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Sample records for cladding incipient crack

  1. Incipient Crack Detection in Composite Wind Turbine Blades

    SciTech Connect

    Taylor, Stuart G.; Choi, Mijin; Jeong, Hyomi; Jang, Jae Kyeong; Park, Gyuhae; Farinholt, Kevin; Farrar, Charles R.; Ammerman, Curtt N.; Todd, Michael D.; Lee, Jung-Ryul

    2012-08-28

    This paper presents some analysis results for incipient crack detection in a 9-meter CX-100 wind turbine blade that underwent fatigue loading to failure. The blade was manufactured to standard specifications, and it underwent harmonic excitation at its first resonance using a hydraulically-actuated excitation system until reaching catastrophic failure. This work investigates the ability of an ultrasonic guided wave approach to detect incipient damage prior to the surfacing of a visible, catastrophic crack. The blade was instrumented with piezoelectric transducers, which were used in an active, pitchcatch mode with guided waves over a range of excitation frequencies. The performance results in detecting incipient crack formation in the fiberglass skin of the blade is assessed over the range of frequencies in order to determine the point at which the incipient crack became detectable. Higher excitation frequencies provide consistent results for paths along the rotor blade's carbon fiber spar cap, but performance falls off with increasing excitation frequencies for paths off of the spar cap. Lower excitation frequencies provide more consistent performance across all sensor paths.

  2. Fatigue crack growth testing of sub-clad defects

    SciTech Connect

    Jones, D.P.; Leax, T.R.

    1998-04-01

    Fatigue crack growth tests were performed on four point bend specimens with crack like defects intentionally placed in A302B low-alloy pressure vessel steel clad with 308/309L weld deposited stainless steel. The defects were placed in the base metal under the cladding by machining a cavity from the side opposite the cladding, electric-discharge machining a very sharp flaw, fatigue pre-cracking the flaw, and then filling up the cavity by a weld repair process. The specimens were stress relieved before fatigue testing. The specimens were fatigue cycled at positive load ratios until the defects broke through to the surface. The specimens were then fractured at liquid nitrogen temperatures to reveal the fracture surfaces. Seven different sub-clad flaw specimens were tested in room temperature air and each test provides a record of cycles to defect break-through. Changes in defect size and shape as a function of applied load cycles were obtained by benchmarking the crack at various stages of the load history. The results provide a set of embedded defect data which can be used for qualifying fatigue crack growth analysis procedures such as those in Section XI of the ASME Boiler and Pressure Vessel Code. A comparison between calculated and measured values shows that the ASME B and PV Section XI fatigue crack growth procedures conservatively predict cycles to defect break-through for small sub-clad defects.

  3. Crack resistance curves determination of tube cladding material

    NASA Astrophysics Data System (ADS)

    Bertsch, J.; Hoffelner, W.

    2006-06-01

    Zirconium based alloys have been in use as fuel cladding material in light water reactors since many years. As claddings change their mechanical properties during service, it is essential for the assessment of mechanical integrity to provide parameters for potential rupture behaviour. Usually, fracture mechanics parameters like the fracture toughness KIC or, for high plastic strains, the J-integral based elastic-plastic fracture toughness JIC are employed. In claddings with a very small wall thickness the determination of toughness needs the extension of the J-concept beyond limits of standards. In the paper a new method based on the traditional J approach is presented. Crack resistance curves (J-R curves) were created for unirradiated thin walled Zircaloy-4 and aluminium cladding tube pieces at room temperature using the single sample method. The procedure of creating sharp fatigue starter cracks with respect to optical recording was optimized. It is shown that the chosen test method is appropriate for the determination of complete J-R curves including the values J0.2 (J at 0.2 mm crack length), Jm (J corresponding to the maximum load) and the slope of the curve.

  4. Detection of small-sized near-surface under-clad cracks for reactor pressure vessels

    SciTech Connect

    Taylor, T.T.; Crawford, S.L.; Doctor, S.R.; Posakony, G.J.

    1983-02-01

    The analysis of pressurized thermal shock (PTS) shows it is necessary for nondestructive evaluation to demonstrate high probability of detecting evaluation to demonstrate high probability of detecting cracks 0.250 inches deep and deeper at the clad/base metal interface. Ultrasonic techniques developed and used in Europe are evaluated in this paper for their applicability to US reactor pressure vessels for detecting cracks of interest for PTS. Flaw detectability experiments were carried out by testing the inspection technique's ability to detect artificial flaws under several types of clad, including some Manual Metal Arc (MMA) clad. Both ground and unground clad surfaces were evaluated. Crack sizing tests of the inspection technique were made using a crack tip diffraction technique.

  5. Simulations of Failure via Three-Dimensional Cracking in Fuel Cladding for Advanced Nuclear Fuels

    SciTech Connect

    Lu, Hongbing; Bukkapatnam, Satish; Harimkar, Sandip; Singh, Raman; Bardenhagen, Scott

    2014-01-09

    Enhancing performance of fuel cladding and duct alloys is a key means of increasing fuel burnup. This project will address the failure of fuel cladding via three-dimensional cracking models. Researchers will develop a simulation code for the failure of the fuel cladding and validate the code through experiments. The objective is to develop an algorithm to determine the failure of fuel cladding in the form of three-dimensional cracking due to prolonged exposure under varying conditions of pressure, temperature, chemical environment, and irradiation. This project encompasses the following tasks: 1. Simulate 3D crack initiation and growth under instantaneous and/or fatigue loads using a new variant of the material point method (MPM); 2. Simulate debonding of the materials in the crack path using cohesive elements, considering normal and shear traction separation laws; 3. Determine the crack propagation path, considering damage of the materials incorporated in the cohesive elements to allow the energy release rate to be minimized; 4. Simulate the three-dimensional fatigue crack growth as a function of loading histories; 5. Verify the simulation code by comparing results to theoretical and numerical studies available in the literature; 6. Conduct experiments to observe the crack path and surface profile in unused fuel cladding and validate against simulation results; and 7. Expand the adaptive mesh refinement infrastructure parallel processing environment to allow adaptive mesh refinement at the 3D crack fronts and adaptive mesh merging in the wake of cracks. Fuel cladding is made of materials such as stainless steels and ferritic steels with added alloying elements, which increase stability and durability under irradiation. As fuel cladding is subjected to water, chemicals, fission gas, pressure, high temperatures, and irradiation while in service, understanding performance is essential. In the fast fuel used in advanced burner reactors, simulations of the nuclear

  6. Stress corrosion cracking of zirconium cladding tubes: I. Proximate local SCC testing method

    NASA Astrophysics Data System (ADS)

    Rozhnov, A. B.; Belov, V. A.; Nikulin, S. A.; Khanzhin, V. G.

    2010-10-01

    The stress corrosion cracking (SCC) methods of testing zirconium cladding tubes are analyzed. A proximate method is proposed for estimating SCC of fuel claddings claddings in a iodine-containing environment with a limited contact zone between a metal and corrosive medium and simultaneous measurement of acoustic emission (AE) from forming corrosion defects. Criteria of estimating the SCC resistance of the tubes are proposed from measured AE and corrosion damage of the tube material. The results of local SCC tests of cladding tubes of E110 and E635 zirconium alloys are presented.

  7. Propagation of stress corrosion cracks in Zr-1% Nb claddings

    NASA Astrophysics Data System (ADS)

    Bibilashvily, Yu. K.; Dolgov, Yu. N.; Nesterov, B. I.; Novikov, V. V.

    1995-09-01

    Experimental results on iodine induced stress corrosion cracking (SCC) are analyzed. The studies were performed at 350°C using Zr-1% Nb tubular specimens. Fatigue crack at internal surface served as an initial defect. The relationship was derived between crack propagation rate and stress intensity factor; the threshold stress intensity factor of 4.8 MPa m{1}/{2} was determined.

  8. An overview of the HSST Full-Thickness Shallow-Crack Clad Beam Testing Program

    SciTech Connect

    Keeney, J.A.; Theiss, T.J.; McAfee, W.J.; Bass, B.R.

    1994-09-01

    A testing program is described that will utilize full-thickness clad beam specimens to quantify fracture toughness for shallow flaws in material for which metallurgical conditions are prototypic of those found in reactor pressure vessels (RPVs). The beam specimens are fabricated from a section of an RPV wall that includes weld, plate and clad material. Metallurgical factors potentially influencing fracture toughness for shallow flaws in the beam specimen include material gradients due to welding and cladding applications, as well as material inhomogeneities in welded regions due to reheating in multiple weld passes. Fracture toughness tests focusing on shallow flaws in plate and weld material will also provide data for evaluating the relative influence of absolute and normalized crack depth on constraint conditions. Pretest finite-element analyses are described that provide near-tip stress and strain fields for characterization of constraint in the shallow-crack specimens in terms of the Q-stress. Analysis results predict a constraint loss in the shallow-crack clad beam specimen similar to that determined for a previously tested shallow-crack single-edge notch homogeneous bend specimen with the same normalized crack depth.

  9. Fracture behavior of shallow cracks in full-thickness clad beams from an RPV wall section

    SciTech Connect

    Keeney, J.A.; Bass, B.R.; McAfee, W.J.

    1995-04-01

    A testing program is described that utilizes full-thickness clad beam specimens to quantify fracture toughness for shallow cracks in weld material for which metallurgical conditions are prototypic of those found in reactor pressure vessels (RPVs). The beam specimens are fabricated from an RPV shell segment that includes weld, plate and clad material. Metallurgical factors potentially influencing fracture toughness for shallow cracks in the beam specimens include material gradients and material inhomogeneities in welded regions. The shallow-crack clad beam specimens showed a significant loss of constraint similar to that of other shallow-crack single-edge notch bend (SENB) specimens. The stress-based Dodds-Anderson scaling model appears to be effective in adjusting the test data to account for in-plane loss of constraint for uniaxially tested beams, but cannot predict the observed effects of out-of-plane biaxial loading on shallow-crack fracture toughness. A strain-based dual-parameter fracture toughness correlation (based on plastic zone width) performed acceptably when applied to the uniaxial and biaxial shallow-crack fracture toughness data.

  10. A fractographic study of iodine-induced stress corrosion cracking in irradiated Zircaloy-2 cladding

    NASA Astrophysics Data System (ADS)

    Shimada, Sachio; Nagai, Masayuki

    1983-02-01

    A fractographic interpretation of stress corrosion cracking (SCC) of Zircaloy-2 was made through detailed scanning electron microscope (SEM) examination of cladding tubes irradiated and subjected to internal pressurization SCC tests in an iodine environment. The SEM examination of the fracture surface revealed that both intergranular and transgranular fracture appeared in the regions of crack initiation. The W-type voids were observed in the intergranular fracture. As the crack proceeded, transgranular fracture, or cleavage facet, became predominant. Cleavage facets were separated by tearing ridges as well as by fluting marks. The appearance of tearing ridges is consistent with the increase of slip systems in α-zirconium with increasing temperature.

  11. Residual stress and crack initiation in laser clad composite layer with Co-based alloy and WC + NiCr

    NASA Astrophysics Data System (ADS)

    Lee, Changmin; Park, Hyungkwon; Yoo, Jaehong; Lee, Changhee; Woo, WanChuck; Park, Sunhong

    2015-08-01

    Although laser cladding process has been widely used to improve the wear and corrosion resistance, there are unwanted cracking issues during and/or after laser cladding. This study investigates the tendency of Co-based WC + NiCr composite layers to cracking during the laser cladding process. Residual stress distributions of the specimen are measured using neutron diffraction and elucidate the correlation between the residual stress and the cracking in three types of cylindrical specimens; (i) no cladding substrate only, (ii) cladding with 100% stellite#6, and (iii) cladding with 55% stellite#6 and 45% technolase40s. The microstructure of the clad layer was composed of Co-based dendrite and brittle eutectic phases at the dendritic boundaries. And WC particles were distributed on the matrix forming intermediate composition region by partial melting of the surface of particles. The overlaid specimen exhibited tensile residual stress, which was accumulated through the beads due to contraction of the coating layer generated by rapid solidification, while the non-clad specimen showed compressive. Also, the specimen overlaid with 55 wt% stellite#6 and 45 wt% technolase40s showed a tensile stress higher than the specimen overlaid with 100% stellite#6 possibly, due to the difference between thermal expansion coefficients of the matrix and WC particles. Such tensile stresses can be potential driving force to provide an easy crack path ways for large brittle fractures combined with the crack initiation sites such as the fractured WC particles, pores and solidification cracks. WC particles directly caused clad cracks by particle fracture under the tensile stress. The pores and solidification cracks also affected as initiation sites and provided an easy crack path ways for large brittle fractures.

  12. Evaluation of the resistance of irradiated zirconium-liner cladding to iodine-induced stress corrosion cracking

    NASA Astrophysics Data System (ADS)

    Shimada, Sachio; Nagai, Masayuki

    1983-02-01

    An evaluation was made of irradiated zirconium-liner cladding for its resistance to iodine-induced stress corrosion cracking (SCC). Emphasis was put on irradiation-induced hardening in zirconium and SCC resistance in zirconium-liner cladding as compared with Zircaloy-2 cladding. The Vickers microhardness test revealed that crystal bar zirconium experienced less hardening than Zircaloy-2 during neutron exposure. The SCC resistance of zirconium-liner cladding was evaluated for failure strains under the tube pressurization SCC test, and compared with the results of Zircaloy-2 cladding. The failure strains of zirconium-liner cladding were significantly larger than those of Zircaloy-2 cladding over all neutron fluence ranges examined, e.g., more than ten times at 1.0 × 10 21n/ cm2 ( E > 1 MeV). Judging from our results on the Vickers microhardness and SCC tests, good SCC resistance of zirconium-liner cladding could be expected even at high fluences.

  13. BWR pipe crack and weld clad overlay studies

    SciTech Connect

    Shack, W.J.; Kassner, T.F.; Maiya, P.S.; Park, J.Y.; Ruther, W.E.; Rybicki, E.F.

    1985-10-01

    This paper presents results on (a) the influence of simulated BWR environments and temperature on the intergranular-stress-corrosion cracking (IGSCC) susceptibility of sensitized stainless steels (SS), (b) the stress-corrosion susceptibility of alternative piping materials, (c) analysis of field components to assess the effectiveness of in-service inspection techniques and the in-reactor performance of weld overlay repairs, and (d) finite-element analyses and experimental measurement of residual stresses in weldments with weld overlays. Fracture-mechanics crack-growth data are presented to confirm correlations between the critical corrosion potentials required to inhibit IGSCC and the level of impurities in the environment. Slow-strain-rate tests show that very low levels of impurities (25 ppb of sulfate) can produce suseptibility to transgranular-stress-corrosion cracking (TGSCC) in Type 316NG SS and that nitrogen levels is SS above 0.1 wt. % appear to increase susceptibility to TGSCC. Preliminary results on a German Type 347NG SS suggest that it is at least as resistant to TGSCC in impurity environments as Type 316NG SS. Measurements on overlay weldments removed from the Hatch-2 reactor confirm that compressive residual stresses are produced on the inner surface of the weldments by the overlay.

  14. Influence of texture on iodine-induced stress corrosion cracking of Zircaloy-4 cladding tubes

    NASA Astrophysics Data System (ADS)

    Schuster, I.; Lemaignan, C.

    1992-07-01

    A specific study was carried out to measure the influence of texture on the behaviour of Zircaloy-4 under iodine-induced stress corrosion cracking. The aim was to determine the relative effects of various metallurgical parameters involved in fuel rod fracture by pellet-clad interaction (PCI). Cladding tubes of different geometries were manufactured from a given Zircaloy-4 ingot. In this way tubes with different textures were obtained. Rings from these tubes were then subjected to slow tensile tests in an inert atmosphere and in an iodine vapour atmosphere. The sensitivity of the tubes to stress corrosion cracking is quantified by the loss of ductility on fracture between the tests in each atmosphere. Combined with the findings of other studies, the results showed that: (a) texture has a strong effect on the stress corrosion cracking behaviour of Zircaloy-4, (b) the mechanical properties do not have any bearing on the material behaviour under stress corrosion cracking, and that the better behaviour of a recrystallized material — compared to the same material in a stress-relieved state — can be explained solely by the texture effect, (c) texture is a more important parameter than chemical composition of Zircaloy-4, on condition that this composition remains within the ASTM specification. The conflict between the various mechanisms involved in stress corrosion crack propagation may explain these observations. Preliminary extrapolation of these conclusions to the irradiated material shows that a more specific study is needed using appropriate parameters.

  15. Stress corrosion cracking of zirconium cladding tubes: IV. Effect of hydrogen saturation

    NASA Astrophysics Data System (ADS)

    Rozhnov, A. B.; Nikulin, S. A.; Khanzhin, V. G.; Belov, V. A.

    2011-04-01

    The effect of hydrogen saturation on the stress corrosion cracking (SCC) resistance of zirconium cladding tubes in an iodine-containing medium is studied. Comparative SCC tests are performed for tubes produced from E110 and E635 alloys with various hydrogen contents (up to 400 ppm). Hydrogen is shown to decrease the SCC resistance of the tubes predominantly because of the activation of pitting formation processes.

  16. Corrosion fatigue crack growth in clad low-alloy steels: Part 1, medium-sulfur forging steel

    SciTech Connect

    James, L.A.; Poskie, T.J.; Auten, T.A; Cullen, W.H.

    1996-04-01

    Corrosion fatigue crack propagation tests were conducted on a medium- sulfur ASTM A508-2 forging steel overlaid with weld-deposited Alloy EN82H cladding. The specimens featured semi-elliptical surface cracks penetrating approximately 6.3 mm of cladding into the underlying steel. The initial crack sizes were relatively large with surface lengths of 30.3--38.3 mm, and depths of 13.1--16.8 mm. The experiments were conducted in a quasi-stagnant low-oxygen (O{sub 2} < 10 ppb) aqueous environment at 243{degrees}C, under loading conditions ({Delta}K, R, and cyclic frequency) conductive to environmentally-assisted cracking (EAC) in higher-sulfur steels under quasi-stagnant conditions. Earlier experiments on unclad compact tension specimens of this heat of steel did not exhibit EAC, and the present experiments on semi-elliptical surface cracks penetrating cladding also did not exhibit EAC.

  17. Crack Free Tungsten Carbide Reinforced Ni(Cr) Layers obtained by Laser Cladding

    NASA Astrophysics Data System (ADS)

    Amado, J. M.; Tobar, M. J.; Yáñez, A.; Amigó, V.; Candel, J. J.

    The development of hardfacing coatings has become technologically significant in many industries A common approach is the production of metal matrix composites (MMC) layers. In this work NiCr-WC MMC hardfacing layers are deposited on C25 steel by means of laser cladding. Spheroidal fused tungsten carbides is used as reinforcement phase. Three different NiCr alloys with different Cr content were tested. Optimum conditions to obtain dense, uniform carbide distribution and hardness close to nominal values were defined. The effect of Cr content respect to the microstructure, susceptibility for cracking and the wear rate of the resulting coating will also be discussed.

  18. Microstructure Instability of Candidate Fuel Cladding Alloys: Corrosion and Stress Corrosion Cracking Implications

    NASA Astrophysics Data System (ADS)

    Jiao, Yinan; Zheng, Wenyue; Guzonas, David; Kish, Joseph

    2016-02-01

    This paper addresses some of the overarching aspects of microstructure instability expected from both high temperature and radiation exposure that could affect the corrosion and stress corrosion cracking (SCC) resistance of the candidate austenitic Fe-Cr-Ni alloys being considered for the fuel cladding of the Canadian supercritical water-cooled reactor (SCWR) concept. An overview of the microstructure instability expected by both exposures is presented prior to turning the focus onto the implications of such instability on the corrosion and SCC resistance. Results from testing conducted using pre-treated (thermally-aged) Type 310S stainless steel to shed some light on this important issue are included to help identify the outstanding corrosion resistance assessment needs.

  19. A simple computer model of pellet/cladding interaction including stress corrosion cracking

    SciTech Connect

    Yaung, J.Y.; Okrent, D.; Wazzan, A.R.

    1985-12-01

    Many unexpected failures, below design criteria, of light water reactor fuel cladding (Zircaloy) have been found during operational power ramps. Such a fuel rod failure can result from pellet/cladding mechanical interaction (PCMI) assisted by fission product stress corrosion cracking (SCC) of the Zircaloy tubing. A deterministic PCMI/SCC model has been coupled with the steady-state fuel behavior code, FRAPCON-2. The resulting code has been benchmarked (against few test cases but comprising many data points) but not fully verified. It is used to simulate two important occurrences: preramp (base) and power ramp irradiation. Because of the limitations of FRAPCON-2, the code is best suited to the simulation of mild power ramps with rates that do not exceed 0.02%/s. Computations with the code for greater power ramp rates, however, gave results which are not inconsistent with some overpower ramp experimental test results. Limited sensitivity studies are performed on the operational parameters and some fuel rod design parameters.

  20. Effect of crack length-to-width ratio on crack resistance of high Cr-ODS steels at high temperature for fuel cladding application

    NASA Astrophysics Data System (ADS)

    Chaouadi, R.; Ramesh, M.; Gavrilov, S.

    2013-11-01

    Oxide dispersion strengthened (ODS) steels with high Cr-content are extensively investigated in Europe, Japan and United States by the nuclear materials community for application to both advanced fission reactors and fusion systems. In comparison to standard high Cr-steels, the expected operation temperature range can be extended to 650 °C or more because of their improved creep resistance. However, their crack resistance behavior in the high temperature range was less investigated.The aim of the present paper is to provide some insight on their fracture behavior at high temperature and different crack configurations, in particular shallow crack. Crack resistance measurements were performed on a 12%Cr-ODS steel using compact tension specimens at 650 °C considering both shallow and deep crack configurations. Finite element calculations were performed on a typical fuel cladding tube geometry to assess the performances in terms of crack resistance. It is found that the temperature gradient across the wall should be maintained low enough to avoid cracking. After irradiation in corrosive environment, the boundary conditions might be further affected limiting therefore the lifetime of ODS cladding.

  1. Modelling pellet-clad mechanical interaction during extended reduced power operation in bonded nuclear fuel

    NASA Astrophysics Data System (ADS)

    Haynes, T. A.; Ball, J. A.; Shea, J. H.; Wenman, M. R.

    2015-10-01

    A 2D-rӨ model of pellet-clad mechanical interaction in advanced gas-cooled reactor fuel is presented. An incipient 5 μm crack is introduced into the inner surface of cladding bonded to a detachable sliver of fuel. Micro-cracking in the sliver is accounted for through a reduced elastic modulus. A test transient consisting of a hold at 70% power for 720 h was applied to the model. The competing effects of the closure of pellet cracks due to irradiation creep in inner regions of the pellet during extended low power operation, and that of thermal creep in the cladding whilst at reduced power alleviating this are investigated. In colder elements, the effect of irradiation creep dominates. In hotter elements, the effect of cladding creep at low power dominates. It was found that adjusting factors related to the pellet shape were unimportant; the sliver thickness, sliver shape and initial pellet crack width had only a small effect upon the extent of PCMI. Adjusting factors relating to the shape of the incipient crack such as the crack radius and depth had a significant effect; as did adjusting the elastic modulus reduction factor accounting for ladder cracking in the sliver and the coefficient of friction used throughout the model. The resulting model was able to predict the trend in average clad bore crack depth with axial position in the core observed in post irradiation examination.

  2. Initial Cladding Condition

    SciTech Connect

    E. Siegmann

    2000-08-22

    The purpose of this analysis is to describe the condition of commercial Zircaloy clad fuel as it is received at the Yucca Mountain Project (YMP) site. Most commercial nuclear fuel is encased in Zircaloy cladding. This analysis is developed to describe cladding degradation from the expected failure modes. This includes reactor operation impacts including incipient failures, potential degradation after reactor operation during spent fuel storage in pool and dry storage and impacts due to transportation. Degradation modes include cladding creep, and delayed hydride cracking during dry storage and transportation. Mechanical stresses from fuel handling and transportation vibrations are also included. This Analysis and Model Report (AMR) does not address any potential damage to assemblies that might occur at the YMP surface facilities. Ranges and uncertainties have been defined. This analysis will be the initial boundary condition for the analysis of cladding degradation inside the repository. In accordance with AP-2.13Q, ''Technical Product Development Planning'', a work plan (CRWMS M&O 2000c) was developed, issued, and utilized in the preparation of this document. There are constraints, caveats and limitations to this analysis. This cladding degradation analysis is based on commercial Pressurized Water Reactor (PWR) fuel with Zircaloy cladding but is applicable to Boiling Water Reactor (BWR) fuel. Reactor operating experience for both PWRs and BWRs is used to establish fuel reliability from reactor operation. It is limited to fuel exposed to normal operation and anticipated operational occurrences (i.e. events which are anticipated to occur within a reactor lifetime), and not to fuel that has been exposed to severe accidents. Fuel burnup projections have been limited to the current commercial reactor licensing environment with restrictions on fuel enrichment, oxide coating thickness and rod plenum pressures. The information provided in this analysis will be used in

  3. Iodine-stress corrosion cracking of Zircaloy-2 cladding under near plane strain and localized stress-strain conditions

    SciTech Connect

    Nobrega, B.N.

    1984-01-01

    The segmented expanding mandrel test (SEMT) method is generally regarded as a good laboratory simulator of pellet-cladding interactions (PCI) in LWR fuel rods. Yet it does not reproduce the low strain failures in Zircaloy cladding typical of PCI-failed fuel elements and commonly observed in other types of laboratory specimens. This investigation addressed this apparent inconsistency. Iodine-stress corrosion cracking (I-SCC) of cold worked, unirradiated Zircaloy-2 cladding was induced in three different types of tubing specimens (known as regular, thin-wall, and chamfered) in a modified SEMT apparatus designed to test mechanical conditions that could lead to slow strain failures. Only the chamfered sample, which has been shown to be subjected to more nearly plane strain conditions than either of the other two specimen types, failed consistently at low (0.8%) total diametral strains in good agreement with in-reactor failure data. Such conditions were numerically and experimentally quantified by means of finite element calculational models and local strain measurements. The numerical analyses and strain measurements provide valuable insight into the PCI simulating power of the segmented expanding mandrel test and its experimental limitations. Failure-strain results for chamfered barrier claddings were obtained and compared with available literature data. The improved I-SCC resistance of this type of cladding was confirmed but the failure strains were significantly lower than reported for regular barrier tubes.

  4. Corrosion fatigue crack growth in clad low-alloy steel. Part 2, Water flow rate effects in high sulfur plate steel

    SciTech Connect

    James, L.A; Lee, H.B.; Wire, G.L.; Novak, S.R.; Cullen, W.H.

    1996-04-01

    Corrosion fatigue crack propagation tests were conducted on a high- sulfur ASTM A302-B plate steel overlaid with weld-deposited Alloy EN82H cladding. The specimens featured semi-elliptical surface cracks penetrating approximately 6.3 mm of cladding into the underlying steel. The initial crack sizes were relatively large with surface lengths of 22.8--27.3 mm, and depths of 10.5--14.1 mm. The experiments were initiated in a quasi-stagnant low-oxygen (O{sub 2} < 10 ppb) aqueous environment at 243{degrees}C, under loading conditions ({Delta}K, R, cyclic frequency) conducive to environmentally-assisted cracking (EAC) under quasi-stagnant conditions. Following fatigue testing under quasi-stagnant conditions where EAC was observed, the specimens were then fatigue tested under conditions where active water flow of either 1.7 m/sec. or 4.7 m/sec. was applied parallel to the crack. Earlier experiments on unclad surface-cracked specimens of the same steel exhibited EAC under quasi- stagnant conditions, but water flow rates at 1.7 m/sec. and 5.0 m/sec. parallel to the crack mitigated EAC. In the present experiments on clad specimens, water flow at approximately the same as the lower of these velocities did not mitigate EAC, and a free stream velocity approximately the same as the higher of these velocities resulted in sluggish mitigation of EAC. The lack of robust EAC mitigation was attributed to the greater crack surface roughness in the cladding interfering with flow induced within the crack cavity. An analysis employing the computational fluid dynamics code, FIDAP, confirmed that frictional forces associated with the cladding crack surface roughness reduced the interaction between the free stream and the crack cavity.

  5. Microstructural study of the interface in laser-clad Ni-Al bronze on Al alloy AA333 and its relation to cracking

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Mazumder, J.; Shibata, K.

    1995-06-01

    The interface toughness between a laser clad and the substrate determines whether the cladding is useful for engineering application. The objective of this investigation is to correlate the interface properties of laser-clad Ni-AI bronze on Al alloy AA333 with the microstructure and crystal structure of the interface. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) combined with energy-dispersive X-ray spectroscopy (EDX) are used to examine the interface. In a good clad track, the interface is an irregular curved zone with a varying width (occasionally keyholing structure) from 30 to 150 μm. A compositional transition from the Cu-rich clad (83 wt pct Cu) to the Al-rich substrate (3.2 wt pct Cu) occurs across this interface. Three phases in the interface are identified in TEM: Al solid solution, θ phase, and γ1 phase, as described in the Cu-Al binary phase diagram. In a good clad track, the θ and γ1 phases are distributed in the Al solid solution. In a clad track with cracks, the interface structure spreads to a much larger scale from 300 μm to the whole clad region. Large areas of θ and γ1 phases are observed. The mechanism of cracking at the interface is related to the formation of a twophase region of θ and γ1 phases. To understand the microstructure, a nonequilibrium quasibinary Cu-Al phase diagram is proposed and compared with the equilibrium binary Cu-Al phase diagram. It is found that the occurrence of many phases such as η1η2, ζ1, ζ2, ɛ1, ɛ2, γ0, β0, and β, as described in the equilibrium binary Cu-Al phase diagram, is suppressed by either the cladding process or by the alloying elements. The three identified phases (Al solid solution, θ phase, and γ1, phase) showed significant extension of solubility.

  6. Temperature dependences of the delayed hydride cracking rate of fuel claddings made of zirconium alloys of various compositions

    NASA Astrophysics Data System (ADS)

    Markelov, V. A.; Gusev, A. Yu.; Kotov, P. V.; Novikov, V. V.; Saburov, N. S.

    2014-04-01

    The temperature dependences of the delayed hydride cracking (DHC) rate of Zr-1Nb and Zr-0.8Nb-0.8Sn-0.3Fe alloy claddings are studied in the range 127-300°C in comparison with the data obtained for Zr-2.5Nb and Zircaloy-4 alloys earlier. The samples are in the state of cold deformation and stress relief at 400°C for 24 h and in the state of preliminary hydrogen saturation to a hydrogen concentration of 0.02 wt %. As the strength of a zirconium alloy decreases and its ductility increases, the DHC rate and its high-temperature limit for a linear Arrhenius equation decreases, and the fractographic patterns of the fracture surfaces are different.

  7. Fracture behavior and microstructural characteristics of irradiated Zircaloy cladding

    SciTech Connect

    Chung, H.M.; Yaggee, F.L.; Kassner, T.F.

    1985-06-01

    Zircaloy cladding tube specimens from commercial power reactor fuel assemblies (burnup >22 MWd/kgU) have been deformed to fracture at 325/sup 0/C by either the internal gas-pressurization or the expanding-mandrel technique in a helium or argon environment containing no fission product species (e.g., I, Cs, or Cd). The fracture surfaces of 11 irradiated specimens fractured by internal gas pressurization were examined by scanning electron microscopy, and 7 specimens were found to contain various degrees of the pseudocleavage feature that is characteristic of pellet-cladding interaction failures. Out of 10 test specimens fractured by expanding-mandrel loading, 5 were found to contain regions of pseudocleavage on the fracture surfaces. The specimens exhibited ''X-marks'' on the outer surface and brittle incipient cracks distributed on the inner surface, which are also characteristic of pellet-cladding interaction failures.

  8. Jets of incipient liquids

    NASA Astrophysics Data System (ADS)

    Reshetnikov, A. V.; Mazheiko, N. A.; Skripov, V. P.

    2000-05-01

    Jets of incipient water escaping into the atmosphere through a short channel are photographed. In some experiments. complete disintegration of the jet is observed. The relationship of this phenomenon with intense volume incipience is considered. The role of the Coanda effect upon complete opening of the jet is revealed. Measurement results of the recoil force R of the jets of incipient liquids are presented. Cases of negative thrust caused by the Coanda effect are noted. Generalization of experimental data is proposed.

  9. Laser Cladding

    NASA Astrophysics Data System (ADS)

    Lepski, Dietrich; Brückner, Frank

    Laser cladding is a modern technology whose uses include, for example, the creation of protective coatings to reduce wear and corrosion on engine parts and tools. The aircraft and automotive industries are examples of industries in which it is much used. This account considers the theory of a number of aspects of the process in detail. The first to be studied is the interaction of the laser beam directly with the powder that is being deposited; the effects of gravity, beam shadowing, and particle heating are investigated. This is followed by a discussion of the mechanisms by which the particles adhere to the surface of the work piece and are absorbed into it. In order to understand the process, a study of the melt pool and the associated temperature distribution is necessary; it is then possible to infer the final bead geometry. An inevitable consequence of a thermal process such as laser cladding is the induced thermal stress and resulting distortion of the work piece. The fundamentals are discussed, a numerical model presented and in addition a simple heuristic model is given. The use of induction-assisted laser cladding as a means of preventing the formation of cracks is discussed.

  10. Crack

    MedlinePlus

    ... sound the drug makes as it heats up. Short-Term Effects Crack is a stimulant that is absorbed through ... quickly, after about 5 or 10 minutes. Other short-term effects include: higher heart rate, breathing rate, blood pressure , ...

  11. Progress in the Research Programs to Elucidate Axial Cracking Fuel Failure at High Burnup

    SciTech Connect

    Ogata, Keizo; Aomi, Masaki; Baba, Toshikazu; Kamimura, Katsuichiro; Etoh, Yoshinori; Ito, Kunio; Kido, Toshiya; Teshima, Hideyuki

    2007-07-01

    A fuel failure with an axial crack starting outside the cladding and penetrating inwards was experienced by high burnup BWR fuel rods in power ramp test. On the other hand, no fuel failure caused by power ramp test has been currently reported on PWR fuel rods at burnups higher than 50 GWd/t. Extensive research programs regarding hydrogen behaviors and mechanical performances on irradiated BWR and PWR fuel claddings have been carried out to clarify the mechanism of the axial cracking and to quantify the conditions to cause fuel failure. Hydrogen solid solubility measurement on irradiated Zircaloy-2 materials showed almost comparable results to those on unirradiated ones. Hydride re-distribution and re-orientation behaviors were tested by heating irradiated BWR claddings with Zr-liner under the conditions of applied radial heat flux (temperature gradient) and circumferential stress. Mechanical performances of BWR claddings were evaluated mainly by the internal pressurizing tests. Internal pressurization tests applying various pressurizing sequences, e.g. stepwise increase in pressure with holding intervals, were also conducted to simulate crack propagation behaviors. Some specimens demonstrated characteristic fracture surfaces similar to those observed on the failed fuel rods after the power ramp. Mechanical performances of irradiated PWR claddings were tested at temperatures of 573 to 723 K. Metallographic examination after tensile tests revealed a large number of incipient cracks within the region of cladding outer rim where a concentrated hydride layer (hydride rim) has been formed during irradiation. Crack propagation test using an expanding mandrel device demonstrated the crack propagation at 573 K but no propagation at 658 K. (authors)

  12. Reactor vessel cladding separate effects studies

    SciTech Connect

    Corwin, W.R.

    1985-01-01

    The existence of a layer of tough weld overlay cladding on the interior of a light-water reactor pressure vessel could mitigate damage caused during certain overcooling transients. The potential benefit of the cladding is that it could keep a short surface flaw, which would otherwise become long, from growing either by impeding crack initiation or by arresting a running crack. Two aspects critical to cladding behavior will be reported: irradiation effects on cladding toughness and the response of mechanically loaded, flawed structures in the presence of cladding. 15 refs., 24 figs., 6 tabs.

  13. Incipient fire detection system

    DOEpatents

    Brooks, Jr., William K.

    1999-01-01

    A method and apparatus for an incipient fire detection system that receives gaseous samples and measures the light absorption spectrum of the mixture of gases evolving from heated combustibles includes a detector for receiving gaseous samples and subjecting the samples to spectroscopy and determining wavelengths of absorption of the gaseous samples. The wavelengths of absorption of the gaseous samples are compared to predetermined absorption wavelengths. A warning signal is generated whenever the wavelengths of absorption of the gaseous samples correspond to the predetermined absorption wavelengths. The method includes receiving gaseous samples, subjecting the samples to light spectroscopy, determining wavelengths of absorption of the gaseous samples, comparing the wavelengths of absorption of the gaseous samples to predetermined absorption wavelengths and generating a warning signal whenever the wavelengths of absorption of the gaseous samples correspond to the predetermined absorption wavelengths. In an alternate embodiment, the apparatus includes a series of channels fluidically connected to a plurality of remote locations. A pump is connected to the channels for drawing gaseous samples into the channels. A detector is connected to the channels for receiving the drawn gaseous samples and subjecting the samples to spectroscopy. The wavelengths of absorption are determined and compared to predetermined absorption wavelengths is provided. A warning signal is generated whenever the wavelengths correspond.

  14. Computational model for residual stresses in a clad plate and clad fracture specimens

    SciTech Connect

    Rybicki, E.F.; Stonesifer, R.B.

    1986-10-01

    This report contains the results from computed residual stresses for three stainless steel clad plate configurations. Each simulates a condition of interest to a study on the effect of surface cracks in the clad layer of reactor pressure vessels. The configurations analyzed were the as-received 118-mm thick clad plate, a 32-mm thick specimen with a full-thickness of cladding weld metal, and a 32-mm thick specimen with a half-thickness of clad layer. The most accurate predictions of the available experimental results were made using the properties of 19Cr-9Ni-Mo-W material. The analytical model assumes that the stresses at the initial condition of 538/sup 0/C for the stress relief anneal are zero. Plastic strains develop during cooling and all subsequent conditions such as machining or temperature changes cause the cladding residual stresses to decrease. In parting-out of specimens from the initial 118-mm thick clad plate, the resulting residual stresses in the clad layer depend upon the sequence of metal removal. If excess base metal is removed first and then somes cladding subsequently removed, the residual stresses in the clad layer are significantly reduced. On the other hand, partial removal of cladding first results in additional plastic deformation in the clad layer and the retention of residual stresses near the material yield strength at the completion of the machining operation.

  15. Further Study of near Solidus Intergranular Cracking in Inconel 718

    NASA Technical Reports Server (NTRS)

    Thompson, R. G.

    1981-01-01

    A series of tests, performed to determine the strain necessary to initiate intergranular cracking in Inconel 718 as a function of temperature, contained enough scatter near the melting temperature that questions remained as to the best curve of curves to fit to the data. Fracture surface analysis showed that the scatter was due to incipient melting in the grain boundary region. The melting contributed to low fracture strain but had only a small on the incipient cracking strain. Gleeble tests, which could be interrupted by water quenching, were used to study the incipient intergranular melting of Inconel 718. This modified weld simulation test provided a sufficiently rapid quench to preserve the intergranular microstructure created during incipient melting. This structure was studied both microscopically and with energy dispensive X-ray analysis. The implications of incipient melting and low-strain incipient cracking on the development of microfissuring envelopes are discussed.

  16. Rock strength reductions during incipient weathering

    NASA Astrophysics Data System (ADS)

    Kelly, P. J.; Anderson, S. P.; Blum, A.

    2012-12-01

    Patrick Kelly, Suzanne Anderson, Alex Blum In rock below the surface, temperature swings are damped, water flow is limited, and biota are few. Yet rock weathers, presumably driven by these environmental parameters. We use rock strength as an indicator of rock weathering in Gordon Gulch in the Boulder Creek Critical Zone Observatory, a watershed at 2500 m underlain by Proterozoic gneiss intruded by the Boulder Creek granodiorite. Fresh rock is found at depths of 8-30 m in this area, and the thickness of the weathered rock zone imaged with shallow seismic refraction is greater on N-facing slopes than S-facing slopes (Befus et al., 2011, Vadose Zone J.). We use the Brazilian splitting test to determine tensile strength of cores collected with a portable drilling rig. Spatial variations in rock strength that we measure in the top 2 m of the weathered rock mantle can be connected to two specific environmental variables: slope aspect and the presence of a soil mantle. We find weaker rock on N-facing slopes and under soil. There is no clear correlation between rock strength and the degree of chemical alteration in these minimally weathered rocks. Denudation rates of 20-30 microns/yr imply residence times of 105-106 years within the weathered rock layers of the critical zone. Given these timescales, rock weathering is more likely to have occurred under glacial climate conditions, when periglacial processes prevailed in this non-glaciated watershed. Incipient weathering of rock appears to be controlled by water and frost cracking in Gordon Gulch. Water is more effectively delivered to the subsurface on N-facing slopes, and is more likely held against rock surfaces under soil than on outcrops. These moisture conditions, and the lower surface temperatures that prevail on N-facing slopes also favor frost cracking as an important weathering process.

  17. A Probabilistic-Micro-mechanical Methodology for Assessing Zirconium Alloy Cladding Failure

    SciTech Connect

    Pan, Y.M.; Chan, K.S.; Riha, D.S.

    2007-07-01

    Cladding failure of fuel rods caused by hydride-induced embrittlement is a reliability concern for spent nuclear fuel after extended burnup. Uncertainties in the cladding temperature, cladding stress, oxide layer thickness, and the critical stress value for hydride reorientation preclude an assessment of the cladding failure risk. A set of micro-mechanical models for treating oxide cracking, blister cracking, delayed hydride cracking, and cladding fracture was developed and incorporated in a computer model. Results obtained from the preliminary model calculations indicate that at temperatures below a critical temperature of 318.5 deg. C [605.3 deg. F], the time to failure by delayed hydride cracking in Zr-2.5%Nb decreased with increasing cladding temperature. The overall goal of this project is to develop a probabilistic-micro-mechanical methodology for assessing the probability of hydride-induced failure in Zircaloy cladding and thereby establish performance criteria. (authors)

  18. Nuclear fuel elements having a composite cladding

    DOEpatents

    Gordon, Gerald M.; Cowan, II, Robert L.; Davies, John H.

    1983-09-20

    An improved nuclear fuel element is disclosed for use in the core of nuclear reactors. The improved nuclear fuel element has a composite cladding of an outer portion forming a substrate having on the inside surface a metal layer selected from the group consisting of copper, nickel, iron and alloys of the foregoing with a gap between the composite cladding and the core of nuclear fuel. The nuclear fuel element comprises a container of the elongated composite cladding, a central core of a body of nuclear fuel material disposed in and partially filling the container and forming an internal cavity in the container, an enclosure integrally secured and sealed at each end of said container and a nuclear fuel material retaining means positioned in the cavity. The metal layer of the composite cladding prevents perforations or failures in the cladding substrate from stress corrosion cracking or from fuel pellet-cladding interaction or both. The substrate of the composite cladding is selected from conventional cladding materials and preferably is a zirconium alloy.

  19. A specimen and method for evaluating the effect of cladding on the behavior of subclad flaws

    SciTech Connect

    McAfee, W.J.; Bryson, J.W.; Cheverton, R.D.; Robinson, G.C.

    1991-01-01

    A specimen that reveals important fracture-related properties of cladding in the presence of a subclad flaw is under development at the Oak Ridge National Laboratory (ORNL). Information developed from testing these specimens, referred to as Jo-Blocks, is being used by the Heavy-Section Steel Technology (HSST) Program in evaluating the behavior of subclad flaws in Pressurized Water Reactors (PWR) pressure vessels during pressurized-thermal-shock (PTS) loading conditions. The cladding can be idealized as a force that holds an otherwise surface flaw closed'' at the surface, reducing the stress intensity factor along the portion of the crack front in the base material. This closing force is approximately equal to the average stress in the cladding, which for postulated severe PTS transients is at yield, multiplied by the cladding thickness. There is a critical amount of stretching of the cladding that results in through-clad flaw propagation, i.e., cladding failure, thus converting the subclad flaw to a surface flaw. The Jo-Block specimen consists of two steel (base metal) blocks with ends butted together to form a crack'' and with opposite edges clad so that the crack terminates at the two fusion zones. Testing of Jo-Block specimens reveals as a minimum the effective yield point'' of the cladding, in the presence of a subclad crack, and the critical value of clad stretching (crack opening displacement). 15 refs., 10 figs.

  20. Weakening inside incipient thrust fault

    NASA Astrophysics Data System (ADS)

    Lacroix, B.; Tesei, T.; Collettini, C.; Oliot, E.

    2013-12-01

    In fold-and-thrust belts, shortening is mainly accommodated by thrust faults that nucleate along décollement levels. Geological and geophysical evidence suggests that these faults might be weak because of a combination of processes such as pressure-solution, phyllosilicates reorientation and delamination, and fluid pressurization. In this study we aim to decipher the processes and the kinetics responsible for weakening of tectonic décollements. We studied the Millaris thrust (Southern Pyrenees): a fault representative of a décollement in its incipient stage. This fault accommodated a total shortening of about 30 meters and is constituted by a 10m thick, intensively foliated phyllonite developed inside a homogeneous marly unit. Detailed chemical and mineralogical analyses have been carried out to characterize the mineralogical change, the chemical transfers and volume change in the fault zone compared to non-deformed parent sediments. We also carried out microstructural analysis on natural and experimentally deformed rocks. Illite and chlorite are the main hydrous minerals. Inside fault zone, illite minerals are oriented along the schistosity whereas chlorite coats the shear surfaces. Mass balance calculations demonstrated a volume loss of up to 50% for calcite inside fault zone (and therefore a relative increase of phyllosilicates contents) because of calcite pressure solution mechanisms. We performed friction experiments in a biaxial deformation apparatus using intact rocks sheared in the in-situ geometry from the Millaris fault and its host sediments. We imposed a range of normal stresses (10 to 50 MPa), sliding velocity steps (3-100 μm/s) and slide-hold slide sequences (3 to 1000 s hold) under saturated conditions. Mechanical results demonstrate that both fault rocks and parent sediments are weaker than average geological materials (friction μ<<0.6) and have velocity-strengthening behavior because of the presence of phyllosilicate horizons. Fault rocks are

  1. Predicting and Preventing Incipient Flameout in Combustors

    NASA Technical Reports Server (NTRS)

    Puster, Richard Lee

    2003-01-01

    A method of predicting and preventing incipient flameout in a combustor has been proposed. The method should be applicable to a variety of liquid- and gas-fueled combustors in furnaces and turbine engines. Until now, there have been methods of detecting flameouts after they have occurred, but there has been no way of predicting incipient flameouts and, hence, no way of acting in time to prevent them. Prevention of flameout could not only prevent damage to equipment but, in the case of aircraft turbine engines, could also save lives.

  2. HIP clad nickel base Alloy 625 for deep sour wells

    SciTech Connect

    Uhl, W.K.; Pendley, M.R.

    1984-05-01

    The hot isostatic pressing (HIP) process was used to clad nickel base Alloy 625 to AISI 4130 low alloy steel. The performance of the HIP clad material in the corrosive environment characteristic of deep, sour oil and gas wells was evaluated in laboratory tests. Included in the test program were NACE TM-01-77 sulfide stress cracking tests, chloride stress corrosion cracking tests in boiling MgCl /SUB 2'/ , and pitting and crevice corrosion tests. The HIP clad 625 performed excellently, displaying essentially the same corrosion resistance as wrought 625. Specifically the HIP clad 625 resisted sulfide stress cracking at applied stresses as high as 120% of yield strength and resisted chloride stress corrosion cracking at stresses exceeding 100% of yield. The HIP clad 625 also displayed immunity to pitting and crevice corrosion, with corrosion rates of <0.025 mm/y (1 mil/y). The 4130 base metal, however, was attacked severly in all tests. SEM/EDX analysis of the 625/4130 interface demonstrated that dilution of the cladding by the base metal was essentially eliminated.

  3. Fracture analysis of full-thickness clad beam specimens

    SciTech Connect

    Keeney, J.A.; Bass, B.R.; McAfee, W.J.

    1997-12-01

    Finite-element analyses were performed on full-thickness clad beam specimens to quantify fracture toughness for shallow cracks in material for which metallurgical conditions are prototypic of those found in reactor pressure vessels (RPVs). The beam specimens are fabricated from a section of an RPV wall (removed from a canceled nuclear plant) that includes weld, plate, and clad material with metallurgical factors potentially influencing fracture toughness for shallow cracks. A summary of the testing program is provided and the analyses of the test data are discussed, including comparisons of measured displacements with finite-element analysis results, applications of toughness estimation techniques, and interpretations of constraint conditions implied by stress-based constraint methodologies. Fracture toughness estimates were obtained from displacement data using finite-element techniques and estimation schemes based on the {eta}-factor method. The J-Q methodology was used to assess crack-tip stress triaxiality in the clad beam specimens. The shallow-crack clad beam specimens showed a significant loss of constraint similar to that of other shallow-crack single-edge notch bend specimens. The stress-based Dodds-Anderson scaling model was also utilized to analyze constraint conditions in the clad beam specimens and appears to be effective in adjusting the test data to account for loss of in-plane constraint for uniaxially tested beams.

  4. Weld overlay cladding with iron aluminides

    SciTech Connect

    Goodwin, G.M.

    1995-08-01

    The hot and cold cracking tendencies of some early iron aluminide alloy compositions have limited their use in applications where good weldability is required. Using hot crack testing techniques invented at ORNL, and experimental determinations of preheat and postweld heat treatment needed to avoid cold cracking, we have developed iron aluminide filler metal compositions which can be successfully used to weld overlay clad various substrate materials, including 9Cr-1Mo steel, 2-1/4Cr-1Mo steel, and 300-series austenitic stainless steels. Dilution must be carefully controlled to avoid crack-sensitive deposit compositions. The technique used to produce the current filler metal compositions is aspiration-casting, i.e. drawing the liquid from the melt into glass rods. Future development efforts will involve fabrication of composite wires of similar compositions to permit mechanized gas tungsten arc (GTA) and/or gas metal arc (GMA) welding.

  5. HYDRIDE-RELATED DEGRADATION OF SNF CLADDING UNDER REPOSITORY CONDITIONS

    SciTech Connect

    K. McCoy

    2000-12-12

    The purpose and scope of this analysis/model report is to analyze the degradation of commercial spent nuclear fuel (CSNF) cladding under repository conditions by the hydride-related metallurgical processes, such as delayed hydride cracking (DHC), hydride reorientation and hydrogen embrittlement, thereby providing a better understanding of the degradation process and clarifying which aspects of the process are known and which need further evaluation and investigation. The intended use is as an input to a more general analysis of cladding degradation.

  6. Electroslag Strip Cladding of Steam Generators With Alloy 690

    SciTech Connect

    Consonni, M.; Maggioni, F.; Brioschi, F.

    2006-07-01

    The present paper details the results of electroslag cladding and tube-to-tubesheet welding qualification tests conducted by Ansaldo-Camozzi ESC with Alloy 690 (Alloy 52 filler metal) on steel for nuclear power stations' steam generators shell, tubesheet and head; the possibility of submerged arc cladding on first layer was also considered. Test results, in terms of chemical analysis, mechanical properties and microstructure are reproducible and confidently applicable to production cladding and show that electroslag process can be used for Alloy 52 cladding with exceptionally stable and regular operation and high productivity. The application of submerged arc cladding process to the first layer leads to a higher base metal dilution, which should be avoided. Moreover, though the heat affected zone is deeper with electroslag cladding, in both cases no coarsened grain zone is found due to recrystallization effect of second cladding layer. Finally, the application of electroslag process to cladding of Alloy 52 with modified chemical composition, was proved to be highly beneficial as it strongly reduces hot cracking sensitivity, which is typical of submerged arc cladded Alloy 52, both during tube-to-tubesheet welding and first re-welding. (authors)

  7. Development and characterisations of WC–12Co microwave clad

    SciTech Connect

    Zafar, Sunny Sharma, Apurbba Kumar

    2014-10-15

    In the present work, WC–12Co based cermet clad was developed on AISI 304 stainless steel using microwave hybrid heating technique. The experimental trials were carried out in a 1.4 kW industrial multimode microwave applicator. The paper explains the major events occurring during microwave irradiation and formation of clad. The developed clads were subsequently characterised through field emission scanning electron microscopy equipped with energy dispersive X-ray spectroscopy, X-ray diffraction, assessment of porosity and microhardness. The WC–12Co clads developed with an approximate thickness of 1 mm, illustrated excellent metallurgical bonding with substrate. The microstructure of the WC–12Co clad mainly consists of skeleton structured carbides embedded in tough metallic phase. The phase analysis of the developed clads indicate the presence of various stable and complex carbides like Co{sub 6}W{sub 6}C, Co{sub 3}W{sub 3}C and Fe{sub 6}W{sub 6}C. The uniform distribution of such carbides with skeleton-like morphology in the microstructure is indicative of high hardness of the clad. The developed clads were free from visible interfacial cracking and the clad porosity was found in the order of approximately 0.98%. The average microhardness of the WC–12Co microwave clads was observed to be 1135 ± 88 HV. - Highlights: • Microwave cladding of WC–12Co on AISI 304 stainless steel is carried out. • Skeleton-like structures of W–Co based carbides are embedded in metallic matrix. • Clad–substrate interface is free from un-melted and un-dissolved carbide particles. • Hardness of clad (1135 ± 88 HV) is 3.5 times that of the substrate (325 ± 49 HV)

  8. Formation and interpretation of dilatant echelon cracks.

    USGS Publications Warehouse

    Pollard, D.D.; Segall, P.; Delaney, P.T.

    1982-01-01

    The relative displacements of the walls of many veins, joints, and dikes demonstrate that these structures are dilatant cracks. We infer that dilatant cracks propagate in a principal stress plane, normal to the maximum tensile or least compressive stress. Arrays of echelon crack segments appear to emerge from the peripheries of some dilatant cracks. Breakdown of a parent crack into an echelon array may be initiated by a spatial or temporal rotation of the remote principal stresses about an axis parallel to the crack propagation direction. Near the parent-crack tip, a rotation of the local principal stresses is induced in the same sense, but not necessarily through the same angle. Incipient echelon cracks form at the parent-crack tip normal to the local maximum tensile stress. Further longitudinal growth along surfaces that twist about axes parallel to the propagation direction realigns each echelon crack into a remote principal stress plane. The walls of these twisted cracks may be idealized as helicoidal surfaces. An array of helicoidal cracks sweeps out less surface area than one parent crack twisting through the same angle. Thus, many echelon cracks grow from a single parent because the work done in creating the array, as measured by its surface area decreases as the number of cracks increases. -from Authors

  9. Artificial water channels--incipient innovative developments.

    PubMed

    Barboiu, Mihail

    2016-04-28

    Aquaporins (AQPs) are biological water channels known for fast water transport (∼10(8)-10(9) water molecules per s per channel), with complete proton/ion exclusion. Few synthetic channels have been designed to mimic this high water permeability and to reject ions at a significant level. This Feature Article will discuss the incipient developments of the first artificial water channel systems. PMID:27046217

  10. Incipient motion of surf zone sediments

    NASA Astrophysics Data System (ADS)

    Frank, Donya; Foster, Diane; Sou, In Mei; Calantoni, Joseph

    2015-08-01

    Incipient motion experiments were conducted with natural gravel, acetate beads, and coarse-gravel-sized electronic grains called Smart Sediment Grains in a Small-Oscillatory Flow Tunnel. Measurements of fluid velocity were made using Particle Image Velocimetry. The strength of the fluid shear stresses and the pressure gradients were examined for a range of oscillatory flow conditions at the onset of motion of the sediment particles to determine which mechanism had induced particle motion. The three sediment types utilized in these experiments facilitated an assessment of the effects of sediment grain size diameter, shape, and density on incipient motion. Results suggested that the onset of sediment motion was dominated by the pressure gradients for flows with small orbital excursion amplitudes, by the shear stresses for flows with large orbital excursion amplitudes and by the combined effects for intermediate flows. The denser, angular gravel required greater free-stream accelerations to trigger sediment motion than the spherical, less dense acetate beads, and Smart Sediment Grains. A combined parameter for incipient motion that accounts for the simultaneous effects of both shear stresses and pressure gradients while depending on the static coefficient of friction and the packing concentration of the mobile bed layer was evaluated for accuracy using a range of sediment types. The results suggested that the combined parameter may be a better indicator of sediment mobilization under oscillatory flows than the typically assumed shear stress criterion.

  11. Influence of irradiation on KISCC of Zr-1%Nb claddings

    NASA Astrophysics Data System (ADS)

    Bibilashvili, Yu. K.; Medvedev, A. V.; Nesterov, B. I.; Novikov, V. V.; Golovanov, V. N.; Eremin, S. G.; Yurtchenko, A. D.

    2000-06-01

    Experimental results on iodine induced stress corrosion cracking (SCC) in irradiated claddings from Zr-1%Nb alloy are analyzed. Fatigue cracks were grown at their inner surfaces. The irradiation was carried on in the liquid sodium cooled BOR-60 to the fluence not lower than 10 22 n/cm 2. The SCC-test was carried at 350°C, in argon gas at constant pressure and iodine surface concentration of 0.2 mg/cm 2. The threshold stress intensity factor for the irradiated Zr-1%Nb claddings was determined to be ˜2.0 MPa√m.

  12. On microstructure and flexural strength of metal-ceramic composite cladding developed through microwave heating

    NASA Astrophysics Data System (ADS)

    Sharma, Apurbba Kumar; Gupta, Dheeraj

    2012-05-01

    A domestic multimode microwave applicator was used to develop carbide reinforced (tungsten-based) metal-matrix composite cladding on austenitic stainless steel substrate. Cladding was developed through microwave irradiation of the preplaced clad materials at 2.45 GHz for 420 s. Clads show metallurgical bonding with substrate by partial dilution of materials. Back scattered images of clad section confirm uniformly distributed reinforced particles in the metallic matrix. Presence of WC, W2C, NiSi, NiW and Co3W3C phases was detected in the clad. Flexural characteristics show two distinct load transitions attributable to deformations of the matrix and the reinforced particles. Clads fail at the upper transition load; further load is taken by the SS-316 substrate. Clads exhibit good stiffness and good adhesion with the substrate. Multi directional cracks were observed at the clad surface; on further loading, cracks get propagated into the clad thickness without getting peeled-off. Mechanism of clad development has been introduced.

  13. Preparation of Plasma Cladding Gradient Wear-Resistant Layer and Study on Its Impact Fatigue Properties

    NASA Astrophysics Data System (ADS)

    Zhang, Dekun; Liu, Yuan; Yin, Yan

    2016-02-01

    Plasma cladding technology is used to prepare plasma cladding gradient wear-resistant specimens, and the performance of these specimens is analyzed and compared with those of single cladding specimens. The results indicate that plasma cladding gradient wear-resistant layers implement the gradient changes in microstructure and hardness from the surface of the outer cladding layer to the fusion line and that the outer and inner cladding layers are well combined, the inner cladding layer can improve rapid decreases in hardness of single wear-resistant samples from the cladding layer to the matrix, changes in hardness from the outer to inner cladding layer are buffered, and the inner cladding layer performs important functions in the transition between the outer cladding layer and substrate. The highest hardness of the outer layer, which reaches 735 HV0.1, is approximately 3.9 times that of the matrix. The impact fatigue resistance performance of the plasma gradient cladding specimens is superior to that of single cladding specimens, and fatigue cracks begin to form only after 1 × 105 cyclical impacts.

  14. Zircaloy-2 lined zirconium barrier fuel cladding

    SciTech Connect

    Williams, C.D.; Marlowe, M.O.; Rand, R.A.; Armijo, J.S.; Adamson, R.B.; Wisner, S.B.

    1996-12-31

    The introduction of Zr-lined barrier fuel clad tubing by GE in the early 1980s to counter the pellet-clad interaction (PCI) failure mechanism in fuel for boiling water reactors provided a major improvement in fuel reliability and operational flexibility. While the frequency of fuel failures has been substantially reduced in the past decade, an increased tendency has been observed for failed fuel rods to exhibit post-failure degradation in the form of longer cracks that allow release of radioactive off-gas and contamination of the reactor coolant circuit with tramp fuel material. One factor involved in this degradation is hydriding of the cladding at a location remote from the initial perforation of the fuel rod. This local hydriding can lead to a secondary crack initiation in the cladding when stressed by the fuel expansion accompanying a power increase. A modification of Zr-lined barrier fuel clad tubing has been developed to retard post-failure local hydriding while retaining the proven PCI resistance of the high-purity sponge Zr barrier. By adding a thin inner layer of corrosion-resistant Zircaloy-2 bonded to the inner surface of the Zr-barrier tube, the resistance to internal corrosion and hydrogen generation in a perforated fuel cladding tube is made equivalent to that of an all-Zircaloy-2 tube. Tests show that the PCI mitigating capability of the Zr barrier. By adding a thin layer of corrosion-resistant Zircaloy-2 bonded to the inner surface of the Zr-barrier tube, the resistance to internal corrosion and hydrogen generation in a perforated fuel cladding tube is made equivalent to that of an all-Zircaloy-2 tube. Tests show that the PCI mitigating capability of the Zr barrier is not compromised by this inner Zircaloy-2 liner. Materials considerations and manufacturing technology used to integrate this optional inner liner with other Zr barrier tubing properties and performance requirements are discussed with a summary of testing experience.

  15. Boiling incipience in a reboiler tube

    SciTech Connect

    Ali, H.; Alam, S.S. )

    1991-03-01

    This heating surface and liquid temperature distributions were experimentally obtained to identify the boiling incipience conditions in a single vertical tube thermosiphon reboiler with water, acetone, ethanol, and ethylene glycol as test liquids. The test section was an electrically heated stainless steel tube of 25.56-mm i.d. and 1900 mm long. The uniform heat flux values were used in the range of 3800--40 000 W/m{sup 2}, while inlet liquid subcooling were varied from 0.2 to 45.5{degrees} C. The liquid submergence was maintained around 100, 75, 50 and 30%. All the data were generated at 1-atm pressure. The maximum superheats attained around boiling incipience were taken from the wall temperature distributions and correlated with heat flux and physical properties of liquids using the expression of Yin and Abdelmessih. The heated sections required for onset of fully developed boiling with net vapor generation were determined assuming a thermal equilibrium model. In this paper a dimensionless correlation relating these values with heat flux, liquid subcooling, and submergence is proposed.

  16. Fatigue cracking of coextruded 304L/CS tubes

    SciTech Connect

    Swindeman, R.W.; Keiser, J.R.; Maziasz, P.J.; Singbeil, D.L.

    1998-03-01

    The mechanical and thermal fatigue of authentic stainless steels was examined for the maximum temperature range expected in coextruded floor tubes of recovery boilers to determine the likelihood that the cracking in the 304L stainless steel cladding could be fatigue related. The microstructures and cracking patterns of fatigue-tested specimens were compared to features observed in cracked cladding and significant differences were found which suggested that fatigue was not the most likely cause for failure. Biaxial thermal fatigue testing of coextruded tubes and panels was performed to gather more evidence of cracking patterns. Here, transient thermal stresses were imposed by rapidly heating the tubing surface with lamps. In spite of high surface temperatures, no cracks were produced in the 304L stainless steel cladding, and this observation was interpreted as evidence that cracking must be corrosion related.

  17. Preliminary Design Report for Modeling of Hydrogen Uptake in Fuel Rod Cladding During Severe Accidents

    SciTech Connect

    Siefken, Larry James

    1999-02-01

    Preliminary designs are described for models of hydrogen and oxygen uptake in fuel rod cladding during severe accidents. Calculation of the uptake involves the modeling of seven processes: (1) diffusion of oxygen from the bulk gas into the boundary layer at the external cladding surface, (2) diffusion from the boundary layer into the oxide layer, (3) diffusion from the inner surface of the oxide layer into the metallic part of the cladding, (4) uptake of hydrogen in the event that the clad-ding oxide layer is dissolved in a steam-starved region, (5) embrittlement of cladding due to hydrogen uptake, (6) cracking of cladding during quenching due to its embrittlement and (7) release of hydrogen from the cladding after cracking of the cladding. An integral diffusion method is described for calculating the diffusion processes in the cladding. Experimental results are presented that show a rapid uptake of hydrogen in the event of dissolution of the oxide layer and a rapid release of hydrogen in the event of cracking of the oxide layer. These experimental results are used as a basis for calculating the rate of hydrogen uptake and the rate of hydrogen release. The uptake of hydrogen is limited to the equilibrium solubility calculated by applying Sievert's law. The uptake of hydrogen is an exothermic reaction that accelerates the heatup of a fuel rod. An embrittlement criteria is described that accounts for hydrogen and oxygen concentration and the extent of oxidation. A design is described for implementing the models for hydrogen and oxygen uptake and cladding embrittlement into the programming framework of the SCDAP/RELAP5 code. A test matrix is described for assessing the impact of the proposed models on the calculated behavior of fuel rods in severe accident conditions. This report is a revision and reissue of the report entitled; "Preliminary Design Report for Modeling of Hydrogen Uptake in Fuel Rod Cladding During Severe Accidents."

  18. Chemical vapor deposition for silicon cladding on advanced ceramics

    NASA Technical Reports Server (NTRS)

    Goela, Jitendra S.; Taylor, Raymond L.

    1989-01-01

    Polycrystalline Si was used to clad several advanced ceramic materials such as SiC, Si3N4, sapphire Al2O3, pyrolytic BN, and Si by a CVD process. The thickness of Si cladding ranged from 0.025 to 3.0 mm. CVD Si adhered quite well to all the above materials except Al3O, where the Si cladding was highly stressed and cracked or delaminated. A detailed material characterization of Si-clad SiC samples showed that Si adherence to SiC does not depend much on the substrate surface preparation; that the thermal cycling and polishing of the samples do not cause delamination; and that, in four-point bend tests, the Si-SiC bond remains intact, with the failure occurring in the Si.

  19. The effect of chromium on the weldability and microstructure of Fe-Cr-Al weld cladding

    SciTech Connect

    Regina, J.R.; Dupont, J.N.; Marder, A.R.

    2007-06-15

    Iron-aluminum-based weld cladding is currently being considered as corrosion-resistant coatings for boiler tubes in coal-fired power plants. Although these alloys could potentially be good coating candidates due to their excellent high-temperature corrosion resistance, Fe-Al weld cladding is susceptible to cracking due to hydrogen embrittlement at elevated aluminum concentrations. Additions of chromium to these iron-aluminum alloys have been shown to improve the corrosion resistance of the alloys and could potentially increase the lifetimes of the coatings. The current study investigated the effect of chromium on the hydrogen cracking susceptibility of Fe-Al weld cladding.

  20. Explosive Welding and Cladding

    NASA Astrophysics Data System (ADS)

    Meuken, D.; Carton, E. P.

    2004-07-01

    Explosive welding or cladding is usually performed on relative thick plates by means of a large scale parallel plate set-up. At TNO-PML several of the explosive welding configurations that were developed mainly in the nineteen sixties and seventies are being investigated for their potential use in modern industrial applications. Configurations for explosive cladding of curved surfaces such as tubes and rods are also being examined. This can be used to make special bimetallic heat exchanger tubes, or for the protection of electrodes that are used in electrolysis. Explosive line and seam welding are important bonding techniques that allow the welding of both similar and dissimilar metal plates and sheets. Here, bonding occurs over a small overlapping fraction of the two surfaces. This requires only a small amount of explosive (e.g. 5 g/m for line welds in thin ductile sheets). Explosive foil cladding can be used as an alternative coating technique. Plates that are clad with a foil on one or both sides were fabricated in one process step. They can be further machined or deformed using conventional techniques, due to the ductility of the bond and clad material.

  1. Preliminary design report for modeling of hydrogen uptake in fuel rod cladding during severe accidents

    SciTech Connect

    Siefken, L.J.

    1998-08-01

    Preliminary designs are described for models of the interaction of Zircaloy and hydrogen and the consequences of this interaction on the behavior of fuel rod cladding during severe accidents. The modeling of this interaction and its consequences involves the modeling of seven processes: (1) diffusion of oxygen from the bulk gas into the boundary layer at the external cladding surface, (2) diffusion from the boundary layer into the oxide layer at the cladding external surface, (3) diffusion from the inner surface of the oxide layer into the metallic part of the cladding, (4) uptake of hydrogen in the event that the cladding oxide layer is dissolved in a steam-starved region, (5) embrittlement of cladding due to hydrogen uptake, (6) cracking of cladding during quenching due to its embrittlement and (7) release of hydrogen from the cladding after cracking of the cladding. An integral diffusion method is described for calculating the diffusion processes in the cladding. Experimental and theoretical results are presented that show the uptake of hydrogen in the event of dissolution of the oxide layer occurs rapidly and that show the release of hydrogen in the event of cracking of the cladding occurs rapidly. These experimental results are used as a basis for calculating the rate of hydrogen uptake and the rate of hydrogen release. The uptake of hydrogen is limited to the equilibrium solubility calculated by applying Sievert`s law. The uptake of hydrogen is an exothermic reaction that accelerates the heatup of a fuel rod. An embrittlement criteria is described that accounts for hydrogen and oxygen concentration and the extent of oxidation. A design is described for implementing the models for Zr-H interaction into the programming framework of the SCDAP/RELAP5 code. A test matrix is described for assessing the impact of the Zr-H interaction models on the calculated behavior of fuel rods in severe accident conditions.

  2. Analysis and optimization of process parameters in Al-SiCp laser cladding

    NASA Astrophysics Data System (ADS)

    Riquelme, Ainhoa; Rodrigo, Pilar; Escalera-Rodríguez, María Dolores; Rams, Joaquín

    2016-03-01

    The laser cladding process parameters have great effect on the clad geometry and on dilution in the single and multi-pass aluminum matrix composite reinforced with SiC particles (Al/SiCp) coatings on ZE41 magnesium alloys deposited using a high-power diode laser (HPLD). The influence of the laser power (500-700 W), scan speed (3-17 mm/s) and laser beam focal position (focus, positive and negative defocus) on the shape factor, cladding-bead geometry, cladding-bead microstructure (including the presence of pores and cracks), and hardness has been evaluated. The correlation of these process parameters and their influence on the properties and ultimately, on the feasibility of the cladding process, is demonstrated. The importance of focal position is demonstrated. The different energy distribution of the laser beam cross section in focus plane or in positive and negative defocus plane affect on the cladding-bead properties.

  3. Corrosion cracking

    SciTech Connect

    Goel, V.S.

    1986-01-01

    Various papers on corrosion cracking are presented. The topics addressed include: unique case studies on hydrogen embrittlement failures in components used in aeronautical industry; analysis of subcritical cracking in a Ti-5Al-2.5Sn liquid hydrogen control valve; corrosion fatigue and stress corrosion cracking of 7475-T7351 aluminum alloy; effects of salt water environment and loading frequency on crack initiation in 7075-T7651 aluminum alloy and Ti-6Al-4V; stress corrosion cracking of 4340 steel in aircraft ignition starter residues. Also discussed are: stress corrosion cracking of a titanium alloy in a hydrogen-free environment; automation in corrosion fatigue crack growth rate measurements; the breaking load method, a new approach for assessing resistance to growth of early stage stress corrosion cracks; stress corrosion cracking properties of 2090 Al-Li alloy; repair welding of cracked free machining Invar 36; radial bore cracks in rotating disks.

  4. Analysis of unclad and sub-clad semi-elliptical flaws in pressure vessel steels

    SciTech Connect

    Irizarry-Quinones, H.; Macdonald, B.D.; McAfee, W.J.

    1996-06-01

    This study was conducted to support warm prestressing experiments on unclad and sub-clad flawed beams loaded in pure bending. Two cladding yield strengths were investigated: 0.6 Sy and 0.8 Sy, where Sy is the yield strength of the base metal. Cladding and base metal were assumed to be stress free at the stress relief temperature for the 3D elastic-plastic finite element analysis used to model the experiments. The model results indicated that when cooled from the stress relief temperature, the cladding was put in tension due to its greater coefficient of thermal expansion. When cooled, the cladding exhibited various amounts of tensile yielding. The degree of yielding depended on the amount of cooling and the strength of the cladding relative to that of the base metal. When subjected to tensile bending stress, the sub-clad flaw elastic-plastic stress intensity factor, K{sub I}(J), was at first dominated by crack closing force due to tensile yielding in the cladding. Thus, imposed loads initially caused no increase in K{sub I}(J) near the clad-base interface. However, K{sub I}(J) at the flaw depth was little affected. When the cladding residual stress was overcome, K{sub I}(J) gradually increased until the cladding began to flow. Thereafter, the rate at which K{sub I}(J) increased with load was the same as that of an unclad beam. A plastic zone corrected K{sub I} approximation for the unclad flaw was found by the superposition of standard Newman and Raju solutions with those due to a cladding crack closure force approximated by the Kaya and Erdogan solution. These elastic estimates of the effect of cladding in reducing the crack driving force were quite in keeping with the 3D elastic-plastic finite element solution for the sub-clad flaw. The results were also compared with the analysis of clad beam experiments by Keeney and the conclusions by Miyazaki, et al. A number of sub-clad flaw specimens not subjected to warm prestressing were thought to have suffered degraded

  5. LWR pellet-cladding interactions: Materials solutions to SCC

    NASA Astrophysics Data System (ADS)

    Edsinger, Kurt; Murty, K. Linga

    2001-07-01

    Zirconium alloys are commonly used as fuel-cladding tubes in water reactors because of their inherent resistance to a variety of environmental conditions. One of the major fuel-reliability issues of the 1970s and early 1980s was pellet cladding interaction (PCI). The mechanism of PCI is one of stress corrosion cracking (SCC) by a combination of aggressive fission products and cladding stress from pellet expansion. The severity of the problem, in particular in boiling water reactors, led to the development of barrier cladding by co-extrusion of Zircaloy-2 with an inner iodide zirconium that essentially eliminated the PCI-related failures. However, the substantially lower corrosion resistance of the zirconium layer led to clad breach and failures by other mechanisms. The difference in corrosion resistance could lead to some dramatic differences in post-failure fuel operations. This article briefly summarizes how PCI-SCC factors led to the development of PCI-resistant fuel cladding and concludes with a note on future research needs.

  6. Laser induction hybrid rapid cladding of WC particles reinforced NiCrBSi composite coatings

    NASA Astrophysics Data System (ADS)

    Zhou, Shengfeng; Dai, Xiaoqin

    2010-05-01

    In order to investigate the microstructure characteristics and properties of Ni-based WC composite coatings containing a relatively large amount of WC particles by laser induction hybrid rapid cladding (LIHRC) and compare to the individual laser cladding without preheating, Ni60A + 35 wt.% WC composite coatings are deposited on A3 steel plates by LIHRC and the individual laser cladding without preheating. The composite coating produced by the individual laser cladding without preheating exhibits many cracks and pores, while the smooth composite coating without cracks and pores is obtained by LIHRC. Moreover, the cast WC particles take on the similar dissolution characteristics in Ni60A + 35 wt.% WC composite coatings by LIHRC and the individual laser cladding without preheating. Namely, the completely dissolved WC particles interact with Ni-based alloy solvent to precipitate the blocky and herringbone carbides, while the partially dissolved WC particles still preserve the primary lamellar eutectic structure. A few WC particles are split at the interface of WC and W 2C, and then interact with Ni-based alloy solvent to precipitate the lamellar carbides. Compared with the individual laser cladding without preheating, LIHRC has the relatively lower temperature gradient and the relatively higher laser scanning speed. Therefore, LIHRC can produce the crack-free composite coating with relatively higher microhardness and relatively more homogeneous distribution of WC particles and is successfully applied to strengthen the corrugated roller, showing that LIHRC process has a higher efficiency and good cladding quality.

  7. Weld overlay cladding with iron aluminides

    SciTech Connect

    Goodwin, G.M.

    1997-12-01

    The author has established a range of compositions for these alloys within which hot cracking resistance is very good, and within which cold cracking can be avoided in many instances by careful control of welding conditions, particularly preheat and postweld heat treatment. For example, crack-free butt welds have been produced for the first time in 12-mm thick wrought Fe{sub 3}Al plate. Cold cracking, however, still remains an issue in many cases. The author has developed a commercial source for composite weld filler metals spanning a wide range of achievable aluminum levels, and are pursuing the application of these filler metals in a variety of industrial environments. Welding techniques have been developed for both the gas tungsten arc and gas metal arc processes, and preliminary work has been done to utilize the wire arc process for coating of boiler tubes. Clad specimens have been prepared for environmental testing in-house, and a number of components have been modified and placed in service in operating kraft recovery boilers. In collaboration with a commercial producer of spiral weld overlay tubing, the author is attempting to utilize the new filler metals for this novel application.

  8. Eddy-Current Detection of Cracks in Tubes

    NASA Technical Reports Server (NTRS)

    Parent, R.; Kettering, D.

    1987-01-01

    Nondestructive device tests narrow, sharply-bent metal tubes. Eddycurrent probe detects incipient cracks inside small metal tubes. Tube-centering device consisting of pair of opposed bars ensures tube centered on eddy-current coil. Probe moves along length of bent tube to inspect repeatably for cracks. Compatible with tubes of different cross sections, oval, flattened, square, rectangular,or irregular. Adapts for inspecting formed tubes in petrochemical, automotive, nuclear, and medical equipment.

  9. EPRI fuel cladding integrity program

    SciTech Connect

    Yang, R.

    1997-01-01

    The objectives of the EPRI fuel program is to supplement the fuel vendor research to assure that utility economic and operational interests are met. To accomplish such objectives, EPRI has conducted research and development efforts to (1) reduce fuel failure rates and mitigate the impact of fuel failures on plant operation, (2) provide technology to extend burnup and reduce fuel cycle cost. The scope of R&D includes fuel and cladding. In this paper, only R&D related to cladding integrity will be covered. Specific areas aimed at improving fuel cladding integrity include: (1) Fuel Reliability Data Base; (2) Operational Guidance for Defective Fuel; (3) Impact of Water Chemistry on Cladding Integrity; (4) Cladding Corrosion Data and Model; (5) Cladding Mechanical Properties; and (6) Transient Fuel Cladding Response.

  10. Morphology Changing at Incipient Crystallization Condition

    NASA Astrophysics Data System (ADS)

    Toshima, Takeshi; Hamai, Ryo; Fujita, Saya; Takemura, Yuka; Takamatsu, Saori; Tafu, Masamoto

    2015-04-01

    Brushite (Dicalcium phosphate dihydrate, (DCPD), CaHPO4·2H2O) is one of key components in calcium phosphate system due to wide attractive material not only as bioceramics but also environmental materials. Morphology of DCPD crystals is important factor when one uses its functionality with chemical reaction; because its surface crystal face, shape and size rule the chemical reactivity, responsiveness. Moreover, physical properties are also changed the morphology; such as cohesion, dispersiveness, permeability and so on. If one uses DCPD crystals as environmental renovation materials to catch the fluoride ions, their shape require 020 crystal surfaces; which usually restricts their shape as plate-like structure. After the chemical reaction, the shape of sludge is not good for handling due to their agglutinate property. Therefore searching an effective parameter and developing the method to control the morphology of DCPD crystals is required. In past, we reported that initial concentration and pH value of starting solution, prepared by dissolving calcium nitrate, Ca(NO3)2 and ammonium dihydrogen phosphate, NH4H2PO4, changes the morphology of DCPD crystals and phase diagram of morphology of DCPD crystal depend on those parameter. The DCPD crystallization shows unique behaviour; products obtained higher initial concentration form single crystal-like structure and under lower condition, they form agglomerate crystal-like structure. These results contradict usual crystallization. Here we report that the effect of mixing process of two solutions. The morphology of DCPD crystals is changed from plate structure to petal structure by the arrangement. Our result suggests that morphology of DCPD crystals strongly depends at incipient crystallization condition and growth form is controllable by setting initial crystallization condition.

  11. Analysis of unclad and sub-clad semi-elliptical flaws in pressure vessel steels

    SciTech Connect

    Irizarry-Quinones, H.; Macdonald, B.D.; McAfee, W.J.

    1997-12-31

    This study was conducted to support warm prestress experiments on unclad and sub-clad flawed beams loaded in pure bending. Two cladding yield strengths were investigated: 0.6 Sy and 0.8 Sy, where Sy is the yield strength of the base metal. Cladding and base metal were assumed to be stress free at the stress relief temperature for the 3D elastic-plastic finite element analysis. The model results indicated that when cooled from the stress relief temperature tensile residual stresses were generated in the cladding due to its greater coefficient of thermal expansion. The magnitude of the residual stresses depended on the amount of cooling and the strength of the cladding relative to that of the base metal. During loading, the sub-clad flaw elastic-plastic stress intensity factor, K{sub I}(J), was at first dominated by crack closing force due to tensile residual stresses in the cladding. After the cladding residual stress were overcome by the applied bending stresses, K{sub I}(J) gradually increased as if it were an unclad beam. A combination of elastic stress intensity factor solutions was used to approximate the effect of cladding in reducing the crack driving force along the flaw. This approximation was quite in keeping with the 3D elastic-plastic finite element solution for the sub-clad flaw. Finally, a number of sub-clad flaw specimens not subjected to warm prestressing were thought to have suffered degraded toughness caused by locally intensified strain ageing embrittlement due to welding over the preexisting flaw.

  12. The Effect of Rare Earth on the Structure and Performance of Laser Clad Coatings

    NASA Astrophysics Data System (ADS)

    Bao, Ruiliang; Yu, Huijun; Chen, Chuanzhong; Dong, Qing

    Laser cladding is one kind of advanced surface modification technology and has the abroad prospect in making the wear-resistant coating on metal substrates. However, the application of laser cladding technology does not achieve the people's expectation in the practical production because of many defects such as cracks, pores and so on. The addiction of rare earth can effectively reduce the number of cracks in the clad coating and enhance the coating wear-resistance. In the paper, the effects of rare earth on metallurgical quality, microstructure, phase structure and wear-resistance are analyzed in turns. The preliminary discussion is also carried out on the effect mechanism of rare earth. At last, the development tendency of rare earth in the laser cladding has been briefly elaborated.

  13. Fuel pin cladding

    DOEpatents

    Vaidyanathan, Swaminathan; Adamson, Martyn G.

    1986-01-01

    An improved fuel pin cladding, particularly adapted for use in breeder reactors, consisting of composite tubing with austenitic steel on the outer portion of the thickness of the tube wall and with nickel and/or ferritic material on the inner portion of the thickness of the tube wall. The nickel forms a sacrificial barrier as it reacts with certain fission products thereby reducing fission product activity at the austenitic steel interface. The ferritic material forms a preventive barrier for the austenitic steel as it is immune to liquid metal embrittlement. The improved cladding permits the use of high density fuel which in turn leads to a better breeding ratio in breeder reactors, and will increase the threshold at which failure occurs during temperature transients.

  14. Fuel pin cladding

    DOEpatents

    Vaidyanathan, S.; Adamson, M.G.

    1983-12-16

    An improved fuel pin cladding, particularly adapted for use in breeder reactors, is described which consist of composite tubing with austenitic steel on the outer portion of the thickness of the tube wall and with nickel an/or ferritic material on the inner portion of the thickness of the tube wall. The nickel forms a sacrificial barrier as it reacts with certain fission products thereby reducing fission product activity at the austenitic steel interface. The ferritic material forms a preventive barrier for the austenitic steel as it is immune to liquid metal embrittlement. The improved cladding permits the use of high density fuel which in turn leads to a better breeding ratio in breeder reactors, and will increase the threshold at which failure occurs during temperature transients.

  15. Fuel pin cladding

    DOEpatents

    Vaidyanathan, S.; Adamson, M.G.

    1986-01-28

    Disclosed is an improved fuel pin cladding, particularly adapted for use in breeder reactors, consisting of composite tubing with austenitic steel on the outer portion of the thickness of the tube wall and with nickel and/or ferritic material on the inner portion of the thickness of the tube wall. The nickel forms a sacrificial barrier as it reacts with certain fission products thereby reducing fission product activity at the austenitic steel interface. The ferritic material forms a preventive barrier for the austenitic steel as it is immune to liquid metal embrittlement. The improved cladding permits the use of high density fuel which in turn leads to a better breeding ratio in breeder reactors, and will increase the threshold at which failure occurs during temperature transients. 2 figs.

  16. Deformation and fracture characteristics of spent Zircaloy fuel cladding

    SciTech Connect

    Chung, H.M.; Yaggee, F.L.

    1982-09-01

    For a better understanding of Zircaloy fuel-rod failure by the pellet-cladding interaction (PCI) phenomenon, a mechanistic study of deformation and fracture behavior of spent power reactor fuel cladding under simulated PCI conditions was conducted. Zircaloy-2 cladding specimens, obtained from fuel assemblies of operating power reactors, were deformed to fracture at 325/sup 0/C by internal gas pressurization in the absence of fission product simulants. Fracture characteristics and microstructures were examined via SEM, TEM, and HVEM. Numerous dislocation tangles and cell structures, observed in TEM specimens of cladding tubes that failed in a ductile manner, were consistent with SEM observations of a limited number of dimples characteristic of microvoid coalescence. A number of brittle-type failures were produced without the influence of fission product simulants. The brittle cracks occurred near the areas compressed by the Swagelok fittings of the internally pressurized tube and propagated from the outer to the inner surface. Since the outer surface was isolated and maintained under a flowing stream of pure helium, it is unlikely that the brittle-type failure was influenced by any fission product traces. SEM fractography of the brittle-type failure revealed a large area of transgranular pseudocleavage with limited areas of ductile fluting, which were similar in appearance to the surfaces produced by in-reactor PCI-type failures. A TEM evaluation of the cladding in the vicinity of the through-wall crack revealed numerous locations that contained an extensive amount of second-phase precipitate (Zr/sub 3/O). We believe that the brittle-type failures of the irradiated spent fuel cladding in the stress rupture experiments are associated with segregation of oxygen, which leads to the formation of the order structure, an immobilization of dislocations, and minimal plastic deformation in the material.

  17. Finite Element Analysis of Laser Engineered Net Shape (LENS™) Tungsten Clad Squeeze Pins

    NASA Astrophysics Data System (ADS)

    Sakhuja, Amit; Brevick, Jerald R.

    2004-06-01

    In the aluminum high-pressure die-casting and indirect squeeze casting processes, local "squeeze" pins are often used to minimize internal solidification shrinkage in heavy casting sections. Squeeze pins frequently fail in service due to molten aluminum adhering to the H13 tool steel pins ("soldering"). A wide variety of coating materials and methods have been developed to minimize soldering on H13. However, these coatings are typically very thin, and experience has shown their performance on squeeze pins is highly variable. The LENS™ process was employed in this research to deposit a relatively thick tungsten cladding on squeeze pins. An advantage of this process was that the process parameters could be precisely controlled in order to produce a satisfactory cladding. Two fixtures were designed and constructed to enable the end and outer diameter (OD) of the squeeze pins to be clad. Analyses were performed on the clad pins to evaluate the microstructure and chemical composition of the tungsten cladding and the cladding-H13 substrate interface. A thermo-mechanical finite element analysis (FEA) was performed to assess the stress distribution as a function of cladding thickness on the pins during a typical casting thermal cycle. FEA results were validated via a physical test, where the clad squeeze pins were immersed into molten aluminum. Pins subjected to the test were evaluated for thermally induced cracking and resistance to soldering of the tungsten cladding.

  18. Formation quality optimization of laser hot wire cladding for repairing martensite precipitation hardening stainless steel

    NASA Astrophysics Data System (ADS)

    Wen, Peng; Feng, Zhenhua; Zheng, Shiqing

    2015-01-01

    Laser cladding is an advantaged repairing technology due to its low heat input and high flexibility. With preheating wire by resistance heat, laser hot wire cladding shows better process stability and higher deposition efficiency compared to laser cold wire/powder cladding. Multi-pass layer were cladded on the surface of martensite precipitation hardening stainless steel FV520B by fiber laser with ER410NiMo wire. Wire feed rate and preheat current were optimized to obtain stable wire transfer, which guaranteed good formation quality of single pass cladding. Response surface methodology (RSM) was used to optimize processing parameters and predict formation quality of multi-pass cladding. Laser power P, scanning speed Vs, wire feed rate Vf and overlap ratio η were selected as the input variables, while flatness ratio, dilution and incomplete fusion value as the responses. Optimal clad layer with flat surface, low dilution and no incomplete fusion was obtained by appropriately reducing Vf, and increasing P, Vs and η. No defect like pore or crack was found. The tensile strength and impact toughness of the clad layer is respectively 96% and 86% of those of the substrate. The clad layer showed nonuniform microstructure and was divided into quenched areas with coarse lath martensite and tempered areas with tempered martensite due to different thermal cycles in adjacent areas. The tempered areas showed similar hardness to the substrate.

  19. Structure-property correlations in nanostructured WC-12Co microwave clad

    NASA Astrophysics Data System (ADS)

    Zafar, Sunny; Sharma, Apurbba Kumar

    2016-05-01

    Nanostructured materials are known for enhanced properties as compared to their conventional counterparts. In the present work, microwave cladding technique was explored for depositing nanostructured WC-12Co clads on stainless steel substrates. Phase analysis of the WC-12Co microwave clads revealed the presence of Co6W6C, Co7W6, Co3W9C4, W2C and WC phases. The microstructure of the WC-12Co clads confirmed uniform distribution of nano-carbides in the form of clusters enclosed in the carbide network. Mechanical characterisation of the nanostructured clads was carried in terms of microhardness assessment and flexural strength measurement. The microwave induced clads exhibited excellent metallurgical bonding with the substrate and were free from interfacial cracks. The average microhardness of the developed clads was found in the order of 1760 ± 128HV. The flexural strength of the developed clads was observed to be 671 ± 28 MPa. The nanostructured clads exhibited good adhesion with the substrate without getting peeled-off under a load of 3.75 kN and a displacement of 3.72 mm.

  20. Calculation of hydrogen and oxygen uptake in fuel rod cladding during severe accidents using the integral diffusion method -- Final Design Report

    SciTech Connect

    Siefken, L.J.

    1999-05-01

    Final designs are described for models of hydrogen and oxygen uptake in fuel rod cladding during severe accidents. Calculation of the uptake involves the modeling of seven processes: (1) diffusion of oxygen from the bulk gas into the boundary layer at the external cladding surface, (2) diffusion from the boundary layer into the oxide layer, (3) diffusion from the inner surface of the oxide layer into the metallic part of the cladding, (4) uptake of hydrogen in the event that the cladding oxide layer is dissolved in a steam-starved region, (5) embrittlement of cladding due to hydrogen uptake, (6) cracking of cladding during quenching due to its embrittlement and (7) release of hydrogen from the cladding after cracking of the cladding. An integral diffusion method is described for calculating the diffusion processes in the cladding. Experimental results are presented that show a rapid uptake of hydrogen in the event of dissolution of the oxide layer and a rapid release of hydrogen in the event of cracking of the oxide layer. These experimental results are used as a basis for calculating the rate of hydrogen uptake and the rate of hydrogen release. A description is given of the implementation of the models for hydrogen and oxygen uptake and cladding embrittlement into the programming framework of the SCDAP/RELAP5/MOD3.3 code.

  1. Calculation of Hydrogen and Oxygen Uptake in Fuel Rod Cladding During Severe Accidents Using the Integral Diffusion Method - Final Design Report

    SciTech Connect

    Siefken, Larry James

    1999-06-01

    Final designs are described for models of hydrogen and oxygen uptake in fuel rod cladding during severe accidents. Calculation of the uptake involves the modeling of seven processes: (1) diffusion of oxygen from the bulk gas into the boundary layer at the external cladding surface, (2) diffusion from the boundary layer into the oxide layer, (3) diffusion from the inner surface of the oxide layer into the metallic part of the cladding, (4) uptake of hydrogen in the event that the cladding oxide layer is dissolved in a steam-starved region, (5) embrittlement of cladding due to hydrogen uptake, (6) cracking of cladding during quenching due to its embrittlement and (7) release of hydrogen from the cladding after cracking of the cladding. An integral diffusion method is described for calculating the diffusion processes in the cladding. Experimental results are presented that show a rapid uptake of hydrogen in the event of dissolution of the oxide layer and a rapid release of hydrogen in the event of cracking of the oxide layer. These experimental results are used as a basis for calculating the rate of hydrogen uptake and the rate of hydrogen release. A description is given of the implementation of the models for hydrogen and oxygen uptake and cladding embrittlement into the programming framework of the SCDAP/RELAP5/MOD3.3 code.

  2. Fracture assessment of weld material from a full-thickness clad RPV shell segment

    SciTech Connect

    Keeney, J.A.; Bass, B.R.; McAfee, W.J.

    1996-07-01

    Fracture analysis was applied to full-thickness clad beam specimens containing shallow cracks in material for which metallurgical conditions are prototypic of those found in reactor pressure vessels (RPV) at beginning of life. The beam specimens were fabricated from a section of an RPV wall (removed from a canceled nuclear plant) that includes weld, plate, and clad material. Metallurgical factors potentially influencing fracture toughness for shallow cracks in the beam specimens include gradients of material properties and residual stresses due to welding and cladding applications. Fracture toughness estimates were obtained from load vs load-line displacement and load vs crack-mouth-opening displacement data using finite-element methods and estimation schemes based on the {eta}-factor method. One of the beams experienced a significant amount of precleavage stable ductile tearing. Effects of precleavage tearing on estimates of fracture toughness were investigated using continuum damage models. Fracture toughness results from the clad beam specimens were compared with other deep- and shallow-crack single-edge notch bend (SENB) data generated previously from A533 Grade B plate material. Range of scatter for the clad beam data is consistent with that from the laboratory-scale SENB specimens tested at the same temperature.

  3. Microstructural examination of high temperature creep failure of Zircaloy-2 cladding in irradiated PHWR fuel pins

    NASA Astrophysics Data System (ADS)

    Mishra, Prerna; Sah, D. N.; Kumar, Sunil; Anantharaman, S.

    2012-10-01

    Cladding samples taken from the ballooned region of the irradiated Zircaloy-2 cladded PHWR fuel pins which failed during isothermal heating tests carried out at 800-900 °C were examined using optical and scanning electron microscopy. The examination of samples from the fuel pin tested at 900 °C showed an intergranular mode of failure in the cladding due to formation of cracks, cavities and zirconium hydride precipitates on the grain boundaries in the cladding material. A thin hard α-Zr(O) layer was observed on outer surface due to dissolution of the oxide layer formed during reactor operation. Grain boundary sliding was identified to be the main mode of creep deformation of Zircaloy-2 at 900 °C. Examination of the cladding tested at 800 °C showed absence of cracks or cavities in the deformed material and no localisation of hydrides was observed at the grain boundaries. The failure of the cladding occurred after necking followed by extensive wall thinning of the cladding tube.

  4. Boiling incipience and convective boiling of neon and nitrogen

    NASA Technical Reports Server (NTRS)

    Papell, S. S.; Hendricks, R. C.

    1977-01-01

    Forced convection and subcooled boiling heat transfer data for liquid nitrogen and liquid neon were obtained in support of a design study for a 30 tesla cryomagnet cooled by forced convection of liquid neon. This design precludes nucleate boiling in the flow channels as they are too small to handle vapor flow. Consequently, it was necessary to determine boiling incipience under the operating conditions of the magnet system. The cryogen data obtained over a range of system pressures, fluid flow rates, and applied heat fluxes were used to develop correlations for predicting boiling incipience and convective boiling heat transfer coefficients in uniformly heated flow channels. The accuracy of the correlating equations was then evaluated. A technique was also developed to calculate the position of boiling incipience in a uniformly heated flow channel. Comparisons made with the experimental data showed a prediction accuracy of plus or minus 15 percent

  5. Signal analysis techniques for incipient failure detection in turbomachinery

    NASA Technical Reports Server (NTRS)

    Coffin, T.

    1985-01-01

    Signal analysis techniques for the detection and classification of incipient mechanical failures in turbomachinery were developed, implemented and evaluated. Signal analysis techniques available to describe dynamic measurement characteristics are reviewed. Time domain and spectral methods are described, and statistical classification in terms of moments is discussed. Several of these waveform analysis techniques were implemented on a computer and applied to dynamic signals. A laboratory evaluation of the methods with respect to signal detection capability is described. Plans for further technique evaluation and data base development to characterize turbopump incipient failure modes from Space Shuttle main engine (SSME) hot firing measurements are outlined.

  6. Boiling incipience and convective boiling of neon and nitrogen

    NASA Technical Reports Server (NTRS)

    Papell, S. S.; Hendricks, R. C.

    1977-01-01

    Forced convection and subcooled boiling heat transfer data for liquid nitrogen and liquid neon were obtained in support of a design study for a 30 tesla cryomagnet cooled by forced convection of liquid neon. The cryogen data obtained over a range of system pressures, fluid flow rates, and applied heat fluxes were used to develop correlations for predicting boiling incipience and convective boiling heat transfer coefficients in uniformly heated flow channels. The accuracy of the correlating equations was then evaluated. A technique was also developed to calculate the position of boiling incipience in a uniformly heated flow channel. Comparisons made with the experimental data showed a prediction accuracy of + or - 15 percent.

  7. Incipient Motion and Particle Transport in Gravel - Streams

    NASA Astrophysics Data System (ADS)

    Matin, Habib

    The incipient motion of sediment particles in gravel-bed rivers is a very important process. It represents the difference between bed stability and bed mobility. A field study was conducted in Oak Creek, Oregon to investigate incipient motion of individual particles in gravel-bed streams. Investigation was also made of the incipient motion of individual gravel particles in the armor layer, using painted gravel placed on the bed of the stream and recovered after successive high flows. The effect of gravel particle shape was examined for a wide range of flow conditions to determine its significance on incipient motion. The result of analysis indicates a wide variation in particle shapes present. Incipient motion and general transport were found to be generally independent of particle shape regardless of particle sizes. A sample of bed material may contain a mixture of shapes such as well-rounded, oval, flat, disc-like, pencil-shaped, angular, and block-like. These are not likely to move in identical manners during transport nor to start motion at the same flow condition. This leads to questions about the role of shape in predicting incipient motion and equal mobility in gravel-bed streams. The study suggests that gravel particles initiate motion in a manner that is independent of particle shape. One explanation may be that for a natural bed surface many particles rest in orientations that give them the best protection against disturbance, probably a result of their coming to rest gradually during a period of decreasing flows, rather than being randomly dumped. But even when tracer particles were placed randomly in the bed surface there was no evident selectively for initiation of motion on the basis of particle shape. It can be concluded from analysis based on the methods of Parker et al. and Komar that there is room for both equal mobility and flow-competence evaluations. However, the equal mobility concept is best applied for conditions near incipient motion and

  8. Aerogel-clad optical fiber

    DOEpatents

    Sprehn, Gregory A.; Hrubesh, Lawrence W.; Poco, John F.; Sandler, Pamela H.

    1997-01-01

    An optical fiber is surrounded by an aerogel cladding. For a low density aerogel, the index of refraction of the aerogel is close to that of air, which provides a high numerical aperture to the optical fiber. Due to the high numerical aperture, the aerogel clad optical fiber has improved light collection efficiency.

  9. Aerogel-clad optical fiber

    DOEpatents

    Sprehn, G.A.; Hrubesh, L.W.; Poco, J.F.; Sandler, P.H.

    1997-11-04

    An optical fiber is surrounded by an aerogel cladding. For a low density aerogel, the index of refraction of the aerogel is close to that of air, which provides a high numerical aperture to the optical fiber. Due to the high numerical aperture, the aerogel clad optical fiber has improved light collection efficiency. 4 figs.

  10. Oxidation resistant claddings for superalloys.

    NASA Technical Reports Server (NTRS)

    Gedwill, M. A.; Grisaffe, S. J.

    1971-01-01

    The oxidation protection afforded IN-100 and WI-52 superalloys by thin claddings of NiCrAlSi and FeCrAlY alloys was examined primarily at 1090 C. Comparisons were made with commercial aluminide coatings using cyclic furnace and high velocity burner rig tests. In furnace tests, NiCrAlSi on IN-100 and FeCrAlY on WI-52 performed as well or better than two aluminide coatings. Burner rig performance of the FeCrAlY cladding was better than that of the NiCrAlSi cladding on IN-100 and the aluminide coating on WI-52, but less than the aluminide coating on IN-100. An aluminized NiCrAlSi cladding performed better than any coating or cladding.

  11. Oxidation resistant claddings for superalloys.

    NASA Technical Reports Server (NTRS)

    Gedwill, M. A.; Grisaffe, S. J.

    1972-01-01

    The oxidation protection afforded IN-100 and WI-52 superalloys by thin claddings of NiCrAlSi and FeCrAlY alloys was examined primarily at 1090 C. Comparisons were made with commercial aluminide coatings, using cyclic furnace and high-velocity burner rig tests. In furnace tests, NiCrAlSi on IN-100 and FeCrAlY on WI-52 performed as well as or better than two aluminide coatings. Burner rig performance of the FeCrAlY cladding was better than that of the NiCrAlSi cladding on IN-100 and the aluminide coating on WI-52, but less than the aluminide coating on IN-100. An aluminized NiCrAlSi cladding performed better than any coating or cladding.

  12. Weld overlay cladding with iron aluminides

    SciTech Connect

    Goodwin, G.M.

    1996-11-01

    The hot and cold cracking tendencies of some early iron aluminide alloy compositions limited their use to applications where good weldability was not required. Considerable progress has been made toward improving this situation. Using hot crack testing techniques developed at ORNL and a systematic study of alloy compositional effects, we have established a range of compositions within which hot cracking resistance is very good, essentially equivalent to stainless steel. Cold cracking, however, remains an issue, and extensive efforts are continuing to optimize composition and welding parameters, especially preheat and postweld heat treatment, to minimize its occurrence. In terms of filler metal and process development, we have progressed from sheared strip through aspiration cast rod and shielded metal arc electrodes to the point where we can now produce composite wire with a steel sheath and aluminum core in coil form, which permits the use of both the gas tungsten arc and gas metal arc processes. This is a significant advancement in that the gas metal arc process lends itself well to automated welding, and is the process of choice for commercial weld overlay applications. Using the newly developed filler metals, we have prepared clad specimens for testing in a variety of environments both in-house and outside ORNL, including laboratory and commercial organizations. As a means of assessing the field performance of this new type of material, we have modified several non-pressure boundary boiler components, including fuel nozzles and port shrouds, by introducing areas of weld overlay in strategic locations, and have placed these components in service in operating boilers for a side-by-side comparison with conventional corrosion-resistant materials.

  13. Three feasible strategies to minimize kidney injury in 'incipient AKI'.

    PubMed

    Perazella, Mark A; Coca, Steven G

    2013-08-01

    Acute kidney injury (AKI) is common and increasing in hospitalized patients. The earlier recognition of renal injury, at a stage described as 'incipient AKI', may allow renoprotective strategies to be initiated at a time when more kidney tissue is salvageable. 'Incipient AKI' represents renal injury as manifested by new-onset proteinuria, cellular activity on urine microscopy, or elevated novel biomarkers of kidney injury in the absence of clinical data that meet current diagnostic criteria for AKI. We propose three strategies to preserve kidney function and minimize further kidney injury in patients with 'incipient AKI'. These include--when appropriate for the prevailing cause of 'incipient AKI'--use of low-chloride-containing intravenous solutions, continued use of renin-angiotensin system antagonists, and use of diuretics to achieve adequate control of intravascular volume. The combined approach of the early diagnosis of AKI and early employment of feasible therapeutic strategies may slow the growth of clinical AKI, AKI requiring renal replacement therapy and chronic kidney disease, and might reduce AKI-associated mortality. PMID:23649020

  14. Results of NDE Technique Evaluation of Clad Hydrides

    SciTech Connect

    Dennis C. Kunerth

    2014-09-01

    This report fulfills the M4 milestone, M4FT-14IN0805023, Results of NDE Technique Evaluation of Clad Hydrides, under Work Package Number FT-14IN080502. During service, zirconium alloy fuel cladding will degrade via corrosion/oxidation. Hydrogen, a byproduct of the oxidation process, will be absorbed into the cladding and eventually form hydrides due to low hydrogen solubility limits. The hydride phase is detrimental to the mechanical properties of the cladding and therefore it is important to be able to detect and characterize the presence of this constituent within the cladding. Presently, hydrides are evaluated using destructive examination. If nondestructive evaluation techniques can be used to detect and characterize the hydrides, the potential exists to significantly increase test sample coverage while reducing evaluation time and cost. To demonstrate the viability this approach, an initial evaluation of eddy current and ultrasonic techniques were performed to demonstrate the basic ability to these techniques to detect hydrides or their effects on the microstructure. Conventional continuous wave eddy current techniques were applied to zirconium based cladding test samples thermally processed with hydrogen gas to promote the absorption of hydrogen and subsequent formation of hydrides. The results of the evaluation demonstrate that eddy current inspection approaches have the potential to detect both the physical damage induced by hydrides, e.g. blisters and cracking, as well as the combined effects of absorbed hydrogen and hydride precipitates on the electrical properties of the zirconium alloy. Similarly, measurements of ultrasonic wave velocities indicate changes in the elastic properties resulting from the combined effects of absorbed hydrogen and hydride precipitates as well as changes in geometry in regions of severe degradation. However, for both approaches, the signal responses intended to make the desired measurement incorporate a number of contributing

  15. Relating climate and sand transport to incipient dune development.

    NASA Astrophysics Data System (ADS)

    van Puijenbroek, Marinka; Limpens, Juul; Gleichman, Maurits; Berendse, Frank

    2014-05-01

    Sea levels are continuously rising, increasing the risk of flooding and coastal erosion in low-elevation countries, such as the Netherlands. Coastal dunes are seen as a flexible and natural type of coastal defence, that is able to keep pace with rising water levels. Until now most research has focussed on dynamics and maintenance of established dunes, largely ignoring two critical transitions in early dune development: the transition from bare beach to vegetated incipient dune and that from incipient dune to established foredune. This knowledge is essential to enable more accurate prediction and even stimulation of new dune formation through sand nourishment. We explored the relative contributions of climate and sand transport to incipient dune development combining a 30 year time-series of aerial photographs (1979 - 2010) of the natural Wadden Island coast with high-resolution monitoring data of sand volume changes and climatic parameters. We selected 20 strips of 2.5 km in length along the coast of the Wadden Islands, with a 2 km buffer between them to avoid autocorrelation. For each of these strips of coast we assessed the changes in presence and area of incipient dunes over periods of 5-6 years. Change in fore dune volume and beach width were derived from high resolution beach elevation data. Seawater level and climate data were derived from a nearby meteorological station Preliminary analysis of the first half of the dataset showed that incipient dune area was positively related to beach width, but negatively to storm intensity. In our poster we will present the whole dataset and discuss the implications of our results for future dune development and anthropogenic sand nourishment schemes.

  16. Experimental Study on Surface Characteristics of Laser Cladding Layer Regulated by High-Frequency Microforging

    NASA Astrophysics Data System (ADS)

    Fan, Xiang Fang; Zhou, Ju; Qiu, Chang Jun; He, Bin; Ye, Jiang; Yuan, Bo; Pi, Zhengqing

    2011-03-01

    High-frequency microforging technology is used to produce micrometer-scale plastic deformation on the surface of material out of the vibration impact of a forging punch, and the cumulative effect of its various frequencies on micrometer-scale plastic deformation can cause changes of surface microstructure and mechanical properties. This study used (1) a self-made machine to treat NiCrBSi alloy, (2) a mechanical comparator and optical microscopy (OM) to study the geometric characteristics of plastic deformation, (3) OM and scanning electric microscopy (SEM) to observe influence on surface microstructure and cracking behavior of the laser cladding layer under microforging, (4) x-ray diffractometer (XRD) to measure the surface residual stress of laser cladding layer before and after forging, and (5) microhardness tester and wearing experimental machine to study changes of microhardness, friction coefficient, and wear characteristics of laser cladding layer after microforging. The results have shown that high-frequency microforging could produce plastic deformation about 150 μm deep on the surface of NiCrBSi alloy clad by laser. Regular dendrite and eutectic crystallization microstructure, which is a peculiar characteristic of the laser cladding layer, was broken into pieces and formed residual compression residual stress on the surface. Resistance to cracking of laser cladding layer improved greatly, microhardness and wearability increased, and the friction coefficient did not under go a noticeable change.

  17. Effects of hydride morphology on the embrittlement of Zircaloy-4 cladding

    NASA Astrophysics Data System (ADS)

    Kim, Ju-Seong; Kim, Tae-Hoon; Kook, Dong-Hak; Kim, Yong-Soo

    2015-01-01

    Spent nuclear fuel claddings discharged from water reactors contain hydrogen up to 800 wppm depending on the burn-up and power history. During long-term dry storage, the cladding temperature slowly decreases with diminishing decay heat and absorbed hydrogen atoms are precipitated in Zr-matrix according to the terminal solid solubility of hydrogen. Under these conditions, hydrides can significantly reduce cladding ductility and impact resistance, especially when the radial hydrides are massively present in the material. In this study, the effects of hydride morphology on the embrittlement of Zircaloy-4 cladding were investigated using a ring compression test. The results show that circumferentially hydrided Zircaloy-4 cladding is brittle at room temperature but its ductility is regained substantially as the temperature goes above 150 °C. On the other hand, radially hydrided cladding remains brittle at 150 °C and micro-cracks developed in the radial hydrides can act as crack propagation paths. Fracture energy analysis shows that ductile to brittle transition temperature is low in between 25 °C and 100 °C in the former case, whereas it lies in between 200 °C and 250 °C in the latter case.

  18. Modeling incipient creep damage effects on Barkhausen noise and magnetoacoustic emission

    NASA Astrophysics Data System (ADS)

    Sablik, M. J.; Augustyniak, B.; Piotrowski, L.

    2004-05-01

    A model is presented for magnetoacoustic emission (MAE) and magnetic Barkhausen emission (HBN) during incipient creep damage stages in Cr-Mo steel. The model qualitatively reproduces the peak in HBN intensity as one goes through the early incipient stages, and also qualitatively reproduces the strong decrease in MAE intensity through all the incipient stages, leading to over a 50% decrease.

  19. 3D analysis of thermal and stress evolution during laser cladding of bioactive glass coatings.

    PubMed

    Krzyzanowski, Michal; Bajda, Szymon; Liu, Yijun; Triantaphyllou, Andrew; Mark Rainforth, W; Glendenning, Malcolm

    2016-06-01

    Thermal and strain-stress transient fields during laser cladding of bioactive glass coatings on the Ti6Al4V alloy basement were numerically calculated and analysed. Conditions leading to micro-cracking susceptibility of the coating have been investigated using the finite element based modelling supported by experimental results of microscopic investigation of the sample coatings. Consecutive temperature and stress peaks are developed within the cladded material as a result of the laser beam moving along the complex trajectory, which can lead to micro-cracking. The preheated to 500°C base plate allowed for decrease of the laser power and lowering of the cooling speed between the consecutive temperature peaks contributing in such way to achievement of lower cracking susceptibility. The cooling rate during cladding of the second and the third layer was lower than during cladding of the first one, in such way, contributing towards improvement of cracking resistance of the subsequent layers due to progressive accumulation of heat over the process. PMID:26953962

  20. Radiographic Inspection of Fueled Clads

    SciTech Connect

    Timothy J. Roney; Karen M. Wendt

    2005-04-01

    Five general purpose heat source (GPHS) fueled clads were radiographically inspected at the Idaho National Laboratory (INL). The girth weld region of each clad had previously passed visual examination, ring gauge test, and leak test but showed “positive” indications on the ultrasonic (UT) test. Positive ultrasonic indications are allowable under certain weld conditions; radiographic inspection provides a secondary nonintrusive means of clad inspection and may confirm allowable anomalies from the UT inspection. All the positive UT indications were found to exhibit allowable weld shield fusion or mismatch conditions. No indication of void defects was found. One additional clad (FCO371) was deemed unacceptable for radiographic inspection due to an unknown black substance that obscured the angular origin on the weld so that the angular offset to the UT indication could not be found.

  1. High power cladding light strippers

    NASA Astrophysics Data System (ADS)

    Wetter, Alexandre; Faucher, Mathieu; Sévigny, Benoit

    2008-02-01

    The ability to strip cladding light from double clad fiber (DCF) fibers is required for many different reasons, one example is to strip unwanted cladding light in fiber lasers and amplifiers. When removing residual pump light for example, this light is characterized by a large numerical aperture distribution and can reach power levels into the hundreds of watts. By locally changing the numerical aperture (N.A.) of the light to be stripped, it is possible to achieve significant attenuation even for the low N.A. rays such as escaped core modes in the same device. In order to test the power-handling capability of this device, one hundred watts of pump and signal light is launched from a tapered fusedbundle (TFB) 6+1x1 combiner into a high power-cladding stripper. In this case, the fiber used in the cladding stripper and the output fiber of the TFB was a 20/400 0.06/0.46 N.A. double clad fiber. Attenuation of over 20dB in the cladding was measured without signal loss. By spreading out the heat load generated by the unwanted light that is stripped, the package remained safely below the maximum operating temperature internally and externally. This is achieved by uniformly stripping the energy along the length of the fiber within the stripper. Different adhesive and heat sinking techniques are used to achieve this uniform removal of the light. This suggests that these cladding strippers can be used to strip hundreds of watts of light in high power fiber lasers and amplifiers.

  2. Process improvement in laser hot wire cladding for martensitic stainless steel based on the Taguchi method

    NASA Astrophysics Data System (ADS)

    Huang, Zilin; Wang, Gang; Wei, Shaopeng; Li, Changhong; Rong, Yiming

    2016-07-01

    Laser hot wire cladding, with the prominent features of low heat input, high energy efficiency, and high precision, is widely used for remanufacturing metal parts. The cladding process, however, needs to be improved by using a quantitative method. In this work, volumetric defect ratio was proposed as the criterion to describe the integrity of forming quality for cladding layers. Laser deposition experiments with FV520B, one of martensitic stainless steels, were designed by using the Taguchi method. Four process variables, namely, laser power (P), scanning speed (V s), wire feed rate (V f), and wire current (I), were optimized based on the analysis of signal-to-noise (S/N) ratio. Metallurgic observation of cladding layer was conducted to compare the forming quality and to validate the analysis method. A stable and continuous process with the optimum parameter combination produced uniform microstructure with minimal defects and cracks, which resulted in a good metallurgical bonding interface.

  3. Cladding corrosion and hydriding in irradiated defected zircaloy fuel rods (LWBR Development Program)

    SciTech Connect

    Clayton, J.C.

    1985-08-01

    Twenty-one LWBR irradiation test rods containing ThO/sub 2/-UO/sub 2/ fuel and Zircaloy cladding with holes or cracks operated successfully. Zircaloy cladding corrosion on the inside and outside diameter surfaces and hydrogen pickup in the cladding were measured. The observed outer surface Zircaloy cladding corrosion oxide thicknesses of the test rods were similar to thicknesses measured for nondefected irradiation test rods. An analysis model, which was developed to calculate outer surface oxide thickness of non-defected rods, gave results which were in reasonable agreement with the outer surface oxide thicknesses of defected rods. When the analysis procedure was modified to account for additional corrosion proportional to fission rate and to time, the calculated values agreed well with measured inner oxide corrosion film values. Hydrogen pickup in the defected rods was not directly proportional to local corrosion oxide weight gain as was the case for non-defected rods. 16 refs., 6 figs., 8 tabs.

  4. Cracking of Composite Modified Alloy 825 Primary Air Port Tubes

    SciTech Connect

    Kish, Joseph R.; Keiser, James R; Singbeil, Douglas; Willoughby, Adam W; Longmire, Hu Foster

    2007-04-01

    Twenty primary air ports fabricated from modified Alloy 825-based composite tubes underwent a metallurgical examination to document the mode and extent of cracking on the external fireside surface of a kraft recovery boiler. Collectively, the crack features found are most consistent with thermal fatigue, but corrosion fatigue cannot be ruled out. Regardless of the true cracking mechanism, temperature cycling is implicated as a critical factor for crack propagation. on the basis of the relative crack lengths observed, membrane welds and tube weld repairs, and their adjacent heat-affected zones, appear to be more susceptible to cracking than the cladding itself. This work suggests that mills should avoid boiler operating conditions that promote large temperature fluctuations, which can cause Alloy 825-based composite tubes to crack.

  5. Preliminary assessment of the fracture behavior of weld material in full-thickness clad beams

    SciTech Connect

    Keeney, J.A.; Bass, B.R.; McAfee, W.J.; Iskander, S.K.

    1994-10-01

    This report describes a testing program that utilizes full-thickness clad beam specimens to quantify fracture toughness for shallow cracks in material for which metallurgical conditions are prototypic of those found in reactor pressure vessels (RPVs). The beam specimens are fabricated from a section of an RPV wall (removed from a canceled nuclear plant) that includes weld, plate, and clad material. Metallurgical factors potentially influencing fracture toughness for shallow cracks in the beam specimens include material gradients due to welding and cladding applications, as well as material inhomogeneities in welded regions due to reheating in multiple weld passes. A summary of the testing program includes a description of the specimen geometry, material properties, the testing procedure, and the experimental results form three specimens. The yield strength of the weld material was determined to be 36% higher than the yield strength of the base material. An irradiation-induced increase in yield strength of the weld material could result in a yield stress that exceeds the upper limit where code curves are valid. The high yield strength for prototypic weld material may have implications for RPV structural integrity assessments. Analyses of the test data are discussed, including comparisons of measured displacements with finite-element analysis results, applications of toughness estimation techniques, and interpretations of constraint conditions implied by stress-based constraint methodologies. Metallurgical conditions in the region of the cladding heat-affected zone are proposed as a possible explanation for the lower-bound fracture toughness measured with one of the shallow-crack clad beam specimens. Fracture toughness data from the three clad beam specimens are compared with other shallow- and deep-crack uniaxial beam and cruciform data generated previously from A 533 Grade B plate material.

  6. Knuckle Cracking

    MedlinePlus

    ... older obese people. Question: Can cracking knuckles / joints lead to arthritis? Answer: There is no evidence of ... or damaged joints due to arthritis could potentially lead more easily to ligament injury or acute trauma ...

  7. Potential corrosion and degradation mechanisms of Zircaloy cladding on spent nuclear fuel in a tuff repository

    SciTech Connect

    Rothman, A.J.

    1984-09-01

    A literature review and analysis were made of corrosion and degradation processes applicable to Zircaloy cladding on spent nuclear fuel in a tuff repository. In particular, lifetime sought for the Zircaloy is 10,000 years. Among the potential failure mechanisms examined were: oxidation by steam, air, and water, including the effects of ions whose presence is anticipated in the water; mechanical overload; stress (creep) rupture; stress-corrosion cracking (SCC); and delayed failure due to hydride cracking. The conclusion is that failure due to oxidation is not credible, although a few experiments are suggested to confirm the effect of aqueous fluoride on the Zircaloy cladding. Mechanical overload is not a problem, and failure from stress-rupture does not appear likely based on a modified Larson-Miller analysis. Analysis shows that delayed hydride cracking is not anticipated for the bulk of spent fuel pins. However, for a minority of pins under high stress, there is some uncertainty in the analysis as a result of: (1) uncertainty about crack depths in spent fuel claddings and (2) the effect of slow cooling on the formation of radially oriented hydride precipitates. Experimental resolution is called for. Finally, insufficient information is currently available on stress-corrosion cracking. While evidence is presented that SCC failure is not likely to occur, it is difficult to demonstrate this conclusively because the process is not clearly understood and data are limited. Further experimental work on SCC susceptibility is especially needed.

  8. Vanadium diffusion coating on HT-9 cladding for mitigating the fuel cladding chemical interactions

    NASA Astrophysics Data System (ADS)

    Lo, Wei-Yang; Yang, Yong

    2014-08-01

    Fuel cladding chemical interaction (FCCI) has been identified as one of the crucial issues for developing Ferritic/Martensitic (F/M) stainless steel claddings for metallic fuels in a fast reactor. The anticipated elevated temperature and high neutron flux can significantly aggravate the FCCI, in terms of formation of inter-diffusion and lower melting point eutectic phases. To mitigate the FCCI, vanadium carbide coating as a diffusion barrier was deposited on the HT-9 substrate using a pack cementation diffusion coating (PCDC) method, and the processing temperature was optimized down to 730 °C. A solid metallurgical bonding between the coating layer and substrate was achieved, and the coating is free from through depth cracks. The microstructural characterizations using SEM and TEM show a nanostructured grain structure. EDS/WDS and XRD analysis confirm the phase of coating layer as V2C. Diffusion couple tests at 660 °C for 100 h demonstrate that V2C layer with a thickness of less than 5 μm can effectively eliminate the inter-diffusion between the lanthanide cerium and HT-9 steel.

  9. Interfacial microstructure and properties of copper clad steel produced using friction stir welding versus gas metal arc welding

    SciTech Connect

    Shen, Z.; Chen, Y.; Haghshenas, M.; Nguyen, T.; Galloway, J.; Gerlich, A.P.

    2015-06-15

    A preliminary study compares the feasibility and microstructures of pure copper claddings produced on a pressure vessel A516 Gr. 70 steel plate, using friction stir welding versus gas metal arc welding. A combination of optical and scanning electron microscopy is used to characterize the grain structures in both the copper cladding and heat affected zone in the steel near the fusion line. The friction stir welding technique produces copper cladding with a grain size of around 25 μm, and no evidence of liquid copper penetration into the steel. The gas metal arc welding of copper cladding exhibits grain sizes over 1 mm, and with surface microcracks as well as penetration of liquid copper up to 50 μm into the steel substrate. Transmission electron microscopy reveals that metallurgical bonding is produced in both processes. Increased diffusion of Mn and Si into the copper cladding occurs when using gas metal arc welding, although some nano-pores were detected in the FSW joint interface. - Highlights: • Cladding of steel with pure copper is possible using either FSW or GMAW. • The FSW yielded a finer grain structure in the copper, with no evidence of cracking. • The FSW joint contains some evidence of nano-pores at the interface of the steel/copper. • Copper cladding by GMAW contained surface cracks attributed to high thermal stresses. • The steel adjacent to the fusion line maintained a hardness value below 248 HV.

  10. Small-crack effects in high-strength aluminum alloys

    NASA Technical Reports Server (NTRS)

    Newman, J. C., Jr.; Wu, X. R.; Venneri, S. L.; Li, C. G.

    1994-01-01

    The National Aeronautics and Space Administration and the Chinese Aeronautical Establishment participated in a Fatigue and Fracture Mechanics Cooperative Program. The program objectives were to identify and characterize crack initiation and growth of small cracks (10 microns to 2 mm long) in commonly used US and PRC aluminum alloys, to improve fracture mechanics analyses of surface- and corner-crack configurations, and to develop improved life-prediction methods. Fatigue and small-crack tests were performed on single-edgenotch tension (SENT) specimens and large-crack tests were conducted on center-crack tension specimens for constant-amplitude (stress ratios of -1, 0, and 0.5) and Mini-TWIST spectrum loading. The plastic replica method was used to monitor the initiation and growth of small fatigue cracks at the semicircular notch. Crack growth results from each laboratory on 7075-T6 bare and LC9cs clad aluminum alloys agreed well and showed that fatigue life was mostly crack propagation from a material defect (inclusion particles or void) or from the cladding layer. Finite-element and weight-function methods were used to determine stress intensity factors for surface and corner cracks in the SENT specimens. Equations were then developed and used in a crack growth and crack-closure model to correlate small- and large-crack data and to make life predictions for various load histories. The cooperative program produced useful experimental data and efficient analysis methods for improving life predictions. The results should ultimately improve aircraft structural reliability and safety.

  11. Calculation of hydrogen and oxygen uptake in fuel rod cladding during severe accidents using the integral diffusion method -- Preliminary design report

    SciTech Connect

    Siefken, L.J.

    1999-02-01

    Preliminary designs are described for models of hydrogen and oxygen uptake in fuel rod cladding during severe accidents. Calculation of the uptake involves the modeling of seven processes: (1) diffusion of oxygen from the bulk gas into the boundary layer at the external cladding surface, (2) diffusion from the boundary layer into the oxide layer, (3) diffusion from the inner surface of the oxide layer into the metallic part of the cladding, (4) uptake of hydrogen in the event that the cladding oxide layer is dissolved in a steam-starved region, (5) embrittlement of cladding due to hydrogen uptake, (6) cracking of cladding during quenching due to its embrittlement and (7) release of hydrogen from the cladding after cracking of the cladding. An integral diffusion method is described for calculating the diffusion processes in the cladding. Experimental results are presented that show a rapid uptake of hydrogen in the event of dissolution of the oxide layer and a rapid release of hydrogen in the event of cracking of the oxide layer. These experimental results are used as a basis for calculating the rate of hydrogen uptake and the rate of hydrogen release. The uptake of hydrogen is limited to the equilibrium solubility calculated by applying Sievert's law. The uptake of hydrogen is an exothermic reaction that accelerates the heatup of a fuel rod. An embrittlement criteria is described that accounts for hydrogen and oxygen concentration and the extent of oxidation. A design is described for implementing the models for hydrogen and oxygen uptake and cladding embrittlement into the programming framework of the SCDAP/RELAP5 code. A test matrix is described for assessing the impact of the proposed models on the calculated behavior of fuel rods in severe accident conditions. This report is a revision and reissue of the report entitled; ``Preliminary Design Report for Modeling of Hydrogen Uptake in Fuel Rod Cladding During Severe Accidents.''

  12. Clad Degradation - FEPs Screening Arguments

    SciTech Connect

    E. Siegmann

    2004-03-17

    The purpose of this report is to document the screening of the cladding degradation features, events, and processes (FEPs) for commercial spent nuclear fuel (CSNF). This report also addresses the effect of some FEPs on both the cladding and the CSNF, DSNF, and HLW waste forms where it was considered appropriate to address the effects on both materials together. This report summarizes the work of others to screen clad degradation FEPs in a manner consistent with, and used in, the Total System Performance Assessment-License Application (TSPA-LA). This document was prepared according to ''Technical Work Plan for Waste Form Degradation Modeling, Testing, and Analyses in Support of LA'' (BSC 2004a [DIRS 167796]).

  13. Weld cladding of hard surfaces

    NASA Astrophysics Data System (ADS)

    Habrekke, T.

    1993-02-01

    A literature study about clad welding of hard surfaces on steel is performed. The purpose was to see what kind of methods are mainly used, and particular attention is paid to clad welding of rolls. The main impression from this study is that several methods are in use. Some of these must be considered as 'too exotic' for the aim of the program, such as laser build-up welding. However, clad welding of hard surfaces to rolls is widely used around the world, and there is no need for particularly advanced welding methods to perform the work. The welding consumables and the way the welding is carried out is of more important character. The report will give some comments to this, and hopefully will give a short review of the current technology in this field.

  14. Silicon cladding for mirror substrates

    NASA Astrophysics Data System (ADS)

    Duston, Christopher J.; Gunda, Nilesh; Schwartz, Jay R.; Robichaud, Joseph L.

    2009-08-01

    To reduce the finishing costs of silicon carbide mirror substrates, silicon claddings are applied allowing the surfaces to be more easily diamond turned and polished than the bare chemical vapor deposited (CVD) silicon carbide or bimodal reaction bonded SiC (RB-SiC). The benefits of using silicon as the optical face will be reviewed as will the process for applying plasma enhanced chemical vapor (PE-CVD) deposited amorphous silicon cladding on substrates. Using one mirror as an example, the successful finishing results will be shared.

  15. Optimizing electroslag cladding with finite element modeling

    SciTech Connect

    Li, M.V.; Atteridge, D.G.; Meekisho, L.

    1996-12-31

    Electroslag cladding of nickel alloys onto carbon steel propeller shafts was optimized in terms of interpass temperatures. A two dimensional finite element model was used in this study to analyze the heat transfer induced by multipass electroslag cladding. Changes of interpass temperatures during a cladding experiment with uniform initial temperature distribution on a section of shaft were first simulated. It was concluded that uniform initial temperature distribution would lead to interpass temperatures out of the optimal range if continuous cladding is expected. The difference in the cooling conditions among experimental and full size shafts and its impact on interpass temperatures during the cladding were discussed. Electroslag cladding onto a much longer shaft, virtually an semi infinite long shaft, was analyzed with specific reference to the practical applications of electroslag cladding. Optimal initial preheating temperature distribution was obtained for continuous cladding on full size shafts which would keep the interpass temperatures within the required range.

  16. EPRI-NASA Cooperative Project on Stress Corrosion Cracking of Zircaloys. [nuclear fuel failures

    NASA Technical Reports Server (NTRS)

    Cubicciotti, D.; Jones, R. L.

    1978-01-01

    Examinations of the inside surface of irradiated fuel cladding from two reactors show the Zircaloy cladding is exposed to a number of aggressive substances, among them iodine, cadmium, and iron-contaminated cesium. Iodine-induced stress corrosion cracking (SCC) of well characterized samples of Zircaloy sheet and tubing was studied. Results indicate that a threshold stress must be exceeded for iodine SCC to occur. The existence of a threshold stress indicates that crack formation probably is the key step in iodine SCC. Investigation of the crack formation process showed that the cracks responsible for SCC failure nucleated at locations in the metal surface that contained higher than average concentrations of alloying elements and impurities. A four-stage model of iodine SCC is proposed based on the experimental results and the relevance of the observations to pellet cladding interaction failures is discussed.

  17. Multi-clad black display panel

    DOEpatents

    Veligdan, James T.; Biscardi, Cyrus; Brewster, Calvin

    2002-01-01

    A multi-clad black display panel, and a method of making a multi-clad black display panel, are disclosed, wherein a plurality of waveguides, each of which includes a light-transmissive core placed between an opposing pair of transparent cladding layers and a black layer disposed between transparent cladding layers, are stacked together and sawed at an angle to produce a wedge-shaped optical panel having an inlet face and an outlet face.

  18. ZIRCONIUM-CLADDING OF THORIUM

    DOEpatents

    Beaver, R.J.

    1961-11-21

    A method of cladding thorium with zirconium is described. The quality of the bond achieved between thorium and zirconium by hot-rolling is improved by inserting and melting a thorium-zirconium alloy foil between the two materials prior to rolling. (AEC)

  19. Toughening of Fe-based laser-clad alloy coating

    NASA Astrophysics Data System (ADS)

    Yao, Chengwu; Huang, Jian; Zhang, Peilei; Li, Zhuguo; Wu, Yixiong

    2011-01-01

    An investigation is reported on crack-free laser clad Fe-based alloy by use of biaxial powder feeding shielded with argon gas. The microstructure and phase structure of the coating were studied, and mechanical properties were analyzed through hardness, tension strength and wear resistance of the coating. Microstructure analysis showed that there was retained austenite with spherical particles distributed therein in the interdendritic and nearby grain boundary regions. The mechanical test results showed that net-like distributed retained austenite in the interdendritic region had certain toughening effect through blunting crack-tip. Under wear condition of high sliding speed and high loading, the wear resistance of the coating with net-like retained austenite was much higher than that of the coating with some discontinuous carbide network or carbide blocks. The results showed that toughening of laser clad Fe-based alloy with high hardness over 850 HV could be achieved by modifying interdendritic phases from net-like carbide to net-like austenite with spherical particles.

  20. Controlling incipient oxidation of pyrite for improved rejection. Final report

    SciTech Connect

    Yoon, R.H.; Richardson, P.E.; Tao, D.P.

    1996-04-01

    It is well known that superficial oxidation of pyrite produces a hydrophobic sulfur-rich surface and creates problems in separating the mineral from coal using surface-based processes such as flotation and agglomeration. Numerous studies of pyrite oxidation have been conducted but most of them were concerned with the advanced stages of oxidation, and as a result it was not possible to establish a relationship between oxidation and flotation behavior. A better understanding of the mechanisms and kinetics of the incipient oxidation reactions, which may vary with the origin, morphology, texture, and solid state properties of pyrite, can lead to the development of new processes that can improve pyrite rejection from coal. This project is aimed at better understanding of the mechanisms involved during the initial stages of pyrite oxidation to foster the development of advanced coal cleaning technologies. Studies were conducted by fracturing pyrite electrodes in-situ in an electrochemical cell to create virgin surfaces. Electrochemical and photoelectrochemical techniques were employed to characterize the incipient oxidation of pyrite in aqueous solutions. Microflotation tests were conducted to obtain information on the hydrophobicity of pyrite under controlled E{sub h} and pH conditions, and the results were correlated with electrochemical studies.

  1. Miller City levee break and incipient meander cutoff

    USGS Publications Warehouse

    Oberg, K.A.; Jacobson, R.B.

    1994-01-01

    On July 15, 1993, the flooding Mississippi River broke through a levee near Miller City, Ill., at the head of the Mississippi Embayment, approximately 55 km upstream from Cairo, Ill. Flow through the break crossed a high-amplitude meander bend and reentered the main channel approximately 24 km upstream from Cairo, bypassing 31 km of the river channel. The incipient meander cutoff is one of the more dramatic examples of geomorphic change accompanying the 1993 flood. Discharge and bathymetry data were collected in the incipient cutoff channel every other day during the 2 weeks before and after the flood peak. During the peak on August 7, as much as 8,100 m3/s, or approximately 25 percent of the Mississippi flood discharge, was bypassing the meander bend. The flow excavated an irregular channel in the flood plain up to 25 m deep. This irregular channel extends as far as 2 km downstream from the levee break. By August 25, as much as 2,900 m3/s was still flowing through the levee break; with recession of the flood, extensive sand deposits were exposed on the margins and downstream from the scoured areas. Preliminary data indicate that local relief, such as relict channels and preexisting county roads, affected the extent of new channel formation.

  2. Kinetics of Elementary Processes Relevant to Incipient Soot Formation

    SciTech Connect

    Lin, M C; Heaven, M C

    2008-04-30

    Soot formation and abatement processes are some of the most important and challenging problems in hydrocarbon combustion. The key reactions involved in the formation of polycyclic aromatic hydrocarbons (PAH's), the precursors to soot, remain elusive. Small aromatic species such as C5H5, C6H6 and their derivatives are believed to play a pivotal role in incipient soot formation. The goal of this project is to establish a kinetic database for elementary reactions relevant to soot formation in its incipient stages. In the past year, we have completed by CRDS the kinetics for the formation and decomposition of C6H5C2H2O2 in the C6H5C2H2 +O2 reaction and the formation of C10H7O2 in the C10H7 + O2 reaction by directly monitoring C6H5C2H2O2 and C10H7O2 radicals in the visible region; their mechanisms have been elucidated computationally by quantum-chemical calculations. The O + C2H5OH reaction has been studied experimentally and computationally and the OH + HNCN reaction has been investigated by ab initio molecular orbital calculation. In addition, a new pulsed slit molecular beam system has been constructed and tested for spectroscopic studies of aromatic radicals and their derivatives by the cavity ringdown technique (CRDS).

  3. Strain-compensated AlGaN /GaN/InGaN cladding layers in homoepitaxial nitride devices

    NASA Astrophysics Data System (ADS)

    Czernecki, R.; Krukowski, S.; Targowski, G.; Prystawko, P.; Sarzynski, M.; Krysko, M.; Kamler, G.; Grzegory, I.; Leszczynski, M.; Porowski, S.

    2007-12-01

    One of the most important problems in III-nitride violet laser diode technology is the lattice mismatch between the AlGaN cladding layers and the rest of the epitaxial structure. For efficiently working devices, it is necessary to have both a high Al content and thick claddings. This leads, however, to severe sample bowing and even cracking of the upper layer. In this work, we propose a cladding structure of strain-compensated AlGaN /GaN/InGaN superlattice grown by metal-organic vapor phase epitaxy on bulk GaN substrates. Various thicknesses and compositions of the layers were employed. We measured the radius of bowing, lattice mismatches, aluminum and indium contents, and densities of threading dislocations. The proposed cladding structures suppress bowing and cracking, which are the two parasitic effects commonly experienced in laser diodes with bulk AlGaN claddings. The suppression of cracking and bowing is shown to occur due to modified strain energy distribution of the superlattices structure.

  4. Effect of zirconium oxide on the stress-corrosion susceptibility of irradiated Zircaloy cladding

    SciTech Connect

    Mattas, R.F.; Yaggee, F.L.; Neimark, L.A.

    1982-01-01

    Cladding specimens were obtained from two fuel rods irradiated in the Big Rock Point Reactor to a burnup of approximately 8 gigawatt days per ton. Both claddings had a uniform, thick (approximately 4/mu/m) zirconium oxide layer on the inner surface. The significant difference between the two rods was the degree of fission-gas release (0.2 versus 14.3 percent). The cladding specimens, with the fuel removed, were subjected to stress-rupture tests to evaluate their stress corrosion cracking (SCC) susceptibility at an initial iodine concentration of 0.6 mg/cm/sup 2/ and a temperature of 325 degree C. Specimens from the high-gas-release rod exhibited significantly increased susceptibility to iodine SCC. The results suggest that the inner-surface oxide provides a barrier to iodine penetration. 10 refs.

  5. Effect of hydride orientation on fracture toughness of Zircaloy-4 cladding

    NASA Astrophysics Data System (ADS)

    Hsu, Hsiao-Hung; Tsay, Leu-Wen

    2011-01-01

    Hydrogen embrittlement is one of the major degradation mechanisms for high burnup fuel cladding during reactor service and spent fuel dry storage, which is related to the hydrogen concentration, morphology and orientation of zirconium hydrides. In this work, the J-integral values for X-specimens with different hydride orientations are measured to evaluate the fracture toughness of Zircaloy-4 (Zry-4) cladding. The toughness values for Zry-4 cladding with various percentages of radial hydrides are much smaller than those with circumferential hydrides only in the same hydrogen content level at 25 °C. The fractograghic features reveal that the crack path is influenced by the orientation of zirconium hydride. Moreover, the fracture toughness measurements for X-specimens at 300 °C are not sensitive to a variation in hydride orientation but to hydrogen concentration.

  6. Glass-clad semiconductor core optical fibers

    NASA Astrophysics Data System (ADS)

    Morris, Stephanie Lynn

    Glass-clad optical fibers comprising a crystalline semiconductor core have garnered considerable recent attention for their potential utility as novel waveguides for applications in nonlinear optics, sensing, power delivery, and biomedicine. As research into these fibers has progressed, it has become evident that excessive losses are limiting performance and so greater understanding of the underlying materials science, coupled with advances in fiber processing, is needed. More specifically, the semiconductor core fibers possess three performance-limiting characteristics that need to be addressed: (a) thermal expansion mismatches between crystalline core and glass cladding that lead to cracks, (b) the precipitation of oxide species in the core upon fiber cooling, which results from partial dissolution of the cladding glass by the core melt, and (c) polycrystallinity; all of which lead to scattering and increased transmission losses. This dissertation systematically studies each of these effects and develops both a fundamental scientific understanding of and practical engineering methods for reducing their impact. With respect to the thermal expansion mismatch and, in part, the dissolution of oxides, for the first time to our knowledge, oxide and non-oxide glass compositions are developed for a series of semiconductor cores based on two main design criteria: (1) matching the thermal expansion coefficient between semiconductor core and glass cladding to minimize cracking and (2) matching the viscosity-temperature dependences, such that the cladding glass draws into fiber at a temperature slightly above the melting point of the semiconductor in order to minimize dissolution and improve the fiber draw process. The x[Na 2O:Al2O3] + (100 - 2x)SiO2 glass compositional family was selected due to the ability to tailor the glass properties to match the aforementioned targets through slight variations in composition and adjusting the ratios of bridging and non-bridging oxygen

  7. Crack tip deformation and fatigue crack growth

    NASA Technical Reports Server (NTRS)

    Liu, H.-W.

    1981-01-01

    Recent research on fatigue crack growth is summarized. Topics discussed include the use of the differential stress intensity factor to characterize crack tip deformation, the use of the unzipping model to study the growth of microcracks and the fatigue crack growth in a ferritic-martensitic steel, and the development of a model of fatige crack growth threshold. It is shown that in the case of small yielding, the differential stress intensity factor provides an adequate description of cyclic plastic deformation at the crack tip and correlates well with the crack growth rate. The unzipping model based on crack tip shear decohesion process is found to be in good agreement with the measured crack growth and striation spacing measurements. The proposed model of crack growth threshold gives correct predictions of the crack growth behavior in the near-threshold region.

  8. Investigation of stainless steel clad fuel rod failures and fuel performance in the Connecticut Yankee Reactor. Final report

    SciTech Connect

    Pasupathi, V.; Klingensmith, R. W.

    1981-11-01

    Significant levels of fuel rod failures were observed in the batch 8 fuel assemblies of the Connecticut Yankee reactor. Failure of 304 stainless steel cladding in a PWR environment was not expected. Therefore a detailed poolside and hot cell examination program was conducted to determine the cause of failure and identify differences between batch 8 fuel and previous batches which had operated without failures. Hot cell work conducted consisted of detailed nondestructive and destructive examination of fuel rods from batches 7 and 8. The results indicate that the batch 8 failure mechanism was stress corrosion cracking initiating on the clad outer surface. The sources of cladding stresses are believed to be (a) fuel pellet chips wedged in the cladding gap, (b) swelling of highly nondensifying batch 8 fuel and (c) potentially harmful effects of a power change event that occurred near the end of the second cycle of irradiation for batch 8.

  9. CLAD DEGRADATION - FEPS SCREENING ARGUMENTS

    SciTech Connect

    R. Schreiner

    2004-10-21

    The purpose of this report is to evaluate and document the screening of the clad degradation features, events, and processes (FEPs) with respect to modeling used to support the Total System Performance Assessment-License Application (TSPA-LA). This report also addresses the effect of certain FEPs on both the cladding and the commercial spent nuclear fuel (CSNF), DOE-owned spent nuclear fuel (DSNF), and defense high-level waste (DHLW) waste forms, as appropriate to address the effects on multiple materials and both components (FEPs 2.1.09.09.0A, 2.1.09.11.0A, 2.1.11.05.0A, 2.1.12.02.0A, and 2.1.12.03.0A). These FEPs are expected to affect the repository performance during the postclosure regulatory period of 10,000 years after permanent closure. Table 1-1 provides the list of cladding FEPs, including their screening decisions (include or exclude). The primary purpose of this report is to identify and document the analysis, screening decision, and TSPA-LA disposition (for included FEPs) or screening argument (for excluded FEPs) for these FEPs related to clad degradation. In some cases, where a FEP covers multiple technical areas and is shared with other FEP reports, this report may provide only a partial technical basis for the screening of the FEP. The full technical basis for shared FEPs is addressed collectively by the sharing FEP reports. The screening decisions and associated TSPA-LA dispositions or screening arguments from all of the FEP reports are cataloged in a project-specific FEPs database.

  10. NUCLEAR REACTOR COMPENENT CLADDING MATERIAL

    DOEpatents

    Draley, J.E.; Ruther, W.E.

    1959-01-27

    Fuel elements and coolant tubes used in nuclear reactors of the heterogeneous, water-cooled type are described, wherein the coolant tubes extend through the moderator and are adapted to contain the fuel elements. The invention comprises forming the coolant tubes and the fuel element cladding material from an alloy of aluminum and nickel, or an alloy of aluminum, nickel, alloys are selected to prevent intergranular corrosion of these components by water at temperatures up to 35O deg C.

  11. Flaw density examinations of a clad boiling water reactor pressure vessel segment

    SciTech Connect

    Cook, K.V.; McClung, R.W.

    1986-01-01

    Flaw density is the greatest uncertainty involved in probabilistic analyses of reactor pressure vessel failure. As part of the Heavy-Section Steel Technology (HSST) Program, studies have been conducted to determine flaw density in a section of reactor pressure vessel cut from the Hope Creek Unit 2 vessel (nominally 0.7 by 3 m (2 by 10 ft)). This section (removed from the scrapped vessel that was never in service) was evaluated nondestructively to determine the as-fabricated status. We had four primary objectives: (1) evaluate longitudinal and girth welds for flaws with manual ultrasonics, (2) evaluate the zone under the nominal 6.3-mm (0.25-in.) clad for cracking (again with manual ultrasonics), (3) evaluate the cladding for cracks with a high-sensitivity fluorescent penetrant method, and (4) determine the source of indications detected.

  12. Incipient failure detection (IFD) of SSME ball bearings

    NASA Technical Reports Server (NTRS)

    1982-01-01

    Because of the immense noise background during the operation of a large engine such as the SSME, the relatively low level unique ball bearing signatures were often buried by the overall machine signal. As a result, the most commonly used bearing failure detection technique, pattern recognition using power spectral density (PSD) constructed from the extracted bearing signals, is rendered useless. Data enhancement techniques were carried out by using a HP5451C Fourier Analyzer. The signal was preprocessed by a Digital Audio Crop. DAC-1024I noise cancelling filter in order to estimate the desired signal corrupted by the backgound noise. Reference levels of good bearings were established. Any deviation of bearing signals from these reference levels indicate the incipient bearing failures.

  13. Incipient seafloor spreading segments: Insights from the Red Sea

    NASA Astrophysics Data System (ADS)

    Almalki, K. A.; Betts, P. G.; Ailleres, L.

    2016-03-01

    Crustal-scale forward models of marine satellite potential field data suggest that the Red Sea comprises a single segment of ocean crust, which extends along ~60% of the Red Sea. The segment "tips" are bounded by continental crust, and there is no evidence for transforms at the segment terminations at the south. These observations indicate that ocean crust formation does not necessarily occur in response to wholesale tearing or "unzipping" of continental lithosphere nor is it necessarily controlled by preexisting transform faults. Ocean crust initiation occurs as a series of isolated segments that coalesce as the basin evolves. The recognition of this process in an orthogonal extension setting is comparable to spreading segmentation in modern ocean systems generated at a highly oblique convergent margin, suggesting that oceanic crust segmentation is not controlled by kinematic boundary conditions. The Red Sea may represent a combination of incipient type I and type II passive margins development.

  14. Incipient fluidization condition for a centrifugal fluidized bed

    SciTech Connect

    Fan, L.T.; Chang, C.C.; Takahashi, T.; Tanaka, Z.; Yu, Y.S.

    1985-06-01

    A model has been proposed for the condition of incipient fluidization in a centrifugal fluidized bed. The model is based on the balance between the overall forces, including the centrifugal and fluid frictional forces, exerted on the fluidized particles and the overall effective weight of the particles. Equations have been derived from the model for predicting the critical fluidizing velocity and the maximum pressure differential (or pressure drop) through the centrifugal bed. A series of experiments was carried out with different solid particles, bed rotational speeds, and bed heights. The resultant data for the critical fluidizing velocity and the maximum pressure drop of the bed indicate that the proposed model is valid and the derived equations are of practical use.

  15. Incipient radiation within the dominant Hawaiian tree Metrosideros polymorpha.

    PubMed

    Stacy, E A; Johansen, J B; Sakishima, T; Price, D K; Pillon, Y

    2014-10-01

    Although trees comprise a primary component of terrestrial species richness, the drivers and temporal scale of divergence in trees remain poorly understood. We examined the landscape-dominant tree, Metrosideros polymorpha, for variation at nine microsatellite loci across 23 populations on young Hawai'i Island, sampling each of the island's five varieties throughout its full geographic range. For four varieties, principal coordinate analysis revealed strong clustering of populations by variety across the 10 430 km(2) island, indicating partitioning of the species into multiple evolutionarily significant units. The single island-endemic form, riparian var. newellii, showed especially strong differentiation from other varieties despite occurring in sympatry with other varieties and likely evolved from a bog form on the oldest volcano, Kohala, within the past 500 000 years. Along with comparable riparian forms on other Pacific Islands, var. newellii appears to represent parallel incipient ecological speciation within Metrosideros. Greater genetic distance among the more common varieties on the oldest volcano and an inverse relationship between allelic diversity and substrate age appear consistent with colonization of Hawai'i Island by older, partially diverged varieties followed by increased hybridization among varieties on younger volcanoes. This study demonstrates that broad population-level sampling is required to uncover patterns of diversification within a ubiquitous and long-lived tree species. Hawaiian Metrosideros appears to be a case of incipient radiation in trees and thus should be useful for studies of divergence and the evolution of reproductive isolating barriers at the early stages of speciation. PMID:24824285

  16. Incipient radiation within the dominant Hawaiian tree Metrosideros polymorpha

    PubMed Central

    Stacy, E A; Johansen, J B; Sakishima, T; Price, D K; Pillon, Y

    2014-01-01

    Although trees comprise a primary component of terrestrial species richness, the drivers and temporal scale of divergence in trees remain poorly understood. We examined the landscape-dominant tree, Metrosideros polymorpha, for variation at nine microsatellite loci across 23 populations on young Hawai'i Island, sampling each of the island's five varieties throughout its full geographic range. For four varieties, principal coordinate analysis revealed strong clustering of populations by variety across the 10 430 km2 island, indicating partitioning of the species into multiple evolutionarily significant units. The single island-endemic form, riparian var. newellii, showed especially strong differentiation from other varieties despite occurring in sympatry with other varieties and likely evolved from a bog form on the oldest volcano, Kohala, within the past 500 000 years. Along with comparable riparian forms on other Pacific Islands, var. newellii appears to represent parallel incipient ecological speciation within Metrosideros. Greater genetic distance among the more common varieties on the oldest volcano and an inverse relationship between allelic diversity and substrate age appear consistent with colonization of Hawai'i Island by older, partially diverged varieties followed by increased hybridization among varieties on younger volcanoes. This study demonstrates that broad population-level sampling is required to uncover patterns of diversification within a ubiquitous and long-lived tree species. Hawaiian Metrosideros appears to be a case of incipient radiation in trees and thus should be useful for studies of divergence and the evolution of reproductive isolating barriers at the early stages of speciation. PMID:24824285

  17. Cladding stress during extended storage of high burnup spent nuclear fuel

    NASA Astrophysics Data System (ADS)

    Raynaud, Patrick A. C.; Einziger, Robert E.

    2015-09-01

    In an effort to assess the potential for low temperature creep and delayed hydride cracking failures in high burnup spent fuel cladding during extended dry storage, the U.S. NRC analytical fuel performance tools were used to predict cladding stress during a 300 year dry storage period for UO2 fuel burned up to 65 GWd/MTU. Fuel swelling correlations were developed and used along with decay gas production and release fractions to produce circumferential average cladding stress predictions with the FRAPCON-3.5 fuel performance code. The resulting stresses did not result in cladding creep failures. The maximum creep strains accumulated were on the order of 0.54-1.04%, but creep failures are not expected below at least 2% strain. The potential for delayed hydride cracking was assessed by calculating the critical flaw size required to trigger this failure mechanism. The critical flaw size far exceeded any realistic flaw expected in spent fuel at end of reactor life.

  18. Process development for cladding APT tungsten targets

    SciTech Connect

    Horner, M H; Barber, R; Dalder, E

    2000-11-27

    This report describes development of processes for cladding APT Target tungsten components with a thin layer (0.127-mm) of Alloy 718, Alloy 600 or 316L stainless steel alloy. The application requires that the cladding be thermally bonded to the tungsten in order to transfer heat generated in the tungsten volume to a surrounding coolant. High temperature diffusion bonding using the hot isostatic processing (HIP) technique was selected as the method for creating a metallurgical bond between pure tungsten tubes and rods and the cladding materials. Bonding studies using a uniaxially loaded vacuum hot press were conducted in preliminary experiments to determine acceptable time-temperature conditions for diffusion bonding. The results were successfully applied in cladding tungsten rods and tubes with these alloys. Temperatures 800-810 C were suitable for cladding tungsten with Alloy 600 and 316L stainless steel alloy, whereas tungsten was clad with Alloy 718 at 1020 C.

  19. Modeling and simulation of hydrogen behavior in Zircaloy-4 fuel cladding

    NASA Astrophysics Data System (ADS)

    Courty, Olivier; Motta, Arthur T.; Hales, Jason D.

    2014-09-01

    As a result of corrosion during normal operation in nuclear reactors, hydrogen can enter the zirconium-alloy fuel cladding and precipitate as brittle hydride platelets, which can severely degrade the cladding ductility. Under a heterogeneous temperature distribution, hydrides tend to accumulate in the colder areas, creating local spots of degraded cladding that can favor crack initiation. Therefore, an estimation of the local hydride distribution is necessary to help predict the risk of cladding failure. The hydride distribution is governed by three competing phenomena. Hydrogen in solid solution diffuses under a concentration gradient due to Fick's law and under a temperature gradient due to the Soret effect. Precipitation of the hydride platelets occurs once the hydrogen solubility limit is reached. A model of these phenomena was implemented in the 3D fuel performance code BISON in order to calculate the hydrogen distribution for arbitrary geometries, such as a nuclear fuel rod, and is now available for BISON users. Simulations have been performed on simple geometries to validate the model and its implementation. The simulations predict that before precipitation occurs, hydrogen tends to accumulate in the colder spots due to the Soret effect. Once the solubility limit is reached, hydrogen precipitates and forms a rim close to the outer edge of the cladding. The simulations also predict that the reactor shut down has little effect on already precipitated hydrides but causes the remaining hydrogen to precipitate homogeneously into hydrides.

  20. Modeling and simulation of hydrogen behavior in Zircaloy-4 fuel cladding

    SciTech Connect

    Jason D. Hales; Various

    2014-09-01

    As a result of corrosion during normal operation in nuclear reactors, hydrogen can enter the zirconium-alloy fuel cladding and precipitate as brittle hydride platelets, which can severely degrade the cladding ductility. Under a heterogeneous temperature distribution, hydrides tend to accumulate in the colder areas, creating local spots of degraded cladding that can favor crack initiation. Therefore, an estimation of the local hydride distribution is necessary to help predict the risk of cladding failure. The hydride distribution is governed by three competing phenomena. Hydrogen in solid solution diffuses under a concentration gradient due to Fick’s law and under a temperature gradient due to the Soret effect. Precipitation of the hydride platelets occurs once the hydrogen solubility limit is reached. A model of these phenomena was implemented in the 3D fuel performance code BISON in order to calculate the hydrogen distribution for arbitrary geometries, such as a nuclear fuel rod, and is now available for BISON users. Simulations have been performed on simple geometries to validate the model and its implementation. The simulations predict that before precipitation occurs, hydrogen tends to accumulate in the colder spots due to the Soret effect. Once the solubility limit is reached, hydrogen precipitates and forms a rim close to the outer edge of the cladding. The simulations also predict that the reactor shut down has little effect on already precipitated hydrides but causes the remaining hydrogen to precipitate homogeneously into hydrides.

  1. Research on mechanisms of stress corrosion cracking in Zircaloy

    SciTech Connect

    Knorr, D.B.; Pelloux, R.M.

    1981-06-01

    The results of internal gas pressurization tests, primarily at 320/sup 0/C, on cladding tubes from two suppliers, Supplier A and Supplier B, are presented. The two lots show a substantial difference in iodine SCC susceptibility so a test matrix is used to resolve the relative contributions of surface condition, residual stress, and texture. Additional tests with constant deflection split-ring specimens and with unstressed cladding segments are used to understand crack initiation and the early crack growth stages of SCC. The difference in SCC susceptibility is due to crystallographic texture. Other variables such as surface finish, stress relief temperature, and residual stress have little or no effect. Mechanical properties, crack initiation, and crack propagation all depend on texture. Both initiation and propagation features are analyzed by scanning electron microscopy. A mechanism for crack initiation consistent with most observations in this study and with the work of other investigators is proposed. At 320/sup 0/C, lifetime is crack initiation limited while several tests at 390/sup 0/C indicate that lifetime is less initiation limited at higher temperature. 31 figures, 9 tables.

  2. Advanced Fuels Campaign Cladding & Coatings Meeting Summary

    SciTech Connect

    Not Listed

    2013-03-01

    The Fuel Cycle Research and Development (FCRD) Advanced Fuels Campaign (AFC) organized a Cladding and Coatings operational meeting February 12-13, 2013, at Oak Ridge National Laboratory (ORNL). Representatives from the U.S. Department of Energy (DOE), national laboratories, industry, and universities attended the two-day meeting. The purpose of the meeting was to discuss advanced cladding and cladding coating research and development (R&D); review experimental testing capabilities for assessing accident tolerant fuels; and review industry/university plans and experience in light water reactor (LWR) cladding and coating R&D.

  3. Protective claddings for high strength chromium alloys

    NASA Technical Reports Server (NTRS)

    Collins, J. F.

    1971-01-01

    The application of a Cr-Y-Hf-Th alloy as a protective cladding for a high strength chromium alloy was investigated for its effectiveness in inhibiting nitrogen embrittlement of a core alloy. Cladding was accomplished by a combination of hot gas pressure bonding and roll cladding techniques. Based on bend DBTT, the cladding alloy was effective in inhibiting nitrogen embrittlement of the chromium core alloy for up to 720 ks (200hours) in air at 1422 K (2100 F). A significant increase in the bend DBTT occurred with longer time exposures at 1422 K or short time exposures at 1589 K (2400 F).

  4. Boulder transport by tsunamis: A laboratory experiment on incipient motion

    NASA Astrophysics Data System (ADS)

    Bressan, Lidia; Antonini, Alessandro; Gaeta, Maria Gabriella; Guerrero, Massimo; Miani, Marco; Petruzzelli, Valentina; Samaras, Achilleas

    2015-04-01

    Coastal boulders transported inland by high-energy events, such as tsunamis or storms, have been found along several coastal areas worldwide. The importance of these deposits relies on their implications on coastal hazard assessment, since they contribute to the identification of past events and to the study of their magnitude and characteristics. However, the identification of the event responsible of the dislocation of the boulder (tsunami or storm) is not trivial given the complexities of the tsunami and storm phenomena, the coastal environment, the initial boulder conditions, the uncertainties of the problem, etc. The hydrodynamics methods usually adopted are 1) the use of simple hydrodynamics formulae to estimate the minimum flow velocity and height required to move a boulder, and 2) numerical simulations that model the boulder transport together with the specific tsunami (or storm) event. The main shortcomings of the first method are the simplifications adopted, while the second approach implies the simulation of the transport event, which might not be practical because of the amount of uncertainties involved. To contribute to this study field, a laboratory experiment on the flow conditions for boulder transport was carried out at the Hydraulic Engineering Laboratory (LIDR) of the University of Bologna, Italy, in a 11 m long and 0.5 m wide flume. The main objective of this experiment is to provide experimental data for the conditions of the incipient motion for boulders, i.e. to relate the threshold flow velocity and depth for transport with the characteristics of the boulders, i.e. weight and geometry. The experimental channel is divided in three parts: on one end of the channel, a water tank is closed by a gate, followed by a central flat bed and a 1:10 slope, where the boulder is located. A bore, generated by quickly opening the gate (simulating a dam-break), flows in the channel, climbs up the slope and hits the boulder. The impact of the flow on the

  5. Brazilian and Mexican experiences in the study of incipient domestication

    PubMed Central

    2014-01-01

    analyses of contrasting and diverse cultural and ecological contexts for a better understanding of evolution under incipient processes of domestication. Conclusion Higher research effort is particularly required in Brazil, where studies on this topic are scarcer than in Mexico but where diversity of human cultures managing their also high plant resources diversity offer high potential for documenting the diversity of mechanisms of artificial selection and evolutionary trends. Comparisons and evaluations of incipient domestication in the regions studied as well as the Andean area would significantly contribute to understanding origins and diffusion of the experience of managing and domesticating plants. PMID:24694009

  6. Fatigue crack growth behavior of Al-Li alloy 1441

    SciTech Connect

    Prakash, R.V.; Parida, B.K.

    1995-12-31

    Fatigue crack growth behavior of Al-Li alloy 1441 having a marginally lower lithium content, compared to 80xx and 20xx series Al-Li alloys is presented in this paper. This investigation was conducted on single edge tension--SE(T)--specimens, under constant amplitude as well as under MiniLCA flight spectrum loading with the specific objective of determining the effects of stress ratio, orientation, thickness and cladding. Three thicknesses were considered: 1.2 mm(clad and unclad), 2.0 mm(clad and unclad) and 8.0 mm unclad. Constant amplitude fatigue tests were conducted at stress ratios of {minus}0.3, 0.1 and 0.7. Testing was performed under ambient conditions and along three orientations, namely L-T, T-L and L+45 degrees. Crack growth characteristics of this alloy are compared with that of BS:L73 (2014-T4 equivalent) for assessing the possibility of replacing BS:L73. Significant effect of stress ratio on crack growth rate was observed in all thicknesses. However, in case of 1.2 and 2.0 mm thick sheets, the effect was minimal at intermediate-crack growth regime. The orientation of the specimen does not adversely affect the fatigue crack growth behavior of 8.0 mm and 2.0 mm thick specimens. However, for 1.2 mm unclad sheet crack growth resistance in L-T direction was found to be superior to that along T-L direction. In majority of test cases considered, no significant effect was observed on crack growth rate due to thickness or cladding. Crack growth characteristics of Al-Li alloy 1441 and Al-Cu alloy BS:L73 under constant amplitude as well as MiniLCA spectrum loading are similar in the low and intermediate-crack growth rate regime. Based on these observations, it is felt that this Al-Li alloy has the potential for future aerospace applications.

  7. Effects of texture and microstructure on the propagation of iodine stress corrosion cracks in Zircaloy

    SciTech Connect

    Knorr, D.B.; Pelloux, R.M.

    1982-01-01

    Failure of some fuel elements in light water nuclear reactors has been attributed to stress corrosion cracking of the fuel cladding. Mechanical interaction between the fuel pellets and cladding tube generates a tensile hoop stress. Release of volatile fission products, most likely iodine, provides a corrosive environment. An investigation of stress corrosion crack propagation is performed at 300/degree/C in four Pa flowing iodine environment. By varying the orientation of fracture mechanics specimens, the effect of crystallographic texture, heat treatment, and microstructure on K/sub I/(SCC) is studied. 27 refs.

  8. Electron pairing in the presence of incipient bands in iron-based superconductors

    NASA Astrophysics Data System (ADS)

    Chen, Xiao; Maiti, S.; Linscheid, A.; Hirschfeld, P. J.

    2015-12-01

    Recent experiments on certain Fe-based superconductors have hinted at a role for paired electrons in "incipient" bands that are close to, but do not cross, the Fermi level. Related theoretical works disagree on whether or not strong-coupling superconductivity is required to explain such effects, and whether a critical interaction strength exists. In this work, we consider various versions of the model problem of pairing of electrons in the presence of an incipient band, within a simple multiband weak-coupling BCS approximation. We categorize the problem into two cases: case (i), where superconductivity arises from the "incipient band pairing" alone, and case (ii), where it is induced on an incipient band by pairing due to Fermi-surface-based interactions. Negative conclusions regarding the importance of incipient bands have been drawn so far largely based on case (i), but we show explicitly that models under case (ii) are qualitatively different, and can explain the nonexponential suppression of Tc, as well as robust large gaps on an incipient band. In the latter situation, large gaps on the incipient band do not require a critical interaction strength. We also model the interplay between phonon and spin fluctuation driven superconductivity and describe situations in which they can enhance each other rather than compete. Finally, we discuss the effect of the dimensionality of the incipient band on our results. We argue that pairing on incipient bands may be significant and important in several Fe-based materials, including LiFeAs, FeSe intercalates, and FeSe monolayers on strontium titanate, and indeed may contribute to high critical temperatures in some cases.

  9. Small Crack Growth and Fatigue Life Predictions for High-Strength Aluminium Alloys. Part 1; Experimental and Fracture Mechanics Analysis

    NASA Technical Reports Server (NTRS)

    Wu, X. R.; Newman, J. C.; Zhao, W.; Swain, M. H.; Ding, C. F.; Phillips, E. P.

    1998-01-01

    The small crack effect was investigated in two high-strength aluminium alloys: 7075-T6 bare and LC9cs clad alloy. Both experimental and analytical investigations were conducted to study crack initiation and growth of small cracks. In the experimental program, fatigue tests, small crack and large crack tests A,ere conducted under constant amplitude and Mini-TWIST spectrum loading conditions. A pronounced small crack effect was observed in both materials, especially for the negative stress ratios. For all loading conditions, most of the fatigue life of the SENT specimens was shown to be crack propagation from initial material defects or from the cladding layer. In the analysis program, three-dimensional finite element and A weight function methods were used to determine stress intensity factors and to develop SIF equations for surface and corner cracks at the notch in the SENT specimens. A plastisity-induced crack-closure model was used to correlate small and large crack data, and to make fatigue life predictions, Predicted crack-growth rates and fatigue lives agreed well with experiments. A total fatigue life prediction method for the aluminum alloys was developed and demonstrated using the crack-closure model.

  10. Probability of incipient spanning clusters in critical square bond percolation

    SciTech Connect

    Shchur, L.N.; Kosyakov, S.S.

    1997-06-01

    The probability of simultaneous occurrence of at least k spanning clusters has been studied by Monte Carlo simulations on the 2D square lattice with free boundaries at the bond percolation threshold p{sub c} = {1/2}. It is found that the probability of k and more Incipient Spanning Clusters (ISC) have the values P(k > 1) {approx} 0.00658(3) and P(k > 2) {approx} 0.00000148(21) provided that the limit of these probabilities for infinite lattice exists. The probability P(k > 3) of more than three ISC could be estimated to be of the order of 10{sup -11} and is beyond the possibility to compute such a value by nowadays computers. So, it is impossible to check in simulations the Aizenman law for the probabilities when k {much_gt} 1. We have detected a single sample with four ISC in a total number of about 10{sup 10} samples investigated. The probability of this single event is 1/10 for the number of samples. The influence of boundary conditions is discussed in the last section.

  11. Genomics of Rapid Incipient Speciation in Sympatric Threespine Stickleback

    PubMed Central

    Marques, David A.; Lucek, Kay; Meier, Joana I.; Mwaiko, Salome; Wagner, Catherine E.; Excoffier, Laurent; Seehausen, Ole

    2016-01-01

    Ecological speciation is the process by which reproductively isolated populations emerge as a consequence of divergent natural or ecologically-mediated sexual selection. Most genomic studies of ecological speciation have investigated allopatric populations, making it difficult to infer reproductive isolation. The few studies on sympatric ecotypes have focused on advanced stages of the speciation process after thousands of generations of divergence. As a consequence, we still do not know what genomic signatures of the early onset of ecological speciation look like. Here, we examined genomic differentiation among migratory lake and resident stream ecotypes of threespine stickleback reproducing in sympatry in one stream, and in parapatry in another stream. Importantly, these ecotypes started diverging less than 150 years ago. We obtained 34,756 SNPs with restriction-site associated DNA sequencing and identified genomic islands of differentiation using a Hidden Markov Model approach. Consistent with incipient ecological speciation, we found significant genomic differentiation between ecotypes both in sympatry and parapatry. Of 19 islands of differentiation resisting gene flow in sympatry, all were also differentiated in parapatry and were thus likely driven by divergent selection among habitats. These islands clustered in quantitative trait loci controlling divergent traits among the ecotypes, many of them concentrated in one region with low to intermediate recombination. Our findings suggest that adaptive genomic differentiation at many genetic loci can arise and persist in sympatry at the very early stage of ecotype divergence, and that the genomic architecture of adaptation may facilitate this. PMID:26925837

  12. CDC42 inhibition suppresses progression of incipient intestinal tumors

    PubMed Central

    Sakamori, Ryotaro; Yu, Shiyan; Zhang, Xiao; Hoffman, Andrew; Sun, Jiaxin; Das, Soumyashree; Vedula, Pavan; Li, Guangxun; Fu, Jiang; Walker, Francesca; Yang, Chung S.; Yi, Zheng; Hsu, Wei; Yu, Da-Hai; Shen, Lanlan; Rodriguez, Alexis J.; Taketo, Makoto M.; Bonder, Edward M.; Verzi, Michael P.; Gao, Nan

    2014-01-01

    Mutations in the APC or β-catenin genes are well established initiators of colorectal cancer (CRC), yet modifiers that facilitate the survival and progression of nascent tumor cells are not well defined. Using genetic and pharmacological approaches in mouse CRC and human CRC xenograft models, we show that incipient intestinal tumor cells activate CDC42, an APC-interacting small GTPase, as a crucial step in malignant progression. In the mouse, Cdc42 ablation attenuated the tumorigenicity of mutant intestinal cells carrying single APC or β-catenin mutations. Similarly, human CRC with relatively higher levels of CDC42 activity were particularly sensitive to CDC42 blockade. Mechanistic studies suggested that Cdc42 may be activated at different levels, including at the level of transcriptional activation of the stem-cell-enriched Rho family exchange factor Arhgef4. Our results suggest that early-stage mutant intestinal epithelial cells must recruit the pleiotropic functions of Cdc42 for malignant progression, suggesting its relevance as a biomarker and therapeutic target for selective CRC intervention. PMID:25113996

  13. The origin of incipient ferroelectricity in lead telluride

    PubMed Central

    Jiang, M. P.; Trigo, M.; Savić, I.; Fahy, S.; Murray, É. D.; Bray, C.; Clark, J.; Henighan, T.; Kozina, M.; Chollet, M.; Glownia, J. M.; Hoffmann, M. C.; Zhu, D.; Delaire, O.; May, A. F.; Sales, B. C.; Lindenberg, A. M.; Zalden, P.; Sato, T.; Merlin, R.; Reis, D. A.

    2016-01-01

    The interactions between electrons and lattice vibrations are fundamental to materials behaviour. In the case of group IV–VI, V and related materials, these interactions are strong, and the materials exist near electronic and structural phase transitions. The prototypical example is PbTe whose incipient ferroelectric behaviour has been recently associated with large phonon anharmonicity and thermoelectricity. Here we show that it is primarily electron-phonon coupling involving electron states near the band edges that leads to the ferroelectric instability in PbTe. Using a combination of nonequilibrium lattice dynamics measurements and first principles calculations, we find that photoexcitation reduces the Peierls-like electronic instability and reinforces the paraelectric state. This weakens the long-range forces along the cubic direction tied to resonant bonding and low lattice thermal conductivity. Our results demonstrate how free-electron-laser-based ultrafast X-ray scattering can be utilized to shed light on the microscopic mechanisms that determine materials properties. PMID:27447688

  14. Stress transmission and incipient yield flow in dense granular materials

    NASA Astrophysics Data System (ADS)

    Blumenfeld, Raphael

    2010-05-01

    Jammed granular matter transmits stresses non-uniformly like no conventional solid, especially when it is on the verge of failure. Jamming is caused by self-organization of granular matter under external loads, often giving rise to networks of force chains that support the loads non-uniformly. An ongoing debate in the literature concerns the correct way to model the static stress field in such media: good old elasticity theory or newcomer isostaticity theory. The two differ significantly and, in particular in 2D, isostaticity theory leads naturally to force chain solutions. More recently, it has been proposed that real granular materials are made of mixtures of regions, some behaving elastically and some isostatically. The theory to describe these systems has been named stato-elasticity. In this paper, I first present the rationale for stato-elasticity theory. An important step towards the construction of this theory is a good understanding of stress transmission in the regions of pure isostatic states. A brief description is given of recently derived general solutions for 2D isostatic regions with nonuniform structures, which go well beyond the over-simplistic picture of force chains. I then show how the static stress equations are related directly to incipient yield flow and derive the equations that govern yield and creep rheology of dense granular matter at the initial stages of failure. These equations are general and describe strains in granular materials of both rigid and compliant particles.

  15. The origin of incipient ferroelectricity in lead telluride.

    PubMed

    Jiang, M P; Trigo, M; Savić, I; Fahy, S; Murray, É D; Bray, C; Clark, J; Henighan, T; Kozina, M; Chollet, M; Glownia, J M; Hoffmann, M C; Zhu, D; Delaire, O; May, A F; Sales, B C; Lindenberg, A M; Zalden, P; Sato, T; Merlin, R; Reis, D A

    2016-01-01

    The interactions between electrons and lattice vibrations are fundamental to materials behaviour. In the case of group IV-VI, V and related materials, these interactions are strong, and the materials exist near electronic and structural phase transitions. The prototypical example is PbTe whose incipient ferroelectric behaviour has been recently associated with large phonon anharmonicity and thermoelectricity. Here we show that it is primarily electron-phonon coupling involving electron states near the band edges that leads to the ferroelectric instability in PbTe. Using a combination of nonequilibrium lattice dynamics measurements and first principles calculations, we find that photoexcitation reduces the Peierls-like electronic instability and reinforces the paraelectric state. This weakens the long-range forces along the cubic direction tied to resonant bonding and low lattice thermal conductivity. Our results demonstrate how free-electron-laser-based ultrafast X-ray scattering can be utilized to shed light on the microscopic mechanisms that determine materials properties. PMID:27447688

  16. Cladding Alloys for Fluoride Salt Compatibility

    SciTech Connect

    Muralidharan, Govindarajan; Wilson, Dane F; Walker, Larry R; Santella, Michael L; Holcomb, David Eugene

    2011-06-01

    This report provides an overview of several candidate technologies for cladding nickel-based corrosion protection layers onto high-temperature structural alloys. The report also provides a brief overview of the welding and weld performance issues associated with joining nickel-clad nickel-based alloys. From the available techniques, two cladding technologies were selected for initial evaluation. The first technique is a line-of-sight method that would be useful for cladding large structures such as vessel interiors or large piping. The line-of-sight method is a laser-based surface cladding technique in which a high-purity nickel powder mixed into a polymer binder is first sprayed onto the surface, baked, and then rapidly melted using a high-power laser. The second technique is a vapor phase technique based on the nickel-carbonyl process that is suitable for cladding inaccessible surfaces such as the interior surfaces of heat exchangers. An initial evaluation for performed on the quality of nickel claddings processed using the two selected cladding techniques.

  17. Mechanics of fatigue crack closure

    NASA Technical Reports Server (NTRS)

    Newman, J. C., Jr. (Editor); Elber, Wolf (Editor)

    1988-01-01

    Papers are presented on plasticity induced crack closure, crack closure in fatigue crack growth, the dependence of crack closure on fatigue loading variables, and a procedure for standardizing crack closure levels. Also considered are a statistical approach to crack closure determination, the crack closure behavior of surface cracks under pure bending, closure measurements on short fatigue cracks, and crack closure under plane strain conditions. Other topics include fatigue crack closure behavior at high stress ratios, the use of acoustic waves for the characterization of closed fatigue cracks, and the influence of fatigue crack wake length and state of stress on crack closure.

  18. Novel Accident-Tolerant Fuel Meat and Cladding

    SciTech Connect

    Robert D. Mariani; Pavel G Medvedev; Douglas L Porter; Steven L Hayes; James I. Cole; Xian-Ming Bai

    2013-09-01

    A novel accident-tolerant fuel meat and cladding are here proposed. The fuel meat design incorporates annular fuel with inserts and discs that are fabricated from a material having high thermal conductivity, for example niobium. The inserts are rods or tubes. Discs separate the fuel pellets. Using the BISON fuel performance code it was found that the peak fuel temperature can be lowered by more than 600 degrees C for one set of conditions with niobium metal as the thermal conductor. In addition to improved safety margin, several advantages are expected from the lower temperature such as decreased fission gas release and fuel cracking. Advantages and disadvantages are discussed. An enrichment of only 7.5% fully compensates the lost reactivity of the displaced UO2. Slightly higher enrichments, such as 9%, allow uprates and increased burnups to offset the initial costs for retooling. The design has applications for fast reactors and transuranic burning, which may accelerate its development. A zirconium silicide coating is also described for accident tolerant applications. A self-limiting degradation behavior for this coating is expected to produce a glassy, self-healing layer that becomes more protective at elevated temperature, with some similarities to MoSi2 and other silicides. Both the fuel and coating may benefit from the existing technology infrastructure and the associated wide expertise for a more rapid development in comparison to other, more novel fuels and cladding.

  19. Stress-intensity-factor influence coefficients for semielliptical inner-surface flaws in clad pressure vessels

    SciTech Connect

    Keeney, J.A.; Bryson, J.W.

    1995-12-31

    A problem of particular interest in pressure vessel technology is the calculation of accurate stress-intensity factors for semielliptical surface cracks in cylinders. Computing costs for direct solution techniques can be prohibitive when applied to three-dimensional (3-D) geometries with time-varying boundary conditions such as those associated with pressurized thermal shock. An alternative superposition technique requires the calculation of a set of influence coefficients for a given 3-D crack model that can be superimposed to obtain mode-I stress-intensity factors. This paper presents stress-intensity-factor influence coefficients (SIFICs) for axially and circumferentially oriented finite-length semielliptical inner-surface flaws with aspect ratios (total crack length (2c) to crack depth (a)) of 2, 6, and 10 for clad cylinders having an internal radius to wall thickness (t) ratio of 10. SIFICs are computed for flaw depths in the range of 0.01 {le} a/t {le} 0.5 and two cladding thicknesses. The incorporate of this SIFIC data base in fracture mechanics codes will facilitate the generation of fracture mechanics solutions for a wide range of flaw geometries as may be required in structural integrity assessments of pressurized-water and boiling-water reactors.

  20. Ion beam mixed oxidation protective coating on Zry-4 cladding

    NASA Astrophysics Data System (ADS)

    Park, Jae-Won; Kim, Jae-Un; Park, Jeong-Yong

    2016-06-01

    In this study, SiC was coated on the surface of Zry-4 cladding to improve the oxidation protectiveness. In the coating of SiC onto Zry-4, the prime concern was adhesion at an elevated temperature. Here, a 70 keV N ion beam was irradiated onto a SiC coating layer of ∼100 nm in thickness; this was deposited via the e-beam evaporation method. Additional coating to a target thickness was then carried out. The films deposited without ion-beam mixing (IBM) often peeled-off at an elevated temperature, while the IBM SiC film always adhered to Zry-4, even after heating to ∼1000 °C; at such a temperature, however, cracks formed in the film. X-ray photoelectron spectroscopy (XPS) analysis showed that the deposited SiC film contained about 20 at.% of O, while after annealing in air, 76 at.% of O was found on the surface layer. This implied that both the surface of SiC film and Zry-4 in the crack lines were oxidized. Comparing the Zr3d peak positions across the interface, a shift of binding energy by ∼1 eV was detected, representing that, in view of favorable thermodynamics, SiC/Zry-4 seems to be an acceptable system to apply IBM. To heal the crack, the process of IBM for a 1 μm thick coating and annealing was repeated. High-resolution field emission secondary electron microscopy (FE-SEM) showed that the crack lines, the main places at which oxidation occurred, were gradually covered as the process was repeated, ensuring enhanced oxidation protectiveness.

  1. Crack, crack house sex, and HIV risk.

    PubMed

    Inciardi, J A

    1995-06-01

    Limited attention has been focused on HIV risk behaviors of crack smokers and their sex partners, yet there is evidence that the crack house and the crack-using life-style may be playing significant roles in the transmission of HIV and other sexually transmitted diseases. The purposes of this research were to study the attributes and patterns of "sex for crack" exchanges, particularly those that occurred in crack houses, and to assess their potential impact on the spread of HIV. Structured interviews were conducted with 17 men and 35 women in Miami, Florida, who were regular users of crack and who had exchanged sex for crack (or for money to buy crack) during the past 30 days. In addition, participant observation was conducted in 8 Miami crack houses. Interview and observational data suggest that individuals who exchange sex for crack do so with considerable frequency, and through a variety of sexual activities. Systematic data indicated that almost a third of the men and 89% of the women had had 100 or more sex partners during the 30-day period prior to study recruitment. Not only were sexual activities anonymous, extremely frequent, varied, uninhibited (often undertaken in public areas of crack houses), and with multiple partners but, in addition, condoms were not used during the majority of contacts. Of the 37 subjects who were tested for HIV and received their test results 31% of the men and 21% of the women were HIV seropositive. PMID:7611845

  2. Microstructure and properties of Fe-based composite coating by laser cladding Fe-Ti-V-Cr-C-CeO2 powder

    NASA Astrophysics Data System (ADS)

    Zhang, Hui; Zou, Yong; Zou, Zengda; Wu, Dongting

    2015-01-01

    In situ TiC-VC reinforced Fe-based cladding layer was obtained on low carbon steel surface by laser cladding with Fe-Ti-V-Cr-C-CeO2 alloy powder. The microstructure, phases and properties of the cladding layer were investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), transmission electron microscopy (TEM), potentio-dynamic polarization and electro-chemical impedance spectroscopy (EIS). Results showed Fe-Ti-V-Cr-C-CeO2 alloy powder formed a good cladding layer without defects such as cracks and pores. The phases of the cladding layer were α-Fe, γ-Fe, TiC, VC and TiVC2. The microstructures of the cladding layer matrix were lath martensite and retained austenite. The carbides were polygonal blocks with a size of 0.5-2 μm and distributed uniformly in the cladding layer. High resolution transmission electron microscopy showed the carbide was a complex matter composed of nano TiC, VC and TiVC2. The cladding layer with a hardness of 1030 HV0.2 possessed good wear and corrosion resistance, which was about 16.85 and 9.06 times than that of the substrate respectively.

  3. Review of environmental effects on fatigue crack growth of austenitic stainless steels

    SciTech Connect

    Shack, W.J.; Kassner, T.F.

    1994-05-01

    Fatigue and environmentally assisted cracking of piping, pressure vessel cladding, and core components in light water reactors are potential concerns to the nuclear industry and regulatory agencies. The degradation processes include intergranular stress corrosion cracking of austenitic stainless steel (SS) piping in boiling water reactors (BWRs), and propagation of fatigue or stress corrosion cracks (which initiate in sensitized SS cladding) into low-alloy ferritic steels in BWR pressure vessels. Crack growth data for wrought and cast austenitic SSs in simulated BWR water, developed at Argonne National Laboratory under US Nuclear Regulatory Commission sponsorship over the past 10 years, have been compiled into a data base along with similar data obtained from the open literature. The data were analyzed to develop corrosion-fatigue curves for austenitic SSs in aqueous environments corresponding to normal BWR water chemistries, for BWRs that add hydrogen to the feedwater, and for pressurized water reactor primary-system-coolant chemistry.

  4. Effect of tip radius on the incipient plasticity of chromium studied by nanoindentation

    SciTech Connect

    Wu, Dong; Morris, James R; Nieh, T. G.

    2015-01-01

    The onset of plasticity in Cr was investigated by nanoindentation using indenters with tip radii ranging from 60 to 759 nm. The stress for incipient plasticity was found to increase with decreasing tip radius. The cumulative pop-in probability on load could be described successfully by a combined model over the full range of tip radius, indicating that the incipient plasticity might be triggered either by the homogeneous nucleation of dislocation or by the activation of existing dislocations underneath the indenter.

  5. Electron pairing in the presence of incipient bands in iron-based superconductors

    NASA Astrophysics Data System (ADS)

    Linscheid, Andy; Chen, Xiao; Maiti, Saurabh; Hirschfeld, Peter

    Recent experiments on certain Fe-based superconductors (SC) have hinted at a role for paired electrons in ``incipient'' bands that are close to, but do not cross the Fermi level. Within a simple multiband weak-coupling BCS approximation, we categorize the problem into two cases: case(I) where SC arises from the incipient band pairing alone, and case(II) where it is induced on an incipient band by pairing due to Fermi-surface based interactions. Negative conclusions regarding the importance of incipient bands are largely based on case(I). However, we show explicitly that models under case(II) can explain the mild suppression of Tc, as well as robust large gaps on an incipient band. We also model the interplay between phonon and spin fluctuation (SF) driven SC and describe the bootstrap of electron-phonon SC by SF coupling the incipient and the regular bands. We argue that pairing on incipient bands may be important in several Fe-based materials, including LiFeAs, FeSe intercalates and FeSe monolayers on SrTiO3, and indeed may contribute to high Tc in some cases. In addition, we address the question whether this conclusion holds if the SF interaction is derived explicitly in the incipient band scenario and retardation effects are included on the level of the Eliashberg equations. SM was supported by NHMFL through NSF-DMR-1157490, AL and PJH were supported in part by DOE DE-FG02-05ER46236.

  6. Incipient corrosion behavior of Haynes 230 under a controlled reducing atmosphere at high temperatures

    NASA Astrophysics Data System (ADS)

    Tung, Hsiao-Ming; Stubbins, James F.

    2012-08-01

    In situ thermogravimetry analysis (TGA) was used to investigate the incipient corrosion behavior of alloy 230 exposed under a reducing environment in a temperature range of 850-1000 °C. Both oxidation and loss of alloying elements of alloy 230 were observed to occur concurrently in these conditions. The surface oxide which formed on the substrate does not appear to be as effective in providing a protective layer during the incipient corrosion period.

  7. Hypersonic incipient separation on delta wing with trailing-edge flap

    NASA Technical Reports Server (NTRS)

    Rao, D. M.

    1975-01-01

    The paper reviews the experimental data on the incipient separation characteristics of planar delta wings of 75 degree sharp leading edges, with full-span trailing edge flap deflected into the windward flow. The local Reynolds number range for these investigations covered laminar, transitional and turbulent conditions. It is shown that, while turbulent boundary layer data correlates with two dimensional results, in the laminar and transitional cases, there is a nearly parallel shift to higher flap angles for incipient separation.

  8. Breakdown in the Process of Incipient Speciation in Anopheles gambiae

    PubMed Central

    Nwakanma, Davis C.; Neafsey, Daniel E.; Jawara, Musa; Adiamoh, Majidah; Lund, Emily; Rodrigues, Amabelia; Loua, Kovana M.; Konate, Lassana; Sy, Ngayo; Dia, Ibrahima; Awolola, T. Samson; Muskavitch, Marc A. T.; Conway, David J.

    2013-01-01

    Understanding genetic causes and effects of speciation in sympatric populations of sexually reproducing eukaryotes is challenging, controversial, and of practical importance for controlling rapidly evolving pests and pathogens. The major African malaria vector mosquito Anopheles gambiae sensu stricto (s.s.) is considered to contain two incipient species with strong reproductive isolation, hybrids between the M and S molecular forms being very rare. Following recent observations of higher proportions of hybrid forms at a few sites in West Africa, we conducted new surveys of 12 sites in four contiguous countries (The Gambia, Senegal, Guinea-Bissau, and Republic of Guinea). Identification and genotyping of 3499 A. gambiae s.s. revealed high frequencies of M/S hybrid forms at each site, ranging from 5 to 42%, and a large spectrum of inbreeding coefficient values from 0.11 to 0.76, spanning most of the range expected between the alternative extremes of panmixia and assortative mating. Year-round sampling over 2 years at one of the sites in The Gambia showed that M/S hybrid forms had similar relative frequencies throughout periods of marked seasonal variation in mosquito breeding and abundance. Genome-wide scans with an Affymetrix high-density single-nucleotide polymorphism (SNP) microarray enabled replicate comparisons of pools of different molecular forms, in three separate populations. These showed strong differentiation between M and S forms only in the pericentromeric region of the X chromosome that contains the molecular form-specific marker locus, with only a few other loci showing minor differences. In the X chromosome, the M/S hybrid forms were more differentiated from M than from S forms, supporting a hypothesis of asymmetric introgression and backcrossing. PMID:23335339

  9. Evidence of incipient forest transition in Southern Mexico.

    PubMed

    Vaca, Raúl Abel; Golicher, Duncan John; Cayuela, Luis; Hewson, Jenny; Steininger, Marc

    2012-01-01

    Case studies of land use change have suggested that deforestation across Southern Mexico is accelerating. However, forest transition theory predicts that trajectories of change can be modified by economic factors, leading to spatial and temporal heterogeneity in rates of change that may take the form of the Environmental Kuznets Curve (EKC). This study aimed to assess the evidence regarding potential forest transition in Southern Mexico by classifying regional forest cover change using Landsat imagery from 1990 through to 2006. Patterns of forest cover change were found to be complex and non-linear. When rates of forest loss were averaged over 342 municipalities using mixed-effects modelling the results showed a significant (p<0.001) overall reduction of the mean rate of forest loss from 0.85% per year in the 1990-2000 period to 0.67% in the 2000-2006 period. The overall regional annual rate of deforestation has fallen from 0.33% to 0.28% from the 1990s to 2000s. A high proportion of the spatial variability in forest cover change cannot be explained statistically. However analysis using spline based general additive models detected underlying relationships between forest cover and income or population density of a form consistent with the EKC. The incipient forest transition has not, as yet, resulted in widespread reforestation. Forest recovery remains below 0.20% per year. Reforestation is mostly the result of passive processes associated with reductions in the intensity of land use. Deforestation continues to occur at high rates in some focal areas. A transition could be accelerated if there were a broader recognition among policy makers that the regional rate of forest loss has now begun to fall. The changing trajectory provides an opportunity to actively restore forest cover through stimulating afforestation and stimulating more sustainable land use practices. The results have clear implications for policy aimed at carbon sequestration through reducing

  10. Evaluation of three electronic noses for detecting incipient wood decay.

    PubMed

    Baietto, Manuela; Wilson, Alphus D; Bassi, Daniele; Ferrini, Francesco

    2010-01-01

    Tree assessment methodologies, currently used to evaluate the structural stability of individual urban trees, usually involve a visual analysis followed by measurements of the internal soundness of wood using various instruments that are often invasive, expensive, or inadequate for use within the urban environment. Moreover, most conventional instruments do not provide an adequate evaluation of decay that occurs in the root system. The intent of this research was to evaluate the possibility of integrating conventional tools, currently used for assessments of decay in urban trees, with the electronic nose-a new innovative tool used in diverse fields and industries for various applications such as quality control in manufacturing, environmental monitoring, medical diagnoses, and perfumery. Electronic-nose (e-nose) technologies were tested for the capability of detecting differences in volatile organic compounds (VOCs) released by wood decay fungi and wood from healthy and decayed trees. Three e-noses, based on different types of operational technologies and analytical methods, were evaluated independently (not directly compared) to determine the feasibility of detecting incipient decays in artificially-inoculated wood. All three e-nose devices were capable of discriminating between healthy and artificially-inoculated, decayed wood with high levels of precision and confidence. The LibraNose quartz microbalance (QMB) e-nose generally provided higher levels of discrimination of sample unknowns, but not necessarily more accurate or effective detection than the AromaScan A32S conducting polymer and PEN3 metal-oxide (MOS) gas sensor e-noses for identifying and distinguishing woody samples containing different agents of wood decay. However, the conducting polymer e-nose had the greater advantage for identifying unknowns from diverse woody sample types due to the associated software capability of utilizing prior-developed, application-specific reference libraries with aroma

  11. Evaluation of Three Electronic Noses for Detecting Incipient Wood Decay

    PubMed Central

    Baietto, Manuela; Wilson, Alphus D.; Bassi, Daniele; Ferrini, Francesco

    2010-01-01

    Tree assessment methodologies, currently used to evaluate the structural stability of individual urban trees, usually involve a visual analysis followed by measurements of the internal soundness of wood using various instruments that are often invasive, expensive, or inadequate for use within the urban environment. Moreover, most conventional instruments do not provide an adequate evaluation of decay that occurs in the root system. The intent of this research was to evaluate the possibility of integrating conventional tools, currently used for assessments of decay in urban trees, with the electronic nose–a new innovative tool used in diverse fields and industries for various applications such as quality control in manufacturing, environmental monitoring, medical diagnoses, and perfumery. Electronic-nose (e-nose) technologies were tested for the capability of detecting differences in volatile organic compounds (VOCs) released by wood decay fungi and wood from healthy and decayed trees. Three e-noses, based on different types of operational technologies and analytical methods, were evaluated independently (not directly compared) to determine the feasibility of detecting incipient decays in artificially-inoculated wood. All three e-nose devices were capable of discriminating between healthy and artificially-inoculated, decayed wood with high levels of precision and confidence. The LibraNose quartz microbalance (QMB) e-nose generally provided higher levels of discrimination of sample unknowns, but not necessarily more accurate or effective detection than the AromaScan A32S conducting polymer and PEN3 metal-oxide (MOS) gas sensor e-noses for identifying and distinguishing woody samples containing different agents of wood decay. However, the conducting polymer e-nose had the greater advantage for identifying unknowns from diverse woody sample types due to the associated software capability of utilizing prior-developed, application-specific reference libraries with

  12. Choice matters: incipient speciation in Gyrodactylus corydori (Monogenoidea: Gyrodactylidae).

    PubMed

    Bueno-Silva, Marlus; Boeger, Walter A; Pie, Marcio R

    2011-05-01

    We investigated how Gyrodactylus corydoriBueno-Silva and Boeger, 2009 exploits two sympatric host species, Corydoras paleatus (Jenyns, 1842) and Corydoras ehrhardti Steindachner, 1910. Specimens of G. corydori were collected from the Piraquara and Miringuava Rivers, State of Paraná, Brazil, between 2005 and 2006. A total of 167 parasites was measured from both host species. Nine morphometric features of the haptoral sclerites were measured and analyzed by discriminant analysis, cluster analysis and multivariate analysis of variance. A fragment of the mitochondrial cytochrome oxidase I gene (COI) (∼740 bp) and the rDNA internal transcribed spacers (ITS) (∼1200 bp) of G. corydori were sequenced. Bayesian and parsimony analyses of COI recognized two genetically structured clades of G. corydori, which corresponded closely with the two species of Corydoras. Twenty-eight haplotypes were detected (18 were exclusive to C. ehrhardti and seven were exclusive to C. paleatus). The same general pattern between parasites and host species was observed in the morphometric analyses. Nevertheless, poor correlation of genetic and morphometric variation strongly supports the plastic nature of the morphological variation of haptoral sclerites. The existence of two clades with limited gene flow would suggest that G. corydori already represents two cryptic species. However, the morphometric and molecular data showed that there is insufficient evidence to support two valid species. The low COI (0.1-6.2%) and ITS (0.09-3.5%) divergence within G. corydori suggest a recent separation of the lineages between distinct host species (less than 1 million years). As the hypothesis of secondary contact of the parasite demographic history was rejected, our results point to the possibility of sympatric incipient ongoing speciation of G. corydori to form distinct parasite lineages adapted to C. ehrhardti and C. paleatus. This may be a common event within the Gyrodactylidae, adding a yet

  13. Evidence of Incipient Forest Transition in Southern Mexico

    PubMed Central

    Vaca, Raúl Abel; Golicher, Duncan John; Cayuela, Luis; Hewson, Jenny; Steininger, Marc

    2012-01-01

    Case studies of land use change have suggested that deforestation across Southern Mexico is accelerating. However, forest transition theory predicts that trajectories of change can be modified by economic factors, leading to spatial and temporal heterogeneity in rates of change that may take the form of the Environmental Kuznets Curve (EKC). This study aimed to assess the evidence regarding potential forest transition in Southern Mexico by classifying regional forest cover change using Landsat imagery from 1990 through to 2006. Patterns of forest cover change were found to be complex and non-linear. When rates of forest loss were averaged over 342 municipalities using mixed-effects modelling the results showed a significant (p<0.001) overall reduction of the mean rate of forest loss from 0.85% per year in the 1990–2000 period to 0.67% in the 2000–2006 period. The overall regional annual rate of deforestation has fallen from 0.33% to 0.28% from the 1990s to 2000s. A high proportion of the spatial variability in forest cover change cannot be explained statistically. However analysis using spline based general additive models detected underlying relationships between forest cover and income or population density of a form consistent with the EKC. The incipient forest transition has not, as yet, resulted in widespread reforestation. Forest recovery remains below 0.20% per year. Reforestation is mostly the result of passive processes associated with reductions in the intensity of land use. Deforestation continues to occur at high rates in some focal areas. A transition could be accelerated if there were a broader recognition among policy makers that the regional rate of forest loss has now begun to fall. The changing trajectory provides an opportunity to actively restore forest cover through stimulating afforestation and stimulating more sustainable land use practices. The results have clear implications for policy aimed at carbon sequestration through reducing

  14. Thermal perturbations beneath the incipient Okavango Rift Zone, northwest Botswana

    NASA Astrophysics Data System (ADS)

    Leseane, Khumo; Atekwana, Estella A.; Mickus, Kevin L.; Abdelsalam, Mohamed G.; Shemang, Elisha M.; Atekwana, Eliot A.

    2015-02-01

    We used aeromagnetic and gravity data to investigate the thermal structure beneath the incipient Okavango Rift Zone (ORZ) in northwestern Botswana in order to understand its role in strain localization during rift initiation. We used three-dimensional (3-D) inversion of aeromagnetic data to estimate the Curie Point Depth (CPD) and heat flow under the rift and surrounding basement. We also used two-dimensional (2-D) power-density spectrum analysis of gravity data to estimate the Moho depth. Our results reveal shallow CPD values (8-15 km) and high heat flow (60-90 mW m-2) beneath a ~60 km wide NE-trending zone coincident with major rift-related border faults and the boundary between Proterozoic orogenic belts. This is accompanied by thin crust (<30 km) in the northeastern and southwestern parts of the ORZ. Within the Precambrian basement areas, the CPD values are deeper (16-30 km) and the heat flow estimates are lower (30-50 mW m-2), corresponding to thicker crust (~40-50 km). We interpret the thermal structure under the ORZ as due to upward migration of hot mantle fluids through the lithospheric column that utilized the presence of Precambrian lithospheric shear zones as conduits. These fluids weaken the crust, enhancing rift nucleation. Our interpretation is supported by 2-D forward modeling of gravity data suggesting the presence of a wedge of altered lithospheric mantle centered beneath the ORZ. If our interpretation is correct, it may result in a potential paradigm shift in which strain localization at continental rift initiation could be achieved through fluid-assisted lithospheric weakening without asthenospheric involvement.

  15. Corrosion Resistant Cladding by YAG Laser Welding in Underwater Environment

    SciTech Connect

    Tsutomi Kochi; Toshio Kojima; Suemi Hirata; Ichiro Morita; Katsura Ohwaki

    2002-07-01

    It is known that stress-corrosion cracking (SCC) will occur in nickel-base alloys used in Reactor Pressure Vessel (RPV) and Internals of nuclear power plants. A SCC sensitivity has been evaluated by IHI in each part of RPV and Internals. There are several water level instrumentation nozzles installed in domestic BWR RPV. In water level instrumentation nozzles, 182 type nickel-base alloys were used for the welding joint to RPV. It is estimated the SCC potential is high in this joint because of a higher residual stress than the yield strength (about 400 MPa). This report will describe a preventive maintenance method to these nozzles Heat Affected Zone (HAZ) and welds by a corrosion resistant cladding (CRC) by YAG Laser in underwater environment (without draining a reactor water). There are many kinds of countermeasures for SCC, for example, Induction Heating Stress Improvement (IHSI), Mechanical Stress Improvement Process (MSIP) and so on. A YAG laser CRC is one of them. In this technology a laser beam is used for heat source and irradiated through an optical fiber to a base metal and SCC resistant material is used for welding wires. After cladding the HAZ and welds are coated by the corrosion resistant materials so their surfaces are improved. A CRC by gas tungsten arc welding (GTAW) in an air environment had been developed and already applied to a couple of operating plants (16 Nozzles). This method was of course good but it spent much time to perform because of an installation of some water-proof working boxes to make a TIG-weldability environment. CRC by YAG laser welding in underwater environment has superior features comparing to this conventional TIG method as follows. At the viewpoint of underwater environment, (1) an outage term reduction (no drainage water). (2) a radioactive exposure dose reduction for personnel. At that of YAG laser welding, (1) A narrower HAZ. (2) A smaller distortion. (3) A few cladding layers. A YAG laser CRC test in underwater

  16. SiC-CMC-Zircaloy-4 Nuclear Fuel Cladding Performance during 4-Point Tubular Bend Testing

    SciTech Connect

    IJ van Rooyen; WR Lloyd; TL Trowbridge; SR Novascone; KM Wendt; SM Bragg-Sitton

    2013-09-01

    and clad configurations. The 2-ply sleeve samples show a higher bend momentum compared to those of the 1-ply sleeve samples. This is applicable to both the hybrid mock-up and bare SiC-CMC sleeve samples. Comparatively both the 1- and 2-ply hybrid mock-up samples showed a higher bend stiffness and strength compared with the standard Zr-4 mock-up sample. The characterization of the hybrid mock-up samples showed signs of distress and preliminary signs of fraying at the protective Zr-4 sleeve areas for the 1-ply SiC-CMC sleeve. In addition, the microstructure of the SiC matrix near the cracks at the region of highest compressive bending strain shows significant cracking and flaking. The 2-ply SiC-CMC sleeve samples showed a more bonded, cohesive SiC matrix structure. This cracking and fraying causes concern for increased fretting during the actual use of the design. Tomography was proven as a successful tool to identify open porosity during pre-test characterization. Although there is currently insufficient data to make conclusive statements regarding the overall merit of the hybrid cladding design, preliminary characterization of this novel design has been demonstrated.

  17. Stress corrosion cracking of Zircaloys. Final report

    SciTech Connect

    Cubicciotti, D.; Jones, R.L.; Syrett, B.C.

    1980-03-01

    The overall aim has been to develop an improved understanding of the stress corrosion cracking (SCC) mechanism considered to be responsible for pellet-cladding interaction (PCI) failures of nuclear fuel rods. The objective of the present phase of the project was to investigate the potential for improving the resistance of Zircaloy to iodine-induced SCC by modifying the manufacturing techniques used in the commercial production of fuel cladding. Several aspects of iodine SCC behavior of potential relevance to cladding performance were experimentally investigated. It was found that the SCC susceptibility of Zircaloy tubing is sensitive to crystallographic texture, surface condition, and residual stress distribution and that current specifications for Zircaloy tubing provide no assurance of an optimum resistance to SCC. Additional evidence was found that iodine-induced cracks initiate at local chemical inhomogeneities in the Zircaloy surface, but laser melting to produce a homogenized surface layer did not improve the SCC resistance. Several results were obtained that should be considered in models of PCI failure. The ratio of axial to hoop stress and the temperature were both shown to affect the SCC resistance whereas the difference in composition between Zircaloy-2 and Zircaloy-4 had no detectable effect. Damage accumulation during iodine SCC was found to be nonlinear: generally, a given life fraction at low stress was more damaging than the same life fraction at higher stress. Studies of the thermochemistry of the zirconium-iodine system (performed under US Department of Energy sponsorship) revealed many errors in the literature and provided important new insights into the mechanism of iodine SCC of Zircaloys.

  18. Testing of uranium nitride fuel in T-111 cladding at 1200 K cladding temperature

    NASA Technical Reports Server (NTRS)

    Rohal, R. G.; Tambling, T. N.; Smith, R. L.

    1973-01-01

    Two groups of six fuel pins each were assembled, encapsulated, and irradiated in the Plum Brook Reactor. The fuel pins employed uranium mononitride (UN) in a tantalum alloy clad. The first group of fuel pins was irradiated for 1500 hours to a maximum burnup of 0.7-atom-percent uranium. The second group of fuel pins was irradiated for about 3000 hours to a maximum burnup of 1.0-atom-percent uranium. The average clad surface temperature during irradiation of both groups of fuel pins was approximately 1200 K. The postirradiation examination revealed the following: no clad failures or fuel swelling occurred; less than 1 percent of the fission gases escaped from the fuel; and the clad of the first group of fuel pins experienced clad embrittlement whereas the second group, which had modified assembly and fabrication procedures to minimize contamination, had a ductile clad after irradiation.

  19. Pellet-clad interaction (PCI) failures of zirconium alloy fuel cladding — A review

    NASA Astrophysics Data System (ADS)

    Cox, B.

    1990-08-01

    This review summarizes the history of the appearance and cure of pellet-cladding interaction (PCI) failures during the operation of Zircaloy clad UO 2 fuel in a number of reactors. The work carried out to permit unrestricted operation of reactors without causing PCI failures has led to the universal adoption of the CANLUB-graphite coated cladding in CANDU reactors, and to the wide adoption of Zr-liner cladding in BWRs. There has only been a low incidence of PCI failures in PWR cladding, and the problem has not loomed large enough to require the adoption of either of the above protective methods in these reactors, although experimental liner cladding has been tested. The extensive work on the mechanism of PCI failures (leading to the conclusion that an SCC process induced by fission product iodine is the most probable cause) is summarised.

  20. Gear Crack Propagation Investigation

    NASA Technical Reports Server (NTRS)

    1995-01-01

    Reduced weight is a major design goal in aircraft power transmissions. Some gear designs incorporate thin rims to help meet this goal. Thin rims, however, may lead to bending fatigue cracks. These cracks may propagate through a gear tooth or into the gear rim. A crack that propagates through a tooth would probably not be catastrophic, and ample warning of a failure could be possible. On the other hand, a crack that propagates through the rim would be catastrophic. Such cracks could lead to disengagement of a rotor or propeller from an engine, loss of an aircraft, and fatalities. To help create and validate tools for the gear designer, the NASA Lewis Research Center performed in-house analytical and experimental studies to investigate the effect of rim thickness on gear-tooth crack propagation. Our goal was to determine whether cracks grew through gear teeth (benign failure mode) or through gear rims (catastrophic failure mode) for various rim thicknesses. In addition, we investigated the effect of rim thickness on crack propagation life. A finite-element-based computer program simulated gear-tooth crack propagation. The analysis used principles of linear elastic fracture mechanics, and quarter-point, triangular elements were used at the crack tip to represent the stress singularity. The program had an automated crack propagation option in which cracks were grown numerically via an automated remeshing scheme. Crack-tip stress-intensity factors were estimated to determine crack-propagation direction. Also, various fatigue crack growth models were used to estimate crack-propagation life. Experiments were performed in Lewis' Spur Gear Fatigue Rig to validate predicted crack propagation results. Gears with various backup ratios were tested to validate crack-path predictions. Also, test gears were installed with special crack-propagation gages in the tooth fillet region to measure bending-fatigue crack growth. From both predictions and tests, gears with backup ratios

  1. Characterization of Cassini GPHS Fueled-Clad Production Girth Welds

    SciTech Connect

    Franco-Ferreira, E.A.

    2000-03-23

    Fueled clads for radioisotope power systems are produced by encapsulating {sup 238}PuO{sub 2} in iridium alloy cups, which are joined at their equators by gas tungsten arc welding. Cracking problems at the girth weld tie-in area during production of the Galileo/Ulysses GPHS capsules led to the development of a first-generation ultrasonic test for girth weld inspection at the Savannah River Plant. A second-generation test and equipment with significantly improved sensitivity and accuracy were jointly developed by the Oak Ridge Y-12 Plant and Westinghouse Savannah River Company for use during the production of Cassini GPHS capsules by the Los Alamos National Laboratory. The test consisted of Lamb wave ultrasonic scanning of the entire girth weld from each end of the capsule combined with a time-of-flight evaluation to aid in characterizing nonrelevant indications. Tangential radiography was also used as a supplementary test for further evaluation of reflector geometry. Each of the 317 fueled GPHS capsules, which were girth welded for the Cassini Program, was subjected to a series of nondestructive tests that included visual, dimensional, helium leak rate, and ultrasonic testing. Thirty-three capsules were rejected prior to ultrasonic testing. Of the 44 capsules rejected by the standard ultrasonic test, 22 were upgraded to flight quality through supplementary testing for an overall process acceptance rate of 82.6%. No confirmed instances of weld cracking were found.

  2. Use of plasma arc welding process to combat hydrogen metallic disbonding of austenitic stainless steel claddings

    SciTech Connect

    Alexandrov, O.A. ); Steklov, O.I.; Alexeev, A.V. )

    1993-11-01

    A separation type crack, metallic disbonding, occurred between austenitic stainless steel weld metal cladding and 2 1/4Cr-1Mo base metal in the hydrodesulfurizing reactor of an oil refining plant. For stainless steel cladding, the submerged arc welding (SAW) process with a strip electrode is usually applied, but the authors experimented with the plasma arc welding (PAW) process with hot wire electrode for the cladding. The metallic disbonding is considered to be attributed to hydrogen accumulation at the transition zone and has been generally studied on a laboratory scale using an autoclave. The authors used a electrolytic hydrogen charging technique for the sake of experimental simplicity and made a comparison with the results for gaseous hydrogen charging. The main conclusions obtained were follows: The PAW stainless steel weld metal cladding is more resistant to metallic disbonding with the PAW process is explained by the desirable microstructure and properties of the first layer of weld metal at the transition zone. Electrolytic hydrogen charging pretty well reproduces the results of autoclave gas phase charging.

  3. Cascaded-cladding-pumped cascaded Raman fiber amplifier.

    PubMed

    Jiang, Huawei; Zhang, Lei; Feng, Yan

    2015-06-01

    The conversion efficiency of double-clad Raman fiber laser is limited by the cladding-to-core area ratio. To get high conversion efficiency, the inner-cladding-to-core area ratio has to be less than about 8, which limits the brightness enhancement. To overcome the problem, a cascaded-cladding-pumped cascaded Raman fiber laser with multiple-clad fiber as the Raman gain medium is proposed. A theoretical model of Raman fiber amplifier with multiple-clad fiber is developed, and numerical simulation proves that the proposed scheme can improve the conversion efficiency and brightness enhancement of cladding pumped Raman fiber laser. PMID:26072764

  4. Evaluation of tantalum-alloy-clad uranium mononitride fuel specimens from 7500-hour, 1040 C pumped-lithium-loop test

    NASA Technical Reports Server (NTRS)

    Watson, G. K.

    1974-01-01

    Simulated nuclear fuel element specimens, consisting of uranium mononitride (UN) fuel cylinders clad with tungsten-lined T-111, were exposed for up to 7500 hr at 1040 C (1900 F) in a pumped-lithium loop. The lithium flow velocity was 1.5 m/sec (5 ft/sec) in the specimen test section. No evidence of any compatibility problems between the specimens and the flowing lithium was found based on appearance, weight change, chemistry, and metallography. Direct exposure of the UN to the lithium through a simulated cladding crack resulted in some erosion of the UN in the area of the defect. The T-111 cladding was ductile after lithium exposure, but it was sensitive to hydrogen embrittlement during post-test handling.

  5. Crack spectra analysis

    SciTech Connect

    Tiernan, M.

    1980-09-01

    Crack spectra derived from velocity data have been shown to exhibit systematics which reflect microstructural and textural differences between samples (Warren and Tiernan, 1980). Further research into both properties and information content of crack spectra have yielded the following: Spectral features are reproducible even at low pressures; certain observed spectral features may correspond to non-in-situ crack populations created during sample retrieval; the functional form of a crack spectra may be diagnostic of the sample's grain texture; hysteresis is observed in crack spectra between up and down pressure runs - it may be due to friction between the faces of closed crack populations.

  6. Incipient flocculation molding: A new ceramic-forming technique

    NASA Astrophysics Data System (ADS)

    Arrasmith, Steven Reade

    Incipient Flocculation Molding (IFM) was conceived as a new near-net-shape forming technique for ceramic components. It was hypothesized that the development of a temperature-dependent deflocculant would result in a forming technique that is flexible, efficient, and capable of producing a superior microstructure with improved mechanical properties from highly reactive, submicron ceramic powders. IFM utilizes a concentrated, nonaqueous, sterically stabilized ceramic powder and/or colloidal suspension which is injected into a non-porous mold. The suspension is then flocculated by destabilizing the suspension by lowering the temperature. Flocculation is both rapid and reversible. Cooling to -20°C produces a green body with sufficient strength for removal from the mold. The solvent is removed from the green body by evaporation. The dried green body is subsequently sintered to form a dense ceramic monolith. This is the first ceramic forming method based upon the manipulation of a sterically-stabilized suspension. To demonstrate IFM, the process of grafting polyethylene glycol (PEG), with molecular weights from 600 to 8000, to alumina powders was investigated. The maximum grafted amounts were achieved by the technique of dispersing the alumina powders in molten polymer at 195°C. The ungrafted PEG was then removed by repeated centrifuging and redispersion in fresh distilled water. The rheological behavior of suspensions of the PEG-grafted powders in water, 2-propanol and 2-butanol were characterized. All of the aqueous suspensions were shear thinning. The PEG 4600-grafted alumina powder aqueous suspensions were the most fluid. Sample rods and bars were molded from 52 vol% PEG-grafted alumina suspensions in 2-butanol. The best results were obtained with a preheated aluminum mold lubricated with a fluorinated oil mold-release. The samples were dried, sintered, and their microstructure and density were compared with sintered samples dry pressed from the same alumina powder

  7. Double-clad nuclear fuel safety rod

    DOEpatents

    McCarthy, William H.; Atcheson, Donald B.; Vaidyanathan, Swaminathan

    1984-01-01

    A device for shutting down a nuclear reactor during an undercooling or overpower event, whether or not the reactor's scram system operates properly. This is accomplished by double-clad fuel safety rods positioned at various locations throughout the reactor core, wherein melting of a secondary internal cladding of the rod allows the fuel column therein to shift from the reactor core to place the reactor in a subcritical condition.

  8. Gear crack propagation investigations

    NASA Technical Reports Server (NTRS)

    Lewicki, David G.; Ballarini, Roberto

    1996-01-01

    Analytical and experimental studies were performed to investigate the effect of gear rim thickness on crack propagation life. The FRANC (FRacture ANalysis Code) computer program was used to simulate crack propagation. The FRANC program used principles of linear elastic fracture mechanics, finite element modeling, and a unique re-meshing scheme to determine crack tip stress distributions, estimate stress intensity factors, and model crack propagation. Various fatigue crack growth models were used to estimate crack propagation life based on the calculated stress intensity factors. Experimental tests were performed in a gear fatigue rig to validate predicted crack propagation results. Test gears were installed with special crack propagation gages in the tooth fillet region to measure bending fatigue crack growth. Good correlation between predicted and measured crack growth was achieved when the fatigue crack closure concept was introduced into the analysis. As the gear rim thickness decreased, the compressive cyclic stress in the gear tooth fillet region increased. This retarded crack growth and increased the number of crack propagation cycles to failure.

  9. Profile of cocaine and crack users in Brazil.

    PubMed

    Duailibi, Lígia Bonacim; Ribeiro, Marcelo; Laranjeira, Ronaldo

    2008-01-01

    This article aims to systematize the profile of cocaine and crack users in Brazil. The study adopted a literature review of the MEDLINE, LILACS, Cochrane Library databases and CAPES thesis/dissertation database. Data were grouped in thematic categories: national household surveys, surveys of specific population groups, profile of patients that seek treatment, and mortality and morbidity. Within each category the principal findings from the Brazilian literature were described and then discussed. The article concludes that the information on cocaine and crack consumption in Brazil is still incipient, but that the scientific community can already draw on a relevant theoretical corpus that can be used to update current public policies on this issue. PMID:18797730

  10. Analysis of microstructure and properties of multilayer coatings produced by laser cladding

    NASA Astrophysics Data System (ADS)

    Bykovskiy, D. P.; Petrovskiy, V. N.; Dzhumaev, P. S.; Polskiy, V. I.; Yermachenko, V. M.

    2016-02-01

    Purpose of the work is to prepare multilayer coatings corresponding to specified requirements to recovery and improvement of surface details. Requirements to coatings: providing durable and reliable adhesion base and filler materials, absence of pores, cracks, delaminations, reducing mixing metal base and cladding. We used iron-based PR-10R6M5 and tungsten carbide Hoganas 44712 powders. Experimental determination of the optimal technological mode of application of the single track, the coefficient of overlapping tracks to create a full layer, the angle of the second cladding layer, relative to the first one and, finally, the determination of the optimal additive tungsten carbide to achieve increased durability were produced to fulfill these requirements.

  11. Chemical aspects of pellet-cladding interaction in light water reactor fuel elements

    SciTech Connect

    Olander, D.R.

    1982-01-01

    In contrast to the extensive literature on the mechanical aspects of pellet-cladding interaction (PCI) in light water reactor fuel elements, the chemical features of this phenomenon are so poorly understood that there is still disagreement concerning the chemical agent responsible. Since the earliest work by Rosenbaum, Davies and Pon, laboratory and in-reactor experiments designed to elucidate the mechanism of PCI fuel rod failures have concentrated almost exclusively on iodine. The assumption that this is the reponsible chemical agent is contained in models of PCI which have been constructed for incorporation into fuel performance codes. The evidence implicating iodine is circumstantial, being based primarily upon the volatility and significant fission yield of this element and on the microstructural similarity of the failed Zircaloy specimens exposed to iodine in laboratory stress corrosion cracking (SCC) tests to cladding failures by PCI.

  12. Cocaine (Coke, Crack) Facts

    MedlinePlus

    ... That People Abuse » Cocaine (Coke, Crack) Facts Cocaine (Coke, Crack) Facts Listen Cocaine is a white ... Version Download "My life was built around getting cocaine and getting high." Stacey is recovering from her ...

  13. Crack propagation in graphene

    NASA Astrophysics Data System (ADS)

    Budarapu, P. R.; Javvaji, B.; Sutrakar, V. K.; Roy Mahapatra, D.; Zi, G.; Rabczuk, T.

    2015-08-01

    The crack initiation and growth mechanisms in an 2D graphene lattice structure are studied based on molecular dynamics simulations. Crack growth in an initial edge crack model in the arm-chair and the zig-zag lattice configurations of graphene are considered. Influence of the time steps on the post yielding behaviour of graphene is studied. Based on the results, a time step of 0.1 fs is recommended for consistent and accurate simulation of crack propagation. Effect of temperature on the crack propagation in graphene is also studied, considering adiabatic and isothermal conditions. Total energy and stress fields are analyzed. A systematic study of the bond stretching and bond reorientation phenomena is performed, which shows that the crack propagates after significant bond elongation and rotation in graphene. Variation of the crack speed with the change in crack length is estimated.

  14. Indenter size effect on the reversible incipient plasticity of Al (001) surface: Quasicontinuum study

    NASA Astrophysics Data System (ADS)

    Tang, Dan; Shao, Yu-Fei; Li, Jiu-Hui; Zhao, Xing; Qi, Yang

    2015-08-01

    Indenter size effect on the reversible incipient plasticity of Al (001) surface is studied by quasicontinuum simulations. Results show that the incipient plasticity under small indenter, the radius of which is less than ten nanometers, is dominated by a simple planar fault defect that can be fully removed after withdrawal of the indenter; otherwise, irreversible incipient plastic deformation driven by a complex dislocation activity is preferred, and the debris of deformation twins, dislocations, and stacking fault ribbons still remain beneath the surface when the indenter has been completely retracted. Based on stress distributions calculated at an atomic level, the reason why the dislocation burst instead of a simple fault ribbon is observed under a large indenter is the release of the intensely accumulated shear stress. Finally, the critical load analysis implies that there exists a reversible-irreversible transition of incipient plasticity induced by indenter size. Our findings provide a further insight into the incipient surface plasticity of face-centered-cubic metals in nano-sized contact issues. Project supported by the National Natural Science Foundation of China (Grant No. 51172040), the National Basic Research Program of China (Grant No. 2011CB606403), and the General Project of Scientific Research from Liaoning Educational Committee, China (Grant No. L2014135).

  15. The wolf in sheep’s clothing: Microtomographic aspects of clinically incipient radiation-related caries

    PubMed Central

    Morais-Faria, Karina; Neves-Silva, Rodrigo; Lopes, Marcio-Ajudarte; Ribeiro, Ana-Carolina-Prado; de Castro Jr, Gilberto; da Conceição-Vasconcelos, Karina-Gondim-Moutinho; Brandão, Thais-Bianca; Santos-Silva, Alan-Roger

    2016-01-01

    Background Radiation-related caries (RRC) can cause rapid progression, with a high potential for dental destruction affecting mainly cervical and incisal areas. Unlike the injuries that occur in the conventional caries, incipient RRC present in unusual surfaces have difficult diagnosis and classification stages of cavitation. Material and Methods Evaluate the radiographic patterns of demineralization of RRC by using micro-CT. Ten teeth with incipient RRC and 10 teeth with incipient conventional caries (control group) matched by anatomic teeth group and caries affected surfaces were evaluated by X-ray microtomography (micro-CT) Skyscan 1174V2 (50Kv, 1.3 megapixel, Kontich, Belgium). Teeth were placed in a standard position for micro-CT (coronal, transaxial and sagittal sections) during images acquisition. Lesions were classified according to the depth of invasion and relationship with enamel, dentin and pulp. Results RRC samples presented deeper lesions with higher involvement of enamel and dentin. Control group presented focal and superficial lesions with lower involvement of enamel and dentin. Conclusions Incipient RRC present aggressive microtomographic patterns of demineralization when compared to conventional caries, as indicated by deep lesions, regardless of its clinically incipient aspects. Key words:Head and neck cancer, radiotherapy, microtomography, radiation caries. PMID:26946198

  16. Clad Degradation- Summary and Abstraction for LA

    SciTech Connect

    D. Stahl

    2004-10-01

    The purpose of this model report is to develop the summary cladding degradation abstraction that will be used in the Total System Performance Assessment for the License Application (TSPA-LA). Most civilian commercial nuclear fuel is encased in Zircaloy cladding. The model addressed in this report is intended to describe the postulated condition of commercial Zircaloy-clad fuel as a function of postclosure time after it is placed in the repository. Earlier total system performance assessments analyzed the waste form as exposed UO{sub 2}, which was available for degradation at the intrinsic dissolution rate. Water in the waste package quickly became saturated with many of the radionuclides, limiting their release rate. In the total system performance assessments for the Viability Assessment and the Site Recommendation, cladding was analyzed as part of the waste form, limiting the amount of fuel available at any time for degradation. The current model is divided into two stages. The first considers predisposal rod failures (most of which occur during reactor operation and associated activities) and postdisposal mechanical failure (from static loading of rocks) as mechanisms for perforating the cladding. Other fuel failure mechanisms including those caused by handling or transportation have been screened out (excluded) or are treated elsewhere. All stainless-steel-clad fuel, which makes up a small percentage of the overall amount of fuel to be stored, is modeled as failed upon placement in the waste packages. The second stage of the degradation model is the splitting of the cladding from the reaction of water or moist air and UO{sub 2}. The splitting has been observed to be rapid in comparison to the total system performance assessment time steps and is modeled to be instantaneous. After the cladding splits, the rind buildup inside the cladding widens the split, increasing the diffusion area from the fuel rind to the waste package interior. This model report summarizes

  17. Short crack growth behavior

    SciTech Connect

    Sadananda, K.; Vasudevan, A.K.

    1997-12-01

    The authors have re-evaluated short crack growth behavior using concepts developed recently, and they show that these concepts provide a unified framework that can explain both short and long crack growth behavior without resorting to the crack closure effect. They consider that the behavior of long cracks, including the effects of load ratio, R, is fundamental. they had shown previously that, since fatigue is at least a two-parameter problem in that at least two load parameters are required for an unambiguous description, there are two critical driving forces required simultaneously for fatigue cracks to grow. In extending this analysis to the growth of short cracks, they reject the current notion of the lack of similitude for short cracks and express the similitude as a fundamental postulate that, for a given crack growth mechanism, equal crack tip driving forces result in equal crack growth rates. Short crack growth behavior confirms the concept that two parameters are required to define fatigue; consequently, for fatigue cracks to grow, two thresholds need to be satisfied simultaneously. The authors present examples from the literature to illustrate the concepts discussed.

  18. Fuel cladding behavior under rapid loading conditions

    NASA Astrophysics Data System (ADS)

    Yueh, K.; Karlsson, J.; Stjärnsäter, J.; Schrire, D.; Ledergerber, G.; Munoz-Reja, C.; Hallstadius, L.

    2016-02-01

    A modified burst test (MBT) was used in an extensive test program to characterize fuel cladding failure behavior under rapid loading conditions. The MBT differs from a normal burst test with the use of a driver tube to simulate the expansion of a fuel pellet, thereby producing a partial strain driven deformation condition similar to that of a fuel pellet expansion in a reactivity insertion accident (RIA). A piston/cylinder assembly was used to pressurize the driver tube. By controlling the speed and distance the piston travels the loading rate and degree of sample deformation could be controlled. The use of a driver tube with a machined gauge section localizes deformation and allows for continuous monitoring of the test sample diameter change at the location of maximum hoop strain, during each test. Cladding samples from five irradiated fuel rods were tested between 296 and 553 K and loading rates from 1.5 to 3.5/s. The test rods included variations of Zircaloy-2 with different liners and ZIRLO, ranging in burn-up from 41 to 74 GWd/MTU. The test results show cladding ductility is strongly temperature and loading rate dependent. Zircaloy-2 cladding ductility degradation due to operational hydrogen pickup started to recover at approximately 358 K for test condition used in the study. This recovery temperature is strongly loading rate dependent. At 373 K, ductility recovery was small for loading rates less than 8 ms equivalent RIA pulse width, but longer than 8 ms the ductility recovery increased exponentially with increasing pulse width, consistent with literature observations of loading rate dependent brittle-to-ductile (BTD) transition temperature. The cladding ductility was also observed to be strongly loading rate/pulse width dependent for BWR cladding below the BTD temperature and Pressurized Water Reactor (PWR) cladding at both 296 and 553 K.

  19. Localization of incipient tip vortex cavitation using ray based matched field inversion method

    NASA Astrophysics Data System (ADS)

    Kim, Dongho; Seong, Woojae; Choo, Youngmin; Lee, Jeunghoon

    2015-10-01

    Cavitation of marine propeller is one of the main contributing factors of broadband radiated ship noise. In this research, an algorithm for the source localization of incipient vortex cavitation is suggested. Incipient cavitation is modeled as monopole type source and matched-field inversion method is applied to find the source position by comparing the spatial correlation between measured and replicated pressure fields at the receiver array. The accuracy of source localization is improved by broadband matched-field inversion technique that enhances correlation by incoherently averaging correlations of individual frequencies. Suggested localization algorithm is verified through known virtual source and model test conducted in Samsung ship model basin cavitation tunnel. It is found that suggested localization algorithm enables efficient localization of incipient tip vortex cavitation using a few pressure data measured on the outer hull above the propeller and practically applicable to the typically performed model scale experiment in a cavitation tunnel at the early design stage.

  20. The Corrosion and Corrosion Fatigue Behavior of Nickel Based Alloy Weld Overlay and Coextruded Claddings

    NASA Astrophysics Data System (ADS)

    Stockdale, Andrew

    The use of low NOx boilers in coal fired power plants has resulted in sulfidizing corrosive conditions within the boilers and a reduction in the service lifetime of the waterwall tubes. As a solution to this problem, Ni-based weld overlays are used to provide the necessary corrosion resistance however; they are susceptible to corrosion fatigue. There are several metallurgical factors which give rise to corrosion fatigue that are associated with the localized melting and solidification of the weld overlay process. Coextruded coatings offer the potential for improved corrosion fatigue resistance since coextrusion is a solid state coating process. The corrosion and corrosion fatigue behavior of alloy 622 weld overlays and coextruded claddings was investigated using a Gleeble thermo-mechanical simulator retrofitted with a retort. The experiments were conducted at a constant temperature of 600°C using a simulated combustion gas of N2-10%CO-5%CO2-0.12%H 2S. An alternating stress profile was used with a minimum tensile stress of 0 MPa and a maximum tensile stress of 300 MPa (ten minute fatigue cycles). The results have demonstrated that the Gleeble can be used to successfully simulate the known corrosion fatigue cracking mechanism of Ni-based weld overlays in service. Multilayer corrosion scales developed on each of the claddings that consisted of inner and outer corrosion layers. The scales formed by the outward diffusion of cations and the inward diffusion of sulfur and oxygen anions. The corrosion fatigue behavior was influenced by the surface finish and the crack interactions. The initiation of a large number of corrosion fatigue cracks was not necessarily detrimental to the corrosion fatigue resistance. Finally, the as-received coextruded cladding exhibited the best corrosion fatigue resistance.

  1. The electrical conductivity during incipient melting in the oceanic low velocity zone

    NASA Astrophysics Data System (ADS)

    Gaillard, Fabrice; Sifre, David; Gardes, Emmanuel; Massuyeau, Malcolm; Hashim, Leila; Hier Majumder, Saswata

    2014-05-01

    A low viscosity layer at the Lithosphere-Asthenosphere Boundary (LAB) is certainly a requirement for plate tectonics but the nature of the rocks presents in this boundary remains controversial. The seismic low velocities and the high electrical conductivities of the LAB are attributed either to sub-solidus water-related defects in olivine minerals or to a few volume percents of partial melt but these two interpretations have shortcomings: (1) The amount of H2O stored in olivine is not expected to be high enough due to several mineralogical processes that have been sometimes ignored; (2) elevated melt volume fractions are impeded by the too cold temperatures prevailing in the LAB and by the high melt mobility that can lead to gravitational segregation. All this has in fact been partly settled 30 years ago, when a petrological LAB has been defined as a region of the upper mantle impregnated by incipient melts; that is small amounts of melt caused by small amount of CO2 and H2O. We show here that incipient melting is a melting regime that is allowed in the entire P-T-fO2 region of the LVZ. The top of the oceanic LVZ (LAB) is then best explained by a melt freezing layer due to a decarbonation reaction, whereas the bottom of the LVZ matches the depth at which redox melting defines the lower boundary of stability of incipient melts. Based on new laboratory measurements, we show here that incipient melts must be the cause of the high electrical conductivities in the oceanic LVZ. Considering relevant mantle abundances of H2O and CO2 and their effect on the petrology of incipient melting, we calculated conductivity profiles across the LAB for various ages. Several electrical discontinuities are predicted and match geophysical observations in a consistent petrological and geochemical framework. We conclude that incipient melts prevail in the LAB, what else?

  2. Effect of tip radius on the incipient plasticity of chromium studied by nanoindentation

    DOE PAGESBeta

    Wu, Dong; Morris, James R.; Nieh, T. G.

    2014-10-01

    The onset of plasticity in Cr was investigated by nanoindentation using indenters with tip radii ranging from 60 to 759 nm. The stress for incipient plasticity was found to increase with decreasing tip radius. We find that the cumulative pop-in probability on load could be described successfully by a combined model over the full range of tip radius, indicating that the incipient plasticity might be triggered either by the homogeneous nucleation of dislocation or by the activation of existing dislocations underneath the indenter.

  3. Bonding Interface and Bending Deformation of Al/316LSS Clad Metal Prepared by Explosive Welding

    NASA Astrophysics Data System (ADS)

    Guo, Xunzhong; Fan, Minyu; Wang, Liuan; Ma, Fuye

    2016-04-01

    The morphology, elemental distribution, and phase analysis of the bonding interface were investigated by means of SEM, EDS, and XRD to evaluate the interface bonding properties of Al/316LSS clad metal prepared by explosive welding method. Furthermore, the micro-hardness and bending properties were also investigated. The results indicated that the linear and wavy bonding interfaces coexisted and intermetallic phases were present in the local interfacial zone. Moreover, the micro-hardness value at the bonding interface with intermetallic phases was higher than that at the interface without any intermetallic phases. In addition, bulk metal compounds could easily lead to the generation of micro-cracks during the bending forming process.

  4. Bonding Interface and Bending Deformation of Al/316LSS Clad Metal Prepared by Explosive Welding

    NASA Astrophysics Data System (ADS)

    Guo, Xunzhong; Fan, Minyu; Wang, Liuan; Ma, Fuye

    2016-06-01

    The morphology, elemental distribution, and phase analysis of the bonding interface were investigated by means of SEM, EDS, and XRD to evaluate the interface bonding properties of Al/316LSS clad metal prepared by explosive welding method. Furthermore, the micro-hardness and bending properties were also investigated. The results indicated that the linear and wavy bonding interfaces coexisted and intermetallic phases were present in the local interfacial zone. Moreover, the micro-hardness value at the bonding interface with intermetallic phases was higher than that at the interface without any intermetallic phases. In addition, bulk metal compounds could easily lead to the generation of micro-cracks during the bending forming process.

  5. Incipient and Progressive Damage in Polyethylene Under Extreme Tensile Conditions

    SciTech Connect

    Furmanski, Jevan; Brown, Eric; Trujillo, Carl P.; Martinez, Daniel Tito; Gray, George T. III

    2012-06-07

    The Dynamic-Tensile-Extrusion (Dyn-Ten-Ext) test was developed at LANL by Gray and coworkers to probe the tensile response of materials at large strains (>1) and high strain-rates (>1000/s) by firing projectiles through a conical die at 300-700 m/s. This technique has recently been applied to various polymers, such as the fluoropolymers PTFE (Teflon) and the chemically similar PCTFE, which respectively exhibited catastrophic fragmentation and distributed dynamic necking. This work details investigations of the Dyn-Ten-Ext response of high density polyethylene, both to failure and sub-critical conditions. At large extrusion ratios ({approx}7.4) and high velocities, such as those previously employed, HDPE catastrophically fragmented in a craze-like manner in the extruded jet. At more modest extrusion ratios and high velocities the specimen extruded a stable jet that ruptured cleanly, and at lower velocities was recovered intact after sustaining substantial internal damage. Thermomechanical finite element simulations showed that the damage corresponded to a locus of shear stress in the presence of hydrostatic tension. X-ray computed tomography corroborated the prediction of a shear damage mechanism by finding the region of partially damaged material to consist of macroscopic shear-mode cracks nearly aligned with the extrusion axis, originating from the location of damage inception.

  6. Ductile-to-brittle transition temperature for high-burnup cladding alloys exposed to simulated drying-storage conditions

    NASA Astrophysics Data System (ADS)

    Billone, M. C.; Burtseva, T. A.; Einziger, R. E.

    2013-02-01

    Structural analyses of dry casks containing high-burnup fuel require cladding mechanical properties and failure limits to assess fuel behavior. Pre-storage drying-transfer operations and early stage storage subject cladding to higher temperatures and much higher pressure-induced tensile hoop stresses relative to in-reactor operation and pool storage. Under these conditions, radial hydrides may precipitate during slow cooling and provide an additional embrittlement mechanism as the cladding temperature decreases below the ductile-to-brittle transition temperature (DBTT). A test procedure was developed to simulate the effects of drying-storage temperature histories. Following drying-storage simulation, samples were subjected to ring-compression test (RCT) loading, which was used as a ductility screening test and to simulate pinch-type loading that may occur during cask transport. RCT samples with <2% offset strain prior to >50% wall cracking were assessed as brittle. Prior to testing high-burnup cladding, many tests were conducted with pre-hydrided Zircaloy-4 (Zry-4) and ZIRLO™ to determine target 400 °C hoop stresses for high-burnup rodlets. Zry-4 cladding segments, from a 67-GWd/MTU fuel rod, with 520-620 wppm hydrogen and ZIRLO™ cladding segments from a 70-GWd/MTU fuel rod, with 350-650 wppm hydrogen were defueled and tested. Following drying-storage simulation, the extent of radial-hydride precipitation was characterized by the radial-hydride continuity factor. It was found that the DBTT was dependent on: cladding material, irradiation conditions, and drying-storage histories (stress at maximum temperature). High-burnup ZIRLO™ exhibited higher susceptible to radial-hydride formation and embrittlement than high-burnup Zry-4. It was also observed that uniformly pre-hydrided, non-irradiated cladding was not a good surrogate for high-burnup cladding because of the high density of circumferential hydrides across the wall and the high metal-matrix ductility for

  7. Grain boundary melting and hot cracking in weld HAZ of a two-phase Ni{sub 3}Al alloy containing Zr

    SciTech Connect

    Li, H.; Chaki, T.K.

    1995-08-01

    Grain boundary melting and its effect on hot cracking in the weld heat-affected zone (HAZ) have been investigated in the investment cast billet of a two-phase ({gamma} + {gamma}{prime}) nickel aluminide alloy (Ni{sub 74.48}Al{sub 16.98}Cr{sub 8.02}Zr{sub 0.51}B{sub 0.10}), designated as IC-218. Due to enrichment of Zr, which can form eutectic alloys with Ni, the dendritic boundaries melted incipiently at 1,150 C. Under thermal stresses during welding the molten layers often opened up producing liquation cracks at the boundaries in the HAZ. Annealing at 1,100 C in argon for 23 h prior to welding reduced the incipient melting temperature to 1,125 C and increased the propensity of liquation cracking in the HAZ.

  8. Roll Casting of Aluminum Alloy Clad Strip

    SciTech Connect

    Nakamura, R.; Tsuge, H.; Haga, T.; Watari, H.; Kumai, S.

    2011-01-17

    Casting of aluminum alloy three layers of clad strip was tried using the two sets of twin roll casters, and effects of the casting parameters on the cladding conditions were investigated. One twin roll caster was mounted on the other twin roll caster. Base strip was 8079 aluminum alloy and overlay strips were 6022 aluminum alloy. Effects of roll-load of upper and lower casters and melt temperature of the lower caster were investigated. When the roll-load of the upper and lower caster was large enough, the overlay strip could be solidified and be connected. The overlay strip could be connected when the melt of the overlay strip cast by the lower caster was low enough. Sound three layers of clad strip could be cast by proper conditions.

  9. Potential effects of gallium on cladding materials

    SciTech Connect

    Wilson, D.F.; Beahm, E.C.; Besmann, T.M.; DeVan, J.H.; DiStefano, J.R.; Gat, U.; Greene, S.R.; Rittenhouse, P.L.; Worley, B.A.

    1997-10-01

    This paper identifies and examines issues concerning the incorporation of gallium in weapons derived plutonium in light water reactor (LWR) MOX fuels. Particular attention is given to the more likely effects of the gallium on the behavior of the cladding material. The chemistry of weapons grade (WG) MOX, including possible consequences of gallium within plutonium agglomerates, was assessed. Based on the calculated oxidation potentials of MOX fuel, the effect that gallium may have on reactions involving fission products and possible impact on cladding performance were postulated. Gallium transport mechanisms are discussed. With an understanding of oxidation potentials and assumptions of mechanisms for gallium transport, possible effects of gallium on corrosion of cladding were evaluated. Potential and unresolved issues and suggested research and development (R and D) required to provide missing information are presented.

  10. Investigation of Helicopter Longeron Cracks

    NASA Technical Reports Server (NTRS)

    Newman, John A.; Baughman, James; Wallace, Terryl A.

    2009-01-01

    Four cracked longerons, containing a total of eight cracks, were provided for study. Cracked regions were cut from the longerons. Load was applied to open the cracks, enabling crack surface examination. Examination revealed that crack propagation was driven by fatigue loading in all eight cases. Fatigue crack initiation appears to have occurred on the top edge of the longerons near geometric changes that affect component bending stiffness. Additionally, metallurgical analysis has revealed a local depletion in alloying elements in the crack initiation regions that may be a contributing factor. Fatigue crack propagation appeared to be initially driven by opening-mode loading, but at a crack length of approximately 0.5 inches (12.7 mm), there is evidence of mixed-mode crack loading. For the longest cracks studied, shear-mode displacements destroyed crack-surface features of interest over significant portions of the crack surfaces.

  11. Capturing reflected cladding modes from a fiber Bragg grating with a double-clad fiber coupler.

    PubMed

    Baiad, Mohamad Diaa; Gagné, Mathieu; Lemire-Renaud, Simon; De Montigny, Etienne; Madore, Wendy-Julie; Godbout, Nicolas; Boudoux, Caroline; Kashyap, Raman

    2013-03-25

    We present a novel measurement scheme using a double-clad fiber coupler (DCFC) and a fiber Bragg grating (FBG) to resolve cladding modes. Direct measurement of the optical spectra and power in the cladding modes is obtained through the use of a specially designed DCFC spliced to a highly reflective FBG written into slightly etched standard photosensitive single mode fiber to match the inner cladding diameter of the DCFC. The DCFC is made by tapering and fusing two double-clad fibers (DCF) together. The device is capable of capturing backward propagating low and high order cladding modes simply and efficiently. Also, we demonstrate the capability of such a device to measure the surrounding refractive index (SRI) with an extremely high sensitivity of 69.769 ± 0.035 μW/RIU and a resolution of 1.433 × 10(-5) ± 8 × 10(-9) RIU between 1.37 and 1.45 RIU. The device provides a large SRI operating range from 1.30 to 1.45 RIU with sufficient discrimination for all individual captured cladding modes. The proposed scheme can be adapted to many different types of bend, temperature, refractive index and other evanescent wave based sensors. PMID:23546069

  12. Acoustic Emission Detection and Prediction of Fatigue Crack Propagation in Composite Patch Repairs Using Neural Networks

    SciTech Connect

    Okafor, A. Chukwujekwu; Singh, Navdeep; Singh, Navrag

    2007-03-21

    An aircraft is subjected to severe structural and aerodynamic loads during its service life. These loads can cause damage or weakening of the structure especially for aging military and civilian aircraft, thereby affecting its load carrying capabilities. Hence composite patch repairs are increasingly used to repair damaged aircraft metallic structures to restore its structural efficiency. This paper presents the results of Acoustic Emission (AE) monitoring of crack propagation in 2024-T3 Clad aluminum panels repaired with adhesively bonded octagonal, single sided boron/epoxy composite patch under tension-tension fatigue loading. Crack propagation gages were used to monitor crack initiation. The identified AE sensor features were used to train neural networks for predicting crack length. The results show that AE events are correlated with crack propagation. AE system was able to detect crack propagation even at high noise condition of 10 Hz loading; that crack propagation signals can be differentiated from matrix cracking signals that take place due to fiber breakage in the composite patch. Three back-propagation cascade feed forward networks were trained to predict crack length based on the number of fatigue cycles, AE event number, and both the Fatigue Cycles and AE events, as inputs respectively. Network using both fatigue cycles and AE event number as inputs to predict crack length gave the best results, followed by Network with fatigue cycles as input, while network with just AE events as input had a greater error.

  13. Transformer Incipient Fault Prediction Using Combined Artificial Neural Network and Various Particle Swarm Optimisation Techniques

    PubMed Central

    2015-01-01

    It is important to predict the incipient fault in transformer oil accurately so that the maintenance of transformer oil can be performed correctly, reducing the cost of maintenance and minimise the error. Dissolved gas analysis (DGA) has been widely used to predict the incipient fault in power transformers. However, sometimes the existing DGA methods yield inaccurate prediction of the incipient fault in transformer oil because each method is only suitable for certain conditions. Many previous works have reported on the use of intelligence methods to predict the transformer faults. However, it is believed that the accuracy of the previously proposed methods can still be improved. Since artificial neural network (ANN) and particle swarm optimisation (PSO) techniques have never been used in the previously reported work, this work proposes a combination of ANN and various PSO techniques to predict the transformer incipient fault. The advantages of PSO are simplicity and easy implementation. The effectiveness of various PSO techniques in combination with ANN is validated by comparison with the results from the actual fault diagnosis, an existing diagnosis method and ANN alone. Comparison of the results from the proposed methods with the previously reported work was also performed to show the improvement of the proposed methods. It was found that the proposed ANN-Evolutionary PSO method yields the highest percentage of correct identification for transformer fault type than the existing diagnosis method and previously reported works. PMID:26103634

  14. Transformer Incipient Fault Prediction Using Combined Artificial Neural Network and Various Particle Swarm Optimisation Techniques.

    PubMed

    Illias, Hazlee Azil; Chai, Xin Rui; Abu Bakar, Ab Halim; Mokhlis, Hazlie

    2015-01-01

    It is important to predict the incipient fault in transformer oil accurately so that the maintenance of transformer oil can be performed correctly, reducing the cost of maintenance and minimise the error. Dissolved gas analysis (DGA) has been widely used to predict the incipient fault in power transformers. However, sometimes the existing DGA methods yield inaccurate prediction of the incipient fault in transformer oil because each method is only suitable for certain conditions. Many previous works have reported on the use of intelligence methods to predict the transformer faults. However, it is believed that the accuracy of the previously proposed methods can still be improved. Since artificial neural network (ANN) and particle swarm optimisation (PSO) techniques have never been used in the previously reported work, this work proposes a combination of ANN and various PSO techniques to predict the transformer incipient fault. The advantages of PSO are simplicity and easy implementation. The effectiveness of various PSO techniques in combination with ANN is validated by comparison with the results from the actual fault diagnosis, an existing diagnosis method and ANN alone. Comparison of the results from the proposed methods with the previously reported work was also performed to show the improvement of the proposed methods. It was found that the proposed ANN-Evolutionary PSO method yields the highest percentage of correct identification for transformer fault type than the existing diagnosis method and previously reported works. PMID:26103634

  15. A Feature Extraction Method for Vibration Signal of Bearing Incipient Degradation

    NASA Astrophysics Data System (ADS)

    Huang, Haifeng; Ouyang, Huajiang; Gao, Hongli; Guo, Liang; Li, Dan; Wen, Juan

    2016-06-01

    Detection of incipient degradation demands extracting sensitive features accurately when signal-to-noise ratio (SNR) is very poor, which appears in most industrial environments. Vibration signals of rolling bearings are widely used for bearing fault diagnosis. In this paper, we propose a feature extraction method that combines Blind Source Separation (BSS) and Spectral Kurtosis (SK) to separate independent noise sources. Normal, and incipient fault signals from vibration tests of rolling bearings are processed. We studied 16 groups of vibration signals (which all display an increase in kurtosis) of incipient degradation after they are processed by a BSS filter. Compared with conventional kurtosis, theoretical studies of SK trends show that the SK levels vary with frequencies and some experimental studies show that SK trends of measured vibration signals of bearings vary with the amount and level of impulses in both vibration and noise signals due to bearing faults. It is found that the peak values of SK increase when vibration signals of incipient faults are processed by a BSS filter. This pre-processing by a BSS filter makes SK more sensitive to impulses caused by performance degradation of bearings.

  16. Elevated temperature crack growth

    NASA Technical Reports Server (NTRS)

    Kim, K. S.; Vanstone, R. H.

    1992-01-01

    The purpose of this program was to extend the work performed in the base program (CR 182247) into the regime of time-dependent crack growth under isothermal and thermal mechanical fatigue (TMF) loading, where creep deformation also influences the crack growth behavior. The investigation was performed in a two-year, six-task, combined experimental and analytical program. The path-independent integrals for application to time-dependent crack growth were critically reviewed. The crack growth was simulated using a finite element method. The path-independent integrals were computed from the results of finite-element analyses. The ability of these integrals to correlate experimental crack growth data were evaluated under various loading and temperature conditions. The results indicate that some of these integrals are viable parameters for crack growth prediction at elevated temperatures.

  17. CRACK MODELLING FOR RADIOGRAPHY

    SciTech Connect

    Chady, T.; Napierala, L.

    2010-02-22

    In this paper, possibility of creation of three-dimensional crack models, both random type and based on real-life radiographic images is discussed. Method for storing cracks in a number of two-dimensional matrices, as well algorithm for their reconstruction into three-dimensional objects is presented. Also the possibility of using iterative algorithm for matching simulated images of cracks to real-life radiographic images is discussed.

  18. Crack Modelling for Radiography

    NASA Astrophysics Data System (ADS)

    Chady, T.; Napierała, L.

    2010-02-01

    In this paper, possibility of creation of three-dimensional crack models, both random type and based on real-life radiographic images is discussed. Method for storing cracks in a number of two-dimensional matrices, as well algorithm for their reconstruction into three-dimensional objects is presented. Also the possibility of using iterative algorithm for matching simulated images of cracks to real-life radiographic images is discussed.

  19. Thermal cracking of butadiene

    SciTech Connect

    Duisters, H.A.M. )

    1994-01-01

    This paper presents experimental data on the thermal cracking of butadiene in a pilot plant, under conditions representative of industrial operation. The product distribution of pure-butadiene cracking is shown. Results from cocracking experiments in naphtha and C[sub 4]-raffinate are also presented. It is shown that butadiene cracking can be an interesting outlet for the increasing butadiene overcapacity in steam crackers. Some aspects of coke formation during butadiene pyrolysis are addressed as well.

  20. Cracking of a layered medium on an elastic foundation under thermal shock

    NASA Technical Reports Server (NTRS)

    Rizk, Abd El-Fattah A.; Erdogan, Fazil

    1988-01-01

    The cladded pressure vessel under thermal shock conditions which is simulated by using two simpler models was studied. The first model (Model 1) assumes that, if the crack size is very small compared to the vessel thickness, the problem can be treated as a semi-infinite elastic medium bonded to a very thin layer of different material. However, if the crack size is of the same order as the vessel thickness, the curvature effects may not be negligible. In this case it is assumed that the relatively thin walled hollow cylinder with cladding can be treated as a composite beam on an elastic foundation (Model 2). In both models, the effect of surface cooling rate is studied by assuming the temperature boundary condition to be a ramp function. The calculated results include the transient temperature, thermal stresses in the uncracked medium and stress intensity factors which are presented as a function of time, and the duration of cooling ramp. The stress intensity factors are also presented as a function of the size and the location of the crack. The problem is solved for two bonded materials of different thermal and mechanical properties. The mathematical formulation results in two singular integral equations which are solved numerically. The results are given for two material pairs, namely an austenitic steel layer welded on a ferritic steel substrate, and a ceramic coating on ferritic steel. In the case of the yielded clad, the stress intensity factors for a crack under the clad are determined by using a plastic strip model and are compared with elastic clad results.

  1. Mechanical and substructural response of incipiently spalled 316L stainless steel.

    SciTech Connect

    Gray, G. T. , III; Bourne, N. K.

    2004-01-01

    316L SS samples were shock prestrained to a peak stress of 6.6 GPa using a 0.75 {mu}sec pulse duration square-topped shock profile and 'soft' recovered while a second sample was similarly shock loaded, without spall momentum trapping, leading to incipient spall damage. Shock prestraining and 'soft' shock recovery to 6.6 GPa led to an increase in the post-shock flow strength of 316L SS by {approx}100 MPa over the starting material while the reload yield strength of the incipiently spall damaged sample increased by {approx}200 MPa. In this paper the sequential processes of defect generation and damage operative during the shock prestraining, spallation, and reloading of incipiently spalled 316L SS is presented. The influence of shock prestraining, using both triangular-wave loading, via both direct HE and triangular-wave pulses on a gas launcher, as well as 'square-topped' shock prestaining via conventional flyer-plate impact, is crucial to understanding the shock hardening and spallation responses of materials(Gray III, et al. [2003]). The development of predictive constitutive models to describe the mechanical response of incipiently damaged metals and alloys requires an understanding of the defect generation and storage due to shock hardening as well as the additional plasticity and damage evolution during spallation. In this paper the influence of shock-wave prestraining on the process of shock hardening and thereafterthe hardeningand damage evolution accompanying incipient spallation in 316L stainless steel (316L SS) on post-shock constitutive behavior is examined using 'soft' recovery techniques and mechanical behavior measurements.

  2. Automatic crack propagation tracking

    NASA Technical Reports Server (NTRS)

    Shephard, M. S.; Weidner, T. J.; Yehia, N. A. B.; Burd, G. S.

    1985-01-01

    A finite element based approach to fully automatic crack propagation tracking is presented. The procedure presented combines fully automatic mesh generation with linear fracture mechanics techniques in a geometrically based finite element code capable of automatically tracking cracks in two-dimensional domains. The automatic mesh generator employs the modified-quadtree technique. Crack propagation increment and direction are predicted using a modified maximum dilatational strain energy density criterion employing the numerical results obtained by meshes of quadratic displacement and singular crack tip finite elements. Example problems are included to demonstrate the procedure.

  3. Laser cladding of nickel-based alloy coatings on copper substrates

    NASA Astrophysics Data System (ADS)

    Balu, Prabu; Rea, Edward; Deng, Justin

    2015-07-01

    The wear resistance of high-value copper components used in the metal casting, automotive, aerospace and electrical equipment industries can be improved by applying nickel (Ni)-based coatings through laser cladding. A high-power diode laser array providing continuous power levels up to 10 kilowatts with beam-shaping optics providing a rectangular focal region of various dimensions was used to deposit Ni-based alloy coatings with controlled thickness ranging from 0.3 mm to 1.6 mm in a single pass on copper (Cu) substrates. Slotted powder feeding plates with various discrete widths delivered uniform streams of powdered metal particles entrained in a carrier gas, matching the selected focal spot dimensions. To enhance laser beam coupling with the substrate and to avoid defects such as cracks, delamination and porosity, Cu substrates were preheated to a temperature of 300°C. The effect of heat input on microstructure of the cladding and extent of the heat-affected zone (HAZ) was evaluated using optical microscopy and scanning electron microscopy. Excessive heat input with longer interaction time increased dilution, porosity and expanded HAZ that significantly reduced the hardness of both the clad and the Cu substrates. Average microhardness of the Ni-C-B-Si-W alloy coating was 572 HV, which was almost 7 times greater than the hardness of the Cu substrate (84 HV).

  4. Cladding For Transversely-Pumped Laser Rod

    NASA Technical Reports Server (NTRS)

    Byer, Robert L.; Fan, Tso Yee

    1989-01-01

    Combination of suitable dimensioning and cladding of neodymium:yttrium aluminum garnet of similar solid-state laser provides for more efficient utilization of transversely-incident pump light from diode lasers. New design overcomes some of limitations of longitudinal- and older transverse-pumping concepts and promotes operation at higher output powers in TEM00 mode.

  5. Advanced ceramic cladding for water reactor fuel

    SciTech Connect

    Feinroth, H.

    2000-07-01

    Under the US Department of Energy's Nuclear Energy Research Initiatives (NERI) program, continuous fiber ceramic composites (CFCCs) are being developed as cladding for water reactor fuel elements. The purpose is to substantially increase the passive safety of water reactors. A development effort was initiated in 1991 to fabricate CFCC-clad tubes using commercially available fibers and a sol-gel process developed by McDermott Technologies. Two small-diameter CFCC tubes were fabricated using pure alumina and alumina-zirconia fibers in an alumina matrix. Densities of {approximately}60% of theoretical were achieved. Higher densities are required to guarantee fission gas containment. This NERI work has just begun, and only preliminary results are presented herein. Should the work prove successful, further development is required to evaluate CFCC cladding and performance, including in-pile tests containing fuel and exploring a marriage of CFCC cladding materials with suitable advanced fuel and core designs. The possibility of much higher temperature core designs, possibly cooled with supercritical water, and achievement of plant efficiencies {ge}50% would be examined.

  6. Pellet cladding mechanical interactions of ceramic claddings fuels under light water reactor conditions

    NASA Astrophysics Data System (ADS)

    Li, Bo-Shiuan

    Ceramic materials such as silicon carbide (SiC) are promising candidate materials for nuclear fuel cladding and are of interest as part of a potential accident tolerant fuel design due to its high temperature strength, dimensional stability under irradiation, corrosion resistance, and lower neutron absorption cross-section. It also offers drastically lower hydrogen generation in loss of coolant accidents such as that experienced at Fukushima. With the implementation of SiC material properties to the fuel performance code, FRAPCON, performances of the SiC-clad fuel are compared with the conventional Zircaloy-clad fuel. Due to negligible creep and high stiffness, SiC-clad fuel allows gap closure at higher burnup and insignificant cladding dimensional change. However, severe degradation of SiC thermal conductivity with neutron irradiation will lead to higher fuel temperature with larger fission gas release. High stiffness of SiC has a drawback of accumulating large interfacial pressure upon pellet-cladding mechanical interactions (PCMI). This large stress will eventually reach the flexural strength of SiC, causing failure of SiC cladding instantly in a brittle manner instead of the graceful failure of ductile metallic cladding. The large interfacial pressure causes phenomena that were previously of only marginal significance and thus ignored (such as creep of the fuel) to now have an important role in PCMI. Consideration of the fuel pellet creep and elastic deformation in PCMI models in FRAPCON provide for an improved understanding of the magnitude of accumulated interfacial pressure. Outward swelling of the pellet is retarded by the inward irradiation-induced creep, which then reduces the rate of interfacial pressure buildup. Effect of PCMI can also be reduced and by increasing gap width and cladding thickness. However, increasing gap width and cladding thickness also increases the overall thermal resistance which leads to higher fuel temperature and larger fission

  7. Microstructure characteristics of Ni/WC composite cladding coatings

    NASA Astrophysics Data System (ADS)

    Yang, Gui-rong; Huang, Chao-peng; Song, Wen-ming; Li, Jian; Lu, Jin-jun; Ma, Ying; Hao, Yuan

    2016-02-01

    A multilayer tungsten carbide particle (WCp)-reinforced Ni-based alloy coating was fabricated on a steel substrate using vacuum cladding technology. The morphology, microstructure, and formation mechanism of the coating were studied and discussed in different zones. The microstructure morphology and phase composition were investigated by scanning electron microscopy, optical microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy. In the results, the coating presents a dense and homogeneous microstructure with few pores and is free from cracks. The whole coating shows a multilayer structure, including composite, transition, fusion, and diffusion-affected layers. Metallurgical bonding was achieved between the coating and substrate because of the formation of the fusion and diffusion-affected layers. The Ni-based alloy is mainly composed of γ-Ni solid solution with finely dispersed Cr7C3/Cr23C6, CrB, and Ni+Ni3Si. WC particles in the composite layer distribute evenly in areas among initial Ni-based alloying particles, forming a special three-dimensional reticular microstructure. The macrohardness of the coating is HRC 55, which is remarkably improved compared to that of the substrate. The microhardness increases gradually from the substrate to the composite zone, whereas the microhardness remains almost unchanged in the transition and composite zones.

  8. Fracture of Hydrided Zircaloy-4 Sheet under Through-Thickness Crack Growth Conditions

    SciTech Connect

    Raynaud, P.A.; Koss, D.A.; Motta, A.T.; Chan, K.S.

    2007-07-01

    The failure of thin-wall components such as fuel cladding may be caused by crack initiation on the component surface and subsequent crack growth through its thickness. This study has determined the fracture toughness of hydrided cold-worked stress relieved Zircaloy-4 sheet subject to through-thickness crack growth at 25 deg. C. The experimental approach utilizes a novel procedure in which a narrow linear strip of brittle hydride blister across the specimen width creates a well-defined pre-crack upon initial loading. The subsequent crack growth resistance is then characterized by four-point bending of the specimen and an elastic-plastic fracture mechanics analysis. At room temperature, the through-thickness fracture toughness (K{sub Q}) is sensitive to the orientation of the hydride platelets, and K{sub Q} {approx_equal} 25 MPavm for crack growth through a mixed in-plane/out-of-plane hydride field. In contrast, K{sub Q} is much higher ({approx_equal} 75 MPavm) when the hydride platelets are oriented predominantly in the plane of the sheet (and therefore normal to both the crack plane and the crack growth direction). The implication of these fracture toughness values to the fracture strain behavior of hydrided Zircaloy-4 under through-thickness crack growth conditions is illustrated. (authors)

  9. Crack layer theory

    NASA Technical Reports Server (NTRS)

    Chudnovsky, A.

    1987-01-01

    A damage parameter is introduced in addition to conventional parameters of continuum mechanics and consider a crack surrounded by an array of microdefects within the continuum mechanics framework. A system consisting of the main crack and surrounding damage is called crack layer (CL). Crack layer propagation is an irreversible process. The general framework of the thermodynamics of irreversible processes are employed to identify the driving forces (causes) and to derive the constitutive equation of CL propagation, that is, the relationship between the rates of the crack growth and damage dissemination from one side and the conjugated thermodynamic forces from another. The proposed law of CL propagation is in good agreement with the experimental data on fatigue CL propagation in various materials. The theory also elaborates material toughness characterization.

  10. Crack layer theory

    NASA Technical Reports Server (NTRS)

    Chudnovsky, A.

    1984-01-01

    A damage parameter is introduced in addition to conventional parameters of continuum mechanics and consider a crack surrounded by an array of microdefects within the continuum mechanics framework. A system consisting of the main crack and surrounding damage is called crack layer (CL). Crack layer propagation is an irreversible process. The general framework of the thermodynamics of irreversible processes are employed to identify the driving forces (causes) and to derive the constitutive equation of CL propagation, that is, the relationship between the rates of the crack growth and damage dissemination from one side and the conjugated thermodynamic forces from another. The proposed law of CL propagation is in good agreement with the experimental data on fatigue CL propagation in various materials. The theory also elaborates material toughness characterization.

  11. Study of formation mechanism of incipient melting in thixo-cast Al–Si–Cu–Mg alloys

    SciTech Connect

    Du, Kang Zhu, Qiang Li, Daquan Zhang, Fan

    2015-08-15

    Mechanical properties of thixo-cast Al–Si–Cu–Mg alloys can be enhanced by T61 heat treatment. Copper and magnesium atoms in aluminum matrix can form homogeneously distributed precipitations after solution and aging treatment which harden the alloys. However, microsegregation of these alloying elements could form numerous tiny multi-compound phases during solidification. These phases could cause incipient melting defects in subsequent heat treatment process and degrade the macro-mechanical properties of productions. This study is to present heterogeneous distribution of Cu, Si, and Mg elements and formation of incipient melting defects (pores). In this study, incipient melting pores that occurred during solution treatment at various temperatures, even lower than common melting points of various intermetallic phases, were identified, in terms of a method of investigating the same surface area in the samples before and after solution treatment in a vacuum environment. The results also show that the incipient melting mostly originates at the clusters with fine intermetallic particles while also some at the edge of block-like Al{sub 2}Cu. The fine particles were determined being Al{sub 2}Cu, Al{sub 5}Cu{sub 2}Mg{sub 8}Si{sub 6} and Al{sub 8}Mg{sub 3}FeSi{sub 2}. Tendency of the incipient melting decreases with decreases of the width of the clusters. The formation mechanism of incipient melting pores in solution treatment process was discussed using both the Fick law and the LSW theory. Finally, a criterion of solution treatment to avoid incipient melting pores for the thixo-cast alloys is proposed. - Highlights: • In-situ comparison technique was used to analysis the change of eutectic phases. • The ralationship between eutectic phase size and incipient melting was studied. • Teat treatment criterion for higher incipient melting resistance was proposed.

  12. Small-crack test methods

    NASA Astrophysics Data System (ADS)

    Larsen, James M.; Allison, John E.

    This book contains chapters on fracture mechanics parameters for small fatigue cracks, monitoring small-crack growth by the replication method, measurement of small cracks by photomicroscopy (experiments and analysis), and experimental mechanics of microcracks. Other topics discussed are the real-time measurement of small-crack-opening behavior using an interferometric strain/displacement gage; direct current electrical potential measurement of the growth of small cracks; an ultrasonic method for the measurement of the size and opening behavior of small fatigue cracks; and the simulation of short crack and other low closure loading conditions, utilizing constant K(max) Delta-K-decreasing fatigue crack growth procedures.

  13. Effect of crack surface geometry on fatigue crack closure

    SciTech Connect

    Drury, W.J.; Gokhale, A.M.; Antolovich, S.D.

    1995-10-01

    The geometry of crack faces often plays a critical role in reducing crack extension forces when crack closure occurs during fatigue crack growth. Most previous studies of fatigue crack closure are concerned with mechanical measure of closure as related to the crack growth rate; very little attention has been given to the geometry of the crack surfaces. The objective is to identify those aspects of crack surface geometry that are important in the closure process, to develop quantitative fractographic techniques to estimate such attributes in a statistically significant and robust manner, and to correlate them to the physical process of crack closure. For this purpose, fatigue crack propagation experiments were performed on a Ni-base superalloy and crack growth rates and crack closure loads were measured. Digital image profilometry and software-based analysis techniques were used for statistically reliable and detailed quantitative characterization of fatigue crack profiles. It is shown that the dimensionless, scale-independent attributes, such a height-to-width ratio of asperities, fractal dimensions, dimensionless roughness parameters, etc., do not represent the aspects of crack geometry that are of primary importance in the crack closure phenomena. Furthermore, it is shown that the scale-dependent characteristics, such as average asperity height, do represent the aspects of crack geometry that play an interactive role in the closure process. These observations have implications concerning the validity of geometry-dependent, closure-based models for fatigue crack growth.

  14. Effect of crack surface geometry on fatigue crack closure

    NASA Astrophysics Data System (ADS)

    Drury, W. J.; Gokhale, Arun M.; Antolovich, S. D.

    1995-10-01

    The geometry of crack faces often plays a critical role in reducing crack extension forces when crack closure occurs during fatigue crack growth. Most previous studies of fatigue crack closure are concerned with mechanical measures of closure as related to the crack growth rate; very little attention has been given to the geometry of the crack surfaces. Our objective is to identify those aspects of crack surface geometry that are important in the closure process, to develop quantitative fractographic techniques to estimate such attributes in a statistically significant and robust manner, and to correlate them to the physical process of crack closure. For this purpose, fatigue crack propagation experiments were performed on a Ni-base superalloy and crack growth rates and crack closure loads were measured. Digital image profilometry and software-based analysis techniques were used for statistically reliable and detailed quantitative characterization of fatigue crack profiles. It is shown that the dimensionless, scale-independent attributes, such as height-to-width ratio of asperities, fractal dimensions, dimensionless roughness parameters, etc., do not represent the aspects of crack geometry that are of primary importance in the crack closure phenomena. Furthermore, it is shown that the scaledependent characteristics, such as average asperity height, do represent the aspects of crack geometry that play an interactive role in the closure process. These observations have implications concerning the validity of geometry-dependent, closure-based models for fatigue crack growth.

  15. Deformation-corrosion interactions for Zr alloys during I-SCC crack initiation. Part I: Chemical contributions

    NASA Astrophysics Data System (ADS)

    Jacques, Patrick; Lefebvre, Florence; Lemaignan, Clément

    1999-01-01

    For a better understanding of the initiation step of iodine-induced stress corrosion cracking in Zr alloys, responsible for pellet-cladding interaction (PCI) fuel rod failures, an analytical study has been undertaken, the aim of which being focused on the respective roles of local chemistry and stress/strain state on the crack nucleation. This first part is mostly related to the chemical environment. From the tensile tests performed under iodine rich and inert environments, it was concluded that no crack initiation could be detected following the tests in an inert atmosphere. The iodine induced stress corrosion initiation mechanism must therefore be analysed as a corrosion-strain interaction.

  16. Early diagnosis of incipient caries based on non-invasive lasers

    NASA Astrophysics Data System (ADS)

    Velescu, A.; Todea, C.; Vitez, B.

    2016-03-01

    AIM: The aim of this study is to detect incipient caries and enamel demineralization using laser fluorescence.This serves only as an auxilary aid to identify and to monitor the development of these lesions. MATERIALS AND METHODS: 6 patients were involved in this study, three females and three male. Each patient underwent a professional cleaning, visual examination of the oral cavity, and then direct inspection using DiagnoCam and DIAGNOdent. After data recording each patient was submitted to retro-alveolar X-ray on teeth that were detected with enamel lesions. All data was collected and analyzed statistically. RESULTS: Of 36 areas considered in clinically healthy, 24 carious surfaces were found using laser fluorescence, a totally non-invasive method for detecting incipient carious lesions compared with the radiographic examination. CONCLUSIONS: This method has good applicability for patients because it improves treatment plan by early detection of caries and involves less fear for anxious patients and children.

  17. Numerical Analysis of Incipient Separation on 53 Deg Swept Diamond Wing

    NASA Technical Reports Server (NTRS)

    Frink, Neal T.

    2015-01-01

    A systematic analysis of incipient separation and subsequent vortex formation from moderately swept blunt leading edges is presented for a 53 deg swept diamond wing. This work contributes to a collective body of knowledge generated within the NATO/STO AVT-183 Task Group titled 'Reliable Prediction of Separated Flow Onset and Progression for Air and Sea Vehicles'. The objective is to extract insights from the experimentally measured and numerically computed flow fields that might enable turbulence experts to further improve their models for predicting swept blunt leading-edge flow separation. Details of vortex formation are inferred from numerical solutions after establishing a good correlation of the global flow field and surface pressure distributions between wind tunnel measurements and computed flow solutions. From this, significant and sometimes surprising insights into the nature of incipient separation and part-span vortex formation are derived from the wealth of information available in the computational solutions.

  18. Method and system for early detection of incipient faults in electric motors

    DOEpatents

    Parlos, Alexander G; Kim, Kyusung

    2003-07-08

    A method and system for early detection of incipient faults in an electric motor are disclosed. First, current and voltage values for one or more phases of the electric motor are measured during motor operations. A set of current predictions is then determined via a neural network-based current predictor based on the measured voltage values and an estimate of motor speed values of the electric motor. Next, a set of residuals is generated by combining the set of current predictions with the measured current values. A set of fault indicators is subsequently computed from the set of residuals and the measured current values. Finally, a determination is made as to whether or not there is an incipient electrical, mechanical, and/or electromechanical fault occurring based on the comparison result of the set of fault indicators and a set of predetermined baseline values.

  19. Catalytic cracking process

    SciTech Connect

    Gladrow, E.M.; Winter, W.E.

    1980-04-29

    The octane number of a cracked naphtha can be significantly improved in a catalytic cracking unit, without significant decrease in naphtha yield, by maintaining certain critical concentrations of metals on the catalyst, suitably by blending or adding a heavy metals-containing component to the gas oil feed. Suitably, in a catalytic cracking process unit wherein a gas oil feed is cracked in a cracking reactor (Zone) at an elevated temperature in the presence of a cracking catalyst, the cracking catalyst is regenerated in a regenerator (Regeneration zone) by burning coke off the catalyst, and catalyst is circulated between the reactor and regenerator, sufficient of a metals-containing heavy feedstock is admixed, intermittantly or continuously, with the gas oil feed to deposit metals on said catalyst and raise the metals-content of said catalyst to a level of from about 1500 to about 6000 parts per million, preferably from about 2500 to about 4000 parts per million expressed as equivalent nickel, base the weight of the catalyst, and said metals level is maintained on the catalyst throughout the operation by withdrawing high metals-containing catalyst and adding low metals-containing catalyst to the regenerator.

  20. Modelling of hydride cracking

    SciTech Connect

    Zheng, X.J.; Metzger, D.R.; Glinka, G.; Dubey, R.N.

    1996-12-01

    Zirconium alloys may be susceptible to hydride formation under certain service conditions, due to hydrogen diffusion and precipitation in the presence of stress concentrations and temperature gradients. The inhomogeneous brittle hydride platelets that form are modeled as plane defects of zero thickness, with fracture toughness less than that of the matrix. A fracture criterion based on sufficient energy and stress is proposed for either delayed hydride cracking (DHC) under constant loading conditions, or hydride cracking at rising loads, such as in a fracture toughness test. The fracture criterion is validated against available experimental data concerning initiation of hydride fracture in smooth specimens, and DHC in cracked specimens under various loading and temperature conditions.

  1. The Midas cichlid species complex: incipient sympatric speciation in Nicaraguan cichlid fishes?

    PubMed

    Barluenga, Marta; Meyer, Axel

    2004-07-01

    Abstract Sympatric speciation is a contentious concept, although theoretical models as well as empirical evidence support its relevance in evolutionary biology. The Midas cichlid species complex (Amphilophus citrinellus, labiatus, zaliosus) from several crater lakes in Nicaragua fits several of the key characteristics of a sympatric speciation model. In particular, in A. citrinellus (i) strong assortative mating on the basis of colour polymorphism and (ii) ecological differentiation based on morphological polymorphisms involving the feeding apparatus and body shape might both be mechanisms of incipient speciation. Seven microsatellite markers and mtDNA control region sequences [836 base pairs (bp)] were used to study the population genetic structure of 519 specimens of Midas cichlid populations from the two Great Lakes Managua and Nicaragua, and three crater lakes in Nicaragua, Central America. The three named species of the species complex occupy different ecological niches, are morphologically distinct and can be distinguished genetically. We uncovered allopatric genetic differentiation of populations of A. citrinellus from different lakes and distant locations within Lake Managua and, more interestingly, incipient genetic differentiation of several sympatric populations based on colouration (in A. citrinellus and A. labiatus) but not on the morphology of the pharyngeal jaws (in A. citrinellus). Sexual selection and assortative mating might be the driven forces of diversification within named species. The Midas cichlid species complex in Nicaragua is an excellent model system for the study of the incipient stages of adaptation, speciation and the formation of species flocks. PMID:15189226

  2. Diagnostic methodology for incipient system disturbance based on a neural wavelet approach

    NASA Astrophysics Data System (ADS)

    Won, In-Ho

    Since incipient system disturbances are easily mixed up with other events or noise sources, the signal from the system disturbance can be neglected or identified as noise. Thus, as available knowledge and information is obtained incompletely or inexactly from the measurements; an exploration into the use of artificial intelligence (AI) tools to overcome these uncertainties and limitations was done. A methodology integrating the feature extraction efficiency of the wavelet transform with the classification capabilities of neural networks is developed for signal classification in the context of detecting incipient system disturbances. The synergistic effects of wavelets and neural networks present more strength and less weakness than either technique taken alone. A wavelet feature extractor is developed to form concise feature vectors for neural network inputs. The feature vectors are calculated from wavelet coefficients to reduce redundancy and computational expense. During this procedure, the statistical features based on the fractal concept to the wavelet coefficients play a role as crucial key in the wavelet feature extractor. To verify the proposed methodology, two applications are investigated and successfully tested. The first involves pump cavitation detection using dynamic pressure sensor. The second pertains to incipient pump cavitation detection using signals obtained from a current sensor. Also, through comparisons between three proposed feature vectors and with statistical techniques, it is shown that the variance feature extractor provides a better approach in the performed applications.

  3. Incipient multiple fault diagnosis in real time with applications to large-scale systems

    SciTech Connect

    Chung, H.Y.; Bien, Z.; Park, J.H.; Seon, P.H. . Dept. of Electrical Engineering)

    1994-08-01

    By using a modified signed directed graph (SDG) together with the distributed artificial neutral networks and a knowledge-based system, a method of incipient multi-fault diagnosis is presented for large-scale physical systems with complex pipes and instrumentations such as valves, actuators, sensors, and controllers. The proposed method is designed so as to (1) make a real-time incipient fault diagnosis possible for large-scale systems, (2) perform the fault diagnosis not only in the steady-state case but also in the transient case as well by using a concept of fault propagation time, which is newly adopted in the SDG model, (3) provide with highly reliable diagnosis results and explanation capability of faults diagnosed as in an expert system, and (4) diagnose the pipe damage such as leaking, break, or throttling. This method is applied for diagnosis of a pressurizer in the Kori Nuclear Power Plant (NPP) unit 2 in Korea under a transient condition, and its result is reported to show satisfactory performance of the method for the incipient multi-fault diagnosis of such a large-scale system in a real-time manner.

  4. Incipient toxicity of lithium to freshwater organisms representing a salmonid habitat

    SciTech Connect

    Emery, R.; Klopfer, D.C.; Skalski, J.R.

    1981-07-01

    Because the eventual development of fusion power reactors could increase the mining, use and disposal of lithium five-fold by the year 2000, potential effects from unusual amounts of lithium in aquatic environments were investigated. Freshwater oganisms representing a Pacific Northwest salmonid habitat were exposed to elevated conentrations of lithium. Nine parameters were used to determine the incipient toxicity of lithium to rainbow trout (Salmo gairdneri), insect larvae (Chironomus sp.), and Columbia River periphyton. All three groups of biota were incipiently sensitive to lithium at concentrations ranging between 0.1 and 1 mg/L. These results correspond with the incipient toxicity of beryllium, a chemically similar component of fusion reactor cores. A maximum lithium concentration of 0.01 mg/L occurs naturally in most freshwater environments (beryllium is rarer). Therefore, a concentration range of 0.01 to 0.1 mg/L may be regarded as approaching toxic concentrations when assessing the hazards of lithium in freshwaters.

  5. Investigation of semiconductor clad optical waveguides

    NASA Technical Reports Server (NTRS)

    Batchman, T. E.; Carson, R. F.

    1985-01-01

    A variety of techniques have been proposed for fabricating integrated optical devices using semiconductors, lithium niobate, and glasses as waveguides and substrates. The use of glass waveguides and their interaction with thin semiconductor cladding layers was studied. Though the interactions of these multilayer waveguide structures have been analyzed here using glass, they may be applicable to other types of materials as well. The primary reason for using glass is that it provides a simple, inexpensive way to construct waveguides and devices.

  6. NUTRITIONAL ECOLOGY OF THE FORMOSAN SUBTERRANEAN TERMITE ISOPTERA RHINOTERMITIDAE)GROWTH AND SURVIVAL OF INCIPIENT COLONIES FEEDING ONPREFERRED WOOD SPECIES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Wood species as food source significantly impacted growth and survival of incipient colonies of Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae). Colonies of C. formosanus feeding on pecan (Carya illinoensis (Wangenh.)) and red gum (Liquidambar styraciflua L.) produced significantly more p...

  7. Sliding mode observer based incipient sensor fault detection with application to high-speed railway traction device.

    PubMed

    Zhang, Kangkang; Jiang, Bin; Yan, Xing-Gang; Mao, Zehui

    2016-07-01

    This paper considers incipient sensor fault detection issue for a class of nonlinear systems with "observer unmatched" uncertainties. A particular fault detection sliding mode observer is designed for the augmented system formed by the original system and incipient sensor faults. The designed parameters are obtained using LMI and line filter techniques to guarantee that the generated residuals are robust to uncertainties and that sliding motion is not destroyed by faults. Then, three levels of novel adaptive thresholds are proposed based on the reduced order sliding mode dynamics, which effectively improve incipient sensor faults detectability. Case study of on the traction system in China Railway High-speed is presented to demonstrate the effectiveness of the proposed incipient senor faults detection schemes. PMID:27156675

  8. PWR cores with silicon carbide cladding

    SciTech Connect

    Dobisesky, J. P.; Carpenter, D.; Pilat, E.; Kazimi, M. S.

    2012-07-01

    The feasibility of using silicon carbide rather than Zircaloy cladding, to reach higher power levels and higher discharge burnups in PWRs has been evaluated. A preliminary fuel design using fuel rods with the same dimensions as in the Westinghouse Robust Fuel Assembly but with fuel pellets having 10 vol% central void has been adopted to mitigate the higher fuel temperatures that occur due to the lower thermal conductivity of the silicon carbide and to the persistence of the open clad-pellet gap over most of the fuel life. With this modified fuel design, it is possible to achieve 18 month cycles that meet present-day operating constraints on peaking factor, boron concentration, reactivity coefficients and shutdown margin, while allowing batch average discharge burnups up to 80 MWD/kgU and peak rod burnups up to 100 MWD/kgU. Power uprates of 10% and possibly 20% also appear feasible. For non-uprated cores, the silicon carbide-clad fuel has a clear advantage that increases with increasing discharge burnup. Even for comparable discharge burnups, there is a savings in enriched uranium. Control rod configuration modifications may be required to meet the shutdown margin criterion for the 20% up-rate. Silicon carbide's ability to sustain higher burnups than Zircaloy also allows the design of a licensable two year cycle with only 96 fresh assemblies, avoiding the enriched uranium penalty incurred with use of larger batch sizes due to their excessive leakage. (authors)

  9. Stress corrosion cracking of Zircaloys in unirradiated and irradiated CsI

    NASA Astrophysics Data System (ADS)

    Cox, B.; Surette, B. A.; Wood, J. C.

    1986-03-01

    Unirradiated split-ring specimens of Zircaloy fuel cladding, coated with CsI, cracked when stressed at elevated temperatures. The specimens have been reexamined fractographically and metallographically in order to confirm that the cause of cracking was stress corrosion (SCC) and not delayed hydride cracking (DHC). Further specimens have been cracked at 350°C by a solution of CsI in a fused mixture of nitrates of rubidium, cesium, strontium and barium, by a similar mechanism. CsI dissolved in a fused molybdate melt was not stable at 400°C, and rapidly evolved iodine, leaving a melt that was incapable of causing SCC. Irradiation of stressed split-ring specimens of Zircaloy fuel cladding in a γ-irradiator of 10 6 R/h and in the U-5 loop in the NRU reactor at an estimated 10 9 R/h caused SCC when the specimens were packed in dry CsI powder. Care had to be taken to dry the CsI, otherwise cracking occurred by a DHC mechanism from hydrogen absorbed from residual moisture in the CsI. Fractography showed that the crack surfaces obtained with dry CsI were typical of iodine-induced SCC rather than cesium-induced metal vapour embrittlement. Thus, if a transport process is provided for the iodide to obtain access to the zirconium surface, CsI is capable of causing SCC of Zircaloy. This transport process might be ionic diffusion in a fission product oxide melt in the fuel-clad gap, however, radiolysis of CsI to form a volatile iodine species in a radiation field is the more probable explanation of PCI failures.

  10. Microstructure, Wear, and Corrosion Characteristics of TiC-Laser Surface Cladding on Low-Carbon Steel

    NASA Astrophysics Data System (ADS)

    El-Labban, Hashem F.; Mahmoud, Essam Rabea Ibrahim; Algahtani, Ali

    2016-04-01

    Laser cladding was used to produce surface composite layer reinforced with TiC particles on low-carbon steel alloy for improving the wear and corrosion resistances. The cladding process was carried out at powers of 2800, 2000, 1500, and 1000 W, and a fixed traveling speed of 4 mm/s. The produced layers are free from any cracks. Some of the TiC particles were melted and then re-solidified in the form of fine acicular dendrites. The amount of the melted TiC was increased by increasing the laser power. The hardness of the produced layers was improved by about 19 times of the base metal. Decreasing laser power led to hardness increment at the free surface. The improvement in wear resistance was reached to about 25 times (in case of 1500 W) of the base metal. Moreover, the corrosion resistance shows remarkable improvement after the laser treatment.

  11. Quantity Effect of Radial Cracks on the Cracking Propagation Behavior and the Crack Morphology

    PubMed Central

    Chen, Jingjing; Xu, Jun; Liu, Bohan; Yao, Xuefeng; Li, Yibing

    2014-01-01

    In this letter, the quantity effect of radial cracks on the cracking propagation behavior as well as the circular crack generation on the impacted glass plate within the sandwiched glass sheets are experimentally investigated via high-speed photography system. Results show that the radial crack velocity on the backing glass layer decreases with the crack number under the same impact conditions during large quantities of repeated experiments. Thus, the “energy conversion factor” is suggested to elucidate the physical relation between the cracking number and the crack propagation speed. Besides, the number of radial crack also takes the determinative effect in the crack morphology of the impacted glass plate. This study may shed lights on understanding the cracking and propagation mechanism in laminated glass structures and provide useful tool to explore the impact information on the cracking debris. PMID:25048684

  12. On the initiation of cracks in Zircaloy tubes by I 2 and Cs/Cd vapours

    NASA Astrophysics Data System (ADS)

    Haddad, R.; Cox, B.

    1986-03-01

    Single, short (5s) compressive stress cycles on sealed fuel cladding tubes previously equilibrated with either I 2 or Cs/Cd produced stress corrosion cracks. This observation strongly implies no incubation time is required for SCC of Zircaloy in these environments. The SCC susceptibility of Zircaloy varied with texture or orientation of the basal plane; no correlation with second phase inclusion or chemical inhomogeneities has been found at the sites of crack initiation. These results support the hypothesis that the chemical corrodent weakens the Zr-Zr bonds at the crack tip through a reduction in the surface energy and thus allows cracking at stresses well below the normal rupture stress for Zircaloy.

  13. Ethylene by Naphta Cracking

    ERIC Educational Resources Information Center

    Wiseman, Peter

    1977-01-01

    Presents a discussion of the manufacture of ethylene by thermal cracking of hydrocarbon feedstocks that is useful for introducing the subject of industrial chemistry into a chemistry curriculum. (MLH)

  14. Elevated temperature crack growth

    NASA Technical Reports Server (NTRS)

    Kim, K. S.; Vanstone, R. H.; Malik, S. N.; Laflen, J. H.

    1988-01-01

    A study was performed to examine the applicability of path-independent (P-I) integrals to crack growth problems in hot section components of gas turbine aircraft engines. Alloy 718 was used and the experimental parameters included combined temperature and strain cycling, thermal gradients, elastic-plastic strain levels, and mean strains. A literature review was conducted of proposed P-I integrals, and those capable of analyzing hot section component problems were selected and programmed into the postprocessor of a finite element code. Detailed elastic-plastic finite element analyses were conducted to simulate crack growth and crack closure of the test specimen, and to evaluate the P-I integrals. It was shown that the selected P-I integrals are very effective for predicting crack growth for isothermal conditions.

  15. Elevated Temperature Crack Propagation

    NASA Technical Reports Server (NTRS)

    Orange, Thomas W.

    1994-01-01

    This paper is a summary of two NASA contracts on high temperature fatigue crack propagation in metals. The first evaluated the ability of fairly simple nonlinear fracture parameters to correlate crack propagation. Hastelloy-X specimens were tested under isothermal and thermomechanical cycling at temperatures up to 980 degrees C (1800 degrees F). The most successful correlating parameter was the crack tip opening displacement derived from the J-integral. The second evaluated the ability of several path-independent integrals to correlate crack propagation behavior. Inconel 718 specimens were tested under isothermal, thermomechanical, temperature gradient, and creep conditions at temperatures up to 650 degrees C (1200 degrees F). The integrals formulated by Blackburn and by Kishimoto correlated the data reasonably well under all test conditions.

  16. Crack-growth analysis

    NASA Technical Reports Server (NTRS)

    Bianca, C.; Creager, M.

    1976-01-01

    Flexible, adaptable, integrative routine, computer program incorporates Collipriest-Ehret and Paris-Forman equations. Calculates growth from initial defect size and terminates calculation when crack is sufficiently large for critical condition. Wheeler, Willenborg, and Grumman Closure models are available.

  17. Thermal cracking of hydrocarbons

    SciTech Connect

    Braun, R.L.; Burnham, A.K.

    1988-09-01

    Knowledge of thermal cracking of hydrocarbons is important in understanding and modeling petroleum maturation. We have reviewed the literature on the thermal cracking of pure hydrocarbons and mixtures of hydrocarbons, with particular attention given to dependence of the kinetics on temperature, pressure, and phase. Major uncertainties remain with regard to pressure dependence. Based on this review, we developed a simple, four-component, three-reaction model for oil-cracking. We also developed a simple, kerogen-maturation, kinetic model that incorporates hydrogen and carbon balance and includes the most important oil- and gas-forming reactions: kerogen pyrolysis, three oil-cracking reactions, and three coke-pyrolysis reactions. Tentative stoichiometry parameters are given for lacustrine and marine kerogens. 35 refs., 5 figs., 5 tabs.

  18. A cross-disciplinary understanding of incipient motion for effective environmental flow setting

    NASA Astrophysics Data System (ADS)

    Neverman, Andrew; Fuller, Ian; Death, Russell; Procter, Jon; Singh, Ranvir

    2016-04-01

    Environmental flow setting as a tool for maintaining ecological health in rivers has been a focus of debate for many years. Environmental flow setting often involves the establishment of base flow levels below impoundment structures as well as setting flushing flows in order to control excess periphyton accrual and sedimentation. The role of bedload transport and substrate stability is recognised as an integral part of effectively managing benthic communities, but environmental flow regulations often do not focus on managing sediment processes. Environmental flows which fail to scour periphyton have been attributed to increased biomass accumulation through increasing nutrient supply to periphyton mats. It may therefore be more effective to establish environmental flow models based on incipient motion thresholds. The aim of these models would be to establish target near-bed velocities as opposed to discharges. Establishment of such models requires an accurate understanding of the threshold conditions for incipient motion. Despite decades of incipient motion studies scientists are unable to consistently and accurately predict bedload transport in natural channels. Incipient motion results from a complex set of geomorphic, hydrologic, and ecological interactions operating over a range of spatial and temporal scales. Direct measurement of these processes can be difficult and time consuming, and has been restricted by a lack of suitable high spatio-temporal resolution methods in the past. This paper presents a cross-disciplinary approach to the study of incipient motion to develop effective environmental flow targets. Recent developments in remote sensing and 3D point cloud analysis are used to characterise substrate surfaces. Groundwater head pressures are measured during floods to examine changes in threshold velocities under different seepage conditions. The onset of bedload transport is recorded using impact plate sensors to relate transport initiation to near

  19. Electrically heated ex-reactor pellet-cladding interaction (PCI) simulations utilizing irradiated Zircaloy cladding. [PWR

    SciTech Connect

    Barner, J.O.; Fitzsimmons, D.E.

    1985-02-01

    In a program sponsored by the Fuel Systems Research Branch of the US Nuclear Regulatory Commission, a series of six electrically heated fuel rod simulation tests were conducted at Pacific Northwest Laboratory. The primary objective of these tests was to determine the susceptibility of irradiated pressurized-water reactor (PWR) Zircaloy-4 cladding to failures caused by pellet-cladding mechanical interaction (PCMI). A secondary objective was to acquire kinetic data (e.g., ridge growth or relaxation rates) that might be helpful in the interpretation of in-reactor performance results and/or the modeling of PCMI. No cladding failures attributable to PCMI occurred during the six tests. This report describes the testing methods, testing apparatus, fuel rod diametral strain-measuring device, and test matrix. Test results are presented and discussed.

  20. The kinked interface crack

    NASA Astrophysics Data System (ADS)

    Heitzer, Joerg

    1992-05-01

    Two methods for the numerical solution of the integral equation describing the kinked interface crack, one proposed by Erdogan et al. (1973) and the other by Theokaris and Iokimidis (1979), are examined. The method of Erdogan et al. is then used to solve the equation in order to determine the kinking angle of the interface crack. Results are presented for two material combinations, aluminum/epoxy and glass/ceramic, under uniaxial tension in the direction normal to the interface.

  1. Grain boundary cavitation and weld underbead cracking in DOP-26 iridium alloy

    SciTech Connect

    Mosley, W.C. Jr.

    1983-01-01

    Plutonium-238 oxide fuel pellets for the General Purpose Heat Source Radioisotopic Thermoelectric Generators to be used on the NASA Galileo Mission to Jupiter and the International Solar Polar Mission are produced and encapsulated in DOP-26 iridium alloy at the Savannah River Plant. DOP-26 iridium alloy was developed at the Oak Ridge National Laboratory (ORNL) and contains nominally 0.3 wt.% tungsten, 60 ppm thorium, and 50 ppm aluminum. Underbead cracks occasionally occur in the girth weld on the iridium alloy cladding in the area where the gas tungsten arc is quenched. Various electron-beam techniques have been used to determine the cause of cracking.

  2. Microstructure and Mechanical Properties of Laser Clad and Post-cladding Tempered AISI H13 Tool Steel

    NASA Astrophysics Data System (ADS)

    Telasang, Gururaj; Dutta Majumdar, Jyotsna; Wasekar, Nitin; Padmanabham, G.; Manna, Indranil

    2015-05-01

    This study reports a detailed investigation of the microstructure and mechanical properties (wear resistance and tensile strength) of hardened and tempered AISI H13 tool steel substrate following laser cladding with AISI H13 tool steel powder in as-clad and after post-cladding conventional bulk isothermal tempering [at 823 K (550 °C) for 2 hours] heat treatment. Laser cladding was carried out on AISI H13 tool steel substrate using a 6 kW continuous wave diode laser coupled with fiber delivering an energy density of 133 J/mm2 and equipped with a co-axial powder feeding nozzle capable of feeding powder at the rate of 13.3 × 10-3 g/mm2. Laser clad zone comprises martensite, retained austenite, and carbides, and measures an average hardness of 600 to 650 VHN. Subsequent isothermal tempering converted the microstructure into one with tempered martensite and uniform dispersion of carbides with a hardness of 550 to 650 VHN. Interestingly, laser cladding introduced residual compressive stress of 670 ± 15 MPa, which reduces to 580 ± 20 MPa following isothermal tempering. Micro-tensile testing with specimens machined from the clad zone across or transverse to cladding direction showed high strength but failure in brittle mode. On the other hand, similar testing with samples sectioned from the clad zone parallel or longitudinal to the direction of laser cladding prior to and after post-cladding tempering recorded lower strength but ductile failure with 4.7 and 8 pct elongation, respectively. Wear resistance of the laser surface clad and post-cladding tempered samples (evaluated by fretting wear testing) registered superior performance as compared to that of conventional hardened and tempered AISI H13 tool steel.

  3. Stress corrosion cracking of LWR fuel: Volume 2, The SCCIG-B model: Final report

    SciTech Connect

    Miller, A.K.; Tasooji, A.

    1988-03-01

    This report describes two major extensions of the SCCIG model for iodine stress corrosion cracking of Zircaloy. The first permits prediction of the effects of texture on SCC; the second (the SCCIG-B model) permits the prediction of the SCC behavior of zirconium-lined ''barrier'' cladding. A fast-running derivative model (CFMIII) has also been developed. A complete users manual for the SCCIG-B FORTRAN program is given. 42 refs.

  4. A metallurgical analysis of laser-clad H13

    SciTech Connect

    Koch, J.; Hetzner, D.; Mazumder, J.

    1996-12-31

    Rapid prototyping and rapid manufacturing processes are being employed to decrease the time required to develop new products. Laser cladding can be used to produce metal parts directly from CAD drawings. To apply this technology, multiple layers of metal clad are first deposited on a substrate. The clad is then tempered or annealed at periodic stages throughout the buildup process and also prior to machining. The component is then hardened and tempered by conventional heat treating procedures and ground or machined to final size. This investigation considers the response of the clad and base metal to this series of processing variables. H13, an air hardening die steel, was selected for the clads and the base metal. This alloy is commonly used for hot working dies. The response of the clad and substrate to the various heat treatments was evaluated.

  5. Transversely polarized source cladding for an optical fiber

    NASA Technical Reports Server (NTRS)

    Egalon, Claudio Oliveira (Inventor); Rogowski, Robert S. (Inventor)

    1994-01-01

    An optical fiber comprising a fiber core having a longitudinal symmetry axis is provided. An active cladding surrounds a portion of the fiber core and comprises light-producing sources which emit light in response to chemical or light excitation. The cladding sources are oriented transversely with respect to the longitudinal axis of the fiber core. This polarization results in a superior power efficiency compared to active cladding sources that are randomly polarized or longitudinally polarized parallel with the longitudinal symmetry axis.

  6. Clad fiber capacitor and method of making same

    SciTech Connect

    Tuncer, Enis

    2012-12-11

    A clad capacitor and method of manufacture includes assembling a preform comprising a ductile, electrically conductive fiber; a ductile, electrically insulating cladding positioned on the fiber; and a ductile, electrically conductive sleeve positioned over the cladding. One or more preforms are then bundled, heated and drawn along a longitudinal axis to decrease the diameter of the ductile components of the preform and fuse the preform into a unitized strand.

  7. Clad fiber capacitor and method of making same

    SciTech Connect

    Tuncer, Enis

    2013-11-26

    A clad capacitor and method of manufacture includes assembling a preform comprising a ductile, electrically conductive fiber; a ductile, electrically insulating cladding positioned on the fiber; a ductile, electrically conductive sleeve positioned over the cladding. One or more of the preforms are then bundled, heated and drawn along a longitudinal axis to decrease the diameter of the ductile components of the preform and fuse the preform into a unitized strand.

  8. Nuclear reactor fuel element with vanadium getter on cladding

    DOEpatents

    Johnson, Carl E.; Carroll, Kenneth G.

    1977-01-01

    A nuclear reactor fuel element is described which has an outer cladding, a central core of fissionable or mixed fissionable and fertile fuel material and a layer of vanadium as an oxygen getter on the inner surface of the cladding. The vanadium reacts with oxygen released by the fissionable material during irradiation of the core to prevent the oxygen from reacting with and corroding the cladding. Also described is a method for coating the inner surface of small diameter tubes of cladding with a layer of vanadium.

  9. An acoustic vibration sensor based on tapered triple cladding fiber

    NASA Astrophysics Data System (ADS)

    Xu, Hui; Pang, Fufei; Zhao, Shiqi; Chen, Zhenyi; Wang, Tingyun

    2014-05-01

    An acoustic vibration sensor is investigated and demonstrated by using a tapered triple cladding fiber (TCF). It is fabricated by tapering a length of 2 cm TCF which is spliced between two single mode fibers (SMF). The TCF consists of core, inner cladding, middle cladding and outer cladding. After the tapering process, this structure becomes a tapered coaxial fiber coupler which presents a periodic filtering transmission spectrum. The surrounding vibration perturbation can be directly demodulated by intensity detection of the transmission power at a particular wavelength. The experimental result shows that the maximum frequency response of 700 kHz is achieved.

  10. Fatigue and environmentally assisted cracking in light water reactors

    SciTech Connect

    Kassner, T.F.; Ruther, W.E.; Chung, H.M.; Hicks, P.D.; Hins, A.G.; Park, J.Y.; Shack, W.J.

    1991-12-01

    Fatigue and environmentally assisted cracking of piping, pressure vessels, and core components in light water reactors (LWRs) are important concerns as extended reactor lifetimes are envisaged. The degradation processes include intergranular stress corrosion cracking (IGSCC) of austenitic stainless steel (SS) piping in boiling water reactors (BWRs), and propagation of fatigue or SCC cracks (which initiate in sensitized SS cladding) into low-alloy ferritic steels in BWR pressure vessels. Similar cracking has also occurred in upper shell-to-transition cone girth welds in pressurized water reactor (PWR) steam generator vessels. Another concern is failure of reactor-core internal components after accumulation of relatively high fluence, which has occurred in both BWRs and PWRs. Research during the past year focused on (1) fatigue and SCC of ferritic steels used in piping and in steam generator and reactor pressure vessels, (2) role of chromate and sulfate in simulated BWR water in SCC of sensitized Type 304 SS, and (3) irradiation-assisted SCC in high- and commercial-purity Type 304 SS specimens from control-blade absorber tubes used in two operating BWRs. Failure after accumulation of relatively high fluence has been attributed to radiation-induced segregation (RIS) of elements such as Si, P, Ni, and Cr. This document provides a summary of research progress in these areas.

  11. Multifrequency Eddy Current Inspection of Corrosion in Clad Aluminum Riveted Lap Joints and Its Effect on Fatigue Life

    SciTech Connect

    Okafor, A. C.; Natarajan, S.

    2007-03-21

    Aging aircraft are prone to corrosion damage and fatigue cracks in riveted lap joints of fuselage skin panels. This can cause catastrophic failure if not detected and repaired. Hence detection of corrosion damage and monitoring its effect on structural integrity are essential. This paper presents multifrequency eddy current (EC) inspection of corrosion damage and machined material loss defect in clad A1 2024-T3 riveted lap joints and its effect on fatigue life. Results of eddy current inspection, corrosion product removal and fatigue testing are presented.

  12. Multifrequency Eddy Current Inspection of Corrosion in Clad Aluminum Riveted Lap Joints and Its Effect on Fatigue Life

    NASA Astrophysics Data System (ADS)

    Okafor, A. C.; Natarajan, S.

    2007-03-01

    Aging aircraft are prone to corrosion damage and fatigue cracks in riveted lap joints of fuselage skin panels. This can cause catastrophic failure if not detected and repaired. Hence detection of corrosion damage and monitoring its effect on structural integrity are essential. This paper presents multifrequency eddy current (EC) inspection of corrosion damage and machined material loss defect in clad A1 2024-T3 riveted lap joints and its effect on fatigue life. Results of eddy current inspection, corrosion product removal and fatigue testing are presented.

  13. Photonic lantern with cladding-removable fibers

    NASA Astrophysics Data System (ADS)

    Sun, Weimin; Yan, Qi; Bi, Yao; Yu, Haijiao; Liu, Xiaoqi; Xue, Jiuling; Tian, He; Liu, Yongjun

    2014-07-01

    Recently, spectral measurement becomes an important tool in astronomy to find exoplanets etc. The fibers are used to transfer light from the focal plate to spectrometers. To get high-resolution spectrum, the input slits of the spectrometers should be as narrow as possible. In opposite, the light spots from the fibers are circle, which diameters are clearly wider than the width of the spectrometer slits. To reduce the energy loss of the fiber-guide star light, many kinds of image slicers were designed and fabricated to transform light spot from circle to linear. Some different setup of fiber slicers are introduced by different research groups around the world. The photonic lanterns are candidates of fiber slicers. Photonic lantern includes three parts: inserted fibers, preform or tubing, taped part of the preform or tubing. Usually the optical fields concentrate in the former-core area, so the light spots are not uniform from the tapered end of the lantern. We designed, fabricated and tested a special kind of photonic lantern. The special fibers consist polymer cladding and doped high-index core. The polymer cladding could be easily removed using acetone bath, while the fiber core remains in good condition. We inserted the pure high-index cores into a pure silica tubing and tapered it. During the tapering process, the gaps between the inserted fibers disappeared. Finally we can get a uniform tapered multimode fiber end. The simulation results show that the longer the taper is, the lower the loss is. The shape of the taper should be controlled carefully. A large-zone moving-flame taper machine was fabricated to make the special photonic lantern. Three samples of photonic lanterns were fabricated and tested. The lanterns with cladding-removable fibers guide light uniform in the tapered ends that means these lanterns could collect more light from those ends.

  14. Refinery ring groove cracking experience

    SciTech Connect

    Ehmke, E.F.

    1982-05-01

    This paper presents the results of a questionnaire on the problem of ring groove cracking in reactors. The results were found to be inconclusive in providing any information on correcting the problem. One report pertaining to a ring groove crack on a 24-inch reactor nozzle served as a warning that cracks may progress beyond the overlay, through it is not known if the base metal can easily crack at low temperatures. The results did not indicate at what point the cracks occurred, but what was common to almost all cracks was that the flange had been in high-temperature, high-pressure hydrogen suggesting that dissolved hydrogen or environmental hydrogen assisted the cracking. The type of stress that contributes in the cracking has not been determined. It is indicated that many cracks were found after the questionnaire was done.

  15. COMPARISON OF CLADDING CREEP RUPTURE MODELS

    SciTech Connect

    P. Macheret

    2000-06-12

    The objective of this calculation is to compare several creep rupture correlations for use in calculating creep strain accrued by the Zircaloy cladding of spent nuclear fuel when it has been emplaced in the repository. These correlations are used to calculate creep strain values that are then compared to a large set of experimentally measured creep strain data, taken from four different research articles, making it possible to determine the best fitting correlation. The scope of the calculation extends to six different creep rupture correlations.

  16. Thermomechanical loading applied on the cladding tube during the pellet cladding mechanical interaction phase of a rapid reactivity initiated accident

    NASA Astrophysics Data System (ADS)

    Hellouin de Menibus, Arthur; Sercombe, Jerome; Auzoux, Quentin; Poussard, Christophe

    2014-10-01

    Calculations of the CABRI REP-Na5 pulse were performed with the ALCYONE code in order to determine the evolution of the thermomechanical loading applied on the cladding tube during the Pellet-Cladding Mechanical Interaction (PCMI) phase of a rapid Reactivity Initiated Accident (RIA) initiated at 280 °C that lasted 8.8 ms. The evolution of the following parameters are reported: the cladding temperature, heating rate, strain rate and loading biaxiality. The impact of these parameters on the cladding mechanical behavior and fracture are then briefly reviewed.

  17. Electrical conductivity during incipient melting in the oceanic low-velocity zone.

    PubMed

    Sifré, David; Gardés, Emmanuel; Massuyeau, Malcolm; Hashim, Leila; Hier-Majumder, Saswata; Gaillard, Fabrice

    2014-05-01

    The low-viscosity layer in the upper mantle, the asthenosphere, is a requirement for plate tectonics. The seismic low velocities and the high electrical conductivities of the asthenosphere are attributed either to subsolidus, water-related defects in olivine minerals or to a few volume per cent of partial melt, but these two interpretations have two shortcomings. First, the amount of water stored in olivine is not expected to be higher than 50 parts per million owing to partitioning with other mantle phases (including pargasite amphibole at moderate temperatures) and partial melting at high temperatures. Second, elevated melt volume fractions are impeded by the temperatures prevailing in the asthenosphere, which are too low, and by the melt mobility, which is high and can lead to gravitational segregation. Here we determine the electrical conductivity of carbon-dioxide-rich and water-rich melts, typically produced at the onset of mantle melting. Electrical conductivity increases modestly with moderate amounts of water and carbon dioxide, but it increases drastically once the carbon dioxide content exceeds six weight per cent in the melt. Incipient melts, long-expected to prevail in the asthenosphere, can therefore produce high electrical conductivities there. Taking into account variable degrees of depletion of the mantle in water and carbon dioxide, and their effect on the petrology of incipient melting, we calculated conductivity profiles across the asthenosphere for various tectonic plate ages. Several electrical discontinuities are predicted and match geophysical observations in a consistent petrological and geochemical framework. In moderately aged plates (more than five million years old), incipient melts probably trigger both the seismic low velocities and the high electrical conductivities in the upper part of the asthenosphere, whereas in young plates, where seamount volcanism occurs, a higher degree of melting is expected. PMID:24784219

  18. The electrical conductivity during incipient melting in the oceanic low velocity zone

    PubMed Central

    Sifré, David; Gardés, Emmanuel; Massuyeau, Malcolm; Hashim, Leila; Hier-Majumder, Saswata; Gaillard, Fabrice

    2014-01-01

    A low viscosity layer in the upper mantle, the Asthenosphere, is a requirement for plate tectonics1. The seismic low velocities and the high electrical conductivities of the Asthenosphere are attributed either to sub-solidus water-related defects in olivine minerals2-4 or to a few volume percents of partial melt5-8 but these two interpretations have shortcomings: (1) The amount of H2O stored in olivine is not expected to be higher than 50 ppm due to partitioning with other mantle phases9, including pargasite amphibole at moderate temperatures10, and partial melting at high temperatures9; (2) elevated melt volume fractions are impeded by the too cold temperatures prevailing in the Asthenosphere and by the high melt mobility that can lead to gravitational segregation11,12. Here we determined the electrical conductivity of CO2-H2O-rich melts, typically produced at the onset of mantle melting. Electrical conductivity modestly increases with moderate amounts of H2O and CO2 but it dramatically increases as CO2 content exceeds 6 wt% in the melt. Incipient melts, long-expected to prevail in the asthenosphere10,13-15, can therefore trigger its high electrical conductivities. Considering depleted and enriched mantle abundances in H2O and CO2 and their effect on the petrology of incipient melting, we calculated conductivity profiles across the Asthenosphere for various plate ages. Several electrical discontinuities are predicted and match geophysical observations in a consistent petrological and geochemical framework. In moderately aged plates (>5Ma), incipient melts most likely trigger both the seismic low velocities and the high electrical conductivities in the upper part of the asthenosphere, whereas for young plates4, where seamount volcanism occurs6, higher degree of melting is expected. PMID:24784219

  19. Sympatric incipient speciation of spiny mice Acomys at “Evolution Canyon,” Israel

    PubMed Central

    Hadid, Yarin; Pavlíček, Tomáš; Beiles, Avigdor; Ianovici, Ron; Raz, Shmuel; Nevo, Eviatar

    2014-01-01

    Does the paucity of empirical evidence of sympatric speciation in nature reflect reality, despite theoretical support? Or is it due to inappropriate searches in nature with overly restrictive assumptions and an incorrect null hypothesis? Spiny mice, Acomys, described here at Evolution Canyon (EC) incipiently and sympatrically speciate owing to microclimatic interslope divergence. The opposite slopes at EC vary dramatically, physically and biotically, representing the dry and hot south-facing slope savannoid-African continent [“African” slope (AS)], abutting with the north-facing slope forested south-European continent [“European” slope (ES)]. African-originated spiny mice, of the Acomys cahirinus complex, colonized Israel 30,000 y ago based on fossils. Genotypically, we showed significantly higher genetic diversity of mtDNA and amplified fragment length polymorphism of Acomys on the AS compared with the ES. This is also true regionally across Israel. In complete mtDNA, 25% of the haplotypes at EC were slope-biased. Phenotypically, the opposite slope’s populations also showed adaptive morphology, physiology, and behavior divergence paralleling regional populations across Israel. Preliminary tests indicate slope-specific mate choices. Colonization of Acomys at the EC first occurred on the AS and then moved to the ES. Strong slope-specific natural selection (both positive and negative) overrules low interslope gene flow. Both habitat slope selection and mate choices suggest ongoing incipient sympatric speciation. We conclude that Acomys at the EC is ecologically and genetically adaptively, incipiently, sympatrically speciating on the ES owing to adaptive microclimatic natural selection. PMID:24402169

  20. Evaluation of Turbulence Models Performance in Predicting Incipient Cavitation in an Enlarged Step-Nozzle

    NASA Astrophysics Data System (ADS)

    Naseri, H.; Koukouvinis, P.; Gavaises, M.

    2015-12-01

    Predictive capability of RANS and LES models to calculate incipient cavitation of water in a step nozzle is assessed. The RANS models namely, Realizable k-ε, SST k-ω and Reynolds Stress Model did not predict any cavitation, due to the limitation of RANS models to predict the low pressure vortex cores. LES WALE model was able to predict the cavitation by capturing the shear layer instability and vortex shedding. The performance of a barotropic cavitation model and Rayleigh-Plesset-based cavitation models was compared using WALE model. Although the phase change formulation is different in these models, the predicted cavitation and flow field were not significantly different.

  1. Image processing applied to laser cladding process

    SciTech Connect

    Meriaudeau, F.; Truchetet, F.

    1996-12-31

    The laser cladding process, which consists of adding a melt powder to a substrate in order to improve or change the behavior of the material against corrosion, fatigue and so on, involves a lot of parameters. In order to perform good tracks some parameters need to be controlled during the process. The authors present here a low cost performance system using two CCD matrix cameras. One camera provides surface temperature measurements while the other gives information relative to the powder distribution or geometric characteristics of the tracks. The surface temperature (thanks to Beer Lambert`s law) enables one to detect variations in the mass feed rate. Using such a system the authors are able to detect fluctuation of 2 to 3g/min in the mass flow rate. The other camera gives them information related to the powder distribution, a simple algorithm applied to the data acquired from the CCD matrix camera allows them to see very weak fluctuations within both gaz flux (carriage or protection gaz). During the process, this camera is also used to perform geometric measurements. The height and the width of the track are obtained in real time and enable the operator to find information related to the process parameters such as the speed processing, the mass flow rate. The authors display the result provided by their system in order to enhance the efficiency of the laser cladding process. The conclusion is dedicated to a summary of the presented works and the expectations for the future.

  2. Material Selection for Accident Tolerant Fuel Cladding

    SciTech Connect

    Pint, Bruce A.; Terrani, Kurt A.; Yamamoto, Yukinori; Snead, Lance Lewis

    2015-01-01

    Alternative cladding materials to Zr-based alloys are being investigated for accident tolerance, which can be defined as > 100X improvement (compared to Zr-based alloys) in oxidation resistance to steam or steam-H2 environments at ≥ 1200°C for short times. After reviewing a wide range of candidates, current steam oxidation testing is being conducted on Mo, MAX phases and FeCrAl alloys. Recently reported low mass losses for Mo in steam at 800°C could not be reproduced. Both FeCrAl and MAX phase Ti2AlC form a protective alumina scale in steam. However, commercial Ti2AlC that was not single phase, formed a much thicker oxide at 1200°C in steam and significant TiO2, and therefore Ti2AlC may be challenging to form as a cladding or a coating. Alloy development for FeCrAl is seeking to maintain its steam oxidation resistance to 1475°C, while reducing its Cr content to minimize susceptibility to irradiation-assisted α´ formation. The composition effects and critical limits to retaining protective scale formation at > 1400°C are still being evaluated.

  3. Material selection for accident tolerant fuel cladding

    SciTech Connect

    Pint, B. A.; Terrani, K. A.; Yamamoto, Y.; Snead, L. L.

    2015-09-14

    Alternative cladding materials are being investigated for accident tolerance, which can be defined as >100X improvement (compared to current Zr-based alloys) in oxidation resistance in steam environments at ≥1200°C for short (≤4 h) times. After reviewing a wide range of candidates, current steam oxidation testing is being conducted on Mo, MAX phases and FeCrAl alloys. Recently reported low mass losses for Mo in steam at 800°C could not be reproduced. Both FeCrAl and MAX phase Ti2AlC form a protective alumina scale in steam. Therefore, commercial Ti2AlC that is not single phase, formed a much thicker oxide at 1200°C in steam and significant TiO2, and therefore may be challenging to use as a cladding or a coating. Alloy development for FeCrAl is seeking to maintain its steam oxidation resistance to 1475°C, while reducing its Cr content to minimize susceptibility to irradiation assisted Cr-rich α’ formation. The composition effects and critical limits to retaining protective scale formation at >1400°C are still being evaluated.

  4. Material selection for accident tolerant fuel cladding

    DOE PAGESBeta

    Pint, B. A.; Terrani, K. A.; Yamamoto, Y.; Snead, L. L.

    2015-09-14

    Alternative cladding materials are being investigated for accident tolerance, which can be defined as >100X improvement (compared to current Zr-based alloys) in oxidation resistance in steam environments at ≥1200°C for short (≤4 h) times. After reviewing a wide range of candidates, current steam oxidation testing is being conducted on Mo, MAX phases and FeCrAl alloys. Recently reported low mass losses for Mo in steam at 800°C could not be reproduced. Both FeCrAl and MAX phase Ti2AlC form a protective alumina scale in steam. Therefore, commercial Ti2AlC that is not single phase, formed a much thicker oxide at 1200°C in steammore » and significant TiO2, and therefore may be challenging to use as a cladding or a coating. Alloy development for FeCrAl is seeking to maintain its steam oxidation resistance to 1475°C, while reducing its Cr content to minimize susceptibility to irradiation assisted Cr-rich α’ formation. The composition effects and critical limits to retaining protective scale formation at >1400°C are still being evaluated.« less

  5. Material Selection for Accident Tolerant Fuel Cladding

    NASA Astrophysics Data System (ADS)

    Pint, B. A.; Terrani, K. A.; Yamamoto, Y.; Snead, L. L.

    2015-09-01

    Alternative cladding materials to Zr-based alloys are being investigated for accident tolerance, which can be defined as >100X improvement (compared to Zr-based alloys) in oxidation resistance to steam or steam-H2 environments at ≥1473 K (1200 °C) for short times. After reviewing a wide range of candidates, current steam oxidation testing is being conducted on Mo, MAX phases, and FeCrAl alloys. Recently reported low-mass losses for Mo in steam at 1073 K (800 °C) could not be reproduced. Both FeCrAl and MAX phase Ti2AlC form a protective alumina scale in steam. However, commercial Ti2AlC that was not single phase, formed a much thicker oxide at 1473 K (1200 °C) in steam and significant TiO2, and therefore, Ti2AlC may be challenging to form as a cladding or a coating. Alloy development for FeCrAl is seeking to maintain its steam oxidation resistance to 1748 K (1475 °C), while reducing its Cr content to minimize susceptibility to irradiation-assisted α' formation. The composition effects and critical limits to retaining protective scale formation at >1673 K (1400 °C) are still being evaluated.

  6. Variable Expression of Neural Cell Adhesion Molecule Isoforms in Renal Tissue: Possible Role in Incipient Renal Fibrosis

    PubMed Central

    Müller, Claudia A.; Tampe, Björn; Ćirović, Sanja; Vještica, Jelena; Tomanović, Nada; Zeisberg, Michael; Müller, Gerhard A.

    2015-01-01

    Rare neural cell adhesion molecule (NCAM) positive cells have been previously described within the normal human adult kidney interstitium, speculating that they could increase in the interstitium with incipient interstitial renal fibrosis (IRF). In the present study, among 93 biopsy samples of various kidney diseases, NCAM+ interstitial cells were detected in 62.4% cases. An increased number of NCAM+ cells was significantly observed only in incipient IRF compared to normal renal tissues and advanced IRF stages (p<0.001), independently of underlying diseases (p = 0.657). All three major NCAM isoforms’ RT-PCR bands were visible either in normal or in kidneys with incipient IRF, albeit their mRNA expression levels measured by qRT-PCR were different. Applying qRT-PCR on pure NCAM+ cells population, obtained by laser capture microdissection, significant mRNA over-expression of NCAM140kD isoform was found in NCAM+ cells within incipient IRF (p = 0.004), while NCAM120kD and NCAM180kD isoforms were not changed significantly (p = 0.750; p = 0.704; respectively). Simultaneously, qRT-PCR also showed significant αSMA (p = 0.014) and SLUG (p = 0.004) mRNAs up-regulation within the NCAM+ cells of incipient IRF, as well as highly decreased matrix metalloproteinases (MMP) -2 and -9 mRNAs (p = 0.028; p = 0.036; respectively). However, using double immunofluorescence MMP-9 could still be detectable on the protein level in rare NCAM+ cells within the incipient IRF. Further characterization of NCAM+ cells by double immunofluorescent labeling revealed their association with molecules involved in fibrosis. Fibroblast growth factor receptor 1 (FGFR1) and α5β1 integrin were extensively expressed on NCAM+ cells within the incipient IRF areas, whereas human epididymis protein-4 (HE4) was found to be present in few NCAM+ cells of both normal and interstitium with incipient fibrosis. Heterogeneity of NCAM+ interstitial cells in normal and incipient IRF, concerning molecules related to

  7. Brazing of Carbon Carbon Composites to Cu-clad Molybdenum for Thermal Management Applications

    NASA Technical Reports Server (NTRS)

    Singh, M.; Asthana, R.; Shpargel, T> P.

    2007-01-01

    Advanced carbon carbon composites were joined to copper-clad molybdenum (Cu/Mo) using four active metal brazes containing Ti (Cu ABA, Cusin-1 ABA, Ticuni, and Ticusil) for potential use in thermal management applications. The brazed joints were characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and Knoop microhardness measurements across the joint region. Metallurgically sound C-C/Cu/Mo joints, devoid of interfacial cracks formed in all cases. The joint interfaces were preferentially enriched in Ti, with Cu ABA joints exhibiting the largest interfacial Ti concentrations. The microhardness measurements revealed hardness gradients across the joint region, with a peak hardness of 300-350 KHN in Cusin-1 ABA and Ticusil joints and 200-250 KHN in Cu ABA and Ticuni joints, respectively.

  8. Hot Forging of a Cladded Component by Automated GMAW Process

    NASA Astrophysics Data System (ADS)

    Rafiq, Muhammad; Langlois, Laurent; Bigot, Régis

    2011-01-01

    Weld cladding is employed to improve the service life of engineering components by increasing corrosion and wear resistance and reducing the cost. The acceptable multi-bead cladding layer depends on single bead geometry. Hence, in first step, the relationship between input process parameters and the single bead geometry is studied and in second step a comprehensive study on multi bead clad layer deposition is carried out. This paper highlights an experimental study carried out to get single layer cladding deposited by automated Gas Metal Arc Welding (GMAW) process and to find the possibility of hot forming of the cladded work piece to get the final hot formed improved structure. GMAW is an arc welding process that uses an arc between a consumable electrode and the welding pool with an external shielding gas and the cladding is done by alongside deposition of weld beads. The experiments for single bead were conducted by varying the three main process parameters wire feed rate, arc voltage and welding speed while keeping other parameters like nozzle to work distance, shielding gas and its flow rate and torch angle constant. The effect of bead spacing and torch orientation on the cladding quality of single layer from the results of single bead deposition was studied. Effect of the dilution rate and nominal energy on the cladded layer hot bending quality was also performed at different temperatures.

  9. Metal clad aramid fibers for aerospace wire and cable

    NASA Astrophysics Data System (ADS)

    Tokarsky, Edward W.; Dunham, Michael G.; Hunt, James E.; Santoleri, E. David; Allen, David B.

    1995-11-01

    High strength light weight metal clad aramid fibers can provide significant weight savings when used to replace conventional metal wire in aerospace cable. An overview of metal clad aramid fiber materials and information on performance and use in braided electrical shielding and signal conductors is provided.

  10. Metal clad aramid fibers for aerospace wire and cable

    NASA Technical Reports Server (NTRS)

    Tokarsky, Edward W.; Dunham, Michael G.; Hunt, James E.; Santoleri, E. David; Allen, David B.

    1995-01-01

    High strength light weight metal clad aramid fibers can provide significant weight savings when used to replace conventional metal wire in aerospace cable. An overview of metal clad aramid fiber materials and information on performance and use in braided electrical shielding and signal conductors is provided.

  11. The Behavior of Gas Powder Laser Clad NiCrBSi Coatings Under Contact Loading

    NASA Astrophysics Data System (ADS)

    Savrai, R. A.; Makarov, A. V.; Soboleva, N. N.; Malygina, I. Yu.; Osintseva, A. L.

    2016-03-01

    The behavior of NiCrBSi coatings obtained by laser cladding from powders with various chromium, carbon and boron contents has been investigated under contact loading through microindentation using a Vickers indenter and via non-impact cyclic loading as per "sphere-to-surface" contact scheme. The phase composition of the coating containing 0.48% C, 14.8% Cr, 2.1% B is γ + Ni3B + Cr23C6 and that of the coating containing 0.92% C, 18.2% Cr, 3.3% B is γ + Ni3B + Cr7C3 + CrB. The established restrictions of the processes of plastic deformation and cracking for the more heavily alloyed and harder coating under contact fatigue loading are substantially due to its increased ability to deform predominantly in the elastic region under the used cyclic loading conditions. This is indicated by the obtained microindentation data and, therefore, the microindentation method (one-time indentation) can be used to assess the ability of the laser clad NiCrBSi coatings to withstand repeated contact loads.

  12. Ultrasonic guided wave detection of scatterers on large clad steel plates

    NASA Astrophysics Data System (ADS)

    Gong, Peng; Harley, Joel B.; Berges, Mario; Junker, Warren R.; Greve, David W.; Oppenheim, Irving J.

    2016-04-01

    "Clad steel" refers to a thick carbon steel structural plate bonded to a corrosion resistant alloy (CRA) plate, such as stainless steel or titanium, and is widely used in industry to construct pressure vessels. The CRA resists the chemically aggressive environment on the interior, but cannot prevent the development of corrosion losses and cracks that limit the continued safe operation of such vessels. At present there are no practical methods to detect such defects from the exposed outer surface of the thick carbon steel plate, often necessitating removing such vessels from service and inspecting them visually from the interior. In previous research, sponsored by industry to detect and localize damage in pressurized piping systems under operational and environmental changes, we investigated a number of data-driven signal processing methods to extract damage information from ultrasonic guided wave pitch-catch records. We now apply those methods to relatively large clad steel plate specimens. We study a sparse array of wafer-type ultrasonic transducers adhered to the carbon steel surface, attempting to localize mass scatterers grease-coupled to the stainless steel surface. We discuss conditions under which localization is achieved by relatively simple first-arrival methods, and other conditions for which data-driven methods are needed; we also discuss observations of plate-like mode properties implied by these results.

  13. Effects of Ta on microstructure and microhardness of Ni based laser clad coating

    NASA Astrophysics Data System (ADS)

    Yu, Ting; Deng, Qilin; Dong, Gang; Yang, Jianguo

    2011-03-01

    Through addition of Tantalum, fine TaC particles were in situ synthesized in a NiCrBSi alloy laser clad composite coating. Microstructure, microhardness and abrasive wear resistance of the composite coating were investigated. The result showed that TaC particles were dispersed in Ni based alloy composite coating, refining the microstructure of the coating after laser cladding. Amount of coarse primary carbides such as M7C3 and eutectic of γ-Ni + M23C6 substantially decreased because the formation of TaC particles suppressed the formation of M7C3 and M23C6. On the one hand, fine TaC particles acted as hard phase, which improved the microhardness of the composite coating; on the other hand, a decrease in amount of the coarse M7C3 and eutectic of γ-Ni + M23C6 reduced the crack susceptibility of the Ni based composite coating. Also, Ta element improved the abrasive wear resistance of the Ni based coating.

  14. Microstructure and corrosion properties of thick WC composite coating formed by plasma cladding

    NASA Astrophysics Data System (ADS)

    Guozhi, Xie; Xiaolong, Song; Dongjie, Zhang; Yuping, Wu; Pinghua, Lin

    2010-08-01

    The thick Ni-coated WC coatings, in a matrix of Nickel-based alloys, were prepared on AISI 1045 steel using plasma cladding equipment. A pre-placed layer of uniform mixture, with different weight fractions of Ni-coated WC powder and Nickel-based alloy powder, on the steel substrate was melted at the high temperature of the plasma jet. The coating composition, microstructure and microhardness were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectrometer (EDS) and microhardness testing. The experimental results show that the metallurgical bond was formed between the coating and substrate. The XRD results show that the coatings contain γ-Ni, carbides (such as M 23C 6 and M 7C 3) and boride (such as Fe 2B, Fe 3B phases). SEM shows that all the coatings are crack-free with lower porosity (<1%). It is found that the microhardness and the electrochemical behavior of the coatings are depended on the content of Ni-coated WC powder. The corrosion mechanism for the coatings may be due to the microgalvance corrosion between the phases in the cladding coatings.

  15. Mechanical properties of silver halide core/clad IR fibers

    NASA Astrophysics Data System (ADS)

    Shalem, Shaul; German, Alla; Moser, Frank; Katzir, Abraham

    1996-04-01

    We have developed core/clad polycrystalline silver halide optical fibers with a loss of roughly 0.3 dB/m at 10.6 micrometers. Such fibers, with core diameters 0.3 - 0.6 mm and lengths of 1 to 2 meters are capable of continuously delivering output power densities as high as 14 KW/cm2. The fibers were repetitively bent in the plastic and elastic regimes and the optical transmission monitored during bending. The mechanical properties of the core/clad fibers and of the core only fibers are similar. It was also demonstrated that the 'bending' properties of the core/clad fibers are determined by the cladding material. Our investigations suggest that proper design of the core/clad structure may give significant improvement in mechanical properties such as more cycles to optical failure. This will be very important especially for endoscopic laser surgery and other medical applications.

  16. Compact cladding-pumped planar waveguide amplifier and fabrication method

    DOEpatents

    Bayramian, Andy J.; Beach, Raymond J.; Honea, Eric; Murray, James E.; Payne, Stephen A.

    2003-10-28

    A low-cost, high performance cladding-pumped planar waveguide amplifier and fabrication method, for deployment in metro and access networks. The waveguide amplifier has a compact monolithic slab architecture preferably formed by first sandwich bonding an erbium-doped core glass slab between two cladding glass slabs to form a multi-layer planar construction, and then slicing the construction into multiple unit constructions. Using lithographic techniques, a silver stripe is deposited and formed at a top or bottom surface of each unit construction and over a cross section of the bonds. By heating the unit construction in an oven and applying an electric field, the silver stripe is then ion diffused to increase the refractive indices of the core and cladding regions, with the diffusion region of the core forming a single mode waveguide, and the silver diffusion cladding region forming a second larger waveguide amenable to cladding pumping with broad area diodes.

  17. Surface crack problems in plates

    NASA Technical Reports Server (NTRS)

    Joseph, P. F.; Erdogan, F.

    1989-01-01

    The mode I crack problem in plates under membrane loading and bending is reconsidered. The purpose is to examine certain analytical features of the problem further and to provide some new results. The formulation and the results given by the classical and the Reissner plate theories for through and part-through cracks are compared. For surface cracks the three-dimensional finite element solution is used as the basis of comparison. The solution is obtained and results are given for the crack/contact problem in a plate with a through crack under pure bending and for the crack interaction problem. Also, a procedure is developed to treat the problem of subcritical crack growth and to trace the evolution of the propagating crack.

  18. Time-frequency atoms-driven support vector machine method for bearings incipient fault diagnosis

    NASA Astrophysics Data System (ADS)

    Liu, Ruonan; Yang, Boyuan; Zhang, Xiaoli; Wang, Shibin; Chen, Xuefeng

    2016-06-01

    Bearing plays an essential role in the performance of mechanical system and fault diagnosis of mechanical system is inseparably related to the diagnosis of the bearings. However, it is a challenge to detect weak fault from the complex and non-stationary vibration signals with a large amount of noise, especially at the early stage. To improve the anti-noise ability and detect incipient fault, a novel fault detection method based on a short-time matching method and Support Vector Machine (SVM) is proposed. In this paper, the mechanism of roller bearing is discussed and the impact time frequency dictionary is constructed targeting the multi-component characteristics and fault feature of roller bearing fault vibration signals. Then, a short-time matching method is described and the simulation results show the excellent feature extraction effects in extremely low signal-to-noise ratio (SNR). After extracting the most relevance atoms as features, SVM was trained for fault recognition. Finally, the practical bearing experiments indicate that the proposed method is more effective and efficient than the traditional methods in weak impact signal oscillatory characters extraction and incipient fault diagnosis.

  19. Soluble IL-1RII and IL-18 are associated with incipient upper extremity soft tissue disorders.

    PubMed

    Rechardt, Martti; Shiri, Rahman; Matikainen, Sampsa; Viikari-Juntura, Eira; Karppinen, Jaro; Alenius, Harri

    2011-05-01

    Previous studies suggest a role for IL-1β in the pathophysiology of upper extremity soft tissue disorders (UESTDs). We studied the levels of interleukin-1 family members in patients with incipient UESTDs and compared them with healthy controls. In this case control study, we included 163 patients with UESTDs and symptom duration shorter than 1 month and 42 healthy controls matched for age and gender at the group level. Serum levels of cytokines IL-1α, IL-1β, IL-1Ra, IL-6, IL-8, IL-18, IL-33, TNFα and sensitized C-reactive protein as well as IL-1 family soluble receptors sIL-1RII and sST2 were assessed. We used unconditional logistic regression models to study the associations between cytokines and UESTDs. After adjustment for potential confounders, the serum levels of sIL-1RII (p<0.001) and sST2 (p=0.014) were higher in the patients than the controls. The level of IL-18 was lower in the patients than the controls (p=0.005). There were no significant differences between the patients and controls regarding the levels of IL-1α, IL-1β, IL-1Ra, IL-33, IL-6, IL-8, TNFα, or sensitized C-reactive protein. The levels of circulating sIL-1RII and IL-18 are associated with incipient UESTDs, suggesting an important role for these IL-1 family members in the early course of UESTDs. PMID:21371906

  20. FROM INCIPIENT TO SUBSTANTIAL: EVOLUTION OF PLACENTOTROPHY IN A PHYLUM OF AQUATIC COLONIAL INVERTEBRATES

    PubMed Central

    Ostrovsky, Andrew N; Fairbairn, D

    2013-01-01

    Matrotrophy has long been known in invertebrates, but it is still poorly understood and has never been reviewed. A striking example of matrotrophy (namely, placentotrophy) is provided by the Bryozoa, a medium-sized phylum of the aquatic colonial filter feeders. Here I report on an extensive anatomical study of placental analogues in 21 species of the bryozoan order Cheilostomata, offering the first review on matrotrophy among aquatic invertebrates. The first anatomical description of incipient placentotrophy in invertebrates is presented together with the evidence for multiple independent origins of placental analogues in this order. The combinations of contrasting oocytic types (macrolecithal or microlecithal) and various degrees of placental development and embryonic enlargement during incubation, found in different bryozoan species, are suggestive of a transitional series from the incipient to the substantial placentotrophy accompanied by an inverse change in oogenesis, a situation reminiscent of some vertebrates. It seems that matrotrophy could trigger the evolution of sexual zooidal polymorphism in some clades. The results of this study show that this phylum, with its wide variety of reproductive patterns, incubation devices, and types of the simple placenta-like systems, offers a promising model for studying parallel evolution of placentotrophy in particular, and matrotrophy in general. PMID:23617914

  1. Curie Point Depth Estimates Beneath the Incipient Okavango Rift Zone, Northwest Botswana

    NASA Astrophysics Data System (ADS)

    Leseane, K.; Atekwana, E. A.; Mickus, K. L.; Mohamed, A.; Atekwana, E. A.

    2013-12-01

    We investigated the regional thermal structure of the crust beneath the Okavango Rift Zone (ORZ), surrounding cratons and orogenic mobile belts using the Curie Point Depth (CPD) estimates. Estimating the depth to the base of magnetic sources is important in understanding and constraining the thermal structure of the crust in zones of incipient continental rifting where no other data are available to image the crustal thermal structure. Our objective was to determine if there are any thermal perturbations within the lithosphere during rift initiation. The top and bottom of the magnetized crust were calculated using the two dimensional (2D) power-density spectra analysis and three dimensional (3D) inversions of the total field magnetic data of Botswana in overlapping square windows of 1degree x 1 degree. The calculated CPD estimates varied between ~8 km and ~24 km. The deepest CPD values (16-24 km) occur under the surrounding cratons and orogenic mobile belts whereas the shallowest CPD values were found within the ORZ. CPD values of 8 to 10 km occur in the northeastern part of ORZ; a site of more developed rift structures and where hot springs are known to occur. CPD values of 12 to 16 km were obtained in the southwestern part of the ORZ where rift structures are progressively less developed and where the rift terminates. The results suggests possible thermal anomaly beneath the incipient ORZ. Further geophysical studies as part of the PRIDE (Project for Rift Initiation Development and Evolution) project are needed to confirm this proposition.

  2. Incipient post-zygotic barrier in a model system of ecological speciation with gene flow.

    PubMed

    Sá-Pinto, A; Martínez-Fernández, M; López-Fernández, C; Ferreira, Z; Pereira, R; Gosálvez, J; Rolán-Alvarez, E

    2013-12-01

    The role of post-zygotic isolation in nonallopatric ecological speciation is still mostly unknown and information on the nature and strength of these barriers in well-known speciation models is essential for a deeper understanding of such processes. The Galician ecotypes of the marine snail Littorina saxatilis represent one of the best studied cases of nonallopatric ecological speciation. Here, we test the existence of incipient post-zygotic isolation by comparing the fertility of male hybrids with that of both pure forms [ridged and banded (RB) and smooth and unbanded (SU) ecotypes]. We analysed the degree of sperm DNA fragmentation (SDF) of individuals morphologically classified as RB, SU and hybrids, sampled from two locations. SDF analyses were chosen to study sperm quality because, in other animal species, SDF rates correlate with important parameters for speciation research, such as fertilization and abortion rates and viability of adult progeny. In the present work, hybrids showed significantly higher SDF rates than RB and SU males in one location and significantly higher variances in both locations. These results suggest the existence of an incipient post-zygotic barrier, the strength of which may vary across the Galician shore, and highlight the potential of SDF analyses for speciation research. PMID:24164692

  3. Incipient fault detection and identification in process systems using accelerating neural network learning

    SciTech Connect

    Parlos, A.G.; Muthusami, J.; Atiya, A.F. . Dept. of Nuclear Engineering)

    1994-02-01

    The objective of this paper is to present the development and numerical testing of a robust fault detection and identification (FDI) system using artificial neural networks (ANNs), for incipient (slowly developing) faults occurring in process systems. The challenge in using ANNs in FDI systems arises because of one's desire to detect faults of varying severity, faults from noisy sensors, and multiple simultaneous faults. To address these issues, it becomes essential to have a learning algorithm that ensures quick convergence to a high level of accuracy. A recently developed accelerated learning algorithm, namely a form of an adaptive back propagation (ABP) algorithm, is used for this purpose. The ABP algorithm is used for the development of an FDI system for a process composed of a direct current motor, a centrifugal pump, and the associated piping system. Simulation studies indicate that the FDI system has significantly high sensitivity to incipient fault severity, while exhibiting insensitivity to sensor noise. For multiple simultaneous faults, the FDI system detects the fault with the predominant signature. The major limitation of the developed FDI system is encountered when it is subjected to simultaneous faults with similar signatures. During such faults, the inherent limitation of pattern-recognition-based FDI methods becomes apparent. Thus, alternate, more sophisticated FDI methods become necessary to address such problems. Even though the effectiveness of pattern-recognition-based FDI methods using ANNs has been demonstrated, further testing using real-world data is necessary.

  4. Adaptive divergence with gene flow in incipient speciation of Miscanthus floridulus/sinensis complex (Poaceae).

    PubMed

    Huang, Chao-Li; Ho, Chuan-Wen; Chiang, Yu-Chung; Shigemoto, Yasumasa; Hsu, Tsai-Wen; Hwang, Chi-Chuan; Ge, Xue-Jun; Chen, Charles; Wu, Tai-Han; Chou, Chang-Hung; Huang, Hao-Jen; Gojobori, Takashi; Osada, Naoki; Chiang, Tzen-Yuh

    2014-12-01

    Young incipient species provide ideal materials for untangling the process of ecological speciation in the presence of gene flow. The Miscanthus floridulus/sinensis complex exhibits diverse phenotypic and ecological differences despite recent divergence (approximately 1.59 million years ago). To elucidate the process of genetic differentiation during early stages of ecological speciation, we analyzed genomic divergence in the Miscanthus complex using 72 randomly selected genes from a newly assembled transcriptome. In this study, rampant gene flow was detected between species, estimated as M = 3.36 × 10(-9) to 1.20 × 10(-6) , resulting in contradicting phylogenies across loci. Nevertheless, beast analyses revealed the species identity and the effects of extrinsic cohesive forces that counteracted the non-stop introgression. As expected, early in speciation with gene flow, only 3-13 loci were highly diverged; two to five outliers (approximately 2.78-6.94% of the genome) were characterized by strong linkage disequilibrium, and asymmetrically distributed among ecotypes, indicating footprints of diversifying selection. In conclusion, ecological speciation of incipient species of Miscanthus probably followed the parapatric model, whereas allopatric speciation cannot be completely ruled out, especially between the geographically isolated northern and southern M. sinensis, for which no significant gene flow across oceanic barriers was detected. Divergence between local ecotypes in early-stage speciation began at a few genomic regions under the influence of natural selection and divergence hitchhiking that overcame gene flow. PMID:25237766

  5. From incipient to substantial: evolution of placentotrophy in a phylum of aquatic colonial invertebrates.

    PubMed

    Ostrovsky, Andrew N

    2013-05-01

    Matrotrophy has long been known in invertebrates, but it is still poorly understood and has never been reviewed. A striking example of matrotrophy (namely, placentotrophy) is provided by the Bryozoa, a medium-sized phylum of the aquatic colonial filter feeders. Here I report on an extensive anatomical study of placental analogues in 21 species of the bryozoan order Cheilostomata, offering the first review on matrotrophy among aquatic invertebrates. The first anatomical description of incipient placentotrophy in invertebrates is presented together with the evidence for multiple independent origins of placental analogues in this order. The combinations of contrasting oocytic types (macrolecithal or microlecithal) and various degrees of placental development and embryonic enlargement during incubation, found in different bryozoan species, are suggestive of a transitional series from the incipient to the substantial placentotrophy accompanied by an inverse change in oogenesis, a situation reminiscent of some vertebrates. It seems that matrotrophy could trigger the evolution of sexual zooidal polymorphism in some clades. The results of this study show that this phylum, with its wide variety of reproductive patterns, incubation devices, and types of the simple placenta-like systems, offers a promising model for studying parallel evolution of placentotrophy in particular, and matrotrophy in general. PMID:23617914

  6. Cracking the Credit Hour

    ERIC Educational Resources Information Center

    Laitinen, Amy

    2012-01-01

    The basic currency of higher education--the credit hour--represents the root of many problems plaguing America's higher education system: the practice of measuring time rather than learning. "Cracking the Credit Hour" traces the history of this time-based unit, from the days of Andrew Carnegie to recent federal efforts to define a credit hour. If…

  7. Catalytic cracking process

    DOEpatents

    Lokhandwala, Kaaeid A.; Baker, Richard W.

    2001-01-01

    Processes and apparatus for providing improved catalytic cracking, specifically improved recovery of olefins, LPG or hydrogen from catalytic crackers. The improvement is achieved by passing part of the wet gas stream across membranes selective in favor of light hydrocarbons over hydrogen.

  8. Cladding embrittlement during postulated loss-of-coolant accidents.

    SciTech Connect

    Billone, M.; Yan, Y.; Burtseva, T.; Daum, R.; Nuclear Engineering Division

    2008-07-31

    The effect of fuel burnup on the embrittlement of various cladding alloys was examined with laboratory tests conducted under conditions relevant to loss-of-coolant accidents (LOCAs). The cladding materials tested were Zircaloy-4, Zircaloy-2, ZIRLO, M5, and E110. Tests were performed with specimens sectioned from as-fabricated cladding, from prehydrided (surrogate for high-burnup) cladding, and from high-burnup fuel rods which had been irradiated in commercial reactors. The tests were designed to determine for each cladding material the ductile-to-brittle transition as a function of steam oxidation temperature, weight gain due to oxidation, hydrogen content, pre-transient cladding thickness, and pre-transient corrosion-layer thickness. For short, defueled cladding specimens oxidized at 1000-1200 C, ring compression tests were performed to determine post-quench ductility at {le} 135 C. The effect of breakaway oxidation on embrittlement was also examined for short specimens oxidized at 800-1000 C. Among other findings, embrittlement was found to be sensitive to fabrication processes--especially surface finish--but insensitive to alloy constituents for these dilute zirconium alloys used as cladding materials. It was also demonstrated that burnup effects on embrittlement are largely due to hydrogen that is absorbed in the cladding during normal operation. Some tests were also performed with longer, fueled-and-pressurized cladding segments subjected to LOCA-relevant heating and cooling rates. Recommendations are given for types of tests that would identify LOCA conditions under which embrittlement would occur.

  9. Review of environmental effects on fatigue crack growth of austenitic stainless steels.

    SciTech Connect

    Shack, W. J.; Kassner, T. F.; Energy Technology

    1994-07-11

    Fatigue and environmentally assisted cracking of piping, pressure vessel cladding, and core components in light water reactors are potential concerns to the nuclear industry and regulatory agencies. The degradation processes include intergranular stress corrosion cracking of austenitic stainless steel (SS) piping in boiling water reactors (BWRs), and propagation of fatigue or stress corrosion cracks (which initiate in sensitized SS cladding) into low-alloy ferritic steels in BWR pressure vessels. Crack growth data for wrought and cast austenitic SSs in simulated BWR water, developed at Argonne National Laboratory under US Nuclear Regulatory Commission sponsorship over the past 10 years, have been compiled into a data base along with similar data obtained from the open literature. The data were analyzed to develop corrosion-fatigue curves for austenitic SSs in aqueous environments corresponding to normal BWR water chemistries, for BWRs that add hydrogen to the feedwater, and for pressurized water reactor primary-system-coolant chemistry. The corrosion-fatigue data and curves in water were compared with the air line in Section XI of the ASME Code.

  10. Crack patterns over uneven substrates.

    PubMed

    Nandakishore, Pawan; Goehring, Lucas

    2016-02-28

    Cracks in thin layers are influenced by what lies beneath them. From buried craters to crocodile skin, crack patterns are found over an enormous range of length scales. Regardless of absolute size, their substrates can dramatically influence how cracks form, guiding them in some cases, or shielding regions from them in others. Here we investigate how a substrate's shape affects the appearance of cracks above it, by preparing mud cracks over sinusoidally varying surfaces. We find that as the thickness of the cracking layer increases, the observed crack patterns change from wavy to ladder-like to isotropic. Two order parameters are introduced to measure the relative alignment of these crack networks, and, along with Fourier methods, are used to characterise the transitions between crack pattern types. Finally, we explain these results with a model, based on the Griffith criteria of fracture, that identifies the conditions for which straight or wavy cracks will be seen, and predicts how well-ordered the cracks will be. Our metrics and results can be applied to any situation where connected networks of cracks are expected, or found. PMID:26762761

  11. Random loading fatigue crack growth: Crack closure considerations

    NASA Technical Reports Server (NTRS)

    Ortiz, Keith

    1987-01-01

    The prediction of fatigue crack growth is an important element of effective fracture control for metallic structures and mechanical components, especially in the aerospace industry. The prediction techniques available and applied today are mostly based on fatigue crack growth measurements determined in constant amplitude testing. However, while many service loadings are constant amplitude, many more loadings are random amplitude. An investigation to determine which statistics of random loadings are relevant to fatigue crack closure was conducted. The fundamentals of random processes and crack closure are briefly reviewed, then the relevance of certain random process parameters to the crack closure calculation are discussed qualitatively. A course for further research is outlined.

  12. High T_{c} via Spin Fluctuations from Incipient Bands: Application to Monolayers and Intercalates of FeSe.

    PubMed

    Linscheid, A; Maiti, S; Wang, Y; Johnston, S; Hirschfeld, P J

    2016-08-12

    We investigate superconductivity in a two-band system with an electronlike and a holelike band, where one of the bands is away from the Fermi level (or "incipient"). We argue that the incipient band contributes significantly to spin-fluctuation pairing in the strong coupling limit where the system is close to a magnetic instability and can lead to a large T_{c}. In this case, T_{c} is limited by a competition between the frequency range of the coupling (set by an isolated paramagnon) and the coupling strength itself, such that a domelike T_{c} dependence on the incipient band position is obtained. The coupling of electrons to phonons is found to further enhance T_{c}. The results are discussed in the context of experiments on monolayers and intercalates of FeSe. PMID:27563992

  13. High Tc via Spin Fluctuations from Incipient Bands: Application to Monolayers and Intercalates of FeSe

    NASA Astrophysics Data System (ADS)

    Linscheid, A.; Maiti, S.; Wang, Y.; Johnston, S.; Hirschfeld, P. J.

    2016-08-01

    We investigate superconductivity in a two-band system with an electronlike and a holelike band, where one of the bands is away from the Fermi level (or "incipient"). We argue that the incipient band contributes significantly to spin-fluctuation pairing in the strong coupling limit where the system is close to a magnetic instability and can lead to a large Tc. In this case, Tc is limited by a competition between the frequency range of the coupling (set by an isolated paramagnon) and the coupling strength itself, such that a domelike Tc dependence on the incipient band position is obtained. The coupling of electrons to phonons is found to further enhance Tc. The results are discussed in the context of experiments on monolayers and intercalates of FeSe.

  14. Acoustic waveguide technique for sensing incipient faults in underground power-transmission cables: Including acousto-optic techniques

    NASA Astrophysics Data System (ADS)

    Harrold, R. T.

    1981-09-01

    Theoretical and practical studies were made of both the acoustic emission, spectrum signatures associated with underground cable incipient faults, and the attenuation of acoustic waves in waterfilled metal tubes used as waveguided. Based on critical data, it can be estimated that in favorable circumstances, the acoustic waveguide system would only be useful for sensing incipient faults in underground cables of approx. 800 meters of less in length. A system were investigated which acoustic emissions from cable incipient faults impinge on a fiber-optic lightguide and locally change its refractive index and modulate laser light transmitted along the light guide. Experiments based on this concept show that is is possible t sense acoustic emissions with energy levels below on micro-joule. A test of this system using a section of compressed gas-insulated cable with an internal flashover was successfully carried out.

  15. Cladding material, tube including such cladding material and methods of forming the same

    DOEpatents

    Garnier, John E.; Griffith, George W.

    2016-03-01

    A multi-layered cladding material including a ceramic matrix composite and a metallic material, and a tube formed from the cladding material. The metallic material forms an inner liner of the tube and enables hermetic sealing of thereof. The metallic material at ends of the tube may be exposed and have an increased thickness enabling end cap welding. The metallic material may, optionally, be formed to infiltrate voids in the ceramic matrix composite, the ceramic matrix composite encapsulated by the metallic material. The ceramic matrix composite includes a fiber reinforcement and provides increased mechanical strength, stiffness, thermal shock resistance and high temperature load capacity to the metallic material of the inner liner. The tube may be used as a containment vessel for nuclear fuel used in a nuclear power plant or other reactor. Methods for forming the tube comprising the ceramic matrix composite and the metallic material are also disclosed.

  16. Tensile Hoop Behavior of Irradiated Zircaloy-4 Nuclear Fuel Cladding

    SciTech Connect

    Jaramillo, Roger A; Hendrich, WILLIAM R; Packan, Nicolas H

    2007-03-01

    A method for evaluating the room temperature ductility behavior of irradiated Zircaloy-4 nuclear fuel cladding has been developed and applied to evaluate tensile hoop strength of material irradiated to different levels. The test utilizes a polyurethane plug fitted within a tubular cladding specimen. A cylindrical punch is used to compress the plug axially, which generates a radial displacement that acts upon the inner diameter of the specimen. Position sensors track the radial displacement of the specimen outer diameter as the compression proceeds. These measurements coupled with ram force data provide a load-displacement characterization of the cladding response to internal pressurization. The development of this simple, cost-effective, highly reproducible test for evaluating tensile hoop strain as a function of internal pressure for irradiated specimens represents a significant advance in the mechanical characterization of irradiated cladding. In this project, nuclear fuel rod assemblies using Zircaloy-4 cladding and two types of mixed uranium-plutonium oxide (MOX) fuel pellets were irradiated to varying levels of burnup. Fuel pellets were manufactured with and without thermally induced gallium removal (TIGR) processing. Fuel pellets manufactured by both methods were contained in fuel rod assemblies and irradiated to burnup levels of 9, 21, 30, 40, and 50 GWd/MT. These levels of fuel burnup correspond to fast (E > 1 MeV) fluences of 0.27, 0.68, 0.98, 1.4 and 1.7 1021 neutrons/cm2, respectively. Following irradiation, fuel rod assemblies were disassembled; fuel pellets were removed from the cladding; and the inner diameter of cladding was cleaned to remove residue materials. Tensile hoop strength of this cladding material was tested using the newly developed method. Unirradiated Zircaloy-4 cladding was also tested. With the goal of determining the effect of the two fuel types and different neutron fluences on clad ductility, tensile hoop strength tests were

  17. Microstructure and Wear Behavior of Laser Clad Multi-layered Fe-based Amorphous Coatings on Steel Substrates

    NASA Astrophysics Data System (ADS)

    Paul, Tanaji; Alavi, S. Habib; Biswas, Sourabh; Harimkar, Sandip P.

    2015-12-01

    Single and multi-layered (with two and three layers) coatings of Fe48Cr15Mo14Y2C15B6 amorphous alloy were applied to AISI 1018 steel substrates via laser cladding. XRD analysis indicated partial retention of the amorphous phase along with the formation of oxide and carbide phases. Cross-sectional SEM micrographs revealed relatively sound coatings laser clad with single layer of amorphous alloy; however, cracks and voids were observed in the two and three layered amorphous coatings. The specimens with single and two layered amorphous coatings exhibited surface hardness of about 650 VHN while the hardness of the specimens with three layered amorphous coatings (~1100 VHN) nearly equaled the hardness of previously reported sintered amorphous alloys of similar compositions. The ball-on-disc wear analysis demonstrated a reverse trend wherein the single and two layered amorphous coatings exhibited lower weight loss during the wear test cycle due to superior surface soundness while the three layered amorphous coatings showed aggravated wear due to internal voids and cracks.

  18. Reliability of hard plastic clad silica fibers

    NASA Astrophysics Data System (ADS)

    Skutnik, Bolesh J.; Spaniol, Stefan

    2006-04-01

    New formulations of cladding materials have become available in recent times for Hard Plastic Clad Silica (HPCS) fibers, Initial data showed gains in some properties, particularly dynamic strength, especially for high numerical aperture (NA) fibers. A systematic study has been undertaken to determine the full strength and fatigue behavior of these HPCS fibers and to make comparisons to earlier HPCS fibers. Preliminary results, now confirmed, has shown improved median dynamic strength and higher Weibull slope. Full results are presented below including fatigue behavior and optical properties. These fibers have many applications and benefits in the high power delivery and medical laser uses as highlighted below. High power diode laser systems with their laser diode bars and arrays not only require special fibers to couple directly to the diode emitters, but also require special fibers to couple from the laser to application sites. These latter power delivery fibers are much larger than the internal fibers but still must be flexible, and have not only good strength but also good fatigue behavior. This particularly important industrial systems using robotic arms to apply the high power laser energy at a treatment site. The optical properties of HPCS fibers are well suited for the needs of the delivery of high power from diode laser bars and arrays to an application site. Benefits of strong median dynamic strengths and tighter flaw distributions in such cases will be discussed. Many medical applications, especially endoscopic ones, can benefit from the use of highly flexible, high NA, cost effective, HPCS optical fibers. Benefits of high strength and good fatigue behavior for such fibers in endoscopic procedures, including laser surgery, are discussed briefly including implications for mechanical reliability in medical and industrial settings.

  19. On the susceptibility to stress corrosion cracking of Zircaloy in an iodine containing environment

    NASA Astrophysics Data System (ADS)

    Tsing-Tyan, Yang; Chuen-Horng, Tsai

    1989-08-01

    The role of iodine and zirconium iodide in the process of stress corrosion cracking (SCC) of Zircaloy is studied by an internal pressurization SCC test and independent corrosion and creep tests, using iodine and zirconium tetraiodide crystals as the attacking species. Measurement of the critical values of iodine potential reveals that irradiated fuel rods should possess enough iodine potential to induce SCC failure of Zircaloy cladding. The difference between tests with I 2 and ZrI 4, and the morphology of microcraks at the site of corrosion pits suggest that the quantity of free iodine may play an important role in the crack initiation stage. Although the thick surface oxide can protect Zircaloy from iodine attack, it will rupture under sustaining a tensile stress, and then the iodine-bearing carrier will penetrate through the cracks to supply the necessary iodine potential and to proceed the propagation.

  20. Surface studies of iridium-alloy grain boundaries associated with weld cracking

    SciTech Connect

    Mosley, W.C.

    1982-01-01

    Plutonium-238 oxide fuel pellets for the General Purpose Heat Source (GPHS) Radioisotopic Thermoelectric Generators to be used on the NASA Galileo Mission to Jupiter and the International Solar Polar Mission are produced and encapsulated in iridium alloy at the Savannah River Plant (SRP). Underbead cracks occasionally occur in the girth weld on the iridium-alloy-clad vent sets in the region where the gas tungsten arc is quenched. Grain-boundary structures and compositions were characterized by scanning electron microscopy/x-ray energy spectroscopy, electron microprobe analysis and scanning Auger microprobe analysis to determine the cause of weld quench area cracking. Results suggest that weld quench area cracking may be caused by gas porosity or liquation in the grain boundaries.

  1. Femtosecond writing of depressed cladding waveguides in strongly cumulative regime

    NASA Astrophysics Data System (ADS)

    Bukharin, Mikhail A.; Khudyakov, Dmitriy V.; Vartapetov, Sergey K.

    2015-05-01

    We proposed a novel approach for direct femtosecond inscription of waveguides. It consisted in formation of cladding with reduced refractive index in fused silica. Depressed cladding was based on peripheral regions of individually written neighbored tracks, which should be inscribed in strongly cumulative regime. It was shown, that due to shot time interval between femtosecond laser pulses and relatively slow thermal diffusion, the exposed focal region surrounds by significantly wide cladding with reduced refracted index. Based on proposed approach we demonstrated depressed cladding waveguide inscription in fused silica using emission directly from commercially available femtosecond oscillator without correcting optical systems and second harmonic generation. It was shown, that the new approach provides formation of easily adjustable single mode waveguides with desired mode field diameter. Such depressed cladding waveguides exploit both advantages of fused silica material and depressed cladding geometry. We also verified our suggestion by experiment and inscribed depressed cladding waveguides with two different mode field diameters at similar femtosecond pulse characteristics. The obtained structures provided low propagation losses and good coupling with Gaussian mode. The waveguides supported propagation of both polarizations with nearly identical characteristics. Obtained experimental results were in good agreement with numerical simulation.

  2. Experimental and numerical investigation on cladding of corrosion-erosion resistant materials by a high power direct diode laser

    NASA Astrophysics Data System (ADS)

    Farahmand, Parisa

    In oil and gas industry, soil particles, crude oil, natural gas, particle-laden liquids, and seawater can carry various highly aggressive elements, which accelerate the material degradation of component surfaces by combination of slurry erosion, corrosion, and wear mechanisms. This material degradation results into the loss of mechanical properties such as strength, ductility, and impact strength; leading to detachment, delamination, cracking, and ultimately premature failure of components. Since the failure of high valued equipment needs considerable cost and time to be repaired or replaced, minimizing the tribological failure of equipment under aggressive environment has been gaining increased interest. It is widely recognized that effective management of degradation mechanisms will contribute towards the optimization of maintenance, monitoring, and inspection costs. The hardfacing techniques have been widely used to enhance the resistance of surfaces against degradation mechanisms. Applying a surface coating improves wear and corrosion resistance and ensures reliability and long-term performance of coated parts. A protective layer or barrier on the components avoids the direct mechanical and chemical contacts of tool surfaces with process media and will reduce the material loss and ultimately its failure. Laser cladding as an advanced hardfacing technique has been widely used for industrial applications in order to develop a protective coating with desired material properties. During the laser cladding, coating material is fused into the base material by means of a laser beam in order to rebuild a damaged part's surface or to enhance its surface function. In the hardfacing techniques such as atmospheric plasma spraying (APS), high velocity oxygen-fuel (HVOF), and laser cladding, mixing of coating materials with underneath surface has to be minimized in order to utilize the properties of the coating material most effectively. In this regard, laser cladding offers

  3. Experimental Constraints on Fluid-Rock Reactions during Incipient Serpentinization of Harzburgite

    NASA Astrophysics Data System (ADS)

    Klein, F.; Grozeva, N. G.; Seewald, J.; McCollom, T. M.; Humphris, S. E.; Moskowitz, B. M.; Berquo, T. S.; Kahl, W. A.

    2014-12-01

    The exposure of mantle peridotite to water at crustal levels leads to a cascade of interconnected dissolution-precipitation and reduction-oxidation reactions - a process referred to as serpentinization. These reactions have major implications for microbial life through the provision of hydrogen (H2). To simulate incipient serpentinization and the release of H2 under well-constrained conditions, we reacted uncrushed harzburgite with chemically modified seawater at 300°C and 35 MPa for ca. 1.5 years (13441 hours), monitored changes in fluid chemistry over time, and examined the secondary mineralogy at the termination of the experiment. Approximately 4 mol % of the protolith underwent alteration forming serpentine, accessory magnetite, chlorite, and traces of calcite and heazlewoodite. Alteration textures bear remarkable similarities to those found in partially serpentinized abyssal peridotites. Neither brucite nor talc precipitated during the experiment. Given that the starting material contained ~3.8 times more olivine than orthopyroxene on a molar basis, mass balance requires that dissolution of orthopyroxene was significantly faster than dissolution of olivine. However, the H2 release rate was not uniform, slowing from ~2 nmol H2(aq) gperidotite-1 s-1 at the beginning of the experiment to ~0.2 nmol H2(aq) gperidotite-1 s-1 at its termination. Serpentinization consumed water but did not release significant amounts of dissolved species (other than H2) suggesting that incipient hydration reactions involved a volume increase of ~40%. The reduced access of water to olivine surfaces due to filling of fractures and coating of primary minerals with alteration products led to decreased rates of serpentinization and H2 release. While this concept might seem at odds with completely serpentinized seafloor peridotites, reaction-driven fracturing offers an intriguing solution to the seemingly self-limiting nature of serpentinization. Indeed, the reacted sample revealed a

  4. Statistical crack mechanics

    SciTech Connect

    Dienes, J.K.

    1983-01-01

    An alternative to the use of plasticity theory to characterize the inelastic behavior of solids is to represent the flaws by statistical methods. We have taken such an approach to study fragmentation because it offers a number of advantages. Foremost among these is that, by considering the effects of flaws, it becomes possible to address the underlying physics directly. For example, we have been able to explain why rocks exhibit large strain-rate effects (a consequence of the finite growth rate of cracks), why a spherical explosive imbedded in oil shale produces a cavity with a nearly square section (opening of bedding cracks) and why propellants may detonate following low-speed impact (a consequence of frictional hot spots).

  5. Elevated temperature crack growth

    NASA Technical Reports Server (NTRS)

    Yau, J. F.; Malik, S. N.; Kim, K. S.; Vanstone, R. H.; Laflen, J. H.

    1985-01-01

    The objective of the Elevated Temperature Crack Growth Project is to evaluate proposed nonlinear fracture mechanics methods for application to combustor liners of aircraft gas turbine engines. During the first year of this program, proposed path-independent (P-I) integrals were reviewed for such applications. Several P-I integrals were implemented into a finite-element postprocessor which was developed and verified as part of the work. Alloy 718 was selected as the analog material for use in the forthcoming experimental work. A buttonhead, single-edge notch specimen was designed and verified for use in elevated-temperature strain control testing with significant inelastic strains. A crack mouth opening displacement measurement device was developed for further use.

  6. Replica-based Crack Inspection

    NASA Technical Reports Server (NTRS)

    Newman, John A.; Smith, Stephen W.; Piascik, R. S.; Willard, Scott A.; Dawicke, David S.

    2007-01-01

    A surface replica-based crack inspection method has recently been developed for use in Space Shuttle main engine (SSME) hydrogen feedline flowliners. These flowliners exist to ensure favorable flow of liquid hydrogen over gimble joint bellows, and consist of two rings each containing 38 elongated slots. In the summer of 2002, multiple cracks ranging from 0.1 inches to 0.6 inches long were discovered; each orbiter contained at least one cracked flowliner. These long cracks were repaired and eddy current inspections ensured that no cracks longer than 0.075 inches were present. However, subsequent fracture-mechanics review of flight rationale required detection of smaller cracks, and was the driving force for development of higher-resolution inspection method. Acetate tape surface replicas have been used for decades to detect and monitor small cracks. However, acetate tape replicas have primarily been limited to laboratory specimens because complexities involved in making these replicas - requiring acetate tape to be dissolved with acetone - are not well suited for a crack inspection tool. More recently developed silicon-based replicas are better suited for use as a crack detection tool. A commercially available silicon-based replica product has been determined to be acceptable for use in SSME hydrogen feedlines. A method has been developed using this product and a scanning electron microscope for analysis, which can find cracks as small as 0.005 inches and other features (e.g., pits, scratches, tool marks, etc.) as small as 0.001 inches. The resolution of this method has been validated with dozens of cracks generated in a laboratory setting and this method has been used to locate 55 cracks (ranging in size from 0.040 inches to 0.004 inches) on space flight hardware. These cracks were removed by polishing away the cracked material and a second round of replicas confirmed the repair.

  7. Subcritical crack growth in marble

    NASA Astrophysics Data System (ADS)

    Nara, Yoshitaka; Nishida, Yuki; Toshinori, Ii; Harui, Tomoki; Tanaka, Mayu; Kashiwaya, Koki

    2016-04-01

    It is essential to study time-dependent deformation and fracturing in various rock materials to prevent natural hazards related to the failure of a rock mass. In addition, information of time-dependent fracturing is essential to ensure the long-term stability of a rock mass surrounding various structures. Subcritical crack growth is one of the main causes of time-dependent fracturing in rock. It is known that subcritical crack growth is influenced by not only stress but also surrounding environment. Studies of subcritical crack growth have been widely conducted for silicate rocks such as igneous rocks and sandstones. By contrast, information of subcritical crack growth in carbonate rocks is not enough. Specifically, influence of surrounding environment on subcritical crack growth in carbonate rock should be clarified to ensure the long-term stability of a rock mass. In this study, subcritical crack growth in marble was investigated. Especially, the influence of the temperature, relative humidity and water on subcritical crack growth in marble is investigated. As rock samples, marbles obtained in Skopje-City in Macedonia and Carrara-City in Italy were used. To measure subcritical crack growth, we used the load relaxation method of the double-torsion (DT) test. All measurements by DT test were conducted under controlled temperature and relative humidity. For both marbles, it was shown that the crack velocity in marble in air increased with increasing relative humidity at a constant temperature. Additionally, the crack velocity in water was much higher than that in air. It was also found that the crack velocity increased with increasing temperature. It is considered that temperature and water have significant influences on subcritical crack growth in marble. For Carrara marble in air, it was recognized that the value of subcritical crack growth index became low when the crack velocity was higher than 10-4 m/s. This is similar to Region II of subcritical crack growth

  8. Fabrication of oxide dispersion strengthened ferritic clad fuel pins

    SciTech Connect

    Zirker, L.R. ); Bottcher, J.H. ); Shikakura, S. ); Tsai, C.L. . Dept. of Welding Engineering); Hamilton, M.L. )

    1991-01-01

    A resistance butt welding procedure was developed and qualified for joining ferritic fuel pin cladding to end caps. The cladding are INCO MA957 and PNC ODS lots 63DSA and 1DK1, ferritic stainless steels strengthened by oxide dispersion, while the end caps are HT9 a martensitic stainless steel. With adequate parameter control the weld is formed without a residual melt phase and its strength approaches that of the cladding. This welding process required a new design for fuel pin end cap and weld joint. Summaries of the development, characterization, and fabrication processes are given for these fuel pins. 13 refs., 6 figs., 1 tab.

  9. Increasing corrosion resistance of carbon steels by surface laser cladding

    NASA Astrophysics Data System (ADS)

    Polsky, V. I.; Yakushin, V. L.; Dzhumaev, P. S.; Petrovsky, V. N.; Safonov, D. V.

    2016-04-01

    This paper presents results of investigation of the microstructure, elemental composition and corrosion resistance of the samples of low-alloy steel widely used in the engineering, after the application of laser cladding. The level of corrosion damage and the corrosion mechanism of cladded steel samples were established. The corrosion rate and installed discharge observed at the total destruction of cladding were obtained. The regularities of structure formation in the application of different powder compositions were obtained. The optimal powder composition that prevents corrosion of samples of low-carbon low-alloy steel was established.

  10. Innovations in laser cladding and direct metal deposition

    NASA Astrophysics Data System (ADS)

    Brückner, Frank; Nowotny, Steffen; Leyens, Christoph

    2012-03-01

    The present paper reviews recent progress in productivity, precision and quality of laser-based cladding and additive layer manufacturing. Recently, we have demonstrated the great benefits obtained from induction assisted laser cladding. This novel hybrid technology combines high deposition rates with excellent cladding properties. Laser-based direct metal deposition is a novel concept for the fabrication of components and repair as well as geometrical surface modifications. Newly developed nozzle design allows focused powder spots to generate wall thicknesses of about 30 μm. An in-depth understanding of the processes and the resulting materials properties is key for the development of technically viable and economically reasonable customized solutions.

  11. Oxidation performance of platinum-clad Mo-47Re alloy

    NASA Technical Reports Server (NTRS)

    Clark, Ronald K.; Wallace, Terryl A.

    1994-01-01

    The alloy Mo-47Re has favorable mechanical properties at temperatures above 1400 C, but it undergoes severe oxidation when used in air with no protective coating. To shield the alloy from oxidation, platinum cladding has been evaluated. The unprotected alloy undergoes catastrophic oxidation under static and dynamic oxidation conditions. The platinum cladding provides good protection from static and dynamic oxidation for moderate times at 1260 C. Samples tested for longer times under static oxidation conditions experienced severe oxidation. The data suggest that oxidation results from the transport of oxygen through the grain boundaries and through the pinhole defects of the platinum cladding.

  12. Cracks and Lines

    NASA Technical Reports Server (NTRS)

    2004-01-01

    6 June 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) picture shows an odd area of the south polar region that has sets of fine, nearly parallel lines running from the northeast (upper right) toward southwest (lower left) and a darker, wider set of cracks with a major trend running almost perpendicular to the finer lines. The appearance of these features is enhanced by seasonal frost. Dark areas have no frost, bright areas still have frozen carbon dioxide ice. In summer, the ice would be gone and the cracks and lines less obvious when viewed from orbit. Although unknown, wind might be responsible for forming the fine set of lines, and perhaps freeze-thaw cycles of ground ice or structural deformation would have contributed to formation of the wider cracks. The image is located near 85.0oS, 324.0oW, and covers an area about 1.5 km (nearly 1 mi) across. The scene is illuminated by sunlight from the upper left.

  13. Effect of grain orientation on aluminum relocation at incipient melt conditions

    DOE PAGESBeta

    Yilmaz, Nadir; Vigil, Francisco M.; Vigil, Miquela S.; Branam, Robert; Tolendino, Greg; Gill, Walt; Burl Donaldson, A.

    2015-09-01

    Aluminum is commonly used for structural applications in the aerospace industry because of its high strength in relation to its weight. It is necessary to understand the mechanical response of aluminum structures at elevated temperatures such as those experienced in a fire. Additionally, aluminum alloys exhibit many complicated behaviors that require further research and understanding, such as aluminum combustion, oxide skin formation and creep behavior. This paper discusses the effect of grain orientation on aluminum deformation subjected to heating at incipient melt conditions. Experiments were conducted by applying a vertical compressive force to aluminum alloy 7075 block test specimens. Furthermore,more » compression testing was done on test specimens with the applied load on the long transverse and short transverse orientations. Our results showed that the grain orientation significantly influences aluminum’s strength and mode of failure.« less

  14. Effect of grain orientation on aluminum relocation at incipient melt conditions

    SciTech Connect

    Yilmaz, Nadir; Vigil, Francisco M.; Vigil, Miquela S.; Branam, Robert; Tolendino, Greg; Gill, Walt; Burl Donaldson, A.

    2015-09-01

    Aluminum is commonly used for structural applications in the aerospace industry because of its high strength in relation to its weight. It is necessary to understand the mechanical response of aluminum structures at elevated temperatures such as those experienced in a fire. Additionally, aluminum alloys exhibit many complicated behaviors that require further research and understanding, such as aluminum combustion, oxide skin formation and creep behavior. This paper discusses the effect of grain orientation on aluminum deformation subjected to heating at incipient melt conditions. Experiments were conducted by applying a vertical compressive force to aluminum alloy 7075 block test specimens. Furthermore, compression testing was done on test specimens with the applied load on the long transverse and short transverse orientations. Our results showed that the grain orientation significantly influences aluminum’s strength and mode of failure.

  15. Kinetics of elementary processes relevant to incipient soot formation. Final technical report

    SciTech Connect

    Lin, M.C.

    1998-03-09

    In order to better understand the mechanism of soot formation (one of the most challenging problems in the study of hydrocarbon combustion chemistry), reliable rate constants for the key reaction steps involved in the formation and polymerization of aromatic hydrocarbons in the inception stage are required for kinetic modeling. In this DOE sponsored work, the authors have developed three new experimental methods: cavity ring-down (CRD) spectrometry, pyrolysis/Fourier transform infrared spectrometry (p/FTIRS) and pulsed laser photolysis/mass spectrometry (PLP/MS) for kinetic measurements of C{sub 6}H{sub 5} reactions pivotal to incipient soot formation chemistry. In addition, the authors have also carried out ab initio molecular orbital (MO) calculations for several key elementary combustion reactions relevant to soot formation. The results are briefly summarized in the report using selected examples for more detailed discussion. 84 refs.

  16. Atomic short-range order and incipient long-range order in high-entropy alloys

    NASA Astrophysics Data System (ADS)

    Singh, Prashant; Smirnov, A. V.; Johnson, D. D.

    2015-06-01

    Within density-functional theory, we apply an electronic-structure-based thermodynamic theory to calculate short-ranged order (SRO) in homogeneously disordered substitutional N -component alloys, and its electronic origin. Using the geometric properties of an (N -1 ) simplex that describes the Gibbs (compositional) space, we derive the analytic transform of the SRO eigenvectors that provides a unique description of high-temperature SRO in N -component alloys and the incipient low-temperature long-range order. We apply the electronic-based thermodynamic theory and the new general analysis to ternaries (A 1 Cu-Ni-Zn and A 2 Nb-Al-Ti) for validation, and then to quinary Al-Co-Cr-Fe-Ni high-entropy alloys for predictive assessment.

  17. Structural disorder and incipient localization effects in NbC thin films

    NASA Astrophysics Data System (ADS)

    Kuwasawa, Yoshinori; Hino, Shoujun; Nakano, Shigeru; Koyama, Atsushi; Matsushita, Tadashi

    1990-08-01

    Films used in this study were classified into three groups, metallic, weak nonmetallic and nonmetallic from the measured results of the temperature dependence of the resistivity and superconducting transition temperature. The results of X-ray diffraction and photoelectron spectroscopy showed that films were NbC of single phase NaCl type structure with vacancies and oxygen atoms at carbon sites.For the nonmetallic type samples, three different Nb-Nb atomic distances were observed in the fluorescence EXAFS mesurements, one of which was much longer than that of bulk NbC. It can be said that such large distortions in lattice and Nb-chain are responsible for the incipient locallization effect.

  18. Incipient Social Groups: An Analysis via In-Vivo Behavioral Tracking.

    PubMed

    Halberstadt, Jamin; Jackson, Joshua Conrad; Bilkey, David; Jong, Jonathan; Whitehouse, Harvey; McNaughton, Craig; Zollmann, Stefanie

    2016-01-01

    Social psychology is fundamentally the study of individuals in groups, yet there remain basic unanswered questions about group formation, structure, and change. We argue that the problem is methodological. Until recently, there was no way to track who was interacting with whom with anything approximating valid resolution and scale. In the current study we describe a new method that applies recent advances in image-based tracking to study incipient group formation and evolution with experimental precision and control. In this method, which we term "in vivo behavioral tracking," we track individuals' movements with a high definition video camera mounted atop a large field laboratory. We report results of an initial study that quantifies the composition, structure, and size of the incipient groups. We also apply in-vivo spatial tracking to study participants' tendency to cooperate as a function of their embeddedness in those crowds. We find that participants form groups of seven on average, are more likely to approach others of similar attractiveness and (to a lesser extent) gender, and that participants' gender and attractiveness are both associated with their proximity to the spatial center of groups (such that women and attractive individuals are more likely than men and unattractive individuals to end up in the center of their groups). Furthermore, participants' proximity to others early in the study predicted the effort they exerted in a subsequent cooperative task, suggesting that submergence in a crowd may predict social loafing. We conclude that in vivo behavioral tracking is a uniquely powerful new tool for answering longstanding, fundamental questions about group dynamics. PMID:27007952

  19. Incipient Social Groups: An Analysis via In-Vivo Behavioral Tracking

    PubMed Central

    Halberstadt, Jamin; Jackson, Joshua Conrad; Bilkey, David; Jong, Jonathan; Whitehouse, Harvey; McNaughton, Craig; Zollmann, Stefanie

    2016-01-01

    Social psychology is fundamentally the study of individuals in groups, yet there remain basic unanswered questions about group formation, structure, and change. We argue that the problem is methodological. Until recently, there was no way to track who was interacting with whom with anything approximating valid resolution and scale. In the current study we describe a new method that applies recent advances in image-based tracking to study incipient group formation and evolution with experimental precision and control. In this method, which we term “in vivo behavioral tracking,” we track individuals’ movements with a high definition video camera mounted atop a large field laboratory. We report results of an initial study that quantifies the composition, structure, and size of the incipient groups. We also apply in-vivo spatial tracking to study participants’ tendency to cooperate as a function of their embeddedness in those crowds. We find that participants form groups of seven on average, are more likely to approach others of similar attractiveness and (to a lesser extent) gender, and that participants’ gender and attractiveness are both associated with their proximity to the spatial center of groups (such that women and attractive individuals are more likely than men and unattractive individuals to end up in the center of their groups). Furthermore, participants’ proximity to others early in the study predicted the effort they exerted in a subsequent cooperative task, suggesting that submergence in a crowd may predict social loafing. We conclude that in vivo behavioral tracking is a uniquely powerful new tool for answering longstanding, fundamental questions about group dynamics. PMID:27007952

  20. Modelling the interactions between grain, hydraulics, and local topography to understand the impact on incipient motion

    NASA Astrophysics Data System (ADS)

    von Boetticher, Albrecht; Turowski, Jens M.

    2013-04-01

    Sediment transport plays the key role in the forming fluvial systems, and it has become a major issue for the management and operation of hydropower plants and shipping channels as well as for the understanding of flooding hazards. The interactions between grain, hydraulics, and local topography are complicated, and it is difficult to quantify them in the laboratory, in the field, or in simple theoretical models based on two-dimensional force balances. In many theoretical models of incipient motion, grains are assumed to have simple geometrical shapes (usually spheres), despite the fact that in the real world grain shapes can vary from platy to elongated to symmetrical, and from angular to rounded. In addition, grain shape may influence protrusion and angle of repose for a grain sitting in the same pocket, and both local grain environment and grain shape in turn influence the local flow field around the grain, and thus the forces acting on it. In this project a numerical model will be developed that is capable of resolving the interaction between the grain and the flow. The model will be used to study the influence of the grain environment and grain shape on initiation of motion. The aims of the project are three-fold. First, we want to develop a numerical model that is adapted to and can efficiently deal with the specific problems occurring in the study of initiation of bedload sediment motion in streams. Second, we want to identify which of the parameters describing grain shape and local topography (e.g., protrusion, angle of repose, grain angularity) dominantly influence the initiation of motion of an individual grain. Third, we want to clarify when and where simple analytical approximations of the sort that have been used in many previous models are applicable. In three tasks we will develop the model, validate it against laboratory and field data, and perform a number of systematic numerical experiments to better understand incipient motion.

  1. Investigation of Cracks Found in Helicopter Longerons

    NASA Technical Reports Server (NTRS)

    Newman, John A.; Baughman, James M.; Wallace, Terryl A.

    2009-01-01

    Four cracked longerons, containing a total of eight cracks, were provided for study. Cracked regions were cut from the longerons. Load was applied to open the cracks, enabling crack surface examination. Examination revealed that crack propagation was driven by fatigue loading in all eight cases. Fatigue crack initiation appears to have occurred on the top edge of the longerons near geometric changes that affect component bending stiffness. Additionally, metallurigical analysis has revealed a local depletion in alloying elements in the crack initiation regions that may be a contributing factor. Fatigue crack propagation appeared to be initially driven by opening-mode loading, but at a crack length of approximately 0.5 inches (12.7 mm), there is evidence of mixed-mode crack loading. For the longest cracks studied, shear-mode displacements destroyed crack-surface features of interest over significant portions of the crack surfaces.

  2. Effect of a Nutritional Metabolism Disrupter on the Development of Incipient Colonies of the Formosan Subterranean Termite (Isoptera:Rhinotermitidae)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Incipient colonies ofthe Formosan subtelTanean termite were ionued by pairing reproductives in plastic dishes conlaining either untreated bait or bait treated with a composition of oxypurinol and xanthine. This composition, termed a nutritional metabolism disrupter (NMD), causes a shutdown of nitrog...

  3. Application of the Billet Casting Method to Determine the Onset of Incipient Melting of 319 Al Alloy Engine Blocks

    NASA Astrophysics Data System (ADS)

    Lombardi, A.; Ravindran, C.; MacKay, R.

    2015-06-01

    The increased use of Al for automotive applications has resulted from the need to improve vehicle fuel efficiency. Aluminum alloy engine blocks fulfil the need of lightweighting. However, there are many challenges associated with thermo-mechanical mismatch between Al and the gray cast iron cylinder liners, which result in large tensile residual stress along the cylinder bores. This requires improced mechanical properties in this region to prevent premature engine failure. In this study, replicating billet castings were used to simulate the engine block solution heat treatment process and determine the onset of incipient melting. Microstructural changes during heat treatment were assessed with SEM and EDX, while thermal analysis was carried out using differential scanning calorimetry. The results suggest that solution heat treatment at 500 °C was effective in dissolving secondary phase particles, while solutionizing at 515 or 530 °C caused incipient melting of Al2Cu and Al5Mg8Cu2Si6. Incipient melting caused the formation ultra-fine eutectic clusters consisting of Al, Al2Cu, and Al5Mg8Cu2Si6 on quenching. In addition, DSC analysis found that incipient melting initiated at 507 °C for all billets, although the quantity of local melting reduced with microstructural refinement as evidenced by smaller endothermic peaks and energy absorption. The results from this study will assist in improving engine block casting integrity and process efficiency.

  4. Incipient-signature identification of mechanical anomalies in a ship-borne satellite antenna system using an ensemble multiwavelet

    NASA Astrophysics Data System (ADS)

    He, Shuilong; Zi, Yanyang; Chen, Jinglong; Zhao, Chenlu; Chen, Binqiang; Yuan, Jing; He, Zhengjia

    2014-10-01

    The instrumented tracking and telemetry ship with a ship-borne satellite antenna (SSA) is the critical device to ensure high quality of space exploration work. To effectively detect mechanical anomalies that can lead to unexpected downtime of the SSA, an ensemble multiwavelet (EM) is presented for identifying the anomaly related incipient-signatures within the measured dynamic signals. Rather than using a predetermined basis as in a conventional multiwavelet, an EM optimizes the matching basis which satisfactorily adapts to the anomaly related incipient-signatures. The construction technique of an EM is based on the conjunction of a two-scale similarity transform (TST) and lifting scheme (LS). For the technique above, the TST improves the regularity by increasing the approximation order of multiscaling functions, while subsequently the LS enhances the smoothness and localizability via utilizing the vanishing moment of multiwavelet functions. Moreover, combining the Hilbert transform with EM decomposition, we identify the incipient-signatures induced by the mechanical anomalies from the measured dynamic signals. A numerical simulation and two successful applications of diagnosis cases (a planetary gearbox and a roller bearing) demonstrate that the proposed technique is capable of dealing with the challenging incipient-signature identification task even though spectral complexity, as well as the strong amplitude/frequency modulation effect, is present in the dynamic signals.

  5. Failure of pheromone traps in detecting incipient populations of boll weevils (Coleoptera: Curculionidae): Investigation of two potential contributing factors

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Progress towards complete eradication of the boll weevil has been delayed in some areas of Texas due to the inconsistent performance of pheromone traps in detecting incipient weevil populations. In 2008 substantial infestations of boll weevils, Anthonomus grandis Boheman, were detected in several c...

  6. Automatic crack growth tracking of bimaterial interface cracks

    NASA Technical Reports Server (NTRS)

    Yehia, Nabil A. B.; Shephard, Mark S.

    1988-01-01

    The propagation process of an interfacial crack in composite material is studied using the modified maximum dilatational strain energy density criterion, NT-criterion. Some necessary assumptions have been adopted to facilitate the use of the NT-criterion in this case. The stress intensity factors at the crack tip are extracted from the complex displacement field and finite element results. A simple algorithm for automatic crack propagation is presented with an illustrative example.

  7. View of building 11050, showing metal clad addition on east ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View of building 11050, showing metal clad addition on east elevation, looking southwest. - Naval Ordnance Test Station Inyokern, China Lake Pilot Plant, Machine Shop, C Street, China Lake, Kern County, CA

  8. Chalcogenide optical microwires cladded with fluorine-based CYTOP.

    PubMed

    Li, Lizhu; Abdukerim, Nurmemet; Rochette, Martin

    2016-08-22

    We demonstrate optical transmission results of highly nonlinear As2Se3 optical microwires cladded with fluorine-based CYTOP, and compare them with microwires cladded with typical hydrogen-based polymers. In the linear optics regime, the CYTOP-cladded microwire transmits light in the spectral range from 1.3 µm up to >2.5 µm without trace of absorption peaks such as those observed using hydrogen-based polymer claddings. The microwire is also pumped in the nonlinear optics regime, showing multiple-orders of four-wave mixing and supercontinuum generation spanning from 1.0 µm to >4.3 µm. We conclude that with such a broadband transparency and high nonlinearity, the As2Se3-CYTOP microwire is an appealing solution for nonlinear optical processing in the mid-infrared. PMID:27557174

  9. Liquid-core, liquid-cladding photonic crystal fibers.

    PubMed

    De Matos, Christiano J; Cordeiro, Cristiano M B; Dos Santos, Eliane M; Ong, Jackson S; Bozolan, Alexandre; Brito Cruz, Carlos H

    2007-09-01

    We experimentally demonstrate a simple and novel technique to simultaneously insert a liquid into the core of a hollow-core photonic crystal fiber (PCF) and a different liquid into its cladding. The result is a liquid-core, liquid-cladding waveguide in which the two liquids can be selected to yield specific guidance characteristics. As an example, we tuned the core-cladding index difference by proper choice of the inserted liquids to obtain control over the number of guided modes. Single-mode guidance was achieved for a particular choice of liquids. We also experimentally and theoretically investigated the nature of light confinement and observed the transition from photonic bandgap to total internal reflection guidance both with the core-cladding index contrast and with the PCF length. PMID:19547475

  10. Composite polymer: Glass edge cladding for laser disks

    DOEpatents

    Powell, H.T.; Wolfe, C.A.; Campbell, J.H.; Murray, J.E.; Riley, M.O.; Lyon, R.E.; Jessop, E.S.

    1987-11-02

    Large neodymium glass laser disks for disk amplifiers such as those used in the Nova laser require an edge cladding which absorbs at 1 micrometer. This cladding prevents edge reflections from causing parasitic oscillations which would otherwise deplete the gain. Nova now utilizes volume-absorbing monolithic-glass claddings which are fused at high temperature to the disks. These perform quite well but are expensive to produce. Absorbing glass strips are adhesively bonded to the edges of polygonal disks using a bonding agent whose index of refraction matches that of both the laser and absorbing glass. Optical finishing occurs after the strips are attached. Laser disks constructed with such claddings have shown identical gain performance to the previous Nova disks and have been tested for hundreds of shots without significant degradation. 18 figs.

  11. Composite polymer-glass edge cladding for laser disks

    DOEpatents

    Powell, Howard T.; Riley, Michael O.; Wolfe, Charles R.; Lyon, Richard E.; Campbell, John H.; Jessop, Edward S.; Murray, James E.

    1989-01-01

    Large neodymium glass laser disks for disk amplifiers such as those used in the Nova laser require an edge cladding which absorbs at 1 micrometer. This cladding prevents edge reflections from causing parasitic oscillations which would otherwise deplete the gain. Nova now utilizes volume-absorbing monolithic-glass claddings which are fused at high temperature to the disks. These perform quite well but are expensive to produce. Absorbing glass strips are adhesively bonded to the edges of polygonal disks using a bonding agent whose index of refraction matches that of both the laser and absorbing glass. Optical finishing occurs after the strips are attached. Laser disks constructed with such claddings have shown identical gain performance to the previous Nova disks and have been tested for hundreds of shots without significant degradation.

  12. High Temperature Steam Corrosion of Cladding for Nuclear Applications: Experimental

    SciTech Connect

    McHugh, Kevin M; Garnier, John E; Sergey Rashkeev; Michael V. Glazoff; George W. Griffith; Shannong M. Bragg-Sitton

    2013-01-01

    Stability of cladding materials under off-normal conditions is an important issue for the safe operation of light water nuclear reactors. Metals, ceramics, and metal/ceramic composites are being investigated as substitutes for traditional zirconium-based cladding. To support down-selection of these advanced materials and designs, a test apparatus was constructed to study the onset and evolution of cladding oxidation, and deformation behavior of cladding materials, under loss-of-coolant accident scenarios. Preliminary oxidation tests were conducted in dry oxygen and in saturated steam/air environments at 1000OC. Tube samples of Zr-702, Zr-702 reinforced with 1 ply of a ß-SiC CMC overbraid, and sintered a-SiC were tested. Samples were induction heated by coupling to a molybdenum susceptor inside the tubes. The deformation behavior of He-pressurized tubes of Zr-702 and SiC CMC-reinforced Zr-702, heated to rupture, was also examined.

  13. Asperities, Crack Front Waves and Crack Self Healing

    NASA Astrophysics Data System (ADS)

    Rajak, Pankaj; Kalia, Rajiv; Nakano, Aiichiro; Vashishta, Priya

    We have performed petascale simulations to study nanomaterial systems capable of sensing and repairing damage in high temperature/high pressure operating conditions. The system we have studied is a ceramic nanocomposite consisting of silicon carbide/silicon dioxide core/shell nanoparticles embedded in alumina. We observe that the interaction of the crack with core/shell asperities gives rise to crack-front waves. We also study crack healing by diffusion of silica into the crack as a function of nanoparticle size and inter-particle distance. Our results are well supported by experimental observations.

  14. On the Crack Bifurcation and Fanning of Crack Growth Data

    NASA Technical Reports Server (NTRS)

    Forman, Royce G.; Zanganeh, Mohammad

    2015-01-01

    Crack growth data obtained from ASTM load shedding method for different R values show some fanning especially for aluminum alloys. It is believed by the authors and it has been shown before that the observed fanning is due to the crack bifurcation occurs in the near threshold region which is a function of intrinsic properties of the alloy. Therefore, validity of the ASTM load shedding test procedure and results is confirmed. However, this position has been argued by some experimentalists who believe the fanning is an artifact of the test procedure and thus the obtained results are invalid. It has been shown that using a special test procedure such as using compressively pre-cracked specimens will eliminate the fanning effect. Since not using the fanned data fit can result in a significantly lower calculated cyclic life, design of a component, particularly for rotorcraft and propeller systems will considerably be impacted and therefore this study is of paramount importance. In this effort both test procedures i.e. ASTM load shedding and the proposed compressive pre-cracking have been used to study the fatigue crack growth behavior of compact tension specimens made of aluminum alloy 2524-T3. Fatigue crack growth paths have been closely observed using SEM machines to investigate the effects of compression pre-cracking on the crack bifurcation behavior. The results of this study will shed a light on resolving the existing argument by better understanding of near threshold fatigue crack growth behavior.

  15. Explosion Clad for Upstream Oil and Gas Equipment

    SciTech Connect

    Banker, John G.; Massarello, Jack; Pauly, Stephane

    2011-01-17

    Today's upstream oil and gas facilities frequently involve the combination of high pressures, high temperatures, and highly corrosive environments, requiring equipment that is thick wall, corrosion resistant, and cost effective. When significant concentrations of CO{sub 2} and/or H{sub 2}S and/or chlorides are present, corrosion resistant alloys (CRA) can become the material of choice for separator equipment, piping, related components, and line pipe. They can provide reliable resistance to both corrosion and hydrogen embrittlement. For these applications, the more commonly used CRA's are 316L, 317L and duplex stainless steels, alloy 825 and alloy 625, dependent upon the application and the severity of the environment. Titanium is also an exceptional choice from the technical perspective, but is less commonly used except for heat exchangers. Explosion clad offers significant savings by providing a relatively thin corrosion resistant alloy on the surface metallurgically bonded to a thick, lower cost, steel substrate for the pressure containment. Developed and industrialized in the 1960's the explosion cladding technology can be used for cladding the more commonly used nickel based and stainless steel CRA's as well as titanium. It has many years of proven experience as a reliable and highly robust clad manufacturing process. The unique cold welding characteristics of explosion cladding reduce problems of alloy sensitization and dissimilar metal incompatibility. Explosion clad materials have been used extensively in both upstream and downstream oil, gas and petrochemical facilities for well over 40 years. The explosion clad equipment has demonstrated excellent resistance to corrosion, embrittlement and disbonding. Factors critical to insure reliable clad manufacture and equipment design and fabrication are addressed.

  16. Double-clad nuclear-fuel safety rod

    DOEpatents

    McCarthy, W.H.; Atcheson, D.B.

    1981-12-30

    A device for shutting down a nuclear reactor during an undercooling or overpower event, whether or not the reactor's scram system operates properly. This is accomplished by double-clad fuel safety rods positioned at various locations throughout the reactor core, wherein melting of a secondary internal cladding of the rod allows the fuel column therein to shift from the reactor core to place the reactor in a subcritical condition.

  17. Explosion Clad for Upstream Oil and Gas Equipment

    NASA Astrophysics Data System (ADS)

    Banker, John G.; Massarello, Jack; Pauly, Stephane

    2011-01-01

    Today's upstream oil and gas facilities frequently involve the combination of high pressures, high temperatures, and highly corrosive environments, requiring equipment that is thick wall, corrosion resistant, and cost effective. When significant concentrations of CO2 and/or H2S and/or chlorides are present, corrosion resistant alloys (CRA) can become the material of choice for separator equipment, piping, related components, and line pipe. They can provide reliable resistance to both corrosion and hydrogen embrittlement. For these applications, the more commonly used CRA's are 316L, 317L and duplex stainless steels, alloy 825 and alloy 625, dependent upon the application and the severity of the environment. Titanium is also an exceptional choice from the technical perspective, but is less commonly used except for heat exchangers. Explosion clad offers significant savings by providing a relatively thin corrosion resistant alloy on the surface metallurgically bonded to a thick, lower cost, steel substrate for the pressure containment. Developed and industrialized in the 1960's the explosion cladding technology can be used for cladding the more commonly used nickel based and stainless steel CRA's as well as titanium. It has many years of proven experience as a reliable and highly robust clad manufacturing process. The unique cold welding characteristics of explosion cladding reduce problems of alloy sensitization and dissimilar metal incompatibility. Explosion clad materials have been used extensively in both upstream and downstream oil, gas and petrochemical facilities for well over 40 years. The explosion clad equipment has demonstrated excellent resistance to corrosion, embrittlement and disbonding. Factors critical to insure reliable clad manufacture and equipment design and fabrication are addressed.

  18. Cladding for transverse-pumped solid-state laser

    NASA Technical Reports Server (NTRS)

    Byer, Robert L. (Inventor); Fan, Tso Y. (Inventor)

    1989-01-01

    In a transverse pumped, solid state laser, a nonabsorptive cladding surrounds a gain medium. A single tranverse mode, namely the Transverse Electromagnetic (TEM) sub 00 mode, is provided. The TEM sub 00 model has a cross sectional diameter greater than a transverse dimension of the gain medium but less than a transverse dimension of the cladding. The required size of the gain medium is minimized while a threshold for laser output is lowered.

  19. Material development for thermionic fuel-cladding systems.

    NASA Technical Reports Server (NTRS)

    Yang, L.; Hudson, R. G.; Johnson, H.; Horner, H.; Allen, D. T.

    1972-01-01

    Fuel-cladding systems capable of maintaining stable dimension and electron emission characteristics at high temperatures under irradiation are essential to the successful operation of nuclear thermionic power sources. Studies regarding two possible systems, involving tungsten clad uranium carbide and uranium oxide, are considered. Out-of-pile developmental efforts and the in-pile evaluation results for the two systems are described. Prototypical emitters have been tested for 8000 hours for the carbide system and 4000 hours for the oxide system.

  20. Optimization of Laser Cladding for Al Coating Production

    NASA Astrophysics Data System (ADS)

    Riveiro, A.; Mejías, A.; Lusquiños, F.; del Val, J.; Comesaña, R.; Pardo, J.; Pou, J.

    The production of aluminum based coatings on a stainless steel (AISI 304) substrate by side laser cladding, and using a high power diode laser was experimentally studied. Relevant processing parameters were found and correlations between them were determined. Furthermore, the influence of the processing parameters on the costs associated to the process was examined. These relationships can be used as a guideline for the selection of proper processing parameters for laser cladding of this kind of materials.

  1. Zircoloy Cladding Oxidation Simulation for LWR under LOCA Conditions

    Energy Science and Technology Software Center (ESTSC)

    2003-04-25

    PRECIP-2 simulates zircaloy cladding oxidation under LOCA conditions of LWR’s. The code calculates oxygen concentration distribution across the cladding wall by solving the diffusion equation with moving boundary conditions, taking into account the structure change of the beta— phase, i.e. alpha precipitation during the cooling period. The code also predicts total oxygen uptake, thicknesses of alpha, beta and oxide layers.

  2. Neutron-absorbing amorphous alloys for cladding coatings

    NASA Astrophysics Data System (ADS)

    Sevryukov, O. N.; Fedotov, V. T.; Polyansky, A. A.

    2016-04-01

    This paper shows developed compositions of neutron-absorbing cladding alloys based on nickel and containing such elements as B, Gd, Hf, and Mn. The techniques for application of coatings from these alloys on the surface of structural steels have been improved. It has been shown that the amorphous neutron-absorbing coating is more uniform than the crystalline one. The experimental data on the adhesion of cladding coatings with a steel substrate and their neutron-absorbing capacity have been obtained.

  3. Supercontinuum Generation in a Microstructured Fiber with an Irregular Cladding

    NASA Astrophysics Data System (ADS)

    Minkovich, V. P.; Sotsky, A. B.; Vaca Pereira G., M.; Dzen, I. S.; Sotskaya, L. I.

    2016-05-01

    A broad-band supercontinuum generation was obtained at excitation of a microstructured optical fiber with an irregular cladding by femtosecond laser pulses. To explain the experimental data, calculations of the mode characteristics of microstructured fibers were performed. It was shown that the creation of air channels with different radii in the fiber cladding makes it possible to involve both the fundamental and high fiber modes in the supercontinuum generation that helps to increase the width of the generation spectrum.

  4. Landscape mulches and termite nutritional ecology: growth and survival of incipient colonies of Coptotermes formosanus (Isoptera: Rhinotermitidae).

    PubMed

    Sun, Jian-Zhong

    2007-04-01

    Alate swarms are one of the major visible signs of the expansion of the Formosan subterranean termite, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae), in an area. Successful establishment of an incipient colony is thought to mainly rely on available food resources and moisture. The large-scale use of tree-based mulches in landscapes may inadvertently contribute to local establishment and growth of C. formosanus colonies. This research investigated the nutritional ecology of incipient colonies of C. formosanus feeding on seven tree-based, weathered, and nonweathered landscape mulches: pine straw, pine bark, cedar wood, water oak, eucalyptus, cypress, and melaleuca. Incipient colonies of C. formosanus feeding on pine straw, either weathered or nonweathered, produced significantly more progeny over the course of 1-yr feeding than colonies feeding on the other mulches tested. Regardless of weathered or not, the incipient colonies feeding on pine straw, eucalyptus, bald cypress, and water oak mulches had significantly greater survival rates after 360 d (53-77%) than colonies feeding on the other mulches tested (0-13%), but colonies feeding on nonweathered water oak had significantly lower survival (8%) than those kept on weathered water oak (58%). Colony fitness values were significantly different between the weathering treatment groups and among the different types of mulches. With regard to colony growth characteristics, three distinct growth patterns were identified: a high number of progeny (>100) with high colony survival rate (>50%), a medium number of progeny (12-50) with high colony survival rate (>50%), and a small number of progeny (0-10) with low colony survival rate (<5%). These findings suggest that different types of mulch substrates could significantly impact the nutritional ecology of the founding pairs and the successful establishment of incipient colonies during the swarming season. PMID:17461078

  5. Preventing Cracking of Anodized Coatings

    NASA Technical Reports Server (NTRS)

    He, Charles C.; Heslin, Thomas M.

    1995-01-01

    Anodized coatings have been used as optical and thermal surfaces in spacecraft. Particulate contamination from cracked coatings is a concern for many applications. The major cause for the cracking is the difference in the coefficient of thermal expansion between the oxide coatings and the aluminum substrate. The loss of water when the coating is exposed to a vacuum also could induce cracking of the coating. Hot-water sealing was identified as the major cause for the cracking of the coatings because of the large temperature change when the parts were immersed in boiling water and the water was absorbed in the coating. when the hot-water sealing process was eliminated, the cracking resistance of the anodized coatings was greatly improved. Also, it was found that dyed black coatings were more susceptible than clear coatings to cracking during thermo-vacuum cyclings.

  6. Fatigue-Crack-Tip Locator

    NASA Technical Reports Server (NTRS)

    Namkung, Min; Clendenin, C. Gerald; Wincheski, Buzz; Fulton, James P.; Todhunter, Ronald G.; Simpson, John W.

    1994-01-01

    Fatigue-testing system includes automated subsystem continuously tracking location of fatigue-crack tip in metal or other highly electrically conductive specimen. Fatigue-crack-tip-locating subsystem also searches specimen to find initial fatigue crack and its tip and to trace out hidden fatigue cracks and other flaws inside specimen. Subsystem operates under overall control of personal computer, which also controls load frame applying prescribed cyclic stresses to specimen. Electromagnetic flaw detector based on eddy-current principle scanned over surface of specimen. Flaw detector described in "Electromagnetic Flaw Detector Is Easier To Use" (LAR-15046). System provides automated control and monitoring of fatigue experiments, saving time for researchers and enabling experiments to run unattended 24 hours a day. All information on crack-tip trajectories and rates of growth of cracks recorded automatically, so researchers have access to more information.

  7. Real-time laser cladding control with variable spot size

    NASA Astrophysics Data System (ADS)

    Arias, J. L.; Montealegre, M. A.; Vidal, F.; Rodríguez, J.; Mann, S.; Abels, P.; Motmans, F.

    2014-03-01

    Laser cladding processing has been used in different industries to improve the surface properties or to reconstruct damaged pieces. In order to cover areas considerably larger than the diameter of the laser beam, successive partially overlapping tracks are deposited. With no control over the process variables this conduces to an increase of the temperature, which could decrease mechanical properties of the laser cladded material. Commonly, the process is monitored and controlled by a PC using cameras, but this control suffers from a lack of speed caused by the image processing step. The aim of this work is to design and develop a FPGA-based laser cladding control system. This system is intended to modify the laser beam power according to the melt pool width, which is measured using a CMOS camera. All the control and monitoring tasks are carried out by a FPGA, taking advantage of its abundance of resources and speed of operation. The robustness of the image processing algorithm is assessed, as well as the control system performance. Laser power is decreased as substrate temperature increases, thus maintaining a constant clad width. This FPGA-based control system is integrated in an adaptive laser cladding system, which also includes an adaptive optical system that will control the laser focus distance on the fly. The whole system will constitute an efficient instrument for part repair with complex geometries and coating selective surfaces. This will be a significant step forward into the total industrial implementation of an automated industrial laser cladding process.

  8. Laser cladding: repairing and manufacturing metal parts and tools

    NASA Astrophysics Data System (ADS)

    Sexton, Leo

    2003-03-01

    Laser cladding is presently used to repair high volume aerospace, automotive, marine, rail or general engineering components where excessive wear has occurred. It can also be used if a one-off high value component is either required or has been accidentally over-machined. The ultimate application of laser cladding is to build components up from nothing, using a laser cladding system and a 3D CAD drawing of the component. It is thus emerging that laser cladding can be classified as a special case of Rapid Prototyping (RP). Up to this point in time RP was seen, and is still seen, as in intermediately step between the design stage of a component and a finished working product. This can now be extended so that laser cladding makes RP a one-stop shop and the finished component is made from tool-steel or some alloy-base material. The marriage of laser cladding with RP is an interesting one and offers an alternative to traditional tool builders, re-manufacturers and injection mould design/repair industries. The aim of this paper is to discuss the emergence of this new technology, along with the transference of the process out of the laboratory and into the industrial workplace and show it is finding its rightful place in the manufacturing/repair sector. It will be shown that it can be used as a cost cutting, strategic material saver and consequently a green technology.

  9. Hollow cylindrical plasma filament waveguide with discontinuous finite thickness cladding

    SciTech Connect

    Alshershby, Mostafa; Hao Zuoqiang; Lin Jingquan

    2013-01-15

    We have explored here a hollow cylindrical laser plasma multifilament waveguide with discontinuous finite thickness cladding, in which the separation between individual filaments is in the range of several millimeters and the waveguide cladding thickness is in the order of the microwave penetration depth. Such parameters give a closer representation of a realistic laser filament waveguide sustained by a long stable propagation of femtosecond (fs) laser pulses. We report how the waveguide losses depend on structural parameters like normalized plasma filament spacing, filament to filament distance or pitch, normal spatial frequency, and radius of the plasma filament. We found that for typical plasma parameters, the proposed waveguide can support guided modes of microwaves in extremely high frequency even with a cladding consisting of only one ring of plasma filaments. The loss of the microwave radiation is mainly caused by tunneling through the discontinuous finite cladding, i.e., confinement loss, and is weakly dependent on the plasma absorption. In addition, the analysis indicates that the propagation loss is fairly large compared with the loss of a plasma waveguide with a continuous infinite thickness cladding, while they are comparable when using a cladding contains more than one ring. Compared to free space propagation, this waveguide still presents a superior microwave transmission to some distance in the order of the filamentation length; thus, the laser plasma filaments waveguide may be a potential channel for transporting pulsed-modulated microwaves if ensuring a long and stable propagation of fs laser pulses.

  10. Residual Stress Measurements of Explosively Clad Cylindrical Pressure Vessels

    SciTech Connect

    Taylor, Douglas J; Watkins, Thomas R; Hubbard, Camden R; Hill, M. R.; Meith, W. A.

    2012-01-01

    Tantalum refractory liners were explosively clad into cylindrical pressure vessels, some of which had been previously autofrettaged. Using explosive cladding, the refractory liner formed a metallurgical bond with the steel of the pressure vessel at a cost of induced strain. Two techniques were employed to determine the residual stress state of the clad steel cylinders: neutron diffraction and mechanical slitting. Neutron diffraction is typically nondestructive; however, due to attenuation along the beam path, the cylinders had to be sectioned into rings that were nominally 25 mm thick. Slitting is a destructive method, requiring the sectioning of the cylindrical samples. Both techniques provided triaxial stress data and useful information on the effects of explosive cladding. The stress profiles in the hoop and radial directions were similar for an autofrettaged, nonclad vessel and a clad, nonautofrettaged vessel. The stress profiles in the axial direction appeared to be different. Further, the data suggested that residual stresses from the autofrettage and explosive cladding processes were not additive, in part due to evidence of reverse yielding. The residual stress data are presented, compared and discussed.

  11. Polymer materials as modified optical fiber cladding for chemical sensors

    NASA Astrophysics Data System (ADS)

    Yuan, Jianming

    An intrinsic fiber optic chemical sensor has been designed and developed by using a polymer material as a modified fiber cladding. The sensor is constructed by replacing a certain portion of the original cladding with a chemically sensitive material, specifically, polyaniline or polypyrrole. Both the light absorption coefficient and the refractive index of the polymers change upon the exposure to different chemical vapors. These changes induce the optical intensity modulation of the fiber optic sensor. Polyaniline or polypyrrole is coated as the modified cladding by either spin-cast or in-situ deposition method for sensing HCl, NH3, H 2O2, and H4N2 vapors. All sensors show rapid and strong response to the chemical vapors. Thus, these sensors demonstrate that polyaniline and polypyrrole are viable candidate materials for the detection of volatile toxic gases. Sensors exhibit better performance when correct parameters, such as modification area, in-situ deposition time, and spin-rate, are used in the cladding modification process. The reversibility of the sensor depends on the reaction between the modified cladding material and the chemical vapors. Polyaniline cladding has better reversibility than polypyrrole. The optimized sensor response and sensitivity can be achieved by selecting an incident light with suitable wavelength, power, and incident angle.

  12. Residual stresses in weld deposited clad pressure vessels and nozzles

    SciTech Connect

    Jones, D.P.; Mabe, W.R.; Shadley, J.R.; Rybicki, E.F.

    1998-04-01

    Results of through-thickness residual stress measurements are provided for a variety of samples of weld deposited 308/309L stainless steel and Alloy 600 cladding on low-alloy pressure vessel ferritic steels. Clad thicknesses between 5 and 9mm on samples that vary in thickness from 45 to 200mm were studied. The samples were taken from flat plates, from a spherical head of a pressure vessel, from a ring-segment of a nozzle bore, and from the transition radius between a nozzle and a pressure vessel shell. A layer removal method was used to measure the residual stresses. The effects of uncertainties in elastic constants (Young`s modulus and Poisson`s ratio) as well as experimental error are assessed. All measurements were done at room temperature. The results of this work indicate that curvature plays a significant role in cladding residual stress and that tensile residual stresses as high as the yield stress can be measured in the cladding material. Since the vessel from which the spherical and nozzle corner samples were taken was hydrotested, and the flat plate specimens were taken from specimens used in mechanical fatigue testing, these results suggest that rather high tensile residual stresses can be retained in the cladding material even after some mechanical loading associated with hydrotesting and that higher levels of hydrotest loading would be required to alter the cladding residual stresses.

  13. Uranium and cesium diffusion in fuel cladding of electrogenerating channel

    SciTech Connect

    Vasil’ev, I. V. Ivanov, A. S.; Churin, V. A.

    2014-12-15

    The results of reactor tests of a carbonitride fuel in a single-crystal cladding from a molybdenum-based alloy can be used in substantiating the operational reliability of fuels in developing a project of a megawatt space nuclear power plant. The results of experimental studies of uranium and cesium penetration into the single-crystal cladding of fuel elements with a carbonitride fuel are interpreted. Those fuel elements passed nuclear power tests in the Ya-82 pilot plant for 8300 h at a temperature of about 1500°C. It is shown that the diffusion coefficients for uranium diffusion into the cladding are virtually coincident with the diffusion coefficients measured earlier for uranium diffusion into polycrystalline molybdenum. It is found that the penetration of uranium into the cladding is likely to occur only in the case of a direct contact between the cladding and fuel. The experimentally observed nonmonotonic uranium-concentration profiles are explained in terms of predominant uranium diffusion along grain boundaries. It is shown that a substantially nonmonotonic behavior observed in our experiment for the uranium-concentration profile may be explained by the presence of a polycrystalline structure of the cladding in the surface region from its inner side. The diffusion coefficient is estimated for the grain-boundary diffusion of uranium. The diffusion coefficients for cesium are estimated on the basis of experimental data obtained in the present study.

  14. Characterization of dilution action in laser-induction hybrid cladding

    NASA Astrophysics Data System (ADS)

    Huang, Yongjun

    2011-07-01

    Based on an experimental study of laser-induction hybrid cladding by powder feeding, the dilution action and elemental composition distribution were investigated in detail. The results indicate that, compared with individual laser cladding, by using laser-induction hybrid cladding it is easier to form a metallurgical bonding coating and the change range of dilution is much larger. Moreover, at the bottom of molten region, the morphology exhibits nearly a straight line. The processing parameters have great influence on dilution in hybrid cladding. With the increase of scanning speed, the tendency of dilution presents a U-shaped profile, i.e., the middle dilution is much less than those of two ends. The dilution increases with the induction energy. Furthermore, the bigger the dilution, the more uniform is the elemental composition throughout coating. In laser-induction hybrid cladding, the microstructure of low dilution coating is relatively fine due to the low hybrid cladding energy. By adjusting the laser energy and induction energy appropriately, i.e., high induction energy—low laser energy, the low dilution coating with fine microstructure and good mechanical properties can be achieved.

  15. Shuttle Fuel Feedliner Cracking Investigation

    NASA Technical Reports Server (NTRS)

    Nesman, Tomas E.; Turner, Jim (Technical Monitor)

    2002-01-01

    This presentation provides an overview of material covered during 'Space Shuttle Fuel Feedliner Cracking Investigation MSFC Fluids Workshop' held November 19-21, 2002. Topics covered include: cracks on fuel feed lines of Orbiter space shuttles, fluid driven cracking analysis, liner structural modes, structural motion in a fluid, fluid borne drivers, three dimensional computational fluid dynamics models, fluid borne drivers from pumps, amplification mechanisms, flow parameter mapping, and flight engine flow map.

  16. Cladding Attachment Over Thick Exterior Insulating Sheathing

    SciTech Connect

    Baker, P.; Eng, P.; Lepage, R.

    2014-01-01

    The addition of insulation to the exterior of buildings is an effective means of increasing the thermal resistance of both wood framed walls as well as mass masonry wall assemblies. For thick layers of exterior insulation (levels greater than 1.5 inches), the use of wood furring strips attached through the insulation back to the structure has been used by many contractors and designers as a means to provide a convenient cladding attachment location (Straube and Smegal 2009, Pettit 2009, Joyce 2009, Ueno 2010). The research presented in this report is intended to help develop a better understanding of the system mechanics involved and the potential for environmental exposure induced movement between the furring strip and the framing. BSC sought to address the following research questions: 1. What are the relative roles of the mechanisms and the magnitudes of the force that influence the vertical displacement resistance of the system? 2. Can the capacity at a specified deflection be reliably calculated using mechanics based equations? 3. What are the impacts of environmental exposure on the vertical displacement of furring strips attached directly through insulation back to a wood structure?

  17. Cladding Attachment Over Thick Exterior Insulating Sheathing

    SciTech Connect

    Baker, P.; Eng, P.; Lepage, R.

    2014-01-01

    The addition of insulation to the exterior of buildings is an effective means of increasing the thermal resistance of both wood framed walls as well as mass masonry wall assemblies. For thick layers of exterior insulation (levels greater than 1.5 inches), the use of wood furring strips attached through the insulation back to the structure has been used by many contractors and designers as a means to provide a convenient cladding attachment location (Straube and Smegal 2009, Pettit 2009, Joyce 2009, Ueno 2010). The research presented in this report is intended to help develop a better understanding of the system mechanics involved and the potential for environmental exposure induced movement between the furring strip and the framing. BSC sought to address the following research questions: 1.What are the relative roles of the mechanisms and the magnitudes of the force that influence the vertical displacement resistance of the system? 2.Can the capacity at a specified deflection be reliably calculated using mechanics based equations? 3.What are the impacts of environmental exposure on the vertical displacement of furring strips attached directly through insulation back to a wood structure?

  18. Aluminum alloy clad fiber optic corrosion sensor

    NASA Astrophysics Data System (ADS)

    Rutherford, Paul S.; Ikegami, Roy; Shrader, John E.; Sherrer, David; Zabaronick, Noel; Zeakes, Jason S.; Murphy, Kent A.; Claus, Richard O.

    1997-06-01

    Life extension programs for military metallic aircraft are becoming increasingly important as defense budgets shrink and world economies realign themselves to an uncertain future. For existing military weapon systems, metallic corrosion damage costs as estimated $DOL8 billion per year. One approach to reducing this cost is to develop a reliable method to detect and monitor corrosion in hidden metallic structure with the use of corrosion sensors which would give an early indication of corrosion without significant disassembly, thereby reducing maintenance costs. This presentation describes the development, analysis, and testing of a fiber optic corrosion sensor developed jointly with the Virginia Polytechnic Fiber and Electro-Optics Research Center and sponsored by Wright Laboratory Materials Directorate. In the sensor which was researched, the normal cladding is removed in the sensor region, and replaced with aluminum alloy and allowed to corrode on coupons representative of C/KC-135 body structure in an ASTM B117 salt spray chamber and a Boeing developed Crevice Corrosion Cell. In this approach, the optical signal output of the sensor was originally designed to increase as corrosion takes place, however interaction with the corrosion byproducts yielded different results than anticipated. These test results to determine a correlation between the sensor output and the structural degradation due to corrosion are discussed.

  19. Retrofitting olefin cracking plants

    SciTech Connect

    Sumner, C.; Fernandez-Baujin, J.M.

    1983-12-01

    This article discusses the retrofitting of liquid crackers which produce olefins so that gaseous feedstocks can be used. Naphtha and gas oil are the predominant design feedstocks for producing olefins. The price of gaseous feedstocks such as ethane, propane and butane have become economically more attractive than liquid feedstocks. Existing liquid crackers will be able to produce ethylene at 85% or higher capacity when cracking propane and butane feedstock with only minor changes. Topics considered include revamping for vacuum gas oil (VGO) feedstocks and revamping for liquefied petroleum gas (LPG) feedstocks.

  20. Mode II fatigue crack propagation.

    NASA Technical Reports Server (NTRS)

    Roberts, R.; Kibler, J. J.

    1971-01-01

    Fatigue crack propagation rates were obtained for 2024-T3 bare aluminum plates subjected to in-plane, mode I, extensional loads and transverse, mode II, bending loads. These results were compared to the results of Iida and Kobayashi for in-plane mode I-mode II extensional loads. The engineering significance of mode I-mode II fatigue crack growth is considered in view of the present results. A fatigue crack growth equation for handling mode I-mode II fatigue crack growth rates from existing mode I data is also discussed.

  1. Three-Dimensional Gear Crack Propagation Studies

    NASA Technical Reports Server (NTRS)

    Lewicki, David G.; Sane, Ashok D.; Drago, Raymond J.; Wawrzynek, Paul A.

    1998-01-01

    Three-dimensional crack growth simulation was performed on a split-tooth gear design using boundary element modeling and linear elastic fracture mechanics. Initial cracks in the fillet of the teeth produced stress intensity factors of greater magnitude (and thus, greater crack growth rates) than those in the root or groove areas of the teeth. Crack growth simulation was performed on a case study to evaluate crack propagation paths. Tooth fracture was predicted from the crack growth simulation for an initial crack in the tooth fillet region. Tooth loads on the uncracked mesh of the split-tooth design were up to five times greater than those on the cracked mesh if equal deflections of the cracked and uncracked teeth were considered. Predicted crack shapes as well as crack propagation life are presented based on calculated stress intensity factors, mixed-mode crack propagation trajectory theories, and fatigue crack growth theories.

  2. Shear fatigue crack growth - A literature survey

    NASA Technical Reports Server (NTRS)

    Liu, H. W.

    1985-01-01

    Recent studies of shear crack growth are reviewed, emphasizing test methods and data analyses. The combined mode I and mode II elastic crack tip stress fields are considered. The development and design of the compact shear specimen are described, and the results of fatigue crack growth tests using compact shear specimens are reviewed. The fatigue crack growth tests are discussed and the results of inclined cracks in tensile panels, center cracks in plates under biaxial loading, cracked beam specimens with combined bending and shear loading, center-cracked panels and double edge-cracked plates under cyclic shear loading are examined and analyzed in detail.

  3. Cyclic fatigue and fracture in pyrolytic carbon-coated graphite mechanical heart-valve prostheses: role of small cracks in life prediction.

    PubMed

    Dauskardt, R H; Ritchie, R O; Takemoto, J K; Brendzel, A M

    1994-07-01

    A fracture-mechanics based study has performed to characterize the fracture toughness and rates of cyclic fatigue-crack growth of incipient flaws in prosthetic heart-valve components made of pyrolytic carbon-coated graphite. Such data are required to predict the safe structural lifetime of mechanical heart-valve prostheses using damage-tolerant analysis. Unlike previous studies where fatigue-crack propagation data were obtained using through-thickness, long cracks (approximately 2-20 mm long), growing in conventional (e.g., compact-tension) samples, experiments were performed on physically small cracks (approximately 100-600 microns long), initiated on the surface of the pyrolytic-carbon coating to simulate reality. Small-crack toughness results were found to agree closely with those measured conventionally with long cracks. However, similar to well-known observations in metal fatigue, it was found that based on the usual computations of the applied (far-field) driving force in terms of the maximum stress intensity, Kmax, small fatigue cracks grew at rates that exceeded those of long cracks at the same applied stress intensity, and displayed a negative dependency on Kmax; moreover, they grew at applied stress intensities less than the fatigue threshold value, below which long cracks are presumed dormant. To resolve this apparent discrepancy, it is shown that long and small crack results can be normalized, provided growth rates are characterized in terms of the total (near-tip) stress intensity (incorporating, for example, the effect of residual stress); with this achieved, in principle, either form of data can be used for life prediction of implant devices. Inspection of the long and small crack results reveals extensive scatter inherent in both forms of growth-rate data for the pyrolytic-carbon material. PMID:8083247

  4. Effect of Crack Opening on Penetrant Crack Detectability

    NASA Technical Reports Server (NTRS)

    Weaver, Devin

    2009-01-01

    Results: From the testing we were able to determine all the cracks within the test range were detectable or better with developer. Many of the indications after development lost their linearity and gave circular indications. Our tests were performed in a laboratory and our procedure would be difficult in an industrial setting. Conclusions: The "V" did not significantly affect our ability to detect the POD cracks with fluorescent penetrant. Conduct same experiment with more cracks. The 0.025 and 0.050 POD specimens are clean and documented with the SEM. Conduct water-wash fluorescent penetrant test at EAFB. The poppet cracks are tighter than the POD specimen cracks. Flight FCV poppets: 0.01 mils (0.3 microns) Langley fatigue cracked poppets: 0.02 mils (0.5 microns) POD specimen (post 5 mils): 0.05 mils (1.4 microns) We could not detect cracks in Langley fatigue-cracked poppets with fluorescent penetrant. Investigate inability of penetrant to wet the poppet surface.

  5. ''KN'' series cracking catalysts

    SciTech Connect

    Klapstov, V.F.; Khlebrikova, M.A.; Maslova, A.A.; Nefedov, B.K.

    1986-09-01

    The basic directions in improving high-activity zeolitic cracking catalysts at the present stage are improvements in the resistance to attrition and increases in the bulk density of the catalysts, along with a changeover to relatively waste-free catalyst manufacturing technology. Catalysts of the ''KN'' series have been synthesized recently with improved quality characteristics. Low-waste technology is used in manufacturing them. Data are presented which show that the KN catalysts are better than the other Soviet catalysts. The starting materials and reagents in preparing the KN catalysts are technical alumina, rare-earth element nitrates, a natural component (such as clay conforming to specification TU-21-25-146-75), sodium hydroxide, and granulated sodium silicate. The preparation of the KN catalysts is described and no silica gel is used in manufacturing the KN series catalyst, in contrast to the RSG-6Ts catalyst. The use of KN series catalysts in place of KMTsR in catalytic cracking units will result in an increase in the naphtha yield by at least 20% by weight, as well as a reduction of the catalyst consumption by a factor of 2-3. A changeover to the commerical production of this catalyst will make it possible to reduce saline waste by a factor of 8-10 and reduce the catalyst cost by a factor of 1.5-2.

  6. Stress intensity factors for an underclad nozzle corner crack subjected to pressure and thermal loading

    SciTech Connect

    Wilkening, W.W.

    1991-06-01

    The opening mode linear elastic stress intensity factor, K{sub I}, was computed, via 3-D elastic finite element techniques, for an embedded elliptical crack located just beneath the cladding at the nozzle corner in a pressure vessel. Pressure loading and several thermal transient loading conditions were analyzed. The underclad crack was explicitly modeled and K{sub I} was computed explicitly, from the energy release rate, J. The variation of the maximum principal stress along the minor axis of the elliptical crack was determined for a companion set of thermal/structural analyses that were performed in the absence of the crack. These stress distributions were linearized into equivalent membrane and bending stress components that were used to compute K{sub I} from the Shah and Kobayashi solutions for near-surface embedded elliptical cracks. The explicitly computed K{sub I} values were found to be in very good agreement with the K{sub I} values computed from the flat plate'' solutions of Reference 1, for all the loading cases analyzed. An additional comparison was made between the energy release rate results and the results obtained by fitting the 1/{radical}r stress singularity to the crack tip stress field at the Gaussian integration points nearest to the crack front. The observed excellent agreement between the two independent explicit'' computational methods served to verify each of the methods and also demonstrated the adequacy of the refinement of the finite element mesh. These observations support the use of the Shah and Kobayashi flat plate K{sub I} solutions for analyzing underclad cracks at the nozzle corner. 7 refs., 11 figs.

  7. Laser fluorescence quantification of remineralisation in situ of incipient enamel lesions: influence of fluoride supplements.

    PubMed

    al-Khateeb, S; Oliveby, A; de Josselin de Jong, E; Angmar-Månsson, B

    1997-01-01

    The aims of this study were to test the laser fluorescence method for quantification of remineralisation in situ of enamel with incipient lesions and to evaluate the enhancement of remineralisation by fluoride (F) supplements when a F dentifrice was used on a regular basis by healthy young subjects. Enamel samples were cut from extracted premolar teeth with the natural surface kept intact, and subjected to a pH-cycling system to produce subsurface demineralisation in vitro. The enamel blocks were then inserted into composite holders bonded to the buccal surfaces of both upper first molars of 12 panelists. Each panelist participated in 3 separate experiments in a randomised order; each lasted for 5 weeks with washout intervals of 2 weeks between experiments; experiment 1: F dentifrice (0.145% F as NaF) only; experiment 2: F dentrifice + F lozenges (0.25 mg F x 6/day); experiment 3: F dentifrice + F chewing-gum (0.25 mg F x 6/day). Fluorescence radiance was measured before, during, and after in vitro demineralisation, and once a week during the in situ experimental periods. The enamel samples were then sectioned and analysed with transverse microradiography (TMR). Anova and Pearson correlation coefficient were used for the statistical analysis. At the end of the 5-week in situ periods, fluorescence radiance had been regained to a level of 80-100% of the value before in vitro demineralisation, indicating remineralisation of the enamel samples. There were no differences in the fluorescence radiance gain between the 3 different F exposures. However, there was a statistically significant time trend (p < 0.001), and a highly significant linear dependence (p < 0.001) between the final measurements obtained with the laser fluorescence method (LAF) and the data obtained from TMR, r = 0.76. It was concluded that: (1) with the sensitive LAF method it was possible to register the small changes in the enamel week by week during in situ remineralisation: (2) when F dentrifice was

  8. Quantitative Index and Abnormal Alarm Strategy Using Sensor-Dependent Vibration Data for Blade Crack Identification in Centrifugal Booster Fans

    PubMed Central

    Chen, Jinglong; Sun, Hailiang; Wang, Shuai; He, Zhengjia

    2016-01-01

    Centrifugal booster fans are important equipment used to recover blast furnace gas (BFG) for generating electricity, but blade crack faults (BCFs) in centrifugal booster fans can lead to unscheduled breakdowns and potentially serious accidents, so in this work quantitative fault identification and an abnormal alarm strategy based on acquired historical sensor-dependent vibration data is proposed for implementing condition-based maintenance for this type of equipment. Firstly, three group dependent sensors are installed to acquire running condition data. Then a discrete spectrum interpolation method and short time Fourier transform (STFT) are applied to preliminarily identify the running data in the sensor-dependent vibration data. As a result a quantitative identification and abnormal alarm strategy based on compound indexes including the largest Lyapunov exponent and relative energy ratio at the second harmonic frequency component is proposed. Then for validation the proposed blade crack quantitative identification and abnormality alarm strategy is applied to analyze acquired experimental data for centrifugal booster fans and it has successfully identified incipient blade crack faults. In addition, the related mathematical modelling work is also introduced to investigate the effects of mistuning and cracks on the vibration features of centrifugal impellers and to explore effective techniques for crack detection. PMID:27171083

  9. Quantitative Index and Abnormal Alarm Strategy Using Sensor-Dependent Vibration Data for Blade Crack Identification in Centrifugal Booster Fans.

    PubMed

    Chen, Jinglong; Sun, Hailiang; Wang, Shuai; He, Zhengjia

    2016-01-01

    Centrifugal booster fans are important equipment used to recover blast furnace gas (BFG) for generating electricity, but blade crack faults (BCFs) in centrifugal booster fans can lead to unscheduled breakdowns and potentially serious accidents, so in this work quantitative fault identification and an abnormal alarm strategy based on acquired historical sensor-dependent vibration data is proposed for implementing condition-based maintenance for this type of equipment. Firstly, three group dependent sensors are installed to acquire running condition data. Then a discrete spectrum interpolation method and short time Fourier transform (STFT) are applied to preliminarily identify the running data in the sensor-dependent vibration data. As a result a quantitative identification and abnormal alarm strategy based on compound indexes including the largest Lyapunov exponent and relative energy ratio at the second harmonic frequency component is proposed. Then for validation the proposed blade crack quantitative identification and abnormality alarm strategy is applied to analyze acquired experimental data for centrifugal booster fans and it has successfully identified incipient blade crack faults. In addition, the related mathematical modelling work is also introduced to investigate the effects of mistuning and cracks on the vibration features of centrifugal impellers and to explore effective techniques for crack detection. PMID:27171083

  10. Reciprocity principle and crack identification

    NASA Astrophysics Data System (ADS)

    Andrieux, Stéphane; Ben Abda, Amel; Duong Bui, Huy

    1999-02-01

    In this paper we are concerned with the planar crack identification problem defined by a unique complete elastostatic overdetermined boundary datum. Based on the reciprocity gap principle, we give a direct process for locating the host plane and we establish a new constuctive identifiability result for 3D planar cracks.

  11. Experiences on IGSCC crack manufacturing

    SciTech Connect

    Veron, P.

    1997-02-01

    The author presents his experience in manufacturing IGSCC realistic defects, mainly in INCONEL 600 MA Steam Generator Tubes. From that experience he extracts some knowledge about this cracking (influence of chemistry in the environment, stress state, crack growth rate, and occurrence in laboratory condition of break before leak).

  12. Interface cracks in piezoelectric materials

    NASA Astrophysics Data System (ADS)

    Govorukha, V.; Kamlah, M.; Loboda, V.; Lapusta, Y.

    2016-02-01

    Due to their intrinsic electromechanical coupling behavior, piezoelectric materials are widely used in sensors, actuators and other modern technologies. It is well known that piezoelectric ceramics are very brittle and susceptible to fracture. In many cases, fracture occurs at interfaces as debonding and cracks. This leads to an undesired degradation of electrical and mechanical performance. Because of the practical and fundamental importance of the problem, interface cracks in piezoelectric materials have been actively studied in the last few decades. This review provides a comprehensive survey of recent works on cracks situated at the interface of two materials, at least one of which has piezoelectric or piezoelectromagnetic properties. Different electric boundary conditions along the crack faces are discussed. The oscillating and contact zone models for in-plane straight interface cracks between two dissimilar piezoelectric materials or between piezoelectric and non-piezoelectric ones are reviewed. Different peculiarities related to the investigation of interface cracks in piezoelectric materials for the anti-plane case, for functionally graded and thermopiezoelectric materials are presented. Papers related to magnetoelectroelastic bimaterials, to steady state motion of interface cracks in piezoelectric bimaterials and to circular arc-cracks at the interface of piezoelectric materials are reviewed, and various methods used to address these problems are discussed. The review concludes with an outlook on future research directions.

  13. Bonded orthotropic strips with cracks

    NASA Technical Reports Server (NTRS)

    Delale, F.; Erdogan, F.

    1979-01-01

    The elastostatic problem for a nonhomogeneous plane which consists of two sets of periodically arranged dissimilar orthotropic strips is considered. It is assumed that the plane contains a series of collinear cracks perpendicular to the interfaces and is loaded in tension away from and perpendicular to the cracks. The problem of cracks fully imbedded into the homogeneous strips is considered. The singular behavior of the stresses for two special crack geometries is studied. The first is the case of a broken laminate in which the crack tips touch the interfaces. The second is the case of cracks crossing the interfaces. An interesting result found from the analysis of the latter is that for certain orthotropic material combinations the stress state at the point of intersection of a crack and an interface may be bounded whereas in isotropic materials at this point stresses are always singular. A number of numerical examples are worked out to separate the primary material parameters influencing the stress intensity factors and the powers of stress singularity, and to determine the trends regarding the influence of the secondary parameters. Some numerical results are given for the stress intensity factors in certain basic crack geometries and for typical material combinations.

  14. Replica-Based Crack Inspection

    NASA Technical Reports Server (NTRS)

    Newman, John A.; Willard, Scott A.; Smith, Stephen W.; Piascik, Robert S.

    2008-01-01

    Surface replication has been proposed as a method for crack detection in space shuttle main engine flowliner slots. The results of a feasibility study show that examination of surface replicas with a scanning electron microscope can result in the detection of cracks as small as 0.005 inch, and surface flaws as small as 0.001 inch, for the flowliner material.

  15. What Crack Does to Babies.

    ERIC Educational Resources Information Center

    Hutchinson, Janice

    1991-01-01

    Describes the effect of crack on the user and on the pregnant user's offspring. Children of the first crack addicts are now in school and exhibit an array of behavioral and cognitive difficulties. Early intervention in a supportive environment has succeeded in preparing some of these children for the classroom. (DM)

  16. Shapes Formed By Interacting Cracks

    NASA Astrophysics Data System (ADS)

    Daniels, K.

    2014-12-01

    Brittle failure through multiple cracks occurs in a wide variety of contexts, from microscopic failures in rocks to geological faults and planetary ice crusts. In each of these situations, with complicated stress geometries and different microscopic mechanisms, pairwise interactions between approaching cracks nonetheless produce characteristically curved fracture paths. We investigate the origins of this widely observed "en passant" crack pattern by fracturing a rectangular slab which is notched on two sides and then subjected to quasistatic uniaxial, biaxial, or shear strain. The two cracks propagate along approximately straight paths until they pass each other, after which they curve and release a lens-shaped fragment. Under uniaxial strain, we find that each crack path has a universal shape and aspect ratio which is independent of the material. By changing the geometry of the applied strain, we are able to achieve different aspect ratios for the crack paths. With birefringent materials, it is possible to interpret these patterns in light of the stress geometry, and we are able to explain the origins of these universal shapes with a simple geometrical model. Since a variety of aspect ratios have similarly been observed in geological contexts, this raises the possibility of using observed crack shapes as a diagnostic for the stress conditions under which cracks were formed in nature. In particular, the shape may serve as a means to infer the boundary loading in situations where history and dynamics are inaccessible.

  17. Laser cladding of quasi-crystal-forming Al-Cu-Fe-Bi on an Al-Si alloy substrate

    NASA Astrophysics Data System (ADS)

    Biswas, Krishanu; Chattopadhyay, Kamanio; Galun, Rolf; Mordike, Barry L.

    2005-07-01

    -sliding wear properties of the samples show the improvement of wear properties for Bi-containing clads. The best tribological properties are observed in the as-clad state, and remelting deteriorates the wear properties. The low coefficient of friction of the as-clad and remelted track is due to the presence of approximant phases. There is evidence of severe subsurface deformation during the wear process leading to cracking of hard phases and a change in the size and shape of soft Bi particles. Using these observations, we have rationalized possible wear mechanisms in the Bi-containing surface-alloyed layers.

  18. Bonded orthotropic strips with cracks

    NASA Technical Reports Server (NTRS)

    Delale, F.; Erdogan, F.

    1978-01-01

    The elastostatic problem for a nonhomogeneous plane which consists of two sets of periodically arranged dissimilar orthotropic strips is considered. First, the problem of cracks fully imbedded into the homogeneous strips is considered. Then, the singular behavior of the stresses for two special crack geometries is studied in some detail. The first is the case of a broken laminate in which the crack tips touch the interfaces. The second is the case of cracks crossing the interfaces. A number of numerical examples are worked out in order to separate the primary material parameters influencing the stress intensity factors and the powers of stress singularity, and to determine the trends regarding the influence of the secondary parameters. Finally, some numerical results are given for the stress intensity factors in certain basic crack geometries and for typical material combinations.

  19. Hydrocarbon cracking and reforming process

    SciTech Connect

    Le, Q.N.; Schipper, P.H.; Owen, H.

    1992-03-31

    This patent describes a process for upgrading paraffinic naphtha to high octane fuel. It comprises: contacting a fresh naphtha feedstock stream containing a major amount of C{sub 7+} alkanes and naphthenes with medium pore acid cracking catalyst under low pressure selective cracking conditions effective to produce 4-C5 isoalkene and C4-C5 isoalkane, the cracking catalyst being substantially free of hydrogenation-dehydrogenation metal components and having an acid cracking activity less than 15; separating cracking effluent to obtain an olefinic fraction rich in C4-C5 isoalkene and a C6+ fraction; etherifying the C4-C5 isoalkene fraction by catalytic reaction with lower alkanol to produce tertiary-alkyl ether product; and reforming the C6+ fraction to provide high octane gasoline components.

  20. High speed thin plate fatigue crack monitor

    NASA Technical Reports Server (NTRS)

    Wincheski, Buzz A. (Inventor); Heyman, Joseph S. (Inventor); Namkung, Min (Inventor); Fulton, James P. (Inventor)

    1996-01-01

    A device and method are provided which non-destructively detect crack length and crack geometry in thin metallic plates. A non-contacting vibration apparatus produces resonant vibrations without introducing extraneous noise. Resulting resonant vibration shifts in cracked plates are correlated to known crack length in plates with similar resonant vibration shifts. In addition, acoustic emissions of cracks at resonance frequencies are correlated to acoustic emissions from known crack geometries.

  1. DNS of self-similar adverse pressure gradient turbulent boundary layer at incipient separation

    NASA Astrophysics Data System (ADS)

    Soria, Julio; Kitsios, Vassili; Atkinson, Callum; Sillero, Juan; Borrell, Guillem; Gungar, Ayse; Jimenez, Javier

    2015-11-01

    A direct numerical simulation of a self-similar adverse pressure gradient turbulent boundary layer (APG-TBL) flow at incipient separation has been carried out. The maximum Reynolds number based on the momentum thickness, Reδ2 , reached in this DNS is 6,500. A wall-normal far-field boundary condition to effect the desired APG that will lead to the desired self-similar flow at the verge of separation has been developed. The self-similar analysis of the mean turbulent boundary layer equations yields the necessary conditions for a self-similar mean flow to exists. These conditions are tested using the DNS APG-TBL data base. First and second order statistics of the velocity across the APG-TBL are also presented in the light of the self-similar analysis results and compared to the results of a zero pressure gradient turbulent boundary layer DNS with similar mean inflow characteristics as the APG-TBL. The support of the ARC, NCI and Pawsey SCC funded by the Australian and Western Australian governments as well as the support of PRACE funded by the European Union are gratefully acknowledged.

  2. Longitudinal quantification of incipient carious lesions in postorthodontic patients using a fluorescence method.

    PubMed

    Aljehani, Abdulaziz; Yousif, Mirgani A; Angmar-Månsson, Birgit; Shi, Xie-Qi

    2006-10-01

    The aims of this study were to evaluate the effect of two caries-preventive programs, and to apply the laser fluorescence method, DIAGNOdent, for longitudinal quantification of changes in incipient carious lesions. Twelve subjects with 127 test teeth exhibiting white spot lesions on the buccal surfaces after completed orthodontic therapy were enrolled in the study. Visual examination was performed at baseline and after 12 months. The subjects were divided into two groups: one group received repeated professional tooth cleaning combined with oral hygiene instruction; and the control group received repeated oral hygiene instruction only. The white spot lesions were measured by DIAGNOdent at baseline, and at 3, 6, 9, and 12 months thereafter. There was a significant difference in the DIAGNOdent readings between the first and the final evaluations. However, there was no statistically significant difference between the two treatment groups regarding changes of DIAGNOdent values over time. In conclusion, it may be possible to use DIAGNOdent for longitudinal quantification of carious lesions on smooth surfaces over a period of 1 yr under in vivo conditions. The combination of professional tooth cleaning and oral hygiene instruction had a similar efficacy to professional tooth cleaning only for promoting the remineralization of white spot lesions. PMID:17026510

  3. Advanced power system protection and incipient fault detection and protection of spaceborne power systems

    NASA Technical Reports Server (NTRS)

    Russell, B. Don

    1989-01-01

    This research concentrated on the application of advanced signal processing, expert system, and digital technologies for the detection and control of low grade, incipient faults on spaceborne power systems. The researchers have considerable experience in the application of advanced digital technologies and the protection of terrestrial power systems. This experience was used in the current contracts to develop new approaches for protecting the electrical distribution system in spaceborne applications. The project was divided into three distinct areas: (1) investigate the applicability of fault detection algorithms developed for terrestrial power systems to the detection of faults in spaceborne systems; (2) investigate the digital hardware and architectures required to monitor and control spaceborne power systems with full capability to implement new detection and diagnostic algorithms; and (3) develop a real-time expert operating system for implementing diagnostic and protection algorithms. Significant progress has been made in each of the above areas. Several terrestrial fault detection algorithms were modified to better adapt to spaceborne power system environments. Several digital architectures were developed and evaluated in light of the fault detection algorithms.

  4. Characterization of an incipiently separated shock wave/turbulent boundary layer interaction

    NASA Astrophysics Data System (ADS)

    Schreyer, A.-M.; Dussauge, J.-P.; Krämer, E.

    2016-05-01

    The turbulence structure in a shock wave/turbulent boundary layer interaction at incipient separation was investigated in order to get insight into turbulence generation and amplification mechanisms in such flow fields. The flow along a two-dimensional 11.5° compression corner was studied experimentally at a Mach number of M=2.53 and with a momentum-thickness Reynolds number of Re_{θ }=5370 . From hot-wire boundary layer traverses and surface heat-flux density fluctuation measurements with the fast-response atomic layer thermopile, the turbulence structure and amplification was described. Space-time correlations of the mass-flux fluctuations across the boundary layer and the surface heat-flux density fluctuations were measured to further characterize the development of the turbulence structure across the interaction. The large-scale boundary layer structures are concealed by shock-related effects in the strongly disturbed shock-foot region. Shortly downstream, however, large-scale structures dominate the signal again, just as in the incoming flow. A mechanism explaining this behavior is suggested.

  5. Evaluation of new treatment for incipient enamel demineralization using 45S5 bioglass.

    PubMed

    Bakry, A S; Takahashi, H; Otsuki, M; Tagami, J

    2014-03-01

    Bioglass 45S5 is a silica-based bioactive glass capable of depositing a layer of hydroxyl carbonate apatite on the surface of the glass when immersed in body fluids. The present paper studies a new technique for treating early human dental enamel caries lesions by using a paste composed of 45S5 bioglass and phosphoric acid. Artificial caries lesions were induced in enamel flat surfaces by means of a decalcification solution. All specimens were exposed to a brushing-abrasion challenge to test the durability of any newly formed layer resulting from the application of 45S5 bioglass paste. The specimens treated with bioglass paste showed complete coverage with a layer of brushite crystals. The brushing-abrasion challenge did not statistically affect the percentage of enamel coverage with the crystalline layer formed by the application of bioglass (p<0.05). These crystals were converted to hydroxyapatite crystals when stored in artificial saliva for 14 days. The current technique suggests the possibility of restoring incipient enamel erosive lesion with an abrasion durable layer of hydroxyapatite crystals. PMID:24433821

  6. Astral microtubules physically redistribute cortical actin filaments to the incipient contractile ring.

    PubMed

    Tseng, Kuo-Fu; Foss, Margit; Zhang, Dahong

    2012-11-01

    Prior to cell cleavage, cytokinetic proteins are recruited into the nascent actomyosin contractile ring, paving the way for formation of a functional cleavage furrow. Interactions between spindle microtubules and the cell cortex may play a critical role in this recruitment, since microtubules have been shown to affect distribution and activation of cytokinetic proteins within the cortex. However, direct evidence for physical interaction between microtubules and the cortex has been lacking. Here, we probed the physical connection between astral microtubules and cortical actin filaments, by micromanipulating the fluorescently tagged cytoskeleton in living spermatocytes of the grasshopper Melanoplus femurrubrum. When microtubules were tugged with a microneedle, they in turn pulled on cortical actin filaments, interrupting the filaments' journey toward the equator. Further displacement of the actin dragged the cell membrane inward, demonstrating that the cortical actin network physically linked spindle microtubules to the cell membrane. Regional disruption of the connection by breaking spindle microtubules prevented actin accumulation in a segment of the ring, which locally inhibited furrowing. We propose a model in which dynamic astral microtubules physically redistribute cortical actin into the incipient contractile ring. PMID:23027710

  7. Incipient fault diagnosis of power transformers using optical spectro-photometric technique

    NASA Astrophysics Data System (ADS)

    Hussain, K.; Karmakar, Subrata

    2015-06-01

    Power transformers are the vital equipment in the network of power generation, transmission and distribution. Mineral oil in oil-filled transformers plays very important role as far as electrical insulation for the winding and cooling of the transformer is concerned. As transformers are always under the influence of electrical and thermal stresses, incipient faults like partial discharge, sparking and arcing take place. As a result, mineral oil deteriorates there by premature failure of the transformer occurs causing huge losses in terms of revenue and assets. Therefore, the transformer health condition has to be monitored continuously. The Dissolved Gas Analysis (DGA) is being extensively used for this purpose, but it has some drawbacks like it needs carrier gas, regular instrument calibration, etc. To overcome these drawbacks, Ultraviolet (UV) -Visible and Fourier Transform Infrared (FTIR) Spectro-photometric techniques are used as diagnostic tools for investigating the degraded transformer oil affected by electrical, mechanical and thermal stresses. The technique has several advantages over the conventional DGA technique.

  8. Ichnotaxonomy and interpretation of "incipient" insect trace fossils in the archaeological context of Abusir (Holocene, Egypt)

    NASA Astrophysics Data System (ADS)

    Mikuláš, R.

    2013-05-01

    Incipient forms of the ichnogenera Celliforma, ? Rebuffoichnus, Tombownichnus, Taenidium, Chubutolites and Machichnus and, in addition, complex forms of probable termite galleries, beetle galleries and mammal burrows were found in masonry, plasters and surrounding (both natural and man-made) deposits in the ancient Abusir necropolis. Among the ways of the classification of the material, the use of standard ichnotaxonomic names appeared to be more objective and more correct than mere estimations of possible tracemakers as made colloquially in the past. The realistic classification enables a useful interpretation in such a context through dating (radiometric dating is possible if the tunnels are lined with organic matter), specification of depth of burrowing/bioerosion (some insect structures show a highly specific depth below the substrate surface) and identification of the tracemaker (insect family, genus, species). Having such information, it is possible, e.g., to recognize that the wall of a building was exposed/unburied during certain time interval and that the environment was favourable for the development of the tracemaker (e.g., clover-pollinating solitary bees). Three basic colonization times were recognized: first, 2760 ± 35 B.P. = ca 750 B.C.; second, 645 ± 30 B.P. i.e. ca 1350 A.D.; third, 225 ± 30 B.P., i.e. ca 1775 A.D.

  9. Progressive deformation textures in granite form from incipient to advanced strains

    SciTech Connect

    Koenemann, F.

    1985-01-01

    In the South Mountain Metamorphic Core Complex (Phoenix, Arizona) a Tertiary granite intruded a Precambrian gneiss. Detachment on a low-angle normal fault followed and cut through the slowly cooling intrusion. The resulting tectonic rock types are granitic gneiss, mylonite, and a cataclasite. Quartz is always deformed. At high T a preferred lattice orientation (PLO) developed at incipient strain. The texture suggests grain boundary migration in low-strain areas and recrystallization in local shear zones. Grain boundary orientations due to migration tend to be bidirectional and independent of the orientation of the involved crystals, but are thought to be dependent on local strain axes. At advanced strains and lower T old large grains decay along deformation bands, by recrystallization and subgrain development. At high strains the grain size is small and stable. The PLO is strongly dependent on the distribution of inhomogeneties (e.g. plag), which due to S/C mesofabric causes the fabric outline to be oblique. Biotite tears apart along faults // and perpendicular (001). Open faults are filled with K-spar, leucoxene and opaques. New biotite grows along two-phase boundaries (qz/plag) suggesting efficient diffusion of its components and chemical interaction with plag. This process causes the mylonite to become a layered rock. Pseudotachylite in the cataclastite developed at biotite grade. Chlorite is mainly a post-tectonic-hydrothermal phase. Cataclastic particles are later cut by ductile faults; thus plastic and cataclastic deformation modes were interactive.

  10. Incipient charge order observed by NMR in the normal state of YBa2Cu3Oy

    PubMed Central

    Wu, Tao; Mayaffre, Hadrien; Krämer, Steffen; Horvatić, Mladen; Berthier, Claude; Hardy, W.N.; Liang, Ruixing; Bonn, D.A.; Julien, Marc-Henri

    2015-01-01

    The pseudogap regime of high-temperature cuprates harbours diverse manifestations of electronic ordering whose exact nature and universality remain debated. Here, we show that the short-ranged charge order recently reported in the normal state of YBa2Cu3Oy corresponds to a truly static modulation of the charge density. We also show that this modulation impacts on most electronic properties, that it appears jointly with intra-unit-cell nematic, but not magnetic, order, and that it exhibits differences with the charge density wave observed at lower temperatures in high magnetic fields. These observations prove mostly universal, they place new constraints on the origin of the charge density wave and they reveal that the charge modulation is pinned by native defects. Similarities with results in layered metals such as NbSe2, in which defects nucleate halos of incipient charge density wave at temperatures above the ordering transition, raise the possibility that order–parameter fluctuations, but no static order, would be observed in the normal state of most cuprates if disorder were absent. PMID:25751448

  11. Comparison of Nano-Hydroxyapatite and Sodium Fluoride Mouthrinse for Remineralization of Incipient Carious Lesions

    PubMed Central

    Haghgoo, Roza; Rezvani, Mohammad Bagher; Salehi Zeinabadi, Mehdi

    2014-01-01

    Objective: Dental caries is an infectious disease that can be prevented in several ways. The aim of this study was to compare the efficacy of sodium fluoride mouthrinse and nano- hydroxyapatite (nano-HA) for the remineralization of incipient caries. Materials and Methods: After obtaining different concentrations of nano-HA (0-2-5-10%), 60 sound premolars fixed in acrylic blocks were coated with nail polish except for one surface. Ten teeth (control group) were stored in distilled water and the remaining 50 samples were demineralized by immersion in 13 ml of 0.1 M lactic acid and 0.2% poly acrylic acid for 48 hours. Their microhardness was then measured and compared to that of the control group. Next, the 50 test teeth were randomly divided into 5 groups of group1 (negative), group 2 (2% nano-HA), group 3 (5% nano-HA), group 4(10% nano-HA) and group 5 (0.2 NAF mouthrinse). The microhardness of the teeth was measured after 12 hours of immersion in the above-mentioned solutions. Data were analyzed using repeated measures analysis of variance (ANOVA). Results: Microhardness of all samples decreased significantly after immersion in the demineralization solution and increased following immersion in nano-HA and NAF mouthrinses; however, this increase was not statistically significant (P=0.711). Conclusion: Nano-HA and NAF mouthrinses can greatly enhance remineralization and increase tooth microhardness. PMID:25584051

  12. Incipient Melt Formation and Devitrification at the Wanapitei Impact Structure, Ontario, Canada

    NASA Technical Reports Server (NTRS)

    Dressler, B. O.; Schuraytz, B. C.; Crabtree, D.

    1997-01-01

    The Wanapitei impact structure is approximately 8 km in diameter and lies within Wanapitei Lake, approximately 34 km northeast of the city of Sudbury. Rocks related to the 37 Ma impact event are found only in Pleistocene glacial deposits south of the lake. Most of the target rocks are metasedimentary rocks of the Proterozoic Huronian Supergroup. An almost completely vitrified, inclusion-bearing sample investigated here represents either an impact melt or a strongly shock metamorphosed, pebbly wacke. In the second, preferred interpretation, a number of partially melted and devitrified clasts are enclosed in an equally highly shock metamorphosed arkosic wacke matrix (i.e., the sample is a shocked pebbly wacke), which records the onset of shock melting. This interpretation is based on the glass composition, mineral relicts in the glass, relict rock textures, and the similar degree of shock metamorphism and incipient melting of all sample components. Boulder matrix and clasts are largely vitrified and preserve various degrees of fluidization, vesiculation, and devitrification. Peak shock pressure of approximately 50-60 GPa and stress experienced by the sample were somewhat below those required for complete melting and development of a homogeneous melt. The rapid cooling and devitrification history of the analyzed sample is comparable to that reported recently from glasses in the suevite of the Ries impact structure in Germany and may indicate that the analyzed sample experienced an annealing temperature after deposition of somewhere between 650 C and 800 C.

  13. Incipient charge order observed by NMR in the normal state of YBa2Cu3Oy

    NASA Astrophysics Data System (ADS)

    Wu, Tao; Mayaffre, Hadrien; Krämer, Steffen; Horvatić, Mladen; Berthier, Claude; Hardy, W. N.; Liang, Ruixing; Bonn, D. A.; Julien, Marc-Henri

    2015-03-01

    The pseudogap regime of high-temperature cuprates harbours diverse manifestations of electronic ordering whose exact nature and universality remain debated. Here, we show that the short-ranged charge order recently reported in the normal state of YBa2Cu3Oy corresponds to a truly static modulation of the charge density. We also show that this modulation impacts on most electronic properties, that it appears jointly with intra-unit-cell nematic, but not magnetic, order, and that it exhibits differences with the charge density wave observed at lower temperatures in high magnetic fields. These observations prove mostly universal, they place new constraints on the origin of the charge density wave and they reveal that the charge modulation is pinned by native defects. Similarities with results in layered metals such as NbSe2, in which defects nucleate halos of incipient charge density wave at temperatures above the ordering transition, raise the possibility that order-parameter fluctuations, but no static order, would be observed in the normal state of most cuprates if disorder were absent.

  14. Dipolar centers in incipient ferroelectrics: Mn and Fe in KTaO3

    NASA Astrophysics Data System (ADS)

    Venturini, E. L.; Samara, G. A.; Laguta, V. V.; Glinchuk, M. D.; Kondakova, I. V.

    2005-03-01

    The influence of lattice disorder produced by Mn and Fe substitution on the dielectric properties of the incipient ferroelectric KTaO3 were investigated. Both substituents produce dipolar centers that exhibit relaxational behavior in the audio frequency range. At a concentration of 0.01 at. %, i.e., in the very dilute limits, the Mn center is reflected in a dielectric loss ( ∈″ or tanδ ) peak, but not to a measurable degree in the real part (∈') of the dielectric function, but a concentration of 0.3 at. % Mn produces measurable anomalies in both ∈'(T) and the dielectric loss. In the case of Fe, a concentration of 0.3 at. % produces anomalies in the dielectric loss, but not in ∈'(T) . Hydrostatic pressure has a considerable influence on the static and dynamic properties of these materials and provides insights into the physics. The results are discussed in terms of microscopic models for these dipolar centers, and it is shown that all the properties can be understood in terms of the temperature and pressure dependences of the correlation length for dipolar interactions in the highly polarizable KTaO3 host lattice—properties unique to soft ferroelectric mode hosts. A model theory was used to describe the influence of random dipolar fields on the reorientation dynamics. The calculations are found to be in good agreement with the experimental data on the 0.3 % Mn where there are weak dipolar correlations.

  15. The structure of the Moho in the Northern Apennines: Evidence for an incipient slab tear fault?

    NASA Astrophysics Data System (ADS)

    Piana Agostinetti, Nicola

    2015-08-01

    This study investigates the geometry of the crust-mantle boundary along the Northern Apennines (Italy) and its relationship to the tectonic evolution of a retreating subduction system. Using receiver function analysis from teleseismic records, the Moho depth was computed beneath 26 seismic stations located in key positions along the orogen. The results show a relatively shallow (~ 20 km) Moho in the Tyrrhenian side, as expected from an extended overriding plate, and a deeper Moho (~ 40 km) in the subducted Adriatic plate, SW-dipping 15-45° beneath the chain. Stations deployed on the Northeastern edge of the Plio-Quaternary extensional basins provide maximum Moho depth estimates, thus supporting the hypothesis that these basins define the zone where the two plates separate at depth. In addition, an abrupt change in the Moho depth is recognized along strike of the orogen, attributed to a 45 km-wide, trench-normal deformation zone that crosses the Northern Apennines in the proximity of the Livorno-Sillaro lineament. This zone is interpreted as an incipient lithospheric tear fault, which accommodates varying rates of trench retreat along the length of the subduction zone.

  16. Cladding Alloys for Fluoride Salt Compatibility Final Report

    SciTech Connect

    Muralidharan, Govindarajan; Wilson, Dane F; Santella, Michael L; Holcomb, David Eugene

    2011-05-01

    This interim report provides an overview of several candidate technologies for cladding nickel-based corrosion protection layers onto high-temperature structural alloys. The report also provides a brief overview of the welding and weld performance issues associated with joining nickel-clad nickel-based alloys. From the available techniques, two cladding technologies were selected for initial evaluation. The first technique is a line-of-sight method that would be useful for coating large structures such as vessel interiors or large piping. The line-of-sight method is a laser-based surface cladding technique in which a high-purity nickel powder mixed into a polymer binder is first sprayed onto the surface, baked, and then rapidly melted using a high power laser. The second technique is a vapor phase technique based on the nickel-carbonyl process that is suitable for coating inaccessible surfaces such as the interior surfaces of heat exchangers. The final project report will feature an experimental evaluation of the performance of the two selected cladding techniques.

  17. Accident Performance of Light Water Reactor Cladding Materials

    SciTech Connect

    Nelson, Andrew T.

    2012-07-24

    During a loss of coolant accident as experienced at Fukushima, inadequate cooling of the reactor core forces component temperatures ever higher where they must withstand aggressive chemical environments. Conventional zirconium cladding alloys will readily oxidize in the presence of water vapor at elevated temperatures, rapidly degrading and likely failing. A cladding breach removes the critical barrier between actinides and fission products and the coolant, greatly increasing the probability of the release of radioactivity in the event of a containment failure. These factors have driven renewed international interest in both study and improvement of the materials used in commercial light water reactors. Characterization of a candidate cladding alloy or oxidation mitigation technique requires understanding of both the oxidation kinetics and hydrogen production as a function of temperature and atmosphere conditions. Researchers in the MST division supported by the DOE-NE Fuel Cycle Research and Development program are working to evaluate and quantify these parameters across a wide range of proposed cladding materials. The primary instrument employed is a simultaneous thermal analyzer (STA) equipped with a specialized water vapor furnace capable of maintaining temperatures above 1200 C in a range of atmospheres and water vapor contents. The STA utilizes thermogravimetric analysis and a coupled mass spectrometer to measure in situ oxidation and hydrogen production of candidate materials. This capability is unprecedented in study of materials under consideration for reactor cladding use, and is currently being expanded to investigate proposed coating techniques as well as the effect of coating defects on corrosion resistance.

  18. Development of ODS FeCrAl alloys for accident-tolerant fuel cladding

    SciTech Connect

    Dryepondt, Sebastien N.; Hoelzer, David T.; Pint, Bruce A.; Unocic, Kinga A.

    2015-09-18

    FeCrAl alloys are prime candidates for accident-tolerant fuel cladding due to their excellent oxidation resistance up to 1400 C and good mechanical properties at intermediate temperature. Former commercial oxide dispersion strengthened (ODS) FeCrAl alloys such as PM2000 exhibit significantly better tensile strength than wrought FeCrAl alloys, which would alloy for the fabrication of a very thin (~250 m) ODS FeCrAl cladding and limit the neutronic penalty from the replacement of Zr-based alloys by Fe-based alloys. Several Fe-12-Cr-5Al ODS alloys where therefore fabricated by ball milling FeCrAl powders with Y2O3 and additional oxides such as TiO2 or ZrO2. The new Fe-12Cr-5Al ODS alloys showed excellent tensile strength up to 800 C but limited ductility. Good oxidation resistance in steam at 1200 and 1400 C was observed except for one ODS FeCrAl alloy containing Ti. Rolling trials were conducted at 300, 600 C and 800 C to simulate the fabrication of thin tube cladding and a plate thickness of ~0.6mm was reached before the formation of multiple edge cracks. Hardness measurements at different stages of the rolling process, before and after annealing for 1h at 1000 C, showed that a thinner plate thickness could likely be achieved by using a multi-step approach combining warm rolling and high temperature annealing. Finally, new Fe-10-12Cr-5.5-6Al-Z gas atomized powders have been purchased to fabricate the second generation of low-Cr ODS FeCrAl alloys. The main goals are to assess the effect of O, C, N and Zr contents on the ODS FeCrAl microstructure and mechanical properties, and to optimize the fabrication process to improve the ductility of the 2nd gen ODS FeCrAl while maintaining good mechanical strength and oxidation resistance.

  19. Ferritic Alloys as Accident Tolerant Fuel Cladding Material for Light Water Reactors

    SciTech Connect

    Rebak, Raul B.

    2014-12-30

    The objective of the GE project is to demonstrate that advanced steels such as iron-chromium-aluminum (FeCrAl) alloys could be used as accident tolerant fuel cladding material in commercial light water reactors. The GE project does not include fuel development. Current findings support the concept that a FeCrAl alloy could be used for the cladding of commercial nuclear fuel. The use of this alloy will benefit the public since it is going to make the power generating light water reactors safer. In the Phase 1A of this cost shared project, GE (GRC + GNF) teamed with the University of Michigan, Los Alamos National Laboratory, Brookhaven National Laboratory, Idaho National Laboratory, and Oak Ridge National Laboratory to study the environmental and mechanical behavior of more than eight candidate cladding materials both under normal operation conditions of commercial nuclear reactors and under accident conditions in superheated steam (loss of coolant condition). The main findings are as follows: (1) Under normal operation conditions the candidate alloys (e.g. APMT, Alloy 33) showed excellent resistance to general corrosion, shadow corrosion and to environmentally assisted cracking. APMT also showed resistance to proton irradiation up to 5 dpa. (2) Under accident conditions the selected candidate materials showed several orders of magnitude improvement in the reaction with superheated steam as compared with the current zirconium based alloys. (3) Tube fabrication feasibility studies of FeCrAl alloys are underway. The aim is to obtain a wall thickness that is below 400 µm. (4) A strategy is outlined for the regulatory path approval and for the insertion of a lead fuel assembly in a commercial reactor by 2022. (5) The GE team worked closely with INL to have four rodlets tested in the ATR. GE provided the raw stock for the alloys, the fuel for the rodlets and the cost for fabrication/welding of the rodlets. INL fabricated the rodlets and the caps and welded them to

  20. Mechanical properties and examination of cracking in TMI-2 pressure vessel lower head material

    SciTech Connect

    Diercks, D.R.; Neimark, L.A.

    1993-09-01

    Mechanical tests have been conducted on material from 15 samples removed from the lower head of the Three Mile Island unit 2 nuclear reactor pressure vessel. Measured properties include tensile properties and hardness profiles at room temperature, tensile and creep properties at temperatures of 600 to 1200{degrees}C, and Charpy V-notch impact properties at {minus}20 to +300{degrees}C. These data, which were used in the subsequent analyses of the margin-to-failure of the lower head during the accident, are presented here. In addition, the results of metallographic and scanning electron microscope examinations of cladding cracking in three of the lower head samples are discussed.

  1. Localisation and characterisation of incipient brown-rot decay within spruce wood cell walls using FT-IR imaging microscopy

    PubMed Central

    Fackler, Karin; Stevanic, Jasna S.; Ters, Thomas; Hinterstoisser, Barbara; Schwanninger, Manfred; Salmén, Lennart

    2010-01-01

    Spruce wood that had been degraded by brown-rot fungi (Gloeophyllum trabeum or Poria placenta) exhibiting mass losses up to 16% was investigated by transmission Fourier transform infrared (FT-IR) imaging microscopy. Here the first work on the application of FT-IR imaging microscopy and multivariate image analysis of fungal degraded wood is presented and the first report on the spatial distribution of polysaccharide degradation during incipient brown-rot of wood. Brown-rot starts to become significant in the outer cell wall regions (middle lamellae, primary cell walls, and the outer layer of the secondary cell wall S1). This pattern was detected even in a sample with non-detectable mass loss. Most significant during incipient decay was the cleavage of glycosidic bonds, i.e. depolymerisation of wood polysaccharides and the degradation of pectic substances. Accordingly, intramolecular hydrogen bonding within cellulose was reduced, while the presence of phenolic groups increased. PMID:21052475

  2. Temperature fields generated by the elastodynamic propagation of shear cracks in the Earth

    NASA Astrophysics Data System (ADS)

    Fialko, Yuri

    2004-01-01

    energy, (2) transition from a crack-like to a pulse-like rupture propagation, or (3) ultimate rupture arrest. Assuming that the pulse-like ruptures heal by incipient fusion, the seismologic observations can be used to place a lower bound on the dynamic fault friction. This bound is found to be of the order of several megapascals, essentially independent of the earthquake size. Further experimental and theoretical studies of melt rheology at high strain rates are needed to quantify the effects of melting on the dynamic fault strength.

  3. Prediction of fatigue crack-growth patterns and lives in three-dimensional cracked bodies

    NASA Technical Reports Server (NTRS)

    Newman, J. C., Jr.; Raju, I. S.

    1984-01-01

    Fatigue crack growth patterns and lives for surface cracks, surface cracks at holes, and corner cracks at holes in three dimensional bodies were predicted using linear-elastic fracture mechanics concepts that were modified to account for crack-closure behavior. The predictions were made by using stress intensity factor equations for these crack configurations and the fatigue crack-growth (delta K against rate) relationship for the material of interest. The crack configurations were subjected to constant-amplitude fatigue loading under either remote tension or bending loads. The predicted crack growth patterns and crack growth lives for aluminum alloys agreed well with test data from the literature.

  4. Acoustic waveguide technique for sensing incipient faults in underground power-transmission cables: including acousto-optic techniques. Final report

    SciTech Connect

    Harrold, R.T.

    1981-09-01

    The feasibility of using acoustic waveguide techniques for sensing incipient faults in underground power transmission cables was determined. Theoretical and practical studies were made of both the acoustic emission spectrum signatures associated with cable incipient faults, and the attenuation of acoustic waves in waterfilled metal tubes used as waveguides. Based on critical data, it can be estimated that in favorable circumstances, the acoustic waveguide system would only be useful for sensing incipient faults in underground cables of approx. 800 meters (approx. 0.5 miles) or less in length. As underground power transmission cables are often several kilometers in length, it was clear at this stage of the study, that simple acoustic waveguide sensing techniques would not be adequate, and some modification would be needed. With DOE approval it was decided to investigate acousto-optic sensing techniques in order to extend the detection range. In particular, a system in which acoustic emissions from cable incipient faults impinge on a fiber-optic lightguide and locally change its refractive indes, and as a consequence, modulate laser light transmitted along the light guide. Experiments based on this concept were successful, and it has been demonstrated that it is possible to sense acoustic emissions with energy levels below one micro-joule. A practical test of this system in the laboratory using a section of compressed gas-insulated cable with an internal flashover was successfully carried out. Long distance fault sensing with this technique should be feasible as laser light can be transmitted several kilometers in fiber optic lightguides. It is believed that laser-acousto-optic fault sensing is a viable technique which, with development, could be applied for fault sensing in power cables and other apparatus.

  5. Acceleration and localization of subcritical crack growth in a natural composite material.

    PubMed

    Lennartz-Sassinek, S; Main, I G; Zaiser, M; Graham, C C

    2014-11-01

    Catastrophic failure of natural and engineered materials is often preceded by an acceleration and localization of damage that can be observed indirectly from acoustic emissions (AE) generated by the nucleation and growth of microcracks. In this paper we present a detailed investigation of the statistical properties and spatiotemporal characteristics of AE signals generated during triaxial compression of a sandstone sample. We demonstrate that the AE event amplitudes and interevent times are characterized by scaling distributions with shapes that remain invariant during most of the loading sequence. Localization of the AE activity on an incipient fault plane is associated with growth in AE rate in the form of a time-reversed Omori law with an exponent near 1. The experimental findings are interpreted using a model that assumes scale-invariant growth of the dominating crack or fault zone, consistent with the Dugdale-Barenblatt "process zone" model. We determine formal relationships between fault size, fault growth rate, and AE event rate, which are found to be consistent with the experimental observations. From these relations, we conclude that relatively slow growth of a subcritical fault may be associated with a significantly more rapid increase of the AE rate and that monitoring AE rate may therefore provide more reliable predictors of incipient failure than direct monitoring of the growing fault. PMID:25493797

  6. Performance of HT9 clad metallic fuel at high temperature

    SciTech Connect

    Pahl, R.G.; Lahm, C.E.; Hayes, S.L.

    1992-12-01

    Steady-state testing of HT9 clad metallic fuel at high temperatures was initiated in EBR-II in November of 1987. At that time U-10 wt. % Zr fuel clad with the low-swelling ferritic/martensitic alloy HT9 was being considered as driver fuel options for both EBR-II and FFTF. The objective of the X447 test described here was to determine the lifetime of HT9 cladding when operated with metallic fuel at beginning of life inside wall temperatures approaching {approximately}660{degree}C. Though stress-temperature design limits for HT9 preclude its use for high burnup applications under these conditions due to excessive thermal creep, the X447 test was carried out to obtain data on high temperature breach phenomena involving metallic fuel since little data existed in that area.

  7. Performance of HT9 clad metallic fuel at high temperature

    SciTech Connect

    Pahl, R.G.; Lahm, C.E.; Hayes, S.L.

    1992-01-01

    Steady-state testing of HT9 clad metallic fuel at high temperatures was initiated in EBR-II in November of 1987. At that time U-10 wt. % Zr fuel clad with the low-swelling ferritic/martensitic alloy HT9 was being considered as driver fuel options for both EBR-II and FFTF. The objective of the X447 test described here was to determine the lifetime of HT9 cladding when operated with metallic fuel at beginning of life inside wall temperatures approaching [approximately]660[degree]C. Though stress-temperature design limits for HT9 preclude its use for high burnup applications under these conditions due to excessive thermal creep, the X447 test was carried out to obtain data on high temperature breach phenomena involving metallic fuel since little data existed in that area.

  8. Clad photon sieve for generating localized hollow beams

    NASA Astrophysics Data System (ADS)

    Cheng, Yiguang; Tong, Junmin; Zhu, Jiangping; Liu, Junbo; Hu, Song; He, Yu

    2016-02-01

    A novel photon sieve structure called clad photon sieve is proposed to generate localized hollow beams and its design principle and focusing properties are studied. The clad photon sieve is composed of the internal zone and external zone with pinholes being positioned on the dark zones. Pinholes in the internal zone and in the external zone give destructive interference to the focus, leading to localized hollow beams being generated on the focal plane. Focusing properties of clad photon sieve with different focal lengths, zone numbers and modulation factors are also studied by theoretical calculations, numerical simulations and experiments, showing that the central dark spot size can be controlled by the focal length and rings number, and the intensity of the central dark spot varies with different modulation factors related with the internal zone and the external zone. This photon sieve can be useful for trapping and manipulating of particles and cooling of atoms.

  9. Nanoscale light-matter interactions in atomic cladding waveguides.

    PubMed

    Stern, Liron; Desiatov, Boris; Goykhman, Ilya; Levy, Uriel

    2013-01-01

    Alkali vapours, such as rubidium, are being used extensively in several important fields of research such as slow and stored light nonlinear optics quantum computation, atomic clocks and magnetometers. Recently, there is a growing effort towards miniaturizing traditional centimetre-size vapour cells. Owing to the significant reduction in device dimensions, light-matter interactions are greatly enhanced, enabling new functionalities due to the low power threshold needed for nonlinear interactions. Here, taking advantage of the mature platform of silicon photonics, we construct an efficient and flexible platform for tailored light-vapour interactions on a chip. Specifically, we demonstrate light-matter interactions in an atomic cladding waveguide, consisting of a silicon nitride nano-waveguide core with a rubidium vapour cladding. We observe the efficient interaction of the electromagnetic guided mode with the rubidium cladding and show that due to the high confinement of the optical mode, the rubidium absorption saturates at powers in the nanowatt regime. PMID:23462991

  10. Nanoscale light–matter interactions in atomic cladding waveguides

    PubMed Central

    Stern, Liron; Desiatov, Boris; Goykhman, Ilya; Levy, Uriel

    2013-01-01

    Alkali vapours, such as rubidium, are being used extensively in several important fields of research such as slow and stored light nonlinear optics quantum computation, atomic clocks and magnetometers. Recently, there is a growing effort towards miniaturizing traditional centimetre-size vapour cells. Owing to the significant reduction in device dimensions, light–matter interactions are greatly enhanced, enabling new functionalities due to the low power threshold needed for nonlinear interactions. Here, taking advantage of the mature platform of silicon photonics, we construct an efficient and flexible platform for tailored light–vapour interactions on a chip. Specifically, we demonstrate light–matter interactions in an atomic cladding waveguide, consisting of a silicon nitride nano-waveguide core with a rubidium vapour cladding. We observe the efficient interaction of the electromagnetic guided mode with the rubidium cladding and show that due to the high confinement of the optical mode, the rubidium absorption saturates at powers in the nanowatt regime. PMID:23462991

  11. Fabrication of stainless steel clad tubing. [gas pressure bonding

    NASA Technical Reports Server (NTRS)

    Kovach, C. W.

    1978-01-01

    The feasibility of producing stainless steel clad carbon steel tubing by a gas pressure bonding process was evaluated. Such a tube product could provide substantial chromium savings over monolithic stainless tubing in the event of a serious chromium shortage. The process consists of the initial assembly of three component tubesets from conventionally produced tubing, the formation of a strong metallurgical bond between the three components by gas pressure bonding, and conventional cold draw and anneal processing to final size. The quality of the tubes produced was excellent from the standpoint of bond strength, mechanical, and forming properties. The only significant quality problem encountered was carburization of the stainless clad by the carbon steel core which can be overcome by further refinement through at least three different approaches. The estimated cost of clad tubing produced by this process is greater than that for monolithic stainless tubing, but not so high as to make the process impractical as a chromium conservation method.

  12. Clad metals, roll bonding and their applications for SOFC interconnects

    NASA Astrophysics Data System (ADS)

    Chen, Lichun; Yang, Zhenguo; Jha, Bijendra; Xia, Guanguang; Stevenson, Jeffry W.

    Metallic interconnects have been becoming an increasingly interesting topic in the development in intermediate temperature solid oxide fuel cells (SOFC). High temperature oxidation resistant alloys are currently considered as candidate materials. Among these alloys however, different groups of alloys demonstrate different advantages and disadvantages, and few if any can completely satisfy the stringent requirements for the application. To integrate the advantages and avoid the disadvantages of different groups of alloys, clad metal has been proposed for SOFC interconnect applications and interconnect structures. This paper gives a brief overview of the cladding approach and its applications, and discuss the viability of this technology to fabricate the metallic layered-structure interconnects. To examine the feasibility of this approach, the austenitic Ni-base alloy Haynes 230 and the ferritic stainless steel AL 453 were selected as examples and manufactured into a clad metal. Its suitability as an interconnect construction material was investigated.

  13. Clad Metals, Roll Bonding and their Applications for SOFC Interconnects

    SciTech Connect

    Chen, L.; Yang, Zhenguo; Jha, B.; Xia, Guanguang; Stevenson, Jeffry W.

    2005-12-01

    High temperature oxidation resistant alloys are currently considered as candidate materials for construction of interconnects in intermediate temperature SOFCs. Among these alloys however, different groups of alloys demonstrate different advantages and disadvantages for the interconnect applications, and few if any can completely satisfied the stringent requirements for the applications. To integrate the advantages and avoid the disadvantages of different groups of alloys, cladding has been proposed as the approach to fabricate metallic layered interconnect structures. To examine the feasibility of this approach, the austenitic Ni-base alloy Haynes 230 and the ferritic stainless steel AL453 were selected as examples and manufactured into a clad metal. It’s suitability as interconnect construction materials were investigated. This paper will give a brief overview of the cladding approach and discuss the viability of this technology to fabricate the metallic layered-structure interconnects.

  14. Clad metals by roll bonding for SOFC interconnects

    SciTech Connect

    Chen, L.; Jha, B; Yang, Z Gary; Xia, Gordon; Stevenson, Jeffry W.; Singh, Prabhakar

    2006-08-01

    Metallic interconnects have been becoming an increasingly interesting topic in the development in intermediate temperature solid oxide fuel cells (SOFC). High temperature oxidation resistant alloys are currently considered as candidate materials. Among these alloys however, different groups of alloys demonstrate different advantages and disadvantages, and few if any can completely satisfy the stringent requirements for the application. To integrate the advantages and avoid the disadvantages of different groups of alloys, clad metal has been proposed for SOFC interconnect applications and interconnect structures. This paper gives a brief overview of the cladding approach and its applications, and discuss the viability of this technology to fabricate the metallic layered-structure interconnects. To examine the feasibility of this approach, the austenitic Ni-base alloy Haynes 230 and the ferritic stainless steel AL 453 were selected as examples and manufactured into a clad metal. Its suitability as an interconnect construction material was investigated.

  15. Clad metals by roll bonding for SOFC interconnects

    NASA Astrophysics Data System (ADS)

    Chen, L.; Jha, B.; Yang, Zhenguo; Xia, Guang-Guang; Stevenson, Jeffry W.; Singh, Prabhakar

    2006-08-01

    High-temperature oxidation-resistant alloys are currently considered as a candidate material for construction of interconnects in intermediate-temperature solid oxide fuel cells. Among these alloys, however, different groups of alloys demonstrate different advantages and disadvantages, and few, if any, can completely satisfy the stringent requirements for the application. To integrate the advantages and avoid the disadvantages of different groups of alloys, cladding has been proposed as one approach in fabricating metallic layered interconnect structures. To examine the feasibility of this approach, the austenitic Ni-base alloy Haynes 230 and the ferritic stainless steel AL 453 were selected as examples and manufactured into a clad metal. Its suitability as an interconnect construction material was investigated. This paper provides a brief overview of the cladding approach and discusses the viability of this technology to fabricate the metallic layered-structure interconnects.

  16. Metal-clad optical waveguides: analytical and experimental study.

    PubMed

    Kaminow, I P; Mammel, W L; Weber, H P

    1974-02-01

    Planar optical waveguides consisting of thin dielectric films with metal cladding have been investigated theoretically and experimentally. A computer program was devised to provide the phase and attenuation constants and wavefunctions for TE and TM modes in symmetric and asymmetric guides. Approximate expressions suitable for slide-rule calculation were also derived. Numerical results and illustrations are given for films of photoresist with Al, Ag, and Au cladding. Direct measurements of the attenuation and phase constants at 0.633 microm of numerous experimental waveguides are in reasonable agreement with theory. Attenuations <1 dB/cm, which is sufficiently small for application in devices, were measured. Calculated wavefunctions illustrate the mismatch of modes at transitions between unclad and metal-clad waveguides. Experimentally, we find substantial losses at such abrupt junctions. They can be overcome by simple tapered transitions. PMID:20125992

  17. Radiation enhancement of stress-corrosion cracking of Zircaloy

    SciTech Connect

    Shann, S.H.

    1981-09-01

    In order to examine the cause of the reactor fuel pin pellet-cladding interaction phenomenon (PCI), stress corrosion cracking (SCC) experiments of Zircaloy under iodine, iron iodide, aluminum iodide, cesium iodide, and cadmium were undertaken. Radiation enhancement tests with CsI were also performed. Iodine, iron iodide, and aluminum iodide can reduce the failure times. Fractography is of cleavage type and is completely different from the ductile dimple type failure for control specimens. There exists a critical stress of 379 MPa for iodine and iron iodide above which burst type failure occurs. Pinhole type failure predominates for lower stresses. Both types showed brittle fracture surfaces. The presence of CsI did not have any influence on failure time of zircaloy. The failure is burst-type, and the fractography is ductile. Radiation enhancement tests with cesium iodide did not cause reduction in failure time either. Failure times were decreased for the tests under cadmium. All specimens failed under cadmium vapor by a burst mode, and fractography showed cleavage brittle characteristics. Chemical parameters such as reaction order, activation energy, and minimum pressure required for SCC were determined. A crack propagation more originally designed for brittle solids for the SCC experimental data well. Variable stresses and surface roughness test results can be correlated quantitatively by the model. 80 figures.

  18. Current research on fatigue cracks

    SciTech Connect

    Tanaka, T.; Jono, M.; Komai, K.

    1987-01-01

    This first volume of CJMR (Current Japanese Materials Research), contains thirteen chapters concerning the above three themes of fatigue cracks. Each chapter is not a single paper as appearing in many academic journals and transactions, but a systematic review of the current achievement by each author with the emphasis on important points. The common feature is that the elaborated experimental techniques and theoretical approaches, some of which are quite unique, are introduced by respective authors to make clear the difficulty arising in the observation of small cracks and analysis of data. Theoretical models are proposed from the viewpoint of fracture mechanics to link the two thresholds of fatigue limit and crack growth, and intensive discussions are made for further development of the theory. Threshold stress intensity factors and the growth rate of medium and long sized cracks are also discussed, together with their opening behavior. The influencing factors are plastic zone size, the stress ratio and residual stress distribution occurring in welded joints. Mode II crack growth is of great significance since the initial fatigue cracks propagate mainly in shear mode. The problems of fatigue crack growth in corrosive environment is highly important since its retardation and enhancement take place in structural steels affected by the variety of factors. Life prediction in such environments poses another important problem. These are systematically discussed in this book.

  19. Password Cracking Using Sony Playstations

    NASA Astrophysics Data System (ADS)

    Kleinhans, Hugo; Butts, Jonathan; Shenoi, Sujeet

    Law enforcement agencies frequently encounter encrypted digital evidence for which the cryptographic keys are unknown or unavailable. Password cracking - whether it employs brute force or sophisticated cryptanalytic techniques - requires massive computational resources. This paper evaluates the benefits of using the Sony PlayStation 3 (PS3) to crack passwords. The PS3 offers massive computational power at relatively low cost. Moreover, multiple PS3 systems can be introduced easily to expand parallel processing when additional power is needed. This paper also describes a distributed framework designed to enable law enforcement agents to crack encrypted archives and applications in an efficient and cost-effective manner.

  20. Deformation-corrosion interactions for Zr alloys during I-SCC crack initiation. Part II: Localised stress and strain contributions

    NASA Astrophysics Data System (ADS)

    Jacques, Patrick; Lefebvre, Florence; Lemaignan, Clément

    1999-01-01

    For a better understanding of the initiation step of iodine induced stress corrosion cracking (SCC) in Zr alloys, responsible for pellet-cladding interaction (PCI) fuel rod failures, an analytical study has been undertaken, the aim of which being focused on the respective roles of local chemistry and stress/strain state on the crack nucleation. This second part is mostly related to the local stress induced by strain incompatibilities between grains. Using EBSP (electron back-scattering pattern) to analyze the crystallographic orientation of all the grains of the samples tested in SCC, it was possible to conclude that the major parameter controlling the nucleation of the intergranular cracks is not related to grain to grain strain incompatibilities, but to the orientation of the grain boundary planes with respect to the tensile stress.

  1. Method and system for edge cladding of laser gain media

    SciTech Connect

    Bayramian, Andrew James; Caird, John Allyn; Schaffers, Kathleen Irene

    2014-03-25

    A gain medium operable to amplify light at a gain wavelength and having reduced transverse ASE includes an input surface and an output surface opposing the input surface. The gain medium also includes a central region including gain material and extending between the input surface and the output surface along a longitudinal optical axis of the gain medium. The gain medium further includes an edge cladding region surrounding the central region and extending between the input surface and the output surface along the longitudinal optical axis of the gain medium. The edge cladding region includes the gain material and a dopant operable to absorb light at the gain wavelength.

  2. Welding fixture for nuclear fuel pin cladding assemblies

    DOEpatents

    Oakley, David J.; Feld, Sam H.

    1986-01-01

    A welding fixture for locating a driver sleeve about the open end of a nuclear fuel pin cladding. The welding fixture includes a holder provided with an open cavity having shoulders for properly positioning the driver sleeve, the end cap, and a soft, high temperature resistant plastic protective sleeve that surrounds a portion of the end cap stem. Ejected contaminant particles spewed forth by closure of the cladding by pulsed magnetic welding techniques are captured within a contamination trap formed in the holder for ultimate removal and disposal of contaminating particles along with the holder.

  3. Welding fixture for nuclear fuel pin cladding assemblies

    DOEpatents

    Oakley, D.J.; Feld, S.H.

    1984-02-22

    A welding fixture is described for locating a driver sleeve about the open end of a nuclear fuel pin cladding. The welding fixture includes a holder provided with an open cavity having shoulders for properly positioning the driver sleeve, the end cap, and a soft, high temperature resistant plastic protective sleeve that surrounds a portion of the end cap stem. Ejected contaminant particles spewed forth by closure of the cladding by pulsed magnetic welding techniques are captured within a contamination trap formed in the holder for ultimate removal and disposal of contaminating particles along with the holder.

  4. CHARACTERIZATION OF HYDROGEN CONTENT IN ZIRCALOY-4 NUCLEAR FUEL CLADDING

    SciTech Connect

    Pfeif, E. A.; Mishra, B.; Olson, D. L.; Lasseigne, A. N.; Krzywosz, K.; Mader, E. V.

    2010-02-22

    Assessment of hydrogen uptake of underwater nuclear fuel clad and component materials will enable improved monitoring of fuel health. Zirconium alloys are used in nuclear reactors as fuel cladding, fuel channels, guide tubes and spacer grids, and are available for inspection in spent fuel pools. With increasing reactor exposure zirconium alloys experience hydrogen ingress due to neutron interactions and water-side corrosion that is not easily quantified without destructive hot cell examination. Contact and non-contact nondestructive techniques, using Seebeck coefficient measurements and low frequency impedance spectroscopy, to assess the hydrogen content and hydride formation within zircaloy 4 material that are submerged to simulate spent fuel pools are presented.

  5. Laser cladding of Stellite #6: a detailed analysis

    NASA Astrophysics Data System (ADS)

    Kathuria, Yash P.; Tsuboi, Akihiko

    1996-09-01

    Potential applications such as hard facing of engine valve seat, turbine engine blade shroud interlock and leading edge of steam turbine blade, with controlled dilution have stimulated the use of laser cladding recently. In this paper, based on the laser beam interaction time, the microscopical study of dendrite structure formation in laser cladding of stellite number 6 on mild steel and Cr-Ni base materials is investigated. The effect of the various parameters such as heat input, beam interaction time, scanning frequency and transverse speed are considered. The applications in the rapid prototyping industries are also discussed.

  6. A computational algorithm for crack determination: The multiple crack case

    NASA Technical Reports Server (NTRS)

    Bryan, Kurt; Vogelius, Michael

    1992-01-01

    An algorithm for recovering a collection of linear cracks in a homogeneous electrical conductor from boundary measurements of voltages induced by specified current fluxes is developed. The technique is a variation of Newton's method and is based on taking weighted averages of the boundary data. The method also adaptively changes the applied current flux at each iteration to maintain maximum sensitivity to the estimated locations of the cracks.

  7. Stress intensity and crack displacement for small edge cracks

    NASA Technical Reports Server (NTRS)

    Orange, Thomas W.

    1988-01-01

    The weight function method was used to derive stress intensity factors and crack mouth displacement coefficients for small edge cracks (less than 20 percent of the specimen width) in common fracture specimen configurations. Contact stresses due to point application of loads were found to be small but significant for three-point bending and insignificant for four-point bending. The results are compared with available equations and numerical solutions from the literature and with unpublished boundary collocation results.

  8. Influence Of The Laser Cladding Strategies On The Mechanical Properties Of Inconel 718

    SciTech Connect

    Lamikiz, A.; Tabernero, I.; Ukar, E.; Lopez de Lacalle, L. N.

    2011-01-17

    This work presents different experimental results of the mechanical properties of Inconel registered 718 test parts built-up by laser cladding. Recently, turbine manufacturers for aeronautical sector have presented high interest on laser cladding processes. This process allows building fully functional structures on superalloys, such as Inconel registered 718, with high flexibility on complex shapes. However, there is limited data on mechanical properties of the laser cladding structures. Moreover, the available data do not include the influence of process parameters and laser cladding strategies. Therefore, a complete study of the influence of the laser cladding parameters and mainly, the variation of the tensile strength with the laser cladding strategy is presented. The results show that there is a high directionality of mechanical properties, depending on the strategies of laser cladding process. In other words, the test parts show a fiber -like structure that should be considered on the laser cladding strategy selection.

  9. Thermal-mechanical properties of cracked UO/sub 2/ pellets

    SciTech Connect

    Williford, R.E.; Mohr, C.L.; Lanning, D.D.

    1980-11-01

    A series of experiments (IFA-431, 432, 513, and 527) sponsored by the Fuel Behavior Research Branch of the USNRC are being irradiated in the Halden Boiling Water Reactor to better define LWR fuel behavior over the normal operating range of power reactor fuel rods. One fuel behavior variable of interest is the thermally induced cracking of UO/sub 2/ fuel pellets. The effects of pellet cracking on the effective thermal conductivity and elastic moduli for the fragmented fuel were found to be primarily dependent on the free area in the r, theta plane of the fuel rod. The free area is defined as the area within the cladding inner surface that is not occupied by the fuel fragments themselves.

  10. Grain-boundary cavitation and weld-underbead cracking in DOP-26 iridium alloy

    SciTech Connect

    Mosley, W.C. Jr.

    1983-01-01

    Plutonium-238 oxide fuel pellets for the General Purpose Heat Source Radioisotopic thermoelectric generators to be used on the NASA Galileo Mission to Jupiter and the International Solar Polar Mission are produced and encapsulated in DOP-26 iridium alloy at the Savannah River Plant. DOP-26 iridium alloy was developed at the Oak Ridge National Laboratory and contains nominally 0.3 weight-percent tungsten, 60-ppM thorium and 50-ppM aluminum. Underbead cracks occasionally occur in the girth weld on the iridium alloy cladding in the area where the gas tungsten arc is quenched. A variety of electron beam techniques have been used to determine the cause of cracking. Results are discussed. (WHK)

  11. Microstructure and Sliding Wear Resistance of Laser Cladded WC/Ni Composite Coatings with Different Contents of WC Particle

    NASA Astrophysics Data System (ADS)

    Xu, J. S.; Zhang, X. C.; Xuan, F. Z.; Wang, Z. D.; Tu, S. T.

    2012-09-01

    The aim of this article was to address the effect of WC content on the microstructure, microhardness, and sliding wear resistance of laser cladded WC/Ni composite coatings. The content of WC particle in the feed powder varied in the range of 0-80 wt.%. Experimental results showed that the laser cladded coatings exhibited homogeneous microstructure without pores or cracks. By comparing with the 45# steel substrate, the microhardness of WC/Ni composite coatings was relatively high. The microhardness of coating increased with increasing the content of WC particles. The wear resistance of WC/Ni composite coatings was strongly dependent on the content of WC particle and their microstructure. When the WC content was lower than 40 wt.% in the feed powder, the wear rate of the coatings decreased with increasing WC content. The two-body abrasive wear was identified as the main wear mechanisms. For the coatings with WC content higher than 40 wt.% in the feed powder, their wear rate increased with increasing WC content. The three-body abrasive wear and fatigue wear were the main failures. The coating with 40 wt.% WC in the feed powder exhibited the best wear resistance.

  12. Carbon stable isotope composition of DNA isolated from an incipient paleosol

    NASA Astrophysics Data System (ADS)

    Jahren, A. Hope; Kelm, Kellie; Wendland, Beverly; Petersen, Gitte; Seberg, Ole

    2006-05-01

    We determined the carbon isotope (δ13C) value of double-stranded DNA (dsDNA) isolated from the organic horizons of a Delaware soil that is actively being covered by an encroaching sand dune. The soil belongs to a Nymphaea odorata Ait. (water lily) wetland, and we regard its active acquisition of a thick (˜24 cm) surface mantle to embody the process of paleopedogenesis; therefore, we have termed it an “incipient paleosol.” In this study, we compared the δ13C value of paleosol dsDNA to the bulk δ13C value of N. odorata, as well as to the δ13C value of plants that had colonized the surface mantle. The isotopic offset between paleosol δ13CdsDNA and N. odorata δ13Ctissue was identical to the relationship between δ13CdsDNA and δ13Ctissue for tracheophytes, which we had previously determined. In contrast, the isotopic offset between paleosol δ13CdsDNA and the δ13Ctissue of plants colonizing the surface mantle differed from this relationship by as much as 4‰. Similarly, the δ13C value of bulk paleosol organic matter was extremely heterogeneous and varied across 6‰. All paleosol DNA polymerase chain reaction (PCR) products produced clear, sharp, 350 base-pair (bp) fragments of rbcL, a gene shared by all photosynthetic organisms. These results open the exciting possibility that stable isotope analysis of dsDNA isolated from paleosol organic matter can be used to infer the δ13C value of the plant that dominated the nucleic acid contribution.

  13. Incipient flow properties of two-component fine powder mixtures: Changing the flowability of smaller particles

    NASA Astrophysics Data System (ADS)

    Kojima, Takehiro; Elliott, James A.

    2013-06-01

    Understanding the flow properties of two-component fine powder systems with micrometre-sized constituents is important for the quality control of electrophotographic printing applications such as photocopiers. In previous work, we studied the incipient flow properties of model powder mixtures of large (d50 ˜ 70 μm) and small (d50 ˜ 6-8 μm) particles under a consolidation stress of 2 kPa, and reported that they were strongly related to the properties of the small particles where the volume ratio of small powder (xs) exceeds ˜0.1 [1]. In this follow-up study, we examine the effect of changing the flowability of the smaller components on the structure and flow properties of the binary mixtures. For the smaller particles, we used poly(styrene-co-divinylbenzene) (PS-DVB) microspheres (d50 = 7.84 μm). The particle surfaces were modified by adding silica nanoparticles in order to prepare PS-DVB powders with a range of flowabilities. These were then mixed with glass ballotini (d50 = 71.9 μm), and the flow properties of these mixtures were evaluated using the shear testing technique. The cohesion of the mixtures showed essentially the same trend as reported in [1] in terms of their dependence on xs and was related to the number of contacts between the PS-DVB particles. Also, it was strongly dependent on the cohesion of the PS-DVB powders despite a very small xs (xs < 0.01). As for the internal angle of friction, although its value for each PS-DVB powder was similar, it also showed a correlation with the number of contacts between PS-DVB particles.

  14. Incipient motion in gravel bed rivers due to energetic turbulent flow events

    NASA Astrophysics Data System (ADS)

    Valyrakis, Manousos

    2013-04-01

    This contribution reviews recent developments and contributions in the field of incipient motion and entrainment of coarse sediment grains due to the action of near bed turbulent flows. Specifically, traditional shear based spatio-temporally averaged concepts and instantaneous stress tensor criteria are contrasted to the newly proposed flow event based impulse and energy criteria. The energy criterion, suggests that only sufficiently energetic turbulent events can remove a particle from its resting position on the bed surface and result on its entrainment downstream. While the impulse and energy criteria are interconnected through the energy-impulse equation, the later appears to be more versatile and appropriate for generalising to sediment transport. These flow event based criteria have a sound physical basis for describing the intermittent character of particle entrainment as inherited by near boundary turbulence at near threshold conditions. These criteria can be derived from fundamental laws of physics such as Newtonian classical mechanics and the Lagrange equations respectively. The energetic events that are capable of performing geomorphic work at the scale of individual particles are shown to follow a power law, meaning that more energetic events (capable of removing larger stones) are expected to occur less frequently. In addition, this paper discusses the role of the coefficient of energy transfer efficiency introduced in the energy equation for particle entrainment. A preliminary investigation from analysis of a series of mobile grain flume experiments illustrates that different signatures of turbulence or sequence of flow structures may have different effectiveness towards particle transport. Characteristic cases of specific energetic flow events and the associated particle response are shown and classified with regard to the time required for complete entrainment. Finally these findings are commented with respect to the implications for sediment

  15. Effects of intramuscular administration of glycosaminoglycan polysulfates on signs of incipient hip dysplasia in growing pups.

    PubMed

    Lust, G; Williams, A J; Burton-Wurster, N; Beck, K A; Rubin, G

    1992-10-01

    We tested the hypothesis that treatment of growing, susceptible (to hip dysplasia) pups by IM administration of glycosaminoglycan polysulfates would mitigate the signs of incipient hip dysplasia. In 1 experiment, 7 pups, selected at random from 2 litters, were administered glycosaminoglycan polysulfates (2.5 mg/kg of body weight, IM) twice weekly, and 7 control pups from the same litters were given sterile buffered 0.9% saline solution from the age of 6 weeks to 8 months. Hip joints were examined by radiography, with pups in the standard, limbs-extended position. At 8 months of age, all pups in this experiment did not manifest femoral head subluxation radiographically. The Norberg angle, a measure of coxofemoral congruity, improved from a mean +/- SEM value of 102 degrees +/- 1 degrees in controls to 106 degrees +/- 1 degrees in treated pups (P = 0.008). Pups were not subjected to necropsy. In the second experiment, 8 pups were selected at random from 2 litters and were administered 5 mg of glycosaminoglycan polysulfates/kg, IM, twice weekly from 6 weeks to 8 months of age. Similarly, 8 control pups were administered saline solution. At 8 months of age, hip joints were examined by radiography with pups in the standard position; at necropsy, intra-articular tissues were evaluated macroscopically and biochemically. Of 8 treated pups, none had subluxation radiographically, whereas 4 of 8 control dogs had femoral head subluxation. Mean Norberg angle on the radiographs was 109.7 degrees +/- 1.6 degrees for the treated group and was 101.5 degrees +/- 1.6 degrees for controls, representing a mean improvement in coxofemoral congruity of 8.2 degrees in the treated pups.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1456530

  16. Incipiently drowned platform deposit in cyclic Ordovician shelf sequence: Lower Ordovician Chepultepec Formation, Virginia

    SciTech Connect

    Bova, J.A.; Read, J.F.

    1983-03-01

    The Chepultepec interval, 145 to 260 m (476 to 853 ft) thick, in Virginia contains the Lower Member up to 150 m (492 ft) thick, and the Upper Member, up to 85 m (279 ft) thick, of peritidal cyclic limestone and dolomite, and a Middle Member, up to 110 m (360 ft) thick, of subtidal limestone and bioherms, passing northwestward into cyclic facies. Calculated long term subsidence rates were 4 to 5 cm/1000 yr (mature passive margin rates), shelf gradients were 6 cm/km, and average duration of cycles was 140,00 years. Peritidal cyclic sequences are upward shallowing sequences of pellet-skeletal limestone, thrombolites, rippled calcisiltites and intraclast grainstone, and laminite caps. They formed by rapid transgression with apparent submergence increments averaging approximately 2 m (6.5 ft) in Lower Member and 3.5 m (11.4 ft), Upper Member. Deposition during Middle Member time was dominated by skeletal limestone-mudstone, calcisiltite with storm generated fining-upward sequences, and burrow-mixed units that were formed near fair-weather wave base, along with thrombolite bioherms. Locally, there are upward shallowing sequences, of basal wackestone/mudstone to calcisiltite to bioherm complexes (locally with erosional scalloped tops). Following each submergence, carbonate sedimentation was able to build to sea level prior to renewed submergence. Large submergence events caused tidal flats to be shifted far to the west, and they were unable to prograde out onto the open shelf because of insufficient time before subsidence was renewed, and because the open shelf setting inhibited tidal flat deposition. The Middle Member represents an incipiently drowned sequence that developed by repeated submergence events.

  17. Fluid flow and mud volcanism in the Eastern Mediterranean incipient collision zones

    NASA Astrophysics Data System (ADS)

    Zitter, T. A. C.; Woodside, J. M.; Mascle, J.

    2003-04-01

    Fluid venting activity, either coupled with mud volcanism or along deep active faults or both, has been investigated in the Eastern Mediterranean Sea, mainly in two areas associated with the incipient collision process between Africa and Eurasia. Mud volcanoes are abundant on the crestal part of the Mediterranean Ridge accretionary prism, in association with thrusts, back-thrusts and transcurrent features. They are also found in the Anaximander Mountains/Florence Rise area, to the west of Cyprus, where a wrench system accommodates the pre-collisional deformation. Combined swath multibeam bathymetry and imagery, seismic profiling (ANAXIPROBE survey, 1995 and PRISMED II survey, 1998) and O.R.E.Tech sidescan sonar data (MEDINETH survey, 1999) indicate the genetic relationship between mud volcanoes and tectonics, particularly potential influence of strike-slip faulting. The in situ observations of mud volcanoes (MEDINAUT survey, 1998) have revealed common characteristics at cold seeps, such as carbonate crust constructions and specific chemosynthetic-based fauna. Ground-truth of the sonar data shows that the geophysical signature of mud volcanoes may be related to spatial and temporal evolution of mud volcanism activity, because the seafloor characteristics (surface of the mud flows, distribution and nature of the crusts) and the degree of colonization by benthic fauna vary with the intensity and age of the fluid seepage. Moreover, clay mineralogy studies on the mud matrix samples give insights into the depositional environment, age, and depth of the lithological unit from which the mud breccia is extruded. The shallow signature of the mud reservoir tends to indicate that the overpressured fluids originate from deeper strata than the solid phase of the expelled material.

  18. The influence of the basalt-eclogite transition on incipient subduction dynamics

    NASA Astrophysics Data System (ADS)

    Hall, C.; Gurnis, M.

    2004-12-01

    Subduction becomes self-sustaining when the negative buoyancy of the slab is larger than the sum of elastic bending, fault friction, and viscous drag. The oceanic lithosphere, consisting of basaltic crust overlying mantle which is depleted in iron, is compositionally buoyant relative to the asthenosphere and will resist subduction. This is not a critical impediment for mature subduction zones because the basaltic crust should metamorphose into denser eclogite, with the result that the slab has nearly neutral compositional buoyancy at depths greater than this phase transition. During subduction initiation, however, compositional buoyancy may offer significant resistance to subduction and initially limit subduction to plates which have gained sufficient negative buoyancy from cooling. We have shown that while including a 6 km thick basaltic crust does not greatly affect the maximum force required to bend the lithosphere, it substantially increases the net work required to reach a self-sustaining state. These earlier models did not consider the basalt-eclogite transition. We use a visco-elastoplastic numerical method to model the evolution of the force balance during incipient subduction occurring at a fixed convergence rate. Phases are tracked using a particle advection scheme. In some cases, the buoyant basaltic crust buoyantly detaches from the mantle lithosphere and rises to the base of the over-riding lithosphere. Buoyant detachment removes most of the compositional impediment to subduction initiation, but will deny the slab of the additional driving force that would occur after the transformation of basalt to eclogite. Crustal detachment is encouraged by mechanical thickening during convergence, and therefore may depend on the degree of coupling and fault strength at the plate interface.

  19. A forensics-based approach for assessing incipient heterogeneity of a hydrologic system.

    NASA Astrophysics Data System (ADS)

    Alves Meira Neto, A.; Matos, K. A.; Wang, Y.; Troch, P. A. A.; Chorover, J.; Ferré, T. P. A.

    2015-12-01

    Hydrologic systems are far from being static in time. Therefore, the study of the evolution of natural systems along with the investigation of the interactions between hydrology, geochemistry and geophysics can be highly beneficial for improving hydrologic predictions. In this study, a combined hydrologic, geophysical and geochemical approach is proposed to investigate the incipient heterogeneity in a small hydrologic system subject to intensive flux of water through a period of one year. The Mini-LEO is a sloping metallic lysimeter containing 1 m3 of granular basalt, constructed as a smaller scale version of Landscape Evolution Observatory (LEO) artificial hillslopes. The initially pristine soil inside the Mini-LEO had undergone several cycles of irrigation, which might have changed the internal structure of this system, as observed by both hydrometric data and corroborated by studies pointing out to a rapid weathering of the basaltic soil. A forensic approach was proposed, where the Mini-LEO was systematically excavated for the investigation of its initial signs of hydrologic co-evolution. The lysimeter was sub-divided in voxels, for which 100 undisturbed soil samples and fragmented subsamples were collected for further analysis of soil hydraulic properties (saturated hydraulic conductivity and characteristic curve) as well as geochemical composition (elemental dissolution/accumulations and mineralogical transformations). Additionally, electrical resistivity (ER) measurements at different water content were measured for each sample. The results of this study are manifold: The expected geochemical signature will be used for validating current hydro-geochemical models of the Mini-LEO, and the superposition of the geochemical and hydraulic analysis will serve as discriminatory data for the results of geophysical investigation.

  20. A preliminary numerical model on the incipient motion conditions of flooded vehicles

    NASA Astrophysics Data System (ADS)

    Arrighi, Chiara; Castelli, Fabio; Oumeraci, Hocine

    2014-05-01

    The constant increase of the population living in cities and the concerns related to the climate change make flood risk in urban areas a crucial issue in terms of potential damages, casualties and injuries to the people. Vehicles are generally recognized as one of the most aggravating factors in case of floodings in the urban environment. On one hand they interact with the flow modifying locally flood parameters or causing obstructions, on the other hand they are indirectly responsible of many fatalities. According to many studies, most of deaths for drowning occurs in the cars and this drives the need to better understand the conditions in which the vehicles become unstable and consequently dangerous for people and infrastructures. In the view of better assessing the vulnerability during a flood, a deepening in the knowledge of this phenomenon is required. The approach proposed consist of a 3D numerical model able to clarify the occurrence of these conditions and the interaction between flood and vehicles. The model relies on the experimental data provided in literature. In this preliminary study the traditional approach typically used for the incipient motion threshold conditions of river sediments is adapted for the specific geometry of a vehicle. The dimensional analysis of the existing experimental data, is the preliminary step in order to design numerical simulations. The proposed conceptual model is the basis for the numerical analysis aiming at the generalization of empirical results. The dimensionless graph coming from the experiments shows a significant difference between vehicles with a density lower (empty car) than water and larger (filled by floodwater) than water. These behaviors represent both realistic conditions during a sudden flood. The 3D numerical simulation clarifies flow behavior around the obstacle and allows some hints on new approaches for flood modeling in the urban environment.

  1. Incipient renal transplant dysfunction associates with tubular syndecan-1 expression and shedding.

    PubMed

    Adepu, Saritha; Rosman, Colin W K; Dam, Wendy; van Dijk, Marcory C R F; Navis, Gerjan; van Goor, Harry; Bakker, Stephan J L; van den Born, Jacob

    2015-07-15

    Syndecan-1 is a transmembrane heparan sulfate proteoglycan involved in regenerative growth and cellular adhesion. We hypothesized that the induction of tubular syndecan-1 is a repair response to incipient renal damage in apparently stable, uncomplicated renal transplant recipients. We quantified tubular syndecan-1 in unselected renal protocol biopsies taken 1 yr after transplantation. Spearman rank correlation analysis revealed an inverse correlation between tubular syndecan-1 expression and creatinine clearance at the time of biopsy (r = -0.483, P < 0.03). In a larger panel of protocol and indication biopsies from renal transplant recipients, tubular syndecan-1 correlated with tubular proliferation marker Ki67 (r = 0.518, P < 0.0001). In a rat renal transplantation model, 2 mo after transplantation, mRNA expression of syndecan-1 and its major sheddase, A disintegrin and metalloproteinase-17, were upregulated (both P < 0.03). Since shed syndecan-1 might end up in the circulation, in a stable cross-sectional human renal transplant population (n = 510), we measured plasma syndecan-1. By multivariate regression analysis, we showed robust independent associations of plasma syndecan-1 with renal (plasma creatinine and plasma urea) and endothelial function parameters (plasma VEGF-A, all P < 0.01). By various approaches, we were not able to localize syndecan-1 in vessel wall or endothelial cells, which makes shedding of syndecan-1 from the endothelial glycocalyx unlikely. Our data suggest that early damage in transplanted kidneys induces repair mechanisms within the graft, namely, tubular syndecan-1 expression for tubular regeneration and VEGF production for endothelial repair. Elevated plasma syndecan-1 levels in renal transplantation patients might be interpreted as repair/survival factor related to loss of tubular and endothelial function in transplanted kidneys. PMID:25972509

  2. Incipient continental rifting: Insights from the Okavango Rift Zone, northwestern Botswana

    NASA Astrophysics Data System (ADS)

    Kinabo, Baraka Damas

    In this dissertation aeromagnetic, gravity, and Shuttle Radar Topography Mission Digital Elevation Model (SRTM DEM) data from the Okavango Rift Zone in northwest Botswana are used to map the distribution of rift and basement structures. The distribution of these structures provide useful insights into the early stages of continental rifting. The objectives of this study are (1) assessing the role of pre-existing structures on rift basin development, (2) characterizing the geometry of the nascent rift basins, (3) documenting fault growth and propagation patterns, and (4) investigating the border fault development. Potential field data especially aeromagnetic data are used to map out structures in the sediment covered basement, whereas SRTM DEM data express the surface morphology of the structures. The azimuth of rift faults parallel the orientation of the fold axes and the prominent foliation directions of the basement rocks. This indicates that pre-existing structures in the basement influenced the development of the rift structures. NE dipping faults consistently exhibit greater displacements than SE dipping faults, suggesting a developing half-graben geometry. Individual faults grow by along axis linkage of small segments that develop from soft linkage (under lapping to overlapping segments) to hard linkage (hooking, fused segments). Major rifts faults are also linking through transfer zones by the process of "fault piracy" to establish an immature border fault system. The relationships between scam heights and vertical throws reveal that the young and active faults are located outside the rift while the faults with no recent activities are in the middle suggesting that the rift is also growing in width. This study demonstrates the utility of potential field data and SRTM DEM to provide a 3-D view of incipient continental rifting processes such as fault growth and propagation.

  3. Comparison of Machine Learning methods for incipient motion in gravel bed rivers

    NASA Astrophysics Data System (ADS)

    Valyrakis, Manousos

    2013-04-01

    Soil erosion and sediment transport of natural gravel bed streams are important processes which affect both the morphology as well as the ecology of earth's surface. For gravel bed rivers at near incipient flow conditions, particle entrainment dynamics are highly intermittent. This contribution reviews the use of modern Machine Learning (ML) methods implemented for short term prediction of entrainment instances of individual grains exposed in fully developed near boundary turbulent flows. Results obtained by network architectures of variable complexity based on two different ML methods namely the Artificial Neural Network (ANN) and the Adaptive Neuro-Fuzzy Inference System (ANFIS) are compared in terms of different error and performance indices, computational efficiency and complexity as well as predictive accuracy and forecast ability. Different model architectures are trained and tested with experimental time series obtained from mobile particle flume experiments. The experimental setup consists of a Laser Doppler Velocimeter (LDV) and a laser optics system, which acquire data for the instantaneous flow and particle response respectively, synchronously. The first is used to record the flow velocity components directly upstream of the test particle, while the later tracks the particle's displacements. The lengthy experimental data sets (millions of data points) are split into the training and validation subsets used to perform the corresponding learning and testing of the models. It is demonstrated that the ANFIS hybrid model, which is based on neural learning and fuzzy inference principles, better predicts the critical flow conditions above which sediment transport is initiated. In addition, it is illustrated that empirical knowledge can be extracted, validating the theoretical assumption that particle ejections occur due to energetic turbulent flow events. Such a tool may find application in management and regulation of stream flows downstream of dams for stream

  4. DECONTAMINATION OF ZIRCALOY CLADDING HULLS FROM SPENT NUCLEAR FUEL

    SciTech Connect

    Rudisill, T.

    2010-09-29

    The feasibility of decontaminating spent fuel cladding hulls using hydrofluoric acid (HF) was investigated as part of the Global Energy Nuclear Partnership (GNEP) Separations Campaign. The concentrations of the fission product and transuranic (TRU) isotopes in the decontaminated hulls were compared to the limits for determining the low level waste (LLW) classification in the United States (US). The {sup 90}Sr and {sup 137}Cs concentrations met the disposal criteria for a Class C LLW; although, in a number of experiments the criteria for disposal as a Class B LLW were met. The TRU concentration in the hulls generally exceeded the Class C LLW limit by at least an order of magnitude. The concentration decreased sharply as the initial 30-40 {micro}m of the cladding hull surface were removed. At depths beyond this point, the TRU activity remained relatively constant, well above the Class C limit. Reprocessing of spent nuclear fuel generates a cladding waste which would likely require disposal as a Greater than Class C LLW in the US. If the cladding hulls could be treated to remove a majority of the actinide and fission product contamination, the hulls could potentially meet acceptance criteria for disposal as a LLW or allow recycle of the Zr metal. Discard of the hulls as a LLW would result in significant cost savings compared to disposal as a Greater than Class C waste which currently has no disposition path. During fuel irradiation and reprocessing, radioactive materials are produced and deposited in the Zircaloy cladding. Due to short depths of penetration, the majority of the fission products and actinide elements are located in the ZrO{sub 2} layer which forms on the surface of the cladding during fuel irradiation. Therefore, if the oxide layer is removed, the majority of the contamination should also be removed. It is very difficult, if not impossible to remove all of the activity from spent fuel cladding since traces of U and Th in the unirradiated Zircaloy

  5. Report on Reactor Physics Assessment of Candidate Accident Tolerant Fuel Cladding Materials in LWRs

    SciTech Connect

    Powers, Jeffrey J.; George, Nathan; Maldonado, G. Ivan; Worrall, Andrew

    2015-08-28

    This work focuses on ATF concepts being researched at Oak Ridge National Laboratory (ORNL), expanding on previous studies of using alternate cladding materials in pressurized water reactors (PWRs). The neutronic performance of two leading alternate cladding materials were assessed in boiling water reactors (BWRs): iron-chromium-aluminum (FeCrAl) cladding, and silicon carbide (SiC)-based composite cladding. This report fulfills ORNL Milestone M3FT-15OR0202332 within the fiscal year 2015 (FY15)

  6. Spot weld attachment of thermocouples to a fuel rod cladding interior surface

    SciTech Connect

    Page, R.E.; Bates, S.O.; Pilger, J.P.

    1984-08-01

    Research was conducted by Pacific Northwest Laboratory to weld 0.020-inch-diameter thermocouples to the interior surface of Zircaloy 4 light-water reactor fuel cladding. Inconel sheathed Type K thermocouples were attached to fuel cladding to register cladding temperatures during loss-of-coolant accident testing. This report describes the development of welding parameters and the effects of thermocouple attachment on the burst strength and integrity of the cladding at temperatures up to 1550/sup 0/F.

  7. Peridynamic model for fatigue cracking.

    SciTech Connect

    Silling, Stewart Andrew; Abe Askari

    2014-10-01

    The peridynamic theory is an extension of traditional solid mechanics in which the field equations can be applied on discontinuities, such as growing cracks. This paper proposes a bond damage model within peridynamics to treat the nucleation and growth of cracks due to cyclic loading. Bond damage occurs according to the evolution of a variable called the "remaining life" of each bond that changes over time according to the cyclic strain in the bond. It is shown that the model reproduces the main features of S-N data for typical materials and also reproduces the Paris law for fatigue crack growth. Extensions of the model account for the effects of loading spectrum, fatigue limit, and variable load ratio. A three-dimensional example illustrates the nucleation and growth of a helical fatigue crack in the torsion of an aluminum alloy rod.

  8. 21 CFR 137.190 - Cracked wheat.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 2 2012-04-01 2012-04-01 false Cracked wheat. 137.190 Section 137.190 Food and... Related Products § 137.190 Cracked wheat. Cracked wheat is the food prepared by so cracking or cutting into angular fragments cleaned wheat other than durum wheat and red durum wheat that, when tested...

  9. 21 CFR 137.190 - Cracked wheat.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 2 2013-04-01 2013-04-01 false Cracked wheat. 137.190 Section 137.190 Food and... Related Products § 137.190 Cracked wheat. Cracked wheat is the food prepared by so cracking or cutting into angular fragments cleaned wheat other than durum wheat and red durum wheat that, when tested...

  10. 21 CFR 137.190 - Cracked wheat.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 2 2014-04-01 2014-04-01 false Cracked wheat. 137.190 Section 137.190 Food and... Related Products § 137.190 Cracked wheat. Cracked wheat is the food prepared by so cracking or cutting into angular fragments cleaned wheat other than durum wheat and red durum wheat that, when tested...

  11. Cocaine/Crack: The Big Lie.

    ERIC Educational Resources Information Center

    National Inst. on Drug Abuse (DHHS/PHS), Rockville, MD.

    This pamphlet focuses on cocaine and crack use and the addictive nature of cocaine/crack. It contains a set of 21 questions about crack and cocaine, each accompanied by a clear and complete response. Interspersed throughout the booklet are photographs and quotes from former cocaine or crack users/addicts. Questions and answers focus on what…

  12. Vibrations Caused By Cracked Turbopump Bearing Race

    NASA Technical Reports Server (NTRS)

    Goggin, David G.; Dweck, Robert A.

    1990-01-01

    Expansion gives rise to eccentricity. Report presents analysis of dynamic effects caused by cracking of inner race of ball bearing in turbopump. Crack manifested itself via increase in vibrations synchronous with rotation and smaller increase at twice frequency of rotation. Analysis conducted to verify these increases were caused solely by crack and to understand implications for future such cracks.

  13. 21 CFR 137.190 - Cracked wheat.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 2 2010-04-01 2010-04-01 false Cracked wheat. 137.190 Section 137.190 Food and... Related Products § 137.190 Cracked wheat. Cracked wheat is the food prepared by so cracking or cutting into angular fragments cleaned wheat other than durum wheat and red durum wheat that, when tested...

  14. Shaft vibrations in turbomachinery excited by cracks

    NASA Technical Reports Server (NTRS)

    Grabowski, B.

    1982-01-01

    During the past years the dynamic behavior of rotors with cracks has been investigated mainly theoretically. This paper deals with the comparison of analytical and experimental results of the dynamics of a rotor with an artificial crack. The experimental results verify the crack model used in the analysis. They show the general possibility to determine a crack by extended vibration control.

  15. Cracking behavior of cored structures

    SciTech Connect

    Wahid, A.; Olson, D.L.; Matlock, D.K. . Center for Welding and Joining Research); Kelly, T.J. )

    1991-01-01

    The effects of compositional gradients, are considered based on a thermodynamic analysis, referred to as the Cahn-Hillard analysis, which describes the degree to which a local surface energy is modified by the presence of a composition gradient. The analysis predicts that both ductile and brittle fracture mechanisms are enhanced by the presence of a composition gradient. Data on stress corrosion cracking and fatigue crack growth in selected FCC alloys are used to illustrate the significance of microsegregation on mechanical properties.

  16. Cracking behavior of cored structures

    SciTech Connect

    Wahid, A.; Olson, D.L.; Matlock, D.K.; Kelly, T.J.

    1991-12-31

    The effects of compositional gradients, are considered based on a thermodynamic analysis, referred to as the Cahn-Hillard analysis, which describes the degree to which a local surface energy is modified by the presence of a composition gradient. The analysis predicts that both ductile and brittle fracture mechanisms are enhanced by the presence of a composition gradient. Data on stress corrosion cracking and fatigue crack growth in selected FCC alloys are used to illustrate the significance of microsegregation on mechanical properties.

  17. Compliance matrices for cracked bodies

    NASA Technical Reports Server (NTRS)

    Ballarini, R.

    1986-01-01

    An algorithm is presented which can be used to develop compliance matrices for cracked bodies. The method relies on the numerical solution of singular integral equations with Cauchy-type kernels and provides an efficient and accurate procedure for relating applied loadings to crack opening displacements. The algorithm should be of interest to those performing repetitive calculations in the analysis of experimental results obtained from fracture specimens.

  18. Characteristics of a long-period fiber grating with reduced cladding for refractive index sensing

    NASA Astrophysics Data System (ADS)

    Chen, Haiyun; Gu, Zhengtian

    2011-10-01

    The sensitivity to surrounding refractive index (SRI) of a long-period fiber grating (LPFG) can be effectively improved by decreasing the cladding radius. When the cladding is reduced, a three-layer model is necessary to evaluate the effective refractive index (ERI) of the core mode. A variation of SRI can induce a greater resonant wavelength shift when the core mode is coupled to a higher-order cladding mode. However, as the cladding is reduced further, the highest-order cladding mode would be cut off, i.e. the number of cladding modes that a given fiber structure can support would be less; thus, the higher-order cladding modes that can be used for higher sensitivity are limited. Hence, the implementation of high sensitivity for SRI sensing with cladding-reduced LPFGs is dependent on the proper combination of cladding radius and cladding mode order. Based on the vector coupled-mode theory, the transmission spectrum and sensitivity are numerically analyzed with respect to the cladding radius, which shows that the SRI sensitivity of the HE12 mode with cladding radius a 2 = 20 µm is 32 times as high as that with a 2 = 62.5 µm and the SRI resolution is available to the order of 10-7.

  19. Analysis of fatigue crack propagation

    NASA Technical Reports Server (NTRS)

    Liu, H. W.

    1972-01-01

    The correlation between fatigue crack propagation and stress intensity factor is analyzed. When determining fatigue crack propagation rate, a crack increment, delta a, and its corresponding increment in load cycles, delta N, are measured. Fatigue crack propagation must be caused by a shear and/or a normal separation mode. Both of these two processes are discrete if one looks at the atomic level. If the average deformation and fracture properties over the crack increments, delta a, can be considered as homogeneous, if the characteristic discrete lengths of sigma a, if the plastic zone size is small, and if a plate is thick enough to insure a plane strain case, da/dN is proportional to delta K squared. Any deviation of empirical data from this relation must be caused by the fact that one or more of these conditions are not satisfied. The effects of plate thickness and material inhomogeneity are discussed in detail. A shear separation mode of fatigue crack propagation is described and is used to illustrate the effects of material inhomogeneity.

  20. Mitigation of Crack Damage in Metallic Materials

    NASA Technical Reports Server (NTRS)

    Leser, Patrick E.; Newman, John A.; Smith, Stephen W.; Leser, William P.; Wincheski, Russell A.; Wallace, Terryl A.; Glaessgen, Edward H.; Piascik, Robert S.

    2014-01-01

    A system designed to mitigate or heal crack damage in metallic materials has been developed where the protected material or component is coated with a low-melting temperature film. After a crack is formed, the material is heated, melting the film which then infiltrates the crack opening through capillary action. Upon solidification, the healing material inhibits further crack damage in two ways. While the crack healing material is intact, it acts like an adhesive that bonds or bridges the crack faces together. After fatigue loading damages, the healing material in the crack mouth inhibits further crack growth by creating artificially-high crack closure levels. Mechanical test data show that this method sucessfully arrests or retards crack growth in laboratory specimens.

  1. IS THE U.S. EXPERIENCING AN INCIPIENT EPIDEMIC OF HALLUCINOGEN USE?

    PubMed Central

    Golub, Andrew; Johnson, Bruce D.; Sifaneck, Stephen J.; Chesluk, Benjamin; Parker, Howard

    2008-01-01

    NHSDA and MTF survey data indicate “epidemic”-like growth in hallucinogen use from 1992-1996 and associated increases in cocaine, crack, heroin and amphetamine use. These trends might have resulted from a proliferation of raves and dance clubs in the U.S. as occurred in Europe and elsewhere, although in contrast to evidence regarding European experiences the American epidemic involves primarily teens as opposed to persons in their twenties and involves primarily use of LSD as opposed to MDMA. This analysis highlights the need for further research into the context, significance, and consequences of these recently popular American drug use practices. PMID:11758819

  2. Iridium alloy Clad Vent Set manufacturing qualification studies

    NASA Astrophysics Data System (ADS)

    Ulrich, George B.

    Metallurgical qualification studies to demonstrate the manufacturing readiness of the iridium alloy Clad Vent Set (CVS) for the General Purpose Heat Source program at the Oak Ridge Y-12 Plant are described. Microstructural data for various materials/test conditions are presented.

  3. 78 FR 7451 - Clad Steel Plate From Japan; Determination

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-01

    ..., 2012 (77 FR 5052) and determined on May 7, 2012 that it would conduct a full review (77 FR 37439, June..., 2012 (77 FR 38825). The hearing was held in Washington, DC, on December 6, 2012, and all persons who... COMMISSION Clad Steel Plate From Japan; Determination On the basis of the record \\1\\ developed in the...

  4. Cladding burst behavior of Fe-based alloys under LOCA

    DOE PAGESBeta

    Terrani, Kurt A.; Dryepondt, Sebastien N.; Pint, Bruce A.; Massey, Caleb P.

    2015-12-17

    Burst behavior of austenitic and ferritic Fe-based alloy tubes has been examined under a simulated large break loss of coolant accident. Specifically, type 304 stainless steel (304SS) and oxidation resistant FeCrAl tubes were studied alongside Zircaloy-2 and Zircaloy-4 that are considered reference fuel cladding materials. Following the burst test, characterization of the cladding materials was carried out to gain insights regarding the integral burst behavior. Given the widespread availability of a comprehensive set of thermo-mechanical data at elevated temperatures for 304SS, a modeling framework was implemented to simulate the various processes that affect burst behavior in this Fe-based alloy. Themore » most important conclusion is that cladding ballooning due to creep is negligible for Fe-based alloys. Thus, unlike Zr-based alloys, cladding cross-sectional area remains largely unchanged up to the point of burst. Furthermore, for a given rod internal pressure, the temperature onset of burst in Fe-based alloys appears to be simply a function of the alloy's ultimate tensile strength, particularly at high rod internal pressures.« less

  5. PERSPECTIVE WITH WEST PORTAL. THE BRIDGE IS CLAD IN HORIZONTAL ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    PERSPECTIVE WITH WEST PORTAL. THE BRIDGE IS CLAD IN HORIZONTAL CLAPBOARD SIDING AND HAS A SHEET METAL ROOF. NOTE THE TWO OPENINGS THAT RUN THE LENGTH OF THE BRIDGE; ONE IS AT THE EAVES AND THE OTHER IS ABOUT 4’ ABOVE THE DECK. - Dreibelbis Station Bridge, Spanning Maiden Creek, Balthaser Road (TR 745), Lenhartsville, Berks County, PA

  6. Cladding burst behavior of Fe-based alloys under LOCA

    SciTech Connect

    Terrani, Kurt A.; Dryepondt, Sebastien N.; Pint, Bruce A.; Massey, Caleb P.

    2015-12-17

    Burst behavior of austenitic and ferritic Fe-based alloy tubes has been examined under a simulated large break loss of coolant accident. Specifically, type 304 stainless steel (304SS) and oxidation resistant FeCrAl tubes were studied alongside Zircaloy-2 and Zircaloy-4 that are considered reference fuel cladding materials. Following the burst test, characterization of the cladding materials was carried out to gain insights regarding the integral burst behavior. Given the widespread availability of a comprehensive set of thermo-mechanical data at elevated temperatures for 304SS, a modeling framework was implemented to simulate the various processes that affect burst behavior in this Fe-based alloy. The most important conclusion is that cladding ballooning due to creep is negligible for Fe-based alloys. Thus, unlike Zr-based alloys, cladding cross-sectional area remains largely unchanged up to the point of burst. Furthermore, for a given rod internal pressure, the temperature onset of burst in Fe-based alloys appears to be simply a function of the alloy's ultimate tensile strength, particularly at high rod internal pressures.

  7. Direct Laser Cladding , Current Status and Future Scope of Application

    NASA Astrophysics Data System (ADS)

    Weisheit, A.; Gasser, A.; Backes, G.; Jambor, T.; Pirch, N.; Wissenbach, K.

    During the last decades Direct Laser Cladding has become an established technique in many industrial fields for applying wear and corrosion protection layers on metallic surfaces as well as for the repair of high value-added components. The most important application fields are die and tool making, turbine components for aero engines and power generation, machine components such as axes and gears, and oil drilling components. Continuous wave (CW) lasers with a power up to 18 kW are used on automated machines with three or more axes, enabling 3D cladding . The outstanding feature of DLC is the high precision which leads to a minimum heat input into the work piece and a very low distortion. Due to the high cooling rates a fine grained microstructure is achieved during solidification. A new development in laser cladding is micro cladding in a size range below 50 \\upmum especially for electronic and medical applications. Furthermore, additive manufacturing is coming again into focus as a clean and resource-efficient method to manufacture and modify functional prototypes as well as unique and small lot parts.

  8. Fundamental metallurgical aspects of axial splitting in zircaloy cladding

    SciTech Connect

    Chung, H. M.

    2000-04-03

    Fundamental metallurgical aspects of axial splitting in irradiated Zircaloy cladding have been investigated by microstructural characterization and analytical modeling, with emphasis on application of the results to understand high-burnup fuel failure under RIA situations. Optical microscopy, SEM, and TEM were conducted on BWR and PWR fuel cladding tubes that were irradiated to fluence levels of 3.3 x 10{sup 21} n cm{sup {minus}2} to 5.9 x 10{sup 21} n cm{sup {minus}2} (E > 1 MeV) and tested in hot cell at 292--325 C in Ar. The morphology, distribution, and habit planes of macroscopic and microscopic hydrides in as-irradiated and posttest cladding were determined by stereo-TEM. The type and magnitude of the residual stress produced in association with oxide-layer growth and dense hydride precipitation, and several synergistic factors that strongly influence axial-splitting behavior were analyzed. The results of the microstructural characterization and stress analyses were then correlated with axial-splitting behavior of high-burnup PWR cladding reported for simulated-RIA conditions. The effects of key test procedures and their implications for the interpretation of RIA test results are discussed.

  9. Optimization of Hydride Rim Formation in Unirradiated Zr 4 Cladding

    SciTech Connect

    Shimskey, Rick W.; Hanson, Brady D.; MacFarlan, Paul J.

    2013-09-30

    The purpose of this work is to build on the results reported in the M2 milestone M2FT 13PN0805051, document number FCRD-USED-2013-000151 (Hanson, 2013). In that work, it was demonstrated that unirradiated samples of zircaloy-4 cladding could be pre-hydrided at temperatures below 400°C in pure hydrogen gas and that the growth of hydrides on the surface could be controlled by changing the surface condition of the samples and form a desired hydride rim on the outside diameter of the cladding. The work performed at Pacific Northwest National Laboratory since the issuing of the M2 milestone has focused its efforts to optimize the formation of a hydride rim on available zircaloy-4 cladding samples by controlling temperature variation and gas flow control during pre-hydriding treatments. Surface conditioning of the outside surface was also examined as a variable. The results of test indicate that much of the variability in the hydride thickness is due to temperature variation occurring in the furnaces as well as how hydrogen gas flows across the sample surface. Efforts to examine other alloys, gas concentrations, and different surface conditioning plan to be pursed in the next FY as more cladding samples become available

  10. Viscoelastic modelling of Zircaloy cladding in-pile transient creep

    NASA Astrophysics Data System (ADS)

    Tulkki, Ville; Ikonen, Timo

    2015-02-01

    In fuel behaviour modelling accurate description of the cladding stress response is important for both operational and safety considerations. The cladding creep determines in part the width of the gas gap, the duration to pellet-cladding contact and the stresses to the cladding due to the pellet expansion. Conventionally the strain hardening rule has been used to describe the creep response to transient loads in engineering applications. However, it has been well documented that the strain hardening rule does not describe well results of tests with load drops or reversals. In our earlier work we have developed a model for primary creep which can be used to simulate the in- and out-of-pile creep tests. Since then several creep experiments have entered into public domain. In this paper we develop the model formulation based on the theory of viscoelasticity, and show that this model can reproduce the new experimental results. We also show that the creep strain recovery encountered in experimental measurements can be explained by viscoelastic behaviour.

  11. Dual function cracking catalyst (DFCC) composition

    SciTech Connect

    Occelli, M.L.

    1986-10-07

    The patent describes a novel catalytic cracking composition comprising a cracking catalyst having high activity and, as a separate and distinct entity, a diluent comprising a substantially catalytically inactive crystalline aluminosilicte having a fresh MAT Activity below about 1. The diluent is clinoptilolite and the cracking catalyst contains a rare earth-exchanged crystalline aluminium silicate. The cracking catalyst comprises from about ten to about 60 weight percent of a zeolite having cracking characteristics dispersed in a refractory metal oxide matrix.

  12. An Innovative Ceramic Corrosion Protection System for Zircaloy Cladding

    SciTech Connect

    Ronald H. Baney, Dr. D. Butt, Dr. P. Demkowicz, Dr. G. Fuchs Department of Materials Science; James S. Tulenko, Department of Nuclear and Radiological Engineering; University of Florida.

    2003-02-19

    Light Water reactor (LWR) fuel performance is currently limited by thermal, chemical and mechanical constraints associated with the design, fabrication, and operation of the fuel in incore operation. Corrosion of the zirconium based (Zircaloy-4) alloy cladding of the fuel is a primary limiting factor. Recent success at the University of Florida in developing thin ceramic films with great adhesive properties for metal substrates offers an innovative breakthrough for eliminating a major weakness of the Zircaloy clad. ?The University of Florida proposes to coat the existing Zircaloy clad tubes with a ceramic coating for corrosion protection. An added bonus of this approach would be the implementation of a boron-containing burnable poison outer layer will also be demonstrated as part of the ceramic coating development. In this proposed effort, emphasis will be on the ceramic coating with only demonstration of feasibility on the burnable outer coating approach. This proposed program i s expected to give a step change (approximately a doubling) in clad lifetime before failure due to corrosion. In the development of ceramic coatings for Zircaloy-4 clad, silicon carbide and zirconium carbide coatings will first be applied to Zircaloy-4 coupons and cladding samples by thermal assisted chemical vapor deposition, plasma assisted chemical vapor deposition or by laser ablation deposition. All of these processes are in use at the University of Florida and have shown great potential. The questions of adhesion and thermal expansion mismatch of the ceramic coating to the Zircaloy substrate will be addressed. Several solutions to these conditions will be examined, if needed. These solutions include the use of a zirconium oxide compliant layer, employment of a laser roughened surface and the use of a gradient composition interlayer. These solutions have already been shown to be effective for other high modulus coatings on metal substrates. Mechanical properties and adhesion of the

  13. Characterization of irradiated Zircaloys: susceptibility to stress corrosion cracking. Final report

    SciTech Connect

    Yaggee, F.L.; Mattas, R.F.; Neimark, L.A.

    1980-10-01

    Irradiated Zircaloy cladding specimens that reached burnups from 6 to 30 MWd/kg U were exposed to iodine to investigate their stress corrosion cracking (SCC) susceptibility. Constant-stress and stress-change tests were performed. Cladding from several sources (including BWRs and PWRs) was tested. Test temperatures ranged from 320 to 360/sup 0/C and applied hoop stresses ranged from 150 to 500 MPa )22 to 72 ksi). Two iodine concentrations, 6.0 and 0.6 mg/cm/sup 2/, were used. Failure times ranged from 360 s (0.1h) at high stresses to 5 x 10/sup 5/ s (142 h) at low stresses. The 24-h failure stress was 171 +- 18 MPa (24.8 +- 2.6 ksi) regardless of the preirradiation metallurgical condition for all specimens that reached a burnup > 10 MWd/kg U. This failure stress is lower than is typically measured on unirradiated Zircaloy. The effect on SCC behavior of an oxide that formed on the inner surface of one cladding type was evaluated. Uniaxial tensile tests were performed on some specimens. An analytical model for iodine-induced SCC of Zircaloy was developed that correlates reasonably well with the measurements.

  14. Non-linearities in the vibrations of elastic structures with a closing crack: A state of the art review

    NASA Astrophysics Data System (ADS)

    Bovsunovsky, A.; Surace, C.

    2015-10-01

    The main purpose of the present review paper is to illustrate the principal achievements of numerous researchers who have studied the non-linear effects caused by a closing crack in the most common types of structural elements such as beams, shafts and plates, the aim being to assess the potential and future prospects of using non-linear behaviour to detect damage. Indeed, for a wide range of practical applications, in order to avoid catastrophic failure, the development of diagnostics techniques which are sufficiently sensitive to incipient cracks in structures and machines is a crucial issue. The main potential advantage of using vibration diagnostics based on the use of non-linear effects is the relatively high sensitivity to the damage of the closing crack type, especially for application to beam-like structures and rotating shafts; instead the potential for application to plate-like structures has been found to be limited. After analysing the state-of-art on this subject in detail, a discussion of the respective merits, drawbacks and prospects of a range of non-linear vibration methods for structural damage detection is presented. The general conclusion which can be drawn from the highly encouraging results of recent research is that further development of these techniques for non-destructive testing of structures with closing cracks would be highly worthwhile.

  15. Active Metal Brazing and Characterization of Brazed Joints in C-C and C-SiC Composites to Copper-Clad-Molybdenum System

    NASA Technical Reports Server (NTRS)

    Singh, M.; Asthana, R.

    2008-01-01

    Carbon/carbon composites with CVI and resin-derived matrices, and C/SiC composites reinforced with T-300 carbon fibers in a CVI SiC matrix were joined to Cu-clad Mo using two Ag-Cu braze alloys, Cusil-ABA (1.75% Ti) and Ticusil (4.5% Ti). The brazed joints revealed good interfacial bonding, preferential precipitation of Ti at the composite/braze interface, and a tendency toward delamination in resin-derived C/C composite. Extensive braze penetration of the inter-fiber channels in the CVI C/C composites was observed. The Knoop microhardness (HK) distribution across the C/C joints indicated sharp gradients at the interface, and a higher hardness in Ticusil than in Cusil-ABA. For the C/SiC composite to Cu-clad-Mo joints, the effect of composite surface preparation revealed that ground samples did not crack whereas unground samples cracked. Calculated strain energy in brazed joints in both systems is comparable to the strain energy in a number of other ceramic/metal systems. Theoretical predictions of the effective thermal resistance suggest that such joined systems may be promising for thermal management applications.

  16. Observation of Intralaminar Cracking in the Edge Crack Torsion Specimen

    NASA Technical Reports Server (NTRS)

    Czabaj, Michael W.; Ratcliffe, James G.; Davidson, Barry D.

    2013-01-01

    The edge crack torsion (ECT) test is evaluated to determine its suitability for measuring fracture toughness associated with mode III delamination growth onset. A series of ECT specimens with preimplanted inserts with different lengths is tested and examined using nondestructive and destructive techniques. Ultrasonic inspection of all tested specimens reveals that delamination growth occurs at one interface ply beneath the intended midplane interface. Sectioning and optical microscopy suggest that the observed delamination growth results from coalescence of angled intralaminar matrix cracks that form and extend across the midplane plies. The relative orientation of these cracks is approximately 45 deg with respect to the midplane, suggesting their formation is caused by resolved principal tensile stresses arising due to the global mode-III shear loading. Examination of ECT specimens tested to loads below the level corresponding to delamination growth onset reveals that initiation of intralaminar cracking approximately coincides with the onset of nonlinearity in the specimen's force-displacement response. The existence of intralaminar cracking prior to delamination growth onset and the resulting delamination extension at an unintended interface render the ECT test, in its current form, unsuitable for characterization of mode III delamination growth onset. The broader implications of the mechanisms observed in this study are also discussed with respect to the current understanding of shear-driven delamination in tape-laminate composites.

  17. Double-cladding photonic crystal fibers with reduced cladding symmetry for Tm-doped lasers

    NASA Astrophysics Data System (ADS)

    Coscelli, Enrico; Molardi, Carlo; Poli, Federica; Cucinotta, Annamaria; Selleri, Stefano

    2014-05-01

    Innovative Photonic Crystal Fibers (PCF) with optimized air-hole matrix, designed to break the C6ν symmetry of the inner cladding while preserving their feasibility through the well-established stack-and-draw technique, are presented. The possibility to provide stable SM guiding at λ = 2 μm with core diameter up to 80 μm and a coupled pump power exceeding 300 W is analyzed by means of a full-vector modal solver based on the finiteelement method with embedded thermal model, to account for the effects of heating on the mode confinement. Simulation results have shown this approach is effective in providing modal discrimination, allowing selective amplification of the sole fundamental mode due to the delocalization of the high-order modes with mirrorsymmetric field distributions. Effective suppression of the high-order modes under a heat load of 340 W/m, while keeping an effective area exceeding 2500 μm2 has been demonstrated.

  18. Cladding hull decontamination and densification process. Part 1. The prototype cladding hull decontamination system

    SciTech Connect

    Lambright, T.M.; Montgomery, D.R.

    1980-04-01

    A prototype system for decontaminating Zircaloy-4 cladding hulls has been assembled and tested at Pacific Northwest Laboratory. The decontamination process consists of treatment with a gaseous mixture of hydrogen fluoride (HF) and argon (Ar) followed by a dilute aqueous etch of ammonium oxalate, ammonium citrate, ammonium fluoride, and hydrogen peroxide. The continuous cleaning process described in this report successfully descaled small portions of most charges, but was unable to handle the original design capacity of 4 kg/hr because of problems in the following areas: control of HF reactor temperatures, regulation of HF and argon mixtures and flows, isolation of the HF reactor atmosphere from the aqueous washer/rinser atmosphere, regulation of undesirable side reactions, and control over hull transport through the system. Due to the limited time available to solve these problems, the system did not attain fully operational status. The work was performed with unirradiated hulls that simulated irradiated hulls. The system was not built to be remotely operable. The process chemistry and system equipment are described in this report with particular emphasis on critical operating areas. Recommendations for improved system operation are included.

  19. BWR pipe crack remedies evaluation

    SciTech Connect

    Shack, W.J.; Kassner, T.F.; Maiya, P.S.; Park, J.Y.; Ruther, W.E.

    1986-10-01

    This paper presents results on: (a) the influence of simulated BWR environments on the stress-corrosion-craking (SCC) susceptibility of Types 304, 316NG, and 347 stainless (SS); (b) fracture-mechanics crack-growth-rate measurements on these materials and weld overlay specimens in different environments; and (c) residual stress measurements and metallographic evaluations of conventional pipe weldments treated by a mechanical-stress-improvement process (MSIP) as well as those produced by a narrow-gap welding procedure. Crack initiation studies on Types 304 and 316NG SS under crevice and non-crevice conditions in 289/sup 0/C water containing 0.25 ppM dissolved oxygen with low sulfate concentrations indicate that SCC initiates at very low strains (<3%) in the nuclear grade material. Crack growth measurements on fracture-mechanics-type specimens, under low-frequency cyclic loading, show that the Type 316NG steel cracks at a somewhat lower rate (approx.40%) than sensitized Type 304 SS in an impurity environment with 0.25 ppM dissolved-oxygen; however, the latter material stops cracking when sulfate is removed from the water. Crack growth in both materials ceases under simulated hydrogen-water chemistry conditions (<5 ppB oxygen) even with 100 ppB sulfate present in the water. An unexpected result was obtained in the test on a weld overlay specimen in the impurity environment, viz., the crack grew to the overlay interface at a nominal rate, branched at 90/sup 0/ in both directions, and then grew at high rate (parallel to the nominal applied load). Residual stress measurements on MSIP-treated weldments and those produced by a narrow-gap welding procedure indicate that these techniques produce compressive stresses over most of the inner surface near the weld and heat-affected zones.

  20. Orientation-Dependent Displacement Sensor Using an Inner Cladding Fiber Bragg Grating.

    PubMed

    Yang, Tingting; Qiao, Xueguang; Rong, Qiangzhou; Bao, Weijia

    2016-01-01

    An orientation-dependent displacement sensor based on grating inscription over a fiber core and inner cladding has been demonstrated. The device comprises a short piece of multi-cladding fiber sandwiched between two standard single-mode fibers (SMFs). The grating structure is fabricated by a femtosecond laser side-illumination technique. Two well-defined resonances are achieved by the downstream both core and cladding fiber Bragg gratings (FBGs). The cladding resonance presents fiber bending dependence, together with a strong orientation dependence because of asymmetrical distribution of the "cladding" FBG along the fiber cross-section. PMID:27626427