Science.gov (United States)

... Accession Number : ADA136144. Title : Characteristics of the Mechanical Properties and the Fractures of an Alpha Beta Titanium Alloy,. ...

CERN Document Server

The nucleation and propagation of hydrofractures by injection of over pressured fluids in an elastic and isotropic medium are studied experimentally. Non-Newtonian fluids are injected inside a gelatine whose mechanical properties are assumed isotropic at the experimental strain rates. Linear elastic theory predicts that plastic deformation associated to breakage of gelatin bonds is limited to a small zone ahead of the tip of the propagating fracture and that propagation will be maintained while the fluid pressure exceeds the normal stress to the fracture walls (Ch\\'avez-\\'Alvarez,2008) (i.e., the minimum compressive stress), resulting in a single mode I fracture geometry. However, we observed the propagation of fractures type II and III as well as nucleation of secondary fractures, with oblique to perpendicular trajectories with respect to the initial ...

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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 ...

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The understanding of transport processes that occur in naturally fractured geothermal systems is far from being complete. Often, evaluation and numerical simulations of fractured geothermal reservoirs, are carried out by assuming equivalent porous media and homogeneous petrophysical properties within big matrix blocks. The purpose of this paper, is to present a comparison between results obtained from numerical studies of a naturally fractured reservoir treated as a simple porous medium and the simulation of some real aspects of the fractured reservoir. A general conclusion outlines the great practical importance of considering even approximately, the true nature of such systems. Our results show that the homogeneous simplified evaluation of the energy resource in a fractured system, could result in unrealistic estimates of the reservoir capacity to generate ...

International Nuclear Information System (INIS)

1972. United States Narayanan, GH Archbold, TF Univ. of California Press.;

British Library Electronic Table of Contents (United Kingdom)

In this study, the influence of Beryllium (Be) content on the fracture behaviour of Al?15%Mg2Si composite was investigated. The results showed an increase in mechanical properties with increasing of Be content. The stress?strain curves of samples showed a same category of serrations reflecting non-uniform deformation. Scanning electron microscopy was employed to examine the crack nucleation and fracture model. The results indicate that Al?15%Mg2Si composite shows different behaviours of crack initiation and fracture for samples with and without Be. Differences observed in the fracture behaviour were attributed to microstructural changes as well as morphological aspects of primary Mg2Si particles.

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Identifying stable isotope variation and mineralogical changes in fractured rock may help establish the history of climatic and geomorphological processes that might affect the isolation properties of a waste repository site. This study examines the use of the stable isotope ratios of oxygen ({sup 18}O/{sup 16}O) and carbon ({sup 13}C/{sup 12}C) in authigenic minerals as hydrogeochemical tools tracing low-temperature rock-water interaction in variably-saturated fractured stuff. Isotopic compositions of fracture-filling and rock matrix minerals in the Apache Leap tuff, near Superior, Arizona were concordant with geothermal temperatures and in equilibrium with water isotopically similar to present-day meteoric water and groundwater. Oxygen and carbon isotope ratios of fracture-filling, in unsaturated fractured tuff, displayed an isotopic gradient believed to ...

International Nuclear Information System (INIS)

The effect of the rare earth element, yttrium, on the mechanical properties of 9Cr-2WVTa low active martensite steel for fusion reactor was studied and the metallurgical behavior of yttrium in the steel was primarily analyzed. The results show that it is easy for yttrium to aggregate and form the blocky yttrium rich inclusions in the steel, which can dissever the continuity of the matrix and produce micro-cracks for fracture. The yttrium rich inclusions were distributed along the rolling direction, which made the fracture surface delaminated in the tensile and impact samples, and reduced the mechanical properties of the steel. (authors)

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Age-related deterioration of the fracture properties of bone, coupled with increased life expectancy, are responsible for increasing incidence of bone fracture in the elderly, and hence, an understanding of how its fracture properties degrade with age is essential. The present study describes ex vivo fracture experiments to quantitatively assess the effect of aging on the fracture toughness properties of human cortical bone in the longitudinal direction. Because cortical bone exhibits rising crack-growth resistance with crack extension, unlike most previous studies the toughness is evaluated in terms of resistance-curve (R-curve) behavior, measured for bone taken from wide range of age groups (34-99 years). Using this approach, both the ex vivo crack-initiation and crack-growth toughness are determined and are found to ...

Science.gov (United States)

Tibial Shaft Fractures in Children

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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}, ...

British Library Electronic Table of Contents (United Kingdom)

Statement of problem Because noble dental casting alloys for metal ceramic restorations have a wide range of mechanical properties, knowledge of these properties is needed for rational alloy selection in different clinical situations where cast metal restorations are indicated. Purpose The purpose of this study was to compare the mechanical properties and examine both the fracture and polished surfaces of 6 noble casting alloys that span many currently marketed systems. Five alloys were designed for metal ceramic restorations, and a sixth Type GPT has Type IV alloy for fixed prosthodontics (Maxigold KF) was included for comparison. Material and methods Specimens (n=6) meeting dimensional requirements for ISO Standards 9693 and 8891 were loaded to failure in tension using a universal testin...

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Analyses of the date obtained from the instrumented impact test and of its correlation with static and dynamic J integral values and various tensile properties are made in this study. It is shown that a dynamic bending yield load recorded in the instrumented Charpy V test can be easily converted to a dynamic tensile yield stress using Server's equation. It is also possible to estimate a true fracture strain, COD value, and SZW easily if the load point displacement is recorded. Temperature dependency of Charpy V energy and J integral values is rather well simulated by a curve fitting method. However, a half value transition temperture obtained in that method has no physical meaning. Dynamic J sub(ID) is larger than a static J sub(IC) in the ductile fracture range in this study. This rise is proportional to the yield stress ratio sigmasub(yd)/sigmasub(y)(--1.2-1.3). It is found, therefore, that the following relation ...

International Nuclear Information System (INIS)

SiAlONs are ceramics with high potential as biomaterials due to their chemical stability, associated with suitable mechanical properties, such as high fracture toughness and fracture resistance. The objective of this work was to investigate the mechanical properties and the cytotoxicity of these ceramic materials. Three different compositions were prepared, using silicon nitride, aluminum nitride and a rare earth oxide mixture as starting powders, yielding Si_3N_4-SiAlON composites or pure SiAlON ceramics, after hot-pressing at 1750 deg. C, for 30 min. The sintered samples were characterized by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). Furthermore, hardness and fracture toughness were determined using the Vicker's indentation method. The biological compatibility was evaluated by in vitro cytotoxicity tests. Ceramic with elevated hardness, ranging ...

Science.gov (United States)

Lecture notes (pdf) on Ceramics is part of a physics course on the properties of matter from the University of Auckland, Department of Chemical and Materials Engineering. The following topics are covered: types of chemical bonding, degree of ionic character, structure of ceramics and crystallography, interstitial sites in different crystal structures, silicate structures, glasses, glass transition temperature, glass viscosity, thermal and mechanical properties of ceramics and glasses, fracture properties of ceramics and processing of ceramic materials. Keywords: ionic bonds; covalent bonds; coordination numbers; thermal shock; grain growth; sintering; green body

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The effect of tsub(A) austenitization temperature in heating for quenching as well as in the cycle of high-temperature thermomechanical treatment (HTMT) on structure, mechanical properties and fracture mode of 40KhN2MA structural steel is investigated. It is shown that heating up to 1200 deg C does not affect essentially sigmasub(b) and sigmasub(0.2) of a quenched material but increases fracture toughness of 200 deg C - tempered precracked specimens and is accompanied by a decrease of impact strength and plasticity of vee-notched specimens. The optimum complex of mechanical properties is attained upon combined treatment comprising heating up to 1200 deg C and HTMT with deformation at 850 deg C.

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The crack growth behavior and fracture toughness of two laminated metal composites (6090/SiC/25p laminated with 5182 and ultrahigh-carbon steel laminated with brass) have been studied in both ``crack arrester`` and ``crack divider`` orientations. The mechanisms of crack growth were analyzed and extrinsic toughening mechanisms were found to contribute significantly to the toughness. The influence of laminate architecture (layer thickness and component volume function), component material properties and residual stress on these mechanisms and the resulting crack growth resistance are discussed.

International Nuclear Information System (INIS)

Effect of cooling rates within the wide range (0.003-45 grad/s) on the complex of mechanical properties of (#alpha#-#beta#)-titanium alloy VT3-1 is studied in the process of heat treatment. Cooling conditions of semifinished product made of this alloy with a different structure providing optimum combination of strength, ductility fracture toughness, heat resistance, and endurance are determined.

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Silicon nitride based ceramics have attracted considerable attention as good candidates for structural applications due to their excellent mechanical properties including strength, hardness, fracture toughness, and high temperature strength. These properties are strongly influenced by grain size and morphology, and by the degree of crystallinity and chemistry of grain boundary phases. In this work, the microstructure of Si{sub 3}N{sub 4} densified with Nd{sub 2}O{sub 3}, Y{sub 2}O{sub 3} and Al{sub 2}O{sub 3} sintering additives was studied. Sintered samples were polished and plasma etched for microstructural analysis using scanning electron microscope. Quantitative evaluation of materials microstructure was accomplished using Quantikov software. Fracture toughness was measured by Vickers indentation method. The observed microstructure is typical of silicon nitride based materials and is characterized ...

International Nuclear Information System (INIS)

A new metastable beta titanium alloy, Beta-CEZ, has been developed by CEZUS. This alloy was designed for use at moderate temperatures up to 450 C (840 F). Alloy requirements also included high mechanical strength, high fracture toughness and improved creep resistance as compared to existing beta alloys. The understanding of the relationships between processing/microstructure/mechanical properties in the alloy may lead to applications of such promising material in current and future airplanes. In this study, a combination of several forging routes, which included through-transus, hot-die and warm-die forging, with subsequent heat treatments were selected in order to evaluate the microstructure-mechanical property relationships. It was found that the recrystallized prior beta grain boundary alpha, characteristic of the through-transus forging process, lead to an improved tensile-fracture toughness ...

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Dynamic fracture toughness tests were performed on materials which had been subjected to one of three long-time post weld type stress relief heat treatments: 48 hours at 1000/degree/F (538/degree/C), 24 hours at 1125/degree/F (607/degree/C), and 48 hours at 1125/degree/F (607/degree/C). Linear elastic K/sub Id/ results were obtained at low temperatures while J-integral techniques were utilized to evaluate dynamic fracture toughness over the transition and upper shelf temperature ranges. Tensile, Charpy impact, and drop weight nil-ductility transition tests as well as room temperature, air environment fatigue crack growth rate tests (SA508 Cl 2a only) were also performed. The fracture toughness of both materials exceeded the ASME specified minimum reference toughness K/sub IR/ curve. 17 refs.

International Nuclear Information System (INIS)

Past elastic-plastic fracture studies for leak-before-break (LBB) assessment of low alloy steel pipings have been focused mostly on the behavior of base metals and their weld metals. In contrast, the heat-affected zone (HAZ) of a welded pipe has not been studied in detail primarily because the size of the HAZ is too small to make specimens for mechanical properties measurements. In this study, microstructural analyses, microhardness tests, tensile tests and J-R tests have been conducted as a function of distance from a fusion line and temperature for HAZ materials of SA106Gr.C low alloy piping steels. For the ferrite-pearlite steels such as SA106Gr.C, the HAZ specimens showed a higher yield strength and fracture toughness compared with those of its base metal. These characteristics, despite of grain coarsening, can be explained by cleaner microstructures of HAZ materials with a finer morphology of carbides compared with ...

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No abstract prepared.

Energy Technology Data Exchange (ETDEWEB)

Two rapidly solidified powders with compositions Al-6.7 wt.% Fe-5.9 wt.% Ce and Al-6.2 wt.% Fe-5.9 wt.% Ce-1.63 wt.% Si were separated into -32 [mu]m and +32 to -63 [mu]m size fractions. Powders from both size fractions were extruded at 500 C. For comparison purposes, extrusion at a lower temperature of 400 C was also performed. In this investigation, tensile property evaluation indicated that processing of finer size fractions at high temperature offers no advantages in terms of the tensile properties but is advantageous in terms of improving the fracture toughness of alloy B. These observations underline the importance of the stability of powder microstructure during thermomechanical processing for the development of optimum mechanical properties. (orig.)

International Nuclear Information System (INIS)

The influence of heat treatment on the structure, mechanical properties and fracture peculiarities of high-strength (#alpha#+#beta#)-titanium alloy VT22 has been studied. It is ascertained that thermal cycling and subsequent high-temperature aging permit to reduce considerably crack growth rate. Thermal cycling is realized in the following mode: heating in #beta#-region, cooling and allowance in (#alpha#+#beta#)-region, heating in #beta#-region.

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Extrusion and subsequent heat treatment of the alloys investigated can lead to reasonable room temperature ductilities and very high strengths being developed compared to the cast + HlPed material. In Ti-45Al-10Nb reasonably room temperature fracture toughness was developed which did not depend on extrusion temperature. For the alloy Ti-48Al-2Cr-0.2C a previously developed solution and ageing heat treatment did not increase the high temperature strength properties when compared to the 'annealed' condition. (orig.)

International Nuclear Information System (INIS)

Minor addition of B to the Ti-6Al-4V alloy reduces the prior #beta# grain size by more than an order of magnitude. TiB formed in-situ in the process has been noted to decorate the grain boundaries. This microstructural modification influences the mechanical behavior of the Ti-6Al-4V alloy significantly. In this paper, an overview of our current research on tensile properties, fracture toughness as well as notched and un-notched fatigue properties of Ti-6Al-4V-xB with x varying between 0.0 to 0.55 wt.% is presented. A quantitative relationship between the microstructural length scales and the various mechanical properties have been developed. Moreover, the effect of the presence of hard and brittle TiB has also been studied.

British Library Electronic Table of Contents (United Kingdom)

ABSTRACT Traditional risk-based design process involves designing the structure based on risk estimates obtained during several iterations of an optimization routine. This approach is computationally expensive for large-scale aircraft structural systems. Therefore, this paper introduces the concept of risk-based design plots that can be used for both structural sizing and risk assessment for fracture strength when maximum allowable crack length is available. In situations when crack length is defined as a probability distribution the presented approach can only be applied for various percentiles of crack lengths. These plots are obtained using normalized probability density models of load and material properties and are applicable for any arbitrary load and strength values. Risk-based desi...

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The steps in assembling the computational tools needed to simulate the explosive fracture of oil shale have been described. The resulting code, with its input data, then was used to simulate 3 explosive field experiments. The results of the calculations are in good agreement with what actually occurred in the field. Further detailed comparisons are in progress for these experiments and the others that have been conducted. The development of computer codes as tools to predict rock breakage makes a variety of studies possible. The properties of the explosive can be changed to see how the extent of rubbling is affected. Studies of spacing and delays for decked charges also are possible. The codes can be applied in situations, such as confined-volume blasting, at the frontiers of blasting technology. These areas are vital to the effective utilization of oil shale resources, especially with in situ techniques. 13 references.

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Fine-grained AZ31 magnesium alloy sheets were prepared through hot rolling process. The superplastic properties of hot-rolled AZ31 Mg alloy was examined by uniaxial tensile tests at a temperature range 250{proportional_to}450 C and strain rate range 0.7 x 10{sup -3}{proportional_to}1.4 x 10{sup -1} s{sup -1}. Optical and scanning electronic microscope (SEM) were used to observe the microstructure evolution and fracture behavior in superplastic deformation of AZ31 Mg alloy and the values of deformation activation energy at various temperatures were calculated. It is demonstrated that, the hot-rolled AZ31 alloy begins to exhibit superplasticity from 300 C and a maximum elongation of 362.5% is obtained at 400 C and 0.7 x 10{sup -3} s{sup -1}. In the temperature range 300{proportional_to}400 C, the dominant superplastic deformation mechanism is grain boundary sliding (GBS) controlled by grain boundary diffusion and the influence of temperature on ...

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The relationship between the fractal dimensions of spatial distributions of aftershocks and pre-existing active faults is examined. Fourteen mainshocks taking place in Japan were followed by aftershocks, and the aftershocks occur in swarms around the mainshocks. The epicentral distributions of the aftershocks exhibit fractal properties, and the fractal dimensions are estimated by using the two-point correlation integral. The pre-existing active fault systems observed in the 14 aftershock regions have fractal structures, and the fractal dimensions are estimated by using the box-counting method. A positive correlation between the estimated fractal dimensions is found, and it is independent on the mainshock magnitude. The correlation shows that aftershock distributions become less clustered with increasing the fractal dimensions of active fault systems. Namely, the fractal clusters of aftershocks are put under the constraint of the fractal ...

UK PubMed Central (United Kingdom)

Bone mineral density is considered to be the standard measure for the diagnosis of osteoporosis and the assessment of fracture risk. The majority of fragility fractures occur in patients with bone mineral...Full Text Available

British Library Electronic Table of Contents (United Kingdom)

Abstract The effects of the type of coupling agent and virgin polypropylene (PP) content on the mechanical properties and water absorption behavior of recycled low-density polyethylene/wood flour (WF) composites were investigated. The fractured surfaces of these recycled wood/plastic composites (rWPCs) were examined to gain insight into the distribution and dispersion of WF within the polymer matrix. The results indicate that the use of 100% recycled polymer led to inferior mechanical properties and to a greater degree of moisture absorption and swelling when compared to recycled polymer-virgin PP wood/plastic composites. This could have been related to the poor melt strength and inferior processability of the recycled polymer. The extent of improvement of the mechanical properties depende...

International Nuclear Information System (INIS)

In the heat-affected zones (HAZ) of low alloy steels used for nuclear pressure vessel, microstructural changes, such as grain coarsening, carbide precipitation, and martensite formation, generally occur and cause a deterioration of toughness and an increase in sensitivity to brittle fracture. Metallographic analyses of low alloy steel welds reveal significantly different regions in HAZ microstructures. In 2-pass welds, there were seven characteristic regions in the HAZ determined by the peak temperature, to which the region was exposed during the weld thermal cycle: a coarse-grained region, a fine-grained region, an intercritical region, and subcritical region. The coarse-grained region can be categorized into four zones according to the reheating temperature as follows : an unaltered coarse-grained zone (UCGHAZ), a supercritically reheated coarse grained zone (SCRCGHAZ), an intercritically reheated coarse-grained zone (ICRCGHAZ), and an subcritically reheated ...

International Nuclear Information System (INIS)

The paper deals with sixteen cases of acetabular fractures studied with CT. After a short description of the normal CT findings, the different kind of fractures are reported. The usefulness of CT examination in evaluating acetabular fractures and their complications is confirmed both in conservative treatment and surgical approach.

International Nuclear Information System (INIS)

An Al-5%Mg-0.18%Mn-0.2%Sc-0.08%Zr-0.002%Be was subjected to equal-channel angular extrusion up to true strains of #approx#3 and #approx#8, that resulted in the formation of partially recrystallized and fully recrystallized structure, respectively. It was shown that the alloy with partially recrystallized structure exhibits highest strength and ductility. The material with fully recrystallized structure showed lowest fatigue crack growth rate and highest value of fracture toughness. Reasons of this unusual effect of microstructure on crack propagation resistance under fatigue are discussed.

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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 ...

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There is an increasing number of applications for hard coatings in engineering where the properties of the single-layer coating are not sufficient. One way to solve this problem is to use a multilayer coating that combines the properties of several coating materials. In this study, TiN-CrAlN and CrN-CrAlN multilayer coatings were deposited on 100Cr6 and S6-5-2 (DIN) steel substrates, by means of unbalanced magnetron sputtering. For comparison, TiN, CrN and CrAlN single-layer coatings were also prepared. For all depositions the coating temperature was below 473 K. Indentation testing, hardness measurements and scratch tests were performed to characterize the mechanical properties. The correlation between the wear behavior in rolling contact and the mechanical properties of the multilayer coatings is reported. A ball crater preparation technique through scratch tests and wear tracks was used to observe ...

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Low-permeability reservoirs are currently being propped with sand, resin-coated sand, intermediate-density proppants, and bauxite. This wide range of proppant cost and performance has resulted in a proliferation of proppant selection models. Initially, a rather vague relationship between well depth and proppant strength dictated the choice of proppant. More recently, computerized models of varying complexity have become available that use net-present-value (NPV) calculations. The input is based on the operator's performance goals for each well and on specific reservoir properties. Simpler, noncomputerized approaches also being used include cost/performance comparisons and nomographs. Each type of model, including several of the computerized models, will be examined. By use of these models and NPV calculations, optimum fracturing treatment designs have been developed for such low-permeability reservoirs as the Prue in Oklahoma. Typical ...

International Nuclear Information System (INIS)

Fly ash from Lagisza power station with addition of kaolin and calculated amount of carbon was reacted in flowing nitrogen at 1520"oC in order to obtain #beta#-sialon. The resulted powder was sintered with and without Y_2O_3 addition. Examinations show that it is possible to sinter that material without any sintering additives, however additive of Y_2O_3 decreases sintering temperature of about 100"oC. Sintering temperature influences the final mechanical properties like: flexural strength, microhardness, Young elastic modulus (E) and fracture toughness (K_I_c). (author)

Science.gov (United States)

A method for determining the critical debond size between the facesheet and the core in composite sandwich panels under in-plane compression is described. The approach uses fracture mechanics together with a buckling criterion for a debonded faceskin. The technique yields predictions for the critical in-plane compressive load for debond propagation as a function of core-to-faceskin debond size, faceskin thickness, lay-up, composite material properties, and honeycomb properties and geometry. A computer program, developed in this work, calculates the critical buckling load and facesheet deformed shape by solving an eigenvalue problem. The output predicts, for several cases, critical initial debond lengths comparable to those that have been observed on tests on sandwich panels.

International Nuclear Information System (INIS)

Ti-10V-2Fe-3Al is high strength, metastable beta titanium alloy developed by the Timet Division, Titanium Metals Corporation of America for enhanced forgeability and excellent mechanical property combinations, including deep hardening characteristics. Ti-10-2-3 has been the subject of intense thermomechanical processing (TMP) development and reduction to commercial practice for the full range of open die, closed-die and precision forged products utilized in aerospace and other applications. With commercially proven TMP, Ti-10-2-3 forgings provide a range of strength-fracture toughness combinations from 180 Ksi (1,240 MPa) minimum U.T.S. to 140 Ksi (965 MPa) minimum U.T.S with commensurate fracture toughness. With optimal TMP and these strength-toughness combinations, Ti-10-2-3 forgings are found provide superior smooth and notched fatigue properties critical to aerospace applications over incumbent ...

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This work contains 27 chapters which cover recent advances in fracture mechanics applied to cement-based composites: concrete, reinforced concrete, and fiber reinforced concrete. The book, based on a NATO Advanced Study Institute, is a comprehensive survey of treating nonlinearity associated with crack growth in brittle materials such as cement composites, rocks and ice. The book is divided into 8 major themes: advances in nonlinear fracture mechanics; fracture processes; numerical modelling of fracture; experimental methods of determining fracture parameters; damage and continuum modelling; strain-rate and dynamic effects of crack propagation; stress-corrosion, time and temperature effects on fracture; and implications for concrete structures.

International Nuclear Information System (INIS)

Fe-Ni-Mn martensitic steels are one of the major groups of ultra-high strength steels that have good mechanical properties and ductility in as annealed condition but they suffer from severe inter-granular embitterment after aging. In this paper, the effect of heavy shaped cold rolling and wire drawing on the mechanical properties of Fe-Ni-Mn steel was investigated. This process could provide a large strain deformation in this alloy. The total strain was #epsilon# #approx#7. Aging behavior and tensile properties of Fe-10Ni-7Mn were studied after aging at 753 K. The results showed that the ultimate tensile strength and ductility after cold rolling, wire drawing and aging increased up to 2540 MPa and 7.1 %, respectively, while the conventional steels show a premature fracture stress of 830 MPa with about zero ductility after aging.

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The usually low wear resistance of titanium materials can be increased by the thermochemical surface treatment nitriding. In result of comparative investigations of gas and plasma nitriding it will be shown that it is possible to obtain a specific variation of the properties in the highly stressed case by means of these both technologies on example of the ({alpha}+{beta}) alloy Ti-6Al-4V. Gas and plasma nitriding was carried out in the temperature range from 650 to 800 C over 4 to 48 h in different gas atmospheres, i.e. 100% NH{sub 3} (gas), 100% N{sub 2} (gas and plasma), 20% H{sub 2} + 80% N{sub 2} and 20% Ar + 20% H{sub 2} (plasma). The temperature range was fixed in the middle of ({alpha}+{beta}) region, because the core properties are influenced negative in the field of {beta}-transustemperature. The relations between the applied nitriding technologies, the layer structure (chemical, phases, geometrical) and selected layer ...

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Low-permeability reservoirs are currently being propped with sand, resin-coated sand, intermediate-density proppants, and bauxite. This wide range of proppant cost and performance has resulted in the proliferation of proppant selection models. Initially, a rather vague relationship between well depth and proppant strength dictated the choice of proppant. More recently, computerized models of varying complexity that use net-present-value (NPV) calculations have become available. The input is based on the operator's performance goals for each well and specific reservoir properties. Simpler, noncomputerized approaches include cost/performance comparisons and nomographs. Each type of model, including several of the computerized models, is examined here. By use of these models and NPV calculations, optimum fracturing treatment designs have been developed for such low-permeability reservoirs as the Prue in Oklahoma. Typical well conditions ...

Science.gov (United States)

The variation of metallic particle size and sample porosity significantly alters the dynamic mechanical properties of high density granular composite materials processed using a cold isostatically pressed mixture of polytetrafluoroethylene (PTFE), aluminum (Al), and tungsten (W) powders. Quasistatic and dynamic experiments are performed with identical constituent mass fractions with variations in the size of the W particles and pressing conditions. The relatively weak polymer matrix allows the strength and fracture modes of this material to be governed by the granular type behavior of agglomerated metal particles. A higher ultimate compressive strength was observed in relatively high porosity samples with small W particles compared to those with coarse W particles in all experiments. Mesoscale granular force chains of the metallic particles explain this unusual phenomenon as observed in hydrocode simulations of a drop-weight test. Macrocracks ...

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This paper describes the derivation of a new equation that can be used to model the permeability behavior of a fractured, sorptive-elastic media, such as coal, under variable stress conditions commonly used during measurement of permeability data in the laboratory. The model is derived for cubic geometry under biaxial or hydrostatic confining pressures. The model is also designed to handle changes in permeability caused by adsorption and desorption of gases from the matrix blocks. The model equations can be used to calculate permeability changes caused by the production of methane from coal as well as the injection of gases, such as carbon dioxide, for sequestration in coal. Sensitivity analysis of the model found that each of the input variables can have a significant impact on the outcome of the permeability forecast as a function of changing pore pressure; thus, accurate input data are essential. The permeability model can also be used as a tool to determine ...

UK PubMed Central (United Kingdom)

Background:High-energy fractures of posterior tibial plateau always need surgical treatment. Generally, posterior fragments of these fractures could not be exposed and reduced...Full Text Available

UK PubMed Central (United Kingdom)

IntroductionSeizures with or without trauma may cause fractures that occur commonly in epileptic seizures. Fracture risk is less reported in non-epileptic seizures. Some metabolic...Full Text Available

UK PubMed Central (United Kingdom)

BackgroundHip fracture patients often have an impaired nutritional status at the time of fracture, which can result in a higher complication rate, prolonged rehabilitation time and...Full Text Available

International Nuclear Information System (INIS)

Silicon nitride-based ceramics behavior is strongly influenced by microstructural parameters, which, in turn are determined by chosen densification method. Highly covalent Si-N bond hind are the silicon nitride densification. Therefore, metal oxides are used in order to get high density. However, such oxides must be carefully selected, because they affect the general macroscopic properties of sintered bodies. In the present work, the viability of rare earth concentrate use to produce #beta#--Si_6_-_xAl_xO_xN_8_-_x and its effect on mechanical properties of the sintering ceramics are studied. Additive composition, heating rate, soaking time and sintering temperature were took as variables. Hardness, fracture toughness, Young's modulus and flexural strength were investigated. Lattice parameter compositional dependence and secondary phases crystallized after past-sintering heat treatment were also determined. The results show ...

International Nuclear Information System (INIS)

The service conditions for high-temperature heat-exchangers with helium coolant of HTGRs and requirements imposed on materials for their production are discussed. The choice of nickel-base alloys with solid-solution hardening for long-term service at high temperatures is grounded. Results of study on properties and structure of types Ni-25Cr-5W-5Mo and Ni-20Cr-20W alloy in the temperature range of 900 deg. - 1,000 deg. C are given. The ageing of Ni-25Cr-5W-5Mo alloy at 900 deg. - 950 deg. C results in decreased corrosion-mechanical properties and is caused by the change of structural metal stability. Alloy with 20% tungsten retains a high stability of both structure and properties after prolonged exposure in helium at above temperatures. The alloy has also increased resistance to delayed fracture and low-cycle fatigue at high temperatures. The developed alloy of type Ni-20Cr-20W with microalloying is ...

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The effects of Fe and B{sub 4}C on the sintering behavior and mechanical properties of TiB{sub 2} ceramics have been studied. Sintering was performed in an Ar atmosphere at 2000{degrees}C using attrition-milled TiB{sub 2} powder. When a small amount of Fe (0.5 wt%) was added, abnormal grain growth occurred and the sintered density was low. In the case of B{sub 4}C added along with 0.5 wt% Fe, however, abnormal grain growth was remarkably suppressed, and the sintered density was increased up to 95% of theoretical. But with excess Fe addition (5 wt%), B{sub 4}C grains did not act as a grain growth inhibitor, and B{sub 4}C grains were frequently trapped in large TiB{sub 2} grains. The best mechanical properties were obtained for the TiB{sub 2}-10 wt% B{sub 4}C-0.5 wt% Fe ceramics, which exhibited a three-point bending strength of 400 MPa and a fracture toughness of 5.5 MPa {center dot} m{sup 1/2}.

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We report a case of stress fracture of the clavicle associated with sternocostoclavicular hyperostosis. A 60-year-old man sustained a stress fracture of the right clavicle with no history of trauma. On radiography, hyperostosis of the anterior chest wall and ankylosis of the sternoclavicular joint were evident in addition to the fracture. Fracture healing was uneventful after 2.5 months. Ankylosis of the sternoclavicular joint may have caused increased stress at the midshaft of the clavicle by daily activity or minor trauma. Such a fracture is a rare complication of sternocostoclavicular hyperostosis. (orig.)

International Nuclear Information System (INIS)

The synthesis of dense sintered sialon with external additives selected from the system Y_2O_3-AlN-SiO_2 is reported. The highest density (3.21 g/cm"3) was achieved at 1750 degrees C at 90 min of sintering with 5 wt% additive. The degree of sialon substitution increased with the amount of liquid; the YSiO_2N crystalline phase formed concurrently. Strength degradation occurred above 1000 degrees C. The fracture toughness of the material sintered with a lower amount of sintering aid remained relatively unchanged to 1200 degrees C. The material with more additive exhibited decreased toughness above 1000 degrees C.

International Nuclear Information System (INIS)

AISI 316L stainless steel was welded by the electron beam (EB) and laser techniques. Microstructural characteristics, hardness profile, creep rupture properties and creep damage of the welds were investigated. Fully austenitic microstructure was obtained in the two welds. The solidification structure of the welds consisted of the cellular and equiaxed dendrites. The creep rupture lives of the two welds were almost the same, and they were reduced by a factor of about two compared to the base metal. Moreover, the rupture elongation of the welds was lower than that of the base metal. Creep damage was observed in the ''parting'' region of the welds and in the heat-affected zone (HAZ), respectively. Final creep fracture occurred in the ''parting'' region of the welds. (orig.).

International Nuclear Information System (INIS)

Bone mineral content as determined by computerized tomography (CT) and mechanical strength on axial loading were compared in 36 cadaveric femur specimens. Based on the CT measurements of density and area, the mass of a transverse slice of the femur was estimated. Highly significant correlations were demonstrated between strength and cancellous bone density. Even higher correlations were revealed when the bone masses of the proximal and distal femoral areas were calculated. Based on these findings, an equal distribution of the effective mass of the femur was postulated. This hypothesis was confirmed in an experimental rotational model. The CT attenuation values were also correlated to direct measurements of bone mineral content, i.e. calcium. Moreover, the strength of different metal implants, commonly used in femoral neck fractures, were assessed in cadaver specimens. 134 refs., 13 figs., 12 tabs.

UK PubMed Central (United Kingdom)

Background:Cemented hip arthroplasty is an established treatment for femoral neck fracture in the mobile elderly. Cement pressurization raises intramedullary pressure and...Full Text Available

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An analytical model is proposed for the design and simulation of in-situ fracture of deep oil sand formations. This model is based on the finite element variational principle in conjunction with special empirical modules to characterize in-situ oil sands behavior. A computer code by the name of SANFRAC was developed to handle the dynamic fracture of formations induced by explosives. Simulation of hydraulic fracture processes can be treated by the same code as special cases using the quasi-static analysis. Numerical case studies by the SANFRAC code indicate that extensive horizontal fracture can be achieved by dynamic loads with proper fracture starters configured at the injection well. The unique advantage of the dynamic fracturing technique over the hydraulic fracture methods is also demonstrated by these studies.

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The use of standard cementitious material creates pulses of pH in the magnitude of 12-13 in the leachates and release alkalis. Such a high pH is detrimental and also unnecessarily complicates the safety analysis of the repository. As no reliable pH-plume models exist, the use of products giving a pH below 11 in the leachates facilitates the safety analysis. Also, according to current understanding, the use of low-pH cement (pH = 11) will not disturb the functioning of the bentonite, although limiting the amount of low-pH cement is recommended. A result of the project is that there are both low-pH cementitious material for grouting larger fractures (= 100 {mu}m) and non-cementitious material for grouting smaller fractures (< 100 {mu}m) that will, after further optimisation work, be recommended for grouting of deep repositories. This project concentrated on the technical development of properties for the low pH grouts. ...

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Lateral and vertical variabilities in the bulk and mechanical properties of silicic volcanic tuff at the potential nuclear waste repository site in Yucca Mountain, NV have been evaluated. Laboratory measurements have been performed on tuff specimens recovered from boreholes located to support the design of the Exploratory Studies Facility/North Ramp. The data include dry and saturated bulk densities, average grain density, porosity, compressional and shear wave velocities, elastic moduli, and compressional and tensional fracture strengths. Data from eight boreholes aligned in a northwest-southeast direction have been collected under the required quality assurance program. Three boreholes have penetrated the potential repository horizon. The information collected provides for an accurate appraisal of the variability of rock properties in the vicinity of the boreholes. As expected, there is substantial variability in the bulk ...

Science.gov (United States)

... Title : THE INFLUENCE OF GRAIN BOUNDARY CARBIDE DENSITY ON THE BRITTLE FRACTURE OF FERRITE PEARLITE STEELS. ...

CSIR Research Space (South Africa)

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This paper examines the seismic signatures of discrete, finite-length fractures, and outlines an approach for elastic, prestack reverse-time imaging of discrete fractures. The results of this study highlight the importance of incorporating fracture-generated P-S converted waves into the imaging method, and presents an alternate imaging condition that can be used in elastic reverse-time imaging when a direct wave is recorded (e.g., for crosswell and VSP acquisition geometries).

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Complications of non-union and avascular necrosis during fracture healing process are the most important problems. Early detection of the evidence of non-union and avascular necrosis and follow-up study of fracture healing process will reduce complications and sequellae in fracture patients. Femoral neck and tibial shaft are the most important fracture sites where non-union and/or avascular necorsis are frequently developed. Osteomedullography was performed in 30 cases of fracture, 21 femoral neck, 8 tibial shafts and 1 talar neck, in the Department of Radiology of national Medical Center during the period form August 1977 to March 1981. The following results were obtained: 1. 16 patients of femoral neck fracture were performed osteomedullography one. Non-union showing no crossing vein through the fracture site was noted in 12 cases from 16 ...

International Nuclear Information System (INIS)

The densification of #alpha#"1-and #alpha#"+#beta#"1-sialon ceramics has been studied by means of in situ dilatometry. It is seen that the densification is greatly affected by the reaction sequences and the grain growth. The formation and densification of sialons start simultaneously as the dissolution of nitrides into the oxide eutectic liquid phase occurs. The formation of sialons is complete at 1800 deg C., while full densification can only be obtained by using gas pressure sintering. The typical microstructure of both #alpha#"'-and mixed #alpha#'+#beta#'-sialon ceramics consists of a crystalline phase of sialons and a small fraction of amorphous phase at grain boundaries. Vickers hardness (HV0.5) was measured by using the indentation technique, and the biaxial bending strength (#sigma#_b_i) was determined with the 'ball-on-ring' test. Fracture toughness was determined by using both the indentation and single-edged notched beam techniques. It is concluded that ...

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The effect of irradiation on the tensile properties of oil palm empty fruit bunch (OPEFB) fiber reinforced poly(vinyl chloride)/epoxidized natural rubber (PVC/ENR) blends were studied. The composites were prepared by mixing the fiber and the PVC/ENR blend using HAAKE Rheomixer at 150 deg. C. The composites were then irradiated by using a 3.0 MeV electron beam machine at doses ranging from 0 to 100 kGy in air and room temperature. The tensile strength, Young's modulus, elongation at break and gel fraction of the composites were measured. Comparative studies were also made by using poly(methyl acrylate) grafted OPEFB fiber in the similar blend system. An increase in tensile strength, Young's modulus and gel fraction, with a concurrent reduction in the elongation at break (Eb) of the PVC/ENR/OPEFB composites were observed upon electron beam irradiation. Studies revealed that grafting of the OPEFB fiber with methyl acrylate did not cause appreciable ...

International Nuclear Information System (INIS)

4.82 wt% AIN and 2.98 wt% Y_2O_3 were added to Si_3N_4 as sintering agents in order to have #alpha#_Sialon composition of x=0.15 and monoclinic ZrO_2 between 0 to 10 wt% was admixed with Si_3N_4 based ceramics were fabricated by hot-pressing at 1,750 deg C for 90 min under 30 MPa in argon and nitrogen atmospheres effects of sintering atmospheres and addition of ZrO_2 on mechanical properties of Si_3N_4 based ceramics were investigated. As ZrO_2 content increased, the fraction of #alpha#-Sialon tended to decrease and the amount of cubic ZrO_2 increased because Y_2O_3 acted as the stabilizer of ZrO_2. The sintering atmospheres didn't affect on the sintering behavior and the product phases in hot-pressing of Si_3N_4. Bending strength increased when ZrO_2 content. ZrO_2 didn't contribute to the increase of fracture toughness because stabilized cubic ZrO_2 was produced by the added Y_2O_3. (Author).

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Experimental discussions were given on effect of V and W addition on the high temperature strength properties of 12% Cr-15% Mn austenite steels. The test samples were added with W at 0% to 3.5% and V at 0% to 0.5% in addition to C and N, and were given aging treatment or solution treatment. This paper describes the following matters on the results of high-temperature strength measurements and structural observation: A remarkable trend was observed that M23 Cb type carbides precipitate in the aging treatment, wherein aging hardening appears prominently which is attributable to ultra-fine deposits of vanadium nitride (VN) in the V-added material; the V addition is very effective in increasing the high-temperature tensile strength and creep fracture strength as compared with single W addition, wherein the said carbides that accelerate the precipitation as a result of the V addition make a large contribution, in addition to that by ultra-fine VN ...

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Yucca Mountain, Nevada is a potential site for a high-level radioactive-waste repository. Uncertainty and sensitivity analyses were performed to estimate critical factors in the performance of the site with respect to a criterion in terms of pre-waste-emplacement ground-water travel time. The degree of failure in the analytical model to meet the criterion is sensitive to the estimate of fracture porosity in the upper welded unit of the problem domain. Fracture porosity is derived from a number of more fundamental measurements including fracture frequency, fracture orientation, and the moisture-retention characteristic inferred for the fracture domain.

International Nuclear Information System (INIS)

In the feasibility study on commercialized FBR systems, the application of 12Cr steel, with its physical properties and high-temperature strength properties, as structural material is considered in order to greatly reduce construction costs by compacted instruments and structures. In this report, creep, fatigue and the creep-fatigue properties of Mod.9Cr-1Mo steel forging (thickness 550mm) weld, representing conventional steels, were evaluated in order to obtain the needed basic data for the evaluation of the high-temperature strength of 12Cr steel weld. The results obtained are as follows: (1) Metal suitable for HAZ was made by applying thermal treatment to simulate the thermal hysteresis during welding to clearly define creep and fatigue properties in a HAZ softened zone. (2) Creep strength of the weld metal and the welded joint was equal to that of the base metal. However, the welded joint ruptured ...

Science.gov (United States)

The governing equations for heat and mass transfer were derived for hydraulically fractured geothermal reservoirs. When converted to nondimensional form it was shown that the equations can be considerably simplified. The resulting equations can be strongly influenced by the effects of buoyancy; the magnitude of the effect is measured by the ratio of the Grashof and Reynolds numbers, and the ratio of the actual permeability of the fracture and the square of the fracture gap width. Significant quantities of energy can be extracted from hydraulic fractures--even without thermal stress fracturing. The amount is limited by the size of the fracture and the low thermal conductivity of rock. The viscous pressure drop in open fractures is insignificant, and depending upon losses in piping and surface equipment, the entire system could be ...

International Nuclear Information System (INIS)

To achieve sufficient thermodynamic efficiency, space nuclear power systems must operate above 1000"0C. A quantitative evaluation of the existing mechanical properties data for the refractory alloys relevant to space nuclear power systems design lifetimes up to seven years at temperatures up to 1400"0C is being conducted. The most important properties for space nuclear power systems are long-term high-temperature (>1000"0C) creep strength and ductility, low-temperature (<400"0C) fracture toughness [including ductile-to-brittle transition temperature, (DBTT)], and ductility at high strain rates; of special concern are the above properties for weldments of refractory alloys, composition, applied stress, test temperature, test environment (e.g., vacuum, lithium), and thermomechanical treatment (TMT) history. Currently being evaluated are, in order of ascending mp, selected alloys of niobium (e.g., ...

Science.gov (United States)

The ability to mechanically reinforce an osteoporotic vertebral body could impede spinal compression fracture and the associated pain and complications. Previous studies have shown that reinforcement of fractured vertebrae with conventional acrylic cement can relieve symptoms and avoid further collapse. In this study, we explored the use of a carbonated apatite cement combined with a minimally invasive injection technique to improve the compressive mechanical properties of cadaveric vertebral bodies. After establishing the biomechanical characteristics of cement formulations intended to have appropriate viscosities, we evaluated the infiltration of the cements into thoracic vertebral bodies using a combined suction-injection technique. The energy-absorption capabilities of the reinforced vertebral bodies were then measured during axial compressive tests and compared with those of nonreinforced vertebrae. The ultimate ...

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Intracapsular femoral neck fractures remain unsolved fractures even after improvement in techniques of diagnosis and internal fixation. Individuals who sustain displaced femoral neck fractures are at high risk of developing avascular necrosis and non-union. Although several methods for predicting the viability of femoral head have been reported, they are not effective or widely used because of unreliability, potential complications and technical difficulties. Dynamic MRI was introduced in the recent past as a simple, non-invasive technique to predict the femoral head viability after the femoral neck fractures. In this study role of dynamic MRI was studied in 30 patients with 31 intracapsular femoral neck fractures. Fractures were divided in to three types according to dynamic curve patterns on MRI evaluation and were followed up for 6 months to 2 years to ...

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The characteristics of fractures in unit 2 of the Tshirege Member of the Bandelier Tuff were documented in Pit 39, a newly excavated 13.7 m deep disposal pit at Material Disposal Area G on Mesita del Buey. The average spacing between fractures is about 1.0 to 1.3 m, the average fracture aperture is about 3 to 5 mm, and the average fracture dip is about 76o to 77o. Fracture spacing and dip in Pit 39 are generally consistent with that reported from other fracture studies on the Pajarito Plateau, although the fracture apertures in Pit 39 are less than reported elsewhere. Measured fracture orientations are strongly affected by biases imparted by the orientations of the pit walls, which, combined with a small data set, make identification of potential preferred orientations dlfflcult. The most prominent ...

British Library Electronic Table of Contents (United Kingdom)

TaC-4wt.% CNT composites were synthesized using spark plasma sintering. Two kinds of CNTs, having long (10-20mm) and short (1-3mm) length, were dispersed by wet chemistry and spray drying techniques respectively. Spark plasma sintering was carried out at 1850^oC at pressures of 100, 255 and 363MPa. Addition of CNTs leads to an increase in the density of 100MPa sample from 89% to 95%. Short CNTs are more effective in increasing the density of the composites whereas long CNTs are more effective grain growth inhibitors. The longer CNTs are more effective in increasing the fracture toughness and an increase up to 60% was observed for 363MPa sample. Hardness and elastic modulus are found to increase by 22% and 18% respectively for 100MPa samples by addition of long CNTs. Raman spectroscopy, SEM...

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Alumina (94 and 99.8% grade compositions) was brazed directly to itself with gold-based active brazing alloys (ABA's) containing vanadium additions of 1,2 and 3 weight percent. The effects of brazing conditions on the joint properties were investigated. Wetting behavior, interfacial reactions, microstructure, hermeticity and tensile strength were determined. Wetting was fair to good for the ABA and base material combinations. Microanalysis identified a discontinuous Al-V-O spinel reaction product at the alumina-braze interface. Tensile strength results for 94% alumina were uniformly good and generally not sensitive to the vanadium concentration, with tensile values of 85-105 MPa. There was more variability in the 99.8% alumina strength results, with values ranging from 25-95 MPa. The highest vanadium concentration (3 wt. %) yielded the highest joint strength for the brazed 99.8% alumina. Failures in the 99.8% alumina samples occurred at the braze-alumina ...

International Nuclear Information System (INIS)

Three high density polyethylene (PE) samples of different origins, with weight average molar masses ranging from 38 to 63 kg mol"-"1 and displaying a semi-ductile behavior with strain at break ?_R values of the order of 100-140%, were gamma irradiated under nitrogen for doses up to 33.3 kGy. Steric exclusion chromatography and rheometry allowed to quantify the crosslink density X. This later reached values ranging from 4.6 to 9.0x10"-"3 mol kg"-"1, i.e. situated below the gelation point. Differential calorimetry, density measurement and small angle X-rays scattering showed the absence of significant changes in the crystalline morphology, especially lamellar dimensions. Tensile testing revealed an unexpected trend towards brittle regime of fracture while yield stress increases significantly at low doses. It appeared that branching disfavors cavitation during yielding, but this effect is not favorable to ductility.

UK PubMed Central (United Kingdom)

Osteoporotic vertebral fractures often lead to pain and disability. They can be successfully treated, and possibly prevented, by injecting cement into the vertebral body, a procedure known as vertebroplasty....Full Text Available

UK PubMed Central (United Kingdom)

BackgroundThere have been reports both supporting and refuting an inverse relationship between hip fracture and hip osteoarthritis (OA). We explore this relationship using a case-control...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

A scintimetric study using Tc-99m MDP was made of 54 patients with delayed union, nonunion, or late segmental collapse of the femoral head, 4-92 months after femoral neck fracture. In radiographically verified collapse, the radionuclide uptake ratio between the femoral head on the fractured and on the intact side (HHR) was significantly higher than in fractures resulting in delayed union or nonunion. On the basis of scintimetric and radiographic findings, the patients with healing disturbances could be divided into three groups, characterized by the following features: (1) Satisfactory post-reduction position of the fracture without subsequent redisplacement and a high HHR, which as a rule turned out to be delayed union; (2) The same radiographic pattern but with a lower HHR, which in most cases resulted in nonunion; (3) Inadequate reduction or early redisplacement of the fracture ...

UK PubMed Central (United Kingdom)

Current drug treatments for post-menopausal osteoporosis cannot eliminate bone fractures, possibly because the mechanisms responsible for bone loss are not fully understood. Although research within...Full Text Available

UK PubMed Central (United Kingdom)

BackgroundThis case series report discusses patients presenting with hemorrhage and hemodymanic compromise due to severe pelvic fractures and undergoing intraoperative angioembolization...Full Text Available

UK PubMed Central (United Kingdom)

BackgroundStress fractures are a significant problem among athletes and soldiers and may result in devastating complications or even permanent handicap. Genetic factors may increase...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

A micro-mechanistic understanding of bone fracture thatencompasses how cracks interact with the underlying microstructure anddefines their local failure mode is lacking, despite extensive research nthe response of bone to a variety of factors like aging, loading, and/ordisease.

UK PubMed Central (United Kingdom)

BackgroundHip dislocation after arthroplasty for femoral neck fractures remains a serious complication. The aim of our study was to investigate the dislocation rate in acute femoral...Full Text Available

UK PubMed Central (United Kingdom)

Failure of bone under monotonic and cyclic loading is related to the bone mineral density, the quality of the bone matrix and the evolution of microcracks. The theory of linear elastic fracture...Full Text Available

Norwegian Open Research Archives (NORA)

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CERN Document Server

Heat exchange during laminar flow is studied at the fracture scale on the basis of the Stokes equation. We used a synthetic aperture model (a self-affine model) that has been shown to be a realistic geometrical description of the fracture morphology. We developed a numerical modelling using a finite difference scheme of the hydrodynamic flow and its coupling with an advection/conduction description of the fluid heat. As a first step, temperature within the surrounding rock is supposed to be constant. Influence of the fracture roughness on the heat flux through the wall, is estimated and a thermalization length is shown to emerge. Implications for the Soultz-sous-For\\^{e}ts geothermal project are discussed.

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Separate abstracts were prepared for thirteen papers. Two papers were abstracted previously for EDB. (MHR)

International Nuclear Information System (INIS)

We treated 13 patients for femoral neck fracture. They consisted of 2 males and 11 females, and were classified according to Garden stage classification; Stage I, 3 cases; Stage II, 2 cases; Stage III, 2 cases; Stage IV, 4 cases. Two trochanteric fracture cases were used by control. We evaluated perfusion of the femoral head after femoral neck fracture using bone scintigraphy, which is considered useful for evaluation of perfusion of the femoral neck before operation. (author)

International Nuclear Information System (INIS)

We apply our work on fracture- and matrix-dominated flow to develop a conceptual model of hydrological flow processes in the unsaturated zone at Yucca Mountain. The possibility of fracture-dominated flow is discussed, and various deductions are made on its impact on natural and total system performance, site characterization activities, and site suitability determination.

International Nuclear Information System (INIS)

Comprehensive Structural Integrity is a reference work which covers all activities involved in the assurance of structural integrity. It provides engineers and scientists with an unparalleled depth of knowledge in the disciplines involved. The new online Volume 11 is dedicated to the mechanical characteristics of materials. This paper contains the chapter 11.02 of this volume and is structured as follows: Test techniques; Analysis; Fracture behavior; Fracture toughness tests for nonmetals.

Science.gov (United States)

This study is a contribution to the growing body of work on the influence of changes in the composition of an acrylic bone cement on various properties of the curing and cured material. The focus is on one commercially-available acrylic bone cement brand, Surgical Simplex P, and three variants of it and a series of properties, namely, setting time, maximum exotherm temperature, activation energy and frequency factor for the polymerization reaction, diffusion coefficient for the uptake of phosphate buffered saline, at 37 degrees C, ultimate compressive strength (UCS), plane-strain fracture toughness, fatigue life (under fully-reversed tension-compression stress), hardness (H) and elastic modulus (both determined using quasi-static nanoindentation), and the variation of the storage and loss moduli with frequency of the applied force in a dynamic nanoindentation test. It was found that (a) a 68% reduction in the volume of the ...

Energy Technology Data Exchange (ETDEWEB)

Forty-five patients with recent cervical hip fractures were included in a prospective, clinical, radiographic and sequential scintimetric study. Striking changes in radionuclide uptake over the entire hip region on the fracture side were found during the first 5 postoperative months. Fractures that healed without complications showed the highest relative femoral head uptake at 1 week and a peak value at 6 weeks, followed by a gradual decline at the subsequent examinations. Fractures with complications (redisplacement, nonunion, or late segmental collapse) showed a lower initial uptake and a more gradual increase and only a slight tendency towards increased uptake after 3 months. The accuracy in predicting nonunion with scintimetric examination alone is high both at 1 and at 6 weeks, and the accuracy is almost equally high with combined scintimetric, radiographic, and clinical assessment 3-5 months ...

British Library Electronic Table of Contents (United Kingdom)

This paper presents a procedure for transferring the CTOD fracture toughness obtained from laboratory specimens to an equivalent CTOD for structural components, taking constraint loss into account. The Weibull stress criterion is applied to correct the CTOD for constraint loss, which leads to an equivalent CTOD ratio, b, defined as b=d/dWP, where d and dWP are CTODs of the standard fracture toughness specimen and the structural component, respectively, at the same level of the Weibull stress. The CTOD ratio b is intended to apply to the fracture assessment of ferritic steel components to stress levels beyond small-scale yielding. Nomographs are given to determine the b-value as a function of the crack type and size in the component, the yield-to-tensile ratio of the material and the Weibul...

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The conference proceedings contains 30 papers of which five are abstracted separately. The subjects covered include fatigue crack growth in aircraft materials, fractographic measurements, fatigue cracks in nylon 66 blends, cyclic inelastic deformation aspects, prestressing, tensile cracks in creeping solids, creep-crack-growth in 304 stainless steel, high-temperature fatigue, parallel impact loading, numerical fracture dynamic code, J-resistance curves, specimen geometry effects, reactor piping systems, temperature dependence of fracture toughness, small-scale yielding, compact specimens, power hardening materials, semi-empirical fracture analyses, pipeline girth welds, wrought steels, and A36 bridge steels.

British Library Electronic Table of Contents (United Kingdom)

A model is developed to represent mechanical strain, stress-enhanced dissolution, and shear dilation as innately hysteretic and interlinked processes in rough contacting fractures. The model is incorporated into a numerical simulator designed to examine permeability change and thermal exchange in chemically active and deformable fractured reservoirs. A candidate engineered geothermal reservoir system (EGS) is targeted. The mechanistic model is able to distinguish differences between the evolution of fluid transmission characteristics of (1) small scale, closely spaced fractures, and (2) large-scale, more widely spaced fractures. Alternate realizations of fracture frequency and scale, exhibiting identical initial bulk permeability, lead to significantly different conclusions regarding perme...

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Twenty-six patients with late complications following femoral neck fracture were examined with both skeletal and bone marrow radionuclide scintimetry. There was no correlation between the methods with respect to the quantitative assessment of femoral head vascularity based on different uptake ratios comparing the fractured and the intact side. Skeletal scintimetry always had good image quality and permitted reliable differentation between nonunion of the fracture and late segmental collapse, in contrast to bone marrow scintimetry which gave poor image quality. Skeletal scintimetry thus seems superior to bone marrow scintimetry for assessment and differential diagnosis of late complications following femoral neck fracture. It is emphasized that the physiological mechanisms for radionuclide uptake must be taken into account when comparing scintimetric studies using different tracers.

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There are currently no accepted industry standards for the tensile strain limits of girth welds. This paper investigated the behavior of girth welds with buried defects subjected to high longitudinal strains caused by soil movement. A strain design methodology based on a crack driving method was used to examine the factors influencing stain limits along with a constraint-sensitive fracture mechanics approach. No strength undermatching was used in the welds, and the defect location had no influence on crack driving force. The weld joint was assumed to have uniform tensile properties. A 3D finite element (FE) model was used to simulate pipe behavior. Symmetric boundary conditions were imposed on the symmetry planes, and uniform remote axial displacement was applied as the primary loading. Automated data processing routines were developed to extract and analyze the data. The crack driving force was computed directly from a crack tip deformation ...

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Superplasticity can be generally achieved by grain boundary sliding (GBS). The GBS in polycrystalline materials sometimes accompanies with intergranular fracture because of stress concentrations at triple points and/or GB irregularities. To develop the superplastic flow, it is necessary to suppress the intergranular cracking. In the present study, therefore, polycrystalline molybdenum with distinct GB microstructures, such as grain boundary character distribution (GBCD), has been employed to clarify the relationship between fracture behaviour and GB microstructures. Microstructures were analyzed using a FE-SEM/EBSP/OIM system prior to 4-points bending tests at 77K, thereafter, crack propagation was observed. The main results obtained are as follows. Stress fluctuations on stress - strain curves were observed for specimens with random oriented grains, whereas such behaviour rarely occurred for ones with textured grains. Difference in the ...

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AIM: To define the value of digital radiography with a clinical flat panel detector system for evaluation of wrist fractures in comparison with state of the art storage phosphor radiography. MATERIAL AND METHODS: Hard copy images of 26 fractured wrist specimens were acquired with the same exposure dose on a state of the art storage phosphor radiography system and a clinical flat panel detector. Image features like cortical bone surface, trabecular bone, soft tissues and fracture delineation were independently analysed by 4 observers using a standardised protocol. Image quality ratings were evaluated with an analysis of variance (ANOVA). RESULTS: Flat panel detector radiographs were rated superior with respect to cortical and trabecular bone representation as well as fracture evaluation, while storage phosphor radiographs produced better soft tissue detail. CONCLUSION: In some of the observed image ...

Science.gov (United States)

In order to understand not only the mechanisms of earthquakes, but also the origin of diverse behavior of faults and plate boundaries, one must integrate (1) field studies on faults to understand deep intrafault processes, (2) laboratory work to reproduce those processes and determine mechanical and transport properties of fault zones, (3) theoretical and numerical studies analyzing fault motion, including earthquake generation processes, based on the constitutive properties determined by laboratory studies, and (4) seismological and geodetic studies revealing dynamic fault motion during earthquakes and diverse aseismic fault behavior. Ideally, such integrated studies should be carried out for a selected fault that produced an earthquake with good seismic/geodetic records so the prediction from (1) to (3) can be fully tested with (4), rather than selecting favorite data in the literature. Present session is organized to promote such integrated ...

International Nuclear Information System (INIS)

Strain rate effects for the high strength, metastable beta-titanium alloy Ti-8Mo-8V-2Fe-3Al are assessed in terms of tensile and fracture toughness behavior. It is shown that as the strain rate increases the yield strength, ultimate tensile strength, and ductility also increase. As a result of the decrease in the amount of intergranular fracture as the strain rate is increased, the dynamic fracture toughness values K/sub Id/ are greater than those obtained under static conditions as given by K/sub Q/.

International Nuclear Information System (INIS)

Two patients with femoral neck fractures, one displaced and one undisplaced, are presented. Preoperative intravital staining with tetracycline and Tc-MDP scintimetry both showed intact femoral head circulation while Tc-MDP-scintimetry 1 week after operation showed pronounced circulatory deficiency. SR"8"5-scintimetry performed at the same time was inconclusive. Segmental collapse was observed radiographically, 8 and 12 months postoperatively. The major vascular injury resulting in avascularity most probably occured during the procedure of osteosynthesis, and Tc-MDP-scintimetry was found suitable for early postoperative recognition of avascular necrosis in both fractures. (author).

Science.gov (United States)

[12] Kusy, R. P. and Turner, D. T.: Influence of molecular-weight ofpoly(methyl methacrylate)on fracture morphology in notched tension, Polymer. ...

International Nuclear Information System (INIS)

... University, Fracture and Reliability Research Institute, Sendai, Miyagi (Japan)

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Purpose: To evaluate MR imaging of the hip in patients with a clinically suspected impacted fracture of the femoral neck in cases where conventional plain films show negative or equivocal findings. Material and Methods: Twenty-seven such patients were prospectively examined by MR imaging with a 1.0 T unit, within 24 hours of admittance to hospital. A coronal T1-weighted turbo spin-echo sequence (n=27), and a coronal STIR sequence (n=25) or a coronal T2-weighted turbo spin-echo fast saturation sequence (n=2) were used. The evaluations were made by 2 radiologists with experience in musculoskeletal radiology. Results: There were 6 patients with a petrochanteric fracture, 2 without and 4 with slight displacement. Five patients had an impacted fracture of the femoral neck, and 3 had a fracture of the superior pubic bone. Of 2 patients with advanced arthrosis, i had an impacted femoral neck ...

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To evaluate injury patterns of facet joints and associated soft tissue injuries in patients with acute traumatic cervical facet joint injuries. From among patients with cervical spine trauma, 27 with facet joint injuries, as seen on CT and MRI, were chosen for this study. CT scans were analyzed with regard to the location of facet joint injury, the presence or absence of facet dislocation or fracture, and other associated fractures. MR images were analyzed with regard to ligament injury, intervertebral disc injury, intervertebral disc herniation, and spinal cord injury. The most common location of facet joint injury was C6-7 level(n=10), followed by C5-6(n=8). Among these 27 patients with facet joint injuries, 12(44%) had bilateral injuries and 15(56%) unilateral injuries. Facet fractures were present in 17 cases(63%) and the fracture of inferior facet was more frequent than superior. Patterns of ...

International Nuclear Information System (INIS)

The authors propose a method for determining the risk of femoral neck fracture in osteoporotic patients that is not based on densitometric techniques. The method is based on a structural analysis performed by a computer on data taken from a single digital anteroposterior projection of the hip. From the image, the effective cross-sectional area and cross-sectional moment of inertia are computed from attenuation principles. Together with other geometric measurements, these data are used in an engineering analysis to compute the yield strength of the proximal femur, under stress applied through the acetabulum in a one-legged stance. An index of fracture risk based on the ratio of estimated yield strength to body weight is proposed. Ultimately it is expected that this work will allow the clinician to estimate hip fracture risk in osteoporotic patient using widely available existing technology, a goal which has eluded bone ...

British Library Electronic Table of Contents (United Kingdom)

Background There is increasing recognition that lower nurse staffing levels are associated with higher morbidity and mortality among medical and surgical patients. The degree to which this applies to elderly patients with hip fractures is unclear. Questions/purposes We conducted a pilot study using administrative data as an initial step in investigating the relationship between nurse staffing levels and in-hospital mortality among elderly patients with hip fractures. Patients and Methods We retrospectively reviewed administrative data for 13,343 patients 65?years or older with a primary diagnosis of hip fracture admitted to 39 Michigan hospitals between 2003 and 2006. We used logistic regression to calculate the change in predicted probability of in-hospital death conferred by differences ...

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Development drilling from Chevron-operated Platform Hermosa, located on OCS-P 0316 of the Point Arguello field, began on January 30, 1987. To date, seven development wells have been drilled in to the northwest-southeast-trending, doubly plunging anticlinal structure. The results from drilling have confirmed the presence of intense folding and fracturing in the targeted Monterey Formation. Over 700 ft of conventional core were recovered from the B-2 well in the lower Sisquoc and Monterey Formations. Analysis of the core material has yielded important information on lithologic variations and fracture patterns in the productive Monterey Formation. Initial results of core studies, DST data, and wireline studies indicate a correlation between rock type and fracturing. Fracture trends and directional permeability suggested by drill-stem testing may affect future drilling patterns in the field.

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ABSTRACT Crack tip opening angle (CTOA) is becoming one of the most accepted methods for characterizing fully plastic fracture. It provides a measure of the resistance to fracture for a material in cases where there is a large degree of stable-tearing crack extension during the fracture process. Our current pipeline research uses the CTOA test as an alternative, or addition, to the CTOD (crack tip opening displacement) and the fracture energy characterization provided by the J-integral approach. A test technique was developed for measurement of CTOA that uses a modified double cantilever beam (MDCB) specimen. A digital camera and image analysis software were used to record the progression of the crack tip and to estimate the CTOA. In this article, CTOA data on crack growth orientations per...

British Library Electronic Table of Contents (United Kingdom)

Experimental results of quasi-static and dynamic fracture of particle-filled polymer composite (PFPCM) "ALTUGLAS EI CH25" with a matrix of polymethylmethacrylate (PMMA) are reported in this paper. PMMA matrix is filled with rubber particles, as result a shock-resistant transparent composite is produced. The main task was to investigate experimentally and theoretically the fracture toughness of this composite under static and dynamic loading. A high-rate loading has been created by impulse magnetic field. Analysis of fracture process and its relation with the load parameters and material microstructure have been established. Application of the original testing method enabled determination of fracture toughness at very short loading times and comparison of the results with material dynamic p...

International Nuclear Information System (INIS)

The creep crack growth properties of two versions of Alloy 800 have been compared at 500 and 600"0C in the Grade II condition in tests up to 10"4 hours duration. The two alloys were a low carbon alloy containing (wt.%) 0.024 C, 0.5 Ti, 0.3 Al (Alloy B) and a higher carbon alloy containing (wt.%) 0.038 C, 0.2-0.3 Ti, 0.2-3.0 Al (Alloy J). At 600"0C, Alloy B attained maximum age hardening in 10"2 hours, whereas J did not harden significantly in time up to 10"4 hours. Both alloys age hardened at 550"0C with Alloy J hardening more rapidly than B. The creep displacements and displacement rates in small compact tension specimens at 600"0C were smaller than Alloy B than in Alloy J. However, failure times were shorter in Alloy B because of lower displacements for crack initiation and propagation and higher crack growth rates. At 550"0C the displacements for initiation and propagation in Alloy J were smaller than at 600"0C. A consequence of this embrittlement was that the ...

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Exploratory experiments of laser welding cast Ni-based superalloy K418 turbo disk and alloy steel 42CrMo shaft were conducted. Microstructure of the welded seam was characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive spectrometer (EDS). Mechanical properties of the welded seam were evaluated by microhardness and tensile strength testing. The corresponding mechanisms were discussed in detail. Results showed that the laser-welded seam had non-equilibrium solidified microstructures consisting of FeCr_0_._2_9Ni_0_._1_6C_0_._0_6 austenite solid solution dendrites as the dominant and some fine and dispersed Ni_3Al #gamma#' phase and Laves particles as well as little amount of MC short stick or particle-like carbides distributed in the interdendritic regions. The average microhardness of the welded seam was relatively uniform and lower than that of the base metal due to partial dissolution and ...

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When a plasma becomes contaminated by foreign particles, generically referred to as dust, the result is called a dusty plasma. At the present time there is a great deal of interest in dusty plasmas because of their roles in terrestrial and extra-terrestrial processes - semiconductor processing, high temperature fusion experiments, stellar formation and the rings of Saturn. This thesis is concerned with the role of dust in processing type plasmas. In the following experiments, artificial dust is introduced into a parallel electrode plasma chamber. Ions and electrons in the plasma charge the dust particles and they become suspended in the plasma due to the balancing of electric and gravitational forces. By illuminating the suspended dust with laser light and using an extremely high speed camera fitted with a macro lens to look at the scattered light, the dust particles are observed directly. Specially written computer software is then able to track and analyse the particles' ...

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Seismic exploration is used to identify the Zapadno Rakushechniy Sea uplift. It is promising with respect to prospecting for oil and gas deposits as a result of its proximity to the Severo Rakushechniy deposit with commercial oil and gas presence in the Triassic sediments. Structural prospecting wells are drilled at the Zapadno Rakushechnyy Sea site which open sediment from the Neogene to the upper Triassic. The Triassic sediments are represented by a thick terrigeneous to carbonate series washed out to a varying degree and covered by Jurassic sediments. A comparison of the lithofacial composition of the Triassic sediments shows that the thickness and lithological composition o the Triassic rocks varies by site, while the sediments of the upper Triassic are sharply reduced in thickness to the southsouthwest. The older are the sediments of the Indskiy stage of the lower Triassic. The isolated stages of the lower, middle and upper Jurassic suffer a reduction in thickness towards the ...

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Experiments of autogenous laser full penetration welding between dissimilar cast Ni-based superalloy K418 and alloy steel 42CrMo flat plates with 3.5 mm thickness were conducted using a 3 kW continuous wave (CW) Nd:YAG laser. The influences of laser welding velocity, flow rate of side-blow shielding gas, defocusing distance were investigated. Microstructure of the welded seam was characterized by optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). Mechanical properties of the welded seam were evaluated by microhardness and tensile strength testing. Results show that high quality full penetration laser-welded joint can be obtained by optimizing the welding velocity, flow rate of shielding gas and defocusing distance. The laser-welded seam have non-equilibrium solidified microstructures consisting of #gamma#-FeCr_0_._2_9Ni_0_._1_6C_0_._0_6 austenite solid solution dendrites as the dominant ...

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The environmental impacts of uranium mining and milling activities are of great concern in many countries for the last three decades. These impacts range from the creation of massive stockpiles of radioactive and toxic waste rock and sand-like tailings to serious contamination of surface and groundwater with radioactive and toxic pollutants, and releases of conventional, toxic and radioactive air pollutants. Uranium mining is also associated with high concentrations of highly toxic heavy metals, which are a major source of surface and groundwater contamination. Depending upon the hydraulic properties of the fractures involved, contaminated ground water may be transported many miles from its point of origin before feeding into an aquifer. Tailings pond may contaminate the groundwater regime by continuous seepage and leaching of radionuclides and other toxic metals due to interaction of rain water through the tailings ponds. The uranium milling ...

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The concept of unstable burst fracture has been discussed since over 50 years and this injury has received much attention in the literature as regards its radiological diagnosis and clinical treatment. The purpose of this article is to review the way we use imaging to diagnose the injury and to guide treatment.

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The radiation life time of reactor pressure vessel (RPV) is the most important limiting factor for the term of exploitation of the whole power unit. The main degradation mechanism of RPV metal is the neutron induced embrittlement. Processes of radiation ageing running in RPV metal lead to fracture toughness decrease and to increased probability of brittle fracture of the vessel under thermal shocks. This explains the importance of RPV integrity assessment and rest life time management

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A selected series of 24 patients with displaced medial femoral neck fracture, treated with closed reduction and osteosynthesis with cancellous bone screws (ASIF), were investigated. During an observation period of 6 to 26 months, serial hip joint scintigraphies were performed and compared with serial X-ray examinations. At the first scintigraphic examination performed on average 5-6 weeks after the fracture, two separate investigators found a decreased amount of activity or no activity in the femoral head of 10 and 8 patients, respectively. At the second scintigraphic examination performed on average 11.1 weeks after the fracture both investigators found no activity or a decreased amount of activity in 8 patients. This figure declined to 7 during the following period, because one patient with decreased activity was recorded as having normal activity 15 months after the fracture. These 7 patients all ...

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This book provides an analysis of pathophysiologic concepts of trauma and reviews the effectiveness of the available imaging modalities in acute trauma of various organ system. Topics covered are chest injuries; abdominal trauma; fractures of long bones; the foot and ankle; the knee; hand and wrist; the elbow; the shoulder; the pelvis hips; the spine; the skull and facial trauma and the clinical assessment of multiple injuries patients. Comparative evaluation of diagnostic techniques of radiography is discussed. Normal anatomy and bone fractures along with soft-tissue injuries are described.

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A 2-year follow-up regarding healing complications, such as redisplacement, nonunion, and segmental collapse of the femoral head, was performed in 306 patients operated on for femoral neck fracture and examined with /sup 99m/Technetium-MDP scintimetry within 2 weeks postoperatively. Scintimetric evaluation was performed by selecting regions of interest over the femoral head on the fracture side and the intact side and by comparing the uptake. A femoral head ratio fractured/intact side thus was obtained. Of 199 patients with an intact femoral head uptake (ratio less than or equal to 1.0), 181 showed no signs of healing complications at 2 years, whereas 18 had developed healing complications. Of 107 cases with a deficient femoral-head uptake (ratio < 1.0), 96 had developed healing complications within 2 years from the operation, while 11 cases had no signs of radiographic complications. We conclude that /sup 99m/Tc-MDP ...

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Fourteen patients with cervical hip fractures were treated with internal fixation using titanium screws. The femoral head vitality was evaluated with "9"9Tc"m-MDP scintigraphy and scintimetry within 2 weeks postoperatively and by serial low field magnetic resonance imaging (MR). Two patients with reduced radionuclide uptake (femoral head ratio =# 1.0), MR revealed a focal decrease of the signal intensity in the femoral head or neck at 2, 3 and 7 months after fracture, respectively. The radiographs in one of these patients were normal at 7 months after fracture. The second one showed signs of necrosis at 16 months and the last one developed delayed/non-union. With a non-ferromagnetic osteosynthesis the healing course after femoral neck fracture can be studied with low field MR equipment without disturbing artifacts. The time period between ischaemia and definite abnormalities on MR may embrace several ...

International Nuclear Information System (INIS)

Thirty-five patients with temporal bone fractures were examined; the fractures were sometimes associated with dislocation of the assicular chain caused by road fatalities. Computed Tomography (CT) was performed either because of the presence of clinical symptoms associated with trauma of the temporal bone, because of a hemotympanum discovered during a CT scan of the brain. Thirty-three fractures were detected: 19 longitudinal, 6 transverse, and 8 complex. An incudostapedial dislocation was also detected, together with a displacement of a stapedial prosthesis from the lenticular process of incus, and 3 incus-malleus dislocation associated with fractures. High resolution CT allows the precise definition of the course of the fractures, of the associated dislocation of the ossicular chain, and of facial nerve lesion, thus allowing a more accurate surgical intervention. In the ...

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In association with excavation of the No. 135 steam producing well in the Onikubi geothermal power plant in Miyagi Prefecture, shapes of production zones and drilling-induced fracture (DIF) were acquired from the borehole televiewer (BHTV) data. The BHTV logging shoots sound waves onto well walls of wells filled with fluid and detects the reflection waves to investigate the state of the well walls. Vertical fracture with opening lengths from 2 to 3 m were found at depths of about 1232 m and 1312 m. Water run-off has occurred at a depth of about 1312 m during the excavation, to which these vertical fractures might have contributed possibly. In depths of about 1232 m and 1312 m, fractures inclining toward north-east direction and south-west direction are predominant. Some fractures in the depth of about 1333 m incline toward east-south-east direction and west-north-west direction. ...

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This paper discusses the use of tracers as a reservoir engineering tool in fractured geothermal reservoirs. The principle concern in injecting cooler spent fluids into a fractured reservoir is that the fluids may move through high permeability channels and return to the production wells after contacting a relatively small volume of rock. As a consequence of this rapid transport, the fluids will be only partially reheated and after a short period time will effectively mine the heat from the limited volume of rock. The production wells will then experience a rapid and premature reduction in thermal output. Tracers can be used to infer the existence of high mobility conduits between injection and production wells and to monitor chemical changes of an injected fluid. Since tracer arrival precedes thermal breakthrough, tracer tests are a very useful forecasting tool.

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The electrochemical behaviour and fracture morphology of homogenized and sensitized type SAE 304 stainless steel U bent specimens, in 3% NaCl solution, at pH=2.0 and pH=7.0 both at room temperature and 100"0C was studied. Polarization curves, galvanostatic and potentiostatic experiments were run. It could be observed that high temperature and low pH favour transgranular cracking and longer sensitization times lower fracture time and tend to give rise to intergranular fracture. Light sensitization can produce transgranular cracking even at room temperature, when the homogenized alloy does not present stress-corrosion cracking for the same condition. (Author).

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In the context of safety assessment of radioactive waste repositories, complex radionuclide transport models covering key safety-relevant processes play a major role. In recent Swiss safety assessments, such as Kristallin-I, an important drawback was the limitation in geosphere modelling capability to account for geosphere heterogeneities. In marked contrast to this limitation in modelling capabilities, great effort has been put into investigating the heterogeneity of the geosphere as it impacts on hydrology. Structural geological methods have been used to look at the geometry of the flow paths on a small scale and the diffusion and sorption properties of different rock materials have been investigated. This huge amount of information could however be only partially applied in geosphere transport modelling. To make use of these investigations the 'PICNIC project' was established as a joint cooperation of PSI/Nagra and QuantiSci to provide a new ...

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Tridimensional localization of bone and soft tissue injuries in complex facial trauma is fundamental for treatment. The face can be conceptualized as 3 groups of interconnected osseous struts that are oriented in the horizontal, sagittal and coronal planes. Each group of struts is closely related to specific soft tissue structures that are susceptible to injury. Any single CT section in the coronal plane or in the axial plane contains parts of one or more these struts. Facial CT in biplane were performed in 32 patients of facial trauma. The most common site of facial fractures is found in middle part of horizontal struts, geometrically in anteromedial portion of the inferior orbital fissure of the face. The most common soft tissue injury combined with facial fracture is hematoma and/or herniated orbital contents into the maxillary sinus. The serious combined soft tissue injuries were ocular rupture, retroorbital hematoma and optic nerve injury ...

UK PubMed Central (United Kingdom)

PurposeSatisfaction of search (SOS) occurs when an abnormality is missed because another abnormality has been detected. This research studied whether the severity...Full Text Available

UK PubMed Central (United Kingdom)

Hypothyroidism and thyrotoxicosis are each associated with an increased risk of fracture. Although thyroxine (T4) is the predominant circulating thyroid hormone, target cell responses are determined...Full Text Available

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It is well known that composite armors, consisting of glass elements confined with metallic tampers, are extraordinarily effective against shaped charge attack. Early experiments showed that jets fired against glass targets appeared to be bombarded by tiny fragments that destroyed alignment and reduced residual jet penetration. This result was attributed to an elastic rebound effect in which the outward radial motion of the target around the jet periphery was supposed to be arrested by tensile hoop stresses which developed behind the divergent shock front. Glass fragments were then accelerated radially inward and these destabilized the jet. To sustain the large tensile hoop stresses required, the glass must not have been fractured by the initial shock, behind which the stress state is typically well above the Hugoniot elastic limit. Modeling the penetration of a jet into glass requires not only determining the spall strength, i.e., the tensile stress at which ...

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With regard to a fracture system in the Hijiori hot dry rock artificial reservoir, an attempt was made on an interpretation which integrates different data. Major factors that characterize development and performance of an artificial reservoir are composed of a fracture system in rocks, which acts as circulating water paths, a heat exchange face and a reservoir space. The system relates not only with crack density distribution, but also with cracks activated by water pressure fracturing, cracks generating acoustic emission (AE), and cracks working as major flow paths, all of which are characterized by having respective behaviors and roles. Characteristics are shown on AE cluster distribution, crack distribution, production zone and estimated stress fields. Mutual relationship among these elements was discussed based on the Coulomb`s theory. The most important paths are characterized by distribution of slippery cracks. ...

UK PubMed Central (United Kingdom)

Lumbar epidural anesthesia is useful in a variety of chronic benign pain syndromes, including lumbar radiculopathy, low back pain syndrome, spinal stenosis, and vertebral compression fractures. Given...Full Text Available

UK PubMed Central (United Kingdom)

BackgroundDiet is considered an important factor for bone health, but is composed of a wide variety of foods containing complex combinations of nutrients. Therefore we investigated...Full Text Available

UK PubMed Central (United Kingdom)

The hierarchical arrangement of collagen and mineral into bone tissue presumabley maximizes fracture resistance with respect to the predominant strain mode in bone. Thus, the ability of cortical...Full Text Available

UK PubMed Central (United Kingdom)

BackgroundBallet Dancers have been shown to have a relatively high incidence of stress fractures of the foot and ankle. It was our objective to examine MR imaging patterns of bone...Full Text Available

UK PubMed Central (United Kingdom)

There is increasing evidence of a biochemical link between lipid oxidation and bone metabolism. Paraoxonase 1 (PON1) prevents the oxidation of low-density lipoprotein (LDL) and metabolizes biologically...Full Text Available

International Nuclear Information System (INIS)

This case report makes evident that in a 75 years old patient with a (cured) femoral neck fracture 15 years ago a refracture at the same site following a new trauma could not be detected by conventional X-ray. The follow-up of a radionuclide bone study, however, enabled the dignosis of a refracture. From these findings, it is further evident that the decreased bone metabolism in older patients has to be considered. Thus, although the initial bone scan following the trauma is negative, a follow-up scan should be performed within a 4 day-period. (orig.).

British Library Electronic Table of Contents (United Kingdom)

Simplified strain-based fracture mechanics equations, established for external surface cracked pipelines subjected to an external bending load, are presented and used in probabilistic assessment of a pipeline girth weld. The model takes into account several parameters, such as variation in crack depth, crack length, internal pressure and material hardening. The critical strain from ductile tearing in the cracked pipeline is found by using the tangency criterion. The reliability problem is solved using first and second order reliability methods for different pipe dimensions and load levels.

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Posttraumatic tibia valga is a well-recognized complication following fracture of the upper tibial metaphysis in young children. We present a case of a child who developed a valgus deformity following fracture of the proximal tibia and fibula in which quantitative bone scintigraphy at 5 months after injury demonstrated increased uptake at the proximal tibial growth plate with proportionally greater uptake on the medial side. This finding suggests that the valgus deformity in this patient was due to a relative increase in vascularity and consequent overgrowth of the medial portion of the proximal tibial physis.

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Measurements of the humeral cortical thickness demonstrate that generalised osteoporosis in female Bantu commences in the fifth decade and gradually increases until, in the ninth decade, all subjects are osteoporotic. The combined cortical thickness (CCT) of the humerus in young adults is very similar to that found previously in a white London population and the loss of cortex with age is very similar. It is concluded that the known low incidence of femoral neck fracture in Bantu is not due to a lower incidence of generalised osteoporosis but to environmental factors. The chief environmental factor postulated is the greater amount of physical work performed by the Bantu. A more careful mode of walking is suggested as a subsidiary cause. (orig.).

International Nuclear Information System (INIS)

The report summarizes ten years of experience in the analysis and evaluation of ultrasonic testing data measured in turbine and generator rotors. Apart from the information on type, position, size and distribution of flaws, the expert knowledge achieved in an interpretation of ultrasonic signals yields further insight, as e.g.: - Confirmation of assumptions taken as a basis for fracture-mechanical analysis of these flaws with regard to crack initiation and crack growth under low-cycle fatigue conditions (O=0.7-1 Rp 0.2, N<25.000 growth in length); - enhanced information on a correlation of ultrasonic testing data with the real flaw size. (orig.).

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The report traces the documented incidences of brittle fracture in composite suspension insulators for use on high voltage transmission lines, and presents the subsequent investigations. It describes the part played by electrical activity, stress corrosion and humidity, and compares similar failures that have taken place in electric traction insulators. It then goes on to review related work on the humidity effects, stress corrosion, fatigue and partial discharges in glass fiber reinforced plastics in general. The final section summarizes the present understanding of the problem and the various measures taken by different manufactures to avoid it in the future. The need for acceptance criteria in this respect is outlined.

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As part of studies into the siting of a deep repository for nuclear waste, Swedish Nuclear Fuel and Waste Management Company (SKB) has commissioned the Alternative Models Project (AMP). The AMP is a comparison of three alternative modeling approaches for geosphere performance assessment for a single hypothetical site. The hypothetical site, arbitrarily named Aberg is based on parameters from the Aespoe Hard Rock Laboratory in southern Sweden. The Aberg model domain, boundary conditions and canister locations are defined as a common reference case to facilitate comparisons between approaches. This report presents the results of a discrete fracture pathways analysis of the Aberg site, within the context of the SR 97 performance assessment exercise. The Aberg discrete fracture network (DFN) site model is based on consensus Aberg parameters related to the Aespoe HRL site. Discrete fracture pathways are identified from canister ...

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(1) To determine the accuracy of computed tomography (CT) in the evaluation of ligament tear and avulsion in patients with tibial plateau fracture. (2) To evaluate whether the presence or severity of fracture gap and articular depression can predict meniscal injury. A fellowship-trained musculoskeletal radiologist retrospectively reviewed knee CT and MRI examinations of 41 consecutive patients presenting to a level 1 trauma center with tibial plateau fractures. Fracture gap, articular depression, ligament tear and footprint avulsions were assessed on CT examinations. The MRI studies were examined for osseous and soft tissue injuries, including meniscal tear, meniscal displacement, ligament tear, and ligament avulsion. CT demonstrated torn ligaments with 80% sensitivity and 98% specificity. Only 2% of ligaments deemed intact on careful CT evaluation had partial or complete tears on MRI. Although the ...

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... Descriptors : *COMBUSTIBLE CARTRIDGE CASES, STYPHNATES, PHYSICAL PROPERTIES, TENSILE PROPERTIES, PRIMERS ...

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Dual energy X-ray absorptiometry (Hologic QDR-1000) was used to quantitatively analyze the diagnosis and prevention of osteoporosis. The peak bone mineral density (BMD) of the spine appeared in normal men in their twenties and in normal women in their thirties. There was acceleration of bone loss in the 50 to 60 year age bracket (premenopause and postmenopause) in normal women. On the contrary, the peak BMD of the femoral neck in normal men and women appeared in their twenties after which it decreased slightly with age. Comparison showed that the femoral neck BMD of normal women was lower than that of men throughout all ages. The fracture threshold, 0.756 g/cm[sup 2] for the spine, was obtained by scanning 73 females with spinal fractures, the mean BMDs for L2-L4 at the 90th percentile level were used as the fracture threshold. The fracture threshold of femoral neck fracture was the ...

International Nuclear Information System (INIS)

Fracture toughness data of pre-cracked Charpy single-edge bend, SE(B), specimens are compared with those of standard compact, C(T), specimens in the upper shelf and ductile-to-brittle transition regimes. Charpy sized SE(B) specimens provide ductile fracture toughness data, which are compatible with those of standard C(T) specimens. Statistical methods such as the exponential curve fitting method (ECF), the engineering lower bound toughness method (ELB), and the Master Curve method (MC) are used to provide meaningful lower bound cleavage fracture toughness estimates from the toughness scatter of the Charpy sized SE(B) specimens in the ductile-to-brittle transition regime. In this regime, according to the ELB and MC methods, SE(B) specimens provide cleavage toughness data, which tend to be non-conservative compared to those of standard C(T) specimens. However, analyses based on the exponential curve fitting method show good ...

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Secondary ischemic necrosis of femoral head due to loss of blood supply following to femoral neck fracture is well known. The regional distribution of bone-seeking radiopharmaceuricals in the skeleton can depend on a number of factors, but bone blood flow is a major physiological determinant of regional skeletal uptake of Tc-99m polyphosphate and bone imaging may thus be used for the evaluation of vascularity of the femoral head. The authors made a comparative study of scintigraphic findings and operative findings of 28 cases of femoral neck fracture treated at Kyung Hee University Hospital from April 1980 to May 1984. The results were as follows: 1. In 16 cases of proven avascular necorsis of femoral head, scintigraphy showed absent or decreased activity in 14 cases (87.5%), while radiography showed increased density in 10 cases (62.5%). 2. In 12 cases of proven vital femoral head, scintigraphy showed increased activity in 9 cases (75%) and ...

International Nuclear Information System (INIS)

Methodology based on probabilistic fracture mechanics (PFM) is finding increasing acceptability in demonstrating safety of Nuclear Power Plant (NPP) piping. In PFM, the methods of fracture mechanics and reliability theory are combined for assessing the reliability of components, which contain cracks. In this work, reliability assessment of Tarapur Atomic Power Plant (TAPP) 3-4 Primary Heat Transport (PHT) piping is done using PFM. Monte Carlo simulation with stratified sampling is used as a variance reduction technique. PFM model assumes a pre-existing circumferential surface crack before the start of plant operation. The crack grows in size during the lifetime of the plant due to the fatigue loading. This part-through wall crack having escaped hydro-test and pre-service inspection, may result in either a through wall flaw (leak) or may lead to the rupture of the piping. R6 method is used as failure criteria. Steam generator inlet (SGI), steam ...

Science.gov (United States)

BACKGROUND: Although definitions vary, infected nonunion has been defined as a state of failure of union and persistence of infection at the fracture site for 6 to 8 months.>). Infected nonunions of the supracondylar region of the femur are uncommon and are mostly due to a severe open fracture with extensive comminution and segmental bone loss or after internal fixation of a comminuted closed fracture. Associated factors include exposed bone devoid of vascularized periosteal coverage for more than 6 weeks, purulent discharge, a positive bacteriological culture from the depth of the wound, and histologic evidence of necrotic bone containing empty lacunae. Soft-tissue loss with multiple sinuses, osteomyelitis, osteopenia, complex deformities with limb-length inequality, stiffness of the adjacent joint, polybacterial multidrug-resistant infection, and smoking all complicate treatment and recovery. Although uncommon in ...

International Nuclear Information System (INIS)

A retrospective study was made of all radionuclide (RN) bone images performed at our institution over a two-year period to evaluate femoral head viability after nonpathologic fracture of the femoral neck. Twelve patients had avascular femoral heads during the perioperative period, of which nine had adequate follow-up. Seven of these nine patients had follow-up bone images. Revascularization occurred in four patients, while three had persistent absence of femoral head uptake. With clinical follow-up ranging from four to 29 months (median: 14 months), only two of these nine patients developed clinical or radiographic evidence of osteonecrosis. RN bone imaging performed in the perioperative period does not reliably predict the development of post-traumatic osteonecrosis of the femoral head and, at present, should not be used to determine prospectively method of treatment of femoral neck fracture.

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Quantitative bone scintigraphy was performed on 23 white females with post-menopausal osteoporosis and vertebral compression fractures. These patients were then entered into a randomized, double-blind clinical trial or sodium fluoride therapy (NaF=14, placebo=9) which included repeat bone scintigraphy every six months. Scintigraphic images were acquired for 500K counts per image over the total body with computer acquisition over the posterior thoracic and lumbar spine. Images were obtained on a wide field-of-view gamma camera two hours after injecting 15 mCi of Tc-99m MDP. Data analysis showed a significant reduction in the activity ratio of abnormal vertebral body to normal vertebral body in those patients treated with sodium fluoride (paired t-test p=0.0095). No significant change was observed in the control group of (p=0.142). These results suggest that sodium fluoride therapy promotes more rapid healing of osteoporotic vertebral fractures. ...

International Nuclear Information System (INIS)

AIM: To assess the impact of the introduction of a computed tomography (CT) imaging protocol for multi-trauma patients on the workload, overall diagnostic yield, and effect on detection of cervical spine injury and pneumothorax. METHOD: Between February 1997 and April 2004, all patients presenting acutely to the Emergency Department (ED) with haemodynamically stable trauma (Abbreviated Injury Scale 3 or more) involving more than two body systems were imaged with a comprehensive pre-set helical CT protocol (including non-contrast head, cervical spine: cranio-cervical and cervico-thoracic junctions; and oral and intravenous contrast-enhanced thoracic, abdomen and pelvis) after initial triage and a standard trauma series of radiographs (chest, lateral C-spine and pelvis). Diagnosis of cervical spine fracture and pneumothorax was noted before and after the CT protocol was carried out and findings from all studies were recorded prospectively. RESULTS: Over the 7-year ...

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Participants in the conference selected to attend two different working group sessions. The working groups discussed different perspectives of system-based approaches to osteoporosis and fracture care. The group on postfracture case management recommended that nurse case managers be used to improve communication among patients, orthopaedic surgeons, and those providing ongoing clinical care. The hospital working group discussed the impact of and barriers to improved postfracture management in the hospital setting. The health systems group emphasized the difference between a closed system in which long-term benefits of interventions were more likely to be appreciated than in fee for service systems. The health information technology group discussed the advantages and challenges of electroni...

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Femoral head replacement was performed for femoral neck fracture or femoral head necrosis on 36 hips of 34 patients on whom Tc-99m MDP scintigraphy was done for analysis of radioisotope uptake around the prosthesis. In the cases with satisfactory clinical course after replacement surgery the uptake was high in the area between the prosthesis and the trochanter, in the area of the stem tip of the prosthesis and in the acetabular area. The high uptake decreased gradually and reached a normal level by 8 months after surgery. The cases with no decrease of high uptake by 8 months after surgery were considered to have had an eventful postoperative course associated with some complication such as infection, fracture, loosening etc. Tc-99m MDP scintigraphy was useful for early detection of complications and to evaluate progress of the operated patients. (author)

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Statement of problem Porcelain fracture associated with an implant-supported, metal ceramic crown or fixed partial denture occurs at a higher rate than in tooth-supported restorations, according to the literature. Implant-specific and patient-specific causes of ceramic failure have not been fully evaluated. Purpose The purpose of this retrospective study was to evaluate the potential statistical predictors for porcelain fracture of implant-supported, metal ceramic restorations. Material and Methods Over a 6-month period, a consecutive series of patients having previously received implant-supported, metal ceramic fixed restorations were examined during periodic recall appointments. The number of supporting implants, number of dental units, type of restoration, date of prosthesis insertion, ...

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Even though the currently intensive research efforts on high- temperature superconducting materials have not yet converged on a well specified practical material, the indications are that such a material may be quite brittle, anisotropic, and may contain many flaws such as microcracks and voids at grain boundaries. Consequently, practical applications of high temperature superconducting materials will require a very careful strength analysis based on fracture mechanics considerations. Because of the high sensitivity of the strength of such materials to the presence of defects, methods of quantitative non-destructive evaluation may be expected to play an important role in strength determinations. This proposal is concerned with the use of ultrasonic methods to detect and characterize isolated cracks, clusters of microcracks and microcracks distributed throughout the material. Particular attention has been, and will continue to be devoted to relating ultrasonic ...

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The three tasks were completed during this reporting period. During this quarter, work focused on a local structural analysis of the Table Rock field, greater Green River basin (GGRB) in southwestern Wyoming. The ultimate objective of the local analysis is to apply the techniques developed and demonstrated during earlier phases of the project in the Rulison Field area of the Piceance basin for sweet-spot delineation. The primary goal of this work is to focus in on the Table Rock field area in the northern Washakie basin of the Greater Green River basin in support of Union Pacific Resources and DOE planned horizontal drilling efforts. The work plan for the quarter of April 1, 1998--June 30, 1998 consisted of three tasks: (1) Acquire necessary seismic data and depth-convert, (2) Map major fault geometry and analyze displacement vectors, (3) Develop and initiate a natural fracture prediction study.

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Analytical and numerical methods have been used in this investigation to model the behavior of geothermal systems under exploitation. The work is divided into three parts: (1) development of a numerical code, (2) theoretical studies of geothermal systems, and (3) field applications. A new single-phase three-dimensional simulator, capable of solving heat and mass flow problems in a saturated, heterogeneous porous or fractured medium has been developed. The simulator uses the integrated finite difference method for formulating the governing equations and an efficient sparse solver for the solution of the linearized equations. In the theoretical studies, various reservoir engineering problems have been examined. These include (a) well-test analysis, (b) exploitation strategies, (c) injection into fractured rocks, and (d) fault-charged geothermal reservoirs.

British Library Electronic Table of Contents (United Kingdom)

Statement of problem Although the esthetic outcome of a collarless metal ceramic restoration is superior to that of a restoration with a metal margin, its mechanical strength has not been evaluated. Purpose The purpose of this study was to evaluate and compare the fracture resistance of metal ceramic restorations with metal margins to that of metal ceramic restorations with circumferential porcelain margins, after exposure to masticatory simulation. Material and methods Twenty-four metal ceramic restorations were fabricated and paired with 24 cobalt-chrome tooth analogs. Twelve of the specimens had metal margins, while the remainder had circumferential porcelain margins. The restorations were cemented on the metal tooth analogs with a resin-modified glass ionomer luting agent (FujiCEM). Al...

International Nuclear Information System (INIS)

The authors have evaluated bone mineral content in the vertebral spongiosa by means of Computed Tomography. The method proposed by Genant and Cann [17, 18] has been applied to examine 164 healthy volunteers and 108 patients. Both healthy males and females showed a progressive bone mineral loss increasing with age; the bone mineral loss was most severe in females during the 4th and 5th decade of life. Pathology included patients with osteoporotic fractures (vertebral and femural neck), patients with partial gastrectomy, renal failure, primary hyperparathyroidism, Cushing syndrome, corticosteroid therapy. Bone mineral values were significantly lower in most pathologic groups. Computed Tomography proves thus to be a valuable method to assess bone mineral content and to identify patients at risk for fractures.

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The authors obtain the critical load levels corresponding to the onset of spalling microdamage for Armco iron and steels St.3 and 12Kh18N10T in a broad temperature range (-196-800 degrees C. The results of the investigation of the effect of the temperature on spalling fracture are presented. The effect of the loading time on the strength of the investigated materials is also given. The authors assume that at -196 degrees C impact-wave strain-hardening may also be characterized by the value of H obtained for the center of the specimen since measurements on great thicknesses, including those reaching as far as the opposite surface, did not reveal any substantial change of microhardness.

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Ten patients with traumatic femoral neck fracture were studied with MR imaging (0.5 T, Magnetom, Siemens): unenhanced (multiecho, TR/TE = 1,600/30--240 [repetition time/echo time, msec]; gradient echo, TR/TE = 315/14, #theta# = 90 degrees) and Gd-DTPA enhanced (0.1 mM/kg body weight, Magnevist, Schering; gradient echo, TR/TE = 315/14, #theta# = 90 degrees). MR images were compared with clinical-radiographic findings. Digital subtraction angiography of the femoral head (FH) in five patients showed complete interruption of blood supply to the FH in three patients (signal intensity of FH did not increase on postcontrast images) and intact FH arteries in two patients (FH signal increased on postcontrast images, as did the healthy-side signal).

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... Accession Number : ADD323869. Title : EFFECTS OF SHIELDING ON PROPERTIES OF EDDY CURRENT PROBES WITH FERRITE CUP CORES. ...

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Aim: To determine whether experience improves the consistency of visual search behaviour in fracture identification in plain radiographs, and the effect of specialization. Material and methods: Twenty-five observers consisting of consultant radiologists, consultant orthopaedic surgeons, orthopaedic specialist registrars, orthopaedic senior house officers, and accident and emergency senior house officers examined 33 skeletal radiographs (shoulder, hand, and knee). Eye movement data were collected using a Tobii 1750 eye tracker with levels of diagnostic confidence collected simultaneously. Kullback-Leibler (KL) divergence and Gaussian mixture model fitting of fixation distance-to-fracture were used to calculate the consistency and the relationship between discovery and reflective visual search phases among different observer groups. Results: Total time spent studying the radiograph was not significantly different between the groups. However, the ...

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An approach to the ductile fracture of ultra high strength steels has been evaluated. According to this approach the critical crack tip opening, delta/sub IC/, will scale with X/sub 0/(R/sub V//R/sub I/vertical bar/sub R//sub 0/. X/sub 0/ is an average inclusion spacing and (R/sub V/R/sub I/)vertical bar/sub R//sub 0/ is the void radius divided by the radius of the inclusion nucleating the void evaluated at the average inclusion size. AF1410 was selected to test this approach because it has exceptionally high fracture toughness on aging at 510/sup 0/C and because its toughness varies markedly with aging temperature. The results from this and earlier work showed a linear relationship exists between delta/sub IC/ and X/sub 0/(R/sub V//R/sub I/)vertical bar /sub R//sub 0/ for values of delta/sub IC/ ranging from about 8 ..mu..m to 60 ..mu..m. The values of (R/sub V//R/sub I/)vertical bar /sub R//sub 0/ for AF1410 aged at 425/sup 0/C and 510/sup ...

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This book presents the papers given at a conference on offshore platforms. Topics considered in this book include risk assessment, crack propagation, fracture control, stress corrosion, the reliability of pile foundations, the thermal conductivity of offshore pipeline coating material, economic analysis, hydrodynamics, simulation, Arctic structure design, composite materials, buoys, deep water drilling, corrosion protection, pollution control equipment, and subsea exhaust gas compressors.

International Nuclear Information System (INIS)

Nine-component vertical seismic profiling has been conducted at the UE-25 UZ No. 16 borehole at Yucca Mountain, Nevada, in support of investigation of the hydrologic significance of fault and fracture systems. A large data set from multi-component sources and receivers allows state-of-the-art advances in processing using polarization filtering and reverse time migration, for enhanced interpretation of geologic features.

International Nuclear Information System (INIS)

Investigated are the characteristics of high-temperature plastic deformation the velocity sensitivity of flow stresses, deformation curves, flow stresses, deformation before rupture - as well as the structure of beryllium alloys containing nickel (0.5-4 %), yttrium (0.5-2 %) and aluminium (38 %). The alloys containing nickel (2%) and yttrium (0.5 %) are superplastic, however, deformation before fracture of the alloys is lower than that of the unalloyed beryllium. The singularities of high-temperature plastic flow of the alloys and the causes of deterioration of their plasticity are determined.