Synthesis of geopolymer from rice husk ash for biodiesel production of Calophyllum inophyllum seed oil

NASA Astrophysics Data System (ADS)

Saputra, E.; Nugraha, M. W.; Helwani, Z.; Olivia, M.; Wang, S.

2018-04-01

In this work, geopolymer was prepared from rice husk ash (RHA) made into sodium silicate then synthesized by reacting metakaolin, NaOH, and water. The catalyst was characterized using Scanning Electron Microscopy (SEM), Energy-dispersive X-Ray analysis (EDX), Brunaeur Emmet Teller (BET), and basic strength. Then, the catalyst used for transesterification of Calophyllum inophyllum seed oil in order to produce biodiesel. The variation of process variables conducted to assess the effect on the yield of biodiesel. The highest yield obtained 87.68% biodiesel with alkyl ester content 99.29%, density 866 kg/m3, viscosity 4.13 mm2/s, the acid number of 0.42 mg-KOH/g biodiesel and the flash point 140 °C. Generally, variations of %w/w catalyst provides a dominant influence on the yield response of biodiesel. The physicochemical properties of the produced biodiesel comply with ASTM standard specifications.

Influence of conduit flow mechanics on magma rheology and the growth style of lava domes

NASA Astrophysics Data System (ADS)

Husain, Taha; Elsworth, Derek; Voight, Barry; Mattioli, Glen; Jansma, Pamela

2018-06-01

We develop a 2-D particle-mechanics model to explore different lava-dome growth styles. These range from endogenous lava dome growth comprising expansion of a ductile dome core to the exogenous extrusion of a degassed lava plug resulting in generation of a lava spine. We couple conduit flow dynamics with surface growth of the evolving lava dome, fuelled by an open-system magma chamber undergoing continuous replenishment. The conduit flow model accounts for the variation in rheology of ascending magma that results from degassing-induced crystallization. A period of reduced effusive flow rates promote enhanced degassing-induced crystallization. A degassed lava plug extrudes exogenously for magmas with crystal contents (ϕ) of 78 per cent, yield strength >1.62 MPa, and at flow rates of <0.5 m3 s-1, while endogenous dome growth is predicted at higher flow rates (Qout > 3 m3 s-1) for magma with lower relative yield strengths (<1 MPa). At moderately high flow rates (Qout = 4 m3 s-1), the extrusion of magma with lower crystal content (62 per cent) and low interparticulate yield strength (0.6 MPa) results in the development of endogenous shear lobes. Our simulations model the periodic extrusion history at Mount St. Helens (1980-1983). Endogenous growth initiates in the simulated lava dome with the extrusion of low yield strength magma (ϕ = 0.63 and τp = 0.76 MPa) after the crystallized viscous plug (ϕ = 0.87 and τp = 3 MPa) at the conduit exit is forced out by the high discharge rate pulse (2 < Qout < 12 m3 s-1). The size of the endogenous viscous plug and the occurrence of exogenous growth depend on magma yield strength and the magma chamber volume, which control the periodicity of the effusion. Our simulations generate dome morphologies similar to those observed at Mount St Helens, and demonstrate the degree to which domes can sag and spread during and following extrusion pulses. This process, which has been observed at Mount St. Helens and other locations, largely reflects gravitational loading of dome with a viscous core, with retardation by yield strength and talus friction.

Elasticity and breaking strength of synthetic suture materials incubated in various equine physiological and pathological solutions.

PubMed

Kearney, C M; Buckley, C T; Jenner, F; Moissonnier, P; Brama, P A J

2014-07-01

Selection of suture material in equine surgery is often based on costs or subjective factors, such as the surgeon's personal experience, rather than objective facts. The amount of objective data available on durability of suture materials with regard to specific equine physiological conditions is limited. To evaluate the effect of various equine physiological and pathological fluids on the rate of degradation of a number of commonly used suture materials. In vitro material testing. Suture materials were exposed in vitro to physiological fluid, followed by biomechanical analysis. Three absorbable suture materials, glycolide/lactide copolymer, polyglactin 910 and polydioxanone were incubated at 37°C for 7, 14 or 28 days in phosphate-buffered saline, equine serum, equine urine and equine peritoneal fluid from an animal with peritonitis. Five strands of each suture material type were tested to failure in a materials testing machine for each time point and each incubation medium. Yield strength, strain and Young's modulus were calculated, analysed and reported. For all suture types, the incubation time had a significant effect on yield strength, percentage elongation and Young's modulus in all culture media (P<0.0001). Suture type was also shown significantly to influence changes in each of yield strength, percentage elongation and Young's modulus in all culture media (P<0.0001). While the glycolide/lactide copolymer demonstrated the highest Day 0 yield strength, it showed the most rapid degradation in all culture media. For each of the 3 material characteristics tested, polydioxanone showed the least variation across the incubation period in each culture medium. The duration of incubation and the type of fluid have significant effects on the biomechanical properties of various suture materials. These findings are important for evidence-based selection of suture material in clinical cases. © 2013 EVJ Ltd.

Repeatability and Reproducibility of Compression Strength Measurements Conducted According to ASTM E9

NASA Technical Reports Server (NTRS)

Luecke, William E.; Ma, Li; Graham, Stephen M.; Adler, Matthew A.

2010-01-01

Ten commercial laboratories participated in an interlaboratory study to establish the repeatability and reproducibility of compression strength tests conducted according to ASTM International Standard Test Method E9. The test employed a cylindrical aluminum AA2024-T351 test specimen. Participants measured elastic modulus and 0.2 % offset yield strength, YS(0.2 % offset), using an extensometer attached to the specimen. The repeatability and reproducibility of the yield strength measurement, expressed as coefficient of variations were cv(sub r)= 0.011 and cv(sub R)= 0.020 The reproducibility of the test across the laboratories was among the best that has been reported for uniaxial tests. The reported data indicated that using diametrically opposed extensometers, instead of a single extensometer doubled the precision of the test method. Laboratories that did not lubricate the ends of the specimen measured yield stresses and elastic moduli that were smaller than those measured in laboratories that lubricated the specimen ends. A finite element analysis of the test specimen deformation for frictionless and perfect friction could not explain the discrepancy, however. The modulus measured from stress-strain data were reanalyzed using a technique that finds the optimal fit range, and applies several quality checks to the data. The error in modulus measurements from stress-strain curves generally increased as the fit range decreased to less than 40 % of the stress range.

Impact of Tunnel-Barrier Strength on Magnetoresistance in Carbon Nanotubes

NASA Astrophysics Data System (ADS)

Morgan, Caitlin; Misiorny, Maciej; Metten, Dominik; Heedt, Sebastian; Schäpers, Thomas; Schneider, Claus M.; Meyer, Carola

2016-05-01

We investigate magnetoresistance in spin valves involving CoPd-contacted carbon nanotubes. Both the temperature and bias-voltage dependence clearly indicate tunneling magnetoresistance as the origin. We show that this effect is significantly affected by the tunnel-barrier strength, which appears to be one reason for the variation between devices previously detected in similar structures. Modeling the data by means of the scattering matrix approach, we find a nontrivial dependence of the magnetoresistance on the barrier strength. Furthermore, an analysis of the spin precession observed in a nonlocal Hanle measurement yields a spin lifetime of τs=1.1 ns , a value comparable with those found in silicon- or graphene-based spin-valve devices.

Microstructure-mechanical property relationships for Al-Cu-Li-Zr alloys with minor additions of cadmium, indium or tin

NASA Technical Reports Server (NTRS)

Blackburn, L. B.; Starke, E. A., Jr.

1989-01-01

Minor amounts of cadmium, indium or tin were added to a baseline alloy with the nominal composition of Al-2.4Cu-2.4Li-0.15Zr. These elements were added in an attempt to increase the age-hardening response of the material such that high strengths could be achieved through heat-treatment alone, without the need for intermediate mechanical working. The alloy variant containing indium achieved a higher peak hardness in comparison to the other alloy variations, including the baseline material, when aged at temperatures ranging from 160 C to 190 C. Tensile tests on specimens peak-aged at 160 indicated the yield strength of the indium-bearing alloy increased by approximately 15 percent compared to that of the peak-aged baseline alloy. In addition, the yield strength obtained in the indium-bearing alloy was comparable to that reported for similar baseline material subjected to a 6 percent stretch prior to peak-aging at 190 C. The higher strength levels obtaied for the indium-bearing alloy are attributed to increased number densities and homogeneity of both the T1 and theta-prime phases, as determined by TEM studies.

The use of ion beam cleaning to obtain high quality cold welds with minimal deformation

NASA Technical Reports Server (NTRS)

Sater, B. L.; Moore, T. J.

1978-01-01

This paper describes a variation of cold welding which utilizes an ion beam to clean mating surfaces prior to joining in a vacuum environment. High quality solid state welds were produced with minimal deformation. Due to experimental fixture limitation in applying pressure work has been limited to a few low yield strength materials.

Yield Strength Testing in Human Cadaver Nasal Septal Cartilage and L-Strut Constructs.

PubMed

Liu, Yuan F; Messinger, Kelton; Inman, Jared C

2017-01-01

To our knowledge, yield strength testing in human nasal septal cartilage has not been reported to date. An understanding of the basic mechanics of the nasal septum may help surgeons decide how much of an L-strut to preserve and how much grafting is needed. To determine the factors correlated with yield strength of the cartilaginous nasal septum and to explore the association between L-strut width and thickness in determining yield strength. In an anatomy laboratory, yield strength of rectangular pieces of fresh cadaver nasal septal cartilage was measured, and regression was performed to identify the factors correlated with yield strength. To measure yield strength in L-shaped models, 4 bonded paper L-struts models were constructed for every possible combination of the width and thickness, for a total of 240 models. Mathematical modeling using the resultant data with trend lines and surface fitting was performed to quantify the associations among L-strut width, thickness, and yield strength. The study dates were November 1, 2015, to April 1, 2016. The factors correlated with nasal cartilage yield strength and the associations among L-strut width, thickness, and yield strength in L-shaped models. Among 95 cartilage pieces from 12 human cadavers (mean [SD] age, 67.7 [12.6] years) and 240 constructed L-strut models, L-strut thickness was the only factor correlated with nasal septal cartilage yield strength (coefficient for thickness, 5.54; 95% CI, 4.08-7.00; P < .001), with an adjusted R2 correlation coefficient of 0.37. The mean (SD) yield strength R2 varied with L-strut thickness exponentially (0.93 [0.06]) for set widths, and it varied with L-strut width linearly (0.82 [0.11]) or logarithmically (0.85 [0.17]) for set thicknesses. A 3-dimensional surface model of yield strength with L-strut width and thickness as variables was created using a 2-dimensional gaussian function (adjusted R2 = 0.94). Estimated yield strengths were generated from the model to allow determination of the desired yield strength with different permutations of L-strut width and thickness. In this study of human cadaver nasal septal cartilage, L-strut thickness was significantly associated with yield strength. In a bonded paper L-strut model, L-strut thickness had a more important role in determining yield strength than L-strut width. Surgeons should consider the thickness of potential L-struts when determining the amount of cartilaginous septum to harvest and graft. NA.

Calcium abundances in giant stars of the globular clusters M3, M13, M15, and M92

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suntzeff, N.B.

The average calcium II H and K line strengths of giant stars in M3, M13, M15, and M92 are found to be closely correlated with the (Fe/H) of the cluster. Simple physical arguments are provided to show the observed average line strengths reproduce the difference in (Fe/H) between the clusters. The observed dispersion in H and K line strengths yields an upper limit of 0.15 dex for M15 and M92, and 0.11 dex for M3+M13 for the average intracluster variation of (Ca/H), provided (Ca/H)=Fe/H). The dispersions drop to half these values if the calcium abundance varies independently of the ironmore » peak abundances.« less

LSS 2018: A double-lined spectroscopic binary central star with an extremely large reflection effect

NASA Technical Reports Server (NTRS)

Drilling, J. S.

1985-01-01

LSS 2018, the central star of the planetry nebulae DS1, was found to be a double-lined spectroscopic binary with a period of 8.571 hours. Light variations with the same period were observed in U, B, and V; in the wavelength regions defined by the two IUE cameras; and in the strength of the CIII 4647 emission line. The light variations can be accurately predicted by a simple reflection effect, and an analysis of the light curves yields the angular diameter and effective temperature of the primary, the radii of the two stars in terms of their separation, and the inclination of the system. Analysis of the radial velocities then yields the masses of the two stars, their separation, the distance of the system, the absolute magnitude of the primary, and the size of the nebula.

Microstructural evolution during aging of an Al-Cu-Li-Ag-Mg-Zr alloy

NASA Technical Reports Server (NTRS)

Kumar, K. S.; Brown, S. A.; Pickens, Joseph R.

1991-01-01

Alloys in the Al-Cu-Li Ag-Mg subsystem were developed that exhibit desirable combinations of strength and ductility. These Weldalite (trademark) alloys, are unique for Al-Cu-Li alloys in that with or without a prior cold stretching operation, they obtain excellent strength-ductility combinations upon natural and artificial aging. This is significant because it enables complex, near-net shape products such as forgings and super plastically formed parts to be heat treated to ultra-high strengths. On the other hand, commercial extrusions, rolled plates and sheets of other Al-Cu-Li alloys are typically subjected to a cold stretching operation before artificial aging to the highest strength tempers to introduce dislocations that provide low-energy nucleation sites for strengthening precipitates such as the T(sub 1) phase. The variation in yield strength (YS) with Li content in the near-peak aged condition for these Weldalite (trademark) alloys and the associated microstructures were examined, and the results are discussed.

High temperature - low mass solar blanket

NASA Technical Reports Server (NTRS)

Mesch, H. G.

1979-01-01

Interconnect materials and designs for use with ultrathin silicon solar cells are discussed, as well as the results of an investigation of the applicability of parallel-gap resistance welding for interconnecting these cells. Data relating contact pull strength and cell electrical degradation to variations in welding parameters such as time, voltage and pressure are presented. Methods for bonding ultrathin cells to flexible substances and for bonding thin (75 micrometers) covers to these cells are described. Also, factors influencing fabrication yield and approaches for increasing yield are discussed. The results of vacuum thermal cycling and thermal soak tests on prototype ultrathin cell test coupons and one solar module blanket are presented.

Inverse methods-based estimation of plate coupling in a plate motion model governed by mantle flow

NASA Astrophysics Data System (ADS)

Ratnaswamy, V.; Stadler, G.; Gurnis, M.

2013-12-01

Plate motion is primarily controlled by buoyancy (slab pull) which occurs at convergent plate margins where oceanic plates undergo deformation near the seismogenic zone. Yielding within subducting plates, lateral variations in viscosity, and the strength of seismic coupling between plate margins likely have an important control on plate motion. Here, we wish to infer the inter-plate coupling for different subduction zones, and develop a method for inferring it as a PDE-constrained optimization problem, where the cost functional is the misfit in plate velocities and is constrained by the nonlinear Stokes equation. The inverse models have well resolved slabs, plates, and plate margins in addition to a power law rheology with yielding in the upper mantle. Additionally, a Newton method is used to solve the nonlinear Stokes equation with viscosity bounds. We infer plate boundary strength using an inexact Gauss-Newton method with line search for backtracking. Each inverse model is applied to two simple 2-D scenarios (each with three subduction zones), one with back-arc spreading and one without. For each case we examine the sensitivity of the inversion to the amount of surface velocity used: 1) full surface velocity data and 2) surface velocity data simplified using a single scalar average (2-D equivalent to an Euler pole) for each plate. We can recover plate boundary strength in each case, even in the presence of highly nonlinear flow with extreme variations in viscosity. Additionally, we ascribe an uncertainty in each plate's velocity and perform an uncertainty quantification (UQ) through the Hessian of the misfit in plate velocities. We find that as plate boundaries become strongly coupled, the uncertainty in the inferred plate boundary strength decreases. For very weak, uncoupled subduction zones, the uncertainty of inferred plate margin strength increases since there is little sensitivity between plate margin strength and plate velocity. This result is significant because it implies we can infer which plate boundaries are more coupled (seismically) for a realistic dynamic model of plates and mantle flow.

On cyclic yield strength in definition of limits for characterisation of fatigue and creep behaviour

NASA Astrophysics Data System (ADS)

Gorash, Yevgen; MacKenzie, Donald

2017-06-01

This study proposes cyclic yield strength as a potential characteristic of safe design for structures operating under fatigue and creep conditions. Cyclic yield strength is defined on a cyclic stress-strain curve, while monotonic yield strength is defined on a monotonic curve. Both values of strengths are identified using a two-step procedure of the experimental stress-strain curves fitting with application of Ramberg-Osgood and Chaboche material models. A typical S-N curve in stress-life approach for fatigue analysis has a distinctive minimum stress lower bound, the fatigue endurance limit. Comparison of cyclic strength and fatigue limit reveals that they are approximately equal. Thus, safe fatigue design is guaranteed in the purely elastic domain defined by the cyclic yielding. A typical long-term strength curve in time-to-failure approach for creep analysis has two inflections corresponding to the cyclic and monotonic strengths. These inflections separate three domains on the long-term strength curve, which are characterised by different creep fracture modes and creep deformation mechanisms. Therefore, safe creep design is guaranteed in the linear creep domain with brittle failure mode defined by the cyclic yielding. These assumptions are confirmed using three structural steels for normal and high-temperature applications. The advantage of using cyclic yield strength for characterisation of fatigue and creep strength is a relatively quick experimental identification. The total duration of cyclic tests for a cyclic stress-strain curve identification is much less than the typical durations of fatigue and creep rupture tests at the stress levels around the cyclic yield strength.

Elucidation of the genetic basis of variation for stem strength characteristics in bread wheat by Associative Transcriptomics.

PubMed

Miller, Charlotte N; Harper, Andrea L; Trick, Martin; Werner, Peter; Waldron, Keith; Bancroft, Ian

2016-07-16

The current approach to reducing the tendency for wheat grown under high fertilizer conditions to collapse (lodge) under the weight of its grain is based on reducing stem height via the introduction of Rht genes. However, these reduce the yield of straw (itself an important commodity) and introduce other undesirable characteristics. Identification of alternative height-control loci is therefore of key interest. In addition, the improvement of stem mechanical strength provides a further way through which lodging can be reduced. To investigate the prospects for genetic alternatives to Rht, we assessed variation for plant height and stem strength properties in a training genetic diversity panel of 100 wheat accessions fixed for Rht. Using mRNAseq data derived from RNA purified from leaves, functional genotypes were developed for the panel comprising 42,066 Single Nucleotide Polymorphism (SNP) markers and 94,060 Gene Expression Markers (GEMs). In the first application in wheat of the recently-developed method of Associative Transcriptomics, we identified associations between trait variation and both SNPs and GEMs. Analysis of marker-trait associations revealed candidates for the causative genes underlying the trait variation, implicating xylan acetylation and the COP9 signalosome as contributing to stem strength and auxin in the control of the observed variation for plant height. Predictive capabilities of key markers for stem strength were validated using a test genetic diversity panel of 30 further wheat accessions. This work illustrates the power of Associative Transcriptomics for the exploration of complex traits of high agronomic importance in wheat. The careful selection of genotypes included in the analysis, allowed for high resolution mapping of novel trait-controlling loci in this staple crop. The use of Gene Expression markers coupled with the more traditional sequence-based markers, provides the power required to understand the biological context of the marker-trait associations observed. This not only adds to the wealth of knowledge that we strive to accumulate regarding gene function and plant adaptation, but also provides breeders with the information required to make more informed decisions regarding the potential consequences of incorporating the use of particular markers into future breeding programmes.

Simulation of fruit-set and trophic competition and optimization of yield advantages in six Capsicum cultivars using functional-structural plant modelling.

PubMed

Ma, Y T; Wubs, A M; Mathieu, A; Heuvelink, E; Zhu, J Y; Hu, B G; Cournède, P H; de Reffye, P

2011-04-01

Many indeterminate plants can have wide fluctuations in the pattern of fruit-set and harvest. Fruit-set in these types of plants depends largely on the balance between source (assimilate supply) and sink strength (assimilate demand) within the plant. This study aims to evaluate the ability of functional-structural plant models to simulate different fruit-set patterns among Capsicum cultivars through source-sink relationships. A greenhouse experiment of six Capsicum cultivars characterized with different fruit weight and fruit-set was conducted. Fruit-set patterns and potential fruit sink strength were determined through measurement. Source and sink strength of other organs were determined via the GREENLAB model, with a description of plant organ weight and dimensions according to plant topological structure established from the measured data as inputs. Parameter optimization was determined using a generalized least squares method for the entire growth cycle. Fruit sink strength differed among cultivars. Vegetative sink strength was generally lower for large-fruited cultivars than for small-fruited ones. The larger the size of the fruit, the larger variation there was in fruit-set and fruit yield. Large-fruited cultivars need a higher source-sink ratio for fruit-set, which means higher demand for assimilates. Temporal heterogeneity of fruit-set affected both number and yield of fruit. The simulation study showed that reducing heterogeneity of fruit-set was obtained by different approaches: for example, increasing source strength; decreasing vegetative sink strength, source-sink ratio for fruit-set and flower appearance rate; and harvesting individual fruits earlier before full ripeness. Simulation results showed that, when we increased source strength or decreased vegetative sink strength, fruit-set and fruit weight increased. However, no significant differences were found between large-fruited and small-fruited groups of cultivars regarding the effects of source and vegetative sink strength on fruit-set and fruit weight. When the source-sink ratio at fruit-set decreased, the number of fruit retained on the plant increased competition for assimilates with vegetative organs. Therefore, total plant and vegetative dry weights decreased, especially for large-fruited cultivars. Optimization study showed that temporal heterogeneity of fruit-set and ripening was predicted to be reduced when fruits were harvested earlier. Furthermore, there was a 20 % increase in the number of extra fruit set.

Mechanical Properties of LaRC(tm) SI Polymer for a Range of Molecular Weights

NASA Technical Reports Server (NTRS)

Whitley, Karen S.; Gates, Thomas S.; Hinkley, Jeffrey A.; Nicholson, Lee M.

2000-01-01

Mechanical testing of an advanced polyimide resin (LaRC(tm)-SI) with known variations in molecular weight was performed over a range of temperatures below the glass transition temperature. Elastic and inelastic properties were characterized as a function of molecular weight and test temperature. It was shown that notched tensile strength is a strong function of both temperature and molecular weight, whereas stiffness is only a strong function of temperature. The combined analysis of calculated yield stress and notched tensile strength indicated that low molecular weight materials tended to fail in a brittle manner, whereas high molecular weight materials exhibited ductile failure. The microphotographs of the failure surfaces also supported these findings.

Elastic Properties in Tension and Shear of High Strength Nonferrous Metals and Stainless Steel - Effect of Previous Deformation and Heat Treatment

NASA Technical Reports Server (NTRS)

Mebs, R W; Mcadam, D J

1947-01-01

A resume is given of an investigation of the influence of plastic deformation and of annealing temperature on the tensile and shear elastic properties of high strength nonferrous metals and stainless steels in the form of rods and tubes. The data were obtained from earlier technical reports and notes, and from unpublished work in this investigation. There are also included data obtained from published and unpublished work performed on an independent investigation. The rod materials, namely, nickel, monel, inconel, copper, 13:2 Cr-Ni steel, and 18:8 Cr-Ni steel, were tested in tension; 18:8 Cr-Ni steel tubes were tested in shear, and nickel, monel, aluminum-monel, and Inconel tubes were tested in both tension and shear. There are first described experiments on the relationship between hysteresis and creep, as obtained with repeated cyclic stressing of annealed stainless steel specimens over a constant load range. These tests, which preceded the measurements of elastic properties, assisted in devising the loading time schedule used in such measurements. From corrected stress-set curves are derived the five proof stresses used as indices of elastic or yield strength. From corrected stress-strain curves are derived the secant modulus and its variation with stress. The relationship between the forms of the stress-set and stress-strain curves and the values of the properties derived is discussed. Curves of variation of proof stress and modulus with prior extension, as obtained with single rod specimens, consist in wavelike basic curves with superposed oscillations due to differences of rest interval and extension spacing; the effects of these differences are studied. Oscillations of proof stress and modulus are generally opposite in manner. The use of a series of tubular specimens corresponding to different amounts of prior extension of cold reduction gave curves almost devoid of oscillation since the effects of variation of rest interval and extension spacing were removed. Comparison is also obtained between the variation of the several properties, as measured in tension and in shear. The rise of proof stress with extension is studied, and the work-hardening rates of the various metals evaluated. The ratio between the tensile and shear proof stresses for the various annealed and cold-worked tubular metals is likewise calculated. The influence of annealing or tempering temperature on the proof stresses and moduli for the cold-worked metals and for air-hardened 13:2 Cr-Ni steel is investigated. An improvement of elastic strength generally is obtained, without important loss of yield strength, by annealing at suitable temperature. The variation of the proof stress and modulus of elasticity with plastic deformation or annealing temperature is explained in terms of the relative dominance of three important factors: namely, (a) internal stress, (b) lattice-expansion or work-hardening, and (c) crystal reorientation. Effective values of Poisson's ratio were computed from tensile and shear moduli obtained on tubular specimens. The variation of Poisson's ratio with plastic deformation and annealing temperature is explained in terms of the degree of anisotropy produced by changes of (a) internal stress and (b) crystal orientation.

Size effects on elasticity, yielding, and fracture of silver nanowires: In situ experiments

NASA Astrophysics Data System (ADS)

Zhu, Yong; Qin, Qingquan; Xu, Feng; Fan, Fengru; Ding, Yong; Zhang, Tim; Wiley, Benjamin J.; Wang, Zhong Lin

2012-01-01

This paper reports the quantitative measurement of a full spectrum of mechanical properties of fivefold twinned silver (Ag) nanowires (NWs), including Young's modulus, yield strength, and ultimate tensile strength. In-situ tensile testing of Ag NWs with diameters between 34 and 130 nm was carried out inside a scanning electron microscope (SEM). Young's modulus, yield strength, and ultimate tensile strength all increased as the NW diameter decreased. The maximum yield strength in our tests was found to be 2.64 GPa, which is about 50 times the bulk value and close to the theoretical value of Ag in the 110 orientation. The size effect in the yield strength is mainly due to the stiffening size effect in the Young's modulus. Yield strain scales reasonably well with the NW surface area, which reveals that yielding of Ag NWs is due to dislocation nucleation from surface sources. Pronounced strain hardening was observed for most NWs in our study. The strain hardening, which has not previously been reported for NWs, is mainly attributed to the presence of internal twin boundaries.

Strengthening Mechanisms in Thermomechanically Processed NbTi-Microalloyed Steel

NASA Astrophysics Data System (ADS)

Kostryzhev, Andrii G.; Marenych, Olexandra O.; Killmore, Chris R.; Pereloma, Elena V.

2015-08-01

The effect of deformation temperature on microstructure and mechanical properties was investigated for thermomechanically processed NbTi-microalloyed steel with ferrite-pearlite microstructure. With a decrease in the finish deformation temperature at 1348 K to 1098 K (1075 °C to 825 °C) temperature range, the ambient temperature yield stress did not vary significantly, work hardening rate decreased, ultimate tensile strength decreased, and elongation to failure increased. These variations in mechanical properties were correlated to the variations in microstructural parameters (such as ferrite grain size, solid solution concentrations, precipitate number density and dislocation density). Calculations based on the measured microstructural parameters suggested the grain refinement, solid solution strengthening, precipitation strengthening, and work hardening contributed up to 32 pct, up to 48 pct, up to 25 pct, and less than 3 pct to the yield stress, respectively. With a decrease in the finish deformation temperature, both the grain size strengthening and solid solution strengthening increased, the precipitation strengthening decreased, and the work hardening contribution did not vary significantly.

Biaxial Normal Strength Behavior in the Axial-Transverse Plane for Human Trabecular Bone—Effects of Bone Volume Fraction, Microarchitecture, and Anisotropy

PubMed Central

Sanyal, Arnav; Keaveny, Tony M.

2013-01-01

The biaxial failure behavior of the human trabecular bone, which has potential relevance both for fall and gait loading conditions, is not well understood, particularly for low-density bone, which can display considerable mechanical anisotropy. Addressing this issue, we investigated the biaxial normal strength behavior and the underlying failure mechanisms for human trabecular bone displaying a wide range of bone volume fraction (0.06–0.34) and elastic anisotropy. Micro-computer tomography (CT)-based nonlinear finite element analysis was used to simulate biaxial failure in 15 specimens (5 mm cubes), spanning the complete biaxial normal stress failure space in the axial-transverse plane. The specimens, treated as approximately transversely isotropic, were loaded in the principal material orientation. We found that the biaxial stress yield surface was well characterized by the superposition of two ellipses—one each for yield failure in the longitudinal and transverse loading directions—and the size, shape, and orientation of which depended on bone volume fraction and elastic anisotropy. However, when normalized by the uniaxial tensile and compressive strengths in the longitudinal and transverse directions, all of which depended on bone volume fraction, microarchitecture, and mechanical anisotropy, the resulting normalized biaxial strength behavior was well described by a single pair of (longitudinal and transverse) ellipses, with little interspecimen variation. Taken together, these results indicate that the role of bone volume fraction, microarchitecture, and mechanical anisotropy is mostly accounted for in determining the uniaxial strength behavior and the effect of these parameters on the axial-transverse biaxial normal strength behavior per se is minor. PMID:24121715

Welding of high chromium steels

NASA Technical Reports Server (NTRS)

Miller, W B

1928-01-01

A brief description is given of different groups of high chromium steels (rustless iron and stainless steels) according to their composition and more generally accepted names. The welding procedure for a given group will be much the same regardless of the slight variations in chemical composition which may exist within a certain group. Information is given for the tensile properties (yield point and ultimate strength) of metal sheets and welds before and after annealing on coupons one and one-half inches wide. Since welds in rustless iron containing 16 to 18 percent chromium and 7 to 12 percent nickel show the best combination of strength and ductility in the 'as welded' or annealed condition, it is considered the best alloy to use for welded construction.

Method of increasing the phase stability and the compressive yield strength of uranium-1 to 3 wt. % zirconium alloy

DOEpatents

Anderson, Robert C.

1986-01-01

A uranium-1 to 3 wt. % zirconium alloy characterized by high strength, high ductility and stable microstructure is fabricated by an improved thermal mechanical process. A homogenous ingot of the alloy which has been reduced in thickness of at least 50% in the two-step forging operation, rolled into a plate with a 75% reduction and then heated in vacuum at a temperature of about 750.degree. to 850.degree. C. and then quenched in water is subjected to further thermal-mechanical operation steps to increase the compressive yield strength approximately 30%, stabilize the microstructure, and decrease the variations in mechanical properties throughout the plate is provided. These thermal-mechanical steps are achieved by cold rolling the quenched plate to reduce the thickness thereof about 8 to 12%, aging the cold rolled plate at a first temperature of about 325.degree. to 375.degree. C. for five to six hours and then aging the plate at a higher temperature ranging from 480.degree. to 500.degree. C. for five to six hours prior to cooling the billet to ambient conditions and sizing the billet or plate into articles provides the desired increase in mechanical properties and phase stability throughout the plate.

Evaluation of mechanical properties of some glycine complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nagaraju, D.; Raja Shekar, P. V., E-mail: pvrsleo@gmail.com; Chandra, Ch. Sateesh

2014-04-24

The variation of Vickers hardness with load for (101) glycine zinc chloride (GZC), (001) glycine lithium sulphate (GLS), (001) triglycine sulphate (TGS) and (010) glycine phosphite (GPI) crystals was studied. From the cracks initiated along the corners of the indentation impression, crack lengths were measured and the fracture toughness value and brittle index number were determined. The hardness related parameters viz. yield strength and Young’s modulus were also estimated. The anisotropic nature of the crystals was studied using Knoop indentation technique.

Safety Analysis of X4 Multi-Tooled Iowa Detonator Loader

DTIC Science & Technology

1980-10-01

D atmosphere. Temperature identification number should be T5.* Personnel Injury Resulting From Machine Incident - Due to the presence of the barricade...ling factor is the yield strength of velostat . 18 the expectancy is 6 x i0-15 accidents per facility hour. Although the spoon is made of phenolic...expression becoms: I- SF (C-2) v (Cv•cp) (xs) (CV,) 2- uthere: C - coefficient of v4riation for the proess ptent’.4 CV% c"of•iclent of variation "or

High-strength bolt corrosion fatigue life model and application.

PubMed

Hui-li, Wang; Si-feng, Qin

2014-01-01

The corrosion fatigue performance of high-strength bolt was studied. Based on the fracture mechanics theory and the Gerberich-Chen formula, the high-strength bolt corrosion fracture crack model and the fatigue life model were established. The high-strength bolt crack depth and the fatigue life under corrosion environment were quantitatively analyzed. The factors affecting high-strength bolt corrosion fatigue life were discussed. The result showed that the high-strength bolt corrosion fracture biggest crack depth reduces along with the material yield strength and the applied stress increases. The material yield strength was the major factor. And the high-strength bolt corrosion fatigue life reduced along with the increase of material strength, the applied stress or stress amplitude. The stress amplitude influenced the most, and the material yield strength influenced the least. Low bolt strength and a low stress amplitude level could extend high-strength bolt corrosion fatigue life.

Mafic-crystal distributions, viscosities, and lava structures of some Hawaiian lava flows

NASA Astrophysics Data System (ADS)

Rowland, Scott K.; Walker, George P. L.

1988-09-01

The distribution patterns of mafic phenocrysts in some Hawaiian basalt flows are consistent with simple in situ gravitational settling. We use the patterns to estimate the crystal settling velocity and hence viscosity of the lava, which in turn can be correlated with surface structures. Numerical modeling generates theoretical crystal concentration profiles through lava flow units of different thicknesses for differing settling velocities. By fitting these curves to field data, crystal-settling rates through the lavas can be estimated, from which the viscosities of the flows can be determined using Stokes' Law. Lavas in which the crystal settling velocity was relatively high (on the order of 5 × 10 -4 cm/sec) show great variations in phenocryst content, both from top to bottom of the same flow unit, and from one flow unit to another. Such lava is invariably pahoehoe, flow units of which are usually less than 1 m thick. Lavas in which the crystal-settling velocity was low show a small but measurable variation in phenocryst content. These lavas are part of a progression from a rough pahoehoe to toothpaste lava to a'a. Toothpaste lava is characterized by spiny texture as well as the ability to retain surface grooves during solidification, and flow units are usually thicker than 1 m. In the thickest of Hawaiian a'a flows, those of the distal type, no systematic crystal variations are observed, and high viscosity coupled with a finite yield strength prevented crystal settling. The amount of crystal settling in pahoehoe indicates that the viscosity ranged from 600 to 6000 Pa s. The limited amount of settling in toothpaste lava indicates a viscosity greater than this value, approaching 12,000 Pa s. We infer that distal-type a'a had a higher viscosity still and also possessed a yield strength.

Microhardness Testing of Aluminum Alloy Welds

NASA Technical Reports Server (NTRS)

Bohanon, Catherine

2009-01-01

A weld is made when two pieces of metal are united or fused together using heat or pressure, and sometimes both. There are several different types of welds, each having their own unique properties and microstructure. Strength is a property normally used in deciding which kind of weld is suitable for a certain metal or joint. Depending on the weld process used and the heat required for that process, the weld and the heat-affected zone undergo microstructural changes resulting in stronger or weaker areas. The heat-affected zone (HAZ) is the region that has experienced enough heat to cause solid-state microstructural changes, but not enough to melt the material. This area is located between the parent material and the weld, with the grain structure growing as it progresses respectively. The optimal weld would have a short HAZ and a small fluctuation in strength from parent metal to weld. To determine the strength of the weld and decide whether it is suitable for the specific joint certain properties are looked at, among these are ultimate tensile strength, 0.2% offset yield strength and hardness. Ultimate tensile strength gives the maximum load the metal can stand while the offset yield strength gives the amount of stress the metal can take before it is 0.2% longer than it was originally. Both of these are good tests, but they both require breaking or deforming the sample in some way. Hardness testing, however, provides an objective evaluation of weld strengths, and also the difference or variation in strength across the weld and HAZ which is difficult to do with tensile testing. Hardness is the resistance to permanent or plastic deformation and can be taken at any desired point on the specimen. With hardness testing, it is possible to test from parent metal to weld and see the difference in strength as you progress from parent material to weld. Hardness around grain boundaries and flaws in the material will show how these affect the strength of the metal while still retaining the sample. This makes hardness testing a good test for identifying grain size and microstructure.

Low-energy modification of the γ strength function of the odd-even nucleus 115In

NASA Astrophysics Data System (ADS)

Versteegen, Maud; Denis-Petit, David; Méot, Vincent; Bonnet, Thomas; Comet, Maxime; Gobet, Franck; Hannachi, Fazia; Tarisien, Medhi; Morel, Pascal; Martini, Marco; Péru, Sophie

2016-10-01

Photoactivation yield measurements on 115In have been performed at the ELSA facility with Bremsstrahlung photon beams over a range of endpoint energies between 4.5 and 18 MeV. The measured photoexcitation yields of the Inm115 metastable state are compared with calculated yields using cross sections obtained with different models of the photon strength function. It is shown that additional photon strength with respect to the general Lorentzian model is needed at 8.1 MeV for the calculated yields to reproduce the data. The origin of this extra strength is unclear, because it is compatible with additional strength predicted in both E 1 and M 1 photon strength distributions by quasiparticle random-phase approximation calculations using the Gogny D1S force.

Length-scales of Slab-induced Asthenospheric Deformation from Geodynamic Modeling, Mantle Deformation Fabric, and Synthetic Shear Wave Splitting

NASA Astrophysics Data System (ADS)

Jadamec, M. A.; MacDougall, J.; Fischer, K. M.

2017-12-01

The viscosity structure of the Earth's interior is critically important, because it places a first order constraint on plate motion and mantle flow rates. Geodynamic models using a composite viscosity based on experimentally derived flow laws for olivine aggregates show that lateral viscosity variations emerge in the upper mantle due to the subduction dynamics. However, the length-scale of this transition is still not well understood. Two-dimensional numerical models of subduction are presented that investigate the effect of initial slab dip, maximum yield stress (slab strength), and viscosity formulation (Newtonian versus composite) on the emergent lateral viscosity variations in the upper-mantle and magnitude of slab-driven mantle flow velocity. Significant viscosity reductions occur in regions of large flow velocity gradients due to the weakening effect of the dislocation creep deformation mechanism. The dynamic reductions in asthenospheric viscosity (less than 1018 Pa s) occur within approximately 500 km from driving force of the slab, with peak flow velocities occurring in models with a lower yield stress (weaker slab) and higher stress exponent. This leads to a sharper definition of the rheological base of the lithosphere and implies lateral variability in tractions along the base of the lithosphere. As the dislocation creep mechanism also leads to mantle deformation fabric, we then examine the spatial variation in the LPO development in the asthenosphere and calculate synthetic shear wave splitting. The models show that olivine LPO fabric in the asthenosphere generally increases in alignment strength with increased proximity to the slab, but can be transient and spatially variable on small length scales. The vertical flow fields surrounding the slab tip can produce shear-wave splitting variations with back-azimuth that deviate from the predictions of uniform trench-normal anisotropy, a result that bears on the interpretation of complexity in shear-wave splitting observed in real subduction zones.

Anisotropic nature of radially strained metal tubes

NASA Astrophysics Data System (ADS)

Strickland, Julie N.

Metal pipes are sometimes swaged by a metal cone to enlarge them, which increases the strain in the material. The amount of strain is important because it affects the burst and collapse strength. Burst strength is the amount of internal pressure that a pipe can withstand before failure, while collapse strength is the amount of external pressure that a pipe can withstand before failure. If the burst or collapse strengths are exceeded, the pipe may fracture, causing critical failure. Such an event could cost the owners and their customers millions of dollars in clean up, repair, and lost time, in addition to the potential environmental damage. Therefore, a reliable way of estimating the burst and collapse strength of strained pipe is desired and valuable. The sponsor currently rates strained pipes using the properties of raw steel, because those properties are easily measured (for example, yield strength). In the past, the engineers assumed that the metal would be work-hardened when swaged, so that yield strength would increase. However, swaging introduces anisotropic strain, which may decrease the yield strength. This study measured the yield strength of strained material in the transverse and axial direction and compared them to raw material, to determine the amount of anisotropy. This information will be used to more accurately determine burst and collapse ratings for strained pipes. More accurate ratings mean safer products, which will minimize risk for the sponsor's customers. Since the strained metal has a higher yield strength than the raw material, using the raw yield strength to calculate burst and collapse ratings is a conservative method. The metal has even higher yield strength after strain aging, which indicates that the stresses are relieved. Even with the 12% anisotropy in the strained and 9% anisotropy in the strain aged specimens, the raw yield strengths are lower and therefore more conservative. I recommend that the sponsor continue using the raw yield strength to calculate these ratings. I set out to characterize the anisotropic nature of swaged metal. As expected, the tensile tests showed a difference between the axial and transverse tensile strength. The correlation was 12% difference in yield strength in the axial and transverse directions for strained material and 9% in strained and aged material. This means that the strength of the metal in the hoop (transverse) direction is approximately 10% stronger than in the axial direction, because the metal was work hardened during the swaging process. Therefore, the metal is more likely to fail in axial tension than in burst or collapse. I presented the findings from the microstructure examination, standard tensile tests, and SEM data. All of this data supported the findings of the mini-tensile tests. This information will help engineers set burst and collapse ratings and allow material scientists to predict the anisotropic characteristics of swaged steel tubes.

Effects of crystallographic and geometric orientation on ion beam sputtering of gold nanorods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hinks, J. A.; Hibberd, F.; Hattar, K.

Nanostructures may be exposed to irradiation during their manufacture, their engineering and whilst in-service. The consequences of such bombardment can be vastly different from those seen in the bulk. In this paper, we combine transmission electron microscopy with in situ ion irradiation with complementary computer modelling techniques to explore the physics governing the effects of 1.7 MeV Au ions on gold nanorods. Phenomena surrounding the sputtering and associated morphological changes caused by the ion irradiation have been explored. In both the experiments and the simulations, large variations in the sputter yields from individual nanorods were observed. These sputter yields havemore » been shown to correlate with the strength of channelling directions close to the direction in which the ion beam was incident. Finally, craters decorated by ejecta blankets were found to form due to cluster emission thus explaining the high sputter yields.« less

Effects of crystallographic and geometric orientation on ion beam sputtering of gold nanorods

DOE PAGES

Hinks, J. A.; Hibberd, F.; Hattar, K.; ...

2018-01-11

Nanostructures may be exposed to irradiation during their manufacture, their engineering and whilst in-service. The consequences of such bombardment can be vastly different from those seen in the bulk. In this paper, we combine transmission electron microscopy with in situ ion irradiation with complementary computer modelling techniques to explore the physics governing the effects of 1.7 MeV Au ions on gold nanorods. Phenomena surrounding the sputtering and associated morphological changes caused by the ion irradiation have been explored. In both the experiments and the simulations, large variations in the sputter yields from individual nanorods were observed. These sputter yields havemore » been shown to correlate with the strength of channelling directions close to the direction in which the ion beam was incident. Finally, craters decorated by ejecta blankets were found to form due to cluster emission thus explaining the high sputter yields.« less

Kinetics model of bainitic transformation with stress

NASA Astrophysics Data System (ADS)

Zhou, Mingxing; Xu, Guang; Hu, Haijiang; Yuan, Qing; Tian, Junyu

2018-01-01

Thermal simulations were conducted on a Gleeble 3800 simulator. The main purpose is to investigate the effects of stress on the kinetics of bainitic transformation in a Fe-C-Mn-Si advanced high strength bainitic steel. Previous studies on modeling the kinetics of stress affected bainitic transformation only considered the stress below the yield strength of prior austenite. In the present study, the stress above the yield strength of prior austenite is taken into account. A new kinetics model of bainitic transformation dependent on the stress (including the stresses below and above the yield strength of prior austenite) and the transformation temperature is proposed. The new model presents a good agreement with experimental results. In addition, it is found that the acceleration degree of stress on bainitic transformation increases with the stress whether its magnitude is below or above the yield strength of austenite, but the increasing rate gradually slows down when the stress is above the yield strength of austenite.

Yield strength measurement of shock-loaded metal by flyer-impact perturbation method

NASA Astrophysics Data System (ADS)

Ma, Xiaojuan; Shi, Zhan

2018-06-01

Yield strength is one of the most important physical properties of a solid material, especially far from its melting line. The flyer-impact perturbation method measures material yield strength on the basis of correlation between the yield strength under shock compression and the damping of oscillatory perturbations in the shape of a shock front passing through the material. We used flyer-impact experiments on targets with machined grooves on the impact surface of shock 6061-T6 aluminum to between 32 and 61 GPa and recorded the evolution of the shock front perturbation amplitude in the sample with electric pins. Simulations using the elastic-plastic model can be matched to the experiments, explaining well the form of the perturbation decay and constraining the yield strength of 6061-T6 aluminum to be 1.31-1.75 GPa. These results are in agreement with values obtained from reshock and release wave profiles. We conclude that the flyer-impact perturbation method is indeed a new means to measure material strength.

Correlation of cervical endplate strength with CT measured subchondral bone density

PubMed Central

Ordway, Nathaniel R.; Lu, Yen-Mou; Zhang, Xingkai; Cheng, Chin-Chang; Fang, Huang

2007-01-01

Cervical interbody device subsidence can result in screw breakage, plate dislodgement, and/or kyphosis. Preoperative bone density measurement may be helpful in predicting the complications associated with anterior cervical surgery. This is especially important when a motion preserving device is implanted given the detrimental effect of subsidence on the postoperative segmental motion following disc replacement. To evaluate the structural properties of the cervical endplate and examine the correlation with CT measured trabecular bone density. Eight fresh human cadaver cervical spines (C2–T1) were CT scanned and the average trabecular bone densities of the vertebral bodies (C3–C7) were measured. Each endplate surface was biomechanically tested for regional yield load and stiffness using an indentation test method. Overall average density of the cervical vertebral body trabecular bone was 270 ± 74 mg/cm3. There was no significant difference between levels. The yield load and stiffness from the indentation test of the endplate averaged 139 ± 99 N and 156 ± 52 N/mm across all cervical levels, endplate surfaces, and regional locations. The posterior aspect of the endplate had significantly higher yield load and stiffness in comparison to the anterior aspect and the lateral aspect had significantly higher yield load in comparison to the midline aspect. There was a significant correlation between the average yield load and stiffness of the cervical endplate and the trabecular bone density on regression analysis. Although there are significant regional variations in the endplate structural properties, the average of the endplate yield loads and stiffnesses correlated with the trabecular bone density. Given the morbidity associated with subsidence of interbody devices, a reliable and predictive method of measuring endplate strength in the cervical spine is required. Bone density measures may be used preoperatively to assist in the prediction of the strength of the vertebral endplate. A threshold density measure has yet to be established where the probability of endplate fracture outweighs the benefit of anterior cervical procedure. PMID:17712574

Mechanical Properties of Elastomeric Impression Materials: An In Vitro Comparison

PubMed Central

De Angelis, Francesco; Caputi, Sergio; D'Amario, Maurizio; D'Arcangelo, Camillo

2015-01-01

Purpose. Although new elastomeric impression materials have been introduced into the market, there are still insufficient data about their mechanical features. The tensile properties of 17 hydrophilic impression materials with different consistencies were compared. Materials and Methods. 12 vinylpolysiloxane, 2 polyether, and 3 hybrid vinylpolyether silicone-based impression materials were tested. For each material, 10 dumbbell-shaped specimens were fabricated (n = 10), according to the ISO 37:2005 specifications, and loaded in tension until failure. Mean values for tensile strength, yield strength, strain at break, and strain at yield point were calculated. Data were statistically analyzed using one-way ANOVA and Tukey's tests (α = 0.05). Results. Vinylpolysiloxanes consistently showed higher tensile strength values than polyethers. Heavy-body materials showed higher tensile strength than the light bodies from the same manufacturer. Among the light bodies, the highest yield strength was achieved by the hybrid vinylpolyether silicone (2.70 MPa). Polyethers showed the lowest tensile (1.44 MPa) and yield (0.94 MPa) strengths, regardless of the viscosity. Conclusion. The choice of an impression material should be based on the specific physical behavior of the elastomer. The light-body vinylpolyether silicone showed high tensile strength, yield strength, and adequate strain at yield/brake; those features might help to reduce tearing phenomena in the thin interproximal and crevicular areas. PMID:26693227

Array of Hall Effect Sensors for Linear Positioning of a Magnet Independently of Its Strength Variation. A Case Study: Monitoring Milk Yield during Milking in Goats

PubMed Central

García-Diego, Fernando-Juan; Sánchez-Quinche, Angel; Merello, Paloma; Beltrán, Pedro; Peris, Cristófol

2013-01-01

In this study we propose an electronic system for linear positioning of a magnet independent of its modulus, which could vary because of aging, different fabrication process, etc. The system comprises a linear array of 24 Hall Effect sensors of proportional response. The data from all sensors are subject to a pretreatment (normalization) by row (position) making them independent on the temporary variation of its magnetic field strength. We analyze the particular case of the individual flow in milking of goats. The multiple regression analysis allowed us to calibrate the electronic system with a percentage of explanation R2 = 99.96%. In our case, the uncertainty in the linear position of the magnet is 0.51 mm that represents 0.019 L of goat milk. The test in farm compared the results obtained by direct reading of the volume with those obtained by the proposed electronic calibrated system, achieving a percentage of explanation of 99.05%. PMID:23793020

Nucleotide diversity, natural variation, and evolution of Flexible culm-1 and Strong culm-2 lodging resistance genes in rice.

PubMed

Rashid, Muhammad Abdul Rehman; Zhao, Yan; Zhang, Hongliang; Li, Jinjie; Li, Zichao

2016-07-01

Lodging resistance is one of the vital traits in yield improvement and sustainability. Culm wall thickness, diameter, and strength are different traits that can govern the lodging resistance in rice. The genes SCM2 and FC1 have been isolated for culm thickness, strength, and flexibility, but their functional nucleotide variations were still unknown. We used a 13× deep sequence of 795 diverse genotypes to present the functional variation and SNP diversity in SCM2 and FC1. The major functional variant for the SCM2 gene was at position 27480181 and for the FC1 gene at position 31072992. Haplotype analysis of both genes provided their various allelic differences among haplotypes. SCM2 alleles further presented the evolution of Oryza sativa L. subsp. indica and subsp. japonica genomes from common parent in different geographical zones, while the haplotypes of FC1 suggested their evolution from different strains of the common parent Oryza rufipogon. SCM2 showed purifying selection and functional associations with rare alleles, while FC1 displayed balanced selection favored by multiple heterozygous alleles. Genotypes with an allelic combination of SCM2-3 and FC1-2 in japonica background exhibited striking resistance against lodging, which can be used in further breeding programs.

Aggregate breakdown of nanoparticulate titania

NASA Astrophysics Data System (ADS)

Venugopal, Navin

Six nanosized titanium dioxide powders synthesized from a sulfate process were investigated. The targeted end-use of this powder was for a de-NOx catalyst honeycomb monolith. Alteration of synthesis parameters had resulted principally in differences in soluble ion level and specific surface area of the powders. The goal of this investigation was to understand the role of synthesis parameters in the aggregation behavior of these powders. Investigation via scanning electron microscopy of the powders revealed three different aggregation iterations at specific length scales. Secondary and higher order aggregate strength was investigated via oscillatory stress rheometry as a means of simulating shear conditions encountered during extrusion. G' and G'' were measured as a function of the applied oscillatory stress. Oscillatory rheometry indicated a strong variation as a function of the sulfate level of the particles in the viscoelastic yield strengths. Powder yield stresses ranged from 3.0 Pa to 24.0 Pa of oscillatory stress. Compaction curves to 750 MPa found strong similarities in extrapolated yield point of stage I and II compaction for each of the powders (at approximately 500 MPa) suggesting that the variation in sulfate was greatest above the primary aggregate level. Scanning electron microscopy of samples at different states of shear in oscillatory rheometry confirmed the variation in the linear elastic region and the viscous flow regime. A technique of this investigation was to approach aggregation via a novel perspective: aggregates are distinguished as being loose open structures that are highly disordered and stochastic in nature. The methodology used was to investigate the shear stresses required to rupture the various aggregation stages encountered and investigate the attempt to realign the now free-flowing constituents comprising the aggregate into a denser configuration. Mercury porosimetry was utilized to measure the pore size of the compact resulting from compaction via dry pressing and tape casting secondary scale aggregates. Mercury porosimetry of tapes cast at 0.85 and 9.09 cm/sec exhibited pore sizes ranging from 200-500 nm suggesting packing of intact micron-sized primary aggregates. Porosimetry further showed that this peak was absent in pressed pellets corroborating arguments of ruptured primary aggregates during compaction to 750 MPa.

Column strength of magnesium alloy AM-57S

NASA Technical Reports Server (NTRS)

Holt, M

1942-01-01

Tests were made to determine the column strength of extruded magnesium alloy AM-57S. Column specimens were tested with round ends and with flat ends. It was found that the compressive properties should be used in computations for column strengths rather than the tensile properties because the compressive yield strength was approximately one-half the tensile yield strength. A formula for the column strength of magnesium alloy AM-57S is given.

3D Rheological Modeling of NW Intraplate Europe, Deciphering Spatial Integrated strength patterns, Mechanical Strong Layering and EET

NASA Astrophysics Data System (ADS)

Beekman, F.; Hardebol, N.; Cloetingh, S.; Tesauro, M.

2006-12-01

Better understanding of 3D rheological heterogeneity of the European Lithosphere provide the key to tie the recorded intraplate deformation pattern to stress fields transmitted into plate interior from plate boundary forces. The first order strain patterns result from stresses transmitted through the European lithosphere that is marked by a patchwork of high strength variability from inherited structural and compositional heterogeneities and upper mantle thermal perturbations. As the lithospheric rheology depends primarily on its spatial structure, composition and thermal estate, the 3D strength model for the European lithosphere relies on a 3D compositional model that yields the compositional heterogeneities and an iteratively calculated thermal cube using Fouriers law for heat conduction. The accurate appraisal of spatial strength variability results from proper mapping and integration of the geophysical compositional and thermal input parameters. Therefore, much attention has been paid to a proper description of first order structural and tectonic features that facilitate compilation of the compositional and thermal input models. As such, the 3D strength model reflects the thermo-mechanical structure inherited from the Europeans polyphase deformation history. Major 3D spatial mechanical strength variability has been revealed. The East-European and Fennoscandian Craton to the NE exhibit high strength (30-50 1012 N/m) from low mantle temperatures and surface heatflow of 35-60 mW/m2 while central and western Europe reflect a polyphase Phanerozoic thermo- tectonic history. Here, regions with high rigidity are formed primarily by patches of thermally stabilized Variscan Massifs (e.g. Rhenish, Armorican, Bohemian, and Iberian Massif) with low heatflow and lithospheric thickness values (50-65 mW/m2; 110-150 km) yielding strengths of ~15-25 1012 N/m. In contrast, major axis of weakened lithosphere coincides with Cenozoic Rift System (e.g. Upper and Lower Rhine Grabens, Pannonian Basin and Massif Central) attributed to the presence of tomographically imaged plumes. This study has elucidated the memory of the present-days Europeans lithosphere induced by compositional and thermal heterogeneities. The resulting lateral strength variations has a clear signature of the pst lithospheres polyphase deformation and also entails active tectonics, tectonically induced topography and surface processes.

Influence of Temperature and Grain Size on Austenite Stability in Medium Manganese Steels

NASA Astrophysics Data System (ADS)

Zhang, Yulong; Wang, Li; Findley, Kip O.; Speer, John G.

2017-05-01

With an aim to elucidate the influence of temperature and grain size on austenite stability, a commercial cold-rolled 7Mn steel was annealed at 893 K (620 °C) for times varying between 3 minutes and 96 hours to develop different grain sizes. The austenite fraction after 3 minutes was 34.7 vol pct, and at longer times was around 40 pct. An elongated microstructure was retained after shorter annealing times while other conditions exhibited equiaxed ferrite and austenite grains. All conditions exhibit similar temperature dependence of mechanical properties. With increasing test temperature, the yield and tensile strength decrease gradually, while the uniform and total elongation increase, followed by an abrupt drop in strength and ductility at 393 K (120 °C). The Olson-Cohen model was applied to fit the transformed austenite fractions for strained tensile samples, measured by means of XRD. The fit results indicate that the parameters α and β decrease with increasing test temperature, consistent with increased austenite stability. The 7Mn steels exhibit a distinct temperature dependence of the work hardening rate. Optimized austenite stability provides continuous work hardening in the temperature range of 298 K to 353 K (25 °C to 80 °C). The yield and tensile strengths have a strong dependence on grain size, although grain size variations have less effect on uniform and total elongation.

Microstructural, mechanical and tribological investigation of 30CrMnSiNi2A ultra-high strength steel under various tempering temperatures

NASA Astrophysics Data System (ADS)

Arslan Hafeez, Muhammad; Farooq, Ameeq

2018-01-01

The aim of the research was to investigate the variation in microstructural, mechanical and tribological characteristics of 30CrMnSiNi2A ultra-high strength steel as a function of tempering temperatures. Steel was quenched at 880 °C and tempered at five different tempering temperatures ranging from 250 °C to 650 °C. Optical microscopy and pin on disc tribometer was used to evaluate the microstructural and wear properties. Results show that characteristics of 30CrMnSiNi2A are highly sensitive to tempering temperatures. Lathe and plate shaped martensite obtained by quenching transform first into ε-carbide, second cementite, third coarsened and spheroidized cementite and finally into recovered ferrite and austenite. Hardness, tensile and yield strengths decreased while elongation increased with tempering temperatures. On the other hand, wear rate first markedly decreased and then increased. Optimum amalgamation of characteristics was achieved at 350 °C.

Constraints on the off-shell Higgs boson signal strength in the high-mass ZZ and WW final states with the ATLAS detector

NASA Astrophysics Data System (ADS)

Aad, G.; Abbott, B.; Abdallah, J.; Abdinov, O.; Aben, R.; Abolins, M.; AbouZeid, O. S.; Abramowicz, H.; Abreu, H.; Abreu, R.; Abulaiti, Y.; Acharya, B. S.; Adamczyk, L.; Adams, D. L.; Adelman, J.; Adomeit, S.; Adye, T.; Affolder, A. A.; Agatonovic-Jovin, T.; Aguilar-Saavedra, J. A.; Agustoni, M.; Ahlen, S. P.; Ahmadov, F.; Aielli, G.; Akerstedt, H.; Åkesson, T. P. A.; Akimoto, G.; Akimov, A. V.; Alberghi, G. L.; Albert, J.; Albrand, S.; Alconada Verzini, M. J.; Aleksa, M.; Aleksandrov, I. N.; Alexa, C.; Alexander, G.; Alexopoulos, T.; Alhroob, M.; Alimonti, G.; Alio, L.; Alison, J.; Alkire, S. P.; Allbrooke, B. M. M.; Allport, P. P.; Aloisio, A.; Alonso, A.; Alonso, F.; Alpigiani, C.; Altheimer, A.; Alvarez Gonzalez, B.; Piqueras, D. Álvarez; Alviggi, M. G.; Amako, K.; Amaral Coutinho, Y.; Amelung, C.; Amidei, D.; Amor Dos Santos, S. P.; Amorim, A.; Amoroso, S.; Amram, N.; Amundsen, G.; Anastopoulos, C.; Ancu, L. S.; Andari, N.; Andeen, T.; Anders, C. F.; Anders, G.; Anderson, K. J.; Andreazza, A.; Andrei, V.; Angelidakis, S.; Angelozzi, I.; Anger, P.; Angerami, A.; Anghinolfi, F.; Anisenkov, A. V.; Anjos, N.; Annovi, A.; Antonelli, M.; Antonov, A.; Antos, J.; Anulli, F.; Aoki, M.; Aperio Bella, L.; Arabidze, G.; Arai, Y.; Araque, J. P.; Arce, A. T. H.; Arduh, F. A.; Arguin, J.-F.; Argyropoulos, S.; Arik, M.; Armbruster, A. J.; Arnaez, O.; Arnal, V.; Arnold, H.; Arratia, M.; Arslan, O.; Artamonov, A.; Artoni, G.; Asai, S.; Asbah, N.; Ashkenazi, A.; Åsman, B.; Asquith, L.; Assamagan, K.; Astalos, R.; Atkinson, M.; Atlay, N. B.; Auerbach, B.; Augsten, K.; Aurousseau, M.; Avolio, G.; Axen, B.; Ayoub, M. K.; Azuelos, G.; Baak, M. A.; Baas, A. E.; Bacci, C.; Bachacou, H.; Bachas, K.; Backes, M.; Backhaus, M.; Badescu, E.; Bagiacchi, P.; Bagnaia, P.; Bai, Y.; Bain, T.; Baines, J. T.; Baker, O. K.; Balek, P.; Balestri, T.; Balli, F.; Banas, E.; Banerjee, Sw.; Bannoura, A. A. E.; Bansil, H. S.; Barak, L.; Baranov, S. P.; Barberio, E. 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N.; Smirnova, O.; Smith, M. N. K.; Smizanska, M.; Smolek, K.; Snesarev, A. A.; Snidero, G.; Snyder, S.; Sobie, R.; Socher, F.; Soffer, A.; Soh, D. A.; Solans, C. A.; Solar, M.; Solc, J.; Soldatov, E. Yu.; Soldevila, U.; Solodkov, A. A.; Soloshenko, A.; Solovyanov, O. V.; Solovyev, V.; Sommer, P.; Song, H. Y.; Soni, N.; Sood, A.; Sopczak, A.; Sopko, B.; Sopko, V.; Sorin, V.; Sosa, D.; Sosebee, M.; Sotiropoulou, C. L.; Soualah, R.; Soueid, P.; Soukharev, A. M.; South, D.; Spagnolo, S.; Spalla, M.; Spanò, F.; Spearman, W. R.; Spettel, F.; Spighi, R.; Spigo, G.; Spiller, L. A.; Spousta, M.; Spreitzer, T.; Denis, R. D. St.; Staerz, S.; Stahlman, J.; Stamen, R.; Stamm, S.; Stanecka, E.; Stanescu, C.; Stanescu-Bellu, M.; Stanitzki, M. M.; Stapnes, S.; Starchenko, E. A.; Stark, J.; Staroba, P.; Starovoitov, P.; Staszewski, R.; Stavina, P.; Steinberg, P.; Stelzer, B.; Stelzer, H. J.; Stelzer-Chilton, O.; Stenzel, H.; Stern, S.; Stewart, G. A.; Stillings, J. A.; Stockton, M. C.; Stoebe, M.; Stoicea, G.; Stolte, P.; Stonjek, S.; Stradling, A. R.; Straessner, A.; Stramaglia, M. E.; Strandberg, J.; Strandberg, S.; Strandlie, A.; Strauss, E.; Strauss, M.; Strizenec, P.; Ströhmer, R.; Strom, D. M.; Stroynowski, R.; Strubig, A.; Stucci, S. A.; Stugu, B.; Styles, N. A.; Su, D.; Su, J.; Subramaniam, R.; Succurro, A.; Sugaya, Y.; Suhr, C.; Suk, M.; Sulin, V. V.; Sultansoy, S.; Sumida, T.; Sun, S.; Sun, X.; Sundermann, J. E.; Suruliz, K.; Susinno, G.; Sutton, M. R.; Suzuki, S.; Suzuki, Y.; Svatos, M.; Swedish, S.; Swiatlowski, M.; Sykora, I.; Sykora, T.; Ta, D.; Taccini, C.; Tackmann, K.; Taenzer, J.; Taffard, A.; Tafirout, R.; Taiblum, N.; Takai, H.; Takashima, R.; Takeda, H.; Takeshita, T.; Takubo, Y.; Talby, M.; Talyshev, A. A.; Tam, J. Y. C.; Tan, K. G.; Tanaka, J.; Tanaka, R.; Tanaka, S.; Tanaka, S.; Tannenwald, B. B.; Tannoury, N.; Tapprogge, S.; Tarem, S.; Tarrade, F.; Tartarelli, G. F.; Tas, P.; Tasevsky, M.; Tashiro, T.; Tassi, E.; Tavares Delgado, A.; Tayalati, Y.; Taylor, F. E.; Taylor, G. N.; Taylor, W.; Teischinger, F. A.; Teixeira Dias Castanheira, M.; Teixeira-Dias, P.; Temming, K. K.; Ten Kate, H.; Teng, P. K.; Teoh, J. J.; Tepel, F.; Terada, S.; Terashi, K.; Terron, J.; Terzo, S.; Testa, M.; Teuscher, R. J.; Therhaag, J.; Theveneaux-Pelzer, T.; Thomas, J. P.; Thomas-Wilsker, J.; Thompson, E. N.; Thompson, P. D.; Thompson, R. J.; Thompson, A. S.; Thomsen, L. A.; Thomson, E.; Thomson, M.; Thun, R. P.; Tibbetts, M. J.; Torres, R. E. Ticse; Tikhomirov, V. O.; Tikhonov, Yu. A.; Timoshenko, S.; Tiouchichine, E.; Tipton, P.; Tisserant, S.; Todorov, T.; Todorova-Nova, S.; Tojo, J.; Tokár, S.; Tokushuku, K.; Tollefson, K.; Tolley, E.; Tomlinson, L.; Tomoto, M.; Tompkins, L.; Toms, K.; Torrence, E.; Torres, H.; Torró Pastor, E.; Toth, J.; Touchard, F.; Tovey, D. R.; Trefzger, T.; Tremblet, L.; Tricoli, A.; Trigger, I. M.; Trincaz-Duvoid, S.; Tripiana, M. F.; Trischuk, W.; Trocmé, B.; Troncon, C.; Trottier-McDonald, M.; Trovatelli, M.; True, P.; Trzebinski, M.; Trzupek, A.; Tsarouchas, C.; Tseng, J. C.-L.; Tsiareshka, P. V.; Tsionou, D.; Tsipolitis, G.; Tsirintanis, N.; Tsiskaridze, S.; Tsiskaridze, V.; Tskhadadze, E. G.; Tsukerman, I. I.; Tsulaia, V.; Tsuno, S.; Tsybychev, D.; Tudorache, A.; Tudorache, V.; Tuna, A. N.; Tupputi, S. A.; Turchikhin, S.; Turecek, D.; Turra, R.; Turvey, A. J.; Tuts, P. M.; Tykhonov, A.; Tylmad, M.; Tyndel, M.; Ueda, I.; Ueno, R.; Ughetto, M.; Ugland, M.; Uhlenbrock, M.; Ukegawa, F.; Unal, G.; Undrus, A.; Unel, G.; Ungaro, F. C.; Unno, Y.; Unverdorben, C.; Urban, J.; Urquijo, P.; Urrejola, P.; Usai, G.; Usanova, A.; Vacavant, L.; Vacek, V.; Vachon, B.; Valderanis, C.; Valencic, N.; Valentinetti, S.; Valero, A.; Valery, L.; Valkar, S.; Valladolid Gallego, E.; Vallecorsa, S.; Valls Ferrer, J. A.; Van Den Wollenberg, W.; Van Der Deijl, P. C.; van der Geer, R.; van der Graaf, H.; Van Der Leeuw, R.; van Eldik, N.; van Gemmeren, P.; Van Nieuwkoop, J.; van Vulpen, I.; van Woerden, M. C.; Vanadia, M.; Vandelli, W.; Vanguri, R.; Vaniachine, A.; Vannucci, F.; Vardanyan, G.; Vari, R.; Varnes, E. W.; Varol, T.; Varouchas, D.; Vartapetian, A.; Varvell, K. E.; Vazeille, F.; Vazquez Schroeder, T.; Veatch, J.; Veloso, F.; Velz, T.; Veneziano, S.; Ventura, A.; Ventura, D.; Venturi, M.; Venturi, N.; Venturini, A.; Vercesi, V.; Verducci, M.; Verkerke, W.; Vermeulen, J. C.; Vest, A.; Vetterli, M. C.; Viazlo, O.; Vichou, I.; Vickey, T.; Vickey Boeriu, O. E.; Viehhauser, G. H. A.; Viel, S.; Vigne, R.; Villa, M.; Villaplana Perez, M.; Vilucchi, E.; Vincter, M. G.; Vinogradov, V. B.; Vivarelli, I.; Vives Vaque, F.; Vlachos, S.; Vladoiu, D.; Vlasak, M.; Vogel, M.; Vokac, P.; Volpi, G.; Volpi, M.; von der Schmitt, H.; von Radziewski, H.; von Toerne, E.; Vorobel, V.; Vorobev, K.; Vos, M.; Voss, R.; Vossebeld, J. H.; Vranjes, N.; Vranjes Milosavljevic, M.; Vrba, V.; Vreeswijk, M.; Vuillermet, R.; Vukotic, I.; Vykydal, Z.; Wagner, P.; Wagner, W.; Wahlberg, H.; Wahrmund, S.; Wakabayashi, J.; Walder, J.; Walker, R.; Walkowiak, W.; Wang, C.; Wang, F.; Wang, H.; Wang, H.; Wang, J.; Wang, J.; Wang, K.; Wang, R.; Wang, S. M.; Wang, T.; Wang, X.; Wanotayaroj, C.; Warburton, A.; Ward, C. P.; Wardrope, D. R.; Warsinsky, M.; Washbrook, A.; Wasicki, C.; Watkins, P. M.; Watson, A. T.; Watson, I. J.; Watson, M. F.; Watts, G.; Watts, S.; Waugh, B. M.; Webb, S.; Weber, M. S.; Weber, S. W.; Webster, J. S.; Weidberg, A. R.; Weinert, B.; Weingarten, J.; Weiser, C.; Weits, H.; Wells, P. S.; Wenaus, T.; Wengler, T.; Wenig, S.; Wermes, N.; Werner, M.; Werner, P.; Wessels, M.; Wetter, J.; Whalen, K.; Wharton, A. M.; White, A.; White, M. J.; White, R.; White, S.; Whiteson, D.; Wickens, F. J.; Wiedenmann, W.; Wielers, M.; Wienemann, P.; Wiglesworth, C.; Wiik-Fuchs, L. A. M.; Wildauer, A.; Wilkens, H. G.; Williams, H. H.; Williams, S.; Willis, C.; Willocq, S.; Wilson, A.; Wilson, J. A.; Wingerter-Seez, I.; Winklmeier, F.; Winter, B. T.; Wittgen, M.; Wittkowski, J.; Wollstadt, S. J.; Wolter, M. W.; Wolters, H.; Wosiek, B. K.; Wotschack, J.; Woudstra, M. J.; Wozniak, K. W.; Wu, M.; Wu, M.; Wu, S. L.; Wu, X.; Wu, Y.; Wyatt, T. R.; Wynne, B. M.; Xella, S.; Xu, D.; Xu, L.; Yabsley, B.; Yacoob, S.; Yakabe, R.; Yamada, M.; Yamaguchi, Y.; Yamamoto, A.; Yamamoto, S.; Yamanaka, T.; Yamauchi, K.; Yamazaki, Y.; Yan, Z.; Yang, H.; Yang, H.; Yang, Y.; Yao, L.; Yao, W.-M.; Yasu, Y.; Yatsenko, E.; Yau Wong, K. H.; Ye, J.; Ye, S.; Yeletskikh, I.; Yen, A. L.; Yildirim, E.; Yorita, K.; Yoshida, R.; Yoshihara, K.; Young, C.; Young, C. J. S.; Youssef, S.; Yu, D. R.; Yu, J.; Yu, J. M.; Yu, J.; Yuan, L.; Yurkewicz, A.; Yusuff, I.; Zabinski, B.; Zaidan, R.; Zaitsev, A. M.; Zalieckas, J.; Zaman, A.; Zambito, S.; Zanello, L.; Zanzi, D.; Zeitnitz, C.; Zeman, M.; Zemla, A.; Zengel, K.; Zenin, O.; Ženiš, T.; Zerwas, D.; Zhang, D.; Zhang, F.; Zhang, J.; Zhang, L.; Zhang, R.; Zhang, X.; Zhang, Z.; Zhao, X.; Zhao, Y.; Zhao, Z.; Zhemchugov, A.; Zhong, J.; Zhou, B.; Zhou, C.; Zhou, L.; Zhou, L.; Zhou, N.; Zhu, C. G.; Zhu, H.; Zhu, J.; Zhu, Y.; Zhuang, X.; Zhukov, K.; Zibell, A.; Zieminska, D.; Zimine, N. I.; Zimmermann, C.; Zimmermann, R.; Zimmermann, S.; Zinonos, Z.; Zinser, M.; Ziolkowski, M.; Živković, L.; Zobernig, G.; Zoccoli, A.; zur Nedden, M.; Zurzolo, G.; Zwalinski, L.

2015-07-01

Measurements of the ZZ and WW final states in the mass range above the and thresholds provide a unique opportunity to measure the off-shell coupling strength of the Higgs boson. This paper presents constraints on the off-shell Higgs boson event yields normalised to the Standard Model prediction (signal strength) in the , and final states. The result is based on pp collision data collected by the ATLAS experiment at the LHC, corresponding to an integrated luminosity of 20.3 fb at a collision energy of TeV. Using the method, the observed 95 confidence level (CL) upper limit on the off-shell signal strength is in the range 5.1-8.6, with an expected range of 6.7-11.0. In each case the range is determined by varying the unknown and background K-factor from higher-order quantum chromodynamics corrections between half and twice the value of the known signal K-factor. Assuming the relevant Higgs boson couplings are independent of the energy scale of the Higgs boson production, a combination with the on-shell measurements yields an observed (expected) 95 CL upper limit on in the range 4.5-7.5 (6.5-11.2) using the same variations of the background K-factor. Assuming that the unknown background K-factor is equal to the signal K-factor, this translates into an observed (expected) 95 CL upper limit on the Higgs boson total width of 22.7 (33.0) MeV.

Relationship between compatibilizer and yield strength of PLA/PP Blend

NASA Astrophysics Data System (ADS)

Jariyakulsith, Pattanun; Puajindanetr, Somchai

2018-01-01

The aim of this research is to study the relationship between compatibilizer and yield strength of polylactic acid (PLA) and polypropylene (PP) blend. The PLA is blended with PP (PLA/PP) at the ratios of 70/30, 50/50 and 30/70. In addition, (1) polypropylene grafted maleic anhydride (PP-g-MAH) as a compatibilizer at 0.3 and 0.7 part per hundred of PLA/PP resin (phr) and (2) dicumyl peroxide (DCP) being an initiator at 0.03 and 0.07 phr are added in each composition. Yield strength is characterized to study the interaction between compatibilizer, initiator and yield strength by using experimental design of multilevel full factorial. The results show that (1) the yield strength of PLA/PP blend are increased after addition of compatibilizer. Because the adding of PP-g-MAH and DCP resulted in improving compatibility between PLA and PP. (2) there are interaction between PP-g-MAH and DCP that have affected the final properties of PLA/PP blend. The highest yield strength of 27.68 MPa is provided at the ratio of 70/30 blend by using the 0.3 phr of PP-g-MAH and 0.03 phr of DCP. Linear regression model is fitted and follow the assumptions of normal distribution.

Brazilian Soybean Yields and Yield Gaps Vary with Farm Size

NASA Astrophysics Data System (ADS)

Jeffries, G. R.; Cohn, A.; Griffin, T. S.; Bragança, A.

2017-12-01

Understanding the farm size-specific characteristics of crop yields and yield gaps may help to improve yields by enabling better targeting of technical assistance and agricultural development programs. Linking remote sensing-based yield estimates with property boundaries provides a novel view of the relationship between farm size and yield structure (yield magnitude, gaps, and stability over time). A growing literature documents variations in yield gaps, but largely ignores the role of farm size as a factor shaping yield structure. Research on the inverse farm size-productivity relationship (IR) theory - that small farms are more productive than large ones all else equal - has documented that yield magnitude may vary by farm size, but has not considered other yield structure characteristics. We examined farm size - yield structure relationships for soybeans in Brazil for years 2001-2015. Using out-of-sample soybean yield predictions from a statistical model, we documented 1) gaps between the 95th percentile of attained yields and mean yields within counties and individual fields, and 2) yield stability defined as the standard deviation of time-detrended yields at given locations. We found a direct relationship between soy yields and farm size at the national level, while the strength and the sign of the relationship varied by region. Soybean yield gaps were found to be inversely related to farm size metrics, even when yields were only compared to farms of similar size. The relationship between farm size and yield stability was nonlinear, with mid-sized farms having the most stable yields. The work suggests that farm size is an important factor in understanding yield structure and that opportunities for improving soy yields in Brazil are greatest among smaller farms.

Fast torsional waves and strong magnetic field within the Earth's core.

PubMed

Gillet, Nicolas; Jault, Dominique; Canet, Elisabeth; Fournier, Alexandre

2010-05-06

The magnetic field inside the Earth's fluid and electrically conducting outer core cannot be directly probed. The root-mean-squared (r.m.s.) intensity for the resolved part of the radial magnetic field at the core-mantle boundary is 0.3 mT, but further assumptions are needed to infer the strength of the field inside the core. Recent diagnostics obtained from numerical geodynamo models indicate that the magnitude of the dipole field at the surface of a fluid dynamo is about ten times weaker than the r.m.s. field strength in its interior, which would yield an intensity of the order of several millitesla within the Earth's core. However, a 60-year signal found in the variation in the length of day has long been associated with magneto-hydrodynamic torsional waves carried by a much weaker internal field. According to these studies, the r.m.s. strength of the field in the cylindrical radial direction (calculated for all length scales) is only 0.2 mT, a figure even smaller than the r.m.s. strength of the large-scale (spherical harmonic degree n

Processing, Microstructures and Properties of a Dual Phase Precipitation-Hardening PM Stainless Steel

NASA Astrophysics Data System (ADS)

Schade, Christopher

To improve the mechanical properties of PM stainless steels in comparison with their wrought counterparts, a PM stainless steel alloy was developed which combines a dual-phase microstructure with precipitation-hardening. The use of a mixed microstructure of martensite and ferrite results in an alloy with a combination of the optimum properties of each phase, namely strength and ductility. The use of precipitation hardening via the addition of copper results in additional strength and hardness. A range of compositions was studied in combination with various sintering conditions to determine the optimal thermal processing to achieve the desired microstructure. The microstructure could be varied from predominately ferrite to one containing a high percentage of martensite by additions of copper and a variation of the sintering temperature before rapid cooling. Mechanical properties (transverse rupture strength (TRS), yield strength, tensile strength, ductility and impact toughness) were measured as a function of the v/o ferrite in the microstructure. A dual phase alloy with the optimal combination of properties served as the base for introducing precipitation hardening. Copper was added to the base alloy at various levels and its effect on the microstructure and mechanical properties was quantified. Processing at various sintering temperatures led to a range of microstructures; dilatometry was used utilized to monitor and understand the transformations and the formation of the two phases. The aging process was studied as a function of temperature and time by measuring TRS, yield strength, tensile strength, ductility, impact toughness and apparent hardness. It was determined that optimum aging was achieved at 538°C for 1h. Aging at slightly lower temperatures led to the formation of carbides, which contributed to reduced hardness and tensile strength. As expected, at the peak aging temperature, an increase in yield strength and ultimate tensile strength as well as apparent hardness was found. Aging also lead to an unexpected and concurrent increase in ductility and impact toughness. The alloys also showed an increase in strain hardening on aging. The increase in ductility varied with the v/o martensite in the microstructure and was shown to occur after short time intervals at the optimum aging temperature. Compressive strength measurements revealed that the increase in ductility was due to the relaxation of residuals stresses that occur when the high temperature austenite transforms to martensite in the dual phase microstructure. The specific volume of martensite is much larger than that of austenite so that when the transformation takes place, a compressive stress is induced in the ferrite. In the sintered state, the residual stress leads to a higher work hardening rate in tension. When the alloy is aged, the work hardening rate is reduced and the ductility is increased compared with the sintered state, even though aging increases the strength and apparent hardness.

An Analysis of Water Line Profiles in Star Formation Regions Observed by SWAS

NASA Technical Reports Server (NTRS)

Ashby, Matthew L. N.; Bergin, Edwin A.; Plume, Rene; Carpenter, John M.; Neufeld, David A.; Chin, Gordon; Erickson, Neal R.; Goldsmith, Paul F.; Harwit, Martin; Howe, J. E.

2000-01-01

We present spectral line profiles for the 557 GHz 1(sub 1,0) yields 1(sub 0,1) ground-state rotational transition of ortho-H2(16)O for 18 galactic star formation regions observed by SWAS. 2 Water is unambiguously detected in every source. The line profiles exhibit a wide variety of shapes, including single-peaked spectra and self-reversed profiles. We interpret these profiles using a Monte Carlo code to model the radiative transport. The observed variations in the line profiles can be explained by variations in the relative strengths of the bulk flow and small-scale turbulent motions within the clouds. Bulk flow (infall, outflow) must be present in some cloud cores, and in certain cases this bulk flow dominates the turbulent motions.

OCEAN CIRCULATION. Observing the Atlantic Meridional Overturning Circulation yields a decade of inevitable surprises.

PubMed

Srokosz, M A; Bryden, H L

2015-06-19

The importance of the Atlantic Meridional Overturning Circulation (AMOC) heat transport for climate is well acknowledged. Climate models predict that the AMOC will slow down under global warming, with substantial impacts, but measurements of ocean circulation have been inadequate to evaluate these predictions. Observations over the past decade have changed that situation, providing a detailed picture of variations in the AMOC. These observations reveal a surprising degree of AMOC variability in terms of the intraannual range, the amplitude and phase of the seasonal cycle, the interannual changes in strength affecting the ocean heat content, and the decline of the AMOC over the decade, both of the latter two exceeding the variations seen in climate models. Copyright © 2015, American Association for the Advancement of Science.

Anomalous softening of yield strength in tantalum at high pressures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jing, Qiumin, E-mail: j-qm@163.com; Wu, Qiang; Xu, Ji-an

2015-02-07

The pressure dependence of the yield strength of tantalum was investigated experimentally up to 101 GPa at room temperature using a diamond anvil cell. A yield strength softening is observed between 52 and 84 GPa, whereas a normal trend is observed below 52 GPa and above 84 GPa. The onset pressure of the softening is in agreement with previous results obtained by the pressure gradient method and shock wave experiments. This unusual strength softening in tantalum is not related with structural transformation, preferred orientation, or material damage. Our measurements indicate that microscopic deviatoric strain is the major reason for the observed strength softening inmore » tantalum.« less

Development of Yield and Tensile Strength Design Curves for Alloy 617

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nancy Lybeck; T. -L. Sham

2013-10-01

The U.S. Department of Energy Very High Temperature Reactor Program is acquiring data in preparation for developing an Alloy 617 Code Case for inclusion in the nuclear section of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (B&PV) Code. A draft code case was previously developed, but effort was suspended before acceptance by ASME. As part of the draft code case effort, a database was compiled of yield and tensile strength data from tests performed in air. Yield strength and tensile strength at temperature are used to set time independent allowable stress for construction materials in B&PVmore » Code, Section III, Subsection NH. The yield and tensile strength data used for the draft code case has been augmented with additional data generated by Idaho National Laboratory and Oak Ridge National Laboratory in the U.S. and CEA in France. The standard ASME Section II procedure for generating yield and tensile strength at temperature is presented, along with alternate methods that accommodate the change in temperature trends seen at high temperatures, resulting in a more consistent design margin over the temperature range of interest.« less

Mechanical properties and mechanism of single crystal Cu pillar by in situ TEM compression and molecular dynamics simulation

NASA Astrophysics Data System (ADS)

Lin, Kai-Peng; Fang, Te-Hua; Lin, Ying-Jhin

2018-02-01

In this study, we investigate the mechanical properties of single-crystal copper (Cu) nanopillars. Critical deformation variations of Cu-nanopillared structures are estimated using in situ transmission electron microscopy compression tests and molecular dynamics simulations. The Young’s moduli of Cu nanopillars with diameters of 2-6 nm were 90.20-124.47 GPa. The contact stiffnesses of the Cu nanopillars with diameters of 400 and 500 nm were 1.33 and 3.86 N m-1, respectively; the Poisson’s ratios for these nanopillars were 0.32 and 0.33. The yield strength of the nanopillars varied from 0.25 GPa at 500 nm to 0.42 GPa at 400 nm; the yield strength of single-crystal Cu nanopillars decreased with increasing diameter. The values of the indented hardness of the Cu block were 0.27 and 1.06 GPa, respectively. Through experimental work and molecular dynamics simulations, we demonstrate that Cu nanopillars exhibit internal stress transmission during compression. When compression reaches the maximum strain, it can be observed that Cu slips. Our results are useful for understanding the mechanical properties, contact, and local deformation of Cu nanopillars.

The behavior of self-compacting concrete (SCC) with bagasse ash

NASA Astrophysics Data System (ADS)

Hanafiah, Saloma, Whardani, Putri Nurul Kusuma

2017-11-01

Self-Compacting Concrete (SCC) has the ability to flow and self-compacting. One of the benefit of SCC can reduced the construction time and labor cost. The materials to be used for see slightly different with the conventional concrete. Less coarse aggregate to be used up to 50%. The maximum size of coarse aggregate was also limited e.g. 10 mm. Other material was quartz sand with grain size of 50-650 µm. For reducing the around of cement, bagasse ash was used as partial replacement of cement. In this research, the variations of w/c to be used, e.g. 0.275, 0.300, 0.325 and the percentage of bagasse ash substitution were 10%, 15%, and 20%. EFNARC standard was conducted for slump flow test following the V-funnel test and L-box shape test. The maximum value of slump flow test was 75.75 cm, V-funnel test was 4.95 second, and L-box test was 1.000 yielded by mixture with w/c = 0.325 and 0% of bagasse ash. The minimum value of slump flow test was 61.50 cm, V-funnel test is 21.05 second, and L-box test was 0.743 yielded by mixture with w/c = 0.275 and 20% of bagasse ash. The maximum value of compressive strength was 67.239 MPa yielded by mixture with w/c = 0.275 and 15% of bagasse ash. And the minimum value of compressive strength was 41.813 MPa yielded by mixture with w/c = 0.325 and 20% bagasse ash.

Design and development of a 3D printed UAV

NASA Astrophysics Data System (ADS)

Banfield, Christopher P.

The purpose of this project was to investigate the viability and practicality of using a desktop 3D printer to fabricate small UAV airframes. To that end, ASTM based bending and tensile tests were conducted to assess the effects of print orientation, infill density, infill pattern, and infill orientation on the structural properties of 3D printed components. A Vernier Structures & Materials Tester was used to record force and displacement data from which stress-strain diagrams, yielding strength, maximum strength, and the moduli of elasticity were found. Results indicated that print orientation and infill density had the greatest impact on strength. In bending, vertically printed test pieces showed the greatest strength, with yield strengths 1.6 - 10.4% higher than conventionally extruded ABS's 64.0MPa average flexural strength. In contrast, the horizontally printed specimens showed yield strengths reduced anywhere from 17.0 - 34.9%. The tensile test specimens also exhibited reduced strength relative to ABS's average tensile yield strength of 40.7MPa. Test pieces with 20% infill density saw strength reductions anywhere from 47.8 - 55.6%, and those with 50% saw strength reductions from 33.6 - 47.8%. Only a single test piece with 100%, 45° crisscross infill achieved tensile performance on par with that of conventionally fabricated ABS. Its yield strength was 43MPa, a positive strength difference of 5.5%. As a supplement to the tensile and bending tests, a prototype printable airplane, the Phoebe, was designed. Its development process in turn provided the opportunity to develop techniques for printing various aircraft components such as fuselage sections, airfoils, and live-in hinges. Initial results seem promising, with the prototype's first production run requiring 19 hours of print time and an additional 4 - 5 hours of assembly time. The maiden flight test demonstrated that the design was stable and controllable in sustained flight.

Mechanical properties of nano and bulk Fe pillars using molecular dynamics and dislocation dynamics simulation

NASA Astrophysics Data System (ADS)

Nath, S. K. Deb

2017-10-01

Using molecular dynamics simulation, tension and bending tests of a Fe nanopillar are carried out to obtain its Young's modulus and yield strength. Then the comparative study of Young's modulus and yield strength of a Fe nanopillar under bending and tension are carried out varying its diameter in the range of diameter 1-15nm. We find out the reasons why bending Young's modulus and yield strength of a Fe nanopillar are higher than those of tension Young's modulus and yield strength of a Fe nanopillar. Using the mobility parameters of bulk Fe from the experimental study [N. Urabe and J. Weertman, Materials Science and Engineering 18, 41 (1975)], its temperature dependent stress-strain relationship, yield strength and strain hardening modulus are obtained from the dislocation dynamics simulations. Strain rate dependent yield strength and strain hardening modulus of bulk Fe pillars under tension are studied. Temperature dependent creep behaviors of bulk Fe pillars under tension are also studied. To verify the soundness of the present dislocation dynamics studies of the mechanical properties of bulk Fe pillars under tension, the stress vs. strain relationship and dislocation density vs. strain of bulk Fe pillars obtained by us are compared with the published results obtained by S. Queyreau, G. Monnet, and B. Devincre, International Journal of Plasticity 25, 361 (2009).

Variation in Adhesion Strength of Balanus Eburneus, Crassostrea Virginica and Hydroides Dianthus to Fouling-Release Coatings

DTIC Science & Technology

2001-03-01

www.informaworld.com/smpp/title~content=t713454511 Variation in adhesion strength of Balanus eburneus, crassostrea virginica and hydroides dianthus to...in adhesion strength of Balanus eburneus, crassostrea virginica and hydroides dianthus to fouling-release coatings’, Biofouling, 17: 2, 155 — 167...4. TITLE AND SUBTITLE Variation in adhesion strength of Balanus eburneus, crassostrea virginica and hydroides dianthus to fouling-release coatings

Variation in Adhesion Strength of Balanus eburneus, Crassostrea virginica and Hydroides dianthus to Fouling-release Coatings

DTIC Science & Technology

2001-07-01

www.informaworld.com/smpp/title~content=t713454511 Variation in adhesion strength of Balanus eburneus, crassostrea virginica and hydroides dianthus to...in adhesion strength of Balanus eburneus, crassostrea virginica and hydroides dianthus to fouling-release coatings’, Biofouling, 17: 2, 155 — 167...4. TITLE AND SUBTITLE Variation in adhesion strength of Balanus eburneus, crassostrea virginica and hydroides dianthus to fouling-release coatings

A Theoretical Model for Estimation of Yield Strength of Fiber Metal Laminate

NASA Astrophysics Data System (ADS)

Bhat, Sunil; Nagesh, Suresh; Umesh, C. K.; Narayanan, S.

2017-08-01

The paper presents a theoretical model for estimation of yield strength of fiber metal laminate. Principles of elasticity and formulation of residual stress are employed to determine the stress state in metal layer of the laminate that is found to be higher than the stress applied over the laminate resulting in reduced yield strength of the laminate in comparison with that of the metal layer. The model is tested over 4A-3/2 Glare laminate comprising three thin aerospace 2014-T6 aluminum alloy layers alternately bonded adhesively with two prepregs, each prepreg built up of three uni-directional glass fiber layers laid in longitudinal and transverse directions. Laminates with prepregs of E-Glass and S-Glass fibers are investigated separately under uni-axial tension. Yield strengths of both the Glare variants are found to be less than that of aluminum alloy with use of S-Glass fiber resulting in higher laminate yield strength than with the use of E-Glass fiber. Results from finite element analysis and tensile tests conducted over the laminates substantiate the theoretical model.

Fatigue behaviour of boron free and boron containing heat treated Ti-13Zr-13Nb alloy for biomedical applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Majumdar, P., E-mail: m.pallab@gmail.com; Singh, S.B.; Chakraborty, M.

2010-12-15

Fatigue behaviour of heat treated Ti-13Zr-13Nb (TZN) and Ti-13Zr-13Nb-0.5B (TZNB) alloys for biomedical implants has been investigated by rotating bending test. It was found that fatigue strength of TZN and TZNB alloys is comparable with that of conventionally used biomedical titanium alloys. Addition of boron to TZN alloy deteriorates fatigue strength. - Research Highlights: {yields}The microstructure of the aged TZN consists of {alpha} phase in {beta} matrix. {yields}Addition of boron to TZN leads to the formation of dispersed acicular TiB. {yields}Presence of TiB deteriorates the fatigue strength of TZN alloy. {yields}Fatigue strength of aged TZN/TZNB alloys is comparable with biomedicalmore » Ti-alloys.« less

Extended Hall-Petch Relationships for Yield, Cleavage and Intergranular Fracture Strengths of bcc Steel and Its Deformation and Fracture Behaviors

NASA Astrophysics Data System (ADS)

Heo, N. H.; Heo, Y.-U.; Kwon, S. K.; Kim, N. J.; Kim, S.-J.; Lee, H.-C.

2018-03-01

Extended Hall-Petch relationships for yield ( σy ), cleavage ( σ_{cl} ) and intergranular fracture ( σ_{ig} ) strengths of pure iron have been established through the direct calculation of the proportional constant (k) and the estimation of the friction stress (σ0 ) . The magnitude orders of k and σ0 are generally ky < k_{cl} < k_{ig} and σ_{y0} < σ_{cl0} < σ_{ig0} , respectively. Based on the Hall-Petch relationships, micro-yielding in a bcc steel occurs at the instance that the pile-up dislocations within a specific grain showing the Schmid factor of 0.5 propagate into the neighboring grain. The initial brittle crack is formed at the instance that the flow strength exceeds the brittle fracture strength. Once the brittle crack is formed, it grows catastrophically. Due to the smallest and ky and σ_{y0} , the cleavage and the intergranular fracture occur always after micro-yielding. The {100} cleavage fracture of the steel is due to the lowest theoretical {100} cleavage strength. Due to the thermal components included in cleavage and intergranular fracture strengths, they show also the temperature and strain rate dependence observed in yield strength. The increase in susceptibility to brittle fracture with decreasing temperature and increasing strain rate is due to the increase in dislocation density which causes the high work hardening rate.

Wood specific gravity variation among five important hardwood species of Kashmir Himalaya.

PubMed

Wani, Bilal Ahmad; Bodha, R H; Khan, Amina

2014-02-01

Wood Specific Gravity (SG) is a measure of the amount of structural material a tree species allocates to support and strength. In the present study, specific gravity varied among the five different woods at three different sites from 0.40 in Populus nigra at site III (Shopian) to 0.80 in Parrotiopsis jacquemontiana at site II (Surasyar). Among the three different sites, specific gravity varied from 0.73 to 0.80 in Parroptiosis jacquemontiana; in Robinia pseudoacacia it varied from 0.71 to 0.79; in Salix alba, it varied from 0.42 to 0.48; In Populus nigra it varied from 0.40 to 0.48 and in Juglans regia it varied from 0.59 to 0.66. On the basis of the specific gravity variation patterns these woods were categorized as light (Salix alba, Populus nigra) moderately heavy (Juglans regia) and moderately heavy to heavy (Robinia pseudoacacia, Parrotiopsis jacquemontiana) which predicts their properties like strength, dimensional stability with moisture content change, ability to retain paint, fiber yield per unit volume, suitability for making particleboard and related wood composite materials and suitability as a raw material for making paper.

HSDP II Drill Core: Preliminary Rock Strength Results and Implications to Flank Stability, Mauna Kea Volcano

NASA Astrophysics Data System (ADS)

Thompson, N.; Watters, R. J.; Schiffman, P.

2004-12-01

Selected portions of the 3-km HSDP II core were tested to provide unconfined rock strength data from hyaloclastite alteration zones and pillow lavas. Though the drilling project was not originally intended for strength purpose, it is believed the core can provide unique rock strength insights into the flank stability of the Hawaiian Islands. The testing showed that very weak rock exists in the hyaloclastite abundant zones in the lower 2-km of the core with strength dependent on the degree of consolidation and type of alteration. Walton and Schiffman identified three zones of alteration, an upper incipient alteration zone (1080-1335m), a smectitic zone (1405-1573m) and a lower palagonitic zone from about 1573 m to the base of the core. These three zones were sampled and tested together with pillow lava horizons for comparison. Traditional cylindrical core was not available as a consequence of the entire core having been split lengthwise for archival purposes. Hence, point load strength testing was utilized which provides the unconfined compressive strength on irregular shaped samples. The lowest unconfined strengths were recorded from incipient alteration zones with a mean value of 9.5 MPa. Smectitic alteration zones yielded mean values of 16.4 MPa, with the highest measured alteration strengths from the palagonite zones with a mean value of 32.1 MPa. As anticipated, the highest strengths were from essentially unaltered lavas with a mean value of 173 MPa. Strength variations of between one to two orders of magnitude were identified in comparing the submarine hyaloclastite with the intercalated submarine lavas. The weakest zones within the hyaloclastites may provide horizons for assisting flank collapse by serving as potential thrust zones and landslide surfaces.

Ethanol production from sorghum by a dilute ammonia pretreatment.

PubMed

Salvi, D A; Aita, G M; Robert, D; Bazan, V

2010-01-01

Sorghum fibers were pretreated with ammonium hydroxide and the effectiveness of the pretreatment evaluated by enzyme hydrolysis and ethanol production. The treatment was carried out by mixing sorghum fibers, ammonia, and water at a ratio of 1:0.14:8 at 160 degrees C for 1 h under 140-160 psi pressure. Approximately 44% lignin and 35% hemicellulose were removed during the process. Untreated and dilute-ammonia-treated fibers at 10% dry solids were hydrolyzed using combinations of commercially available enzymes, Spezyme CP and Novozyme 188. Enzyme combinations were tested at full strength (60 FPU Spezyme CP and 64 CBU Novozyme 188/g glucan) and at half strength (30 FPU Spezyme CP and 32 CBU Novozyme 188/g glucan). Biomass enzyme hydrolysis was conducted for 24 h. Saccharomyces cerevisiae D(5)A was added post hydrolysis for conversion of glucose to ethanol. Theoretical cellulose yields for treated biomass were 84% and 73%, and hemicellulose yields were 73% and 55% for full strength and half strength, respectively. Average cellulose yield was 38% and hemicellulose yield was 14.5% for untreated biomass. Ethanol yields were 25 g/100 g dry biomass and 21 g/100 g dry biomass for full strength and half strength enzyme concentrations, respectively. Controls averaged 10 g ethanol/100 g dry biomass.

Stress analysis on passenger deck due to modification from passenger ship to vehicle-carrying ship

NASA Astrophysics Data System (ADS)

Zubaydi, A.; Sujiatanti, S. H.; Hariyanto, T. R.

2018-03-01

Stress is a basic concept in learning about material mechanism. The main focus that needs to be brought to attention in analyzing stress is strength, which is the structural capacity to carry or distribute loads. The structural capacity not only measured by comparing the maximum stress with the material’s yield strength but also with the permissible stress required by the Indonesian Classification Bureau (BKI), which certainly makes it much safer. This final project analyzes stress in passenger deck that experiences modification due to load changes, from passenger load to vehicle one, carrying: 6-wheels truck with maximum weight of 14 tons, a passenger car with maximum weight of 3.5 tons, and a motorcycle with maximum weight of 0.4 tons. The deck structure is modelled using finite element software. The boundary conditions given to the structural model are fix and simple constraint. The load that works on this deck is the deck load which comes from the vehicles on deck with three vehicles’ arrangement plans. After that, software modelling is conducted for analysis purpose. Analysis result shows a variation of maximum stress that occurs i.e. 135 N/mm2, 133 N/mm2, and 152 N/mm2. Those maximum stresses will not affect the structure of passenger deck’s because the maximum stress that occurs indicates smaller value compared to the Indonesian Classification Bureau’s permissible stress (175 N/mm2) as well as the material’s yield strength (235 N/mm2). Thus, the structural strength of passenger deck is shown to be capable of carrying the weight of vehicles in accordance with the three vehicles’ arrangement plans.

Factors that determine the level of the yield strength and the return of the yield-point elongation in low-alloy ferrite-martensite steels

NASA Astrophysics Data System (ADS)

Fonstein, N.; Kapustin, M.; Pottore, N.; Gupta, I.; Yakubovsky, O.

2007-09-01

The results of laboratory investigations of dual-phase steels with different contents of carbon and alloying elements after the controlled cooling from the two-phase field and the final low-temperature tempering are presented. It is shown that the ratio of the yield strength to the tensile strength of dual-phase steels, just as the return of the yield-point elongation, depends on the volume fraction of martensite, temperature of the martensite transformation of the austenite component, quenching stresses, concentration of carbon in ferrite, and the temperature of the final tempering.

Strengthening and Improving Yield Asymmetry of Magnesium Alloys by Second Phase Particle Refinement Under the Guidance of Integrated Computational Materials Engineering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Dongsheng; Lavender, Curt

2015-05-08

Improving yield strength and asymmetry is critical to expand applications of magnesium alloys in industry for higher fuel efficiency and lower CO 2 production. Grain refinement is an efficient method for strengthening low symmetry magnesium alloys, achievable by precipitate refinement. This study provides guidance on how precipitate engineering will improve mechanical properties through grain refinement. Precipitate refinement for improving yield strengths and asymmetry is simulated quantitatively by coupling a stochastic second phase grain refinement model and a modified polycrystalline crystal viscoplasticity φ-model. Using the stochastic second phase grain refinement model, grain size is quantitatively determined from the precipitate size andmore » volume fraction. Yield strengths, yield asymmetry, and deformation behavior are calculated from the modified φ-model. If the precipitate shape and size remain constant, grain size decreases with increasing precipitate volume fraction. If the precipitate volume fraction is kept constant, grain size decreases with decreasing precipitate size during precipitate refinement. Yield strengths increase and asymmetry approves to one with decreasing grain size, contributed by increasing precipitate volume fraction or decreasing precipitate size.« less

TRIP effect in austenitic-martensitic VNS9-Sh steel at various strain rates

NASA Astrophysics Data System (ADS)

Terent'ev, V. F.; Slizov, A. K.; Prosvirnin, D. V.

2016-10-01

The mechanical properties of austenitic-martensitic VNS9-Sh (23Kh15N5AM3-Sh) steel are studied at a static strain rate from 4.1 × 10-5 to 17 × 10-3 s-1 (0.05-20 mm/min). It is found that, as the strain rate increases, the ultimate tensile strength decreases and the physical yield strength remains unchanged (≈1400 MPa). As the strain rate increases, the yield plateau remains almost unchanged and the relative elongation decreases continuously. Because of high microplastic deformation, the conventional yield strength is lower than the physical yield strength over the entire strain rate range under study. The influence of the TRIP effect on the changes in the mechanical properties of VNS9-Sh steel at various strain rates is discussed.

Effects of annealing conditions on microstructure and mechanical properties of low carbon, manganese transformation-induced plasticity steel

NASA Astrophysics Data System (ADS)

Jang, Jae-Myeong; Kim, Sung-Joon; Kang, Nam Hyun; Cho, Kyung-Mox; Suh, Dong-Woo

2009-12-01

The effects of annealing conditions on microstructural evolution and mechanical properties have been investigated in low carbon, manganese TRIP (Mn TRIP) steel based on a 0.12C-6Mn-0.5Si-3Al alloy system. The microstructure of cold-rolled sheet subjected to annealing at 760 °C to 800 °C for 30 s to 1800 s consists of a recrystallized ferrite matrix and fine-grained austenite with a phase fraction of 25 % to 35 %. Variation of the annealing conditions remarkably influenced the characteristics of constituent phases and thus affected the tensile strength and elongation. Optimization of microstructural parameters such as grain size and fraction of constituent phases, which control the yield strength, overall work hardening, and the kinetics of strain-induced martensite formation, is thus critical for obtaining an exceptional mechanical balance of the alloy.

Precipitation Effect on Mechanical Properties and Phase Stability of High Manganese Steel

NASA Astrophysics Data System (ADS)

Bae, Cheoljun; Kim, Rosa; Lee, Un-Hae; Kim, Jongryoul

2017-09-01

High manganese (Mn) steels are attractive for automotive applications due to their excellent tensile strength and superior elongation. However, the relatively low yield strength of Mn steels compared to other advanced high-strength steels is a critical problem limiting their use in structural parts. In order to increase the yield strength, the precipitation hardening effect of Mn steels was investigated by the addition of carbide-forming elements. Changes in the austenite phase stability were also evaluated in terms of stacking fault energy (SFE). As a result, fine V(C,N) precipitates were found to increase the yield strength effectively but to lower the SFE by the consumption of matrix carbons. For achieving precipitation hardening without sacrificing austenite stability, the soluble carbon content was discussed.

Effect of prolonged isothermal heat treatment on the mechanical behavior of advanced NANOBAIN steel

NASA Astrophysics Data System (ADS)

Avishan, Behzad

2017-09-01

The microstructural evolution and consequent changes in strength and ductility of advanced NANOBAIN steel during prolonged isothermal heat-treatment stages were investigated. The microstructure and mechanical properties of nanostructured bainite were not expected to be influenced by extending the heat-treatment time beyond the optimum value because of the autotempering phenomenon and high tempering resistance. However, experimental results indicated that the microstructure was thermodynamically unstable and that prolonged austempering resulted in carbon depletion from high-carbon retained austenite and carbide precipitations. Therefore, austenite became thermally less stable and partially transformed into martensite during cooling to room temperature. Prolonged austempering did not lead to the typical tempering sequence of bainite, and the sizes of the microstructural constituents were independent of the extended heat-treatment times. This independence, in turn, resulted in almost constant ultimate tensile strength values. However, microstructural variations enhanced the yield strength and the hardness of the material at extended isothermal heat-treatment stages. Finally, although microstructural changes decreased the total elongation and impact toughness, considerable combinations of mechanical properties could still be achieved.

Comparing convective heat fluxes derived from thermodynamics to a radiative-convective model and GCMs

NASA Astrophysics Data System (ADS)

Dhara, Chirag; Renner, Maik; Kleidon, Axel

2015-04-01

The convective transport of heat and moisture plays a key role in the climate system, but the transport is typically parameterized in models. Here, we aim at the simplest possible physical representation and treat convective heat fluxes as the result of a heat engine. We combine the well-known Carnot limit of this heat engine with the energy balances of the surface-atmosphere system that describe how the temperature difference is affected by convective heat transport, yielding a maximum power limit of convection. This results in a simple analytic expression for convective strength that depends primarily on surface solar absorption. We compare this expression with an idealized grey atmosphere radiative-convective (RC) model as well as Global Circulation Model (GCM) simulations at the grid scale. We find that our simple expression as well as the RC model can explain much of the geographic variation of the GCM output, resulting in strong linear correlations among the three approaches. The RC model, however, shows a lower bias than our simple expression. We identify the use of the prescribed convective adjustment in RC-like models as the reason for the lower bias. The strength of our model lies in its ability to capture the geographic variation of convective strength with a parameter-free expression. On the other hand, the comparison with the RC model indicates a method for improving the formulation of radiative transfer in our simple approach. We also find that the latent heat fluxes compare very well among the approaches, as well as their sensitivity to surface warming. What our comparison suggests is that the strength of convection and their sensitivity in the climatic mean can be estimated relatively robustly by rather simple approaches.

The precision and torque production of common hip adductor squeeze tests used in elite football.

PubMed

Light, N; Thorborg, K

2016-11-01

Decreased hip adductor strength is a known risk factor for groin injury in footballers, with clinicians testing adductor strength in various positions and using different protocols. Understanding how reliable and how much torque different adductor squeeze tests produce will facilitate choosing the most appropriate method for future testing. In this study, the reliability and torque production of three common adductor squeeze tests were investigated. Test-retest reliability and cross-sectional comparison. Twenty elite level footballers (16-33 years) without previous or current groin pain were recruited. Relative and absolute test-retest reliability, and torque production of three adductor squeeze tests (long-lever in abduction, short-lever in adduction and short-lever in abduction/external rotation) were investigated. Each participant performed a series of isometric strength tests measured by hand-held dynamometry in each position, on two test days separated by two weeks. No systematic variation was seen for any of the tests when using the mean of three measures (ICC=0.84-0.97, MDC%=6.6-19.5). The smallest variation was observed when taking the mean of three repetitions in the long-lever position (ICC=0.97, MDC%=6.6). The long-lever test also yielded the highest mean torque values, which were 69% and 11% higher than the short-lever in adduction test and short-lever in abduction/external rotation test respectively (p<0.001). All three tests described in this study are reliable methods of measuring adductor squeeze strength. However, the test performed in the long-lever position seems the most promising as it displays high test-retest precision and the highest adductor torque production. Copyright © 2015 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Al2O3 Nanoparticle Addition to Commercial Magnesium Alloys: Multiple Beneficial Effects

PubMed Central

Paramsothy, Muralidharan; Chan, Jimmy; Kwok, Richard; Gupta, Manoj

2012-01-01

The multiple beneficial effects of Al2O3 nanoparticle addition to cast magnesium based systems (followed by extrusion) were investigated, constituting either: (a) enhanced strength; or (b) simultaneously enhanced strength and ductility of the corresponding magnesium alloys. AZ31 and ZK60A nanocomposites containing Al2O3 nanoparticle reinforcement were each fabricated using solidification processing followed by hot extrusion. Compared to monolithic AZ31 (tension levels), the corresponding nanocomposite exhibited higher yield strength (0.2% tensile yield strength (TYS)), ultimate strength (UTS), failure strain and work of fracture (WOF) (+19%, +21%, +113% and +162%, respectively). Compared to monolithic AZ31 (compression levels), the corresponding nanocomposite exhibited higher yield strength (0.2% compressive yield strength (CYS)) and ultimate strength (UCS), lower failure strain and higher WOF (+5%, +5%, −4% and +11%, respectively). Compared to monolithic ZK60A (tension levels), the corresponding nanocomposite exhibited lower 0.2% TYS and higher UTS, failure strain and WOF (−4%, +13%, +170% and +200%, respectively). Compared to monolithic ZK60A (compression levels), the corresponding nanocomposite exhibited lower 0.2% CYS and higher UCS, failure strain and WOF (−10%, +7%, +15% and +26%, respectively). The capability of Al2O3 nanoparticles to enhance the properties of cast magnesium alloys in a way never seen before with micron length scale reinforcements is clearly demonstrated. PMID:28348301

Diurnal and day-to-day variation of isometric muscle strength in myasthenia gravis.

PubMed

Vinge, Lotte; Jakobsen, Johannes; Pedersen, Asger Roer; Andersen, Henning

2016-01-01

In patients with myasthenia gravis (MG), muscle strength is expected to decrease gradually during the day due to physical activities. Isometric muscle strength at the shoulder, knee, and ankle was determined in 10 MG patients (MGFA class II-IV) who were receiving usual medical treatment and in 10 control subjects. To determine diurnal and day-to-day variation, muscle strength was measured 4 times during day 1 and once at day 2. Knee extension strength decreased during the day in both patients and controls. Neither diurnal nor day-to-day variation of muscle strength was higher in patients compared with controls. Patients with mild to moderate MG did not have increased variation of isometric muscle strength during the day or from day-to-day compared with controls. This suggests that isometric muscle performance can be determined with high reproducibility in similar groups of MG patients without regard to time of day. © 2015 Wiley Periodicals, Inc.

Nose Fairing Modeling and Simulation to Support Trident II D5 Lifecycle Extension

DTIC Science & Technology

2013-09-01

Rupture Flexural Modulus Flexural Yield strength Compressive Yield strength Poissons Ratio Machinabi lily Shear strength Impact Work to...Categories: Ceramic; Glass; Glass Fiber , other Engineeting Material; C<>mposite Rbers Material Notes: Used as a reinforcing agent in fiber glass compos~es...MATWEB AMERICAN SITKA SPRUCE WOOD .......................35 APPENDIX B. MATWEB E–GLASS FIBER , GENERIC ......................................37 APPENDIX

Material strength measured by flyer-impact perturbation method

NASA Astrophysics Data System (ADS)

Ma, Xiaojuan; Asimow, Paul; Fatyanov, Oleg; Liu, Fusheng

2017-06-01

Yield strength is one of the most important physical properties of a solid material, especially far from its melting line. The flyer-impact perturbation method measures material yield strength on the basis of correlation between the yield strength under shock compression and the damping of oscillatory perturbations in the shape of a shock front passing through the material. We used flyer-plate impacts experiments on targets with machined grooves on the impact surface to shock aluminum to between 32 and 71 GPa and recorded the evolution of the shock front perturbation amplitude in the sample with electric pins and fibers. Simulations using the elastic-plastic model can be matched to the experiments, explaining well the form of the perturbation decay and constraining the yield strength of aluminum to be 1.3-3.1 GPa. These results are in agreement with values obtained from reshock and release wave profiles as well as the result deduced from the SCG model. We conclude that the flyer-impact perturbation method is indeed a reliable means to measure material strength. This work was supported by the National Natural Science Foundation of China (Grant No. 41674088) and the State Scholarship Fund of China Scholarship Council.

Shock induced spall fracture in polycrystalline copper

NASA Astrophysics Data System (ADS)

Mukherjee, D.; Rav, Amit; Sur, Amit; Joshi, K. D.; Gupta, Satish C.

2014-04-01

The plate impact experiments have been conducted on commercially available 99.99% pure polycrystalline samples of copper using single stage gas gun facility. The free surface velocity history of the sample plate measured using VISAR instrument is utilized to determine the dynamic yield strength and spall strength of copper. The dynamic yield strength and spall strength of polycrystalline copper sample has been determined to be 0.14 GPa and 1.32 GPa, respectively with corresponding strain rates of the order of 104/s.

Variation of the uniaxial tensile behavior of ultrafine-grained pure aluminum after cyclic pre-deformation

NASA Astrophysics Data System (ADS)

Yan, Ying; Chen, Li-jia; Zhang, Guo-qiang; Han, Dong; Li, Xiao-wu

2018-06-01

To explore the influence of cyclic pre-deformation on the mechanical behavior of ultrafine-grained (UFG) materials with a high stacking fault energy (SFE), UFG Al processed by equal-channel angular pressing (ECAP) was selected as a target material and its tensile behavior at different pre-cyclic levels D ( D = N i / N f, where N i and N f are the applied cycles and fatigue life at a constant stress amplitude of 50 MPa, respectively) along with the corresponding microstructures and deformation features were systematically studied. The cyclic pre-deformation treatment on the ECAPed UFG Al led to a decrease in flow stress, and a stress quasi-plateau stage was observed after yielding for all of the different-state UFG Al samples. The yield strength σ YS, ultimate tensile strength σ UTS, and uniform strain ɛ exhibited a strong dependence on D when D ≤ 20%; however, when D was in the range from 20% to 50%, no obvious change in mechanical properties was observed. The micro-mechanism for the effect of cyclic pre-deformation on the tensile properties of the ECAPed UFG Al was revealed and compared with that of ECAPed UFG Cu through the observations of deformation features and microstructures.

Agarose electrophoresis of DNA in discontinuous buffers, using a horizontal slab apparatus and a buffer system with improved properties.

PubMed

Zsolnai, A; Orbán, L; Chrambach, A

1993-03-01

Using a horizontal slab apparatus with a buffer in the reservoirs at the level of the gel ("sea-level electrophoresis"), the retrograde discontinuous buffer system reported by Wiltfang et al. for sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of proteins was applied to DNA electrophoresis. This application yielded the advantages of an increased displacement rate of the moving boundary front and a decrease in the concentration of the counterion base in the resolving phase, which yielded reduced relative mobility values at equivalent gel concentrations and practicable low buffer concentrations. The change of relative mobilities (Rf) with a variation of field strength is decreased compared to that of the migration rate in the continuous Tris-boric-acid-EDTA (TBE) buffer and thus the robustness of the system is improved, as well as the efficiency of separation. The system of Wiltfang et al. has in common with previously described discontinuous DNA system, that it is able to stack DNA from dilute samples and is insensitive to sample components with lower net mobilities than DNA, such as acetate. However, the variance of Rf at constant current density in the discontinuous buffer system is not improved over that of the migration rate at constant field strength in the continuous TBE buffer.

Tensile strength/yield strength (TS/YS) ratios of high-strength steel (HSS) reinforcing bars

NASA Astrophysics Data System (ADS)

Tavio, Anggraini, Retno; Raka, I. Gede Putu; Agustiar

2018-05-01

The building codes such as American Concrete Institute (ACI) 318M-14 and Standard National Indonesia (SNI) 2847:2013 require that the ratio of tensile strength (TS) and yield strength (YS) should not less than 1.25. The requirement is based on the assumption that a capability of a structural member to develop inelastic rotation capacity is a function of the length of the yield region. This paper reports an investigation on various steel grades, namely Grades 420, 550, 650, and 700 MPa, to examine the impact of different TS/YS ratios if it is less or greater than the required value. Grades 550, 650, and 700 MPa were purposely selected with the intention to examine if these higher grades are still promising to be implemented in special structural systems since they are prohibited by the building codes for longitudinal reinforcement, whereas Grade 420 MPa bars are the maximum limit of yield strength of reinforcing bars that is allowable for longitudinal reinforcement of special structural systems. Tensile tests of these steel samples were conducted under displacement controlled mode to capture the complete stress-strain curves and particularly the post-yield response of the steel bars. From the study, it can be concluded that Grade 420 performed higher TS/YS ratios and they were able to reach up to more than 1.25. However, the High Strength Still (HSS) bars (Grades 550, 600, and 700 MPa) resulted in lower TS/YS ratios (less than 1.25) compared with those of Grade 420 MPa.

Correlation of Fiber Composite Tensile Strength with the Ultrasonic Stress Wave Factor

NASA Technical Reports Server (NTRS)

Vary, A.; Lark, R. F.

1978-01-01

An ultrasonic-acoustic technique was used to indicate the strength variations of tensile specimens of a graphite-epoxy composite. A stress wave factor was determined and its value was found to depend on variations of the fiber-resin bonding as well as fiber orientation. The fiber orientations studied were 0 deg (longitudinal), 10 deg (off-axis), 90 deg (transverse), 0 deg + or - 45 deg/0 deg symmetrical, and + or - 45 deg] symmetrical. The stress wave factor can indicate variations of the tensile and shear strengths of composite materials. The stress wave factor was also found to be sensitive to strength variations associated with microporosity and differences in fiber-resin ratio.

Optimization of BI test parameters to investigate mechanical properties of Grade 92 steel

NASA Astrophysics Data System (ADS)

Barbadikar, Dipika R.; Vincent, S.; Ballal, Atul R.; Peshwe, Dilip R.; Mathew, M. D.

2018-04-01

The ball indentation (BI) testing is used to evaluate the tensile properties of materials namely yield strength, strength coefficient, ultimate tensile strength, and strain hardening exponent. The properties evaluated depend on a number of BI test parameters. These parameters include the material constants like yield slope (YS), constraint factor (CF), yield offset parameter (YOP). Number of loading/unloading cycles, preload, indenter size and depth of penetration of indenter also affects the properties. In present investigation the effect of these parameters on the stress-strain curve of normalized and tempered Grade 92 steel is evaluated. Grade 92 is a candidate material for power plant application over austenitic stainless steel and derives its strength from M23C6, MX precipitates and high dislocation density. CF, YS and YOP changed the strength properties considerably. Indenter size effect resulted in higher strength for smaller indenter. It is suggested to use larger indenter diameter and higher number of loading cycles for GRADE 92 steel to get best results using BI technique.

Cryogenic Properties of Aluminum Beryllium and Beryllium Materials

NASA Technical Reports Server (NTRS)

Gamwell, Wayne R.; McGill, Preston B.

2003-01-01

Ultimate tensile strength, yield strength, and elongation were obtained for the aluminum-beryllium alloy, AlBeMetl62 (38%Al-62%Be), at cryogenic (-195.5 C (-320 F) and (-252.8 C) (-423 F)) temperatures, and for an optical grade beryllium, O-30H (99%Be), at -252.8 C. AlBeMetl62 material was purchased to the requirements of SAE-AMS7912, "Aluminum-Beryllium Alloy, Extrusions." O-30H material was purchased to the requirements of Brush Wellman Inc. specification O-30H Optical Grade Beryllium. The ultimate tensile and yield strengths for extruded AlBeMetl62 material increased with decreasing temperature, and the percent elongation decreased with decreasing temperature. Design properties for the ultimate tensile strength, yield strength, and percent elongation for extruded AlBeMetl62 were generated. It was not possible to distinguish a difference in the room and cryogenic ultimate strength for the hot isostatically pressed (HIP'ed) O-30H material. The O30H elongation decreased with decreasing temperature.

Abundances in the red giants of M13 and M22

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lehnert, M.D.; Bell, R.A.; Cohen, J.G.

Abundances of Ca, Na, and Fe are derived for 10 red giant branch stars in the globular clusters M13 and M22, by means of model atmosphere analyses of high-dispersion spectra. It was found that M13 and M22 represent two different types of globular clusters. M13 is similar to M92 and many other globular clusters in that it displays variations in CH and CN band strengths, while showing no variation in either Ca or Fe abundance. The Na abundance was found to vary and its variation correlates with CN band strengths. This suggests that the source of the observed CN bandmore » strength variation is the same as that of the Na variation. M22, on the other hand, is similar to Omega Cen, in that it displays variations in Ca, Na, and Fe abundances, and these variations correlate with variations in CH and CN band strengths. These correlations suggest that the cause of the variations in M22 is largely primordial, and that mixing may only make a relatively small contribution to the C and N variations observed. 61 refs.« less

Summary of Structural Evaluation and Design Support for the Underground Nuclear Test Program.

DTIC Science & Technology

1979-07-01

consider using API -5LX pipe as this pipe has been shown to have high ductility (better than A36). This pipe comes in several grades (X42, X46, X52 , X56, X60...X65, X70) with the grade number representing the yield strength (ksi) of the steel. Grades X42 and X52 are readily available while the higher yield...strength steels are less readily available. I believe X52 has certainly a high enough yield strength (52,000 psi) for your application and that even

Strength and texture of Pt compressed to 63 GPa

NASA Astrophysics Data System (ADS)

Dorfman, Susannah M.; Shieh, Sean R.; Duffy, Thomas S.

2015-02-01

Angle- and energy-dispersive X-ray diffraction experiments in a radial geometry were performed in the diamond anvil cell on polycrystalline platinum samples at pressures up to 63 GPa. Observed yield strength and texture depend on grain size. For samples with 70-300-nm particle size, the yield strength is 5-6 GPa at ˜60 GPa. Coarse-grained (˜2-μm particles) Pt has a much lower yield strength of 1-1.5 GPa at ˜60 GPa. Face-centered cubic metals Pt and Au have lower strength to shear modulus ratio than body-centered cubic or hexagonal close-packed metals. While a 300-nm particle sample exhibits the <110> texture expected of face-centered-cubic metals under compression, smaller and larger particles show a weak mixed <110> and <100> texture under compression. Differences in texture development may also occur due to deviations from uniaxial stress under compression in the diamond anvil cell.

Effect of Tempering Temperature on the Microstructure and Properties of Fe-2Cr-Mo-0.12C Pressure Vessel Steel

NASA Astrophysics Data System (ADS)

Wang, Qi-wen; Li, Chang-sheng; Peng, Huan; Chen, Jie; Zhang, Jian

2018-03-01

To obtain the high-temperature strength and toughness of the medium-high-temperature-pressure steel, the microstructure evolution and mechanical properties of Fe-2Cr-Mo-0.12C steel subjected to three different tempering temperatures after being normalized were investigated. The results show that the microstructure of the sample, tempered in the range 675-725 °C for 50 min, did not change dramatically, yet the martensite/austenite constituents decomposed, and the bainite lath merged together and transformed into polygonal ferrite. At the same time, the precipitate size increased with an increase in tempering temperature. With the increase in the tempering temperature from 675 to 725 °C, the impact absorbed energy of the Fe-2Cr-Mo-0.12C steel at -40 °C increased from 257 to 325 J, and the high-temperature yield strength decreased; however, the high-temperature ultimate tensile strength tempered at 700 °C was outstanding (422-571 MPa) at different tested temperatures. The variations of the properties were attributed to the decomposition of M/A constituents and the coarsening of the precipitates. Fe-2Cr-Mo-0.12C steel normalized at 930 °C and tempered at 700 °C was found to have the best combination of ductility and strength.

Structure-Property Correlations in Al-Li Alloy Integrally Stiffened Extrusions

NASA Technical Reports Server (NTRS)

Hales, Stephen J.; Hafley, Robert A.

2001-01-01

The objective of this investigation was to establish the relationship between mechanical property anisotropy, microstructure and crystallographic texture in integrally 'T'-stiffened extruded panels fabricated from the Al-Li alloys 2195, 2098 and 2096. In-plane properties were measured as a function of orientation at two locations in the panels, namely mid-way between (Skin), and directly beneath (Base), the integral 'T' stiffeners. The 2195 extrusion exhibited the best combination of strength and toughness, but was the most anisotropic. The 2098 extrusion exhibited lower strength and comparable toughness, but was more isotropic than 2195. The 2096 extrusion exhibited the lowest strength and poor toughness, but was the most isotropic. All three alloys exhibited highly elongated grain structures and similar location-dependent variations in grain morphology. The textural characteristics comprised a beta + <100> fiber texture, similar to rolled product, in the Skin regions and alpha <111> + <100> fiber texture, comparable to axisymmetric extruded product, in the Base regions. In an attempt to quantitatively correlate texture with yield strength anisotropy, the original 'full constraint' Taylor model and a variant of the 'relaxed constraint' model, explored by Wert et al., were applied to the data. A comparison of the results revealed that the Wert model was consistently more accurate than the Taylor model.

Mechanical Loading during Growth Is Associated with Plane-specific Differences in Vertebral Geometry: A Cross-sectional Analysis Comparing Artistic Gymnasts vs. Non-gymnasts

PubMed Central

Dowthwaite, Jodi N.; Rosenbaum, Paula F.; Scerpella, Tamara A.

2011-01-01

Lumbar spine geometry, density and indices of bone strength were assessed relative to menarche status, using artistic gymnastics exposure during growth as a model of mechanical loading. Paired posteroanterior (PA) and supine lateral (LAT) DXA scans of L3 for 114 females (60 ex/gymnasts and 54 non-gymnasts) yielded output for comparison of paired (PALAT) versus standard PA and LAT outcomes. BMC, areal BMD, vertebral body dimensions, bone mineral apparent density (BMAD), axial compressive strength (IBS) and a fracture risk index were evaluated, modeling vertebral body geometry as an ellipsoid cylinder. Two-factor ANCOVA tested statistical effects of gymnastic exposure, menarche status and their interaction, adjusting for age and height as appropriate. Compared to non-gymnasts, ex/gymnasts exhibited greater PABMD, PABMC, PAWIDTH, PA CROSS-SECTIONAL AREA (CSA), PAVOLUME, LATBMD, LATBMAD, PALATCSA and PALATIBS (p<0.05). Non-gymnasts exhibited greater LATDEPTH/PAWIDTH, LATBMC/PABMC, LATVHEIGHT, LATAREA and Fracture Risk Index. Using ellipsoid vertebral geometric models, no significant differences were detected for PA or PALAT BMAD. In contrast, cuboid model results (Carter 1992) suggested erroneous ex/gymnast PABMAD advantages, resulting from invalid assumptions of proportional variation in linear skeletal dimensions. Gymnastic exposure was associated with shorter, wider vertebral bodies, yielding greater axial compressive strength and lower fracture risk, despite no BMAD advantage. Our results suggest the importance of plane-specific vertebral geometric adaptation to mechanical loading during growth. Paired scan output provides a more accurate assessment of this adaptation than PA or LAT plane scans alone. PMID:21839871

The effects of internal heating and large scale climate variations on tectonic bi-stability in terrestrial planets

NASA Astrophysics Data System (ADS)

Weller, M. B.; Lenardic, A.; O'Neill, C.

2015-06-01

We use 3D mantle convection and planetary tectonics models to explore the links between tectonic regimes and the level of internal heating within the mantle of a planet (a proxy for thermal age), planetary surface temperature, and lithosphere strength. At both high and low values of internal heating, for moderate to high lithospheric yield strength, hot and cold stagnant-lid (single plate planet) states prevail. For intermediate values of internal heating, multiple stable tectonic states can exist. In these regions of parameter space, the specific evolutionary path of the system has a dominant role in determining its tectonic state. For low to moderate lithospheric yield strength, mobile-lid behavior (a plate tectonic-like mode of convection) is attainable for high degrees of internal heating (i.e., early in a planet's thermal evolution). However, this state is sensitive to climate driven changes in surface temperatures. Relatively small increases in surface temperature can be sufficient to usher in a transition from a mobile- to a stagnant-lid regime. Once a stagnant-lid mode is initiated, a return to mobile-lid is not attainable by a reduction of surface temperatures alone. For lower levels of internal heating, the tectonic regime becomes less sensitive to surface temperature changes. Collectively our results indicate that terrestrial planets can alternate between multiple tectonic states over giga-year timescales. Within parameter space regions that allow for bi-stable behavior, any model-based prediction as to the current mode of tectonics is inherently non-unique in the absence of constraints on the geologic and climatic histories of a planet.

Prediction of the Dynamic Yield Strength of Metals Using Two Structural-Temporal Parameters

NASA Astrophysics Data System (ADS)

Selyutina, N. S.; Petrov, Yu. V.

2018-02-01

The behavior of the yield strength of steel and a number of aluminum alloys is investigated in a wide range of strain rates, based on the incubation time criterion of yield and the empirical models of Johnson-Cook and Cowper-Symonds. In this paper, expressions for the parameters of the empirical models are derived through the characteristics of the incubation time criterion; a satisfactory agreement of these data and experimental results is obtained. The parameters of the empirical models can depend on some strain rate. The independence of the characteristics of the incubation time criterion of yield from the loading history and their connection with the structural and temporal features of the plastic deformation process give advantage of the approach based on the concept of incubation time with respect to empirical models and an effective and convenient equation for determining the yield strength in a wider range of strain rates.

Pressure and temperature dependence of shear modulus and yield strength for aluminum, copper, and tungsten under shock compression

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peng Jianxiang; Jing Fuqian; Li Dahong

2005-07-01

Experimental data for the shear modulus and yield strength of shocked aluminum, copper, and tungsten were systematically analyzed. Comparisons between these data and calculations using the Steinberg-Cochran-Guinan (SCG) constitutive model [D. J. Steinberg, S. G. Cochran, and M. W. Guinan, J. Appl. Phys. 51, 1498 (1980)] indicate that the yield strength has the same dependence on pressure and temperature as the shear modulus for aluminum for shock pressures up to 50 GPa, for copper to 100 GPa, and for tungsten to 200 GPa. Therefore, the assumption of Y{sub p}{sup '}/Y{sub 0}=G{sub p}{sup '}/G{sub 0},Y{sub T}{sup '}/Y{sub 0}=G{sub T}{sup '}/G{sub 0}more » is basically acceptable for these materials, and the SCG model can be used to describe the shear modulus and yield strength of the shocked material at high pressure and temperature.« less

Comparative Thermal Aging Effects on PM-HIP and Forged Inconel 690

NASA Astrophysics Data System (ADS)

Bullens, Alexander L.; Bautista, Esteban; Jaye, Elizabeth H.; Vas, Nathaniel L.; Cain, Nathan B.; Mao, Keyou; Gandy, David W.; Wharry, Janelle P.

2018-03-01

This study compares thermal aging effects in Inconel 690 (IN690) produced by forging and powder metallurgy with hot isostatic pressing (PM-HIP). Isothermal aging is carried out over 400-800°C for up to 1000 h and then metallography and nanoindentation are utilized to relate grain microstructure with hardness and yield strength. The PM-HIP IN690 maintains a constant grain size through all aging conditions, while the forged IN690 exhibits limited grain growth at the highest aging temperature and longest aging time. The PM-HIP IN690 exhibits comparable mechanical integrity as the forged material throughout aging: hardness and yield strength are unchanged with 100 h aging, but increase after 1000 h aging at all temperatures. In both the PM-HIP and forged IN690, the Hall-Petch relationship for Ni-based superalloys predicts yield strength for 0-100 h aged specimens, but underestimates yield strength in the 1000 h aged specimens because of thermally induced precipitation.

TEMPEST code modifications and testing for erosion-resisting sludge simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Onishi, Y.; Trent, D.S.

The TEMPEST computer code has been used to address many waste retrieval operational and safety questions regarding waste mobilization, mixing, and gas retention. Because the amount of sludge retrieved from the tank is directly related to the sludge yield strength and the shear stress acting upon it, it is important to incorporate the sludge yield strength into simulations of erosion-resisting tank waste retrieval operations. This report describes current efforts to modify the TEMPEST code to simulate pump jet mixing of erosion-resisting tank wastes and the models used to test for erosion of waste sludge with yield strength. Test results formore » solid deposition and diluent/slurry jet injection into sludge layers in simplified tank conditions show that the modified TEMPEST code has a basic ability to simulate both the mobility and immobility of the sludges with yield strength. Further testing, modification, calibration, and verification of the sludge mobilization/immobilization model are planned using erosion data as they apply to waste tank sludges.« less

Effect of different surface treatments on shear bond strength of zirconia to three resin cements

NASA Astrophysics Data System (ADS)

Dadjoo, Nisa

Statement of problem: There are no standard guidelines for material selection to obtain acceptable bonding to high-strength zirconium oxide ceramic. Studies suggest resin cements in combination with MDP-containing primer is a reasonable choice, however, the other cements cannot be rejected and need further investigation. Objective: The purpose of this in vitro study was the evaluation of the shear bond strength of three composite resin cements to zirconia ceramic after using different surface conditioning methods. Materials and methods: One hundred and twenty sintered Y-TZP ceramic (IPS e.max ZirCAD) squares (8 x 8 x 4 mm) were embedded in acrylic molds, then divided into three groups (n=40) based on the type of cement used. Within each group, the specimens were divided into four subgroups (n=10) and treated as follows: (1) Air abrasion with 50microm aluminum oxide (Al2O 3) particles (ALO); (2) Air abrasion + Scotchbond Universal adhesive (SBU); (3) Air abrasion + Monobond Plus (MBP); (4) Air abrasion + Z-Prime Plus (ZPP). Composite cylinders were used as carriers to bond to conditioned ceramic using (1) RelyX Ultimate adhesive resin cement (RX); (2) Panavia SA self-adhesive resin cement (PSA); (3) Calibra esthetic cement (CAL). The bonded specimens were submerged in distilled water and subjected to 24-hour incubation period at 37°C. All specimens were stressed in shear at a constant crosshead speed of 0.5 mm/min until failure. Statistical analysis was performed by ANOVA. The bond strength values (MPa), means and standard deviations were calculated and data were analyzed using analysis of variance with Fisher's PLSD multiple comparison test at the 0.05 level of significance. The nature of failure was recorded. Results: The two-way ANOVA showed Panavia SA to have the highest strength at 44.3 +/- 16.9 MPa (p<0.05). The combination of Scotchbond Universal surface treatment with Panavia SA cement showed statistically higher bond strength (p=0.0054). The highest bond strengths for all three cements were observed with Scotchbond Universal surface treatment (p=0.0041). Calibra in combination with aluminum oxide air abrasion resulted in statistically lowest bond strength at 12.0 +/- 3.9 MPa. The predominant mode of failure was cohesive with cement remaining principally on the zirconium oxide samples in 57.5% of the specimens, followed by cement found on both the zirconium oxide samples and composite rods (mixed) in 32.5% of the samples. Only 10% of the specimens were found with cement on the composite rods (adhesive failure). Conclusions: Within the limitations of this in vitro study, the MDP-containing resin cement, Panavia SA, yielded the strongest bond to Y-TZP ceramic when compared to adhesive (RelyX Ultimate) or esthetic (Calibra) resin cements. Air abrasion particle + Scotchbond Universal surface treatment demonstrated the highest bond strength regardless of the cement. Significance: The variation of surface conditioning methods yielded different results in accordance with the cement types. Overall, Scotchbond Universal adhesive + air abrasion yielded the highest bond strengths among all three surface treatments. The phosphate monomer-containing luting system, Panavia SA, is acceptable for bonding to zirconia ceramics.

The decrease in yield strength in NiAl due to hydrostatic pressure

NASA Technical Reports Server (NTRS)

Margevicius, R. W.; Lewandowski, J. J.; Locci, I.

1992-01-01

The decrease in yield strength in NiAl due to hydrostatic pressure is examined via a comparison of the tensile flow behavior in the low strain regime at 0.1 MPa for NiAl which was cast, extruded, and annealed for 2 hr at 827 C in argon and very slowly cooled to room temperature. Pressurization to 1.4 GPa produces a subsequent reduction at 0.1 MP in proportional limit by 40 percent as well as a 25-percent reduction in the 0.2-percent offset yield strength, while pressurization with lower pressures produces a similar reduction, although smaller in magnitude.

Dynamics of lava flow - Thickness growth characteristics of steady two-dimensional flow

NASA Technical Reports Server (NTRS)

Park, S.; Iversen, J. D.

1984-01-01

The thickness growth characteristics of flowing lava are investigated using a heat balance model and a two-dimensional model for flow of a Bingham plastic fluid down an inclined plane. It is found that yield strength plays a crucial role in the thickening of a lava flow of given flow rate. To illustrate this point, downstream thickness profiles and yield strength distributions were calculated for flows with mass flow rates of 10,000 and 100,000 kg/m-sec. Higher flow rates led to slow cooling rates which resulted in slow rate of increase of yield strength and thus greater flow lengths.

High Strength and Thermally Stable Nanostructured Magnesium Alloys and Nanocomposites

NASA Astrophysics Data System (ADS)

Chang, Yuan-Wei

Magnesium and its alloys are currently in the spotlight of global research because of the need to limit energy consumption and reduce the environmental impact. In particular, their low densities compared to other structural metals make them a very attractive alternative in the automobile and aerospace industries. However, their low strength compared to other structural materials (e.g. Al and steels) has limited their widespread application. This dissertation presents the results of developing and investigation of a high strength nanostructured magnesium-aluminum alloy and composite. The nanostructured magnesium alloy is prepared by cryomilling and consolidated by spark-plasma-sintering. Focused ion beam is used to prepare micropillars with different diameters ranging from 1.5 to 8 mum and micro-compression test is conducted by nanoindenter in order to evaluate the mechanical properties. The yield strength obtained in the present study is around three times higher than conventional magnesium alloys (120 MPa vs. 370 MPa). The yield strength of the nanostructured magnesium alloy is further improved through hot extrusion, resulting in a yield strength of 550 MPa and an ultimate strength of 580 MPa. The nanostructured magnesium alloy exhibits a strong size-dependence, and a significant improvement in strength is observed when the pillar diameter is reduced to below 3.5 mum. The deformation mechanisms of the compressed pillars were characterized using transmission electron microscopy. The size-induced strengthening is attributed to a less number of dislocation sources along with a higher activity of non-basal deformation mechanisms. We have also developed a high strength and thermally stable nanostructured magnesium composite by adding diamantane. A yield strength of 500 MPa is achieved, moreover, excellent thermal stability is demonstrated in the magnesium alloy containing diamantanes. The strength and grain size are thermally stable after annealing at 400°C for 100 hours. In contrast, the yield strength of the alloy without diamantanes decreases significantly after annealing due to severe grain growth. These results suggest that diamantanes are pinning the grain boundaries and inhibiting grain growth at elevated temperatures. Finally, molecular dynamics simulations and finite element analysis are used to explore the deformation mechanisms of magnesium with different grain sizes at atomic resolutions and correct tapering effect on micro-compression test, respectively. The results in the dissertation show that nanostructured Mg-Al alloy and Mg-Al-Diamantane composite are promising materials for aerospace and automobile industries.

Chain Ends and the Ultimate Tensile Strength of Polyethylene Fibers

NASA Astrophysics Data System (ADS)

O'Connor, Thomas C.; Robbins, Mark O.

Determining the tensile yield mechanisms of oriented polymer fibers remains a challenging problem in polymer mechanics. By maximizing the alignment and crystallinity of polyethylene (PE) fibers, tensile strengths σ ~ 6 - 7 GPa have been achieved. While impressive, first-principal calculations predict carbon backbone bonds would allow strengths four times higher (σ ~ 20 GPa) before breaking. The reduction in strength is caused by crystal defects like chain ends, which allow fibers to yield by chain slip in addition to bond breaking. We use large scale molecular dynamics (MD) simulations to determine the tensile yield mechanism of orthorhombic PE crystals with finite chains spanning 102 -104 carbons in length. The yield stress σy saturates for long chains at ~ 6 . 3 GPa, agreeing well with experiments. Chains do not break but always yield by slip, after nucleation of 1D dislocations at chain ends. Dislocations are accurately described by a Frenkel-Kontorova model, parametrized by the mechanical properties of an ideal crystal. We compute a dislocation core size ξ = 25 . 24 Å and determine the high and low strain rate limits of σy. Our results suggest characterizing such 1D dislocations is an efficient method for predicting fiber strength. This research was performed within the Center for Materials in Extreme Dynamic Environments (CMEDE) under the Hopkins Extreme Materials Institute at Johns Hopkins University. Financial support was provided by Grant W911NF-12-2-0022.

Effect of a heat treatment on the precipitation behavior and tensile properties of alloy 690 steam generator tubes

NASA Astrophysics Data System (ADS)

Lee, Tae-Hyuk; Suh, Ho-Young; Han, Seul-Ki; Noh, Jae-Soo; Lee, Jong-Hyeon

2016-10-01

The intergranular carbide precipitation behavior and its effect on the tensile properties were investigated in alloy 690. The precipitation of intergranular carbides, identified as Cr-rich M23C6, was retarded on the low-angle grain boundaries and the coincidence-site lattice boundaries. The M23C6 carbides have a cube-cube orientation relationship with the matrix. The ultimate tensile strength, yield strength, and elongation of the solution annealed alloy 690 are 648.2 ± 8.2 MPa, 242.8 ± 10.5 MPa and 44.9 ± 2.3%, respectively. The ultimate tensile strength and the yield strength increased to 764.8 ± 7.8 MPa and 364.8 ± 10.2 MPa until the aging time reached 16 h. This increase is ascribed to the M23C6 carbide acting as reinforcements. However, when the aging time exceed 16 h, these properties gradually decreased with increasing aging time. The decrease in ultimate tensile strength, yield strength, and elongation were mainly caused by the intergranular cracking due to the low bond strength between the carbide and the matrix.

Fabrication and mechanical behavior of dye-doped polymer optical fiber

NASA Astrophysics Data System (ADS)

Jiang, Changhong; Kuzyk, Mark G.; Ding, Jow-Lian; Johns, William E.; Welker, David J.

2002-07-01

The purpose of this article is to study the materials physics behind dye-doped polymethyl metharcylate (PMMA) that is important for the optical fiber drawing process. We report effects of the fabrication process on the mechanical properties of the final fiber. The qualitative degree of polymer chain alignment is found to increase with the drawing force, which in turn decreases with the drawing temperature and increases with the drawing ratio. The chain alignment relaxes when the fibers are annealed at 95 degC with a commensurate decrease in fiber length and increase in diameter. The annealed fiber has higher ductility but lower strength than the unannealed fiber. Both the yield and tensile strengths are dependent on the strain rate. The relationship between tensile strength, sigmab, and fiber diameter, d, is found empirically to be sigmab[is proportional to]d-0.5. The yield strength appears to be less sensitive to the fiber diameter than the tensile strength. For PMMA doped with disperse red 1 azo dye, the yield strength, tensile strength, and Young's modulus peak at a dye concentration of 0.0094 wt %. These results are useful for designing polymer optical fibers with well-defined mechanical properties.

Effects of heat treating PM Rene' 95 slightly below the gamma-prime solvus

NASA Technical Reports Server (NTRS)

Dreshfield, R. L.

1977-01-01

An investigation was performed on As-HIP Rene' 95 to obtain additional information on the variation of the amount of gamma-prime with solutioning temperatures near the gamma-prime solvus temperature and the resulting effects on tensile and stress rupture strengths of As-HIP Rene' 95. The amount of gamma-prime phase was found to increase at a rate of about 0.5% per degree Celsius as the temperature decreased from the solvus temperature to about 50 C below the gamma-prime solvus temperature. The change in the amount of gamma-prime phase with decreasing solutioning temperature was observed to be primarily associated with decreasing solubilities of Al+Ti+Nb and increasing solubility of Cr in the gamma phase. For As-HIP Rene' 95 solutioned at either 1107 or 1135 C and subsequently water-quenched and double aged for 4 hours at 815 C followed by 24 hours at 650 C, the higher solution temperature resulted in significantly greater yield strengths at room temperature and 650 C as well as a greater room-temperature ultimate strength. Also, longer stress rupture lives at 650 C were associated with the higher solution temperature.

Mechanical behavior of monocrystalline aluminum-lithium alloy at low temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Z.G.; Liu, W.; Xu, Y.B.

1994-12-01

Investigations have indicated that at low temperature aluminum- lithium alloys display improved toughness and an improved strength-toughness relationship. The yield strength, ultimate tensile strength, elongation and the fracture toughness increase with decreasing temperatures. Several mechanisms have been proposed to explain this most striking feature. Webster claimed that low melting point impurities, such as sodium and potassium, are responsible for the improvement of mechanical properties in Al-Li alloys at low temperatures. However, Venkateswara Rao et al. indicated that the increased delamination at low temperatures can increase the degree of in-plane crack deflection, resulting in toughening of the alloys. On the basismore » of their own results, Xu and coworker pointed out that the improvement of tensile and fatigue properties at liquid nitrogen temperatures is also presumably attributable to the delamination. Therefore, the mechanisms responsible for the variation in mechanical properties with temperature are not currently well-understood. In order to elucidate the real situation, single crystals of a binary aluminum-lithium alloy were adopted in the present study. This paper is devoted to the description of the behavior of the load-displacement curves and the associated slip traces on the sample surfaces.« less

49 CFR 192.107 - Yield strength (S) for steel pipe.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 3 2013-10-01 2013-10-01 false Yield strength (S) for steel pipe. 192.107 Section 192.107 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS... (S) for steel pipe. (a) For pipe that is manufactured in accordance with a specification listed in...

49 CFR 192.107 - Yield strength (S) for steel pipe.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 3 2014-10-01 2014-10-01 false Yield strength (S) for steel pipe. 192.107 Section 192.107 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS... (S) for steel pipe. (a) For pipe that is manufactured in accordance with a specification listed in...

49 CFR 192.107 - Yield strength (S) for steel pipe.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 3 2012-10-01 2012-10-01 false Yield strength (S) for steel pipe. 192.107 Section 192.107 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS... (S) for steel pipe. (a) For pipe that is manufactured in accordance with a specification listed in...

49 CFR 192.107 - Yield strength (S) for steel pipe.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 3 2010-10-01 2010-10-01 false Yield strength (S) for steel pipe. 192.107 Section 192.107 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS... (S) for steel pipe. (a) For pipe that is manufactured in accordance with a specification listed in...

49 CFR 192.107 - Yield strength (S) for steel pipe.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 3 2011-10-01 2011-10-01 false Yield strength (S) for steel pipe. 192.107 Section 192.107 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS... (S) for steel pipe. (a) For pipe that is manufactured in accordance with a specification listed in...

Peanut peg strength and associated pod yield and loss by cultivar

USDA-ARS?s Scientific Manuscript database

Peanut (Arachis hypogaea L.) peg strength and associated pod yield and digging loss were documented for nine cultivars and two breeding genotypes across three harvest dates at two Southwest Georgia locations during 2010 and 2011. Cultivars selected were Georgia Green, Georgia Greener, Georgia-02C, G...

Enhancing paper strength by optimizing defect configuration

Treesearch

J.M. Considine; W. Skye; W. Chen; D. Matthys; David W. Vahey; K. Turner; R. Rowlands

2009-01-01

Poor formation in paper, as denoted by large local variation of mass, tends to reduce maximum tensile strength but has not been well characterized. The effect of grammage variation on tensile strength was studied by introducing carefully placed holes in tensile specimens made of three different paper materials. Previous researchers demonstrated that the point-stress...

Physically-based strength model of tantalum incorporating effects of temperature, strain rate and pressure

DOE PAGES

Lim, Hojun; Battaile, Corbett C.; Brown, Justin L.; ...

2016-06-14

In this work, we develop a tantalum strength model that incorporates e ects of temperature, strain rate and pressure. Dislocation kink-pair theory is used to incorporate temperature and strain rate e ects while the pressure dependent yield is obtained through the pressure dependent shear modulus. Material constants used in the model are parameterized from tantalum single crystal tests and polycrystalline ramp compression experiments. It is shown that the proposed strength model agrees well with the temperature and strain rate dependent yield obtained from polycrystalline tantalum experiments. Furthermore, the model accurately reproduces the pressure dependent yield stresses up to 250 GPa.more » The proposed strength model is then used to conduct simulations of a Taylor cylinder impact test and validated with experiments. This approach provides a physically-based multi-scale strength model that is able to predict the plastic deformation of polycrystalline tantalum through a wide range of temperature, strain and pressure regimes.« less

Cup-Drawing Behavior of High-Strength Steel Sheets Containing Different Volume Fractions of Martensite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choi, Shi-Hoon; Kim, Dae-Wan; Yang, Hoe-Seok

Planar anisotropy and cup-drawing behavior were investigated for high-strength steel sheets containing different volume fractions of martensite. Macrotexture analysis using XRD was conducted to capture the effect of crystallographic orientation on the planar anisotropy of high-strength steel sheets. A phenomenological yield function, Yld96, which accounts for the anisotropy of yield stress and r-values, was implemented into ABAQUS using the user subroutine UMAT. Cup drawing of high-strength steel sheets was simulated using the FEM code. The profiles of earing and thickness strain were compared with the experimentally measured results.

Mechanical Properties Analysis of 4340 Steel Specimen Heat Treated in Oven and Quenching in Three Different Fluids

NASA Astrophysics Data System (ADS)

Fakir, Rachid; Barka, Noureddine; Brousseau, Jean

2018-03-01

This paper proposes a statistical approach to analyze the mechanical properties of a standard test specimen, of cylindrical geometry and in steel 4340, with a diameter of 6 mm, heat-treated and quenched in three different fluids. Samples were evaluated in standard tensile test to access their characteristic quantities: hardness, modulus of elasticity, yield strength, tensile strength and ultimate deformation. The proposed approach is gradually being built (a) by a presentation of the experimental device, (b) a presentation of the experimental plan and the results of the mechanical tests, (c) anova analysis of variance and a representation of the output responses using the RSM response surface method, and (d) an analysis of the results and discussion. The feasibility and effectiveness of the proposed approach leads to a precise and reliable model capable of predicting the variation of mechanical properties, depending on the tempering temperature, the tempering time and the cooling capacity of the quenching medium.

Climate variation explains a third of global crop yield variability

PubMed Central

Ray, Deepak K.; Gerber, James S.; MacDonald, Graham K.; West, Paul C.

2015-01-01

Many studies have examined the role of mean climate change in agriculture, but an understanding of the influence of inter-annual climate variations on crop yields in different regions remains elusive. We use detailed crop statistics time series for ~13,500 political units to examine how recent climate variability led to variations in maize, rice, wheat and soybean crop yields worldwide. While some areas show no significant influence of climate variability, in substantial areas of the global breadbaskets, >60% of the yield variability can be explained by climate variability. Globally, climate variability accounts for roughly a third (~32–39%) of the observed yield variability. Our study uniquely illustrates spatial patterns in the relationship between climate variability and crop yield variability, highlighting where variations in temperature, precipitation or their interaction explain yield variability. We discuss key drivers for the observed variations to target further research and policy interventions geared towards buffering future crop production from climate variability. PMID:25609225

Correlation analysis of the variation of weld seam and tensile strength in laser welding of galvanized steel

NASA Astrophysics Data System (ADS)

Sinha, Amit Kumar; Kim, Duck Young; Ceglarek, Darek

2013-10-01

Many advantages of laser welding technology such as high speed and non-contact welding make the use of the technology more attractive in the automotive industry. Many studies have been conducted to search the optimal welding condition experimentally that ensure the joining quality of laser welding that relies both on welding system configuration and welding parameter specification. Both non-destructive and destructive techniques, for example, ultrasonic inspection and tensile test are widely used in practice for estimating the joining quality. Non-destructive techniques are attractive as a rapid quality testing method despite relatively low accuracy. In this paper, we examine the relationship between the variation of weld seam and tensile shear strength in the laser welding of galvanized steel in a lap joint configuration in order to investigate the potential of the variation of weld seam as a joining quality estimator. From the experimental analysis, we identify a trend in between maximum tensile shear strength and the variation of weld seam that clearly supports the fact that laser welded parts having larger variation in the weld seam usually have lower tensile strength. The discovered relationship leads us to conclude that the variation of weld seam can be used as an indirect non-destructive testing method for estimating the tensile strength of the welded parts.

Magnetic Field Strengths and Grain Alignment Variations in the Local Bubble Wall

NASA Astrophysics Data System (ADS)

Medan, Ilija; Andersson, B.-G.

2018-01-01

Optical and infrared continuum polarization is known to be due to irregular dust grains aligned with the magnetic field. This provides an important tool to probe the geometry and strength of those fields, particularly if the variations in the grain alignment efficiencies can be understood. Here, we examine polarization variations observed throughout the Local Bubble for b>30○, using a large polarization survey of the North Galactic cap from Berdyugin et al. (2014). These data are supported by archival photometric and spectroscopic data along with the mapping of the Local Bubble by Lallement et al. (2003). We can accurately model the observational data assuming that the grain alignment variations are due to the radiation from the OB associations within 1 kpc of the sun. This strongly supports radiatively driven grain alignment. We also probe the relative strength of the magnetic field in the wall of the Local Bubble using the Davis-Chandrasekhar-Fermi method. We find evidence for a bimodal field strength distribution, where the variations in the field are correlated with the variations in grain alignment efficiency, indicating that the higher strength regions might represent a compression of the wall by the interaction of the outflow in the Local Bubble and the opposing flows by the surrounding OB associations.

Constraints on the off-shell Higgs boson signal strength in the high-mass ZZ and WW final states with the ATLAS detector.

PubMed

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Tashiro, T; Tassi, E; Tavares Delgado, A; Tayalati, Y; Taylor, F E; Taylor, G N; Taylor, W; Teischinger, F A; Teixeira Dias Castanheira, M; Teixeira-Dias, P; Temming, K K; Ten Kate, H; Teng, P K; Teoh, J J; Tepel, F; Terada, S; Terashi, K; Terron, J; Terzo, S; Testa, M; Teuscher, R J; Therhaag, J; Theveneaux-Pelzer, T; Thomas, J P; Thomas-Wilsker, J; Thompson, E N; Thompson, P D; Thompson, R J; Thompson, A S; Thomsen, L A; Thomson, E; Thomson, M; Thun, R P; Tibbetts, M J; Torres, R E Ticse; Tikhomirov, V O; Tikhonov, Yu A; Timoshenko, S; Tiouchichine, E; Tipton, P; Tisserant, S; Todorov, T; Todorova-Nova, S; Tojo, J; Tokár, S; Tokushuku, K; Tollefson, K; Tolley, E; Tomlinson, L; Tomoto, M; Tompkins, L; Toms, K; Torrence, E; Torres, H; Torró Pastor, E; Toth, J; Touchard, F; Tovey, D R; Trefzger, T; Tremblet, L; Tricoli, A; Trigger, I M; Trincaz-Duvoid, S; Tripiana, M F; Trischuk, W; Trocmé, B; Troncon, C; Trottier-McDonald, M; Trovatelli, M; True, P; Trzebinski, M; Trzupek, A; Tsarouchas, C; Tseng, J C-L; Tsiareshka, P V; Tsionou, D; Tsipolitis, G; Tsirintanis, N; Tsiskaridze, S; Tsiskaridze, V; Tskhadadze, E G; Tsukerman, I I; Tsulaia, V; Tsuno, S; Tsybychev, D; Tudorache, A; Tudorache, V; Tuna, A N; Tupputi, S A; Turchikhin, S; Turecek, D; Turra, R; Turvey, A J; Tuts, P M; Tykhonov, A; Tylmad, M; Tyndel, M; Ueda, I; Ueno, R; Ughetto, M; Ugland, M; Uhlenbrock, M; Ukegawa, F; Unal, G; Undrus, A; Unel, G; Ungaro, F C; Unno, Y; Unverdorben, C; Urban, J; Urquijo, P; Urrejola, P; Usai, G; Usanova, A; Vacavant, L; Vacek, V; Vachon, B; Valderanis, C; Valencic, N; Valentinetti, S; Valero, A; Valery, L; Valkar, S; Valladolid Gallego, E; Vallecorsa, S; Valls Ferrer, J A; Van Den Wollenberg, W; Van Der Deijl, P C; van der Geer, R; van der Graaf, H; Van Der Leeuw, R; van Eldik, N; van Gemmeren, P; Van Nieuwkoop, J; van Vulpen, I; van Woerden, M C; Vanadia, M; Vandelli, W; Vanguri, R; Vaniachine, A; Vannucci, F; Vardanyan, G; Vari, R; Varnes, E W; Varol, T; Varouchas, D; Vartapetian, A; Varvell, K E; Vazeille, F; Vazquez Schroeder, T; Veatch, J; Veloso, F; Velz, T; Veneziano, S; Ventura, A; Ventura, D; Venturi, M; Venturi, N; Venturini, A; Vercesi, V; Verducci, M; Verkerke, W; Vermeulen, J C; Vest, A; Vetterli, M C; Viazlo, O; Vichou, I; Vickey, T; Vickey Boeriu, O E; Viehhauser, G H A; Viel, S; Vigne, R; Villa, M; Villaplana Perez, M; Vilucchi, E; Vincter, M G; Vinogradov, V B; Vivarelli, I; Vives Vaque, F; Vlachos, S; Vladoiu, D; Vlasak, M; Vogel, M; Vokac, P; Volpi, G; Volpi, M; von der Schmitt, H; von Radziewski, H; von Toerne, E; Vorobel, V; Vorobev, K; Vos, M; Voss, R; Vossebeld, J H; Vranjes, N; Vranjes Milosavljevic, M; Vrba, V; Vreeswijk, M; Vuillermet, R; Vukotic, I; Vykydal, Z; Wagner, P; Wagner, W; Wahlberg, H; Wahrmund, S; Wakabayashi, J; Walder, J; Walker, R; Walkowiak, W; Wang, C; Wang, F; Wang, H; Wang, H; Wang, J; Wang, J; Wang, K; Wang, R; Wang, S M; Wang, T; Wang, X; Wanotayaroj, C; Warburton, A; Ward, C P; Wardrope, D R; Warsinsky, M; Washbrook, A; Wasicki, C; Watkins, P M; Watson, A T; Watson, I J; Watson, M F; Watts, G; Watts, S; Waugh, B M; Webb, S; Weber, M S; Weber, S W; Webster, J S; Weidberg, A R; Weinert, B; Weingarten, J; Weiser, C; Weits, H; Wells, P S; Wenaus, T; Wengler, T; Wenig, S; Wermes, N; Werner, M; Werner, P; Wessels, M; Wetter, J; Whalen, K; Wharton, A M; White, A; White, M J; White, R; White, S; Whiteson, D; Wickens, F J; Wiedenmann, W; Wielers, M; Wienemann, P; Wiglesworth, C; Wiik-Fuchs, L A M; Wildauer, A; Wilkens, H G; Williams, H H; Williams, S; Willis, C; Willocq, S; Wilson, A; Wilson, J A; Wingerter-Seez, I; Winklmeier, F; Winter, B T; Wittgen, M; Wittkowski, J; Wollstadt, S J; Wolter, M W; Wolters, H; Wosiek, B K; Wotschack, J; Woudstra, M J; Wozniak, K W; Wu, M; Wu, M; Wu, S L; Wu, X; Wu, Y; Wyatt, T R; Wynne, B M; Xella, S; Xu, D; Xu, L; Yabsley, B; Yacoob, S; Yakabe, R; Yamada, M; Yamaguchi, Y; Yamamoto, A; Yamamoto, S; Yamanaka, T; Yamauchi, K; Yamazaki, Y; Yan, Z; Yang, H; Yang, H; Yang, Y; Yao, L; Yao, W-M; Yasu, Y; Yatsenko, E; Yau Wong, K H; Ye, J; Ye, S; Yeletskikh, I; Yen, A L; Yildirim, E; Yorita, K; Yoshida, R; Yoshihara, K; Young, C; Young, C J S; Youssef, S; Yu, D R; Yu, J; Yu, J M; Yu, J; Yuan, L; Yurkewicz, A; Yusuff, I; Zabinski, B; Zaidan, R; Zaitsev, A M; Zalieckas, J; Zaman, A; Zambito, S; Zanello, L; Zanzi, D; Zeitnitz, C; Zeman, M; Zemla, A; Zengel, K; Zenin, O; Ženiš, T; Zerwas, D; Zhang, D; Zhang, F; Zhang, J; Zhang, L; Zhang, R; Zhang, X; Zhang, Z; Zhao, X; Zhao, Y; Zhao, Z; Zhemchugov, A; Zhong, J; Zhou, B; Zhou, C; Zhou, L; Zhou, L; Zhou, N; Zhu, C G; Zhu, H; Zhu, J; Zhu, Y; Zhuang, X; Zhukov, K; Zibell, A; Zieminska, D; Zimine, N I; Zimmermann, C; Zimmermann, R; Zimmermann, S; Zinonos, Z; Zinser, M; Ziolkowski, M; Živković, L; Zobernig, G; Zoccoli, A; Zur Nedden, M; Zurzolo, G; Zwalinski, L

Measurements of the ZZ and WW final states in the mass range above the [Formula: see text] and [Formula: see text] thresholds provide a unique opportunity to measure the off-shell coupling strength of the Higgs boson. This paper presents constraints on the off-shell Higgs boson event yields normalised to the Standard Model prediction (signal strength) in the [Formula: see text], [Formula: see text] and [Formula: see text] final states. The result is based on pp collision data collected by the ATLAS experiment at the LHC, corresponding to an integrated luminosity of 20.3 fb[Formula: see text] at a collision energy of [Formula: see text] TeV. Using the [Formula: see text] method, the observed 95 [Formula: see text] confidence level (CL) upper limit on the off-shell signal strength is in the range 5.1-8.6, with an expected range of 6.7-11.0. In each case the range is determined by varying the unknown [Formula: see text] and [Formula: see text] background K-factor from higher-order quantum chromodynamics corrections between half and twice the value of the known signal K-factor. Assuming the relevant Higgs boson couplings are independent of the energy scale of the Higgs boson production, a combination with the on-shell measurements yields an observed (expected) 95 [Formula: see text] CL upper limit on [Formula: see text] in the range 4.5-7.5 (6.5-11.2) using the same variations of the background K-factor. Assuming that the unknown [Formula: see text] background K-factor is equal to the signal K-factor, this translates into an observed (expected) 95 [Formula: see text] CL upper limit on the Higgs boson total width of 22.7 (33.0) MeV.

Survey of long-term durability of fiberglass reinforced plastic structures

NASA Technical Reports Server (NTRS)

Lieblein, S.

1981-01-01

Included are fluid containment vessels, marine structures, and aircraft components with up to 19 years of service. Correlations were obtained for the variation of static fatigue strength, cyclic fatigue strength, and residual burst strength for pressure vessels. In addition, data are presented for the effects of moisture on strength retention. Data variations were analyzed, and relationships and implications for testing are discussed. Change in strength properties for complete structures was examined for indications of the effects of environmental conditions such as moisture and outdoor exposure (ultraviolet radiation, weathering) on long term durability.

Does It Matter where We Live?: The Urban Psychology of Character Strengths

ERIC Educational Resources Information Center

Park, Nansook; Peterson, Christopher

2010-01-01

Psychology has neglected the study of variation across cities. An urban psychology is needed that takes seriously such variation and focuses on strengths and assets contributing to the good life as much as on problems of urbanization. To illustrate the value of an urban psychology, we describe studies of character strengths among residents in the…

Thermoplastic composites for veneering posterior teeth-a feasibility study.

PubMed

Gegauff, Anthony G; Garcia, Jose L; Koelling, Kurt W; Seghi, Robert R

2002-09-01

This pilot study was conducted to explore selected commercially-available thermoplastic composites that potentially had physical properties superior to currently available dental systems for restoring esthetic posterior crowns. Polyurethane, polycarbonate, and poly(ethylene/tetrafluoroethylene) (ETFE) composites and unfilled polyurethane specimens were injection molded to produce shapes adaptive to five standardized mechanical tests. The mechanical testing included abrasive wear rate, yield strength, apparent fracture toughness (strength ratio), flexural strength, and compressive strength. Compared to commercially available dental composites, abrasion wear rates were lower for all materials tested, yield strength was greater for the filled polycarbonates and filled polyurethane resins, fracture toughness testing was invalid (strength ratios were calculated for comparison of the pilot test materials), flexural strength was roughly similar except for the filled ETFE which was significantly greater, and compressive strength was lower. Commercially available thermoplastic resin composites, such as polyurethane, demonstrate the potential for development of an artificial crown material which exceeds the mechanical properties of currently available esthetic systems, if compressive strength can be improved.

Effect of moisture content on dowel-bearing strength

Treesearch

Douglas R. Rammer; Steve G. Winistorfer

2001-01-01

Dowel bearing strength (embedment strength) is a critical component of wood connection design. Previous tests have concentrated on defining the relationship between dowel-bearing strength, specific gravity, and fastener characteristics such as diameter. However, because adoption of yield theory in defining connection strength is relatively new in the United States, few...

49 CFR 195.306 - Test medium.

Code of Federal Regulations, 2010 CFR

2010-10-01

... which produces a hoop stress of 50 percent of specified minimum yield strength; (3) The test section is... pressure is equal to or greater than a pressure that produces a hoop stress of 50 percent of specified minimum yield strength; (3) The maximum hoop stress during the test does not exceed 80 percent of...

49 CFR 195.306 - Test medium.

Code of Federal Regulations, 2012 CFR

2012-10-01

... which produces a hoop stress of 50 percent of specified minimum yield strength; (3) The test section is... pressure is equal to or greater than a pressure that produces a hoop stress of 50 percent of specified minimum yield strength; (3) The maximum hoop stress during the test does not exceed 80 percent of...

Effect of Nb on microstructure and yield strength of a high temperature tempered martensitic steel

NASA Astrophysics Data System (ADS)

Wang, Qian; Sun, Yu; Zhang, Chuanyou; Wang, Qingfeng; Zhang, Fucheng

2018-04-01

Martensitic steels based on a composition of 25CrMo47NbVTi with different concentrations of Nb (0.003%–0.060%) were quenched (Q) at 900 °C and tempered (T) at 700 °C to obtain oil country tubular goods (OCTG) with higher yield strength. The precipitation and microstructures were characterized and quantified by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and x-ray diffraction (XRD). The results show that the increased Nb content led to an enhanced overall precipitation, the rising solution-precipitation temperature, the increased mass or volume fraction of the Nb-containing precipitates, and the decreased average diameter of Nb-containing particles. With the enhanced precipitation of small sized Nb-containing particles, the austenite grain and corresponding martensitic packet and block were evidently refined. In addition, the dislocation density increased slightly with increasing Nb addition. The yield strength was experimentally measured and quantitatively estimated. The findings based on theoretical calculations indicated that as a consequence of intensified strengthening from grain boundaries, precipitates and dislocations, the yield strength was enhanced significantly by Nb addition.

Tribology behavior on scratch tests: Effects of yield strength

DOE PAGES

Feng, Biao

2017-03-07

In this paper, a three-dimensional (3D) scratch model is proposed to investigate the effects of yield strength of both coatings and substrates. With the help of combined Coulomb and plastic friction, the obtained results comprehensively interpret the experimental phenomena in most metals that with the growth of hardness after heat treatment the scratch friction coefficient (SFC) increases. This interpretation could not be done before. Scratch tests on the surface with or without the coating are discussed. Without the coating the SFC increases due to the decrease of the area with plastic slippage and/or the increase of friction stress during themore » increase of the yield strength in the material. With a softer substrate the friction stress decreases but the SFC increases, which is caused by the growth of the entire contact area and surface deformation. Conversely, with a stronger substrate the SFC decreases due to an intensified plastic slippage In conclusion, the obtained results pave a new way to understanding the effects of yield strength on scratch tests, interpret experimental phenomena, and should be helpful for an optimum design in experiments.« less

Tribology behavior on scratch tests: Effects of yield strength

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Biao

In this paper, a three-dimensional (3D) scratch model is proposed to investigate the effects of yield strength of both coatings and substrates. With the help of combined Coulomb and plastic friction, the obtained results comprehensively interpret the experimental phenomena in most metals that with the growth of hardness after heat treatment the scratch friction coefficient (SFC) increases. This interpretation could not be done before. Scratch tests on the surface with or without the coating are discussed. Without the coating the SFC increases due to the decrease of the area with plastic slippage and/or the increase of friction stress during themore » increase of the yield strength in the material. With a softer substrate the friction stress decreases but the SFC increases, which is caused by the growth of the entire contact area and surface deformation. Conversely, with a stronger substrate the SFC decreases due to an intensified plastic slippage In conclusion, the obtained results pave a new way to understanding the effects of yield strength on scratch tests, interpret experimental phenomena, and should be helpful for an optimum design in experiments.« less

Yield stress and scaling of polyelectrolyte multilayer modified suspensions: effect of polyelectrolyte conformation during multilayer assembly.

PubMed

Hess, Andreas; Aksel, Nuri

2013-09-10

The yield stress of polyelectrolyte multilayer modified suspensions exhibits a surprising dependence on the polyelectrolyte conformation of multilayer films. The rheological data scale onto a universal master curve for each polyelectrolyte conformation as the particle volume fraction, φ, and the ionic strength of the background fluid, I, are varied. It is shown that rough films with highly coiled, brushy polyelectrolytes significantly enhance the yield stress. Moreover, via the ionic strength I of the background fluid, the dynamic yield stress of brushy polyelectrolyte multilayers can be finely adjusted over 2 decades.

Biomechanical monitoring of healing bone based on acoustic emission technology.

PubMed

Hirasawa, Yasusuke; Takai, Shinro; Kim, Wook-Cheol; Takenaka, Nobuyuki; Yoshino, Nobuyuki; Watanabe, Yoshinobu

2002-09-01

Acoustic emission testing is a well-established method for assessment of the mechanical integrity of general construction projects. The purpose of the current study was to investigate the usefulness of acoustic emission technology in monitoring the yield strength of healing callus during external fixation. Thirty-five patients with 39 long bones treated with external fixation were evaluated for fracture healing by monitoring load for the initiation of acoustic emission signal (yield strength) under axial loading. The major criteria for functional bone union based on acoustic emission testing were (1) no acoustic emission signal on full weightbearing, and (2) a higher estimated strength than body weight. The yield strength monitored by acoustic emission testing increased with the time of healing. The external fixator could be removed safely and successfully in 97% of the patients. Thus, the acoustic emission method has good potential as a reliable method for monitoring the mechanical status of healing bone.

Optimizing the coupled effects of Hall-Petch and precipitation strengthening in a Al 0.3 CoCrFeNi high entropy alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gwalani, B.; Soni, Vishal; Lee, Michael

2017-05-01

A successful demonstration of applying integrated strengthening using Hall-Petch strengthening (grains size effect) and precipitation strengthening is shown in the fcc based high entropy alloy (HEA) Al0.3CoCrFeNi, leading to quantitative determinations of the Hall-Petch coefficients for both hardness and tensile yield strength, aswell as the enhancements in the yield strength fromtwo distinct types of ordered precipitates, L12 and B2. An excellent combination of yield strength (~490MPa), ultimate tensile strength (~850MPa), and ductility (~45% elongation) was achieved by optimizing and coupling both strengtheningmechanisms, resulting from a refined grain size as well as both L12 and B2 ordered precipitates. This opens upmore » new avenues for the future development of HEAs, with the appropriate balance of properties required for engineering applications.« less

Influence of layer charge and charge distribution of smectites on the flow behaviour and swelling of bentonites

USGS Publications Warehouse

Christidis, G.E.; Blum, A.E.; Eberl, D.D.

2006-01-01

The influence of layer charge and charge distribution of dioctahedral smectites on the rheological and swelling properties of bentonites is examined. Layer charge and charge distribution were determined by XRD using the LayerCharge program [Christidis, G.E., Eberl, D.D., 2003. Determination of layer charge characteristics of smectites. Clays Clay Miner. 51, 644-655.]. The rheological properties were determined, after sodium exchange using the optimum amount of Na2CO3, from free swelling tests. Rheological properties were determined using 6.42% suspensions according to industrial practice. In smectites with layer charges of - 0.425 to - 0.470 per half formula unit (phfu), layer charge is inversely correlated with free swelling, viscosity, gel strength, yield strength and thixotropic behaviour. In these smectites, the rheological properties are directly associated with the proportion of low charge layers. By contrast, in low charge and high charge smectites there is no systematic relation between layer charge or the proportion of low charge layers and rheological properties. However, low charge smectites yield more viscous suspensions and swell more than high charge smectites. The rheological properties of bentonites also are affected by the proportion of tetrahedral charge (i.e. beidellitic charge), by the existence of fine-grained minerals having clay size, such as opal-CT and to a lesser degree by the ionic strength and the pH of the suspension. A new method for classification of smectites according to the layer charge based on the XRD characteristics of smecites is proposed, that also is consistent with variations in rheological properties. In this classification scheme the term smectites with intermediate layer charge is proposed. ?? 2006 Elsevier B.V. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aad, G.; Abbott, B.; Abdallah, J.

Measurements of the ZZ and WW final states in the mass range above the 2m Z and 2m W thresholds provide a unique opportunity to measure the off-shell coupling strength of the Higgs boson. This paper presents constraints on the off-shell Higgs boson event yields normalised to the Standard Model prediction (signal strength) in the ZZ→4ℓ, ZZ→2ℓ2ν and WW→eνμν final states. The result is based on pp collision data collected by the ATLAS experiment at the LHC, corresponding to an integrated luminosity of 20.3 fb -1 at a collision energy of √s=8 TeV. Using the CL s method, the observedmore » 95 %% confidence level (CL) upper limit on the off-shell signal strength is in the range 5.1–8.6, with an expected range of 6.7–11.0. In each case the range is determined by varying the unknown gg→ZZ and gg→WW background K-factor from higher-order quantum chromodynamics corrections between half and twice the value of the known signal K-factor. Assuming the relevant Higgs boson couplings are independent of the energy scale of the Higgs boson production, a combination with the on-shell measurements yields an observed (expected) 95 % CL upper limit on ΓH/Γ SM H in the range 4.5–7.5 (6.5–11.2) using the same variations of the background K-factor. Assuming that the unknown gg→VV background K-factor is equal to the signal K-factor, this translates into an observed (expected) 95 % CL upper limit on the Higgs boson total width of 22.7 (33.0) MeV.« less

Modeling the Transformational Communications System Urban Land Mobile Satellite Channel

DTIC Science & Technology

2007-12-01

interference of time - delayed signals). The “slow” variations are usually associated with specific shadowing events by foliage, terrain or buildings. The...by F. P. Fontan et al. [24].......................11 Figure 4. Short, medium and long-term variation of signal strength with time . Long- term...long-term variation of signal strength with time . Long- term (“very slow”) variation is modeled by state transitions shown in Figure 3. C

The effect of microstructure on the deformation modes and mechanical properties of Ti-6Al-2Nb-1Ta-0.8Mo: Part II. Equiaxed structures

NASA Astrophysics Data System (ADS)

Lin, Fu-Shiong; Starke, E. A.; Gysler, A.

1984-10-01

The Ti-6Al-2Nb-lTa-0.8Mo alloy was processed to develop both near-basal and transverse textures. Samples were annealed at different temperatures to vary the equiaxed alpha grain size and the thick-ness of the grain boundary beta, and subsequently quenched in order to transform the beta phase to either martensite, tempered martensite, or Widmanstätten alpha + beta. The effect of microstructure and texture on tensile properties and on fracture toughness was investigated. In addition, yield locus diagrams were constructed in order to study the texture strengthening effect. The yield strength was found to be strongly dependent on the thickness and Burgers relationship of the transformed beta phase surrounding the alpha grains. A texture hardening effect as large as 60 pct was found for the basal-texture material but only 15 pct for the transverse texture material. These variations are asso-ciated with differences in deformation behavior.

Satellite-based studies of maize yield spatial variations and their causes in China

NASA Astrophysics Data System (ADS)

Zhao, Y.

2013-12-01

Maize production in China has been expanding significantly in the past two decades, but yield has become relatively stagnant in the past few years, and needs to be improved to meet increasing demand. Multiple studies found that the gap between potential and actual yield of maize is as large as 40% to 60% of yield potential. Although a few major causes of yield gap have been qualitatively identified with surveys, there has not been spatial analysis aimed at quantifying relative importance of specific biophysical and socio-economic causes, information which would be useful for targeting interventions. This study analyzes the causes of yield variation at field and village level in Quzhou county of North China Plain (NCP). We combine remote sensing and crop modeling to estimate yields in 2009-2012, and identify fields that are consistently high or low yielding. To establish the relationship between yield and potential factors, we gather data on those factors through a household survey. We select targeted survey fields such that not only both extremes of yield distribution but also all soil texture categories in the county is covered. Our survey assesses management and biophysical factors as well as social factors such as farmers' access to agronomic knowledge, which is approximated by distance to the closest demonstration plot or 'Science and technology backyard'. Our survey covers 10 townships, 53 villages and 180 fields. Three to ten farmers are surveyed depending on the amount of variation present among sub pixels of each field. According to survey results, we extract the amount of variation within as well as between villages and or soil type. The higher within village or within field variation, the higher importance of management factors. Factors such as soil type and access to knowledge are more represented by between village variation. Through regression and analysis of variance, we gain more quantitative and thorough understanding of causes to yield variation at village scale, which further explains the gap between average and highest achieved yield.

Temperature effects on the mechanical properties of annealed and HERF 304L stainless steel.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Antoun, Bonnie R.

2004-11-01

The effect of temperature on the tensile properties of annealed 304L stainless steel and HERF 304L stainless steel forgings was determined by completing experiments over the moderate range of -40 F to 160 F. Temperature effects were more significant in the annealed material than the HERF material. The tensile yield strength of the annealed material at -40 F averaged twenty two percent above the room temperature value and at 160 F averaged thirteen percent below. The tensile yield strength for the three different geometry HERF forgings at -40 F and 160 F changed less than ten percent from room temperature.more » The ultimate tensile strength was more temperature dependent than the yield strength. The annealed material averaged thirty six percent above and fourteen percent below the room temperature ultimate strength at -40 F and 160 F, respectively. The HERF forgings exhibited similar, slightly lower changes in ultimate strength with temperature. For completeness and illustrative purposes, the stress-strain curves are included for each of the tensile experiments conducted. The results of this study prompted a continuation study to determine tensile property changes of welded 304L stainless steel material with temperature, documented separately.« less

Mechanical and low-cycle fatigue behavior of stainless reinforcing steel for earthquake engineering applications

NASA Astrophysics Data System (ADS)

Zhou, Yihui; Ou, Yu-Chen; Lee, George C.; O'Connor, Jerome S.

2010-09-01

Use of stainless reinforcing steel (SRS) in reinforced concrete (RC) structures is a promising solution to corrosion issues. However, for SRS to be used in seismic applications, several mechanical properties need to be investigated. These include specified and actual yield strengths, tensile strengths, uniform elongations and low-cycle fatigue behavior. Three types of SRSs (Talley S24100, Talley 316LN and Talley 2205) were tested and the results are reported in this paper. They were compared with the properties of A706 carbon reinforcing steel (RS), which is typical for seismic applications, and MMFX II, which is a high strength, corrosion resistant RS. Low-cycle fatigue tests of the RS coupons were conducted under strain control with constant amplitude to obtain strain life models of the steels. Test results show that the SRSs have slightly lower moduli of elasticity, higher uniform elongations before necking, and better low-cycle fatigue performance than A706 and MMFX II. All five types of RSs tested satisfy the requirements of the ACI 318 code on the lower limit of the tensile to yield strength ratio. Except Talley 2205, the other four types of RSs investigated meet the ACI 318 requirement that the actual yield strength does not exceed the specified yield strength by more than 18 ksi (124 MPa). Among the three types of SRSs tested, Talley S24100 possesses the highest uniform elongation before necking, and the best low-cycle fatigue performance.

Hardness - Yield Strength Relation of Al-Mg-Si Alloys

NASA Astrophysics Data System (ADS)

Praveen Sekhar, Aluru; Nandy, Supriya; Ray, Kalyan Kumar; Das, Debdulal

2018-03-01

Assessing the mechanical properties of materials through indentation hardness test is an attractive method, rather than obtaining the properties through destructive approach like tensile testing. The present work emphasizes on the relation between hardness and yield strength of Al-Mg-Si alloys considering Tabor type equations. Al-0.5Mg-0.4Si alloy has been artificially aged at various temperatures (100 to 250 °C) for different time durations (0.083 to 1000 h) and the ageing response has been assessed by measuring the Vickers hardness and yield strength. Correlations of the existing data from the open literature have also been reviewed. Lastly, it has been explained that the deviation in obtained relation from Tabor’s equation is owing to the dislocation accumulation during indentation.

The Effect of Artificial Aging on the Tensile Properties of Alclad 24S-T and 24S-T Aluminum Alloy

NASA Technical Reports Server (NTRS)

Kotanchik, Joseph N.; Woods, Walter; Zender, George W.

1943-01-01

An experimental study was made to determine the effect of artificial aging on the tensile properties of alclad 24S-T and 24S-T aluminum-alloy sheet material. The results of the tests show that certain combinations of aging time and temperature cause a marked increase in the yield strength and a small increase in the ultimate strength; these increases are accompanied by a very large decrease in elongation. A curve is presented that shows the maximum yield strengths that can be obtained by aging this material at various combinations of time and temperature. The higher values of yield stress are obtained in material aged at relatively longer times and lower temperatures.

Variation of inulin content, inulin yield and water use efficiency for inulin yield in Jerusalem artichoke genotypes under different water regimes

USDA-ARS?s Scientific Manuscript database

The information on genotypic variation for inulin content, inulin yield and water use efficiency of inulin yield (WUEi) in response to drought is limited. This study was to investigate the genetic variability in inulin content, inulin yield and WUEi of Jerusalem artichoke (Helianthus tuberosus L.) ...

Variation in work tasks in relation to pinch grip strength among middle-aged female dentists.

PubMed

Ding, Hebo; Leino-Arjas, Päivi; Murtomaa, Heikki; Takala, Esa-Pekka; Solovieva, Svetlana

2013-11-01

We aimed to investigate the relationship of task variation during dental work history with pinch grip strength among dentists. We measured pinch grip strength among 295 female Finnish dentists aged 45-63 years. Variation in dental work tasks during work history was empirically defined by cluster analysis. Three clusters of task variation emerged: low (most work time in restoration treatment/endodontics), moderate (about 50% in the former and 50% in prosthodontics/periodontics/surgery), and high (variable tasks including administrative duties). Hand radiographs were examined for the presence of OA in the wrist and each joint of the 1-3rd fingers. Information on hand-loading leisure-time activities, and joint pain was obtained by questionnaire. Glove size was used as a proxy for hand size. BMI (kg/m2) was based on measured weight and self-reported height. Dentists with low variation of work task history had an increased risk of low pinch grip strength in the right hand (OR 2.3, 95% CI 1.2-4.3), but not in the left (1.13, 0.62-2.08), compared to dentists with high task variation, independent of age, hand size, hand-loading leisure-time activities, BMI and symptomatic hand OA. The dentists with the most hand-loading tasks were at an increased risk of low pinch grip strength, independent of e.g. symptomatic hand OA. It is advisable among dentists to perform as diverse work tasks as possible to reduce the risk of decreased pinch grip strength. Copyright © 2013 Elsevier Ltd and The Ergonomics Society. All rights reserved.

The stress-strain relationships in wood and fiber-reinforced plastic laminae of reinforced glued-laminated wood beams

NASA Astrophysics Data System (ADS)

Tingley, Daniel Arthur

The reinforcement of wood and wood composite structural products to improve their mechanical properties has been in practice for many years. Recently, the use of high-strength fiber-reinforced plastic (FRP) as a reinforcement in such applications has been commercialized. The reinforcement is manufactured using a standard pultrusion process or alternatively a sheet-forming process commonly referred to as "pulforming". The high-modulus fibers are predominately unidirectional, although off-axis fibers are often used to enhance off-axis properties. The fibers used are either of a single type or multiple types, which are called "hybrids". Unidirectional, single, and hybrid fiber FRP physical properties and characteristics were compared to wood. Full-scale reinforced glulams were tested. Aramid-reinforced plastics (ARP) used as tensile reinforcements were found to be superior in strength applications to other types of FRP made with fiber, such as carbon and fiberglass. Carbon/aramid-reinforced plastic (CARP) was shown to be superior in both modulus and strength design situations. Fiberglass was shown to be suitable only in hybrid situations with another fiber such as aramid or carbon and only in limited use situations where modulus was a design criteria. The testing and analysis showed that the global response of reinforced glulam beams is controlled by localized strength variations in the wood such as slope of grain, knots, finger joints, etc. in the tensile zone. The elemental tensile strains in the extreme wood tensile laminae, due to global applied loads, were found to be well below the strain at failure in clear wood samples recovered from the failure area. Two areas affecting the relationship between the wood and the FRP were investigated: compatibility of the wood and FRP materials and interface characteristics between the wood and FRP. The optimum strain value at yield point for an FRP was assessed to be slightly higher than the clear wood value in tension for a species/grade to be reinforced. The effects of localized strength variations in the tensile wood laminae adjacent to the FRP were found to be the predominate cause of failure in full-scale reinforced glulams with less than 1.5% by cross section reinforcement.

Peat soil properties and erodibility: what factors affect erosion and suspended sediment yields in peat extraction areas?

NASA Astrophysics Data System (ADS)

Tuukkanen, Tapio; Marttila, Hannu; Kløve, Bjørn

2014-05-01

Peatland drainage and peat extraction operations change soil properties and expose bare peat to erosion forces, resulting in increased suspended sediment (SS) loads to downstream water bodies. SS yields from peat extraction areas are known to vary significantly between sites, but the contribution of peat properties and catchment characteristics to this variation is not well understood. In this study, we investigated peat erosion at 20 Finnish peat extraction sites by conducting in situ and laboratory measurements on peat erodibility and associated peat properties (degree of humification, peat type, bulk density, loss on ignition, porosity, moisture content, and shear strength), and by comparing the results with monitored long-term SS concentrations and loads at each catchment outlet. Here, we used a cohesive strength meter (CSM) to measure direct erosion thresholds for undisturbed soil cores collected from each study site. The results suggested that the degree of peat decomposition clearly affects peat erodibility and explains much of the variation in SS concentration between the study sites. According to CSM tests, critical shear stresses for particle entrainment were lowest (on average) in well-decomposed peat samples, while undecomposed, dry and fiber rich peat generally resisted erosion very well. Furthermore, the results indicated that two separate critical shear stresses often exist in moderately decomposed peat. In these cases, the well-decomposed parts of peat samples eroded first at relatively low shear stresses and remaining peat fibers prevented further erosion until a much higher shear stress was reached. In addition to peat soil properties, the study showed that the erosion of mineral subsoil may play a key role in runoff water SS concentration at peat extraction areas with drainage ditches extending into the mineral soil. The interactions between peat properties and peat erodibility found in this study as well as critical shear stress values obtained can be used for several purposes in e.g. water conservation and sediment management planning for peat extraction areas and other bare peat-covered catchments.

Flow Strength of Shocked Aluminum in the Solid-Liquid Mixed Phase Region

NASA Astrophysics Data System (ADS)

Reinhart, William

2011-06-01

Shock waves have been used to determine material properties under high shock stresses and very-high loading rates. The determination of mechanical properties such as compressive strength under shock compression has proven to be difficult and estimates of strength have been limited to approximately 100 GPa or less in aluminum. The term ``strength'' has been used in different ways. For a Von-Mises solid, the yield strength is equal to twice the shear strength of the material and represents the maximum shear stress that can be supported before yield. Many of these concepts have been applied to materials that undergo high strain-rate dynamic deformation, as in uni-axial strain shock experiments. In shock experiments, it has been observed that the shear stress in the shocked state is not equal to the shear strength, as evidenced by elastic recompressions in reshock experiments. This has led to an assumption that there is a yield surface with maximum (loading)and minimum (unloading), shear strength yet the actual shear stress lies somewhere between these values. This work provides the first simultaneous measurements of unloading velocity and flow strength for transition of solid aluminum to the liquid phase. The investigation describes the flow strength observed in 1100 (pure), 6061-T6, and 2024 aluminum in the solid-liquid mixed phase region. Reloading and unloading techniques were utilized to provide independent data on the two unknowns (τc and τo) , so that the actual critical shear strength and the shear stress at the shock state could be estimated. Three different observations indicate a change in material response for stresses of 100 to 160 GPa; 1) release wave speed (reloading where applicable) measurements, 2) yield strength measurements, and 3) estimates of Poisson's ratio, all of which provide information on the melt process including internal consistency and/or non-equilibrium and rate-dependent melt behavior. The study investigates the strength properties in the solid region and as the material transverses the solid-mixed-liquid regime. Differences observed appear to be the product of alloying and/or microstructural composition of the aluminum. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

Lithospheric strength variations as a control on new plate boundaries: examples from the northern Red Sea region

NASA Astrophysics Data System (ADS)

Steckler, Michael S.; ten Brink, Uri S.

1986-08-01

The complex plate boundary between Arabia and Africa at the northern end of the Red Sea includes the Gulf of Suez rift and the Gulf of Aqaba—Dead Sea transform. Geologic evidence indicates that during the earliest phase of rifting the Red Sea propagated NNW towards the Mediterranean Sea creating the Gulf of Suez. Subsequently, the majority of the relative movement between the plates shifted eastward to the Dead Sea transform. We propose that an increase in the strength of the lithosphere across the Mediterranean continental margin acted as a barrier to the propagation of the rift. A new plate boundary, the Dead Sea transform formed along a zone of minimum strength. We present an analysis of lithospheric strength variations across the Mediterranean continental margin. The main factors controlling these variations are the geotherm, crustal thickness and composition, and sediment thickness. The analysis predicts a characteristic strength profile at continental margins which consists of a marked increase in strength seaward of the hinge zone and a strength minimum landward of the hinge zone. This strength profile also favors the creation of thin continental slivers such as the Levant west of the Dead Sea transform and the continental promontory containing Socotra Island at the mouth of the Gulf of Aden. Calculations of strength variations based on changes of crustal thickness, geotherm and sediment thickness can be extended to other geologic settings as well. They can explain the location of rerifting events at intracratonic basins, of backarc basins and of major continental strike-slip zones.

Stochastic metallic-glass cellular structures exhibiting benchmark strength.

PubMed

Demetriou, Marios D; Veazey, Chris; Harmon, John S; Schramm, Joseph P; Johnson, William L

2008-10-03

By identifying the key characteristic "structural scales" that dictate the resistance of a porous metallic glass against buckling and fracture, stochastic highly porous metallic-glass structures are designed capable of yielding plastically and inheriting the high plastic yield strength of the amorphous metal. The strengths attainable by the present foams appear to equal or exceed those by highly engineered metal foams such as Ti-6Al-4V or ferrous-metal foams at comparable levels of porosity, placing the present metallic-glass foams among the strongest foams known to date.

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.

Environmental Effects on Long Term Displacement Data of Woven Fabric Webbings Under Constant Load for Inflatable Structures

NASA Technical Reports Server (NTRS)

Kenner, WInfred S.; Jones, Thomas C.; Doggett, William R.; Duncan, Quinton; Plant, James

2015-01-01

An experimental study of the effects of environmental temperature and humidity conditions on long-term creep displacement data of high strength Kevlar and VectranTM woven fabric webbings under constant load for inflatable structures is presented. The restraint layer of an inflatable structure for long-duration space exploration missions is designed to bear load and consists of an assembly of high strength webbings. Long-term creep displacement data of webbings can be utilized by designers to validate service life parameters of restraint layers of inflatable structures. Five groups of high-strength webbings were researched over a two year period. Each group had a unique webbing length, load rating, applied load, and test period. The five groups consisted of 1.) 6K Vectran webbings loaded to 49% ultimate tensile strength (UTS), 2.) 6K Vectran webbings loaded to 55% UTS, 3.) 12.5K Vectran webbings loaded to 22% UTS, 4.) 6K Kevlar webbings loaded to 40% and 43% UTS, and 5.) 6K Kevlar webbings loaded to 48% UTS. Results show that all webbing groups exhibit the initial two stages of three of a typical creep curve of an elastic material. Results also show that webbings exhibit unique local wave patterns over the duration of the test period. Data indicate that the local pattern is primarily generated by daily variations in relative humidity values within the test facility. Data indicate that after a three to six month period, where webbings reach a steady-state creep condition, an annual sinusoidal displacement pattern is exhibited, primarily due to variations in annual mean temperature values. Data indicates that variations in daily temperature values and annual mean humidity values have limited secondary effects on creep displacement behavior. Results show that webbings in groups 2 and 5 do not exhibit well defined annual displacement patterns because the magnitude of the applied loads cause large deformations, and data indicate that material yielding within a webbing tends to neutralize the annual sinusoidal displacement pattern. Study indicates that applied load, environmental effects, mechanical strength, coefficient of thermal expansion, and hygroscopic properties of webbings are fundamental requirements for quantifying accurate creep displacements and behaviors over multiple year time periods. Results from a study of the environmental effects on long-term creep displacement data of Kevlar and Vectran woven webbings are presented to increase the knowledge base of webbing materials and to enhance designs of inflatable space structures for long-duration space missions.

Spherical Nanoindentation Stress-Strain Measurements of BOR-60 14YWT-NFA1 Irradiated Tubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weaver, Jordan; Carvajal Nunez, Ursula; Krumwiede, David

Spherical nanoindentation stress-strain protocols were applied to characterize unirradiated and fast neutron irradiated nanostructured ferritic alloy (NFA) 14YWT and compared against Berkovich nanohardness and available tensile data. The predicted uniaxial yield strength from spherical, 100 and 5 micron radii, indentation yield strength measurements was 1100-1400 MPa which compares well with the predictions from Berkovich nanohardness, 1200 MPa, and available tensile data, ~1100 MPa. However, spherical indentation measurements predict an increase in the uniaxial yield strength of ~1 GPa while Berkovich nanohardness measurements predict an increase of only ~250 MPa. No tensile data exists on the irradiated condition. It is believedmore » the difference in the predicted uniaxial yield strength between spherical and Berkovich nanoindentation are due to a low number of tests on the irradiated sample combined with the significant heterogeneity in the microstructure, the differences in sensitivity to sample preparation on the irradiated sample between the two indentation protocols , and/or in how strain localizes under the indenter with the possibility of dislocation channeling under Berkovich hardness indents leading to strain softening. Nanoindentation capabilities to test neutron irradiated samples in a radiological area were realized.« less

The role of grain size and shape in the strengthening of dispersion hardened nickel alloys

NASA Technical Reports Server (NTRS)

Wilcox, B. A.; Clauer, A. H.

1972-01-01

Thermomechanical processing was used to develop various microsstructures in Ni, Ni-2ThO2, Ni-20Cr, Ni-20CR-2ThO2, Ni-20Cr-10W-and Ni-20Cr-10W-2ThO2. The yield strength at 25 C increased with substructure refinement according to the Hall-Petch relation, and substructure refinement was a much more potent means of strengthening than was dispersion hardening. At elevated temperature (1093 C), the most important microstructural feature affecting strength was the grain aspect ratio (grain length, L, divided by grain width, 1. The yield strength and creep strength increased linearly with increasing L/1.

Impact of surface porosity and topography on the mechanical behavior of high strength biomedical polymers.

PubMed

Evans, Nathan T; Irvin, Cameron W; Safranski, David L; Gall, Ken

2016-06-01

The ability to control the surface topography of orthopedic implant materials is desired to improve osseointegration but is often at the expense of mechanical performance in load bearing environments. Here we investigate the effects of surface modifications, roughness and porosity, on the mechanical properties of a set of polymers with diverse chemistry and structure. Both roughness and surface porosity resulted in samples with lower strength, failure strain and fatigue life due to stress concentrations at the surface; however, the decrease in ductility and fatigue strength were greater than the decrease in monotonic strength. The fatigue properties of the injection molded polymers did not correlate with yield strength as would be traditionally observed in metals. Rather, the fatigue properties and the capacity to maintain properties with the introduction of surface porosity correlated with the fracture toughness of the polymers. Polymer structure impacted the materials relative capacity to maintain monotonic and cyclic properties in the face of surface texture and porosity. Generally, amorphous polymers with large ratios of upper to lower yield points demonstrated a more significant drop in ductility and fatigue strength with the introduction of porosity compared to crystalline polymers with smaller ratios in their upper to lower yield strength. The latter materials have more effective dissipation mechanisms to minimize the impact of surface porosity on both monotonic and cyclic damage. Copyright © 2016 Elsevier Ltd. All rights reserved.

The effect of yield strength and ductility to fatigue damage

NASA Technical Reports Server (NTRS)

Yeh, H. Y.

1973-01-01

The cumulative damage of aluminium alloys with different yield strength and various ductility due to seismic loads was studied. The responses of an idealized beam with a centered mass at one end and fixed at the other end to El Centro's and Taft's earthquakes are computed by assuming that the alloys are perfectly elastoplastic materials and by using numerical technique. Consequently, the corresponding residual plastic strain can be obtained from the stress-strain relationship. The revised Palmgren-Miner cumulative damage theorem is utilized to calculate the fatigue damage. The numerical results show that in certain cases, the high ductility materials are more resistant to seismic loads than the high yield strength materials. The results also show that if a structure collapse during the earthquake, the collapse always occurs in the very early stage.

F2 layer characteristics and electrojet strength over an equatorial station

NASA Astrophysics Data System (ADS)

Adebesin, B. O.; Adeniyi, J. O.; Adimula, I. A.; Reinisch, B. W.; Yumoto, K.

2013-09-01

The data presented in this work describes the diurnal and seasonal variation in hmF2, NmF2, and the electrojet current strength over an African equatorial station during a period of low solar activity. The F2 region horizontal magnetic element H revealed that the Solar quiet Sq(H) daily variation rises from early morning period to maximum around local noon and falls to lower values towards evening. The F2 ionospheric current responsible for the magnetic field variations is inferred to build up at the early morning hours, attaining maximum strength around 1200 LT. The Sq variation across the entire months was higher during the daytime than nighttime. This is ascribed to the variability of the ionospheric parameters like conductivity and winds structure in this region. Seasonal daytime electrojet (EEJ) current strength for June solstice, March and September equinoxes, respectively had peak values ranging within 27-35 nT (at 1400 LT) , 30-40 nT (at 1200 LT) and 35-45 nT (at 1500 LT). The different peak periods of the EEJ strength were attributed to the combined effects of the peak electron density and electric field. Lastly, the EEJ strength was observed to be higher during the equinoxes than the solstice period.

Terapascal static pressure generation with ultrahigh yield strength nanodiamond.

PubMed

Dubrovinskaia, Natalia; Dubrovinsky, Leonid; Solopova, Natalia A; Abakumov, Artem; Turner, Stuart; Hanfland, Michael; Bykova, Elena; Bykov, Maxim; Prescher, Clemens; Prakapenka, Vitali B; Petitgirard, Sylvain; Chuvashova, Irina; Gasharova, Biliana; Mathis, Yves-Laurent; Ershov, Petr; Snigireva, Irina; Snigirev, Anatoly

2016-07-01

Studies of materials' properties at high and ultrahigh pressures lead to discoveries of unique physical and chemical phenomena and a deeper understanding of matter. In high-pressure research, an achievable static pressure limit is imposed by the strength of available strong materials and design of high-pressure devices. Using a high-pressure and high-temperature technique, we synthesized optically transparent microballs of bulk nanocrystalline diamond, which were found to have an exceptional yield strength (~460 GPa at a confining pressure of ~70 GPa) due to the unique microstructure of bulk nanocrystalline diamond. We used the nanodiamond balls in a double-stage diamond anvil cell high-pressure device that allowed us to generate static pressures beyond 1 TPa, as demonstrated by synchrotron x-ray diffraction. Outstanding mechanical properties (strain-dependent elasticity, very high hardness, and unprecedented yield strength) make the nanodiamond balls a unique device for ultrahigh static pressure generation. Structurally isotropic, homogeneous, and made of a low-Z material, they are promising in the field of x-ray optical applications.

Terapascal static pressure generation with ultrahigh yield strength nanodiamond

PubMed Central

Dubrovinskaia, Natalia; Dubrovinsky, Leonid; Solopova, Natalia A.; Abakumov, Artem; Turner, Stuart; Hanfland, Michael; Bykova, Elena; Bykov, Maxim; Prescher, Clemens; Prakapenka, Vitali B.; Petitgirard, Sylvain; Chuvashova, Irina; Gasharova, Biliana; Mathis, Yves-Laurent; Ershov, Petr; Snigireva, Irina; Snigirev, Anatoly

2016-01-01

Studies of materials’ properties at high and ultrahigh pressures lead to discoveries of unique physical and chemical phenomena and a deeper understanding of matter. In high-pressure research, an achievable static pressure limit is imposed by the strength of available strong materials and design of high-pressure devices. Using a high-pressure and high-temperature technique, we synthesized optically transparent microballs of bulk nanocrystalline diamond, which were found to have an exceptional yield strength (~460 GPa at a confining pressure of ~70 GPa) due to the unique microstructure of bulk nanocrystalline diamond. We used the nanodiamond balls in a double-stage diamond anvil cell high-pressure device that allowed us to generate static pressures beyond 1 TPa, as demonstrated by synchrotron x-ray diffraction. Outstanding mechanical properties (strain-dependent elasticity, very high hardness, and unprecedented yield strength) make the nanodiamond balls a unique device for ultrahigh static pressure generation. Structurally isotropic, homogeneous, and made of a low-Z material, they are promising in the field of x-ray optical applications. PMID:27453944

Gradient twinned 304 stainless steels for high strength and high ductility

DOE PAGES

Chen, Aiying; Liu, Jiabin; Wang, Hongtao; ...

2016-04-23

Gradient materials often have attractive mechanical properties that outperform uniform microstructure counterparts. It remains a difficult task to investigate and compare the performance of various gradient microstructures due to the difficulty of fabrication, the wide range of length scales involved, and their respective volume percentage variations. We have investigated four types of gradient microstructures in 304 stainless steels that utilize submicrotwins, nanotwins, nanocrystalline-, ultrafine- and coarse-grains as building blocks. Tensile tests reveal that the gradient microstructure consisting of submicrotwins and nanotwins has a persistent and stable work hardening rate and yields an impressive combination of high strength and high ductility,more » leading to a toughness that is nearly 50% higher than that of the coarse-grained counterpart. Ex- and in-situ transmission electron microscopy indicates that nanoscale and submicroscale twins help to suppress and limit martensitic phase transformation via the confinement of martensite within the twin lamellar. Twinning and detwinning remain active during tensile deformation and contribute to the work hardening behavior. We discuss the advantageous properties of using submicrotwins as the main load carrier and nanotwins as the strengthening layers over those coarse and nanocrystalline grains. Furthermore, our work uncovers a new gradient design strategy to help metals and alloys achieve high strength and high ductility.« less

Evaluating community–environment relationships along fine to broad taxonomic resolutions reveals evolutionary forces underlying community assembly

PubMed Central

Lu, Hsiao-Pei; Yeh, Yi-Chun; Sastri, Akash R; Shiah, Fuh-Kwo; Gong, Gwo-Ching; Hsieh, Chih-hao

2016-01-01

We propose a method for detecting evolutionary forces underlying community assembly by quantifying the strength of community–environment relationships hierarchically along taxonomic ranks. This approach explores the potential role of phylogenetic conservatism on habitat preferences: wherein, phylogenetically related taxa are expected to exhibit similar environmental responses. Thus, when niches are conserved, broader taxonomic classification should not diminish the strength of community–environment relationships and may even yield stronger associations by summarizing occurrences and abundances of ecologically equivalent finely resolved taxa. In contrast, broader taxonomic classification should weaken community–environment relationships when niches are under great divergence (that is, by combining finer taxa with distinct environmental responses). Here, we quantified the strength of community–environment relationships using distance-based redundancy analysis, focusing on soil and seawater prokaryotic communities. We considered eight case studies (covering a variety of sampling scales and sequencing strategies) and found that the variation in community composition explained by environmental factors either increased or remained constant with broadening taxonomic resolution from species to order or even phylum level. These results support the niche conservatism hypothesis and indicate that broadening taxonomic resolution may strengthen niche-related signals by removing uncertainty in quantifying spatiotemporal distributions of finely resolved taxa, reinforcing the current notion of ecological coherence in deep prokaryotic branches. PMID:27177191

High-rate deformation and fracture of steel 09G2S

NASA Astrophysics Data System (ADS)

Balandin, Vl. Vas.; Balandin, Vl. Vl.; Bragov, A. M.; Igumnov, L. A.; Konstantinov, A. Yu.; Lomunov, A. K.

2014-11-01

The results of experimental and theoretical studies of steel 09G2S deformation and fracture laws in a wide range of strain rates and temperature variations are given. The dynamic deformation curves and the ultimate characteristics of plasticity in high-rate strain were determined by the Kolsky method in compression, extension, and shear tests. The elastoplastic properties and spall strength were studied by using the gaseous gun of calibre 57 mm and the interferometer VISAR according to the plane-wave experiment technique. The data obtained by the Kolsky method were used to determine the parameters of the Johnson-Cook model which, in the framework of the theory of flow, describes how the yield surface radius depends on the strain, strain rate, and temperature.

Crack Damage Parameters and Dilatancy of Artificially Jointed Granite Samples Under Triaxial Compression

NASA Astrophysics Data System (ADS)

Walton, G.; Alejano, L. R.; Arzua, J.; Markley, T.

2018-06-01

A database of post-peak triaxial test results was created for artificially jointed planes introduced in cylindrical compression samples of a Blanco Mera granite. Aside from examining the artificial jointing effect on major rock and rock mass parameters such as stiffness, peak strength and residual strength, other strength parameters related to brittle cracking and post-yield dilatancy were analyzed. Crack initiation and crack damage values for both the intact and artificially jointed samples were determined, and these damage envelopes were found to be notably impacted by the presence of jointing. The data suggest that with increased density of jointing, the samples transition from a combined matrix damage and joint slip yielding mechanism to yield dominated by joint slip. Additionally, post-yield dilation data were analyzed in the context of a mobilized dilation angle model, and the peak dilation angle was found to decrease significantly when there were joints in the samples. These dilatancy results are consistent with hypotheses in the literature on rock mass dilatancy.

Nanoscale Roughness of Natural Fault Surfaces Controlled by Scale-Dependent Yield Strength

NASA Astrophysics Data System (ADS)

Thom, C. A.; Brodsky, E. E.; Carpick, R. W.; Pharr, G. M.; Oliver, W. C.; Goldsby, D. L.

2017-09-01

Many natural fault surfaces exhibit remarkably similar scale-dependent roughness, which may reflect the scale-dependent yield strength of rocks. Using atomic force microscopy (AFM), we show that a sample of the Corona Heights Fault exhibits isotropic surface roughness well-described by a power law, with a Hurst exponent of 0.75 +/- 0.05 at all wavelengths from 60 nm to 10 μm. The roughness data and a recently proposed theoretical framework predict that yield strength varies with length scale as λ-0.25+/-0.05. Nanoindentation tests on the Corona Heights sample and another fault sample whose topography was previously measured with AFM (the Yair Fault) reveal a scale-dependent yield stress with power-law exponents of -0.12 +/- 0.06 and -0.18 +/- 0.08, respectively. These values are within one to two standard deviations of the predicted value, and provide experimental evidence that fault roughness is controlled by intrinsic material properties, which produces a characteristic surface geometry.

On the superposition of strengthening mechanisms in dispersion strengthened alloys and metal-matrix nanocomposites: Considerations of stress and energy

NASA Astrophysics Data System (ADS)

Ferguson, J. B.; Schultz, Benjamin F.; Venugopalan, Dev; Lopez, Hugo F.; Rohatgi, Pradeep K.; Cho, Kyu; Kim, Chang-Soo

2014-03-01

Yield strength improvement in dispersion strengthened alloys and nano particle-reinforced composites by well-known strengthening mechanisms such as solid solution, grain refinement, coherent and incoherent dispersed particles, and increased dislocation density resulting from work-hardening can all be described individually. However, there is no agreed upon description of how these mechanisms combine to determine the yield strength. In this work, we propose an analytical yield strength prediction model combining arithmetic and quadratic addition approaches based on the consideration of two types of yielding mechanisms; stress-activated and energy-activated. Using data available in the literature for materials of differing grain sizes, we consider the cases of solid solutions and coherent precipitates to show that they follow stress-activated behavior. Then, we applied our model with some empirical parameters to precipitationhardenable materials of various grain sizes in both coherent and incoherent precipitate conditions, which demonstrated that grain boundary and Orowan-strengthening can be treated as energy-activated mechanisms.

49 CFR 195.12 - What requirements apply to low-stress pipelines in rural areas?

Code of Federal Regulations, 2014 CFR

2014-10-01

... corresponding to: (A) A stress level equal to or less than 20-percent of the specified minimum yield strength of the line pipe; or (B) If the stress level is unknown or the pipeline is not constructed with steel... of the specified minimum yield strength of the line pipe; or (B) If the stress level is unknown or...

49 CFR 195.12 - What requirements apply to low-stress pipelines in rural areas?

Code of Federal Regulations, 2013 CFR

2013-10-01

... corresponding to: (A) A stress level equal to or less than 20-percent of the specified minimum yield strength of the line pipe; or (B) If the stress level is unknown or the pipeline is not constructed with steel... of the specified minimum yield strength of the line pipe; or (B) If the stress level is unknown or...

49 CFR 195.12 - What requirements apply to low-stress pipelines in rural areas?

Code of Federal Regulations, 2012 CFR

2012-10-01

... corresponding to: (A) A stress level equal to or less than 20-percent of the specified minimum yield strength of the line pipe; or (B) If the stress level is unknown or the pipeline is not constructed with steel... of the specified minimum yield strength of the line pipe; or (B) If the stress level is unknown or...

A viscoplastic shear-zone model for episodic slow slip events in oceanic subduction zones

NASA Astrophysics Data System (ADS)

Yin, A.; Meng, L.

2016-12-01

Episodic slow slip events occur widely along oceanic subduction zones at the brittle-ductile transition depths ( 20-50 km). Although efforts have been devoted to unravel their mechanical origins, it remains unclear about the physical controls on the wide range of their recurrence intervals and slip durations. In this study we present a simple mechanical model that attempts to account for the observed temporal evolution of slow slip events. In our model we assume that slow slip events occur in a viscoplastic shear zone (i.e., Bingham material), which has an upper static and a lower dynamic plastic yield strength. We further assume that the hanging wall deformation is approximated as an elastic spring. We envision the shear zone to be initially locked during forward/landward motion but is subsequently unlocked when the elastic and gravity-induced stress exceeds the static yield strength of the shear zone. This leads to backward/trenchward motion damped by viscous shear-zone deformation. As the elastic spring progressively loosens, the hanging wall velocity evolves with time and the viscous shear stress eventually reaches the dynamic yield strength. This is followed by the termination of the trenchward motion when the elastic stress is balanced by the dynamic yield strength of the shear zone and the gravity. In order to account for the zig-saw slip-history pattern of typical repeated slow slip events, we assume that the shear zone progressively strengthens after each slow slip cycle, possibly caused by dilatancy as commonly assumed or by progressive fault healing through solution-transport mechanisms. We quantify our conceptual model by obtaining simple analytical solutions. Our model results suggest that the duration of the landward motion increases with the down-dip length and the static yield strength of the shear zone, but decreases with the ambient loading velocity and the elastic modulus of the hanging wall. The duration of the backward/trenchward motion depends on the thickness, viscosity, and dynamic yield strength of the shear zone. Our model predicts a linear increase in slip with time during the landward motion and an exponential decrease in slip magnitude during the trenchward motion.

The role of grain size and shape in strengthening of dispersion hardened nickel alloys.

NASA Technical Reports Server (NTRS)

Wilcox, B. A.; Clauer, A. H.

1972-01-01

Thermomechanical processing was used to develop various microstructures in Ni, Ni-2ThO2, Ni-20Cr, Ni-20Cr-2ThO2, Ni-20Cr-10W and Ni-20Cr-10W-2ThO2, and the influence of microstructure on room temperature and elevated temperature strength was investigated. The yield strength at 25 C increased with substructure refinement according to the Hall-Petch relation. It was found that substructure refinement was a much more potent means of strengthening at room temperature than was dispersion hardening. At elevated temperature (1093 C), the most important microstructural feature affecting strength of dispersion hardened nickel alloys was the grain aspect ratio, i.e. grain length, L, divided by grain width,l. The yield strength and creep strength increased linearly with increasing L/l.

Evaluation of the stress corrosion cracking resistance of several high strength low alloy steels

NASA Technical Reports Server (NTRS)

Humphries, T. S.; Nelson, E. E.

1980-01-01

The stress corrosion cracking resistance was studied for high strength alloy steels 4130, 4340, for H-11 at selected strength levels, and for D6AC and HY140 at a single strength. Round tensile and C-ring type specimens were stressed up to 100 percent of their yield strengths and exposed to alternate immersion in salt water, salt spray, the atmosphere at Marshall Space Flight Center, and the seacoast at Kennedy Space Center. Under the test conditions, 4130 and 4340 steels heat treated to a tensile strength of 1240 MPa (180 ksi), H-11 and D6AC heat treated to a tensile strength of 1450 MPa (210 ksi), and HY140 (1020 MPa, 148 ksi) are resistant to stress corrosion cracking because failures were not encountered at stress levels up to 75 percent of their yield strengths. A maximum exposure period of one month for alternate immersion in salt water or salt spray and three months for seacoast is indicated for alloy steel to avoid false indications of stress corrosion cracking because of failure resulting from severe pitting.

Microdomain Yield Behaviour in an Ultra-High Strength Low Alloy Steel for Marine Use with Low Sensitivity of SCC

NASA Astrophysics Data System (ADS)

Yin, Jiang; Tao, Anxiang; Xu, Pingguang; Ping, Dehai

The present paper involves a fundamental research on microdomain yield behavior of an ultrahigh strength low alloy steel with high temperature tempered bainite. The smooth cylinder specimen was took from deep water mooring chain links from the steel with the chemical composition of 0.23C-0.25Si -0.70Mn-3.55 (Cr+Ni+Mo) -0.13 (V+Nb+Ti) (mass %) ,which was quenched from 1253K and then tempered at 873K Its macroscopic yield strength is 1120MPa and the tensile strength is 1250MPa In-situ neutron diffraction measurements of loading tension have suggested that a good linear elastic deformation can be kept up to 500MPa stress, and then (200) priority non-linear elastic strain, that is the yield of crystal lattice occur at 700MPa and the (110) non-linear elastic strain was found at 800MPa. The (200) and (110) nonlinear elastic strain increases gradually when the stress was further increased, however, the (211) kept its linear elastic deformation stage as before. The sub-microstructural analysis carried out using TEM and additional determine the nature and quantitative analysis has revealed that there are three kinds of alloy carbides: (1) θ-M3C cementites with an average particle size of less than 50 nm which inside laths and lath boundaries; (2) ɛ-M2C formed uniformly within the ferrites with a length of less than 200 nm and width of less than 20 nm; (3) ultra-fine high density MC cohered with matrix α-Fe and its particle size is about 2 nm. The whole microdomain yield behaviour of the material was possibly influenced by the fcc-MC with high density. The results of CLT (constant load), SSRT (slow strain rate) and KIscc test of the present chain in seawater solution indicate, that threshold value of SCC (stress corrosion cracking) stress exceed 0.8 tensile strength and the chain's KIscc value is double of KIscc value of 4340 steel type parts. MC not only form strong hydrogen trap, but also slow down microdomain yield likely by means of increasing yield strength of crystal lattice, thus reduce SCC sensibility of the steel.

Invariance of evoked-potential echo-responses to target strength and distance in an echolocating false killer whale

NASA Astrophysics Data System (ADS)

Supin, Alexander Ya.; Nachtigall, Paul E.; Au, Whitlow W. L.; Breese, Marlee

2005-06-01

Brain auditory evoked potentials (AEPs) were recorded in a false killer whale Pseudorca crassidens trained to accept suction-cup EEG electrodes and to detect targets by echolocation. AEP collection was triggered by echolocation pulses transmitted by the animal. The target strength varied from -22 to -40 dB the distance varied from 1.5 to 6 m. All the records contained two AEP sets: the first one of a constant latency (transmission-related AEP) and a second one with a delay proportional to the distance (echo-related AEP). The amplitude of echo-related AEPs was almost independent of both target strength and distance, though combined variation of these two parameters resulted in echo intensity variation within a range of 42 dB. The amplitude of transmission-related AEPs was independent of distance but dependent on target strength: the less the target strength, the higher the amplitude. Recording of transmitted pulses has not shown their intensity dependence on target strength. It is supposed that the constancy of echo-related AEP results from variation of hearing sensitivity depending on the target strength and release of echo-related responses from masking by transmitted pulses depending on the distance. .

Invariance of evoked-potential echo-responses to target strength and distance in an echolocating false killer whale.

PubMed

Supin, Alexander Ya; Nachtigall, Paul E; Au, Whitlow W L; Breese, Marlee

2005-06-01

Brain auditory evoked potentials (AEPs) were recorded in a false killer whale Pseudorca crassidens trained to accept suction-cup EEG electrodes and to detect targets by echolocation. AEP collection was triggered by echolocation pulses transmitted by the animal. The target strength varied from -22 to -40 dB; the distance varied from 1.5 to 6 m. All the records contained two AEP sets: the first one of a constant latency (transmission-related AEP) and a second one with a delay proportional to the distance (echo-related AEP). The amplitude of echo-related AEPs was almost independent of both target strength and distance, though combined variation of these two parameters resulted in echo intensity variation within a range of 42 dB. The amplitude of transmission-related AEPs was independent of distance but dependent on target strength: the less the target strength, the higher the amplitude. Recording of transmitted pulses has not shown their intensity dependence on target strength. It is supposed that the constancy of echo-related AEP results from variation of hearing sensitivity depending on the target strength and release of echo-related responses from masking by transmitted pulses depending on the distance.

Comparisons in fluctuation of muscle strength and function in patients with immune-mediated neuropathy treated with intravenous versus subcutaneous immunoglobulin.

PubMed

Christiansen, Ingelise; Markvardsen, Lars H; Jakobsen, Johannes

2018-04-01

Variations in muscle strength and function have not been studied in patients with chronic inflammatory demyelinating polyneuropathy and multifocal motor neuropathy whose treatment regimen has been changed from intravenous to subcutaneous immunoglobulin (IVIg to SCIg). In a prospective, open-label study, patients were changed from monthly IVIg to weekly SCIg. The primary endpoint was variation in isokinetic muscle strength (cIKS). Secondary endpoints were variations in Medical Research Council (MRC) score, grip strength (GS), 9-hole-peg test (9-HPT), and 40-meter-walk test (40-MWT). The coefficient of variance of cIKS during the IVIg and SCIg treatment periods was unchanged (mean ± SD: 6.97 ± 4.83% vs. 5.50 ± 3.13%, P = 0.21). The variations in the 9-HPT and 40-MWT were significantly lower in the SCIg group (P = 0.01 and P = 0.005, respectively). When therapy was changed from IVIg to SCIg, fluctuation of muscle strength was unchanged, but performance fluctuations were diminished. Muscle Nerve 57: 610-614, 2018. © 2017 Wiley Periodicals, Inc.

The Strength and Characteristics of VPPA Welded 2219-T87 Aluminum Alloy

NASA Technical Reports Server (NTRS)

Jemian, W. A.

1985-01-01

A study of the variable polarity plasma arc (VPPA) welding process and those factors that control the structure and properties of VPPA welded aluminum alloy 2219-T87 was conducted. The importance of joint preparation, alignment of parts and welding process variables are already established. Internal weld defects have been eliminated. However, a variation of properties was found to be due to the size variation of interdendritic particles in the fusion zone. These particles contribute to the void formation process, which controls the ultimate tensile strength of the welded alloy. A variation of 150 microns in particle size correlated with a 10 ksi variation of ultimate tensile strength. It was found that all fracture surfaces were of the dimple rupture type, with fracture initiating within the fusion zone.

Earthflow yield strength constrained by lateral levee morphology

NASA Astrophysics Data System (ADS)

Nereson, A. L.; Finnegan, N. J.

2015-12-01

Slow-moving landslides, or earthflows, are characterized by persistent, flow-like motion that is commonly modeled using various viscous and viscoplastic rheologies. One of the manifestations of viscoplastic flow down a slope is the emergence of stationary bodies of fluid at the margins of the flow (i.e. lateral levees). These levees are common signatures of earthflow morphology and, while they are frequently used to outline boundaries for mapping purposes, they have received little attention for what they may indicate about the history and properties of the flow itself. In contrast, lateral levees along lava flows have long been used by physical volcanologists as tools to learn about their non-Newtonian rheologies and chemical compositions. Hulme (1974) was the first to note that, for a given slope, levee width may be characteristic of a fluids's yield strength and his methodology has been subsequently used to infer properties of lavas on the Earth, the Moon, and Mars. Using these lavas as analogies, we apply Hulme's approach to earthflows in a variety of settings globally. We find that calculated yield strengths for individual earthflows fall within a relatively narrow range between 101-102 kPa. In addition, individual earthflow complexes often preserve multiple generations of levees, which in some cases may record apparent reductions in yield strength over time for a given flow, possibly from weakening of previously failed material. Knowledge of earthflow yield strength permits the calculation of a critical earthflow thickness below which there will be no downslope motion for a given slope angle. Thicknesses calculated in this manner could thus be used to estimate the flux of landslide material for earthflows without direct depth constraints, provided that surface velocity measurements are obtained by other methods (e.g. InSAR, GPS, manual feature tracking).

Quantitative Ultrasonic Evaluation of Mechanical Properties of Engineering Materials

NASA Technical Reports Server (NTRS)

Vary, A.

1978-01-01

Progress in the application of ultrasonic techniques to nondestructive measurement of mechanical strength of engineering materials is reviewed. A dormant concept in nondestructive evaluation (NDE) is invoked. The availability of ultrasonic methods that can be applied to actual parts to assess their potential susceptibility to failure under design conditions is discussed. It was shown that ultrasonic methods yield measurements of elastic moduli, microstructure, hardness, fracture toughness, tensile strength, yield strength, and shear strength for a wide range of materials (including many types of metals, ceramics, and fiber composites). It was also indicated that although most of these methods were shown feasible in laboratory studies, more work is needed before they can be used on actual parts in processing, assembly, inspection, and maintenance lines.

An alternative approach for modeling strength differential effect in sheet metals with symmetric yield functions

NASA Astrophysics Data System (ADS)

Kurukuri, Srihari; Worswick, Michael J.

2013-12-01

An alternative approach is proposed to utilize symmetric yield functions for modeling the tension-compression asymmetry commonly observed in hcp materials. In this work, the strength differential (SD) effect is modeled by choosing separate symmetric plane stress yield functions (for example, Barlat Yld 2000-2d) for the tension i.e., in the first quadrant of principal stress space, and compression i.e., third quadrant of principal stress space. In the second and fourth quadrants, the yield locus is constructed by adopting interpolating functions between uniaxial tensile and compressive stress states. In this work, different interpolating functions are chosen and the predictive capability of each approach is discussed. The main advantage of this proposed approach is that the yield locus parameters are deterministic and relatively easy to identify when compared to the Cazacu family of yield functions commonly used for modeling SD effect observed in hcp materials.

Micromechanical models to guide the development of synthetic ‘brick and mortar’ composites

NASA Astrophysics Data System (ADS)

Begley, Matthew R.; Philips, Noah R.; Compton, Brett G.; Wilbrink, David V.; Ritchie, Robert O.; Utz, Marcel

2012-08-01

This paper describes a micromechanical analysis of the uniaxial response of composites comprising elastic platelets (bricks) bonded together with thin elastic perfectly plastic layers (mortar). The model yields closed-form results for the spatial variation of displacements in the bricks as a function of constituent properties, which can be used to calculate the effective properties of the composite, including elastic modulus, strength and work-to-failure. Regime maps are presented which indicate critical stresses for failure of the bricks and mortar as a function of constituent properties and brick architecture. The solution illustrates trade-offs between elastic modulus, strength and dissipated work that are a result of transitions between various failure mechanisms associated with brick rupture and rupture of the interfaces. Detailed scaling relationships are presented with the goal of providing material developers with a straightforward means to identify synthesis targets that balance competing mechanical behaviors and optimize material response. Ashby maps are presented to compare potential brick and mortar composites with existing materials, and identify future directions for material development.

Effect of ferrite transformation on the tensile and stress corrosion properties of type 316 L stainless steel weld metal thermally aged at 873 K

NASA Astrophysics Data System (ADS)

Shaikh, H.; Khatak, H. S.; Seshadri, S. K.; Gnanamoorthy, J. B.; Rodriguez, P.

1995-07-01

This article deals with the effect of the microstructural changes, due to transformation of delta ferrite, on the associated variations that take place in the tensile and stress corrosion properties of type 316 L stainless steel weld deposits when subjected to postweld heat treatment at 873 K for prolonged periods (up to 2000 hours). On aging for short durations (up to 20 hours), carbide/ carbonitride was the dominant transformation product, whereas sigma phase was dominant at longer aging times. The changes in the tensile and stress corrosion behavior of the aged weld metal have been attributed to the two competitive processes of matrix softening and hardening. Yield strength (YS) was found to depend predominantly on matrix softening only, while sig-nificant changes in the ultimate tensile strength (UTS) and the work-hardening exponent, n, occurred due to matrix hardening. Ductility and stress corrosion properties were considerably affected by both factors. Fractographic observations on the weld metal tested for stress-corrosion cracking (SCC) indicated a combination of transgranular cracking of the austenite and interface cracking.

The flexural properties of endodontic post materials.

PubMed

Stewardson, Dominic A; Shortall, Adrian C; Marquis, Peter M; Lumley, Philip J

2010-08-01

To measure the flexural strengths and moduli of endodontic post materials and to assess the effect on the calculated flexural properties of varying the diameter/length (D/L) ratio of three-point bend test samples. Three-point bend testing of samples of 2mm diameter metal and fiber-reinforced composite (FRC) rods was carried out and the mechanical properties calculated at support widths of 16 mm, 32 mm and 64 mm. Weibull analysis was performed on the strength data. The flexural strengths of all the FRC post materials exceeded the yield strengths of the gold and stainless steel samples; the flexural strengths of two FRC materials were comparable with the yield strength of titanium. Stainless steel recorded the highest flexural modulus while the titanium and the two carbon fiber materials exhibited similar values just exceeding that of gold. The remaining glass fiber materials were of lower modulus within the range of 41-57 GPa. Weibull modulus values for the FRC materials ranged from 16.77 to 30.09. Decreasing the L/D ratio produced a marked decrease in flexural modulus for all materials. The flexural strengths of FRC endodontic post materials as new generally exceed the yield strengths of metals from which endodontic posts are made. The high Weibull modulus values suggest good clinical reliability of FRC posts. The flexural modulus values of the tested posts were from 2-6 times (FRC) to 4-10 times (metal) that of dentin. Valid measurement of flexural properties of endodontic post materials requires that test samples have appropriate L/D ratios. Copyright 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Holographic study of conventional and negative Poisson's ratio metallic foams - Elasticity, yield and micro-deformation

NASA Technical Reports Server (NTRS)

Chen, C. P.; Lakes, R. S.

1991-01-01

An experimental study by holographic interferometry is reported of the following material properties of conventional and negative Poisson's ratio copper foams: Young's moduli, Poisson's ratios, yield strengths and characteristic lengths associated with inhomogeneous deformation. The Young's modulus and yield strength of the conventional copper foam were comparable to those predicted by microstructural modeling on the basis of cellular rib bending. The reentrant copper foam exhibited a negative Poisson's ratio, as indicated by the elliptical contour fringes on the specimen surface in the bending tests. Inhomogeneous, non-affine deformation was observed holographically in both foam materials.

Investigation of specimen size effects by in-situ microcompression of equal channel angular pressed copper

DOE Office of Scientific and Technical Information (OSTI.GOV)

Howard, C.; Frazer, D.; Lupinacci, A.

Here, micropillar compression testing was implemented on Equal Channel Angular Pressed copper samples ranging from 200 nm to 10 µm in side length in order to measure the mechanical properties yield strength, first load drop during plastic deformation at which there was a subsequent stress decrease with increasing strain, work hardening, and strain hardening exponent. Several micropillars containing multiple grains were investigated in a 200 nm grain sample. The effective pillar diameter to grain size ratios, D/d, were measured to be between 1.9 and 27.2. Specimens having D/d ratios between 0.2 and 5 were investigated in a second sample thatmore » was annealed at 200 °C for 2 h with an average grain size of 1.3 µm. No yield strength or elastic modulus size effects were observed in specimens in the 200 nm grain size sample. However work hardening increases with a decrease in critical ratios and first stress drops occur at much lower stresses for specimens with D/d ratios less than 5. For comparison, bulk tensile testing of both samples was performed, and the yield strength values of all micropillar compression tests for the 200 nm grained sample are in good agreement with the yield strength values of the tensile tests.« less

Investigation of specimen size effects by in-situ microcompression of equal channel angular pressed copper

DOE PAGES

Howard, C.; Frazer, D.; Lupinacci, A.; ...

2015-09-30

Here, micropillar compression testing was implemented on Equal Channel Angular Pressed copper samples ranging from 200 nm to 10 µm in side length in order to measure the mechanical properties yield strength, first load drop during plastic deformation at which there was a subsequent stress decrease with increasing strain, work hardening, and strain hardening exponent. Several micropillars containing multiple grains were investigated in a 200 nm grain sample. The effective pillar diameter to grain size ratios, D/d, were measured to be between 1.9 and 27.2. Specimens having D/d ratios between 0.2 and 5 were investigated in a second sample thatmore » was annealed at 200 °C for 2 h with an average grain size of 1.3 µm. No yield strength or elastic modulus size effects were observed in specimens in the 200 nm grain size sample. However work hardening increases with a decrease in critical ratios and first stress drops occur at much lower stresses for specimens with D/d ratios less than 5. For comparison, bulk tensile testing of both samples was performed, and the yield strength values of all micropillar compression tests for the 200 nm grained sample are in good agreement with the yield strength values of the tensile tests.« less

The Resilience and Strengths of Low-Income Families

ERIC Educational Resources Information Center

Orthner, Dennis K.; Jones-Sanpei, Hinckley; Williamson, Sabrina

2004-01-01

This study examines indicators of family strength among a random sample of low-income households with children. The Family Strength Index assesses strength according to economic, problem-solving, communication, family cohesion, and social support assets. Variations in family strength are explained according to parental status and level of…

Metallurgical/Alloy Optimization of High Strength and Wear Resistant Structural Quench and Tempered Steels

NASA Astrophysics Data System (ADS)

Stalheim, Douglas G.; Peimao, Fu; Linhao, Gu; Yongqing, Zhang

Structural steels with yield strength requirements greater or equal to 690 MPa can be produced through controlled recrystallization hot rolling coupled with precipitation strengthening or purposeful heat treatment through quench and tempering (Q&T). High strength structural steel and wear/abrasion resistant requirements greater or equal to 360 Brinell hardness (BHN) are produced by the development of microstructures of tempered lower bainite and/or martensite through the Q&T process. While these Q&T microstructures can produce very high strengths and hardness levels making them ideal for 690 MPa plus yield strength or wear/abrasion resistant applications, they lack toughness/ductility and hence are very brittle and prone to cracking. While tempering the microstructures helps in improving the toughness/ductility and reducing the brittleness, strength and hardness can be sacrificed. In addition, these steels typically consist of alloy designs containing boron with carbon equivalents (CE) greater than 0.50 to achieve the desired microstructures. The higher CE has a negative influence on weldability.

Experimental Study of Damage Evolution in Circular Stirrup-Confined Concrete

PubMed Central

Li, Zuohua; Peng, Zhihan; Teng, Jun; Wang, Ying

2016-01-01

This paper presents an experimental study on circular stirrup-confined concrete specimens under uniaxial and monotonic load. The effects of stirrup volume ratio, stirrup yield strength and concrete strength on damage evolution of stirrup-confined concrete were investigated. The experimental results showed that the strength and ductility of concrete are improved by appropriate arrangement of the stirrup confinement. Firstly, the concrete damage evolution can be relatively restrained with the increase of the stirrup volume ratio. Secondly, higher stirrup yield strength usually causes larger confining pressures and slower concrete damage evolution. In contrast, higher concrete strength leads to higher brittleness, which accelerates the concrete damage evolution. A plastic strain expression is obtained through curve fitting, and a damage evolution equation for circular stirrup-confined concrete is proposed by introducing a confinement factor (C) based on the experimental data. The comparison results demonstrate that the proposed damage evolution model can accurately describe the experimental results. PMID:28773402

Experimental Study of Damage Evolution in Circular Stirrup-Confined Concrete.

PubMed

Li, Zuohua; Peng, Zhihan; Teng, Jun; Wang, Ying

2016-04-08

This paper presents an experimental study on circular stirrup-confined concrete specimens under uniaxial and monotonic load. The effects of stirrup volume ratio, stirrup yield strength and concrete strength on damage evolution of stirrup-confined concrete were investigated. The experimental results showed that the strength and ductility of concrete are improved by appropriate arrangement of the stirrup confinement. Firstly, the concrete damage evolution can be relatively restrained with the increase of the stirrup volume ratio. Secondly, higher stirrup yield strength usually causes larger confining pressures and slower concrete damage evolution. In contrast, higher concrete strength leads to higher brittleness, which accelerates the concrete damage evolution. A plastic strain expression is obtained through curve fitting, and a damage evolution equation for circular stirrup-confined concrete is proposed by introducing a confinement factor ( C ) based on the experimental data. The comparison results demonstrate that the proposed damage evolution model can accurately describe the experimental results.

Changes In the Pickup Ion Cutoff Under Variable Solar Wind Conditions

NASA Astrophysics Data System (ADS)

Bower, J.; Moebius, E.; Taut, A.; Berger, L.; Drews, C.; Lee, M. A.; Farrugia, C. J.

2017-12-01

We present the first systematic analysis to determine pickup ion (PUI) cutoff speed variations,both during compression regions, identified by their structure, and during times of highly variablesolar wind (SW) speed or magnetic field strength. This study is motivated by the attempt toremove or correct these effects on the determination of the longitude of the interstellar neutralgas flow from the flow pattern related variation of the PUI cutoff with ecliptic longitude. At thesame time, this study sheds light on the physical mechanisms that lead to energy transferbetween the SW and the embedded PUI population. Using 2007-2014 STEREO A PLASTICobservations we identify compression regions in the solar wind and analyze the PUI velocitydistribution function (VDF). We developed a routine to identify stream interaction regions andCIRs, by identifying the stream interface and the successive velocity increase in the solar windspeed and density. Characterizing these individual compression events and combining them in asuperposed epoch analysis allows us to analyze the PUI population in similar conditions andfind the local cutoff shift with adequate statistics. The result of this method yields cutoff shifts forcompression regions with large solar wind speed gradients. Additionally, through sorting theentire set of PUI VDFs at high time resolution we obtain a noticeable correlation of the cutoffshift with gradients in the SW speed and interplanetary magnetic field strength. We willdiscuss implications for the understanding of the PUI VDF evolution and the PUI cutoff analysisof the interstellar gas flow.

Sensitivity Studies for In-Situ Automated Tape Placement of Thermoplastic Composites

NASA Technical Reports Server (NTRS)

Costen, Robert C.; Marchello, Joseph M.

2004-01-01

This modeling effort seeks to improve the interlaminate bond strength of thermoplastic carbon composites produced by the in-situ automated tape placement (ATP) process. An existing high productivity model is extended to lower values of the Peclet number that correspond to the present operating conditions of the Langley ATP robot. (The Peclet number is the dimensionless ratio of inertial to diffusive heat transfer.) In sensitivity studies, all of the process and material parameters are individually varied. The model yields the corresponding variations in the effective bonding time (EBT) referred to the glass transition temperature. According to reptation theory, the interlaminate bond strength after wetting occurs is proportional to the one-fourth power of EBT. The model also computes the corresponding variations in the thermal input power (TIP) and the mass and volumetric process rates. Process studies show that a 10 percent increase in the consolidation length results in a 20 percent increase in EBT and a 5 percent increase in TIP. A surprising result is that a 10 K decrease in the tooling temperature results in a 25 percent increase in EBT and an 8 percent increase in TIP. Material studies show that a 10 K decrease in glass transition temperature results in an 8 percent increase in EBT and a 8 percent decrease in TIP. A 20 K increase in polymer degradation temperature results in a 23 percent increase in EBT with no change in TIP.

The relationship between magnetic anisotropy, rock-strength anisotropy and vein emplacement in gold-bearing metabasalts of Gadag (South India)

NASA Astrophysics Data System (ADS)

Vishnu, C. S.; Lahiri, Sivaji; Mamtani, Manish A.

2018-01-01

In this study the importance of rock strength and its anisotropy in controlling vein emplacement is evaluated by integrating anisotropy of magnetic susceptibility (AMS) with rock mechanics data from massive (visibly isotropic) metabasalts of Gadag region (Dharwar Craton, South India). Orientation of magnetic foliation (MF) is first recognized from AMS. Subsequently, rock mechanics tests viz. ultrasonic P-wave velocity (Vp), uniaxial compressive strength (UCS) and point load strength (Is(50)) are done in cores extracted parallel and perpendicular to MF. Vp is found to be higher in direction parallel to MF than perpendicular to it. In contrast rock strength (UCS and Is(50)) is greater in direction perpendicular to MF, than parallel to it. This proves that rocks from the gold mineralized belt of Gadag have rock strength anisotropy. Orientation of MF in Gadag region is NW-SE, which is also the mean orientation of quartz veins. Previous studies indicate that emplacement of veins in the region took place during regional D3 (NW-SE shortening). Based on the present study, it is concluded that vein emplacement took place in NW-SE orientation because the rocks have strength anisotropy and are weaker in this direction (orientation of MF), which dilated to accommodate fluid flow. In addition, vein intensities are measured along three traverses and found to be variable. It is argued that since mineralization is favoured when the system gets saturated with fluid, variation in fluid flow could not have been responsible for variation in vein intensities in the study area. Since the rock strength of the different blocks investigated here is not uniform, it is envisaged that variation in rock strength played an important role in controlling the vein intensities. It is concluded that rock strength variation controlled strain partitioning and channelized fluid flow thus influencing vein emplacement and mineralization and formation of lodes.

Spall fracture in aluminium alloy at high strain rates

NASA Astrophysics Data System (ADS)

Joshi, K. D.; Rav, Amit; Sur, Amit; Kaushik, T. C.; Gupta, Satish C.

2016-05-01

Spall fracture strength and dynamic yield strength has been measured in 8mm thick target plates of aluminium alloy Al2024-T4 at high strain rates generated in three plate impact experiments carried out at impact velocities of 180 m/s, 370 m/s and 560m/s, respectively, using single stage gas gun facility. In each experiment, the free surface velocity history of the Al2024-T4 sample plate measured employing velocity interferometer system for any reflector (VISAR) is used to determine the spall strength and dynamic yield strength of this material. The spall strength of 1.11 GPa, 1.16 GPa and 1.43 GPa, determined from measured free surface velocity history of sample material in three experiments performed at impact velocity of 180 m/s, 370 m/s and 560 m/s, respectively, are higher than the quasi static value of 0.469 GPa and display almost linearly increasing trend with increasing impact velocity or equivalently with increasing strain rates. The average strain rates just ahead of the spall fracture are determined to be 1.9×10 4/s, 2.0×104/s and 2.5×104/s, respectively. The dynamic yield strength determined in the three experiments range from 0.383 GPa to 0.407 GPa, which is higher than the quasi static value of 0.324GPa.

Enhancement of Strength and Ductility of Mg96Zn2Y2 Rolled Sheet by Controlling Structure and Plastic Deformation

NASA Astrophysics Data System (ADS)

Noda, Masafumi; Kawamura, Yoshihito; Sakurai, Hiroshi; Funami, Kunio

Mg-Zn-Y alloys are well known to possess greatly enhanced strength during plastic deformation because of the presence of kink bands in the LPSO phase and refinement of the grains of the alpha Mg phase. On the other hand, Mg-rare earth (RE) and Mg-Zn-RE alloys with a long period stacking order (LPSO) phase show a high tensile yield strength when subjected to an extrusion process but it is not known whether the LPSO and alpha Mg phases develop during plastic deformation. We examined the effect of the finely dispersed LPSO phase and the alpha Mg phase on the development of high strength in sheets of Mg96Zn2Y2 subjected to a few passes of rolling. The mechanical properties and thermal stability of the alloy were also investigated. The tensile yield strength of rolled sheets of Mg96Zn2Y2 was 360 MPa and its elongation was 5% when the material was subjected to thermomechanically controlled processing at 673 K with a four-pass rolling schedule. However, the tensile yield strength decreased and the elongation increased at annealing temperature of 623 K or above, because of the presence of grain growth in the alpha Mg phase and the restoration of kink bands in the LPSO phase.

The Relationship of Red and Photographic Infrared Spectral Data to Grain Yield Variation Within a Winter Wheat Field

NASA Technical Reports Server (NTRS)

Tucker, C. J.; Holben, B. N.; Elgin, J. H., Jr.; Mcmurtrey, J. E., III

1979-01-01

Two band hand-held radiometer data from a winter wheat field, collected on 21 dates during the spring growing season, were correlated within field final grain yield. Significant linear relationships were found between various combinations of the red and photographic infrared radiance data collected and the grain yield. The spectral data explained approximately 64 percent of the within field grain yield variation. This variation in grain yield could not be explained using meteorological data as these were similar for all areas of the wheat field. Most importantly, data collected early in the spring were highly correlated with grain yield, a five week time window existed from stem elongation through antheses in which the spectral data were most highly correlated with grain yield, and manifestations of wheat canopy water stress were readily apparent in the spectral data.

Flat growth of 7075, 7475, 7050 and 7049 aluminum alloy plate in stress corrosion environments: 2-year marine atmosphere results

NASA Technical Reports Server (NTRS)

Dorward, R. C.; Hasse, K. R.

1978-01-01

Marine atmospheric exposure of smooth and precracked specimens from 7075, 7475, 7050 and 7049 plates support the conclusion that for a given strength level, the short transverse stress corrosion resistance of 7050-T7X and 7049-T7X is superior to that of 7075-T7X. The threshold stress intensity (K sub Iscc) for these alloys is about 25 MPa square root m at a yield strength of about 460 MPa; the corresponding yield strength level for 7075-T7X at this SCR level is about 425 MPa. Additional tests on two lots of high-toughness 7475 plate indicate that this alloy is capable of achieving K sub Iscc values of about 35 MPa square root m at yield strengths of 400-450 MPa. Precracked specimens from all these 7XXX-series alloys are subject to self loading from corrosion product wedging. This effect causes stress corrosion cracks to continue growing at very low apparent stress intensities, and should therefore be considered a potential driving force for stress corrosion in design and materials selection.

Extraction optimization and characterization of gelatine from fish dry skin of Spanish mackerel (Scomberromorus commersoni)

NASA Astrophysics Data System (ADS)

Kusumaningrum, I.; Pranoto, Y.; Hadiwiyoto, S.

2018-04-01

This work was to optimized gelatin extraction from dry skin of Spanish mackerel (Scomberromorus commersoni) using Response Surface Methodology (RSM). The aim of this study was to determine the optimal condition of temperature and time for extraction process and properties of the gelatin extracted from dry mackerel skin. The optimal condition for extraction was 59.71°C for 4.25 hours. Results showed that predicted yield by RSM was 13.69% and predicted gel strength was 291.93 Bloom, whereas the actual experiment for yield and gel strength were 13.03% and 291.33 Bloom, respectively. The gelatin extracted from dried skin were analyzed for their proximate composition, yield, gel strength, viscosity, color, and amino acid composition. The results of dried skin gelatin properties compared to the commercial gelatin. Gelatin extracted from the dried skin gave content lower moisture, ash and protein content but higher fat compared to commercial gelatin. This study also shows that the gelatin extracted from the dried skin gave higher gel strength and pH but the lower amino acid composition compared to commercial gelatin.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Plucknett, K.P.; Becher, P.F.; Waters, S.B.

TiC/Ni{sub 3}Al composites were prepared using a simple melt-infiltration process, performed at either 1300 or 1400 C, with the Ni{sub 3}Al content varied over the range of 8--25 vol%. Densities >96% of theoretical were obtained for all composites. Four-point flexure strengths at 22 C increased as the Ni{sub 3}Al content increased (i.e., {approximately}1,100 MPa at 20 vol% Ni{sub 3}Al), with the highest strengths being observed for composites processed at 1300 C, because of reduced TiC grain size. Strengths at elevated temperatures increased with test temperature, up to {approximately}1,000 C. As with the yielding behavior of the Ni{sub 3}Al alloy used,more » a maximum in composite strength ({approximately}1,350 MPa) versus temperature was observed; this occurred at 950 C, which is {approximately}300 C above the yield maximum for the alloy. Extensive plastic strain was achieved in the composites even at high loading rates at 1,135 C, and the yield stress was dependent on the applied loading rate.« less

Effect of different hardness nanoparticles on friction properties of magnetorheological fluids

NASA Astrophysics Data System (ADS)

Zhao, Mingmei; Zhang, Jinqiu; Yao, Jun

2017-10-01

Magnetorheological fluids (MRFs) exhibit different wear performance when nanoparticles with different hardness are added. In this study, three solid particles with different hardness are considered to study the variation in MRF performance. The friction and wear properties of the MRF are measured by using a four-ball friction and wear tester, and the surface of the steel ball was observed using a three-dimensional white light interferometer. Also, the rheological properties of MRF are tested by using an Anton-Paar rheometer. The results show that the addition of graphite yields a stable friction process and does not degrade the rheological properties of MRF. Nano-diamond increases the shear yield strength and reduces the wall slip to a greater extent. However, the wear is more serious in this case. Copper particles are unstable, and their surface activity is too high to get adsorbed on the surface of iron powder aggravating the settlement rate. The above three MRFs with different kinds of nano-particles present a more regular grinding spot, and the nano-particles have a certain repair function to the surface.

Use of Niobium High Strength Steels with 450 MPA Yield Strength for Construction

NASA Astrophysics Data System (ADS)

Silvestre, Leonardo; Langenberg, Peter; Amaral, Thiago; Carboni, Marcelo; Meira, Marcos; Jordão, Alexandre

This paper presents an actual case of a new industrial building at CBMM's plant in Araxá, Brazil as an example of lean design using microalloyed steels. The structure consists mostly of microalloyed ASTM A572 steel grades 65 and 50 instead of the conventional carbon manganese ASTM A36 steel. The application of grade 65 with more than 450 MPa of yield strength is an innovative solution for this type of construction in South America. A complete welding evaluation performed on the low carbon, niobium microalloyed grade 65 steel showed the welding properties and benefits. Niobium's effect of increasing strength and toughness simultaneously resulted in relevant savings in total steel consumption for the project. The paper also quantifies the expected savings in costs, energy and carbon dioxide emissions.

The Structure and Mechanical Properties of High-Strength Bulk Ultrafine-Grained Cobalt Prepared Using High-Energy Ball Milling in Combination with Spark Plasma Sintering

PubMed Central

Marek, Ivo; Vojtěch, Dalibor; Michalcová, Alena; Kubatík, Tomáš František

2016-01-01

In this study, bulk ultrafine-grained and micro-crystalline cobalt was prepared using a combination of high-energy ball milling and subsequent spark plasma sintering. The average grain sizes of the ultrafine-grained and micro-crystalline materials were 200 nm and 1 μm, respectively. Mechanical properties such as the compressive yield strength, the ultimate compressive strength, the maximum compressive deformation and the Vickers hardness were studied and compared with those of a coarse-grained as-cast cobalt reference sample. The bulk ultrafine-grained sample showed an ultra-high compressive yield strength that was greater than 1 GPa, which is discussed with respect to the preparation technique and a structural investigation. PMID:28773514

Cold-Worked Inconel(R) 718 Bars

NASA Technical Reports Server (NTRS)

Montano, J. W.

1988-01-01

Cold working and double aging yield high strength without sacrifice of resistance to corrosion. Report presents data on mechanical properties and stress-corrosion resistance of triple-melted, solution-treated, work-strengthened, direct-double-aged Inconel(R) 718 alloy. Triple melting consists of vacuum induction melting, electro-slag remelting, and vacuum arm remelting. Data indicate advance in processing of large-diameter bars. New process increases yield strength without reducing the elongation, reduction of area, and grain size.

Development of Low-Carbon, Copper-Strengthened HSLA Steel Plate for Naval Ship Construction

DTIC Science & Technology

1990-06-01

steel plate microstructures, 2% nital etch . ...................................................... 13 2. Charpy V-notch impact energy transition for...met a minimum yield strength requirement of 80 ksi yield strength through 3/4 inch gage, had high Charpy V-notch impact energy at low tempera- tures...tempered HSLA line-pipe steels, which typically could not meet the minimum Charpy V-notch impact toughness requirement of 35 ft-lb at -1 200 F. In 1984

Effect of wear on the burst strength of l-80 steel casing

NASA Astrophysics Data System (ADS)

Irawan, S.; Bharadwaj, A. M.; Temesgen, B.; Karuppanan, S.; Abdullah, M. Z. B.

2015-12-01

Casing wear has recently become one of the areas of research interest in the oil and gas industry especially in extended reach well drilling. The burst strength of a worn out casing is one of the significantly affected mechanical properties and is yet an area where less research is done The most commonly used equations to calculate the resulting burst strength after wear are Barlow, the initial yield burst, the full yield burst and the rupture burst equations. The objective of this study was to estimate casing burst strength after wear through Finite Element Analysis (FEA). It included calculation and comparison of the different theoretical bursts pressures with the simulation results along with effect of different wear shapes on L-80 casing material. The von Misses stress was used in the estimation of the burst pressure. The result obtained shows that the casing burst strength decreases as the wear percentage increases. Moreover, the burst strength value of the casing obtained from the FEA has a higher value compared to the theoretical burst strength values. Casing with crescent shaped wear give the highest burst strength value when simulated under nonlinear analysis.

Correlation of the neutron yield from the plasma focus upon variations in the magnetic field energy of the discharge circuit

NASA Astrophysics Data System (ADS)

Ablesimov, V. E.; Dolin, Yu. N.; Kalinychev, A. E.; Tsibikov, Z. S.

2017-10-01

The relation between neutron yield Y and magnetic field energy variations Δ W in the discharge circuit has been studied for a Mather-type plasma-focus camera. The activation technique (activation of silver isotopes) has been used to measure the integral yield of DD neutrons from the source. The time dependence of the neutron yield has been recorded by scintillation detectors. For the device used in the investigations, the neutron yield exhibits a linear dependence on variations in the magnetic field energy Δ W in the discharge circuit at the instant of neutron generation. It is also found that this dependence is related to the initial deuteron pressure in the discharge chamber.

On the Yield Strength of Oceanic Lithosphere

NASA Astrophysics Data System (ADS)

Jain, C.; Korenaga, J.; Karato, S. I.

2017-12-01

The origin of plate tectonic convection on Earth is intrinsically linked to the reduction in the strength of oceanic lithosphere at plate boundaries. A few mechanisms, such as deep thermal cracking [Korenaga, 2007] and strain localization due to grain-size reduction [e.g., Ricard and Bercovici, 2009], have been proposed to explain this reduction in lithospheric strength, but the significance of these mechanisms can be assessed only if we have accurate estimates on the strength of the undamaged oceanic lithosphere. The Peierls mechanism is likely to govern the rheology of old oceanic lithosphere [Kohlstedt et al., 1995], but the flow-law parameters for the Peierls mechanism suggested by previous studies do not agree with each other. We thus reanalyze the relevant experimental deformation data of olivine aggregates using Markov chain Monte Carlo inversion, which can handle the highly nonlinear constitutive equation of the Peierls mechanism [Korenaga and Karato, 2008; Mullet et al., 2015]. Our inversion results indicate nontrivial nonuniqueness in every flow-law parameter for the Peierls mechanism. Moreover, the resultant flow laws, all of which are consistent with the same experimental data, predict substantially different yield stresses under lithospheric conditions and could therefore have different implications for the origin of plate tectonics. We discuss some future directions to improve our constraints on lithospheric yield strength.

Effect of yield curves and porous crush on hydrocode simulations of asteroid airburst

NASA Astrophysics Data System (ADS)

Robertson, D. K.; Mathias, D. L.

2017-03-01

Simulations of asteroid airburst are being conducted to obtain best estimates of damage areas and assess sensitivity to variables for asteroid characterization and mitigation efforts. The simulations presented here employed the ALE3D hydrocode to examine the breakup and energy deposition of asteroids entering the Earth's atmosphere, using the Chelyabinsk meteor as a test case. This paper examines the effect of increasingly complex material models on the energy deposition profile. Modeling the meteor as a rock having a single strength can reproduce airburst altitude and energy deposition reasonably well but is not representative of real rock masses (large bodies of material). Accounting for a yield curve that includes different tensile, shear, and compressive strengths shows that shear strength determines the burst altitude. Including yield curves and compaction of porous spaces in the material changes the detailed mechanics of the breakup but only has a limited effect on the burst altitude and energy deposition. Strong asteroids fail and create peak energy deposition close to the altitude at which ram dynamic pressure equals the material strength. Weak asteroids, even though they structurally fail at high altitude, require the increased pressure at lower altitude to disrupt and disperse the rubble. As a result, a wide range of weaker asteroid strengths produce peak energy deposition at a similar altitude.

Elastic and Plastic Behavior of an Ultrafine-Grained Mg Reinforced with BN Nanoparticles

NASA Astrophysics Data System (ADS)

Trojanová, Zuzanka; Dash, Khushbu; Máthis, Kristián; Lukáč, Pavel; Kasakewitsch, Alla

2018-04-01

Pure microcrystalline magnesium (µMg) was reinforced with hexagonal boron nitride (hBN) nanoparticles and was fabricated by powder metallurgy process followed by hot extrusion. For comparison pure magnesium powder was consolidated by hot extrusion too. Both materials exhibited a significant fiber texture. Mg-hBN nanocomposites (nc) and pure Mg specimens were deformed between room temperature and 300 °C under tension and compression mode. The yield strength and ultimate tensile and compression strength as well as characteristic stresses were evaluated and reported. The tensile and compressive strengths of Mg-hBN nc are quiet superior in values compared to monolithic counterpart as well as Mg alloys. The compressive yield strength of µMg was recorded as 90 MPa, whereas the Mg-hBN nancomposite shows 125 MPa at 200 °C. The tensile yield strength of µMg was computed as 67 MPa which is quite lower as compared to Mg-hBN nanocomposite's value which was recorded as 157 MPa at 200 °C. Under tensile stress the true stress-strain curves are flat in nature, whereas the stress-strain curves observed in compression at temperatures up to 100 °C exhibited small local maxima at the onset of deformation followed by a significant work hardening.

Strength enhancement process for prealloyed powder superalloys

NASA Technical Reports Server (NTRS)

Waters, W. J.; Freche, J. C.

1977-01-01

A technique involving superplastic processing and high pressure autoclaving was applied to a nickel base prealloyed powder alloy. Tensile strengths as high as 2865 MN/sq m at 480 C were obtained with as-superplastically deformed material. Appropriate treatments yielding materials with high temperature tensile and stress rupture strengths were also devised.

Flowability parameters for chopped switchgrass, wheat straw and corn stover

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chevanan, Nehru; Womac, A.R.; Bitra, V.S.P.

2009-02-01

A direct shear cell to measure the shear strength and flow properties of chopped switchgrass, wheat straw, and corn stover was designed, fabricated, and tested. Yield loci (r2=0.99) determined at pre-consolidation pressures of 3.80 kPa and 5.02 kPa indicated that chopped biomass followed Mohr-Coulomb failure. Normal stress significantly affected the displacement required for shear failure, as well as the friction coefficient values for all three chopped biomass types. Displacement at shear failure ranged from 30 to 80 mm, and depended on pre-consolidation pressure, normal stress, and particle size. Friction coefficient was inversely related to normal stress, and was highest formore » chopped corn stover. Also, chopped corn stover exhibited the highest angle of internal friction, unconfined yield strength, major consolidation strength, and cohesive strength, all of which indicated increased challenges in handling chopped corn stover. The measured angle of internal friction and cohesive strength indicated that chopped biomass cannot be handled by gravity alone. The measured angle of internal friction and cohesive strength were 43 and 0.75 kPa for chopped switchgrass; 44 and 0.49 kPa for chopped wheat straw; and 48 and 0.82 kPa for chopped corn stover. Unconfined yield strength and major consolidation strength used for characterization of bulk flow materials and design of hopper dimensions were 3.4 and 10.4 kPa for chopped switchgrass; 2.3 and 9.6 kPa for chopped wheat straw and 4.2 and 11.8 kPa for chopped corn stover. These results are useful for development of efficient handling, storage, and transportation systems for biomass in biorefineries.« less

Transcriptome Analysis Suggests That Chromosome Introgression Fragments from Sea Island Cotton (Gossypium barbadense) Increase Fiber Strength in Upland Cotton (Gossypium hirsutum).

PubMed

Lu, Quanwei; Shi, Yuzhen; Xiao, Xianghui; Li, Pengtao; Gong, Juwu; Gong, Wankui; Liu, Aiying; Shang, Haihong; Li, Junwen; Ge, Qun; Song, Weiwu; Li, Shaoqi; Zhang, Zhen; Rashid, Md Harun Or; Peng, Renhai; Yuan, Youlu; Huang, Jinling

2017-10-05

As high-strength cotton fibers are critical components of high quality cotton, developing cotton cultivars with high-strength fibers as well as high yield is a top priority for cotton development. Recently, chromosome segment substitution lines (CSSLs) have been developed from high-yield Upland cotton ( Gossypium hirsutum ) crossed with high-quality Sea Island cotton ( G. barbadense ). Here, we constructed a CSSL population by crossing CCRI45, a high-yield Upland cotton cultivar, with Hai1, a Sea Island cotton cultivar with superior fiber quality. We then selected two CSSLs with significantly higher fiber strength than CCRI45 (MBI7747 and MBI7561), and one CSSL with lower fiber strength than CCRI45 (MBI7285), for further analysis. We sequenced all four transcriptomes at four different time points postanthesis, and clustered the 44,678 identified genes by function. We identified 2200 common differentially-expressed genes (DEGs): those that were found in both high quality CSSLs (MBI7747 and MBI7561), but not in the low quality CSSL (MBI7285). Many of these genes were associated with various metabolic pathways that affect fiber strength. Upregulated DEGs were associated with polysaccharide metabolic regulation, single-organism localization, cell wall organization, and biogenesis, while the downregulated DEGs were associated with microtubule regulation, the cellular response to stress, and the cell cycle. Further analyses indicated that three genes, XLOC_036333 [mannosyl-oligosaccharide-α-mannosidase ( MNS1 )], XLOC_029945 ( FLA8 ), and XLOC_075372 ( snakin-1 ), were potentially important for the regulation of cotton fiber strength. Our results suggest that these genes may be good candidates for future investigation of the molecular mechanisms of fiber strength formation and for the improvement of cotton fiber quality through molecular breeding. Copyright © 2017 Lu et al.

Tensile Properties of 17-7 PH and 12 MoV Stainless-Steel Sheet under Rapid-Heating and Constant-Temperature Conditions

NASA Technical Reports Server (NTRS)

Manning, Charles R., Jr.; Price, Howard L.

1961-01-01

Results are presented of rapid-heating tests of 17-7 PH and 12 MoV stainless-steel sheet heated to failure at temperature rates from about 1 F to 170 F per second under constant-load conditions. Yield and rupture strengths obtained from rapid-heating tests are compared with yield and tensile strengths obtained from short-time elevated-temperature tensile tests (30-minute exposure). A rate-temperature parameter was used to construct master curves from which yield and rupture stresses or temperatures can be predicted. A method for measuring strain by optical means is described.

Polarization Coupling in Ferroelectric Multilayers as a Function of Interface Charge Concentration

NASA Astrophysics Data System (ADS)

Okatan, Mahmut; Mantese, Joseph; Alpay, Pamir

2009-03-01

Intriguing properties of multilayered and graded ferroelectrics follow from the electrostatic and electromechanical interactions. The strength of the interlayer coupling depends on the concentration of interfacial defects with short-range local electrostatic fields. Defects may locally relax polarization differences and thus reduce the commensurate bound charge concentration at the interlayer interfaces. In this talk, we develop a theoretical analysis based on non-linear thermodynamics coupled with basic electrostatic relations to understand the role of charge compensation at the interlayer interfaces. The results show multilayered ferroelectrics with systematic variations in the composition may display a colossal dielectric response depending upon the interlayer electrostatic interactions. It is expected that other properties such as the pyroelectric and piezoelectric response will yield concomitant increases through the dielectric permittivity.

Cold denaturation as a tool to measure protein stability

PubMed Central

Sanfelice, Domenico; Temussi, Piero Andrea

2016-01-01

Protein stability is an important issue for the interpretation of a wide variety of biological problems but its assessment is at times difficult. The most common parameter employed to describe protein stability is the temperature of melting, at which the populations of folded and unfolded species are identical. This parameter may yield ambiguous results. It would always be preferable to measure the whole stability curve. The calculation of this curve is greatly facilitated whenever it is possible to observe cold denaturation. Using Yfh1, one of the few proteins whose cold denaturation occurs at neutral pH and low ionic strength, we could measure the variation of its full stability curve under several environmental conditions. Here we show the advantages of gauging stability as a function of external variables using stability curves. PMID:26026885

A feast of visualization

NASA Astrophysics Data System (ADS)

2008-12-01

Strength through structure The visualization and assessment of inner human bone structures can provide better predictions of fracture risk due to osteoporosis. Using micro-computed tomography (µCT), Christoph Räth from the Max Planck Institute for Extraterrestrial Physics and colleagues based in Munich, Vienna and Salzburg have shown how complex lattice-shaped bone structures can be visualized. The structures were quantified by calculating certain "texture measures" that yield new information about the stability of the bone. A 3D visualization showing the variation with orientation of one of the texture measures for four different bone specimens (from left to right) is shown above. Such analyses may help us to improve our understanding of disease and drug-induced changes in bone structure (C Räth et al. 2008 New J. Phys. 10 125010).

Yield strength of Cu and an engineered material of Cu with 1% Pb

NASA Astrophysics Data System (ADS)

Buttler, William; Gray, George, III; Fensin, Saryu; Grover, Mike; Stevens, Gerald; Stone, Joseph; Turley, William

2015-06-01

To study the effects of engineered elastic-plastic yield on the mass-ejection from shocked materials we fielded explosively driven Cu and CuPb experiments. The Cu and CuPb experiments fielded fully annealed disks in contact with PBX 9501; the CuPb was extruded with 1% Pb that aggregates at the Cu grain boundaries. The elastic-plastic yield strength is explored as a difference of ejecta production of CuPb versus Cu, where the ejecta production of solid materials ties directly to the surface perturbation geometries of wavelengths (fixed at 65 μm) and amplitudes (which were varied). We observed that the Cu performs as expected, with ejecta turning on at the previously observed yield threshold, but the CuPb ejects mass in much larger quantities, at much lower wavenumber (k = 2 π/ λ) amplitude (h) products (kh), implying a reduced elastic-plastic yield stress of the engineered material, CuPb.

Transgressive variation for yield components and dynamic traits in Jefferson (Oryza sativa) x O. rufipogon introgression lines

USDA-ARS?s Scientific Manuscript database

Alleles from wild progenitors of crops can be a source of transgressive variation in modern cultivars. Introgressions from the Oryza rufipogon donor (IRGC104591) in an O. sativa tropical japonica cultivar (Jefferson) were shown to confer a yield advantage in multi-location field trials. Yield loci...

Process Improvement of Reactive Dye Synthesis Using Six Sigma Concept

NASA Astrophysics Data System (ADS)

Suwanich, Thanapat; Chutima, Parames

2017-06-01

This research focuses on the problem occurred in the reactive dye synthesis process of a global manufacturer in Thailand which producing various chemicals for reactive dye products to supply global industries such as chemicals, textiles and garments. The product named “Reactive Blue Base” is selected in this study because it has highest demand and the current chemical yield shows a high variation, i.e. yield variation of 90.4% - 99.1% (S.D. = 2.405 and Cpk = -0.08) and average yield is 94.5% (lower than the 95% standard set by the company). The Six Sigma concept is applied aiming at increasing yield and reducing variation of this process. This approach is suitable since it provides a systematic guideline with five improvement phases (DMAIC) to effectively tackle the problem and find the appropriate parameter settings of the process. Under the new parameter settings, the process yield variation is reduced to range between 96.5% - 98.5% (S.D. = 0.525 and Cpk = 1.83) and the average yield is increased to 97.5% (higher than the 95% standard set by the company).

Development of improved electroforming technique. [for fabricating regeneratively cooled thrust chambers

NASA Technical Reports Server (NTRS)

Mccandles, L. C.; Davies, L. G.

1973-01-01

Techniques were studied to reinforce or strengthen electroformed nickel to allow a fuller utilization of electroforming as a reliable and low cost fabrication technique for regenerately cooled thrust chambers. Techniques for wire wrapping while electrodepositing were developed that can result in a structurally strong wall with less weight than a conventional electroformed wall. Also a technique of codepositing submicron sized THO2 particles with the nickel to form a dispersion strengthened structure was evaluated. The standard nickel cylinders exhibited an average hoop strength of 80,000 psi with a yield strength of 65,000 psi and a modulus of 25.6 x 10 to the 6th power psi. The as produced dispersion strengthened nickel showed a hoop strength of 97,000 psi with a yield strength of 67,000 psi. This is an increase of 17,000 psi or 21% over the standard nickel hoop strength. The wire wrapping cylinders showed an increased strength over the standard nickel test samples of 26,000 to 66,800 psi which is in the range of 26 to 104% increase in strength over the base standard nickel. These latter test results are indicative of a volume percent wire reinforcement from 15 to 31. The measured hoop strengths agree with calculated composite strengths based upon rule of mixtures.

Structural, mechanical and light yield characterisation of heat treated LYSO:Ce single crystals for medical imaging applications

NASA Astrophysics Data System (ADS)

Mengucci, P.; André, G.; Auffray, E.; Barucca, G.; Cecchi, C.; Chipaux, R.; Cousson, A.; Davì, F.; Di Vara, N.; Rinaldi, D.; Santecchia, E.

2015-06-01

Five single crystals of cerium-doped lutetium yttrium oxyorthosilicate (LYSO:Ce) grown by the Czochralski method were submitted to structural characterisation by X-ray (XRD) and neutron (ND) diffraction, scanning (SEM) and transmission (TEM) electron microscopy and energy dispersive microanalysis (EDS). The Ultimate Tensile Strength (UTS), the Young Modulus (YM) and the Light Yield (LY) of the samples were also measured in order to correlate the mechanical and the optical behaviour of the crystals with the characteristics of their microstructure. Two of the samples analysed were also heat treated at 300 °C for 10 h to evidence possible variations induced by the temperature in the optical and mechanical response of the crystals. Results showed that the mean compositional variations evidenced by the structural analyses do not affect the mechanical and optical behaviour of the samples. On the contrary, the thermal treatment could induce the formation of coherent spherical particles (size 10 to 15 nm), not uniformly distributed inside the sample, that strongly reduce the UTS and YM values, but it does not affect the optical response of the crystal. This latter result was attributed to the low value of the heating temperature (300 °C) that is not sufficiently high to induce annealing of the oxygen vacancies traps that are responsible of the deterioration of the scintillation properties of the LYSO:Ce crystals. This study was carried out in the framework of the Crystal Clear Collaboration (CCC).

RESPECT-ED: Rates of Pulmonary Emboli (PE) and Sub-Segmental PE with Modern Computed Tomographic Pulmonary Angiograms in Emergency Departments: A Multi-Center Observational Study Finds Significant Yield Variation, Uncorrelated with Use or Small PE Rates.

PubMed

Mountain, David; Keijzers, Gerben; Chu, Kevin; Joseph, Anthony; Read, Catherine; Blecher, Gabriel; Furyk, Jeremy; Bharat, Chrianna; Velusamy, Karthik; Munro, Andrew; Baker, Kylie; Kinnear, Frances; Mukherjee, Ahses; Watkins, Gina; Buntine, Paul; Livesay, Georgia; Fatovich, Daniel

2016-01-01

Overuse of CT Pulmonary Angiograms (CTPA) for diagnosing pulmonary embolism (PE), particularly in Emergency Departments (ED), is considered problematic. Marked variations in positive CTPA rates are reported, with American 4-10% yields driving most concerns. Higher resolution CTPA may increase sub-segmental PE (SSPE) diagnoses, which may be up to 40% false positive. Excessive use and false positives could increase harm vs. benefit. These issues have not been systematically examined outside America. To describe current yield variation and CTPA utilisation in Australasian ED, exploring potential factors correlated with variation. A retrospective multi-centre review of consecutive ED-ordered CTPA using standard radiology reports. ED CTPA report data were inputted onto preformatted data-sheets. The primary outcome was site level yield, analysed both intra-site and against a nominated 15.3% yield. Factors potentially associated with yield were assessed for correlation. Fourteen radiology departments (15 ED) provided 7077 CTPA data (94% ≥64-slice CT); PE were reported in 1028 (yield 14.6% (95%CI 13.8-15.4%; range 9.3-25.3%; site variation p <0.0001) with four sites significantly below and one above the 15.3% target. Admissions, CTPA usage, PE diagnosis rates and size of PE were uncorrelated with yield. Large PE (≥lobar) were 55% (CI: 52.1-58.2%) and SSPE 8.8% (CI: 7.1-10.5%) of positive scans. CTPA usage (0.2-1.5% adult attendances) was correlated (p<0.006) with PE diagnosis but not SSPE: large PE proportions. We found significant intra-site CTPA yield variation within Australasia. Yield was not clearly correlated with CTPA usage or increased small PE rates. Both SSPE and large PE rates were similar to higher yield historical cohorts. CTPA use was considerably below USA 2.5-3% rates. Higher CTPA utilisation was positively correlated with PE diagnoses, but without evidence of increased proportions of small PE. This suggests that increased diagnoses seem to be of clinically relevant sized PE.

Consumer interaction strength may limit the diversifying effect of intraspecific competition: a test in alewife (Alosa pseudoharengus).

PubMed

Jones, Andrew W; Post, David M

2013-06-01

Intraspecific competition is considered a principal driver of dietary variation, but empirical studies provide mixed support for this mechanism. Here we link comparative and experimental work testing the effects of competition and resource availability on the dietary variation of the alewife (Alosa pseudoharengus). The alewife, a consumer with extreme effects on its resources, was specifically utilized to additionally test the idea that strong interactions between a consumer and its resources can diminish the diversifying effect of competition. First, we compared the short- and long-term diet measures of wild populations across a wide range of densities. Second, in a pair of large-scale field mesocosm experiments, we explored the influence of competition and interaction strength on alewife dietary variation. Results from a whole-lake comparison and field experiments indicated that increasing competition was negatively correlated with population dietary variation. Further, altering the strength of the interaction between the alewife and its prey via prey supplementation eliminated this negative relationship. Collectively, our results suggest that competitive interactions may not drive dietary diversification in the alewife and, potentially, in other highly effective consumers. Our results also indicate that further consideration of the strength of species interactions (and the consumer traits that underlie them) would improve our understanding of the link between intraspecific competition and variation.

Mechanical Properties of Fe-Ni Meteorites

NASA Astrophysics Data System (ADS)

Roberta, Mulford; El Dasher, B.

2010-10-01

Iron-nickel meteorites exhibit a unique lamellar microstructure, Widmanstatten patterns, consisting of small regions with steep-iron-nickel composition gradients.1,2 The microstructure arises as a result of extremely slow cooling in a planetary core or other large mass. Mechanical properties of these structures have been investigated using microindentation, x-ray fluorescence, and EBSD. Observation of local mechanical properties in these highly structured materials supplements bulk measurements, which can exhibit large variation in dynamic properties, even within a single sample. 3 Accurate mechanical properties for meteorites may enable better modeling of planetary cores, the likely origin of these objects. Appropriate values for strength are important in impact and crater modeling and in understanding the consequences of observed impacts on planetary crusts. Previous studies of the mechanical properties of a typical iron-nickel meteorite, a Diablo Canyon specimen, indicated that the strength of the composite was higher by almost an order of magnitude than values obtained from laboratory-prepared specimens.4 This was ascribed to the extreme work-hardening evident in the EBSD measurements. This particular specimen exhibited only residual Widmanstatten structures, and may have been heated and deformed during its traverse of the atmosphere. Additional specimens from the Canyon Diablo fall (type IAB, coarse octahedrite) and examples from the Muonionalusta meteorite and Gibeon fall ( both IVA, fine octahedrite), have been examined to establish a range of error on the previously measured yield, to determine the extent to which deformation upon re-entry contributes to yield, and to establish the degree to which the strength varies as a function of microstructure. 1. A. Christiansen, et.al., Physica Scripta, 29 94-96 (1984.) 2. Goldstein and Ogilvie, Geochim Cosmochim Acta, 29 893-925 (1965.) 3. M. D. Furnish, M.B. Boslough, G.T. Gray II, and J.L. Remo, Int. J. Impact Eng, 17 341-352 (1995.) 4. J.J. Petrovic, J. Mater. Sci., 36 1579-1583 (2001.)

Laterality in hand use across four tool-use behaviors among the wild chimpanzees of Bossou, Guinea, West Africa.

PubMed

Humle, Tatyana; Matsuzawa, Tetsuro

2009-01-01

Population-level right handedness is a human universal, whose evolutionary origins are the source of considerable empirical and theoretical debate. Although our closest neighbor, the chimpanzee, shows some evidence for population-level handedness in captivity, there is little evidence from the wild. Tool-use measures of hand use in chimpanzees have yielded a great deal of variation in directionality and strength in hand preference, which still remains largely unexplored and unexplained. Data on five measures of hand use across four tool-use skills--ant-dipping, algae-scooping, pestle-pounding and nut-cracking--among the wild chimpanzees of Bossou, Guinea, West Africa, are presented here. This study aims to explore age- and sex-class effects, as well as the influence of task motor, cognitive and haptic demands, on the strength and directionality of hand preference within and across all five measures of hand use. Although there was no age- or sex-class effect on the directionality of hand preference, immature

Stress and deformation analysis of tapered cantilever castellated beam using numerical method

NASA Astrophysics Data System (ADS)

Ilham Maulana, Taufiq; Soebandono, Bagus; Satria Jagad, Beta; Prayuda, Hakas

2018-05-01

The castellated beam is often used in buildings because of its lighter weight compared with a normal steel beam. There are many types of an opening in the castellated beam, one of which is hexagonal openings. This paper will discuss the analysis of stress and deformation on castellated beam with a variation of openings diameter, space between holes, and angle of hexagonal openings. Furthermore, stress distribution on specimen will be seen under static loading. This study used IWF section 150x75x5x7 with 4 variations of the span with one fixed support, and yield strength is 400 MPa. Linear finite element analysis is used with 10-node tetrahedron solid element, by observing von Misses stress. The software used in this study are freeware, which is LISAFEA 8.0 for analyzing and FreeCAD for drawing. The result shows that value of stress and deformation for each sample is quite volatile, but it can be concluded that stress distribution around the opening is larger than in web and flange.

Long-term irradiance observation and short-term flare prediction with LYRA on PROBA2

NASA Astrophysics Data System (ADS)

Dammasch, Ingolf; Dominique, Marie; West, Matthew; Katsiyannis, Thanassis; Ryan, Daniel; Wauters, Laurence

The solar radiometer LYRA on board the ESA micro-satellite PROBA2 has observed the Sun continuously since January 2010 in various spectral band passes, and has gained a considerable data base. Two of the LYRA channels cover the irradiance between soft X-ray and extreme ultraviolet. The variation of the sunspot number appears to show a strong similarity with the variation of these channels, when their long-range development is taken into account. The same holds for SXR levels observed by the GOES satellites. Due to LYRA's bandwidth and coverage of various active-region temperatures, its relatively smooth development may yield some information on the structure of the current solar cycle. On its websites, LYRA presents not only EUV and SXR time series in near real-time, but also information on flare parameters and long-term irradiance and sunspot levels. It will be demonstrated whether it is possible to aid space weather forecast with these statistical data, especially for the prediction of expected flare strength on a daily basis.

An in-depth analysis of the physico-mechanical properties imparted by agricultural fibers and food processing residues in polypropylene biocomposites

NASA Astrophysics Data System (ADS)

Murdy, Rachel Campbell; Mak, Michelle; Misra, Manjusri; Mohanty, Amar K.

2015-05-01

The use of agricultural and food processing residues as potential reinforcements in plastics has been extensively studied. However, there is a large variation in the mechanical performance of agricultural fiber-based biocomposites due to different processing materials and parameters. An in-depth comparison of the resulting effect of the agricultural filler on the matrix is often not possible given the discrepancy in processing conditions. This study seeks to determine the intrinsic properties of agricultural fibers and food processing residues for their use in polypropylene biocomposites based on a standardization of experimental design. The effect of 25wt% loading of miscanthus, fall-and spring-harvest switchgrass, wheat straw, oat hull, soy hull, soy stalk, hemp and flax on the physico-mechanical properties of polypropylene biocomposites was investigated. The addition of fiber led to an improvement in flexural strength, flexural modulus, and tensile modulus, and a general decrease in tensile strength at yield, elongation at break and Izod impact strength. Scanning electron microscopy highlighted the interfacial adhesion, orientation and distribution of the fibers within the matrix, confirming that fiber length and dispersion within the matrix are positively correlated with mechanical properties. The crystallization of the polypropylene phase and a compositional analysis of the agricultural fibers and processing residues were also compared to offer insight into the effect of the filler's intrinsic properties on the resulting material performance.

[Spatial-temporal variations of spring maize potential yields in a changing climate in Northeast China.

PubMed

Liu, Zhi Juan; Yang, Xiao Guang; Lyu, Shuo; Wang, Jing; Lin, Xiao Mao

2018-01-01

Based on meteorological data, agro-meteorological observations, and agricultural statistical data in Northeast China (NEC), by using the validated Agricultural Production System sIMulator (APSIM-maize), the potential, attainable, potential farmers' and actual farmers' yields of spring maize during the period 1961 to 2015 were analyzed, and the effects of climate variation on maize potential yield in NEC were quantified. Results indicated that the potential yield of spring maize was 12.2 t·hm -2 during the period 1961 to 2015, with those in northeast being lower than southwest within the study region. The attainable yield of spring maize was 11.3 t·hm -2 , and showed a similar spatial distribution with potential yield. Under the current farmers' management practices, mean simulated potential and actual farmers' yields were 6.5 and 4.5 t·hm -2 , respectively. Assuming there were no changes in cultivars and management practices in NEC, the mean potential, attainable, and potential farmers' yields of spring maize would decrease by 0.34, 0.25 and 0.10 t·hm -2 per decade in NEC. However, the actual farmers' yields increased with the value of 1.27 t·hm -2 per decade averaged over NEC. Due to climate variation, year-to-year variations of spring maize potential, attainable, and potential farmers' yields were significant, ranging from 10.0 to 14.4, 9.8 to 13.3, 4.4 to 8.5 t·hm -2 , respectively.

Radiative rates and electron impact excitation rate coefficients for Ne-like selenium, Se XXV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, K.; Chen, C.Y., E-mail: chychen@fudan.edu.cn; Huang, M.

2011-07-15

In this article we report calculations of energy levels, radiative rates, electron impact collision strengths, and effective collision strengths for transitions among the 241 fine-structure levels arising from 2l{sup 8} and 2l{sup 7}n{sup '}l{sup '} (n{sup '{<=}}6 and l{sup '{<=}}n{sup '}-1) configurations of Ne-like Se XXV using the Flexible Atomic Code. Energy levels and radiative rates are calculated within the relativistic configuration-interaction method. Direct excitation collision strengths are calculated using the relativistic distorted-wave approximation and high-energy collision strengths are obtained in the relativistic plane-wave approximation. Resonance contributions through the relevant Na-like doubly-excited configurations 2l{sup 7}n'l'n''l'' (3{<=}n'{<=}7, l'{<=}n'-1, n'{<=}n''{<=}50, and l''{<=}8)more » are explicitly taken into account via the independent-process and isolated-resonance approximation using distorted waves. Resonant stabilizing transitions and possibly important radiative decays from the resonances toward low-lying autoionizing levels are considered. In addition, the resonance contributions from Na-like 2l{sup 6}3l'3l'''n''' (n'''=3-6) configurations are included and found to be predominant for many transitions among the singly-excited states in Ne-like Se XXV. We present the radiative rates, oscillator strengths, and line strengths for all electric dipole, magnetic dipole, electric quadrupole, magnetic quadrupole, electric octopole, and magnetic octopole transitions among the 241 levels. The effective collision strengths are reported for all 28920 transitions among the 241 levels over a wide temperature range up to 10 keV. To assess the reliability and accuracy of the present collisional data, we have performed a 27-state close-coupling calculation, employing the Dirac R-matrix theory. The results from the close-coupling calculation and the independent-process calculation for the identical target states are found to be in good agreement. - Highlights: {yields} Radiative and collisional atomic data are presented for the lowest 241 fine-structure levels in Ne-like Se. {yields} Calculations are performed using the FAC package. {yields} Resonances enhance significantly a large amount of transitions. {yields} Radiative damping effects are significant for many transitions. {yields} Close-coupling effects are small in Ne-like Se.« less

Development of steel foam processing methods and characterization of metal foam

NASA Astrophysics Data System (ADS)

Park, Chanman

2000-10-01

Steel foam was synthesized by a powder metallurgical route, resulting in densities less than half that of steel. Process parameters for foam synthesis were investigated, and two standard powder formulations were selected consisting of Fe-2.5% C and 0.2 wt% foaming agent (either MgCO3 or SrCO3). Compression tests were performed on annealed and pre-annealed foam samples of different density to determine mechanical response and energy absorption behavior. The stress-strain response was strongly affected by annealing, which reduced the carbon content and converted much of the pearlitic structure to ferrite. Different powder blending methods and melting times were employed and the effects on the geometric structure of steel foam were examined. Dispersion of the foaming agent affected the pore size distribution of the expanded foams. With increasing melt time, pores coalesced, leading to the eventual collapse of the foam. Inserting interlayer membranes in the powder compacts inhibited coalescence of pores and produced foams with more uniform cell size and distribution. The closed-cell foam samples exhibited anisotropy in compression, a phenomenon that was caused primarily by the ellipsoidal cell shapes within the foam. Yield strengths were 3x higher in the transverse direction than in the longitudinal direction. Yield strength also showed a power-law dependence on relative density (n ≅ 1.8). Compressive strain was highly localized and occurred in discrete bands that extended transverse to the loading direction. The yield strength of foam samples showed stronger strain rate dependence at higher strain rates. The increased strain rate dependence was attributed to microinertial hardening. Energy absorption was also observed to increase with strain rate. Measurements of cell wall curvature showed that an increased mean curvature correlated with a reduced yield strength, and foam strengths generally fell below predictions of Gibson-Ashby theory. Morphological defects reduced yield strength and altered the dependence on density. Microstructural analysis was performed on a porous Mg and AZ31 Mg alloy synthesized by the GASAR process. The pore distribution depended on the distance from the chill end of ingots. TEM observations revealed apparent gas tracks neat the pores and ternary intermetallic phases in the alloy.

Mapping quantitative trait loci for lint yield and fiber quality across environments in a Gossypium hirsutum × Gossypium barbadense backcross inbred line population.

PubMed

Yu, Jiwen; Zhang, Ke; Li, Shuaiyang; Yu, Shuxun; Zhai, Honghong; Wu, Man; Li, Xingli; Fan, Shuli; Song, Meizhen; Yang, Daigang; Li, Yunhai; Zhang, Jinfa

2013-01-01

Identification of stable quantitative trait loci (QTLs) across different environments and mapping populations is a prerequisite for marker-assisted selection (MAS) for cotton yield and fiber quality. To construct a genetic linkage map and to identify QTLs for fiber quality and yield traits, a backcross inbred line (BIL) population of 146 lines was developed from a cross between Upland cotton (Gossypium hirsutum) and Egyptian cotton (Gossypium barbadense) through two generations of backcrossing using Upland cotton as the recurrent parent followed by four generations of self pollination. The BIL population together with its two parents was tested in five environments representing three major cotton production regions in China. The genetic map spanned a total genetic distance of 2,895 cM and contained 392 polymorphic SSR loci with an average genetic distance of 7.4 cM per marker. A total of 67 QTLs including 28 for fiber quality and 39 for yield and its components were detected on 23 chromosomes, each of which explained 6.65-25.27% of the phenotypic variation. Twenty-nine QTLs were located on the At subgenome originated from a cultivated diploid cotton, while 38 were on the Dt subgenome from an ancestor that does not produce spinnable fibers. Of the eight common QTLs (12%) detected in more than two environments, two were for fiber quality traits including one for fiber strength and one for uniformity, and six for yield and its components including three for lint yield, one for seedcotton yield, one for lint percentage and one for boll weight. QTL clusters for the same traits or different traits were also identified. This research represents one of the first reports using a permanent advanced backcross inbred population of an interspecific hybrid population to identify QTLs for fiber quality and yield traits in cotton across diverse environments. It provides useful information for transferring desirable genes from G. barbadense to G. hirsutum using MAS.

Crack Arrest Toughness of Two High Strength Steels (AISI 4140 and AISI 4340)

NASA Astrophysics Data System (ADS)

Ripling, E. J.; Mulherin, J. H.; Crosley, P. B.

1982-04-01

The crack initiation toughness ( K c ) and crack arrest toughness ( K a ) of AISI 4140 and AISI 4340 steel were measured over a range of yield strengths from 965 to 1240 MPa, and a range of test temperatures from -53 to +74°C. Emphasis was placed on K a testing since these values are thought to represent the minimum toughness of the steel as a function of loading rate. At the same yield strengths and test temperatures, K a for the AISI 4340 was about twice as high as it was for the AISI 4140. In addition, the K a values showed a more pronounced transition temperature than the K c values, when the data were plotted as a function of test temperature. The transition appeared to be associated with a change in fracture mechanism from cleavage to dimpled rupture as the test temperature was increased. The occurrence of a “pop-in” behavior at supertransition temperatures has not been found in lower strength steels, and its evaluation in these high strength steels was possible only because they are not especially tough at their supertransition temperatures. There is an upper toughness limit at which pop-in will not occur, and this was found for the AISI 4340 steel when it was tempered to its lowest yield strength (965 MPa). All the crack arrest data were identified as plane strain values, while only about one-half of the initiation values could be classified this way.

Experimental and theoretical investigation of the role of clay in subaqueous sediment flows and its effect on run-out distance

NASA Astrophysics Data System (ADS)

Hermidas, Navid; Luthi, Stefan; Eggenhuisen, Joris; Silva Jacinto, Ricardo; Toth, Ferenc; Pohl, Florian; de Leeuw, Jan

2016-04-01

Debris flows are driven by gravity, which in the tail region is overcome by the yield strength of the flow, forcing it to freeze. These flows are capable of achieving staggeringly large run-out distances on low gradients. The case in point, described in previous publications, is the flow which resulted in the deposit of Bed 5 of the Agadir megaslide on the north-west African margin. Debrites of this flow have been recorded several hundred kilometres away from the original landslide. Previous studies have attributed such long run-out distances to hydroplaning, low yield strength, and flow transformation. It is known that the net force acting on a volume of fluid in equilibrium is zero. In this work we show that clay-laden flows are capable of approaching equilibrium. The flows which can achieve the maximum run-out distance are cohesive enough to resist some of the surrounding disturbances, that can upset the equilibrium, and reach close to equilibrium conditions, yet are dilute enough to have low viscous stress, and relatively low yield strength and lose little sediment due to deposition. A flow that is not in equilibrium will always seek to approach equilibrium conditions by speeding up or slowing down, depositing sediment, eroding the substrate, contracting in the form of the tail approaching the head, stretching, entraining water and growing in height, or dewatering and collapsing. Here we present a theory that shows that two dimensional (2D) flows in equilibrium do not grow in height. 2D flume experiments were conducted on different mixtures of kaolinite, sand, silt, and water, on varying slopes and a transitionally rough bed (sand glued), and using various discharge rates, in order to map out different stages in the evolution of a density flow from a cohesive plug flow into a turbidity current. The following flow types were observed: high density turbidity currents, plug flows, and no flow. From the velocity profiles, certain runs demonstrated close to equilibrium behaviour. For these flows, very little flow height growth and velocity variation was observed over the length of the flume. In all cases the flow appeared to be laminar within the boundary layer with Kelvin-Helmholtz instabilities at the top which were suppressed to a large extent for higher sediment concentrations. A deposit consisting of thick muddy sand, with approximately uniform thickness, was observed for higher sediment concentrations, indicating relatively higher yield strength values, while a thinner more sandy deposit was observed for more dilute flows. It was concluded that high sediment concentrations on more moderate slopes result in slower moving plug flows which are capable of suppressing turbulence at the top, while lower sediment concentrations on steeper slopes result in faster moving, more turbulent currents. The flows which can achieve the largest run-out distance are located between these two extremes.

Correlation Between Precipitation and Crop Yield for Corn and Cotton Produced in Alabama

NASA Technical Reports Server (NTRS)

Hayes, Carol E.; Perkey, Donald J.

1998-01-01

In this study, variations in precipitation during the time of corn silking are compared to Alabama corn yields. Also, this study compares precipitation variations during bloom to Alabama cotton yield. The goal is to obtain mathematical correlations between rainfall during the crop's critical period and the crop amount harvested per acre.

Lithospheric flexural strength and effective elastic thicknesses of the Eastern Anatolia (Turkey) and surrounding region

NASA Astrophysics Data System (ADS)

Oruç, Bülent; Gomez-Ortiz, David; Petit, Carole

2017-12-01

The Lithospheric structure of Eastern Anatolia and the surrounding region, including the northern part of the Arabian platform is investigated via the analysis and modeling of Bouguer anomalies from the Earth Gravitational Model EGM08. The effective elastic thickness of the lithosphere (EET) that corresponds to the mechanical cores of the crust and lithospheric mantle is determined from the spectral coherence between Bouguer anomalies and surface elevation data. Its average value is 18.7 km. From the logarithmic amplitude spectra of Bouguer anomalies, average depths of the lithosphere-asthenosphere boundary (LAB), Moho, Conrad and basement in the study area are constrained at 84 km, 39 km, 16 km and 7 km, respectively. The geometries of the LAB and Moho are then estimated using the Parker-Oldenburg inversion algorithm. We also present a lithospheric strength map obtained from the spatial variations of EET determined by Yield Stress Envelopes (YSE). The EET varies in the range of 12-23 km, which is in good agreement with the average value obtained from spectral analysis. Low EET values are interpreted as resulting from thermal and flexural lithospheric weakening. According to the lithospheric strength of the Eastern Anatolian region, the rheology model consists of a strong but brittle upper crust, a weak and ductile lower crust, and a weak lower part of the lithosphere. On the other hand, lithosphere strength corresponds to weak and ductile lower crust, a strong upper crust and a strong uppermost lithospheric mantle for the northern part of the Arabian platform.

Modelling the effect of shear strength on isentropic compression experiments

NASA Astrophysics Data System (ADS)

Thomson, Stuart; Howell, Peter; Ockendon, John; Ockendon, Hilary

2017-01-01

Isentropic compression experiments (ICE) are a way of obtaining equation of state information for metals undergoing violent plastic deformation. In a typical experiment, millimetre thick metal samples are subjected to pressures on the order of 10 - 102 GPa, while the yield strength of the material can be as low as 10-2 GPa. The analysis of such experiments has so far neglected the effect of shear strength, instead treating the highly plasticised metal as an inviscid compressible fluid. However making this approximation belies the basic elastic nature of a solid object. A more accurate method should strive to incorporate the small but measurable effects of shear strength. Here we present a one-dimensional mathematical model for elastoplasticity at high stress which allows for both compressibility and the shear strength of the material. In the limit of zero yield stress this model reproduces the hydrodynamic models currently used to analyse ICEs. Numerical solutions of the governing equations will then be presented for problems relevant to ICEs in order to investigate the effects of shear strength compared with a model based purely on hydrodynamics.

Novel 1.5 GPa-strength with 50%-ductility by transformation-induced plasticity of non-recrystallized austenite in duplex steels.

PubMed

Sohn, Seok Su; Song, Hyejin; Jo, Min Chul; Song, Taejin; Kim, Hyoung Seop; Lee, Sunghak

2017-04-28

Needs for steel designs of ultra-high strength and excellent ductility have been an important issue in worldwide automotive industries to achieve energy conservation, improvement of safety, and crashworthiness qualities. Because of various drawbacks in existing 1.5-GPa-grade steels, new development of formable cold-rolled ultra-high-strength steels is essentially needed. Here we show a plausible method to achieve ultra-high strengths of 1.0~1.5 GPa together with excellent ductility above 50% by actively utilizing non-recrystallization region and TRansformation-Induced Plasticity (TRIP) mechanism in a cold-rolled and annealed Fe-Mn-Al-C-based steel. We adopt a duplex microstructure composed of austenite and ultra-fine ferrite in order to overcome low-yield-strength characteristics of austenite. Persistent elongation up to 50% as well as ultra-high yield strength over 1.4 GPa are attributed to well-balanced mechanical stability of non-crystallized austenite with critical strain for TRIP. Our results demonstrate how the non-recrystallized austenite can be a metamorphosis in 1.5-GPa-grade steel sheet design.

Data of the properties of rebar steel brands in Lagos, Nigerian market used in reinforced concrete applications.

PubMed

Joshua, Opeyemi; Olusola, Kolapo O; Oyeyemi, Kehinde D; Ogunde, Ayodeji O; Amusan, Lekan M; Nduka, David O; Abuka-Joshua, Joyce

2018-04-01

The data presented herein are compilations of the research summary of "Assessment of the Quality of Steel Reinforcement Bars Available in Nigerian Market" (Joshua et al., 2013) [1]. This data article provides information on the properties and cost of steel rebars used in reinforced concrete in Lagos, Nigeria. The data is based on the properties of 12 mm rebar brands which are the most used steel diameter in construction and they include actual diameters, yield strengths, ultimate strengths, ultimate/yield strength ratio, ductility and the cost of each brand. This data also contains the limiting standard properties of the highlighted properties in this data.

The effect of microstructure and strength on the fracture toughness of an 18 Ni, 300 grade maraging steel

NASA Technical Reports Server (NTRS)

Psioda, J. A.; Low, J. R., Jr.

1977-01-01

Fractography and metallographic sectioning were used to investigate the influence of microstructure and strength on the fracture toughness (KIc) and fracture mechanism of an 18 Ni, 300 grade maraging steel. Increased yield strength from 1442 to 2070 MN/m squared through precipitation hardening results in a KIc loss from 143 to 55 MN/m superscript 3/2. Ti (C,N) Ti2S, and TiC inclusions in sizes from 1 to 8, 1 to 15, and 0.1 to 2 microns respectively serve as sites for void nucleation and lead to fracture by the dimpled rupture process in all strength levels considered. TiC nucleated dimples occupy more than half the fracture in all conditions. Void nucleation rate and resultant number of dimples per unit area of fracture increase with increasing yield strength. Average dimple size decreases with increasing strength and/or overaging which follows from the decreasing amount of stable void growth measured by sectioning tensile specimens. Void growth is assisted by crack branching along a path of TiC inclusions. Coalescence occurs in the highest strength materials by a combination of TiC void nucleation and premature separation at strengthening precipitates.

Microstructure evolution and mechanical properties degradation of HPNb alloy after a five-year service

NASA Astrophysics Data System (ADS)

Guo, Jingfeng; Cao, Tieshan; Cheng, Congqian; Meng, Xianming; Zhao, Jie

2018-04-01

The microstructure and mechanical properties of ethylene cracking furnace tube (HPNb alloy) are investigated by scanning electronic microscopy (SEM), tensile tests and Charpy impact tests at room temperature, tensile tests and creep tests at high temperature in this paper. The primary carbides of HPNb alloy coarsened and formed a continuous network after a five-year service. Furthermore, a lot of fine secondary carbides precipitated in the dendrite interior. The primary carbides M7C3 and NbC transformed into M23C6 and G phase after service, respectively. The furnace tube after service exhibits higher yield strength, lower tensile strength, worse ductility and toughness than as-cast tube at room temperature. At high temperature, the tensile strength and yield strength of service tube are higher than as-cast tube, but its tensile elongation is lower. The creep strength of HPNb alloy at high temperature decreases after a five-year service. Both microstructure and mechanical properties of ethylene cracking furnace tube have deteriorated after a five-year service.

Development of High-Strength High-Temperature Cast Al-Ni-Cr Alloys Through Evolution of a Novel Composite Eutectic Structure

NASA Astrophysics Data System (ADS)

Pandey, P.; Kashyap, S.; Tiwary, C. S.; Chattopadhyay, K.

2017-12-01

Aiming to develop high-strength Al-based alloys with high material index (strength/density) for structural application, this article reports a new class of multiphase Al alloys in the Al-Ni-Cr system that possess impressive room temperature and elevated temperature (≥ 200 °C) mechanical properties. The ternary eutectic and near eutectic alloys display a complex microstructure containing intermetallic phases displaying hierarchically arranged plate and rod morphologies that exhibit extraordinary mechanical properties. The yield strengths achieved at room temperatures are in excess of 350 MPa with compressive plastic strains of more than 30 pct (without fracturing) for these alloys. The stability of the complex microstructure also leads to a yield stress of 191 ± 8 to 232 ± 5 MPa at 250 °C. It is argued that the alloys derive their high strength and impressive plasticity through synergic effects of refined nanoeutectics of two different morphologies forming a core shell type of architecture.

The strength and hemispheric asymmetry of Equatorial Ionization Anomaly during two geomagnetic storms in 2013 from Global Ionosphere Map and SAMI2

NASA Astrophysics Data System (ADS)

Luo, Weihua; Zhu, Zhengping; Lan, Jiaping

2016-08-01

The variations of the strength and the hemispheric asymmetry of EIA were studied by Global Ionosphere Map (GIM) and SAMI2 during two geomagnetic storm periods in March and June 2013. Compared with the 30-days median TEC, the TEC at the two crests of EIA had small variations while the TEC at the trough had a more remarkable variation for the two storms after the SSC. The TEC difference between the two EIA peaks had an increase or decrease several hours after the SSC, the asymmetry between the two crests of EIA represented by the defined asymmetry index has no obvious variations except several hours after the SSC, and EIA strength represented by the Crest-to-Trough Ratio (CTR) had a remarkable increase one day after the SSC day for March storm and decrease several hours after the SSC for June storm. The variations last several hours, with more than 40% variations compared with the value during the quiet period. The EIA peaks were also found to move toward the equator after the SSC during the two storms. The simulation from SAMI2 and HWM07 also shows that EIA crests would move toward the equator during storm time and EIA strength would decrease, which suggests that the disturbed neutral wind and disturbed electric field may be important factors affecting the EIA during the storm periods.

Variation in the strength of reproductive interference from an alien congener to a native species in Taraxacum.

PubMed

Nishida, Sachiko; Hashimoto, Keisuke; Kanaoka, Masahiro M; Takakura, Ko-Ichi; Nishida, Takayoshi

2017-01-01

Reproductive interference (RI) may be a contributing factor to the displacement of native species by an alien congener, and RI strength has been shown theoretically to affect distributional relationships between species. Thus, variations in RI strength from alien to native species result in different consequences of invasions and efforts to conserve native species, but the variations have seldom been examined empirically. We therefore investigated RI strength variations from the alien species Taraxacum officinale and its hybrids to eight populations of native dandelions, four T. japonicum populations and two populations each of two subspecies of T. platycarpum. We examined the association between alien relative abundance and native seed set in field surveys, and we also performed hand-pollination experiments to investigate directly the sensitivity of native flowers to alien pollen. We found that the effect of alien relative abundance on native seed set of even the same native species could differ greatly in different regions, and that the sensitivity of native flowers to alien pollen was also dependent on region. Our results, together with those of previous studies, show that RI from the alien to the native species is strong in regions where the alien species outnumbers the native species and marginal where it does not; this result suggests that alien RI can critically affect distributional relationships between native and alien species. Our study highlights the importance of performing additional empirical investigations of RI strength variation and of giving due attention to alien RI in efforts to conserve regional native biodiversity.

46 CFR 154.630 - Cargo tank material.

Code of Federal Regulations, 2010 CFR

2010-10-01

... alloy in the annealed condition. (c) Increased yield strength and tensile strength of a material at low temperature for independent tanks type A, B, and C must be specially approved by the Commandant (CG-522). [CGD...

Tensile and Microindentation Stress-Strain Curves of Al-6061

DOE Data Explorer

Weaver, Jordan S [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Center for Integrated Nanotechnologies (CINT); Khosravani, Ali [Georgia Inst. of Technology, Atlanta, GA (United States); Castillo, Andrew [Georgia Inst. of Technology, Atlanta, GA (United States); Kalidind, Surya R [Georgia Inst. of Technology, Atlanta, GA (United States)

2016-07-13

Recent spherical microindentation stress-strain protocols were developed and validated on Al-6061 (DOI: 10.1186/s40192-016-0054-3). The scaling factor between the uniaxial yield strength and the indentation yield strength was determined to be about 1.9. The microindentation stress-strain protocols were then applied to a microstructurally graded sample in an effort to extract high throughput process-property relationships. The tensile and microindentation force-displacement and stress-strain data are presented in this data set.

Variation in the ovine MYF5 gene and its effect on carcass lean meat yield in New Zealand Romney sheep.

PubMed

Wang, Jiqing; Zhou, Huitong; Forrest, Rachel H J; Hu, Jiang; Liu, Xiu; Li, Shaobin; Luo, Yuzhu; Hickford, Jon G H

2017-09-01

Myogenic factor 5 (MYF5) plays an important role in regulating skeletal muscle, but to date there have been no reports on whether the gene is variable and whether this variation is associated with meat yield in sheep. In this study, four variants (A to D) of ovine MYF5 containing two Single Nucleotide Polymorphisms (SNPs) and one basepair (bp) insertion/deletion were detected by Polymerase Chain Reaction - Single Stranded Conformational Polymorphism (PCR-SSCP) analysis. Breed differences in variant frequencies were observed. The effect of variation in ovine MYF5 on lean meat yield, predicted using VIAScan® technology, was investigated in 388 male NZ Romney lambs. Only genotypes AA and AB were found in these lambs. Lambs with genotype AA had a higher leg yield (P=0.044), loin yield (P=0.002) and total yield (P=0.012) than those with genotype AB. No association with shoulder yield was detected. These results suggest that ovine MYF5 may be a valuable genetic marker for improved lean meat yield. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effects of vegetation on runoff generation, sediment yield and soil shear strength on road-side slopes under a simulation rainfall test in the Three Gorges Reservoir Area, China.

PubMed

Liu, Yao-Jun; Wang, Tian-Wei; Cai, Chong-Fa; Li, Zhao-Xia; Cheng, Dong-Bing

2014-07-01

Vegetation recolonization has often been used to control roadside slope erosion, and in this paper, four restoration models - Natural Restoration, Grass, Grass & Shrub, Sodded Strip - were chosen to recolonize the plants on a newly built unpaved roadside slope in the Three Gorges Reservoir Area. After eight months growth, eight rainfall simulations (intensity of 90 mm h(-1) for 60 min) and in-situ soil shear strength test were then carried out to identify the impacts of vegetation on roadside slope erosion and soil shear strength. The erosion on cutslopes was higher than that on fillslopes. The runoff coefficient and soil detachment rate were significantly lower on the Grass & Shrub model (4.3% and 1.99 g m(-2) min(-1), respectively) compared with the other three, which had the highest surface cover (91.4%), aboveground biomass (1.44 kg m(-2)) and root weight density (3.94 kg m(-3)). The runoff coefficient and soil detachment rate on roadside slopes showed a logarithmic decrease with the root weight density, root length density and aboveground biomass. The soil shear strength measured before and after the rainfall was higher on Grass & Shrub (59.29 and 53.73 kPa) and decreased on Grass (46.93 and 40.48 kPa), Sodded Strip (31.20 and 18.87 kPa) and Natural Restoration (25.31 and 9.36 kPa). Negative linear correlations were found between the soil shear strength reduction and aboveground biomass, root weight density and root length density. The variation of soil shear strength reduction was closely related to the roadside slope erosion, a positive linear correlation was found between runoff coefficient and soil shear strength reduction, and a power function was shown between soil detachment rate and soil shear strength reduction. This study demonstrated that Grass and Grass & Shrub were more suitable and highly cost-effective in controlling initial period erosion of newly built low-volume unpaved road. Copyright © 2014 Elsevier B.V. All rights reserved.

Optimisation of gelatin extraction from Unicorn leatherjacket (Aluterus monoceros) skin waste: response surface approach.

PubMed

Hanjabam, Mandakini Devi; Kannaiyan, Sathish Kumar; Kamei, Gaihiamngam; Jakhar, Jitender Kumar; Chouksey, Mithlesh Kumar; Gudipati, Venkateshwarlu

2015-02-01

Physical properties of gelatin extracted from Unicorn leatherjacket (Aluterus monoceros) skin, which is generated as a waste from fish processing industries, were optimised using Response Surface Methodology (RSM). A Box-Behnken design was used to study the combined effects of three independent variables, namely phosphoric acid (H3PO4) concentration (0.15-0.25 M), extraction temperature (40-50 °C) and extraction time (4-12 h) on different responses like yield, gel strength and melting point of gelatin. The optimum conditions derived by RSM for the yield (10.58%) were 0.2 M H3PO4 for 9.01 h of extraction time and hot water extraction of 45.83 °C. The maximum achieved gel strength and melting point was 138.54 g and 22.61 °C respectively. Extraction time was found to be most influencing variable and had a positive coefficient on yield and negative coefficient on gel strength and melting point. The results indicated that Unicorn leatherjacket skins can be a source of gelatin having mild gel strength and melting point.

Study of MA Effect on Yield Strength and Ductility of X80 Linepipe Steels Weld

NASA Astrophysics Data System (ADS)

Huda, Nazmul; Lazor, Robert; Gerlich, Adrian P.

2017-09-01

Multipass GMAW (Gas Metal Arc Welding) welding was used to join X80 linepipe materials using two weld metals of slightly different compositions. Welding wires with diameters of 0.984 and 0.909 mm were used while applying the same heat input in each pass. The slight difference in the wire diameters resulted in different HAZ microstructures. The microstructures in the doubly reheated HAZ of both welds were found to contain bainite-ferrite. However, etching also revealed a difference in martensite-austenite (MA) fraction in these reheated zones. The MA exhibited twice the hardness of ferrite when measured by nanoindentation. Tensile testing from the reheated zone of both welds revealed a difference in yield strength, tensile strength and elongation of the transverse weld specimens. In the reheated zone of weld A, (produced with a 0.984 mm wire) a higher fraction of MA was observed, which resulted in higher strength but lower elongation compared to weld B. The ductility of weld A was found severely impaired (to nearly half of weld B) due to formation of closely spaced voids around the MA, along with debonding of MA from the matrix, which occurs just above the yield stress.

Possibilities for specific utilization of material properties for an optimal part design

NASA Astrophysics Data System (ADS)

Beier, T.; Gerlach, J.; Roettger, R.; Kuhn, P.

2017-09-01

High-strength, cold-formable steels offer great potential for meeting cost and safety requirements in the automotive industry. In view of strengths of up to 1200 MPa now attainable, certain aspects need to be analysed and evaluated in advance in the development process using these materials. In addition to early assessment of crash properties, it is also highly important to adapt the forming process to match the material potential. The steel making companies have widened their portfolios of cold-rolled dual-phase steels well beyond the conventional high-strength steels. There are added new grades which offer a customized selection of high energy absorption, deformation resistance or enhanced cold-forming properties. In this article the necessary components for material modelling for finite element simulation are discussed. Additionally the required tests for material model calibration are presented and the potentials of the thyssenkrupp Steel material data base are introduced. Besides classical tensile tests at different angles to rolling direction and the forming limit curve, the hydraulic bulge test is now available for a wide range of modern steel grades. Using the conventional DP-K®60/98 and the DP-K®700Y980T with higher yield strength the method for calibrating yield locus, hardening and formability is given. With reference to the examples of an A-pillar reinforcement and different crash tests the procedure is shown how the customer can evaluate an optimal steel grade for specific requirements. Although the investigated materials have different yield strengths, no large differences in the forming process between the two steel grades can be found. However some advantages of the high-yield grade can be detected in crash performance depending on the specific boundary and loading conditions.

Grain orientation effects on dynamic strength of FCC multicrystals at low shock pressures: a hydrodynamic instability study

DOE PAGES

Peralta, P.; Loomis, E.; Chen, Y.; ...

2015-04-09

Variability in local dynamic plasticity due to material anisotropy in polycrystalline metals is likely to be important on damage nucleation and growth at low pressures. Hydrodynamic instabilities could be used to study these plasticity effects by correlating measured changes in perturbation amplitudes at free surfaces to local plastic behaviour and grain orientation, but amplitude changes are typically too small to be measured reliably at low pressures using conventional diagnostics. Correlations between strength at low shock pressures and grain orientation were studied in copper (grain size ≈ 800 μm) using the Richtmyer–Meshkov instability with a square-wave surface perturbation (wavelength = 150 μm, amplitude = 5 μm), shocked at 2.7 GPa using symmetric plate impacts. A Plexiglas window was pressed against the peaks of the perturbation, keeping valleys as free surfaces. This produced perturbation amplitude changes much larger than those predicted without the window. Amplitude reductions from 64 to 88% were measured in recovered samples and grains oriented close tomore » $$\\langle$$0 0 1$$\\rangle$$ parallel to the shock had the largest final amplitude, whereas grains with shocks directions close to $$\\langle$$1 0 1$$\\rangle$$ had the lowest. Finite element simulations were performed with elastic-perfectly plastic models to estimate yield strengths leading lead to those final amplitudes. Anisotropic elasticity and these yield strengths were used to calculate the resolved shear stresses at yielding for the two orientations. In conclusion, results are compared with reports on orientation dependence of dynamic yielding in Cu single crystals and the higher values obtained suggest that strength estimations via hydrodynamic instabilities are sensitive to strain hardening and strain rate effects.« less

Dynamic tensile characterization of Vascomax® maraging C250 and C300 alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Bo; Wakeland, Peter Eric; Furnish, Michael D.

Vascomax® maraging C250 and C300 alloys were dynamically characterized in tension with Kolsky tension bar techniques. Compared with conventional Kolsky tension bar experiments, a pair of lock nuts was used to minimize the pseudo stress peak and a laser system was applied to directly measure the specimen displacement. Dynamic engineering stress–strain curves of the C250 and C300 alloys were obtained in tension at 1000 and 3000 s –1. The dynamic yield strengths for both alloys were similar, but significantly higher than those obtained from quasi-static indentation tests. Both alloys exhibited insignificant strain-rate effect on dynamic yield strength. The C300 alloymore » showed approximately 10 % higher in yield strength than the C250 alloy at the same strain rates. Necking was observed in both alloys right after yield. The Bridgman correction was applied to calculate the true stress and strain at failure for both alloys. The true failure stress showed a modest strain rate effect for both alloys but no significant difference between the two alloys at the same strain rate. As a result, the C250 alloy was more ductile than the C300 alloy under dynamic loading.« less

Dynamic tensile characterization of Vascomax® maraging C250 and C300 alloys

DOE PAGES

Song, Bo; Wakeland, Peter Eric; Furnish, Michael D.

2015-04-14

Vascomax® maraging C250 and C300 alloys were dynamically characterized in tension with Kolsky tension bar techniques. Compared with conventional Kolsky tension bar experiments, a pair of lock nuts was used to minimize the pseudo stress peak and a laser system was applied to directly measure the specimen displacement. Dynamic engineering stress–strain curves of the C250 and C300 alloys were obtained in tension at 1000 and 3000 s –1. The dynamic yield strengths for both alloys were similar, but significantly higher than those obtained from quasi-static indentation tests. Both alloys exhibited insignificant strain-rate effect on dynamic yield strength. The C300 alloymore » showed approximately 10 % higher in yield strength than the C250 alloy at the same strain rates. Necking was observed in both alloys right after yield. The Bridgman correction was applied to calculate the true stress and strain at failure for both alloys. The true failure stress showed a modest strain rate effect for both alloys but no significant difference between the two alloys at the same strain rate. As a result, the C250 alloy was more ductile than the C300 alloy under dynamic loading.« less

Effects of grain size on the strength and ductility of Ni sub 3 Al and Ni sub 3 Al + boron

DOE Office of Scientific and Technical Information (OSTI.GOV)

Viens, D.V.; Weihs, T.P.; Baker, I.

Tensile and compression experiments have been performed on Ni{sub 3}Al and on Ni{sub 3}Al + B at 77K to 1023K at 1 {times} 10{sup {minus}4}s{sup {minus}1}. At low temperatures yielding occurs discontinuously and the yield strength obeys the relationship {sigma}{sub y} = {sigma}{sub i} + kd{sup {minus}3/4} where {sigma}{sub i} and k are constants. Grain refinement has little effect on the ductility of the binary alloy, but leads to a brittle to ductile transition in the alloy containing boron. At high temperatures, grain refinement weakens the material, owing to grain boundary sliding. Dynamic recrystalization occurs and leads to another brittlemore » to ductile transition upon refining the grains. Under all conditions investigated, fracture occurs intergranularly. An analysis based upon a work-hardening model is given for the d{sup {minus}3/4} dependence of the yield strength at low temperatures.« less

A study on tensile deformation at room temperature and 650 °C in the directional solidified Ni-base superalloy GTD-111

NASA Astrophysics Data System (ADS)

Pauzi, AA; Ghaffar, MH Abdul; Chang, SY; Ng, GP; Husin, S.

2017-10-01

GTD-111 DS generally used for gas turbine blades is a high performance Ni-base superalloy. This alloy, with high volume of γ’ phase, has excellent tensile properties at high temperature. The effect of temperature on the tensile deformation of GTD-111 DS was investigated by using tensile test and microstructure evaluation of the fractured specimens. The tensile behaviour of GTD-111 DS was studied in the room temperature (RT) and 650 °C. From the yield strength results, the yield strength decreases from the average of 702.72 MPa to the average of 645.62 MPa with the increase of temperature from RT to 650 °C. The scanning electron microscope (SEM) results on fractured specimens confirmed that the tensile behaviour affected by deformation of the surface at 650 °C compared to fractured surface at RT. Based on the laboratory testing results, the correlation between tensile deformation of fractured surface and yield strength were discussed.

Controlling the mechanical properties of carbon steel by thermomechanical treatment

NASA Astrophysics Data System (ADS)

Balavar, Mohsen; Mirzadeh, Hamed

2018-01-01

The effect of thermomechanical processing and heat treatment on the microstructure and mechanical properties of low carbon steel was studied. It was revealed that the dual phase ferritic-martensitic microstructure shows a good combination of tensile strength and ductility along with superior work hardening response. On the other hand, the bimodal-sized structure containing ultrafine grained (UFG) and micron-sized ferrite phase can be easily produced by cold rolling and annealing of the dual phase starting microstructure. This steel showed high yield stress, tensile strength, and ductility, but poor work hardening ability. The full annealed ferritic-pearlitic sheet with banded morphology exhibited low strength and high total elongation with the appearance of the yield point phenomenon. The martensitic steels, however, had high tensile strength and low ductility. By comparing the tensile properties of these steels, it was shown that it is possible to control the mechanical properties of low carbon steel by simple processing routes.

Metal nanoplates: Smaller is weaker due to failure by elastic instability

NASA Astrophysics Data System (ADS)

Ho, Duc Tam; Kwon, Soon-Yong; Park, Harold S.; Kim, Sung Youb

2017-11-01

Under mechanical loading, crystalline solids deform elastically, and subsequently yield and fail via plastic deformation. Thus crystalline materials experience two mechanical regimes: elasticity and plasticity. Here, we provide numerical and theoretical evidence to show that metal nanoplates exhibit an intermediate mechanical regime that occurs between elasticity and plasticity, which we call the elastic instability regime. The elastic instability regime begins with a decrease in stress, during which the nanoplates fail via global, and not local, deformation mechanisms that are distinctly different from traditional dislocation-mediated plasticity. Because the nanoplates fail via elastic instability, the governing strength criterion is the ideal strength, rather than the yield strength, and as a result, we observe a unique "smaller is weaker" trend. We develop a simple surface-stress-based analytic model to predict the ideal strength of the metal nanoplates, which accurately reproduces the smaller is weaker behavior observed in the atomistic simulations.

Effect of heat treatment on microstructure and mechanical properties of Mg-4Y-1.6Nd-1Sm-0.5Zr alloy

NASA Astrophysics Data System (ADS)

Jia, Guilong; Guo, Erjun; Feng, Yicheng; Wang, Liping; Wang, Changliang

2018-03-01

Microstructure and mechanical properties of Mg-4Y-1.6Nd-1Sm-0.5Zr alloy during heat treatments were investigated, while the room-temperature tensile fractographs were observed and analyzed. The results show that the eutectic phases almost dissolve into the matrix after being solutionized at 525 °C for 8 h. The ultimate tensile strength, yield strength and elongation reach 300 MPa, 219 MPa, 6.5% respectively after being under-aged at 200 °C for 16 h. The ultimate tensile strength and yield strength of the alloy decrease gradually, while the elongation increases gradually with increasing the test temperatures. The room-temperature tensile fracture modes of the as-cast alloy, solutionized alloy, aged alloy are mixed fracture of transgranular and intergranular, transgranular cleavage fracture, transgranular fracture, respectively.

Withdrawal Strength and Bending Yield Strength of Stainless Steel Nails

Treesearch

Douglas R. Rammer; Samuel L. Zelinka

2015-01-01

It has been well established that stainless steel nails have superior corrosion performance compared to carbon steel or galvanized nails in treated wood; however, their mechanical fastening behavior is unknown. In this paper, the performance of stainless steel nails is examined with respect to two important properties used in wood connection design: withdrawal strength...

Strength of orthotropic materials subjected to combined stresses

Treesearch

Charles B. Norris

1962-01-01

A theory of the strength of orthotropic materials subjected to combined stresses, based on the Henky-von Mises theory of energy due to change of shape, is presented. When this theory is applied to macroscopically isotropic materials, it yields the diagram currently used in design with metals. Equations relating the strength of orthotropic materials subjected to a...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Aiying; Liu, Jiabin; Wang, Hongtao

Gradient materials often have attractive mechanical properties that outperform uniform microstructure counterparts. It remains a difficult task to investigate and compare the performance of various gradient microstructures due to the difficulty of fabrication, the wide range of length scales involved, and their respective volume percentage variations. We have investigated four types of gradient microstructures in 304 stainless steels that utilize submicrotwins, nanotwins, nanocrystalline-, ultrafine- and coarse-grains as building blocks. Tensile tests reveal that the gradient microstructure consisting of submicrotwins and nanotwins has a persistent and stable work hardening rate and yields an impressive combination of high strength and high ductility,more » leading to a toughness that is nearly 50% higher than that of the coarse-grained counterpart. Ex- and in-situ transmission electron microscopy indicates that nanoscale and submicroscale twins help to suppress and limit martensitic phase transformation via the confinement of martensite within the twin lamellar. Twinning and detwinning remain active during tensile deformation and contribute to the work hardening behavior. We discuss the advantageous properties of using submicrotwins as the main load carrier and nanotwins as the strengthening layers over those coarse and nanocrystalline grains. Furthermore, our work uncovers a new gradient design strategy to help metals and alloys achieve high strength and high ductility.« less

Method for improving the mechanical properties of uranium-1 to 3 wt % zirconium alloy

DOEpatents

Anderson, R.C.

1983-11-22

A uranium-1 to 3 wt % zirconium alloy characterized by high strength, high ductility and stable microstructure is fabricated by an improved thermal mechanical process. A homogenous ingot of the alloy which has been reduced in thickness of at least 50% in the two-step forging operation, rolled into a plate with a 75% reduction and then heated in vacuum at a temperature of about 750 to 850/sup 0/C and then quenched in water, is subjected to further thermal-mechanical operation steps to increase the compressive yield strength approximately 30%, stabilize the microstructure, and decrease the variations in mechanical properties throughout the plate is provided. These thermal-mechanical steps are achieved by cold rolling the quenchd plate to reduce the thickness thereof about 8 to 12%, aging the cold rolled plate at a first temperature of about 325 to 375/sup 0/C for five to six hours and then aging the plate at a higher temperature ranging from 480 to 500/sup 0/C for five to six hours prior to cooling the billet to ambient conditions and sizing the billet or plate into articles provides the desired increase in mechanical properties and phase stability throughout the plate.

Mechanical design of mussel byssus: material yield enhances attachment strength

PubMed

Bell; Gosline

1996-01-01

The competitive dominance of mussels in the wave-swept rocky intertidal zone is in part due to their ability to maintain a secure attachment. Mussels are tethered to the substratum by a byssus composed of numerous extracellular, collagenous threads secreted by the foot. Each byssal thread has three serially arranged parts: a corrugated proximal region, a smooth distal region and an adhesive plaque. This study examines the material and structural properties of the byssal threads of three mussel species: Mytilus californianus, M. trossulus, and M. galloprovincialis. Tensile tests in general reveal similar material properties among species: the proximal region has a lower initial modulus, a lower ultimate stress and a higher ultimate strain than the distal region. The distal region also yields at a stress well below its ultimate value. In whole thread tests, the proximal region and adhesive plaque are common sites of structural failure and are closely matched in strength, while the distal region appears to be excessively strong. We propose that the high strength of the distal region is the byproduct of a material designed to yield and extend before structural failure occurs. Experimental and theoretical evidence is presented suggesting that thread yield and extensibility provide two important mechanisms for increasing the overall attachment strength of the mussel: (1) the reorientation of threads towards the direction of applied load, and (2) the 'recruitment' of more threads into tension and the consequent distribution of applied load over a larger cross-sectional area, thereby reducing the stress on each thread. This distal region yield behavior is most striking for M. californianus and may be a key to its success in extreme wave-swept environments.

New QCT analysis approach shows the importance of fall orientation on femoral neck strength.

PubMed

Carpenter, R Dana; Beaupré, Gary S; Lang, Thomas F; Orwoll, Eric S; Carter, Dennis R

2005-09-01

The influence of fall orientation on femur strength has important implications for understanding hip fracture risk. A new image analysis technique showed that the strength of the femoral neck in 37 males varied significantly along the neck axis and that bending strength varied by a factor of up to 2.8 for different loading directions. Osteoporosis is associated with decreased BMD and increased hip fracture risk, but it is unclear whether specific osteoporotic changes in the proximal femur lead to a more vulnerable overall structure. Nonhomogeneous beam theory, which is used to determine the mechanical response of composite structures to applied loads, can be used along with QCT to estimate the resistance of the femoral neck to axial forces and bending moments. The bending moment [My(theta)] sufficient to induce yielding within femoral neck sections was estimated for a range of bending orientations (theta) using in vivo QCT images of 37 male (mean age, 73 years; range, 65-87 years) femora. Volumetric BMD, axial stiffness, average moment at yield (M(y,avg)), maximum and minimum moment at yield (M(y,max) and M(y,min)), bone strength index (BSI), stress-strain index (SSI), and density-weighted moments of resistance (Rx and Ry) were also computed. Differences among the proximal, mid-, and distal neck regions were detected using ANOVA. My(theta) was found to vary by as much as a factor of 2.8 for different bending directions. Axial stiffness, M(y,avg), M(y,max), M(y,min), BSI, and Rx differed significantly between all femoral neck regions, with an overall trend of increasing axial stiffness and bending strength when moving from the proximal neck to the distal neck. Mean axial stiffness increased 62% between the proximal and distal neck, and mean M(y,avg) increased 53% between the proximal and distal neck. The results of this study show that femoral neck strength strongly depends on both fall orientation and location along the neck axis. Compressive yielding in the superior portion of the femoral neck is expected to initiate fracture in a fall to the side.

Elucidating the impact of temperature variability and extremes on cereal croplands through remote sensing.

PubMed

Duncan, John M A; Dash, Jadunandan; Atkinson, Peter M

2015-04-01

Remote sensing-derived wheat crop yield-climate models were developed to highlight the impact of temperature variation during thermo-sensitive periods (anthesis and grain-filling; TSP) of wheat crop development. Specific questions addressed are: can the impact of temperature variation occurring during the TSP on wheat crop yield be detected using remote sensing data and what is the impact? Do crop critical temperature thresholds during TSP exist in real world cropping landscapes? These questions are tested in one of the world's major wheat breadbaskets of Punjab and Haryana, north-west India. Warming average minimum temperatures during the TSP had a greater negative impact on wheat crop yield than warming maximum temperatures. Warming minimum and maximum temperatures during the TSP explain a greater amount of variation in wheat crop yield than average growing season temperature. In complex real world cereal croplands there was a variable yield response to critical temperature threshold exceedance, specifically a more pronounced negative impact on wheat yield with increased warming events above 35 °C. The negative impact of warming increases with a later start-of-season suggesting earlier sowing can reduce wheat crop exposure harmful temperatures. However, even earlier sown wheat experienced temperature-induced yield losses, which, when viewed in the context of projected warming up to 2100 indicates adaptive responses should focus on increasing wheat tolerance to heat. This study shows it is possible to capture the impacts of temperature variation during the TSP on wheat crop yield in real world cropping landscapes using remote sensing data; this has important implications for monitoring the impact of climate change, variation and heat extremes on wheat croplands. © 2014 John Wiley & Sons Ltd.

RESPECT-ED: Rates of Pulmonary Emboli (PE) and Sub-Segmental PE with Modern Computed Tomographic Pulmonary Angiograms in Emergency Departments: A Multi-Center Observational Study Finds Significant Yield Variation, Uncorrelated with Use or Small PE Rates

PubMed Central

Chu, Kevin; Joseph, Anthony; Read, Catherine; Blecher, Gabriel; Furyk, Jeremy; Bharat, Chrianna; Velusamy, Karthik; Munro, Andrew; Baker, Kylie; Kinnear, Frances; Mukherjee, Ahses; Watkins, Gina; Buntine, Paul; Livesay, Georgia

2016-01-01

Introduction Overuse of CT Pulmonary Angiograms (CTPA) for diagnosing pulmonary embolism (PE), particularly in Emergency Departments (ED), is considered problematic. Marked variations in positive CTPA rates are reported, with American 4–10% yields driving most concerns. Higher resolution CTPA may increase sub-segmental PE (SSPE) diagnoses, which may be up to 40% false positive. Excessive use and false positives could increase harm vs. benefit. These issues have not been systematically examined outside America. Aims To describe current yield variation and CTPA utilisation in Australasian ED, exploring potential factors correlated with variation. Methods A retrospective multi-centre review of consecutive ED-ordered CTPA using standard radiology reports. ED CTPA report data were inputted onto preformatted data-sheets. The primary outcome was site level yield, analysed both intra-site and against a nominated 15.3% yield. Factors potentially associated with yield were assessed for correlation. Results Fourteen radiology departments (15 ED) provided 7077 CTPA data (94% ≥64-slice CT); PE were reported in 1028 (yield 14.6% (95%CI 13.8–15.4%; range 9.3–25.3%; site variation p <0.0001) with four sites significantly below and one above the 15.3% target. Admissions, CTPA usage, PE diagnosis rates and size of PE were uncorrelated with yield. Large PE (≥lobar) were 55% (CI: 52.1–58.2%) and SSPE 8.8% (CI: 7.1–10.5%) of positive scans. CTPA usage (0.2–1.5% adult attendances) was correlated (p<0.006) with PE diagnosis but not SSPE: large PE proportions. Discussion/ Conclusions We found significant intra-site CTPA yield variation within Australasia. Yield was not clearly correlated with CTPA usage or increased small PE rates. Both SSPE and large PE rates were similar to higher yield historical cohorts. CTPA use was considerably below USA 2.5–3% rates. Higher CTPA utilisation was positively correlated with PE diagnoses, but without evidence of increased proportions of small PE. This suggests that increased diagnoses seem to be of clinically relevant sized PE. PMID:27918576

Quantification of isotopic turnover in agricultural systems

NASA Astrophysics Data System (ADS)

Braun, A.; Auerswald, K.; Schnyder, H.

2012-04-01

The isotopic turnover, which is a proxy for the metabolic rate, is gaining scientific importance. It is quantified for an increasing range of organisms, from microorganisms over plants to animals including agricultural livestock. Additionally, the isotopic turnover is analyzed on different scales, from organs to organisms to ecosystems and even to the biosphere. In particular, the quantification of the isotopic turnover of specific tissues within the same organism, e.g. organs like liver and muscle and products like milk and faeces, has brought new insights to improve understanding of nutrient cycles and fluxes, respectively. Thus, the knowledge of isotopic turnover is important in many areas, including physiology, e.g. milk synthesis, ecology, e.g. soil retention time of water, and medical science, e.g. cancer diagnosis. So far, the isotopic turnover is quantified by applying time, cost and expertise intensive tracer experiments. Usually, this comprises two isotopic equilibration periods. A first equilibration period with a constant isotopic input signal is followed by a second equilibration period with a distinct constant isotopic input signal. This yields a smooth signal change from the first to the second signal in the object under consideration. This approach reveals at least three major problems. (i) The input signals must be controlled isotopically, which is almost impossible in many realistic cases like free ranging animals. (ii) Both equilibration periods may be very long, especially when the turnover rate of the object under consideration is very slow, which aggravates the first problem. (iii) The detection of small or slow pools is improved by large isotopic signal changes, but large isotopic changes also involve a considerable change in the input material; e.g. animal studies are usually carried out as diet-switch experiments, where the diet is switched between C3 and C4 plants, since C3 and C4 plants differ strongly in their isotopic signal. The additional change in nutrition induces changes in physiology that are likely to bias the estimation of the isotopic turnover. We designed an experiment with lactating cows which were successively exposed to the diet's natural isotopic variation and a diet-switch. We examined whether the same turnover information can be obtained from the natural (uncontrolled, short-term) isotopic variation as from the diet-switch experiment. Statistical methods to retrieve the turnover characteristics comprised multi-pool compartmental modeling for the diet-switch experiment as well as correlation analysis to perform wiggle-matching and quantification of autocorrelation (geostatistics) for the analysis of the natural variation. All three methods yielded similar results but differed in their strengths and weaknesses that will be highlighted. Combining the strengths of the new methods can make this tool even more advantageous than diet-switch experiments in many cases. In particular, the new approach empowers studying isotope turnover under a wider range of keepings, wildlife conditions and species, yielding turnover estimates that are not biased by changes in nutrition.

Experimental investigation of the influence of nanoparticles on water-based mud

NASA Astrophysics Data System (ADS)

Dhiman, Paritosh; Cheng, Yaoze; Zhang, Yin; Patil, Shirish

2018-03-01

This study has investigated the influence of nanoparticles including nanoparticle concentration, size, and type on water-based mud (WBM) properties including rheology, filtration, and lubricity through experimental tests, while the influence of temperature and aging on these properties have been investigated. It has been found that adding SiO2 nanoparticles increase the plastic viscosity and decrease the yield points and gel strengths with the increase of nanoparticle concentration. At fixed 0.5 wt%, the plastic viscosity decreases with the increase of TiO2 nanoparticle size, but the influence of TiO2 nanoparticle size on yield points and gel strengths is not monotonous. In general, adding negative charged SiO2 nanoparticles reduce the yield points and gel strengths, while adding positively charged TiO2, Al2O3, and Fe3O4 nanoparticles increase yield points and gel strengths. Adding lower concentrations (< 0.05 wt%) of SiO2 nanoparticles improved mud filtration and lubricity properties, but higher concentrations are adverse to these properties and adding 0.5 wt% TiO2, Al2O3 and Fe3O4 nanoparticles impaired these properties. Besides, it is found that there is no consistent influence of aging on mud properties and adding nanoparticles cannot improve aging resistance of mud. Although adding nanoparticles can significantly affect WBM properties, their influences are not consistency, depending on the integrated impact of the nanoparticle properties, such as surface electrical property, specific surface area, concentration, and size.

Naval Structural Materials: Requirements, Issues, and Opportunities.

DTIC Science & Technology

1981-04-10

because of the alloy’s relatively good corrosion resistance at high strength levels. The data 0 of Fig. 5 show the effects of electrochemical potential...STRENGTH,a-y (ksi) Fig. 5 Stress corrosion cracking data for high strength stainless steel (17-4PH) of different yield strengths under four electrochemical ... behavior . In contrast to the previously discussed results for low-carbon steel , heat treatment has only a small effect on the fatigue behavior of either

[Effects of slope gradient on slope runoff and sediment yield under different single rainfall conditions].

PubMed

He, Ji-Jun; Cai, Qiang-Guo; Liu, Song-Bo

2012-05-01

Based on the field observation data of runoff and sediment yield produced by single rainfall events in runoff plots, this paper analyzed the variation patterns of runoff and sediment yield on the slopes with different gradients under different single rainfall conditions. The differences in the rainfall conditions had little effects on the variation patterns of slope runoff with the gradient. Under the conditions of six different rainfall events in the study area, the variation patterns of slope runoff with the gradient were basically the same, i. e., the runoff increased with increasing gradient, but the increment of the runoff decreased slightly with increasing gradient, which was mainly determined by the infiltration flux of atmospheric precipitation. Rainfall condition played an important role on the slope sediment yield. Generally, there existed a critical slope gradient for slope erosion, but the critical gradient was not a fixed value, which varied with rainfall condition. The critical slope gradient for slope erosion increased with increasing slope gradient. When the critical slope gradient was greater, the variation of slope sediment yield with slope gradient always became larger.

The influence of heat treatments on several types of base-metal removable partial denture alloys.

PubMed

Morris, H F; Asgar, K; Rowe, A P; Nasjleti, C E

1979-04-01

Four removable partial denture alloys, Vitallium (Co-Cr alloy), Dentillium P.D. (Fe-Cr alloy), Durallium L.G. (Co-Cr-Ni alloy), and Ticonium 100 (Ni-Cr alloy), were evaluated in the as-cast condition and after heat treatment for 15 minutes at 1,300 degrees, 1,600 degrees, 1,900 degrees, and 2,200 degrees F followed by quenching in water. The following properties were determined and compared for each alloy at each heat treatment condition: the yield strengths at 0.01%, 0.1%, and 0.2% offsets, the ultimate tensile strength, the percent elongation, the modulus of elasticity, and the Knoop microhardness. The results were statistically analyzed. Photomicrographs were examined for each alloy and test condition. The following conclusions were made: 1. The "highest values" were exhibited by the as-cast alloy. 2. Heat treatment of the partial denture alloys tested resulted in reductions in strength, while the elongations varied. This study demonstrates that, in practice, one should avoid (a) prolonged "heat-soaking" while soldering and (b) grinding or polishing of the casting until the alloy is "red hot". 3. Durallium L.G. was the least affected by the various heat treatment conditions. 4. Conventional reporting of the yield strength at 0.2% offset, the ultimate tensile strength, and percent elongation are not adequate to completely describe and compare the mechanical behavior of alloys. The reporting of the yield strength at 0.01% offset, in addition to the other reported properties, will provide a more complete description of the behavior of the dental alloys.

Evaluation of omniweave reinforcement for composite fabrication

NASA Technical Reports Server (NTRS)

Belman, R.; Edighoffer, H.; Fenton, R.; Lowe, D.; Wexler, M.

1971-01-01

Molded composites made from type-2 Morganite and/or boron are suitable for structural skins. Layered-in-depth omniweave construction yields higher in-plane strength characteristics than fiber-pitch angle construction, and strength and moduli data vary with fiber orientation.

Crystal growth for high-efficiency silicon solar cells workshop: Summary

NASA Technical Reports Server (NTRS)

Dumas, K. A.

1985-01-01

The state of the art in the growth of silicon crystals for high-efficiency solar cells are reviewed, sheet requirements are defined, and furture areas of research are identified. Silicon sheet material characteristics that limit cell efficiencies and yields were described as well as the criteria for the ideal sheet-growth method. The device engineers wish list to the material engineer included: silicon sheet with long minority carrier lifetime that is uniform throughout the sheet, and which doesn't change during processing; and sheet material that stays flat throughout device processing, has uniform good mechanical strength, and is low cost. Impurities in silicon solar cells depreciate cell performance by reducing diffusion length and degrading junctions. The impurity behavior, degradation mechanisms, and variations in degradation threshold with diffusion length for silicon solar cells were described.

Probabilistic Structural Analysis Methods (PSAM) for Select Space Propulsion System Components

NASA Technical Reports Server (NTRS)

1999-01-01

Probabilistic Structural Analysis Methods (PSAM) are described for the probabilistic structural analysis of engine components for current and future space propulsion systems. Components for these systems are subjected to stochastic thermomechanical launch loads. Uncertainties or randomness also occurs in material properties, structural geometry, and boundary conditions. Material property stochasticity, such as in modulus of elasticity or yield strength, exists in every structure and is a consequence of variations in material composition and manufacturing processes. Procedures are outlined for computing the probabilistic structural response or reliability of the structural components. The response variables include static or dynamic deflections, strains, and stresses at one or several locations, natural frequencies, fatigue or creep life, etc. Sample cases illustrates how the PSAM methods and codes simulate input uncertainties and compute probabilistic response or reliability using a finite element model with probabilistic methods.

Development of high strength and high ductility nanostructured TWIP steel

NASA Astrophysics Data System (ADS)

Kou, Hong Ning

Strength and ductility are two exclusive mechanical properties of structural materials. One challenge for material research is to develop bulk nanostructured metals with simultaneous high strength and good ductility. To meet this objective, steels with twinning induced plasticity (TWIP) effect are selected for surface mechanical attrition treatment (SMAT) in this study. Tensile tests reveal extremely high yield strength and simultaneously sufficient ductility in these SMATed TWIP steel samples. With the duration increase of SMAT, both yield strength and tensile strength firstly monotonically increase to a maximum value of 2.25GPa with 18% total elongation. However, further increase of SMAT duration results in decreases of both strength and elongation. The excellent ductility of coarse-grained TWIP steels is attributed to the instantaneous generation of deformation twins in tension. Based on this, an interesting hierarchically tertiary twinning system is revealed by TEM/HRTEM in SMATed samples, composed of multi-scale twins respectively produced by annealing treatment, SMAT and tensile deformation. On one hand, boundaries of hierarchical twins with different orientations form three-dimensional networks that restrict each other and act as strong barriers to dislocation motion, leading to ultrahigh strength. On the other hand, stress concentration is relieved due to deformation transfer caused by twinning from grain to grain, resulting in large plasticity. Therefore, the hierarchical twinning structure is regarded as the most effective element that induces both extraordinary ultrahigh strength and good elongation in SMATed TWIP. The stable austenite also contributes to the preservation of good ductility. Martensite is only observed in SMATed TWIP by longest SMAT duration. Another route of fabricating nanostructured TWIP is performed by combining SMAT and thermomechanical treatment. The interval heat treatment between double SMAT benefits the total elongation to over 50%, with 980 MPa yield strength. Nanograins are observed at 60mum depth, different from their usual emergence on top surface. Martensitic phase transformation is discovered. Most nanostructured SMATed TWIP samples demonstrate typical ductile fractures with large quantities of dimples in different sizes, following the same trend of gradient grains. Long SMAT duration produces slight brittle crack with tearing ribs. Microvoids coalescence with manganese carbides leads to final rupture.

Food and fitness: associations between crop yields and life-history traits in a longitudinally monitored pre-industrial human population.

PubMed

Hayward, Adam D; Holopainen, Jari; Pettay, Jenni E; Lummaa, Virpi

2012-10-22

Severe food shortage is associated with increased mortality and reduced reproductive success in contemporary and historical human populations. Studies of wild animal populations have shown that subtle variation in environmental conditions can influence patterns of mortality, fecundity and natural selection, but the fitness implications of such subtle variation on human populations are unclear. Here, we use longitudinal data on local grain production, births, marriages and mortality so as to assess the impact of crop yield variation on individual age-specific mortality and fecundity in two pre-industrial Finnish populations. Although crop yields and fitness traits showed profound year-to-year variation across the 70-year study period, associations between crop yields and mortality or fecundity were generally weak. However, post-reproductive individuals of both sexes, and individuals of lower socio-economic status experienced higher mortality when crop yields were low. This is the first longitudinal, individual-based study of the associations between environmental variation and fitness traits in pre-industrial humans, which emphasizes the importance of a portfolio of mechanisms for coping with low food availability in such populations. The results are consistent with evolutionary ecological predictions that natural selection for resilience to food shortage is likely to weaken with age and be most severe on those with the fewest resources.

Effect of hot extrusion, other constituents, and temperature on the strength and fracture of polycrystalline MgO

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rice, R.W.

Improved agreement was confirmed between the Petch intercept and single-crystal yield stresses at 22 C. Hot-extruded MgO crystal specimens stressed parallel with the resultant axial texture (1) gave the highest and least-scattered strength-grain size results at 22 C, (2) showed direct fractographic evidence of microplastic initiated fracture at 22 C and showed macroscopic yield at 1,315 and especially 1,540 C, and (3) fractured entirely via transgranular cleavage, except for intergranular failure initiation from one or a few grain boundary surfaces exposed on the subsequent fracture surface, mainly at 1,540 C. Hot-extruded, hot-pressed MgO billets gave comparable strength when fracture initiatedmore » transgranularly, but lower strength when fracture initiated from one or especially a few grain boundary surfaces exposed on the fracture. The extent and frequency of such boundary fracture increased with test temperature. While oxide additions of [<=] 5% or impurities in hot-pressed or hot-extruded MgO can make limited strength increases at larger grain sizes, those having limited solubility can limit strength at finer grain sizes, as can coarser surface finish. Overall, MgO strength is seen as a balance between flaw and microplastic controlled failure, with several parameters shifting the balance.« less

Spatial and Temporal Patterns of Suspended Sediment Yields in Nested Urban Catchments

NASA Astrophysics Data System (ADS)

Kemper, J. T.; Miller, A. J.; Welty, C.

2017-12-01

In a highly regulated area such as the Chesapeake Bay watershed, suspended sediment is a matter of primary concern. Near real-time turbidity and discharge data have been collected continuously for more than four years at five stream gages representing three nested watershed scales (1-2 sq km, 5-6 sq km, 14 sq km) in the highly impervious Dead Run watershed, located in Baltimore County, MD. Using turbidity-concentration relationships based on sample analyses at the gage site, sediment yields for each station can be quantified for a variety of temporal scales. Sediment yields have been calculated for 60+ different storms across four years. Yields show significant spatial variation, both at equivalent sub-watershed scales and from headwaters to mouth. Yields are higher at the headwater station with older development and virtually no stormwater management (DR5) than at the station with more recent development and more extensive stormwater management (DR2). However, this pattern is reversed for the stations at the next larger scale: yields are lower at DR4, downstream of DR5, than at DR3, downstream of DR2. This suggests spatial variation in the dominant sediment sources within each subwatershed. Additionally, C-Q hysteresis curves display consistent counterclockwise behavior at the DR4 station, in contrast to the consistent clockwise behavior displayed at the DR3 station. This further suggests variation in dominant sediment sources (perhaps distal vs local, respectively). We observe consistent seasonal trends in the relative magnitudes of sediment yield for different subwatersheds (e.g. DR3>DR4 in summer, DR5>DR2 in spring). We also observe significant year-to-year variation in sediment yield at the headwater and intermediate scales, whereas yields at the 14 sq km scale are largely similar across the monitored years. This observation would be consistent with the possibility that internal storage and remobilization tend to modulate downstream yields even with spatial and temporal variation in upstream sources. The fine-scale design of this study represents a unique opportunity to compare and contrast sediment yields across a variety of spatial and temporal scales, and provide insight into sediment transport dynamics within an urbanized watershed.

The effect of shear strength on isentropic compression experiments

NASA Astrophysics Data System (ADS)

Thomson, Stuart; Howell, Peter; Ockendon, John; Ockendon, Hilary

2015-06-01

Isentropic compression experiments (ICE) are a novel way of obtaining equation of state information for metals undergoing violent plastic deformation. In a typical experiment, millimetre thick metal samples are subjected to pressures on the order of 10 -102 GPa, while the yield strength of the material can be as low as 10-1GPa. The analysis of such experiments has so far neglected the effect of shear strength, instead treating the highly plasticised metal as an inviscid compressible fluid. However making this approximation belies the basic elastic nature of a solid object. A more accurate method should strive to incorporate the small but measurable effects of shear strength. Here we present a one-dimensional mathematical model for elastoplasticity at high stress which allows for both compressibility and the shear strength of the material. In the limit of zero yield stress this model reproduces the hydrodynamic models currently used to analyse ICEs. We will also show using a systematic asymptotic analysis that entropy changes are universally negligible in the absence of shocks. Numerical solutions of the governing equations will then be presented for problems relevant to ICEs in order to investigate the effects of shear strength over a model based purely on hydrodynamics.

Investigation on mechanical behavior and material characteristics of various weight composition of SiCp reinforced aluminium metal matrix composite

NASA Astrophysics Data System (ADS)

Pichumani, Sivachidambaram; Srinivasan, Raghuraman; Ramamoorthi, Venkatraman

2018-02-01

Aluminium - silicon carbide (Al - SiC) metal matrix composite is produced with following wt % of SiC reinforcement (4%, 8% & 12%) using stir casting method. Mechanical testing such as micro hardness, tensile testing and bend testing were performed. Characterizations, namely micro structure, X-ray diffraction (XRD) analysis, inductive coupled plasma - optical emission spectroscopy (ICP-OES) and scanning electron microscopy (SEM) analysis, were carried out on Al - SiC composites. The presence of SiC on Al - SiC composite is confirmed through XRD technique and microstructure. The percentage of SiC was confirmed through ICP-OES technique. Increase in weight percentage of SiC tends to increase micro hardness, ultimate strength & yield strength but it reduces the bend strength and elongation (%) of the material. SEM factrography of tensile tested fractured samples of Al - 8% SiC & Al - 12% SiC showed fine dimples on fractured surface & coarse dimples fractured surface respectively. This showed significant fracture differences between Al - 8% SiC & Al - 12% SiC. From the above experiment, Al - 8% SiC had good micro hardness, ultimate strength & yield strength without significant loss in elongation (%) & bend strength.

The Effect of Fiber Strength Stochastics and Local Fiber Volume Fraction on Multiscale Progressive Failure of Composites

NASA Technical Reports Server (NTRS)

Ricks, Trenton M.; Lacy, Jr., Thomas E.; Bednarcyk, Brett A.; Arnold, Steven M.

2013-01-01

Continuous fiber unidirectional polymer matrix composites (PMCs) can exhibit significant local variations in fiber volume fraction as a result of processing conditions that can lead to further local differences in material properties and failure behavior. In this work, the coupled effects of both local variations in fiber volume fraction and the empirically-based statistical distribution of fiber strengths on the predicted longitudinal modulus and local tensile strength of a unidirectional AS4 carbon fiber/ Hercules 3502 epoxy composite were investigated using the special purpose NASA Micromechanics Analysis Code with Generalized Method of Cells (MAC/GMC); local effective composite properties were obtained by homogenizing the material behavior over repeating units cells (RUCs). The predicted effective longitudinal modulus was relatively insensitive to small (8%) variations in local fiber volume fraction. The composite tensile strength, however, was highly dependent on the local distribution in fiber strengths. The RUC-averaged constitutive response can be used to characterize lower length scale material behavior within a multiscale analysis framework that couples the NASA code FEAMAC and the ABAQUS finite element solver. Such an approach can be effectively used to analyze the progressive failure of PMC structures whose failure initiates at the RUC level. Consideration of the effect of local variations in constituent properties and morphologies on progressive failure of PMCs is a central aspect of the application of Integrated Computational Materials Engineering (ICME) principles for composite materials.

Variations in Compressive Strength of Geopolymer due to the CaO Added Fly Ash

NASA Astrophysics Data System (ADS)

Zhao, Yuqing; Koumoto, Tatsuya; Kondo, Fumiyoshi

Recently, geopolymer has been a noteworthy material which can be used as a replacement for portland cement. The mechanical characteristics and consistency of the geopolymer are strongly affected by its chemical components of fly ash. The variations in compressive strength of geopolymer due to the CaO added fly ash were investigated in this paper. The compressive strengths of geopolymer were increased with an increase in the curing period, and the characteristics changed from the one of plastic soil material to brittle material such as concrete, regardless of CaO content. Also, the results of compressive strength and modulus of deformation showed their maximum value in the case of 8-10% CaO content. From this result, the maximum characteristics of the strengths were assumed to be exerted in case which the water draining process of geopolymer was balanced with the water absorbing process of additional CaO.

Research on Submarine Pipeline Steel with High Performance

NASA Astrophysics Data System (ADS)

Ren, Yi; Liu, Wenyue; Zhang, Shuai; Wang, Shuang; Gao, Hong

Submarine pipeline steel has largely uniform elongation, low yield ratio and good balance between high strength and high plasticity because of the microstructure with dual phase. In this work, the microstructure and properties of the submarine pipeline steel are studied. The results show that the matrix structure is consisted of ferrite, bainite and martensite -austenite islands. The structure has a tight relationship with the thermal-mechanical controlled process. Fine dual phase shows good plasticity and low yield ratio, which can support the good balance between high strength and high plasticity.

Static Properties of Fibre Metal Laminates

NASA Astrophysics Data System (ADS)

Hagenbeek, M.; van Hengel, C.; Bosker, O. J.; Vermeeren, C. A. J. R.

2003-07-01

In this article a brief overview of the static properties of Fibre Metal Laminates is given. Starting with the stress-strain relation, an effective calculation tool for uniaxial stress-strain curves is given. The method is valid for all Glare types. The Norris failure model is described in combination with a Metal Volume Fraction approach leading to a useful tool to predict allowable blunt notch strength. The Volume Fraction approach is also useful in the case of the shear yield strength of Fibre Metal Laminates. With the use of the Iosipescu test shear yield properties are measured.

Variation among slash pine families in chlorophyll fluorescence traits

Treesearch

Anita C. Koehn; James H. Roberds; Robert L. Doudrick

2003-01-01

Abstract: Photochemical quenching, nonphotochemical quenching, and yield of photosystem II were measured on seedlings of full-sibling, open-, and self-pollinated slash pine (Pinus elliottii Engelm. var. elliottii) families. Our results reveal that genetic variation in photochemical quenching and yield of...

Testing Bonds Between Brittle And Ductile Films

NASA Technical Reports Server (NTRS)

Wheeler, Donald R.; Ohsaki, Hiroyuki

1989-01-01

Simple uniaxial strain test devised to measure intrinsic shear strength. Brittle film deposited on ductile stubstrate film, and combination stretched until brittle film cracks, then separates from substrate. Dimensions of cracked segments related in known way to tensile strength of brittle film and shear strength of bond between two films. Despite approximations and limitations of technique, tests show it yields semiquantitative measures of bond strengths, independent of mechanical properties of substrates, with results reproducible with plus or minus 6 percent.

The effects of artificial aging on the microstructure and fracture toughness of Al-Cu-Li alloy 2195

NASA Astrophysics Data System (ADS)

Chen, P. S.; Kuruvilla, A. K.; Malone, T. W.; Stanton, W. P.

1998-10-01

Aluminum-lithium alloys have shown promise for aerospace applications, and National Aeronautics and Space Administration (NASA) has selected the aluminum-lithium Alloy 2195 for the main structural alloy of the super light weight tank (SLWT) for the space shuttle. This alloy has significantly higher strength than conventional 2xxx alloys (such as 2219) at both ambient and cryogenic temperatures. If properly processed and heat treated, this alloy can display higher fracture toughness at cryogenic temperature than at ambient temperature. However, the properties of production materials have shown greater variation than those of other established alloys, as is the case with any new alloy that is being transitioned to a demanding application. Recently, some commercial 2195 plates for the SLWT program were rejected, mostly due to low CFT or FTR at ambient and cryogenic temperatures. Investigation of the microstructure property relationships of Al-Cu-Li based alloys indicates that the poor fracture toughness properties can be attributed to excessive T1 precipitation at subgrain boundaries. Lowering the aging temperature is one way to avoid excessive T1 precipitation at subgrain boundaries. However, this approach results in a significant drop in yield strength. In addition, low-temperature aging is associated with sluggish aging kinetics, which are not desirable for industrial mass production. Therefore, the present study was undertaken to develop an aging process that can improve fracture toughness without sacrificing yield and tensile strength. A multistep heating-rate controlled (MSRC) aging treatment has been developed that can improve the cryogenic fracture toughness of aluminum-lithium Alloy 2195. At the same levels of yield strength (YS), this treatment results in considerably higher fracture toughness than that found in Alloy 2195, which has received conventional (isothermal) aging. Transmission electron microscopy revealed that the new treatment greatly reduces the size and density of subgrain-boundary T1 precipitates. In addition, it promotes T1 and θ" nucleation, resulting in a fine and dense distribution of precipitate particles in the matrix. The MSRC aging treatment consists of (a) aging at 127‡C (260‡F) for 5 h, (b) heating continuously from 127‡C (260‡F) to 135‡C (275‡F) at a rate of 0.556‡C/h (1‡F/h), (c) holding at 135‡C (275‡F) for 5 h, (d) heating continuously from 135 to 143‡C (275 to 290‡F) at a rate of 0.556‡C/h (1‡F/h), and (e) holding at 143‡C (290‡F) for 25 h to obtain a near peak-aged condition.

Near-Unity Internal Quantum Efficiency of Luminescent Silicon Nanocrystals with Ligand Passivation.

PubMed

Sangghaleh, Fatemeh; Sychugov, Ilya; Yang, Zhenyu; Veinot, Jonathan G C; Linnros, Jan

2015-07-28

Spectrally resolved photoluminescence (PL) decays were measured for samples of colloidal, ligand-passivated silicon nanocrystals. These samples have PL emission energies with peak positions in the range ∼1.4-1.8 eV and quantum yields of ∼30-70%. Their ensemble PL decays are characterized by a stretched-exponential decay with a dispersion factor of ∼0.8, which changes to an almost monoexponential character at fixed detection energies. The dispersion factors and decay rates for various detection energies were extracted from spectrally resolved curves using a mathematical approach that excluded the effect of homogeneous line width broadening. Since nonradiative recombination would introduce a random lifetime variation, leading to a stretched-exponential decay for an ensemble, we conclude that the observed monoexponential decay in size-selected ensembles signifies negligible nonradiative transitions of a similar strength to the radiative one. This conjecture is further supported as extracted decay rates agree with radiative rates reported in the literature, suggesting 100% internal quantum efficiency over a broad range of emission wavelengths. The apparent differences in the quantum yields can then be explained by a varying fraction of "dark" or blinking nanocrystals.

On the discovery of K I 7699 Å line strength variation during the 1982-1984 eclipse of ε Aurigae

NASA Astrophysics Data System (ADS)

Parthasarathy, M.

2017-02-01

The discovery of K I 7699 Å line strength variations during the 1982-1984 eclipse of ε Aurigae is described. The equivalent widths and radial velocities of the K I 7699 Å line derived from spectra obtained during 1981 November-1983 July with the 2.1 m Otto Struve reflector telescope of the McDonald observatory are presented.

Effect of dislocation pile-up on size-dependent yield strength in finite single-crystal micro-samples

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan, Bo; Shibutani, Yoji, E-mail: sibutani@mech.eng.osaka-u.ac.jp; Zhang, Xu

2015-07-07

Recent research has explained that the steeply increasing yield strength in metals depends on decreasing sample size. In this work, we derive a statistical physical model of the yield strength of finite single-crystal micro-pillars that depends on single-ended dislocation pile-up inside the micro-pillars. We show that this size effect can be explained almost completely by considering the stochastic lengths of the dislocation source and the dislocation pile-up length in the single-crystal micro-pillars. The Hall–Petch-type relation holds even in a microscale single-crystal, which is characterized by its dislocation source lengths. Our quantitative conclusions suggest that the number of dislocation sources andmore » pile-ups are significant factors for the size effect. They also indicate that starvation of dislocation sources is another reason for the size effect. Moreover, we investigated the explicit relationship between the stacking fault energy and the dislocation “pile-up” effect inside the sample: materials with low stacking fault energy exhibit an obvious dislocation pile-up effect. Our proposed physical model predicts a sample strength that agrees well with experimental data, and our model can give a more precise prediction than the current single arm source model, especially for materials with low stacking fault energy.« less

A Constitutive Equation Relating Composition and Microstructure to Properties in Ti-6Al-4V: As Derived Using a Novel Integrated Computational Approach

NASA Astrophysics Data System (ADS)

Ghamarian, Iman; Samimi, Peyman; Dixit, Vikas; Collins, Peter C.

2015-11-01

While it is useful to predict properties in metallic materials based upon the composition and microstructure, the complexity of real, multi-component, and multi-phase engineering alloys presents difficulties when attempting to determine constituent-based phenomenological equations. This paper applies an approach based upon the integration of three separate modeling approaches, specifically artificial neural networks, genetic algorithms, and Monte Carlo simulations to determine a mechanism-based equation for the yield strength of α+ β processed Ti-6Al-4V (all compositions in weight percent) which consists of a complex multi-phase microstructure with varying spatial and morphological distributions of the key microstructural features. Notably, this is an industrially important alloy yet an alloy for which such an equation does not exist in the published literature. The equation ultimately derived in this work not only can accurately describe the properties of the current dataset but also is consistent with the limited and dissociated information available in the literature regarding certain parameters such as intrinsic yield strength of pure hexagonal close-packed alpha titanium. In addition, this equation suggests new interesting opportunities for controlling yield strength by controlling the relative intrinsic strengths of the two phases through solid solution strengthening.

Porcelain surface conditioning protocols and shear bond strength of orthodontic brackets.

PubMed

Lestrade, Ashley M; Ballard, Richard W; Xu, Xiaoming; Yu, Qingzhao; Kee, Edwin L; Armbruster, Paul C

2016-05-01

The objective of the present study was to determine which of six bonding protocols yielded a clinically acceptable shear bond strength (SBS) of metal orthodontic brackets to CAD/CAM lithium disilicate porcelain restorations. A secondary aim was to determine which bonding protocol produced the least surface damage at debond. Sixty lithium disilicate samples were fabricated to replicate the facial surface of a mandibular first molar using a CEREC CAD/CAM machine. The samples were split into six test groups, each of which received different mechanical/chemical pretreatment protocols to roughen the porcelain surface prior to bonding a molar orthodontic attachment. Shear bond strength testing was conducted using an Instron machine. The mean, maximum, minimal, and standard deviation SBS values for each sample group including an enamel control were calculated. A t-test was used to evaluate the statistical significance between the groups. No significant differences were found in SBS values, with the exception of surface roughening with a green stone prior to HFA and silane treatment. This protocol yielded slightly higher bond strength which was statistically significant. Chemical treatment alone with HFA/silane yielded SBS values within an acceptable clinical range to withstand forces applied by orthodontic treatment and potentially eliminates the need to mechanically roughen the ceramic surface.

Microstructure and properties of thermomechanically strengthened reinforcement bars: A comparative assessment of plain-carbon and low-alloy steel grades

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ray, A.; Mukerjee, D.; Sen, S.K.

1997-06-01

An extensive investigation has been carried out to study structure-property characteristics and corrosion behavior in three varieties of thermomechanically treated (TMT) reinforcement bars (rebars) produced in an integrated steel plant under the Steel Authority of India Limited. Three experimental steel heats--one of plain-carbon and two of low-alloy chemistry--were chosen for the study. Of the two low-alloy heats, one was copper-bearing and the other contained both copper and chromium for improved corrosion resistance. Hot-rolled bars for each specific chemistry were subjected to in-line thermomechanical treatment, where quenching parameters were altered to achieve different yield strength levels. All the TMT rebars, regardlessmore » of chemistry and strength level, exhibited a composite microstructure consisting of ferrite-pearlite at the core and tempered martensite at the rim. Although a tendency toward formation of Widmanstaetten ferrite was evident in bars of 500 and 550 MPa yield strength levels, no adverse effect on their strength and ductility was observed. From the standpoint of mechanical properties, the rebars not only conformed to minimum yield strength requirements, but also exhibited high elongation values (21 to 28%) and excellent bendability. Corrosion studies of both TMT and cold-twisted and deformed (CTD) rebars subjected to different laboratory tests indicated that corrosion resistance increased in this order: CTD, plain-carbon TMT, copper-bearing TMT, and copper/chromium-bearing TMT.« less

Peanut peg strength and post harvest pod scavenging for full phenotypic yield over digging date and variety

USDA-ARS?s Scientific Manuscript database

New peanut cultivars are available with very high yield potential and high levels of disease resistance. With rising input costs and shrinking return margins, all efforts must be made to harvest the full yield produced. Peanut crops are susceptible to high levels of pod loss during digging from a ...

An in-depth analysis of the physico-mechanical properties imparted by agricultural fibers and food processing residues in polypropylene biocomposites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murdy, Rachel Campbell; Mak, Michelle; Misra, Manjusri

The use of agricultural and food processing residues as potential reinforcements in plastics has been extensively studied. However, there is a large variation in the mechanical performance of agricultural fiber-based biocomposites due to different processing materials and parameters. An in-depth comparison of the resulting effect of the agricultural filler on the matrix is often not possible given the discrepancy in processing conditions. This study seeks to determine the intrinsic properties of agricultural fibers and food processing residues for their use in polypropylene biocomposites based on a standardization of experimental design. The effect of 25wt% loading of miscanthus, fall-and spring-harvest switchgrass,more » wheat straw, oat hull, soy hull, soy stalk, hemp and flax on the physico-mechanical properties of polypropylene biocomposites was investigated. The addition of fiber led to an improvement in flexural strength, flexural modulus, and tensile modulus, and a general decrease in tensile strength at yield, elongation at break and Izod impact strength. Scanning electron microscopy highlighted the interfacial adhesion, orientation and distribution of the fibers within the matrix, confirming that fiber length and dispersion within the matrix are positively correlated with mechanical properties. The crystallization of the polypropylene phase and a compositional analysis of the agricultural fibers and processing residues were also compared to offer insight into the effect of the filler’s intrinsic properties on the resulting material performance.« less

High Strength and Ductility of Additively Manufactured 316L Stainless Steel Explained

NASA Astrophysics Data System (ADS)

Shamsujjoha, Md.; Agnew, Sean R.; Fitz-Gerald, James M.; Moore, William R.; Newman, Tabitha A.

2018-04-01

Structure-property relationships of an additively manufactured 316L stainless steel were explored. A scanning electron microscope and electron backscattered diffraction (EBSD) analysis revealed a fine cellular-dendritic (0.5 to 2 μm) substructure inside large irregularly shaped grains ( 100 μm). The cellular structure grows along the <100> crystallographic directions. However, texture analysis revealed that the main <100> texture component is inclined by 15 deg from the building direction. X-ray diffraction line profile analysis indicated a high dislocation density of 1 × 1015 m-2 in the as-built material, which correlates well with the observed EBSD microstructure and high-yield strength, via the traditional Taylor hardening equation. Significant variations in strain hardening behavior and ductility were observed for the horizontal (HB) and vertical (VB) built samples. Ductility of HB and VB samples measured 49 and 77 pct, respectively. The initial growth texture and subsequent texture evolution during tensile deformation are held responsible for the observed anisotropy. Notably, EBSD analysis of deformed samples showed deformation twins, which predominately form in the grains with <111> aligned parallel to the loading direction. The VB samples showed higher twinning activity, higher strain hardening rates at high strain, and therefore, higher ductility. Analysis of annealed samples revealed that the observed microstructures and properties are thermally stable, with only a moderate decrease in strength and very similar levels of ductility and anisotropy, compared with the as-built condition.

Effects of Casting Size on Microstructure and Mechanical Properties of Spheroidal and Compacted Graphite Cast Irons: Experimental Results and Comparison with International Standards

NASA Astrophysics Data System (ADS)

Ceschini, L.; Morri, Alessandro; Morri, Andrea

2017-05-01

The aim of this research was to investigate the effects of casting size (10-210 mm) on the microstructure and mechanical properties of spheroidal (SGI) and compacted (CGI) graphite cast irons. A comparison of the experimental mechanical data with those specified by ISO standards is presented and discussed. The study highlighted that the microstructure and mechanical properties of SGI (also known as ductile or nodular cast iron) are more sensitive to casting size than CGI (also known as vermicular graphite cast irons). In particular, in both types of cast iron, hardness, yield strength and ultimate tensile strength decreased, with increasing casting size, by 27% in SGI and 17% in CGI. Elongation to failure showed, instead, an opposite trend, decreasing from 5 to 3% in CGI, while increasing from 5 to 11% in SGI. These results were related to different microstructures, the ferritic fraction being more sensitive to the casting size in SGI than CGI. Degeneration of spheroidal graphite was observed at casting size above 120 mm. The microstructural similarities between degenerated SGI and CGI suggested the proposal of a unified empirical constitutional law relating the most important microstructural parameters to the ultimate tensile strength. An outstanding result was also the finding that standard specifications underestimated the mechanical properties of both cast irons (in particular SGI) and, moreover, did not take into account their variation with casting size, at thicknesses over 60 mm.

High Strength and Ductility of Additively Manufactured 316L Stainless Steel Explained

NASA Astrophysics Data System (ADS)

Shamsujjoha, Md.; Agnew, Sean R.; Fitz-Gerald, James M.; Moore, William R.; Newman, Tabitha A.

2018-07-01

Structure-property relationships of an additively manufactured 316L stainless steel were explored. A scanning electron microscope and electron backscattered diffraction (EBSD) analysis revealed a fine cellular-dendritic (0.5 to 2 μm) substructure inside large irregularly shaped grains ( 100 μm). The cellular structure grows along the <100> crystallographic directions. However, texture analysis revealed that the main <100> texture component is inclined by 15 deg from the building direction. X-ray diffraction line profile analysis indicated a high dislocation density of 1 × 1015 m-2 in the as-built material, which correlates well with the observed EBSD microstructure and high-yield strength, via the traditional Taylor hardening equation. Significant variations in strain hardening behavior and ductility were observed for the horizontal (HB) and vertical (VB) built samples. Ductility of HB and VB samples measured 49 and 77 pct, respectively. The initial growth texture and subsequent texture evolution during tensile deformation are held responsible for the observed anisotropy. Notably, EBSD analysis of deformed samples showed deformation twins, which predominately form in the grains with <111> aligned parallel to the loading direction. The VB samples showed higher twinning activity, higher strain hardening rates at high strain, and therefore, higher ductility. Analysis of annealed samples revealed that the observed microstructures and properties are thermally stable, with only a moderate decrease in strength and very similar levels of ductility and anisotropy, compared with the as-built condition.

Assessment of Musculoskeletal Strength and Levels of Fatigue during Different Phases of Menstrual Cycle in Young Adults

PubMed Central

D Souza, Urban John; Shivaprakash, G

2017-01-01

Introduction Some of the physiological factors and athletic performance might show variation along the phases of menstrual cycle. The alterations seen in these physiological parameters of various systems relating to oscillations in hormonal levels do affect the autonomic nervous system and metabolic functions. Former studies heave inconclusively about the influence of hormones on exercise performance, predominantly muscle strength and rate of fatigue during different phases of the menstrual cycle. Studies regarding influence of these variations during bleeding phase were not done. Aim To evaluate the muscle strength variations and also the rate of fatigue during various phases of the menstrual cycle in young adults. Materials and Methods This was a prospective study conducted among 100 healthy adult female volunteers aged 18-24 years, with normal regular menstrual cycles persistent between 26- 32 days (average of 28 days), for a minimum of last 6 months. Muscle strength was assessed by calculating the work done and fatigue rate using Mosso’s ergograph and by handgrip dynamometer strength. Each subject was evaluated consecutively for two menstrual cycles in all three phases which were classified as Phase 1- Menstrual phase, Phase 2- Follicular phase and Phase 3- Luteal phase. The data obtained was analysed by statistical tool One-way ANOVA followed by a post-hoc Tukeys test. A p-value of ≤ 0.05 was considered significant. Results The amount of work done and handgrip strength was significantly higher in phase 2 (p<0.001) and relatively reduced in phase 1 and 3 (p<0.001) of menstrual cycle. In terms of fatigue rate percentage, phase 2 showed significantly lesser values (p<0.001) as compared to phase 1 and 3 of menstrual cycle. Conclusion We conclude that the cyclical variation in endogenous reproductive hormones increases the muscle strength in follicular phase of the menstrual cycle. Thus provide support for the influence of these hormones in regulation of these parameters in the premenopausal age group. PMID:28384857

Static strength of molybdenum to 92 GPa under radial X-ray diffraction

NASA Astrophysics Data System (ADS)

Xiong, L.; Tu, P.; Li, B.; Wu, S. Y.; Hao, J. B.; Bai, L. G.; Li, X. D.; Liu, J.

2018-06-01

The high-pressure strength of molybdenum (Mo) to 92 GPa has been studied by radial X-ray diffraction (RXRD) technique. The ratio of t/G is found to decrease above ˜24 GPa, showing the yield of Mo which is caused by plastic deformation at this pressure. Combined with high-pressure shear modulus, it was found that the differential stress corresponding to the yield of Mo at 24 GPa due to plastic deformation is 1.73 GPa. The second increase of t values occurs after ˜66 GPa, suggesting the strength of Mo with a differential stress of ˜1.93 GPa. In addition, the maximum difference stress of molybdenum at 87 GPa is 3.01 GPa.

The effect of fusion-relevant helium levels on the mechanical properties of isotopically tailored ferritic alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hankin, G.L.; Hamilton, M.L.; Gelles, D.S.

1997-04-01

The yield and maximum strengths of an irradiated series of isotopically tailored ferritic alloys were evaluated using the shear punch test. The composition of three of the alloys was Fe-12Cr-1.5Ni. Different balances of nickel isotopes were used in each alloy in order to produce different helium levels. A fourth alloy, which contained no nickel, was also irradiated. The addition of nickel at any isotopic balance to the Fe-12Cr base alloy significantly increased the shear yield and maximum strengths of the alloys, and as expected, the strength of the alloys decreased with increasing irradiation temperature. Helium itself, up to 75 appmmore » over 7 dpa appears to have little effect on the mechanical properties of the alloys.« less

Ductility and fracture in B2 FeAl alloys. Ph.D. Thesis Final Report

NASA Technical Reports Server (NTRS)

Crimp, Martin A.

1987-01-01

The mechanical behavior of B2FeAl alloys was studied. Stoichiometric Fe-50Al exhibits totally brittle behavior while iron-rich Fe-40Al yields and displays about 3% total strain. This change in behavior results from large decreases in the yield strength with iron-rich deviations from stoichiometry while the fracture stress remains essentially constant. Single crystal studies show that these yield strength decreases are directly related to decreases in the critical resolved shear stress for a group of zone axes /111/ set of (110) planes slip. This behavior is rationalized in terms of the decrease in antiphase boundary energy with decreasing aluminum content. The addition of boron results in improvements in the mechanical behavior of alloys on the iron-rich side of stoichiometry. These improvements are increased brittle fracture stresses of near-stoichiometric alloys, and enhanced ductility of up to 6% in Fe-40Al. These effects were attributed to increased grain boundary adhesion as reflected by changes in fracture mode from intergranular to transgranular failure. The increases in yield strength, which are observed in both polycrystals and single crystals, result from the quenching in of large numbers of thermal vacancies. Hall-Petch plots show that the cooling rate effects are a direct result of changes in the Hall-Petch intercept/lattice resistance flow.

Microstructurally based variations on the dwell fatgue life of titanium alloy IMI 834

NASA Technical Reports Server (NTRS)

Thomsen, Mark L.; Hoeppner, David W.

1994-01-01

An experimental study was undertaken to determine the role of microstructure on the fatigue life reduction observed in titanium alloy IMI 834 under dwell loading conditions. The wave forms compared were a trapezoid with 15 and 30 second hold times at the maximum test load and a baseline, 10 Hertz, haversine. The stress ratio for both loading wave forms was 0.10. The fatigue loading of each specimen was conducted in a vacuum within a scanning electron microscope chamber which minimized the possibility that the laboratory environment would adversely affect the material behavior. Two microstructural conditions were investigated in the experimental program. The first involved standard 'disk' material with equiaxed alpha in a transformed beta matrix. The second material was cut from the same disk forging as the first but was heat treated to obtain a martensitic alpha prime microstructure. Tensile tests were performed prior to the onset of the fatigue loading portion of the study, and it was determined that the yield strengths of the specimens from both material conditions were within ten percent. The maximum fatigue loads were chosen to be 72 percent of the average yield strength for both materials as determined from the tensile tests. It was found that the cycles to failure from the 10 Hertz loading wave form were reduced by a factor of approximately five when the loading was changed to the trapezoidal wave form for the standard 'disk' material. The fatigue life reduction for the martensitic structure under identical test conditions was approximately 1.75. The improvement observed with the martensitic structure also was accompanied by an increase in overall fatigue life for the wave forms tested. This paper will review the results and conclusions of this effort.

Maize proximate composition and physical properties correlations to dry-grind ethanol concentrations

USDA-ARS?s Scientific Manuscript database

Dry grind ethanol plants incur economic losses due to seasonal variations in ethanol yields. One possible cause associated with ethanol yield variability is incoming grain quality. There is little published information on factors causing variation in dry grind ethanol concentrations. The objective o...

Genome-wide association analysis of milk yield traits in Nordic Red Cattle using imputed whole genome sequence variants.

PubMed

Iso-Touru, T; Sahana, G; Guldbrandtsen, B; Lund, M S; Vilkki, J

2016-03-22

The Nordic Red Cattle consisting of three different populations from Finland, Sweden and Denmark are under a joint breeding value estimation system. The long history of recording of production and health traits offers a great opportunity to study production traits and identify causal variants behind them. In this study, we used whole genome sequence level data from 4280 progeny tested Nordic Red Cattle bulls to scan the genome for loci affecting milk, fat and protein yields. Using a genome-wise significance threshold, regions on Bos taurus chromosomes 5, 14, 23, 25 and 26 were associated with fat yield. Regions on chromosomes 5, 14, 16, 19, 20 and 25 were associated with milk yield and chromosomes 5, 14 and 25 had regions associated with protein yield. Significantly associated variations were found in 227 genes for fat yield, 72 genes for milk yield and 30 genes for protein yield. Ingenuity Pathway Analysis was used to identify networks connecting these genes displaying significant hits. When compared to previously mapped genomic regions associated with fertility, significantly associated variations were found in 5 genes common for fat yield and fertility, thus linking these two traits via biological networks. This is the first time when whole genome sequence data is utilized to study genomic regions affecting milk production in the Nordic Red Cattle population. Sequence level data offers the possibility to study quantitative traits in detail but still cannot unambiguously reveal which of the associated variations is causative. Linkage disequilibrium creates difficulties to pinpoint the causative genes and variations. One solution to overcome these difficulties is the identification of the functional gene networks and pathways to reveal important interacting genes as candidates for the observed effects. This information on target genomic regions may be exploited to improve genomic prediction.

Dynamical basis sets for algebraic variational calculations in quantum-mechanical scattering theory

NASA Technical Reports Server (NTRS)

Sun, Yan; Kouri, Donald J.; Truhlar, Donald G.; Schwenke, David W.

1990-01-01

New basis sets are proposed for linear algebraic variational calculations of transition amplitudes in quantum-mechanical scattering problems. These basis sets are hybrids of those that yield the Kohn variational principle (KVP) and those that yield the generalized Newton variational principle (GNVP) when substituted in Schlessinger's stationary expression for the T operator. Trial calculations show that efficiencies almost as great as that of the GNVP and much greater than the KVP can be obtained, even for basis sets with the majority of the members independent of energy.

Global atmospheric concentrations and source strength of ethane

NASA Technical Reports Server (NTRS)

Blake, D. R.; Rowland, F. S.

1986-01-01

A study of the variation in ethane (C2H6) concentration between northern and southern latitudes over three years is presented together with a new estimate of its source strength. Ethane concentrations vary from 0.07 to 2 p.p.b.v. (parts per billion by volume) in air samples collected in remote surface locations in the Pacific (latitude 71 N-47 S) in all four seasons between September 1984 and June 1985. The variations are consistent with southerly transport from sources located chiefly in the Northern Hemisphere, further modified by seasonal variations in the strength of the reaction of C2H6 with OH radicals. These global data can be combined with concurrent data for CH4 and the laboratory reaction rates of each with OH to provide an estimate of three months as the average atmospheric lifetime for C2H6 and 13 + or - 3 Mtons for its annual atmospheric release.

GLACE: The Global Land-Atmosphere Coupling Experiment Part 2: Analysis

NASA Technical Reports Server (NTRS)

Guo, Zhichang; Dirmeyer, Paul A.; Koster, Randal D.; Bonan, Gordon; Chan, Edmond; Cox, Peter; Gordon, C. T.; Kanae, Shinjiro; Kowalczyk, Eva; Lawrence, David

2005-01-01

The twelve weather and climate models participating in the Global Land-Atmosphere Coupling Experiment (GLACE) show both a wide variation in the strength of land-atmosphere coupling and some intriguing commonalities. In this paper, we address the causes of variations in coupling strength - both the geographic variations within a given model and the model-to-model differences. The ability of soil moisture to affect precipitation is examined in two stages, namely, the ability of the soil moisture to affect evaporation, and the ability of evaporation to affect precipitation. Most of the differences between the models and within a given model are found to be associated with the first stage - an evaporation rate that varies strongly and consistently with soil moisture tends to lead to a higher coupling strength. The first stage differences reflect identifiable differences in model parameterization and model climate. Intermodel differences in the evaporation-precipitation connection, however, also play a key role.

Synthesis of improved phenolic resins

NASA Technical Reports Server (NTRS)

Delano, C. B.; Mcleod, A. H.

1979-01-01

Twenty seven addition cured phenolic resin compositions were prepared and tested for their ability to give char residues comparable to state-of-the-art phenolic resins. Cyanate, epoxy, allyl, acrylate, methacrylate and ethynyl derivatized phenolic oligomers were investigated. The novolac-cyanate and propargyl-novolac resins provided anaerobic char yields at 800 C of 58 percent. A 59 percent char yield was obtained from modified epoxy novolacs. A phosphonitrilic derivative was found to be effective as an additive for increasing char yields. The novolac-cyanate, epoxy-novolac and methacrylate-epoxy-novolac systems were investigated as composite matrices with Thornel 300 graphite fiber. All three resins showed good potential as composite matrices. The free radical cured methacrylate-epoxy-novolac graphite composite provided short beam shear strengths at room temperature of 93.3 MPa (13.5 ksi). The novolac-cyanate graphite composite produced a short beam shear strength of 74 MPa (10.7 ksi) and flexural strength of 1302 MPa (189 ksi) at 177 C. Air heat aging of the novolac-cyanate and epoxy novolac based composites for 12 weeks at 204 C showed good property retention.

Controls of Lithospheric Mechanical Strength on the Deformation Pattern of Tien Shan

NASA Astrophysics Data System (ADS)

Li, Y.; Xiong, X.; Zheng, Y.; Hu, X.; Zhang, Y.

2015-12-01

The Tien Shan is an outstanding example of intracontinental mountain belt, which was built rapidly and formed far away from plate boundaries. It exhibits 300~500 km in width and extends ~2000 km EW, located in central Asia. The Tien Shan is a key area for solution of the problems relating to intracontinental geodynamics. During last decades, despite a large amount of results based on various geological, geophysical and geodetic data about the Tien Shan, however, deformation mechanism remains controversial and other several principal problems related to its structure and evolution also have not been completely resolved. As for patterns of continental deformation, they are always controlled by both the forces applied to the lithosphere and by lithospheric resistance to the forces. The latter is often measured by the mechanical strength of lithosphere. The lateral variation of strength of lithosphere has been recognized to be an important factor controlling the spatial construction and temporal evolution of continent. In this study, we investigate the mechanical strength (Te) of lithosphere in the Tien Shan using wavelet coherency between Bouguer anomaly and topography. The patterns of Te variations are closely related to major tectonic boundaries and blocks. Mechanical strength exhibits a weak zone (Te~5-20km) beneath the Tien Shan while its surrounding blocks including Tarim Basin, Junggar Basin and Kazakh platform are characterized by a strong lithosphere (Te>40km). The lateral variations in mechanical strength and velocity field of horizontal movement with GPS demonstrate that strain localization appears at the margins of Tarim Basin, which is also the strong lithospheric domain. It is suggested that the weak lithosphere allows the crustal stress accumulation and the strong lithosphere helps to stress transfer. There is also a good agreement between mechanical strength and shear wave velocity structure in upper mantle. It indicates a strong domain located in the lower crust and lithospheric mantle. Combined with results of analog models, the location and style of deformation are preliminary determined and thus the related topography evolution in the Tien Shan is mainly controlled by the lateral and depth variation in lithospheric mechanical strength of surrounding areas.

Controlling the Morphology of Side Chain Liquid Crystalline Block Copolymer Thin Films through Variations in Liquid Crystalline Content

PubMed Central

Verploegen, Eric; Zhang, Tejia; Jung, Yeon Sik; Ross, Caroline; Hammond, Paula T.

2009-01-01

In this paper we describe methods for manipulating the morphology of side-chain liquid crystalline block copolymers through variations in the liquid crystalline content. By systematically controlling the covalent attachment of side chain liquid crystals to a block copolymer (BCP) backbone, the morphology of both the liquid crystalline (LC) mesophase and the phase segregated BCP microstructures can be precisely manipulated. Increases in LC functionalization lead to stronger preferences for the anchoring of the LC mesophase relative to the substrate and the inter-material dividing surface (IMDS). By manipulating the strength of these interactions the arrangement and ordering of the ultrathin film block copolymer nanostructures can be controlled, yielding a range of morphologies that includes perpendicular and parallel cylinders, as well as both perpendicular and parallel lamellae. Additionally, we demonstrate the utilization of selective etching to create a nanoporous liquid crystalline polymer thin film. The unique control over the orientation and order of the self-assembled morphologies with respect to the substrate will allow for the custom design of thin films for specific nano-patterning applications without manipulation of the surface chemistry or the application of external fields. PMID:18763835

Spatial evolution of 26-day recurrent galactic cosmic ray decreases: Correlated Ulysses COSPIN/KET and SOHO COSTEP observations

NASA Technical Reports Server (NTRS)

Heber, B.; Bothmer, V.; Droege, W.; Kunow, H.; Mueller-Mellin, R.; Posner, A.; Ferrando, P.; Raviart, A.; Paizis, C.; McComas, D.;

Controlling the morphology of side chain liquid crystalline block copolymer thin films through variations in liquid crystalline content.

PubMed

Verploegen, Eric; Zhang, Tejia; Jung, Yeon Sik; Ross, Caroline; Hammond, Paula T

2008-10-01

In this paper, we describe methods for manipulating the morphology of side-chain liquid crystalline block copolymers through variations in the liquid crystalline content. By systematically controlling the covalent attachment of side chain liquid crystals to a block copolymer (BCP) backbone, the morphology of both the liquid crystalline (LC) mesophase and the phase-segregated BCP microstructures can be precisely manipulated. Increases in LC functionalization lead to stronger preferences for the anchoring of the LC mesophase relative to the substrate and the intermaterial dividing surface. By manipulating the strength of these interactions, the arrangement and ordering of the ultrathin film block copolymer nanostructures can be controlled, yielding a range of morphologies that includes perpendicular and parallel cylinders, as well as both perpendicular and parallel lamellae. Additionally, we demonstrate the utilization of selective etching to create a nanoporous liquid crystalline polymer thin film. The unique control over the orientation and order of the self-assembled morphologies with respect to the substrate will allow for the custom design of thin films for specific nanopatterning applications without manipulation of the surface chemistry or the application of external fields.

Can feedback analysis be used to uncover the physical origin of climate sensitivity and efficacy differences?

NASA Astrophysics Data System (ADS)

Rieger, Vanessa S.; Dietmüller, Simone; Ponater, Michael

2017-10-01

Different strengths and types of radiative forcings cause variations in the climate sensitivities and efficacies. To relate these changes to their physical origin, this study tests whether a feedback analysis is a suitable approach. For this end, we apply the partial radiative perturbation method. Combining the forward and backward calculation turns out to be indispensable to ensure the additivity of feedbacks and to yield a closed forcing-feedback-balance at top of the atmosphere. For a set of CO2-forced simulations, the climate sensitivity changes with increasing forcing. The albedo, cloud and combined water vapour and lapse rate feedback are found to be responsible for the variations in the climate sensitivity. An O3-forced simulation (induced by enhanced NOx and CO surface emissions) causes a smaller efficacy than a CO2-forced simulation with a similar magnitude of forcing. We find that the Planck, albedo and most likely the cloud feedback are responsible for this effect. Reducing the radiative forcing impedes the statistical separability of feedbacks. We additionally discuss formal inconsistencies between the common ways of comparing climate sensitivities and feedbacks. Moreover, methodical recommendations for future work are given.

Annual Crop-Yield Variation, Child Survival, and Nutrition Among Subsistence Farmers in Burkina Faso.

PubMed

Belesova, Kristine; Gasparrini, Antonio; Sié, Ali; Sauerborn, Rainer; Wilkinson, Paul

2018-02-01

Whether year-to-year variation in crop yields affects the nutrition, health, and survival of subsistence-farming populations is relevant to the understanding of the potential impacts of climate change. However, the empirical evidence is limited. We examined the associations of child survival with interannual variation in food crop yield and middle-upper arm circumference (MUAC) in a subsistence-farming population of rural Burkina Faso. The study was of 44,616 children aged <5 years included in the Nouna Health and Demographic Surveillance System, 1992-2012, whose survival was analyzed in relation to the food crop yield in the year of birth (which ranged from 65% to 120% of the period average) and, for a subset of 16,698 children, to MUAC, using shared-frailty Cox proportional hazards models. Survival was appreciably worse in children born in years with low yield (full-adjustment hazard ratio = 1.11 (95% confidence interval: 1.02, 1.20) for a 90th- to 10th-centile decrease in annual crop yield) and in children with small MUAC (hazard ratio = 2.72 (95% confidence interval: 2.15, 3.44) for a 90th- to 10th-centile decrease in MUAC). These results suggest an adverse impact of variations in crop yields, which could increase under climate change. © The Author(s) 2017. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Yttria Nanoparticle Reinforced Commercially Pure (CP) Titanium

DTIC Science & Technology

2011-09-01

nanoparticles as well as titanium boride (TiB) reinforcements were produced through gas atomization. After consolidation and extrusion, room temperature...pure FE iron O oxygen Ti titanium TiB titanium boride TYS tensile yield strength UTS ultimate tensile strength wt% weight percent Y2O3

Bearing Strengths of Some Wrought-aluminum Alloys

NASA Technical Reports Server (NTRS)

Moore, R L; Wescoat, C

1943-01-01

Although a number of investigations of the bearing strength of aluminum alloys have been made, the problem remains one of considerable interest to the aircraft industry. For this reason it has seemed advisable to make additional tests of the commonly used aircraft alloys in an effort to establish a better basis for the selection of allowable bearing values. Current design practice does not recognize the effect of edge distance upon bearing strengths, and for this reason edge distance was one of the principal variables considered in this investigation. The increasing emphasis being placed upon permanent set limitations makes it essential that more information on bearing yield phenomena be obtained. The object of this investigation was to determine bearing yield and ultimate strengths of the following aluminum alloy products: 17S-T, 24S-T, Alclad 24S-T, 24S-RT, 52S-0, 52S-1/2H, 52S-H, 53S-T, and 61S-T extrusions. Ratios of these bearing properties to tensile properties were also determined.

The effectiveness of stone ash and volcanic ash of mount Sinabung as a filler on the initial strength of self-compacting concrete

NASA Astrophysics Data System (ADS)

Karolina, R.; Muhammad, W.; Saragih, M. D. S. M.; Mustaqa, T.

2018-02-01

Self Compacting Concrete is a concrete variant that has a high degree of workability and also has great initial strength, but low water cement factor. It is also self-flowable that can be molded on formwork with a very little or no compacted use of compactors. This concrete, using a variety of aggregate sizes, aggregate portions and superplasticizer admixture to achieve a special viscosity that allows it to flow on its own without the aid of a compactor. Lightweight concrete brick is a type of brick made from cement, sand, water, and developers. Lightweight concrete bricks are divided into 2 based on the developed materials used are AAC (Autoclave Aerated Concrete) using aluminum paste and CLC (Cellular Lightweight Concrete) that use Foaming Agent from BASF as a developer material. In this experiment, the lightweight bricks that will be made are CLC type which uses Foaming Agent as the developer material by mixing the Ash Stone produced by Stone Crusher machine which has the density of 2666 kg / m3 as Partial Pair Substitution. In this study the variation of Ash Stone used is 10%, 15%, and 20% of the planned amount of sand. After doing the tasting the result is obtained for 10% variation. Compressive Strength and Absorption Increase will decrease by 25.07% and 39.005% and Variation of 15% compressive strength will decrease by 65,8% and decrease of absorbtion equal to 17,441% and variation of 20% compressive strength will decreased by 67,4 and absorption increase equal to 17,956%.

A novel method of testing the shear strength of thick honeycomb composites

NASA Technical Reports Server (NTRS)

Hodge, A. J.; Nettles, A. T.

1991-01-01

Sandwich composites of aluminum and glass/phenolic honeycomb core were tested for shear strength before and after impact damage. The assessment of shear strength was performed in two ways; by four point bend testing of sandwich beams and by a novel double lap shear (DLS) test. This testing technique was developed so smaller specimens could be used, thus making the use of common lab scale fabrication and testing possible. The two techniques yielded similar data. The DLS test gave slightly lower shear strength values of the two methods but were closer to the supplier's values for shear strength.

Accessing ultrahigh-pressure, quasi-isentropic states of mattera)

NASA Astrophysics Data System (ADS)

Lorenz, K. T.; Edwards, M. J.; Glendinning, S. G.; Jankowski, A. F.; McNaney, J.; Pollaine, S. M.; Remington, B. A.

2005-05-01

A new approach to the study of material strength of metals at extreme pressures has been developed on the Omega laser, using a ramped plasma piston drive. The laser drives a shock through a solid plastic reservoir that unloads at the rear free surface, expands across a vacuum gap, and stagnates on the metal sample under study. This produces a gently increasing ram pressure, compressing the sample nearly isentropically. The peak pressure on the sample, inferred from interferometric measurements of velocity, can be varied by adjusting the laser energy and pulse length, gap size, and reservoir density, and obeys a simple scaling relation [J. Edwards et al., Phys. Rev. Lett. 92, 075002 (2004)]. In an important application, using in-flight x-ray radiography, the material strength of solid-state samples at high pressure can be inferred by measuring the reductions in the growth rates (stabilization) of Rayleigh-Taylor unstable interfaces. This paper reports the first attempt to use this new laser-driven, quasi-isentropic technique for determining material strength in high-pressure solids. Modulated foils of Al-6061-T6 were accelerated and compressed to peak pressures of ˜200kbar. Modulation growth was recorded at a series of times after peak acceleration and well into the release phase. Fits to the growth data, using a Steinberg-Guinan constitutive strength model, give yield strengths 38% greater than those given by the nominal parameters for Al-6061-T6. Calculations indicate that the dynamic enhancement to the yield strength at ˜200kbar is a factor of ˜3.6× over the ambient yield strength of 2.9kbar. Experimental designs based on this drive developed for the National Ignition Facility laser [W. Hogan, E. Moses, B. Warner, M. Sorem, and J. Soures, Nuclear Fusion 41, 567 (2001)] predict that solid-state samples can be quasi-isentropically driven to pressures an order of magnitude higher than on Omega, accessing new regimes of dense, high-pressure matter.

Recent climate variability and its impacts on soybean yields in Southern Brazil

NASA Astrophysics Data System (ADS)

Ferreira, Danielle Barros; Rao, V. Brahmananda

2011-08-01

Recent climate variability in rainfall, temperatures (maximum and minimum), and the diurnal temperature range is studied with emphasis on its influence over soybean yields in southern Brazil, during 1969 to 2002. The results showed that the soybean ( Glycine max L. Merril) yields are more affected by changes in temperature during summer, while changes in rainfall are more important during the beginning of plantation and at its peak of development. Furthermore, soybean yields in Paraná are more sensitive to rainfall variations, while soybean yields in the Rio Grande do Sul are more sensitive to variations in temperature. Effects of interannual climatic variability on soybean yields are evaluated through three agro-meteorological models: additive Stewart, multiplicative Rao, and multiplicative Jensen. The Jensen model is able to reproduce the interannual behavior of soybean yield reasonably well.

Effect of Brake Forming on the Strength of 24S-T Aluminum-alloy Sheet

NASA Technical Reports Server (NTRS)

Heimerl, George J; Woods, Walter

1946-01-01

Tests were made to determine the effect of brake forming on the strength of 24S-T aluminum alloy sheet that had been formed to an inside bend radius of three times the sheet thickness. The results for both directions of the grain of the material showed that the compressive yield stresses were appreciably increased, that the tensile yield stresses were moderately increased, that the ultimate tensile stresses were only slightly increased, that the elongations were considerably reduced, and that the shapes of the tensile and compressive stress-strain curves were markedly changed.

Dual-component video image analysis system (VIASCAN) as a predictor of beef carcass red meat yield percentage and for augmenting application of USDA yield grades.

PubMed

Cannell, R C; Tatum, J D; Belk, K E; Wise, J W; Clayton, R P; Smith, G C

1999-11-01

An improved ability to quantify differences in the fabrication yields of beef carcasses would facilitate the application of value-based marketing. This study was conducted to evaluate the ability of the Dual-Component Australian VIASCAN to 1) predict fabricated beef subprimal yields as a percentage of carcass weight at each of three fat-trim levels and 2) augment USDA yield grading, thereby improving accuracy of grade placement. Steer and heifer carcasses (n = 240) were evaluated using VIASCAN, as well as by USDA expert and online graders, before fabrication of carcasses to each of three fat-trim levels. Expert yield grade (YG), online YG, VIASCAN estimates, and VIASCAN estimated ribeye area used to augment actual and expert grader estimates of the remaining YG factors (adjusted fat thickness, percentage of kidney-pelvic-heart fat, and hot carcass weight), respectively, 1) accounted for 51, 37, 46, and 55% of the variation in fabricated yields of commodity-trimmed subprimals, 2) accounted for 74, 54, 66, and 75% of the variation in fabricated yields of closely trimmed subprimals, and 3) accounted for 74, 54, 71, and 75% of the variation in fabricated yields of very closely trimmed subprimals. The VIASCAN system predicted fabrication yields more accurately than current online yield grading and, when certain VIASCAN-measured traits were combined with some USDA yield grade factors in an augmentation system, the accuracy of cutability prediction was improved, at packing plant line speeds, to a level matching that of expert graders applying grades at a comfortable rate.

Changes of strength characteristics of pervious concrete due to variations in water to cement ratio

NASA Astrophysics Data System (ADS)

Kovac, M.; Sicakova, A.

2017-10-01

Pervious concrete is considered to be a sustainable pavement material due to high water permeability. The experiment presented in this paper was aimed at study the influence of water to cement ratio on both the compressive and splitting tensile strength of pervious concrete. Typically, less water content in concrete mixture leads to less porosity of cement paste and thus it provides desirable mechanical properties. In case of conventional dense concrete, the lower is the water to cement ratio, the higher or better is the strength, density and durability of concrete. This behaviour is not quite clear in case of pervious concrete because of low amount of cement paste present. Results of compressive and splitting tensile strength of pervious concrete are discussed in the paper while taking into account values measured after 2 and 28 days of hardening and variations in water to cement ratio. The results showed that changes of water to cement ratio from 0.25 to 0.35 caused only slight differences in strength characteristics, and this applied to both types of tested strength.

Three-Dimensional Dynamic Loading of Sand

DTIC Science & Technology

2011-02-01

strength yield strength of 40 MPa. In addition the inclusion of grain-on-grain stiction (friction) plays a major role in the compaction of sand at low...strains Figure 5 Stress-strain behavior for various grain and strength configurations When compared to experimental stre ss-strain data, both...of Materials, DYMAT 2009 Brussels Belgium, pg 1545–1551 [xi] Crawford, D.A. 2005. Using mesoscale modeling to investigate the role of material

Characterization of Environmentally Assisted Cracking for Design: State of the Art.

DTIC Science & Technology

1982-01-01

Barsom, J.M., Effect of cyclic stress form on corrosion fatigue crack propagation below Kiscc in a high yield strength steel , in Corrosion Fatigue... Effect of Prestressing on the Stress Corrosion Resistance of Two High Strength Steels , Boeing Document D6-25275, Boeing Company, Seattle, Washington...sT’e Residual stress Crack growth High strength steel Seawater Crack initiation Hydrogen embrittlement Stress corrosion Design Linear elastic fracture

Influence of the Atmospheric Model on Hanle Diagnostics

NASA Astrophysics Data System (ADS)

Ishikawa, Ryohko; Uitenbroek, Han; Goto, Motoshi; Iida, Yusuke; Tsuneta, Saku

2018-05-01

We clarify the uncertainty in the inferred magnetic field vector via the Hanle diagnostics of the hydrogen Lyman-α line when the stratification of the underlying atmosphere is unknown. We calculate the anisotropy of the radiation field with plane-parallel semi-empirical models under the nonlocal thermal equilibrium condition and derive linear polarization signals for all possible parameters of magnetic field vectors based on an analytical solution of the atomic polarization and Hanle effect. We find that the semi-empirical models of the inter-network region (FAL-A) and network region (FAL-F) show similar degrees of anisotropy in the radiation field, and this similarity results in an acceptable inversion error ( e.g., {˜} 40 G instead of 50 G in field strength and {˜} 100° instead of 90° in inclination) when FAL-A and FAL-F are swapped. However, the semi-empirical models of FAL-C (averaged quiet-Sun model including both inter-network and network regions) and FAL-P (plage regions) yield an atomic polarization that deviates from all other models, which makes it difficult to precisely determine the magnetic field vector if the correct atmospheric model is not known ( e.g., the inversion error is much larger than 40% of the field strength; {>} 70 G instead of 50 G). These results clearly demonstrate that the choice of model atmosphere is important for Hanle diagnostics. As is well known, one way to constrain the average atmospheric stratification is to measure the center-to-limb variation of the linear polarization signals. The dependence of the center-to-limb variations on the atmospheric model is also presented in this paper.

Nondestructive tests of regenerative chambers. [evaluating nondestructive methods of determining metal bond integrity

NASA Technical Reports Server (NTRS)

Malone, G. A.; Vecchies, L.; Wood, R.

1974-01-01

The capabilities and limitations of nondestructive evaluation methods were studied to detect and locate bond deficiencies in regeneratively cooled thrust chambers for rocket engines. Flat test panels and a cylinder were produced to simulate regeneratively cooled thrust chamber walls. Planned defects with various bond integrities were produced in the panels to evaluate the sensitivity, accuracy, and limitations of nondestructive methods to define and locate bond anomalies. Holography, acoustic emission, and ultrasonic scan were found to yield sufficient data to discern bond quality when used in combination and in selected sequences. Bonding techniques included electroforming and brazing. Materials of construction included electroformed nickel bonded to Nickel 200 and OFHC copper, electroformed copper bonded to OFHC copper, and 300 series stainless steel brazed to OFHC copper. Variations in outer wall strength, wall thickness, and defect size were evaluated for nondestructive test response.

Electric field-induced emission enhancement and modulation in individual CdSe nanowires.

PubMed

Vietmeyer, Felix; Tchelidze, Tamar; Tsou, Veronica; Janko, Boldizsar; Kuno, Masaru

2012-10-23

CdSe nanowires show reversible emission intensity enhancements when subjected to electric field strengths ranging from 5 to 22 MV/m. Under alternating positive and negative biases, emission intensity modulation depths of 14 ± 7% are observed. Individual wires are studied by placing them in parallel plate capacitor-like structures and monitoring their emission intensities via single nanostructure microscopy. Observed emission sensitivities are rationalized by the field-induced modulation of carrier detrapping rates from NW defect sites responsible for nonradiative relaxation processes. The exclusion of these states from subsequent photophysics leads to observed photoluminescence quantum yield enhancements. We quantitatively explain the phenomenon by developing a kinetic model to account for field-induced variations of carrier detrapping rates. The observed phenomenon allows direct visualization of trap state behavior in individual CdSe nanowires and represents a first step toward developing new optical techniques that can probe defects in low-dimensional materials.

Boundary Concentration for Eigenvalue Problems Related to the Onset of Superconductivity

NASA Astrophysics Data System (ADS)

del Pino, Manuel; Felmer, Patricio L.; Sternberg, Peter

We examine the asymptotic behavior of the eigenvalue μ(h) and corresponding eigenfunction associated with the variational problem in the regime h>>1. Here A is any vector field with curl equal to 1. The problem arises within the Ginzburg-Landau model for superconductivity with the function μ(h) yielding the relationship between the critical temperature vs. applied magnetic field strength in the transition from normal to superconducting state in a thin mesoscopic sample with cross-section Ω 2. We first carry out a rigorous analysis of the associated problem on a half-plane and then rigorously justify some of the formal arguments of [BS], obtaining an expansion for μ while also proving that the first eigenfunction decays to zero somewhere along the sample boundary when Ω is not a disc. For interior decay, we demonstrate that the rate is exponential.

Controlled shear/tension fixture

DOEpatents

Hsueh, Chun-Hway [Knoxville, TN; Liu, Chain-tsuan [Knoxville, TN; George, Easo P [Knoxville, TN

2012-07-24

A test fixture for simultaneously testing two material test samples is provided. The fixture provides substantially equal shear and tensile stresses in each test specimens. By gradually applying a load force to the fixture only one of the two specimens fractures. Upon fracture of the one specimen, the fixture and the load train lose contact and the second specimen is preserved in a state of upset just prior to fracture. Particular advantages of the fixture are (1) to control the tensile to shear load on the specimen for understanding the effect of these stresses on the deformation behavior of advanced materials, (2) to control the location of fracture for accessing localized material properties including the variation of the mechanical properties and residual stresses across the thickness of advanced materials, (3) to yield a fractured specimen for strength measurement and an unfractured specimen for examining the microstructure just prior to fracture.

Near-island biological hotspots in barren ocean basins.

PubMed

Gove, Jamison M; McManus, Margaret A; Neuheimer, Anna B; Polovina, Jeffrey J; Drazen, Jeffrey C; Smith, Craig R; Merrifield, Mark A; Friedlander, Alan M; Ehses, Julia S; Young, Charles W; Dillon, Amanda K; Williams, Gareth J

2016-02-16

Phytoplankton production drives marine ecosystem trophic-structure and global fisheries yields. Phytoplankton biomass is particularly influential near coral reef islands and atolls that span the oligotrophic tropical oceans. The paradoxical enhancement in phytoplankton near an island-reef ecosystem--Island Mass Effect (IME)--was first documented 60 years ago, yet much remains unknown about the prevalence and drivers of this ecologically important phenomenon. Here we provide the first basin-scale investigation of IME. We show that IME is a near-ubiquitous feature among a majority (91%) of coral reef ecosystems surveyed, creating near-island 'hotspots' of phytoplankton biomass throughout the upper water column. Variations in IME strength are governed by geomorphic type (atoll vs island), bathymetric slope, reef area and local human impacts (for example, human-derived nutrient input). These ocean oases increase nearshore phytoplankton biomass by up to 86% over oceanic conditions, providing basal energetic resources to higher trophic levels that support subsistence-based human populations.

Age hardening of 6061/alumina-silica fiber composite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khangaonkar, P.R.; Shamsul, J.B.; Azmi, R.

1994-12-31

Continuous alumina-silica fiber (Altex of Sumitomo) which yields high performance composites with some aluminium alloys was tried for squeeze cast 6061 based composites with volume fractions of 0.5 and 0.32, and the matrix microhardness and resistivity changes during age hardening were studied. The matrix in the composites hardened much more than the unreinforced alloy. Microhardness increases of up to 70 VPN above the solution treated condition at various aging temperatures were observed. The resistivity variation indicated an appreciable state of internal stress which continued to persist even when hardness fell by overaging. Energy dispersive X-ray analysis indicated that the regionsmore » close to the fibers had a higher silicon content than the matrix, and amorphous silica in the fiber may have a role in the formation of an enriched layer which may help the bonding and strength in the composite.« less

Mechanics of Interface Cracks

DTIC Science & Technology

1990-09-27

strength and thus were intended to provide a full account is taken of finite changes in geometry, comprehensive picture of stress and strain fields large...b, serv’es as a ecritical normal separation beyond which allappit matrix yield strength. Within the context of atom- adhesion is lost. Thus the

Impact of heterozygosity and heterogeneity on cotton lint yield stability: II. Lint yield components

USDA-ARS?s Scientific Manuscript database

In order to determine which yield components may contribute to yield stability, an 18-environment field study was undertaken to observe the mean, standard deviation (SD), and coefficient of variation (CV) for cotton lint yield components in population types that differed for lint yield stability. Th...

In situ frustum indentation of nanoporous copper thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Ran; Pathak, Siddhartha; Mook, William M.

Mechanical properties of thin films are often obtained solely from nanoindentation. At the same time, such measurements are characterized by a substantial amount of uncertainty, especially when mean pressure or hardness are used to infer uniaxial yield stress. In this paper we demonstrate that indentation with a pyramidal flat tip (frustum) indenter near the free edge of a sample can provide a significantly better estimate of the uniaxial yield strength compared to frequently used Berkovich indenter. This is first demonstrated using a numerical model for a material with an isotropic pressure sensitive yield criterion. Numerical simulations confirm that the indentermore » geometry provides a clear distinction of the mean pressure at which a material transitions to inelastic behavior. The mean critical pressure is highly dependent on the plastic Poisson ratio ν p so that at the 1% offset of normalized indent depth, the critical pressure p m c normalized to the uniaxial yield strength σ 0 is 1 < p m c/σ 0 < 1.3 for materials with 0 < ν p < 0.5. Choice of a frustum over Berkovich indenter reduces uncertainty in hardness by a factor of 3. These results are used to interpret frustum indentation experiments on nanoporous (NP) Copper with struts of typical diameter of 45 nm. An estimate of the yield strength of NP Copper is obtained 230 MPa < σ 0 < 300 MPa. Edge indentation further allows one to obtain in-plane strain maps near the critical pressure. Finally, comparison of the experimentally obtained in-plane strain maps of NP Cu during deformation and the strain field for different plastic Poisson ratios suggest that this material has a plastic Poisson ratio of the order of 0.2–0.3. However, existing constitutive models may not adequately capture post-yield behavior of NP metals.« less

In situ frustum indentation of nanoporous copper thin films

DOE PAGES

Liu, Ran; Pathak, Siddhartha; Mook, William M.; ...

2017-07-24

Mechanical properties of thin films are often obtained solely from nanoindentation. At the same time, such measurements are characterized by a substantial amount of uncertainty, especially when mean pressure or hardness are used to infer uniaxial yield stress. In this paper we demonstrate that indentation with a pyramidal flat tip (frustum) indenter near the free edge of a sample can provide a significantly better estimate of the uniaxial yield strength compared to frequently used Berkovich indenter. This is first demonstrated using a numerical model for a material with an isotropic pressure sensitive yield criterion. Numerical simulations confirm that the indentermore » geometry provides a clear distinction of the mean pressure at which a material transitions to inelastic behavior. The mean critical pressure is highly dependent on the plastic Poisson ratio ν p so that at the 1% offset of normalized indent depth, the critical pressure p m c normalized to the uniaxial yield strength σ 0 is 1 < p m c/σ 0 < 1.3 for materials with 0 < ν p < 0.5. Choice of a frustum over Berkovich indenter reduces uncertainty in hardness by a factor of 3. These results are used to interpret frustum indentation experiments on nanoporous (NP) Copper with struts of typical diameter of 45 nm. An estimate of the yield strength of NP Copper is obtained 230 MPa < σ 0 < 300 MPa. Edge indentation further allows one to obtain in-plane strain maps near the critical pressure. Finally, comparison of the experimentally obtained in-plane strain maps of NP Cu during deformation and the strain field for different plastic Poisson ratios suggest that this material has a plastic Poisson ratio of the order of 0.2–0.3. However, existing constitutive models may not adequately capture post-yield behavior of NP metals.« less

MBE growth of VCSELs for high volume applications

NASA Astrophysics Data System (ADS)

Jäger, Roland; Riedl, Michael C.

2011-05-01

Mass market applications like laser computer mouse or optical data transmission based on vertical-cavity surface-emitting laser (VCSEL) chips need a high over all yield including epitaxy, processing, dicing, mounting and testing. One yield limitation for VCSEL structures is the emission wavelength variation of the substrate surface area leading to the fraction on laser chips which are below or above the specification limits. For most 850 nm VCSEL products a resonator wavelength variation of ±2 nm is common. This represents an average resonator thickness variation of much less than 1% which is quite challenging to be fulfilled on the entire processed wafer surface area. A high over all yield is demonstrated on MBE grown VCSEL structures.

Variations in the milk yield and milk composition of dairy cows during lactation.

PubMed

Bedö, S; Nikodémusz, E; Percsich, K; Bárdos, L

1995-01-01

Variations in the milk yield and milk composition of a dairy cow colony (n = 23) were analyzed during 11 months of lactation. Milk yield followed a characteristic decreasing pattern in negative correlations with solid components (milk protein, lactose, total solids, milk fat). Titrable acidity (degree SH) was significantly (p < 0.1) higher in the milk of fresh-milking cows and it correlated negatively with lactose and positively with milk protein, milk fat and total solids. The concentrations of Zn, Fe and Cu tended to decrease, while Mn showed insignificant variation during lactation. Milk vitamin A showed a significant positive whilst milk vitamin E had a negative correlation with milk fat.

Yield Potential of Sugar Beet – Have We Hit the Ceiling?

PubMed Central

Hoffmann, Christa M.; Kenter, Christine

2018-01-01

The yield of sugar beet has continuously increased in the past decades. The question arises, whether this progress will continue in the future. A key factor for increasing yield potential of the crop is breeding progress. It was related to a shift in assimilate partitioning in the plant toward more storage carbohydrates (sucrose), whereas structural carbohydrates (leaves, cell wall compounds) unintendedly declined. The yield potential of sugar beet was estimated at 24 t sugar ha-1. For maximum yield, sufficient growth factors have to be available and the crop has to be able to fully utilize them. In sugar beet, limitations result from the lacking coincidence of maximum irradiation rates and full canopy cover, sink strength for carbon assimilation and high water demand, which cannot be met by rainfall alone. After harvest, sugar losses during storage occur. The paper discusses options for a further increase in yield potential, like autumn sowing of sugar beet, increasing sink strength and related constraints. It is prospected that yield increase by further widening the ratio of storage and structural carbohydrates will come to its natural limit as a certain cell wall stability is necessary. New challenges caused by climate change and by prolonged processing campaigns will occur. Thus breeding for improved pathogen resistance and storage properties will be even more important for successful sugar beet production than a further increase in yield potential itself. PMID:29599787

A Model for Determining Strength for Embedded Elliptical Crack in Ultra-high-temperature Ceramics

PubMed Central

Wang, Ruzhuan; Li, Weiguo

2015-01-01

A fracture strength model applied at room temperature for embedded elliptical crack in brittle solid was obtained. With further research on the effects of various physical mechanisms on material strength, a thermo-damage strength model for ultra-high-temperature ceramics was applied to each temperature phase. Fracture strength of TiC and the changing trends with elliptical crack shape variations under different temperatures were studied. The study showed that under low temperature, the strength is sensitive to the crack shape variation; as the temperature increases, the sensitivities become smaller. The size of ellipse’s minor axes has great effect on the material strength when the ratio of ellipse’s minor and major axes is lower than 0.5, even under relatively high temperatures. The effect of the minor axes of added particle on material properties thus should be considered under this condition. As the crack area is set, the fracture strength decreases firstly and then increases with the increase of ratio of ellipse’s minor and major axes, and the turning point is 0.5. It suggests that for the added particles the ratio of ellipse’s minor and major axes should not be 0.5. All conclusions significantly coincided with the results obtained by using the finite element software ABAQUS. PMID:28793488

A Model for Determining Strength for Embedded Elliptical Crack in Ultra-high-temperature Ceramics.

PubMed

Wang, Ruzhuan; Li, Weiguo

2015-08-05

A fracture strength model applied at room temperature for embedded elliptical crack in brittle solid was obtained. With further research on the effects of various physical mechanisms on material strength, a thermo-damage strength model for ultra-high-temperature ceramics was applied to each temperature phase. Fracture strength of TiC and the changing trends with elliptical crack shape variations under different temperatures were studied. The study showed that under low temperature, the strength is sensitive to the crack shape variation; as the temperature increases, the sensitivities become smaller. The size of ellipse's minor axes has great effect on the material strength when the ratio of ellipse's minor and major axes is lower than 0.5, even under relatively high temperatures. The effect of the minor axes of added particle on material properties thus should be considered under this condition. As the crack area is set, the fracture strength decreases firstly and then increases with the increase of ratio of ellipse's minor and major axes, and the turning point is 0.5. It suggests that for the added particles the ratio of ellipse's minor and major axes should not be 0.5. All conclusions significantly coincided with the results obtained by using the finite element software ABAQUS.

Improvement of high-yield pulp properties by using a small amount of bleached wheat straw pulp.

PubMed

Zhang, Hongjie; He, Zhibin; Ni, Yonghao

2011-02-01

In this study, the potential of using bleached wheat straw pulp (BWSP) was explored to improve the tensile strength of the high-yield pulp (HYP) while preserving its high bulk property. The results showed that with the addition of 5-10% refined BWSP, the HYP tensile strength can be increased by about 10-20% without sacrificing the bulk. Similar results were obtained by adding refined BWSP into a mixed furnish of bleached kraft pulps (BKPs) and HYP. The explanation was that micro fines from refined BWSP can act as binders to improve the HYP interfiber bonding, as a result, the HYP tensile strength can be improved by using a small amount of BWSP, while the HYP bulk is not significantly affected. Copyright © 2010 Elsevier Ltd. All rights reserved.

Some problems in applications of the linear variational method

NASA Astrophysics Data System (ADS)

Pupyshev, Vladimir I.; Montgomery, H. E.

2015-09-01

The linear variational method is a standard computational method in quantum mechanics and quantum chemistry. As taught in most classes, the general guidance is to include as many basis functions as practical in the variational wave function. However, if it is desired to study the patterns of energy change accompanying the change of system parameters such as the shape and strength of the potential energy, the problem becomes more complicated. We use one-dimensional systems with a particle in a rectangular or in a harmonic potential confined in an infinite rectangular box to illustrate situations where a variational calculation can give incorrect results. These situations result when the energy of the lowest eigenvalue is strongly dependent on the parameters that describe the shape and strength of the potential. The numerical examples described in this work are provided as cautionary notes for practitioners of numerical variational calculations.

MRI Estimates of Brain Iron Concentration in Normal Aging Using Quantitative Susceptibility Mapping

PubMed Central

Bilgic, Berkin; Pfefferbaum, Adolf; Rohlfing, Torsten; Sullivan, Edith V.; Adalsteinsson, Elfar

2011-01-01

Quantifying tissue iron concentration in vivo is instrumental for understanding the role of iron in physiology and in neurological diseases associated with abnormal iron distribution. Herein, we use recently-developed Quantitative Susceptibility Mapping (QSM) methodology to estimate the tissue magnetic susceptibility based on MRI signal phase. To investigate the effect of different regularization choices, we implement and compare ℓ1 and ℓ2 norm regularized QSM algorithms. These regularized approaches solve for the underlying magnetic susceptibility distribution, a sensitive measure of the tissue iron concentration, that gives rise to the observed signal phase. Regularized QSM methodology also involves a pre-processing step that removes, by dipole fitting, unwanted background phase effects due to bulk susceptibility variations between air and tissue and requires data acquisition only at a single field strength. For validation, performances of the two QSM methods were measured against published estimates of regional brain iron from postmortem and in vivo data. The in vivo comparison was based on data previously acquired using Field-Dependent Relaxation Rate Increase (FDRI), an estimate of MRI relaxivity enhancement due to increased main magnetic field strength, requiring data acquired at two different field strengths. The QSM analysis was based on susceptibility-weighted images acquired at 1.5T, whereas FDRI analysis used Multi-Shot Echo-Planar Spin Echo images collected at 1.5T and 3.0T. Both datasets were collected in the same healthy young and elderly adults. The in vivo estimates of regional iron concentration comported well with published postmortem measurements; both QSM approaches yielded the same rank ordering of iron concentration by brain structure, with the lowest in white matter and the highest in globus pallidus. Further validation was provided by comparison of the in vivo measurements, ℓ1-regularized QSM versus FDRI and ℓ2-regularized QSM versus FDRI, which again yielded perfect rank ordering of iron by brain structure. The final means of validation was to assess how well each in vivo method detected known age-related differences in regional iron concentrations measured in the same young and elderly healthy adults. Both QSM methods and FDRI were consistent in identifying higher iron concentrations in striatal and brain stem ROIs (i.e., caudate nucleus, putamen, globus pallidus, red nucleus, and substantia nigra) in the older than in the young group. The two QSM methods appeared more sensitive in detecting age differences in brain stem structures as they revealed differences of much higher statistical significance between the young and elderly groups than did FDRI. However, QSM values are influenced by factors such as the myelin content, whereas FDRI is a more specific indicator of iron content. Hence, FDRI demonstrated higher specificity to iron yet yielded noisier data despite longer scan times and lower spatial resolution than QSM. The robustness, practicality, and demonstrated ability of predicting the change in iron deposition in adult aging suggest that regularized QSM algorithms using single-field-strength data are possible alternatives to tissue iron estimation requiring two field strengths. PMID:21925274

Thermal stress effects in intermetallic matrix composites

NASA Technical Reports Server (NTRS)

Wright, P. K.; Sensmeier, M. D.; Kupperman, D. S.; Wadley, H. N. G.

1993-01-01

Intermetallic matrix composites develop residual stresses from the large thermal expansion mismatch (delta-alpha) between the fibers and matrix. This work was undertaken to: establish improved techniques to measure these thermal stresses in IMC's; determine residual stresses in a variety of IMC systems by experiments and modeling; and, determine the effect of residual stresses on selected mechanical properties of an IMC. X ray diffraction (XRD), neutron diffraction (ND), synchrotron XRD (SXRD), and ultrasonics (US) techniques for measuring thermal stresses in IMC were examined and ND was selected as the most promising technique. ND was demonstrated on a variety of IMC systems encompassing Ti- and Ni-base matrices, SiC, W, and Al2O3 fibers, and different fiber fractions (Vf). Experimental results on these systems agreed with predictions of a concentric cylinder model. In SiC/Ti-base systems, little yielding was found and stresses were controlled primarily by delta-alpha and Vf. In Ni-base matrix systems, yield strength of the matrix and Vf controlled stress levels. The longitudinal residual stresses in SCS-6/Ti-24Al-llNb composite were modified by thermomechanical processing. Increasing residual stress decreased ultimate tensile strength in agreement with model predictions. Fiber pushout strength showed an unexpected inverse correlation with residual stress. In-plane shear yield strength showed no dependence on residual stress. Higher levels of residual tension led to higher fatigue crack growth rates, as suggested by matrix mean stress effects.

Jet formation in cerium metal to examine material strength

DOE PAGES

Jensen, B. J.; Cherne, F. J.; Prime, M. B.; ...

2015-11-18

Examining the evolution of material properties at extreme conditions advances our understanding of numerous high-pressure phenomena from natural events like meteorite impacts to general solid mechanics and fluid flow behavior. Some recent advances in synchrotron diagnostics coupled with dynamic compression platforms have introduced new possibilities for examining in-situ, spatially resolved material response with nanosecond time resolution. In this work, we examined jet formation from a Richtmyer-Meshkov instability in cerium initially shocked into a transient, high-pressure phase, and then released to a low-pressure, higher-temperature state. Cerium's rich phase diagram allows us to study the yield stress following a shock induced solid-solidmore » phase transition. X-ray imaging was used to obtain images of jet formation and evolution with 2–3 μm spatial resolution. And from these images, an analytic method was used to estimate the post-shock yield stress, and these results were compared to continuum calculations that incorporated an experimentally validated equation-of-state (EOS) for cerium coupled with a deviatoric strength model. Reasonable agreement was observed between the calculations and the data illustrating the sensitivity of jet formation on the yield stress values. Finally, the data and analysis shown here provide insight into material strength during dynamic loading which is expected to aid in the development of strength aware multi-phase EOS required to predict the response of matter at extreme conditions.« less

Mechanical Properties, Short Time Creep, and Fatigue of an Austenitic Steel

PubMed Central

Brnic, Josip; Turkalj, Goran; Canadija, Marko; Lanc, Domagoj; Krscanski, Sanjin; Brcic, Marino; Li, Qiang; Niu, Jitai

2016-01-01

The correct choice of a material in the process of structural design is the most important task. This study deals with determining and analyzing the mechanical properties of the material, and the material resistance to short-time creep and fatigue. The material under consideration in this investigation is austenitic stainless steel X6CrNiTi18-10. The results presenting ultimate tensile strength and 0.2 offset yield strength at room and elevated temperatures are displayed in the form of engineering stress-strain diagrams. Besides, the creep behavior of the steel is presented in the form of creep curves. The material is consequently considered to be creep resistant at temperatures of 400 °C and 500 °C when subjected to a stress which is less than 0.9 of the yield strength at the mentioned temperatures. Even when the applied stress at a temperature of 600 °C is less than 0.5 of the yield strength, the steel may be considered as resistant to creep. Cyclic tensile fatigue tests were carried out at stress ratio R = 0.25 using a servo-pulser machine and the results were recorded. The analysis shows that the stress level of 434.33 MPa can be adopted as a fatigue limit. The impact energy was also determined and the fracture toughness assessed. PMID:28773424

Papermaking properties of aspen ultrahigh-yield mechanical pulps

Treesearch

J. N. McGovern; T. H. Wegner

1991-01-01

Eleven types of aspen ultra-high-yield (90% and above) mechanical pubs were evaluated for their chemical compositions (including sulfur), handsheet strength, and optical properties, fiber length indices, and fiberizing energies. The pulping processes were stone groundwood, pressurized stone groundwood, refiner mechanical, thermomechanical, chemimechanical (alkaline...

Dynamic Yielding and Spall Behavior of Commercially Pure Grade 4 Titanium

NASA Astrophysics Data System (ADS)

Thadhani, Naresh; Whelchel, R. L.; Sanders, Tom; Mehkote, D. S.; Iyer, K. A.; Georgia Instiutute of Technology Collaboration; Johns Hopkins University, Applied Physics Labortaory Collaboration

2015-06-01

The dynamic yielding and fracture (spalling) of commercially pure (grade 4) titanium are investigated using symmetric plate impact experiments over a peak stress range of 5.6 GPa to 12.5 GPa, using the 80-mm single-stage gas-gun. VISAR rear free surface velocity profiles display both a Hugoniot elastic limit (HEL) and a velocity pullback, which are indicative of dynamic compressive yielding and tensile fracture (spalling), respectively. The HEL values appear to show a slight decrease with peak stress from 2.2 GPa to 2.0 GPa along with a corresponding increase in twinning observed in recovered impacted samples. The spall strength on the other hand increases with peak stress from a value of 3.3 GPa to 3.8 GPa and shows a good power law fit with the decompression strain rate. The differing responses in dynamic yield and fracture behavior suggest that void nucleation may be the dominant mechanism affecting the spall strength of grade 4 titanium.

Yielding and deformation behavior of the single crystal nickel-base superalloy PWA 1480

NASA Technical Reports Server (NTRS)

Milligan, W. W., Jr.

1986-01-01

Interrupted tensile tests were conducted to fixed plastic strain levels in 100 ordered single crystals of the nickel based superalloy PWA 1480. Testing was done in the range of 20 to 1093 C, at strain rate of 0.5 and 50%/min. The yield strength was constant from 20 to 760 C, above which the strength dropped rapidly and became a stong function of strain rate. The high temperature data were represented very well by an Arrhenius type equation, which resulted in three distinct temperature regimes. The deformation substructures were grouped in the same three regimes, indicating that there was a fundamental relationship between the deformation mechanisms and activation energies. Models of the yielding process were considered, and it was found that no currently available model was fully applicable to this alloy. It was also demonstrated that the initial deformation mechanism (during yielding) was frequently different from that which would be inferred by examining specimens which were tested to failure.

Character strengths and well-being across the life span: data from a representative sample of German-speaking adults living in Switzerland

PubMed Central

Martínez-Martí, María L.; Ruch, Willibald

2014-01-01

Character strengths are positive, morally valued traits of personality. This study aims at assessing the relationship between character strengths and subjective well-being (i.e., life satisfaction, positive and negative affect) in a representative sample of German-speaking adults living in Switzerland (N = 945). We further test whether this relationship is consistent at different stages in life. Results showed that hope, zest, love, social intelligence and perseverance yielded the highest positive correlations with life satisfaction. Hope, zest, humor, gratitude and love presented the highest positive correlations with positive affect. Hope, humor, zest, honesty, and open-mindedness had the highest negative correlations with negative affect. When examining the relationship between strengths and well-being across age groups, in general, hope, zest and humor consistently yielded the highest correlations with well-being. Additionally, in the 27–36 years group, strengths that promote commitment and affiliation (i.e., kindness and honesty) were among the first five positions in the ranking of the relationship between strengths and well-being. In the 37–46 years group, in addition to hope, zest and humor, strengths that promote the maintenance of areas such as family and work (i.e., love, leadership) were among the first five positions in the ranking. Finally, in the 47–57 years group, in addition to hope, zest and humor, strengths that facilitate integration and a vital involvement with the environment (i.e., gratitude, love of learning) were among the first five positions in the ranking. This study partially supports previous findings with less representative samples on the association between character strengths and well-being, and sheds light on the relative importance of some strengths over others for well-being across the life span. PMID:25408678

Residual Strength Prediction of Fuselage Structures with Multiple Site Damage

NASA Technical Reports Server (NTRS)

Chen, Chuin-Shan; Wawrzynek, Paul A.; Ingraffea, Anthony R.

1999-01-01

This paper summarizes recent results on simulating full-scale pressure tests of wide body, lap-jointed fuselage panels with multiple site damage (MSD). The crack tip opening angle (CTOA) fracture criterion and the FRANC3D/STAGS software program were used to analyze stable crack growth under conditions of general yielding. The link-up of multiple cracks and residual strength of damaged structures were predicted. Elastic-plastic finite element analysis based on the von Mises yield criterion and incremental flow theory with small strain assumption was used. A global-local modeling procedure was employed in the numerical analyses. Stress distributions from the numerical simulations are compared with strain gage measurements. Analysis results show that accurate representation of the load transfer through the rivets is crucial for the model to predict the stress distribution accurately. Predicted crack growth and residual strength are compared with test data. Observed and predicted results both indicate that the occurrence of small MSD cracks substantially reduces the residual strength. Modeling fatigue closure is essential to capture the fracture behavior during the early stable crack growth. Breakage of a tear strap can have a major influence on residual strength prediction.

Effects of porosity on weld-joint tensile strength of aluminum alloys

NASA Technical Reports Server (NTRS)

Lovoy, C. V.

1974-01-01

Tensile properties in defect-free weldments of aluminum alloys 2014-T6 and 2219-T87 (sheet and plate) are shown to be related to the level or concentration of induced simulated porosity. The scatter diagram shows that the ultimate tensile strength of the weldments displays the most pronounced linear relationship with the level of porosity. The relationships between yield strength or elongation and porosity are either trivial or inconsequential in the lower and intermediate levels of porosity content. In highly concentrated levels of porosity, both yield strength and elongation values decrease markedly. Correlation coefficients were obtained by simple straight line regression analysis between the variables of ultimate tensile strength and pore level. The coefficients were greater, indicating a better correlation, using a pore area accumulation concept or pore volume accumulation than the accumulation of the pore diameters. These relationships provide a useful tool for assessing the existing aerospace radiographic acceptance standards with respect to permissible porosity. In addition, these relationships, in combination with known design load requirements, will serve as an engineering guideline in determining when a weld repair is necessary based on accumulative pore level as detected by radiographic techniques.

Study made of pneumatic high pressure piping materials /10,000 psi/

NASA Technical Reports Server (NTRS)

Loeb, M. B.; Smith, J. C.

1967-01-01

Evaluations of five types of steel for use in high pressure pneumatic piping systems include tests for impact strength, tensile and yield strengths, elongation and reduction in area, field weldability, and cost. One type, AISI 4615, was selected as most advantageous for extensive use in future flight vehicles.

Accelerated curing and strength-modulus correlation for lime-stabilized soils : final report, January 2010.

DOT National Transportation Integrated Search

2010-01-01

This study sought to identify the equivalent 105F curing duration for lime-stabilized soil (LSS) that will : yield the equivalent unconfined compressive strength (UCS) to that resulting from 28-day, 73F curing. Both : 5-day and 7-day 105F (or 1...

Improved Warm-Working Process For An Iron-Base Alloy

NASA Technical Reports Server (NTRS)

Cone, Fred P.; Cryns, Brendan J.; Miller, John A.; Zanoni, Robert

1992-01-01

Warm-working process produces predominantly unrecrystallized grain structure in forgings of iron-base alloy A286 (PWA 1052 composition). Yield strength and ultimate strength increased, and elongation and reduction of area at break decreased. Improved process used on forgings up to 10 in. thick and weighing up to 900 lb.

An evaluation of GTAW-P versus GTA welding of alloy 718

NASA Technical Reports Server (NTRS)

Gamwell, W. R.; Kurgan, C.; Malone, T. W.

1991-01-01

Mechanical properties were evaluated to determine statistically whether the pulsed current gas tungsten arc welding (GTAW-P) process produces welds in alloy 718 with room temperature structural performance equivalent to current Space Shuttle Main Engine (SSME) welds manufactured by the constant current GTAW-P process. Evaluations were conducted on two base metal lots, two filler metal lots, two heat input levels, and two welding processes. The material form was 0.125-inch (3.175-mm) alloy 718 sheet. Prior to welding, sheets were treated to either the ST or STA-1 condition. After welding, panels were left as welded or heat treated to the STA-1 condition, and weld beads were left intact or machined flush. Statistical analyses were performed on yield strength, ultimate tensile strength (UTS), and high cycle fatigue (HCF) properties for all the post welded material conditions. Analyses of variance were performed on the data to determine if there were any significant effects on UTS or HCF life due to variations in base metal, filler metal, heat input level, or welding process. Statistical analyses showed that the GTAW-P process does produce welds with room temperature structural performance equivalent to current SSME welds manufactured by the GTAW process, regardless of prior material condition or post welding condition.

Driven Bose-Hubbard model with a parametrically modulated harmonic trap

NASA Astrophysics Data System (ADS)

Mann, N.; Bakhtiari, M. Reza; Massel, F.; Pelster, A.; Thorwart, M.

2017-04-01

We investigate a one-dimensional Bose-Hubbard model in a parametrically driven global harmonic trap. The delicate interplay of both the local interaction of the atoms in the lattice and the driving of the global trap allows us to control the dynamical stability of the trapped quantum many-body state. The impact of the atomic interaction on the dynamical stability of the driven quantum many-body state is revealed in the regime of weak interaction by analyzing a discretized Gross-Pitaevskii equation within a Gaussian variational ansatz, yielding a Mathieu equation for the condensate width. The parametric resonance condition is shown to be modified by the atom interaction strength. In particular, the effective eigenfrequency is reduced for growing interaction in the mean-field regime. For a stronger interaction, the impact of the global parametric drive is determined by the numerically exact time-evolving block decimation scheme. When the trapped bosons in the lattice are in a Mott insulating state, the absorption of energy from the driving field is suppressed due to the strongly reduced local compressibility of the quantum many-body state. In particular, we find that the width of the local Mott region shows a breathing dynamics. Finally, we observe that the global modulation also induces an effective time-independent inhomogeneous hopping strength for the atoms.

Colloid mobilization and seasonal variability in a semiarid headwater stream

USGS Publications Warehouse

Mills, Taylor J.; Suzanne P. Ancerson,; Bern, Carleton; Aguirre, Arnulfo; Derry, Louis A.

2017-01-01

Colloids can be important vectors for the transport of contaminants in the environment, but little is known about colloid mobilization at the watershed scale. We present colloid concentration, composition, and flux data over a large range of hydrologic conditions from a small watershed (Gordon Gulch) in the foothills of the Colorado Front Range. Colloids, consisting predominantly of Si, Fe, and Al, were present in most stream samples but were not detected in groundwater samples. Mineralogical and morphological analysis indicated that the colloids were composed of kaolinite and illite clays with lesser amounts of amorphous Fe-hydroxides. Although colloid composition remained relatively constant over the sampled flow conditions, colloid concentrations varied considerably and increased as ionic strength of stream water decreased. The highest concentrations occurred during precipitation events after extended dry periods. These observations are consistent with laboratory studies that have shown colloids can be mobilized by decreases in pore-water ionic strength, which likely occurs during precipitation events. Colloidal particles constituted 30 to 35% of the Si mass flux and 93 to 97% of the Fe and Al mass fluxes in the <0.45-µm fraction in the stream. Colloids are therefore a significant and often overlooked component of mass fluxes whose temporal variations may yield insight into hydrologic flowpaths in this semiarid catchment.

Genetic diversity affects the strength of population regulation in a marine fish.

PubMed

Johnson, D W; Freiwald, J; Bernardi, G

2016-03-01

Variation is an essential feature of biological populations, yet much of ecological theory treats individuals as though they are identical. This simplifying assumption is often justified by the perception that variation among individuals does not have significant effects on the dynamics of whole populations. However, this perception may be skewed by a historic focus on studying single populations. A true evaluation of the extent to which among-individual variation affects the dynamics of populations requires the study of multiple populations. In this study, we examined variation in the dynamics of populations of a live-bearing, marine fish (black surfperch; Embiotoca jacksoni). In collaboration with an organization of citizen scientists (Reef Check California), we were able to examine the dynamics of eight populations that were distributed throughout approximately 700 km of coastline, a distance that encompasses much of this species' range. We hypothesized that genetic variation within a local population would be related to the intensity of competition and to the strength of population regulation. To test this hypothesis, we examined whether genetic diversity (measured by the diversity of mitochondrial DNA haplotypes) was related to the strength of population regulation. Low-diversity populations experienced strong density dependence in population growth rates and population sizes were regulated much more tightly than they were in high-diversity populations. Mechanisms that contributed to this pattern include links between genetic diversity, habitat use, and spatial crowding. On average, low-diversity populations used less of the available habitat and exhibited greater spatial clustering (and more intense competition) for a given level of density (measured at the scale of the reef). Although the populations we studied also varied with respect to exogenous characteristics (habitat complexity, densities of predators, and interspecific competitors), none of these characteristics was significantly related to the strength of population regulation. In contrast, an endogenous characteristic of the population (genetic diversity) explained 77% of the variation in the strength of population regulation (95% CI: 27-94%). Our results suggest that the genetic and phenotypic composition of populations can play a major role in their dynamics.

WE-G-18C-05: Characterization of Cross-Vendor, Cross-Field Strength MR Image Intensity Variations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paulson, E; Prah, D

2014-06-15

Purpose: Variations in MR image intensity and image intensity nonuniformity (IINU) can challenge the accuracy of intensity-based image segmentation and registration algorithms commonly applied in radiotherapy. The goal of this work was to characterize MR image intensity variations across scanner vendors and field strengths commonly used in radiotherapy. Methods: ACR-MRI phantom images were acquired at 1.5T and 3.0T on GE (450w and 750, 23.1), Siemens (Espree and Verio, VB17B), and Philips (Ingenia, 4.1.3) scanners using commercial spin-echo sequences with matched parameters (TE/TR: 20/500 ms, rBW: 62.5 kHz, TH/skip: 5/5mm). Two radiofrequency (RF) coil combinations were used for each scanner: bodymore » coil alone, and combined body and phased-array head coils. Vendorspecific B1- corrections (PURE/Pre-Scan Normalize/CLEAR) were applied in all head coil cases. Images were transferred offline, corrected for IINU using the MNI N3 algorithm, and normalized. Coefficients of variation (CV=σ/μ) and peak image uniformity (PIU = 1−(Smax−Smin)/(Smax+Smin)) estimates were calculated for one homogeneous phantom slice. Kruskal-Wallis and Wilcoxon matched-pairs tests compared mean MR signal intensities and differences between original and N3 image CV and PIU. Results: Wide variations in both MR image intensity and IINU were observed across scanner vendors, field strengths, and RF coil configurations. Applying the MNI N3 correction for IINU resulted in significant improvements in both CV and PIU (p=0.0115, p=0.0235). However, wide variations in overall image intensity persisted, requiring image normalization to improve consistency across vendors, field strengths, and RF coils. These results indicate that B1- correction routines alone may be insufficient in compensating for IINU and image scaling, warranting additional corrections prior to use of MR images in radiotherapy. Conclusions: MR image intensities and IINU vary as a function of scanner vendor, field strength, and RF coil configuration. A two-step strategy consisting of MNI N3 correction followed by normalization was required to improve MR image consistency. Funding provided by Advancing a Healthier Wisconsin.« less

Investigation of the plastic fracture of high strength steels

NASA Technical Reports Server (NTRS)

Cox, T. B.; Low, J. R., Jr.

1972-01-01

An investigation of the plastic fracture process to improve tensile strength in high strength steels is presented. Two generic types of steels are considered: a quenched and tempered grade and a maraging grade, in order to compare two different matrix microstructures. Each type of steel was studied in commercial grade purity and in special melted high purity form, low in residual and impurity elements. The specific alloys dealt with include AISI 4340 and 18 Ni, 200 grade maraging steel, both heat treated to the same yield strength level of approximately 200 ksi.

Probabilistic and Possibilistic Analyses of the Strength of a Bonded Joint

NASA Technical Reports Server (NTRS)

Stroud, W. Jefferson; Krishnamurthy, T.; Smith, Steven A.

2001-01-01

The effects of uncertainties on the strength of a single lap shear joint are explained. Probabilistic and possibilistic methods are used to account for uncertainties. Linear and geometrically nonlinear finite element analyses are used in the studies. To evaluate the strength of the joint, fracture in the adhesive and material strength failure in the strap are considered. The study shows that linear analyses yield conservative predictions for failure loads. The possibilistic approach for treating uncertainties appears to be viable for preliminary design, but with several qualifications.

Measurements of aquifer-storage change and specific yield using gravity surveys

USGS Publications Warehouse

Pool, D.R.; Eychaner, J.H.

1995-01-01

Pinal Creek is an intermittent stream that drains a 200-square-mile alluvial basin in central Arizona. Large changes in water levels and aquifer storage occur in an alluvial aquifer near the stream in response to periodic recharge and ground-water withdrawals. Outflow components of the ground-water budget and hydraulic properties of the alluvium are well-defined by field measurements; however, data are insufficient to adequately describe recharge, aquifer-storage change, and specific-yield values. An investigation was begun to assess the utility of temporal-gravity surveys to directly measure aquifer-storage change and estimate values of specific yield.The temporal-gravity surveys measured changes in the differences in gravity between two reference stations on bedrock and six stations at wells; changes are caused by variations in aquifer storage. Specific yield was estimated by dividing storage change by water-level change. Four surveys were done between February 21, 1991, and March 31, 1993. Gravity increased as much as 158 microGal ± 1 to 6 microGal, and water levels rose as much as 58 feet. Average specific yield at wells ranged from 0.16 to 0.21, and variations in specific yield with depth correlate with lithologic variations. Results indicate that temporal-gravity surveys can be used to estimate aquifer-storage change and specific yield of water-table aquifers where significant variations in water levels occur. Direct measurement of aquifer-storage change can eliminate a major unknown from the ground-water budget of arid basins and improve residual estimates of recharge.

Histograms showing variations in oil yield, water yield, and specific gravity of oil from Fischer assay analyses of oil-shale drill cores and cuttings from the Piceance Basin, northwestern Colorado

USGS Publications Warehouse

Dietrich, John D.; Brownfield, Michael E.; Johnson, Ronald C.; Mercier, Tracey J.

2014-01-01

Recent studies indicate that the Piceance Basin in northwestern Colorado contains over 1.5 trillion barrels of oil in place, making the basin the largest known oil-shale deposit in the world. Previously published histograms display oil-yield variations with depth and widely correlate rich and lean oil-shale beds and zones throughout the basin. Histograms in this report display oil-yield data plotted alongside either water-yield or oil specific-gravity data. Fischer assay analyses of core and cutting samples collected from exploration drill holes penetrating the Eocene Green River Formation in the Piceance Basin can aid in determining the origins of those deposits, as well as estimating the amount of organic matter, halite, nahcolite, and water-bearing minerals. This report focuses only on the oil yield plotted against water yield and oil specific gravity.

Comments on extracting the resonance strength parameter from yield data

DOE PAGES

Croft, Stephen; Favalli, Andrea

2015-06-23

The F(α,n) reaction is the focus of on-going research in part because it is an important source of neutrons in the nuclear fuel cycle which can be exploited to assay nuclear materials, especially uranium in the form of UF 6. At the present time there remains some considerable uncertainty (of the order of ± 20%) in the thick target integrated over angle (α,n) yield from 19F (100% natural abundance) and its compounds as discussed. An important thin target cross-section measurement is that of Wrean and Kavanagh who explore the region from below threshold (2.36 MeV) to approximately 3.1 MeV withmore » fine energy resolution. Integration of their cross-section data over the slowing down history of a stopping α-particle allows the thick target yield to be calculated for incident energies up to 3.1 MeV. This trend can then be combined with data from other sources to obtain a thick target yield curve over the wider range of interest to the fuel cycle (roughly threshold to 10 MeV to include all relevant α-emitters). To estimate the thickness of the CaF 2 target they used, Wrean and Kavanagh separately measured the integrated yield of the 6.129 MeV γ-rays from the resonance at 340.5 keV (laboratory α-particle kinetic energy) in the 19F(p,αγ) reaction. To interpret the data they adopted a resonance strength parameter of (22.3 ± 0.8) eV based on a determination by Becker et al. The value and its uncertainty directly affects the thickness estimate and the extracted (α,n) cross-section values. In their citation to Becker et al's work, Wrean and Kavanagh comment that they did not make use of an alternative value of (23.7±1.0) eV reported by Croft because they were unable to reproduce the value from the data given in that paper. The value they calculated for the resonance strength from the thick target yield given by Croft was 21.4 eV. The purpose of this communication is to revisit the paper by Croft published in this journal and specifically to explain the origin of the reported resonance strength. Fortunately the original notes spanning the period 12 January 1988 to 16 January 1990 were available to consult. Finally, in hindsight there is certainly a case of excessive brevity to rectify. In essence the step requiring explanation is how to compute the resonance strength, ω γ, from the reported thick target resonance yield Y.« less

A model for extreme plasticity

NASA Astrophysics Data System (ADS)

Thomson, S. J.; Howell, P. D.

2016-09-01

We present a mathematical model for elastoplasticity in the regime where the applied stress greatly exceeds the yield stress. This scenario is typically found in violent impact testing, where millimetre thick metal samples are subjected to pressures on the order of 10-102 GPa, while the yield stress can be as low as 10-2 GPa. In such regimes the metal can be treated as a barotropic compressible fluid in which the strength, measured by the ratio of the yield stress to the applied stress, is negligible to lowest order. Our approach is to exploit the smallness of this ratio by treating the effects of strength as a small perturbation to a leading order barotropic model. We find that for uniaxial deformations, these additional effects give rise to features in the response of the material which differ significantly from the predictions of barotropic flow.

Alloys For Corrosive, Hydrogen-Rich Environments

NASA Technical Reports Server (NTRS)

Mcpherson, William B.; Bhat, Biliyar N.; Chen, Po-Shou; Kuruvilla, A. K.; Panda, Binayak

1993-01-01

"NASA-23" denotes class of alloys resisting both embrittlement by hydrogen and corrosion. Weldable and castable and formed by such standard processes as rolling, forging, and wire drawing. Heat-treated to obtain desired combinations of strength and ductility in ranges of 100 to 180 kpsi yield strength, 120 to 200 kpsi ultimate tensile strength, and 10 to 30 percent elongation at break. Used in place of most common aerospace structural alloy, Inconel(R) 718.

In healthy elderly postmenopausal women variations in BMD and BMC at various skeletal sites are associated with differences in weight and lean body mass rather than by variations in habitual physical activity, strength or VO2max.

PubMed

Schöffl, I; Kemmler, W; Kladny, B; Vonstengel, S; Kalender, W A; Engelke, K

2008-01-01

The objective of this study was an integrated cross-sectional investigation for answering the question whether differences in bone mineral density in elderly postmenopausal women are associated with differences in habitual physical activity and unspecific exercise levels. Two hundred and ninety nine elderly women (69-/+3 years), without diseases or medication affecting bone metabolism were investigated. The influence of weight, body composition and physical activity on BMD was measured at multiple sites using different techniques (DXA, QCT, and QUS). Physical activity and exercise level were assessed by questionnaire, maximum strength of the legs and aerobic capacity. Variations in physical activity or habitual exercise had no effect on bone. The only significant univariate relation between strength/VO(2)max and BMD/BMC that remained after adjusting for confounding variables was between arm BMD (DXA) and hand-grip strength. The most important variable for explaining BMD was weight and for cortical BMC of the femur (QCT) lean body mass. Weight and lean body mass emerge as predominant predictors of BMD in normal elderly women, whereas the isolated effect of habitual physical activity, unspecific exercise participation, and muscle strength on bone parameters is negligible. Thus, an increase in the amount of habitual physical activity will probably have no beneficial impact on bone.

ENSO and PDO-related climate variability impacts on Midwestern United States crop yields.

PubMed

Henson, Chasity; Market, Patrick; Lupo, Anthony; Guinan, Patrick

2017-05-01

An analysis of crop yields for the state of Missouri was completed to determine if an interannual or multidecadal variability existed as a result of the El Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO). Corn and soybean yields were recorded in kilograms per hectare for each of the six climate regions of Missouri. An analysis using the Mokhov "method of cycles" demonstrated interannual, interdecadal, and multidecadal variations in crop yields. Cross-spectral analysis was used to determine which region was most impacted by ENSO and PDO influenced seasonal (April-September) temperature and precipitation. Interannual (multidecadal) variations found in the spectral analysis represent a relationship to ENSO (PDO) phase, while interdecadal variations represent a possible interaction between ENSO and PDO. Average crop yields were then calculated for each combination of ENSO and PDO phase, displaying a pronounced increase in corn and soybean yields when ENSO is warm and PDO is positive. Climate regions 1, 2, 4, and 6 displayed significant differences (p value of 0.10 or less) in yields between El Niño and La Niña years, representing 55-70 % of Missouri soybean and corn productivity, respectively. Final results give the opportunity to produce seasonal predictions of corn and soybean yields, specific to each climate region in Missouri, based on the combination of ENSO and PDO phases.

Estimation of regional material yield from coastal landslides based on historical digital terrain modelling

USGS Publications Warehouse

Hapke, C.J.

2005-01-01

High-resolution historical (1942) and recent (1994) digital terrain models were derived from aerial photographs along the Big Sur coastline in central California to measure the long-term volume of material that enters the nearshore environment. During the 52-year measurement time period, an average of 21 000 ?? 3100 m3 km-1 a-1 of material was eroded from nine study sections distributed along the coast, with a low yield of 1000 ?? 240 m3 km-1 a-1 and a high of 46 700 ?? 7300 m3 km-1 a-1. The results compare well with known volumes from several deep-seated landslides in the area and suggest that the processes by which material is delivered to the coast are episodic in nature. In addition, a number of parameters are investigated to determine what influences the substantial variation in yield along the coast. It is found that the magnitude of regional coastal landslide sediment yield is primarily related to the physical strength of the slope-forming material. Coastal Highway 1 runs along the lower portion of the slope along this stretch of coastline, and winter storms frequently damage the highway. The California Department of Transportation is responsible for maintaining this scenic highway while minimizing the impacts to the coastal ecosystems that are part of the Monterey Bay National Marine Sanctuary. This study provides environmental managers with critical background data on the volumes of material that historically enter the nearshore from landslides, as well as demonstrating the application of deriving historical digital terrain data to model landscape evolution. Published in 2005 by John Wiley & Sons, Ltd.

Mapping the natural variation in whole bone stiffness and strength across skeletal sites.

PubMed

Schlecht, Stephen H; Bigelow, Erin M R; Jepsen, Karl J

2014-10-01

Traits of the skeletal system are coordinately adjusted to establish mechanical homeostasis in response to genetic and environmental factors. Prior work demonstrated that this 'complex adaptive' process is not perfect, revealing a two-fold difference in whole bone stiffness of the tibia across a population. Robustness (specifically, total cross-sectional area relative to length) varies widely across skeletal sites and between sexes. However, it is unknown whether the natural variation in whole bone stiffness and strength also varies across skeletal sites and between men and women. We tested the hypotheses that: 1) all major long bones of the appendicular skeleton demonstrate inherent, systemic constraints in the degree to which morphological and compositional traits can be adjusted for a given robustness; and 2) these traits covary in a predictable manner independent of body size and robustness. We assessed the functional relationships among robustness, cortical area (Ct.Ar), cortical tissue mineral density (Ct.TMD), and bone strength index (BSI) across the long bones of the upper and lower limbs of 115 adult men and women. All bones showed a significant (p<0.001) positive regression between BSI and robustness after adjusting for body size, with slender bones being 1.7-2.3 times less stiff and strong in men and 1.3-2.8 times less stiff and strong in women compared to robust bones. Our findings are the first to document the natural inter-individual variation in whole bone stiffness and strength that exist within populations and that is predictable based on skeletal robustness for all major long bones. Documenting and further understanding this natural variation in strength may be critical for differentially diagnosing and treating skeletal fragility. Copyright © 2014 Elsevier Inc. All rights reserved.

The influence of using volcanic ash and lime ash as filler on compressive strength in self compacting concrete

NASA Astrophysics Data System (ADS)

Karolina, Rahmi; Panatap Simanjuntak, Murydrischy

2018-03-01

Self Compacting Concrete (SCC) is a technology which is developing today in which concrete solidifies by itself without using vibrator. Casting conventional concrete which has a lot of reinforcement bars sometimes finds difficulty in achieving optimal solidity. The method used to solve this problem is by using SCC technology. SCC was made by using filler, volcanic ash, and lime ash as the filling materials so that the concrete became more solid and hollow space could be filled up. The variation of using these two materials was 10%, 15%, 20%, and 25% of the cementitious mass and using 1% of superplasticizer from cementitious material. The supporting testing was done by using the test when the concrete was still fluid and when it was solid. Malleable concrete was tested by using EFNARC 2002 standard in slump flow test, v-funnel test, l-shaped box test, and j-ring test to obtain filling ability and passing ability. In this malleable lime concrete test, there was the decrease, compared with normal SCC concrete without adding volcanic ash and lime ash. Testing was also done in solid concrete in compressive strength, tensile strength, and concrete absorption. The result of the testing showed that the optimum tensile strength in Variation 1, without volcanic ash and lime ash – with 1% of superplasticizer was 39.556 MPa, the optimum tensile strength in Variation 1, without volcanic ash and lime ash- with 1% of super-plasticizer was 3.563 MPa, while the value of optimum absorption which occurred in Variation 5 (25% of volcanic ash + 25% of lime ash + 50% of cement + 1% of superplasticizer) was 1.313%. This was caused by the addition of volcanic ash and lime ash which had high water absorption.

The Redshift Evolution of Rest-UV Spectroscopic Properties in Lyman-break Galaxies at z ∼ 2–4

NASA Astrophysics Data System (ADS)

Du, Xinnan; Shapley, Alice E.; Reddy, Naveen A.; Jones, Tucker; Stark, Daniel P.; Steidel, Charles C.; Strom, Allison L.; Rudie, Gwen C.; Erb, Dawn K.; Ellis, Richard S.; Pettini, Max

2018-06-01

We present the first comprehensive evolutionary analysis of the rest-frame UV spectroscopic properties of star-forming galaxies at z ∼ 2–4. We match samples at different redshifts in UV luminosity and stellar mass, and perform systematic measurements of spectral features and stellar population modeling. By creating composite spectra grouped according to Lyα equivalent width (EW) and various galaxy properties, we study the evolutionary trends among Lyα, low- and high-ionization interstellar (LIS and HIS) absorption features, and integrated galaxy properties. We also examine the redshift evolution of Lyα and LIS absorption kinematics, and fine-structure emission EWs. The connections among the strengths of Lyα, LIS lines, and dust extinction are redshift independent, as is the decoupling of the Lyα and HIS line strengths, and the bulk outflow kinematics as traced by the LIS lines. Stronger Lyα emission is observed at higher redshift at fixed UV luminosity, stellar mass, SFR, and age. Much of this variation in the average Lyα strength with redshift, and the variation in Lyα strength at fixed redshift, can be explained in terms of variations in the neutral gas covering fraction and/or dust content in the ISM and CGM. However, based on the connection between Lyα and C III] emission strengths, we additionally find evidence for variations in the intrinsic production rate of Lyα photons at the highest Lyα EWs. The challenge now is to understand the observed evolution of the neutral gas covering fraction and dust extinction within a coherent model for galaxy formation, and make robust predictions for the escape of ionizing radiation at z > 6.

Mapping the natural variation in whole bone stiffness and strength across skeletal sites

PubMed Central

Schlecht, Stephen H.; Bigelow, Erin M.R.; Jepsen, Karl J.

2016-01-01

Traits of the skeletal system are coordinately adjusted to establish mechanical homeostasis in response to genetic and environmental factors. Prior work demonstrated that this `complex adaptive' process is not perfect, revealing a two-fold difference in whole bone stiffness of the tibia across a population. Robustness (specifically, total cross-sectional area relative to length) varies widely across skeletal sites and between sexes. However, it is unknown whether the natural variation in whole bone stiffness and strength also varies across skeletal sites and between men and women. We tested the hypotheses that: 1) all major long bones of the appendicular skeleton demonstrate inherent, systemic constraints in the degree to which morphological and compositional traits can be adjusted for a given robustness; and 2) these traits covary in a predictable manner independent of body size and robustness. We assessed the functional relationships among robustness, cortical area (Ct.Ar), cortical tissue mineral density (Ct.TMD), and bone strength index (BSI) across the long bones of the upper and lower limbs of 115 adult men and women. All bones showed a significant (p < 0.001) positive regression between BSI and robustness after adjusting for body size, with slender bones being 1.7–2.3 times less stiff and strong in men and 1.3–2.8 times less stiff and strong in women compared to robust bones. Our findings are the first to document the natural inter-individual variation in whole bone stiffness and strength that exist within populations and that is predictable based on skeletal robustness for all major long bones. Documenting and further understanding this natural variation in strength may be critical for differentially diagnosing and treating skeletal fragility. PMID:24999223

Selecting Magnet Laminations Recipes Using the Meth-od of Sim-u-la-ted Annealing

NASA Astrophysics Data System (ADS)

Russell, A. D.; Baiod, R.; Brown, B. C.; Harding, D. J.; Martin, P. S.

1997-05-01

The Fermilab Main Injector project is building 344 dipoles using more than 7000 tons of steel. Budget and logistical constraints required that steel production, lamination stamping and magnet fabrication proceed in parallel. There were significant run-to-run variations in the magnetic properties of the steel (Martin, P.S., et al., Variations in the Steel Properties and the Excitation Characteristics of FMI Dipoles, this conference). The large lamination size (>0.5 m coil opening) resulted in variations of gap height due to differences in stress relief in the steel after stamping. To minimize magnet-to-magnet strength and field shape variations the laminations were shuffled based on the available magnetic and mechanical data and assigned to magnets using a computer program based on the method of simulated annealing. The lamination sets selected by the program have produced magnets which easily satisfy the design requirements. Variations of the average magnet gap are an order of magnitude smaller than the variations in lamination gaps. This paper discusses observed gap variations, the program structure and the strength uniformity results.

Acoustic Emission Characteristics of Red Sandstone Specimens Under Uniaxial Cyclic Loading and Unloading Compression

NASA Astrophysics Data System (ADS)

Meng, Qingbin; Zhang, Mingwei; Han, Lijun; Pu, Hai; Chen, Yanlong

2018-04-01

To explore the acoustic emission (AE) characteristics of rock materials during the deformation and failure process under periodic loads, a uniaxial cyclic loading and unloading compression experiment was conducted based on an MTS 815 rock mechanics test system and an AE21C acoustic emissions test system. The relationships among stress, strain, AE activity, accumulated AE activity and duration for 180 rock specimens under 36 loading and unloading rates were established. The cyclic AE evolutionary laws with rock stress-strain variation at loading and unloading stages were analyzed. The Kaiser and Felicity effects of rock AE activity were disclosed, and the impact of the significant increase in the scale of AE events on the Felicity effect was discussed. It was observed that the AE characteristics are closely related to the stress-strain properties of rock materials and that they are affected by the developmental state and degree of internal microcracks. AE events occur in either the loading or unloading stages if the strain is greater than zero. Evolutionary laws of AE activity agree with changes in rock strain. Strain deformation is accompanied by AE activity, and the density and intensity of AE events directly reflect the damage degree of the rock mass. The Kaiser effect exists in the linear elastic stage of rock material, and the Felicity effect is effective in the plastic yield and post-peak failure stages, which are divided by the elastic yield strength. This study suggests that the stress level needed to determine a significant increase in AE activity was 70% of the i + 1 peak stress. The Felicity ratio of rock specimens decreases with the growth of loading-unloading cycles. The cycle magnitude and variation of the Felicity effect, in which loading and unloading rates play a weak role, are almost consistent.

Solvent Dependency in the Quantum Efficiency of 4-[(4-Aminophenyl)-(4-imino-1-cyclohexa-2, 5- dienylidene) methyl] Aniline Hydrochloride.

PubMed

Pathrose, Bini; Nampoori, V P N; Radhakrishnan, P; Sahira, H; Mujeeb, A

2015-05-01

In the present work dual beam thermal lens technique is used for studying the solvent dependency on the quantum efficiency of a novel dye used for biomedical applications. The role of solvent in the absolute fluorescence quantum yield of 4-[(4-Aminophenyl)-(4-imino-1-cyclohexa-2, 5- dienylidene) methyl] aniline hydrochloride is studied using thermal lens technique. It is observed that the variation in solvents and its concentration results considerable variations in the fluorescence quantum yield. These variations are due to the non-radiative relaxation of the absorbed energy and because of the different solvent properties. The highest quantum yield of the dye is observed in the polar protic solvent-water.

Microstructural Design for Improving Ductility of An Initially Brittle Refractory High Entropy Alloy.

PubMed

Soni, V; Senkov, O N; Gwalani, B; Miracle, D B; Banerjee, R

2018-06-11

Typically, refractory high-entropy alloys (RHEAs), comprising a two-phase ordered B2 + BCC microstructure, exhibit extraordinarily high yield strengths, but poor ductility at room temperature, limiting their engineering application. The poor ductility is attributed to the continuous matrix being the ordered B2 phase in these alloys. This paper presents a novel approach to microstructural engineering of RHEAs to form an "inverted" BCC + B2 microstructure with discrete B2 precipitates dispersed within a continuous BCC matrix, resulting in improved room temperature compressive ductility, while maintaining high yield strength at both room and elevated temperature.

An Experimental Study on the Edgewise Compressive Failure of Paper Honeycomb Sandwich Panels with Respect to Various Aspect Ratios

NASA Astrophysics Data System (ADS)

Samad, W. A.; Warsame, A. A.; Khan, A.

2018-04-01

The present work investigates the edgewise compression failure for honeycomb paperboards. Various panels are tested under a fixed loading rate with varying aspect ratios. The influence of the varying properties aspect ratio on yield strength is recorded. The experimental results indicate that the honeycomb paperboards are subject a decrease in yield strength with an increase in aspect ratio towards more slender bodies. Buckling was not observed in any of the tested specimens. All experiments are conducted under the general framework of ASTM C364/C364M -16 with a few noted changes.

High strength W/TiNi micro-laminated composite with transformation-mediated ductility

DOE PAGES

Shao, Yang; Yu, Kaiyuan; Jiang, Daqiang; ...

2016-06-06

A laminated W/TiNi composite is fabricated by hot pressing under vacuum and subsequent forging. The W and TiNi constituents are about 250 μm and 80 μm respectively in thicknesses and their interfaces are chemically sharp with negligible intermixing. The material exhibits two yielding plateaus and excellent strength-ductility combination during compression tests. In situ X-ray technique is employed to demonstrate that the unusual yielding phenomenon is related to the reversible thermoelastic phase transformation of TiNi layers. Furthermore, such mechanisms also contribute to the damage tolerance of the materials by inhibiting crack propagation in W.

Transformation of localized necking of strain space into stress space for advanced high strength steel sheet

NASA Astrophysics Data System (ADS)

Nakwattanaset, Aeksuwat; Suranuntchai, Surasak

2018-03-01

Normally, Forming Limit Curves (FLCs) can’t explain for shear fracture better than Damage Curve, this article aims to show the experimental of Forming Limit Curve (FLC) for Advanced High Strength Steel (AHSS) sheets grade JAC780Y with the Nakazima forming test and tensile tests of different sample geometries. From these results, the Forming Limit Curve (strain space) was transformed to damage curve (stress space) between plastic strain and stress triaxiality. Therefore, Stress space transformed using by Hill-48 and von-Mises yield function. This article shows that two of these yield criterions can use in the transformation.

Data-driven reduced order models for effective yield strength and partitioning of strain in multiphase materials

NASA Astrophysics Data System (ADS)

Latypov, Marat I.; Kalidindi, Surya R.

2017-10-01

There is a critical need for the development and verification of practically useful multiscale modeling strategies for simulating the mechanical response of multiphase metallic materials with heterogeneous microstructures. In this contribution, we present data-driven reduced order models for effective yield strength and strain partitioning in such microstructures. These models are built employing the recently developed framework of Materials Knowledge Systems that employ 2-point spatial correlations (or 2-point statistics) for the quantification of the heterostructures and principal component analyses for their low-dimensional representation. The models are calibrated to a large collection of finite element (FE) results obtained for a diverse range of microstructures with various sizes, shapes, and volume fractions of the phases. The performance of the models is evaluated by comparing the predictions of yield strength and strain partitioning in two-phase materials with the corresponding predictions from a classical self-consistent model as well as results of full-field FE simulations. The reduced-order models developed in this work show an excellent combination of accuracy and computational efficiency, and therefore present an important advance towards computationally efficient microstructure-sensitive multiscale modeling frameworks.

Prediction of Precipitation Strengthening in the Commercial Mg Alloy AZ91 Using Dislocation Dynamics

DOE PAGES

Aagesen, L. K.; Miao, J.; Allison, J. E.; ...

2018-03-05

In this paper, dislocation dynamics simulations were used to predict the strengthening of a commercial magnesium alloy, AZ91, due to β-Mg 17Al 12 formed in the continuous precipitation mode. The precipitate distributions used in simulations were determined based on experimental characterization of the sizes, shapes, and number densities of the precipitates for 10-hour aging and 50-hour aging. For dislocations gliding on the basal plane, which is expected to be the dominant contributor to plastic deformation at room temperature, the critical resolved shear stress to bypass the precipitate distribution was 3.5 MPa for the 10-hour aged sample and 16.0 MPa formore » the 50-hour aged sample. The simulation results were compared to an analytical model of strengthening in this alloy, and the analytical model was found to predict critical resolved shear stresses that were approximately 30 pct lower. A model for the total yield strength was developed and compared with experiment for the 50-hour aged sample. Finally, the predicted yield strength, which included the precipitate strengthening contribution from the DD simulations, was 132.0 MPa, in good agreement with the measured yield strength of 141 MPa.« less

Ultrahigh Elastic Strain Energy Storage in Metal-Oxide-Infiltrated Patterned Hybrid Polymer Nanocomposites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dusoe, Keith J.; Ye, Xinyi; Kisslinger, Kim

Modulus of resilience, the measure of a material’s capacity to store and release elastic strain energy, is critical for realizing advanced mechanical actuation technologies in micro/nanoelectromechanical systems. In general, engineering the modulus of resilience is difficult because it requires asymmetrically increasing yield strength and Young’s modulus against their mutual scaling behavior. This task becomes further challenging if it needs to be carried out at the nanometer scale. Here, we demonstrate organic–inorganic hybrid composite nanopillars with one of the highest modulus of resilience per density by utilizing vapor-phase aluminum oxide infiltration in lithographically patterned negative photoresist SU-8. In situ nanomechanical measurementsmore » reveal a metal-like high yield strength (~500 MPa) with an unusually low, foam-like Young’s modulus (~7 GPa), a unique pairing that yields ultrahigh modulus of resilience, reaching up to ~24 MJ/m 3 as well as exceptional modulus of resilience per density of ~13.4 kJ/kg, surpassing those of most engineering materials. The hybrid polymer nanocomposite features lightweight, ultrahigh tunable modulus of resilience and versatile nanoscale lithographic patternability with potential for application as nanomechanical components which require ultrahigh mechanical resilience and strength.« less

Ultrahigh Elastic Strain Energy Storage in Metal-Oxide-Infiltrated Patterned Hybrid Polymer Nanocomposites

DOE PAGES

Dusoe, Keith J.; Ye, Xinyi; Kisslinger, Kim; ...

2017-10-19

Modulus of resilience, the measure of a material’s capacity to store and release elastic strain energy, is critical for realizing advanced mechanical actuation technologies in micro/nanoelectromechanical systems. In general, engineering the modulus of resilience is difficult because it requires asymmetrically increasing yield strength and Young’s modulus against their mutual scaling behavior. This task becomes further challenging if it needs to be carried out at the nanometer scale. Here, we demonstrate organic–inorganic hybrid composite nanopillars with one of the highest modulus of resilience per density by utilizing vapor-phase aluminum oxide infiltration in lithographically patterned negative photoresist SU-8. In situ nanomechanical measurementsmore » reveal a metal-like high yield strength (~500 MPa) with an unusually low, foam-like Young’s modulus (~7 GPa), a unique pairing that yields ultrahigh modulus of resilience, reaching up to ~24 MJ/m 3 as well as exceptional modulus of resilience per density of ~13.4 kJ/kg, surpassing those of most engineering materials. The hybrid polymer nanocomposite features lightweight, ultrahigh tunable modulus of resilience and versatile nanoscale lithographic patternability with potential for application as nanomechanical components which require ultrahigh mechanical resilience and strength.« less

Prediction of Precipitation Strengthening in the Commercial Mg Alloy AZ91 Using Dislocation Dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aagesen, L. K.; Miao, J.; Allison, J. E.

In this paper, dislocation dynamics simulations were used to predict the strengthening of a commercial magnesium alloy, AZ91, due to β-Mg 17Al 12 formed in the continuous precipitation mode. The precipitate distributions used in simulations were determined based on experimental characterization of the sizes, shapes, and number densities of the precipitates for 10-hour aging and 50-hour aging. For dislocations gliding on the basal plane, which is expected to be the dominant contributor to plastic deformation at room temperature, the critical resolved shear stress to bypass the precipitate distribution was 3.5 MPa for the 10-hour aged sample and 16.0 MPa formore » the 50-hour aged sample. The simulation results were compared to an analytical model of strengthening in this alloy, and the analytical model was found to predict critical resolved shear stresses that were approximately 30 pct lower. A model for the total yield strength was developed and compared with experiment for the 50-hour aged sample. Finally, the predicted yield strength, which included the precipitate strengthening contribution from the DD simulations, was 132.0 MPa, in good agreement with the measured yield strength of 141 MPa.« less

Prediction of Precipitation Strengthening in the Commercial Mg Alloy AZ91 Using Dislocation Dynamics

NASA Astrophysics Data System (ADS)

Aagesen, L. K.; Miao, J.; Allison, J. E.; Aubry, S.; Arsenlis, A.

2018-03-01

Dislocation dynamics simulations were used to predict the strengthening of a commercial magnesium alloy, AZ91, due to β-Mg17Al12 formed in the continuous precipitation mode. The precipitate distributions used in simulations were determined based on experimental characterization of the sizes, shapes, and number densities of the precipitates for 10-hour aging and 50-hour aging. For dislocations gliding on the basal plane, which is expected to be the dominant contributor to plastic deformation at room temperature, the critical resolved shear stress to bypass the precipitate distribution was 3.5 MPa for the 10-hour aged sample and 16.0 MPa for the 50-hour aged sample. The simulation results were compared to an analytical model of strengthening in this alloy, and the analytical model was found to predict critical resolved shear stresses that were approximately 30 pct lower. A model for the total yield strength was developed and compared with experiment for the 50-hour aged sample. The predicted yield strength, which included the precipitate strengthening contribution from the DD simulations, was 132.0 MPa, in good agreement with the measured yield strength of 141 MPa.

Optimization of physico-chemical properties of gelatin extracted from fish skin of rainbow trout (Onchorhynchus mykiss).

PubMed

Tabarestani, H Shahiri; Maghsoudlou, Y; Motamedzadegan, A; Mahoonak, A R Sadeghi

2010-08-01

Physico-chemical properties of gelatin extracted from rainbow trout (Onchorhynchus mykiss) skin were optimized using response surface methodology (RSM). Central rotatable composite design was applied to study the combined effects of NaOH concentration (0.01-0.21 N), acetic acid concentration (0.01-0.21 N) and pre-treatment time (1-3h) on yield, molecular weight distribution, gel strength, viscosity and melting point of gelatin. Regression models were developed to predict the variables. Predict values of multiple response at optimal condition were that yield=9.36%, alpha(1)/alpha(2) chain ratio=1.76, beta chain percent=32.81, gel strength=459 g, viscosity=3.2 mPa s and melting point=20.4 degrees C. The optimal condition was obtained using 0.19 N NaOH and 0.121 N acetic acid for 3h. The results showed that the concentration of H(+) during pre-treatment had significant effect on molecular weight distribution, melting point and gel strength. The concentration of OH(-) had significant effect on viscosity and for extraction yield, pretreatment time was the critical factor. (c) 2010 Elsevier Ltd. All rights reserved.

Normalized Rotational Multiple Yield Surface Framework (NRMYSF) stress-strain curve prediction method based on small strain triaxial test data on undisturbed Auckland residual clay soils

NASA Astrophysics Data System (ADS)

Noor, M. J. Md; Ibrahim, A.; Rahman, A. S. A.

2018-04-01

Small strain triaxial test measurement is considered to be significantly accurate compared to the external strain measurement using conventional method due to systematic errors normally associated with the test. Three submersible miniature linear variable differential transducer (LVDT) mounted on yokes which clamped directly onto the soil sample at equally 120° from the others. The device setup using 0.4 N resolution load cell and 16 bit AD converter was capable of consistently resolving displacement of less than 1µm and measuring axial strains ranging from less than 0.001% to 2.5%. Further analysis of small strain local measurement data was performed using new Normalized Multiple Yield Surface Framework (NRMYSF) method and compared with existing Rotational Multiple Yield Surface Framework (RMYSF) prediction method. The prediction of shear strength based on combined intrinsic curvilinear shear strength envelope using small strain triaxial test data confirmed the significant improvement and reliability of the measurement and analysis methods. Moreover, the NRMYSF method shows an excellent data prediction and significant improvement toward more reliable prediction of soil strength that can reduce the cost and time of experimental laboratory test.

Improved silicon carbide for advanced heat engines

NASA Technical Reports Server (NTRS)

Whalen, Thomas J.

1988-01-01

This is the third annual technical report for the program entitled, Improved Silicon Carbide for Advanced Heat Engines, for the period February 16, 1987 to February 15, 1988. The objective of the original program was the development of high strength, high reliability silicon carbide parts with complex shapes suitable for use in advanced heat engines. Injection molding is the forming method selected for the program because it is capable of forming complex parts adaptable for mass production on an economically sound basis. The goals of the revised program are to reach a Weibull characteristic strength of 550 MPa (80 ksi) and a Weibull modulus of 16 for bars tested in 4-point loading. Two tasks are discussed: Task 1 which involves materials and process improvements, and Task 2 which is a MOR bar matrix to improve strength and reliability. Many statistically designed experiments were completed under task 1 which improved the composition of the batches, the mixing of the powders, the sinter and anneal cycles. The best results were obtained by an attritor mixing process which yielded strengths in excess of 550 MPa (80 ksi) and an individual Weibull modulus of 16.8 for a 9-sample group. Strengths measured at 1200 and 1400 C were equal to the room temperature strength. Annealing of machined test bars significantly improved the strength. Molding yields were measured and flaw distributions were observed to follow a Poisson process. The second iteration of the Task 2 matrix experiment is described.

In-situ biogas sparging enhances the performance of an anaerobic membrane bioreactor (AnMBR) with mesh filter in low-strength wastewater treatment.

PubMed

Li, Na; Hu, Yi; Lu, Yong-Ze; Zeng, Raymond J; Sheng, Guo-Ping

2016-07-01

In the recent years, anaerobic membrane bioreactor (AnMBR) technology is being considered as a very attractive alternative for wastewater treatment due to the striking advantages such as upgraded effluent quality. However, fouling control is still a problem for the application of AnMBR. This study investigated the performance of an AnMBR using mesh filter as support material to treat low-strength wastewater via in-situ biogas sparging. It was found that mesh AnMBR exhibited high and stable chemical oxygen demand (COD) removal efficiencies with values of 95 ± 5 % and an average methane yield of 0.24 L CH4/g CODremoved. Variation of transmembrane pressure (TMP) during operation indicated that mesh fouling was mitigated by in-situ biogas sparging and the fouling rate was comparable to that of aerobic membrane bioreactor with mesh filter reported in previous researches. The fouling layer formed on the mesh exhibited non-uniform structure; the porosity became larger from bottom layer to top layer. Biogas sparging could not change the composition but make thinner thickness of cake layer, which might be benefit for reducing membrane fouling rate. It was also found that ultrasonic cleaning of fouled mesh was able to remove most foulants on the surface or pores. This study demonstrated that in-situ biogas sparging enhanced the performance of AnMBRs with mesh filter in low-strength wastewater treatment. Apparently, AnMBRs with mesh filter can be used as a promising and sustainable technology for wastewater treatment.

Temporal Variations in Metabolic and Autotrophic Indices for Acropora digitifera and Acropora spicifera – Implications for Monitoring Projects

PubMed Central

Hinrichs, Saskia; Patten, Nicole L.; Waite, Anya M.

2013-01-01

Coral health indices are important components of the management assessments of coral reefs, providing insight into local variation in reef condition, as well as tools for comparisons between reefs and across various time scales. Understanding how such health indices vary in space and time is critical to their successful implementation as management tools. Here we compare autotrophic and heterotrophic coral health indices, examining specifically the temporal variation driven by the local environmental variation, at three scales (diel, daily and seasonal). We compared metabolic indices (RNA/DNA ratio, protein concentration) and autotrophic indices (Chlorophyll a (Chl a), zooxanthellae density, effective quantum yield (yield) and relative electron transport rate (rETR)) for two dominant Acropora species, A. digitifera and A. spicifera at Ningaloo Reef (north-western Australia) in August 2010 (austral winter) and February 2011 (austral summer). Clear seasonal patterns were documented for metabolic indices, zooxanthellae density and rETR, while cyclic diel patterns only occurred for yield and rETR, and RNA/DNA ratio. Significant daily variation was observed for RNA/DNA ratio, Chl a concentration, yield and rETR. Results suggest that zooxanthellae density and protein concentrations are good long-term indicators of coral health whose variance is largely seasonal, while RNA/DNA ratio and rETR can be used for both long-term (seasonal) and short-term (diel) coral monitoring. Chl a can be used to describe changes between days and yield for both diel and daily variations. Correlations between health indices and light history showed that short-term changes in irradiance had the strongest impact on all health indices except zooxanthellae density for A. digitifera; for A. spicifera no correlation was observed at all. However, cumulative irradiance over the several days before sampling showed significant correlations with most health indices suggesting that a time-lag effect has to be taken into account when interpreting diel variations in coral condition. PMID:23696848

Temporal variations in metabolic and autotrophic indices for Acropora digitifera and Acropora spicifera--implications for monitoring projects.

PubMed

Hinrichs, Saskia; Patten, Nicole L; Waite, Anya M

2013-01-01

Coral health indices are important components of the management assessments of coral reefs, providing insight into local variation in reef condition, as well as tools for comparisons between reefs and across various time scales. Understanding how such health indices vary in space and time is critical to their successful implementation as management tools. Here we compare autotrophic and heterotrophic coral health indices, examining specifically the temporal variation driven by the local environmental variation, at three scales (diel, daily and seasonal). We compared metabolic indices (RNA/DNA ratio, protein concentration) and autotrophic indices (Chlorophyll a (Chl a), zooxanthellae density, effective quantum yield (yield) and relative electron transport rate (rETR)) for two dominant Acropora species, A. digitifera and A. spicifera at Ningaloo Reef (north-western Australia) in August 2010 (austral winter) and February 2011 (austral summer). Clear seasonal patterns were documented for metabolic indices, zooxanthellae density and rETR, while cyclic diel patterns only occurred for yield and rETR, and RNA/DNA ratio. Significant daily variation was observed for RNA/DNA ratio, Chl a concentration, yield and rETR. Results suggest that zooxanthellae density and protein concentrations are good long-term indicators of coral health whose variance is largely seasonal, while RNA/DNA ratio and rETR can be used for both long-term (seasonal) and short-term (diel) coral monitoring. Chl a can be used to describe changes between days and yield for both diel and daily variations. Correlations between health indices and light history showed that short-term changes in irradiance had the strongest impact on all health indices except zooxanthellae density for A. digitifera; for A. spicifera no correlation was observed at all. However, cumulative irradiance over the several days before sampling showed significant correlations with most health indices suggesting that a time-lag effect has to be taken into account when interpreting diel variations in coral condition.

Stress corrosion evaluation of HP 9Ni-4Co-0.20C steel

NASA Technical Reports Server (NTRS)

Torres, Pablo D.

1993-01-01

A stress corrosion cracking (SCC) evaluation was undertaken on HP 9Ni-4Co-0.20C steel in support of the Advanced Solid Rocket Motor (ASRM) program. This alloy was tested in plate, bar, and ring forging forms. Several heat treating procedures yielded ultimate tensile strengths ranging from 1,407 to 1,489 MPa (204 to 216 ksi). The test environments were high humidity, alternate immersion in 3.5-percent NaCl, and 5-percent salt spray. Stress levels ranged from 25 to 90 percent of the yield strengths. The majority of the tests were conducted for 90 days. Even though the specimens rusted significantly in salt spray and alternate immersion, no failures occurred. Therefore, it can be concluded that this alloy, in the forms and at the strength levels tested, is highly resistant to SCC in salt and high humidity environments.

Procedure for chromatography involving sample solvent with higher elution strength than the mobile phase.

PubMed

Patil, Nitin S; Mendhe, Rakesh B; Sankar, Ajeet A; Iyer, Harish

2008-01-11

In preparative chromatography, often the solubility of the sample in the mobile phase is limited, making the mobile phase unsuitable as a solvent for preparation of load. Generally, solvents that have high solubility for the sample also have higher elution strengths than the mobile phase. Additionally, at high loading volumes, these strong sample solvents are known to adversely affect the band profiles leading to poor chromatographic performance. Here, we show that controlling the mobile phase strength during loading and post-load elution resulted in improved band profiles when the sample solvent was stronger than the mobile phase. Such an approach improves performance in preparative chromatography by allowing either higher sample loading or higher organic content in mobile phase (without loss of yield). Alternately, the approach can be used for improvement in performance by increase in yield or product purity.

On the Yield Strength of Oceanic Lithosphere

NASA Astrophysics Data System (ADS)

Jain, Chhavi; Korenaga, Jun; Karato, Shun-ichiro

2017-10-01

The yield strength of oceanic lithosphere determines the mode of mantle convection in a terrestrial planet, and low-temperature plasticity in olivine aggregates is generally believed to govern the plastic rheology of the stiffest part of lithosphere. Because, so far, proposed flow laws for this mechanism exhibit nontrivial discrepancies, we revisit the recent high-pressure deformation data of Mei et al. (2010) with a comprehensive inversion approach based on Markov chain Monte Carlo sampling. Our inversion results indicate that the uncertainty of the relevant flow law parameters is considerably greater than previously thought. Depending on the choice of flow law parameters, the strength of oceanic lithosphere would vary substantially, carrying different implications for the origin of plate tectonics on Earth. To reduce the flow law ambiguity, we suggest that it is important to establish a theoretical basis for estimating macroscopic stress in high-pressure experiments and also to better utilize marine geophysical observations.

Mechanical Properties of Lightweight Porous Magnesium Processed Through Powder Metallurgy

NASA Astrophysics Data System (ADS)

Zou, Ning; Li, Qizhen

2018-02-01

Porous magnesium (Mg) samples with various overall porosities (28.4 ± 1.8%, 35.5 ± 2.5%, 45.4 ± 1.9%, and 62.4 ± 2.2%) were processed through powder metallurgy and characterized to study their mechanical properties. Different porosities were obtained by utilizing different mass fractions of space holder camphene. Camphene was removed by sublimation before sintering and contributed to processing porous Mg with high purity and small average pore size. The average pore size increased from 5.2 µm to 15.1 µm with increase of the porosity from 28.4 ± 1.8% to 62.4 ± 2.2%. Compressive strain-stress data showed that the strain hardening rate, yield strength, and ultimate compressive strength decreased with increase of the porosity. The theoretical yield strength of porous Mg obtained using the Gibson-Ashby model agreed with experimental data.

Two-dimensional simulation research of secondary electron emission avalanche discharge on vacuum insulator surface

NASA Astrophysics Data System (ADS)

Cai, Libing; Wang, Jianguo; Zhu, Xiangqin; Wang, Yue; Zhang, Dianhui

2015-01-01

Based on the secondary electron emission avalanche (SEEA) model, the SEEA discharge on the vacuum insulator surface is simulated by using a 2D PIC-MCC code developed by ourselves. The evolutions of the number of discharge electrons, insulator surface charge, current, and 2D particle distribution are obtained. The effects of the strength of the applied electric field, secondary electron yield coefficient, rise time of the pulse, length of the insulator on the discharge are investigated. The results show that the number of the SEEA electrons presents a quadratic dependence upon the applied field strength. The SEEA current, which is on the order of Ampere, is directly proportional to the field strength and secondary electron yield coefficient. Finally, the electron-stimulated outgassing is included in the simulation code, and a three-phase discharge curve is presented by the simulation, which agrees with the experimental data.

Long-term variation of Surface Ozone, NO2, temperature and relative humidity on crop yield over Andhra Pradesh (AP), India

NASA Astrophysics Data System (ADS)

Arunachalam, M. S.; Obili, Manjula; Srimurali, M.

2016-07-01

Long-term variation of Surface Ozone, NO2, Temperature, Relative humidity and crop yield datasets over thirteen districts of Andhra Pradesh(AP) has been studied with the help of OMI, MODIS, AIRS, ERA-Interim re-analysis and Directorate of Economics and Statistics (DES) of AP. Inter comparison of crop yield loss estimates according to exposure metrics such as AOT40 (accumulated ozone exposure over a threshold of 40) and non-linear variation of surface temperature for twenty and eighteen varieties of two major crop growing seasons namely, kharif (April-September) and rabi (October-March), respectively has been made. Study is carried to establish a new crop-yield-exposure relationship for different crop cultivars of AP. Both ozone and temperature are showing a correlation coefficient of 0.66 and 0.87 with relative humidity; and 0.72 and 0.80 with NO2. Alleviation of high surface ozone results in high food security and improves the economy thereby reduces the induced warming of the troposphere caused by ozone. Keywords: Surface Ozone, NO2, Temperature, Relative humidity, Crop yield, AOT 40.

Hydrothermal deformation of granular quartz sand

NASA Astrophysics Data System (ADS)

Karner, Stephen L.; Kronenberg, Andreas K.; Chester, Frederick M.; Chester, Judith S.; Hajash, Andrew

2008-05-01

Isotropic and triaxial compression experiments were performed on porous aggregates of St Peter quartz sand to explore the influence of temperature (to 225°C). During isotropic stressing, samples loaded at elevated temperature exhibit the same sigmoidal stress-strain curves and non-linear acoustic emission rates as have previously been observed from room temperature studies on sands, sandstones, and soils. However, results from our hydrothermal experiments show that the critical effective pressure (P*) associated with the onset of significant pore collapse and pervasive cataclastic flow is lower at increased temperature. Samples subjected to triaxial loading at elevated temperature show yield behavior resembling that observed from room temperature studies on granular rocks and soils. When considered in terms of distortional and mean stresses, the yield strength data for a given temperature define an elliptical envelope consistent with critical state and CAP models from soil mechanics. For the conditions we tested, triaxial yield data at low effective pressure are essentially temperature-insensitive whereas yield levels at high effective pressure are lowered as a function of elevated temperature. We interpret our yield data in a manner consistent with Arrhenius behavior expected for thermally assisted subcritical crack growth. Taken together, our results indicate that increased stresses and temperatures associated with subsurface burial will significantly alter the yield strength of deforming granular media in systematic and predictable ways.

Breeding progress, variation, and correlation of grain and quality traits in winter rye hybrid and population varieties and national on-farm progress in Germany over 26 years.

PubMed

Laidig, Friedrich; Piepho, Hans-Peter; Rentel, Dirk; Drobek, Thomas; Meyer, Uwe; Huesken, Alexandra

2017-05-01

Grain yield of hybrid varieties and population varieties in official German variety trials increased by 23.3 and 18.1%, respectively, over the last 26 years. On-farm gain in grain yield (18.9%) was comparable to that of population varieties in variety trials, yet at a level considerably lower than in variety trials. Rye quality is subject to large year-to-year fluctuation. Increase in grain yield and decline of protein concentration did not negatively influence quality traits. Performance progress of grain and quality traits of 78 winter rye varieties tested in official German trials to assess the value for cultivation and use (VCU) were evaluated during 1989 and 2014. We dissected progress into a genetic and a non-genetic component for hybrid and population varieties by applying mixed models, including regression components to model trends. VCU trial results were compared with grain yield and quality data from a national harvest survey (on-farm data). Yield gain for hybrid varieties was 23.3% (18.9 dt ha -1 ) and for population varieties 18.1% (13.0 dt ha -1 ) relative to 1989. On-farm yield progress of 18.9% (8.7 dt ha -1 ) was considerably lagging behind VCU trials, and mean yield levels were substantially lower than in field trials. Most of the yield progress was generated by genetic improvement. For hybrid varieties, ear density was the determining yield component, whereas for population varieties, it was thousand grain mass. Results for VCU trials showed no statistically significant gains or losses in rye quality traits. For on-farm data, we found a positive but non-significant gain in falling number and amylogram viscosity and temperature. Variation of grain and quality traits was strongly influenced by environments, whereas genotypic variation was less than 19% of total variation. Grain yield was strongly negatively associated with protein concentration, yet was weakly to moderately positively associated with quality traits. In general, our results from VCU trials and on-farm data indicated that increasing grain yield and decreasing protein concentration did not negatively affect rye quality traits.

Distal radius geometry and skeletal strength indices after peripubertal artistic gymnastics.

PubMed

Dowthwaite, J N; Scerpella, T A

2011-01-01

Development of optimal skeletal strength should decrease adult bone fragility. Nongymnasts (NON): were compared with girls exposed to gymnastics during growth (EX/GYM: ), using peripheral quantitative computed tomography (pQCT) to evaluate postmenarcheal bone geometry, density, and strength. Pre- and perimenarcheal gymnastic loading yields advantages in indices of postmenarcheal bone geometry and skeletal strength. Two prior studies using pQCT have reported bone density and size advantages in Tanner I/II gymnasts, but none describe gymnasts' bone properties later in adolescence. The current study used pQCT to evaluate whether girls exposed to gymnastics during late childhood growth and perimenarcheal growth exhibited greater indices of distal radius geometry, density, and skeletal strength. Postmenarcheal subjects underwent 4% and 33% distal radius pQCT scans, yielding: 1) vBMD and cross-sectional areas (CSA) (total bone, compartments); 2) polar strength-strain index; 3) index of structural strength in axial compression. Output was compared for EX/GYM: vs. NON: , adjusting for gynecological age and stature (maturity and body size), reporting means, standard errors, and significance. Sixteen postmenarcheal EX/GYM: (age 16.7 years; gynecological age 3.4 years) and 13 NON: (age 16.2 years; gynecological age 3.6 years) were evaluated. At both diaphysis and metaphysis, EX/GYM: exhibited greater CSA and bone strength indices than NON; EX/GYM: exhibited 79% larger intramedullary CSA than NON: (p < 0.05). EX/GYM: had significantly higher 4% trabecular vBMD; differences were not detected for 4% total vBMD and 33% cortical vBMD. Following pre-/perimenarcheal gymnastic exposure, relative to nongymnasts, postmenarcheal EX/GYM: demonstrated greater indices of distal radius geometry and skeletal strength (metaphysis and diaphysis) with greater metaphyseal trabecular vBMD; larger intramedullary cavity size was particularly striking.

Distal radius geometry and skeletal strength indices after peripubertal artistic gymnastics

PubMed Central

Scerpella, T. A.

2011-01-01

Summary Development of optimal skeletal strength should decrease adult bone fragility. Nongymnasts (NON) were compared with girls exposed to gymnastics during growth (EX/GYM), using peripheral quantitative computed tomography (pQCT) to evaluate postmenarcheal bone geometry, density, and strength. Pre- and perimenarcheal gymnastic loading yields advantages in indices of postmenarcheal bone geometry and skeletal strength. Introduction Two prior studies using pQCT have reported bone density and size advantages in Tanner I/II gymnasts, but none describe gymnasts’ bone properties later in adolescence. The current study used pQCT to evaluate whether girls exposed to gymnastics during late childhood growth and perimenarcheal growth exhibited greater indices of distal radius geometry, density, and skeletal strength. Methods Postmenarcheal subjects underwent 4% and 33% distal radius pQCT scans, yielding: 1) vBMD and cross-sectional areas (CSA) (total bone, compartments); 2) polar strength-strain index; 3) index of structural strength in axial compression. Output was compared for EX/GYM vs. NON, adjusting for gynecological age and stature (maturity and body size), reporting means, standard errors, and significance. Results Sixteen postmenarcheal EX/GYM (age 16.7 years; gynecological age 3.4 years) and 13 NON (age 16.2 years; gynecological age 3.6 years) were evaluated. At both diaphysis and metaphysis, EX/GYM exhibited greater CSA and bone strength indices than NON; EX/GYM exhibited 79% larger intramedullary CSA than NON (p<0.05). EX/GYM had significantly higher 4% trabecular vBMD; differences were not detected for 4% total vBMD and 33% cortical vBMD. Conclusions Following pre-/perimenarcheal gymnastic exposure, relative to nongymnasts, postmenarcheal EX/GYM demonstrated greater indices of distal radius geometry and skeletal strength (metaphysis and diaphysis) with greater metaphyseal trabecular vBMD; larger intramedullary cavity size was particularly striking. PMID:20419293

SPATIAL VARIATION OF THE EVOLUTION AND STRUCTURE OF THE URBAN BOUNDARY LAYER

EPA Science Inventory

The spatial variation of the nocturnal urban boundary layer structure and the time variation of the mixing height, the nocturnal inversion top and strength after sunrise are presented for urban sites located upwind, downwind, and near the center of the heat island and for upwind ...

49 CFR 195.112 - New pipe.

Code of Federal Regulations, 2013 CFR

2013-10-01

... with the following: (a) The pipe must be made of steel of the carbon, low alloy-high strength, or alloy... sets forth the chemical requirements for the pipe steel and mechanical tests for the pipe to provide... made, the specified minimum yield strength or grade, and the pipe size. The marking must be applied in...

49 CFR 195.112 - New pipe.

Code of Federal Regulations, 2012 CFR

2012-10-01

... with the following: (a) The pipe must be made of steel of the carbon, low alloy-high strength, or alloy... sets forth the chemical requirements for the pipe steel and mechanical tests for the pipe to provide... made, the specified minimum yield strength or grade, and the pipe size. The marking must be applied in...

49 CFR 195.112 - New pipe.

Code of Federal Regulations, 2014 CFR

2014-10-01

... with the following: (a) The pipe must be made of steel of the carbon, low alloy-high strength, or alloy... sets forth the chemical requirements for the pipe steel and mechanical tests for the pipe to provide... made, the specified minimum yield strength or grade, and the pipe size. The marking must be applied in...

49 CFR 195.112 - New pipe.

Code of Federal Regulations, 2011 CFR

2011-10-01

... with the following: (a) The pipe must be made of steel of the carbon, low alloy-high strength, or alloy... sets forth the chemical requirements for the pipe steel and mechanical tests for the pipe to provide... made, the specified minimum yield strength or grade, and the pipe size. The marking must be applied in...

49 CFR 195.112 - New pipe.

Code of Federal Regulations, 2010 CFR

2010-10-01

... with the following: (a) The pipe must be made of steel of the carbon, low alloy-high strength, or alloy... sets forth the chemical requirements for the pipe steel and mechanical tests for the pipe to provide... made, the specified minimum yield strength or grade, and the pipe size. The marking must be applied in...

49 CFR 238.230 - Safety appliances-new equipment.

Code of Federal Regulations, 2010 CFR

2010-10-01

... a minimum weld strength, based on yield, of three times the strength of the number of SAE grade 2, 1...; (v) The weld is designed for infinite fatigue life in the application that it will be placed; (vi... upon request. At a minimum, this record shall include the date, time, location, identification of the...

Estimating Critical Values for Strength of Alignment among Curriculum, Assessments, and Instruction

ERIC Educational Resources Information Center

Fulmer, Gavin W.

2010-01-01

School accountability decisions based on standardized tests hinge on the degree of alignment of the test with a state's standards. Yet no established criteria were available for judging strength of alignment. Previous studies of alignment among tests, standards, and teachers' instruction have yielded mixed results that are difficult to interpret…

Estimating Critical Values for Strength of Alignment among Curriculum, Assessments, and Instruction

ERIC Educational Resources Information Center

Fulmer, Gavin W.

2011-01-01

School accountability decisions based on standardized tests hinge on the degree of alignment of the test with the state's standards documents. Yet, there exist no established criteria for judging strength of alignment. Previous measures of alignment among tests, standards, and teachers' instruction have yielded mixed results that are difficult to…

Geometric constrained variational calculus. III: The second variation (Part II)

NASA Astrophysics Data System (ADS)

Massa, Enrico; Luria, Gianvittorio; Pagani, Enrico

2016-03-01

The problem of minimality for constrained variational calculus is analyzed within the class of piecewise differentiable extremaloids. A fully covariant representation of the second variation of the action functional based on a family of local gauge transformations of the original Lagrangian is proposed. The necessity of pursuing a local adaptation process, rather than the global one described in [1] is seen to depend on the value of certain scalar attributes of the extremaloid, here called the corners’ strengths. On this basis, both the necessary and the sufficient conditions for minimality are worked out. In the discussion, a crucial role is played by an analysis of the prolongability of the Jacobi fields across the corners. Eventually, in the appendix, an alternative approach to the concept of strength of a corner, more closely related to Pontryagin’s maximum principle, is presented.

Low temperature mechanical properties, fractographic and metallographic evaluation of several alloy steels

NASA Technical Reports Server (NTRS)

Montano, J. W.

1973-01-01

The mechanical properties are presented of alloy steels, 4130, 4140, 4340, 6150, and 8740. Test specimens were manufactured from approximately 1.00 inch (2.54 cm) diameter bar stock which had been heat treated to two different hardness levels. The following mechanical tests were performed at temperatures of 80 F (+26.7 C), 0 F (-17.8 C), -100 F (-73 C), and -200 F (-129 C): (1) tensile test (Ultimate, yield, modulus, elongation, and reduction of area), (2) notched tensile test, (3) charpy V-notched impact test (impact energy), and (4) double shear strength test (ultimate and yield). The test data indicate excellent tensile strength, notched/unnotched tensile ratios, ductility, impact, and shear properties at all test temperatures, except at -200 F (-129 C) where the impact strength of the higher strength group of alloy steels, 4130 (Rc-37) and 4140 (Rc-44) decreased to approximately 9 ft. lbs. (12 joules) and 6 ft. lbs. (8 joules), respectively. Chemical, metallographic, and fractographic analyses were also performed to evaluate microstructure, microhardness and the effect of decrease in temperature on the ductile to brittle failure transition.

Materials studies for magnetic fusion energy applications at low temperatures, 7

NASA Astrophysics Data System (ADS)

Reed, R. P.; Simon, N. J.

1984-05-01

Work leading toward development of strong, tough structural alloys for use in superconducting magnets of magnetic fusion power plants is reported. Low temperature studies were conducted to assess the quantitative dependence of the yield strength, density, and elastic constants of AISI 304 stainless steels upon carbon and nitrogen concentration. Tensile property measurements of developmental austenitic steels confirmed the dependence of yield strength upon temperature. Evidence is presented to show that the flow strength and austenite stability of stainless steels are not significantly affected by 8-T fields at 4 K. Instrumentation developed for low temperature testing included a computer assisted apparatus used to measure threshold fatigue. Low temperature welding research involved an investigation of the weld reinforcement effect on the weld joint strength and measurements of the 4 K fracture toughness of magnesium-chromium steel weldments and electroodes. In the area of non-metallics, a standardized test specimen was devised to aid in screening radiation-resistant composites for magnet insulation. Mechanical properties of concrete mortar and polyurethane foam at 4 K are reported.

Effect of ZnO nanoparticles to mechanical properties of thixoformed Mg-Al-Zn alloy

NASA Astrophysics Data System (ADS)

Kusharjanto; Soepriyanto, Syoni; Ardian Korda, Akhmad; Adi Dwiwanto, Supono

2018-03-01

Magnesium alloys are lightweight metallic materials with low mechanical properties. Therefore, in order to meet the requirements in various industrial sector applications such as automotive, aerospace and electronic frame, improvement strength and ductility is required. The purpose of this research is to investigate the effect of adding ZnO nanoparticles to changes in microstructure, hardness, mechanical properties regarding with yield and ultimate strength. In this research, the molten Mg-Al-Zn alloy is added ZnO nanoparticles with a various range of 0, 1; 3 and 5 wt% and then cooling in the room temperature. Futhermore, Mg-Al-Zn-ZnO is heated at a temperature of 530 °C (in the semi-solid temperature range 470 °C–595 °C or 53% solid fraction) and then thixoforming process is performed. The characterization results of the thixoforming product show that, the microstructure is globular in shape with maximum hardness value of 107.14 VHN, the yield strength of 214.87 MPa, and the ultimate tensile strength of 311.25 MPa in 5 wt% ZnO nanoparticles.

Strengthening of Aluminum Alloy 2219 by Thermo-mechanical Treatment

NASA Astrophysics Data System (ADS)

Li, Xifeng; Lei, Kun; Song, Peng; Liu, Xinqin; Zhang, Fei; Li, Jianfei; Chen, Jun

2015-10-01

Strengthening of aluminum alloy 2219 by thermo-mechanical treatment has been compared with artificial aging. Three simple deformation modes including pre-stretching, compression, and rolling have been used in thermo-mechanical treatment. The tensile strength, elongation, fracture feature, and precipitated phase have been investigated. The results show that the strengthening effect of thermo-mechanical treatment is better than the one of artificial aging. Especially, the yield strength significantly increases with a small decrease of elongation. When the specimen is pre-stretched to 8.0%, the yield strength reaches 385.0 MPa and increases by 22.2% in comparison to the one obtained in aging condition. The maximum tensile strength of 472.4 MPa is achieved with 4.0% thickness reduction by compression. The fracture morphology reveals locally ductile and brittle failure mechanism, while the coarse second-phase particles distribute on the fracture surface. The intermediate phases θ″ or θ' orthogonally precipitate in the matrix after thermo-mechanical treatment. As compared to artificial aging, the cold plastic deformation increases distribution homogeneity and the volume fraction of θ'' or θ' precipitates. These result in a better strengthening effect.

Dynamics of absence seizures

NASA Astrophysics Data System (ADS)

Deeba, Farah; Sanz-Leon, Paula; Robinson, Peter

A neural field model of the corticothalamic system is used to investigate the dynamics of absence seizures in the presence of temporally varying connection strength between the cerebral cortex and thalamus. Variation of connection strength from cortex to thalamus drives the system into seizure once a threshold is passed and a supercritical Hopf bifurcation occurs. The dynamics and spectral characteristics of the resulting seizures are explored as functions of maximum connection strength, time above threshold, and ramp rate. The results enable spectral and temporal characteristics of seizures to be related to underlying physiological variations via nonlinear dynamics and neural field theory. Notably, this analysis adds to neural field modeling of a wide variety of brain activity phenomena and measurements in recent years. Australian Research Council Grants FL1401000225 and CE140100007.

Relationship between hip and core strength and frontal plane alignment during a single leg squat.

PubMed

Stickler, Laurie; Finley, Margaret; Gulgin, Heather

2015-02-01

The purpose of this study was to examine the relationship between frontal plane kinematics of the single leg squat and strength of the trunk and hip in females. Forty healthy females participated in this study. An isometric "make" test using a dynamometer was used to assess peak force normalized to body weight for hip abduction, hip extension, hip external rotation, and a sidelying plank test. Two-dimensional software was used to analyze the frontal plane projection angle (FPPA) and pelvic angle during a single leg squat to 60°. All 4 strength factors were significantly correlated with the FPPA, ranging from r = 0.396 to r = 0.466. During multiple regression analysis, hip abduction strength was the greatest predictor of the variation in FPPA at r(2) = 0.22, p = 0.002. Thus, hip abduction strength accounted for 22% of the variation in the FPPA during the single leg squat. The only strength factor demonstrating a significant correlation with the pelvic angle was hip extension strength (r = 0.550, p < 0.001). Clinicians should consider the role of the hip abductors, hip external rotators, hip extensors and core musculature on the impact on the FPPA during a single squat, with focus on the hip abductors. Copyright © 2014 Elsevier Ltd. All rights reserved.

An investigation into the immediate effects of pelvic taping on hamstring eccentric force in an elite male sprinter - A case report.

PubMed

Macdonald, Ben

2017-11-01

Hamstring Injuries commonly cause missed training and competition time in elite sports. Injury surveillance studies have demonstrated high injury and re-injury rates, which have not improved across sports despite screening and prevention programmes being commonplace. The most commonly suggested intervention for hamstring prevention and rehabilitation is eccentric strength assessment and training. This case study describes the management of an elite sprinter with a history of hamstring injury. A multi-variate screening process based around lumbar-pelvic dysfunction and hamstring strength assessment using the Nordbord is employed. The effect of external pelvic compression using a taping technique, on eccentric hamstring strength is evaluated. A persistent eccentric strength asymmetry of 17% was recorded as well as lumbar-pelvic control deficits. Pelvic taping appears to improve load transfer capability across the pelvis, resulting in correction of eccentric strength asymmetry. Screening strategies and interventions to prevent hamstring injury have failed to consistently improve injury rates across various sports. In this case study external pelvic compression resulted in normalising eccentric strength deficits assessed using the Nordbord. The inclusion of lumbar-pelvic motor control assessment, in relation to hamstring strength and function, as part of a multi-variate screening strategy requires further research. Copyright © 2017 Elsevier Ltd. All rights reserved.

Fabrication and characterization of bolus material using polydimethyl-siloxane

NASA Astrophysics Data System (ADS)

Wiratma Jaya, Gede; Sutanto, Heri

2018-01-01

Bolus has been used in radiotherapy to reduce tissue harm and to increase the superficial dose for skin cancer treatment. Commonly, a bolus is made of melamine in several hospitals. In this research, polydimethyl-siloxane (PDMS) material was used for bolus fabrication. The aims of the study are to investigate bolus density, percentage surface dose and its structural strength for each various composition. In bolus preparation, bolus material used composition variation between PDMS volume and catalyst volume. Composition variation were 20:1, 22:1, 24:1, 26:1, 28:1, 30:1 and 32:1. PDMS and catalyst were mixed by chemical solution deposition method. Bolus was molded by using glass cast with the size of 10 × 10 × 0.5 cm3. Bolus density was analyzed by mass per volume equation, for bolus radiation was examined by the linear accelerator using two electron energy (5 and 7 MeV) and bolus strain and tensile strength were examined by Brookfield CT 3 machine. The results of bolus density were similar with soft tissue density, while the lowest and highest density each variation are 22:1 and 28:1. In general, the use of bolus has increased the surface dose. Percentage of surface dose at 5 MeV energy is higher than 7 MeV energy. The highest percentage of surface dose at 5 MeV energy with 0.5 and 1.0 cm bolus thickness was achieved at composition of 32:1. For strain and tensile strength result, the lowest and highest strain each variation are 22:1 and 28:1, then the lowest and highest tensile strength each variation are 32:1 and 28:1. These results is important to select composition material for bolus fabrication in radiotherapy treatment.

Development of Ferrium S53 High-Strength, Corrosion-Resistant Steel

DTIC Science & Technology

2009-01-01

strength steel used in landing gear, and equivalent in corrosion resistance to the lower strength 15-5PH stainless steel used in actuators. It also...5PH stainless steel used in modern aerospace actuators. These objectives were met, with two minor exceptions: (1) the tensile yield of S53 is... stainless steel used in modern aerospace actuators. The work was initially funded as a 1-year SERDP proof-of-principle project. In this first

Application of natural seaweed modified mortar for sustainable concrete production

NASA Astrophysics Data System (ADS)

Siddique, M. N. I.; Zularisam, A. W.

2018-04-01

The effect of seaweed such as Eucheuma Cottonii (gel) and Gracilaria Sp. modified mortar on the properties of sustainable concrete was investigated. Pre-experiment and main-experiment was conducted to carry out this study. Pre-experiment was conducted to study the compressive strength of the sustainable concrete. The main-experiment studied the compressive and splitting strength. Results showed that seaweed modified mortar yielded satisfactory compressive and splitting strength of 30 MPa and 5 MPa at 28 days.

Advanced powder metallurgy aluminum alloys via rapid solidification technology, phase 2

NASA Technical Reports Server (NTRS)

Ray, Ranjan; Jha, Sunil C.

1987-01-01

Marko's rapid solidification technology was applied to processing high strength aluminum alloys. Four classes of alloys, namely, Al-Li based (class 1), 2124 type (class 2), high temperature Al-Fe-Mo (class 3), and PM X7091 type (class 4) alloy, were produced as melt-spun ribbons. The ribbons were pulverized, cold compacted, hot-degassed, and consolidated through single or double stage extrusion. The mechanical properties of all four classes of alloys were measured at room and elevated temperatures and their microstructures were investigated optically and through electron microscopy. The microstructure of class 1 Al-Li-Mg alloy was predominantly unrecrystallized due to Zr addition. Yield strengths to the order of 50 Ksi were obtained, but tensile elongation in most cases remained below 2 percent. The class 2 alloys were modified composition of 2124 aluminum alloy, through addition of 0.6 weight percent Zr and 1 weight percent Ni. Nickel addition gave rise to a fine dispersion of intermetallic particles resisting coarsening during elevated temperature exposure. The class 2 alloy showed good combination of tensile strength and ductility and retained high strength after 1000 hour exposure at 177 C. The class 3 Al-Fe-Mo alloy showed high strength and good ductility both at room and high temperatures. The yield and tensile strength of class 4 alloy exceeded those of the commercial 7075 aluminum alloy.

Artificial Neural Network-Based Early-Age Concrete Strength Monitoring Using Dynamic Response Signals.

PubMed

Kim, Junkyeong; Lee, Chaggil; Park, Seunghee

2017-06-07

Concrete is one of the most common materials used to construct a variety of civil infrastructures. However, since concrete might be susceptible to brittle fracture, it is essential to confirm the strength of concrete at the early-age stage of the curing process to prevent unexpected collapse. To address this issue, this study proposes a novel method to estimate the early-age strength of concrete, by integrating an artificial neural network algorithm with a dynamic response measurement of the concrete material. The dynamic response signals of the concrete, including both electromechanical impedances and guided ultrasonic waves, are obtained from an embedded piezoelectric sensor module. The cross-correlation coefficient of the electromechanical impedance signals and the amplitude of the guided ultrasonic wave signals are selected to quantify the variation in dynamic responses according to the strength of the concrete. Furthermore, an artificial neural network algorithm is used to verify a relationship between the variation in dynamic response signals and concrete strength. The results of an experimental study confirm that the proposed approach can be effectively applied to estimate the strength of concrete material from the early-age stage of the curing process.

Artificial Neural Network-Based Early-Age Concrete Strength Monitoring Using Dynamic Response Signals

PubMed Central

Kim, Junkyeong; Lee, Chaggil; Park, Seunghee

2017-01-01

Concrete is one of the most common materials used to construct a variety of civil infrastructures. However, since concrete might be susceptible to brittle fracture, it is essential to confirm the strength of concrete at the early-age stage of the curing process to prevent unexpected collapse. To address this issue, this study proposes a novel method to estimate the early-age strength of concrete, by integrating an artificial neural network algorithm with a dynamic response measurement of the concrete material. The dynamic response signals of the concrete, including both electromechanical impedances and guided ultrasonic waves, are obtained from an embedded piezoelectric sensor module. The cross-correlation coefficient of the electromechanical impedance signals and the amplitude of the guided ultrasonic wave signals are selected to quantify the variation in dynamic responses according to the strength of the concrete. Furthermore, an artificial neural network algorithm is used to verify a relationship between the variation in dynamic response signals and concrete strength. The results of an experimental study confirm that the proposed approach can be effectively applied to estimate the strength of concrete material from the early-age stage of the curing process. PMID:28590456

The Tension and Puncture Properties of HDPE Geomembrane under the Corrosion of Leachate.

PubMed

Xue, Qiang; Zhang, Qian; Li, Zhen-Ze; Xiao, Kai

2013-09-17

To investigate the gradual failure of high-density polyethylene (HDPE) geomembrane as a result of long-term corrosion, four dynamic corrosion tests were conducted at different temperatures and durations. By combining tension and puncture tests, we systematically studied the variation law of tension and puncture properties of the HDPE geomembrane under different corrosion conditions. Results showed that tension and puncture failure of the HDPE geomembrane was progressive, and tensile strength in the longitudinal grain direction was evidently better than that in the transverse direction. Punctures appeared shortly after puncture force reached the puncture strength. The tensile strength of geomembrane was in inversely proportional to the corrosion time, and the impact of corrosion was more obvious in the longitudinal direction than transverse direction. As corrosion time increased, puncture strength decreased and corresponding deformation increased. As with corrosion time, the increase of corrosion temperature induced the decrease of geomembrane tensile strength. Tensile and puncture strength were extremely sensitive to temperature. Overall, residual strength had a negative correlation with corrosion time or temperature. Elongation variation increased initially and then decreased with the increase in temperature. However, it did not show significant law with corrosion time. The reduction in puncture strength and the increase in puncture deformation had positive correlations with corrosion time or temperature. The geomembrane softened under corrosion condition. The conclusion may be applicable to the proper designing of the HDPE geomembrane in landfill barrier system.

A TEM quantitative evaluation of strengthening in an Mg-RE alloy reinforced with SiC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cabibbo, Marcello, E-mail: m.cabibbo@univpm.it; Spigarelli, Stefano

2011-10-15

Magnesium alloys containing rare earth elements are known to have high specific strength, good creep and corrosion resistance up to 523 K. The addition of SiC ceramic particles strengthens the metal matrix composite resulting in better wear and creep resistance while maintaining good machinability. The role of the reinforcement particles in enhancing strength can be quantitatively evaluated using transmission electron microscopy (TEM). This paper presents a quantitative evaluation of the different strengthening contributions, determined through TEM inspections, in an SiC Mg-RE composite alloy containing yttrium, neodymium, gadolinium and dysprosium. Compression tests at temperatures ranging between 290 and 573 K weremore » carried out. The microstructure strengthening mechanism was studied for all the compression conditions. Strengthening was compared to the mechanical results and the way the different contributions were combined is also discussed and justified. - Research Highlights: {yields} TEM yield strengthening terms evaluation on a Mg-RE SiC alloy. {yields} The evaluation has been extended to different compression temperature conditions. {yields} Linear and Quadratic sum has been proposed and validated. {yields} Hall-Petch was found to be the most prominent strengthening contributions.« less

A Tensile Specimen of Tailor Rolled Blanks with Equal Probability in Yield and Its Mechanical Behavior Analysis

PubMed Central

Zhang, Sijia; Liu, Xianghua; Liu, Lizhong

2018-01-01

In this paper, the microstructure and mechanical properties that distribute regulation along the rolling direction of tailor rolled blanks (TRB) were investigated. A tensile specimen with equal probability in yield (EYS) was first designed considering variation both in thickness and in material strength. The uniaxial tension test was carried out with a digital image correlation method to analyze the mechanical behaviors. The results showed that the strain distribution of EYS was homogeneous. From the results, it can be known that a new design philosophy for a TRB tensile specimen is reasonable and EYS is suitable to characterize the mechanical behavior of TRB. The true stress-strain curves of metal in different cross sections of TRB were calculated. On the basis of the true stress-strain curves, a material model of TRB was constructed and then implemented into finite element simulations of TRB uniaxial tensile tests. The strain distribution of numerical and experimental results was similar and the error between the elongation of the specimen after fracture obtained by experiment and FE ranged from 9.51% to 13.06%. Therefore, the simulation results match well with the experimental results and the material model has high accuracy and as well as practicability. PMID:29710772

Evaluation of weldments in type 21-6-9 stainless steel for compact ignition tokamak structural applications, phase 1

NASA Astrophysics Data System (ADS)

Alexander, D. J.; Goodwin, G. M.; Bloom, E. E.

1991-06-01

Primary design considerations for the Compact Ignition Tokamak toroidal field-coil cases are yield strength and toughness in the temperature range from 77 to 300 K. Type 21-6-9 stainless steel, also still known by its original Armco Steel Company trade name Nitronic 40, is the proposed alloy for this application. It has high yield strength and usually adequate base metal toughness, but weldments in thick sections have not been adequately characterized in terms of mechanical properties or hot-cracking propensity. In this study, weldability of the alloy in heavy sections and the mechanical properties of the resultant welds were investigated including tensile yield strength and Charpy V-notch toughness at 77 K and room temperature. Weldments were made in four different base metals using seven different filler metals. None of the weldments showed any indication of hot-cracking problems. All base metals, including weldment heat-affected zones, were found to have adequate strength and impact toughness at both test temperatures. Weld metals, on the other hand, except ERNiCr-3 and ENiCrFe-3, had impact toughnesses of less than 67 J at 77 K. Inconel 82 had an average weld metal impact toughness of over 135 J at 77 K, and although its strength at 77 K is less than that of type 21-6-9 base metal, at this point it is considered to be the first-choice filler metal. Phase 2 of this program will concentrate on composition refinement and process/procedure optimization for the generic ERNiCr-3 composition and will generate a design data base for base and weld metal, including tensile, fracture toughness, and crack growth rate data.

The fracture strength by a torsion test at the implant-abutment interface.

PubMed

Watanabe, Fumihiko; Hiroyasu, Kazuhiko; Ueda, Kazuhiko

2015-12-01

Fractured connections between implants and implant abutments or abutment screws are frequently encountered in a clinical setting. The purpose of this study was to investigate fracture strength using a torsion test at the interface between the implant and the abutment. Thirty screw-type implant with diameters of 3.3, 3.8, 4.3, 5.0, and 6.0 mm were submitted to a torsion test. Implants of each size were connected to abutments with abutment screws tightened to 20 N · cm. Mechanical stress was applied with a rotational speed of 3.6 °/min until fracture occurred, and maximum torque (fracture torque) and torsional yield strength were measured. The mean values were calculated and then compared using Tukey's test. The abutments were then removed, and the implant-abutment interfaces were examined using a scanning electron microscope (SEM). No significant differences in mean fracture torque were found among 3.3, 3.8, and 4.3 mm-diameter implants, but significant differences were found between these sizes and 5.0 and 6.0 mm-diameter implants (p < 0.01). Concerning mean torsional yield strength, significant differences were found between 3.3, 3.8, and 4.3 mm-diameter and 5.0 and 6.0 mm-diameter implants (p < 0.01). Observations under the SEM showed that all the projections of the abutment corresponding to the internal notches of the implant body had been destroyed. Smaller diameter implants demonstrated lower fracture torque and torsional yield strength than implants with larger diameters. In internal tube-in-tube connections, three abutment projections corresponding to rotation-prevention notches were destroyed in each implant.

Macroscopic anisotropic bone material properties in children with severe osteogenesis imperfecta.

PubMed

Albert, Carolyne; Jameson, John; Tarima, Sergey; Smith, Peter; Harris, Gerald

2017-11-07

Children with severe osteogenesis imperfecta (OI) typically experience numerous fractures and progressive skeletal deformities over their lifetime. Recent studies proposed finite element models to assess fracture risk and guide clinicians in determining appropriate intervention in children with OI, but lack of appropriate material property inputs remains a challenge. This study aimed to characterize macroscopic anisotropic cortical bone material properties and investigate relationships with bone density measures in children with severe OI. Specimens were obtained from tibial or femoral shafts of nine children with severe OI and five controls. The specimens were cut into beams, characterized in bending, and imaged by synchrotron radiation X-ray micro-computed tomography. Longitudinal modulus of elasticity, yield strength, and bending strength were 32-65% lower in the OI group (p<0.001). Yield strain did not differ between groups (p≥0.197). In both groups, modulus and strength were lower in the transverse direction (p≤0.009), but anisotropy was less pronounced in the OI group. Intracortical vascular porosity was almost six times higher in the OI group (p<0.001), but no differences were observed in osteocyte lacunar porosity between the groups (p=0.086). Volumetric bone mineral density was lower in the OI group (p<0.001), but volumetric tissue mineral density was not (p=0.770). Longitudinal OI bone modulus and strength were correlated with volumetric bone mineral density (p≤0.024) but not volumetric tissue mineral density (p≥0.099). Results indicate that cortical bone in children with severe OI yields at the same strain as normal bone, and that their decreased bone material strength is associated with reduced volumetric bone mineral density. These results will enable the advancement of fracture risk assessment capability in children with severe OI. Copyright © 2017 Elsevier Ltd. All rights reserved.

Microstructure evolution and mechanical properties of nano-SiCp/AZ91 composite processed by extrusion and equal channel angular pressing (ECAP)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qiao, X.G.; Ying, T.

Nano-SiCp/AZ91 magnesium matrix composite was fabricated by stir casting. The as-cast ingots were extruded at 350 °C, then processed by equal channel angular pressing (ECAP) at various temperatures (250 °C, 300 °C and 350 °C). Grains are significantly refined after the extrusion and the ECAP. A basal fibre texture was detected by neutron diffraction after the extrusion, which inclines about 45° to the extrusion direction (ED) after the ECAP. Nano-scaled SiC particles agglomerate in the as-cast composite. After the extrusion, the agglomeration tends to form continuous or discontinuous strips along the extrusion direction. By application of the ECAP, the agglomeratedmore » SiC particles are partly dispersed and the strips formed during the extrusion tend to be thinner and broken with the increasing pass number. The yield tensile strength (YTS) and the ultimate tensile strength (UTS) of the composite are dramatically increased after the extrusion. ECAP for one pass at various temperatures further increases the strength, however, the YTS decreases with the increasing ECAP temperature and the pass number. The Orowan equations predict the maximum YTS of the composite may be up to 400 MPa providing SiC particles are homogenously distributed in the matrix. - Highlights: •Nano-scaled SiC particles were successfully added into AZ91 by stirring casting. •Agglomeration of nano-particles were improved by extrusion and ECAP. •Yield strength of the composite is 328 MPa after one pass of ECAP. •Further ECAP process with optimized parameters may fully disperse nano-particles. •Yield strength is predicted to up to 400 MPa when particles are fully dispersed.« less

Serrated Flow and Dynamic Strain Aging in Fe-Mn-C TWIP Steel

NASA Astrophysics Data System (ADS)

Lan, Peng; Zhang, Jiaquan

2018-01-01

The tensile behavior, serrated flow, and dynamic strain aging of Fe-(20 to 24)Mn-(0.4 to 0.6)C twinning-induced plasticity (TWIP) steel have been investigated. A mathematical approach to analyze the DSA and PLC band parameters has been developed. For Fe-(20 to 24)Mn-(0.4 to 0.6)C TWIP steel with a theoretical ordering index (TOI) between 0.1 and 0.3, DSA can occur at the very beginning of plastic deformation and provide serrations during work hardening, while for TOI less than 0.1 the occurrence of DSA is delayed and twinning-dominant work hardening remains relatively smooth. The critical strain for the onset of DSA and PLC bands in Fe-Mn-C TWIP steels decreases as C content increases, while the numbers of serrations and bands increase. As Mn content increases, the critical strain for DSA and PLC band varies irregularly, but the numbers of serrations and bands increase. For Fe-(20 to 24)Mn-(0.4 to 0.6)C TWIP steel with grain size of about 10 to 20 μm, the twinning-induced work hardening rate is about 2.5 to 3.0 GPa, while the DSA-dominant hardening rate is about 2.0 GPa on average. With increasing engineering strain from 0.01 to 0.55 at an applied strain rate of 0.001s-1, the cycle time for PLC bands in Fe-Mn-C TWIP steel increases from 6.5 to 162 seconds, while the band velocity decreases from 4.5 to 0.5 mm s-1, and the band strain increases from 0.005 to 0.08. Increasing applied strain rate leads to a linear increase of band velocity despite composition differences. In addition, the influence of the Mn and C content on the tensile properties of Fe-Mn-C TWIP steel has been also studied. As C content increases, the yield strength and tensile strength of Fe-Mn-C TWIP steel increase, but the total elongation variation against C content is dependent on Mn content. As Mn content increases, the yield strength and tensile strength decrease, while the total elongation increases, despite C content. Taking both tensile properties and serrated flow behavior into consideration, Fe-22Mn-0.4C TWIP steel shows excellent mechanical performance with a high product of tensile strength and total elongation and a slightly serrated stress-strain response. To suppress the negative effect of DSA in Fe-Mn-C TWIP steels on the stability of tensile behavior, a TOI lower than 0.1 is strongly suggested.

Photosensitized electron transfer processes in SiO2 colloids and sodium lauryl sulfate micellar systems: Correlation of quantum yields with interfacial surface potentials

PubMed Central

Laane, Colja; Willner, Itamar; Otvos, John W.; Calvin, Melvin

1981-01-01

The effectiveness of negatively charged colloidal SiO2 particles in controlling photosensitized electron transfer reactions has been studied and compared with that of the negatively charged sodium lauryl sulfate (NaLauSO4) micellar system. In particular, the photosensitized reduction of the zwitterionic electron acceptor propylviologen sulfonate (PVS0) with tris(2,2′-bipyridinium)ruthenium(II) [Ru(bipy)32+] as the sensitizer and triethanolamine as the electron donor is found to have a quantum yield of 0.033 for formation of the radical anion (PVS[unk]) in the SiO2 colloid compared with 0.005 in the homogeneous system and 0.0086 in a NaLauSO4 micellar solution. The higher quantum yields obtained with the SiO2 colloidal system are attributed to substantial stabilization against back reaction of the intermediate photoproducts—i.e., Ru(bipy)33+ and PVS[unk]—by electrostatic repulsion of the reduced electron acceptor from the negatively charged particle surface. The binding properties of the SiO2 particles and NaLauSO4 micelles were investigated by flow dialysis. The results show that the sensitizer binds to both interfaces and that the SiO2 interface is characterized by a much higher surface potential than the micellar interface (≈-170 mV vs. -85 mV). The effect of ionic strength on the surface potential was estimated from the Gouy-Chapman theory, and the measured quantum yields of photosensitized electron transfer were correlated with surface potential at different ionic strengths. This correlation shows that the quantum yield is not affected by surface potentials smaller than ≈-40 mV. At larger potentials, the quantum yield increases rapidly. The quantum yield obtained in the micellar system at different strengths fits nicely on the correlation curve for the colloid SiO2 system. These results indicate that the surface potential is the dominant factor in the quantum yield improvement for PVS0 reduction. PMID:16593095

Effects of Molybdenum and Vanadium Addition on Tensile and Charpy Impact Properties of API X70 Linepipe Steels

NASA Astrophysics Data System (ADS)

Kim, Young Min; Shin, Sang Yong; Lee, Hakcheol; Hwang, Byoungchul; Lee, Sunghak; Kim, Nack J.

2007-08-01

This study is concerned with the effects of V and Mo addition on tensile and Charpy impact properties of API X70 linepipe steels. Twelve kinds of steel specimens were produced by varying V and Mo additions and rolling conditions. The addition of V and Mo promoted the formation of acicular ferrite (AF), banitic ferrite (BF), and martensite-austenite (MA) constituents, while suppressing the formation of polygonal ferrite (PF) or pearlite (P). The tensile test results indicated that the tensile strength of the specimens rolled in the two-phase region increased with the addition of V and Mo, while the yield strength did not vary much in these specimens except the water-cooled specimens, which showed the increased yield strength with addition of Mo. The tensile strength of specimens rolled in the single-phase region followed by water cooling increased with increasing V and Mo contents. The yield strength, however, did not vary much with increasing V content or with addition of Mo to the low-V alloy. In these specimens, a substantial increase in the strengths was achieved only when Mo was added to the high-V alloy. The specimens rolled in the single-phase region had higher upper-shelf energy (USE) and lower ductile-brittle transition temperature (DBTT) than the specimens rolled in the two-phase region, because their microstructures were composed of AF and fine PF. According to the electron backscatter diffraction (EBSD) analysis data, the effective grain size in AF was determined by crystallographic packets composed of a few fine grains having similar orientations. Thus, the decreased DBTT in the specimens rolled in the single-phase region could be explained by the decrease in the overall effective grain size due to the presence of AF having smaller effective grain size.

Hydrodynamics with strength: scaling-invariant solutions for elastic-plastic cavity expansion models

NASA Astrophysics Data System (ADS)

Albright, Jason; Ramsey, Scott; Baty, Roy

2017-11-01

Spherical cavity expansion (SCE) models are used to describe idealized detonation and high-velocity impact in a variety of materials. The common theme in SCE models is the presence of a pressure-driven cavity or void within a domain comprised of plastic and elastic response sub-regions. In past work, the yield criterion characterizing material strength in the plastic sub-region is usually taken for granted and assumed to take a known functional form restrictive to certain classes of materials, e.g. ductile metals or brittle geologic materials. Our objective is to systematically determine a general functional form for the yield criterion under the additional requirement that the SCE admits a similarity solution. Solutions determined under this additional requirement have immediate implications toward development of new compressible flow algorithm verification test problems. However, more importantly, these results also provide novel insight into modeling the yield criteria from the perspective of hydrodynamic scaling.

Runoff and sediment variation in the areas with high and coarse sediment yield of the middle Yellow River

NASA Astrophysics Data System (ADS)

Zhang, Pan; Yao, Wenyi; Xiao, Peiqing; Sun, Weiying

2018-02-01

Massive water and soil conservation works (WSCW) have been conducted in the areas with high and coarse sediment yield of the middle Yellow River since 1982. With the impending effects of climate change, it is necessary to reconsider the effects of WSCW on runoff and sediment variation at decadal and regional scales. Using long-term official and synthesized data, the WSCW impacts on reducing water and soil loss were studied in Sanchuanhe River watershed. Results showed that the sediment and runoff generated from this area showed a decreasing trend in the past 50 years. A great progress has been achieved in erosion control since the 1970s. After the 4 soil and water conservation harnessing stages during the period from 1970 to 2006, the sediment and runoff yield showed decreases with the extension of harnessing. The results revealed that human activities exerted the largest effects on the sediment reduction and explained 66.6% of the variation in the specific sediment yield. The contribution of rainfall variation to runoff reduction was as large as human activities. A great benefit have been obtained in water and soil loss control in this area.

Persistent fluctuations in stride intervals under fractal auditory stimulation.

PubMed

Marmelat, Vivien; Torre, Kjerstin; Beek, Peter J; Daffertshofer, Andreas

2014-01-01

Stride sequences of healthy gait are characterized by persistent long-range correlations, which become anti-persistent in the presence of an isochronous metronome. The latter phenomenon is of particular interest because auditory cueing is generally considered to reduce stride variability and may hence be beneficial for stabilizing gait. Complex systems tend to match their correlation structure when synchronizing. In gait training, can one capitalize on this tendency by using a fractal metronome rather than an isochronous one? We examined whether auditory cues with fractal variations in inter-beat intervals yield similar fractal inter-stride interval variability as isochronous auditory cueing in two complementary experiments. In Experiment 1, participants walked on a treadmill while being paced by either an isochronous or a fractal metronome with different variation strengths between beats in order to test whether participants managed to synchronize with a fractal metronome and to determine the necessary amount of variability for participants to switch from anti-persistent to persistent inter-stride intervals. Participants did synchronize with the metronome despite its fractal randomness. The corresponding coefficient of variation of inter-beat intervals was fixed in Experiment 2, in which participants walked on a treadmill while being paced by non-isochronous metronomes with different scaling exponents. As expected, inter-stride intervals showed persistent correlations similar to self-paced walking only when cueing contained persistent correlations. Our results open up a new window to optimize rhythmic auditory cueing for gait stabilization by integrating fractal fluctuations in the inter-beat intervals.

Persistent Fluctuations in Stride Intervals under Fractal Auditory Stimulation

PubMed Central

Marmelat, Vivien; Torre, Kjerstin; Beek, Peter J.; Daffertshofer, Andreas

2014-01-01

Stride sequences of healthy gait are characterized by persistent long-range correlations, which become anti-persistent in the presence of an isochronous metronome. The latter phenomenon is of particular interest because auditory cueing is generally considered to reduce stride variability and may hence be beneficial for stabilizing gait. Complex systems tend to match their correlation structure when synchronizing. In gait training, can one capitalize on this tendency by using a fractal metronome rather than an isochronous one? We examined whether auditory cues with fractal variations in inter-beat intervals yield similar fractal inter-stride interval variability as isochronous auditory cueing in two complementary experiments. In Experiment 1, participants walked on a treadmill while being paced by either an isochronous or a fractal metronome with different variation strengths between beats in order to test whether participants managed to synchronize with a fractal metronome and to determine the necessary amount of variability for participants to switch from anti-persistent to persistent inter-stride intervals. Participants did synchronize with the metronome despite its fractal randomness. The corresponding coefficient of variation of inter-beat intervals was fixed in Experiment 2, in which participants walked on a treadmill while being paced by non-isochronous metronomes with different scaling exponents. As expected, inter-stride intervals showed persistent correlations similar to self-paced walking only when cueing contained persistent correlations. Our results open up a new window to optimize rhythmic auditory cueing for gait stabilization by integrating fractal fluctuations in the inter-beat intervals. PMID:24651455

Microstructure and Mechanical Properties in Hot-Rolled Extra High-Yield-Strength Steel Plates for Offshore Structure and Shipbuilding

NASA Astrophysics Data System (ADS)

Liu, Dongsheng; Li, Qingliang; Emi, Toshihiko

2011-05-01

Key parameters for a thermomechanically controlled processing and accelerated cooling process (TMCP-AcC) were determined for integrated mass production to produce extra high-yield-strength microalloyed low carbon SiMnCrNiCu steel plates for offshore structure and bulk shipbuilding. Confocal scanning microscopy was used to make in-situ observations on the austenite grain growth during reheating. A Gleeble 3800 thermomechanical simulator was employed to investigate the flow stress behavior, static recrystallization (SRX) of austenite, and decomposition behavior of the TMCP conditioned austenite during continuous cooling. The Kocks-Mecking model was employed to describe the constitutive behavior, while the Johnson-Mehl-Avrami-Kolmogorov (JMAK) approach was used to predict the SRX kinetics. The effects of hot rolling schedule and AcC on microstructure and properties were investigated by test-scale rolling trials. The bridging between the laboratory observations and the process parameter determination to optimize the mass production was made by integrated industrial production trials on a set of a 5-m heavy plate mill equipped with an accelerated cooling system. Successful production of 60- and 50-mm-thick plates with yield strength in excess of 460 MPa and excellent toughness at low temperature (213 K (-60 °C)) in the parent metal and the simulated coarse-grained heat affected zone (CGHAZ) provides a useful integrated database for developing advanced high-strength steel plates via TMCP-AcC.

Evaluation of the cyclic behavior of aircraft turbine disk alloys

NASA Technical Reports Server (NTRS)

Cowles, B. A.; Sims, D. L.; Warren, J. R.

1978-01-01

Five aircraft turbine disk alloys representing various strength and processing histories were evaluated at 650 C to determine if recent strength advances in powder metallurgy have resulted in corresponding increases in low cycle fatigue (LCF) capability. Controlled strain LCF tests and controlled load crack propagation tests were performed. Results were used for direct material comparisons and in the analysis of an advanced aircraft turbine disk, having a fixed design and operating cycle. Crack initiation lives were found to increase with increasing tensile yield strength, while resistance to fatigue crack propagation generally decreased with increasing strength.

Vibrational properties of quasi-two-dimensional colloidal glasses with varying interparticle attraction.

PubMed

Gratale, Matthew D; Ma, Xiaoguang; Davidson, Zoey S; Still, Tim; Habdas, Piotr; Yodh, A G

2016-10-01

We measure the vibrational modes and particle dynamics of quasi-two-dimensional colloidal glasses as a function of interparticle interaction strength. The interparticle attractions are controlled via a temperature-tunable depletion interaction. Specifically, the interparticle attraction energy is increased gradually from a very small value (nearly hard-sphere) to moderate strength (∼4k_{B}T), and the variation of colloidal particle dynamics and vibrations are concurrently probed. The particle dynamics slow monotonically with increasing attraction strength, and the particle motions saturate for strengths greater than ∼2k_{B}T, i.e., as the system evolves from a nearly repulsive glass to an attractive glass. The shape of the phonon density of states is revealed to change with increasing attraction strength, and the number of low-frequency modes exhibits a crossover for glasses with weak compared to strong interparticle attraction at a threshold of ∼2k_{B}T. This variation in the properties of the low-frequency vibrational modes suggests a new means for distinguishing between repulsive and attractive glass states.

Spatial variability effects on precision and power of forage yield estimation

USDA-ARS?s Scientific Manuscript database

Spatial analyses of yield trials are important, as they adjust cultivar means for spatial variation and improve the statistical precision of yield estimation. While the relative efficiency of spatial analysis has been frequently reported in several yield trials, its application on long-term forage y...

Elevated temperature mechanical properties of line pipe steels

NASA Astrophysics Data System (ADS)

Jacobs, Taylor Roth

The effects of test temperature on the tensile properties of four line pipe steels were evaluated. The four materials include a ferrite-pearlite line pipe steel with a yield strength specification of 359 MPa (52 ksi) and three 485 MPa (70 ksi) yield strength acicular ferrite line pipe steels. Deformation behavior, ductility, strength, strain hardening rate, strain rate sensitivity, and fracture behavior were characterized at room temperature and in the temperature range of 200--350 °C, the potential operating range for steels used in oil production by the steam assisted gravity drainage process. Elevated temperature tensile testing was conducted on commercially produced as-received plates at engineering strain rates of 1.67 x 10 -4, 8.33 x 10-4, and 1.67 x 10-3 s-1. The acicular ferrite (X70) line pipe steels were also tested at elevated temperatures after aging at 200, 275, and 350 °C for 100 h under a tensile load of 419 MPa. The presence of serrated yielding depended on temperature and strain rate, and the upper bound of the temperature range where serrated yielding was observed was independent of microstructure between the ferrite-pearlite (X52) steel and the X70 steels. Serrated yielding was observed at intermediate temperatures and continuous plastic deformation was observed at room temperature and high temperatures. All steels exhibited a minimum in ductility as a function of temperature at testing conditions where serrated yielding was observed. At the higher temperatures (>275 °C) the X52 steel exhibited an increase in ductility with an increase in temperature and the X70 steels exhibited a maximum in ductility as a function of temperature. All steels exhibited a maximum in flow strength and average strain hardening rate as a function of temperature. The X52 steel exhibited maxima in flow strength and average strain hardening rate at lower temperatures than observed for the X70 steels. For all steels, the temperature where the maximum in both flow strength and strain hardening occurred increased with increasing strain rate. Strain rate sensitivities were measured using flow stress data from multiple tensile tests and strain rate jump tests on single tensile samples. In flow stress strain rate sensitivity measurements, a transition from negative to positive strain rate sensitivity was observed in the X52 steel at approximately 275--300 °C, and negative strain rate sensitivity was observed at all elevated temperature testing conditions in the X70 steels. In jump test strain rate sensitivity measurements, all four steels exhibited a transition from negative to positive strain rate sensitivity at approximately 250--275 °C. Anisotropic deformation in the X70 steels was observed by measuring the geometry of the fracture surfaces of the tensile samples. The degree of anisotropy changed as a function of temperature and minima in the degree of anisotropy was observed at approximately 300 °C for all three X70 steels. DSA was verified as an active strengthening mechanism at elevated temperatures for all line pipe steels tested resulting in serrated yielding, a minimum in ductility as a function of temperature, a maximum in flow strength as a function of temperature, a maximum in average strain hardening rate as a function of temperature, and negative strain rate sensitivities. Mechanical properties of the X70 steels exhibited different functionality with respect to temperature compared to the X52 steels at temperatures greater than 250 ºC. Changes in the acicular ferrite microstructure during deformation such as precipitate coarsening, dynamic precipitation, tempering of martensite in martensite-austenite islands, or transformation of retained austenite could account for differences in tensile property functionality between the X52 and X70 steels. Long term aging under load (LTA) testing of the X70 steels resulted in increased yield strength compared to standard elevated temperature tensile tests at all temperatures as a result of static strain aging. LTA specimen ultimate tensile strengths (UTS) increased slightly at 200 °C, were comparable at 275 °C, and decreased significantly at 350 °C when compared to as-received (standard) tests at 350 °C. Observed reductions in UTS were a result of decreased strain hardening in the LTA specimens compared to standard tensile specimens. Ideal elevated temperature operating conditions (based on tensile properties) for the X70 line pipe steels in the temperature range relevant to the steam assisted gravity drainage process are around 275--325 °C at the strain rates tested. In the temperature range of 275--325 °C the X70 steels exhibited continuous plastic deformation, a maximum in ductility, a maximum in flow stress, improved strain hardening compared to intermediate temperatures, reduced anisotropic deformation, and after extended use at elevated temperatures, yield strength increases with little change in UTS.

A Study of Poisson's Ratio in the Yield Region

NASA Technical Reports Server (NTRS)

Gerard, George; Wildhorn, Sorrel

1952-01-01

In the yield region of the stress-strain curve the variation in Poisson's ratio from the elastic to the plastic value is most pronounced. This variation was studied experimentally by a systematic series of tests on several aluminum alloys. The tests were conducted under simple tensile and compressive loading along three orthogonal axes. A theoretical variation of Poisson's ratio for an orthotropic solid was obtained from dilatational considerations. The assumptions used in deriving the theory were examined by use of the test data and were found to be in reasonable agreement with experimental evidence.

Performance of Underwater Weldments

DTIC Science & Technology

1990-09-05

gas or cathodic overprotection remains to be investigation. Subcritical crack propagation from corrosion fatigue must be considered. Crack propagation...toughness = .83 c. There is no redundancy so 1.8 times maximum stress or 1.0 times yield stress. Since the yield stress of the parent plate is being used...on the stress is required even though the stress will now be below yield strength in the parent plate. Since K is directly proportional to the stress

Microstructure and Mechanical Properties of Fiber-Laser-Welded and Diode-Laser-Welded AZ31 Magnesium Alloy

NASA Astrophysics Data System (ADS)

Chowdhury, S. M.; Chen, D. L.; Bhole, S. D.; Powidajko, E.; Weckman, D. C.; Zhou, Y.

2011-07-01

The microstructures, tensile properties, strain hardening, and fatigue strength of fiber-laser-welded (FLW) and diode-laser-welded (DLW) AZ31B-H24 magnesium alloys were studied. Columnar dendrites near the fusion zone (FZ) boundary and equiaxed dendrites at the center of FZ, with divorced eutectic β-Mg17Al12 particles, were observed. The FLW joints had smaller dendrite cell sizes with a narrower FZ than the DLW joints. The heat-affected zone consisted of recrystallized grains. Although the DLW joints fractured at the center of FZ and exhibited lower yield strength (YS), ultimate tensile strength (UTS), and fatigue strength, the FLW joints failed at the fusion boundary and displayed only moderate reduction in the YS, UTS, and fatigue strength with a joint efficiency of ~91 pct. After welding, the strain rate sensitivity basically vanished, and the DLW joints exhibited higher strain-hardening capacity. Stage III hardening occurred after yielding in both base metal (BM) and welded samples. Dimple-like ductile fracture characteristics appeared in the BM, whereas some cleavage-like flat facets together with dimples and river marking were observed in the welded samples. Fatigue crack initiated from the specimen surface or near-surface defects, and crack propagation was characterized by the formation of fatigue striations along with secondary cracks.

The column strength of aluminum alloy 75S-T extruded shapes

NASA Technical Reports Server (NTRS)

Holt, Marshall; Leary, J R

1946-01-01

Because the tensile strength and tensile yield strength of alloy 75S-T are appreciably higher than those of the materials used in the tests leading to the use of the straight-line column curve, it appeared advisable to establish the curve of column strength by test rather than by extrapolation of relations determined empirically in the earlier tests. The object of this investigation was to determine the curve of column strength for extruded aluminum alloy 75S-T. In addition to three extruded shapes, a rolled-and-drawn round rod was included. Specimens of various lengths covering the range of effective slenderness ratios up to about 100 were tested.

Phenotypic Stability of Zea mays Grain Yield and Its Attributing Traits under Drought Stress

PubMed Central

Ali, Fawad; Ahsan, Muhammad; Ali, Qurban; Kanwal, Naila

2017-01-01

Phenotypic stability under stress environment facilitate the fitness of genotype and opens new horizons to explore the cryptic genetic variation. Variation in tolerance to drought stress, a major grain yield constraint to global maize production, was identified, at the phenotypic and genotypic level. Here we found a prominent hybrid H9 that showed fitness over four growing seasons for grain yield under water stress conditions. Genotypic and phenotypic correlation of yield attributing traits over four seasons demonstrated that cobs per plant, 100 seed weight, number of grains rows per cob, total dry matter, cob diameter had positive association (r2 = 0.3–0.9) to grain yield. The perturbation was found for chlorophyll content as it showed moderate to strong association (P < 0.01) over four seasons, might be due to environment or genotype dependent. Highest heritability (95%) and genetic advance (79%) for grain yield was found in H9 over four consecutive crop growing seasons. Combined analysis over four seasons showed that studied variables together explained 85% of total variation in dependent structure (grain yield) obtained by Principal component analysis. This significant finding is the best example of phenotypic stability of grain yield in H9 and made it best fitted for grain yield under drought stress scenario. Detailed genetic analysis of H9 will help us to identify significant loci and alleles that made H9 the best fitted and it could serve as a potential source to generate novel transgressive levels of tolerance for drought stress in arid/semiarid regions. PMID:28878785

Phenotypic Stability of Zea mays Grain Yield and Its Attributing Traits under Drought Stress.

PubMed

Ali, Fawad; Ahsan, Muhammad; Ali, Qurban; Kanwal, Naila

2017-01-01

Phenotypic stability under stress environment facilitate the fitness of genotype and opens new horizons to explore the cryptic genetic variation. Variation in tolerance to drought stress, a major grain yield constraint to global maize production, was identified, at the phenotypic and genotypic level. Here we found a prominent hybrid H 9 that showed fitness over four growing seasons for grain yield under water stress conditions. Genotypic and phenotypic correlation of yield attributing traits over four seasons demonstrated that cobs per plant, 100 seed weight, number of grains rows per cob, total dry matter, cob diameter had positive association ( r 2 = 0.3-0.9) to grain yield. The perturbation was found for chlorophyll content as it showed moderate to strong association ( P < 0.01) over four seasons, might be due to environment or genotype dependent. Highest heritability (95%) and genetic advance (79%) for grain yield was found in H 9 over four consecutive crop growing seasons. Combined analysis over four seasons showed that studied variables together explained 85% of total variation in dependent structure (grain yield) obtained by Principal component analysis. This significant finding is the best example of phenotypic stability of grain yield in H 9 and made it best fitted for grain yield under drought stress scenario. Detailed genetic analysis of H 9 will help us to identify significant loci and alleles that made H 9 the best fitted and it could serve as a potential source to generate novel transgressive levels of tolerance for drought stress in arid/semiarid regions.

Understanding the weather signal in national crop-yield variability

NASA Astrophysics Data System (ADS)

Frieler, Katja; Schauberger, Bernhard; Arneth, Almut; Balkovič, Juraj; Chryssanthacopoulos, James; Deryng, Delphine; Elliott, Joshua; Folberth, Christian; Khabarov, Nikolay; Müller, Christoph; Olin, Stefan; Pugh, Thomas A. M.; Schaphoff, Sibyll; Schewe, Jacob; Schmid, Erwin; Warszawski, Lila; Levermann, Anders

2017-06-01

Year-to-year variations in crop yields can have major impacts on the livelihoods of subsistence farmers and may trigger significant global price fluctuations, with severe consequences for people in developing countries. Fluctuations can be induced by weather conditions, management decisions, weeds, diseases, and pests. Although an explicit quantification and deeper understanding of weather-induced crop-yield variability is essential for adaptation strategies, so far it has only been addressed by empirical models. Here, we provide conservative estimates of the fraction of reported national yield variabilities that can be attributed to weather by state-of-the-art, process-based crop model simulations. We find that observed weather variations can explain more than 50% of the variability in wheat yields in Australia, Canada, Spain, Hungary, and Romania. For maize, weather sensitivities exceed 50% in seven countries, including the United States. The explained variance exceeds 50% for rice in Japan and South Korea and for soy in Argentina. Avoiding water stress by simulating yields assuming full irrigation shows that water limitation is a major driver of the observed variations in most of these countries. Identifying the mechanisms leading to crop-yield fluctuations is not only fundamental for dampening fluctuations, but is also important in the context of the debate on the attribution of loss and damage to climate change. Since process-based crop models not only account for weather influences on crop yields, but also provide options to represent human-management measures, they could become essential tools for differentiating these drivers, and for exploring options to reduce future yield fluctuations.

Texture-induced anisotropy and high-strain rate deformation in metals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schiferl, S.K.; Maudlin, P.J.

1990-01-01

We have used crystallographic texture calculations to model anisotropic yielding behavior for polycrystalline materials with strong preferred orientations and strong plastic anisotropy. Fitted yield surfaces were incorporated into an explicit Lagrangian finite-element code. We consider different anisotropic orientations, as well as different yield-surface forms, for Taylor cylinder impacts of hcp metals such as titanium and zirconium. Some deformed shapes are intrinsic to anisotropic response. Also, yield surface curvature, as distinct from strength anisotropy, has a strong influence on plastic flow. 13 refs., 5 figs.

Noncontact Atomic Force Microscopy: An Emerging Tool for Fundamental Catalysis Research.

PubMed

Altman, Eric I; Baykara, Mehmet Z; Schwarz, Udo D

2015-09-15

Although atomic force microscopy (AFM) was rapidly adopted as a routine surface imaging apparatus after its introduction in 1986, it has not been widely used in catalysis research. The reason is that common AFM operating modes do not provide the atomic resolution required to follow catalytic processes; rather the more complex noncontact (NC) mode is needed. Thus, scanning tunneling microscopy has been the principal tool for atomic scale catalysis research. In this Account, recent developments in NC-AFM will be presented that offer significant advantages for gaining a complete atomic level view of catalysis. The main advantage of NC-AFM is that the image contrast is due to the very short-range chemical forces that are of interest in catalysis. This motivated our development of 3D-AFM, a method that yields quantitative atomic resolution images of the potential energy surfaces that govern how molecules approach, stick, diffuse, and rebound from surfaces. A variation of 3D-AFM allows the determination of forces required to push atoms and molecules on surfaces, from which diffusion barriers and variations in adsorption strength may be obtained. Pushing molecules towards each other provides access to intermolecular interaction between reaction partners. Following reaction, NC-AFM with CO-terminated tips yields textbook images of intramolecular structure that can be used to identify reaction intermediates and products. Because NC-AFM and STM contrast mechanisms are distinct, combining the two methods can produce unique insight. It is demonstrated for surface-oxidized Cu(100) that simultaneous 3D-AFM/STM yields resolution of both the Cu and O atoms. Moreover, atomic defects in the Cu sublattice lead to variations in the reactivity of the neighboring O atoms. It is shown that NC-AFM also allows a straightforward imaging of work function variations which has been used to identify defect charge states on catalytic surfaces and to map charge transfer within an individual molecule. These advances highlight the potential for NC-AFM-based methods to become the cornerstone upon which a quantitative atomic scale view of each step of a catalytic process may be gained. Realizing this potential will rely on two breakthroughs: (1) development of robust methods for tip functionalization and (2) simplification of NC-AFM instrumentation and control schemes. Quartz force sensors may offer paths forward in both cases. They allow any material with an atomic asperity to be used as a tip, opening the door to a wide range of surface functionalization chemistry. In addition, they do not suffer from the instabilities that motivated the initial adoption of complex control strategies that are still used today.

Tempering of Mn and Mn-Si-V dual-phase steels

NASA Astrophysics Data System (ADS)

Speich, G. R.; Schwoeble, A. J.; Huffman, G. P.

1983-06-01

Changes in the yield behavior, strength, and ductility of a Mn and a Mn-Si-V d11Al-phase (ferrite-martensite) steel were investigated after tempering one hour at 200 to 600 °C. The change in yield behavior was complex in both steels with the yield strength first increasing and then decreasing as the tempering temperature was increased. This complex behavior is attributed to a combination of factors including carbon segregation to dislocations, a return of discontinuous yielding, and the relief of resid11Al stresses. In contrast, the tensile strength decreased continuously as the tempering temperature was increased in a manner that could be predicted from the change in hardness of the martensite phase using a simple composite strengthening model. The initial tensile ductility (total elongation) of the Mn-Si-V steel was much greater than that of the Mn steel. However, upon tempering up to 400 °C, the ductility of the Mn-Si-V decreased whereas that of the Mn steel increased. As a result, both steels had similar ductilities after tempering at 400 °C or higher temperatures. These results are attributed to the larger amounts of retained austenite in the Mn-Si-V steel (9 pct) compared to the Mn steel (3 pct) and its contribution to tensile ductility by transforming to martensite during plastic straining. Upon tempering at 400 °C, the retained austenite decomposes to bainite and its contribution to tensile ductility is eliminated.

Orientation influence on grain size-effects in ultrafine-grained magnesium

DOE PAGES

Fan, Haidong; Aubry, Sylvie; Arsenlis, A.; ...

2014-11-08

The mechanical behavior of ultrafine-grained magnesium was studied by discrete dislocation dynamics (DDD) simulations. Our results show basal slip yields a strong size effect, while prismatic and pyramidal slips produce a weak one. We developed a new size-strength model that considers dislocation transmission across grain boundaries. Good agreement between this model, current DDD simulations and previous experiments is observed. These results reveal that the grain size effect depends on 3 factors: Peierls stress, dislocation source strength and grain boundary strength.

Constraints on the off-shell Higgs boson signal strength in the high-mass ZZ and WW final states with the ATLAS detector

DOE PAGES

Aad, G.

2015-07-17

The measurements of the ZZ and WW final states in the mass range above the \\(2m_Z\\) and \\(2m_W\\) thresholds provide a unique opportunity to measure the off-shell coupling strength of the Higgs boson. This paper presents constraints on the off-shell Higgs boson event yields normalised to the Standard Model prediction (signal strength) in the \\(ZZ \\rightarrow 4\\ell \\), \\(ZZ\\rightarrow 2\\ell 2\

Hydrogen Induced Stress Cracking of Materials Under Cathodic Protection

NASA Astrophysics Data System (ADS)

LaCoursiere, Marissa P.

Hydrogen embrittlement of AISI 4340, InconelRTM 718, Alloy 686 and Alloy 59 was studied using slow strain rate tests of both smooth and notched cylindrical specimens. Two heat treatments of the AISI 4340 material were used as a standard for two levels of yield strength: 1479 MPa, and 1140 MPa. A subset of the 1140 MPa AISI 4340 material also underwent plasma nitriding. The InconelRTM 718 material was hardened following AMS 5663M to obtain a yield strength of 1091 MPa. The Alloy 686 material was obtained in the Grade 3 condition with a minimum yield strength of 1034 MPa. The Alloy 59 material was obtained with a cold worked condition similar to the Alloy 686 and with a minimum yield strength of 1034 MPa. Ninety-nine specimens were tested, including smooth cylindrical tensile test specimens and smooth and notched cylindrical slow strain rate tensile tests specimens. Testing included specimens that had been precharged with hydrogen in 3.5% NaCl at 50°C for 2 weeks (AISI 4340), 4 weeks (InconelRTM 718, Alloy 686, Alloy 59) and 16 weeks (InconelRTM 718, Alloy 686, Alloy 59) using a potentiostat to deliver a cathodic potential of -1100 mV vs. SCE. The strain rate over the gauge section for the smooth specimens and in the notch root for the notched specimens was 1 x 10-6 /s. It was found that the AISI 4340 was highly embrittled in simulated ocean water when compared to the nickel based superalloys. The higher strength AISI 4340 showed much more embrittlement, as expected. Testing of the AISI 4340 at both 20°C and 4°C showed that the temperature had no effect on the hydrogen embrittlement response. The InconelRTM 718 was highly embrittled when precharged, although it only showed low levels of embrittlement when unprecharged. Both the Alloy 686 and Alloy 59 showed minimal embrittlement in all conditions. Therefore, for the materials examined, the use of Alloy 686 and Alloy 59 for components in salt water environments when under a cathodic potential of -1100 mV vs. SCE is recommended.

Biomass yield and heterosis of crosses within and between European winter cultivars of turnip rape (Brassica rapa L.).

PubMed

Ofori, Atta; Schierholt, Antje; Becker, Heiko C

2012-02-01

Because of its high growth rate at low temperatures in early spring, there is renewed interest in Brassica rapa as a winter crop for biomass production in Europe. The available cultivars are not developed for this purpose however. An approach for breeding bioenergy cultivars of B. rapa could be to establish populations from two or more different cultivars with high combining ability. The objective of this study was to evaluate the heterosis for biomass yield in the European winter B. rapa genepool. The genetic variation and heterosis of the biomass parameters: dry matter content, fresh and dry biomass yields were investigated in three cultivars representing different eras of breeding by comparing full-sibs-within and full-sibs-between the cultivars. Field trials were performed at two locations in Germany in 2005-2006. Mean mid-parent heterosis was low with 2.5% in fresh and 3.0% in dry biomass yield in full-sibs-between cultivars. Mean values of individual crosses revealed a higher variation in mid-parent heterosis ranging from 14.6% to -7.5% in fresh biomass yield and from 19.7% to -12.7% in dry biomass yield. The low heterosis observed in hybrids between European winter cultivars can be explained by the low genetic variation between these cultivars as shown earlier with molecular markers. In conclusion, a B. rapa breeding program for biomass production in Europe should not only use European genetic resources, but should also utilize the much wider worldwide variation in this species.

Recruitment synchrony of yellow perch (Perca flavescens, Percidae) in the Great Lakes region, 1966–2008

USGS Publications Warehouse

Honsey, Andrew E.; Bunnell, David B.; Troy, Cary D.; Fielder, David G.; Thomas, Michael V.; Knight, Carey T.; Chong, Stephen; Hook, Tomas O.

2016-01-01

Population-level reproductive success (recruitment) of many fish populations is characterized by high inter-annual variation and related to annual variation in key environmental factors (e.g., climate). When such environmental factors are annually correlated across broad spatial scales, spatially separated populations may display recruitment synchrony (i.e., the Moran effect). We investigated inter-annual (1966–2008) variation in yellow perch (Perca flavescens, Percidae) recruitment using 16 datasets describing populations located in four of the five Laurentian Great Lakes (Erie, Huron, Michigan, and Ontario) and Lake St. Clair. We indexed relative year class strength using catch-curve residuals for each year-class across 2–4 years and compared relative year-class strength among sampling locations. Results indicate that perch recruitment is positively synchronized across the region. In addition, the spatial scale of this synchrony appears to be broader than previous estimates for both yellow perch and freshwater fish in general. To investigate potential factors influencing relative year-class strength, we related year-class strength to regional indices of annual climatic conditions (spring-summer air temperature, winter air temperature, and spring precipitation) using data from 14 weather stations across the Great Lakes region. We found that mean spring-summer temperature is significantly positively related to recruitment success among Great Lakes yellow perch populations.

Saltmarsh creek bank stability: Biostabilisation and consolidation with depth

NASA Astrophysics Data System (ADS)

Chen, Y.; Thompson, C. E. L.; Collins, M. B.

2012-03-01

The stability of cohesive sediments of a saltmarsh in Southern England was measured in the field and the laboratory using a Cohesive Strength Meter (CSM) and a shear vane apparatus. Cores and sediment samples were collected from two tidal creek banks, covered by Atriplex portulacoides (Sea Purslane) and Juncus maritimus (Sea Rush), respectively. The objectives of the study were to examine the variation of sediment stability throughout banks with cantilevers present and investigate the influence of roots and downcore consolidation on bank stability. Data on erosion threshold and shear strength were interpreted with reference to bank depth, sediment properties and biological influences. The higher average erosion threshold was from the Sea Purslane bank whilst the Sea Rush bank showed higher average vane shear strength. The vertical variation in core sediment stability was mainly affected by roots and downcore consolidation with depth. The data obtained from the bank faces revealed that vertical variations in both erosion threshold and vane shear strength were affected primarily by roots and algae. A quantitative estimate of the relative contributions of roots and downcore consolidation to bank sediment stability was undertaken using the bank stability data and sediment density data. This showed that roots contributed more to the Sea Purslane bank stability than downcore consolidation, whilst downcore consolidation has more pronounced effects on the Sea Rush bank stability.

Optimization of pre-sowing magnetic field doses through RSM in pea

NASA Astrophysics Data System (ADS)

Iqbal, M.; Ahmad, I.; Hussain, S. M.; Khera, R. A.; Bokhari, T. H.; Shehzad, M. A.

2013-09-01

Seed pre-sowing magnetic field treatment was reported to induce biochemical and physiological changes. In the present study, response surface methodology was used for deduction of optimal magnetic field doses. Improved growth and yield responses in the pea cultivar were achieved using a rotatable central composite design and multivariate data analysis. The growth parameters such as root and shoot fresh masses and lengths as well as yield were enhanced at a certain magnetic field level. The chlorophyll contents were also enhanced significantly vs. the control. The low magnetic field strength for longer duration of exposure/ high strength for shorter exposure were found to be optimal points for maximum responses in root fresh mass, chlorophyll `a' contents, and green pod yield/plant, respectively and a similar trend was observed for other measured parameters. The results indicate that the magnetic field pre-sowing seed treatment can be used practically to enhance the growth and yield in pea cultivar and response surface methodology was found an efficient experimental tool for optimization of the treatment level to obtain maximum response of interest.

Modeling the Effect of Nail Corrosion on the Lateral Strength of Joints

Treesearch

Samuel L. Zelinka; Douglas R. Rammer

2012-01-01

This article describes a theoretical method of linking fastener corrosion in wood connections to potential reduction in lateral shear strength. It builds upon published quantitative data of corrosion rates of metals in contact with treated wood for several different wood preservatives. These corrosion rates are then combined with yield theory equations to calculate a...

Advanced Cast Aluminum Alloys

DTIC Science & Technology

2009-02-01

This production route has demonstrated that aluminum alloys with yield strengths in excess of 690 MPa with good elongation (reportedly 8%) are...series of aluminum alloys have poor-to-fair general corrosion resistance and poor-to-good stress corrosion cracking resistance. Wrought 2519...aluminum alloy has good strength, good ballistic performance, good stress corrosion cracking resistance but only fair general corrosion resistance

The strength of Norwegian glued laminated beams

Treesearch

Kjell Solli; Erik Aasheim; Robert H. Falk

1992-01-01

This paper focuses on the characterization and the performance of glued laminated (glulam) timber beams manufactured from machine stress graded Norwegian spruce in comparison to developing CEN standards. Material property testing indicated that the supplied laminating timber can be represented by two CEN strength classes, C37-14E and C30-12E, with about 50% yield in...

The Cryogenic Tensile Properties of an Extruded Aluminum-Beryllium Alloy

NASA Technical Reports Server (NTRS)

Gamwell, W. R.

2002-01-01

Basic mechanical properties; i.e., ultimate tensile strength, yield strength, percent elongation, and elastic modulus, were obtained for the aluminum-beryllium alloy, AlBeMet162, at cryogenic (-195.5 C (-320 F) and -252.8 C (-423 F)) temperatures. The material evaluated was purchased to the requirements of SAE-AMS7912, "Aluminum-Beryllium Alloy, Extrusions."

Hypersonic Wind Tunnel Nozzle Survivability for T&E

DTIC Science & Technology

2007-03-01

Room-Temperature Compression Tests ..............................................................43 10. Strength of Hot-Rolled Inconel 600 (Ni-16Cr...6Fe, wt %) ...................................................45 11. Physical Properties of Inconel 600...Table 10. Strength of Hot-Rolled Inconel 600 (Ni-16Cr-6Fe, wt%) T, °C 0.2% Yield Stress (MPa) Ultimate Tensile Stress (MPa) 20 250 590 400 185 560

Quantifying the impacts of climatic trend and fluctuation on crop yields in northern China.

PubMed

Qiao, Jianmin; Yu, Deyong; Liu, Yupeng

2017-10-01

Climate change plays a critical role in crop yield variations, which has attracted a great deal of concern worldwide. However, the mechanisms of how climatic trend and fluctuations affect crop yields are not well understood and need to be further investigated. Thus, using the GIS-based Environmental Policy Integrated Climate (EPIC) model, we simulated the yields of major crops (i.e., wheat, maize, and rice) and evaluated the impacts of climatic factors on crop yields in the Agro-Pastoral Transitional Zone (APTZ) of northern China between 1980 and 2010. The partial least squares regression model was used to assess the contribution rates of climatic factors (i.e., precipitation, photosynthetically active radiation (PAR), minimum temperature (T min ), maximum temperature (T max )) to the variation of crop yields. The Breaks for Additive Season and Trend (BFAST) model was adopted to decompose the climate factors into trend and fluctuation components, and the relative contributions of climate trend and fluctuation were then evaluated. The results indicated that the contributions of climatic factors to yield variations of wheat, maize, and rice were 31.7, 37.7, and 23.1%, respectively. That is, climate change had larger impacts on maize than wheat and rice. More cultivated areas were significantly and positively correlated with precipitation than with other climatic factors due to the limited precipitation in the APTZ. Also, climatic trend component had positive impacts on crop yields in the whole region, whereas the climate fluctuation was associated mainly with the areas where the crop yields decreased. This study helps improve our understanding of the mechanisms of climate change impacts on crop yields, and provides useful scientific information for designing regional-scale strategies of adaptation to climate change.

Anisotropy of high temperature strength in precipitation-hardened nickel-base superalloy single crystals

NASA Technical Reports Server (NTRS)

Nakagawa, Y. G.; Terashima, H.; Yoshizawa, H.; Ohta, Y.; Murakami, K.

1986-01-01

The anisotropy of high temperature strength of nickel-base superalloy, Alloy 454, in service for advanced jet engine turbine blades and vanes, was investigated. Crystallographic orientation dependence of tensile yield strength, creep and creep rupture strength was found to be marked at about 760C. In comparison with other single crystal data, a larger allowance in high strength off-axial orientation from the 001 axis, and relatively poor strength at near the -111 axis were noted. From transmission electron microscopy the anisotropic characteristics of this alloy were explained in terms of available slip systems and stacking geometries of gamma-prime precipitate cuboids which are well hardened by a large tantalum content. 100 cube slip was considered to be primarily responsible for the poor strength of the -111 axis orientation replacing the conventional 111 plane slip systems.

Comparison between linear and daily undulating periodized resistance training to increase strength.

PubMed

Prestes, Jonato; Frollini, Anelena B; de Lima, Cristiane; Donatto, Felipe F; Foschini, Denis; de Cássia Marqueti, Rita; Figueira, Aylton; Fleck, Steven J

2009-12-01

To determine the most effective periodization model for strength and hypertrophy is an important step for strength and conditioning professionals. The aim of this study was to compare the effects of linear (LP) and daily undulating periodized (DUP) resistance training on body composition and maximal strength levels. Forty men aged 21.5 +/- 8.3 and with a minimum 1-year strength training experience were assigned to an LP (n = 20) or DUP group (n = 20). Subjects were tested for maximal strength in bench press, leg press 45 degrees, and arm curl (1 repetition maximum [RM]) at baseline (T1), after 8 weeks (T2), and after 12 weeks of training (T3). Increases of 18.2 and 25.08% in bench press 1 RM were observed for LP and DUP groups in T3 compared with T1, respectively (p < or = 0.05). In leg press 45 degrees , LP group exhibited an increase of 24.71% and DUP of 40.61% at T3 compared with T1. Additionally, DUP showed an increase of 12.23% at T2 compared with T1 and 25.48% at T3 compared with T2. For the arm curl exercise, LP group increased 14.15% and DUP 23.53% at T3 when compared with T1. An increase of 20% was also found at T2 when compared with T1, for DUP. Although the DUP group increased strength the most in all exercises, no statistical differences were found between groups. In conclusion, undulating periodized strength training induced higher increases in maximal strength than the linear model in strength-trained men. For maximizing strength increases, daily intensity and volume variations were more effective than weekly variations.

Dependence of the duration of geomagnetic polarity reversals on site latitude.

PubMed

Clement, Bradford M

2004-04-08

An important constraint on the processes governing the geodynamo--the flow in the outer core responsible for generating Earth's magnetic field--is the duration of geomagnetic polarity reversals; that is, how long it takes for Earth's magnetic field to reverse. It is generally accepted that Earth's magnetic field strength drops to low levels during polarity reversals, and the field direction progresses through a 180 degrees change while the field is weak. The time it takes for this process to happen, however, remains uncertain, with estimates ranging from a few thousand up to 28,000 years. Here I present an analysis of the available sediment records of the four most recent polarity reversals. These records yield an average estimate of about 7,000 years for the time it takes for the directional change to occur. The variation about this mean duration is not random, but instead varies with site latitude, with shorter durations observed at low-latitude sites, and longer durations observed at mid- to high-latitude sites. Such variation of duration with site latitude is predicted by simple geometrical reversal models, in which non-dipole fields are allowed to persist while the axial dipole decays through zero and then builds in the opposite direction, and provides a constraint on numerical dynamo models.

Response of winter and spring wheat grain yields to meteorological variation

NASA Technical Reports Server (NTRS)

Feyerherm, A. M.; Kanemasu, E. T.; Paulsen, G. M.

1977-01-01

Mathematical models which quantify the relation of wheat yield to selected weather-related variables are presented. Other sources of variation (amount of applied nitrogen, improved varieties, cultural practices) have been incorporated in the models to explain yield variation both singly and in combination with weather-related variables. Separate models were developed for fall-planted (winter) and spring-planted (spring) wheats. Meteorological variation is observed, basically, by daily measurements of minimum and maximum temperatures, precipitation, and tabled values of solar radiation at the edge of the atmosphere and daylength. Two different soil moisture budgets are suggested to compute simulated values of evapotranspiration; one uses the above-mentioned inputs, the other uses the measured temperatures and precipitation but replaces the tabled values (solar radiation and daylength) by measured solar radiation and satellite-derived multispectral scanner data to estimate leaf area index. Weather-related variables are defined by phenological stages, rather than calendar periods, to make the models more universally applicable.

A comparative assessment of the fracture toughness behavior of ferritic-martensitic steels and nanostructured ferritic alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Byun, Thak Sang; Hoelzer, David T.; Kim, Jeoung Han

The Fe-Cr alloys with ultrafine microstructures are primary candidate materials for advanced nuclear reactor components because of their excellent high temperature strength and high resistance to radiation-induced damage such as embrittlement and swelling. Mainly two types of Fe-Cr alloys have been developed for the high temperature reactor applications: the quenched and tempered ferritic-martensitic (FM) steels hardened primarily by ultrafine laths and carbonitrides and the powder metallurgy-based nanostructured ferritic alloys (NFAs) by nanograin structure and nanoclusters. This paper aims at elucidating the differences and similarities in the temperature and strength dependences of fracture toughness in the Fe-Cr alloys to provide amore » comparative assessment of their high-temperature structural performance. The K JQ versus yield stress plots confirmed that the fracture toughness was inversely proportional to yield strength. It was found, however, that the toughness data for some NFAs were outside the band of the integrated dataset at given strength level, which indicates either a significant improvement or deterioration in mechanical properties due to fundamental changes in deformation and fracture mechanisms. When compared to the behavior of NFAs, the FM steels have shown much less strength dependence and formed narrow fracture toughness data bands at a significantly lower strength region. It appeared that at high temperatures ≥600 °C the NFAs cannot retain the nanostructure advantage of high strength and high toughness either by high-temperature embrittlement or by excessive loss of strength. Finally, irradiation studies have revealed, however, that the NFAs have much stronger radiation resistance than tempered martensitic steels, such as lower radiation-induced swelling, finer helium bubble formation, lower irradiation creep rate and reduced low temperature embrittlement.« less

A comparative assessment of the fracture toughness behavior of ferritic-martensitic steels and nanostructured ferritic alloys

DOE PAGES

Byun, Thak Sang; Hoelzer, David T.; Kim, Jeoung Han; ...

2016-12-07

The Fe-Cr alloys with ultrafine microstructures are primary candidate materials for advanced nuclear reactor components because of their excellent high temperature strength and high resistance to radiation-induced damage such as embrittlement and swelling. Mainly two types of Fe-Cr alloys have been developed for the high temperature reactor applications: the quenched and tempered ferritic-martensitic (FM) steels hardened primarily by ultrafine laths and carbonitrides and the powder metallurgy-based nanostructured ferritic alloys (NFAs) by nanograin structure and nanoclusters. This paper aims at elucidating the differences and similarities in the temperature and strength dependences of fracture toughness in the Fe-Cr alloys to provide amore » comparative assessment of their high-temperature structural performance. The K JQ versus yield stress plots confirmed that the fracture toughness was inversely proportional to yield strength. It was found, however, that the toughness data for some NFAs were outside the band of the integrated dataset at given strength level, which indicates either a significant improvement or deterioration in mechanical properties due to fundamental changes in deformation and fracture mechanisms. When compared to the behavior of NFAs, the FM steels have shown much less strength dependence and formed narrow fracture toughness data bands at a significantly lower strength region. It appeared that at high temperatures ≥600 °C the NFAs cannot retain the nanostructure advantage of high strength and high toughness either by high-temperature embrittlement or by excessive loss of strength. Finally, irradiation studies have revealed, however, that the NFAs have much stronger radiation resistance than tempered martensitic steels, such as lower radiation-induced swelling, finer helium bubble formation, lower irradiation creep rate and reduced low temperature embrittlement.« less

A comparative assessment of the fracture toughness behavior of ferritic-martensitic steels and nanostructured ferritic alloys

NASA Astrophysics Data System (ADS)

Byun, Thak Sang; Hoelzer, David T.; Kim, Jeoung Han; Maloy, Stuart A.

2017-02-01

The Fe-Cr alloys with ultrafine microstructures are primary candidate materials for advanced nuclear reactor components because of their excellent high temperature strength and high resistance to radiation-induced damage such as embrittlement and swelling. Mainly two types of Fe-Cr alloys have been developed for the high temperature reactor applications: the quenched and tempered ferritic-martensitic (FM) steels hardened primarily by ultrafine laths and carbonitrides and the powder metallurgy-based nanostructured ferritic alloys (NFAs) by nanograin structure and nanoclusters. This study aims at elucidating the differences and similarities in the temperature and strength dependences of fracture toughness in the Fe-Cr alloys to provide a comparative assessment of their high-temperature structural performance. The KJQ versus yield stress plots confirmed that the fracture toughness was inversely proportional to yield strength. It was found, however, that the toughness data for some NFAs were outside the band of the integrated dataset at given strength level, which indicates either a significant improvement or deterioration in mechanical properties due to fundamental changes in deformation and fracture mechanisms. When compared to the behavior of NFAs, the FM steels have shown much less strength dependence and formed narrow fracture toughness data bands at a significantly lower strength region. It appeared that at high temperatures ≥600 °C the NFAs cannot retain the nanostructure advantage of high strength and high toughness either by high-temperature embrittlement or by excessive loss of strength. Irradiation studies have revealed, however, that the NFAs have much stronger radiation resistance than tempered martensitic steels, such as lower radiation-induced swelling, finer helium bubble formation, lower irradiation creep rate and reduced low temperature embrittlement.

Size effects in olivine control strength in low-temperature plasticity regime

NASA Astrophysics Data System (ADS)

Kumamoto, K. M.; Thom, C.; Wallis, D.; Hansen, L. N.; Armstrong, D. E. J.; Goldsby, D. L.; Warren, J. M.; Wilkinson, A. J.

2017-12-01

The strength of the lithospheric mantle during deformation by low-temperature plasticity controls a range of geological phenomena, including lithospheric-scale strain localization, the evolution of friction on deep seismogenic faults, and the flexure of tectonic plates. However, constraints on the strength of olivine in this deformation regime are difficult to obtain from conventional rock-deformation experiments, and previous results vary considerably. We demonstrate via nanoindentation that the strength of olivine in the low-temperature plasticity regime is dependent on the length-scale of the test, with experiments on smaller volumes of material exhibiting larger yield stresses. This "size effect" has previously been explained in engineering materials as a result of the role of strain gradients and associated geometrically necessary dislocations in modifying plastic behavior. The Hall-Petch effect, in which a material with a small grain size exhibits a higher strength than one with a large grain size, is thought to arise from the same mechanism. The presence of a size effect resolves discrepancies among previous experimental measurements of olivine, which were either conducted using indentation methods or were conducted on polycrystalline samples with small grain sizes. An analysis of different low-temperature plasticity flow laws extrapolated to room temperature reveals a power-law relationship between length-scale (grain size for polycrystalline deformation and contact radius for indentation tests) and yield strength. This suggests that data from samples with large inherent length scales best represent the plastic strength of the coarse-grained lithospheric mantle. Additionally, the plastic deformation of nanometer- to micrometer-sized asperities on fault surfaces may control the evolution of fault roughness due to their size-dependent strength.

Enhancement of yield strength in zirconium metal through high-pressure induced structural phase transition

NASA Astrophysics Data System (ADS)

Zhao, Yusheng; Zhang, Jianzhong

2007-11-01

We report here a high-pressure phase-transition induced strengthening in ultrapure zirconium metal. The determined yield strength shows more than sixfold abrupt increase at the transition pressure of Pc=6GPa, from σyα≈180MPa in the low-pressure phase of α-Zr to σyω≈1180MPa in the high-pressure phase of ω-Zr. The observed enhancement provides an alternate route for material strengthening and is the most significant among the known strengthening techniques for metals. Our findings support the theoretical simulations of the substantial covalent bonding and "rougher" corrugation of slip planes for dislocations in the ω-phase of zirconium.

Adhesion, friction, and deformation of ion-beam-deposited boron nitride films

NASA Technical Reports Server (NTRS)

Miyoshi, Kazuhisa; Buckley, Donald H.; Alterovitz, Samuel A.; Pouch, John J.; Liu, David C.

1987-01-01

The tribological properties and mechanical strength of boron nitride films were investigated. The BN films were predominantly amorphous and nonstoichiometric and contained small amounts of oxides and carbides. It was found that the yield pressure at full plasticity, the critical load to fracture, and the shear strength of interfacial adhesive bonds (considered as adhesion) depended on the type of metallic substrate on which the BN was deposited. The harder the substrate, the greater the critical load and the adhesion. The yield pressures of the BN film were 12 GPa for the 440C stainless steel substrate, 4.1 GPa for the 304 stainless steel substrate, and 3.3 GPa for the titanium substrate.

Adhesion, friction and deformation of ion-beam-deposited boron nitride films

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.; Alterovitz, S. A.; Pouch, J. J.; Liu, D. C.

1987-01-01

The tribological properties and mechanical strength of boron nitride films were investigated. The BN films were predominantly amorphous and nonstoichiometric and contained small amounts of oxides and carbides. It was found that the yield pressure at full plasticity, the critical load to fracture, and the shear strength of interfacial adhesive bonds (considered as adhesion) depended on the type of metallic substrate on which the BN was deposited. The harder the substrate, the greater the critical load and the adhesion. The yield pressures of the BN film were 12 GPa for the 440C stainless steel substrate, 4.1 GPa for the 304 stainless steel substrate, and 3.3 GPa for the titanium substrate.

Spatiotemporal variation in local adaptation of a specialist insect herbivore to its long-lived host plant.

PubMed

Kalske, Aino; Leimu, Roosa; Scheepens, J F; Mutikainen, Pia

2016-09-01

Local adaptation of interacting species to one another indicates geographically variable reciprocal selection. This process of adaptation is central in the organization and maintenance of genetic variation across populations. Given that the strength of selection and responses to it often vary in time and space, the strength of local adaptation should in theory vary between generations and among populations. However, such spatiotemporal variation has rarely been explicitly demonstrated in nature and local adaptation is commonly considered to be relatively static. We report persistent local adaptation of the short-lived herbivore Abrostola asclepiadis to its long-lived host plant Vincetoxicum hirundinaria over three successive generations in two studied populations and considerable temporal variation in local adaptation in six populations supporting the geographic mosaic theory. The observed variation in local adaptation among populations was best explained by geographic distance and population isolation, suggesting that gene flow reduces local adaptation. Changes in herbivore population size did not conclusively explain temporal variation in local adaptation. Our results also imply that short-term studies are likely to capture only a part of the existing variation in local adaptation. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

PHOTOMETRIC TRENDS IN THE VISIBLE SOLAR CONTINUUM AND THEIR SENSITIVITY TO THE CENTER-TO-LIMB PROFILE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peck, C. L.; Rast, M. P.

2015-08-01

Solar irradiance variations over solar rotational timescales are largely determined by the passage of magnetic structures across the visible solar disk. Variations on solar cycle timescales are thought to be similarly due to changes in surface magnetism with activity. Understanding the contribution of magnetic structures to total solar irradiance and solar spectral irradiance requires assessing their contributions as a function of disk position. Since only relative photometry is possible from the ground, the contrasts of image pixels are measured with respect to a center-to-limb intensity profile. Using nine years of full-disk red and blue continuum images from the Precision Solarmore » Photometric Telescope at the Mauna Loa Solar Observatory, we examine the sensitivity of continuum contrast measurements to the center-to-limb profile definition. Profiles which differ only by the amount of magnetic activity allowed in the pixels used to determine them yield oppositely signed solar cycle length continuum contrast trends, either agreeing with previous results and showing negative correlation with solar cycle or disagreeing and showing positive correlation with solar cycle. Changes in the center-to-limb profile shape over the solar cycle are responsible for the contradictory contrast results, and we demonstrate that the lowest contrast structures, internetwork and network, are most sensitive to these. Thus the strengths of the full-disk, internetwork, and network photometric trends depend critically on the magnetic flux density used in the quiet-Sun definition. We conclude that the contributions of low contrast magnetic structures to variations in the solar continuum output, particularly to long-term variations, are difficult, if not impossible, to determine without the use of radiometric imaging.« less