogical composition and mechanical properties, but under the influence of different stress conditions, albeit at similar overall stress magnitude.

  17. Petrophysical and Mechanical Properties of Fractured Aquifers in the Northern Newark Basin: Implications for Carbon Sequestration

    NASA Astrophysics Data System (ADS)

    Zakharova, N. V.; Goldberg, D.; Collins, D.; Olsen, P. E.

    2012-12-01

    One of the key factors in predicting the performance of low-permeability fractured reservoirs is a detailed understanding of the in-situ state of stress and the distribution and orientation of natural fractures and faults. In this study we analyze borehole geophysical data from a deep characterization well in the northern Newark Basin, a candidate CO2-storage site, and provide petrophysical and geomechanical characterization of fractured sedimentary and igneous formations. Previous studies in the northern Newark basin demonstrated no unique relationship between hydraulic conductivity and degree of fracturing, fracture apertures or orientation. Therefore, in the absence of hydraulic testing data predicting fracture behavior under CO2 injection condition presents a significant challenge for baseline formation characterization. Moreover, fluid injection in deep wells can cause reactivation of existing faults or new fracture initiation due to significant increase in the pore pressure. We analyze electrical resistivity images and full-wave sonic data to constrain the state of the current in-situ stress in the northern Newark basin, and to evaluate how the interaction between in-situ stress and the distribution and orientation of natural fractures influences their hydraulic properties. We then combine it with the full suite of wireline logs to describe petrophysical, hydraulic, and geomechanical properties of the fractured aquifers at the locality. The Sandia Technologies, LLC Tandem Lot #1 geologic characterization well (Rockland County, NY) is about 6,800 ft deep and transects Triassic terrestrial sediments and the Palisades diabase sill that are both characterized by abundant natural fractures. A suite of standard wireline logs, high-resolution electrical resistivity images and full-wave sonic data were collected in the borehole but no hydraulic data or in-situ stress estimates are available. Borehole breakouts are clearly observed in the resistivity images in

  18. Tissue-Level Mechanical Properties of Bone Contributing to Fracture Risk.

    PubMed

    Nyman, Jeffry S; Granke, Mathilde; Singleton, Robert C; Pharr, George M

    2016-08-01

    Tissue-level mechanical properties characterize mechanical behavior independently of microscopic porosity. Specifically, quasi-static nanoindentation provides measurements of modulus (stiffness) and hardness (resistance to yielding) of tissue at the length scale of the lamella, while dynamic nanoindentation assesses time-dependent behavior in the form of storage modulus (stiffness), loss modulus (dampening), and loss factor (ratio of the two). While these properties are useful in establishing how a gene, signaling pathway, or disease of interest affects bone tissue, they generally do not vary with aging after skeletal maturation or with osteoporosis. Heterogeneity in tissue-level mechanical properties or in compositional properties may contribute to fracture risk, but a consensus on whether the contribution is negative or positive has not emerged. In vivo indentation of bone tissue is now possible, and the mechanical resistance to microindentation has the potential for improving fracture risk assessment, though determinants are currently unknown.

  19. Fracture properties from tight reservoir outcrop analogues with application to geothermal exploration

    NASA Astrophysics Data System (ADS)

    Philipp, Sonja L.; Reyer, Dorothea; Afsar, Filiz; Bauer, Johanna F.; Meier, Silke; Reinecker, John

    2015-04-01

    In geothermal reservoirs, similar to other tight reservoirs, fluid flow may be intensely affected by fracture systems, in particular those associated with fault zones. When active (slipping) the fault core, that is, the inner part of a fault zone, which commonly consists of breccia or gouge, can suddenly develop high permeability. Fault cores of inactive fault zones, however, may have low permeabilities and even act as flow barriers. In the outer part of a fault zone, the damage zone, permeability depends mainly on the fracture properties, that is, the geometry (orientation, aperture, density, connectivity, etc.) of the fault-associated fracture system. Mineral vein networks in damage zones of deeply eroded fault zones in palaeogeothermal fields demonstrate their permeability. In geothermal exploration, particularly for hydrothermal reservoirs, the orientation of fault zones in relation to the current stress field as well as their internal structure, in particular the properties of the associated fracture system, must be known as accurately as possible for wellpath planning and reservoir engineering. Here we present results of detailed field studies and numerical models of fault zones and associated fracture systems in palaeogeo¬thermal fields and host rocks for geothermal reservoirs from various stratigraphies, lithologies and tectonic settings: (1) 74 fault zones in three coastal sections of Upper Triassic and Lower Jurassic age (mudstones and limestone-marl alternations) in the Bristol Channel Basin, UK. (2) 58 fault zones in 22 outcrops from Upper Carboniferous to Upper Cretaceous in the Northwest German Basin (siliciclastic, carbonate and volcanic rocks); and (3) 16 fault zones in 9 outcrops in Lower Permian to Middle Triassic (mainly sandstone and limestone) in the Upper Rhine Graben shoulders. Whereas (1) represent palaeogeothermal fields with mineral veins, (2) and (3) are outcrop analogues of reservoir horizons from geothermal exploration. In the study

  20. Are the High Hip Fracture Rates Among Norwegian Women Explained by Impaired Bone Material Properties?

    PubMed

    Duarte Sosa, Daysi; Vilaplana, Laila; Güerri, Roberto; Nogués, Xavier; Wang-Fagerland, Morten; Diez-Perez, Adolfo; F Eriksen, Erik

    2015-10-01

    Hip fracture rates in Norway rank among the highest in the world, more than double that of Spanish women. Previous studies were unable to demonstrate significant differences between the two populations with respect to bone mass or calcium metabolism. In order to test whether the difference in fracture propensity between both populations could be explained by differences in bone material quality we assessed bone material strength using microindentation in 42 Norwegian and 46 Spanish women with normal BMD values, without clinical or morphometric vertebral fractures, no clinical or laboratory signs of secondary osteoporosis, and without use of drugs with known influence on bone metabolism. Bone material properties were assessed by microindentation of the thick cortex of the mid tibia following local anesthesia of the area using the Osteoprobe device (Active Life Scientific, Santa Barbara, CA, USA). Indentation distance was standardized against a calibration phantom of methylmethacrylate and results, as percentage of this reference value, expressed as bone material strength index units (BMSi). We found that the bone material properties reflected in the BMSi value of Norwegian women was significantly inferior when compared to Spanish women (77 ± 7.1 versus 80.7 ± 7.8, p < 0.001). Total hip BMD was significantly higher in Norwegian women (1.218 g/cm(2) versus 0.938 g/cm(2) , p < 0.001) but regression analysis revealed that indentation values did not vary with BMD r(2)  = 0.03 or age r(2)  = 0.04. In conclusion Norwegian women show impaired bone material properties, higher bone mass, and were taller than Spanish women. The increased height will increase the impact on bone after falls, and impaired bone material properties may further enhance the risk fracture after such falls. These ethnic differences in bone material properties may partly explain the higher propensity for fracture in Norwegian women.

  1. Effects of chemical alteration on fracture mechanical properties in hydrothermal systems

    NASA Astrophysics Data System (ADS)

    Callahan, O. A.; Eichhubl, P.; Olson, J. E.

    2015-12-01

    Fault and fracture networks often control the distribution of fluids and heat in hydrothermal and epithermal systems, and in related geothermal and mineral resources. Additional chemical influences on conduit evolution are well documented, with dissolution and precipitation of mineral species potentially changing the permeability of fault-facture networks. Less well understood are the impacts of chemical alteration on the mechanical properties governing fracture growth and fracture network geometry. We use double-torsion (DT) load relaxation tests under ambient air conditions to measure the mode-I fracture toughness (KIC) and subcritical fracture growth index (SCI) of variably altered rock samples obtained from outcrop in Dixie Valley, NV. Samples from southern Dixie Valley include 1) weakly altered granite, characterized by minor sericite in plagioclase, albitization and vacuolization of feldspars, and incomplete replacement of biotite with chlorite, and 2) granite from an area of locally intense propylitic alteration with chlorite-calcite-hematite-epidote assemblages. We also evaluated samples of completely silicified gabbro obtained from the Dixie Comstock epithermal gold deposit. In the weakly altered granite KIC and SCI are 1.3 ±0.2 MPam1/2 (n=8) and 59 ±25 (n=29), respectively. In the propylitic assemblage KIC is reduced to 0.6 ±0.1 MPam1/2 (n=11), and the SCI increased to 75 ±36 (n = 33). In both cases, the altered materials have lower fracture toughness and higher SCI than is reported for common geomechanical standards such as Westerly Granite (KIC ~1.7 MPam1/2; SCI ~48). Preliminary analysis of the silicified gabbro shows a significant increase in fracture toughness, 3.6 ±0.4 MPam1/2 (n=2), and SCI, 102 ±45 (n=19), compared to published values for gabbro (2.9 MPam1/2 and SCI = 32). These results suggest that mineralogical and textural changes associated with different alteration assemblages may result in spatially variable rates of fracture

  2. Altered distributions of bone tissue mineral and collagen properties in women with fragility fractures.

    PubMed

    Wang, Zhen Xiang; Lloyd, Ashley A; Burket, Jayme C; Gourion-Arsiquaud, Samuel; Donnelly, Eve

    2016-03-01

    Heterogeneity of bone tissue properties is emerging as a potential indicator of altered bone quality in pathologic tissue. The objective of this study was to compare the distributions of tissue properties in women with and without histories of fragility fractures using Fourier transform infrared (FTIR) imaging. We extended a prior study that examined the relationship of the mean FTIR properties to fracture risk by analyzing in detail the widths and the tails of the distributions of FTIR properties in biopsies from fracture and non-fracture cohorts. The mineral and matrix properties of cortical and trabecular iliac crest tissue were compared in biopsies from women with a history of fragility fracture (+Fx; n=21, age: mean 54±SD 15y) and with no history of fragility fracture (-Fx; n=12, age: 57±5y). A subset of the patients included in the -Fx group were taking estrogen-plus-progestin hormone replacement therapy (HRT) (-Fx+HRT n=8, age: 58±5y) and were analyzed separately from patients with no history of HRT (-Fx-HRT n=4, age: 56±7y). When the FTIR parameter mean values were examined by treatment group, the trabecular tissue of -Fx-HRT patients had a lower mineral:matrix ratio (M:M) and collagen maturity (XLR) than that of -Fx+HRT patients (-22% M:M, -18% XLR) and +Fx patients (-17% M:M, -18% XLR). Across multiple FTIR parameters, tissue from the -Fx-HRT group had smaller low-tail (5th percentile) values than that from the -Fx+HRT or +Fx groups. In trabecular collagen maturity and crystallinity (XST), the -Fx-HRT group had smaller low-tail values than those in the -Fx+HRT group (-16% XLR, -5% XST) and the +Fx group (-17% XLR, -7% XST). The relatively low values of trabecular mineral:matrix ratio and collagen maturity and smaller low-tail values of collagen maturity and crystallinity observed in the -Fx-HRT group are characteristic of younger tissue. Taken together, our data suggest that the presence of newly formed tissue that includes small/imperfect crystals

  3. TRITIUM AND DECAY HELIUM EFFECTS ON THE FRACTURE TOUGHNESS PROPERTIES OF STAINLESS STEEL WELDMENTS

    SciTech Connect

    Morgan, M; Scott West, S; Michael Tosten, M

    2007-08-31

    J-Integral fracture toughness tests were conducted on tritium-exposed-and-aged Types 304L and 21-6-9 stainless steel weldments in order to measure the combined effects of tritium and its decay product, helium-3 on the fracture toughness properties. Initially, weldments have fracture toughness values about three times higher than base-metal values. Delta-ferrite phase in the weld microstructure improved toughness provided no tritium was present in the microstructure. After a tritium-exposure-and-aging treatment that resulted in {approx}1400 atomic parts per million (appm) dissolved tritium, both weldments and base metals had their fracture toughness values reduced to about the same level. The tritium effect was greater in weldments (67 % reduction vs. 37% reduction) largely because the ductile discontinuous delta-ferrite interfaces were embrittled by tritium and decay helium. Fracture toughness values decreased for both base metals and weldments with increasing decay helium content in the range tested (50-200 appm).

  4. Estimating large-scale fractured rock properties from radon data collected in a ventilated tunnel

    SciTech Connect

    Unger, Andre; Finsterle, Stefan; Bodvarsson, Gudmundur S.

    2003-05-12

    To address regulatory issues regarding worker safety, radon gas concentrations have been monitored as part of the operation of a deep tunnel excavated from a highly fractured tuff formation. The objective of this study was to examine the potential use of the radon data to estimate large-scale formation properties of fractured rock. An iTOUGH2 model was developed to predict radon concentrations for prescribed ventilation rates. The numerical model was used (1) to estimate the permeability and porosity of the fractured formation at the length scale of the tunnel and extending tens of meters into the surrounding rock, and (2) to understand the mechanism leading to radon concentrations that potentially exceed the regulatory limit. The mechanism controlling radon concentrations in the tunnel is a function of atmospheric barometric fluctuations propagated down the tunnel. In addition, a slight suction is induced by the ventilation system. The pressure fluctuations are dampened in the fractured formation according to its permeability and porosity. Consequently, as the barometric pressure in the tunnel drops, formation gases from the rock are pulled into the opening, resulting in high radon concentrations. Model calibration to both radon concentration data measured in the tunnel and gas phase pressure fluctuations observed in the formation yielded independent estimates of effective, large-scale fracture permeability and porosity. The calibrated model was then used as a design tool to predict the effect of adjusting the ventilation-system operation strategy for reducing the probability that radon gas concentrations will exceed the regulatory limit.

  5. An automated system for measuring multi-dimensional, time dependent mechanical properties of a human tibial fracture.

    PubMed

    Ogrodnik, Peter J; Moorcroft, C Ian; Thomas, Peter B M

    2007-12-01

    An automated loading and measurement device has been developed for assessment of the mechanical properties of a healing human tibial fracture. The characteristics of the device are presented with assessments of errors. This paper constitutes a small part of a long term research project determining a clinically quantifiable end point for fracture healing in humans, hence a sample of results is presented to demonstrate the potential application of the device. A more detailed analysis of the results will be the basis of further publications. The initial results confirm that the non-linear behaviour of callus cannot be ignored in fracture assessment methodologies. They further reinforce the requirement to measure load-rate when measuring fracture stiffness. Polar plots of stiffness demonstrate that when measuring fracture stiffness not only should load-rate be considered, but also the orientation of measurement. The results from this work support the view that fracture stiffness should be measured in at least two planes. A new material property for the assessment of fracture healing, the gamma ratio gamma, is examined and preliminary results are shown. The paper also demonstrates how creep properties of a healing tibia can be assessed and proposes that this property may form the basis for future fracture assessment investigations. PMID:17875395

  6. Effect of isothermal forging on the fracture properties of binary [gamma]-base titanium aluminides at room temperature

    SciTech Connect

    Gnanamoorthy, R.; Mutoh, Y. ); Masahashi, N.; Mizuhara, Y. )

    1994-07-15

    Gamma base titanium aluminides are light in weight and possess excellent high temperature properties such as strength, stiffness and oxidation resistance. Mechanical properties of [gamma]-base titanium aluminides depend on the microstructure, alloying addition and processing route. Influences of microstructure and alloying addition on the fracture properties have been investigated. However, the influence of processing route on fracture properties is not clear at present. In the present study, the flexural strength, the flexural strength, fracture toughness and fatigue crack growth properties of (a) cast and heat treated and (b) cast, heat treated and subsequently isothermal forged binary Ti-50Al (compositions are mentioned in atomic percent) with equiaxed microstructures are investigated. Fracture surface and crack growth path investigations are performed.

  7. Permanent effect of a cryogenic spill on fracture properties of structural steels

    NASA Astrophysics Data System (ADS)

    Keseler, H.; Westermann, I.; Kandukuri, S. Y.; Nøkleby, J. O.; Holmedal, B.

    2015-12-01

    Fracture analysis of a standard construction steel platform deck, which had been exposed to a liquid nitrogen spill, showed that the brittle fracture started at a flaw in the weld as a consequence of low-temperature embrittlement and thermal stresses experienced by the material. In the present study, the permanent effect of a cryogenic spill on the fracture properties of carbon steels has been investigated. Charpy V-notch impact testing was carried out at 0 °C using specimens, from the platform deck material. The average impact energy appeared to be below requirements only for transverse specimens. No pre-existing damage was found when examining the fracture surfaces and cross sections in the scanning electron microscope. Specimens of the platform deck material and a DOMEX S355 MCD carbon steel were tensile tested immersed in liquid nitrogen. Both steels showed a considerable increase in yield- and fracture strength and a large increase in the Lüders strain compared to the room temperature behavior. A cryogenic spill was simulated by applying a constant tensile force to the specimens for 10 min, at -196 C. Subsequent tensile tests at room temperature showed no significant influence on the stress-strain curve of the specimens. A small amount of microcracks were found after holding a DOMEX S355 MCD specimen at a constant force below the yield point. In a platform deck material tensile tested to fracture in liquid nitrogen, cracks associated with elongated MnS inclusions were found through the whole test region. These cracks probably formed as a result of the inclusions having a higher thermal contraction rate than the steel, causing decohesion at the inclusion-matrix interface on cooling. Simultaneous deformation may have caused formation of cracks. Both the microcracks and sulphide related damage may give permanently reduced impact energy after a cryogenic exposure.

  8. Characterization of the Microstructure, Fracture, and Mechanical Properties of Aluminum Alloys 7085-O and 7175-T7452 Hollow Cylinder Extrusions

    NASA Astrophysics Data System (ADS)

    Benoit, Samuel G.; Chalivendra, Vijaya B.; Rice, Matthew A.; Doleski, Robert F.

    2016-09-01

    Microstructural, tensile, and fracture characterizations of cylindrically forged forms of aluminum alloys AA7085-O and AA7175-T7452 were performed. Mechanical and fracture properties were investigated along radial, circumferential, and longitudinal directions to determine directional dependency. American Society for Testing and Materials (ASTM) test methods (ASTM E8-04 and ASTM E1820) were employed for both the tensile and fracture characterizations, respectively. The tensile and fracture properties were related to microstructure in each direction. The strength, elongation at break, and ultimate tensile strength of AA7085-O were higher than those of AA7175-T7452. AA7175-T7452 alloy failed in a brittle manner during fracture studies. AA7085-O outperformed AA7175-T7452 on fracture energy in all of the orientations studied. Smaller grain sizes on the planes normal to circumferential and longitudinal directions showed improvement in both elongation at break and fracture energy values compared to those of radial direction. Scanning electron microscopy images demonstrated cleavage fracture in AA7175-T7452 and transgranular fracture in AA7085-O.

  9. Tiltmeters as Tools for Characterizing Geometrical and Hydrodynamical Properties of Fractured Crystalline Aquifers and Fault Zones

    NASA Astrophysics Data System (ADS)

    Schuite, J.; Longuevergne, L.; Bour, O.; Lavenant, N.; Boudin, F.

    2014-12-01

    In many geological reservoirs, open fractures or fault zones generally induce high spatial variability of hydrodynamical properties and shape the main deep-seated flow paths. It is of crucial interest to determine their structure and properties in order to achieve a sound and sustained exploitation of resources or to estimate the risk of failure of any underground storage. Tiltmeters have emerged as new tools to observe deformation generated by groundwater flow. As such instruments are highly sensitive to pressure gradients, they are perfectly suited for monitoring channelized flow in connected fractures and fault zones. Hence, they provide a unique insight of these reservoirs' geometry and dynamics over broad time scales. Here we demonstrate that continuous tilt data from surface long baseline tiltmeters (LBT) can be used alone to evaluate the general functioning of a fractured hardrock system and estimate the hydraulic properties of its main conductive features. The study is applied to the pumping site of Ploemeur observatory (Brittany, France) which is well documented and instrumented, and therefore forms a convenient setting for introducing LBT as tools for fractured media hydrology. On the short term, tilt signals are strongly correlated with pumping cycles and associated head level changes in well-connected boreholes. Besides, when pumps are stopped the maximal tilt direction is systematically perpendicular to a subvertical fault zone whose azimuth of strike has thereby been refined down to degree precision. By using a semi-analytical model of deformation, we establish the link between tilt and pressure change during pumping interruptions which then allows for hydraulic properties estimation from tilt measurements only. Finally, we validate our results with previous estimates obtained from other studies and discuss the orientation of future work that could enhance these estimates.

  10. Determination of design allowable properties. Fracture of 2219-T87 aluminum alloy

    NASA Technical Reports Server (NTRS)

    Engstrom, W. L.

    1972-01-01

    A literature survey was conducted to provide a comprehensive report of available valid data on tensile properties, fracture toughness, fatigue crack propagation, and sustained load behavior of 2219-T87 aluminum alloy base metal and weldments, as applicable to manned spacecraft tankage. Most of the data found were from tests conducted at room temperature, -320 F and -423 F. Data are presented in graphical and tabular form, and areas in which data are lacking are established.

  11. Effects of Inclusions on Delayed Fracture Properties of Three TWinning Induced Plasticity (TWIP) Steels

    NASA Astrophysics Data System (ADS)

    Hong, Seokmin; Shin, Sang Yong; Kim, Hyoung Seop; Lee, Sunghak; Kim, Sung-Kyu; Chin, Kwang-Geun; Kim, Nack J.

    2013-02-01

    In the present study, delayed fracture properties of a high-Mn TWinning Induced Plasticity (TWIP) steel and two Al-added TWIP steels were examined by dipping tests of cup specimens in the boiled water, after which the microcrack formation behavior was analyzed. The TWIP steels contained a small amount of elongated MnS inclusions, spherical-shaped AlN particles, and submicron-sized (Fe,Mn)3C carbides. Since MnS inclusions worked as crack initiation sites, longitudinal cracks were formed along the cup forming direction mostly by MnS inclusions. These cracks were readily grown when high tensile residual stresses affected the cracking or hydrogen atoms were gathered inside cracks, which resulted in the delayed fracture. In the Al-added steels, MnS inclusions acted as crack initiation and propagation sites during cup forming or boiled-water dipping test, but residual stresses applied to MnS might be low for the crack initiation and growth. Thus, longitudinal cracks formed by MnS inclusions did not work much for delayed fracture. AlN particles present in the Al-added steels hardly acted as crack initiation or growth sites for the delayed fracture because of their spherical shape.

  12. Fracture properties of polycrystalline silicon - a material for micro-electro-mechanical systems

    SciTech Connect

    Johnson, G.C.; Jones, P.T.

    1995-12-31

    A great deal of research has been performed during the past few years to apply the microfabrication technology used for making integrated circuits to the manufacture of microscopic pressure sensors, accelerometers, and other micro-electro-mechanical systems (MEMS). One result of this work has been the choice of polycrystalline silicon (polysilicon) as a primary structural material employed in MEMS devices, particularly when the polysilicon has been doped with such elements as phosphorus for improved electrical and mechanical properties. As MEMS devices become more relied upon for real world applications, it will be necessary to establish design rules to ensure adequate product lifetimes. However, very little work has been done to deter- mine the failure mechanisms of polysilicon. The work presented here offers an experimental evaluation of the ultimate strength and fracture toughness of polysilicon with regard to the effects of exposure to hydrofluoric acid, a commonly used etchant in MEMS fabrication. A series of micromechanical structures have been designed to measure the strain at fracture and fracture toughness of a thin film. These test structures are patterned onto a thin film of polysilicon covering a silicon wafer using standard microfabrication techniques. Since the structures have dimensions on the order of microns, hundreds of multiple test structures are patterned on a single wafer providing a large amount of statistical data. Results using these structures indicate that prolonged exposure to HF can result in a decrease in the fracture strength of polysilicon.

  13. Molecular composites via ionic interactions and their deformation/fracture properties

    SciTech Connect

    Parker, G.; Chen, W.; Hara, M.

    1995-12-01

    Homogeneous molecular composites have been made from ionic PPTA and PVP, in which a good dispersion of rod molecules is achieved via ion-dipole interactions. Appearance of a single T{sub g} as well as morphological observations by TEM have indicated good dispersion of the rigid-rod PPTA molecules. The deformation mode of the matrix polymer is modified significantly with the addition of rod molecules: while crazing is the only deformation mechanism of PVP, an addition of ionic PPTA molecules into the PVP matrix induces shear deformation. This suggests better fracture properties of these molecular composites. Initial studies have indicated significant enhancement in mechanical properties.

  14. Martensitic stainless steel AISI 420—mechanical properties, creep and fracture toughness

    NASA Astrophysics Data System (ADS)

    Brnic, J.; Turkalj, G.; Canadija, M.; Lanc, D.; Krscanski, S.

    2011-11-01

    In this paper some experimental results and analyses regarding the behavior of AISI 420 martensitic stainless steel under different environmental conditions are presented. That way, mechanical properties like ultimate tensile strength and 0.2 percent offset yield strength at lowered and elevated temperatures as well as short-time creep behavior for selected stress levels at selected elevated temperatures of mentioned material are shown. The temperature effect on mentioned mechanical properties is also presented. Fracture toughness was calculated on the basis of Charpy impact energy. Experimentally obtained results can be of importance for structure designers.

  15. Characterization of Mode I Fracture and Morphological Properties of PLLA Blends with Addition of Lysine Triisocyanate

    NASA Astrophysics Data System (ADS)

    Vannaladsaysy, Vilay; Todo, Mitsugu

    Poly(L-lactic acid) (PLLA) was toughened by blending with three different ductile biopolymers such as poly (ε-caprolactone) (PCL), poly(butylene succinate-co-e-caprolactone) (PBSC), poly (butylene succinate-co-L-lactate) (PBSL). The blend ratio was fixed to 50:50. Lysine triisocyanate (LTI) was added to the blends as a compatibilizer. Characterizations such as Fourier transform infra-red (FT-IR) spectroscopy, field-emission electron microscope (FE-SEM), and mode I fracture test were used to characterize the effectiveness of LTI on the mechanical and morphological properties of various PLLA blends. It was found that PLLA/PCL blend shows the highest toughness energy among the binary blends. On the other hand, addition of LTI in PLLA/PBSC blend exhibits the best toughness property. Based on the FE-SEM observation, fractured surfaces of PLLA blends with LTI indicate ductile fracture with dense elongated fibrils. The largest damage zone is generated in the vicinity of crack-trip, suggesting that high energy dissipation occurred in the crack-trip region. FT-IR analysis also suggested that the NCO groups of LTI were acted as a compatibilizer, as the results of interaction between the two phases of the polymer blends.

  16. Friction Stir-Welded Titanium Alloy Ti-6Al-4V: Microstructure, Mechanical and Fracture Properties

    NASA Astrophysics Data System (ADS)

    Sanders, D. G.; Edwards, P.; Cantrell, A. M.; Gangwar, K.; Ramulu, M.

    2015-05-01

    Friction stir welding (FSW) has been refined to create butt welds from two sheets of Ti-6Al-4V alloy to have an ultra-fine grain size. Weld specimen testing was completed for three different FSW process conditions: As welded, stress relieved, stress relieved and machined, and for the un-welded base material. The investigation includes macrostructure, microstructure, microhardness, tensile property testing, notched bar impact testing, and fracture toughness evaluations. All experiments were conducted in accordance with industry standard testing specifications. The microstructure in the weld nugget was found to consist of refined and distorted grains of alpha in a matrix of transformed beta containing acicular alpha. The enhanced fracture toughness of the welds is a result of increased hardness, which is attributed to an increase in alpha phase, increase in transformed beta in acicular alpha, and grain refinement during the weld process. The noted general trend in mechanical properties from as welded, to stress relieved, to stress relieved and machined conditions exhibited a decrease in ultimate tensile strength, and yield strength with a small increase in ductility and a significant increase in fracture toughness.

  17. Effects of Strain Rates on Mechanical Properties and Fracture Mechanism of DP780 Dual Phase Steel

    NASA Astrophysics Data System (ADS)

    Li, Shengci; Kang, Yonglin; Zhu, Guoming; Kuang, Shuang

    2015-06-01

    The mechanical properties of DP780 dual phase steel were measured by quasi-static and high-speed tensile tests at strain rates between 0.001 and 1000 s-1 at room temperature. The deformation and fracture mechanisms were analyzed by observation of the tensile fracture and microstructure near the fracture. Dynamic factor and feret ratio quantitative methods were applied to study the effect of strain rate on the microstructure and properties of DP780 steel. The constitutive relation was described by a modified Johnson-Cook and Zerilli-Armstrong model. The results showed that the strain rate sensitivity of yield strength is bigger than that of ultimate tensile strength; as strain rate increased, the formation of microcracks and voids at the ferrite/martensite interface can be alleviated; the strain rate effect is unevenly distributed in the plastic deformation region. Moreover, both models can effectively describe the experimental results, while the modified Zerilli-Armstrong model is more accurate because the strain-hardening rate of this model is independent of strain rate.

  18. Measuring multi-dimensional, time-dependent mechanical properties of a human tibial fracture using an automated system.

    PubMed

    Ogrodnik, P J; Moorcroft, C I; Thomas, P B

    2007-08-01

    This paper presents an element of a long-term research project determining a clinically quantifiable end point for fracture healing in humans. An automated loading and measurement device is presented. It has been developed as a research tool for the assessment of the mechanical properties of a healing human tibial fracture. The device has been specifically designed for use with patients treated with external fixation. The characteristics of the device have been presented together with an assessment of errors. A typical sample of results has been presented to demonstrate the significance of the device; subsequent papers will examine the whole data set in greater depth. The results presented here confirm the non-linear behaviour of callus and reinforce the requirement to measure the load rate when measuring the fracture stiffness. A new material property for the assessment of fracture healing, namely gamma, is examined and preliminary results are shown. Polar plots of stiffness demonstrate that, when measuring fracture stiffness, not only should the load rate be considered, but also the orientation of measurement. The results from this work support the view that the fracture stiffness should be measured in at least two planes. Currently a fracture can be considered healed when the fracture stiffness exceeds 15 N m/deg; this paper questions whether this value is now valid and suggests that it should be re-examined. PMID:17937203

  19. Effects of Atomic-Scale Structure on the Fracture Properties of Amorphous Carbon - Carbon Nanotube Composites

    NASA Technical Reports Server (NTRS)

    Jensen, Benjamin D.; Wise, Kristopher E.; Odegard, Gregory M.

    2015-01-01

    The fracture of carbon materials is a complex process, the understanding of which is critical to the development of next generation high performance materials. While quantum mechanical (QM) calculations are the most accurate way to model fracture, the fracture behavior of many carbon-based composite engineering materials, such as carbon nanotube (CNT) composites, is a multi-scale process that occurs on time and length scales beyond the practical limitations of QM methods. The Reax Force Field (ReaxFF) is capable of predicting mechanical properties involving strong deformation, bond breaking and bond formation in the classical molecular dynamics framework. This has been achieved by adding to the potential energy function a bond-order term that varies continuously with distance. The use of an empirical bond order potential, such as ReaxFF, enables the simulation of failure in molecular systems that are several orders of magnitude larger than would be possible in QM techniques. In this work, the fracture behavior of an amorphous carbon (AC) matrix reinforced with CNTs was modeled using molecular dynamics with the ReaxFF reactive forcefield. Care was taken to select the appropriate simulation parameters, which can be different from those required when using traditional fixed-bond force fields. The effect of CNT arrangement was investigated with three systems: a single-wall nanotube (SWNT) array, a multi-wall nanotube (MWNT) array, and a SWNT bundle system. For each arrangement, covalent bonds are added between the CNTs and AC, with crosslink fractions ranging from 0-25% of the interfacial CNT atoms. The SWNT and MWNT array systems represent ideal cases with evenly spaced CNTs; the SWNT bundle system represents a more realistic case because, in practice, van der Waals interactions lead to the agglomeration of CNTs into bundles. The simulation results will serve as guidance in setting experimental processing conditions to optimize the mechanical properties of CNT

  20. Control On Fluid Flow Properties In Sandstone: Interactions Between Diagenesis Processes And Fracture Corridors

    NASA Astrophysics Data System (ADS)

    Bossennec, Claire; Géraud, Yves; Moretti, Isabelle; Mattioni, Luca

    2016-04-01

    During the development of a fault zone, processes occur at different scales: secondary faults and fractures development in the damage zone while "diagenetic" processes, i.e: fluid rock interaction at the grains size scale, contribute to modify the matrix features. Spatial distribution of these processes is clearly controlled by microstructural transformations induced by fractured corridors and their location. Understanding flowing properties in the associated damage zone contributes to the better modeling of the fluid flow in faulted and fractured reservoirs which could be oil, gas or water bearing. The Lower Triassic Buntsandstein sandstones outcrop of Cleebourg is located in the Hochwald Horst affected by a major NNE-SSW striking fault, and the structure globally dips with 30° toward Rhenish Fault (Upper Rhine Graben main western border fault). The study of the outcrop aims to decipher the fluid-flow scheme and interactions between fracture network and diagenetic features distribution in the damage zone of a fault, located close to major faulted areas, through field and laboratories petrophysical measurements (permeability, thermic conductivity), and samples microstructural and diagenetical descriptions. The outcrop is structurally divided into a 14 meters thick fault core, surrounded by 5 meters thick transition zones, and damage zone of minimum thickness of 40 meters (total thickness unknown, due to the limits of the outcrop). Damage zone includes three fractured corridors, perpendicular to bedding and from 2 to 5 meters thick. Results presented here were acquired in 2 different layers with similar lithology but only on damage zone samples. In entire damage zone, porosity results and thin section description allow to distinguish two different facies: • Fa1 Intermediate porous (porosity of 12%) sandstone with major illite cement and clay content up to 20% (detrital and diagenetic); • Fa2 High porous (porosity >15%) sandstone with quartz feeding

  1. TRITIUM AGING EFFECTS ON THE FRACTURE TOUGHNESS PROPERTIES OF STAINLESS STEEL BASE METAL AND WELDS

    SciTech Connect

    Morgan, M.

    2009-07-30

    Tritium reservoirs are constructed from welded stainless steel forgings. While these steels are highly resistant to the embrittling effects of hydrogen isotopes and helium from tritium decay; they are not immune. Tritium embrittlement is an enhanced form of hydrogen embrittlement because of the presence of helium-3 from tritium decay which nucleates as nanometer-sized bubbles on dislocations, grain boundaries, and other microstructural defects. Steels with decay helium bubble microstructures are hardened and less able to deform plastically and become more susceptible to embrittlement by hydrogen and its isotopes. Ductility, elongation-to-failure, and fracture toughness are reduced by exposures to tritium and the reductions increase with time as helium-3 builds into the material from tritium permeation and radioactive decay. Material and forging specifications have been developed for optimal material compatibility with tritium. These specifications cover composition, mechanical properties, and select microstructural characteristics like grain size, flow-line orientation, inclusion content, and ferrite distribution. For many years, the forming process of choice for reservoir manufacturing was high-energy-rate forging (HERF), principally because the DOE forging facility owned only HERF hammers. Today, some reservoir forgings are being made that use a conventional, more common process known as press forging (PF or CF). One of the chief differences between the two forging processes is strain rate: Conventional hydraulic or mechanical forging presses deform the metal at 4-8 ft/s, about ten-fold slower than the HERF process. The material specifications continue to provide successful stockpile performance by ensuring that the two forging processes produce similar reservoir microstructures. While long-term life storage tests have demonstrated the general tritium compatibility of tritium reservoirs, fracture-toughness properties of both conventionally forged and high

  2. Cryogenic Interlaminar Fracture Properties of Woven Glass/Epoxy Composite Laminates Under Mixed-Mode I/III Loading Conditions

    NASA Astrophysics Data System (ADS)

    Miura, Masaya; Shindo, Yasuhide; Takeda, Tomo; Narita, Fumio

    2013-08-01

    We characterize the combined Mode I and Mode III delamination fracture behavior of woven glass fiber reinforced polymer (GFRP) composite laminates at cryogenic temperatures. The eight-point bending plate (8PBP) tests were conducted at room temperature, liquid nitrogen temperature (77 K) and liquid helium temperature (4 K) using a new test fixture. A three-dimensional finite element analysis was also performed to calculate the energy release rate distribution along the delamination front, and the delamination fracture toughnesses were evaluated for various mixed-mode I/III ratios. Furthermore, the microscopic examinations of the fracture surfaces were carried out with scanning electron microscopy (SEM), and the mixed-mode I/III delamination fracture mechanisms in the woven GFRP laminates at cryogenic temperatures were assessed. The fracture properties were then correlated with the observed characteristics.

  3. Quantitative local topological texture properties obtained from radiographs of the proximal femur in patients with pertrochanteric and transcervical hip fractures

    NASA Astrophysics Data System (ADS)

    Boehm, H. F.; Lutz, J.; Koerner, M.; Notohamiprodjo, M.; Reiser, M.

    2009-02-01

    The incidence of osteoporosis and associated fractures becomes an increasingly relevant issue for the public health institutions of industrialized nations. Fractures of the hip represent the worst complication of osteoporosis with a significantly elevated rate of mortality. Prediction of fracture risk is a major focus of osteoporosis research and, over the years, has been approched from different angles. There exist two distinct subtypes of transcervical and pertrochanteric hip fracture that can be distinguished on the basis of the anatomical location of the injury. While the epidemiology of hip fractures has been well described, typically, little or no distinction is made between the subtypes. The object of this study was to determine whether local topological texture properties based on the Minkowski Functionals (MF) obtained from standard radiographs of the proximal femur in patients with hip fracture can be used to differentiate between the two types of fracture pattern. The texture features were extracted from standardized regions of interest (femoral head, neck, and pertrochanteric region) in clinical radiographs of the hip obtained from 90 post-menopausal women (69.8 +/- 7.9 yrs). 30 of the women had sustained pertrochanteric fractures, 30 had transcervical hip fractures and 30 were age-matched controls. We determined an optimized topological parameter MF2Dloc using an integrative filtering procedure based on a sliding-windows algorithm. Statistical relationship between the fracture type (pertrochanteric/transcervical) and the value of MF2Dloc was assessed by receiver-operator characteristic (ROC) analysis. Depending on the anatomical location of the region of interest for texture analysis correct classification of tanscervial and pertrochanteric fractures ranged from AUC = 0.79 to 0.98. In conclusion, quantitative texture properties of trabecular bone extracted from radiographs of the hip can be used to identify patients with hip fracture and to distinguish

  4. Modeling and additive manufacturing of bio-inspired composites with tunable fracture mechanical properties.

    PubMed

    Dimas, Leon S; Buehler, Markus J

    2014-07-01

    Flaws, imperfections and cracks are ubiquitous in material systems and are commonly the catalysts of catastrophic material failure. As stresses and strains tend to concentrate around cracks and imperfections, structures tend to fail far before large regions of material have ever been subjected to significant loading. Therefore, a major challenge in material design is to engineer systems that perform on par with pristine structures despite the presence of imperfections. In this work we integrate knowledge of biological systems with computational modeling and state of the art additive manufacturing to synthesize advanced composites with tunable fracture mechanical properties. Supported by extensive mesoscale computer simulations, we demonstrate the design and manufacturing of composites that exhibit deformation mechanisms characteristic of pristine systems, featuring flaw-tolerant properties. We analyze the results by directly comparing strain fields for the synthesized composites, obtained through digital image correlation (DIC), and the computationally tested composites. Moreover, we plot Ashby diagrams for the range of simulated and experimental composites. Our findings show good agreement between simulation and experiment, confirming that the proposed mechanisms have a significant potential for vastly improving the fracture response of composite materials. We elucidate the role of stiffness ratio variations of composite constituents as an important feature in determining the composite properties. Moreover, our work validates the predictive ability of our models, presenting them as useful tools for guiding further material design. This work enables the tailored design and manufacturing of composites assembled from inferior building blocks, that obtain optimal combinations of stiffness and toughness. PMID:24700202

  5. Effect of property gradients on enamel fracture in human molar teeth.

    PubMed

    Barani, Amir; Bush, Mark B; Lawn, Brian R

    2012-11-01

    A model for the fracture of tooth enamel with graded elastic modulus and toughness is constructed using an extended finite element modeling (XFEM) package. The property gradients are taken from literature data on human molars, with maximum in modulus at the outer enamel surface and in toughness at the inner surface. The tooth is modeled as a brittle shell (enamel) and a compliant interior (dentin), with occlusal loading from a hard, flat contact at the cusp. Longitudinal radial (R) and margin (M) cracks are allowed to extend piecewise along the enamel walls under the action of an incrementally increasing applied load. A simple stratagem is deployed in which fictitious temperature profiles generate the requisite property gradients. The resulting XFEM simulations demonstrate that the crack fronts become more segmented as the property gradients become more pronounced, with enhanced propagation at the outer surface and inhibited propagation at the inner. Whereas the growth history of the cracks is profoundly influenced by the gradients, the ultimate critical loads required to attain full fractures are relatively unaffected. Some implications concerning dentistry are considered. PMID:23032432

  6. Modeling and additive manufacturing of bio-inspired composites with tunable fracture mechanical properties.

    PubMed

    Dimas, Leon S; Buehler, Markus J

    2014-07-01

    Flaws, imperfections and cracks are ubiquitous in material systems and are commonly the catalysts of catastrophic material failure. As stresses and strains tend to concentrate around cracks and imperfections, structures tend to fail far before large regions of material have ever been subjected to significant loading. Therefore, a major challenge in material design is to engineer systems that perform on par with pristine structures despite the presence of imperfections. In this work we integrate knowledge of biological systems with computational modeling and state of the art additive manufacturing to synthesize advanced composites with tunable fracture mechanical properties. Supported by extensive mesoscale computer simulations, we demonstrate the design and manufacturing of composites that exhibit deformation mechanisms characteristic of pristine systems, featuring flaw-tolerant properties. We analyze the results by directly comparing strain fields for the synthesized composites, obtained through digital image correlation (DIC), and the computationally tested composites. Moreover, we plot Ashby diagrams for the range of simulated and experimental composites. Our findings show good agreement between simulation and experiment, confirming that the proposed mechanisms have a significant potential for vastly improving the fracture response of composite materials. We elucidate the role of stiffness ratio variations of composite constituents as an important feature in determining the composite properties. Moreover, our work validates the predictive ability of our models, presenting them as useful tools for guiding further material design. This work enables the tailored design and manufacturing of composites assembled from inferior building blocks, that obtain optimal combinations of stiffness and toughness.

  7. The influence of fracture properties on ground-water flow at the Bunker Hill Mine, Kellogg, Idaho

    SciTech Connect

    Lachmar, T.E.

    1993-12-01

    The Bunker Hill Mine in northern Idaho is a large underground lead-zinc mine located in Precambrian metaquartzite rocks with virtually no primary porosity. Ground-water flow through these types of rocks is largely dependent upon the properties of fractures such as joints, faults and relict bedding planes. Ground water that flows into the mine via the fractures is contaminated by heavy metals and by the production of acid water, which results in a severe acid mine drainage problem. A more complete understanding of how the fractures influence the ground-water flow system is a prerequisite to the evaluation of reclamation alternatives to reduce acid drainage from the mine. Fracture mapping techniques were used to obtain detailed information on the fracture properties observed in the New East Reed drift of the Bunker Hill Mine. The data obtained include: (a) fracture type, (b) orientation, (c) trace length, (d) the number of visible terminations, (e) roughness (small-scale asperities), (f) waviness (larger-scale undulations), (g) infilling material, and (h) a qualitative measure of the amount of water flowing through each fracture.

  8. Does the casting mode influence microstructure, fracture and properties of different metal ceramic alloys?

    PubMed

    Bauer, José Roberto de Oliveira; Grande, Rosa Helena Miranda; Rodrigues-Filho, Leonardo Eloy; Pinto, Marcelo Mendes; Loguercio, Alessandro Dourado

    2012-01-01

    The aim of the present study was to evaluate the tensile strength, elongation, microhardness, microstructure and fracture pattern of various metal ceramic alloys cast under different casting conditions. Two Ni-Cr alloys, Co-Cr and Pd-Ag were used. The casting conditions were as follows: electromagnetic induction under argon atmosphere, vacuum, using blowtorch without atmosphere control. For each condition, 16 specimens, each measuring 25 mm long and 2.5 mm in diameter, were obtained. Ultimate tensile strength (UTS) and elongation (EL) tests were performed using a Kratos machine. Vickers Microhardness (VM), fracture mode and microstructure were analyzed by SEM. UTS, EL and VM data were statistically analyzed using ANOVA. For UTS, alloy composition had a direct influence on casting condition of alloys (Wiron 99 and Remanium CD), with higher values shown when cast with Flame/Air (p < 0.05). The factors 'alloy" and 'casting condition" influenced the EL and VM results, generally presenting opposite results, i.e., alloy with high elongation value had lower hardness (Wiron 99), and casting condition with the lowest EL values had the highest VM values (blowtorch). Both factors had significant influence on the properties evaluated, and prosthetic laboratories should select the appropriate casting method for each alloy composition to obtain the desired property. PMID:22641437

  9. Scaling and geometric properties of extensional fracture systems in the proterozoic basement of Yemen. Tectonic interpretation and fluid flow implications

    NASA Astrophysics Data System (ADS)

    Le Garzic, Edouard; de L'Hamaide, Thibaut; Diraison, Marc; Géraud, Yves; Sausse, Judith; de Urreiztieta, Marc; Hauville, Benoît; Champanhet, Jean-Michel

    2011-04-01

    Multi-scale mappings of fracture systems in the crystalline basement of Yemen are presented. Fracture datasets are described through statistical analyses of direction, length, spacing, density, and spatial distribution. Results are combined with field observations and can be directly used to model the geometry of the fracture networks in analog basement rocks, from multi-kilometric to decametric scales. The fractured reservoir analog is defined with a dual porosity model in which tectonic and joint systems correspond to the basement reservoir "backbone" and "matrix" respectively. These two end-members reveal contrasting geometrical, reservoir, and scaling properties. In tectonic systems, multi-scale geometries are "self-similar", the fracture network shows fractal behavior (power-law length distribution and clustered spacing), and fault zones show hierarchical organization of geometrical parameters such as length, thickness, and spacing. In joint systems, the fracture network is scale dependent with exponential length distribution, and shows anti-clustered spacing. However, these two end-members have both well-connected properties, with fault zones acting as main drain and joint systems acting as the fluid supply.

  10. Implementing ground surface deformation tools to characterize field-scale properties of a fractured aquifer during a short hydraulic test

    NASA Astrophysics Data System (ADS)

    Schuite, Jonathan; Longuevergne, Laurent; Bour, Olivier; Boudin, Frédérick; Durand, Stéphane

    2016-04-01

    In naturally fractured reservoirs, fluid flow is governed by the structural and hydromechanical properties of fracture networks or conductive fault zones. In order to ensure a sustained exploitation of resources or to assess the safety of underground storage, it is necessary to evaluate these properties. As they generally form highly heterogeneous and anisotropic reservoirs, fractured media may be well characterized by means of several complementary experimental methods or sounding techniques. In this framework, the observation of ground deformation has been proved useful to gain insight of a fractured reservoir's geometry and hydraulic properties. Commonly, large conductive structures like faults can be studied from surface deformation from satellite methods at monthly time scales, whereas meter scale fractures have to be examined under short-term in situ experiments using high accuracy intruments like tiltmeters or extensometers installed in boreholes or at the ground's surface. To the best of our knowledge, the feasability of a field scale (~ 100 m) characterization of a fractured reservoir with geodetic tools in a short term experiment has not yet been addressed. In the present study, we implement two complementary ground surface geodetic tools, namely tiltmetry and optical leveling, to monitor the deformation induced by a hydraulic recovery test at the Ploemeur hydrological observatory (France). Employing a simple purely elastic modeling approach, we show that the joint use of time constraining data (tilt) and spatially constraining data (vertical displacement) makes it possible to evaluate the geometry (dip, root depth and lateral extent) and the storativity of a hydraulically active fault zone, in good agreement with previous studies. Hence we demonstrate that the adequate use of two complementary ground surface deformation methods offer a rich insight of large conductive structure's properties using a single short term hydraulic load. Ground surface

  11. Epidemiologic Properties of Pediatric Fractures in a Metropolitan Area of Turkey.

    PubMed

    Issin, Ahmet; Kockara, Nizamettin; Oner, Ali; Sahin, Vedat

    2015-10-01

    Occurrence of fractures is highly dependent on lifestyle. Domestic data should be used when needed. In this cross-sectional study, the authors aim to find the most recent distribution of pediatric fracture types and the attributes of fracture occurrence within a large sample size in a metropolitan area of Turkey.This study consists of 4879 pediatric age patients with a fracture who took advantage of the emergency service of a trauma center in a metropolitan area between March 2010 and December 2013 (1397 days). Date, hour, age, sex, fracture type, and social security status of the patients were studied.A total of 65% of the patients were men and 35% were women. A total of 81% of the fractures were in the upper extremities, whereas 19% of them were in the lower extremities. In 22 patients (0.5%), there were open fractures. Fractures showed some seasonal, daily, and circadian variations. Different types of fractures showed some specific patterns in different age groups. Ankle, elbow, and shoulder fractures were more common in girls, whereas wrist and forearm fractures were more in boys and the difference was statistically significant (P < 0.05).Fractures in pediatric ages vary depending on the age, sex, season, and the hour of the day. Types of fractures show some obvious patterns especially depending on the age. This data can be useful in making optimizations in fracture care units. Considering these specific patterns would enable more effective planning of providing preventive measures for pediatric injuries. PMID:26512602

  12. Measuring Fracture Properties of Meteorites: 3D Scans and Disruption Experiments.

    NASA Astrophysics Data System (ADS)

    Cotto-Figueroa, Desireé; Asphaug, Erik; Morris, Melissa A.; Garvie, Laurence

    2014-11-01

    The Arizona State University (ASU) Center for Meteorite Studies (CMS) houses over 30,000 specimens that represent almost every known meteorite type. A number of these are available for fragmentation experiments in small samples, but in most cases non-destructive experiments are desired in order to determine the fundamental mechanical properties of meteorites, and by extension, the Near-Earth Asteroids (NEAs) and other planetary bodies they derive from. We present results from an ongoing suite of measurements and experiments, featuring automated 3D topographic scans of a comprehensive suite of meteorites in the CMS collection, basic mechanical studies, and culminating in catastrophic fragmentation of four representative meteorites: Tamdakht (H5), Allende (CV3), Northwest Africa 869 (L3-6) and Chelyabinsk (LL5). Results will include high-resolution 3D color-shape models of meteorites, including specimens such as the 349g oriented and fusion crusted Martian (shergottite) Tissint, and the delicately fusion crusted and oriented 131g Whetstone Mountains (H5) ordinary chondrite. The 3D color-shape models will allow us to obtain basic physical properties (such as volume to derive density) and to derive fractal dimensions of fractured surfaces. Fractal dimension is closely related to the internal structural heterogeneity and fragmentation of the material, to macroscopic optical properties, and to rubble friction and cohesion. Freshly fractured surfaces of fragments that will result from catastrophic hypervelocity impact experiments will be subsequently scanned and analyzed in order to determine whether fractal dimension is preserved or if it changes with surface maturation.

  13. Tensile and fracture toughness properties of alumina trihydrate filled epoxy resins

    SciTech Connect

    Pritchard, G.; Wainwright, R.

    1993-12-31

    Certain non-halogen fire retardants such as alumina trihydrate (ATH) are effective in organic matrix composite materials only when they constitute a very high volume fraction of the total material and therefore have major effects on mechanical properties. ATH particles have weak cleavage planes and are easily fractured; their effects are rather different from those of stronger fillers. This paper is concerned with the importance of various particle characteristics, especially size distribution, in ATH filled epoxy resin castings. Tensile strength, modulus, and elongation were measured, and fracture parameters were also determined as a function of filler volume fraction for various grades. Surface treatment reduced the modulus of filled resins, except for ATH particles produced by a precipitation process. The changes were nevertheless broadly consistent with those predicted by published equations such as the Nielsen equation. The size of the largest particles had a major effect on strength and elongation. The strength typically fell to 35% of the strength of the unfilled epoxy resin, for volume fractions of 0.45 approximately, as predicted by Nicolais and Schrager equations.

  14. Influence of cooling rate on interlaminar fracture properties of unidirectional commingled CF/PEEK composites

    NASA Astrophysics Data System (ADS)

    Beehag, Andrew; Ye, Lin

    1995-05-01

    The influence of cooling rates on the mechanical property profile (transverse flexure properties and modes-I and -II interlaminar fracture toughness) has been investigated for unidirectional commingled CF/PEEK composites. A laboratory hot press with a steel mould was used to process the composites at 400°C for 60 min, at an applied pressure of 1 MPa. Cooling rates from fast (quenching in oil) to slow (hot press cooling) were achieved at ambient pressure. The results indicate that different matrix morphology was found at different cooling conditions, although deconsolidation occurred in the CF/PEEK composites during cooling. When the cooling rate was shifted from slow to fast, consolidation quality of the CF/PEEK composites was improved. The resulting effect of the consolidation quality and cooling rates on the mechanical property profile of commingled CF/PEEK composites is presented. It was found that the effect of the cooling rate on the mechanical property profile of the commingled CF/PEEK composites could not be isolated from the consolidation quality.

  15. Measuring fracture properties of meteorites: 3D scans and disruption experiments

    NASA Astrophysics Data System (ADS)

    Cotto-Figueroa, D.; Asphaug, E.; Morris, M.; Garvier, L.

    2014-07-01

    Many meteorite studies are focused on chemical and isotopic composition, which provide insightful information regarding the age, formation, and evolution of the Solar System. However, their fundamental mechanical properties have received less attention. It is important to determine these properties as they are related to disruption and fragmentation of bolides and asteroids, and activities related to sample return and hazardous asteroid mitigation. Here we present results from an ongoing suite of measurements and experiments focusing on maps of surface texture that connect to the dynamic geological properties of a diverse range of meteorites from the Center for Meteorite Studies (CMS) collection at Arizona State University (ASU). Results will include high-resolution 3D color-shape models and texture maps from which we derive fractal dimensions of fractured surfaces. Fractal dimension is closely related to the internal structural heterogeneity and fragmentation of rock, and to macroscopic optical properties, and to rubble friction and cohesion. Selected meteorites, in particular Tamdakht (H5), Allende (CV3), and Chelyabinsk (LL5), will subsequently be disrupted in catastrophic hypervelocity impact experiments. The fragments obtained from these experiments will be scanned, and the results compared with the fragments obtained in numerical hydrocode simulations, whose initial conditions are set up precisely from 3D scans of the original meteorite. By attaining the best match we will obtain key parameters for models of asteroid and bolide disruption.

  16. Predicting Fracture Toughness of TRIP 800 using Phase Properties Characterized by In-Situ High Energy X-Ray Diffraction

    SciTech Connect

    Soulami, Ayoub; Choi, Kyoo Sil; Liu, Wenning N.; Sun, Xin; Khaleel, Mohammad A.; Ren, Yang; Wang, Yan-Dong

    2010-05-01

    TRansformation Induced Plasticity (TRIP) steel is a typical representative of 1st generation advanced high strength steel (AHSS) which exhibits a combination of high strength and excellent ductility due to its multiphase microstructure. In this paper, we study the crack propagation behavior and fracture resistance of a TRIP 800 steel using a microstructure-based finite element method with the various phase properties characterized by in-situ high energy Xray diffraction (HEXRD) technique. Uniaxial tensile tests on the notched TRIP 800 sheet specimens were also conducted, and the experimentally measured tensile properties and R-curves (Resistance curves) were used to calibrate the modeling parameters and to validate the overall modeling results. The comparison between the simulated and experimentally measured results suggests that the micromechanics based modeling procedure can well capture the overall complex crack propagation behaviors and the fracture resistance of TRIP steels. The methodology adopted here may be used to estimate the fracture resistance of various multiphase materials.

  17. Particle-matrix interfacial bonding: Effect on the fracture properties of rubber-modified epoxy polymers

    SciTech Connect

    Huang, Y.; Kinloch, A.J.; Bertsch, R.J.; Siebert, A.R.

    1993-12-31

    This study employed various butadiene-acrylonitrile rubbers and showed that both the functionality of the end groups and the acrylonitrile content have a strong influence on the microstructure and the interfacial bonding that are observed in the resulting rubber-toughened epoxy. For the rubbers examined, significant toughening is recorded only when the rubber forms a separate phase in the epoxy matrix with a particle size on the order of micrometers. These microstructural features are affected by both the functionality of the end groups and the acrylonitrile content of the rubber employed. However, once phase separation of the rubber has been achieved to give particles on the order of micrometers in size, then the interfacial bonding between the rubber particles and the epoxy matrix has only a small effect on the fracture properties of the rubber-toughened epoxy polymers. 28 refs., 6 figs., 3 tabs.

  18. Petrophysical properties, mineralogy, fractures, and flow tests in 25 deep boreholes at Yucca Mountain, Nevada

    USGS Publications Warehouse

    Nelson, Philip H.; Kibler, Joyce E.

    2014-01-01

    As part of a site investigation for the disposal of radioactive waste, numerous boreholes were drilled into a sequence of Miocene pyroclastic flows and related deposits at Yucca Mountain, Nevada. This report contains displays of data from 25 boreholes drilled during 1979–1984, relatively early in the site investigation program. Geophysical logs and hydrological tests were conducted in the boreholes; core and cuttings analyses yielded data on mineralogy, fractures, and physical properties; and geologic descriptions provided lithology boundaries and the degree of welding of the rock units. Porosity and water content were computed from the geophysical logs, and porosity results were combined with mineralogy from x-ray diffraction to provide whole-rock volume fractions. These data were composited on plates and used by project personnel during the 1990s. Improvements in scanning and computer technology now make it possible to publish these displays.

  19. Effects of compositions of filler, binder and porosity on elastic and fracture properties of nuclear graphite

    NASA Astrophysics Data System (ADS)

    Kyaw, S. T.; Sun, W.; Becker, A. A.

    2015-02-01

    Physical mechanisms at different length scales have to be taken into account while predicting the overall failure of nuclear graphite structures of advanced gas cooled graphite reactors. In this paper, the effect of composition of meso graphite phases and porosity on the aggregate elastic properties is predicted using the Eshelby homogenisation method. Results indicate an overall decrease in elastic modulus with an increase in porosity. Subsequently, the moduli at different porosity levels are used to predict the critical strain energy release rates for crack propagation of graphite, and fracture behaviour is studied using compact tension and four point bending tests. Compared to flexural strength at zero porosity level, significant reduction in strength of up to 80% at 30% porosity level is observed. Evolution of flexural strength due to porosity is also compared against available experimental values of graphite from UK nuclear plants.

  20. Review of fracture properties of nuclear materials determined by Hertzian indentation

    SciTech Connect

    Routbort, J.; Matzke, H.

    1985-01-01

    A brief description of the determination of the surface fracture energy and the fracture toughness from a Hertzian indentation test is given. A number of theoretical and experimental problems are discussed. Results obtained on a variety of nuclear fuels and nuclear-waste-containment materials are reviewed and compared with values measured by other techniques. The Hertzian indentation test yields reliable fracture parameters.

  1. Determination of Transport Properties From Flowing Fluid Temperature LoggingIn Unsaturated Fractured Rocks: Theory And Semi-Analytical Solution

    SciTech Connect

    Mukhopadhyay, Sumit; Tsang, Yvonne W.

    2008-08-01

    Flowing fluid temperature logging (FFTL) has been recently proposed as a method to locate flowing fractures. We argue that FFTL, backed up by data from high-precision distributed temperature sensors, can be a useful tool in locating flowing fractures and in estimating the transport properties of unsaturated fractured rocks. We have developed the theoretical background needed to analyze data from FFTL. In this paper, we present a simplified conceptualization of FFTL in unsaturated fractured rock, and develop a semianalytical solution for spatial and temporal variations of pressure and temperature inside a borehole in response to an applied perturbation (pumping of air from the borehole). We compare the semi-analytical solution with predictions from the TOUGH2 numerical simulator. Based on the semi-analytical solution, we propose a method to estimate the permeability of the fracture continuum surrounding the borehole. Using this proposed method, we estimated the effective fracture continuum permeability of the unsaturated rock hosting the Drift Scale Test (DST) at Yucca Mountain, Nevada. Our estimate compares well with previous independent estimates for fracture permeability of the DST host rock. The conceptual model of FFTL presented in this paper is based on the assumptions of single-phase flow, convection-only heat transfer, and negligible change in system state of the rock formation. In a sequel paper [Mukhopadhyay et al., 2008], we extend the conceptual model to evaluate some of these assumptions. We also perform inverse modeling of FFTL data to estimate, in addition to permeability, other transport parameters (such as porosity and thermal conductivity) of unsaturated fractured rocks.

  2. Fracture and fatigue properties of acrylic bone cement: the effects of mixing method, sterilization treatment, and molecular weight.

    PubMed

    Graham, J; Pruitt, L; Ries, M; Gundiah, N

    2000-12-01

    The purpose of this study was to characterize the relative and combined effects of sterilization, molecular weight, and mixing method on the fracture and fatigue performance of acrylic bone cement. Palacos R brand bone cement powder was sterilized using ethylene oxide gas (EtO) or gamma irradiation. Nonsterile material was used as a control. Molecular weights of the bone-cement powders and cured cements were measured using gel permeation chromatography. Hand and vacuum mixing were employed to mold single edge-notched bend specimens for fracture toughness testing. Molded dog-bone specimens were used for fatigue tests. Electron microscopy was used to study fracture mechanisms. Analysis of variance and Student t-tests were used to compare fracture and fatigue performance between sterilization and mixing groups. Our results indicate that vacuum mixing improved significantly the fracture and fatigue resistance (P<.05, P<.07) over hand mixing in radiation-sterilized and EtO-sterilized groups. In vacuum-mixed cement, the degradation in molecular weight resulting from gamma irradiation decreased fracture resistance significantly when compared with EtO sterilization and control (P<.05). A corresponding decrease in fatigue resistance was observed in the cement that was degraded severely by a radiation dose of 10 MRad (P<.05). In contrast, EtO sterilization did not result in a significantly different fracture resistance when compared with unsterilized controls for vacuum-mixed cement (P>.1). For hand-mixed cement, fracture and fatigue resistance appeared to be independent of sterilization method. This independence is believed to be the result of higher porosity that compromised the mechanical properties and obscures any effect of sterilization. Our results indicate that a combination of nonionizing sterilization and vacuum mixing resulted in the best mechanical performance and is most likely to contribute to enhanced longevity in vivo.

  3. Innovative Field Methods for Characterizing the Hydraulic Properties of a Complex Fractured Rock Aquifer (Ploemeur, Brittany)

    NASA Astrophysics Data System (ADS)

    Bour, O.; Le Borgne, T.; Longuevergne, L.; Lavenant, N.; Jimenez-Martinez, J.; De Dreuzy, J. R.; Schuite, J.; Boudin, F.; Labasque, T.; Aquilina, L.

    2014-12-01

    Characterizing the hydraulic properties of heterogeneous and complex aquifers often requires field scale investigations at multiple space and time scales to better constrain hydraulic property estimates. Here, we present and discuss results from the site of Ploemeur (Brittany, France) where complementary hydrological and geophysical approaches have been combined to characterize the hydrogeological functioning of this highly fractured crystalline rock aquifer. In particular, we show how cross-borehole flowmeter tests, pumping tests and frequency domain analysis of groundwater levels allow quantifying the hydraulic properties of the aquifer at different scales. In complement, we used groundwater temperature as an excellent tracer for characterizing groundwater flow. At the site scale, measurements of ground surface deformation through long-base tiltmeters provide robust estimates of aquifer storage and allow identifying the active structures where groundwater pressure changes occur, including those acting during recharge process. Finally, a numerical model of the site that combines hydraulic data and groundwater ages confirms the geometry of this complex aquifer and the consistency of the different datasets. The Ploemeur site, which has been used for water supply at a rate of about 106 m3 per year since 1991, belongs to the French network of hydrogeological sites H+ and is currently used for monitoring groundwater changes and testing innovative field methods.

  4. THE EFFECTS OF HYDROGEN, TRITIUM, AND HEAT TREATMENT ON THE DEFORMATION AND FRACTURE TOUGHNESS PROPERTIES OF STAINLESS STEEL

    SciTech Connect

    Morgan, M.; Tosten, M.; Chapman, G.

    2013-09-06

    The deformation and fracture toughness properties of forged stainless steels pre-charged with tritium were compared to the deformation and fracture toughness properties of the same steels heat treated at 773 K or 873 K and precharged with hydrogen. Forged stainless steels pre-charged with tritium exhibit an aging effect: Fracture toughness values decrease with aging time after precharging because of the increase in concentration of helium from tritium decay. This study shows that forged stainless steels given a prior heat treatment and then pre-charged with hydrogen also exhibit an aging effect: Fracture toughness values decrease with increasing time at temperature. A microstructural analysis showed that the fracture toughness reduction in the heat-treated steels was due to patches of recrystallized grains that form within the forged matrix during the heat treatment. The combination of hydrogen and the patches of recrystallized grains resulted in more deformation twinning. Heavy deformation twinning on multiple slip planes was typical for the hydrogen-charged samples; whereas, in the non-charged samples, less twinning was observed and was generally limited to one slip plane. Similar effects occur in tritium pre-charged steels, but the deformation twinning is brought on by the hardening associated with decay helium bubbles in the microstructure.

  5. Effects of Annealing Treatment Prior to Cold Rolling on Delayed Fracture Properties in Ferrite-Austenite Duplex Lightweight Steels

    NASA Astrophysics Data System (ADS)

    Sohn, Seok Su; Song, Hyejin; Kim, Jung Gi; Kwak, Jai-Hyun; Kim, Hyoung Seop; Lee, Sunghak

    2016-02-01

    Tensile properties of recently developed automotive high-strength steels containing about 10 wt pct of Mn and Al are superior to other conventional steels, but the active commercialization has been postponed because they are often subjected to cracking during formation or to the delayed fracture after formation. Here, the delayed fracture behavior of a ferrite-austenite duplex lightweight steel whose microstructure was modified by a batch annealing treatment at 1023 K (750 °C) prior to cold rolling was examined by HCl immersion tests of cup specimens, and was compared with that of an unmodified steel. After the batch annealing, band structures were almost decomposed as strong textures of {100}<011> α-fibers and {111}<112> γ-fibers were considerably dissolved, while ferrite grains were refined. The steel cup specimen having this modified microstructure was not cracked when immersed in an HCl solution for 18 days, whereas the specimen having unmodified microstructure underwent the delayed fracture within 1 day. This time delayed fracture was more critically affected by difference in deformation characteristics such as martensitic transformation and deformation inhomogeneity induced from concentration of residual stress or plastic strain, rather than the difference in initial microstructures. The present work gives a promise for automotive applications requiring excellent mechanical and delayed fracture properties as well as reduced specific weight.

  6. Effective Hydro-Mechanical Properties of Fluid-Saturated Fracture Networks

    NASA Astrophysics Data System (ADS)

    Pollmann, N.; Vinci, C.; Renner, J.; Steeb, H.

    2015-12-01

    Consideration of hydro-mechanical processes is essential for the characterization of liquid-resources as well as for many engineering applications. Furthermore, the modeling of seismic waves in fractured porous media finds application not only in geophysical exploration but also reservoir management. Fractures exhibit high-aspect-ratio geometries, i.e. they constitute thin and long hydraulic conduits. Motivated by this peculiar geometry, the investigation of the hydro-mechanically coupled processes is performed by means of a hybrid-dimensional modeling approach. The effective material behavior of domains including complex fracture patterns in a porous rock is assessed by investigating the fluid pressure and the solid displacement of the skeleton saturated by compressible fluids. Classical balance equations are combined with a Poiseuille-type flow in the dimensionally reduced fracture. In the porous surrounding rock, the classical Biot-theory is applied. For simple geometries, our findings show that two main fluid-flow processes occur, leak-off from fractures to the surrounding rock and fracture flow within and between the connected fractures. The separation of critical frequencies of the two flow processes is not straightforward, in particular for systems containing a large number of fractures. Our aim is to model three dimensional hydro-mechanically coupled processes within complex fracture patterns and in particular determine the frequency-dependent attenuation characteristics. Furthermore, the effect of asperities of the fracture surfaces on the fracture stiffness and on the hydraulic conductivity will be added to the approach.

  7. Bridging micro to macroscale fracture properties in highly heterogeneous brittle solids: weak pinning versus fingering

    NASA Astrophysics Data System (ADS)

    Vasoya, Manish; Lazarus, Véronique; Ponson, Laurent

    2016-10-01

    The effect of strong toughness heterogeneities on the macroscopic failure properties of brittle solids is investigated in the context of planar crack propagation. The basic mechanism at play is that the crack is locally slowed down or even trapped when encountering tougher material. The induced front deformation results in a selection of local toughness values that reflect at larger scale on the material resistance. To unravel this complexity and bridge micro to macroscale in failure of strongly heterogeneous media, we propose a homogenization procedure based on the introduction of two complementary macroscopic properties: An apparent toughness defined from the loading required to make the crack propagate and an effective fracture energy defined from the rate of energy released by unit area of crack advance. The relationship between these homogenized properties and the features of the local toughness map is computed using an iterative perturbation method. This approach is applied to a circular crack pinned by a periodic array of obstacles invariant in the radial direction, which gives rise to two distinct propagation regimes: A weak pinning regime where the crack maintains a stationary shape after reaching an equilibrium position and a fingering regime characterized by the continuous growth of localized regions of the fronts while the other parts remain trapped. Our approach successfully bridges micro to macroscopic failure properties in both cases and illustrates how small scale heterogeneities can drastically affect the overall failure response of brittle solids. On a broader perspective, we believe that our approach can be used as a powerful tool for the rational design of heterogeneous brittle solids and interfaces with tailored failure properties.

  8. Nose fracture

    MedlinePlus

    Fracture of the nose; Broken nose; Nasal fracture; Nasal bone fracture; Nasal septal fracture ... A fractured nose is the most common fracture of the face. It ... with other fractures of the face. Sometimes a blunt injury can ...

  9. Structural control of weathering processes within exhumed granitoids: Compartmentalisation of geophysical properties by faults and fractures

    NASA Astrophysics Data System (ADS)

    Place, J.; Géraud, Y.; Diraison, M.; Herquel, G.; Edel, J.-B.; Bano, M.; Le Garzic, E.; Walter, B.

    2016-03-01

    In the latter stages of exhumation processes, rocks undergo weathering. Weathering halos have been described in the vicinity of structures such as faults, veins or dykes, with a lateral size gradually narrowing with depth, symmetrically around the structures. In this paper, we describe the geophysical characterisation of such alteration patterns on two granitoid outcrops of the Catalan Coastal Ranges (Spain), each of which is affected by one major fault, as well as minor faults and fractures. Seismic, electric and ground penetrating radar surveys were carried out to map the spatial distribution of P-wave velocity, electrical resistivity and to identify reflectors of electromagnetic waves. The analysis of this multi-method and complementary dataset revealed that, at shallow depth, geophysical properties of the materials are compartmentalised and asymmetric with respect to major and subsidiary faults affecting the rock mass. This compartmentalisation and asymmetry both tend to attenuate with depth, whereas the effect of weathering is more symmetric with respect to the major structure of the outcrops. We interpret such compartmentalisation as resulting from the role of hydraulic and mechanical boundaries played by subsidiary faults, which tend to govern both the chemical and physical alterations involved in weathering. Thus, the smoothly narrowing halo model is not always accurate, as weathering halos can be strongly asymmetrical and present highly irregular contours delimiting sharp contrasts of geophysical properties. These results should be considered when investigating and modelling fluid storage and transfer in top crystalline rock settings for groundwater applications, hydrocarbon or geothermal reservoirs, as well as mineral deposits.

  10. Effect of thickness and loading mode on the fracture properties of V-4Cr-4Ti at room temperature

    SciTech Connect

    Li, H.; Kurtz, R.J.; Jones, R.H.

    1998-03-01

    The effect of thickness on the room temperature (RT) mode I fracture behavior of V-4Cr-4Ti has been investigated. Mode i fracture properties were measured from J-integral tests of compact tension (CT) specimens ranging in thickness from 6.4 mm to 25.4 mm. All specimens were machined in the T-L orientation and vacuum annealed following final matching. Two heats of V-4Cr-4Ti were tested. Specimens 6.4 mm and 12.7 mm thick were taken from ANL Heat No. 832665. The 25.4 mm thick specimens were obtained from GA Heat No. 832864. J-R curves were generated by the single specimen unload-compliance test technique in accordance with ASTM E813. All tests were performed in laboratory air at 25 C. Fracture of V-4Cr-4Ti under mixed-mode loading conditions showed the same trend observed previously for V-5Cr-5Ti and for other tough materials. For materials which fail by microvoid coalescence, the addition of an out-of-plane shear loading component introduces incompatibility stresses at particle interfaces in the trajectory of the crack. These incompatibility stresses cause particle/matrix decohesion or particle fracture which leads to void formation that limits the mode i plastic flow field. The present results demonstrates that fracture of V-4Cr-4Ti is sensitive to the addition of shear loading components and that model fracture toughness tests may not give the most conservative measure of resistance to ductile fracture.

  11. Architecture, fracture system, mechanical properties and permeability structure of a fault zone in Lower Triassic sandstone, Upper Rhine Graben

    NASA Astrophysics Data System (ADS)

    Bauer, Johanna F.; Meier, Silke; Philipp, Sonja L.

    2015-04-01

    Close to the western Upper Rhine Graben Main Fault, Alsace, a NNE-SSW-striking fault zone, crosscutting porous, thick bedded Lower Triassic Bunter sandstone was investigated in detail, including its architecture, discontinuity system, mechanical rock properties and implications on its permeability structure and fault zone type. Field observations indicate a three-part fault zone structure including core-, transition- and damage zone. The at least 14 m thick fault core is composed of various slip surfaces and deformation bands, which encompass fractured host rock lenses. When connected, host rock lenses may transport fluids through the core zone. Adjacent transition zones are highly fractured in R1-orientation, show folded beds and contain P1-oriented deformation bands. R1 and P1-fractures are synthetic shear fractures and project with an acute angle (10-20°) toward the fault plane. Only in the damage zone, fault-parallel striking fractures occur. Here, increasing fracture apertures and connectivity may increase the permeability toward the fault core. Mechanical rock properties from 12 rock samples (Young's modulus, uniaxial compressive strength, tensile strength) measured in all the parts of the fault zone, show highest values within the transition zone. In-situ measurements of rebound-hardnesses with a Schmidt-Hammer and analytical approaches, however, indicate that effective Young's moduli are two to sixteen times lower than the Young's moduli of intact rock. Values clearly decrease toward the fault core, even in the transition zone and are in average lower than effective Young's moduli in the damage zone. Although many fault zones in sandstone are sealing structures these field study show, that fault zones in porous sandstone may allow fluid flow.

  12. J-integral fracture toughness, Tearing modulus and tensile properties of Vitamin E stabilized radiation crosslinked UHMWPE.

    PubMed

    Bellare, Anuj; Dorfman, Robert; Samuel, Ashwanth; Thornhill, Thomas S

    2016-08-01

    Radiation crosslinking of ultra-high molecular weight polyethylene (UHMWPE) increases its wear resistance in total joint replacement prostheses. Unfortunately, it is accompanied by a dose-dependent decrease in several mechanical properties. In this study, the tensile properties and fracture behavior of radiation crosslinked, Vitamin E stabilized UHMWPE was studied as a function of radiation dose. The Rice and Sorensen model, applicable to elastic-plastic materials, was utilized to obtain the initial crack driving force, J1c, steady state J-integral fracture toughness, Jss and the Tearing modulus. Tensile tests showed the dependence of tensile properties on radiation dose. Jss of non-crosslinked UHMWPE was higher than for crosslinked UHMWPE׳s but there was no dose dependent change in Jss whereas there was almost no change in J1c over the entire dose range. Finally, a monotonic decrease in Tearing modulus was observed with radiation dose. PMID:27128734

  13. J-integral fracture toughness, Tearing modulus and tensile properties of Vitamin E stabilized radiation crosslinked UHMWPE.

    PubMed

    Bellare, Anuj; Dorfman, Robert; Samuel, Ashwanth; Thornhill, Thomas S

    2016-08-01

    Radiation crosslinking of ultra-high molecular weight polyethylene (UHMWPE) increases its wear resistance in total joint replacement prostheses. Unfortunately, it is accompanied by a dose-dependent decrease in several mechanical properties. In this study, the tensile properties and fracture behavior of radiation crosslinked, Vitamin E stabilized UHMWPE was studied as a function of radiation dose. The Rice and Sorensen model, applicable to elastic-plastic materials, was utilized to obtain the initial crack driving force, J1c, steady state J-integral fracture toughness, Jss and the Tearing modulus. Tensile tests showed the dependence of tensile properties on radiation dose. Jss of non-crosslinked UHMWPE was higher than for crosslinked UHMWPE׳s but there was no dose dependent change in Jss whereas there was almost no change in J1c over the entire dose range. Finally, a monotonic decrease in Tearing modulus was observed with radiation dose.

  14. Characterization of Spatial Variability of Hydrogeologic Properties for Unsaturated Flow in the Fractured Rocks at Yucca Mountain, Nevada

    SciTech Connect

    Zhou, Quanlin; Bodvarsson, Gudmundur S.; Liu, Hui-Hai; Oldenburg, Curtis M.

    2002-05-21

    The spatial variability of layer-scale hydrogeologic properties of the unsaturated zone (UZ) at Yucca Mountain, Nevada, is investigated using inverse modeling. The thick UZ is grouped into five hydrostratigraphic units and further into 35 hydrogeologic layers. For each layer, lateral variability is represented by the variations in calibrated values of layer-scale properties at different individual deep boreholes. In the calibration model, matrix and fracture properties are calibrated for the one-dimensional vertical column at each individual borehole using the ITOUGH2 code. The objective function is the summation of the weighted misfits between the ambient unsaturated flow (represented by measured state variables: water saturation, water potential, and pneumatic pressure) and the simulated one in the one-dimensional flow system. The objective function also includes the weighted misfits between the calibrated properties and their prior information. Layer-scale state variables and prior rock properties are obtained from their core-scale measurements. Because of limited data, the lateral variability of three most sensitive properties (matrix permeability, matrix of the van Genuchten characterization, and fracture permeability) is calibrated, while all other properties are fixed at their calibrated layer-averaged values. Considerable lateral variability of hydrogeologic properties is obtained. For example, the lateral variability of is two to three orders of magnitude and that of and is one order of magnitude. The effect of lateral variability on site-scale flow and transport will be investigated in a future study.

  15. Fracture Behavior and Properties of Functionally Graded Fiber-Reinforced Concrete

    SciTech Connect

    Roesler, Jeffery; Bordelon, Amanda; Gaedicke, Cristian; Park, Kyoungsoo; Paulino, Glaucio

    2008-02-15

    In concrete pavements, a single concrete mixture design is selected to resist mechanical loading without attempting to adversely affect the concrete pavement shrinkage, ride quality, or noise attenuation. An alternative approach is to design distinct layers within the concrete pavement surface which have specific functions thus achieving higher performance at a lower cost. The objective of this research was to address the structural benefits of functionally graded concrete materials (FGCM) for rigid pavements by testing and modeling the fracture behavior of different combinations of layered plain and synthetic fiber-reinforced concrete materials. Fracture parameters and the post-peak softening behavior were obtained for each FGCM beam configuration by the three point bending beam test. The peak loads and initial fracture energy between the plain, fiber-reinforced, and FGCM signified similar crack initiation. The total fracture energy indicated improvements in fracture behavior of FGCM relative to full-depth plain concrete. The fracture behavior of FGCM depended on the position of the fiber-reinforced layer relative to the starter notch. The fracture parameters of both fiber-reinforced and plain concrete were embedded into a finite element-based cohesive zone model. The model successfully captured the experimental behavior of the FGCMs and predicted the fracture behavior of proposed FGCM configurations and structures. This integrated approach (testing and modeling) demonstrates the viability of FGCM for designing layered concrete pavements system.

  16. The fracture energy and some mechanical properties of a polyurethane elastomer.

    NASA Technical Reports Server (NTRS)

    Mueller, H. K.; Knauss, W. G.

    1971-01-01

    The energy required to form a unit of new surface in the fracture of a polyurethane elastomer is determined. The rate sensitivity of the material has been reduced by swelling it in toluene. This paper primarily describes the experimental work of measuring the lower limit of the fracture energy. With this value and the creep compliance as a basis, the rate dependence of fracture energy for the unswollen material has been determined. It is thus shown that the dependence of the fracture energy on the rate of crack propagation can be explained by energy dissipation around the tip of the crack. Good agreement between the theoretically and experimentally determined relationships for the rate-sensitive fracture energy is demonstrated.

  17. Fatigue and fracture properties of a super-austenitic stainless steel at 295 K and 4 K

    NASA Astrophysics Data System (ADS)

    McRae, D. M.; Walsh, R. P.; Dalder, E. N. C.; Litherland, S.; Trosen, M.; Kuhlmann, D. J.

    2014-01-01

    The tie plate structure for the ITER Central Solenoid (CS) is required to have high strength and good fatigue and fracture behavior at both room temperature and 4 K. A super-austenitic stainless steel - UNS 20910, commonly referred to by its trade name, Nitronic 50 (N50) - has been chosen for consideration to fulfill this task, due to its good room temperature and cryogenic yield strengths and weldability. Although N50 is often considered for cryogenic applications, little published data exists at 4 K. Here, a full series of tests have been conducted at 295 K and 4 K, and static tensile properties of four forgings of commercially-available N50 are reported along with fatigue life, fatigue crack growth rate (FCGR), and fracture toughness data. This study makes a significant contribution to the cryogenic mechanical properties database of high strength, paramagnetic alloys with potential for superconducting magnet applications.

  18. Subtask 12F4: Effects of neutron irradiation on the impact properties and fracture behavior of vanadium-base alloys

    SciTech Connect

    Chung, H.M.; Loomis, B.A.; Smith, D.L.

    1995-03-01

    Up-to-date results on the effects of neutron irradiation on the impact properties and fracture behavior of V, V-Ti, V-Cr-Ti and V-Ti-Si alloys are presented in this paper, with an emphasis on the behavior of the U.S. reference alloys V-4Cr-4Ti containing 500-1000 wppm Si. Database on impact energy and cluctile-brittle transition temperature (DBTT) has been established from Charpy impact tests of one-third-size specimens irradiated at 420{degrees}C-600{degrees}C up to {approx}50 dpa in lithium environment in fast fission reactors. To supplement the Charpy impact tests fracture behavior was also characterized by quantitative SEM fractography on miniature tensile and disk specimens that were irradiated to similar conditions and fractured at -196{degrees}C to 200{degrees}C by multiple bending. For similar irradiation conditions irradiation-induced increase in DBTT was influenced most significantly by Cr content, indicating that irradiation-induced clustering of Cr atoms takes place in high-Cr (Cr {ge} 7 wt.%) alloys. When combined contents of Cr and Ti were {le}10 wt.%, effects of neutron irradiation on impact properties and fracture behavior were negligible. For example, from the Charpy-impact and multiple-bend tests there was no indication of irradiation-induced embrittlement for V-5Ti, V-3Ti-1Si and the U.S. reference alloy V-4Cr-4Ti after irradiation to {approx}34 dpa at 420{degrees}C to 600{degrees}C, and only ductile fracture was observed for temperatures as low as -196{degrees}C. 14 refs., 8 figs., 1 tab.

  19. Impact of reservoir properties and fractures on gas production, antrim shale, Michigan Basin. Topical report, January 1994

    SciTech Connect

    Caramanica, F.P.; Lorenzen, J.

    1994-01-01

    Eleven wells in Olsego, Ogemaw, and Sanilac Counties, Michigan were analyzed by use of the Antrim Shale specific log analysis model, and showed average porosities in each of three Antrim Shale Units (Lachine, Paxton, Norwood Shales) were constant for each unit in the three counties. The Norwood has the highest average porosity and the Paxton has the lowest. The Norwood Shale has the highest bulk volume hydrocarbons (BVH), whereas those values in the Lachine and Paxton are lower. The high BVH values for the Ogemaw County wells were not reflected in gas production rates, and commercial rates of gas production are not tied to the reservoir properties of: porosity, volume hydrocarbons, water saturation, formation resistivity, kerogen volume, and bulk volume of water. Enhanced formation image analysis techniques showed that the abundance of open and partially open fractures, as well as fracture intersections in the Lachine and Norwood Shales, are controlling factors for gas production. Fractures were mapped with respect to the borehole in 12 wells in the three counties. A fracture factor Z(sub f) was plotted against average gas production rates (Q) for eight Olsego County wells and one Ogemaw County well, and a relationship between the two may be established.

  20. Influence of injection mode on transport properties in kilometer-scale three-dimensional discrete fracture networks

    SciTech Connect

    Hyman, Jeffrey De'Haven; Painter, S. L.; Viswanathan, H.; Makedonska, N.; Karra, S.

    2015-09-12

    We investigate how the choice of injection mode impacts transport properties in kilometer-scale three-dimensional discrete fracture networks (DFN). The choice of injection mode, resident and flux-weighted, is designed to mimic different physical phenomena. It has been hypothesized that solute plumes injected under resident conditions evolve to behave similarly to solutes injected under flux-weighted conditions. Previously, computational limitations have prohibited the large-scale simulations required to investigate this hypothesis. We investigate this hypothesis by using a high-performance DFN suite, dfnWorks, to simulate flow in kilometer-scale three-dimensional DFNs based on fractured granite at the Forsmark site in Sweden, and adopt a Lagrangian approach to simulate transport therein. Results show that after traveling through a pre-equilibrium region, both injection methods exhibit linear scaling of the first moment of travel time and power law scaling of the breakthrough curve with similar exponents, slightly larger than 2. Lastly, the physical mechanisms behind this evolution appear to be the combination of in-network channeling of mass into larger fractures, which offer reduced resistance to flow, and in-fracture channeling, which results from the topology of the DFN.

  1. Influence of injection mode on transport properties in kilometer-scale three-dimensional discrete fracture networks

    DOE PAGES

    Hyman, Jeffrey De'Haven; Painter, S. L.; Viswanathan, H.; Makedonska, N.; Karra, S.

    2015-09-12

    We investigate how the choice of injection mode impacts transport properties in kilometer-scale three-dimensional discrete fracture networks (DFN). The choice of injection mode, resident and flux-weighted, is designed to mimic different physical phenomena. It has been hypothesized that solute plumes injected under resident conditions evolve to behave similarly to solutes injected under flux-weighted conditions. Previously, computational limitations have prohibited the large-scale simulations required to investigate this hypothesis. We investigate this hypothesis by using a high-performance DFN suite, dfnWorks, to simulate flow in kilometer-scale three-dimensional DFNs based on fractured granite at the Forsmark site in Sweden, and adopt a Lagrangian approachmore » to simulate transport therein. Results show that after traveling through a pre-equilibrium region, both injection methods exhibit linear scaling of the first moment of travel time and power law scaling of the breakthrough curve with similar exponents, slightly larger than 2. Lastly, the physical mechanisms behind this evolution appear to be the combination of in-network channeling of mass into larger fractures, which offer reduced resistance to flow, and in-fracture channeling, which results from the topology of the DFN.« less

  2. The Impacts of Rock Composition and Properties on the Ability to Stimulate Production of Ultra-Low Permeability Oil and Gas Reservoirs Through Hydraulic Fracturing

    NASA Astrophysics Data System (ADS)

    Zoback, M. D.; Sone, H.; Kohli, A. H.; Heller, R. J.

    2014-12-01

    In this talk, we present the results of several research projects investigating how rock properties, natural fractures and the state of stress affect the success of hydraulic fracturing operations during stimulation of shale gas and tight oil reservoirs. First, through laboratory measurements on samples of the Barnett, Eagle Ford, Haynesville and Horn River shales, we discuss pore structure, adsorption and permeability as well as the importance of clay content on the viscoplastic behavior of shale formations. Second, we present several lines of evidence that indicates that the principal way in which hydraulic fracturing stimulates production from shale gas reservoirs is by inducing slow slip on pre-existing fractures and faults, which are not detected by conventional microseismic monitoring, Finally, we discuss how hydraulic fracturing can be optimized in response to variations of rock properties.

  3. Fracture properties of growth plate cartilage compared to cortical and trabecular bone in ovine femora.

    PubMed

    Tschegg, E K; Celarek, A; Fischerauer, S F; Stanzl-Tschegg, S; Weinberg, A M

    2012-10-01

    Fracture mechanical parameters (notch tensile strength, specific fracture energy/crack resistance and specific crack initiation energy) of epiphyseal plate cartilage, trabecular bone (metaphysis) and cortical bone (diaphysis) were determined on ovine femur specimens. The fracture behaviour before and after crack initiation was recorded in force-displacement diagrams from wedge splitting tests. Crack propagation was stable both during and after the formation of a principal crack. This is the main advantage of the wedge-splitting method by Tschegg in comparison with tensile tests. Microscopy of the epiphyseal plate during fracture showed fibre elongation and tearing in the crack tip region. The results of this study can help to understand the mechanics of epiphyseal plate injuries and the obtained values can be used for computational simulations and models. PMID:23022566

  4. Using microstructure observations to quantify fracture properties and improve reservoir simulations. Final report, September 1998

    SciTech Connect

    Laubach, S.E.; Marrett, R.; Rossen, W.; Olson, J.; Lake, L.; Ortega, O.; Gu, Y.; Reed, R.

    1999-01-01

    The research for this project provides new technology to understand and successfully characterize, predict, and simulate reservoir-scale fractures. Such fractures have worldwide importance because of their influence on successful extraction of resources. The scope of this project includes creation and testing of new methods to measure, interpret, and simulate reservoir fractures that overcome the challenge of inadequate sampling. The key to these methods is the use of microstructures as guides to the attributes of the large fractures that control reservoir behavior. One accomplishment of the project research is a demonstration that these microstructures can be reliably and inexpensively sampled. Specific goals of this project were to: create and test new methods of measuring attributes of reservoir-scale fractures, particularly as fluid conduits, and test the methods on samples from reservoirs; extrapolate structural attributes to the reservoir scale through rigorous mathematical techniques and help build accurate and useful 3-D models of the interwell region; and design new ways to incorporate geological and geophysical information into reservoir simulation and verify the accuracy by comparison with production data. New analytical methods developed in the project are leading to a more realistic characterization of fractured reservoir rocks. Testing diagnostic and predictive approaches was an integral part of the research, and several tests were successfully completed.

  5. Tensile Properties and Fracture Behavior of Different Carbon Nanotube-Grafted Polyacrylonitrile-Based Carbon Fibers

    NASA Astrophysics Data System (ADS)

    Naito, Kimiyoshi

    2014-11-01

    The tensile properties and fracture behavior of different carbon nanotube (CNT)-grafted polyacrylonitrile-based (T1000GB) single carbon fibers were investigated. Grafting of CNTs was achieved via chemical vapor deposition (CVD). When Fe(C5H5)2 (also applied via CVD) was used as the catalyst, the tensile strength and Weibull modulus of the carbon fibers were improved, possibly due to the growth of dense CNT networks on the carbon fibers, which may have led to a reduction in the number of strength-limiting defects. Separately, at lower concentrations of an Fe(NO3)3·9H2O catalyst in ethanol, which was applied via dipping, the tensile strength of CNT-grafted fibers was nearly identical to that of the as-received fibers, although the Weibull modulus was higher. For higher concentrations of the Fe(NO3)3·9H2O catalyst, however, the tensile strength and the Weibull modulus were lower than those for the as-received material. Although the density of the CNT network increased with the concentration of the Fe(NO3)3·9H2O catalyst in the ethanol solution, heating of the ethanolic Fe(NO3)3·9H2O catalyst solution generated nitric acid (HNO3) due to decomposition, which damaged the fiber surfaces, resulting in an increase in the number of flaws and consequently a reduction in the tensile strength. Therefore, the tensile strength and Weibull modulus of CNT-grafted carbon fibers vary due to the combination of these effects and as a function of the catalyst concentration.

  6. Multiwell fracturing experiments. [Nitrogen foam fracture treatment

    SciTech Connect

    Warpinski, N.

    1985-01-01

    The objective of the Multiwell fracturing experiments is to test and develop the technology for the efficient stimulation of tight, lenticular gas sands. This requires basic understanding of: (1) fracture behavior and geometry in this complex lithologic environment, and (2) subsequent production into the created fracture. The intricate interplay of the hydraulic fracture with the lens geometry, the internal reservoir characteristics (fractures, reservoir breaks, etc.), the in situ stresses, and the mechanical defects (fracture, bedding, etc.) need to be defined in order to develop a successful stimulation program. The stimulation phase of the Multiwell Experiment is concerned with: (1) determining important rock/reservoir properties that influence or control fracture geometry and behavior, (2) designing fracture treatments to achieve a desired size and objectives, and (3) conducting post-treatment analyses to evaluate the effectiveness of the treatment. Background statement, project description, results and evaluation of future plans are presented. 5 refs., 2 figs., 2 tabs.

  7. Tensile properties and translaminar fracture toughness of glass fiber reinforced unsaturated polyester resin composites aged in distilled and salt water

    NASA Astrophysics Data System (ADS)

    Sugiman, Gozali, M. Hulaifi; Setyawan, Paryanto Dwi

    2016-03-01

    Glass fiber reinforced polymer has been widely used in chemical industry and transportation due to lightweight and cost effective manufacturing. However due to the ability to absorb water from the environment, the durability issue is of interest for up to days. This paper investigated the water uptake and the effect of absorbed water on the tensile properties and the translaminar fracture toughness of glass fiber reinforced unsaturated polyester composites (GFRP) aged in distilled and salt water up to 30 days at a temperature of 50°C. It has been shown that GFRP absorbed more water in distilled water than in salt water. In distilled water, the tensile strength of GFRP tends to decrease steeply at 7 days and then slightly recovered for further immersion time. In salt water, the tensile strength tends to decrease continually up to 30 days immersion. The translaminar fracture toughness of GFRP aged in both distilled and salt-water shows the similar behavior. The translaminar fracture toughness increases after 7 days immersion and then tends to decrease beyond that immersion time. In the existence of ionics content in salt water, it causes more detrimental effect on the mechanical properties of fiberglass/unsaturated polyester composites compared to that of distilled water.

  8. Flow properties through a single fracture in Neogene-Quaternary siltstone on effective pressure increasing and decreasing processes

    NASA Astrophysics Data System (ADS)

    Uehara, S. I.; Noguchi, M.

    2015-12-01

    To evaluate flow (or seal) properties of mudstone layers, it is essential to reveal stress conditions at which fractures in mudstone can act as effective flow channels. Dependencies of an effective pressure Pe on a fracture permeability should be examined, because Pe conditions of mudstone layers may change in some cases such as tectonic subsidence and uplifting, or CO2 injection at geological storage processes. The purpose of this study is to reveal how a fracture permeability in mudstone changes at Pe increasing and decreasing processes, and how the features depend on yield stress condition of the rock. This study conducted water permeability tests with Neogene-Quaternary siltstones from the Kazusa Group, Japan; siltstones from the Ohara Formation (OHR3) and the Kiwada Formation (KWD2), of which the yield stress conditions are different from each other. A tensile fracture was artificially made in these cylinder rock specimens, and permeability was measured under several Pe compression-and-decompression cycles with increasing the maximum Pe (2-21 MPa). All results had two characteristic Pe cycles; a cycle at which differences in permeability between process of compression and decompression become clear (a cycle Y), and a cycle at which the permeability becomes almost the same as the intact rock permeability (a cycle C). The maximum Pe of the cycles C is 5-9 MPa for OHR3 and 17-21 MPa for KWD2, and the maximum Pe of the cycles Y is 5 MPa for OHR3 and 3-9 MPa for KWD2. The maximum Pe conditions for the cycles C almost equal the yield conditions of the intact rocks obtained by isotropic compressional test. While, the cycles Y tend to appear lower pressure conditions than the yield conditions of the intact rocks, which may be because stress at real contact areas is larger than Pe: that is, conditions for fracture closure depend on the yield condition of rock, while conditions for initiation of fracture surface yielding also depend on conditions of fracture occlusion.

  9. Tritium and decay helium effects on the fracture toughness properties of types 316L, 304L and 21Cr-6Ni-9Mn stainless steels

    SciTech Connect

    Morgan, M.J.; Tosten, M.H

    1994-10-01

    J-integral fracture mechanics techniques and electron microscopy observations were used to investigate the effects of tritium and its radioactive decay product, {sup 3}He, on Types 316L, 304L and 21Cr-6Ni-9Mn stainless steels. Tritium-exposed-and-aged steels had lower fracture-toughness values and shallower sloped crack-growth-resistance curves than unexposed steels. Both fracture-toughness parameters decreased with increasing concentrations of {sup 3}He. The fracture-toughness reductions were accompanied by a change in fracture mode from microvoid-nucleation-and-growth processes in control samples to grain-and-twin-boundary fracture in tritium-charged-and-aged samples. Type 316L stainless steel had the highest fracture-toughness values and Type 21Cr-6Ni-9Mn had the lowest. Samples containing {sup 3}He but degassed of tritium had fracture toughness properties that were similar to uncharged samples. The results indicate that helium bubbles enhance the embrittlement effects of hydrogen by affecting the deformation properties and by increasing localized hydrogen concentrations through trapping effects.

  10. Determining the shear fracture properties of HIP joints of reduced-activation ferritic/martensitic steel by a torsion test

    NASA Astrophysics Data System (ADS)

    Nozawa, Takashi; Noh, Sanghoon; Tanigawa, Hiroyasu

    2012-08-01

    Hot isostatic pressing (HIP) is a key technology used to fabricate a first wall with cooling channels for the fusion blanket system utilizing a reduced-activation ferritic/martensitic steel. To qualify the HIPped components, small specimen test techniques are beneficial not only to evaluate the thin-wall cooling channels containing the HIP joint but also to use in neutron irradiation studies. This study aims to develop the torsion test method with special emphasis on providing a reasonable and comprehensive method to determine interfacial shear properties of HIP joints during the torsional fracture process. Torsion test results identified that the torsion process shows yield of the base metal followed by non-elastic deformation due to work hardening of the base metal. By considering this work hardening issue, we propose a reasonable and realistic solution to determine the torsional yield shear stress and the ultimate torsional shear strength of the HIPped interface. Finally, a representative torsion fracture process was identified.

  11. Biomechanical properties of a structurally optimized carbon-fibre/epoxy intramedullary nail for femoral shaft fracture fixation.

    PubMed

    Samiezadeh, Saeid; Fawaz, Zouheir; Bougherara, Habiba

    2016-03-01

    Intramedullary nails are the golden treatment option for diaphyseal fractures. However, their high stiffness can shield the surrounding bone from the natural physiologic load resulting in subsequent bone loss. Their stiff structure can also delay union by reducing compressive loads at the fracture site, thereby inhibiting secondary bone healing. Composite intramedullary nails have recently been introduced to address these drawbacks. The purpose of this study is to evaluate the mechanical properties of a previously developed composite IM nail made of carbon-fibre/epoxy whose structure was optimized based on fracture healing requirements using the selective stress shielding approach. Following manufacturing, the cross-section of the composite nail was examined under an optical microscope to find the porosity of the structure. Mechanical properties of the proposed composite intramedullary nail were determined using standard tension, compression, bending, and torsion tests. The failed specimens were then examined to obtain the modes of failure. The material showed high strength in tension (403.9±7.8MPa), compression (316.9±10.9MPa), bending (405.3±8.1MPa), and torsion (328.5±7.3MPa). Comparing the flexural modulus (41.1±0.9GPa) with the compressive modulus (10.0±0.2GPa) yielded that the material was significantly more flexible in compression than in bending. This customized flexibility along with the high torsional stiffness of the nail (70.7±2.0Nm(2)) has made it ideal as a fracture fixation device since this unique structure can stabilize the fracture while allowing for compression of fracture ends. Negligible moisture absorption (~0.5%) and low porosity of the laminate structure (< 3%) are other advantages of the proposed structure. The findings suggested that the carbon-fibre/epoxy intramedullary nail is flexible axially while being relatively rigid in bending and torsion and is strong enough in all types of physiologic loading, making it a potential

  12. Biomechanical properties of a structurally optimized carbon-fibre/epoxy intramedullary nail for femoral shaft fracture fixation.

    PubMed

    Samiezadeh, Saeid; Fawaz, Zouheir; Bougherara, Habiba

    2016-03-01

    Intramedullary nails are the golden treatment option for diaphyseal fractures. However, their high stiffness can shield the surrounding bone from the natural physiologic load resulting in subsequent bone loss. Their stiff structure can also delay union by reducing compressive loads at the fracture site, thereby inhibiting secondary bone healing. Composite intramedullary nails have recently been introduced to address these drawbacks. The purpose of this study is to evaluate the mechanical properties of a previously developed composite IM nail made of carbon-fibre/epoxy whose structure was optimized based on fracture healing requirements using the selective stress shielding approach. Following manufacturing, the cross-section of the composite nail was examined under an optical microscope to find the porosity of the structure. Mechanical properties of the proposed composite intramedullary nail were determined using standard tension, compression, bending, and torsion tests. The failed specimens were then examined to obtain the modes of failure. The material showed high strength in tension (403.9±7.8MPa), compression (316.9±10.9MPa), bending (405.3±8.1MPa), and torsion (328.5±7.3MPa). Comparing the flexural modulus (41.1±0.9GPa) with the compressive modulus (10.0±0.2GPa) yielded that the material was significantly more flexible in compression than in bending. This customized flexibility along with the high torsional stiffness of the nail (70.7±2.0Nm(2)) has made it ideal as a fracture fixation device since this unique structure can stabilize the fracture while allowing for compression of fracture ends. Negligible moisture absorption (~0.5%) and low porosity of the laminate structure (< 3%) are other advantages of the proposed structure. The findings suggested that the carbon-fibre/epoxy intramedullary nail is flexible axially while being relatively rigid in bending and torsion and is strong enough in all types of physiologic loading, making it a potential

  13. Geophysical assessment of the hydraulic property of the fracture systems around Lake Nasser-Egypt: In sight of polarimetric borehole radar

    NASA Astrophysics Data System (ADS)

    Mansour, Khamis; Basheer, Alhussein A.; Rabeh, Taha; Khalil, Ahmed; Eldin, A. A. Essam; Sato, Motoyuki

    2014-06-01

    Hydraulic property of the subsurface structures is a complicated mission. In this work, the polarimetric analysis for the measured dataset applied by the polarimetric borehole radar system in order to delineate the characteristics of subsurface fractures. Two different locations in USA and Egypt were selected to perform our investigation. The first polarimetric dataset has been acquired at Mirror Lake, USA which is well known as a standard site for testing the hydraulic properties of subsurface fractures (Sato et al., 1999). The results show the presence of nine fracture zones in one borehole FSE-1. The hydraulic properties were detected and the subsurface fractures were differentiated into four categories fracture zones after deriving the radar polarimetric analysis of alpha, entropy and anisotropy parameters at 30 MHz frequency. The fracture zones at 24.75, 47.8 and 55.2 m depths have the highest hydraulic transmissivity while the fracture zones at 28.5, 36.15 m have the lowest hydraulic transmissivity. These results show a good consistency with the hydraulic permeability tracer test and the structures exist in the area. Similarly, we used the same technique to characterize the subsurface fracture systems detected by geoelectric and geomagnetic methods around Lake Nasser in Egypt using the previous results of Mirror Lake as a key guide. The results show a great correlation with detected structures prevailed in the sedimentary and basement rocks. These results illustrate an ideal explanation for the prevailed subsurface structures and the recharging of the main Nubian sandstone aquifer from Lake Nasser. Also, these results also show that the northeast fracture zone trends are most probably having the highest hydraulic transmissivity whereas the northwest fracture zones have the lowest one. The integration of surface geophysical measurements with the polarimetric borehole radar and the polarimetric analysis of its datasets introduce better understanding of the

  14. Tissue level microstructure and mechanical properties of the femoral head in the proximal femur of fracture patients

    NASA Astrophysics Data System (ADS)

    Lü, Linwei; Meng, Guangwei; Gong, He; Zhu, Dong; Gao, Jiazi; Fan, Yubo

    2015-04-01

    This study aims to investigate the regional variations of trabecular morphological parameters and mechanical parameters of the femoral head, as well as to determine the relationship between trabecular morphological and mechanical parameters. Seven femoral heads from patients with fractured proximal femur were scanned using a micro-CT system. Each femoral head was divided into 12 sub-regions according to the trabecular orientation. One trabecular cubic model was reconstructed from each sub-region. A total of 81 trabecular models were reconstructed, except three destroyed sub-regions from two femoral heads during the surgery. Trabecular morphological parameters, i.e. trabecular separation (Tb.Sp), trabecular thickness (Tb.Th), specific bone surface (BS/BV), bone volume fraction (BV/TV), structural model index (SMI), and degree of anisotropy (DA) were measured. Micro-finite element analyses were performed for each cube to obtain the apparent Young's modulus and tissue level von Mises stress distribution under 1 % compressive strain along three orthogonal directions, respectively. Results revealed significant regional variations in the morphological parameters (). Young's moduli along the trabecular orientation were significantly higher than those along the other two directions. In general, trabecular mechanical properties in the medial region were lower than those in the lateral region. Trabecular mechanical parameters along the trabecular orientation were significantly correlated with BS/BV, BV/TV, Tb.Th, and DA. In this study, regional variations of microstructural features and mechanical properties in the femoral head of patients with proximal femur fracture were thoroughly investigated at the tissue level. The results of this study will help to elucidate the mechanism of femoral head fracture for reducing fracture risk and developing treatment strategies for the elderly.

  15. Influence of implant properties and local delivery systems on the outcome in operative fracture care.

    PubMed

    Metsemakers, W-J; Moriarty, T F; Nijs, S; Pape, H C; Richards, R G

    2016-03-01

    Fracture fixation devices are implanted into a growing number of patients each year. This may be attributed to an increase in the popularity of operative fracture care and the development of ever more sophisticated implants, which may be used in even the most difficult clinical cases. Furthermore, as the general population ages, fragility fractures become more frequent. With the increase in number of surgical interventions, the absolute number of complications of these surgical treatments will inevitably rise. Implant-related infection and compromised fracture healing remain the most challenging and prevalent complications in operative fracture care. Any strategy that can help to reduce these complications will not only lead to a faster and more complete resumption of activities, but will also help to reduce the socio-economic impact. In this review we describe the influence of implant design and material choice on complication rates in trauma patients. Furthermore, we discuss the importance of local delivery systems, such as implant coatings and bone cement, and how these systems may have an impact on the prevalence, prevention and treatment outcome of these complications. PMID:26847958

  16. Fracture properties of atomic layer deposited aluminum oxide free-standing membranes

    SciTech Connect

    Berdova, Maria Rontu, Ville; Franssila, Sami; Ylivaara, Oili M. E.; Puurunen, Riikka L.; Törmä, Pekka T.

    2015-01-01

    The fracture strength of Al{sub 2}O{sub 3} membranes deposited by atomic layer deposition at 110, 150, 200, and 300 °C was investigated. The fracture strength was found to be in the range of 2.25–3.00 GPa using Weibull statistics and nearly constant as a function of deposition temperature. This strength is superior to common microelectromechanical systems materials such as diamondlike carbon, SiO{sub 2}, or SiC. As-deposited membranes sustained high cycling pressure loads >10 bar/s without fracture. Films featured, however, significant reduction in the resistance to failure after annealing (800 °C) or high humidity (95%, 60 °C) treatments.

  17. Mechanical Properties and Fracture Surfaces of Thixoformed HP9/4/30 Steel

    SciTech Connect

    Omar, M. Z.; Jaharah, A. G.; Atkinson, H. V.; Kapranos, P.

    2007-04-07

    Most work in semi-solid metal processing has been focused on relatively low-melting temperature materials such as aluminium, magnesium, tin, lead and their composites. Because of the high melting temperatures and related measurement difficulties, there is relatively small amount of experimental data available on the thixoforming of high temperature materials such as steels. This paper discusses the relationships between tensile tests data and the fracture surfaces of HP9/4/30 steel samples, in as-received and as-thixoformed conditions. Some of the as-thixoformed samples were subjected to commercial heat treatments before the tests were carried out. The as-received samples showed a typical ductile fracture of 'cup' and 'cone' surface appearance. The thixoformed samples, although showing some significant increase in tensile strength values, failed in a brittle manner, with the fracture surfaces showing a 'cobbled' surface appearance. The application of the commercial heat treatment to the thixoformed samples has significantly improved their ductility.

  18. Dynamic Mechanical Properties and Fracture Surface Morphologies of Core-Shell Rubber (CSR) Toughened Epoxy at Liquid Nitrogen (Ln2) Temperatures

    NASA Technical Reports Server (NTRS)

    Wang, J.; Magee, D.; Schneider, J. A.

    2009-01-01

    The dynamic mechanical properties and fracture surface morphologies were evaluated for a commercial epoxy resin toughened with two types of core-shell rubber (CSR) toughening agents (Kane Ace(Registered TradeMark) MX130 and MX960). The impact resistance (R) was evaluated by the resulting breaking energy measured in Charpy impact tests conducted on an instrumented drop tower. The resulting fracture surface morphologies were examined using Scanning Electron Microscopy (SEM). Fractographic observations of the CSR toughened epoxy tested at ambient temperature, showed a fracture as characterized by slender dendrite textures with large voids. The increasing number of dendrites and decreasing size of scale-like texture with more CSR particles corresponded with increased R. As the temperature decreased to Liquid Nitrogen (LN 2), the fracture surfaces showed a fracture characterized by a rough, torn texture containing many river markings and deep furrows.

  19. The effects of tritium and decay helium on the fracture toughness properties of stainless steels

    SciTech Connect

    Morgan, M.J.

    1991-01-01

    J-integral fracture mechanics techniques and scanning electron microscopy observations were used to investigate the effects of tritium and its decay product, helium-3, on Types 304L, 316L, 21-6-9, A286, and JBK-75 (Modified A286) stainless steels. Tritium-exposed samples of each steel had lower fracture toughness values and less resistance to stable crack growth than control samples. Type 316L stainless steel was more resistant to the embrittling effects of tritium and decay helium than the other steels.

  20. The effects of tritium and decay helium on the fracture toughness properties of stainless steels

    SciTech Connect

    Morgan, M.J.

    1991-12-31

    J-integral fracture mechanics techniques and scanning electron microscopy observations were used to investigate the effects of tritium and its decay product, helium-3, on Types 304L, 316L, 21-6-9, A286, and JBK-75 (Modified A286) stainless steels. Tritium-exposed samples of each steel had lower fracture toughness values and less resistance to stable crack growth than control samples. Type 316L stainless steel was more resistant to the embrittling effects of tritium and decay helium than the other steels.

  1. Double torsion testing and finite element analysis for determining the electric fracture properties of piezoelectric ceramics

    SciTech Connect

    Shindo, Yasuhide; Narita, Fumio; Mikami, Masaru

    2005-06-01

    This paper presents the results of an experimental and numerical investigation in electric fracture behavior of composite [Pb(Zr,Ti)O{sub 3}] double torsion (DT) specimens. DT tests were conducted on a commercial piezoelectric ceramic bonded between two metals. Fracture loads under different electric fields were obtained from the experiment. Nonlinear three-dimensional finite element analysis was also employed to calculate the energy release rate for DT specimens based on the exact (permeable) and approximate (impermeable) crack models. The effects of applied electric field and domain switching on the energy release rate are discussed, and the model predictions are compared with the results of the experiments.

  2. Characterization and modeling of the stress and pore-fluid dependent acoustic properties of fractured porous rocks

    NASA Astrophysics Data System (ADS)

    Almrabat, Abdulhadi M.

    The thesis presents the results of a study of the characterization and modeling of the stress and pore-fluid dependent acoustic properties of fractured porous rocks. A new laboratory High Pressure and High Temperature (HPHT) triaxial testing system was developed to characterize the seismic properties of sandstone under different levels of effective stress confinement and changes in pore-fluid composition. An intact and fractured of Berea sandstones core samples were used in the experimental studies. The laboratory test results were used to develop analytical models for stress-level and pore-fluid dependent seismic velocity of sandstones. Models for stress-dependent P and S-wave seismic velocities of sandstone were then developed based on the assumption that stress-dependencies come from the nonlinear elastic response of micro-fractures contained in the sample under normal and shear loading. The contact shear stiffness was assumed to increase linearly with the normal stress across a micro-fracture, while the contact normal stiffness was assumed to vary as a power law with the micro-fracture normal stress. Both nonlinear fracture normal and shear contact models were validated by experimental data available in the literature. To test the dependency of seismic velocity of sandstone on changes in pore-fluid composition, another series of tests were conducted where P and S-wave velocities were monitored during injection of supercritical CO 2 in samples of Berea sandstone initially saturated with saline water and under constant confining stress. Changes in seismic wave velocity were measured at different levels of supercritical CO2 saturation as the initial saline water as pore-fluid was displaced by supercritical CO 2. It was found that the P- iv wave velocity significantly decreased while the S-wave velocity remained almost constant as the sample supercritical CO2 saturation increased. The dependency of the seismic velocity on changes on pore fluid composition during

  3. Measurement of adhesive joint fracture properties as a function of environmental degradation

    SciTech Connect

    Wylde, J.W.; Spelt, J.K.

    1996-12-31

    The increased use of structural adhesives in industry would benefit from a comprehensive failure load prediction tool to ensure competent design. The work of Fernlund and Spelt has proposed a fracture envelope that relates the critical strain energy release rate to the nominal phase angle of loading. The work of Plasinus and Spelt extended this work to incorporate the viscoelastic effect of the adhesive. The objective of the present research is to incorporate the effects of temperature and water absorption into the prediction of adhesive joint fracture. Ample evidence exists to demonstrate the notion that absorbed water has an effect predominantly detrimental, on the strength of an adhesive joint. Past work was concentrated on degrading typical, in service joints such as the Single Lap Shear (SLS) joint or the Cracked Lap Shear (CLS) joint. Since water is absorbed through the exposed edges, typically small in area compared to the volume of the joint, degradation times are usually long and the water concentration varies both with time and spatially throughout the joint. In this research, a novel method of degrading adhesive fracture specimens to a spatially constant degradation condition is being used to incorporate environmental effects into the fracture load prediction tool of Spelt et al.

  4. Effect of an Aging Heat Treatment on the 4 K Fracture and Fatigue Properties of 316LN and Haynes 242

    SciTech Connect

    Walsh, R. P.; Toplosky, V. J.; Han, K.; Miller, J. R.

    2006-03-31

    Since the introduction of the cable-in-conduit conductor (CICC) concept, a variety of alloys have been proposed for fabricating the jacket. The jacket provides primary containment of the liquid helium coolant and is typically also the primary structural component for the magnet coils. These functions create requirements for strength, toughness, fatigue crack resistance, and fabricability. When the CICC uses Nb3Sn superconductor, the conduit alloy must retain good mechanical properties after exposure to the superconductor's reaction heat treatment. Here we present data from cryogenic fracture toughness and fatigue crack growth rate tests on 316LN and a Cr-Mo-Ni base super-alloy (Haynes 242) at 4 K before and after the exposure to the heat treatment. These alloys are presently being considered as candidates for use in the next-generation series connected hybrid magnet for the NHMFL. Both of the alloys are found to have adequate fatigue and fracture properties for the CICC application while the superalloy has distinctly better elastic properties of modulus and thermal expansion.

  5. Effect of an Aging Heat Treatment on the 4 K Fracture and Fatigue Properties of 316LN and Haynes 242

    NASA Astrophysics Data System (ADS)

    Walsh, R. P.; Toplosky, V. J.; Han, K.; Miller, J. R.

    2006-03-01

    Since the introduction of the cable-in-conduit conductor (CICC) concept, a variety of alloys have been proposed for fabricating the jacket. The jacket provides primary containment of the liquid helium coolant and is typically also the primary structural component for the magnet coils. These functions create requirements for strength, toughness, fatigue crack resistance, and fabricability. When the CICC uses Nb3Sn superconductor, the conduit alloy must retain good mechanical properties after exposure to the superconductor's reaction heat treatment. Here we present data from cryogenic fracture toughness and fatigue crack growth rate tests on 316LN and a Cr-Mo-Ni base super-alloy (Haynes 242) at 4 K before and after the exposure to the heat treatment. These alloys are presently being considered as candidates for use in the next-generation series connected hybrid magnet for the NHMFL. Both of the alloys are found to have adequate fatigue and fracture properties for the CICC application while the superalloy has distinctly better elastic properties of modulus and thermal expansion.

  6. Fundamental properties of fracture and seismicity in a non extensive statistical physics framework.

    NASA Astrophysics Data System (ADS)

    Vallianatos, Filippos

    2010-05-01

    A fundamental challenge in many scientific disciplines concerns upscaling, that is, of determining the regularities and laws of evolution at some large scale, from those known at a lower scale. Earthquake physics is no exception, with the challenge of understanding the transition from the laboratory scale to the scale of fault networks and large earthquakes. In this context, statistical physics has a remarkably successful work record in addressing the upscaling problem in physics. It is natural then to consider that the physics of many earthquakes has to be studied with a different approach than the physics of one earthquake and in this sense we can consider the use of statistical physics not only appropriate but necessary to understand the collective properties of earthquakes [see Corral 2004, 2005a,b,c;]. A significant attempt is given in a series of works [Main 1996; Rundle et al., 1997; Main et al., 2000; Main and Al-Kindy, 2002; Rundle et al., 2003; Vallianatos and Triantis, 2008a] that uses classical statistical physics to describe seismicity. Then a natural question arises. What type of statistical physics is appropriate to commonly describe effects from fracture level to seismicity scale?? The application of non extensive statistical physics offers a consistent theoretical framework, based on a generalization of entropy, to analyze the behavior of natural systems with fractal or multi-fractal distribution of their elements. Such natural systems where long - range interactions or intermittency are important, lead to power law behavior. We note that this is consistent with a classical thermodynamic approach to natural systems that rapidly attain equilibrium, leading to exponential-law behavior. In the frame of non extensive statistical physics approach, the probability function p(X) is calculated using the maximum entropy formulation of Tsallis entropy which involves the introduction of at least two constraints (Tsallis et al., 1998). The first one is the

  7. Effects of Oxides on Tensile and Charpy Impact Properties and Fracture Toughness in Heat Affected Zones of Oxide-Containing API X80 Linepipe Steels

    NASA Astrophysics Data System (ADS)

    Sung, Hyo Kyung; Sohn, Seok Su; Shin, Sang Yong; Oh, Kyung Shik; Lee, Sunghak

    2014-06-01

    This study is concerned with effects of complex oxides on acicular ferrite (AF) formation, tensile and Charpy impact properties, and fracture toughness in heat affected zones (HAZs) of oxide-containing API X80 linepipe steels. Three steels were fabricated by adding Mg and O2 to form oxides, and various HAZ microstructures were obtained by conducting HAZ simulation tests under different heat inputs. The no. of oxides increased with increasing amount of Mg and O2, while the volume fraction of AF present in the steel HAZs increased with increasing the no. of oxides. The strengths of the HAZ specimens were generally higher than those of the base metals because of the formation of hard microstructures of bainitic ferrite and granular bainite. When the total Charpy absorbed energy was divided into the fracture initiation and propagation energies, the fracture initiation energy was maintained constant at about 75 J at room temperature, irrespective of volume fraction of AF. The fracture propagation energy rapidly increased from 75 to 150 J and saturated when the volume fraction of AF exceeded 30 pct. At 253 K (-20 °C), the total absorbed energy increased with increasing volume fraction of AF, as the cleavage fracture was changed to the ductile fracture when the volume fraction of AF exceeded 45 pct. Thus, 45 vol pct of AF at least was needed to improve the Charpy impact energy, which could be achieved by forming a no. of oxides. The fracture toughness increased with increasing the no. of oxides because of the increased volume fraction of AF formed around oxides. The fracture toughness did not show a visible correlation with the Charpy absorbed energy at room temperature, because toughness properties obtained from these two toughness testing methods had different significations in view of fracture mechanics.

  8. Fractures in anisotropic media

    NASA Astrophysics Data System (ADS)

    Shao, Siyi

    Rocks may be composed of layers and contain fracture sets that cause the hydraulic, mechanical and seismic properties of a rock to be anisotropic. Coexisting fractures and layers in rock give rise to competing mechanisms of anisotropy. For example: (1) at low fracture stiffness, apparent shear-wave anisotropy induced by matrix layering can be masked or enhanced by the presence of a fracture, depending on the fracture orientation with respect to layering, and (2) compressional-wave guided modes generated by parallel fractures can also mask the presence of matrix layerings for particular fracture orientations and fracture specific stiffness. This report focuses on two anisotropic sources that are widely encountered in rock engineering: fractures (mechanical discontinuity) and matrix layering (impedance discontinuity), by investigating: (1) matrix property characterization, i.e., to determine elastic constants in anisotropic solids, (2) interface wave behavior in single-fractured anisotropic media, (3) compressional wave guided modes in parallel-fractured anisotropic media (single fracture orientation) and (4) the elastic response of orthogonal fracture networks. Elastic constants of a medium are required to understand and quantify wave propagation in anisotropic media but are affected by fractures and matrix properties. Experimental observations and analytical analysis demonstrate that behaviors of both fracture interface waves and compressional-wave guided modes for fractures in anisotropic media, are affected by fracture specific stiffness (controlled by external stresses), signal frequency and relative orientation between layerings in the matrix and fractures. A fractured layered medium exhibits: (1) fracture-dominated anisotropy when the fractures are weakly coupled; (2) isotropic behavior when fractures delay waves that are usually fast in a layered medium; and (3) matrix-dominated anisotropy when the fractures are closed and no longer delay the signal. The

  9. Fracture Toughness, Mechanical Property, And Chemical Characterization Of A Critical Modification To The NASA SLS Solid Booster Internal Material System

    NASA Technical Reports Server (NTRS)

    Pancoast, Justin; Garrett, William; Moe, Gulia

    2015-01-01

    A modified propellant-liner-insulation (PLI) bondline in the Space Launch System (SLS) solid rocket booster required characterization for flight certification. The chemical changes to the PLI bondline and the required additional processing have been correlated to mechanical responses of the materials across the bondline. Mechanical properties testing and analyses included fracture toughness, tensile, and shear tests. Chemical properties testing and analyses included Fourier transform infrared (FTIR) spectroscopy, cross-link density, high-performance liquid chromatography (HPLC), gas chromatography (GC), gel permeation chromatography (GPC), and wave dispersion X-ray fluorescence (WDXRF). The testing identified the presence of the expected new materials and found the functional bondline performance of the new PLI system was not significantly changed from the old system.

  10. Characterization of Gas Transport Properties of Fractured Rocks By Borehole and Chamber Tests.

    NASA Astrophysics Data System (ADS)

    Shimo, M.; Shimaya, S.; Maejima, T.

    2014-12-01

    Gas transport characteristics of fractured rocks is a great concern to variety of engineering applications such as underground storage of LPG, nuclear waste disposal, CCS and gas flooding in the oil field. Besides absolute permeability, relative permeability and capillary pressure as a function of water saturation have direct influences to the results of two phase flow simulation. However, number of the reported gas flow tests for fractured rocks are limited, therefore, the applicability of the conventional two-phase flow functions used for porous media, such as Mualem-van Genuchten model, to prediction of the gas transport in the fractured rock mass are not well understood. The authors conducted the two types of in-situ tests, with different scales, a borehole gas-injection test and a chamber gas-injection test in fractured granitic rock. These tests were conducted in the Cretaceous granitic rocks at the Namikata underground LPG storage cavern construction site in Ehime Prefecture in Japan, preceding to the cavern scale gas-tightness test. A borehole injection test was conducted using vertical and sub-vertical boreholes drilled from the water injection tunnel nearly at the depth of the top of the cavern, EL-150m. A new type downhole gas injection equipment that is capable to create a small 'cavern' within a borehole was developed. After performing a series of preliminary tests to investigate the hydraulic conductivity and gas-tightness, i.e. threshold pressure, gas injection tests were conducted under different gas pressure. Fig.1 shows an example of the test results From a chamber test using a air pressurizing chamber with volume of approximately166m3, the gas-tightness was confirmed within the uncertainty of 22Pa under the storage pressure of 0.7MPa, however, significant air leakage occurred possibly through an open fracture intersecting the chamber just after cavern pressure exceeds the initial hydrostatic pressure at the ceiling level of the chamber. Anomalies

  11. Effect of chemical environment and rock composition on fracture mechanics properties of reservoir lithologies in context of CO2 sequestration

    NASA Astrophysics Data System (ADS)

    Major, J. R.; Eichhubl, P.; Callahan, O. A.

    2015-12-01

    The coupled chemical and mechanical response of reservoir and seal rocks to injection of CO2 have major implications on the short and long term security of sequestered carbon. Many current numerical models evaluating behavior of reservoirs and seals during and after CO2 injection in the subsurface consider chemistry and mechanics separately and use only simple mechanical stability criteria while ignoring time-dependent failure parameters. CO2 injection irreversibly alters the subsurface chemical environment which can then affect geomechanical properties on a range of time scales by altering rock mineralogy and cements through dissolution, remobilization, and precipitation. It has also been documented that geomechanical parameters such as fracture toughness (KIC) and subcritical index (SCI) are sensitive to chemical environment. Double torsion fracture mechanics testing of reservoir lithologies under controlled environmental conditions relevant to CO2 sequestration show that chemical environment can measurably affect KIC and SCI. This coupled chemical-mechanical behavior is also influenced by rock composition, grains, amount and types of cement, and fabric. Fracture mechanics testing of the Aztec Sandstone, a largely silica-cemented, subarkose sandstone demonstrate it is less sensitive to chemical environment than Entrada Sandstone, a silty, clay-rich sandstone. The presence of de-ionized water lowers KIC by approximately 20% and SCI 30% in the Aztec Sandstone relative to tests performed in air, whereas the Entrada Sandstone shows reductions on the order of 70% and 90%, respectively. These results indicate that rock composition influences the chemical-mechanical response to deformation, and that the relative chemical reactivity of target reservoirs should be recognized in context of CO2 sequestration. In general, inert grains and cements such as quartz will be less sensitive to the changing subsurface environment than carbonates and clays.

  12. Inhibition of GSK-3β rescues the impairments in bone formation and mechanical properties associated with fracture healing in osteoblast selective connexin 43 deficient mice.

    PubMed

    Loiselle, Alayna E; Lloyd, Shane A J; Paul, Emmanuel M; Lewis, Gregory S; Donahue, Henry J

    2013-01-01

    Connexin 43 (Cx43) is the most abundant gap junction protein in bone and is required for osteoblastic differentiation and bone homeostasis. During fracture healing, Cx43 is abundantly expressed in osteoblasts and osteocytes, while Cx43 deficiency impairs bone formation and healing. In the present study we selectively deleted Cx43 in the osteoblastic lineage from immature osteoblasts through osteocytes and tested the hypothesis that Cx43 deficiency results in delayed osteoblastic differentiation and impaired restoration of biomechanical properties due to attenuated β-catenin expression relative to wild type littermates. Here we show that Cx43 deficiency results in alterations in the mineralization and remodeling phases of healing. In Cx43 deficient fractures the mineralization phase is marked by delayed expression of osteogenic genes. Additionally, the decrease in the RankL/Opg ratio, osteoclast number and osteoclast size suggest decreased osteoclast bone resorption and remodeling. These changes in healing result in functional deficits as shown by a decrease in ultimate torque at failure. Consistent with these impairments in healing, β-catenin expression is attenuated in Cx43 deficient fractures at 14 and 21 days, while Sclerostin (Sost) expression, a negative regulator of bone formation is increased in Cx43cKO fractures at 21 days, as is GSK-3β, a key component of the β-catenin proteasomal degradation complex. Furthermore, we show that alterations in healing in Cx43 deficient fractures can be rescued by inhibiting GSK-3β activity using Lithium Chloride (LiCl). Treatment of Cx43 deficient mice with LiCl restores both normal bone formation and mechanical properties relative to LiCl treated WT fractures. This study suggests that Cx43 is a potential therapeutic target to enhance fracture healing and identifies a previously unknown role for Cx43 in regulating β-catenin expression and thus bone formation during fracture repair.

  13. Effects of Thermal Aging on Material Properties, Stress Corrosion Cracking, and Fracture Toughness of AISI 316L Weld Metal

    NASA Astrophysics Data System (ADS)

    Lucas, Timothy; Forsström, Antti; Saukkonen, Tapio; Ballinger, Ronald; Hänninen, Hannu

    2016-08-01

    Thermal aging and consequent embrittlement of materials are ongoing issues in cast stainless steels, as well as duplex, and high-Cr ferritic stainless steels. Spinodal decomposition is largely responsible for the well-known "748 K (475 °C) embrittlement" that results in drastic reductions in ductility and toughness in these materials. This process is also operative in welds of either cast or wrought stainless steels where δ-ferrite is present. While the embrittlement can occur after several hundred hours of aging at 748 K (475 °C), the process is also operative at lower temperatures, at the 561 K (288 °C) operating temperature of a boiling water reactor (BWR), for example, where ductility reductions have been observed after several tens of thousands of hours of exposure. An experimental program was carried out in order to understand how spinodal decomposition may affect changes in material properties in Type 316L BWR piping weld metals. The study included material characterization, nanoindentation hardness, double-loop electrochemical potentiokinetic reactivation (DL-EPR), Charpy-V, tensile, SCC crack growth, and in situ fracture toughness testing as a function of δ-ferrite content, aging time, and temperature. SCC crack growth rates of Type 316L stainless steel weld metal under simulated BWR conditions showed an approximate 2 times increase in crack growth rate over that of the unaged as-welded material. In situ fracture toughness measurements indicate that environmental exposure can result in a reduction of toughness by up to 40 pct over the corresponding at-temperature air-tested values. Material characterization results suggest that spinodal decomposition is responsible for the degradation of material properties measured in air, and that degradation of the in situ properties may be a result of hydrogen absorbed during exposure to the high-temperature water environment.

  14. Potential Impacts of Spilled Hydraulic Fracturing Fluid Chemicals on Water Resources: Types, Volumes, and Physical-chemical Properties of Chemicals

    NASA Astrophysics Data System (ADS)

    Knightes, C. D.; Daiss, R.; Williams, L.; Singer, A.

    2015-12-01

    Hydraulic fracturing (HF) fluid chemicals spilled on-site may impact drinking water resources. While chemicals generally make up <2% of the total injected fluid composition by mass, spills may have undiluted concentrations. HF fluids typically consist of a mixture of base fluid, proppant, and additives. Additives, comprised of one or more chemicals, are serve a specific engineering purpose (e.g., friction reducer, scale inhibitor, biocide). As part of the USEPA's Draft Assessment of the Potential Impacts of Hydraulic Fracturing for Oil and Gas on Drinking Water Resources, we investigated the different types, volumes injected, and physical-chemical properties of HF fluid chemicals. The USEPA identified 1,076 chemicals used in HF fluids, based on 10 sources covering chemical use from 2005 to 2013. These chemicals fall into different classes: acids, alcohols, aromatic hydrocarbons, bases, hydrocarbon mixtures, polysaccharides, and surfactants. The physical-chemical properties of these chemicals vary, which affects their movement through the environment if spilled. Properties range from fully miscible to insoluble, from highly hydrophobic to highly hydrophilic. Most of these chemicals are not volatile. HF fluid composition varies from site to site depending on a range of factors. No single chemical or set of chemicals are used at every site. A median of 14 chemicals are used per well, with a range of four to 28 (5th and 95th percentiles). Methanol was the chemical most commonly reported in FracFocus 1.0 (72% of disclosures), and hydrotreated light petroleum distillates and hydrochloric acid were both reported in over half the disclosures. Operators store chemicals on-site, often in multiple containers (typically in 760 to 1,500 L totes). We estimated that the total volume of all chemicals used per well ranges from approximately 10,000 to 110,000 L. The views expressed here are those of the authors and do not necessarily represent the views or policies of the USEPA.

  15. Tensile deformation and fracture properties of a 14YWT nanostructured ferritic alloy

    DOE PAGES

    Alam, M. Ershadul; Pal, Soupitak; Fields, Kirk; Maloy, S. A.; Hoelzer, David T.; Odette, George R.

    2016-08-13

    Here, a new larger heat of a 14YWT nanostructured ferritic alloy (NFA), FCRD NFA-1, was synthesized by ball milling FeO and argon atomized Fe-14Cr-3W-0.4Ti-0.2Y (wt%) powders, followed by hot extrusion, annealing and cross rolling to produce an ≈10 mm-thick plate. NFA-1 contains a bimodal size distribution of pancake-shaped, mostly very fine scale, grains. The as-processed plate also contains a large population of microcracks running parallel to its broad surfaces. The small grains and large concentration of Y–Ti–O nano-oxides (NOs) result in high strength up to 800 °C. The uniform and total elongations range from ≈1–8%, and ≈10–24%, respectively. The strengthmore » decreases more rapidly above ≈400 °C and deformation transitions to largely viscoplastic creep by ≈600 °C. While the local fracture mechanism is generally ductile-dimple microvoid nucleation, growth and coalescence, perhaps the most notable feature of tensile deformation behavior of NFA-1 is the occurrence of periodic delamination, manifested as fissures on the fracture surfaces.« less

  16. Scale dependence of the hydraulic properties of a fractured aquifer estimated using transfer functions

    NASA Astrophysics Data System (ADS)

    Pedretti, D.; Russian, A.; Sanchez-Vila, X.; Dentz, M.

    2016-07-01

    We present an investigation of the scale dependence of hydraulic parameters in fractured media based on the concept of transfer functions (TF). TF methods provide an inexpensive way to perform aquifer parameter estimation, as they relate the fluctuations of an observation time series (hydraulic head fluctuations) to an input function (aquifer recharge) in frequency domain. Fractured media are specially sensitive to this approach as hydraulic parameters are strongly scale-dependent, involving nonstationary statistical distributions. Our study is based on an extensive data set, involving up to 130 measurement points with periodic head measurements that in some cases extend for more than 30 years. For each point, we use a single-porosity and dual-continuum TF formulation to obtain a distribution of transmissivities and storativities in both mobile and immobile domains. Single-porosity TF estimates are compared with data obtained from the interpretation of over 60 hydraulic tests (slug and pumping tests). Results show that the TF is able to estimate the scale dependence of the hydraulic parameters, and it is consistent with the behavior of estimates from traditional hydraulic tests. In addition, the TF approach seems to provide an estimation of the system variance and the extension of the ergodic behavior of the aquifer (estimated in approximately 500 m in the analyzed aquifer). The scale dependence of transmissivity seems to be independent from the adopted formulation (single or dual-continuum), while storativity is more sensitive to the presence of multiple continua.

  17. Water mass properties on their way over the Mid-Atlantic-Ridge through the Faraday Fracture Zone

    NASA Astrophysics Data System (ADS)

    Denker, C.; Kieke, D.; Klein, B.; Klein, H.; Rhein, M.

    2012-04-01

    Over the last decades there have been major changes in the water mass properties and production of Labrador Sea Water (LSW) in the subpolar North Atlantic. A dedicated work package in the framework of the German research project "North Atlantic" examines therefore the variability of deep water formation in the Labrador Sea and connections to transport variations of the North Atlantic Current (NAC), the strength of the subpolar gyre and the propagation of water masses into the East Atlantic. In the focus of this study are the pathways of the NAC over the Mid-Atlantic-Ridge (MAR) and the LSW T/S- properties that are carried over the MAR in the LSW range below the NAC. Since November 2009 three moorings have been collecting data at the western entrance of the Faraday Fracture Zone (FFZ) to monitor water mass variability. FFZ is situated south of the Charlie-Gibbs-Fracture Zone (CGFZ) and is one of the major passages for deep water masses across the MAR into the East Atlantic basin. Moorings have been serviced annually and data from the first two deployments are presented here. The analysis presented here combines in-situ time series from the moorings with satellite and Argo data to identify the pathways of the NAC over the MAR in local velocity and temperature and salinity data. First results show a persistent occurrence of the NAC over the FFZ from mid 2009 until early 2010 based on sea surface height fields, which is reflected in strong convergent velocity signals at the mooring sites. From 2010 onward, a northern NAC branch over the CGFZ is prominent in the altimeter record but the core seem to split again in mid 2010 into a northern and a southern branch. The branching of the NAC is also reflected in the trajectories of Argo floats over the MAR which are locked to the various fracture zones. The T/S - time series from the moored instruments show extreme saline as well as fresh variations of the LSW, which are related to the variability of the current system. Argo

  18. The effect of material properties and tooling design on deformation and fracture during equal channel angular extrusion

    SciTech Connect

    Semiatin, S.L.; Delo, D.P.; Shell, E.B.

    2000-05-11

    The effects of material constitutive behavior, tooling design, and friction conditions on metal flow, stress fields, and the tendency for tensile fracture during equal channel angular extrusion (ECAE) were established using a finite element modeling (FEM) technique. Three different material behaviors, typical of those encountered during cold and hot working, were investigated; these comprised (1) string hardening, (2) rigid, perfectly plastic, and (3) flow softening types of behavior. The tooling geometries consisted of a so-called simple design with no moving channel members and a complex design with a sliding bottom floor. The FEM results indicated that the most uniform flow was obtained during ECAE of a strain-hardening material having a low strain-rate sensitivity in tolling with a sharp inner corner (front leg) radius. The ECAE of materials with other constitutive behaviors or in tooling with a radiused front leg showed some degree of flow nonuniformity, even away from the head and tail of the extrusion. Tooling design and material properties were also predicted to have an important influence on the tensile stresses and hence tensile damage developed during ECAE. The FEM results were validated using visioplasticity and fracture observations for AISI 4340 steel and a near-gamma titanium aluminide alloy.

  19. Processing and properties of ceramic nanocomposites designed for improved fracture toughness

    NASA Astrophysics Data System (ADS)

    Kuntz, Joshua D.

    2005-11-01

    Nanocrystalline-matrix ceramic composites specifically designed for applications requiring improved fracture toughness were investigated. While the models and theory of toughening mechanisms for microcrystalline composites are well developed, the same cannot be said for their nanocrystalline counterparts. The mechanisms of ductile-phase toughening, fiber toughening, transformation toughening, and microcrack toughening have been fully investigated in microcrystalline-matrix ceramics. Both ductile-phase toughening and fiber toughening are theoretically viable as toughening mechanisms in nanocrystalline ceramics. The experimental demonstration of these mechanisms has been investigated through alumina-matrix nanocomposites with second phases of niobium (ductile-phase toughening) and carbon nanotubes (fiber toughening). The difficulty in producing fully consolidated ceramic composites that retain a nanocrystalline structure is the main hurdle to thorough investigations in this area. Thus, much of the research currently in the literature on so-called "nanocomposites" has been on materials with microcrystalline matrices and nanometric second phases. Using novel processing techniques, fully dense composites with nanocrystalline matrices were produced from commercially available starting powders. The consolidation technique, which allowed the retention of the nanocrystalline grain size, was spark plasma sintering (SPS). SPS is a moderate-pressure sintering method based on the theory of plasma momentarily generated in the gaps between powder materials by electrical discharge during DC pulsing. It has been proposed that the on--off DC pulse energizing method could generate (1) spark plasma, (2) spark impact pressure, (3) Joule heating, and (4) an electrical-field diffusion effect. SPS can rapidly consolidate powders to full density through the combined actions of rapid heating, applying pressure, and proposed powder surface cleaning. Al2O3-10 vol.% Nb ductile-phase toughened

  20. Evaluation of Fatigue Crack Growth and Fracture Properties of Cryogenic Model Materials

    NASA Technical Reports Server (NTRS)

    Newman, John A.; Forth, Scott C.; Everett, Richard A., Jr.; Newman, James C., Jr.; Kimmel, William M.

    2002-01-01

    The criteria used to prevent failure of wind-tunnel models and support hardware were revised as part of a project to enhance the capabilities of cryogenic wind tunnel testing at NASA Langley Research Center. Specifically, damage-tolerance fatigue life prediction methods are now required for critical components, and material selection criteria are more general and based on laboratory test data. The suitability of two candidate model alloys (AerMet 100 and C-250 steel) was investigated by obtaining the fatigue crack growth and fracture data required for a damage-tolerance fatigue life analysis. Finally, an example is presented to illustrate the newly implemented damage tolerance analyses required of wind-tunnel model system components.

  1. Anisotropic and heterogeneous mechanical properties of a stratified shale/limestone sequence at Nash Point, South Wales: A case study for hydraulic fracture propagation through a layered medium

    NASA Astrophysics Data System (ADS)

    Forbes Inskip, Nathaniel; Meredith, Philip; Gudmundsson, Agust

    2016-04-01

    While considerable effort has been expended on the study of fracture propagation in rocks in recent years, our understanding of how fractures propagate through layered sedimentary rocks with different mechanical and elastic properties remains poorly constrained. Yet this is a key issue controlling the propagation of both natural and anthropogenic hydraulic fractures in layered sequences. Here we report measurements of the contrasting mechanical and elastic properties of the Lower Lias at Nash Point, South Wales, which comprises an interbedded sequence of shale and limestone layers, and how those properties may influence fracture propagation. Elastic properties of both materials have been characterised via ultrasonic wave velocity measurements as a function of azimuth on samples cored both normal and parallel to bedding. The shale is highly anisotropic, with P-wave velocities varying from 2231 to 3890 m s-1, giving an anisotropy of ~55%. By contrast, the limestone is essentially isotropic, with a mean P-wave velocity of 5828 m s-1 and an anisotropy of ~2%. The dynamic Young's modulus of the shale, calculated from P- and S-wave velocity data, is also anisotropic with a value of 36 GPa parallel to bedding and 12 GPa normal to bedding. The modulus of the limestone is again isotropic with a value of 80 GPa. It follows that for a vertical fracture propagating (i.e. normal to bedding) the modulus contrast is 6.6. This is important because the contrast in elastic properties is a key factor in controlling whether fractures arrest, deflect, or propagate across interfaces between layers in a sequence. There are three principal mechanisms by which a fracture may deflect across or along an interface, namely: Cook-Gordon debonding, stress barrier, and elastic mismatch. Preliminary numerical modelling results (using a Finite Element Modelling software) of induced fractures at Nash Point suggest that all three are important. The results demonstrate a rotation of the maximum

  2. An ORMOSIL-containing orthodontic acrylic resin with concomitant improvements in antimicrobial and fracture toughness properties.

    PubMed

    Gong, Shi-qiang; Epasinghe, Jeevani; Rueggeberg, Frederick A; Niu, Li-na; Mettenberg, Donald; Yiu, Cynthia K Y; Blizzard, John D; Wu, Christine D; Mao, Jing; Drisko, Connie L; Pashley, David H; Tay, Franklin R

    2012-01-01

    Global increase in patients seeking orthodontic treatment creates a demand for the use of acrylic resins in removable appliances and retainers. Orthodontic removable appliance wearers have a higher risk of oral infections that are caused by the formation of bacterial and fungal biofilms on the appliance surface. Here, we present the synthetic route for an antibacterial and antifungal organically-modified silicate (ORMOSIL) that has multiple methacryloloxy functionalities attached to a siloxane backbone (quaternary ammonium methacryloxy silicate, or QAMS). By dissolving the water-insoluble, rubbery ORMOSIL in methyl methacrylate, QAMS may be copolymerized with polymethyl methacrylate, and covalently incorporated in the pressure-processed acrylic resin. The latter demonstrated a predominantly contact-killing effect on Streptococcus mutans ATCC 36558 and Actinomyces naselundii ATCC 12104 biofilms, while inhibiting adhesion of Candida albicans ATCC 90028 on the acrylic surface. Apart from its favorable antimicrobial activities, QAMS-containing acrylic resins exhibited decreased water wettability and improved toughness, without adversely affecting the flexural strength and modulus, water sorption and solubility, when compared with QAMS-free acrylic resin. The covalently bound, antimicrobial orthodontic acrylic resin with improved toughness represents advancement over other experimental antimicrobial acrylic resin formulations, in its potential to simultaneously prevent oral infections during appliance wear, and improve the fracture resistance of those appliances.

  3. An ORMOSIL-Containing Orthodontic Acrylic Resin with Concomitant Improvements in Antimicrobial and Fracture Toughness Properties

    PubMed Central

    Rueggeberg, Frederick A.; Niu, Li-na; Mettenberg, Donald; Yiu, Cynthia K. Y.; Blizzard, John D.; Wu, Christine D.; Mao, Jing; Drisko, Connie L.; Pashley, David H.; Tay, Franklin R.

    2012-01-01

    Global increase in patients seeking orthodontic treatment creates a demand for the use of acrylic resins in removable appliances and retainers. Orthodontic removable appliance wearers have a higher risk of oral infections that are caused by the formation of bacterial and fungal biofilms on the appliance surface. Here, we present the synthetic route for an antibacterial and antifungal organically-modified silicate (ORMOSIL) that has multiple methacryloloxy functionalities attached to a siloxane backbone (quaternary ammonium methacryloxy silicate, or QAMS). By dissolving the water-insoluble, rubbery ORMOSIL in methyl methacrylate, QAMS may be copolymerized with polymethyl methacrylate, and covalently incorporated in the pressure-processed acrylic resin. The latter demonstrated a predominantly contact-killing effect on Streptococcus mutans ATCC 36558 and Actinomyces naselundii ATCC 12104 biofilms, while inhibiting adhesion of Candida albicans ATCC 90028 on the acrylic surface. Apart from its favorable antimicrobial activities, QAMS-containing acrylic resins exhibited decreased water wettability and improved toughness, without adversely affecting the flexural strength and modulus, water sorption and solubility, when compared with QAMS-free acrylic resin. The covalently bound, antimicrobial orthodontic acrylic resin with improved toughness represents advancement over other experimental antimicrobial acrylic resin formulations, in its potential to simultaneously prevent oral infections during appliance wear, and improve the fracture resistance of those appliances. PMID:22870322

  4. The effect of friction stir processing on the microstructure, mechanical properties and fracture behavior of investment cast titanium aluminum vanadium

    NASA Astrophysics Data System (ADS)

    Pilchak, Adam L.

    . Thus, the mechanical properties were investigated using micropillar compression and microtensile specimens. The effect of friction stir processing on crack initiation resistance was assessed using high cycle fatigue tests conducted in four-point bend which put only the stir zone in maximum tension. The results indicated that at constant stress amplitude, there was greater than an order of magnitude increase in fatigue life after friction stir processing. In addition, the fatigue strength of the investment cast material was improved between 20 pct. and 60 pct. by friction stir processing. These improvements have been verified with a statistically significant number of tests. Finally, the wide range of microstructures created by friction stir processing provided an opportunity to study the effect of underlying microstructure on the fracture behavior of alpha + beta titanium alloys. For this purpose, high resolution fractography coupled with quantitative tilt fractography and electron backscatter diffraction was used to provide a direct link between microstructure, crystallography and fracture topography. These techniques have been used extensively to study the early stages of post-initiation crack growth in Ti-6Al-4V, especially at low stress intensity ranges (DeltaK) in the as-cast material. A limited number of experiments were also performed on Ti-6Al-4V specimens in other microstructural conditions to assess the generality of the detailed results obtained for the fully lamellar material. The results show that fracture topography depends strongly on DeltaK and microstructural length scale. In addition, many of the features observed on the fracture surface were directly related to the underlying crystallographic orientation.

  5. Theoretical and experimental determination of matrix diffusion and related solute transport properties of fractured tuffs from the Nevada Test Site

    SciTech Connect

    Walter, G.R.

    1982-10-01

    Theoretical and experimental studies of the chemical and physical factors which affect molecular diffusion of dissolved substances from fractures into a tuffaceous rock matrix have been made on rocks from G-Tunnel and Yucca Mountain at the Nevada Test Site (NTS). A variety of groundwater tracers, which may be useful in field tests at the NTS, have also been developed and tested. Although a number of physical/chemical processes may cause nonconvective transport of dissolved species from fractures into the tuff matrix, molecular diffusion seems to be the most important process. Molecular diffusion in these rocks is controlled by the composition of the groundwater through multicomponent effects and several rock properties. The porosities of the samples studied ranged from about 0.1 to 0.4. The constrictivity-tortuosity parameter ranged from 0.1 and 0.3 and effective matrix-diffusion coefficients were measured to be between 2 to 17. x 10{sup -7} c,{sup 2}/s for sodium halides and sodium pentafluorobenzoate. Total porosity was found to be the principle factor accounting for the variation in effective diffusion coefficients. The constrictivity-tortuosity factor was found to have a fair correlation (r = 0.75) with the median pore diameters measured by mercury intrusion. Measurements of bulk-rock electrical impedance changes with frequency indicate that the constrictivity factor has a maximum value of 0.8 to 1, but may be smaller. If the larger values are correct, then the diffusion paths in tuff are more tortuous than in granular media. Computation of the full diffusion-coefficient matrix for various tracers in J-13 well water from the NTS indicates coupling of the diffusion fluxes of all ionic species. These effects are being incorporated into a numerical model of multicomponent-matrix diffusion.

  6. Subtask 12G3: Fracture properties of V-4Cr-4Ti irradiated in the dynamic helium charging experiment

    SciTech Connect

    Chung, H.M.; Nowicki, L.J.; Busch, D.E.; Smith, D.L.

    1995-03-01

    The objective of this work is to determine the effect of simultaneous displacement damage and dynamically charged helium on the ductile-brittle transition behavior of V-4Cr-4Ti specimens irradiated to 18-31 dpa at 425-600{degrees}C in the Dynamic Helium Charging Experiment (DHCE). One property of vanadium-base alloys that is not well understood in terms of their potential use as fusion reactor structural materials is the effect of simultaneous generation of helium and neutron damage under conditions relevant to fusion reactor operation. In the present DHCE, helium was produced uniformly in the specimen at linear rates ranging from {approx}0.4 to 4.2 appm helium/dpa by the decay of tritium during irradiation to 18-31 dpa at 425-600{degrees}C in Li-filled DHCE capsules in the Fast Flux Test Facility. Ductile-brittle transition behavior of V-4Cr-4Ti, recently identified as the most promising vanadium-base alloy for fusion reactor use, was determined from multiple-bending tests (at -196{degrees}C to 50{degrees}C) and quantitative SEM fractography on TEM disks (0.3-mm thick) and broken tensile specimens (1.0-mm thick). No brittle behavior was observed at temperatures >-150{degrees}C, and predominantly brittle-cleavage fracture morphologies were observed only at -196{degrees}C in some specimens irradiated to 31 dpa at 425{degrees}C during DHCE. Ductile-brittle transition temperatures (DBTTs) were -200{degrees}C to -175{degrees}C for both types of specimens. In strong contrast to tritium-trick experiments in which dense coalescence of helium bubbles is produced on grain boundaries in the absence of displacement damage, no intergranular fracture was observed in the bend-tested specimens irradiated in the DHCE. 24 refs., 3 figs., 2 tabs.

  7. Fracture healing in mice lacking Pten in osteoblasts: a micro-computed tomography image-based analysis of the mechanical properties of the femur.

    PubMed

    Collins, Caitlyn J; Vivanco, Juan F; Sokn, Scott A; Williams, Bart O; Burgers, Travis A; Ploeg, Heidi-Lynn

    2015-01-21

    In the United States, approximately eight million osseous fractures are reported annually, of which 5-10% fail to create a bony union. Osteoblast-specific deletion of the gene Pten in mice has been found to stimulate bone growth and accelerate fracture healing. Healing rates at four weeks increased in femurs from Pten osteoblast conditional knock-out mice (Pten-CKO) compared to wild-type mice (WT) of the same genetic strain as measured by an increase in mechanical stiffness and failure load in four-point bending tests. Preceding mechanical testing, each femur was imaged using a Skyscan 1172 micro-computed tomography (μCT) scanner (Skyscan, Kontich, Belgium). The present study used µCT image-based analysis to test the hypothesis that the increased femoral fracture force and stiffness in Pten-CKO were due to greater section properties with the same effective material properties as that of the WT. The second moment of area and section modulus were computed in ImageJ 1.46 (National Institutes of Health) and used to predict the effective flexural modulus and the stress at failure for fourteen pairs of intact and callus WT and twelve pairs of intact and callus Pten-CKO femurs. For callus and intact femurs, the failure stress and tissue mineral density of the Pten-CKO and WT were not different; however, the section properties of the Pten-CKO were more than twice as large 28 days post-fracture. It was therefore concluded, when the gene Pten was conditionally knocked-out in osteoblasts, the resulting increased bending stiffness and force to fracture were due to increased section properties.

  8. Fracture Healing in Mice Lacking Pten in Osteoblasts: A Micro-Computed Tomography Image-Based Analysis of the Mechanical Properties of the Femur

    PubMed Central

    Collins, Caitlyn J.; Vivanco, Juan; Sokn, Scott; Williams, Bart O.; Burgers, Travis A.; Ploeg, Heidi-Lynn

    2014-01-01

    In the United States, approximately 8 million osseous fractures are reported annually, of which 5-10% fail to create a bony union. Osteoblast-specific deletion of the gene Pten in mice has been found to stimulate bone growth and accelerate fracture healing. Healing rates at four weeks increased in femurs from Pten osteoblast conditional knock-out mice (Pten-CKO) compared to wild-type mice (WT) of the same genetic strain as measured by an increase in mechanical stiffness and failure load in four-point bending tests. Preceding mechanical testing, each femur was imaged using a Skyscan 1172 micro-computed tomography (μCT) scanner (Skyscan, Kontich, Belgium). The present study used μCT image-based analysis to test the hypothesis that the increased femoral fracture force and stiffness in Pten-CKO were due to greater section properties with the same effective material properties as that of the WT. The second moment of area and section modulus were computed in ImageJ 1.46 (National Institutes of Health) and used to predict the effective flexural modulus and the stress at failure for fourteen pairs of intact and callus WT and twelve pairs of intact and callus Pten-CKO femurs. For callus and intact femurs, the failure stress and tissue mineral density of the Pten-CKO and WT were not different; however, the section properties of the Pten-CKO were more than twice as large 28 days post-fracture. It was therefore concluded, when the gene Pten was conditionally knocked-out in osteoblasts, the resulting increased bending stiffness and force to fracture were due to increased section properties. PMID:25498366

  9. Changes in proximal femur bone properties following ovariectomy and their association with resistance to fracture.

    PubMed

    Fonseca, Hélder; Moreira-Gonçalves, Daniel; Vaz, Mário; Fernandes, Maria Helena; Ferreira, Rita; Amado, Francisco; Mota, Maria Paula; Duarte, José Alberto

    2012-05-01

    Bone strength depends on several material and structural properties, but findings concerning the best predictors of bone mechanical performance are conflicting. The aim of this study was to investigate how a broad set of bone properties in the proximal femur are influenced by age and hormonal status, and how these properties together determine bone strength. Twenty-five Wistar rats were ovariectomized (OVX, n = 13) or sham operated (SHAM, n = 12) at 5 months of age, and killed after 9 months. Another group of rats was killed at 5 months as baseline control (BSL, n = 7). At sacrifice, serum 17β-estradiol and bone turnover marker concentrations were determined in the serum. Both femurs were collected for assessment of trabecular microarchitecture, femoral neck geometry, radiographic absorptiometry, calcium and phosphate content, and biomechanical properties. While stiffness was mostly associated with proximal femur trabecular microarchitecture and mineralization degree, bone strength was mostly linked to bone size and femoral neck geometry, which predicted almost 50% of its variance. Despite the decrease in cortical and trabecular bone as well as in mineralization degree following estrogen loss, bone strength was not reduced in OVX animals compared to BSL or sham-operated rats. This was due to a change in femoral neck geometry as well as to an increase in femur size in OVX, which apparently compensated their lower bone volume and mineral content, thereby preserving bone strength. Estrogen loss leads to a deterioration of bone tissue quality, but bone strength was preserved at the expense of geometric adaptations.

  10. Cotton fiber properties relative humidity and its effect on flat bundle strength elongation and fracture morphology

    Technology Transfer Automated Retrieval System (TEKTRAN)

    It is well known that cotton fibers readily exchange moisture content with their surrounding atmosphere. As moisture exchange progresses, several physical properties of the fiber are significantly affected. In this study, the effects of relative humidity (RH), a factor that affects the atmospheric m...

  11. Fracture Characterization of Meteorites

    NASA Astrophysics Data System (ADS)

    Bryson, K. L.; Agrawal, P.; Ostrowski, D. R.; Sears, D. W. G.

    2015-07-01

    NASA ARC has been tasked with understanding the behavior of ~100m asteroids entering the atmosphere and quantifying the impact hazard. As part of this task, we report the initial results of a survey of the fracture properties of meteorites.

  12. Inulin and erythritol as sucrose replacers in short-dough cookies: sensory, fracture, and acoustic properties.

    PubMed

    Laguna, Laura; Primo-Martín, Cristina; Salvador, Ana; Sanz, Teresa

    2013-05-01

    The effect of sucrose replacement by erythritol and inulin was studied in short-dough cookies using instrumental and sensory analysis. Two levels of replacement were used (25% and 50% of total sucrose content). Descriptive sensory analysis showed that the sucrose replacement affects visual and texture cookies characteristics, being the differences perceived by mouth greater than by hand. In general, sucrose substitutes produced a less crispy cookie and lower consumer acceptability, with the exception of 25% sucrose replacement by inulin. Matrix aeration attributes such as open and crumbly obtained by trained panel were important properties, and correlated positively with consumer acceptance and negatively with maximum force at break (hardness). Inulin cookies sensory properties were more similar to the control than the erythritol cookies. Also, consumer overall acceptance decreased significantly with sucrose replacement by erythritol. The analysis of texture and sound revealed that inulin cookies were softer whereas erythritol cookies were harder in comparison with control cookies; despite this difference, inulin cookies had similar sound characteristics to erythritol cookies.

  13. Inference of Fractured Rock Transport Properties by Joint Inversion of Push-Pull and Single-Hole Ground Penetrating Radar Data

    NASA Astrophysics Data System (ADS)

    Shakas, A.; Linde, N.; Bour, O.; Le Borgne, T.

    2015-12-01

    Flow and transport characterization of fractured rock formations is very challenging and important for a multitude of applications that include groundwater extraction, nuclear waste storage and geothermal energy production. One popular hydrogeological method to study fractured rock is a push-pull test, in which injection and retrieval of a tracer is made at the same depth interval in a borehole. In theory, push-pull tests are not sensitive to changes in the heterogeneity of the tracer flow path since the retrieval at the injection location minimizes advective effects and makes the test more sensitive to time-dependent transport processes. This assumption is limiting in the presence of a natural hydraulic gradient or if non-neutrally buoyant tracers are used, but these limitations can be reduced by monitoring push-pull tests with ground penetrating radar (GPR). We present a methodology for combined modeling and inversion of a series of push-pull tests that we monitored with the single hole ground penetrating radar (GPR) method. For the GPR modeling we use a newly developed approach to simulate the GPR response in fractured rock. We coupled the GPR model to a flow-and-transport simulator that we use to define the electrical properties of the fracture filling. The combined model can cope with heterogeneous fractures of any orientation, aperture and size and allows for the effect of density driven flow (that is strong during the saline tracer tests). We use the combined simulator to create synthetic datasets for both the time-series of the GPR traces at different locations and the tracer breakthrough curves. Since the combined problem is highly non-linear and the inverse solution is ill-posed, we use stochastic inversion techniques to obtain probabilistic estimates of the parameters of interest (fracture length, orientation and aperture distribution) and assess the use of different measures to compare the simulated and experimental data.

  14. Enhancement of the antimicrobial properties of orthorhombic molybdenum trioxide by thermal induced fracturing of the hydrates.

    PubMed

    Shafaei, Shahram; Van Opdenbosch, Daniel; Fey, Tobias; Koch, Marcus; Kraus, Tobias; Guggenbichler, Josef Peter; Zollfrank, Cordt

    2016-01-01

    The oxides of the transition metal molybdenum exhibit excellent antimicrobial properties. We present the preparation of molybdenum trioxide dihydrate (MoO3 × 2H2O) by an acidification method and demonstrate the thermal phase development and morphological evolution during and after calcination from 25 °C to 600 °C. The thermal dehydration of the material was found to proceed in two steps. Microbiological roll-on tests using Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa were performed and exceptional antimicrobial activities were determined for anhydrous samples with orthorhombic lattice symmetry and a large specific surface area. The increase in the specific surface area is due to crack formation and to the loss of the hydrate water after calcination at 300 °C. The results support the proposed antimicrobial mechanism for transition metal oxides, which based on a local acidity increase as a consequence of the augmented specific surface area.

  15. Mechanical Properties and Fracture Surface Morphologies in Unnotched Specimens of Rubber-PMMA Composites

    NASA Astrophysics Data System (ADS)

    Gong, Shiyun; Bandyopadhyay, Sri

    2007-10-01

    Correlations between mechanical properties and microscopic features were investigated using unnotched specimens of rubber-PMMA composites in very low to medium range of cross head speeds. It is found that: (1) a trapezoid-shaped smooth region and fish scale-like texture with bands in rough region correlates with brittle failure in pure PMMA, while a quarter circle-shaped smooth region and hackle-like texture, and the presence of dimples and/or voids correlate with ductile failure in rubber-PMMA composites; (2) decrease in degree of roughness in rubber-PMMA composites can be correlated with decrease in Young’s modulus; (3) decrease in size of the smooth region with increasing speed can be correlated with decrease in modulus of toughness; (4) larger smooth region in rubber-PMMA composites containing more rubber correlates with higher modulus of toughness.

  16. Enhancement of the antimicrobial properties of orthorhombic molybdenum trioxide by thermal induced fracturing of the hydrates.

    PubMed

    Shafaei, Shahram; Van Opdenbosch, Daniel; Fey, Tobias; Koch, Marcus; Kraus, Tobias; Guggenbichler, Josef Peter; Zollfrank, Cordt

    2016-01-01

    The oxides of the transition metal molybdenum exhibit excellent antimicrobial properties. We present the preparation of molybdenum trioxide dihydrate (MoO3 × 2H2O) by an acidification method and demonstrate the thermal phase development and morphological evolution during and after calcination from 25 °C to 600 °C. The thermal dehydration of the material was found to proceed in two steps. Microbiological roll-on tests using Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa were performed and exceptional antimicrobial activities were determined for anhydrous samples with orthorhombic lattice symmetry and a large specific surface area. The increase in the specific surface area is due to crack formation and to the loss of the hydrate water after calcination at 300 °C. The results support the proposed antimicrobial mechanism for transition metal oxides, which based on a local acidity increase as a consequence of the augmented specific surface area. PMID:26478404

  17. The effects of weld-repair and hot isostatic pressing on the fracture properties of Ti-5Al-2.5Sn ELI castings

    NASA Technical Reports Server (NTRS)

    Misra, M. S.; Lemeshewsky, S.; Bolstad, D.

    1982-01-01

    The Ti-5Al-2.5Sn extremely low interstitial alloy employed in the large castings which form the critical attachment fittings of the Space Shuttle External Tank was selected because of its high fracture resistance at cryogenic temperatures. Casting was selected over alternative fabrication methods because of its lower cost and adaptability to design changes, although it was found necessary to weld-repair surface and subsurface casting defects in order to reduce the scrap rate and maintain the inherent cost advantage of the castings. Hot Isostatic Pressing was experimentally found to heal the surface and internal defects of the castings, but did not improve tensile or fracture properties and was therefore rejected as a production technique. Production castings are instead weld-repaired, without any mechanical property degradation.

  18. Fracture property of Y-shaped cracks of brittle materials under compression.

    PubMed

    Zhang, Xiaoyan; Zhu, Zheming; Liu, Hongjie

    2014-01-01

    In order to investigate the properties of Y-shaped cracks of brittle materials under compression, compression tests by using square cement mortar specimens with Y-shaped crack were conducted. A true triaxial loading device was applied in the tests, and the major principle stresses or the critical stresses were measured. The results show that as the branch angle θ between the branch crack and the stem crack is 75°, the cracked specimen has the lowest strength. In order to explain the test results, numerical models of Y-shaped cracks by using ABAQUS code were established, and the J-integral method was applied in calculating crack tip stress intensity factor (SIF). The results show that when the branch angle θ increases, the SIF K I of the branch crack increases from negative to positive and the absolute value K II of the branch crack first increases, and as θ is 50°, it is the maximum, and then it decreases. Finally, in order to further investigate the stress distribution around Y-shaped cracks, photoelastic tests were conducted, and the test results generally agree with the compressive test results. PMID:25013846

  19. Fracture Property of Y-Shaped Cracks of Brittle Materials under Compression

    PubMed Central

    Zhang, Xiaoyan; Zhu, Zheming; Liu, Hongjie

    2014-01-01

    In order to investigate the properties of Y-shaped cracks of brittle materials under compression, compression tests by using square cement mortar specimens with Y-shaped crack were conducted. A true triaxial loading device was applied in the tests, and the major principle stresses or the critical stresses were measured. The results show that as the branch angle θ between the branch crack and the stem crack is 75°, the cracked specimen has the lowest strength. In order to explain the test results, numerical models of Y-shaped cracks by using ABAQUS code were established, and the J-integral method was applied in calculating crack tip stress intensity factor (SIF). The results show that when the branch angle θ increases, the SIF KI of the branch crack increases from negative to positive and the absolute value KII of the branch crack first increases, and as θ is 50°, it is the maximum, and then it decreases. Finally, in order to further investigate the stress distribution around Y-shaped cracks, photoelastic tests were conducted, and the test results generally agree with the compressive test results. PMID:25013846

  20. Fracture properties of a neutron-irradiated stainless steel submerged arc weld cladding overlay

    SciTech Connect

    Corwin, W.R.; Berggren, R.G.; Nanstad, R.K.

    1984-01-01

    The ability of stainless steel cladding to increase the resistance of an operating nuclear reactor pressure vessel to extension of surface flaws depends greatly on the properties of the irradiated cladding. Therefore, weld overlay cladding irradiated at temperatures and fluences relevant to power reactor operation was examined. The cladding was applied to a pressure vessel steel plate by the submerged arc, single-wire, oscillating-electrode method. Three layers of cladding provided a thickness adequate for fabrication of test specimens. The first layer was type 309, and the upper two layers were type 308 stainless steel. The type 309 was diluted considerably by excessive melting of the base plate. Specimens were taken from near the base plate-cladding interface and also from the upper layers. Charpy V-notch and tensile specimens were irradiated at 288/sup 0/C to a fluence of 2 x 10/sup 23/ neutrons/m/sup 2/ (>1 MeV). 10 refs., 16 figs., 4 tabs.

  1. Rock fracture processes in chemically reactive environments

    NASA Astrophysics Data System (ADS)

    Eichhubl, P.

    2015-12-01

    Rock fracture is traditionally viewed as a brittle process involving damage nucleation and growth in a zone ahead of a larger fracture, resulting in fracture propagation once a threshold loading stress is exceeded. It is now increasingly recognized that coupled chemical-mechanical processes influence fracture growth in wide range of subsurface conditions that include igneous, metamorphic, and geothermal systems, and diagenetically reactive sedimentary systems with possible applications to hydrocarbon extraction and CO2 sequestration. Fracture processes aided or driven by chemical change can affect the onset of fracture, fracture shape and branching characteristics, and fracture network geometry, thus influencing mechanical strength and flow properties of rock systems. We are investigating two fundamental modes of chemical-mechanical interactions associated with fracture growth: 1. Fracture propagation may be aided by chemical dissolution or hydration reactions at the fracture tip allowing fracture propagation under subcritical stress loading conditions. We are evaluating effects of environmental conditions on critical (fracture toughness KIc) and subcritical (subcritical index) fracture properties using double torsion fracture mechanics tests on shale and sandstone. Depending on rock composition, the presence of reactive aqueous fluids can increase or decrease KIc and/or subcritical index. 2. Fracture may be concurrent with distributed dissolution-precipitation reactions in the hostrock beyond the immediate vicinity of the fracture tip. Reconstructing the fracture opening history recorded in crack-seal fracture cement of deeply buried sandstone we find that fracture length growth and fracture opening can be decoupled, with a phase of initial length growth followed by a phase of dominant fracture opening. This suggests that mechanical crack-tip failure processes, possibly aided by chemical crack-tip weakening, and distributed

  2. Micro-scale measurement of the mechanical properties of compressed pharmaceutical powders. 1: The elasticity and fracture behavior of microcrystalline cellulose.

    PubMed

    Hancock, B C; Clas, S D; Christensen, K

    2000-11-19

    The feasibility of using very small compacts ( approximately 8.0 x 4.5 x 0.4 mm; approximately 20 mg) to determine the elasticity and fracture behavior of compressed pharmaceutical powders using the three-point beam-bending technique was evaluated. Compacts of microcrystalline cellulose with a range of porosities were tested using a thermomechanical analyzer and values for the Young's modulus and critical stress intensity factor at zero porosity (E(0) and K(IC0)) were determined by extrapolation. The value of E(0) measured at ambient relative humidity on un-notched beams was found to be in close agreement with that reported for much larger samples, and the value of K(IC0) for the small notched compacts was at the lower limit of the accepted range of values for microcrystalline cellulose. The fracture toughness (R) and total energy of fracture (U) for the notched specimens were also determined and used to estimate the apparent surface energies for crack initiation (gamma(i)) and for total fracture (gamma(f)). To further probe the utility of the micro-scale mechanical testing techniques, the effects of humidity on the various mechanical properties of the small microcrystalline compacts were examined and it was found that E(0), K(IC0), R(0), gamma(i0) and gamma(f0) each decreased as the surrounding humidity (and water content of the samples) increased.

  3. Numerical Modeling of Fracture Propagation in Naturally Fractured Formations

    NASA Astrophysics Data System (ADS)

    Wang, W.; Prodanovic, M.; Olson, J. E.; Schultz, R.

    2015-12-01

    Hydraulic fracturing consists of injecting fluid at high pressure and high flowrate to the wellbore for the purpose of enhancing production by generating a complex fracture network. Both tensile failure and shear failure occur during the hydraulic fracturing treatment. The shear event can be caused by slip on existing weak planes such as faults or natural fractures. From core observation, partially cemented and fully cemented opening mode natural fractures, often with considerable thickness are widely present. Hydraulic fractures can propagate either within the natural fracture (tensile failure) or along the interface between the natural fracture and the rock matrix (tensile/shear failure), depending on the relative strength of cement and rock matrix materials, the bonding strength of interface, as well as the presence of any heterogeneities. In this study, we evaluate the fracture propagation both experimentally and numerically. We embed one or multiple inclusions of different mechanical properties within synthetic hydrostone samples in order to mimic cemented natural fractures and rock. A semi-circular bending test is performed for each set of properties. A finite element model built with ABAQUS is used to mimic the semi-circular bending test and study the fracture propagation path, as well as the matrix-inclusion bonding interface status. Mechanical properties required for the numerical model are measured experimentally. The results indicate that the match between experiment and modeling fracture path are extremely sensitive to the chosen interface (bonding) model and related parameters. The semi-circular bending test is dry and easily conducted, providing a good platform for validating numerical approaches. A validated numerical model will enable us to add pressurized fluid within the crack and simulate hydraulic fracture-natural fracture interaction in the reservoir conditions, ultimately providing insights into the extent of the fracture network.

  4. Phenomenological and mechanics aspects of nondestructive evaluation and characterization by sound and ultrasound of material and fracture properties

    NASA Technical Reports Server (NTRS)

    Fu, L. S. W.

    1982-01-01

    Developments in fracture mechanics and elastic wave theory enhance the understanding of many physical phenomena in a mathematical context. Available literature in the material, and fracture characterization by NDT, and the related mathematical methods in mechanics that provide fundamental underlying principles for its interpretation and evaluation are reviewed. Information on the energy release mechanism of defects and the interaction of microstructures within the material is basic in the formulation of the mechanics problems that supply guidance for nondestructive evaluation (NDE).

  5. Effects of Al3(Sc,Zr) and Shear Band Formation on the Tensile Properties and Fracture Behavior of Al-Mg-Sc-Zr Alloy

    NASA Astrophysics Data System (ADS)

    Huang, Hongfeng; Jiang, Feng; Zhou, Jiang; Wei, Lili; Qu, Jiping; Liu, Lele

    2015-11-01

    The mechanical properties and microstructures of Al-6Mg-0.25Sc-0.1Zr alloy (wt.%) during annealing were investigated by means of uniaxial tensile testing, optical microscope, scanning electron microscope, transmission electron microscope, and high-resolution transmission electron microscope. The results show that a large number of micro and grain-scale shear bands form in this alloy after cold rolling. As the tensile-loading force rises, strain softening would generate in shear bands, resulting in the occurrence of shear banding fracture in cold-rolled Al-Mg-Sc-Zr alloys. Recrystallization takes place preferentially in shear bands during annealing. Due to the formation of coarse-grain bands constructed by new subgrains, recrystallization softening tends to occur in these regions. During low-temperature annealing, recrystallization is inhibited by nano-scale Al3(Sc,Zr) precipitates which exert significant coherency strengthening and modulus hardening. However, the strengthening effect of Al3(Sc,Zr) decreases with the increasing of particle diameter at elevated annealing temperature. The mechanical properties of the recrystallized Al-Mg-Sc-Zr alloy decrease to a minimum level, and the fracture plane exhibits pure ductile fracture characteristics.

  6. Earth-Tide Derived Aquifer Properties in Fractured Granite: Results from a Groundwater Monitoring Well Network in the Peninsular Ranges Batholith

    NASA Astrophysics Data System (ADS)

    Weinberger, J. L.; Quinlan, P. T.; Tartakovsky, D. M.

    2014-12-01

    Fractured rock aquifers are difficult to characterize because of the three dimensional spatial heterogeneity of the fracture networks. Aquifer properties cannot be determined from a single borehole and traditional aquifer tests are difficult to design and analyze without prior knowledge of the subsurface permeability distribution. Using passive monitoring of the water level responses to tidal strains in wells allows for characterization of the aquifer over greater spatial extent and can be used to guide the design and implementation of aquifer tests. In this study, the water level response to tidal strains measured in over 20 groundwater wells, spaced irregularly over an approximately 48 km2 area, was used to estimate the specific storage and transmissivity of the surrounding granite aquifer. The water level data were corrected to remove barometric pressure effects before the amplitude and phase shifts for the O1 and M2 components of the tidal potential were calculated. Systematic differences in the calculated aquifer characteristics were observed. The differences correlate with the density of fractures observed in borehole geophysical logs. The aquifer properties derived from the earth-tide analysis were compared to those derived from aquifer tests conducted at two of the wells analyzed. The two methods yielded similar results.

  7. Elbow Fractures

    MedlinePlus

    ... and held together with pins and wires or plates and screws. Fractures of the distal humerus (see ... doctor. These fractures usually require surgical repair with plates and/or screw, unless they are stable. SIGNS ...

  8. Characterisation of the mechanical and fracture properties of a uni-weave carbon fibre/epoxy non-crimp fabric composite.

    PubMed

    Bru, Thomas; Hellström, Peter; Gutkin, Renaud; Ramantani, Dimitra; Peterson, Göran

    2016-03-01

    A complete database of the mechanical properties of an epoxy polymer reinforced with uni-weave carbon fibre non-crimp fabric (NCF) is established. In-plane and through-the-thickness tests were performed on unidirectional laminates under normal loading and shear loading. The response under cyclic shear loading was also measured. The material has been characterised in terms of stiffness, strength, and failure features for the different loading cases. The critical energy release rates associated with different failure modes in the material were measured from interlaminar and translaminar fracture toughness tests. The stress-strain data of the tensile, compressive, and shear test specimens are included. The load-deflection data for all fracture toughness tests are also included. The database can be used in the development and validation of analytical and numerical models of fibre reinforced plastics (FRPs), in particular FRPs with NCF reinforcements. PMID:26958626

  9. Characterisation of the mechanical and fracture properties of a uni-weave carbon fibre/epoxy non-crimp fabric composite.

    PubMed

    Bru, Thomas; Hellström, Peter; Gutkin, Renaud; Ramantani, Dimitra; Peterson, Göran

    2016-03-01

    A complete database of the mechanical properties of an epoxy polymer reinforced with uni-weave carbon fibre non-crimp fabric (NCF) is established. In-plane and through-the-thickness tests were performed on unidirectional laminates under normal loading and shear loading. The response under cyclic shear loading was also measured. The material has been characterised in terms of stiffness, strength, and failure features for the different loading cases. The critical energy release rates associated with different failure modes in the material were measured from interlaminar and translaminar fracture toughness tests. The stress-strain data of the tensile, compressive, and shear test specimens are included. The load-deflection data for all fracture toughness tests are also included. The database can be used in the development and validation of analytical and numerical models of fibre reinforced plastics (FRPs), in particular FRPs with NCF reinforcements.

  10. Characterisation of the mechanical and fracture properties of a uni-weave carbon fibre/epoxy non-crimp fabric composite

    PubMed Central

    Bru, Thomas; Hellström, Peter; Gutkin, Renaud; Ramantani, Dimitra; Peterson, Göran

    2016-01-01

    A complete database of the mechanical properties of an epoxy polymer reinforced with uni-weave carbon fibre non-crimp fabric (NCF) is established. In-plane and through-the-thickness tests were performed on unidirectional laminates under normal loading and shear loading. The response under cyclic shear loading was also measured. The material has been characterised in terms of stiffness, strength, and failure features for the different loading cases. The critical energy release rates associated with different failure modes in the material were measured from interlaminar and translaminar fracture toughness tests. The stress–strain data of the tensile, compressive, and shear test specimens are included. The load–deflection data for all fracture toughness tests are also included. The database can be used in the development and validation of analytical and numerical models of fibre reinforced plastics (FRPs), in particular FRPs with NCF reinforcements. PMID:26958626

  11. High-frequency electromagnetic properties of soft magnetic Nd2Co17 micron flakes fractured along c crystal plane with natural resonance frequency exceeding 10 GHz

    NASA Astrophysics Data System (ADS)

    Zhang, Yongbo; Wang, Peng; Ma, Tianyong; Wang, Ying; Qiao, Liang; Wang, Tao

    2016-02-01

    Planar anisotropy Nd2Co17 flakes fractured along c crystal plane were fabricated by surfactant-assisted high-energy ball milling technique. The magnetic flakes have a diameter range of 5-20 μm and a typical thickness of approximately 120 nm. The frequency dependence of complex permeability of Nd2Co17 epoxy resin composite has been investigated in the frequency range of 0.1-18 GHz. The measurement results show that the natural resonance frequency reaches 12.5 GHz while the initial permeability survives up to 2.26. The superior high frequency properties come from the large out-of-plane anisotropy field and the flake structure fractured along the c crystal plane of Nd2Co17. The planar anisotropic Nd2Co17 flakes have significant potential applications in the high-frequency devices working in the frequency beyond 10 GHz.

  12. Estimating fracture geometry in the naturally fractured Antrim Shale

    SciTech Connect

    Hopkins, C.W.; Frantz, J.H. Jr.; Hill, D.G.

    1995-12-31

    The Antrim Shale of the Michigan Basin has been an active gas play with over 3,500 wells drilled over the last 5 years. There is substantial evidence that the Antrim must be fracture stimulated to be economical and that two-stage treatments provide the best results. However, due to the shallow depths (500-2300 ft) and naturally fractured nature of the Antrim, fracture geometry is complex, and determination of optimal fracture treatments is not straight forward. Because historical field comparisons did not provide insight on the optimal fracture treatments, the Gas Research Institute (GRI) instituted a field-based project for the specific purpose of evaluating the geometry of hydraulic fractures in the Antrim. Open- and cased-hole tests were performed on two separate Antrim wells - a shallow producer (600 {+-} ft) and a deep producer (1550 {+-} ft). Open-hole testing and data collection consisted of in-situ stress and mechanical property testing with Halliburton`s THE{trademark} Tool (9 tests) and a detailed suite of geophysical logs including dipole sonic logs and natural fracture detection logs. Cased-hole testing consisted of pre- and post-fracture injection/falloff tests, minifracture treatments, multiple isotope tracer and tracer logs, and treating pressure and production data analysis. The shallow depths, low in-situ stresses, and extremely fractured nature of the Antrim probably results in the preferential opening of existing fractures instead of the creation of new fracture planes. As a result, the creation of multiple fractures and severe near wellbore tortuosity is likely. Therefore, the natural fractures are responsible for increased leakoff and will greatly impact created fracture geometry. The results also suggest that creating long propped hydraulic fractures in the Antrim is not likely due to the creation of multiple fractures.

  13. Facial fractures.

    PubMed Central

    Carr, M. M.; Freiberg, A.; Martin, R. D.

    1994-01-01

    Emergency room physicians frequently see facial fractures that can have serious consequences for patients if mismanaged. This article reviews the signs, symptoms, imaging techniques, and general modes of treatment of common facial fractures. It focuses on fractures of the mandible, zygomaticomaxillary region, orbital floor, and nose. Images p520-a p522-a PMID:8199509

  14. Dynamic Fracture Properties of Rocks Subjected to Static Pre-load Using Notched Semi-circular Bend Method

    NASA Astrophysics Data System (ADS)

    Chen, Rong; Li, Kang; Xia, Kaiwen; Lin, Yuliang; Yao, Wei; Lu, Fangyun

    2016-10-01

    A dynamic load superposed on a static pre-load is a key problem in deep underground rock engineering projects. Based on a modified split Hopkinson pressure bar test system, the notched semi-circular bend (NSCB) method is selected to investigate the fracture initiation toughness of rocks subjected to pre-load. In this study, a two-dimensional ANSYS finite element simulation model is developed to calculate the dimensionless stress intensity factor. Three groups of NSCB specimen are tested under a pre-load of 0, 37 and 74 % of the maximum static load and with the loading rate ranging from 0 to 60 GPa m1/2 s-1. The results show that under a given pre-load, the fracture initiation toughness of rock increases with the loading rate, resembling the typical rate dependence of materials. Furthermore, the dynamic rock fracture toughness decreases with the static pre-load at a given loading rate. The total fracture toughness, defined as the sum of the dynamic fracture toughness and initial stress intensity factor calculated from the pre-load, increases with the pre-load at a given loading rate. An empirical equation is used to represent the effect of loading rate and pre-load force, and the results show that this equation can depict the trend of the experimental data.

  15. Metatarsal fractures.

    PubMed

    Rammelt, Stefan; Heineck, Jan; Zwipp, Hans

    2004-09-01

    Metatarsal fractures are relatively common and if malunited, a frequent source of pain and disability. Nondisplaced fractures and fractures of the second to fourth metatarsal with displacement in the horizontal plane can be treated conservatively with protected weight bearing in a cast shoe for 4-6 weeks. In most displaced fractures, closed reduction can be achieved but maintenance of the reduction needs internal fixation. Percutaneous pinning is suitable for most fractures of the lesser metatarsals. Fractures with joint involvement and multiple fragments frequently require open reduction and plate fixation. Transverse fractures at the metaphyseal-diaphyseal junction of the fifth metatarsal ("Jones fractures") require an individualized approach tailored to the level of activity and time to union. Avulsion fractures of the fifth metatarsal bone are treated by open reduction and tension-band wiring or screw fixation if displaced more than 2 mm or with more that 30% of the joint involved. The metatarsals are the most common site of stress fractures, most of which are treated nonoperatively. Symptomatic posttraumatic deformities need adequate correction, in most cases by osteotomy across the former fracture site.

  16. A metallographic study of porosity and fracture behavior in relation to the tensile properties in 319.2 end chill castings

    SciTech Connect

    Samuel, A.M.; Samuel, F.H.

    1995-09-01

    A metallographic study of the porosity and fracture behavior in unidirectionally solidified end chill castings of 319.2 aluminum alloy (Al-6.2 pct Si-3.8 pct Cu-0.5 pct Fe-0.14 pct Mn-0.06 pct Mg-0.073 pct Ti) was carried out using optical microscopy and scanning electron microscopy (SEM) to determine their relationship with the tensile properties. The parameters varied in the production of these castings were the hydrogen ({approximately}0.1 and {approximately}0.37 mL/100 g Al), modifier (0 and 300 ppm Sr), and grain refiner (0 and 0.03 wt pct Ti) concentrations, as well as the solidification time, which increased with decreasing distance from the end chill bottom of the casting, giving dendrite arm spacings (DASs) ranging from {approximately}15 to {approximately}95 {micro}m. Image analysis and energy dispersive X-ray (EDX) analysis were employed for quantification of porosity/microstructural constituents and fracture surface analysis (phase identification), respectively. The results showed that the local solidification time (viz. DAS) significantly influences the ductility at low hydrogen levels; at higher levels, however, hydrogen has a more pronounced effect (porosity related) on the drop in ductility. Porosity is mainly observed in the form of elongated pores along the grain boundaries, with Sr increasing the porosity volume percent and grain refining increasing the probability for pore branching. The beneficial effect of Sr modification, however, improves the alloy ductility. Fracture of the Si, {beta}-Al{sub 5}FeSi, {alpha}-Al{sub 15}(Fe,Mn){sub 3}Si{sub 2}, and Al{sub 2}Cu phases takes place within the phase particles rather than at the particle/Al matrix interface. Sensitivity of tensile properties to DAS allows for the use of the latter as an indicator of the expected properties of the alloy.

  17. Mechanical properties of heterophase polymer blends of cryogenically fractured soy flour composite filler and poly(styrene-butadiene)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Reinforcement effect of cryogenically fractured soy Flour composite filler in soft polymer was investigated in this study. Polymer composites were prepared by melt-mixing polymer and soy flour composite fillers in an internal mixer. Soy flour composite fillers were prepared by blending aqueous dis...

  18. Potential Impacts of Spilled Hydraulic Fracturing Fluid Chemicals on Water Resources: Types, volumes, and physical-chemical properties of chemicals

    EPA Science Inventory

    Hydraulic fracturing (HF) fluid chemicals spilled on-site may impact drinking water resources. While chemicals generally make up <2% of the total injected fluid composition by mass, spills may have undiluted concentrations. HF fluids typically consist of a mixture of base flui...

  19. Transport of radon gas into a tunnel at Yucca Mountain—estimating large-scale fractured tuff hydraulic properties and implications for the operation of the ventilation system

    NASA Astrophysics Data System (ADS)

    Unger, André; Finsterle, Stefan; Bodvarsson, Gudmundur

    2004-06-01

    Radon gas concentrations have been monitored as part of the operation of a tunnel (the Exploratory Studies Facility—ESF) at Yucca Mountain to ensure worker safety. The objective of this study was to examine the potential use of the radon data to estimate large-scale formation properties of fractured tuffs. This objective was examined by developing a numerical model, based upon the characteristics of the ESF and the Topopah Spring welded (TSw) tuff unit, capable of predicting radon concentrations for prescribed ventilation conditions. The model was used to address two specific issues. First, it was used to estimate the permeability and porosity of the fractures in the TSw at the length scale of the ESF and extending tens of meters into the TSw, which surrounds the ESF. Second, the model was used to understand the mechanism leading to radon concentrations exceeding a specified level within the ESF. The mechanism controlling radon concentrations in the ESF is a function of atmospheric barometric fluctuations being propagated down the ESF along with ventilated air flow and the slight suction induced by the ventilation exhaust fans at the South Portal of the ESF. These pressure fluctuations are dampened in the TSw fracture continuum according to its permeability and porosity. Consequently, as the barometric pressure in the ESF drops rapidly, formation gases from the TSw are pulled into the ESF, resulting in an increase in radon concentrations. Model calibration to both radon concentrations measured in the ESF and gas-phase pressure fluctuations in the TSw yielded concurrent estimates of TSw fracture permeability and porosity of 1×10 -11 m 2 and 0.00034, respectively. The calibrated model was then used as a design tool to predict the effect of adjusting the current ventilation-system operation strategy for reducing the probability of radon gas concentrations exceeding a specified level.

  20. Transport of Radon Gas into a Tunnel at Yucca Mountain-Estimating Large-Scale Fractured Tuff Hydraulic Properties and Implications for the Operation of the Ventilation System

    SciTech Connect

    A. Unger; S. Finsterle; G. Bodvarsson

    2003-06-06

    Radon gas concentrations have been monitored as part of the operation of a tunnel (the Exploratory Studies Facility-ESF) at Yucca Mountain to ensure worker safety. The objective of this study was to examine the potential use of the radon data to estimate large-scale formation properties of fractured tuffs. This objective was examined by developing a numerical model, based upon the characteristics of the ESF and the Topopah Spring welded (TSw) tuff unit, capable of predicting radon concentrations for prescribed ventilation conditions. The model was used to address two specific issues. First, it was used to estimate the permeability and porosity of the fractures in the TSw at the length scale of the ESF and extending tens of meters into the TSw, which surrounds the ESF. Second, the model was used to understand the mechanism leading to radon concentrations exceeding a specified level within the ESF. The mechanism controlling radon concentrations in the ESF is a function of atmospheric barometric fluctuations being propagated down the ESF along with ventilated air flow and the slight suction induced by the ventilation exhaust fans at the South Portal of the ESF. These pressure fluctuations are dampened in the TSw fracture continuum according to its permeability and porosity. Consequently, as the barometric pressure in the ESF drops rapidly, formation gases from the TSw are pulled into the ESF, resulting in an increase in radon concentrations. Model calibration to both radon concentrations measured in the ESF and gas-phase pressure fluctuations in the TSw yielded concurrent estimates of TSw fracture permeability and porosity of l x 10{sup -11} m{sup 2} and 0.00034, respectively. The calibrated model was then used as a design tool to predict the effect of adjusting the current ventilation-system operation strategy for reducing the probability of radon gas concentrations exceeding a specified level.

  1. Hydraulic fracture propagation modeling and data-based fracture identification

    NASA Astrophysics Data System (ADS)

    Zhou, Jing

    Successful shale gas and tight oil production is enabled by the engineering innovation of horizontal drilling and hydraulic fracturing. Hydraulically induced fractures will most likely deviate from the bi-wing planar pattern and generate complex fracture networks due to mechanical interactions and reservoir heterogeneity, both of which render the conventional fracture simulators insufficient to characterize the fractured reservoir. Moreover, in reservoirs with ultra-low permeability, the natural fractures are widely distributed, which will result in hydraulic fractures branching and merging at the interface and consequently lead to the creation of more complex fracture networks. Thus, developing a reliable hydraulic fracturing simulator, including both mechanical interaction and fluid flow, is critical in maximizing hydrocarbon recovery and optimizing fracture/well design and completion strategy in multistage horizontal wells. A novel fully coupled reservoir flow and geomechanics model based on the dual-lattice system is developed to simulate multiple nonplanar fractures' propagation in both homogeneous and heterogeneous reservoirs with or without pre-existing natural fractures. Initiation, growth, and coalescence of the microcracks will lead to the generation of macroscopic fractures, which is explicitly mimicked by failure and removal of bonds between particles from the discrete element network. This physics-based modeling approach leads to realistic fracture patterns without using the empirical rock failure and fracture propagation criteria required in conventional continuum methods. Based on this model, a sensitivity study is performed to investigate the effects of perforation spacing, in-situ stress anisotropy, rock properties (Young's modulus, Poisson's ratio, and compressive strength), fluid properties, and natural fracture properties on hydraulic fracture propagation. In addition, since reservoirs are buried thousands of feet below the surface, the

  2. Mechanical Properties and Fracture Behaviors of the As-Extruded Mg-5Al-3Ca Alloys Containing Yttrium at Elevated Temperature.

    PubMed

    Son, Hyeon-Taek; Kim, Yong-Ho; Kim, Taek-Soo; Lee, Seong-Hee

    2016-02-01

    Effects of yttrium (Y) addition on mechanical properties and fracture behaviors of the as-extruded Mg-Al-Ca based alloys at elevated temperature were investigated by a tensile test. After hot extrusion, the average grain size was refined by Y addition and eutectic phases were broken down into fine particles. Y addition to Mg-5Al-3Ca based alloy resulted in the improvement of strength and ductility at elevated temperature due to fine grain and suppression of grain growth by formation of thermally stable Al2Y intermetallic compound.

  3. Mechanical Properties and Fracture Behaviors of the As-Extruded Mg-5Al-3Ca Alloys Containing Yttrium at Elevated Temperature.

    PubMed

    Son, Hyeon-Taek; Kim, Yong-Ho; Kim, Taek-Soo; Lee, Seong-Hee

    2016-02-01

    Effects of yttrium (Y) addition on mechanical properties and fracture behaviors of the as-extruded Mg-Al-Ca based alloys at elevated temperature were investigated by a tensile test. After hot extrusion, the average grain size was refined by Y addition and eutectic phases were broken down into fine particles. Y addition to Mg-5Al-3Ca based alloy resulted in the improvement of strength and ductility at elevated temperature due to fine grain and suppression of grain growth by formation of thermally stable Al2Y intermetallic compound. PMID:27433675

  4. Effect of Interfacial Microstructure Evolution on Mechanical Properties and Fracture Behavior of Friction Stir-Welded Al-Cu Joints

    NASA Astrophysics Data System (ADS)

    Xue, P.; Xiao, B. L.; Ma, Z. Y.

    2015-07-01

    The interfacial microstructure evolution of Al-Cu joints during friction stir welding and post-welding annealing and its influence on the tensile strength and the fracture behavior were investigated in detail. An obvious interface including three sub-layers of α-Al, Al2Cu, and Al4Cu9 intermetallic compound (IMC) layers is generated in the as-FSW joint. With the development of annealing process, the α-Al layer disappeared and a new IMC layer of AlCu formed between initial two IMC layers of Al2Cu and Al4Cu9. The growth rate of IMC layers was diffusion controlled before the formation of Kirkendall voids, with activation energy of 117 kJ/mol. When the total thickness of IMC layers was less than the critical value of 2.5 μm, the FSW joints fractured at the heat-affected zone of Al side with a high ultimate tensile strength (UTS) of ~100 MPa. When the thickness of IMC layers exceeded 2.5 μm, the joints fractured at the interface. For relatively thin IMC layer, the joints exhibited a slightly decreased UTS of ~90 MPa and an inter-granular fracture mode with crack propagating mainly between the Al2Cu and AlCu IMC layers. However, when the IMC layer was very thick, crack propagated in the whole IMC layers and the fracture exhibited trans-granular mode with a greatly decreased UTS of 50-60 MPa.

  5. Effect of nicotine and tobacco administration method on the mechanical properties of healing bone following closed fracture.

    PubMed

    Hastrup, Sidsel Gaarn; Chen, Xinqian; Bechtold, Joan E; Kyle, Richard F; Rahbek, Ole; Keyler, Daniel E; Skoett, Martin; Soeballe, Kjeld

    2010-09-01

    We previously showed different effects of tobacco and nicotine on fracture healing, but due to pump reservoir limits, maximum exposure period was 4 weeks. To allow flexibility in pre- and post-fracture exposure periods, the objective of this study was to compare a new oral administration route for nicotine to the established pump method. Four groups were studied: (1) pump saline, (2) pump saline + oral tobacco, (3) pump saline/nicotine + oral tobacco, and (4) pump saline + oral nicotine/tobacco. Sprague-Dawley rats (n = 84) received a transverse femoral fracture stabilized with an intramedullary pin 1 week after initiating dosing. After 3 weeks, no difference was found in torsional strength or stiffness between oral nicotine/tobacco or pump nicotine + tobacco, while energy absorption with oral nicotine/tobacco was greater than pump nicotine + tobacco (p < 0.05). Compared to saline control, strength for oral nicotine/tobacco was higher than control (p < 0.05), and stiffnesses for pump nicotine + tobacco and oral nicotine/tobacco were higher than control (p < 0.05). No differences in energy were found for either nicotine-tobacco group compared to saline control. Mean serum cotinine (stable nicotine metabolite) was different between pump and oral nicotine at 1 and 4 weeks, but all groups were in the range of 1-2 pack/day smokers. In summary, relevant serum cotinine levels can be reached in rats with oral nicotine, and, in the presence of tobacco, nicotine can influence mechanical aspects of fracture healing, dependent on administration method. Caution should be exercised when comparing results of fracture healing studies using different methods of nicotine administration.

  6. Characterisation and monitoring of the Excavation Disturbed Zone (EDZ) in fractured gneisses of the Roselend underground laboratory: permeability measurements, transport property changes and related radon bursts

    NASA Astrophysics Data System (ADS)

    Wassermann, Jérôme; Sabroux, Jean-Christophe; Richon, Patrick; Pontreau, Sébastien; Guillon, Sophie; Pili, Eric

    2010-05-01

    pressure measurements between an obturated borehole and the tunnel is conducted to monitor the possible modifications of the transport properties of the EDZ due to hydraulical and/or mechanical sollicitations of the nearby Roselend reservoir lake. As radon level is controlled by emanation and transport path through the medium. The observed bursts of radon should be due to changes of the radon transport properties (Trique et al. 1999) of the EDZ. A correlation between the differential pressure variations and radon bursts is clearly observed. Radon bursts seem to be related to overpressure events that take place in the instrumented borehole. Which external sollicitations, hydraulical or mechanical, or both, induce such a behaviour? References Bossart, P., Meier, P. M., Moeri, A., Trick, T., and J.-C. Mayor (2002). Geological and hydraulic characterisation of the excavation disturbed zone in the Opalinus Clay of the Mont Terri Rock Laboratory, Engineering Geology, 66, 19-38. Dezayes, C., and T. Villemin (2002). Etat de la fracturation dans la galerie CEA de Roselend et analyse de la déformation cassante dans le massif du Méraillet, technical report, Lab. de Geodyn. de Chaisnes Alp., Univ. de Savoie, Savoie, France. Jakubick, A. T., and T. Franz (1993). Vacuum testing of the permeability of the excavation damaged zone, Rock Mech. Rock Engng., 26(2), 165-182. Patriarche, D., Pili, E., Adler, P. M., and J.-F. Thovert (2007). Stereological analysis of fractures in the Roselend tunnel and permeability determination, Water Resour. Res., 43, W09421. Richon, P., Perrier, F., Sabroux, J.-C., Trique, M., Ferry, C., Voisin, V., and E. Pili (2004). Spatial and time variations of radon-222 concentration in the atmosphere of a dead-end horizontal tunnel, J. Environ. Radioact., 78, 179-198. Richon, P., Perrier, F., Pili, E., and J.-C. Sabroux (2009). Detectability and significance of the 12hr barometric tide in radon-222 signal, dripwater flow rate, air temperature and carbon dioxide

  7. An evaluation of the fatigue crack growth and fracture toughness properties of beryllium-copper alloy CDA172

    NASA Technical Reports Server (NTRS)

    Forman, Royce G.; Henkener, Julie A.

    1990-01-01

    A series of fracture mechanics tests, using the Be-Cu alloy CDA172 in the round rod product form, was conducted in a lab air environment at room temperature. Tensile data is presented in both the L and C directions and K sub Ic data in both the C-R and C-L orientations. Fracture toughness values were derived from M(T) (center cracked), PS(T) (surface cracked) and CC01 (corner cracked) specimens of varying thickness. Fatigue crack growth data were obtained for the C-R orientation at stress ratio of 0.1, 0.4, and 0.7 and for the C-L orientation at stress ratios of 0.1, 0.3, 0.4, and 0.7.

  8. The properties and fracture behavior of ion plasma sprayed TiN coating on stainless steel substrate

    NASA Astrophysics Data System (ADS)

    Orlova, Dina V.; Goncharenko, Igor M.; Danilov, Vladimir I.; Lobach, Maxim I.; Danilova, Lidiya V.; Shlyakhova, Galina V.

    2015-10-01

    The wear resistance and fracture behavior of ion plasma sprayed TiN coating were studied; the results are presented. The coating was applied to the stainless steel substrate using a vacuum arc method. The samples were tested by active loading. With varying coating thickness, its characteristics were found to change. Multiple cracking would occur in the deformed sample, with fragment borders aligned normal to the extension axis.

  9. Effects of through-the-thickness stitching on impact and interlaminar fracture properties of textile graphite/epoxy laminates

    NASA Technical Reports Server (NTRS)

    Sharma, Suresh K.; Sankar, Bhavani V.

    1995-01-01

    This study investigated the effects of through-the-thickness stitching on impact damage resistance, impact damage tolerance, and mode I and mode II fracture toughness of textile graphite/epoxy laminates. Uniweave resin-transfer-molded 48 ply graphite/epoxy (AS4/3501-6) laminates were stitched with Kevlar and glass yarns of different linear densities and stitch spacings. Delaminations were implanted during processing to simulate impact damage. Sublaminate buckling tests were performed to determine the effects of stitching on the compressive strength. The results showed outstanding improvements of up to 400 percent in the compression strength over the unstitched laminates. In impact and static indentation tests the onset of damage occurred at the same level, but the extent of damage was less in stitched laminates. Mode I fracture toughness of 24 ply Uniweave unidirectional (AS4/3501-6) stitched laminates was measured by conducting double-cantilever-beam tests. The critical strain energy release rate (G(sub Ic)) was found to be up to 30 times higher than the unstitched laminates. Mode II fracture toughness of the Uniweave laminates was measured by performing end-notched-flexure tests. Two new methods to compute the apparent G(sub IIc) are presented. The apparent G(sub IIc) was found to be at least 5-15 times higher for the stitched laminates.

  10. Fracture toughness of graphene.

    PubMed

    Zhang, Peng; Ma, Lulu; Fan, Feifei; Zeng, Zhi; Peng, Cheng; Loya, Phillip E; Liu, Zheng; Gong, Yongji; Zhang, Jiangnan; Zhang, Xingxiang; Ajayan, Pulickel M; Zhu, Ting; Lou, Jun

    2014-04-29

    Perfect graphene is believed to be the strongest material. However, the useful strength of large-area graphene with engineering relevance is usually determined by its fracture toughness, rather than the intrinsic strength that governs a uniform breaking of atomic bonds in perfect graphene. To date, the fracture toughness of graphene has not been measured. Here we report an in situ tensile testing of suspended graphene using a nanomechanical device in a scanning electron microscope. During tensile loading, the pre-cracked graphene sample fractures in a brittle manner with sharp edges, at a breaking stress substantially lower than the intrinsic strength of graphene. Our combined experiment and modelling verify the applicability of the classic Griffith theory of brittle fracture to graphene. The fracture toughness of graphene is measured as the critical stress intensity factor of and the equivalent critical strain energy release rate of 15.9 J m(-2). Our work quantifies the essential fracture properties of graphene and provides mechanistic insights into the mechanical failure of graphene.

  11. Epidemiology of fracture risk with advancing age.

    PubMed

    Ensrud, Kristine E

    2013-10-01

    Bone loss and structural damage with advancing age lead to skeletal fragility as manifested by low bone mass and deficits in bone geometry, microarchitecture, and material properties. Skeletal fragility, in combination with a greater propensity to fall, results in an increased susceptibility to fractures with aging, known as fragility fractures. Fragility fractures exceed 2 million per year in number and account for nearly 20 billion dollars per year in health care costs in the United States. Advanced age, low bone mass, and previous fracture are strong risk factors for fractures at nearly all skeletal sites, but each type of fracture also has its own set of unique risk factors. Hip fractures are most strongly associated with adverse consequences, but these account for only a minority of fragility fractures. Vertebral fractures comprise the most common manifestation of fragility fracture, but the majority of these fractures are asymptomatic. Most research has focused on the epidemiology of fractures at the hip, vertebrae, and wrist and less is known about other fracture types, which account for 40% of total fragility fractures that are clinically recognized. Future research focused on identification of older adults at high risk of disabling fractures is warranted. PMID:23833201

  12. Fatigue Fractures

    PubMed Central

    Morris, James M.

    1968-01-01

    Fatigue (or stress) fracture of bone in military recruits has been recognized for many years. Most often it is a metatarsal bone that is involved but the tarsal bones, calcaneus, tibia, fibula, femur, and pelvis are occasionally affected. Reports of such fractures in the ribs, ulna and vertebral bodies may be found in the literature. In recent years, there has been increasing awareness of the occurrence of fatigue fractures in the civilian population. Weekend sportsmen, athletes in an early phase of training, and persons engaged in unaccustomed, repetitive, vigorous activity are potential victims of such a fracture. The signs and symptoms, roentgenographic findings, treatment and etiology of fatigue fractures are dealt with in this presentation. ImagesFigure 1.Figure 2.Figure 3.Figure 4.Figure 5.Figure 6. PMID:5652745

  13. Generating fracture networks using iterated function systems

    NASA Astrophysics Data System (ADS)

    Mohrlok, U.; Liedl, R.

    In order to model flow and transport in fractured rocks it is important to know the geometry of the fracture network. A stochastic approach is commonly used to generate a synthetic fracture network from the statistics measured at a natural fracture network. The approach presented herein is able to incorporate the structures found in a natural fracture network into the synthetic fracture network. These synthetic fracture networks are the images generated by Iterated Function Systems (IFS) as introduced by Barnsley (1988). The conditions these IFS have to fulfil to determine images resembling fracture networks and the effects of their parameters on the images are discussed. It is possible to define the parameters of the IFS in order to generate some properties of a fracture network. The image of an IFS consists of many single points and has to be suitably processed for further use.

  14. Generating fracture networks using iterated function systems

    NASA Astrophysics Data System (ADS)

    Mohrlok, U.; Liedl, R.

    1996-03-01

    In order to model flow and transport in fractured rocks it is important to know the geometry of the fracture network. A stochastic approach is commonly used to generate a synthetic fracture network from the statistics measured at a natural fracture network. The approach presented herein is able to incorporate the structures found in a natural fracture network into the synthetic fracture network. These synthetic fracture networks are the images generated by Iterated Function Systems (IFS) as introduced by Barnsley (1988). The conditions these IFS have to fulfil to determine images resembling fracture networks and the effects of their parameters on the images are discussed. It is possible to define the parameters of the IFS in order to generate some properties of a fracture network. The image of an IFS consists of many single points and has to be suitably processed for further use.

  15. Injection through fractures

    SciTech Connect

    Johns, R.A.

    1987-05-01

    Tracer tests are conducted in geothermal reservoirs as an aid in forecasting thermal breakthrough of reinjection water. To interpret tracer tests, mathematical models have been developed based on the various transport mechanisms in these highly fractured reservoirs. These tracer flow models have been applied to interpret field tests. The resulting matches between the model and field data were excellent and the model parameters were used to estimate reservoir properties. However, model fitting is an indirect process and the model's ability to estimate reservoir properties cannot be judged solely on the quality of the match between field data and model predictions. The model's accuracy in determining reservoir characteristics must be independently verified in a closely controlled environment. In this study, the closely controlled laboratory environment was chosen to test the validity and accuracy of tracer flow models developed specifically for flow in fractured rocks. The laboratory tracer tests were performed by flowing potassium iodide (KI) through artificially fractured core samples. The tracer test results were then analyzed with several models to determine which best fit the measured data. A Matrix Diffusion model was found to provide the best match of the tracer experiments. The core properties, as estimated by the Matrix Diffusion model parameters generated from the indirect matching process, were then determined. These calculated core parameters were compared to the measured core properties and were found to be in agreement. This verifies the use of the Matrix Diffusion flow model in estimating fracture widths from tracer tests.

  16. Fracture permeability and seismic wave scattering--Poroelastic linear-slip interface model for heterogeneous fractures

    SciTech Connect

    Nakagawa, S.; Myer, L.R.

    2009-06-15

    Schoenberg's Linear-slip Interface (LSI) model for single, compliant, viscoelastic fractures has been extended to poroelastic fractures for predicting seismic wave scattering. However, this extended model results in no impact of the in-plane fracture permeability on the scattering. Recently, we proposed a variant of the LSI model considering the heterogeneity in the in-plane fracture properties. This modified model considers wave-induced, fracture-parallel fluid flow induced by passing seismic waves. The research discussed in this paper applies this new LSI model to heterogeneous fractures to examine when and how the permeability of a fracture is reflected in the scattering of seismic waves. From numerical simulations, we conclude that the heterogeneity in the fracture properties is essential for the scattering of seismic waves to be sensitive to the permeability of a fracture.

  17. Effect of strain rate on shear properties and fracture characteristics of DP600 and AA5182-O sheet metal alloys

    NASA Astrophysics Data System (ADS)

    Rahmaan, Taamjeed; Butcher, Cliff; Abedini, Armin; Worswick, Michael

    2015-09-01

    Shear tests were performed at strain rates ranging from quasi-static (.01 s-1) to 600 s-1 for DP600 steel and AA5182-O sheet metal alloys at room temperature. A miniature sized shear specimen was modified and validated in this work to perform high strain rate shear testing. Digital image correlation (DIC) techniques were employed to measure the strains in the experiments, and a criterion to detect the onset of fracture based on the hardening rate of the materials is proposed. At equivalent strains greater than 20%, the DP600 and AA5182 alloys demonstrated a reduced work hardening rate at elevated strain rates. At lower strains, the DP600 shows positive rate sensitivity while the AA5182 was not sensitive to strain rate. For both alloys, the equivalent fracture strain and elongation to failure decreased with strain rate. A conversion of the shear stress to an equivalent stress using the von Mises yield criterion provided excellent agreement with the results from tensile tests at elevated strain rates. Unlike the tensile test, the shear test is not limited by the onset of necking so the equivalent stress can be determined over a larger range of strain.

  18. Fundamentals of reservoir surface energy as related to surface properties, wettability, capillary action, and oil recovery from fractured reservoirs by spontaneous imbibition

    SciTech Connect

    Norman R. Morrow; Herbert Fischer; Yu Li; Geoffrey Mason; Douglas Ruth; Siddhartha Seth; Jason Zhengxin Tong; Peigui Yin; Shaochang Wo

    2006-02-01

    The objective of this project is to increase oil recovery from fractured reservoirs through improved fundamental understanding of the process of spontaneous imbibition by which oil is displaced from the rock matrix into the fractures. Spontaneous imbibition is fundamentally dependent on the reservoir surface free energy but this has never been investigated for rocks. In this project, the surface free energy of rocks will be determined by using liquids that can be solidified within the rock pore space at selected saturations. Thin sections of the rock then provide a two-dimensional view of the rock minerals and the occupant phases. Saturations and oil/rock, water/rock, and oil/water surface areas will be determined by advanced petrographic analysis and the surface free energy which drives spontaneous imbibition will be determined as a function of increase in wetting phase saturation. The inherent loss in surface free energy resulting from capillary instabilities at the microscopic (pore level) scale will be distinguished from the decrease in surface free energy that drives spontaneous imbibition. A mathematical network/numerical model will be developed and tested against experimental results of recovery versus time over broad variation of key factors such as rock properties, fluid phase viscosities, sample size, shape and boundary conditions. Two fundamentally important, but not previously considered, parameters of spontaneous imbibition, the capillary pressure acting to oppose production of oil at the outflow face and the pressure in the nonwetting phase at the no-flow boundary versus time, will also be measured and modeled. Simulation and network models will also be tested against special case solutions provided by analytic models. In the second stage of the project, application of the fundamental concepts developed in the first stage of the project will be demonstrated. The fundamental ideas, measurements, and analytic/numerical modeling will be applied to mixed

  19. FUNDAMENTALS OF RESERVOIR SURFACE ENERGY AS RELATED TO SURFACE PROPERTIES, WETTABILITY, CAPILLARY ACTION, AND OIL RECOVERY FROM FRACTURED RESERVOIRS BY SPONTANEOUS IMBIBITION

    SciTech Connect

    Norman R. Morrow

    2004-05-01

    The objective of this project is to increase oil recovery from fractured reservoirs through improved fundamental understanding of the process of spontaneous imbibition by which oil is displaced from the rock matrix into the fractures. Spontaneous imbibition is fundamentally dependent on the reservoir surface free energy but this has never been investigated for rocks. In this project, the surface free energy of rocks will be determined by using liquids that can be solidified within the rock pore space at selected saturations. Thin sections of the rock then provide a two-dimensional view of the rock minerals and the occupant phases. Saturations and oil/rock, water/rock, and oil/water surface areas will be determined by advanced petrographic analysis and the surface free energy which drives spontaneous imbibition will be determined as a function of increase in wetting phase saturation. The inherent loss in surface free energy resulting from capillary instabilities at the microscopic (pore level) scale will be distinguished from the decrease in surface free energy that drives spontaneous imbibition. A mathematical network/numerical model will be developed and tested against experimental results of recovery versus time over broad variation of key factors such as rock properties, fluid phase viscosities, sample size, shape and boundary conditions. Two fundamentally important, but not previously considered, parameters of spontaneous imbibition, the capillary pressure acting to oppose production of oil at the outflow face and the pressure in the nonwetting phase at the no-flow boundary versus time, will also be measured and modeled. Simulation and network models will also be tested against special case solutions provided by analytic models. In the second stage of the project, application of the fundamental concepts developed in the first stage of the project will be demonstrated. The fundamental ideas, measurements, and analytic/numerical modeling will be applied to mixed

  20. FUNDAMENTALS OF RESERVOIR SURFACE ENERGY AS RELATED TO SURFACE PROPERTIES, WETTABILITY, CAPILLARY ACTION, AND OIL RECOVERY FROM FRACTURED RESERVOIRS BY SPONTANEOUS IMBIBITION

    SciTech Connect

    Norman R. Morrow

    2004-07-01

    The objective of this project is to increase oil recovery from fractured reservoirs through improved fundamental understanding of the process of spontaneous imbibition by which oil is displaced from the rock matrix into the fractures. Spontaneous imbibition is fundamentally dependent on the reservoir surface free energy but this has never been investigated for rocks. In this project, the surface free energy of rocks will be determined by using liquids that can be solidified within the rock pore space at selected saturations. Thin sections of the rock then provide a two-dimensional view of the rock minerals and the occupant phases. Saturations and oil/rock, water/rock, and oil/water surface areas will be determined by advanced petrographic analysis and the surface free energy which drives spontaneous imbibition will be determined as a function of increase in wetting phase saturation. The inherent loss in surface free energy resulting from capillary instabilities at the microscopic (pore level) scale will be distinguished from the decrease in surface free energy that drives spontaneous imbibition. A mathematical network/numerical model will be developed and tested against experimental results of recovery versus time over broad variation of key factors such as rock properties, fluid phase viscosities, sample size, shape and boundary conditions. Two fundamentally important, but not previously considered, parameters of spontaneous imbibition, the capillary pressure acting to oppose production of oil at the outflow face and the pressure in the nonwetting phase at the no-flow boundary versus time, will also be measured and modeled. Simulation and network models will also be tested against special case solutions provided by analytic models. In the second stage of the project, application of the fundamental concepts developed in the first stage of the project will be demonstrated. The fundamental ideas, measurements, and analytic/numerical modeling will be applied to mixed

  1. Fundamentals of Reservoir Surface Energy as Related to Surface Properties, Wettability, Capillary Action and Oil Recovery from Fractured Reservoirs by Spontaneous Imbibition

    SciTech Connect

    Norman R. Morrow; Herbert Fischer; Yu Li; Geoffrey Mason; Douglas Ruth; Peigui Yin; Shaochang Wo

    2006-12-08

    The objective of this project is to increase oil recovery from fractured reservoirs through improved fundamental understanding of the process of spontaneous imbibition by which oil is displaced from the rock matrix into the fractures. Spontaneous imbibition is fundamentally dependent on the reservoir surface free energy but this has never been investigated for rocks. In this project, the surface free energy of rocks will be determined by using liquids that can be solidified within the rock pore space at selected saturations. Thin sections of the rock then provide a two-dimensional view of the rock minerals and the occupant phases. Saturations and oil/rock, water/rock, and oil/water surface areas will be determined by advanced petrographic analysis and the surface free energy which drives spontaneous imbibition will be determined as a function of increase in wetting phase saturation. The inherent loss in surface free energy resulting from capillary instabilities at the microscopic (pore level) scale will be distinguished from the decrease in surface free energy that drives spontaneous imbibition. A mathematical network/numerical model will be developed and tested against experimental results of recovery versus time over broad variation of key factors such as rock properties, fluid phase viscosities, sample size, shape and boundary conditions. Two fundamentally important, but not previously considered, parameters of spontaneous imbibition, the capillary pressure acting to oppose production of oil at the outflow face and the pressure in the non-wetting phase at the no-flow boundary versus time, will also be measured and modeled. Simulation and network models will also be tested against special case solutions provided by analytic models. In the second stage of the project, application of the fundamental concepts developed in the first stage of the project will be demonstrated. The fundamental ideas, measurements, and analytic/numerical modeling will be applied to mixed

  2. Fundamentals of Reservoir Surface Energy as Related to Surface Properties, Wettability, Capillary Action, and Oil Recovery from Fractured Reservoirs by Spontaneous Imbibition

    SciTech Connect

    Norman Morrow; Herbert Fischer; Yu Li; Geoffrey Mason; Douglas Ruth; Siddhartha Seth; Zhengxin Tong; Evren Unsal; Siluni Wickramathilaka; Shaochang Wo; Peigui Yin

    2008-06-30

    The objective of this project is to increase oil recovery from fractured reservoirs through improved fundamental understanding of the process of spontaneous imbibition by which oil is displaced from the rock matrix into the fractures. Spontaneous imbibition is fundamentally dependent on the reservoir surface free energy but this has never been investigated for rocks. In this project, the surface free energy of rocks will be determined by using liquids that can be solidified within the rock pore space at selected saturations. Thin sections of the rock then provide a two-dimensional view of the rock minerals and the occupant phases. Saturations and oil/rock, water/rock, and oil/water surface areas will be determined by advanced petrographic analysis and the surface free energy which drives spontaneous imbibition will be determined as a function of increase in wetting phase saturation. The inherent loss in surface free energy resulting from capillary instabilities at the microscopic (pore level) scale will be distinguished from the decrease in surface free energy that drives spontaneous imbibition. A mathematical network/numerical model will be developed and tested against experimental results of recovery versus time over broad variation of key factors such as rock properties, fluid phase viscosities, sample size, shape and boundary conditions. Two fundamentally important, but not previously considered, parameters of spontaneous imbibition, the capillary pressure acting to oppose production of oil at the outflow face and the pressure in the non-wetting phase at the no-flow boundary versus time, will also be measured and modeled. Simulation and network models will also be tested against special case solutions provided by analytic models. In the second stage of the project, application of the fundamental concepts developed in the first stage of the project will be demonstrated. The fundamental ideas, measurements, and analytic/numerical modeling will be applied to mixed

  3. FUNDAMENTALS OF RESERVOIR SURFACE ENERGY AS RELATED TO SURFACE PROPERTIES, WETTABILITY, CAPILLARY ACTION, AND OIL RECOVERY FROM FRACTURED RESERVOIRS BY SPONTANEOUS IMBIBITION

    SciTech Connect

    Norman R. Morrow; Herbert Fischer; Yu Li; Geoffrey Mason; Douglas Ruth; Siddhartha Seth; Peigui Yin; Shaochang Wo

    2005-04-01

    The objective of this project is to increase oil recovery from fractured reservoirs through improved fundamental understanding of the process of spontaneous imbibition by which oil is displaced from the rock matrix into the fractures. Spontaneous imbibition is fundamentally dependent on the reservoir surface free energy but this has never been investigated for rocks. In this project, the surface free energy of rocks will be determined by using liquids that can be solidified within the rock pore space at selected saturations. Thin sections of the rock then provide a two-dimensional view of the rock minerals and the occupant phases. Saturations and oil/rock, water/rock, and oil/water surface areas will be determined by advanced petrographic analysis and the surface free energy which drives spontaneous imbibition will be determined as a function of increase in wetting phase saturation. The inherent loss in surface free energy resulting from capillary instabilities at the microscopic (pore level) scale will be distinguished from the decrease in surface free energy that drives spontaneous imbibition. A mathematical network/numerical model will be developed and tested against experimental results of recovery versus time over broad variation of key factors such as rock properties, fluid phase viscosities, sample size, shape and boundary conditions. Two fundamentally important, but not previously considered, parameters of spontaneous imbibition, the capillary pressure acting to oppose production of oil at the outflow face and the pressure in the nonwetting phase at the no-flow boundary versus time, will also be measured and modeled. Simulation and network models will also be tested against special case solutions provided by analytic models. In the second stage of the project, application of the fundamental concepts developed in the first stage of the project will be demonstrated. The fundamental ideas, measurements, and analytic/numerical modeling will be applied to mixed

  4. Ambient and elevated temperature fracture and cyclic-fatigue properties in a series of Al-containing silicon carbides

    SciTech Connect

    Yuan, Rong

    2004-01-01

    A series of in situ toughened, Al, B and C containing, silicon carbide ceramics (ABC-SiC) has been examined with Al contents varying from 3 to 7 wt%. With increasing Al additions, the grain morphology in the as-processed microstructures varied from elongated to bimodal to equiaxed, with a change in the nature of the grain-boundary film from amorphous to partially crystalline to fully crystalline. Fracture toughness and cyclic fatigue tests on these microstructures revealed that although the 7 wt.% Al containing material (7ABC) was extremely brittle, the 3 and particularly 5 wt.% Al materials (3ABC and 5ABC, respectively) displayed excellent crack-growth resistance at both ambient (25°C) and elevated (1300 C) temperatures. Indeed, no evidence of creep damage, in the form of grain-boundary cavitation, was seen at temperatures at 1300°C or below. The enhanced toughness of the higher Al-containing materials was associated with extensive crack bridging from both interlocking grains (in 3ABC) and uncracked ligaments (in 5ABC); in contrast, the 7ABC SiC showed no such bridging, concomitant with a marked reduction in the volume fraction of elongated grains. Mechanistically, cyclic fatigue-crack growth in 3ABC and 5ABC SiC involved the progressive degradation of such bridging ligaments in the crack wake, with the difference in the degree of elastic vs. frictional bridging affecting the slope, i.e., Paris law exponent, of the crack-growth curve. In addition an investigation of fracture resistance in non-transforming ceramics toughened by grain bridging mechanism is presented using linear elastic fracture mechanics (LEFM). Linear superposition theorems are used for the superposition of crack opening displacements, as well as stress intensity factors, resulting from the external tractions and the internal compressive bridging stresses. Specifically weight functions are used to relate the CODs, stress intensity factors, and tractions and the bridging stress. Expressions are

  5. Fracture Management

    MedlinePlus

    ... to hold the fracture in the correct position. • Fiberglass casting is lighter and stronger and the exterior ... with your physician if this occurs. • When a fiberglass cast is used in conjunction with a GORE- ...

  6. Lisfranc fractures.

    PubMed

    Wright, Amanda; Gerhart, Ann E

    2009-01-01

    Injuries of the tarsometatarsal, or Lisfranc, joint are rarely seen. Lisfranc fractures and fracture dislocations are among the most frequently misdiagnosed foot injuries in the emergency department. A misdiagnosed injury may have severe consequences including chronic pain and loss of foot biomechanics. Evaluation of a foot injury should include a high level of suspicion of a Lisfranc injury, and a thorough work-up is needed for correct diagnosis.

  7. Cancellous bone lamellae strongly affect microcrack propagation and apparent mechanical properties: Separation of patients with osteoporotic fracture from normal controls using a 2D nonlinear finite element method (biomechanical stereology)

    PubMed Central

    Wang, Xiang; Zauel, Roger R.; Rao, D. Sudhaker; Fyhrie, David P.

    2009-01-01

    Biomechanical stereology is proposed as a two-dimensional (2D) finite element (FE) method to estimate the ability of bone tissue to sustain damage and to separate patients with osteoporotic fracture from normal controls. Briefly, 2D nonlinear compact tension FE models were created from quantitative back scattered electron images taken of iliac crest bone specimens collected from the individuals with or without osteoporotic fracture history. The effects of bone mineral microstructure on predicted bone fracture toughness and microcrack propagation were examined. The 2D FE models were used as surrogates for the real bone tissues. The calculated microcrack propagation results and bone mechanical properties were examined as surrogates for measurements from mechanical testing of actual specimens. The results for the 2D FE simulation separated patients with osteoporotic fracture from normal controls even though only the variability in tissue mineral microstructure was used to build the models. The models were deliberately created to ignore all differences in mean mineralization. Hence, the current results support the following hypotheses: (1) that material heterogeneity is important to the separation of patients with osteoporotic fracture from normal controls and; and (2) that 2D nonlinear finite element modeling can produce surrogate mechanical parameters that separate patients with fracture from normal controls. PMID:18378204

  8. Effect of argon purity on mechanical properties, microstructure and fracture mode of commercially pure (cp) Ti and Ti-6Al-4V alloys for ceramometal dental prostheses.

    PubMed

    Bauer, José; Cella, Suelen; Pinto, Marcelo M; Filho, Leonardo E Rodrigues; Reis, Alessandra; Loguercio, Alessandro D

    2009-12-01

    Provision of an inert gas atmosphere with high-purity argon gas is recommended for preventing titanium castings from contamination although the effects of the level of argon purity on the mechanical properties and the clinical performance of Ti castings have not yet been investigated. The purpose of this study was to evaluate the effect of argon purity on the mechanical properties and microstructure of commercially pure (cp) Ti and Ti-6Al-4V alloys. The castings were made using either high-purity and/or industrial argon gas. The ultimate tensile strength (UTS), proportional limit (PL), elongation (EL) and microhardness (VHN) at different depths were evaluated. The microstructure of the alloys was also revealed and the fracture mode was analyzed by scanning electron microscopy. The data from the mechanical tests and hardness were subjected to a two-and three-way ANOVA and Tukey's test (alpha = 0.05). The mean values of mechanical properties were not affected by the argon gas purity. Higher UTS, PL and VHN, and lower EL were observed for Ti-6Al-4V. The microhardness was not influenced by the argon gas purity. The industrial argon gas can be used to cast cp Ti and Ti-6Al-4V.

  9. Kevlar fiber-epoxy adhesion and its effect on composite mechanical and fracture properties by plasma and chemical treatment

    SciTech Connect

    Shyu, S.S.; Wu, S.R.; Sheu, G.S.

    1996-12-31

    Kevlar 49 fibers were surface modified by gas (ammonia, oxygen, and water vapor) plasmas etching and chlorosulfonation and subsequent reaction with some reagents (glycine, deionized water, ethylenediamine, and 1-butanol) to improve the adhesion to epoxy resin. After these treatments, the changes in fiber topography, chemical compositions of the fiber surfaces and the surface functional groups introduced to the surface of fibers were identified by SEM XPS and static SIMS. Interlaminar shear strength (ILSS) and T-peel strength between the fiber and epoxy resin were markedly improved by gas plasma and chlorosulfonation (0.1% and 0.25% ClSO{sub 3}H at 30 s). However, it is clear from the similar G{sub IC} values of the treated and untreated fiber composites that the fiber/matrix interfacial bond strength is only a minor contributor to G{sub IC}. SEM was also used to study the surface topography of the fracture surfaces of composites in T-peel test.

  10. Characterizing Hydraulic Properties and Ground-Water Chemistry in Fractured-Rock Aquifers: A User's Manual for the Multifunction Bedrock-Aquifer Transportable Testing Tool (BAT3)

    USGS Publications Warehouse

    Shapiro, Allen M.

    2007-01-01

    packers, the submersible pump, and other downhole components to land surface. Borehole geophysical logging must be conducted prior to deploying the Multifunction BAT3 in bedrock boreholes. In particular, it is important to identify the borehole diameter as a function of depth to avoid placing the packers over rough sections of the borehole, where they may be damaged during inflation. In addition, it is advantageous to identify the location of fractures intersecting the borehole wall, for example, using an acoustic televiewer log or a borehole camera. A knowledge of fracture locations is helpful in designing the length of the test interval and the locations where hydraulic tests and geochemical sampling are to be conducted. The Multifunction BAT3 is configured to conduct both fluid-injection and fluid-withdrawal tests. Fluid-injection tests are used to estimate the hydraulic properties of low-permeability fractures intersecting the borehole. The lower limit of the transmissivity that can be estimated using the configuration of the Multifunction BAT3 described in this report is approximately 10-3 square feet per day (ft2/d). Fluid-withdrawal tests are used to collect water samples for geochemical analyses and estimate the hydraulic properties of high-permeability fractures intersecting the borehole. The Multifunction BAT3 is configured with a submersible pump that can support pumping rates ranging from approximately 0.05 to 2.5 gallons per minute, and the upper limit of the of the transmissivity that can be estimated is approximately 104 ft2/d. The Multifunction BAT3 also can be used to measure the ambient hydraulic head of a section of a bedrock borehole, and to conduct single-hole tracer tests by injecting and later withdrawing a tracer solution.

  11. Galeazzi fracture.

    PubMed

    Atesok, Kivanc I; Jupiter, Jesse B; Weiss, Arnold-Peter C

    2011-10-01

    Galeazzi fracture is a fracture of the radial diaphysis with disruption at the distal radioulnar joint (DRUJ). Typically, the mechanism of injury is forceful axial loading and torsion of the forearm. Diagnosis is established on radiographic evaluation. Underdiagnosis is common because disruption of the ligamentous restraints of the DRUJ may be overlooked. Nonsurgical management with anatomic reduction and immobilization in a long-arm cast has been successful in children. In adults, nonsurgical treatment typically fails because of deforming forces acting on the distal radius and DRUJ. Open reduction and internal fixation is the preferred surgical option. Anatomic reduction and rigid fixation should be followed by intraoperative assessment of the DRUJ. Further intraoperative interventions are based on the reducibility and postreduction stability of the DRUJ. Misdiagnosis or inadequate management of Galeazzi fracture may result in disabling complications, such as DRUJ instability, malunion, limited forearm range of motion, chronic wrist pain, and osteoarthritis.

  12. Pediatric Thighbone (Femur) Fracture

    MedlinePlus

    ... fractures in infants under 1 year old is child abuse. Child abuse is also a leading cause of thighbone fracture ... contact sports • Being in a motor vehicle accident • Child abuse Types of Femur Fractures (Classification) Femur fractures vary ...

  13. Effect of heat treatment on the structure, properties and fracture of Nd:YAG laser welded Ti-14. 8 wt% Al-21. 3 wt% Nb

    SciTech Connect

    Baeslack, W.A. III ); Cieslak, M.J. )

    1989-05-01

    A recent investigation by the authors showed that pulsed Nd:YAG laser welding can produce defect-free, comparatively ductile weldments in a Ti-14.8 wt% Al-21.3 wt% Nb titanium aluminide. The achievement of a bend ductility across the weldment equivalent to that of the {alpha}/{beta} processed base material was attributed to the effect of high laser weld cooling rates in suppressing {beta} decomposition to a brittle {alpha}{sub 2} microstructure and instead promoting the formation of an ordered {beta} superlattice (B2,CsCl type). Proposed aerospace applications of {alpha}{sub 2} titanium aluminides will require excursions to elevated temperatures approaching 600{degrees}C. Exposure to such thermal conditions even for relatively short durations would be expected to promote decomposition of the metastable weld fusion and heat-affected zone (HAZ) microstructures, thereby altering their mechanical properties. The purpose of the study presented in this paper was to investigate the influence of postweld heat treatment at 565{degrees}C on {beta} decomposition in the Nd:YAG laser weld fusion zone and the resulting microstructure, mechanical properties and fracture characteristics.

  14. Mechanical and transport properties of rocks at high temperatures and pressures. Task II: fracture permeability of crystalline rocks as a function of temperature, pressure, and hydrothermal alteration

    SciTech Connect

    Not Available

    1981-01-01

    The primary objective is to measure and understand the variation of the fracture permeability of quartzite subjected to hydrothermal conditions. Pore fluids will consist of distilled water and aqueous Na/sub 2/CO/sub 3/ solutions at temperatures to 250/sup 0/C, fluid pressures to 20 MPa and effective normal stresses to 70 MPa. Fluid flow rates will be controllable to rates at least as small as 0.2 ml/day (approx. 4 fracture volumes). Experiments are designed to assess what role, if any, pressure solution may play at time scales of those of the experiments (less than or equal to 2 weeks). Secondary objectives are: (1) continue simulated fracture studies, incorporating inelastic deformation into model and characterize the nature of inelastic deformation occurring on loaded tensile fractures in quartzite; (2) continue dissolution experiment, with emphasis on dissolution modification of tensile fracture surfaces on quartzite; and (3) study natural fractures in a quartzite exhibiting hydrothermal dissolution features.

  15. Fluid Compressibility Effects during Hydraulic Fracture: an Opportunity for Gas Fracture Revival

    NASA Astrophysics Data System (ADS)

    Mighani, S.; Boulenouar, A.; Moradian, Z.; Evans, J. B.; Bernabe, Y.

    2015-12-01

    Hydraulic fracturing results when internal pore pressure is increased above a critical value. As the fracture extends, the fluid flows to the crack tip. The fracturing process depends strongly on the physical properties of both the porous solid and the fluid (e.g. porosity and elastic moduli for the solid, viscosity and compressibility for the fluid). It is also affected by the in-situ stress and pore pressure conditions. Here, we focus on the effect of fluid properties on hydraulic fracturing under conventional triaxial loading. Cylinders of Solnhofen limestone (a fine-grained, low permeability rock) were prepared with a central borehole through which different pressurized fluids such as oil, water or argon, were introduced. Preliminary experiments were performed using a confining pressure of 5 MPa and axial stress of 7 MPa. Our goal was to monitor fracture extension using strain gauges, acoustic emissions (AE) recording and ultrasonic velocity measurements. We also tried to compare the data with analytical models of fracture propagation. Initial tests showed that simple bi-wing fractures form when the fracturing fluid is relatively incompressible. With argon as pore fluid, a complex fracture network was formed. We also observed that the breakdown pressure was higher with argon than with less compressible fluids. After fracturing occurred, we cycled fluid pressure for several times. During the first cycles, re-opening of the fracture was associated with additional propagation. In general, it took 4 cycles to inhibit further propagation. Analytical models suggest that initial fractures occurring with compressible fluids tend to stabilize. Hence, formation and extension of additional fractures may occur, leading to a more complex morphology. Conversely, fractures formed by incompressible fluids remain critically stressed as they extend, thus producing a simple bi-wing fracture. Using compressible fracturing fluids could be a suitable candidate for an efficient

  16. Arcuate Fractures

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site]

    In the upper left corner of this VIS image are a series of fractures. Where the fractures are exposed on the surface it is impossible to tell the plane of the fracture; however where the fractures are visible in the cliff wall it is possible to see that the fractures dip to the north. This image shows part of the caldera of Tharsis Tholus.

    Image information: VIS instrument. Latitude 1.7, Longitude 176.5 East (183.5 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  17. Development of Reservoir Characterization Techniques and Production Models for Exploiting Naturally Fractured Reservoirs

    SciTech Connect

    Wiggins, Michael L.; Brown, Raymon L.; Civan, Frauk; Hughes, Richard G.

    2001-08-15

    Research continues on characterizing and modeling the behavior of naturally fractured reservoir systems. Work has progressed on developing techniques for estimating fracture properties from seismic and well log data, developing naturally fractured wellbore models, and developing a model to characterize the transfer of fluid from the matrix to the fracture system for use in the naturally fractured reservoir simulator.

  18. Wave Propagation in Isotropic Media with Two Orthogonal Fracture Sets

    NASA Astrophysics Data System (ADS)

    Shao, S.; Pyrak-Nolte, L. J.

    2016-10-01

    Orthogonal intersecting fracture sets form fracture networks that affect the hydraulic and mechanical integrity of a rock mass. Interpretation of elastic waves propagated through orthogonal fracture networks is complicated by guided modes that propagate along and between fractures, by multiple internal reflections, as well as by scattering from fracture intersections. The existence of some or all of these potentially overlapping modes depends on local stress fields that can preferentially close or open either one or both sets of fractures. In this study, an acoustic wave front imaging system was used to examine the effect of bi-axial loading conditions on acoustic wave propagation in isotropic media containing two orthogonal fracture sets. From the experimental data, orthogonal intersecting fracture sets support guided waves that depend on fracture spacing and fracture-specific stiffnesses. In addition, fracture intersections have stronger effects on propagating wave fronts than merely the superposition of the effects of two independent fractures because of energy partitioning among transmitted/reflected waves, scattered waves and guided modes. Interpretation of the properties of fractures or fracture sets from seismic measurements must consider non-uniform fracture stiffnesses within and among fracture sets, as well as considering the striking effects of fracture intersections on wave propagation.

  19. Coupling fracture facies with in situ permeability measurements to generate stochastic simulations of tight carbonate aquifer properties: example from the Lower Cretaceous aquifer, Northern Provence, SE France

    NASA Astrophysics Data System (ADS)

    Bruna, Pierre-Olivier; Guglielmi, Yves; Viseur, Sophie; Lamarche, Juliette

    2015-04-01

    The relationships between fracture facies and permeability distribution have been explored using a well-constrained 3D implicit structural model of hemipelagic low porosity/low permeability carbonate from the Northern Provence region, SE France. Fracture and permeability facies were determined using an extensive dataset of 99 hydrogeological boreholes wells. Data processing was undertaken using a step-by-step approach, involving: i) identification of the fracture facies based on well logs detailing structure and stratigraphy ; ii) determination of permeability facies from the a priori correlation between the dimension of the hydraulic radius of influence (deduced from slug test analyses) and the type of reservoir heterogeneity (fissure, fracture, fault zone, etc.); iii) three dimensional plot of fracture and permeability facies in the geological model using a variographic analysis of data. Thirty-three sequential indicator simulations (SIS) were realised on both fracture and permeability facies. Finally, a connectivity algorithm was developed to compute the probability of connection between selected infiltration areas and the major aquifer springs via moderate-to high-permeability geological bodies. Key results are: i) fault zones have a greater role in controlling permeability facies distribution than on fracture facies repartition; ii) there is little correlation between permeability and fracture facies distributions ; iii) connectivity results highlight the compartmentalization of aquifers in the Cadarache area, the extensions of permeable geological bodies being limited by the N130 faults.

  20. A Quantitative Comparison of Fracture Attributes and Fracture Patterns: Insights From Deformation Bands and Basement-hosted Fractures

    NASA Astrophysics Data System (ADS)

    Awdal, A. H.; Healy, D.; Alsop, G.

    2012-12-01

    Fractures can act as conduits or barriers to fluid flow, and understanding the geometrical attributes of individual fractures and their patterns is a crucial step in quantifying their connectivity. The quantification of fracture attributes and fracture patterns from outcrop analogues can guide the construction of testable expressions for multidimensional scaling relationships. These relationships may offer a key to better fracture prediction in the subsurface. Deformation band and basement fracture datasets have been collected from selected outcrops with a variety of sub-horizontal and sub-vertical rock faces. Cataclastic deformation bands and their patterns have been mapped and quantified in outcrops of aeolian sandstones of the Entrada formation in SE Utah (USA) and Hopeman formation in Moray (Scotland). Basement-hosted fracture data has been collected from outcrops of Lewisian gneiss and Torridonian sandstone in Clachtoll (Scotland), and Moine gneiss and Devonian sandstone in Portskerra (Scotland). Fracture orientations and spacing have been measured from maps, sections and linear scanlines, and fracture intensity, density and mean trace lengths have all been estimated through the application of the circular scan window method. Fracture trace angles and lengths have been calculated from 2D maps and sections using custom image analysis software. In addition, we have quantified the geometrical attributes of lozenges and lenses, the area or volume of relatively undeformed rock situated between two strands of a composite deformation band. We have investigated the statistical trends among different lozenge and lens datasets (Goblin Valley, Hopeman, Bartlett Wash) and explored their potential correlation to other attributes of the fracture pattern and petrophysical properties. Quantitative statistical analysis of these natural fracture datasets from 3 approximately orthogonal planes will allow us to test multidimensional scaling relationships of fracture attributes

  1. Factors Controlling Wellbore Imaging of Fractures

    NASA Astrophysics Data System (ADS)

    Al-Fahmi, M. M.; Cartwright, J. A.

    2015-12-01

    There are many scientific and engineering methods in petroleum industry for collecting data about small fractures in subsurface. The acquired data is predominantly indirect, and constrained by the bounds of technology and the subtle nature of small fractures. Among the various data types, cores and wellbore images reliably provide the data to observe small fractures, and help characterize important fracture properties such as density, geometry and aperture. There is, however, a major uncertainty about how thorough is the illustration of the small fractures in the wellbore electrical images which are widely used instead of cutting core for practical and economical grounds. We present novel results to help with understanding the potential and limits of wellbore electrical imagers to detect small fractures. We compare and discuss observations from high-quality microresistivity images and their equivalent core samples that are obtained from sub-horizontal wells drilled into carbonate hydrocarbon reservoirs in eastern Arabia. We observed that the wellbore images give limited and inconsistent fracture sampling. The reduction in fracture sampling is related to the fracture nature that defies the imager-resolution capacity. We propose that the imaging capacity is constrained by: 1) degree of fracture roughness, 2) contrast between resistivity and conductivity of the geologic features, 3) effective stress action that is increasing and decreasing fracture aperture, and 4) fracture intake of drilling fluids under a variable fluid pressure balancing between wellbore and reservoir. The wellbore imaging outcomes influence fracture studies, particularly the areas of measuring static and dynamic properties of reservoir fractures and estimating trends and magnitudes of in situ stress.

  2. a Fractal Network Model for Fractured Porous Media

    NASA Astrophysics Data System (ADS)

    Xu, Peng; Li, Cuihong; Qiu, Shuxia; Sasmito, Agus Pulung

    2016-04-01

    The transport properties and mechanisms of fractured porous media are very important for oil and gas reservoir engineering, hydraulics, environmental science, chemical engineering, etc. In this paper, a fractal dual-porosity model is developed to estimate the equivalent hydraulic properties of fractured porous media, where a fractal tree-like network model is used to characterize the fracture system according to its fractal scaling laws and topological structures. The analytical expressions for the effective permeability of fracture system and fractured porous media, tortuosity, fracture density and fraction are derived. The proposed fractal model has been validated by comparisons with available experimental data and numerical simulation. It has been shown that fractal dimensions for fracture length and aperture have significant effect on the equivalent hydraulic properties of fractured porous media. The effective permeability of fracture system can be increased with the increase of fractal dimensions for fracture length and aperture, while it can be remarkably lowered by introducing tortuosity at large branching angle. Also, a scaling law between the fracture density and fractal dimension for fracture length has been found, where the scaling exponent depends on the fracture number. The present fractal dual-porosity model may shed light on the transport physics of fractured porous media and provide theoretical basis for oil and gas exploitation, underground water, nuclear waste disposal and geothermal energy extraction as well as chemical engineering, etc.

  3. Mechanical and transport properties of rocks at high temperatures and pressures. Task I, the physical nature of fracturing at depth. Technical progress report No. 1, 1 March 1980-30 November 1980

    SciTech Connect

    Carter, N.L.

    1980-12-15

    Research progress is reported in the following areas: (1) the delineation of the boundary separating elastic-brittle and transient-1 semibrittle behavior of granite and of its volcanic and metamorphic equivalents, rhyolite and granite gneiss; (2) the variation of fracture permeability in Sioux Quartzite, Westerly Granite and a fine-1 grained gabbro as a function of effective pressure and hydrothermal alterations; and (3) determine the mechanical properties of selected rocks at high temperatures and pressures. (ACR)

  4. Fracture toughness and compressive properties of cancellous bone at the head of the femur and relationships to non-invasive skeletal assessment measurements.

    PubMed

    Cook, R B; Curwen, C; Tasker, T; Zioupos, P

    2010-11-01

    Osteoporosis defines a causal relationship between reduced bone density, reduced mechanical competence of the bone tissue of the sufferers and concomitantly an increased risk of fracture in life. The aims of the present study is: (1) to provide further evidence to support the use of Quantitative Ultrasound (QUS) results from peripheral sites to provide a prediction of the density of the proximal femur; and (2) to provide rational evidence for the well-proven ability of QUS to predict directly 'risk of fracture'. 20 femoral heads were obtained from 15 Caucasian females and 5 Caucasian males undergoing emergency surgery for a fractured neck of femur. QUS investigations of the calcaneus, proximal phalanx, distal radius and mid-shaft tibia were undertaken on the donors with 72h of surgery. 128 fracture toughness samples and 20 compression cores were manufactured and tested. Significant relationships were found between QUS parameters determined in vivo and the apparent density (g/cm(3)) of the tissue at the proximal femur and both the fracture toughness and strength determined in vitro from the same donor individual. In this study we relate QUS results obtained in vivo to the actual apparent density of bone tissue from the proximal femur, donated by the same individual, and the fracture toughness and compressive strength. The study demonstrates the ability of QUS investigations at peripheral sites to accurately predict the density of bone from the proximal femur and provides evidence to support the use of QUS to predict the 'risk of fracture' directly.

  5. Wave Propagation in Fractured Anisotropic Media

    NASA Astrophysics Data System (ADS)

    Shao, S.; Pyrak-Nolte, L. J.

    2012-12-01

    Discontinuities such as fractures, joints and faults occur in the Earth's crusts in a variety of rock types. While much theoretical, experimental and computational research have examined seismic wave propagation in fractured isotropic rock, few experimental studies have investigated seismic wave propagation in fractured anisotropic media. The co-existence of fractures and layers can complicate the interpretation of seismic properties because of the discrete guided modes that propagate along or are confined by the fractures. In this study, we use seismic arrays and acoustic wavefront imaging techniques to examine the competing sources of seismic anisotropy from fractures and from layers. Samples with textural anisotropy (100 mm x 100 mm x 100 mm) were fabricated from garolite, an epoxy - cloth laminate, with layer thickness 0f ~ 0.5 mm. Two sets of fractured samples were fabricated: (1) two single fractured samples with one fracture either parallel or (and) perpendicular to layers, and (2) four multi-fractured samples with 5 parallel fractures oriented either parallel, 30 degrees, 60 degrees or perpendicular to the layers. An intact sample containing no fractures was used as a standard orthorhombic medium for reference. Seismic arrays were used on the first set of samples to measure bulk waves and fracture interface waves as a function of stress. The seismic array contained two compressional and five shear-wave source-receiver pairs with a central frequency of 1 MHz. Shear wave transducers were polarized both perpendicular and parallel to the layering as well as to the fracture. Measurements were made for a range of stresses (0.4 - 4MPa). From these measurements it was observed that a fractured layered medium appears more isotropic or anisotropic than the orthorhombic background, depending on the orientation of the fracture relative to layers. The matrix anisotropy was recovered by increasing the normal stress on a fracture (i.e., by closing the fracture). For the

  6. Fracture property and quantitative strain evaluation of hetero-epitaxial single crystal 3C-SiC membrane

    NASA Astrophysics Data System (ADS)

    Anzalone, R.; D'Arrigo, G.; Camarda, M.; Piluso, N.; La Via, F.

    2014-03-01

    The following paper explores the development of a combined bulge test/micro-Raman analysis. This analysis, together with a refined load-deflection model (valid in both small and large deformation regimes, defined as the regimes in which the ratio between membrane deflection and width is smaller or larger than 1:10), allowed the determination of the elastic and optical properties of high quality single-crystal 3C-SiC squared membranes. Specifically we have evaluated the breaking strain of the membranes by measuring the breaking pressure for various membrane widths. The relation between the shift of the Raman Transverse Optical (TO) mode and the total residual strain (Δa/a) has been determined by measuring the TO shift for different membrane deflections. This relation, which allows determination of the residual strain by simply measuring the TO shift, was known only for thick samples (Olego et al) and high-oriented (100) thin films (Rohmfeld et al). Finally, we have calculated the TO stress-free value of high-quality thin single-crystal 3C-SiC/Si(100) films as 796.71 ± 0.04 cm-1.

  7. Effect of fracture compliance on wave propagation within a fluid-filled fracture.

    PubMed

    Nakagawa, Seiji; Korneev, Valeri A

    2014-06-01

    Open and partially closed fractures can trap seismic waves. Waves propagating primarily within fluid in a fracture are sometimes called Krauklis waves, which are strongly dispersive at low frequencies. The behavior of Krauklis waves has previously been examined for an open, fluid-filled channel (fracture), but the impact of finite fracture compliance resulting from contacting asperities and porous fillings in the fracture (e.g., debris, proppants) has not been fully investigated. In this paper, a dispersion equation is derived for Krauklis wave propagation in a fracture with finite fracture compliance, using a modified linear-slip-interface model (seismic displacement-discontinuity model). The resulting equation is formally identical to the dispersion equation for the symmetric fracture interface wave, another type of guided wave along a fracture. The low-frequency solutions of the newly derived dispersion equations are in good agreement with the exact solutions available for an open fracture. The primary effect of finite fracture compliance on Krauklis wave propagation is to increase wave velocity and attenuation at low frequencies. These effects can be used to monitor changes in the mechanical properties of a fracture. PMID:24907784

  8. Effect of fracture compliance on wave propagation within a fluid-filled fracture.

    PubMed

    Nakagawa, Seiji; Korneev, Valeri A

    2014-06-01

    Open and partially closed fractures can trap seismic waves. Waves propagating primarily within fluid in a fracture are sometimes called Krauklis waves, which are strongly dispersive at low frequencies. The behavior of Krauklis waves has previously been examined for an open, fluid-filled channel (fracture), but the impact of finite fracture compliance resulting from contacting asperities and porous fillings in the fracture (e.g., debris, proppants) has not been fully investigated. In this paper, a dispersion equation is derived for Krauklis wave propagation in a fracture with finite fracture compliance, using a modified linear-slip-interface model (seismic displacement-discontinuity model). The resulting equation is formally identical to the dispersion equation for the symmetric fracture interface wave, another type of guided wave along a fracture. The low-frequency solutions of the newly derived dispersion equations are in good agreement with the exact solutions available for an open fracture. The primary effect of finite fracture compliance on Krauklis wave propagation is to increase wave velocity and attenuation at low frequencies. These effects can be used to monitor changes in the mechanical properties of a fracture.

  9. Radial head fracture - aftercare

    MedlinePlus

    Elbow fracture - radial head - aftercare ... to 2 weeks. If you have a small fracture and your bones did not move around much, ... to see a bone doctor (orthopedic surgeon). Some fractures require surgery to: Insert pins and plates to ...

  10. In situ tracer tests to determine retention properties of a block scale fracture network in granitic rock at the Aspö Hard Rock Laboratory, Sweden.

    PubMed

    Andersson, Peter; Byegård, Johan; Tullborg, Eva-Lena; Doe, Thomas; Hermanson, Jan; Winberg, Anders

    2004-06-01

    Experiments were conducted at the Aspö Hard Rock Laboratory in order to improve the understanding of radionuclide retention properties of fractured crystalline bedrock in the 10-100 m scale (TRUE Block Scale Project, jointly funded by ANDRA, ENRESA, Nirex, JNC, Posiva and SKB). A series of tracer experiments were performed using sorbing tracers in three different flow paths. The different flow paths had Euclidian lengths of 14, 17 and 33 m, respectively, and one to three water conducting structures. Four tests were performed using different cocktails made up of radioactive sorbing tracers (22,24Na+, 42K+, 47Ca2+, 85Sr2+, 83,86Rb+, 131,133Ba2+ and 134,137Cs+). For each tracer injection, the breakthrough of sorbing tracers was compared to the breakthrough of a conservative tracer, 82Br-, 131I-, HTO and 186ReO4-, respectively. In the two longer flow paths, no breakthrough of 83Rb+ and 137Cs+ was observed after 8 months of pumping. Selected tracer tests were subject to basic modelling in which a one-dimensional (1D) advection-dispersion model, including surface sorption, and an unlimited matrix diffusion were used for the interpretation of the results. The results of the modelling indicated that there is a slightly higher mass transfer into a highly porous material in the block-scale experiment compared with in situ experiments performed over shorter distances and significantly higher than what would have been expected from laboratory data obtained from studies of the interactions in nonaltered intact rock.

  11. In situ tracer tests to determine retention properties of a block scale fracture network in granitic rock at the Äspö Hard Rock Laboratory, Sweden

    NASA Astrophysics Data System (ADS)

    Andersson, Peter; Byegård, Johan; Tullborg, Eva-Lena; Doe, Thomas; Hermanson, Jan; Winberg, Anders

    2004-06-01

    Experiments were conducted at the Äspö Hard Rock Laboratory in order to improve the understanding of radionuclide retention properties of fractured crystalline bedrock in the 10-100 m scale (TRUE Block Scale Project, jointly funded by ANDRA, ENRESA, Nirex, JNC, Posiva and SKB). A series of tracer experiments were performed using sorbing tracers in three different flow paths. The different flow paths had Euclidian lengths of 14, 17 and 33 m, respectively, and one to three water conducting structures. Four tests were performed using different cocktails made up of radioactive sorbing tracers ( 22,24Na +, 42K +, 47Ca 2+, 85Sr 2+, 83,86Rb +, 131,133Ba 2+ and 134,137Cs +). For each tracer injection, the breakthrough of sorbing tracers was compared to the breakthrough of a conservative tracer, 82Br -, 131I -, HTO and 186ReO 4-, respectively. In the two longer flow paths, no breakthrough of 83Rb + and 137Cs + was observed after 8 months of pumping. Selected tracer tests were subject to basic modelling in which a one-dimensional (1D) advection-dispersion model, including surface sorption, and an unlimited matrix diffusion were used for the interpretation of the results. The results of the modelling indicated that there is a slightly higher mass transfer into a highly porous material in the block-scale experiment compared with in situ experiments performed over shorter distances and significantly higher than what would have been expected from laboratory data obtained from studies of the interactions in nonaltered intact rock.

  12. Electronics reliability fracture mechanics. Volume 2: Fracture mechanics

    NASA Astrophysics Data System (ADS)

    Kallis, J.; Duncan, L.; Buechler, D.; Backes, P.; Sandkulla, D.

    1992-05-01

    This is the second of two volumes. The other volume (WL-TR-92-3015) is 'Causes of Failures of Shop Replaceable Units and Hybrid Microcircuits.' The objective of the Electronics Reliability Fracture Mechanics (ERFM) program was to develop and demonstrate a life prediction technique for electronic assemblies, when subjected to environmental stresses of vibration and thermal cycling, based upon the mechanical properties of the materials and packaging configurations which make up an electronic system. The application of fracture mechanics to microscale phenomena in electronic assemblies was a pioneering research effort. The small scale made the experiments very difficult; for example, the 1-mil-diameter bond wires in microelectronic devices are 1/3 the diameter of a human hair. A number of issues had to be resolved to determine whether a fracture mechanics modelling approach is correct for the selected failures; specifically, the following two issues had to be resolved: What fraction of the lifetime is spent in crack initiation? Are macro fracture mechanics techniques, used in large structures such as bridges, applicable to the tiny structures in electronic equipment? The following structural failure mechanisms were selected for modelling: bondwire fracture from mechanical cycling; bondwire fracture from thermal (power) cycling; plated through hole (PTH) fracture from thermal cycling. The bondwire fracture test specimens were A1-1 percent Si wires, representative of wires used in the parts in the modules selected for detailed investigation in this program (see Vol. 1 of this report); 1-mil-diameter wires were tested in this program. The PTH test specimens were sections of 14-layer printed wiring boards of the type used.

  13. Fractured Surface

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Context image for PIA03084 Fractured Surface

    These fractures and graben are part of Gordii Fossae, a large region that has undergone stresses which have cracked the surface.

    Image information: VIS instrument. Latitude 16.6S, Longitude 234.3E. 18 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  14. Fracture mechanics validity limits

    NASA Technical Reports Server (NTRS)

    Lambert, Dennis M.; Ernst, Hugo A.

    1994-01-01

    Fracture behavior is characteristics of a dramatic loss of strength compared to elastic deformation behavior. Fracture parameters have been developed and exhibit a range within which each is valid for predicting growth. Each is limited by the assumptions made in its development: all are defined within a specific context. For example, the stress intensity parameters, K, and the crack driving force, G, are derived using an assumption of linear elasticity. To use K or G, the zone of plasticity must be small as compared to the physical dimensions of the object being loaded. This insures an elastic response, and in this context, K and G will work well. Rice's J-integral has been used beyond the limits imposed on K and G. J requires an assumption of nonlinear elasticity, which is not characteristic of real material behavior, but is thought to be a reasonable approximation if unloading is kept to a minimum. As well, the constraint cannot change dramatically (typically, the crack extension is limited to ten-percent of the initial remaining ligament length). Rice, et al investigated the properties required of J-type parameters, J(sub x), and showed that the time rate, dJ(sub x)/dt, must not be a function of the crack extension rate, da/dt. Ernst devised the modified-J parameter, J(sub M), that meets this criterion. J(sub M) correlates fracture data to much higher crack growth than does J. Ultimately, a limit of the validity of J(sub M) is anticipated, and this has been estimated to be at a crack extension of about 40-percent of the initial remaining ligament length. None of the various parameters can be expected to describe fracture in an environment of gross plasticity, in which case the process is better described by deformation parameters, e.g., stress and strain. In the current study, various schemes to identify the onset of the plasticity-dominated behavior, i.e., the end of fracture mechanics validity, are presented. Each validity limit parameter is developed in

  15. Natural fracture characterization using passive seismic illumination

    SciTech Connect

    Nihei, K.T.

    2003-01-08

    The presence of natural fractures in reservoir rock can significantly enhance gas production, especially in tight gas formations. Any general knowledge of the existence, location, orientation, spatial density, and connectivity of natural fractures, as well as general reservoir structure, that can be obtained prior to active seismic acquisition and drilling can be exploited to identify key areas for subsequent higher resolution active seismic imaging. Current practices for estimating fracture properties before the acquisition of surface seismic data are usually based on the assumed geology and tectonics of the region, and empirical or fracture mechanics-based relationships between stratigraphic curvature and fracturing. The objective of this research is to investigate the potential of multicomponent surface sensor arrays, and passive seismic sources in the form of local earthquakes to identify and characterize potential fractured gas reservoirs located near seismically active regions. To assess the feasibility of passive seismic fracture detection and characterization, we have developed numerical codes for modeling elastic wave propagation in reservoir structures containing multiple, finite-length fractures. This article describes our efforts to determine the conditions for favorable excitation of fracture converted waves, and to develop an imaging method that can be used to locate and characterize fractures using multicomponent, passive seismic data recorded on a surface array.

  16. Laser Excitation of a Fracture Source for Elastic Waves

    SciTech Connect

    Blum, Thomas E.; Wijk, Kasper van; Snieder, Roel; Willis, Mark E.

    2011-12-30

    We show that elastic waves can be excited at a fracture inside a transparent sample by focusing laser light directly onto this fracture. The associated displacement field, measured by a laser interferometer, has pronounced waves that are diffracted at the fracture tips. We confirm that these are tip diffractions from direct excitation of the fracture by comparing them with tip diffractions from scattered elastic waves excited on the exterior of the sample. Being able to investigate fractures - in this case in an optically transparent material - via direct excitation opens the door to more detailed studies of fracture properties in general.

  17. X-ray radiography of fracture flow and matrix imbibition

    SciTech Connect

    Roberts, J.J.; Lin, Wunan

    1995-10-27

    Knowledge of how water flows through unsaturated, fractured rock is critical for understanding and predicting the performance of a high- level nuclear waste repository. For instance, during gravity driven fracture flow, the distance that water can travel through a fracture network might be controlled by (1) the amount of water available, (2) the fracture aperture, (3) the capillary properties of the matrix, and (4) the saturation of the matrix. We have experimentally investigated fracture flow and fracture-matrix interactions using x- ray radiography to image some of the above factors and processes.

  18. Fracture and fatigue properties of Mo-Mo{sub 3}Si-Mo{sub 5}SiB{sub 2} refractory intermetallic alloys at ambient to elevated temperatures (25-1300 degrees Centigrade)

    SciTech Connect

    Choe, Heeman; Schneibel, J.H.; Ritchie, R.O.

    2002-08-01

    The need for structural materials with high-temperature strength and oxidation resistance coupled with adequate lower-temperature toughness for potential use at temperatures above {approx} 1000 degrees C has remained a persistent challenge in materials science. In this work, one promising class of intermetallic alloys is examined, namely boron-containing molybdenum silicides, with compositions in the range Mo (bal), 12-17 at. percentSi, 8.5 at. percentB, processed using both ingot (I/M) and powder (P/M) metallurgy methods. Specifically, the oxidation (''pesting''), fracture toughness and fatigue-crack propagation resistance of four such alloys, which consisted of {approx}21 to 38 vol. percent a-Mo phase in an intermetallic matrix of Mo3Si and Mo5SiB2 (T2), were characterized at temperatures between 25 degrees and 1300 degrees C. The boron additions were found to confer superior ''pest'' resistance (at 400 degrees to 900 degrees C) as compared to unmodified molybdenum silicides, such as Mo5Si3. Moreover , although the fracture and fatigue properties of the finer-scale P/M alloys were only marginally better than those of MoSi2, for the I/M processed microstructures with coarse distributions of the a-Mo phase, fracture toughness properties were far superior, rising from values above 7 MPa sqrt m at ambient temperatures to almost 12 MPa sqrt m at 1300 degrees C.

  19. San Juan Fracture Characterization Project: Status and current results

    SciTech Connect

    Majer, E.L.; Daley, T.M.; Myer, L.R.; Nihei, K.; Queen, J.; Sinton, J.; Murphy, J.; Fortuna, M.; Lynn, H.B.; Imhoff, M.A.; Wilson, R.

    2001-02-26

    The overall objectives of this report are to extend current state-of-the-art 3-D imaging to extract the optimal information for fracture quantification and to develop next generation capability in fracture imaging for true 3-D imaging of the static and dynamic fracture properties.

  20. Flow upscaling in propped fracture

    NASA Astrophysics Data System (ADS)

    Jasinski, Lukasz; Dabrowski, Marcin

    2016-04-01

    Proppants in combination with hydraulic fracturing are widely used to maintain the production of oil or gas from low permeability formations (i.e. shale rocks). There are also examples of proppants use in geothermal reservoirs. Flow patterns in propped fracture control transport processes and give information about fracture/matrix exchange surface. Our main motivation is to understand flow behavior in such structures using direct numerical simulations and to find a good upscaling technique to be able to investigate models on reservoir scale. We study fracture made of two parallel plane walls, where void space between them is filled with partial monolayer of proppant. As the fracture is affected by closing pressure, the proppant grains are squeezed between two opposite fracture walls which can change the grain shapes or embed the grains into impermeable rock matrix. To take this effect into account and simplify the geometry, the grains are approximated as cylinders. Imposed macroscopic pressure gradient invokes flow in such medium. As the flow is considered in the low Reynolds number regime, a stationary velocity flow field is obtained by solving the Stokes equations in 3D by means of finite element method. Void space between the grains is accurately discretized by using tetrahedral mesh. To reduce computational effort, the Stokes equation is reduced over the fracture aperture to 2D Stokes-Brinkman equation, which is further numerically solved and compared against numerical solution in 3D. Systematic flow calculations using 2D Stokes-Brinkman equation are performed for periodic domain and no slip boundary condition on the grain surface. Results are discussed in terms of effective properties as a function of geometrical parameters of the medium, such as proppant packing fraction and proppant grain diameter to fracture aperture ratio.

  1. Optimal scaling in ductile fracture

    NASA Astrophysics Data System (ADS)

    Fokoua Djodom, Landry

    This work is concerned with the derivation of optimal scaling laws, in the sense of matching lower and upper bounds on the energy, for a solid undergoing ductile fracture. The specific problem considered concerns a material sample in the form of an infinite slab of finite thickness subjected to prescribed opening displacements on its two surfaces. The solid is assumed to obey deformation-theory of plasticity and, in order to further simplify the analysis, we assume isotropic rigid-plastic deformations with zero plastic spin. When hardening exponents are given values consistent with observation, the energy is found to exhibit sublinear growth. We regularize the energy through the addition of nonlocal energy terms of the strain-gradient plasticity type. This nonlocal regularization has the effect of introducing an intrinsic length scale into the energy. We also put forth a physical argument that identifies the intrinsic length and suggests a linear growth of the nonlocal energy. Under these assumptions, ductile fracture emerges as the net result of two competing effects: whereas the sublinear growth of the local energy promotes localization of deformation to failure planes, the nonlocal regularization stabilizes this process, thus resulting in an orderly progression towards failure and a well-defined specific fracture energy. The optimal scaling laws derived here show that ductile fracture results from localization of deformations to void sheets, and that it requires a well-defined energy per unit fracture area. In particular, fractal modes of fracture are ruled out under the assumptions of the analysis. The optimal scaling laws additionally show that ductile fracture is cohesive in nature, i.e., it obeys a well-defined relation between tractions and opening displacements. Finally, the scaling laws supply a link between micromechanical properties and macroscopic fracture properties. In particular, they reveal the relative roles that surface energy and microplasticity

  2. Proximal fifth metatarsal fractures.

    PubMed

    Ramponi, Denise R

    2013-01-01

    The most common fracture of the foot is a fracture of the proximal fifth metatarsal. In general, there are 3 types of fractures involving the proximal fifth metatarsal area, including a proximal diaphyseal stress fracture, a Jones fracture, and an avulsion fracture of the tuberosity. Some fractures of the fifth metatarsal heal without difficulty, whereas some have the potential for nonunion or delayed healing. Each fracture has some variation in the anatomical location on the fifth metatarsal, the mechanism of injury, the radiographic findings, and the treatment plan. Avulsion fractures of the tuberosity often heal without difficulty, yet fractures distal to the area of insertion of the peroneus brevis tendon are prone to nonunion and delayed healing (). Differential diagnosis of a fifth metatarsal midfoot injury includes ankle sprains, midfoot sprains, plantar facial ruptures, peroneus tendon ruptures, and other foot fractures.

  3. Analysis of well test data---Application of probabilistic models to infer hydraulic properties of fractures. [Contains list of standardized terminology or nomenclatue used in statistical models

    SciTech Connect

    Osnes, J.D. ); Winberg, A.; Andersson, J.E.; Larsson, N.A. )

    1991-09-27

    Statistical and probabilistic methods for estimating the probability that a fracture is nonconductive (or equivalently, the conductive-fracture frequency) and the distribution of the transmissivities of conductive fractures from transmissivity measurements made in single-hole injection (well) tests were developed. These methods were applied to a database consisting of over 1,000 measurements made in nearly 25 km of borehole at five sites in Sweden. The depths of the measurements ranged from near the surface to over 600-m deep, and packer spacings of 20- and 25-m were used. A probabilistic model that describes the distribution of a series of transmissivity measurements was derived. When the parameters of this model were estimated using maximum likelihood estimators, the resulting estimated distributions generally fit the cumulative histograms of the transmissivity measurements very well. Further, estimates of the mean transmissivity of conductive fractures based on the maximum likelihood estimates of the model's parameters were reasonable, both in magnitude and in trend, with respect to depth. The estimates of the conductive fracture probability were generated in the range of 0.5--5.0 percent, with the higher values at shallow depths and with increasingly smaller values as depth increased. An estimation procedure based on the probabilistic model and the maximum likelihood estimators of its parameters was recommended. Some guidelines regarding the design of injection test programs were drawn from the recommended estimation procedure and the parameter estimates based on the Swedish data. 24 refs., 12 figs., 14 tabs.

  4. Experimental and Analytical Research on Fracture Processes in ROck

    SciTech Connect

    Herbert H.. Einstein; Jay Miller; Bruno Silva

    2009-02-27

    Experimental studies on fracture propagation and coalescence were conducted which together with previous tests by this group on gypsum and marble, provide information on fracturing. Specifically, different fracture geometries wsere tested, which together with the different material properties will provide the basis for analytical/numerical modeling. INitial steps on the models were made as were initial investigations on the effect of pressurized water on fracture coalescence.

  5. Probabilistic Simulation for Nanocomposite Fracture

    NASA Technical Reports Server (NTRS)

    Chamis, Christos C.

    2010-01-01

    A unique probabilistic theory is described to predict the uniaxial strengths and fracture properties of nanocomposites. The simulation is based on composite micromechanics with progressive substructuring down to a nanoscale slice of a nanofiber where all the governing equations are formulated. These equations have been programmed in a computer code. That computer code is used to simulate uniaxial strengths and fracture of a nanofiber laminate. The results are presented graphically and discussed with respect to their practical significance. These results show smooth distributions from low probability to high.

  6. Hydrogen fracture toughness tester completion

    SciTech Connect

    Morgan, Michael J.

    2015-09-30

    The Hydrogen Fracture Toughness Tester (HFTT) is a mechanical testing machine designed for conducting fracture mechanics tests on materials in high-pressure hydrogen gas. The tester is needed for evaluating the effects of hydrogen on the cracking properties of tritium reservoir materials. It consists of an Instron Model 8862 Electromechanical Test Frame; an Autoclave Engineering Pressure Vessel, an Electric Potential Drop Crack Length Measurement System, associated computer control and data acquisition systems, and a high-pressure hydrogen gas manifold and handling system.

  7. Optimized Design and Use of Induced Complex Fractures in Horizontal Wellbores of Tight Gas Reservoirs

    NASA Astrophysics Data System (ADS)

    Zeng, F. H.; Guo, J. C.

    2016-04-01

    Multistage hydraulic fracturing is being increasing use in the establishment of horizontal wells in tight gas reservoirs. Connecting hydraulic fractures to natural and stress-induced fractures can further improve well productivity. This paper investigates the fracture treatment design issues involved in the establishment of horizontal wellbores, including the effects of geologic heterogeneity, perforation parameters, fracturing patterns, and construction parameters on stress anisotropy during hydraulic fracturing and on natural fractures during hydraulic fracture propagation. The extent of stress reversal and reorientation was calculated for fractures induced by the creation of one or more propped fractures. The effects of stress on alternate and sequential fracturing horizontal well and on the reservoir's mechanical properties, including the spatial extent of stress reorientation caused by the opening of fractures, were assessed and quantified. Alternate sequencing of transverse fractures was found to be an effective means of enhancing natural fracture stimulation by allowing fractures to undergo less stress contrast during propagation. The goal of this paper was to present a new approach to design that optimizes fracturing in a horizontal wellbore from the perspectives of both rock mechanics and fluid production. The new design is a modified version of alternate fracturing, where the fracture-initiation sequence was controlled by perforation parameters with a staggered pattern within a horizontal wellbore. Results demonstrated that the modified alternate fracturing performed better than original sequence fracturing and that this was because it increased the contact area and promoted more gas production in completed wells.

  8. An investigation of fracture toughness, fatigue-crack growth, sustained-load flaw growth, and impact properties of three pressure vessel steels

    NASA Technical Reports Server (NTRS)

    Hudson, C. M.; Newman, J. C., Jr.; Lewis, P. E.

    1975-01-01

    The elastic fracture toughness of the three steels is shown to not decrease significantly with decreasing temperature from room temperature to about 244 K (-20 F.). The elastic fracture toughness of the three steels increased with increasing specimen width and thickness. The fatigue-crack-growth data for all three steels fall into relatively narrow scatter bands on plots of rate against stress-intensity range. An equation is shown to predict the upper bounds of the scatter bands reasonably well. Charpy impact energies decreased with decreasing temperature in the nominal temperature range from room temperature to 244 K (-20 F). The nil-ductility temperatures of the steels are discussed.

  9. Effect of osteoporosis medications on fracture healing.

    PubMed

    Hegde, V; Jo, J E; Andreopoulou, P; Lane, J M

    2016-03-01

    Antiosteoporotic medications are often used to concurrently treat a patient's fragility fractures and underlying osteoporosis. This review evaluates the existing literature from animal and clinical models to determine these drugs' effects on fracture healing. The data suggest that these medications may enhance bone healing, yet more thorough prospective studies are warranted. Pharmacologic agents that influence bone remodeling are an essential component of osteoporosis management. Because many patients are first diagnosed with osteoporosis when presenting with a fragility fracture, it is critical to understand how osteoporotic medications influence fracture healing. Vitamin D and its analogs are essential for the mineralization of the callus and may also play a role in callus formation and remodeling that enhances biomechanical strength. In animal models, antiresorptive medications, including bisphosphonates, denosumab, calcitonin, estrogen, and raloxifene, do not impede endochondral fracture healing but may delay repair due to impaired remodeling. Although bisphosphonates and denosumab delay callus remodeling, they increase callus volume and result in unaltered biomechanical properties. Calcitonin increases cartilage formation and callus maturation, resulting in improved biomechanical properties. Parathyroid hormone, an anabolic agent, has demonstrated promise in animal models, resulting in accelerated healing with increased callus volume and density, more rapid remodeling to mature bone, and improved biomechanical properties. Clinical data with parathyroid hormone have demonstrated enhanced healing in distal radius and pelvic fractures as well as postoperatively following spine surgery. Strontium ranelate, which may have both antiresorptive and anabolic properties, affects fracture healing differently in normal and osteoporotic bone. While there is no effect in normal bone, in osteoporotic bone, strontium ranelate increases callus bone formation, maturity, and

  10. Physical significance of interfaces on fracture growth

    SciTech Connect

    Wang, J.J.; Guo, Q. )

    1993-08-01

    Details of the interfaces between two geologic materials are normally neglected in predicting the growth of hydraulic fractures. In addition, perfect bonding is assumed across the interface. However, due to a combination of reasons, the perfect bonding assumption is violated to various degrees. Assessment for potential slippage is important to fracture-growth modeling. As a fracture approaches an interface, both mode I (for a fracture crossing the interface) and mode II (for a fracture extending in the interface) stress-intensity factors need to be evaluated. Should the interface properties be such that the mode I stress-intensity factor reach the critical value, the fracture will cross the interface. Should the converse happen and the mode II stress-intensity factor become critical, slippage along the interface will occur. If both the critical stress intensity factors are reached simultaneously, both fractures across the interface and slippage will occur. Good description of the interface material is needed to model the fracturing process. Methodology to model the physical significance of interfaces for calculating two-dimensional fracture growth includes descriptions of applications to oil/gas recovery and the injection of contaminants in isolated formations.

  11. Fractures of the forefoot.

    PubMed

    Mandracchia, Vincent J; Mandi, Denise M; Toney, Patris A; Halligan, Jennifer B; Nickles, W Ashton

    2006-04-01

    Fractures of the forefoot are common injuries of various causes. Although not crippling, forefoot fractures can be debilitating if they go undiagnosed or are mistreated. Whenever patients complain of foot pain with ambulation or difficulty ambulating, radiographs should be taken as part of a standard routine to assess for bony pathology. This article discusses the classification and treatment of metatarsal fractures, digital and sesamoid fractures, and open fractures about the forefoot.

  12. Fatigue properties for the fracture strength of columnar accessory minerals embedded within metamorphic tectonites: implications for stress magnitude in continental crust at the depth of the brittle-plastic transition zone

    NASA Astrophysics Data System (ADS)

    Kimura, N.; Iwashita, N.; Masuda, T.

    2009-04-01

    1. Introduction Previous studies have compiled yield-strength profiles of continental lithosphere based on the results of laboratory measurements and numerical calculations; however, yield-strength values remain poorly constrained, especially at depths below the brittle-plastic transition zone. Recent studies by the authors have refined the microboudin technique for estimating palaeostress magnitude in the deep crust (> 10 km depth). This technique has the potential to provide important information on stress levels in the deep continental crust, an environment to which available in situ stress measurements and palaeopiezometric methods cannot be applied. In applying the microboudinage technique, obtaining an estimate of the palaeostress magnitude requires knowledge of the fracture strength of columnar accessory minerals (e.g., tourmaline, amphibole, and epidote) that are subjected to brittle fracturing during plastic deformation of the surrounding matrix minerals. The absolute magnitude of fracture strength is known to show a marked reduction in the case of fatigue fracture. Fatigue fracture falls into two categories: static fatigue and cyclic fatigue. In the field of experimental rock deformation, stress corrosion by water molecules (static fatigue) is commonly invoked as the mechanism of fatigue fracture; however, evidence of both static and cyclic fatigue has been reported from studies of natural geological samples. The present study focused on the fatigue properties of columnar accessory minerals at high temperatures, with the aim of improving the accuracy of estimates of natural palaeostress magnitude at depth in the crust. 2. Constant stress-rate test A constant stress-rate test was performed to determine the influence of static fatigue on the strength of columnar accessory minerals. The test was conducted under three-point bending with a span distance of 10 mm. Temperature conditions and the crosshead speed were set in the ranges of ambient to 600°C, and 0

  13. A Spatial Clustering Approach for Stochastic Fracture Network Modelling

    NASA Astrophysics Data System (ADS)

    Seifollahi, S.; Dowd, P. A.; Xu, C.; Fadakar, A. Y.

    2014-07-01

    Fracture network modelling plays an important role in many application areas in which the behaviour of a rock mass is of interest. These areas include mining, civil, petroleum, water and environmental engineering and geothermal systems modelling. The aim is to model the fractured rock to assess fluid flow or the stability of rock blocks. One important step in fracture network modelling is to estimate the number of fractures and the properties of individual fractures such as their size and orientation. Due to the lack of data and the complexity of the problem, there are significant uncertainties associated with fracture network modelling in practice. Our primary interest is the modelling of fracture networks in geothermal systems and, in this paper, we propose a general stochastic approach to fracture network modelling for this application. We focus on using the seismic point cloud detected during the fracture stimulation of a hot dry rock reservoir to create an enhanced geothermal system; these seismic points are the conditioning data in the modelling process. The seismic points can be used to estimate the geographical extent of the reservoir, the amount of fracturing and the detailed geometries of fractures within the reservoir. The objective is to determine a fracture model from the conditioning data by minimizing the sum of the distances of the points from the fitted fracture model. Fractures are represented as line segments connecting two points in two-dimensional applications or as ellipses in three-dimensional (3D) cases. The novelty of our model is twofold: (1) it comprises a comprehensive fracture modification scheme based on simulated annealing and (2) it introduces new spatial approaches, a goodness-of-fit measure for the fitted fracture model, a measure for fracture similarity and a clustering technique for proposing a locally optimal solution for fracture parameters. We use a simulated dataset to demonstrate the application of the proposed approach

  14. Paratrooper's Ankle Fracture: Posterior Malleolar Fracture

    PubMed Central

    Young, Ki Won; Cho, Jae Ho; Kim, Hyung Seuk; Cho, Hun Ki; Lee, Kyung Tai

    2015-01-01

    Background We assessed the frequency and types of ankle fractures that frequently occur during parachute landings of special operation unit personnel and analyzed the causes. Methods Fifty-six members of the special force brigade of the military who had sustained ankle fractures during parachute landings between January 2005 and April 2010 were retrospectively analyzed. The injury sites and fracture sites were identified and the fracture types were categorized by the Lauge-Hansen and Weber classifications. Follow-up surveys were performed with respect to the American Orthopedic Foot and Ankle Society ankle-hindfoot score, patient satisfaction, and return to preinjury activity. Results The patients were all males with a mean age of 23.6 years. There were 28 right and 28 left ankle fractures. Twenty-two patients had simple fractures and 34 patients had comminuted fractures. The average number of injury and fractures sites per person was 2.07 (116 injuries including a syndesmosis injury and a deltoid injury) and 1.75 (98 fracture sites), respectively. Twenty-three cases (41.07%) were accompanied by posterior malleolar fractures. Fifty-five patients underwent surgery; of these, 30 had plate internal fixations. Weber type A, B, and C fractures were found in 4, 38, and 14 cases, respectively. Based on the Lauge-Hansen classification, supination-external rotation injuries were found in 20 cases, supination-adduction injuries in 22 cases, pronation-external rotation injuries in 11 cases, tibiofibular fractures in 2 cases, and simple medial malleolar fractures in 2 cases. The mean follow-up period was 23.8 months, and the average follow-up American Orthopedic Foot and Ankle Society ankle-hindfoot score was 85.42. Forty-five patients (80.36%) reported excellent or good satisfaction with the outcome. Conclusions Posterior malleolar fractures occurred in 41.07% of ankle fractures sustained in parachute landings. Because most of the ankle fractures in parachute injuries were

  15. Hydraulic-fracture propagation in layered rock: experimental studies of fracture containment

    SciTech Connect

    Teufel, L. W.; Clark, J. A.

    1981-01-01

    Fracture geometry is an important concern in the design of a massive hydraulic fracture treatment for improved natural gas recovery from tight gas sands. Possible prediction of vertical fracture growth and containment in layered rock requires an improved understanding of the parameters which may control fracture growth across layer interfaces. We have conducted laboratory hydraulic fracture experiments and elastic finite element studies which show that at least two distinct geologic conditions may inhibit or contain the vertical growth of hydraulic fractures in layered rock; (1) a weak interfacial shear strength of the layers and (2) a compressional increase in the minimum horizontal stress in the bounding layer. The second condition is more important and more likely to occur at depth. Variations in the horizontal stress can result from differences in elastic properties of individual layers in a layered rock sequence. A compressional increase in the minimum horizontal stress can occur in going from high shear modulus into low shear modulus layers.

  16. [Fractures of the forefoot].

    PubMed

    Richter, M

    2011-10-01

    Fractures of the forefoot are common and comprise approximately two thirds of all foot fractures. Forefoot fractures are caused by direct impact or the effect of indirect force. The forces exerted can range from repetitive minor load (stress fractures) to massive destructive forces (complex trauma). The clinical course in forefoot fractures is typically more favourable than in fractures of the mid- and hindfoot. The incidence of complications like infection or pseudarthrosis is low. Exceptions are rare fractures of the proximal shaft of the fifth metatarsal and the sesamoids with higher pseudarthrosis rates. Malunited metatarsal fractures can cause painful conditions that should even be treated operatively. Differences in structure and function of the different forefoot areas and specific fracture types require an adapted management of these special injuries.

  17. Epidemiology of fragility fractures.

    PubMed

    Friedman, Susan M; Mendelson, Daniel Ari

    2014-05-01

    As the world population of older adults-in particular those over age 85-increases, the incidence of fragility fractures will also increase. It is predicted that the worldwide incidence of hip fractures will grow to 6.3 million yearly by 2050. Fractures result in significant financial and personal costs. Older adults who sustain fractures are at risk for functional decline and mortality, both as a function of fractures and their complications and of the frailty of the patients who sustain fractures. Identifying individuals at high risk provides an opportunity for both primary and secondary prevention.

  18. Fracture and Medium Modeling, by Analizing Hidraulic Fracturing Induced Microseismicity

    NASA Astrophysics Data System (ADS)

    Gomez Alba, S.; Vargas Jiménez, C. A.

    2014-12-01

    Hydraulic fracturing is an essential technology for most unconventional hydrocarbon resources and many conventional ones as well. The primary limitation on the improvement and optimization of the fracturing process is the minimal access to observe the behavior of the fracture in the subsurface. Without direct observational evidence, hypothetical mechanisms must be assumed and then tested for their validity with indirect information such as wellbore measurements, indirect production and pressure behavior. One of the most important sources of information today is the relation made between micro seismic source mechanisms and fracture behavior. Hydraulic fractures induce some level of micro seismicity when the stress conditions in the Earth are altered by changes in stress during the operations. The result is the sudden movement between rock elements and the radiation of both compressional and shear energy in a seismic range that can be detected and recorded with sensitive receivers. The objective of this work is to provide reasonable information when applying inversion methods in order to estimate the vertical and horizontal spatial heterogeneities in medium and energy radiation distribution of microseisms while fracking operations. The method consist in record microseisms at a previous lineal array of stations (triaxial accelerometers) which are located close to the source coordinates and cover the area of study. The analysis clarify some ideas about what information can be gained from the micro seismic source data and according to the obtained results, what kind of comparisons and associations might be done to evaluate the fracking performance operation. Non uniformities in medium such as faults would be revealed by interpreted scattering coefficients. Fracture properties like distance, velocity and orientation would be also determined by analyzing energy radiation.

  19. Numerical Investigation of Fracture Propagation in Geomaterials

    NASA Astrophysics Data System (ADS)

    Newell, P.; Borowski, E.; Major, J. R.; Eichhubl, P.

    2015-12-01

    Fracture in geomaterials is a critical behavior that affects the long-term structural response of geosystems. The processes involving fracture initiation and growth in rocks often span broad time scales and size scales, contributing to the complexity of these problems. To better understand fracture behavior, the authors propose an initial investigation comparing the fracture testing techniques of notched three-point bending (N3PB), short rod (SR), and double torsion (DT) on geomaterials using computational analysis. Linear softening cohesive fracture modeling (LCFM) was applied using ABAQUS to computationally simulate the three experimental set-ups. By applying material properties obtained experimentally, these simulations are intended to predict single-trace fracture growth. The advantages and limitations of the three testing techniques were considered for application to subcritical fracture propagation taking into account the accuracy of constraints, load applications, and modes of fracture. This work is supported as part of the Geomechanics of CO2 Reservoir Seals, a DOE-NETL funded under Award Number DE-FOA-0001037. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  20. Infant skull fracture (image)

    MedlinePlus

    Skull fractures may occur with head injuries. Although the skull is both tough and resilient and provides excellent ... or blow can result in fracture of the skull and may be accompanied by injury to the ...

  1. Nasal fracture (image)

    MedlinePlus

    A nasal fracture is a break in the bone over the ridge of the nose. It usually results from a blunt ... and is one of the most common facial fracture. Symptoms of a broken nose include pain, blood ...

  2. Metatarsal stress fractures - aftercare

    MedlinePlus

    The metatarsal bones are the long bones in your foot that connect your ankle to your toes. A stress fracture is a break in the bone that happens with repeated injury or stress. Stress fractures are caused ...

  3. Displaced patella fractures.

    PubMed

    Della Rocca, Gregory J

    2013-10-01

    Displaced patella fractures often result in disruption of the extensor mechanism of the knee. An intact extensor mechanism is a requirement for unassisted gait. Therefore, operative treatment of the displaced patella fracture is generally recommended. The evaluation of the patella fracture patient includes examination of extensor mechanism integrity. Operative management of patella fractures normally includes open reduction with internal fixation, although partial patellectomy is occasionally performed, with advancement of quadriceps tendon or patellar ligament to the fracture bed. Open reduction with internal fixation has historically been performed utilizing anterior tension band wiring, although comminution of the fracture occasionally makes this fixation construct inadequate. Supplementation or replacement of the tension band wire construct with interfragmentary screws, cerclage wire or suture, and/or plate-and-screw constructs may add to the stability of the fixation construct. Arthrosis of the patellofemoral joint is very common after healing of patella fractures, and substantial functional deficits may persist long after fracture healing has occurred.

  4. Percolation Theory and Modern Hydraulic Fracturing

    NASA Astrophysics Data System (ADS)

    Norris, J. Q.; Turcotte, D. L.; Rundle, J. B.

    2015-12-01

    During the past few years, we have been developing a percolation model for fracking. This model provides a powerful tool for understanding the growth and properties of the complex fracture networks generated during a modern high volume hydraulic fracture stimulations of tight shale reservoirs. The model can also be used to understand the interaction between the growing fracture network and natural reservoir features such as joint sets and faults. Additionally, the model produces a power-law distribution of bursts which can easily be compared to observed microseismicity.

  5. Hydraulic fracture design optimization

    SciTech Connect

    Lee, Tae-Soo; Advani, S.H.

    1992-01-01

    This research and development investigation, sponsored by US DOE and the oil and gas industry, extends previously developed hydraulic fracture geometry models and applied energy related characteristic time concepts towards the optimal design and control of hydraulic fracture geometries. The primary objective of this program is to develop rational criteria, by examining the associated energy rate components during the hydraulic fracture evolution, for the formulation of stimulation treatment design along with real-time fracture configuration interpretation and control.

  6. Hydraulic fracture design optimization

    SciTech Connect

    Lee, Tae-Soo; Advani, S.H.

    1992-06-01

    This research and development investigation, sponsored by US DOE and the oil and gas industry, extends previously developed hydraulic fracture geometry models and applied energy related characteristic time concepts towards the optimal design and control of hydraulic fracture geometries. The primary objective of this program is to develop rational criteria, by examining the associated energy rate components during the hydraulic fracture evolution, for the formulation of stimulation treatment design along with real-time fracture configuration interpretation and control.

  7. Clavicle fractures: individualizing treatment for fracture type.

    PubMed

    Housner, Jeffrey A; Kuhn, John E

    2003-12-01

    Clavicle fractures are common injuries in both children and adults. In most cases, the diagnosis can be made readily from the patient's history and physical examination. X-rays are helpful to confirm the diagnosis, to assess the severity of the fracture, and to follow interval healing. Most fractures are treated nonoperatively, and surgical intervention is typically reserved for unstable distal clavicle fractures. Nonoperative options involve either a sling-and-swathe or figure-of-eight splint. Return-to-play decisions should be individualized based on the age of the patient, location and severity of the fracture, degree of clinical and radiographic healing, and the sport in which the athlete will be participating.

  8. Poroelastic modeling of fracture-seismic wave interaction

    SciTech Connect

    Nakagawa, Seiji

    2008-08-15

    Rock containing a compliant, fluid-filled fracture can be viewed as one case of heterogeneous poroelastic media. When this fracture is subjected to seismic waves, a strong contrast in the elastic stiffness between the fracture itself and the background can result in enhanced grain-scale local fluid flow. Because this flow--relaxing the pressure building up within the fracture--can increase the dynamic compliance of the fracture and change energy dissipation (attenuation), the scattering of seismic waves can be enhanced. Previously, for a flat, infinite fracture, we derived poroelastic seismic boundary conditions that describe the relationship between a finite jump in the stress and displacement across a fracture, expressed as a function of the stress and displacement at the boundaries. In this paper, we use these boundary conditions to determine frequency-dependent seismic wave transmission and reflection coefficients. Fluid-filled fractures with a range of mechanical and hydraulic properties are examined. From parametric studies, we found that the hydraulic permeability of a fracture fully saturated with water has little impact on seismic wave scattering. In contrast, the seismic response of a partially water-saturated fracture and a heterogeneous fracture filled with compliant liquid (e.g., supercritical CO{sub 2}) depended on the fracture permeability.

  9. Fracture ventilation by surface winds

    NASA Astrophysics Data System (ADS)

    Nachshon, U.; Dragila, M. I.; Weisbrod, N.

    2011-12-01

    Gas exchange between the Earth subsurface and the atmosphere is an important mechanism, affecting hydrological, agricultural and environmental processes. From a hydrological aspect, water vapor transport is the most important process related to Earth-atmosphere gas exchange. In respect to agriculture, gas transport in the upper soil profile is important for soil aeration. From an environmental aspect, emission of volatile radionuclides, such as 3H, 14C and Rd from radioactive waste disposal facilities; volatile organic components from industrial sources and Rn from natural sources, all found in the upper vadose zone, can greatly affect public health when emissions occur in populated areas. Thus, it is vital to better understand gas exchange processes between the Earth's upper crust and atmosphere. Four major mechanisms are known to transfer gases between ground surface and atmosphere: (1) Diffusion; (2) Pressure gradients between ground pores and atmosphere due to changes in barometric pressure; (3) Density-driven gas flow in respond to thermal gradients in the ground; and (4) Winds above the ground surface. Herein, the wind ventilation mechanism is studied. Whereas the wind's impact on ground ventilation was explored in several studies, the physical mechanisms governing this process were hardly quantified or characterized. In this work the physical properties of fracture ventilation due to wind blowing along land surface were explored and quantified. Both field measurements and Hele-Shaw experiments under controlled conditions in the laboratory were used to study this process. It was found that winds in the range of 0.3 m/s result in fracture ventilation down to a depth of 0.2 m. As wind velocity increases, the depth of the ventilation inside the fracture increases respectively, in a linear manner. In addition, the fracture aperture also affects the depth of ventilation, which grows as fracture aperture increases. For the maximal examined aperture of 2 cm and wind

  10. Osteoporotic vertebral fractures redux.

    PubMed

    Lentle, B C; Gordon, P; Ward, L

    2008-02-01

    Osteoporosis remains an important cause of morbidity and mortality especially in the elderly. This fact is largely due to fractures of the proximal femur and spine. As recently recognized, vertebral fractures are as much a threat to health and longevity as fractures of the proximal femur. In recent decades, the development of tools to evaluate fracture risk as well as medications to treat osteoporosis has altered the management of people who are at fracture risk. At the same time identification and management procedures concerning spinal fracturing are not very clear. Besides there is not even clear consensus about what exactly constitutes a vertebral fracture, particularly those of minor degree. While height loss is a simple and valuable tool to detect vertebral fractures, it is neither sensitive nor specific enough to replace radiographs. Some 65% of fractures cause no symptoms. Often vertebral fractures are misdiagnosed, especially if they have occurred silently and if the opportunity for diagnosis arises fortuitously. It is to the patient's benefit that radiologists report and physicians identify vertebral fractures evident on a chest or other radiograph, no matter how incidental to the immediate clinical indication for the examination. Technological evolution now allows dual-energy x-ray absorptiometry machines to be used to take spine images while doing a densitometry. The images are adequate, even if not of high radiographic quality, and, more important, the patient undergoes a smaller radiation dose than with conventional spinal radiographs. Such technology may promote fracture recognition. The recognition of vertebral fractures, as well as the prevention and treatment of further fractures, will likely do much to reduce both the burden of osteoporosis-related morbidity and mortality, as well as fracture-related costs to healthcare systems.

  11. Reactivation of a Propped Hydraulic Fracture

    NASA Astrophysics Data System (ADS)

    Sarvaramini, E.; Garagash, D.

    2014-12-01

    The problem of massive fluid injection into a pre-existing fracture has many applications in petroleum industry including underground liquid waste disposal and waterflooding to increase recovery from a hydrocarbon reservoir. Understanding the conditions leading to the re-activation of pre-existing fractures and ensuing propagation is critical for a successful injection project design, and it may also help to mitigate potential environmental hazards, such as contamination of underground aquifers and induced seismicity. The problem of injection of a low viscosity fluid into a permeable formation can be distinguished from conventional hydraulic fracture by the mechanism of fluid leak-off. In conventional fracturing, high viscosity and cake building properties of injected fluid limit leak-off to a 1-D boundary layer incasing the crack. In the case of injection of low viscosity fluid into a fracture, leak-off and related pore fluid diffusion will take place over wider range of scales, from 1-D to 2 or 3-D. We consider a pre-existing stationary propped hydraulic fracture with constrained height into which a fluid is injected under constant flow rate. Although the net effective stress on the crack is initially compressive, the proppant keeps the crack open. It is worthwhile to note that during injection and related pressurization of a propped crack, the fracture breakdown is to be achieved prior to the fracture re-opening. Therefore, the effect of the change of the propped fracture storage on the pressurization dynamics can be neglected. The objective of this work is to study the transient pressurization and the onset of the propagation for a propped fracture. To the end, we formulate and solve a general problem of injection into a fracture accounting for viscous dissipation (i.e. non-uniform pressure distribution). We quantify how the fracture breakdown condition depends upon the rock and fluid properties, the in-situ stress and the fluid injection rate. We also

  12. Scratching as a Fracture Process: From Butter to Steel

    NASA Astrophysics Data System (ADS)

    Akono, A.-T.; Reis, P. M.; Ulm, F.-J.

    2011-05-01

    We present results of a hybrid experimental and theoretical investigation of the fracture scaling in scratch tests and show that scratching is a fracture dominated process. Validated for paraffin wax, cement paste, Jurassic limestone and steel, we derive a model that provides a quantitative means to relate quantities measured in scratch tests to fracture properties of materials at multiple scales. The scalability of scratching for different probes and depths opens new venues towards miniaturization of our technique, to extract fracture properties of materials at even smaller length scales.

  13. Proximal humerus fractures.

    PubMed

    Price, Matthew C; Horn, Pamela L; Latshaw, James C

    2013-01-01

    Proximal humerus fractures are among the most common fractures associated with osteoporosis. With an aging population, incidence of these fractures will only increase. The proximal humerus not only forms the lateral portion of the shoulder articulation but also has significant associations with musculoskeletal and neurovascular structures. As a result, fractures of the proximal humerus can significantly impact not only the function of the shoulder joint, but the health and function of the entire upper extremity as well. Understanding of these fractures, the management options, and associated nursing care, can help reduce morbidity rate and improve functional outcomes.

  14. Talus fractures: surgical principles.

    PubMed

    Rush, Shannon M; Jennings, Meagan; Hamilton, Graham A

    2009-01-01

    Surgical treatment of talus fractures can challenge even the most skilled foot and ankle surgeon. Complicated fracture patterns combined with joint dislocation of variable degrees require accurate assessment, sound understanding of principles of fracture care, and broad command of internal fixation techniques needed for successful surgical care. Elimination of unnecessary soft tissue dissection, a low threshold for surgical reduction, liberal use of malleolar osteotomy to expose body fracture, and detailed attention to fracture reduction and joint alignment are critical to the success of treatment. Even with the best surgical care complications are common and seem to correlate with injury severity and open injuries. PMID:19121756

  15. MULTI-PHASE FRACTURE-MATRIX INTERACTIONS UNDER STRESS CHANGES

    SciTech Connect

    A.S. Grader; D. Elsworth; P.M. Halleck; F. Alvarado; A. Alajmi; Z. Karpyn; N. Mohammed; S. Al-Enezi

    2005-06-15

    The main objectives of this project are to quantify the changes in fracture porosity and multiphase transport properties as a function of confining stress. These changes will be integrated into conceptual and numerical models that will improve our ability to predict and optimize fluid transport in fractured system. This report details our progress on: (a) developing the direct experimental measurements of fracture aperture and topology and fluid occupancy using high-resolution x-ray micro-tomography, (b) quantifying the effect of confining stress on the distribution of fracture aperture, and (c) characterization of shear fractures and their impact on multi-phase flow. The three-dimensional surface that describes the large-scale structure of the fracture in the porous medium can be determined using x-ray micro-tomography with significant accuracy. Several fractures have been scanned and the fracture aperture maps have been extracted. The success of the mapping of fracture aperture was followed by measuring the occupancy of the fracture by two immiscible phases, water and decane, and water and kerosene. The distribution of fracture aperture depends on the effective confining stress on the nature of the rock and the type and distribution of the asperities that keep the fracture open. Fracture apertures at different confining stresses were obtained by micro-tomography covering a range of about two thousand psig. Initial analysis of the data shows a significant aperture closure with increase in effective confining stress. Visual descriptions of the process are shown in the report while detailed analysis of the behavior of the distribution of fracture aperture is in progress. Both extensional and shear fractures are being considered. The initial multi-phase flow tests were done in extensional fractures. Several rock samples with induced shear fracture are being studied, and some of the new results are presented in this report. These samples are being scanned in order to

  16. MULTI-PHASE FRACTURE-MATRIX INTERACTIONS UNDER STRESS CHANGES

    SciTech Connect

    A.S. Grader; D. Elsworth; P.M. Halleck; F. Alvarado; A. Alajmi; Z. Karpyn; N. Mohammed; S. Al-Enezi

    2005-06-15

    The main objectives of this project are to quantify the changes in fracture porosity and multiphase transport properties as a function of confining stress. These changes will be integrated into conceptual and numerical models that will improve our ability to predict and optimize fluid transport in fractured system. This report details our progress on: (a) developing the direct experimental measurements of fracture aperture and topology and fluid occupancy using high-resolution x-ray micro-tomography, (b) quantifying the effect of confining stress on the distribution of fracture aperture, and (c) characterization of shear fractures and their impact on multi-phase flow. The three-dimensional surface that describes the large-scale structure of the fracture in the porous medium can be determined using x-ray micro-tomography with significant accuracy. Several fractures have been scanned and the fracture aperture maps have been extracted. The success of the mapping of fracture aperture was followed by measuring the occupancy of the fracture by two immiscible phases, water and decane, and water and kerosene. The distribution of fracture aperture depends on the effective confining stress on the nature of the rock and the type and distribution of the asperities that keep the fracture open. Fracture apertures at different confining stresses were obtained by micro-tomography covering a range of about two thousand psig. Initial analysis of the data shows a significant aperture closure with increase in effective confining stress. Visual descriptions of the process are shown in the report while detailed analysis of the behavior of the distribution of fracture aperture is in progress. Both extensional and shear fractures are being considered. The initial multi-phase flow tests were done in extensional fractures. Several rock samples with induced shear fracture are being studies, and some of the new results are presented in this report. These samples are being scanned in order to

  17. Epidemiology of clavicle fractures.

    PubMed

    Postacchini, Franco; Gumina, Stefano; De Santis, Pierfrancesco; Albo, Francesco

    2002-01-01

    An epidemiologic study of 535 isolated clavicle fractures treated in a hospital of a large metropolis during an 11-year period was performed. Data regarding patient's age and sex, side involved, mechanism of injury, and season in which the fracture occurred were obtained from the clinical records. Radiographic classification was performed with the Allman system. Clavicle fractures represented 2.6% of all fractures and 44% of those in the shoulder girdle. Most patients were men (68%), and the left side was involved in 61% of cases. Fractures of the middle third of the clavicle, which were the most common (81%), were displaced in 48% of cases and comminuted in 19%. Fractures of the medial third were the least common (2%). The prevalence of midclavicular fractures was found to decrease progressively with age, starting from the first decade of life when they represented 88.2% of all clavicle fractures and were undisplaced in 55.5% of cases. In adults, the incidence of displaced fractures, independent of location, was higher than that of undisplaced fractures. Traffic accidents were the most common cause of the injury. In the period under study, the incidence of fractures showed no significant change over time and no seasonal variation. PMID:12378163

  18. Subsurface fracture spacing

    SciTech Connect

    Lorenz, J.C. ); Hill, R.E. )

    1991-01-01

    This study was undertaken in order to document and analyze the unique set of data on subsurface fracture characteristics, especially spacing, provided by the US Department of Energy's Slant Hole Completion Test well (SHCT-1) in the Piceance Basin, Colorado. Two hundred thirty-six (236) ft (71.9 m) of slant core and 115 ft (35.1 m) of horizontal core show irregular, but remarkably close, spacings for 72 natural fractures cored in sandstone reservoirs of the Mesaverde Group. Over 4200 ft (1280 m) of vertical core (containing 275 fractures) from the vertical Multiwell Experiment wells at the same location provide valuable information on fracture orientation, termination, and height, but only data from the SHCT-1 core allow calculations of relative fracture spacing. Within the 162-ft (49-m) thick zone of overlapping core from the vertical and deviated wellbores, only one fracture is present in vertical core whereas 52 fractures occur in the equivalent SHCT-1 core. The irregular distribution of regional-type fractures in these heterogeneous reservoirs suggests that measurements of average fracture spacing'' are of questionable value as direct input parameters into reservoir engineering models. Rather, deviated core provides data on the relative degree of fracturing, and confirms that cross fractures can be rare in the subsurface. 13 refs., 11 figs.

  19. Atraumatic sternum fracture

    PubMed Central

    Abrahamsen, Sebastian Ørskov; Madsen, Christina Friis

    2014-01-01

    The spine, pelvic bones and long bones of the lower extremities are common sites for insufficiency fractures. Cases of sternum insufficiency fractures have rarely been reported among elderly patients. Insufficiency fractures tend to occur in bones with decreased mechanical strength especially among elderly patients, in postmenopausal women and patients with underlying diseases. We describe a case of spontaneous sternum insufficiency fracture in a healthy man, with no known risk factors to fracture, or previous history of fractures. Sternum insufficiency fracture is a rare cause of chest pain. This case serves to remind the emergency physician to remain vigilant for other non-cardiac, non-pulmonary and non-traumatic causes of chest pain, especially among patients with known risk factors such as osteoporosis, chronic obstructive pulmonary disease, rheumatoid arthritis, systemic lupus erythematosus and patients on long-term steroid treatment. If diagnosed correctly, these patients can be discharged and treated as outpatients as this case emphasises. PMID:25326566

  20. [Fractures of carpal bones].

    PubMed

    Lögters, T; Windolf, J

    2016-10-01

    Fractures of the carpal bones are uncommon. On standard radiographs fractures are often not recognized and a computed tomography (CT) scan is the diagnostic method of choice. The aim of treatment is to restore pain-free and full functioning of the hand. A distinction is made between stable and unstable carpal fractures. Stable non-displaced fractures can be treated conservatively. Unstable and displaced fractures have an increased risk of arthritis and non-union and should be stabilized by screws or k‑wires. If treated adequately, fractures of the carpal bones have a good prognosis. Unstable and dislocated fractures have an increased risk for non-union. The subsequent development of carpal collapse with arthrosis is a severe consequence of non-union, which has a heterogeneous prognosis.

  1. Posterior malleolus fracture.

    PubMed

    Irwin, Todd A; Lien, John; Kadakia, Anish R

    2013-01-01

    Posterior malleolus fractures are a common component of ankle fractures. The morphology is variable; these fractures range from small posterolateral avulsion injuries to large displaced fracture fragments. The integrity of the posterior malleolus and its ligamentous attachment is important for tibiotalar load transfer, posterior talar stability, and rotatory ankle stability. Fixation of posterior malleolus fractures in the setting of rotational ankle injuries has certain benefits, such as restoring articular congruity and rotatory ankle stability, as well as preventing posterior talar translation, but current indications are unclear. Fragment size as a percentage of the anteroposterior dimension of the articular surface is often cited as an indication for fixation, although several factors may contribute to the decision, such as articular impaction, comminution, and syndesmotic stability. Outcome studies show that, in patients with ankle fractures, the presence of a posterior malleolus fracture negatively affects prognosis. Notable variability is evident in surgeon practice. PMID:23281469

  2. Reservoir Fracturing in the Geysers Hydrothermal System: Fact or Fallacy?

    SciTech Connect

    Hebein, Jeffrey J.

    1986-01-21

    Proper application of proven worldwide fracture determination analyses adequately aids in the detection and enhanced exploitation of reservoir fractures in The Geysers steam field. Obsolete, superficial ideas concerning fracturing in this resource have guided various malformed judgements of the actual elusive trends. Utilizing regional/local tectonics with theoretical rack mechanics and drilling statistics, offers the most favorable method of fracture comprehension. Exploitation philosophies should favor lateral drilling trends along local tensional components and under specific profound drainage/faulting manifestations to enhance high productivities. Drill core observations demonstrate various degrees of fracture filling, brecciation, strain responses, and rock fracture properties, giving the most favorable impression of subsurface reservoir conditions. Considerably more work utilizing current fracturing principles and geologic thought is required to adequately comprehend and economically exploit this huge complex resource.

  3. Flow focusing in unsaturated fracture networks: A numerical investigation

    SciTech Connect

    Zhang, Keni; Wu, Yu-Shu; Bodvarsson, G.S.; Liu, Hui-Hai

    2003-04-17

    A numerical modeling study is presented to investigate flow-focusing phenomena in a large-scale fracture network, constructed using field data collected from the unsaturated zone of Yucca Mountain, Nevada, the proposed repository site for high-level nuclear waste. The two-dimensional fracture network for an area of 100 m x 150 m contains more than 20,000 fractures. Steady-state unsaturated flow in the fracture network is investigated for different boundary conditions and rock properties. Simulation results indicate that flow paths are generally vertical, and that horizontal fractures mainly provide pathways between neighboring vertical paths. In addition to fracture properties, flow-focusing phenomena are also affected by rock-matrix permeability, with lower matrix permeability leading to a high degree of flow focusing. The simulation results further indicate that the average spacing between flow paths in a layered system tends to increase and flow tends to becomes more focused, with depth.

  4. Smart magnetic markers use in hydraulic fracturing.

    PubMed

    Zawadzki, Jarosław; Bogacki, Jan

    2016-11-01

    One of the main challenges and unknowns during shale gas exploration is to assess the range and efficiency of hydraulic fracturing. It is also essential to assess the distribution of proppant, which keeps the fracture pathways open. Solving these problems may considerably increase the efficiency of the shale gas extraction. Because of that, the idea of smart magnetic marker, which can be detected when added to fracturing fluid, has been considered for a long time. This study provides overview of the possibilities of magnetic marker application for shale gas extraction. The imaging methods using electromagnetic markers, are considered or developed in two directions. The first possibility is the markers' electromagnetic activity throughout the whole volume of the fracturing fluid. Thus, it can be assumed that the whole fracturing fluid is the marker. Among these type of hydraulic fracturing solutions, ferrofluid could be considered. The second possibility is marker, which is just one of many components of the fracturing fluid. In this case feedstock magnetic materials, ferrites and nanomaterials could be considered. Magnetic properties of magnetite could be too low and ferrofluids' or nanomaterials' price is unacceptably high. Because of that, ferrites, especially ZnMn ferrites seems to be the best material for magnetic marker. Because of the numerous applications in electronics, it is cheap and easily available, although the price is higher, then that of magnetite. The disadvantage of using ferrite, could be too small mechanical strength. It creates an essential need for combining magnetic marker with proppant into magnetic-ceramic composite. PMID:27475294

  5. Smart magnetic markers use in hydraulic fracturing.

    PubMed

    Zawadzki, Jarosław; Bogacki, Jan

    2016-11-01

    One of the main challenges and unknowns during shale gas exploration is to assess the range and efficiency of hydraulic fracturing. It is also essential to assess the distribution of proppant, which keeps the fracture pathways open. Solving these problems may considerably increase the efficiency of the shale gas extraction. Because of that, the idea of smart magnetic marker, which can be detected when added to fracturing fluid, has been considered for a long time. This study provides overview of the possibilities of magnetic marker application for shale gas extraction. The imaging methods using electromagnetic markers, are considered or developed in two directions. The first possibility is the markers' electromagnetic activity throughout the whole volume of the fracturing fluid. Thus, it can be assumed that the whole fracturing fluid is the marker. Among these type of hydraulic fracturing solutions, ferrofluid could be considered. The second possibility is marker, which is just one of many components of the fracturing fluid. In this case feedstock magnetic materials, ferrites and nanomaterials could be considered. Magnetic properties of magnetite could be too low and ferrofluids' or nanomaterials' price is unacceptably high. Because of that, ferrites, especially ZnMn ferrites seems to be the best material for magnetic marker. Because of the numerous applications in electronics, it is cheap and easily available, although the price is higher, then that of magnetite. The disadvantage of using ferrite, could be too small mechanical strength. It creates an essential need for combining magnetic marker with proppant into magnetic-ceramic composite.

  6. [Fracture endoprosthesis of distal humerus fractures].

    PubMed

    Müller, L P; Wegmann, K; Burkhart, K J

    2013-08-01

    The treatment of choice for fractures of the distal humerus is double plate osteosynthesis. Due to anatomical preshaped angle stable plates the primary stability and management of soft tissues has been improved. However, osteoporotic comminuted fractures in the elderly are often not amenable to stable osteosynthesis and total elbow arthroplasty has been established as an alternative therapy. Although complication rates have been reduced, complications of total elbow arthroplasty are still much more frequent than in total hip replacement. Furthermore, patients are advised not to exceed a weight bearing of 5 kg. Therefore, the indications for elbow arthroplasty must be evaluated very strictly and should be reserved for comminuted distal humeral fractures in the elderly with poor bone quality that are not amenable to stable osteosynthesis or for simple fractures in cases of preexisting symptomatic osteoarthritis. This article introduces and discusses modern concepts of elbow arthroplasty, such as modular convertible prosthesis systems, hemiarthroplasty and radial head replacement in total elbow arthroplasty.

  7. Fracture corridors in carbonates

    NASA Astrophysics Data System (ADS)

    Chatelée, Sébastien; Lamarche, Juliette; Gauthier, Bertrand D. M.

    2015-04-01

    Among fractures, Fracture Corridors (FC) are anomalous structures made of highly persistent fracture clusters having a strong effect on multi-phase fluid flow in the subsurface. While mechanical and geological conditions for diffuse fracture systems are well constrained, FC genetic conditions remain a matter of questioning. FC can be localized in larger structures such as folds and fault zones but recent studies suggest that a large amount of fractures and FC also arise as distributed in the host rock and formed in tabular layers during burial with early rock mechanical differentiation. In addition, while the mechanical stratigraphy is of prime importance for fracture stratigraphy, it is still unknown which factor prevails on FC genesis among the local versus regional stress-state, the host rock mechanical stratigraphy or the sedimentary facies. We present a study of fractures in a 400×300 m wide quarry (Calvisson, SE France) dug in homogeneous marly limestones of Hauterivian age. The quarry exhibits diffuse fractures as well as 16 FC. The aim of this study is to reveal the genetics factor for FC development, their global geometry and internal morphologic variations, but also to clear the impact of fracture corridors on diffuse fracture. For that, we measured >2500 fractures (strike, dip, spacing, filling, aperture, etc.) and studied microstructures in 80 thin sections. We calculated fracture density and acquired LiDAR data with >90 million points with a resolution of 4 to 15mm. Diffuse fractures are organized as two perpendicular sets, a main set NE-SW-trending and minor set NW-SE-trending. The FC have the same trend, but the NW-SE trend prevail on the NE-SW one. The LiDAR acquisition allows to visualize the 3D lateral continuity with corridors with a minimal extension of 30m. We distinguish 4 internal morphologic types in FC, depending on fracture morphology, occurrence of breccia and number of zones. The types may occur in a single FC with a lateral transition

  8. Cavitation, Elasticity and Fracture in Strong Hydrogels

    NASA Astrophysics Data System (ADS)

    Cui, Jun; Madkour, Ahmad; Tew, Gregory; Crosby, Alfred

    2010-03-01

    The interplay between the molecular network and material microstructure of a polymer-based hydrogel is critical for determining both the low strain elastic properties and fracture toughness. We present a novel complex hydrogel network developed by introducing polydimethylsiloxane (PDMS) into a polyethylene glycol (PEG)-based network. Using a combination of conventional characterization techniques, as well as the recently developed technique of cavitation rheology, we investigate the balance of elasticity and fracture in these complex networks. The polymer network maintains elasticity, with negligible hysteresis, at large strains over a wide range of swelling ratios. These properties are investigated across a continuum of length scales ranging from microns to centimeters by taking advantage of cavitation rheology, which uses the onset of an elastic instability to quantify local network mechanics. We compare our results with established scaling theories to describe both the elastic and fracture properties as a function of polymer volume fraction.

  9. Hydraulic fracture extending into network in shale: reviewing influence factors and their mechanism.

    PubMed

    Ren, Lan; Zhao, Jinzhou; Hu, Yongquan

    2014-01-01

    Hydraulic fracture in shale reservoir presents complex network propagation, which has essential difference with traditional plane biwing fracture at forming mechanism. Based on the research results of experiments, field fracturing practice, theory analysis, and numerical simulation, the influence factors and their mechanism of hydraulic fracture extending into network in shale have been systematically analyzed and discussed. Research results show that the fracture propagation in shale reservoir is influenced by the geological and the engineering factors, which includes rock mineral composition, rock mechanical properties, horizontal stress field, natural fractures, treating net pressure, fracturing fluid viscosity, and fracturing scale. This study has important theoretical value and practical significance to understand fracture network propagation mechanism in shale reservoir and contributes to improving the science and efficiency of shale reservoir fracturing design. PMID:25032240

  10. Hydraulic Fracture Extending into Network in Shale: Reviewing Influence Factors and Their Mechanism

    PubMed Central

    Ren, Lan; Zhao, Jinzhou; Hu, Yongquan

    2014-01-01

    Hydraulic fracture in shale reservoir presents complex network propagation, which has essential difference with traditional plane biwing fracture at forming mechanism. Based on the research results of experiments, field fracturing practice, theory analysis, and numerical simulation, the influence factors and their mechanism of hydraulic fracture extending into network in shale have been systematically analyzed and discussed. Research results show that the fracture propagation in shale reservoir is influenced by the geological and the engineering factors, which includes rock mineral composition, rock mechanical properties, horizontal stress field, natural fractures, treating net pressure, fracturing fluid viscosity, and fracturing scale. This study has important theoretical value and practical significance to understand fracture network propagation mechanism in shale reservoir and contributes to improving the science and efficiency of shale reservoir fracturing design. PMID:25032240

  11. Stress fractures in athletes.

    PubMed

    Fredericson, Michael; Jennings, Fabio; Beaulieu, Christopher; Matheson, Gordon O

    2006-10-01

    A stress fracture is a partial or complete bone fracture that results from repeated application of stress lower than the stress required to fracture the bone in a single loading. Otherwise healthy athletes, especially runners, sustain stress injuries or fractures. Prevention or early intervention is the preferable treatment. However, it is difficult to predict injury because runners vary with regard to biomechanical predisposition, training methods, and other factors such as diet, muscle strength, and flexibility. Stress fractures account for 0.7% to 20% of all sports medicine clinic injuries. Track-and-field athletes have the highest incidence of stress fractures compared with other athletes. Stress fractures of the tibia, metatarsals, and fibula are the most frequently reported sites. The sites of stress fractures vary from sport to sport (eg, among track athletes, stress fractures of the navicular, tibia, and metatarsal are common; in distance runners, it is the tibia and fibula; in dancers, the metatarsals). In the military, the calcaneus and metatarsals were the most commonly cited injuries, especially in new recruits, owing to the sudden increase in running and marching without adequate preparation. However, newer studies from the military show the incidence and distribution of stress fractures to be similar to those found in sports clinics. Fractures of the upper extremities are relatively rare, although most studies have focused only on lower-extremity injuries. The ulna is the upper-extremity bone injured most frequently. Imaging plays a key role in the diagnosis and management of stress injuries. Plain radiography is useful when positive, but generally has low sensitivity. Radionuclide bone scanning is highly sensitive, but lacks specificity and the ability to directly visualize fracture lines. In this article, we focus on magnetic resonance imaging, which provides highly sensitive and specific evaluation for bone marrow edema, periosteal reaction as well

  12. Tensile and fracture toughness properties of the nanostructured oxide dispersion strengthened ferritic alloy 13Cr-1W-0.3Ti-0.3Y 2O 3

    NASA Astrophysics Data System (ADS)

    Eiselt, Ch. Ch.; Klimenkov, M.; Lindau, R.; Möslang, A.; Odette, G. R.; Yamamoto, T.; Gragg, D.

    2011-10-01

    The realization of fusion power as an attractive energy source requires advanced structural materials that can cope with ultra-severe thermo-mechanical loads and high neutron fluxes experienced by fusion power plant components, such as the first wall, divertor and blanket structures. Towards this end, two variants of a 13Cr-1W-0.3Ti-0.3Y 2O 3 reduced activation ferritic (RAF-) ODS steel were produced by ball milling phase blended Fe-13Cr-1W, 0.3Y 20 3 and 0.3Ti powders in both argon and hydrogen atmospheres. The milled powders were consolidated by hot isostatic pressing (HIP). The as-HIPed alloys were then hot rolled into 6 mm plates. Microstructural, tensile and fracture toughness characterization of the hot rolled alloys are summarized here and compared to results previously reported for the as-HIPed condition.

  13. Natural fracturing, by depth

    NASA Astrophysics Data System (ADS)

    Hooker, John; Laubach, Stephen

    2013-04-01

    Natural opening-mode fractures commonly fall upon a spectrum whose end-members are veins, which have wide ranges of sizes and are mostly or thoroughly cemented, and joints, which have little opening displacement and little or no cement. The vein end-member is common in metamorphic rocks, whose high temperature and pressure of formation place them outside typical reservoir settings; conversely, many uncemented joints likely form near the surface and so too have limited relevance to subsurface exploration. Sampling of cores retrieved from tight-gas sandstone reservoirs suggest that it is intermediate fractures, not true joints or veins, that provide natural porosity and permeability. Such fractures have abundant pore space among fracture-bridging cements, which may hold fractures open despite varying states of stress through time. Thus the more sophisticated our understanding of the processes that form veins and joints, i.e., how natural fracturing varies by depth, the better our ability to predict intermediate fractures. Systematic differences between veins and joints, in terms of size-scaling and lateral and stratigraphic spatial arrangement, have been explained in the literature by the mechanical effects of sedimentary layering, which likely exert more control over fracture patterns at shallower depths. Thus stratabound joints commonly have narrow size ranges and regular spacing; non-stratabound veins have a wide range of sizes and spacings. However, new fieldwork and careful literature review suggest that the effects of mechanical layering are only half the story. Although atypical, veins may be highly stratabound and yet spatially clustered; non-stratabound fractures may nonetheless feature narrow size ranges. These anomalous fracture arrangements are better explained by the presence of precipitating cements during fracture opening than by mechanical layering. Cement is thought to be highly important for fracture permeability, but potential effects of

  14. Streaming potential modeling in fractured rock: Insights into the identification of hydraulically active fractures

    NASA Astrophysics Data System (ADS)

    Roubinet, D.; Linde, N.; Jougnot, D.; Irving, J.

    2016-05-01

    Numerous field experiments suggest that the self-potential (SP) geophysical method may allow for the detection of hydraulically active fractures and provide information about fracture properties. However, a lack of suitable numerical tools for modeling streaming potentials in fractured media prevents quantitative interpretation and limits our understanding of how the SP method can be used in this regard. To address this issue, we present a highly efficient two-dimensional discrete-dual-porosity approach for solving the fluid flow and associated self-potential problems in fractured rock. Our approach is specifically designed for complex fracture networks that cannot be investigated using standard numerical methods. We then simulate SP signals associated with pumping conditions for a number of examples to show that (i) accounting for matrix fluid flow is essential for accurate SP modeling and (ii) the sensitivity of SP to hydraulically active fractures is intimately linked with fracture-matrix fluid interactions. This implies that fractures associated with strong SP amplitudes are likely to be hydraulically conductive, attracting fluid flow from the surrounding matrix.

  15. Identifying novel clinical surrogates to assess human bone fracture toughness

    PubMed Central

    Granke, Mathilde; Makowski, Alexander J; Uppuganti, Sasidhar; Does, Mark D; Nyman, Jeffry S

    2015-01-01

    Fracture risk does not solely depend on strength but also on fracture toughness, i.e. the ability of bone material to resist crack initiation and propagation. Because resistance to crack growth largely depends on bone properties at the tissue level including collagen characteristics, current X-ray based assessment tools may not be suitable to identify age-, disease-, or treatment-related changes in fracture toughness. To identify useful clinical surrogates that could improve the assessment of fracture resistance, we investigated the potential of 1H nuclear magnetic resonance spectroscopy (NMR) and reference point indentation (RPI) to explain age-related variance in fracture toughness. Harvested from cadaveric femurs (62 human donors), single-edge notched beam (SENB) specimens of cortical bone underwent fracture toughness testing (R-curve method). NMR-derived bound water showed the strongest correlation with fracture toughness properties (r=0.63 for crack initiation, r=0.35 for crack growth, and r=0.45 for overall fracture toughness; p<0.01). Multivariate analyses indicated that the age-related decrease in different fracture toughness properties were best explained by a combination of NMR properties including pore water and RPI-derived tissue stiffness with age as a significant covariate (adjusted R2 = 53.3%, 23.9%, and 35.2% for crack initiation, crack growth, and overall toughness, respectively; p<0.001). These findings reflect the existence of many contributors to fracture toughness and emphasize the utility of a multimodal assessment of fracture resistance. Exploring the mechanistic origin of fracture toughness, glycation-mediated, non-enzymatic collagen crosslinks and intra-cortical porosity are possible determinants of bone fracture toughness and could explain the sensitivity of NMR to changes in fracture toughness. Assuming fracture toughness is clinically important to the ability of bone to resist fracture, our results suggest that improvements in fracture

  16. Multiple noncontiguous spine fractures.

    PubMed

    Henderson, R L; Reid, D C; Saboe, L A

    1991-02-01

    The data from a prospective study of 508 spine injuries were reviewed to determine the incidence of multiple noncontiguous spine fractures. All patients were examined at admission and at 1 and 2 years postinjury. This series identified 77 (15.2%) multilevel fractures. Motor vehicle accidents were the primary cause of these fractures. The incidence of neurologic injury was not significantly different between multiple noncontiguous and single fractures. Failure to use seat belts and ejection from the vehicle were the main factors associated with multiple noncontiguous spine injuries. Seven major fracture patterns were identified, which accounted for 60% of these injuries. The prognosis for multilevel spine fractures was not significantly worse that that for single-level injuries. PMID:2011766

  17. Evaluation of permeable fractures in rock aquifers

    NASA Astrophysics Data System (ADS)

    Bok Lee, Hang

    2015-04-01

    In this study, the practical usefulness and fundamental applicability of a self-potential (SP) method for identifying the permeable fractures were evaluated by a comparison of SP methods with other geophysical logging methods and hydraulic tests. At a 10 m-shallow borehole in the study site, the candidates of permeable fractures crossing the borehole were first determined by conventional geophysical methods such as an acoustic borehole televiwer, temperature, electrical conductivity and gamma-gamma loggings, which was compared to the analysis by the SP method. Constant pressure injection and recovery tests were conducted for verification of the hydraulic properties of the fractures identified by various logging methods. The acoustic borehole televiwer and gamma-gamma loggings detected the open space or weathering zone within the borehole, but they cannot prove the possibility of a groundwater flow through the detected fractures. The temperature and electrical conductivity loggings had limitations to detect the fractured zones where groundwater in the borehole flows out to the surrounding rock aquifers. Comparison of results from different methods showed that there is a best correlation between the distribution of hydraulic conductivity and the variation of the SP signals, and the SP logging can estimate accurately the hydraulic activity as well as the location of permeable fractures. Based on the results, the SP method is recommended for determining the hydraulically-active fractures rather than other conventional geophysical loggings. This self-potential method can be effectively applied in the initial stage of a site investigation which selects the optimal location and evaluates the hydrogeological property of fractures in target sites for the underground structure including the geothermal reservoir and radioactive waste disposal.

  18. From Stochastic toward Deterministic Characterization of Discrete Fracture Network via Thermal Tracer Tests

    NASA Astrophysics Data System (ADS)

    Somogyvari, M.; Jalali, M.; Bayer, P.; Jiménez Parras, S.

    2015-12-01

    The presence of fractures play an essential role in different disciplines, including hydrogeology, geothermal and hydrocarbon industries, as fractures introduce new pathways for flow and transport in the host rocks. Understanding the physical properties of these planar features would reduce the uncertainty of the numerical models and enhance the reliability of their results. Among the fracture properties, orientation and spacing are relatively easily estimated via borehole logs, core images, and outcrops, whereas the fracture geometry (i.e. length, width, and height) is more difficult to investigate. As the fracture geometry controls the hydraulic and thermal behavior of the fracture network through the strong dependency of the fracture conductivity with fracture aperture, it is possible to estimate these geometrical properties indirectly through hydraulic and thermal tomography investigations. To reach this goal, an innovative approach is introduced for discrete fracture network (DFN) characterization of heterogeneous fractured media via active thermal tracer testing. A synthetic DFN model is constructed based on the geological properties of an arbitrary fracture medium such as fracture orientation, length, spacing and persistency. Different realization are then constructed by considering all the above mentioned fracture properties except the length of fracture segments. Pressure and temperature fields are estimated inside the fracture network by means of an implicit upwind finite difference method, which is used to compute heat tracer travel times between injection and observation points and record the full temperature breakthrough curves at the monitoring points. A trans-dimensional inversion is then adopted to update the lengths fracture segment (add or remove) of the DFN model by comparison between proposed and observed travel times (Figure 1). The resulting assemble of the models can be used as an input geometry for deterministic simulations of fracture

  19. [Femoral neck fracture].

    PubMed

    Gierer, P; Mittlmeier, T

    2015-03-01

    The incidence of femoral neck fractures increases exponentially with rising age. Young patients are rarely affected but when they are it is mostly due to high energy accidents, whereas older patients suffer from femoral neck fractures by low energy trauma due to osteoporotic changes of the bone mineral density. Treatment options have not essentially changed over the last few years. Non-operative treatment may be a choice in non-dislocated and impacted fractures. Due to the high risk of secondary fracture displacement prophylactic screw osteosynthesis is recommended even in Garden type I fractures. Osteosynthetic fracture stabilization with cannulated screws or angle stable sliding screws, is usually applied in non-displaced fractures and fractures in younger patients. Older patients need rapid mobilization after surgery; therefore, total hip arthroplasty and hemiarthroplasty are commonly used with a low incidence of secondary complications. In addition to sufficient operative treatment a guideline conform osteoprosis therapy should be initiated for the prophylaxis of further fractures and patients should undertake a suitable rehabilitation.

  20. Pathological fractures in children

    PubMed Central

    De Mattos, C. B. R.; Binitie, O.; Dormans, J. P.

    2012-01-01

    Pathological fractures in children can occur as a result of a variety of conditions, ranging from metabolic diseases and infection to tumours. Fractures through benign and malignant bone tumours should be recognised and managed appropriately by the treating orthopaedic surgeon. The most common benign bone tumours that cause pathological fractures in children are unicameral bone cysts, aneurysmal bone cysts, non-ossifying fibromas and fibrous dysplasia. Although pathological fractures through a primary bone malignancy are rare, these should be recognised quickly in order to achieve better outcomes. A thorough history, physical examination and review of plain radiographs are crucial to determine the cause and guide treatment. In most benign cases the fracture will heal and the lesion can be addressed at the time of the fracture, or after the fracture is healed. A step-wise and multidisciplinary approach is necessary in caring for paediatric patients with malignancies. Pathological fractures do not have to be treated by amputation; these fractures can heal and limb salvage can be performed when indicated. PMID:23610658

  1. Fracture detection logging tool

    DOEpatents

    Benzing, William M.

    1992-06-09

    A method and apparatus by which fractured rock formations are identified and their orientation may be determined includes two orthogonal motion sensors which are used in conjunction with a downhole orbital vibrator. The downhole vibrator includes a device for orienting the sensors. The output of the sensors is displayed as a lissajou figure. The shape of the figure changes when a subsurface fracture is encountered in the borehole. The apparatus and method identifies fractures rock formations and enables the azimuthal orientation of the fractures to be determined.

  2. Natural fracture systems studies

    SciTech Connect

    Lorenz, J.C.; Warpinski, N.R.

    1992-09-01

    The objectives of this program are (1) to develop a basinal-analysis methodology for natural fracture exploration and exploitation, and (2) to determine the important characteristics of natural fracture systems for use in completion, stimulation, and production operations. Natural-fracture basinal analysis begins with studies of fractures in outcrop, core and logs in order to determine the type of fracturing and the relationship of the fractures to the lithologic environment. Of particular interest are the regional fracture systems that are pervasive in western US tight sand basins. A Methodology for applying this analysis is being developed, with the goal of providing a structure for rationally characterizing natural fracture systems basin-wide. Such basin-wide characterizations can then be expanded and supplemented locally, at sites where production may be favorable. Initial application of this analysis is to the Piceance basin where there is a wealth of data from the Multiwell Experiment (MWX), DOE cooperative wells, and other basin studies conducted by Sandia, CER Corporation, and the USGS (Lorenz and Finley, 1989, Lorenz et aI., 1989, and Spencer and Keighin, 1984). Such a basinal approach has been capable of explaining the fracture characteristics found throughout the southern part of the Piceance basin and along the Grand Hogback.

  3. Radiation-induced alterations of fracture healing biomechanics

    SciTech Connect

    Pelker, R.R.; Friedlaender, G.E.; Panjabi, M.M.; Kapp, D.; Doganis, A.

    1984-01-01

    The effects of irradiation on the normal temporal progression of the physical properties of healing fractures were studied in a rat model. Fractures were surgically produced in the femur, stabilized with an intramedullary pin, and irradiated. One group of rats was exposed to 2,500 rads in divided doses over 2 weeks, beginning 3 days after fracture, and compared to a control group with fractures which were not irradiated. Animals were sacrificed at periodic intervals and the bones were tested to failure in torsion. The torque, stiffness, and energy increased and the angle decreased for the nonirradiated specimens in the expected fashion. This progression was deleteriously altered in the irradiated femurs.

  4. A new computer code for discrete fracture network modelling

    NASA Astrophysics Data System (ADS)

    Xu, Chaoshui; Dowd, Peter

    2010-03-01

    The authors describe a comprehensive software package for two- and three-dimensional stochastic rock fracture simulation using marked point processes. Fracture locations can be modelled by a Poisson, a non-homogeneous, a cluster or a Cox point process; fracture geometries and properties are modelled by their respective probability distributions. Virtual sampling tools such as plane, window and scanline sampling are included in the software together with a comprehensive set of statistical tools including histogram analysis, probability plots, rose diagrams and hemispherical projections. The paper describes in detail the theoretical basis of the implementation and provides a case study in rock fracture modelling to demonstrate the application of the software.

  5. Vibrational modes of hydraulic fractures: Inference of fracture geometry from resonant frequencies and attenuation

    NASA Astrophysics Data System (ADS)

    Lipovsky, Bradley P.; Dunham, Eric M.

    2015-02-01

    Oscillatory seismic signals arising from resonant vibrations of hydraulic fractures are observed in many geologic systems, including volcanoes, glaciers and ice sheets, and hydrocarbon and geothermal reservoirs. To better quantify the physical dimensions of fluid-filled cracks and properties of the fluids within them, we study wave motion along a thin hydraulic fracture waveguide. We present a linearized analysis, valid at wavelengths greater than the fracture aperture, that accounts for quasi-static elastic deformation of the fracture walls, as well as fluid viscosity, inertia, and compressibility. In the long-wavelength limit, anomalously dispersed guided waves known as crack or Krauklis waves propagate with restoring force from fracture wall elasticity. At shorter wavelengths, the waves become sound waves within the fluid channel. Wave attenuation in our model is due to fluid viscosity, rather than seismic radiation from crack tips or fracture wall roughness. We characterize viscous damping at both low frequencies, where the flow is always fully developed, and at high frequencies, where the flow has a nearly constant velocity profile away from viscous boundary layers near the fracture walls. Most observable seismic signals from resonating fractures likely arise in the boundary layer crack wave limit, where fluid-solid coupling is pronounced and attenuation is minimal. We present a method to estimate the aperture and length of a resonating hydraulic fracture using both the seismically observed quality factor and characteristic frequency. Finally, we develop scaling relations between seismic moment and characteristic frequency that might be useful when interpreting the statistics of hydraulic fracture events.

  6. Frequency-Dependent Seismic Waves in Fluid-Saturated Fractured Rock

    NASA Astrophysics Data System (ADS)

    Korneev, V. A.; Goloshubin, G.

    2015-12-01

    Fractures are the natural and essential elements of rock. Fracture systems are the most important features that define rock permeability and strength, as well as their anisotropy properties. Recent advancement in induced fracturing is a core part of the gas/oil shale technology, where fracture monitoring and control became a special topic of interest. Krauklis wave (K-wave) is the result of interaction between a fluid mass and elasticity of fracture walls, and it propagates primarily along the fracture systems in the fluid. At the fracture tips and fracture intersections it partially converts into the body waves. It is quite clear that incorporation of K-waves in a theory of wave propagation in fractured rock is one of the most important problems to solve for understanding of their seismic properties. One of the most fundamental properties of fractured rock is a fractal fracture distribution and it is rarely, if ever, taken into account in existing wave propagation theories. However, this property exists on a widest variety of scales and in particular reveals itself in a form of Gutenberg-Richter Law experimentally proven, starting from laboratory measurements and up to the global seismicity. We computed P and S-wave velocities of the rock containing fluid (and proppant) filled fractures, considering the effect of extremely slow and dispersive wave propagation within individual fractures. This was made possible by introducing the concept of "effective fracture-wave volume," and by evaluating the elastic constants of rock containing a complex, fractal network of fractures. These velocities were used to compute seismic waves reflected normally from a fractured reservoir. We demonstrate that by taking into account the Krauklis wave phenomenon for the fractally distributed fluid-filled fractures, it is possible to explain the observed low-frequency anomalies above the underground natural reservoirs. These anomalies include increase of amplitude and a phase delay of

  7. Statistical Physics of Fracture Surfaces Morphology

    NASA Astrophysics Data System (ADS)

    Bouchbinder, Eran; Procaccia, Itamar; Sela, Shani

    2006-12-01

    Experiments on fracture surface morphologies offer increasing amounts of data that can be analyzed using methods of statistical physics. One finds scaling exponents associated with correlation and structure functions, indicating a rich phenomenology of anomalous scaling. We argue that traditional models of fracture fail to reproduce this rich phenomenology and new ideas and concepts are called for. We present some recent models that introduce the effects of deviations from homogeneous linear elasticity theory on the morphology of fracture surfaces, successfully reproducing the multiscaling phenomenology at least in 1+1 dimensions. For surfaces in 2+1 dimensions we introduce novel methods of analysis based on projecting the data on the irreducible representations of the SO(2) symmetry group. It appears that this approach organizes effectively the rich scaling properties. We end up proposing new experiments in which the rotational symmetry is not broken, such that the scaling properties should be particularly simple.

  8. Pneumothorax complicating isolated clavicle fracture.

    PubMed

    Hani, Redouane; Ennaciri, Badr; Jeddi, Idriss; El Bardouni, Ahmed; Mahfoud, Mustapha; Berrada, Mohamed Saleh

    2015-01-01

    Isolated clavicle fractures are among the commonest of traumatic fractures in the emergency department. Complications of isolated clavicle fractures are rare. Pneumothorax has been described as a complication of a fractured clavicle only rarely in English literature. In all the reported cases, the pneumothorax was treated by a thoracostomy and the clavicle fracture was treated conservatively. In our case, the pneumothorax required a chest drain insertion and the clavicle fracture was treated surgically with good result.

  9. Mixed-Mode Fracture Behavior and Related Surface Topography Feature of a Typical Sandstone

    NASA Astrophysics Data System (ADS)

    Ren, L.; Xie, L. Z.; Xie, H. P.; Ai, T.; He, B.

    2016-08-01

    The geo-mechanical properties of reservoirs, especially the morphology of the rock surface and the fracture properties of rocks, are of great importance in the modeling and simulation of hydraulic processes. To better understand these fundamental issues, five groups of mixed-mode fracture tests were conducted on sandstone using edge-cracked semi-circular bend specimens. Accordingly, the fracture loads, growth paths and fracture surfaces for different initial mixities of the mixed-mode loadings from pure mode I to pure mode II were then determined. A surface topography measurement for each rough fracture surface was conducted using a laser profilometer, and the fractal properties of these surfaces were then investigated. The fracture path evolution mechanism was also investigated via optical microscopy. Moreover, the mixed-mode fracture strength envelope and the crack propagation trajectories of sandstone were theoretically modeled using three widely accepted fracture criteria (i.e., the MTS, MSED and MERR criterions). The published test results in Hasanpour and Choupani (World Acad Sci Eng Tech 41:764-769, 2008) for limestone were also theoretically investigated to further examine the effectiveness of the above fracture criteria. However, none of these criteria could accurately predict the fracture envelopes of both sandstone and limestone. To better estimate the fracture strength of mixed-mode fractures, an empirical maximum tensile stress (EMTS) criterion was proposed and found to achieve good agreement with the test results. Finally, a uniformly pressurized fracture model was simulated for low pressurization rates using this criterion.

  10. Osteosynthesis of fragility fractures.

    PubMed

    Tarantino, Umberto; Iundusi, Riccardo; Lecce, Domenico; Tempesta, Valerio; Perrone, Fabio Luigi; Rao, Cecilia; Cerocchi, Irene; Gasbarra, Elena

    2011-04-01

    The deepening knowledge about bone pathophysiology, together with the development of less invasive bone implants, fitted for the treatment of fragility fractures, the continuous advances in the creation of osteoconductive and osteoinductive biomaterials, the availability of bone active agents, capable of modulating fracture healing, actually represent the orthopaedic "weapons" to improve the surgical outcome and quality of life in patients with osteoporosis.

  11. TIBIAL SHAFT FRACTURES

    PubMed Central

    Kojima, Kodi Edson; Ferreira, Ramon Venzon

    2015-01-01

    The long-bone fractures occur most frequently in the tibial shaft. Adequate treatment of such fractures avoids consolidation failure, skewed consolidation and reoperation. To classify these fractures, the AO/OTA classification method is still used, but it is worthwhile getting to know the Ellis classification method, which also includes assessment of soft-tissue injuries. There is often an association with compartmental syndrome, and early diagnosis can be achieved through evaluating clinical parameters and constant clinical monitoring. Once the diagnosis has been made, fasciotomy should be performed. It is always difficult to assess consolidation, but the RUST method may help in this. Radiography is assessed in two projections, and points are scored for the presence of the fracture line and a visible bone callus. Today, the dogma of six hours for cleaning the exposed fracture is under discussion. It is considered that an early start to intravenous antibiotic therapy and the lesion severity are very important. The question of early or late closure of the lesion in an exposed fracture has gone through several phases: sometimes early closure has been indicated and sometimes late closure. Currently, whenever possible, early closure of the lesion is recommended, since this diminishes the risk of infection. Milling of the canal when the intramedullary nail is introduced is still a controversial subject. Despite strong personal positions in favor of milling, studies have shown that there may be some advantage in relation to closed fractures, but not in exposed fractures. PMID:27026999

  12. [Stress shielding and fracture healing].

    PubMed

    Liu, J G; Xu, X X

    1994-08-01

    The influence of stress shielding after fracture fixation with plate on fracture healing was studied. The results of animal and biomechanical experiments as well as the clinical observations demonstrated that rigidity of the plate was not the only factor causing stress redistribution and stress shielding effects of bone. Either the internal fixation with different implants or external fixation with fixators all might lead to physical and chemical characteristic changes of bone tissue. In the early stage, the disturbance of blood supply and the bone structure remodeling may be the main reasons. Reaction to the implant was another cause in the middle stage. If the affected limb can take weight-bearing normally at late stage, the influences of plate on fracture healing mechanical properties of bone and the osteoporosis cause by stress shielding effects will become much less. The tissue of the affected limb was the most important factor which may cause osteoporosis and refracture. Osteoporosis, bone atrophy and immobilization syndrome of bone and joint can be prevented and treated by taking normal weight-bearing and overcoming infection and implant reaction. PMID:7994658

  13. Spinal fractures in patients with ankylosing spondylitis.

    PubMed

    Leone, Antonio; Marino, Marzia; Dell'Atti, Claudia; Zecchi, Viola; Magarelli, Nicola; Colosimo, Cesare

    2016-10-01

    The ankylosed spine is prone to fracture even after minor trauma due to its changed biomechanical properties. The two central features of ankylosing spondylitis (AS) that promote the pathological remodeling of the spine are inflammation and new bone formation. AS is also associated with osteoporosis that is attributed to an uncoupling of the bone formation and bone resorption processes. Therefore, bone resorption occurs and promotes weakening of the spine as well as increased risk of vertebral fractures which can be hugely different in terms of clinical relevance. Even in the presence of symptomatic clinical vertebral fractures, the diagnosis can be overruled by attributing the pain to disease activity. Furthermore, given the highly abnormal structure of the spine, vertebral fracture diagnosis can be difficult on the basis of radiography alone. CT can show the fractures in detail. Magnetic resonance imaging is considered the method of choice for the imaging of spinal cord injuries, and a reasonable option for exclusion of occult fractures undetected by CT. Since it is equally important for radiologists and clinicians to have a common knowledge base rather than a compartmentalized view, the aim of this review article was to provide the required clinical knowledge that radiologists need to know and the relevant radiological semiotics that clinicians require in diagnosing clinically significant injury to the ankylosed spine.

  14. Three-phase fracturing in granular material

    NASA Astrophysics Data System (ADS)

    Campbell, James; Sandnes, Bjornar

    2015-04-01

    There exist numerous geo-engineering scenarios involving the invasion of a gas into a water-saturated porous medium: in fracking, this may occur during the fracking process itself or during subsequent gas penetration into propant beds; the process is also at the heart of carbon dioxide sequestration. We use a bed of water-saturated glass beads confined within a Hele-Shaw cell as a model system to illuminate these processes. Depending on packing density, injection rate and other factors, air injected into this system may invade in a broad variety of patterns, including viscous fingering, capillary invasion, bubble formation and fracturing. Here we focus primarily on the latter case. Fracturing is observed when air is injected into a loosely packed bed of unconsolidated granular material. Our approach allows us to image the complete fracture pattern as it forms, and as such to study both the topographical properties of the resulting pattern (fracture density, braching frequency etc) and the dynamics of its growth. We present an overview of the fracturing phenomenon within the context of pattern formation in granular fluids as a whole. We discuss how fracturing arises from an interplay between frictional, capillary and viscous forces, and demonstrate the influence of various parameters on the result.

  15. Spinal fractures in patients with ankylosing spondylitis.

    PubMed

    Leone, Antonio; Marino, Marzia; Dell'Atti, Claudia; Zecchi, Viola; Magarelli, Nicola; Colosimo, Cesare

    2016-10-01

    The ankylosed spine is prone to fracture even after minor trauma due to its changed biomechanical properties. The two central features of ankylosing spondylitis (AS) that promote the pathological remodeling of the spine are inflammation and new bone formation. AS is also associated with osteoporosis that is attributed to an uncoupling of the bone formation and bone resorption processes. Therefore, bone resorption occurs and promotes weakening of the spine as well as increased risk of vertebral fractures which can be hugely different in terms of clinical relevance. Even in the presence of symptomatic clinical vertebral fractures, the diagnosis can be overruled by attributing the pain to disease activity. Furthermore, given the highly abnormal structure of the spine, vertebral fracture diagnosis can be difficult on the basis of radiography alone. CT can show the fractures in detail. Magnetic resonance imaging is considered the method of choice for the imaging of spinal cord injuries, and a reasonable option for exclusion of occult fractures undetected by CT. Since it is equally important for radiologists and clinicians to have a common knowledge base rather than a compartmentalized view, the aim of this review article was to provide the required clinical knowledge that radiologists need to know and the relevant radiological semiotics that clinicians require in diagnosing clinically significant injury to the ankylosed spine. PMID:27379763

  16. Tensile properties and fracture behavior of Ti[sub 52]Al[sub 48] and Ti[sub 50]Al[sub 48]Cr[sub 2] prepared from elemental powders

    SciTech Connect

    Dogan, B.; Wang, G.X.; Dahms, M. )

    1993-10-01

    Titanium aluminide alloys, based on gamma TiAl, are currently of interest because of potential applications in high performance airframe and gas turbines. Their low densities, high melting temperatures, good elevated temperature strength and modulus retention, and environmental resistance favors them for these applications. However, their practical use are largely limited by their poor workability and ductility at temperatures lower than 700 C. Although the ductility has been improved in two phase TiAl alloys by adding alloying elements such as Cr, Mn, Nb and V, and by microstructural control in recent years, the ability to manufacture them still remains a problem. The reactive powder processing method offers a promising alternative to overcome this problem. This method involves cold-extrusion of an elemental powder mixture and reactive sintering. The as-extruded material can easily be machined or reformed into different shapes, since titanium aluminides are not present at this stage. The reactive sintering is conducted as the last step to form the desired titanium aluminides in the finished products. By this route, the poor workability of titanium aluminides can be avoided. In the present paper, a binary alloy Ti[sub 52]Al[sub 48](TiAl) and a ternary alloy Ti[sub 50]Al[sub 48]Cr[sub 2](TiAlCr), prepared in the same way from elemental powders, are investigated. The tensile tests were carried out at room temperature to 900 C in air. The influence of 2 at.% Cr addition on the tensile properties and fracture behavior of the alloys are reported. An emphasis is placed on the correlation between microstructure and deformation, and fracture behavior of the alloys.

  17. Dual permeability modeling of flow in a fractured geothermal reservoir

    SciTech Connect

    Miller, J.D.; Allman, D.W.

    1986-01-01

    A three dimensional fracture system synthesis and flow simulation has been developed to correlate drawdown characteristics measured in a geothermal well and to provide the basis for an analysis of tracer tests. A new dual permeability approach was developed which incorporates simulations at two levels to better represent a discrete fracture system within computer limitations. The first incorporates a discrete simulation of the largest fractures in the system plus distributed or representative element stimulation of the smaller fractures. The second determines the representative element properties by discrete simulation of the smaller fractures. The fracture system was synthesized from acoustic televiewer data on the orientation and separation of three distinct fracture sets, together with additional data from the literature. Lognormal and exponential distributions of fracture spacing and radius were studied with the exponential distribution providing more reasonable results. Hydraulic apertures were estimated as a function of distance from the model boundary to a constant head boundary. Mean values of 6.7, 101 and 46 ..mu..m were chosen as the most representative values for the three fracture sets. Recommendations are given for the additional fracture characterization needed to reduce the uncertainties in the model. 20 refs., 6 figs.

  18. Scattering characteristics in heterogeneously fractured reservoirs from waveform estimation

    NASA Astrophysics Data System (ADS)

    Shen, Feng; Toksöz, M. Nafi

    2000-02-01

    Offset-dependent characteristics of seismic scattering are useful for characterizing fractured reservoirs. We use two models that have different background medium properties and different azimuthal AVO responses to study elastic wave propagation and scattering in gas-saturated, heterogeneously fractured reservoirs. Heterogeneous fracture density distributions are built through stochastic modelling. Synthetic seismograms are generated by 3-D finite difference modelling, and waveforms along crack-normal and strike directions are considered in this paper. The multiple signal classification (MUSIC) frequency estimator is used in waveform estimation to provide frequency-domain attributes related to seismic wave scattering by fracture heterogeneity. Our results indicate that the strength of the scattering field is a function of the background medium. The strength also increases with increasing fracture scatterer density and with decreasing correlation length of spatial variations of fracture density. The scattering field is weak at the top of the fractured reservoir. The first-order results are dominated by velocity anisotropy of the mean fracture density field. However, the base of the fractured reservoir corresponds to a strong scattering field on which fracture heterogeneity has a larger effect and is characterized by the loss of coherence.

  19. A biomechanical study on fracture risks in ulnohumeral arthroplasty.

    PubMed

    Degreef, I; Van Audekercke, R; Boogmans, T; De Smet, L

    2011-06-01

    In the Outerbridge-Kashiwagi ulnohumeral arthroplasty, bone strength may be weakened significantly as a result of the humeral fenestration. Therefore, fracture risks may be increased, particularly in the immediate postoperative period. The objective of this biomechanical cadaver study is to study the humeral bone strength after ulnohumeral arthroplasty. A biomechanical cadaveric study was done in which differences in force needed to fracture the humerus with and without fenestration was measured. First, the diaphysis of 12 distal humeri was embedded and a posterior force was applied until a fracture occurred. Second, a similar study was done with fixed humeral columns, to specifically compare the column strength. In the first part, the force needed to fracture was reduced by 17% after ulnohumeral arthroplasty, which was not statistically significant. However, a shift in the fracture pattern occurred: from diaphyseal fracture towards column fractures after the arthroplasty. In the second part, the force needed to fracture the columns proved to be significantly reduced by 41% after humeral perforation. Alterations in the biomechanical properties of the distal humerus after ulnohumeral arthroplasty may lead to a shift in fracture patterns from diaphyseal to column fractures. The strength of the columns is strongly reduced by 41%. PMID:21592841

  20. Study of a subsurface fracture zone by vertical seismic profiling

    NASA Astrophysics Data System (ADS)

    Stewart, Robert R.; Turpening, Roger M.; Toksoz, M. Nafi

    Remotely estimating the properties of subsurface fracture zones is important in characterizing the structure of the shallow earth. We present a vertical seismic profiling (VSP) technique to make this fracture zone estimation and discuss the results of a VSP experiment performed in the upper 770 m of the Michigan Basin. Both P and SH waves were used to observe an explosively-fractured volume of Antrim shale. The experiment was divided into two parts: a "before" survey run on the unaltered rock, then an identical "after" survey executed across the fractured volume. A seismic velocity structure of the basin was calculated from the "before" survey. Comparison of the "after" observations to the "before" data, elucidated the fracture volume and its effective elastic parameters. From travel-time delays, amplitude attenuation, converted and scattered waves, we estimated the depth (395 m), shape (ellipsoidal), size (10 m × 20 m × 30 m) and porosity (20%) of the fracture zone.

  1. Abnormality in fracture strength of polycrystalline silicene

    NASA Astrophysics Data System (ADS)

    Liu, Ning; Hong, Jiawang; Pidaparti, Ramana; Wang, Xianqiao

    2016-09-01

    Silicene, a silicon-based homologue of graphene, arouses great interest in nano-electronic devices due to its outstanding electronic properties. However, its promising electronic applications are greatly hindered by lack of understanding in the mechanical strength of silicene. Therefore, in order to design mechanically reliable devices with silicene, it is necessary to thoroughly explore the mechanical properties of silicene. Due to current fabrication methods, graphene is commonly produced in a polycrystalline form; the same may hold for silicene. Here we perform molecular dynamics simulations to investigate the mechanical properties of polycrystalline silicene. First, an annealing process is employed to construct a more realistic modeling structure of polycrystalline silicene. Results indicate that a more stable structure is formed due to the breaking and reformation of bonds between atoms on the grain boundaries. Moreover, as the grain size decreases, the efficiency of the annealing process, which is quantified by the energy change, increases. Subsequently, biaxial tensile tests are performed on the annealed samples in order to explore the relation between grain size and mechanical properties, namely in-plane stiffness, fracture strength and fracture strain etc. Results indicate that as the grain size decreases, the fracture strain increases while the fracture strength shows an inverse trend. The decreasing fracture strength may be partly attributed to the weakening effect from the increasing area density of defects which acts as the reservoir of stress-concentrated sites on the grain boundary. The observed crack localization and propagation and fracture strength are well-explained by a defect-pileup model.

  2. Transphyseal Distal Humerus Fracture.

    PubMed

    Abzug, Joshua; Ho, Christine Ann; Ritzman, Todd F; Brighton, Brian

    2016-01-01

    Transphyseal distal humerus fractures typically occur in children younger than 3 years secondary to birth trauma, nonaccidental trauma, or a fall from a small height. Prompt and accurate diagnosis of a transphyseal distal humerus fracture is crucial for a successful outcome. Recognizing that the forearm is not aligned with the humerus on plain radiographs may aid in the diagnosis of a transphyseal distal humerus fracture. Surgical management is most commonly performed with the aid of an arthrogram. Closed reduction and percutaneous pinning techniques similar to those used for supracondylar humerus fractures are employed. Cubitus varus caused by a malunion, osteonecrosis of the medial condyle, or growth arrest is the most common complication encountered in the treatment of transphyseal distal humerus fractures. A corrective lateral closing wedge osteotomy can be performed to restore a nearly normal carrying angle.

  3. Diplopia following midfacial fractures.

    PubMed

    al-Qurainy, I A; Stassen, L F; Dutton, G N; Moos, K F; el-Attar, A

    1991-10-01

    Over a period of 2 years, 363 patients who had sustained a total of 438 midfacial fractures due to blunt trauma received a full ophthalmological examination within 1 week of injury. Of these, 72 patients (19.8%) developed diplopia. Diplopia was most common following road traffic accidents (31%) and least common with simple falls (10%). Blow-out fractures of the orbit led to double vision in 58% of cases. Eighty two percent of patients recovered from diplopia within 6 months of injury; only 1 patient required squint surgery for double vision. The principal risk factors for diplopia comprise road traffic accidents, blow-out fractures and comminuted malar fractures. Early surgical reconstruction of midfacial fractures with conservative management of concomitant motility disorders has, in our series, resulted in very few patients having diplopia in the long term. PMID:1742259

  4. Geological and geometrical characteristics of reservoir fracturing throughout the Middle East

    SciTech Connect

    Nurmi, R. ) Akbar, M. ); Standen, E. )

    1993-09-01

    The geometry and basic characteristics (length, density/intensity, aperture, and porosity) of fractures (joints) have been defined recently for a number of Middle East reservoirs. The factors that determine the occurrence of natural, open, permeable fractures within Middle East reservoirs are nature and degree of folding and/or faulting, in-situ stresses, and changes in rock properties such as porosity, lithology, and especially shaliness. Fracture distribution and orientation within Mesozoic Arabian/Persian Gulf halo-kinetic structures is important to reservoir development and modeling, although the fractures generally only assist productivity. In the deeper Paleozoic reservoirs, fractures become increasingly important. Fractures are best developed in relatively anhydrite free, low porosity, dolomite facies, and with few exceptions their orientation is related to regional trends, only slightly modified by local tectonic features. Exploration for deep-fracture reservoirs needs to consider that the probability of uncemented fractures will be present only where the timing of hydrocarbon migration was close in timing to fracturing. Examination of fractured reservoirs in the Zagros-Bitlis orogenic belt from Turkey through Syria, Iraq, Iran and the northern Emirates demonstrates that the fracturing is dominantly related to folding, with only minor karst fracturing or fault-related fracturing, whereas the fractures in the Gulf of Suez are closely related to the faulting history with some of the most intense fracturing of the low-porosity Eocene limestones forming a fracture reservoir near fault zones. Studies of basement fracturing reveals that decreases in fracture apertures generally accompanies increases in fracture density. The distribution of fractures within the northern Sinai closely fit a wrench-tectonic model, where the greatest density and largest apertures occur in the dolomitic facies and have an orientation parallel to synthetic faulting of the wrench system.

  5. A Bayesian framework for fracture characterization from surface seismic data

    NASA Astrophysics Data System (ADS)

    Zamanian, S. Ahmad; Fehler, Michael C.; Fang, Xinding; Burns, Daniel R.

    2014-11-01

    We describe a methodology for quantitatively characterizing the fractured nature of a hydrocarbon or geothermal reservoir from surface seismic data under a Bayesian inference framework. The method combines different kinds of measurements of fracture properties to find a best-fitting model while providing estimates of the uncertainty of model parameters. Fractures provide pathways for fluid flow in a reservoir, and hence, knowledge about a reservoir's fractured nature can be used to enhance production from the reservoir. The fracture properties of interest in this study (to be inferred) are fracture orientation and excess compliance, where each of these properties are assumed to vary spatially over a 2-D horizontal grid which is assumed to represent the top of a reservoir. The Bayesian framework in which the inference problem is cast has the key benefits of (1) utilization of a prior model that allows geological information to be incorporated, (2) providing a straightforward means of incorporating all measurements (across the 2-D spatial grid) into the estimates at each gridpoint, (3) allowing different types of measurements to be combined under a single inference procedure and (4) providing a measure of uncertainty in the estimates. The observed data are taken from a 2-D array of surface seismic receivers responding to an array of surface sources. Well understood features from the seismic traces are extracted and treated as the observed data, namely the P-wave reflection amplitude variation with acquisition azimuth and offset (amplitude versus azimuth data) and fracture transfer function (FTF) data. Amplitude versus azimuth data are known to be more sensitive to fracture properties when the fracture spacing is significantly smaller than the seismic wavelength, whereas FTF data are more sensitive to fracture properties when the fracture spacing is on the order of the seismic wavelength. Combining these two measurements has the benefit of allowing inferences to be

  6. Fracture size and transmissivity correlations: Implications for transport simulations in sparse three-dimensional discrete fracture networks following a truncated power law distribution of fracture size

    DOE PAGES

    Hyman, Jeffrey De'Haven; Aldrich, Garrett Allen; Viswanathan, Hari S.; Makedonska, Nataliia; Karra, Satish

    2016-08-25

    We characterize how different fracture size-transmissivity relationships influence flow and transport simulations through sparse three-dimensional discrete fracture networks. Although it is generally accepted that there is a positive correlation between a fracture's size and its transmissivity/aperture, the functional form of that relationship remains a matter of debate. Relationships that assume perfect correlation, semicorrelation, and noncorrelation between the two have been proposed. To study the impact that adopting one of these relationships has on transport properties, we generate multiple sparse fracture networks composed of circular fractures whose radii follow a truncated power law distribution. The distribution of transmissivities are selected somore » that the mean transmissivity of the fracture networks are the same and the distributions of aperture and transmissivity in models that include a stochastic term are also the same. We observe that adopting a correlation between a fracture size and its transmissivity leads to earlier breakthrough times and higher effective permeability when compared to networks where no correlation is used. While fracture network geometry plays the principal role in determining where transport occurs within the network, the relationship between size and transmissivity controls the flow speed. Lastly, these observations indicate DFN modelers should be aware that breakthrough times and effective permeabilities can be strongly influenced by such a relationship in addition to fracture and network statistics.« less

  7. Characterizing Fractured Rock with Geo-structural and Micro-structural Models

    NASA Astrophysics Data System (ADS)

    Dershowitz, William

    2015-04-01

    Fracture spatial structure and hydro-mechanical properties are key to the understanding of fractured rock geomechanical stability, hydrodynamics, and solute transport. This paper presents a quantitative approach to fracture characterization to provide information useful for stability and flow analysis, and for coupled flow/geomechanics. The approach presented is based on the concept of geo-structural, hydro-mechanical, and microstructural models. This approach is applicable for data collected from exposed surfaces (mapping, LiDAR, aero-magnetics), boreholes (core, optical images, and images based on resistivity and geophysical methods), and three dimensional imaging (seismic attributes and microseismics). Examples are presented comparing the results of conventional fracture characterization procedures and the recommended procedure. Fracture characterization for geo-structural fracture models is based on the idea that the geologically based fracture spatial pattern is the key, rather than individual fracture statistics. For example, while fracture intensity statistics can useful, the three dimensional fracture pattern for a bedded sedimentary rock can be better reproduced from the combination of a mechanical bedding model and a correlation between fracture spacing and bed height. In a fracture geo-structural model, the fracture spatial pattern, orientation, and intensity should be characterized in a combination of global and local coordinate systems. While some fracture sets may be oriented relative to the regional tectonics (the global coordinate system), other fracture sets are oriented relative to bedding (a local coordinate system). Fracture hydro-mechanical models define the combination of (a) conductive fractures, (b) flow-barrier fractures, (c) fractures which provide storage porosity, (d) fractures of significance for kinematic stability, and (e) fractures of significance for rock mass strength and deformability. The hydromechanical fractures are a subset of

  8. On the study of crack-initiation fracture toughness of fiber glass asphalt shingles

    SciTech Connect

    Shiao, M.L.

    1999-07-01

    The fracture behavior of fiber glass asphalt shingles was examined by measuring their J-integral fracture toughness at crack initiation. The corresponding fracture mechanisms were also studied by in situ fracture observation and by scanning electron microscopy. The applicability of using J-integral fracture toughness to characterize asphalt shingles was discussed and its relationships to other mechanical properties was established. The results indicated that the fracture toughness at crack initiation can be accurately measured for fiber glass shingles and the values may be used to characterize their cracking resistance. Fracture toughness measured from various shingle samples was found to correlate to the shingle's tensile toughness and to its tear strength. Preliminary results on fracture mechanisms suggested that failure in the asphalt coatings by micro-cavitation may be the controlling event leading to crack advance. The importance of the glass fiber mat on a shingle's resistance to fracture was also discussed.

  9. Approaching a universal scaling relationship between fracture stiffness and fluid flow.

    PubMed

    Pyrak-Nolte, Laura J; Nolte, David D

    2016-01-01

    A goal of subsurface geophysical monitoring is the detection and characterization of fracture alterations that affect the hydraulic integrity of a site. Achievement of this goal requires a link between the mechanical and hydraulic properties of a fracture. Here we present a scaling relationship between fluid flow and fracture-specific stiffness that approaches universality. Fracture-specific stiffness is a mechanical property dependent on fracture geometry that can be monitored remotely using seismic techniques. A Monte Carlo numerical approach demonstrates that a scaling relationship exists between flow and stiffness for fractures with strongly correlated aperture distributions, and continues to hold for fractures deformed by applied stress and by chemical erosion as well. This new scaling relationship provides a foundation for simulating changes in fracture behaviour as a function of stress or depth in the Earth and will aid risk assessment of the hydraulic integrity of subsurface sites. PMID:26868649

  10. Approaching a universal scaling relationship between fracture stiffness and fluid flow

    PubMed Central

    Pyrak-Nolte, Laura J.; Nolte, David D.

    2016-01-01

    A goal of subsurface geophysical monitoring is the detection and characterization of fracture alterations that affect the hydraulic integrity of a site. Achievement of this goal requires a link between the mechanical and hydraulic properties of a fracture. Here we present a scaling relationship between fluid flow and fracture-specific stiffness that approaches universality. Fracture-specific stiffness is a mechanical property dependent on fracture geometry that can be monitored remotely using seismic techniques. A Monte Carlo numerical approach demonstrates that a scaling relationship exists between flow and stiffness for fractures with strongly correlated aperture distributions, and continues to hold for fractures deformed by applied stress and by chemical erosion as well. This new scaling relationship provides a foundation for simulating changes in fracture behaviour as a function of stress or depth in the Earth and will aid risk assessment of the hydraulic integrity of subsurface sites. PMID:26868649

  11. Fracture assessment of Savannah River Reactor carbon steel piping

    SciTech Connect

    Mertz, G.E.; Stoner, K.J.; Caskey, G.R. ); Begley, J.A. )

    1991-01-01

    The Savannah River Site (SRS) production reactors have been in operation since the mid-1950's. One postulated failure mechanism for the reactor piping is brittle fracture of the original A285 and A53 carbon steel piping. Material testing of archival piping determined (1) the static and dynamic tensile properties; (2) Charpy impact toughness; and (3) the static and dynamic compact tension fracture toughness properties. The nil-ductility transition temperature (NDTT), determined by Charpy impact test, is above the minimum operating temperature for some of the piping materials. A fracture assessment was performed to demonstrate that potential flaws are stable under upset loading conditions and minimum operating temperatures. A review of potential degradation mechanisms and plant operating history identified weld defects as the most likely crack initiation site for brittle fracture. Piping weld defects, as characterized by radiographic and metallographic examination, and low fracture toughness material properties were postulated at high stress locations in the piping. Normal operating loads, upset loads, and residual stresses were assumed to act on the postulated flaws. Calculated allowable flaw lengths exceed the size of observed weld defects, indicating adequate margins of safety against brittle fracture. Thus, a detailed fracture assessment was able to demonstrate that the piping systems will not fail by brittle fracture, even though the NDTT for some of the piping is above the minimum system operating temperature.

  12. Aluminum penetration and fracture of titanium diboride

    SciTech Connect

    Dorward, R.C.

    1982-01-01

    Relatively porous titanium diboride (/approximately equals/96% dense) is penetrated with aluminum metal when used as a cathode in aluminum reduction cells operating at 970/sup 0/C. Metal penetration changes the predominant fracture mode from transgranular to intergranular, and has potentially important ramifications on mechanical properties. 3 refs.

  13. Transmissivity and conductivity of single fractures

    NASA Astrophysics Data System (ADS)

    Adler, Pierre; Mourzenko, Valeri; Thovert, Jean-François

    2013-04-01

    A single fracture can be represented as a void space between two rough surfaces which touch one another. Transmissivity and conductivity can be determined numerically by solving the Stokes and the Laplace equations between these two rough surfaces. These problems were first solved and published by the same authors between 1995 and 2001 (see the corresponding references in [1]). The major purpose of this presentation is to provide updated, complete and more precise results for fractures with surfaces of two different types. Each surface of a fracture can be schematized as a random surface which oscillates around an average plane; this surface is characterized by the probability density of the heights and the autocorrelation function C(u) of these heights; the standard deviation of the height is the roughness sigma. In addition a fracture requires the knowledge of the distance bm between the two average planes and the intercorrelation coefficient theta between the heights. There are two major classes of autocorrelation functions, namely the Gaussian and the self-affine autocorrelation which are both characterized by a length scale l_c, which is a typical scale for the surface features in the Gaussian case and a cut-off length in the self-affine case. There is a major difference between these two classes since the first one corresponds to statistically homogeneous surfaces and the second one to self-affine surfaces; in the latter case which necessitates the introduction of another parameter which is the Hurst exponent, the average properties of the fracture depend on the size of the sample in contrast with the former case. Systematic calculations were performed for these two classes and master curves are provided and discussed. Systematic results for Gaussian fractures are displayed as functions of b_m/sigma, l_c/sigma and theta; the influence of theta is negligible when the ratio l_c/sigma is small enough. It is also shown that the Reynolds approximation does not

  14. Spartan Release Engagement Mechanism (REM) stress and fracture analysis

    NASA Technical Reports Server (NTRS)

    Marlowe, D. S.; West, E. J.

    1984-01-01

    The revised stress and fracture analysis of the Spartan REM hardware for current load conditions and mass properties is presented. The stress analysis was performed using a NASTRAN math model of the Spartan REM adapter, base, and payload. Appendix A contains the material properties, loads, and stress analysis of the hardware. The computer output and model description are in Appendix B. Factors of safety used in the stress analysis were 1.4 on tested items and 2.0 on all other items. Fracture analysis of the items considered fracture critical was accomplished using the MSFC Crack Growth Analysis code. Loads and stresses were obtaind from the stress analysis. The fracture analysis notes are located in Appendix A and the computer output in Appendix B. All items analyzed met design and fracture criteria.

  15. Numerical modeling of thermal conductive heating in fractured bedrock.

    PubMed

    Baston, Daniel P; Falta, Ronald W; Kueper, Bernard H

    2010-01-01

    Numerical modeling was employed to study the performance of thermal conductive heating (TCH) in fractured shale under a variety of hydrogeological conditions. Model results show that groundwater flow in fractures does not significantly affect the minimum treatment zone temperature, except near the beginning of heating or when groundwater influx is high. However, fracture and rock matrix properties can significantly influence the time necessary to remove all liquid water (i.e., reach superheated steam conditions) in the treatment area. Low matrix permeability, high matrix porosity, and wide fracture spacing can contribute to boiling point elevation in the rock matrix. Consequently, knowledge of these properties is important for the estimation of treatment times. Because of the variability in boiling point throughout a fractured rock treatment zone and the absence of a well-defined constant temperature boiling plateau in the rock matrix, it may be difficult to monitor the progress of thermal treatment using temperature measurements alone.

  16. A new device for characterizing fracture networks and measuring groundwater and contaminant fluxes in fractured rock aquifers

    NASA Astrophysics Data System (ADS)

    Klammler, Harald; Hatfield, Kirk; Newman, Mark A.; Cho, Jaehyun; Annable, Michael D.; Parker, Beth L.; Cherry, John A.; Perminova, Irina

    2016-07-01

    This paper presents the fundamental theory and laboratory test results on a new device that is deployed in boreholes in fractured rock aquifers to characterize vertical distributions of water and contaminant fluxes, aquifer hydraulic properties, and fracture network properties (e.g., active fracture density and orientation). The device, a fractured rock passive flux meter (FRPFM), consists of an inflatable core assembled with upper and lower packers that isolate the zone of interest from vertical gradients within the borehole. The outer layer of the core consists of an elastic fabric mesh equilibrated with a visible dye which is used to provide visual indications of active fractures and measures of fracture location, orientation, groundwater flux, and the direction of that flux. Beneath the outer layer is a permeable sorbent that is preloaded with known amounts of water soluble tracers which are eluted at rates proportional to groundwater flow. This sorbent also captures target contaminants present in intercepted groundwater. The mass of contaminant sorbed is used to quantify cumulative contaminant flux; whereas, the mass fractions of resident tracers lost are used to provide measures of water flux. In this paper, the FRPFM is bench tested over a range of fracture velocities (2-20 m/day) using a single fracture flow apparatus (fracture aperture = 0.5 mm). Test results show a discoloration in visible dye corresponding to the location of the active fracture. The geometry of the discoloration can be used to discern fracture orientation as well as direction and magnitude of flow in the fracture. Average contaminant fluxes were measured within 16% and water fluxes within 25% of known imposed fluxes.

  17. Studies on tensile properties and fracture behavior of Al-6Si-0.5Mg (-Cu or/and Ni) alloys at various strain rates

    NASA Astrophysics Data System (ADS)

    Hossain, A.; Gulshan, F.; Kurny, A. S. W.

    2016-07-01

    The aim of this paper is to evaluate the effects of various strain rates on the tensile properties of Al-6Si-0.5Mg cast alloys with Cu or/and Ni additions and to establish data on the stress-strain behavior of the alloys with applications in automotive engineering. Experimental alloys of the following composition were prepared by melt processing technique. Both microstructure and the mechanical properties were investigated. The uniaxial tension test was carried out at strain rates ranging from 10-4s-1 to 10-2s-1. Tensile strengths were found to increase with ageing temperature and the maximum being attained at peak age condition (1hr at 225°C). The additions of Cu or/and Ni resulted in an increase in tensile strength and 2wt% Cu content alloy (Al-6Si-0.5Mg-2Cu) showed maximum strength. Evaluation of tensile properties at three strain rates (10-4, 10-3 and 10-2s-1) showed that strain rates affected the tensile properties significantly. At higher strain rates the strength was better but ductility was poor.

  18. Experimental and Numerical Analysis of Capillary Imbibition in Fractured Sandstone under Controlled Fracture Flow Conditions

    NASA Astrophysics Data System (ADS)

    Lee, C.; Karpyn, Z. T.

    2010-12-01

    Fractures serve as primary conduits and have great impact on the migration of injected fluid into fractured permeable media. Appropriate transport properties such as relative permeability and capillary pressures are essential for successful simulation and prediction of multi-phase flow in such systems. However, the lack of thorough understanding of the dynamics governing immiscible displacement in fractured media, limit our ability to properly represent their macroscopic transport properties. The present work is one component of a multi-variable analysis of factors affecting fracture-matrix imbibition, including injection rates, fluid properties, and fracture orientation. We conduct laboratory experiments to monitor spatial and temporal evolution of saturation distributions in fractured sandstone samples. Air-brine, kerosene-brine and mixed oil-brine were used as three different fluid pairs in separate sets of experiments. Results were then mimicked using an automated history matching approach to obtain representative relative permeability and capillary pressure curves to further investigate the interplay of gravity, capillary and viscous forces, on predictive simulation tests. Sensitive analyses, in combination with direct experimental observation, allowed us to explore the relative importance of injection flow rate, gravity effect, and fluid properties on the evolving imbibition front. High fracture flow rates favor faster recovery from the matrix, at the expense of higher pore volume injected, and generate a sharp saturation transition at the edge of the imbibing front. Water saturation in the imbibed zone remains constant at around 0.5 to 0.6, suggesting a dynamic equilibrium in the mobility of the fluid phases. Liquid-liquid and gas-liquid imbibition results show significant differences in the shape of the imbibing front, breakthrough time, and saturation profiles. Results from this work also assist in the identification of favorable conditions for cocurrent

  19. Predicting Hip Fracture Type With Cortical Bone Mapping (CBM) in the Osteoporotic Fractures in Men (MrOS) Study.

    PubMed

    Treece, Graham M; Gee, Andrew H; Tonkin, Carol; Ewing, Susan K; Cawthon, Peggy M; Black, Dennis M; Poole, Kenneth E S

    2015-11-01

    Hip fracture risk is known to be related to material properties of the proximal femur, but fracture prediction studies adding richer quantitative computed tomography (QCT) measures to dual-energy X-ray (DXA)-based methods have shown limited improvement. Fracture types have distinct relationships to predictors, but few studies have subdivided fracture into types, because this necessitates regional measurements and more fracture cases. This work makes use of cortical bone mapping (CBM) to accurately assess, with no prior anatomical presumptions, the distribution of properties related to fracture type. CBM uses QCT data to measure the cortical and trabecular properties, accurate even for thin cortices below the imaging resolution. The Osteoporotic Fractures in Men (MrOS) study is a predictive case-cohort study of men over 65 years old: we analyze 99 fracture cases (44 trochanteric and 55 femoral neck) compared to a cohort of 308, randomly selected from 5994. To our knowledge, this is the largest QCT-based predictive hip fracture study to date, and the first to incorporate CBM analysis into fracture prediction. We show that both cortical mass surface density and endocortical trabecular BMD are significantly different in fracture cases versus cohort, in regions appropriate to fracture type. We incorporate these regions into predictive models using Cox proportional hazards regression to estimate hazard ratios, and logistic regression to estimate area under the receiver operating characteristic curve (AUC). Adding CBM to DXA-based BMD leads to a small but significant (p < 0.005) improvement in model prediction for any fracture, with AUC increasing from 0.78 to 0.79, assessed using leave-one-out cross-validation. For specific fracture types, the improvement is more significant (p < 0.0001), with AUC increasing from 0.71 to 0.77 for trochanteric fractures and 0.76 to 0.82 for femoral neck fractures. In contrast, adding DXA-based BMD to a CBM-based predictive model

  20. NASGRO(registered trademark): Fracture Mechanics and Fatigue Crack Growth Analysis Software

    NASA Technical Reports Server (NTRS)

    Forman, Royce; Shivakumar, V.; Mettu, Sambi; Beek, Joachim; Williams, Leonard; Yeh, Feng; McClung, Craig; Cardinal, Joe

    2004-01-01

    This viewgraph presentation describes NASGRO, which is a fracture mechanics and fatigue crack growth analysis software package that is used to reduce risk of fracture in Space Shuttles. The contents include: 1) Consequences of Fracture; 2) NASA Fracture Control Requirements; 3) NASGRO Reduces Risk; 4) NASGRO Use Inside NASA; 5) NASGRO Components: Crack Growth Module; 6) NASGRO Components:Material Property Module; 7) Typical NASGRO analysis: Crack growth or component life calculation; and 8) NASGRO Sample Application: Orbiter feedline flowliner crack analysis.

  1. Origin of Permeability and Structure of Flows in Fractured Media

    NASA Astrophysics Data System (ADS)

    De Dreuzy, J.; Darcel, C.; Davy, P.; Erhel, J.; Le Goc, R.; Maillot, J.; Meheust, Y.; Pichot, G.; Poirriez, B.

    2013-12-01

    After more than three decades of research, flows in fractured media have been shown to result from multi-scale geological structures. Flows result non-exclusively from the damage zone of the large faults, from the percolation within denser networks of smaller fractures, from the aperture heterogeneity within the fracture planes and from some remaining permeability within the matrix. While the effect of each of these causes has been studied independently, global assessments of the main determinisms is still needed. We propose a general approach to determine the geological structures responsible for flows, their permeability and their organization based on field data and numerical modeling [de Dreuzy et al., 2012b]. Multi-scale synthetic networks are reconstructed from field data and simplified mechanical modeling [Davy et al., 2010]. High-performance numerical methods are developed to comply with the specificities of the geometry and physical properties of the fractured media [Pichot et al., 2010; Pichot et al., 2012]. And, based on a large Monte-Carlo sampling, we determine the key determinisms of fractured permeability and flows (Figure). We illustrate our approach on the respective influence of fracture apertures and fracture correlation patterns at large scale. We show the potential role of fracture intersections, so far overlooked between the fracture and the network scales. We also demonstrate how fracture correlations reduce the bulk fracture permeability. Using this analysis, we highlight the need for more specific in-situ characterization of fracture flow structures. Fracture modeling and characterization are necessary to meet the new requirements of a growing number of applications where fractures appear both as potential advantages to enhance permeability and drawbacks for safety, e.g. in energy storage, stimulated geothermal energy and non-conventional gas productions. References Davy, P., et al. (2010), A likely universal model of fracture scaling and

  2. Geomechanically Coupled Simulation of Flow in Fractured Reservoirs

    NASA Astrophysics Data System (ADS)

    Barton, C.; Moos, D.; Hartley, L.; Baxter, S.; Foulquier, L.; Holl, H.; Hogarth, R.

    2012-12-01

    Capturing the necessary and sufficient detail of reservoir hydraulics to accurately evaluate reservoir behavior remains a significant challenge to the exploitation and management of fracture-dominated geothermal reservoirs. In these low matrix permeability reservoirs, stimulation response is controlled largely by the properties of natural and induced fracture networks, which are in turn controlled by the in situ stresses, the fracture distribution and connectivity and the hydraulic behavior of the fractures. This complex interaction of fracture flow systems with the present-day stress field compounds the problem of developing an effective and efficient simulation to characterize, model and predict fractured reservoir performance. We discuss here a case study of the integration of geological, geophysical, geomechanical, and reservoir engineering data to characterize the in situ stresses, the natural fracture network and the controls on fracture permeability in geothermal reservoirs. A 3D geomechanical reservoir model includes constraints on stress magnitudes and orientations, and constraints on mechanical rock properties and the fractures themselves. Such a model is essential to understanding reservoir response to stimulation and production in low matrix permeability, fracture-dominated reservoirs. The geomechanical model for this study was developed using petrophysical, drilling, and wellbore image data along with direct well test measurements and was mapped to a 3D structural grid to facilitate coupled simulation of the fractured reservoir. Wellbore image and stimulation test data were used along with microseismic data acquired during the test to determine the reservoir fracture architecture and to provide control points for a realistic inter-connected discrete fracture network. As most fractures are stress-sensitive, their hydraulic conductivities will change with changes in bottomhole flowing and reservoir pressures, causing variations in production profiles

  3. Metatarsal shaft fractures and fractures of the proximal fifth metatarsal.

    PubMed

    Fetzer, Gary B; Wright, Rick W

    2006-01-01

    Metatarsal fractures represent a relatively common injury, especially in athletes. The pertinent anatomy, evaluation, diagnosis, classification, and treatment of acute and chronic (stress) metatarsal shaft fractures are discussed. Fractures of the proximal fifth metatarsal, which are unique and important injuries, are also discussed. Treatment remains relatively straightforward for the traumatic metatarsal injury, whereas traditional stress fractures typically heal with decreased activity. The problematic proximal fifth metatarsal fracture (Jones fracture) frequently requires surgical intervention in patients who want to avoid non-weight-bearing cast immobilization. The authors' current treatment for this fracture includes the option of intramedullary fixation versus cast immobilization.

  4. Particle Swarm Transport in Fracture Networks

    NASA Astrophysics Data System (ADS)

    Pyrak-Nolte, L. J.; Mackin, T.; Boomsma, E.

    2012-12-01

    Colloidal particles of many types occur in fractures in the subsurface as a result of both natural and industrial processes (e.g., environmental influences, synthetic nano- & micro-particles from consumer products, chemical and mechanical erosion of geologic material, proppants used in gas and oil extraction, etc.). The degree of localization and speed of transport of such particles depends on the transport mechanisms, the chemical and physical properties of the particles and the surrounding rock, and the flow path geometry through the fracture. In this study, we investigated the transport of particle swarms through artificial fracture networks. A synthetic fracture network was created using an Objet Eden 350V 3D printer to build a network of fractures. Each fracture in the network had a rectangular cross-sectional area with a constant depth of 7 mm but with widths that ranged from 2 mm to 11 mm. The overall dimensions of the network were 132 mm by 166 mm. The fracture network had 7 ports that were used either as the inlet or outlet for fluid flow through the sample or for introducing a particle swarm. Water flow rates through the fracture were controlled with a syringe pump, and ranged from zero flow to 6 ml/min. Swarms were composed of a dilute suspension (2% by mass) of 3 μm fluorescent polystyrene beads in water. Swarms with volumes of 5, 10, 20, 30 and 60 μl were used and delivered into the network using a second syringe pump. The swarm behavior was imaged using an optical fluorescent imaging system illuminated by green (525 nm) LED arrays and captured by a CCD camera. For fracture networks with quiescent fluids, particle swarms fell under gravity and remained localized within the network. Large swarms (30-60 μl) were observed to bifurcate at shallower depths resulting in a broader dispersal of the particles than for smaller swarm volumes. For all swarm volumes studied, particle swarms tended to bifurcate at the intersection between fractures. These

  5. Modern Workflows for Fracture Rock Hydrogeology

    NASA Astrophysics Data System (ADS)

    Doe, T.

    2015-12-01

    Discrete Fracture Network (DFN) is a numerical simulation approach that represents a conducting fracture network using geologically realistic geometries and single-conductor hydraulic and transport properties. In terms of diffusion analogues, equivalent porous media derive from heat conduction in continuous media, while DFN simulation is more similar to electrical flow and diffusion in circuits with discrete pathways. DFN modeling grew out of pioneering work of David Snow in the late 1960s with additional impetus in the 1970's from the development of the development of stochastic approaches for describing of fracture geometric and hydrologic properties. Research in underground test facilities for radioactive waste disposal developed the necessary linkages between characterization technologies and simulation as well as bringing about a hybrid deterministic stochastic approach. Over the past 40 years DFN simulation and characterization methods have moved from the research environment into practical, commercial application. The key geologic, geophysical and hydrologic tools provide the required DFN inputs of conductive fracture intensity, orientation, and transmissivity. Flow logging either using downhole tool or by detailed packer testing identifies the locations of conducting features in boreholes, and image logging provides information on the geology and geometry of the conducting features. Multi-zone monitoring systems isolate the individual conductors, and with subsequent drilling and characterization perturbations help to recognize connectivity and compartmentalization in the fracture network. Tracer tests and core analysis provide critical information on the transport properties especially matrix diffusion unidentified conducting pathways. Well test analyses incorporating flow dimension boundary effects provide further constraint on the conducting geometry of the fracture network.

  6. Periprosthetic patellar fractures.

    PubMed

    Adigweme, Obinna O; Sassoon, Adam A; Langford, Joshua; Haidukewych, George J

    2013-10-01

    Periprosthetic patellar fractures represent a spectrum of injuries to a patient with a total knee arthroplasty. They range in severity from an inconsequential injury, which does not compromise function, to a severely debilitating injury that may require advanced reconstructive measures. This article will outline the epidemiology and risk factors associated with periprosthetic patellar fractures. Treatment options as they relate to injury mechanism, fracture severity, patellar component stability, and remaining bone stock will also be discussed. Finally, a review of the current literature regarding the results of treatment will be presented.

  7. Biomechanical Characteristics of Osteoporotic Fracture Healing in Ovariectomized Rats: A Systematic Review.

    PubMed

    Chen, Lin; Yang, Long; Yao, Min; Cui, Xue-Jun; Xue, Chun-Chun; Wang, Yong-Jun; Shu, Bing

    2016-01-01

    Biomechanical tests are widely used in animal studies on osteoporotic fracture healing. However, the biomechanical recovery process is still unknown, leading to difficulty in choosing time points for biomechanical tests and in correctly assessing osteoporotic fracture healing. To determine the biomechanical recovery process during osteoporotic fracture healing, studies on osteoporotic femur fracture healing with biomechanical tests in ovariectomized rat (OVX) models were collected from PUBMED, EMBASE, and Chinese databases. Quadratic curves of fracture healing time and maximum load were fitted with data from the analyzed studies. In the fitted curve for normal fractures, the predicted maximum load was 145.56 N, and the fracture healing time was 88.0 d. In the fitted curve for osteoporotic fractures, the predicted maximum load was 122.30 N, and the fracture healing time was 95.2 d. The maximum load of fractured femurs in OVX rats was also lower than that in sham rats at day 84 post-fracture (D84 PF). The fracture healing time was prolonged and maximum load at D84 PF decreased in OVX rats with closed fractures. The maximum load of Wister rats was higher than that of Sprague-Dawley (SD) rats, but the fracture healing time of SD and Wister rats was similar. Osteoporotic fracture healing was delayed in rats that were < = 12 weeks old when ovariectomized, and at D84 PF, the maximum load of rats < = 12 weeks old at ovariectomy was lower than that of rats >12 weeks old at ovariectomy. There was no significant difference in maximum load at D84 PF between rats with an osteoporosis modeling time <12 weeks and > = 12 weeks. In conclusion, fracture healing was delayed and biomechanical property decreased by osteoporosis. Time points around D95.2 PF should be considered for biomechanical tests of osteoporotic femur fracture healing in OVX rat models. Osteoporotic fracture healing in OVX rats was affected by the fracture type but not by the strain of the rat. PMID:27055104

  8. Biomechanical Characteristics of Osteoporotic Fracture Healing in Ovariectomized Rats: A Systematic Review.

    PubMed

    Chen, Lin; Yang, Long; Yao, Min; Cui, Xue-Jun; Xue, Chun-Chun; Wang, Yong-Jun; Shu, Bing

    2016-01-01

    Biomechanical tests are widely used in animal studies on osteoporotic fracture healing. However, the biomechanical recovery process is still unknown, leading to difficulty in choosing time points for biomechanical tests and in correctly assessing osteoporotic fracture healing. To determine the biomechanical recovery process during osteoporotic fracture healing, studies on osteoporotic femur fracture healing with biomechanical tests in ovariectomized rat (OVX) models were collected from PUBMED, EMBASE, and Chinese databases. Quadratic curves of fracture healing time and maximum load were fitted with data from the analyzed studies. In the fitted curve for normal fractures, the predicted maximum load was 145.56 N, and the fracture healing time was 88.0 d. In the fitted curve for osteoporotic fractures, the predicted maximum load was 122.30 N, and the fracture healing time was 95.2 d. The maximum load of fractured femurs in OVX rats was also lower than that in sham rats at day 84 post-fracture (D84 PF). The fracture healing time was prolonged and maximum load at D84 PF decreased in OVX rats with closed fractures. The maximum load of Wister rats was higher than that of Sprague-Dawley (SD) rats, but the fracture healing time of SD and Wister rats was similar. Osteoporotic fracture healing was delayed in rats that were < = 12 weeks old when ovariectomized, and at D84 PF, the maximum load of rats < = 12 weeks old at ovariectomy was lower than that of rats >12 weeks old at ovariectomy. There was no significant difference in maximum load at D84 PF between rats with an osteoporosis modeling time <12 weeks and > = 12 weeks. In conclusion, fracture healing was delayed and biomechanical property decreased by osteoporosis. Time points around D95.2 PF should be considered for biomechanical tests of osteoporotic femur fracture healing in OVX rat models. Osteoporotic fracture healing in OVX rats was affected by the fracture type but not by the strain of the rat.

  9. Biomechanical Characteristics of Osteoporotic Fracture Healing in Ovariectomized Rats: A Systematic Review

    PubMed Central

    Chen, Lin; Yang, Long; Yao, Min; Cui, Xue-Jun; Xue, Chun-Chun; Wang, Yong-Jun; Shu, Bing

    2016-01-01

    Biomechanical tests are widely used in animal studies on osteoporotic fracture healing. However, the biomechanical recovery process is still unknown, leading to difficulty in choosing time points for biomechanical tests and in correctly assessing osteoporotic fracture healing. To determine the biomechanical recovery process during osteoporotic fracture healing, studies on osteoporotic femur fracture healing with biomechanical tests in ovariectomized rat (OVX) models were collected from PUBMED, EMBASE, and Chinese databases. Quadratic curves of fracture healing time and maximum load were fitted with data from the analyzed studies. In the fitted curve for normal fractures, the predicted maximum load was 145.56 N, and the fracture healing time was 88.0 d. In the fitted curve for osteoporotic fractures, the predicted maximum load was 122.30 N, and the fracture healing time was 95.2 d. The maximum load of fractured femurs in OVX rats was also lower than that in sham rats at day 84 post-fracture (D84 PF). The fracture healing time was prolonged and maximum load at D84 PF decreased in OVX rats with closed fractures. The maximum load of Wister rats was higher than that of Sprague-Dawley (SD) rats, but the fracture healing time of SD and Wister rats was similar. Osteoporotic fracture healing was delayed in rats that were < = 12 weeks old when ovariectomized, and at D84 PF, the maximum load of rats < = 12 weeks old at ovariectomy was lower than that of rats >12 weeks old at ovariectomy. There was no significant difference in maximum load at D84 PF between rats with an osteoporosis modeling time <12 weeks and > = 12 weeks. In conclusion, fracture healing was delayed and biomechanical property decreased by osteoporosis. Time points around D95.2 PF should be considered for biomechanical tests of osteoporotic femur fracture healing in OVX rat models. Osteoporotic fracture healing in OVX rats was affected by the fracture type but not by the strain of the rat. PMID:27055104

  10. Surgery for scapula process fractures

    PubMed Central

    Anavian, Jack; Wijdicks, Coen A; Schroder, Lisa K; Vang, Sandy

    2009-01-01

    Background Generally, scapula process fractures (coracoid and acromion) have been treated nonoperatively with favorable outcome, with the exception of widely displaced fractures. Very little has been published, however, regarding the operative management of such fractures and the literature that is available involves very few patients. Our hypothesis was that operative treatment of displaced acromion and coracoid fractures is a safe and effective treatment that yields favorable surgical results. Methods We reviewed 26 consecutive patients (27 fractures) treated between 1998 and 2007. Operative indications for these process fractures included either a painful nonunion, a concomitant ipsilateral operative scapula fracture, ≥ 1 cm of displacement on X-ray, or a multiple disruption of the superior shoulder suspensory complex. All patients were followed until they were asymptomatic, displayed radiographic fracture union, and had recovered full motion with no pain. Patients and results 21 males and 5 females, mean age 36 (18–67) years, were included in the study. 18 patients had more than one indication for surgery. Of the 27 fractures, there were 13 acromion fractures and 14 coracoid fractures. 1 patient was treated for both a coracoid and an acromion fracture. Fracture patterns for the acromion included 6 acromion base fractures and 7 fractures distal to the base. Coracoid fracture patterns included 11 coracoid base fractures and 3 fractures distal to the base. Mean follow-up was 11 (2–42) months. All fractures united and all patients had recovered full motion with no pain at the time of final follow-up. 3 patients underwent removal of hardware due to irritation from hardware components that were too prominent. There were no other complications. Interpretation While most acromion and coracoid fractures can be treated nonoperatively with satisfactory results, operative management may be indicated for displaced fractures and double lesions of the superior shoulder

  11. Mechanical Coal-Face Fracturer

    NASA Technical Reports Server (NTRS)

    Collins, E. R., Jr.

    1984-01-01

    Radial points on proposed drill bit take advantage of natural fracture planes of coal. Radial fracture points retracted during drilling and impacted by piston to fracture coal once drilling halts. Group of bits attached to array of pneumatic drivers to fracture large areas of coal face.

  12. Fracture Toughness Prediction for MWCNT Reinforced Ceramics

    SciTech Connect

    Henager, Charles H.; Nguyen, Ba Nghiep

    2013-09-01

    This report describes the development of a micromechanics model to predict fracture toughness of multiwall carbon nanotube (MWCNT) reinforced ceramic composites to guide future experimental work for this project. The modeling work described in this report includes (i) prediction of elastic properties, (ii) development of a mechanistic damage model accounting for matrix cracking to predict the composite nonlinear stress/strain response to tensile loading to failure, and (iii) application of this damage model in a modified boundary layer (MBL) analysis using ABAQUS to predict fracture toughness and crack resistance behavior (R-curves) for ceramic materials containing MWCNTs at various volume fractions.

  13. Material Characterization for Ductile Fracture Prediction

    NASA Technical Reports Server (NTRS)

    Hill, Michael R.

    2000-01-01

    The research summarized in this document provides valuable information for structural health evaluation of NASA infrastructure. Specifically, material properties are reported which will enable calibration of ductile fracture prediction methods for three high-toughness metallic materials and one aluminum alloy which can be found in various NASA facilities. The task of investigating these materials has also served to validate an overall methodology for ductile fracture prediction is currently being employed at NASA. In facilitating the ability to incorporate various materials into the prediction scheme, we have provided data to enable demonstration of the overall generality of the approach.

  14. The effects of roughness and offset on fracture compliance ratio

    NASA Astrophysics Data System (ADS)

    Ahmadi, M.; Taleghani, A. Dahi; Sayers, C. M.

    2016-04-01

    Fractures are a source of extra compliance in the rock mass. The mechanical properties of the rock matrix as well as the propagation of seismic waves inside the rock medium are dependent on the magnitude of roughness and offset between the imperfect fracture interfaces. Fracture compliance can estimate the degree of contact between fracture faces, type of fluid filling the fracture and the fracture roughness. To characterize these fracture properties, compliance ratio, known by the ratio of normal-to-shear compliance, can be a potential tool in the subsurface studies to improve the well layout design. The focus of this study is to illustrate how the compliance ratio of a rough fracture, with or without the offset between the fracture faces, can diverge from the compliance ratio of a fracture with smooth interface. Quasi-static and dynamic methods are two common ways to calculate the compliance. The former calculates the compliance by measuring the change in the displacement with the applied stress, while the latter estimates the compliance through monitoring the changes in propagation of seismic waves. To compare the compliance ratios of fractures with imperfect and smooth interfaces in an infinite medium, a numerical finite-element model is built in commercial finite-element software. The imperfect interface of the fracture is modeled with saw-tooth-like structures where they can be partially or fully in contact. The defined saw-tooth-like structures of contact asperities impose an in-plane asymmetry in the shear direction. This asymmetry causes two different values for the compliance in shear direction, known as the soft and stiff shear compliance. Our numerical simulations suggest the increase in the degree of contact between the fracture faces increases the compliance ratio in the stiff direction more than the soft direction. The compliance ratio of the fracture with the imperfect interface is larger than the compliance ratio of the smooth fracture. We suggest

  15. MULTI-PHASE FRACTURE-MATRIX INTERACTIONS UNDER STRESS CHANGES

    SciTech Connect

    A.S. Grader; D. Elsworth; P.M. Halleck; F. Alvarado; H. Yasuhara; A. Alajmi; Z. Karpyn

    2002-10-28

    The main objectives of this project are to quantify the changes in fracture porosity and multiphase transport properties as a function of confining stress. These changes will be integrated into conceptual and numerical models that will improve our ability to predict and optimize fluid transport in fractured system. This report details our progress on: (1) developing the direct experimental measurements of fracture aperture and topology using high-resolution x-ray microtomography, (2) modeling of fracture permeability in the presence of asperities and confining stress, and (3) simulation of two-phase fluid flow in a fracture and a layered matrix. The three-dimensional surface that describes the large-scale structure of the fracture in the porous medium can be determined using x-ray micro-tomography with significant accuracy. The distribution of fracture aperture is a difficult issue that we are studying and developing methods of quantification. The difficulties are both numerical and conceptual. Numerically, the three-dimensional data sets include millions, and sometimes, billions of points, and pose a computational challenge. The conceptual difficulties derive from the rough nature of the fracture surfaces, and the heterogeneous nature of the rock matrix. However, the high-resolution obtained by the imaging system provides us a much needed measuring environment on rock samples that are subjected to simultaneous fluid flow and confining stress. Pilot multi-phase experiments have been performed, proving the ability to detect two phases in certain large fractures. The absolute permeability of a fracture depends on the behavior of the asperities that keep it open. A model is being developed that predicts the permeability and average aperture of a fracture as a function of time under steady flow of water including the pressure solution at the asperity contact points. Several two-phase flow experiments in the presence of a fracture tip were performed in the past. At the

  16. Property.

    ERIC Educational Resources Information Center

    Piele, Philip K.

    Several court cases involving acquisition, use, and disposal of property by institutions of higher education are briefly summarized in this chapter. Cases discussed touch on such topics as municipal annexation of university property; repurchase of properties temporarily allocated to faculty members; implications of zoning laws and zoning board…

  17. Interphase effect on intralaminar fracture toughness

    SciTech Connect

    Hrivnak, J.A.; Dagastine, R.R.; McCullough, R.L.

    1996-12-31

    In fiber reinforced thermoset composites there is a growing body of experimental evidence which has pointed to a region at the fiber/matrix boundary with properties that differ from the fiber or matrix. This region extends beyond the two dimensional interface at the fiber/matrix boundary to have a finite thickness with chemical and structural property gradients. This leads to the concept of an interphase region. The interphase has a large effect on the thermal and mechanical properties of the composite such as fracture toughness, glass transition temperature and the coefficient of thermal expansion. Understanding the interphase region becomes crucial to tailoring a composite to a desired set of properties.

  18. Fracture Intersection Waves: Theory and Experiment

    NASA Astrophysics Data System (ADS)

    Abell, B.; Pyrak-Nolte, L. J.

    2013-12-01

    Fractures and fracture intersections are found nearly everywhere on earth and have also been observed on planetary surfaces within our solar system. The presence of fracture intersections adds complexity to the three-dimensional flow paths through rock and alters the scattered seismic wave field in a manner that does not occur for single fractures or parallel sets of fractures. A main challenge in working with intersecting fractures is how to determine the properties of intersections, whether intersections act as barriers to flow or as highly conductive paths. In this study, we determine theoretically and experimentally that the existence and velocity of intersection waves depends on the specific stiffness of the intersection which is stress dependent. It is well known that a single block supports a wedge wave along the corner or edge of a block. Conceptually, an intersection between two orthogonal fractures can be represented as four blocks coupled along their edges or as the coupling of four wedge waves. In this study, displacement discontinuity boundary conditions (discontinuity in displacement with continuity in stress) were used to represent the coupling among the blocks that form the fractures and the fracture intersection. Based on this approach, intersection waves were derived that are dispersive and range in velocity from a single wedge-mode to the bulk shear wave velocity. For low intersection stiffness, an intersection wave travels at the single wedge wave velocity because the intersection behaves as a free surface. As the intersection stiffness increases, the intersection wave velocity increases continuously to the Rayleigh velocity when two of the blocks forming the intersection are coupled. Finally, the intersection wave velocity increases continuously to the bulk shear wave velocity as coupling between all four blocks approaches the condition of a welded interface as the stiffness of the intersection and fractures increases. The velocity of the

  19. Fracturing and brittleness index analyses of shales

    NASA Astrophysics Data System (ADS)

    Barnhoorn, Auke; Primarini, Mutia; Houben, Maartje

    2016-04-01

    The formation of a fracture network in rocks has a crucial control on the flow behaviour of fluids. In addition, an existing network of fractures , influences the propagation of new fractures during e.g. hydraulic fracturing or during a seismic event. Understanding of the type and characteristics of the fracture network that will be formed during e.g. hydraulic fracturing is thus crucial to better predict the outcome of a hydraulic fracturing job. For this, knowledge of the rock properties is crucial. The brittleness index is often used as a rock property that can be used to predict the fracturing behaviour of a rock for e.g. hydraulic fracturing of shales. Various terminologies of the brittleness index (BI1, BI2 and BI3) exist based on mineralogy, elastic constants and stress-strain behaviour (Jin et al., 2014, Jarvie et al., 2007 and Holt et al., 2011). A maximum brittleness index of 1 predicts very good and efficient fracturing behaviour while a minimum brittleness index of 0 predicts a much more ductile shale behaviour. Here, we have performed systematic petrophysical, acoustic and geomechanical analyses on a set of shale samples from Whitby (UK) and we have determined the three different brittleness indices on each sample by performing all the analyses on each of the samples. We show that each of the three brittleness indices are very different for the same sample and as such it can be concluded that the brittleness index is not a good predictor of the fracturing behaviour of shales. The brittleness index based on the acoustic data (BI1) all lie around values of 0.5, while the brittleness index based on the stress strain data (BI2) give an average brittleness index around 0.75, whereas the mineralogy brittleness index (BI3) predict values below 0.2. This shows that by using different estimates of the brittleness index different decisions can be made for hydraulic fracturing. If we would rely on the mineralogy (BI3), the Whitby mudstone is not a suitable

  20. Ankle fracture - aftercare

    MedlinePlus

    ... that surgery can allow faster and more reliable healing. In children, the fracture involves the part of ... will use a special walking boot as the healing progresses. You will need to learn: How to ...

  1. Geothermal Ultrasonic Fracture Imager

    SciTech Connect

    Patterson, Doug; Leggett, Jim

    2013-07-29

    The Geothermal Ultrasonic Fracture Imager project has a goal to develop a wireline ultrasonic imager that is capable of operating in temperatures up to 300°C (572°F) and depths up to 10 km (32,808 ft). This will address one of the critical needs in any EGS development of understanding the hydraulic flow paths in the reservoir. The ultrasonic imaging is well known in the oil and gas industry as one of the best methods for fracture evaluation; providing both high resolution and complete azimuthal coverage of the borehole. This enables fracture detection and characterization, both natural and induced, providing information as to their location, dip direction and dip magnitude. All of these factors are critical to fully understand the fracture system to enable the optimization of the thermal drainage through injectors and producers in a geothermal resource.

  2. Management of condylar fractures.

    PubMed

    Montazem, André H; Anastassov, George

    2009-03-01

    Management of condylar fractures remains a source of ongoing controversy. While it appears that many condylar fractures can be managed nonsurgically, recognition of cases that require surgical intervention and selection of an appropriate procedure are paramount to success in treating these injuries. There are a variety of special considerations that are peculiar to the condylar region. This article discusses anatomic considerations, classification of condylar fractures, indications for surgery, treatment options, and complications. The goals of treatment include restoration of function and esthetics. Careful consideration and attention to the principles of fracture management, and the role of the condyle as an articulating unit and growth center, must be taken into account for the successful management of these injuries.

  3. Etiology of zygomatic fractures.

    PubMed

    Cotter, C J; Ogunbowale, A; Beirne, C

    2005-01-01

    We report on the etiology of zygomatic fractures in an Irish population. More than half of these injuries are related to interpersonal assault. Treatment of these injuries places a considerable burden on the health service. PMID:16445148

  4. Sprains, Strains and Fractures

    MedlinePlus

    ... are useful for finding soft issue injuries (including torn ligaments) and stress fractures. Treatment will depend on ... weeks. Professional athletes may undergo surgery to repair torn ligaments. Oral anti-inflammatory medication, such as ibuprofen, ...

  5. Lisfranc (Midfoot) Fractures

    MedlinePlus

    ... broken or ligaments that support the midfoot are torn. The severity of the injury can vary from ... bones are broken (fractured) or the ligaments are torn (ruptured). Injuries can vary, from a simple injury ...

  6. Clavicle Fracture (Broken Collarbone)

    MedlinePlus

    ... place and the fragments are severely out of alignment. A large bump over the fracture site may ... bone fragments are first repositioned into their normal alignment, and then held in place with special screws ...

  7. Hay balers' fractures.

    PubMed

    Mayba, I I

    1984-03-01

    Two cases of fractures of the sternum and T12 vertebra are presented, which appear to be a characteristic combination of injuries to farmers when hay bales fall on them. The mechanism of injury proposed is a severe forward flexion, producing vertebral collapse at the dorsolumbar junction, and fracture of the sternum from direct trauma against the steering wheel. These fractures should always be suspected in persons injured while baling hay. It is proposed to call this complex of injuries hay balers' fractures. Preventive measures suggested are: operator caution when hay bales are lifted; addition of locks to the loader forks; increasing the size of the loader, or placing a screen or cage over the operators to keep hay bales from falling on them.

  8. Adult orbital trapdoor fracture.

    PubMed

    Kum, Clarissa; McCulley, Timothy J; Yoon, Michael K; Hwang, Thomas N

    2009-01-01

    Trapdoor fractures occur almost exclusively in the pediatric population. The authors describe an adult with an entrapped inferior rectus muscle sheath in a trapdoor fracture. A 37-year-old man presented with persistent diplopia 3 weeks after blunt right orbital trauma. The only abnormal findings on clinical examination were limited vertical ductions. No bony defect or displacement was evident on CT. However, several small pockets of air were visible adjacent to the inferior rectus muscle. On surgical exploration, a linear nondisplaced orbital floor fracture was confirmed, and the entrapped inferior rectus muscle was released. One month postoperatively, extraocular motility had improved with no diplopia in primary or reading positions. This case demonstrates that trapdoor fractures can occur in adults and should be considered when suggestive findings are encountered. Clinicians should be aware of this because timely diagnosis and treatment might achieve more favorable outcomes.

  9. Hay balers' fractures.

    PubMed

    Mayba, I I

    1984-03-01

    Two cases of fractures of the sternum and T12 vertebra are presented, which appear to be a characteristic combination of injuries to farmers when hay bales fall on them. The mechanism of injury proposed is a severe forward flexion, producing vertebral collapse at the dorsolumbar junction, and fracture of the sternum from direct trauma against the steering wheel. These fractures should always be suspected in persons injured while baling hay. It is proposed to call this complex of injuries hay balers' fractures. Preventive measures suggested are: operator caution when hay bales are lifted; addition of locks to the loader forks; increasing the size of the loader, or placing a screen or cage over the operators to keep hay bales from falling on them. PMID:6708148

  10. Poroelastic modeling of seismic boundary conditions across a fracture.

    PubMed

    Nakagawa, Seiji; Schoenberg, Michael A

    2007-08-01

    Permeability of a fracture can affect how the fracture interacts with seismic waves. To examine this effect, a simple mathematical model that describes the poroelastic nature of wave-fracture interaction is useful. In this paper, a set of boundary conditions is presented which relate wave-induced particle velocity (or displacement) and stress including fluid pressure across a compliant, fluid-bearing fracture. These conditions are derived by modeling a fracture as a thin porous layer with increased compliance and finite permeability. Assuming a small layer thickness, the boundary conditions can be derived by integrating the governing equations of poroelastic wave propagation. A finite jump in the stress and velocity across a fracture is expressed as a function of the stress and velocity at the boundaries. Further simplification for a thin fracture yields a set of characteristic parameters that control the seismic response of single fractures with a wide range of mechanical and hydraulic properties. These boundary conditions have potential applications in simplifying numerical models such as finite-difference and finite-element methods to compute seismic wave scattering off nonplanar (e.g., curved and intersecting) fractures.

  11. Specification of matrix cleanup goals in fractured porous media.

    PubMed

    Rodríguez, David J; Kueper, Bernard H

    2013-01-01

    Semianalytical transient solutions have been developed to evaluate what level of fractured porous media (e.g., bedrock or clay) matrix cleanup must be achieved in order to achieve compliance of fracture pore water concentrations within a specified time at specified locations of interest. The developed mathematical solutions account for forward and backward diffusion in a fractured porous medium where the initial condition comprises a spatially uniform, nonzero matrix concentration throughout the domain. Illustrative simulations incorporating the properties of mudstone fractured bedrock demonstrate that the time required to reach a desired fracture pore water concentration is a function of the distance between the point of compliance and the upgradient face of the domain where clean groundwater is inflowing. Shorter distances correspond to reduced times required to reach compliance, implying that shorter treatment zones will respond more favorably to remediation than longer treatment zones in which back-diffusion dominates the fracture pore water response. For a specified matrix cleanup goal, compliance of fracture pore water concentrations will be reached sooner for decreased fracture spacing, increased fracture aperture, higher matrix fraction organic carbon, lower matrix porosity, shorter aqueous phase decay half-life, and a higher hydraulic gradient. The parameters dominating the response of the system can be measured using standard field and laboratory techniques.

  12. Relative permeability through fractures

    SciTech Connect

    Diomampo, Gracel, P.

    2001-08-01

    The mechanism of two-phase flow through fractures is of importance in understanding many geologic processes. Currently, two-phase flow through fractures is still poorly understood. In this study, nitrogen-water experiments were done on both smooth and rough parallel plates to determine the governing flow mechanism for fractures and the appropriate methodology for data analysis. The experiments were done using a glass plate to allow visualization of flow. Digital video recording allowed instantaneous measurement of pressure, flow rate and saturation. Saturation was computed using image analysis techniques. The experiments showed that gas and liquid phases flow through fractures in nonuniform separate channels. The localized channels change with time as each phase path undergoes continues breaking and reforming due to invasion of the other phase. The stability of the phase paths is dependent on liquid and gas flow rate ratio. This mechanism holds true for over a range of saturation for both smooth and rough fractures. In imbibition for rough-walled fractures, another mechanism similar to wave-like flow in pipes was also observed. The data from the experiments were analyzed using Darcy's law and using the concept of friction factor and equivalent Reynold's number for two-phase flow. For both smooth- and rough-walled fractures a clear relationship between relative permeability and saturation was seen. The calculated relative permeability curves follow Corey-type behavior and can be modeled using Honarpour expressions. The sum of the relative permeabilities is not equal one, indicating phase interference. The equivalent homogeneous single-phase approach did not give satisfactory representation of flow through fractures. The graphs of experimentally derived friction factor with the modified Reynolds number do not reveal a distinctive linear relationship.

  13. Interlaminar fracture of composites

    NASA Technical Reports Server (NTRS)

    Obrien, T. K.

    1984-01-01

    Fracture mechanics has been found to be a useful tool for understanding composite delamination. Analyses for calculating strain energy release rates associated with delamination growth have been developed. These analyses successfully characterized delamination onset and growth for particular sources of delamination. Low velocity impact has been found to be the most severe source of composite delamination. A variety of test methods for measuring interlaminar fracture toughness are being developed to identify new composite materials with enhanced delamination resistance.

  14. Experimental Fracture Measurements of Functionally Graded Materials

    NASA Astrophysics Data System (ADS)

    Carpenter, Ray Douglas

    The primary objective of this research was to extend established fracture toughness testing methods to a new class of engineering materials known as functionally graded materials (FGMs). Secondary goals were to compare experimental results to those predicted by finite element models and to provide fracture test results as feedback toward optimizing processing parameters for the in-house synthesis of a MoSi2/SiC FGM. Preliminary experiments were performed on commercially pure (CP) Ti and uniform axial tensile tests resulted in mechanical property data including yield strength, 268 MPa, ultimate tensile strength, 470 MPa and Young's modulus, 110 GPa. Results from 3-point bending fracture experiments on CP Ti demonstrated rising R-curve behavior and experimentally determined JQ fracture toughness values ranged between 153 N/mm and 254 N/mm. Similar experimental protocols were used for fracture experiments on a 7- layered Ti/TiB FGM material obtained from Cercom in Vista, California. A novel technique for pre-cracking in reverse 4-point bending was developed for this ductile/brittle FGM material. Fracture test results exhibited rising R-curve behavior and estimated JQ fracture toughness values ranged from 0.49 N/mm to 2.63 N/mm. A 5- layered MoSi2/SiC FGM was synthesized using spark plasma sintering (SPS). Samples of this material were fracture tested and the results again exhibited a rising R-curve with KIC fracture toughness values ranging from 2.7 MPa-m1/2 to 6.0 MPa-m1/2. Finite Element Models predicted rising R-curve behavior for both of the FGM materials tested. Model results were in close agreement for the brittle MoSi2/SiC FGM. For the relatively more ductile Ti/TiB material, results were in close agreement at short crack lengths but diverged at longer crack lengths because the models accounted for fracture toughening mechanisms at the crack tip but not those acting in the crack wake.

  15. SIZE SCALING RELATIONSHIPS IN FRACTURE NETWORKS

    SciTech Connect

    Thomas H. Wilson

    2000-01-01

    The research conducted under DOE grant DE-FG26-98FT40385 provides a detailed assessment of size scaling issues in natural fracture and active fault networks that extend over scales from several tens of kilometers to less than a tenth of a meter. This study incorporates analysis of data obtained from several sources, including: natural fracture patterns photographed in the Appalachian field area, natural fracture patterns presented by other workers in the published literature, patterns of active faulting in Japan mapping at a scale of 1:100,000, and lineament patterns interpreted from satellite-based radar imagery obtained over the Appalachian field area. The complexity of these patterns is always found to vary with scale. In general,but not always, patterns become less complex with scale. This tendency may reverse as can be inferred from the complexity of high-resolution radar images (8 meter pixel size) which are characterized by patterns that are less complex than those observed over smaller areas on the ground surface. Model studies reveal that changes in the complexity of a fracture pattern can be associated with dominant spacings between the fractures comprising the pattern or roughly to the rock areas bounded by fractures of a certain scale. While the results do not offer a magic number (the fractal dimension) to characterize fracture networks at all scales, the modeling and analysis provide results that can be interpreted directly in terms of the physical properties of the natural fracture or active fault complex. These breaks roughly define the size of fracture bounded regions at different scales. The larger more extensive sets of fractures will intersect and enclose regions of a certain size, whereas smaller less extensive sets will do the same--i.e. subdivide the rock into even smaller regions. The interpretation varies depending on the number of sets that are present, but the scale breaks in the logN/logr plots serve as a guide to interpreting the

  16. Structural behavior of composites with progressive fracture

    NASA Technical Reports Server (NTRS)

    Minnetyan, Levon; Chamis, Christos C.; Murthy, Pappu L. N.

    1990-01-01

    Structural characteristics such as natural frequencies and buckling loads with corresponding mode shapes were investigated during progressive fracture of multilayer, angle-plied polymer matrix composites. A computer program was used to generate the numerical results for overall mechanical response of damaged composites. Variations in structural characteristics as a function of the previously applied loading were studied. Results indicate that most of the overall structural properties were preserved throughout a significant proportion of the ultimate fracture load. For the cases studied, changes in structural behavior began to occur after 70 percent of the ultimate fracture load was applied. However, the individual nature of the structural change was rather varied depending on the laminate configuration, fiber orientation, and the boundary conditions.

  17. IPIRG programs - advances in pipe fracture technology

    SciTech Connect

    Wilkowski, G.; Olson, R.; Scott, P.

    1997-04-01

    This paper presents an overview of the advances made in fracture control technology as a result of the research performed in the International Piping Integrity Research Group (IPIRG) program. The findings from numerous experiments and supporting analyses conducted to investigate the behavior of circumferentially flawed piping and pipe systems subjected to high-rate loading typical of seismic events are summarized. Topics to be discussed include; (1) Seismic loading effects on material properties, (2) Piping system behavior under seismic loads, (3) Advances in elbow fracture evaluations, and (4) {open_quotes}Real{close_quotes} piping system response. The presentation for each topic will be illustrated with data and analytical results. In each case, the state-of-the-art in fracture mechanics prior to the first IPIRG program will be contrasted with the state-of-the-art at the completion of the IPIRG-2 program.

  18. Elastocapillary Deformations and Fracture of Soft Gels

    NASA Astrophysics Data System (ADS)

    Daniels, Karen; Grzelka, Marion; Bostwick, Joshua

    When a droplet is placed on the surface of a soft gel, the surface deforms by an amount proportional to the elastocapillary length calculated from the ratio of surface tension and elastic modulus. For sufficiently large deformations, the gel can fracture due to the forces generated under the liquid-gel contact line. We observe that a starburst of channel fractures forms at the surface of the gel, driven by fluid propagating away from the central droplet. To understand the initiation of these cracks, we model the substrate as an incompressible, linear-elastic solid and quantify the elastic response. This provides quantitative agreement with experimental measurements of the number of fracture arms as a function of material properties and geometric parameters. In addition, we find that the initiation process is thermally-activated, with delay time that decreases as a function of the elastocapillary length.

  19. Orthobiologics in the augmentation of osteoporotic fractures.

    PubMed

    Watson, J Tracy; Nicolaou, Daemeon A

    2015-02-01

    Many orthobiologic adjuvants are available and widely utilized for general skeletal restoration. Their use for the specific task of osteoporotic fracture augmentation is less well recognized. Common conductive materials are reviewed for their value in this patient population including the large group of allograft adjuvants categorically known as the demineralized bone matrices (DBMs). Another large group of alloplastic materials is also examined-the calcium phosphate and sulfate ceramics. Both of these materials, when used for the proper indications, demonstrate efficacy for these patients. The inductive properties of bone morphogenic proteins (BMPs) and platelet concentrates show no clear advantages for this group of patients. Systemic agents including bisphosphonates, receptor activator of nuclear factor κβ ligand (RANKL) inhibitors, and parathyroid hormone augmentation all demonstrate positive effects with this fracture cohort. Newer modalities, such as trace ion bioceramic augmentation, are also reviewed for their positive effects on osteoporotic fracture healing. PMID:25431160

  20. Treatment of Thoracolumbar Fracture

    PubMed Central

    Kim, Byung-Guk; Shin, Dong-Eun

    2015-01-01

    The most common fractures of the spine are associated with the thoracolumbar junction. The goals of treatment of thoracolumbar fracture are leading to early mobilization and rehabilitation by restoring mechanical stability of fracture and inducing neurologic recovery, thereby enabling patients to return to the workplace. However, it is still debatable about the treatment methods. Neurologic injury should be identified by thorough physical examination for motor and sensory nerve system in order to determine the appropriate treatment. The mechanical stability of fracture also should be evaluated by plain radiographs and computed tomography. In some cases, magnetic resonance imaging is required to evaluate soft tissue injury involving neurologic structure or posterior ligament complex. Based on these physical examinations and imaging studies, fracture stability is evaluated and it is determined whether to use the conservative or operative treatment. The development of instruments have led to more interests on the operative treatment which saves mobile segments without fusion and on instrumentation through minimal invasive approach in recent years. It is still controversial for the use of these treatments because there have not been verified evidences yet. However, the morbidity of patients can be decreased and good clinical and radiologic outcomes can be achieved if the recent operative treatments are used carefully considering the fracture pattern and the injury severity. PMID:25705347

  1. FRACTURING FLUID CHARACTERIZATION FACILITY

    SciTech Connect

    Subhash Shah

    2000-08-01

    Hydraulic fracturing technology has been successfully applied for well stimulation of low and high permeability reservoirs for numerous years. Treatment optimization and improved economics have always been the key to the success and it is more so when the reservoirs under consideration are marginal. Fluids are widely used for the stimulation of wells. The Fracturing Fluid Characterization Facility (FFCF) has been established to provide the accurate prediction of the behavior of complex fracturing fluids under downhole conditions. The primary focus of the facility is to provide valuable insight into the various mechanisms that govern the flow of fracturing fluids and slurries through hydraulically created fractures. During the time between September 30, 1992, and March 31, 2000, the research efforts were devoted to the areas of fluid rheology, proppant transport, proppant flowback, dynamic fluid loss, perforation pressure losses, and frictional pressure losses. In this regard, a unique above-the-ground fracture simulator was designed and constructed at the FFCF, labeled ''The High Pressure Simulator'' (HPS). The FFCF is now available to industry for characterizing and understanding the behavior of complex fluid systems. To better reflect and encompass the broad spectrum of the petroleum industry, the FFCF now operates under a new name of ''The Well Construction Technology Center'' (WCTC). This report documents the summary of the activities performed during 1992-2000 at the FFCF.

  2. Subduction of fracture zones

    NASA Astrophysics Data System (ADS)

    Constantin Manea, Vlad; Gerya, Taras; Manea, Marina; Zhu, Guizhi; Leeman, William

    2013-04-01

    Since Wilson proposed in 1965 the existence of a new class of faults on the ocean floor, namely transform faults, the geodynamic effects and importance of fracture zone subduction is still little studied. It is known that oceanic plates are characterized by numerous fracture zones, and some of them have the potential to transport into subduction zones large volumes of water-rich serpentinite, providing a fertile water source for magma generated in subduction-related arc volcanoes. In most previous geodynamic studies, subducting plates are considered to be homogeneous, and there is no clear indication how the subduction of a fracture zone influences the melting pattern in the mantle wedge and the slab-derived fluids distribution in the subarc mantle. Here we show that subduction of serpentinized fracture zones plays a significant role in distribution of melt and fluids in the mantle wedge above the slab. Using high-resolution tree-dimensional coupled petrological-termomechanical simulations of subduction, we show that fluids, including melts and water, vary dramatically in the region where a serpentinized fracture zone enters into subduction. Our models show that substantial hydration and partial melting tend to concentrate where fracture zones are being subducted, creating favorable conditions for partially molten hydrous plumes to develop. These results are consistent with the along-arc variability in magma source compositions and processes in several regions, as the Aleutian Arc, the Cascades, the Southern Mexican Volcanic Arc, and the Andean Southern Volcanic Zone.

  3. Wavefront Imaging in Fractured Transversely-Isotropic Media

    NASA Astrophysics Data System (ADS)

    Shao, S.; Pyrak-Nolte, L. J.

    2013-12-01

    Fractures in the Earth's crust are a source of stress-dependent mechanical anisotropy that affect seismic wave attenuation and velocity. While many theoretical and experimental studies have investigated seismic wave propagation in single or multi- fractured isotropic rocks, few studies have examined the seismic response of a fractured anisotropic medium. Fractures and layering each contribute to the mechanical anisotropy of the crust. The coexistence of these two sources of anisotropy complicates the interpretation of the seismic properties of crustal rock. In this study, laboratory wavefront imaging was performed to capture the seismic response of layered media containing multiple parallel fractures. We determined that whether the observed anisotropy is dominated by the matrix anisotropy or by the fracture orientation depends on the applied stress and that late-arriving guided-modes provide information on the orientation of the fractures. Four cubic garolite samples (~102 mm on edge) each containing 5 parallel fractures were used in this study. The fractures were oriented normal, parallel or at acute angles (30 degrees, 60 degrees) to the layering. The fracture and layer spacing were approximately 10mm and 0.5mm, respectively. An intact sample containing no fractures was used as a standard orthorhombic medium for reference. Stress was applied to the samples with a servo-controlled loading machine. Two spherically-focused water-coupled transducers (central frequency 1MHz) were used; one as a fixed-source and the other as a translating receiver. Each sample was scanned over a 60mm×60mm region in 1 mm increments to map out the arriving wavefront (i.e. 3600 signals were recorded) as a function of time. The measured wavefront in the intact reference sample (which contained no fractures) was elliptical with the major axis parallel to the layers as expected and was stress-independent. When the fracture samples were subjected to low stress (<4 MPa), the observed seismic

  4. Fracture characterization and fracture-permeability estimation at the underground research laboratory in southeastern Manitoba, Canada

    USGS Publications Warehouse

    Paillet, Frederick L.

    1988-01-01

    Various conventional geophysical well logs were obtained in conjunction with acoustic tube-wave amplitude and experimental heat-pulse flowmeter measurements in two deep boreholes in granitic rocks on the Canadian shield in southeastern Manitoba. The objective of this study is the development of measurement techniques and data processing methods for characterization of rock volumes that might be suitable for hosting a nuclear waste repository. One borehole, WRA1, intersected several major fracture zones, and was suitable for testing quantitative permeability estimation methods. The other borehole, URL13, appeared to intersect almost no permeable fractures; it was suitable for testing methods for the characterization of rocks of very small permeability and uniform thermo-mechanical properties in a potential repository horizon. Epithermal neutron , acoustic transit time, and single-point resistance logs provided useful, qualitative indications of fractures in the extensively fractured borehole, WRA1. A single-point log indicates both weathering and the degree of opening of a fracture-borehole intersection. All logs indicate the large intervals of mechanically and geochemically uniform, unfractured granite below depths of 300 m in the relatively unfractured borehole, URL13. Some indications of minor fracturing were identified in that borehole, with one possible fracture at a depth of about 914 m, producing a major acoustic waveform anomaly. Comparison of acoustic tube-wave attenuation with models of tube-wave attenuation in infinite fractures of given aperture provide permeability estimates ranging from equivalent single-fractured apertures of less than 0.01 mm to apertures of > 0.5 mm. One possible fracture anomaly in borehole URL13 at a depth of about 914 m corresponds with a thin mafic dike on the core where unusually large acoustic contrast may have produced the observed waveform anomaly. No indications of naturally occurring flow existed in borehole URL13; however

  5. Deformation and Fracture Mechanisms of Polymer-Silicate Nanocomposites

    NASA Astrophysics Data System (ADS)

    Harcup, Jason; Yee, Albert

    1998-03-01

    The deformation and fracture behavior of a series of nanocomposites comprising polyamide, silicate and in some cases rubber has been studied. Mechanical properties including Young modulus and fracture toughness were measured and it was found that compared to conventional composites, the nanocomposites exhibited far greater improvement in properties over the neat matrix for a given silicate fraction. It was also found that the addition of the rubber phase produced an increase in toughness. The arrested crack tip process zone was obtained using the Double Notch Four Point Bend test geometry and the process zone morphology was studied using TEM and TOM. Fracture surfaces were probed with XEDS and SEM. The use of these techniques enabled the mechanisms which occur during fracture to be studied and related to the mechanical properties and toughening of these materials.

  6. Computer Simulation of Fracture in Aerogels

    NASA Technical Reports Server (NTRS)

    Good, Brian S.

    2006-01-01

    Aerogels are of interest to the aerospace community primarily for their thermal properties, notably their low thermal conductivities. While the gels are typically fragile, recent advances in the application of conformal polymer layers to these gels has made them potentially useful as lightweight structural materials as well. In this work, we investigate the strength and fracture behavior of silica aerogels using a molecular statics-based computer simulation technique. The gels' structure is simulated via a Diffusion Limited Cluster Aggregation (DLCA) algorithm, which produces fractal structures representing experimentally observed aggregates of so-called secondary particles, themselves composed of amorphous silica primary particles an order of magnitude smaller. We have performed multi-length-scale simulations of fracture in silica aerogels, in which the interaction b e e n two secondary particles is assumed to be described by a Morse pair potential parameterized such that the potential range is much smaller than the secondary particle size. These Morse parameters are obtained by atomistic simulation of models of the experimentally-observed amorphous silica "bridges," with the fracture behavior of these bridges modeled via molecular statics using a Morse/Coulomb potential for silica. We consider the energetics of the fracture, and compare qualitative features of low-and high-density gel fracture.

  7. From fractures to flow: A field-based quantitative analysis of an outcropping carbonate reservoir

    NASA Astrophysics Data System (ADS)

    Agosta, F.; Alessandroni, M.; Antonellini, M.; Tondi, E.; Giorgioni, M.

    2010-07-01

    Fractures can play an important role in the fluid storage-migration properties of fault damage zones. In this present contribution, we document the role exerted by fractures on fluid flow in carbonate damage zones of hydrocarbon-bearing, km-long, oblique-slip normal faults with 10's of m-throw. The carbonate fault damage zones were analysed by mean of scan line surveys conducted in both tar-free and tar-rich outcrops. In this way, the relationships among the individual fracture characteristics (length, spacing, aperture, orientation, connectivity and distance from slip surfaces pertaining to small faults of the fault damage zones) and hydrocarbons have been established. Data obtained by scan line surveys were also used to compute the amount of fracture porosity, the degree of fracture connectivity and, based upon simple assumptions, the orientation of the local σhmax at times of faulting. Additionally, scan line surveys were also carried out along outcrops exposing unfaulted carbonate host rocks. The results of our computation are consistent with a carbonate host rock made up of a quite isotropic fracture array comprised of isolated and coupled fractures, in which individual fracture sets have negative exponential spacing distributions. In terms of fluid flow, the fracture array of the carbonate host rock enhances the fluid storage. Conversely, the fracture array of the fault damage zones is characterized by a pronounced anisotropy due to interconnected fractures, which enhance the fluid migration. Fractures in the fault damage zones include those inherited from background deformation and others related to the faulting processes. The latter fracture sets are characterized by power law spacing distributions. In conclusion, counter-intuitively, both fracture length and fracture spacing do not have any correlation with hydrocarbons in the fault damage zones. On the contrary, fracture anisotropy, fracture spread and fracture orientation are positively correlated with

  8. MULTI-PHASE FRACTURE-MATRIX INTERACTIONS UNDER STRESS CHANGES

    SciTech Connect

    A.S. Grader; D. Elsworth; P.M. Halleck; F. Alvarad; H. Yasuhara; A. Alajmi

    2002-04-20

    The main objectives of this project are to quantify the changes in fracture porosity and multi-phase transport properties as a function of confining stress. These changes will be integrated into conceptual and numerical models that will improve our ability to predict and optimize fluid transport in fractured system. This report details our progress on: (1) developing the direct experimental measurements of fracture aperture and topology using high-resolution x-ray micro-tomography, (2) modeling of fracture permeability in the presence of asperities and confining stress, and (3) simulation of two-phase fluid flow in a fracture and a layered matrix. The three-dimensional surface that describes the large-scale structure of the fracture in the porous medium can be determined using x-ray micro-tomography with significant accuracy. The distribution of fracture aperture is a difficult issue that we are studying and developing methods of quantification. The difficulties are both numerical and conceptual. Numerically, the three-dimensional data sets include millions, and sometimes, billions of points, and pose a computational challenge. The conceptual difficulties derive from the rough nature of the fracture surfaces, and the heterogeneous nature of the rock matrix. However, the high-resolution obtained by the imaging system provides us a much needed measuring environment on rock samples that are subjected to simultaneous fluid flow and confining stress. The absolute permeability of a fracture depends on the behavior of the asperities that keep it open. A model is being developed that predicts the permeability and average aperture of a fracture as a function of time under steady flow of water including the pressure solution at the asperity contact points. Several two-phase flow experiments in the presence of a fracture tip were performed in the past. At the present time, we are developing an inverse process using a simulation model to understand the fluid flow patterns in

  9. Damage and fracture mechanics of composite materials

    NASA Astrophysics Data System (ADS)

    Abdussalam, Saleh Ramadan

    The design of structural systems in the aerospace industry has been characterized by a continuing search for strong, yet lightweight, materials to achieve maximum payload capability for minimum weight. In recent years, this search has led to a wide use of fiber reinforced composites, such as carbon, glass and kevelar based composites. Comparison of these new materials with the traditional ones (metals) according to the basic properties, such as density, elastic modulus and also long-time and short-time strength, shows their superiority over traditional materials, when weight is a major design factor, like in the aerospace industry. Most composite materials of interest to aerospace applications have been adequately characterized under static loading conditions. Related work to study their fracture behaviour has been limited. Since most failure mechanisms involve crack growth and/or delamination, design of such components requires knowledge and understanding of their fracture properties. This thesis includes an experimental and analytical investigation of fracture characteristics of composite materials. The post-peak response of notched specimens subjected to uniaxial cyclic loading is established to evaluate the fracture energy associated with progressive matrix damage and subsequent crack growth. A total of 75 uniaxial tension specimens were tested. The experimental work consisted of first testing several un-notched specimens with different thickness (number of layers) to determine the initial and secondary elastic modulus as well as the tensile strength. The investigation studied the effect of the various fracture parameters, including thickness, fiber orientation, and crack width ratio (a/w) on the behaviour of crack propagation, peak load, and post-peak response. The specimens used in this research were prepared using the vacuum bagging technique, with a chosen number of fiber glass cloth layers and fiber orientation. The experimental results provided

  10. Analysis of styress heterogeneity in deep fractured chrystalline rock

    NASA Astrophysics Data System (ADS)

    Sahara, David; Kohl, Thomas

    2016-04-01

    The mechanical properties variation, the fracture characteristic and the inclination of the well might perturbed the development of wellbore failures and, hence, affect the estimation of the stress state in fractured rocks. A detailed analysis of 1221 and 827 compressional and tensional wellbore failures, respectively, in a 3.5 km crystalline rock observed in the GPK4 well in Soultz-sous-Forêts enables us to analyze the different pattern of stress heterogeneities which might be related to several factors. The inclination of the well affects the stress distribution by a few MPa which is found to have a significant effect of the development of wellbore, i.e. the limitation of tensile failures in part of the well which is inclined by less than 10°, and the delay of compressional failures occurrence by about 300 m in a 25° inclined well. Fractures and alteration reduced the compressional strength of the crystalline by approximately 30% and, hence, promoted the development of breakout at a smaller far-field stress. The orientation of wellbore failures in such fractured zones are found to be heterogeneously distributed, hence, lower the quality of the stress estimation. Furthermore, the first and second order of stress heterogeneities pattern in the vicinity of major and minor fractures, respectively, in a highly fractured zone at depth 4600 to 4850 m are observed. The numerical modeling of the development of breakouts that take into account the weak zone as a results of fracturing process developed in this study shows a systematic analysis of the variation of the breakout orientation and the reduction of the mechanical properties. In fractured rock, wellbore failures do not correlate to the principal stress only, but also to the variation of the mechanical properties and the properties of fractures. Hence, a long continuous section of wellbore failures is a must to have a sufficient stress-related failures data.

  11. In Vitro Fracture of Human Cortical Bone: Local Fracture Criteria and Toughening Mechanisms

    SciTech Connect

    Nalla, R; Stolken, J; Kinney, J; Ritchie, R

    2004-08-18

    A micro-mechanistic understanding of bone fracture that encompasses how cracks interact with the underlying microstructure and defines their local failure mode is lacking, despite extensive research on the response of bone to a variety of factors like aging, loading, and/or disease. Micro-mechanical models for fracture incorporating such local failure criteria have been widely developed for metallic and ceramic materials systems; however, few such deliberations have been undertaken for the fracture of bone. In fact, although the fracture event in mineralized tissues such as bone is commonly believed to be locally strain controlled, until recently there has been little experimental evidence to support this widely held belief. In the present study, a series of in vitro experiments involving a double-notch bend test geometry are performed in order to shed further light on the nature of the local cracking events that precede catastrophic fracture in bone and to define their relationship to the microstructure. Specifically, crack-microstructure interactions are examined to determine the salient toughening mechanisms in human cortical bone and to characterize how these may affect the anisotropy in fracture properties. Based on preliminary micro-mechanical models of these processes, in particular crack deflection and uncracked ligament bridging, the relative importance of these toughening mechanisms is established.

  12. Scaling of the flow-stiffness relationship in weakly correlated single fractures

    NASA Astrophysics Data System (ADS)

    Petrovitch, Christopher L.

    The remote characterization of the hydraulic properties of fractures in rocks is important in many subsurface projects. Fractures create uncertainty in the hydraulic properties of the subsurface in that their topology controls the amount of flow that can occur in addition to that from the matrix. In turn, the fracture topology is also affected by stress which alters the topology as the stress changes directly. This alteration of fracture topology with stress is captured by fracture specific stiffness. The specific stiffness of a single fracture can be remotely probed from the attenuation and velocity of seismic waves. The hydromechanical coupling of single fractures, i.e. the relationship between flow and stiffness, holds the key to finding a method to remotely characterize a fractures hydraulic properties. This thesis is separated into two parts: (1) a description of the hydromechanical coupling of fractures based on numerical models used to generate synthetic fractures, compute the flow through a fracture, and deform fracture topologies to unravel the scaling function that is fundamental to the hydromechanical coupling of single fractures; (2) a Discontinuous Galerkin (DG) method was developed to accurately simulate the scattered seismic waves from realistic fracture topologies. The scaling regimes of fluid flow and specific stiffness in weakly correlated fractures are identified by using techniques from Percolation Theory and initially treating the two processes separately. The fixed points associated with fluid flow were found to display critical scaling while the fixed points for specific stiffness were trivial. The two processes could be indirectly related because the trivial scaling of the mechanical properties allowed the specific stiffness to be used as surrogate to the void area fraction. The dynamic transport exponent was extracted at threshold by deforming fracture geometries within the effective medium regime (near the ``cubic law'' regime) to the

  13. Modeling Electric Current Flow in 3D Fractured Media

    NASA Astrophysics Data System (ADS)

    Demirel, S.; Roubinet, D.; Irving, J.

    2014-12-01

    equivalent properties and synthetic simulations of electrical surveys. [1] Roubinet, D., and J. Irving (2014), Discrete-dual-porosity model for electric current flow in fractured rock, JGR-Solid Earth, 119

  14. Analysis of fracture patterns and local stress field variations in fractured reservoirs

    NASA Astrophysics Data System (ADS)

    Deckert, Hagen; Drews, Michael; Fremgen, Dominik; Wellmann, J. Florian

    2010-05-01

    A meaningful qualitative evaluation of permeabilities in fractured reservoirs in geothermal or hydrocarbon industry requires the spatial description of the existing discontinuity pattern within the area of interest and an analysis how these fractures might behave under given stress fields. This combined information can then be used for better estimating preferred fluid pathway directions within the reservoir, which is of particular interest for defining potential drilling sites. A description of the spatial fracture pattern mainly includes the orientation of rock discontinuities, spacing relationships between single fractures and their lateral extent. We have examined and quantified fracture patterns in several outcrops of granite at the Costa Brava, Spain, and in the Black Forest, Germany, for describing reservoir characteristics. For our analysis of fracture patterns we have used photogrammetric methods to create high-resolution georeferenced digital 3D images of outcrop walls. The advantage of this approach, compared to conventional methods for fracture analysis, is that it provides a better 3D description of the fracture geometry as the entity of position, extent and orientation of single fractures with respect to their surrounding neighbors is conserved. Hence for instance, the method allows generating fracture density maps, which can be used for a better description of the spatial distribution of discontinuities in a given outcrop. Using photogrammetric techniques also has the advantage to acquire very large data sets providing statistically sound results. To assess whether the recorded discontinuities might act as fluid pathways information on the stress field is needed. A 3D model of the regional tectonic structure was created and the geometry of the faults was put into a mechanical 3D Boundary Element (BE) Model. The model takes into account the elastic material properties of the geological units and the orientation of single fault segments. The

  15. Property.

    ERIC Educational Resources Information Center

    Piele, Philip K.; Johnson, Margaret M.

    This chapter deals with 1981 cases involving disputes over property. Cases involving the detachment and attachment of land continue to dominate the property chapter with 11 cases reported, the same number summarized in last year's chapter. One case involving school board referenda raised the interesting question of whether or not a state could…

  16. Property.

    ERIC Educational Resources Information Center

    Bickel, Robert D.; Zeller, Trisha A.

    A number of cases related to property issues involving institutions of higher education are examined in this chapter. Cases discussed touch on such topics as funding for property and equipment acquisition; opposition to building construction or demolition; zoning issues; building construction and equipment contracts; and lease agreements. Current…

  17. The influence of fracture anisotropy on CO2 flow

    NASA Astrophysics Data System (ADS)

    Bond, Clare E.; Wightman, Ruth; Ringrose, Philip S.

    2013-04-01

    gas mitigation through geological storage of carbon dioxide is dependent on rock formations storing CO2 effectively. Secure containment for periods of 100 × 105 years nee7ds to be verifiable. The effectiveness of geological storage is reliant on the chemical and physical properties of the geological storage complex and its ability to inhibit migration of CO2. Petroleum reservoir data and field evidence show that fracture networks often act as pathways for fluid movement, potentially allowing fluids to migrate to the surface within the time scale of interest. We demonstrate the importance of predicting the effects of fracture networks on flow, using a case study from the In Salah CO2 storage site, and show how fracture permeability is closely controlled by the stress regime determining the conductive fracture network. Our results demonstrate that fracture network prediction combined with present-day stress analysis can be used to successfully predict CO2 movement in the subsurface.

  18. Intergranular fracture of low-alloy cast steel

    SciTech Connect

    Cao Li; Zhou Guangying

    1996-02-01

    A series of microstructural, macrostructural, and fracture observations, mechanical properties tests, and analyses of electroextracted nonmetallic inclusions have been made on samples from two high-carbon Cr and Cr-Mo cast-steel rolls. The fracture comparison test at 950 C and room temperature showed that intercrystalline fracture occurs at high temperatures. AlN precipitates were extracted from the surfaces of rock-candy-type fractures. Well-defined dendrites are seen in some places in the cracked area. Close to them, coarse carbide needles and ledeburites, which are rich in Cr and Mn, are precipitated along the primary austenite grain boundaries. An explanation is given for the occurrence of the intercrystalline fracture in accordance with the test results, and measures are suggested to eliminate this kind of defect.

  19. Property development for biaxial drawing of ethylene-tetrafluoroehtylene copolymer films and resultant fractural behavior analyzed by in situ X-ray measurements.

    PubMed

    Uehara, Hiroki; Ono, Yasunori; Kakiage, Masaki; Sakamura, Takumi; Masunaga, Hiroyasu; Yukawa, Yasumasa; Higuchi, Yoshiaki; Kamiya, Hiroki; Yamanobe, Takeshi

    2015-03-19

    The property development of the ethylene-tetrafluoroethylene copolymer (ETFE) membrane induced by simultaneous biaxial drawing was investigated. Commonly, tensile strength can be increased by drawing; conversely, tear resistance decreases. In this study, the balance between tensile strength and tear resistance for the resultant ETFE membrane was optimized achieved by a combination of lamination of low molecular weight (LMW) and high molecular weight (HMW) layers and subsequent biaxial drawing. The structural factor determining tear resistance of these biaxially drawn membranes was determined based on in situ small-angle X-ray scattering (SAXS) measurement during tensile deformation simulating tearing tests. Lozenge shaped scattering, which indicated inclined lamellae, was observed during such tensile deformation of the resultant membranes. Remarkably, this inclined lamellar structure was observed for the pure LMW membrane; however, it also appeared at the interface between LMW and HMW layers within biaxially drawn membranes. For the membrane exhibiting the highest tearing strength, the fraction of such inclined lamella increased up to the critical strain corresponding to the actual sample breaking. These results confirm that the inclined lamellar structure absorbed strain during membrane tearing. PMID:25697812

  20. Analysis of Fracture in Cores from the Tuff Confining Unit beneath Yucca Flat, Nevada Test Site

    SciTech Connect

    Lance Prothro

    2008-03-01

    The role fractures play in the movement of groundwater through zeolitic tuffs that form the tuff confining unit (TCU) beneath Yucca Flat, Nevada Test Site, is poorly known. This is an important uncertainty, because beneath most of Yucca Flat the TCU lies between the sources of radionuclide contaminants produced by historic underground nuclear testing and the regional carbonate aquifer. To gain a better understanding of the role fractures play in the movement of groundwater and radionuclides through the TCU beneath Yucca Flat, a fracture analysis focusing on hydraulic properties was performed on conventional cores from four vertical exploratory holes in Area 7 of Yucca Flat that fully penetrate the TCU. The results of this study indicate that the TCU is poorly fractured. Fracture density for all fractures is 0.27 fractures per vertical meter of core. For open fractures, or those observed to have some aperture, the density is only 0.06 fractures per vertical meter of core. Open fractures are characterized by apertures ranging from 0.1 to 10 millimeter, and averaging 1.1 millimeter. Aperture typically occurs as small isolated openings along the fracture, accounting for only 10 percent of the fracture volume, the rest being completely healed by secondary minerals. Zeolite is the most common secondary mineral occurring in 48 percent of the fractures observed.

  1. Preliminary Study of 2D Fracture Upscaling of Geothermal Rock Using IFS Fractal Model

    NASA Astrophysics Data System (ADS)

    Tobing, Prana F. L.; Feranie, Selly; Latief, Fourier D. E.

    2016-08-01

    Fractured rock plays important role in reservoir production. In larger scale, fractures are more likely to be heterogeneous and considered to be fractal in its nature. One of the characteristics of fractal structure is the scale independence. An investigation of fractal properties on natural fractured rock is therefore needed for modelling larger fracture. We have investigated the possibilities of fractal upscaling method to produce a larger geothermal fracture model based on smaller fracture data. We generate Iterated Function System (IFS) fractal model using parameters e.g. scale factor, angle between branch, initial line direction, and branch thickness. All the model parameters are obtained from smaller fracture data. We generate higher iteration model to be compared with larger geothermal fracture. The similarity between the IFS fractal model and natural fracture is measured by 2D box counting fractal dimension (D). The fractal dimension of first to fourth generation fractal model is (1.86 ± 0.02). The fractal dimension of the reference geothermal site is (1.86 ± 0.04). Besides of D, we found significant similarity of fracture parameters there are intensity and density between fracture model and natural fracture. Based on these result, we conclude that fractal upscaling using IFS fractal model is potential to model larger scale of 2D fracture.

  2. Thrower's fracture of the humerus.

    PubMed

    Miller, Andrew; Dodson, Christopher C; Ilyas, Asif M

    2014-10-01

    Thrower's fractures are spiral fractures of the humerus caused by forceful throwing of a ball. Although these fractures have been cited in the literature, little research exists regarding the significance of stress fractures and fatigue injuries that may precede these injuries. This article presents 3 cases of middle-aged recreational baseball pitchers who sustained mid to distal third spiral humerus fractures, reviews the biomechanics of a thrower's fracture, and provides a detailed review of the literature to help better understand this condition and guide treatment.

  3. Pelvic Insufficiency Fractures

    PubMed Central

    O’Connor, Timothy J.

    2014-01-01

    Pelvic insufficiency fractures may occur in the absence of trauma or as a result of low-energy trauma in osteoporotic bone. With a growing geriatric population, the incidence of pelvic insufficiency fracture has increased over the last 3 decades and will continue to do so. These fractures can cause considerable pain, loss of independence, and economic burden to both the patient and the health care system. While many of these injuries are identified and treated based on plain radiographs, some remain difficult to diagnose. The role of advanced imaging in these cases is discussed. In addition to treating the fracture, medical comorbidities contributing to osteoporosis should be identified and corrected. Specific attention has been given to 25-OH serum vitamin D screening and repletion. Treatment generally consists of providing pain control and assisting patients with mobilization while allowing weight bearing as tolerated. In those unable to do so, invasive techniques such as sacroplasty as well as internal fixation may be beneficial. The role of operative fixation in insufficiency fractures is also discussed. PMID:26246940

  4. Frontal bone fractures.

    PubMed

    Marinheiro, Bruno Henrique; de Medeiros, Eduardo Henrique Pantosso; Sverzut, Cássio Edvard; Trivellato, Alexandre Elias

    2014-11-01

    The aim of this retrospective study was to evaluate the epidemiology, treatment, and complications of frontal bone fractures associated, or not, with other facial fractures. This evaluation also sought to minimize the influence of the surgeon's skills and the preference for any rigid internal fixation system. The files from 3758 patients who attended the Oral and Maxillofacial Surgery Department of the School of Dentistry of Ribeirao Preto, University of Sao Paulo, from March 2004 to November 2011 and presented with facial trauma were scanned, and 52 files were chosen for the review. Eleven (21.15%) of these patients had pure fractures of the frontal bone, and trauma incidence was more prevalent in men (92.3%), whites (61.53%), and adults (50%). Despite the use of helmets at the moment of the trauma, motorcycle crashes were the most common etiological factor (32.69%). Fracture of the anterior wall of the frontal sinus with displacement was the main injury observed (54.9%), and the most common treatment was internal fixation with a plate and screws (45.09%). Postoperative complications were observed in 35.29% of the cases. The therapy applied was effective in handling this type of fracture, and the success rate was comparable to that reported in other published studies. PMID:25377971

  5. Direct Measurement of Changes to a Sheared Shale Fracture

    NASA Astrophysics Data System (ADS)

    Stadleman, M.; Bromhal, G. S.; Moore, J.; Gill, M.; Crandall, D.

    2015-12-01

    Shales are of particular interest both for their energy production potential and their ability to provide seals for sequestered CO2. It is imperative to understand the processes that influence fracture properties in order to accurately predict subsurface behavior. In order to evaluate the coupled hydrologic and geometric changes to a fracture undergoing shear displacement, a novel apparatus was used to produce real-time shearing of fractured shale at elevated pressures. Intermittent computed tomography (CT) scans were performed during each shearing event and transmissivity measurements taken to characterize both the mechanical evolution as well as the hydrodynamic response of the fracture. The initial fractures examined had small apertures and high resistance to flow, with most aperture values below the resolution of the CT scanner and low transmissivities. Initial shearing events, with total displacement less than two mm, minimally increased the aperture and increased the transmissivity. Further shearing resulted in fracture apertures that were large with pressure differentials across the core below the detection limit of the pressure measurement equipment. Flow models using the complex fracture geometries obtained from the CT scanning was performed to examine the micro-scale impacts of fracture evolution on the flow field that were not apparent in the bulk data. These results showed strong flow channelization within the larger aperture regions and showed that hydraulic aperture was significantly different than average mechanical apertures. Fracture aperture evolution due to shearing was characterized with the resulting mechanical and hydrologic responses. Apertures showed increases after each shearing event. Additionally, this increased aperture resulted in increased transmissivity and subsequent increases in hydraulic aperture. Coupling the experimental work with computational analysis provided further insight into the evolution of fracture flow properties.

  6. Fracture-Flow-Enhanced Solute Diffusion into Fractured Rock

    SciTech Connect

    Wu, Yu-Shu; Ye, Ming; Sudicky, E.A.

    2007-12-15

    We propose a new conceptual model of fracture-flow-enhanced matrix diffusion, which correlates with fracture-flow velocity, i.e., matrix diffusion enhancement induced by rapid fluid flow within fractures. According to the boundary-layer or film theory, fracture flow enhanced matrix diffusion may dominate mass-transfer processes at fracture-matrix interfaces, because rapid flow along fractures results in large velocity and concentration gradients at and near fracture-matrix interfaces, enhancing matrix diffusion at matrix surfaces. In this paper, we present a new formulation of the conceptual model for enhanced fracture-matrix diffusion, and its implementation is discussed using existing analytical solutions and numerical models. In addition, we use the enhanced matrix diffusion concept to analyze laboratory experimental results from nonreactive and reactive tracer breakthrough tests, in an effort to validate the new conceptual model.

  7. Multi-Phase Fracture-Matrix Interactions Under Stress Changes

    SciTech Connect

    A.S. Grader; D. Elsworth; P.M. Halleck; F. Alvarao; A. Alajmi; Z. Karpyn; N. Mohammed; S. Al-Enezi

    2005-12-07

    The main objectives of this project are to quantify the changes in fracture porosity and multi-phase transport properties as a function of confining stress. These changes will be integrated into conceptual and numerical models that will improve our ability to predict and optimize fluid transport in fractured system. This report details our progress on: (a) developing the direct experimental measurements of fracture aperture and topology and fluid occupancy using high-resolution x-ray micro-tomography, (b) counter-current fluid transport between the matrix and the fracture, (c) studying the effect of confining stress on the distribution of fracture aperture and two-phase flow, and (d) characterization of shear fractures and their impact on multi-phase flow. The three-dimensional surface that describes the large-scale structure of the fracture in the porous medium can be determined using x-ray micro-tomography with significant accuracy. Several fractures have been scanned and the fracture aperture maps have been extracted. The success of the mapping of fracture aperture was followed by measuring the occupancy of the fracture by two immiscible phases, water and decane, and water and kerosene. The distribution of fracture aperture depends on the effective confining stress, on the nature of the rock, and the type and distribution of the asperities that keep the fracture open. Fracture apertures at different confining stresses were obtained by micro-tomography covering a range of about two thousand psig. Initial analysis of the data shows a significant aperture closure with increase in effective confining stress. Visual and detailed descriptions of the process are shown in the report. Both extensional and shear fractures have been considered. A series of water imbibition tests were conducted in which water was injected into a fracture and its migration into the matrix was monitored with CT and DR x-ray techniques. The objective was to understand the impact of the

  8. Fracture Genesis and Fracture Filling In Hydrate Systems

    NASA Astrophysics Data System (ADS)

    Daigle, H.; Dugan, B.

    2009-12-01

    Steady-state models of coupled flow through fractures and porous media predict that millions of years are required to accumulate the very high hydrate saturation (>50%) necessary to form hydraulic fractures by fluid pressure buildup; however, once a fracture system is formed, it will fill with hydrate in roughly 15 kyr. This modeling is a first step towards understanding heterogeneous, fracture-hosted methane hydrate deposits that have been observed in marine hydrate systems worldwide. In fine-grained sediments, methane hydrate is frequently observed in pores as well as in veins and fractures. One possible explanation is hydrate forms in pores and fluid pressure increases until fractures form. Fluid then flows through the fractures and forms hydrate-filled fractures. To study this, we ran 1-D numerical simulations with a prescribed flow rate of methane-charged fluid through a porous medium. As hydrate forms, pores are occluded and permeability is reduced, causing an increase in fluid pressure to maintain the constant flow rate. We assume that hydraulic fractures form when the fluid pressure reaches 90% of the overburden stress. Simulations of Blake Ridge (offshore South Carolina) indicate that fractures occur after 7.4 million years with a hydrate saturation (Sh) of 95% at the base of the methane hydrate stability zone (MHSZ). Simulations of Keathley Canyon (Gulf of Mexico) achieve the fracture criterion after 7.9 million years with Sh = 54% at the base of the MHSZ. Once fractures are formed they fill with hydrate after 15,000 years. Our results indicate that the time scale of pressure buildup assuming present-day fluxes is very long, and that lower-permeability sediments require lower hydrate saturations to reach the fracture criterion. However, once fractures form, they are filled with hydrate rapidly. This suggests that fractures may provide short-term migration pathways between higher-permeability layers, but also that additional research is needed to constrain

  9. Treatment of Clavicle Fractures

    PubMed Central

    Paladini, P; Pellegrini, A; Merolla, G; Campi, F; Porcellini, G

    2012-01-01

    Summary Clavicle fractures are very common injuries in adults (2–5%) and children (10–15%) (1) and represent the 44–66% of all shoulder fractures (2). Despite the high frequency the choice of proper treatment is still a challenge for the orthopedic surgeon. With this review we wants to focus the attention on the basic epidemiology, anatomy, classification, evaluation and management of surgical treatments in relationship with the gravity of injuries. Both conservative and surgical management are possible, and surgeons must choose the most appropriate management modality according to the biologic age, functional demands, and type of lesion. We performed a review of the English literature thought PubMed to produce an evidence-based review of current concept and management of clavicle fracture. We finished taking a comparison with our survey in order to underline our direct experience. PMID:23905044

  10. Pediatric foot fractures.

    PubMed

    Ribbans, William J; Natarajan, Ramanathan; Alavala, Sairam

    2005-03-01

    Fractures of the foot in children usually have a good prognosis and generally are treated nonoperatively. Displaced fractures of the talus and calcaneus and tarsometatarsal dislocations are rare in children and their outcome is generally good in the younger child. Older adolescents with these injuries need treatment similar to how an adult would be treated for the same injury in order to achieve a good result. Foot fractures in children may pose a diagnostic challenge particularly in the absence of obvious radiographic changes. Repeated clinical examination and judicious use of imaging techniques such as isotope bone scans and magnetic resonance imaging are needed to establish a diagnosis. Knowledge of the anatomy and significance of accessory bones of the foot and disorders of the growing foot skeleton are helpful in managing injuries of child's foot. In this study, we review common injuries of a child's foot and include a discussion on differential diagnosis.

  11. DEM Particle Fracture Model

    SciTech Connect

    Zhang, Boning; Herbold, Eric B.; Homel, Michael A.; Regueiro, Richard A.

    2015-12-01

    An adaptive particle fracture model in poly-ellipsoidal Discrete Element Method is developed. The poly-ellipsoidal particle will break into several sub-poly-ellipsoids by Hoek-Brown fracture criterion based on continuum stress and the maximum tensile stress in contacts. Also Weibull theory is introduced to consider the statistics and size effects on particle strength. Finally, high strain-rate split Hopkinson pressure bar experiment of silica sand is simulated using this newly developed model. Comparisons with experiments show that our particle fracture model can capture the mechanical behavior of this experiment very well, both in stress-strain response and particle size redistribution. The effects of density and packings o the samples are also studied in numerical examples.

  12. Fracture of the cuboid.

    PubMed

    Borrelli, Joseph; De, Sayan; VanPelt, Michael

    2012-07-01

    Cuboid fracture accounts for a minority of all foot fractures in adults and often is indicative of a multiply injured foot. Understanding the normal anatomy and function of the cuboid and its relation to foot biomechanics is necessary for appropriate management. Clinical evaluation includes history, physical examination, and thorough assessment of the skin and soft tissues. Plain radiographs and CT are helpful in preoperative planning. Cuboid fractures may be managed either nonsurgically (splinting or casting) or surgically (closed reduction and external fixation or open reduction and internal fixation). Careful handling of the soft tissues is important, as is restoration of articular congruity, lateral column length, and a stable midfoot. Postoperative care consists of prolonged immobilization followed by 3 months of progressive weight bearing. Published reports of long-term outcomes and functional postoperative assessments are lacking. PMID:22751166

  13. Fracking, fracture, and permeability

    NASA Astrophysics Data System (ADS)

    Turcotte, D. L.; Norris, J.; Rundle, J. B.

    2013-12-01

    Injections of large volumes of water into tight shale reservoirs allows the extraction of oil and gas not previously accessible. This large volume 'super' fracking induces damage that allows the oil and/or gas to flow to an extraction well. The purpose of this paper is to provide a model for understanding super fracking. We assume that water is injected from a small spherical cavity into a homogeneous elastic medium. The high pressure of the injected water generates hoop stresses that reactivate natural fractures in the tight shales. These fractures migrate outward as water is added creating a spherical shell of damaged rock. The porosity associated with these fractures is equal to the water volume injected. We obtain an analytic expression for this volume. We apply our model to a typical tight shale reservoir and show that the predicted water volumes are in good agreement with the volumes used in super fracking.

  14. Semiautomatic fracture zone tracking

    NASA Astrophysics Data System (ADS)

    Wessel, Paul; Matthews, Kara J.; Müller, R. Dietmar; Mazzoni, Aline; Whittaker, Joanne M.; Myhill, Robert; Chandler, Michael T.

    2015-07-01

    Oceanic fracture zone traces are widely used in studies of seafloor morphology and plate kinematics. Satellite altimetry missions have resulted in high-resolution gravity maps in which all major fracture zones and other tectonic fabric can be identified, and numerous scientists have digitized such lineaments. We have initiated a community effort to maintain low-cost infrastructure that allows seafloor fabric lineaments to be stored, accessed, and updated. A key improvement over past efforts is our processing software (released as a GMT5 supplement) that allows for semiautomatic corrections to previously digitized fracture zone traces given improved gridded data sets. Here we report on our seafloor fabric processing tools, which complement our database of seafloor fabric lineations, magnetic anomaly identifications, and plate kinematic models.

  15. Talar neck fractures.

    PubMed

    Berlet, G C; Lee, T H; Massa, E G

    2001-01-01

    Clinical management of talar neck fractures is complex and fraught with complications. As Gaius Julius Caesar stated: "The die is cast"; often the outcome of a talar neck fracture is determined at the time of injury. The authors believe, however, that better results can be achieved by following some simple guidelines. The authors advocate prompt and precise anatomic surgical reduction, preferring the medial approach with secondary anterolateral approach. Preservation of blood supply can be achieved by a thorough understanding of vascular pathways and efforts to stay within appropriate surgical intervals. The authors advocate bone grafting of medial neck comminution (if present) to prevent varus malalignment and rigid internal fixation to allow for joint mobilization postoperatively. These guidelines may seem simple, but when dealing with the complexity of talar neck fractures, the foot and ankle surgeon needs to focus and rely on easily grasped concepts to reduce poor outcomes. PMID:11465133

  16. Deformation and Fracture of Shale at the Nanoscale

    NASA Astrophysics Data System (ADS)

    Bennett, K. C.; Borja, R. I.

    2013-12-01

    The deformation and fracture properties of shales depend on the mechanical properties of their basic constituents, including the solid clay particles, inclusions such as silt and organics, and the multi-scale porosity comprised of existing micro-fractures and the nano-scale porosity of the porous clay matrix. A great deal of understanding of the overall macroscopic (field scale) mechanical properties of shales can be gained by studying the deformation and fracture properties of these constituents along with their composite behavior, i.e., the mechanisms of deformation and fracture of shale. This project builds upon our recently acquired ability to image with fixed ion beam scanning electron microscopy (FIB-SEM) the 3D geometry of a porous shale sample to nanometer resolution, as well as to test this sample on a nanoindenter at both the particle and composite scales, in order to develop a 3D mechanistic model to interpret the results of nanoindentation tests. The pore-scale study considers the intrinsic deformation and fracture properties of clay particles, and the effect of silt inclusions and particle packing into an anisotropic composite matrix. The analysis accounts for anisotropic and heterogeneous shale elasticity, plasticity, damage, and fissility. A finite element (FE) model is being developed which uses a recently developed finite deformation crystal plasticity algorithm and an enhanced FE method for capturing strong discontinuity. The model aims to capture the effects of the particle elasticity, plastic yielding, and the damage induced by the indenter, including the fracturing and chipping within the mineral grains and around the perimeter of the indent. Anisotropy of fracture properties is examined with respect to delamination of the clay matrix in the bed-parallel direction and to breaking of plate-like clay particles. The ultimate goal of this research is to establish a framework for investigating the poromechanical properties of shale at the nano

  17. [Supracondylar fractures in children].

    PubMed

    Petrov, N; Gucev, S; Kirkov, Lj; Dajljevik, S; Ruso, B

    1982-01-01

    In the Department of Pediatric surgery, during the last ten years, 190 patients with supracondylar fractures (second and third degree, according to Bauman's classification) have been treated. The operation was performed in only 5% of all hospitalized cases. There were only one patient with neurological and vascular complications in the early stage, but without any complications in the late stage. The presented cases showed a high percentage of flexion type of fractures. The conservative treatment by a reposition has given the most satisfactory results.

  18. Complications of mandibular fractures.

    PubMed

    Zweig, Barry E

    2009-03-01

    Before any definitive treatment of mandibular fractures, the patient needs to be evaluated for more potentially life-threatening injuries. Complications can and do occur with treatment of mandibular fractures and can occur during any of the phases of treatment. The development of an accurate diagnosis and appropriate treatment plan is vital in achieving optimal success and decreasing complications. Knowledge of the anatomy and the principles of bone healing is also an important factor in preventing complications. To limit long-term untoward effects, complications should be recognized early and the appropriate treatment should be started before a minor complication becomes a complex one that is more difficult to manage.

  19. Fractured Petroleum Reservoirs

    SciTech Connect

    Firoozabadi, Dr. Abbas

    2000-01-18

    In this report the results of experiments of water injection in fractured porous media comprising a number of water-wet matrix blocks are reported for the first time. The blocks experience an advancing fracture-water level (FWL). Immersion-type experiments are performed for comparison; the dominant recovery mechanism changed from co-current to counter-current imbibition when the boundary conditions changed from advancing FWL to immersion-type. Single block experiments of co-current and counter-current imbibition was performed and co-current imbibition leads to more efficient recovery was found.

  20. Pediatric Orbital Fractures

    PubMed Central

    Oppenheimer, Adam J.; Monson, Laura A.; Buchman, Steven R.

    2013-01-01

    It is wise to recall the dictum “children are not small adults” when managing pediatric orbital fractures. In a child, the craniofacial skeleton undergoes significant changes in size, shape, and proportion as it grows into maturity. Accordingly, the craniomaxillofacial surgeon must select an appropriate treatment strategy that considers both the nature of the injury and the child's stage of growth. The following review will discuss the management of pediatric orbital fractures, with an emphasis on clinically oriented anatomy and development. PMID:24436730

  1. On the fracture toughness of advanced materials

    SciTech Connect

    Launey, Maximilien E.; Ritchie, Robert O.

    2008-11-24

    Few engineering materials are limited by their strength; rather they are limited by their resistance to fracture or fracture toughness. It is not by accident that most critical structures, such as bridges, ships, nuclear pressure vessels and so forth, are manufactured from materials that are comparatively low in strength but high in toughness. Indeed, in many classes of materials, strength and toughness are almost mutually exclusive. In the first instance, such resistance to fracture is a function of bonding and crystal structure (or lack thereof), but can be developed through the design of appropriate nano/microstructures. However, the creation of tough microstructures in structural materials, i.e., metals, polymers, ceramics and their composites, is invariably a compromise between resistance to intrinsic damage mechanisms ahead of the tip of a crack (intrinsic toughening) and the formation of crack-tip shielding mechanisms which principally act behind the tip to reduce the effective 'crack-driving force' (extrinsic toughening). Intrinsic toughening is essentially an inherent property of a specific microstructure; it is the dominant form of toughening in ductile (e.g., metallic) materials. However, for most brittle (e.g., ceramic) solids, and this includes many biological materials, it is largely ineffective and toughening conversely must be developed extrinsically, by such shielding mechanisms as crack bridging. From a fracture mechanics perspective, this results in toughening in the form of rising resistance-curve behavior where the fracture resistance actually increases with crack extension. The implication of this is that in many biological and high-strength advanced materials, toughness is developed primarily during crack growth and not for crack initiation. This is an important realization yet is still rarely reflected in the way that toughness is measured, which is invariably involves the use of single-value (crack-initiation) parameters such as the

  2. Bone fracture repair - series (image)

    MedlinePlus

    The three main treatment options for bone fractures are: Casting Open reduction, and internal fixation- this involves a surgery to repair the fracture-frequently, metal rods, screws or plates are used to repair the ...

  3. Fracture After Total Hip Replacement

    MedlinePlus

    ... er Total Hip Replacement cont. • Dislocation • Limb length inequality • Poor fracture healing • Repeat fracture • Lack of in- ... Surgeons (AAOS). To learn more about your orthopaedic health, please visit orthoinfo.org. Page ( 5 ) AAOS does ...

  4. Distal Radius Fracture (Broken Wrist)

    MedlinePlus

    ... choice depends on many factors, such as the nature of the fracture, your age and activity level, ... causing the cast to loosen. Depending on the nature of the fracture, your doctor may closely monitor ...

  5. Progressive Fracture of Composite Structures

    NASA Technical Reports Server (NTRS)

    Chamis, Christos C.; Minnetyan, Levon

    2008-01-01

    A new approach is described for evaluating fracture in composite structures. This approach is independent of classical fracture mechanics parameters like fracture toughness. It relies on computational simulation and is programmed in a stand-alone integrated computer code. It is multiscale, multifunctional because it includes composite mechanics for the composite behavior and finite element analysis for predicting the structural response. It contains seven modules; layered composite mechanics (micro, macro, laminate), finite element, updating scheme, local fracture, global fracture, stress based failure modes, and fracture progression. The computer code is called CODSTRAN (Composite Durability Structural ANalysis). It is used in the present paper to evaluate the global fracture of four composite shell problems and one composite built-up structure. Results show that the composite shells and the built-up composite structure global fracture are enhanced when internal pressure is combined with shear loads.

  6. Vertebroplasty for Spine Fracture Pain

    MedlinePlus

    MENU Return to Web version Vertebroplasty for Spine Fracture Pain Vertebroplasty for Spine Fracture Pain More than 40 million people in the United States have osteoporosis (a decrease in the amount ...

  7. Multi-scale modeling of inter-granular fracture in UO2

    SciTech Connect

    Chakraborty, Pritam; Zhang, Yongfeng; Tonks, Michael R.; Biner, S. Bulent

    2015-03-01

    A hierarchical multi-scale approach is pursued in this work to investigate the influence of porosity, pore and grain size on the intergranular brittle fracture in UO2. In this approach, molecular dynamics simulations are performed to obtain the fracture properties for different grain boundary types. A phase-field model is then utilized to perform intergranular fracture simulations of representative microstructures with different porosities, pore and grain sizes. In these simulations the grain boundary fracture properties obtained from molecular dynamics simulations are used. The responses from the phase-field fracture simulations are then fitted with a stress-based brittle fracture model usable at the engineering scale. This approach encapsulates three different length and time scales, and allows the development of microstructurally informed engineering scale model from properties evaluated at the atomistic scale.

  8. Fracture characteristics of PEEK at various stress triaxialities.

    PubMed

    Chen, Fei; Gatea, Shakir; Ou, Hengan; Lu, Bin; Long, Hui

    2016-12-01

    Polyether-ether-ketone (PEEK) is an alternative to metal alloys in orthopaedic applications. It gives significant advantages including excellent mechanical properties and non-toxicity. In this work, a set of specimens with different notched radii were selected to examine the effect of triaxial state of stress on the fracture behavior of PEEK. Fractographic analysis via scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) further elucidated the fracture micromechanisms. Distinct fracture patterns were identified under different stress triaxialities. In addition, the microstructural inclusion properties in PEEK specimen such as inclusion size and chemical composition were analysed and determined. Finite element simulations were carried out to evaluate the correlation of observed fracture characteristics with different stress triaxialities. PMID:27498427

  9. Hydraulic and solute-transport properties and simulated advective transport of contaminated ground water in a fractured rock aquifer at the Naval Air Warfare Center, West Trenton, New Jersey, 2003

    USGS Publications Warehouse

    Lewis-Brown, Jean C.; Carleton, Glen B.; Imbrigiotta, Thomas E.

    2006-01-01

    Volatile organic compounds, predominantly trichloroethylene and its degradation products, have been detected in ground water at the Naval Air Warfare Center (NAWC), West Trenton, New Jersey. An air-stripping pump-and-treat system has been in operation at the NAWC since 1998. An existing ground-water-flow model was used to evaluate the effect of a change in the configuration of the network of recovery wells in the pump-and-treat system on flow paths of contaminated ground water. The NAWC is underlain by a fractured-rock aquifer composed of dipping layers of sedimentary rocks of the Lockatong and Stockton Formations. Hydraulic and solute-transport properties of the part of the aquifer composed of the Lockatong Formation were measured using aquifer tests and tracer tests. The heterogeneity of the rocks causes a wide range of values of each parameter measured. Transmissivity ranges from 95 to 1,300 feet squared per day; the storage coefficient ranges from 9 x 10-5 to 5 x 10-3; and the effective porosity ranges from 0.0003 to 0.002. The average linear velocity of contaminated ground water was determined for ambient conditions (when no wells at the site are pumped) using an existing ground-water-flow model, particle-tracking techniques, and the porosity values determined in this study. The average linear velocity of flow paths beginning at each contaminated well and ending at the streams where the flow paths terminate ranges from 0.08 to 130 feet per day. As a result of a change in the pump-and-treat system (adding a 165-foot-deep well pumped at 5 gallons per minute and reducing the pumping rate at a nearby 41-foot-deep well by the same amount), water in the vicinity of three 100- to 165-foot-deep wells flows to the deep well rather than the shallower well.

  10. Mechanics of nanocrack: Fracture, dislocation emission, and amorphization

    NASA Astrophysics Data System (ADS)

    Huang, Shan; Zhang, Sulin; Belytschko, Ted; Terdalkar, Sachin S.; Zhu, Ting

    2009-05-01

    Understanding the nanoscale fracture mechanisms is critical for tailoring the mechanical properties of materials at small length scales. We perform an atomistic study to characterize the formation and extension of nano-sized cracks. By using atomistic reaction pathway calculations, we determine the energetics governing the brittle and ductile responses of an atomically sharp crack in silicon, involving the competing processes of cleavage bond breaking, dislocation emission, and amorphization by the formation of five- and seven-membered rings. We show that the nanoscale fracture process depends sensitively on the system size and loading method. Our results offer new perspectives on the brittle-to-ductile transition of fracture at the nanoscale.

  11. Adhesive fracture mechanics. [stress analysis for bond line interface

    NASA Technical Reports Server (NTRS)

    Bennett, S. J.; Devries, K. L.; Williams, M. L.

    1974-01-01

    In studies of fracture mechanics the adhesive fracture energy is regarded as a fundamental property of the adhesive system. It is pointed out that the value of the adhesive fracture energy depends on surface preparation, curing conditions, and absorbed monolayers. A test method reported makes use of a disk whose peripheral part is bonded to a substrate material. Pressure is injected into the unbonded central part of the disk. At a certain critical pressure value adhesive failure can be observed. A numerical stress analysis involving arbitrary geometries is conducted.

  12. Correlation of Hip Fracture with Other Fracture Types: Toward a Rational Composite Hip Fracture Endpoint

    PubMed Central

    Colón-Emeric, Cathleen; Pieper, Carl F.; Grubber, Janet; Van Scoyoc, Lynn; Schnell, Merritt L; Van Houtven, Courtney Harold; Pearson, Megan; Lafleur, Joanne; Lyles, Kenneth W.; Adler, Robert A.

    2016-01-01

    Purpose With ethical requirements to the enrollment of lower risk subjects, osteoporosis trials are underpowered to detect reduction in hip fractures. Different skeletal sites have different levels of fracture risk and response to treatment. We sought to identify fracture sites which cluster with hip fracture at higher than expected frequency; if these sites respond to treatment similarly, then a composite fracture endpoint could provide a better estimate of hip fracture reduction. Methods Cohort study using Veterans Affairs and Medicare administrative data. Male Veterans (n=5,036,536) aged 50-99 years receiving VA primary care between1999-2009 were included. Fractures were ascertained using ICD9 and CPT codes and classified by skeletal site. Pearson correlation coefficients, logistic regression and kappa statistics, were used to describe the correlation between each fracture type and hip fracture within individuals, without regards to the timing of the events. Results 595,579 (11.8%) men suffered 1 or more fractures and 179,597 (3.6%) suffered 2 or more fractures during the time under study. Of those with one or more fractures, rib was the most common site (29%), followed by spine (22%), hip (21%) and femur (20%). The fracture types most highly correlated with hip fracture were pelvic/acetabular (Pearson correlation coefficient 0.25, p<0.0001), femur (0.15, p<0.0001), and shoulder (0.11, p<0.0001). Conclusions Pelvic, acetabular, femur, and shoulder fractures cluster with hip fractures within individuals at greater than expected frequency. If we observe similar treatment risk reductions within that cluster, subsequent trials could consider use of a composite endpoint to better estimate hip fracture risk. PMID:26151123

  13. Elastic cavitation and fracture via injection.

    PubMed

    Hutchens, Shelby B; Fakhouri, Sami; Crosby, Alfred J

    2016-03-01

    The cavitation rheology technique extracts soft materials mechanical properties through pressure-monitored fluid injection. Properties are calculated from the system's response at a critical pressure that is governed by either elasticity or fracture (or both); however previous elementary analysis has not been capable of accurately determining which mechanism is dominant. We combine analyses of both mechanisms in order to determine how the full system thermodynamics, including far-field compliance, dictate whether a bubble in an elastomeric solid will grow through either reversible or irreversible deformations. Applying these analyses to experimental data, we demonstrate the sensitivity of cavitation rheology to microstructural variation via a co-dependence between modulus and fracture energy. PMID:26837798

  14. Interlaminar fracture toughness of thermoplastic composites

    NASA Technical Reports Server (NTRS)

    Hinkley, J. A.; Johnston, N. J.; Obrien, T. K.

    1988-01-01

    Edge delamination tension and double cantilever beam tests were used to characterize the interlaminar fracture toughness of continuous graphite-fiber composites made from experimental thermoplastic polyimides and a model thermoplastic. Residual thermal stresses, known to be significant in materials processed at high temperatures, were included in the edge delamination calculations. In the model thermoplastic system (polycarbonate matrix), surface properties of the graphite fiber were shown to be significant. Critical strain energy release rates for two different fibers having similar nominal tensile properties differed by 30 to 60 percent. The reason for the difference is not clear. Interlaminar toughness values for the thermoplastic polyimide composites (LARC-TPI and polyimidesulfone) were 3 to 4 in-lb/sq in. Scanning electron micrographs of the EDT fracture surfaces suggest poor fiber/matrix bonding. Residual thermal stresses account for up to 32 percent of the strain energy release in composites made from these high-temperature resins.

  15. Osteoporotic Hip and Spine Fractures

    PubMed Central

    Hill, Brian W.

    2014-01-01

    Hip and spine fractures represent just a portion of the burden of osteoporosis; however, these fractures require treatment and often represent a major change in lifestyle for the patient and their family. The orthopedic surgeon plays a crucial role, not only in the treatment of these injuries but also providing guidance in prevention of future osteoporotic fractures. This review provides a brief epidemiology of the fractures, details the surgical techniques, and outlines the current treatment guidelines for orthopedic surgeons. PMID:26246944

  16. Clinical consequences of vertebral fractures.

    PubMed

    Ross, P D

    1997-08-18

    People with vertebral fractures have greater pain, disability, and healthcare utilization, on average, than those without fractures. Most studies of acute pain and disability have been limited to patients with clinically diagnosed fractures (a subset of all symptomatic patients), representing about one third of all patients with fractures identified radiographically. Acute symptoms vary widely. Some patients experience intolerable pain that can be completely debilitating for several weeks or months, whereas about half of all patients with radiographically identified fractures report having had no symptoms. The reasons for this variability are unknown. Chronic pain and disability among patients with vertebral fractures are significantly greater on average than among people without fractures, even after adjusting for comorbid conditions that are common among the elderly. Similar to acute symptoms, chronic symptoms vary widely and often persist for at least several years. The risk of pain and disability increases progressively with the number and severity of vertebral deformities: the risk is multiplied several times with each additional fracture. On average, physical function is impaired among people with vertebral fractures, whether or not they currently report back pain. Declines in physical function and changes in appearance contribute to social isolation and loss of self-esteem, impairing quality of life. The cumulative impact of vertebral fractures on quality of life may rival that of hip fractures because hip fractures are less frequent and occur later in life. As many as 40% of symptomatic vertebral fractures are initially misdiagnosed, signaling a need for greater awareness among physicians and patients. Prevention of initial vertebral fractures should be actively encouraged; even if the initial fracture is asymptomatic, it indicates a greatly increased risk of subsequent fractures, pain, and physical impairment. PMID:9302895

  17. Talar fractures: three case studies.

    PubMed

    Jimenez, A L; Morgan, J H

    2001-09-01

    Three case studies of fractures are presented that demonstrate the potential morbidity that these injuries can cause as well as the acceptable outcomes if treated appropriately. Two of the cases are talar fracture dislocations; the third is an osteochondral fracture of the talus. The importance of early treatment with open reduction and internal fixation is demonstrated. Success following surgical intervention in a nonhealed osteochondral fracture of the talus is also demonstrated.

  18. Ballistic Fracturing of Carbon Nanotubes.

    PubMed

    Ozden, Sehmus; Machado, Leonardo D; Tiwary, ChandraSekhar; Autreto, Pedro A S; Vajtai, Robert; Barrera, Enrique V; Galvao, Douglas S; Ajayan, Pulickel M

    2016-09-21

    Advanced materials with multifunctional capabilities and high resistance to hypervelocity impact are of great interest to the designers of aerospace structures. Carbon nanotubes (CNTs) with their lightweight and high strength properties are alternative to metals and/or metallic alloys conventionally used in aerospace applications. Here we report a detailed study on the ballistic fracturing of CNTs for different velocity ranges. Our results show that the highly energetic impacts cause bond breakage and carbon atom rehybridizations, and sometimes extensive structural reconstructions were also observed. Experimental observations show the formation of nanoribbons, nanodiamonds, and covalently interconnected nanostructures, depending on impact conditions. Fully atomistic reactive molecular dynamics simulations were also carried out in order to gain further insights into the mechanism behind the transformation of CNTs. The simulations show that the velocity and relative orientation of the multiple colliding nanotubes are critical to determine the impact outcome. PMID:27564421

  19. Ballistic Fracturing of Carbon Nanotubes.

    PubMed

    Ozden, Sehmus; Machado, Leonardo D; Tiwary, ChandraSekhar; Autreto, Pedro A S; Vajtai, Robert; Barrera, Enrique V; Galvao, Douglas S; Ajayan, Pulickel M

    2016-09-21

    Advanced materials with multifunctional capabilities and high resistance to hypervelocity impact are of great interest to the designers of aerospace structures. Carbon nanotubes (CNTs) with their lightweight and high strength properties are alternative to metals and/or metallic alloys conventionally used in aerospace applications. Here we report a detailed study on the ballistic fracturing of CNTs for different velocity ranges. Our results show that the highly energetic impacts cause bond breakage and carbon atom rehybridizations, and sometimes extensive structural reconstructions were also observed. Experimental observations show the formation of nanoribbons, nanodiamonds, and covalently interconnected nanostructures, depending on impact conditions. Fully atomistic reactive molecular dynamics simulations were also carried out in order to gain further insights into the mechanism behind the transformation of CNTs. The simulations show that the velocity and relative orientation of the multiple colliding nanotubes are critical to determine the impact outcome.

  20. Correlations between ultrasonic and fracture toughness factors in metallic materials

    NASA Technical Reports Server (NTRS)

    Vary, A.

    1978-01-01

    A heuristic mathematical basis was proposed for the experimental correlations found between ultrasonic propagation factors and fracture toughness factors in metallic materials. A crack extension model was developed wherein spontaneous stress (elastic) waves produced during microcracking are instrumental in promoting the onset of unstable crack extension. Material microstructural factors involved in the process are measurable by ultrasonic probing. Experimental results indicate that ultrasonic attenuation and velocity measurements will produce significant correlations with fracture toughness properties and also yield strength.

  1. Management of osteoporotic vertebral fractures

    PubMed Central

    Dionyssiotis, Yannis

    2010-01-01

    Osteoporotic vertebral fractures are associated with considerable reduction of quality of life, morbidity, and mortality. The management of patients with vertebral fractures should include treatment for osteoporosis and measures to reduce pain and improve mobility. This article provides information for management and rehabilitation of vertebral fractures based on clinical experience and literature. PMID:20689689

  2. Transmissivity and conductivity of single fractures

    NASA Astrophysics Data System (ADS)

    Adler, P. M.; Thovert, J. F.; Mourzenko, V. V.

    2015-12-01

    A fracture can be seen as a void space between two rough surfaces in partial contact. Transmissivity and conductivity can be determined numerically by solving the Stokes and Laplace equations between these two surfaces. These problems were first solved and published by the same authors between 1995 and 2001. Updated, more complete and precise results are presented here. Each surface of a fracture can be schematized as a random surface oscillating around an average plane, characterized by the probability density and autocorrelation function C(u) of the heights; their standard deviation is the roughness sigma. The two surfaces are separated by a mean distance b_m and their heights are correlated with an intercorrelation coefficient theta. The two major classes for C(u), namely the Gaussian and the self-affine autocorrelations with Hurst exponent H, are both characterized by a length scale l_c, which is a typical scale for the surface features in the Gaussian case and a cut-off length in the self-affine case. Gaussian surfaces are statistically homogeneous while the mean properties in the self-affine case are size-dependent. Systematic calculations were performed for these two classes, with recent emphasis put on the Gaussian fractures. The results are modeled as functions of b_m/sigma, l_c/sigma and theta. Cubic law applies for large b_m/sigma in terms of the aperture reduced by the hydraulic thickness of the surface rugosity. Another cubic law applies in the opposite limit of tight fractures with an offset depending on theta and a prefactor which depends on theta and l_c. A transition takes place between these two regimes. It is also shown that the Reynolds approximation may overestimate the true transmissivity by almost an order of magnitude. Similar calculations were performed for conductivity. The whole work is summarized by a series of master curves and models which can be used to estimate the properties of real fractures.

  3. Stress Analysis and Fracture in Nanolaminate Composites

    NASA Technical Reports Server (NTRS)

    Chamis, Christos C.

    2008-01-01

    A stress analysis is performed on a nanolaminate subjected to bending. A composite mechanics computer code that is based on constituent properties and nanoelement formulation is used to evaluate the nanolaminate stresses. The results indicate that the computer code is sufficient for the analysis. The results also show that when a stress concentration is present, the nanolaminate stresses exceed their corresponding matrix-dominated strengths and the nanofiber fracture strength.

  4. Hydraulic fracturing and associated stress modeling for the Eastern Gas Shales Project. Final report

    SciTech Connect

    Advani, S.H.

    1980-12-01

    Frac fluid flow, structure, and fracture mechanics simulations are developed for predicting and optimizing fracture dimensions and fluid leak-offs. Roles of in situ stress and material properties for possible vertical migration of fractures from the pay zone are discussed. Rationale for foam and dendritic fracturing experiments is presented along with numerical experiments for examining the phenomena of spalling of the fracture faces and conditions for secondary fracture initiation. Assignment of conventional, foam, cyrogenic, dendritic, and explosive fracturing treatments for specific reservoir properties is considered. Variables include fracture density and extent, shale thickness, in-situ stress gradients, energy assist mechanisms, well clean-up, shale-frac fluid interaction, proppant selection, and fracture height control. The analysis suggests that correlation with prevailing in situ stress gradients are promising diagnostic indicators for fracture treatment selection and design. In conclusion, the comprehensive development of an economical strategy requires extensive and controlled field testing with supporting predictive analyses of reservoir responses. Finite element modeling of reservoir in situ stress trajectories and the flow and fracture responses in the reservoir is recommended.

  5. Hip fracture surgery

    MedlinePlus

    ... thigh bone. The thigh bone is called the femur. It is part of the hip joint. Hip pain is a related topic. ... to 4 hours. If you have an intertrochanteric fracture (the area below the femur neck), your surgeon will use a special metal ...

  6. Femur fracture repair - discharge

    MedlinePlus

    ... surgery, your surgeon will make a cut to open your fracture. Your surgeon will then use special metal devices to hold your bones in place while they heal. These devices are called ... is open reduction and internal fixation (ORIF). In the most ...

  7. Fracture design modelling

    SciTech Connect

    Crichlow, H.B.; Crichlow, H.B.

    1980-02-07

    A design tool is discussed whereby the various components that enter the design process of a hydraulic fracturing job are combined to provide a realistic appraisal of a stimulation job in the field. An interactive computer model is used to solve the problem numerically to obtain the effects of various parameters on the overall behavior of the system.

  8. Infiltration into Fractured Bedrock

    SciTech Connect

    Salve, Rohit; Ghezzehei, Teamrat A.; Jones, Robert

    2007-09-01

    One potential consequence of global climate change and rapid changes in land use is an increased risk of flooding. Proper understanding of floodwater infiltration thus becomes a crucial component of our preparedness to meet the environmental challenges of projected climate change. In this paper, we present the results of a long-term infiltration experiment performed on fractured ash flow tuff. Water was released from a 3 x 4 m{sup 2} infiltration plot (divided into 12 square subplots) with a head of {approx}0.04 m, over a period of {approx}800 days. This experiment revealed peculiar infiltration patterns not amenable to current infiltration models, which were originally developed for infiltration into soils over a short duration. In particular, we observed that in part of the infiltration plot, the infiltration rate abruptly increased a few weeks into the infiltration tests. We suggest that these anomalies result from increases in fracture permeability during infiltration, which may be caused by swelling of clay fillings and/or erosion of infill debris. Interaction of the infiltration water with subsurface natural cavities (lithophysal cavities) could also contribute to such anomalies. This paper provides a conceptual model that partly describes the observed infiltration patterns in fractured rock and highlights some of the pitfalls associated with direct extension of soil infiltration models to fractured rock over a long period.

  9. Statistical Physics of Fracture

    SciTech Connect

    Alava, Mikko; Nukala, Phani K; Zapperi, Stefano

    2006-05-01

    Disorder and long-range interactions are two of the key components that make material failure an interesting playfield for the application of statistical mechanics. The cornerstone in this respect has been lattice models of the fracture in which a network of elastic beams, bonds, or electrical fuses with random failure thresholds are subject to an increasing external load. These models describe on a qualitative level the failure processes of real, brittle, or quasi-brittle materials. This has been particularly important in solving the classical engineering problems of material strength: the size dependence of maximum stress and its sample-to-sample statistical fluctuations. At the same time, lattice models pose many new fundamental questions in statistical physics, such as the relation between fracture and phase transitions. Experimental results point out to the existence of an intriguing crackling noise in the acoustic emission and of self-affine fractals in the crack surface morphology. Recent advances in computer power have enabled considerable progress in the understanding of such models. Among these partly still controversial issues, are the scaling and size-effects in material strength and accumulated damage, the statistics of avalanches or bursts of microfailures, and the morphology of the crack surface. Here we present an overview of the results obtained with lattice models for fracture, highlighting the relations with statistical physics theories and more conventional fracture mechanics approaches.

  10. Bipartite patella fracture.

    PubMed

    Canizares, George H; Selesnick, F Harlan

    2003-02-01

    Bipartite patella fracture is an uncommon injury that has rarely been described in the literature. It can be quite debilitating in the competitive athlete and is often overlooked by the treating physician. A bone scan can be helpful in confirming the diagnosis, and appropriate treatment often results in a successful outcome.

  11. Dorsal radiocarpal fracture dislocation.

    PubMed

    Tanzer, T L; Horne, J G

    1980-11-01

    A case of a rare radiocarpal fracture dislocation in a 17-year-old girl, with persisting loss of radiocarpal joint space following reduction under hematoma block, is described. The wrist joint was exposed, and two osteochondral fragments were rotated 90 degrees and secured with 2.7-mm AO screws. Satisfactory healing followed 3 months postinjury.

  12. Integrated remodeling-to-fracture finite element model of human proximal femur behavior.

    PubMed

    Hambli, Ridha; Lespessailles, Eric; Benhamou, Claude-Laurent

    2013-01-01

    The purpose of this work was to develop an integrated remodeling-to-fracture finite element model allowing for the combined simulation of (i) simulation of a human proximal femur remodeling under a given boundary conditions, (ii) followed by the simulation of its fracture behavior (force-displacement curve and fracture pattern) under quasi-static load. The combination of remodeling and fracture simulation into one unified model consists in considering that the femur properties resulting from the remodeling simulation correspond to the initial state for the fracture prediction. The remodeling model is based on phenomenological one based on a coupled strain and fatigue damage stimulus. The fracture model is based on continuum damage mechanics in order to predict the progressive fracturing process which allows to predict the fracture pattern and the complete force-displacement curve under quasi-static load. To prevent mesh-dependence that generally affects the damage propagation rate, regularization technique was applied in the current work. To investigate the potential of the proposed unified remodeling-to-fracture model, we performed remodeling simulations on a 3D proximal femur model for a duration of 365 days under five different daily loading conditions followed by a side fall fracture simulation reproducing previously published experimental tests (de Bakker et al. (2009), case C, male, 72 years old). We show here that the implementation of an integrated remodeling-to-fracture model provides more realistic prediction strategy to assess the bone remodeling effects on the fracture risk of bone.

  13. Numerical simulations examining the relationship between wall-roughness and fluid flow in rock fractures

    SciTech Connect

    Crandall, Dustin; Bromhal, Grant; Karpyn, Zuleima T.

    2010-07-01

    Understanding how fracture wall-roughness affects fluid flow is important when modeling many subsurface transport problems. Computed tomography scanning provides a unique view of rock fractures, allowing the measurement of fracture wall-roughness, without destroying the initial rock sample. For this computational fluid dynamics study, we used several different methods to obtain three-dimensional meshes of a computed tomography scanned fracture in Berea sandstone. These volumetric meshes had different wall-roughnesses, which we characterized using the Joint Roughness Coefficient and the fractal dimension of the fracture profiles. We then related these macroscopic roughness parameters to the effective flow through the fractures, as determined from Navier-Stokes numerical models. Thus, we used our fracture meshes to develop relationships between the observed roughness properties of the fracture geometries and flow parameters that are of importance for modeling flow through fractures in field scale models. Fractures with high Joint Roughness Coefficients and fractal dimensions were shown to exhibit tortuous flow paths, be poorly characterized by the mean geometric aperture, and have a fracture transmissivity 35 times smaller than the smoother modeled fracture flows.

  14. Fractures in Tharsis Tholus

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site]

    In the upper left corner of this VIS image are a series of fractures. Where the fractures are exposed on the surface it is impossible to tell the plane of the fracture; however where the fractures are visible in the cliff wall it is possible to see that the fractures dip to the north. This image shows part of the caldera of Tharsis Tholus.

    Image information: VIS instrument. Latitude 13.5, Longitude 268.9 East (91.1 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  15. Entablature: fracture types and mechanisms

    NASA Astrophysics Data System (ADS)

    Forbes, A. E. S.; Blake, S.; Tuffen, H.

    2014-05-01

    Entablature is the term used to describe zones or tiers of irregular jointing in basaltic lava flows. It is thought to form when water from rivers dammed by the lava inundates the lava flow surface, and during lava-meltwater interaction in subglacial settings. A number of different fracture types are described in entablature outcrops from the Búrfell lava and older lava flows in Þjórsárdalur, southwest Iceland. These are: striae-bearing, column-bounding fractures and pseudopillow fracture systems that themselves consist of two different fracture types—master fractures with dimpled surface textures and subsidiary fractures with curved striae. The interaction of pseudopillow fracture systems and columnar jointing in the entablature produces the chevron fracture patterns that are commonly observed in entablature. Cube-jointing is a more densely fractured version of entablature, which likely forms when more coolant enters the hot lava. The entablature tiers display closely spaced striae and dendritic crystal shapes which indicate rapid cooling. Master fracture surfaces show a thin band with an evolved composition at the fracture surface; mineral textures in this band also show evidence of quenching of this material. This is interpreted as gas-driven filter pressing of late-stage residual melt that is drawn into an area of low pressure immediately preceding or during master fracture formation by ductile extensional fracture of hot, partially crystallised lava. This melt is then quenched by an influx of water and/or steam when the master fracture fully opens. Our findings suggest that master fractures are the main conduit for coolant entering the lava flow during entablature formation.

  16. Flow and Transport Through Unsaturated Fractured Rock

    NASA Astrophysics Data System (ADS)

    Evans, Daniel D.; Nicholson, Thomas J.; Rasmussen, Todd C.

    This monograph is an update and revision of the first edition, Geophysical Monograph 42, on ground-water flow and transport through unsaturated, fractured rock, published by AGU in 1987. The first edition evolved from a special symposium held during the American Geophysical Union fall meetings in San Francisco in December 1986. Invited and contributed papers at that AGU session, as well as panel presentations, focused on conceptualizing, measuring and modeling flow and transport through unsaturated fractured rock. As noted in the preface to the first edition, "the expanded interest in the topic (water flow and contaminant transport through unsaturated fractured rock) was initiated when the U.S. Geological Survey proposed that deep unsaturated zones in arid regions be considered in the site selection for the first high-level, commercially generated radioactive waste repository." Much of the research reported in that first edition was motivated by the U.S. Department of Energy's program to investigate Yucca Mountain at the Nevada Test Site as a possible geologic repository for commercially generated, high-level radioactive waste. As noted in the overview paper of the first edition, "characterization methods and modeling are in their developmental stage with the greatest lack of knowledge being the interaction between fracture and matrix flow and transport properties." Although the first edition of this monograph reflected the state-of-the science, laboratory and field experimental programs were novel and limited and, in general, followed from the principles and methods developed in the soil science community.

  17. Fracture investigation in starch-based foods.

    PubMed

    Skamniotis, C G; Patel, Y; Charalambides, M N; Elliott, M

    2016-06-01

    The study of oral processing and specifically cutting of the food piece during mastication can lead towards optimization of products for humans or animals. Food materials are complex biocomposites with a highly nonlinear constitutive response. Their fracture properties have not been largely investigated, while the need for models capable of predicting food breakdown increases. In this study, the blade cutting and the essential work of fracture (EWF) methodologies assessed the fracture behaviour of starch-based pet food. Tensile tests revealed rate-dependent stiffness and stress softening effects, attributed to viscoplasticity and micro-cracking, respectively. Cutting data were collected for 5, 10 and 30 mm s(-1) sample feed rates, whereas the EWF tests were conducted at 1.7, 3.3 and 8.3 mm s(-1) crosshead speeds corresponding to average crack speeds of 4, 7 and 15 mm s(-1), respectively. A reasonable agreement was achieved between cutting and EWF, reporting 1.26, 1.78, 1.76 kJ m(-2) and 1.52, 1.37, 1.45 kJ m(-2) values, respectively, for the corresponding crack speeds. These toughness data were used in a novel numerical model simulating the 'first' bite mastication process. A viscoplastic material model is adopted for the food piece, combined with a damage law that enabled predicting fracture patterns in the product. PMID:27274805

  18. Comprehensive evaluation of fracture parameters by dual laterolog data

    NASA Astrophysics Data System (ADS)

    Saboorian-Jooybari, Hadi; Dejam, Morteza; Chen, Zhangxin; Pourafshary, Peyman

    2016-08-01

    Reservoir quality and productivity of tight formations depend heavily on the degree of fracture development. In fact, hard and dense carbonate formations may not be considered as net pay without the presence of fractures that convey fluids towards the wellbore. The evaluation of fractures is key to effective reservoir characterization for purposes like well drilling and completion as well as development and simulation of fractured reservoirs. Although imaging technologies such as Formation Micro-Scanners and Imagers (FMS and FMI) provide useful information about fracture properties (i.e., dip angle, porosity, aperture, and permeability), they are very expensive and may not be available in all wells. In this work, fracture parameters are estimated using conventional dual laterolog (DLL) resistivity which includes shallow (LLS) and deep (LLD) responses. This technique is based on electrical resistivity anomalies resulting from the separation of shallow and deep laterolog curves. Fracture parameters that can be calculated by DLL include dip angle, aperture, porosity, permeability, and cementation factor. The accuracy of the parameters calculated using DLL data is validated by the results of FMI in a well in one of the Iranian fractured reservoirs. Contrary to the image logs, the conventional DLL is run routinely in all drilled wells. Therefore, if a reservoir has limited and insufficient data of image logs, as it is often the case, the DLLs can be used as a reliable replacement in the construction of fracture models. Furthermore, DLL has an advantage of deeper evaluation of fractures in comparison with the immediate borehole investigation of image logs.

  19. Variability and Anisotropy of Fracture Toughness of Cortical Bone Tissue

    NASA Astrophysics Data System (ADS)

    Abdel-Wahab, Adel; Nordin, Norhaziqah; Silberschmidt, Vadim

    2012-08-01

    Bones form protective and load-bearing framework of the body. Therefore, their structural integrity is vital for the quality of life. Unfortunately, bones can only sustain a load until a certain limit, beyond which they fail. Therefore, it is essential to study their mechanical and fracture behaviours in order to get an in-depth understanding of the origins of its fracture resistance that, in turn, can assist diagnosis and prevention of bone's trauma. This can be achieved by studying mechanical properties of bone, such as its fracture toughness. Generally, most of bone fractures occur for long bones that consist mostly of cortical bone. Therefore, in this study, only a cortical bone tissue was studied. Since this tissue has an anisotropic behaviour and possesses hierarchical and complex structure, in this paper, an experimental analysis for the fracture toughness of cortical bone tissue is presented in terms of J-integral. The data was obtained using single-edge-notch bending (SENB) cortical specimens of bone tested in a three-point bending setup. Variability of values of fracture toughness was investigated by testing specimens cut from different cortex positions of bovine femur called anterior, posterior, medial, and lateral. In addition, anisotropy ratios of fracture toughness were considered by examining specimens cut from three different orientations: longitudinal, transverse and radial. Moreover, in order to link cortical bone fracture mechanisms with its underlying microstructure, fracture surfaces of specimens from different cortices and along different orientations were studied. Experimental results of this study provide a clear understanding of both variability and anisotropy of cortical bone tissue with regard to its fracture toughness.

  20. [Pathogenesis of atypical femoral fracture].

    PubMed

    Iwata, Ken; Mashiba, Tasuku

    2016-01-01

    We demonstrated microdamage accumulation in the fracture sites in the patients of subtrochanteric atypical femoral fracture with long term bisphosphonate therapy and of incomplete shaft fracture of lateral femoral bowing without bisphosphonate therapy. Based on these findings, pathogenesis of atypical femoral fracture is revealed stress fracture caused by accumulation of microdamages between distal to the lesser trochanter and proximal to the supracondylar flare in the femur in association with severely suppressed bone turnover and/or abnormal lower limb alignment, that causes stress concentration on the lateral side cortex of the femur. PMID:26728533

  1. Tibial Stress Fractures in Athletes.

    PubMed

    Feldman, John J; Bowman, Eric N; Phillips, Barry B; Weinlein, John C

    2016-10-01

    Tibial stress fractures are common in the athlete. There are various causes of these fractures, the most common being a sudden increase in training intensity. Most of these injuries are treated conservatively; however, some may require operative intervention. Intervention is mostly dictated by location of the fracture and failure of conservative treatment. There are several surgical options available to the treating surgeon, each with advantages and disadvantages. The physician must understand the nature of the fracture and the likelihood for it to heal in a timely manner in order to best treat these fractures in this patient subset. PMID:27637660

  2. Biomechanical Concepts for Fracture Fixation.

    PubMed

    Bottlang, Michael; Schemitsch, Christine E; Nauth, Aaron; Routt, Milton; Egol, Kenneth A; Cook, Gillian E; Schemitsch, Emil H

    2015-12-01

    Application of the correct fixation construct is critical for fracture healing and long-term stability; however, it is a complex issue with numerous significant factors. This review describes a number of common fracture types and evaluates their currently available fracture fixation constructs. In the setting of complex elbow instability, stable fixation or radial head replacement with an appropriately sized implant in conjunction with ligamentous repair is required to restore stability. For unstable sacral fractures with vertical or multiplanar instabilities, "standard" iliosacral screw fixation is not sufficient. Periprosthetic femur fractures, in particular Vancouver B1 fractures, have increased stability when using 90/90 fixation versus a single locking plate. Far cortical locking combines the concept of dynamization with locked plating to achieve superior healing of a distal femur fracture. Finally, there is no ideal construct for syndesmotic fracture stabilization; however, these fractures should be fixed using a device that allows for sufficient motion in the syndesmosis. In general, orthopaedic surgeons should select a fracture fixation construct that restores stability and promotes healing at the fracture site, while reducing the potential for fixation failure.

  3. On the possibility of magnetic nano-markers use for hydraulic fracturing in shale gas mining

    NASA Astrophysics Data System (ADS)

    Zawadzki, Jaroslaw; Bogacki, Jan

    2016-04-01

    Recently shale gas production became essential for the global economy, thanks to fast advances in shale fracturing technology. Shale gas extraction can be achieved by drilling techniques coupled with hydraulic fracturing. Further increasing of shale gas production is possible by improving the efficiency of hydraulic fracturing and assessing the spatial distribution of fractures in shale deposits. The latter can be achieved by adding magnetic markers to fracturing fluid or directly to proppant, which keeps the fracture pathways open. After that, the range of hydraulic fracturing can be assessed by measurement of vertical and horizontal component of earth's magnetic field before and after fracturing. The difference in these components caused by the presence of magnetic marker particles may allow to delineate spatial distribution of fractures. Due to the fact, that subterranean geological formations may contain minerals with significant magnetic properties, it is important to provide to the markers excellent magnetic properties which should be also, independent of harsh chemical and geological conditions. On the other hand it is of great significance to produce magnetic markers at an affordable price because of the large quantities of fracturing fluids or proppants used during shale fracturing. Examining the properties of nano-materials, it was found, that they possess clearly superior magnetic properties, as compared to the same structure but having a larger particle size. It should be then possible, to use lower amount of magnetic marker, to obtain the same effect. Although a research on properties of new magnetic nano-materials is very intensive, cheap magnetic nano-materials are not yet produced on a scale appropriate for shale gas mining. In this work we overview, in detail, geological, technological and economic aspects of using magnetic nano-markers in shale gas mining. Acknowledgment This work was supported by the NCBiR under Grant "Electromagnetic method to

  4. Linear elastic fracture mechanics primer

    NASA Technical Reports Server (NTRS)

    Wilson, Christopher D.

    1992-01-01

    This primer is intended to remove the blackbox perception of fracture mechanics computer software by structural engineers. The fundamental concepts of linear elastic fracture mechanics are presented with emphasis on the practical application of fracture mechanics to real problems. Numerous rules of thumb are provided. Recommended texts for additional reading, and a discussion of the significance of fracture mechanics in structural design are given. Griffith's criterion for crack extension, Irwin's elastic stress field near the crack tip, and the influence of small-scale plasticity are discussed. Common stress intensities factor solutions and methods for determining them are included. Fracture toughness and subcritical crack growth are discussed. The application of fracture mechanics to damage tolerance and fracture control is discussed. Several example problems and a practice set of problems are given.

  5. Fracture properties and behavior of transparent ceramics

    NASA Astrophysics Data System (ADS)

    Patel, Parimal J.; Swab, Jeffrey J.; Gilde, Gary A.

    2000-10-01

    For the past several decades, the Army has been interested in materials transparent to visible and infrared wavelengths for use in armor, IR windows and sensor windows. Future requirements for transparent armor are systems that can defeat greater threats without increased weight and thickness and minimal optical distortion. The Army Research Laboratory is developing transparent armor systems to increase the performance of new windows. Aluminum oxynitride spinel and single-crystal sapphire are two of the ceramic candidates for advanced transparent armor applications.

  6. Fatigue and fracture mechanics in pressure vessels and piping. PVP-Volume 304

    SciTech Connect

    Mehta, H.S.; Wilkowski, G.; Takezono, S.; Bloom, J.; Yoon, K.; Aoki, S.; Rahman, S.; Nakamura, T.; Brust, F.; Yoshimura, S.

    1995-11-01

    Fracture mechanics and fatigue evaluations are an important part of the structural integrity analyses to assure safe operation of pressure vessels and piping components during their service life. The paper presented in this volume illustrate the application of fatigue and fracture mechanics techniques to assess the structural integrity of a wide variety of Pressure Vessels and Piping components. The papers are organized in six sections: (1) fatigue and fracture--vessels; (2) fatigue and fracture--piping; (3) fatigue and fracture--material property evaluations; (4) constraint effects in fracture mechanics; (5) probabilistic fracture mechanics analyses; and (6) user`s experience with failure assessment diagrams. Separate abstracts were prepared for most of the papers in this book.

  7. INVESTIGATION OF EFFICIENCY IMPROVEMENTS DURING CO2 INJECTION IN HYDRAULICALLY AND NATURALLY FRACTURED RESERVOIRS

    SciTech Connect

    David S. Schechter

    2005-04-27

    This report describes the work performed during the fourth year of the project, ''Investigating of Efficiency Improvements during CO{sub 2} Injection in Hydraulically and Naturally Fractured Reservoirs.'' The objective of this project is to perform unique laboratory experiments with artificially fractured cores (AFCs) and X-ray CT scanner to examine the physical mechanisms of bypassing in hydraulically fractured reservoirs (HFR) and naturally fractured reservoirs (NFR) that eventually result in more efficient CO{sub 2} flooding in heterogeneous or fracture-dominated reservoirs. I