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Sample records for steels amorcage propagation

  1. Fatigue crack propagation behavior in dual-phase steel

    SciTech Connect

    Sarwar, M.; Priestner, R.

    1999-04-01

    The fatigue crack propagation in dual-phase steel was studied with the objective of developing ferritic-martensitic microstructures via intercritical annealing and thermomechanical processing. It was found that the changes in fatigue crack propagation rates and in the threshold stress intensity range, {Delta}K{sub th}, resulting from microstructural variations, were directly related to tensile strength in the same manner that was observed in other types of structural steels. it was also observed that the relationship between tensile strength and fatigue crack propagation in intercritically annealed and thermomechanically processed dual-phase steel was much the same as for conventional steels of similar strength level.

  2. Fatigue crack propagation in carburized X-2M steel

    NASA Astrophysics Data System (ADS)

    Averbach, B. L.; Lou, Bingzhe; Pearson, P. K.; Fairchild, R. E.; Bamberger, E. N.

    1985-07-01

    The growth rates of fatigue cracks propagating through the case and into the core have been studied for carburized X-2M steel (0.14 C, 4.91 Cr, 1.31 Mo, 1.34 W, 0.42 V). Fatigue cracks were propagated at constant stress intensities, ΔK, and also at a constant cyclic peak load, and the crack growth rates were observed to pass through a minimum value as the crack traversed the carburized case. The reduction in the crack propagation rates is ascribed to the compressive stresses which were developed in the case, and a pinched clothespin model is used to make an approximate calculation of the effects of internal stress on the crack propagation rates. We define an effective stress intensity, Ke = Ka + Ki, where Ka is the applied stress intensity, Ki = σid{i/1/2}, σi is the internal stress, and di is a characteristic distance associated with the depth of the internal stress field. In our work, a value of di = 11 mm (0.43 inch) fits the data quite well. A good combination of resistance to fatigue crack propagation in the case and fracture toughness in the core can be achieved in carburized X-2M steel, suggesting that this material will be useful in heavy duty gears and in aircraft gas turbine mainshaft bearings operating under high hoop stresses.

  3. Mode III fatigue crack propagation in low alloy steel

    SciTech Connect

    Ritchie, R.O.; McClintock, F.A.; Nayeb-Hashemi, H.; Ritter, M.A.

    1982-01-01

    To provide a basis for estimating fatigue life in large rotating generator shafts subjected to transient oscillations, a study is made of fatigue crack propagation in Mode III (anti-plane shear) in torsionally-loaded spheroidized AISI 4340 steel. Results are compared to analogous behavior in Mode I. The approach investigated the feasibility of using continuum fracture mechanics and preliminary mechanistic modeling to serve as a basis for defect-tolerant life estimation procedures. 38 refs.

  4. Fatigue crack propagation behavior of stainless steel welds

    NASA Astrophysics Data System (ADS)

    Kusko, Chad S.

    The fatigue crack propagation behavior of austenitic and duplex stainless steel base and weld metals has been investigated using various fatigue crack growth test procedures, ferrite measurement techniques, light optical microscopy, stereomicroscopy, scanning electron microscopy, and optical profilometry. The compliance offset method has been incorporated to measure crack closure during testing in order to determine a stress ratio at which such closure is overcome. Based on this method, an empirically determined stress ratio of 0.60 has been shown to be very successful in overcoming crack closure for all da/dN for gas metal arc and laser welds. This empirically-determined stress ratio of 0.60 has been applied to testing of stainless steel base metal and weld metal to understand the influence of microstructure. Regarding the base metal investigation, for 316L and AL6XN base metals, grain size and grain plus twin size have been shown to influence resulting crack growth behavior. The cyclic plastic zone size model has been applied to accurately model crack growth behavior for austenitic stainless steels when the average grain plus twin size is considered. Additionally, the effect of the tortuous crack paths observed for the larger grain size base metals can be explained by a literature model for crack deflection. Constant Delta K testing has been used to characterize the crack growth behavior across various regions of the gas metal arc and laser welds at the empirically determined stress ratio of 0.60. Despite an extensive range of stainless steel weld metal FN and delta-ferrite morphologies, neither delta-ferrite morphology significantly influence the room temperature crack growth behavior. However, variations in weld metal da/dN can be explained by local surface roughness resulting from large columnar grains and tortuous crack paths in the weld metal.

  5. Fatigue crack propagation in carburized high alloy bearing steels

    NASA Astrophysics Data System (ADS)

    Averbach, B. L.; Lou, Bingzhe; Pearson, P. K.; Fairchild, R. E.; Bamberger, E. N.

    1985-07-01

    Fatigue cracks were propagated through carburized cases in M-50NiL (0.1 C,4 Mo, 4 Cr, 1.3 V, 3.5 Ni) and CBS-1000M (0.1 C, 4.5 Mo, 1 Cr, 0.5 V, 3 Ni) steels at constant stress intensity ranges, ΔK, and at a constant cyclic peak load. Residual compressive stresses of the order of 140 MPa (20 Ksi) were developed in the M-50NiL cases, and in tests carried out at constant ΔK values it was observed that the fatigue crack propagation rates, da/dN, slowed significantly. In some tests, at constant peak loads, cracks were stopped in regions with high compressive stresses. The residual stresses in the cases in CBS-1000M steel were predominantly tensile, probably because of the presence of high retained austenite contents, and da/dN was accelerated in these cases. The effects of residual stress on the fatigue crack propagation rates are interpreted in terms of a pinched clothespin model in which the residual stresses introduce an internal stress intensity, Ki where Ki, = σid{i/1/2} (σi = internal stress, di = characteristic distance associated with the internal stress distribution). The effective stress intensity becomes Ke = Ka + Ki where Ka is the applied stress intensity. Values of Ki were calculated as a function of distance from the surface using experimental measurements of σi and a value of di = 11 mm (0.43 inch). The resultant values of Ke were taken to be equivalent to effective ΔK values, and da/dN was determined at each point from experimental measurements of fatigue crack propagation obtained separately for the case and core materials. A reasonably good fit was obtained with data for crack growth at a constant ΔK and at a constant cyclic peak load. The carburized case depths were approximately 4 mm, and the possible effects associated with the propagation of short cracks were considered. The major effects were observed at crack lengths of about 2 mm, but the contributions of short crack phenomena were considered to be small in these experiments, since the

  6. Mode III fatigue crack propagation in low alloy steel

    NASA Astrophysics Data System (ADS)

    Ritchie, R. O.; McClintock, F. A.; Nayeb-Hashemi, H.; Ritter, M. A.

    1982-01-01

    To provide a basis for estimating fatigue life in large rotating generator shafts subjected to transient oscillations, a study is made of fatigue crack propagation in Mode III (anti-plane shear) in torsionally-loaded spheroidized AISI4340 steel, and results compared to analogous behavior in Mode I. Torsional S/N curves, determined on smooth bars containing surface defects, showed results surprisingly close to expected unnotched Mode I data, with lifetime increasing from 104 cycles at nominal yield to 106 cycles at half yield. Fatigue crack growth rates in Mode III, measured on circumferentially-notched samples, were found to be slower than in Mode I, although still power-law related to the alternating stress intensity (△K III) for small-scale yielding. Mode III growth rates were only a small fraction (0.002 to 0.0005) of cyclic crack tip displacements (△CTD III) per cycle, in contrast to Mode I where the fraction was much larger (0.1 to 0.01). A micromechanical model for Mode III growth is proposed, where crack advance is considered to take place by a Mode II coalescence of cracks, initiated at inclusions ahead of the main crack front. This mechanism is consistent with the crack increment being a small fraction of △CTDIII per cycle.

  7. On propagating instabilities in nickel-titanium and steel alloys

    NASA Astrophysics Data System (ADS)

    Iadicola, Mark Anthony

    A study of material systems that exhibit material level instabilities is presented. In recent years, there has been growing interest in using NiTi Shape Memory Alloys (SMAs) for novel applications. Unfortunately, the complex material behavior has made development of robust constitutive models difficult, prompting the need for more experimental data. A new experimental setup for uniaxial testing SMAs is developed that overcomes some long-standing difficulties including extreme rate and environmental sensitivities, propagating transformation fronts, and associated gripping artifacts. A special temperature control apparatus is used to reduce the effects of gripping and to better control the ambient environment, resulting in accurate measurement of nucleation and propagation stresses without machining the specimen. Additionally, the setup allows full-field optical and infrared imaging to monitor transformation fronts kinetics. Cyclic experiments are performed using this setup where the front kinetics are measured during cyclic softening for the first time. The surprisingly large change in mechanical response for only an 8°C change in temperature results from a change in the front kinetics, and the stabilized mechanical response is shown to still occur through inhomogeneous deformation. Additionally, nucleations are seen to occur at the locations of previous nucleation or front coalescence, suggesting additional damage at these locations, which could lead eventually to fatigue failure. A parameter study of the ambient media and rate sensitivities for monotonic loading is presented using a finite element analysis (FEA) with a special non-isothermal plasticity model. The parameters of interest are shown to be the non-dimensional thermal conductivity and the non-dimensional heat transfer coefficient, which correlate to the number of transformation fronts and to the average temperature rise, respectively. Non-dimensional design curves are developed to categorize the

  8. Evaluation on Fatigue Crack Propagation of Reduced Activation Ferritic Steel (JLF-1) at High Temperature

    NASA Astrophysics Data System (ADS)

    Yoon, Han Ki; Kim, Sa Woong; Lee, Sang Pill; Katoh, Yutai; Kohyama, Akira

    Recently, reduced activation ferritic/martensitic steel, vanadium alloy and SiC/SiC composite are embossed for nuclear fusion reactor in accordance with the coolant. Especially, reduced activation ferritic/martensitic steel is very suitable material for nuclear fusion reactor, because it has low coefficient of thermal expansion and excellent heat conductivity. The objective of this study is to investigate fatigue crack propagation behavior in the Reduced Activation Ferritic Steel (JLF-1). The fatigue crack propagation behavior of the JLF-1 steel was investigated by the constant-amplitude loading test for the stress ratios R = 0.1, 0.3 and 0.5 respectively. The fatigue crack growth tests carried out at room temperature and 400°C for base metal and weld metal. The effects of stress ratio, test temperature, specimen size and TIG welding on the fatigue crack propagation behaviors for JLF-1 steel were discussed within the Paris law. Particularly, the fatigue crack propagation rate of a weld metal was similar to that of base metal at the stress ratio of 0.3. Also, the fatigue crack propagation rate of a half size specimen was similar to that of a full size specimen at the stress ratios of 0.1, 0.3 and 0.5 respectively. From this result, we can recognize that the fatigue crack propagation behavior of this material can be evaluated by using the half size specimens.

  9. Numerical modeling of the thermomechanical behavior of steels with allowance for the propagation of Luders bands

    NASA Astrophysics Data System (ADS)

    Balokhonov, R. R.; Romanova, V. A.

    2007-09-01

    A thermomechanical model based on physical representations of the motion of dislocation continuum and a model for the initiation and propagation of plastic shear are proposed to describe slow flows of the type of Luders bands. Two-dimensional calculations of Luders band propagation are performed for HSLA-65 steel samples under compression at various strain rates and temperatures. The calculation results are in good agreement with experimental data.

  10. Initiation and propagation of a single pit on stainless steel using a local probe technique.

    PubMed

    Heurtault, Stéphane; Robin, Raphaël; Rouillard, Fabien; Vivier, Vincent

    2015-01-01

    Experiments about single pit initiation and propagation were performed on 316L stainless steel with the aim to determine the pitting corrosion behaviour for nuclear waste containers. The experimental setup permits to control the pit development at will and to create reproducible single pits in three dimensions. Radial and deep evolutions of a disc shaped pit were studied for propagation times of up to 10 hours. These evolutions were used to determine what limiting mechanism takes place during long-term pit propagation. Special attention has been paid to the chloride ion action on pitting. A minimum chloride concentration was found to be necessary in the bulk electrolyte to support pit propagation. The existence of a critical pit depth of 230 μm was also underlined. PMID:25901720

  11. Study of Near-Threshold Fatigue Crack Propagation in Pipeline Steels in High Pressure Environments

    NASA Technical Reports Server (NTRS)

    Mitchell, M.

    1981-01-01

    Near threshold fatigue crack propagation in pipeline steels in high pressure environments was studied. The objective was to determine the level of threshold stress intensity for fatigue crack growth rate behavior in a high strength low alloy X60 pipeline-type steel. Complete results have been generated for gaseous hydrogen at ambient pressure, laboratory air at ambient pressure and approximately 60% relative humidity as well as vacuum of 0.000067 Pa ( 0.0000005 torr) at R-ratios = K(min)/K(max) of 0.1, 0.5, and 0.8. Fatigue crack growth rate behavior in gaseous hydrogen, methane, and methane plus 10 percent hydrogen at 6.89 MPa (100 psi) was determined.

  12. Fatigue-crack propagation behavior of ASTM A27 cast steel in simulated Hanford groundwater

    SciTech Connect

    James, L.A.

    1986-09-01

    Fatigue-crack propagation (FCP) tests were conducted on specimens of cast ASTM A27 steel in simulated Hanford ground-water at 150/sup 0/C and 250C/sup 0/C. Fatigue loadings were employed as the most feasible means of accelerating the environmentally assisted cracking (EAC) process. A tentative threshold for EAC was established, and an example calculation was used to show how such a threshold can be related to allowable stress levels and flaw sizes to assure that EAC will not occur.

  13. Low-pH stress corrosion crack propagation in API X-65 line pipe steel

    SciTech Connect

    Harle, B.A.; Beavers, J.A. )

    1993-10-01

    Preliminary results of ongoing crack growth studies being performed on an API X-65 line pipe steel in a low-pH cracking environment were reported. Objectives were to reproduce low-pH crack propagation in the laboratory, to identify a crack driving force parameter, and to evaluate the influence of environmental and mechanical parameters on crack growth. A J-integral test technique was used in the study. Significant crack growth was observed. The parameter J appeared to be a good driving force parameter to describe crack growth.

  14. Hydrogen-Assisted Crack Propagation in Austenitic Stainless Steel Fusion Welds

    NASA Astrophysics Data System (ADS)

    Somerday, B. P.; Dadfarnia, M.; Balch, D. K.; Nibur, K. A.; Cadden, C. H.; Sofronis, P.

    2009-10-01

    The objective of this study was to characterize hydrogen-assisted crack propagation in gas-tungsten arc (GTA) welds of the nitrogen-strengthened, austenitic stainless steel 21Cr-6Ni-9Mn (21-6-9), using fracture mechanics methods. The fracture initiation toughness and crack growth resistance curves were measured using fracture mechanics specimens that were thermally precharged with 230 wppm (1.3 at. pct) hydrogen. The fracture initiation toughness and slope of the crack growth resistance curve for the hydrogen-precharged weld were reduced by as much as 60 and 90 pct, respectively, relative to the noncharged weld. A physical model for hydrogen-assisted crack propagation in the welds was formulated from microscopy evidence and finite-element modeling. Hydrogen-assisted crack propagation proceeded by a sequence of microcrack formation at the weld ferrite, intense shear deformation in the ligaments separating microcracks, and then fracture of the ligaments. One salient role of hydrogen in the crack propagation process was promoting microcrack formation at austenite/ferrite interfaces and within the ferrite. In addition, hydrogen may have facilitated intense shear deformation in the ligaments separating microcracks. The intense shear deformation could be related to the development of a nonuniform distribution of hydrogen trapped at dislocations between microcracks, which in turn created a gradient in the local flow stress.

  15. Task 1 Final Report, Theoretical/Mathematical Modeling of Ultrasonic Wave Propagation in Anisotropic Polycrystalline Stainless Steels

    SciTech Connect

    Ahmed, Salahuddin; Anderson, Michael T.

    2009-04-20

    One of the tasks of the U.S. Nuclear Regulatory Commission-sponsored project titled "Reliability of Nondestructive Examination (NDE) for Nuclear Power Plant (NPP) Inservice Examination (ISI)" is to provide collaborative assistance to Commissariat à l’Energie Atomique (CEA) in France through theoretical predictions of ultrasonic scattering by grains of cast stainless steels (CASS) components. More specifically, a mathematical treatment of ultrasonic scattering in media having duplex micro¬structure is sought because cast stainless steel components often contains larger-scale macrograins that are composed of sub-grains/colonies. In this report, we present formal mathematical theories for ultrasonic wave propagation in polycrystalline aggregates having both simple (composed of grains only) and complex microstructures (having macrograins and sub-grains/colonies). Computations based on these theories are then carried out for ultrasonic backscatter power, attenuation due to scattering, and phase velocity dispersions. Specifically, numerical results are presented for backscatter coefficient for plane longitudinal wave propagating in duplex steel containing macrograins and colonies. Furthermore, the expected propagation characteristics (attenuation coefficient and phase velocity) are computed and described in this report for plane longitudinal waves propagating in (1) steels composed of randomly oriented grains, (2) [001] aligned grains encountered in austenitic stainless steel welds and casts, and (3) duplex steels.

  16. Prediction of Contact Fatigue Life of Alloy Cast Steel Rolls Using Back-Propagation Neural Network

    NASA Astrophysics Data System (ADS)

    Jin, Huijin; Wu, Sujun; Peng, Yuncheng

    2013-12-01

    In this study, an artificial neural network (ANN) was employed to predict the contact fatigue life of alloy cast steel rolls (ACSRs) as a function of alloy composition, heat treatment parameters, and contact stress by utilizing the back-propagation algorithm. The ANN was trained and tested using experimental data and a very good performance of the neural network was achieved. The well-trained neural network was then adopted to predict the contact fatigue life of chromium alloyed cast steel rolls with different alloy compositions and heat treatment processes. The prediction results showed that the maximum value of contact fatigue life was obtained with quenching at 960 °C, tempering at 520 °C, and under the contact stress of 2355 MPa. The optimal alloy composition was C-0.54, Si-0.66, Mn-0.67, Cr-4.74, Mo-0.46, V-0.13, Ni-0.34, and Fe-balance (wt.%). Some explanations of the predicted results from the metallurgical viewpoints are given. A convenient and powerful method of optimizing alloy composition and heat treatment parameters of ACSRs has been developed.

  17. Microbe-enhanced environmental fatigue crack propagation in HY130 steel

    SciTech Connect

    Gangloff, R.P.; Kelly, R.G. . Dept. of Materials Science and Engineering)

    1994-05-01

    Research was undertaken to characterize the effect of sulfate-reducing bacteria (SRB) on aqueous environment-enhanced fatigue cracking in a high-strength alloy steel. Desulfovibrio vulgaris in Postgate C solution greatly increased rates of ambient-temperature fatigue crack propagation (FCP) in tempered martensitic HY130 steel (MIL-S-24371A) under cathodic polarization and low-frequency, constant stress intensity range ([Delta]K) loading. Crack growth rates (da/dN) in the SRB solution increased 50- to 1,000-fold relative to FCP in sterile sodium chloride (NaCl) solution at [minus]1,000 mV[sub SCE] and under vacuum, respectively. The presence of microbes shifted fatigue cracking from a transgranular path (typical in sterile NaCl) to an intergranular crack path consistent with the enhanced growth rates. The SRB reduced fatigue crack initiation resistance, countering the beneficial effect of cathodic polarization for sterile NaCl. Metal embrittlement and increased hydrogen uptake at the occluded crack tip caused by bacterially produced hydrosulfide (HS[sup [minus

  18. Influence of gaseous environments on rates of near-threshold fatigue crack propagation in nicrmov steel

    NASA Astrophysics Data System (ADS)

    Liaw, Peter K.; Hudak, S. J.; Donald, J. Keith

    1982-09-01

    The influence of hydrogen environment (448 kPa) on near-threshold fatigue crack propagation rates was examined in a 779 MPa yield strength NiCrMoV steel at 93 °C. An automatically decreasing and increasing stress intensity technique was employed to generate crack growth rates at three load ratios (R = 0.1, 0.5, and 0.8). Results show that the crack propagation rates in hydrogen are slower than those in air for levels of stress intensity range, ΔK, below about 12 MPa√m. The crack closure concept does not explain the slower crack growth rates in hydrogen than in air. Near-threshold growth rates appear to be controlled by the levels of residual moisture in the environments. In argon and air, the fracture morphology is transgranular, while in H2 the amount of intergranularity varies with ΔK and achieves a maximum when the cyclic plastic zone is approximately equal to the prior austenite grain size.

  19. SCC Propagation Rate of Type 304, 304L Steels Under Oceanic Air Environment

    SciTech Connect

    Akio Kosaki

    2006-07-01

    Corrosion integrity of canister in the concrete cask for spent fuel storage is very important because the canister serves to maintain the sealability over the storage period of 40 to 60 years. Natural exposure and accelerated corrosion tests of conventional stainless steels for canister, that are Type 304, 304L, and 316(LN), for concrete cask's canister have been conducted by using many three Point Bending (3PB) test specimens and compared. The SCC propagation rates in Type 304 and 304L at the natural condition were about 1.2 E-12 to 1.8 E-11 m/s at the K (Stress Intensity Factor) range of 0.6 to 9.0 MPa/m, and that of the accelerate test (60 degrees C, 95%RHS., filled with NaCl mist.) were about 1.0 E-10 to 3.5 E-9 m/s at the K range of 0.3 to 32 MPa/m. The SCC propagation rates under both natural and accelerated conditions were independent with K. Both da/dt values of the direct exposure test and of the under glass exposure test were in the same scattering band. (author)

  20. Crack propagation in stainless steels and nickel base alloys in a commercial operating BWR

    SciTech Connect

    Jenssen, A.; Morin, U.; Bengtsson, B.; Jansson, C.

    1995-12-31

    Crack propagation was investigated to study critical stress intensity factors for intergranular stress corrosion cracking (IGSCC), and crack growth rates in various materials. Modified bolt loaded compact tension (CT) specimens were exposed to BWR normal water chemistry (NWC) in a commercially operating BWR. The test facility was a pressure vessel, originally designed for high temperature magnetite filters. Stainless steels (SS) of Types 304 SS and 316 SS were included in the test matrix, as well as the Ni base weld materials alloys 82 and 182. The SS were investigated both in sensitized and in cold worked condition. For alloy 182 various parameters were studied, such as the effect of the carbon stabilization parameter, and the as-welded condition versus a post weld heat treatment (PWHT). Crack growth was measured annually, during the normal outages, by an optical microscope. The results were evaluated as crack growth rate as a function of stress intensity. A few specimens have been removed from testing for fractographic examination. Most of the specimens were exposed to NWC for more than 30,000 hours. Alloy 82 in as welded condition was found to be susceptible to IGSCC, at least at stress intensities above 30 MPa{radical}m. For alloy 182, in as welded condition, significant crack growth was detected in all specimens. No beneficial effect of the carbon stabilization parameter could be found. PWHT had a beneficial effect on the IGSCC susceptibility of alloy 182, and at stress intensities below 30 MPa{radical}m the crack growth rates were one to two orders of magnitude lower, compared to alloy 182 in as welded condition. As expected, an increasing susceptibility to IGSCC with increasing degree of cold work was found for stainless steel. At 5% cold work Type 304 SS cracked at a higher rate than Type 316NG with the same degree of cold work. At 20% cold work Type 304 SS and Type 316NG cracked at essentially the same rate.

  1. The fatigue-crack propagation behavior of ASTM A533-B steel tested in vacuo at LWR operating temperatures

    SciTech Connect

    James, L.A.

    1987-01-01

    The fatigue-crack propagation (FCP) behavior of ASTM A533-B-1 steel was characterized in vacuo at 288/sup 0/C. Tests were conducted at two stress ratios: R = 0.05 and R = 0.7. Results of these tests were compared with results from previous studies for the same type of steel tested in an air environment, and FCP rates in vacuo were generally lower than those in air. Stress ratio effects in vacuo were not as great as those in air, and both stress ratio effects and environmental effects are discussed from the standpoint of crack closure concepts.

  2. Fracture Profile and Crack Propagation of Ultra-High Strength Hot-Stamped Boron Steel During Mechanical Trimming Process

    NASA Astrophysics Data System (ADS)

    Han, Xianhong; Yang, Kun; Chen, Sisi; Chen, Jun

    2015-10-01

    Mechanical trimming process for ultra-high strength boron steel after hot stamping was carried out in this study. Shear and tensile tests were designed to analyze the influences of stress state on the fracture mode; trimmed fracture surface and profile were observed and compared to other commonly used steels such as DP980 and Q235 etc.; the crack propagation during trimming process was studied through step-by-step tests. The observation and analysis reveal that the fracture mode of hot-stamped boron steel is highly related to the stress state, it belongs to cleavage fracture on low stress triaxiality but dimple fracture on high stress triaxiality. Such phenomenon is reflected in the trimming process, during which the stress state changes from shear-dominated state to tensile-dominated state. In addition, the burnish zone of trimmed boron steel is much smaller than other high strength steels, and the profile of cutting surface shows an `S'-like shape which is destructive to the trimming tool. Moreover, during the trimming process, most martensite laths near the cutting edge are stretched and rotated markedly to the direction of the shear band, and the main crack expands along those grain boundaries, which may penetrate through a few martensite laths and form small crack branches.

  3. The effect of aqueous environments upon the initiation and propagation of fatigue cracks in low-alloy steels

    SciTech Connect

    James, L.A.; Van Der Sluys, W.A.

    1996-01-01

    The effect of elevated temperature aqueous environments upon the initiation and propagation of fatigue cracks in low-alloy steels is discussed in terms of the several parameters which influence such behavior. These parameters include water chemistry, impurities within the steels themselves, as well as factors such as the water flow rate, loading waveform and loading rates. Some of these parameters have similar effects upon both crack initiation and propagation, while others exhibit different effects in the two stages of cracking. In the case of environmentally-assisted crack (EAC) growth, the most important impurities within the steel are metallurgical sulfide inclusions which dissolve upon contact with the water. A ``critical`` concentration of sulfide ions at the crack tip can then induce environmentally-assisted cracking which proceeds at significantly increased crack growth rates over those observed in air. The occurrence, or non-occurrence, of EAC is governed by the mass-transport of sulfide ions to and from the crack-tip region, and the mass-transport is discussed in terms of diffusion, ion migration, and convection induced within the crack enclave. Examples are given of convective mass-transport within the crack enclave resulting from external free stream flow. The initiation of fatigue cracks in elevated temperature aqueous environments, as measured by the S-N fatigue lifetimes, is also strongly influenced by the parameters identified above. The influence of sulfide inclusions does not appear to be as strong on the crack initiation process as it is on crack propagation. The oxygen content of the environment appears to be the dominant factor, although loading frequency (strain rate) and temperature are also important factors.

  4. Enhanced quench propagation in 2G-HTS coils co-wound with stainless steel or anodised aluminium tapes

    NASA Astrophysics Data System (ADS)

    Núñez-Chico, A. B.; Martínez, E.; Angurel, L. A.; Navarro, R.

    2016-08-01

    Early quench detection and thermal stability of superconducting coils are of great relevance for practical applications. Magnets made with second generation high temperature superconducting (2G-HTS) tapes present low quench propagation velocities and therefore slow voltage development and high local temperature rises, which may cause irreversible damage. Since quench propagation depends on the anisotropy of the thermal conductivity, this may be used to achieve an improvement of the thermal stability and robustness of 2G-HTS coils. On pancake type coils, the thermal conductivity along the tapes (coil’s azimuthal direction) is mostly fixed by the 2G-HTS tape characteristics, so that the reduction of anisotropy relies on the improvement of the radial thermal conductivity, which depends on the used materials between superconducting tapes, as well as on the winding and impregnation processes. In this contribution, we have explored two possibilities for such anisotropy reduction: by using anodised aluminium or stainless steel tapes co-wound with the 2G-HTS tapes. For all the analysed coils, critical current distribution, minimum quench energy values and both tangential and radial quench propagation velocities at different temperatures and currents are reported and compared with the results of similar coils co-wound with polyimide (Kapton®) tapes.

  5. Effects of Laser Peening Treatment on High Cycle Fatigue and Crack Propagation Behaviors in Austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Masaki, Kiyotaka; Ochi, Yasuo; Matsumura, Takashi; Ikarashi, Takaaki; Sano, Yuji

    Laser peening without protective coating (LPwC) treatment is one of surface enhancement techniques using an impact wave of high pressure plasma induced by laser pulse irradiation. High compressive residual stress was induced by the LPwC treatment on the surface of low-carbon type austenitic stainless steel SUS316L. The affected depth reached about 1mm from the surface. High cycle fatigue tests with four-points rotating bending loading were carried out to confirm the effects of the LPwC treatment on fatigue strength and surface fatigue crack propagation behaviors. The fatigue strength was remarkably improved by the LPwC treatment over the whole regime of fatigue life up to 108 cycles. Specimens with a pre-crack from a small artificial hole due to fatigue loading were used for the quantitative study on the effect of the LPwC treatment. The fracture mechanics investigation on the pre-cracked specimens showed that the LPwC treatment restrained the further propagation of the pre-crack if the stress intensity factor range ΔK on the crack tip was less than 7.6 MPa√m. Surface cracks preferentially propagated into the depth direction as predicted through ΔK analysis on the crack by taking account of the compressive residual stresses due to the LPwC treatment.

  6. Modeling of ultrasonic propagation in heavy-walled centrifugally cast austenitic stainless steel based on EBSD analysis.

    PubMed

    Chen, Yao; Luo, Zhongbing; Zhou, Quan; Zou, Longjiang; Lin, Li

    2015-05-01

    The ultrasonic inspection of heavy-walled centrifugally cast austenitic stainless steel (CCASS) is challenging due to the complex metallurgical structure. Numerical modeling could provide quantitative information on ultrasonic propagation and plays an important role in developing advanced and reliable ultrasonic inspection techniques. But the fundamental obstacle is the accurate description of the complex metallurgical structure. To overcome this difficulty, a crystal orientation map of a CCASS specimen in the 96 mm × 12 mm radial-axial cross section was acquired based on the electron backscattered diffraction (EBSD) technique and it was used to describe the coarse-grained structure and grain orientation. A model of ultrasonic propagation for CCASS was built according to the EBSD map. The ultrasonic responses of the CCASS sample were also tested. Some experimental phenomena such as structural noise and signal distortion were reproduced. The simulated results showed a good consistence with the experiments. The modeling method is expected to be effective for the precise interpretation of ultrasonic propagation in the polycrystalline structures of CCASS. PMID:25670411

  7. Influences of gaseous environment on low growth-rate fatigue crack propagation in steels. Annual report No. 1, January 1980. Report No. FPL/R/80/1030

    SciTech Connect

    Ritchie, R.O.; Suresh, S.; Toplosky, J.

    1980-01-01

    The influence of gaseous environment is examined on fatigue crack propagation behavior in steels. Specifically, a fully martensitic 300-M ultrahigh strength steel and a fully bainitic 2-1/4Cr-1Mo lower strength steel are investigated in environments of ambient temperature moist air and low pressure dehumidified hydrogen and argon gases over a wide range of growth rates from 10/sup -8/ to 10/sup -2/ mm/cycle, with particular emphasis given to behavior near the crack propagation threshold ..delta..K/sub 0/. It is found that two distinct growth rate regimes exist where hydrogen can markedly accelerate crack propagation rates compared to air, (1) at near-threshold levels below (5 x 10/sup -6/ mm/cycle) and (2) at higher growth rates, typically around 10/sup -5/ mm/cycle above a critical maximum stress intensity K/sub max//sup T/. Hydrogen-assisted crack propagation at higher growth rates is attributed to a hydrogen embrittlement mechanism, with K/sub max//sup T/ nominally equal to K/sub Iscc/ (the sustained load stress corrosion threshold) in high strength steels, and far below K/sub Iscc/ in the strain-rate sensitive lower strength steels. Hydrogen-assisted crack propagation at near-threshold levels is attributed to a new mechanism involving fretting-oxide-induced crack closure generated in moist (or oxygenated) environments. The absence of hydrogen embrittlement mechanisms at near-threshold levels is supported by tests showing that ..delta..K/sub 0/ values in dry gaseous argon are similar to ..delta..K/sub 0/ values in hydrogen. The potential ramifications of these results are examined in detail.

  8. In situ investigation of the effect of hydrogen on the plastic deformation ahead of the crack tip and the crack propagation of 0.15C-1.5Mn-0.17V-0.012N steel

    SciTech Connect

    Liao, B.; Nan, Y.; Hu, Y.; Kang, D.T.

    1998-02-01

    The influence of hydrogen on the deformation ahead of the crack tip and the crack propagation were observed and studied in situ under transmission electron microscopy with dynamic tensile deformation for steel. The results show that hydrogen can promote local plastic deformation ahead of the crack tip and change the mode of crack propagation so that the crack will propagate in a zigzag path.

  9. S-N Fatigue and Fatigue Crack Propagation Behaviors of X80 Steel at Room and Low Temperatures

    NASA Astrophysics Data System (ADS)

    Jung, Dae-Ho; Kwon, Jae-Ki; Woo, Nam-Sub; Kim, Young-Ju; Goto, Masahiro; Kim, Sangshik

    2014-02-01

    In the present study, the S-N fatigue and the fatigue crack propagation (FCP) behaviors of American Petroleum Institute X80 steel were examined in the different locations of the base metal (BM), weld metal (WM), and heat-affected zone (HAZ) at 298 K, 223 K, and 193 K (25 °C, -50 °C, and -80 °C). The resistance to S-N fatigue of X80 BM specimen increased greatly with decreasing temperature from 298 K to 193 K (25 °C to -80 °C) and showed a strong dependency on the flow strength (½(yield strength + tensile strength)). The FCP rates of X80 BM specimen were substantially reduced with decreasing temperature from 298 K to 223 K (25 °C to -50 °C) over the entire ∆ K regime, while further reduction in FCP rates was not significant with temperature from 223 K to 193 K (-50 °C to -80 °C). The FCP rates of the X80 BM and the WM specimens were comparable with each other, while the HAZ specimen showed slightly better FCP resistance than the BM and the WM specimens over the entire ∆K regime at 298 K (25 °C). Despite the varying microstructural characteristics of each weld location, the residual stress appeared to be a controlling factor to determine the FCP behavior. The FCP behaviors of high strength X80 steel were discussed based on the microstructural and the fractographic observations.

  10. Internal Crack Propagation in a Continuously Cast Austenitic Stainless Steel Analyzed by Actual Residual Stress Tensor Distributions

    NASA Astrophysics Data System (ADS)

    Saito, Youichi; Tanaka, Shun-Ichiro

    2016-04-01

    Initiation, propagation, and termination of internal cracks in a continuously cast austenitic stainless steel has been investigated with emphasis on stress loading of the solidified shell during casting. Cracks were formed at the center of the slab, parallel to the width of the cast, and were observed near the narrow faces. Optimized two-dimensional X-ray diffraction method was employed to measure residual stress tensor distributions around the cracks in the as-cast slab with coarse and strongly preferentially oriented grains. The tensor distributions had a sharp peak, as high as 430 MPa, at the crack end neighboring the columnar grains. On the other hand, lower values were measured at the crack end neighboring the equiaxed grains, where the local temperatures were higher during solidification. The true residual stress distributions were determined by evaluating the longitudinal elastic constant for each measured position, resulting in more accurate stress values than before. Electron probe micro-analysis at the terminal crack position showed that Ni, Ti, and Si were concentrated at the boundaries of the equiaxed grains, where the tensile strength was estimated to be lower than at the primary grains. A model of the crack formation and engineering recommendations to reduce crack formation are proposed.

  11. Elevated temperature creep-fatigue crack propagation in nickel-base alloys and 1 Cr-Mo-V steel

    NASA Astrophysics Data System (ADS)

    Nazmy, M.; Hoffelner, W.; Wüthrich, C.

    1988-04-01

    The crack growth behavior of several high temperature nickel-base alloys, under cyclic and static loading, is studied and reviewed. In the oxide dispersion strengthened (ODS) MA 6000 and MA 754 alloys, the high temperature crack propagation exhibited orientation dependence under cyclic as well as under static loading. The creep crack growth (CCG) behavior of cast nickel-base IN-738 and IN-939* superalloys at 850 °C could be characterized by the stress intensity factor, K 1. In the case of the alloy IN-901 at 500 °C and 600 °C, K 1 was found to be the relevant parameter to characterize the creep crack growth behavior. The energy rate line integral, C*, may be the appropriate loading parameter to describe the creep crack growth behavior of the nickel-iron base IN-800H alloy at 800 °C. The creep crack growth data of 1 Cr-Mo-V steel, with bainitic microstructure, at 550 °C could be correlated better by C * than by K 1.

  12. Measurements of the helium propagation at 4.4 K in a 480 m long stainless steel pipe

    SciTech Connect

    Hseuh, H.C.; Wallen, E.

    1997-12-01

    The Relativistic Heavy Ion Collider (RHIC), with two concentric rings 3.8 km in circumference, uses superconducting magnets to focus the high energy beams. Each sextant of RHIC will have continuous cryostats up to 480 m in length housing the magnets and the cold beam pipes. For an acceptable lifetime of the stored beam, the pressure in the cold beam pipe will be < 10{sup {minus}11} Torr. The characteristics of He pressure front propagation due to He leaks will be of importance for beam lifetimes and for vacuum monitoring due to the high vapor pressure of He at 4.4 K, even with small surface coverage. The travel of the He pressure fronts along a 480 m long, 6.9 cm I.D. stainless steel beam pipe cooled to 4.4 K has recently been measured during the RHIC first sextant test. The experiment was carried out over a 12-day period by bleeding in a calibrated He leak of 3 {times} 10{sup {minus}5} Torr{center_dot}l/s (20 C) while measuring the He pressures along this 480 m cold tube at {approximately} 30 m intervals. The measured speed of the pressure fronts and the pressure profiles are summarized and compared with the calculated ones.

  13. Measurements of the helium propagation at 4.4 K in a 480 m long stainless steel pipe

    SciTech Connect

    Hseuh, H.C.; Wallen, E.

    1998-05-01

    The relativistic heavy ion collider (RHIC), with two concentric rings 3.8 km in circumference, uses superconducting magnets to focus the high energy beams. Each sextant of RHIC will have continuous cryostats up to 480 m in length housing the magnets and the cold beam pipes. For an acceptable lifetime of the stored beam, the pressure in the cold beam pipe will be {lt}10{sup {minus}11} Torr. The characteristics of He pressure front propagation due to He leaks will be of importance for beam lifetimes and for vacuum monitoring due to the high vapor pressure of He at 4.4 K, even with small surface coverage. The travels of the He pressure fronts along a 480 m long, 6.9 cm I.D. stainless steel beam pipe cooled to 4.4 K have recently been measured during the RHIC first sextant test. The experiment was carried out over a 12-day period by bleeding in a calibrated He leak of 3{times}10{sup {minus}5}Torrl/s (20{degree}C) while measuring the He pressures along this 480 m cold tube at approximately 30 m intervals. The measured speed of the pressure fronts and the pressure profiles are summarized and compared with the calculated ones. {copyright} {ital 1998 American Vacuum Society.}

  14. Effect of Decarburization on Notch Sensitivity and Fatigue-Crack-Propagation Rates in 12 MoV Stainless-Steel Sheet

    NASA Technical Reports Server (NTRS)

    Herrnstein, William H., III; McEvily, Arthur J., Jr.

    1961-01-01

    Tests were conducted in order to determine the effect of surface decarburization on the notch sensitivity and rate of fatigue crack propagation in 12 MoV stainless-steel sheet at room temperature. Three specimen configurations were utilized in the course of the investigation: standard tensile specimen, 9-inch-wide specimens containing fatigue cracks or thread-cut notches of 0.005-inch radius, and 2-inch-wide specimens containing fatigue cracks. The 12 MoV stainless-steel sheet in the normal condition was found to have an ultimate tensile strength of 251 ksi and to be extremely notch sensitive. The material in the decarburized condition was found to have an ultimate tensile strength of 210 ksi and to be considerably stronger than the normal material in the presence of fatigue cracks. Decarburization did not appear to have any significant influence on the rate of fatigue crack propagation in the 2-inch-wide specimens at the stress levels considered. In addition to the tests, two methods for predicting residual static strength and their application to the material are discussed.

  15. The inhibitive mechanisms of nitrite and molybdate anions on initiation and propagation of pitting corrosion for mild steel in chloride solution

    NASA Astrophysics Data System (ADS)

    Zhou, Yong; Zuo, Yu

    2015-10-01

    The inhibitive mechanism of NO2- and MoO42- on the initiation and propagation of pitting corrosion for mild steel in chloride solution was studied with electrochemical methods and X-ray photoelectron spectroscopy (XPS). In 0.1 M NaCl solution both the addition of 0.2 M NaNO2 and 0.2 M Na2MoO4 effectively promoted passivation of mild steel. The passive film on the steel surface formed in NaCl + NO2- solution was composed of mainly γ-Fe2O3, and the film formed in NaCl + MoO42- solution was composed of two components: one is Fe2(MoO4)3 and the other is an oxide composed of Fe and O. The film formed in NaNO2 solution has lower oxygen vacancies and larger impedance than the film formed in Na2MoO4 solution. NO2- shows better inhibition to the initiation of pitting corrosion than MoO42-, which is attributed to its strong oxidability that results in the formation of a stable γ-Fe2O3 film. However, in NaNO2 solution, once a pit forms, it is more difficult to get repassivated than the situation in Na2MoO4 solution. The main reason is due to that in a propagating pit MoO42- anions result in increased solution pH value, but conversely NO2- anions lead to a decreased solution pH value within a pit.

  16. Computer simulation of fast crack propagation and arrest in steel plate with temperature gradient based on local fracture stress criterion

    SciTech Connect

    Machida, Susumu; Yoshinari, Hitoshi; Aihara, Shuji

    1997-12-31

    A fracture mechanics model for fast crack propagation and arrest is proposed based on the local fracture stress criterion. Dynamic fracture toughness (K{sub D}) for a propagating crack is calculated as a function of crack velocity and temperature. The model is extended to incorporate the effect of unbroken ligament (UL) formed near the plate surfaces and crack-front-tunneling. The model simulates acceleration, deceleration and arrest of a crack in a ESSO or a double-tension test plate with temperature-gradient. Calculated arrested crack lengths compare well with experimental results. It is shown that the conventional crack arrest toughness calculated from applied stress and arrested crack length depends on temperature-gradient and the toughness is not a unique material property.

  17. Mechanistic dissimilarities between environmentally-influenced fatigue-crack propagation at near-threshold and higher growth rates in lower-strength steels

    SciTech Connect

    Suresh, S.; Ritchie, R. O.

    1981-11-01

    The role of hydrogen gas in influencing fatigue crack propagation is examined for several classes of lower strength pressure vessel and piping steels. Based on measurements over a wide range of growth rates from 10/sup -8/ to 10/sup -2/ mm/cycle, crack propagation rates are found to be significantly higher in dehumidified gaseous hydrogen compared to moist air in two distinct regimes of crack growth, namely (i) at the intermediate range of growth typically above approx. 10/sup -5/ mm/cycle, and (ii) at the near-threshold region below approx. 10/sup -6/ mm/cycle approaching lattice dimensions per cycle. Both effects are seen at maximum stress intensities (K/sub max/) far below the sustained-load threshold stress intensity for hydrogen-assisted cracking (K/sub Iscc/). Characteristics of environmentally influenced fatigue crack growth in each regime are shown to be markedly different with regard to fractography and the effect of such variables as load ratio and frequency. It is concluded that the primary mechanisms responsible for the influence of the environment in each regime are distinctly different. Whereas corrosion fatigue behavior at intermediate growth rates can be attributed to hydrogen embrittlement processes, the primary role of moist environments at near-threshold levels is shown to involve a contribution from enhanced crack closure due to the formation of crack surface corrosion deposits at low load ratios.

  18. Metal magnetic memory technique used to predict the fatigue crack propagation behavior of 0.45%C steel

    NASA Astrophysics Data System (ADS)

    Chongchong, Li; Lihong, Dong; Haidou, Wang; Guolu, Li; Binshi, Xu

    2016-05-01

    Monitoring fatigue crack propagation behavior of ferromagnetic components is very important. In this paper, the tension-tension fatigue tests of center cracked tension (CCT) specimens were carried out; the variation regularity of both tangential and normal components of magnetic signals during fatigue process were investigated. The results showed that the initial abnormal signals which appeared at the notch were reversed after cyclic loading. The abnormal magnetic signals became more significant with the increase of fatigue cycles and reversed again after failure. The characteristic parameters, i.e., the peak value of tangential component, Btp, and maximum gradient value of normal component, Km, showed similar variation trends during the fatigue process, which can be divided into three different stages. An approximate linear relationship was found between the characteristic parameters and fatigue crack length 2a. The feasibility of predicting the fatigue crack propagation using the abnormal magnetic signals was discussed. What's more, the variation and distribution of the magnetic signals were also analyzed based on the theory of magnetic charge.

  19. Effect of proof testing on the flaw growth characteristics of 304 stainless steel. [crack propagation in welded joints

    NASA Technical Reports Server (NTRS)

    Finger, R. W.

    1974-01-01

    The effects of proof overload frequency and magnitude on the cyclic crack growth rates of 304 stainless steel weldments were investigated. The welding procedure employed was typical of those used on over-the-road cryogenic vessels. Tests were conducted at room temperature with an overload ratio of 1.50 to determine the effect of overload frequency. Effect of overload magnitude was determined from tests where a room temperature overload was applied between blocks of 1000 cycles applied at 78 K (-320 F). The cyclic stress level used in all tests was typical of the nominal membrane stress generally encountered in full scale vessels. Test results indicate that judicious selection of proof overload frequency and magnitude can reduce crack growth rates for cyclic stress levels.

  20. Flank wears Simulation by using back propagation neural network when cutting hardened H-13 steel in CNC End Milling

    NASA Astrophysics Data System (ADS)

    Hazza, Muataz Hazza F. Al; Adesta, Erry Y. T.; Riza, Muhammad

    2013-12-01

    High speed milling has many advantages such as higher removal rate and high productivity. However, higher cutting speed increase the flank wear rate and thus reducing the cutting tool life. Therefore estimating and predicting the flank wear length in early stages reduces the risk of unaccepted tooling cost. This research presents a neural network model for predicting and simulating the flank wear in the CNC end milling process. A set of sparse experimental data for finish end milling on AISI H13 at hardness of 48 HRC have been conducted to measure the flank wear length. Then the measured data have been used to train the developed neural network model. Artificial neural network (ANN) was applied to predict the flank wear length. The neural network contains twenty hidden layer with feed forward back propagation hierarchical. The neural network has been designed with MATLAB Neural Network Toolbox. The results show a high correlation between the predicted and the observed flank wear which indicates the validity of the models.

  1. The Crack Initiation and Propagation in threshold regime and S-N curves of High Strength Spring Steels

    NASA Astrophysics Data System (ADS)

    Gubeljak, N.; Predan, J.; Senčič, B.; Chapetti, M. D.

    2016-03-01

    An integrated fracture mechanics approach is proposed to account for the estimation of the fatigue resistance of component. Applications, estimations and results showed very good agreements with experimental results. The model is simple to apply, accounts for the main geometrical, mechanical and material parameters that define the fatigue resistance, and allows accurate predictions. It offers a change in design philosophy: It could be used for design, while simultaneously dealing with crack propagation thresholds. Furthermore, it allows quantification of the material defect sensitivity. In the case of the set of fatigue tests carried out by rotational bending of specimens without residual stresses, the estimated results showed good agreement and that an initial crack length of 0.5 mm can conservatively explain experimental data. In the case of fatigue tests carried out on the springs at their final condition with bending at R = 0.1 our data shows the influence of compressive residual stresses on fatigue strength. Results also showed that the procedures allow us to analyze the different combinations of initial crack length and residual stress levels, and how much the fatigue resistance can change by changing that configuration. For this set of tests, the fatigue resistance estimated for an initial crack length equal to 0.35 mm, can explain all testing data observed for the springs.

  2. Crack Propagation Resistance of α-Al2O3 Reinforced Pulsed Laser-Deposited Hydroxyapatite Coating on 316 Stainless Steel

    NASA Astrophysics Data System (ADS)

    Bajpai, Shubhra; Gupta, Ankur; Pradhan, Siddhartha Kumar; Mandal, Tapendu; Balani, Kantesh

    2014-09-01

    Hydroxyapatite (HA) is a widely used bioceramic known for its chemical similarity with that of bone and teeth (Ca/P ratio of 1.67). But, owing to its extreme brittleness, α-Al2O3 is reinforced with HA and processed as a coating via pulsed laser deposition (PLD). Reinforcement of α-Al2O3 (50 wt.%) in HA via PLD on 316L steel substrate has shown modulus increase by 4% and hardness increase by 78%, and an improved adhesion strength of 14.2 N (improvement by 118%). Micro-scratching has shown an increase in the coefficient-of-friction from 0.05 (pure HA) to 0.17 (with 50 wt.% Al2O3) with enhancement in the crack propagation resistance (CPR) up to 4.5 times. Strong adherence of PLD HA-Al2O3 coatings (~4.5 times than that of HA coating) is attributed to efficient release of stored tensile strain energy (~17 × 10-3 J/m2) in HA-Al2O3 composites, making it a potential damage-tolerant bone-replacement surface coating.

  3. Laboratory examination of SCC initiation and propagation mechanisms in austenitic stainless steel weldment Type 304 in boiling MgCl{sub 2} solutions at various concentrations: A chemo-physical approach

    SciTech Connect

    Sadek, A.Z.; Reheem Aly, N.A.A.; El-Demerdash, M.F.; El-Sheikh, A.M.

    1999-11-01

    Constant strain rate tests were conducted on welded austenitic AISI 304 (UNS 30400) in boiling MgCl{sub 2} solutions at concentrations stainless steel of 32% and 37% weight respectively. Potentiodynamic anodic polarization tests were carried out on unstressed welded coupons. Open circuit potential measurements on stressed specimens showed that weldments exhibited free corrosion behavior in the active-passive region. Residual ferrite phase in weldments was detected using experimental and analytical methods. The presence of residual delta ferrite in weldments is hypothesized to have been responsible for the formation of microgalvanic cells that lead to the selective dissolution of the ferrite phase in favor of the austenitic matrix. This situation provided suitable nucleation sites for cracking, and its simultaneous occurrence promoted crack propagation. Optical and electron microscopy investigations support this hypothesis and show that weldment interdendritic spaces suffered selective dissolution and that crack propagation followed a preferential path along delta ferrite rich interdendritic arms. It was also revealed by the optical and electron microscopy investigations that crack growth took place by the union of longitudinally aligned interdendritic arms. The results are in agreement with the Parkins model of crack nucleation by simultaneous action of passive film formation, film rupture.

  4. Compilation of fatigue, fatigue-crack propagation, and fracture data for 2024 and 7075 aluminum, Ti-6Al-4V titanium, and 300M steel. Volume 1: Description of data and data storage on magnetic tape. Volume 2: Data tape (7-track magnetic tape)

    NASA Technical Reports Server (NTRS)

    Rice, R. C.; Reynolds, J. L.

    1976-01-01

    Fatigue, fatigue-crack-propagation, and fracture data compiled and stored on magnetic tape are documented. Data for 202 and 7075 aluminum alloys, Ti-6Al-4V titanium alloy, and 300M steel are included in the compilation. Approximately 4,500 fatigue, 6,500 fatigue-crack-propagation, and 1,500 fracture data points are stored on magnetic tape. Descriptions of the data, an index to the data on the magnetic tape, information on data storage format on the tape, a listing of all data source references, and abstracts of other pertinent test information from each data source reference are included.

  5. Atmospheric Propagation

    NASA Technical Reports Server (NTRS)

    Embleton, Tony F. W.; Daigle, Gilles A.

    1991-01-01

    Reviewed here is the current state of knowledge with respect to each basic mechanism of sound propagation in the atmosphere and how each mechanism changes the spectral or temporal characteristics of the sound received at a distance from the source. Some of the basic processes affecting sound wave propagation which are present in any situation are discussed. They are geometrical spreading, molecular absorption, and turbulent scattering. In geometrical spreading, sound levels decrease with increasing distance from the source; there is no frequency dependence. In molecular absorption, sound energy is converted into heat as the sound wave propagates through the air; there is a strong dependence on frequency. In turbulent scattering, local variations in wind velocity and temperature induce fluctuations in phase and amplitude of the sound waves as they propagate through an inhomogeneous medium; there is a moderate dependence on frequency.

  6. Rift propagation

    NASA Technical Reports Server (NTRS)

    Parmentier, E. M.; Schubert, G.

    1989-01-01

    A model for rift propagation which treats the rift as a crack in an elastic plate which is filled from beneath by upwelling viscous asthenosphere as it lengthens and opens. Growth of the crack is driven by either remotely applied forces or the pressure of buoyant asthenosphere in the crack and is resisted by viscous stresses associated with filling the crack. The model predicts a time for a rift to form which depends primarily on the driving stress and asthenosphere viscosity. For a driving stress on the order of 10 MPa, as expected from the topography of rifted swells, the development of rifts over times of a few Myr requires an asthenosphere viscosity of 10 to the 16th Pa s (10 to the 17th poise). This viscosity, which is several orders of magnitude less than values determined by postglacial rebound and at least one order of magnitude less than that inferred for spreading center propagation, may reflect a high temperature or large amount of partial melting in the mantle beneath a rifted swell.

  7. Laser-Based Instrument Measures Propagation Of Cracks

    NASA Technical Reports Server (NTRS)

    Lee, Rupert U.; Cox, Robert B.; Youngquist, Robert C.; Sentz, John T.; Rose, Kenneth A.

    1995-01-01

    Report describes use of commerical laser displacement meter to measure propagation of cracks in stainless-steel specimens in stress tests in corrosive (salt-spray) environment. Measurements directed toward determining time from beginning of each test until onset of propagation of crack.

  8. Clean steel technology -- Fundamental to the development of high performance steels

    SciTech Connect

    Wilson, A.D.

    1999-07-01

    The use of clean steel technology (low sulfur with calcium treatment for inclusion shape control) is a fundamental building block in the development of high performance plate steels. A brief review will be presented of the benefits of calcium treatment and its effect on non-metallic inclusions (sulfides and oxides) and reducing sulfur levels. During the past thirty years the requirements for low sulfur levels have been reduced from 0.010% maximum to 0.001% maximum. The effects of clean steel practices on specific properties will be reviewed including tensile ductility, Charpy V-notch and fracture toughness, fatigue crack propagation and hydrogen-induced-cracking resistance. Traditional low sulfur plate steel applications have included pressure vessels. offshore platforms, plastic injection molds and line-pipe skelp. More recent applications will be discussed including bridge steels, high strength structural steels to 130 ksi (897 MPa) minimum yield strength, 9% nickel steels for cryogenic applications, and military armor.

  9. The universal propagator

    NASA Technical Reports Server (NTRS)

    Klauder, John R.

    1993-01-01

    For a general Hamiltonian appropriate to a single canonical degree of freedom, a universal propagator with the property that it correctly evolves the coherent-state Hilbert space representatives for an arbitrary fiducial vector is characterized and defined. The universal propagator is explicitly constructed for the harmonic oscillator, with a result that differs from the conventional propagators for this system.

  10. Wave propagation in damage assessment of ground anchors

    NASA Astrophysics Data System (ADS)

    Zima, B.; Rucka, M.

    2015-07-01

    The inspection possibilities of ground anchors are limited to destructive test such as pull-out test. Guided wave propagation gives an opportunity to develop an inspection system dedicated to determine the condition of inspected element without violation of their integrity. In this paper the experimental study on wave propagation in laboratory models of ground anchors are presented. Experiments were conducted for different bonding lengths and different frequencies of excitation. Waves were generated by a piezoelectric actuator and the laser vibrometry technique was used to register velocity signals. For all tested anchors it was possible to identify the boundary between steel and concrete based on the registered reflections in wave propagation signals.

  11. NASA Propagation Studies Website

    NASA Technical Reports Server (NTRS)

    Angkasa, Krisjani S.

    1996-01-01

    The NASA propagation studies objective is to enable the development of new commercial satellite communication systems and services by providing timely data and models about propagation of satellite radio signals through the intervening environment and to support NASA missions. In partnership with industry and academia, the program leverages unique NASA assets (currently Advanced Communications Technology Satellite) to obtain propagation data. The findings of the study are disseminated through referred journals, NASA reference publications, workshops, electronic media, and direct interface with industry.

  12. Limitations in scatter propagation

    NASA Astrophysics Data System (ADS)

    Lampert, E. W.

    1982-04-01

    A short description of the main scatter propagation mechanisms is presented; troposcatter, meteor burst communication and chaff scatter. For these propagation modes, in particular for troposcatter, the important specific limitations discussed are: link budget and resulting hardware consequences, diversity, mobility, information transfer and intermodulation and intersymbol interference, frequency range and future extension in frequency range for troposcatter, and compatibility with other services (EMC).

  13. NASA Propagation Information Center

    NASA Technical Reports Server (NTRS)

    Smith, Ernest K.; Flock, Warren L.

    1989-01-01

    The NASA Propagation Information Center became formally operational in July 1988. It is located in the Department of Electrical and Computer Engineering of the University of Colorado at Boulder. The Center is several things: a communications medium for the propagation with the outside world, a mechanism for internal communication within the program, and an aid to management.

  14. NASA propagation information center

    NASA Technical Reports Server (NTRS)

    Smith, Ernest K.; Flock, Warren L.

    1990-01-01

    The NASA Propagation Information Center became formally operational in July 1988. It is located in the Department of Electrical and Computer Engineering of the University of Colorado at Boulder. The center is several things: a communications medium for the propagation with the outside world, a mechanism for internal communication within the program, and an aid to management.

  15. Propagation research in Japan

    NASA Technical Reports Server (NTRS)

    Wakana, Hiromitsu

    1991-01-01

    L-band propagation measurements for land-mobile, maritime, and aeronautical satellite communications have been carried out by using the Japanese Engineering Test Satellite-Five (ETS-5) which was launched in Aug. 1987. This paper presents propagation characteristics for each of the mobile satellite communication channels.

  16. Wave propagation phenomena

    NASA Astrophysics Data System (ADS)

    Groenenboom, P. H. L.

    The phenomenon of wave propagation is encountered frequently in a variety of engineering disciplines. It has been realized that for a growing number of problems the solution can only be obtained by discretization of the boundary. Advantages of the Boundary Element Method (BEM) over domain-type methods are related to the reduction of the number of space dimensions and of the modelling effort. It is demonstrated how the BEM can be applied to wave propagation phenomena by establishing the fundamental relationships. A numerical solution procedure is also suggested. In connection with a discussion of the retarded potential formulation, it is shown how the wave propagation problem can be cast into a Boundary Integral Formulation (BIF). The wave propagation problem in the BIF can be solved by time-successive evaluation of the boundary integrals. The example of pressure wave propagation following a sodium-water reaction in a Liquid Metal cooled Fast Breeder Reactor steam generator is discussed.

  17. 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.

  18. Elastic Wave Propagation in Concrete and Continuous Wavelet Transform

    SciTech Connect

    Chiang, C.-H.; Gi, Y.-F.; Pan, C.-L.; Cheng, C.-C.

    2005-04-09

    Elastic wave methods, such as the ultrasonic pulse velocity and the impact echo, are often subject to multiple reflections at the boundaries of various constituents of concrete. Current study aims to improve the feature identification of elastic wave propagation due to buried objects in concrete slabs and cylinders. Embedded steel reinforcement, steel and PVC tubes, wooden disks, and rubber spheres are tested. The received signals are analyzed using continuous wavelet transform. As a result, signals are decomposed into distinctive frequency bands with transient information preserved. The interpretation of multiple reflections at different boundary conditions thus becomes more straightforward. Features related to reflections from steel bar, PVC tube, and steel tube can be readily identified in the magnitude plot of wavelet coefficients. Vibration modes of the concrete slab corresponding to different buried objects can also be separated based on corresponding time duration.

  19. Elastic Wave Propagation in Concrete and Continuous Wavelet Transform

    NASA Astrophysics Data System (ADS)

    Chiang, Chih-Hung; Gi, Yu-Fung; Pan, Chi-Ling; Cheng, Chia-Chi

    2005-04-01

    Elastic wave methods, such as the ultrasonic pulse velocity and the impact echo, are often subject to multiple reflections at the boundaries of various constituents of concrete. Current study aims to improve the feature identification of elastic wave propagation due to buried objects in concrete slabs and cylinders. Embedded steel reinforcement, steel and PVC tubes, wooden disks, and rubber spheres are tested. The received signals are analyzed using continuous wavelet transform. As a result, signals are decomposed into distinctive frequency bands with transient information preserved. The interpretation of multiple reflections at different boundary conditions thus becomes more straightforward. Features related to reflections from steel bar, PVC tube, and steel tube can be readily identified in the magnitude plot of wavelet coefficients. Vibration modes of the concrete slab corresponding to different buried objects can also be separated based on corresponding time duration.

  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. Propagation of Environmental Noise

    ERIC Educational Resources Information Center

    Lyon, R. H.

    1973-01-01

    Solutions for environmental noise pollution lie in systematic study of many basic processes such as reflection, scattering, and spreading. Noise propagation processes should be identified in different situations and assessed for their relative importance. (PS)

  2. NASA Propagation Studies Website

    NASA Technical Reports Server (NTRS)

    Angkasa, Krisjani S.

    1996-01-01

    This paper describes an Internet website which provides information to enable the development of new commerical satellite systems and services by providing timely data and models about the propagation of satellite radio signals. In partnership with industry and academia, the program leverages NASA assets, currently the Advanced Communications Technology Satellite (ACTS), to obtain propagation data. The findings of the study are disseminated through refereed journals, NASA reference publications, workshops, electronic media, and direct interface with industry.

  3. Database for propagation models

    NASA Technical Reports Server (NTRS)

    Kantak, Anil V.

    1991-01-01

    A propagation researcher or a systems engineer who intends to use the results of a propagation experiment is generally faced with various database tasks such as the selection of the computer software, the hardware, and the writing of the programs to pass the data through the models of interest. This task is repeated every time a new experiment is conducted or the same experiment is carried out at a different location generating different data. Thus the users of this data have to spend a considerable portion of their time learning how to implement the computer hardware and the software towards the desired end. This situation may be facilitated considerably if an easily accessible propagation database is created that has all the accepted (standardized) propagation phenomena models approved by the propagation research community. Also, the handling of data will become easier for the user. Such a database construction can only stimulate the growth of the propagation research it if is available to all the researchers, so that the results of the experiment conducted by one researcher can be examined independently by another, without different hardware and software being used. The database may be made flexible so that the researchers need not be confined only to the contents of the database. Another way in which the database may help the researchers is by the fact that they will not have to document the software and hardware tools used in their research since the propagation research community will know the database already. The following sections show a possible database construction, as well as properties of the database for the propagation research.

  4. Wave Propagation Program

    Energy Science and Technology Software Center (ESTSC)

    2007-01-08

    WPP is a massively parallel, 3D, C++, finite-difference elastodynamic wave propagation code. Typical applications for wave propagation with WPP include: evaluation of seismic event scenarios and damage from earthquakes, non-destructive evaluation of materials, underground facility detection, oil and gas exploration, predicting the electro-magnetic fields in accelerators, and acoustic noise generation. For more information, see User’s Manual [1].

  5. 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.

  6. 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.

  7. Turbofan Duct Propagation Model

    NASA Technical Reports Server (NTRS)

    Lan, Justin H.; Posey, Joe W. (Technical Monitor)

    2001-01-01

    The CDUCT code utilizes a parabolic approximation to the convected Helmholtz equation in order to efficiently model acoustic propagation in acoustically treated, complex shaped ducts. The parabolic approximation solves one-way wave propagation with a marching method which neglects backwards reflected waves. The derivation of the parabolic approximation is presented. Several code validation cases are given. An acoustic lining design process for an example aft fan duct is discussed. It is noted that the method can efficiently model realistic three-dimension effects, acoustic lining, and flow within the computational capabilities of a typical computer workstation.

  8. 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.

  9. DROMO propagator revisited

    NASA Astrophysics Data System (ADS)

    Urrutxua, Hodei; Sanjurjo-Rivo, Manuel; Peláez, Jesús

    2016-01-01

    In the year 2000 an in-house orbital propagator called DROMO (Peláez et al. in Celest Mech Dyn Astron 97:131-150, 2007. doi: 10.1007/s10569-006-9056-3) was developed by the Space Dynamics Group of the Technical University of Madrid, based in a set of redundant variables including Euler-Rodrigues parameters. An original deduction of the DROMO propagator is carried out, underlining its close relation with the ideal frame concept introduced by Hansen (Abh der Math-Phys Cl der Kon Sachs Ges der Wissensch 5:41-218, 1857). Based on the very same concept, Deprit (J Res Natl Bur Stand Sect B Math Sci 79B(1-2):1-15, 1975) proposed a formulation for orbit propagation. In this paper, similarities and differences with the theory carried out by Deprit are analyzed. Simultaneously, some improvements are introduced in the formulation, that lead to a more synthetic and better performing propagator. Also, the long-term effect of the oblateness of the primary is studied in terms of DROMO variables, and new numerical results are presented to evaluate the performance of the method.

  10. GRC RF Propagation Studies

    NASA Technical Reports Server (NTRS)

    Nessel, James

    2013-01-01

    NASA Glenn Research Center has been involved in the characterization of atmospheric effects on space communications links operating at Ka-band and above for the past 20 years. This presentation reports out on the most recent activities of propagation characterization that NASA is currently involved in.

  11. PROPER: Optical propagation routines

    NASA Astrophysics Data System (ADS)

    Krist, John E.

    2014-05-01

    PROPER simulates the propagation of light through an optical system using Fourier transform algorithms (Fresnel, angular spectrum methods). Distributed as IDL source code, it includes routines to create complex apertures, aberrated wavefronts, and deformable mirrors. It is especially useful for the simulation of high contrast imaging telescopes (extrasolar planet imagers like TPF).

  12. Supertough Stainless Bearing Steel

    NASA Technical Reports Server (NTRS)

    Olson, Gregory B.

    1995-01-01

    Composition and processing of supertough stainless bearing steel designed with help of computer-aided thermodynamic modeling. Fracture toughness and hardness of steel exceeds those of other bearing steels like 440C stainless bearing steel. Developed for service in fuel and oxidizer turbopumps on Space Shuttle main engine. Because of strength and toughness, also proves useful in other applications like gears and surgical knives.

  13. A Database for Propagation Models

    NASA Technical Reports Server (NTRS)

    Kantak, Anil V.; Rucker, James

    1997-01-01

    The Propagation Models Database is designed to allow the scientists and experimenters in the propagation field to process their data through many known and accepted propagation models. The database is an Excel 5.0 based software that houses user-callable propagation models of propagation phenomena. It does not contain a database of propagation data generated out of the experiments. The database not only provides a powerful software tool to process the data generated by the experiments, but is also a time- and energy-saving tool for plotting results, generating tables and producing impressive and crisp hard copy for presentation and filing.

  14. Notch-Fatigue Properties of Advanced TRIP-Aided Bainitic Ferrite Steels

    NASA Astrophysics Data System (ADS)

    Yoshikawa, Nobuo; Kobayashi, Junya; Sugimoto, Koh-ichi

    2012-11-01

    To develop a transformation-induced plasticity (TRIP)-aided bainitic ferrite steel (TBF steel) with high hardenability for a common rail of the next generation diesel engine, 0.2 pct C-1.5 pct Si-1.5 pct Mn-0.05 pct Nb TBF steels with different contents of Cr, Mo, and Ni were produced. The notch-fatigue strength of the TBF steels was investigated and was related to the microstructural and retained austenite characteristics. If Cr, Mo, and/or Ni were added to the base steel, then the steels achieved extremely higher notch-fatigue limits and lower notch sensitivity than base TBF steel and the conventional structural steels. This was mainly associated with (1) carbide-free and fine bainitic ferrite lath structure matrix without proeutectoid ferrite, (2) a large amount of fine metastable retained austenite, and (3) blocky martensite phase including retained austenite, which may suppress a fatigue crack initiation and propagation.

  15. Atmospheric sound propagation

    NASA Technical Reports Server (NTRS)

    Cook, R. K.

    1969-01-01

    The propagation of sound waves at infrasonic frequencies (oscillation periods 1.0 - 1000 seconds) in the atmosphere is being studied by a network of seven stations separated geographically by distances of the order of thousands of kilometers. The stations measure the following characteristics of infrasonic waves: (1) the amplitude and waveform of the incident sound pressure, (2) the direction of propagation of the wave, (3) the horizontal phase velocity, and (4) the distribution of sound wave energy at various frequencies of oscillation. Some infrasonic sources which were identified and studied include the aurora borealis, tornadoes, volcanos, gravity waves on the oceans, earthquakes, and atmospheric instability waves caused by winds at the tropopause. Waves of unknown origin seem to radiate from several geographical locations, including one in the Argentine.

  16. Transionospheric Propagation Code (TIPC)

    SciTech Connect

    Roussel-Dupre, R.; Kelley, T.A.

    1990-10-01

    The Transionospheric Propagation Code is a computer program developed at Los Alamos National Lab to perform certain tasks related to the detection of vhf signals following propagation through the ionosphere. The code is written in Fortran 77, runs interactively and was designed to be as machine independent as possible. A menu format in which the user is prompted to supply appropriate parameters for a given task has been adopted for the input while the output is primarily in the form of graphics. The user has the option of selecting from five basic tasks, namely transionospheric propagation, signal filtering, signal processing, DTOA study, and DTOA uncertainty study. For the first task a specified signal is convolved against the impulse response function of the ionosphere to obtain the transionospheric signal. The user is given a choice of four analytic forms for the input pulse or of supplying a tabular form. The option of adding Gaussian-distributed white noise of spectral noise to the input signal is also provided. The deterministic ionosphere is characterized to first order in terms of a total electron content (TEC) along the propagation path. In addition, a scattering model parameterized in terms of a frequency coherence bandwidth is also available. In the second task, detection is simulated by convolving a given filter response against the transionospheric signal. The user is given a choice of a wideband filter or a narrowband Gaussian filter. It is also possible to input a filter response. The third task provides for quadrature detection, envelope detection, and three different techniques for time-tagging the arrival of the transionospheric signal at specified receivers. The latter algorithms can be used to determine a TEC and thus take out the effects of the ionosphere to first order. Task four allows the user to construct a table of delta-times-of-arrival (DTOAs) vs TECs for a specified pair of receivers.

  17. Transionospheric Propagation Code (TIPC)

    NASA Astrophysics Data System (ADS)

    Roussel-Dupre, Robert; Kelley, Thomas A.

    1990-10-01

    The Transionospheric Propagation Code is a computer program developed at Los Alamos National Lab to perform certain tasks related to the detection of VHF signals following propagation through the ionosphere. The code is written in FORTRAN 77, runs interactively and was designed to be as machine independent as possible. A menu format in which the user is prompted to supply appropriate parameters for a given task has been adopted for the input while the output is primarily in the form of graphics. The user has the option of selecting from five basic tasks, namely transionospheric propagation, signal filtering, signal processing, delta times of arrival (DTOA) study, and DTOA uncertainty study. For the first task a specified signal is convolved against the impulse response function of the ionosphere to obtain the transionospheric signal. The user is given a choice of four analytic forms for the input pulse or of supplying a tabular form. The option of adding Gaussian-distributed white noise of spectral noise to the input signal is also provided. The deterministic ionosphere is characterized to first order in terms of a total electron content (TEC) along the propagation path. In addition, a scattering model parameterized in terms of a frequency coherence bandwidth is also available. In the second task, detection is simulated by convolving a given filter response against the transionospheric signal. The user is given a choice of a wideband filter or a narrowband Gaussian filter. It is also possible to input a filter response. The third task provides for quadrature detection, envelope detection, and three different techniques for time-tagging the arrival of the transionospheric signal at specified receivers. The latter algorithms can be used to determine a TEC and thus take out the effects of the ionosphere to first order. Task four allows the user to construct a table of DTOAs vs TECs for a specified pair of receivers.

  18. Florida's propagation report

    NASA Technical Reports Server (NTRS)

    Helmken, Henry; Henning, Rudolf

    1994-01-01

    One of the key goals of the Florida Center is to obtain a maximum of useful information on propagation behavior unique to its subtropical weather and subtropical climate. Such weather data is of particular interest when it is (or has the potential to become) useful for developing and implementing techniques to compensate for adverse weather effects. Also discussed are data observations, current challenges, CDF's, sun movement, and diversity experiments.

  19. OPEX: (Olympus Propagation EXperiment)

    NASA Technical Reports Server (NTRS)

    Brussaard, Gert

    1988-01-01

    The Olympus-1 satellite carries four distinct payloads for experimental utilization and research in the field of satellite communications: (1) the Direct Broadcasting Service (DBS) payload; (2) the Specialized Services Payload; (3) the 20/30 GHz Advanced Communications Payload; and (4) the Propagation Payload. Experimental utilization of the first three payloads involves ground transmissions to the satellite and hence sharing of available satellite time among experimenters. This is coordinated through the Olympus Utilization Program.

  20. The ACTS propagation program

    NASA Technical Reports Server (NTRS)

    Chakraborty, D.; Davarian, Faramaz

    1992-01-01

    The success or failure of the ACTS experiment will depend on how accurately the rain-fade statistics and fade dynamics can be predicted in order to derive an appropriate algorithm that will combat weather vagaries, specifically for links with small terminals, such as very small aperture terminals (VSAT's) where the power margin is a premium. The planning process and hardware development program that will comply with the recommendations of the ACTS propagation study groups are described.

  1. Olympus propagation experiments

    NASA Technical Reports Server (NTRS)

    Arbesser-Rastburg, Bertram

    1994-01-01

    A summary of the activities of the OPEX (Olympus Propagation EXperimenters) group is given and some of the recent findings are presented. OLYMPUS, a telecommunication satellite owned by the European Space Agency, was launched on 12 June 1989. After the in-orbit tests were completed (in September 1989) the first propagation experiments started. Throughout 1990 the spacecraft functioned very well and a large number of experimenters received the beacon signals. On 29 May 1991 the spacecraft became inoperational after a major technical problem. With a series of complicated procedures OLYMPUS was recovered on 15 August 1991 - the first time in history that a civilian telecommunications satellite was brought back to service after losing power and telemetry. The propagation experiments were back on track. However, the recovery had used up so much fuel that the North-South station keeping had to be abandoned, which led to a natural increase of inclination at a rate of about 0.8 deg per year. On 10 October 1992 the second 30 GHz beacon tube failed, causing a loss of this beacon signal. The other two beacon frequencies continued to deliver a stable signal for more than two years. On 12 August 1993 the spacecraft experienced another problem with the altitude control, but this time there was not enough fuel left for a recovery maneuver and thus the mission came to an end.

  2. Olympus propagation experiments

    NASA Astrophysics Data System (ADS)

    Arbesser-Rastburg, Bertram

    1994-08-01

    A summary of the activities of the OPEX (Olympus Propagation EXperimenters) group is given and some of the recent findings are presented. OLYMPUS, a telecommunication satellite owned by the European Space Agency, was launched on 12 June 1989. After the in-orbit tests were completed (in September 1989) the first propagation experiments started. Throughout 1990 the spacecraft functioned very well and a large number of experimenters received the beacon signals. On 29 May 1991 the spacecraft became inoperational after a major technical problem. With a series of complicated procedures OLYMPUS was recovered on 15 August 1991 - the first time in history that a civilian telecommunications satellite was brought back to service after losing power and telemetry. The propagation experiments were back on track. However, the recovery had used up so much fuel that the North-South station keeping had to be abandoned, which led to a natural increase of inclination at a rate of about 0.8 deg per year. On 10 October 1992 the second 30 GHz beacon tube failed, causing a loss of this beacon signal. The other two beacon frequencies continued to deliver a stable signal for more than two years. On 12 August 1993 the spacecraft experienced another problem with the altitude control, but this time there was not enough fuel left for a recovery maneuver and thus the mission came to an end.

  3. Burn propagation rates of metals and alloys in gaseous oxygen

    NASA Technical Reports Server (NTRS)

    Benz, F. J.; Shaw, R. C.; Homa, J. M.

    1986-01-01

    The average burn rates of several metals and alloys were determined at oxygen pressures between 3.45 and 68.91 MPa (500 and 10,000 psig) and ambient temperature. Several materials were tested at elevated sample temperatures. The test materials were fabricated into solid cylindrical rods and mounted vertically in the test chamber. A magnesium igniter was positioned at the bottom end of each test specimen to promote upward burn propagations. Nickel 200 and copper 102 could not be ignited at all oxygen pressures tested whereas Monel 400 appeared to ignite but quickly self-extinguished. The other materials tested burned the entire length of the test sample. Aluminum 6061 exhibited the fastest burn propagation rate. Inconel 718 burned slower than aluminum but faster than the stainless steels (types 304 and 316). Increasing oxygen pressure generally increased the burn propagation rate of the materials. Increasing the ambient temperature of the test specimens for several materials to approximately 850 K (1070 F) had little effect upon the ignition or burn properties of nickel 200 or Monel 400. Type 316 stainless steel exhibited an increase in its burn propagation rate at this higher temperature.

  4. Experimental study of thermodynamics propagation fatigue crack in metals

    SciTech Connect

    Vshivkov, A. Iziumova, A. Plekhov, O.

    2015-10-27

    This work is devoted to the development of an experimental method for studying the energy balance during cyclic deformation and fracture. The studies were conducted on 304 stainless steel AISE samples. The investigation of the fatigue crack propagation was carried out on flat samples with stress concentrators. The stress concentrator was three central holes. The heat flux sensor was developed based on the Seebeck effect. This sensor was used for measuring the heat dissipation power in the examined samples during the fatigue tests. The measurements showed that the rate of fatigue crack growth depends on the heat flux at the crack tip and there are two propagation mode of fatigue crack with different link between the propagation mode and heat flux from crack tip.

  5. Propagation in the ionosphere, A

    NASA Astrophysics Data System (ADS)

    Cannon, Paul S.

    1994-09-01

    The use of ionospheric models and ray tracing models as components of a propagation model are discussed. These can be used as decision aids to support human interpretation of ionospheric propagation. The physical basis for ionospheric decision aids is introduced by reference to ionospheric morphology and the basic theory of ionospheric propagation, which, along with ray tracing techniques, is then reviewed.

  6. Ultrahigh carbon steels, Damascus steels, and superplasticity

    SciTech Connect

    Sherby, O.D.; Wadsworth, J.

    1997-04-01

    The processing properties of ultrahigh carbon steels (UHCSs) have been studied at Stanford University over the past twenty years. These studies have shown that such steels (1 to 2.1% C) can be made superplastic at elevated temperature and can have remarkable mechanical properties at room temperature. It was the investigation of these UHCSs that eventually brought us to study the myths, magic, and metallurgy of ancient Damascus steels, which in fact, were also ultrahigh carbon steels. These steels were made in India as castings, known as wootz, possibly as far back as the time of Alexander the Great. The best swords are believed to have been forged in Persia from Indian wootz. This paper centers on recent work on superplastic UHCSs and on their relation to Damascus steels. 32 refs., 6 figs.

  7. Tropospheric propagation assessment

    NASA Astrophysics Data System (ADS)

    Anderson, K. D.; Richter, J. H.; Hitney, H. V.

    1984-02-01

    It is well known that microwave propagation in a marine environment frequently exhibits unexpected behavior. The deviation from 4/3 earth propagation calculations is due to the fact that the vertical refractivity distribution of the troposphere rarely follows the standard lapse rate of -39 N/km. Instead, the troposphere is generally composed of horizontally stratified layers of differing refractivity gradients. The most striking propagation anomalies result when a layer gradient is less than -157 N/km, forming a trapping layer. In the marine environment, there are two mechanisms which produce such layers. An elevated trapping layer is created by the advection of a warm, dry air mass over a cold, moist air mass producing either a surface-based or an elevated duct which may affect frequencies as low as 100 MHz. A very persistent surface trapping layer is due to water evaporation at the air-sea interface. This surface, or evaporation duct is generally thin, on the order of 10 m in vertical extent, and is an effective trapping mechanism for frequencies greater than 3 GHz. With the introduction of the Integrated Refraction Effects Prediction System (IREPS) into the US Navy, fleet units now have the capability to evaluate accurately the performance of their EM systems when the refractive environment is known. However, these units may have to plan for operations thousands of miles away under different refractivity conditions. To assist in planning, a worldwide upper air and surface climatology has been developed for use through the IREPS programs. The IREPS concept is reviewed and a description of the tropospheric ducting data base is presented.

  8. PIV uncertainty propagation

    NASA Astrophysics Data System (ADS)

    Sciacchitano, Andrea; Wieneke, Bernhard

    2016-08-01

    This paper discusses the propagation of the instantaneous uncertainty of PIV measurements to statistical and instantaneous quantities of interest derived from the velocity field. The expression of the uncertainty of vorticity, velocity divergence, mean value and Reynolds stresses is derived. It is shown that the uncertainty of vorticity and velocity divergence requires the knowledge of the spatial correlation between the error of the x and y particle image displacement, which depends upon the measurement spatial resolution. The uncertainty of statistical quantities is often dominated by the random uncertainty due to the finite sample size and decreases with the square root of the effective number of independent samples. Monte Carlo simulations are conducted to assess the accuracy of the uncertainty propagation formulae. Furthermore, three experimental assessments are carried out. In the first experiment, a turntable is used to simulate a rigid rotation flow field. The estimated uncertainty of the vorticity is compared with the actual vorticity error root-mean-square, with differences between the two quantities within 5–10% for different interrogation window sizes and overlap factors. A turbulent jet flow is investigated in the second experimental assessment. The reference velocity, which is used to compute the reference value of the instantaneous flow properties of interest, is obtained with an auxiliary PIV system, which features a higher dynamic range than the measurement system. Finally, the uncertainty quantification of statistical quantities is assessed via PIV measurements in a cavity flow. The comparison between estimated uncertainty and actual error demonstrates the accuracy of the proposed uncertainty propagation methodology.

  9. Pulse Propagation in Phaseonium

    NASA Astrophysics Data System (ADS)

    Rahman, Ashiqur; Eberly, J. H.

    1996-05-01

    Phaseonium [1] is a medium where the quantum atomic phase is held fixed for long times compared with various relaxation processes. In inhomogeneously broadened two-level phaseonium, we have found a new area theorem (similar to self-induced transparency [2]) for pulse propagation, where pulses of arbitrary area can be stable instead of 2π area. We will also report results for inhomogeneously broadened three-level phaseonium. Research partially supported by NSF grant PHY94-08733. [1] M.O. Scully, Phys. Rev. Lett. 55, 2802 (1985), also Quant. Opt. 6, 203 (1994). [2] S. L. McCall and E. L. Hahn, Phys. Rev. 183, 457 (1969).

  10. Transport with Feynman propagators

    SciTech Connect

    White, R.H.

    1990-11-06

    Richard Feynman's formulation of quantum electrodynamics suggests a Monte Carlo algorithm for calculating wave propagation. We call this the Sum Over All Paths (SOAP) method. The method is applied to calculate diffraction by double slits of finite width and by a reflection grating. Calculations of reflection by plane and parabolic mirrors of finite aperture and from several figured surfaces are shown. An application to a one-dimensional scattering problem is discussed. A variation of SOAP can be applied to the diffusion equation. 2 refs., 8 figs.

  11. Temporal scaling in information propagation

    NASA Astrophysics Data System (ADS)

    Huang, Junming; Li, Chao; Wang, Wen-Qiang; Shen, Hua-Wei; Li, Guojie; Cheng, Xue-Qi

    2014-06-01

    For the study of information propagation, one fundamental problem is uncovering universal laws governing the dynamics of information propagation. This problem, from the microscopic perspective, is formulated as estimating the propagation probability that a piece of information propagates from one individual to another. Such a propagation probability generally depends on two major classes of factors: the intrinsic attractiveness of information and the interactions between individuals. Despite the fact that the temporal effect of attractiveness is widely studied, temporal laws underlying individual interactions remain unclear, causing inaccurate prediction of information propagation on evolving social networks. In this report, we empirically study the dynamics of information propagation, using the dataset from a population-scale social media website. We discover a temporal scaling in information propagation: the probability a message propagates between two individuals decays with the length of time latency since their latest interaction, obeying a power-law rule. Leveraging the scaling law, we further propose a temporal model to estimate future propagation probabilities between individuals, reducing the error rate of information propagation prediction from 6.7% to 2.6% and improving viral marketing with 9.7% incremental customers.

  12. Temporal scaling in information propagation.

    PubMed

    Huang, Junming; Li, Chao; Wang, Wen-Qiang; Shen, Hua-Wei; Li, Guojie; Cheng, Xue-Qi

    2014-01-01

    For the study of information propagation, one fundamental problem is uncovering universal laws governing the dynamics of information propagation. This problem, from the microscopic perspective, is formulated as estimating the propagation probability that a piece of information propagates from one individual to another. Such a propagation probability generally depends on two major classes of factors: the intrinsic attractiveness of information and the interactions between individuals. Despite the fact that the temporal effect of attractiveness is widely studied, temporal laws underlying individual interactions remain unclear, causing inaccurate prediction of information propagation on evolving social networks. In this report, we empirically study the dynamics of information propagation, using the dataset from a population-scale social media website. We discover a temporal scaling in information propagation: the probability a message propagates between two individuals decays with the length of time latency since their latest interaction, obeying a power-law rule. Leveraging the scaling law, we further propose a temporal model to estimate future propagation probabilities between individuals, reducing the error rate of information propagation prediction from 6.7% to 2.6% and improving viral marketing with 9.7% incremental customers. PMID:24939414

  13. Crack propagation and arrest in pressurized containers

    NASA Technical Reports Server (NTRS)

    Erdogan, F.; Delale, F.; Owczarek, J. A.

    1977-01-01

    The problem of crack propagation and arrest in a finite volume cylindrical container filled with pressurized gas is considered. It is assumed that the cylinder contains a symmetrically located longitudinal part-through crack with a relatively small net ligament. The net ligament suddenly ruptures initiating the process of fracture propagation and depressurization in the cylinder. The problem is formulated by making two major assumptions, namely, that the shell problem is quasi-static and the gas dynamics problem is one-dimensional. The problem is reduced to a proper initial value problem by introducing a dynamic fracture criterion which relates the crack acceleration to the difference between a load factor and the corresponding strength parameter. The main results are demonstrated by considering two examples, an aluminum cylinder which may behave in a quasi-brittle manner, and a steel cylinder which undergoes ductile fracture. The results indicate that generally in gas-filled cylinders fracture arrest is not possible unless the material behaves in a ductile manner and the container is relatively long.

  14. Supporting steel

    SciTech Connect

    Badra, C.

    1995-10-01

    The US Department of Energy (DOE) and the American Iron and Steel Institute (AISI) have just completed a pilot program on the technical and economic viability of direct ironmaking by a process based on bath smelting. In this process, oxygen, prereduced iron ore pellets, coal, and flux are charged into a molten slag bath containing a high percentage of carbon. The carbon removes oxygen from the iron ore and generates carbon monoxide and liquid iron. Oxygen is then injected to burn some of the carbon monoxide gas before it leaves the smelting vessel. The partially combusted gas is sued to preheat and prereduced the ore before it is injected into the bath. There are several competing cokeless ironmaking processes in various stages of development around the world. A brief comparison of these processes provides a useful perspective with which to gauge the progress and objectives of the AISI-DOE research initiative. The principal competing foreign technologies include the Corex process, DIOS, HIsmelt, and Jupiter. The advantages of the direct ironmaking process examined by AISI-DOE were not sufficiently demonstrated to justify commercialization without further research. However, enough knowledge was gained from laboratory and pilot testing to teach researchers how to optimize the direct ironmaking process and to provide the foundation for future research. Researchers now better understand issues such as the dissolution of materials, reduction mechanisms and rates, slag foaming and control, the behavior of sulfur, dust generation, and the entire question of energy efficiency--including post combustion and the role of coal/volatile matter.

  15. White-Etching Matter in Bearing Steel. Part I: Controlled Cracking of 52100 Steel

    NASA Astrophysics Data System (ADS)

    Solano-Alvarez, W.; Bhadeshia, H. K. D. H.

    2014-10-01

    Although most of the research performed in bearing steel metallurgy aims to prevent crack nucleation and propagation, some applications require the exact opposite in order to study the role that disconnected surfaces inside the bulk material play when load is applied, or when fluids entrapped in surface cracks propagate tensile stresses or exacerbate corrosion. Four heat treatments have been designed to create controlled arrays of crack types and distributions in quenched and untempered steel normally used in the manufacture of bearings. The varieties of cracks studied include sparsely distributed martensite-plate cracks, fine-grain-boundary cracks, abundant martensite-plate cracks, and surface cracks. The intention was to create samples which can then be subjected to appropriate mechanical testing so that phenomena such as the appearance of "white-etching areas" or "white-etching cracks," crack-lubricant interactions, or hydrogen trapping can be studied further.

  16. Fatigue crack retardation of low carbon steel in saltwater

    SciTech Connect

    Kokaji, K.; Ando, Z.; Kojima, T.

    1984-01-01

    The crack propagation behavior following the application of a single tensile overload in 3 percent saltwater was examined using a low carbon steel, which has a considerably lower static strength than high strength steel used in previous report. Experiments were carried out under sinusoidally varying loads at a load ratio of O and a frequency of 10 Hz, and the effects of saltwater were evaluated by comparing with the result in air and result on high strength steel. A single tensile overload was found to cause delayed retardation, just as it did in air. The overload affected zone size was not affected by saltwater and showed the same value in both environments. This observed trend differed from the result on high strength steel in which the overload affected zone size was larger in 3 percent saltwater than in air, and thus it was found that the effect of saltwater on retardation behavior was different even in the similar steels. Retardation cycles were smaller in 3 percent saltwater than in air. Since the overload affected zone size was not affected by saltwater, the decrease in retardation cycles was attributed to the higher rates of fatigue crack propagation in 3 percent saltwater. Thinner specimen showed stronger retardation than thicker one. The behavior at midthickness of thicker specimen showed delayed retardation as well as the result in air. Moreover, the crack propagation behavior following the application of a single tensile overload in 3 percent saltwater was well explained by the crack closure concept.

  17. Balance fatigue design of cast steel nodes in tubular steel structures.

    PubMed

    Wang, Libin; Jin, Hui; Dong, Haiwei; Li, Jing

    2013-01-01

    Cast steel nodes are being increasingly popular in steel structure joint application as their advanced mechanical performances and flexible forms. This kind of joints improves the structural antifatigue capability observably and is expected to be widely used in the structures with fatigue loadings. Cast steel node joint consists of two parts: casting itself and the welds between the node and the steel member. The fatigue resistances of these two parts are very different; the experiment results showed very clearly that the fatigue behavior was governed by the welds in all tested configurations. This paper focuses on the balance fatigue design of these two parts in a cast steel node joint using fracture mechanics and FEM. The defects in castings are simulated by cracks conservatively. The final crack size is decided by the minimum of 90% of the wall thickness and the value deduced by fracture toughness. The allowable initial crack size could be obtained through the integral of Paris equation when the crack propagation life is considered equal to the weld fatigue life; therefore, the two parts in a cast steel node joint will have a balance fatigue life. PMID:24163621

  18. Balance Fatigue Design of Cast Steel Nodes in Tubular Steel Structures

    PubMed Central

    Wang, Libin; Jin, Hui; Li, Jing

    2013-01-01

    Cast steel nodes are being increasingly popular in steel structure joint application as their advanced mechanical performances and flexible forms. This kind of joints improves the structural antifatigue capability observably and is expected to be widely used in the structures with fatigue loadings. Cast steel node joint consists of two parts: casting itself and the welds between the node and the steel member. The fatigue resistances of these two parts are very different; the experiment results showed very clearly that the fatigue behavior was governed by the welds in all tested configurations. This paper focuses on the balance fatigue design of these two parts in a cast steel node joint using fracture mechanics and FEM. The defects in castings are simulated by cracks conservatively. The final crack size is decided by the minimum of 90% of the wall thickness and the value deduced by fracture toughness. The allowable initial crack size could be obtained through the integral of Paris equation when the crack propagation life is considered equal to the weld fatigue life; therefore, the two parts in a cast steel node joint will have a balance fatigue life. PMID:24163621

  19. Shaping propagation invariant laser beams

    NASA Astrophysics Data System (ADS)

    Soskind, Michael; Soskind, Rose; Soskind, Yakov

    2015-11-01

    Propagation-invariant structured laser beams possess several unique properties and play an important role in various photonics applications. The majority of propagation invariant beams are produced in the form of laser modes emanating from stable laser cavities. Therefore, their spatial structure is limited by the intracavity mode formation. We show that several types of anamorphic optical systems (AOSs) can be effectively employed to shape laser beams into a variety of propagation invariant structured fields with different shapes and phase distributions. We present a propagation matrix approach for designing AOSs and defining mode-matching conditions required for preserving propagation invariance of the output shaped fields. The propagation matrix approach was selected, as it provides a more straightforward approach in designing AOSs for shaping propagation-invariant laser beams than the alternative technique based on the Gouy phase evolution, especially in the case of multielement AOSs. Several practical configurations of optical systems that are suitable for shaping input laser beams into a diverse variety of structured propagation invariant laser beams are also presented. The laser beam shaping approach was applied by modeling propagation characteristics of several input laser beam types, including Hermite-Gaussian, Laguerre-Gaussian, and Ince-Gaussian structured field distributions. The influence of the Ince-Gaussian beam semifocal separation parameter and the azimuthal orientation between the input laser beams and the AOSs onto the resulting shape of the propagation invariant laser beams is presented as well.

  20. An analysis of rumor propagation based on propagation force

    NASA Astrophysics Data System (ADS)

    Zhao, Zhen-jun; Liu, Yong-mei; Wang, Ke-xi

    2016-02-01

    A propagation force is introduced into the analysis of rumor propagation to address uncertainty in the process. The propagation force is portrayed as a fuzzy variable, and a category of new parameters with fuzzy variables is defined. The classic susceptible, infected, recovered (SIR) model is modified using these parameters, a fuzzy reproductive number is introduced into the modified model, and the rationality of the fuzzy reproductive number is illuminated through calculation and comparison. Rumor control strategies are also discussed.

  1. Comminuting irradiated ferritic steel

    DOEpatents

    Bauer, Roger E.; Straalsund, Jerry L.; Chin, Bryan A.

    1985-01-01

    Disclosed is a method of comminuting irradiated ferritic steel by placing the steel in a solution of a compound selected from the group consisting of sulfamic acid, bisulfate, and mixtures thereof. The ferritic steel is used as cladding on nuclear fuel rods or other irradiated components.

  2. Welding Rustproof Steels

    NASA Technical Reports Server (NTRS)

    Hoffmann, W

    1929-01-01

    The following experimental results will perhaps increase the knowledge of the process of welding rustproof steels. The experiments were made with two chrome-steel sheets and with two chrome-steel-nickel sheets having the composition shown in Table I.

  3. Fundamental Study on Inspection of Steel Pipe Covered with Insulator in Oil Complex

    NASA Astrophysics Data System (ADS)

    Kawamura, Youhei; Noro, Kosuke; Ko, Takanari; Mizutani, Koichi; Aoshima, Nobuharu

    2006-05-01

    In a steel pipe composed of a three layer structure, an insulator material is rolled around the initial pipe and another pipe is rolled around the whole pipe used in an oil complex. The insulator material becomes an obstacle for inspecting initial pipe. Thus, in this study, a new inspection method is proposed. An ultrasonic waveform is inputted into the transport pipe that is used for transferring fluid such as oil using a transducer. Its propagation path was inspected and it was found that the wave behaves as a cylindrical wave known as the Lamb wave. Two fundamental experiments for a steel plate and a steel pipe were carried out for its verification. Cross-correlation analysis was used to obtain propagation time, then propagation velocity was calculated. Whether both can be regarded as an equivalent of the theory was confirmed by experiments for propagation velocity in each frequency when there was no welding on the pipe structure.

  4. ACTS propagation experiment discussion: Ka-band propagation measurements using the ACTS propagation terminal and the CSU-CHILL and Space Communications Technology Center Florida propagation program

    NASA Technical Reports Server (NTRS)

    Bringi, V. N.; Chandrasekar, V.; Mueller, Eugene A.; Turk, Joseph; Beaver, John; Helmken, Henry F.; Henning, Rudy

    1993-01-01

    Papers on Ka-band propagation measurements using the ACTS propagation terminal and the Colorado State University CHILL multiparameter radar and on Space Communications Technology Center Florida Propagation Program are discussed. Topics covered include: microwave radiative transfer and propagation models; NASA propagation terminal status; ACTS channel characteristics; FAU receive only terminal; FAU terminal status; and propagation testbed.

  5. ACTS mobile propagation campaign

    NASA Technical Reports Server (NTRS)

    Goldhirsh, Julius; Vogel, Wolfhard J.; Torrence, Geoffrey W.

    1994-01-01

    Preliminary results are presented for three propagation measurement campaigns involving a mobile receiving laboratory and 20 GHz transmissions from the Advanced Communications Technology Satellite (ACTS). Four 1994 campaigns were executed during weekly periods in and around Austin, Texas in February and May, in Central Maryland during March, and in Fairbanks, Alaska and environs in June. Measurements tested the following effects at 20 GHz: (1) attenuation due to roadside trees with and without foliage, (2) multipath effects for scenarios in which line-of-sight paths were unshadowed, (3) fades due to terrain and roadside obstacles, (4) fades due to structures in urban environs, (5) single tree attenuation, and (6) effects of fading at low elevation angles (8 deg in Fairbanks, Alaska) and high elevation angles (55 deg in Austin, Texas). Results presented here cover sampled measurements in Austin, Texas for foliage and non-foliage cases and in Central Maryland for non-foliage runs.

  6. Research in LMSS propagation

    NASA Technical Reports Server (NTRS)

    Barts, R. M.; Stutzman, W. L.; Pratt, T.

    1989-01-01

    The Virginia Tech Satellite Communications Group has participated in the Land Mobile Satellite System (LMSS) program through JPL sponsorship since 1985. Involvement has mainly been in modeling and simulation of propagation characteristics and effects. Models developed to predict cummulative fade distributions for fading LMSS signals include LMSSMOD and the Simple Models which approximate LMSSMOD. Models to predict the mean and standard deviation of signal attenuation through roadside vegetation, namely the Average Path Model, were developed. In the area of simulation, efforts have centered around the development of a software simulator that uses data bases derived from experimental data to generate simulated data with arbitrary statistical behavior. This work has progressed to the development of an integrated analysis and simulation package, LIPS. The basic theory and results for the models and simulator have been previously documented in reports and papers. All LMSS activities are summarized and details of this year's efforts are given.

  7. The ACTS propagation program

    NASA Technical Reports Server (NTRS)

    Chakraborty, Dayamoy; Davarian, Faramaz

    1991-01-01

    The purpose of the Advanced Communications Technology Satellite (ACTS) is to demonstrate the feasibility of the Ka-band (20 and 30 GHz) spectrum for satellite communications, as well as to help maintain U.S. leadership in satellite communications. ACTS incorporates such innovative schemes as time division multiple access (TDMA), microwave and baseband switching, onboard regeneration, and adaptive application of coding during rain-fade conditions. The success or failure of the ACTS experiment will depend on how accurately the rain-fade statistics and fade dynamics can be predicted in order to derive an appropriate algorithm that will combat weather vagaries, specifically for links with small terminals, such as very small aperture terminals (VSAT's) where the power margin is a premium. This article describes the planning process and hardware development program that will comply with the recommendations of the ACTS propagation study groups.

  8. Influence of fretting on flexural fatigue of 304 stainless steel and mild steel

    NASA Technical Reports Server (NTRS)

    Bill, R. C.; Rohn, D. A.

    1978-01-01

    Fretting fatigue experiments conducted on 304 stainless steel using a flexural fatigue test arrangement with bolted on fretting pads demonstrated that fatigue life is reduced by at least a factor of 10 in the 265 to 334 MPa (38,500 - to 48,500 psi) nominal flexural fatigue stress range. In addition, experiments in which the fretting pads were removed after selected numbers of cycles, followed by continued flexural fatigue without fretting show that continued fretting beyond 50,000 cycles does not significantly further reduce fatigue life of 304 stainless steel at 317 MPa (46,000 psi). Microscopic examination of the fretted contact areas revealed fracture initiation sites as well as numerous cracks that did not propagate to failure. Flexural fretting fatigue experiments performed on mild steel showed an insensitivity of fatigue life to the incidence of fretting under flexural stress conditions of from 162 to 217 MPa (23,500 to 31,500 psi).

  9. Numerical propagator through PIAA optics

    NASA Astrophysics Data System (ADS)

    Pueyo, Laurent; Shaklan, Stuart; Give'On, Amir; Krist, John

    2009-08-01

    In this communication we address two outstanding issues pertaining the modeling of PIAA coronagraphs, accurate numerical propagation of edge effects and fast propagation of mid spatial frequencies for wavefront control. In order to solve them, we first derive a quadratic approximation of the Huygens wavelets that allows us to develop an angular spectrum propagator for pupil remapping. Using this result we introduce an independent method to verify the ultimate contrast floor, due to edge propagation effects, of PIAA units currently being tested in various testbeds. We then delve into the details of a novel fast algorithm, based on the recognition that angular spectrum computations with a pre-apodised system are computationally light. When used for the propagation of mid spatial frequencies, such a fast propagator will ultimately allow us to develop robust wavefront control algorithms with DMs located before the pupil remapping mirrors.

  10. Interferometric Propagation Delay

    NASA Technical Reports Server (NTRS)

    Goldstein, Richard

    1999-01-01

    Radar interferometry based on (near) exact repeat passes has lately been used by many groups of scientists, worldwide, to achieve state of the art measurements of topography, glacier and ice stream motion, earthquake displacements, oil field subsidence, lava flows, crop-induced surface decorrelation, and other effects. Variations of tropospheric and ionospheric propagation delays limit the accuracy of all such measurements. We are investigating the extent of this limitation, using data from the Shuttle radar flight, SIR-C, which is sensitive to the troposphere, and the Earth Resources Satellites, ERS-1/2, which are sensitive to both the troposphere and the ionosphere. We are presently gathering statistics of the delay variations over selected, diverse areas to determine the best accuracy possible for repeat track interferometry. The phases of an interferogram depend on both the topography of the scene and variations in propagation delay. The delay variations can be caused by movement of elements in the scene, by changes in tropospheric water vapor and by changes of the charge concentrations in the ionosphere. We plan to separate these causes by using the data from a third satellite visit (three-pass interferometry). The figure gives the geometry of the three-pass observations. The page of the figure is taken to be perpendicular to the spacecraft orbits. The three observational locations are marked on the figure, giving baselines B-12 and B-13, separated by the angle alpha. These parameters are almost constant over the whole scene. However, each pixel has an individual look angle, theta, which is related to the topography, rho is the slant range. A possible spurious time delay is shown. Additional information is contained in the original.

  11. Propagation Terminal Design and Measurements

    NASA Technical Reports Server (NTRS)

    Nessel, James

    2015-01-01

    The NASA propagation terminal has been designed and developed by the Glenn Research Center and is presently deployed at over 5 NASA and partner ground stations worldwide collecting information on the effects of the atmosphere on Ka-band and millimeter wave communications links. This lecture provides an overview of the fundamentals and requirements of the measurement of atmospheric propagation effects and, specifically, the types of hardware and digital signal processing techniques employed by current state-of-the-art propagation terminal systems.

  12. Propagation into an unstable state

    SciTech Connect

    Dee, G.

    1985-06-01

    We describe propagating front solutions of the equations of motion of pattern-forming systems. We make a number of conjectures concerning the properties of such fronts in connection with pattern selection in these systems. We describe a calculation which can be used to calculate the velocity and state selected by certain types of propagating fronts. We investigate the propagating front solutions of the amplitude equation which provides a valid dynamical description of many pattern-forming systems near onset.

  13. Cascade dynamics of complex propagation

    NASA Astrophysics Data System (ADS)

    Centola, Damon; Eguíluz, Víctor M.; Macy, Michael W.

    2007-01-01

    Random links between otherwise distant nodes can greatly facilitate the propagation of disease or information, provided contagion can be transmitted by a single active node. However, we show that when the propagation requires simultaneous exposure to multiple sources of activation, called complex propagation, the effect of random links can be just the opposite; it can make the propagation more difficult to achieve. We numerically calculate critical points for a threshold model using several classes of complex networks, including an empirical social network. We also provide an estimation of the critical values in terms of vulnerable nodes.

  14. Electrodynamic Approach for Visualization of Sound Propagation in Solids

    NASA Astrophysics Data System (ADS)

    Völz, U.; Mrasek, H.; Matthies, K.; Wü; stenberg, H.; Kreutzbruck, M.

    2009-03-01

    The visualization of sound propagation in solids is vital for transducer adaptation and better understanding of complex test samples and their wave propagation modeling. In this work we present an electrodynamic technique detecting the grazing sound beam with a 10 mm-sized electrodynamic probe. The particle displacement along the sample's surface was then measured as a function of time and position. Adapting the electrodynamic probe and its coil alignment allows for measuring the displacement components in all three dimensions. Thus horizontal and vertical particle displacement with respect to the surface can be detected. A SNR of up to 40 dB could be achieved within ferromagnetic and high conductive chrome steel when using a shear wave generated by an angle beam probe. When dealing with nonconductive materials such as PMMA we obtained a reduced SNR of 12 dB. We report on measurements of the sound field in complex weld joints. One example shows a narrow gap weld joining a nickel alloy with a chrome steel. The weld of the 80 mm-thick test block shows a distinct anisotropic texture. The system enables us to visualize the wave propagation within the weld and indicates the reflection and scattering scenario and the energy losses due to both the anisotropic structure and material defects.

  15. Thermal Fatigue Testing of Plasma Transfer Arc Stellite Coatings on Hot Work Tool Steels under Steel Thixoforming Conditions

    NASA Astrophysics Data System (ADS)

    Birol, Yucel; Kayihan, Agca B.

    2011-11-01

    The thermal fatigue performance of Stellite 12 coating deposited on X32CrMoV33 hot work tool steel via the plasma transfer arc (PTA) process was investigated under steel thixoforming conditions. Stellite 12 coating has made a favorable impact on the thermal fatigue performance of the X32CrMoV33 hot work tool steel. The latter survived steel thixoforming conditions lasting much longer, for a total of 5000 cycles, when coated with a PTA Stellite 12 layer. This marked improvement is attributed to the higher resistance to oxidation and to temper softening of the Stellite 12 alloy. The Cr-rich oxides, which form during thermal cycling, provide adequate protection to high-temperature oxidation. In contrast to hot work tool steel, Stellite 12 alloy enjoys hardening upon thermal exposure under steel thixoforming conditions. This increase in the strength of the coating is produced by the formation of carbides and contributes to the superior thermal fatigue resistance of the Stellite 12 alloy. When the crack finally initiates, it propagates via the fracture of hard interdendritic carbides. The transformation of M7C3 to M23C6, which is more voluminous than M7C3, promotes crack propagation.

  16. The steel scrap age.

    PubMed

    Pauliuk, Stefan; Milford, Rachel L; Müller, Daniel B; Allwood, Julian M

    2013-04-01

    Steel production accounts for 25% of industrial carbon emissions. Long-term forecasts of steel demand and scrap supply are needed to develop strategies for how the steel industry could respond to industrialization and urbanization in the developing world while simultaneously reducing its environmental impact, and in particular, its carbon footprint. We developed a dynamic stock model to estimate future final demand for steel and the available scrap for 10 world regions. Based on evidence from developed countries, we assumed that per capita in-use stocks will saturate eventually. We determined the response of the entire steel cycle to stock saturation, in particular the future split between primary and secondary steel production. During the 21st century, steel demand may peak in the developed world, China, the Middle East, Latin America, and India. As China completes its industrialization, global primary steel production may peak between 2020 and 2030 and decline thereafter. We developed a capacity model to show how extensive trade of finished steel could prolong the lifetime of the Chinese steelmaking assets. Secondary steel production will more than double by 2050, and it may surpass primary production between 2050 and 2060: the late 21st century can become the steel scrap age. PMID:23442209

  17. Methods of forming steel

    DOEpatents

    Branagan, Daniel J.; Burch, Joseph V.

    2001-01-01

    In one aspect, the invention encompasses a method of forming a steel. A metallic glass is formed and at least a portion of the glass is converted to a crystalline steel material having a nanocrystalline scale grain size. In another aspect, the invention encompasses another method of forming a steel. A molten alloy is formed and cooled the alloy at a rate which forms a metallic glass. The metallic glass is devitrified to convert the glass to a crystalline steel material having a nanocrystalline scale grain size. In yet another aspect, the invention encompasses another method of forming a steel. A first metallic glass steel substrate is provided, and a molten alloy is formed over the first metallic glass steel substrate to heat and devitrify at least some of the underlying metallic glass of the substrate.

  18. Measurement and modeling of dispersive pulse propagation in draw wire waveguides

    NASA Technical Reports Server (NTRS)

    Madaras, Eric I.; Kohl, Thomas W.; Rogers, Wayne P.

    1995-01-01

    An analytical model of dispersive pulse propagation in semi-infinite cylinders due to transient axially symmetric end conditions has been experimentally investigated. Specifically, the dispersive propagation of the first axially symmetric longitudinal mode in thin wire waveguides, which have ends in butt contact with longitudinal piezoelectric ultrasonic transducers, is examined. The method allows for prediction of a propagated waveform given a measured source waveform, together with the material properties of the cylinder. Alternatively, the source waveform can be extracted from measurement of the propagated waveform. The material properties required for implementation of the pulse propagation model are determined using guided wave phase velocity measurements. Hard tempered aluminum 1100 and 304 stainless steel wires, with 127, 305, and 406 micron diam., were examined. In general, the drawn wires were found to behave as transversely isotropic media.

  19. Measurement and Modeling of Dispersive Pulse Propagation in Drawn Wire Waveguides

    NASA Technical Reports Server (NTRS)

    Madaras, Eric I.; Kohl, Thomas W.; Rogers, Wayne P.

    1995-01-01

    An analytical model of dispersive pulse propagation in semi-infinite cylinders due to transient axially symmetric end conditions has been experimentally investigated. Specifically, the dispersive propagation of the first axially symmetric longitudinal mode in thin wire waveguides, which have ends in butt contact with longitudinal piezoelectric ultrasonic transducers, is examined. The method allows for prediction of a propagated waveform given a measured source waveform, together with the material properties of the cylinder. Alternatively, the source waveform can be extracted from measurement of the propagated waveform. The material properties required for implementation of the pulse propagation model are determined using guided wave phase velocity measurements. Hard tempered aluminum 1100 and 304 stainless steel wires, with 127, 305, and 406 micron diam., were examined. In general, the drawn wires were found to behave as transversely isotropic media.

  20. Seismic wave propagation modeling

    SciTech Connect

    Jones, E.M.; Olsen, K.B.

    1998-12-31

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). A hybrid, finite-difference technique was developed for modeling nonlinear soil amplification from three-dimensional, finite-fault radiation patters for earthquakes in arbitrary earth models. The method was applied to the 17 January 1994 Northridge earthquake. Particle velocities were computed on a plane at 5-km depth, immediately above the causative fault. Time-series of the strike-perpendicular, lateral velocities then were propagated vertically in a soil column typical of the San Fernando Valley. Suitable material models were adapted from a suite used to model ground motions at the US Nevada Test Site. The effects of nonlinearity reduced relative spectral amplitudes by about 40% at frequencies above 1.5 Hz but only by 10% at lower frequencies. Runs made with source-depth amplitudes increased by a factor of two showed relative amplitudes above 1.5 Hz reduced by a total of 70% above 1.5 Hz and 20% at lower frequencies. Runs made with elastic-plastic material models showed similar behavior to runs made with Masing-Rule models.

  1. Directed HK propagator

    NASA Astrophysics Data System (ADS)

    Kocia, Lucas; Heller, Eric J.

    2015-09-01

    We offer a more formal justification for the successes of our recently communicated "directed Heller-Herman-Kluk-Kay" (DHK) time propagator by examining its performance in one-dimensional bound systems which exhibit at least quasi-periodic motion. DHK is distinguished by its single one-dimensional integral—a vast simplification over the usual 2N-dimensional integral in full Heller-Herman-Kluk-Kay (for an N-dimensional system). We find that DHK accurately captures particular coherent state autocorrelations when its single integral is chosen to lie along these states' fastest growing manifold, as long as it is not perpendicular to their action gradient. Moreover, the larger the action gradient, the better DHK will perform. We numerically examine DHK's accuracy in a one-dimensional quartic oscillator and illustrate that these conditions are frequently satisfied such that the method performs well. This lends some explanation for why DHK frequently seems to work so well and suggests that it may be applicable to systems exhibiting quite strong anharmonicity.

  2. Modeling turbulent flame propagation

    SciTech Connect

    Ashurst, W.T.

    1994-08-01

    Laser diagnostics and flow simulation techniques axe now providing information that if available fifty years ago, would have allowed Damkoehler to show how turbulence generates flame area. In the absence of this information, many turbulent flame speed models have been created, most based on Kolmogorov concepts which ignore the turbulence vortical structure, Over the last twenty years, the vorticity structure in mixing layers and jets has been shown to determine the entrainment and mixing behavior and these effects need to be duplicated by combustion models. Turbulence simulations reveal the intense vorticity structure as filaments and simulations of passive flamelet propagation show how this vorticity Creates flame area and defines the shape of the expected chemical reaction surface. Understanding how volume expansion interacts with flow structure should improve experimental methods for determining turbulent flame speed. Since the last decade has given us such powerful new tools to create and see turbulent combustion microscopic behavior, it seems that a solution of turbulent combustion within the next decade would not be surprising in the hindsight of 2004.

  3. Join-Graph Propagation Algorithms

    PubMed Central

    Mateescu, Robert; Kask, Kalev; Gogate, Vibhav; Dechter, Rina

    2010-01-01

    The paper investigates parameterized approximate message-passing schemes that are based on bounded inference and are inspired by Pearl's belief propagation algorithm (BP). We start with the bounded inference mini-clustering algorithm and then move to the iterative scheme called Iterative Join-Graph Propagation (IJGP), that combines both iteration and bounded inference. Algorithm IJGP belongs to the class of Generalized Belief Propagation algorithms, a framework that allowed connections with approximate algorithms from statistical physics and is shown empirically to surpass the performance of mini-clustering and belief propagation, as well as a number of other state-of-the-art algorithms on several classes of networks. We also provide insight into the accuracy of iterative BP and IJGP by relating these algorithms to well known classes of constraint propagation schemes. PMID:20740057

  4. 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.

  5. Crosshole EM in steel-cased boreholes

    SciTech Connect

    Wilt, M.; Lee, K.H.; Becker, A.; Spies, B.; Wang, B.

    1996-07-01

    The application of crosshole EM methods through steel well-casing was investigated in theoretical, laboratory and field studies. A numerical code was developed that calculates the attenuation and phase delay of an EM dipole signal propagated through a steel well casing lodged in a homogeneous medium. The code was validated with a scale model and used for sensitivity studies of casing and formation properties. Finally, field measurements were made in an oil field undergoing waterflooding. Our most important findings are that (1) crosshole surveys are feasible using a well pair with one metallic and one non-metallic casing. (2) The casing effect seems be localized within the pipe section that includes the sensor. (3) The effects of the casing can be corrected using simple means and (4) crosshole field data that are sensitive to both formation and casing were acquired in a working environment.

  6. Dike Propagation Near Drifts

    SciTech Connect

    NA

    2002-03-04

    The purpose of this Analysis and Model Report (AMR) supporting the Site Recommendation/License Application (SR/LA) for the Yucca Mountain Project is the development of elementary analyses of the interactions of a hypothetical dike with a repository drift (i.e., tunnel) and with the drift contents at the potential Yucca Mountain repository. This effort is intended to support the analysis of disruptive events for Total System Performance Assessment (TSPA). This AMR supports the Process Model Report (PMR) on disruptive events (CRWMS M&O 2000a). This purpose is documented in the development plan (DP) ''Coordinate Modeling of Dike Propagation Near Drifts Consequences for TSPA-SR/LA'' (CRWMS M&O 2000b). Evaluation of that Development Plan and the work to be conducted to prepare Interim Change Notice (ICN) 1 of this report, which now includes the design option of ''Open'' drifts, indicated that no revision to that DP was needed. These analyses are intended to provide reasonable bounds for a number of expected effects: (1) Temperature changes to the waste package from exposure to magma; (2) The gas flow available to degrade waste containers during the intrusion; (3) Movement of the waste package as it is displaced by the gas, pyroclasts and magma from the intruding dike (the number of packages damaged); (4) Movement of the backfill (Backfill is treated here as a design option); (5) The nature of the mechanics of the dike/drift interaction. These analyses serve two objectives: to provide preliminary analyses needed to support evaluation of the consequences of an intrusive event and to provide a basis for addressing some of the concerns of the Nuclear Regulatory Commission (NRC) expressed in the Igneous Activity Issue Resolution Status Report.

  7. Tool steels. 5. edition

    SciTech Connect

    Roberts, G.; Krauss, G.; Kennedy, R.

    1998-12-31

    The revision of this authoritative work contains a significant amount of new information from the past nearly two decades presented in an entirely new outline, making this a must have reference for engineers involved in tool-steel production, as well as in the selection and use of tool steels in metalworking and other materials manufacturing industries. The chapter on tool-steel manufacturing includes new production processes, such as electroslag refining, vacuum arc remelting, spray deposition processes (Osprey and centrifugal spray), and powder metal processing. The seven chapters covering tool-steel types in the 4th Edition have been expanded to 11 chapters covering nine main groups of tool steels as well as other types of ultrahigh strength steels sometimes used for tooling. Each chapter discusses in detail processing, composition, and applications specific to the particular group. In addition, two chapters have been added covering surface modification and trouble shooting production and performance problems.

  8. Gaseous hydrogen embrittlement of high strength steels

    NASA Technical Reports Server (NTRS)

    Gangloff, R. P.; Wei, R. P.

    1977-01-01

    The effects of temperature, hydrogen pressure, stress intensity, and yield strength on the kinetics of gaseous hydrogen assisted crack propagation in 18Ni maraging steels were investigated experimentally. It was found that crack growth rate as a function of stress intensity was characterized by an apparent threshold for crack growth, a stage where the growth rate increased sharply, and a stage where the growth rate was unchanged over a significant range of stress intensity. Cracking proceeded on load application with little or no detectable incubation period. Gaseous hydrogen embrittlement susceptibility increased with increasing yield strength.

  9. Laser Propagation in Uranium Hexafluoride

    NASA Astrophysics Data System (ADS)

    Chu, Danny

    1990-01-01

    Several researchers have simulated the laser pulse propagation through simple N-level systems; but, for UF _6 models, large CPU time and memory is required. In an attempt to efficiently yet accurately characterize laser pulse propagation through a UF _6 molecule, a model of UF_6 is created and analyzed by adiabatic excitation. A minimax numerical method is developed to solve the time -dependent Schrodinger equation and then applied to the study of laser excitation of UF_6 using various Gaussian pulses. The process of laser isotope separation is also discussed. The results from the laser excitation of UF_6 are used to simulate laser propagation through ^{235} UF_6.

  10. A database for propagation models

    NASA Technical Reports Server (NTRS)

    Kantak, Anil V.; Suwitra, Krisjani S.

    1992-01-01

    In June 1991, a paper at the fifteenth NASA Propagation Experimenters Meeting (NAPEX 15) was presented outlining the development of a database for propagation models. The database is designed to allow the scientists and experimenters in the propagation field to process their data through any known and accepted propagation model. The architecture of the database also incorporates the possibility of changing the standard models in the database to fit the scientist's or the experimenter's needs. The database not only provides powerful software to process the data generated by the experiments, but is also a time- and energy-saving tool for plotting results, generating tables, and producing impressive and crisp hard copy for presentation and filing.

  11. Reconstruction of nonlinear wave propagation

    DOEpatents

    Fleischer, Jason W; Barsi, Christopher; Wan, Wenjie

    2013-04-23

    Disclosed are systems and methods for characterizing a nonlinear propagation environment by numerically propagating a measured output waveform resulting from a known input waveform. The numerical propagation reconstructs the input waveform, and in the process, the nonlinear environment is characterized. In certain embodiments, knowledge of the characterized nonlinear environment facilitates determination of an unknown input based on a measured output. Similarly, knowledge of the characterized nonlinear environment also facilitates formation of a desired output based on a configurable input. In both situations, the input thus characterized and the output thus obtained include features that would normally be lost in linear propagations. Such features can include evanescent waves and peripheral waves, such that an image thus obtained are inherently wide-angle, farfield form of microscopy.

  12. The NASA radiowave propagation program

    NASA Technical Reports Server (NTRS)

    Davarian, Faramaz

    1990-01-01

    The objectives of the NASA radiowave Propagation Program are to enable new satellite communication applications and to enhance existing satellite communication networks. These objectives are achieved by supporting radio wave propagation studies and disseminating the study results in a timely fashion. Studies initiated by this program in the 1980s enabled the infant concept of conducting mobile communications via satellite to reach a state of relative maturity in 1990. The program also supported the satellite communications community by publishing and revising two handbooks dealing with radio wave propagation effects for frequencies below and above 10 GHz, respectively. The program has served the international community through its support of the International Telecommunications Union. It supports state of the art work at universities. Currently, the program is focusing on the Advanced Communications Technology Satellite (ACTS) and its propagation needs. An overview of the program's involvement in the ACTS project is given.

  13. Wear formulation for aircraft brake material sliding against steel

    NASA Technical Reports Server (NTRS)

    Ho, T. L.; Peterson, M. B.

    1977-01-01

    Predictions of wear on contemporary copper-based brake material sliding against 17-22 AS grade steel, wear testing equipment, formulation of wear, and test results are discussed. An initial investigation of worn surfaces of the brake material and a mating steel rotor was carried out. A wear model proposed suggests initiation of cracks at a hard particle inclusion site in the surface layer of the brake material; crack propagation allows particles to be removed by intersection of cracks. Mutual relations between sliding variables, load, time, hardness, and surface temperature are studied. Empirical formulas are exhibited.

  14. Nonlinear competition in nematicon propagation.

    PubMed

    Laudyn, Urszula A; Kwasny, Michał; Piccardi, Armando; Karpierz, Mirosław A; Dabrowski, Roman; Chojnowska, Olga; Alberucci, Alessandro; Assanto, Gaetano

    2015-11-15

    We investigate the role of competing nonlinear responses in the formation and propagation of bright spatial solitons. We use nematic liquid crystals (NLCs) exhibiting both thermo-optic and reorientational nonlinearities with continuous-wave beams. In a suitably prepared dye-doped sample and dual beam collinear geometry, thermal heating in the visible affects reorientational self-focusing in the near infrared, altering light propagation and self-trapping. PMID:26565843

  15. Semiclassical propagation of Wigner functions

    SciTech Connect

    Dittrich, T.; Gomez, E. A.; Pachon, L. A.

    2010-06-07

    We present a comprehensive study of semiclassical phase-space propagation in the Wigner representation, emphasizing numerical applications, in particular as an initial-value representation. Two semiclassical approximation schemes are discussed. The propagator of the Wigner function based on van Vleck's approximation replaces the Liouville propagator by a quantum spot with an oscillatory pattern reflecting the interference between pairs of classical trajectories. Employing phase-space path integration instead, caustics in the quantum spot are resolved in terms of Airy functions. We apply both to two benchmark models of nonlinear molecular potentials, the Morse oscillator and the quartic double well, to test them in standard tasks such as computing autocorrelation functions and propagating coherent states. The performance of semiclassical Wigner propagation is very good even in the presence of marked quantum effects, e.g., in coherent tunneling and in propagating Schroedinger cat states, and of classical chaos in four-dimensional phase space. We suggest options for an effective numerical implementation of our method and for integrating it in Monte-Carlo-Metropolis algorithms suitable for high-dimensional systems.

  16. Steel Industry Wastes.

    ERIC Educational Resources Information Center

    Schmidtke, N. W.; Averill, D. W.

    1978-01-01

    Presents a literature review of wastes from steel industry, covering publications of 1976-77. This review covers: (1) coke production; (2) iron and steel production; (3) rolling operations; and (4) surface treatment. A list of 133 references is also presented. (NM)

  17. Modern Steel Framed Schools.

    ERIC Educational Resources Information Center

    American Inst. of Steel Construction, Inc., New York, NY.

    In view of the cost of structural framing for school buildings, ten steel-framed schools are examined to review the economical advantages of steel for school construction. These schools do not resemble each other in size, shape, arrangement or unit cost; some are original in concept and architecture, and others are conservative. Cost and…

  18. The Steel Band.

    ERIC Educational Resources Information Center

    Weil, Bruce

    1996-01-01

    Describes studying the steel drum, an import from Trinidad, as an instrument of intellectual growth. Describes how developing a steel drum band provided Montessori middle school students the opportunity to experience some important feelings necessary to emotional growth during this difficult age: competence, usefulness, independence, and…

  19. Propagation of sound waves in drill strings

    NASA Astrophysics Data System (ADS)

    Drumheller, D. S.; Knudsen, S. D.

    1995-04-01

    Deep wells are commonly drilled while steering the drill bit. The steering process is completely controlled by the drilling-rig operator. A key element of this procedure is the measurement and communication of navigation information from the bottom of the well to the operator. Pressure pulses modulated onto the flow of the drill fluid are now employed in some cases to communicate this information. However, data rates are only a few binary bits per second with this method. This drastically limits the quantity of data available to the operator. As an alternative method, elastic waves generated within the steel drill string can be used as a carrier signal to transmit data. The drill string is commonly assembled from 10-m segments of threaded pipe and forms a periodic structure. The elastic wavelengths of interest are shorter than this periodic length. Consequently, these waves undergo significant dispersion. This paper presents new data for the propagation of elastic waves in a 2-km drill string. The influence of aperiodicity in the drill string, rotation of the drill string, and noise levels are studied in detail. The data verify a method for reducing the attenuation of a carrier signal by a factor of 2.

  20. A propagating mode extraction algorithm for microwave waveguide using variational mode decomposition

    NASA Astrophysics Data System (ADS)

    Yin, Aijun; Ren, Hongji

    2015-09-01

    One microwave propagating mode extraction algorithm is proposed for microwave waveguide using variational mode decomposition (VMD). The reflected signal acquired by the waveguide can be seen as the mixture of the propagating mode and evanescent modes. The propagating mode contains information regarding defects and evanescent modes can be treated as noise. By using VMD, the propagating mode can be extracted. Currently, decomposition models are mostly limited by lacking mathematical theory, backward error correction not being allowed in most methods due to the recursive sifting, or the inability to properly cope with noise. In VMD, the bands have been determined adaptively and the corresponding modes are estimated concurrently. An ensemble of modes are derived, and these modes collectively reproduce the input signal while each is being smoothed after demodulation into the baseband. This proposed model is particularly robust to sampling and noise. The bridge between the physical and mathematical models is demonstrated. A coated steel defect detection experiment is conducted using an X-band open-ended rectangular waveguide to evaluate the efficacy of the VMD method. Two samples are demonstrated. The steel with hole sample has a regular and clear defect, whereas the defect of steel with peening is fuzzy. For both samples, the VMD results can accurately identify the defects.

  1. The physical theory and propagation model of THz atmospheric propagation

    NASA Astrophysics Data System (ADS)

    Wang, R.; Yao, J. Q.; Xu, D. G.; Wang, J. L.; Wang, P.

    2011-02-01

    Terahertz (THz) radiation is extensively applied in diverse fields, such as space communication, Earth environment observation, atmosphere science, remote sensing and so on. And the research on propagation features of THz wave in the atmosphere becomes more and more important. This paper firstly illuminates the advantages and outlook of THz in space technology. Then it introduces the theoretical framework of THz atmospheric propagation, including some fundamental physical concepts and processes. The attenuation effect (especially the absorption of water vapor), the scattering of aerosol particles and the effect of turbulent flow mainly influence THz atmosphere propagation. Fundamental physical laws are illuminated as well, such as Lamber-beer law, Mie scattering theory and radiative transfer equation. The last part comprises the demonstration and comparison of THz atmosphere propagation models like Moliere(V5), SARTre and AMATERASU. The essential problems are the deep analysis of physical mechanism of this process, the construction of atmospheric propagation model and databases of every kind of material in the atmosphere, and the standardization of measurement procedures.

  2. EAST ELEVATION, LTV STEEL (FORMERLY REPUBLIC STEEL), 8" BAR MILL, ...

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

    EAST ELEVATION, LTV STEEL (FORMERLY REPUBLIC STEEL), 8" BAR MILL, BUFFALO PLANT. VIEW LOOKING SOUTHWEST FROM ROLL SHOP. 8" BAR MILL DESIGNED AND BUILT BY DONNER STEEL CO. (PREDECESSOR OF REPUBLIC), 1919-1920. FOR DESCRIPTION OF ORIGINAL MILL SEE "IRON AGE", 116\\4 (23 JULY 1925): 201-204. - LTV Steel, 8-inch Bar Mill, Buffalo Plant, Buffalo, Erie County, NY

  3. An Intelligent Sensor System for Monitoring Fatigue Damage in Welded Steel Components

    SciTech Connect

    Fernandes, B.; Gaydecki, P.; Burdekin, F. Michael

    2005-04-09

    A system for monitoring fatigue damage in steel components is described. The sensor, a thin steel sheet with a pre-crack in it, is attached to the component. Its crack length increases by fatigue in service and is recorded using a microcontroller. Measurement is accomplished using conductive tracks in a circuit whose output voltage changes when the crack propagates past a track. Data stored in memory can be remotely downloaded using Bluetooth{sup TM} technology to a PC.

  4. The geometry of propagating rifts

    NASA Astrophysics Data System (ADS)

    McKenzie, Dan

    1986-03-01

    The kinematics of two different processes are investigated, both of which have been described as rift propagation. Courtillot uses this term to describe the change from distributed to localised extension which occurs during the early development of an ocean basin. The term localisation is instead used here to describe this process, to distinguish it from Hey's type of propagation. Localisation generally leads to rotation of the direction of magnetisation. To Hey propagation means the extension of a rift into the undeformed plate beyond a transform fault. Detail surveys of the Galapagos rift have shown that the propagating and failing rifts are not connected by a single transform fault, but by a zone which is undergoing shear. The principal deformation is simple shear, and the kinematics of this deformation are investigated in some detail. The strike of most of the lineations observed in the area can be produced by such deformation. The mode of extension on the propagating rift appears to be localised for some periods but to be distributed for others. Neither simple kinematic arguments nor stretching of the lithosphere with conservation of crust can account for the observed variations in water depth.

  5. User needs for propagation data

    NASA Technical Reports Server (NTRS)

    Sullivan, Thomas M.

    1993-01-01

    New and refined models of radio signal propagation phenomena are needed to support studies of evolving satellite services and systems. Taking an engineering perspective, applications for propagation measurements and models in the context of various types of analyses that are of ongoing interest are reviewed. Problems that were encountered in the signal propagation aspects of these analyses are reviewed, and potential solutions to these problems are discussed. The focus is on propagation measurements and models needed to support design and performance analyses of systems in the Mobile-Satellite Service (MSS) operating in the 1-3 GHz range. These systems may use geostationary or non-geostationary satellites and Frequency Division Multiple Access (FDMA), Time Division Multiple Access Digital (TDMA), or Code Division Multiple Access (CDMA) techniques. Many of the propagation issues raised in relation to MSS are also pertinent to other services such as broadcasting-satellite (sound) at 2310-2360 MHz. In particular, services involving mobile terminals or terminals with low gain antennas are of concern.

  6. Wave propagation in isogrid structures

    NASA Astrophysics Data System (ADS)

    Reynolds, Whitney D.; Doyle, Derek; Arritt, Brandon

    2011-04-01

    This work focuses on an analysis of wave propagation in isogrid structures as it relates to Structural Health Monitoring (SHM) methods. Assembly, integration, and testing (AI&T) of satellite structures in preparation for launch includes significant time for testing and reworking any issues that may arise. SHM methods are being investigated as a means to validate the structure during assembly and truncate the number of tests needed to qualify the structure for the launch environment. The most promising of these SHM methods uses an active wave-based method in which an actuator propagates a Lamb wave through the structure; the Lamb wave is then received by a sensor and evaluated over time to detect structural changes. To date this method has proven effective in locating structural defects in a complex satellite panel; however, the attributes associated with the first wave arrival change significantly as the wave travels through ribs and joining features. Previous studies have been conducted in simplified ribbed structures, giving initial insight into the complex wave propagation phenomena. In this work, the study has been extended numerically to the isogrid plate case. Wave propagation was modeled using commercial finite element analysis software. The results of the analyses offer further insight into the complexities of wave propagation in isogrid structures.

  7. Nuclear transmutation in steels

    NASA Astrophysics Data System (ADS)

    Belozerova, A. R.; Shimanskii, G. A.; Belozerov, S. V.

    2009-05-01

    The investigations of the effects of nuclear transmutation in steels that are widely used in nuclear power and research reactors and in steels that are planned for the application in thermonuclear fusion plants, which are employed under the conditions of a prolonged action of neutron irradiation with different spectra, made it possible to study the effects of changes in the isotopic and chemical composition on the tendency of changes in the structural stability of these steels. For the computations of nuclear transmutation in steels, we used a program complex we have previously developed on the basis of algorithms for constructing branched block-type diagrams of nuclide transformations and for locally and globally optimizing these diagrams with the purpose of minimizing systematic errors in the calculation of nuclear transmutation. The dependences obtained were applied onto a Schaeffler diagram for steels used for structural elements of reactors. For the irradiation in fission reactors, we observed only a weak influence of the effects of nuclear transmutation in steels on their structural stability. On the contrary, in the case of irradiation with fusion neutrons, a strong influence of the effects of nuclear transmutation in steels on their structural stability has been noted.

  8. Effect of Steel Fibres Distribution on Impact Resistance Performance of Steel Fibre Reinforced Concrete (SFRC)

    NASA Astrophysics Data System (ADS)

    Che Muda, Zakaria; Liyana Mohd Kamal, Nur; Syamsir, Agusril; Shao Yang, Chen; Beddu, Salmia; Nasharuddin Mustapha, Kamal; Thiruchelvam, Sivadass; Usman, Fathoni; Itam, Zarina; Ashraful Alam, Md; Birima, Ahmed H.; Zaroog, O. S.

    2016-03-01

    This paper investigate the effect of the mesh distribution on the impact performance of steel fibre reinforced concrete (SFRC) for the concrete slab of 300mm × 300mm size reinforced with varied thickness and fraction volume subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.236 kg drop at 0.57 m height has been used in this research work. The objective of this research is to study the effect of the mesh distribution on the impact resistance SFRC for various slab thickness and fraction volume. Random fibre distribution is the more effective than the top and bottom fibre distribution in terms of absorption of impact energy, crack resistance, the ability to control crack formation and propagation against impact energy.

  9. Propagated repolarization in heart muscle.

    PubMed

    CRANEFIELD, P F; HOFFMAN, B F

    1958-03-20

    The effect of current flow on the transmembrane action potential of single fibers of ventricular muscle has been examined. Pulses of repolarizing current applied during the plateau of the action potential displace membrane potential much more than do pulses of depolarizing current. The application of sufficiently strong pulses of repolarizing current initiates sustained repolarization which persists after the end of the pulse. This sustained repolarization appears to propagate throughout the length of the fiber. Demonstration of propagated repolarization is made difficult by appearance of break excitation at the end of the repolarizing pulse. The thresholds for sustained repolarization and break excitation are separated by reducing the concentration of Ca(++) in the environment of the fiber. In fibers in such an environment it is easier to demonstrate apparently propagated repolarization and also, by further increase of the strength of the repolarizing current, to demonstrate graded break excitation. PMID:13514000

  10. Modification of tropospheric propagation conditions

    NASA Astrophysics Data System (ADS)

    Jeske, H.

    1990-10-01

    The propagation mechanisms of ultra-short radio waves and microwaves are governed by the composition of the troposphere and their space-time structure of the refractive index field. Useful effects are obtained by chaff clouds concerning communication channels, masking of targets or meteorological research. A wide field of posiibilities seems to be within the scope of weather modification experiments. But due to the huge variability of cloud and rain parameters only minor propagation changes are to be expected. A successful application of remotely determining atmospheric temperature profiles is the modulation of the atmospheric refractive index field by sound waves and tracking the acoustic wave fronts by a Doppler radar (Radio Acoustic Sounding System). Oil and alga slicks on water surfaces may change the reflection/scattering and emission properties for radar waves. They also suppress evaporation which may influence the development of tropical storms but just so evaporation duct propagation of microwaves.

  11. Non-destructive ultrasonic measurements of case depth. [in steel

    NASA Technical Reports Server (NTRS)

    Flambard, C.; Lambert, A.

    1978-01-01

    Two ultrasonic methods for nondestructive measurements of the depth of a case-hardened layer in steel are described. One method involves analysis of ultrasonic waves diffused back from the bulk of the workpiece. The other method involves finding the speed of propagation of ultrasonic waves launched on the surface of the work. Procedures followed in the two methods for measuring case depth are described.

  12. Dynamical Realism and Uncertainty Propagation

    NASA Astrophysics Data System (ADS)

    Park, Inkwan

    In recent years, Space Situational Awareness (SSA) has become increasingly important as the number of tracked Resident Space Objects (RSOs) continues their growth. One of the most significant technical discussions in SSA is how to propagate state uncertainty in a consistent way with the highly nonlinear dynamical environment. In order to keep pace with this situation, various methods have been proposed to propagate uncertainty accurately by capturing the nonlinearity of the dynamical system. We notice that all of the methods commonly focus on a way to describe the dynamical system as precisely as possible based on a mathematical perspective. This study proposes a new perspective based on understanding dynamics of the evolution of uncertainty itself. We expect that profound insights of the dynamical system could present the possibility to develop a new method for accurate uncertainty propagation. These approaches are naturally concluded in goals of the study. At first, we investigate the most dominant factors in the evolution of uncertainty to realize the dynamical system more rigorously. Second, we aim at developing the new method based on the first investigation enabling orbit uncertainty propagation efficiently while maintaining accuracy. We eliminate the short-period variations from the dynamical system, called a simplified dynamical system (SDS), to investigate the most dominant factors. In order to achieve this goal, the Lie transformation method is introduced since this transformation can define the solutions for each variation separately. From the first investigation, we conclude that the secular variations, including the long-period variations, are dominant for the propagation of uncertainty, i.e., short-period variations are negligible. Then, we develop the new method by combining the SDS and the higher-order nonlinear expansion method, called state transition tensors (STTs). The new method retains advantages of the SDS and the STTs and propagates

  13. NASA Propagation Program Status and Propagation Needs of Satcom Industry

    NASA Technical Reports Server (NTRS)

    Golshan, Nassar

    1996-01-01

    The program objective is to enable the development of new commercial satellite systems and services and to support NASA's programs by providing timely data and models about propagation of satellite radio signals though the intervening environment. Provisions include new services, higher frequencies, higher data rates, different environments (mobile, indoors, fixed), and different orbits (geostationary, low earth orbit).

  14. SIS Epidemic Propagation on Hypergraphs.

    PubMed

    Bodó, Ágnes; Katona, Gyula Y; Simon, Péter L

    2016-04-01

    Mathematical modelling of epidemic propagation on networks is extended to hypergraphs in order to account for both the community structure and the nonlinear dependence of the infection pressure on the number of infected neighbours. The exact master equations of the propagation process are derived for an arbitrary hypergraph given by its incidence matrix. Based on these, moment closure approximation and mean-field models are introduced and compared to individual-based stochastic simulations. The simulation algorithm, developed for networks, is extended to hypergraphs. The effects of hypergraph structure and the model parameters are investigated via individual-based simulation results. PMID:27033348

  15. Strength gradient enhances fatigue resistance of steels.

    PubMed

    Ma, Zhiwei; Liu, Jiabin; Wang, Gang; Wang, Hongtao; Wei, Yujie; Gao, Huajian

    2016-01-01

    Steels are heavily used in infrastructure and the transportation industry, and enhancing their fatigue resistance is a major challenge in materials engineering. In this study, by introducing a gradient microstructure into 304 austenitic steel, which is one of the most widely used types of stainless steel, we show that a strength gradient substantially enhances the fatigue life of the material. Pre-notched samples with negative strength gradients in front of the notch's tip endure many more fatigue cycles than do samples with positive strength gradients during the crack initiation stage, and samples with either type of gradient perform better than do gradient-free samples with the same average yield strength. However, as a crack grows, samples with positive strength gradients exhibit better resistance to fatigue crack propagation than do samples with negative gradients or no gradient. This study demonstrates a simple and promising strategy for using gradient structures to enhance the fatigue resistance of materials and complements related studies of strength and ductility. PMID:26907708

  16. Strength gradient enhances fatigue resistance of steels

    PubMed Central

    Ma, Zhiwei; Liu, Jiabin; Wang, Gang; Wang, Hongtao; Wei, Yujie; Gao, Huajian

    2016-01-01

    Steels are heavily used in infrastructure and the transportation industry, and enhancing their fatigue resistance is a major challenge in materials engineering. In this study, by introducing a gradient microstructure into 304 austenitic steel, which is one of the most widely used types of stainless steel, we show that a strength gradient substantially enhances the fatigue life of the material. Pre-notched samples with negative strength gradients in front of the notch’s tip endure many more fatigue cycles than do samples with positive strength gradients during the crack initiation stage, and samples with either type of gradient perform better than do gradient-free samples with the same average yield strength. However, as a crack grows, samples with positive strength gradients exhibit better resistance to fatigue crack propagation than do samples with negative gradients or no gradient. This study demonstrates a simple and promising strategy for using gradient structures to enhance the fatigue resistance of materials and complements related studies of strength and ductility. PMID:26907708

  17. Strength gradient enhances fatigue resistance of steels

    NASA Astrophysics Data System (ADS)

    Ma, Zhiwei; Liu, Jiabin; Wang, Gang; Wang, Hongtao; Wei, Yujie; Gao, Huajian

    2016-02-01

    Steels are heavily used in infrastructure and the transportation industry, and enhancing their fatigue resistance is a major challenge in materials engineering. In this study, by introducing a gradient microstructure into 304 austenitic steel, which is one of the most widely used types of stainless steel, we show that a strength gradient substantially enhances the fatigue life of the material. Pre-notched samples with negative strength gradients in front of the notch’s tip endure many more fatigue cycles than do samples with positive strength gradients during the crack initiation stage, and samples with either type of gradient perform better than do gradient-free samples with the same average yield strength. However, as a crack grows, samples with positive strength gradients exhibit better resistance to fatigue crack propagation than do samples with negative gradients or no gradient. This study demonstrates a simple and promising strategy for using gradient structures to enhance the fatigue resistance of materials and complements related studies of strength and ductility.

  18. Cast Stainless Steel Ferrite and Grain Structure

    SciTech Connect

    Ruud, Clayton O.; Ramuhalli, Pradeep; Meyer, Ryan M.; Mathews, Royce; Diaz, Aaron A.; Anderson, Michael T.

    2012-09-01

    In-service inspection requirements dictate that piping welds in the primary pressure boundary of light-water reactors be subject to a volumetric examination based on the rules contained within the American Society of Mechanical Engineers Boiler and Pressure Vessel Code, Section XI. The purpose of the inspection is the reliable detection and accurate sizing of service-induced degradation and/or material flaws introduced during fabrication. The volumetric inspection is usually carried out using ultrasonic testing (UT) methods. However, the varied metallurgical macrostructures and microstructures of cast austenitic stainless steel piping and fittings, including statically cast stainless steel and centrifugally cast stainless steel (CCSS), introduce significant variations in the propagation and attenuation of ultrasonic energy. These variations complicate interpretation of the UT responses and may compromise the reliability of UT inspection. A review of the literature indicated that a correlation may exist between the microstructure and the delta ferrite content of the casting alloy. This paper discusses the results of a recent study where the goal was to determine if a correlation existed between measured and/or calculated ferrite content and grain structure in CCSS pipe.

  19. Cleavage-quasi cleavage in ferritic and martensitic steels

    SciTech Connect

    Odette, G.R.; Edsinger, K.V.; Lucas, G.E.

    1997-12-31

    Confocal microscopy-fracture reconstruction and SEM were used to characterize the sequence-of-events leading to cleavage in a low alloy pressure vessel steel and two 8--12 Cr martensitic steels as a function of temperature. While differences between the steels were observed, they shared some common characteristics that differ from the conventional view of cleavage. Most notably cleavage does not occur as a single weakest link event; rather it is the consequence of a critical condition when a previously nucleated dispersion of microcracks suddenly coalesce to form a large, rapidly propagating macroscopic crack. It is argued that the critical event can be treated as a bridging instability. The stabilizing effect of the ductile ligaments separating the cleavage facets increases with increasing temperature. Indeed, even in the ductile tearing regime cleavage facets form a significant fraction of nuclei for larger microvoids.

  20. Ultrasonic characterization of centrifugally cast stainless steel: Topical report

    SciTech Connect

    Jeong, P.

    1987-06-01

    Ultrasonic wave propagation in centrifugally cast stainless steel (CCSS) was investigated. The difficulties of inspecting CCSS material stem from elastic anisotropy that hampers defect location and severe attenuation caused by coarse grains within the structure that makes defect detection difficult. During this investigation, grain effects on ultrasonic wave propagation were investigated, techniques for identifying different grain structures were developed, and compensation methods for grain effects were addressed. Each step is explained analytically based on relevant theory and proven experimentally. Experiments were conducted on specially designed test specimens: angled blocks, polygonal blocks, wedge blocks, and calibration blocks. Wave parameters such as phase velocity, skew angle, energy velocity, attenuation, beam width, amplitude variation patterns, and frequency dependence on grain structures were all measured with these specimens. CCSS grain structures investigated were equiaxed-fine grains, columnar-dendritic grains, and coarse grains. For comparison purposes, additional types of material such as static-cast stainless steel, forged stainless steel, and carbon steel materials were also investigated. Longitudinal wave, horizontally and vertically polarized shear wave modes were all considered in experiments. The use of an automated ultrasonic system was also demonstrated for grain structure identification.

  1. Structural Amorphous Steels

    NASA Astrophysics Data System (ADS)

    Lu, Z. P.; Liu, C. T.; Thompson, J. R.; Porter, W. D.

    2004-06-01

    Recent advancement in bulk metallic glasses, whose properties are usually superior to their crystalline counterparts, has stimulated great interest in fabricating bulk amorphous steels. While a great deal of effort has been devoted to this field, the fabrication of structural amorphous steels with large cross sections has remained an alchemist’s dream because of the limited glass-forming ability (GFA) of these materials. Here we report the discovery of structural amorphous steels that can be cast into glasses with large cross-section sizes using conventional drop-casting methods. These new steels showed interesting physical, magnetic, and mechanical properties, along with high thermal stability. The underlying mechanisms for the superior GFA of these materials are discussed.

  2. Glass Stronger than Steel

    DOE R&D Accomplishments Database

    Yarris, Lynn

    2011-03-28

    A new type of damage-tolerant metallic glass, demonstrating a strength and toughness beyond that of steel or any other known material, has been developed and tested by a collaboration of researchers from Berkeley Lab and Caltech.

  3. Cobalt free maraging steel

    SciTech Connect

    Floreen, S.

    1984-04-17

    The subject invention is directed to ferrous-base alloys, particularly to a cobalt-free maraging steel of novel chemistry characterized by a desired combination of strength and toughness, notwithstanding that cobalt is non-essential.

  4. Life after Steel

    ERIC Educational Resources Information Center

    Mangan, Katherine

    2013-01-01

    Bobby Curran grew up in a working-class neighborhood in Baltimore, finished high school, and followed his grandfather's steel-toed bootprints straight to Sparrows Point, a 3,000-acre sprawl of industry on the Chesapeake Bay. College was not part of the plan. A gritty but well-paying job at the RG Steel plant was Mr. Curran's ticket to a secure…

  5. Effects of microstructure on the fatigue crack propagation resistance in composite microstructure by 3D fabric modeling for energy transport

    SciTech Connect

    Ishihara, T.; Kim, J.K.; Kobayashi, Y.

    1995-10-01

    In this study, martensite-ferrite dual phase steel composed of martensite in hard phase and ferrite in soft phase is made 3 dimensions fabric composite for energy transport and the difference in fatigue crack propagation behavior resulting from the structural size is investigated by fracture mechanics and microstructural method. The main results obtained are as follows: (1) the fatigue crack propagation rate is influenced by the ferrite grain size, in other words, in the low {Delta}K region the fatigue crack propagation rate is decreased with decreasing of the grain size but the difference of propagation rate resulted from the structural size is decreased as {Delta}K is increased; (2) the above results are explained by the degree of crack arrest effect of the martensite phase for the fatigue crack propagation depending on the ratio of reversed plastic zone size to the ferrite grain size.

  6. Near earth propagation: physics revealed

    NASA Astrophysics Data System (ADS)

    Wert, R.; Goroch, A.; Worthington, E.; Wong, V.

    2007-04-01

    Both the military and consumer sectors are pursuing distributed networked systems and sensors. A major stumbling block to deployment of these sensors will be the radio frequency (RF) propagation environment within a few wavelengths of the earth. Increasing transmit power (battery consumption) is not a practical solution to the problem. This paper will discuss some of the physical phenomena related to the near earth propagation (NEP) problem. When radiating near the earth the communications link is subjected to a list of physical impairments. On the list are the expected Fresnel region encroachment and multipath reflections. Additionally, radiation pattern changes and near earth boundary layer perturbations exist. A significant amount of data has been collected on NEP. Disturbances in the NEP atmosphere can have a time varying attenuation related to the time of day and these discoveries will be discussed. Solutions, or workarounds, to the near earth propagation problem hinge on dynamic adaptive RF elements. Adaptive RF elements will allow the distributed sensor to direct energy, beam form, impedance correct, increase communication efficiency, and decrease battery consumption. Small electrically controllable elements are under development to enable antenna impedance matching in a dynamic environment. Additionally, small dynamic beam forming arrays are under development to focus RF energy in the direction of need. With an increased understanding of the near earth propagation problem, distributed autonomous networked sensors can become a reality within a few centimeters of the earth.

  7. Microwave Propagation in Dielectric Fluids.

    ERIC Educational Resources Information Center

    Lonc, W. P.

    1980-01-01

    Describes an undergraduate experiment designed to verify quantitatively the effect of a dielectric fluid's dielectric constant on the observed wavelength of microwave radiation propagating through the fluid. The fluid used is castor oil, and results agree with the expected behavior within 5 percent. (Author/CS)

  8. 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.

  9. Balloon atmospheric propagation experiment measurements

    NASA Technical Reports Server (NTRS)

    Minott, P. O.

    1973-01-01

    High altitude balloon measurements on laser beam fading during propagation through turbulent atmosphere show that a correlation between fading strength and stellar scintillation magnitudes exists. Graphs for stellar scintillation as a function of receiver aperture are used to predict fading bit error rates for neodymium-yag laser communication system.

  10. Articles comprising ferritic stainless steels

    DOEpatents

    Rakowski, James M.

    2016-06-28

    An article of manufacture comprises a ferritic stainless steel that includes a near-surface region depleted of silicon relative to a remainder of the ferritic stainless steel. The article has a reduced tendency to form an electrically resistive silica layer including silicon derived from the steel when the article is subjected to high temperature oxidizing conditions. The ferritic stainless steel is selected from the group comprising AISI Type 430 stainless steel, AISI Type 439 stainless steel, AISI Type 441 stainless steel, AISI Type 444 stainless steel, and E-BRITE.RTM. alloy, also known as UNS 44627 stainless steel. In certain embodiments, the article of manufacture is a fuel cell interconnect for a solid oxide fuel cell.

  11. Improving the toughness of ultrahigh strength steel

    NASA Astrophysics Data System (ADS)

    Sato, Koji

    2002-01-01

    The ideal structural steel combines high strength with high fracture toughness. This dissertation discusses the toughening mechanism of the Fe/Co/Ni/Cr/Mo/C steel, AerMet 100, which has the highest toughness/strength combination among all commercial ultrahigh strength steels. The possibility of improving the toughness of this steel was examined by considering several relevant factors. Chapter 1 reviews the mechanical properties of ultrahigh strength steels and the physical metallurgy of AerMet 100. It also describes the fracture mechanisms of steel, i.e. ductile microvoid coalescence, brittle transgranular cleavage, and intergranular separation. Chapter 2 examines the strength-toughness relationship for three heats of AerMet 100. A wide variation of toughness is obtained at the same strength level. The toughness varies despite the fact that all heat fracture in the ductile fracture mode. The difference originates from the inclusion content. Lower inclusion volume fraction and larger inclusion spacing gives rise to a greater void growth factor and subsequently a higher fracture toughness. The fracture toughness value, JIc, is proportional to the particle spacing of the large non-metallic inclusions. Chapter 3 examines the ductile-brittle transition of AerMet 100 and the effect of a higher austenitization temperature, using the Charpy V-notch test. The standard heat treatment condition of AerMet 100 shows a gradual ductile-brittle transition due to its fine effective grain size. Austenitization at higher temperature increases the prior austenite grain size and packet size, leading to a steeper transition at a higher temperature. Both transgranular cleavage and intergranular separation are observed in the brittle fracture mode. Chapter 4 examines the effect of inclusion content, prior austenite grain size, and the amount of austenite on the strength-toughness relationship. The highest toughness is achieved by low inclusion content, small prior austenite grain size

  12. Profiles in garbage: Steel cans

    SciTech Connect

    Miller, C.

    1998-02-01

    Steel mills are the largest market for steel cans. Integrated mills use the basic oxygen process to manufacture tinplate, appliances, car bodies, and steel framing. Electric arc furnaces use 100% scrap to produce steel shapes such as railroad ties and bridge spans. Electric arc furnaces are more geographically diverse and tend to have smaller capacities than basic oxygen furnaces. Detinners remove the tin from steel cans for resale to tin using industries. With less tin use in steel cans, the importance of the detinning market has declined substantially. Foundries use scrap as a raw material in making castings and molds for industrial users.

  13. Toughening by the addition of phosphorus to a high-strength steel with ultrafine elongated grain structure

    NASA Astrophysics Data System (ADS)

    Jafari, Meysam; Kimura, Yuuji; Tsuzaki, Kaneaki

    2013-02-01

    Phosphorus-doped high-strength steels are typically brittle at room temperature. In contrast to the non-hardening embrittlement of body-centred cubic (bcc) steels which decreases toughness without increasing strength, we observed an increase in toughness of about 20% by adding a large amount (0.053 wt%) of phosphorus (P) to a high-strength bcc steel with an ultrafine elongated ferrite grain structure processed by warm calibre rolling at 500 °C which produced a 91% reduction in area. The enhanced toughness is attributed to P segregation, which causes grain boundaries to become feasible crack propagation paths, thereby enhancing delamination toughening. The 0.053% P steel showed a microstructure and tensile properties similar to those of 0.001% P steel (reference steel).

  14. Hydrogen-induced crack nucleation in tensile testing of EUROFER 97 and ODS-EUROFER steels at elevated temperature

    NASA Astrophysics Data System (ADS)

    Malitckii, Evgenii; Yagodzinskyy, Yuriy; Hänninen, Hannu

    2015-11-01

    The effect of continuous hydrogen charging on tensile properties of EUROFER 97 and ODS-EUROFER steels was studied at room and elevated temperatures of 100 °C and 300 °C. The hydrogen effect decreases with increase of the temperature for ODS-EUROFER steel, while susceptibility to hydrogen of EUROFER 97 steel remains approximately the same at all testing temperatures. Continuous hydrogen charging results in a reduction of the grain boundary cohesion of the EUROFER 97 and ODS-EUROFER steels tested at RT. With increase of the testing temperature up to 300 °C EUROFER 97 steel exhibits relatively high amount of micro-cracks which agglomerate in sub-micrometer size cracks, while the hydrogen-induced intergranular crack nucleation in ODS-EUROFER steel is effectively suppressed. Possible mechanism of the hydrogen-induced crack nucleation and propagation under applied external stress is discussed.

  15. View northwest, wharf A, sheet steel bulkhead, steel lift tower ...

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

    View northwest, wharf A, sheet steel bulkhead, steel lift tower - U.S. Coast Guard Sandy Hook Station, Western Docking Structure, West of intersection of Canfield Road & Hartshorne Drive, Highlands, Monmouth County, NJ

  16. Fracture propagation, pipe deformation study

    SciTech Connect

    Aloe, A.; Di Candia, A.; Bramante, M.

    1983-04-15

    Shear fracture propagation has become an important research subject connected with design aspects of gas pipelines. Difficulties involved in predicting safe service conditions from pure theoretical studies require 1:1 scale experiments. Through these tests, semiempirical design criteria was formulated where the minimum level of material quality, indicated by Charpy V energy in the ductile range, is determined as a function of pipe geometry and hoop stress. Disagreements exist among these criteria. Different arrest energy predictions at high hoop stresses and different effects ascribed to the thickness have called for further research in the field. Some interesting indications were obtained about shape and size of the plastic zone ahead of the propagating crack. Burst tests have been conducted and are discussed.

  17. Atmospheric propagation of THz radiation.

    SciTech Connect

    Wanke, Michael Clement; Mangan, Michael A.; Foltynowicz, Robert J.

    2005-11-01

    In this investigation, we conduct a literature study of the best experimental and theoretical data available for thin and thick atmospheres on THz radiation propagation from 0.1 to 10 THz. We determined that for thick atmospheres no data exists beyond 450 GHz. For thin atmospheres data exists from 0.35 to 1.2 THz. We were successful in using FASE code with the HITRAN database to simulate the THz transmission spectrum for Mauna Kea from 0.1 to 2 THz. Lastly, we successfully measured the THz transmission spectra of laboratory atmospheres at relative humidities of 18 and 27%. In general, we found that an increase in the water content of the atmosphere led to a decrease in the THz transmission. We identified two potential windows in an Albuquerque atmosphere for THz propagation which were the regions from 1.2 to 1.4 THz and 1.4 to 1.6 THz.

  18. Improved beam propagation method equations.

    PubMed

    Nichelatti, E; Pozzi, G

    1998-01-01

    Improved beam propagation method (BPM) equations are derived for the general case of arbitrary refractive-index spatial distributions. It is shown that in the paraxial approximation the discrete equations admit an analytical solution for the propagation of a paraxial spherical wave, which converges to the analytical solution of the paraxial Helmholtz equation. The generalized Kirchhoff-Fresnel diffraction integral between the object and the image planes can be derived, with its coefficients expressed in terms of the standard ABCD matrix. This result allows the substitution, in the case of an unaberrated system, of the many numerical steps with a single analytical step. We compared the predictions of the standard and improved BPM equations by considering the cases of a Maxwell fish-eye and of a Luneburg lens. PMID:18268554

  19. Sound propagation in choked ducts

    NASA Technical Reports Server (NTRS)

    Hersh, A. S.; Liu, C. Y.

    1976-01-01

    The linearized equations describing the propagation of sound in variable area ducts containing flow are shown to be singular when the duct mean flow is sonic. The singularity is removed when previously ignored nonlinear terms are retained. The results of a numerical study, for the case of plane waves propagating in a one-dimensional converging-diverging duct, show that the sound field is adequately described by the linearized equations only when the axial mean flow Mach number at the duct throat M sub th 0.6. For M sub th 0.6, the numerical results showed that acoustic energy flux was not conserved. An attempt was made to extend the study to include the nonlinear behavior of the sound field. Meaningful results were not obtained due, primarily, to numerical difficulties.

  20. Propagation in multiscale random media

    NASA Astrophysics Data System (ADS)

    Balk, Alexander M.

    2003-10-01

    Many studies consider media with microstructure, which has variations on some microscale, while the macroproperties are under investigation. Sometimes the medium has several microscales, all of them being much smaller than the macroscale. Sometimes the variations on the macroscale are also included, which are taken into account by some procedures, like WKB or geometric optics. What if the medium has variations on all scales from microscale to macroscale? This situation occurs in several practical problems. The talk is about such situations, in particular, passive tracer in a random velocity field, wave propagation in a random medium, Schrödinger equation with random potential. To treat such problems we have developed the statistical near-identity transformation. We find anomalous attenuation of the pulse propagating in a multiscale medium.

  1. A database for propagation models

    NASA Technical Reports Server (NTRS)

    Kantak, Anil V.; Suwitra, Krisjani; Le, Chuong

    1995-01-01

    A database of various propagation phenomena models that can be used by telecommunications systems engineers to obtain parameter values for systems design is presented. This is an easy-to-use tool and is currently available for either a PC using Excel software under Windows environment or a Macintosh using Excel software for Macintosh. All the steps necessary to use the software are easy and many times self explanatory.

  2. Light propagation through atomic vapours

    NASA Astrophysics Data System (ADS)

    Siddons, Paul

    2014-05-01

    This tutorial presents the theory necessary to model the propagation of light through an atomic vapour. The history of atom-light interaction theories is reviewed, and examples of resulting applications are provided. A numerical model is developed and results presented. Analytic solutions to the theory are found, based on approximations to the numerical work. These solutions are found to be in excellent agreement with experimental measurements.

  3. Propagator for finite range potentials

    SciTech Connect

    Cacciari, Ilaria; Moretti, Paolo

    2006-12-15

    The Schroedinger equation in integral form is applied to the one-dimensional scattering problem in the case of a general finite range, nonsingular potential. A simple expression for the Laplace transform of the transmission propagator is obtained in terms of the associated Fredholm determinant, by means of matrix methods; the particular form of the kernel and the peculiar aspects of the transmission problem play an important role. The application to an array of delta potentials is shown.

  4. Wave propagation in modified gravity

    NASA Astrophysics Data System (ADS)

    Lindroos, Jan Ø.; Llinares, Claudio; Mota, David F.

    2016-02-01

    We investigate the propagation of scalar waves induced by matter sources in the context of scalar-tensor theories of gravity which include screening mechanisms for the scalar degree of freedom. The usual approach when studying these theories in the nonlinear regime of cosmological perturbations is based on the assumption that scalar waves travel at the speed of light. Within general relativity this approximation is valid and leads to no loss of accuracy in the estimation of observables. We find, however, that mass terms and nonlinearities in the equations of motion lead to propagation and dispersion velocities significantly different from the speed of light. As the group velocity is the one associated with the propagation of signals, a reduction of its value has direct impact on the behavior and dynamics of nonlinear structures within modified gravity theories with screening. For instance, the internal dynamics of galaxies and satellites submerged in large dark matter halos could be affected by the fact that the group velocity is smaller than the speed of light. It is therefore important, within such a framework, to take into account the fact that different parts of a galaxy will see changes in the environment at different times. A full nonstatic analysis may be necessary under those conditions.

  5. Jet propagation through energetic materials

    SciTech Connect

    Pincosy, P; Poulsen, P

    2004-01-08

    In applications where jets propagate through energetic materials, they have been observed to become sufficiently perturbed to reduce their ability to effectively penetrate subsequent material. Analytical calculations of the jet Bernoulli flow provides an estimate of the onset and extent of such perturbations. Although two-dimensional calculations show the back-flow interaction pressure pulses, the symmetry dictates that the flow remains axial. In three dimensions the same pressure impulses can be asymmetrical if the jet is asymmetrical. The 3D calculations thus show parts of the jet having a significant component of radial velocity. On the average the downstream effects of this radial flow can be estimated and calculated by a 2D code by applying a symmetrical radial component to the jet at the appropriate position as the jet propagates through the energetic material. We have calculated the 3D propagation of a radio graphed TOW2 jet with measured variations in straightness and diameter. The resultant three-dimensional perturbations on the jet result in radial flow, which eventually tears apart the coherent jet flow. This calculated jet is compared with jet radiographs after passage through the energetic material for various material thickness and plate thicknesses. We noted that confinement due to a bounding metal plate on the energetic material extends the pressure duration and extent of the perturbation.

  6. Turbofan Acoustic Propagation and Radiation

    NASA Technical Reports Server (NTRS)

    Eversman, Walter

    2000-01-01

    This document describes progress in the development of finite element codes for the prediction of near and far field acoustic radiation from the inlet and aft fan ducts of turbofan engines. The report consists of nine papers which have appeared in archival journals and conference proceedings, or are presently in review for publication. Topics included are: 1. Aft Fan Duct Acoustic Radiation; 2. Mapped Infinite Wave Envelope Elements for Acoustic Radiation in a Uniformly Moving Medium; 3. A Reflection Free Boundary Condition for Propagation in Uniform Flow Using Mapped Infinite Wave Envelope Elements; 4. A Numerical Comparison Between Multiple-Scales and FEM Solution for Sound Propagation in Lined Flow Ducts; 5. Acoustic Propagation at High Frequencies in Ducts; 6. The Boundary Condition at an Impedance Wall in a Nonuniform Duct with Potential Flow; 7. A Reverse Flow Theorem and Acoustic Reciprocity in Compressible Potential Flows; 8. Reciprocity and Acoustics Power in One Dimensional Compressible Potential Flows; and 9. Numerical Experiments on Acoustic Reciprocity in Compressible Potential Flows.

  7. Premixed Turbulent Flame Propagation in Microgravity

    NASA Technical Reports Server (NTRS)

    Menon, S.; Disseau, M.; Chakravarthy, V. K.; Jagoda, J.

    1997-01-01

    Papers included address the following topics: (1) Turbulent premixed flame propagation in microgravity; (2) The effect of gravity on turbulent premixed flame propagation - a preliminary cold flow study; and (3) Characteristics of a subgrid model for turbulent premixed combustion.

  8. Continuous steel production and apparatus

    DOEpatents

    Peaslee, Kent D.; Peter, Jorg J.; Robertson, David G. C.; Thomas, Brian G.; Zhang, Lifeng

    2009-11-17

    A process for continuous refining of steel via multiple distinct reaction vessels for melting, oxidation, reduction, and refining for delivery of steel continuously to, for example, a tundish of a continuous caster system, and associated apparatus.

  9. Brazing titanium to stainless steel

    NASA Technical Reports Server (NTRS)

    Batista, R. I.

    1980-01-01

    Titanium and stainless-steel members are usually joined mechanically for lack of any other effective method. New approach using different brazing alloy and plating steel member with nickel resolves problem. Process must be carried out in inert atmosphere.

  10. Calculations of precursor propagation in dispersive dielectrics.

    SciTech Connect

    Bacon, Larry Donald

    2003-08-01

    The present study is a numerical investigation of the propagation of electromagnetic transients in dispersive media. It considers propagation in water using Debye and composite Rocard-Powles-Lorentz models for the complex permittivity. The study addresses this question: For practical transmitted spectra, does precursor propagation provide any features that can be used to advantage over conventional signal propagation in models of dispersive media of interest? A companion experimental study is currently in progress that will attempt to measure the effects studied here.

  11. Alloyed steel wastes utilization

    SciTech Connect

    Sokol, I.V.

    1995-12-31

    Alloyed steel chips and swarf formed during metal processing are looked upon as additional raw materials in metallurgical production. This paper presents some new methods for steel waste chips and swarf cleaning. One of them is swarf and steel chips cleaning in tetrachloroethylene with ultrasonic assistance and solvent regeneration. Thermal cleaning of waste chips and swarf provides off gas products utilization. The catalyst influence of the metal surface on the thermal decomposition of liquid hydrocarbons during the cleaning process has been studied. It has been determined that the efficiency of this metal waste cleaning technique depends on the storage time of the swarf. The waste chips and swarf cleaning procedures have been proven to be economically advantageous and environmentally appropriate.

  12. Effects of Thermally Sprayed Aluminum Coating on the Corrosion Fatigue Behavior of X80 Steel in 3.5 wt.% NaCl

    NASA Astrophysics Data System (ADS)

    Zhao, Weimin; Zhang, Timing; Xin, Ruofei; Wang, Manman; Ai, Hua; Sun, Jianbo; Wang, Yong

    2015-08-01

    Corrosion fatigue and fatigue crack propagation experiments were conducted using X80 steel (with and without aluminum coating) in 3.5 wt.% NaCl solution. Results show that the aluminum coating could significantly improve the corrosion fatigue life of the steel substrate, and that this influence would be enhanced by decreasing the applied stress. However, the crack growth rate of the aluminum-coated X80 steel was slightly higher than that of bare X80 steel. Therefore, the presence of aluminum coating extends the crack initiation stage, and the inhibiting effect of aluminum coating on crack initiation outweighs its promotion of crack propagation. The acting mechanisms of the aluminum coating on crack initiation and propagation were discussed.

  13. Slow-Slip Propagation Speeds

    NASA Astrophysics Data System (ADS)

    Rubin, A. M.; Ampuero, J.

    2007-12-01

    Combined seismic and geodetic data from subduction zones and the Salton Trough have revealed slow slip events with reasonably well-defined propagation speeds. This in turn is suggestive of a more-or-less well- defined front separating nearly locked regions outside the slipping zone from interior regions that slide much more rapidly. Such crack-like nucleation fronts arise naturally in models of rate-and-state friction for lab-like values of a/b, where a and b are the coefficients of the velocity- and state-dependence of the frictional strength (with the surface being velocity-neutral for a/b=1). If the propagating front has a quasi-steady shape, the propagation and slip speeds are kinematically tied via the local slip gradient. Given a sufficiently sharp front, the slip gradient is given dimensionally by Δτp- r/μ', where Δτp-r is the peak-to-residual stress drop at the front and μ' the effective elastic shear modulus. Rate-and-state simulations indicate that Δτp-r is given reasonably accurately by bσ\\ln(Vmaxθi/Dc), where σ is the effective normal stress, Vmax is the maximum slip speed behind the propagating front, θi is the the value of "state" ahead of the propagating front, and Dc is the characteristic slip distance for state evolution. Except for a coefficient of order unity, Δτp-r is independent of the evolution law. This leads to Vprop/Vmax ~μ'/[bσ\\ln(Vmaxθi/Dc)]. For slip speeds a few orders of magnitude above background, \\ln(Vmaxθi/Dc) can with reasonable accuracy be assigned some representative value (~4-5, for example). Subduction zone transients propagate on the order of 10 km/day or 10-1 m/s. Geodetic data constrain the average slip speed to be a few times smaller than 1 cm/day or 10-7 m/s. However, numerical models indicate that the maximum slip speed at the front may be several times larger than the average, over a length scale that is probably too small to resolve geodetically, so a representative value of Vprop/Vmax may be ~106

  14. Japanese propagation experiments with ETS-5

    NASA Technical Reports Server (NTRS)

    Ikegami, Tetsushi

    1989-01-01

    Propagation experiments for maritime, aeronautical, and land mobile satellite communications were performed using Engineering Test Satellite-Five (ETS-5). The propagation experiments are one of major mission of Experimental Mobile Satellite System (EMSS) which is aimed for establishing basic technology for future general mobile satellite communication systems. A brief introduction is presented for the experimental results on propagation problems of ETS-5/EMSS.

  15. 49 CFR 195.111 - Fracture propagation.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 3 2014-10-01 2014-10-01 false Fracture propagation. 195.111 Section 195.111... PIPELINE Design Requirements § 195.111 Fracture propagation. A carbon dioxide pipeline system must be designed to mitigate the effects of fracture propagation....

  16. 49 CFR 195.111 - Fracture propagation.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 3 2010-10-01 2010-10-01 false Fracture propagation. 195.111 Section 195.111... PIPELINE Design Requirements § 195.111 Fracture propagation. A carbon dioxide pipeline system must be designed to mitigate the effects of fracture propagation....

  17. 49 CFR 195.111 - Fracture propagation.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 3 2012-10-01 2012-10-01 false Fracture propagation. 195.111 Section 195.111... PIPELINE Design Requirements § 195.111 Fracture propagation. A carbon dioxide pipeline system must be designed to mitigate the effects of fracture propagation....

  18. 49 CFR 195.111 - Fracture propagation.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 3 2011-10-01 2011-10-01 false Fracture propagation. 195.111 Section 195.111... PIPELINE Design Requirements § 195.111 Fracture propagation. A carbon dioxide pipeline system must be designed to mitigate the effects of fracture propagation....

  19. 49 CFR 195.111 - Fracture propagation.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 3 2013-10-01 2013-10-01 false Fracture propagation. 195.111 Section 195.111... PIPELINE Design Requirements § 195.111 Fracture propagation. A carbon dioxide pipeline system must be designed to mitigate the effects of fracture propagation....

  20. A review of transhorizon propagation phenomena

    NASA Technical Reports Server (NTRS)

    Crane, R. K.

    1981-01-01

    Interference problems underlie the current interest in transhorizon propagation. In particular, statistics of the rare, high-level fields are of interest. This paper reviews the propagation mechanisms which produce the high-level fields and summarizes recent work in the modeling of the transhorizon propagation.

  1. Acoustic Propagation in a Water-Filled Cylindrical Pipe

    SciTech Connect

    Sullivan, E J; Candy, J V

    2003-06-01

    This study was concerned with the physics of the propagation of a tone burst of high frequency sound in a steel water-filled pipe. The choice of the pulse was rather arbitrary, so that this work in no way can be considered as recommending a particular pulse form. However, the MATLAB computer codes developed in this study are general enough to carry out studies of pulses of various forms. Also, it should be pointed out that the codes as written are quite time consuming. A computation of the complete field, including all 5995 modes, requires several hours on a desktop computer. The time required by such computations as these is a direct consequence of the bandwidths, frequencies and sample rates employed. No attempt was made to optimize these codes, and it is assumed that much can be done in this regard.

  2. Wave propagation in granular chains with local resonances.

    PubMed

    Bonanomi, Luca; Theocharis, Georgios; Daraio, Chiara

    2015-03-01

    We study wave propagation in a chain of spherical particles containing a local resonator. The resonant particles are made of an aluminum outer spherical shell and a steel inner mass connected by a polymeric plastic structure acting as a spring. We characterize the dynamic response of individual particles and the transmitted linear spectra of a chain of particles in contact. A wide band gap is observed both in theoretical and experimental results. We show the ability to tune the acoustic transmission by varying the contact interaction between particles. Higher driving amplitude leads to the generation of nonlinearities both in the response of a single particle and that of the whole chain. For a single resonant particle, we observe experimentally a resonant frequency downshift, which follows a complex nonlinear behavior. In the chain of particles, nonlinearity leads to the generation of nonlinear harmonics and the presence of localized modes inside the band gap. PMID:25871239

  3. Improvement of Anisotropic Mechanical Behavior by Sulfide Control in Quenched and Tempered 4340 Steel

    NASA Astrophysics Data System (ADS)

    Jung, Jae-Hoon; Shin, Jung-Ho; Lee, Seok-Jae

    2015-07-01

    The anisotropic mechanical behavior of quenched and tempered 4340 steel with different Ca contents was investigated by means of a macro/micrograph analysis, Charpy impact test, and rotating bending fatigue test. The 4340 steel with Ca added formed small spherical (Ca,Mn)S inclusions and effectively decreased both the inclusion size and the aspect ratio (length to width) of the MnS inclusions as compared to the Ca-free 4340 steel. The anisotropic impact value and fatigue strength were effectively improved due to the Ca addition that prevented the growth of MnS inclusions, which provided increased resistance against deformation to maintain a spherical shape because the elongated MnS inclusions acted as a crack propagation path and promoted the crack propagation due to higher stress concentrations.

  4. A-3 steel work completed

    NASA Technical Reports Server (NTRS)

    2009-01-01

    Stennis Space Center engineers celebrated a key milestone in construction of the A-3 Test Stand on April 9 - completion of structural steel work. Workers with Lafayette (La.) Steel Erector Inc. placed the last structural steel beam atop the stand during a noon ceremony attended by more than 100 workers and guests.

  5. Detection of stress corrosion cracking of high-strength steel used in prestressed concrete structures by acoustic emission technique

    NASA Astrophysics Data System (ADS)

    Ramadan, S.; Gaillet, L.; Tessier, C.; Idrissi, H.

    2008-02-01

    The stress corrosion cracking (SCC) of high-strength steel used in prestressed concrete structures was studied by acoustic emission technique (AE). A simulated concrete pore (SCP) solution at high-alkaline (pH ≈ 12) contaminated by sulphate, chloride, and thiocyanate ions was used. The evolution of the acoustic activity recorded during the tests shows the presence of several stages related respectively to cracks initiation due to the local corrosion imposed by corrosives species, cracks propagation and steel failure. Microscopic examinations pointed out that the wires exhibited a brittle fracture mode. The cracking was found to propagate in the transgranular mode. The role of corrosives species and hydrogen in the rupture mechanism of high-strength steel was also investigated. This study shows promising results for an potential use in situ of AE for real-time health monitoring of eutectoid steel cables used in prestressed concrete structures.

  6. Low Frequency-SAFT Inspection Methodology for Coarse-Grained Steel Rail Components (Manganese Steel Frogs)

    SciTech Connect

    Diaz, Aaron A.; Andersen, Eric S.; Samuel, Todd J.

    2004-11-01

    In the rail industry, sections of high strength Manganese steel are employed at critical locations in railroad networks. Ultrasonic inspections of Manganese steel microstructures are difficult to inspect with conventional means, as the propagation medium is highly attenuative, coarse-grained, anisotropic and nonhomogeneous in nature. Current in-service inspection methods are ineffective while pre-service X-ray methods (used for full-volumetric examinations of components prior to shipment) are time-consuming, costly, require special facilities and highly trained personnel for safe operations, and preclude manufacturers from inspecting statistically meaningful numbers of frogs for effective quality assurance. In-service examinations consist of visual inspections only and by the time a defect or flaw is visually detected, the structural integrity of the component may already be compromised, and immediate repair or replacement is required. A novel ultrasonic inspection technique utilizing low frequency ultrasound (100 to 500 kHz) combined with a synthetic aperture focusing technique (SAFT) for effective reduction of signal clutter and noise, and extraction of important features in the data, has proven to be effective for these coarse grained steel components. Results from proof-of-principal tests in the laboratory demonstrate an effective means to detect and localize reflectors introduced as a function of size and depth from the top of the frog rail. Using non-optimal, commercially available transducers coupled with the low-frequency/SAFT approach, preliminary evaluations were conducted to study the effects of the material microstructure on ultrasonic propagation, sensitivity and resolution in thick section frog components with machined side-drilled holes. Results from this study will be presented and discussed.

  7. Microbial-Influenced Corrosion of Corten Steel Compared with Carbon Steel and Stainless Steel in Oily Wastewater by Pseudomonas aeruginosa

    NASA Astrophysics Data System (ADS)

    Mansouri, Hamidreza; Alavi, Seyed Abolhasan; Fotovat, Meysam

    2015-07-01

    The microbial corrosion behavior of three important steels (carbon steel, stainless steel, and Corten steel) was investigated in semi petroleum medium. This work was done in modified nutrient broth (2 g nutrient broth in 1 L oily wastewater) in the presence of Pseudomonas aeruginosa and mixed culture (as a biotic media) and an abiotic medium for 2 weeks. The behavior of corrosion was analyzed by spectrophotometric and electrochemical methods and at the end was confirmed by scanning electron microscopy. The results show that the degree of corrosion of Corten steel in mixed culture, unlike carbon steel and stainless steel, is less than P. aeruginosa inoculated medium because some bacteria affect Corten steel less than other steels. According to the experiments, carbon steel had less resistance than Corten steel and stainless steel. Furthermore, biofilm inhibits separated particles of those steels to spread to the medium; in other words, particles get trapped between biofilm and steel.

  8. Effect of Aging on the Fracture Behavior of Lean Duplex Stainless Steels

    NASA Astrophysics Data System (ADS)

    Straffelini, G.; Baldo, S.; Calliari, I.; Ramous, E.

    2009-11-01

    The influence of aging in the range of 550 °C to 850 °C for 5 to 120 minutes on the impact fracture behavior of 2101 and 2304 lean duplex stainless steels (DSS) was investigated in the present study. The 2304 steel displayed ductile behavior irrespective of aging conditions. In contrast, the 2101 steel displayed a ductile behavior only in the case of aging for 5 minutes at 550 °C and 650 °C, whereas in all other cases, it fractured in a brittle manner. The brittle fracture behavior of the 2101 steel has been attributed to the precipitation of small black particles at the α/ α and α/ γ grain boundaries (nitrides), which form paths for easy crack propagation. In the 2304 steel, such particles precipitated at 750 °C and 850 °C, but they were located inside the austenitic grains because of the formation of secondary austenite. They therefore did not embrittle the steel. The larger Ni content of the 2304 steel favored the formation of the secondary austenite that is absent in the 2101 steel.

  9. Structural factors governing steel resistance during operation in corrosive media under cavitation conditions

    SciTech Connect

    Berezovskaya, V.V.

    1988-05-01

    To evaluate the effect of structural factors on the corrosion resistance of steel under cavitation, a study was made of the effect of cavitation on chromium (95Kh18) and chromium-nickel (12Kh18N9T) corrosion-resistant steels and also on maraging steel 03Kh10N5K5M3KTYuS, specially developed for the loading conditions being studied, together with the austenitic steel 03Kh23N28M3D3T. A study of the effect of martensite content on corrosion and cavitation-corrosion resistance was carried out on steels 12Kh18N9T and 95Kh18 after different treatments. Corrosion tests were conducted in solutions of H/sub 2/SO/sub 4/ and H/sub 3/PO/sub 4/ and scanning electron microscopy was used to assess phase and corrosion behavior. Maraging steels treated for maximum hardness and overaging exhibited high cavitation-corrosion resistance in acid solutions owing to high strength and resistance to microcrack initiation and propagation. It was recommended that under cavitation conditions in corrosive media, high alloy austenitic corrosion-resistant steels are substituted by maraging steels.

  10. Cutting line determination for plant propagation

    NASA Astrophysics Data System (ADS)

    Lo, Li-Yun; Hsia, Chi-Chun; Sun, Hua-Hong; Chen, Hsiang-Ju; Wu, Xin-Ting; Hu, Min-Chun

    2014-01-01

    Investigating an efficient method for plant propagation can help not only prevent extinction of plants but also facilitate the development of botanical industries. In this paper, we propose to use image processing techniques to determine the cutting-line for the propagation of two kinds of plants, i.e. Melaleuca alternifolia Cheel and Cinnamomum kanehirai Hay, which have quite different characteristics in terms of shape, structure, and propagation way (e.g. propagation by seeding and rooting, respectively). The proposed cutting line determination methods can be further applied to develop an automatic control system to reduce labor cost and increase the effectiveness of plant propagation.

  11. Wave Propagation in Bimodular Geomaterials

    NASA Astrophysics Data System (ADS)

    Kuznetsova, Maria; Pasternak, Elena; Dyskin, Arcady; Pelinovsky, Efim

    2016-04-01

    Observations and laboratory experiments show that fragmented or layered geomaterials have the mechanical response dependent on the sign of the load. The most adequate model accounting for this effect is the theory of bimodular (bilinear) elasticity - a hyperelastic model with different elastic moduli for tension and compression. For most of geo- and structural materials (cohesionless soils, rocks, concrete, etc.) the difference between elastic moduli is such that their modulus in compression is considerably higher than that in tension. This feature has a profound effect on oscillations [1]; however, its effect on wave propagation has not been comprehensively investigated. It is believed that incorporation of bilinear elastic constitutive equations within theory of wave dynamics will bring a deeper insight to the study of mechanical behaviour of many geomaterials. The aim of this paper is to construct a mathematical model and develop analytical methods and numerical algorithms for analysing wave propagation in bimodular materials. Geophysical and exploration applications and applications in structural engineering are envisaged. The FEM modelling of wave propagation in a 1D semi-infinite bimodular material has been performed with the use of Marlow potential [2]. In the case of the initial load expressed by a harmonic pulse loading strong dependence on the pulse sign is observed: when tension is applied before compression, the phenomenon of disappearance of negative (compressive) strains takes place. References 1. Dyskin, A., Pasternak, E., & Pelinovsky, E. (2012). Periodic motions and resonances of impact oscillators. Journal of Sound and Vibration, 331(12), 2856-2873. 2. Marlow, R. S. (2008). A Second-Invariant Extension of the Marlow Model: Representing Tension and Compression Data Exactly. In ABAQUS Users' Conference.

  12. Microwave propagation in chiral metamaterials

    NASA Astrophysics Data System (ADS)

    Prybylski, Aida; Yon, Luis; Noginova, Natalia

    Chiral hyperbolic metamaterials are predicted to show interesting properties associated with possible topological photonic states in these materials, which present new opportunities for light control and manipulation. As prototypes, we consider two metal-dielectric systems designed for microwave range: a twisted wires array, where chirality is associated with shape of metal inclusions, and a rotated layer system, with parallel wires in each layer, and direction of the wires orientation rotated from layer to layer. Systems with different content of metal and layer-to-layer distance were fabricated and studied in the free space propagation experiment. The results were discussed in terms of effective media consideration.

  13. Continuous propagation of microalgae. III.

    NASA Technical Reports Server (NTRS)

    Hanson, D. T.; Fredrickson, A. G.; Tsuchiya, H. M.

    1971-01-01

    Data are presented which give the specific photosynthetic rate and the specific utilization rates of urea and carbon dioxide as functions of specific growth rate for Chlorella. A mathematical model expresses a set of mass balance relations between biotic and environmental materials. Criteria of validity are used to test this model. Predictive procedures are complemented by a particular model of microbial growth. Methods are demonstrated for predicting substrate utilization rates, production rates of extracellular metabolites, growth limiting conditions, and photosynthetic quotients from propagator variables.

  14. Energy propagation throughout chemical networks.

    PubMed

    Le Saux, Thomas; Plasson, Raphaël; Jullien, Ludovic

    2014-06-14

    In order to maintain their metabolism from an energy source, living cells rely on chains of energy transfer involving functionally identified components and organizations. However, propagation of a sustained energy flux through a cascade of reaction cycles has only been recently reproduced at a steady state in simple chemical systems. As observed in living cells, the spontaneous onset of energy-transfer chains notably drives local generation of singular dissipative chemical structures: continuous matter fluxes are dynamically maintained at boundaries between spatially and chemically segregated zones but in the absence of any membrane or predetermined material structure. PMID:24681890

  15. Photon propagator in skewon electrodynamics

    NASA Astrophysics Data System (ADS)

    Itin, Yakov

    2016-01-01

    Electrodynamics with a local and linear constitutive law is used as a framework for models violating Lorentz covariance. The constitutive tensor of such a construction is irreducibly decomposed into three independent pieces. The principal part is the anisotropic generalization of the standard electrodynamics. The two other parts, axion and skewon, represent nonclassical modifications of electrodynamics. We derive the expression for the photon propagator in the Minkowski spacetime endowed with a skewon field. For a relatively small (antisymmetric) skewon field, a modified Coulomb law is exhibited.

  16. 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.

  17. ACTS and OLYMPUS propagation experiments

    NASA Technical Reports Server (NTRS)

    Bostian, Charles W.; Baker, Kenneth R.

    1988-01-01

    The OLYMPUS and ACTS satellites both provide opportunities for 10 to 30 GHz propagation measurements. The spacecraft are sufficiently alike that OLYMPUS can be used to test some prototype ACTS equipment and experiments. Data are particularly needed on short term signal behavior and in support of uplink power control and adaptive forward error correction (FEC) techniques. The Virginia Tech Satellite Communications Group has proposed a set of OLYMPUS experiments including attenuation and fade rate measurements, data communications, uplink power control, rain scatter interference, and small-scale site diversity operation. A digital signal processing receiver for the OLYMPUS and ACTS beacon signals is being developed.

  18. Braze alloy spreading on steel

    NASA Technical Reports Server (NTRS)

    Siewert, T. A.; Heine, R. W.; Lagally, M. G.

    1978-01-01

    Scanning electron microscopy (SEM) and Auger electron microscopy (AEM) were employed to observe elemental surface decomposition resulting from the brazing of a copper-treated steel. Two types of steel were used for the study, stainless steel (treated with a eutectic silver-copper alloy), and low-carbon steel (treated with pure copper). Attention is given to oxygen partial pressure during the processes; a low enough pressure (8 x 10 to the -5th torr) was found to totally inhibit the spreading of the filler material at a fixed heating cycle. With both types of steel, copper treatment enhanced even spreading at a decreased temperature.

  19. Sensitization of stainless steel

    NASA Technical Reports Server (NTRS)

    Nagy, James P.

    1990-01-01

    The objective of this experiment is to determine the corrosion rates of 18-8 stainless steels that have been sensitized at various temperatures and to show the application of phase diagrams. The laboratory instructor will assign each student a temperature, ranging from 550 C to 1050 C, to which the sample will be heated. Further details of the experimental procedure are detailed.

  20. Long distance laser ultrasonic propagation imaging system for damage visualization

    NASA Astrophysics Data System (ADS)

    Lee, Jung-Ryul; Shin, He-Jin; Chia, Chen Ciang; Dhital, Dipesh; Yoon, Dong-Jin; Huh, Yong-Hak

    2011-12-01

    Wind turbine blade failure is the most prominent and common type of damage occurring in operating wind turbine systems. Conventional nondestructive testing systems are not available for in situ wind turbine blades. We propose a portable long distance ultrasonic propagation imaging (LUPI) system that uses a laser beam targeting and scanning system to excite, from a long distance, acoustic emission sensors installed in the blade. An examination of the beam collimation effect using geometric parameters of a commercial 2 MW wind turbine provided Lamb wave amplitude increases of 41.5 and 23.1 dB at a distance of 40 m for symmetrical and asymmetrical modes, respectively, in a 2 mm-thick stainless steel plate. With this improvement in signal-to-noise ratio, a feasibility study of damage detection was conducted with a 5 mm-thick composite leading edge specimen. To develop a reliable damage evaluation system, the excitation/sensing technology and the associated damage visualization algorithm are equally important. Hence, our results provide a new platform based on anomalous wave propagation imaging (AWPI) methods with adjacent wave subtraction, reference wave subtraction, reference image subtraction, and the variable time window amplitude mapping method. The advantages and disadvantages of AWPI algorithms are reported in terms of reference data requirements, signal-to-noise ratios, and damage evaluation accuracy. The compactness and portability of the proposed UPI system are also important for in-field applications at wind farms.

  1. Experimental and theoretical study of Rayleigh-Lamb wave propagation

    NASA Technical Reports Server (NTRS)

    Rogers, Wayne P.; Datta, Subhendu K.; Ju, T. H.

    1990-01-01

    Many space structures, such as the Space Station Freedom, contain critical thin-walled components. The structural integrity of thin-walled plates and shells can be monitored effectively using acoustic emission and ultrasonic testing in the Rayleigh-Lamb wave frequency range. A new PVDF piezoelectric sensor has been developed that is well suited to remote, inservice nondestructive evaluation of space structures. In the present study the new sensor was used to investigate Rayleigh-Lamb wave propagation in a plate. The experimental apparatus consisted of a glass plate (2.3 m x 25.4 mm x 5.6 mm) with PVDF sensor (3 mm diam.) mounted at various positions along its length. A steel ball impact served as a simulated acoustic emission source, producing surface waves, shear waves and longitudinal waves with dominant frequencies between 1 kHz and 200 kHz. The experimental time domain wave-forms were compared with theoretical predictions of the wave propagation in the plate. The model uses an analytical solution for the Green's function and the measured response at a single position to predict response at any other position in the plate. Close agreement was found between the experimental and theoretical results.

  2. Nonlinear wave propagation in constrained solids subjected to thermal loads

    NASA Astrophysics Data System (ADS)

    Nucera, Claudio; Lanza di Scalea, Francesco

    2014-01-01

    The classical mathematical treatment governing nonlinear wave propagation in solids relies on finite strain theory. In this scenario, a system of nonlinear partial differential equations can be derived to mathematically describe nonlinear phenomena such as acoustoelasticity (wave speed dependency on quasi-static stress), wave interaction, wave distortion, and higher-harmonic generation. The present work expands the topic of nonlinear wave propagation to the case of a constrained solid subjected to thermal loads. The origin of nonlinear effects in this case is explained on the basis of the anharmonicity of interatomic potentials, and the absorption of the potential energy corresponding to the (prevented) thermal expansion. Such "residual" energy is, at least, cubic as a function of strain, hence leading to a nonlinear wave equation and higher-harmonic generation. Closed-form solutions are given for the longitudinal wave speed and the second-harmonic nonlinear parameter as a function of interatomic potential parameters and temperature increase. The model predicts a decrease in longitudinal wave speed and a corresponding increase in nonlinear parameter with increasing temperature, as a result of the thermal stresses caused by the prevented thermal expansion of the solid. Experimental measurements of the ultrasonic nonlinear parameter on a steel block under constrained thermal expansion confirm this trend. These results suggest the potential of a nonlinear ultrasonic measurement to quantify thermal stresses from prevented thermal expansion. This knowledge can be extremely useful to prevent thermal buckling of various structures, such as continuous-welded rails in hot weather.

  3. a New Approach to Bulk Wave Propagation in Anisotropic Media.

    NASA Astrophysics Data System (ADS)

    Tverdokhlebov, Andrey

    A new approach to a theoretical description of ultrasonic bulk wave propagation through anisotropic media is developed from the retarded potential representation which was obtained for the Green's function of the elastic wave equation in anisotropic media. The general formulation of the problem and the method of solution are presented. On the basis of the theoretical development, a quantitative model was obtained that yields and properly describes all major features of the phenomena of an anisotropic filter influence. A comparison with other contemporary methods and models for the quantitative evaluation of the bulk wave propagation in anisotropic media is outlined and briefly discussed. The experimental proof of principle was established by ultrasonic measurements performed on centrifugally cast stainless steel (CCSS) and unidirectional graphite fiber -epoxy composite specimens. The experimental technique used a skip-distance arrangement of the identical quasi -point probes serving as a sender and a receiver. Consistent experimental results were attained allowing us to consider the suggested experimental arrangements as a basis for the future development of NDE technique for anisotropic material characterization. Three different types of pilot computer software were developed from this generalized retarded potential model. The results of the simulation runs turn out to be self- and mutually consistent and supported by experiments. The phenomena, such as beam skewing, beam splitting, beam focusing, unsymmetrical beams and other anisotropic effects, some of which have been already known from earlier experimental observations, emerge as computational results of the software developed from the model.

  4. Joint Acoustic Propagation Experiment (JAPE)

    NASA Technical Reports Server (NTRS)

    Carnes, Benny L.; Olsen, Robert O.; Kennedy, Bruce W.

    1993-01-01

    The Joint Acoustic Propagation Experiment (JAPE), performed under the auspices of NATO and the Acoustics Working Group, was conducted at White Sands Missile Range, New Mexico, USA, during the period 11-28 Jul. 1991. JAPE consisted of 220 trials using various acoustic sources including speakers, propane cannon, various types of military vehicles, helicopters, a 155mm howitzer, and static high explosives. Of primary importance to the performance of these tests was the intensive characterization of the atmosphere before and during the trials. Because of the wide range of interests on the part of the participants, JAPE was organized in such a manner to provide a broad cross section of test configurations. These included short and long range propagation from fixed and moving vehicles, terrain masking, and vehicle detection. A number of independent trials were also performed by individual participating agencies using the assets available during JAPE. These tests, while not documented in this report, provided substantial and important data to those groups. Perhaps the most significant feature of JAPE is the establishment of a permanent data base which can be used by not only the participants but by others interested in acoustics. A follow-on test was performed by NASA LaRC during the period 19-29 Aug. 1991 at the same location. These trials consisted of 59 overflights of supersonic aircraft in order to establish the relationship between atmospheric turbulence and the received sonic boom energy at the surface.

  5. Orbit propagation in Minkowskian geometry

    NASA Astrophysics Data System (ADS)

    Roa, Javier; Peláez, Jesús

    2015-09-01

    The geometry of hyperbolic orbits suggests that Minkowskian geometry, and not Euclidean, may provide the most adequate description of the motion. This idea is explored in order to derive a new regularized formulation for propagating arbitrarily perturbed hyperbolic orbits. The mathematical foundations underlying Minkowski space-time are exploited to describe hyperbolic orbits. Hypercomplex numbers are introduced to define the rotations, vectors, and metrics in the problem: the evolution of the eccentricity vector is described on the Minkowski plane in terms of hyperbolic numbers, and the orbital plane is described on the inertial reference using quaternions. A set of eight orbital elements is introduced, namely a time-element, the components of the eccentricity vector in , the semimajor axis, and the components of the quaternion defining the orbital plane. The resulting formulation provides a deep insight into the geometry of hyperbolic orbits. The performance of the formulation in long-term propagations is studied. The orbits of four hyperbolic comets are integrated and the accuracy of the solution is compared to other regularized formulations. The resulting formulation improves the stability of the integration process and it is not affected by the perihelion passage. It provides a level of accuracy that may not be reached by the compared formulations, at the cost of increasing the computational time.

  6. Burst propagation in Texas Helimak

    NASA Astrophysics Data System (ADS)

    Pereira, F. A. C.; Toufen, D. L.; Guimarães-Filho, Z. O.; Caldas, I. L.; Gentle, K. W.

    2016-05-01

    We present investigations of extreme events (bursts) propagating in the Texas Helimak, a toroidal plasma device in which the radial electric field can be changed by application of bias. In the experiments analyzed, a large grid of Langmuir probes measuring ion saturation current fluctuations is used to study the burst propagation and its dependence on the applied bias voltage. We confirm previous results reported on the turbulence intermittency in the Texas Helimak, extending them to a larger radial interval with a density ranging from a uniform decay to an almost uniform value. For our analysis, we introduce an improved procedure, based on a multiprobe bidimensional conditional averaging method, to assure precise determination of burst statistical properties and their spatial profiles. We verify that intermittent bursts have properties that vary in the radial direction. The number of bursts depends on the radial position and on the applied bias voltage. On the other hand, the burst characteristic time and size do not depend on the applied bias voltage. The bias voltage modifies the vertical and radial burst velocity profiles differently. The burst velocity is smaller than the turbulence phase velocity in almost all the analyzed region.

  7. The application of low frequency longitudinal guided wave mode for the inspection of multi-hole steel floral pipes

    NASA Astrophysics Data System (ADS)

    Liu, Z. H.; Xie, X. D.; Wu, B.; Li, Y. H.; He, C. F.

    2012-03-01

    Shed-pipe grouting technology, an effective advanced supporting method, is often used in the excavation of soft strata. Steel floral pipes are one of the key load-carrying components of shed-pipe grouting supporting structures. Guided waves are a very attractive methodology to inspect multi-hole steel floral pipes as they offer long range inspection capability, mode and frequency tuning, and cost effectiveness. In this contribution, preliminary experiments are described for the inspection of steel floral pipes using a low frequency longitudinal guided wave mode, L(0,2). The relation between the number of grouting holes and the peak-to-peak amplitude of the first end-reflected signal was obtained. The effect of the grouting holes in steel floral pipes on the propagation velocity of the L(0,2) mode at 30 kHz was analyzed. Experimental results indicate that the typical grouting holes in steel floral pipe have no significant effect on the propagation of this mode. As a result, low frequency longitudinal guided wave modes have potential for the non-destructive long range inspection of multi-hole steel floral pipes. Furthermore, the propagation velocity of the investigated L(0,2) mode at 30 kHz decreases linearly with the increase of the number of grouting holes in a steel floral pipe. It is also noticeable that the effect of the grouting holes cumulates along with the increase in the number of grouting holes and subsequent increase in reflection times of longitudinal guided waves in the steel floral pipe. The application potential of the low frequency longitudinal guided wave technique for the inspection of embedded steel floral pipes is discussed.

  8. Special steel production on common carbon steel production line

    NASA Astrophysics Data System (ADS)

    Pi, Huachun; Han, Jingtao; Hu, Haiping; Bian, Ruisheng; Kang, Jianjun; Xu, Manlin

    2004-06-01

    The equipment and technology of small bar tandem rolling line of Shijiazhuang Iron & Steel Co. in China has reached the 90's international advanced level in the 20th century, but products on the line are mostly of common carbon steel. Currently there are few steel plants in China to produce 45 steel bars for cold drawing, which is a kind of shortage product. Development of 45 steel for cold drawing has a wide market outlook in China. In this paper, continuous cooling transformation (CCT) curve of 45 steel for cold drawing used for rolling was set out first. According to the CCT curve, we determined some key temperature points such as Ac3 temperature and Ac1 temperature during the cooling procedure and discussed the precipitation microstructure at different cooling rate. Then by studying thermal treatment process of 45 steel bars for cold drawing, the influence of cooling time on microstructure was analyzed and the optimum cooling speed has been found. All results concluded from the above studies are the basis of regulating controlled cooling process of 45 steel bars for cold drawing. Finally, the feasible production process of 45 steel bars for cold drawing on common carbon steel production line combined with the field condition was recommended.

  9. Ferritic steel melt and FLiBe/steel experiment : melting ferritic steel.

    SciTech Connect

    Troncosa, Kenneth P.; Smith, Brandon M.; Tanaka, Tina Joan

    2004-11-01

    In preparation for developing a Z-pinch IFE power plant, the interaction of ferritic steel with the coolant, FLiBe, must be explored. Sandia National Laboratories Fusion Technology Department was asked to drop molten ferritic steel and FLiBe in a vacuum system and determine the gas byproducts and ability to recycle the steel. We tried various methods of resistive heating of ferritic steel using available power supplies and easily obtained heaters. Although we could melt the steel, we could not cause a drop to fall. This report describes the various experiments that were performed and includes some suggestions and materials needed to be successful. Although the steel was easily melted, it was not possible to drip the molten steel into a FLiBe pool Levitation melting of the drop is likely to be more successful.

  10. 77 FR 30589 - SteelRiver Infrastructure Partners LP, SteelRiver Infrastructure Associates LLC, SteelRiver...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-23

    ... Surface Transportation Board SteelRiver Infrastructure Partners LP, SteelRiver Infrastructure Associates LLC, SteelRiver Infrastructure Fund North America LP, and Patriot Funding LLC--Control Exemption--Patriot Rail Corp., et al. SteelRiver Infrastructure Partners LP (SRIP LP), SteelRiver...

  11. New-type steel plate with ultra high crack-arrestability

    SciTech Connect

    Ishikawa, T.; Nomiyama, Y.; Hagiwara, Y.; Yoshikawa, H.; Oshita, S.; Mabuchi, H.

    1995-12-31

    A new-type steel plate has been developed by controlling the microstructure of the surface layers. The surface layer consists of ultra fine grain ferrite microstructure, which provides excellent fracture toughness even at cryogenic temperature. When an unstable brittle crack propagates in the developed steel plate, shear-lips can be easily formed due to the surface layers with ultra fine grain microstructure. Since unstable running crack behavior is strongly affected by side-ligaments (shear-lips), which are associated with extensive plastic deformation, enhanced formation of the shear-lips can improve crack arrestability. This paper describes the developed steel plates of HT500MPa tensile strength class for shipbuilding use. Fracture mechanics investigations using large-scale fracture testings (including ultrawide duplex ESSO tests) clarified that the developed steel plates have ultra high crack-arrestability. It was also confirmed that the plates possess sufficient properties, including weldability and workability, for ship building use.

  12. Influence of preliminary tension on the low-cycle fatigue of 40Kh13 steel in gaseous hydrogen

    SciTech Connect

    Romaniv, A.N.

    1985-05-01

    Information is lacking on the influence of hydrogen entering from an electrolyte or an external gaseous medium on the low-cycle fatigue of steels after preliminary tension. Since preliminary plastic deformation by tension increases the elastic limit and hardness of the steel while reducing its toughness, this must be reflected in the processes of crack origin and propagation in low-cycle loading in hydrogen. The purpose of this work was to study the influence of the degree of preliminary tension on the low-cycle failure resistance of 40Kh13 martensitic class steel in an atmosphere of gaseous hydrogen.

  13. Reliability-based condition assessment of steel containment and liners

    SciTech Connect

    Ellingwood, B.; Bhattacharya, B.; Zheng, R.

    1996-11-01

    Steel containments and liners in nuclear power plants may be exposed to aggressive environments that may cause their strength and stiffness to decrease during the plant service life. Among the factors recognized as having the potential to cause structural deterioration are uniform, pitting or crevice corrosion; fatigue, including crack initiation and propagation to fracture; elevated temperature; and irradiation. The evaluation of steel containments and liners for continued service must provide assurance that they are able to withstand future extreme loads during the service period with a level of reliability that is sufficient for public safety. Rational methodologies to provide such assurances can be developed using modern structural reliability analysis principles that take uncertainties in loading, strength, and degradation resulting from environmental factors into account. The research described in this report is in support of the Steel Containments and Liners Program being conducted for the US Nuclear Regulatory Commission by the Oak Ridge National Laboratory. The research demonstrates the feasibility of using reliability analysis as a tool for performing condition assessments and service life predictions of steel containments and liners. Mathematical models that describe time-dependent changes in steel due to aggressive environmental factors are identified, and statistical data supporting the use of these models in time-dependent reliability analysis are summarized. The analysis of steel containment fragility is described, and simple illustrations of the impact on reliability of structural degradation are provided. The role of nondestructive evaluation in time-dependent reliability analysis, both in terms of defect detection and sizing, is examined. A Markov model provides a tool for accounting for time-dependent changes in damage condition of a structural component or system. 151 refs.

  14. History of ultrahigh carbon steels

    SciTech Connect

    Wadsworth, J.; Sherby, O.D.

    1997-06-20

    The history and development of ultrahigh carbon steels (i.e., steels containing between 1 and 2.l percent C and now known as UHCS) are described. The early use of steel compositions containing carbon contents above the eutectoid level is found in ancient weapons from around the world. For example, both Damascus and Japanese sword steels are hypereutectoid steels. Their manufacture and processing is of interest in understanding the role of carbon content in the development of modern steels. Although sporadic examples of UHCS compositions are found in steels examined in the early part of this century, it was not until the mid-1970s that the modern study began. This study had its origin in the development of superplastic behavior in steels and the recognition that increasing the carbon content was of importance in developing that property. The compositions that were optimal for superplasticity involved the development of steels that contained higher carbon contents than conventional modern steels. It was discovered, however, that the room temperature properties of these compositions were of interest in their own right. Following this discovery, a period of intense work began on understanding their manufacture, processing, and properties for both superplastic forming and room temperature applications. The development of superplastic cast irons and iron carbides, as well as those of laminated composites containing UHCS, was an important part of this history.

  15. Propagation Speed in Myelinated Nerve

    PubMed Central

    Hardy, W. L.

    1973-01-01

    The Hodgkin-Huxley (H.H.) equations modified by Dodge for Rana pipiens myelinated nerve have been solved to determine how well the theory predicts the effects of changes of temperature and [Na+]0 on propagation. Conduction speed θ was found to have an approximately exponential dependence on temperature as was found experimentally, but the theoretical temperature coefficient (Q10) was low; 1.5 compared with the experimental finding of 2.95. θ was found to be a linear function of log ([Na+]0) in contrast to the experimental finding of a square root dependence on [Na+]0. θ is 50% greater at one-fourth normal [Na+]0 than the theory predicts. The difference between the theoretical θ([Na+]0) and the experimental θ([Na+]0) is probably due to an imprecisely known variation of parameters and not to a fundamental inadequacy of the theory. PMID:4542941

  16. Flame propagation through periodic vortices

    SciTech Connect

    Dold, J.W.; Kerr, O.S.; Nikolova, I.P.

    1995-02-01

    The discovery of a new class of Navier-Stokes solutions representing steady periodic stretched vortices offers a useful test-bed for examining interactions between flames and complex flow-fields. After briefly describing these vortex solutions and their wide-ranging parameterization in terms of wavelength and amplitude, this article examines their effect on flames of constant normal propagation speed as observed through numerical solutions of an eikonal equation. Over certain ranges of vortex amplitude and flame-speed, a corridor of enhanced flame passage is seen to be created as a leading flame-tip managers to leap-frog between successive vortices. However, for large enough amplitudes of vorticity or small enough flame-speeds, the flame fails to be able to benefit from the advection due to the vortices. It is shown that the leading tips of such flames are effectively trapped by the stretched vortices.

  17. Vibration Propagation in Spider Webs

    NASA Astrophysics Data System (ADS)

    Hatton, Ross; Otto, Andrew; Elias, Damian

    Due to their poor eyesight, spiders rely on web vibrations for situational awareness. Web-borne vibrations are used to determine the location of prey, predators, and potential mates. The influence of web geometry and composition on web vibrations is important for understanding spider's behavior and ecology. Past studies on web vibrations have experimentally measured the frequency response of web geometries by removing threads from existing webs. The full influence of web structure and tension distribution on vibration transmission; however, has not been addressed in prior work. We have constructed physical artificial webs and computer models to better understand the effect of web structure on vibration transmission. These models provide insight into the propagation of vibrations through the webs, the frequency response of the bare web, and the influence of the spider's mass and stiffness on the vibration transmission patterns. Funded by NSF-1504428.

  18. Supershells and propagating star formation

    NASA Technical Reports Server (NTRS)

    Maclow, M. M.; Mccray, R.; Kafatos, M.

    1986-01-01

    Correlated supernovae from an OB association can carve large cavities (greater than 100 pc) in the interstellar medium (ISM), and can punch holes completely through the disk of a spiral galaxy. Supernova remnant energy within such a cavity is thermalized before the shock reaches the supershell. Thus stellar wind theory may be used to model these superbubbles. We describe how the evolution of the superbubble depends on the density distribution of the galactic disk gas and the rate of supernovae in the OB association. At a radius of 100 to 300 pc, the supershell becomes gravitationally unstable, forming giant molecular clouds which are the sites for new star formation. This gravitational instability of the supershells provides a physical mechanism for propagating star formation and may account for the observation of bursts of star formation in galaxies.

  19. Theory of directional pulse propagation

    SciTech Connect

    Kinsler, P.; Radnor, S. B. P.; New, G. H. C.

    2005-12-15

    We construct combined electric and magnetic field variables which independently represent energy flows in the forward and backward directions, respectively, and use these to reformulate Maxwell's equations. These variables enable us to not only judge the effect and significance of backward-traveling field components, but also to discard them when appropriate. They thereby have the potential to simplify numerical simulations, leading to potential speed gains of up to 100% over standard finite difference time-domain (FDTD) or pseudospectral spatial-domain (PSSD) simulations. We present results for various illustrative situations, including an example application to second harmonic generation in periodically poled lithium niobate. These field variables are also used to derive both envelope equations useful for narrow-band pulse propagation, and a second order wave equation. Alternative definitions are also presented.

  20. Line of sight microwave propagation

    NASA Technical Reports Server (NTRS)

    Strohbehn, J. W.

    1969-01-01

    A review of the uses of microwave line-of-sight propagation in remote atmospheric probing is given. The review concentrates on use of the following types of measurements: (1) the use of total electrical path length for measuring average density and water vapor content; (2) the use of amplitude and phase fluctuations over a single path for determining the form of the turbulence spectrum; (3) the use of angle-of-arrival data for measuring the decrease in refractivity; and (4) the use of multiple-element receiving antennas in determining wind speed, atmospheric parameters, and atmospheric models. A review is given of the connection between microwave measurements and meteorological parameters, and the basic electromagnetic theory on which the analyses are made. A few suggestions for future work in these areas is given.

  1. Progress in front propagation research

    NASA Astrophysics Data System (ADS)

    Fort, Joaquim; Pujol, Toni

    2008-08-01

    We review the progress in the field of front propagation in recent years. We survey many physical, biophysical and cross-disciplinary applications, including reduced-variable models of combustion flames, Reid's paradox of rapid forest range expansions, the European colonization of North America during the 19th century, the Neolithic transition in Europe from 13 000 to 5000 years ago, the description of subsistence boundaries, the formation of cultural boundaries, the spread of genetic mutations, theory and experiments on virus infections, models of cancer tumors, etc. Recent theoretical advances are unified in a single framework, encompassing very diverse systems such as those with biased random walks, distributed delays, sequential reaction and dispersion, cohabitation models, age structure and systems with several interacting species. Directions for future progress are outlined.

  2. Probabilistic modeling of propagating explosions

    SciTech Connect

    Luck, L.B.; Eisenhawer, S.W.; Bott, T.F.

    1996-03-01

    Weapons containing significant quantities of high explosives (HE) are sometimes located in close proximity to one another. If an explosion occurs in a weapon, the possibility of propagation to one or more additional weapons may exist, with severe consequences possibly resulting. In the general case, a system of concern consists of multiple weapons and various other objects in a complex, three-dimensional geometry. In each weapon, HE is enclosed by (casing) materials that function as protection in the event of a neighbor detonation but become a source of fragments if the HE is initiated. The protection afforded by the casing means that only high-momentum fragments, which occur rarely, are of concern. These fragments, generated in an initial donor weapon are transported to other weapons either directly or by ricochet. Interaction of a fragment with an acceptor weapon can produce a reaction in the acceptor HE and result in a second detonation. In this paper we describe a comprehensive methodology to estimate the probability of various consequences for fragment-induced propagating detonations in arrays of weapons containing HE. Analysis of this problem requires an approach that can both define the circumstances under which rare events can occur and calculate the probability of such occurrences. Our approach is based on combining process tree methodology with Monte Carlo transport simulation. Our Monte Carlo technique very effectively captures important features of these differences. Process tree methodology is described and its use is discussed for a simplified problem and to illustrate the power of Monte Carlo simulation in estimating fragment-induced detonation of an acceptor weapon.

  3. Near-neutral pH SCC in pipelines: Effects of pressure fluctuations on crack propagation

    SciTech Connect

    Beavers, J.A.; Jaake, C.E.

    1998-12-31

    Currently, there is a poor understanding of the effects of pressure related parameters (operating pressure, pressure fluctuations, and hydrostatic testings) on external stress corrosion crack propagation in pipelines in near-neutral-pH environments. A better definition of the role of these parameters on crack propagation is needed to aid in the prediction of crack growth rates on operating pipelines and to develop strategies to mitigate this form of cracking. The objective of the research described in this paper was to determine the roles and synergistic effects of operating pressure, pressure fluctuations, and hydrostatic testing on crack growth in line pipe steels in a near-neutral-pH SCC environment. All testing was performed on one X-65 line pipe steel in a near-neutral-pH cracking environment, designated NS4. Fatigue precracked compact-type specimens of the line pipe steel were cyclically loaded while immersed in the cracking environment. The desired loading regime was applied using a servo-hydraulic tensile testing machine. Crack growth was monitored using the electric potential drop technique. The loading conditions applied to the specimen were related to field conditions using the J-integral parameter. It was found that the prior load history applied to the specimens had a significant effect on crack growth behavior. Overloading inhibited crack growth while unloading stimulated crack growth. Hydrostatic testing, which combines overloading and unloading, caused some crack extension but reduced the crack velocity.

  4. Behavior of stainless steels in pressurized water reactor primary circuits

    NASA Astrophysics Data System (ADS)

    Féron, D.; Herms, E.; Tanguy, B.

    2012-08-01

    Stainless steels are widely used in primary circuits of pressurized water reactors (PWRs). Operating experience with the various grades of stainless steels over several decades of years has generally been excellent. Nevertheless, stress corrosion failures have been reported in few cases. Two main factors contributing to SCC susceptibility enhancement are investigated in this study: cold work and irradiation. Irradiation is involved in the stress corrosion cracking and corrosion of in-core reactor components in PWR environment. Irradiated assisted stress corrosion cracking (IASCC) is a complex and multi-physics phenomenon for which a predictive modeling able to describe initiation and/or propagation is not yet achieved. Experimentally, development of initiation smart tests and of in situ instrumentation, also in nuclear reactors, is an important axis in order to gain a better understanding of IASCC kinetics. A strong susceptibility for SCC of heavily cold worked austenitic stainless steels is evidenced in hydrogenated primary water typical of PWRs. It is shown that for a given cold-working procedure, SCC susceptibility of austenitic stainless steels materials increases with increasing cold-work. Results have shown also strong influences of the cold work on the oxide layer composition and of the maximum stress on the time to fracture.

  5. Overview of near millimeter wave propagation

    NASA Astrophysics Data System (ADS)

    Flood, W. A.

    1981-02-01

    Near millimeter wave (NMMW) propagation problems are divided into three classes: propagation through homogeneous, turbid, and turbulent atmospheres. These classical forms include anomalous water vapor absorption in a homogeneous atmosphere as well as scintillation phenomena associated with propagation through severe weather and 'dirty battlefield' environments. Examples of the existing, inadequate, scintillation data base are given and the lack of supporting meteorological data noted. Carefully designed NMMW scintillation experiments with equally carefully designed micro-meteorological support are needed.

  6. Wave propagation in solids and fluids

    SciTech Connect

    Davis, J. L.

    1988-01-01

    The fundamental principles of mathematical analysis for wave phenomena in gases, solids, and liquids are presented in an introduction for scientists and engineers. Chapters are devoted to oscillatory phenomena, the physics of wave propagation, partial differential equations for wave propagation, transverse vibration of strings, water waves, and sound waves. Consideration is given to the dynamics of viscous and inviscid fluids, wave propagation in elastic media, and variational methods in wave phenomena. 41 refs.

  7. 46 CFR 59.20-1 - Carbon-steel or alloy-steel castings.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 2 2013-10-01 2013-10-01 false Carbon-steel or alloy-steel castings. 59.20-1 Section 59... BOILERS, PRESSURE VESSELS AND APPURTENANCES Welding Repairs to Castings § 59.20-1 Carbon-steel or alloy-steel castings. Defects in carbon-steel or alloy-steel castings may be repaired by welding. The...

  8. 46 CFR 59.20-1 - Carbon-steel or alloy-steel castings.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 2 2012-10-01 2012-10-01 false Carbon-steel or alloy-steel castings. 59.20-1 Section 59... BOILERS, PRESSURE VESSELS AND APPURTENANCES Welding Repairs to Castings § 59.20-1 Carbon-steel or alloy-steel castings. Defects in carbon-steel or alloy-steel castings may be repaired by welding. The...

  9. 46 CFR 59.20-1 - Carbon-steel or alloy-steel castings.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Carbon-steel or alloy-steel castings. 59.20-1 Section 59... BOILERS, PRESSURE VESSELS AND APPURTENANCES Welding Repairs to Castings § 59.20-1 Carbon-steel or alloy-steel castings. Defects in carbon-steel or alloy-steel castings may be repaired by welding. The...

  10. 46 CFR 59.20-1 - Carbon-steel or alloy-steel castings.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 2 2011-10-01 2011-10-01 false Carbon-steel or alloy-steel castings. 59.20-1 Section 59... BOILERS, PRESSURE VESSELS AND APPURTENANCES Welding Repairs to Castings § 59.20-1 Carbon-steel or alloy-steel castings. Defects in carbon-steel or alloy-steel castings may be repaired by welding. The...

  11. 46 CFR 59.20-1 - Carbon-steel or alloy-steel castings.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 2 2014-10-01 2014-10-01 false Carbon-steel or alloy-steel castings. 59.20-1 Section 59... BOILERS, PRESSURE VESSELS AND APPURTENANCES Welding Repairs to Castings § 59.20-1 Carbon-steel or alloy-steel castings. Defects in carbon-steel or alloy-steel castings may be repaired by welding. The...

  12. Monitoring microstructural evolution in irradiated steel with second harmonic generation

    SciTech Connect

    Matlack, Kathryn H.; Kim, Jin-Yeon; Jacobs, Laurence J.; Wall, James J.; Qu, Jianmin

    2015-03-31

    Material damage in structural components is driven by microstructural evolution that occurs at low length scales and begins early in component life. In metals, these microstructural features are known to cause measurable changes in the acoustic nonlinearity parameter. Physically, the interaction of a monochromatic ultrasonic wave with microstructural features such as dislocations, precipitates, and vacancies, generates a second harmonic wave that is proportional to the acoustic nonlinearity parameter. These nonlinear ultrasonic techniques thus have the capability to evaluate initial material damage, particularly before crack initiation and propagation occur. This paper discusses how the nonlinear ultrasonic technique of second harmonic generation can be used as a nondestructive evaluation tool to monitor microstructural changes in steel, focusing on characterizing neutron radiation embrittlement in nuclear reactor pressure vessel steels. Current experimental evidence and analytical models linking microstructural evolution with changes in the acoustic nonlinearity parameter are summarized.

  13. Nanoprecipitates in Steels

    SciTech Connect

    Schneibel, Joachim H; Lu, Zhao Ping; Shim, Sang Hoon

    2007-01-01

    The creep strength of ferritic steels can be substantially improved by the incorporation of a high number density of nano-scale dispersoids. Examples for such alloys are the oxide dispersion strengthened steels MA956, MA957, and PM2000. The dispersoids in these steels contain Y and Ti, or Y and Al. They can be as small as a few nanometers in size. Processing is traditionally carried out by mechanical alloying of elemental or pre-alloyed powders mixed with Y{sub 2}O{sub 3} powder. The goal of the present research is to identify alternative ways of producing ultrafine dispersoids. One possible way is internal oxidation, in which reactive elements dissolved in a metallic matrix are selectively oxidized. Internal oxidation experiments were carried out with Fe-Y, Fe-Ti-Y, and Fe-Al-Y precursors. Microstructural analysis showed that dispersoid dimensions as small as 10 nm could be achieved. Atomized Fe-0.25 at% Y powder was internally oxidized and consolidated by hot forging. An increase in the high-temperature creep strength by {approx} 20% was observed. Since it is likely that the composition of the precursor alloys is crucial for maximizing the number density and thermal stability of the oxides, experiments allowing the rapid screening of different compositions have been initiated.

  14. Nanoprecipitates in Steels

    SciTech Connect

    Schneibel, Joachim H; Kad, Bimal

    2008-01-01

    The creep strength of ferritic steels can be substantially improved by the incorporation of a high number density of nano-scale dispersoids. Examples for such alloys are the oxide dispersion strengthened steels MA956, MA957, and PM2000. The dispersoids in these steels contain Y and Ti, or Y and Al. They can be as small as a few nanometers in size. Processing is traditionally carried out by mechanical alloying of elemental or pre-alloyed powders mixed with Y{sub 2}O{sub 3} powder. The goal of the present research is to identify alternative ways of producing ultrafine dispersoids. One possible way is internal oxidation, in which reactive elements dissolved in a metallic matrix are selectively oxidized. Internal oxidation experiments were carried out with Fe-Y, Fe-Ti-Y, and Fe-Al-Y precursors. Microstructural analysis showed that dispersoid dimensions as small as 10 nm could be achieved. Atomized Fe-0.25 at% Y powder was internally oxidized and consolidated by hot forging. An increase in the high-temperature creep strength by {approx} 20% was observed. Since it is likely that the composition of the precursor alloys is crucial for maximizing the number density and thermal stability of the oxides, experiments allowing the rapid screening of different compositions have been initiated.

  15. Stainless Steel Permeability

    SciTech Connect

    Buchenauer, Dean A.; Karnesky, Richard A.

    2015-09-01

    An understanding of the behavior of hydrogen isotopes in materials is critical to predicting tritium transport in structural metals (at high pressure), estimating tritium losses during production (fission environment), and predicting in-vessel inventory for future fusion devices (plasma driven permeation). Current models often assume equilibrium diffusivity and solubility for a class of materials (e.g. stainless steels or aluminum alloys), neglecting trapping effects or, at best, considering a single population of trapping sites. Permeation and trapping studies of the particular castings and forgings enable greater confidence and reduced margins in the models. For FY15, we have continued our investigation of the role of ferrite in permeation for steels of interest to GTS, through measurements of the duplex steel 2507. We also initiated an investigation of the permeability in work hardened materials, to follow up on earlier observations of unusual permeability in a particular region of 304L forgings. Samples were prepared and characterized for ferrite content and coated with palladium to prevent oxidation. Issues with the poor reproducibility of measurements at low permeability were overcome, although the techniques in use are tedious. Funding through TPBAR and GTS were secured for a research grade quadrupole mass spectrometer (QMS) and replacement turbo pumps, which should improve the fidelity and throughput of measurements in FY16.

  16. Quench propagation velocity for highly stabilized conductors

    SciTech Connect

    Mints, R.G. |; Ogitsu, T. |; Devred, A.

    1995-05-01

    Quench propagation velocity in conductors having a large amount of stabilizer outside the multifilamentary area is considered. It is shown that the current redistribution process between the multifilamentary area and the stabilizer can strongly effect the quench propagation. A criterion is derived determining the conditions under which the current redistribution process becomes significant, and a model of effective stabilizer area is suggested to describe its influence on the quench propagation velocity. As an illustration, the model is applied to calculate the adiabatic quench propagation velocity for a conductor geometry with a multifilamentary area embedded inside the stabilizer.

  17. Neural network construction via back-propagation

    SciTech Connect

    Burwick, T.T.

    1994-06-01

    A method is presented that combines back-propagation with multi-layer neural network construction. Back-propagation is used not only to adjust the weights but also the signal functions. Going from one network to an equivalent one that has additional linear units, the non-linearity of these units and thus their effective presence is then introduced via back-propagation (weight-splitting). The back-propagated error causes the network to include new units in order to minimize the error function. We also show how this formalism allows to escape local minima.

  18. Summary of the First ACTS Propagation Workshop

    NASA Technical Reports Server (NTRS)

    Rogers, David V.

    1990-01-01

    The first Advanced Communications Technology Satellite (ACTS) Propagation Studies Workshop (APSW I), organized by NASA/Jet Propulsion Laboratory (JPL) to plan propagation experiments and studies with NASA's ACTS, convened in Santa Monica, California, during November 28 and 29, 1989. The objectives of APSW I were to identify general and ACTS-related propagation needs, and to prepare recommendations for a study plan incorporating scientific and systems requirements related to deployment of 8 to 10 propagation terminals in the USA in support of ACTS experimental activities. A summary of workshop activities is given.

  19. GALPROP: New Developments in CR Propagation Code

    NASA Technical Reports Server (NTRS)

    Moskalenko, I. V.; Jones, F. C.; Mashnik, S. G.; Strong, A. W.; Ptuskin, V. S.

    2003-01-01

    The numerical Galactic CR propagation code GALPROP has been shown to reproduce simultaneously observational data of many kinds related to CR origin and propagation. It has been validated on direct measurements of nuclei, antiprotons, electrons, positrons as well as on astronomical measurements of gamma rays and synchrotron radiation. Such data provide many independent constraints on model parameters while revealing some contradictions in the conventional view of Galactic CR propagation. Using a new version of GALPROP we study new effects such as processes of wave-particle interactions in the interstellar medium. We also report about other developments in the CR propagation code.

  20. Specific Features of the Nucleation and Growth of Fatigue Cracks in Steel under Cyclic Dynamic Compression

    NASA Astrophysics Data System (ADS)

    Popelyukh, A. I.; Popelyukh, P. A.; Bataev, A. A.; Nikulina, A. A.; Smirnov, A. I.

    2016-03-01

    The processes of the fracture of 40Kh and U8 steels under cyclic dynamic compression are studied. It has been found that the main cause for the fracture of the cyclically compressed specimens is the propagation of cracks due to the effect of residual tensile stresses, which arise near the tips of the cracks at the stage of the unloading of the specimens. The growth rate of a crack has the maximum value at the initial stage of its propagation in the vicinity of the stress concentrator. As the crack propagates deep into the specimen, its growth rate decreases and depends only slightly on the real cross section of the specimen. The model of the process of the fatigue fracture of the steels under dynamic loading by a cyclically varied compressive force is proposed. It has been found that the high fatigue endurance is provided by tempering at 200°C for the 40Kh steel and at 300°C for the U8 steel.

  1. Factors affecting stress assisted corrosion cracking of carbon steel under industrial boiler conditions

    NASA Astrophysics Data System (ADS)

    Yang, Dong

    Failure of carbon steel boiler tubes from waterside has been reported in the utility boilers and industrial boilers for a long time. In industrial boilers, most waterside tube cracks are found near heavy attachment welds on the outer surface and are typically blunt, with multiple bulbous features indicating a discontinuous growth. These types of tube failures are typically referred to as stress assisted corrosion (SAC). For recovery boilers in the pulp and paper industry, these failures are particularly important as any water leak inside the furnace can potentially lead to smelt-water explosion. Metal properties, environmental variables, and stress conditions are the major factors influencing SAC crack initation and propagation in carbon steel boiler tubes. Slow strain rate tests (SSRT) were conducted under boiler water conditions to study the effect of temperature, oxygen level, and stress conditions on crack initation and propagation on SA-210 carbon steel samples machined out of boiler tubes. Heat treatments were also performed to develop various grain size and carbon content on carbon steel samples, and SSRTs were conducted on these samples to examine the effect of microstructure features on SAC cracking. Mechanisms of SAC crack initation and propagation were proposed and validated based on interrupted slow strain tests (ISSRT). Water chemistry guidelines are provided to prevent SAC and fracture mechanics model is developed to predict SAC failure on industrial boiler tubes.

  2. Process for dezincing galvanized steel

    DOEpatents

    Morgan, William A.; Dudek, Frederick J.; Daniels, Edward J.

    1998-01-01

    A process for removing zinc from galvanized steel. The galvanized steel is immersed in an electrolyte containing at least about 15% by weight of sodium or potassium hydroxide and having a temperature of at least about 75.degree. C. and the zinc is galvanically corroded from the surface of the galvanized steel. The material serving as the cathode is principally a material having a standard electrode potential which is intermediate of the standard electrode potentials of zinc and cadmium in the electrochemical series. The corrosion rate may be accelerated by (i) increasing the number density of corrosion sites in the galvanized steel by mechanically abrading or deforming the galvanized steel, (ii) heating the galvanized steel to form an alloy of zinc on the surface of the galvanized steel, (iii) mixing the galvanized steel with a material having a standard electrode potential which is intermediate of the standard electrode potentials of zinc and cadmium in the electrochemical series, or (iv) moving the galvanized steel relative to itself and to the electrolyte while immersed in the electrolyte.

  3. High strength, tough alloy steel

    DOEpatents

    Thomas, Gareth; Rao, Bangaru V. N.

    1979-01-01

    A high strength, tough alloy steel is formed by heating the steel to a temperature in the austenite range (1000.degree.-1100.degree. C.) to form a homogeneous austenite phase and then cooling the steel to form a microstructure of uniformly dispersed dislocated martensite separated by continuous thin boundary films of stabilized retained austenite. The steel includes 0.2-0.35 weight % carbon, at least 1% and preferably 3-4.5% chromium, and at least one other substitutional alloying element, preferably manganese or nickel. The austenite film is stable to subsequent heat treatment as by tempering (below 300.degree. C.) and reforms to a stable film after austenite grain refinement.

  4. Process for dezincing galvanized steel

    DOEpatents

    Morgan, W.A.; Dudek, F.J.; Daniels, E.J.

    1998-07-14

    A process is described for removing zinc from galvanized steel. The galvanized steel is immersed in an electrolyte containing at least about 15% by weight of sodium or potassium hydroxide and having a temperature of at least about 75 C and the zinc is galvanically corroded from the surface of the galvanized steel. The material serving as the cathode is principally a material having a standard electrode potential which is intermediate of the standard electrode potentials of zinc and cadmium in the electrochemical series. The corrosion rate may be accelerated by (1) increasing the number density of corrosion sites in the galvanized steel by mechanically abrading or deforming the galvanized steel, (2) heating the galvanized steel to form an alloy of zinc on the surface of the galvanized steel, (3) mixing the galvanized steel with a material having a standard electrode potential which is intermediate of the standard electrode potentials of zinc and cadmium in the electrochemical series, or (4) moving the galvanized steel relative to itself and to the electrolyte while immersed in the electrolyte. 1 fig.

  5. Induction heat treatment of steel

    SciTech Connect

    Semiatin, S.L.; Stutz, D.E.

    1985-01-01

    This book discusses the induction heating. After reviewing heat treating operations for steel and the principles of the heat treatment of steel, an overview of induction heat treating is provided. Next, consideration is given to equipment and equipment selection, coil design, power requirements and temperature control. A discussion of surface and through hardening of steel is provided, including information on frequency and power selection and quenching apparatus. Tempering is considered, followed by information on control of residual stresses, cracking, temper brittleness and the important metallurgical and hardness differences between induction and furnace treated steel.

  6. Activation response of martensitic steels

    SciTech Connect

    Forty, C.B.A.

    1997-09-01

    A hypothetical martensitic steel has been compositionally designed in order to optimize both metallurgical and reduced activation properties. When compared with two other martensitic steels, its activation characteristics are shown to be superior for all activation indices examined. However, these excellent properties are found to be due to the assumed absence of deleterious tramp impurities. When limiting impurity concentrations are determined for the hypothetical steel, they are found to be extremely stringent, and wholly unachievable using industrial scale production methods. It is concluded that only slight improvements can be made to currently available low activation martensitic steels to reduce residual activity responses further. 26 refs., 1 fig., 2 tabs.

  7. Activation Response of Martensitic Steels

    NASA Astrophysics Data System (ADS)

    Forty, C. B. A.

    1997-09-01

    A hypothetical martensitic steel has been compositionally designed in order to optimize both metallurgical and reduced activation properties. When compared with two other martensitic steels, its activation characteristics are shown to be superior for all activation indices examined. However, these excellent properties are found to be due to the assumed absence of deleterious tramp impurities. When limiting impurity concentrations are determined for the hypothetical steel, they are found to be extremely stringent, and wholly unachievable using industrial scale production methods. It is concluded that only slight improvements can be made to currently available low activation martensitic steels to reduce residual activity responses further.

  8. Explosion propagation in inert porous media.

    PubMed

    Ciccarelli, G

    2012-02-13

    Porous media are often used in flame arresters because of the high surface area to volume ratio that is required for flame quenching. However, if the flame is not quenched, the flow obstruction within the porous media can promote explosion escalation, which is a well-known phenomenon in obstacle-laden channels. There are many parallels between explosion propagation through porous media and obstacle-laden channels. In both cases, the obstructions play a duel role. On the one hand, the obstruction enhances explosion propagation through an early shear-driven turbulence production mechanism and then later by shock-flame interactions that occur from lead shock reflections. On the other hand, the presence of an obstruction can suppress explosion propagation through momentum and heat losses, which both impede the unburned gas flow and extract energy from the expanding combustion products. In obstacle-laden channels, there are well-defined propagation regimes that are easily distinguished by abrupt changes in velocity. In porous media, the propagation regimes are not as distinguishable. In porous media the entire flamefront is affected, and the effects of heat loss, turbulence and compressibility are smoothly blended over most of the propagation velocity range. At low subsonic propagation speeds, heat loss to the porous media dominates, whereas at higher supersonic speeds turbulence and compressibility are important. This blending of the important phenomena results in no clear transition in propagation mechanism that is characterized by an abrupt change in propagation velocity. This is especially true for propagation velocities above the speed of sound where many experiments performed with fuel-air mixtures show a smooth increase in the propagation velocity with mixture reactivity up to the theoretical detonation wave velocity. PMID:22213663

  9. Effects of transformed ferrite growth on the tensile fracture characteristics of a dual-phase steel

    NASA Astrophysics Data System (ADS)

    Jeong, W. C.; Kim, C. H.

    1988-02-01

    The effects of transformed ferrite growth on the tensile fracture characteristics of a dual-phase steel were investigated by observing crack initiation, propagation, and fracture behaviors. Crack initiation occurred by decohesion between martensite and ferrite. However, cracks propagated along the ferrite-martensite interface in a high temperature quenched specimen, whereas in specimens quenched from lower temperature cracks propagated into the martensite particle. Tensile fracture behaviors were not strongly influenced by the cooling rate. At both cooling rates of 5.6 and 0.1 °C/sec, specimens quenched from high temperature fractured by partially brittle fracture mode, but fracture mode changed to ductile mode as the quenching temperature decreased. The effect of transformed ferrite on the fracture mode was not substantially different from that of retained ferrite. However, the crack initiation and propagation was influenced by the variation in martensite distribution caused by different growth behavior of transformed ferrite.

  10. Elevation, looking SE. Concrete and steel bridge with exposed steel ...

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

    Elevation, looking SE. Concrete and steel bridge with exposed steel frame is the central of three bridges crossing Brush Street between east Baltimore and Piquette. The bridge links Old Lake Shore and Michigan Central Main Line on the western side to a New York Central siding on the eastern side - Railroad Overpass, East Milwaukee & Hastings Avenues, Detroit, MI

  11. Propagation modeling for land mobile satellite systems

    NASA Technical Reports Server (NTRS)

    Barts, R. Michael; Stutzman, Warren L.

    1988-01-01

    A simplified empirical model for predicting primary fade statistics for a vegetatively shadowed mobile satellite signal is presented, and predictions based on the model are presented using propagation parameter values from experimental data. Results from the empirical model are used to drive a propagation simulator to produce the secondary fade statistics of average fade duration.

  12. Managing Data From Signal-Propagation Experiments

    NASA Technical Reports Server (NTRS)

    Kantak, Anil V.

    1992-01-01

    Report dicusses system for management of data from Pilot Field Experiment (PiFEx) program, which consists of series of experiments on propagation of signals from transmitter at one fixed location to transponder on tower at another fixed location and from transponder to mobile receiver in van. Purpose of experiments to simulate signal-propagation conditions of land-mobile/satellite communication system.

  13. Steps toward quantitative infrasound propagation modeling

    NASA Astrophysics Data System (ADS)

    Waxler, Roger; Assink, Jelle; Lalande, Jean-Marie; Velea, Doru

    2016-04-01

    Realistic propagation modeling requires propagation models capable of incorporating the relevant physical phenomena as well as sufficiently accurate atmospheric specifications. The wind speed and temperature gradients in the atmosphere provide multiple ducts in which low frequency sound, infrasound, can propagate efficiently. The winds in the atmosphere are quite variable, both temporally and spatially, causing the sound ducts to fluctuate. For ground to ground propagation the ducts can be borderline in that small perturbations can create or destroy a duct. In such cases the signal propagation is very sensitive to fluctuations in the wind, often producing highly dispersed signals. The accuracy of atmospheric specifications is constantly improving as sounding technology develops. There is, however, a disconnect between sound propagation and atmospheric specification in that atmospheric specifications are necessarily statistical in nature while sound propagates through a particular atmospheric state. In addition infrasonic signals can travel to great altitudes, on the order of 120 km, before refracting back to earth. At such altitudes the atmosphere becomes quite rare causing sound propagation to become highly non-linear and attenuating. Approaches to these problems will be presented.

  14. Propagation of almond rootstocks and trees

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Millions of almond trees in production in California and elsewhere were propagated by nurseries using the grafting technique called budding. This gives a uniform orchard and allows the grower to select nut cultivar (scion) and rootstock combinations. Grafting is a form of clonal propagation and resu...

  15. Diagnostics for the ATA beam propagation experiments

    SciTech Connect

    Fessenden, T.J.; Atchison, W.L.; Barletta, W.A.

    1981-11-01

    This report contains a discussion of the diagnostics required for the beam propagation experiment to be done with the ATA accelerator. Included are a list of the diagnostics needed; a description of the ATA experimental environment; the status of beam diagnostics available at Livermore including recent developments, and a prioritized list of accelerator and propagation diagnostics under consideration or in various stages of development.

  16. Vehicular sources in acoustic propagation experiments

    NASA Technical Reports Server (NTRS)

    Prado, Gervasio; Fitzgerald, James; Arruda, Anthony; Parides, George

    1990-01-01

    One of the most important uses of acoustic propagation models lies in the area of detection and tracking of vehicles. Propagation models are used to compute transmission losses in performance prediction models and to analyze the results of past experiments. Vehicles can also provide the means for cost effective experiments to measure acoustic propagation conditions over significant ranges. In order to properly correlate the information provided by the experimental data and the propagation models, the following issues must be taken into consideration: the phenomenology of the vehicle noise sources must be understood and characterized; the vehicle's location or 'ground truth' must be accurately reproduced and synchronized with the acoustic data; and sufficient meteorological data must be collected to support the requirements of the propagation models. The experimental procedures and instrumentation needed to carry out propagation experiments are discussed. Illustrative results are presented for two cases. First, a helicopter was used to measure propagation losses at a range of 1 to 10 Km. Second, a heavy diesel-powered vehicle was used to measure propagation losses in the 300 to 2200 m range.

  17. Uncertainty Propagation in an Ecosystem Nutrient Budget.

    EPA Science Inventory

    New aspects and advancements in classical uncertainty propagation methods were used to develop a nutrient budget with associated error for a northern Gulf of Mexico coastal embayment. Uncertainty was calculated for budget terms by propagating the standard error and degrees of fr...

  18. Nondestructive evaluation of pyroshock propagation using hydrocodes

    NASA Astrophysics Data System (ADS)

    Lee, Juho; Hwang, Dae-Hyeon; Jang, Jae-Kyeong; Lee, Jung-Ryul; Han, Jae-Hung

    2016-04-01

    Pyroshock or pyrotechnic shock generated by explosive events of pyrotechnic devices can induce fatal failures in electronic payloads. Therefore, understanding and estimation of pyroshock propagation through complex structures are necessary. However, an experimental approach using real pyrotechnic devices is quite burdensome because pyrotechnic devices can damage test structures and newly manufactured test structures are necessary for each experiment. Besides, pyrotechnic experiments are quite expensive, time-consuming, and dangerous. Consequently, nondestructive evaluation (NDE) of pyroshock propagation without using real pyrotechnic devices is necessary. In this study, nondestructive evaluation technique for pyroshock propagation estimation using hydrocodes is proposed. First, pyroshock propagation is numerically analyzed using AUTODYN, a commercial hydrocodes. Hydrocodes can handle stress wave propagation including elastic, plastic, and shock wave in the time domain. Test structures are modeled and pyroshock time history is applied to where the pyroshock propagation originates. Numerical NDE results of pyroshock propagation on test structures are analyzed in terms of acceleration time histories and acceleration shock response spectra (SRS) results. To verify the proposed numerical methodology, impact tests using airsoft gun are performed. The numerical analysis results for the impact tests are compared with experimental results and they show good agreements. The proposed numerical techniques enable us to nondestructively characterize pyroshock propagation.

  19. Propagation of a fluidization - combustion wave

    SciTech Connect

    Pron, G.P.; Gusachenko, L.K.; Zarko, V.E.

    1994-05-01

    A fluidization-combustion wave propagating through a fixed and initially cool bed was created by igniting coal at the top surface of the bed. The proposed physical interpretation of the phenomenon is in qualitative agreement with the experimental dependences of the characteristics of the process on determining parameters. A kindling regime with forced wave propagation is suggested.

  20. Rapid vegetative propagation method for carob

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Many fruit species are propagated by vegetative methods such as budding, grafting, cutting, suckering, layering etc. to avoid heterozygosity. Carob trees (Ceratonia siliqua L.) are of highly economical value and it is among the most difficult-to-propagate fruit species. In this study, air-layering p...

  1. Propagation testing multi-cell batteries.

    SciTech Connect

    Orendorff, Christopher J.; Lamb, Joshua; Steele, Leigh Anna Marie; Spangler, Scott Wilmer

    2014-10-01

    Propagation of single point or single cell failures in multi-cell batteries is a significant concern as batteries increase in scale for a variety of civilian and military applications. This report describes the procedure for testing failure propagation along with some representative test results to highlight the potential outcomes for different battery types and designs.

  2. 3D Elastic Seismic Wave Propagation Code

    Energy Science and Technology Software Center (ESTSC)

    1998-09-23

    E3D is capable of simulating seismic wave propagation in a 3D heterogeneous earth. Seismic waves are initiated by earthquake, explosive, and/or other sources. These waves propagate through a 3D geologic model, and are simulated as synthetic seismograms or other graphical output.

  3. S-Band propagation measurements

    NASA Technical Reports Server (NTRS)

    Briskman, Robert D.

    1994-01-01

    A geosynchronous satellite system capable of providing many channels of digital audio radio service (DARS) to mobile platforms within the contiguous United States using S-band radio frequencies is being implemented. The system is designed uniquely to mitigate both multipath fading and outages from physical blockage in the transmission path by use of satellite spatial diversity in combination with radio frequency and time diversity. The system also employs a satellite orbital geometry wherein all mobile platforms in the contiguous United States have elevation angles greater than 20 deg to both of the diversity satellites. Since implementation of the satellite system will require three years, an emulation has been performed using terrestrial facilities in order to allow evaluation of DARS capabilities in advance of satellite system operations. The major objective of the emulation was to prove the feasibility of broadcasting from satellites 30 channels of CD quality programming using S-band frequencies to an automobile equipped with a small disk antenna and to obtain quantitative performance data on S-band propagation in a satellite spatial diversity system.

  4. Topographic effects on infrasound propagation.

    PubMed

    McKenna, Mihan H; Gibson, Robert G; Walker, Bob E; McKenna, Jason; Winslow, Nathan W; Kofford, Aaron S

    2012-01-01

    Infrasound data were collected using portable arrays in a region of variable terrain elevation to quantify the effects of topography on observed signal amplitude and waveform features at distances less than 25 km from partially contained explosive sources during the Frozen Rock Experiment (FRE) in 2006. Observed infrasound signals varied in amplitude and waveform complexity, indicating propagation effects that are due in part to repeated local maxima and minima in the topography on the scale of the dominant wavelengths of the observed data. Numerical simulations using an empirically derived pressure source function combining published FRE accelerometer data and historical data from Project ESSEX, a time-domain parabolic equation model that accounted for local terrain elevation through terrain-masking, and local meteorological atmospheric profiles were able to explain some but not all of the observed signal features. Specifically, the simulations matched the timing of the observed infrasound signals but underestimated the waveform amplitude observed behind terrain features, suggesting complex scattering and absorption of energy associated with variable topography influences infrasonic energy more than previously observed. PMID:22280569

  5. In vitro propagation of jojoba.

    PubMed

    Llorente, Berta E; Apóstolo, Nancy M

    2013-01-01

    Jojoba (Simmondsia chinensis (Link) Schn.) is a nontraditional crop in arid and semi-arid areas. Vegetative propagation can be achieved by layering, grafting, or rooting semi-hardwood cuttings, but the highest number of possible propagules is limited by the size of the plants and time of the year. Micropropagation is highly recommended strategy for obtaining jojoba elite clones. For culture initiation, single-node explants are cultivated on Murashige and Skoog medium (MS) supplemented with Gamborg's vitamins (B5), 11.1 μM BA (N(6)-benzyl-adenine), 0.5 μM IBA (indole-3-butyric acid), and 1.4 μM GA(3) (gibberellic acid). Internodal and apical cuttings proliferate on MS medium containing B5 vitamins and 4.4 μM BA. Rooting is achieved on MS medium (half strength mineral salt) amended with B5 vitamins and 14.7 μM IBA during 7 days and transferred to develop in auxin-free rooting medium. Plantlets are acclimatized using a graduated humidity regime on soil: peat: perlite (5:1:1) substrate. This micropagation protocol produces large numbers of uniform plants from selected genotypes of jojoba. PMID:23179687

  6. Scaling analysis of affinity propagation.

    PubMed

    Furtlehner, Cyril; Sebag, Michèle; Zhang, Xiangliang

    2010-06-01

    We analyze and exploit some scaling properties of the affinity propagation (AP) clustering algorithm proposed by Frey and Dueck [Science 315, 972 (2007)]. Following a divide and conquer strategy we setup an exact renormalization-based approach to address the question of clustering consistency, in particular, how many cluster are present in a given data set. We first observe that the divide and conquer strategy, used on a large data set hierarchically reduces the complexity O(N2) to O(N((h+2)/(h+1))) , for a data set of size N and a depth h of the hierarchical strategy. For a data set embedded in a d -dimensional space, we show that this is obtained without notably damaging the precision except in dimension d=2 . In fact, for d larger than 2 the relative loss in precision scales such as N((2-d)/(h+1)d). Finally, under some conditions we observe that there is a value s* of the penalty coefficient, a free parameter used to fix the number of clusters, which separates a fragmentation phase (for ss*) of the underlying hidden cluster structure. At this precise point holds a self-similarity property which can be exploited by the hierarchical strategy to actually locate its position, as a result of an exact decimation procedure. From this observation, a strategy based on AP can be defined to find out how many clusters are present in a given data set. PMID:20866473

  7. Fatigue crack retardation of high strength steel in saltwater

    SciTech Connect

    Tokaji, K.; Ando, Z.; Imai, T.; Kojima, T.

    1983-04-01

    A high strength steel was studied in 3 percent saltwater to investigate the effects of a corrosive environment and sheer thickness on fatigue crack propagation behavior following the application of a single tensile overload. Experiments were carried out under sinusoidally varying loads at a load ratio of 0 and frequency of 10 H /SUB z/ . A single tensile overload was found to cause delayed retardation, and the crack propagation rate at first increased, followed by fairly rapid decrease to a minimum value and then increased gradually to its steady-state value, just as it did in air. The overload affected zone size and the retardation cycles increased with decreasing sheet thickness, just as they did in air. However, the zone size and the cycles were larger in 3 percent saltwater than in air. Since the crack propagation rates through the overload affected zone were not affected by the test environment, the longer retardation cycles in 3 percent saltwater were attributed to an enlargement of the overload affected zone size. The crack propagation behavior following the application of a single tensile overload in 3 percent saltwater was well explained by the crack closure concept.

  8. Liquid-metal-induced fracture mode of martensitic T91 steels

    SciTech Connect

    Martin, M.L.; Auger, T.; Johnson, Duane, Robertson, I.M.

    2012-04-04

    The liquid–metal-induced fracture mode of T91 martensitic steel was investigated by using transmission electron microscopy techniques to characterize the microstructure and crack network in specimens obtained from focused-ion beam machining at and immediately below the fracture surface. Contrary to previous claims of quasi-cleavage fracture, the dominant fracture mode is intergranular cracking at martensite laths and prior austenite grain boundaries. These fracture mode results clarify an outstanding issue in liquid–metal embrittlement of steels that generally occur in a heavily-deformed microstructure. Several cracks were arrested at intergranular carbides, suggesting a metallurgical strategy for impeding liquid–metal-induced crack propagation.

  9. Effects of microstructure banding on hydrogen assisted fatigue crack growth in X65 pipeline steels

    SciTech Connect

    Ronevich, Joseph A.; Somerday, Brian P.; San Marchi, Chris W.

    2015-09-10

    Banded ferrite-pearlite X65 pipeline steel was tested in high pressure hydrogen gas to evaluate the effects of oriented pearlite on hydrogen assisted fatigue crack growth. Test specimens were oriented in the steel pipe such that cracks propagated either parallel or perpendicular to the banded pearlite. The ferrite-pearlite microstructure exhibited orientation dependent behavior in which fatigue crack growth rates were significantly lower for cracks oriented perpendicular to the banded pearlite compared to cracks oriented parallel to the bands. Thus the reduction of hydrogen assisted fatigue crack growth across the banded pearlite is attributed to a combination of crack-tip branching and impeded hydrogen diffusion across the banded pearlite.

  10. Coupled Multi-Electrode Investigation of Crevice Corrosion of AISI 316 Stainless Steel

    SciTech Connect

    F. Bocher; F. Presuel-Moreno; N.D. Budinasky; J.R. Scully

    2006-06-23

    Close packed coupled multi-electrodes arrays (MEA) simulating a planar electrode were used to measure the current evolution as a function of position during initiation and propagation of crevice corrosion of AISI 316 stainless steel. Scaling laws derived from polarization data enabled the use of rescaled crevices providing spatial resolution. Crevice corrosion of AISI 316 stainless steel in 0.6 M NaCl at 50 C was found to initiate close to the crevice mouth and to spread inwards with time. The local crevice current density increased dramatically over a short period to reach a limiting value.

  11. Propagation of an atmospheric pressure plasma plume

    SciTech Connect

    Lu, X.; Xiong, Q.; Xiong, Z.; Hu, J.; Zhou, F.; Gong, W.; Xian, Y.; Zou, C.; Tang, Z.; Jiang, Z.; Pan, Y.

    2009-02-15

    The ''plasma bullet'' behavior of atmospheric pressure plasma plumes has recently attracted significant interest. In this paper, a specially designed plasma jet device is used to study this phenomenon. It is found that a helium primary plasma can propagate through the wall of a dielectric tube and keep propagating inside the dielectric tube (secondary plasma). High-speed photographs show that the primary plasma disappears before the secondary plasma starts to propagate. Both plumes propagate at a hypersonic speed. Detailed studies on the dynamics of the plasma plumes show that the local electric field induced by the charges on the surface of the dielectric tube plays an important role in the ignition of the secondary plasma. This indicates that the propagation of the plasma plumes may be attributed to the local electric field induced by the charges in the bulletlike plasma volume.

  12. Propagation prediction for the North Sea environment

    NASA Astrophysics Data System (ADS)

    Vieth, R.

    1989-09-01

    Evaporation ducting can have an important influence on the propagation of electromagnetic waves. The dependence of those ducting conditions on geographic location requires an estimate of occurrence and effects of ducting in various areas. Duct height statistics using long term statistical meteorological data in combination with propagation models are used for this purpose. Jeske's propagation measurements during 1961 at the German coast of the North Sea were taken and compared with the calculated results from the combination of the statistical weather data base and the propagation models, as well as another measurement program performed in Greece. A brief description of the models is followed by an example of the results of the Greek measurements. The German experimental data and duct height distributions for that region are described. Finally the results of measurements and calculations are discussed. A good agreement was found between measured propagation data and predictions based on climatological averages.

  13. Crack propagation driven by crystal growth

    SciTech Connect

    A. Royne; Paul Meaking; A. Malthe-Sorenssen; B. Jamtveit; D. K. Dysthe

    2011-10-01

    Crystals that grow in confinement may exert a force on their surroundings and thereby drive crack propagation in rocks and other materials. We describe a model of crystal growth in an idealized crack geometry in which the crystal growth and crack propagation are coupled through the stress in the surrounding bulk solid. Subcritical crack propagation takes place during a transient period, which may be very long, during which the crack velocity is limited by the kinetics of crack propagation. When the crack is sufficiently large, the crack velocity becomes limited by the kinetics of crystal growth. The duration of the subcritical regime is determined by two non-dimensional parameters, which relate the kinetics of crack propagation and crystal growth to the supersaturation of the fluid and the elastic properties of the surrounding material.

  14. Photodesorption from stainless steels

    NASA Technical Reports Server (NTRS)

    Mesarwi, A.; Ignatiev, A.

    1988-01-01

    The photodesorption by low-energy photons from three types of stainless steels is examined. For all these systems both CO and CO2 were observed to photodesorb with high yields: about 0.001 molecules/photon for CO2 and about 0.0001 molecules/photon for CO at 250 nm. The observed threshold energies were found to be the same for all systems at E0 = 2.92 eV for CO2 and E0 = 2.92-3.10 eV for CO.

  15. Switch to duplex stainless steels

    SciTech Connect

    Quik, J.M.A.; Geudeke, M.

    1994-11-01

    Duplex stainless steels contain approximately equal proportions of ferrite and austenite. These stainless steels have become an established material of construction in the chemical process industries (CPI). Duplexes offer benefits over austenitic stainless steels and carbon steels because of their higher strength, and good toughness and ductility, in combination with equivalent resistance to general corrosion, as well as better resistance to localized corrosion and stress corrosion cracking. Additionally, duplex materials have thermal-conductivity and thermal-expansion coefficients similar to those of ferritic materials, are tough at low (sub-zero) temperatures, and have a high resistance to erosion and abrasion. In some of the highly corrosive environments encountered in the CPI, the super duplex stainless steels offer cost-effective options not possible with the standard austenitic stainless steels. The initial applications were almost exclusively as heat exchanger tubing in water-cooled service. In recent times, duplex stainless steels have been used in the oil, gas, and chemical industries. Examples include service in sweet and mildly sour corrosive environments, on offshore platforms where weight savings can be realized, and as a replacement for standard austenitic stainless steel in chemical-processing plants.

  16. The industrial ecology of steel

    SciTech Connect

    Considine, Timothy J.; Jablonowski, Christopher; Considine, Donita M.M.; Rao, Prasad G.

    2001-03-26

    This study performs an integrated assessment of new technology adoption in the steel industry. New coke, iron, and steel production technologies are discussed, and their economic and environmental characteristics are compared. Based upon detailed plant level data on cost and physical input-output relations by process, this study develops a simple mathematical optimization model of steel process choice. This model is then expanded to a life cycle context, accounting for environmental emissions generated during the production and transportation of energy and material inputs into steelmaking. This life-cycle optimization model provides a basis for evaluating the environmental impacts of existing and new iron and steel technologies. Five different plant configurations are examined, from conventional integrated steel production to completely scrap-based operations. Two cost criteria are used to evaluate technology choice: private and social cost, with the latter including the environmental damages associated with emissions. While scrap-based technologies clearly generate lower emissions in mass terms, their emissions of sulfur dioxide and nitrogen oxides are significantly higher. Using conventional damage cost estimates reported in the literature suggests that the social costs associated with scrap-based steel production are slightly higher than with integrated steel production. This suggests that adopting a life-cycle viewpoint can substantially affect environmental assessment of new technologies. Finally, this study also examines the impacts of carbon taxes on steel production costs and technology choice.

  17. Microstructural changes induced near crack tip during corrosion fatigue tests in austenitic-ferritic steel.

    PubMed

    Gołebiowski, B; Swiatnicki, W A; Gaspérini, M

    2010-03-01

    Microstructural changes occurring during fatigue tests of austenitic-ferritic duplex stainless steel (DSS) in air and in hydrogen-generating environment have been investigated. Hydrogen charging of steel samples during fatigue crack growth (FCG) tests was performed by cathodic polarization of specimens in 0.1M H(2)SO(4) aqueous solution. Microstructural investigations of specimens after FCG tests were carried out using transmission electron microscopy to reveal the density and arrangement of dislocations formed near crack tip. To determine the way of crack propagation in the microstructure, electron backscatter diffraction investigations were performed on fatigue-tested samples in both kinds of environment. To reveal hydrogen-induced phase transformations the atomic force microscopy was used. The above investigations allowed us to define the character of fatigue crack propagation and microstructural changes near the crack tip. It was found that crack propagation after fatigue tests in air is accompanied with plastic deformation; a high density of dislocations is observed at large distance from the crack. After fatigue tests performed during hydrogen charging the deformed zone containing high density of dislocations is narrow compared to that after fatigue tests in air. It means that hydrogenation leads to brittle character of fatigue crack propagation. In air, fatigue cracks propagate mostly transgranularly, whereas in hydrogen-generating environment the cracks have mixed transgranular/interfacial character. PMID:20500395

  18. Fluctuation-controlled front propagation

    NASA Astrophysics Data System (ADS)

    Ridgway, Douglas Thacher

    1997-09-01

    the symmetry of the absorbing state, but which is unsuccessful at capturing the behavior of diffusion-limited growth. In an effort to find a simpler model system, we turned to modelling fitness increases in evolution. The work was motivated by an experiment on vesicular stomatitis virus, a short (˜9600bp) single-stranded RNA virus. A highly bottlenecked viral population increases in fitness rapidly until a certain point, after which the fitness increases at a slower rate. This is well modeled by a constant population reproducing and mutating on a smooth fitness landscape. Mean field theory of this system displays the same infinite propagation velocity blowup as mean field diffusion-limited aggregation. However, we have been able to make progress on a number of fronts. One is solving systems of moment equations, where a hierarchy of moments is truncated arbitrarily at some level. Good results for front propagation velocity are found with just two moments, corresponding to inclusion of the basic finite population clustering effect ignored by mean field theory. In addition, for small mutation rates, most of the population will be entirely on a single site or two adjacent sites, and the density of these cases can be described and solved. (Abstract shortened by UMI.)

  19. Ensemble modeling of CME propagation

    NASA Astrophysics Data System (ADS)

    Lee, C. O.; Arge, C. N.; Henney, C. J.; Odstrcil, D.; Millward, G. H.; Pizzo, V. J.

    2014-12-01

    The Wang-Sheeley-Arge(WSA)-Enlil-cone modeling system is used for making routine arrival time forecasts of the Earth-directed "halo" coronal mass ejections (CMEs), since they typically produce the most geoeffective events. A major objective of this work is to better understand the sensitivity of the WSA-Enlil modeling results to input model parameters and how these parameters contribute to the overall model uncertainty and performance. We present ensemble modeling results for a simple halo CME event that occurred on 15 February 2011 and a succession of three halo CME events that occurred on 2-4 August 2011. During this period the Solar TErrestrial RElations Observatory (STEREO) A and B spacecraft viewed the CMEs over the solar limb, thereby providing more reliable constraints on the initial CME geometries during the manual cone fitting process. To investigate the sensitivity of the modeled CME arrival times to small variations in the input cone properties, for each CME event we create an ensemble of numerical simulations based on multiple sets of cone parameters. We find that the accuracy of the modeled arrival times not only depends on the initial input CME geometry, but also on the reliable specification of the background solar wind, which is driven by the input maps of the photospheric magnetic field. As part of the modeling ensemble, we simulate the CME events using the traditional daily updated maps as well as those that are produced by the Air Force data Assimilative Photospheric flux Transport (ADAPT) model, which provide a more instantaneous snapshot of the photospheric field distribution. For the August 2011 events, in particular, we find that the accuracy in the arrival time predictions also depends on whether the cone parameters for all three CMEs are specified in a single WSA-Enlil simulation. The inclusion/exclusion of one or two of the preceding CMEs affects the solar wind conditions through which the succeeding CME propagates.

  20. Magnetoacoustic stress measurements in steel

    NASA Technical Reports Server (NTRS)

    Namkung, M.; Utrata, D.; Allison, S. G.; Heyman, J. S.

    1985-01-01

    Uniaxial stress effects on the low-field magnetoacoustic interaction have been studied using bulk compressional waves and Rayleigh surface waves in numerous steel samples having various impurity concentrations (Namkung et al., 1984). The results invariably showed that the initial slope of acoustic natural velocity variations, with respect to net induced magnetization parallel to the stress axis, is positive under tension and negative under compression. The results of current measurements in railroad rail steel having about 0.68 wt percent carbon content are typical for medium range carbon steels. The low-field natural velocity slope in this particular type of steel, which is almost zero when unstressed, becomes steeper with increased magnitude of stress in both directions. Hence, the nondestructive determination of the sign of residual stress in railroad wheels and rails is possible using this technique. This paper discusses the basic physical mechanism underlying the experimental observations and presents the results obtained in railroad rail steel.

  1. Mechanistic model of stress corrosion cracking (scc) of carbon steel in acidic solution with the presence of H2s

    NASA Astrophysics Data System (ADS)

    Asmara, Y. P.; Juliawati, A.; Sulaiman, A.; Jamiluddin

    2013-12-01

    In oil and gas industrial environments, H2S gas is one of the corrosive species which should be a main concern in designing infrastructure made of carbon steel. Combination between the corrosive environment and stress condition will cause degradation of carbon steel increase unpredictably due to their simultaneous effects. This paper will design a model that involves electrochemical and mechanical theories to study crack growth rate under presence of H2S gas. Combination crack and corrosion propagation of carbon steel, with different hydrogen concentration has been investigated. The results indicated that high concentration of hydrogen ions showed a higher crack propagation rate. The comparison between corrosion prediction models and corrosion model developed by researchers used to verify the model accuracy showed a good agreement.

  2. Analysis of fatigue, fatique-crack propagation, and fracture data. [design of metallic aerospace structural components

    NASA Technical Reports Server (NTRS)

    Jaske, C. E.; Feddersen, C. E.; Davies, K. B.; Rice, R. C.

    1973-01-01

    Analytical methods have been developed for consolidation of fatigue, fatigue-crack propagation, and fracture data for use in design of metallic aerospace structural components. To evaluate these methods, a comprehensive file of data on 2024 and 7075 aluminums, Ti-6A1-4V, and 300M and D6Ac steels was established. Data were obtained from both published literature and unpublished reports furnished by aerospace companies. Fatigue and fatigue-crack-propagation analyses were restricted to information obtained from constant-amplitude load or strain cycling of specimens in air at room temperature. Fracture toughness data were from tests of center-cracked tension panels, part-through crack specimens, and compact-tension specimens.

  3. Sensitivity Analysis and Uncertainty Propagation in a General-Purpose Thermal Analysis Code

    SciTech Connect

    Blackwell, Bennie F.; Dowding, Kevin J.

    1999-08-04

    Methods are discussed for computing the sensitivity of field variables to changes in material properties and initial/boundary condition parameters for heat transfer problems. The method we focus on is termed the ''Sensitivity Equation Method'' (SEM). It involves deriving field equations for sensitivity coefficients by differentiating the original field equations with respect to the parameters of interest and numerically solving the resulting sensitivity field equations. Uncertainty in the model parameters are then propagated through the computational model using results derived from first-order perturbation theory; this technique is identical to the methodology typically used to propagate experimental uncertainty. Numerical results are presented for the design of an experiment to estimate the thermal conductivity of stainless steel using transient temperature measurements made on prototypical hardware of a companion contact conductance experiment. Comments are made relative to extending the SEM to conjugate heat transfer problems.

  4. Effects of Microalloying on the Impact Toughness of Ultrahigh-Strength TRIP-Aided Martensitic Steels

    NASA Astrophysics Data System (ADS)

    Kobayashi, Junya; Ina, Daiki; Nakajima, Yuji; Sugimoto, Koh-ichi

    2013-11-01

    The effects of the addition of Cr, Mo, and/or Ni on the Charpy impact toughness of a 0.2 pct C-1.5 pct Si-1.5 pct Mn-0.05 pct Nb transformation-induced plasticity (TRIP)-aided steel with a lath-martensite structure matrix ( i.e., a TRIP-aided martensitic steel or TM steel) were investigated with the aim of using the steel in automotive applications. In addition, the relationship between the toughness of the various alloyed steels and their metallurgical characteristics was determined. When Cr, Cr-Mo, or Cr-Mo-Ni was added to the base steel, the TM steel exhibited a high upper-shelf Charpy impact absorbed value that ranged from 100 to 120 J/cm2 and a low ductile-brittle fracture appearance transition temperature that ranged from 123 K to 143 K (-150 °C to -130 °C), while also exhibiting a tensile strength of about 1.5 GPa. This impact toughness of the alloyed steels was far superior to that of conventional martensitic steel and was caused by the presence of (i) a softened wide lath-martensite matrix, which contained only a small amount of carbide and hence had a lower carbon concentration, (ii) a large amount of finely dispersed martensite-retained austenite complex phase, and (iii) a metastable retained austenite phase of 2 to 4 vol pct in the complex phase, which led to plastic relaxation via strain-induced transformation and played an important role in the suppression of the initiation and propagation of voids and/or cleavage cracks.

  5. Why stainless steel corrodes.

    PubMed

    Ryan, Mary P; Williams, David E; Chater, Richard J; Hutton, Bernie M; McPhail, David S

    2002-02-14

    Stainless steels are used in countless diverse applications for their corrosion resistance. Although they have extremely good general resistance, they are nevertheless susceptible to pitting corrosion. This localized dissolution of an oxide-covered metal in specific aggressive environments is one of the most common and catastrophic causes of failure of metallic structures. The pitting process has been described as random, sporadic and stochastic and the prediction of the time and location of events remains extremely difficult. Many contested models of pitting corrosion exist, but one undisputed aspect is that manganese sulphide inclusions play a critical role. Indeed, the vast majority of pitting events are found to occur at, or adjacent to, such second-phase particles. Chemical changes in and around sulphide inclusions have been postulated as a mechanism for pit initiation but such variations have never been measured. Here we use nanometre-scale secondary ion mass spectroscopy to demonstrate a significant reduction in the Cr:Fe ratio of the steel matrix around MnS particles. These chromium-depleted zones are susceptible to high-rate dissolution that 'triggers' pitting. The implications of these results are that materials processing conditions control the likelihood of corrosion failures, and these data provide a basis for optimizing such conditions. PMID:11845203

  6. 2169 Steel Waveform Experiments

    NASA Astrophysics Data System (ADS)

    Furnish, M.; Alexander, C.; Reinhart, W.; Brown, J.

    2013-06-01

    In support of efforts to develop multiscale models of materials, we performed eight gas gun impact experiments on 2169 steel (21% Cr, 6% Ni, 9% Mn). These experiments provided shock, reshock and release velocimetry data, with initial shock stresses ranging from 10 to 50 GPa (particle velocities from 0.25 to 1.05 km/s). Both windowed and free-surface measurements were used, with samples 1 to 5 mm thick. The study focused on dynamic strength determination via the release/reshock paths. Reshock tests with explosively welded impactors produced clean results. The free-surface samples, which were steps on a single piece of steel, showed lower wavespeeds for thin (1 mm) samples than for thicker (2 or 4 mm) samples. A configuration used for the last three shots allowed release information to be determined from these free surface samples as well. The sample strength appears to increase with stress from ~1 GPa to ~3 GPa over this range, consistent with other recent work but about 40% above the Steinberg model. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  7. Propagation considerations in land mobile satellite transmission

    NASA Technical Reports Server (NTRS)

    Vogel, W. J.; Smith, E. K.

    1985-01-01

    It appears likely that the Land Mobile Satellite Services (LMSS) will be authorized by the FCC for operation in the 800 to 900 MHz (UHF) and possibly near 1500 MHz (L-band). Propagation problems are clearly an important factor in the effectiveness of this service, but useful measurements are few, and produced contradictory interpretations. A first order overview of existing measurements is presented with particular attention to the first two NASA balloon to mobile vehicle propagation experiments. Some physical insight into the interpretation of propagation effects in LMSS transmissions is provided.

  8. Computing Propagation Of Sound In Engine Ducts

    NASA Technical Reports Server (NTRS)

    Saylor, Silvia

    1995-01-01

    Frequency Domain Propagation Model (FREDOM) computer program accounts for acoustic loads applied to components of engines. Models propagation of noise through fluids in ducts between components and through passages within components. Used not only to analyze hardware problems, but also for design purposes. Updated version of FREQPL program easier to use. Devised specifically for use in analyzing acoustic loads in rocket engines. Underlying physical and mathematical concepts implemented also applicable to acoustic propagation in other enclosed spaces; analyzing process plumbing and ducts in industrial buildings with view toward reducing noise in work areas.

  9. Asymmetric counter propagation of domain walls

    NASA Astrophysics Data System (ADS)

    Andrade-Silva, I.; Clerc, M. G.; Odent, V.

    2016-07-01

    Far from equilibrium systems show different states and domain walls between them. These walls, depending on the type of connected equilibria, exhibit a rich spatiotemporal dynamics. Here, we investigate the asymmetrical counter propagation of domain walls in an in-plane-switching cell filled with a nematic liquid crystal. Experimentally, we characterize the shape and speed of the domain walls. Based on the molecular orientation, we infer that the counter propagative walls have different elastic deformations. These deformations are responsible of the asymmetric counter propagating fronts. Theoretically, based on symmetry arguments, we propose a simple bistable model under the influence of a nonlinear gradient, which qualitatively describes the observed dynamics.

  10. Propagation of sound through a sheared flow

    NASA Technical Reports Server (NTRS)

    Woolley, J. P.; Smith, C. A.; Karamcheti, K.

    1978-01-01

    Sound generated in a moving fluid must propagate through a shear layer in order to be measured by a fixed instrument. These propagation effects were evaluated for noise sources typically associated with single and co-flowing subsonic jets and for subcritical flow over airfoils in such jets. The techniques for describing acoustic propagation fall into two categories: geometric acoustics and wave acoustics. Geometric acoustics is most convenient and accurate for high frequency sound. In the frequency range of interest to the present study (greater than 150 Hz), the geometric acoustics approach was determined to be most useful and practical.

  11. Photon propagator in light-shell gauge

    NASA Astrophysics Data System (ADS)

    Georgi, Howard; Kestin, Greg; Sajjad, Aqil

    2016-05-01

    We derive the photon propagator in light-shell gauge (LSG) vμAμ=0 , where vμ=(1,r ^ ) μ . This gauge is an important ingredient of the light-shell effective theory—an effective theory for describing high energy jet processes on a 2-dimensional spherical shell expanding at the speed of light around the point of the initial collision producing the jets. Since LSG is a noncovariant gauge, we cannot calculate the LSG propagator by using the standard procedure for covariant gauges. We therefore employ a new technique for computing the propagator, which we hope may be of relevance in other gauges as well.

  12. Propagating confined states in phase dynamics

    NASA Technical Reports Server (NTRS)

    Brand, Helmut R.; Deissler, Robert J.

    1992-01-01

    Theoretical treatment is given to the possibility of the existence of propagating confined states in the nonlinear phase equation by generalizing stationary confined states. The nonlinear phase equation is set forth for the case of propagating patterns with long wavelengths and low-frequency modulation. A large range of parameter values is shown to exist for propagating confined states which have spatially localized regions which travel on a background with unique wavelengths. The theoretical phenomena are shown to correspond to such physical systems as spirals in Taylor instabilities, traveling waves in convective systems, and slot-convection phenomena for binary fluid mixtures.

  13. Probabilistic Fatigue And Flaw-Propagation Analysis

    NASA Technical Reports Server (NTRS)

    Moore, Nicholas; Newlin, Laura; Ebbeler, Donald; Sutharshana, Sravan; Creager, Matthew

    1995-01-01

    Probabilistic Failure Assessment for Fatigue and Flaw Propagation (PFAFAT II) package of software utilizing probabilistic failure-assessment (PFA) methodology to model flaw-propagation and low-cycle-fatigue modes of failure of structural components. Comprises one program for performing probabilistic crack-growth analysis and two programs for performing probabilistic low-cycle-fatigue analysis. These programs perform probabilistic fatigue and crack-propagation analysis by means of Monte Carlo simulation. PFAFAT II is extension of, rather than replacement for, PFAFAT software (NPO-18965). Written in FORTRAN 77.

  14. Electromagnetic Propagation Prediction Inside Aircraft Cabins

    NASA Technical Reports Server (NTRS)

    Hankins, Genevieve; Vahala, Linda; Beggs, John H.

    2004-01-01

    Electromagnetic propagation models for signal strength prediction within aircraft cabins are essential for evaluating and designing a wireless communication system to be implemented onboard aircraft. A model was developed using Wireless Valley's SitePlanner; which is commercial grade software intended for predictions within office buildings. The performance of the model was evaluated through a comparison with test data measurements taken on several aircraft. The comparison concluded that the model can accurately predict power propagation within the cabin. This model can enhance researchers understanding of power propagation within aircraft cabins and will aid in future research.

  15. Propagation of Light Elements in the Galaxy

    NASA Technical Reports Server (NTRS)

    Moskalenko, I. V.; Strong, A. W.; Mashnik, S. G.; Jones, F. C.

    2003-01-01

    The origin and evolution of isotopes of the lightest elements d, He-3, Li, Be, and B in the universe is a key problem in such fields as astrophysics of CR, Galactic evolution, non-thermal nucleosynthesis, and cosmological studies. One of the major sources of these species is spallation by CR nuclei in the interstellar medium. On the other hand, it is the Boron/Carbon ratio in CR and Be-10 abundance which are used to fix the propagation parameters and thus spallation rate. We study production and Galactic propagation of these species using the numerical propagation code GALPROP and updated production cross sections.

  16. Pulsed holographic microscopy as a measurement method of dynamic fracture toughness for fast propagating cracks

    NASA Astrophysics Data System (ADS)

    Suzuki, Shinichi; Homma, Hiroomi; Kusaka, Riichiro

    A METHOD OF pulsed holographic microscopy is applied to take instantaneous microscopic photographs of the neighborhoods of crack tips propagating through PMMA or through AISI 4340 steel specimens at a speed of several hundred meters per second. The cracks are in the opening mode. A fast propagating crack is recorded as a hologram at an instant during its propagation. A microscopic photograph of the crack is taken with a conventional microscope to magnify the reconstructed image from the hologram. From the microscopic photograph, crack opening displacement (COD) is measured along the crack in the vicinity of the crack tip. The COD is of the order often to one hundred microns, and in proportion to the square root of the distance from the crack tip. The dynamic fracture toughness KID is obtained using the formula for COD in the singular stress field of a fast propagating crack. Simultaneous KID measurement both through pulsed holographic microscopy and through the caustic method is furthermore carried out with PMMA specimens. The values of KID obtained through pulsed holographic microscopy are in agreement with those through the caustic method. Microcracks accompanied by a main crack are also photographed with the method of pulsed holographic microscopy.

  17. Ultrasound Propagation in Colloidal Dispersions.

    NASA Astrophysics Data System (ADS)

    Sherman, Nigel E.

    Available from UMI in association with The British Library. This thesis describes apparatus and techniques for making ultrasonic measurements in fluids and applications of them to measurements of ultrasonic parameters in colloidal dispersions. A brief description of the properties and uses of ultrasound propagation in dispersions is followed by an extensive review of theories which relate the particulate properties of the dispersions to the measurable ultrasonic parameters, velocity (c) and attenuation (alpha ). Measurement principles are outlined related to the design of near-field measurement methods and the development of three techniques is described. These are shown to give results which are both highly self-consistent and in excellent agreement with a far-field method. Measurements of alpha and c for model dispersions of glass spheres in Newtonian liquids are shown to be in good agreement with the relevant theory when particle polydispersity is taken into account. For structured fluids as the continuous phase, the alpha and c data for suspensions of spheres are used to obtain the continuous phase viscosity ( eta). The alpha data agree approximately with the macroscopic viscosity, but the velocity data requires the introduction of a shear elastic term and the revision of theory in order to obtain agreement. Attenuation as a function of barite concentration in Newtonian liquids was investigated and the ultrasonic particle radius was found to be systematically larger than expected. This is attributed to particle rugosity. Measurements of alpha and c using non-gelling aqueous kaolinite suspensions are shown to agree well with theory when the eccentricity and the interactions of particles are taken into account. For gelling aqueous bentonite suspensions, alpha and c were found to be time-dependent over a period of several days following initial dispersion. The observed increases in both alpha and c are interpreted in terms of a growth in gel fraction and shear

  18. State-of-the-Science of High Manganese TWIP Steels for Automotive Applications

    NASA Astrophysics Data System (ADS)

    de Cooman, B. C.; Chen, L.; Kim, Han Soo; Estrin, Y.; Kim, S. K.; Voswinckel, H.

    Recent trends in automotive industry towards improved passenger safety and reduced weight have led to a great interest in AHSS (Advanced High Strength Steel), and DP, TRIP, CP, MA and high-Mn TWIP (TWinning Induced Plasticity) steels are particularly promising due to their superior toughness and ductility. The properties of low SFE (Stacking Fault Energy) austenitic high Mn FeMnC steel exhibiting twinning-induced plasticity have recently been analyzed in detail. It is argued that although the mechanical properties of TRIP and TWIP steels are often assumed to be solely due to effects related to straininduced transformation and deformation twinning, respectively, other mechanisms may also play an essential role such as point-defect cluster formation, planar glide, pseudo-twinning, short range ordering, and dynamic strain ageing, e.g. in the case of TWIP steel. At low strain rates, the plastic deformation of TWIP steels is often controlled by the movement of very few well-defined localized deformation bands. The formation and propagation of these Portevin-LeChatelier (PLC) bands lead to serrated stress-strain curves, exhibiting a small negative strain rate sensitivity.

  19. Finite element simulation for damage detection of surface rust in steel rebars using elastic waves

    NASA Astrophysics Data System (ADS)

    Tang, Qixiang; Yu, Tzuyang

    2016-04-01

    Steel rebar corrosion reduces the integrity and service life of reinforced concrete (RC) structures and causes their gradual and sudden failures. Early stage detection of steel rebar corrosion can improve the efficiency of routine maintenance and prevent sudden failures from happening. In this paper, detecting the presence of surface rust in steel rebars is investigated by the finite element method (FEM) using surface-generated elastic waves. Simulated wave propagation mimics the sensing scheme of a fiber optic acoustic generator mounted on the surface of steel rebars. Formation of surface rust in steel rebars is modeled by changing material's property at local elements. In this paper, various locations of a fiber optic acoustic transducer and a receiver were considered. Megahertz elastic waves were used and different sizes of surface rust were applied. Transient responses of surface displacement and pressure were studied. It is found that surface rust is most detectable when the rust location is between the transducer and the receiver. Displacement response of intact steel rebar is needed in order to obtain background-subtracted response with a better signal-to-noise ratio. When the size of surface rust increases, reduced amplitude in displacement was obtained by the receiver.

  20. Microstructural Effects on Fracture Behavior of Ferritic and Martensitic Structural Steels

    NASA Astrophysics Data System (ADS)

    Ibrahim, Omyma H.; Elshazly, Ezzat S.

    2013-02-01

    The effect of microstructure on fracture behavior of 1Cr-0.5Mo and 9Cr-1Mo structural steels was evaluated. 1Cr-0.5Mo steel is used in steam pipes and superheater tubes of power stations. Its microstructure is typically comprised of bainite in a pre-eutectoid ferrite matrix with an average grain size of 10 μm. 9Cr-1Mo steel was developed for applications in steam power stations and as a candidate structural material for first-wall and blanket components of future fusion reactors. Its microstructure consisted of a fully martensitic structure with a prior austenite grain size of 25 μm. The fracture properties were measured using instrumented impact testing at temperatures between -196 and 300 °C. The total impact fracture energy, the crack initiation and propagation energy, the dynamic yield strength, the brittleness temperature, and the cleavage fracture stress were measured. The bainitic-ferritic alloy steel exhibited much higher resistance to ductile fracture at high test temperatures, while its resistance to brittle fracture at low test temperatures was reduced compared to that of the fully martensitic alloy steel. The results were discussed in terms of the chemical composition and microstructure of the two steel types.

  1. 49 CFR 192.55 - Steel pipe.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 3 2011-10-01 2011-10-01 false Steel pipe. 192.55 Section 192.55 Transportation... BY PIPELINE: MINIMUM FEDERAL SAFETY STANDARDS Materials § 192.55 Steel pipe. (a) New steel pipe is... in accordance with paragraph (c) or (d) of this section. (b) Used steel pipe is qualified for...

  2. 49 CFR 192.55 - Steel pipe.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 3 2014-10-01 2014-10-01 false Steel pipe. 192.55 Section 192.55 Transportation... BY PIPELINE: MINIMUM FEDERAL SAFETY STANDARDS Materials § 192.55 Steel pipe. (a) New steel pipe is... in accordance with paragraph (c) or (d) of this section. (b) Used steel pipe is qualified for...

  3. 49 CFR 192.55 - Steel pipe.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 3 2013-10-01 2013-10-01 false Steel pipe. 192.55 Section 192.55 Transportation... BY PIPELINE: MINIMUM FEDERAL SAFETY STANDARDS Materials § 192.55 Steel pipe. (a) New steel pipe is... in accordance with paragraph (c) or (d) of this section. (b) Used steel pipe is qualified for...

  4. 49 CFR 192.55 - Steel pipe.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 3 2010-10-01 2010-10-01 false Steel pipe. 192.55 Section 192.55 Transportation... BY PIPELINE: MINIMUM FEDERAL SAFETY STANDARDS Materials § 192.55 Steel pipe. (a) New steel pipe is... in accordance with paragraph (c) or (d) of this section. (b) Used steel pipe is qualified for...

  5. 49 CFR 192.55 - Steel pipe.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 3 2012-10-01 2012-10-01 false Steel pipe. 192.55 Section 192.55 Transportation... BY PIPELINE: MINIMUM FEDERAL SAFETY STANDARDS Materials § 192.55 Steel pipe. (a) New steel pipe is... in accordance with paragraph (c) or (d) of this section. (b) Used steel pipe is qualified for...

  6. Occupational Profiles in the European Steel Industry.

    ERIC Educational Resources Information Center

    Franz, Hans-Werner; And Others

    The steel industry in Europe has faced great changes, with resulting layoffs and restructuring. Now that the most basic changes seem to be over, it has become evident that the remaining steel industry requires more highly trained workers than was the case previously. Although steel maintenance employees were always highly skilled, steel production…

  7. Improving the toughness of ultrahigh strength steel

    SciTech Connect

    Soto, Koji

    2002-08-15

    The ideal structural steel combines high strength with high fracture toughness. This dissertation discusses the toughening mechanism of the Fe/Co/Ni/Cr/Mo/C steel, AerMet 100, which has the highest toughness/strength combination among all commercial ultrahigh strength steels. The possibility of improving the toughness of this steel was examined by considering several relevant factors.

  8. Irradiation effects in ferritic steels

    NASA Astrophysics Data System (ADS)

    Lechtenberg, Thomas

    1985-08-01

    Since 1979 the Alloy Development for Irradiation Performance (ADIP) task funded by the US Department of Energy has been studying the 2-12Cr class of ferritic steels to establish the feasibility of using them in fusion reactor first wall/breeding blanket (FW/B) applications. The advantages of ferritic steels include superior swelling resistance, low thermal stresses compared to austenitic stainless steels, attractive mechanical properties up to 600°C. and service histories exceeding 100 000 h. These steels are commonly used in a range of microstructural conditions which include ferritic, martensitic. tempered martensitic, bainitic etc. Throughout this paper where the term "ferritic" is used it should be taken to mean any of these microstructures. The ADIP task is studying several candidate alloy systems including 12Cr-1MoWV (HT-9), modified 9Cr-1MoVNb, and dual-phased steels such as EM-12 and 2 {1}/{4}Cr-Mo. These materials are ferromagnetic (FM), body centered cubic (bcc), and contain chromium additions between 2 and 12 wt% and molybdenum additions usually below 2%. The perceived issues associated with the application of this class of steel to fusion reactors are the increase in the ductile-brittle transition temperature (DBTT) with neutron damage, the compatibility of these steels with liquid metals and solid breeding materials, and their weldability. The ferromagnetic character of these steels can also be important in reactor design. It is the purpose of this paper to review the current understanding of these bcc steels and the effects of irradiation. The major points of discussion will be irradiation-induced or -enhanced dimensional changes such as swelling and creep, mechanical properties such as tensile strength and various measurements of toughness, and activation by neutron interactions with structural materials.

  9. Pulse Wave Propagation in the Arterial Tree

    NASA Astrophysics Data System (ADS)

    van de Vosse, Frans N.; Stergiopulos, Nikos

    2011-01-01

    The beating heart creates blood pressure and flow pulsations that propagate as waves through the arterial tree that are reflected at transitions in arterial geometry and elasticity. Waves carry information about the matter in which they propagate. Therefore, modeling of arterial wave propagation extends our knowledge about the functioning of the cardiovascular system and provides a means to diagnose disorders and predict the outcome of medical interventions. In this review we focus on the physical and mathematical modeling of pulse wave propagation, based on general fluid dynamical principles. In addition we present potential applications in cardiovascular research and clinical practice. Models of short- and long-term adaptation of the arterial system and methods that deal with uncertainties in personalized model parameters and boundary conditions are briefly discussed, as they are believed to be major topics for further study and will boost the significance of arterial pulse wave modeling even more.

  10. Promoted Combustion Test Propagation Rate Data

    NASA Technical Reports Server (NTRS)

    Borstorff, J.; Jones, P.; Lowery, F.

    2002-01-01

    Combustion propagation rate data were examined for potential use in benchmarking a thermal model of the Promoted Combustion Test (PCT), and also for potential use in measuring the repeatability of PCT results.

  11. In vitro propagation of Paphiopedilum orchids.

    PubMed

    Zeng, Songjun; Huang, Weichang; Wu, Kunlin; Zhang, Jianxia; da Silva, Jaime A Teixeira; Duan, Jun

    2016-01-01

    Paphiopedilum is one of the most popular and rare orchid genera. Members of the genus are sold and exhibited as pot plants and cut flowers. Wild populations of Paphiopedilum are under the threat of extinction due to over-collection and loss of suitable habitats. A reduction in their commercial value through large-scale propagation in vitro is an option to reduce pressure from illegal collection, to attempt to meet commercial needs and to re-establish threatened species back into the wild. Although they are commercially propagated via asymbiotic seed germination, Paphiopedilum are considered to be difficult to propagate in vitro, especially by plant regeneration from tissue culture. This review aims to cover the most important aspects and to provide an up-to-date research progress on in vitro propagation of Paphiopedilum and to emphasize the importance of further improving tissue culture protocols for ex vitro-derived explants. PMID:25582733

  12. Fick's Law Assisted Propagation for Semisupervised Learning.

    PubMed

    Gong, Chen; Tao, Dacheng; Fu, Keren; Yang, Jie

    2015-09-01

    How to propagate the label information from labeled examples to unlabeled examples is a critical problem for graph-based semisupervised learning. Many label propagation algorithms have been developed in recent years and have obtained promising performance on various applications. However, the eigenvalues of iteration matrices in these algorithms are usually distributed irregularly, which slow down the convergence rate and impair the learning performance. This paper proposes a novel label propagation method called Fick's law assisted propagation (FLAP). Unlike the existing algorithms that are directly derived from statistical learning, FLAP is deduced on the basis of the theory of Fick's First Law of Diffusion, which is widely known as the fundamental theory in fluid-spreading. We prove that FLAP will converge with linear rate and show that FLAP makes eigenvalues of the iteration matrix distributed regularly. Comprehensive experimental evaluations on synthetic and practical datasets reveal that FLAP obtains encouraging results in terms of both accuracy and efficiency. PMID:25532192

  13. The ghost propagator in Coulomb gauge

    SciTech Connect

    Watson, P.; Reinhardt, H.

    2011-05-23

    We present results for a numerical study of the ghost propagator in Coulomb gauge whereby lattice results for the spatial gluon propagator are used as input to solving the ghost Dyson-Schwinger equation. We show that in order to solve completely, the ghost equation must be supplemented by a boundary condition (the value of the inverse ghost propagator dressing function at zero momentum) which determines if the solution is critical (zero value for the boundary condition) or subcritical (finite value). The various solutions exhibit a characteristic behavior where all curves follow the same (critical) solution when going from high to low momenta until 'forced' to freeze out in the infrared to the value of the boundary condition. The boundary condition can be interpreted in terms of the Gribov gauge-fixing ambiguity; we also demonstrate that this is not connected to the renormalization. Further, the connection to the temporal gluon propagator and the infrared slavery picture of confinement is discussed.

  14. Gram-Schmidt algorithms for covariance propagation

    NASA Technical Reports Server (NTRS)

    Thornton, C. L.; Bierman, G. J.

    1977-01-01

    This paper addresses the time propagation of triangular covariance factors. Attention is focused on the square-root free factorization, P = UD(transpose of U), where U is unit upper triangular and D is diagonal. An efficient and reliable algorithm for U-D propagation is derived which employs Gram-Schmidt orthogonalization. Partitioning the state vector to distinguish bias and coloured process noise parameters increase mapping efficiency. Cost comparisons of the U-D, Schmidt square-root covariance and conventional covariance propagation methods are made using weighted arithmetic operation counts. The U-D time update is shown to be less costly than the Schmidt method; and, except in unusual circumstances, it is within 20% of the cost of conventional propagation.

  15. Gram-Schmidt algorithms for covariance propagation

    NASA Technical Reports Server (NTRS)

    Thornton, C. L.; Bierman, G. J.

    1975-01-01

    This paper addresses the time propagation of triangular covariance factors. Attention is focused on the square-root free factorization, P = UDU/T/, where U is unit upper triangular and D is diagonal. An efficient and reliable algorithm for U-D propagation is derived which employs Gram-Schmidt orthogonalization. Partitioning the state vector to distinguish bias and colored process noise parameters increases mapping efficiency. Cost comparisons of the U-D, Schmidt square-root covariance and conventional covariance propagation methods are made using weighted arithmetic operation counts. The U-D time update is shown to be less costly than the Schmidt method; and, except in unusual circumstances, it is within 20% of the cost of conventional propagation.

  16. Propagation Regime of Iron Dust Flames

    NASA Technical Reports Server (NTRS)

    Tang, Francois-David; Goroshin, Samuel; Higgins, Andrew J.

    2012-01-01

    A flame propagating through an iron-dust mixture can propagate in two asymptotic regimes. When the characteristic time of heat transfer between particles is much smaller than the characteristic time of particle combustion, the flame propagates in the continuum regime where the heat released by reacting particles can be modelled as a space-averaged function. In contrast, when the characteristic time of heat transfer is much larger than the particle reaction time, the flame can no longer be treated as a continuum due to dominating effects associated with the discrete nature of the particle reaction. The discrete regime is characterized by weak dependence of the flame speed on the oxygen concentration compared to the continuum regime. The discrete regime is observed in flames propagating through an iron dust cloud within a gas mixture containing xenon, while the continuum regime is obtained when xenon is substituted with helium.

  17. Electromagnetic wave propagation characteristics in unimolecular reactions

    NASA Astrophysics Data System (ADS)

    Liu, Xingpeng; Huang, Kama

    2016-01-01

    Microwave-assisted chemical reactions have attracted interests because of their benefits for enhancement of reaction rates. However, the problems, such as hot spots and thermal runaway, limit the application of microwaves in the chemical industry. To study the characteristics of electromagnetic wave propagation in a chemical reaction is critical to solve the problems. The research on the characteristics of electromagnetic wave propagation in the unimolecular reaction that is a simple model reaction, can be generalized to the research in a chemical reaction. The approximate expressions of the attenuation and dispersion characteristics of electromagnetic wave propagation in the unimolecular reaction are derived by the nonlinear propagation theory. Specially, when the reaction rate is zero, the derived approximate expressions can be reduced to the formulas in low-loss dispersive media. Moreover, a 1D mold is used to validate the feasibility of the approximate expressions. The influences of the reaction rate and initial reactant concentration on the characteristics are obtained.

  18. Radio wave propagation and acoustic sounding

    NASA Astrophysics Data System (ADS)

    Singal, S. P.

    Radio wave propagation of the decimetric and centimetric waves depends to a large extent on the boundary layer meteorological conditions which give rise to severe fadings, very often due to multipath propagation. Sodar is one of the inexpensive remote sensing techniques which can be employed to probe the boundary layer structure. In the paper a historical perspective has been given of the simultaneously conducted studies on radio waves and sodar at various places. The radio meteorological information needed for propagation studies has been clearly spelt out and conditions of a ray path especially in the presence of a ducting layer have been defined as giving rise to fading or signal enhancement conditions. Finally the potential of the sodar studies to obtain information about the boundary layer phenomena has been stressed, clearly spelling out the use of acoustic sounding in radio wave propagation studies.

  19. ACTS Project and Propagation Program Update

    NASA Technical Reports Server (NTRS)

    Bauer, Robert

    1996-01-01

    Spacecraft operations continue to be nominal and the sixth eclipse season completed. Battery reconditioning to be re-evaluated before the fall eclipse. Other topics covered include: Inclined orbit; Experiments program; Reorganizations; Program timeline; and propagation program status.

  20. The limit of strength and toughness of steel

    NASA Astrophysics Data System (ADS)

    Guo, Zhen

    The ideal structural steel combines high strength with high fracture toughness. This dissertation discusses the governing principles of strength and toughness, along with the approaches that can be used to improve these properties and the inherent limits to how strong and tough a steel can be. Chapter I provides the background on fracture mechanics and describes the factors that affect cleavage fracture from atomic, microstructural and macroscopic levels. From such considerations, the inherent resistance to cleavage fracture is apparent. Chapter II discusses the ideal fracture strength and the critical fracture strength in high strength steels. Recent ab intio computations predict an ideal cleavage strength of Fe near 14 GPa on {100} planes, indicating that the normal fracture mode of high strength steel, characterized by a yield strength greater than about 4 GPa is brittle. A preliminary study of the effect of alloying with Ni shows a trend of decreasing brittle behavior with increasing Ni content. More sophisticated methods to study this effect are proposed. Chapter III examines the practical methods for achieving properties that approach the limits of strength and toughness of steel. The discussion focuses on grain refinement through thermal treatments in lath martensitic steels. The objective is to limit the crystallographic coherence length for transgranular cleavage propagation. A new method is presented for directly disrupting the crystallographic orientation alignment within a martensitic packet, and thereby achieving submicron effective grain size. This has been accomplished in AerMet 100 and 9Ni steel by an alternate "intercritical annealing" (L) and "reversion" (Q) treatment. An "L" treatment creates a dual-phase microstructure containing fine parallel laths with different alloy contents. Subsequent austenite reversion ("Q" treatment) leads to a two-step martensitic transformation during cooling, disrupting the laths within a packet and generating a

  1. Role of Grain Boundaries and Microstructure on the Environment Assisted Cracking of Pipeline Steels

    NASA Astrophysics Data System (ADS)

    Arafin, Muhammad

    2011-12-01

    In this research, two common types of environment assisted cracking (EAC) of pipeline steels, namely the intergranular stress corrosion cracking (IGSCC) and the hydrogen induced cracking (HIC), have been studied, and computer models have been developed to simulate the intergranular stress corrosion crack propagation behaviour in pipeline steel as well as to predict the intergranular fracture susceptibility, due to mechanical loading in non-corrosive environment, of polycrystalline materials. First, a new understanding of the IGSCC resistance of pipeline steel has been obtained by studying the grain boundary character and crystallographic orientation in both cracked and non-cracked pipeline steel samples using electron backscattered diffraction (EBSD) and X-ray texture measurements. It has been found that the low-angle and certain types of special boundaries, known as the coincident site lattice (CSL) boundaries (S5, S11, and S13b types), are crack-resistant while the random high angle boundaries are prone to cracking. However, it has been also observed that the grain boundaries associated with {110} and {111} neighbour grain orientations having <110> and <111> rotation axis, respectively, are crack-resistant, while the cracked boundaries are mainly linked to the {100} orientation with <100> rotation axis. Subsequently, a novel integrated modeling approach, combining Voronoi Algorithm, Markov Chain theory, and Monte Carlo simulations, has been developed in order to predict the IGSCC behaviour of pipeline steels. The model takes both the physical microstructural features, such as the grain shape and grain size distribution, as well as the grain boundary characters and their orientations with respect to the external stress axis into account. The predicted crack propagation behaviour has been found to be in excellent agreement with the experimental crack-propagation and arrest data in API X65 pipeline steel. In addition, a texture based grain boundary character

  2. Stress corrosion cracking of duplex stainless steels in caustic solutions

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Ananya

    Duplex stainless steels (DSS) with roughly equal amount of austenite and ferrite phases are being used in industries such as petrochemical, nuclear, pulp and paper mills, de-salination plants, marine environments, and others. However, many DSS grades have been reported to undergo corrosion and stress corrosion cracking in some aggressive environments such as chlorides and sulfide-containing caustic solutions. Although stress corrosion cracking of duplex stainless steels in chloride solution has been investigated and well documented in the literature but the SCC mechanisms for DSS in caustic solutions were not known. Microstructural changes during fabrication processes affect the overall SCC susceptibility of these steels in caustic solutions. Other environmental factors, like pH of the solution, temperature, and resulting electrochemical potential also influence the SCC susceptibility of duplex stainless steels. In this study, the role of material and environmental parameters on corrosion and stress corrosion cracking of duplex stainless steels in caustic solutions were investigated. Changes in the DSS microstructure by different annealing and aging treatments were characterized in terms of changes in the ratio of austenite and ferrite phases, phase morphology and intermetallic precipitation using optical micrography, SEM, EDS, XRD, nano-indentation and microhardness methods. These samples were then tested for general and localized corrosion susceptibility and SCC to understand the underlying mechanisms of crack initiation and propagation in DSS in the above-mentioned environments. Results showed that the austenite phase in the DSS is more susceptible to crack initiation and propagation in caustic solutions, which is different from that in the low pH chloride environment where the ferrite phase is the more susceptible phase. This study also showed that microstructural changes in duplex stainless steels due to different heat treatments could affect their SCC

  3. High-strength, low-alloy steels.

    PubMed

    Rashid, M S

    1980-05-23

    High-strength, low-alloy (HSLA) steels have nearly the same composition as plain carbon steels. However, they are up to twice as strong and their greater load-bearing capacity allows engineering use in lighter sections. Their high strength is derived from a combination of grain refinement; precipitation strengthening due to minor additions of vanadium, niobium, or titanium; and modifications of manufacturing processes, such as controlled rolling and controlled cooling of otherwise essentially plain carbon steel. HSLA steels are less formable than lower strength steels, but dualphase steels, which evolved from HSLA steels, have ferrite-martensite microstructures and better formability than HSLA steels of similar strength. This improved formability has substantially increased the utilization potential of high-strength steels in the manufacture of complex components. This article reviews the development of HSLA and dual-phase steels and discusses the effects of variations in microstructure and chemistry on their mechanical properties. PMID:17772810

  4. Hydrogen-enhanced SCC of 304 austenitic stainless steel in MgCl{sub 2}

    SciTech Connect

    Gao, K.W.; Qiao, L.J.; Luo, J.L.

    1998-12-31

    SCC of 304 stainless steel(ss) in boiling MgCl{sub 2} at 416K was performed to investigate the effect of hydrogen during test. Results showed that the existence of hydrogen enhanced the susceptibility of SCC of 304ss. The fractography of specimen charged with hydrogen contained more intergranular than that of uncharged ones, and for both specimens charged or uncharged with hydrogen, SCC initiated and propagated along {l_brace}111{r_brace} plane.

  5. Microdrilling in steel using ultrashort pulsed laser beams with radial and azimuthal polarization.

    PubMed

    Kraus, Martin; Ahmed, Marwan Abdou; Michalowski, Andreas; Voss, Andreas; Weber, Rudolf; Graf, Thomas

    2010-10-11

    A linear to radial and/or azimuthal polarization converter (LRAC) has been inserted into the beam delivery of a micromachining station equipped with a picosecond laser system. Percussion drilling and helical drilling in steel have been performed using radially as well as azimuthally polarized infrared radiation at 1030 nm. The presented machining results are discussed on the basis of numerical simulations of the polarization-dependent beam propagation inside the fabricated capillaries. PMID:20941131

  6. Molecular dynamics simulation of propagating cracks

    NASA Technical Reports Server (NTRS)

    Mullins, M.

    1982-01-01

    Steady state crack propagation is investigated numerically using a model consisting of 236 free atoms in two (010) planes of bcc alpha iron. The continuum region is modeled using the finite element method with 175 nodes and 288 elements. The model shows clear (010) plane fracture to the edge of the discrete region at moderate loads. Analysis of the results obtained indicates that models of this type can provide realistic simulation of steady state crack propagation.

  7. Light propagation in Swiss-cheese cosmologies

    NASA Astrophysics Data System (ADS)

    Szybka, Sebastian J.

    2011-08-01

    We study the effect of inhomogeneities on light propagation. The Sachs equations are solved numerically in the Swiss-cheese models with inhomogeneities modeled by the Lemaître-Tolman solutions. Our results imply that, within the models we study, inhomogeneities may partially mimic the accelerated expansion of the Universe provided the light propagates through regions with lower than the average density. The effect of inhomogeneities is small and full randomization of the photons’ trajectories reduces it to an insignificant level.

  8. Comments on 'Rapid pulsed microwave propagation'

    NASA Astrophysics Data System (ADS)

    Tichy-Racs, Adam

    1992-05-01

    Giakos and Ishii (1991) indicated that the leading edge of the pulse-modulated microwaves propagates with the velocity c/cos theta in a direction theta in open space. This is tantamount to a claim that their measurements indicate a propagation velocity faster than the speed of light. Giakos and Ishii reply to all technical points raised in the present comment and defend their experimental observations.

  9. Quark propagators in confinement and deconfinement phases

    SciTech Connect

    Hamada, Masatoshi; Yahiro, Masanobu; Kouno, Hiroaki; Nakamura, Atsushi; Saito, Takuya

    2010-05-01

    We study quark propagators near the confinement/deconfinement phase transition temperature in quenched-lattice simulation of QCD. We find that there is no qualitative change for the quark propagators in both phases. In the confinement phase, those effective quark masses in units of the critical temperature behave as a constant as a function of the temperature, while above the critical temperature, the value of the effective quark mass drops to circa half value.

  10. POPPY: Physical Optics Propagation in PYthon

    NASA Astrophysics Data System (ADS)

    Perrin, Marshall; Long, Joseph; Douglas, Ewan; Sivaramakrishnan, Anand; Slocum, Christine

    2016-02-01

    POPPY (Physical Optics Propagation in PYthon) simulates physical optical propagation including diffraction. It implements a flexible framework for modeling Fraunhofer and Fresnel diffraction and point spread function formation, particularly in the context of astronomical telescopes. POPPY provides the optical modeling framework for WebbPSF (ascl:1504.007) and was developed as part of a simulation package for JWST, but is available separately and is broadly applicable to many kinds of imaging simulations.

  11. Combustion front propagation in underground coal gasification

    SciTech Connect

    Dobbs, R.L. II; Krantz, W.B.

    1990-10-01

    Reverse Combustion (RC) enhances coal seam permeability prior to Underground Coal Gasification. Understanding RC is necessary to improve its reliability and economics. A curved RC front propagation model is developed, then solved by high activation energy asymptotics. It explicitly incorporates extinction (stoichiometric and thermal) and tangential heat transport (THT) (convection and conduction). THT arises from variation in combustion front temperature caused by tangential variation in the oxidant gas flux to the channel surface. Front temperature depends only weakly on THT; front velocity is strongly affected, with heat loss slowing propagation. The front propagation speed displays a maximum with respect to gas flux. Combustion promoters speed front propagation; inhibitors slow front propagation. The propagation model is incorporated into 2-D simulations of RC channel evolution utilizing the boundary element method with cubic hermetian elements to solve the flow from gas injection wells through the coal to the convoluted, temporally evolving, channel surface, and through the channel to a gas production well. RC channel propagation is studied using 17 cm diameter subbituminous horizontally drilled coal cores. Sixteen experiments at pressures between 2000 and 3600 kPa, injected gas oxygen contents between 21% and 75%, and flows between 1 and 4 standard liters per minute are described. Similarity analysis led to scaling-down of large RC ({approx}1 m) to laboratory scale ({approx}5 cm). Propagation velocity shows a strong synergistic increase at high levels of oxygen, pressure, and gas flow. Char combustion is observed, leaving ash-filled, irregularly shaped channels. Cracks are observed to penetrate the char zone surrounding the channel cores. 69 refs., 54 figs., 4 tabs.

  12. Error Propagation in a System Model

    NASA Technical Reports Server (NTRS)

    Schloegel, Kirk (Inventor); Bhatt, Devesh (Inventor); Oglesby, David V. (Inventor); Madl, Gabor (Inventor)

    2015-01-01

    Embodiments of the present subject matter can enable the analysis of signal value errors for system models. In an example, signal value errors can be propagated through the functional blocks of a system model to analyze possible effects as the signal value errors impact incident functional blocks. This propagation of the errors can be applicable to many models of computation including avionics models, synchronous data flow, and Kahn process networks.

  13. Managing Mobile/Satellite Propagation Data

    NASA Technical Reports Server (NTRS)

    Kantak, Anil V.

    1990-01-01

    "Data Management System for Mobile Satellite Propagation" software package collection of FORTRAN programs and UNIX shell scripts designed to handle huge amounts of data resulting from mobile/satellite radio-propagation experiments. Data from experiments converted into standard and more useful forms. Software package contains program to convert binary format of data into standard ASCII format suitable for use with wide variety of computing-machine architectures. Written in either FORTRAN 77 or UNIX shell scripts.

  14. Propagation measurements in Alaska using ACTS beacons

    NASA Technical Reports Server (NTRS)

    Mayer, Charles E.

    1991-01-01

    The placement of an ACTS propagation terminal in Alaska has several distinct advantages. First is the inclusion of a new and important climatic zone to the global propagation model. Second is the low elevation look angle from Alaska to ACTS. These two unique opportunities also present problems unique to the location, such as extreme temperatures and lower power levels. These problems are examined and compensatory solutions are presented.

  15. Welding tritium exposed stainless steel

    SciTech Connect

    Kanne, W.R. Jr.

    1994-11-01

    Stainless steels that are exposed to tritium become unweldable by conventional methods due to buildup of decay helium within the metal matrix. With longer service lives expected for tritium containment systems, methods for welding on tritium exposed material will become important for repair or modification of the systems. Solid-state resistance welding and low-penetration overlay welding have been shown to mitigate helium embrittlement cracking in tritium exposed 304 stainless steel. These processes can also be used on stainless steel containing helium from neutron irradiation, such as occurs in nuclear reactors.

  16. Stainless steel display evaluation

    NASA Astrophysics Data System (ADS)

    Hopper, Darrel G.; Meyer, Frederick M.; Longo, Sam J.; Trissell, Terry L.

    2007-04-01

    Active matrix organic light emitting diode (AMOLED) technology is one candidate to become a low power alternative in some applications to the currently dominant, active matrix liquid crystal display (AMLCD), technology. Furthermore, fabrication of the AMOLED on stainless steel (SS) foil rather than the traditional glass substrate, while presenting a set of severe technical challenges, opens up the potential for displays that are both lighter and less breakable. Also, transition to an SS foil substrate may enable rollable displays - large when used but small for stowage within gear already worn or carried or installed. Research has been initiated on AMOLED/SS technology and the first 320 x 240 color pixel 4-in. demonstration device has been evaluated in the AFRL Display Test and Evaluation Laboratory. Results of this evaluation are reported along with a research roadmap.

  17. Fatigue Crack Propagation in Intercritically Tempered Fe-9Ni-0.1C and Fe-4Mn-0.15C

    NASA Astrophysics Data System (ADS)

    Choi, H. J.; Schwartz, L. H.

    1983-06-01

    Fatigue crack propagation was studied for two intercritically tempered cryogenic steels, Fe-9Ni-0.1C and Fe-4Mn-0.15C, at both intermediate (stage II) and low (stage I, near threshold) stress intensity ranges. Propagation rates were determined for varying intercritical tempering times corresponding to varying amounts of retained austenite and untempered martensite. The results show that the heat treatments that optimize impact fracture properties in the nickel steel are also beneficial with respect to the fatigue crack propagation rate in stage I, while no beneficial effect beyond that attributable to carbon redistribution was observed for stage II. For the manganese steel, heat treatments leading to increased concentrations of retained austenite also increased the threshold stress even though no improvement in fracture toughness was observed. To clarify the origin of this improved behavior, the fracture surface was analyzed by Mössbauer Spectroscopy and Auger Electron Microprobe. The Mössbauer results indicated that the retained austenite in the crack path is transformed to martensite as was earlier shown in this laboratory for Charpy specimens. Auger composition analysis suggested a tendency for a stage I crack tip to avoid the mechanically induced brittle untempered martensite in the Fe-Mn steel, while no such preference was observed for stage II.

  18. 2169 steel waveform experiments.

    SciTech Connect

    Furnish, Michael David; Alexander, C. Scott; Reinhart, William Dodd; Brown, Justin L.

    2012-11-01

    In support of LLNL efforts to develop multiscale models of a variety of materials, we have performed a set of eight gas gun impact experiments on 2169 steel (21% Cr, 6% Ni, 9% Mn, balance predominantly Fe). These experiments provided carefully controlled shock, reshock and release velocimetry data, with initial shock stresses ranging from 10 to 50 GPa (particle velocities from 0.25 to 1.05 km/s). Both windowed and free-surface measurements were included in this experiment set to increase the utility of the data set, as were samples ranging in thickness from 1 to 5 mm. Target physical phenomena included the elastic/plastic transition (Hugoniot elastic limit), the Hugoniot, any phase transition phenomena, and the release path (windowed and free-surface). The Hugoniot was found to be nearly linear, with no indications of the Fe - phase transition. Releases were non-hysteretic, and relatively consistent between 3- and 5-mm-thick samples (the 3 mm samples giving slightly lower wavespeeds on release). Reshock tests with explosively welded impactors produced clean results; those with glue bonds showed transient releases prior to the arrival of the reshock, reducing their usefulness for deriving strength information. The free-surface samples, which were steps on a single piece of steel, showed lower wavespeeds for thin (1 mm) samples than for thicker (2 or 4 mm) samples. A configuration used for the last three shots allows release information to be determined from these free surface samples. The sample strength appears to increase with stress from ~1 GPa to ~ 3 GPa over this range, consistent with other recent work but about 40% above the Steinberg model.

  19. JPDR vessel steel examination

    SciTech Connect

    Corwin, W.R.; Broadhead, B.L.; Sokolov, M.A.

    1995-10-01

    There is a need to validate the results of irradiation effects research by the examination of material taken directly from the wall of a pressure vessel which has been irradiated during normal service. This task has been included with the HSSI Program to provide just such an evaluation of material from the wall of the pressure vessel from the JPDR. The JPDR was a small BWR that began operation in 1963. It operated until 1976, accumulating {approximately}17,000 h of operation, of which a little over 14,000 h were with the original 45-MWTh core, and the remaining fraction, late in life, with an upgraded 90-MWTh core. The pressure vessel of the JPDR, fabricated from A 302, grade B, modified steel with an internal weld overlay cladding of 304 stainless steel, is approximately 2 m ID and 73 mm thick. It was fabricated from two shell halves joined by longitudinal seam welds located 180{degrees} from each other. The rolling direction of the shell plates is parallel to the axis of the vessel. It operated at 273{degrees}C and reached a maximum fluence of about 2.3 x 10{sup 18} n/cm{sup 2} (> 1 MeV). The impurity contents in the base metal are 0.10 to 0.11% Cu and 0.010 to 0.017% P with a nickel content of 0.63 to 0.65%. Impurity contents of the weld metal are 0.11 to 0.14% Cu and 0.025 to 0.039% P with a nickel content of 0.59%.

  20. Premixed flame propagation in vertical tubes

    NASA Astrophysics Data System (ADS)

    Kazakov, Kirill A.

    2016-04-01

    Analytical treatment of the premixed flame propagation in vertical tubes with smooth walls is given. Using the on-shell flame description, equations for a quasi-steady flame with a small but finite front thickness are obtained and solved numerically. It is found that near the limits of inflammability, solutions describing upward flame propagation come in pairs having close propagation speeds and that the effect of gravity is to reverse the burnt gas velocity profile generated by the flame. On the basis of these results, a theory of partial flame propagation driven by a strong gravitational field is developed. A complete explanation is given of the intricate observed behavior of limit flames, including dependence of the inflammability range on the size of the combustion domain, the large distances of partial flame propagation, and the progression of flame extinction. The role of the finite front-thickness effects is discussed in detail. Also, various mechanisms governing flame acceleration in smooth tubes are identified. Acceleration of methane-air flames in open tubes is shown to be a combined effect of the hydrostatic pressure difference produced by the ambient cold air and the difference of dynamic gas pressure at the tube ends. On the other hand, a strong spontaneous acceleration of the fast methane-oxygen flames at the initial stage of their evolution in open-closed tubes is conditioned by metastability of the quasi-steady propagation regimes. An extensive comparison of the obtained results with the experimental data is made.

  1. Active Wave Propagation and Sensing in Plates

    NASA Technical Reports Server (NTRS)

    Ghoshal, Anindya; Martin, William N.; Sundaresan, Mannur J.; Schulz, Mark J.; Ferguson, Frederick

    2001-01-01

    Health monitoring of aerospace structures can be done using an active interrogation approach with diagnostic Lamb waves. Piezoelectric patches are often used to generate the waves, and it is helpful to understand how these waves propagate through a structure. To give a basic understanding of the actual physical process of wave propagation, a model is developed to simulate asymmetric wave propagation in a panel and to produce a movie of the wave motion. The waves can be generated using piezoceramic patches of any size or shape. The propagation, reflection, and interference of the waves are represented in the model. Measuring the wave propagation is the second important aspect of damage detection. Continuous sensors are useful for measuring waves because of the distributed nature of the sensor and the wave. Two sensor designs are modeled, and their effectiveness in measuring acoustic waves is studied. The simulation model developed is useful to understand wave propagation and to optimize the type of sensors that might be used for health monitoring of plate-like structures.

  2. Heavy-Section Steel Technology program fracture issues

    SciTech Connect

    Pennell, W.E.

    1989-10-01

    Large scale fracture mechanics tests have resulted in the identification of a number of fracture technology issues. Identification of additional issues has come from the reactor vessel materials irradiation test program and from reactor operating experience. This paper provides a review of fracture issues with an emphasis on their potential impact on a reactor vessel pressurized thermal shock (PTS) analysis. Mixed mode crack propagation emerges as a major issue, due in large measure to the poor performance of existing models for the prediction of ductile tearing. Rectification of ductile tearing technology deficiencies may require extending the technology to include a more complete treatment of stress state and loading history effects. The effect of cladding on vessel fracture remains uncertain to the point that it is not possible to determine at this time if the net effect will be positive or negative. Enhanced fracture toughness for shallow flaws has been demonstrated for low strength structural steels. Demonstration of a similar effect in reactor pressure vessel steels could have a significant beneficial effect on the probabilistic analysis of reactor vessel fracture. Further development of existing fracture mechanics models and concepts is required to meet the special requirements for fracture evaluation of circumferential flaws in the welds of ring forged vessels. Fracture technology advances required to address the issues discussed in this paper are the major objective for the ongoing Heavy Section Steel Technology (HSST) program at ORNL. 24 refs., 18 figs.

  3. Mechanical Properties of Austenitic Stainless Steel Made by Additive Manufacturing.

    PubMed

    Luecke, William E; Slotwinski, John A

    2014-01-01

    Using uniaxial tensile and hardness testing, we evaluated the variability and anisotropy of the mechanical properties of an austenitic stainless steel, UNS S17400, manufactured by an additive process, selective laser melting. Like wrought materials, the mechanical properties depend on the orientation introduced by the processing. The recommended stress-relief heat treatment increases the tensile strength, reduces the yield strength, and decreases the extent of the discontinuous yielding. The mechanical properties, assessed by hardness, are very uniform across the build plate, but the stress-relief heat treatment introduced a small non-uniformity that had no correlation to position on the build plate. Analysis of the mechanical property behavior resulted in four conclusions. (1) The within-build and build-to-build tensile properties of the UNS S17400 stainless steel are less repeatable than mature engineering structural alloys, but similar to other structural alloys made by additive manufacturing. (2) The anisotropy of the mechanical properties of the UNS S17400 material of this study is larger than that of mature structural alloys, but is similar to other structural alloys made by additive manufacturing. (3) The tensile mechanical properties of the UNS S17400 material fabricated by selective laser melting are very different from those of wrought, heat-treated 17-4PH stainless steel. (4) The large discontinuous yielding strain in all tests resulted from the formation and propagation of Lüders bands. PMID:26601037

  4. Heavy-Section Steel Technology Program fracture issues

    SciTech Connect

    Pennell, W.E.

    1991-01-01

    Large-scale fracture mechanics tests have resulted in the identification of a number of fracture-technology issues. Identification of additional issues has come from the reactor vessel materials-irradiation test program and from reactor operating experience. This paper provides a review of fracture issues with an emphasis on their potential impact on a reactor vessel pressurized-thermal-shock (PTS) analysis. Mixed-mode crack propagation emerges as a major issue, due in large measure to the poor performance of existing models for the prediction of ductile tearing. Rectification of ductile tearing technology deficiencies may require extending the technology to include a more complete treatment of stress-state and loading history effects. The effect of cladding on vessel fracture remains uncertain to the point that it is not possible to determine at this time if the net effect will be positive or negative. Enhanced fracture toughness for shallow flaws has been demonstrated for low-strength structural steels. Demonstration of a similar effect in reactor pressure vessel steels could have a significant beneficial effect on the probabilistic analysis of reactor vessel fracture. Further development of existing fracture-mechanics models and concepts is required to meet the special requirements for fracture evaluation of circumferential flaws in the welds of ring-forged vessels. Fracture technology advances required to address the issues discussed in this paper are the major objective for the ongoing Heavy-Section Steel Technology (HSST) Program at Oak Ridge National Laboratory (ORNL). 22 refs., 18 figs.

  5. Thermal Aging Phenomena in Cast Duplex Stainless Steels

    NASA Astrophysics Data System (ADS)

    Byun, T. S.; Yang, Y.; Overman, N. R.; Busby, J. T.

    2016-02-01

    Cast stainless steels (CASSs) have been extensively used for the large components of light water reactor (LWR) power plants such as primary coolant piping and pump casing. The thermal embrittlement of CASS components is one of the most serious concerns related to the extended-term operation of nuclear power plants. Many past researches have concluded that the formation of Cr-rich α'-phase by Spinodal decomposition of δ-ferrite phase is the primary mechanism for the thermal embrittlement. Cracking mechanism in the thermally-embrittled duplex stainless steels consists of the formation of cleavage at ferrite and its propagation via separation of ferrite-austenite interphase. This article intends to provide an introductory overview on the thermal aging phenomena in LWR-relevant conditions. Firstly, the thermal aging effect on toughness is discussed in terms of the cause of embrittlement and influential parameters. An approximate analysis of thermal reaction using Arrhenius equation was carried out to scope the aging temperatures for the accelerated aging experiments to simulate the 60 and 80 years of services. Further, an equilibrium precipitation calculation was performed for model CASS alloys using the CALPHAD program, and the results are used to describe the precipitation behaviors in duplex stainless steels. These results are also to be used to guide an on-going research aiming to provide knowledge-based conclusive prediction for the integrity of the CASS components of LWR power plants during the service life extended up to and beyond 60 years.

  6. Mechanical Properties of Austenitic Stainless Steel Made by Additive Manufacturing

    PubMed Central

    Luecke, William E; Slotwinski, John A

    2014-01-01

    Using uniaxial tensile and hardness testing, we evaluated the variability and anisotropy of the mechanical properties of an austenitic stainless steel, UNS S17400, manufactured by an additive process, selective laser melting. Like wrought materials, the mechanical properties depend on the orientation introduced by the processing. The recommended stress-relief heat treatment increases the tensile strength, reduces the yield strength, and decreases the extent of the discontinuous yielding. The mechanical properties, assessed by hardness, are very uniform across the build plate, but the stress-relief heat treatment introduced a small non-uniformity that had no correlation to position on the build plate. Analysis of the mechanical property behavior resulted in four conclusions. (1) The within-build and build-to-build tensile properties of the UNS S17400 stainless steel are less repeatable than mature engineering structural alloys, but similar to other structural alloys made by additive manufacturing. (2) The anisotropy of the mechanical properties of the UNS S17400 material of this study is larger than that of mature structural alloys, but is similar to other structural alloys made by additive manufacturing. (3) The tensile mechanical properties of the UNS S17400 material fabricated by selective laser melting are very different from those of wrought, heat-treated 17-4PH stainless steel. (4) The large discontinuous yielding strain in all tests resulted from the formation and propagation of Lüders bands. PMID:26601037

  7. Structural characterization and magnetic properties of steels subjected to fatigue

    NASA Astrophysics Data System (ADS)

    Lo, C. C. H.; Tang, F.; Biner, S. B.; Jiles, D. C.

    2000-05-01

    Studies have been made on the effects of residual stress and microstructure on the variations of magnetic properties of steels during fatigue. Strain-controlled fatigue tests have been conducted on 0.2wt% C steel samples which were (1) cold-worked, (2) cold-worked and annealed at 500 °C to relieve residual stress, and (3) annealed at 905 °C to produce a ferrite/pearlite structure. The changes of surface microstructure were studied by SEM replica technique. The dislocation structures of samples fatigued for different numbers of cycle were studied by TEM. In the initial stage of fatigue coercivity was found to behave differently for samples which have different residual stress levels. In the intermediate stage the magnetic hysteresis parameters became stable as the dislocation cell structure developed in the samples. In the final stage the magnetic parameters decreased dramatically. The decrease rate is related to the propagation rate of fatigue cracks observed in the SEM study, which was found to be dependent on the sample microstructure. The present results indicate that the magnetic inspection technique is able to differentiate the residual stress effects from the fatigue damage induced by cyclic loading, and therefore it is possible to detect the onset of fatigue failure in steel components via measurements of the changes in magnetic properties.—This work was sponsored by the National Science Foundation, under grant number CMS-9532056.

  8. Estimation of corrosion damage in steel reinforced mortar using waveguides

    NASA Astrophysics Data System (ADS)

    Reis, Henrique; Ervin, Benjamin L.; Kuchma, Daniel A.; Bernhard, Jennifer

    2005-05-01

    Corrosion of reinforced concrete is a chronic infrastructure problem, particularly in areas with deicing salt and marine exposure. To maintain structural integrity, a testing method is needed to identify areas of corroding reinforcement. For purposes of rehabilitation, the method must also be able to evaluate the degree, rate and location of damage. Towards the development of a wireless embedded sensor system to monitor and assess corrosion damage in reinforced concrete, reinforced mortar specimens were manufactured with seeded defects to simulate corrosion damage. Taking advantage of waveguide effects of the reinforcing bars, these specimens were then tested using an ultrasonic approach. Using the same ultrasonic approach, specimens without seeded defects were also monitored during accelerated corrosion tests. Both the ultrasonic sending and the receiving transducers were mounted on the steel rebar. Advantage was taken of the lower frequency (<250 kHz) fundamental flexural propagation mode because of its relatively large displacements at the interface between the reinforcing steel and the surrounding concrete. Waveform energy (indicative of attenuation) is presented and discussed in terms of corrosion damage. Current results indicate that the loss of bond strength between the reinforcing steel and the surrounding concrete can be detected and evaluated.

  9. Thermal Aging Phenomena in Cast Duplex Stainless Steels

    SciTech Connect

    Byun, T. S.; Yang, Y.; Overman, N. R.; Busby, J. T.

    2015-11-12

    We used cast stainless steels (CASSs)for the large components of light water reactor (LWR) power plants such as primary coolant piping and pump casing. The thermal embrittlement of CASS components is one of the most serious concerns related to the extended-term operation of nuclear power plants. Many past researches have concluded that the formation of Cr-rich alpha-phase by Spinodal decomposition of delta-ferrite phase is the primary mechanism for the thermal embrittlement. Cracking mechanism in the thermally-embrittled duplex stainless steels consists of the formation of cleavage at ferrite and its propagation via separation of ferrite-austenite interphase. This article intends to provide an introductory overview on the thermal aging phenomena in LWR-relevant conditions. Firstly, the thermal aging effect on toughness is discussed in terms of the cause of embrittlement and influential parameters. Moreover, an approximate analysis of thermal reaction using Arrhenius equation was carried out to scope the aging temperatures for the accelerated aging experiments to simulate the 60 and 80 years of services. Further, an equilibrium precipitation calculation was performed for model CASS alloys using the CALPHAD program, and the results are used to describe the precipitation behaviors in duplex stainless steels. Our results are also to be used to guide an on-going research aiming to provide knowledge-based conclusive prediction for the integrity of the CASS components of LWR power plants during the service life extended up to and beyond 60 years.

  10. Fabrication of stainless steel foil utilizing chromized steel strip

    NASA Astrophysics Data System (ADS)

    Loria, Edward A.

    1980-10-01

    Stainless steel foil has properties which are, in many respects, unmatched by alternative thin films. The high strength to weight ratio and resistance to corrosion and oxidation at elevated temperatures are generally advantageous. The aerospace and automotive industries have used Type 430 and 304 foil in turbine engine applications. Foil around 2 mils (5.1 × 10-3 cm) thick has been appropriate for the recuperator or heat exchanger and this product has also been used in honeycomb and truss-core structures. Further, such foil has been employed as a wrap to protect tool steel parts from contamination during heat treating. A large part of the high cost of producing stainless steel foil by rolling is due to the complicated and expensive rolling mill and annealing equipment involved. A method will be described which produces (solid) stainless steel foil from chromized (coated) steel which can be cheaper than the conventional processing stainless steel, such as Type 430, from ingot to foil. Also, the material is more ductile and less work hardenable during processing to foil and consequently intermediate annealing treatments are eliminated and scrap losses minimized.

  11. Corrosion of Steels in Steel Reinforced Concrete in Cassava Juice

    NASA Astrophysics Data System (ADS)

    Oluwadare, G. O.; Agbaje, O.

    The corrosion of two types of construction steels, ST60Mn and RST37-2♦, in a low cyanide concentration environment (cassava juice) and embedded in concrete had been studied. The ST60 Mn was found to be more corrosion resistant in both ordinary water and the cassava juice environment. The cyanide in cassava juice does not attack the steel but it provides an environment of lower pH around the steel in the concrete which leads to breakdown of the passivating film provided by hydroxyl ions from cement. Other factors such as the curing time of the concrete also affect the corrosion rates of the steel in the concrete. The corrosion rate of the steel directly exposed to cassava juice i.e., steel not embedded in concrete is about twice that in concrete. Long exposure of concrete structure to cassava processing effluent might result in deterioration of such structures. Careful attention should therefore be paid to disposal of cassava processing effluents, especially in a country like Nigeria where such processing is now on the increase.

  12. Comparison of fatigue crack propagation in Modes I and III

    SciTech Connect

    Ritchie, R.O.

    1985-06-01

    The propagation behavior of fatigue cracks in Mode III (anti-plane shear), measured under cyclic torsion, is described and compared with more commonly encountered behavior under Mode I (tensile opening) loads. It is shown that a unique, global characterization of Mode III growth rates, akin to the Paris ''law'' in Mode I, is only possible if characterizating parameters appropriate to large-scale yielding are employed and allowance is made for crack tip shielding from sliding crack surface interference (i.e., friction and abrasion) between mating fracture surfaces. Based on the crack tip stress and deformation fields for Mode III stationary cracks, the cyclic crack tip displacement, (..delta..CTD/sub III/, and plastic strain intensity range ..delta..GAMMA/sub III/, have been proposed and are found to provide an adequate description of behavior in a range of steels, provided crack surface interference is minimized. The magnitude of this interference, which is somewhat analogous to crack closure in Mode I, is further examined in the light of the complex fractography of torsional fatigue failures and the question of a ''fatigue threshold'' for Mode III crack growth. Finally, micro-mechanical models for cyclic crack extension in anti-plane shear are briefly described, and the contrasting behavior between Mode III and Mode I cracks subjected to simple variable amplitude spectra is examined in terms of the differing role of crack tip blunting and closure in influencing shear, as opposed to tensile opening, modes of crack growth.

  13. Numerical investigation of elastic modes of propagation in helical waveguides.

    PubMed

    Treyssède, Fabien

    2007-06-01

    Steel multi-wire cables are widely employed in civil engineering. They are usually made of a straight core and one layer of helical wires. In order to detect material degradation, nondestructive evaluation methods based on ultrasonics are one of the most promising techniques. However, their use is complicated by the lack of accurate cable models. As a first step, the goal of this paper is to propose a numerical method for the study of elastic guided waves inside a single helical wire. A finite element (FE) technique is used based on the theory of wave propagation inside periodic structures. This method avoids the tedious writing of equilibrium equations in a curvilinear coordinate system yielding translational invariance along the helix centerline. Besides, no specific programming is needed inside a conventional FE code because it can be implemented as a postprocessing step of stiffness, mass and damping matrices. The convergence and accuracy of the proposed method are assessed by comparing FE results with Pochhammer-Chree solutions for the infinite isotropic cylinder. Dispersion curves for a typical helical waveguide are then obtained. In the low-frequency range, results are validated with a helical Timoshenko beam model. Some significant differences with the cylinder are observed. PMID:17552691

  14. The propagation of sound waves in drill strings

    SciTech Connect

    Drumheller, D.S. ); Knudsen, S.D. )

    1995-04-01

    Deep wells are commonly drilled while steering the drill bit. The steering process is completely controlled by the drilling-rig operator. A key element of this procedure is the measurement and communication of navigation information from the bottom of the well to the operator. Pressure pulses modulated onto the flow of the drill fluid are now employed in some cases to communicate this information. However, data rates are only a few binary bits per second with this method. This drastically limits the quantity of data available to the operator. As an alternative method, elastic waves generated within the steel drill string can be used as a carrier signal to transmit data. The drill string is commonly assembled from 10-m segments of threaded pipe and forms a periodic structure. The elastic wavelengths of interest are shorter than this periodic length. Consequently, these waves undergo significant dispersion. This paper presents new data for the propagation of elastic waves in a 2-km drill string. The influence of aperiodicity in the drill string, rotation of the drill string, and noise levels are studied in detail. The data verify a method for reducing the attenuation of a carrier signal by a factor of 2.

  15. Ultrasonic investigations of cermets elastic properties in dependence on steel concentration and temperature of sintering

    NASA Astrophysics Data System (ADS)

    Abramovich, A.

    2012-12-01

    Cermets is a ceramic-metal composite usually produced by sintering a precompacted mixture of the initial powders. These composite materials were created for industrial applications to produce engineering structures possessing a high strength, thermal stability and resistance to aggressive media. In the present work elastic properties of cermets samples, obtained by sintering of corundum (α-Al2O3) and stainless steel powders were investigated in dependence on steel concentration 5 - 35% wt. and on temperature of sintering in vacuum 1400-1700°C. It was stated that values of elastic moduli are in complex dependence on concentration and temperature, reach maxima at steel concentration 15 - 20% wt. and increase with sintering temperature rise. In the work also the results of cermets microstructure researches and discussion of these results are presented. The results are discussed from stand view of ultrasound propagation through medium having grain boundaries which influence on the physical properties of composite.

  16. Acoustic Emission Methodology to Evaluate the Fracture Toughness in Heat Treated AISI D2 Tool Steel

    NASA Astrophysics Data System (ADS)

    Mostafavi, Sajad; Fotouhi, Mohamad; Motasemi, Abed; Ahmadi, Mehdi; Sindi, Cevat Teymuri

    2012-10-01

    In this article, fracture toughness behavior of tool steel was investigated using Acoustic Emission (AE) monitoring. Fracture toughness ( K IC) values of a specific tool steel was determined by applying various approaches based on conventional AE parameters, such as Acoustic Emission Cumulative Count (AECC), Acoustic Emission Energy Rate (AEER), and the combination of mechanical characteristics and AE information called sentry function. The critical fracture toughness values during crack propagation were achieved by means of relationship between the integral of the sentry function and cumulative fracture toughness (KICUM). Specimens were selected from AISI D2 cold-work tool steel and were heat treated at four different tempering conditions (300, 450, 525, and 575 °C). The results achieved through AE approaches were then compared with a methodology proposed by compact specimen testing according to ASTM standard E399. It was concluded that AE information was an efficient method to investigate fracture characteristics.

  17. Metallographic etching and microstructure characterization of NiCrMoV rotor steels for nuclear power

    NASA Astrophysics Data System (ADS)

    Liu, Peng; Lu, Feng-gui; Liu, Xia; Gao, Yu-lai

    2013-12-01

    The grain size of prior austenite has a distinct influence on the microstructure and final mechanical properties of steels. Thus, it is significant to clearly reveal the grain boundaries and therefore to precisely characterize the grain size of prior austenite. For NiCrMoV rotor steels quenched and tempered at high temperature, it is really difficult to display the grain boundaries of prior austenite clearly, which limits a further study on the correlation between the properties and the corresponding microstructure. In this paper, an effective etchant was put forward and further optimized. Experimental results indicated that this agent was effective to show the details of grain boundaries, which help analyze fatigue crack details along the propagation path. The optimized corrosion agent is successful to observe the microstructure characteristics and expected to help analyze the effect of microstructure for a further study on the mechanical properties of NiCrMoV rotor steels used in the field of nuclear power.

  18. Making and Propagating Elastic Waves: Overview of the new wave propagation code WPP

    SciTech Connect

    McCandless, K P; Petersson, N A; Nilsson, S; Rodgers, A; Sjogreen, B; Blair, S C

    2006-05-09

    We are developing a new parallel 3D wave propagation code at LLNL called WPP (Wave Propagation Program). WPP is being designed to incorporate the latest developments in embedded boundary and mesh refinement technology for finite difference methods, as well as having an efficient portable implementation to run on the latest supercomputers at LLNL. We are currently exploring seismic wave applications, including a recent effort to compute ground motions for the 1906 Great San Francisco Earthquake. This paper will briefly describe the wave propagation problem, features of our numerical method to model it, implementation of the wave propagation code, and results from the 1906 Great San Francisco Earthquake simulation.

  19. Radiowave propagation measurements in Nigeria (preliminary reports)

    NASA Astrophysics Data System (ADS)

    Falodun, S. E.; Okeke, P. N.

    2013-07-01

    International conferences on frequency coordination have, in recent years, required new information on radiowave propagation in tropical regions and, in particular, on propagation in Africa. The International Telecommunications Union (ITU-R) initiated `radio-wave propagation measurement campaign' in some African countries some years back. However, none of the ITU-initiated experiments were mounted in Nigeria, and hence, there is lack of adequate understanding of the propagation mechanisms associated with this region of the tropics. The Centre for Basic Space Science (CBSS) of NASRDA has therefore embarked on propagation data collection from the different climatic zones of Nigeria (namely Coastal, Guinea Savannah, Midland, and Sahelian) with the aim of making propagation data available to the ITU, for design and prediction purposes in order to ensure a qualitative and effective communication system in Nigeria. This paper focuses on the current status of propagation data from Nigeria (collected by CBSS), identifying other parameters that still need to be obtained. The centre has deployed weather stations to different locations in the country for refractivity measurements in clear atmosphere, at the ground surface and at an altitude of 100 m, being the average height of communication mast in Nigeria. Other equipments deployed are Micro Rain Radar and Nigerian Environmental and Climatic Observing Program equipments. Some of the locations of the measurement stations are Nsukka (7.4° E, 6.9° N), Akure (5.12° E, 7.15° N), Minna (6.5° E, 9.6° N), Sokoto (5.25° E, 13.08° N), Jos (8.9° E, 9.86° N), and Lagos (3.35° E, 6.6° N). The results obtained from the data analysis have shown that the refractivity values vary with climatic zones and seasons of the year. Also, the occurrence probability of abnormal propagation events, such as super refraction, sub-refraction, and ducting, depends on the location as well as the local time. We have also attempted to identify

  20. Effect of Residual Stress on Fatigue Failure of Carbonitrided Low-Carbon Steel

    NASA Astrophysics Data System (ADS)

    Kanchanomai, C.; Limtrakarn, W.

    2008-12-01

    The effect of residual stress on fatigue behavior and mechanisms of carbonitrided AISI 1015 steel under uniaxial cyclic loading has been experimentally studied. By progressive removal of thin surface layers using an electropolishing technique and subsequent residual stress measurements using an x-ray diffraction technique, the compressive residual stress at the surface was approximately 900 MPa. The stress decreased toward the center, and became stable tensile residual stress of approximately 20 MPa. The fatigue resistance of carbonitrided AISI 1015 steel was higher than that of AISI 1015 steel due to the presence of compressive residual stress in case layer. The fatigue limit of AISI 1015 steels with and without carbonitriding was 340 and 300 MPa, respectively. Subsurface cracks initiated at the case-core interface, i.e. approximately 400 μm from the surface. With increasing number of stress cycles, the subsurface cracks coalesced and propagated intergranularly through the case layer. After some incubation cycles, the subsurface cracks reached the surface of specimen, and became a main crack. During this stage, the stress increased, and caused the formation of voids in core material. Consequently, the crack propagated through the core material, interacted with voids, and caused complete fracture.

  1. Great Lakes Steel -- PCI facility

    SciTech Connect

    Eichinger, F.T.; Dake, S.H.; Wagner, E.D.; Brown, G.S.

    1997-12-31

    This paper discusses the planning, design, and start-up of the 90 tph PCI facility for National Steel`s Great Lakes Steel Division in River Rouge, MI. This project is owned and operated by Edison Energy Services, and was implemented on a fast-track basis by Raytheon Engineers and Constructors, Babcock Material Handling, and Babcock and Wilcox. This paper presents important process issues, basic design criteria, an the challenges of engineering and building a state-of-the-art PCI facility in two existing plants. Pulverized coal is prepared at the River Rouge Power Plant of Detroit Edison, is pneumatically conveyed 6,000 feet to a storage silo at Great Lakes Steel, and is injected into three blast furnaces.

  2. Corrosion resistance of stainless steels

    SciTech Connect

    Dillon, C.P.

    1995-12-31

    This book reviews the mechanisms and forms of corrosion and examines the corrosion of stainless steels and similar chromium-bearing nickel containing higher alloys, detailing various corrosive environments including atmospheric and fire-side corrosion, corrosion by water and soil, and corrosion caused by particular industrial processes. It provides information on specific groups and grades of stainless steels; summarizes typical applications for specific stainless alloys; describes common corrosion problems associated with stainless steels; presents the acceptable isocorrosion parameters of concentration and temperature for over 250 chemicals for which stainless steels are the preferred materials of construction; discusses product forms and their availability; elucidates fabrication, welding, and joining techniques; and covers the effects of pickling and passivation.

  3. Hydrogen embrittlement of structural steels.

    SciTech Connect

    Somerday, Brian P.

    2010-06-01

    Carbon-manganese steels are candidates for the structural materials in hydrogen gas pipelines, however it is well known that these steels are susceptible to hydrogen embrittlement. Decades of research and industrial experience have established that hydrogen embrittlement compromises the structural integrity of steel components. This experience has also helped identify the failure modes that can operate in hydrogen containment structures. As a result, there are tangible ideas for managing hydrogen embrittement in steels and quantifying safety margins for steel hydrogen containment structures. For example, fatigue crack growth aided by hydrogen embrittlement is a key failure mode for steel hydrogen containment structures subjected to pressure cycling. Applying appropriate structural integrity models coupled with measurement of relevant material properties allows quantification of safety margins against fatigue crack growth in hydrogen containment structures. Furthermore, application of these structural integrity models is aided by the development of micromechanics models, which provide important insights such as the hydrogen distribution near defects in steel structures. The principal objective of this project is to enable application of structural integrity models to steel hydrogen pipelines. The new American Society of Mechanical Engineers (ASME) B31.12 design code for hydrogen pipelines includes a fracture mechanics-based design option, which requires material property inputs such as the threshold for rapid cracking and fatigue crack growth rate under cyclic loading. Thus, one focus of this project is to measure the rapid-cracking thresholds and fatigue crack growth rates of line pipe steels in high-pressure hydrogen gas. These properties must be measured for the base materials but more importantly for the welds, which are likely to be most vulnerable to hydrogen embrittlement. The measured properties can be evaluated by predicting the performance of the pipeline

  4. Effect of Mn Addition on Microstructural Modification and Cracking Behavior of Ferritic Light-Weight Steels

    NASA Astrophysics Data System (ADS)

    Sohn, Seok Su; Lee, Byeong-Joo; Lee, Sunghak; Kwak, Jai-Hyun

    2014-11-01

    In the present study, effects of Mn addition on cracking phenomenon occurring during cold rolling of ferritic light-weight steels were clarified in relation to microstructural modification involving κ-carbide, austenite, and martensite. Four steels were fabricated by varying Mn contents of 3 to 12 wt pct, and edge areas of steel sheets containing 6 to 9 wt pct Mn were cracked during the cold rolling. The steels were basically composed of ferrite and austenite in a band shape, but a considerable amount of κ-carbide or martensite existed in the steels containing 3 to 6 wt pct Mn. Microstructural observation of the deformed region of fractured tensile specimens revealed that cracks which were initiated at ferrite/martensite interfacial κ-carbides readily propagated along ferrite/martensite interfaces or into martensite areas in the steel containing 6 wt pct Mn, thereby leading to the center or edge cracking during the cold rolling. In the steel containing 9 wt pct Mn, edge cracks were found in the final stage of cold rolling because of the formation of martensite by the strain-induced austenite to martensite transformation, whereas they were hardly formed in the steel containing 12 wt pct Mn. To prevent or minimize the cracking, it was recommended that the formation of martensite during the cooling from the hot rolling temperature or during the cold rolling should be suppressed, which could be achieved by the enhancement of thermal or mechanical stability of austenite with decreasing austenite grain size or increasing contents of austenite stabilizers.

  5. Process Hood Stand Support Steel

    SciTech Connect

    VAN KATWIJK, C.

    2000-04-03

    This package is written to comply with EN-6-035-00 for upgrade dedication of commercial grade items (CGI). The SNF-5953 CGI package provides the Technical evaluation to identify the critical characteristics and the acceptance criteria associated with the safety function of the Hood Stand Support Steel. Completion of the technical and quality requirements identified in the dedication package will provide enough data to be reasonably assured that CGI Hood Stand Support Steel will perform its SC function.

  6. Fatigue handbook: Offshore steel structures

    SciTech Connect

    Almarnaess, A.

    1985-01-01

    The contents of this book are: Overview of Offshore Steel Structures; Loads on Ocean Structures; Fracture Mechanics As a Tool in Fatigue Analysis; Basic Fatigue Properties of Welded Joints; Significance of Defects; Improving the Fatigue Strength of Welded Joints; Effects of Marine Environment and Cathodic Protection on Fatigue of Structural Steels Fatigue of Tubular Joints; Unstable Fracture; Fatigue Life Calculations; and Fatigue in Building Codes Background and Applications.

  7. Analysis of plasma nitrided steels

    NASA Technical Reports Server (NTRS)

    Salik, J.; Ferrante, J.; Honecy, F.; Hoffman, R., Jr.

    1987-01-01

    The analysis of plasma nitrided steels can be divided to two main categories - structural and chemical. Structural analysis can provide information not only on the hardening mechanisms but also on the fundamental processes involved. Chemical analysis can be used to study the kinetics for the nitriding process and its mechanisms. In this paper preliminary results obtained by several techniques of both categories are presented and the applicability of those techniques to the analysis of plasma-nitrided steels is discussed.

  8. Wear of steel by rubber

    NASA Technical Reports Server (NTRS)

    Gent, A. N.; Pulford, C. T. R.

    1978-01-01

    Wear of a steel blade used as a scraper to abrade rubber surfaces has been found to take place much more rapidly on a cis-polyisoprene (natural rubber) surface than on a cis-polybutadiene surface, and much more rapidly in an inert atmosphere than in air. These observations are attributed to the direct attack upon steel of free-radical species generated by mechanical rupture of elastomer molecules during abrasion.

  9. Accurate orbit propagation with planetary close encounters

    NASA Astrophysics Data System (ADS)

    Baù, Giulio; Milani Comparetti, Andrea; Guerra, Francesca

    2015-08-01

    We tackle the problem of accurately propagating the motion of those small bodies that undergo close approaches with a planet. The literature is lacking on this topic and the reliability of the numerical results is not sufficiently discussed. The high-frequency components of the perturbation generated by a close encounter makes the propagation particularly challenging both from the point of view of the dynamical stability of the formulation and the numerical stability of the integrator. In our approach a fixed step-size and order multistep integrator is combined with a regularized formulation of the perturbed two-body problem. When the propagated object enters the region of influence of a celestial body, the latter becomes the new primary body of attraction. Moreover, the formulation and the step-size will also be changed if necessary. We present: 1) the restarter procedure applied to the multistep integrator whenever the primary body is changed; 2) new analytical formulae for setting the step-size (given the order of the multistep, formulation and initial osculating orbit) in order to control the accumulation of the local truncation error and guarantee the numerical stability during the propagation; 3) a new definition of the region of influence in the phase space. We test the propagator with some real asteroids subject to the gravitational attraction of the planets, the Yarkovsky and relativistic perturbations. Our goal is to show that the proposed approach improves the performance of both the propagator implemented in the OrbFit software package (which is currently used by the NEODyS service) and of the propagator represented by a variable step-size and order multistep method combined with Cowell's formulation (i.e. direct integration of position and velocity in either the physical or a fictitious time).

  10. NLO error propagation exercise: statistical results

    SciTech Connect

    Pack, D.J.; Downing, D.J.

    1985-09-01

    Error propagation is the extrapolation and cumulation of uncertainty (variance) above total amounts of special nuclear material, for example, uranium or /sup 235/U, that are present in a defined location at a given time. The uncertainty results from the inevitable inexactness of individual measurements of weight, uranium concentration, /sup 235/U enrichment, etc. The extrapolated and cumulated uncertainty leads directly to quantified limits of error on inventory differences (LEIDs) for such material. The NLO error propagation exercise was planned as a field demonstration of the utilization of statistical error propagation methodology at the Feed Materials Production Center in Fernald, Ohio from April 1 to July 1, 1983 in a single material balance area formed specially for the exercise. Major elements of the error propagation methodology were: variance approximation by Taylor Series expansion; variance cumulation by uncorrelated primary error sources as suggested by Jaech; random effects ANOVA model estimation of variance effects (systematic error); provision for inclusion of process variance in addition to measurement variance; and exclusion of static material. The methodology was applied to material balance area transactions from the indicated time period through a FORTRAN computer code developed specifically for this purpose on the NLO HP-3000 computer. This paper contains a complete description of the error propagation methodology and a full summary of the numerical results of applying the methodlogy in the field demonstration. The error propagation LEIDs did encompass the actual uranium and /sup 235/U inventory differences. Further, one can see that error propagation actually provides guidance for reducing inventory differences and LEIDs in future time periods.

  11. Development of New Stainless Steel

    SciTech Connect

    Robert F. Buck

    2005-08-30

    A new family of innovative martensitic stainless steels, 521-A, 521-B, and 521-C has been developed by Advanced Steel Technology, LLC (Trafford, PA) as high strength fastener (bolt) materials for use at moderate temperatures in turbine engines, including steam turbines, gas turbines, and aircraft engines. The primary objective of the development program was to create a martensitic stainless steel with high strength at moderate temperatures, and which could replace the expensive nickel-based superalloy IN 718 in some fasteners applications. A secondary objective was to replace conventional 12Cr steels such as AISI 422 used as blades, buckets and shafts that operate at intermediate temperatures in turbine engines with stronger steel. The composition of the new alloys was specifically designed to produce excellent mechanical properties while integrating heat treatment steps into production to reduce energy consumption during manufacturing. As a result, production costs and energy consumption during production of rolled bar products is significantly lower than conventional materials. Successful commercialization of the new alloys would permit the installed cost of certain turbine engines to be reduced without sacrificing high availability or operational flexibility, thereby enhancing the global competitiveness of U.S. turbine engine manufacturers. Moreover, the domestic specialty steel industry would also benefit through increased productivity and reduced operating costs, while increasing their share of the international market for turbine engine fasteners, blades, buckets and shafts.

  12. Hydrogen Permeation in Nanostructured Bainitic Steel

    NASA Astrophysics Data System (ADS)

    Kazum, Oluwole; Beladi, Hossein; Timokhina, Ilana B.; He, Yinghe; Bobby Kannan, M.

    2016-07-01

    Hydrogen permeation of nanostructured bainitic steel, produced at two different transformation temperatures, i.e., 473.15 K (200 °C) BS-200 and 623.15 K (350 °C) BS-350, was determined using Devanathan-Stachurski hydrogen permeation cell and compared with that of mild steel. Nanostructured bainitic steel showed lower effective diffusivity of hydrogen as compared to the mild steel. The BS-200 steel, which exhibited higher volume fraction of bainitic ferrite phase, showed lower effective diffusivity than BS-350 steel. The finer microstructural constituents (bainitic ferrite laths and retained austenite films) and higher dislocation density in the bainitic ferrite phase of BS-200 steel can be attributed to its lower effective diffusivity as compared to BS-350 steel and mild steel.

  13. Controls on flood and sediment wave propagation

    NASA Astrophysics Data System (ADS)

    Bakker, Maarten; Lane, Stuart N.; Costa, Anna; Molnar, Peter

    2015-04-01

    The understanding of flood wave propagation - celerity and transformation - through a fluvial system is of generic importance for flood forecasting/mitigation. In association with flood wave propagation, sediment wave propagation may induce local erosion and sedimentation, which will affect infrastructure and riparian natural habitats. Through analysing flood and sediment wave propagation, we gain insight in temporal changes in transport capacity (the flood wave) and sediment availability and transport (the sediment wave) along the river channel. Heidel (1956) was amongst the first to discuss the progressive lag of sediment concentration behind the corresponding flood wave based on field measurements. Since then this type of hysteresis has been characterized in a number of studies, but these were often based on limited amount of floods and measurement sites, giving insufficient insight into associated forcing mechanisms. Here, as part of a project concerned with the hydrological and geomorphic forcing of sediment transfer processes in alpine environments, we model the downstream propagation of short duration, high frequency releases of water and sediment (purges) from a flow intake in the Borgne d'Arolla River in south-west Switzerland. A total of >50 events were measured at 1 minute time intervals using pressure transducers and turbidity probes at a number of sites along the river. We show that flood and sediment wave propagation can be well represented through simple convection diffusion models. The models are calibrated/validated to describe the set of measured waves and used to explain the observed variation in wave celerity and diffusion. In addition we explore the effects of controlling factors including initial flow depth, flood height, flood duration, bed roughness, bed slope and initial sediment concentration, on the wave propagation processes. We show that the effects of forcing mechanisms on flood and sediment wave propagation will lead to different

  14. Classification of neocortical interneurons using affinity propagation

    PubMed Central

    Santana, Roberto; McGarry, Laura M.; Bielza, Concha; Larrañaga, Pedro; Yuste, Rafael

    2013-01-01

    In spite of over a century of research on cortical circuits, it is still unknown how many classes of cortical neurons exist. In fact, neuronal classification is a difficult problem because it is unclear how to designate a neuronal cell class and what are the best characteristics to define them. Recently, unsupervised classifications using cluster analysis based on morphological, physiological, or molecular characteristics, have provided quantitative and unbiased identification of distinct neuronal subtypes, when applied to selected datasets. However, better and more robust classification methods are needed for increasingly complex and larger datasets. Here, we explored the use of affinity propagation, a recently developed unsupervised classification algorithm imported from machine learning, which gives a representative example or exemplar for each cluster. As a case study, we applied affinity propagation to a test dataset of 337 interneurons belonging to four subtypes, previously identified based on morphological and physiological characteristics. We found that affinity propagation correctly classified most of the neurons in a blind, non-supervised manner. Affinity propagation outperformed Ward's method, a current standard clustering approach, in classifying the neurons into 4 subtypes. Affinity propagation could therefore be used in future studies to validly classify neurons, as a first step to help reverse engineer neural circuits. PMID:24348339

  15. Classification of neocortical interneurons using affinity propagation.

    PubMed

    Santana, Roberto; McGarry, Laura M; Bielza, Concha; Larrañaga, Pedro; Yuste, Rafael

    2013-01-01

    In spite of over a century of research on cortical circuits, it is still unknown how many classes of cortical neurons exist. In fact, neuronal classification is a difficult problem because it is unclear how to designate a neuronal cell class and what are the best characteristics to define them. Recently, unsupervised classifications using cluster analysis based on morphological, physiological, or molecular characteristics, have provided quantitative and unbiased identification of distinct neuronal subtypes, when applied to selected datasets. However, better and more robust classification methods are needed for increasingly complex and larger datasets. Here, we explored the use of affinity propagation, a recently developed unsupervised classification algorithm imported from machine learning, which gives a representative example or exemplar for each cluster. As a case study, we applied affinity propagation to a test dataset of 337 interneurons belonging to four subtypes, previously identified based on morphological and physiological characteristics. We found that affinity propagation correctly classified most of the neurons in a blind, non-supervised manner. Affinity propagation outperformed Ward's method, a current standard clustering approach, in classifying the neurons into 4 subtypes. Affinity propagation could therefore be used in future studies to validly classify neurons, as a first step to help reverse engineer neural circuits. PMID:24348339

  16. Toward an improved understanding of MCS propagation

    NASA Astrophysics Data System (ADS)

    Peters, J. M.

    2015-12-01

    Processes that drive the propagation of elevated mesoscale convective systems (MCSs) have been the topic of a growing body of recent research. Elevated MCSs are responsible for a large percentage of warm season rainfall in the continental United States, and produce flash floods more frequently than other modes of convection. A comprehensive understanding of the dynamics of MCS propagation is important, since propagation sometimes opposes other environmental forces that influence MCS motion. This leads to nearly stationary MCSs that produce prolific local rainfall totals. The ingredients-based Propagation index (IPI) is introduced in this research. IPI is defined as the normalized product of horizontal warm thermal advection (a proxy for lifting), convective available potential energy (CAPE), and relative humidity. Horizontal plots of IPI are useful in identifying regions of probable convective initiation, including the intersections between potentially unstable flow and outflow boundaries, regions of mesoscale lift along the nose of the low-level jet, convectively induced gravity waves, and frontogenesis. Effective inflow-layer shear vectors are also introduced, and found to be useful for scenarios where IPI does yield predictive insight, such as the traditional "RKW" scenario where the forward propagation of an MCS is driven by thunderstorm outflow. It is argued that horizontal maps of IPI and EILS vectors will contribute significantly to short-term (e.g. 1-2 hr) predictions of the movement of MCSs, and to the subsequent assessment of their potential for flash flood production.

  17. Effects of fluctuations on propagating fronts

    NASA Astrophysics Data System (ADS)

    Panja, Debabrata

    Propagating fronts are seen in varieties of nonequilibrium pattern forming systems in Physics, Chemistry and Biology. In the last two decades, many researchers have contributed to the understanding of the underlying dynamics of the propagating fronts. Of these, the deterministic and mean-field dynamics of the fronts were mostly understood in late 1980s and 1990s. On the other hand, although the earliest work on the effect of fluctuations on propagating fronts dates back to early 1980s, the subject of fluctuating fronts did not reach its adolescence until the mid 1990s. From there onwards the last few years witnessed a surge in activities in the effect of fluctuations on propagating fronts. Scores of papers have been written on this subject since then, contributing to a significant maturity of our understanding, and only recently a full picture of fluctuating fronts has started to emerge. This review is an attempt to collect all the works on fluctuating (propagating) fronts in a coherent and cogent manner in proper perspective. It is based on the idea of making our knowledge in this field available to a broader audience, and it is also expected to help to collect bits and pieces of loose thread-ends together for possible further investigation.

  18. Gain-assisted superluminal light propagation

    PubMed

    Wang; Kuzmich; Dogariu

    2000-07-20

    Einstein's theory of special relativity and the principle of causality imply that the speed of any moving object cannot exceed that of light in a vacuum (c). Nevertheless, there exist various proposals for observing faster-than-c propagation of light pulses, using anomalous dispersion near an absorption line, nonlinear and linear gain lines, or tunnelling barriers. However, in all previous experimental demonstrations, the light pulses experienced either very large absorption or severe reshaping, resulting in controversies over the interpretation. Here we use gain-assisted linear anomalous dispersion to demonstrate superluminal light propagation in atomic caesium gas. The group velocity of a laser pulse in this region exceeds c and can even become negative, while the shape of the pulse is preserved. We measure a group-velocity index of n(g) = -310(+/- 5); in practice, this means that a light pulse propagating through the atomic vapour cell appears at the exit side so much earlier than if it had propagated the same distance in a vacuum that the peak of the pulse appears to leave the cell before entering it. The observed superluminal light pulse propagation is not at odds with causality, being a direct consequence of classical interference between its different frequency components in an anomalous dispersion region. PMID:10917523

  19. Forecasting Corrosion of Steel in Concrete Introducing Chloride Threshold Dependence on Steel Potential

    NASA Astrophysics Data System (ADS)

    Sanchez, Andrea Nathalie

    Corrosion initiates in reinforced concrete structures exposed to marine environments when the chloride ion concentration at the surface of an embedded steel reinforcing bar exceeds the chloride corrosion threshold (CT) value. The value of CT is generally assumed to have a conservative fixed value ranging from 0.2% to - 0.5 % of chloride ions by weight of cement. However, extensive experimental investigations confirmed that C T is not a fixed value and that the value of CT depends on many variables. Among those, the potential of passive steel embedded in concrete is a key influential factor on the value of CT and has received little attention in the literature. The phenomenon of a potential-dependent threshold (PDT) permits accounting for corrosion macrocell coupling between active and passive steel assembly components in corrosion forecast models, avoiding overly conservative long-term damage projections and leading to more efficient design. The objectives of this investigation was to 1) expand by a systematic experimental assessment the knowledge and data base on how dependent the chloride threshold is on the potential of the steel embedded in concrete and 2) introduce the chloride threshold dependence on steel potential as an integral part of corrosion-related service life prediction of reinforced concrete structures. Experimental assessments on PDT were found in the literature but for a limited set of conditions. Therefore, experiments were conducted with mortar and concrete specimens and exposed to conditions more representative of the field than those previously available. The experimental results confirmed the presence of the PDT effect and provided supporting information to use a value of -550 mV per decade of Cl- for the cathodic prevention slope betaCT, a critical quantitative input for implementation in a practical model. A refinement of a previous corrosion initiation-propagation model that incorporated PDT in a partially submerged reinforced concrete

  20. Characterization and Prediction of Cracks in Coated Materials: Direction and Length of Crack Propagation in Bimaterials.

    PubMed

    Pruncu, C I; Azari, Z; Casavola, C; Pappalettere, C

    2015-01-01

    The behaviour of materials is governed by the surrounding environment. The contact area between the material and the surrounding environment is the likely spot where different forms of degradation, particularly rust, may be generated. A rust prevention treatment, like bluing, inhibitors, humidity control, coatings, and galvanization, will be necessary. The galvanization process aims to protect the surface of the material by depositing a layer of metallic zinc by either hot-dip galvanizing or electroplating. In the hot-dip galvanizing process, a metallic bond between steel and metallic zinc is obtained by immersing the steel in a zinc bath at a temperature of around 460°C. Although the hot-dip galvanizing procedure is recognized to be one of the most effective techniques to combat corrosion, cracks can arise in the intermetallic δ layer. These cracks can affect the life of the coated material and decrease the lifetime service of the entire structure. In the present paper the mechanical response of hot-dip galvanized steel submitted to mechanical loading condition is investigated. Experimental tests were performed and corroborative numerical and analytical methods were then applied in order to describe both the mechanical behaviour and the processes of crack/cracks propagation in a bimaterial as zinc-coated material. PMID:27347531

  1. Characterization and Prediction of Cracks in Coated Materials: Direction and Length of Crack Propagation in Bimaterials

    PubMed Central

    Azari, Z.; Pappalettere, C.

    2015-01-01

    The behaviour of materials is governed by the surrounding environment. The contact area between the material and the surrounding environment is the likely spot where different forms of degradation, particularly rust, may be generated. A rust prevention treatment, like bluing, inhibitors, humidity control, coatings, and galvanization, will be necessary. The galvanization process aims to protect the surface of the material by depositing a layer of metallic zinc by either hot-dip galvanizing or electroplating. In the hot-dip galvanizing process, a metallic bond between steel and metallic zinc is obtained by immersing the steel in a zinc bath at a temperature of around 460°C. Although the hot-dip galvanizing procedure is recognized to be one of the most effective techniques to combat corrosion, cracks can arise in the intermetallic δ layer. These cracks can affect the life of the coated material and decrease the lifetime service of the entire structure. In the present paper the mechanical response of hot-dip galvanized steel submitted to mechanical loading condition is investigated. Experimental tests were performed and corroborative numerical and analytical methods were then applied in order to describe both the mechanical behaviour and the processes of crack/cracks propagation in a bimaterial as zinc-coated material. PMID:27347531

  2. Thermal Acoustic Wave Propagation Within a Slightly Compressible Viscous Fluid-Filled Impermeable Cylindrical Elastic Tube.

    NASA Astrophysics Data System (ADS)

    Liang, Paul Nan-Jiune

    1990-01-01

    Three dimensional mode shapes for thermoelastic waves in a viscous, compressible, fluid-filled infinite annular elastic concentric cylinder are studied using the exact coupled three dimensional equations for the vibrations in the n = 0, 1 circumferential modes. These results are related to those which arise under circumstances where uncoupled shear modes in the wall and the fluid have similar axial phase velocities and therefore are in a state sometimes called "coincidence". Three dimensional dispersion curves and modal wave plots are presented for a range of parameters including a steel tube containing water, glycerin and air. The corresponding axial mode shapes and radial mode shapes and their three dimensional equivalents are plotted so that the types of wave motion can be identified. The thermal effect for wave propagation in a fluid -filled annular elastic steel tube is found to be very important. This effect can cause a 15% difference (the average for water and glycerin) with that neglecting the thermal effect with the system equations. However, for an elastic steel tube or a fluid line alone, the thermal effect is small (< 1%) under the conditions of room temperature and the radius ratio of inner to outer radii is 0.93. The mechanism for the importance of the thermal effect in the coupled fluid-solid problem is related to the relatively higher thermal conductivity at the solid wall which conducts away heat from the relatively insulated viscous liquid boundary layer.

  3. Kinetics of fracture in Fe-3Si steel under mode I loading

    NASA Technical Reports Server (NTRS)

    Bessendorf, Michael H.

    1989-01-01

    This paper deals with experimental studies of fatigue crack propagation (FCP) in Fe-3Si steel. The FCP experiments were performed on single-edge crack specimens. Results show that an extensive damage zone consisting of slip bands surrounds and precedes the propagating crack. The system of the crack and the damage zone constitutes the crack layer (CL). The results demonstrate that fracture propagates by the translation, expansion, and distortion of the part of CL called the active zone. The contours of the damage distribution show that different loading stresses may cause significantly different shapes of damage. Application of the stability criteria is demonstrated. It was shown that the critical energy release rate depends on the history of loading.

  4. Review on Cold-Formed Steel Connections

    PubMed Central

    Tan, Cher Siang; Mohammad, Shahrin; Md Tahir, Mahmood; Shek, Poi Ngian

    2014-01-01

    The concept of cold-formed light steel framing construction has been widespread after understanding its structural characteristics with massive research works over the years. Connection serves as one of the important elements for light steel framing in order to achieve its structural stability. Compared to hot-rolled steel sections, cold-formed steel connections perform dissimilarity due to the thin-walled behaviour. This paper aims to review current researches on cold-formed steel connections, particularly for screw connections, storage rack connections, welded connections, and bolted connections. The performance of these connections in the design of cold-formed steel structures is discussed. PMID:24688448

  5. Nonlinear Force Propagation During Granular Impact

    NASA Astrophysics Data System (ADS)

    Clark, Abram H.; Petersen, Alec J.; Kondic, Lou; Behringer, Robert P.

    2015-04-01

    We experimentally study nonlinear force propagation into granular material during impact from an intruder, and we explain our observations in terms of the nonlinear grain-scale force relation. Using high-speed video and photoelastic particles, we determine the speed and spatial structure of the force response just after impact. We show that these quantities depend on a dimensionless parameter, M'=tcv0/d , where v0 is the intruder speed at impact, d is the particle diameter, and tc is the collision time for a pair of grains impacting at relative speed v0. The experiments access a large range of M' by using particles of three different materials. When M'≪1 , force propagation is chainlike with a speed, vf, satisfying vf∝d /tc. For larger M', the force response becomes spatially dense and the force propagation speed departs from vf∝d /tc, corresponding to collective stiffening of a strongly compressed packing of grains.

  6. Propagation of shock waves through petroleum suspensions

    NASA Astrophysics Data System (ADS)

    Mukuk, K. V.; Makhkamov, S. M.; Azizov, K. K.

    1986-01-01

    Anomalous shock wave propagation through petroleum with a high paraffin content was studied in an attempt to confirm the theoretically predicted breakdown of a forward shock wave into oscillating waves and wave packets as well as individual solitons. Tests were performed in a shock tube at 10, 20, and 50 to 60 C, with pure kerosene as reference and with kerosene + 5, 10, 15, and 20% paraffin. The addition of paraffin was found to radically alter the rheodynamic characteristics of the medium and, along with it, the pattern of shock wave propagation. The integro-differential equation describing a one dimensional hydraulic shock process in viscoelastic fluids is reduced to the Burgers-Korteweg-deVries equation, which is solved numerically for given values of the system parameters. The results indicate that the theory of shock wave propagation through such an anomalous suspension must be modified.

  7. Heat pulse propagation studies in TFTR

    SciTech Connect

    Fredrickson, E.D.; Callen, J.D.; Colchin, R.J.; Efthimion, P.C.; Hill, K.W.; Izzo, R.; Mikkelsen, D.R.; Monticello, D.A.; McGuire, K.; Bell, J.D.

    1986-02-01

    The time scales for sawtooth repetition and heat pulse propagation are much longer (10's of msec) in the large tokamak TFTR than in previous, smaller tokamaks. This extended time scale coupled with more detailed diagnostics has led us to revisit the analysis of the heat pulse propagation as a method to determine the electron heat diffusivity, chi/sub e/, in the plasma. A combination of analytic and computer solutions of the electron heat diffusion equation are used to clarify previous work and develop new methods for determining chi/sub e/. Direct comparison of the predicted heat pulses with soft x-ray and ECE data indicates that the space-time evolution is diffusive. However, the chi/sub e/ determined from heat pulse propagation usually exceeds that determined from background plasma power balance considerations by a factor ranging from 2 to 10. Some hypotheses for resolving this discrepancy are discussed. 11 refs., 19 figs., 1 tab.

  8. Flame propagation in partially premixed conditions

    NASA Astrophysics Data System (ADS)

    Ruetsch, G.; Poinsot, T.; Veynante, D.; Trouvé, A.

    1996-11-01

    Turbulent flame propagation is studied under inhomogenously premixed conditions via data from direct numerical simulations. Departures from the premixed case are studied using four different configurations, ranging from one dimensional unsteady flames to turbulent three-dimensional simulations. Simulations are performed in these cases with various values of the mean equivalence ratio, fluctuations about the mean equivlalence ratio, correlation length scales, and probability denisty functions of the mixture composition. Propagation characteristics are described in terms of the flamelet approach, where the the main contribution of partial premixing on flame propagation is due to flame wrinkling relative to modification of the mean flamelet structure. This behavior is consistent over a broad range of conditions, with the exception being extreme departures from stoichiometric conditions where flamability limits are exceeded and flame quenching is observed.

  9. Propagation of intense UV filaments and vortices

    NASA Astrophysics Data System (ADS)

    Sukhinin, Alexey

    The goal of this dissertation is to investigate the propagation of ultrashort high intensity UV laser pulses of order of nanoseconds in atmosphere. It is believed that they have a potential for stable and diffractionless propagation over the extended distances. Consequently, it creates a new array of applications in areas of communication, sensing, energy transportation and others. The theoretical model derived from Maxwell's equations represents unidirectional envelope propagation and plasma creation equations. It was shown numerically through Newton's iterations that the stationary model permits the localized fundamental and vortex solutions. Discussion of the stability of steady states involves different approaches and their limitations. Finally, model equations are integrated numerically to study the dynamics of the beams in the stationary model as well as nanosecond pulses in the full (3+1)D model using parallel computation.

  10. Shock unsteadiness creation and propagation: experimental analysis

    NASA Astrophysics Data System (ADS)

    Benay, R.; Alaphilippe, M.; Severac, N.

    2012-09-01

    The possibility of creating unsteady distortions of the tip shock by waves emitted from an aircraft is assessed experimentally. The model chosen is a cylindrical fore body equipped with a spike. This configuration is known for generating an important level of unsteadiness around the spike in supersonic regime. The wind tunnel Mach number is equal to 2. The experiments show that waves emitted from this source propagate along the tip shock and interact with it. It is then assessed that this interaction produces a periodic distortion of the shock that propagates to the external flow. Unsteady pressure sensors, high speed schlieren films, hot wire probing and laser Doppler velocimetry are used as complementary experimental means. The final result is a coherent representation of the complex mechanism of wave propagation that has been evidenced. The principle of creating unsteady shock deformation by onboard equipments could be examined as a possibly promising method of sonic boom control.

  11. Wave propagation into the middle atmosphere

    NASA Technical Reports Server (NTRS)

    Hirota, I.

    1989-01-01

    Recent observations of various types of waves propagating into the middle atmosphere are reviewed. Emphasis is made on the excitation processes in the lower atmosphere and their vertical propagation through the background flow as a function of the latitude, height and season. The following subjects are discussed: (1) Vertical propagation of quasi-stationary forced Rossby waves into the winter stratosphere in connection with the sudden warming; (2) Spectral distribution and seasonal characteristics of normal mode (free) Rossby waves and the asymmetry of the Northern and Southern Hemispheres; and (3) Seasonal variation of internal gravity waves in the middle atmosphere. Further discussions are presented for future studies based on accumulated observational data during the MAP period.

  12. Propagation studies using a theoretical ionosphere model

    NASA Technical Reports Server (NTRS)

    Lee, M.

    1973-01-01

    The mid-latitude ionospheric and neutral atmospheric models are coupled with an advanced three dimensional ray tracing program to see what success would be obtained in predicting the wave propagation conditions and to study to what extent the use of theoretical ionospheric models is practical. The Penn State MK 1 ionospheric model, the Mitra-Rowe D region model, and the Groves' neutral atmospheric model are used throughout this work to represent the real electron densities and collision frequencies. The Faraday rotation and differential Doppler velocities from satellites, the propagation modes for long distance high frequency propagation, the group delays for each mode, the ionospheric absorption, and the spatial loss are all predicted.

  13. 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.

  14. Microdomain Effects on Transverse Cardiac Propagation

    PubMed Central

    Lin, Joyce; Keener, James P.

    2014-01-01

    The effect of gap junctional coupling, sodium ion channel distribution, and extracellular conductivity on transverse conduction in cardiac tissue is explored using a microdomain model that incorporates aspects of the inhomogeneous cellular structure. The propagation velocities found in our model are compared to those in the classic bidomain model and indicate a strong ephaptic microdomain contribution to conduction depending on the parameter regime. We show that ephaptic effects can be quite significant in the junctional spaces between cells, and that the cell activation sequence is modified substantially by these effects. Further, we find that transverse propagation can be maintained by ephaptic effects, even in the absence of gap junctional coupling. The mechanism by which this occurs is found to be cablelike in that the junctional regions act like inverted cables. Our results provide insight into several recent experimental studies that indirectly indicate a mode of action potential propagation that does not rely exclusively on gap junctions. PMID:24559995

  15. Propagation of polarized waves in inhomogeneous media.

    PubMed

    Charnotskii, Mikhail

    2016-07-01

    A parabolic equation for electromagnetic wave propagation in a random medium is extended to include the depolarization effects in the narrow-angle, forward-scattering setting. Closed-form parabolic equations for propagation of the coherence tensor are derived under a Markov approximation model. For a general partially coherent and partially polarized beam wave, this equation can be reduced to a system of ordinary differential equations, allowing a simple numeric solution. An analytical solution exists for statistically homogeneous waves. Estimates based on the perturbation solution support the common knowledge that the depolarization at the optical frequencies is negligible for atmospheric turbulence propagation. These results indicate that the recently published theory [Opt. Lett.40, 3077 (2015)10.1364/OL.40.003077] is not valid for atmospheric turbulence. PMID:27409697

  16. Study of propagation along nonuniform excitable fibers

    SciTech Connect

    Zhou, Y.

    1992-01-01

    Two related reaction diffusion systems which support traveling wave solutions when parameters are constant are studied when there are jump discontinuities in the diffusion coefficient. The first system represents a classical axon model where the fiber has a jump in diameter at discrete locations, and the membrane dynamics represents that of barnacle muscle (which we call Morris-Lecar dynamics). The second model represents a passive cable with a uniform density of spines which have Morris-Lecar dynamics. Use of a conditional comparison principle establishes conditions where a traveling wave solution can be blocked from propagating beyond the change in fiber diameter. The authors then examine numerically for both models conditions on physical parameters which show that traveling wave solutions are blocked by changes in the fiber diameter, when propagation is successful, and when there is both forward propagation and the formation of a reflecting (echo) wave.

  17. Displacement of squeezed propagating microwave states

    NASA Astrophysics Data System (ADS)

    Fedorov, Kirill G.; Zhong, Ling; Pogorzalek, Stefan; Eder, Peter; Fischer, Michael; Goetz, Jan; Wulschner, Friedrich; Xie, Edwar; Menzel, Edwin; Deppe, Frank; Marx, Achim; Gross, Rudolf

    Displacement of propagating squeezed states is a fundamental operation for quantum communications. It can be applied to fundamental studies of macroscopic quantum coherence and has an important role in quantum teleportation protocols with propagating microwaves. We generate propagating squeezed states using a Josephson parametric amplifier and implement displacement using a cryogenic directional coupler. We study single- and two-mode displacement regimes. For the single-mode displacement we find that the squeezing level of the displaced squeezed state does not depend on the displacement amplitude. Also, we observe that quantum entanglement between two spatially separated channels stays constant across 4 orders of displacement power. We acknowledge support by the German Research Foundation through SFB 631 and FE 1564/1-1, the EU project PROMISCE, and Elite Network of Bavaria through the program ExQM.

  18. Microbial corrosion of stainless steel.

    PubMed

    Ibars, J R; Moreno, D A; Ranninger, C

    1992-11-01

    Stainless steel, developed because of their greater resistance to corrosion in different aggressive environments, have proved to be affected, however, by various processes and types of corrosion. Some of these types of corrosion, mainly pitting, is activated and developed in the presence of microorganisms, which acting in an isolated or symbiotic way, according to their adaptation to the environment, create a favorable situation for the corrosion of these steel. The microorganisms that are involved, mainly bacteria of both the aerobic and anaerobic type, modify the environment where the stainless steel is found, creating crevices, differential aeration zones or a more aggressive environment with the presence of metabolites. In these circumstances, a local break of the passive and passivating layer is produced, which is proper to these types of steel and impedes the repassivation that is more favorable to corrosion. In the study and research of these types of microbiologically influenced corrosion are found electrochemical techniques, since corrosion is fundamentally an electrochemical process, and microbiological techniques for the identification, culture, and evaluation of the microorganisms involved in the process, as well as in the laboratory or field study of microorganism-metal pairs. Microstructural characterization studies of stainless steel have also been considered important, since it is known that the microstructure of steel can substantially modify their behavior when faced with corrosion. As for surface analysis studies, it is known that corrosion is a process that is generated on and progresses from the surface. The ways of dealing with microbiologically influenced corrosion must necessarily include biocides, which are not always usable or successful, the design of industrial equipment or components that do not favor the adherence of microorganisms, using microstructures in steel less sensitive to corrosion, or protecting the materials. PMID:1492953

  19. 38. Photocopy of photograph. STEEL PLANT, BOILERS UNDER CONSTRUCTION IN ...

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

    38. Photocopy of photograph. STEEL PLANT, BOILERS UNDER CONSTRUCTION IN BOILER PLANT LOCATED EAST OF MAIN STEEL PLANT, 1909. (From the Bethlehem Steel Corporation collection, Seattle, WA) - Irondale Iron & Steel Plant, Port Townsend, Jefferson County, WA

  20. Complex singularities in the quark propagator

    SciTech Connect

    Roberts, C.D.; Frank, M.R.

    1995-08-01

    The Dyson-Schwinger equation for the quark propagator is being studied in the rainbow approximation using a gluon propagator that incorporates asymptotic freedom and is an entire function. The gluon propagator has a number of parameters that may be varied in order to obtain a good description of low-energy pion observables; such as f{sub {pi}} and the {pi}-{pi} scattering lengths. This provides a direct means of relating hadronic observables to the form of the quark-quark interaction in the infrared and serves as an adjunct and extension of the separable Ansatz approach discussed above. It also provides a means of examining the pole structure of the quark propagator, which may hold the key to understanding quark confinement. The preliminary results are encouraging. It was demonstrated that it is possible to obtain a good description of pion observables in this approach. Further, when the strength of the quark-quark interaction in the infrared becomes larger than a given critical value, the pole in the quark propagator bifurcates into a pair of complex conjugate poles: m{sub q} = m{sub q}{sup R} {plus_minus} im{sub q}{sup I}, which is a signal of confinement. The interpretation in this case is of 1/m{sub q}{sup I} as the distance over which a quark may propagate before fragmenting. Further, there are indications from these studies that T{sub c}{sup D} < T{sub c}{sup {chi}}, where T{sub c}{sup D} is the critical temperature for deconfinement and T{sub c}{sup {chi}} is the critical temperature for chiral symmetry restoration; i.e., indications that deconfinement occurs at a lower temperature than chiral symmetry restoration. Available results from this work will be presented at the Washington meeting of the APS.

  1. Satellite sound broadcast propagation studies and measurements

    NASA Technical Reports Server (NTRS)

    Vogel, Wolfhard J.; Torrence, Geoffrey W.

    1990-01-01

    Satellite Sound Broadcasting is an attractive satellite application. Before regulatory decisions can be made in 1992, the propagation effects encountered have to be characterized. The Electrical Engineering Research Laboratory has nearly completed a system which will allow amplitude measurements to be made over 10 MHz bandwidths in the 800 to 1800 MHz frequency range. The system uses transmission from a transportable tower, and reception inside buildings or in the shadow of trees or utility poles. The goal is to derive propagation models for use by systems engineers who are about to design satellite broadcast systems. The advance of fiber-optics technology has helped to focus future development of satellite services into areas where satellites are uniquely competitive. One of these preferred satellite applications is the broadcasting of high-quality sound for stationary or mobile reception by listeners using low-cost, consumer-grade receivers. Before such services can be provided, however, the political hurdles of spectrum allocation have to be surmounted and the technical questions of standardization for world-wide compatibility have to be resolved. In order to arrive at an optimal system design, efficient in the use of our scarce spectral resources, affordable both to the broadcaster and the listener, and providing predictable performance, the propagation effects to which the service is subjected have to be characterized. Consequently, the objective of the research project is to make basic propagation measurements for direct Satellite Sound Broadcasting Service (SSBS). The data obtained should allow the development of propagation models to be used by communications engineers designing the operational systems. Such models shall describe the effects of shadowing and multipath propagation on SSBS receivers operating in a specified environment, such as inside commercial or residential buildings of various construction and also in the shadow of trees or utility poles

  2. The discrete regime of flame propagation

    NASA Astrophysics Data System (ADS)

    Tang, Francois-David; Goroshin, Samuel; Higgins, Andrew

    The propagation of laminar dust flames in iron dust clouds was studied in a low-gravity envi-ronment on-board a parabolic flight aircraft. The elimination of buoyancy-induced convection and particle settling permitted measurements of fundamental combustion parameters such as the burning velocity and the flame quenching distance over a wide range of particle sizes and in different gaseous mixtures. The discrete regime of flame propagation was observed by substitut-ing nitrogen present in air with xenon, an inert gas with a significantly lower heat conductivity. Flame propagation in the discrete regime is controlled by the heat transfer between neighbor-ing particles, rather than by the particle burning rate used by traditional continuum models of heterogeneous flames. The propagation mechanism of discrete flames depends on the spa-tial distribution of particles, and thus such flames are strongly influenced by local fluctuations in the fuel concentration. Constant pressure laminar dust flames were observed inside 70 cm long, 5 cm diameter Pyrex tubes. Equally-spaced plate assemblies forming rectangular chan-nels were placed inside each tube to determine the quenching distance defined as the minimum channel width through which a flame can successfully propagate. High-speed video cameras were used to measure the flame speed and a fiber optic spectrometer was used to measure the flame temperature. Experimental results were compared with predictions obtained from a numerical model of a three-dimensional flame developed to capture both the discrete nature and the random distribution of particles in the flame. Though good qualitative agreement was obtained between model predictions and experimental observations, residual g-jitters and the short reduced-gravity periods prevented further investigations of propagation limits in the dis-crete regime. The full exploration of the discrete flame phenomenon would require high-quality, long duration reduced gravity environment

  3. Propagation characteristics of acoustic waves in snow

    NASA Astrophysics Data System (ADS)

    Capelli, Achille; Kapil, Jagdish Chandra; Reiweger, Ingrid; Schweizer, Jürg; Or, Dani

    2015-04-01

    Acoustic emission analysis is a promising technique for monitoring snow slope stability with potential for application in early warning systems for avalanches. Current research efforts focus on identification and localization of acoustic emission features preceding snow failure and avalanches. However, our knowledge of sound propagation characteristics in snow is still limited. A review of previous studies showed that significant gaps exist and that the results of the various studies are partly contradictory. Furthermore, sound velocity and attenuation have been determined for the frequency range below 10 kHz, while recent snow failure experiments suggest that the peak frequency is in the ultrasound range between 30 kHz to 500 kHz. We therefore studied the propagation of pencil lead fracture (PLF) signals through snow in the ultrasound frequency range. This was achieved by performing laboratory experiments with columns of artificially produced snow of varying density and temperature. The attenuation constant was obtained by varying the size of the columns to eliminate possible influences of the snow-sensor coupling. The attenuation constant was measured for the entire PLF burst signal and for single frequency components. The propagation velocity was calculated from the arrival time of the acoustic signal. We then modelled the sound propagation for our experimental setup using Biot's model for wave propagation in porous media. The Model results were in good agreement with our experimental results. For the studied samples, the acoustic signals propagated as fast and slow longitudinal waves, but the main part of the energy was carried by the slow waves. The Young's modulus of our snow samples was determined from the sound velocity. This is highly relevant, as the elastic properties of snow are not well known.

  4. Arrest of Avalanche Propagation by Discontinuities on Snow Cover

    NASA Astrophysics Data System (ADS)

    Frigo, B.; Chiaia, B.

    2009-04-01

    Considering the spatial variability of the snow cover, the paper analyses, in the framework of Fracture Mechanics, the Mode II fracture propagation on snow cover that leads to large dry slab avalanches. Under the hypothesis of a perfectly brittle phenomenon, avalanche triggering is usually investigated numerically by means of Linear Elastic Fracture Mechanics (McClung, 1979; Chiaia et al., 2008). Since, however, the real phenomenon is intrinsically dynamical, another aspect to investigate is represented by dynamic fracture propagation. In this paper, we model dynamic crack propagation into a dry snow slab, to assess the possibility of crack arrest due to the presence of weak zones distributed along the snow slope. As a consequence of the first triggering mechanism (the Mode II fracture propagation on the weak plane), the secondary Mode I crack propagation in the crown is studied by means of numerical simulations based on Dynamic Elastic Fracture Mechanics and on the theory of crack arresters. By taking into account kinetic energy and using the FEM software FRANC 2D (Wawrzynek and Ingraffea, 1993), several paths of crown fracture propagation and their stability have been investigated. The snowpack is considered as a linear-elastic plate (2D problem), whose physical and mechanical parameters are chosen according to classical literature values. To investigate the possible arrest of crown fracture, we apply the theory of crack arresters, usually adopted for pipelines and perforated steel sheets fracture problems. To study crack arrest, different crack paths are simulated, in discontinuous (equipped with different shapes and geometries of artificial voids) snowpacks. The simulations show the effectiveness of these weak zones, to reduce substantially the crack driving force of the propagating fracture. This means that, increasing spatial variability tends to stabilize the snow slope, eventually splitting a major avalanche event into smaller, independent avalanches. Our

  5. Light propagation in the South Pole ice

    SciTech Connect

    Williams, Dawn; Collaboration: IceCube Collaboration

    2014-11-18

    The IceCube Neutrino Observatory is located in the ice near the geographic South Pole. Particle showers from neutrino interactions in the ice produce light which is detected by IceCube modules, and the amount and pattern of deposited light are used to reconstruct the properties of the incident neutrino. Since light is scattered and absorbed by ice between the neutrino interaction vertex and the sensor, IceCube event reconstruction depends on understanding the propagation of light through the ice. This paper presents the current status of modeling light propagation in South Pole ice, including the recent observation of an azimuthal anisotropy in the scattering.

  6. Atmospheric propagation issues relevant to optical communications

    NASA Technical Reports Server (NTRS)

    Churnside, James H.; Shaik, Kamran

    1989-01-01

    Atmospheric propagation issues relevant to space-to-ground optical communications for near-earth applications are studied. Propagation effects, current optical communication activities, potential applications, and communication techniques are surveyed. It is concluded that a direct-detection space-to-ground link using redundant receiver sites and temporal encoding is likely to be employed to transmit earth-sensing satellite data to the ground some time in the future. Low-level, long-term studies of link availability, fading statistics, and turbulence climatology are recommended to support this type of application.

  7. Displacement of Propagating Squeezed Microwave States.

    PubMed

    Fedorov, Kirill G; Zhong, L; Pogorzalek, S; Eder, P; Fischer, M; Goetz, J; Xie, E; Wulschner, F; Inomata, K; Yamamoto, T; Nakamura, Y; Di Candia, R; Las Heras, U; Sanz, M; Solano, E; Menzel, E P; Deppe, F; Marx, A; Gross, R

    2016-07-01

    Displacement of propagating quantum states of light is a fundamental operation for quantum communication. It enables fundamental studies on macroscopic quantum coherence and plays an important role in quantum teleportation protocols with continuous variables. In our experiments, we have successfully implemented this operation for propagating squeezed microwave states. We demonstrate that, even for strong displacement amplitudes, there is no degradation of the squeezing level in the reconstructed quantum states. Furthermore, we confirm that path entanglement generated by using displaced squeezed states remains constant over a wide range of the displacement power. PMID:27447495

  8. Atmospheric propagation effects relevant to optical communications

    NASA Technical Reports Server (NTRS)

    Shaik, K. S.

    1988-01-01

    A number of atmospheric phenomena affect the propagation of light. The effects of clear air turbulence are reviewed as well as atmospheric turbidity on optical communications. Among the phenomena considered are astronomical and random refraction, scintillation, beam broadening, spatial coherence, angle of arrival, aperture averaging, absorption and scattering, and the effect of opaque clouds. An extensive reference list is also provided for further study. Useful information on the atmospheric propagation of light in relation to optical deep space communications to an earth based receiving station is available, however, further data must be generated before such a link can be designed with committed performance.

  9. Optimization of directional elastic energy propagation

    NASA Astrophysics Data System (ADS)

    Andreassen, Erik; Chang, Hannah R.; Ruzzene, Massimo; Jensen, Jakob Søndergaard

    2016-09-01

    The aim of this paper is to demonstrate how topology optimization can be used to design a periodically perforated plate, in order to obtain a tailored anisotropic group velocity profile. The main method is demonstrated on both low and high frequency bending wave propagation in an aluminum plate, but is general in the sense that it could be used to design periodic structures with frequency dependent group velocity profiles for any kind of elastic wave propagation. With the proposed method the resulting design is manufacturable. Measurements on an optimized design compare excellently with the numerical results.

  10. Flame propagation and extinction in particle clouds

    NASA Technical Reports Server (NTRS)

    Berlad, A. L.; Joshi, N. D.

    1986-01-01

    Two phase flame propagation and extinction theory required to support the corresponding experiments planned for the space shuttle is being developed. Also being planned are specialized collaborative, experimental and theoretical NASA UCSD studies needed to support the ongoing definition of needed experimental hardware, experimental procedures, data acquisition philosophy, and other ground based support activities required to assure the success of space shuttle based experiments concerned with combustion of clouds of particulates at reduced gravitational conditions. The further development of relations delineating premixed particle cloud and premixed gaseous systems as well as burner stabilized and freely propagating flame systems is considered.

  11. Laser propagation in underdense plasmas: Scaling arguments

    SciTech Connect

    Garrison, J.C.

    1993-05-01

    The propagation of an intense laser beam in the underdense plasma is modelled by treating the plasma as a relativistic, zero temperature, charged fluid. For paraxial propagation and a sufficiently underdense plasma ({omega}p/{omega} {much_lt} 1), a multiple-scales technique is used to expand the exact equations in powers of the small parameter {theta} {equivalent_to} {omega}p/{omega}. The zeroth order equations are used in a critical examination of previous work on this problem, and to derive a scaling law for the threshold power required for cavitation.

  12. Comments on 'Rapid pulsed microwave propagation'

    NASA Technical Reports Server (NTRS)

    Steffes, Paul G.; Rodrigue, George P.

    1992-01-01

    Giakos and Ishii (1991) claim conclusive experimental evidence that microwave pulse propagation in waveguides and in air occurs at velocities exceeding the free-space speed of light, and assert that it is possible to transmit both energy and information in a non-TEM waveguiding medium at the lightspeed-exceeding phase velocity. The present analysis of their results reveals several significant potential sources of error in both their laboratory findings and those findings' interpretation. Giakos and Ishii reply that the accuracy of the propagation measurements presented in their study exceeds 0.2 percent.

  13. Comments on 'Rapid pulsed microwave propagation'

    NASA Astrophysics Data System (ADS)

    Steffes, Paul G.; Rodrigue, George P.

    1992-05-01

    Giakos and Ishii (1991) claim conclusive experimental evidence that microwave pulse propagation in waveguides and in air occurs at velocities exceeding the free-space speed of light, and assert that it is possible to transmit both energy and information in a non-TEM waveguiding medium at the lightspeed-exceeding phase velocity. The present analysis of their results reveals several significant potential sources of error in both their laboratory findings and those findings' interpretation. Giakos and Ishii reply that the accuracy of the propagation measurements presented in their study exceeds 0.2 percent.

  14. Acceleration and propagation of solar cosmic rays

    NASA Astrophysics Data System (ADS)

    Podgorny, I. M.; Podgorny, A. I.

    2015-12-01

    Analysis of the solar cosmic ray measurements on the Geostationary Orbital Environmental Satellite (GOES) spacecraft indicated that the duration of solar flare relativistic proton large pulses is comparable with the solar wind propagation duration from the Sun to the Earth. The front of the proton flux from flares on the western solar disk approaches the Earth with a flight time along the Archimedean spiral magnetic field line of 15-20 min. The proton flux from eastern flares is registered in the Earth's orbit 3-5 h after the flare onset. These particles apparently propagate across IMF owing to diffusion.

  15. Surface acoustic wave propagation in graphene film

    SciTech Connect

    Roshchupkin, Dmitry Plotitcyna, Olga; Matveev, Viktor; Kononenko, Oleg; Emelin, Evgenii; Irzhak, Dmitry; Ortega, Luc; Zizak, Ivo; Erko, Alexei; Tynyshtykbayev, Kurbangali; Insepov, Zinetula

    2015-09-14

    Surface acoustic wave (SAW) propagation in a graphene film on the surface of piezoelectric crystals was studied at the BESSY II synchrotron radiation source. Talbot effect enabled the visualization of the SAW propagation on the crystal surface with the graphene film in a real time mode, and high-resolution x-ray diffraction permitted the determination of the SAW amplitude in the graphene/piezoelectric crystal system. The influence of the SAW on the electrical properties of the graphene film was examined. It was shown that the changing of the SAW amplitude enables controlling the magnitude and direction of current in graphene film on the surface of piezoelectric crystals.

  16. Mean Element Propagations Using Numerical Averaging

    NASA Technical Reports Server (NTRS)

    Ely, Todd A.

    2009-01-01

    The long-term evolution characteristics (and stability) of an orbit are best characterized using a mean element propagation of the perturbed two body variational equations of motion. The averaging process eliminates short period terms leaving only secular and long period effects. In this study, a non-traditional approach is taken that averages the variational equations using adaptive numerical techniques and then numerically integrating the resulting EOMs. Doing this avoids the Fourier series expansions and truncations required by the traditional analytic methods. The resultant numerical techniques can be easily adapted to propagations at most solar system bodies.

  17. Propagation of polymer slugs through porous media

    SciTech Connect

    Lecourtier, J.; Chauveteau, G.

    1984-09-01

    This paper describes an experimental and theoretical study of the mechanisms governing polymer slug propagation through porous media. An analytical model taking into account the macromolecule exclusion from pore walls is proposed to predict rodlike polymer velocity in porous media and thus the spreading out of polydispersed polymer slugs. Under conditions where this wall exclusion is maximum, i.e. at low shear rates and polymer concentrations, the experiments show that xanthan propagation is effectively predicted by this model. At higher flow rates and polymer concentrations, the effects of hydrodynamic dispersion and viscous fingering are analyzed. A new fractionation method for determining molecular weight distribution of polymers used in EOR is proposed.

  18. Sources, Propagators, and Sinks of Space Weather

    NASA Astrophysics Data System (ADS)

    Pesnell, W. D.

    Space Weather is a complex web of sources propagators and sinks of energy mass and momentum A complete understanding of Space Weather would require specifying and an ability to predict each link in this web One important problem in Space Weather is ranking the importance of a particular measurement or model in a research program One way to do this ranking is to identify the sources propagators and sinks and produce the simplest linked diagram of the components Such a diagram will be shown and used to discuss how longterm effects of Space Weather can be separated from the impulsive effects

  19. Acoustic propagation in a thermally stratified atmosphere

    NASA Technical Reports Server (NTRS)

    Vanmoorhem, W. K.

    1984-01-01

    This report describes the activities during the fourth six month period of the investigation of acoustic propagation in the atmosphere with a realistic lapse temperature profile. A significant error was detected since the previous semi-annual report and has been corrected in both the plane wave and point source solutions. This report then describes both of these problems in some detail along with presenting some numerical results from the model. Work will begin this summer on the model of propagation in an inversion.

  20. Enhancement of in vitro Guayule propagation

    NASA Technical Reports Server (NTRS)

    Dastoor, M. N.; Schubert, W. W.; Petersen, G. R. (Inventor)

    1982-01-01

    A method for stimulating in vitro propagation of Guayule from a nutrient medium containing Guayule tissue by adding a substituted trialkyl amine bioinducing agent to the nutrient medium is described. Selective or differentiated propagation of shoots or callus is obtained by varying the amounts of substituted trialky amine present in the nutrient medium. The luxuriant growth provided may be processed for its poly isoprene content or may be transferred to a rooting medium for production of whole plants as identical clones of the original tissue. The method also provides for the production of large numbers of Guayule plants having identical desirable properties such as high polyisoprene levels.

  1. Displacement of Propagating Squeezed Microwave States

    NASA Astrophysics Data System (ADS)

    Fedorov, Kirill G.; Zhong, L.; Pogorzalek, S.; Eder, P.; Fischer, M.; Goetz, J.; Xie, E.; Wulschner, F.; Inomata, K.; Yamamoto, T.; Nakamura, Y.; Di Candia, R.; Las Heras, U.; Sanz, M.; Solano, E.; Menzel, E. P.; Deppe, F.; Marx, A.; Gross, R.

    2016-07-01

    Displacement of propagating quantum states of light is a fundamental operation for quantum communication. It enables fundamental studies on macroscopic quantum coherence and plays an important role in quantum teleportation protocols with continuous variables. In our experiments, we have successfully implemented this operation for propagating squeezed microwave states. We demonstrate that, even for strong displacement amplitudes, there is no degradation of the squeezing level in the reconstructed quantum states. Furthermore, we confirm that path entanglement generated by using displaced squeezed states remains constant over a wide range of the displacement power.

  2. Atmospheric Propagation Effects Relevant to Optical Communications

    NASA Technical Reports Server (NTRS)

    Shaik, K. S.

    1988-01-01

    A number of atmospheric phenomena affect the propagation of light. This article reviews the effects of clear-air turbulence as well as atmospheric turbidity on optical communications. Among the phenomena considered are astronomical and random refraction, scintillation, beam broadening, spatial coherence, angle of arrival, aperture averaging, absorption and scattering, and the effect of opaque clouds. An extensive reference list is also provided for further study, Useful information on the atmospheric propagation of light in resolution to optical deep-space communications to an earth-based receiving station is available, however, further data must be generated before such a link can be designed with committed performance.

  3. Proceedings of the Thirteenth NASA Propagation Experimenters Meeting (NAPEX 13)

    NASA Technical Reports Server (NTRS)

    Davarian, Faramaz (Editor)

    1989-01-01

    The NASA Propagation Experimenters Meeting (NAPEX), supported by the NASA Propagation Program, is convened annually to discuss studies made on radio wave propagation by investigators from domestic and international organizations. The meeting was organized into three technical sessions: the first focused on mobile satellite propagation; the second examined the propagation effects for frequencies above 10 GHz; and the third addressed studies devoted exclusively to the Olympus/Advanced Communications Technology Satellite (ACTS) Program.

  4. Anodized Steel Electrodes for Supercapacitors.

    PubMed

    Sagu, Jagdeep S; Wijayantha, K G Upul; Bohm, Mallika; Bohm, Siva; Kumar Rout, Tapan

    2016-03-01

    Steel was anodized in 10 M NaOH to enhance its surface texture and internal surface area for application as an electrode in supercapacitors. A mechanism was proposed for the anodization process. Field-emission gun scanning electron microscopy (FEGSEM) studies of anodized steel revealed that it contains a highly porous sponge like structure ideal for supercapacitor electrodes. X-ray photoelectron spectroscopy (XPS) measurements showed that the surface of the anodized steel was Fe2O3, whereas X-ray diffraction (XRD) measurements indicated that the bulk remained as metallic Fe. The supercapacitor performance of the anodized steel was tested in 1 M NaOH and a capacitance of 18 mF cm(-2) was obtained. Cyclic voltammetry measurements showed that there was a large psueudocapacitive contribution which was due to oxidation of Fe to Fe(OH)2 and then further oxidation to FeOOH, and the respective reduction of these species back to metallic Fe. These redox processes were found to be remarkably reversible as the electrode showed no loss in capacitance after 10000 cycles. The results demonstrate that anodization of steel is a suitable method to produce high-surface-area electrodes for supercapacitors with excellent cycling lifetime. PMID:26891093

  5. Carbide transformations in constructional steels

    SciTech Connect

    Vinokur, B.B.

    1986-01-01

    In connection with the type of carbides formed in general purpose constructional steels or on the mechanisms of carbide transformations and the influence of carbide formation on the properties, this work presents an investigation that was made of medium-carbon chrome-nickel and chrome-manganese steels with 1, 2, and 3% Cr, 1% Ni, and 1% Mn additionally alloyed with 0.25-2% Mo or W (every 0.25%). All of the steels were hardened from temperatures providing the fullest solution of carbides in austenite and were tempered at 400-650/sup 0/C every 25-50/sup 0/C. The composition of the carbides and their type were established by chemical, x-ray diffraction, and microdiffraction methods and the mechanism of the carbide transformations was determined on the basis of the changes in distortions of the second and third order of the matrix electrical resistance, and coercive force of the steel. All of the carbideforming elements present in steel participate in saturation of the carbides, as a result of which the formation of a special carbide is eased and the degree of alloying of the matrix increases. In the carbide transformation with a certain share of carbide phase an increase or retarding of the reduction in strength with an increase in tempering temperature with constant plasticity and impact strength is possible.

  6. Applications of infrared thermography for nondestructive testing of fatigue cracks in steel bridges

    NASA Astrophysics Data System (ADS)

    Sakagami, Takahide; Izumi, Yui; Kobayashi, Yoshihiro; Mizokami, Yoshiaki; Kawabata, Sunao

    2014-05-01

    In recent years, fatigue crack propagations in aged steel bridge which may lead to catastrophic structural failures have become a serious problem. For large-scale steel structures such as orthotropic steel decks in highway bridges, nondestructive inspection of deteriorations and fatigue damages are indispensable for securing their safety and for estimating their remaining strength. As conventional NDT techniques for steel bridges, visual testing, magnetic particle testing and ultrasonic testing have been commonly employed. However, these techniques are time- and labor- consuming techniques, because special equipment is required for inspection, such as scaffolding or a truck mount aerial work platform. In this paper, a new thermography NDT technique, which is based on temperature gap appeared on the surface of structural members due to thermal insulation effect of the crack, is developed for detection of fatigue cracks. The practicability of the developed technique is demonstrated by the field experiments for highway steel bridges in service. Detectable crack size and factors such as measurement time, season or spatial resolution which influence crack detectability are investigated.

  7. Fracture toughness and fracture behavior of SA508-III steel at different temperatures

    NASA Astrophysics Data System (ADS)

    Liu, Jia-hua; Wang, Lei; Liu, Yang; Song, Xiu; Luo, Jiong; Yuan, Dan

    2014-12-01

    The fracture toughness of SA508-III steel was studied in the temperature range from room temperature to 320°C using the J-integral method. The fracture behavior of the steel was also investigated. It was found that the conditional fracture toughness ( J Q) of the steel first decreased and then increased with increasing test temperature. The maximum and minimum values of J Q were 517.4 kJ/m2 at 25°C and 304.5 kJ/m2 at 180°C, respectively. Dynamic strain aging (DSA) was also observed to occur when the temperature exceeded 260°C with a certain strain rate. Both the dislocation density and the number of small dislocation cells effectively increased because of the occurrence of DSA; as a consequence, crack propagation was more strongly inhibited in the steel. Simultaneously, an increasing number of fine carbides precipitated under high stress at temperatures greater than 260°C. Thus, the deformation resistance of the steel was improved and the J Q was enhanced.

  8. Fire Propagation Performance of Intumescent Fire Protective Coatings Using Eggshells as a Novel Biofiller

    PubMed Central

    Yew, M. C.; Ramli Sulong, N. H.; Yew, M. K.; Amalina, M. A.; Johan, M. R.

    2014-01-01

    This paper aims to synthesize and characterize an effective intumescent fire protective coating that incorporates eggshell powder as a novel biofiller. The performances of thermal stability, char formation, fire propagation, water resistance, and adhesion strength of coatings have been evaluated. A few intumescent flame-retardant coatings based on these three ecofriendly fire retardant additives ammonium polyphosphate phase II, pentaerythritol and melamine mixed together with flame-retardant fillers, and acrylic binder have been prepared and designed for steel. The fire performance of the coatings has conducted employing BS 476: Part 6-Fire propagation test. The foam structures of the intumescent coatings have been observed using field emission scanning electron microscopy. On exposure, the coated specimens' B, C, and D had been certified to be Class 0 due to the fact that their fire propagation indexes were less than 12. Incorporation of ecofriendly eggshell, biofiller into formulation D led to excellent performance in fire stopping (index value, (I) = 4.3) and antioxidation of intumescent coating. The coating is also found to be quite effective in water repellency, uniform foam structure, and adhesion strength. PMID:25136687

  9. Fire propagation performance of intumescent fire protective coatings using eggshells as a novel biofiller.

    PubMed

    Yew, M C; Ramli Sulong, N H; Yew, M K; Amalina, M A; Johan, M R

    2014-01-01

    This paper aims to synthesize and characterize an effective intumescent fire protective coating that incorporates eggshell powder as a novel biofiller. The performances of thermal stability, char formation, fire propagation, water resistance, and adhesion strength of coatings have been evaluated. A few intumescent flame-retardant coatings based on these three ecofriendly fire retardant additives ammonium polyphosphate phase II, pentaerythritol and melamine mixed together with flame-retardant fillers, and acrylic binder have been prepared and designed for steel. The fire performance of the coatings has conducted employing BS 476: Part 6-Fire propagation test. The foam structures of the intumescent coatings have been observed using field emission scanning electron microscopy. On exposure, the coated specimens' B, C, and D had been certified to be Class 0 due to the fact that their fire propagation indexes were less than 12. Incorporation of ecofriendly eggshell, biofiller into formulation D led to excellent performance in fire stopping (index value, (I) = 4.3) and antioxidation of intumescent coating. The coating is also found to be quite effective in water repellency, uniform foam structure, and adhesion strength. PMID:25136687

  10. Consolidation of fatigue and fatigue-crack-propagation data for design use

    NASA Technical Reports Server (NTRS)

    Rice, R. C.; Davies, K. B.; Jaske, C. E.; Feddersen, C. E.

    1975-01-01

    Analytical methods developed for consolidation of fatigue and fatigue-crack-propagation data for use in design of metallic aerospace structural components are evaluated. A comprehensive file of data on 2024 and 7075 aluminums, Ti-6Al-4V alloy, and 300M steel was established by obtaining information from both published literature and reports furnished by aerospace companies. Analyses are restricted to information obtained from constant-amplitude load or strain cycling of specimens in air at room temperature. Both fatigue and fatigue-crack-propagation data are analyzed on a statistical basis using a least-squares regression approach. For fatigue, an equivalent strain parameter is used to account for mean stress or stress ratio effects and is treated as the independent variable; cyclic fatigue life is considered to be the dependent variable. An effective stress-intensity factor is used to account for the effect of load ratio on fatigue-crack-propagation and treated as the independent variable. In this latter case, crack-growth rate is considered to be the dependent variable. A two term power function is used to relate equivalent strain to fatigue life, and an arc-hyperbolic-tangent function is used to relate effective stress intensity to crack-growth rate.

  11. Guided wave propagation based damage detection in welded rectangular tubular structures

    NASA Astrophysics Data System (ADS)

    Lu, Xi; Lu, M. Y.; Zhou, L. M.; Su, Z. Q.; Cheng, Li; Ye, Lin; Meng, Guang

    2009-07-01

    Guided wave based methods have shown great potential to practical use and have been the object of many researches for structural health monitoring (SHM). In this paper, a welded steel structure with rectangular section, which is almost 1:1 scale model for a bogie frame segment of train, is investigated by using both finite element method (FEM) and experimental analysis for the purpose of damage detection. Finite element models are established to simulate the propagation behavior of guided waves in the structure. An active actuator/sensor network is employed to generate guided waves propagating in the structures and collect response signals. Excitations at selected frequency are used to minimize the effect of the intrinsic multi-mode phenomenon of guided waves on the consequent signal interpretation. Modern signal processing approaches, such as continuous wavelet transform (CWT) and Hilbert transform (HT), are applied to all collected signals. An algorithm based on the concept of damage presence probability (DPP) is proposed for estimation of damage location. The results indicate that the recommended guided wave propagation based approach is reasonable for damage detection in such kind of structures.

  12. Effects of self-propagating synthesis reactant compact character on ignition, propagation, and microstructure

    SciTech Connect

    Rice, R.W.; Richardson, G.Y.; Kunetz, J.M.; Schroeter, T.; McDonough, W.J. )

    1987-07-01

    Studies of reactions involving Ti to produce TiC, TiB{sub 2}, TiC + TiB{sub 2}, or 3TiB{sub 2} + 5Al{sub 2}O{sub 3} ignited at one end of test plates showed that reactant powder compact densities were a major factor in the reaction propagation rate along the plate, i.e., a maximum in propagation rate was observed at {approx}60 {plus minus} 10% of theoretical density. At higher densities, propagation rates not only decreased but terminated due to self extinction in some cases or failed to ignite and propagate, typically at {ge}90% of theoretical density. Both reactant particle size and shape can also affect results, i.e., compacts of large (200 {mu}m in diameter) Ti particles, Ti flakes or foil, or wires failed to ignite or had slower propagation rates. Also, the ignition and propagation rates of carbon fiber tows infiltrated with titanium metal powders depended significantly on the local thermal conductivity. However, overall propagation rates for a given range of reactant compact microstructures increased with the heat of the reaction involved.

  13. Steel erected at A-3 Test Stand

    NASA Technical Reports Server (NTRS)

    2008-01-01

    Workers erect the first fabricated steel girders to arrive at the A-3 Test Stand at Stennis Space Center. Steel work began at the construction site Oct. 29 and is scheduled to continue into next spring.

  14. High-temperature brazing of stainless steel

    NASA Technical Reports Server (NTRS)

    Beuyukian, C. S.; Heisman, R. M.; Mitchell, M. J.

    1978-01-01

    Prevention of iron contamination of platens is eliminated by placing alumina/silica ceramic-fiber blankets between platens and carbon-steel plate. Carbon-steel plates provide rigidity and improve heat transfer.

  15. Propagating waves can explain irregular neural dynamics.

    PubMed

    Keane, Adam; Gong, Pulin

    2015-01-28

    Cortical neurons in vivo fire quite irregularly. Previous studies about the origin of such irregular neural dynamics have given rise to two major models: a balanced excitation and inhibition model, and a model of highly synchronized synaptic inputs. To elucidate the network mechanisms underlying synchronized synaptic inputs and account for irregular neural dynamics, we investigate a spatially extended, conductance-based spiking neural network model. We show that propagating wave patterns with complex dynamics emerge from the network model. These waves sweep past neurons, to which they provide highly synchronized synaptic inputs. On the other hand, these patterns only emerge from the network with balanced excitation and inhibition; our model therefore reconciles the two major models of irregular neural dynamics. We further demonstrate that the collective dynamics of propagating wave patterns provides a mechanistic explanation for a range of irregular neural dynamics, including the variability of spike timing, slow firing rate fluctuations, and correlated membrane potential fluctuations. In addition, in our model, the distributions of synaptic conductance and membrane potential are non-Gaussian, consistent with recent experimental data obtained using whole-cell recordings. Our work therefore relates the propagating waves that have been widely observed in the brain to irregular neural dynamics. These results demonstrate that neural firing activity, although appearing highly disordered at the single-neuron level, can form dynamical coherent structures, such as propagating waves at the population level. PMID:25632135

  16. Using Least Squares for Error Propagation

    ERIC Educational Resources Information Center

    Tellinghuisen, Joel

    2015-01-01

    The method of least-squares (LS) has a built-in procedure for estimating the standard errors (SEs) of the adjustable parameters in the fit model: They are the square roots of the diagonal elements of the covariance matrix. This means that one can use least-squares to obtain numerical values of propagated errors by defining the target quantities as…

  17. Propagation of coherent light pulses with PHASE

    NASA Astrophysics Data System (ADS)

    Bahrdt, J.; Flechsig, U.; Grizzoli, W.; Siewert, F.

    2014-09-01

    The current status of the software package PHASE for the propagation of coherent light pulses along a synchrotron radiation beamline is presented. PHASE is based on an asymptotic expansion of the Fresnel-Kirchhoff integral (stationary phase approximation) which is usually truncated at the 2nd order. The limits of this approximation as well as possible extensions to higher orders are discussed. The accuracy is benchmarked against a direct integration of the Fresnel-Kirchhoff integral. Long range slope errors of optical elements can be included by means of 8th order polynomials in the optical element coordinates w and l. Only recently, a method for the description of short range slope errors has been implemented. The accuracy of this method is evaluated and examples for realistic slope errors are given. PHASE can be run either from a built-in graphical user interface or from any script language. The latter method provides substantial flexibility. Optical elements including apertures can be combined. Complete wave packages can be propagated, as well. Fourier propagators are included in the package, thus, the user may choose between a variety of propagators. Several means to speed up the computation time were tested - among them are the parallelization in a multi core environment and the parallelization on a cluster.

  18. LMSS propagation modeling at Virginia Tech

    NASA Technical Reports Server (NTRS)

    Stutzman, Warren L.; Barts, R. Michael; Bostian, Charles W.

    1988-01-01

    Recent efforts in the modeling of land mobile satellite systems are reported. These include descriptions of a simple model for prediction of fading statistics, a propagation simulator, and results from studies using the simulator. Predictions are compared to available measured data.

  19. Cosmic Ray Origin, Acceleration and Propagation

    NASA Technical Reports Server (NTRS)

    Baring, Matthew G.

    2000-01-01

    This paper summarizes highlights of the OG3.1, 3.2 and 3.3 sessions of the 26th International Cosmic Ray Conference in Salt Lake City, which were devoted to issues of origin/composition, acceleration and propagation.

  20. Propagation handbook, frequencies above 10 GHz

    NASA Technical Reports Server (NTRS)

    Ippolito, Louis J.

    1988-01-01

    The progress and accomplishments in the developmet of the Fourth Edition of the NASA Propagation Effects Handbook for Satellite Systems Design, for frequencies 10 to 100 GHz, NASA Reference Publication 1082(04), dated May 1988, prepared by Westighouse Electric Corporation for the Jet Propulsion Laboratory are discussed.

  1. Optical system defect propagation in ABCD systems.

    PubMed

    McKinley, W G; Yura, H T; Hanson, S G

    1988-05-01

    We describe how optical system defects (tilt/jitter, decenter, and despace) propagate through an arbitrary paraxial optical system that can be described by an ABCD ray transfer matrix. A pedagogical example is given that demonstrates the effect of alignment errors on a typical optical system. PMID:19745889

  2. Effect-specific analysis of propagation parameters

    NASA Technical Reports Server (NTRS)

    Ortgies, G.; Ruecker, F.; Dintelmann, F.; Jakoby, R.

    1992-01-01

    Results of propagation measurements with the satellite OLYMPUS carried out at 12.5, 20, and 30 GHz at the Research Center of the Deutsche Bundespost Telekom are discussed. In particular, attenuation, scintillation, and depolarization measurements are analyzed with special emphasis on frequency scaling of the various effects.

  3. Virus isolation and propagation in embryonating eggs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The embryonating egg is one of the most versatile, easy to work with, and widely used host systems for the isolation and propagation of avian viruses. The embryonating chicken egg (ECE) is the most commonly available system that is both specific pathogen free and supports the replication of viruses...

  4. Antenna Construction and Propagation of Radio Waves.

    ERIC Educational Resources Information Center

    Marine Corps Inst., Washington, DC.

    Developed as part of the Marine Corps Institute (MCI) correspondence training program, this course on antenna construction and propagation of radio waves is designed to provide communicators with instructions in the selection and/or construction of the proper antenna(s) for use with current field radio equipment. Introductory materials include…

  5. Detonation propagation in a high loss configuration

    SciTech Connect

    Jackson, Scott I; Shepherd, Joseph E

    2009-01-01

    This work presents an experimental study of detonation wave propagation in tubes with inner diameters (ID) comparable to the mixture cell size. Propane-oxygen mixtures were used in two test section tubes with inner diameters of 1.27 mm and 6.35 mm. For both test sections, the initial pressure of stoichiometric mixtures was varied to determine the effect on detonation propagation. For the 6.35 mm tube, the equivalence ratio {phi} (where the mixture was {phi} C{sub 3}H{sub 8} + 50{sub 2}) was also varied. Detonations were found to propagate in mixtures with cell sizes as large as five times the diameter of the tube. However, under these conditions, significant losses were observed, resulting in wave propagation velocities as slow as 40% of the CJ velocity U{sub CJ}. A review of relevant literature is presented, followed by experimental details and data. Observed velocity deficits are predicted using models that account for boundary layer growth inside detonation waves.

  6. PROPAGATION AND LINKAGE OF OCEANIC RIDGE SEGMENTS.

    USGS Publications Warehouse

    Pollard, David D.; Aydin, Atilla

    1984-01-01

    An investigation was made of spreading ridges and the development of structures that link ridge segments using an analogy between ridges and cracks in elastic plates. The ridge-propagation force and a path factor that controls propagation direction were calculated for echelon ridge segments propagating toward each other. The ridge-propagation force increases as ridge ends approach but then declines sharply as the ends pass, so ridge segments may overlap somewhat. The sign of the path factor changes as ridge ends approach and pass, so the overlapping ridge ends may diverge and then converge following a hook-shaped path. The magnitudes of shear stresses in the plane of the plate and orientations of maximum shear planes between adjacent ridge segments were calculated to study transform faulting. For different loading conditions simulating ridge push, plate pull, and ridge suction, a zone of intense mechanical interaction between adjacent ridge ends in which stresses are concentrated was identified. The magnitudes of mean stresses in the plane of the plate and orientations of principal stress planes were also calculated.

  7. Predicting clutter during anomalous propagation conditions

    NASA Astrophysics Data System (ADS)

    Lee, Susan C.; Maurer, Donald E.; Musser, Keith L.

    1988-06-01

    Excessive clutter caused by anomalous propagation conditions severely degrades radar performance in many regions of the world. This article describes methods that can be used to predict anomalous clutter amplitude for site-specific radar parameters, terrain features, and atmospheric conditions and to predict the effects of radar Doppler processing on evaporation-ducted sea clutter.

  8. Rupture Propagation for Stochastic Fault Models

    NASA Astrophysics Data System (ADS)

    Favreau, P.; Lavallee, D.; Archuleta, R.

    2003-12-01

    The inversion of strong motion data of large earhquakes give the spatial distribution of pre-stress on the ruptured faults and it can be partially reproduced by stochastic models, but a fundamental question remains: how rupture propagates, constrained by the presence of spatial heterogeneity? For this purpose we investigate how the underlying random variables, that control the pre-stress spatial variability, condition the propagation of the rupture. Two stochastic models of prestress distributions are considered, respectively based on Cauchy and Gaussian random variables. The parameters of the two stochastic models have values corresponding to the slip distribution of the 1979 Imperial Valley earthquake. We use a finite difference code to simulate the spontaneous propagation of shear rupture on a flat fault in a 3D continuum elastic body. The friction law is the slip dependent friction law. The simulations show that the propagation of the rupture front is more complex, incoherent or snake-like for a prestress distribution based on Cauchy random variables. This may be related to the presence of a higher number of asperities in this case. These simulations suggest that directivity is stronger in the Cauchy scenario, compared to the smoother rupture of the Gauss scenario.

  9. ACTS propagation terminal prototype planning and design

    NASA Technical Reports Server (NTRS)

    Davarian, Faramaz; Pergal, F.; Chakraborty, D.; Stutzman, Warren L.

    1990-01-01

    The planning and design of a prototype propagation receiving terminal for beacon signals at 27 and 20 GHz bands are examined. The developmental plan is discussed, followed by technical design considerations including, the Advanced Communications Technology Satellite (ACTS) system salient features and frequency plan, beacon signal parameters and specifications, system calculations, and terminal hardware design issues.

  10. Vertical laser beam propagation through the troposphere

    NASA Technical Reports Server (NTRS)

    Minott, P. O.; Bufton, J. L.; Schaefer, W. H.; Grolemund, D. A.

    1974-01-01

    The characteristics of the earth's atmosphere and its effects upon laser beams was investigated in a series of balloon borne, optical propagation experiments. These experiments were designed to simulate the space to ground laser link. An experiment to determine the amplitude fluctuation, commonly called scintillation, caused by the atmosphere was described.

  11. Aircraft noise and its nearfield propagation computations

    NASA Astrophysics Data System (ADS)

    Zhang, Xin

    2012-08-01

    Noise generated by civil transport aircraft during take-off and approach-to-land phases of operation is an environmental problem. The aircraft noise problem is firstly reviewed in this article. The review is followed by a description and assessment of a number of sound propagation methods suitable for applications with a background mean flow field pertinent to aircraft noise. Of the three main areas of the noise problem, i.e. generation, propagation, and radiation, propagation provides a vital link between near-field noise generation and far-field radiation. Its accurate assessment ensures the overall validity of a prediction model. Of the various classes of propagation equations, linearised Euler equations are often casted in either time domain or frequency domain. The equations are often solved numerically by computational aeroacoustics techniques, bur are subject to the onset of Kelvin-Helmholtz (K-H) instability modes which may ruin the solutions. Other forms of linearised equations, e.g. acoustic perturbation equations have been proposed, with differing degrees of success.

  12. Propagation of Innovations in Networked Groups

    ERIC Educational Resources Information Center

    Mason, Winter A.; Jones, Andy; Goldstone, Robert L.

    2008-01-01

    A novel paradigm was developed to study the behavior of groups of networked people searching a problem space. The authors examined how different network structures affect the propagation of information in laboratory-created groups. Participants made numerical guesses and received scores that were also made available to their neighbors in the…

  13. Wave propagation on a random lattice

    SciTech Connect

    Sahlmann, Hanno

    2010-09-15

    Motivated by phenomenological questions in quantum gravity, we consider the propagation of a scalar field on a random lattice. We describe a procedure to calculate the dispersion relation for the field by taking a limit of a periodic lattice. We use this to calculate the lowest order coefficients of the dispersion relation for a specific one-dimensional model.

  14. Relativistic shock propagation in nonuniform media

    NASA Astrophysics Data System (ADS)

    Gnatyk, B. I.

    1985-10-01

    Strong shocks will propagate in much the same way whether they are non- or ultrarelativistic. An approximate law is proposed to describe the motion of a strong, adiabatic, arbitrarily relativistic shock through an initially nonrelativistic medium having any desired density distribution.

  15. Electrical optimization of power delivery through thick steel barriers using piezoelectric transducers

    NASA Astrophysics Data System (ADS)

    Lawry, T. J.; Wilt, K. R.; Roa-Prada, S.; Ashdown, J. D.; Saulnier, G. J.; Scarton, H. A.; Das, P. K.; Pinezich, J. D.

    2010-04-01

    In many commercial, industrial, and military applications, supplying power to electronics through a thick metallic barrier without compromising its structural integrity would provide tremendous advantages over many existing barrier-penetrating techniques. The Faraday shielding presented by thick metallic barriers prevents the use of electromagnetic power-transmission techniques. This work describes the electrical optimization of continuouswave power delivery through thick steel barriers using ultrasound. Ultrasonic channels are formed by attaching pairs of coaxially-aligned piezoelectric transducers to opposite sides of thick steel blocks. The thickness of the steel considered is on the order of, or greater than, one quarter wavelength of the acoustic power signal inside of steel, requiring the use of wave propagation theory to properly analyze the system. A characterization and optimization methodology is presented which measures the linear two-port electrical scattering parameters of the transducersteel- transducer channel. Using these measurements, the simultaneous conjugate impedance-matching conditions at both transducers are calculated, and electrical matching-networks are designed to optimize the power transfer from a 50Ω power amplifier on one side of the steel block to a 50Ω load on the opposite side. In addition, the impacts of, and interactions between, transducer and steel geometries are discussed, and some general guidelines for selecting their relationships are presented. Measurements of optimized systems using transducers designed to resonate at 1 MHz with diameters from 12.7 mm to 66.7 mm, and steel block thicknesses from 9.5 mm to 63.5 mm, reveal power transfer efficiencies as high as 55%, and linear delivery of 81 watts through an optimized channel.

  16. Longitudinal nonlinear wave propagation through soft tissue.

    PubMed

    Valdez, M; Balachandran, B

    2013-04-01

    In this paper, wave propagation through soft tissue is investigated. A primary aim of this investigation is to gain a fundamental understanding of the influence of soft tissue nonlinear material properties on the propagation characteristics of stress waves generated by transient loadings. Here, for computational modeling purposes, the soft tissue is modeled as a nonlinear visco-hyperelastic material, the geometry is assumed to be one-dimensional rod geometry, and uniaxial propagation of longitudinal waves is considered. By using the linearized model, a basic understanding of the characteristics of wave propagation is developed through the dispersion relation and in terms of the propagation speed and attenuation. In addition, it is illustrated as to how the linear system can be used to predict brain tissue material parameters through the use of available experimental ultrasonic attenuation curves. Furthermore, frequency thresholds for wave propagation along internal structures, such as axons in the white matter of the brain, are obtained through the linear analysis. With the nonlinear material model, the authors analyze cases in which one of the ends of the rods is fixed and the other end is subjected to a loading. Two variants of the nonlinear model are analyzed and the associated predictions are compared with the predictions of the corresponding linear model. The numerical results illustrate that one of the imprints of the nonlinearity on the wave propagation phenomenon is the steepening of the wave front, leading to jump-like variations in the stress wave profiles. This phenomenon is a consequence of the dependence of the local wave speed on the local deformation of the material. As per the predictions of the nonlinear material model, compressive waves in the structure travel faster than tensile waves. Furthermore, it is found that wave pulses with large amplitudes and small elapsed times are attenuated over shorter spans. This feature is due to the elevated

  17. ESF GROUND SUPPORT - STRUCTURAL STEEL ANALYSIS

    SciTech Connect

    T. Misiak

    1996-06-26

    The purpose and objective of this analysis are to expand the level of detail and confirm member sizes for steel sets included in the Ground Support Design Analysis, Reference 5.20. This analysis also provides bounding values and details and defines critical design attributes for alternative configurations of the steel set. One possible configuration for the steel set is presented. This analysis covers the steel set design for the Exploratory Studies Facility (ESF) entire Main Loop 25-foot diameter tunnel.

  18. Proceedings of the Twentieth NASA Propagation Experimenters Meeting (NAPEX XX) and the Advanced Communications Technology Satellite (ACTS) Propagation Studies Miniworkshop

    NASA Technical Reports Server (NTRS)

    Golshan, Nassar (Editor)

    1996-01-01

    The NASA Propagation Experimenters (NAPEX) Meeting and associated Advanced Communications Technology Satellite (ACTS) Propagation Studies Miniworkshop convene yearly to discuss studies supported by the NASA Propagation Program. Representatives from the satellite communications (satcom)industry, academia, and government with an interest in space-ground radio wave propagation have peer discussion of work in progress, disseminate propagation results, and interact with the satcom industry. NAPEX XX, in Fairbanks, Alaska, June 4-5, 1996, had three sessions: (1) "ACTS Propagation Study: Background, Objectives, and Outcomes," covered results from thirteen station-years of Ka-band experiments; (2) "Propagation Studies for Mobile and Personal Satellite Applications," provided the latest developments in measurement, modeling, and dissemination of propagation phenomena of interest to the mobile, personal, and aeronautical satcom industry; and (3)"Propagation Research Topics," covered a range of topics including space/ground optical propagation experiments, propagation databases, the NASA Propagation Web Site, and revision plans for the NASA propagation effects handbooks. The ACTS Miniworkshop, June 6, 1996, covered ACTS status, engineering support for ACTS propagation terminals, and the ACTS Propagation Data Center. A plenary session made specific recommendations for the future direction of the program.

  19. The Temporal Morphology of Infrasound Propagation

    NASA Astrophysics Data System (ADS)

    Drob, Douglas P.; Garcés, Milton; Hedlin, Michael; Brachet, Nicolas

    2010-05-01

    Expert knowledge suggests that the performance of automated infrasound event association and source location algorithms could be greatly improved by the ability to continually update station travel-time curves to properly account for the hourly, daily, and seasonal changes of the atmospheric state. With the goal of reducing false alarm rates and improving network detection capability we endeavor to develop, validate, and integrate this capability into infrasound processing operations at the International Data Centre of the Comprehensive Nuclear Test-Ban Treaty Organization. Numerous studies have demonstrated that incorporation of hybrid ground-to-space (G2S) enviromental specifications in numerical calculations of infrasound signal travel time and azimuth deviation yields significantly improved results over that of climatological atmospheric specifications, specifically for tropospheric and stratospheric modes. A robust infrastructure currently exists to generate hybrid G2S vector spherical harmonic coefficients, based on existing operational and emperical models on a real-time basis (every 3- to 6-hours) (D rob et al., 2003). Thus the next requirement in this endeavor is to refine numerical procedures to calculate infrasound propagation characteristics for robust automatic infrasound arrival identification and network detection, location, and characterization algorithms. We present results from a new code that integrates the local (range-independent) τp ray equations to provide travel time, range, turning point, and azimuth deviation for any location on the globe given a G2S vector spherical harmonic coefficient set. The code employs an accurate numerical technique capable of handling square-root singularities. We investigate the seasonal variability of propagation characteristics over a five-year time series for two different stations within the International Monitoring System with the aim of understanding the capabilities of current working knowledge of the

  20. NASA Lunar Base Wireless System Propagation Analysis

    NASA Technical Reports Server (NTRS)

    Hwu, Shian U.; Upanavage, Matthew; Sham, Catherine C.

    2007-01-01

    There have been many radio wave propagation studies using both experimental and theoretical techniques over the recent years. However, most of studies have been in support of commercial cellular phone wireless applications. The signal frequencies are mostly at the commercial cellular and Personal Communications Service bands. The antenna configurations are mostly one on a high tower and one near the ground to simulate communications between a cellular base station and a mobile unit. There are great interests in wireless communication and sensor systems for NASA lunar missions because of the emerging importance of establishing permanent lunar human exploration bases. Because of the specific lunar terrain geometries and RF frequencies of interest to the NASA missions, much of the published literature for the commercial cellular and PCS bands of 900 and 1800 MHz may not be directly applicable to the lunar base wireless system and environment. There are various communication and sensor configurations required to support all elements of a lunar base. For example, the communications between astronauts, between astronauts and the lunar vehicles, between lunar vehicles and satellites on the lunar orbits. There are also various wireless sensor systems among scientific, experimental sensors and data collection ground stations. This presentation illustrates the propagation analysis of the lunar wireless communication and sensor systems taking into account the three dimensional terrain multipath effects. It is observed that the propagation characteristics are significantly affected by the presence of the lunar terrain. The obtained results indicate the lunar surface material, terrain geometry and antenna location are the important factors affecting the propagation characteristics of the lunar wireless systems. The path loss can be much more severe than the free space propagation and is greatly affected by the antenna height, surface material and operating frequency. The

  1. SH wave propagation in piezoelectric coupled plates.

    PubMed

    Wang, Quan

    2002-05-01

    The propagation of shear horizontal (SH) wave in a piezoelectric coupled plate is investigated in this paper. Full account is taken of the piezoelectric coupling effect to the isotropic metal core in the mathematical model. One of the applications of this research is in the damage detection of the host metal structure from the wave propagation signal excited by the piezoelectric layer which is surface bonded on the surface of a metal core. This research is distinct from the previous works on SH propagation in piezoelectric structures because the piezoelectric materials were used as the core structure in the previous studies, and the potential of the studies was mainly on time-delay devices. The dispersive characteristics and the mode shapes of the transverse displacement and the electric potential of the piezoelectric layer are theoretically derived. The results from numerical simulations show that the phase velocity of the plate structure tends to the bulk shear wave velocity of the host metal core at high wavenumber when the shear wave velocity of host plate is larger than that of PZT bonded on it. Furthermore, there are three asymptotic solutions of wave propagation when the shear wave velocity of the host plate is smaller than that of PZT. The mode shape of the electric potential of the piezoelectric layer changes from the quadratic shape at lower wavenumber and with thinner piezoelectric layer to the shape with more zero nodes at higher wavenumber and with thicker piezoelectric layer. These findings are significant in the application of wave propagation in piezoelectric coupled structures. PMID:12046935

  2. Shock wave propagation in glow discharges

    NASA Astrophysics Data System (ADS)

    Ganguly, B. N.

    1998-10-01

    The modification of acoustic shock wave propagation characteristics in a 25 cm long positive column low pressure (10 to 50 Torr), low current density (2 to 10 mA/cm^2) argon and N2 dc discharges have been measured by laser beam deflection technique. The simultaneous multi point shock velocity, dispersion and damping have been measured both inside and outside the glow discharge region. The local shock velocity is found to increase with the increased propagation path length through the discharge; for Mach number greater than 1.7 the upstream velocity exceeded the downstream velocity in contrast to the opposite behavior in neutral gas. The damping and dispersion are also dependent on the propagation distance. The recovery of the shock dispersion and damping in the post discharge region, for a given discharge condition, are functions of the initial Mach number. The optical measurement of the wall and the gas (rotational) temperatures suggest the observed shock features can not be solely explained by the gas heating in a self sustained discharge. The results are similar for both Ar and N2 discharges showing that vibrational excitation and relaxation are not essential^1. The explanation of the observed weak shock propagation properties in a glow discharge appears to require long range cooperative interactions that enhance heavy particle collisional energy transfer rates for the measured discharge conditions. Unlike collisional shock wave propagation in highly ionized plasmas^2,3, the exact energy coupling mechanism between the nonequilibrium weakly ionized plasma and shock is not understood. 1. A.I. Osipov and A.V. Uvarov, Sov. Phys. Usp. 35, 903 (1992) and other references there in. 2. M. Casanova, O. Larroche and J-P Matte, Phys. Rev. Lett. 67, 2143 (1991). 3. M.C.M. van de Sanden, R. van den Bercken and D.C. Schram, Plasma Sources Sci.Technol. 3, 511 (1994).

  3. Metallography of maraging 350 steel

    SciTech Connect

    Hutson, S.M.; Merten, C.W.

    1987-01-01

    A technique for etching maraging 350 steel with Glyceregia is described. Surface activation procedures are integral to this technique. Microstructural features revealed by this technique are compared with those obtained with Kalling's reagent, Fry's reagent, and 5% Nital, three etchants commonly used to reveal microstructures of maraging steels. Features which may be simultaneously revealed using Glyceregia include prior austenite grain boundaries, martensitic structure, precipitates, titanium carbo-nitrides, and reverted austenite. The other etchants examined in this investigation typically reveal only a few of the microstructural features detailed above at any one time. 11 refs., 10 figs., 2 tabs.

  4. Steel industry wastes. [Wastewater treatment

    SciTech Connect

    Vachon, D.T.; Schmidt, J.W.; Schmidtke, N.W.

    1982-06-01

    A literature review dealing with waste processing of steel industry wastes is presented. The costs for the U.S. steel industry to comply with environmental standards are such that water reuse and recycling may be necessary. The review examines conventional coke plant wastewater treatments such as flotation, phenol extraction, ammonia stripping, and biological nitrification, and alternative treatment processes for blast furnace scrubber blowdown such as alkaline chlorination, ozonation, and reverse osmosis. A review of pickling operations and finishing processes is also included with their appropriate waste methods highlighted.

  5. Plating on stainless steel alloys

    SciTech Connect

    Dini, J.W.; Johnson, H.R.

    1981-09-11

    Quantitative adhesion data are presented for a variety of electroplated stainless steel type alloys. Results show that excellent adhesion can be obtained by using a Wood's nickel strike or a sulfamate nickel strike prior to final plating. Specimens plated after Wood's nickel striking failed in the deposit rather than at the interface between the substrate and the coating. Flyer plate quantitative tests showed that use of anodic treatment in sulfuric acid prior to Wood's nickel striking even further improved adhesion. In contrast activation of stainless steels by immersion or cathodic treatment in hydrochloric acid resulted in very reduced bond strengths with failure always occurring at the interface between the coating and substrate.

  6. Susceptibility of irradiated steels to hydrogen embrittlement

    NASA Technical Reports Server (NTRS)

    Rossin, A. D.

    1968-01-01

    Investigation determined whether irradiated pressure-vessel steels 4340 and 212-B are susceptible to hydrogen embrittlement and to catastrophic failure. Hydrogen-charging conditions which completely embrittled 4340 steel had negligible effect on 212-B steel in tensile and delayed-failure tests.

  7. Steel erected at A-3 Test Stand

    NASA Technical Reports Server (NTRS)

    2008-01-01

    Fabricated steel began arriving by truck Oct. 24 for construction of the A-3 Test Stand that will be used to test the engine for the nation's next generation of moon rockets. Within days workers from Lafayette Steel Erector Inc. began assembling the 16 steel stages needed on the foundation and footings poured in the previous year.

  8. Steeling and Resilience in Art Education

    ERIC Educational Resources Information Center

    Heise, Donalyn

    2014-01-01

    Steel is an incredibly strong alloy of iron and carbon. Due to its incredible strength and durability, this resilient material is commonly used for constructing buildings. The transitive verb "steeling" is defined in Miriam-Webster dictionary as "to fill with resolution or determination, as in, she 'steeled herself to face the…

  9. Teaching Steel Connections Using an Interactive Virtual Steel Sculpture

    ERIC Educational Resources Information Center

    Moaveni, Saeed; Chou, Karen C.

    2015-01-01

    Steel connections play important roles in the integrity of a structure, and many structural failures are attributed to connection failures. Connections are the glue that holds a structure together. The failures of the Hartford Coliseum in 1977, the Hyatt Regency Hotel in Kansas City in 1980, and the I-35W Bridge in Minneapolis in 2007 are all…

  10. Investigation of guided waves propagation in pipe buried in sand

    SciTech Connect

    Leinov, Eli; Cawley, Peter; Lowe, Michael J.S.

    2014-02-18

    The inspection of pipelines by guided wave testing is a well-established method for the detection of corrosion defects in pipelines, and is currently used routinely in a variety of industries, e.g. petrochemical and energy. When the method is applied to pipes buried in soil, test ranges tend to be significantly compromised because of attenuation of the waves caused by energy radiating into the soil. Moreover, the variability of soil conditions dictates different attenuation characteristics, which in-turn results in different, unpredictable, test ranges. We investigate experimentally the propagation and attenuation characteristics of guided waves in pipes buried in fine sand using a well characterized full scale experimental apparatus. The apparatus consists of an 8 inch-diameter, 5.6-meters long steel pipe embedded over 3 meters of its length in a rectangular container filled with fine sand, and an air-bladder for the application of overburden pressure. Longitudinal and torsional guided waves are excited in the pipe and recorded using a transducer ring (Guided Ultrasonics Ltd). Acoustic properties of the sand are measured independently in-situ and used to make model predictions of wave behavior in the buried pipe. We present the methodology and the systematic measurements of the guided waves under a range of conditions, including loose and compacted sand. It is found that the application of overburden pressure modifies the compaction of the sand and increases the attenuation, and that the measurement of the acoustic properties of sand allows model prediction of the attenuation of guided waves in buried pipes with a high level of confidence.

  11. Low-pH SCC: Mechanical effects on crack propagation

    SciTech Connect

    Beavers, J.A.; Hagerdorn, E.L.

    1996-09-06

    A better definition of the role of mechanical factors on low-pH stress corrosion crack propagation is needed to aid in the prediction of crack growth rates on operating pipelines and to develop strategies to mitigate this form of cracking. The overall objective of the project was to determine the roles and synergistic effects of pressure, pressure fluctuations, and hydrotesting on low-pH stress corrosion crack growth. All testing was performed in a low-pH electrolyte (NS4 solution) under cyclic load conditions on pre-cracked specimens of one X-65 line pipe steel. The cyclic load conditions in the testing were related to field conditions using the J-integral parameter. This project consisted of the following three tasks, Task 1 - Development of Test Protocol, Task 2 - Mechanical Effects, and Task 3 - Effects of Hydrotesting. The purposes of Task 1 were to prepare the test specimens and experimental apparatus and to establish a standard test protocol for conducting the cyclic load tests and analyzing the test data. The specimen preparation procedures and environmental conditions were similar to those used in a previous project for TransCanada PipeLines (TCPL). The most significant difference between the tests performed in this project and the previous research was in the mode of loading. The previous work was performed under constant extension rate loading while this project was performed under cyclic load conditions. It is difficult to relate test conditions under constant extension rate loading with field conditions. However, the cyclic load conditions in the laboratory test can be directly related to field test conditions using the J-integral parameter. Modifications also were necessary in the data analysis procedure to account for the change in loading mode.

  12. Three-Dimensional Gear Crack Propagation Studied

    NASA Technical Reports Server (NTRS)

    Lewicki, David G.

    1999-01-01

    Gears used in current helicopters and turboprops are designed for light weight, high margins of safety, and high reliability. However, unexpected gear failures may occur even with adequate tooth design. To design an extremely safe system, the designer must ask and address the question, "What happens when a failure occurs?" With gear-tooth bending fatigue, tooth or rim fractures may occur. A crack that propagates through a rim will be catastrophic, leading to disengagement of the rotor or propeller, loss of an aircraft, and possible fatalities. This failure mode should be avoided. A crack that propagates through a tooth may or may not be catastrophic, depending on the design and operating conditions. Also, early warning of this failure mode may be possible because of advances in modern diagnostic systems. One concept proposed to address bending fatigue fracture from a safety aspect is a splittooth gear design. The prime objective of this design would be to control crack propagation in a desired direction such that at least half of the tooth would remain operational should a bending failure occur. A study at the NASA Lewis Research Center analytically validated the crack-propagation failsafe characteristics of a split-tooth gear. It used a specially developed three-dimensional crack analysis program that was based on boundary element modeling and principles of linear elastic fracture mechanics. Crack shapes as well as the crack-propagation life were predicted on the basis of the calculated stress intensity factors, mixed-mode crack-propagation trajectory theories, and fatigue crack-growth theories. The preceding figures show the effect of the location of initial cracks on crack propagation. 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 was simulated in a case study to evaluate crack-propagation paths. Tooth

  13. Superhard Nanocrystalline Homometallic Stainless Steel on Steel for Seamless Coatings

    NASA Technical Reports Server (NTRS)

    Tobin, Eric J.; Hafley, R. (Technical Monitor)

    2002-01-01

    The objective of this work is to deposit nanocrystalline stainless steel onto steel substrates (homometallic) for enhanced wear and corrosion resistance. Homometallic coatings provide superior adhesion, and it has been shown that ultrafine-grained materials exhibit the increased hardness and decreased permeability desired for protective coatings. Nanocrystals will be produced by controlling nucleation and growth and use of an ion beam during deposition by e-beam evaporation or sputtering. Phase I is depositing 31 6L nanocrystalline stainless steel onto 31 6L stainless steel substrates. These coatings exhibit hardnesses comparable to those normally obtained for ceramic coatings such ZrO2, and possess the superior adhesion of seamless, homometallic coatings. Hardening the surface with a similar material also enhances adhesion, by avoiding problems associated with thermal and lattice mismatch. So far we have deposited nanocrystalline homometallic 316L stainless steel coatings by varying the ions and the current density of the ion beams. For all deposition conditions we have produced smooth, uniform, superhard coatings. All coatings exhibit hardness of at least 200% harder than that of bulk materials. Our measurements indicate that there is a direct relationship between nanohardness and the current density of the ion beam. Stress measurements indicate that stress in the films is increasingly proportional to current density of the ion beam. TEM, XPS, and XRD results indicate that the coated layers consist of FCC structure nanocrystallites with a dimension of about 10 to 20 nm. The Ni and Mo concentration of these coating are lower than those of bulk 316L but the concentration of Cr is higher.

  14. Amplitude-Preserving Propagator and its Applications in Computational Wave Propagation and Seismic Imaging

    NASA Astrophysics Data System (ADS)

    Eslaminia, Mehran

    A novel method is developed to approximately solve acoustic wave equation in the frequency domain. The key idea of the method is to partition the domain into smaller subdomains and solve for the wavefield in each subdomain sequentially, which is facilitated by special interface (continuity) conditions. The sequential solution is performed in two steps: First the downward propagating wavefield is computed considering only downward propagation and transmission at the interfaces. The wavefield is then corrected by adding the upward propagating wavefield resulting from reflections and body forces. It is shown that the proposed method results in accurate amplitudes for downward propagation and primary reflections and is hence called the Amplitude-Preserving Propagator. This novel wave propagator leads to three disparate contributions in large scale computational wave modeling and seismic imaging: forward modeling, migration imaging and full waveform inversion. Forward Modeling: The amplitude-preserving propagator is implemented as a preconditioner to iteratively solve the Helmholtz equation. The effectiveness of the proposed preconditioner is studied using various numerical experiments. We show three significant properties of the proposed preconditioner. First, number of iterations grows very slowly with increasing frequency which is a significant advantage compared to other methods, e.g. sweeping preconditioner. Second, the mesh size (i.e. number of elements per wavelength) does not change number of iterations. Third, and the most important one, the computational time is much less than many other preconditioners. Migration Imaging: In the context of migration imaging, the amplitude-preserving propagator is implemented as an efficient forward solver to perform wave propagation simulation in the frequency domain. We show that the propagator results in a new migration algorithm that is almost as accurate as full-wave migration, while being significantly more efficient

  15. Effects of friction and high torque on fatigue crack propagation in Mode III

    NASA Astrophysics Data System (ADS)

    Nayeb-Hashemi, H.; McClintock, F. A.; Ritchie, R. O.

    1982-12-01

    Turbo-generator and automotive shafts are often subjected to complex histories of high torques. To provide a basis for fatigue life estimation in such components, a study of fatigue crack propagation in Mode III (anti-plane shear) for a mill-annealed AISI 4140 steel (RB88, 590 MN/m2 tensile strength) has been undertaken, using torsionally-loaded, circumferentially-notched cylindrical specimens. As demonstrated previously for higher strength AISI 4340 steel, Mode III cyclic crack growth rates (dc/dN) IIIcan be related to the alternating stress intensity factor ΔKIII for conditions of small-scale yielding. However, to describe crack propagation behavior over an extended range of crack growth rates (˜10-6 to 10-2 mm per cycle), where crack growth proceeds under elastic-plastic and full plastic conditions, no correlation between (dc/dN) III and ΔKIII is possible. Accordingly, a new parameter for torsional crack growth, termed the plastic strain intensity Γ III, is introduced and is shown to provide a unique description of Mode III crack growth behavior for a wide range of testing conditions, provided a mean load reduces friction, abrasion, and interlocking between mating fracture surfaces. The latter effect is found to be dependent upon the mode of applied loading (i.e., the presence of superimposed axial loads) and the crack length and torque level. Mechanistically, high-torque surfaces were transverse, macroscopically flat, and smeared. Lower torques showed additional axial cracks (longitudinal shear cracking) perpendicular to the main transverse surface. A micro-mechanical model for the main radi l Mode III growth, based on the premise that crack advance results from Mode II coalescence of microcracks initiated at inclusions ahead of the main crack front, is extended to high nominal stress levels, and predicts that Mode III fatigue crack propagation rates should be proportional to the range of plastic strain intensity (ΔΓIII if local Mode II growth rates are

  16. Beam propagation method using a [(p- 1)/ p] Padé approximant of the propagator.

    PubMed

    Lu, Ya Yan; Ho, Pui Lin

    2002-05-01

    A new beam propagation method (BPM) is developed based on a direct approximation to the propagator by its [(p-1)/p] Padé approximant. The approximant is simple to construct and has the desired damping effect for the evanescent modes. The method is applied to a tapered waveguide for TM-polarized waves, based on the energy-conserving improvement of the one-way Helmholtz equation. Numerical results are compared with those obtained with other variants of the BPM. PMID:18007898

  17. Solitons in wave propagation and spin systems

    NASA Astrophysics Data System (ADS)

    Loutsenko, Igor

    1999-10-01

    This thesis consists of three parts: In the first part, a solution of the restricted Hadamard problem is presented. The classical Hadamard problem consists in determining (up to equivalence) all the second order differential operators which satisfy Huygens' Principle in the narrow sense. Physically, such operators describe systems where the diffusion of waves is absent and where signals propagate with maximal velocity. Unlike the original principle of superposition of secondary waves, which holds for all wave propagation phenomena, Huygens' principle in the narrow sense of Hadamard applies only to a very restricted range of wave processes, with sharp signals. We present a new class of Huygens' operators on Minkowski space-time and establish a new link between Huygens' principle and the solitons of the Korteveg-de Vries equation. In the second part, a new class of exactly solvable models in statistical mechanics is presented. We study the connections between the soliton solutions of certain integrable nonlinear equations (hierarchies of equations) and the thermodynamic quantities of one-dimensional Ising models with different types of interactions between spins. The exact solvability of these models can be traced back to this connection. We consider a model linked to soliton solutions of the Korteveg de Vries and of the B-type Kadomtsev-Petiashvili hierarchies. A connection between these Ising chains and random matrix models is considered as well. In the third part, we study solitonic mechanisms of exciton superfluidity. We provide a theoretical explanation of recent experiments on the propagation of excitons in semiconductors. In these experiments, the excitonic transport under the action of a laser pulse has been studied. It turned out that under certain conditions this transport becomes anomalous and the excitons propagate through the crystal in a wave packet without diffusion. We propose a model for this phenomenon which relies on the presence of an exciton

  18. Efficient Geometric Sound Propagation Using Visibility Culling

    NASA Astrophysics Data System (ADS)

    Chandak, Anish

    2011-07-01

    Simulating propagation of sound can improve the sense of realism in interactive applications such as video games and can lead to better designs in engineering applications such as architectural acoustics. In this thesis, we present geometric sound propagation techniques which are faster than prior methods and map well to upcoming parallel multi-core CPUs. We model specular reflections by using the image-source method and model finite-edge diffraction by using the well-known Biot-Tolstoy-Medwin (BTM) model. We accelerate the computation of specular reflections by applying novel visibility algorithms, FastV and AD-Frustum, which compute visibility from a point. We accelerate finite-edge diffraction modeling by applying a novel visibility algorithm which computes visibility from a region. Our visibility algorithms are based on frustum tracing and exploit recent advances in fast ray-hierarchy intersections, data-parallel computations, and scalable, multi-core algorithms. The AD-Frustum algorithm adapts its computation to the scene complexity and allows small errors in computing specular reflection paths for higher computational efficiency. FastV and our visibility algorithm from a region are general, object-space, conservative visibility algorithms that together significantly reduce the number of image sources compared to other techniques while preserving the same accuracy. Our geometric propagation algorithms are an order of magnitude faster than prior approaches for modeling specular reflections and two to ten times faster for modeling finite-edge diffraction. Our algorithms are interactive, scale almost linearly on multi-core CPUs, and can handle large, complex, and dynamic scenes. We also compare the accuracy of our sound propagation algorithms with other methods. Once sound propagation is performed, it is desirable to listen to the propagated sound in interactive and engineering applications. We can generate smooth, artifact-free output audio signals by applying

  19. Environment-Assisted Cracking in Custom 465 Stainless Steel

    NASA Astrophysics Data System (ADS)

    Lee, E. U.; Goswami, R.; Jones, M.; Vasudevan, A. K.

    2011-02-01

    The influence of cold work and aging on the environment-assisted cracking (EAC) behavior and mechanical properties of Custom 465 stainless steel (SS) was studied. Four sets of specimens were made and tested. All specimens were initially solution annealed, rapidly cooled, and refrigerated (SAR condition). The first specimen set was steel in the SAR condition. The second specimen set was aged to the H1000 condition. The third specimen set was 60 pct cold worked, and the fourth specimen set was 60 pct cold worked and aged at temperatures ranging from 755 K to 825 K (482 °C to 552 °C) for 4 hours in air. The specimens were subsequently subjected to EAC and mechanical testing. The EAC testing was conducted, using the rising step load (RSL) technique, in aqueous solutions of NaCl of pH 7.3 with concentrations ranging from 0.0035 to 3.5 pct at room temperature. The microstructure, dislocation substructure, and crack paths, resulting from the cold work, aging, or subsequent EAC testing, were examined by optical microscopy, transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The aging of the cold-worked specimens induced carbide precipitation within the martensite lath, but not at the lath or packet boundaries. In the aged specimens, as aging temperature rose, the threshold stress intensity for EAC (KIEAC), elongation, and fracture toughness increased, but the strength and hardness decreased. The KIEAC also decreased with increasing yield strength and NaCl concentration. In the SAR and H1000 specimens, the EAC propagated along the prior austenite grain boundary, while in the cold-worked and cold-worked and aged specimens, the EAC propagated along the martensite lath, and its packet and prior austenite grain boundaries. The controlling mechanism for the observed EAC was identified to be hydrogen embrittlement.

  20. GALVANIZED STEEL: NATIONAL DISTRIBUTION STUDY

    EPA Science Inventory

    This report describes a field survey done to observe the extent and application of bare galvanized steel in the United States. or purposes of the analysis, the conterminous 48 states were grouped into four regions. ndustrial and rural areas were considered In the study which exam...