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Sample records for plastic strain energy

  1. A work-hardening and softening constitutive model for sand: modified plastic strain energy approach

    Institute of Scientific and Technical Information of China (English)

    Fangle Peng; M.S.A. Siddiquee; Shaoming Liao

    2005-01-01

    The paper describes an energy-based constitutive model for sand, which is modified based on the modified plastic strain energy approach, represented by a unique relationship between the modified plastic strain energy and a stress parameter, independent of stress history. The modified plastic strain energy approach was developed based on results from a series of drained plastic strain compression tests along various stress paths on saturated dense Toyoura sand with accurate stress and strain measurements. The proposed model is coupled with an isotropically work-hardening and softening, non-associtated, elasto-plastic material description. The constitutive model concerns the inherent and stress systeminduced cross-anisotropic elastic deformation properties of sand. It is capable of simulating the deformation characteristics of stress history and stress path, the effects of pressure level, anisotropic strength and void ratio, and the strain localization.

  2. The exponentiated Hencky-logarithmic strain energy: part III—coupling with idealized multiplicative isotropic finite strain plasticity

    Science.gov (United States)

    Neff, Patrizio; Ghiba, Ionel-Dumitrel

    2016-03-01

    We investigate an immediate application in finite strain multiplicative plasticity of the family of isotropic volumetric-isochoric decoupled strain energies F mapsto W_eH(F):= widehat{W}_eH(U) := μ/k e^{k | dev_n log {U}|^2}+κ/2 {widehat{k}} e^{widehat{k} [ tr(log U)]^2}&quad if& det F > 0, + ∞ & quad if & det F ≤ 0, based on the Hencky-logarithmic (true, natural) strain tensor {log U} . Here, {μ > 0} is the infinitesimal shear modulus, {κ=2 μ+3λ/3 > 0} is the infinitesimal bulk modulus with λ the first Lamé constant, {k,widehat{k}} are additional dimensionless material parameters, {F=nabla \\varphi} is the gradient of deformation, {U=√{F^T F}} is the right stretch tensor, and dev n {log {U} =log {U}-1/n tr(log {U})\\cdot{1}} is the deviatoric part of the strain tensor {log U} . Based on the multiplicative decomposition {F=F_e F_p} , we couple these energies with some isotropic elasto-plastic flow rules {F_p {dt}/[F_p^{-1}]in-partial χ(dev_3 Σe)} defined in the plastic distortion F p , where {partial χ} is the subdifferential of the indicator function {χ} of the convex elastic domain {E_e({Σe},1/3{σ}_{y}^2)} in the mixed-variant {Σe} -stress space, {Σe=F_e^T D_{F_e}W_iso(F_e)} , and {W_iso(F_e)} represents the isochoric part of the energy. While {W_eH} may loose ellipticity, we show that loss of ellipticity is effectively prevented by the coupling with plasticity, since the ellipticity domain of {W_eH} on the one hand and the elastic domain in {Σe} -stress space on the other hand are closely related. Thus, the new formulation remains elliptic in elastic unloading at any given plastic predeformation. In addition, in this domain, the true stress-true strain relation remains monotone, as observed in experiments.

  3. Computational Strain Gradient Crystal Plasticity

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Kysar, Jeffrey W.

    2011-01-01

    A model for strain gradient crystal visco-plasticity is formulated along the lines proposed by Fleck andWillis (2009) for isotropic plasticity. Size-effects are included in the model due to the addition of gradient terms in both the free energy as well as through a dissipation potential. A finite...... element solution method is presented, which delivers the slip-rate field and the velocity-field based on two minimum principles. Some plane deformation problems relevant for certain specific orientations of a face centered cubic crystal under plane loading conditions are studied, and effective in......-plane parameters are developed based on the crystallographic properties of the material. The problem of cyclic shear of a single crystal between rigid platens is studied as well as void growth of a cylindrical void....

  4. Computational strain gradient crystal plasticity

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Kysar, Jeffrey W.

    2014-01-01

    of plane crystal plasticity are studied: pure shear of a single crystal between rigid platens as well as plastic deformation around cylindrical voids in hexagonal close packed and face centered cubic crystals. Effective in-plane constitutive slip parameters for plane strain deformation of specifically...

  5. The role of dissipation and defect energy in variational formulations of problems in strain-gradient plasticity. Part 2: single-crystal plasticity

    Science.gov (United States)

    Reddy, B. D.

    2011-11-01

    Variational formulations are constructed for rate-independent problems in small-deformation single-crystal strain-gradient plasticity. The framework, based on that of Gurtin (J Mech Phys Solids 50: 5-32, 2002), makes use of the flow rule expressed in terms of the dissipation function. Provision is made for energetic and dissipative microstresses. Both recoverable and non-recoverable defect energies are incorporated into the variational framework. The recoverable energies include those that depend smoothly on the slip gradients, the Burgers tensor, or on the dislocation densities (Gurtin et al. J Mech Phys Solids 55:1853-1878, 2007), as well as an energy proposed by Ohno and Okumura (J Mech Phys Solids 55:1879-1898, 2007), which leads to excellent agreement with experimental results, and which is positively homogeneous and therefore not differentiable at zero slip gradient. Furthermore, the variational formulation accommodates a non-recoverable energy due to Ohno et al. (Int J Mod Phys B 22:5937-5942, 2008), which is also positively homogeneous, and a function of the accumulated dislocation density. Conditions for the existence and uniqueness of solutions are established for the various examples of defect energy, with or without the presence of hardening or slip resistance.

  6. PLASTICITY AND NON-LINEAR ELASTIC STRAINS

    Science.gov (United States)

    conditions existing in plane waves in an extended medium to give the time rate of change of stress as a function of the time rate of change of strain, the stress invariants, the total strain and the plastic strain. (Author)

  7. Distributions of energy storage rate and microstructural evolution in the area of plastic strain localization during uniaxial tension of austenitic steel

    Science.gov (United States)

    Oliferuk, W.; Maj, M.

    2015-08-01

    The presented work is devoted to an experimental determination of the energy storage rate in the area of strain localization. The experimental procedure involves two complementary techniques: i.e. infrared thermography (IRT) and visible light imaging. The results of experiments have shown that during the evolution of plastic strain localization the energy storage rate in some areas of the deformed specimen drops to zero. To interpret the decrease of the energy storage rate in terms of micro-mechanisms, microstructural observations using Transmission Electron Microscopy (TEM) and Electron Back Scattered Diffraction (EBSC) were performed. On the basis of microstructural studies it is believed that a 0 value of energy storage rate corresponds to the state in which only two dominant components of the texture appear, creating conditions for crystallographic shear banding.

  8. On lower order strain gradient plasticity theories

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Hutchinson, J. W.

    2003-01-01

    the tangent moduli governing increments of stress and strain. It is shown that the modification is far from benign from a mathematical standpoint, changing the qualitative character of solutions and leading to a new type of localization that is at odds with what is expected from a strain gradient theory......By way of numerical examples, this paper explores the nature of solutions to a class of strain gradient plasticity theories that employ conventional stresses, equilibrium equations and boundary conditions. Strain gradients come into play in these modified conventional theories only to alter....... The findings raise questions about the physical acceptability of this class of strain gradient theories....

  9. On lower order strain gradient plasticity theories

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Hutchinson, J. W.

    2002-01-01

    By way of numerical examples, this paper explores the nature of solutions to a class of strain gradient plasticity theories that employ conventional stresses, equilibrium equations and boundary conditions. Strain gradients come into play in these modified conventional theories only to alter the t...... the tangential moduli governing increments of stress and strain. It is shown that the modification is far from benign from a mathematical standpoint, changing the qualitative character of solutions and leading to a new type of localization that appears to be unphysical.......By way of numerical examples, this paper explores the nature of solutions to a class of strain gradient plasticity theories that employ conventional stresses, equilibrium equations and boundary conditions. Strain gradients come into play in these modified conventional theories only to alter...

  10. Strain rate dependence in plasticized and un-plasticized PVC

    Directory of Open Access Journals (Sweden)

    Siviour C.R.

    2012-08-01

    Full Text Available An experimental and analytical investigation has been made into the mechanical behaviour of two poly (vinyl chloride (PVC polymers – an un-plasticized PVC and a diisononyl phthalate (DINP-plasticized PVC. Measurements of the compressive stress-strain behaviour of the PVCs at strain rates ranging from 10−3 to 103s−1 and temperatures from − 60 to 100∘C are presented. Dynamic Mechanical Analysis was also performed in order to understand the material transitions observed in compression testing as the strain rate is increased. This investigation develops a better understanding of the interplay between the temperature dependence and rate dependence of polymers, with a focus on locating the temperature and rate-dependent material transitions that occur during high rate testing.

  11. Strain rate dependence in plasticized and un-plasticized PVC

    Science.gov (United States)

    Kendall, M. J.; Siviour, C. R.

    2012-08-01

    An experimental and analytical investigation has been made into the mechanical behaviour of two poly (vinyl chloride) (PVC) polymers - an un-plasticized PVC and a diisononyl phthalate (DINP)-plasticized PVC. Measurements of the compressive stress-strain behaviour of the PVCs at strain rates ranging from 10-3 to 103s-1 and temperatures from - 60 to 100∘C are presented. Dynamic Mechanical Analysis was also performed in order to understand the material transitions observed in compression testing as the strain rate is increased. This investigation develops a better understanding of the interplay between the temperature dependence and rate dependence of polymers, with a focus on locating the temperature and rate-dependent material transitions that occur during high rate testing.

  12. On fracture in finite strain gradient plasticity

    DEFF Research Database (Denmark)

    Martínez Pañeda, Emilio; Niordson, Christian Frithiof

    2016-01-01

    In this work a general framework for damage and fracture assessment including the effect of strain gradients is provided. Both mechanism-based and phenomenological strain gradient plasticity (SGP) theories are implemented numerically using finite deformation theory and crack tip fields are invest......In this work a general framework for damage and fracture assessment including the effect of strain gradients is provided. Both mechanism-based and phenomenological strain gradient plasticity (SGP) theories are implemented numerically using finite deformation theory and crack tip fields...... are investigated. Differences and similarities between the two approaches within continuum SGP modeling are highlighted and discussed. Local strain hardening promoted by geometrically necessary dislocations (GNDs) in the vicinity of the crack leads to much higher stresses, relative to classical plasticity...... predictions. These differences increase significantly when large strains are taken into account, as a consequence of the contribution of strain gradients to the work hardening of the material. The magnitude of stress elevation at the crack tip and the distance ahead of the crack where GNDs significantly alter...

  13. A mathematical basis for strain-gradient plasticity theory. Part II: Tensorial plastic multiplier

    Science.gov (United States)

    Fleck, N. A.; Willis, J. R.

    2009-07-01

    A phenomenological, flow theory version of gradient plasticity for isotropic and anisotropic solids is constructed along the lines of Gudmundson [Gudmundson, P., 2004. A unified treatment of strain-gradient plasticity. J. Mech. Phys. Solids 52, 1379-1406]. Both energetic and dissipative stresses are considered in order to develop a kinematic hardening theory, which in the absence of gradient terms reduces to conventional J 2 flow theory with kinematic hardening. The dissipative stress measures, work-conjugate to plastic strain and its gradient, satisfy a yield condition with associated plastic flow. The theory includes interfacial terms: elastic energy is stored and plastic work is dissipated at internal interfaces, and a yield surface is postulated for the work-conjugate stress quantities at the interface. Uniqueness and extremum principles are constructed for the solution of boundary value problems, for both the rate-dependent and the rate-independent cases. In the absence of strain gradient and interface effects, the minimum principles reduce to the classical extremum principles for a kinematically hardening elasto-plastic solid. A rigid-hardening version of the theory is also stated and the resulting theory gives rise to an extension to the classical limit load theorems. This has particular appeal as previous trial fields for limit load analysis can be used to generate immediately size-dependent bounds on limit loads.

  14. Stored Energy of Plastic Deformation in Tube Bending Processes

    Science.gov (United States)

    Śloderbach, Z.; Pająk, J.

    2013-03-01

    The paper presents an aproximate analytic method for determination of the stored energy of plastic deformation during cold bending of metal tubes at bending machines. Calculations were performed for outer points of the tube layers subjected to tension and compression (the points of maximum strains). The percentage of stored energy related to the plastic strain work was determined and the results were presented in graphs. The influence and importance of the stored energy of plastic deformation on the service life of pipeline bends are discussed.

  15. Strain gradient plasticity effects in whisker-reinforced metals

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof

    2002-01-01

    A metal reinforced by fibers in the micron range is studied using the strain gradient plasticity theory of Fleck and Hutchinson (2001). Cell-model analyzes are used to study the influence of the material length parameters numerically. Different higher order boundary conditions are considered...... at the fiber-matrix interface. The results are presented as overall stress-strain curves for the whisker-reinforced metal, and also contour plots of effective plastic strain are shown. The strain gradient plasticity theory predicts a significant stiffening effect when compared to conventional models...

  16. A novel limiting strain energy strength theory

    Institute of Scientific and Technical Information of China (English)

    LIU Guang-lian

    2009-01-01

    With applied dislocation theory,the effects of shear and normal stresses on the slide and climb motions at the same section of a crystal were analyzed.And,based on the synergetic effect of both normal and shear strain specific energies,the concept of the total equivalent strain specific energy (TESSE) at an oblique section and a new strength theory named as limiting strain energy strength theory (LSEST) were proposed.As for isotropic materials,the plastic yielding or brittle fracture of under uniaxial stress state would occur when the maximum TESSE reached the strain specific energy,also the expressions on the equivalent stresses and a function of failure of the LSEST under different principal stress states were obtained.Relationship formulas among the tensile,compressive and shear yield strengths for plastic metals were derived.These theoretical predictions,according to the LSEST,were consistent very well with experiment results of tensile,compressive and torsion tests of three plastic metals and other experiment results from open literatures.This novel LSEST might also help for strength calculation of other materials.

  17. Strain hardening of polymer glasses: Entanglements, energetics, and plasticity

    Science.gov (United States)

    Hoy, Robert S.; Robbins, Mark O.

    2008-03-01

    Simulations are used to examine the microscopic origins of strain hardening in polymer glasses. While stress-strain curves for a wide range of temperature can be fit to the functional form predicted by entropic network models, many other results are fundamentally inconsistent with the physical picture underlying these models. Stresses are too large to be entropic and have the wrong trend with temperature. The most dramatic hardening at large strains reflects increases in energy as chains are pulled taut between entanglements rather than a change in entropy. A weak entropic stress is only observed in shape recovery of deformed samples when heated above the glass transition. While short chains do not form an entangled network, they exhibit partial shape recovery, orientation, and strain hardening. Stresses for all chain lengths collapse when plotted against a microscopic measure of chain stretching rather than the macroscopic stretch. The thermal contribution to the stress is directly proportional to the rate of plasticity as measured by breaking and reforming of interchain bonds. These observations suggest that the correct microscopic theory of strain hardening should be based on glassy state physics rather than rubber elasticity.

  18. Equivalent Plastic Strain Gradient Plasticity with Grain Boundary Hardening and Comparison to Discrete Dislocation Dynamics

    CERN Document Server

    Bayerschen, E; Wulfinghoff, S; Weygand, D; Böhlke, T

    2015-01-01

    The gradient crystal plasticity framework of Wulfinghoff et al. [53] incorporating an equivalent plastic strain and grain boundary yielding, is extended with additional grain boundary hardening. By comparison to averaged results from many discrete dislocation dynamics (DDD) simulations of an aluminum type tricrystal under tensile loading, the new hardening parameter in the continuum model is calibrated. It is shown that although the grain boundaries (GBs) in the discrete simulations are impenetrable, an infinite GB yield strength corresponding to microhard GB conditions, is not applicable in the continuum model. A combination of a finite GB yield strength with an isotropic bulk Voce hardening relation alone also fails to model the plastic strain profiles obtained by DDD. Instead, a finite GB yield strength in combination with GB hardening depending on the equivalent plastic strain at the GBs is shown to give a better agreement to DDD results. The differences in the plastic strain profiles obtained in DDD simu...

  19. Strain gradient crystal plasticity effects on flow localization

    DEFF Research Database (Denmark)

    Borg, Ulrik

    2007-01-01

    In metal grains one of the most important failure mechanisms involves shear band localization. As the band width is small, the deformations are affected by material length scales. To study localization in single grains a rate-dependent crystal plasticity formulation for finite strains is presented...... in the absence of strain gradients. The model is used to study the effect of an internal material length scale on the localization of plastic flow in shear bands in a single crystal under plane strain tension. It is shown that the mesh sensitivity is removed when using the nonlocal material model considered...... for metals described by the reformulated Fleck-Hutchinson strain gradient plasticity theory. The theory is implemented numerically within a finite element framework using slip rate increments and displacement increments as state variables. The formulation reduces to the classical crystal plasticity theory...

  20. Estimating the plastic strain with the use of acoustic anisotropy

    Science.gov (United States)

    Belyaev, A. K.; Lobachev, A. M.; Modestov, V. S.; Pivkov, A. V.; Polyanskii, V. A.; Semenov, A. S.; Tret'yakov, D. A.; Shtukin, L. V.

    2016-09-01

    Experimental verification is used to show that reference specimens and structure unloading do not permit obtaining an adequate estimate of plastic strain by measuring the acoustic anisotropy. Analytic estimates of the speed of propagation of a plane acoustic wave of various polarizations in an elastoplastic material in the direction orthogonal to the action of preliminary uniaxial stress are obtained. An analysis of the obtained relations reveala an advantage of using absolute values of the velocity of longitudinal and transverse waves for the plastic strain identification. In contrast to acoustic anisotropy, the velocities vary monotonically in a wider range of plastic strains. At the same time, the elastic strain does not affect the longitude wave velocity, which allows one to use the measurement results to estimate the character of strains.

  1. High strain rate loading of polymeric foams and solid plastics

    Science.gov (United States)

    Dick, Richard D.; Chang, Peter C.; Fourney, William L.

    2000-04-01

    The split-Hopkinson pressure bar (SHPB) provided a technique to determine the high strain rate response for low density foams and solid ABS and polypropylene plastics. These materials are used in the interior safety panels of automobiles and crash test dummies. Because the foams have a very low impedance, polycarbonate bars were used to acquire the strain rate data in the 100 to 1600 l/s range. An aluminum SPHB setup was used to obtain the solid plastics data which covered strain rates of 1000 to 4000 l/s. The curves for peak strain rate versus peak stress for the foams over the test range studied indicates only a slight strain rate dependence. Peak strain rate versus peak stress curves for polypropylene shows a strain rate dependence up to about 1500 l/s. At that rate the solid poly propylene indicates no strain rate dependence. The ABS plastics are strain rate dependent up to 3500 l/s and then are independent at larger strain rates.

  2. Slip transfer and plastic strain accumulation across grain boundaries in Hastelloy X

    Science.gov (United States)

    Abuzaid, Wael Z.; Sangid, Michael D.; Carroll, Jay D.; Sehitoglu, Huseyin; Lambros, John

    2012-06-01

    In this study, high resolution ex situ digital image correlation (DIC) was used to measure plastic strain accumulation with sub-grain level spatial resolution in uniaxial tension of a nickel-based superalloy, Hastelloy X. In addition, the underlying microstructure was characterized with similar spatial resolution using electron backscatter diffraction (EBSD). With this combination of crystallographic orientation data and plastic strain measurements, the resolved shear strains on individual slip systems were spatially calculated across a substantial region of interest, i.e., we determined the local slip system activity in an aggregate of ˜600 grains and annealing twins. The full-field DIC measurements show a high level of heterogeneity in the plastic response with large variations in strain magnitudes within grains and across grain boundaries (GBs). We used the experimental results to study these variations in strain, focusing in particular on the role of slip transmission across GBs in the development of strain heterogeneities. For every GB in the polycrystalline aggregate, we have established the most likely dislocation reaction and used that information to calculate the residual Burgers vector and plastic strain magnitudes due to slip transmission across each interface. We have also used molecular dynamics simulations (MD) to establish the energy barriers to slip transmission for selected cases yielding different magnitudes of the residual Burgers vector. From our analysis, we show an inverse relation between the magnitudes of the residual Burgers vector and the plastic strains across GBs. Also, the MD simulations reveal a higher energy barrier for slip transmission at high magnitudes of the residual Burgers vector. We therefore emphasize the importance of considering the magnitude of the residual Burgers vector to obtain a better description of the GB resistance to slip transmission, which in turn influences the local plastic strains in the vicinity of grain

  3. A strain gradient plasticity theory with application to wire torsion

    KAUST Repository

    Liu, J. X.

    2014-06-05

    Based on the framework of the existing strain gradient plasticity theories, we have examined three kinds of relations for the plastic strain dependence of the material intrinsic length scale, and thus developed updated strain gradient plasticity versions with deformation-dependent characteristic length scales. Wire torsion test is taken as an example to assess existing and newly built constitutive equations. For torsion tests, with increasing plastic strain, a constant intrinsic length predicts too high a torque, while a decreasing intrinsic length scale can produce better predictions instead of the increasing one, different from some published observations. If the Taylor dislocation rule is written in the Nix-Gao form, the derived constitutive equations become singular when the hardening exponent gets close to zero, which seems questionable and calls for further experimental clarifications on the exact coupling of hardening due to statistically stored dislocations and geometrically necessary dislocations. Particularly, when comparing the present model with the mechanism-based strain gradient plasticity, the present model satisfies the reciprocity relation naturally and gives different predictions even under the same parameter setting. © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

  4. Theory of Lattice Strain for Materials Undergoing Plastic Deformation

    Science.gov (United States)

    Karato, S.

    2008-12-01

    Radial x-ray diffraction is used to probe physical properties of materials including elastic and plastic properties. The theory used behind such an practice is the one developed by Singh (1993) in which the relation between lattice strain and elastic constants and macroscopic stress is derived. In this theory, the variation of inferred stress with the crystallographic planes, (hkl), is due to the elastic anisotropy. However, recent experimental studies showed that in many cases, the variation of stress with (hkl) far exceeds the value expected from this theory. I have developed a modified theory to rectify this problem with Singh's theory. In Singh's theory, the stress distribution in a polycrystalline material is treated only either unrelaxed or relaxed state. The role of plastic deformation is included only to the extent that plastic flow influences this stress state. Such an assumption corresponds to a Voigt model behavior, which is not an appropriate model at high temperatures where continuing plastic flow occurs with concurrent microscopic equilibrium, elastic deformation. This is a Maxwell model type behavior, and my model provides a stress analysis in a Maxwell material with anisotropic and non-linear power-law rheology. In this theory, the lattice strain corresponding to an imposed macroscopic strain-rate is calculated by three steps: (i) conversion of macroscopic strain-rate to macroscopic stress, (ii) conversion of macroscopic stress to microscopic stress at individual grains, and (iii) calculation of microscopic strain due to microscopic stress. The first step involves anisotropy in macroscopic viscosity that depends on anisotropy in crystal plasticity and lattice-preferred orientation. The second step involves anisotropic crystal plasticity and finally the third step involves elastic crystal anisotropy. In most cases, the influence of LPO is weak and in such a case, the lattice strain depends on (hkl) due to the anisotropy in both elastic and plastic

  5. Fracture of anisotropic materials with plastic strain-gradient effects

    DEFF Research Database (Denmark)

    Legarth, Brian Nyvang

    2013-01-01

    parameter is adopted. The fracture process along the fiber-matrix interface is modeled using a recently proposed cohesive law extension having an additional material length parameter. Due to the fiber-matrix fracture a sudden stress-drop is seen in the macroscopic stress-strain response which defines......A unit cell is adopted to numerically analyze the effect of plastic anisotropy on frac-ture evolution in a micro-reinforced fiber-composite. The matrix material exhibit size-effects and an anisotropic strain-gradient plasticity model accounting for such size-effects through a mate-rial length scale...... the failure strain of the composite. The effect of the two material length parameters on the failure strain of the composite is studied. For small values of the material length scale parameter conventional predictions are obtained. Larger values of the material length scale parameter result in corresponding...

  6. Strain gradient plasticity analysis of elasto-plastic contact between rough surfaces

    Science.gov (United States)

    Song, H.; Van der Giessen, E.; Liu, X.

    2016-11-01

    From a microscopic point of view, the real contact area between two rough surfaces is the sum of the areas of contact between facing asperities. Since the real contact area is a fraction of the nominal contact area, the real contact pressure is much higher than the nominal contact pressure, which results in plastic deformation of asperities. As plasticity is size dependent at size scales below tens of micrometers, with the general trend of smaller being harder, macroscopic plasticity is not suitable to describe plastic deformation of small asperities and thus fails to capture the real contact area and pressure accurately. Here we adopt conventional mechanism-based strain gradient plasticity (CMSGP) to analyze the contact between a rigid platen and an elasto-plastic solid with a rough surface. Flattening of a single sinusoidal asperity is analyzed first to highlight the difference between CMSGP and J2 isotropic plasticity. For the rough surface contact, besides CMSGP, pure elastic and J2 isotropic plasticity analysis is also carried out for comparison. In all cases, the contact area A rises linearly with the applied load, but with a different slope which implies that the mean contact pressures are different. CMSGP produces qualitative changes in the distributions of local contact pressures compared with pure elastic and J2 isotropic plasticity analysis, furthermore, bounded by the two.

  7. Stress-strain response of plastic waste mixed soil.

    Science.gov (United States)

    Babu, G L Sivakumar; Chouksey, Sandeep Kumar

    2011-03-01

    Recycling plastic waste from water bottles has become one of the major challenges worldwide. The present study provides an approach for the use plastic waste as reinforcement material in soil. The experimental results in the form of stress-strain-pore water pressure response are presented. Based on experimental test results, it is observed that the strength of soil is improved and compressibility reduced significantly with addition of a small percentage of plastic waste to the soil. The use of the improvement in strength and compressibility response due to inclusion of plastic waste can be advantageously used in bearing capacity improvement and settlement reduction in the design of shallow foundations. Copyright © 2010 Elsevier Ltd. All rights reserved.

  8. Constitutive modeling and computational implementation for finite strain plasticity

    Science.gov (United States)

    Reed, K. W.; Atluri, S. N.

    1985-01-01

    This paper describes a simple alternate approach to the difficult problem of modeling material behavior. Starting from a general representation for a rate-tpe constitutive equation, it is shown by example how sets of test data may be used to derive restrictions on the scalar functions appearing in the representation. It is not possible to determine these functions from experimental data, but the aforementioned restrictions serve as a guide in their eventual definition. The implications are examined for hypo-elastic, isotropically hardening plastic, and kinematically hardening plastic materials. A simple model for the evolution of the 'back-stress,' in a kinematic-hardening plasticity theory, that is entirely analogous to a hypoelastic stress-strain relation is postulated and examined in detail in modeling finitely plastic tension-torsion test. The implementation of rate-type material models in finite element algorithms is also discussed.

  9. Strain gradient plasticity effects in whisker-reinforced metals

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof

    2003-01-01

    A metal reinforced by fibers in the micron range is studied using the strain gradient plasticity theory of Fleck and Hutchinson (J. Mech. Phys. Solids 49 (2001) 2245). Cell-model analyses are used to study the influence of the material length parameters numerically, for both a single parameter...... version and the multiparameter theory, and significant differences between the predictions of the two models are reported. It is shown that modeling fiber elasticity is important when using the present theories. A significant stiffening effect when compared to conventional models is predicted, which...... is a result of a significant decrease in the level of plastic strain. Moreover, it is shown that the relative stiffening effect increases with fiber volume fraction. The higher-order nature of the theories allows for different higher-order boundary conditions at the fiber-matrix interface, and these boundary...

  10. Tensile plastic strain localization in single crystals of austenite steel electrolytically saturated with hydrogen

    Science.gov (United States)

    Barannikova, S. A.; Nadezhkin, M. V.; Mel'Nichuk, V. A.; Zuev, L. B.

    2011-09-01

    The effect of interstitial hydrogen atoms on the mechanical properties and plastic strain localization patterns in tensile tested Fe-18Cr-12Ni-2Mo single crystals of austenite steel with low stacking-fault energy has been studied using a double-exposure speckle photography technique. The main parameters of plastic-flow localization at various stages of the deformation hardening of crystals have been determined in single crystals of steel electrolytically saturated with hydrogen in a three-electrode electrochemical cell at a controlled constant cathode potential.

  11. Strain Hardening of Polymer Glasses: Entanglements, Energetics, and Plasticity

    OpenAIRE

    Hoy, Robert S.; Robbins, Mark O.

    2007-01-01

    Simulations are used to examine the microscopic origins of strain hardening in polymer glasses. While stress-strain curves for a wide range of temperature can be fit to the functional form predicted by entropic network models, many other results are fundamentally inconsistent with the physical picture underlying these models. Stresses are too large to be entropic and have the wrong trend with temperature. The most dramatic hardening at large strains reflects increases in energy as chains are ...

  12. On the homogenization of metal matrix composites using strain gradient plasticity

    DEFF Research Database (Denmark)

    Azizi, Reza; Niordson, Christian Frithiof; Legarth, Brian Nyvang

    2014-01-01

    The homogenized response of metal matrix composites (MMC) is studied using strain gradient plasticity. The material model employed is a rate independent formulation of energetic strain gradient plasticity at the micro scale and conventional rate independent plasticity at the macro scale. Free...

  13. Relationship between burgers vectors of dislocations and plastic strain localization patterns in compression-strained alkali halide crystals

    Science.gov (United States)

    Barannikova, S. A.; Nadezhkin, M. V.; Zuev, L. B.

    2011-08-01

    Plastic strain localization patterns in compression-strained alkali halide (NaCl, KCl, and LiF) crystals have been studied using a double-exposure speckle photography technique. The main parameters of strain localization autowaves at the linear stages of deformation hardening in alkali halide crystals have been determined. A quantitative relationship between the macroscopic parameters of plastic flow localization and microscopic parameters of strained alkali halide crystals has been established.

  14. Plasticity of Cu nanoparticles: Dislocation-dendrite-induced strain hardening and a limit for displacive plasticity

    Directory of Open Access Journals (Sweden)

    Antti Tolvanen

    2013-03-01

    Full Text Available The plastic behaviour of individual Cu crystallites under nanoextrusion is studied by molecular dynamics simulations. Single-crystal Cu fcc nanoparticles are embedded in a spherical force field mimicking the effect of a contracting carbon shell, inducing pressure on the system in the range of gigapascals. The material is extruded from a hole of 1.1–1.6 nm radius under athermal conditions. Simultaneous nucleation of partial dislocations at the extrusion orifice leads to the formation of dislocation dendrites in the particle causing strain hardening and high flow stress of the material. As the extrusion orifice radius is reduced below 1.3 Å we observe a transition from displacive plasticity to solid-state amorphisation.

  15. A new macroscopically anisotropic pressure dependent yield function for metal matrix composite based on strain gradient plasticity for the microstructure

    DEFF Research Database (Denmark)

    Azizi, Reza; Legarth, Brian Nyvang; Niordson, Christian Frithiof

    2013-01-01

    Metal matrix composites with long aligned elastic fibers are studied using an energetic rate independent strain gradient plasticity theory with an isotropic pressure independent yield function at the microscale. The material response is homogenized to obtain a conventional macroscopic model...... that exhibits anisotropic yield properties with a pressure dependence. At the microscale free energy includes both elastic strains and plastic strain gradients, and the theory demands higher order boundary conditions in terms of plastic strain or work conjugate higher order tractions. The mechanical response...... of the composite is inclined compared to a standard pressure independent yield surfaces. The evolution of the macroscopic yield surface is investigated by quantifying both anisotropic hardening (expansion) and kinematic hardening (translation), where the coefficients of anisotropy and the Bauschinger stress...

  16. Discussion and calculation on welding residual longitudinal stress and plastic strain by finite element method

    Institute of Scientific and Technical Information of China (English)

    Hong-yuan FANG; Xue-qiu ZHANG; Jian-guo WANG; Xue-song LIU; Shen QU

    2009-01-01

    In recent years, some researchers have put forward the new viewpoint that the weld is merely formed during the cooling process, not concerned with the heating process. According to this view, it can be concluded that it is not the compressive but the tensile plastic strain that may remain in the weld. To analyze the formation mechanism of the longitudinal residual stress and plastic strain, finite element method (FEM) is employed in this paper to model the welding longitudinal residual stress and plastic strain. The calculation results show that both the residual compressive plastic strain and the tensile stress in the longitudinal direction can be found in the weld.

  17. Strain gradient polycrystal plasticity for micro-forming

    Science.gov (United States)

    Yalçinkaya, Tuncay; Simonovski, Igor; Özdemir, Izzet

    2016-10-01

    The developments in the micro-device industry has produced a substantial demand for the miniaturized metallic components with ultra-thin sheet materials that have thickness dimensions on the order of 50-500 µm which are produced through micro-forming processes. It is essential to have predictive tools to simulate the constitutive behavior of the materials at this length scale taking into account the physical and statistical size effect. Recent studies have shown that on the scale of several micrometers and below, crystalline materials behave differently from their bulk equivalent due to micro-structural effects (e.g. grain size, lattice defects and impurities), gradient effects (e.g. lattice curvature due to a non-uniform deformation field) and surface constraints (e.g. hard coatings or free interfaces). These effects could lead to stronger or weaker material response depending on the size and unique micro-structural features of the material. In this paper a plastic slip based strain gradient crystal plasticity model is used to address the effect of microstructural features (e.g. grain size, orientation and the number of grains) on the macroscopic constitutive response and the local behavior of polycrystalline materials.

  18. Plastic incompatibility stresses and stored elastic energy in plastically deformed copper

    Energy Technology Data Exchange (ETDEWEB)

    Baczmanski, A. [Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, al. Mickiewicza 30, 30-059 Krakow (Poland)], E-mail: baczman@ftj.agh.edu.pl; Hfaiedh, N.; Francois, M. [LASMIS, Universite de Technologie de Troyes, 11 rue Marie Curie, B.P. 2060, 10010 Troyes (France); Wierzbanowski, K. [Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, al. Mickiewicza 30, 30-059 Krakow (Poland)

    2009-02-15

    The X-ray diffraction method and theoretical model of elastoplastic deformation were used to examine the residual stresses in polycrystalline copper. To this end, the {l_brace}2 2 0{r_brace} strain pole figures were determined for samples subjected to different magnitudes of tensile deformation. Using diffraction data and the self-consistent model, the tensor of plastic incompatibility stress was found for each orientation of a polycrystalline grain. Crystallographic textures, macroscopic and second-order residual stresses were considered in the analysis. As a result, the distributions of elastic stored energy and von Mises equivalent stress were presented in Euler space and correlated with the preferred orientations of grains. Moreover, using the model prediction, the variation of the critical resolved shear stress with grain orientation was determined.

  19. Plastic Strain Induced Damage Evolution and Martensitic Transformation in Ductile Materials at Cryogenic Temperatures

    CERN Document Server

    Garion, C

    2002-01-01

    The Fe-Cr-Ni stainless steels are well known for their ductile behaviour at cryogenic temperatures. This implies development and evolution of plastic strain fields in the stainless steel components subjected to thermo-mechanical loads at low temperatures. The evolution of plastic strain fields is usually associated with two phenomena: ductile damage and strain induced martensitic transformation. Ductile damage is described by the kinetic law of damage evolution. Here, the assumption of isotropic distribution of damage (microcracks and microvoids) in the Representative Volume Element (RVE) is made. Formation of the plastic strain induced martensite (irreversible process) leads to the presence of quasi-rigid inclusions of martensite in the austenitic matrix. The amount of martensite platelets in the RVE depends on the intensity of the plastic strain fields and on the temperature. The evolution of the volume fraction of martensite is governed by a kinetic law based on the accumulated plastic strain. Both of thes...

  20. An alternative treatment of phenomenological higher-order strain-gradient plasticity theory

    DEFF Research Database (Denmark)

    Kuroda, Mitsutoshi; Tvergaard, Viggo

    2010-01-01

    strain is discussed, applying a dislocation theory-based consideration. Then, a differential equation for the equivalent plastic strain-gradient is introduced as an additional governing equation. Its weak form makes it possible to deduce and impose extra boundary conditions for the equivalent plastic...

  1. Gurson-type elastic-plastic damage model based on strain-rate plastic potential

    Science.gov (United States)

    Balan, Tudor; Cazacu, Oana

    2013-12-01

    Ductile damage is generally described by stress-space analytical potentials. In this contribution, it is shown that strain rate potentials, which are exact conjugate of the stress-based potentials, can be equally used to describe the dilatational response of porous metals. This framework is particularly appropriate for porous materials with matrix described by complex yield criteria for which a closed-form expression of the stress-based potential is not available. Illustration of the new approach is done for porous metals containing randomly distributed spherical voids in a von Mises elasto-plastic matrix. Furthermore, a general time integration algorithm for simulation of the mechanical response using this new formulation is developed and implemented in Abaqus/Standard. The proposed model and algorithm are validated with respect to the Abaqus built-in GTN model, which is based on a stress potential, through the simulation of a tensile test on a round bar.

  2. Micromechanical modeling of damage in periodic composites using strain gradient plasticity

    DEFF Research Database (Denmark)

    Azizi, Reza

    2012-01-01

    Damage evolution at the fiber matrix interface in Metal Matrix Composites (MMCs) is studied using strain gradient theory of plasticity. The study includes the rate independent formulation of energetic strain gradient plasticity for the matrix, purely elastic model for the fiber and cohesive zone...... model under simple shear and transverse uniaxial tension using plane strain and periodic boundary conditions. The result of the overall response curve, effective plastic strain, effective stress and higher order stress distributions are shown. The effect of the material length scale, maximum stress...

  3. Dynamic analysis of fault rockburst based on gradient-dependent plasticity and energy criterion

    Institute of Scientific and Technical Information of China (English)

    Xuebin Wang; Xiaobin Yang; Zhihui Zhang; Yishan Pan

    2004-01-01

    Fault rockburst is treated as a strain localization problem under dynamic loading condition considering strain gradient and strain rate. As a kind of dynamic fracture phenomena, rockburst has characteristics of strain localization, which is considered as a one-dimensional shear problem subjected to normal compressive stress and tangential shear stress. The constitutive relation of rock material is bilinear (elastic and strain softening) and sensitive to shear strain rate. The solutions proposed based on gradientdependent plasticity show that intense plastic strain is concentrated in fault band and the thickness of the band depends on the characteristic length of rock material. The post-peak stiffness of the fault band was determined according to the constitutive parameters of rock material and shear strain rate. Fault band undergoing strain softening and elastic rock mass outside the band constitute a system and the instability criterion of the system was proposed based on energy theory. The criterion depends on the constitutive relation of rock material, the structural size and the strain rate. The static result regardless of the strain rate is the special case of the present analytical solution. High strain rate can lead to instability of the system.

  4. Features of plastic strain localization at the yield plateau in Hadfield steel single crystals

    Science.gov (United States)

    Barannikova, S. A.; Zuev, L. B.

    2008-07-01

    Spatiotemporal distributions of local components of the plastic distortion tensor in Hadfield steel single crystals oriented for single twinning have been studied under active tensile straining conditions using the double-exposure speckle photography technique. Features of the macroscopically inhomogeneous strain localization at the yield plateau are considered. Relations between local components of the plastic distortion tensor in the zone of strain localization are analyzed.

  5. Texture Control of Aluminum, Iron, and Magnesium Alloy Sheets to Increase Their Plastic Strain Ratios

    Science.gov (United States)

    Lee, Dong Nyung; Han, Heung Nam

    2011-08-01

    It is known that the limiting drawing ratio of sheet metals is proportional to their plastic strain ratios, and the plastic strain ratios of fcc and bcc metal sheets increase with increasing //ND component in their textures. Conventional cold rolling and subsequent annealing of fcc metals cannot give rise to the //ND component. Specifically, the cold rolling texture of polycrystalline fcc metals is characterized by the fiber connecting the {112}, {123}, and {011} orientations in the Euler space, which is often called the β-fiber. The density of each component in the fiber depends on the stacking fault energy of metals. The {112} and {123} textured Al alloy sheets evolve the {001} texture, when recrystallized. The low plastic strain ratios of the Al alloy sheets are attributed to the {001} texture. The //ND texture can be obtained in shear deformed fcc sheets. Bcc steels develop the //ND texture when cold rolled and recrystallized. However, the density of //ND depends on the content of dissolved interstitial elements such as carbon and nitrogen. The density of the //ND component decreases with increasing concentration of the dissolved interstitial elements. For a given steel, the density of the //ND component can vary with varying thermomechanical treatment. Magnesium alloy sheets are subjected to sheet forming processes at temperatures of 200 °C or higher because of their basal plane texture, or the //ND orientation. Many studies have been made to alleviate the component so that the magnesium alloy sheets can have better formability. In this article, the above issues are briefly reviewed and discussed.

  6. Neutron-diffraction measurement of the evolution of strain for non-uniform plastic deformation

    CERN Document Server

    Rogge, R B; Boyce, D

    2002-01-01

    Neutrons are particularly adept for the validation of modeling predictions of stress and strain. In recent years, there has been a significant effort to model the evolution of both the macroscopic stresses and the intergranular stress during plastic deformation. These have had broad implications with regard to understanding the evolution of residual stress and to diffraction-based measurements of strain. Generally the modeling and associated measurements have been performed for simple uniaxial tension, leaving questions with regard to plastic deformation under multi-axial stress and non-uniform stress. Extensive measurements of the strain profile across a plastic hinge for each of a series of loading and unloading cycles to progressively higher degrees of plastic deformation are presented. These measurements are used to assess multiple-length-scale finite-element modeling (FEM) of the plastic hinge, in which the elements will range in size from single crystallites (as used in successful simulations of uniaxia...

  7. Strain gradient plasticity modeling of hydrogen diffusion to the crack tip

    DEFF Research Database (Denmark)

    Martínez Pañeda, Emilio; del Busto, S.; Niordson, Christian Frithiof

    2016-01-01

    In this work hydrogen diffusion towards the fracture process zone is examined accounting for local hardening due to geometrically necessary dislocations (GNDs) by means of strain gradient plasticity (SGP). Finite element computations are performed within the finite deformation theory...

  8. An incremental flow theory for crystal plasticity incorporating strain gradient effects

    DEFF Research Database (Denmark)

    Nellemann, Christopher; Niordson, Christian Frithiof; Nielsen, Kim Lau

    2017-01-01

    The present work investigates a new approach to formulating a rate-independent strain gradient theory for crystal plasticity. The approach takes as offset recent discussions published in the literature for isotropic plasticity, and a key ingredient of the present work is the manner in which a gra...

  9. Plasticity dependent damage evolution in composites with strain-gradient effects

    DEFF Research Database (Denmark)

    Legarth, Brian Nyvang

    2015-01-01

    A unit cell approach is adopted to numerically analyze the effect of reinforcement size on fracture evolution in metal matrix composites. The matrix material shows plastic size-effects and is modeled by an anisotropic version of the single parameter strain-gradient (higher-order) plasticity model...

  10. Elasto-plastic strain analysis by a semi-analytical method

    Indian Academy of Sciences (India)

    Debabrata Das; Prasanta Sahoo; Kashinath Saha

    2008-08-01

    The aim of this paper is to develop a simulation model of large deformation problems following a semi-analytical method, incorporating the complications of geometric and material non-linearity in the formulation. The solution algorithm is based on the method of energy principle in structural mechanics, as applicable for conservative systems. A one-dimensional solid circular bar problem has been solved in post-elastic range assuming linear elastic, linear strain hardening material behaviour. Type of loading includes uniform uniaxial loading and gravity loading due to body force, whereas the geometry of the bar is considered to be non-uniformly taper. Results are validated successfully with benchmark solution and some new results have also been reported. The location of initiation of elasto-plastic front and its growth are found to be functions of geometry of the bar and loading conditions. Some indicative results have been presented for static and dynamic problems and the solution methodology developed for one-dimension has been extended to the elasto-plastic analysis of two-dimensional strain field problems of a rotating disk.

  11. CYCLIC PLASTIC BEHAVIOUR OF UFG COPPER UNDER CONTROLLED STRESS AND STRAIN LOADING

    Directory of Open Access Journals (Sweden)

    Lucie Navrátilová

    2012-01-01

    Full Text Available The influence of stress- and strain-controlled loading on microstructure and cyclic plastic behaviour of ultrafine-grained copper prepared by equal channel angular pressing was examined. The stability of microstructure is a characteristic feature for stress-controlled test whereas grain coarsening and development of bimodal structure was observed after plastic strain-controlled tests. An attempt to explain the observed behaviour was made.

  12. Energy Harvesting Wireless Strain Networks Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Prime Research LC (PPLC) and Virginia Tech (VT) propose to develop an energy harvesting wireless strain node technology that utilizes single-crystal piezoelectric...

  13. Monte Carlo calculation of radiation energy absorbed in plastic scintillators

    Energy Technology Data Exchange (ETDEWEB)

    Mainardi, R.T.; Bonzi, E.V. [Universidad Nacional de Cordoba (Argentina). Facultad de Matematica, Astronomia y Fisica

    1995-05-01

    Monte Carlo calculations of the rate of absorbed energy from a photon beam were carried out to compare the response of commercial plastic scintillators with that of air in the energy region below 1 MeV. We have found that for photon energies above 100 keV, the response of different kinds of plastics is proportional to that of air, while below this value of energy, we have obtained differences between the responses of plastics and air. In a literature search, we have also found discrepancies with other authors as well as among them. In this paper, we investigate the possibilities of eliminating these differences and explaining discrepancies. We found that doping a plastic scintillator with silicon makes the composite materials behave like air from 2 keV up to 600 keV, making the ratio of absorbed energy constant. This energy region is of interest in radiology and surface radiotherapy and we conclude that a plastic scintillator with truly air-equivalent behavior is of importance to carry out more precise dosimetry. Other elements such as fluorine and magnesium were also considered, but silicon was found to be more appropriate due to its greater atomic number and its interchangeability with carbon in hydrocarbon molecules. (author).

  14. Reassessing the Plastic Hinge Model for Energy Dissipation of Axially Loaded Columns

    Directory of Open Access Journals (Sweden)

    R. M. Korol

    2014-01-01

    Full Text Available This paper investigates the energy dissipation potential of axially loaded columns and evaluates the use of a plastic hinge model for analysis of hi-rise building column collapse under extreme loading conditions. The experimental program considered seven axially loaded H-shaped extruded aluminum structural section columns having slenderness ratios that would be typical of floor-to-ceiling heights in buildings. All seven test specimens initially experienced minor-axis overall buckling followed by formation of a plastic hinge at the mid-height region, leading to local buckling of the flanges on the compression side of the plastic hinge, and eventual folding of the compression flanges. The experimental energy absorption, based on load-displacement relations, was compared to the energy estimates based on section plastic moment resistance based on measured yield stress and based on measured hinge rotations. It was found that the theoretical plastic hinge model underestimates a column’s actual ability to absorb energy by a factor in the range of 3 to 4 below that obtained from tests. It was also noted that the realizable hinge rotation is less than 180°. The above observations are based, of course, on actual columns being able to sustain high tensile strains at hinge locations without fracturing.

  15. Automobile materials competition: energy implications of fiber-reinforced plastics

    Energy Technology Data Exchange (ETDEWEB)

    Cummings-Saxton, J.

    1981-10-01

    The embodied energy, structural weight, and transportation energy (fuel requirement) characteristics of steel, fiber-reinforced plastics, and aluminum were assessed to determine the overall energy savings of materials substitution in automobiles. In body panels, a 1.0-lb steel component with an associated 0.5 lb in secondary weight is structurally equivalent to a 0.6-lb fiber-reinforced plastic component with 0.3 lb in associated secondary weight or a 0.5-lb aluminum component with 0.25 lb of secondary weight. (Secondary weight refers to the combined weight of the vehicle's support structure, engine, braking system, and drive train, all of which can be reduced in response to a decrease in total vehicle weight.) The life cycle transportation energy requirements of structurally equivalent body panels (including their associated secondary weights) are 174.4 x 10/sup 3/ Btu for steel, 104.6 x 10/sup 3/ Btu for fiber-reinforced plastics, and 87.2 x 10/sup 3/ Btu for aluminum. The embodied energy requirements are 37.2 x 10/sup 3/ Btu for steel, 22.1 x 10/sup 3/ Btu for fiber-reinforced plastics, and 87.1 x 10/sup 3/ Btu for aluminum. These results can be combined to yield total energy requirements of 211.6 x 10/sup 3/ Btu for steel, 126.7 x 10/sup 3/ Btu for fiber-reinforced plastics, and 174.3 x 10/sup 3/ Btu for aluminum. Fiber-reinforced plastics offer the greatest improvements over steel in both embodied and total energy requirements. Aluminum achieves the greatest savings in transportation energy.

  16. Generalizing J2 flow theory: Fundamental issues in strain gradient plasticity

    Institute of Scientific and Technical Information of China (English)

    John W. Hutchinson

    2012-01-01

    It has not been a simple matter to obtain a sound extension of the classical J2 flow theory of plasticity that incorporates a dependence on plastic strain gradients and that is capable of capturing size-dependent behaviour of metals at the micron scale.Two classes of basic extensions of classical J2 theory have been proposed:one with increments in higher order stresses related to increments of strain gradients and the other characterized by the higher order stresses themselves expressed in terms of increments of strain gradients. The theories proposed by Muhlhaus and Aifantis in 1991 and Fleck and Hutchinson in 2001 are in the first class,and,as formulated,these do not always satisfy thermodynamic requirements on plastic dissipation.On the other hand,theories of the second class proposed by Gudmundson in 2004 and Gurtin and Anand in 2009 have the physical deficiency that the higher order stress quantities can change discontinuously for bodies subject to arbitrarily small load changes.The present paper lays out this background to the quest for a sound phenomenological extension of the rateindependent J2 flow theory of plasticity to include a dependence on gradients of plastic strain.A modification of the Fleck-Hutchinson formulation that ensures its thermo dynamic integrity is presented and contrasted with a comparable formulation of the second class where in the higher order stresses are expressed in terms of the plastic strain rate.Both versions are constructed to reduce to the classical J2 flow theory of plasticity when the gradients can be neglected and to coincide with the simpler and more readily formulated J2 deformation theory of gradient plasticity for deformation histories characterized by proportional straining.

  17. Modelling plastic deformation of metals over a wide range of strain rates using irreversible thermodynamics

    NARCIS (Netherlands)

    Huang, M.; Rivera-Diaz-del-Castillo, P.E.J.; Bouaziz, O.; Van der Zwaag, S.

    2009-01-01

    Based on the theory of irreversible thermodynamics, the present work proposes a dislocation-based model to describe the plastic deformation of FCC metals over wide ranges of strain rates. The stress-strain behaviour and the evolution of the average dislocation density are derived. It is found that t

  18. Prediction of thermal strains in fibre reinforced plastic matrix by discretisation of the temperature exposure history

    Science.gov (United States)

    Ngoy, E. K.

    2016-07-01

    Prediction of environmental effects on fibre reinforced plastics habitually is made difficult due to the complex variability of the natural service environment. This paper suggests a method to predict thermal strain distribution over the material lifetime by discretisation of the exposure history. Laboratory results show a high correlation between predicted and experimentally measured strain distribution

  19. Suppressed plastic deformation at blunt crack tips due to strain gradient effects

    DEFF Research Database (Denmark)

    Mikkelsen, Lars Pilgaard; Goutianos, Stergios

    2009-01-01

    Large deformation gradients occur near a crack-tip and strain gradient dependent crack-tip deformation and stress fields are expected. Nevertheless, for material length scales much smaller than the scale of the deformation gradients, a conventional elastic-plastic solution is obtained. On the other...... hand, for significant large material length scales, a conventional elastic solution is obtained. This transition in behaviour is investigated based on a finite strain version of the Fleck-Hutchinson strain gradient plasticity model from 2001. The predictions show that for a wide range of material...

  20. Unexpected Patterns of Plastic Energy Allocation in Stochastic Environments

    Science.gov (United States)

    Fischer, Barbara; Taborsky, Barbara; Dieckmann, Ulf

    2012-01-01

    When environmental conditions vary stochastically, individuals accrue fitness benefits by exhibiting phenotypic plasticity. Here we analyze a general dynamic-programming model describing an individual’s optimal energy allocation in a stochastic environment. After maturation, individuals repeatedly decide how to allocate incoming energy between reproduction and maintenance. We analyze the optimal fraction of energy invested in reproduction and the resultant degree of plasticity in dependence on environmental variability and predictability. Our analyses reveal unexpected patterns of optimal energy allocation. When energy availability is low, all energy is allocated to reproduction, although this implies that individuals will not survive after reproduction. Above a certain threshold of energy availability, the optimal reproductive investment decreases to a minimum and even vanishes entirely in highly variable environments. With further improving energy availability, optimal reproductive investment gradually increases again. Costs of plasticity affect this allocation pattern only quantitatively. Our results show that optimal reproductive investment does not increase monotonically with growing energy availability and that small changes in energy availability can lead to major variations in optimal energy allocation. Our results help to unify two apparently opposing predictions from life-history theory, that organisms should increase reproductive investment both with improved environmental conditions and when conditions deteriorate (“terminal investment”). PMID:19196158

  1. Finite element implementation and numerical issues of strain gradient plasticity with application to metal matrix composites

    DEFF Research Database (Denmark)

    Frederiksson, Per; Gudmundson, Peter; Mikkelsen, Lars Pilgaard

    2009-01-01

    A framework of finite element equations for strain gradient plasticity is presented. The theoretical framework requires plastic strain degrees of freedom in addition to displacements and a plane strain version is implemented into a commercial finite element code. A couple of different elements...... of quadrilateral type are examined and a few numerical issues are addressed related to these elements as well as to strain gradient plasticity theories in general. Numerical results are presented for an idealized cell model of a metal matrix composite under shear loading. It is shown that strengthening due...... to fiber size is captured but strengthening due to fiber shape is not. A few modelling aspects of this problem are discussed as well. An analytic solution is also presented which illustrates similarities to other theories....

  2. Mode I and mixed mode crack-tip fields in strain gradient plasticity

    DEFF Research Database (Denmark)

    Goutianos, Stergios

    2011-01-01

    Strain gradients develop near the crack-tip of Mode I or mixed mode cracks. A finite strain version of the phenomenological strain gradient plasticity theory of Fleck–Hutchinson (2001) is used here to quantify the effect of the material length scales on the crack-tip stress field for a sharp...... stationary crack under Mode I and mixed mode loading. It is found that for material length scales much smaller than the scale of the deformation gradients, the predictions converge to conventional elastic–plastic solutions. For length scales sufficiently large, the predictions converge to elastic solutions....... Thus, the range of length scales over which a strain gradient plasticity model is necessary is identified. The role of each of the three material length scales, incorporated in the multiple length scale theory, in altering the near-tip stress field is systematically studied in order to quantify...

  3. PLASTIC DEFORMATION BEHAVIOR OF ELECTROFORMED COPPER LINER OF SHAPED CHARGE AT DIFFERENT STRAIN RATES

    Institute of Scientific and Technical Information of China (English)

    H.Y.Gao; Q.Sun

    2003-01-01

    The paper deals with different plastic deformation behavior of electroformed copper liner of shaped charge,depormed at high strain rate(about 1×107s-1) and normal strain rate (4×10-4s-1).The crystallographic orientation distribution of grains in recovered slugs which had undergone high-strain-rate plastic deformation during ex-plosive detonation was investigated by electron backscattering Kikuchi pattern tech-nique.Cellualar structures formed by tangled disocations and sub-grain boundaries consisting of dislocation arrays were detected in the recovered slugs.Some twins and slip dislocations were observed in specimen deformed at normal strain rate.It was found that dynamic recovery and recrystallization take place during high-strain-rate deformation due to the temperature rising,whereas the conventional slip mechanism operates during deformation at normal strain rate.

  4. Effect of transient change in strain rate on plastic flow behaviour of low carbon steel

    Indian Academy of Sciences (India)

    A Ray; P Barat; P Mukherjee; A Sarkar; S K Bandyopadhyay

    2007-02-01

    Plastic flow behaviour of low carbon steel has been studied at room temperature during tensile deformation by varying the initial strain rate of 3.3 × 10-4 s-1 to a final strain rate ranging from 1.33 × 10-3 s-1 to 2 × 10-3 s-1 at a fixed engineering strain of 12%. Haasen plot revealed that the mobile dislocation density remained almost invariant at the juncture where there was a sudden increase in stress with a change in strain rate and the plastic flow was solely dependent on the velocity of mobile dislocations. In that critical regime, the variation of stress with time was fitted with a Boltzmann type Sigmoid function. The increase in stress was found to increase with final strain rate and the time elapsed in attaining these stress values showed a decreasing trend. Both of these parameters saturated asymptotically at a higher final strain rate.

  5. Validation of a crystal plasticity model using high energy diffraction microscopy

    Science.gov (United States)

    Beaudoin, A. J.; Obstalecki, M.; Storer, R.; Tayon, W.; Mach, J.; Kenesei, P.; Lienert, U.

    2012-03-01

    High energy diffraction microscopy is used to measure the crystallographic orientation and evolution of lattice strain in an Al-Li alloy. The relative spatial arrangement of the several pancake-shaped grains in a tensile sample is determined through in situ and ex situ techniques. A model for crystal plasticity with continuity of lattice spin is posed, where grains are represented by layers in a finite element mesh following the arrangement indicated by experiment. Comparison is drawn between experiment and simulation.

  6. Validation of a Crystal Plasticity Model Using High Energy Diffraction Microscopy

    Science.gov (United States)

    Beaudoin, A. J.; Obstalecki, M.; Storer, R.; Tayon, W.; Mach, J.; Kenesei, P.; Lienert, U.

    2012-01-01

    High energy diffraction microscopy is used to measure the crystallographic orientation and evolution of lattice strain in an Al Li alloy. The relative spatial arrangement of the several pancake-shaped grains in a tensile sample is determined through in situ and ex situ techniques. A model for crystal plasticity with continuity of lattice spin is posed, where grains are represented by layers in a finite element mesh following the arrangement indicated by experiment. Comparison is drawn between experiment and simulation.

  7. Suppression of dislocations at high strain rate deformation in a twinning-induced plasticity steel

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Z.Y. [Shenzhen Institute of Research and Innovation, The University of Hong Kong, Shenzhen (China); Department of Mechanical Engineering, The University of Hong Kong, Hong Kong (China); Huang, W., E-mail: whuang@szu.edu.cn [Department of Civil Engineering, Shenzhen University, Shenzhen (China); Huang, M.X., E-mail: mxhuang@hku.hk [Shenzhen Institute of Research and Innovation, The University of Hong Kong, Shenzhen (China); Department of Mechanical Engineering, The University of Hong Kong, Hong Kong (China)

    2015-03-25

    The increase of strain rate generally enhances dislocation evolution in face-centred cubic (FCC) metals. However, by synchrotron X-ray diffraction experiments, the present work demonstrates for the first time that a higher strain rate leads to a lower dislocation density in a twinning-induced plasticity steel with an FCC structure. This unexpected suppression of dislocation evolution has been attributed to the temperature increase due to dissipative heating at high strain rate deformation.

  8. Response of Polypmeric Foams and ABS Plastics to High Strain Rate Loading

    Science.gov (United States)

    Dick, Richard; Chang, Peter; Fourney, William

    1999-06-01

    The split-Hopkinson pressure bar (SHPB) technique was utilized to obtain high strain rate response data for low-density foams and solid ABS and polypropylene plastics. General Motors provided the materials for this study. These materials are used in the interior panels of automobiles. Because the foams have a very low impedance, polycarbonate bars were used to acquire the strain rate data in the 100 to 1600 per second range. An aluminum SHPB was used to obtain the solid plastics data that covered strain rates of 1000 to 4000 pre second. The experimental data indicate that the foams over the test range are only slightly strain rate dependent while the polypropylene appears to be strain rate independent above 1000 per second and the ABS plastics are strain rate independent above 3000 per second. The projectile length was varied to provide a wide range of induced strains ranging from 10 to 70 per cent for the foams and up to 20 per cent for the plastic materials.

  9. Isogeometric Analysis of Nearly Incompressible Large Strain Plasticity

    Science.gov (United States)

    2011-11-01

    distribution unlimited 13. SUPPLEMENTARY NOTES 14. ABSTRACT We study the behavior of NURBS -based Isogeometric Analysis on problems of large-deformation...plasticity. We evaluate the performance of standard NURBS elements and elements based on the F formulation of Elguedj et al. (T. Elguedj, Y. Bazilevs... NURBS elements, Com- puter Methods in Applied Mechanics and Engineering, 197 (2008), 2732{2762). We determine that standard measures of evaluation

  10. The development of strain anisotropy during plastic deformation of an aluminium polycrystal

    Energy Technology Data Exchange (ETDEWEB)

    Korsunsky, A.M. [Oxford Univ. (United Kingdom). Dept. of Engineering Science; Daymond, M.R. [ISIS Facility, Rutherford Appleton Lab., Chilton, Oxon (United Kingdom); Wells, K.E. [Dept. of Mechanical, Materials and Mfg. Engineering, Univ. of Newcastle (United Kingdom)

    2000-07-01

    To measure internal strains in an Al MMC, time-of-flight (TOF) neutron diffraction was used on the ENGIN instrument at ISIS, RAL, in Oxfordshire, and a monochromated X-ray beam was employed on the BM16 beamline at the ESRF in Grenoble. The development of intergranular stresses between groups of grains possessing certain crystallographic orientations was studied using diffraction of penetrating radiation. Due to aluminium's highly isotropic elastic modulus, the variation of measured strains in the alloy matrix with orientation can be attributed to the anisotropy of the crystal yield surface and plastic flow parameters. A simple illustrative model is presented which explains the observed correlation between the amount of plastic strain (PS) and the measured anisotropy strain (AS) values. In particular, the model explains why a linear relationship is observed between AS and PS for low strain values, and how saturation of AS sets in at higher imposed PS levels. (orig.)

  11. PLASTIC DEFORMATION BEHAVIOR OF ELECTROFORMED COPPER LINER OF SHAPED CHARGE AT DIFFERENT STRAIN RATES

    Institute of Scientific and Technical Information of China (English)

    H.Y. Gao; W.H. Tian; A.L. Fan; Q. Sun

    2003-01-01

    The paper deals with different plastic deformation behavior of electroformed copperliner of shaped charge, deformed at high strain rate (about 1×107 s-1) and normalstrain rate (4×10-4 s-1). The crystallographic orientation distribution of grains inrecovered slugs which had undergone high-strain-rate plastic deformation during ex-plosive detonation was investigated by electron backscattering Kikuchi pattern tech-nique. Cellular structures formed by tangled dislocations and sub-grain boundariesconsisting of dislocation arrays were detected in the recovered slugs. Some twins andslip dislocations were observed in specimen deformed at normal strain rate. It wasfound that dynamic recovery and recrystallization take place during high-strain-ratedeformation due to the temperature rising, whereas the conventional slip mechanismoperates during deformation at normal strain rate.

  12. Strain gradient crystal plasticity: A continuum mechanics approach to modeling micro-structural evolution

    DEFF Research Database (Denmark)

    El-Naaman, Salim Abdallah; Nielsen, Kim Lau; Niordson, Christian Frithiof

    2015-01-01

    In agreement with dislocation theory, recent experiments show, both quantitatively and qualitatively, how geometrically necessary dislocations (GNDs) distribute in dislocation wall and cell structures. Hence, GND density fields are highly localized with large gradients and discontinuities occurring...... between the cells. This behavior is not typical for strain gradient crystal plasticity models. The present study employs a higher order extension of conventional crystal plasticity theory in which the viscous slip rate is influenced by the gradients of GND densities through a back stress...

  13. Strain gradient crystal plasticity: A continuum mechanics approach to modeling micro-structural evolution

    DEFF Research Database (Denmark)

    El-Naaman, Salim Abdallah; Nielsen, Kim Lau; Niordson, Christian Frithiof

    2015-01-01

    In agreement with dislocation theory, recent experiments show, both quantitatively and qualitatively, how geometrically necessary dislocations (GNDs) distribute in dislocation wall and cell structures. Hence, GND density fields are highly localized with large gradients and discontinuities occurring...... between the cells. This behavior is not typical for strain gradient crystal plasticity models. The present study employs a higher order extension of conventional crystal plasticity theory in which the viscous slip rate is influenced by the gradients of GND densities through a back stress...

  14. Metabolic regulation of neuronal plasticity by the energy sensor AMPK.

    Directory of Open Access Journals (Sweden)

    Wyatt B Potter

    Full Text Available Long Term Potentiation (LTP is a leading candidate mechanism for learning and memory and is also thought to play a role in the progression of seizures to intractable epilepsy. Maintenance of LTP requires RNA transcription, protein translation and signaling through the mammalian Target of Rapamycin (mTOR pathway. In peripheral tissue, the energy sensor AMP-activated Protein Kinase (AMPK negatively regulates the mTOR cascade upon glycolytic inhibition and cellular energy stress. We recently demonstrated that the glycolytic inhibitor 2-deoxy-D-glucose (2DG alters plasticity to retard epileptogenesis in the kindling model of epilepsy. Reduced kindling progression was associated with increased recruitment of the nuclear metabolic sensor CtBP to NRSF at the BDNF promoter. Given that energy metabolism controls mTOR through AMPK in peripheral tissue and the role of mTOR in LTP in neurons, we asked whether energy metabolism and AMPK control LTP. Using a combination of biochemical approaches and field-recordings in mouse hippocampal slices, we show that the master regulator of energy homeostasis, AMPK couples energy metabolism to LTP expression. Administration of the glycolytic inhibitor 2-deoxy-D-glucose (2DG or the mitochondrial toxin and anti-Type II Diabetes drug, metformin, or AMP mimetic AICAR results in activation of AMPK, repression of the mTOR pathway and prevents maintenance of Late-Phase LTP (L-LTP. Inhibition of AMPK by either compound-C or the ATP mimetic ara-A rescues the suppression of L-LTP by energy stress. We also show that enhanced LTP via AMPK inhibition requires mTOR signaling. These results directly link energy metabolism to plasticity in the mammalian brain and demonstrate that AMPK is a modulator of LTP. Our work opens up the possibility of using modulators of energy metabolism to control neuronal plasticity in diseases and conditions of aberrant plasticity such as epilepsy.

  15. Waste-to-energy: Dehalogenation of plastic-containing wastes.

    Science.gov (United States)

    Shen, Yafei; Zhao, Rong; Wang, Junfeng; Chen, Xingming; Ge, Xinlei; Chen, Mindong

    2016-03-01

    The dehalogenation measurements could be carried out with the decomposition of plastic wastes simultaneously or successively. This paper reviewed the progresses in dehalogenation followed by thermochemical conversion of plastic-containing wastes for clean energy production. The pre-treatment method of MCT or HTT can eliminate the halogen in plastic wastes. The additives such as alkali-based metal oxides (e.g., CaO, NaOH), iron powders and minerals (e.g., quartz) can work as reaction mediums and accelerators with the objective of enhancing the mechanochemical reaction. The dehalogenation of waste plastics could be achieved by co-grinding with sustainable additives such as bio-wastes (e.g., rice husk), recyclable minerals (e.g., red mud) via MCT for solid fuels production. Interestingly, the solid fuel properties (e.g., particle size) could be significantly improved by HTT in addition with lignocellulosic biomass. Furthermore, the halogenated compounds in downstream thermal process could be eliminated by using catalysts and adsorbents. Most dehalogenation of plastic wastes primarily focuses on the transformation of organic halogen into inorganic halogen in terms of halogen hydrides or salts. The integrated process of MCT or HTT with the catalytic thermal decomposition is a promising way for clean energy production. The low-cost additives (e.g., red mud) used in the pre-treatment by MCT or HTT lead to a considerable synergistic effects including catalytic effect contributing to the follow-up thermal decomposition.

  16. Derivation of Relations and Analysis of Tube Bending Processes Using Discontinuous Fields of Plastic Strains

    Science.gov (United States)

    Śloderbach, Z.

    2015-05-01

    The generalized strain scheme in bending metal tubes at bending machines with the use of a mandrel presented in Śloderbach (1999; 2002; 20131,2; 2014) satisfies initial and boundary kinematic conditions of bending, conditions of continuity and inseparability of strains. This paper introduces three formal simplifications gradually imposed into forms of principal components of the generalized strain model giving suitable simplifications of the 1st, 2nd and 3rd types. Such mathematical simplifications cause that the obtained strain fields do not satisfy the condition of consistency of displacements and strain continuity. The simplified methods determine safer values of the wall thickness than those from the generalized continuous strain scheme. The condition of plastic incompressibility was used for the derivation of an expression for distribution of wall thickness of the bent elbow in the layers subjected to tension and compression for three examples of discontinuous kinematic strain fields.

  17. Pre-strain direction effect on microstructure evolution and energy storage process during uniaxial tension of austenitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Maj, M; Oliferuk, W, E-mail: mimaj@ippt.gov.p [Institute of Fundamental Technological Research Polish Academy of Sciences, Pawinskiego 5b, 02-106 Warsaw (Poland)

    2010-07-01

    In the present paper the influence of pre-strain direction on energy balance during deformation of austenitic steel was investigated and the analysis of microscopic phenomena responsible for this influence was performed. The specimens with different pre-strain directions were prepared and the ratio of the stored energy increment to plastic work increment, called energy storage rate, as a function of plastic strain was experimentally determined. At the initial stage of plastic deformation of annealed materials this quantity vs. plastic strain has a maximum. It has been shown that for specimens strained in the same direction as pre-strain the energy storage rate decreases monotonically with deformation while for specimens where strain path was changed, the maximum of the energy storage rate is observed (as in case of annealed material). The study of slip and microstructure evolution at meso- and micro-scales have shown that the change in pre-strain direction leads to the redistribution of internal stresses generated by incompatible slip in neighbouring grains of different orientation. Just after change in strain direction the accommodation of these stresses takes place not only by generation of geometrically necessary dislocations but also by micro-shear banding.

  18. On the localization of plastic strain under compression of LiF crystals

    Science.gov (United States)

    Barannikova, S. A.; Nadezhkin, M. V.; Zuev, L. B.

    2010-07-01

    The plastic flow localization patterns for alkali halide LiF crystals under compression have been investigated. The main spatiotemporal regularities of the strain localization at different stages of deformation hardening in the single crystals have been established. The relation has been traced between the orientation of localized strain zones and the crystallography of slip systems of the test specimens studied simultaneously by the double-exposure speckle photography and photoelasticity methods.

  19. Spacecraft Dynamic Characterization by Strain Energies Method

    Science.gov (United States)

    Bretagne, J.-M.; Fragnito, M.; Massier, S.

    2002-01-01

    In the last years the significant increase in satellite broadcasting demand, with the wide band communication dawn, has given a great impulse to the telecommunication satellite market. The big demand is translated from operators (such as SES/Astra, Eutelsat, Intelsat, Inmarsat, EuroSkyWay etc.) in an increase of orders of telecom satellite to the world industrials. The largest part of these telecom satellite orders consists of Geostationary platforms which grow more and more in mass (over 5 tons) due to an ever longer demanded lifetime (up to 20 years), and become more complex due to the need of implementing an ever larger number of repeaters, antenna reflectors and feeds, etc... In this frame, the mechanical design and verification of these large spacecraft become difficult and ambitious at the same time, driven by the dry mass limitation objective. By the Finite Element Method (FEM), and on the basis of the telecom satellite heritage of a world leader constructor such as Alcatel Space Industries it is nowadays possible to model these spacecraft in a realistic and confident way in order to identify the main global dynamic aspects such as mode shapes, mass participation and/or dynamic responses. But on the other hand, one of the main aims consists in identifying soon in a program the most critical aspects of the system behavior in the launch dynamic environment, such as possible dynamic coupling between the different subsystems and secondary structures of the spacecraft (large deployable reflectors, thrusters, etc.). To this aim a numerical method has been developed in the frame of the Alcatel SPACEBUS family program, using MSC/Nastran capabilities and it is presented in this paper. The method is based on Spacecraft sub-structuring and strain energy calculation. The method mainly consists of two steps : 1) subsystem modal strain energy ratio (with respect to the global strain energy); 2) subsystem strain energy calculation for each mode according to the base driven

  20. A deformation mechanism map for polycrystals modeled using strain gradient plasticity and interfaces that slide and separate

    DEFF Research Database (Denmark)

    Dahlberg, Carl F.O.; Faleskog, Jonas; Niordson, Christian Frithiof

    2013-01-01

    Small scale strain gradient plasticity is coupled with a model of grain boundaries that take into account the energetic state of a plastically strained boundary and the slip and separation between neighboring grains. A microstructure of hexagonal grains is investigated using a plane strain finite...... element model. The results show that three different microstructural deformation mechanisms can be identified. The standard plasticity case in which the material behaves as expected from coarse grained experiments, the nonlocal plasticity region where size of the microstructure compared to some intrinsic...

  1. New renewable source of energy from municipal solid waste plastics

    Energy Technology Data Exchange (ETDEWEB)

    Sarker, Moinuddin; Zaman, Ashiquz; Mamunor Rashid, Mohammad

    2010-09-15

    Renewable energy plays an important role in the supply of energy. When energy sources are used, the demand for fossil fuels is reduced. Emissions from the evaporation and combustion of these traditional fossil fuels contributing to a range of environmental and health problems, causing poor air quality, and emitting greenhouse gases that contribute to global warming. Alternative fuel created from domestic sources has been proposed as a solution to these problems and many alternative fuels are being developed based on solar, wind and biomass. Natural State Research has developed different alternative hydrocarbon fuel produced from abundant waste plastic materials.

  2. Three-dimensional frictional plastic strain partitioning during oblique rifting

    Science.gov (United States)

    Duclaux, Guillaume; Huismans, Ritske S.; May, Dave

    2017-04-01

    Throughout the Wilson cycle the obliquity between lithospheric plate motion direction and nascent or existing plate boundaries prompts the development of intricate three-dimensional tectonic systems. Where oblique divergence dominates, as in the vast majority of continental rift and incipient oceanic domains, deformation is typically transtensional and large stretching in the brittle upper crust is primarily achieved by the accumulation of displacement on fault networks of various complexity. In continental rift depressions such faults are initially distributed over tens to hundreds of kilometer-wide regions, which can ultimately stretch and evolve into passive margins. Here, we use high-resolution 3D thermo-mechanical finite element models to investigate the relative timing and distribution of localised frictional plastic deformation in the upper crust during oblique rift development in a simplified layered lithosphere. We vary the orientation of a wide oblique heterogeneous weak zone (representing a pre-existing geologic feature like a past orogenic domain), and test the sensitivity of the shear zones orientation to a range of noise distribution. These models allow us to assess the importance of material heterogeneities for controlling the spatio-temporal shear zones distribution in the upper crust during oblique rifting, and to discuss the underlying controls governing oblique continental breakup.

  3. A numerical investigation of grain shape and crystallographic texture effects on the plastic strain localization in friction stir weld zones

    Science.gov (United States)

    Romanova, V.; Balokhonov, R.; Batukhtina, E.; Shakhidjanov, V.

    2015-10-01

    Crystal plasticity approaches were adopted to build models accounting for the microstructure and texture observed in different friction stir weld zones. To this end, a numerical investigation of crystallographic texture and grain shape effects on the plastic strain localization in a friction stir weld of an aluminum-base alloy was performed. The presence of texture was found to give rise to pronounced mesoscale plastic strain localization.

  4. A numerical basis for strain-gradient plasticity theory: Rate-independent and rate-dependent formulations

    DEFF Research Database (Denmark)

    Nielsen, Kim Lau; Niordson, Christian Frithiof

    2014-01-01

    of a single plastic zone is analyzed to illustrate the agreement with earlier published results, whereafter examples of (ii) multiple plastic zone interaction, and (iii) elastic–plastic loading/unloading are presented. Here, the simple shear problem of an infinite slab constrained between rigid plates......–plastic loading/unloading and the interaction of multiple plastic zones, is proposed. The predicted model response is compared to the corresponding rate-dependent version of visco-plastic origin, and coinciding results are obtained in the limit of small strain-rate sensitivity. First, (i) the evolution...

  5. Attaining the rate-independent limit of a rate-dependent strain gradient plasticity theory

    DEFF Research Database (Denmark)

    El-Naaman, Salim Abdallah; Nielsen, Kim Lau; Niordson, Christian Frithiof

    2016-01-01

    The existence of characteristic strain rates in rate-dependent material models, corresponding to rate-independent model behavior, is studied within a back stress based rate-dependent higher order strain gradient crystal plasticity model. Such characteristic rates have recently been observed...... for steady-state processes, and the present study aims to demonstrate that the observations in fact unearth a more widespread phenomenon. In this work, two newly proposed back stress formulations are adopted to account for the strain gradient effects in the single slip simple shear case, and characteristic...

  6. Hardening in Two-Phase Materials. II. Plastic Strain and Mean Stress Hardening Rate

    DEFF Research Database (Denmark)

    Lilholt, Hans

    1977-01-01

    The strain parameters which are relevant in a tensile experiment, are analysed and related to the geometry of deformation and to the mean stress of two-phase materials. The hardening rate of the mean stress with respect to plastic strain is found to be useful in comparison between experiments and...... and theories, and it allows theories to be probed over a range of strains. Previous experiments on the fibre-reinforced material of copper-tungsten are analysed in relation to the geometry of deformation....

  7. The Microstructure Evolution of Dual-Phase Pipeline Steel with Plastic Deformation at Different Strain Rates

    Science.gov (United States)

    Ji, L. K.; Xu, T.; Zhang, J. M.; Wang, H. T.; Tong, M. X.; Zhu, R. H.; Zhou, G. S.

    2017-07-01

    Tensile properties of the high-deformability dual-phase ferrite-bainite X70 pipeline steel have been investigated at room temperature under the strain rates of 2.5 × 10-5, 1.25 × 10-4, 2.5 × 10-3, and 1.25 × 10-2 s-1. The microstructures at different amount of plastic deformation were examined by using scanning and transmission electron microscopy. Generally, the ductility of typical body-centered cubic steels is reduced when its stain rate increases. However, we observed a different ductility dependence on strain rates in the dual-phase X70 pipeline steel. The uniform elongation (UEL%) and elongation to fracture (EL%) at the strain rate of 2.5 × 10-3 s-1 increase about 54 and 74%, respectively, compared to those at 2.5 × 10-5 s-1. The UEL% and EL% reach to their maximum at the strain rate of 2.5 × 10-3 s-1. This phenomenon was explained by the observed grain structures and dislocation configurations. Whether or not the ductility can be enhanced with increasing strain rates depends on the competition between the homogenization of plastic deformation among the microconstituents (ultra-fine ferrite grains, relatively coarse ferrite grains as well as bainite) and the progress of cracks formed as a consequence of localized inconsistent plastic deformation.

  8. Dynamic recrystallization of electroformed copper liners of shaped charges in high-strain-rate plastic deformation

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The microstructures in the electroformed copper liners of shaped charges after high-strain-rate plastic deformation were investigated by transmission electron microscopy (TEM). Meanwhile, the orientation distribution of the grains in the recovered slug was examined by the electron backscattering Kikuchi pattern (EBSP) technique. EBSP analysis illustrated that unlike the as-formed electroformed copper linersof shaped charges the grain orientations in the recovered slug are distributed along randomly all the directions after undergoing heavily strain deformation at high-strain rate. Optical microscopy shows a typical recrystallization structure, and TEM examination reveals dislocation cells existed in the thin foil specimen. These results indicate that dynamic recovery and recrystallization occur during this plastic deformation process, and the associated deformation temperature is considered to be higher than 0.6 times the melting point of copper.

  9. Energy Efficient Sparse Connectivity from Imbalanced Synaptic Plasticity Rules.

    Directory of Open Access Journals (Sweden)

    João Sacramento

    2015-06-01

    Full Text Available It is believed that energy efficiency is an important constraint in brain evolution. As synaptic transmission dominates energy consumption, energy can be saved by ensuring that only a few synapses are active. It is therefore likely that the formation of sparse codes and sparse connectivity are fundamental objectives of synaptic plasticity. In this work we study how sparse connectivity can result from a synaptic learning rule of excitatory synapses. Information is maximised when potentiation and depression are balanced according to the mean presynaptic activity level and the resulting fraction of zero-weight synapses is around 50%. However, an imbalance towards depression increases the fraction of zero-weight synapses without significantly affecting performance. We show that imbalanced plasticity corresponds to imposing a regularising constraint on the L1-norm of the synaptic weight vector, a procedure that is well-known to induce sparseness. Imbalanced plasticity is biophysically plausible and leads to more efficient synaptic configurations than a previously suggested approach that prunes synapses after learning. Our framework gives a novel interpretation to the high fraction of silent synapses found in brain regions like the cerebellum.

  10. In-situ strain localization analysis in low density transformation-twinning induced plasticity steel using digital image correlation

    Science.gov (United States)

    Eskandari, M.; Yadegari-Dehnavi, M. R.; Zarei-Hanzaki, A.; Mohtadi-Bonab, M. A.; Basu, R.; Szpunar, J. A.

    2015-04-01

    The effect of deformation temperature on the strain localization has been evaluated by an adapted digital image correlation (DIC) technique during tensile deformation. The progress of strain localization was traced by the corresponding strain maps. The electron backscatter diffraction analysis and tint etching technique were utilized to determine the impact of martensitic transformation and deformation twinning on the strain localization in both elastic and plastic regimes. In elastic regime the narrow strain bands which are aligned perpendicular to the tension direction were observed in temperature range of 25 to 180 °C due to the stress-assisted epsilon martensite. The strain bands were disappeared by increasing the temperature to 300 °C and reappeared at 400 °C due to the stress-assisted deformation twinning. In plastic regime strain localization continued at 25 °C and 180 °C due to the strain-induced alfa-martensite and deformation twinning, respectively. The intensity of plastic strain localization was increased by increasing the strain due to the enhancement of martensite and twin volume fraction. The plastic strain showed more homogeneity at 300 °C due to the lack of both strain-induced martensite and deformation twinning. Effect of deformation mechanism by changing temperature on strain localization is investigated by digital image correlation. EBSD technique is served to validate deformation mechanism as well as microstructural evolution. Strain induced martensite as well as deformation twinning is activated in the present steel affecting strain localization.

  11. Explicit mixed strain-displacement finite elements for compressible and quasi-incompressible elasticity and plasticity

    Science.gov (United States)

    Cervera, M.; Lafontaine, N.; Rossi, R.; Chiumenti, M.

    2016-09-01

    This paper presents an explicit mixed finite element formulation to address compressible and quasi-incompressible problems in elasticity and plasticity. This implies that the numerical solution only involves diagonal systems of equations. The formulation uses independent and equal interpolation of displacements and strains, stabilized by variational subscales. A displacement sub-scale is introduced in order to stabilize the mean-stress field. Compared to the standard irreducible formulation, the proposed mixed formulation yields improved strain and stress fields. The paper investigates the effect of this enhancement on the accuracy in problems involving strain softening and localization leading to failure, using low order finite elements with linear continuous strain and displacement fields ( P1 P1 triangles in 2D and tetrahedra in 3D) in conjunction with associative frictional Mohr-Coulomb and Drucker-Prager plastic models. The performance of the strain/displacement formulation under compressible and nearly incompressible deformation patterns is assessed and compared to analytical solutions for plane stress and plane strain situations. Benchmark numerical examples show the capacity of the mixed formulation to predict correctly failure mechanisms with localized patterns of strain, virtually free from any dependence of the mesh directional bias. No auxiliary crack tracking technique is necessary.

  12. Micromorphic approach for gradient-extended thermo-elastic-plastic solids in the logarithmic strain space

    Science.gov (United States)

    Aldakheel, Fadi

    2017-05-01

    The coupled thermo-mechanical strain gradient plasticity theory that accounts for microstructure-based size effects is outlined within this work. It extends the recent work of Miehe et al. (Comput Methods Appl Mech Eng 268:704-734, 2014) to account for thermal effects at finite strains. From the computational viewpoint, the finite element design of the coupled problem is not straightforward and requires additional strategies due to the difficulties near the elastic-plastic boundaries. To simplify the finite element formulation, we extend it toward the micromorphic approach to gradient thermo-plasticity model in the logarithmic strain space. The key point is the introduction of dual local-global field variables via a penalty method, where only the global fields are restricted by boundary conditions. Hence, the problem of restricting the gradient variable to the plastic domain is relaxed, which makes the formulation very attractive for finite element implementation as discussed in Forest (J Eng Mech 135:117-131, 2009) and Miehe et al. (Philos Trans R Soc A Math Phys Eng Sci 374:20150170, 2016).

  13. An Elastic Plastic Contact Model with Strain Hardening for the LAMMPS Granular Package

    Energy Technology Data Exchange (ETDEWEB)

    Kuhr, Bryan [Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States); Brake, Matthew Robert [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Component Science and Mechanics; Lechman, Jeremy B. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Nanoscale and Reactive Processes

    2015-03-01

    The following details the implementation of an analytical elastic plastic contact model with strain hardening for normal im pacts into the LAMMPS granular package. The model assumes that, upon impact, the co llision has a period of elastic loading followed by a period of mixed elastic plas tic loading, with contributions to each mechanism estimated by a hyperbolic seca nt weight function. This function is implemented in the LAMMPS source code as the pair style gran/ep/history. Preliminary tests, simulating the pouring of pure nickel spheres, showed the elastic/plastic model took 1.66x as long as similar runs using gran/hertz/history.

  14. Effect of hydrogen on plastic strain localization and fracture of steels

    Science.gov (United States)

    Nadjozhkin, M. V.; Lunev, A. G.; Li, Yu V.; Barannikova, S. A.

    2016-02-01

    The effect of interstitial hydrogen atoms on the mechanical properties and plastic strain localization patterns in tensile tested specimens of low-carbon steels have been studied using a double exposure speckle photography technique. It is found that the mechanical properties of low-carbon steels are affected adversely by hydrogen embrittlement. The deformation diagrams were examined for the deformed samples of low-carbon steels. These are found to show all the plastic flow stages: the linear, parabolic and pre-failure stages would occur for the respective values of the exponent n from the Ludwik-Holomon equation.

  15. Distribution of energy storage rate in area of strain localization during tension of austenitic steel

    Science.gov (United States)

    Oliferuk, W.; Maj, M.; Zembrzycki, K.

    2015-01-01

    The present work is devoted to experimental determination of the energy storage rate in the area of strain localization. The experimental procedure involves two complementary techniques: i.e. infrared thermography (IRT) and visible light imaging. The results of experiments have shown that during the evolution of plastic strain localization the energy storage rate in some areas of the deformed specimen drops to zero. To interpret the decrease of the energy storage rate in terms of micro-mechanisms, microstructural observations using electron back scattered diffraction (EBSC) were performed.

  16. Towards ultra-high ductility TRIP-assisted multiphase steels controlled by strain gradient plasticity effects

    Science.gov (United States)

    Hatami, M. K.; Pardoen, T.; Lacroix, G.; Berke, P.; Jacques, P. J.; Massart, T. J.

    2017-01-01

    TRansformation Induced Plasticity (TRIP) is a very effective mechanism to increase the strain hardening capacity of multiphase steels containing a fraction of metastable austenite, leading to both high strength and large uniform elongation. Excellent performances have been reached in the past 20 years, with recent renewed interest through the development of the 3rd generation of high strength steels often involving a TRIP effect. The microstructure and composition optimization is complex due to the interplay of coupled effects on the transformation kinetics and work hardening such as phase stability, size of retained austenite grains, temperature and loading path. In particular, recent studies have shown that the TRIP effect can only be quantitatively captured for realistic microstructures if strain gradient plasticity effects are taken into account, although direct experimental validation of this claim is missing. Here, an original computational averaging scheme is developed for predicting the elastoplastic response of TRIP aided multiphase steels based on a strain gradient plasticity model. The microstructure is represented by an aggregate of many elementary unit cells involving each a fraction of retained austenite with a specified stability. The model parameters, involving the transformation kinetics, are identified based on experimental tensile tests performed at different temperatures. The model is further assessed towards original experiments, involving temperature changes during deformation. A classical size independent plasticity model is shown unable to capture the TRIP effect on the mechanical response. Conversely, the strain gradient formulation properly predicts substantial variations of the strain hardening with deformation and temperature, hence of the uniform elongation in good agreement with the experiments. A parametric study is performed to get more insight on the effect of the material length scale as well as to determine optimum transformation

  17. A Novel Creep-Fatigue Life Prediction Model for P92 Steel on the Basis of Cyclic Strain Energy Density

    Science.gov (United States)

    Ji, Dongmei; Ren, Jianxing; Zhang, Lai-Chang

    2016-09-01

    A novel creep-fatigue life prediction model was deduced based on an expression of the strain energy density in this study. In order to obtain the expression of the strain energy density, the load-controlled creep-fatigue (CF) tests of P92 steel at 873 K were carried out. Cyclic strain of P92 steel under CF load was divided into elastic strain, applying and unloading plastic strain, creep strain, and anelastic strain. Analysis of cyclic strain indicates that the damage process of P92 steel under CF load consists of three stages, similar to pure creep. According to the characteristics of the strains above, an expression was defined to describe the strain energy density for each cycle. The strain energy density at stable stage is inversely proportional to the total strain energy density dissipated by P92 steel. However, the total strain energy densities under different test conditions are proportional to the fatigue life. Therefore, the expression of the strain energy density at stable stage was chosen to predict the fatigue life. The CF experimental data on P92 steel were employed to verify the rationality of the novel model. The model obtained from the load-controlled CF test of P92 steel with short holding time could predict the fatigue life of P92 steel with long holding time.

  18. A Novel Creep-Fatigue Life Prediction Model for P92 Steel on the Basis of Cyclic Strain Energy Density

    Science.gov (United States)

    Ji, Dongmei; Ren, Jianxing; Zhang, Lai-Chang

    2016-11-01

    A novel creep-fatigue life prediction model was deduced based on an expression of the strain energy density in this study. In order to obtain the expression of the strain energy density, the load-controlled creep-fatigue (CF) tests of P92 steel at 873 K were carried out. Cyclic strain of P92 steel under CF load was divided into elastic strain, applying and unloading plastic strain, creep strain, and anelastic strain. Analysis of cyclic strain indicates that the damage process of P92 steel under CF load consists of three stages, similar to pure creep. According to the characteristics of the strains above, an expression was defined to describe the strain energy density for each cycle. The strain energy density at stable stage is inversely proportional to the total strain energy density dissipated by P92 steel. However, the total strain energy densities under different test conditions are proportional to the fatigue life. Therefore, the expression of the strain energy density at stable stage was chosen to predict the fatigue life. The CF experimental data on P92 steel were employed to verify the rationality of the novel model. The model obtained from the load-controlled CF test of P92 steel with short holding time could predict the fatigue life of P92 steel with long holding time.

  19. Modelling plastic deformation of metals over a wide range of strain rates using irreversible thermodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Huang Mingxin; Rivera-Diaz-del-Castillo, Pedro E J; Zwaag, Sybrand van der [Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS, Delft (Netherlands); Bouaziz, Olivier, E-mail: mingxin.huang@arcelormittal.com [ArcelorMittal Maizieres, Research and Development, Voie Romaine-BP30320, 57283 Maizieres-les-Metz Cedex (France)

    2009-07-15

    Based on the theory of irreversible thermodynamics, the present work proposes a dislocation-based model to describe the plastic deformation of FCC metals over wide ranges of strain rates. The stress-strain behaviour and the evolution of the average dislocation density are derived. It is found that there is a transitional strain rate ({approx} 10{sup 4} s{sup -1}) over which the phonon drag effects appear, resulting in a significant increase in the flow stress and the average dislocation density. The model is applied to pure Cu deformed at room temperature and at strain rates ranging from 10{sup -5} to 10{sup 6} s{sup -1} showing good agreement with experimental results.

  20. Limit analysis of viscoplastic thick-walled cylinder and spherical shell under internal pressure using a strain gradient plasticity theory

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Plastic limit load of viscoplastic thick-walled cylinder and spherical shell subjected to internal pressure is investigated analytically using a strain gradient plastic-itv theory. As a result, the current solutions can capture the size effect at the micron scale. Numerical results show that the smaller the inner radius of the cylinder or spherical shell, the more significant the scale effects. Results also show that the size effect is more evident with increasing strain or strain-rate sensitivity index. The classical plastic-based solutions of the same problems are shown to be a special case of the present solution.

  1. Strain gradient plasticity-based modeling of hydrogen environment assisted cracking

    DEFF Research Database (Denmark)

    Martínez Pañeda, Emilio; Niordson, Christian Frithiof; P. Gangloff, Richard

    2016-01-01

    Finite element analysis of stress about a blunt crack tip, emphasizing finite strain and phenomenologicaland mechanism-based strain gradient plasticity (SGP) formulations, is integrated with electrochemical assessment of occluded-crack tip hydrogen (H) solubility and two H-decohesion models......; it is imperative to account for SGP in H cracking models. Predictions of the threshold stress intensity factor and H-diffusion limited Stage II crack growth rate agree with experimental data for a high strength austenitic Ni-Cusuperalloy (Monel®K-500) and two modern ultra-high strength martensitic steels (Aer...

  2. Response of plastic scintillators to low-energy photons.

    Science.gov (United States)

    Peralta, Luis; Rêgo, Florbela

    2014-08-21

    Diagnostic radiology typically uses x-ray beams between 25 and 150 kVp. Plastic scintillation detectors (PSDs) are potentially successful candidates as field dosimeters but careful selection of the scintillator is crucial. It has been demonstrated that they can suffer from energy dependence in the low-energy region, an undesirable dosimeter characteristic. This dependence is partially due to the nonlinear light yield of the scintillator to the low-energy electrons set in motion by the photon beam. In this work, PSDs made of PMMA, PVT or polystyrene were studied for the x-ray beam range 25 to 100 kVp. For each kVp data has been acquired for additional aluminium filtrations of 0.5, 1.0, 2.0 and 4.0 mm. Absolute dose in the point of measurement was obtained with an ionization chamber calibrated to dose in water. From the collected data, detector sensitivities were obtained as function of the beam kVp and additional filtration. Using Monte Carlo simulations relative scintillator sensitivities were computed. For some of the scintillators these sensitivities show strong energy-dependence for beam average energy below 35 keV for each additional filtration but fair constancy above. One of the scintillators (BC-404) has smaller energy-dependence at low photon average energy and could be considered a candidate for applications (like mammography) where beam energy has small span.

  3. Elastic-Plastic Strain Acceptance Criteria for Structures Subject to Rapidly Applied Transient Dynamic Loading

    Energy Technology Data Exchange (ETDEWEB)

    W.R. Solonick

    2003-04-01

    Rapidly applied transient dynamic loads produce stresses and deflections in structures that typically exceed those from static loading conditions. Previous acceptance criteria for structures designed for rapidly applied transient dynamic loading limited stresses to those determined from elastic analysis. Different stress limits were established for different grades of structure depending upon the amount of permanent set considered acceptable. Structure allowed to sustain very limited permanent set is designed to stress limits not significantly greater than yield stress. Greater permanent set in structure under rapidly applied transient dynamic loading conditions is permitted by establishing stress limits that are significantly greater than yield stress but still provide adequate safety margin (with respect to failure). This paper presents a strain-based elastic-plastic (i.e., inelastic) analysis criterion developed as an alternative to the more conservative stress-based elastic analysis stress criterion for structures subjected to rapidly applied transient dynamic loading. The strain limits established are based on material ductility considerations only and are set as a fraction of the strain at ultimate stress obtained from an engineering stress/strain curve of the material. Strains limits are categorized by type as membrane or surface and by region as general, local , or concentrated. The application of the elastic-plastic criterion provides a more accurate, less conservative design/analysis basis for structures than that used in elastic stress-based analysis criteria, while still providing adequate safety margins.

  4. Grain-size-independent plastic flow at ultrahigh pressures and strain rates.

    Science.gov (United States)

    Park, H-S; Rudd, R E; Cavallo, R M; Barton, N R; Arsenlis, A; Belof, J L; Blobaum, K J M; El-dasher, B S; Florando, J N; Huntington, C M; Maddox, B R; May, M J; Plechaty, C; Prisbrey, S T; Remington, B A; Wallace, R J; Wehrenberg, C E; Wilson, M J; Comley, A J; Giraldez, E; Nikroo, A; Farrell, M; Randall, G; Gray, G T

    2015-02-13

    A basic tenet of material science is that the flow stress of a metal increases as its grain size decreases, an effect described by the Hall-Petch relation. This relation is used extensively in material design to optimize the hardness, durability, survivability, and ductility of structural metals. This Letter reports experimental results in a new regime of high pressures and strain rates that challenge this basic tenet of mechanical metallurgy. We report measurements of the plastic flow of the model body-centered-cubic metal tantalum made under conditions of high pressure (>100  GPa) and strain rate (∼10(7)  s(-1)) achieved by using the Omega laser. Under these unique plastic deformation ("flow") conditions, the effect of grain size is found to be negligible for grain sizes >0.25  μm sizes. A multiscale model of the plastic flow suggests that pressure and strain rate hardening dominate over the grain-size effects. Theoretical estimates, based on grain compatibility and geometrically necessary dislocations, corroborate this conclusion.

  5. Phase field simulations of plastic strain-induced phase transformations under high pressure and large shear

    Science.gov (United States)

    Javanbakht, Mahdi; Levitas, Valery I.

    2016-12-01

    Pressure and shear strain-induced phase transformations (PTs) in a nanograined bicrystal at the evolving dislocations pile-up have been studied utilizing a phase field approach (PFA). The complete system of PFA equations for coupled martensitic PT, dislocation evolution, and mechanics at large strains is presented and solved using the finite element method (FEM). The nucleation pressure for the high-pressure phase (HPP) under hydrostatic conditions near a single dislocation was determined to be 15.9 GPa. Under shear, a dislocation pile-up that appears in the left grain creates strong stress concentration near its tip and significantly increases the local thermodynamic driving force for PT, which causes nucleation of HPP even at zero pressure. At pressures of 1.59 and 5 GPa and shear, a major part of a grain transforms to HPP. When dislocations are considered in the transforming grain as well, they relax stresses and lead to a slightly smaller stationary HPP region than without dislocations. However, they strongly suppress nucleation of HPP and require larger shear. Unexpectedly, the stationary HPP morphology is governed by the simplest thermodynamic equilibrium conditions, which do not contain contributions from plasticity and surface energy. These equilibrium conditions are fulfilled either for the majority of points of phase interfaces or (approximately) in terms of stresses averaged over the HPP region or for the entire grain, despite the strong heterogeneity of stress fields. The major part of the driving force for PT in the stationary state is due to deviatoric stresses rather than pressure. While the least number of dislocations in a pile-up to nucleate HPP linearly decreases with increasing applied pressure, the least corresponding shear strain depends on pressure nonmonotonously. Surprisingly, the ratio of kinetic coefficients for PT and dislocations affect the stationary solution and the nanostructure. Consequently, there are multiple stationary solutions

  6. Micro-Structural Evolution and Size-Effects in Plastically Deformed Single Crystals: Strain Gradient Continuum Modeling

    DEFF Research Database (Denmark)

    El-Naaman, Salim Abdallah

    , to focus on their ability to capture realistic micro-structural evolution. This challenge is the main focus of the present thesis, which takes as starting point a non-work conjugate type back stress based higher order crystal plasticity theory. Within this framework, several possibilities for the back......An extensive amount of research has been devoted to the development of micro-mechanics based gradient plasticity continuum theories, which are necessary for modeling micron-scale plasticity when large spatial gradients of plastic strain appear. While many models have proven successful in capturing...... the macroscopic effects related to strain gradients, most predict smooth micro-structures. The evolution of dislocation micro-structures, during plastic straining of ductile crystalline materials, is highly complex and nonuniform. Published experimental measurements on deformed metal crystals show distinct...

  7. Instability criterion for the system composed of elastic beam and strain-softening pillar based on gradient-dependent plasticity

    Institute of Scientific and Technical Information of China (English)

    Xuebin Wang

    2005-01-01

    A mechanical model is proposed for the system of elastic beam and strain-softening pillar where strain localization is initiated at peak shear stress. To obtain the plastic deformation of the pillar due to the shear slips of multiple shear bands, the pillar is divided into several narrow slices where compressive deformation is treated as uniformity. In the light of the compatibility condition of deformation, the total compressive displacement of the pillar is equal to the displacement of the beam in the middle span. An insta bility criterion is derived analytically based on the energy principle using a known size of localization band according to gradientdependent plasticity. The main advantage of the present model is that the effects of the constitutive parameters of rock and the geometrical size of structure are reflected in the criterion. The condition that the derivative of distributed load with respect to the deflection of the beam in the middle span is less than zero is not only equivalent to, but also even more concise in form than the instability criterion. To study the influences of constitutive parameters and geometrical size on stability, some examples are presented.

  8. Strain gradient crystal plasticity analysis of a single crystal containing a cylindrical void

    DEFF Research Database (Denmark)

    Borg, Ulrik; Kysar, J.W.

    2007-01-01

    The effects of void size and hardening in a hexagonal close-packed single crystal containing a cylindrical void loaded by a far-field equibiaxial tensile stress under plane strain conditions are studied. The crystal has three in-plane slip systems oriented at the angle 60 degrees with respect...... to one another. Finite element simulations are performed using a strain gradient crystal plasticity formulation with an intrinsic length scale parameter in a non-local strain gradient constitutive framework. For a vanishing length scale parameter the non-local formulation reduces to a local crystal...... to three times higher for smaller void sizes than for larger void sizes in the non-local material....

  9. Effects of constraints on lattice re-orientation and strain in polycrystal plasticity simulations

    DEFF Research Database (Denmark)

    Haldrup, Martin Kristoffer; McGinty, R.D.; McDowell, D.L.

    2009-01-01

    Employing a rate-dependent crystal plasticity model implemented in a novel and fast algorithm, two instantiations of an OFHC copper microstructure have been simulated by FE modelling to 11% tensile engineering strain with two different sets of boundary conditions. Analysis of lattice rotations......, strain distributions and global stress–strain response show the effect of changing from free to periodic boundary conditions to be a perturbation of a response dictated by the microstructure. Average lattice rotation for each crystallographic grain has been found to be in fair agreement with Taylor......-constraint simulations while fine scale element-resolved analysis shows large deviations from this prediction. Locally resolved analysis shows the existence of large domains dominated by slip on only a few slip systems. The modelling results are discussed in the light of recent experimental advances with respect to 2...

  10. Quantitative calculation for the dissipated energy of fault rock burst based on gradient-dependent plasticity

    Institute of Scientific and Technical Information of China (English)

    Xuebin Wang; Shuhong Dai; Long Hai

    2004-01-01

    The capacity of energy absorption by fault bands after rock burst was calculated quantitatively according to shear stressshear deformation curves considering the interactions and interplaying among microstructures due to the heterogeneity of strain softening rock materials. The post-peak stiffness of rock specimens subjected to direct shear was derived strictly based on gradientdependent plasticity, which can not be obtained from the classical elastoplastic theory. Analytical solutions for the dissipated energy of rock burst were proposed whether the slope of the post-peak shear stress-shear deformation curve is positive or not. The analytical solutions show that shear stress level, confining pressure, shear strength, brittleness, strain rate and heterogeneity of rock materials have important influence on the dissipated energy. The larger value of the dissipated energy means that the capacity of energy dissipation in the form of shear bands is superior and a lower magnitude of rock burst is expected under the condition of the same work done by external shear force. The possibility of rock burst is reduced for a lower softening modulus or a larger thickness of shear bands.

  11. The strain capacitor: A novel energy storage device

    OpenAIRE

    Pranoy Deb Shuvra; Shamus McNamara

    2014-01-01

    A novel electromechanical energy storage device is reported that has the potential to have high energy densities. It can efficiently store both mechanical strain energy and electrical energy in the form of an electric field between the electrodes of a strain-mismatched bilayer capacitor. When the charged device is discharged, both the electrical and mechanical energy are extracted in an electrical form. The charge-voltage profile of the device is suitable for energy storage applications since...

  12. The Activation Energy Of Ignition Calculation For Materials Based On Plastics

    OpenAIRE

    Rantuch Peter; Wachter Igor; Martinka Jozef; Kuracina Marcel

    2015-01-01

    This article deals with the activation energy of ignition calculation of plastics. Two types of polyamide 6 and one type of polypropylene and polyurethane were selected as samples. The samples were tested under isothermal conditions at several temperatures while times to ignition were observed. From the obtained data, activation energy relating to the moment of ignition was calculated for each plastics. The values for individual plastics were different. The highest activation energies (129.5 ...

  13. High-rate Plastic Deformation of Nanocrystalline Tantalum to Large Strains: Molecular Dynamics Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Rudd, R E

    2009-02-05

    Recent advances in the ability to generate extremes of pressure and temperature in dynamic experiments and to probe the response of materials has motivated the need for special materials optimized for those conditions as well as a need for a much deeper understanding of the behavior of materials subjected to high pressure and/or temperature. Of particular importance is the understanding of rate effects at the extremely high rates encountered in those experiments, especially with the next generation of laser drives such as at the National Ignition Facility. Here we use large-scale molecular dynamics (MD) simulations of the high-rate deformation of nanocrystalline tantalum to investigate the processes associated with plastic deformation for strains up to 100%. We use initial atomic configurations that were produced through simulations of solidification in the work of Streitz et al [Phys. Rev. Lett. 96, (2006) 225701]. These 3D polycrystalline systems have typical grain sizes of 10-20 nm. We also study a rapidly quenched liquid (amorphous solid) tantalum. We apply a constant volume (isochoric), constant temperature (isothermal) shear deformation over a range of strain rates, and compute the resulting stress-strain curves to large strains for both uniaxial and biaxial compression. We study the rate dependence and identify plastic deformation mechanisms. The identification of the mechanisms is facilitated through a novel technique that computes the local grain orientation, returning it as a quaternion for each atom. This analysis technique is robust and fast, and has been used to compute the orientations on the fly during our parallel MD simulations on supercomputers. We find both dislocation and twinning processes are important, and they interact in the weak strain hardening in these extremely fine-grained microstructures.

  14. Immune response to Bifidobacterium bifidum strains support Treg/Th17 plasticity.

    Directory of Open Access Journals (Sweden)

    Patricia López

    Full Text Available In this work we analyzed the immune activation properties of different Bifidobacterium strains in order to establish their ability as inductors of specific effector (Th or regulatory (Treg responses. First, we determined the cytokine pattern induced by 21 Bifidobacterium strains in peripheral blood mononuclear cells (PBMCs. Results showed that four Bifidobacterium bifidum strains showed the highest production of IL-17 as well as a poor secretion of IFNγ and TNFα, suggesting a Th17 profile whereas other Bifidobacterium strains exhibited a Th1-suggestive profile. Given the key role of Th17 subsets in mucosal defence, strains suggestive of Th17 responses and the putative Th1 Bifidobacterium breve BM12/11 were selected to stimulate dendritic cells (DC to further determine their capability to induce the differentiation of naïve CD4(+ lymphocytes toward different Th or Treg cells. All selected strains were able to induce phenotypic DC maturation, but showed differences in cytokine stimulation, DC treated with the putative Th17 strains displaying high IL-1β/IL-12 and low IL-12/IL-10 index, whereas BM12/11-DC exhibited the highest IL-12/IL-10 ratio. Differentiation of naïve lymphocytes confirmed Th1 polarization by BM12/11. Unexpectedly, any B. bifidum strain showed significant capability for Th17 generation, and they were able to generate functional Treg, thus suggesting differences between in vivo and vitro responses. In fact, activation of memory lymphocytes present in PBMCS with these bacteria, point out the presence in vivo of specific Th17 cells, supporting the plasticity of Treg/Th17 populations and the key role of commensal bacteria in mucosal tolerance and T cell reprogramming when needed.

  15. Effect of initial plastic strain on mechanical training of non-modulated Ni–Mn–Ga martensite structure

    Energy Technology Data Exchange (ETDEWEB)

    Szczerba, M.J., E-mail: m.szczerba@imim.pl [Institute of Metallurgy and Materials Science, Polish Academy of Sciences, 25 Reymonta Street, 30-059 Kraków (Poland); Chulist, R. [Institute of Metallurgy and Materials Science, Polish Academy of Sciences, 25 Reymonta Street, 30-059 Kraków (Poland); Kopacz, S.; Szczerba, M.S. [Department of Materials Science and Non-Ferrous Metals Engineering, AGH University of Science and Technology, 30 Mickiewicza Ave., 30-059 Kraków (Poland)

    2014-08-12

    The influence of plastic pre-straining on the mechanical training process of Ni–Mn–Ga single crystals with a non-modulated martensite structure was examined using uniaxial quasi static compression tests and electron backscatter diffraction technique. Firstly, the optimal pre-straining temperature, for which a large plastic strain can be imposed to as-grown crystals with low flow stress and low rate of strain hardening, was established. Then, the maximum value of plastic pre-straining which allows performing successful room temperature mechanical training was found to be of about 20% of total sample thickness reduction. Below this value, training process leads to single variant state, which is able to accommodate true plastic strain of about 0.14 in each step of further training. Above 20% of deformation a multiple martensite variant state of characteristic triangular arrangements is generated. The latter structure cannot practically afford any plastic accommodation during further training; thus the training process fails to operate.

  16. Numerical simulation of strain localization and damage evolution in large plastic deformation using mixed finite element method

    Institute of Scientific and Technical Information of China (English)

    Zhanghua Chen; Jiajian Jin; Jiumei Xiao

    2004-01-01

    An investigation of computer simulation is presented to analyze the effects of strain localization and damage evolution in large plastic deformation. The simulation is carried out by using an elastic-plastic-damage coupling finite element program that is developed based on the concept of mixed interpolation of displacement/pressure. This program has been incorporated into a damage mechanics model as well as the corresponding damage criterion. To illustrate the performance of the proposed approach, a typical strain localization problem has been simulated. The results show that the proposed approach is of good capability to capture strain localization and predict the damage evolution.

  17. Interaction of heat production, strain rate and stress power in a plastically deforming body under tensile test

    Science.gov (United States)

    Paglietti, A.

    1982-01-01

    At high strain rates the heat produced by plastic deformation can give rise to a rate dependent response even if the material has rate independent constitutive equations. This effect has to be evaluated when interpreting a material test, or else it could erroneously be ascribed to viscosity. A general thermodynamic theory of tensile testing of elastic-plastic materials is given in this paper; it is valid for large strain at finite strain rates. It enables discovery of the parameters governing the thermodynamic strain rate effect, provides a method for proper interpretation of the results of the tests of dynamic plasticity, and suggests a way of planning experiments in order to detect the real contribution of viscosity.

  18. Interaction of heat production, strain rate and stress power in a plastically deforming body under tensile test

    Science.gov (United States)

    Paglietti, A.

    1982-01-01

    At high strain rates the heat produced by plastic deformation can give rise to a rate dependent response even if the material has rate independent constitutive equations. This effect has to be evaluated when interpreting a material test, or else it could erroneously be ascribed to viscosity. A general thermodynamic theory of tensile testing of elastic-plastic materials is given in this paper; it is valid for large strain at finite strain rates. It enables discovery of the parameters governing the thermodynamic strain rate effect, provides a method for proper interpretation of the results of the tests of dynamic plasticity, and suggests a way of planning experiments in order to detect the real contribution of viscosity.

  19. Multi-Layer Strain Rate Field Controlled by Netlike Plastic-Flow in the Lithosphere in Central-Eastern Asia

    Institute of Scientific and Technical Information of China (English)

    Wang Sheng-zu

    2006-01-01

    According to the "Netlike Plastic-Flow (NPF)" continental dynamics model, the transition of the deformation regime from brittle in shallow layers to ductile in deep layers in the lithosphere, and the controlling effect of NPF in the lower lithosphere result in intraplate multilayer tectonic deformation. NPF is a viscous (plastic) flow accompanied by shear strain localization, forming a plastic-flow network in the lower lithosphere. The strain rates in the seismogenic layer can be estimated using the "earthquake-recurrence-interval" method, in which the strain rate is calculated in terms of the recurrence interval of two sequential carthquakes and the seismic probability of the second earthquake. The strains in the lower lithosphere are estimated using the "conjugate-angle" method, which takes the relationship between the conjugate angles and the compressive strains of the network, and calculates the characteristic strain rates in this layer from the strains and the durations of deformation inferred. The contour map of characteristic maximum principal compressive strain rates in the lower lithosphere in central-eastern Asia given in the paper shows strain rates with magnitudes on the order of 10-15 ~ 10-14/s in this region. The strain rates within the plastic-flow belts,which control seismic activities in the seismogenic layer, are greater than the characteristic strain rates of the network and, in addition, the strain rates and seismic activities in the seismogenic layer are also influenced by other factors, including the directive action of driving boundary along the upper crust, the effects of plastic-flow waves and the existence of the transitional weak layer distributed discontinuously between the upper and lower layers. The comparison between the strain rates in the seismogenic layer and the characteristic strain rates in the lower lithosphere for 11 potential hypocenter areas in the region from the Qinghai-Xizang (Tibet) plateau to the North China plain

  20. A plastic-composite-plastic structure high performance flexible energy harvester based on PIN-PMN-PT single crystal/epoxy 2-2 composite

    Science.gov (United States)

    Zeng, Zhou; Gai, Linlin; Wang, Xian; Lin, Di; Wang, Sheng; Luo, Haosu; Wang, Dong

    2017-03-01

    We present a high performance flexible piezoelectric energy harvester constituted by a Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) single crystal/epoxy 2-2 composite flake, a polyethylene terephthalate (PET) substrate, and a PET cover, which is capable of harvesting energy from biomechanical movements. Electrical properties of the device under different epoxy volume fractions, load resistances, and strains are studied systematically. Both theoretical and experimental results show that the plastic-composite-plastic structure contributes to the flexibility of the device, and a high performance bulk PIN-PMN-PT single crystal (a thickness of 50 μm) results in its high electrical output. At a low excitation frequency of 4.2 Hz, the optimal flexible energy harvester (with ve = 21%) can generate a peak voltage of 12.9 V and a maximum power density of 0.28 mW/cm3 under a bending radius of 10.5 mm, and maintain its performance after 40 000 bending-unbending cycles. High flexibility and excellent electrical output at low operational frequency demonstrate the promise of the device in biomechanical motion energy harvesting for wireless and portable low-power electronics.

  1. The industrial metabolism of plastics : analysis of material flows, energy consumption and CO2 emissions in the lifecycle of plastics

    NARCIS (Netherlands)

    Joosten, Ludovicus Antonius Josephus

    2001-01-01

    This thesis deals with the question: Which are promising options for decreasing material consumption, energy consumption and CO2 emissions in the lifecycle of plastics? The research described in this thesis mainly focuses on measures that change the material system, i.e. measures that change the

  2. The industrial metabolism of plastics : analysis of material flows, energy consumption and CO2 emissions in the lifecycle of plastics

    NARCIS (Netherlands)

    Joosten, Ludovicus Antonius Josephus

    2002-01-01

    This thesis deals with the question: Which are promising options for decreasing material consumption, energy consumption and CO2 emissions in the lifecycle of plastics? The research described in this thesis mainly focuses on measures that change the material system, i.e. measures that change the pat

  3. Strain Engineering to Modify the Electrochemistry of Energy Storage Electrodes

    Science.gov (United States)

    Muralidharan, Nitin; Carter, Rachel; Oakes, Landon; Cohn, Adam P.; Pint, Cary L.

    2016-01-01

    Strain engineering has been a critical aspect of device design in semiconductor manufacturing for the past decade, but remains relatively unexplored for other applications, such as energy storage. Using mechanical strain as an input parameter to modulate electrochemical potentials of metal oxides opens new opportunities intersecting fields of electrochemistry and mechanics. Here we demonstrate that less than 0.1% strain on a Ni-Ti-O based metal-oxide formed on superelastic shape memory NiTi alloys leads to anodic and cathodic peak potential shifts by up to ~30 mV in an electrochemical cell. Moreover, using the superelastic properties of NiTi to enable strain recovery also recovers the electrochemical potential of the metal oxide, providing mechanistic evidence of strain-modified electrochemistry. These results indicate that mechanical energy can be coupled with electrochemical systems to efficiently design and optimize a new class of strain-modulated energy storage materials. PMID:27283872

  4. Simple structures test for elastic-plastic strain acceptance criterion validation

    Energy Technology Data Exchange (ETDEWEB)

    Trimble, T.F. [Electric Boat Corp., Groton, CT (United States); Krech, G.R. [Wyle Labs., Inc., Huntsville, AL (United States)

    1997-11-01

    A Simple Structures Test Program was performed where several cantilevered beam and fixed-end beam test specimens (fabricated from HY-80 steel) were subjected to a series of analytically predetermined rapidly applied transient dynamic input loads. The primary objective of the test program was to obtain dynamic nonlinear response for simple structures subjected to these load inputs. Data derived from these tests was subsequently used to correlate to analysis predictions to assess the capability to analytically predict elastic-plastic nonlinear material behavior in structures using typical time-dependent (transient) design methods and the ABAQUS finite element analysis code. The installation of a significant amount of instrumentation on these specimens and post-test measurements enabled the monitoring and recording of strain levels, displacements, accelerations, and permanent set. An assessment of modeling parameters such as the element type and mesh refinement was made using these test results. In addition, currently available material models and the incremental time step procedure used in the transient analyses were evaluated. Comparison of test data to analysis results shows that displacements, accelerations, and peak strain can be predicted with a reasonable level of accuracy using detailed solid models of the tested specimens. Permanent set is overpredicted by a factor of approximately two. However, the accuracy of the prediction of permanent set is being enhanced by updating material modeling in the ABAQUS code to account for effects of strain reversal in oscillatory behavior of dynamically loaded specimens.

  5. A strain gradient crystal plasticity analysis of grain size effects in polycrystals

    DEFF Research Database (Denmark)

    Borg, Ulrik

    2007-01-01

    individually oriented grains, in a unit cell, each having three planar slip systems. An energy potential that penalizes crystallographic slip at grain boundaries is included in the analyzes. The polycrystal is subjected to plane strain tension for various grain sizes and higher order boundary conditions...

  6. Effect of large elastic strains on cavitation instability predictions for elastic-plastic solids

    DEFF Research Database (Denmark)

    Tvergaard, Viggo

    1999-01-01

    For an infinite solid containing a void, the cavitation instability limit is defined as the remote stress-and strain state, at which the void grows without bound, driven by the elastic energy stored in the surrounding material. Such cavitation limits have been analysed by a number of authors...

  7. Strain-dependent variations in spatial learning and in hippocampal synaptic plasticity in the dentate gyrus of freely behaving rats

    Directory of Open Access Journals (Sweden)

    Denise eManahan-Vaughan

    2011-03-01

    Full Text Available Hippocampal synaptic plasticity is believed to comprise the cellular basis for spatial learning. Strain-dependent differences in synaptic plasticity in the CA1 region have been reported. However, it is not known whether these differences extend to other synapses within the trisynaptic circuit, although there is evidence for morphological variations within that path. We investigated whether Wistar and Hooded Lister (HL rat strains express differences in synaptic plasticity in the dentate gyrus in vivo. We also explored whether they exhibit differences in the ability to engage in spatial learning in an 8-arm radial maze. Basal synaptic transmission was stable over a 24h period in both rat strains, and the input-output relationship of both strains was not significantly different. Paired-pulse analysis revealed significantly less paired-pulse facilitation in the Hooded Lister strain when pulses were given 40-100 msec apart. Low frequency stimulation at 1Hz evoked long-term depression (>24h in Wistar and short-term depression (<2h in HL rats; 200Hz stimulation induced long-term potentiation (>24h in Wistar, and a transient, significantly smaller potentiation (<1h in HL rats, suggesting that HL rats have higher thresholds for expression of persistent synaptic plasticity. Training for 10d in an 8-arm radial maze revealed that HL rats master the working memory task faster than Wistar rats, although both strains show an equivalent performance by the end of the trial period. HL rats also perform more efficiently in a double working and reference memory task. On the other hand, Wistar rats show better reference memory performance on the final (8-10 days of training. Wistar rats were less active and more anxious than HL rats.These data suggest that strain-dependent variations in hippocampal synaptic plasticity occur in different hippocampal synapses. A clear correlation with differences in spatial learning is not evident however.

  8. Numerical implementation of a crystal plasticity model with dislocation transport for high strain rate applications

    Science.gov (United States)

    Mayeur, Jason R.; Mourad, Hashem M.; Luscher, Darby J.; Hunter, Abigail; Kenamond, Mark A.

    2016-05-01

    This paper details a numerical implementation of a single crystal plasticity model with dislocation transport for high strain rate applications. Our primary motivation for developing the model is to study the influence of dislocation transport and conservation on the mesoscale response of metallic crystals under extreme thermo-mechanical loading conditions (e.g. shocks). To this end we have developed a single crystal plasticity theory (Luscher et al (2015)) that incorporates finite deformation kinematics, internal stress fields caused by the presence of geometrically necessary dislocation gradients, advection equations to model dislocation density transport and conservation, and constitutive equations appropriate for shock loading (equation of state, drag-limited dislocation velocity, etc). In the following, we outline a coupled finite element-finite volume framework for implementing the model physics, and demonstrate its capabilities in simulating the response of a [1 0 0] copper single crystal during a plate impact test. Additionally, we explore the effect of varying certain model parameters (e.g. mesh density, finite volume update scheme) on the simulation results. Our results demonstrate that the model performs as intended and establishes a baseline of understanding that can be leveraged as we extend the model to incorporate additional and/or refined physics and move toward a multi-dimensional implementation.

  9. Composite Behavior of Lath Martensite Steels Induced by Plastic Strain, a New Paradigm for the Elastic-Plastic Response of Martensitic Steels

    Science.gov (United States)

    Ungár, Tamás; Harjo, Stefanus; Kawasaki, Takuro; Tomota, Yo; Ribárik, Gábor; Shi, Zengmin

    2017-01-01

    Based on high-resolution neutron diffraction experiments, we will show that in lath martensite steels, the initially homogeneous dislocation structure, i.e., homogeneous on the length scale of grain size, is disrupted by plastic deformation, which, in turn, produces a composite on the length scale of martensite lath packets. The diffraction patterns of plastically strained martensitic steel reveal characteristically asymmetric peak profiles in the same way as has been observed in materials with heterogeneous dislocation structures. The quasi homogeneous lath structure, formed by quenching, is disrupted by plastic deformation producing a composite structure. Lath packets oriented favorably or unfavorably for dislocation glide become soft or hard. Two lath packet types develop by work softening or work hardening in which the dislocation densities become smaller or larger compared to the initial average dislocation density. The decomposition into soft and hard lath packets is accompanied by load redistribution and the formation of long-range internal stresses between the two lath packet types. The composite behavior of plastically deformed lath martensite opens a new way to understand the elastic-plastic response in this class of materials.

  10. The Activation Energy Of Ignition Calculation For Materials Based On Plastics

    Science.gov (United States)

    Rantuch, Peter; Wachter, Igor; Martinka, Jozef; Kuracina, Marcel

    2015-06-01

    This article deals with the activation energy of ignition calculation of plastics. Two types of polyamide 6 and one type of polypropylene and polyurethane were selected as samples. The samples were tested under isothermal conditions at several temperatures while times to ignition were observed. From the obtained data, activation energy relating to the moment of ignition was calculated for each plastics. The values for individual plastics were different. The highest activation energies (129.5 kJ.mol-1 and 106.2 kJ.mol-1) were achieved by polyamides 6, while the lowest was determined for a sample of polyurethane.

  11. The Activation Energy Of Ignition Calculation For Materials Based On Plastics

    Directory of Open Access Journals (Sweden)

    Rantuch Peter

    2015-06-01

    Full Text Available This article deals with the activation energy of ignition calculation of plastics. Two types of polyamide 6 and one type of polypropylene and polyurethane were selected as samples. The samples were tested under isothermal conditions at several temperatures while times to ignition were observed. From the obtained data, activation energy relating to the moment of ignition was calculated for each plastics. The values for individual plastics were different. The highest activation energies (129.5 kJ.mol−1 and 106.2 kJ.mol−1 were achieved by polyamides 6, while the lowest was determined for a sample of polyurethane.

  12. Greenhouse gas mitigation for U.S. plastics production: energy first, feedstocks later

    Science.gov (United States)

    Posen, I. Daniel; Jaramillo, Paulina; Landis, Amy E.; Griffin, W. Michael

    2017-03-01

    Plastics production is responsible for 1% and 3% of U.S. greenhouse gas (GHG) emissions and primary energy use, respectively. Replacing conventional plastics with bio-based plastics (made from renewable feedstocks) is frequently proposed as a way to mitigate these impacts. Comparatively little research has considered the potential for green energy to reduce emissions in this industry. This paper compares two strategies for reducing greenhouse gas emissions from U.S. plastics production: using renewable energy or switching to renewable feedstocks. Renewable energy pathways assume all process energy comes from wind power and renewable natural gas derived from landfill gas. Renewable feedstock pathways assume that all commodity thermoplastics will be replaced with polylactic acid (PLA) and bioethylene-based plastics, made using either corn or switchgrass, and powered using either conventional or renewable energy. Corn-based biopolymers produced with conventional energy are the dominant near-term biopolymer option, and can reduce industry-wide GHG emissions by 25%, or 16 million tonnes CO2e/year (mean value). In contrast, switching to renewable energy cuts GHG emissions by 50%–75% (a mean industry-wide reduction of 38 million tonnes CO2e/year). Both strategies increase industry costs—by up to 85/tonne plastic (mean result) for renewable energy, and up to 3000 tonne‑1 plastic for renewable feedstocks. Overall, switching to renewable energy achieves greater emission reductions, with less uncertainty and lower costs than switching to corn-based biopolymers. In the long run, producing bio-based plastics from advanced feedstocks (e.g. switchgrass) and/or with renewable energy can further reduce emissions, to approximately 0 CO2e/year (mean value).

  13. Determining the amount of waste plastics in the feed of Austrian waste-to-energy facilities.

    Science.gov (United States)

    Schwarzböck, Therese; Van Eygen, Emile; Rechberger, Helmut; Fellner, Johann

    2017-02-01

    Although thermal recovery of waste plastics is widely practiced in many European countries, reliable information on the amount of waste plastics in the feed of waste-to-energy plants is rare. In most cases the amount of plastics present in commingled waste, such as municipal solid waste, commercial, or industrial waste, is estimated based on a few waste sorting campaigns, which are of limited significance with regard to the characterisation of plastic flows. In the present study, an alternative approach, the so-called Balance Method, is used to determine the total amount of plastics thermally recovered in Austria's waste incineration facilities in 2014. The results indicate that the plastics content in the waste feed may vary considerably among different plants but also over time. Monthly averages determined range between 8 and 26 wt% of waste plastics. The study reveals an average waste plastics content in the feed of Austria's waste-to-energy plants of 16.5 wt%, which is considerably above findings from sorting campaigns conducted in Austria. In total, about 385 kt of waste plastics were thermally recovered in all Austrian waste-to-energy plants in 2014, which equals to 45 kg plastics cap(-1). In addition, the amount of plastics co-combusted in industrial plants yields a total thermal utilisation rate of 70 kg cap(-1) a(-1) for Austria. This is significantly above published rates, for example, in Germany reported rates for 2013 are in the range of only 40 kg of waste plastics combusted per capita.

  14. Fatigue damage accumulation of details in cars according to criterion of specific energy of total strain

    Directory of Open Access Journals (Sweden)

    L.I. Vakulenko

    2013-08-01

    Full Text Available Purpose. Modern ideas about the accumulation of fatigue damages in the details of railway vehicles are based on models that estimate the durability of metal systems and depend on the number of cycles and the magnitude of deformations or stresses. These models allow one to assess with a sufficient degree of adequacy the weakening of metal systems in polycyclic fatigue and at the presence of the elastic strain only in the details of rolling stock. However, the possibility of plastic deformation appearing during operation of rail transport structures is not taken into account. The aim of this work is a construction of a mathematical model that allows estimating the durability of metal systems with regard to the appearing of the plastic component in the process of deformation of parts of railway vehicles. Methodology. With the use of modern methods of solid mechanics the influence of the parameters of plastic deformation on the durability of highly loaded structural elements was analyzed. Findings. The effect of elastic and plastic deformation on the energy dissipation under cyclic loading was studied. Originality. It was shown analytically that the softening parameters of metal systems are related to the total energy of deformation, which characterizes features of the degradation processes in the metal structures under external loads. Practical value. Ratios were proposed, they allow estimating residual life of details in a sequential multilevel cyclic loading.

  15. Influence of plastic strain on the hydrogen evolution reaction on nickel (100) single crystal surfaces to improve hydrogen embrittlement

    Energy Technology Data Exchange (ETDEWEB)

    Lekbir, C., E-mail: choukri.lekbir@univ-lr.fr; Creus, J.; Sabot, R.; Feaugas, X.

    2013-08-20

    Hydrogen-induced embrittlement can be accountable for premature failure of structure in relation with physical and/or chemical processes occurring on material's surface or in the bulk of the material. Hydrogen Evolution Reaction (HER) corresponding to the early step of hydrogen ingress in the material is explored in present study in relation with plastic strain. HER on nickel (100) single crystal in sulphuric acid medium can be related by a Volmer–Heyrovsky mechanism. The corresponding elementary kinetic parameters as symmetry coefficients, activation enthalpies, and number of active sites have been identified via a thermokinetic model using experimental data. These parameters can be affected by defects associated with plastic strain. Irreversible plastic strain modifies the density and the distribution of storage dislocations affecting the surface roughness at atomic scale and generating additional active adsorption sites. Furthermore, surface emergence of mobile dislocations induces the formation of slip bands, which modify the surface roughness and the electronic state of the surface and increases the (111) surface density. The consequence of plastic strain on HER is explored and discussed in relation with both processes.

  16. Cutinase-like enzyme from the yeast Cryptococcus sp. strain S-2 hydrolyzes polylactic acid and other biodegradable plastics.

    Science.gov (United States)

    Masaki, Kazuo; Kamini, Numbi Ramudu; Ikeda, Hiroko; Iefuji, Haruyuki

    2005-11-01

    A purified lipase from the yeast Cryptococcus sp. strain S-2 exhibited remote homology to proteins belonging to the cutinase family rather than to lipases. This enzyme could effectively degrade the high-molecular-weight compound polylactic acid, as well as other biodegradable plastics, including polybutylene succinate, poly (epsilon-caprolactone), and poly(3-hydroxybutyrate).

  17. ELASTO-PLASTIC CONSTITUTIVE MODEL OF SOIL-STRUCTURE INTERFACE IN CONSIDERATION OF STRAIN SOFTENING AND DILATION

    Institute of Scientific and Technical Information of China (English)

    Aizhao Zhou; Tinghao Lu

    2009-01-01

    The behavior of soil-structure interface plays a major role in the definition of soil-structure interaction. In this paper a bi-potential surface elasto-plastic model for soil-structure interface is proposed in order to describe the interface deformation behavior, including strain softening and normal dilatancy. The model is formulated in the framework of generalized potential theory, in which the soil-structure interface problem is regard as a two-dimensional mathematical problem in stress field, and plastic state equations are used to replace the traditional field surface. The relation curves of shear stress and tangential strain are fitted by a piecewise function composed by hyperbolic functions and hyperbolic secant functions, while the relation curves of normal strain and tangential strain are fitted by another piecewise function composed by quadratic functions and hyperbolic secant functions. The approach proposed has the advantage of deriving an elasto-plastic constitutive matrix without postulating the plastic potential functions and yield surface. Moreover, the mathematical principle is clear, and the entire model parameters can be identified by experimental tests. Finally, the predictions of the model have been compared with experimental results obtained from simple shear tests under normal stresses, and results show the model is reasonable and practical.

  18. Cutinase-Like Enzyme from the Yeast Cryptococcus sp. Strain S-2 Hydrolyzes Polylactic Acid and Other Biodegradable Plastics

    Science.gov (United States)

    Masaki, Kazuo; Kamini, Numbi Ramudu; Ikeda, Hiroko; Iefuji, Haruyuki

    2005-01-01

    A purified lipase from the yeast Cryptococcus sp. strain S-2 exhibited remote homology to proteins belonging to the cutinase family rather than to lipases. This enzyme could effectively degrade the high-molecular-weight compound polylactic acid, as well as other biodegradable plastics, including polybutylene succinate, poly (ɛ-caprolactone), and poly(3-hydroxybutyrate). PMID:16269800

  19. Microstructure and annealing behavior of a modified 9Cr-1Mo steel after dynamic plastic deformation to different strains

    DEFF Research Database (Denmark)

    Zhang, Zhenbo; Mishin, Oleg; Tao, N.R.;

    2015-01-01

    The microstructure, hardness and tensile properties of a modified 9Cr-1Mo steel processed by dynamic plastic deformation (DPD) to different strains (0.5 and 2.3) have been investigated in the as-deformed and annealed conditions. It is found that significant structural refinement and a high level...... of strength can be achieved by DPD to a strain of 2.3, and that the microstructure at this strain contains a large fraction of high angle boundaries. The ductility of the DPD processed steel is however low. Considerable structural coarsening of the deformed microstructure without pronounced recrystallization...

  20. Quenching Factor for Low Energy Nuclear Recoils in a Plastic Scintillator

    OpenAIRE

    Reichhart, L.; Akimov, D. Yu.; Araujo, H. M.; Barnes, E. J.; Belov, V. A.; Burenkov, A. A.; Chepel, V.; Currie, A; DeViveiros, L.; Edwards, B.; Francis, V.; Ghag, C.; Hollingsworth, A.; Horn, M.; Kalmus, G.E.

    2011-01-01

    Plastic scintillators are widely used in industry, medicine and scientific research, including nuclear and particle physics. Although one of their most common applications is in neutron detection, experimental data on their response to low-energy nuclear recoils are scarce. Here, the relative scintillation efficiency for neutron-induced nuclear recoils in a polystyrene-based plastic scintillator (UPS-923A) is presented, exploring recoil energies between 125 keV and 850 keV. Monte Carlo simula...

  1. Two phase modeling of the influence of plastic strain on the magnetic and magnetostrictive behaviors of ferromagnetic materials

    Science.gov (United States)

    Hubert, Olivier; Lazreg, Said

    2017-02-01

    A growing interest of automotive industry in the use of high performance steels is observed. These materials are obtained thanks to complex manufacturing processes whose parameters fluctuations lead to strong variations of microstructure and mechanical properties. The on-line magnetic non-destructive monitoring is a relevant response to this problem but it requires fast models sensitive to different parameters of the forming process. The plastic deformation is one of these important parameters. Indeed, ferromagnetic materials are known to be sensitive to stress application and especially to plastic strains. In this paper, a macroscopic approach using the kinematic hardening is proposed to model this behavior, considering a plastic strained material as a two phase system. Relationship between kinematic hardening and residual stress is defined in this framework. Since stress fields are multiaxial, an uniaxial equivalent stress is calculated and introduced inside the so-called magneto-mechanical multidomain modeling to represent the effect of plastic strain. The modeling approach is complemented by many experiments involving magnetic and magnetostrictive measurements. They are carried out with or without applied stress, using a dual-phase steel deformed at different levels. The main interest of this material is that the mechanically hard phase, soft phase and the kinematic hardening can be clearly identified thanks to simple experiments. It is shown how this model can be extended to single phase materials.

  2. A two-speed model for finite-strain elasto-plasticity

    OpenAIRE

    Rindler, Filip

    2015-01-01

    This work presents a new modeling approach to macroscopic, polycrystalline elasto-plasticity starting from first principles and a few well-defined structural assumptions, incorporating the mildly rate-dependent (viscous) nature of plastic flow and the microscopic origins of plastic deformations. For the global dynamics, we start from a two-stage time-stepping scheme, expressing the fact that in most real materials plastic flow is much slower than elastic deformations, and then perform a detai...

  3. Towards Understanding Fatigue Disbond Growth via Cyclic Strain Energy

    NARCIS (Netherlands)

    Pascoe, J.A.; Alderliesten, R.C.; Benedictus, R.

    2014-01-01

    The concept of relating fatigue disbond growth to the strain energy release rate (SERR) is critically examined. It is highlighted that the common practise of using only the maximum SERR or only the SERR range is insufficient to correctly characterize a load cycle. As crack growth requires energy, it

  4. Energy scavenging strain absorber: application to kinetic dielectric elastomer generator

    Science.gov (United States)

    Jean-Mistral, C.; Beaune, M.; Vu-Cong, T.; Sylvestre, A.

    2014-03-01

    Dielectric elastomer generators (DEGs) are light, compliant, silent energy scavengers. They can easily be incorporated into clothing where they could scavenge energy from the human kinetic movements for biomedical applications. Nevertheless, scavengers based on dielectric elastomers are soft electrostatic generators requiring a high voltage source to polarize them and high external strain, which constitutes the two major disadvantages of these transducers. We propose here a complete structure made up of a strain absorber, a DEG and a simple electronic power circuit. This new structure looks like a patch, can be attached on human's wear and located on the chest, knee, elbow… Our original strain absorber, inspired from a sailing boat winch, is able to heighten the external available strain with a minimal factor of 2. The DEG is made of silicone Danfoss Polypower and it has a total area of 6cm per 2.5cm sustaining a maximal strain of 50% at 1Hz. A complete electromechanical analytical model was developed for the DEG associated to this strain absorber. With a poling voltage of 800V, a scavenged energy of 0.57mJ per cycle is achieved with our complete structure. The performance of the DEG can further be improved by enhancing the imposed strain, by designing a stack structure, by using a dielectric elastomer with high dielectric permittivity.

  5. Energy dissipation and contour integral characterizing fracture behavior of incremental plasticity

    Institute of Scientific and Technical Information of China (English)

    Qi-Lin He; Lin-Zhi Wu; Ming Li; Hong-Bo Chen

    2011-01-01

    Jep-integral is derived for characterizing the fracture behavior of elastic-plastic materials. The Jep-integral differs from Rice's J-integral in that the free energy density rather than the stress working density is employed to define energy-momentum tensor. The Jep-integral is proved to be path-dependent regardless of incremental plasticity and deformation plasticity. The Jep-integral possesses clearly clear physical meaning: (1) the value Jeptjp evaluated on the infinitely small contour surrounding the crack tip represents the crack tip energy dissipation; (2) when the global steadystate crack growth condition is approached, the value of Jepfar-ss calculated along the boundary contour equals to the sum of crack tip dissipation and bulk dissipation of plastic zone. The theoretical results are verified by simulating mode I crack problems.

  6. A review of higher order strain gradient theories of plasticity: Origins, thermodynamics and connections with dislocation mechanics

    Indian Academy of Sciences (India)

    Suman Guha; Sandeep Sangal; Sumit Basu

    2015-06-01

    In this paper we review developments in higher order strain gradient theories. Several variants of these theories have been proposed in order to explain the effects of size on plastic properties that are manifest in several experiments with micron sized metallic structures. It is generally appreciated that the size effect arises from the storage of geometrically necessary dislocations (GNDs) over and above the statistically stored dislocations (SSDs) required for homogeneous deformations. We review developments that show that the GNDs result from the non-homogeneous nature of the deformation field. Though the connection between GNDs and strain gradients are established in the framework of single crystal plasticity, generalisations to polycrystal plasticity has been made. Strain gradient plasticity inherently involves an intrinsic length scale. In our review, we show, through a few illustrative problems, that conventional plasticity solutions can always be reduced to a scale independent form. The same problems are solved with a simple higher order strain gradient formulation to capture the experimentally observed size effects. However, higher order theories need to be thermodynamically consistent. It has recently been shown that only a few of the existing theories pass this test. We review a few that do. Higher order theories require higher order boundary conditions that enable us to model effects of dislocation storage at impermeable boundaries. But these additional boundary conditions also lead to unique conceptual issues that are not encountered in conventional theories. We review attempts at resolving these issues pertaining to higher order boundary conditions. Finally, we review the future of such theories, their relevance and experimental validation.

  7. Decay Time Measurement for Different Energy Depositions of Plastic Scintillator Fabricated by High Temperature Polymerization Reaction

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Cheol Ho; Son, Jaebum; Lee, Sangmin; Kim, Tae Hoon; Kim, Yong-Kyun [Hanyang University, Seoul (Korea, Republic of)

    2016-10-15

    Plastic scintillators are based on organic fluorite. They have many advantages such as fast rise and decay time, high optical transmission, ease of manufacturing, low cost, and large available size. For these reasons they are widely used for particle identification. Also, protection of people against a variety of threats (such as nuclear, radiological, and explosive) represents a true challenge along with the continuing development of science and technology. The plastic scintillator is widely used in various devise, which serves for nuclear, photonics, quantum, and high-energy physics. The plastic scintillator is probably the most widely used organic detector, and polystyrene is one of the most widely used materials in the making of the plastic scintillator detector. Thus, a styrene monomer as a solvent was used to fabricate the plastic scintillator by using high temperature polymerization reaction, and then the emission wavelength and the decay times for different energy depositions were measured by using the fabricated plastic scintillator. A plastic scintillator was fabricated to measure decay time for different energy depositions using the high temperature polymerization. Emission wavelength was measured of 426.05 nm to confirm a scintillator property using the spectrophotometer. Four gamma-ray sources (Cs-137, Co-60, Na-22, and Ba-133) were used to evaluate effect for decay time of different energy depositions. The average decay time of the fabricated plastic scintillator was measured to approximately 4.72 ns slightly higher more than commercial plastic scintillator. In future, light output and linearity will be measured to evaluate other property compared with the commercial scintillator.

  8. Parametric analysis of plastic strain and force distribution in single pass metal spinning

    Energy Technology Data Exchange (ETDEWEB)

    Choudhary, Shashank, E-mail: shashankbit08@gmail.com, E-mail: mohantejesh93@gmail.com, E-mail: regalla@hyderabad.bits-pilani.ac.in, E-mail: ksuresh@hyderabad.bits-pilani.ac.in; Tejesh, Chiruvolu Mohan, E-mail: shashankbit08@gmail.com, E-mail: mohantejesh93@gmail.com, E-mail: regalla@hyderabad.bits-pilani.ac.in, E-mail: ksuresh@hyderabad.bits-pilani.ac.in; Regalla, Srinivasa Prakash, E-mail: shashankbit08@gmail.com, E-mail: mohantejesh93@gmail.com, E-mail: regalla@hyderabad.bits-pilani.ac.in, E-mail: ksuresh@hyderabad.bits-pilani.ac.in; Suresh, Kurra, E-mail: shashankbit08@gmail.com, E-mail: mohantejesh93@gmail.com, E-mail: regalla@hyderabad.bits-pilani.ac.in, E-mail: ksuresh@hyderabad.bits-pilani.ac.in [Department of Mechanical Engineering, BITS-Pilani, Hyderabad Campus, Shamirpet, Hyderabad, 500078, Andhra Pradesh (India)

    2013-12-16

    Metal spinning also known as spin forming is one of the sheet metal working processes by which an axis-symmetric part can be formed from a flat sheet metal blank. Parts are produced by pressing a blunt edged tool or roller on to the blank which in turn is mounted on a rotating mandrel. This paper discusses about the setting up a 3-D finite element simulation of single pass metal spinning in LS-Dyna. Four parameters were considered namely blank thickness, roller nose radius, feed ratio and mandrel speed and the variation in forces and plastic strain were analysed using the full-factorial design of experiments (DOE) method of simulation experiments. For some of these DOE runs, physical experiments on extra deep drawing (EDD) sheet metal were carried out using En31 tool on a lathe machine. Simulation results are able to predict the zone of unsafe thinning in the sheet and high forming forces that are hint to the necessity for less-expensive and semi-automated machine tools to help the household and small scale spinning workers widely prevalent in India.

  9. Optimization of the wavelength shifter ratio in a polystyrene based plastic scintillator through energy spectrum analysis

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ye Won; Kim, Myung Soo; Yoo, Hyun Jun; Lee, Dae Hee; Cho, Gyu Seong [Dept. of Nuclear and Quantum Engineering, KAIST, Daejeon (Korea, Republic of); Moon, Myung Kook [Neutron Instrumentation Division, Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2017-02-15

    The scintillation efficiency of the polystyrene based plastic scintillator depends on the ratio of the wavelength shifters, organic fluors (PPO and POPOP). Thus, 24 samples of the plastic scintillator were fabricated in order to find out the optimum ratio of the wavelength shifters in the plastic scintillator. The fabricated plastic scintillators were trimmed through a cutting and polishing process. They were used in gamma energy spectrum measurement with the {sup 137}Cs emitting monoenergy photon with 662 keV for the comparison of the scintillation efficiency. As a result, it was found out that the scintillator sample with 1.00 g of PPO (2,5-Diphenyloxazole) and 0.50 g of POPOP (1,4-Bis(5-phnyl-2oxidazolyl)benzene) dissolved in 100 g of styrene solution has the optimum ratio in terms of the light yield of the polystyrene based plastic scintillator.

  10. Creation of High-Yield Polyhydroxyalkanoates Engineered Strains by Low Energy Ion Implantation

    Science.gov (United States)

    Qian, Shiquan; Cheng, Ying; Zhu, Suwen; Cheng, Beijiu

    2008-12-01

    Polyhydroxyalkanoates (PHAs), as a candidate for biodegradable plastic materials, can be synthesized by numerous microorganisms. However, as its production cost is high in comparison with those of chemically synthesized plastics, a lot of research has been focused on the efficient production of PHAs using different methods. In the present study, the mutation effects of PHAs production in strain pCB4 were investigated with implantation of low energy ions. It was found that under the implantation conditions of 7.8 × 1014 N+/cm2 at 10 keV, a high-yield PHAs strain with high genetic stability was generated from many mutants. After optimizing its fermentation conditions, the biomass, PHAs concentration and PHAs content of pCBH4 reached 2.26 g/L, 1.81 g/L, and 80.08% respectively, whereas its wild type controls were about 1.24 g/L, 0.61 g/L, and 49.20%. Moreover, the main constituent of PHAs was identified as poly-3-hydroxybutyrates (PHB) in the mutant stain and the yield of this compound was increased up to 41.33% in contrast to that of 27.78% in the wild type strain.

  11. Creation of High-Yield Polyhydroxyalkanoates Engineered Strains by Low Energy Ion Implantation

    Institute of Scientific and Technical Information of China (English)

    QIAN Shiquan; CHENG Ying; ZHU Suwen; CHENG Beijiu

    2008-01-01

    Polyhydroxyalkanoates (PHAs), as a candidate for biodegradable plastic materials, can be synthesized by numerous microorganisms. However, as its production cost is high in comparison with those of chemically synthesized plastics, a lot of research has been focused on the efficient production of PHAs using different methods. In the present study, the mutation effects of PHAs production in strain pCB4 were investigated with implantation of low energy ions. It was found that under the implantation conditions of 7.8×1014 N+/cm2 at 10 keV, a high-yield PHAs strain with high genetic stability was generated from many mutants. After optimizing its fermentation conditions, the biomass, PHAs concentration and PHAs content of pCBH4reached 2.26 g/L, 1.81 g/L, and 80.08% respectively, whereas its wild type controls were about 1.24 g/L, 0.61 g/L, and 49.20%. Moreover, the main constituent of PHAs was identified as poly-3-hydroxybutyrates (PHB) in the mutant stain and the yield of this compound was increased up to 41.33% in contrast to that of 27.78% in the wild type strain.

  12. A model for plasticity kinetics and its role in simulating the dynamic behavior of Fe at high strain rates

    Energy Technology Data Exchange (ETDEWEB)

    Colvin, J D; Minich, R W; Kalantar, D H

    2007-03-29

    The recent diagnostic capability of the Omega laser to study solid-solid phase transitions at pressures greater than 10 GPa and at strain rates exceeding 10{sup 7} s{sup -1} has also provided valuable information on the dynamic elastic-plastic behavior of materials. We have found, for example, that plasticity kinetics modifies the effective loading and thermodynamic paths of the material. In this paper we derive a kinetics equation for the time-dependent plastic response of the material to dynamic loading, and describe the model's implementation in a radiation-hydrodynamics computer code. This model for plasticity kinetics incorporates the Gilman model for dislocation multiplication and saturation. We discuss the application of this model to the simulation of experimental velocity interferometry data for experiments on Omega in which Fe was shock compressed to pressures beyond the {alpha}-to-{var_epsilon} phase transition pressure. The kinetics model is shown to fit the data reasonably well in this high strain rate regime and further allows quantification of the relative contributions of dislocation multiplication and drag. The sensitivity of the observed signatures to the kinetics model parameters is presented.

  13. Use of pultruded reinforced plastics in energy generation and energy related applications

    Science.gov (United States)

    Anderson, R.

    Applications of pultrusion-formed fiber-reinforced plastics (FRP) in the wind, oil, and coal derived energy industries are reviewed. FRP is noted to be a viable alternative to wood, aluminum, and steel for reasons of availability, price, and weight. Attention is given to the development of FRP wind turbine blades for the DOE 8 kW low cost, high reliability wind turbine program. The blades feature a NACA 23112 profile with a 15 in. chord on the system which was tested at Rocky Flats, CO. Fabricating the blades involved a plus and minus 45 deg roving orientation, a heavy fiber-glass nose piece to assure blade strength, and a separately manufactured foam core. Additional uses for FRP products have been found in the structural members of coal stack scrubbers using a vinyl ester resin in a fire retardant formulation, and as low cost, light weight sucker rods for deep well oil drilling.

  14. RIGID-PLASTIC/RIGID-VISCOPLASTIC FEM BASED ON LINEAR PROGRAMMING-THEORETICAL MODELING AND APPLICATION FOR PLANE-STRAIN PROBLEMS

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    A new rigid-plastic/rigid-viscoplastic (RP/RVP) FEM based on linear programming (LP) for plane-strain metal forming simulation is proposed. Compared with the traditional RP/RVP FEM based on iteration solution, it has some remarkable advantages, such as it's free of convergence problem and its convenience in contact, incompressibility constraint and rigid zone treatment. Two solution examples are provided to validate its accuracy and efficiency.

  15. The strain capacitor: A novel energy storage device

    Directory of Open Access Journals (Sweden)

    Pranoy Deb Shuvra

    2014-12-01

    Full Text Available A novel electromechanical energy storage device is reported that has the potential to have high energy densities. It can efficiently store both mechanical strain energy and electrical energy in the form of an electric field between the electrodes of a strain-mismatched bilayer capacitor. When the charged device is discharged, both the electrical and mechanical energy are extracted in an electrical form. The charge-voltage profile of the device is suitable for energy storage applications since a larger portion of the stored energy can be extracted at higher voltage levels compared to a normal capacitor. Its unique features include the potential for long lifetime, safety, portability, wide operating temperature range, and environment friendliness. The device can be designed to operate over varied operating voltage ranges by selecting appropriate materials and by changing the dimensions of the device. In this paper a finite element model of the device is developed to verify and demonstrate the potential of the device as an energy storage element. This device has the potential to replace conventional energy storage devices.

  16. The strain capacitor: A novel energy storage device

    Energy Technology Data Exchange (ETDEWEB)

    Deb Shuvra, Pranoy; McNamara, Shamus, E-mail: shamus.mcnamara@louisville.edu [Department of Electrical and Computer Engineering, University of Louisville, Louisville, KY 40292 (United States)

    2014-12-15

    A novel electromechanical energy storage device is reported that has the potential to have high energy densities. It can efficiently store both mechanical strain energy and electrical energy in the form of an electric field between the electrodes of a strain-mismatched bilayer capacitor. When the charged device is discharged, both the electrical and mechanical energy are extracted in an electrical form. The charge-voltage profile of the device is suitable for energy storage applications since a larger portion of the stored energy can be extracted at higher voltage levels compared to a normal capacitor. Its unique features include the potential for long lifetime, safety, portability, wide operating temperature range, and environment friendliness. The device can be designed to operate over varied operating voltage ranges by selecting appropriate materials and by changing the dimensions of the device. In this paper a finite element model of the device is developed to verify and demonstrate the potential of the device as an energy storage element. This device has the potential to replace conventional energy storage devices.

  17. Constitutive modelling and identification of parameters of the plastic strain-induced martensitic transformation in 316L stainless steel at cryogenic temperatures

    CERN Document Server

    Garion, C; Sgobba, Stefano

    2006-01-01

    The present paper is focused on constitutive modelling and identification of parameters of the relevant model of plastic strain- induced martensitic transformation in austenitic stainless steels at low temperatures. The model used to describe the FCCrightward arrow BCC phase transformation in austenitic stainless steels is based on the assumption of linearization of the most intensive part of the transformation curve. The kinetics of phase transformation is described by three parameters: transformation threshold (p/sub xi/), slope (A) and saturation level (xi/sub L/). It is assumed that the phase transformation is driven by the accumulated plastic strain p. In addition, the intensity of plastic deformation is strongly coupled to the phase transformation via the description of mixed kinematic /isotropic linear plastic hardening based on the Mori-Tanaka homogenization. The theory of small strains is applied. Small strain fields, corresponding to phase transformation, are decomposed into the volumic and the shea...

  18. Features of energy impact on a billet material when cutting with outstripping plastic deformation

    Directory of Open Access Journals (Sweden)

    V. M. Yaroslavtsev

    2014-01-01

    Full Text Available In the last decades the so-called combined machining methods based on parallel, serial or parallelserial combination of different types of energy impacts on the billet are designed and developed. Combination of two or more sources of external energy in one method of machining can be directed to the solution of different technological tasks, such as: improvement of a basic method to enhance technicaland-economic and technological indicators of machining, expansion of technological capabilities of the method, increase of reliability and stability of technological process to produce details, etc. Besides, the combined methods of machining are considered as one of the means, which enables reducing the number of operations in technological process, allows the growth of workforce productivity.When developing the combined technologies, one of the main scientific tasks is to define the general regularities of interaction and mutual influence of the energy fluxes brought to the zone of machining. The result of such mutual influence becomes apparent from the forming technological parameters of machining and determines the most rational operating conditions of technological process.In the context of conducted in BMSTU researches on the combined cutting method with outstripping plastic deformation (OPD the mutual influence of the energetic components of machining has been quantitatively assessed. The paper shows a direct relationship between the rational ratio of the two types of the mechanical energy brought in the machining zone, the machining conditions, and the optimum operating conditions.The paper offers a physical model of chip formation when machining with OPD. The essence of model is that specific works spent on material deformation of a cut-off layer are quantitatively compared at usual cutting and at cutting with OPD. It is experimentally confirmed that the final strain-deformed material states of a cut-off layer, essentially, coincide in both

  19. Particle fracture and plastic deformation in vanadium pentoxide powders induced by high energy vibrational ball-mill

    Indian Academy of Sciences (India)

    Partha Chatterjee; S P Sen Gupta; Suchitra Sen

    2001-04-01

    An X-ray powder profile analysis in vanadium pentoxide powder milled in a high energy vibrational ball-mill for different lengths of time (0–250 h), is presented. The strain and size induced broadening of the Bragg reflection for two different crystallographic directions ([001] and [100]) was determined by Warren–Averbach analysis using a pattern-decomposition method assuming a Pseudo–Voigt function. The deformation process caused a decrease in the crystallite size and a saturation of crystallite size of ∼ 10 nm was reached after severe milling. The initial stages of milling indicated a propensity of size-broadening due to fracture of the powder particles caused by repeated ball-to-powder impact whereas with increasing milling time microstrain broadening was predominant. WA analysis indicated significant plastic strain along with spatial confinement of the internal strain fields in the crystallite interfaces. Significant strain anisotropy was noticed in the different crystallographic directions. A near-isotropy in the crystallite size value was noticed for materials milled for 200 h and beyond. The column-length distribution function obtained from the size Fourier coefficients progressively narrowed down with the milling time.

  20. Thermal recycling of plastic waste using pyrolysis-gasification process for energy production

    Energy Technology Data Exchange (ETDEWEB)

    Forbit, George Teke

    2012-04-04

    The disposal of mixed waste in landfills, dump sites and open burning without material and energy recovery leads to resource loss, causes health problems, pollution and littering. Increasing energy demand for industrial and domestic application with rising costs due to scarcity motivates a constant search for alternative clean energy sources. Recovering energy from waste presents various incentives e.g. creating jobs, alleviating poverty, combating and mitigating climate change, protecting the environment and reducing dependence on traditional fuels sources. Hence, plastics end up in landfills, surface waters and ocean bed with serious negative impact on terrestrial and aquatic biodiversity. Plastic waste with high calorific value (36-46MJ/kg) occupies the greatest portion of landfill space. Hence, using an appropriate technology to transform waste plastic to a hot gaseous mixture which is burned in-situ produces enormous amount of energy without pollution. Based on this hypothesis, the study objectives accomplished were to: 1. Characterise, quantify and classify waste fractions and plastic components common in MSW by manual sorting 2. Evaluate options for sustainable plastic waste management especially for developing countries 3. Design, construct, test and optimize an appropriate technology that applies pyrolysis and gasification processes to convert non-PVC plastic waste to energy 4. Assess the efficiency of the technology based on the functioning, the engineering, mass and energy analysis including socioeconomic and environmental impacts An integrated methodology involving review of current literature, field and laboratory experiments on mixed waste and plastic waste analysis was used. In addition, the pyrolysis-gasification technology (PGT) was conceptualised, designed, constructed, tested and optimised at BTU Cottbus, Germany; Lagos, Nigeria and Dschang, Cameroon. Field studies involving natural observation, interviews, personal discussions and visits to

  1. Cellular basis of morphological variation and temperature-related plasticity in Drosophila melanogaster strains with divergent wing shapes.

    Science.gov (United States)

    Torquato, Libéria Souza; Mattos, Daniel; Matta, Bruna Palma; Bitner-Mathé, Blanche Christine

    2014-12-01

    Organ shape evolves through cross-generational changes in developmental patterns at cellular and/or tissue levels that ultimately alter tissue dimensions and final adult proportions. Here, we investigated the cellular basis of an artificially selected divergence in the outline shape of Drosophila melanogaster wings, by comparing flies with elongated or rounded wing shapes but with remarkably similar wing sizes. We also tested whether cellular plasticity in response to developmental temperature was altered by such selection. Results show that variation in cellular traits is associated with wing shape differences, and that cell number may play an important role in wing shape response to selection. Regarding the effects of developmental temperature, a size-related plastic response was observed, in that flies reared at 16 °C developed larger wings with larger and more numerous cells across all intervein regions relative to flies reared at 25 °C. Nevertheless, no conclusive indication of altered phenotypic plasticity was found between selection strains for any wing or cellular trait. We also described how cell area is distributed across different intervein regions. It follows that cell area tends to decrease along the anterior wing compartment and increase along the posterior one. Remarkably, such pattern was observed not only in the selected strains but also in the natural baseline population, suggesting that it might be canalized during development and was not altered by the intense program of artificial selection for divergent wing shapes.

  2. Microstructure and annealing behavior of a modified 9Cr-1Mo steel after dynamic plastic deformation to different strains

    Science.gov (United States)

    Zhang, Z. B.; Mishin, O. V.; Tao, N. R.; Pantleon, W.

    2015-03-01

    The microstructure, hardness and tensile properties of a modified 9Cr-1Mo steel processed by dynamic plastic deformation (DPD) to different strains (0.5 and 2.3) have been investigated in the as-deformed and annealed conditions. It is found that significant structural refinement and a high level of strength can be achieved by DPD to a strain of 2.3, and that the microstructure at this strain contains a large fraction of high angle boundaries. The ductility of the DPD processed steel is however low. Considerable structural coarsening of the deformed microstructure without pronounced recrystallization takes place during annealing of the low-strain and high-strain samples for 1 h at 650 °C and 600 °C, respectively. Both coarsening and partial recrystallization occur in the high-strain sample during annealing at 650 °C for 1 h. For this sample, it is found that whereas coarsening alone results in a loss of strength with only a small gain in ductility, coarsening combined with pronounced partial recrystallization enables a combination of appreciably increased ductility and comparatively high strength.

  3. Microstructure and annealing behavior of a modified 9Cr−1Mo steel after dynamic plastic deformation to different strains

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Z.B.; Mishin, O.V. [Danish-Chinese Center for Nanometals, Section for Materials Science and Advanced Characterization, Department of Wind Energy, Technical University of Denmark, Risø Campus, 4000 Roskilde (Denmark); Sino-Danish Center for Education and Research (China); Sino-Danish Center for Education and Research (Denmark); Tao, N.R. [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Science, Shenyang 110016 (China); Sino-Danish Center for Education and Research (China); Sino-Danish Center for Education and Research (Denmark); Pantleon, W., E-mail: pawo@dtu.dk [Section for Materials and Surface Engineering, Department of Mechanical Engineering, Technical University of Denmark, 2800 Kgs. Lyngby (Denmark); Sino-Danish Center for Education and Research (China); Sino-Danish Center for Education and Research (Denmark)

    2015-03-15

    The microstructure, hardness and tensile properties of a modified 9Cr−1Mo steel processed by dynamic plastic deformation (DPD) to different strains (0.5 and 2.3) have been investigated in the as-deformed and annealed conditions. It is found that significant structural refinement and a high level of strength can be achieved by DPD to a strain of 2.3, and that the microstructure at this strain contains a large fraction of high angle boundaries. The ductility of the DPD processed steel is however low. Considerable structural coarsening of the deformed microstructure without pronounced recrystallization takes place during annealing of the low-strain and high-strain samples for 1 h at 650 °C and 600 °C, respectively. Both coarsening and partial recrystallization occur in the high-strain sample during annealing at 650 °C for 1 h. For this sample, it is found that whereas coarsening alone results in a loss of strength with only a small gain in ductility, coarsening combined with pronounced partial recrystallization enables a combination of appreciably increased ductility and comparatively high strength.

  4. adaptation of plastic waste to energy development in lagos

    African Journals Online (AJOL)

    user

    specific months were primarily used as a case study to portray the fact that all measures put in place by ... people. Nigeria seems to have been in energy deficit for a long time and successive .... Aluminium (%) .... process involves core use of Simpson's rule for the ... possible way to inject sanity into waste management.

  5. FEM solutions for plane stress mode-I and mode-II cracks in strain gradient plasticity

    Institute of Scientific and Technical Information of China (English)

    邱信明; 郭田福; 黄克智

    2000-01-01

    The strain gradient plasticity theory is used to investigate the crack-tip field in a power law hardening material. Numerical solutions are presented for plane-stress mode I and mode II cracks under small scale yielding conditions. A comparison is made with the existing asymptotic fields. It is found that the size of the dominance zone for the near-tip asymptotic field, recently obtained by Chen et al., is on the order 5% of the intrinsic material length I. Remote from the dominance zone, the computed stress field tends to be the classical HRR field. Within the plastic zone only force-stress dominated solution is found for either mode I or mode II crack.

  6. Energy and raw material saving through recycling of plastics materials extracted from urban waste. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Michaux, J.

    The study is divided into 3 parts: Technical feasibility study, economic feasibility study, study of a factory handling 2,400 tons/year of plastics waste, and technico-economic feasibility study and market research, with an analysis of energy savings.

  7. Flow Curve Determination at Large Plastic Strain Levels to Accurately Constitutive Equations of AHSS in Forming Simulation

    Science.gov (United States)

    Lemoine, X.; Sriram, S.; Kergen, R.

    2011-05-01

    ArcelorMittal continuously develops new steel grades (AHSS) with high performance for the automotive industry to improve the weight reduction and the passive safety. The wide market introduction of AHSS raises a new challenge for manufacturers in terms of material models in the prediction of forming—especially formability and springback. The relatively low uniform elongation, the high UTS and the low forming limit curve of these AHSS may cause difficulties in forming simulations. One of these difficulties is the consequence of the relatively low uniform elongation on the parameters identification of isotropic hardening model. Different experimental tests allow to reach large plastic strain levels (hydraulic bulge test, stack compression test, shear test…). After a description on how to determine the flow curve in these experimental tests, a comparison of the different flow curves is made for different steel grades. The ArcelorMittal identification protocol for hardening models is only based on stress-strain curves determined in uniaxial tension. Experimental tests where large plastic strain levels are reached are used to validate our identification protocol and to recommend some hardening models. Finally, the influence of isotropic hardening models and yield loci in forming prediction for AHSS steels will be presented.

  8. Strain energy minimization in SSC (Superconducting Super Collider) magnet winding

    Energy Technology Data Exchange (ETDEWEB)

    Cook, J.M.

    1990-09-24

    Differential geometry provides a natural family of coordinate systems, the Frenet frame, in which to specify the geometric properties of magnet winding. By a modification of the Euler-Bernoulli thin rod model, the strain energy is defined with respect to this frame. Then it is minimized by a direct method from the calculus of variations. The mathematics, its implementation in a computer program, and some analysis of an SSC dipole by the program will be described. 16 refs.

  9. Effects of Strain Rate and Plastic Work on Martensitic Transformation Kinetics of Austenitic Stainless Steel 304

    Institute of Scientific and Technical Information of China (English)

    Fang PENG; Xiang-huai DONG; Kai LIU; Huan-yang XIE

    2015-01-01

    The martensitic transformation behavior and mechanical properties of austenitic stainless steel 304 were studied by both experiments and numerical simulation. Room temperature tensile tests were carried out at various strain rates to investigate the effect on volume fraction of martensite, temperature increase and flow stress. The results show that with increasing strain rate, the local temperature increases, which suppresses the transformation of martensite. To take into account the dependence on strain level, strain rate sensitivity and thermal effects, a kinetic model of martensitic transformation was proposed and constitutive modeling on stress-strain response was conducted. The validity of the proposed model has been proved by comparisons between simulation results and experimental ones.

  10. Micro-scale measurements of plastic strain field, and local contributions of slip and twinning in TWIP steels during in situ tensile tests

    Energy Technology Data Exchange (ETDEWEB)

    Yang, H.K. [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China); Laboratoire de Mécanique des Solides, Ecole Polytechnique, CNRS UMR7649, Université Paris-Saclay, 91128 Palaiseau (France); Doquet, V., E-mail: doquet@lms.polytechnique.fr [Laboratoire de Mécanique des Solides, Ecole Polytechnique, CNRS UMR7649, Université Paris-Saclay, 91128 Palaiseau (France); Zhang, Z.F. [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China)

    2016-08-30

    In-situ tensile tests were carried out on Fe22Mn0.6C and Fe22Mn0.6C3Al (wt%) twinning-induced plasticity (TWIP) steels specimens covered with gold micro-grids. High resolution atomic force microscopy (AFM) and scanning electron microscope (SEM) images were periodically captured. The latter were used for measurements of the plastic strain field, using digital image correlation (DIC). Although no meso-scale localization bands appeared, some areas were deformed three times more than average. Plastic deformation inside the grains was more heterogeneous in Fe22Mn0.6C, but at meso-scale, the degree of strain heterogeneity was not higher, at least up to 12% strain. Plastic deformation started from grain boundaries or annealing twin boundaries in both materials, due to a high elastic anisotropy of the grains. An original method based on DIC was developed to estimate the twin fraction in grains that exhibit a single set of slip/twin bands. Deformation twinning accommodated 60–80% of the plastic strain in some favorably oriented grains, from the onset of plastic flow in Fe22Mn0.6C, but was not observed in the Al-bearing steel until 12% strain. The back stress was important in both materials, but significantly higher in Fe22Mn0.6C.

  11. Reduction of Large Seismic Deformations using Elasto-plastic Passive Energy Dissipaters

    Directory of Open Access Journals (Sweden)

    K. Sathish Kumar

    2003-01-01

    Full Text Available The design of supporting systems for pipelines carrying highly toxic or radioactive liquids at very high temperature, is an important issue in the safety aspect for a nuclear power installation. These pipeline systems are normally designed to be held rigid by conventional snubber supports for protection from earthquake. The pipeline system design must balance the seismic deformations and other deformations due to thermal effect. A rigid pipeline system using conventional snubber supports always leads to an increase in thermal stresses, hence a rational seismic design for pipeline supporting systems becomes essential. Contrary to this rigid design, it is possible to design a flexible pipeline system and to decrease the seismic response by increasing the damping using passive energy absorbing (PEA element, which dissipates vibration energy. An X-shaped or a hourglass-shaped metal element is a classic example of elasto-plastic passive energy absorber of metallic yielding type. The inherent ductile property of metals like steel, which undergoes stable energy dissipation in the plastic region, is made use of in achieving energy loss. This paper presents the experimental and analytical studies carried out on yielding-type elasto-plastic PEA elements to be used in a passive energy dissipating device for the control of large seismic deformations of pipelines subjected to earthquake loading.

  12. Energy Payback Time of a Solar Photovoltaic Powered Waste Plastic Recyclebot System

    Directory of Open Access Journals (Sweden)

    Shan Zhong

    2017-06-01

    Full Text Available The growth of both plastic consumption and prosumer 3-D printing are driving an interest in producing 3-D printer filaments from waste plastic. This study quantifies the embodied energy of a vertical DC solar photovoltaic (PV powered recyclebot based on life cycle energy analysis and compares it to horizontal AC recyclebots, conventional recycling, and the production of a virgin 3-D printer filament. The energy payback time (EPBT is calculated using the embodied energy of the materials making up the recyclebot itself and is found to be about five days for the extrusion of a poly lactic acid (PLA filament or 2.5 days for the extrusion of an acrylonitrile butadiene styrene (ABS filament. A mono-crystalline silicon solar PV system is about 2.6 years alone. However, this can be reduced by over 96% if the solar PV system powers the recyclebot to produce a PLA filament from waste plastic (EPBT is only 0.10 year or about a month. Likewise, if an ABS filament is produced from a recyclebot powered by the solar PV system, the energy saved is 90.6–99.9 MJ/kg and 26.33–29.43 kg of the ABS filament needs to be produced in about half a month for the system to pay for itself. The results clearly show that the solar PV system powered recyclebot is already an excellent way to save energy for sustainable development.

  13. Plasticity induced by pre-existing defects during high strain-rate loading

    Science.gov (United States)

    Bringa, Eduardo

    2014-03-01

    High strain-rate deformation of metals has been typically studied for perfect monocrystals. Computational advances now allow more realistic simulations of materials including defects, which lower the Hugoniot Elastic Limit, and lead to microstructures differing from the ones from perfect monocrystals. As pre-existing defects one can consider vacancy clusters, dislocation loops, grain boundaries, etc. New analysis tools allow analysis of dislocation densities and twin fractions, for both f.c.c. and b.c.c. metals. Recent results for defective single crystal Ta [Tramontina et al.., High Energy Den. Phys. 10, 9 (2014), and Ruestes et al., Scripta Mat. 68, 818 (2013)], and for polycrystalline b.c.c metals [Tang et al., Mat. Sci. Eng. A 580, 414 (2013), and Gunkelmann et al., Phys. Rev. B 86, 144111 (2012)] will be highlighted, alongside new results for nanocrystalline Cu, Ta, Fe, and Zr [Ruestes et al., Scripta Mat. 71, 9 (2014)]. This work has been carried out in collaboration with D. Tramontina, C. Ruestes, E. Millan, J. Rodriguez-Nieva, M.A. Meyers, Y. Tang, H. Urbassek, N. Gunkelmann, A. Stukowski, M. Ruda, G. Bertolino, D. Farkas, A. Caro, J. Hawreliak, B. Remington, R. Rudd, P. Erhart, R. Ravelo, T. Germann, N. Park, M. Suggit, S. Michalik, A. Higginbotham and J. Wark. Funding by PICT2008-1325 and SeCTyP U.N. Cuyo.

  14. SOME MISUNDERSTANDINGS ON ROTATION OF CRYSTALS AND REASONABLE PLASTIC STRAIN RATE

    Institute of Scientific and Technical Information of China (English)

    赵祖武

    2001-01-01

    It is pointed out that crystals are discrete but not continuous materials. Hence the rotation R in decomposition F = RU and spin W in F F-1 are not correct. Errors will arise in plastic deformation rate if it is directly expressed with amounts of velocity of slips in glide systems such as γv n . The geometrical figure of crystal lattices does not change after slips and based on this idea a simple way in mechanics of continuous media to get the plastic deformations rate induced by slips is proposed. Constitutive equations are recommended.

  15. Mechanical heterogeneity and mechanism of plasticity in metallic glasses

    Science.gov (United States)

    Wang, J. G.; Zhao, D. Q.; Pan, M. X.; Shek, C. H.; Wang, W. H.

    2009-01-01

    The mechanical heterogeneity is quantified based on the spatial nanohardness distributions in three bulk metallic glasses with different plasticities. It is found that the metallic glass with high mechanical heterogeneity is more plastic. We propose that the appropriate mechanical heterogeneity makes the metallic glasses meliorate their plasticity by increasing inelastic strained area and promoting energy dissipation.

  16. The surface-forming energy release rate based fracture criterion for elastic-plastic crack propagation

    Science.gov (United States)

    Xiao, Si; Wang, He-Ling; Liu, Bin; Hwang, Keh-Chih

    2015-11-01

    The J-integral based criterion is widely used in elastic-plastic fracture mechanics. However, it is not rigorously applicable when plastic unloading appears during crack propagation. One difficulty is that the energy density with plastic unloading in the J-integral cannot be defined unambiguously. In this paper, we alternatively start from the analysis on the power balance, and propose a surface-forming energy release rate (ERR), which represents the energy available for separating the crack surfaces during the crack propagation and excludes the loading-mode-dependent plastic dissipation. Therefore the surface-forming ERR based fracture criterion has wider applicability, including elastic-plastic crack propagation problems. Several formulae are derived for calculating the surface-forming ERR. From the most concise formula, it is interesting to note that the surface-forming ERR can be computed using only the stress and deformation of the current moment, and the definition of the energy density or work density is avoided. When an infinitesimal contour is chosen, the expression can be further simplified. For any fracture behaviors, the surface-forming ERR is proven to be path-independent, and the path-independence of its constituent term, so-called Js-integral, is also investigated. The physical meanings and applicability of the proposed surface-forming ERR, traditional ERR, Js-integral and J-integral are compared and discussed. Besides, we give an interpretation of Rice paradox by comparing the cohesive fracture model and the surface-forming ERR based fracture criterion.

  17. A general methodology for full-field plastic strain measurements using X-ray absorption tomography and internal markers

    DEFF Research Database (Denmark)

    Haldrup, Martin Kristoffer; Nielsen, Søren Fæster; Wert, John A.

    2008-01-01

    Probing the strain locally and throughout the bulk of various materials has long been of interest in Materials Science. This article presents a general methodology for assessing the plastic strain in terms of the displacement gradient tensor throughout the bulk of opaque samples. The method relies...... on a homogenous distribution of marker particles throughout the bulk of a sample, markers which are detected through the application of synchrotron X-ray tomography. Making use of the morphology of individual markers, motion of individual markers is tracked during deformation allowing the local displacement field...... to be determined throughout the bulk. The local displacement gradient tensor is derived from the displacement field. Spatial resolution is directly related to marker particle density in the sample, here 30 mu m. The accuracy of the displacement gradient tensor calculation is dependent on the accuracy with which...

  18. Effect of slow plastic and elastic straining on sulphide stress cracking and hydrogen embrittlement of 3. 5% Ni steel and APL 5L X60 pipeline steel

    Energy Technology Data Exchange (ETDEWEB)

    Erlings, J.G.; Groot, H.W. de; Nauta, J.

    1987-01-01

    A procedure is presented with which the roles of elastic and elastic-plastic straining in stress corrosion cracking (SCC) and hydrogen embrittlement (HE) can be determined. Premature failure of 3.5% Ni steels in sour and sweet environments due to SCC was only found when slow plastic straining was applied. With purely elastic slow straining the material remained crack-free, even in a buffered NACE solution. Depending on the sourness of the environment, the API 5L X60 pipeline material did not always need plastic straining to suffer HE cracking. Under none of the test conditions studied was hardened material susceptible to SCC or HE cracking. The non-hardened material tested was not susceptible to SCC in the various CO/sub 2/- and/or H/sub 2/S-containing media used.

  19. Temperature increase of Zircaloy-4 cladding tubes due to plastic heat dissipation during tensile tests at 0.1-10 s-1 strain rates

    Science.gov (United States)

    Hellouin de Menibus, Arthur; Auzoux, Quentin; Besson, Jacques; Crépin, Jérôme

    2014-11-01

    This study is focused on the impact of rapid Reactivity Initiated Accident (RIA) representative strain rates (about 1 s-1 NEA, 2010) on the behavior and fracture of unirradiated cold work stress relieved Zircaloy-4 cladding tubes. Uniaxial ring tests (HT) and plane strain ring tensile tests (PST) were performed in the 0.1-10 s-1 strain rate range, at 25 °C. The local temperature increase due to plastic dissipation was measured with a high-speed infrared camera. Limited temperature increases were measured at 0.1 s-1 strain rate. Limited but not strongly localized temperature increases were measured at 1 s-1. Large temperature increase were measured at 5 and 10 s-1 (142 °C at 5 s-1 strain rate in HT tests). The local temperature increase induced heterogeneous temperature fields, which enhanced strain localization and resulted in a reduction of the plastic elongation at fracture.

  20. Basic Strain Gradient Plasticity Theories with Application to Constrained Film Deformation

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Hutchinson, John W.

    2011-01-01

    with the deformation theory under proportional straining, analogous to the corresponding coincidence in the conventional J(2) theories. The generality of proportional straining is demonstrated for pure power-law materials, and the utility of power-law solutions is illustrated for the constrained deformation of thin...

  1. Elastic strain energy behavior in the polymer nanocrystals

    Directory of Open Access Journals (Sweden)

    Alexander I. Slutsker

    2016-06-01

    Full Text Available In the paper, the changes in axial and contour lengths of skeletal interatomic bonds in the chain molecules of polyethylene nanocrystals have been measured using X-ray diffractometry and Raman spectrometry. In the course of the measurements the samples were subjected to stretching and heating (mechanical and thermal actions. The measured force and temperature dependences were analyzed and the calculated description of the polymer nanocrystal strain was inferred from them. In so doing the original results were obtained for the thermal action. The potential energy components related to both the skeletal bond stretching and the chain molecule bending were determined for the strained polymer crystal. The sharp distinction between the ratios of these components for the object under mechanical and thermal actions was found.

  2. On valence electron density, energy dissipation and plasticity of bulk metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Pang, J.J.; Tan, M.J. [School of Mechanical and Aerospace Engineering, Nanyang Technological University, 639798 Singapore (Singapore); Liew, K.M., E-mail: kmliew@cityu.edu.hk [Department of Civil and Architectural Engineering, City University of Hong Kong, Kowloon (Hong Kong)

    2013-11-15

    Highlights: ► Relationship between valence electron density and plasticity of metallic glasses. ► Poisson's ratio increases as electron density decreases. ► Energy dissipation proposed to understand plasticity. ► Low electron density indicates small activation energy. -- Abstract: In conventional crystalline alloys, valence electron density (VED) is one of the most significant factors in determining their phase stability and mechanical properties. Extending the concept to metallic glasses (MGs), it is found, not totally surprisingly, that their mechanical properties are VED-dependent as in crystalline alloys. Interestingly, the whole VED region can be separated into two zones: Zone 1 consists of Mg-, Ca-, and RE-based (RE for rare earth) alloys; Zone 2 consists of the rest of MGs. In either zone, for each type of MGs, Poisson's ratio generally decreases as VED increases. From the energy dissipation viewpoint proposed recently, the amorphous plasticity is closely related to the activation energy for the operation of shear-transformation-zones (STZs). Smaller STZ activation energy suggests higher ductility because STZs with lower activation energy are able to convert deformation work more efficiently into configurational energy rather than heat, which yields mechanical softening and advances the growth of shear bands (SBs). Following this model, it is revealed that the activation energies for STZ operation and crystallization are certainly proportional to VED. Thus, it is understood that, in Zone 2, MGs have a smaller VED and hence lower activation energies which are favorable for ductility and Poisson's ratio. In Zone 1, MGs have the lowest VED but apparent brittleness because either of low glass transition temperature and poor resistance to oxidation or of a large fraction of covalent bonds.

  3. Dietary fructose aggravates the pathobiology of traumatic brain injury by influencing energy homeostasis and plasticity.

    Science.gov (United States)

    Agrawal, Rahul; Noble, Emily; Vergnes, Laurent; Ying, Zhe; Reue, Karen; Gomez-Pinilla, Fernando

    2016-05-01

    Fructose consumption has been on the rise for the last two decades and is starting to be recognized as being responsible for metabolic diseases. Metabolic disorders pose a particular threat for brain conditions characterized by energy dysfunction, such as traumatic brain injury. Traumatic brain injury patients experience sudden abnormalities in the control of brain metabolism and cognitive function, which may worsen the prospect of brain plasticity and function. The mechanisms involved are poorly understood. Here we report that fructose consumption disrupts hippocampal energy homeostasis as evidenced by a decline in functional mitochondria bioenergetics (oxygen consumption rate and cytochrome C oxidase activity) and an aggravation of the effects of traumatic brain injury on molecular systems engaged in cell energy homeostasis (sirtuin 1, peroxisome proliferator-activated receptor gamma coactivator-1alpha) and synaptic plasticity (brain-derived neurotrophic factor, tropomyosin receptor kinase B, cyclic adenosine monophosphate response element binding, synaptophysin signaling). Fructose also worsened the effects of traumatic brain injury on spatial memory, which disruption was associated with a decrease in hippocampal insulin receptor signaling. Additionally, fructose consumption and traumatic brain injury promoted plasma membrane lipid peroxidation, measured by elevated protein and phenotypic expression of 4-hydroxynonenal. These data imply that high fructose consumption exacerbates the pathology of brain trauma by further disrupting energy metabolism and brain plasticity, highlighting the impact of diet on the resilience to neurological disorders.

  4. Processing and properties of a solid energy fuel from municipal solid waste (MSW) and recycled plastics.

    Science.gov (United States)

    Gug, JeongIn; Cacciola, David; Sobkowicz, Margaret J

    2015-01-01

    Diversion of waste streams such as plastics, woods, papers and other solid trash from municipal landfills and extraction of useful materials from landfills is an area of increasing interest especially in densely populated areas. One promising technology for recycling municipal solid waste (MSW) is to burn the high-energy-content components in standard coal power plant. This research aims to reform wastes into briquettes that are compatible with typical coal combustion processes. In order to comply with the standards of coal-fired power plants, the feedstock must be mechanically robust, free of hazardous contaminants, and moisture resistant, while retaining high fuel value. This study aims to investigate the effects of processing conditions and added recyclable plastics on the properties of MSW solid fuels. A well-sorted waste stream high in paper and fiber content was combined with controlled levels of recyclable plastics PE, PP, PET and PS and formed into briquettes using a compression molding technique. The effect of added plastics and moisture content on binding attraction and energy efficiency were investigated. The stability of the briquettes to moisture exposure, the fuel composition by proximate analysis, briquette mechanical strength, and burning efficiency were evaluated. It was found that high processing temperature ensures better properties of the product addition of milled mixed plastic waste leads to better encapsulation as well as to greater calorific value. Also some moisture removal (but not complete) improves the compacting process and results in higher heating value. Analysis of the post-processing water uptake and compressive strength showed a correlation between density and stability to both mechanical stress and humid environment. Proximate analysis indicated heating values comparable to coal. The results showed that mechanical and moisture uptake stability were improved when the moisture and air contents were optimized. Moreover, the briquette

  5. Insertion sequence content reflects genome plasticity in strains of the root nodule actinobacterium Frankia

    Directory of Open Access Journals (Sweden)

    Tisa Louis S

    2009-10-01

    Full Text Available Abstract Background Genome analysis of three Frankia sp. strains has revealed a high number of transposable elements in two of the strains. Twelve out of the 20 major families of bacterial Insertion Sequence (IS elements are represented in the 148 annotated transposases of Frankia strain HFPCcI3 (CcI3 comprising 3% of its total coding sequences (CDS. EAN1pec (EAN has 183 transposase ORFs from 13 IS families comprising 2.2% of its CDS. Strain ACN14a (ACN differs significantly from the other strains with only 33 transposase ORFs (0.5% of the total CDS from 9 IS families. Results Insertion sequences in the Frankia genomes were analyzed using BLAST searches, PHYML phylogenies and the IRF (Inverted Repeat Finder algorithms. To identify putative or decaying IS elements, a PSI-TBLASTN search was performed on all three genomes, identifying 36%, 39% and 12% additional putative transposase ORFs than originally annotated in strains CcI3, EAN and ACN, respectively. The distribution of transposase ORFs in each strain was then analysed using a sliding window, revealing significant clustering of elements in regions of the EAN and CcI3 genomes. Lastly the three genomes were aligned with the MAUVE multiple genome alignment tool, revealing several Large Chromosome Rearrangement (LCR events; many of which correlate to transposase clusters. Conclusion Analysis of transposase ORFs in Frankia sp. revealed low inter-strain diversity of transposases, suggesting that the majority of transposase proliferation occurred without recent horizontal transfer of novel mobile elements from outside the genus. Exceptions to this include representatives from the IS3 family in strain EAN and seven IS4 transposases in all three strains that have a lower G+C content, suggesting recent horizontal transfer. The clustering of transposase ORFs near LCRs revealed a tendency for IS elements to be associated with regions of chromosome instability in the three strains. The results of this

  6. Structural features of plastic deformation in bulk metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Scudino, S., E-mail: s.scudino@ifw-dresden.de; Shakur Shahabi, H.; Stoica, M.; Kühn, U. [IFW Dresden, Institut für Komplexe Materialien, D-01069 Dresden (Germany); Kaban, I.; Escher, B.; Eckert, J. [IFW Dresden, Institut für Komplexe Materialien, D-01069 Dresden (Germany); TU Dresden, Institut für Werkstoffwissenschaft, D-01062 Dresden (Germany); Vaughan, G. B. M. [European Synchrotron Radiation Facilities ESRF, BP220, 38043 Grenoble (France)

    2015-01-19

    Spatially resolved strain maps of a plastically deformed bulk metallic glass (BMG) have been created by using high-energy X-ray diffraction. The results reveal that plastic deformation creates a spatially heterogeneous atomic arrangement, consisting of strong compressive and tensile strain fields. In addition, significant shear strain is introduced in the samples. The analysis of the eigenvalues and eigenvectors of the strain tensor indicates that considerable structural anisotropy occurs in both the magnitude and direction of the strain. These features are in contrast to the behavior observed in elastically deformed BMGs and represent a distinctive structural sign of plastic deformation in metallic glasses.

  7. Processing and properties of a solid energy fuel from municipal solid waste (MSW) and recycled plastics

    Energy Technology Data Exchange (ETDEWEB)

    Gug, JeongIn, E-mail: Jeongin_gug@student.uml.edu; Cacciola, David, E-mail: david_cacciola@student.uml.edu; Sobkowicz, Margaret J., E-mail: Margaret_sobkowiczkline@uml.edu

    2015-01-15

    Highlights: • Briquetting was used to produce solid fuels from municipal solid waste and recycled plastics. • Optimal drying, processing temperature and pressure were found to produce stable briquettes. • Addition of waste plastics yielded heating values comparable with typical coal feedstocks. • This processing method improves utilization of paper and plastic diverted from landfills. - Abstract: Diversion of waste streams such as plastics, woods, papers and other solid trash from municipal landfills and extraction of useful materials from landfills is an area of increasing interest especially in densely populated areas. One promising technology for recycling municipal solid waste (MSW) is to burn the high-energy-content components in standard coal power plant. This research aims to reform wastes into briquettes that are compatible with typical coal combustion processes. In order to comply with the standards of coal-fired power plants, the feedstock must be mechanically robust, free of hazardous contaminants, and moisture resistant, while retaining high fuel value. This study aims to investigate the effects of processing conditions and added recyclable plastics on the properties of MSW solid fuels. A well-sorted waste stream high in paper and fiber content was combined with controlled levels of recyclable plastics PE, PP, PET and PS and formed into briquettes using a compression molding technique. The effect of added plastics and moisture content on binding attraction and energy efficiency were investigated. The stability of the briquettes to moisture exposure, the fuel composition by proximate analysis, briquette mechanical strength, and burning efficiency were evaluated. It was found that high processing temperature ensures better properties of the product addition of milled mixed plastic waste leads to better encapsulation as well as to greater calorific value. Also some moisture removal (but not complete) improves the compacting process and results in

  8. Development of plastic heat exchangers for ocean thermal energy conversion. Final report, August 1976--December 1978

    Energy Technology Data Exchange (ETDEWEB)

    Hart, G.K.; Lee, C.O.; Latour, S.R.

    1979-01-01

    Materials and processes have been selected and design information obtained for plastic ocean thermal energy conversion (OTEC) heat exchangers as the result of a program comprising five types of laboratory experiments. Tests to evaluate the chemical resistance of seven commercially available thermoplastics to sea water and several possible working fluids were conducted with emphasis placed on compatibility with ammonia. Environmental rupture tests involving exposure of stressed specimens to sea water or liquid ammonia indicated that the high density polyethylene (HDPE) is the best suited candidate and produced an extrapolated 100,000 hour failure stress of 1060 psi for HDPE. Long term durability tests of extruded HDPE plate-tube panel confirmed that plastic heat transfer surface is mechanically reliable in an OTEC environment. Thermal conductivity measurements of acetylene black filled HDPE indicated that conductivity may be increased by 50% with a 35% by weight filler loading. The permeability coefficient measured for liquid ammonia through HDPE was higher than previous estimates. Test showed that the rate can be significantly reduced by sulfonation of HDPE. A review of biofouling mechanisms revealed that the permeable nature of the plastic heat exchanger surface may be used to control primary biofouling form formation by allowing incorporation of non-toxic organic repellents into the plastic. A preliminary design and fabrication development program suggests that construction of an ammonia condenser test unit is feasible using currently available materials and manufacturing techniques.

  9. Quenching Factor for Low Energy Nuclear Recoils in a Plastic Scintillator

    CERN Document Server

    Reichhart, L; Araujo, H M; Barnes, E J; Belov, V A; Burenkov, A A; Chepel, V; Currie, A; DeViveiros, L; Edwards, B; Francis, V; Ghag, C; Hollingsworth, A; Horn, M; Kalmus, G E; Kobyakin, A S; Kovalenko, A G; Lebedenko, V N; Lindote, A; Lopes, M I; Luscher, R; Majewski, P; Murphy, A St J; Neves, F; Paling, S M; da Cunha, J Pinto; Preece, R; Quenby, J J; Scovell, P R; Silva, C; Solovov, V N; Smith, N J T; Smith, P F; Stekhanov, V N; Sumner, T J; Thorne, C; Walker, R J

    2011-01-01

    Plastic scintillators are widely used in industry, medicine and scientific research, including nuclear and particle physics. Although one of their most common applications is in neutron detection, experimental data on their response to low-energy nuclear recoils are scarce. Here, the relative scintillation efficiency for neutron-induced nuclear recoils in a polystyrene-based plastic scintillator (UPS-923A) is presented, exploring recoil energies between 125 keV and 850 keV. Monte Carlo simulations, incorporating light collection efficiency and energy resolution effects, are used to generate neutron scattering spectra which are matched to observed distributions of scintillation signals to parameterise the energy-dependent quenching factor. At energies above 300 keV the dependence is reasonably described using the semi-empirical formulation of Birks and a kB factor of (0.014+/-0.002) g/MeVcm^2 has been determined. Below that energy the measured quenching factor falls more steeply than predicted by the Birks for...

  10. Strain-based plastic instability acceptance criteria for ferritic steel safety class 1 nuclear components under level D service loads

    Directory of Open Access Journals (Sweden)

    Ji-Su Kim

    2015-04-01

    Full Text Available This paper proposes strain-based acceptance criteria for assessing plastic instability of the safety class 1 nuclear components made of ferritic steel during level D service loads. The strain-based criteria were proposed with two approaches: (1 a section average approach and (2 a critical location approach. Both approaches were based on the damage initiation point corresponding to the maximum load-carrying capability point instead of the fracture point via tensile tests and finite element analysis (FEA for the notched specimen under uni-axial tensile loading. The two proposed criteria were reviewed from the viewpoint of design practice and philosophy to select a more appropriate criterion. As a result of the review, it was found that the section average approach is more appropriate than the critical location approach from the viewpoint of design practice and philosophy. Finally, the criterion based on the section average approach was applied to a simplified reactor pressure vessel (RPV outlet nozzle subject to SSE loads. The application shows that the strain-based acceptance criteria can consider cumulative damages caused by the sequential loads unlike the stress-based acceptance criteria and can reduce the overconservatism of the stress-based acceptance criteria, which often occurs for level D service loads.

  11. Modeling anisotropic plasticity: Eulerian hydrocode applications of high strain-rate deformation processes

    Energy Technology Data Exchange (ETDEWEB)

    Clancy, S.P.; Burkett, M.W.; Maudlin, P.J.

    1997-05-01

    Previously developed constitutive models and solution algorithms for anisotropic elastoplastic material strength are implemented in the two-dimensional MESA hydrodynamics code. Quadratic yield functions fitted from polycrystal simulations for a metallic hexagonal-close-packed structure are utilized. An associative flow strength formulation incorporating these yield functions is solved using a geometric normal return method. A stretching rod problem is selected to investigate the effects of material anisotropy on a tensile plastic instability (necking). The rod necking rate and topology are compared for MESA simulations performed for both isotropic and anisotropic cases utilizing the Mechanical Threshold Stress flow stress model.

  12. On the formulations of higher-order strain gradient crystal plasticity models

    DEFF Research Database (Denmark)

    Kuroda, M.; Tvergaard, Viggo

    2008-01-01

    Recently, several higher-order extensions to the crystal plasticity theory have been proposed to incorporate effects of material length scales that were missing links in the conventional continuum mechanics. The extended theories are classified into work-conjugate and non-work-conjugate types...... backgrounds and very unlike mathematical representations. Nevertheless, both types of theories predict the same kind of material length scale effects. We have recently shown that there exists some equivalency between the two approaches in the special situation of two-dimensional single slip under small...

  13. Thermal recycling of plastic waste using pyrolysis-gasification process for energy production

    Energy Technology Data Exchange (ETDEWEB)

    Forbit, George Teke

    2012-04-04

    The disposal of mixed waste in landfills, dump sites and open burning without material and energy recovery leads to resource loss, causes health problems, pollution and littering. Increasing energy demand for industrial and domestic application with rising costs due to scarcity motivates a constant search for alternative clean energy sources. Recovering energy from waste presents various incentives e.g. creating jobs, alleviating poverty, combating and mitigating climate change, protecting the environment and reducing dependence on traditional fuels sources. Hence, plastics end up in landfills, surface waters and ocean bed with serious negative impact on terrestrial and aquatic biodiversity. Plastic waste with high calorific value (36-46MJ/kg) occupies the greatest portion of landfill space. Hence, using an appropriate technology to transform waste plastic to a hot gaseous mixture which is burned in-situ produces enormous amount of energy without pollution. Based on this hypothesis, the study objectives accomplished were to: 1. Characterise, quantify and classify waste fractions and plastic components common in MSW by manual sorting 2. Evaluate options for sustainable plastic waste management especially for developing countries 3. Design, construct, test and optimize an appropriate technology that applies pyrolysis and gasification processes to convert non-PVC plastic waste to energy 4. Assess the efficiency of the technology based on the functioning, the engineering, mass and energy analysis including socioeconomic and environmental impacts An integrated methodology involving review of current literature, field and laboratory experiments on mixed waste and plastic waste analysis was used. In addition, the pyrolysis-gasification technology (PGT) was conceptualised, designed, constructed, tested and optimised at BTU Cottbus, Germany; Lagos, Nigeria and Dschang, Cameroon. Field studies involving natural observation, interviews, personal discussions and visits to

  14. Bulk Nanolayered Composites: Interfacial Influence on Microstructural Evolution at Large Plastic Strains

    Energy Technology Data Exchange (ETDEWEB)

    Mara, Nathan A. [Los Alamos National Laboratory; Carpenter, John S. [Los Alamos National Laboratory; Han, Weizhong [Los Alamos National Laboratory; Zheng, Shijian [Los Alamos National Laboratory; McCabe, Rodney J. [Los Alamos National Laboratory; Wang, Jian [Los Alamos National Laboratory; Beyerlein, Irene J. [Los Alamos National Laboratory

    2012-07-31

    Conclusions are: (1) As-processed ARB material has similar morphology, chemistry as PVD, but different interfacial structure; (2) Density of interfaces AND interfacial structure play a role in determining hardness, an example is twinning in Cu at the {l_brace}112{r_brace}Cu//{l_brace}112{r_brace}Nb interface and higher strength, no twinning in Cu in the {l_brace}111{r_brace}Cu//{l_brace}110{r_brace}Nb interface; and (3) Need to understand effects of processing history to predict the effects on the interfaces we produce - Amount of strain, Strain Path, Annealing.

  15. Fatigue Crack Propagation Under Variable Amplitude Loading Analyses Based on Plastic Energy Approach

    Directory of Open Access Journals (Sweden)

    Sofiane Maachou

    2014-04-01

    Full Text Available Plasticity effects at the crack tip had been recognized as “motor” of crack propagation, the growth of cracks is related to the existence of a crack tip plastic zone, whose formation and intensification is accompanied by energy dissipation. In the actual state of knowledge fatigue crack propagation is modeled using crack closure concept. The fatigue crack growth behavior under constant amplitude and variable amplitude loading of the aluminum alloy 2024 T351 are analyzed using in terms energy parameters. In the case of VAL (variable amplitude loading tests, the evolution of the hysteretic energy dissipated per block is shown similar with that observed under constant amplitude loading. A linear relationship between the crack growth rate and the hysteretic energy dissipated per block is obtained at high growth rates. For lower growth rates values, the relationship between crack growth rate and hysteretic energy dissipated per block can represented by a power law. In this paper, an analysis of fatigue crack propagation under variable amplitude loading based on energetic approach is proposed.

  16. Numerical simulation of elasto-plastic electro-osmosis consolidation at large strain

    NARCIS (Netherlands)

    Yuan, J.; Hicks, M.A.

    2015-01-01

    n this paper, a numerical solution for the electro-osmosis consolidation of clay in multi-dimensional domains at large strains is presented, with the coupling of the soil mechanical behaviour, pore water transport and electrical fields being considered. In particular, the Modified Cam Clay model is

  17. Numerical simulation of elasto-plastic electro-osmosis consolidation at large strain

    NARCIS (Netherlands)

    Yuan, J.; Hicks, M.A.

    2015-01-01

    n this paper, a numerical solution for the electro-osmosis consolidation of clay in multi-dimensional domains at large strains is presented, with the coupling of the soil mechanical behaviour, pore water transport and electrical fields being considered. In particular, the Modified Cam Clay model is

  18. A new approach for elasto-plastic finite strain analysis of cantilever beams subjected to uniform bending moment

    Indian Academy of Sciences (India)

    GOKHAN T TAYYAR

    2016-04-01

    The reliability and limits of solutions for static structural analysis depend on the accuracy of the curvature and deflection calculations. Even if the material model is close to the actual material behavior, physically unrealistic deflections or divergence problems are unavoidable in the analysis if an appropriate fundamental kinematic theory is not chosen. Moreover, accurate deflection calculation plays an important role in ultimate strength analysis where in-plane stresses are considered. Therefore, a more powerful method is neededto achieve reliable deflection calculation and modeling. For this purpose, a new advanced step was developed by coupling the elasto-plastic material behavior with precise general planar kinematic analysis. The deflection is generated precisely without making geometric assumptions or using differential equations of the deflection curve. An analytical finite strain solution was derived for an elasto-plastic prismatic/non-prismatic rectangular cross-sectioned beam under a uniform moment distribution. A comparison of the analytical results with thosefrom the Abaqus FEM software package reveals a coherent correlation.

  19. Effects of gasket on coupled plastic flow and strain-induced phase transformations under high pressure and large torsion in a rotational diamond anvil cell

    Science.gov (United States)

    Feng, Biao; Levitas, Valery I.

    2016-01-01

    Combined plastic flow and strain-induced phase transformations (PTs) under high pressure in a sample within a gasket subjected to three dimensional compression and torsion in a rotational diamond anvil cell (RDAC) are studied using a finite element approach. The results are obtained for the weaker, equal-strength, and stronger high-pressure phases in comparison with low-pressure phases. It is found that, due to the strong gasket, the pressure in the sample is relatively homogenous and the geometry of the transformed zones is mostly determined by heterogeneity in plastic flow. For the equal-strength phases, the PT rate is higher than for the weaker and stronger high-pressure phases. For the weaker high-pressure phase, transformation softening induces material instability and leads to strain and PT localization. For the stronger high-pressure phase, the PT is suppressed by strain hardening during PT. The effect of the kinetic parameter k that scales the PT rate in the strain-controlled kinetic equation is also examined. In comparison with a traditional diamond anvil cell without torsion, the PT progress is much faster in RDAC under the same maximum pressure in the sample. Finally, the gasket size and strength effects are discussed. For a shorter and weaker gasket, faster plastic flow in radial and thickness directions leads to faster PT kinetics in comparison with a longer and stronger gasket. The rates of PT and plastic flows are not very sensitive to the modest change in a gasket thickness. Multiple experimental results are reproduced and interpreted. Obtained results allow one to design the desired pressure-plastic strain loading program in the experiments for searching new phases, reducing PT pressure by plastic shear, extracting kinetic properties from experiments with heterogeneous fields, and controlling homogeneity of all fields and kinetics of PTs.

  20. The Flo11p-deficient Saccharomyces cerevisiae strain background S288c can adhere to plastic surfaces

    DEFF Research Database (Denmark)

    Mortensen, Henrik Dam; Dupont, Kitt; Jespersen, Lene;

    2007-01-01

    The effects of four types of plastic surfaces and four pre-incubation media, containing high/low glucose and +/- amino acids, on adhesion of Saccharomyces cerevisiae BY4742 wild type and Deltaflo11 mutant (strain background S288c) were investigated. No difference in adhesive ability between the two...... yeast strains was observed in any of our experiments, thus confirming that FLO11 is not operational in the S. cerevisiae S288c strain background. The adhesive abilities of both yeast strains depended on the plastic type and pre-incubation conditions. The poorest adhesion was observed on hydrophilic...... hydrophobicity and enhanced the adhesion to all four types of polystyrene. Lack of amino acids in the pre-incubation media increased the cell surface hydrophobicity and enhanced the adhesion especially to polystyrene surfaces with combined hydrophilic/hydrophobic domains. Our results suggest that glucose...

  1. Stress-strain curves of aluminum nanowires: Fluctuations in the plastic regime and absence of hardening

    Science.gov (United States)

    Pastor-Abia, L.; Caturla, M. J.; Sanfabián, E.; Chiappe, G.; Louis, E.

    2008-10-01

    The engineering stress-strain curves of aluminum nanowires have been investigated by means of molecular dynamics. Nanowires were stretched at constant strain rate and at a temperature of 4.2 K. Atoms at fixed positions with velocities randomly distributed according to Maxwell distribution were taken as initial conditions. Averaging over at least 1500 realizations allows the conclusion that, beyond the yield point, the system does not harden, in line with experimental results for larger nanowires of gold measured at room temperature. Fluctuations of the heat exchanged in the nonlinear regime have been investigated by analyzing around 1.5 million data. The results indicate the presence of non-Gaussian tails in the heat probability distribution.

  2. Theoretical and experimental characterization of novel water-equivalent plastics in clinical high-energy carbon-ion beams

    Science.gov (United States)

    Lourenço, A.; Wellock, N.; Thomas, R.; Homer, M.; Bouchard, H.; Kanai, T.; MacDougall, N.; Royle, G.; Palmans, H.

    2016-11-01

    Water-equivalent plastics are frequently used in dosimetry for experimental simplicity. This work evaluates the water-equivalence of novel water-equivalent plastics specifically designed for light-ion beams, as well as commercially available plastics in a clinical high-energy carbon-ion beam. A plastic- to-water conversion factor {{H}\\text{pl,w}} was established to derive absorbed dose to water in a water phantom from ionization chamber readings performed in a plastic phantom. Three trial plastic materials with varying atomic compositions were produced and experimentally characterized in a high-energy carbon-ion beam. Measurements were performed with a Roos ionization chamber, using a broad un-modulated beam of 11  ×  11 cm2, to measure the plastic-to-water conversion factor for the novel materials. The experimental results were compared with Monte Carlo simulations. Commercially available plastics were also simulated for comparison with the plastics tested experimentally, with particular attention to the influence of nuclear interaction cross sections. The measured H\\text{pl,w}\\exp correction increased gradually from 0% at the surface to 0.7% at a depth near the Bragg peak for one of the plastics prepared in this work, while for the other two plastics a maximum correction of 0.8%-1.3% was found. Average differences between experimental and numerical simulations were 0.2%. Monte Carlo results showed that for polyethylene, polystyrene, Rando phantom soft tissue and A-150, the correction increased from 0% to 2.5%-4.0% with depth, while for PMMA it increased to 2%. Water-equivalent plastics such as, Plastic Water, RMI-457, Gammex 457-CTG, WT1 and Virtual Water, gave similar results where maximum corrections were of the order of 2%. Considering the results from Monte Carlo simulations, one of the novel plastics was found to be superior in comparison with the plastic materials currently used in dosimetry, demonstrating that it is feasible to tailor plastic

  3. Enhancement of Biodegradable Plastic-degrading Enzyme Production from Paraphoma-like Fungus, Strain B47-9.

    Science.gov (United States)

    Sameshima-Yamashita, Yuka; Koitabashi, Motoo; Tsuchiya, Wataru; Suzuki, Ken; Watanabe, Takashi; Shinozaki, Yukiko; Yamamoto-Tamura, Kimiko; Yamazaki, Toshimasa; Kitamoto, Hiroko

    2016-01-01

    To improve the productivity of Paraphoma-like fungal strain B47-9 for biodegradable plastic (BP)-degrading enzyme (PCLE), the optimal concentration of emulsified poly(butylene succinate-co-adipate) (PBSA) in the medium was determined. Emulsified PBSA was consumed as a sole carbon source and an inducer of PCLE production by strain B47-9. Among the various concentrations of emulsified PBSA [0.09-0.9% (w/v)] used in flask cultivation, 0.27% yielded the maximum enzyme activity within a short cultivation period. To evaluate the residual concentration of emulsified PBSA in culture, emulsified PBSA in aliquots of culture supernatant was digested in vitro, and the concentration of released monomerised succinic acid was determined. Regardless of the initial concentration of emulsified PBSA in medium, PCLE activity was detected after residual succinic acid decreased below 0.04 mg/mL in culture broth. Jarfermentation was performed at a 0.27% PBSA concentration. Among the various airflow rates tested, 1 LPM resulted in a PCLE production rate of 1.0 U/mL/day. The enzyme activity in the resulting culture filtrate (4.2 U/2 mL) was shown to degrade commercial BP films (1 × 1 cm, 20 µm thickness) within 8 hours.

  4. Elasto-plastic constitutive modeling for granular materials

    Institute of Scientific and Technical Information of China (English)

    彭芳乐; 李建中

    2004-01-01

    Based on the modified plastic strain energy approach, an elasto-plastic constitutive modeling for sand was proposed. The hardening function between the modified plastic strain energy and a stress parameter was presented, which was independent of stress history and stress paths. The proposed model was related to an isotropically work-hardening and softening, non-associated and elasto-plastic material description. It is shown that the constitutive modeling, the inherent and stress system-induced cross-anisotropic elasticity is also considered. The constitutive model is capable of simulating the effects on the deformation characteristics of stress history and stress path, pressure level and anisotropic strength.

  5. Dynamic Strength and Accumulated Plastic Strain Development Laws and Models of the Remolded Red Clay under Long-Term Cyclic Loads: Laboratory Test Results

    Directory of Open Access Journals (Sweden)

    Li Jian

    2015-09-01

    Full Text Available The dynamic strength and accumulated plastic strain are two important parameters for evaluating the dynamic response of soil. As a special clay, the remolded red clay is often used as the high speed railway subgrade filling, but studies on its dynamic characteristics are few. For a thorough analysis of the suitability of the remolded red clay as the subgrade filling, a series of long-term cyclic load triaxial test under different load histories are carried out. Considering the influence of compactness, confining pressure, consolidation ratio, vibration frequency and dynamic load to the remolded red clay dynamic property, the tests obtain the development curves of the dynamic strength and accumulated plastic strain under different test conditions. Then, through curve fitting method, two different hyperbolic models respectively for the dynamic strength and accumulated plastic strain are built, which can match the test datum well. By applying the dynamic strength model, the critical dynamic strength of the remolded red clay are gained. Meanwhile, for providing basic datum and reference for relevant projects, all key parameters for the dynamic strength and accumulated plastic strain of the remolded red clay are given in the paper.

  6. Investigation of Deformation Mechanisms in Deep-Drawn and Tensile-Strained Austenitic Mn-Based Twinning Induced Plasticity (TWIP) Steel

    NARCIS (Netherlands)

    Van Tol, R.T.; Zhao, L.; Schut, H.; Sietsma, J.

    2012-01-01

    The effect of strain on the deformation mechanisms in an austenitic Mn-based twinning induced plasticity (TWIP) steel is investigated using magnetic measurements, XRD, positron beam Doppler spectroscopy, and finite element method simulations. The experimental observations reveal the formation of a0-

  7. Strain and plastic composite support (PCS) selection for vitamin K (Menaquinone-7) production in biofilm reactors.

    Science.gov (United States)

    Mahdinia, Ehsan; Demirci, Ali; Berenjian, Aydin

    2017-06-30

    Menaquinone-7 (MK-7), a subtype of vitamin K, has received a significant attention due to its effect on improving bone and cardiovascular health. Current fermentation strategies, which involve static fermentation without aeration or agitation, are associated with low productivity and scale-up issues and hardly justify the commercial production needs of this vitamin. Previous studies indicate that static fermentation is associated with pellicle and biofilm formations, which are critical for MK-7 secretion while posing significant operational issues. Therefore, the present study is undertaken to evaluate the possibility of using a biofilm reactor as a new strategy for MK-7 fermentation. Bacillus species, namely, Bacillus subtilis natto, Bacillus licheniformis, and Bacillus amyloliquifaciens as well as plastic composite, supports (PCS) were investigated in terms of MK-7 production and biofilm formation. Results show the possibility of using a biofilm reactor for MK-7 biosynthesis. Bacillus subtilis natto and soybean flour yeast extract PCS in glucose medium were found as the most potent combination for production of MK-7 as high as 35.5 mg/L, which includes both intracellular and extracellular MK-7.

  8. Effects of surface roughness on plastic strain localization in polycrystalline aggregates

    Directory of Open Access Journals (Sweden)

    Guilhem Yoann

    2014-06-01

    Full Text Available The surface state of mechanical components differs according to applied loadings. Industrial processes may produce specific features at the surface, such as roughness, local hardening, residual stresses or recrystallization. Under fatigue loading, all these parameters will affect the component lifetime, but in different manner. A better understanding of each surface state parameter, separately first and then all combined, will provide a better prediction of fatigue life. The study focuses on the effect of surface roughness. Crystal plasticity finite element computations have been carried out on three-dimensional polycrystalline aggregates with different roughness levels. Local mechanical fields have been analyzed both at the surface and inside the bulk to highlight the competition between crystallography and roughness to impose localization patterns. As soon as surface roughness is strong enough, classical localization bands driven by grains orientation are replaced by localizations patterns driven by the local roughness topology. Nevertheless, this effect tends to decrease gradually under the surface, and it becomes usually negligible after the first layer of grains. The discussion allows us to characterize the influence of the surface state on the local mechanical fields.

  9. Solid-shape energy fuels from recyclable municipal solid waste and plastics

    Science.gov (United States)

    Gug, Jeongin

    Diversion of waste streams, such as plastics, wood and paper, from municipal landfills and extraction of useful materials from landfills is an area of increasing interest across the country, especially in densely populated areas. One promising technology for recycling MSW (municipal solid waste) is to burn the high energy content components in standard coal boilers. This research seeks to reform wastes into briquette that are compatible with typical coal combustion processes. In order to comply with the standards of coal-fired power plants, the feedstock must be mechanically robust, moisture resistance, and retain high fuel value. Household waste with high paper and fibers content was used as the base material for this study. It was combined with recyclable plastics such as PE, PP, PET and PS for enhanced binding and energy efficiency. Fuel pellets were processed using a compression molding technique. The resulting moisture absorption, proximate analysis from burning, and mechanical properties were investigated after sample production and then compared with reference data for commercial coals and biomass briquettes. The effects of moisture content, compression pressure and processing temperature were studied to identify the optimal processing conditions with water uptake tests for the durability of samples under humid conditions and burning tests to examine the composition of samples. Lastly, mechanical testing revealed the structural stability of solid fuels. The properties of fuel briquettes produced from waste and recycled plastics improved with higher processing temperature but without charring the material. Optimization of moisture content and removal of air bubbles increased the density, stability and mechanical strength. The sample composition was found to be more similar to biomass fuels than coals because the majority of the starting material was paper-based solid waste. According to the proximate analysis results, the waste fuels can be expected to have

  10. Dynamic response of Cu4Zr54 metallic glass to high strain rate shock loading: plasticity, spall and atomic-level structures

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Shengnian [Los Alamos National Laboratory; Arman, Bedri [Los Alamos National Laboratory; Germann, Timothy C [Los Alamos National Laboratory; Cagin, Tahir [TEXAS A& M UNIV

    2009-01-01

    We investigate dynamic response of Cu{sub 46}Zr{sub 54} metallic glass under adiabatic planar shock wave loading (one-dimensional strain) wjth molecular dynamics simulations, including Hugoniot (shock) states, shock-induced plasticity and spallation. The Hugoniot states are obtained up to 60 CPa along with the von Mises shear flow strengths, and the dynamic spall strength, at different strain rates and temperatures. The spall strengths likely represent the limiting values achievable in experiments such as laser ablation. For the steady shock states, a clear elastic-plastic transition is identified (e.g., in the shock velocity-particle velocity curve), and the shear strength shows strain-softening. However, the elastic-plastic transition across the shock front displays transient stress overshoot (hardening) above the Hugoniot elastic limit followed by a relatively sluggish relaxation to the steady shock state, and the plastic shock front steepens with increasing shock strength. The local von Mises shear strain analysis is used to characterize local deformation, and the Voronoi tessellation analysis, the corresponding short-range structures at various stages of shock, release, tension and spallation. The plasticity in this glass is manifested as localized shear transformation zones and of local structure rather than thermal origin, and void nucleation occurs preferentially at the highly shear-deformed regions. The Voronoi and shear strain analyses show that the atoms with different local structures are of different shear resistances that lead to shear localization (e.g., the atoms indexed with (0,0,12,0) are most shear-resistant, and those with (0,2,8,1) are highly prone to shear flow). The dynamic changes in local structures are consistent with the observed deformation dynamics.

  11. A systematic characterization of the low-energy photon response of plastic scintillation detectors.

    Science.gov (United States)

    Boivin, Jonathan; Beddar, Sam; Bonde, Chris; Schmidt, Daniel; Culberson, Wesley; Guillemette, Maxime; Beaulieu, Luc

    2016-08-01

    To characterize the low energy behavior of scintillating materials used in plastic scintillation detectors (PSDs), 3 PSDs were developed using polystyrene-based scintillating materials emitting in different wavelengths. These detectors were exposed to National Institute of Standards and Technology (NIST)-matched low-energy beams ranging from 20 kVp to 250 kVp, and to (137)Cs and (60)Co beams. The dose in polystyrene was compared to the dose in air measured by NIST-calibrated ionization chambers at the same location. Analysis of every beam quality spectrum was used to extract the beam parameters and the effective mass energy-absorption coefficient. Monte Carlo simulations were also performed to calculate the energy absorbed in the scintillators' volume. The scintillators' expected response was then compared to the experimental measurements and an energy-dependent correction factor was identified to account for low-energy quenching in the scintillators. The empirical Birks model was then compared to these values to verify its validity for low-energy electrons. The clear optical fiber response was below 0.2% of the scintillator's light for x-ray beams, indicating that a negligible amount of fluorescence contamination was produced. However, for higher-energy beams ((137)Cs and (60)Co), the scintillators' response was corrected for the Cerenkov stem effect. The scintillators' response increased by a factor of approximately 4 from a 20 kVp to a (60)Co beam. The decrease in sensitivity from ionization quenching reached a local minimum of about [Formula: see text] between 40 keV and 60 keV x-ray beam mean energy, but dropped by 20% for very low-energy (13 keV) beams. The Birks model may be used to fit the experimental data, but it must take into account the energy dependence of the kB quenching parameter. A detailed comprehension of intrinsic scintillator response is essential for proper calibration of PSD dosimeters for radiology.

  12. Topology Optimal Design of Material Microstructures Using Strain Energy-based Method

    Institute of Scientific and Technical Information of China (English)

    Zhang Weihong; Wang Fengwen; Dai Gaoming; Sun Shiping

    2007-01-01

    Sensitivity analysis and topology optimization of microstructures using strain energy-based method is presented. Compared with homogenization method, the strain energy-based method has advantages of higher computing efficiency and simplified programming.Both the dual convex programming method and perimeter constraint scheme are used to optimize the 2D and 3D microstructures. Numerical results indicate that the strain energy-based method has the same effectiveness as that of homogenization method for orthotropic materials.

  13. Energy efficient microwave heating of carbon fibre reinforced plastic; Energieeffiziente Mikrowellentemperierung von kohlenstofffaserverstaerkten Duroplasten

    Energy Technology Data Exchange (ETDEWEB)

    Danilov, Maksim

    2013-07-01

    The polymerization of carbon fiber reinforced thermosetting composites (CFRP) is a dull process step with high energy requirements within the production chain. His improvement would affect the economic and ecological balance of the fiber reinforced materials in a positive way. One possible approach investigated here is tempering of raw materials in a microwave oven. In this work the material to be processed - a carbon fiber-reinforced plastic laminate - is being characterized in the microwave field through electromagnetic and thermal parameters. The relationship between its design parameters (fiber orientation and number of layers), the energy levels (reflection, absorption and transmittance) and the thermal process parameters (temperature gradient achievable) will be established. Afterwards, constructive options will be examined and evaluated which are suitable to install a low-loss (both by means of wave reflections and heat losses) industrial process.

  14. The plasticity of global proteome and genome expression analyzed in closely related W3110 and MG1655 strains of a well-studied model organism, Escherichia coli-K12.

    Science.gov (United States)

    Vijayendran, Chandran; Polen, Tino; Wendisch, Volker F; Friehs, Karl; Niehaus, Karsten; Flaschel, Erwin

    2007-03-10

    The use of Escherichia coli as a model organism has provided a great deal of basic information in biomolecular sciences. Examining trait differences among closely related strains of the same species addresses a fundamental biological question: how much diversity is there at the single species level? The main aim of our research was to identify significant differences in the activities of groups of genes between two laboratory strains of an organism closely related in genome structure. We demonstrate that despite strict and controlled growth conditions, there is high plasticity in the global proteome and genome expression in two closely related E. coli K12 sub-strains (W3110 and MG1655), which differ insignificantly in genome structure. The growth patterns of these two sub-strains were very similar in a well-equipped bioreactor, and their genome structures were shown to be almost identical by DNA microarray. However, detailed profiling of protein and gene expression by 2-dimensional gel electrophoresis and microarray analysis showed many differentially expressed genes and proteins, combinations of which were highly correlated. The differentially regulated genes and proteins belonged to the following functional categories: genes regulated by sigma subunit of RNA polymerase (RpoS), enterobactin-related genes, and genes involved in central metabolism. Genes involved in central cell metabolism - the glycolysis pathway, the tricarboxylic acid cycle and the glyoxylate bypass - were differentially regulated at both the mRNA and proteome levels. The strains differ significantly in central metabolism and thus in the generation of precursor metabolites and energy. This high plasticity probably represents a universal feature of metabolic activities in closely related species, and has the potential to reveal differences in regulatory networks. We suggest that unless care is taken in the choice of strains for any validating experiment, the results might be misleading.

  15. Low-energy theory for strained graphene: an approach up to second-order in the strain tensor

    Science.gov (United States)

    Oliva-Leyva, Maurice; Wang, Chumin

    2017-04-01

    An analytical study of low-energy electronic excited states in uniformly strained graphene is carried out up to second-order in the strain tensor. We report a new effective Dirac Hamiltonian with an anisotropic Fermi velocity tensor, which reveals the graphene trigonal symmetry being absent in first-order low-energy theories. In particular, we demonstrate the dependence of the Dirac-cone elliptical deformation on the stretching direction with respect to graphene lattice orientation. We further analytically calculate the optical conductivity tensor of strained graphene and its transmittance for a linearly polarized light with normal incidence. Finally, the obtained analytical expression of the Dirac point shift allows a better determination and understanding of pseudomagnetic fields induced by nonuniform strains.

  16. Demonstrations of the Action and Reaction Law and the Energy Conservation Law Using Fine Spherical Plastic Beads

    Science.gov (United States)

    Khumaeni, A.; Tanaka, S.; Kobayashi, A.; Lee, Y. I.; Kurniawan, K. H.; Ishii, K.; Kagawa, K.

    2008-01-01

    Equipment for demonstrating Newton's third law and the energy conservation law in mechanics have successfully been constructed utilizing fine spherical plastic beads in place of metal ball bearings. To demonstrate Newton's third law, special magnetized Petri dishes were employed as objects, while to examine the energy conservation law, a…

  17. Machined and plastic copings in three-element prostheses with different types of implantabutment joints: a strain gauge comparative analysis

    Directory of Open Access Journals (Sweden)

    Renato Sussumu Nishioka

    2010-06-01

    Full Text Available OBJECTIVE: Using strain gauge (SG analysis, the aim of this in vitro study was quantify the strain development during the fixation of three-unit screw implant-supported fixed partial dentures, varying the types of implant-abutment joints and the type of prosthetic coping. The hypotheses were that the type of hexagonal connection would generate different microstrains and the type of copings would produce similar microstrains after prosthetic screws had been tightened onto microunit abutments. MATERIALS AND METHODS: Three dental implants with external (EH and internal (IH hexagonal configurations were inserted into two polyurethane blocks. Microunit abutments were screwed onto their respective implant groups, applying a torque of 20 Ncm. Machined Co-Cr copings (M and plastic prosthetic copings (P were screwed onto the abutments, which received standard wax patterns. The wax patterns were cast in Co-Cr alloy (n=5, forming four groups: G1 EH/M; G2 EH/P; G3 IH/M and G4 IH/P. Four SGs were bonded onto the surface of the block tangentially to the implants, SG 1 mesially to implant 1, SG 2 and SG 3 mesially and distally to implant 2, respectively, and SG 4 distally to implant 3. The superstructure's occlusal screws were tightened onto microunit abutments with 10 Ncm torque using a manual torque driver. The magnitude of microstrain on each SG was recorded in units of microstrain (µε. The data were analyzed statistically by ANOVA and Tukey's test (p0.05. The hypotheses were partially accepted. CONCLUSIONS: It was concluded that the type of hexagonal connection and coping presented similar mechanical behavior under tightening conditions.

  18. Direct strain energy harvesting in automobile tires using piezoelectric PZT–polymer composites

    NARCIS (Netherlands)

    Van den Ende, D.A.; Van de Wiel, H.J.; Groen, W.A.; Van der Zwaag, S.

    2011-01-01

    Direct piezoelectric strain energy harvesting can be used to power wireless autonomous sensors in environments where low frequency, high strains are present, such as in automobile tires during operation. However, these high strains place stringent demands on the materials with respect to mechanical

  19. Direct strain energy harvesting in automobile tires using piezoelectric PZT-polymer composites

    NARCIS (Netherlands)

    Ende, D.A. van den; Wiel, H.J. van de; Groen, W.A.; Zwaag, S. van der

    2012-01-01

    Direct piezoelectric strain energy harvesting can be used to power wireless autonomous sensors in environments where low frequency, high strains are present, such as in automobile tires during operation. However, these high strains place stringent demands on the materials with respect to mechanical

  20. Linking Neuromodulated Spike-Timing Dependent Plasticity with the Free-Energy Principle.

    Science.gov (United States)

    Isomura, Takuya; Sakai, Koji; Kotani, Kiyoshi; Jimbo, Yasuhiko

    2016-09-01

    The free-energy principle is a candidate unified theory for learning and memory in the brain that predicts that neurons, synapses, and neuromodulators work in a manner that minimizes free energy. However, electrophysiological data elucidating the neural and synaptic bases for this theory are lacking. Here, we propose a novel theory bridging the information-theoretical principle with the biological phenomenon of spike-timing dependent plasticity (STDP) regulated by neuromodulators, which we term mSTDP. We propose that by integrating an mSTDP equation, we can obtain a form of Friston's free energy (an information-theoretical function). Then we analytically and numerically show that dopamine (DA) and noradrenaline (NA) influence the accuracy of a principal component analysis (PCA) performed using the mSTDP algorithm. From the perspective of free-energy minimization, these neuromodulatory changes alter the relative weighting or precision of accuracy and prior terms, which induces a switch from pattern completion to separation. These results are consistent with electrophysiological findings and validate the free-energy principle and mSTDP. Moreover, our scheme can potentially be applied in computational psychiatry to build models of the faulty neural networks that underlie the positive symptoms of schizophrenia, which involve abnormal DA levels, as well as models of the NA contribution to memory triage and posttraumatic stress disorder.

  1. An experimental method to obtain the elastic strain energy function from torsion-tension tests

    Science.gov (United States)

    Peng, S. T. J.; Landel, R. F.

    1976-01-01

    It is shown that by employing a torsion-tension test, it is possible to have a complete mapping near the origin of the two principal strain invariants associated with the rate of change of the strain energy function. However, the mathematical representation of the twist moment and normal forces vs strain and the strain energy function are complex. This problem is solved by using a set of solid cylindrical bars with different diameters such that the difference in diameter of two successive bars is small. The stress-strain equations can be grossly oversimplified by considering differences in twist moment and normal force as a function of difference in radius.

  2. Crystal Plasticity Model Validation Using Combined High-Energy Diffraction Microscopy Data for a Ti-7Al Specimen

    Science.gov (United States)

    Turner, Todd J.; Shade, Paul A.; Bernier, Joel V.; Li, Shiu Fai; Schuren, Jay C.; Kenesei, Peter; Suter, Robert M.; Almer, Jonathan

    2017-02-01

    High-Energy Diffraction Microscopy (HEDM) is a 3-d X-ray characterization method that is uniquely suited to measuring the evolving micro-mechanical state and microstructure of polycrystalline materials during in situ processing. The near-field and far-field configurations provide complementary information; orientation maps computed from the near-field measurements provide grain morphologies, while the high angular resolution of the far-field measurements provides intergranular strain tensors. The ability to measure these data during deformation in situ makes HEDM an ideal tool for validating micro-mechanical deformation models that make their predictions at the scale of individual grains. Crystal Plasticity Finite Element Models (CPFEM) are one such class of micro-mechanical models. While there have been extensive studies validating homogenized CPFEM response at a macroscopic level, a lack of detailed data measured at the level of the microstructure has hindered more stringent model validation efforts. We utilize an HEDM dataset from an alpha-titanium alloy (Ti-7Al), collected at the Advanced Photon Source, Argonne National Laboratory, under in situ tensile deformation. The initial microstructure of the central slab of the gage section, measured via near-field HEDM, is used to inform a CPFEM model. The predicted intergranular stresses for 39 internal grains are then directly compared to data from 4 far-field measurements taken between 4 and 80 pct of the macroscopic yield strength. The evolution of the elastic strain state from the CPFEM model and far-field HEDM measurements up to incipient yield are shown to be in good agreement, while residual stress at the individual grain level is found to influence the intergranular stress state even upon loading. Implications for application of such an integrated computational/experimental approach to phenomena such as fatigue are discussed.

  3. Finite Element Analysis of Bend Test of Sandwich Structures Using Strain Energy Based Homogenization Method

    Directory of Open Access Journals (Sweden)

    Hassan Ijaz

    2017-01-01

    Full Text Available The purpose of this article is to present a simplified methodology for analysis of sandwich structures using the homogenization method. This methodology is based upon the strain energy criterion. Normally, sandwich structures are composed of hexagonal core and face sheets and a complete and complex hexagonal core is modeled for finite element (FE structural analysis. In the present work, the hexagonal core is replaced by a simple equivalent volume for FE analysis. The properties of an equivalent volume were calculated by taking a single representative cell for the entire core structure and the analysis was performed to determine the effective elastic orthotropic modulus of the equivalent volume. Since each elemental cell of the hexagonal core repeats itself within the in-plane direction, periodic boundary conditions were applied to the single cell to obtain the more realistic values of effective modulus. A sandwich beam was then modeled using determined effective properties. 3D FE analysis of Three- and Four-Point Bend Tests (3PBT and 4PBT for sandwich structures having an equivalent polypropylene honeycomb core and Glass Fiber Reinforced Plastic (GFRP composite face sheets are performed in the present study. The authenticity of the proposed methodology has been verified by comparing the simulation results with the experimental bend test results on hexagonal core sandwich beams.

  4. Flow Curve Determination at Large Plastic Strain Levels: Limitations of the Membrane Theory in the Analysis of the Hydraulic Bulge Test

    Science.gov (United States)

    Lemoine, X.; Iancu, A.; Ferron, G.

    2011-05-01

    Nowadays, an accurate determination of the true stress-strain curve is a key-element for all finite element (FE) forming predictions. Since the introduction of Advanced High Strength Steels (AHSS) for the automotive market, the standard uniaxial tension test suffers the drawback of relatively low uniform elongations. The extrapolation of the uniaxial stress-strain curve up to large strains is not without consequence in forming predictions—especially formability and springback. One of the means to solve this problem is to use experimental tests where large plastic strain levels can be reached. The hydraulic bulge test is one of these tests. The effective plastic strain levels reached in the bulge test are of about 0.7. From an experimental standpoint, the biaxial flow stress is estimated using measurement of fluid pressure, and calculation of thickness and curvature at the pole, via appropriate measurements and assumptions. The biaxial stress at the pole is determined using the membrane equilibrium equation. The analysis proposed in this paper consists of performing "virtual experiments" where the results obtained by means of FE calculations are used as input data for determining the biaxial stress-strain law in agreement with the experimental procedure. In this way, a critical discussion of the experimental procedure can be made, by comparing the "experimental" stress-strain curve (Membrane theory curve) with the "reference" one introduced in the simulations. In particular, the influences of the "(die diameter)/thickness" ratio and of the plastic anisotropy are studied, and limitations of the hydraulic bulge test analysis are discussed.

  5. Structural Damage Identification via Pseudo Strain Energy Density and Wavelet Packet Transform

    Institute of Scientific and Technical Information of China (English)

    CHEN Xiao-qiang; ZHU Hong-ping; GE Dong-dong

    2009-01-01

    Based on strain signals,a new time-domain methodology for detecting the beam local damage has been developed.The pseudo strain energy density (PSED) is defined and used to build two major damage indexes,the average pseudo strain energy density (APSED) and the average pseudo strain energy density rate (APSEDR).Probability and mathematical statistics are utilized to derive a standardized damage index.Furthermore,by applying the analytic relation between the strain energy release rate and the stress intensity factor,an analytic solution of crack depth is derived.For the dynamic strain signals,the wavelet packet transform is used to pre-process measured data.Finally,a numerical simulation indicates that this method can effectively identify the damage location and its absolute severity.

  6. Thermal-Work Strain and Energy Expenditure during Marine Rifle Squad Operations in Afghanistan (August 2013)

    Science.gov (United States)

    2015-08-10

    TECHNICAL REPORT NO. T15-7 DATE August 2015 ADA THERMAL-WORK STRAIN AND ENERGY EXPENDITURE ...USARIEM TECHNICAL REPORT T15-7 THERMAL-WORK STRAIN AND ENERGY EXPENDITURE DURING MARINE RIFLE SQUAD OPERATIONS IN AFGHANISTAN...0704-0188 The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for

  7. Compensated bismuth-loaded plastic scintillators for neutron detection using low-energy pseudo-spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Dumazert, Jonathan, E-mail: jonathan.dumazert@cea.fr [CEA, LIST, Laboratoire Capteurs Architectures Electroniques, 91191 Gif-sur-Yvette (France); Coulon, Romain; Bertrand, Guillaume H.V.; Normand, Stéphane [CEA, LIST, Laboratoire Capteurs Architectures Electroniques, 91191 Gif-sur-Yvette (France); Méchin, Laurence [CNRS, UCBN, Groupe de Recherche en Informatique, Image, Automatique et Instrumentation de Caen, 14050 Caen (France); Hamel, Matthieu [CEA, LIST, Laboratoire Capteurs Architectures Electroniques, 91191 Gif-sur-Yvette (France)

    2016-05-21

    Gadolinium-covered modified plastic scintillators show a high potential for the deployment of cost-effective neutron detectors. Taking advantage of the low-energy photon and electron signature of thermal neutron captures in gadolinium-155 and gadolinium-157 however requires a background correction. In order to display a trustable rate, dual compensation schemes appear as an alternative to Pulse Shape Discrimination. This paper presents the application of such a compensation scheme to a two-bismuth loaded plastic scintillator system. A detection scintillator interacts with incident photon and fast neutron radiations and is covered with a gadolinium converter to become thermal neutron-sensitive as well. In the meantime, an identical compensation scintillator, covered with terbium, solely interacts with the photon and fast neutron part of incident radiations. After the acquisition and the treatment of the counting signals from both sensors, a hypothesis test determines whether the resulting count rate after subtraction falls into statistical fluctuations or provides a robust image of neutron activity. A laboratory prototype is tested under both photon and neutron radiations, allowing us to investigate the performance of the overall compensation system. The study reveals satisfactory results in terms of robustness to a cesium-137 background and in terms of sensitivity in presence of a californium-252 source.

  8. Compensated bismuth-loaded plastic scintillators for neutron detection using low-energy pseudo-spectroscopy

    Science.gov (United States)

    Dumazert, Jonathan; Coulon, Romain; Bertrand, Guillaume H. V.; Normand, Stéphane; Méchin, Laurence; Hamel, Matthieu

    2016-05-01

    Gadolinium-covered modified plastic scintillators show a high potential for the deployment of cost-effective neutron detectors. Taking advantage of the low-energy photon and electron signature of thermal neutron captures in gadolinium-155 and gadolinium-157 however requires a background correction. In order to display a trustable rate, dual compensation schemes appear as an alternative to Pulse Shape Discrimination. This paper presents the application of such a compensation scheme to a two-bismuth loaded plastic scintillator system. A detection scintillator interacts with incident photon and fast neutron radiations and is covered with a gadolinium converter to become thermal neutron-sensitive as well. In the meantime, an identical compensation scintillator, covered with terbium, solely interacts with the photon and fast neutron part of incident radiations. After the acquisition and the treatment of the counting signals from both sensors, a hypothesis test determines whether the resulting count rate after subtraction falls into statistical fluctuations or provides a robust image of neutron activity. A laboratory prototype is tested under both photon and neutron radiations, allowing us to investigate the performance of the overall compensation system. The study reveals satisfactory results in terms of robustness to a cesium-137 background and in terms of sensitivity in presence of a californium-252 source.

  9. Multiplying decomposition of stress/strain, constitutive/compliance relations, and strain energy

    CERN Document Server

    Lee, HyunSuk

    2012-01-01

    To account for phenomenological theories and a set of invariants, stress and strain are usually decomposed into a pair of pressure and deviatoric stress and a pair of volumetric strain and deviatoric strain. However, the conventional decomposition method only focuses on individual stress and strain, so that cannot be directly applied to either formulation in Finite Element Method (FEM) or Boundary Element Method (BEM). In this paper, a simpler, more general, and widely applicable decomposition is suggested. A new decomposition method adopts multiplying decomposition tensors or matrices to not only stress and strain but also constitutive and compliance relation. With this, we also show its practical usage on FEM and BEM in terms of tensors and matrices.

  10. Dual energy CT inspection of a carbon fibre reinforced plastic composite combined with metal components

    Directory of Open Access Journals (Sweden)

    Daniel Vavrik

    2016-11-01

    Full Text Available This work is focused on the inspection of carbon fibre reinforced plastic composites (CFRP combined with metal components. It is well known that the high absorption of metallic parts degrades the quality of radiographic measurements (contrast and causes typical metal artefacts in X-ray computed tomography (CT reconstruction. It will be shown that these problems can be successfully solved utilizing the dual energy CT method (DECT, which is typically used for the material decomposition of complex objects. In other words, DECT can help differentiate object components with a similar overall attenuation or visualise low attenuation components that are next to high attenuation ones. The application of DECT to analyse honeycomb sandwich panels and CFRP parts joined with metal fasteners will be presented in the article.

  11. A systematic characterization of the low-energy photon response of plastic scintillation detectors

    Science.gov (United States)

    Boivin, Jonathan; Beddar, Sam; Bonde, Chris; Schmidt, Daniel; Culberson, Wesley; Guillemette, Maxime; Beaulieu, Luc

    2016-08-01

    To characterize the low energy behavior of scintillating materials used in plastic scintillation detectors (PSDs), 3 PSDs were developed using polystyrene-based scintillating materials emitting in different wavelengths. These detectors were exposed to National Institute of Standards and Technology (NIST)-matched low-energy beams ranging from 20 kVp to 250 kVp, and to 137Cs and 60Co beams. The dose in polystyrene was compared to the dose in air measured by NIST-calibrated ionization chambers at the same location. Analysis of every beam quality spectrum was used to extract the beam parameters and the effective mass energy-absorption coefficient. Monte Carlo simulations were also performed to calculate the energy absorbed in the scintillators’ volume. The scintillators’ expected response was then compared to the experimental measurements and an energy-dependent correction factor was identified to account for low-energy quenching in the scintillators. The empirical Birks model was then compared to these values to verify its validity for low-energy electrons. The clear optical fiber response was below 0.2% of the scintillator’s light for x-ray beams, indicating that a negligible amount of fluorescence contamination was produced. However, for higher-energy beams (137Cs and 60Co), the scintillators’ response was corrected for the Cerenkov stem effect. The scintillators’ response increased by a factor of approximately 4 from a 20 kVp to a 60Co beam. The decrease in sensitivity from ionization quenching reached a local minimum of about 11%+/- 1% between 40 keV and 60 keV x-ray beam mean energy, but dropped by 20% for very low-energy (13 keV) beams. The Birks model may be used to fit the experimental data, but it must take into account the energy dependence of the kB quenching parameter. A detailed comprehension of intrinsic scintillator response is essential for proper calibration of PSD dosimeters for radiology.

  12. Tunable low energy, compact and high performance neuromorphic circuit for spike-based synaptic plasticity.

    Directory of Open Access Journals (Sweden)

    Mostafa Rahimi Azghadi

    Full Text Available Cortical circuits in the brain have long been recognised for their information processing capabilities and have been studied both experimentally and theoretically via spiking neural networks. Neuromorphic engineers are primarily concerned with translating the computational capabilities of biological cortical circuits, using the Spiking Neural Network (SNN paradigm, into in silico applications that can mimic the behaviour and capabilities of real biological circuits/systems. These capabilities include low power consumption, compactness, and relevant dynamics. In this paper, we propose a new accelerated-time circuit that has several advantages over its previous neuromorphic counterparts in terms of compactness, power consumption, and capability to mimic the outcomes of biological experiments. The presented circuit simulation results demonstrate that, in comparing the new circuit to previous published synaptic plasticity circuits, reduced silicon area and lower energy consumption for processing each spike is achieved. In addition, it can be tuned in order to closely mimic the outcomes of various spike timing- and rate-based synaptic plasticity experiments. The proposed circuit is also investigated and compared to other designs in terms of tolerance to mismatch and process variation. Monte Carlo simulation results show that the proposed design is much more stable than its previous counterparts in terms of vulnerability to transistor mismatch, which is a significant challenge in analog neuromorphic design. All these features make the proposed design an ideal circuit for use in large scale SNNs, which aim at implementing neuromorphic systems with an inherent capability that can adapt to a continuously changing environment, thus leading to systems with significant learning and computational abilities.

  13. Tunable low energy, compact and high performance neuromorphic circuit for spike-based synaptic plasticity.

    Science.gov (United States)

    Rahimi Azghadi, Mostafa; Iannella, Nicolangelo; Al-Sarawi, Said; Abbott, Derek

    2014-01-01

    Cortical circuits in the brain have long been recognised for their information processing capabilities and have been studied both experimentally and theoretically via spiking neural networks. Neuromorphic engineers are primarily concerned with translating the computational capabilities of biological cortical circuits, using the Spiking Neural Network (SNN) paradigm, into in silico applications that can mimic the behaviour and capabilities of real biological circuits/systems. These capabilities include low power consumption, compactness, and relevant dynamics. In this paper, we propose a new accelerated-time circuit that has several advantages over its previous neuromorphic counterparts in terms of compactness, power consumption, and capability to mimic the outcomes of biological experiments. The presented circuit simulation results demonstrate that, in comparing the new circuit to previous published synaptic plasticity circuits, reduced silicon area and lower energy consumption for processing each spike is achieved. In addition, it can be tuned in order to closely mimic the outcomes of various spike timing- and rate-based synaptic plasticity experiments. The proposed circuit is also investigated and compared to other designs in terms of tolerance to mismatch and process variation. Monte Carlo simulation results show that the proposed design is much more stable than its previous counterparts in terms of vulnerability to transistor mismatch, which is a significant challenge in analog neuromorphic design. All these features make the proposed design an ideal circuit for use in large scale SNNs, which aim at implementing neuromorphic systems with an inherent capability that can adapt to a continuously changing environment, thus leading to systems with significant learning and computational abilities.

  14. EFFECT OF STRAIN FIELD ON THRESHOLD DISPLACEMENT ENERGY OF TUNGSTEN STUDIED BY MOLECULAR DYNAMICS SIMULATION

    Energy Technology Data Exchange (ETDEWEB)

    Wang, D.; Gao, Ning; Setyawan, Wahyu; Kurtz, Richard J.; Gao, X.; He, W. H.

    2016-03-31

    The influence of hydrostatic strain on point defect formation energy and threshold displacement energy (Ed) in body-centered cubic (BCC) tungsten was studied with molecular dynamics simulations. Two different tungsten potentials (Fikar and Juslin) were used. The minimum Ed direction calculated with the Fikar-potential was <100>, but with the Juslin-potential it was <111>. The most stable self-interstitial (SIA) configuration was a <111>-crowdion for both potentials. The stable SIA configuration did not change with applied strain. Varying the strain from compression to tension increased the vacancy formation energy but decreased the SIA formation energy. The SIA formation energy changed more significantly than for a vacancy such that Ed decreased with applied strain from compression to tension.

  15. Using Omega and NIF to Advance Theories of High-Pressure, High-Strain-Rate Tantalum Plastic Flow

    Science.gov (United States)

    Rudd, R. E.; Arsenlis, A.; Barton, N. R.; Cavallo, R. M.; Huntington, C. M.; McNaney, J. M.; Orlikowski, D. A.; Park, H.-S.; Prisbrey, S. T.; Remington, B. A.; Wehrenberg, C. E.

    2015-11-01

    Precisely controlled plasmas are playing an important role as both pump and probe in experiments to understand the strength of solid metals at high energy density (HED) conditions. In concert with theory, these experiments have enabled a predictive capability to model material strength at Mbar pressures and high strain rates. Here we describe multiscale strength models developed for tantalum and vanadium starting with atomic bonding and extending up through the mobility of individual dislocations, the evolution of dislocation networks and so on up to full scale. High-energy laser platforms such as the NIF and the Omega laser probe ramp-compressed strength to 1-5 Mbar. The predictions of the multiscale model agree well with the 1 Mbar experiments without tuning. The combination of experiment and theory has shown that solid metals can behave significantly differently at HED conditions; for example, the familiar strengthening of metals as the grain size is reduced has been shown not to occur in the high pressure experiments. Work performed under the auspices of the U.S. Dept. of Energy by Lawrence Livermore National Lab under contract DE-AC52-07NA273.

  16. Fibre-reinforced plastic composites - Determination of the in-plane shear stress/shear strain response, including the in-plane shear modulus and strength, by the plus or minus 45 degree tension test method

    CERN Document Server

    International Organization for Standardization. Geneva

    1997-01-01

    Fibre-reinforced plastic composites - Determination of the in-plane shear stress/shear strain response, including the in-plane shear modulus and strength, by the plus or minus 45 degree tension test method

  17. Contribution to the theoretical study of the plastic strain localization in porous materials; Contribution a l'etude theorique de la localisation plastique dans les poreux

    Energy Technology Data Exchange (ETDEWEB)

    Willot, F

    2007-01-15

    This work presents a study in theoretical mechanics, in the classical framework of homogenization of heterogeneous media. It addresses a notoriously problematical situation of non-linear behavior and infinite contrast between two phases, one of which is a plastic solid phase and the other one, the porosity of the medium. Its aim is to investigate how plastic strain localization manifests itself at the level of the overall effective behavior of the medium in presence of pores, and in particular in the non-trivial limit of small porosity. This question, important to the understanding of ductile damage, is examined both numerically and theoretically, in the restricted situation of bi-dimensional systems, and using a deformation theory approach of plasticity. The numerical investigations consist of quasi-exact computations of the strain and stress fields in the voided medium, by means of a Fast Fourier Transform method, and using a particular Green function. The theoretical approach makes use of exact solutions, which can be obtained in particular cases of a periodic void lattice, as well as of a recent 'second-order' nonlinear homogenization approach. The virtues of the latter are evaluated in two steps, first by studying the underlying linear anisotropic homogenization step (an essential ingredient), then by studying the nonlinear step itself. The nature and significance of the singularities of the theory which appear in the limit of small porosity, confirmed by numerical computations, are partly elucidated. Finally, original observations are presented as to the relation between plastic deformation patterns in an ideal disordered medium, and some features of the macroscopic strain/stress curve. (author)

  18. Strain Energy Density in the Elastodynamics of the Spacetime Continuum and the Electromagnetic Field

    Directory of Open Access Journals (Sweden)

    Millette P. A.

    2013-04-01

    Full Text Available We investigate the strain energy density of the spacetime continuum in the Elasto- dynamics of the Spacetime Continuum by applying continuum m echanical results to strained spacetime. The strain energy density is a scalar. W e find that it is separated into two terms: the first one expresses the dilatation energy density (the “mass” longitu- dinal term while the second one expresses the distortion en ergy density (the “massless” transverse term. The quadratic structure of the energy rel ation of Special Relativity is found to be present in the theory. In addition, we find that the kinetic energy pc is car- ried by the distortion part of the deformation, while the dil atation part carries only the rest-mass energy. The strain energy density of the electrom agnetic energy-momentum stress tensor is calculated. The dilatation energy density (the rest-mass energy density of the photon is found to be 0 as expected. The transverse dis tortion energy density is found to include a longitudinal electromagnetic energy fl ux term, from the Poynting vector, that is massless as it is due to distortion, not dilatation, of the spacetime con- tinuum. However, because this energy flux is along the direct ion of propagation (i.e. longitudinal, it gives rise to the particle aspect of the el ectromagnetic field, the photon.

  19. Validating plastic scintillation detectors for photon dosimetry in the radiologic energy range

    Energy Technology Data Exchange (ETDEWEB)

    Lessard, Francois; Archambault, Louis; Plamondon, Mathieu [Departement de physique, de genie physique et d' optique, Universite Laval, Quebec, Quebec G1K 7P4, Canada and Departement de radio-oncologie, Hotel-Dieu de Quebec, Centre hospitalier universitaire de Quebec, Quebec G1R 2J6 (Canada); Departement de physique, de genie physique et d' optique, Universite Laval, Quebec, Quebec G1K 7P4 (Canada); Departement de radio-oncologie, Hotel-Dieu de Quebec, Centre hospitalier universitaire de Quebec, Quebec G1R 2J6 (Canada) and Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, Texas 77030 (United States); Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, Texas 77030 (United States); Departement de physique, de genie physique et d' optique, Universite Laval, Quebec, Quebec G1K 7P4, Canada and Departement de radio-oncologie, Hotel-Dieu de Quebec, Centre hospitalier universitaire de Quebec, Quebec G1R 2J6 (Canada); and others

    2012-09-15

    Purpose: Photon dosimetry in the kilovolt (kV) energy range represents a major challenge for diagnostic and interventional radiology and superficial therapy. Plastic scintillation detectors (PSDs) are potentially good candidates for this task. This study proposes a simple way to obtain accurate correction factors to compensate for the response of PSDs to photon energies between 80 and 150 kVp. The performance of PSDs is also investigated to determine their potential usefulness in the diagnostic energy range. Methods: A 1-mm-diameter, 10-mm-long PSD was irradiated by a Therapax SXT 150 unit using five different beam qualities made of tube potentials ranging from 80 to 150 kVp and filtration thickness ranging from 0.8 to 0.2 mmAl + 1.0 mmCu. The light emitted by the detector was collected using an 8-m-long optical fiber and a polychromatic photodiode, which converted the scintillation photons to an electrical current. The PSD response was compared with the reference free air dose rate measured with a calibrated Farmer NE2571 ionization chamber. PSD measurements were corrected using spectra-weighted corrections, accounting for mass energy-absorption coefficient differences between the sensitive volumes of the ionization chamber and the PSD, as suggested by large cavity theory (LCT). Beam spectra were obtained from x-ray simulation software and validated experimentally using a CdTe spectrometer. Correction factors were also obtained using Monte Carlo (MC) simulations. Percent depth dose (PDD) measurements were compensated for beam hardening using the LCT correction method. These PDD measurements were compared with uncorrected PSD data, PDD measurements obtained using Gafchromic films, Monte Carlo simulations, and previous data. Results: For each beam quality used, the authors observed an increase of the energy response with effective energy when no correction was applied to the PSD response. Using the LCT correction, the PSD response was almost energy independent, with

  20. The pulverization and handling of soft plastics for energy recovery; Soenderdelning och hantering av mjuka plaster foer energiutvinning

    Energy Technology Data Exchange (ETDEWEB)

    Wiklund, Sven-Erik

    2000-10-01

    The purpose of the project has primarily been to investigate suitable equipment (mills, crushers, shredders) for the pulverization of different types of soft plastics from the agricultural sector (large sacks and silage plastic) and the peat extraction industry (plastic covers) with the aim of being able to use the plastic material as fuel in conventional solid waste-fired plants. Many of the mills that are used for pulverizing different types of biofuel have proved not to be particularly suitable for soft plastics. The project has comprised the following: * Contact with a number of plant owners with different types of plants (grate, CFB and BFB boilers) for a review of existing fuel handling and fuel feed equipment as well as the demands they make on the fuel that is to be fired. * Contact with Trio Plast concerning previous tests carried out in connection with the collection, baling, handling, pulverization and combustion of plastics from the agricultural sector. * Contact with mill suppliers for participation in the tests and for feedback on experience gained in connection with the pulverization of soft plastics. * Choice of a suitable plant for practical trials based on contact with the above plant owners as a reference group. * Practical trials in 5 mills with the pulverization of soft plastics from agriculture (silage plastic and large sacks) as well as plastic from peat extraction (plastic covers) and * Evaluation of technical, economic, energy-related and environmental preconditions. Following contact with several owners of solid waste-fired combustion plants, and after hearing their opinions, it became clear that many of them were doubtful about the combustion of plastic. They are primarily afraid of tripping superheaters, etc. Consequently, two plants without superheaters, one in Oestersund and the other in Malmoe, were chosen for the tests. The mills that were tested were: * A SIM mill from WahIkvist, Oedeshoeg Plant - a mobile slow-action pulverizer for

  1. Strain coordination of quasi-plane-hypothesis for reinforced concrete beam strengthened by epoxy-bonded glass fiber reinforced plastic plate

    Institute of Scientific and Technical Information of China (English)

    ZENG Xian-tao; DING Ya-hong; WANG Xing-guo

    2006-01-01

    The testing of thirteen reinforced concrete (RC) beams strengthened by epoxy-bonded glass fiber reinforced plastic plate (GFRP) shows that the RC beam and the GFRP plate with epoxy bonding on it can work fairly well in coordination to each other. But there is relative slipping between RC beam and GFRP plate. And the strain of GFRP and steel rebar of RC beam satisfies the quasi-plane-hypothesis, that is, the strain of longitudinal fiber that parallels to the neutral axis of plated beam within the scope of effective height (h0) of the cross section is in direct proportion to the distance from the fiber to the neutral axis. The strain of GFRP and steel rebar satisfies the equation: εCFRP = Kεsteel.

  2. INFLUENCES OF EDGING ROLL SHAPE ON THE PLASTIC STRAIN DISTRIBUTION OF SLAB DURING MULTI-PASS V-H ROLLING PROCESS

    Institute of Scientific and Technical Information of China (English)

    H.L. Yu; X.H. Liu; C.S. Li; X.M. Zhao; Y. Kusaba

    2006-01-01

    Multi-pass slab vertical-horizontal (V-H) rolling process with variable edging roll shape have been simulated with explicit dynamic finite element method and updating geometric method. The distributions of plastic strain contour in slab during rolling process with different edging roll and under different rolling stage have been obtained. The results show that there exist two thin strain assembling zones in slab when the flat edging roll is used, and there just exist one strain assembling zone in slab when the edging roll with groove is used. And compared the deformation equality between flat edging roll and edging rollwith groove, the lateris better than the former, which supplies the theory prove to the slab deformation distribution during V-H rolling process and is helpful for predicting the slab texture.

  3. Surface geometry and strain energy effects in the failure of a (Ni, Pt)Al/EB-PVD thermal barrier coating

    Energy Technology Data Exchange (ETDEWEB)

    Vaidyanathan, Krishnakumar; Jordan, Eric H.; Gell, Maurice

    2004-03-08

    Thermal cycling tests were conducted on a commercial yttria-stabilized zirconia electron beam-physical vapor deposited thermal barrier coating (TBC) on a platinum aluminide ({beta}-(Ni, Pt)Al) bond coat. Surprisingly, the longest life sample lasted 10 times longer than the shortest life sample. Two distinct mechanisms have been found responsible for the observed damage initiation and progression at the thermally grown oxide (TGO)/bond coat interface. The first mechanism leads to localized debonding at the TGO/bond coat interface due to increasing out-of-plane tensile stresses at ridges that form along bond coat grain boundaries. The second mechanism is driven by cyclic plasticity of the bond coat that leads to cavity formation at the TGO/bond coat interface. The primary finding of this work is that the first mechanism, involving tensile stress at ridge tops, is life limiting. Based on this mechanism, it is demonstrated that the variation in bond coat ridge aspect ratio can explain the unusual 10x variation in observed sample life. It is proposed that ridge top spallation leads to debonds of sufficient size to result in unstable fracture driven by the strain energy stored in the TGO. The criticality of the flaw created by local debonding is supported by experimental determination of the strain energy available in the TGO through measurement of TGO stress and thickness combined with published fracture mechanics solutions of the relevant flaw geometry.

  4. Vibration based structural health monitoring in fibre reinforced composites employing the modal strain energy method

    NARCIS (Netherlands)

    Ooijevaar, T.H.; Loendersloot, R.; Warnet, L.L.; Boer, de A.; Akkerman, R.

    2009-01-01

    The feasibility of a vibration based damage identification method is shown. The Modal Strain Energy method is applied to a T-joint structure. Both finite element analysis and experimental validation of an undamaged and delaminated structure are presented.

  5. Evaluation of the water-equivalence of plastic materials in low- and high-energy clinical proton beams.

    Science.gov (United States)

    Lourenço, A; Shipley, D; Wellock, N; Thomas, R; Bouchard, H; Kacperek, A; Fracchiolla, F; Lorentini, S; Schwarz, M; MacDougall, N; Royle, G; Palmans, H

    2017-05-21

    The aim of this work was to evaluate the water-equivalence of new trial plastics designed specifically for light-ion beam dosimetry as well as commercially available plastics in clinical proton beams. The water-equivalence of materials was tested by computing a plastic-to-water conversion factor, [Formula: see text]. Trial materials were characterized experimentally in 60 MeV and 226 MeV un-modulated proton beams and the results were compared with Monte Carlo simulations using the FLUKA code. For the high-energy beam, a comparison between the trial plastics and various commercial plastics was also performed using FLUKA and Geant4 Monte Carlo codes. Experimental information was obtained from laterally integrated depth-dose ionization chamber measurements in water, with and without plastic slabs with variable thicknesses in front of the water phantom. Fluence correction factors, [Formula: see text], between water and various materials were also derived using the Monte Carlo method. For the 60 MeV proton beam, [Formula: see text] and [Formula: see text] factors were within 1% from unity for all trial plastics. For the 226 MeV proton beam, experimental [Formula: see text] values deviated from unity by a maximum of about 1% for the three trial plastics and experimental results showed no advantage regarding which of the plastics was the most equivalent to water. Different magnitudes of corrections were found between Geant4 and FLUKA for the various materials due mainly to the use of different nonelastic nuclear data. Nevertheless, for the 226 MeV proton beam, [Formula: see text] correction factors were within 2% from unity for all the materials. Considering the results from the two Monte Carlo codes, PMMA and trial plastic #3 had the smallest [Formula: see text] values, where maximum deviations from unity were 1%, however, PMMA range differed by 16% from that of water. Overall, [Formula: see text] factors were deviating more from unity than [Formula: see text] factors

  6. Earthquake volume, fault plane area, seismic energy, strain, deformation and related quantities

    Directory of Open Access Journals (Sweden)

    S. J. DUDA

    1964-06-01

    Full Text Available An effort is made to improve Benioff's method for investigation
    of strain release in aftershock sequences. The improvement
    may be summarized as follows:
    1. Earthquake volume increases with magnitude, instead of being
    constant. A relation is given, relating volume to magnitude.
    2. A revised energy-magnitude formula is used.
    3. The seismic gain ratio, i. e. the ratio between seismic energy and
    elastic strain energy, probably increases with magnitude, instead of being
    constant. Likewise, the ratio of fault plane area of the main shock to the
    vertical section through the aftershock volume increases with magnitude.
    4. The seismic energy density, the elastic strain energy density as
    well as strain are independent of magnitude.
    5. The deformation, i. e. the total strain in the aftershock zone, increases
    with magnitude at the same rate as seismic energy and volume do.
    As a consequence of these improvements some earlier published strain
    release characteristics are reconstructed, this time as deformation characteristics
    instead.

  7. Magnetic Anisotropic Energy Gap and Strain Effect in Au Nanoparticles

    Directory of Open Access Journals (Sweden)

    Shih Po-Hsun

    2009-01-01

    Full Text Available Abstract We report on the observation of the size effect of thermal magnetization in Au nanoparticles. The thermal deviation of the saturation magnetization departs substantially from that predicted by the Bloch T3/2-law, indicating the existence of magnetic anisotropic energy. The results may be understood using the uniaxial anisotropy Heisenberg model, in which the surface atoms give rise to polarized moments while the magnetic anisotropic energy decreases as the size of the Au nanoparticles is reduced. There is a significant maximum magnetic anisotropic energy found for the 6 nm Au nanoparticles, which is associated with the deviation of the lattice constant due to magnetocrystalline anisotropy.

  8. Intersubband energies in strain-compensated InGaN/AlInN quantum well structures

    Energy Technology Data Exchange (ETDEWEB)

    Park, Seoung-Hwan, E-mail: shpark@cu.ac.kr [Department of Electronics Engineering, Catholic University of Daegu, Hayang, Kyeongsan, Kyeongbuk, 712-702 (Korea, Republic of); Ahn, Doyeol [Institute of Quantum Information Processing and Systems, University of Seoul, 90 Jeonnong, Tongdaimoon-Gu, Seoul, Korea 130-743 (Korea, Republic of)

    2016-01-15

    Intersubband transition energies in the conduction band for strain-compensated InGaN/AlInN quantum well (QW) structures were investigated as a function of strain based on an effective mass theory with the nonparabolicity taken into account. In the case of an InGaN/AlInN QW structure lattice-matched to GaN, the wavelength is shown to be longer than 1.55 μm. On the other hand, strain-compensated QW structures show that the wavelength of 1.55 μm can be reached even for the QW structure with a relatively small strain of 0.3 %. Hence, the strain-compensated QW structures can be used for telecommunication applications at 1.55 μm with a small strain, compared to conventional GaN/AlN QW structure.

  9. Plasticity in Ultra Fine Grained Materials

    Energy Technology Data Exchange (ETDEWEB)

    Koslowski, Marisol [Purdue Univ., West Lafayette, IN (United States)

    2015-04-15

    Understanding the mechanisms of deformation of nanocrystalline (nc) materials is critical to the design of micro and nano devices and to develop materials with superior fracture strength and wear resistance for applications in new energy technologies. In this project we focused on understanding the following plastic deformation processes described in detail in the following sections: 1. Plastic strain recovery (Section 1). 2. Effect of microstructural variability on the yield stress of nc metals (Section 2). 3. The role of partial and extended full dislocations in plastic deformation of nc metals (Section 3).

  10. Strain-Induced Energy Band Gap Opening in Two-Dimensional Bilayered Silicon Film

    Science.gov (United States)

    Ji, Z.; Zhou, R.; Lew Yan Voon, L. C.; Zhuang, Y.

    2016-10-01

    This work presents a theoretical study of the structural and electronic properties of bilayered silicon film (BiSF) under in-plane biaxial strain/stress using density functional theory (DFT). Atomic structures of the two-dimensional (2-D) silicon films are optimized by using both the local-density approximation (LDA) and generalized gradient approximation (GGA). In the absence of strain/stress, five buckled hexagonal honeycomb structures of the BiSF with triangular lattice have been obtained as local energy minima, and their structural stability has been verified. These structures present a Dirac-cone shaped energy band diagram with zero energy band gaps. Applying a tensile biaxial strain leads to a reduction of the buckling height. Atomically flat structures with zero buckling height have been observed when the AA-stacking structures are under a critical biaxial strain. Increase of the strain between 10.7% and 15.4% results in a band-gap opening with a maximum energy band gap opening of ˜0.17 eV, obtained when a 14.3% strain is applied. Energy band diagrams, electron transmission efficiency, and the charge transport property are calculated. Additionally, an asymmetric energetically favorable atomic structure of BiSF shows a non-zero band gap in the absence of strain/stress and a maximum band gap of 0.15 eV as a -1.71% compressive strain is applied. Both tensile and compressive strain/stress can lead to a band gap opening in the asymmetric structure.

  11. Shaping development through mechanical strain: the transcriptional basis of diet-induced phenotypic plasticity in a cichlid fish.

    Science.gov (United States)

    Gunter, Helen M; Fan, Shaohua; Xiong, Fan; Franchini, Paolo; Fruciano, Carmelo; Meyer, Axel

    2013-09-01

    Adaptive phenotypic plasticity, the ability of an organism to change its phenotype to match local environments, is increasingly recognized for its contribution to evolution. However, few empirical studies have explored the molecular basis of plastic traits. The East African cichlid fish Astatoreochromis alluaudi displays adaptive phenotypic plasticity in its pharyngeal jaw apparatus, a structure that is widely seen as an evolutionary key innovation that has contributed to the remarkable diversity of cichlid fishes. It has previously been shown that in response to different diets, the pharyngeal jaws change their size, shape and dentition: hard diets induce an adaptive robust molariform tooth phenotype with short jaws and strong internal bone structures, while soft diets induce a gracile papilliform tooth phenotype with elongated jaws and slender internal bone structures. To gain insight into the molecular underpinnings of these adaptations and enable future investigations of the role that phenotypic plasticity plays during the formation of adaptive radiations, the transcriptomes of the two divergent jaw phenotypes were examined. Our study identified a total of 187 genes whose expression differs in response to hard and soft diets, including immediate early genes, extracellular matrix genes and inflammatory factors. Transcriptome results are interpreted in light of expression of candidate genes-markers for tooth size and shape, bone cells and mechanically sensitive pathways. This study opens up new avenues of research at new levels of biological organization into the roles of phenotypic plasticity during speciation and radiation of cichlid fishes.

  12. Modelling of plastic flow localization and damage development in friction stir welded 6005A aluminium alloy using physics based strain hardening law

    DEFF Research Database (Denmark)

    Nielsen, Kim Lau; Pardoen, Thomas; Tvergaard, Viggo

    2010-01-01

    Plastic flow localisation and ductile failure during tensile testing of friction stir welded aluminium spec- imens are investigated with a specific focus on modelling the local, finite strain, hardening response. In the experimental part, friction stir welds in a 6005A-T6 aluminium alloy were...... prepared and analysed using digital image correlation (DIC) during tensile testing as well as scanning electron microscopy (SEM) on polished samples and on fracture surfaces. The locations of the various regions of the weld were determined based on hardness measurements, while the flow behaviour...

  13. Effects of plastic pre-straining level on the creep deformation, crack initiation and growth behaviour of 316H stainless steel

    OpenAIRE

    Mehmanparast, Ali; Davies, C M; Dean, David W.; Nikbin, Kamran

    2016-01-01

    The effects of the material pre-straining level, in the form of plastic pre-compression at room temperature, on the tensile, creep deformation, creep crack initiation and growth behaviour of 316H stainless steel have been examined at 550 °C. Experiments have been performed on the 4%, 8% and 12% pre-compressed specimens and the results are compared with existing data on the pre-compressed material to investigate the change in mechanical response, creep failure, creep crack initiation and growt...

  14. The synchronous improvement of strength and plasticity (SISP) in new Ni-Co based disc superalloys by controling stacking fault energy

    OpenAIRE

    Xu, H.; Zhang, Z.J.; P Zhang; Cui, C. Y.; Jin, T; Zhang, Z. F.

    2017-01-01

    It is a great challenge to improve the strength of disc superalloys without great loss of plasticity together since the microstructures benefiting the strength always do not avail the plasticity. Interestingly, this study shows that the trade-off relationship between strength and plasticity can be broken through decreasing stacking fault energy (SFE) in newly developed Ni-Co based disc superalloys. Axial tensile tests in the temperature range of 25 to 725??C were carried out in these alloys w...

  15. Stored energy and recrystallized microstructures in nickel processed by accumulative roll bonding to different strains

    DEFF Research Database (Denmark)

    Zhang, Yubin; Mishin, Oleg

    2017-01-01

    The stored energy and the microstructure have been investigated in polycrystalline Ni processed by accumulative roll bonding (ARB) to different von Mises strains, epsilon(vM) = 1.6-6.4. The stored energy in Ni after ARB is found to be higher than that in conventionally rolled Ni samples after...

  16. Community challenges when using large plastic bottles for Solar Energy Disinfection of Water (SODIS)

    National Research Council Canada - National Science Library

    Borde, Preeti; Elmusharaf, Khalifa; McGuigan, Kevin G; Keogh, Michael B

    2016-01-01

    .... The exposure to sunlight is typically carried out in small volume plastic beverage bottles (up to 2 l). Given the water requirements of consumption and basic personal hygiene, this may not always meet the needs of communities...

  17. Improving Energy Efficiency at U.S. Plastics Manufacturing Plants Summary Report and Case Studies

    Energy Technology Data Exchange (ETDEWEB)

    none,

    2010-06-25

    Industrial Technologies Program’s BestPractices report based on a comprehensive plant assessment project with ITP’s Industrial Assessment Center, The Society of the Plastics Industry, Inc., and several of its member companies.

  18. Improving Energy Efficiency at U.S. Plastics Manufacturing Plants: Summary Report and Case Studies

    Energy Technology Data Exchange (ETDEWEB)

    2005-09-01

    Industrial Technologies Programs BestPractices report based on a comprehensive plant assessment project with ITP's Industrial Assessment Center, The Society of the Plastics Industry, Inc., and several of its member companies.

  19. Plastic collapse and energy absorption of circular filled tubes under quasi-static loads by computational analysis

    Energy Technology Data Exchange (ETDEWEB)

    Beng, Yeo Kiam; Tzeng, Woo Wen [Universiti Malaysia Sabah, Sabah (Malaysia)

    2017-02-15

    This study presents the finite element analysis of plastic collapse and energy absorption of polyurethane-filled aluminium circular tubes under quasi-static transverse loading. Increasing focuses were given to impact damage of structures where energy absorbed during impact could be controlled to avoid total structure collapse of energy absorbers and devices designed to dissipate energy. ABAQUS finite element analysis application was utilized for modelling and simulating the polyurethane-filled aluminium tubes, different set of diameterto- thickness ratios and span lengths, subjected to transverse three-point-bending load. Different sets of polyurethane-filled aluminium tubes subjected to the transverse loading were modelled and simulated. The failure modes and mechanisms of filled tubes and its capabilities as energy absorbers to further improve and strengthening of empty tube were also identified. The results showed that plastic deformation response was affected by the geometric constraints and parameters of the specimens. The diameter-to-thickness ratio and span lengths had shown to play crucial role in optimizing the PU-filled tube as energy absorber.

  20. The role of microstructure in the modelling of plastic flow in P/M superalloys at forging temperatures and strain rate

    Science.gov (United States)

    Immarigeon, J. P.

    1984-09-01

    The application of computer aided plasticity analysis to model the deformation of alloys during forging with a view to optimizing the microstructure in forged components is presented. Finite element modelling techniques and a methodology for predicting local changes in grain size as a function of local deformation history predict the final grain sizes in the rim and the bore regions of a disc via process modelling and determines the processing conditions under which an optimum microstructure is produced. The effects of thermomechanical history on the evolution of microstructure in P/M superalloys under isothermal forging conditions and formulation of physically realistic constitutive relations for plastic flow which quantify the effects of the microstructural evolution, thereby allowing the prediction of final microstructure in forgings were studied. Using constant true strain rate uniaxial compression tests, microstructure flow property data were generated at isothermal foring temperatures and strain rates for a number of compacts. Deformation modelling for microstructural control is discussed. It is shown that the rate of change of grain size is an important parameter which governs changes in flow strength and is considered in the formulation of constitutive relations for compacts both in a coarse grained and in a fine grained superplastic condition. A deformation model for grain size and rate sensitive P/M superalloys and a methodology that can be applied to predict grain size distributions in forgings are presented.

  1. A Mixed Plasticizer for the Preparation of Thermoplastic Starch

    Institute of Scientific and Technical Information of China (English)

    Xiao Fei MA; Jiu Gao YU; Jin FENG

    2004-01-01

    In this paper, formamide was firstly used as plasticizer to prepare thermoplastic starch (TPS), which could suppress the retrogradation of TPS by X-ray diffractometry (XRD) and show a good flexibility, but was weaker than conventional glycerol-plasticized TPS (GPTPS). When urea was introduced into plasticizer, both the retrogradation and mechanical properties were ameliorated. The tensile stress, strain and energy break of TPS plasticized by urea (wt. 20%) and formamide (wt.10%), respectively, reached 4.83 MPa, 104.6 % and 2.17 N?m (Newton?meter) after it had been stored at relative humidity (RH) 30% for one week.

  2. Quasi-plane-hypothesis of strain coordination for RC beams seismically strengthened with externally-bonded or near-surface mounted fiber reinforced plastic

    Science.gov (United States)

    Ren, Zhenhua; Zeng, Xiantao; Liu, Hanlong; Zhou, Fengjun

    2013-03-01

    The application of fiber reinforced plastic (FRP), including carbon FRP and glass FRP, for structural repair and strengthening has grown due to their numerous advantages over conventional materials such as externally bonded reinforcement (EBR) and near-surface mounted (NSM) strengthening techniques. This paper summarizes the results from 21 reinforced concrete beams strengthened with different methods, including externally-bonded and near-surface mounted FRP, to study the strain coordination of the FRP and steel rebar of the RC beam. Since there is relative slipping between the RC beam and the FRP, the strain of the FRP and steel rebar of the RC beam satisfy the quasi-plane-hypothesis; that is, the strain of the longitudinal fiber that parallels the neutral axis of the plated beam within the scope of the effective height ( h 0) of the cross section is in direct proportion to the distance from the fiber to the neutral axis. The strain of the FRP and steel rebar satisfies the equation: ɛ FRP= βɛ steel, and the value of β is equal to 1.1-1.3 according to the test results.

  3. A study on synthesis of energy fuel from waste plastic and assessment of its potential as an alternative fuel for diesel engines.

    Science.gov (United States)

    Kaimal, Viswanath K; Vijayabalan, P

    2016-05-01

    The demand for plastic is ever increasing and has produced a huge amount of plastic waste. The management and disposal of plastic waste have become a major concern, especially in developing cities. The idea of waste to energy recovery is one of the promising techniques used for managing the waste plastic. This paper assesses the potential of using Waste Plastic Oil (WPO), synthesized using pyrolysis of waste plastic, as an alternative for diesel fuel. In this research work, the performance and emission characteristics of a single cylinder diesel engine fuelled with WPO and its blends with diesel are studied. In addition to neat plastic oil, three blends (PO25, PO50 and PO75) were prepared on a volumetric basis and the engine was able to run on neat plastic oil. Brake thermal efficiency of blends was lower compared to diesel, but PO25 showed similar performance to that of diesel. The emissions were reduced considerably while using blends when compared to neat plastic oil. The smoke and NOX were reduced by 22% and 17.8% respectively for PO25 than that of plastic oil. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Possible Mechanism of Plasticity Influenced by Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    LIU Zhao-Long; FAN Tian-You; HU Hai-Yun

    2006-01-01

    The strain energy of an edge dislocation in an external static magnetic field is determined by the theory of elasticity and electrodynamics according to the Volterra dislocation model for continuous media. The results show that the strain energy of the edge dislocation in paramagnetic states is increased due to static magnetic field and the increase in the energy of the dislocation is capable of influencing the dislocation depinning which leads to the change of plasticity. This gives an explanation on plasticity induced by magnetic field.

  5. Strain controlled ferromagnetic-ferrimagnetic transition and vacancy formation energy of defective graphene.

    Science.gov (United States)

    Zhang, Yajun; Sahoo, Mpk; Wang, Jie

    2016-09-23

    Single vacancy (SV)-induced magnetism in graphene has attracted much attention motivated by its potential in achieving new functionalities. However, a much higher vacancy formation energy limits its direct application in electronic devices and the dependency of spin interaction on the strain is unclear. Here, through first-principles density-functional theory calculations, we investigate the possibility of strain engineering towards lowering vacancy formation energy and inducing new magnetic states in defective graphene. It is found that the SV-graphene undergoes a phase transition from an initial ferromagnetic state to a ferrimagnetic state under a biaxial tensile strain. At the same time, the biaxial tensile strain significantly lowers the vacancy formation energy. The charge density, density of states and band theory successfully identify the origin and underlying physics of the transition. The predicted magnetic phase transition is attributed to the strain driven spin flipping at the C-atoms nearest to the SV-site. The magnetic semiconducting graphene induced by defect and strain engineering suggests an effective way to modulate both spin and electronic degrees of freedom in future spintronic devices.

  6. Strain controlled ferromagnetic-ferrimagnetic transition and vacancy formation energy of defective graphene

    Science.gov (United States)

    Zhang, Yajun; Sahoo, MPK; Wang, Jie

    2016-10-01

    Single vacancy (SV)-induced magnetism in graphene has attracted much attention motivated by its potential in achieving new functionalities. However, a much higher vacancy formation energy limits its direct application in electronic devices and the dependency of spin interaction on the strain is unclear. Here, through first-principles density-functional theory calculations, we investigate the possibility of strain engineering towards lowering vacancy formation energy and inducing new magnetic states in defective graphene. It is found that the SV-graphene undergoes a phase transition from an initial ferromagnetic state to a ferrimagnetic state under a biaxial tensile strain. At the same time, the biaxial tensile strain significantly lowers the vacancy formation energy. The charge density, density of states and band theory successfully identify the origin and underlying physics of the transition. The predicted magnetic phase transition is attributed to the strain driven spin flipping at the C-atoms nearest to the SV-site. The magnetic semiconducting graphene induced by defect and strain engineering suggests an effective way to modulate both spin and electronic degrees of freedom in future spintronic devices.

  7. Effect of Strain Field on Threshold Displacement Energy of Tungsten Studied by Molecular Dynamics Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Dong; Gao, Ning; Setyawan, W.; Kurtz, R. J.; Wang, Zhi-Guang; Gao, Xing; He, Wen-Hao; Pang, Li-Long

    2016-09-01

    The influence of strain field on defect formation energy and threshold displacement energy (Ed) in body-centered cubic (BCC) tungsten (W) has been studied with molecular dynamics simulations. Two different W potentials (Fikar and Juslin) were compared and the results indicate that the connection distance and selected function linking the short-range and long-range portions of the potentials affects the threshold displacement energy and its direction-specific values. The minimum Ed direction calculated with the Fikar-potential is <100> and with the Juslin-potential is <111>. Nevertheless, the most stable self-interstitial configuration is found to be a <111>-crowdion for both potentials. This stable configuration does not change with applied strain. Varying the strain from compression to tension increases the vacancy formation energy but decreases the self-interstitial formation energy. The formation energy of a self-interstitial changes more significantly than a vacancy such that Ed decreases with applied hydrostatic strain from compression to tension.

  8. The exponentiated Hencky-logarithmic strain energy. Part II: Coercivity, planar polyconvexity and existence of minimizers

    Science.gov (United States)

    Neff, Patrizio; Lankeit, Johannes; Ghiba, Ionel-Dumitrel; Martin, Robert; Steigmann, David

    2015-08-01

    We consider a family of isotropic volumetric-isochoric decoupled strain energies based on the Hencky-logarithmic (true, natural) strain tensor log U, where μ > 0 is the infinitesimal shear modulus, is the infinitesimal bulk modulus with the first Lamé constant, are dimensionless parameters, is the gradient of deformation, is the right stretch tensor and is the deviatoric part (the projection onto the traceless tensors) of the strain tensor log U. For small elastic strains, the energies reduce to first order to the classical quadratic Hencky energy which is known to be not rank-one convex. The main result in this paper is that in plane elastostatics the energies of the family are polyconvex for , extending a previous finding on its rank-one convexity. Our method uses a judicious application of Steigmann's polyconvexity criteria based on the representation of the energy in terms of the principal invariants of the stretch tensor U. These energies also satisfy suitable growth and coercivity conditions. We formulate the equilibrium equations, and we prove the existence of minimizers by the direct methods of the calculus of variations.

  9. Effect of strain and temperature on the threshold displacement energy in body-centered cubic iron

    Science.gov (United States)

    Beeler, Benjamin; Asta, Mark; Hosemann, Peter; Grønbech-Jensen, Niels

    2016-06-01

    The threshold displacement energy (TDE) is the minimum amount of kinetic energy required to displace an atom from its lattice site. The magnitude of the TDE displays significant variance as a function of the crystallographic direction, system temperature and applied strain, among a variety of other factors. It is critically important to determine an accurate value of the TDE in order to calculate the total number of displacements due to a given irradiation condition, and thus to understand the materials response to irradiation. In this study, molecular dynamics simulations have been performed to calculate the threshold displacement energy in body-centered cubic iron as a function of strain and temperature. With applied strain, a decrease of the TDE of up to approximately 14 eV was observed. A temperature increase from 300 K to 500 K can result in an increase of the TDE of up to approximately 9 eV.

  10. Study of a detector system for high-energy astrophysical objects using a combination of plastic scintillator and MPPC

    Energy Technology Data Exchange (ETDEWEB)

    Nakaoka, Tatsuya; Mizuno, Tsunefumi; Takahashi, Hiromitsu; Fukazawa, Yasushi

    2016-09-21

    We have investigated a hard X-ray detector system using a combination of a plastic scintillator and multi-pixel photon counters (MPPC). Photomultiplier tubes (PMTs) have typically been adopted to read scintillators because of their high gain and large photoelectric surface, and studies on PMT and scintillator systems are well advanced. However, PMTs have limitations; for example, they are relatively large in size, require high voltage to operate, and cannot be used in strong magnetic fields. On the other hand, MPPCs do not have such limitations and instead possess high quantum efficiency and a large compact size. Therefore, we have studied a detector system that combines an MPPC with a plastic scintillator. The system is primarily intended to be used for polarization measurements of high-energy astrophysical objects. We achieved an energy threshold of as low as ~5 keV while operating the detector at low temperature (−10 °C), reading the signal with short integration time (50 ns), and using a low-noise MPPC. We also confirmed that the light yield of our MPPC+plastic scintillator system is comparable to that obtained using a conventional PMT to read the scintillator signal. Herein, we report test results and future prospects.

  11. A new method to predict fatigue crack growth rate of materials based on average cyclic plasticity strain damage accumulation

    Institute of Scientific and Technical Information of China (English)

    Chen Long; Cai Lixun; Yao Di

    2013-01-01

    By introducing a fatigue blunting factor,the cyclic elasto-plastic Hutchinson-RiceRosengren (HRR) field near the crack tip under the cyclic loading is modified.And,an average damage per loading-cycle in the cyclic plastic deformation region is defined due to Manson-Coffin law.Then,according to the linear damage accumulation theory-Miner law,a new model for predicting the fatigue crack growth (FCG) of the opening mode crack based on the low cycle fatigue (LCF) damage is set up.The step length of crack propagation is assumed to be the size of cyclic plastic zone.It is clear that every parameter of the new model has clearly physical meaning which does not need any human debugging.Based on the LCF test data,the FCG predictions given by the new model are consistent with the FCG test results of Cr2Ni2MoV and X12CrMoWVNbN 10-1-1.What's more,referring to the relative researches,the good predictability of the new model is also proved on six kinds of materials.

  12. A FRACTURE-ENERGY-BASED ELASTO-SOFTENING-PLASTIC CONSTITUTIVE MODEL FOR JOINTS OF GEOMATERIALS

    Institute of Scientific and Technical Information of China (English)

    沈新普; 沈国晓

    2002-01-01

    On the basis of plasticity and fracture mechanics for quasi- brittle materials, this article presented a constitutive model for gradual softening behavior of joints of geomaterials. Corresponding numerical tests are carried out at the local level. Characteristics of the model proposed are 1 ) plastic softening and dilatancy behavior are directly related to the fracture process of joint, and much less material and model parameters are required compared with those proposed by references; 2) the process of decohesion coupled with friction al sliding at both micro-scale and macro-scale is described.

  13. Energy absorption at high strain rate of glass fiber reinforced mortars

    Directory of Open Access Journals (Sweden)

    Fenu Luigi

    2015-01-01

    Full Text Available In this paper, the dynamic behaviour of cement mortars reinforced with glass fibers was studied. The influence of the addition of glass fibers on energy absorption and tensile strength at high strain-rate was investigated. Static tests in compression, in tension and in bending were first performed. Dynamic tests by means of a Modified Hopkinson Bar were then carried out in order to investigate how glass fibers affected energy absorption and tensile strength at high strain-rate of the fiber reinforced mortar. The Dynamic Increase Factor (DIF was finally evaluated.

  14. Tunable Photocontrolled Motions Using Stored Strain Energy in Malleable Azobenzene Liquid Crystalline Polymer Actuators.

    Science.gov (United States)

    Lu, Xili; Guo, Shengwei; Tong, Xia; Xia, Hesheng; Zhao, Yue

    2017-07-01

    A new strategy for enhancing the photoinduced mechanical force is demonstrated using a reprocessable azobenzene-containing liquid crystalline network (LCN). The basic idea is to store mechanical strain energy in the polymer beforehand so that UV light can then be used to generate a mechanical force not only from the direct light to mechanical energy conversion upon the trans-cis photoisomerization of azobenzene mesogens but also from the light-triggered release of the prestored strain energy. It is shown that the two mechanisms can add up to result in unprecedented photoindued mechanical force. Together with the malleability of the polymer stemming from the use of dynamic covalent bonds for chain crosslinking, large-size polymer photoactuators in the form of wheels or spring-like "motors" can be constructed, and, by adjusting the amount of prestored strain energy in the polymer, a variety of robust, light-driven motions with tunable rolling or moving direction and speed can be achieved. The approach of prestoring a controllable amount of strain energy to obtain a strong and tunable photoinduced mechanical force in azobenzene LCN can be further explored for applications of light-driven polymer actuators. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Enhancing inhibition-induced plasticity in tinnitus--spectral energy contrasts in tailor-made notched music matter.

    Science.gov (United States)

    Stein, Alwina; Engell, Alva; Lau, Pia; Wunderlich, Robert; Junghoefer, Markus; Wollbrink, Andreas; Bruchmann, Maximilian; Rudack, Claudia; Pantev, Christo

    2015-01-01

    Chronic tinnitus seems to be caused by reduced inhibition among frequency selective neurons in the auditory cortex. One possibility to reduce tinnitus perception is to induce inhibition onto over-activated neurons representing the tinnitus frequency via tailor-made notched music (TMNM). Since lateral inhibition is modifiable by spectral energy contrasts, the question arises if the effects of inhibition-induced plasticity can be enhanced by introducing increased spectral energy contrasts (ISEC) in TMNM. Eighteen participants suffering from chronic tonal tinnitus, pseudo randomly assigned to either a classical TMNM or an ISEC-TMNM group, listened to notched music for three hours on three consecutive days. The music was filtered for both groups by introducing a notch filter centered at the individual tinnitus frequency. For the ISEC-TMNM group a frequency bandwidth of 3/8 octaves on each side of the notch was amplified, additionally, by about 20 dB. Before and after each music exposure, participants rated their subjectively perceived tinnitus loudness on a visual analog scale. During the magnetoencephalographic recordings, participants were stimulated with either a reference tone of 500 Hz or a test tone with a carrier frequency representing the individual tinnitus pitch. Perceived tinnitus loudness was significantly reduced after TMNM exposure, though TMNM type did not influence the loudness ratings. Tinnitus related neural activity in the N1m time window and in the so called tinnitus network comprising temporal, parietal and frontal regions was reduced after TMNM exposure. The ISEC-TMNM group revealed even enhanced inhibition-induced plasticity in a temporal and a frontal cortical area. Overall, inhibition of tinnitus related neural activity could be strengthened in people affected with tinnitus by increasing spectral energy contrast in TMNM, confirming the concepts of inhibition-induced plasticity via TMNM and spectral energy contrasts.

  16. Plastic Deformation of Metal Surfaces

    DEFF Research Database (Denmark)

    Hansen, Niels; Zhang, Xiaodan; Huang, Xiaoxu

    2013-01-01

    parameters by TEM and EBSD and apply strength-structural relationships established for the bulk metal deformed to high strains. This technique has been applied to steel deformed by high energy shot peening and a calculated stress gradient at or near the surface has been successfully validated by hardness......Plastic deformation of metal surfaces by sliding and abrasion between moving parts can be detrimental. However, when the plastic deformation is controlled for example by applying different peening techniques hard surfaces can be produced which can increase the fracture resistance and fatigue life...... of metal components. An optimization of processes and material parameters must be based on a quantification of stress and strain gradients at the surface and in near surface layer where the structural scale can reach few tens of nanometers. For such fine structures it is suggested to quantify structural...

  17. Residual strain gradient determination in metal matrix composites by synchrotron X-ray energy dispersive diffraction

    Science.gov (United States)

    Kuntz, Todd A.; Wadley, Haydn N. G.; Black, David R.

    1993-01-01

    An X-ray technique for the measurement of internal residual strain gradients near the continuous reinforcements of metal matrix composites has been investigated. The technique utilizes high intensity white X-ray radiation from a synchrotron radiation source to obtain energy spectra from small (0.001 cu mm) volumes deep within composite samples. The viability of the technique was tested using a model system with 800 micron Al203 fibers and a commercial purity titanium matrix. Good agreement was observed between the measured residual radial and hoop strain gradients and those estimated from a simple elastic concentric cylinders model. The technique was then used to assess the strains near (SCS-6) silicon carbide fibers in a Ti-14Al-21Nb matrix after consolidation processing. Reasonable agreement between measured and calculated strains was seen provided the probe volume was located 50 microns or more from the fiber/matrix interface.

  18. Robust piezoelectric composites for energy harvesting in high-strain environments

    NARCIS (Netherlands)

    Ende, D.A. van der; Groen, W.A.; Zwaag, S. van der

    2013-01-01

    High-strain environments, such as are found in automobile tires, provide deformation energy that can be harvested using piezoelectric materials, for instance, for powering electronics such as wireless sensors. Despite numerous efforts, none of the present devices easily satisfy the stringent operati

  19. On the relationship between disbond growth and the release of strain energy

    NARCIS (Netherlands)

    Pascoe, J.A.; Alderliesten, R.C.; Benedictus, R.

    2014-01-01

    Current prediction methods for growth of disbonds under fatigue loading are generally based on a correlation with either the maximum strain energy release rate (SERR) or the SERR range. This paper highlights some issues with this approach. In particular, it is argued that the maximum SERR or the SE

  20. Modal Strain Energy Based Structural Damage Localization for Offshore Platform using Simulated and Measured Data

    Institute of Scientific and Technical Information of China (English)

    WANG Shuqing; LIU Fushun; ZHANG Min

    2014-01-01

    Modal strain energy based methods for damage detection have received much attention. However, most of published articles use numerical methods and some studies conduct modal tests with simple 1D or 2D structures to verify the damage detection algorithms. Only a few studies utilize modal testing data from 3D frame structures. Few studies conduct performance comparisons between two different modal strain energy based methods. The objective of this paper is to investigate and compare the effectiveness of a traditional modal strain energy method (Stubbs index) and a recently developed modal strain energy decomposition (MSED) method for damage localization, for such a purpose both simulated and measured data from an offshore platform model being used. Particularly, the mode shapes used in the damage localization are identified and synthesized from only two measurements of one damage scenario because of the limited number of sensors. The two methods were first briefly reviewed. Next, using a 3D offshore platform model, the damage detection algorithms were implemented with different levels of damage severities for both single damage and multiple damage cases. Finally, a physical model of an offshore steel platform was constructed for modal testing and for validat-ing the applicability. Results indicate that the MSED method outperforms the Stubbs index method for structural damage detection.

  1. A high energy microscope for local strain measurements within bulk materials

    DEFF Research Database (Denmark)

    Lienert, U.; Poulsen, H.F.; Martins, R.V.

    2000-01-01

    A novel diffraction technique for local, three dimensional strain scanning within bulk materials is presented. The technique utilizes high energy, micro-focussed synchrotron radiation which can penetrate several millimeters into typical metals. The spatial resolution can be as narrow as 1 mum....... Case studies demonstrate that steep macrostrain gradients can be resolved. Techniques for the local measurement of macro- and microstrains are discussed....

  2. Modal Strain Energy Based Structural Health Monitoring on Rib Stiffened Composite Panels

    NARCIS (Netherlands)

    Hwang, Joong Sun; Loendersloot, Richard; Tinga, Tiedo

    2016-01-01

    Previously, an evaluation study has been conducted on a Structural Health Monitoring (SHM) strategy applied to a composite aileron by deriving the Modal Strain Energy Damage Indicator (MSE-DI). MSE-DI was used to localize the impact damage location. However, this study has also shown that the damage

  3. Vibration based structural health monitoring in fibre reinforced composites employing the modal strain energy method

    NARCIS (Netherlands)

    Loendersloot, Richard; Ooijevaar, Ted; Warnet, Laurent; Akkerman, Remko; Boer, de André; Meguid, S.A.; Gomes, J.F.S.

    2009-01-01

    The feasibility of a vibration based damage identification method is investigated. The Modal Strain Energy method is applied to a T–beam structure. The dynamic response of an intact structure and a damaged, delaminated structure is analysed employing a commercially available Finite Element package.

  4. Analogy of strain energy density based bone-remodeling algorithm and structural topology optimization.

    Science.gov (United States)

    Jang, In Gwun; Kim, Il Yong; Kwak, Byung Ban

    2009-01-01

    In bone-remodeling studies, it is believed that the morphology of bone is affected by its internal mechanical loads. From the 1970s, high computing power enabled quantitative studies in the simulation of bone remodeling or bone adaptation. Among them, Huiskes et al. (1987, "Adaptive Bone Remodeling Theory Applied to Prosthetic Design Analysis," J. Biomech. Eng., 20, pp. 1135-1150) proposed a strain energy density based approach to bone remodeling and used the apparent density for the characterization of internal bone morphology. The fundamental idea was that bone density would increase when strain (or strain energy density) is higher than a certain value and bone resorption would occur when the strain (or strain energy density) quantities are lower than the threshold. Several advanced algorithms were developed based on these studies in an attempt to more accurately simulate physiological bone-remodeling processes. As another approach, topology optimization originally devised in structural optimization has been also used in the computational simulation of the bone-remodeling process. The topology optimization method systematically and iteratively distributes material in a design domain, determining an optimal structure that minimizes an objective function. In this paper, we compared two seemingly different approaches in different fields-the strain energy density based bone-remodeling algorithm (biomechanical approach) and the compliance based structural topology optimization method (mechanical approach)-in terms of mathematical formulations, numerical difficulties, and behavior of their numerical solutions. Two numerical case studies were conducted to demonstrate their similarity and difference, and then the solution convergences were discussed quantitatively.

  5. Multi-layer plastic scintillation detector for intermediate- and high-energy neutrons with n- γ discrimination capability

    Science.gov (United States)

    Yu, L.; Terashima, S.; Ong, H. J.; Chan, P. Y.; Tanihata, I.; Iwamoto, C.; Tran, D. T.; Tamii, A.; Aoi, N.; Fujioka, H.; Gey, G.; Sakaguchi, H.; Sakaue, A.; Sun, B. H.; Tang, T. L.; Wang, T. F.; Watanabe, Y. N.; Zhang, G. X.

    2017-09-01

    A new type of neutron detector, named Stack Structure Solid organic Scintillator (S4), consisting of multi-layer plastic scintillators with capability to suppress low-energy γ rays under high-counting rate has been constructed and tested. To achieve n- γ discrimination, we exploit the difference in the ranges of the secondary charged particles produced by the interactions of neutrons and γ rays in the scintillator material. The thickness of a plastic scintillator layer was determined based on the results of Monte Carlo simulations using the Geant4 toolkit. With layer thicknesses of 5 mm, we have achieved a good separation between neutrons and γ rays at 5 MeVee threshold setting. We have also determined the detection efficiencies using monoenergetic neutrons at two energies produced by the d + d → n+3He reaction. The results agree well with the Geant4 simulations implementing the Li e ̀ge Intranuclear Cascade hadronic model (INCL++) and the high-precision model of low-energy neutron interactions (NeutronHP).

  6. Distribution of Energy Deposited in Plastic Tubing and Copper-Wire Insulation by Electron Beam Irradiation

    DEFF Research Database (Denmark)

    Pedersen, Walther Batsberg; Miller, Arne; Pejtersen, K.

    1978-01-01

    Scanned electron beam treatment is used to improve the physical properties of certain polymers, such as shrinkable plastic tubing and insulated wire and cable. Tubing or wires are passed at high speed under the beam scanner, and the material is irradiated to absorbed doses of several Mrad...... as uniformly as possible, usually by means of a multipass arrangement. In the present study, using irradiation by a scanned 0.4 MeV electron beam, measurements were made of high-resolution distributions of absorbed dose in polyethylene tubing and copper wire coated with polyethylene, nylon, or polyvinyl...... chloride insulation. Radiochromic dye films equivalent to the insulating materials were used as accurate dosimeters having a response independent of dose rate. Irradiations were in various geometries, wire and plastic thicknesses, positions along the beam scan, and with different backing materials near...

  7. The synchronous improvement of strength and plasticity (SISP) in new Ni-Co based disc superalloys by controling stacking fault energy.

    Science.gov (United States)

    Xu, H; Zhang, Z J; Zhang, P; Cui, C Y; Jin, T; Zhang, Z F

    2017-08-14

    It is a great challenge to improve the strength of disc superalloys without great loss of plasticity together since the microstructures benefiting the strength always do not avail the plasticity. Interestingly, this study shows that the trade-off relationship between strength and plasticity can be broken through decreasing stacking fault energy (SFE) in newly developed Ni-Co based disc superalloys. Axial tensile tests in the temperature range of 25 to 725 °C were carried out in these alloys with Co content ranging from 5% to 23% (wt.%). It is found that the ultimate tensile strength (UTS) and uniform elongation (UE) are improved synchronously when microtwinning is activated by decreasing the SFE at 650 and 725 °C. In contrast, only UTS is improved when stacking fault (SF) dominates the plastic deformation at 25 and 400 °C. These results may be helpful for designing advanced disc superalloys with relatively excellent strength and plasticity simultaneously.

  8. Multi-layered controllable stiffness beams for morphing: energy, actuation force, and material strain considerations

    Science.gov (United States)

    Murray, Gabriel; Gandhi, Farhan

    2010-04-01

    Morphing aerospace structures could benefit from the ability of structural elements to transition from a stiff load-bearing state to a relatively compliant state that can undergo large deformation at low actuation cost. The present paper focuses on multi-layered beams with controllable flexural stiffness—comprising polymer layers affixed to the surfaces of a base beam and cover layers, in turn, affixed to the surfaces of the polymer layers. Heating the polymer through the glass transition reduces its shear modulus, decouples the cover layers from the base beam and reduces the overall flexural stiffness. Although the stiffness and actuation force required to bend the beam reduce, the energy required to heat the polymer layer must also be considered. Results show that for beams with low slenderness ratios, relatively thick polymer layers, and cover layers whose extensional stiffness is high, the decoupling of the cover layers through softening of the polymer layers can result in flexural stiffness reductions of over 95%. The energy savings are also highest for these configurations, and will increase as the deformation of the beam increases. The decoupling of the cover layers from the base beam through the softening of the polymer reduces the axial strains in the cover layers significantly; otherwise material failure would prevent large deformation. Results show that when the polymer layer is stiff, the cover layers are the dominant contributors to the total energy in the beam, and the energy in the polymer layers is predominantly axial strain energy. When the polymer layers are softened the energy in the cover layers is a small contributor to the total energy which is dominated by energy in the base beam and shear strain energy in the polymer layer.

  9. On consistent micromechanical estimation of macroscopic elastic energy, coherence energy and phase transformation strains for SMA materials

    Science.gov (United States)

    Ziółkowski, Andrzej

    2016-09-01

    An apparatus of micromechanics is used to isolate the key ingredients entering macroscopic Gibbs free energy function of a shape memory alloy (SMA) material. A new self-equilibrated eigenstrains influence moduli (SEIM) method is developed for consistent estimation of effective (macroscopic) thermostatic properties of solid materials, which in microscale can be regarded as amalgams of n-phase linear thermoelastic component materials with eigenstrains. The SEIM satisfy the self-consistency conditions, following from elastic reciprocity (Betti) theorem. The method allowed expressing macroscopic coherency energy and elastic complementary energy terms present in the general form of macroscopic Gibbs free energy of SMA materials in the form of semilinear and semiquadratic functions of the phase composition. Consistent SEIM estimates of elastic complementary energy, coherency energy and phase transformation strains corresponding to classical Reuss and Voigt conjectures are explicitly specified. The Voigt explicit relations served as inspiration for working out an original engineering practice-oriented semiexperimental SEIM estimates. They are especially conveniently applicable for an isotropic aggregate (composite) composed of a mixture of n isotropic phases. Using experimental data for NiTi alloy and adopting conjecture that it can be treated as an isotropic aggregate of two isotropic phases, it is shown that the NiTi coherency energy and macroscopic phase strain are practically not influenced by the difference in values of austenite and martensite elastic constants. It is shown that existence of nonzero fluctuating part of phase microeigenstrains field is responsible for building up of so-called stored energy of coherency, which is accumulated in pure martensitic phase after full completion of phase transition. Experimental data for NiTi alloy show that the stored coherency energy cannot be neglected as it considerably influences the characteristic phase transition

  10. On consistent micromechanical estimation of macroscopic elastic energy, coherence energy and phase transformation strains for SMA materials

    Science.gov (United States)

    Ziółkowski, Andrzej

    2017-01-01

    An apparatus of micromechanics is used to isolate the key ingredients entering macroscopic Gibbs free energy function of a shape memory alloy (SMA) material. A new self-equilibrated eigenstrains influence moduli (SEIM) method is developed for consistent estimation of effective (macroscopic) thermostatic properties of solid materials, which in microscale can be regarded as amalgams of n-phase linear thermoelastic component materials with eigenstrains. The SEIM satisfy the self-consistency conditions, following from elastic reciprocity (Betti) theorem. The method allowed expressing macroscopic coherency energy and elastic complementary energy terms present in the general form of macroscopic Gibbs free energy of SMA materials in the form of semilinear and semiquadratic functions of the phase composition. Consistent SEIM estimates of elastic complementary energy, coherency energy and phase transformation strains corresponding to classical Reuss and Voigt conjectures are explicitly specified. The Voigt explicit relations served as inspiration for working out an original engineering practice-oriented semiexperimental SEIM estimates. They are especially conveniently applicable for an isotropic aggregate (composite) composed of a mixture of n isotropic phases. Using experimental data for NiTi alloy and adopting conjecture that it can be treated as an isotropic aggregate of two isotropic phases, it is shown that the NiTi coherency energy and macroscopic phase strain are practically not influenced by the difference in values of austenite and martensite elastic constants. It is shown that existence of nonzero fluctuating part of phase microeigenstrains field is responsible for building up of so-called stored energy of coherency, which is accumulated in pure martensitic phase after full completion of phase transition. Experimental data for NiTi alloy show that the stored coherency energy cannot be neglected as it considerably influences the characteristic phase transition

  11. Electric field induced strain, switching and energy storage behaviour of lead free Barium Zirconium Titanate ceramic

    Science.gov (United States)

    Badapanda, T.; Chaterjee, S.; Mishra, Anupam; Ranjan, Rajeev; Anwar, S.

    2017-09-01

    There is a huge demand of lead-free high performance ceramics with large strain, low hysteresis loss and high-energy storage ability at room temperature. In this context, we investigated the large electric field induced strain, switching behaviour and energy storage properties of BaZr0.05Ti0.95O3 ceramic (BZT) prepared by high energy ball milling technique, reportedly exhibiting a triple point transition near the room temperature. The X-ray diffraction of the BZT ceramic confirms orthorhombic symmetry with space group Amm2 at room temperature. The room temperature dielectric study reveals that there is a negligible variation of dielectric constant and dielectric loss with frequency. The polarization behaviour at various applied electric fields was studied and the energy storage densities were obtained from the integral area of P-E loops. Electric field induced strain behaviour has been studied with due emphasis on the electrostrictive response at room temperature. The ferroelectric and electromechanical properties derived from the P-E and S-E loops suggest that the present ceramic encompass the properties of actuation and energy storage simultaneously.

  12. Implementation of a strain energy-based nonlinear finite element in the object-oriented environment

    Science.gov (United States)

    Wegner, Tadeusz; Pęczak, Andrzej

    2010-03-01

    The objective of the paper is to describe a novel finite element computational method based on a strain energy density function and to implement it in the object-oriented environment. The original energy-based finite element was put into the known standard framework of classes and handled in a different manner. The nonlinear properties of material are defined with a modified strain energy density function. The local relaxation procedure proposed as a method used to resolve a nonlinear problem is implemented in C++ language. The hexahedral element with eight nodes as well as the adaptation of the nonlinear finite element is introduced. The chosen numerical model is made of nearly incompressible hyperelastic material. The application of the proposed element is shown on the example of a rectangular parallelepiped with a hollow port.

  13. Remaining stress-state and strain-energy in tempered glass fragments

    DEFF Research Database (Denmark)

    Nielsen, Jens Henrik

    2016-01-01

    , nanoscale materials, composites, glass and fundamentals, Springer, Houston, 2005) have proposed models for the fragments size based on an energy approach. Often an estimate of the remaining strain energy in the fragment is used; which leaves the questions: (a) what parameters are important for the remaining......When tempered glass breaks, it shatters into relatively small pieces depending on the residual stress state in the glass. This has been known for centuries and is currently used in standards for classifying whether a piece of glass is tempered or not. However, the process of fragmentation...... is complex and only a few, relatively simple, models have been suggested for predicting the fragment size. The full theoretical explanation is still to be found and this work aims at providing another brick to the puzzle. The strain-energy present in tempered glass is obviously contributing...

  14. Elastic strain relaxation in interfacial dislocation patterns: I. A parametric energy-based framework

    Science.gov (United States)

    Vattré, A.

    2017-08-01

    A parametric energy-based framework is developed to describe the elastic strain relaxation of interface dislocations. By means of the Stroh sextic formalism with a Fourier series technique, the proposed approach couples the classical anisotropic elasticity theory with surface/interface stress and elasticity properties in heterogeneous interface-dominated materials. For any semicoherent interface of interest, the strain energy landscape is computed using the persistent elastic fields produced by infinitely periodic hexagonal-shaped dislocation configurations with planar three-fold nodes. A finite element based procedure combined with the conjugate gradient and nudged elastic band methods is applied to determine the minimum-energy paths for which the pre-computed energy landscapes yield to elastically favorable dislocation reactions. Several applications on the Au/Cu heterosystems are given. The simple and limiting case of a single set of infinitely periodic dislocations is introduced to determine exact closed-form expressions for stresses. The second limiting case of the pure (010) Au/Cu heterophase interfaces containing two crossing sets of straight dislocations investigates the effects due to the non-classical boundary conditions on the stress distributions, including separate and appropriate constitutive relations at semicoherent interfaces and free surfaces. Using the quantized Frank-Bilby equation, it is shown that the elastic strain landscape exhibits intrinsic dislocation configurations for which the junction formation is energetically unfavorable. On the other hand, the mismatched (111) Au/Cu system gives rise to the existence of a minimum-energy path where the fully strain-relaxed equilibrium and non-regular intrinsic hexagonal-shaped dislocation rearrangement is accompanied by a significant removal of the short-range elastic energy.

  15. Experimental investigation of the quality characteristics of agricultural plastic wastes regarding their recycling and energy recovery potential.

    Science.gov (United States)

    Briassoulis, D; Hiskakis, M; Babou, E; Antiohos, S K; Papadi, C

    2012-06-01

    A holistic environmentally sound waste management scheme that transforms agricultural plastic waste (APW) streams into labelled guaranteed quality commodities freely traded in open market has been developed by the European research project LabelAgriWaste. The APW quality is defined by the APW material requirements, translated to technical specifications, for recycling or energy recovery. The present work investigates the characteristics of the APW quality and the key factors affecting it from the introduction of the virgin product to the market to the APW stream reaching the disposer. Samples of APW from different countries were traced from their application to the field through their storage phase and transportation to the final destination. The test results showed that the majority of APW retained their mechanical properties after their use preserving a "very good quality" for recycling in terms of degradation. The degree of soil contamination concerning the APW recycling and energy recovery potential fluctuates depending on the agricultural plastic category and application. The chlorine and heavy metal content of the tested APW materials was much lower than the maximum acceptable limits for their potential use in cement industries.

  16. Modelling the torsion of thin metal wires by distortion gradient plasticity

    Science.gov (United States)

    Bardella, Lorenzo; Panteghini, Andrea

    2015-05-01

    Under small strains and rotations, we apply a phenomenological higher-order theory of distortion gradient plasticity to the torsion problem, here assumed as a paradigmatic benchmark of small-scale plasticity. Peculiar of the studied theory, proposed about ten years ago by Morton E. Gurtin, is the constitutive inclusion of the plastic spin, affecting both the free energy and the dissipation. In particular, the part of the free energy, called the defect energy, which accounts for Geometrically Necessary Dislocations, is a function of Nye's dislocation density tensor, dependent on the plastic distortion, including the plastic spin. For the specific torsion problem, we implement this distortion gradient plasticity theory into a Finite Element (FE) code characterised by implicit (Backward Euler) time integration, numerically robust and accurate for both viscoplastic and rate-independent material responses. We show that, contrariwise to other higher-order theories of strain gradient plasticity (neglecting the plastic spin), the distortion gradient plasticity can predict some strengthening even if a quadratic defect energy is chosen. On the basis of the results of many FE analyses, concerned with (i) cyclic loading, (ii) switch in the higher-order boundary conditions during monotonic plastic loading, (iii) the use of non-quadratic defect energies, and (iv) the prediction of experimental data, we mainly show that (a) including the plastic spin contribution in a gradient plasticity theory is highly recommendable to model small-scale plasticity, (b) less-than-quadratic defect energies may help in describing the experimental results, but they may lead to anomalous cyclic behaviour, and (c) dissipative (unrecoverable) higher-order finite stresses are responsible for an unexpected mechanical response under non-proportional loading.

  17. Synergistic effect of austenitizing temperature and hot plastic deformation strain on the precipitation behavior in novel HSLA steel

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Chih-Yuan, E-mail: chen6563@gmail.com [Department of Energy Engineering, National United University, Miaoli 36003, Taiwan (China); Department of Materials Science and Engineering, National Taiwan University, Taipei 10617, Taiwan (China); Chen, Chien-Chon [Department of Energy Engineering, National United University, Miaoli 36003, Taiwan (China); Yang, Jer-Ren, E-mail: jryang@ntu.edu.tw [Department of Materials Science and Engineering, National Taiwan University, Taipei 10617, Taiwan (China)

    2015-07-15

    Examination of thin foils of specimens with various austenitizing conditions by transmission electron microscopy revealed randomly homogeneous precipitation in the ferrite for each experimental condition. Though no interphase precipitation was found in the present study, two types of random precipitation morphologies were identified in the ferrite matrix. One was randomly and homogeneously precipitated carbides of smaller size (<10 nm), and the other was randomly precipitated carbides of larger size (10–30 nm). Transmission electron microscopy results provided evidence that both types of precipitation carbides could be associated with the supersaturation of microalloying elements in the ferrite and austenite, respectively. A higher austenitizing temperature treatment can lead to more microalloying elements dissolving in the austenite such that many tiny carbides precipitation at the low isothermal holding temperature, which is believed to effectively strengthen the ferrite. Vickers hardness data revealed that, in specimens austenitized at 1200 °C and deformed at 900 °C with strains of 10% and 30%, the ranges of hardness distribution were 250–360 HV 0.1 and 310–400 HV 0.1, respectively. For specimens austenitized at 1000 °C and deformed at 900 °C with strains of 10% and 30%, the ranges of hardness distribution were 220–250 HV 0.1 and 220–260 HV 0.1, respectively. Therefore, the average Vickers hardness increased with the austenitizing temperature and deformation strain. However, a wider range of hardness distribution occurred in specimens that underwent treatment at higher austenitizing temperatures. The wider Vickers hardness distribution reflects non-uniform precipitation in each ferrite grain.

  18. Effect of intense plastic straining on microstructure and mechanical properties of an Al-Mg-Sc alloy

    Energy Technology Data Exchange (ETDEWEB)

    Kaibyshev, R [Belgorod State University, Pobeda 85, Belgorod, 308015 (Russian Federation); Avtokratova, E; Sitdikov, O, E-mail: rustam_kaibyshev@bsu.edu.r [Institute for Metals Superplasticity Problems, Khalturina 39, Ufa, 450001 (Russian Federation)

    2010-07-01

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

  19. Effect of intense plastic straining on microstructure and mechanical properties of an Al-Mg-Sc alloy

    Science.gov (United States)

    Kaibyshev, R.; Avtokratova, E.; Sitdikov, O.

    2010-07-01

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

  20. Study of the Elasto-plastic Properties of Mineralized Biomaterials via Synchrotron High-energy X-ray Diffraction

    Science.gov (United States)

    Deymier-Black, Alix Christine

    Synchrotron high-energy X-ray diffraction was employed to investigate the strains in the hydroxyapatite (HAP) platelets and mineralized collagen fibrils in bovine dentin and cortical bone. The HAP and the fibrillar apparent moduli, defined as the applied stress divided by the phase strain, in dentin were measured as 27+/-7.2 and 16+/-4.9 GPa. The HAP apparent modulus ( EHAPapp ) is less than the lower bound calculated for EHAPapp from the Voigt model. This discrepancy is probably due to stress concentrators or decreases in the HAP Young's modulus due to size or composition effects. EHAPapp and Efibapp in dentin vary significantly within a single tooth in both the apical-cervical direction and the buccal-lingual direction. However, the variation between teeth is minimal. The HAP and fibrillar apparent moduli are not affected by freezing in dentin or by X-ray irradiation in bone and dentin. X-ray irradiation causes a decrease in HAP residual strain in bone. This decrease suggests the presence of HAP-collagen interfacial damage. It was determined from the HAP 00.2 peak broadening that irradiation damage mostly affects the HAP unit cells which are under the highest strain. From this it was theorized that irradiation may damage highly-strained bonds at stress concentrators and/or calcium-mediated electrostatic bonds. The fact that the apparent modulus does not change with irradiation suggests that the interfacial damage must be reversible. Bone and dentin both undergo creep when loaded to high stresses. At low irradiation doses, both the fibrillar and HAP strains increase with creep time indicating that load is being transferred from the matrix to the HAP. However, at high doses, the strain on the HAP decreases with creep time. This supports the interfacial damage theory which would allow the HAP to release its elastic load upon interfacial debonding. At -80 MPa, beyond a dose of 50 kGy, the rate of change in HAP strain with time begins to increase, becoming positive at

  1. Phase field approach with anisotropic interface energy and interface stresses: Large strain formulation

    Science.gov (United States)

    Levitas, Valery I.; Warren, James A.

    2016-06-01

    A thermodynamically consistent, large-strain, multi-phase field approach (with consequent interface stresses) is generalized for the case with anisotropic interface (gradient) energy (e.g. an energy density that depends both on the magnitude and direction of the gradients in the phase fields). Such a generalization, if done in the "usual" manner, yields a theory that can be shown to be manifestly unphysical. These theories consider the gradient energy as anisotropic in the deformed configuration, and, due to this supposition, several fundamental contradictions arise. First, the Cauchy stress tensor is non-symmetric and, consequently, violates the moment of momentum principle, in essence the Herring (thermodynamic) torque is imparting an unphysical angular momentum to the system. In addition, this non-symmetric stress implies a violation of the principle of material objectivity. These problems in the formulation can be resolved by insisting that the gradient energy is an isotropic function of the gradient of the order parameters in the deformed configuration, but depends on the direction of the gradient of the order parameters (is anisotropic) in the undeformed configuration. We find that for a propagating nonequilibrium interface, the structural part of the interfacial Cauchy stress is symmetric and reduces to a biaxial tension with the magnitude equal to the temperature- and orientation-dependent interface energy. Ginzburg-Landau equations for the evolution of the order parameters and temperature evolution equation, as well as the boundary conditions for the order parameters are derived. Small strain simplifications are presented. Remarkably, this anisotropy yields a first order correction in the Ginzburg-Landau equation for small strains, which has been neglected in prior works. The next strain-related term is third order. For concreteness, specific orientation dependencies of the gradient energy coefficients are examined, using published molecular dynamics

  2. Testing and evaluation of stretching strain in clamped–clamped beams for energy harvesting

    Science.gov (United States)

    Emad, Ahmed; Mahmoud, Mohamed A. E.; Ghoneima, Maged; Dessouky, Mohamed

    2016-11-01

    In this paper, evaluation of stretching strain capabilities to harvest energy from a piezoelectric clamped–clamped beam is theoretically modeled and experimentally tested. The utilization of stretching strain has many advantages as: elimination of any substrate material, and the simple electrode configuration. The doubly clamped structure exhibits a highly nonlinear frequency response (Hardening Duffing) that widens the bandwidth during the frequency up-ward sweep. The wide bandwidth makes it suitable for practical applications. A design of 53.5 {{mm}}3 (29.7 {{mm}}3 piezoelectric material + 23.8 {{mm}}3 proof mass) energy harvester was tested using PVDF (polyvinylidene fluoride) that can generate up to 15 μW from vibrations of 0.5{g} at 128 {Hz} and 2 MΩ load. The design can also generate up to 41 μ {{W}} from vibrations of 1{g} at 140 {Hz} and 2 MΩ load.

  3. Plastic Surgery

    Science.gov (United States)

    ... Surgery? A Week of Healthy Breakfasts Shyness Plastic Surgery KidsHealth > For Teens > Plastic Surgery Print A A ... forehead lightened with a laser? What Is Plastic Surgery? Just because the name includes the word "plastic" ...

  4. Strengths and strain energies of volcanic edifices: implications for eruptions, collapse calderas, and landslides

    Directory of Open Access Journals (Sweden)

    A. Gudmundsson

    2012-07-01

    Full Text Available Natural hazards associated with volcanic edifices depend partly on how fracture resistant the edifices are, i.e. on their strengths. Observations worldwide indicate that large fluid-driven extension fractures (dikes, inclined sheets, shear fractures (landslides, and mixed-mode fractures (ring dikes and ring faults normally propagate more easily in a basaltic edifice (shield volcano than in a stratovolcano. For example, dike-fed eruptions occur once every few years in many basaltic edifices but once every 102-3 yr in many stratovolcanoes. Large landslides and caldera collapses also appear to be more common in a typical basaltic edifice/shield volcano than in a typical stratovolcano. In contrast to a basaltic edifice, a stratovolcano is composed of mechanically dissimilar rock layers, i.e. layers with mismatching elastic properties (primarily Young's modulus. Elastic mismatch encourages fracture deflection and arrest at contacts and increases the amount of energy needed for a large-scale edifice failure. Fracture-related hazards depend on the potential energy available to propagate the fractures which, in turn, depends on the boundary conditions during fracture propagation. Here there are two possible scenarios: one in which the outer boundary of the volcanic edifice or rift zone does not move during the fracture propagation (constant displacement; the other in which the boundary moves (constant load. In the former, the total potential energy is the strain energy stored in the volcano before fracture formation; in the latter, the total potential energy is the strain energy plus the work done by the forces moving the boundary. Constant-displacement boundary conditions favor small eruptions, landslides, and caldera collapses, whereas constant-load conditions favor comparatively large eruptions, landslides, and collapses. For a typical magma chamber (sill-like with a diameter of 8 km, the strain energy change due to magma-chamber inflation

  5. Strain and Cohesive Energy of TiN Deposit on Al(001) Surface: Density Functional Calculation

    Science.gov (United States)

    Ren, Yuan; Liu, Xuejie

    2016-07-01

    To apply the high hardness of TiN film to soft and hard multilayer composite sheets, we constructed a new type of composite structural material with ultra-high strength. The strain of crystal and cohesive energy between the atoms in the eight structures of N atom, Ti atom, 2N2Ti island and TiN rock salt deposited on the Al(001) surface were calculated with the first-principle ultra-soft pseudopotential approach of the plane wave based on the density functional theory. The calculations of the cohesive energy showed that N atoms could be deposited in the face-centered-cubic vacancy position of the Al(001) surface and results in a cubic structure AlN surface. The TiN film could be deposited on the interface of β-AlN. The calculations of the strains showed that the strain in the TiN film deposited on the Al(001) surface was less than that in the 2N2Ti island deposited on the Al(001) surface. The diffusion behavior of interface atom N was investigated by a nudged elastic band method. Diffusion energy calculation showed that the N atom hardly diffused to the substrate Al layer.

  6. Elastic Strain Energy Storage and Neighboring Organ Assistance for Fluid Propulsion

    Science.gov (United States)

    Arun, C. P.

    2003-11-01

    Storage of elastic strain energy by non-muscular structures such as tendons and ligaments, is a common scheme employed by jumping animals. Also, since skeletal muscle is attached to bone, mechanical advantage is obtained, allowing a burst of power that is unobtainable by muscle contraction alone. This is important at launch since force may be applied for only the brief period when the legs are in contact with the ground. Liquid propelling structures such as the urinary bladder and the heart face the similar problem of being able to impart force to the content only as long as the wall is in a stretched state. Using data from videocystometry and cardiac catheterisation we show that the means employed to achieve liquid propulsion appears to involve a combination of isometric contraction (contraction against a closed sphincter or valve) with hyperelastic stretch of the wall, elastic strain energy storage by the wall, overshoot past the undistended state and neighboring organ assistance (NOA). Thus, the heart, a partially collapsible thick muscular shell without the benefit of NOA manages an ejection fraction of about 70%. Using all of the above means, the collapsible urinary bladder is able to nearly always empty. Elastic strain energy storage and NOA appear to be important strategies for liquid propulsion employed by hollow viscera.

  7. Scaling of brain metabolism with a fixed energy budget per neuron: implications for neuronal activity, plasticity and evolution.

    Science.gov (United States)

    Herculano-Houzel, Suzana

    2011-03-01

    It is usually considered that larger brains have larger neurons, which consume more energy individually, and are therefore accompanied by a larger number of glial cells per neuron. These notions, however, have never been tested. Based on glucose and oxygen metabolic rates in awake animals and their recently determined numbers of neurons, here I show that, contrary to the expected, the estimated glucose use per neuron is remarkably constant, varying only by 40% across the six species of rodents and primates (including humans). The estimated average glucose use per neuron does not correlate with neuronal density in any structure. This suggests that the energy budget of the whole brain per neuron is fixed across species and brain sizes, such that total glucose use by the brain as a whole, by the cerebral cortex and also by the cerebellum alone are linear functions of the number of neurons in the structures across the species (although the average glucose consumption per neuron is at least 10× higher in the cerebral cortex than in the cerebellum). These results indicate that the apparently remarkable use in humans of 20% of the whole body energy budget by a brain that represents only 2% of body mass is explained simply by its large number of neurons. Because synaptic activity is considered the major determinant of metabolic cost, a conserved energy budget per neuron has several profound implications for synaptic homeostasis and the regulation of firing rates, synaptic plasticity, brain imaging, pathologies, and for brain scaling in evolution.

  8. Effect of specimen size on energy dissipation characteristics of red sandstone under high strain rate

    Institute of Scientific and Technical Information of China (English)

    Li Ming; Mao Xianbiao; Lu Aihong; Tao Jing; Zhang Guanghui; Zhang Lianying; Li Chong

    2014-01-01

    In this experiment, red sandstone specimens, having slenderness ratios of 0.5, 0.7, 0.9 and 1.1 respec-tively, were subjected to blow tests using a Split Hopkinson Pressure Bar (SHPB) system at a pressure of 0.4 atmospheres. In this paper, we have analyzed the effect of slenderness ratio on the mechanical properties and energy dissipation characteristics of red sandstone under high strain rates. The processes of compaction, elastic deformation and stress softening deformation of specimens contract with an increase in slenderness ratio, whilst the nonlinear deformation process extends correspondingly. In addi-tion, degrees of damage of specimens reduced gradually and the type of destruction showed a transfor-mation trend from stretching failure towards shear failure when the slenderness ratio increased. A model of dynamic damage evolution in red sandstone was established and the parameters of the constitutive model at different ratios of length to diameter were determined. By comparison with the experimental curve, the accuracy of the model, which could reflect the stress-strain dynamic characteristics of red sandstone, was verified. From the view of energy dissipation, an increase in slenderness ratio of a specimen decreased the proportion of energy dissipation and caused a gradual fall in the capability of energy dissipation during the specimen failure process. To some extent, the study indicated the effects of slenderness ratios on the mechanical properties and energy dissipation characteristics of red sandstone under the high strain rate, which provides valuable references to related engineering designs and academic researches.

  9. Comparison of methods for quantitating Salmonella enterica Typhimurium and Heidelberg strain attachment to reusable plastic shipping container coupons and preliminary assessment of sanitizer efficacy.

    Science.gov (United States)

    Shi, Zhaohao; Baker, Christopher A; Lee, Sang In; Park, Si Hong; Kim, Sun Ae; Ricke, Steven C

    2016-09-01

    Salmonella serovars, one of the leading contributors to foodborne illness and are especially problematic for foods that are not cooked before consumption, such as fresh produce. The shipping containers that are used to transport and store fresh produce may play a role in cross contamination and subsequent illnesses. However, methods for quantitatively attached cells are somewhat variable. The overall goal of this study was to compare conventional plating with molecular methods for quantitating attached representative strains for Salmonella Typhimurium and Heidelberg on reusable plastic containers (RPC) coupons, respectively. We attached Salmonella enterica serovar Typhimurium ATCC 14028 and serovar Heidelberg SL486 (parent and an antibiotic resistant marker strain) to plastic coupons (2.54 cm(2)) derived from previously used shipping containers by growing for 72 h in tryptic soy broth. The impact of the concentration of sanitizer on log reductions between unsanitized and sanitized coupons was evaluated by exposing attached S. Typhimurium cells to 200 ppm and 200,000 ppm sodium hypochlorite (NaClO). Differences in sanitizer effectiveness between serovars were also evaluated with attached S. Typhimurium compared to attached S. Heidelberg populations after being exposed to 200 ppm peracetic acid (PAA). Treatment with NaClO caused an average of 2.73 ± 0.23 log CFU of S. Typhimurium per coupon removed with treatment at 200 ppm while 3.36 ± 0.54 log CFU were removed at 200,000 ppm. Treatment with PAA caused an average of 2.62 ± 0.15 log CFU removed for S. Typhimurium and 1.41 ± 0.17 log CFU for S. Heidelberg (parent) and 1.61 ± 0.08 log CFU (marker). Lastly, scanning electron microscopy (SEM) was used to visualize cell attachment and coupon surface topography. SEM images showed that remaining attached cell populations were visible even after sanitizer application. Conventional plating and qPCR yielded similar levels of enumerated bacterial populations

  10. 考虑摩擦热的弹塑性平面接触应力及塑性应变分析%Analysis of Elastic-Plastic Plane Contact Stress and Plastic Strain Considering Frictional Heat

    Institute of Scientific and Technical Information of China (English)

    李鹏阳; 陈欢; 王世军; 王权岱; 傅卫平

    2015-01-01

    The influence of surface contact friction heat on the failure and the life of the parts was studied .The thermal stress of elastic-plastic surface contact was calculated using Fortran language ,the contact surface temperature distribution and the influence of friction heat on the surface pressure distribution were analyzed ,and the subsurface of the Mises stress field and the influence of plastic strain of the contact surface were discussed .The results show :With the increase of surface friction heat flux , the surface maximum pressure is increased .The maximum stress under the surface is decreased and the maximum stress zone of subsurface is always moving gradually to the contact surface .The contact surface temperature increases with the increase of sliding speed .The location of highest temperature point slowly shifts ,with increase of sliding speed ,to the sliding velocity direction .%研究了降低表面接触摩擦热对材料失效和零件寿命的影响。应用Fortran编程语言对弹塑性表面接触中产生的热应力进行了计算,分析了接触表面温度分布及摩擦热对接触表面压力分布、表面下米塞斯应力场及塑性应变的影响。分析结果表明:随着表面摩擦热流的增加,表面上最大接触压力逐渐变大,而表面下最大应力值逐渐减小,最大应力区域逐渐向接触表面上移动。接触表面温度的大小随滑动速度的提高而升高,且最高温度点的位置随滑动速度的提高缓慢向滑动速度方向偏移。

  11. Tuning the energy gap of bilayer α-graphyne by applying strain and electric field

    Science.gov (United States)

    Yang, Hang; Wu, Wen-Zhi; Jin, Yu; Wan-Lin, Guo

    2016-02-01

    Our density functional theory calculations show that the energy gap of bilayer α-graphyne can be modulated by a vertically applied electric field and interlayer strain. Like bilayer graphene, the bilayer α-graphyne has electronic properties that are hardly changed under purely mechanical strain, while an external electric field can open the gap up to 120 meV. It is of special interest that compressive strain can further enlarge the field induced gap up to 160 meV, while tensile strain reduces the gap. We attribute the gap variation to the novel interlayer charge redistribution between bilayer α-graphynes. These findings shed light on the modulation of Dirac cone structures and potential applications of graphyne in mechanical-electric devices. Project supported by the National Key Basic Research Program of China (Grant Nos. 2013CB932604 and 2012CB933403), the National Natural Science Foundation of China (Grant Nos. 51472117 and 51535005), the Research Fund of State Key Laboratory of Mechanics and Control of Mechanical Structures, China (Grant No. 0414K01), the Nanjing University of Aeronautics and Astronautics (NUAA) Fundamental Research Funds, China (Grant No. NP2015203), and the Priority Academic Program Development of Jiangsu Higher Education Institutions.

  12. Dimensionless Analysis of Segmented Constrained Layer Damping Treatments with Modal Strain Energy Method

    Directory of Open Access Journals (Sweden)

    Shitao Tian

    2016-01-01

    Full Text Available Constrained layer damping treatments promise to be an effective method to control vibration in flexible structures. Cutting both the constraining layer and the viscoelastic layer, which leads to segmentation, increases the damping efficiency. However, this approach is not always effective. A parametric study was carried out using modal strain energy method to explore interaction between segmentation and design parameters, including geometry parameters and material properties. A finite element model capable of handling treatments with extremely thin viscoelastic layer was developed based on interlaminar continuous shear stress theories. Using the developed method, influence of placing cuts and change in design parameters on the shear strain field inside the viscoelastic layer was analyzed, since most design parameters act on the damping efficiency through their influence on the shear strain field. Furthermore, optimal cut arrangements were obtained by adopting a genetic algorithm. Subject to a weight limitation, symmetric and asymmetric configurations were compared. It was shown that symmetric configurations always presented higher damping. Segmentation was found to be suitable for treatments with relatively thin viscoelastic layer. Provided that optimal viscoelastic layer thickness was selected, placing cuts would only be applicable to treatments with low shear strain level inside the viscoelastic layer.

  13. Determining Individual Phase Flow Properties in a Quench and Partitioning Steel with In Situ High-Energy X-Ray Diffraction and Multiphase Elasto-Plastic Self-Consistent Method

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Xiaohua; Choi, Kyoo Sil; Sun, Xin; Ren, Yang; Wang, Yangdong

    2016-02-26

    The micromechanical properties of the constituent phases were characterized for an advanced high strength steels (AHSS) produced by a quenching and partitioning (Q&P) process with in-situ tensile loading under Synchrotron-based high energy X-ray diffraction. The constituent phases present are retained austenite and three martensites (tempered, untempered and freshly formed martensites). For the material investigated, the 200 and 220 lattice strains of the retained austenite phase were calculated by examining the changes of the X-ray diffraction peak positions during deformation. The 200 and 211 lattice strains of the various martensitic phases with similar crystal structures were determined by separating their overlapped diffraction peaks. Apart from tempered and untempered martensite, the diffraction peaks of freshly formed martensite as a result of austenite to martensite transformation can also be able separated due to high initial austenite volume fraction. The phase stresses are first estimated with an empirical relationship through the X-ray diffraction elastic constants (XREC). A multi-phase elasto-plastic self constant model (EPSC) is next used for more accurate determination of the constitutive behaviors of the various phases by comparing the predicted lattice strain distributions and global stress-strain curves with the measured ones. The determined constitutive laws will be used for microstructure-based modeling for sheet formability of the Q&P AHSS steel.

  14. Determining Individual Phase Flow Properties in a Quench and Partitioning Steel with In Situ High-Energy X-Ray Diffraction and Multiphase Elasto-Plastic Self-Consistent Method

    Science.gov (United States)

    Hu, Xiaohua; Choi, Kyoo Sil; Sun, Xin; Ren, Yang; Wang, Yangdong

    2016-12-01

    The micromechanical properties of the constituent phases were characterized for advanced high-strength steels (AHSS) produced by a quenching and partitioning (Q&P) process with in situ tensile loading under synchrotron-based, high-energy X-ray diffraction. The constituent phases present are retained austenite and three martensites (tempered, untampered, and freshly formed martensites). For the material investigated, the 200 and 220 lattice strains of the retained austenite phase were calculated by examining the changes of the X-ray diffraction peak positions during deformation. The 200 and 211 lattice strains of the various martensitic phases with similar crystal structures were determined by separating their overlapped diffraction peaks. Apart from tempered and untempered martensite, the diffraction peaks of freshly formed martensite as a result of austenite-to-martensite transformation can also be separated due to a high initial austenite volume fraction. The phase stresses are first estimated with an empirical relationship through the X-ray diffraction elastic constants. A multiphase elasto-plastic self-consistent model is next used for more accurate determination of the constitutive behaviors of the various phases by comparing the predicted lattice strain distributions and global stress-strain curves with the measured ones. The determined constitutive laws will be used for microstructure-based modeling for sheet formability of the Q&P AHSS steel.

  15. Energy Storage in Strained Organic Molecules: (Spectro)Electrochemical Characterization of Norbornadiene and Quadricyclane.

    Science.gov (United States)

    Brummel, Olaf; Besold, Daniel; Döpper, Tibor; Wu, Yanlin; Bochmann, Sebastian; Lazzari, Federica; Waidhas, Fabian; Bauer, Udo; Bachmann, Philipp; Papp, Christian; Steinrück, Hans-Peter; Görling, Andreas; Libuda, Jörg; Bachmann, Julien

    2016-06-22

    We have investigated the electrochemically triggered cycloreversion of quadricyclane (QC) to norbornadiene (NBD), a system that holds the potential to combine both energy storage and conversion in a single molecule. Unambiguous voltammetric traces are obtained for pure NBD and pure QC, the latter a strained polycyclic isomer of the former. The difference in redox potentials is smaller than the energy difference between the neutral molecules. This is owing to a significant energy difference between the corresponding radical cations, as demonstrated by density functional theory (DFT) calculations. The vibrational modes of each pure compound are characterized experimentally in the fingerprint region and identified by DFT methods. Thermal and electrochemical transformations of NBD and QC are monitored in situ by IR spectroelectrochemical methods. The kinetics of the cycloreversion of QC to NBD, which is catalyzed by oxidizing equivalents, can be controlled by an applied electrode potential, which implies the ability to adjust in real time the release of thermal power stored in QC.

  16. Purification, characterization, and cloning of the gene for a biodegradable plastic-degrading enzyme from Paraphoma-related fungal strain B47-9.

    Science.gov (United States)

    Suzuki, Ken; Noguchi, Masako Tsujimoto; Shinozaki, Yukiko; Koitabashi, Motoo; Sameshima-Yamashita, Yuka; Yoshida, Shigenobu; Fujii, Takeshi; Kitamoto, Hiroko K

    2014-05-01

    Paraphoma-related fungal strain B47-9 secreted a biodegradable plastic (BP)-degrading enzyme which amounted to 68 % (w/w) of the total secreted proteins in a culture medium containing emulsified poly(butylene succinate-co-adipate) (PBSA) as sole carbon source. The gene for this enzyme was found to be composed of an open reading frame consisting of 681 nucleotides encoding 227 amino acids and two introns. Southern blot analysis showed that this gene exists as a single copy. The deduced amino acid sequence suggested that this enzyme belongs to the cutinase (E.C.3.1.1.74) family; thus, it was named P araphoma-related fungus cutinase-like enzyme (PCLE). It degraded various types of BP films, such as poly(butylene succinate), PBSA, poly(butylene adipate-co-terephthalate), poly(ε-caprolactone), and poly(DL-lactic acid). It has a molecular mass of 19.7 kDa, and an optimum pH and temperature for degradation of emulsified PBSA of 7.2 and 45 °C, respectively. Ca(2+) ion at a concentration of about 1.0 mM markedly enhanced the degradation of emulsified PBSA.

  17. Modeling shock responses of plastic bonded explosives using material point method

    Science.gov (United States)

    Shang, Hailin; Zhao, Feng; Fu, Hua

    2017-01-01

    Shock responses of plastic bonded explosives are modeled using material point method as implemented in the Uintah Computational Framework. Two-dimensional simulation model was established based on the micrograph of PBX9501. Shock loading for the explosive was performed by a piston moving at a constant velocity. Unreactive simulation results indicate that under shock loading serious plastic strain appears on the boundary of HMX grains. Simultaneously, the plastic strain energy transforms to thermal energy, causing the temperature to rise rapidly on grain boundary areas. The influence of shock strength on the responses of explosive was also investigated by increasing the piston velocity. And the results show that with increasing shock strength, the distribution of plastic strain and temperature does not have significant changes, but their values increase obviously. Namely, the higher the shock strength is, the higher the temperature rise will be.

  18. Final Report: Development of Renewable Microbial Polyesters for Cost Effective and Energy- Efficient Wood-Plastic Composites

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, David N.; Emerick, Robert W.; England, Alfred B.; Flanders, James P.; Loge, Frank J.; Wiedeman, Katherine A.; Wolcott, Michael P.

    2010-03-31

    In this project, we proposed to produce wood fiber reinforced thermoplastic composites (WFRTCs) using microbial thermoplastic polyesters in place of petroleum-derived plastic. WFRTCs are a rapidly growing product area, averaging a 38% growth rate since 1997. Their production is dependent on substantial quantities of petroleum based thermoplastics, increasing their overall energy costs by over 230% when compared to traditional Engineered Wood Products (EWP). Utilizing bio-based thermoplastics for these materials can reduce our dependence on foreign petroleum. We have demonstrated that biopolymers (polyhydroxyalkanoates, PHA) can be successfully produced from wood pulping waste streams and that viable wood fiber reinforced thermoplastic composite products can be produced from these materials. The results show that microbial polyester (PHB in this study) can be extruded together with wastewater-derived cell mass and wood flour into deck products having performance properties comparable to existing commercial HDPE/WF composite products. This study has thus proven the underlying concept that the microbial polyesters produced from waste effluents can be used to make cost-effective and energy-efficient wood-plastic composites. The cost of purified microbial polyesters is about 5-20 times that of HDPE depending on the cost of crude oil, due to high purification (40%), carbon substrate (40%) and sterilized fermentation (20%) costs for the PHB. Hence, the ability to produce competitive and functional composites with unpurified PHA-biomass mixtures from waste carbon sources in unsterile systems—without cell debris removal—is a significant step forward in producing competitive value-added structural composites from forest products residuals using a biorefinery approach. As demonstrated in the energy and waste analysis for the project, significant energy savings and waste reductions can also be realized using this approach. We recommend that the next step for development of

  19. Anisotropic Lithium Insertion Behavior in Silicon Nanowires: Binding Energy, Diffusion Barrier, and Strain Effect

    KAUST Repository

    Zhang, Qianfan

    2011-05-19

    Silicon nanowires (SiNWs) have recently been shown to be promising as high capacity lithium battery anodes. SiNWs can be grown with their long axis along several different crystallographic directions. Due to distinct atomic configuration and electronic structure of SiNWs with different axial orientations, their lithium insertion behavior could be different. This paper focuses on the characteristics of single Li defects, including binding energy, diffusion barriers, and dependence on uniaxial strain in [110], [100], [111], and [112] SiNWs. Our systematic ab initio study suggests that the Si-Li interaction is weaker when the Si-Li bond direction is aligned close to the SiNW long axis. This results in the [110] and [111] SiNWs having the highest and lowest Li binding energy, respectively, and it makes the diffusion barrier along the SiNW axis lower than other pathways. Under external strain, it was found that [110] and [001] SiNWs are the most and least sensitive, respectively. For diffusion along the axial direction, the barrier increases (decreases) under tension (compression). This feature results in a considerable difference in the magnitude of the energy barrier along different diffusion pathways. © 2011 American Chemical Society.

  20. Phase-field slip-line theory of plasticity

    Science.gov (United States)

    Freddi, Francesco; Royer-Carfagni, Gianni

    2016-09-01

    A variational approach to determine the deformation of an ideally plastic substance is proposed by solving a sequence of energy minimization problems under proper conditions to account for the irreversible character of plasticity. The flow is driven by the local transformation of elastic strain energy into plastic work on slip surfaces, once that a certain energetic barrier for slip activation has been overcome. The distinction of the elastic strain energy into spherical and deviatoric parts is used to incorporate in the model the idea of von Mises plasticity and isochoric plastic strain. This is a "phase field model" because the matching condition at the slip interfaces is substituted by the evolution of an auxiliary phase field that, similar to a damage field, is unitary on the elastic phase and null on the yielded phase. The slip lines diffuse in bands, whose width depends upon a material length-scale parameter. Numerical experiments on representative problems in plane strain give solutions with noteworthy similarities with the results from classical slip-line field theory, but the proposed model is much richer because, accounting for elastic deformations, it can describe the formation of slip bands at the local level, which can nucleate, propagate, widen and diffuse by varying the boundary conditions. In particular, the solution for a long pipe under internal pressure is very different from the one obtainable from the classical macroscopic theory of plasticity. For this case, the location of the plastic bands may be an insight to explain the premature failures that are sometimes encountered during the manufacturing process. This practical example enhances the importance of this new theory based on the mathematical sciences.

  1. Protein-energy malnutrition alters hippocampal plasticity-associated protein expression following global ischemia in the gerbil.

    Science.gov (United States)

    Prosser-Loose, Erin J; Verge, Valerie M K; Cayabyab, Francisco S; Paterson, Phyllis G

    2010-11-01

    Previously it has been demonstrated that protein-energy malnutrition (PEM) impairs habituation in the open field test following global ischemia. The present study examined the hypothesis that PEM exerts some of its deleterious effects on functional outcome by altering the post-ischemic expression of the plasticity-associated genes brain-derived neurotrophic factor (BDNF), its receptor tropomyosin-related kinase B (trkB), and growth-associated protein-43 (GAP-43). Male, Mongolian gerbils (11-12 wk) were randomized to either control diet (12.5% protein) or PEM (2% protein) for 4 wk, and then underwent 5 min bilateral common carotid artery occlusion or sham surgery. Tympanic temperature was maintained at 36.5 ± 0.5°C during surgery. Brains collected at 1, 3 and 7 d post-surgery were processed by in-situ hybridization or immunofluorescence. BDNF and trkB mRNA expression was increased in hippocampal CA1 neurons after ischemia at all time points and was not significantly influenced by diet. However, increased trkB protein expression after ischemia was exacerbated by PEM at 7 d in the CA1 region. Post-ischemic GAP-43 protein increased at 3 and 7 d in the CA1 region, and PEM intensified this response and extended it to the CA3 and hilar regions. PEM exerted these effects without exacerbating CA1 neuron loss caused by global ischemia. The findings suggest that PEM increases the stress response and/or hyper-excitability in the hippocampus after global ischemia. Nutritional care appears to have robust effects on plasticity mechanisms important to recovery after brain ischemia.

  2. Neuromodulation and Synaptic Plasticity for the Control of Fast Periodic Movement:Energy Efficiency in Coupled Compliant Joints via PCA

    Directory of Open Access Journals (Sweden)

    Philipp eStratmann

    2016-03-01

    Full Text Available There are multiple indications that the nervous system of animals tunes muscle output to exploit natural dynamics of the elastic locomotor system and the environment. This is an advantageous strategy especially in fast periodic movements, since the elastic elements store energy and increase energy efficiency and movement speed.Experimental evidence suggests that coordination among joints involves proprioceptive input and neuromodulatory influence originating in the brain stem. However, the neural strategies underlying the coordination of fast periodic movements remain poorly understood.Based on robotics control theory, we suggest that the nervous system implements a mechanism to accomplish coordination between joints by a linear coordinate transformation from the multi-dimensional space representing proprioceptive input at the joint level into a one-dimensional controller space. In this one-dimensional subspace, the movements of a whole limb can be driven by a single oscillating unit as simple as a reflex interneuron. The output of the oscillating unit is transformed back to joint space via the same transformation. The transformation weights correspond to the dominant principal component of the movement.In this study, we propose a biologically plausible neural network to exemplify that the central nervous system may encode our controller design. Using theoretical considerations and computer simulations, we demonstrate that spike-timing-dependent plasticity for the input mapping and serotonergic neuromodulation for the output mapping can extract the dominant principal component of sensory signals. Our simulations show that our network can reliably control mechanical systems of different complexity and increase the energy efficiency of ongoing cyclic movements.The proposed network is simple and consistent with previous biologic experiments. Thus, our controller could serve as a candidate to describe the neural control of fast, energy

  3. Neuromodulation and Synaptic Plasticity for the Control of Fast Periodic Movement: Energy Efficiency in Coupled Compliant Joints via PCA.

    Science.gov (United States)

    Stratmann, Philipp; Lakatos, Dominic; Albu-Schäffer, Alin

    2016-01-01

    There are multiple indications that the nervous system of animals tunes muscle output to exploit natural dynamics of the elastic locomotor system and the environment. This is an advantageous strategy especially in fast periodic movements, since the elastic elements store energy and increase energy efficiency and movement speed. Experimental evidence suggests that coordination among joints involves proprioceptive input and neuromodulatory influence originating in the brain stem. However, the neural strategies underlying the coordination of fast periodic movements remain poorly understood. Based on robotics control theory, we suggest that the nervous system implements a mechanism to accomplish coordination between joints by a linear coordinate transformation from the multi-dimensional space representing proprioceptive input at the joint level into a one-dimensional controller space. In this one-dimensional subspace, the movements of a whole limb can be driven by a single oscillating unit as simple as a reflex interneuron. The output of the oscillating unit is transformed back to joint space via the same transformation. The transformation weights correspond to the dominant principal component of the movement. In this study, we propose a biologically plausible neural network to exemplify that the central nervous system (CNS) may encode our controller design. Using theoretical considerations and computer simulations, we demonstrate that spike-timing-dependent plasticity (STDP) for the input mapping and serotonergic neuromodulation for the output mapping can extract the dominant principal component of sensory signals. Our simulations show that our network can reliably control mechanical systems of different complexity and increase the energy efficiency of ongoing cyclic movements. The proposed network is simple and consistent with previous biologic experiments. Thus, our controller could serve as a candidate to describe the neural control of fast, energy

  4. Energy-related application of composite material. Carbon fiber reinforced plastics (CFRP); Enerugi kanren yoto to CFRP

    Energy Technology Data Exchange (ETDEWEB)

    Higuchi, T. [Toray Industries, Tokyo (Japan)

    2000-01-15

    Carbon fiber reinforced plastics (CFRP) with advantages such as high strength, high relative elastic modulus, high chemical stability, and excellent thermal/electric properties, is widely used in aviation/space, sports, and industries. This paper takes up CNG tank, flywheel, and windmill blade, as examples of energy-related application development. For the purpose of weight reduction of CNG car, big three car manufacturers of the U.S. and Honda adopted CNG tank. Flywheel with CFRP rotor can store 3.8 times energy compared with that of steel. Windmill blade used in windmill power generation is mostly made of 3 blades and presently GFRP is used, but CFRP will become a main stream when the windmill is scaled up. In the future, it is necessary to reduce the cost of carbon fiber and its treatment process, as well as to solve the targets such as standardization of design, recognition by users, and verification in environmental use, and to develop further applications. (NEDO)

  5. Strain relaxation of CdTe on Ge studied by medium energy ion scattering

    Science.gov (United States)

    Pillet, J. C.; Pierre, F.; Jalabert, D.

    2016-10-01

    We have used the medium energy ion scattering (MEIS) technique to assess the strain relaxation in molecular-beam epitaxial (MBE) grown CdTe (2 1 1)/Ge (2 1 1) system. A previous X-ray diffraction study, on 10 samples of the same heterostructure having thicknesses ranging from 25 nm to 10 μm has allowed the measurement of the strain relaxation on a large scale. However, the X-ray diffraction measurements cannot achieve a stress measurement in close proximity to the CdTe/Ge interface at the nanometer scale. Due to the huge lattice misfit between the CdTe and Ge, a high degree of disorder is expected at the interface. The MEIS in channeling mode is a good alternative in order to profile defects with a high depth resolution. For a 21 nm thick CdTe layer, we observed, at the interface, a high density of Cd and/or Te atoms moved from their expected crystallographic positions followed by a rapid recombination of defects. Strain relaxation mechanisms in the vicinity of the interface are discussed

  6. Variation of strain energy release rate with plate thickness. [fracture mode transition

    Science.gov (United States)

    Sih, G. C.; Hartranft, R. J.

    1973-01-01

    An analytical model of a through-thickness crack in a statically stretched plate is presented in which the crack front stress state is permitted to vary in the direction of the plate thickness. The amplitude or intensity of this stress field can be made nearly constant over a major portion of the interior crack front which is in a state of plane strain. The average amount of work available for extending a small segment of the crack across the thickness is associated with an energy release rate quantity in a manner similar to the two-dimensional Griffith crack model. The theoretically calculated energy release rate is shown to increase with increasing plate thickness, indicating that available work for crack extension is higher in a thicker plate.

  7. Do Anti-Bredt Natural Products Exist? Olefin Strain Energy as a Predictor of Isolability.

    Science.gov (United States)

    Krenske, Elizabeth H; Williams, Craig M

    2015-09-01

    Bredt's rule holds a special place in the realm of physical organic chemistry, but its application to natural products chemistry—the field in which the rule was originally formulated—is not well defined. Herein, the use of olefin strain (OS) energy as a readily calculated predictor of the stability of natural products containing a bridgehead alkene is introduced. Schleyer first used OS energies to classify parent bridgehead alkenes into "isolable", "observable", and "unstable" classes. OS calculations on natural products, using contemporary forcefield methods, unequivocally predict all structurally verified bridgehead alkene natural products to be "isolable". Thus, when one assigns the structure of a putative bridgehead alkene natural product, an OS in the "observable" or "unstable" ranges is a red flag for error.

  8. Dynamic simulation for tempo-spatial distribution of strain energy density in inhomogeneous stratified crust

    Institute of Scientific and Technical Information of China (English)

    CHEN Yu-kun; NIE Yong-an

    2000-01-01

    Through simulating the research on dynamic variations of strain energy density (SED) in seismogenic model with hard inclusion, the authors have gained further knowledge to such problems as the process of earthquake preparation, initial rupture, conditions of the initial rupture and fracture propagation direction, etc. Results of the research show that SED (strain energy density) in soft inclusion is very high during the initial period of earthquake preparation. And the increment of SED in the soft area decreases at the later stage of the process. Meanwhile, the increment increases quickly in hard inclusion and in the intersection zone of the inclusion with an erecting fault, where the increment of SED is maximum. Thus, the intersection zone between hard inclusion with larger elastic modulus and erecting fault becomes the place where the initial rupture or earthquake occurs. The fracture in the end part of the hard inclusion spreads along a direction nearly vertical to the erecting fault, so the theoretical fracture direction is consistent with that calculated by digital simulation.

  9. Paper-Thin Plastic Film Soaks Up Sun to Create Solar Energy

    Science.gov (United States)

    2006-01-01

    A non-crystallized silicon known as amorphous silicon is the semiconductor material most frequently chosen for deposition, because it is a strong absorber of light. According to the U.S. Department of Energy, amorphous silicon absorbs solar radiation 40 times more efficiently than single-crystal silicon, and a thin film only about 1-micrometer (one one-millionth of a meter) thick containing amorphous silicon can absorb 90 percent of the usable light energy shining on it. Peak efficiency and significant reduction in the use of semiconductor and thin film materials translate directly into time and money savings for manufacturers. Thanks in part to NASA, thin film solar cells derived from amorphous silicon are gaining more and more attention in a market that has otherwise been dominated by mono- and poly-crystalline silicon cells for years. At Glenn Research Center, the Photovoltaic & Space Environments Branch conducts research focused on developing this type of thin film solar cell for space applications. Placing solar cells on thin film materials provides NASA with an attractively priced solution to fabricating other types of solar cells, given that thin film solar cells require significantly less semiconductor material to generate power. Using the super-lightweight solar materials also affords NASA the opportunity to cut down on payload weight during vehicle launches, as well as the weight of spacecraft being sent into orbit.

  10. 单轴循环荷载对煤弹塑性和能量积聚耗散的影响%Influence of cyclic uniaxial loading on coal elastic-plastic properties and energy accumulation and dissipation

    Institute of Scientific and Technical Information of China (English)

    刘江伟; 黄炳香; 魏民涛

    2012-01-01

    In order to investigate the influence of cyclic loading on the coal-rock elastic-plastic properties and energy accumulation & dissipation, the cyclic loading test on uniaxial compression on Coal 22 was conducted in this study. Based on the analysis results, the first loading and unloading, and reloading are positively correlated with elasticity modulus. With the increase of cycle number, the elastic strain appears in an inverted U-shape change while the plastic strain exhibits a U-shape change. AH the elasticity modulus E, elastic energy index Wet and energy dissipating rate Wed caused by strain follows an inverted U-shape change. The first average variation rate n of elasticity modulus is 30%, and the energy dissipation φ>sd follows a U-shape change. When elastic energy index Wet reaches its maximum, a burst phenomenon will easily occur. With the increase of stress amplitude, the speed of production and propagation of micro-crack will increase, as well as the micro-plastic deformation speed will also increase. With the increase of loading level, the elastic energy index shows a tendency of increasing earlier and decreasing later during the compression and linear elasticity period, and reaches the maximum at "elastic-plastic critical point".%为了研究循环加载对煤岩弹塑性和能量积聚耗散的影响,对二2煤进行了单轴压缩循环加载实验,分析得出首次加载、卸载、再加载弹性模量呈正相关关系;随着循环数的增加,弹性应变会表现出倒“U”形变化,塑性应变表现出“U”形变化的规律,由应变引起的弹性模量E、弹性能量指数Wet和能量耗散率Wed都表现出倒“U”形变化的规律,首个平均弹性模量变化率η为30%,耗散的能量(ψ)sd呈“U”形变化,当弹性能量指数Wet达到最大值时,冲击现象最容易发生;分析出微裂纹的萌生传播速度随应力振幅的增加而增加,微塑性变形速度也随之增加,弹性能量指数在压密

  11. Enhanced Efficiency in Plastic Solar Cells via Energy Matched Solution Processed NiOx Interlayers

    Energy Technology Data Exchange (ETDEWEB)

    Steirer, K. Xerxes [Colorado School of Mines, Golden, CO (United States); Ndione, Paul F. [National Renewable Energy Lab. (NREL), Golden, CO (United States). National Center for Photovoltaics; Widjonarko, N. Edwin [Univ. of Colorado, Boulder, CO (United States). Dept. of Physics; Lloyd, Matthew T. [National Renewable Energy Lab. (NREL), Golden, CO (United States). National Center for Photovoltaics; Meyer, Jens [Princeton Univ., NJ (United States). Electrical Engineering Dept.; Ratcliff, Erin L. [Univ. of Arizona, Tucson, AZ (United States). Dept. of Chemistry and Biochemistry and Center for Interface Science: Solar Electric Materials (CISSEM); Kahn, Antoine [Princeton Univ., NJ (United States). Electrical Engineering Dept.; Armstrong, Neal R. [Univ. of Arizona, Tucson, AZ (United States). Dept. of Chemistry and Biochemistry and Center for Interface Science: Solar Electric Materials (CISSEM); Curtis, Calvin J. [National Renewable Energy Lab. (NREL), Golden, CO (United States). National Center for Photovoltaics; Ginley, David S. [National Renewable Energy Lab. (NREL), Golden, CO (United States). National Center for Photovoltaics; Berry, Joseph J. [National Renewable Energy Lab. (NREL), Golden, CO (United States). National Center for Photovoltaics; Olson, Dana C. [National Renewable Energy Lab. (NREL), Golden, CO (United States). National Center for Photovoltaics

    2011-07-18

    We show enhanced efficiency and stability of a high performance organic solar cell (OPV) when the work-function of the hole collecting indium-tin oxide (ITO) contact, modified with a solution-processed nickel oxide (NiOx) hole-transport layer (HTL), is matched to the ionization potential of the donor material in a bulk-heterojunction solar cell. Addition of the NiOx HTL to the hole collecting contact results in a power conversion efficiency (PCE) of 6.7%, which is a 17.3% net increase in performance over the 5.7% PCE achieved with a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) HTL on ITO. The impact of these NiOx films is evaluated through optical and electronic measurements as well as device modeling. The valence and conduction band energies for the NiOx HTL are characterized in detail through photoelectron spectroscopy studies while spectroscopic ellipsometry is used to characterize the optical properties. Oxygen plasma treatment of the NiOx HTL is shown to provide superior contact properties by increasing the ITO/NiOx contact work-function by 500 meV. Enhancement of device performance is attributed to reduction of the band edge energy offset at the ITO/NiOx interface with the poly(N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothidiazole) (PCDTBT):[6,6]-phenyl-C61 butyric acid methyl ester PCBM and [6,6]-phenyl-C71 butyric acid methyl ester (PC₇₀BM) active layer. A high work-function hole collecting contact is therefore the appropriate choice for high ionization potential donor materials in order to maximize OPV performance.

  12. Enhanced Efficiency in Plastic Solar Cells via Energy Matched Solution Processed NiOx Interlayers

    Energy Technology Data Exchange (ETDEWEB)

    Steirer, K. Xerxes; Ndione, Paul F.; Widjonarko, N. Edwin; Lloyd, Matthew T.; Meyer, Jens; Ratcliff, Erin L.; Kahn, Antoine; Armstrong, Neal R.; Curtis, Calvin J.; Ginley, David S.; Berry, Joseph J.; Olson, Dana C.

    2011-07-18

    We show enhanced efficiency and stability of a high performance organic solar cell (OPV) when the work-function of the hole collecting indium-tin oxide (ITO) contact, modified with a solution-processed nickel oxide (NiOx) hole-transport layer (HTL), is matched to the ionization potential of the donor material in a bulk-heterojunction solar cell. Addition of the NiOx HTL to the hole collecting contact results in a power conversion efficiency (PCE) of 6.7%, which is a 17.3% net increase in performance over the 5.7% PCE achieved with a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) HTL on ITO. The impact of these NiOx films is evaluated through optical and electronic measurements as well as device modeling. The valence and conduction band energies for the NiOx HTL are characterized in detail through photoelectron spectroscopy studies while spectroscopic ellipsometry is used to characterize the optical properties. Oxygen plasma treatment of the NiOx HTL is shown to provide superior contact properties by increasing the ITO/NiOx contact work-function by 500 meV. Enhancement of device performance is attributed to reduction of the band edge energy offset at the ITO/NiOx interface with the poly(N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothidiazole) (PCDTBT):[6,6]-phenyl-C61 butyric acid methyl ester PCBM and [6,6]-phenyl-C71 butyric acid methyl ester (PC70BM) active layer. A high work-function hole collecting contact is therefore the appropriate choice for high ionization potential donor materials in order to maximize OPV performance.

  13. Photoswitchable Dihydroazulene Macrocycles for Solar Energy Storage: The Effects of Ring Strain.

    Science.gov (United States)

    Vlasceanu, Alexandru; Frandsen, Benjamin N; Skov, Anders B; Hansen, Anne Schou; Rasmussen, Mads Georg; Kjaergaard, Henrik G; Mikkelsen, Kurt V; Nielsen, Mogens Brøndsted

    2017-09-11

    Efficient energy storage and release are two major challenges of solar energy harvesting technologies. The development of molecular solar thermal systems presents one approach to address these issues by tuning the isomerization reactions of photo/thermoswitches. Here we show that the incorporation of photoswitches into macrocyclic structures is a particularly attractive solution for increasing the storage time. We present the synthesis and properties of a series of macrocycles incorporating two dihydroazulene (DHA) photoswitching subunits, bridged by linkers of varying chain length. Independent of ring size, all macrocycles exhibit stepwise, light-induced, ring-opening reactions (DHA-DHA to DHA-VHF to VHF-VHF; VHF = vinylheptafulvene) with the first DHA undergoing isomerization with a similar efficiency as the uncyclized parent system while the second (DHA-VHF to VHF-VHF) is significantly slower. The energy-releasing, VHF-to-DHA, ring closures also occur in a stepwise manner and are systematically found to proceed slower in the more strained (smaller) cycles, but in all cases with a remarkably slow conversion of the second VHF to DHA. We managed to increase the half-life of the second VHF-to-DHA conversion from 65 to 202 h at room temperature by simply decreasing the ring size. A computational study reveals the smallest macrocycle to have the most energetic VHF-VHF state and hence highest energy density.

  14. Modeling interactions of intermediate-energy neutrons in a plastic scintillator array with GEANT4

    Energy Technology Data Exchange (ETDEWEB)

    Kohley, Z., E-mail: zkohley@gmail.com [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Lunderberg, E.; DeYoung, P.A. [Department of Physics, Hope College, Holland, MI 49423 (United States); Roeder, B.T. [LPC-Caen, ENSICAEN, IN2P3/CNRS et Universite de Caen, 14050 Caen cedex (France); Baumann, T. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Christian, G.; Mosby, S.; Smith, J.K.; Snyder, J.; Spyrou, A.; Thoennessen, M. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States)

    2012-08-01

    A Monte Carlo simulation of a large-area neutron time-of-flight detector, built on the GEANT4 framework, has been compared with an experimental measurement of the {sup 16}B{yields}{sup 15}B+n decay produced from a 55 MeV/u{sup 17}C beam. The ability of the Monte Carlo simulation to reproduce the intermediate-energy neutron interactions within the detector has been explored using both the stock GEANT4 physics processes and a custom neutron interaction model, MENATE{sub R}. The stock GEANT4 physics processes were unable to reproduce the experimental observables, while excellent agreement was obtained through the inclusion of the MENATE{sub R} model within GEANT4. The differences between the two approaches are shown to be related to the modeling of the neutron-carbon inelastic reactions. Additionally, the use of MENATE{sub R} provided accurate reproduction of experimental signals associated with neutron scattering within the detector. These results provide validation of the Monte Carlo simulation for modeling measurements of multiple neutrons where the identification and removal of false neutron signals, due to multiple neutron scattering, are required.

  15. On a consistent finite-strain plate theory based on 3-D energy principle

    CERN Document Server

    Dai, Hui-Hui

    2014-01-01

    This paper derives a finite-strain plate theory consistent with the principle of stationary three-dimensional (3-D) potential energy under general loadings with a third-order error. Staring from the 3-D nonlinear elasticity (with both geometrical and material nonlinearity) and by a series expansion, we deduce a vector plate equation with three unknowns, which exhibits the local force-balance structure. The success relies on using the 3-D field equations and bottom traction condition to derive exact recursion relations for the coefficients. Associated weak formulations are considered, leading to a 2-D virtual work principle. An alternative approach based on a 2-D truncated energy is also provided, which is less consistent than the first plate theory but has the advantage of the existence of a 2-D energy function. As an example, we consider the pure bending problem of a hyperelastic block. The comparison between the analytical plate solution and available exact one shows that the plate theory gives second-order...

  16. Plasticity theory

    CERN Document Server

    Lubliner, Jacob

    2008-01-01

    The aim of Plasticity Theory is to provide a comprehensive introduction to the contemporary state of knowledge in basic plasticity theory and to its applications. It treats several areas not commonly found between the covers of a single book: the physics of plasticity, constitutive theory, dynamic plasticity, large-deformation plasticity, and numerical methods, in addition to a representative survey of problems treated by classical methods, such as elastic-plastic problems, plane plastic flow, and limit analysis; the problem discussed come from areas of interest to mechanical, structural, and

  17. Strain energy density gradients in bone marrow predict osteoblast and osteoclast activity: a finite element study.

    Science.gov (United States)

    Webster, Duncan; Schulte, Friederike A; Lambers, Floor M; Kuhn, Gisela; Müller, Ralph

    2015-03-18

    Huiskes et al. hypothesized that mechanical strains sensed by osteocytes residing in trabecular bone dictate the magnitude of load-induced bone formation. More recently, the mechanical environment in bone marrow has also been implicated in bone׳s response to mechanical stimulation. In this study, we hypothesize that trabecular load-induced bone formation can be predicted by mechanical signals derived from an integrative µFE model, incorporating a description of both the bone and marrow phase. Using the mouse tail loading model in combination with in vivo micro-computed tomography (µCT) we tracked load induced changes in the sixth caudal vertebrae of C57BL/6 mice to quantify the amount of newly mineralized and eroded bone volumes. To identify the mechanical signals responsible for adaptation, local morphometric changes were compared to micro-finite element (µFE) models of vertebrae prior to loading. The mechanical parameters calculated were strain energy density (SED) on trabeculae at bone forming and resorbing surfaces, SED in the marrow at the boundary between bone forming and resorbing surfaces, along with SED in the trabecular bone and marrow volumes. The gradients of each parameter were also calculated. Simple regression analysis showed mean SED gradients in the trabecular bone matrix to significantly correlate with newly mineralized and eroded bone volumes R(2)=0.57 and 0.41, respectively, pbone marrow plays a significant role in determining osteoblast and osteoclast activity.

  18. Tendon elastic strain energy in the human ankle plantar-flexors and its role with increased running speed.

    Science.gov (United States)

    Lai, Adrian; Schache, Anthony G; Lin, Yi-Chung; Pandy, Marcus G

    2014-09-01

    The human ankle plantar-flexors, the soleus and gastrocnemius, utilize tendon elastic strain energy to reduce muscle fiber work and optimize contractile conditions during running. However, studies to date have considered only slow to moderate running speeds up to 5 m s(-1). Little is known about how the human ankle plantar-flexors utilize tendon elastic strain energy as running speed is advanced towards maximum sprinting. We used data obtained from gait experiments in conjunction with musculoskeletal modeling and optimization techniques to calculate muscle-tendon unit (MTU) work, tendon elastic strain energy and muscle fiber work for the ankle plantar-flexors as participants ran at five discrete steady-state speeds ranging from jogging (~2 m s(-1)) to sprinting (≥8 m s(-1)). As running speed progressed from jogging to sprinting, the contribution of tendon elastic strain energy to the positive work generated by the MTU increased from 53% to 74% for the soleus and from 62% to 75% for the gastrocnemius. This increase was facilitated by greater muscle activation and the relatively isometric behavior of the soleus and gastrocnemius muscle fibers. Both of these characteristics enhanced tendon stretch and recoil, which contributed to the bulk of the change in MTU length. Our results suggest that as steady-state running speed is advanced towards maximum sprinting, the human ankle plantar-flexors continue to prioritize the storage and recovery of tendon elastic strain energy over muscle fiber work.

  19. Strain energy analysis of screw dislocations in 4H-SiC by molecular dynamics

    Science.gov (United States)

    Kawamura, Takahiro; Mizutani, Mitsutoshi; Suzuki, Yasuyuki; Kangawa, Yoshihiro; Kakimoto, Koichi

    2016-03-01

    We simulated screw dislocations with the Burgers vector parallel to the [0001] direction in 4H-SiC by a classical molecular dynamics method. A stable structure of an extended dislocation generated by the dissociation of a screw dislocation was identified by calculating the strain energy caused by dislocation cores and stacking faults. As a result, we conclude that the most expected structure of the extended dislocation is made of partial dislocations with the Burgers vector b = 1/2c + 1/2c (c is equal to the thickness of one period in the c-axis direction of 4H-SiC) and the stacking fault that is parallel to the a-plane, and that the distance between the dislocation cores is less than about 44 Å.

  20. Depth strain profile with sub-nm resolution in a thin silicon film using medium energy ion scattering

    Energy Technology Data Exchange (ETDEWEB)

    Jalabert, D.; Rouviere, J.L. [CEA-INAC/UJF-Grenoble 1 UMR-E, SP2M, LEMMA, MINATEC Campus, Grenoble (France); Pelloux-Gervais, D.; Canut, B. [Institut des Nanotechnologies de Lyon, Universite de Lyon, INL-UMR5270, CNRS, INSA de Lyon, Villeurbanne 69621 (France); Beche, A. [CEA-INAC/UJF-Grenoble 1 UMR-E, SP2M, LEMMA, MINATEC Campus, Grenoble (France); FEI Company, Eindhoven (Netherlands); Hartmann, J.M.; Gergaud, P. [CEA-Leti, MINATEC, Grenoble (France)

    2012-02-15

    The depth strain profile in silicon from the Si(001) substrate to the surface of a 2 nm thick Si/12 nm thick SiGe/bulk Si heterostructure has been determined by medium energy ion scattering (MEIS). It shows with sub-nanometer resolution and high strain sensitivity that the thin Si cap presents residual compressive strain caused by Ge diffusion coming from the fully strained SiGe layer underneath. The strain state of the SiGe buffer have been checked by X-ray diffraction (XRD) and nano-beam electron diffraction (NBED) measurements. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Spectral Modeling of Residual Stress and Stored Elastic Strain Energy in Thermal Barrier Coatings

    Energy Technology Data Exchange (ETDEWEB)

    Donegan, Sean; Rolett, Anthony

    2013-12-31

    Solutions to the thermoelastic problem are important for characterizing the response under temperature change of refractory systems. This work extends a spectral fast Fourier transform (FFT) technique to analyze the thermoelastic behavior of thermal barrier coatings (TBCs), with the intent of probing the local origins of failure in TBCs. The thermoelastic FFT (teFFT) approach allows for the characterization of local thermal residual stress and strain fields, which constitute the origins of failure in TBC systems. A technique based on statistical extreme value theory known as peaks-over-threshold (POT) is developed to quantify the extreme values ("hot spots") of stored elastic strain energy (i.e., elastic energy density, or EED). The resolution dependence of the teFFT method is assessed through a sensitivity study of the extreme values in EED. The sensitivity study is performed both for the local (point-by-point) eld distributions as well as the grain scale eld distributions. A convergence behavior to a particular distribution shape is demonstrated for the local elds. The grain scale fields are shown to exhibit a possible convergence to a maximum level of EED. To apply the teFFT method to TBC systems, 3D synthetic microstructures are created to approximate actual TBC microstructures. The morphology of the grains in each constituent layer as well as the texture is controlled. A variety of TBC materials, including industry standard materials and potential future materials, are analyzed using the teFFT. The resulting hot spots are quantified using the POT approach. A correlation between hot spots in EED and interface rumpling between constituent layers is demonstrated, particularly for the interface between the bond coat (BC) and the thermally grown oxide (TGO) layer.

  2. Static and dynamic strain energy release rates in toughened thermosetting composite laminates

    Science.gov (United States)

    Cairns, Douglas S.

    1992-01-01

    In this work, the static and dynamic fracture properties of several thermosetting resin based composite laminates are presented. Two classes of materials are explored. These are homogeneous, thermosetting resins and toughened, multi-phase, thermosetting resin systems. Multi-phase resin materials have shown enhancement over homogenous materials with respect to damage resistance. The development of new dynamic tests are presented for composite laminates based on Width Tapered Double Cantilevered Beam (WTDCB) for Mode 1 fracture and the End Notched Flexure (ENF) specimen. The WTDCB sample was loaded via a low inertia, pneumatic cylinder to produce rapid cross-head displacements. A high rate, piezo-electric load cell and an accelerometer were mounted on the specimen. A digital oscilloscope was used for data acquisition. Typical static and dynamic load versus displacement plots are presented. The ENF specimen was impacted in three point bending with an instrumented impact tower. Fracture initiation and propagation energies under static and dynamic conditions were determined analytically and experimentally. The test results for Mode 1 fracture are relatively insensitive to strain rate effects for the laminates tested in this study. The test results from Mode 2 fracture indicate that the toughened systems provide superior fracture initiation and higher resistance to propagation under dynamic conditions. While the static fracture properties of the homogeneous systems may be relatively high, the apparent Mode 2 dynamic critical strain energy release rate drops significantly. The results indicate that static Mode 2 fracture testing is inadequate for determining the fracture performance of composite structures subjected to conditions such as low velocity impact. A good correlation between the basic Mode 2 dynamic fracture properties and the performance is a combined material/structural Compression After Impact (CAI) test is found. These results underscore the importance of

  3. Adhesive-Bonded Composite Joint Analysis with Delaminated Surface Ply Using Strain-Energy Release Rate

    Science.gov (United States)

    Chadegani, Alireza; Yang, Chihdar; Smeltzer, Stanley S. III

    2012-01-01

    This paper presents an analytical model to determine the strain energy release rate due to an interlaminar crack of the surface ply in adhesively bonded composite joints subjected to axial tension. Single-lap shear-joint standard test specimen geometry with thick bondline is followed for model development. The field equations are formulated by using the first-order shear-deformation theory in laminated plates together with kinematics relations and force equilibrium conditions. The stress distributions for the adherends and adhesive are determined after the appropriate boundary and loading conditions are applied and the equations for the field displacements are solved. The system of second-order differential equations is solved to using the symbolic computation tool Maple 9.52 to provide displacements fields. The equivalent forces at the tip of the prescribed interlaminar crack are obtained based on interlaminar stress distributions. The strain energy release rate of the crack is then determined by using the crack closure method. Finite element analyses using the J integral as well as the crack closure method are performed to verify the developed analytical model. It has been shown that the results using the analytical method correlate well with the results from the finite element analyses. An attempt is made to predict the failure loads of the joints based on limited test data from the literature. The effectiveness of the inclusion of bondline thickness is justified when compared with the results obtained from the previous model in which a thin bondline and uniform adhesive stresses through the bondline thickness are assumed.

  4. Edge effects on band gap energy in bilayer 2H-MoS{sub 2} under uniaxial strain

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Liang; Wang, Jin; Dongare, Avinash M., E-mail: dongare@uconn.edu [Department of Materials Science and Engineering and Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269 (United States); Namburu, Raju [Computational and Information Sciences Directorate, U.S. Army Research Laboratory, Aberdeen Proving Ground, Maryland 21005 (United States); O' Regan, Terrance P.; Dubey, Madan [Sensors and Electron Devices Directorate, U.S. Army Research Laboratory, Adelphi, Maryland 20783 (United States)

    2015-06-28

    The potential of ultrathin MoS{sub 2} nanostructures for applications in electronic and optoelectronic devices requires a fundamental understanding in their electronic structure as a function of strain. Previous experimental and theoretical studies assume that an identical strain and/or stress state is always maintained in the top and bottom layers of a bilayer MoS{sub 2} film. In this study, a bilayer MoS{sub 2} supercell is constructed differently from the prototypical unit cell in order to investigate the layer-dependent electronic band gap energy in a bilayer MoS{sub 2} film under uniaxial mechanical deformations. The supercell contains an MoS{sub 2} bottom layer and a relatively narrower top layer (nanoribbon with free edges) as a simplified model to simulate the as-grown bilayer MoS{sub 2} flakes with free edges observed experimentally. Our results show that the two layers have different band gap energies under a tensile uniaxial strain, although they remain mutually interacting by van der Waals interactions. The deviation in their band gap energies grows from 0 to 0.42 eV as the uniaxial strain increases from 0% to 6% under both uniaxial strain and stress conditions. The deviation, however, disappears if a compressive uniaxial strain is applied. These results demonstrate that tensile uniaxial strains applied to bilayer MoS{sub 2} films can result in distinct band gap energies in the bilayer structures. Such variations need to be accounted for when analyzing strain effects on electronic properties of bilayer or multilayered 2D materials using experimental methods or in continuum models.

  5. The Breeding of a Pigment Mutant Strain of Steroid Hydroxylation Aspergillus Flavus by Low Energy Ion Implantation

    Institute of Scientific and Technical Information of China (English)

    YE Hui; MA Jingming; FENG Chun; CHENG Ying; ZHU Suwen; CHENG Beijiu

    2009-01-01

    In the process of the fermentation of steroid C11α-hydroxylgenation strain Aspergillus flavus AF-ANo208.a red pigment is derived.which will affect the isolation and purification of the target product.Low energy ion beam implantation is a new tool for breeding excellent mutant strains.In this study,the ion beam implantation experiments were performed by infusing two different ions:argon ion(Ar+)and nitrogen ion(N+).The results showed that the optimal ion implantation was N+ with an optimum dose of 2.08×1015 ions/cm2.with which the mutant strain AF-ANml6 that produced no red pigment was obtained.The strain had high genetic stability and kept the strong capacity of C11α-hydroxylgenation,which could be utilized in industrial fermentation.The difierences between the original strain and the mutant strain at a molecular level were analyzed by randomly amplified polymorphic DNA(RAPD).The results indicated that the frequency of variation Was 7.00%,which would establish the basis of application investigation into the breeding of pigment mutant strains by low energy ion implantation.

  6. Size effects in crystal plasticity

    DEFF Research Database (Denmark)

    Borg, Ulrik

    2007-01-01

    Numerical analyses of plasticity size effects have been carried out for different problems using a developed strain gradient crystal plasticiy theory. The theory employs higher order stresses as work conjugates to slip gradients and uses higher order boundary conditions. Problems on localization...... of plastic flow in a single crystal, grain boundary effects in a bicrystal, and grain size effects in a polycrystal are studied. Single crystals containing micro-scale voids have also been analyzed at different loading conditions with focus on the stress and deformation fields around the voids, on void...... growth and interaction between neighboring voids, and on a comparison between the developed strain gradient crystal plasticity theory and a discrete dislocation plasticity theory. Furthermore, voids and rigid inclusions in isotropic materials have been studied using a strain gradient plasticity theory...

  7. Metastability and hysteretic vortex pinning near the order-disorder transition in NbSe2: Interplay between plastic and elastic energy barriers

    Science.gov (United States)

    Marziali Bermúdez, M.; Louden, E. R.; Eskildsen, M. R.; Dewhurst, C. D.; Bekeris, V.; Pasquini, G.

    2017-03-01

    We studied thermal and dynamic history effects in the vortex lattice (VL) near the order-disorder transition in clean NbSe2 single crystals. Comparing the evolution of the effective vortex pinning and the bulk VL structure, we observed metastable superheated and supercooled VL configurations that coexist with a hysteretic effective pinning response due to thermal cycling of the system. A novel scenario, governed by the interplay between (lower) elastic and (higher) plastic energy barriers, is proposed as an explanation for our observations: Plastic barriers, which prevent the annihilation or creation of topological defects, require dynamic assistance to be overcome and to achieve a stable VL at each temperature. Conversely, thermal hysteresis in the pining response is ascribed to low energy barriers, which inhibit rearrangement within a single VL correlation volume and are easily overcome as the relative strength of competing interactions changes with temperature.

  8. The waste-to-energy framework for integrated multi-waste utilization: Waste cooking oil, waste lubricating oil, and waste plastics

    Energy Technology Data Exchange (ETDEWEB)

    Singhabhandhu, Ampaitepin; Tezuka, Tetsuo [Energy Economics Laboratory, Department of Socio-Environmental Energy Science, Graduate School of Energy Science, Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto 606-8501 (Japan)

    2010-06-15

    Energy generation by wastes is considered one method of waste management that has the benefit of energy recovery. From the waste-to-energy point of view, waste cooking oil, waste lubricating oil, and waste plastics have been considered good candidates for feedstocks for energy conversion due to their high heating values. Compared to the independent management of these three wastes, the idea of co-processing them in integration is expected to gain more benefit. The economies of scale and the synergy of co-processing these wastes results in higher quality and higher yield of the end products. In this study, we use cost-benefit analysis to evaluate the integrated management scenario of collecting the three wastes and converting them to energy. We report the total heat of combustion of pyrolytic oil at the maximum and minimum conversion rates, and conduct a sensitivity analysis in which the parameters of an increase of the electricity cost for operating the process and increase of the feedstock transportation cost are tested. We evaluate the effects of economy of scale in the case of integrated waste management. We compare four cases of waste-to-energy conversion with the business as usual (BAU) scenario, and our results show that the integrated co-processing of waste cooking oil, waste lubricating oil, and waste plastics is the most profitable from the viewpoints of energy yield and economics. (author)

  9. Constitutive model of discontinuous plastic flow at cryogenic temperatures

    CERN Document Server

    Skoczen, B; Bielski, J; Marcinek, D

    2010-01-01

    FCC metals and alloys are frequently used in cryogenic applications, nearly down to the temperature of absolute zero, because of their excellent physical and mechanical properties including ductility. Some of these materials, often characterized by the low stacking fault energy (LSFE), undergo at low temperatures three distinct phenomena: dynamic strain ageing (DSA), plastic strain induced transformation from the parent phase (gamma) to the secondary phase (alpha) and evolution of micro-damage. The constitutive model presented in the paper is focused on the discontinuous plastic flow (serrated yielding) and takes into account the relevant thermodynamic background. The discontinuous plastic flow reflecting the DSA effect is described by the mechanism of local catastrophic failure of Lomer-Cottrell (LC) locks under the stress fields related to the accumulating edge dislocations (below the transition temperature from the screw dislocations to the edge dislocations mode T-1). The failure of LC locks leads to mass...

  10. New perspectives in plastic biodegradation.

    Science.gov (United States)

    Sivan, Alex

    2011-06-01

    During the past 50 years new plastic materials, in various applications, have gradually replaced the traditional metal, wood, leather materials. Ironically, the most preferred property of plastics--durability--exerts also the major environmental threat. Recycling has practically failed to provide a safe solution for disposal of plastic waste (only 5% out of 1 trillion plastic bags, annually produced in the US alone, are being recycled). Since the most utilized plastic is polyethylene (PE; ca. 140 million tons/year), any reduction in the accumulation of PE waste alone would have a major impact on the overall reduction of the plastic waste in the environment. Since PE is considered to be practically inert, efforts were made to isolate unique microorganisms capable of utilizing synthetic polymers. Recent data showed that biodegradation of plastic waste with selected microbial strains became a viable solution. Copyright © 2011 Elsevier Ltd. All rights reserved.

  11. Plastic Jellyfish.

    Science.gov (United States)

    Moseley, Christine

    2000-01-01

    Presents an environmental science activity designed to enhance students' awareness of the hazards of plastic waste for wildlife in aquatic environments. Discusses how students can take steps to reduce the effects of plastic waste. (WRM)

  12. Density Functional Study of the Optimized Structure, Enthalpy of Formation, Strain Energy, and Vibrational Properties of the Highly-Strained Carbon Complex: [15]Triangulane

    Science.gov (United States)

    Richardson, Steven L.; Pederson, Mark R.

    2002-03-01

    In organic chemistry, cyclopropane (C_3H_6) is a highly-strained three-membered carbon ring which can be networked to form [n]triangulanes, which are branched hydrocarbons consisting entirely of spiroannulated cyclopropyl groups. The C_2v-symmetric branched [15]triangulane (C_31H_34) have been recently synthesized (M. von Seebach, S. I. Kozhushkov, R. Boese, J. Benet-Buchholz, D. S. Yufit, J. A. K. Howard, and A. de Meijere, Angew. Chem. Int. Ed. 39,) 2495 (2001). and is the largest triangulane molecule experimentally known to date. We report accurate density functional studies(M. R. Pederson and K. A. Jackson, Phys. Rev. B41,) 7453 (1990). of [15]triangulane which determine its optimized geometry and have calculated an enthalpy of formation and strain energy, using the appropriate isodesmic and homodesmotic reactions. The vibrational frequencies of [15]triangulane are also computed and our results are compared to experimental results, where available.

  13. An experimental study of plastic deformation of materials

    DEFF Research Database (Denmark)

    Knudsen, Tine

    in the investigated hot deformed samples (lnZ= 27.5 to 32) in general are cell block structures, and that the alignment of the cell block boundaries at low strain depends on the grain orientation, often in the same manner as in cold deformation. Part II investigates the energy stored in the dislocation structure...... after cold deformation by calorimetry and by analysis of the dislocation structure. The stored energy measured by calorimetry is found to be larger than that determined from the dislocation structure by a factor between 1.9 and 2.7, and this factor decreases with the plastic strain. Part III aimed...

  14. Studies on Mutation Breeding of High-Yielding Xylanase Strains by Low-Energy Ion Beam Implantation

    Institute of Scientific and Technical Information of China (English)

    LI Shichang; YAO Jianming; YU Zhengling

    2007-01-01

    As a new mutagenetic method,low-energy ion implantation has been used widely in many research areas in recent years.In order to obtain some industrial strains with high xylanase yield,the wild type strain Aspergillus niger A3 was mutated by means of nitrogen ions implantation (10 keV,2.6 × 1014~1.56 × 1015 ions/cm2) and a mutant N212 was isolated subsequently.However,it was found that the initial screening means of the high-yielding xylanase strains such as transparent halos was unfit for first screening.Compared with that of the wild type strain,xylanase production of the mutant N212 was increased from 320 IU/ml to 610 IU/ml,and the optimum fermentation temperature was increased from 28 ℃ to 30 ℃.

  15. Influence of plastic strain localization on the stress corrosion cracking of austenitic stainless steels; Influence de la localisation de la deformation plastique sur la CSC d'aciers austenitiques inoxydables

    Energy Technology Data Exchange (ETDEWEB)

    Cisse, S.; Tanguy, B. [CEA Saclay, DEN, SEMI, 91 - Gif-sur-Yvette (France); Andrieu, E.; Laffont, L.; Lafont, M.Ch. [Universite de Toulouse. CIRIMAT, UPS/INPT/CNRS, 31 - Toulous (France)

    2010-03-15

    The authors present a research study of the role of strain localization on the irradiation-assisted stress corrosion cracking (IASCC) of vessel steel in PWR-type (pressurized water reactor) environment. They study the interaction between plasticity and intergranular corrosion and/or oxidation mechanisms in austenitic stainless steels with respect to sublayer microstructure transformations. The study is performed on three austenitic stainless grades which have not been sensitized by any specific thermal treatment: the A286 structurally hardened steel, and the 304L and 316L austenitic stainless steels

  16. MULTIAXIAL LOCAL STRESS-STRAIN APPROACH BASED ON A-F TYPE CYCLIC PLASTICITY THEORY%基于A-F类循环塑性理论的多轴局部应力应变法

    Institute of Scientific and Technical Information of China (English)

    邱宝象; 王效贵; 高增梁; Jiang Y

    2011-01-01

    提出预测缺口构件疲劳寿命的多轴局部应力应变法.采用Armstrong-Frederick (A-F)类循环塑性理论,描述具有非Masing特性的16MnR材料的循环塑性行为.结合A-F类循环塑性模型和增量式Neuber法,分析比例和非比例加载下缺口根部处的多轴应力应变状态.将局部应力应变应用于基于临界面的多轴疲劳损伤模型,对缺口构件进行疲劳损伤分析和疲劳寿命预测.分析结果表明,基于A-F类循环塑性理论的多轴局部应力应变法,能很好地描述缺口根部处的多轴应力应变状态,疲劳寿命的预测结果与试验数据基本吻合.%A multiaxial local stress-strain method was proposed to predict the fatigue life of notched components. The Armstrong-Frederick (A-F) type cyclic plasticity theory was adopted to describe the cyclic plasticity behavior. This newly developed cyclic plasticity theory is able to characterize the non-Masing behavior of 16MnR steel. The multiaxial stress-strain state at the notch root of notched components subjected to proportional and non-proportional loading was predicted by combining the A-F cyclic plasticity model and the incremental Neuber's rule. On the basis of the multiaxial local stress-strain state and a critical plane based multiaxial fatigue damage criterion, the fatigue damage of the notched components was analyzed and then the fatigue life was predicted. The numerical results show that the proposed multiaxial local stress-strain method can describe the multiaxial stress state at the notch root very well, and the predicted fatigue lives correlate well with the experimental data.

  17. Possibility of Prediction of Properties of High-Toughness Materials by Complex Analysis of the Size of Zones of Plastic Strain and Other Parameters of Steel 09G2S

    Science.gov (United States)

    Simonov, M. Yu.; Shaimanov, G. S.; Simonov, Yu. N.; Khanov, A. M.

    2016-05-01

    Relations between the parameters of dynamic crack resistance, impact toughness, sizes of zones of plastic strain in the start region, hardness of the unstrained material, strength characteristics, and tempering temperature of steel 09G2S are determined. The linear regression equations are used to construct mathematical and graphical models for predicting the level of properties in quenched and tempered steel 09G2S. The method is used to predict the properties of a tubular billet from steel 09G2S with composition somewhat different from the rated one after quenching and high tempering at 570°C.

  18. Effects of constitutive parameters on adiabatic shear localization for ductile metal based on JOHNSON-COOK and gradient plasticity models

    Institute of Scientific and Technical Information of China (English)

    WANG Xue-bin

    2006-01-01

    By using the widely used JOHNSON-COOK model and the gradient-dependent plasticity to consider microstmctural effect beyond the occurrence of shear strain localization, the distributions of local plastic shear strain and deformation in adiabatic shear band(ASB) were analyzed. The peak local plastic shear strain is proportional to the average plastic shear strain, while it is inversely proportional to the critical plastic shear strain corresponding to the peak flow shear stress. The relative plastic shear deformation between the top and base of ASB depends on the thickness of ASB and the average plastic shear strain. A parametric study was carried out to study the influence of constitutive parameters on shear strain localization. Higher values of static shear strength and work to heat conversion factor lead to lower critical plastic shear strain so that the shear localization is more apparent at the same average plastic shear strain. Higher values of strain-hardening exponent, strain rate sensitive coefficient, melting point,thermal capacity and mass density result in higher critical plastic shear strain, leading to less apparent shear localization at the same average plastic shear strain. The strain rate sensitive coefficient has a minor influence on the critical plastic shear strain, the distributions of local plastic shear strain and deformation in ASB. The effect of strain-hardening modulus on the critical plastic shear strain is not monotonous. When the maximum critical plastic shear strain is reached, the least apparent shear localization occurs.

  19. Effects of strain rate and elevated temperature on compressive flow stress and absorbed energy of polyimide foam

    Directory of Open Access Journals (Sweden)

    Horikawa K.

    2012-08-01

    Full Text Available In this study, at first, the effect of strain rate on the strength and the absorbed energy of polyimide foam was experimentally examined by carrying out a series of compression tests at various strain rates, from 10−3 to 103 s−1. This polyimide foam has open cell structure with small cell size of 0.3 ∼ 0.6 mm. In the measurement of impact load, a special load cell with a small part for sensing load was adopted. For the measurement of the displacement, a high-speed camera was used. It was found that the flow stress of polyimide foam and the absorbed energy up to a strain of 0.4 increased with the increase of the strain rates. Secondly, the effect of ambient temperature on the strength and absorbed energy of polyimide foam was also investigated by using a sprit Hopkinson pressure bar apparatus and testing at elevated temperatures of 100 and 200 ∘C. With the increase of temperature, the strength and absorbed energy decreased and the effect is smaller in dynamic tests than static tests.

  20. Breakdown of anomalous channeling with ion energy for accurate strain determination in GaN-based heterostructures

    NARCIS (Netherlands)

    Redondo-Cubero, A.; Lorenz, K.; Gago, R.; Franco, N.; Fernandez-Garrido, S.; Smulders, P. J. M.; Munoz, E.; Calleja, E.; Watson, I. M.; Alves, E.

    2009-01-01

    The influence of the beam energy on the determination of strain state with ion channeling in GaN-based heterostructures (HSs) is addressed. Experimental results show that anomalous channeling may hinder an accurate analysis due to the steering effects at the HS interface, which are more intense at l

  1. Characterization of anisotropic elastic properties of the arteries by exponential and polynomial strain energy functions.

    Science.gov (United States)

    Hudetz, A G; Monos, E

    1981-01-01

    Three-dimensional quasi-static mechanical measurements were carried out on cylindrical segments of the dog carotid and iliac arteries for determination of the passive anisotropic elastic properties of the vessel wall. On the basis of passive characteristics of outer diameter vs. intraluminal pressure, and axial extending force vs. intraluminal pressure, picked up at various fixed initial vascular length values, the incremental Young moduli and poisson ratios of the vessel wall were calculated in the 0--33 kPa (0--250 mm Hg) pressure range. The strain energy function of the arteries was approximated by polynomial and exponential models. We found that an exponential energy function with 4-parameters gives more accurate results than the 7- or 12-parameter polynomial functions. According to the results the axial modulus reaches higher values than the tangential and radial moduli at a low tangential stretch level, while at high tangential stretch the tangential modulus is the highest in both carotid and iliac arteries. After elevation of the initial tangential stretch the increase in the tangential modulus is the most pronounced, while the values of radial and axial moduli increased less. A change in the initial axial stretch influences the axial and radial moduli to a similar extent, but has no substantial effect on the value of the tangential modulus. The values of corresponding poisson ratios depend in a similar way on the initial deformation state. The different behaviour of the two Poisson ratios characterizing the mechanical coupling between tangential and axial directions, indicates that the structural coupling between the two main directions is asymmetrical. It is assumed that this property of the passive vascular structure can be explained by the network arrangement of collagen fibres in the vessel wall.

  2. A new extension algorithm for cubic B-splines based on minimal strain energy

    Institute of Scientific and Technical Information of China (English)

    MO Guo-liang; ZHAO Ya-nan

    2006-01-01

    Extension ora B-spline curve or surface is a useful function in a CAD system. This paper presents an algorithm for extending cubic B-spline curves or surfaces to one or more target points. To keep the extension curve segment GC2-continuous with the original one, a family of cubic polynomial interpolation curves can be constructed. One curve is chosen as the solution from a sub-class of such a family by setting one GC2 parameter to be zero and determining the second GC2 parameter by minimizing the strain energy. To simplify the final curve representation, the extension segment is reparameterized to achieve C2-continuity with the given B-spline curve, and then knot removal from the curve is done. As a result, a sub-optimized solution subject to the given constraints and criteria is obtained. Additionally, new control points of the extension B-spline segment can be determined by solving lower triangular linear equations. Some computing examples for comparing our method and other methods are given.

  3. Structural damage identification based on change in geometric modal strain energy-eigenvalue ratio

    Science.gov (United States)

    Nguyen, Khac-Duy; Chan, Tommy HT; Thambiratnam, David P.

    2016-07-01

    This study presents a new damage identification method to locate and quantify damage using measured mode shapes and natural frequencies. A new vibration parameter, ratio of geometric modal strain energy to eigenvalue (GMSEE), has been developed and its change due to stiffness reduction has been formulated using a sensitivity matrix. This sensitivity matrix is estimated with measured modal parameters and basic information of the structure. For damage identification, firstly, the locations of damage and the correlative damage extents are identified by maximizing the correlation level between an analytical GMSEE change vector and a measured one. Herein, the genetic algorithm, which is a powerful evolutionary optimization algorithm, is utilized to solve this optimization problem. Secondly, the size of damage can be estimated using the proposed GMSEE technique and compared with a conventional technique using frequency change. A numerical 2D Truss bridge is used to demonstrate the performance of the proposed method in identifying single and multiple damage cases. Also, practicality of the method is tested with a laboratory eight degree-of-freedom system and a real bridge. Results illustrate the high capability of the method to identify structural damage with less modeling efforts.

  4. Local strain energy density to assess the multiaxial fatigue strength of titanium alloys

    Directory of Open Access Journals (Sweden)

    Filippo Berto

    2016-07-01

    Full Text Available The present paper investigates the multiaxial fatigue strength of sharp V-notched components made of titanium grade 5 alloy (Ti-6Al-4V. Axisymmetric notched specimens have been tested under combined tension and torsion fatigue loadings, both proportional and non-proportional, taking into account different nominal load ratios (R = -1 and 0. All tested samples have a notch root radius about equal to 0.1 mm, a notch depth of 6 mm and an opening angle of 90 degrees. The fatigue results obtained by applying multiaxial loadings are discussed together with those related to pure tension and pure torsion experimental fatigue tests, carried out on both smooth and notched specimens at load ratios R ranging between -3 and 0.5. Altogether, more than 250 fatigue results (19 S-N curves are examined, first on the basis of nominal stress amplitudes referred to the net area and secondly by means of the strain energy density averaged over a control volume embracing the V-notch tip. The effect of the loading mode on the control volume size has been analysed, highlighting a wide difference in the notch sensitivity of the considered material under tension and torsion loadings. Accordingly, the control radius of the considered titanium alloy (Ti-6Al-4V is found to be strongly affected by the loading mode.

  5. The strain energy release approach for modeling cracks in rotors: A state of the art review

    Science.gov (United States)

    Papadopoulos, Chris A.

    2008-05-01

    The strain energy release rate (SERR) theory, combined with Linear Fracture Mechanics and Rotordynamics theories, has been widely used over the last three decades in order to calculate the compliance that causes a transverse surface crack in a rotating shaft. In this paper, the basic theory of this approach is presented, along with some extensions and limitations of its usage. The SERR theory is applied to a rotating crack and gives good results. The linear or nonlinear cracked rotor behavior depends on the mechanism of opening and closure of the crack during the shaft rotation. A brief history of the SERR theory is presented. In the 1970s, this theory met with rotordynamics as a result of research conducted on the causes of rotor failures in power industries. The main goal of this research was to give the engineer an early warning about the cracked situation of the rotor—in other words, to make the identification of the crack possible. Different methods of crack identification are presented here as well as those for multi-crack identification.

  6. Plastic deformation modelling of tempered martensite steel block structure by a nonlocal crystal plasticity model

    Directory of Open Access Journals (Sweden)

    Martin Boeff

    2014-01-01

    Full Text Available The plastic deformations of tempered martensite steel representative volume elements with different martensite block structures have been investigated by using a nonlocal crystal plasticity model which considers isotropic and kinematic hardening produced by plastic strain gradients. It was found that pronounced strain gradients occur in the grain boundary region even under homogeneous loading. The isotropic hardening of strain gradients strongly influences the global stress–strain diagram while the kinematic hardening of strain gradients influences the local deformation behaviour. It is found that the additional strain gradient hardening is not only dependent on the block width but also on the misorientations or the deformation incompatibilities in adjacent blocks.

  7. Influence of strain amount on stabilization of {omega}-phase in pure Ti by severe plastic deformation under high-pressure torsion

    Energy Technology Data Exchange (ETDEWEB)

    Todaka, Y; Azuma, H; Ohnishi, Y; Umemoto, M [Department of Production Systems Engineering, Toyohashi University of Technology, Hibarigaoka 1-1, Tempaku, Toyohashi, Aichi 441-8580 (Japan); Suzuki, H, E-mail: todaka@martens.pse.tut.ac.j [Quantum Beam Science Directorate, Japan Atomic Energy Agency, Shirakata-Shirane 2-4, Tokai, Naka, Ibaraki 319-1195 (Japan)

    2010-07-01

    In pure Ti, the influence of shear deformation on the {alpha} to {omega} transformation and the development of texture in the {omega}-phase under high-pressure torsion (HPT) straining were investigated by means of X-ray and neutron diffractions. The fraction of {omega}-phase increased with strain in the {omega}-phase state. Bulk submicrocrystalline {omega}-Ti was fabricated by HPT-straining under the compressive pressure P = 5 GPa with the equivalent strain {epsilon}{sub eq} > 110 at the rotation speed of 3.3 x 10{sup -3} rev. per sec. (0.2 rev. per min.) at room temperature. The texture of {omega}-phase evolved by HPT-straining with the prismatic planes parallel to the shear direction of HPT-straining and the basal planes perpendicular to it.

  8. Charge, energy and LET spectra of high LET primary and secondary particles in CR-39 plastic nuclear track detectors of the P0006 experiment

    Science.gov (United States)

    Csige, I.; Frigo, L. A.; Benton, E. V.; Oda, K.

    1995-01-01

    We have measured the charge, energy and linear energy transfer (LET) spectra of about 800 high LET (LET(sub infinity) H2O greater than 50 keV/micron) particles in CR-39 plastic nuclear track detectors in the P0006 experiment of LDEF. Primary particles with residual range at the reference surface greater than about 2 microns and secondary particles produced in the detector material with total range greater than about 4 microns were measured. We have used a multi-etch technique and an internal calibration to identify and measure the energy of the particles at the reference surface. The LET spectrum was obtained from the charge and energy distribution of the particles.

  9. New Class of Plastic Bulk Metallic Glass

    Science.gov (United States)

    Chen, L. Y.; Fu, Z. D.; Zhang, G. Q.; Hao, X. P.; Jiang, Q. K.; Wang, X. D.; Cao, Q. P.; Franz, H.; Liu, Y. G.; Xie, H. S.; Zhang, S. L.; Wang, B. Y.; Zeng, Y. W.; Jiang, J. Z.

    2008-02-01

    An intrinsic plastic Cu45Zr46Al7Ti2 bulk metallic glass (BMG) with high strength and superior compressive plastic strain of up to 32.5% was successfully fabricated by copper mold casting. The superior compressive plastic strain was attributed to a large amount of randomly distributed free volume induced by Ti minor alloying, which results in extensive shear band formation, branching, interaction and self-healing of minor cracks. The mechanism of plasticity presented here suggests that the creation of a large amount of free volume in BMGs by minor alloying or other methods might be a promising new way to enhance the plasticity of BMGs.

  10. Effect of Plastic Pre-straining on Residual Stress and Composition Profiles in Low-Temperature Surface-Hardened Austenitic Stainless Steel

    DEFF Research Database (Denmark)

    Bottoli, Federico; Christiansen, Thomas Lundin; Winther, Grethe

    2016-01-01

    or nitrocarburized. The residual stress profiles resulting from the thermochemical low-temperature surface treatment were measured. The results indicate high-residual compressive stresses of several GPa’s in the nitrided region, while lower-compressive stresses are produced in the carburized case. Plastic...

  11. Elastic Deformation in Yield Zones for the Elastic-Plastic Plane Strain Problems%弹塑性变形中的弹性效应

    Institute of Scientific and Technical Information of China (English)

    田常录; 那日苏

    2007-01-01

    In the solution procedures of elastic-plastic problems the elastic deformation in yield zones was generally omitted due to the mathematical difficulty,and some simplified constitutive equations such as the incompressible model are widely employed in the classical plasticity. The analogy results derived in this work are compared with those of the common elastic-plastic methods, and the merit of the analogy results and the improvements in some respects are presented. Based on the basic stress element,the effects of elasticity in different stress states of non-linear elastic-plastic problems are evaluated in detail.%由于数学上的困难,弹塑性问题分析中一般忽略弹性变形.而且,求解时对本构方程的一些简化方法如不可压缩假设等被广泛采用.本文分析了一种比拟解答的优点和其在某些方面的改进,并以平面应变下的弹塑性单元体为例,详细计算和分析了不同应力状态下弹塑性变形过程中的弹性效应.

  12. Preferred orientation in carbon and boron nitride: Does a thermodynamic theory of elastic strain energy get it right. [C; BN

    Energy Technology Data Exchange (ETDEWEB)

    McCarty, K.F. (Sandia National Laboratories, Livermore, California 94550 (United States))

    1999-09-01

    We address whether the elastic strain-energy theory (minimizing the Gibbs energy of a stressed crystal) of McKenzie and co-workers [D. R. McKenzie and M. M. M. Bilek, J. Vac. Sci. Technol. A [bold 16], 2733 (1998)] adequately explains the preferred orientation observed in carbon and BN films. In the formalism, the Gibbs energy of the cubic materials diamond and cubic boron includes the strain that occurs when the phases form, through specific structural transformations, from graphitic precursors. This treatment violates the requirement of thermodynamics that the Gibbs energy be a path-independent, state function. If the cubic phases are treated using the same (path-independent) formalism applied to the graphitic materials, the crystallographic orientation of lowest Gibbs energy is not that observed experimentally. For graphitic (hexagonal) carbon and BN, an elastic strain approach seems inappropriate because the compressive stresses in energetically deposited films are orders of magnitude higher than the elastic limit of the materials. Furthermore, using the known elastic constants of either ordered or disordered graphitic materials, the theory does not predict the orientation observed by experiment. [copyright] [ital 1999 American Vacuum Society.

  13. Internal field induced exciton binding energy and the optical transition in a strained Mg based II–VI quantum well

    Energy Technology Data Exchange (ETDEWEB)

    Elangovan, P. [Department of Physics, Maamallan Institute of Technology, Chennai 602105 (India); John Peter, A., E-mail: a.john.peter@gmail.com [Department of Physics, Government Arts College, Melur 625 106. Madurai (India); Kyoo Yoo, Chang [Center for Environmental Studies/Green Energy Center, Deptartment of Environmental Science and Engineering, College of Engineering, Kyung Hee University, Seocheon-dong 1, Giheung-gu, Yongin-Si, Gyeonggi-Do, 446-701 (Korea, Republic of)

    2013-11-15

    Binding energy of an exciton in a wurtzite ZnO/Zn{sub 1−x}Mg{sub x}O strained quantum well is investigated theoretically in which the strong built-in electric field due to the spontaneous and piezoelectric polarizations is included. Numerical calculations are performed using variational procedure within the single band effective mass approximation by varying the Mg composition in the barrier. The exciton oscillator strength and the exciton lifetime for radiative recombination as functions of well width and Mg content have been computed. The internal field induced interband emission energy of strained ZnO/Zn{sub 1−x}Mg{sub x}O well is investigated with the various structural parameters. The total optical absorption coefficients and the changes of refractive index as a function of normalized photon energy in the presence of built-in internal field are analyzed. The result shows that the strong built-in electric field has influence on the oscillator strength and the recombination life time of the exciton. The optical absorption coefficients and the refractive index changes strongly depend on Mg composition. The occurred blue shift of the resonant peak due to the incorporation of Mg ions will give the information about the variation of two energy levels in the quantum well. -- Highlights: • Binding energy of an exciton in a wurtzite ZnO/Zn{sub 1−x}Mg{sub x}O strained quantum well is investigated. • The built-in internal fields due to the spontaneous and piezoelectric polarizations are included. • The oscillator strength and the exciton lifetime for radiative recombination are computed. • The internal field induced transition energy of strained ZnO/Zn{sub 1−x}Mg{sub x}O well is investigated. • The results show that the nonlinear optical properties strongly depend on Mg composition.

  14. International Technical Exchange on 2D Atomic Sheets: Optoelectronics, Strain, and Energy Applications

    Science.gov (United States)

    2015-01-15

    and transverse electric field. At zero magnetic field the chemical potential reveals a strongly non- linear dependence on density, with an electric...show potential to generate strain states larger than those achievable using flexible substrate approaches. Under some circumstances, an annular ...adsorption pattern generates homogeneous tensile strains of approximately 2% in graphene inside an annular adsorption region, or approximately 30% of the

  15. Extensional Flow Properties of Externally Plasticized Cellulose Acetate: Influence of Plasticizer Content

    Directory of Open Access Journals (Sweden)

    Hans-Joachim Radusch

    2013-07-01

    Full Text Available Elongational flow properties of polymer melts are very important for numerous polymer processing technologies such as blown film extrusion or foam extrusion. Rheotens tests were conducted to investigate the influence of plasticizer content on elongational flow properties of cellulose acetate (CA. Triethyl citrate (TEC was used as plasticizer. Melt strength decreases whereas melt extensibility increases with increasing plasticizer content. Melt strength was further studied as a function of zero shear viscosity. The typical draw resonance of the Rheotens curve shifts to higher drawdown velocity and the amplitude of the draw resonance decreases with increasing TEC content. With respect to foam extrusion, not only are melt strength and melt extensibility important but the elongational behavior at low strain rates and the area under the Rheotens curve are also significant. Therefore, elongational viscosity as well as specific energy input were calculated and investigated with respect to plasticizer content. Preliminary foam extrusion tests of externally plasticized CA using chemical blowing agents confirm the results from rheological characterization.

  16. Some characteristics of X-ray imaging for energy region of over 100 keV using plastic scintillation fiber array

    Institute of Scientific and Technical Information of China (English)

    TANG Shibiao; MA Qingli; YIN Zejie; HUANG Huan

    2007-01-01

    In this work, characteristics of using PSFs (plastic scintillation fibers) coupled with CCD (charge-coupled devices ) to build area detectors for high energy X-ray imaging are studied with a Monte Carlo simulation, which cover an energy range of a few hundred kev to about 20 MeV. It was found that the efficiency of PSF in detecting X-ray with energy above a few hundred kev is low. We can use large incident flux to increase the output signal to noise ratio (SNR). The performance can also be improved by coating PSF with X-ray absorption layers and the MTF of the system is presented. By optimizing the absorption layer thickness, the crosstalk of the area detector built with PSF decreases.

  17. Theoretical analysis and numerical simulation of strain localization in nonlocal plasticity model%基于非局部塑性模型的应变局部化理论分析及数值模拟

    Institute of Scientific and Technical Information of China (English)

    吕玺琳; 黄茂松

    2011-01-01

    通过求解一个第二类Fredholm方程,得到了基于非局部塑性软化模型的应变局部化问题理论解,结果表明,只有在当采用过非局部修正形式的非局部塑性软化模型才能得到应变局部化解,且得到的塑性应变分布和荷载响应依赖于所引入的特征长度及过非局部权参数。通过一维应变局部化有限元数值解,验证了非局部理论的引入能克服计算结果的网格敏感性,塑性应变分布和荷载响应计算结果随着网格细化趋近于理论解。将非局部塑性软化模型用于双轴应变局部化试验数值模拟,并分析了非局部理论引入的参数对计算结果的影响及计算过程的收敛特性。%By solving a Fredholm equation of the second kind, the analytical solution was derived for strain localization in nonlocal softening material, the solutions show that the distributions of plastic strain and load-displacement curve rely on the characteristic length and nonlocal parameter. It was validated by one-dimensional numerical solution that nonlocal model could make the distributions of plastic strain and the global load-displacement response mesh independent and approaching to analytical solutions with mesh refinement. The nonlocal formulation of softening plasticity was employed in the numerical simulation of strain localization in bi-axial compression test. The influence of the over-nonlocal parameter and characteristic length on the numerical results and the convergence of the equilibrium itera- tion were both obtained.

  18. The pan-genome of the animal pathogen Corynebacterium pseudotuberculosis reveals differences in genome plasticity between the biovar ovis and equi strains.

    Directory of Open Access Journals (Sweden)

    Siomar C Soares

    Full Text Available Corynebacterium pseudotuberculosis is a facultative intracellular pathogen and the causative agent of several infectious and contagious chronic diseases, including caseous lymphadenitis, ulcerative lymphangitis, mastitis, and edematous skin disease, in a broad spectrum of hosts. In addition, Corynebacterium pseudotuberculosis infections pose a rising worldwide economic problem in ruminants. The complete genome sequences of 15 C. pseudotuberculosis strains isolated from different hosts and countries were comparatively analyzed using a pan-genomic strategy. Phylogenomic, pan-genomic, core genomic, and singleton analyses revealed close relationships among pathogenic corynebacteria, the clonal-like behavior of C. pseudotuberculosis and slow increases in the sizes of pan-genomes. According to extrapolations based on the pan-genomes, core genomes and singletons, the C. pseudotuberculosis biovar ovis shows a more clonal-like behavior than the C. pseudotuberculosis biovar equi. Most of the variable genes of the biovar ovis strains were acquired in a block through horizontal gene transfer and are highly conserved, whereas the biovar equi strains contain great variability, both intra- and inter-biovar, in the 16 detected pathogenicity islands (PAIs. With respect to the gene content of the PAIs, the most interesting finding is the high similarity of the pilus genes in the biovar ovis strains compared with the great variability of these genes in the biovar equi strains. Concluding, the polymerization of complete pilus structures in biovar ovis could be responsible for a remarkable ability of these strains to spread throughout host tissues and penetrate cells to live intracellularly, in contrast with the biovar equi, which rarely attacks visceral organs. Intracellularly, the biovar ovis strains are expected to have less contact with other organisms than the biovar equi strains, thereby explaining the significant clonal-like behavior of the biovar ovis

  19. A correlative approach to segmenting phases and ferrite morphologies in transformation-induced plasticity steel using electron back-scattering diffraction and energy dispersive X-ray spectroscopy.

    Science.gov (United States)

    Gazder, Azdiar A; Al-Harbi, Fayez; Spanke, Hendrik Th; Mitchell, David R G; Pereloma, Elena V

    2014-12-01

    Using a combination of electron back-scattering diffraction and energy dispersive X-ray spectroscopy data, a segmentation procedure was developed to comprehensively distinguish austenite, martensite, polygonal ferrite, ferrite in granular bainite and bainitic ferrite laths in a thermo-mechanically processed low-Si, high-Al transformation-induced plasticity steel. The efficacy of the ferrite morphologies segmentation procedure was verified by transmission electron microscopy. The variation in carbon content between the ferrite in granular bainite and bainitic ferrite laths was explained on the basis of carbon partitioning during their growth. Copyright © 2014 Elsevier B.V. All rights reserved.

  20. Constructing a Plastic Bottle Wind Turbine as a Practical Aid for Learning about Using Wind Energy to Generate Electricity

    Science.gov (United States)

    Appleyard, S. J.

    2009-01-01

    A simple horizontal axis wind turbine can be easily constructed using a 1.5 l PET plastic bottle, a compact disc and a small dynamo. The turbine operates effectively at low wind speeds and has a rotational speed of 500 rpm at a wind speed of about 14 km h[superscript -1]. The wind turbine can be used to demonstrate the relationship between open…

  1. Strain dependence of the direct energy bandgap in thin silicon on insulator layers

    OpenAIRE

    Munguía, J; Bluet, J-M; Chouaib, H.; Bremond, G.; Mermoux, Michel; Bru-Chevallier, C

    2010-01-01

    Abstract Photoreflectance spectroscopy is applied on tensilely-strained silicon on insulator (sSOI) thin layers in order to evaluate the biaxial strain effect on the Si direct bandgap. The measured redshift of the transition (i.e. direct bandgap) with strain (~ -100 meV/%), corresponds to theoretical predictions. The hydrostatic and valence band deformation potential parameters for E 1 (i.e. transition close to L-point along the ?-direction) are also measured: and ' 0 E eV D 5. 0 5 . 7 1 1...

  2. Bacterial production of the biodegradable plastics polyhydroxyalkanoates.

    Science.gov (United States)

    Urtuvia, Viviana; Villegas, Pamela; González, Myriam; Seeger, Michael

    2014-09-01

    Petroleum-based plastics constitute a major environmental problem due to their low biodegradability and accumulation in various environments. Therefore, searching for novel biodegradable plastics is of increasing interest. Microbial polyesters known as polyhydroxyalkanoates (PHAs) are biodegradable plastics. Life cycle assessment indicates that PHB is more beneficial than petroleum-based plastics. In this report, bacterial production of PHAs and their industrial applications are reviewed and the synthesis of PHAs in Burkholderia xenovorans LB400 is described. PHAs are synthesized by a large number of microorganisms during unbalanced nutritional conditions. These polymers are accumulated as carbon and energy reserve in discrete granules in the bacterial cytoplasm. 3-hydroxybutyrate and 3-hydroxyvalerate are two main PHA units among 150 monomers that have been reported. B. xenovorans LB400 is a model bacterium for the degradation of polychlorobiphenyls and a wide range of aromatic compounds. A bioinformatic analysis of LB400 genome indicated the presence of pha genes encoding enzymes of pathways for PHA synthesis. This study showed that B. xenovorans LB400 synthesize PHAs under nutrient limitation. Staining with Sudan Black B indicated the production of PHAs by B. xenovorans LB400 colonies. The PHAs produced were characterized by GC-MS. Diverse substrates for the production of PHAs in strain LB400 were analyzed.

  3. Energy-efficient strain gauges for the wireless condition monitoring systems in mechanical engineering

    Energy Technology Data Exchange (ETDEWEB)

    Berndt, Michael; Fellner, Thomas; Zeiser, Roderich; Wilde, Juergen [Freiburg Univ. (Germany). Dept. for Microsystems Engineering (IMTEK)

    2012-07-01

    This work focuses on the development of novel strain gauges, which are suited for the operation in autonomous wireless condition monitoring systems. For this purpose, capacitive as well as highly resistive strain gauges were designed and fabricated. The C- and R-sensors were utilised in combination with demonstration circuits, which integrate the circuits for instrumentation, A/D-conversion and furthermore comprise a microcontroller with a wireless transceiver system, all on a small separate printed wiring board. (orig.)

  4. Modifications to the Method of Modal Strain Energy for Improved Estimates of Loss Factors for Damped Structures

    OpenAIRE

    Torvik, Peter J.; Brian Runyon

    2007-01-01

    The method of Modal Strain Energy (MSE) enables predictions of modal loss factors for vibrating systems from finite element analyses without evaluation of a complex-valued frequency response or a complex-valued frequency. While the method is simple, some error results; especially if the dissipative material has the high loss factor characteristic of materials added to increase system damping. Several methods for reducing this error through modifications to MSE have been suggested. In this wor...

  5. Mechanical plasticity of cells

    Science.gov (United States)

    Bonakdar, Navid; Gerum, Richard; Kuhn, Michael; Spörrer, Marina; Lippert, Anna; Schneider, Werner; Aifantis, Katerina E.; Fabry, Ben

    2016-10-01

    Under mechanical loading, most living cells show a viscoelastic deformation that follows a power law in time. After removal of the mechanical load, the cell shape recovers only incompletely to its original undeformed configuration. Here, we show that incomplete shape recovery is due to an additive plastic deformation that displays the same power-law dynamics as the fully reversible viscoelastic deformation response. Moreover, the plastic deformation is a constant fraction of the total cell deformation and originates from bond ruptures within the cytoskeleton. A simple extension of the prevailing viscoelastic power-law response theory with a plastic element correctly predicts the cell behaviour under cyclic loading. Our findings show that plastic energy dissipation during cell deformation is tightly linked to elastic cytoskeletal stresses, which suggests the existence of an adaptive mechanism that protects the cell against mechanical damage.

  6. Effects of the volume changes and elastic-strain energies on the phase transition in the Li-Sn battery

    Science.gov (United States)

    Zhang, Fan; Wang, Jianchuan; Liu, Shuhong; Du, Yong

    2016-10-01

    Sn and Sn-based compounds have been attracting a great interest as promising alternative materials for commercial anodes in lithium ion batteries. In this study, the phase evolution of the Li-Sn system during the lithiated processes and the effect of the elastic-strain energies caused by volume change on the phase transition are investigated by means of first-principles calculations. Our calculated results demonstrate that the distorted Li7Sn3 crystal tends to be formed in order to decrease the elastic-strain energy. In addition, our work indicates that the whole lithiated processes under the elastically constrained condition could be classified into two steps. The first step is the two-phase equilibrium process, in which the thermodynamic driving force is large enough to facilitate the phase transition and the plateau voltage could be established. The second step is considered to be the selective equilibrium, in which the thermodynamic driving force is not enough to facilitate the nucleation of the new equilibrium phase due to the elastically constrained conditions and the plateau voltage unformed. Besides, we find that in the Li0.4Sn matrix the nucleation of the αSn is more preferential than the βSn due to the effects of the elastic-strain energies.

  7. Plastics Technology.

    Science.gov (United States)

    Barker, Tommy G.

    This curriculum guide is designed to assist junior high schools industrial arts teachers in planning new courses and revising existing courses in plastics technology. Addressed in the individual units of the guide are the following topics: introduction to production technology; history and development of plastics; safety; youth leadership,…

  8. Analytical and finite-element study of optimal strain distribution in various beam shapes for energy harvesting applications

    Institute of Scientific and Technical Information of China (English)

    B L Ooi; J M Gilbert; A Rashid A Aziz

    2016-01-01

    Owing to the increasing demand for harvesting energy from environmental vibration for use in self-powered electronic applications, cantilever-based vibration energy harvesting has attracted considerable interest from various parties and has become one of the most common approaches to converting redundant mechanical energy into electrical energy. As the output voltage produced from a piezoelec-tric material depends largely on the geometric shape and the size of the beam, there is a need to model and compare the performance of cantilever beams of differing geometries. This paper presents the study of strain distribution in various shapes of cantilever beams, including a convex and concave edge profile elliptical beam that have not yet been discussed in any prior literature. Both analytical and finite-element models are derived and the resultant strain distributions in the beam are computed based on a MATLAB solver and ANSYS finite-element analysis tools. An optimum geome-try for a vibration-based energy harvesting system is verified. Finally, experimental results comparing the power density for triangular and rectangular piezoelectric beams are also pre-sented to validate the findings of the study, and the claim, as suggested in the literature, is verified.

  9. Analytical and finite-element study of optimal strain distribution in various beam shapes for energy harvesting applications

    Science.gov (United States)

    Ooi, B. L.; Gilbert, J. M.; Aziz, A. Rashid A.

    2016-08-01

    Owing to the increasing demand for harvesting energy from environmental vibration for use in self-powered electronic applications, cantilever-based vibration energy harvesting has attracted considerable interest from various parties and has become one of the most common approaches to converting redundant mechanical energy into electrical energy. As the output voltage produced from a piezoelectric material depends largely on the geometric shape and the size of the beam, there is a need to model and compare the performance of cantilever beams of differing geometries. This paper presents the study of strain distribution in various shapes of cantilever beams, including a convex and concave edge profile elliptical beam that have not yet been discussed in any prior literature. Both analytical and finite-element models are derived and the resultant strain distributions in the beam are computed based on a MATLAB solver and ANSYS finite-element analysis tools. An optimum geometry for a vibration-based energy harvesting system is verified. Finally, experimental results comparing the power density for triangular and rectangular piezoelectric beams are also presented to validate the findings of the study, and the claim, as suggested in the literature, is verified.

  10. Study of combustion and emission characteristics of fuel derived from waste plastics by various waste to energy (W-t-E) conversion processes

    Science.gov (United States)

    Hazrat, M. A.; Rasul, M. G.; Khan, M. M. K.

    2016-07-01

    Reduction of plastic wastes by means of producing energy can be treated as a good investment in the waste management and recycling sectors. In this article, conversion of plastics into liquid fuel by two thermo-chemical processes, pyrolysis and gasification, are reviewed. The study showed that the catalytic pyrolysis of homogenous waste plastics produces better quality and higher quantity of liquefied fuel than that of non-catalytic pyrolysis process at a lower operating temperature. The syngas produced from gasification process, which occurs at higher temperature than the pyrolysis process, can be converted into diesel by the Fischer-Tropsch (FT) reaction process. Conducive bed material like Olivine in the gasification conversion process can remarkably reduce the production of tar. The waste plastics pyrolysis oil showed brake thermal efficiency (BTE) of about 27.75%, brake specific fuel consumption (BSFC) of 0.292 kg/kWh, unburned hydrocarbon emission (uHC) of 91 ppm and NOx emission of 904 ppm in comparison with the diesel for BTE of 28%, BSFC of 0.276 kg/kWh, uHC of 57 ppm and NOx of 855 ppm. Dissolution of Polystyrene (PS) into biodiesel also showed the potential of producing alternative transport fuel. It has been found from the literature that at higher engine speed, increased EPS (Expanded Polystyrene) quantity based biodiesel blends reduces CO, CO2, NOx and smoke emission. EPS-biodiesel fuel blend increases the brake thermal efficiency by 7.8%, specific fuel consumption (SFC) by 7.2% and reduces brake power (Pb) by 3.2%. More study using PS and EPS with other thermoplastics is needed to produce liquid fuel by dissolving them into biodiesel and to assess their suitability as a transport fuel. Furthermore, investigation to find out most suitable W-t-E process for effective recycling of the waste plastics as fuel for internal combustion engines is necessary to reduce environmental pollution and generate revenue which will be addressed in this article.

  11. Self-correcting models driven by seismic strain, moment or energy. Applications to the Italian seismicity

    Science.gov (United States)

    Varini, Elisa; Rotondi, Renata; Basili, Roberto; Barba, Salvatore; Betrò, Bruno

    2013-04-01

    The stress release model (Vere-Jones, 1978) provides a stochastic version of the Reid's elastic-rebound theory, which is commonly accepted as the most feasible physical description of the long-term evolution of the earthquake process. It assumes that the stress X, which governs the state of the system in a region, increases linearly with time at a constant loading rate ? imposed by external tectonic forces until it exceeds the strength of the medium and decreases abruptly generating an earthquake. This hypothesis is formalised by a self-correcting point process with conditional intensity function ?(t | Ht) = exp{α + β[?t - S(t)]}, where Ht is the seismic history up to time t, S(t) is the cumulative stress release due to all the earthquakes up to t and α, β and ? are model parameters. X can be any physical parameter that constitutes a proxy measure of the strength of an earthquake, therefore we propose four possible definitions of X and consequently four versions of the stress release model. Let mw denote the moment magnitude of an earthquake and A be its rupture area. We consider two classical versions of the model: in the former X = 100.75(mw-5.3) is the Benioff strain, in the latter X = 101.5(mw-5.3) is the seismic moment. Then we propose two new versions: the third model is based on seismic energy X = 102.25(mw-5.3)-A, the fourth one on the scaled energy X = 100.75(mw-5.3)-A, as defined by Senatorski (2005, 2012). The rupture area A is evaluated by the Wells and Coppersmith regression with parameters depending on the faulting type of the earthquake. We analyse the Italian historical seismicity on a regional basis by subdividing the Italian territory into eight tectonically-coherent large regions. For each model and region, a fully Bayesian analysis is carried out in order to estimate the posterior distributions of the model parameters. We also deal with the forecast problem by evaluating, for each region, the probability distribution F(t | Hs) of the time t

  12. Mechanical energy losses in plastically deformed and electron plus neutron irradiated high purity single crystalline molybdenum at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Zelada, Griselda I. [Laboratorio de Materiales, Escuela de Ingenieria Electrica, Facultad de Ciencias Exactas, Ingenieria y Agrimensura, Universidad Nacional de Rosario, Avda. Pellegrini 250, 2000 Rosario (Argentina); Lambri, Osvaldo Agustin [Laboratorio de Materiales, Escuela de Ingenieria Electrica, Facultad de Ciencias Exactas, Ingenieria y Agrimensura, Universidad Nacional de Rosario, Avda. Pellegrini 250, 2000 Rosario (Argentina); Instituto de Fisica Rosario - CONICET, Member of the CONICET& #x27; s Research Staff, Avda. Pellegrini 250, 2000 Rosario (Argentina); Bozzano, Patricia B. [Laboratorio de Microscopia Electronica, Unidad de Actividad Materiales, Centro Atomico Constituyentes, Comision Nacional de Energia Atomica, Avda. Gral. Paz 1499, 1650 San Martin (Argentina); Garcia, Jose Angel [Departamento de Fisica Aplicada II, Facultad de Ciencias y Tecnologia, Universidad del Pais Vasco, Apdo. 644, 48080 Bilbao, Pais Vasco (Spain)

    2012-10-15

    Mechanical spectroscopy (MS) and transmission electron microscopy (TEM) studies have been performed in plastically deformed and electron plus neutron irradiated high purity single crystalline molybdenum, oriented for single slip, in order to study the dislocation dynamics in the temperature range within one third of the melting temperature. A damping peak related to the interaction of dislocation lines with both prismatic loops and tangles of dislocations was found. The peak temperature ranges between 900 and 1050 K, for an oscillating frequency of about 1 Hz. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Plastic deformation of nanocrystalline nickel

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    A high-resolution electron microscopy study has uncovered the plastic behavior of accommodating large strains in nanocrystalline (NC) Ni subject to cold rolling at liquid nitrogen temperature. The activation of grain-boundary-mediated-plasticity is evidenced in NC-Ni, including twinning and formation of stacking fault via partial dislocation slips from the grain boundary. The formation and storage of 60? full dislocations are observed inside NC-grains. The grain/twin boundaries act as the barriers of dislocation slips, leading to dislocation pile-up, severe lattice distortion, and formation of sub-grain boundary. The vicinity of grain/twin boundary is where defects preferentially accumulate and likely the favorable place for onset of plastic deformation. The present results indicate the heterogeneous and multiple natures of accommodating plastic strains in NC-grains.

  14. Plastic deformation of nanocrystalline nickel

    Institute of Scientific and Technical Information of China (English)

    WU XiaoLei

    2009-01-01

    A high-resolution electron microscopy study has uncovered the plastic behavior of accommodating large strains in nanocrystalline(NC)Ni subject to cold rolling at liquid nitrogen temperature.The acti vation of grain-boundary-mediated-plasticity is evidenced in NC-Ni,including twinning and formation of stacking fault via partial dislocation slips from the grain boundary.The formation and storage of 60° full dislocations are observed inside NC-grains.The grain/twin boundaries act as the barriers of dislocation slips,leading to dislocation pile-up,severe lattice distortion,and formation of sub-grain boundary.The vicinity of grain/twin boundary is where defects preferentially accumulate and likely the favorable place for onset of plastic deformation.The present results indicate the heterogeneous and multiple natures of accommodating plastic strains in NC-grains.

  15. Severe local strain and the plastic deformation of Guinier-Preston zones in the Al-Ag system revealed by three-dimensional electron tomography

    Energy Technology Data Exchange (ETDEWEB)

    Inoke, Koji [Department of Materials Science and Engineering, Faculty of Engineering, Kyushu University, Room 650, West 4 Building, 744 Motooka, Nishi-ku, Fukuoka 819-0395 (Japan); FEI Company Japan Ltd., 13-34, Kohnan 2, Minato-ku, Tokyo 108-0075 (Japan); Kaneko, Kenji [Department of Materials Science and Engineering, Faculty of Engineering, Kyushu University, Room 650, West 4 Building, 744 Motooka, Nishi-ku, Fukuoka 819-0395 (Japan)]. E-mail: kaneko@zaiko.kyushu-u.ac.jp; Weyland, Matthew [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Midgley, Paul A. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Higashida, Kenji [Department of Materials Science and Engineering, Faculty of Engineering, Kyushu University, Room 650, West 4 Building, 744 Motooka, Nishi-ku, Fukuoka 819-0395 (Japan); Horita, Zenji [Department of Materials Science and Engineering, Faculty of Engineering, Kyushu University, Room 650, West 4 Building, 744 Motooka, Nishi-ku, Fukuoka 819-0395 (Japan)

    2006-06-15

    A severe bulk strain, {gamma} {approx} 1, intentionally introduced into an Al-Ag specimen by the equal-channel angular pressing process caused nearly spherical Guinier-Preston (GP) zones and {l_brace}1 1 1{r_brace} planar {gamma}' phases to be sheared by dislocation motion. Although distortion of GP zones in the Al-Ag system was observed by Nicholson and Nutting in 1961, the three-dimensional morphology or the amount of strain of the deformed GP zones has not been studied to date. The presence of fine-scale distorted (ellipsoidal) GP zones parallel to the {l_brace}1 1 1{r_brace} slip planes is revealed using three-dimensional atomic number, Z-contrast electron tomography. The GP zones lie within localized shear bands, which result from the introduction of the severe strain. The local shear strain, measured at the nanoscale, within the shear band was determined to be 1.83 {+-} 0.272, a value considerably more than previously expected.

  16. Strain energy density-distance criterion for the initiation of stress corrosion cracking of alloy X-750

    Energy Technology Data Exchange (ETDEWEB)

    Hall, M.M. Jr.; Symons, D.M.

    1996-05-01

    A strain energy density-distance criterion was previously developed and used to correlate rising-load K{sub c} initiation data for notched and fatigue precracked specimens of hydrogen precharged Alloy X-750. This criterion, which was developed for hydrogen embrittlement (HE) cracking, is used here to correlate static-load stress corrosion cracking (SCC) initiation times obtained for smooth geometry, notched and fatigue precracked specimens. The onset of SCC crack growth is hypothesized to occur when a critical strain, which is due to environment-enhanced creep, is attained within the specimen interior. For notched and precracked specimens, initiation is shown by analysis to occur at a variable distance from notch and crack tips. The initiation site varies from very near the crack tip, for highly loaded sharp cracks, to a site that is one grain diameter from the notch, for lower loaded, blunt notches. The existence of hydrogen gradients, which are due to strain-induced hydrogen trapping in the strain fields of notch and crack tips, is argued to be controlling the site for initiation of cracking. By considering the sources of the hydrogen, these observations are shown to be consistent with those from the previous HE study, in which the characteristic distance for crack initiation was found to be one grain diameter from the notch tip, independent of notch radius, applied stress intensity factor and hydrogen level.

  17. Effects of Sex, Strain, and Energy Intake on Hallmarks of Aging in Mice

    DEFF Research Database (Denmark)

    Mitchell, Sarah J.; Madrigal-Matute, Julio; Scheibye-Knudsen, Morten

    2016-01-01

    Calorie restriction (CR) is the most robust non-genetic intervention to delay aging. However, there are a number of emerging experimental variables that alter CR responses. We investigated the role of sex, strain, and level of CR on health and survival in mice. CR did not always correlate...

  18. Effect of Plastic Pre-straining on Residual Stress and Composition Profiles in Low-Temperature Surface-Hardened Austenitic Stainless Steel

    Science.gov (United States)

    Bottoli, Federico; Christiansen, Thomas L.; Winther, Grethe; Somers, Marcel A. J.

    2016-08-01

    The present work deals with the evaluation of the residual stress profiles in expanded austenite by applying grazing incidence X-ray diffraction (GI-XRD) combined with successive sublayer removal. Annealed and deformed ( ɛ eq=0.5) samples of stable stainless steel EN 1.4369 were nitrided or nitrocarburized. The residual stress profiles resulting from the thermochemical low-temperature surface treatment were measured. The results indicate high-residual compressive stresses of several GPa's in the nitrided region, while lower-compressive stresses are produced in the carburized case. Plastic deformation in the steel prior to thermochemical treatment has a hardly measurable influence on the nitrogen-rich zone, while it has a measurable effect on the stresses and depth of the carbon-rich zone.

  19. Interfacial interactions between plastic particles in plastics flotation.

    Science.gov (United States)

    Wang, Chong-qing; Wang, Hui; Gu, Guo-hua; Fu, Jian-gang; Lin, Qing-quan; Liu, You-nian

    2015-12-01

    Plastics flotation used for recycling of plastic wastes receives increasing attention for its industrial application. In order to study the mechanism of plastics flotation, the interfacial interactions between plastic particles in flotation system were investigated through calculation of Lifshitz-van der Waals (LW) function, Lewis acid-base (AB) Gibbs function, and the extended Derjaguin-Landau-Verwey-Overbeek potential energy profiles. The results showed that van der Waals force between plastic particles is attraction force in flotation system. The large hydrophobic attraction, caused by the AB Gibbs function, is the dominant interparticle force. Wetting agents present significant effects on the interfacial interactions between plastic particles. It is found that adsorption of wetting agents promotes dispersion of plastic particles and decreases the floatability. Pneumatic flotation may improve the recovery and purity of separated plastics through selective adsorption of wetting agents on plastic surface. The relationships between hydrophobic attraction and surface properties were also examined. It is revealed that there exists a three-order polynomial relationship between the AB Gibbs function and Lewis base component. Our finding provides some insights into mechanism of plastics flotation.

  20. Giant strain-sensitivity of acoustic energy dissipation in solids containing dry and saturated cracks with wavy interfaces

    CERN Document Server

    Zaitsev, V Yu

    2011-01-01

    Mechanisms of acoustic energy dissipation in heterogeneous solids attract much attention in view of their importance for material characterization, nondestructive testing, and geophysics. Due to the progress in measurement techniques in recent years it has been revealed that rocks can demonstrate extremely high strain sensitivity of seismo-acoustic loss. In particular, it has been found that strains of order $10^{-8}$ produced by lunar and solar tides are capable to cause variations in the seismoacoustic decrement on the order of several percents. Some laboratory data (although obtained for higher frequencies) also indicate the presence of very high dissipative nonlinearity. Conventionally discussed dissipation mechanisms (thermoelastic loss in dry solids, Biot and squirt-type loss in fluid-saturated ones) do not suffice to interpret such data. Here, the dissipation at individual cracks is revised taking into account the influence of wavy asperities of their surfaces quite typical of real cracks, which can dr...

  1. Disorientations and work-hardening behaviour during severe plastic deformation

    DEFF Research Database (Denmark)

    Pantleon, Wolfgang

    2012-01-01

    Orientation differences develop during plastic deformation even in grains of originally uniform orientation. The evolution of these disorientations is modelled by dislocation dynamics taking into account different storage mechanisms. The predicted average disorientation angles across different...... types of boundaries are in agreement with experimental data for small and moderate plastic strains. At large plastic strains after severe plastic deformation, saturation of the measured average disorientation angle is observed. This saturation is explained as an immediate consequence of the restriction...

  2. Plastic bronchitis

    National Research Council Canada - National Science Library

    Singhi, Anil Kumar; Vinoth, Bharathi; Kuruvilla, Sarah; Sivakumar, Kothandam

    2015-01-01

    Plastic bronchitis, a rare but serious clinical condition, commonly seen after Fontan surgeries in children, may be a manifestation of suboptimal adaptation to the cavopulmonary circulation with unfavorable hemodynamics...

  3. Advanced Micromechanical Model for Transformation-Induced Plasticity Steels with Application of In-Situ High-Energy X-Ray Diffraction Method

    Science.gov (United States)

    Choi, K. S.; Liu, W. N.; Sun, X.; Khaleel, M. A.; Ren, Y.; Wang, Y. D.

    2008-12-01

    Compared to other advanced high-strength steels, transformation-induced plasticity (TRIP) steels exhibit better ductility at a given strength level and can be used to produce complicated automotive parts. This enhanced formability comes from the transformation of retained austenite to martensite during plastic deformation. In this study, as a first step in predicting optimum processing parameters in TRIP steel productions, a micromechanical finite element model is developed based on the actual microstructure of a TRIP 800 steel. The method uses a microstructure-based representative volume element (RVE) to capture the complex deformation behavior of TRIP steels. The mechanical properties of the constituent phases of the TRIP 800 steel and the fitting parameters describing the martensite transformation kinetics are determined using the synchrotron-based in-situ high-energy X-ray diffraction (HEXRD) experiments performed under a uniaxial tensile deformation. The experimental results suggest that the HEXRD technique provides a powerful tool for characterizing the phase transformation behavior and the microstress developed due to the phase-to-phase interaction of TRIP steels during deformation. The computational results suggest that the response of the RVE well represents the overall macroscopic behavior of the TRIP 800 steel under deformation. The methodology described in this study may be extended for studying the effects of the various processing parameters on the macroscopic behaviors of TRIP steels.

  4. Metamorphosis of strain/stress on optical band gap energy of ZAO thin films via manipulation of thermal annealing process

    Energy Technology Data Exchange (ETDEWEB)

    Malek, M.F., E-mail: firz_solarzelle@yahoo.com [NANO-ElecTronic Centre (NET), Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor (Malaysia); NANO-SciTech Centre (NST), Institute of Science (IOS), Universiti Teknologi MARA UiTM, 40450 Shah Alam, Selangor (Malaysia); Mamat, M.H. [NANO-ElecTronic Centre (NET), Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor (Malaysia); Musa, M.Z. [NANO-ElecTronic Centre (NET), Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor (Malaysia); Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM) Pulau Pinang, Jalan Permatang Pauh, 13500 Permatang Pauh, Pulau Pinang (Malaysia); Soga, T. [Department of Frontier Materials, Nagoya Institute of Technology (NITech), Nagoya 466-8555 (Japan); Rahman, S.A. [Low Dimensional Materials Research Centre (LDMRC), Department of Physics, Faculty of Science, Universiti Malaya (UM), 50603 Kuala Lumpur (Malaysia); Alrokayan, Salman A.H.; Khan, Haseeb A. [Department of Biochemistry, College of Science, King Saud University (KSU), Riyadh 11451 (Saudi Arabia); Rusop, M. [NANO-ElecTronic Centre (NET), Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor (Malaysia); NANO-SciTech Centre (NST), Institute of Science (IOS), Universiti Teknologi MARA UiTM, 40450 Shah Alam, Selangor (Malaysia)

    2015-04-15

    We report on the growth of Al-doped ZnO (ZAO) thin films prepared by the sol–gel technique associated with dip-coating onto Corning 7740 glass substrates. The influence of varying thermal annealing (T{sub a}) temperature on crystallisation behaviour, optical and electrical properties of ZAO films has been systematically investigated. All films are polycrystalline with a hexagonal wurtzite structure with a preferential orientation according to the direction 〈0 0 2〉. The metamorphosis of strain/stress effects in ZAO thin films has been investigated using X-ray diffraction. The as growth films have a large compressive stress of 0.55 GPa, which relaxed to 0.25 GPa as the T{sub a} was increased to 500 °C. Optical parameters such as optical transmittance, absorption coefficient, refractive index and optical band gap energy have been studied and discussed with respect to T{sub a}. All films exhibit a transmittance above 80–90% along the visible–NIR range up to 1500 nm and a sharp absorption onset below 400 nm corresponding to the fundamental absorption edge of ZnO. Experimental results show that the tensile stress in the films reveals an incline pattern with the optical band gap energy, while the compressive stress shows opposite relation. - Highlights: • Minimum stress of highly c-axis oriented ZAO was grown at suitable T{sub a} temperature. • The ZAO crystal orientation was influenced by strain/stress of the film. • Minimum stress/strain of ZAO film leads to lower defects. • Bandgap and defects were closely intertwined with strain/stress. • We report additional optical and electrical properties based on T{sub a} temperature.

  5. Plastic Fishes

    CERN Multimedia

    Trettnak, Wolfgang

    2015-01-01

    In terms of weight, the plastic pollution in the world’s oceans is estimated to be around 300,000 tonnes. This plastic comes from both land-based and ocean-based sources. A lecture at CERN by chemist Wolfgang Trettnak addressed this issue and highlighted the role of art in raising people’s awareness. The slideshow below gives you a taste of the artworks by Wolfgang Trettnak and Margarita Cimadevila.

  6. Plastic Bridge

    Institute of Scientific and Technical Information of China (English)

    履之

    1994-01-01

    Already ubiquitous in homes and cars, plastic is now appearing inbridges. An academic-industrial consortium based at the University ofCalifornia in San Diego is launching a three-year research program aimed atdeveloping the world’s first plastic highway bridge, a 450-foot span madeentirely from glass-,carbon,and polymer-fiber-reinforced composite mate-rials, the stuff of military aircraft. It will cross Interstate 5 to connect thetwo sides of the school’s campus.

  7. New plastic recycling technology

    Science.gov (United States)

    Greater than 60% of the total plastic content of municipal solid waste is comprised of polyolefins (high-density, low-density, and linear polyethylene and polypropylene. Polyethylene (PE) is the largest-volume component but presents a challenge due to the absence of low-energy de...

  8. SPRING Project on Mechanical Energy on Demand from High Strain Actuators

    Science.gov (United States)

    2009-09-02

    the U pol term in equation (4) is known to be ‘made of’ two parts: −U pol = −U polel +U pold , where U polel represents the magnitude of the potential...energy of the electron in the polarization field and U pold represents the energy required to create this polarization (‘deformation energy’); with the...optimal polarization, U pold = U polel /2. Both energy functionals (1) and (4) assume that the electron and hole energies are measured from the band

  9. GREEN PLASTIC: A NEW PLASTIC FOR PACKAGING

    OpenAIRE

    Mr. Pankaj Kumar*, Sonia

    2016-01-01

    This paper gives a brief idea about a new type of plastic called as bio-plastic or green plastic. Plastic is used as a packaging material for various products, but this plastic is made up of non renewable raw materials. There are various disadvantages of using conventional plastic like littering, CO2 production, non-degradable in nature etc. To overcome these problems a new type of plastic is discovered called bio-plastic or green plastic. Bio-plastic is made from renewable resources and also...

  10. 含氧塑料薄膜在清洁能源电池中的应用%APPLICATION OF FLUORINE CONTAINING PLASTIC FILM IN CLEAN ENERGY BATTERY

    Institute of Scientific and Technical Information of China (English)

    苑会林

    2011-01-01

    Fluoride plastic film in clean energy battery applications was briefly reviewed. The application and production method of PVDF membrane used in lithium battery, perfluorinated sulfonic acid ion-exchange membrane used in fuel cells and wind power storage vanadium batteries were introduced respectively. The status of author's latest research results in related fields was also introduced.%简述了含氟塑料薄膜在清洁能源电池中的应用.分别论述了用于锂电池的PVDF隔离膜,以及用于燃料电池、风力发电蓄能电池钒电池的全氟磺酸离子膜的应用与制作方法.介绍了笔者在相关领域的最新研究成果.

  11. Low temperature creep plasticity

    Directory of Open Access Journals (Sweden)

    Michael E. Kassner

    2014-07-01

    Full Text Available The creep behavior of crystalline materials at low temperatures (T < 0.3Tm is discussed. In particular, the phenomenological relationships that describe primary creep are reviewed and analyzed. A discussion of the activation energy for creep at T < 0.3Tm is discussed in terms of the context of higher temperature activation energy. The basic mechanism(s of low temperature creep plasticity are discussed, as well.

  12. A Modified Method for Calculating Notch-Root Stresses and Strains under Multiaxial Loading

    Directory of Open Access Journals (Sweden)

    Liu Jianhui

    2014-04-01

    Full Text Available Based on the analysis of notch-root stresses and strains in bodies subjected to multiaxial loading, a quantitative relationship between Neuber rule and the equivalent strain energy density method is found. In the case of elastic range, both Neuber rule and the equivalent strain energy density method get the same estimation of the local stresses and strains. Whereas in the case of elastic-plastic range, Neuber rule generally overestimates the notch-root stresses and strains and the equivalent strain energy density method tends to underestimate the notch-root stresses and strains. A modified method is presented considering the material constants of elastic-plastic Poisson's ratio, elastic modulus, shear elastic modulus, and yield stress. The essence of the modified model is to add a modified coefficient to Neuber rule, which makes the calculated results tend to be more precise and reveals its energy meaning. This approach considers the elastic-plastic properties of the material itself and avoids the blindness of selecting coefficient values. Finally the calculation results using the modified model are validated with the experimental data.

  13. High-energy transmission Laue micro-beam X-ray diffraction: a probe for intra-granular lattice orientation and elastic strain in thicker samples.

    Science.gov (United States)

    Hofmann, Felix; Song, Xu; Abbey, Brian; Jun, Tea-Sung; Korsunsky, Alexander M

    2012-05-01

    An understanding of the mechanical response of modern engineering alloys to complex loading conditions is essential for the design of load-bearing components in high-performance safety-critical aerospace applications. A detailed knowledge of how material behaviour is modified by fatigue and the ability to predict failure reliably are vital for enhanced component performance. Unlike macroscopic bulk properties (e.g. stiffness, yield stress, etc.) that depend on the average behaviour of many grains, material failure is governed by `weakest link'-type mechanisms. It is strongly dependent on the anisotropic single-crystal elastic-plastic behaviour, local morphology and microstructure, and grain-to-grain interactions. For the development and validation of models that capture these complex phenomena, the ability to probe deformation behaviour at the micro-scale is key. The diffraction of highly penetrating synchrotron X-rays is well suited to this purpose and micro-beam Laue diffraction is a particularly powerful tool that has emerged in recent years. Typically it uses photon energies of 5-25 keV, limiting penetration into the material, so that only thin samples or near-surface regions can be studied. In this paper the development of high-energy transmission Laue (HETL) micro-beam X-ray diffraction is described, extending the micro-beam Laue technique to significantly higher photon energies (50-150 keV). It allows the probing of thicker sample sections, with the potential for grain-level characterization of real engineering components. The new HETL technique is used to study the deformation behaviour of individual grains in a large-grained polycrystalline nickel sample during in situ tensile loading. Refinement of the Laue diffraction patterns yields lattice orientations and qualitative information about elastic strains. After deformation, bands of high lattice misorientation can be identified in the sample. Orientation spread within individual scattering volumes is

  14. Thermal image analysis of plastic deformation and fracture behavior by a thermo-video measurement system

    Science.gov (United States)

    Ohbuchi, Yoshifumi; Sakamoto, Hidetoshi; Nagatomo, Nobuaki

    2016-12-01

    The visualization of the plastic region and the measurement of its size are necessary and indispensable to evaluate the deformation and fracture behavior of a material. In order to evaluate the plastic deformation and fracture behavior in a structural member with some flaws, the authors paid attention to the surface temperature which is generated by plastic strain energy. The visualization of the plastic deformation was developed by analyzing the relationship between the extension of the plastic deformation range and the surface temperature distribution, which was obtained by an infrared thermo-video system. Furthermore, FEM elasto-plastic analysis was carried out with the experiment, and the effectiveness of this non-contact measurement system of the plastic deformation and fracture process by a thermography system was discussed. The evaluation method using an infrared imaging device proposed in this research has a feature which does not exist in the current evaluation method, i.e. the heat distribution on the surface of the material has been measured widely by noncontact at 2D at high speed. The new measuring technique proposed here can measure the macroscopic plastic deformation distribution on the material surface widely and precisely as a 2D image, and at high speed, by calculation from the heat generation and the heat propagation distribution.

  15. RESEARCH FOR THE STRAIN ENERGY RELEASE RATE OF COMPLEX CRACKS BY USING POINT-BY-POINT CLOSED EXTRAPOLATION APPROACH

    Institute of Scientific and Technical Information of China (English)

    郭茂林; 孟庆元; 王彪

    2003-01-01

    A new extrapolation approach was proposed to calculate the strain energy release rates of complex cracks. The point-by-point closed method was used to calculate the closed energy, thus the disadvantage of self inconsistency in some published papers can be avoided. The disadvantage is that the closed energy is repeatedly calculated: when closed nodal number along radial direction is more than two, the displacement of nodes behind the crack tip that is multiplied by nodal forces, the closed energy has been calculated and the crack surfaces have been closed, and that closed energy of middle point is calculated repeatedly. A DCB ( double cantilever beam) specimen was calculated and compared with other theoretical results, it is shown that a better coincidence is obtained. In addition the same results are also obtained for compact tension specimen, three point bend specimen and single edge cracked specinen. In comparison with theoretical results, the error can be limited within 1 per cent. This method can be extended to analyze the fracture of composite laminates with various delamination cracks.

  16. Phyllosphere yeasts rapidly break down biodegradable plastics.

    Science.gov (United States)

    Kitamoto, Hiroko K; Shinozaki, Yukiko; Cao, Xiao-Hong; Morita, Tomotake; Konishi, Masaaki; Tago, Kanako; Kajiwara, Hideyuki; Koitabashi, Motoo; Yoshida, Shigenobu; Watanabe, Takashi; Sameshima-Yamashita, Yuka; Nakajima-Kambe, Toshiaki; Tsushima, Seiya

    2011-11-29

    The use of biodegradable plastics can reduce the accumulation of environmentally persistent plastic wastes. The rate of degradation of biodegradable plastics depends on environmental conditions and is highly variable. Techniques for achieving more consistent degradation are needed. However, only a few microorganisms involved in the degradation process have been isolated so far from the environment. Here, we show that Pseudozyma spp. yeasts, which are common in the phyllosphere and are easily isolated from plant surfaces, displayed strong degradation activity on films made from poly-butylene succinate or poly-butylene succinate-co-adipate. Strains of P. antarctica isolated from leaves and husks of paddy rice displayed strong degradation activity on these films at 30°C. The type strain, P. antarctica JCM 10317, and Pseudozyma spp. strains from phyllosphere secreted a biodegradable plastic-degrading enzyme with a molecular mass of about 22 kDa. Reliable source of biodegradable plastic-degrading microorganisms are now in our hands.

  17. Strain Limits within the Scope of the Integrity Assessment of Piping Systems

    Energy Technology Data Exchange (ETDEWEB)

    Mutz, Alexander [EnBW, Durlacher Allee 93, Karlsruhe 76131 (Germany)

    2008-07-01

    Allowable stresses in nuclear power plant piping resulting from loading conditions to be considered in Germany are determined on the basis of the German Safety Standards of the Nuclear Safety Standards Commission, KTA. The limitation of the different stress categories within the analysis of the mechanical behaviour is based on a linear elastic material behaviour. Because of the ductile material used in high energy nuclear piping, a more realistic assessment can be performed on the basis of allowable strains using elastic plastic material behaviour. In the present work comparison between the analysis of piping systems considering the elastic material model and the actual elastic plastic material behaviour is performed. The possibilities of allocating plastic strains to calculated elastic stresses is discussed. A parametric study on straight pipes with the actual elastic plastic material model under pure bending is the basis of deriving the elastic plastic strains for the calculated elastic stresses. Strain limits are suggested which correspond to the different stress categories. The aim is to utilize the deformation possibilities of ductile materials used in German nuclear piping and the allocation of maximum strains to different load categories. Keywords: strain limit, ductile material, stress category. (author)

  18. Modifications to the Method of Modal Strain Energy for Improved Estimates of Loss Factors for Damped Structures

    Directory of Open Access Journals (Sweden)

    Peter J. Torvik

    2007-01-01

    Full Text Available The method of Modal Strain Energy (MSE enables predictions of modal loss factors for vibrating systems from finite element analyses without evaluation of a complex-valued frequency response or a complex-valued frequency. While the method is simple, some error results; especially if the dissipative material has the high loss factor characteristic of materials added to increase system damping. Several methods for reducing this error through modifications to MSE have been suggested. In this work, the exact loss factor for a simple mechanical system is found. The method of Modal Strain Energy (MSE is then used to find the loss factor for that prototype system and errors are evaluated in terms of system parameters. Comparisons are also made to predictions with several modifications to MSE. A modification due to Rongong is found to provide significant improvement. The use of this modification together with MSE is shown to lead to lower and upper bounds for the system loss factor. As the prototype system is shown to be mechanically equivalent to constrained layer damping configurations, the findings are applicable to the analysis and design of optimized sandwich beams, plates, and damping tapes. Results are given for beams and plates with constrained layer treatments.

  19. Plastic condoms.

    Science.gov (United States)

    1968-01-01

    Only simple equipment, simple technology and low initial capital investment are needed in their manufacture. The condoms can be made by people who were previously unskilled or only semi-skilled workers. Plastic condoms differ from those made of latex rubber in that the nature of the plastic film allows unlimited shelf-life. Also, the plastic has a higher degree of lubricity than latex rubber; if there is a demand for extra lubrication in a particular market, this can be provided. Because the plastic is inert, these condoms need not be packaged in hermetically sealed containers. All these attributes make it possible to put these condoms on the distributors' shelves in developing countries competitively with rubber condoms. The shape of the plastic condom is based on that of the lamb caecum, which has long been used as luxury-type condom. The plastic condom is made from plastic film (ethylene ethyl acrilate) of 0.001 inch (0.0254 mm.) thickness. In addition, a rubber ring is provided and sealed into the base of the condom for retention during coitus. The advantage of the plastic condom design and the equipment on which it is made is that production can be carried out either in labour-intensive economy or with varying degrees of mechanization and automation. The uniform, finished condom if made using previously untrained workers. Training of workers can be done in a matter of hours on the two machines which are needed to produce and test the condoms. The plastic film is provided on a double wound roll, and condom blanks are prepared by means of a heat-sealing die on the stamping machine. The rubber rings are united to the condom blanks on an assembly machine, which consists of a mandrel and heat-sealing equipment to seal the rubber ring to the base of the condom. Built into the assembly machine is a simple air-testing apparatus that can detect the smallest pinhole flaw in a condom. The manufacturing process is completed by unravelling the condom from the assembly

  20. Genetic diversity in the plasticity zone and the presence of the chlamydial plasmid differentiates Chlamydia pecorum strains from pigs, sheep, cattle, and koalas.

    Science.gov (United States)

    Jelocnik, Martina; Bachmann, Nathan L; Kaltenboeck, Bernhard; Waugh, Courtney; Woolford, Lucy; Speight, K Natasha; Gillett, Amber; Higgins, Damien P; Flanagan, Cheyne; Myers, Garry S A; Timms, Peter; Polkinghorne, Adam

    2015-11-04

    Chlamydia pecorum is a globally recognised pathogen of livestock and koalas. To date, comparative genomics of C. pecorum strains from sheep, cattle and koalas has revealed that only single nucleotide polymorphisms (SNPs) and a limited number of pseudogenes appear to contribute to the genetic diversity of this pathogen. No chlamydial plasmid has been detected in these strains despite its ubiquitous presence in almost all other chlamydial species. Genomic analyses have not previously included C. pecorum from porcine hosts. We sequenced the genome of three C. pecorum isolates from pigs with differing pathologies in order to re-evaluate the genetic differences and to update the phylogenetic relationships between C. pecorum from each of the hosts. Whole genome sequences for the three porcine C. pecorum isolates (L1, L17 and L71) were acquired using C. pecorum-specific sequence capture probes with culture-independent methods, and assembled in CLC Genomics Workbench. The pairwise comparative genomic analyses of 16 pig, sheep, cattle and koala C. pecorum genomes were performed using several bioinformatics platforms, while the phylogenetic analyses of the core C. pecorum genomes were performed with predicted recombination regions removed. Following the detection of a C. pecorum plasmid, a newly developed C. pecorum-specific plasmid PCR screening assay was used to evaluate the plasmid distribution in 227 C. pecorum samples from pig, sheep, cattle and koala hosts. Three porcine C. pecorum genomes were sequenced using C. pecorum-specific sequence capture probes with culture-independent methods. Comparative genomics of the newly sequenced porcine C. pecorum genomes revealed an increased average number of SNP differences (~11 500) between porcine and sheep, cattle, and koala C. pecorum strains, compared to previous C. pecorum genome analyses. We also identified a third copy of the chlamydial cytotoxin gene, found only in porcine C. pecorum isolates. Phylogenetic analyses

  1. A finite element framework for distortion gradient plasticity with applications to bending of thin foils

    DEFF Research Database (Denmark)

    Martínez Pañeda, Emilio; Niordson, Christian Frithiof; Bardella, Lorenzo

    2016-01-01

    A novel general purpose Finite Element framework is presented to study small-scale metal plasticity. A distinct feature of the adopted distortion gradient plasticity formulation, with respect to strain gradient plasticity theories, is the constitutive inclusion of the plastic spin, as proposed...... by Gurtin (2004) through the prescription of a free energy dependent on Nye’s dislocation density tensor. The proposed numerical scheme is developed by following and extending the mathematical principles established by Fleck and Willis (2009). The modeling of thin metallic foils under bending reveals......, if either viscoplasticity or isotropic hardening are included in the model. In order to study the effect of dissipative higher-order stresses, the mechanical response under non-proportional loading is also investigated....

  2. Plastic Bronchitis.

    Science.gov (United States)

    Rubin, Bruce K

    2016-09-01

    Plastic bronchitis is an uncommon and probably underrecognized disorder, diagnosed by the expectoration or bronchoscopic removal of firm, cohesive, branching casts. It should not be confused with purulent mucous plugging of the airway as seen in patients with cystic fibrosis or bronchiectasis. Few medications have been shown to be effective and some are now recognized as potentially harmful. Current research directions in plastic bronchitis research include understanding the genetics of lymphatic development and maldevelopment, determining how abnormal lymphatic malformations contribute to cast formation, and developing new treatments. Copyright © 2016 Elsevier Inc. All rights reserved.

  3. Candidate genes in ocular dominance plasticity

    NARCIS (Netherlands)

    M.L. Rietman; J.-P. Sommeijer; C.N. Levelt; J.A. Heimel; A.B. Brussaard; J.G.G. Borst; Y. Elgersma; N. Galjart; G.T. van der Horst; C.M. Pennartz; A.B. Smit; B.M. Spruijt; M. Verhage; C.I. de Zeeuw

    2012-01-01

    Many studies have been devoted to the identification of genes involved in experience-dependent plasticity in the visual cortex. To discover new candidate genes, we have reexamined data from one such study on ocular dominance (OD) plasticity in recombinant inbred BXD mouse strains. We have correlated

  4. Plastics recycling: challenges and opportunities.

    Science.gov (United States)

    Hopewell, Jefferson; Dvorak, Robert; Kosior, Edward

    2009-07-27

    Plastics are inexpensive, lightweight and durable materials, which can readily be moulded into a variety of products that find use in a wide range of applications. As a consequence, the production of plastics has increased markedly over the last 60 years. However, current levels of their usage and disposal generate several environmental problems. Around 4 per cent of world oil and gas production, a non-renewable resource, is used as feedstock for plastics and a further 3-4% is expended to provide energy for their manufacture. A major portion of plastic produced each year is used to make disposable items of packaging or other short-lived products that are discarded within a year of manufacture. These two observations alone indicate that our current use of plastics is not sustainable. In addition, because of the durability of the polymers involved, substantial quantities of discarded end-of-life plastics are accumulating as debris in landfills and in natural habitats worldwide. Recycling is one of the most important actions currently available to reduce these impacts and represents one of the most dynamic areas in the plastics industry today. Recycling provides opportunities to reduce oil usage, carbon dioxide emissions and the quantities of waste requiring disposal. Here, we briefly set recycling into context against other waste-reduction strategies, namely reduction in material use through downgauging or product reuse, the use of alternative biodegradable materials and energy recovery as fuel. While plastics have been recycled since the 1970s, the quantities that are recycled vary geographically, according to plastic type and application. Recycling of packaging materials has seen rapid expansion over the last decades in a number of countries. Advances in technologies and systems for the collection, sorting and reprocessing of recyclable plastics are creating new opportunities for recycling, and with the combined actions of the public, industry and governments it

  5. Plastics recycling: challenges and opportunities

    Science.gov (United States)

    Hopewell, Jefferson; Dvorak, Robert; Kosior, Edward

    2009-01-01

    Plastics are inexpensive, lightweight and durable materials, which can readily be moulded into a variety of products that find use in a wide range of applications. As a consequence, the production of plastics has increased markedly over the last 60 years. However, current levels of their usage and disposal generate several environmental problems. Around 4 per cent of world oil and gas production, a non-renewable resource, is used as feedstock for plastics and a further 3–4% is expended to provide energy for their manufacture. A major portion of plastic produced each year is used to make disposable items of packaging or other short-lived products that are discarded within a year of manufacture. These two observations alone indicate that our current use of plastics is not sustainable. In addition, because of the durability of the polymers involved, substantial quantities of discarded end-of-life plastics are accumulating as debris in landfills and in natural habitats worldwide. Recycling is one of the most important actions currently available to reduce these impacts and represents one of the most dynamic areas in the plastics industry today. Recycling provides opportunities to reduce oil usage, carbon dioxide emissions and the quantities of waste requiring disposal. Here, we briefly set recycling into context against other waste-reduction strategies, namely reduction in material use through downgauging or product reuse, the use of alternative biodegradable materials and energy recovery as fuel. While plastics have been recycled since the 1970s, the quantities that are recycled vary geographically, according to plastic type and application. Recycling of packaging materials has seen rapid expansion over the last decades in a number of countries. Advances in technologies and systems for the collection, sorting and reprocessing of recyclable plastics are creating new opportunities for recycling, and with the combined actions of the public, industry and governments it

  6. Mixed plastics recycling technology

    CERN Document Server

    Hegberg, Bruce

    1995-01-01

    Presents an overview of mixed plastics recycling technology. In addition, it characterizes mixed plastics wastes and describes collection methods, costs, and markets for reprocessed plastics products.

  7. Fracture toughness of shape memory alloy actuators: effect of transformation-induced plasticity

    Science.gov (United States)

    Jape, Sameer; Solomou, Alexandros; Baxevanis, Theocharis; Lagoudas, Dimitris C.

    2016-04-01

    Numerical analysis of static cracks in a plane strain center-cracked infinite medium shape memory alloy (SMA) panel subjected to cyclic thermal variations and a constant mechanical load is conducted using the finite element method. In solid-state SMA actuators, permanent changes in the material's microstructure in the form of dislocations are caused during cyclic thermomechanical loading, leading to macroscopic irreversible strains, known as transformation induced plastic (TRIP) strains. The influence of these accumulated TRIP strains on mechanical fields close to the crack tip is investigated in the present paper. Virtual crack growth technique (VCCT) in ABAQUS FEA suite is employed to calculate the crack tip energy release rate and crack is assumed to be stationary (or static) so that the crack tip energy release rate never reaches the material specific critical value. Increase in the crack tip energy release rate is observed during cooling and its relationship with accumulation of TRIP due to cyclic transformation is studied.

  8. Plastic fish

    CERN Multimedia

    Antonella Del Rosso

    2015-01-01

    In terms of weight, the plastic pollution in the world’s oceans is estimated to be around 300,000 tonnes. This plastic comes from both land-based and ocean-based sources. A lecture at CERN by chemist Wolfgang Trettnak addressed this issue and highlighted the role of art in raising people’s awareness.   Artwork by Wolfgang Trettnak. Packaging materials, consumer goods (shoes, kids’ toys, etc.), leftovers from fishing and aquaculture activities… our oceans and beaches are full of plastic litter. Most of the debris from beaches is plastic bottles. “PET bottles have high durability and stability,” explains Wolfgang Trettnak, a chemist by education and artist from Austria, who gave a lecture on this topic organised by the Staff Association at CERN on 26 May. “PET degrades very slowly and the estimated lifetime of a bottle is 450 years.” In addition to the beach litter accumulated from human use, rivers bring several ki...

  9. Plastic zonnecellen

    NARCIS (Netherlands)

    Roggen, Marjolein

    1998-01-01

    De zonnecel van de toekomst is in de maak. Onderzoekers van uiteenlopend pluimage werken eendrachtig aan een plastic zonnecel. De basis is technisch gelegd met een optimale, door invallend licht veroorzaakte, vorming van ladingdragers binnen een composiet van polymeren en buckyballs. Nu is het zaak

  10. Exposure of clinical MRSA heterogeneous strains to β-lactams redirects metabolism to optimize energy production through the TCA cycle.

    Directory of Open Access Journals (Sweden)

    Mignon A Keaton

    adaptation that HeR-MRSA clinical strains undergo when exposed to β-lactam pressure, indicating that the energy production is redirected to supply the cell wall synthesis/metabolism, which in turn contributes to the survival response in the presence of β-lactam antibiotics.

  11. Finite strain effects in piezoelectric energy harvesters under direct and parametric excitations

    Science.gov (United States)

    Mam, Koliann; Peigney, Michaël; Siegert, Dominique

    2017-02-01

    This paper addresses the dynamic behavior of piezoelectric cantilevers under base excitations. Such devices are frequently used for applications in energy harvesting. An Euler-Bernoulli model that accounts for large-deflection effects and piezoelectric nonlinearities is proposed. Closed-form expressions of the frequency response are derived, both for direct excitation (i.e. with a base acceleration transverse to the axis of the cantilever) and parametric excitation (i.e. with a base acceleration along the axis of the cantilever). Experimental results are reported and used for assessing the validity of the proposed model. Building on the model presented, some critical issues related to energy-harvesting are investigated, such as the influence of nonlinearities on the optimal load resistance, the limits of validity of linear models, and hysteresis effects in the electrical power. The efficiency of direct and parametric excitation is also compared in detail.

  12. Formation Energies of Native Point Defects in Strained-Layer Superlattices (Postprint)

    Science.gov (United States)

    2017-06-05

    1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law , no...POSTPRINT) 5a. CONTRACT NUMBER FA8650-11-D-5800-0008 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62102F 6. AUTHOR(S) 1) Zhi-Gang Yu...native point defect (NPD) formation energies and absence of mid-gap levels. In this Letter we use first- principles calculations to study the formation

  13. Energetic reuse: the use of energy from organic material from urban waste for plastics recycling; Reaproveitamento energetico: uso de energia proveniente de material organico dos residuos urbanos para reciclar plasticos

    Energy Technology Data Exchange (ETDEWEB)

    Carneiro, Priscila Alves; Rocha, Carlos Roberto [Universidade Federal de Itajuba (EXCEN/UNIFEI), MG (Brazil). Centro de Excelencia em Eficiencia Energetica

    2008-07-01

    The population growth and the elevation of the purchasing status due to economic development impel the gradual increase of residues produced a year. The discarding of these residues represents a great economic and environmental challenge, mainly because of discarded plastic concentration with no energetic and economic use, a also because of the organic material that, after decomposing, produces methane, one of the most responsible for global heating when in contact with atmosphere with no control. The recycling of plastic residues is a solution to minimize its discard and to guarantee an environmental improvement for saving raw matter, however the high consumption of energy endears the process, making it difficult its economic viability. This takes the search of new alternatives for attainment of low cost energy. In the problem of discard of the organic matter it can be the solution for the recycling of these residues. The decomposition of the organic matter produces fuel (biogas) useful as power plant for the generation of necessary electricity to the recycling process. The present study analyses an alternative to recycle plastic residues, after being consumed, in some places for discarding and using energy from biogas produced in landfills or biodigestors. Initially it was carried through a data-collecting and analysis of the physical composition of the residues, indispensable to the development of the study, which allowed to daily find the average percentage of plastics (12,9%) and organic matter (41,9%) made use by the involved population. On the basis of the data of organic matter the determination in such a way of the potential of generation of the biogas as of the electric power 'recycled' was possible to leave of that they would be discarded without any use. Data-collecting on equipment used in the plastic recycling had been essential for attainment of the necessary average energy demand to the process in such a way not only for soft plastic and

  14. Quasi-static responses and variational principles in gradient plasticity

    Science.gov (United States)

    Nguyen, Quoc-Son

    2016-12-01

    Gradient models have been much discussed in the literature for the study of time-dependent or time-independent processes such as visco-plasticity, plasticity and damage. This paper is devoted to the theory of Standard Gradient Plasticity at small strain. A general and consistent mathematical description available for common time-independent behaviours is presented. Our attention is focussed on the derivation of general results such as the description of the governing equations for the global response and the derivation of related variational principles in terms of the energy and the dissipation potentials. It is shown that the quasi-static response under a loading path is a solution of an evolution variational inequality as in classical plasticity. The rate problem and the rate minimum principle are revisited. A time-discretization by the implicit scheme of the evolution equation leads to the increment problem. An increment of the response associated with a load increment is a solution of a variational inequality and satisfies also a minimum principle if the energy potential is convex. The increment minimum principle deals with stables solutions of the variational inequality. Some numerical methods are discussed in view of the numerical simulation of the quasi-static response.

  15. Plastic Surgery Statistics

    Science.gov (United States)

    ... PSN PSEN GRAFT Contact Us News Plastic Surgery Statistics Plastic surgery procedural statistics from the American Society of Plastic Surgeons. Statistics by Year Print 2016 Plastic Surgery Statistics 2015 ...

  16. The Development of High Efficiency and Energy Saving Three-row-middle-envelope Plastic Bag Making Machine%高效节能三列中封全自动制袋机开发

    Institute of Scientific and Technical Information of China (English)

    彭杭; 张建桃; 张铁民; 辛少荣; 彭泽光

    2014-01-01

    In order to increase productivity of flexible packaging plastic bag making machine ,save energy and reduce emission ,a three-row bag making technical method is proposed .According the optimized design of the institutions and electrical control ,a high efficiency and energy saving three-row-middle-envelope plastic bag making machine is developed in this paper , which running speed reaches 36 000 p/h and yield exceed 99 .6%.Compared with the double-row-middle-envelope plastic bag making machine ,the three-row-middle-en-velope plastic bag making machine not only increases the bag making efficiency 50%,but also reduces energy consumption by 33 %.%针对塑料软包装袋制袋机需不断提高制袋效率、节能减排的要求,提出采用三列制袋模式提高制袋效率和降低产品能耗的技术方案,通过机构和电气控制优化设计,研制出三列中封全自动制袋机,其制袋能力达36000袋/h,成品率超过99.6%,与双列中封制袋机相比,制袋速率提高50%,单位产品能耗降低33%。

  17. Effects of applied stress and plastic strain on. gamma. r reversible. epsilon. martensitic transformation in high Mn alloy polyctystals. Ko Mn tetsu gokin takessho ni okeru. gamma. r reversible. epsilon. martensite hentai ni oyobosu gairyoku to hizumi no eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Tomota, Y.; Piao, M.; Hasunuma, T.; Kimura, Y. (Ibaraki Univ., Ibaraki (Japan))

    1990-06-20

    The influences of applied stress and plastic strain on a transformation austenite ({gamma}) to hcp martensite ({epsilon}) were studied on Fe-16wt%Mn, Fe-24wt%Mn, and Fe-24%Mn-6%Si alloy, and a transformation mechanism and a shape memory phenomenon were more deeply examined. As the quenching structure of three kinds of the alloys consists of two phases of {gamma} and {epsilon}, the specimens were cooled after heated above the A {sub f} temperature to keep {gamma} single phase, and then the tensile tests were carried out. Positive temperature dependence was found under the 0.2% proof stress due to stress-induced {gamma}{yields} {epsilon} transformation in each of Fe-Mn alloy and Fe-24%Mn-6%Si alloy. When {gamma} phase of Fe-24%Mn alloy stabilized due to cyclic transformation was stretched at room temperature, the yield stress was remarkably lowered by the stress-induced {gamma}{r arrow}{epsilon} transformation. When the specimens were stretched at 523K under stress which was larger than the yield strength and then cooled, the elongation along the applied stress direction due to martensitic tranformation was recognized. A shape recovery was remarkable in Si content alloys. 22 refs., 5 figs.

  18. PARAMETRIC VARIATIONAL PRINCIPLE BASED ELASTIC-PLASTIC ANALYSIS OF COSSERAT CONTINUUM

    Institute of Scientific and Technical Information of China (English)

    Zhang Hongwu; Wang Hui; Chen Biaosong; Xie Zhaoqian

    2007-01-01

    A new algorithm is developed based on the parametric variational principle for elastic-plastic analysis of Cosserat continuum. The governing equations of the classic elastic-plastic problem are regularized by adding rotational degrees of freedom to the conventional translational degrees of freedom in conventional continuum mechanics. The parametric potential energy principle of the Cosserat theory is developed, from which the finite element formulation of the Cosserat theory and the corresponding parametric quadratic programming model are constructed. Strain localization problems are computed and the mesh independent results are obtained.

  19. Plasticity size effects in voided crystals

    DEFF Research Database (Denmark)

    Hussein, M. I.; Borg, Ulrik; Niordson, Christian Frithiof;

    The shear and equi-biaxial straining responses of periodic voided single crystals are analysed using discrete dislocation plasticity and a continuum strain gradient crystal plasticity theory. In the discrete dislocation formulation the dislocations are all of edge character and are modelled as line...... predictions of the two formulations for all crystal types and void volume fractions considered when the material length scale in the non-local plasticity model chosen to be $0.325\\mu m$ (around ten times the slip plane spacing in the discrete dislocation models)....

  20. FINITE DEFORMATION ELASTO-PLASTIC THEORY AND CONSISTENT ALGORITHM

    Institute of Scientific and Technical Information of China (English)

    Liu Xuejun; Li Mingrui; Huang Wenbin

    2001-01-01

    By using the logarithmic strain, the finite deformation plastic theory, corresponding to the infinitesimal plastic theory, is established successively. The plastic consistent algorithm with first order accuracy for the finite element method (FEM) is developed. Numerical examples are presented to illustrate the validity of the theory and effectiveness of the algorithm.

  1. Plastic bronchitis

    Directory of Open Access Journals (Sweden)

    Anil Kumar Singhi

    2015-01-01

    Full Text Available Plastic bronchitis, a rare but serious clinical condition, commonly seen after Fontan surgeries in children, may be a manifestation of suboptimal adaptation to the cavopulmonary circulation with unfavorable hemodynamics. They are ominous with poor prognosis. Sometimes, infection or airway reactivity may provoke cast bronchitis as a two-step insult on a vulnerable vascular bed. In such instances, aggressive management leads to longer survival. This report of cast bronchitis discusses its current understanding.

  2. Characterization of plastic blends made from mixed plastics waste of different sources.

    Science.gov (United States)

    Turku, Irina; Kärki, Timo; Rinne, Kimmo; Puurtinen, Ari

    2017-02-01

    This paper studies the recyclability of construction and household plastic waste collected from local landfills. Samples were processed from mixed plastic waste by injection moulding. In addition, blends of pure plastics, polypropylene and polyethylene were processed as a reference set. Reference samples with known plastic ratio were used as the calibration set for quantitative analysis of plastic fractions in recycled blends. The samples were tested for the tensile properties; scanning electron microscope-energy-dispersive X-ray spectroscopy was used for elemental analysis of the blend surfaces and Fourier transform infrared (FTIR) analysis was used for the quantification of plastics contents.

  3. Recovery of electric energy from formate by using a recombinant strain of Escherichia coli.

    Science.gov (United States)

    Ojima, Yoshihiro; Kawata, Teruyoshi; Matsuo, Nahoko; Nishinoue, Yosuke; Taya, Masahito

    2014-10-01

    Recombinant Escherichia coli cells were applied for the recovery of electric energy from formate. Initially, the fdh gene, which encodes formate dehydrogenase (FDH) of Mycobacterium vaccae, was introduced into E. coli cells to allow efficient degradation of formate. The constructed microbial fuel cell (MFC) with E. coli BW25113 cells carrying fdh gene showed appreciable generation of current density in the presence of formate as a substrate. Current density and polarization curves revealed that the performance of MFC under examined conditions was limited by the electron transfer from bulk liquid to the electrode surface; accordingly, agitation resulted in an increase in the current density and achieved a coulombic efficiency of 21.7 % on the basis of formate consumed. Thus, gene recombination enables E. coli cells to utilize formate as a fuel for MFC.

  4. Reversible strain-induced magnetization switching in FeGa nanomagnets: Pathway to a rewritable, non-volatile, non-toggle, extremely low energy straintronic memory

    Science.gov (United States)

    Ahmad, Hasnain; Atulasimha, Jayasimha; Bandyopadhyay, Supriyo

    2015-12-01

    We report reversible strain-induced magnetization switching between two stable/metastable states in ~300 nm sized FeGa nanomagnets delineated on a piezoelectric PMN-PT substrate. Voltage of one polarity applied across the substrate generates compressive strain in a nanomagnet and switches its magnetization to one state, while voltage of the opposite polarity generates tensile strain and switches the magnetization back to the original state. The two states can encode the two binary bits, and, using the right voltage polarity, one can write either bit deterministically. This portends an ultra-energy-efficient non-volatile “non-toggle” memory.

  5. A new water-equivalent 2D plastic scintillation detectors array for the dosimetry of megavoltage energy photon beams in radiation therapy

    Energy Technology Data Exchange (ETDEWEB)

    Guillot, Mathieu; Beaulieu, Luc; Archambault, Louis; Beddar, Sam; Gingras, Luc [Departement de Physique, de Genie Physique et d' Optique, Universite Laval, Quebec, Quebec G1K 7P4 (Canada) and Departement de Radio-Oncologie, Hotel-Dieu de Quebec, Centre Hospitalier Universitaire de Quebec, Quebec, Quebec G1R 2J6 (Canada); Department of Radiation Physics, Unit 94, University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030 (United States); Departement de Physique, de Genie Physique et d' Optique, Universite Laval, Quebec, Quebec G1K 7P4 (Canada) and Departement de Radio-Oncologie, Hotel-Dieu de Quebec, Centre Hospitalier Universitaire de Quebec, Quebec, Quebec G1R 2J6 (Canada)

    2011-12-15

    Purpose: The objective of this work is to present a new 2D plastic scintillation detectors array (2D-PSDA) designed for the dosimetry of megavoltage (MV) energy photon beams in radiation therapy and to characterize its basic performance. Methods: We developed a 2D detector array consisting of 781 plastic scintillation detectors (PSDs) inserted into a plane of a water-equivalent phantom. The PSDs were distributed on a 26 x 26 cm{sup 2} grid, with an interdetector spacing of 10 mm, except for two perpendicular lines centered on the detection plane, where the spacing was 5 mm. Each PSD was made of a 1 mm diameter by 3 mm long cylindrical polystyrene scintillating fiber coupled to a clear nonscintillating plastic optical fiber. All of the light signals emitted by the PSDs were read simultaneously with an optical system at a rate of one measurement per second. We characterized the performance of the optical system, the angular dependency of the device, and the perturbation of dose distributions caused by the hundreds of PSDs inserted into the phantom. We also evaluated the capacity of the system to monitor complex multileaf collimator (MLC) sequences such as those encountered in step-and-shoot intensity modulated radiation therapy (IMRT) plans. We compared our results with calculations performed by a treatment planning system and with measurements taken with a 2D ionization chamber array and with a radiochromic film. Results: The detector array that we developed allowed us to measure doses with an average precision of better than 1% for cumulated doses equal to or greater than 6.3 cGy. Our results showed that the dose distributions produced by the 6-MV photon beam are not perturbed (within {+-}1.1%) by the presence of the hundreds of PSDs located into the phantom. The results also showed that the variations in the beam incidences have little effect on the dose response of the device. For all incidences tested, the passing rates of the gamma tests between the 2D-PSDA and

  6. A Technique for Mapping Characteristic Lengths to Preserve Energy Dissipated via Strain Softening in a Multiscale Analysis

    Science.gov (United States)

    Pineda, Evan J.; Bednarcyk, Brett A.; Arnold, Steven M.

    2014-01-01

    It is often advantageous to account for the microstructure of the material directly using multiscale modeling. For computational tractability, an idealized repeating unit cell (RUC) is used to capture all of the pertinent features of the microstructure. Typically, the RUC is dimensionless and depends only on the relative volume fractions of the different phases in the material. This works well for non-linear and inelastic behavior exhibiting a positive-definite constitutive response. Although, once the material exhibits strain softening, or localization, a mesh objective failure theories, such as smeared fracture theories, nodal and element enrichment theories (XFEM), cohesive elements or virtual crack closure technique (VCCT), can be utilized at the microscale, but the dimensions of the RUC must then be defined. One major challenge in multiscale progressive damage modeling is relating the characteristic lengths across the scales in order to preserve the energy that is dissipated via localization at the microscale. If there is no effort to relate the size of the macroscale element to the microscale RUC, then the energy that is dissipated will remain mesh dependent at the macroscale, even if it is regularized at the microscale. Here, a technique for mapping characteristic lengths across the scales is proposed. The RUC will be modeled using the generalized method of cells (GMC) micromechanics theory, and local failure in the matrix constituent subcells will be modeled using the crack band theory. The subcell characteristic lengths used in the crack band calculations will be mapped to the macroscale finite element in order to regularize the local energy in a manner consistent with the global length scale. Examples will be provided with and without the regularization, and they will be compared to a baseline case where the size and shape of the element and RUC are coincident (ensuring energy is preserved across the scales).

  7. Enhanced efficiency in plastic solar cells via energy matched solution processed NiO{sub x} interlayers

    Energy Technology Data Exchange (ETDEWEB)

    Steirer, K. Xerxes [Colorado School of Mines, Physics Dept., Golden, CO (United States); Ndione, Paul F.; Lloyd, Matthew T.; Curtis, Calvin J.; Ginley, David S.; Berry, Joseph J.; Olson, Dana C. [National Center for Photovoltaics, National Renewable Energy Laboratory, Golden, CO (United States); Widjonarko, N. Edwin [University of Colorado, Physics Dept., Boulder, CO (United States); Meyer, Jens; Kahn, Antoine [Princeton University, Electrical Engineering Dept., Princeton, NJ (United States); Ratcliff, Erin L.; Armstrong, Neal R. [University of Arizona, Dept. of Chemistry and Biochemistry and Center for Interface Science, Solar Electric Materials, Tucson, AZ (United States)

    2011-10-15

    We show enhanced efficiency and stability of a high performance organic solar cell (OPV) when the work-function of the hole collecting indium-tin oxide (ITO) contact, modified with a solution-processed nickel oxide (NiO{sub x}) hole-transport layer (HTL), is matched to the ionization potential of the donor material in a bulk-heterojunction solar cell. Addition of the NiO{sub x} HTL to the hole collecting contact results in a power conversion efficiency (PCE) of 6.7%, which is a 17.3% net increase in performance over the 5.7% PCE achieved with a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) HTL on ITO. The impact of these NiO{sub x} films is evaluated through optical and electronic measurements as well as device modeling. The valence and conduction band energies for the NiO{sub x} HTL are characterized in detail through photoelectron spectroscopy studies while spectroscopic ellipsometry is used to characterize the optical properties. Oxygen plasma treatment of the NiO{sub x} HTL is shown to provide superior contact properties by increasing the ITO/NiO{sub x} contact work-function by 500 meV. Enhancement of device performance is attributed to reduction of the band edge energy offset at the ITO/NiO{sub x} interface with the poly(N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothidiazole)) (PCDTBT):[6,6]-phenyl-C61 butyric acid methyl ester PCBM and [6,6]-phenyl-C71 butyric acid methyl ester (PC{sub 70}BM) active layer. A high work-function hole collecting contact is therefore the appropriate choice for high ionization potential donor materials in order to maximize OPV performance. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. BOOK REVIEW: Introduction to Computational Plasticity

    Science.gov (United States)

    Hartley, P.

    2006-04-01

    . Chapter two introduces one of several yield criteria, that normally attributed to von Mises (though historians of mechanics might argue over who was first to develop the theory of yielding associated with strain energy density), and its two or three-dimensional representation as a yield surface. The expansion of the yield surface during plastic deformation, its translation due to kinematic hardening and the Bauschinger effect in reversed loading are described with a direct link to the material stress-strain curve. The assumption, that the increment of strain is normal to the yield surface, the normality principle, is introduced. Uniaxial loading of an elastic-plastic material is used as an example in which to develop expressions to describe increments in stress and strain. The full presentation of numerous expressions, tensors and matrices with a clear explanation of their development, is a recurring, and commendable, feature of the book, which provides an invaluable introduction for those new to the subject. The chapter moves on from time-independent behaviour to introduce viscoplasticity and creep. Chapter three takes the theories of deformation another stage further to consider the problems associated with large deformation in which an important concept is the separation of the phenomenon into material stretch and rotation. The latter is crucial to allow correct measures of strain and stress to be developed in which the effects of rigid body rotation do not contribute to these variables. Hence, the introduction of 'objective' measures for stress and strain. These are described with reference to deformation gradients, which are clearly explained; however, the introduction of displacement gradients passes with little comment, although velocity gradients appear later in the chapter. The interpretation of different strain measures, e.g. Green--Lagrange and Almansi, is covered briefly, followed by a description of the spin tensor and its use in developing the objective

  9. Single-shot full strain tensor determination with microbeam X-ray Laue diffraction and a two-dimensional energy-dispersive detector.

    Science.gov (United States)

    Abboud, A; Kirchlechner, C; Keckes, J; Conka Nurdan, T; Send, S; Micha, J S; Ulrich, O; Hartmann, R; Strüder, L; Pietsch, U

    2017-06-01

    The full strain and stress tensor determination in a triaxially stressed single crystal using X-ray diffraction requires a series of lattice spacing measurements at different crystal orientations. This can be achieved using a tunable X-ray source. This article reports on a novel experimental procedure for single-shot full strain tensor determination using polychromatic synchrotron radiation with an energy range from 5 to 23 keV. Microbeam X-ray Laue diffraction patterns were collected from a copper micro-bending beam along the central axis (centroid of the cross section). Taking advantage of a two-dimensional energy-dispersive X-ray detector (pnCCD), the position and energy of the collected Laue spots were measured for multiple positions on the sample, allowing the measurement of variations in the local microstructure. At the same time, both the deviatoric and hydrostatic components of the elastic strain and stress tensors were calculated.

  10. Printed highly conductive Cu films with strong adhesion enabled by low-energy photonic sintering on low-Tg flexible plastic substrate

    Science.gov (United States)

    Wu, Xinzhou; Shao, Shuangshuang; Chen, Zheng; Cui, Zheng

    2017-01-01

    Copper (Cu) films and circuits were fabricated by screen-printing Cu nanoink on low-Tg (glass transition temperature) flexible plastic substrates (PEN and PET) instead of widely used high-Tg polyimide (PI) substrate. Photonic sintering of printed Cu films was carried out using intensive pulsed light (IPL). Low resistivities of 28 μΩ · cm on PEN and 44 μΩ · cm on PET were obtained without damaging the substrates. The sintered Cu films exhibited strong adhesion to PEN and PET substrates, with measured adhesion strength of 5B by the ASTM D3359 international standard, whereas the top part of the copper film on the PI substrate was stripped off during the adhesion test. The sintered Cu films also showed excellent stability in harsh conditions and mechanical flexibility in rolling tests. The underlying mechanisms of the high conductivity and strong adhesion on PEN and PET substrates with low-energy IPL sintering were investigated. Simple circuits and radio frequency identification antennas were made by screen-printing Cu nanoink and IPL sintering, demonstrating the technique’s feasibility for practical applications.

  11. A correlative approach to segmenting phases and ferrite morphologies in transformation-induced plasticity steel using electron back-scattering diffraction and energy dispersive X-ray spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Gazder, Azdiar A., E-mail: azdiar@uow.edu.au [Electron Microscopy Centre, University of Wollongong, New South Wales 2500 (Australia); Al-Harbi, Fayez; Spanke, Hendrik Th. [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, New South Wales 2522 (Australia); Mitchell, David R.G. [Electron Microscopy Centre, University of Wollongong, New South Wales 2500 (Australia); Pereloma, Elena V. [Electron Microscopy Centre, University of Wollongong, New South Wales 2500 (Australia); School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, New South Wales 2522 (Australia)

    2014-12-15

    Using a combination of electron back-scattering diffraction and energy dispersive X-ray spectroscopy data, a segmentation procedure was developed to comprehensively distinguish austenite, martensite, polygonal ferrite, ferrite in granular bainite and bainitic ferrite laths in a thermo-mechanically processed low-Si, high-Al transformation-induced plasticity steel. The efficacy of the ferrite morphologies segmentation procedure was verified by transmission electron microscopy. The variation in carbon content between the ferrite in granular bainite and bainitic ferrite laths was explained on the basis of carbon partitioning during their growth. - Highlights: • Multi-condition segmentation of austenite, martensite, polygonal ferrite and ferrite in bainite. • Ferrites in granular bainite and bainitic ferrite segmented by variation in relative carbon counts. • Carbon partitioning during growth explains variation in carbon content of ferrites in bainites. • Developed EBSD image processing tools can be applied to the microstructures of a variety of alloys. • EBSD-based segmentation procedure verified by correlative TEM results.

  12. Size effect in plastically deformed passivated thin films

    Institute of Scientific and Technical Information of China (English)

    HWANG; Keh-Chih

    2009-01-01

    The flow theory of mechanism-based strain gradient plasticity theory (MSG) developed by Qiu et al. (2003) is extended for incompressible material. The MSG flow theory is used to predict the increase of plastic work hardening for plane strain tension of surface-passivated Cu thin film. The theoretical predictions agree well with experiments for suitably chosen material parameters.

  13. Catalytically Triggered Energy Release from Strained Organic Molecules: The Surface Chemistry of Quadricyclane and Norbornadiene on Pt(111).

    Science.gov (United States)

    Bauer, Udo; Mohr, Susanne; Döpper, Tibor; Bachmann, Philipp; Späth, Florian; Düll, Fabian; Schwarz, Matthias; Brummel, Olaf; Fromm, Lukas; Pinkert, Ute; Görling, Andreas; Hirsch, Andreas; Bachmann, Julien; Steinrück, Hans-Peter; Libuda, Jörg; Papp, Christian

    2017-01-31

    We have investigated the surface chemistry of the polycyclic valence-isomer pair norbornadiene (NBD) and quadricyclane (QC) on Pt(111). The NBD/QC system is considered to be a prototype for energy storage in strained organic compounds. By using a multimethod approach, including UV photoelectron, high-resolution X-ray photoelectron, and IR reflection-absorption spectroscopic analysis and DFT calculations, we could unambiguously identify and differentiate between the two molecules in the multilayer phase, which implies that the energy-loaded QC molecule is stable in this state. Upon adsorption in the (sub)monolayer regime, the different spectroscopies yielded identical spectra for NBD and QC at 125 and 160 K, when multilayer desorption takes place. This behavior is explained by a rapid cycloreversion of QC to NBD upon contact with the Pt surface. The NBD adsorbs in a η(2) :η(1) geometry with an agostic Pt-H interaction of the bridgehead CH2 subunit and the surface. Strong spectral changes are observed between 190 and 220 K because the hydrogen atom that forms the agostic bond is broke. This reaction yields a norbornadienyl intermediate species that is stable up to approximately 380 K. At higher temperatures, the molecule dehydrogenates and decomposes into smaller carbonaceous fragments.

  14. The effect of martensite plasticity on the cyclic deformation of super-elastic NiTi shape memory alloy

    Science.gov (United States)

    Song, Di; Kang, Guozheng; Kan, Qianhua; Yu, Chao; Zhang, Chuanzeng

    2014-01-01

    Based on stress-controlled cyclic tension-unloading experiments with different peak stresses, the effect of martensite plasticity on the cyclic deformation of super-elastic NiTi shape memory alloy micro-tubes is investigated and discussed. The experimental results show that the reverse transformation from the induced martensite phase to the austenite phase is gradually restricted by the plastic deformation of the induced martensite phase caused by an applied peak stress that is sufficiently high (higher than 900 MPa), and the extent of such restriction increases with further increasing the peak stress. The residual and peak strains of super-elastic NiTi shape memory alloy accumulate progressively, i.e., transformation ratchetting occurs during the cyclic tension-unloading with peak stresses from 600 to 900 MPa, and the transformation ratchetting strain increases with the increase of the peak stress. When the peak stress is higher than 900 MPa, the peak strain becomes almost unchanged, but the residual strain accumulates and the dissipation energy per cycle decreases very quickly with the increasing number of cycles due to the restricted reverse transformation by the martensite plasticity. Furthermore, a quantitative relationship between the applied stress and the stabilized residual strain is obtained to reasonably predict the evolution of the peak strain and the residual strain.

  15. Plastic equation of state determined by nano indentation

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    In order to characterize the plastic state of a deformed material, an indentation method to determine the plastic equation of state (PES) was developed. The work-hardening coefficient and the strain rate sensitivity coefficient of the plastic mechanic equation of state were determined by two kinds of indentation tests respectively. Therefore, the PES of materials under deformation can be obtained, and the plastic state of materials can be determined.

  16. Effect of plastic straining on the F and M centres kinetics in {gamma}-irradiated NaCl; Efecto de la deformacion plastica sobre la Cinetica de Centro de color F y M en NaCl, irradiado con rayos {gamma}

    Energy Technology Data Exchange (ETDEWEB)

    Agullo Lopez, F.

    1966-07-01

    The effect of plastic straining on the room-temperature F and H growth curves in a {gamma}-radiation field has been analyzed. Cristal are strained after F-saturation is reached and then irradiation is continued. The new F growth curve consists of an initial fast growing stage due to additional vacancies created by deformation being turned into F centre, followed by a linear stage. Its slope is higher than that prior to straining. Also the role of straining on M centre thermal decay as well as on the F{yields}M reaction under F light, has been investigated. This reaction has been shown to preferentially occur where intense gliding has developed. (Author) 44 refs.

  17. First-principles investigation of strain effects on the stacking fault energies, dislocation core structure, and Peierls stress of magnesium and its alloys

    Science.gov (United States)

    Zhang, S. H.; Beyerlein, I. J.; Legut, D.; Fu, Z. H.; Zhang, Z.; Shang, S. L.; Liu, Z. K.; Germann, T. C.; Zhang, R. F.

    2017-06-01

    Taking pure Mg, Mg-Al, and Mg-Zn as prototypes, the effects of strain on the stacking fault energies (SFEs), dislocation core structure, and Peierls stress were systematically investigated by means of density functional theory and the semidiscrete variational Peierls-Nabarro model. Our results suggest that volumetric strain may significantly influence the values of SFEs of both pure Mg and its alloys, which will eventually modify the dislocation core structure, Peierls stress, and preferred slip system, in agreement with recent experimental results. The so-called "strain factor" that was previously proposed for the solute strengthening could be justified as a major contribution to the strain effect on SFEs. Based on multivariate regression analysis, we proposed universal exponential relationships between the dislocation core structure, the Peierls stress, and the stable or unstable SFEs. Electronic structure calculations suggest that the variations of these critical parameters controlling strength and ductility under strain can be attributed to the strain-induced electronic polarization and redistribution of valence charge density at hollow sites. These findings provide a fundamental basis for tuning the strain effect to design novel Mg alloys with both high strength and ductility.

  18. Endochronic Plasticity

    Science.gov (United States)

    1987-12-01

    Axial Load Histories." CEAE Dept. University of Colorado. Boulder. Colorado (1983). I £ 1-12 2. THEORETICAL FOUNDATIONS OF THE THEORY 2.1 Basic...Gerstle and H. Y. Ko. "Stress-Strain Curves for Concrete Under Multiaxial Load Histories." CEAE Department. University of Colorado. Boulder. (1983

  19. Applications and societal benefits of plastics.

    Science.gov (United States)

    Andrady, Anthony L; Neal, Mike A

    2009-07-27

    This article explains the history, from 1600 BC to 2008, of materials that are today termed 'plastics'. It includes production volumes and current consumption patterns of five main commodity plastics: polypropylene, polyethylene, polyvinyl chloride, polystyrene and polyethylene terephthalate. The use of additives to modify the properties of these plastics and any associated safety, in use, issues for the resulting polymeric materials are described. A comparison is made with the thermal and barrier properties of other materials to demonstrate the versatility of plastics. Societal benefits for health, safety, energy saving and material conservation are described, and the particular advantages of plastics in society are outlined. Concerns relating to littering and trends in recycling of plastics are also described. Finally, we give predictions for some of the potential applications of plastic over the next 20 years.

  20. Strain gradient effects on cyclic plasticity

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Legarth, Brian Nyvang

    2010-01-01

    hardening materials it is quantified how dissipative and energetic gradient effects promote hardening above that of conventional predictions. Usually, increased hardening is attributed to energetic gradient effects, but here it is found that also dissipative gradient effects lead to additional hardening...... in the presence of conventional material hardening. Furthermore, it is shown that dissipative gradient effects can lead to both an increase and a decrease in the dissipation per load cycle depending on the magnitude of the dissipative length parameter, whereas energetic gradient effects lead to decreasing...... dissipation for increasing energetic length parameter. For dissipative gradient effects it is found that dissipation has a maximum value for some none zero value of the material length parameter, which depends on the magnitude of the deformation cycles....

  1. Analysis of elastic stiffness for the leaf type holddown spring assembly with uniformly tapered thickness based on strain energy method

    Energy Technology Data Exchange (ETDEWEB)

    Song, Ki Nam [Korea Atomic Energy Research Institute, Daeduk (Korea, Republic of)

    1996-03-01

    A formula to evaluate the elastic stiffness of the leaf type holddown spring (HDS)assembly with uniformly tapered thickness from t{sub 0} to t{sub 1} (t{sub 0} < t{sub 1}) has been analytically derived by applying the engineering beam theory and Casiliano`s theorem based on strain energies due to bending moment, shear and axial force. Comparisons on the elastic stiffnesses have been made with test results and evaluated values from the derived formula for the 14x14 and 17x17 type KOFA HDS, and it has found that most of the differences were in the range of 1-2% of the evaluated elastic stiffnesses and that the elastic stiffness of the HDS was mainly caused by bending moment because effects of shear and axial forces on the elastic stiffness were in the range of 0.09-0.16%. And in addition, it has found that the derived formula could be applicable to HDS designed by Westinghouse. Therefore, the derived formula could be applicable to evaluating the elastic stiffness of any HDS with tapered thickness only with the informations of the geometric data and material properties of leaf springs regardness of the manufacturing companies. 8 tabs., 4 figs., 22 refs. (Author) .new.

  2. Averaged strain energy density-based synthesis of crack initiation life in notched steel bars under torsional fatigue

    Directory of Open Access Journals (Sweden)

    Filippo Berto

    2016-10-01

    Full Text Available The torsional fatigue behaviour of circumferentially notched specimens made of austenitic stainless steel, SUS316L, and carbon steel, SGV410, characterized by different notch root radii has been recently investigated by Tanaka. In that contribution, it was observed that the total fatigue life of the austenitic stainless steel increases with increasing stress concentration factor for a given applied nominal shear stress amplitude. By using the electrical potential drop method, Tanaka observed that the crack nucleation life was reduced with increasing stress concentration, on the other hand the crack propagation life increased. The experimental fatigue results, originally expressed in terms of nominal shear stress amplitude, have been reanalysed by means of the local strain energy density (SED averaged over a control volume having radius R0 surrounding the notch tip. To exclude all extrinsic effects acting during the fatigue crack propagation phase, such as sliding contact and/or friction between fracture surfaces, crack initiation life has been considered in the present work. In the original paper, initiation life was defined in correspondence of a 0.1÷0.4-mm-deep crack. The control radius R0 for fatigue strength assessment of notched components, thought of as a material property, has been estimated by imposing the constancy of the averaged SED for both smooth and cracked specimens at NA = 2 million loading cycles

  3. Analysis of elastic stiffness for the leaf type holddown spring assembly with uniformly tapered width base on strain energy method

    Energy Technology Data Exchange (ETDEWEB)

    Song, Ki Nam [Korea Atomic Energy Research Institute, Daeduk (Korea, Republic of)

    1996-03-01

    A formula for the elastic stiffness of the leaf type holddown spring assembly with uniformly tapered width from w{sub 0} to w{sub 1} (w{sub 0} < w{sub 1}) has been analytically derived by applying the engineering beam theory and Casiliano`s theory based on strain energy. Elastic stiffnesses for the leaf type holddown springs which are newly designed in the same dimensional design spaces as 14x14 type and 17x17 type KOFA holddown spring assembly have been estimated from the derived formula and also their elastic stiffnesses have been compared with those of KOFA holddown spring assemblies. It is found that elastic stiffnesses of the newly designed leaf type holddown spring assemblies have been about 32-33% about higher than those of KOFA holddown spring assemblies and that effects of axial and shear force on the elastic stiffness have been 0.15-0.21% of the elastic stiffness. Therefore in case that the newly designed holddown spring assemblies have been adapted in KOFA, it is expected that numbers of leaves composing a holddown spring assembly could be lessened by on due to their having a high elastic stiffness and in addition, manufacturing cost of the newly designed holddown spring assembly may be reduced due to easy machinability of each leaf. 4 tabs., 4 figs., 16 refs. (Author) .new.

  4. Environmental evaluation of plastic waste management scenarios

    DEFF Research Database (Denmark)

    Rigamonti, L.; Grosso, M.; Møller, Jacob

    2014-01-01

    The management of the plastic fraction is one of the most debated issues in the discussion on integrated municipal solid waste systems. Both material and energy recovery can be performed on such a waste stream, and different separate collection schemes can be implemented. The aim of the paper...... is to contribute to the debate, based on the analysis of different plastic waste recovery routes. Five scenarios were defined and modelled with a life cycle assessment approach using the EASEWASTE model. In the baseline scenario (P0) the plastic is treated as residual waste and routed partly to incineration...... with energy recovery and partly to mechanical biological treatment. A range of potential improvements in plastic management is introduced in the other four scenarios (P1–P4). P1 includes a source separation of clean plastic fractions for material recycling, whereas P2 a source separation of mixed plastic...

  5. Overcoming maladaptive plasticity through plastic compensation

    Directory of Open Access Journals (Sweden)

    Matthew R.J. MORRIS, Sean M. ROGERS

    2013-08-01

    Full Text Available Most species evolve within fluctuating environments, and have developed adaptations to meet the challenges posed by environmental heterogeneity. One such adaptation is phenotypic plasticity, or the ability of a single genotype to produce multiple environmentally-induced phenotypes. Yet, not all plasticity is adaptive. Despite the renewed interest in adaptive phenotypic plasticity and its consequences for evolution, much less is known about maladaptive plasticity. However, maladaptive plasticity is likely an important driver of phenotypic similarity among populations living in different environments. This paper traces four strategies for overcoming maladaptive plasticity that result in phenotypic similarity, two of which involve genetic changes (standing genetic variation, genetic compensation and two of which do not (standing epigenetic variation, plastic compensation. Plastic compensation is defined as adaptive plasticity overcoming maladaptive plasticity. In particular, plastic compensation may increase the likelihood of genetic compensation by facilitating population persistence. We provide key terms to disentangle these aspects of phenotypic plasticity and introduce examples to reinforce the potential importance of plastic compensation for understanding evolutionary change [Current Zoology 59 (4: 526–536, 2013].

  6. Overcoming maladaptive plasticity through plastic compensation

    Institute of Scientific and Technical Information of China (English)

    Matthew R.J.MORRIS; Sean M.ROGERS

    2013-01-01

    Most species evolve within fluctuating environments,and have developed adaptations to meet the challenges posed by environmental heterogeneity.One such adaptation is phenotypic plasticity,or the ability of a single genotype to produce multiple environmentally-induced phenotypes.Yet,not all plasticity is adaptive.Despite the renewed interest in adaptive phenotypic plasticity and its consequences for evolution,much less is known about maladaptive plasticity.However,maladaptive plasticity is likely an important driver of phenotypic similarity among populations living in different environments.This paper traces four strategies for overcoming maladaptive plasticity that result in phenotypic similarity,two of which involve genetic changes (standing genetic variation,genetic compensation) and two of which do not (standing epigenetic variation,plastic compensation).Plastic compensation is defined as adaptive plasticity overcoming maladaptive plasticity.In particular,plastic compensation may increase the likelihood of genetic compensation by facilitating population persistence.We provide key terms to disentangle these aspects of phenotypic plasticity and introduce examples to reinforce the potential importance of plastic compensation for understanding evolutionary change.

  7. Plastic theory for the multi-crystal metals-From infinitesimal deformation to finite deformation

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Multi-crystal metals have the property of volume conservation in the plastic state. In the infinitesimal deformation plasticity the strain tensor can be split into a deviator part and a volumetric part. The vanishing of the first variant of the strain tensor is equivalent to the volume conservation. Furthermore, the split of the strain into an elastic part and a plastic part is also adopted widely. The flow rule is thus established. These two splits are not confirmed in the finite deformation plasticity. The plasticity criterion and the flow rule are thus facing great challenge. There are various definitions of strain measures in the finite deformation theory. Though the choosing of strain measure is arbitrary in the elastic problem, it is strongly restricted in the plastic problem. By theoretical and experimental studies, it is shown that the logarithmic strain is the only suitable strain measure in the metal forming problem.

  8. Computer Modeling of the Dynamic Strength of Metal-Plastic Cylindrical Shells Under Explosive Loading

    Science.gov (United States)

    Abrosimov, N. A.; Novosel'tseva, N. A.

    2017-05-01

    A technique for numerically analyzing the dynamic strength of two-layer metal-plastic cylindrical shells under an axisymmetric internal explosive loading is developed. The kinematic deformation model of the layered package is based on a nonclassical theory of shells. The geometric relations are constructed using relations of the simplest quadratic version of the nonlinear elasticity theory. The stress and strain tensors in the composite macrolayer are related by Hooke's law for an orthotropic body with account of degradation of the stiffness characteristics of the multilayer package due to local failure of some its elementary layers. The physical relations in the metal layer are formulated in terms of a differential theory of plasticity. An energy-correlated resolving system of dynamic equations for the metal-plastic cylindrical shells is derived by minimizing the functional of total energy of the shells as three-dimensional bodies. The numerical method for solving the initial boundary-value problem formulated is based on an explicit variational-difference scheme. The reliability of the technique considered is verified by comparing numerical results with experimental data. An analysis of the ultimate strains and strength of one-layer basalt-and glass-fiber-reinforced plastic and two-layer metalplastic cylindrical shells is carried out.

  9. Strain in epitaxial Bi{sub 2}Se{sub 3} grown on GaN and graphene substrates: A reflection high-energy electron diffraction study

    Energy Technology Data Exchange (ETDEWEB)

    Li, Bin; Guo, Xin; Ho, Wingkin; Xie, Maohai, E-mail: mhxie@hku.hk [Department of Physics, The University of Hong Kong, Pokfulam Road (Hong Kong)

    2015-08-24

    Topological insulator (TI) has been one of the focus research themes in condensed matter physics in recent years. Due to the relatively large energy bandgap, Bi{sub 2}Se{sub 3} has been identified as one of the most promising three-dimensional TIs with application potentials. Epitaxial Bi{sub 2}Se{sub 3} by molecular-beam epitaxy has been reported by many groups using different substrates. A common feature is that Bi{sub 2}Se{sub 3} grows readily along the c-axis direction irrespective of the type and condition of the substrate. Because of the weak van der Waals interaction between Bi{sub 2}Se{sub 3} quintuple layers, the grown films are reported to be strain-free, taking the lattice constant of the bulk crystal. At the very initial stage of Bi{sub 2}Se{sub 3} deposition, however, strain may still exist depending on the substrate. Strain may bring some drastic effects to the properties of the TIs and so achieving strained TIs can be of great fundamental interests as well as practical relevance. In this work, we employ reflection high-energy electron diffraction to follow the lattice constant evolution of Bi{sub 2}Se{sub 3} during initial stage depositions on GaN and graphene, two very different substrates. We reveal that epitaxial Bi{sub 2}Se{sub 3} is tensile strained on GaN but strain-free on graphene. Strain relaxation on GaN is gradual.

  10. Microelectronics plastic molded packaging

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, D.R. [Ktech Corp., Albuquerque, NM (United States); Palmer, D.W.; Peterson, D.W. [Sandia National Lab., Albuquerque, NM (United States)] [and others

    1997-02-01

    The use of commercial off-the-shelf (COTS) microelectronics for nuclear weapon applications will soon be reality rather than hearsay. The use of COTS for new technologies for uniquely military applications is being driven by the so-called Perry Initiative that requires the U.S. Department of Defense (DoD) to accept and utilize commercial standards for procurement of military systems. Based on this philosophy, coupled with several practical considerations, new weapons systems as well as future upgrades will contain plastic encapsulated microelectronics. However, a conservative Department of Energy (DOE) approach requires lifetime predictive models. Thus, the focus of the current project is on accelerated testing to advance current aging models as well as on the development of the methodology to be used during WR qualification of plastic encapsulated microelectronics. An additional focal point involves achieving awareness of commercial capabilities, materials, and processes. One of the major outcomes of the project has been the definition of proper techniques for handling and evaluation of modern surface mount parts which might be used in future systems. This program is also raising the familiarity level of plastic within the weapons complex, allowing subsystem design rules accommodating COTS to evolve. A two year program plan is presented along with test results and commercial interactions during this first year.

  11. Crack-tip strain field mapping and the toughness of metallic glasses.

    Directory of Open Access Journals (Sweden)

    Todd C Hufnagel

    Full Text Available We have used high-energy x-ray scattering to map the strain fields around crack tips in fracture specimens of a bulk metallic glass under load at room temperature and below. From the measured strain fields we can calculate the components of the stress tensor as a function of position and determine the size and shape of the plastic process zone around the crack tip. Specimens tested at room temperature develop substantial plastic zones and achieve high stress intensities ((K(If = 76 MPa m(1/2 prior to fracture. Specimens tested at cryogenic temperatures fail at reduced but still substantial stress intensities (K(If = 39 MPa m(1/2 and show only limited evidence of crack-tip plasticity. We propose that the difference in behavior is associated with changes in the flow stress and elastic constants, which influence the number density of shear bands in the plastic zone and thus the strain required to initiate fracture on an individual band. A secondary effect is a change in the triaxial state of stress around the crack tip due to the temperature dependence of Poisson's ratio. It is likely that this ability to map elastic strains on the microscale will be useful in other contexts, although interpreting shifts in the position of the scattering peaks in amorphous materials in terms of elastic strains must be done with caution.

  12. Recycling of Plastic

    DEFF Research Database (Denmark)

    Christensen, Thomas Højlund; Fruergaard, Thilde

    2011-01-01

    Plastic is produced from fossil oil. Plastic is used for many different products. Some plastic products like, for example, wrapping foil, bags and disposable containers for food and beverage have very short lifetimes and thus constitute a major fraction of most waste. Other plastic products like......, good strength and long durability. Recycling of plastic waste from production is well-established, while recycling of postconsumer plastic waste still is in its infancy. This chapter describes briefly how plastic is produced and how waste plastic is recycled in the industry. Quality requirements...

  13. Ductile damage Cam-Clay plasticity and fracture modeling of shale based on nano-characterization experiment

    Science.gov (United States)

    Bennett, K. C.; Borja, R. I.

    2015-12-01

    A finite strain ductile damage formulation of Modified Cam-Clay (MCC) plasticity has been developed in order to model the observed elastoplastic behavior of shale at nano- to micro-scales. Nano-indentation combined with both 2D and 3D imaging was performed on a sample of Woodford shale. Significant plastic deformation was observed in the nano-indentation testing, and nano-scale resolution FIB-SEM imaging of the post-indented regions has revealed that the plastic deformation is accompanied by extensive micro-fracture of the shale's highly heterogeneous micro-structure. A spatial tensor that is similar to Eshelby's energy momentum tensor is shown to be energy conjugate to the plastic velocity gradient under large inelastic volume strain. These results are cast in MCC framework drawing on the concept of continuum damage. The resulting formulation provides a connection between density (porosity), elastic (and plastic) moduli, and micro damage/healing. Nonlinear finite element modeling is used for implementation of the constitutive model in simulation of both laboratory-scale and nano- to micro-scale experiments. The results show that the model is able to predict the inception and propagation of micro-fractures around inhomogeneities, as well as capture the resulting behavior observed at the much larger laboratory scale.

  14. Source properties of dynamic rupture pulses with off-fault plasticity

    KAUST Repository

    Gabriel, A.-A.

    2013-08-01

    Large dynamic stresses near earthquake rupture fronts may induce an inelastic response of the surrounding materials, leading to increased energy absorption that may affect dynamic rupture. We systematically investigate the effects of off-fault plastic energy dissipation in 2-D in-plane dynamic rupture simulations under velocity-and-state-dependent friction with severe weakening at high slip velocity. We find that plasticity does not alter the nature of the transitions between different rupture styles (decaying versus growing, pulse-like versus crack-like, and subshear versus supershear ruptures) but increases their required background stress and nucleation size. We systematically quantify the effect of amplitude and orientation of background shear stresses on the asymptotic properties of self-similar pulse-like ruptures: peak slip rate, rupture speed, healing front speed, slip gradient, and the relative contribution of plastic strain to seismic moment. Peak slip velocity and rupture speed remain bounded. From fracture mechanics arguments, we derive a nonlinear relation between their limiting values, appropriate also for crack-like and supershear ruptures. At low background stress, plasticity turns self-similar pulses into steady state pulses, for which plastic strain contributes significantly to the seismic moment. We find that the closeness to failure of the background stress state is an adequate predictor of rupture speed for relatively slow events. Our proposed relations between state of stress and earthquake source properties in the presence of off-fault plasticity may contribute to the improved interpretation of earthquake observations and to pseudodynamic source modeling for ground motion prediction.

  15. Three-dimensional elastic image registration based on strain energy minimization: application to prostate magnetic resonance imaging.

    Science.gov (United States)

    Zhang, Bao; Arola, Dwayne D; Roys, Steve; Gullapalli, Rao P

    2011-08-01

    The use of magnetic resonance (MR) imaging in conjunction with an endorectal coil is currently the clinical standard for the diagnosis of prostate cancer because of the increased sensitivity and specificity of this approach. However, imaging in this manner provides images and spectra of the prostate in the deformed state because of the insertion of the endorectal coil. Such deformation may lead to uncertainties in the localization of prostate cancer during therapy. We propose a novel 3-D elastic registration procedure that is based on the minimization of a physically motivated strain energy function that requires the identification of similar features (points, curves, or surfaces) in the source and target images. The Gauss-Seidel method was used in the numerical implementation of the registration algorithm. The registration procedure was validated on synthetic digital images, MR images from prostate phantom, and MR images obtained on patients. The registration error, assessed by averaging the displacement of a fiducial landmark in the target to its corresponding point in the registered image, was 0.2 ± 0.1 pixels on synthetic images. On the prostate phantom and patient data, the registration errors were 1.0 ± 0.6 pixels (0.6 ± 0.4 mm) and 1.8 ± 0.7 pixels (1.1 ± 0.4 mm), respectively. Registration also improved image similarity (normalized cross-correlation) from 0.72 ± 0.10 to 0.96 ± 0.03 on patient data. Registration results on digital images, phantom, and prostate data in vivo demonstrate that the registration procedure can be used to significantly improve both the accuracy of localized therapies such as brachytherapy or external beam therapy and can be valuable in the longitudinal follow-up of patients after therapy.

  16. Influence of screw length and diameter on tibial strain energy density distribution after anterior cruciate ligament reconstruction

    Science.gov (United States)

    Yao, Jie; Kuang, Guan-Ming; Wong, Duo Wai-Chi; Niu, Wen-Xin; Zhang, Ming; Fan, Yu-Bo

    2014-04-01

    Postoperative tunnel enlargement has been frequently reported after anterior cruciate ligament (ACL) reconstruction. Interference screw, as a surgical implant in ACL reconstruction, may influence natural loading transmission and contribute to tunnel enlargement. The aims of this study are (1) to quantify the alteration of strain energy den sity (SED) distribution after the anatomic single-bundle ACL reconstruction; and (2) to characterize the influence of screw length and diameter on the degree of the SED alteration. A validated finite element model of human knee joint was used. The screw length ranging from 20 to 30mm with screw diameter ranging from 7 to 9 mm were investigated. In the post-operative knee, the SED increased steeply at the extra-articular tunnel aperture under compressive and complex loadings, whereas the SED decreased beneath the screw shaft and nearby the intra-articular tunnel aperture. Increasing the screw length could lower the SED deprivation in the proximal part of the bone tunnel; whereas increasing either screw length or diameter could aggravate the SED deprivation in the distal part of the bone tunnel. Decreasing the elastic modulus of the screw could lower the bone SED deprivation around the screw. In consideration of both graft stability and SED alteration, a biodegradable interference screw with a long length is recommended, which could provide a beneficial mechanical environment at the distal part of the tunnel, and meanwhile decrease the bone-graft motion and synovial fluid propagation at the proximal part of the tunnel. These findings together with the clinical and histological factors could help to improve surgical outcome, and serve as a preliminary knowledge for the following study of biodegradable interference screw. [Figure not available: see fulltext.

  17. Identification of energy storage rate components. Theoretical and experimental approach

    Energy Technology Data Exchange (ETDEWEB)

    Oliferuk, W; Maj, M, E-mail: wolif@ippt.gov.p [Fundamental Technological Research, Polish Academy of Sciences, Pawinskiego 5b, 02-106 Warszawa (Poland)

    2010-07-01

    The subject of the present paper is decomposition of energy storage rate into terms related to different mode of deformation. The stored energy is the change in internal energy due to plastic deformation after specimen unloading. Hence, this energy describes the state of the cold-worked material. Whereas, the ratio of the stored energy increment to the appropriate increment of plastic work is the measure of energy conversion process. This ratio is called the energy storage rate. Experimental results show that the energy storage rate is dependent on plastic strain. This dependence is influenced by different microscopic deformation mechanisms. It has been shown that the energy storage rate can be presented as a sum of particular components. Each of them is related to the separate internal microscopic mechanism. Two of the components are identified. One of them is the storage rate of statistically stored dislocation energy related to uniform deformation. Another one is connected with non-uniform deformation at the grain level. It is the storage rate of the long range stresses energy and geometrically necessary dislocation energy. The maximum of energy storage rate, that appeared at initial stage of plastic deformation is discussed in terms of internal micro-stresses.

  18. Plastics - the sustainable way to use Oil and Gas

    Energy Technology Data Exchange (ETDEWEB)

    Siebourg, Wolfgang

    2009-07-01

    Conclusions (drawn by the author): Plastics are a sustainable use of oil and gas - Plastic products enable significant savings of energy and GHG emissions particularly in the use phase; - Plastic products help use resources in the most efficient way. Restricting plastics relative growth would result in increased energy consumption. Diversion from landfill would increase resource efficiency. Waste-to-Energy is an additional resource and is complementary to mechanical recycling. Plastics producers and the Oil and Gas industry should cooperate to produce reliable consumption data. Oil and Gas industry should develop and maintain European (world) eco-profiles (cradle to gate) for their respective industry. (author)

  19. FINITE ELEMENT ANALYSIS ABOUT STRESS AND STRAIN OF SURFACE PEELING IN Cu-Fe-P SHEET

    Institute of Scientific and Technical Information of China (English)

    Su Juanhua; Li Hejun; Dong Qiming; Liu Ping; Kang Buxi

    2005-01-01

    The microstructure of surface peeling in finish rolled Cu-0.1Fe-0.03P sheet is analyzed by scanning electron microscope and energy dispersive spectroscope. Fe-rich areas of different contents are observed in the matrix. The stress distributions and strain characteristics at the interface between Cu matrix and Fe particle are studied by elastic-plastic finite element plane strain model. Larger Fe particles and higher deforming extent of finish rolling are attributed to the intense stress gradient and significant non-homogeneity equivalent strain at the interface and accelerate surface peeling of Cu-0.1Fe-0.03P lead frame sheet.

  20. Tunable plasticity in amorphous silicon carbide films.

    Science.gov (United States)

    Matsuda, Yusuke; Kim, Namjun; King, Sean W; Bielefeld, Jeff; Stebbins, Jonathan F; Dauskardt, Reinhold H

    2013-08-28

    Plasticity plays a crucial role in the mechanical behavior of engineering materials. For instance, energy dissipation during plastic deformation is vital to the sufficient fracture resistance of engineering materials. Thus, the lack of plasticity in brittle hybrid organic-inorganic glasses (hybrid glasses) often results in a low fracture resistance and has been a significant challenge for their integration and applications. Here, we demonstrate that hydrogenated amorphous silicon carbide films, a class of hybrid glasses, can exhibit a plasticity that is even tunable by controlling their molecular structure and thereby leads to an increased and adjustable fracture resistance in the films. We decouple the plasticity contribution from the fracture resistance of the films by estimating the "work-of-fracture" using a mean-field approach, which provides some insight into a potential connection between the onset of plasticity in the films and the well-known rigidity percolation threshold.

  1. Tuning the terahertz low-energy charge dynamics by simultaneous effect of epitaxial and anisotropic strain in PrNi O3 thin films

    Science.gov (United States)

    Phanindra, V. Eswara; Das, Sarmistha; Kumar, K. Santhosh; Agarwal, Piyush; Rana, Rakesh; Rana, D. S.

    2017-02-01

    The interplay of charge, spin, and lattice correlations strongly influence the insulator-metal (I-M) transition and magnetic ordering in rare earth nickelates. In this context, we explored the low-energy charge dynamics in structurally modulated PrNi O3 (PNO) thin films to unravel the complexity of ground state across I-M transition using terahertz (THz) spectroscopy. The THz optical constants of compressive film on LaAl O3 (100) substrate and the tensile films on NdGa O3 (100), (001), (110), and (111) substrates with varying orthorhombic distortion exhibit remarkably distinct features as a function of frequency and temperature. The THz conductivity of compressive film sans any I-M transition follows the Drude model. In contrast, the tensile strained films exhibit non-Drude THz conductivity, a giant positive dielectric permittivity, and negative imaginary conductivity, all of which can be explained by the Drude-Smith model. This rich variety of low-energy dynamics manifests as a function of temperature, strain, and crystal orientation. Such distinct THz spectral features, as induced by a subtle variation in strain while crossing over from tensile to compressive strain and with varying degree of orthorhombicity coupled with oxygen vacancies, reveal a novel facet of structure-property relationship of PNO.

  2. Plastic deformation and hysteresis for hydrogen storage in Pd–Rh alloys

    Energy Technology Data Exchange (ETDEWEB)

    Cappillino, P.J., E-mail: pcappil@sandia.gov [Sandia National Laboratories, PO Box 969, Mail Stop 9292, Livermore, CA 94551 (United States); Lavernia, E.J. [Department of Chemical Engineering and Materials Science, University of California, Davis, CA 95616 (United States); Ong, M.D. [Department of Physics, Whitworth University, Spokane, WA 99251 (United States); Wolfer, W.G.; Yang, N.Y. [Sandia National Laboratories, PO Box 969, Mail Stop 9292, Livermore, CA 94551 (United States)

    2014-02-15

    Highlights: • Experimental evidence of plastic work resulting from hydriding of palladium is presented. • A model of this plastic work was generated and correlated to hysteresis losses. • This hysteresis is thought to be important to the lifetime of hydrogen storage materials. • Yield strength values predicted by this model agree with measured hardness. -- Abstract: The hysteresis observed when reversibly absorbing and desorbing hydrogen in metals is currently not fully understood. In general, a hysteresis represents energy that is dissipated during a cycle, but the underlying mechanism of dissipation is still uncertain. It has been suggested that the hysteresis arises either from plastic work, or from elastic strains associated with the accommodation of the hydride phase, or from both. We present here experimental evidence that implicates plastic deformation as the cause of the hysteresis in a Pd–Rh alloy. The plastic work is evident from the increased dislocation density, from the accumulation of surface steps from slip bands, from line broadening of X-ray diffraction peaks, and from an increase in hardness with the number of hydriding cycles. A model of this plastic work is developed that depends on an effective yield strength. When this model is correlated with the measured hysteresis losses, two values are found for the effective yield strength. The lower value is shown to agree with yield strength values derived from Vickers hardness measurements. The hysteresis areas for repeated cycles of absorption and desorption decrease little with the number of cycles which is reminiscent of the plastic deformation hysteresis during low-cycle fatigue of metals. This similarity further confirms the plastic nature of the hydriding hysteresis.

  3. Giant voltage manipulation of MgO-based magnetic tunnel junctions via localized anisotropic strain: A potential pathway to ultra-energy-efficient memory technology

    Science.gov (United States)

    Zhao, Zhengyang; Jamali, Mahdi; D'Souza, Noel; Zhang, Delin; Bandyopadhyay, Supriyo; Atulasimha, Jayasimha; Wang, Jian-Ping

    2016-08-01

    Voltage control of magnetization via strain in piezoelectric/magnetostrictive systems is a promising mechanism to implement energy-efficient straintronic memory devices. Here, we demonstrate giant voltage manipulation of MgO magnetic tunnel junctions (MTJ) on a Pb(Mg1/3Nb2/3)0.7Ti0.3O3 piezoelectric substrate with (001) orientation. It is found that the magnetic easy axis, switching field, and the tunnel magnetoresistance (TMR) of the MTJ can be efficiently controlled by strain from the underlying piezoelectric layer upon the application of a gate voltage. Repeatable voltage controlled MTJ toggling between high/low-resistance states is demonstrated. More importantly, instead of relying on the intrinsic anisotropy of the piezoelectric substrate to generate the required strain, we utilize anisotropic strain produced using a local gating scheme, which is scalable and amenable to practical memory applications. Additionally, the adoption of crystalline MgO-based MTJ on piezoelectric layer lends itself to high TMR in the strain-mediated MRAM devices.

  4. An experimental investigation of energy absorption in TRIP steel under impact three-point bending deformation

    OpenAIRE

    Pham Hang; Iwamoto Takeshi

    2015-01-01

    TRIP (Transformation-induced Plasticity) steel is nowadays in widespread use in the automobile industry because of their favorable mechanical properties such as high strength, excellent formability and toughness because of strain-induced martensitic transformation. Moreover, when TRIP steel is applied to the components of the vehicles, it is expected that huge amount of kinetic energy will be absorbed into both plastic deformation and martensitic transformation during the collision. Basically...

  5. CO{sub 2} reduction potential of the use of plastic wastes as feedstock in various energy conversion processes; CO{sub 2}-Reduktionspotential durch den Einsatz von Plastikabfaellen in verschiedenen Energiewandlungsprozessen

    Energy Technology Data Exchange (ETDEWEB)

    Romey, I.; Obladen, M. [Essen Univ. (Germany)

    2000-07-01

    Plastic wastes are available in large quantities in Germany (almost 800,000 t per year) and their reutilisation is compulsory under the Recycling Economy Law. This may either be done by raw material recycling or by energy conversion processes. The use of plastic wastes characterised by a high calorific value and low specific CO{sub 2} emissions constitutes a high potential for reducing CO{sub 2} emissions. The CO{sub 2} emissions caused by the additional energy input for preparing and pretreating the plastic are in most cases more than compensated for by the favourable H/C ratio. This paper compares altogether six energy conversion processes in terms of their CO{sub 2} balance. Each individual process is compared with and assessed on the basis of a reference scenario, in accordance with the method of Life Cycle Analysis (LCA). It transpires that in general none of the three process variants materials recycling, raw material recycling, and energy recovery is superior to any other in terms of the CO{sub 2} balance. With the more favourable processes the use of plastic wastes results in a reduction of up to 10% in CO{sub 2} emissions. [German] Plastikabfaelle sind in Deutschland in einer grossen Menge (knapp 800.000 t pro anno) verfuegbar und muessen gemaess Kreislaufwirtschaftsgesetz wiederverwertet werden. Dies ist sowohl durch Rohstoffrecycling als auch in Energiewandlungsprozessen moeglich. Durch den Einsatz von Plastikabfall mit einem charakteristisch hohen Brennwert und niedrigen spezifischen CO{sub 2}-Emissionen ergibt sich ein hohes Potential zur Reduzierung der CO{sub 2}-Emissionen. Die CO{sub 2}-Emissionen bedingt durch den Mehraufwand an Energie fuer die Aufbereitung und die Vorbehandlung des Plastik werden in der Regel durch den Einsatz des Brennstoffs mit dem guenstigeren H/C-Verhaeltnis ueberkompensiert. Im einzelnen werden sechs Energiewandlungsprozesse dargestellt und unter dem Aspekt der CO{sub 2}-Bilanz miteinander verglichen. Dabei wird gemaess der

  6. Prediction of crack growth direction by Strain Energy Sih's Theory on specimens SEN under tension-compression biaxial loading employing Genetic Algorithms

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez-MartInez R; Lugo-Gonzalez E; Urriolagoitia-Calderon G; Urriolagoitia-Sosa G; Hernandez-Gomez L H; Romero-Angeles B; Torres-San Miguel Ch, E-mail: rrodriguezm@ipn.mx, E-mail: urrio332@hotmail.com, E-mail: guiurri@hotmail.com, E-mail: luishector56@hotmail.com, E-mail: romerobeatriz98@hotmail.com, E-mail: napor@hotmail.com [INSTITUTO POLITECNICO NACIONAL Seccion de Estudios de Posgrado e Investigacion (SEPI), Escuela Superior de Ingenieria Mecanica y Electrica (ESIME), Edificio 5. 2do Piso, Unidad Profesional Adolfo Lopez Mateos ' Zacatenco' Col. Lindavista, C.P. 07738, Mexico, D.F. (Mexico)

    2011-07-19

    Crack growth direction has been studied in many ways. Particularly Sih's strain energy theory predicts that a fracture under a three-dimensional state of stress spreads in direction of the minimum strain energy density. In this work a study for angle of fracture growth was made, considering a biaxial stress state at the crack tip on SEN specimens. The stress state applied on a tension-compression SEN specimen is biaxial one on crack tip, as it can observed in figure 1. A solution method proposed to obtain a mathematical model considering genetic algorithms, which have demonstrated great capacity for the solution of many engineering problems. From the model given by Sih one can deduce the density of strain energy stored for unit of volume at the crack tip as dW = [1/2E({sigma}{sup 2}{sub x} + {sigma}{sup 2}{sub y}) - {nu}/E({sigma}{sub x}{sigma}{sub y})]dV (1). From equation (1) a mathematical deduction to solve in terms of {theta} of this case was developed employing Genetic Algorithms, where {theta} is a crack propagation direction in plane x-y. Steel and aluminium mechanical properties to modelled specimens were employed, because they are two of materials but used in engineering design. Obtained results show stable zones of fracture propagation but only in a range of applied loading.

  7. Temperature dependence of strain energy and thermodynamic properties of V2 O5 -based single-walled nanotubes: Zone-folding approach.

    Science.gov (United States)

    Porsev, Vitaly V; Bandura, Andrei V; Evarestov, Robert A

    2016-06-15

    A zone-folding approach is applied to estimate the thermodynamic properties of V2 O5 -based nanotubes. The results obtained are compared with those from the direct calculations. It is shown that the zone-folding approximation allows an accurate estimation of nanotube thermodynamic properties and gives a gain in computation time compared to their direct calculations. Both approaches show that temperature effects do not change the relative stability of V2 O5 free layers and nanotubes derived from the α- and γ-phase. The internal energy thermal contributions into the strain energy of nanotubes are small and can be ignored. © 2016 Wiley Periodicals, Inc.

  8. Energy balance analysis on the pyrolysis process of aluminum-plastic package waste%铝塑包装废物热解过程能量平衡分析

    Institute of Scientific and Technical Information of China (English)

    宋薇; 岳东北; 刘建国; 姚远; 聂永丰

    2012-01-01

    Pyrolysis is an efficient way in the separation of the organics and Al in aluminum-plastic packaging waste.The experiment was performed in a fixed bed reactor heated externally to investigate the trend of mass and energy transfer.The results show that:(1) the optimal temperature for the pyrolysis of aluminum-plastic packaging waste is 723~773 K;(2) the energy recycled is much more than that of pyrolysis required;(3) the net energy recycle rate is 62%~63%.%热解是实现铝塑包装废物中有机物和金属铝分离的有效方法。利用外热式固定床反应系统对其进行热解实验,研究热解时物质与能量流向的变化趋势。结果表明:(1)铝塑包装废物最佳热解温度为723~773 K;(2)热解产生的可回收能量远大于反应所需能量,可以实现热解系统的自供热;(3)铝塑包装废物热解的净能源回收效率为62%~63%。

  9. Recycling of Plastic

    DEFF Research Database (Denmark)

    Christensen, Thomas Højlund; Fruergaard, Thilde

    2011-01-01

    Plastic is produced from fossil oil. Plastic is used for many different products. Some plastic products like, for example, wrapping foil, bags and disposable containers for food and beverage have very short lifetimes and thus constitute a major fraction of most waste. Other plastic products like......, for example, gutters, window frames, car parts and transportation boxes have long lifetimes and thus appear as waste only many years after they have been introduced on the market. Plastic is constantly being used for new products because of its attractive material properties: relatively cheap, easy to form......, good strength and long durability. Recycling of plastic waste from production is well-established, while recycling of postconsumer plastic waste still is in its infancy. This chapter describes briefly how plastic is produced and how waste plastic is recycled in the industry. Quality requirements...

  10. Breeding of Coenzyme Q10 Produced Strain by Low-Energy Ion Implantation and Optimization of Coenzyme Q10 Fermentation

    Institute of Scientific and Technical Information of China (English)

    XU Dejun; ZHENG Zhiming; WANG Peng; WANG Li; YUAN Hang; YU Zengliang

    2008-01-01

    In order to increase the production efficiency of coenzyme Q10, the original strain Agrobacterium tumefaciens ATCC 4452 was mutated by means of Nitrogen ions implantation. A mutant strain, ATX 12, with high contents of coenzyme Q10 was selected. Subsequently, the conditions such as carbohydrate concentration, nitrogen source concentration, inoculum's size, seed age, aeration and temperature which might affect the production of CoQ10 were investigated in detail. Under optimal conditions, the maximum concentration of the intracellular CoQ10 reached 200.3 mg/L after 80 h fed-batch fermentation, about 245% increasing in CoQ10 production after ion implantation, compared to the original strain.

  11. Contribution of plastic waste recovery to greenhouse gas (GHG) savings in Spain

    OpenAIRE

    Sevigné Itoiz, Eva; Martínez Gasol, Carles; Rieradevall, Joan; Gabarrell Durany, Xavier

    2015-01-01

    This paper concentrates on the quantification of greenhouse gas (GHG) emissions of post-consumer plastic waste recovery (material or energy) by considering the influence of the plastic waste quality (high or low), the recycled plastic applications (virgin plastic substitution or non-plastic substitution) and the markets of recovered plastic (regional or global). The aim is to quantify the environmental consequences of different alternatives in order to evaluate opportunities and limitations t...

  12. Micromechanical and Thermodynamic Aspects of the Plastic Spin

    NARCIS (Netherlands)

    Giessen, E. van der

    1991-01-01

    The paper focuses on the concept of plastic spin and its constitutive description in phenomenological theories for macroscopic large strain elastoplasticity. An overview is given of kinematic descriptions of the plastic spin and of constitutive relationships which have been proposed in the literatur

  13. Some Aspects of High Manganese Twinning-Induced Plasticity (TWIP) Steel, A Review

    Institute of Scientific and Technical Information of China (English)

    Liqing CHEN; Yang ZHAO; Xiaomei QIN

    2013-01-01

    High manganese twinning-induced plasticity (TWIP) steel is a new kind of structural material and possesses both high strength and superior plasticity and can meet the weight-lightening requirement for manufacturing vehicle body.The excellent formability of the TWIP steel comes from the extraordinary strain hardening effect during plastic deformation.The reduction of specific weight by aluminum alloying and strain hardening effect can lead to an effective weight reduction of the steel components,and provide a better choice for materials in vehicle body design.The TWIP effect in high Mn steels is generally associated with the successive workhardening generated by twins and influenced by some factors,such as Mn content,AI addition revealed by stacking fault energy (SFE),grain size,deformation temperature and strain rate.The present review introduces some aspects of the TWIP steels relating to their physical metallurgy,influencing factors associated with their deformation mechanisms,and a prospect for the future investigation is also described.Moreover,as a potential candidate for replacing Ni-Cr austenitic stainless steel,researches on the oxidation behavior and corrosion resistance of Fe-Mn-AI-C system steels are also reviewed.

  14. Bounds on the Rate Dependent Plastic Flow of Tantalum up to 75 GPa

    Science.gov (United States)

    Reed, Bryan; Patterson, Reed; Kumar, Mukul

    2013-06-01

    We report improvements in a general thermodynamics-based velocimetry analysis method designed to extract strength and plastic-flow information from shock and ramp compression experiments. The method allows extraction of thermodynamic histories, including deviatoric stress and plastic strain, including nonsteady rate-dependent features. The improved method includes free-surface corrections for pullback waves, reduced noise sensitivity, and application to pressures of 75 GPa and higher. Specifically, we show results for shock waves in tantalum, including bounds on the plastic flow behavior at strain rates exceeding 1e7/s.The deviatoric stress appears to be almost entirely dependent on strain rate, with very little pressure dependence.The deviatoric stress in the post-shock plateau state appears to be very small at higher pressures, calling into question the value of considering strength as a steady- state pressure-dependent quantity. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  15. Silica-Based and Borate-Based, Titania-Containing Bioactive Coatings Characterization: Critical Strain Energy Release Rate, Residual Stresses, Hardness, and Thermal Expansion.

    Science.gov (United States)

    Rodriguez, Omar; Matinmanesh, Ali; Phull, Sunjeev; Schemitsch, Emil H; Zalzal, Paul; Clarkin, Owen M; Papini, Marcello; Towler, Mark R

    2016-12-01

    Silica-based and borate-based glass series, with increasing amounts of TiO₂ incorporated, are characterized in terms of their mechanical properties relevant to their use as metallic coating materials. It is observed that borate-based glasses exhibit CTE (Coefficient of Thermal Expansion) closer to the substrate's (Ti6Al4V) CTE, translating into higher mode I critical strain energy release rates of glasses and compressive residual stresses and strains at the coating/substrate interface, outperforming the silica-based glasses counterparts. An increase in the content of TiO₂ in the glasses results in an increase in the mode I critical strain energy release rate for both the bulk glass and for the coating/substrate system, proving that the addition of TiO₂ to the glass structure enhances its toughness, while decreasing its bulk hardness. Borate-based glass BRT3, with 15 mol % TiO₂ incorporated, exhibits superior properties overall compared to the other proposed glasses in this work, as well as 45S5 Bioglass(®) and Pyrex.

  16. 77 FR 54930 - Carlyle Plastics and Resins, Formerly Known as Fortis Plastics, A Subsidiary of Plastics...

    Science.gov (United States)

    2012-09-06

    ... Employment and Training Administration Carlyle Plastics and Resins, Formerly Known as Fortis Plastics, A... plastic parts. New information shows that Fortis Plastics is now called Carlyle Plastics and Resins. In... of Carlyle Plastics and Resins, formerly known as Fortis Plastics, a subsidiary of...

  17. Electronic Effects versus Distortion Energies During Strain-Promoted Alkyne-Azide Cycloadditions: A Theoretical Tool to Predict Reaction Kinetics

    NARCIS (Netherlands)

    Garcia-Hartjes, J.; Dommerholt, J.; Wennekes, T.; Delft, van F.L.; Zuilhof, H.

    2013-01-01

    Second-order reaction kinetics of known strain-promoted azide–alkyne cycloaddition (SPAAC) reactions were compared with theoretical data from a range of ab initio methods. This produced both detailed insights into the factors determining the reaction rates and two straightforward theoretical tools t

  18. Non-uniform plastic deformation of micron scale objects

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Hutchinson, J. W.

    2003-01-01

    Significant increases in apparent flow strength are observed when non-uniform plastic deformation of metals occurs at the scale ranging from roughly one to ten microns. Several basic plane strain problems are analyzed numerically in this paper based on a new formulation of strain gradient plastic...... in the numerical analysis of the higher order gradient theory will be discussed and related to prior formulations having some of the same features....

  19. Novel synchrotron based techniques for characterization of energy materials

    Energy Technology Data Exchange (ETDEWEB)

    Poulsen, H.F.; Nielsen, S.F.; Olsen, U.L.; Schmidt, S. (Risoe DTU, Materials Research Dept., Roskilde (Denmark)); Wright, J. (European Synchrotron Radiation Facility, Grenoble Cedex (France))

    2008-10-15

    Two synchrotron techniques are reviewed, both based on the use of high energy x-rays, and both applicable to in situ studies of bulk materials. Firstly, 3DXRD microscopy, which enables 3D characterization of the position, morphology, phase, elastic strain and crystallographic orientation of the individual embedded grains in polycrystalline specimens. In favourable cases, hundreds of grains can be studied simultaneously during processing. Secondly, plastic strain tomography: a unique method for determining the plastic strain field within materials during processing the potential applications of these techniques for basic and applied studies of four types of energy materials are discussed: polymer composites for wind turbines, solid oxide fuel cells, hydrogen storage materials and superconducting tapes. Furthermore, progress on new detectors aiming at improving the spatial and temporal resolution of such measurements is described. (au)

  20. Adiabatic shear localization evolution for steel based on the Johnson-Cook model and gradient-dependent plasticity

    Institute of Scientific and Technical Information of China (English)

    Xuebin Wang

    2006-01-01

    Gradient-dependent plasticity is introduced into the phenomenological Johnson-Cook model to study the effects of strainhardening, strain rate sensitivity, thermal-softening, and microstructure. The microstructural effect (interactions and interplay among microstructures) due to heterogeneity of texture plays an important role in the process of development or evolution of an adiabatic shear band with a certain thickness depending on the grain diameter. The distributed plastic shear strain and deformation in the shear band are derived and depend on the critical plastic shear strain corresponding to the peak flow shear stress, the coordinate or position, the internal length parameter, and the average plastic shear strain or the flow shear stress. The critical plastic shear strain, the distributed plastic shear strain, and deformation in the shear band are numerically predicted for a kind of steel deformed at a constant shear strain rate.Beyond the peak shear stress, the local plastic shear strain in the shear band is highly nonuniform and the local plastic shear deformation in the band is highly nonlinear. Shear localization is more apparent with the increase of the average plastic shear strain. The calculated distributions of the local plastic shear strain and deformation agree with the previous numerical and experimental results.