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Sample records for uniaxial stress state

  1. Effective stress coefficient for uniaxial strain condition

    DEFF Research Database (Denmark)

    Alam, M.M.; Fabricius, I.L.

    2012-01-01

    one dimensional rock mechanical deformation. We further investigated the effect of boundary condition on the stress dependency of effective stress coefficient and discussed its application in reservoir study. As stress field in the reservoirs are most unlikely to be hydrostatic, effective stress...... determined under uniaxial strain condition will be more relevant in reservoir studies. Copyright 2012 ARMA, American Rock Mechanics Association....

  2. Thermal expansion, modulus of elasticity, shrinkage, creep and residual strength of concrete for PCRVs at uniaxial stress state and elevated temperatures

    International Nuclear Information System (INIS)

    Aschl, H.; Stoeckl, S.

    1981-01-01

    At the Institut fuer Massivbau of the Technical University of Munich testing machines were built, which allow to test sealed and unsealed cylinders with uniaxial stress state at elevated temperatures till 523 K (250 0 C). With this equipment tests were carried out at predried, unsealed and sealed specimens to study - thermal expansion coefficient - modulus of elasticity - shrinkage and - creep of concrete at elevated temperatures of 353 K (80 0 C) and 393 K (120 0 C) and at a normal temperature of 293 K (20 0 C). In addition the residual strength of all specimens was measured. In the worst case (unsealed, i.e. drying specimens) some showed a maximum decrease in strength up to 60%. (orig.) [de

  3. Effect of uniaxial stress on the acceptor ground state and on the hopping conduction in p-type germanium and silicon

    International Nuclear Information System (INIS)

    Buczko, R.; Chroboczek, J.A.

    1983-08-01

    We constructed variational wave functions, with correct asymptotic behaviour, for the ground state of shallow acceptors in Ge and Si, utilizing the spherical tensor representation of the effective mass hamiltonian of Baldereschi and Lipari (1973), at uniaxial stress, X, resulting from the application of a tensile or compressive force along the [001] orientation (respectively X 0). Energies of the components of the ground state, computed variationally, account very well for the X-induced displacements of the binding energies and the stress splitting of shallow acceptors in both Ge and Si, at X>0 (no data for X 0. However, they account only qualitatively for the rho(X) data available for Si (X>0 only), probably because of a larger chemical shift of the acceptor ground state in Si and its possible variation with X. At larger acceptor concentrations rho(X) decreases, at large X, much stronger than predicted for both Ge and Si. We attribute this discrepancy to the increase of the contribution to electron transport of multiple hopping transitions at large X values. (author)

  4. Electronic processes in uniaxially stressed p-type germanium

    Energy Technology Data Exchange (ETDEWEB)

    Dubon, Jr., Oscar Danilo [Univ. of California, Berkeley, CA (United States)

    1996-02-01

    Effect of uniaxial stress on acceptor-related electronic processes in Ge single crystals doped with Ga, Be, and Cu were studied by Hall and photo-Hall effect measurements in conjunction with infrared spectroscopy. Stress dependence of hole lifetime in p-type Ge single crystals is used as a test for competing models of non-radiative capture of holes by acceptors. Photo-Hall effect shows that hole lifetime in Ga- and Be-doped Ge increases by over one order of magnitude with uniaxial stress at liq. He temps. Photo-Hall of Ge:Be shows a stress-induced change in the temperature dependence of hole lifetime. This is consistent with observed increase of responsivity of Ge:Ga detectors with uniaxial stress. Electronic properties of Ge:Cu are shown to change dramatically with uniaxial stress; the results provide a first explanation for the performance of uniaxially stressed, Cu-diffused Ge:Ga detectors which display a high conductivity in absence of photon signal and therefore have poor sensitivity.

  5. Magnetic phase transitions and hydrostatic pressure or uniaxial stress experiments

    International Nuclear Information System (INIS)

    Bloch, D.

    1980-01-01

    Crystals submitted to high hydrostatic pressure or uniaxial stress have been investigated by means of neutron scattering. The techniques used are described and applications to pressure or stress induced T = 0 magnetic to nonmagnetic transitions (Pr,PrSb) and continuous to discontinuous order-disorder transitions (MnO) are given. (orig.)

  6. Uniaxially stressed Ge:Ga and Ge:Be

    Energy Technology Data Exchange (ETDEWEB)

    Dubon, Jr., Oscar Danilo [Univ. of California, Berkeley, CA (United States)

    1992-12-01

    The application of a large uniaxial stress to p-type Ge single crystals changes the character of both the valence band and the energy levels associated with the acceptors. Changes include the splitting of the fourfold degeneracy of the valence band top and the reduction of the ionization energy of shallow acceptors. In order to study the effect of uniaxial stress on transport properties of photoexcited holes, a variable temperature photo-Hall effect system was built in which stressed Ge:Ga and Ge:Be could be characterized. Results indicate that stress increases the lifetime and Hall mobility of photoexcited holes. These observations may help further the understanding of fundamental physical processes that affect the performance of stressed Ge photoconductors including the capture of holes by shallow acceptors.

  7. On generalization uniaxial stress-strain relation

    International Nuclear Information System (INIS)

    Sahay, C.; Dubey, R.N.

    1980-01-01

    Different forms of constitutive relations have been advanced for elastic, plastic and elastic-plastic behaviour of materials. It is shown that the various forms of the stress-strain relationship are specialized forms of generalization of a single stress-strain relation. For example, it is shown how the laws of elastic deformation, and the incremental and total deformation relationship for plastic behaviour are derivable from the Ramberg-Osgood relation. (orig.)

  8. Enhanced electron-lattice coupling under uniaxial stress in layered double hydroxides intercalated with samarium complexes

    International Nuclear Information System (INIS)

    Park, Ta-Ryeong

    2004-01-01

    We have applied uniaxial stress to samarium complexes by intercalating them into the gallery of a layered material and by using a diamond-anvil cell at 28 K. Although uniaxial stress reduces symmetry and removes degeneracy, the overall number of photoluminescence (PL) peaks evidently decreased with the application of uniaxial stress. This contradictory observation is explained by an increased electron-lattice coupling strength under uniaxial stress. This behavior is also confirmed by time-resolved PL data.

  9. Influence of an uniaxial stress on point defects

    International Nuclear Information System (INIS)

    Beuneu, B.

    1984-03-01

    We study two effects of an elastic external uniaxial stress on point defects (created by electron irradiation): 1.- We measure the linear variation of their resistivity rhosub(D) under the elastic strain epsilon in Copper. It gives the specific elastoresistivity (E.R.S.) chisub(D)=delta rhosub(D)/epsilon. With the help of the results of VON STEBUT (fast neutrons) we show that the E.R.S. is characteristic of a defect and of its configuration. 2.- By means of resistivity measurements in molybdenum, we observe a paraelastic phenomenon. It is thermally activated (νsub(0) approximately= 10 12 s -1 and E approximately= 72 meV) and we attribute it to the reorientation of a dumbell interstitial under the uniaxial stress. The resistivity of this dumbbell is higher along its axis than perpendicularly to it. We have completed these results with some configuration energy calculations for the dumbbell and with a simple kinetic model [fr

  10. Surface Wave Velocity-Stress Relationship in Uniaxially Loaded Concrete

    DEFF Research Database (Denmark)

    Shokouhi, Parisa; Zoëga, Andreas; Wiggenhauser, Herbert

    2012-01-01

    The sonic surface wave (or Rayleigh wave) velocity measured on prismatic concrete specimens under uniaxial compression was found to be highly stress-dependent. At low stress levels, the acoustoelastic effect and the closure of existing microcracks results in a gradual increase in surface wave...... velocities. At higher stress levels, concrete suffers irrecoverable damage: the existing microcracks widen and coalesce and new microcracks form. This progressive damage process leads first to the flattening and eventually the drop in the velocity-stress curves. Measurements on specimens undergoing several...... loading cycles revealed that the velocities show a stress-memory effect in good agreement with the Kaiser effect. Comparing the velocities measured during loading and unloading, the effects of stress and damage on the measured velocities could be differentiated. Moreover, the stress dependency of surface...

  11. Raman study of lead zirconate titanate under uniaxial stress

    International Nuclear Information System (INIS)

    Tallant, David R.; Simpson, Regina L.; Grazier, J. Mark; Zeuch, David H.; Olson, Walter R.; Tuttle, Bruce A.

    2000-01-01

    The authors used micro-Raman spectroscopy to monitor the ferroelectric (FE) to antiferroelectric (AFE) phase transition in PZT ceramic bars during the application of uniaxial stress. They designed and constructed a simple loading device, which can apply sufficient uniaxial force to transform reasonably large ceramic bars while being small enough to fit on the mechanical stage of the microscope used for Raman analysis. Raman spectra of individual grains in ceramic PZT bars were obtained as the stress on the bar was increased in increments. At the same time gauges attached to the PZT bar recorded axial and lateral strains induced by the applied stress. The Raman spectra were used to calculate an FE coordinate, which is related to the fraction of FE phase present. The authors present data showing changes in the FE coordinates of individual PZT grains and correlate these changes to stress-strain data, which plot the macroscopic evolution of the FE-to-AFE transformation. Their data indicates that the FE-to-AFE transformation does not occur simultaneously for all PZT grains but that grains react individually to local conditions

  12. Magnetic properties of URu2Si2 under uniaxial stress by neutron scattering

    International Nuclear Information System (INIS)

    Bourdarot, Frederic; Martin, Nicolas; Raymond, Stephane; Regnault, Louis-Pierre; Aoki, Dai; Taufour, Valentin; Flouquet, Jacques

    2011-01-01

    The aim of this study is to compare the magnetic behavior of URu 2 Si 2 under uniaxial stress along the a axis with the behavior under hydrostatic pressure. Both are very similar, but uniaxial stress presents a critical stress σ x a [0.33(5) GPa] that is smaller than the hydrostatic critical pressure p x (0.5 GPa) where the ground state switches from a HO (hidden-order) to AF (antiferromagnetic) ground state. From these critical values and Larmor neutron diffraction, we conclude that the magnetic properties are governed by the shortest U-U distance in the plane (a lattice parameter). Under stress, the orthorhombic unit cell stays centered. A key point shown by this study is the presence of a threshold for the uniaxial stress along the a axis before the appearance of the large AF moment, which indicates no mixture of the order parameter between the HO ground state and the AF one as under hydrostatic pressure. The two most intense longitudinal magnetic excitations at Q 0 =(1,0,0) and Q 1 =(0.6,0,0) were measured in the HO state: the excitation at Q 0 decreases in energy while the excitation at Q 1 increases in energy with the uniaxial stress along the a axis. The decrease of the energy of the excitation at Q 0 seems to indicate a critical energy-gap value of 1.2(1) meV at σ x a . A similar value was derived from studies under hydrostatic pressure at p x .

  13. Analysis of threshold current of uniaxially tensile stressed bulk Ge and Ge/SiGe quantum well lasers.

    Science.gov (United States)

    Jiang, Jialin; Sun, Junqiang; Gao, Jianfeng; Zhang, Ruiwen

    2017-10-30

    We propose and design uniaxially tensile stressed bulk Ge and Ge/SiGe quantum well lasers with the stress along direction. The micro-bridge structure is adapted for introducing uniaxial stress in Ge/SiGe quantum well. To enhance the fabrication tolerance, full-etched circular gratings with high reflectivity bandwidths of ~500 nm are deployed in laser cavities. We compare and analyze the density of state, the number of states between Γ- and L-points, the carrier injection efficiency, and the threshold current density for the uniaxially tensile stressed bulk Ge and Ge/SiGe quantum well lasers. Simulation results show that the threshold current density of the Ge/SiGe quantum well laser is much higher than that of the bulk Ge laser, even combined with high uniaxial tensile stress owing to the larger number of states between Γ- and L- points and extremely low carrier injection efficiency. Electrical transport simulation reveals that the reduced effective mass of the hole and the small conduction band offset cause the low carrier injection efficiency of the Ge/SiGe quantum well laser. Our theoretical results imply that unlike III-V material, uniaxially tensile stressed bulk Ge outperforms a Ge/SiGe quantum well with the same strain level and is a promising approach for Si-compatible light sources.

  14. Heat induced fracturing of rock in an existing uniaxial stress field

    International Nuclear Information System (INIS)

    Mathis, J.; Stephansson, O.; Bjarnason, B.; Hakami, H.; Herdocia, A.; Mattila, U.; Singh, U.

    1986-01-01

    This study was initiated under the premise that it may be possible to determine the state of stress in the earth's crust by heat induced fracturing of the rock surrounding a borehole. The theory involved is superficially simple, involving the superposition of the stress field around a borehole due to the existing virgin stresses and the uniform stress field of thermally loaded rock as induced by a heater. Since the heat stress field is uniform, varying only in magnitude and gradient as a function of heater input, fracturing should be controlled by the non-uniform virgin stress field. To determine if the method was, in fact, feasible, a series of laboratory test were conducted. These tests consisted of physically loading center drilled cubes of rock, 0.3 m on a side, uniaxially from 0 to 25 MPa. The blocks were then thermally loaded with a nominally rated 3.7 kW heater until failure occurred. Results from these laboratory tests were then compared to analytical studies of the problem, i.e., finite element and discrete theoretical analysis. Overall, results were such that the method is likely eliminated as a stress measurement technique. The immediate development of a thermal compressive zone on the borehole wall overlaps the tensile zone created by the uniaxial stress field, forcing the failure is thus controlled largely by the power input of the heater, being retarded by the small compressive stresses genrated by the uniaxial stress field. This small retardation effect is of such low magnitude that the retardation effect is of such low magnitude that the fracture time is relatively insensitive to the local virgin stress field. (authors)

  15. 2D magnetization of grain-oriented 3%-Si steel under uniaxial stress

    International Nuclear Information System (INIS)

    Permiakov, V.; Dupre, L.; Pulnikov, A.; Melkebeek, J.

    2005-01-01

    Magnetization in electrical steels is strongly affected by mechanical stress. The stress dependence of magnetic properties of non-oriented steels has been studied at one- and two-dimensional magnetization. This paper deals with the stress effect on one- and two-dimensional magnetization in grain-oriented 3%-Si steel. The special magnetic measurements system is applied to combine uniaxial stress and 2D magnetic measurements. The uniaxial stress ranges from 10 MPa compressive stress to 100 MPa tensile stress. A domain theory is a suitable tool for prediction and a physical explanation of stress dependency in grain-oriented steel

  16. The impact of uniaxial stress on subband structure and mobility of strain Si NMOSFETs

    International Nuclear Information System (INIS)

    Chang, S.T.; Liao, S.H.; Lin, C.-Y.

    2008-01-01

    An effect of stress distortion on the conduction band structure was derived by k.p method considering a second order perturbation. From k.p conduction band calculations, stress-induced band edge split and the change of effective mass are quantitatively evaluated. The physical reasons of warped subband structure and abnormal mobility enhancement by uniaxial stress are investigated. Variation rates of experimental electron mobility in the silicon n-channel metal-oxide-semiconductor field-effect-transistors under a [110] uniaxial stress as a function of channel direction is theoretically studied

  17. Electric signal emissions during repeated abrupt uniaxial compressional stress steps in amphibolite from KTB drilling

    Directory of Open Access Journals (Sweden)

    D. Triantis

    2007-01-01

    Full Text Available Laboratory experiments have confirmed that the application of uniaxial stress on rock samples is accompanied by the production of weak electric currents, to which the term Pressure Stimulated Currents – PSC has been attributed. In this work the PSC emissions in amphibolite samples from KTB drilling are presented and commented upon. After having applied sequential loading and unloading cycles on the amphibolite samples, it was ascertained that in every new loading cycle after unloading, the emitted PSC exhibits lower peaks. This attitude of the current peaks is consistent with the acoustic emissions phenomena, and in this work is verified for PSC emissions during loading – unloading procedures. Consequently, the evaluation of such signals can help to correlate the state and the remaining strength of the sample with respect to the history of its mechanical stress.

  18. Diffraction Plane Dependence of Micro Residual Stresses in Uniaxially Extended Carbon Steels

    Directory of Open Access Journals (Sweden)

    T. Hanabusa

    2010-12-01

    Full Text Available In the stress measurement using X-ray or neutron diffraction, an elastic anisotropy as well as a plastic anisotropy of crystal must be carefully considered. In the X-ray and neutron diffraction stress measurement for polycrystalline materials, a particular {hkl} plane is used in measuring lattice strains. The dependence of an X-ray elastic constant on a diffraction plane is a typical example caused by an elastic anisotropy of the crystal. The yield strength and the work hardening rate of a single crystal depend on a crystallographic direction of the crystal. The difference in the yield strength and the work hardening rate relating to the crystallographic direction develops different residual stresses measured on each {hkl} diffraction after plastic deformation of a polycrystalline material. The present paper describes the result of the neutron stress measurement on uniaxially extended low and middle carbon steels. A tri-axial residual stress state developed in the extended specimens was measured on different kind of {hkl} diffraction plane. The measurement on the {110}, {200} and {211} diffraction showed that residual stresses increased with increasing the plastic elongation and the residual stresses on {110} were compressive, {200} were tensile and those on {211} were the middle of the former two planes.

  19. A novel method for estimating soil precompression stress from uniaxial confined compression tests

    DEFF Research Database (Denmark)

    Lamandé, Mathieu; Schjønning, Per; Labouriau, Rodrigo

    2017-01-01

    . Stress-strain curves were obtained by performing uniaxial, confined compression tests on undisturbed soil cores for three soil types at three soil water potentials. The new method performed better than the Gompertz fitting method in estimating precompression stress. The values of precompression stress...... obtained from the new method were linearly related to the maximum stress experienced by the soil samples prior to the uniaxial, confined compression test at each soil condition with a slope close to 1. Precompression stress determined with the new method was not related to soil type or dry bulk density......The concept of precompression stress is used for estimating soil strength of relevance to fieldtraffic. It represents the maximum stress experienced by the soil. The most recently developed fitting method to estimate precompression stress (Gompertz) is based on the assumption of an S-shape stress...

  20. Refractive indices of K2ZnCl4 crystals in an incommensurate phase under uniaxial stresses

    International Nuclear Information System (INIS)

    Gaba, V.M.; Kogut, Z.O.; Brezvin, R.S.; Stadnik, V.I.

    2010-01-01

    The influence of uniaxial mechanical stresses directed along the principal crystallophysical axes on refractiveindex temperature dependences in K 2 ZnCl 4 crystals was studied. It is established that the refractive indices ni are quite sensitive to uniaxial stresses. Significant baric shifts of the paraphase-incommensurate-commensurate phase transition points to different temperature regions were observed, which is due to the effect of the uniaxial stress on the K 2 ZnCl 4 crystal structure. It is found that applying uniaxial pressure increases the value of the temperature hysteresis of the commensurate-incommensurate phase transition. (authors)

  1. Terahertz absorption and emission upon the photoionization of acceptors in uniaxially stressed silicon

    Energy Technology Data Exchange (ETDEWEB)

    Zhukavin, R. Kh., E-mail: zhur@ipmras.ru; Kovalevsky, K. A.; Orlov, M. L.; Tsyplenkov, V. V. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Hübers, H.-W. [DLR Institute of Optical Sensor Systems (Germany); Dessmann, N. [Humboldt University of Berlin, Institute of Physics (Germany); Kozlov, D. V.; Shastin, V. N. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)

    2016-11-15

    Experimental data on the spontaneous emission and absorption modulation in boron-doped silicon under CO{sub 2} laser excitation depending on the uniaxial stress applied along the [001] and [011] crystallographic directions are presented. Room-temperature radiation is used as the probe radiation. Low stress (less than 0.5 kbar) is shown to reduce losses in the terahertz region by 20%. The main contribution to absorption modulation at zero and low stress is made by A{sup +} centers. Intersubband free hole transitions additionally contribute to terahertz absorption at higher stress. These contributions can be minimized by compensation.

  2. Kinetics of interstitial defects in α-Fe: The effect from uniaxial stress

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Changwoo [Department of Nuclear Engineering, Texas A& M University, College Station, TX 77843 (United States); Wang, Qingyu [College of Nuclear Science and Technology, Harbin Engineering University, Harbin 150001 (China); Shao, Lin, E-mail: lshao@tamu.edu [Department of Nuclear Engineering, Texas A& M University, College Station, TX 77843 (United States)

    2017-03-15

    Understanding defect kinetics in a stress field is important for multiscale modeling of materials degradation of nuclear materials. By means of molecular dynamics and molecular statics simulations, we calculate formation and migration energies of self-interstitial atoms (SIA) and SIA clusters (up to size of 5 interstitials) in alpha Fe and identify their stable configurations under uniaxial tensile strains. By applying uniaxial stress along [111], <111> oriented single SIA defects become more stable than <110> oriented SIA, which is opposite to stress-free condition. Diffusion of single SIA defects under [111] tensile stress is facilitated along [111] direction and the diffusion becomes one dimensional (1D). For SIA clusters, their diffusion under zero stress has gradual transition from three dimensional (3D) for small clusters to one dimensional (1D) for large clusters. Under the tensile stress along [111], the 3D to 1D transition is accelerated. For large SIA clusters, the stress effect is quickly saturated with less diffusivity enhancement in comparison with small SIA clusters.

  3. Performance enhancement in uniaxially tensile stressed GeSn n-channel fin tunneling field-effect transistor: Impact of stress direction

    Science.gov (United States)

    Wang, Hongjuan; Han, Genquan; Jiang, Xiangwei; Liu, Yan; Zhang, Chunfu; Zhang, Jincheng; Hao, Yue

    2017-04-01

    In this work, the boosting effect on the performance of GeSn n-channel fin tunneling FET (nFinTFET) enabled by uniaxial tensile stress is investigated theoretically. As the fin rotates within the (001) plane, the uniaxial tensile stress is always along its direction. The electrical characteristics of tensile-stressed GeSn nFinTFETs with point and line tunneling modes are computed utilizing the technology computer aided design (TCAD) simulator in which the dynamic nonlocal band-to-band tunneling (BTBT) algorithm is employed. In comparison with the relaxed devices, tensile-stressed GeSn nFinTFETs achieve a substantial enhancement in band-to-band tunneling generation rate (G BTBT) and on-state current I ON owing to the reduced bandgap E G induced by the tensile stress. Performance improvement of GeSn nFinTFETs induced by tensile stress demonstrates a strong dependence on channel direction and tunneling modes. Under the same magnitude of stress, line-nFinTFETs obtain a more pronounced I ON enhancement over the transistors with point tunneling mode.

  4. Determination of Hot-Carrier Distribution Functions in Uniaxially Stressed p-Type Germanium

    DEFF Research Database (Denmark)

    Christensen, Ove

    1973-01-01

    This paper gives a description of an experimental determination of distribution functions in k→ space of hot holes in uniaxially compressed germanium. The hot-carrier studies were made at 85°K at fields up to 1000 V/cm and uniaxial stresses up to 11 800 kg/cm2. The field and stress were always in...... probabilities with stress. A model based on the nonparabolicity of the upper p3 / 2 level is proposed for the negative differential conductivity in stressed p-type Ge....... function has been assumed. The parameters of the distribution function are then fitted to the experimental modulation. The calculation of absorption was performed numerically, using a four-band k→·p→ model. This model was checked for consistency by comparing with piezoabsorption measurements performed...... in thermal equilibrium. The average carrier energy calculated from the distribution function shows a fast increase with stress and almost saturates when the strain splitting of the two p3 / 2 levels reaches the optical-phonon energy. This saturation is interpreted in terms of the change in scattering...

  5. An effective uniaxial tensile stress-strain relationship for prestressed concrete

    International Nuclear Information System (INIS)

    Chitnuyanondh, L.; Rizkalla, S.; Murray, D.W.; MacGregor, J.G.

    1979-02-01

    This report evaluates the direct tensile strength and an equivalent uniaxial tensile stress-strain relationship for prestressed concrete using data from specimens tested at the University of Alberta which represent segments from the wall of a containment vessel. The stress-strain relationship, when used in conjunction with the BOSOR5 program, enables prediction of the response of prestressed concrete under any biaxial combination of compressive and/or tensile stresses. Comparisons between the experimental and analytical (BOSOR5) load-strain response of the wall segments are also presented. It is concluded that the BOSOR5 program is able to predict satisfactorily the response of the wall segments and multi-layered shell structures. (author)

  6. Uniaxial stress influence on electrical conductivity of thin epitaxial lanthanum-strontium manganite films

    Energy Technology Data Exchange (ETDEWEB)

    Stankevič, V., E-mail: wstan@pfi.lt [Center for Physical Sciences and Technology, Semiconductor Physics Institute, A.Gostauto 11, Vilnius (Lithuania); Vilnius Gediminas Technical University, Sauletekio 11, Vilnius (Lithuania); Šimkevičius, Č.; Balevičius, S.; Žurauskienė, N. [Center for Physical Sciences and Technology, Semiconductor Physics Institute, A.Gostauto 11, Vilnius (Lithuania); Vilnius Gediminas Technical University, Sauletekio 11, Vilnius (Lithuania); Cimmperman, P. [Center for Physical Sciences and Technology, Semiconductor Physics Institute, A.Gostauto 11, Vilnius (Lithuania); Abrutis, A. [Vilnius University, Dept. of General and Inorganic Chemistry, Naugarduko 24, Vilnius (Lithuania); Plaušinaitienė, V. [Center for Physical Sciences and Technology, Semiconductor Physics Institute, A.Gostauto 11, Vilnius (Lithuania); Vilnius University, Dept. of General and Inorganic Chemistry, Naugarduko 24, Vilnius (Lithuania)

    2013-07-01

    This is a study of the influence of external uniaxial mechanical strains on the transport properties of thin epitaxial La{sub 0.83}Sr{sub 0.17}MnO{sub 3} (LSMO) films. Our measurements were carried out using standard isosceles triangle-shaped cantilever. Films which were tensed in-plane or compressed or were subjected to both tension and compression strains were grown onto SrTiO{sub 3} (STO), LaAlO{sub 3} (LAO) and (001) NdGaO{sub 3} (NGO) substrates, respectively. It was found that for thin films (less than 100 nm), the uniaxial compression of such films which were initially tensed in-plane (grown onto STO substrates) produces a decrease of their resistance, whereas the compression of initially compressed films (on LAO substrates) produces an increase of the films' resistance. The same results were obtained for LSMO films grown onto (001) NGO substrates when they were compressed along the [010] and [100] directions, respectively. For thicker films (more than 100 nm), the resistance behavior after uniaxial compression was found to be identical to that produced by hydrostatic compression, namely, the resistance decreases irrespective of the substrate. These experiments also reveal an increase of resistance and a shift of metal–insulator transition temperature T{sub m} to lower temperatures corresponding to a decrease of the film thickness. The occurrence of this effect is also independent of the kind of substrate used. Thus it was concluded that the influence of film thickness on its resistance as well as on the behavior of such films while under external uniaxial compression cannot be explained fully by only the presence of residual stress in these films. A possible reason is that the inhomogeneous distribution of the mechanical stresses in the films can lead to the appearance of two conductivity phases, each having a different mechanism. The results which were obtained when these films were subjected to hydrostatic compression were also explained by this

  7. NbSe3: Fermi surface and magnetoresistance under uniaxial stress

    International Nuclear Information System (INIS)

    Tessema, G.X.; Gamble, B.K.; Kuh, J.; Skove, M.J.; Lacerda, A.H.; Bennett, M.

    1999-01-01

    The Fermi surface of NbSe 3 below the two CDW transitions is still not very clear. Large magnetoresistance and giant quantum oscillations have been seen at low temperature below the second CDW transition. The SdH oscillations are attributed to one or several small pieces of electron or hole pockets spared by the two CDW transitions at 145 and 59 K. In a previous low field study (μ 0 H<8 T) of the transverse magnetoresistance (H in the (b,c) plane) we have shown that the extremal area of one of these pockets decreases linearly with strain, ε, vanishing at ε = 2.5%. Here we extend our study into the high magnetic field regime (pulsed 60 T) and investigate the effect of uniaxial stress on the magnetoresistance (I//H). Our high field study is consistent with the fermiology study and shows that uniaxial stress leads to the obliteration of a small closed pocket. Above 1% strain the magnetoresistance is linear with H with no sign of saturation. (orig.)

  8. Stress relaxation of entangled polystyrene solution after constant-rate, uniaxial elongation

    DEFF Research Database (Denmark)

    Matsumiya, Yumi; Masubuchi, Yuichi; Watanabe, Hiroshi

    For an entangled solution of linear polystyrene (PS 545k; M = 545k) in dibutyl phthalate (DBP), the stress relaxation after constant-rate uniaxial elongation was examined with an extensional viscosity fixture mounted on ARES (TA Instruments). The PS concentration, c = 52 wt%, was chosen in a way...... that the entanglement density M/Me of the solution coincided with that of PS 290k melt (M = 290k). After the elongation at the Rouse-based Weissenberg number Wi(R) ~ 3 up to the Hencky strain of 3, the short time stress relaxation of the solution was accelerated by a factor of ~4, which was less significant compared...... and the lack of monotonic thinning observed for the semidilute solutions. Results for less concentrated solutions will be also presented on site....

  9. High Temperature Uniaxial Compression and Stress-Relaxation Behavior of India-Specific RAFM Steel

    Science.gov (United States)

    Shah, Naimish S.; Sunil, Saurav; Sarkar, Apu

    2018-05-01

    India-specific reduced activity ferritic martensitic steel (INRAFM), a modified 9Cr-1Mo grade, has been developed by India as its own structural material for fabrication of the Indian Test Blanket Module (TBM) to be installed in the International Thermonuclear Energy Reactor (ITER). The extensive study on mechanical and physical properties of this material has been currently going on for appraisal of this material before being put to use in the ITER. High temperature compression, stress-relaxation, and strain-rate change behavior of the INRAFM steel have been investigated. The optical microscopic and scanning electron microscopic characterizations were carried out to observe the microstructural changes that occur during uniaxial compressive deformation test. Comparable true plastic stress values at 300 °C and 500 °C and a high drop in true plastic stress at 600 °C were observed during the compression test. Stress-relaxation behaviors were investigated at 500 °C, 550 °C, and 600 °C at a strain rate of 10-3 s-1. The creep properties of the steel at different temperatures were predicted from the stress-relaxation test. The Norton's stress exponent (n) was found to decrease with the increasing temperature. Using Bird-Mukherjee-Dorn relationship, the temperature-compensated normalized strain rate vs stress was plotted. The stress exponent (n) value of 10.05 was obtained from the normalized plot. The increasing nature of the strain rate sensitivity (m) with the test temperature was found from strain-rate change test. The low plastic stability with m 0.06 was observed at 600 °C. The activation volume (V *) values were obtained in the range of 100 to 300 b3. By comparing the experimental values with the literature, the rate-controlling mechanisms at the thermally activated region of high temperature were found to be the nonconservative movement of jogged screw dislocations and thermal breaking of attractive junctions.

  10. Effect of uniaxial stress on the electrochemical properties of graphene with point defects

    Science.gov (United States)

    Szroeder, Paweł; Sagalianov, Igor Yu.; Radchenko, Taras M.; Tatarenko, Valentyn A.; Prylutskyy, Yuriy I.; Strupiński, Włodzimierz

    2018-06-01

    We report a calculational study of electron states and the resulting electrochemical properties of uniaxially strained graphene with point defects. For this study the reduction of ferricyanide to ferrocyanide serves as a benchmark electrochemical reaction. We find that the heterogeneous electron transfer activity of the perfect graphene electrode rises under uniaxial strain. However, evolution of the cathodic reaction rate depends on the direction of strain. For moderate lattice deformations, the zigzag strain improves electrochemical performance better than the armchair strain. Standard rate constant increases by 50% at the zigzag strain of 10%. Vacancies, covalently bonded moieties, charged adatoms and substitutional impurities in the zigzag strained graphene induce changes in the shape of the curve of the cathodic reaction rate. However, this changes do not translate into the electrocatalytic activity. Vacancies and covalently bonded moieties at concentration of 0.1% do not affect the electrochemical performance. Charged adatoms and substitutional impurities give a slight increase in the standard rate constant by, respectively, 2.2% and 3.4%.

  11. A study on stress analysis of small punch-creep test and its experimental correlations with uniaxial-creep test

    International Nuclear Information System (INIS)

    Lee, Song In; Baek, Seoung Se; Kwon, Il Hyun; Yu, Hyo Sun

    2002-01-01

    A basic research was performed to ensure the usefulness of Small Punch-creep(SP-creep) test for residual life evaluation of heat resistant components effectively. This paper presents analytical results of initial stress and strain distributions in SP specimen caused by constant loading for SP-creep test and its experimental correlations with uniaxial creep(Ten-creep) test on 9CrlMoVNb steel. It was shown that the initial maximum equivalent stress, σ eq · max from FE analysis was correlated with steady-state equivalent creep strain rate, ε qf-ss , rupture time, t r , activation energy, Q and Larson-Miller parameter, LMP during SP-creep deformation. The simple correlation laws, σ SP - σ TEN , P SP -σ TEN and Q SP -Q TEN adopted to established a quantitative correlation between SP-creep and Ten-creep test data. Especially, the activation energy obtained from SP-creep test is linearly related to that from Ten-creep test at 650 deg. C as follows : Q SP-P =1.37 Q TEN , Q SP-σ =1.53 Q TEN

  12. Pressure-induced α->ω transition in titanium metal: a systematic study of the effects of uniaxial stress

    International Nuclear Information System (INIS)

    Errandonea, Daniel; Meng, Y.; Somayazulu, M.; Haeusermann, D.

    2005-01-01

    The effects of uniaxial stress on the pressure-induced α->ω transition in pure titanium (Ti) are investigated by means of angle dispersive X-ray diffraction in a diamond-anvil cell. Experiments under four different pressure environments reveal that: (1) the onset of the transition depends on the pressure medium used, going from 4.9GPa (no pressure medium) to 10.5GPa (argon pressure medium); (2) the α and ω phases coexist over a rather large pressure range, which depends on the pressure medium employed; (3) the hysteresis and quenchability of the ω phase is affected by differences in the sample pressure environment; and (4) a short-term laser heating of Ti lowers the α->ω transition pressure. Possible transition mechanisms are discussed in the light of the present results, which clearly demonstrate the influence of uniaxial stress in the α->ω transition

  13. Analytical description of changes in the magnetic states of chromium-nickel steel under uniaxial elastic deformation

    Science.gov (United States)

    Gorkunov, E. S.; Yakushenko, E. I.; Zadvorkin, S. M.; Mushnikov, A. N.

    2017-12-01

    Dependences of magnetization and magnetic permeability of the 15KhN4D structural steel on the value of uniaxial stresses and magnetic field strength are obtained. A polynomial approximation fairly accurately describing the observed changes is proposed on the basis of experimental data.

  14. Uniaxial stress-driven coupled grain boundary motion in hexagonal close-packed metals: A molecular dynamics study

    International Nuclear Information System (INIS)

    Zong, Hongxiang; Ding, Xiangdong; Lookman, Turab; Li, Ju; Sun, Jun

    2015-01-01

    Stress-driven grain boundary (GB) migration has been evident as a dominant mechanism accounting for plastic deformation in crystalline solids. Using molecular dynamics (MD) simulations on a Ti bicrystal model, we show that a uniaxial stress-driven coupling is associated with the recently observed 90° GB reorientation in shock simulations and nanopillar compression measurements. This is not consistent with the theory of shear-induced coupled GB migration. In situ atomic configuration analysis reveals that this GB motion is accompanied by the glide of two sets of parallel dislocation arrays, and the uniaxial stress-driven coupling is explained through a composite action of symmetrically distributed dislocations and deformation twins. In addition, the coupling factor is calculated from MD simulations over a wide range of temperatures. We find that the coupled motion can be thermally damped (i.e., not thermally activated), probably due to the absence of the collective action of interface dislocations. This uniaxial coupled mechanism is believed to apply to other hexagonal close-packed metals

  15. High pressure measurement of the uniaxial stress of host layers on intercalants and staging transformation of intercalation compounds

    CERN Document Server

    Park, T R; Kim, H; Min, P

    2002-01-01

    A layered double-hydroxide intercalation compound was synthesized to measure the uniaxial stress the host layers exert on the intercalants. To measure the uniaxial stress, we employed the photoluminescence (PL) from the intercalated species, the Sm ion complex, as it is sensitive to the deformation of the intercalants. Of the many PL peaks the Sm ion complex produces, the one that is independent of the counter-cation environment was chosen for the measurement since the Sm ion complexes are placed under a different electrostatic environment after intercalation. The peak position of the PL was redshifted linearly with increasing hydrostatic pressure on the intercalated sample. Using this pressure-induced redshifting rate and the PL difference at ambient pressure between the pre-intercalation and the intercalated ions, we found that, in the absence of external pressure, the uniaxial stress exerted on the samarium ion complexes by the host layers was about 13.9 GPa at room temperature. Time-resolved PL data also ...

  16. Stress state dependence of transient irradiation creep in 20% cold worked 316 stainless steel

    International Nuclear Information System (INIS)

    Foster, J.P.; Gilbert, E.R.

    1998-01-01

    Irradiation creep tests were performed in fast reactors using the stress states of uniaxial tension, biaxial tension, bending and torsion. In order to compare the saturated transient strain irradiation creep component, the test data were converted to equivalent strain and equivalent stress. The saturated transient irradiation creep component was observed to depend on the stress state. The highest value was exhibited by the uniaxial tension stress state, and the lowest by the torsion stress state. The biaxial tension and bending stress state transient component values were intermediate. This behavior appears to be related to the dislocation or microscopic substructure resulting from fabrication processing and the applied stress direction. (orig.)

  17. Stress state in perforated plates

    International Nuclear Information System (INIS)

    Visner, J.

    1977-01-01

    The method is described of photoelastic measurement of stress concentration factors (s.c.f) in plates perforated by a square, triangular and diagonal grid of circular holes and loaded by uniaxial or biaxial tensile stress. A loading equipment which was developed and its modifications are described. Stress concentration factors found are compared with theoretical and experimental results given in references. (author)

  18. Shock-induced transformations in crystalline RDX: a uniaxial constant-stress Hugoniostat molecular dynamics simulation study.

    Science.gov (United States)

    Bedrov, Dmitry; Hooper, Justin B; Smith, Grant D; Sewell, Thomas D

    2009-07-21

    Molecular dynamics (MD) simulations of uniaxial shock compression along the [100] and [001] directions in the alpha polymorph of hexahydro-1,3,5-trinitro-1,3,5-triazine (alpha-RDX) have been conducted over a wide range of shock pressures using the uniaxial constant stress Hugoniostat method [Ravelo et al., Phys. Rev. B 70, 014103 (2004)]. We demonstrate that the Hugoniostat method is suitable for studying shock compression in atomic-scale models of energetic materials without the necessity to consider the extremely large simulation cells required for an explicit shock wave simulation. Specifically, direct comparison of results obtained using the Hugoniostat approach to those reported by Thompson and co-workers [Phys. Rev. B 78, 014107 (2008)] based on large-scale MD simulations of shocks using the shock front absorbing boundary condition (SFABC) approach indicates that Hugoniostat simulations of systems containing several thousand molecules reproduced the salient features observed in the SFABC simulations involving roughly a quarter-million molecules, namely, nucleation and growth of nanoscale shear bands for shocks propagating along the [100] direction and the polymorphic alpha-gamma phase transition for shocks directed along the [001] direction. The Hugoniostat simulations yielded predictions of the Hugoniot elastic limit for the [100] shock direction consistent with SFABC simulation results.

  19. Experimental observations on uniaxial whole-life transformation ratchetting and low-cycle stress fatigue of super-elastic NiTi shape memory alloy micro-tubes

    Science.gov (United States)

    Song, Di; Kang, Guozheng; Kan, Qianhua; Yu, Chao; Zhang, Chuanzeng

    2015-07-01

    In this work, the low-cycle fatigue failure of super-elastic NiTi shape memory alloy micro-tubes with a wall thickness of 150 μm is investigated by uniaxial stress-controlled cyclic tests at human body temperature 310 K. The effects of mean stress, peak stress, and stress amplitude on the uniaxial whole-life transformation ratchetting and fatigue failure of the NiTi alloy are observed. It is concluded that the fatigue life depends significantly on the stress levels, and the extent of martensite transformation and its reverse play an important role in determining the fatigue life. High peak stress or complete martensite transformation shortens the fatigue life.

  20. Experimental observations on uniaxial whole-life transformation ratchetting and low-cycle stress fatigue of super-elastic NiTi shape memory alloy micro-tubes

    International Nuclear Information System (INIS)

    Song, Di; Kang, Guozheng; Kan, Qianhua; Yu, Chao; Zhang, Chuanzeng

    2015-01-01

    In this work, the low-cycle fatigue failure of super-elastic NiTi shape memory alloy micro-tubes with a wall thickness of 150 μm is investigated by uniaxial stress-controlled cyclic tests at human body temperature 310 K. The effects of mean stress, peak stress, and stress amplitude on the uniaxial whole-life transformation ratchetting and fatigue failure of the NiTi alloy are observed. It is concluded that the fatigue life depends significantly on the stress levels, and the extent of martensite transformation and its reverse play an important role in determining the fatigue life. High peak stress or complete martensite transformation shortens the fatigue life. (paper)

  1. Measurement of the uniaxial mechanical properties of rat skin using different stress-strain definitions.

    Science.gov (United States)

    Karimi, A; Navidbakhsh, M

    2015-05-01

    The mechanical properties of skin tissue may vary according to the anatomical locations of a body. There are different stress-strain definitions to measure the mechanical properties of skin tissue. However, there is no agreement as to which stress-strain definition should be implemented to measure the mechanical properties of skin at different anatomical locations. Three stress definitions (second Piola-Kichhoff stress, engineering stress, and true stress) and four strain definitions (Almansi-Hamel strain, Green-St. Venant strain, engineering strain, and true strain) are employed to determine the mechanical properties of skin tissue at back and abdomen locations of a rat body. The back and abdomen skins of eight rats are excised and subjected to a series of tensile tests. The elastic modulus, maximum stress, and strain of skin tissues are measured using three stress definitions and four strain definitions. The results show that the effect of varying the stress definition on the maximum stress measurements of the back skin is significant but not when calculating the elastic modulus and maximum strain. No significant effects are observed on the elastic modulus, maximum stress, and strain measurements of abdomen skin by varying the stress definition. In the true stress-strain diagram, the maximum stress (20%), and elastic modulus (35%) of back skin are significantly higher than that of abdomen skin. The true stress-strain definition is favored to measure the mechanical properties of skin tissue since it gives more accurate measurements of the skin's response using the instantaneous values. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  2. Experimental study under uniaxial cyclic behavior at room and high temperature of 316L stainless steel

    International Nuclear Information System (INIS)

    Kang Guozheng; Gao Qing; Yang Xianjie; Sun Yafang

    2001-01-01

    An experimental study was carried out of the cyclic properties of 316L stainless steel subjected to uniaxial strain and stress at room and high temperature. The effects of cyclic strain amplitude, temperature and their histories on the cyclic deformation behavior of 316L stainless steel are investigated. And, the influences of stress amplitude, mean stress, temperature and their histories on ratcheting are also analyzed. It is shown that either uniaxial cyclic property under cyclic strain or ratcheting under asymmetric uniaxial cyclic stress depends not only on the current temperature and loading state, but also on the previous temperature and loading history. Some significant results are obtained

  3. Computational and experimental investigation of local stress fiber orientation in uniaxially and biaxially constrained microtissues

    NARCIS (Netherlands)

    Obbink - Huizer, C.; Foolen, J.; Oomens, C.W.J.; Borochin, M.A.; Chen, C.S.; Bouten, C.V.C.; Baaijens, F.P.T.

    2014-01-01

    The orientation of cells and associated F-actin stress fibers is essential for proper tissue functioning. We have previously developed a computational model that qualitatively describes stress fiber orientation in response to a range of mechanical stimuli. In this paper, the aim is to quantitatively

  4. Stress growth and relaxation of dendritically branched macromolecules in shear and uniaxial extension

    DEFF Research Database (Denmark)

    Huang, Qian; Costanzo, S.; Das, C.

    2017-01-01

    stress relaxation, suggesting a strong ‘elastic memory’ of the material. These results are 2 described by BoB semi-quantitatively, both in linear and nonlinear shear and extensional regimes. Given the fact that the segments between branch points are less than 3 entanglements long, this is a very...... of stretches of different parts of the polymer appears to be the origin of the slower subsequent relaxation of extensional stress. Concerning the latter effect, for which predictions are not available, it is hoped that the present experimental findings and proposed framework of analysis will motivate further...

  5. Effect of combined external uniaxial stress and dc bias on the dielectric property of BaTiO3-based dielectrics in multilayer ceramic capacitor: thermodynamics and experiments

    International Nuclear Information System (INIS)

    Yang Gang; Yue Zhenxing; Sun Tieyu; Gou Huanlin; Li Longtu

    2008-01-01

    The dielectric properties of (Nb, Y)-doped BaTiO 3 in a multilayer ceramic capacitor (MLCC) under combined external uniaxial compressive stress and dc bias field were investigated at room temperature by using a modified Ginsburg-Landau-Devonshire thermodynamic theory and the dielectric measurement. It is found that although dc bias decreases the dielectric properties dominantly, the influence of the external uniaixial compressive stress should not be neglected. When applied along a direction perpendicular to the internal electrode layer in the MLCC, the external uniaixal compressive stress will strengthen the negative effect of dc bias. In contrast, the external uniaxial compressive stress along a direction parallel to the internal electrode layer in the MLCC will increase the dielectric permittivity under dc bias field, i.e. improve the ε-V response of the MLCC. Furthermore, although there is a difference between the calculated permittivity and the measured permittivity, the effects of the combined external uniaxial compressive stress and dc bias field on the dielectric permittivity described through two approaches are in good agreement

  6. Effect of uniaxial stress on free and bismuth-bound excitons in InP

    International Nuclear Information System (INIS)

    Weber, G.; Ruehle, W.

    1979-01-01

    The reduction of the shear deformation potentials of holes bound to the isoelectronic impurity Bi in InP is determined by piezoluminescence. It is compared with the corresponding reduction for holes bound to the Coulomb-type acceptors C and Zn. The theory for an effective mass acceptor describes well the cases of C and Zn. However, additional effects as local strain and Stark fields must be involved in the case of Bi leading to an extremely large reduction of the deformation potentials. No change in binding energy with applied stress as well as no exchange splitting of the Bi-bound exciton can be detected within experimental accuracy. The stress dependence of the free exciton reflectance reveals values for the band deformation potentials and a value of 0.07 meV for the exchange splitting of the free exciton in InP. (author)

  7. Stress distribution and lattice distortions in Nb3Sn multifilament wires under uniaxial tensile loading at 4.2 K

    International Nuclear Information System (INIS)

    Scheuerlein, C; Flükiger, R; Kadar, J; Bordini, B; Ballarino, A; Bottura, L; Di Michiel, M; Buta, F; Seeber, B; Senatore, C; Siegrist, T; Besara, T

    2014-01-01

    The lattice parameter changes in three types of Nb 3 Sn superconducting wires during uniaxial stress–strain measurements at 4.2 K have been measured by high-energy synchrotron x-ray diffraction. The nearly-stress-free Nb 3 Sn lattice parameter has been determined using extracted filaments, and the elastic strain in the axial and transverse wire directions in the different wire phases has been calculated. The mechanical properties of the PIT and RRP wire are mainly determined by the properties of Nb 3 Sn and unreacted Nb. This is in contrast to the bronze route wire, where the matrix can carry substantial loads. In straight wires the axial Nb 3 Sn pre-strain is strongest in the bronze route wire, its value being smaller in the PIT and RRP wires. A strong reduction of the non-Cu elastic modulus of about 30% is observed during cool-down from ambient temperature to 4.2 K. The Nb 3 Sn Poisson ratio at 4.2 K measured in the untwisted bronze route wire is 0.35. The present study also shows that the process route has a strong influence on the Nb 3 Sn texture. (paper)

  8. Recombination luminescence in irradiated silicon-effects of uniaxial stress and temperature variations.

    Science.gov (United States)

    Jones, C. E.; Compton, W. D.

    1971-01-01

    Demonstration that luminescence in irradiated silicon consists of a spectral group between 0.80 and 1.0 eV which seems to be independent of impurities, while a lower energy group between 0.60 and 0.80 eV is seen only in pulled crystals. The small halfwidth and temperature dependence of the sharp zero-phonon lines observed in these spectra indicate that the luminescence arises from a bound-to-bound transition. A model is proposed for the transition mechanism. Stress data taken on the 0.79-eV zero-phonon line in pulled crystals can be fit by either a tetragonal 100 (in brackets) defect symmetry or by conduction-band splitting effects. It is suggested that the 0.79-eV zero-phonon line and the 0.60- to 0.80-eV spectral group arise from the EPR G-15 center. Stress data on a zero-phonon line at 0.97 eV associated with the 0.80- to 1.0-eV spectral group can be explained by a trigonal 111 (in brackets) defect. The divacancy is tentatively suggested as responsible for this luminescence spectra.

  9. Experimental and numerical modeling of basalt textile reinforced mortar behavior under uniaxial tensile stress

    International Nuclear Information System (INIS)

    Larrinaga, Pello; Chastre, Carlos; Biscaia, Hugo C.; San-José, José T.

    2014-01-01

    Highlights: • Making more deepen the knowledge of textile reinforced mortar in tensile stress. • Analyzing the effect of the reinforcing ratio of the composite. • To compare results with Aveston–Cooper–Kelly theory. • To develop a numerical model based on a finite element code. • Considering the importance of the bond-slip law of the mortar-to-textile-interface. - Abstract: During the last years several projects and studies have improved the knowledge about textile reinforced mortar (TRM) technology. TRM has already been used in strengthening masonry and reinforced concrete structural elements such as walls, arches, columns and beams. This material is presented as a real alternative to the use of fiber-reinforced polymers (FRP) in situations where these composites have presented some drawbacks or their use is banned. Textile reinforced mortar show a complex mechanical behavior derived from the heterogeneity of the constituent materials. This paper aims to deepen the knowledge of this composite material in terms of tensile behavior. Following this scope, this paper presents an experimental campaign focused on thirty-one TRM specimens reinforced with four different reinforcing ratios. The results are analyzed and contrasted with two distinct models. (i) The Aveston–Cooper–Kelly theory (ACK) which is based on a tri-linear analytical approach; and (ii) a non-linear numerical simulation with a 3D finite element code. The finite element analysis (FEA) of the TRM tensile tests also showed no significant dependence on the basalt-to-mortar interface, i.e., the choice of a bond-slip curve in order to reproduce the bond stresses and slippages along the interface is irrelevant and it can be simply considered as rigid interface

  10. Reaction rim growth in the system MgO-Al2O3-SiO2 under uniaxial stress

    Science.gov (United States)

    Götze, Lutz Christoph; Abart, Rainer; Rybacki, Erik; Keller, Lukas M.; Petrishcheva, Elena; Dresen, Georg

    2010-07-01

    We synthesize reaction rims between thermodynamically incompatible phases in the system MgO-Al2O3-SiO2 applying uniaxial load using a creep apparatus. Synthesis experiments are done in the MgO-SiO2 and in the MgO-Al2O3 subsystems at temperatures ranging from 1150 to 1350 °C imposing vertical stresses of 1.2 to 29 MPa at ambient pressure and under a constant flow of dry argon. Single crystals of synthetic and natural quartz and forsterite, synthetic periclase and synthetic corundum polycrystals are used as starting materials. We produce enstatite rims at forsterite-quartz contacts, enstatite-forsterite double rims at periclase-quartz contacts and spinel rims at periclase-corundum contacts. We find that rim growth under the “dry” conditions of our experiments is sluggish compared to what has been found previously in nominally “dry” piston cylinder experiments. We further observe that the nature of starting material, synthetic or natural, has a major influence on rim growth rates, where natural samples are more reactive than synthetic ones. At a given temperature the effect of stress variation is larger than what is anticipated from the modification of the thermodynamic driving force for reaction due to the storage of elastic strain energy in the reactant phases. We speculate that this may be due to modification of the physical properties of the polycrystals that constitute the reaction rims or by deformation under the imposed load. In our experiments rim growth is very sluggish at forsterite-quartz interfaces. Rim growth is more rapid at periclase-quartz contacts. The spinel rims that are produced at periclase-corundum interfaces show parabolic growth indicating that reaction rim growth is essentially diffusion controlled. From the analysis of time series done in the MgO-Al2O3 subsystem we derive effective diffusivities for the Al2O3 and the MgO components in a spinel polycrystal as D_{MgO} = 1.4 ± 0.2 \\cdot 10^{-15} m2/s and D_{Al_2O_3} = 3.7 ± 0

  11. Application of the Raman technique to measure stress states in individual Si particles in a cast Al-Si alloy

    International Nuclear Information System (INIS)

    Harris, Stephen J.; O'Neill, Ann; Boileau, James; Donlon, William; Su, Xuming; Majumdar, B.S.

    2007-01-01

    While Raman spectroscopy is often used to measure stresses, the analyses are almost always limited to cases with simple stress states (uniaxial, equibiaxial). Recently we provided an experimental methodology to determine the full state of stress in Si wafers. Here we extend that methodology to interrogate stress states in Si particles embedded in an Al-Si alloy. Such determinations will ultimately be valuable for predicting ductility of cast Al, since a primary source of damage is cracking of eutectic Si particles. We combine electron back-scattered diffraction with the frequency shift, polarization and intensity of the Raman light to determine stress states. Stress states are measured both in the as-received residually stressed state and under in situ uniaxial loading. Comparison with finite element calculations shows good agreement. As an application of the technique, we show the determination of strength of an individual Si particle and compare the stress evolution with various models

  12. Effects of aspect ratio and specimen size on uniaxial failure stress of iron green bodies at high strain rates

    Directory of Open Access Journals (Sweden)

    Kuroyanagi Yuki

    2015-01-01

    Full Text Available Powder metallurgy is used for the production of a number of mechanical parts and is an essential production method. These are great advantages such as product cost effectiveness and product uniqueness. In general, however parts created by powder metallurgy have low strength because of low density. In order to increase strength as well as density, new techniques such as high-velocity-compaction (HVC was developed and further investigation has been conducted on improvement of techniques and optimum condition using computer simulation. In this study, the effects of aspect ratio and specimen size of iron green bodies on failure strength of uniaxial compression and failure behavior were examined using a split Hopkinson pressure Bar. The diameters of specimens were 12.5 mm and 25 mm the aspect ratios (thickness/diameter were 0.8 and 1.2.

  13. A comparative study on the uniaxial mechanical properties of the umbilical vein and umbilical artery using different stress-strain definitions.

    Science.gov (United States)

    Karimi, Alireza; Navidbakhsh, Mahdi

    2014-12-01

    The umbilical cord is part of the fetus and generally includes one umbilical vein (UV) and two umbilical arteries (UAs). As the saphenous vein and UV are the most commonly used veins for the coronary artery disease treatment as a coronary artery bypass graft (CABG), understating the mechanical properties of UV has a key asset in its performance for CABG. However, there is not only a lack of knowledge on the mechanical properties of UV and UA but there is no agreement as to which stress-strain definition should be implemented to measure their mechanical properties. In this study, the UV and UA samples were removed after caesarean from eight individuals and subjected to a series of tensile testing. Three stress definitions (second Piola-Kichhoff stress, engineering stress, and true stress) and four strain definitions (Almansi-Hamel strain, Green-St. Venant strain, engineering strain, and true strain) were employed to determine the linear mechanical properties of UVs and UAs. The nonlinear mechanical behavior of UV/UA was computationally investigated using hyperelastic material models, such as Ogden and Mooney-Rivlin. The results showed that the effect of varying the stress definition on the maximum stress measurements of the UV/UA is significant but not when calculating the elastic modulus. In the true stress-strain diagram, the maximum strain of UV was 92 % higher, while the elastic modulus and maximum stress were 162 and 42 % lower than that of UA. The Mooney-Rivlin material model was designated to represent the nonlinear mechanical behavior of the UV and UA under uniaxial loading.

  14. Damage-based life prediction model for uniaxial low-cycle stress fatigue of super-elastic NiTi shape memory alloy microtubes

    Science.gov (United States)

    Song, Di; Kang, Guozheng; Kan, Qianhua; Yu, Chao; Zhang, Chuanzeng

    2015-08-01

    Based on the experimental observations for the uniaxial low-cycle stress fatigue failure of super-elastic NiTi shape memory alloy microtubes (Song et al 2015 Smart Mater. Struct. 24 075004) and a new definition of damage variable corresponding to the variation of accumulated dissipation energy, a phenomenological damage model is proposed to describe the damage evolution of the NiTi microtubes during cyclic loading. Then, with a failure criterion of Dc = 1, the fatigue lives of the NiTi microtubes are predicted by the damage-based model, the predicted lives are in good agreement with the experimental ones, and all of the points are located within an error band of 1.5 times.

  15. Damage-based life prediction model for uniaxial low-cycle stress fatigue of super-elastic NiTi shape memory alloy microtubes

    International Nuclear Information System (INIS)

    Song, Di; Kang, Guozheng; Kan, Qianhua; Yu, Chao; Zhang, Chuanzeng

    2015-01-01

    Based on the experimental observations for the uniaxial low-cycle stress fatigue failure of super-elastic NiTi shape memory alloy microtubes (Song et al 2015 Smart Mater. Struct. 24 075004) and a new definition of damage variable corresponding to the variation of accumulated dissipation energy, a phenomenological damage model is proposed to describe the damage evolution of the NiTi microtubes during cyclic loading. Then, with a failure criterion of D c = 1, the fatigue lives of the NiTi microtubes are predicted by the damage-based model, the predicted lives are in good agreement with the experimental ones, and all of the points are located within an error band of 1.5 times. (paper)

  16. Magnetic property variation in carbon steel and chrome-molybdenum steel as a function of uniaxial stress noncoaxial with the magnetic field (abstract)

    International Nuclear Information System (INIS)

    Sablik, M.J.; Kaminski, D.A.; Jiles, D.C.; Biner, S.B.

    1993-01-01

    Magnescope 1 magnetic measurements were made on carbon steel specimens ranging from 0.1--0.8 wt %C and on chrome-molybdenum steel specimens cut from electric power plant pipes previously in service. The carbon steel specimens were heat-treated using three procedures: (1) spheroidization, (2) quenching, and (3) quench and tempering. The specimens were subjected to uniaxial tension up to 40 ksi. The inspection head was aligned so that the magnetic field was oriented at different angles with respect to the stress axis. Magnetic properties (such as coercivity and maximum differential permeability) were extracted from digitized magnetic hysteresis loop measurements. Magnetic properties were studied as a function of stress at each angle of stress-field orientation. To our knowledge, such a comprehensive study of noncoaxial stress and field effects has never been accomplished before for such a wide variety of steel specimens. Results for the various materials are presented for different orientation angles and compared to numerical results from the noncoaxial magnetomechanical hysteresis model of Sablik et al. 2

  17. A kinematic hardening constitutive model for the uniaxial cyclic stress-strain response of magnesium sheet alloys at room temperature

    Science.gov (United States)

    He, Zhitao; Chen, Wufan; Wang, Fenghua; Feng, Miaolin

    2017-11-01

    A kinematic hardening constitutive model is presented, in which a modified form of von Mises yield function is adopted, and the initial asymmetric tension and compression yield stresses of magnesium (Mg) alloys at room temperature (RT) are considered. The hardening behavior was classified into slip, twinning, and untwinning deformation modes, and these were described by two forms of back stress to capture the mechanical response of Mg sheet alloys under cyclic loading tests at RT. Experimental values were obtained for AZ31B-O and AZ31B sheet alloys under both tension-compression-tension (T-C-T) and compression-tension (C-T) loadings to calibrate the parameters of back stresses in the proposed model. The predicted parameters of back stresses in the twinning and untwinning modes were expressed as a cubic polynomial. The predicted curves based on these parameters showed good agreement with the tests.

  18. Probing Earth's State of Stress

    Science.gov (United States)

    Delorey, A. A.; Maceira, M.; Johnson, P. A.; Coblentz, D. D.

    2016-12-01

    The state of stress in the Earth's crust is a fundamental physical property that controls both engineered and natural systems. Engineered environments including those for hydrocarbon, geothermal energy, and mineral extraction, as well those for storage of wastewater, carbon dioxide, and nuclear fuel are as important as ever to our economy and environment. Yet, it is at spatial scales relevant to these activities where stress is least understood. Additionally, in engineered environments the rate of change in the stress field can be much higher than that of natural systems. In order to use subsurface resources more safely and effectively, we need to understand stress at the relevant temporal and spatial scales. We will present our latest results characterizing the state of stress in the Earth at scales relevant to engineered environments. Two important components of the state of stress are the orientation and magnitude of the stress tensor, and a measure of how close faults are to failure. The stress tensor at any point in a reservoir or repository has contributions from both far-field tectonic stress and local density heterogeneity. We jointly invert seismic (body and surface waves) and gravity data for a self-consistent model of elastic moduli and density and use the model to calculate the contribution of local heterogeneity to the total stress field. We then combine local and plate-scale contributions, using local indicators for calibration and ground-truth. In addition, we will present results from an analysis of the quantity and pattern of microseismicity as an indicator of critically stressed faults. Faults are triggered by transient stresses only when critically stressed (near failure). We show that tidal stresses can trigger earthquakes in both tectonic and reservoir environments and can reveal both stress and poroelastic conditions.

  19. The influence of the stress state on Ksub(Ic)

    International Nuclear Information System (INIS)

    Aurich, D.; Helms, R.; Schmidt, P.; Veith, H.; Ziebs, J.

    1977-01-01

    To get a first impression of the influence of stress states of higher multi-axiality than plane strain on Ksub(c) a specimen has been created, in which a bi-axial nominal stress state arises by uniaxial tension. This is attained by tension superimposed by transverse bending stress. The stress distribution without crack was analysed by photoelasticity as well as by finite element method. The results were identical. The stress distribution in the fracture (crack) plane was somewhat inhomogeneous, of course. But the ratio of the stress parallel to the tension axis to that perpendicular to it was max. 1:0.3 with a mean value 1:0.15. Specimens of this type were machined from a rolled sheet of the steel 22 NiMoCr 37, with specimen thickness of about 50 mm. For comparison single-edge notched specimens of the same cross section were prepared from the same material. Fatigue cracks were made following ASTM Recommendations. The fracture mechanics tests were carried out at a temperature of -100 0 C. Although valid Ksub(Ic)-values following the rigorous intention of the linear elastic fracture mechanics (ASTM Recommendations) were not obtained, the differences between the results of the two types of specimens and stress states were significant. The Ksub(Q)-values of the bi-axial stressed specimen were about 25% lower than that of the single-edge notched specimen. The deviation of the load-displacement trace from the linear elastic behavior was greater for the single-edge notched specimens than for the bi-axial stressed specimens. The consequences of these results for the assessment of flaws in pressure vessels are evident considering that bi-axial nominal stress states occur in pressure vessels

  20. The influence of stress state on the reorientation of hydrides in a zirconium alloy

    International Nuclear Information System (INIS)

    Cinbiz, Mahmut N.; Koss, Donald A.; Motta, Arthur T.

    2016-01-01

    Hydride reorientation can occur in spent nuclear fuel cladding when subjected to a tensile hoop stress above a threshold value during cooling. Because in these circumstances the cladding is under a multiaxial stress state, the effect of stress biaxiality on the threshold stress for hydride reorientation is investigated using hydrided CWSR Zircaloy-4 sheet specimens containing ∼180 wt ppm of hydrogen and subjected to a two-cycle thermo-mechanical treatment. The study is based on especially designed specimens within which the stress biaxiality ratios range from uniaxial (σ_2/σ_1 = 0) to “near-equibiaxial” tension (σ_2/σ_1 = 0.8). The threshold stress is determined by mapping finite element calculations of the principal stresses and of the stress biaxiality ratio onto the hydride microstructure obtained after the thermo-mechanical treatment. The results show that the threshold stress (maximum principal stress) decreases from 155 to 75 MPa as the stress biaxiality increases from uniaxial to “near-equibiaxial” tension.

  1. Uniaxial ratcheting behavior of Zircaloy-4 tubes at room temperature

    International Nuclear Information System (INIS)

    Wen, Mingjian; Li, Hua; Yu, Dunji; Chen, Gang; Chen, Xu

    2013-01-01

    In this study, a series of uniaxial tensile, strain cycling and uniaxial ratcheting tests were conducted at room temperature on Zircaloy-4 (Zr-4) tubes used as nuclear fuel cladding in Pressurized Water Reactors (PWRs) for the purpose to investigate the uniaxial ratcheting behavior of Zr-4 and the factors which may influence it. The experimental results show that at room temperature this material features cyclic softening remarkably within the strain range of 1.6%, and former cycling under larger strain amplitude cannot retard cyclic softening of later cycling under lower strain amplitude. Uniaxial ratcheting strain accumulates in the direction of mean stress, and the ratcheting stain level is larger under tensile mean stress than that under compressive mean stress. Uniaxial ratcheting strain level increases with the increase of mean stress and stress amplitude, and decreases with the increase of loading rate. The sequence of loading rate appears to have no effects on the final ratcheting strain accumulation. Loading history has great influence on the uniaxial ratcheting behavior. Lower stress level after loading history with higher stress level leads to the shakedown of ratcheting. Higher loading rate after loading history with lower loading rate brings down the ratcheting strain rate. Uniaxial ratcheting behavior is sensitive to compressive pre-strain, and the decay rate of the ratcheting strain rate is slowed down by pre-compression

  2. Uniaxial backfill block compaction

    International Nuclear Information System (INIS)

    Koskinen, V.

    2012-05-01

    The main parts of the project were: to make a literature survey of the previous uniaxial compaction experiments; do uniaxial compaction tests in laboratory scale; and do industrial scale production tests. Object of the project was to sort out the different factors affecting the quality assurance chain of the backfill block uniaxial production and solve a material sticking to mould problem which appeared during manufacturing the blocks of bentonite and cruched rock mixture. The effect of mineralogical and chemical composition on the long term functionality of the backfill was excluded from the project. However, the used smectite-rich clays have been tested for mineralogical consistency. These tests were done in B and Tech OY according their SOPs. The objective of the Laboratory scale tests was to find right material- and compaction parameters for the industrial scale tests. Direct comparison between the laboratory scale tests and industrial scale tests is not possible because the mould geometry and compaction speed has a big influence for the compaction process. For this reason the selected material parameters were also affected by the previous compaction experiments. The industrial scale tests were done in summer of 2010 in southern Sweden. Blocks were done with uniaxial compaction. A 40 tons of the mixture of bentonite and crushed rock blocks and almost 50 tons of Friedland-clay blocks were compacted. (orig.)

  3. Change of residual stresses during plastic deformation under uniaxial tension test; Variacion de las tensiones residuales con la deformacion plastica en el ensayo de traccion

    Energy Technology Data Exchange (ETDEWEB)

    Benito, J. A.; Jorba, J.; Roca, A.

    2001-07-01

    Hang of longitudinal and transverse residual stresses was studied by X Ray diffraction method as the applied plastic deformation, measured as A% was increased in a standard tension test. The starting material, hot rolling Armco iron, has values close to 0 MPa in longitudinal direction. But it reaches 600 MPa with only A=1,5%, this value remains constant until necking is produced. In transverse direction the stating values are 300 MPa, changes are small and residual stresses remain compressive until the end of tension test. In addition, studies of the changes of residual stresses with time and with misalignment between incident X Ray and drawing direction are presented. (Author) 5 refs.

  4. The effects of stress concentrations on reaction progress: an example from experimental growth of magnesio-aluminate spinel at corundum - periclase interfaces under uniaxial load

    Science.gov (United States)

    Jerabek, Petr; Abart, Rainer; Rybacki, Erik; Habler, Gerlinde

    2014-05-01

    The study aims to understand the reaction progress and chemical, microstructural and textural evolution of magnesio-aluminate spinel reaction rims formed at varying experimental settings (load, temperature and experiment duration). The spinel rims were grown at the contacts between periclase and corundum at temperatures of 1250°C to 1350°C and dry atmosphere, maintained by a constant argon gas flow, under uniaxial load of 0.026 and 0.26 kN per 9 mm2 of initial contact area. Single crystals of periclase with [100] and of corundum with [0001] perpendicular to the polished reaction interface as well as polycrystalline corundum were used as starting materials. Two loading procedures, immediate application of the load before heating and loading after the desired temperature had been reached, were used. An important byproduct of our experiments stemmed from the immediate application of the load, which led to deformation twinning and fracturing of corundum. This internal deformation of corundum disturbed the reaction interface and introduced loci of concentrated stress due to opening of void spaces in between the reactant crystals. Whenever cracks formed in the initial stages of an experiment, the void space opened immediately and no spinel formed along these interface segments. In the case of deformation twinning, the decreased rim thickness indicates later opening of void spaces. This is because next to twins, the reaction interface is characterized by tight physical contact on the one side and less tight contact on the other side of the twin individual. The tight contacts are characterized by enhanced reaction progress which together with the overall positive volume change of the reaction and limits on plasticity of the studied phases led to the opening of void spaces at places characterized by less tight contacts. The thickness variations are less pronounced in our high load (0.26 kN) experiments where periclase behaves plastically and to some extent reduces the

  5. Modelling of the deformation of shot peened cylindrical specimens of 42 CrMo4 in uniaxial tension and deformation and of the resulting macro residual stresses

    International Nuclear Information System (INIS)

    Schulze, V.; Voehringer, O.; Macherauch, E.

    1998-01-01

    Tensile and compressive stress-strain-curves of shot peened and unpeened specimens of quenched and tempered 42 CrMo 4 (AISI 4140) with a diameter of 5 mm only differ in the yield strengths and in the Lueders-deformation. In comparison to the core the regions close to the surface of shot peened cylindrical specimens bear relatively large axial and tangential residual stresses and show different deformation properties. A multi-layer-model was developed to describe both the tensile as well as the compressive deformation behaviour of shot peened cylindrical specimens quantitatively. The calculated transitions from the elastic to the elastic-plastic deformation state during tensile and compressive loading agree quite well with the experimental observations. Also the changes of axial and tangential macro residual stresses after distinct tensile or compressive deformations are in best agreement with the measurements. (orig.)

  6. Constitutive relations describing creep deformation for multi-axial time-dependent stress states

    Science.gov (United States)

    McCartney, L. N.

    1981-02-01

    A THEORY of primary and secondary creep deformation in metals is presented, which is based upon the concept of tensor internal state variables and the principles of continuum mechanics and thermodynamics. The theory is able to account for both multi-axial and time-dependent stress and strain states. The wellknown concepts of elastic, anelastic and plastic strains follow naturally from the theory. Homogeneous stress states are considered in detail and a simplified theory is derived by linearizing with respect to the internal state variables. It is demonstrated that the model can be developed in such a way that multi-axial constant-stress creep data can be presented as a single relationship between an equivalent stress and an equivalent strain. It is shown how the theory may be used to describe the multi-axial deformation of metals which are subjected to constant stress states. The multi-axial strain response to a general cyclic stress state is calculated. For uni-axial stress states, square-wave loading and a thermal fatigue stress cycle are analysed.

  7. Experimental study on uniaxial cyclic ratcheting behavior of 304 stainless steel at room temperature

    International Nuclear Information System (INIS)

    Yang Xianjie; Gao Qing; Cai Lixun; Liu Yujie

    2004-01-01

    The cyclic tests for 304 stainless steel with solution heat treatment under uni-axial cyclic straining and stressing were carried out systematically. The effects of the cyclic engineering stress amplitude history with constant mean stress, the mean engineering stress history with constant cyclic stress amplitude and the stress amplitude histories with the specific mean stress increment per cycle on the uni-axial ratcheting deformation behavior were investigated. Some significant results are obtained

  8. Viscosity overshoot followed by steady state measured in uni-axial elongation of LDPE. Ole Hassager, Henrik Koblitz Rasmussen, Anders Bach and Jens Kromann Nielsen

    DEFF Research Database (Denmark)

    Rasmussen, Henrik Koblitz; Hassager, Ole; Bach, Anders

    2004-01-01

    The transient (e.g. start up of) elongational viscosity of three low-density polyethylene (LDPE) melts (BASF Lupolen 1810H, 1840D and 3020D) was measured using a filament stretching rheometer (FSR) capable of measuring at elevated temperatures. The transient uni-axial elongational viscosity showe...

  9. The effect of stress state on zirconium hydride reorientation

    Science.gov (United States)

    Cinbiz, Mahmut Nedim

    Prior to storage in a dry-cask facility, spent nuclear fuel must undergo a vacuum drying cycle during which the spent fuel rods are heated up to elevated temperatures of ≤ 400°C to remove moisture the canisters within the cask. As temperature increases during heating, some of the hydride particles within the cladding dissolve while the internal gas pressure in fuel rods increases generating multi-axial hoop and axial stresses in the closed-end thin-walled cladding tubes. As cool-down starts, the hydrogen in solid solution precipitates as hydride platelets, and if the multiaxial stresses are sufficiently large, the precipitating hydrides reorient from their initial circumferential orientation to radial orientation. Radial hydrides can severely embrittle the spent nuclear fuel cladding at low temperature in response to hoop stress loading. Because the cladding can experience a range of stress states during the thermo-mechanical treatment induced during vacuum drying, this study has investigated the effect of stress state on the process of hydride reorientation during controlled thermo-mechanical treatments utilizing the combination of in situ X-ray diffraction and novel mechanical testing analyzed by the combination of metallography and finite element analysis. The study used cold worked and stress relieved Zircaloy-4 sheet containing approx. 180 wt. ppm hydrogen as its material basis. The failure behavior of this material containing radial hydrides was also studied over a range of temperatures. Finally, samples from reactor-irradiated cladding tubes were examined by X-ray diffraction using synchrotron radiation. To reveal the stress state effect on hydride reorientation, the critical threshold stress to reorient hydrides was determined by designing novel mechanical test samples which produce a range of stress states from uniaxial to "near-equibiaxial" tension when a load is applied. The threshold stress was determined after thermo-mechanical treatments by

  10. Investigations on the influence of the stress state on fracture-mechanical values

    International Nuclear Information System (INIS)

    Schmidt, P.

    1979-01-01

    Fracture toughness obtained from specimen can be applied to construction elements only when the same stress state exists. In standardised fracture-mechanical tests plain strain is realised. Using the stress intensity factor, a critical crack length or a critical load can be obtained. Above these values a crack propagates in an unstable way. The specimen are tested under uni-axial load. In this paper investigations have been made whether a biaxial load increases the stress state over the plain strain and whether consequently a decrease of the critical fracture toughness and a shift of the temperatures Tsub(g)sub(y) and Tsub(s) results which characterise the fracture behaviour of steel. In order to answer these questions the tests were made which induced due to their geometry an additional nominal stress parallel to the crack front in spite of uni-axial loading. The results were compared with those from specimen without an additional nominal stress and having in their cross section under same test conditions nearly the same plain strain. The fracture toughness of both specimen types were compared at temperatures between 142 K and 252 K and correlated to other material-characterising values. The tests were completed by stress analysis and by comparing the crack opening displacement. Due to the additional stress, Tsub(g)sub(y) was found to be 20 K higher than for the reference specimen. The fracture toughness decreases significantly in certain temperature ranges. The plastic stress concentration factor was comperatively higher and the remaining plastic crack opening decreases up to 25%. (orig.) [de

  11. Cyclic uniaxial compression of human stem cells seeded on a bone biomimetic nanocomposite decreases anti-osteogenic commitment evoked by shear stress.

    Science.gov (United States)

    Baumgartner, Walter; Schneider, Isabelle; Hess, Samuel C; Stark, Wendelin J; Märsmann, Sonja; Brunelli, Marzia; Calcagni, Maurizio; Cinelli, Paolo; Buschmann, Johanna

    2018-04-05

    Chemical supplementation of culture media to induce differentiation of adult stem cells seeded on a scaffold may mask other differentiation triggers such as scaffold stiffness, chemical composition or mechanical stimulation. However, stem cells can be differentiated towards osteoblasts without any supplementation given an appropriate osteogenic scaffold and an adequate mechanical stimulation. Electrospun meshes of poly-lactic-co-glycolic acid and amorphous calcium phosphate nanoparticles (PLGA/aCaP) in a weight ratio of 60:40 were seeded with human adipose-derived stem cells (ASCs) and cultured in DMEM. After two weeks of static cultivation, they were either further cultivated statically for another two weeks (group 1), or placed in a Bose® bioreactor with a flow rate per area of 0.16 mL cm -2 min 1 (group 2). Furthermore, group 3 was also cultivated under perfusion, however, with an additional uniaxial cyclic compression. Stiffness of the scaffolds was assessed as a function of time. After a total of four weeks, minimum stem cell criteria markers as well as typical markers for osteogenesis, endothelial cell differentiation, adipogenesis and chondrogenesis were analyzed by quantitative real-time PCR, cell distribution within the scaffolds by histology and protein expression by immunohistochemistry. Dynamic conditions (perfusion ± uniaxial cyclic compression) significantly upregulated gene and protein expression of PPAR-γ-2 compared to static cultivation, while osteogenic markers were slightly downregulated. However, the compression in the perfusion bioreactor favored osteogenesis compared to mere perfusion as indicated by upregulation of ALP, Runx2 and collagen I. This behavior was not only attributed to the compressive load, but also to the significant increase in stiffness of the scaffold. Furthermore, CD105 was significantly upregulated under compression. Although an osteogenic electrospun composite material with an organic (PLGA) and an inorganic phase

  12. Characteristics of Crushing Energy and Fractal of Magnetite Ore under Uniaxial Compression

    Science.gov (United States)

    Gao, F.; Gan, D. Q.; Zhang, Y. B.

    2018-03-01

    The crushing mechanism of magnetite ore is a critical theoretical problem on the controlling of energy dissipation and machine crushing quality in ore material processing. Uniaxial crushing tests were carried out to research the deformation mechanism and the laws of the energy evolution, based on which the crushing mechanism of magnetite ore was explored. The compaction stage and plasticity and damage stage are two main compression deformation stages, the main transitional forms from inner damage to fracture are plastic deformation and stick-slip. In the process of crushing, plasticity and damage stage is the key link on energy absorption for that the specimen tends to saturate energy state approaching to the peak stress. The characteristics of specimen deformation and energy dissipation can synthetically reply the state of existed defects inner raw magnetite ore and the damage process during loading period. The fast releasing of elastic energy and the work done by the press machine commonly make raw magnetite ore thoroughly broken after peak stress. Magnetite ore fragments have statistical self-similarity and size threshold of fractal characteristics under uniaxial squeezing crushing. The larger ratio of releasable elastic energy and dissipation energy and the faster energy change rate is the better fractal properties and crushing quality magnetite ore has under uniaxial crushing.

  13. Electroluminescence in quantum well heterostructures p-Al{sub x}Ga{sub 1-x}As/GaAs{sub 1-y}P{sub y}/n-Al{sub x}Ga{sub 1-x}As under uniaxial stress

    Energy Technology Data Exchange (ETDEWEB)

    Berman, Irina V. [Physics Department, San Jose State University, CA (United States); Bogdanov, Evgeniy V.; Minina, Natalia Ya.; Shirokov, Stanislav S.; Yunovich, Alexander E. [Physics Department, Lomonosov Moscow State University (Russian Federation); Kissel, Heiko [R and D Department, DILAS Diodenlaser GmbH, (Germany)

    2009-03-15

    We present new results on the influence of uniaxial stress up to P=4 kbar on the electroluminescence spectra and current-voltage characteristics of p-Al{sub x}Ga{sub 1-x}As/GaAs{sub 1-y}P{sub y}/n-Al{sub x}Ga{sub 1-x}As double heterostructures usually used in TM emitting 808 nm high-power diode lasers. With increasing stress, the emission spectra demonstrate a blue shift of up to 25 meV at a pressure of P=4 kbar, while the electroluminescence intensity increases under compression. The different behavior of the current-voltage characteristics under uniaxial stress along[110] and[1 anti 10] directions is mainly determined by the arising piezoelectric field. The results are also discussed in terms of changes in the band structure under uniaxial compression. The construction of the cryostat for optical measurements under uniaxial stress at liquid nitrogen temperature is described in the paper. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. Conduction band structure and electron mobility in uniaxially strained Si via externally applied strain in nanomembranes

    Energy Technology Data Exchange (ETDEWEB)

    Chen Feng [Xi' an Jiaotong University, Xi' an, Shaanxi 710049 (China); Euaruksakul, Chanan; Himpsel, F J; Lagally, Max G [University of Wisconsin-Madison, Madison, WI 53706 (United States); Liu Zheng; Liu Feng, E-mail: lagally@engr.wisc.edu [University of Utah, Salt Lake City, UT 84112 (United States)

    2011-08-17

    Strain changes the band structure of semiconductors. We use x-ray absorption spectroscopy to study the change in the density of conduction band (CB) states when silicon is uniaxially strained along the [1 0 0] and [1 1 0] directions. High stress can be applied to silicon nanomembranes, because their thinness allows high levels of strain without fracture. Strain-induced changes in both the sixfold degenerate {Delta} valleys and the eightfold degenerate L valleys are determined quantitatively. The uniaxial deformation potentials of both {Delta} and L valleys are directly extracted using a strain tensor appropriate to the boundary conditions, i.e., confinement in the plane in the direction orthogonal to the straining direction, which correspond to those of strained CMOS in commercial applications. The experimentally determined deformation potentials match the theoretical predictions well. We predict electron mobility enhancement created by strain-induced CB modifications.

  15. Chamber for uniaxial pressure application at low temperatures

    International Nuclear Information System (INIS)

    Grillo, M.L.N.; Carmo, L.C.S. do; Picon, A.P.

    1984-08-01

    A chamber for alignment of low temperature ferroelastic domains in crystals by the use of uniaxial stress was built. The system allows the use of EPR and optical techniques, as well as X-ray irradiation at temperatures as low as 77K. (Author) [pt

  16. Effect of hexane treatment and uniaxial stretching on bending ...

    African Journals Online (AJOL)

    PVDF) film was studied. The quantity, β31, defined as the bending piezoelectric stress constant, was calculated. After hexane treatment and uniaxial stretching of the PVDF film, the value of β31 was 5.75 mV/m and 8.00 mV/m for draw ratio of ...

  17. Development of a stress-induced martensitic transformation criterion for a Cu–Al–Be polycrystalline shape memory alloy undergoing uniaxial tension

    International Nuclear Information System (INIS)

    García-Castillo, F.N.; Cortés-Pérez, J.; Amigó, V.; Sánchez-Arévalo, F.M.; Lara-Rodríguez, G.A.

    2015-01-01

    This study presents a criterion for predicting the martensitic variants (MVs) that appear during the stress-induced martensitic transformation (SIMT) in a polycrystalline sample of Cu–11.5% wt. Al–0.5% wt. Be under simple tension. Our criterion is based on crystallographic parameters, such as the crystal orientation and Schmid factor (SF). The displacement vector fields (DVFs) were obtained in the observation system by a mathematical model and were used to distort the boundary of a set of grains. From the DVF, the strain tensor for each grain was obtained, and the strain ratio (SR) in the observation system was calculated. Electron backscattering diffraction (EBSD) measurements were performed to determine the crystal orientation of the grains. The inverse SF was used to determine the in-plane stress transformation diagrams (STDs) for each studied grain. The combination of a balance criterion (BC) and STD provided a criterion that allowed us to predict the possible order of stress-induced MVs formed as a function of the crystal orientation and thermomechanical parameters of the shape memory alloy (SMA) with higher accuracy than when using the criteria separately. To validate our criteria, we tested other researchers’ published results. Our results were in agreement and were capable of predicting the stress-induced MVs in a polycrystalline SMA

  18. The State of Stress Beyond the Borehole

    Science.gov (United States)

    Johnson, P. A.; Coblentz, D. D.; Maceira, M.; Delorey, A. A.; Guyer, R. A.

    2015-12-01

    The state of stress controls all in-situ reservoir activities and yet we lack the quantitative means to measure it. This problem is important in light of the fact that the subsurface provides more than 80 percent of the energy used in the United States and serves as a reservoir for geological carbon sequestration, used fuel disposition, and nuclear waste storage. Adaptive control of subsurface fractures and fluid flow is a crosscutting challenge being addressed by the new Department of Energy SubTER Initiative that has the potential to transform subsurface energy production and waste storage strategies. Our methodology to address the above mentioned matter is based on a novel Advance Multi-Physics Tomographic (AMT) approach for determining the state of stress, thereby facilitating our ability to monitor and control subsurface geomechanical processes. We developed the AMT algorithm for deriving state-of-stress from integrated density and seismic velocity models and demonstrate the feasibility by applying the AMT approach to synthetic data sets to assess accuracy and resolution of the method as a function of the quality and type of geophysical data. With this method we can produce regional- to basin-scale maps of the background state of stress and identify regions where stresses are changing. Our approach is based on our major advances in the joint inversion of gravity and seismic data to obtain the elastic properties for the subsurface; and coupling afterwards the output from this joint-inversion with theoretical model such that strain (and subsequently) stress can be computed. Ultimately we will obtain the differential state of stress over time to identify and monitor critically stressed faults and evolving regions within the reservoir, and relate them to anthropogenic activities such as fluid/gas injection.

  19. Uniaxial Tension Test of Slender Reinforced Early Age Concrete Members

    Directory of Open Access Journals (Sweden)

    Wenbo Zhang

    2011-08-01

    Full Text Available The present study aims to obtain the tensile properties of early age concrete based on a uniaxial tension test employing RC slender members. First, the paper shows that concrete strain is equal to the strain of rebar at the mid-span of the RC member. The tensile Young’s modulus and the strain capacity of early age concrete are estimated using strain measurements. The experiment indicated that the tensile Young’s modulus at an early age is higher than the compressive modulus. This observation was similar to one found in a previous investigation which used a direct tension test of early age concrete. Moreover, the paper describes how an empirical equation for mature concrete can be applied to the relation between uniaxial tensile strength and splitting tensile strength even in early age concrete. Based on a uniaxial tension test, the paper proposes an empirical equation for the relationship between standard bond stresses and relative slip.

  20. Comparison between uniaxially and isostatically compacted bentonite

    International Nuclear Information System (INIS)

    Kalbantner, P.; Sjoeblom, R.; Boergesson, Lennart

    2001-12-01

    The purpose of the present report is to provide the Swedish Nuclear Fuel and Waste Management Company (SKB) with the knowledge base needed for their selection of reference method for manufacturing of bentonite blocks. The purpose is also to provide support for the direction of the further development work. Three types of blocks are compared in the present report: uniaxially compacted medium high blocks, isostatically compacted medium high blocks, isostatically compacted high blocks. The analyses is based on three process systems relating to the sequence of excavation of bentonite-transport-powder preparation-compaction-handling and emplacement of bentonite blocks. The need for further knowledge has been identified and documented in conjunction with these analyses. The comparison is primarily made with regard to the criteria safety/risk, quality/ technique and economy. It is carried out through identification of issues of significance and subsequent analysis and evaluation as well as more formally in a simplified AHP (AHP = Analytical Hierarchic Process). The result of the analyses is that the isostatic technique is applicable for the production of high as well as medium size blocks. The pressed blocks are assessed to fulfil the basic requirements with a very large margin. The result of the analyses is also that the uniaxial technique is applicable for the preparation of medium size blocks, which are assessed to fulfil the basic requirements with a large margin. The need for development and process control is assessed to be somewhat higher for the uniaxial technique. One example is the friction against the walls of the die during the compaction, including the significance of this friction for the development of stresses and discontinuities in the block. These results support a selection of the isostatic technique as the reference technique as it provides flexibility in the choice of block height. The uniaxial technique can form a second alternative if medium high

  1. Uniaxial and Multiaxial Creep Testing of Copper

    International Nuclear Information System (INIS)

    Auerkari, Pertti; Holmstroem, Stefan; Veivo, Juha; Salonen, Jorma; Nenonen, Pertti; Laukkanen, Anssi

    2003-12-01

    Multiaxial (compact tension, CT) creep testing has been performed for copper with 79 ppm phosphorus and 60 ppm oxygen. The test load levels were selected according to results from preceding uniaxial creep testing and FE analysis of the CT specimens. Interrupted testing was used for metallographic inspection of the specimens for creep damage. After 7,900 h and 10,300 h of testing at 150 deg C and 46 MPa (reference stress), inspected CT specimens showed cavity indications with a low maximum density ( 2 ) and a typical maximum dimension of less than about 1 μm near the notch tip. From previous experience on creep cavitation damage, the expected minimum life to crack initiation at the notch tip would be at least 40,000 hours, but could be considerably longer because the cavity indications are suspected to originate at least partly from precipitates in specimen preparation. The interrupted testing of CT specimens also showed a 'segregation zone' along some grain boundaries, mainly near the notch tip. This zone appears to contain more P and O than the surrounding matrix, but less than the narrow grain boundary films that are already present in the as-new material. The zone is readily etched and shows a relatively sharp edge towards the matrix without an obvious phase boundary. Using converted multiaxial (CT) testing results, the predicted isothermal uniaxial creep life at 150 deg C/46 MPa is about 1,900 years. The corresponding creep life directly predicted from uniaxial data is 3,100 years, when estimated from a parametric best fit expression according to PD6605. Although the two results are satisfactorily within a factor of two in time, the uncertainties in the extended extrapolations remain large. Further testing is recommended, with at least two creep enhancing factors present. Such testing could include notched creep testing at 120-180 deg C in a corrosive environment, and notched model vessel creep testing at elevated pressure. It is also recommended that longer

  2. In-pile creep behaviour of Zry-4 and ZrNb3Sn1 cladding under uniaxial and biaxial stress

    International Nuclear Information System (INIS)

    Boehner, G.; Wildhagen, B.; Wilhelm, H.

    1987-01-01

    An irradiation programme - started in 1977 - was performed at the research reactor FRG-2 at Geesthacht, Germany, as a joint project of GKSS and KWU in order to study the in-pile creep behaviour of zirconium alloy cladding tubes of PWR fuel rods. The test objective was to establish a data base which allows refined modelling of the in-pile creep phenomenon. A wide test matrix was realized in which each of the precisely monitored test conditions (hoop stress, temperature, fast neutron flux) was varied separately. Different cladding materials (Zircaloy-4 and Zirconium-Niob-Tin alloy ZrNb3Sn1) were subjected to those varying test conditions. Cladding tube specimens of 10.75 mm outer diameter were irradiated in test capsules under various stress conditions and levels up to approx. 6000 h, at temperatures ranging from 300 0 C to 400 0 C and fast neutron flux (E > 1 MeV) of approx. 3x10 13 cm -2 .s -1 . Diametrical and/or axial creep deformation of all tubes were measured in the Hot Cells several times in the course of the tests. In order to extract the irradiation induced creep strain some out-pile experiments were carried out under the very same test conditions as the in-pile tests concerned. (orig./GL)

  3. Uniaxial ratcheting behavior of sintered nanosilver joint for electronic packaging

    International Nuclear Information System (INIS)

    Chen, Gang; Yu, Lin; Mei, Yunhui; Li, Xin; Chen, Xu; Lu, Guo-Quan

    2014-01-01

    Uniaxial ratcheting behavior and the fatigue life of sintered nanosilver joint were investigated at room temperature. All tests were carried out under stress-controlled mode. Force–displacement data were recorded during the entire fatigue lifespan by a non-contact displacement detecting system. Effects of stress amplitude, mean stress, stress rate, and stress ratio on the uniaxial ratcheting behavior of the sintered nanosilver joint were discussed. Stress-life (S–N) curves of the sintered joints were also obtained. The Smith–Watson–Topper (SWT) model, the Gerber model and the modified Goodman model, all of which took effect of mean stress into consideration, were compared for predicting the fatigue life of the sintered joint. Both the ratcheting strain and its rate increased with increasing stress amplitude or mean stress. The increase in stress amplitude and mean stress both reduced the fatigue life of the sintered joint, while the fatigue life prolonged with the increase in stress rate and stress ratio. The modified Goodman model predicted the fatigue life of the sintered joints well

  4. Large deformation of uniaxially loaded slender microbeams on the basis of modified couple stress theory: Analytical solution and Galerkin-based method

    Science.gov (United States)

    Kiani, Keivan

    2017-09-01

    Large deformation regime of micro-scale slender beam-like structures subjected to axially pointed loads is of high interest to nanotechnologists and applied mechanics community. Herein, size-dependent nonlinear governing equations are derived by employing modified couple stress theory. Under various boundary conditions, analytical relations between axially applied loads and deformations are presented. Additionally, a novel Galerkin-based assumed mode method (AMM) is established to solve the highly nonlinear equations. In some particular cases, the predicted results by the analytical approach are also checked with those of AMM and a reasonably good agreement is reported. Subsequently, the key role of the material length scale on the load-deformation of microbeams is discussed and the deficiencies of the classical elasticity theory in predicting such a crucial mechanical behavior are explained in some detail. The influences of slenderness ratio and thickness of the microbeam on the obtained results are also examined. The present work could be considered as a pivotal step in better realizing the postbuckling behavior of nano-/micro- electro-mechanical systems consist of microbeams.

  5. Stress Exposure, Food Intake, and Emotional State

    Science.gov (United States)

    Ulrich-Lai, Yvonne M.; Fulton, Stephanie; Wilson, Mark; Petrovich, Gorica; Rinaman, Linda

    2016-01-01

    This manuscript summarizes the proceedings of the symposium entitled, “Stress, Palatable Food and Reward”, that was chaired by Drs. Linda Rinaman and Yvonne Ulrich-Lai at the 2014 Neurobiology of Stress Workshop held in Cincinnati, OH. This symposium comprised research presentations by four neuroscientists whose work focuses on the biological bases for complex interactions among stress, food intake and emotion. First, Dr. Ulrich-Lai describes her rodent research exploring mechanisms by which the rewarding properties of sweet palatable foods confer stress relief. Second, Dr. Stephanie Fulton discusses her work in which excessive, long-term intake of dietary lipids, as well as their subsequent withdrawal, promotes stress-related outcomes in mice. Third, Dr. Mark Wilson describes his group’s research examining the effects of social hierarchy-related stress on food intake and diet choice in group-housed female rhesus macaques, and compared the data from monkeys to results obtained in analogous work using rodents. Lastly, Dr. Gorica Petrovich discusses her research program that is aimed at defining cortical–amygdalar–hypothalamic circuitry responsible for curbing food intake during emotional threat (i.e., fear anticipation) in rats. Their collective results reveal the complexity of physiological and behavioral interactions that link stress, food intake and emotional state, and suggest new avenues of research to probe the impact of genetic, metabolic, social, experiential, and environmental factors. PMID:26303312

  6. Stress exposure, food intake and emotional state.

    Science.gov (United States)

    Ulrich-Lai, Yvonne M; Fulton, Stephanie; Wilson, Mark; Petrovich, Gorica; Rinaman, Linda

    2015-01-01

    This manuscript summarizes the proceedings of the symposium entitled, "Stress, Palatable Food and Reward", that was chaired by Drs. Linda Rinaman and Yvonne Ulrich-Lai at the 2014 Neurobiology of Stress Workshop held in Cincinnati, OH. This symposium comprised research presentations by four neuroscientists whose work focuses on the biological bases for complex interactions among stress, food intake and emotion. First, Dr Ulrich-Lai describes her rodent research exploring mechanisms by which the rewarding properties of sweet palatable foods confer stress relief. Second, Dr Stephanie Fulton discusses her work in which excessive, long-term intake of dietary lipids, as well as their subsequent withdrawal, promotes stress-related outcomes in mice. Third, Dr Mark Wilson describes his group's research examining the effects of social hierarchy-related stress on food intake and diet choice in group-housed female rhesus macaques, and compared the data from monkeys to results obtained in analogous work using rodents. Finally, Dr Gorica Petrovich discusses her research program that is aimed at defining cortical-amygdalar-hypothalamic circuitry responsible for curbing food intake during emotional threat (i.e. fear anticipation) in rats. Their collective results reveal the complexity of physiological and behavioral interactions that link stress, food intake and emotional state, and suggest new avenues of research to probe the impact of genetic, metabolic, social, experiential and environmental factors on these interactions.

  7. Strength of SiCf-SiCm composite tube under uniaxial and multiaxial loading

    Science.gov (United States)

    Shapovalov, Kirill; Jacobsen, George M.; Alva, Luis; Truesdale, Nathaniel; Deck, Christian P.; Huang, Xinyu

    2018-03-01

    The authors report mechanical strength of nuclear grade silicon carbide fiber reinforced silicon carbide matrix composite (SiCf-SiCm) tubing under several different stress states. The composite tubing was fabricated via a Chemical Vapor Infiltration (CVI) process, and is being evaluated for accident tolerant nuclear fuel cladding. Several experimental techniques were applied including uniaxial tension, elastomer insert burst test, open and closed end hydraulic bladder burst test, and torsion test. These tests provided critical stress and strain values at proportional limit and at ultimate failure points. Full field strain measurements using digital image correlation (DIC) were obtained in order to acquire quantitative information on localized deformation during application of stress. Based on the test results, a failure map was constructed for the SiCf-SiCm composites.

  8. Simulation of Texture Evolution during Uniaxial Deformation of Commercially Pure Titanium

    Science.gov (United States)

    Bishoyi, B.; Debta, M. K.; Yadav, S. K.; Sabat, R. K.; Sahoo, S. K.

    2018-03-01

    The evolution of texture in commercially pure (CP) titanium during uniaxial tension and compression through VPSC (Visco-plastic self-consistent) simulation is reported in the present study. CP-titanium was subjected to both uniaxial tension and compression upto 35% deformation. During uniaxial tension, tensile twin of \\{10\\bar{1}2\\}\\unicode{x003C;}\\bar{1}011\\unicode{x003E;} type and compressive twin of \\{11\\bar{2}2\\}\\unicode{x003C;}11\\bar{2}\\bar{3}\\unicode{x003E;} type were observed in the samples. However, only tensile twin of \\{10\\bar{1}2\\}\\unicode{x003C;}\\bar{1}011\\unicode{x003E;} type and compressive twin of type was observed in the samples during uniaxial compression. Volume fractions of the twins were increased linearly as a function of percentage deformation during uniaxial tension. Whereas, during uniaxial compression the twinning volume fraction was increased up to 20% deformation and then decreased rapidly on further increasing the percentage deformation. During uniaxial tension, the general t-type textures were observed in the samples irrespective of the percentage deformation. The initial non-basal texture was oriented to split basal texture during uniaxial compression of the sample. VPSC formulation was used for simulating the texture development in the material. Different hardening parameters were estimated through correlating the simulated stress-strain curve with the experimental stress-strain data. It was observed that, prismatic slip \\{10\\bar{1}0\\}\\unicode{x003C;}11\\bar{2}0\\unicode{x003E;} operated as the primary deformation mode during uniaxial tension whereas basal slip \\{0001\\}\\unicode{x003C;}11\\bar{2}0\\unicode{x003E;} acquired the leading role during deformation through uniaxial compression. It was also revealed that active deformation modes were fully depending on percentage deformation, loading direction, and orientation of grains.

  9. Field-Induced Rheology in Uniaxial and Biaxial Fields

    International Nuclear Information System (INIS)

    MARTIN, JAMES E.

    1999-01-01

    Steady and oscillatory shear 3-D simulations of electro- and magnetorheology in uniaxial and biaxial fields are presented, and compared to the predictions of the chain model. These large scale simulations are three dimensional, and include the effect of Brownian motion. In the absence of thermal fluctuations, the expected shear thinning viscosity is observed in steady shear, and a striped phase is seen to rapidly form in a uniaxial field, with a shear slip zone in each sheet. However, as the influence of Brownian motion increases, the fluid stress decreases, especially at lower Mason numbers, and the striped phase eventually disappears, even when the fluid stress is still high. In a biaxial field, an opposite trend is seen, where Brownian motion decreases the stress most significantly at higher Mason numbers. to account for the uniaxial steady shear data they propose a microscopic chain model of the role played by thermal fluctuations on the rheology of ER and MR fluids that delineates the regimes where an applied field can impact the fluid viscosity, and gives an analytical prediction for the thermal effect. In oscillatory shear, a striped phase again appears in uniaxial field, at strain amplitudes greater than(approx) 0.15, and the presence of a shear slip zone creates strong stress nonlinearities at low strain amplitudes. In a biaxial field, a shear slip zone is not created, and so the stress nonlinearities develop only at expected strain amplitudes. The nonlinear dynamics of these systems is shown to be in good agreement with the Kinetic Chain Model

  10. Effect of Stress State on Fracture Features

    Science.gov (United States)

    Das, Arpan

    2018-02-01

    Present article comprehensively explores the influence of specimen thickness on the quantitative estimates of different ductile fractographic features in two dimensions, correlating tensile properties of a reactor pressure vessel steel tested under ambient temperature where the initial crystallographic texture, inclusion content, and their distribution are kept unaltered. It has been investigated that the changes in tensile fracture morphology of these steels are directly attributable to the resulting stress-state history under tension for given specimen dimensions.

  11. Effect of insulin pump infusion on comprehensive stress state of ...

    African Journals Online (AJOL)

    Effect of insulin pump infusion on comprehensive stress state of patients with diabetic ketoacidosis. ... Relevant diabetes-associated serum indices, oxidative stress and stress hormone levels were compared between the ... from 32 Countries:.

  12. Fracture assessment of shallow-flaw cruciform beams tested under uniaxial and biaxial loading conditions

    International Nuclear Information System (INIS)

    Bass, B.R.; McAfee, W.J.; Williams, P.T.; Pennell, W.E.

    1999-01-01

    A technology to determine shallow-flaw fracture toughness of reactor pressure vessel (RPV) steels is being developed for application to the safety assessment of RPVs containing postulated shallow surface flaws. Matrices of cruciform beam tests were developed to investigate and quantify the effects of temperature, biaxial loading, and specimen size on fracture initiation toughness of two-dimensional (constant depth), shallow, surface flaws. The cruciform beam specimens were developed at Oak Ridge National Laboratory (ORNL) to introduce a far-field, out-of-plane biaxial stress component in the test section that approximates the nonlinear stresses resulting from pressurized-thermal-shock or pressure-temperature loading of an RPV. Tests were conducted under biaxial load ratios ranging from uniaxial to equibiaxial. These tests demonstrated that biaxial loading can have a pronounced effect on shallow-flaw fracture toughness in the lower transition temperature region for an RPV material. The cruciform fracture toughness data were used to evaluate fracture methodologies for predicting the observed effects of biaxial loading on shallow-flaw fracture toughness. Initial emphasis was placed on assessment of stress-based methodologies, namely, the J-Q formulation, the Dodds-Anderson toughness scaling model, and the Weibull approach. Applications of these methodologies based on the hydrostatic stress fracture criterion indicated an effect of loading-biaxiality on fracture toughness; the conventional maximum principal stress criterion indicated no effect. A three-parameter Weibull model based on the hydrostatic stress criterion is shown to correlate with the experimentally observed biaxial effect on cleavage fracture toughness by providing a scaling mechanism between uniaxial and biaxial loading states. (orig.)

  13. Dynamic Uniaxial Compression of HSLA-65 Steel at Elevated Temperatures

    Science.gov (United States)

    Dike, Shweta; Wang, Tianxue; Zuanetti, Bryan; Prakash, Vikas

    2017-12-01

    In the present study, the dynamic response of a high-strength, low alloy Grade 65 (HSLA-65) steel, used by the United States Navy for ship hull construction, is investigated under dynamic uniaxial compression at temperatures ranging from room temperature to 1000 °C using a novel elevated temperature split-Hopkinson pressure bar. These experiments are designed to probe the dynamic response of HSLA-65 steel in its single α-ferrite phase, mixed α + γ-austenite phase, and the single γ-austenite phase, as a function of temperature. The investigation is conducted at two different average strain rates—1450 and 2100/s. The experimental results indicate that at test temperatures in the range from room temperature to lower than 600 °C, i.e. prior to the development of the mixed α + γ phase, a net softening in flow strength is observed at all levels of plastic strain with increase in test temperatures. As the test temperatures are increased, the rate of this strain softening with temperature is observed to decrease, and at 600 °C the trend reverses itself resulting in an increase in flow stress at all strains tested. This increase in flow stress is understood be due to dynamic strain aging, where solute atoms play a distinctive role in hindering dislocation motion. At 800 °C, a (sharp) drop in the flow stress, equivalent to one-half of its value at room temperature, is observed. As the test temperature are increased to 900 and 1000 °C, further drop in flow stress are observed at all plastic strain levels. In addition, strain hardening in flow stress is observed at all test temperatures up to 600 °C; beyond 800 °C the rate of strain hardening is observed to decrease, with strain softening becoming dominant at temperatures of 900 °C and higher. Moreover, comparing the high strain rate stress versus strain data gathered on HSLA 65 in the current investigation with those available in the literature at quasi-static strain rates, strain-rate hardening can be

  14. Pressure and Stress Prediction in the Nankai Accretionary Prism: A Critical State Soil Mechanics Porosity-Based Approach

    Science.gov (United States)

    Flemings, Peter B.; Saffer, Demian M.

    2018-02-01

    We predict pressure and stress from porosity in the Nankai accretionary prism with a critical state soil model that describes porosity as a function of mean stress and maximum shear stress, and assumes Coulomb failure within the wedge and uniaxial burial beneath it. At Ocean Drilling Program Sites 1174 and 808, we find that pore pressure in the prism supports 70% to 90% of the overburden (λu = 0.7 to 0.9), for a range of assumed friction angles (5-30°). The prism pore pressure is equal to or greater than that in the underthrust sediments even though the porosity is lower within the prism. The high pore pressures lead to a mechanically weak wedge that supports low maximum shear stress, and this in turn requires very low basal traction to remain consistent with the observed narrowly tapered wedge geometry. We estimate the décollement friction coefficient (μb) to be 0.08-0.38 (ϕb' = 4.6°-21°). Our approach defines a pathway to predict pressure in a wide range of environments from readily observed quantities (e.g., porosity and seismic velocity). Pressure and stress control the form of the Earth's collisional continental margins and play a key role in its greatest earthquakes. However, heretofore, there has been no systematic approach to relate material state (e.g., porosity), pore pressure, and stress in these systems.

  15. [Methods and Applications of Psychological Stress State Assessment].

    Science.gov (United States)

    Li, Xin; Yang, Yadan; Hou, Yongjie; Chen, Zetao

    2015-08-01

    In this paper, the response of individual's physiological system under psychological stress state is discussed, and the theoretical support for psychological stress assessment research is provided. The two methods, i.e., the psychological stress assessment of questionnaire and physiological parameter assessment used for current psychological stress assessment are summarized. Then, the future trend of development of psychological stress assessment research is pointed out. We hope that this work could do and provide further support and help to psychological stress assessment studies.

  16. Notch effects in uniaxial tension specimens

    International Nuclear Information System (INIS)

    Delph, T.J.

    1979-03-01

    Results of a literature survey on the effect of notches on the time-dependent failure of uniaxial tension specimens at elevated temperatures are presented. Particular attention is paid to the failure of notched specimens containing weldments

  17. Biaxial nominal state of stress at the crack front

    International Nuclear Information System (INIS)

    Dietmann, H.; Kussmaul, K.

    1979-01-01

    In fracture toughness testing with CT-specimens there is an unaxial nominal stress state caused by the nominal stress psub(y) perpendicular to the crack surface. This paper investigates the question whether the fracture toughness, or generally speaking, the fracture load, is influenced by additional nominal stresses psub(x) and psub(z) in the crack surface, i.e. by a multiaxial stress state. (orig.)

  18. Experimental research of the influence of the strength of ore samples on the parameters of an electromagnetic signal during acoustic excitation in the process of uniaxial compression

    Science.gov (United States)

    Yavorovich, L. V.; Bespal`ko, A. A.; Fedotov, P. I.

    2018-01-01

    Parameters of electromagnetic responses (EMRe) generated during uniaxial compression of rock samples under excitation by deterministic acoustic pulses are presented and discussed. Such physical modeling in the laboratory allows to reveal the main regularities of electromagnetic signals (EMS) generation in rock massive. The influence of the samples mechanical properties on the parameters of the EMRe excited by an acoustic signal in the process of uniaxial compression is considered. It has been established that sulfides and quartz in the rocks of the Tashtagol iron ore deposit (Western Siberia, Russia) contribute to the conversion of mechanical energy into the energy of the electromagnetic field, which is expressed in an increase in the EMS amplitude. The decrease in the EMS amplitude when the stress-strain state of the sample changes during the uniaxial compression is observed when the amount of conductive magnetite contained in the rock is increased. The obtained results are important for the physical substantiation of testing methods and monitoring of changes in the stress-strain state of the rock massive by the parameters of electromagnetic signals and the characteristics of electromagnetic emission.

  19. Crystallinity of polyethylene in uni-axial extensional flow

    DEFF Research Database (Denmark)

    Wingstrand, Sara Lindeblad; van Drongelen, Martin; Mortensen, Kell

    Flow history of polymer melts in processing greatly influences the crystallinity and hence the solid properties of the final material. A wide range of polymer processes involve extensional flows e.g. fiber spinning, blow moulding etc. However, due to instrumental difficulties, experimental studies...... on polymer crystallization in controlled uniaxial extension are quite rare compared to studies of crystallization in shear. Inherently uniaxial extensional flows are strong and simple relative to shear flows, in the sense that chain stretch is easily obtained and that the molecules experience no tumbling...... such that crystallization from a stretched state can take place. In this work we explore this feature in the attempt to link the nonlinear extensional rheology to the final morphology. We investigate polyethylenes (PE) of various chain architectures and observe that, even for complex architectures like long chain branched...

  20. The state of stress in British rocks

    International Nuclear Information System (INIS)

    Klein, R.J.; Brown, E.T.

    1983-03-01

    When designing underground works, it is necessary to take account of not only the vertical stresses arising predictably from the weight of the rock overhead, but also horizontal stresses which may vary from one direction to another as a result of past tectonic action. This report discussed the techniques that have been used to measure such stresses. Few determinations have been made in Great Britain, so it has been necessary to augment what little is known by reference to fault systems, relying on correlations between the measured magnitude and direction of maximum horizontal stress with local tectonic history. This has enabled general conclusions to be reached for Great Britain. (author)

  1. Scale effect in fatigue resistance under complex stressed state

    International Nuclear Information System (INIS)

    Sosnovskij, L.A.

    1979-01-01

    On the basis the of the fatigue failure statistic theory obtained is the formula for calculated estimation of probabillity of failure under complex stressed state according to partial probabilities of failure under linear stressed state with provision for the scale effect. Also the formula for calculation of equivalent stress is obtained. The verification of both formulae using literary experimental data for plane stressed state torsion has shown that the error of estimations does not exceed 10% for materials with the ultimate strength changing from 61 to 124 kg/mm 2

  2. Creep properties of phosphorus alloyed oxygen free copper under multiaxial stress state

    International Nuclear Information System (INIS)

    Rui Wu; Sandstroem, Rolf; Seitisleam, Facredin

    2009-10-01

    Phosphorus alloyed oxygen free copper (Cu-OFP) canisters are planned to be used for spent nuclear fuel in Sweden. The copper canisters will be subjected to creep under multiaxial stress states in the repository. Creep tests have therefore been carried out at 75 deg C using double notch specimens with notch acuities of 0.5, 2, 5, and 18.8, respectively. The creep lifetime for notched specimens is considerably longer than that for the smooth one at a given net section stress, indicating that the investigated Cu-OFP is notch insensitive (notch strengthening). The notch strengthening factor in time is, for instance, greater than 70 at 180 MPa for the bluntest notch (notch acuity = 0.5). The creep lifetime is notch acuity dependent. The sharper the notch, the longer the creep lifetime is. The creep deformation is to a significant extent concentrated to the region around the notches. Different deformation on the two notches is observed. Both axial and radial strains on the failed notch are several times larger than those on the unbroken one. Linear relation between the axial and the radial strains on the notches is found. Transgranular failure is predominant, independent of stress, rupture time, and notch acuity. Adjacent to fracture, elongated grains along the stress direction, separate pores and cavities are often visible. On the unbroken notch, fewer separate cavities and cracks are only seen intergranularly for the sharper notches (notch acuity > 2). To interpret the tests for the notched creep specimens, finite element computations have been performed. A fundamental model for primary and secondary creep without fitting parameters has been used as constitutive equation. The FEM-modelling could represent the creep strain versus time curves for the notched specimens in a satisfactory way. In these curves the strain on loading is included. From the FEM-computations a stationary creep stress could be assessed, which is close to the reference stress. For a given

  3. Warm temperature (170-280°C) uniaxial compresion of SiC reinforced MMCs

    CSIR Research Space (South Africa)

    Gxowa, Zizo

    2017-10-01

    Full Text Available and constant strain of 0.3. Engineering stress-strain curves showed that the best deformation was achieved when sintered MMC compacts were uniaxially compressed at 280°C and strain rate of 5s-1 using a soaking time of 20min.The best deformation was achieved...

  4. Design aspects of the Alpha Repository: III. Uniaxial quasi-static and creep properties of the site rock. Technical memorandum report RSI-0029

    International Nuclear Information System (INIS)

    Hansen, F.D.; Gnirk, P.F.

    1975-01-01

    Candidate mining horizons for the Alpha Repository have been tentatively selected at depths of 1,900, 2,100, and 2,700 ft in the massive salt formations underlying Eddy and Lea counties in New Mexico. The rock salt in the mining horizon at 1,900 ft exhibits average tensile and uniaxial compressive strengths of 200 and 2,445 psi, while the rock salt in the 2,700 ft horizon is 20 to 35 percent stronger. The elastic constants were essentially identical for the two horizons, with an average Young's modulus of 1.94 x 10 6 psi and a Poisson's ratio of 0.33 to 0.34. The anhydrite exhibits tensile and uniaxial compressive strengths of 830 and 13,085 psi, and its Poisson's ratio is 0.35, essentially the same as for rock salt, but its Young's modulus is 10.2 x 10 6 psi, five times greater than that of rock salt. In general, rock salt exhibits a type of bilinear stress-strain curve, with a discontinuity in slope occurring at about 750 psi. Rock salt appears to fail by crushing, rather than in an abrupt ''brittle fracture'' fashion. Anhydrite exhibits a linear stress-strain relationship, with abrupt and distinct failure at the level required for rupture. Uniaxial creep tests were performed on specimens from the 1,900 ft and 2,700 ft horizons using stress levels of 750 and 1,500 psi from 30 to over 200 hours. Results indicate that, for a constant stress level, strain is a function of time to the power of 0.20 to 0.24 and strain appears to be a nonlinear function of the deviatoric stress. Neither steady-state nor tertiary creep was observed

  5. Condition For Strain-Hardening In Ecc Uniaxial Test Specimen

    DEFF Research Database (Denmark)

    Dick-Nielsen, Lars; Stang, Henrik; Poulsen, Peter Noe

    2006-01-01

    and infinite sheets under uniaxial tension. The crack is assumed to be cohesive and the cohesive law applied takes into account fiber as well as mortar properties. It is shown that the maximum crack opening observed during crack propagation in various test specimen geometries is small, 20 m and also small......This paper discusses the adequateness of the steady state flat crack criterion for crack propagation in Engineered Cementitious Composites. The investigation is performed by use of a semi-analytical model as well as a Finite Element Model. The simulations are for one crack propagating in finite...

  6. Time Dependent and Steady Uni-axial Elongational Viscosity

    DEFF Research Database (Denmark)

    Nielsen, Jens K.; Rasmussen, Henrik Koblitz; Hassager, Ole

    2005-01-01

    Here we present measurements of transient and steady uni-axial elongational viscosity, using the Filament Stretching Rheometer1 or FSR1 (see Fig. 1) of the following melts: Four narrow MMD polystyrene (PS) samples with weight-average molar mass Mw in the range of 50k to 390k. Three different bi......-disperse samples, mixed from the narrow MMD PS. Two low-density polyethylene (LDPE) melts (Lupolen 1840D and 3020D). A steady-state viscosity was kept for 1-2.5 Hencky strain units in all measurements....

  7. Slow strain rate stress corrosion cracking under multiaxial deformation conditions: technique and application to admiralty brass

    International Nuclear Information System (INIS)

    Blanchard, W.K.; Heldt, L.A.; Koss, D.

    1984-01-01

    A set of straightforward experimental techniques are described for the examination of slow strain rate stress corrosion cracking (SCC) of sheet deforming under nearly all multiaxial deformation conditions which result in sheet thinning. Based on local fracture strain as a failure criterion, the results contrast stress corrosion susceptibility in uniaxial tension with those in both plane strain and balanced biaxial tension. These results indicate that the loss of ductility of the brass increases as the stress state changes from uniaxial toward balanced biaxial tension

  8. Thermo-mechanical fatigue behaviour of the near-{gamma}-titanium aluminide alloy TNB-V5 under uniaxial and multiaxial loading

    Energy Technology Data Exchange (ETDEWEB)

    Brookes, Stephen Peter

    2009-12-19

    With increasing environmental awareness and the general need to economise on the use of fossil fuels, there is growing pressure for industry to produce lighter, more efficient, gas turbine engines. One such material that will help to achieve these improvements is the intermetallic gamma titanium aluminide ({gamma}-TiAl) alloy. At only half the density of current nickel-based superalloys its weight saving capability is highly desirable, however, its mechanical properties have not yet been fully explored especially, when it is to be considered for structural components in aeronautical gas turbine engines. Critical components in these engines typically experience large variations in temperatures and multiaxial states of stress under non-isothermal conditions. These stress states are known as tri-axial thermo-mechanical fatigue (TMF). The work presented here investigates the effects these multi-axial stresses, have on a {gamma}-TiAl, (Ti-45Al-5Nb-0.2B-0.2C) alloy under TMF conditions. The uniaxial, torsional and axialtorsional TMF behaviour of this {gamma}-TiAl alloy have been examined at 400 - 800 C with strain amplitudes ranging from 0.15% to 0.7%. The tests were conducted at both thermomechanical in-phase (IP) and out-of-phase (OP). Selected tests additionally contained a 180 seconds hold period. Fatigue lifetimes are strongly influenced by the strain amplitude, a small increase in amplitude reduces the lifetime considerably. The uniaxial IP tests showed significantly longer fatigue lifetimes than of all the tests performed. Torsional loading although have shorter fatigue lifetimes than the uniaxial IP loading they have longer fatigue lifetimes than the uniaxial OP loading. The non-proportional axial-torsional 90 degree OP test is most damaging which resulted in a shorter lifetime than the uniaxial OP test with the same Mises equivalent mechanical strain amplitude. A hold period at maximum temperatures reduced the lifetime for all tests regardless of the temperature

  9. In situ grain fracture mechanics during uniaxial compaction of granular solids

    Science.gov (United States)

    Hurley, R. C.; Lind, J.; Pagan, D. C.; Akin, M. C.; Herbold, E. B.

    2018-03-01

    Grain fracture and crushing are known to influence the macroscopic mechanical behavior of granular materials and be influenced by factors such as grain composition, morphology, and microstructure. In this paper, we investigate grain fracture and crushing by combining synchrotron x-ray computed tomography and three-dimensional x-ray diffraction to study two granular samples undergoing uniaxial compaction. Our measurements provide details of grain kinematics, contacts, average intra-granular stresses, inter-particle forces, and intra-grain crystal and fracture plane orientations. Our analyses elucidate the complex nature of fracture and crushing, showing that: (1) the average stress states of grains prior to fracture vary widely in their relation to global and local trends; (2) fractured grains experience inter-particle forces and stored energies that are statistically higher than intact grains prior to fracture; (3) fracture plane orientations are primarily controlled by average intra-granular stress and contact fabric rather than the orientation of the crystal lattice; (4) the creation of new surfaces during fracture accounts for a very small portion of the energy dissipated during compaction; (5) mixing brittle and ductile grain materials alters the grain-scale fracture response. The results highlight an application of combined x-ray measurements for non-destructive in situ analysis of granular solids and provide details about grain fracture that have important implications for theory and modeling.

  10. Stress and Strain State Analysis of Defective Pipeline Portion

    Science.gov (United States)

    Burkov, P. V.; Burkova, S. P.; Knaub, S. A.

    2015-09-01

    The paper presents computer simulation results of the pipeline having defects in a welded joint. Autodesk Inventor software is used for simulation of the stress and strain state of the pipeline. Places of the possible failure and stress concentrators are predicted on the defective portion of the pipeline.

  11. Thermal fatigue appears to be more damaging than uniaxial isothermal fatigue for the austentic stainless steels, and application of multiaxial fatigue criteria

    International Nuclear Information System (INIS)

    Fissolo, Antoine; Gourdin, Cedric; Vincent, Ludovic

    2009-01-01

    For nuclear reactor components, uniaxial isothermal fatigue curves are used to estimate the crack initiation under thermal fatigue. However, such approach would be not sufficient in some cases where cracking was observed. To investigate differences between uniaxial and thermal fatigue damage, tests have been carried out at CEA using the thermal fatigue devices SPLASH and FAT3D: a bi-dimensional (2-D) loading status is obtained in SPLASH, whereas a tri-dimensional (3-D) loading status is obtained in FAT3D. All the analysed tests clearly show that crack initiation in thermal fatigue is faster than in uniaxial isothermal fatigue conditions: for identical levels of strain, the number of cycles required to achieve crack initiation is significantly lower. The enhanced damaging effect probably results from a pure mechanical origin: a nearly perfect biaxial state corresponds to an increased hydrostatic stress. Consequently, multiaxial fatigue criteria must be applied. The Zamrik's strain criterion and the energy criterion proposed by Ecole Polytechnique provide the best estimations. In that framework, the proposed new method coupling both RCC-MR strain estimations and Zamrik's criterion appears to be more promising for the designer. (orig.)

  12. Thermal fatigue appears to be more damaging than uniaxial isothermal fatigue for the austentic stainless steels, and application of multiaxial fatigue criteria

    Energy Technology Data Exchange (ETDEWEB)

    Fissolo, Antoine; Gourdin, Cedric [DM2S/SEMT/LISN, Gif sur Yvette (France); Vincent, Ludovic [DMN/SRMA/LCD, Gif sur Yvette (France)

    2009-07-01

    For nuclear reactor components, uniaxial isothermal fatigue curves are used to estimate the crack initiation under thermal fatigue. However, such approach would be not sufficient in some cases where cracking was observed. To investigate differences between uniaxial and thermal fatigue damage, tests have been carried out at CEA using the thermal fatigue devices SPLASH and FAT3D: a bi-dimensional (2-D) loading status is obtained in SPLASH, whereas a tri-dimensional (3-D) loading status is obtained in FAT3D. All the analysed tests clearly show that crack initiation in thermal fatigue is faster than in uniaxial isothermal fatigue conditions: for identical levels of strain, the number of cycles required to achieve crack initiation is significantly lower. The enhanced damaging effect probably results from a pure mechanical origin: a nearly perfect biaxial state corresponds to an increased hydrostatic stress. Consequently, multiaxial fatigue criteria must be applied. The Zamrik's strain criterion and the energy criterion proposed by Ecole Polytechnique provide the best estimations. In that framework, the proposed new method coupling both RCC-MR strain estimations and Zamrik's criterion appears to be more promising for the designer. (orig.)

  13. An updated stress map of the continental United States reveals heterogeneous intraplate stress

    Science.gov (United States)

    Levandowski, Will; Herrmann, Robert B.; Briggs, Rich; Boyd, Oliver; Gold, Ryan

    2018-06-01

    Knowledge of the state of stress in Earth's crust is key to understanding the forces and processes responsible for earthquakes. Historically, low rates of natural seismicity in the central and eastern United States have complicated efforts to understand intraplate stress, but recent improvements in seismic networks and the spread of human-induced seismicity have greatly improved data coverage. Here, we compile a nationwide stress map based on formal inversions of focal mechanisms that challenges the idea that deformation in continental interiors is driven primarily by broad, uniform stress fields derived from distant plate boundaries. Despite plate-boundary compression, extension dominates roughly half of the continent, and second-order forces related to lithospheric structure appear to control extension directions. We also show that the states of stress in several active eastern United States seismic zones differ significantly from those of surrounding areas and that these anomalies cannot be explained by transient processes, suggesting that earthquakes are focused by persistent, locally derived sources of stress. Such spatially variable intraplate stress appears to justify the current, spatially variable estimates of seismic hazard. Future work to quantify sources of stress, stressing-rate magnitudes and their relationship with strain and earthquake rates could allow prospective mapping of intraplate hazard.

  14. Graphene Foam: Uniaxial Tension Behavior and Fracture Mode Based on a Mesoscopic Model.

    Science.gov (United States)

    Pan, Douxing; Wang, Chao; Wang, Tzu-Chiang; Yao, Yugui

    2017-09-26

    Because of the combined advantages of both porous materials and two-dimensional (2D) graphene sheets, superior mechanical properties of three-dimensional (3D) graphene foams have received much attention from material scientists and energy engineers. Here, a 2D mesoscopic graphene model (Modell. Simul. Mater. Sci. Eng. 2011, 19, 054003), was expanded into a 3D bonded graphene foam system by utilizing physical cross-links and van der Waals forces acting among different mesoscopic graphene flakes by considering the debonding behavior, to evaluate the uniaxial tension behavior and fracture mode based on in situ SEM tensile testing (Carbon 2015, 85, 299). We reasonably reproduced a multipeak stress-strain relationship including its obvious yielding plateau and a ductile fracture mode near 45° plane from the tensile direction including the corresponding fracture morphology. Then, a power scaling law of tensile elastic modulus with mass density and an anisotropic strain-dependent Poisson's ratio were both deduced. The mesoscopic physical mechanism of tensile deformation was clearly revealed through the local stress state and evolution of mesostructure. The fracture feature of bonded graphene foam and its thermodynamic state were directly navigated to the tearing pattern of mesoscopic graphene flakes. This study provides an effective way to understand the mesoscopic physical nature of 3D graphene foams, and hence it may contribute to the multiscale computations of micro/meso/macromechanical performances and optimal design of advanced graphene-foam-based materials.

  15. Effects of Consolidation Stress State on Normally Consolidated Clay

    DEFF Research Database (Denmark)

    Lade, Poul V.

    2000-01-01

    The effect of consolidation stress state on the stress-strain and strength characteristics has been studied from experiments on undisturbed block samples of a natural, normally consolidated clay known as San Francisco Bay Mud. The results of experiments on K0-consolidated, hollow cylinder specimens...... and on isotropically consolidated, cubical specimens, both tested in triaxial compression and extension, clearly showed the influence of the undisturbed fabric as well as the effect of the initial consolidation stress states. While the K0-consolidated specimens appeared to retain their original fabric and exhibit...

  16. Uniaxial Elongational viscosity of bidisperse polystyrene melts

    DEFF Research Database (Denmark)

    Nielsen, Jens Kromann; Rasmussen, Henrik K.; Hassager, Ole

    2006-01-01

    The startup and steady uniaxial elongational viscosity have been measured for three bidisperse polystyrene (PS) melts, consisting of blends of monodisperse PS with molecular weights of 52 kg/mole or 103 kg/mole and 390 kg/mole. The bidisperse melts have a maximum in the steady elongational...... viscosity, of up to a factor of 7 times the Trouton limit of 3 times the zero-shear viscosity....

  17. Oxidatively generated DNA/RNA damage in psychological stress states

    DEFF Research Database (Denmark)

    Jørgensen, Anders

    2013-01-01

    age-related somatic disorders. The overall aim of the PhD project was to investigate the relation between psychopathology, psychological stress, stress hormone secretion and oxidatively generated DNA and RNA damage, as measured by the urinary excretion of markers of whole-body DNA/RNA oxidation (8...... between the 24 h urinary cortisol excretion and the excretion of 8-oxodG/8-oxoGuo, determined in the same samples. Collectively, the studies could not confirm an association between psychological stress and oxidative stress on nucleic acids. Systemic oxidatively generated DNA/RNA damage was increased......Both non-pathological psychological stress states and mental disorders are associated with molecular, cellular and epidemiological signs of accelerated aging. Oxidative stress on nucleic acids is a critical component of cellular and organismal aging, and a suggested pathogenic mechanism in several...

  18. Change in behavior of uniaxial compression due to degradation of salt water and freezing and thawing for rock

    International Nuclear Information System (INIS)

    Yamamoto, Kiyohito; Kobayashi, Akira; Aoyama, Shigeyasu

    2007-01-01

    To investigate the effect of the degradation on the mechanical behavior, the degraded rock samples were prepared to the uniaxial compression test. The degradation methods are divided into two types. One type is submerged in the 10% saline water (10%NaCl) for 90 days, and another one is freezing and thawing for 240 cycles. The degraded Smaland-granites were preserved in saline water. Kurihashi-granodiorite, Tage-tuff and Funyu-tuff were imposed on freezing and thawing test to make degraded state. The damage parameters were identified from the stress-strain relation obtained from the uniaxial compression tests. The damage parameters are K υ , n υ , K d , n d and B 0 . K υ and n υ are related to expansive strain. K d , n d and B 0 are subject to behavior of Young's modulus. By investigating the change in the damage parameters of the degraded rock, the effect of the degradation was tried to infer. As the results, it was inferred using the damage parameters that the Smaland-granite becomes more expansive material and the damage occurs earlier due to saline water degradation. Moreover, it was considered that the Kurihashi-granodiorite and Tage-tuff become more expansive and the axial strain at the failure decreases by freezing and thawing degradation, however the axial strain of the Funyu-tuff at the failure becomes large. It was found the proposed damage parameters can be good index for volumetric strain behavior after degradation. (author)

  19. Acoustic Emission Characteristics of Red Sandstone Specimens Under Uniaxial Cyclic Loading and Unloading Compression

    Science.gov (United States)

    Meng, Qingbin; Zhang, Mingwei; Han, Lijun; Pu, Hai; Chen, Yanlong

    2018-04-01

    To explore the acoustic emission (AE) characteristics of rock materials during the deformation and failure process under periodic loads, a uniaxial cyclic loading and unloading compression experiment was conducted based on an MTS 815 rock mechanics test system and an AE21C acoustic emissions test system. The relationships among stress, strain, AE activity, accumulated AE activity and duration for 180 rock specimens under 36 loading and unloading rates were established. The cyclic AE evolutionary laws with rock stress-strain variation at loading and unloading stages were analyzed. The Kaiser and Felicity effects of rock AE activity were disclosed, and the impact of the significant increase in the scale of AE events on the Felicity effect was discussed. It was observed that the AE characteristics are closely related to the stress-strain properties of rock materials and that they are affected by the developmental state and degree of internal microcracks. AE events occur in either the loading or unloading stages if the strain is greater than zero. Evolutionary laws of AE activity agree with changes in rock strain. Strain deformation is accompanied by AE activity, and the density and intensity of AE events directly reflect the damage degree of the rock mass. The Kaiser effect exists in the linear elastic stage of rock material, and the Felicity effect is effective in the plastic yield and post-peak failure stages, which are divided by the elastic yield strength. This study suggests that the stress level needed to determine a significant increase in AE activity was 70% of the i + 1 peak stress. The Felicity ratio of rock specimens decreases with the growth of loading-unloading cycles. The cycle magnitude and variation of the Felicity effect, in which loading and unloading rates play a weak role, are almost consistent.

  20. Preparation, structure and properties of uniaxially oriented polyethylene-silver nanocomposites

    NARCIS (Netherlands)

    Dirix, Y.J.L.; Bastiaansen, C.W.M.; Caseri, W.R.; Smith, P.

    1999-01-01

    Uniaxially oriented composites of high-density polyethylene and silver nanoparticles were prepared using solution-casting, melt-extrusion and solid-state drawing techniques. The absorption spectrum in the visible wavelength range of the drawn nanocomposites was observed to strongly depend on the

  1. Uniaxial compression test series on Bullfrog Tuff

    International Nuclear Information System (INIS)

    Price, R.H.; Jones, A.K.; Nimick, K.G.

    1982-04-01

    Nineteen uniaxial compressive experiments were performed on samples of the Bullfrog Member of the Crater Flat Tuff, obtained from drillhole USW-G1 at Yucca Mountain on the Nevada Test Site. The water saturated samples were deformed at a nominal strain rate of 10 -5 sec -1 , atmospheric pressure and room temperature. Resultant unconfined compressive strengths, axial strains to failure, Young's moduli and Poisson's ratios ranged from 4.63 to 153. MPa, .0028 to .0058, 2.03 to 28.9 GPa and .08 to .16, respectively

  2. Stress state during fixation determines susceptibility to fatigue-linked biodegradation in bioprosthetic heart valve materials.

    Science.gov (United States)

    Margueratt, Sean D; Lee, J Michael

    2002-01-01

    Mechanical loading contributes to the structural deterioration of bioprosthetic heart valves. The influence of stress state during fixation may play a substantial role in their failure, linking fatigue damage caused by buckling and tension and the enzymatic degradation of glutaraldehyde-crosslinked collagen. Bovine pericardia were obtained immediately postmortem and 100 mm x 15 mm samples were cut in the base-to-apex direction. Half the samples were subjected to a uniaxial tensile stress of 250 kPa and half remained unloaded during a crosslinking treatment in 0.5% glutaraldehyde. Tissue samples were rinsed and cut into 16 mm x 4 mm test strips. Half of these strips were exposed to cyclic compressive buckling and alternating tension at 30 Hz for 20 million cycles (approx. 7.5 days) using a custom-built multi-sample fatigue system. Fatigue-damaged and non-damaged samples were subsequently incubated at 37 C for 48 hrs in: (i) Type I bacterial collagenase (20 U/ml) buffered in 0.05 M Tris, 10 mM CaCl2 2H2O (pH 7.4) or (ii) 0.05 M Tris buffer (pH 7.4) only. In both cases, the samples were loaded sinusoidally between 40 and 80 g using a previously described microtensile culture system. Tissue removed from the bath was rinsed in 0.1 M EDTA solution and mounted in a servo-hydraulic mechanical testing system (MTS). Ultimate tensile strength (UTS), maximum tissue modulus, and fracture strain were determined. The percent collagen solubilized was assessed by a colourmetric hydroxyproline assay of the enzyme bath and tissue sample. All data were analyzed by analysis of variance (ANOVA). The results confirmed the synergy between fatigue damage and collagenase proteolysis in these materials; however, there were no significant differences in this effect between simple fixation and stress-fixation up to 20 million cycles. There were significant decreases in the mechanical properties and an increase in the amount of collagen solubilized with increased exposure to fatigue cycling.

  3. Mechanical characterisation of porcine rectus sheath under uniaxial and biaxial tension.

    LENUS (Irish Health Repository)

    Lyons, Mathew

    2014-06-03

    Incisional hernia development is a significant complication after laparoscopic abdominal surgery. Intra-abdominal pressure (IAP) is known to initiate the extrusion of intestines through the abdominal wall, but there is limited data on the mechanics of IAP generation and the structural properties of rectus sheath. This paper presents an explanation of the mechanics of IAP development, a study of the uniaxial and biaxial tensile properties of porcine rectus sheath, and a simple computational investigation of the tissue. Analysis using Laplace׳s law showed a circumferential stress in the abdominal wall of approx. 1.1MPa due to an IAP of 11kPa, commonly seen during coughing. Uniaxial and biaxial tensile tests were conducted on samples of porcine rectus sheath to characterise the stress-stretch responses of the tissue. Under uniaxial tension, fibre direction samples failed on average at a stress of 4.5MPa at a stretch of 1.07 while cross-fibre samples failed at a stress of 1.6MPa under a stretch of 1.29. Under equi-biaxial tension, failure occurred at 1.6MPa with the fibre direction stretching to only 1.02 while the cross-fibre direction stretched to 1.13. Uniaxial and biaxial stress-stretch plots are presented allowing detailed modelling of the tissue either in silico or in a surrogate material. An FeBio computational model of the tissue is presented using a combination of an Ogden and an exponential power law model to represent the matrix and fibres respectively. The structural properties of porcine rectus sheath have been characterised and add to the small set of human data in the literature with which it may be possible to develop methods to reduce the incidence of incisional hernia development.

  4. Measurements of the state of stress in deep drill holes

    International Nuclear Information System (INIS)

    Vaeaetaeinen, A.; Saerkkae, P.

    1985-05-01

    The state of stress in rock is one of the most important parameters in the safe planning of stable underground openings in rock. At the same time, it is very difficult to be determined from a great distance. The common methods for the determination of state of stress in bedrock are usually not able to do this from a distance over 30 m. This work is a survey on rock stress determination methods usable in deep, over 500 m, drill holes. It also contains a recommendation for a method to determine the state of stress in Lavia test hole. The presented recommendation for the measurement of the state of stress contains an estimation on the working time for the measurement as well as the amount and location of the measuring points. The examination of the methods has been concentrated on three methods, hydraulic fracturing, overcoring by Vattenfall and differential strain analysis. Theoretical background of these methods has been analyzed. A special interest has been laid on the fundamental assumptions of different methods and their influence on the reliability of the results and the interpretation of the state of stress. The comparison of the methods has been made by literature and user interviews. Equipment and personnel needed, and way of measurement are described for the methods. The parameters measured and their possible sources of errors are described, too, as well as the fundamental assumptions and potential difficulties in the measurement. The organizations in Scandinavia performing measurements and their abilities to do measurements and interpretation are presented. Readiness to interpretation in Finland is described shortly

  5. Mechanochemical formation of heterogeneous diamond structures during rapid uniaxial compression in graphite

    Science.gov (United States)

    Kroonblawd, Matthew P.; Goldman, Nir

    2018-05-01

    We predict mechanochemical formation of heterogeneous diamond structures from rapid uniaxial compression in graphite using quantum molecular dynamics simulations. Ensembles of simulations reveal the formation of different diamondlike products starting from thermal graphite crystal configurations. We identify distinct classes of final products with characteristic probabilities of formation, stress states, and electrical properties and show through simulations of rapid quenching that these products are nominally stable and can be recovered at room temperature and pressure. Some of the diamond products exhibit significant disorder and partial closure of the energy gap between the highest-occupied and lowest-unoccupied molecular orbitals (i.e., the HOMO-LUMO gap). Seeding atomic vacancies in graphite significantly biases toward forming products with small HOMO-LUMO gap. We show that a strong correlation between the HOMO-LUMO gap and disorder in tetrahedral bonding configurations informs which kinds of structural defects are associated with gap closure. The rapid diffusionless transformation of graphite is found to lock vacancy defects into the final diamond structure, resulting in configurations that prevent s p3 bonding and lead to localized HOMO and LUMO states with a small gap.

  6. PRESENTDAY STRESS STATE OF THE SHANXI TECTONIC BELT

    Directory of Open Access Journals (Sweden)

    Wang Kaiying

    2012-01-01

    Full Text Available The Shanxi tectonic belt is a historically earthquakeabundant area. For the majority of strong earthquakes in this area, the distribution of earthquake foci was controlled by the N–S oriented local structures on the tectonic belt. Studies of the present stress state of the Shanxi tectonic belt can contribute to the understanding of the relationship between strong earthquakes’ occurrence and their structural distribution and also facilitate assessments of regional seismic danger and determination of the regions wherein strong earthquakes may occur in future. Using the Cataclastic Analysis Method (CAM, we performed stress inversion based on the focal mechanism data of earthquakes which took place in the Shanxi tectonic belt from 1967 to 2010. Our results show that orientations of the maximum principal compressive stress axis of the Shanxi tectonic belt might have been variable before and after the 2001 Kunlun MS=8.1 strong earthquake, with two different superior trends of the NW–SE and NE–SW orientation in different periods. When the maximum principal compressive stress axis is oriented in the NE–SW direction, the pattern of the space distribution of the seismic events in the Shanxi tectonic belt shows a trend of their concentration in the N–S oriented tectonic segments. At the same time, the stress state is registered as horizontal shearing and horizontal extension in the N–S and NE–SW oriented local segments in turn. When the maximum principal compressive stress axis is NW–SE oriented, the stress state of the N–S and NE–SW oriented tectonic segments is primarily registered as horizontal shearing. Estimations of plunges of stress axes show that seismicity in the Shanxi belt  corresponds primarily to the activity of lowangle faults, and highangle stress sites are located in the NE–SW oriented extensional tectonic segments of the Shanxi belt. This indicates that the stress change of the Shanxi belt is

  7. Ion-beam texturing of uniaxially textured Ni films

    International Nuclear Information System (INIS)

    Park, S.J.; Norton, D.P.; Selvamanickam, Venkat

    2005-01-01

    The formation of biaxial texture in uniaxially textured Ni thin films via Ar-ion irradiation is reported. The ion-beam irradiation was not simultaneous with deposition. Instead, the ion beam irradiates the uniaxially textured film surface with no impinging deposition flux, which differs from conventional ion-beam-assisted deposition. The uniaxial texture is established via a nonion beam process, with the in-plane texture imposed on the uniaxial film via ion beam bombardment. Within this sequential ion beam texturing method, grain alignment is driven by selective etching and grain overgrowth

  8. Superconductivity under uniaxial compression in β-(BDA-TTP) salts

    International Nuclear Information System (INIS)

    Suzuki, T.; Onari, S.; Ito, H.; Tanaka, Y.

    2009-01-01

    In order to clarify the mechanism of organic superconductor β-(BDA-TTP) salts. We study the superconductivity under uniaxial compression with non-dimerized two-band Hubbard model. We have calculated the uniaxial compression dependence of T c by solving the Eliashberg's equation using the fluctuation exchange (FLEX) approximation. The transfer integral under the uniaxial compression was estimated by the extended Huckel method. We have found that non-monotonic behaviors of T c in experimental results under uniaxial compression are understood taking the spin frustration and spin fluctuation into account.

  9. Superconductivity under uniaxial compression in β-(BDA-TTP) salts

    Science.gov (United States)

    Suzuki, T.; Onari, S.; Ito, H.; Tanaka, Y.

    2009-10-01

    In order to clarify the mechanism of organic superconductor β-(BDA-TTP) salts. We study the superconductivity under uniaxial compression with non-dimerized two-band Hubbard model. We have calculated the uniaxial compression dependence of T c by solving the Eliashberg’s equation using the fluctuation exchange (FLEX) approximation. The transfer integral under the uniaxial compression was estimated by the extended Huckel method. We have found that non-monotonic behaviors of T c in experimental results under uniaxial compression are understood taking the spin frustration and spin fluctuation into account.

  10. Superconductivity under uniaxial compression in beta-(BDA-TTP) salts

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, T., E-mail: suzuki@rover.nuap.nagoya-u.ac.j [Department of Applied Physics and JST, TRIP, Nagoya University, Chikusa, Nagoya 464-8603 (Japan); Onari, S.; Ito, H.; Tanaka, Y. [Department of Applied Physics and JST, TRIP, Nagoya University, Chikusa, Nagoya 464-8603 (Japan)

    2009-10-15

    In order to clarify the mechanism of organic superconductor beta-(BDA-TTP) salts. We study the superconductivity under uniaxial compression with non-dimerized two-band Hubbard model. We have calculated the uniaxial compression dependence of T{sub c} by solving the Eliashberg's equation using the fluctuation exchange (FLEX) approximation. The transfer integral under the uniaxial compression was estimated by the extended Huckel method. We have found that non-monotonic behaviors of T{sub c} in experimental results under uniaxial compression are understood taking the spin frustration and spin fluctuation into account.

  11. STRESS AND STRAIN STATE OF REPAIRING SECTION OF PIPELINE

    Directory of Open Access Journals (Sweden)

    V. V. Nikolaev

    2015-01-01

    Full Text Available Reliability of continuous operation of pipelines is an actual problem. For this reason should be developed an effective warning system of the main pipelines‘  failures and accidents not only in design and operation but also in selected repair. Changing of linear, unloaded by bending position leads to the change of stress and strain state of pipelines. And besides this, the stress and strain state should be determined and controlled in the process of carrying out the repair works. The article presents mathematical model of pipeline’s section straining in viscoelastic setting taking into account soils creep and high-speed stress state of pipeline with the purpose of stresses evaluation and load-supporting capacity of repairing section of pipeline, depending on time.  Stress and strain state analysis of pipeline includes longitudinal and circular stresses calculation  with  account of axis-asymmetrical straining and  was  fulfilled  on  the base of momentless theory of shells. To prove the consistency of data there were compared the calcu- lation results and the solution results by analytical methods for different cases (long pipeline’s section strain only under influence of cross-axis action; long pipeline’s section strain under in- fluence of longitudinal stress; long pipeline’s section strain; which is on the elastic foundation, under influence of cross-axis action. Comparison results shows that the calculation error is not more than 3 %.Analysis of stress-strain state change of pipeline’s section was carried out with development  of  this  model,  which  indicates  the  enlargement  of  span  deflection  in  comparison with problem’s solution in elastic approach. It is also proved, that for consistent assessment of pipeline maintenance conditions, it is necessary to consider the areolas of rheological processes of soils. On the base of complex analysis of pipelines there were determined stresses and time

  12. Failure of Sierra White granite under general states of stress

    Science.gov (United States)

    Ingraham, M. D.; Dewers, T. A.; Lee, M.; Holdman, O.; Cheung, C.; Haimson, B. C.

    2017-12-01

    The effect of the intermediate principal stress on the failure of Sierra White granite was investigated by performing tests under true triaxial states of stress. Tests were performed under constant Lode angle conditions with Lode angles ranging from 0 to 30°, pure shear to axisymmetric compression. Results show that the failure of Sierra White granite is heavily dependent on the intermediate principal stress which became more dramatic as the mean stress increased. An analysis of the shear bands formed at failure was performed using an associated flow rule and the Rudnicki and Rice (1975) localization criteria. The localization analysis showed excellent agreement with experimental results. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA0003525.

  13. Measurements and predictions of strain pole figures for uniaxially compressed stainless steel

    International Nuclear Information System (INIS)

    Larsson, C.; Clausen, B.; Holden, T.M.; Bourke, M.A.M.

    2004-01-01

    Strain pole figures representative of residual intergranular strains were determined from an -2.98% uniaxially compressed austenitic stainless steel sample. The measurements were made using neutron diffraction on the recently commissioned Spectrometer for Materials Research at Temperature and Stress (SMARTS) at Los Alamos National Laboratory, USA. The measurements were compared with predictions from an elasto-plastic self-consistent model and found to be in good agreement

  14. Measurements and predictions of strain pole figures for uniaxially compressed stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Larsson, C. [Division of Engineering Materials, Department of Mechanical Engineering, Linkoeping University, 58183 Linkoeping (Sweden)]. E-mail: clarsson@cfl.rr.com; Clausen, B. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Holden, T.M. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Bourke, M.A.M. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    2004-09-15

    Strain pole figures representative of residual intergranular strains were determined from an -2.98% uniaxially compressed austenitic stainless steel sample. The measurements were made using neutron diffraction on the recently commissioned Spectrometer for Materials Research at Temperature and Stress (SMARTS) at Los Alamos National Laboratory, USA. The measurements were compared with predictions from an elasto-plastic self-consistent model and found to be in good agreement.

  15. Mechanical behavior and dynamic failure of high-strength ultrafine grained tungsten under uniaxial compression

    International Nuclear Information System (INIS)

    Wei, Q.; Jiao, T.; Ramesh, K.T.; Ma, E.; Kecskes, L.J.; Magness, L.; Dowding, R.; Kazykhanov, V.U.; Valiev, R.Z.

    2006-01-01

    We have systematically investigated the quasi-static and dynamic mechanical behavior (especially dynamic failure) of ultra-fine grained (UFG) tungsten (W) under uniaxial compression. The starting material is of commercial purity and large grain size. We utilized severe plastic deformation to achieve the ultrafine microstructure characterized by grains and subgrains with sizes of ∼500 nm, as identified by transmission electron microscopy. Results of quasi-static compression show that the UFG W behaves in an elastic-nearly perfect plastic manner (i.e., vanishing strain hardening), with its flow stress approaching 2 GPa, close to twice that of conventional coarse grain W. Post-mortem examinations of the quasi-statically loaded samples show no evidence of cracking, in sharp contrast to the behavior of conventional W (where axial cracking is usually observed). Under uniaxial dynamic compression (strain rate ∼10 3 s -1 ), the true stress-true strain curves of the UFG W exhibit significant flow softening, and the peak stress is ∼3 GPa. Furthermore, the strain rate sensitivity of the UFG W is reduced to half the value of the conventional W. Both in situ high-speed photography and post-mortem examinations reveal shear localization and as a consequence, cracking of the UFG W under dynamic uniaxial compression. These observations are consistent with recent observations on other body-centered cubic metals with nanocrystalline or ultrafine microstructures. The experimental results are discussed using existing models for adiabatic shear localization in metals

  16. Stress among Secondary School Teachers in Ebonyi State, Nigeria: Suggested Interventions in the Worksite Milieu

    Science.gov (United States)

    Nwimo, Ignatius O.; Onwunaka, Chinagorom

    2015-01-01

    The aim of the study was to determine the level of stress experienced by secondary school teachers in Ebonyi State. The dimensions of stress studied included physical stress, mental stress, emotional stress and social stress. The study adopted the cross-sectional survey design using a sample of 660 (male 259, female 401) teachers randomly drawn…

  17. Uniaxial creep behavior of V-4Cr-4Ti alloy

    International Nuclear Information System (INIS)

    Natesan, K.; Soppet, W.K.; Purohit, A.

    2002-01-01

    We are undertaking a systematic study at Argonne National Laboratory to evaluate the uniaxial creep behavior of V-Cr-Ti alloys in a vacuum environment as a function of temperature in the range of 650-800 deg. C and at applied stress levels of 75-380 MPa. Creep strain in the specimens is measured by a linear-variable-differential transducer, which is attached between the fixed and movable pull rods of the creep assembly. Strain is measured at sufficiently frequent intervals during testing to define the creep strain/time curve. A linear least-squares analysis function is used to ensure consistent extraction of minimum creep rate, onset of tertiary creep and creep strain at the onset of tertiary creep. Creep test data, obtained at 650, 700, 725 and 800 deg. C, showed power-law creep behavior. Extensive analysis of the tested specimens is conducted to establish hardness profiles, oxygen content and microstructural characteristics. The data are also quantified by the Larson-Miller approach, and correlations are developed to relate time to rupture, onset of tertiary creep, times for 1% and 2% strain, exposure temperature and applied stress

  18. Modeling of residual stress state in turning of 304L

    International Nuclear Information System (INIS)

    Valiorgue, F.; Rech, J.; Bergheau, J.M.

    2010-01-01

    Research presented in this paper aims to link machining parameters to residual stress state and helps understanding mechanisms responsible of machined surface properties modifications. The first presented works are based on an experimental campaign. They reproduce the finishing turning operation of 304L and allow observing the residual stress state evolution at the work piece surface and for an affected depth of 0.2 mm for such processes. Then, the finishing turning operation is simulated numerically in order to realize the same sensitivity study to cutting parameters. This simulation is based on an hybrid approach mixing experimental data and numerical simulation. This method allows getting round the classical difficulties of turning simulation by applying equivalent thermo mechanical loadings onto the work piece surface without modeling the material separation phenomena. Moreover the numerical model uses an hardening law taking into account dynamic recrystallization phenomena. (authors)

  19. Personal determinants of positive states and stress in psychology students

    Directory of Open Access Journals (Sweden)

    G.S. Kozhukhar

    2013-07-01

    Full Text Available We report study results of personality characteristics as predictors of positive states (active, optimistic, emotional, subjective comfort and stress experience in adults with one higher education and ongoing training in Psychology. The respondents were 107 people aged 23 to 52 years. Diagnostic methods we used were: "SMIL" (L. Sobchik, Optimism and Activity Scale (adapted by E. Vodopyanova, C. Izard Differential Emotions Scale (adapted by A. Leonova, Subjective Comfort Scale (adapted by A. Leonova, PSM-25 Scale by Lemyr-Tessier-Fillion. The regression analysis revealed that in subjects ongoing training in Psychology, basic predictor of positive emotions and stress experience is anxiety. Cluster analysis revealed three types of subjects by their positive states experiences, which differ primarily by the level of baseline anxiety and related personality characteristics. The group of risk comprised Psychology students with a tendency to depression and negative emotions and specific personality profile.

  20. Influence of alkali-silica reaction and crack orientation on the uniaxial compressive strength of concrete cores from slab bridges

    DEFF Research Database (Denmark)

    Antonio Barbosa, Ricardo; Gustenhoff Hansen, Søren; Hansen, Kurt Kielsgaard

    2018-01-01

    ASR-damaged flat slab bridges in service. Furthermore, the influence of the ASR-induced crack orientation on the compressive strength and the Young’s modulus is investigated. Uniaxial compression tests, visual observations, and thin section examinations were performed on more than 100 cores drilled...... from the three severely ASR-damaged flat slab bridges. It was found that the orientation of ASR-induced cracks has a significant influence on the uniaxial compressive strength and the stress-strain relationship of the tested cores. The compressive strength in a direction parallel to ASR cracks can...

  1. Interface states in stressed semiconductor heterojunction with antiferromagnetic ordering

    International Nuclear Information System (INIS)

    Kantser, V.G.

    1995-08-01

    The stressed heterojunctions with antiferromagnetic ordering in which the constituents have opposite band edge symmetry and their gaps have opposite signs have been investigated. The interface states have been shown to appear in these heterojunctions and they are spin-split. As a result if the Fermi level gets into one of the interface bands then it leads to magnetic ordering in the interface plane. That is if the interface magnetization effect can be observed. (author). 14 refs, 2 figs

  2. A methodology to investigate size scale effects in crystalline plasticity using uniaxial compression testing

    International Nuclear Information System (INIS)

    Uchic, Michael D.; Dimiduk, Dennis M.

    2005-01-01

    A methodology for performing uniaxial compression tests on samples having micron-size dimensions is presented. Sample fabrication is accomplished using focused ion beam milling to create cylindrical samples of uniform cross-section that remain attached to the bulk substrate at one end. Once fabricated, samples are tested in uniaxial compression using a nanoindentation device outfitted with a flat tip, and a stress-strain curve is obtained. The methodology can be used to examine the plastic response of samples of different sizes that are from the same bulk material. In this manner, dimensional size effects at the micron scale can be explored for single crystals, using a readily interpretable test that minimizes imposed stretch and bending gradients. The methodology was applied to a single-crystal Ni superalloy and a transition from bulk-like to size-affected behavior was observed for samples 5 μm in diameter and smaller

  3. A fiber bundle-plastic chain model for quasi-brittle materials under uniaxial loading

    International Nuclear Information System (INIS)

    Shan, Zhi; Yu, Zhiwu

    2015-01-01

    A fiber bundle-plastic chain model for quasi-brittle materials under both uniaxial compression and tension conditions is developed. By introducing a plastic chain model into the fiber bundle model, a bundle-chain model for quasi-brittle materials is proposed with physical considerations. The model achieves a novel and convenient approach to describe the stochastic effective stress-driven plasticity. It is found that the numerical solutions obtained with this model agree with experimental results when subjected to both monotonic and cyclic uniaxial loading. The model generates a numerical solution with higher accuracy than the present models, when compared with the experimental results on certain problems. An example is shown which utilizes this model to describe the stochastic properties of a constitutive model given as standard. Furthermore, the difference between the existing plastic fiber bundle models in the literature and this model is also obtained in this work. (paper)

  4. Three-dimensional finite element modelling of the uniaxial tension test

    DEFF Research Database (Denmark)

    Østergaard, Lennart; Stang, Henrik

    2002-01-01

    . One of the most direct methods for determination of the σ-w relationship is the uniaxial tension test, where a notched specimen is pulled apart while the tensile load and the crack opening displacement is observed. This method is appealing since the interpretation is straightforward. The method......Experimental determination of the stress-crack opening relationship (σ-w) for concrete as defined in the fictitious crack model has proven to be difficult. This is due to the problems that may arise from application of the inverse analysis method necessary for the derivation of the relationship...... is examined in this paper through three dimensional finite element analyses. It is concluded that the interpretation of the uniaxial tension test is indeed straightforward, if the testing machine stiffness is sufficiently high....

  5. Uniaxial tension test on Rubber at constant true strain rate

    Directory of Open Access Journals (Sweden)

    Sourne H.L.

    2012-08-01

    Full Text Available Elastomers are widely used for damping parts in different industrial contexts because of their remarkable dissipation properties. Indeed, they can undergo severe mechanical loading conditions, i.e., high strain rates and large strains. Nevertheless, the mechanical response of these materials can vary from purely rubber-like to glassy depending on the strain rate undergone. Classically, uniaxial tension tests are made in order to find a relation between the stress and the strain in the material at various strain rates. However, even if the strain rate is searched to be constant, it is the nominal strain rate that is considered. Here we develop a test at constant true strain rate, i.e. the strain rate that is experienced by the material. In order to do such a test, the displacement imposed by the machine is an exponential function of time. This test has been performed with a high speed hydraulic machine for strain rates between 0.01/s and 100/s. A specific specimen has been designed, yielding a uniform strain field (and so a uniform stress field. Furthermore, an instrumented aluminum bar has been used to take into account dynamic effects in the measurement of the applied force. A high speed camera enables the determination of strain in the sample using point tracking technique. Using this method, the stress-strain curve of a rubber-like material during a loading-unloading cycle has been determined, up to a stretch ratio λ = 2.5. The influence of the true strain rate both on stiffness and on dissipation of the material is then discussed.

  6. Tremor frequency characteristics in Parkinson's disease under resting-state and stress-state conditions.

    Science.gov (United States)

    Lee, Hong Ji; Lee, Woong Woo; Kim, Sang Kyong; Park, Hyeyoung; Jeon, Hyo Seon; Kim, Han Byul; Jeon, Beom S; Park, Kwang Suk

    2016-03-15

    Tremor characteristics-amplitude and frequency components-are primary quantitative clinical factors for diagnosis and monitoring of tremors. Few studies have investigated how different patient's conditions affect tremor frequency characteristics in Parkinson's disease (PD). Here, we analyzed tremor characteristics under resting-state and stress-state conditions. Tremor was recorded using an accelerometer on the finger, under resting-state and stress-state (calculation task) conditions, during rest tremor and postural tremor. The changes of peak power, peak frequency, mean frequency, and distribution of power spectral density (PSD) of tremor were evaluated across conditions. Patients whose tremors were considered more than "mild" were selected, for both rest (n=67) and postural (n=25) tremor. Stress resulted in both greater peak powers and higher peak frequencies for rest tremor (pstate condition. The distributions of PSD of tremor were symmetrical, regardless of conditions. Tremor is more evident and typical tremor characteristics, namely a lower frequency as amplitude increases, are different in stressful condition. Patient's conditions directly affect neural oscillations related to tremor frequencies. Therefore, tremor characteristics in PD should be systematically standardized across patient's conditions such as attention and stress levels. Copyright © 2016. Published by Elsevier B.V.

  7. Influence of thyroid states on stress gastric ulcer formation

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez, D.E.; Walker, C.H.; Mason, G.A.

    1988-01-01

    This study was designed to test the hypothesis that thyroid states may affect the acute development of gastric lesions induced by cold-resistant stress. Normal (euthyroid), hyperthyroid and hypothyroid rats were used. Gastric lesion incidence and severity was significantly increased in hypothyroid rats, whereas in contrast hyperthyroid rats developed significantly less gastric lesions. As anticipated, plasma levels of thyroxin (T/sub 4/) were significantly elevated in hyperthyroid rats, and undetectable in hypothyroid rats. Acute pretreatment with i.p. cimetidine, but not T/sub 4/ 1 h prior to stress completely prevented gastric lesions formation in hypothyroid rats. Finally, binding of /sup 3/H-dihydroalprenolol to ..beta..-adrenergic receptors on brain membranes prepared from frontal cortex was reduced by 20% in hypothyroid rats after 3 h of stress. These and other data contained herein suggest that thyroid hormones contribute to modulate the responsiveness of the gastric mucosa to stress. The increase rate of ulcerogenesis observed in hypothyroid rats appears to be mediated by gastric acid secretion. The central mechanism for this response may involve decreased brain nonadrenergic receptor function.

  8. Influence of thyroid states on stress gastric ulcer formation

    International Nuclear Information System (INIS)

    Hernandez, D.E.; Walker, C.H.; Mason, G.A.

    1988-01-01

    This study was designed to test the hypothesis that thyroid states may affect the acute development of gastric lesions induced by cold-resistant stress. Normal (euthyroid), hyperthyroid and hypothyroid rats were used. Gastric lesion incidence and severity was significantly increased in hypothyroid rats, whereas in contrast hyperthyroid rats developed significantly less gastric lesions. As anticipated, plasma levels of thyroxin (T 4 ) were significantly elevated in hyperthyroid rats, and undetectable in hypothyroid rats. Acute pretreatment with i.p. cimetidine, but not T 4 1 h prior to stress completely prevented gastric lesions formation in hypothyroid rats. Finally, binding of 3 H-dihydroalprenolol to β-adrenergic receptors on brain membranes prepared from frontal cortex was reduced by 20% in hypothyroid rats after 3 h of stress. These and other data contained herein suggest that thyroid hormones contribute to modulate the responsiveness of the gastric mucosa to stress. The increase rate of ulcerogenesis observed in hypothyroid rats appears to be mediated by gastric acid secretion. The central mechanism for this response may involve decreased brain nonadrenergic receptor function

  9. Failure Mechanisms of Brittle Rocks under Uniaxial Compression

    Science.gov (United States)

    Liu, Taoying; Cao, Ping

    2017-09-01

    The behaviour of a rock mass is determined not only by the properties of the rock matrix, but mostly by the presence and properties of discontinuities or fractures within the mass. The compression test on rock-like specimens with two prefabricated transfixion fissures, made by pulling out the embedded metal inserts in the pre-cured period was carried out on the servo control uniaxial loading tester. The influence of the geometry of pre-existing cracks on the cracking processes was analysed with reference to the experimental observation of crack initiation and propagation from pre-existing flaws. Based on the rock fracture mechanics and the stress-strain curves, the evolution failure mechanism of the fissure body was also analyzed on the basis of exploring the law of the compression-shear crack initiation, wing crack growth and rock bridge connection. Meanwhile, damage fracture mechanical models of a compression-shear rock mass are established when the rock bridge axial transfixion failure, tension-shear combined failure, or wing crack shear connection failure occurs on the specimen under axial compression. This research was of significance in studying the failure mechanism of fractured rock mass.

  10. Application of laser interferometry for assessment of surface residual stress by determination of stress-free state

    International Nuclear Information System (INIS)

    Kim, Dong Won; Kwon, Dong Il; Lee, Nak Kyu; Choi, Tae Hoon; Na, Kyoung Hoan

    2003-01-01

    The total relaxed stress in annealing and the thermal strain/stress were obtained from the identification of the residual stress-free state using Electronic Speckle Pattern Interferometry (ESPI). The residual stress fields in case of both single and film/substrate systems were modeled using the thermo-elastic theory and the relationship between relaxed stresses and displacements. We mapped the surface residual stress fields on the indented bulk Cu and the 0.5 μm Au film by ESPI. In indented Cu, the normal and shear residual stress are distributed over -1.7 GPa to 700 MPa and -800 GPa to 600 MPa respectively around the indented point and in deposited Au film on Si wafer, the tensile residual stress is uniformly distributed on the Au film from 500 MPa to 800 MPa. Also we measured the residual stress by the X-Ray Diffractometer (XRD) for the verification of above residual stress results by ESPI

  11. Analysis of electromagnetic scattering by uniaxial anisotropic bispheres.

    Science.gov (United States)

    Li, Zheng-Jun; Wu, Zhen-Sen; Li, Hai-Ying

    2011-02-01

    Based on the generalized multiparticle Mie theory and the Fourier transformation approach, electromagnetic (EM) scattering of two interacting homogeneous uniaxial anisotropic spheres with parallel primary optical axes is investigated. By introducing the Fourier transformation, the EM fields in the uniaxial anisotropic spheres are expanded in terms of the spherical vector wave functions. The interactive scattering coefficients and the expansion coefficients of the internal fields are derived through the continuous boundary conditions on which the interaction of the bispheres is considered. Some selected calculations on the effects of the size parameter, the uniaxial anisotropic absorbing dielectric, and the sphere separation distance are described. The backward radar cross section of two uniaxial anisotropic spheres with a complex permittivity tensor changing with the sphere separation distance is numerically studied. The authors are hopeful that the work in this paper will help provide an effective calibration for further research on the scattering characteristic of an aggregate of anisotropic spheres or other shaped anisotropic particles.

  12. Stress and charge transfer in uniaxially strained CVD graphene

    Czech Academy of Sciences Publication Activity Database

    Bouša, Milan; Anagnostopoulos, G. C.; del Corro, Elena; Drogowska, Karolina; Pekárek, J.; Kalbáč, Martin; Parthenios, J.; Papagelis, K.; Galiotis, C.; Frank, Otakar

    2016-01-01

    Roč. 253, č. 12 (2016), s. 2355-2361 ISSN 0370-1972 R&D Projects: GA ČR GA14-15357S; GA MŠk LL1301 Institutional support: RVO:61388955 Keywords : chemical vapour deposition * graphene * Raman spectroscopy Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.674, year: 2016

  13. Mechanical Behavior of Red Sandstone under Incremental Uniaxial Cyclical Compressive and Tensile Loading

    Directory of Open Access Journals (Sweden)

    Baoyun Zhao

    2017-01-01

    Full Text Available Uniaxial experiments were carried out on red sandstone specimens to investigate their short-term and creep mechanical behavior under incremental cyclic compressive and tensile loading. First, based on the results of short-term uniaxial incremental cyclic compressive and tensile loading experiments, deformation characteristics and energy dissipation were analyzed. The results show that the stress-strain curve of red sandstone has an obvious memory effect in the compressive and tensile loading stages. The strains at peak stresses and residual strains increase with the cycle number. Energy dissipation, defined as the area of the hysteresis loop in the stress-strain curves, increases nearly in a power function with the cycle number. Creep test of the red sandstone was also conducted. Results show that the creep curve under each compressive or tensile stress level can be divided into decay and steady stages, which cannot be described by the conventional Burgers model. Therefore, an improved Burgers creep model of rock material is constructed through viscoplastic mechanics, which agrees very well with the experimental results and can describe the creep behavior of red sandstone better than the Burgers creep model.

  14. Uniaxial pressure-induced half-metallic ferromagnetic phase transition in LaMnO3

    Science.gov (United States)

    Rivero, Pablo; Meunier, Vincent; Shelton, William

    2016-03-01

    We use first-principles theory to predict that the application of uniaxial compressive strain leads to a transition from an antiferromagnetic insulator to a ferromagnetic half-metal phase in LaMnO3. We identify the Q2 Jahn-Teller mode as the primary mechanism that drives the transition, indicating that this mode can be used to tune the lattice, charge, and spin coupling. Applying ≃6 GPa of uniaxial pressure along the [010] direction activates the transition to a half-metallic pseudocubic state. The half-metallicity opens the possibility of producing colossal magnetoresistance in the stoichiometric LaMnO3 compound at significantly lower pressure compared to recently observed investigations using hydrostatic pressure.

  15. On the in-plane uniaxial anisotropy formation by using Fe–Co–Zr–N films: A theoretical and experimental investigation

    Energy Technology Data Exchange (ETDEWEB)

    Seemann, K., E-mail: klaus.seemann@kit.edu; Beirle, S.; Leiste, H.

    2016-09-01

    In the present paper a simple theoretical approach for the in-plane uniaxial anisotropy evolution in thin films is introduced. In order to show, what are the conditions for a uniaxial anisotropy formation during annealing a ferromagnetic film in an external static magnetic field, a Hamiltonian, i.e., mean energy balances were established with introducing their annealing temperature dependence. At this point, a 1-dimesional chain-like arrangement of Fe and Co elements for an “isotropic” and uniaxial anisotropy state for the numerical computation was assumed. It was shown that a critical energy and annealing temperature (temperature threshold) can be attained from which a uniaxial anisotropy arises. Comparatively, calculations according to the Neél theory delivered the activation energy for inducing a uniaxial anisotropy. The experimental verification of the calculations, by using Fe{sub 40}Co{sub 37}Zr{sub 11}N{sub 12} films which were produced by reactive magnetron sputtering, yielded the activation energy of about 250 meV. Annealing temperatures above 473 K (200 °C) enabled marked uniaxial anisotropies. This correlated with the numerical quantum mechanical estimations which yielded a critical annealing temperature of approximately 449 K (176 °C). The calculated critical energy of 243 meV was in a good agreement with the verified experiments if one assumes a short range order of at least 10 ferromagnetic atoms in line (5Fe+5Co) for computation. - Highlights: • Model and theoretical description of the uniaxial anisotropy in ferromagnetic films. • Critical energy and a critical temperature for inducing the uniaxial anisotropy. • Investigation of the activation energy for inducing the uniaxial anisotropy. • Comparison with the model and according to the Neél theory.

  16. Assessment of brain activities during an emotional stress state using fMRI

    International Nuclear Information System (INIS)

    Hayashi, Takuto; Mizuno-Matsumoto, Yuko; Kawasaki, Aika; Kato, Makoto; Murata, Tsutomu

    2011-01-01

    We investigated cerebrum activation using functional magnetic resonance imaging during a mental stress state. Thirty-four healthy adults participated. Before the experiment, we assessed their stress states using the Stress Self-rating Scale and divided the participants into Stress and Non-stress groups. The experiment consisted of 6 trials. Each trial consisted of a 20-s block of emotional audio-visual stimuli (4-s stimulation x 5 slides) and a fixation point. These processes were performed 3 times continuously (Relaxed, Pleasant, Unpleasant stimuli) in a random order. These results showed that the Non-stress group indicated activation of the amygdala and hippocampus in the Pleasant and Unpleasant stimuli while the Stress group indicated activation of the hippocampus in Pleasant stimuli, and the amygdala and hippocampus in Unpleasant stimuli. These findings suggested that the mental stress state engages the reduction of emotional processing. Also, the responsiveness of the memory system remained during and after the emotional stress state. (author)

  17. Phase transitions in random uniaxial systems with dipolar interactions

    International Nuclear Information System (INIS)

    Schuster, H.G.

    1977-01-01

    The critical behaviour of random uniaxial ferromagnetic (ferroelectric) systems with both short range and long range dipolar interactions is investigated, using the field theoretic renormalization method of Brezin et al. for the free energy above and below transition point Tsub(c). The randomness is due to externally introduced fluctuations in the short range interactions (quenched case) or (and) magneto-elastic coupling to the lattice (annealed case). Strong deviations in the critical behaviour with respect to the pure systems are found. In the quenched case, e.g., the specific heat C and the coefficient f 2 (of M 3 in the equation of state, where M is the magnetization) change from C proportional to abs ln abs t abs abssup(1/3), f 2 proportional to abs ln abs t abs abs sup(1/3), f 2 proportional to abs ln abs t abs abs -1 in the pure system to C = A+- + C+-exp[-4√ 3 106 abs ln abs t abs abs], f 2 proportional to abs ln abs t abs abs sup(-1/2) (where t = (T-Tsub(c)) / Tsub(c) is the reduced temperature and A+-, C+- are constants) in the random situation. (orig.) [de

  18. Plain-Woven, 600-Denier Kevlar KM2 Fabric Under Quasistatic, Uniaxial Tension

    Science.gov (United States)

    2005-03-01

    respectively, along the direction of applied tensile loading, and Sfail and Efail denote the values corresponding to material failure. 2.2 Least...uniaxial tension along the fill direction. 7 Table 1. Failure strain and failure stress (strength) from each test. Test Efail Sfail (GPa) W1 0.122633...14539.8 7214.87 d (GPa) –4898.41 –10674.6 –33428.5 –14475.3 e –22.0527 –15.6910 –34.3400 –28.6378 f 465.297 476.711 2137.94 1266.84 Efail 0.132930

  19. Strength and stiffness of uniaxially tensioned reinforced concrete panels subjected to membrane shear. Technical report

    International Nuclear Information System (INIS)

    Hilmy, S.I.; White, R.N.; Gergely, P.

    1982-06-01

    This report presents experimental and analytical results on internal pressurization effects and seismic shear effects in a concrete containment vessel that is cracked by tension in one direction only. The experimental program, which was restricted to 6 in. thick flat specimens with two-way reinforcement, included establishment of (a) extensional stiffness for uniaxially tensioned specimens stressed to 0.6fy, and (b) shear strength and stiffness of these cracked specimens with tension levels ranging from 0 to 0.9fy; values were about 10 to 15 percent higher than in similar biaxially tensioned specimens. Eleven (11) specimens were tested (6 in monotonic shear and 5 in reversing cyclic shear)

  20. Posttraumatic stress disorder: a state-of-the-science review.

    Science.gov (United States)

    Nemeroff, Charles B; Bremner, J Douglas; Foa, Edna B; Mayberg, Helen S; North, Carol S; Stein, Murray B

    2006-02-01

    This article reviews the state-of-the-art research in posttraumatic stress disorder (PTSD) from several perspectives: (1) Sex differences: PTSD is more frequent among women, who tend to have different types of precipitating traumas and higher rates of comorbid panic disorder and agoraphobia than do men. (2) Risk and resilience: The presence of Group C symptoms after exposure to a disaster or act of terrorism may predict the development of PTSD as well as comorbid diagnoses. (3) Impact of trauma in early life: Persistent increases in CRF concentration are associated with early life trauma and PTSD, and may be reversed with paroxetine treatment. (4) Imaging studies: Intriguing findings in treated and untreated depressed patients may serve as a paradigm of failed brain adaptation to chronic emotional stress and anxiety disorders. (5) Neural circuits and memory: Hippocampal volume appears to be selectively decreased and hippocampal function impaired among PTSD patients. (6) Cognitive behavioral approaches: Prolonged exposure therapy, a readily disseminated treatment modality, is effective in modifying the negative cognitions that are frequent among PTSD patients. In the future, it would be useful to assess the validity of the PTSD construct, elucidate genetic and experiential contributing factors (and their complex interrelationships), clarify the mechanisms of action for different treatments used in PTSD, discover ways to predict which treatments (or treatment combinations) will be successful for a given individual, develop an operational definition of remission in PTSD, and explore ways to disseminate effective evidence-based treatments for this condition.

  1. Stress among Accounting Educators in the United States.

    Science.gov (United States)

    Seiler, Robert E.; Pearson, Della A.

    1984-01-01

    Stress among accounting educators was investigated and relationships between stress levels and work satisfaction levels, personality traits, and stress-coping techniques were examined. The most important personality charcteristics of higher stress individuals were impatience, assertiveness, workaholism, and idealism. (Author/MLW)

  2. Dislocation based controlling of kinematic hardening contribution to simulate primary and secondary stages of uniaxial ratcheting

    Science.gov (United States)

    Bhattacharjee, S.; Dhar, S.; Acharyya, S. K.

    2017-07-01

    The primary and secondary stages of the uniaxial ratcheting curve for the C-Mn steel SA333 have been investigated. Stress controlled uniaxial ratcheting experiments were conducted with different mean stresses and stress amplitudes to obtain curves showing the evolution of ratcheting strain with number of cycles. In stage-I of the ratcheting curve, a large accumulation of ratcheting strain occurs, but at a decreasing rate. In contrast, in stage-II a smaller accumulation of ratcheting strain is found and the ratcheting rate becomes almost constant. Transmission electron microscope observations reveal that no specific dislocation structures are developed during the early stages of ratcheting. Rather, compared with the case of low cycle fatigue, it is observed that sub-cell formation is delayed in the case of ratcheting. The increase in dislocation density as a result of the ratcheting strain is obtained using the Orowan equation. The ratcheting strain is obtained from the shift of the plastic strain memory surface. The dislocation rearrangement is incorporated in a functional form of dislocation density, which is used to calibrate the parameters of a kinematic hardening law. The observations are formulated in a material model, plugged into the ABAQUS finite element (FE) platform as a user material subroutine. Finally the FE-simulated ratcheting curves are compared with the experimental curves.

  3. Analysis of the Mechanical Behavior, Creep Resistance and Uniaxial Fatigue Strength of Martensitic Steel X46Cr13

    Science.gov (United States)

    Brnic, Josip; Krscanski, Sanjin; Lanc, Domagoj; Brcic, Marino; Turkalj, Goran; Canadija, Marko; Niu, Jitai

    2017-01-01

    The article deals with the analysis of the mechanical behavior at different temperatures, uniaxial creep and uniaxial fatigue of martensitic steel X46Cr13 (1.4034, AISI 420). For the purpose of considering the aforementioned mechanical behavior, as well as determining the appropriate resistance to creep and fatigue strength levels, numerous uniaxial tests were carried out. Tests related to mechanical properties performed at different temperatures are presented in the form of engineering stress-strain diagrams. Short-time creep tests performed at different temperatures and different stress levels are presented in the form of creep curves. Fatigue tests carried out at stress ratios R=0.25 and R=−1 are shown in the form of S–N (fatigue) diagrams. The finite fatigue regime for each of the mentioned stress ratios is modeled by an inclined log line, while the infinite fatigue regime is modeled by a horizontal line, which represents the fatigue limit of the material and previously was calculated by the modified staircase method. Finally, the fracture toughness has been calculated based on the Charpy V-notch impact energy. PMID:28772749

  4. State of charge estimation for lithium-ion pouch batteries based on stress measurement

    International Nuclear Information System (INIS)

    Dai, Haifeng; Yu, Chenchen; Wei, Xuezhe; Sun, Zechang

    2017-01-01

    State of charge (SOC) estimation is one of the important tasks of battery management system (BMS). Being different from other researches, a novel method of SOC estimation for pouch lithium-ion battery cells based on stress measurement is proposed. With a comprehensive experimental study, we find that, the stress of the battery during charge/discharge is composed of the static stress and the dynamic stress. The static stress, which is the measured stress in equilibrium state, corresponds to SOC, this phenomenon facilitates the design of our stress-based SOC estimation. The dynamic stress, on the other hand, is influenced by multiple factors including charge accumulation or depletion, current and historical operation, thus a multiple regression model of the dynamic stress is established. Based on the relationship between static stress and SOC, as well as the dynamic stress modeling, the SOC estimation method is founded. Experimental results show that the stress-based method performs well with a good accuracy, and this method offers a novel perspective for SOC estimation. - Highlights: • A State of Charge estimator based on stress measurement is proposed. • The stress during charge and discharge is investigated with comprehensive experiments. • Effects of SOC, current, and operation history on battery stress are well studied. • A multiple regression model of the dynamic stress is established.

  5. Unified Drain Current Model of Armchair Graphene Nanoribbons with Uniaxial Strain and Quantum Effect

    Directory of Open Access Journals (Sweden)

    EngSiew Kang

    2014-01-01

    Full Text Available A unified current-voltage I-V model of uniaxial strained armchair graphene nanoribbons (AGNRs incorporating quantum confinement effects is presented in this paper. The I-V model is enhanced by integrating both linear and saturation regions into a unified and precise model of AGNRs. The derivation originates from energy dispersion throughout the entire Brillouin zone of uniaxial strained AGNRs based on the tight-binding approximation. Our results reveal the modification of the energy band gap, carrier density, and drain current upon strain. The effects of quantum confinement were investigated in terms of the quantum capacitance calculated from the broadening density of states. The results show that quantum effect is greatly dependent on the magnitude of applied strain, gate voltage, channel length, and oxide thickness. The discrepancies between the classical calculation and quantum calculation were also measured and it has been found to be as high as 19% drive current loss due to the quantum confinement. Our finding which is in good agreement with the published data provides significant insight into the device performance of uniaxial strained AGNRs in nanoelectronic applications.

  6. Direct Observation of Magnetocrystalline Anisotropy Tuning Magnetization Configurations in Uniaxial Magnetic Nanomaterials

    KAUST Repository

    Zhu, Shimeng; Fu, Jiecai; Li, Hongli; Zhu, Liu; Hu, Yang; Xia, Weixing; Zhang, Xixiang; Peng, Yong; Zhang, Junli

    2018-01-01

    Discovering the effect of magnetic anisotropy on the magnetization configurations of magnetic nanomaterials is essential and significant for not only enriching the fundamental knowledge of magnetics but also facilitating the designs of desired magnetic nanostructures for diverse technological applications, such as data storage devices, spintronic devices, and magnetic nanosensors. Herein, we present a direct observation of magnetocrystalline anisotropy tuning magnetization configurations in uniaxial magnetic nanomaterials with hexagonal structure by means of three modeled samples. The magnetic configuration in polycrystalline BaFe12O19 nanoslice is a curling structure, revealing that the effect of magnetocrystalline anisotropy in uniaxial magnetic nanomaterials can be broken by forming an amorphous structure or polycrystalline structure with tiny grains. Both single crystalline BaFe12O19 nanoslice and individual particles of single-particle-chain BaFe12O19 nanowire appear in a single domain state, revealing a dominant role of magnetocrystalline anisotropy in the magnetization configuration of uniaxial magnetic nanomaterials. These observations are further verified by micromagnetic computational simulations.

  7. Direct Observation of Magnetocrystalline Anisotropy Tuning Magnetization Configurations in Uniaxial Magnetic Nanomaterials

    KAUST Repository

    Zhu, Shimeng

    2018-03-20

    Discovering the effect of magnetic anisotropy on the magnetization configurations of magnetic nanomaterials is essential and significant for not only enriching the fundamental knowledge of magnetics but also facilitating the designs of desired magnetic nanostructures for diverse technological applications, such as data storage devices, spintronic devices, and magnetic nanosensors. Herein, we present a direct observation of magnetocrystalline anisotropy tuning magnetization configurations in uniaxial magnetic nanomaterials with hexagonal structure by means of three modeled samples. The magnetic configuration in polycrystalline BaFe12O19 nanoslice is a curling structure, revealing that the effect of magnetocrystalline anisotropy in uniaxial magnetic nanomaterials can be broken by forming an amorphous structure or polycrystalline structure with tiny grains. Both single crystalline BaFe12O19 nanoslice and individual particles of single-particle-chain BaFe12O19 nanowire appear in a single domain state, revealing a dominant role of magnetocrystalline anisotropy in the magnetization configuration of uniaxial magnetic nanomaterials. These observations are further verified by micromagnetic computational simulations.

  8. Measured resolved shear stresses and Bishop-Hill stress states in individual grains of austenitic stainless steel

    DEFF Research Database (Denmark)

    Juul, Nicolai Ytterdal; Oddershede, Jette; Beaudoin, Armand

    2017-01-01

    somewhat from the theoretical expectation. These deviations are found to originate from a larger tensile stress component than in the theoretical Bishop-Hill stress states and to be associated also with deviations from axisymmetric plastic strain. This conclusion was supported by finite-element crystal...

  9. Effect of stress-state and spacing on voids in a shear-field

    DEFF Research Database (Denmark)

    Tvergaard, Viggo

    2012-01-01

    in the overall average stress state can be prescribed. This also allows for studies of the effect of different initial void spacing in the two in-plane coordinate directions. The stress states considered are essentially simple shear, with various levels of tensile stresses or compressive stresses superposed, i.......e. low positive stress triaxiality or even negative stress triaxiality. For high aspect ratio unit cells a clear localization band is found inside the cell, which actually represents several parallel bands, due to periodicity. In the materials represented by a low aspect ratio unit cell localization...

  10. Elastic properties of uniaxial-fiber reinforced composites - General features

    Science.gov (United States)

    Datta, Subhendu; Ledbetter, Hassel; Lei, Ming

    The salient features of the elastic properties of uniaxial-fiber-reinforced composites are examined by considering the complete set of elastic constants of composites comprising isotropic uniaxial fibers in an isotropic matrix. Such materials exhibit transverse-isotropic symmetry and five independent elastic constants in Voigt notation: C(11), C(33), C(44), C(66), and C(13). These C(ij) constants are calculated over the entire fiber-volume-fraction range 0.0-1.0, using a scattered-plane-wave ensemple-average model. Some practical elastic constants such as the principal Young moduli and the principal Poisson ratios are considered, and the behavior of these constants is discussed. Also presented are the results for the four principal sound velocities used to study uniaxial-fiber-reinforced composites: v(11), v(33), v(12), and v(13).

  11. Effect of insulin pump infusion on comprehensive stress state of ...

    African Journals Online (AJOL)

    a control group (120 cases), administered continuous intravenous insulin, and a ... oxidative stress and stress hormone levels were compared between the ... metabolic acidosis and ketonuria, as a result of .... This resulting energy insufficiency.

  12. Switching the uniaxial magnetic anisotropy by ion irradiation induced compensation

    Science.gov (United States)

    Yuan, Ye; Amarouche, Teyri; Xu, Chi; Rushforth, Andrew; Böttger, Roman; Edmonds, Kevin; Campion, Richard; Gallagher, Bryan; Helm, Manfred; Jürgen von Bardeleben, Hans; Zhou, Shengqiang

    2018-04-01

    In the present work, the uniaxial magnetic anisotropy of GaMnAsP is modified by helium ion irradiation. According to the micro-magnetic parameters, e.g. resonance fields and anisotropy constants deduced from ferromagnetic resonance measurements, a rotation of the magnetic easy axis from out-of-plane [0 0 1] to in-plane [1 0 0] direction is achieved. From the application point of view, our work presents a novel avenue in modifying the uniaxial magnetic anisotropy in GaMnAsP with the possibility of lateral patterning by using lithography or focused ion beam.

  13. Modelling of the deformation of shot peened cylindrical specimens of 42 CrMo4 in uniaxial tension and deformation and of the resulting macro residual stresses; Modellierung der einachsigen Zug- und Druck-Verformung kugelgestrahlter Zylinderproben aus verguetetem 42 CrMo4 und der dabei auftretenden Makroeigenspannungsaenderungen

    Energy Technology Data Exchange (ETDEWEB)

    Schulze, V.; Voehringer, O.; Macherauch, E. [Karlsruhe Univ. (T.H.) (Germany). Inst. fuer Werkstoffkunde 1

    1998-10-01

    Tensile and compressive stress-strain-curves of shot peened and unpeened specimens of quenched and tempered 42 CrMo 4 (AISI 4140) with a diameter of 5 mm only differ in the yield strengths and in the Lueders-deformation. In comparison to the core the regions close to the surface of shot peened cylindrical specimens bear relatively large axial and tangential residual stresses and show different deformation properties. A multi-layer-model was developed to describe both the tensile as well as the compressive deformation behaviour of shot peened cylindrical specimens quantitatively. The calculated transitions from the elastic to the elastic-plastic deformation state during tensile and compressive loading agree quite well with the experimental observations. Also the changes of axial and tangential macro residual stresses after distinct tensile or compressive deformations are in best agreement with the measurements. (orig.) 29 refs.

  14. Modeling of uniaxial ratchetting behavior of SA333 carbon manganese steel

    International Nuclear Information System (INIS)

    Shit, J.; Dhar, S.; Acharyya, S.K.; Goyal, S.

    2012-01-01

    The paper deals with uniaxial ratcheting phenomenon of cyclic plasticity behavior of the materials SA333 carbon Manganese steel. A mechanistic model for the ratcheting phenomenon has been proposed. It is observed that von Mises yield criterion together with Chaboche’s kinematic hardening rules are not sufficient to model ratcheting phenomenon. Other associated phenomena like plastic strain memory surface, back stress memory points and over all the extra hardening behavior have to be incorporated to get a complete material model for ratcheting. The proposed model assembled all these ideas together with von Mises yield criterion and Chabache’s kinematic hardening rule. Low cycle fatigue tests and uniaxial ratcheting tests have been conducted for the materials. The material constants are identified and derived from experimental results. The ratcheting coefficients have been properly calibrated with these material constants. The material model, as mentioned above, for the ratcheting phenomenon has been implemented in an elastic plastic finite element code. The ratcheting results for different stress controlled ratcheting loads have been computed. The good feature of this model is that it reduces to symmetric low cycle fatigue model when loop closes. - Highlights: ► A common material model to simulate symmetric LCF and ratcheting. ► Extra hardening to take care the shift of plastic strain centre. ► Material parameters from tensile and LCF tests. ► Saturated loop in LCF and ratcheting strain rate is compared with experiment. ► Consideration of loading path, memory path and their directions.

  15. Flavour fields in steady state: stress tensor and free energy

    International Nuclear Information System (INIS)

    Banerjee, Avik; Kundu, Arnab; Kundu, Sandipan

    2016-01-01

    The dynamics of a probe brane in a given gravitational background is governed by the Dirac-Born-Infeld action. The corresponding open string metric arises naturally in studying the fluctuations on the probe. In Gauge-String duality, it is known that in the presence of a constant electric field on the worldvolume of the probe, the open string metric acquires an event horizon and therefore the fluctuation modes on the probe experience an effective temperature. In this article, we bring together various properties of such a system to a formal definition and a subsequent narration of the effective thermodynamics and the stress tensor of the corresponding flavour fields, also including a non-vanishing chemical potential. In doing so, we point out a potentially infinitely-degenerate scheme-dependence of regularizing the free energy, which nevertheless yields a universal contribution in certain cases. This universal piece appears as the coefficient of a log-divergence in free energy when a space-filling probe brane is embedded in AdS d+1 -background, for d=2,4, and is related to conformal anomaly. For the special case of d=2, the universal factor has a striking resemblance to the well-known heat current formula in (1+1)-dimensional conformal field theory in steady-state, which endows a plausible physical interpretation to it. Interestingly, we observe a vanishing conformal anomaly in d=6.

  16. Functional possibilities of nonlinear crystals for frequency conversion: uniaxial crystals

    Energy Technology Data Exchange (ETDEWEB)

    Andreev, Yu M [Institute of Monitoring of Climatic and Ecological Systems, Siberian Branch of the Russian Academy of Sciences, Tomsk (Russian Federation); Arapov, Yu D; Kasyanov, I V [E.I. Zababakhin All-Russian Scientific-Research Institute of Technical Physics, Russian Federal Nuclear Centre, Snezhinsk, Chelyabinsk region (Russian Federation); Grechin, S G; Nikolaev, P P [N.E. Bauman Moscow State Technical University, Moscow (Russian Federation)

    2016-01-31

    The method and results of the analysis of phase-matching and nonlinear properties for all point groups of symmetry of uniaxial crystals that determine their functional possibilities for solving various problems of nonlinear frequency conversion of laser radiation are presented. (nonlinear optical phenomena)

  17. Technique for measurements of plane waves of uniaxial strain

    International Nuclear Information System (INIS)

    Graham, R.A.

    1977-01-01

    The measurement of plane waves in uniaxial strain, in which large surface areas are loaded and the measurements are restricted to a central region that is not influenced by lateral boundaries, is discussed. Measuring techniques are covered and instruments are discussed

  18. Microwave holography in a uniaxial anial anisotropic plasma

    International Nuclear Information System (INIS)

    Nagai, Keinosuke; Suzuki, Michio

    1974-01-01

    Properties of a hologram constructed in a uniaxial anisotropic medium, namely in a gyro-plasma were investigated theoretically. We considered the interference patterns of ordinary waves and extraordinary waves from a source such as a hologram. An element of permitivity tensor can be measured by the reconstruction process from this hologram. (auth.)

  19. Quasi-static and ratcheting properties of trabecular bone under uniaxial and cyclic compression.

    Science.gov (United States)

    Gao, Li-Lan; Wei, Chao-Lei; Zhang, Chun-Qiu; Gao, Hong; Yang, Nan; Dong, Li-Min

    2017-08-01

    The quasi-static and ratcheting properties of trabecular bone were investigated by experiments and theoretical predictions. The creep tests with different stress levels were completed and it is found that both the creep strain and creep compliance increase rapidly at first and then increase slowly as the creep time goes by. With increase of compressive stress the creep strain increases and the creep compliance decreases. The uniaxial compressive tests show that the applied stress rate makes remarkable influence on the compressive behaviors of trabecular bone. The Young's modulus of trabecular bone increases with increase of stress rate. The stress-strain hysteresis loops of trabecular bone under cyclic load change from sparse to dense with increase of number of cycles, which agrees with the change trend of ratcheting strain. The ratcheting strain rate rapidly decreases at first, and then exhibits a relatively stable and small value after 50cycles. Both the ratcheting strain and ratcheting strain rate increase with increase of stress amplitude or with decrease of stress rate. The creep model and the nonlinear viscoelastic constitutive model of trabecular bone were proposed and used to predict its creep property and rate-dependent compressive property. The results show that there are good agreements between the experimental data and predictions. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Anisotropic Material Behavior of Uni-axially Compacted Graphite Matrix for HTGR Fuel Compact Fabrication

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Young-Woo; Yeo, Seunghwan; Yoon, Ji-Hae; Cho, Moon Sung [KAERI, Daejeon (Korea, Republic of)

    2016-05-15

    In developing the fuel compact fabrication technology, and fuel graphite material to meet the required material properties, it is essential to investigate the relationship among the process parameters of the matrix graphite powder preparation, the fabrication parameters of fuel element green compact and the heat treatments conditions and the material properties of fuel element. It was observed, during this development, that the pressing technique employed for the compaction fabrication prior to the two successive heat treatments (carbonization and final high temperature heat treatment) was of extreme importance in determining the material properties of the final compact product. In this work, the material behavior of the uni-axially pressed graphite matrix during the carbonization and final heat treatment are evaluated and summarized along the different directions, viz., perpendicular and parallel directions to pressing direction. In this work, the dimensional variations and variations in thermal expansion, thermal conductivity and Vickers hardness of the graphite matrix compact samples in the axial and radial directions prepared by uni-axial pressing are evaluated, and compared with those of samples prepared by cold isostatic pressing with the available data. From this work, the followings are observed. 1) Dimensional changes of matrix graphite green compacts during carbonization show that the difference in radial and axial variations shows a large anisotropic behavior in shrinkage. The radial variation is very small while the axial variation is large. During carbonization, the stresses caused by the force would be released in to the axial direction together with the phenolic resin vapor. 2) Dimensional variation of compact samples in perpendicular and parallel directions during carbonization shows a large difference in behavior when compact sample is prepared by uni-axial pressing. However, when compact sample is prepared by cold isostatic pressing, there is

  1. Anisotropic Material Behavior of Uni-axially Compacted Graphite Matrix for HTGR Fuel Compact Fabrication

    International Nuclear Information System (INIS)

    Lee, Young-Woo; Yeo, Seunghwan; Yoon, Ji-Hae; Cho, Moon Sung

    2016-01-01

    In developing the fuel compact fabrication technology, and fuel graphite material to meet the required material properties, it is essential to investigate the relationship among the process parameters of the matrix graphite powder preparation, the fabrication parameters of fuel element green compact and the heat treatments conditions and the material properties of fuel element. It was observed, during this development, that the pressing technique employed for the compaction fabrication prior to the two successive heat treatments (carbonization and final high temperature heat treatment) was of extreme importance in determining the material properties of the final compact product. In this work, the material behavior of the uni-axially pressed graphite matrix during the carbonization and final heat treatment are evaluated and summarized along the different directions, viz., perpendicular and parallel directions to pressing direction. In this work, the dimensional variations and variations in thermal expansion, thermal conductivity and Vickers hardness of the graphite matrix compact samples in the axial and radial directions prepared by uni-axial pressing are evaluated, and compared with those of samples prepared by cold isostatic pressing with the available data. From this work, the followings are observed. 1) Dimensional changes of matrix graphite green compacts during carbonization show that the difference in radial and axial variations shows a large anisotropic behavior in shrinkage. The radial variation is very small while the axial variation is large. During carbonization, the stresses caused by the force would be released in to the axial direction together with the phenolic resin vapor. 2) Dimensional variation of compact samples in perpendicular and parallel directions during carbonization shows a large difference in behavior when compact sample is prepared by uni-axial pressing. However, when compact sample is prepared by cold isostatic pressing, there is

  2. Effect of Strain Rate on Microscopic Deformation Behavior of High-density Polyethylene under Uniaxial Stretching

    Directory of Open Access Journals (Sweden)

    Kida Takumitsu

    2017-01-01

    Full Text Available The microscopic deformation behaviors such as the load sharing and the molecular orientation of high-density polyethylene under uniaxial stretching at various strain rates were investigated by using in-situ Raman spectroscopy. The chains within crystalline phase began to orient toward the stretching direction beyond the yielding region and the orientation behavior was not affected by the strain rate. While the stretching stress along the crystalline chains was also not affected by the strain rate, the peak shifts of the Raman bands at 1130, 1418, 1440 and 1460 cm-1, which are sensitive to the interchain interactions obviously, depended on the strain rate; the higher strain rates lead to the stronger stretching stress or negative pressure on the crystalline and amorphous chains. These effects of the strain rate on the microscopic deformation was associated with the cavitation and the void formation leading to the release of the internal pressure.

  3. Irradiation creep, stress relaxation and a mechanical equation of state

    International Nuclear Information System (INIS)

    Foster, J.P.

    1976-01-01

    Irradiation creep and stress relaxation data are available from the United Kingdom for 20 percent CW M316, 20 percent CW FV 548 and FHT PE16 using pure torsion in the absence of swelling at 300 0 C. Irradiation creep models were used to calculate the relaxation and permanent deflection of the stress relaxation tests. Two relationships between irradiation creep and stress relaxation were assessed by comparing the measured and calculated stress relaxation and permanent deflection. The results show that for M316 and FV548, the stress relaxation and deflection may be calculated using irradiation creep models when the stress rate term arising from the irradiation creep model is set equal to zero. In the case of PE16, the inability to calculate the stress relaxation and permanent deflection from the irradiation creep data was attributed to differences in creep behavior arising from lot-to-lot variations in alloying elements and impurity content. A modification of the FV548 and PE16 irradiation creep coefficients was necessary in order to calculate the stress relaxation and deflection. The modifications in FV548 and PE16 irradiation creep properties reduces the large variation in the transient or incubation parameter predicted by irradiation creep tests for M316, FV548 and PE16

  4. Be Cool with Academic Stress: The Association between Emotional States and Regulatory Strategies among Chinese Adolescents

    Science.gov (United States)

    Sang, Biao; Pan, Tingting; Deng, Xinmei; Zhao, Xu

    2018-01-01

    Numerous studies have suggested that academic stress has negative impact on adolescents' psychological function, few of those studies, however, considered whether and how the impact of stress on adolescents' emotional states is moderated by corresponding regulation. This study aimed to examine the fluctuation of emotional states before and after…

  5. Relationship between Organizational Climate, Job Stress and Job Performance Officer at State Education Department

    Science.gov (United States)

    Suandi, Turiman; Ismail, Ismi Arif; Othman, Zulfadli

    2014-01-01

    This research aims at finding out the relationship between Organizational Climate, job stress and job performance among State Education Department (JPN) officers . The focus of the research is to determine the job performance of state education department officers, level of job stress among the officers, level of connection between organizational…

  6. The influence of the anisotropic stress state on the intermediate strain properties of granular material

    KAUST Repository

    Goudarzy, M.

    2017-07-20

    This paper shows the effect of anisotropic stress state on intermediate strain properties of cylindrical samples containing spherical glass particles. Tests were carried out with the modified resonant column device available at Ruhr-Universität Bochum. Dry samples were subjected to two anisotropic stress states: (a) cell pressure, σ′h, constant and vertical stress, σ′v, increased (stress state GB-I) and (b) σ′v/σ′h equal to 2 (stress state GB-II). The experimental results revealed that the effect of stress state GB-II on the modulus and damping ratio was more significant and obvious than stress state GB-I. The effect of the anisotropic stress state was explained through the impact of confining pressure and anisotropic stress components on the stiffness and damping ratio. The results showed that: (a) G(γ) increased, η(γ) decreased and their strain non-linearity decreased with an increase in the confining pressure component σ′vσ′h; (b) G(γ) decreased, η(γ) increased and their strain non-linearity increased with an increase in the anisotropic stress component, σ′v/σ′h. The analysis of results revealed that reference shear strain was also affected by anisotropic stress state. Therefore, an empirical relationship was developed to predict the reference shear strain, as a function of confining pressure and anisotropic stress components. Additionally, the damping ratio was written as a function of the minimum damping ratio and the reference shear strain.

  7. Stress state evaluation in low carbon and TRIP steels by magnetic permeability

    International Nuclear Information System (INIS)

    Kouli, M.-E.; Giannakis, M

    2016-01-01

    Magnetic permeability is an indicative factor for the steel health monitoring. The measurements of magnetic permeability lead to the evaluation of the stress state of any ferromagnetic steel. The magnetic permeability measurements were conducted on low carbon and TRIP steel samples, which were subjected to both tensile and compressive stresses. The results indicated a direct correlation of the magnetic permeability with the mechanical properties, the stress state and the microstructural features of the examined samples. (paper)

  8. GASICA: Generic Automated Stress Induction and Control ApplicationDesign of an application for controlling the stress state

    Directory of Open Access Journals (Sweden)

    Benny Van Der Vijgh

    2014-12-01

    Full Text Available 1.In a multitude of research and therapy paradigms it is relevant to know, and desirably to control, the stress state of a patient or participant. Examples include research paradigms in which the stress state is the dependent or independent variable, or therapy paradigms where this state indicates the boundaries of the therapy. To our knowledge, no application currently exists that focuses specifically on the automated control of the stress state while at the same time being generic enough to be used in various therapy and research purposes. Therefore, we introduce GASICA, an application aimed at the automated control of the stress state in a multitude of therapy and research paradigms. The application consists of three components: a digital stressor game, a set of measurement devices and a feedback model. These three components form a closed loop (called a biocybernetic loop by Pope, Bogart, & Bartolome, 1995 and Fairclough, 2009 that continuously presents an acute psychological stressor, measures several physiological responses to this stressor, and adjusts the stressor intensity based on these measurements by means of the feedback model, hereby aiming to control the stress state. In this manner GASICA presents multidimensional and ecological valid stressors, whilst continuously in control of the form and intensity of the presented stressors, aiming at the automated control of the stress state. Furthermore, the application is designed as a modular open-source application to easily implement different therapy and research tasks using a high-level programming interface and configuration file, and allows for the addition of (existing measurement equipment, making it usable for various paradigms.

  9. GASICA: generic automated stress induction and control application design of an application for controlling the stress state.

    Science.gov (United States)

    van der Vijgh, Benny; Beun, Robbert J; van Rood, Maarten; Werkhoven, Peter

    2014-01-01

    In a multitude of research and therapy paradigms it is relevant to know, and desirably to control, the stress state of a patient or participant. Examples include research paradigms in which the stress state is the dependent or independent variable, or therapy paradigms where this state indicates the boundaries of the therapy. To our knowledge, no application currently exists that focuses specifically on the automated control of the stress state while at the same time being generic enough to be used in various therapy and research purposes. Therefore, we introduce GASICA, an application aimed at the automated control of the stress state in a multitude of therapy and research paradigms. The application consists of three components: a digital stressor game, a set of measurement devices, and a feedback model. These three components form a closed loop (called a biocybernetic loop by Pope et al. (1995) and Fairclough (2009) that continuously presents an acute psychological stressor, measures several physiological responses to this stressor, and adjusts the stressor intensity based on these measurements by means of the feedback model, hereby aiming to control the stress state. In this manner GASICA presents multidimensional and ecological valid stressors, whilst continuously in control of the form and intensity of the presented stressors, aiming at the automated control of the stress state. Furthermore, the application is designed as a modular open-source application to easily implement different therapy and research tasks using a high-level programming interface and configuration file, and allows for the addition of (existing) measurement equipment, making it usable for various paradigms.

  10. Analysis of residual stress state in sheet metal parts processed by single point incremental forming

    Science.gov (United States)

    Maaß, F.; Gies, S.; Dobecki, M.; Brömmelhoff, K.; Tekkaya, A. E.; Reimers, W.

    2018-05-01

    The mechanical properties of formed metal components are highly affected by the prevailing residual stress state. A selective induction of residual compressive stresses in the component, can improve the product properties such as the fatigue strength. By means of single point incremental forming (SPIF), the residual stress state can be influenced by adjusting the process parameters during the manufacturing process. To achieve a fundamental understanding of the residual stress formation caused by the SPIF process, a valid numerical process model is essential. Within the scope of this paper the significance of kinematic hardening effects on the determined residual stress state is presented based on numerical simulations. The effect of the unclamping step after the manufacturing process is also analyzed. An average deviation of the residual stress amplitudes in the clamped and unclamped condition of 18 % reveals, that the unclamping step needs to be considered to reach a high numerical prediction quality.

  11. Influence of Simulated Acid Rain Corrosion on the Uniaxial Tensile Mechanical Properties of Concrete

    Directory of Open Access Journals (Sweden)

    Ying-zi Zhang

    2012-01-01

    Full Text Available An experimental study on the uniaxial tensile property of concrete exposed to the acid rain environment was carried out. Acid rain with pH level of 1.0 was deposed by the mixture of sulfate and nitric acid solution in the laboratory. Dumbbell-shaped concrete specimens were immersed in the simulated acid rain completely. After being exposed to the deposed mixture for a certain period, uniaxial tensile test was performed on the concrete specimens. The results indicate that elastic modulus, tensile strength, and peak strain have a slight increase at the initial corrosion stage, and with the extension of corrosion process, elastic modulus and tensile strength decrease gradually, while the peak strain still increases. It is found that the compressive strength is more sensitive than the tensile strength in aggressive environment. Based on the experimental results, an equation was proposed to describe the ascending branch of the stress-strain curve of the concrete corroded by acid rain.

  12. A uniaxial cyclic elastoplastic constitutive law with a discrete memory variable

    International Nuclear Information System (INIS)

    Taheri, S.

    1991-01-01

    At present, the study on cyclic elastoplastic constitutive laws is focused on nonproportional loading, but for uniaxial loading, some problems still exist. For example, the possibility for a law to describe simultaneously the ratcheting in nonsymmetrical load-controlled test, elastic and plastic shakedown in symmetrical and nonsymmetrical ones. Here a law is presented, which in addition to previous phenomena, describes the cyclic hardening in a pushpull test, the cyclic softening after overloading and also the dependence of cyclic strain-stress curves on the history of loading. These are the usual properties of 316 stainless steel at room temperature. This law uses an internal discrete memory variable: the plastic strain at the last unloading. On the other hand, the choice of all macroscopic variables is justified by a microscopic analysis. This law has been also extended to a three-dimensional case. Regarding the microstructure under cyclic loading, plastic shakedown and ratcheting are discussed. The definition of macroscopic variables taking account of microstructure and uniaxial constitutive law are described. (K.I.)

  13. Mathematical model of polyethylene pipe bending stress state

    Science.gov (United States)

    Serebrennikov, Anatoly; Serebrennikov, Daniil

    2018-03-01

    Introduction of new machines and new technologies of polyethylene pipeline installation is usually based on the polyethylene pipe flexibility. It is necessary that existing bending stresses do not lead to an irreversible polyethylene pipe deformation and to violation of its strength characteristics. Derivation of the mathematical model which allows calculating analytically the bending stress level of polyethylene pipes with consideration of nonlinear characteristics is presented below. All analytical calculations made with the mathematical model are experimentally proved and confirmed.

  14. [Study on the relationship between occupational stress and psychological health state among oil workers].

    Science.gov (United States)

    Liu, Jiwen; Wang, Zhiming; Wang, Mianzhen; Lan, Yajia; Zhan, Chenglie; Zhao, Xiaoguo

    2002-02-01

    To study the relationship between occupational stress and psychological health state among oil workers. 1,230 oil workers in 122 work types of oil industry were selected and written occupational stress questionary(OSQ) and symptom check list (SCL-90). Petroleum workers' psychological health states were poor with increasing occupational stress degree. The scores in physical symptoms(1.87 +/- 0.80, 1.72 +/- 0.70), depression(1.74 +/- 0.76, 1.62 +/- 0.67), horror(1.48 +/- 0.65, 1.39 +/- 0.55) in the high and medium stress group were obviously higher than those in low stress group(1.55 +/- 0.61, 1.43 +/- 0.54, 1.28 +/- 0.46, respectively, P < 0.05). The score of mood state in the high and medium stress group was obviously higher than that in low stress group(P < 0.05). Psychological health states and mood state in the petroleum workers with short service length are significantly poorer than that with long service length(P < 0.01). Occupational stress should affect psychological health state of petroleum workers.

  15. Four dimensional X-ray imaging of deformation modes in organic-rich Green River Shale retorted under uniaxial compression

    Science.gov (United States)

    Kobchenko, M.; Pluymakers, A.; Cordonnier, B.; Tairova, A.; Renard, F.

    2017-12-01

    Time-lapse imaging of fracture network development in organic-rich shales at elevated temperatures while kerogen is retorted allows characterizing the development of microfractures and the onset of primary migration. When the solid organic matter is transformed to hydrocarbons with lower molecular weight, the local pore-pressure increases and drives the propagation of hydro-fractures sub-parallel to the shale lamination. On the scale of samples of several mm size, these fractures can be described as mode I opening, where fracture walls dilate in the direction of minimal compression. However, so far experiments coupled to microtomography in situ imaging have been performed on samples where no load was imposed. Here, an external load was applied perpendicular to the sample laminations and we show that this stress state slows down, but does not stop, the propagation of fracture along bedding. Conversely, microfractures also propagate sub-perpendicular to the shale lamination, creating a percolating network in three dimensions. To monitor this process we have used a uniaxial compaction rig combined with in-situ heating from 50 to 500 deg C, while capturing three-dimensional X-ray microtomography scans at a voxel resolution of 2.2 μm; Data were acquired at beamline ID19 at the European Synchrotron Radiation Facility. In total ten time-resolved experiments were performed at different vertical loading conditions, with and without lateral passive confinement and different heating rates. At high external load the sample fails by symmetric bulging, while at lower external load the reaction-induced fracture network develops with the presence of microfractures both sub-parallel and sub-perpendicular to the bedding direction. In addition, the variation of experimental conditions allows the decoupling of the effects of the hydrocarbon decomposition reaction on the deformation process from the influence of thermal stress heating on the weakening and failure mode of immature

  16. Specific strain work as a failure criterion in plane stress state

    International Nuclear Information System (INIS)

    Zuchowski, R.; Zietkowski, L.

    1985-01-01

    An experimental verification of failure criterion based on specific strain work was performed. Thin-walled cylindrical specimens were examined by loading with constant force and constant torque moment, assuming different values for particular tests, at the same time keeping stress intensity constant, and by subjecting to thermal cycling. It was found that the critical value of failure did not depend on axial-to-shearing stresses ratio, i.e., on the type of state of stress. Thereby, the validity of the analysed failure criterion in plane stress was confirmed. Besides, a simple description of damage development in plane stress was suggested. (orig./RF)

  17. Microstructure of depleted uranium under uniaxial strain conditions

    International Nuclear Information System (INIS)

    Zurek, A.K.; Embury, J.D.; Kelly, A.; Thissell, W.R.; Gustavsen, R.L.; Vorthman, J.E.; Hixson, R.H.

    1997-01-01

    Uranium samples of two different purities were used for spall strength measurements. Samples of depleted uranium were taken from very high purity material (38 ppM carbon) and from material containing 280 ppM C. Experimental conditions were chosen to effectively arrest the microstructural damage at two places in the development to full spall separation. Samples were soft recovered and characterized with respect to the microstructure and the form of damage. This allowed determination of the dependence of spall mechanisms on stress level, stress state, and sample purity. This information is used in developing a model to predict the mode of fracture

  18. General multimode polarization splitter design in uniaxial media

    Science.gov (United States)

    Teixeira, Poliane A.; Silva, Daniely G.; Gabrielli, Lucas H.; Spadoti, Danilo H.; Junqueira, Mateus A. F. C.

    2018-03-01

    Quasiconformal transformation optics is used to design two-dimensional polarization beam splitters. The resulting media present inhomogeneous uniaxial permittivity and nonmagnetic response. The compact devices are theoretically designed and investigated for symmetrical and asymmetrical geometries, with footprint of 64 and 110 μm2, respectively. The polarization splitter performance is evaluated for the fundamental mode and third mode, exhibiting an insertion loss closer to 0 dB and extinction ratio above 40 dB over a broad wavelength range.

  19. Ultrasonic detection of cracks in uniaxial glass fibre rods

    CSIR Research Space (South Africa)

    Loveday, PW

    2006-01-01

    Full Text Available Conference on Computational and Applied Mechanics SACAM06 Cape Town, 16-18 January 2006 �SACAM ULTRASONIC DETECTION OF CRACKS IN UNIAXIAL GLASS FIBRE RODS Derren Wood and Philip Loveday Sensor Science and Technology, CSIR Materials Science... means of detecting internal and/or surface damage in composites which is safe, quick and relatively cost effective. Various ultrasonic techniques have been applied in the past to detect defects in composite media, the most well known being perhaps...

  20. Numerical study on core damage and interpretation of in situ state of stress

    Energy Technology Data Exchange (ETDEWEB)

    Hakala, M. [Gridpoint Finland Oy (Finland)

    1999-06-01

    Core disking is a phenomenon where a diamond cored core sample will be sliced when released from a stressed host rock. Ring disking is a similar phenomenon which takes place during overcoring with a pilot hole. Because of the uniform shape and spacing of disk fracturing, it has the potential to be used for estimating the in situ state of stress. If this is feasible, it could be used in high stress states where the traditional stress measuring techniques are not valid or even possible. In this work the both the core disking and ring disking phenomena were studied based on the elastic bottom hole stress application developed and a series of fracture growth stability simulations. The results-showed that both phenomena are very complicated and site specific, but the spacing, shape, extent and initiation point are clearly stress state dependent. Throughout the work, guidelines for the in situ stress field interpretation method were developed and implemented for the borehole aligned orthogonal stress field and Poisson`s ratio of 0.25. Based on this study, the in situ state of stress can be estimated with acceptable accuracy if information on both core disking and ring disking is available. On the other hand, as an indirect method, there are no reasons to use it if direct measurements can be used. (orig.) 35 refs.

  1. Numerical study on core damage and interpretation of in situ state of stress

    International Nuclear Information System (INIS)

    Hakala, M.

    1999-06-01

    Core disking is a phenomenon where a diamond cored core sample will be sliced when released from a stressed host rock. Ring disking is a similar phenomenon which takes place during overcoring with a pilot hole. Because of the uniform shape and spacing of disk fracturing, it has the potential to be used for estimating the in situ state of stress. If this is feasible, it could be used in high stress states where the traditional stress measuring techniques are not valid or even possible. In this work the both the core disking and ring disking phenomena were studied based on the elastic bottom hole stress application developed and a series of fracture growth stability simulations. The results-showed that both phenomena are very complicated and site specific, but the spacing, shape, extent and initiation point are clearly stress state dependent. Throughout the work, guidelines for the in situ stress field interpretation method were developed and implemented for the borehole aligned orthogonal stress field and Poisson's ratio of 0.25. Based on this study, the in situ state of stress can be estimated with acceptable accuracy if information on both core disking and ring disking is available. On the other hand, as an indirect method, there are no reasons to use it if direct measurements can be used. (orig.)

  2. Local Stress States and Microstructural Damage Response Associated with Deformation Twins in Hexagonal Close Packed Metals

    Directory of Open Access Journals (Sweden)

    Indranil Basu

    2017-12-01

    Full Text Available The current work implements a correlative microscopy method utilizing electron back scatter diffraction, focused ion beam and digital image correlation to accurately determine spatially resolved stress profiles in the vicinity of grain/twin boundaries and tensile deformation twin tips in commercially pure titanium. Measured local stress gradients were in good agreement with local misorientation values. The role of dislocation-boundary interactions on the buildup of local stress gradients is elucidated. Stress gradients across the twin-parent interface were compressive in nature with a maximum stress magnitude at the twin boundary. Stress profiles near certain grain boundaries initially display a local stress minimum, followed by a typically observed “one over square root of distance” variation, as was first postulated by Eshelby, Frank and Nabarro. The observed trends allude to local stress relaxation mechanisms very close to the grain boundaries. Stress states in front of twin tips showed tensile stress gradients, whereas the stress state inside the twin underwent a sign reversal. The findings highlight the important role of deformation twins and their corresponding interaction with grain boundaries on damage nucleation in metals.

  3. Mechanical Behavior of Shale Rock under Uniaxial Cyclic Loading and Unloading Condition

    Directory of Open Access Journals (Sweden)

    Baoyun Zhao

    2018-01-01

    Full Text Available In order to investigate the mechanical behavior of shale rock under cyclic loading and unloading condition, two kinds of incremental cyclic loading tests were conducted. Based on the result of the short-term uniaxial incremental cyclic loading test, the permanent residual strain, modulus, and damage evolution were analyzed firstly. Results showed that the relationship between the residual strains and the cycle number can be expressed by an exponential function. The deformation modulus E50 and elastic modulus ES first increased and then decreased with the peak stress under the loading condition, and both of them increased approximately linearly with the peak stress under the unloading condition. On the basis of the energy dissipation, the damage variables showed an exponential increasing with the strain at peak stress. The creep behavior of the shale rock was also analyzed. Results showed that there are obvious instantaneous strain, decay creep, and steady creep under each stress level and the specimen appears the accelerated creep stage under the 4th stress of 51.16 MPa. Based on the characteristics of the Burgers creep model, a viscoelastic-plastic creep model was proposed through viscoplastic mechanics, which agrees very well with the experimental results and can better describe the creep behavior of shale rock better than the Burgers creep model. Results can provide some mechanics reference evidence for shale gas development.

  4. Experimental research data on stress state of salt rock mass around an underground excavation

    Science.gov (United States)

    Baryshnikov, VD; Baryshnikov, DV

    2018-03-01

    The paper presents the experimental stress state data obtained in surrounding salt rock mass around an excavation in Mir Mine, ALROSA. The deformation characteristics and the values of stresses in the adjacent rock mass are determined. Using the method of drilling a pair of parallel holes in a stressed area, the authors construct linear relationship for the radial displacements of the stress measurement hole boundaries under the short-term loading of the perturbing hole. The resultant elasticity moduli of rocks are comparable with the laboratory core test data. Pre-estimates of actual stresses point at the presence of a plasticity zone in the vicinity of the underground excavation. The stress state behavior at a distance from the excavation boundary disagrees with the Dinnik–Geim hypothesis.

  5. Simulation of Stress-Strain State of Shovel Rotary Support Kingpin

    Science.gov (United States)

    Khoreshok, A. A.; Buyankin, P. V.; Vorobiev, A. V.; Dronov, A. A.

    2016-04-01

    The article presents the sequence of computational simulation of stress-strain state of shovel’s rotary support. Computation results are analyzed, the kingpin is specified as the most loaded element, maximum stress zones are identified. Kingpin design modification such as enhancement of fillet curvature radius to 25 mm and displacement of eyebolt holes on the diameter of 165 mm are proposed, thus diminishing impact of stress concentrators and improving reliability of the rotary support.

  6. Synthesis of full Poincaré beams by means of uniaxial crystals

    Science.gov (United States)

    Piquero, G.; Monroy, L.; Santarsiero, M.; Alonzo, M.; de Sande, J. C. G.

    2018-06-01

    A simple optical system is proposed to generate full-Poincaré beams (FPBs), i.e. beams presenting all possible states of (total) polarization across their transverse section. The method consists in focusing a uniformly polarized laser beam onto a uniaxial crystal having its optic axis parallel to the propagation axis of the impinging beam. A simple approximated model is used to obtain the analytical expression of the beam polarization at the output of the crystal. The output beam is then proved to be a FPB. By changing the polarization state of the input field, full-Poincaré beams are still obtained, but presenting different distributions of the polarization state across the beam section. Experimental results are reported, showing an excellent agreement with the theoretical predictions.

  7. Stress evaluation of metallic material under steady state based on nonlinear critically refracted longitudinal wave

    Science.gov (United States)

    Mao, Hanling; Zhang, Yuhua; Mao, Hanying; Li, Xinxin; Huang, Zhenfeng

    2018-06-01

    This paper presents the study of applying the nonlinear ultrasonic wave to evaluate the stress state of metallic materials under steady state. The pre-stress loading method is applied to guarantee components with steady stress. Three kinds of nonlinear ultrasonic experiments based on critically refracted longitudinal wave are conducted on components which the critically refracted longitudinal wave propagates along x, x1 and x2 direction. Experimental results indicate the second and third order relative nonlinear coefficients monotonically increase with stress, and the normalized relationship is consistent with simplified dislocation models, which indicates the experimental result is logical. The combined ultrasonic nonlinear parameter is proposed, and three stress evaluation models at x direction are established based on three ultrasonic nonlinear parameters, which the estimation error is below 5%. Then two stress detection models at x1 and x2 direction are built based on combined ultrasonic nonlinear parameter, the stress synthesis method is applied to calculate the magnitude and direction of principal stress. The results show the prediction error is within 5% and the angle deviation is within 1.5°. Therefore the nonlinear ultrasonic technique based on LCR wave could be applied to nondestructively evaluate the stress of metallic materials under steady state which the magnitude and direction are included.

  8. Compressive Properties of PTFE/Al/Ni Composite Under Uniaxial Loading

    Science.gov (United States)

    Wang, Huai-xi; Li, Yu-chun; Feng, Bin; Huang, Jun-yi; Zhang, Sheng; Fang, Xiang

    2017-05-01

    To investigate the mechanical properties of pressed and sintered PTFE/Al/Ni (polytetrafluoroethylene/aluminum/nickel) composite, uniaxial quasi-static and dynamic compression experiments were conducted at strain rates from 10-2 to 3 × 103/s. The prepared samples were tested by an electrohydraulic press with 300 kN loading capacity and a split Hopkinson pressure bar (SHPB) device at room temperature. Experimental results show that PTFE/Al/Ni composite exhibits evident strain hardening and strain rate hardening. Additionally, a bilinear relationship between stress and {{log(}}\\dot{ɛ} ) is observed. The experimental data were fit to Johnson-Cook constitutive model, and the results are in well agreement with measured data.

  9. Mechanical and microstructural stability of P92 steel under uniaxial tension at high temperature

    International Nuclear Information System (INIS)

    Giroux, P.F.; Dalle, F.; Sauzay, M.; Malaplate, J.; Fournier, B.; Gourgues-Lorenzon, A.F.

    2010-01-01

    9-12%Cr creep-resistant ferritic-martensitic steels are candidates for structural components of Generation IV nuclear power plants. However, they are sensitive to softening during low-cycle fatigue, creep and creep-fatigue tests, due to the destabilisation of the tempered martensite microstructure, possibly inducing a decrease in further creep resistance. To better identify the softening mechanisms in P92 steel during uniaxial deformation, tensile tests were carried out at 823 K, showing an extended and stable softening stage on true stress-strain curves after some work-hardening. Three phenomena were studied in order to understand this behaviour: mechanical instability (necking), damage and grain size evolution. Examination of fractured and non-fractured tensile specimens (light optical and electron microscopy, macrohardness) suggested that the physical mechanisms responsible for softening are mainly (sub)grain size evolution and diffuse necking. Models were proposed to predict grain growth and beginning of the mechanical instability during homogeneous deformation.

  10. On the role of the residual stress state in product manufacturing

    NARCIS (Netherlands)

    Zijlstra, G.; Groen, M.; Post, J.; Ocelik, V.; de Hosson, J.Th.M.

    2016-01-01

    This paper concentrates on the effect of the residual stress state during product manufacturing of AISI 420 steel on the final shape of the product. The work includes Finite Element (FE) calculations of the distribution of the residual stresses after metal forming and a heat treatment. The evolution

  11. Stress state of thin – walled member of the structure with operation damages under nonuniform loading

    Directory of Open Access Journals (Sweden)

    В.В. Астанін

    2004-01-01

    Full Text Available  The publication is dedicated to determining of stress state in particular the stress concentration factors for thin – walled members of the structures subject to nonuniform tension. A structure member has obtained the operation damage generation by corrosion and other causes.

  12. Material law for concrete under multiaxial stress

    International Nuclear Information System (INIS)

    Geistefeldt, H.

    1977-01-01

    In this paper a general triaxial set of finite strain-stress relations is derived, which can include a step-by-step way nearly all known factors and curves of material response. The finite constitutive equations representing the behaviour of concrete are related to the main strain-directions. The elastic part, the functions for uniaxial behaviour, those for biaxial response and finally the relation-parts, nonzero only in triaxial stress-state, can be reset separately by suitable functions which have been adjusted to the material response of actual concrete known from special tests. With a new and very short biaxial failure criterion for concrete, which has been stated and compared with test results, the analytic description of the biaxial behaviour of Kupfer's concrete is completed. With some additional assumptions the proposed failure criteria and the strain-stress equations for concrete are extended to the biaxial response of uncracked orthogonally reinforced concrete response. (Auth.)

  13. The influence of the anisotropic stress state on the intermediate strain properties of granular material

    KAUST Repository

    Goudarzy, M.; Kö nig, D.; Santamarina, Carlos; Schanz, T.

    2017-01-01

    This paper shows the effect of anisotropic stress state on intermediate strain properties of cylindrical samples containing spherical glass particles. Tests were carried out with the modified resonant column device available at Ruhr

  14. Stress responses during aerobic exercise in relation to motivational dominance and state.

    Science.gov (United States)

    Thatcher, Joanne; Kuroda, Yusuke; Legrand, Fabien D; Thatcher, Rhys

    2011-02-01

    We examined the hypothesis that congruence between motivational dominance and state results in optimal psychological responses and performance during exercise. Twenty participants (10 telic dominant and 10 paratelic dominant) rated their stress at 5 min intervals as they cycled on an ergometer at gas exchange threshold for 30 min in both telic and paratelic state manipulated conditions. Participants then performed a test to exhaustion at a resistance equivalent to 110% of VO(2max). The hypothesized interaction between condition and dominance was significant for internal tension stress, as paratelic dominants were more stressed than telic dominants when exercising in the telic state and telic dominants were more stressed than paratelic dominants when exercising in the paratelic state. Similarly, the condition × dominance interaction for internal stress discrepancy was significant, as paratelic dominants reported greater internal stress discrepancy exercising in the telic compared with the paratelic state. Findings are discussed in relation to the application of reversal theory for understanding stress responses during aerobic exercise.

  15. From point-wise stress data to a continuous description of the 3D crustal in situ stress state

    Science.gov (United States)

    Heidbach, O.; Ziegler, M.; Reiter, K.; Hergert, T.

    2017-12-01

    The in situ stress is a key parameter for the safe and sustainable management of geo-reservoirs or storage of waste and energy in deep geological repositories. It is also an essential initial condition for thermo-hydro-mechanical (THM) models that investigate man-made induced processes e.g. seismicity due to fluid injection/extraction, reservoir depletion or storage of heat producing high-level radioactive waste. Without a reasonable assumption on the initial stress condition it is not possible to assess if a man-made process is pushing the system into a critical state or not. However, modelling the initial 3D stress state on reservoir scale is challenging since data are hardly available before drilling in the area of interest. This is in particular the case for the stress magnitude data which are a prerequisite for a reliable model calibration. Here, we present a multi-stage 3D geomechani­cal-numerical model approach to estimate for a reservoir-scale volume the 3D in situ stress state. First, we set up a large-scale model which is calibrated by stress data and use the modelled stress field subsequently to calibrate a small-scale model located within the large-scale model. The local model contains a significantly higher resolution representation of the subsurface geometry around boreholes of a projected geothermal power plant. This approach incorporates two models and is an alternative to the required trade-off between resolution, computational cost and calibration data which is inevitable for a single model; an extension to a three-stage approach would be straight forward. We exemplify the two-stage approach for the area around Munich in the German Molasse Basin. The results of the reservoir-scale model are presented in terms of values for slip tendency as a measure for the criticality of fault reactivation. The model results show that variations due to uncertainties in the input data are mainly introduced by the uncertain material properties and missing

  16. In situ synchrotron X-ray diffraction of ferroelastic La0.8Ca0.2CoO3 ceramics during uniaxial compression

    International Nuclear Information System (INIS)

    Vullum, Per Erik; Mastin, Johann; Wright, Jonathan; Einarsrud, Mari-Ann; Holmestad, Randi; Grande, Tor

    2006-01-01

    Uniaxial compression of rhombohedral La 0.8 Ca 0.2 CoO 3 ceramics has been studied in situ using synchrotron X-ray diffraction. The intensities of Bragg reflections parallel and perpendicular to the stress field were simultaneously detected as a function of the stress. Reorientation of ferroelastic domains due to the uniaxial stress was demonstrated. With increasing stress the volume fraction of domains with the hexagonal c-axis parallel to the stress axis increased at the expense of domains with the c-axis perpendicular to the stress axis. The strain in the polycrystalline materials evolved unevenly with increasing stress due to crystallographic anisotropy. In energetically favourable domains with the c-axis parallel to the stress axis, the rhombohedral distortion from cubic symmetry increased, while the crystal structure became closer to cubic in domains with the c-axis perpendicular to the stress. Successive compression/decompression cycles to higher maximum stress resulted in a higher volume fraction of reoriented domains both at maximum stress and after decompression

  17. A novel method for calculating the energy barriers for carbon diffusion in ferrite under heterogeneous stress

    Science.gov (United States)

    Tchitchekova, Deyana S.; Morthomas, Julien; Ribeiro, Fabienne; Ducher, Roland; Perez, Michel

    2014-07-01

    A novel method for accurate and efficient evaluation of the change in energy barriers for carbon diffusion in ferrite under heterogeneous stress is introduced. This method, called Linear Combination of Stress States, is based on the knowledge of the effects of simple stresses (uniaxial or shear) on these diffusion barriers. Then, it is assumed that the change in energy barriers under a complex stress can be expressed as a linear combination of these already known simple stress effects. The modifications of energy barriers by either uniaxial traction/compression and shear stress are determined by means of atomistic simulations with the Climbing Image-Nudge Elastic Band method and are stored as a set of functions. The results of this method are compared to the predictions of anisotropic elasticity theory. It is shown that, linear anisotropic elasticity fails to predict the correct energy barrier variation with stress (especially with shear stress) whereas the proposed method provides correct energy barrier variation for stresses up to ˜3 GPa. This study provides a basis for the development of multiscale models of diffusion under non-uniform stress.

  18. A novel method for calculating the energy barriers for carbon diffusion in ferrite under heterogeneous stress

    International Nuclear Information System (INIS)

    Tchitchekova, Deyana S.; Morthomas, Julien; Perez, Michel; Ribeiro, Fabienne; Ducher, Roland

    2014-01-01

    A novel method for accurate and efficient evaluation of the change in energy barriers for carbon diffusion in ferrite under heterogeneous stress is introduced. This method, called Linear Combination of Stress States, is based on the knowledge of the effects of simple stresses (uniaxial or shear) on these diffusion barriers. Then, it is assumed that the change in energy barriers under a complex stress can be expressed as a linear combination of these already known simple stress effects. The modifications of energy barriers by either uniaxial traction/compression and shear stress are determined by means of atomistic simulations with the Climbing Image-Nudge Elastic Band method and are stored as a set of functions. The results of this method are compared to the predictions of anisotropic elasticity theory. It is shown that, linear anisotropic elasticity fails to predict the correct energy barrier variation with stress (especially with shear stress) whereas the proposed method provides correct energy barrier variation for stresses up to ∼3 GPa. This study provides a basis for the development of multiscale models of diffusion under non-uniform stress

  19. A novel method for calculating the energy barriers for carbon diffusion in ferrite under heterogeneous stress

    Energy Technology Data Exchange (ETDEWEB)

    Tchitchekova, Deyana S. [IRSN, PSN, SEMIA, LPTM, Saint-Paul-Lez-Durance (France); Univ. Lyon, INSA Lyon, MATEIS, UMR CNRS 5510, Villeurbanne (France); Morthomas, Julien; Perez, Michel [Univ. Lyon, INSA Lyon, MATEIS, UMR CNRS 5510, Villeurbanne (France); Ribeiro, Fabienne [IRSN, PSN, SEMIA, LPTM, Saint-Paul-Lez-Durance (France); Ducher, Roland [IRSN, PSN, SAG, LETR, Saint-Paul-Lez-Durance (France)

    2014-07-21

    A novel method for accurate and efficient evaluation of the change in energy barriers for carbon diffusion in ferrite under heterogeneous stress is introduced. This method, called Linear Combination of Stress States, is based on the knowledge of the effects of simple stresses (uniaxial or shear) on these diffusion barriers. Then, it is assumed that the change in energy barriers under a complex stress can be expressed as a linear combination of these already known simple stress effects. The modifications of energy barriers by either uniaxial traction/compression and shear stress are determined by means of atomistic simulations with the Climbing Image-Nudge Elastic Band method and are stored as a set of functions. The results of this method are compared to the predictions of anisotropic elasticity theory. It is shown that, linear anisotropic elasticity fails to predict the correct energy barrier variation with stress (especially with shear stress) whereas the proposed method provides correct energy barrier variation for stresses up to ∼3 GPa. This study provides a basis for the development of multiscale models of diffusion under non-uniform stress.

  20. Shallow Lunar Seismic Activity and the Current Stress State of the Moon

    Science.gov (United States)

    Watters, Thomas R.; Weber, Renee C.; Collins, Geoffrey C.; Johnson, Catherine L.

    2017-01-01

    A vast, global network of more than 3200 lobate thrust fault scarps has been revealed in high resolution Lunar Reconnaissance Orbiter Camera (LROC) images. The fault scarps are very young, less than 50 Ma, based on their small scale and crisp appearance, crosscutting relations with small-diameter impact craters, and rates of infilling of associated small, shallow graben and may be actively forming today. The population of young thrust fault scarps provides a window into the recent stress state of the Moon and offers insight into the origin of global lunar stresses. The distribution of orientations of the fault scarps is non-random, inconsistent with isotropic stresses from late-stage global contraction as the sole source of stress. Modeling shows that tidal stresses contribute significantly to the current stress state of the lunar crust. Tidal stresses (orbital recession and diurnal tides) superimposed on stresses from global contraction result in non-isotropic compressional stress and may produce thrust faults consistent with lobate scarp orientations. At any particular point on the lunar surface, peak compressive stress will be reached at a certain time in the diurnal cycle. Coseismic slip events on currently active thrust faults are expected to be triggered when peak stresses are reached. Analysis of the timing of the 28 the shallow moonquakes recorded by the Apollo seismic network shows that 19 indeed occur when the Moon is closer to apogee, while only 9 shallow events occur when the Moon is closer to perigee. Here we report efforts to refine the model for the current stress state of the Moon by investigating the contribution of polar wander. Progress on relocating the epicentral locations of the shallow moonquakes using an algorithm designed for sparse networks is also reported.

  1. Structural and electronic properties of armchair graphene nanoribbons under uniaxial strain

    Science.gov (United States)

    Qu, Li-Hua; Zhang, Jian-Min; Xu, Ke-Wei; Ji, Vincent

    2014-02-01

    We theoretically investigate the structures, relative stabilities and electronic properties of the armchair graphene nanoribbons (AGNRs) under uniaxial strain via first-principles calculations. The results show that, although each bond length decreases (increases) with increasing compression (tension) strain especially for the axial bonds a1, a4 and a7, the ribbon geometrical width d increases (decreases) with increasing compression (tension) strain due to the rotation of the zigzag bonds a2, a3, a5 and a6. For each nanoribbon, as expected, the lowest average energy corresponds to the unstrained state and the larger contract (elongate) deformation corresponds to the higher average energy. At a certain strain, the average energy increases with decreasing the ribbon width n. The average energy increases quadratically with the absolute value of the uniaxial strain, showing an elastic behavior. The dependence of the band gap on the strain is sensitive to the ribbon width n which can be classified into three distinct families n=3I, 3I+1 and 3I+2, where I is an integer. The ribbon width leads to oscillatory band gaps due to quantum confinement effect.

  2. Uniaxial cyclic strain enhances adipose-derived stem cell fusion with skeletal myocytes

    Energy Technology Data Exchange (ETDEWEB)

    Andersen, Jens Isak; Juhl, Morten; Nielsen, Thøger; Emmersen, Jeppe; Fink, Trine; Zachar, Vladimir; Pennisi, Cristian Pablo, E-mail: cpennisi@hst.aau.dk

    2014-07-25

    Highlights: • Uniaxial cyclic tensile strain (CTS) applied to ASCs alone or in coculture with myogenic precursors. • CTS promoted the formation of a highly ordered array of parallel ASCs. • Without biochemical supplements, CTS did not support advanced myogenic differentiation of ASCs. • Mechanical stimulation of cocultures boosted fusion of ASCs with skeletal myoblasts. - Abstract: Although adult muscle tissue possesses an exceptional capacity for regeneration, in the case of large defects, the restoration to original state is not possible. A well-known source for the de novo regeneration is the adipose-derived stem cells (ASCs), which can be readily isolated and have been shown to have a broad differentiation and regenerative potential. In this work, we employed uniaxial cyclic tensile strain (CTS), to mechanically stimulate human ASCs to participate in the formation skeletal myotubes in an in vitro model of myogenesis. The application of CTS for 48 h resulted in the formation of a highly ordered array of parallel ASCs, but failed to support skeletal muscle terminal differentiation. When the same stimulation paradigm was applied to cocultures with mouse skeletal muscle myoblasts, the percentage of ASCs contributing to the formation of myotubes significantly exceeded the levels reported in the literature hitherto. In perspective, the mechanical strain may be used to increase the efficiency of incorporation of ASCs in the skeletal muscles, which could be found useful in diverse traumatic or pathologic scenarios.

  3. Impact of repeated uniaxial mechanical strain on flexible a-IGZO thin film transistors with symmetric and asymmetric structures

    Science.gov (United States)

    Liao, Po-Yung; Chang, Ting-Chang; Su, Wan-Ching; Chen, Bo-Wei; Chen, Li-Hui; Hsieh, Tien-Yu; Yang, Chung-Yi; Chang, Kuan-Chang; Zhang, Sheng-Dong; Huang, Yen-Yu; Chang, Hsi-Ming; Chiang, Shin-Chuan

    2017-06-01

    This letter investigates repeated uniaxial mechanical stress-induced degradation behavior in flexible amorphous In-Ga-Zn-O thin-film transistors (TFTs) of different geometric structures. Two types of via-contact structure TFTs are investigated: symmetrical and UI structure (TFTs with I- and U-shaped asymmetric electrodes). After repeated mechanical stress, I-V curves for the symmetrical structure show a significant negative threshold voltage (VT) shift, due to mechanical stress-induced oxygen vacancy generation. However, degradation in the UI structure TFTs after stress is a negative VT shift along with the parasitic transistor characteristic in the forward-operation mode, with this hump not evident in the reverse-operation mode. This asymmetrical degradation is clarified by the mechanical strain simulation of the UI TFTs.

  4. EVALUATION OF STRAIN-STRESS STATE OF THE RAILS IN THE PRODUCTION

    Directory of Open Access Journals (Sweden)

    V. V. Muravev

    2017-01-01

    Full Text Available High values of residual stresses is one of the most common reason of breaking lots of metal constructions, including rails. These stresses can reach values of flow limit, especially in the area of faults. Estimation of residual stresses values allows to get information about technical condition of the rail and also allow to avoid abnormal situations So, the aim of the research is creating the model of stress-strain state of the rail, which was hardened in its top and bottom, and to compare modeling results with experimental measurements of stresses and discrepancy of the housing.For creating the model and making evaluations by finite element method we used a program COMSOL. Forces on the top and bottom of the rail cause tension stresses, forces on the web of the rail cause tensile stresses. We compared calculated values of stresses with discrepancy of the housing. The discrepancy of the housing is informative characteristic for estimating the residual stresses according to standards. For experimental measurements we used an acoustic structuroscope SEMA. This structuroscope uses the acoustoelastic phenomenon for measurements. We made measurements of the five rails.According to the calculation results of the model, critical discrepancy of the housing in 2 mm corresponded to the following values of maximum stresses: –54 MPa in the top of the rail, 86 MPa in the web and –62 MPa in the bottom of the rail. Experimental measurements are the following: from –48 MPa to – 64 MPa in the top of the rail, 54 MPa to 93 MPa in the web of the rail, and –59 MPA to –74 MPa in the bottom of the rail. Absolute error was ±5 MPa.Thus we created the model, which allowed to analyze strain-stress state and compare real values of stresses with discrepancy of the housing. Results of the modeling showed coincidence with structure of distribution of residual stresses in five probes of rails. 

  5. Modelling of the Residual Stress State in a new Type of Residual Stress Specimen

    DEFF Research Database (Denmark)

    Jakobsen, Johnny; Andreasen, Jens Henrik

    2014-01-01

    forms the experimental case which is analysed. A FE model of the specimen is used for analysing the curing history and the residual stress build up. The model is validated against experimental strain data which are recorded by a Fibre Brag Grating sensor and good agreement has been achieved.......The paper presents a study on a new type residual stress specimen which is proposed as a simple way to conduct experimental validation for model predictions. A specimen comprising of a steel plate with circular hole embedded into a stack of CSM glass fibre and further infused with an epoxy resin...

  6. Defect-dependent elasticity: Nanoindentation as a probe of stress state

    International Nuclear Information System (INIS)

    Jarausch, K. F.; Kiely, J. D.; Houston, J. E.; Russell, P. E.

    2000-01-01

    Using an interfacial force microscope, the measured elastic response of 100-nm-thick Au films was found to be strongly correlated with the films' stress state and thermal history. Large, reversible variations (2x) of indentation modulus were recorded as a function of applied stress. Low-temperature annealing caused permanent changes in the films' measured elastic properties. The measured elastic response was also found to vary in close proximity to grain boundaries in thin films and near surface steps on single-crystal surfaces. These results demonstrate a complex interdependence of stress state, defect structure, and elastic properties in thin metallic films. (c) 2000 Materials Research Society

  7. Investigation of the Residual Stress State in an Epoxy Based Specimen

    DEFF Research Database (Denmark)

    Baran, Ismet; Jakobsen, Johnny; Andreasen, Jens Henrik

    2015-01-01

    Abstract. Process induced residual stresses may play an important role under service loading conditions for fiber reinforced composite. They may initiate premature cracks and alter the internal stress level. Therefore, the developed numerical models have to be validated with the experimental...... observations. In the present work, the formation of the residual stresses/strains are captured from experimental measurements and numerical models. An epoxy/steel based sample configuration is considered which creates an in-plane biaxial stress state during curing of the resin. A hole drilling process...... material models, i.e. cure kinetics, elastic modulus, CTE, chemical shrinkage, etc. together with the drilling process using the finite element method. The measured and predicted in-plane residual strain states are compared for the epoxy/metal biaxial stress specimen....

  8. Nonintrusive biological signal monitoring in a car to evaluate a driver's stress and health state.

    Science.gov (United States)

    Baek, Hyun Jae; Lee, Haet Bit; Kim, Jung Soo; Choi, Jong Min; Kim, Ko Keun; Park, Kwang Suk

    2009-03-01

    Nonintrusive monitoring of a driver's physiological signals was introduced and evaluated in a car as a test of extending the concept of ubiquitous healthcare to vehicles. Electrocardiogram, photoplethysmogram, galvanic skin response, and respiration were measured in the ubiquitous healthcare car (U-car) using nonintrusively installed sensors on the steering wheel, driver's seat, and seat belt. Measured signals were transmitted to the embedded computer via Bluetooth(R) communication and processed. We collected and analyzed physiological signals during driving in order to estimate a driver's stress state while using this system. In order to compare the effect of stress on physical and mental conditions, two categories of stresses were defined. Experimental results show that a driver's physiological signals were measured with acceptable quality for analysis without interrupting driving, and they were changed meaningfully due to elicited stress. This nonintrusive monitoring can be used to evaluate a driver's state of health and stress.

  9. Acculturation stress among Maya in the United States.

    Science.gov (United States)

    Millender, Eugenia

    2012-01-01

    Abstract: As health care disparities become more evident in our multicultural nation, culture sensitive health research needs to be a priority in order for good health care to take place. This article will explore the literature related to acculturation stress and mental health disparities among the Mayan population. Literatures of similar but distinct groups are included due to the limited amount of research of the Mayan population. Using Leiniger's Transcultural nursing theory, these findings suggest that nurses have a large gap to fill to address the mental health disparities of specific cultural groups like the indigenous Maya, thereby satisfying their nursing obligations.

  10. Relationship of Challenge and Hindrance Stress with Coping Style and Job Satisfaction in Chinese State-Owned Enterprises

    OpenAIRE

    Yamaguchi, Hiroyuki; Zhao, Dong Mei

    2008-01-01

    This study aimed to categorize stresses prevalent in Chinese state-owned enterprises and to investigate the relationships among stresses, coping styles and job satisfaction. Data ( n = 549) were collected from three state-owned enterprises in Cang Zhou, He Bei Province, Mainland China. The result of a factor analysis yielded the following three factors: enterprise stress, interpersonal stress, and challenge stress. In order to test the moderator effect of problem-focused coping and emotion-fo...

  11. Uniaxial ferromagnetism of local uranium moments in hexagonal UBeGe

    Science.gov (United States)

    Gumeniuk, Roman; Yaresko, Alexander N.; Schnelle, Walter; Nicklas, Michael; Kvashnina, Kristina O.; Hennig, Christoph; Grin, Yuri; Leithe-Jasper, Andreas

    2018-05-01

    The new intermetallic uranium beryllium germanide UBeGe and its thorium analogon ThBeGe crystallize with the hexagonal ZrBeSi type of structure. Studies of magnetic, thermal, and transport properties were performed on polycrystalline samples between 1.8 and 750K. UBeGe is a uniaxial ferromagnet and there are indications for two magnetic transitions at TC(1 )≈160 K and TC(2 )≈150 K . The high paramagnetic effective moment μeff≈3.1 μB , x-ray absorption near-edge spectroscopy (XANES, 17-300 K), as well as theoretical DFT calculations indicate localized U 5 f2 states in UBeGe. ThBeGe is a diamagnetic metallic material with low density of states at the Fermi level.

  12. Deciphering Stress State of Seismogenic Faults in Oklahoma and Kansas Based on High-resolution Stress Maps

    Science.gov (United States)

    Qin, Y.; Chen, X.; Haffener, J.; Trugman, D. T.; Carpenter, B.; Reches, Z.

    2017-12-01

    Induced seismicity in Oklahoma and Kansas delineates clear fault trends. It is assumed that fluid injection reactivates faults which are optimally oriented relative to the regional tectonic stress field. We utilized recently improved earthquake locations and more complete focal mechanism catalogs to quantitatively analyze the stress state of seismogenic faults with high-resolution stress maps. The steps of analysis are: (1) Mapping the faults by clustering seismicity using a nearest-neighbor approach, manually picking the fault in each cluster and calculating the fault geometry using principal component analysis. (2) Running a stress inversion with 0.2° grid spacing to produce an in-situ stress map. (3) The fault stress state is determined from fault geometry and a 3D Mohr circle. The parameter `understress' is calculated to quantify the criticalness of these faults. If it approaches 0, the fault is critically stressed; while understress=1 means there is no shear stress on the fault. Our results indicate that most of the active faults have a planar shape (planarity>0.8), and dip steeply (dip>70°). The fault trends are distributed mainly in conjugate set ranges of [50°,70°] and [100°,120°]. More importantly, these conjugate trends are consistent with mapped basement fractures in southern Oklahoma, suggesting similar basement features from regional tectonics. The fault length data shows a loglinear relationship with the maximum earthquake magnitude with an expected maximum magnitude range from 3.2 to 4.4 for most seismogenic faults. Based on 3D local Mohr circle, we find that 61% of the faults have low understress (0.5) are located within highest-rate injection zones and therefore are likely to be influenced by high pore pressure. The faults that hosted the largest earthquakes, M5.7 Prague and M5.8 Pawnee are critically stressed (understress 0.2). These differences may help in understanding earthquake sequences, for example, the predominantly aftershock

  13. Stress drops of induced and tectonic earthquakes in the central United States are indistinguishable.

    Science.gov (United States)

    Huang, Yihe; Ellsworth, William L; Beroza, Gregory C

    2017-08-01

    Induced earthquakes currently pose a significant hazard in the central United States, but there is considerable uncertainty about the severity of their ground motions. We measure stress drops of 39 moderate-magnitude induced and tectonic earthquakes in the central United States and eastern North America. Induced earthquakes, more than half of which are shallower than 5 km, show a comparable median stress drop to tectonic earthquakes in the central United States that are dominantly strike-slip but a lower median stress drop than that of tectonic earthquakes in the eastern North America that are dominantly reverse-faulting. This suggests that ground motion prediction equations developed for tectonic earthquakes can be applied to induced earthquakes if the effects of depth and faulting style are properly considered. Our observation leads to the notion that, similar to tectonic earthquakes, induced earthquakes are driven by tectonic stresses.

  14. Stress

    Science.gov (United States)

    ... can be life-saving. But chronic stress can cause both physical and mental harm. There are at least three different types of stress: Routine stress related to the pressures of work, family, and other daily responsibilities Stress brought about ...

  15. Domain shape instabilities and dendrite domain growth in uniaxial ferroelectrics

    Science.gov (United States)

    Shur, Vladimir Ya.; Akhmatkhanov, Andrey R.

    2018-01-01

    The effects of domain wall shape instabilities and the formation of nanodomains in front of moving walls obtained in various uniaxial ferroelectrics are discussed. Special attention is paid to the formation of self-assembled nanoscale and dendrite domain structures under highly non-equilibrium switching conditions. All obtained results are considered in the framework of the unified kinetic approach to domain structure evolution based on the analogy with first-order phase transformation. This article is part of the theme issue `From atomistic interfaces to dendritic patterns'.

  16. Self-assembly of heterogeneous supramolecular structures with uniaxial anisotropy.

    Science.gov (United States)

    Ruiz-Osés, M; Gonzalez-Lakunza, N; Silanes, I; Gourdon, A; Arnau, A; Ortega, J E

    2006-12-28

    Uniaxial anisotropy in two-dimensional self-assembled supramolecular structures is achieved by the coadsorption of two different linear molecules with complementary amine and imide functionalization. The two-dimensional monolayer is defined by a one-dimensional stack of binary chains, which can be forced to line up along steps in vicinal surfaces. The competing driving forces in the self-organization process are discussed in light of the structures observed during single molecule adsorption and coadsorption on flat and vicinal surfaces and the corresponding theoretical calculations.

  17. Uniaxial compression tests on diesel contaminated frozen silty soil specimens

    International Nuclear Information System (INIS)

    Chenaf, D.; Stampli, N.; Bathurst, R.; Chapuis, R.P.

    1999-01-01

    Results of a uniaxial, unconfined compression test on artificial diesel-contaminated and uncontaminated frozen silty soils are discussed. The testing program involved 59 specimens. The results show that for the same fluid content, diesel contamination reduced the strength of the frozen specimens by increasing the unfrozen water content. For example, in specimens containing 50 per cent diesel oil of the fluid content by weight the maximum strength was reduced by 95 per cent compared to the strength of an uncontaminated specimen. Diesel contamination was also shown to contribute to the slippage between soil particles by acting as a lubricant, thus accelerating the loss of compressive strength.13 refs., 18 figs

  18. Theoretical study of Cherenkov radiation emission in anisotropic uniaxial crystals

    Energy Technology Data Exchange (ETDEWEB)

    Delbart, A; Derre, J

    1996-04-01

    A theoretical review of the Cherenkov radiation emission in uniaxial crystals is presented. The formalism of C. Muzicar in terms of energetic properties of the emitted waves are corrected. This formalism is used to simulate the Cherenkov radiation emission in a strongly birefringent sodium nitrate crystal (NaNO{sub 3}) and to investigate the consequences of the slight anisotropy of sapphire (Al{sub 2}O{sub 3}) on the design of the Optical Trigger. (author). 12 refs. Submitted to Physical Review, D (US).

  19. Natural fiber composite design and characterization for limit stress prediction in multiaxial stress state

    Directory of Open Access Journals (Sweden)

    Christopher C. Ihueze

    2015-07-01

    Full Text Available This paper focuses on the design of natural fiber composites and analysis of multiaxial stresses in relation to yield limit stresses of composites loaded off the fibers axis. ASTM D638-10 standard for tensile test was used to design and compose composites of plantain fiber reinforced polyester (PFRP. While the rule of mixtures was used in the evaluation of properties of composites in the fiber direction the evaluation of properties perpendicular or transverse to the fiber direction was done based on the value of the orthogonal stresses evaluated using ANSYS finite element software, the application of the Brintrup equation and Halpin–Tai equation. The yield strength for the plantain empty fruit bunch fiber reinforced polyester resin (PEFBFRP was estimated as 33.69 MPa while the yield strength of plantain pseudo stem fiber reinforced polyester resin (PPSFRP was estimated as 29.24 MPa. Above all, the PEFBFRP with average light absorbance peak of 45.47 was found to have better mechanical properties than the PPSFRP with average light absorbance peak of 45.77.

  20. Examination stress at unified state examination: student destabilization or success factor?

    Directory of Open Access Journals (Sweden)

    Svetlana N. Kostromina

    2017-01-01

    Full Text Available The aim of the research is to clear up the influence of examination stress on the results of completing examination papers by students in the situation of trial General and Unified State Examinations, imitating the real-life environment of unified state certification of schoolchildren. The tasks of the research included determining the dynamics of psychophysiological stress indices at different examination stages, and evaluating additional factors (the subject in which the examination is held, the strategy of solving the variant, success of solving the task etc., influencing the quantity and quality of stress reactions at the examination.The novelty of the research is in the attempt to overcome the problem of confusing the notions of examination stress and examination anxiety, caused by metering the students’ state either before or after the examination. The technology of online monitoring the students’ psychophysiological state is used in the work, which makes it possible to eliminate a number of restrictions occurring during subjective evaluation of the state by the students themselves. Telemetric cardiorhythmography was chosen as the basic method. The method is based on a three-component model of extreme states with consequent domination of one of the three stress-reactive systems. A cardiointervalogramm was being registered in the research process in the online mode and underwent spectral analysis. The following indices of heart rate variability were recorded in order to determine stress reactions: the total power of the spectrum (TP, the spectrum power in low-frequency (LF and high-frequency (HF regions, and a vegetative balance index (relation of the spectrum powers in low-frequency and high-frequency regions (LF/HF. When the total power of the heart rate fell and, at the same time, the vegetative balance index rose, a conclusion was made of there being a stress reaction. Twenty-five students of an illustrious school were examined

  1. Influence of Health Behaviors and Occupational Stress on Prediabetic State among Male Office Workers.

    Science.gov (United States)

    Ryu, Hosihn; Moon, Jihyeon; Jung, Jiyeon

    2018-06-14

    This study examined the influence of health behaviors and occupational stress on the prediabetic state of male office workers, and identified related risks and influencing factors. The study used a cross-sectional design and performed an integrative analysis on data from regular health checkups, health questionnaires, and a health behavior-related survey of employees of a company, using Spearman’s correlation coefficients and multiple logistic regression analysis. The results showed significant relationships of prediabetic state with health behaviors and occupational stress. Among health behaviors, a diet without vegetables and fruits (Odds Ratio (OR) = 3.74, 95% Confidence Interval (CI) = 1.93⁻7.66) was associated with a high risk of prediabetic state. In the subscales on occupational stress, organizational system in the 4th quartile (OR = 4.83, 95% CI = 2.40⁻9.70) was significantly associated with an increased likelihood of prediabetic state. To identify influencing factors of prediabetic state, the multiple logistic regression was performed using regression models. The results showed that dietary habits (β = 1.20, p = 0.002), total occupational stress score (β = 1.33, p = 0.024), and organizational system (β = 1.13, p = 0.009) were significant influencing factors. The present findings indicate that active interventions are needed at workplace for the systematic and comprehensive management of health behaviors and occupational stress that influence prediabetic state of office workers.

  2. Oxidative Stress and Heart Failure in Altered Thyroid States

    Directory of Open Access Journals (Sweden)

    Pallavi Mishra

    2012-01-01

    Full Text Available Increased or reduced action of thyroid hormone on certain molecular pathways in the heart and vasculature causes relevant cardiovascular derangements. It is well established that hyperthyroidism induces a hyperdynamic cardiovascular state, which is associated with a faster heart rate, enhanced left ventricular systolic and diastolic function whereas hypothyroidism is characterized by the opposite changes. Hyperthyroidism and hypothyroidism represent opposite clinical conditions, albeit not mirror images. Recent experimental and clinical studies have suggested the involvement of ROS tissue damage under altered thyroid status. Altered-thyroid state-linked changes in heart modify their susceptibility to oxidants and the extent of the oxidative damage they suffer following oxidative challenge. Chronic increase in the cellular levels of ROS can lead to a catastrophic cycle of DNA damage, mitochondrial dysfunction, further ROS generation and cellular injury. Thus, these cellular events might play an important role in the development and progression of myocardial remodeling and heart failure in altered thyroid states (hypo- and hyper-thyroidism. The present review aims at elucidating the various signaling pathways mediated via ROS and their modulation under altered thyroid state and the possibility of antioxidant therapy.

  3. Computer modeling of the stress-strain state of welded construction

    Science.gov (United States)

    Nurguzhin, Marat; Danenova, Gulmira; Akhmetzhanov, Talgat

    2017-11-01

    At the present time the maintenance of the welded construction serviceability over normative service life is provided by the maintenance system on the basis of the guiding documents according to the concept of "fail safe". However, technology factors relating to welding such as high residual stresses and significant plastic strains are not considered in the guiding documents. The design procedure of the stressed-strained state of welded constructions is suggested in the paper. The procedure investigates welded constructions during welding and the external load using the program ANSYS. In this paper, the model of influence of the residual stress strain state on the factor of stress intensity is proposed. The calculation method of the residual stressed-strained state (SSS) taking into account the phase transition is developed by the authors. Melting and hardening of a plate material during heating and cooling is considered. The thermomechanical problem of heating a plate by a stationary heat source is solved. The setup of the heating spot center on distance (190 mm) from the crack top in a direction of its propagation leads to the fact that the value of total factor of stress intensity will considerably decrease under action of the specified residual compressing stresses. It can lower the speed of the crack propagation to zero. The suggested method of survivability maintenance can be applied during operation with the purpose of increasing the service life of metal constructions up to running repair of technological machines.

  4. Diagnostic Inspection of Pipelines for Estimating the State of Stress in Them

    Science.gov (United States)

    Subbotin, V. A.; Kolotilov, Yu. V.; Smirnova, V. Yu.; Ivashko, S. K.

    2017-12-01

    The diagnostic inspection used to estimate the technical state of a pipeline is described. The problems of inspection works are listed, and a functional-structural scheme is developed to estimate the state of stress in a pipeline. Final conclusions regarding the actual loading of a pipeline section are drawn upon a cross analysis of the entire information obtained during pipeline inspection.

  5. Occupational Stress and Management Strategies of Secondary School Principals in Cross River State, Nigeria

    Science.gov (United States)

    Anyanwu, Joy; Ezenwaji, Ifeyinwa; Okenjom, Godian; Enyi, Chinwe

    2015-01-01

    The study aimed at finding out sources and symptoms of occupational stress and management strategies of principals in secondary schools in Cross River State, Nigeria. Descriptive survey research design was adopted for the study with a population of 420 principals (304 males and 116 females) in secondary schools in Cross River State, Nigeria. Three…

  6. Rheological-dynamical continuum damage model for concrete under uniaxial compression and its experimental verification

    Directory of Open Access Journals (Sweden)

    Milašinović Dragan D.

    2015-01-01

    Full Text Available A new analytical model for the prediction of concrete response under uniaxial compression and its experimental verification is presented in this paper. The proposed approach, referred to as the rheological-dynamical continuum damage model, combines rheological-dynamical analogy and damage mechanics. Within the framework of this approach the key continuum parameters such as the creep coefficient, Poisson’s ratio and damage variable are functionally related. The critical values of the creep coefficient and damage variable under peak stress are used to describe the failure mode of the concrete cylinder. The ultimate strain is determined in the post-peak regime only, using the secant stress-strain relation from damage mechanics. The post-peak branch is used for the energy analysis. Experimental data for five concrete compositions were obtained during the examination presented herein. The principal difference between compressive failure and tensile fracture is that there is a residual stress in the specimens, which is a consequence of uniformly accelerated motion of load during the examination of compressive strength. The critical interpenetration displacements and crushing energy are obtained theoretically based on the concept of global failure analysis. [Projekat Ministarstva nauke Republike Srbije, br. ON 174027: Computational Mechanics in Structural Engineering i br. TR 36017: Utilization of by-products and recycled waste materials in concrete composites for sustainable construction development in Serbia: Investigation and environmental assessment of possible applications

  7. Effect of second to first normal stress difference ratio at the die exit on neck-in phenomenon in polymeric flat film production

    Science.gov (United States)

    Barborik, Tomas; Zatloukal, Martin

    2017-05-01

    In this study, viscoelastic modeling of the extrusion film casting process, based on the lD membrane model and modified Leonov constitutive equation, was conducted and the effect of the viscoelastic stress state at the die exit (captured here via second to first normal stress difference ratio) on the unwanted neck-in phenomenon has been analyzed for wide range of Deborah numbers and materials having different level of uniaxial and planar extensional strain hardening. Relevant experimental data for LDPE and theoretical predictions based on multimode eXtended Pom-Pom model acquired from the open literature were used for the validation purposes. It was found that firstly, the predicting capabilities of both constitutive equations for given material and processing conditions are comparable even if the single mode modified Leonov model was used and secondly, the agreement between theoretical and experimental data on neck-in is fairly good. Results of the theoretical study revealed that the viscoelastic stress state at the die exit (i.e. -N2/N1 ratio) increases the level of neck-in if uniaxial extensional strain hardening, planar to uniaxial extensional viscosity ratio and Deborah number increases. It has also been revealed that there exists threshold value for Deborah number and extensional strain hardening below which the neck-in becomes independent on the die exit stress state.

  8. Numerical evaluation of state boundary surface through rotation of principal stress axes in sand

    International Nuclear Information System (INIS)

    Sadrnejad, S. A.

    2001-01-01

    In applying shear stress to saturated soil with arbitrary stress paths, the prediction of the exact value of strains is difficult because of mainly its stress path dependent nature. Rotation of the principal stress axes during shearing of the soil is a feature of stress paths associated with many field loading situations. A proper understanding of the effects of principal stress rotation on soil behavior can be provided if the anisotropy existing prior to stress rotation and induced anisotropy due to plastic flow in soil are clearly understood and modeled. A multi laminate based model for soil is developed and used to compute and present the influence of rotation of principal stress axes on the plastic behavior of soil. This is fulfilled by distributing the effects of boundary condition changes into several predefined sampling orientations at one point and summing the micro-results up as the macro-result. The validity of the presented model examined by comparing numerical and test results showing the mentioned aspect. In this paper, the state boundary surface is numerically obtained by a multi laminate based model capable of predicting the behavior of sand under the influences of rotation of the direction of principal stress axes and induced anisotropy. the predicted numerical results are tally in agreement with experiments

  9. Experimental investigation of the strength and failure behavior of layered sandstone under uniaxial compression and Brazilian testing

    Science.gov (United States)

    Yin, Peng-Fei; Yang, Sheng-Qi

    2018-05-01

    As a typical inherently anisotropic rock, layered sandstones can differ from each other in several aspects, including grain size, type of material, type of cementation, and degree of compaction. An experimental study is essential to obtain and convictive evidence to characterize the mechanical behavior of such rock. In this paper, the mechanical behavior of a layered sandstone from Xuzhou, China, is investigated under uniaxial compression and Brazilian test conditions. The loading tests are conducted on 7 sets of bedding inclinations, which are defined as the angle between the bedding plane and horizontal direction. The uniaxial compression strength (UCS) and elastic modulus values show an undulatory variation when the bedding inclination increases. The overall trend of the UCS and elastic modulus values with bedding inclination is decreasing. The BTS value decreases with respect to the bedding inclination and the overall trend of it is approximating a linear variation. The 3D digital high-speed camera images reveal that the failure and fracture of a specimen are related to the surface deformation. Layered sandstone tested under uniaxial compression does not show a typical failure mode, although shear slip along the bedding plane occurs at high bedding inclinations. Strain gauge readings during the Brazilian tests indicate that the normal stress on the bedding plane transforms from compression to tension as the bedding inclination increases. The stress parallel to the bedding plane in a rock material transforms from tension to compression and agrees well with the fracture patterns; "central fractures" occur at bedding inclinations of 0°-75°, "layer activation" occurs at high bedding inclinations of 75°-90°, and a combination of the two occurs at 75°.

  10. Family Environments and Children's Executive Function: The Mediating Role of Children's Affective State and Stress.

    Science.gov (United States)

    He, Zhong-Hua; Yin, Wen-Gang

    2016-09-01

    There is increasing evidence that inadequate family environments (family material environment and family psychosocial environment) are not only social problems but also factors contributing to adverse neurocognitive outcomes. In the present study, the authors investigated the relationship among family environments, children's naturalistic affective state, self-reported stress, and executive functions in a sample of 157 Chinese families. These findings revealed that in inadequate family material environments, reduced children's cognitive flexibility is associated with increased naturalistic negative affectivity and self-reported stress. In addition, naturalistic negative affectivity mediated the association between family expressiveness and children's cognitive flexibility. The authors used a structural equation model to examine the mediation model hypothesis, and the results confirmed the mediating roles of naturalistic negative affectivity and self-reported stress between family environments and the cognitive flexibility of Chinese children. These findings indicate the importance of reducing stress and negative emotional state for improving cognitive functions in children of low socioeconomic status.

  11. Numerical Analysis of the Influence of Clearance on Stress State and Contact Pressure in Plain Bearings

    Directory of Open Access Journals (Sweden)

    Vasile Cojocaru

    2017-12-01

    Full Text Available In the analysis of plain bearings by finite element method it is important to model as closely to real state the aspects that influence the stress and contact pressure: the loading mode, the properties of the materials, the lubrication system, the clearance between the shaft and the bearing body, the evolution in time of clearance correlated with the wear, etc. In order to study the effect of the clearance on the stress state, a plain bearing with nominal diameter d=40 mm was modeled. The contact pressure and the equivalent stress were computed for six discrete values of clearance, range from c=0 to c=0.3 mm. It has been shown that the increase of clearance generates an increase of the equivalent stress and contact pressure. The growth rate is higher for contact pressure, due to the decrease of the contact surface between the shaft and the bearing body

  12. Influence of cold rolling and fatigue on the residual stress state of a metal matrix composite

    International Nuclear Information System (INIS)

    Hanus, E.; Ericsson, T.; Lu, J.; Decomps, F.

    1993-01-01

    The large difference in the coefficient of thermal expansion between the matrix alloy and the particle in a metal matrix composite gives rise to residual stresses in the material. In the present work the effect of cold rolling and four-point bending fatigue on the residual stress state of a silicon carbide particle reinforced aluminium alloy (AA 2014) has been investigated. The three dimensional stress state measured in both phases: matrix and reinforcement, has been determined by using an X-ray diffraction technique. It was found that cold rolling induces surface compressive macrostresses of about -250 MPa, with a penetration depth around 2 mm. The absolute values of the pseudomacrostresses in both phases are significantly reduced due to the single track rolling. Stress relaxation occurs during four-point bending fatigue. (orig.)

  13. The contribution of trait negative affect and stress to recall for bodily states.

    Science.gov (United States)

    Ma-Kellams, Christine; Lai, Lei; Taylor, Shelley E; Lerner, Jennifer S

    2016-12-01

    How does trait negative affect shape somatic memory of stressful events? We hypothesized that negative affect would impair accurate recall of one's own heart rate during stressful situations. Two bio-behavioral studies used a new paradigm to test retrospective visceral perception and assessed whether negative affective states experienced during aversive events (i.e., the Trier Stress Task-Time 1) would retrospectively shape recall of past heart rate (Time 2), even when accounting for actual heart rate at the time of each stressful event (Time 1). Results across both studies showed that individual differences in negative affect in response to a stressful task predicted visceral recollections, and those who experienced more negative affect were more inaccurate. Negative affect was associated with a tendency to remember visceral reactions as worse than they actually were. Copyright © 2016 Elsevier Inc. All rights reserved.

  14. Uniaxial in-plane magnetization of iron nanolayers grown within an amorphous matrix

    Energy Technology Data Exchange (ETDEWEB)

    Ghafari, M., E-mail: mohammad.ghafari@kit.edu; Hahn, H. [Herbert Gleiter Institute of Nanoscience, Nanjing University of Science and Technology, Nanjing 210094 (China); Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Mattheis, R. [Leibniz Institute for Photonic Technology IPHT, Jena (Germany); McCord, J. [Institute for Materials Science, Kiel University Kiel, Kaiserstraße 2, 24143 Kiel (Germany); Brand, R. A. [Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Macedo, W. A. A. [Laboratório de Física Aplicada, Centro de Desenvolvimento da Tecnologia Nuclear (CDTN), 31270-901 Belo Horizonte, MG (Brazil)

    2014-08-18

    Conversion electron Mössbauer spectroscopy is used to determine the magnetic ground state at zero magnetic field of four-monolayer thick amorphous iron layers as part of a CoFeB-Fe multilayer stack. By comparing the intensities of the magnetic hyperfine field, an easy in-plane axis of the amorphous embedded Fe layer is verified, which is collinear to the uniaxial anisotropy axis of the neighboring amorphous CoFeB. Despite the soft magnetic character of the Fe layers, external fields up to 4 T perpendicular to the film plane are insufficient to completely align the embedded Fe moments parallel to the magnetic field due to a local disorder of the magnetic moments of the Fe atoms.

  15. Uni-axial Elongational Viscosity of Linear and Branched polymer melts

    DEFF Research Database (Denmark)

    Hassager, Ole; Nielsen, Jens Kromann; Rasmussen, Henrik Koblitz

    2005-01-01

    About 40 years ago interest in the measurement of elongational viscosity of polymer melts started to grow. Here we present measurements of transient (and steady) uni-axial elongational viscosity, using the FSR, of the following melts: Four narrow MMD polystyrene (PS) samples with weight......-average molar mass Mw in the range of 50k to 390k. Three different bi-disperse samples, mixed from the narrow MMD PS. Two low-density polyethylene (LDPE) melts (Lupolen 1840D and 3020D). A steady-state viscosity was kept for 1-2.5 Hencky strain units in all measurements.The measurements on the bi-disperse PS...... melts have demonstrated that both the transient and steady elongational viscosity is quite sensitive to polydispersity. Bi-disperse PS resembles the behaviour of mono-disperse melts only at elongational rates larger then the inverse of maximal time constant of the smallest molecule. As observed in Boger...

  16. Stress-induced state transitions in flexible liquid-crystal devices

    International Nuclear Information System (INIS)

    Ho, I-Lin; Chang, Yia-Chung

    2012-01-01

    This work studies the stress-strain dynamics for the transient optoelectronic characteristics of flexible liquid-crystal (LC) devices. Due to the fast response of LC directors, the configuration of the LC is assumed to be in quasi-equilibrium during the process of elastic deformations of the flexible structures. The LC medium hence can be treated effectively as a thin-film layer and can approximately follow the strain-stress mechanism in the solids. Relevant theoretical algorithms are studied in this work, and numerical results present the stress-induced state transitions in the π cell.

  17. Stress state of main stop valve with 500 mm nominal diameter white thermomechanical loading

    International Nuclear Information System (INIS)

    Koklyuev, G.A.; Plotnikov, V.P.

    1987-01-01

    The method of finite elements was applied to calculate the stress-strain state of the main isolation valve case with 500 mm nominal diameter while thermomechanical loading. Maximum stress takes place in the zone of joining nozzles with a spherical case and it attains the value of 138 MPa at working pressure of 12.5 MPa. The stress level in the point of nozzle-case welding is essentially lower than in zones of stres concentration and when excluding water hitting the slot of the lack of fusion in the route of the weld the weld service life is attained during the calculated service life

  18. Residual stress state in pipe cut ring specimens for fracture toughness testing

    Energy Technology Data Exchange (ETDEWEB)

    Damjanovic, Darko [J.J. Strossmayer Univ. of Osijek, Slavonski Brod (Croatia). Mechanical Engineering Faculty; Kozak, Drazan [Zagreb Univ. (Croatia). Dept. for Mechanical Design; Marsoner, Stefan [Materials Center, Leoben (Austria).; Gubeljak, Nenad [Maribor Univ. (Slovenia). Chair of Mechanics

    2017-07-01

    Thin-walled pipes are not suitable for measuring fracture toughness parameters of vital importance because longitudinal crack failure is the most common failure mode in pipes. This is due to the impossibility to manufacture standard specimens for measuring fracture toughness, such as SENB or CT specimens, from the thin wall of the pipe. Previous works noticed this problem, but until now, a good and convenient solution has not been found or developed. To overcome this problem, very good alternative solution was proposed, the so-called pipe ring notched bend specimen (PRNB) [1-5]. Until now, only the idealized geometry PRNB specimen is analyzed, i. e., a specimen which is not cut out from an actual pipe but produced from steel plate. Based on that, residual stresses are neglected along with the imperfections in geometry (elliptical and eccentricity). The aim of this research is to estimate the residual stress state(s) in real pipes used in the boiler industry produced by hot rolling technique. These types of pipes are delivered only in normalized condition, but not stress relieved. Therefore, there are residual stresses present due to the manufacturing technique, but also due to uneven cooling after the production process. Within this paper, residual stresses are estimated by three methods: the incremental hole drilling method (IHMD), X-ray diffraction (XRD) and the splitting method (SM). Knowing the residual stress state in the ring specimen, it is possible to assess their impact on fracture toughness measured on the corresponding PRNB specimen(s).

  19. Residual stress state in pipe cut ring specimens for fracture toughness testing

    International Nuclear Information System (INIS)

    Damjanovic, Darko; Kozak, Drazan; Marsoner, Stefan; Gubeljak, Nenad

    2017-01-01

    Thin-walled pipes are not suitable for measuring fracture toughness parameters of vital importance because longitudinal crack failure is the most common failure mode in pipes. This is due to the impossibility to manufacture standard specimens for measuring fracture toughness, such as SENB or CT specimens, from the thin wall of the pipe. Previous works noticed this problem, but until now, a good and convenient solution has not been found or developed. To overcome this problem, very good alternative solution was proposed, the so-called pipe ring notched bend specimen (PRNB) [1-5]. Until now, only the idealized geometry PRNB specimen is analyzed, i. e., a specimen which is not cut out from an actual pipe but produced from steel plate. Based on that, residual stresses are neglected along with the imperfections in geometry (elliptical and eccentricity). The aim of this research is to estimate the residual stress state(s) in real pipes used in the boiler industry produced by hot rolling technique. These types of pipes are delivered only in normalized condition, but not stress relieved. Therefore, there are residual stresses present due to the manufacturing technique, but also due to uneven cooling after the production process. Within this paper, residual stresses are estimated by three methods: the incremental hole drilling method (IHMD), X-ray diffraction (XRD) and the splitting method (SM). Knowing the residual stress state in the ring specimen, it is possible to assess their impact on fracture toughness measured on the corresponding PRNB specimen(s).

  20. Interpretation of the Haestholmen in situ state of stress based on core damage observations

    International Nuclear Information System (INIS)

    Hakala, M.

    2000-01-01

    At the Haestholmen investigation site, direct in situ stress measurements, overcoring and hydraulic fracturing have been unsuccessful because of ring disking and horizontal hydraulic fracturing. Prior to this study, a detailed study on both core disking and ring disking was made, and based on those results an in situ state of stress interpretation method was developed. In this work this method is applied to the Haestholmen site. The interpretation is based on disk fracture type, spacing and shape. Also, the Hoek-Brown strength envelope and Poisson's ratio of intact rock are needed. The interpretation result is most reliable if both core disking and ring disking information at the same depth levels is available. A detailed core logging showed that ring disking is systematic below the -365 m level in the vertical overcoring stress measurement hole, HH-KR6. On the other hand, no representative core disking exists except for two points in two differently oriented subvertical boreholes HH-KR2 and HHKR7. Because the interpretation has to be based on ring disking only, upper and lower estimates for the vertical stress were set. These were gravitational and 67% of gravitational. Furthermore, the in situ stress state was assumed to be in horizontal and vertical planes, because the disking in vertical borehole HH-KR6 was not inclined. The interpretation resulted in a good estimate for the major horizontal stress but none of the horizontal stress rations ( 0.25, 0.5, 0.75 and 1.0 ) or vertical stress assumptions studied are clearly more probable the others. At the 500 m level the resulting maximum horizontal stress is 41 MPa. If a linear fit through the zero depth and zero stress point is applied, the maximum horizontal stress gradient is 0.0818 z MPa/m with a standard deviation between 5 and 12 per cent. The orientation of the major horizontal stress is 108 with standard deviation of 21 degrees. The interpreted major horizontal stress state also indicated that systematic

  1. Fatigue Behavior under Multiaxial Stress States Including Notch Effects and Variable Amplitude Loading

    Science.gov (United States)

    Gates, Nicholas R.

    The central objective of the research performed in this study was to be able to better understand and predict fatigue crack initiation and growth from stress concentrations subjected to complex service loading histories. As such, major areas of focus were related to the understanding and modeling of material deformation behavior, fatigue damage quantification, notch effects, cycle counting, damage accumulation, and crack growth behavior under multiaxial nominal loading conditions. To support the analytical work, a wide variety of deformation and fatigue tests were also performed using tubular and plate specimens made from 2024-T3 aluminum alloy, with and without the inclusion of a circular through-thickness hole. However, the analysis procedures implemented were meant to be general in nature, and applicable to a wide variety of materials and component geometries. As a result, experimental data from literature were also used, when appropriate, to supplement the findings of various analyses. Popular approaches currently used for multiaxial fatigue life analysis are based on the idea of computing an equivalent stress/strain quantity through the extension of static yield criteria. This equivalent stress/strain is then considered to be equal, in terms of fatigue damage, to a uniaxial loading of the same magnitude. However, it has often been shown, and was shown again in this study, that although equivalent stress- and strain-based analysis approaches may work well in certain situations, they lack a general robustness and offer little room for improvement. More advanced analysis techniques, on the other hand, provide an opportunity to more accurately account for various aspects of the fatigue failure process under both constant and variable amplitude loading conditions. As a result, such techniques were of primary interest in the investigations performed. By implementing more advanced life prediction methodologies, both the overall accuracy and the correlation of fatigue

  2. The study on stress-strain state of the spring at high temperature using ABAQUS

    Directory of Open Access Journals (Sweden)

    H Sun

    2014-01-01

    Full Text Available Cylindrical helical springs are widely used in the elements of thermal energy devices. It is necessary to guarantee the stability of the stress state of spring in high temperature. Relaxation phenomenon of stress is studied in this paper. Calculations are carried out in the environment of ABAQUS. The verification is taken out using analytical calculations.This paper describes the distribution and character of stress contour lines on the cross section of spring under the condition of instantaneous load, explicates the relaxation law with time. Research object is cylindrical helical spring, that working at high temperature. The purpose of this work is to get the stress relaxation law of spring, and to guarantee the long-term strength.This article presents the basic theory of helical spring. Establishes spring mathematical model of creep under the loads of compression and torsion. The stress formulas of each component in the cross section of spring are given. The calculation process of relaxation is analyzed in the program ABAQUS.In this paper compare the analytical formulas of spring stress with the simulation results, which are created by program ABAQUS.Finite element model for stress creep analysis in the cross section is created, material of spring – stainless steel 10X18N9T, springs are used at the temperature 650℃.At the beginning, stress-stain of spring is in the elastic state. Analyzes the change law of creep stress under the condition of constant load and a fixed compression.When analyzing under the condition of a fixed compression, the stresses are quickly decreased in most area in the cross section of spring, and the point of minimum shear stress gradually moves to the direction of outer diameter, because of this, stresses in a small area near the center increase slowly at first then decrease gradually with time. When analyzing under the condition of constant load, the stresses are quickly decreased in the around area and in creased

  3. Mindfulness meditation training alters stress-related amygdala resting state functional connectivity: a randomized controlled trial.

    Science.gov (United States)

    Taren, Adrienne A; Gianaros, Peter J; Greco, Carol M; Lindsay, Emily K; Fairgrieve, April; Brown, Kirk Warren; Rosen, Rhonda K; Ferris, Jennifer L; Julson, Erica; Marsland, Anna L; Bursley, James K; Ramsburg, Jared; Creswell, J David

    2015-12-01

    Recent studies indicate that mindfulness meditation training interventions reduce stress and improve stress-related health outcomes, but the neural pathways for these effects are unknown. The present research evaluates whether mindfulness meditation training alters resting state functional connectivity (rsFC) of the amygdala, a region known to coordinate stress processing and physiological stress responses. We show in an initial discovery study that higher perceived stress over the past month is associated with greater bilateral amygdala-subgenual anterior cingulate cortex (sgACC) rsFC in a sample of community adults (n = 130). A follow-up, single-blind randomized controlled trial shows that a 3-day intensive mindfulness meditation training intervention (relative to a well-matched 3-day relaxation training intervention without a mindfulness component) reduced right amygdala-sgACC rsFC in a sample of stressed unemployed community adults (n = 35). Although stress may increase amygdala-sgACC rsFC, brief training in mindfulness meditation could reverse these effects. This work provides an initial indication that mindfulness meditation training promotes functional neuroplastic changes, suggesting an amygdala-sgACC pathway for stress reduction effects. © The Author (2015). Published by Oxford University Press. For Permissions, please email: journals.permissions@oup.com.

  4. Uniaxial creep as a control on mercury intrusion capillary pressure in consolidating rock salt

    Energy Technology Data Exchange (ETDEWEB)

    Dewers, Thomas [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Heath, Jason E. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Leigh, Christi D. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)

    2015-09-01

    The nature of geologic disposal of nuclear waste in salt formations requires validated and verified two - phase flow models of transport of brine and gas through intact, damaged, and consolidating crushed salt. Such models exist in oth er realms of subsurface engineering for other lithologic classes (oil and gas, carbon sequestration etc. for clastics and carbonates) but have never been experimentally validated and parameterized for salt repository scenarios or performance assessment. Mo dels for waste release scenarios in salt back - fill require phenomenological expressions for capillary pressure and relative permeability that are expected to change with degree of consolidation, and require experimental measurement to parameterize and vali date. This report describes a preliminary assessment of the influence of consolidation (i.e. volume strain or porosity) on capillary entry pressure in two phase systems using mercury injection capillary pressure (MICP). This is to both determine the potent ial usefulness of the mercury intrusion porosimetry method, but also to enable a better experimental design for these tests. Salt consolidation experiments are performed using novel titanium oedometers, or uniaxial compression cells often used in soil mech anics, using sieved run - of - mine salt from the Waste Isolation Pilot Plant (WIPP) as starting material. Twelve tests are performed with various starting amounts of brine pore saturation, with axial stresses up to 6.2 MPa (%7E900 psi) and temperatures to 90 o C. This corresponds to UFD Work Package 15SN08180211 milestone "FY:15 Transport Properties of Run - of - Mine Salt Backfill - Unconsolidated to Consolidated". Samples exposed to uniaxial compression undergo time - dependent consolidation, or creep, to various deg rees. Creep volume strain - time relations obey simple log - time behavior through the range of porosities (%7E50 to 2% as measured); creep strain rate increases with temperature and applied stress as

  5. Off-state stress and pulse response investigation of InAl/Ga HFET

    International Nuclear Information System (INIS)

    Florovic, M.; Hronec, P.; Kovac, J.; Skriniarova, J.; Donoval, D.; Kordos, P.

    2011-01-01

    In this study In 0.18 Al 0.82 N/GaN HFETs were off-state tested under high drain bias, I-V characteristics were measured using standard DC voltage source (drain-source, gate-source). Subsequently drain current responses on pulse gate-source voltage for various drain-source voltages were recorded and analysed. Static performance of InAlN/GaN HFETs with AlN buffer layer prepared at different conditions were analysed before, during and after the off-state stress. The static output I-V characteristics show the maximum drain current I d ≅ 0,44 A/mm for V gs = 6 V, the device has pinch-off at V gs - 4.4 V. The drain and gate currents of the InAlN/GaN HFET were measured continuously during the off-state stress (V ds = 30 V, V gs = -4.4 V), a partial increase of the drain/gate current was observed after this interruption, which indicates on some recovery effect. The devices were characterised in details after the total stress time of 60 min., as well as after 30 min without the stress, the output I-V characteristic show permanent off-state stress degradation. This effect will be studied in details in the next. (authors)

  6. The influence of normal fault on initial state of stress in rock mass

    Directory of Open Access Journals (Sweden)

    Tajduś Antoni

    2016-03-01

    Full Text Available Determination of original state of stress in rock mass is a very difficult task for rock mechanics. Yet, original state of stress in rock mass has fundamental influence on secondary state of stress, which occurs in the vicinity of mining headings. This, in turn, is the cause of the occurrence of a number of mining hazards, i.e., seismic events, rock bursts, gas and rock outbursts, falls of roof. From experience, it is known that original state of stress depends a lot on tectonic disturbances, i.e., faults and folds. In the area of faults, a great number of seismic events occur, often of high energies. These seismic events, in many cases, are the cause of rock bursts and damage to the constructions located inside the rock mass and on the surface of the ground. To estimate the influence of fault existence on the disturbance of original state of stress in rock mass, numerical calculations were done by means of Finite Element Method. In the calculations, it was tried to determine the influence of different factors on state of stress, which occurs in the vicinity of a normal fault, i.e., the influence of normal fault inclination, deformability of rock mass, values of friction coefficient on the fault contact. Critical value of friction coefficient was also determined, when mutual dislocation of rock mass part separated by a fault is impossible. The obtained results enabled formulation of a number of conclusions, which are important in the context of seismic events and rock bursts in the area of faults.

  7. The influence of normal fault on initial state of stress in rock mass

    Science.gov (United States)

    Tajduś, Antoni; Cała, Marek; Tajduś, Krzysztof

    2016-03-01

    Determination of original state of stress in rock mass is a very difficult task for rock mechanics. Yet, original state of stress in rock mass has fundamental influence on secondary state of stress, which occurs in the vicinity of mining headings. This, in turn, is the cause of the occurrence of a number of mining hazards, i.e., seismic events, rock bursts, gas and rock outbursts, falls of roof. From experience, it is known that original state of stress depends a lot on tectonic disturbances, i.e., faults and folds. In the area of faults, a great number of seismic events occur, often of high energies. These seismic events, in many cases, are the cause of rock bursts and damage to the constructions located inside the rock mass and on the surface of the ground. To estimate the influence of fault existence on the disturbance of original state of stress in rock mass, numerical calculations were done by means of Finite Element Method. In the calculations, it was tried to determine the influence of different factors on state of stress, which occurs in the vicinity of a normal fault, i.e., the influence of normal fault inclination, deformability of rock mass, values of friction coefficient on the fault contact. Critical value of friction coefficient was also determined, when mutual dislocation of rock mass part separated by a fault is impossible. The obtained results enabled formulation of a number of conclusions, which are important in the context of seismic events and rock bursts in the area of faults.

  8. Software for determining the direction of movement, shear and normal stresses of a fault under a determined stress state

    Science.gov (United States)

    Álvarez del Castillo, Alejandra; Alaniz-Álvarez, Susana Alicia; Nieto-Samaniego, Angel Francisco; Xu, Shunshan; Ochoa-González, Gil Humberto; Velasquillo-Martínez, Luis Germán

    2017-07-01

    In the oil, gas and geothermal industry, the extraction or the input of fluids induces changes in the stress field of the reservoir, if the in-situ stress state of a fault plane is sufficiently disturbed, a fault may slip and can trigger fluid leakage or the reservoir might fracture and become damaged. The goal of the SSLIPO 1.0 software is to obtain data that can reduce the risk of affecting the stability of wellbores. The input data are the magnitudes of the three principal stresses and their orientation in geographic coordinates. The output data are the slip direction of a fracture in geographic coordinates, and its normal (σn) and shear (τ) stresses resolved on a single or multiple fracture planes. With this information, it is possible to calculate the slip tendency (τ/σn) and the propensity to open a fracture that is inversely proportional to σn. This software could analyze any compressional stress system, even non-Andersonian. An example is given from an oilfield in southern Mexico, in a region that contains fractures formed in three events of deformation. In the example SSLIPO 1.0 was used to determine in which deformation event the oil migrated. SSLIPO 1.0 is an open code application developed in MATLAB. The URL to obtain the source code and to download SSLIPO 1.0 are: http://www.geociencias.unam.mx/ alaniz/main_code.txt, http://www.geociencias.unam.mx/ alaniz/ SSLIPO_pkg.exe.

  9. Metallographic examinations of Type 304 stainless steel (heat 9T2796) tested in high-temperature uniaxial and multiaxial experiments

    Energy Technology Data Exchange (ETDEWEB)

    Swindeman, R.W.; Houck, C.W.

    1984-03-01

    The results obtained from a number of metallographic examinations of Type 304 stainless steel specimens were compiled. Samples were obtained from uniaxial and multiaxial tests covering a very broad span of temperatures and times. Special emphasis was on the identification of failure modes, cracking patterns, grain distortion, and grain-boundary microstructures. Uniaxial specimens exhibited the following sequence of failure modes with increasing temperature and time: ductile plastic tearing, ductile plastic shear, wedge cracking, and microvoid cracking. Over most of the temperature range examined (482 to 871/sup 0/C), M/sub 23/C/sub 6/ precipitated on grain boundaries at long times. Sigma phase and possibly ferrite were often present in the stressed areas at temperatures as low as 482/sup 0/C (900/sup 0/F). These metallurgical features promoted a severe loss in creep ductility at long times and low temperatures. Most multiaxial tests were performed under conditions that promoted wedge cracking. Stress gradients also favored surface crack initiation rather than bulk damage. Testing times for multiaxial tests were less than 10,000 h; hence, there was insufficient time for the development of embrittling features such as microvoids, sigma, and ferrite. Long-time multiaxial tests to failure are recommended.

  10. Influence of fatigue crack wake length and state of stress on crack closure

    Science.gov (United States)

    Telesman, Jack; Fisher, Douglas M.

    1988-01-01

    The location of crack closure with respect to crack wake and specimen thickness under different loading conditions was determined. The rate of increase of K sub CL in the crack wake was found to be significantly higher for plasticity induced closure in comparison to roughness induced closure. Roughness induced closure was uniform throughout the thickness of the specimen while plasticity induced closure levels were 50 percent higher in the near surface region than in the midthickness. The influence of state of stress on low-high load interaction effects was also examined. Load interaction effects differed depending upon the state of stress and were explained in terms of delta K sub eff.

  11. Structure of vortices in superfluid 3He A-like phase in uniaxially stretched aerogel

    International Nuclear Information System (INIS)

    Aoyama, Kazushi; Ikeda, Ryusuke

    2009-01-01

    Possible vortex-core transitions in A-like phase of superfluid 3 He in uniaxially stretched aerogel are investigated. Since the global anisotropy in this system induces the polar pairing state in a narrow range close to the superfluid transition in addition to the A-like and B-like phases, the polar state may occur in the core of a vortex in the A-like phase identified with the ABM pairing state, like in the case of the bulk B phase where a core including the ABM state is realized at higher pressures. We examine the core structure of a single vortex under the boundary condition compatible with the Mermin-Ho vortex in the presence of the dipole interaction. Following Salomaa and Volovik's approach, we numerically solve the Ginzburg-Landau equation for an axially symmetric vortex and, by examining its stability against nonaxisymmetric perturbations, discuss possible vortex core states. It is found that a first order transition on core states may occur on warming from an axisymmetric vortex with a nonunitary core to a singular vortex with the polar core.

  12. Structure of vortices in superfluid 3He A-like phase in uniaxially stretched aerogel

    Science.gov (United States)

    Aoyama, Kazushi; Ikeda, Ryusuke

    2009-02-01

    Possible vortex-core transitions in A-like phase of superfluid 3He in uniaxially stretched aerogel are investigated. Since the global anisotropy in this system induces the polar pairing state in a narrow range close to the superfluid transition in addition to the A-like and B-like phases, the polar state may occur in the core of a vortex in the A-like phase identified with the ABM pairing state, like in the case of the bulk B phase where a core including the ABM state is realized at higher pressures. We examine the core structure of a single vortex under the boundary condition compatible with the Mermin-Ho vortex in the presence of the dipole interaction. Following Salomaa and Volovik's approach, we numerically solve the Ginzburg-Landau equation for an axially symmetric vortex and, by examining its stability against nonaxisymmetric perturbations, discuss possible vortex core states. It is found that a first order transition on core states may occur on warming from an axisymmetric vortex with a nonunitary core to a singular vortex with the polar core.

  13. Fabrication and morphology of uniaxially aligned perylenediimide nanowires

    Science.gov (United States)

    Machida, Shinjiro; Tanikatsu, Makoto; Itaya, Akira; Ikeda, Noriaki

    2017-06-01

    Uniaxial alignment of crystalline nanowires consisting of N,N‧-dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C8) was achieved on poly(tetrafluoroethylene) (PTFE) layers prepared by friction transfer method on a glass substrate. The nanowires were formed by spin-coating a trifluoroacetic acid (TFA) solution of PTCDI-C8 on the PTFE layers and were further grown under TFA vapor atmosphere. The morphology of the PTCDI-C8 nanowires were characterized using atomic force microscope (AFM) and fluorescence optical microscope with changing the dye concentration in the spin coating solution, annealing time in the TFA vapor, and substrate materials. The nanowires prepared on the PTFE layer on a silica-coated silicon or a mica substrate did not grow so well as those on the glass substrate. This result suggests that the surface roughness would affect the PTFE layer and the growth of the PTCDI nanowires.

  14. Mechanical response of human female breast skin under uniaxial stretching.

    Science.gov (United States)

    Kumaraswamy, N; Khatam, Hamed; Reece, Gregory P; Fingeret, Michelle C; Markey, Mia K; Ravi-Chandar, Krishnaswamy

    2017-10-01

    Skin is a complex material covering the entire surface of the human body. Studying the mechanical properties of skin to calibrate a constitutive model is of great importance to many applications such as plastic or cosmetic surgery and treatment of skin-based diseases like decubitus ulcers. The main objective of the present study was to identify and calibrate an appropriate material constitutive model for skin and establish certain universal properties that are independent of patient-specific variability. We performed uniaxial tests performed on breast skin specimens freshly harvested during mastectomy. Two different constitutive models - one phenomenological and another microstructurally inspired - were used to interpret the mechanical responses observed in the experiments. Remarkably, we found that the model parameters that characterize dependence on previous maximum stretch (or preconditioning) exhibited specimen-independent universal behavior. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Uniaxially aligned ceramic nanofibers obtained by chemical mechanical processing

    Energy Technology Data Exchange (ETDEWEB)

    Tararam, R. [Univ Estadual Paulista – UNESP – Instituto de Química, Rua Prof. Francisco Degni n° 55, CEP 14800-900 Araraquara, SP (Brazil); Foschini, C.R. [Univ Estadual Paulista – UNESP – Faculdade de Engenharia de Bauru, Dept. de Eng. Mecanica, Av. Eng. Luiz Edmundo C. Coube 14-01, CEP 17033-360 Bauru, SP (Brazil); Destro, F.B. [Univ Estadual Paulista – UNESP – Faculdade de Engenharia de Guaratinguetá, Guaratinguetá 12516-410, SP (Brazil); Simões, A.Z., E-mail: alezipo@yahoo.com [Univ Estadual Paulista – UNESP – Faculdade de Engenharia de Guaratinguetá, Guaratinguetá 12516-410, SP (Brazil); Longo, E.; Varela, J.A. [Univ Estadual Paulista – UNESP – Instituto de Química, Rua Prof. Francisco Degni n° 55, CEP 14800-900 Araraquara, SP (Brazil)

    2014-08-01

    For this study, we investigated a simple method to generate well aligned nanofibers over large areas using an organic polymer stretched over the substrate surface With this method, ZnO and CuO 3D parallel nanowire arrays were successfully prepared by calcinations of the polymer fibers. X-ray diffraction (XRD) analysis revealed that the copper oxide has a monoclinic structure while the zinc oxide has a hexagonal structure. Scanning electron microscopy (SEM) analysis showed ceramic nanofibers with an average diameter of 120 nm which were composed of small nanoparticles which are 10 nm in diameter. The ability to obtain uniaxially aligned nanofibers reveals a range of interesting properties with potential applications for sensors, catalysts and energy technologies.

  16. Mechanical properties of graphene nanoribbons under uniaxial tensile strain

    Science.gov (United States)

    Yoneyama, Kazufumi; Yamanaka, Ayaka; Okada, Susumu

    2018-03-01

    Based on the density functional theory with the generalized gradient approximation, we investigated the mechanical properties of graphene nanoribbons in terms of their edge shape under a uniaxial tensile strain. The nanoribbons with armchair and zigzag edges retain their structure under a large tensile strain, while the nanoribbons with chiral edges are fragile against the tensile strain compared with those with armchair and zigzag edges. The fracture started at the cove region, which corresponds to the border between the zigzag and armchair edges for the nanoribbons with chiral edges. For the nanoribbons with armchair edges, the fracture started at one of the cove regions at the edges. In contrast, the fracture started at the inner region of the nanoribbons with zigzag edges. The bond elongation under the tensile strain depends on the mutual arrangement of covalent bonds with respect to the strain direction.

  17. Dynamic hysteresis of a uniaxial superparamagnet: Semi-adiabatic approximation

    International Nuclear Information System (INIS)

    Poperechny, I.S.; Raikher, Yu.L.; Stepanov, V.I.

    2014-01-01

    The semi-adiabatic theory of magnetic response of a uniaxial single-domain ferromagnetic particle is presented. The approach is developed in the context of the kinetic theory and allows for any orientation of the external field. Within this approximation, the dynamic magnetic hysteresis loops in an ac field are calculated. It is demonstrated that they very closely resemble those obtained by the full kinetic theory. The behavior of the effective coercive force is analyzed in detail, and for it a simple formula is proposed. This relation accounts not only for the temperature behavior of the coercive force, as the previous ones do, but also yields the dependence on the frequency and amplitude of the applied field

  18. Uniaxial Compressive Strengths of Rocks Drilled at Gale Crater, Mars

    Science.gov (United States)

    Peters, G. H.; Carey, E. M.; Anderson, R. C.; Abbey, W. J.; Kinnett, R.; Watkins, J. A.; Schemel, M.; Lashore, M. O.; Chasek, M. D.; Green, W.; Beegle, L. W.; Vasavada, A. R.

    2018-01-01

    Measuring the physical properties of geological materials is important for understanding geologic history. Yet there has never been an instrument with the purpose of measuring mechanical properties of rocks sent to another planet. The Mars Science Laboratory (MSL) rover employs the Powder Acquisition Drill System (PADS), which provides direct mechanical interaction with Martian outcrops. While the objective of the drill system is not to make scientific measurements, the drill's performance is directly influenced by the mechanical properties of the rocks it drills into. We have developed a methodology that uses the drill to indicate the uniaxial compressive strengths of rocks through comparison with performance of an identically assembled drill system in terrestrial samples of comparable sedimentary class. During this investigation, we utilize engineering data collected on Mars to calculate the percussive energy needed to maintain a prescribed rate of penetration and correlate that to rock strength.

  19. Multi-cracking in uniaxial and biaxial fatigue of 304L stainless steel

    International Nuclear Information System (INIS)

    Rupil, J.

    2012-01-01

    When a mechanical part is subjected to a repeated mechanical stress, it may be damaged after a number of cycles by several cracks initiation and propagation of a main crack. This is the phenomenon of fatigue damage. The thesis deals specifically with possible damage to some components of nuclear plants due to thermal fatigue. Unlike conventional mechanical fatigue damage where a main crack breaks the part, the thermal fatigue damage usually results in the appearance of a surface crack network. Two aspects are discussed in the thesis. The first is the experimental study of fatigue multiple cracking stage also called multi-cracking. Two mechanical test campaigns with multi-cracking detection by digital image correlation were conducted. These campaigns involve uniaxial and equi-biaxial mechanical loads in tension/compression without mean stress. This work allows to monitor and to observe the evolution of different networks of cracks through mechanical solicitations. The second is the numerical simulation of the phenomenon of fatigue damage. Several types of model are used (stochastic, probabilistic, cohesive finite elements). The experimental results have led to identify a multiple crack initiation law in fatigue which is faced with the numerical results. This comparison shows the relevance of the use of an analytical probabilistic model to find statistical results on the density of cracks that can be initiated with thermal and mechanical fatigue loadings. (author) [fr

  20. Nonparaxial propagation of Lorentz-Gauss beams in uniaxial crystal orthogonal to the optical axis.

    Science.gov (United States)

    Wang, Xun; Liu, Zhirong; Zhao, Daomu

    2014-04-01

    Analytical expressions for the three components of nonparaxial propagation of a polarized Lorentz-Gauss beam in uniaxial crystal orthogonal to the optical axis are derived and used to investigate its propagation properties in uniaxial crystal. The influences of the initial beam parameters and the parameters of the uniaxial crystal on the evolution of the beam-intensity distribution in the uniaxial crystal are examined in detail. Results show that the statistical properties of a nonparaxial Lorentz-Gauss beam in a uniaxial crystal orthogonal to the optical axis are closely determined by the initial beam's parameters and the parameters of the crystal: the beam waist sizes-w(0), w(0x), and w(0y)-not only affect the size and shape of the beam profile in uniaxial crystal but also determine the nonparaxial effect of a Lorentz-Gauss beam; the beam profile of a Lorentz-Gauss beam in uniaxial crystal is elongated in the x or y direction, which is determined by the ratio of the extraordinary refractive index to the ordinary refractive index; with increasing deviation of the ratio from unity, the extension of the beam profile augments. The results indicate that uniaxial crystal provides an effective and convenient method for modulating the Lorentz-Gauss beams. Our results may be valuable in some fields, such as optical trapping and nonlinear optics, where a light beam with a special profile and polarization is required.

  1. On the identifiability of the Hill-1948 model with one uniaxial tensile test

    Science.gov (United States)

    Bertin, Morgan; Hild, François; Roux, Stéphane

    2017-06-01

    A uniaxial experiment is performed on an ultra-thin specimen made of 17-7 precipitation hardened stainless steel. An anti-wrinkling setup allows for the characterization of the mechanical behavior with Integrated Digital Image Correlation (IDIC). The result shows that a single uniaxial experiment investigated via IDIC possesses enough data (and even more) to characterize a complete anisotropic elastoplastic model.

  2. Effect of surface stress state on dissolution property of Alloy 690 in simulated primary water condition

    International Nuclear Information System (INIS)

    Kim, Kyung Mo; Shim, Hee-Sang; Lee, Eun Hee; Seo, Myung Ji; Han, Jung Ho; Hur, Do Haeng

    2014-01-01

    The dissolution control of nickel is important to reduce the radioactive dose rate and deterioration of fuel performance in the operation of nuclear power plants (PWR). The corrosion properties are affected by the metal surface residual stress introduced in manufacture process such as work hardening. This work studied the effect of surface modification on the release rate of Alloy 690, nickel-base alloy for a steam generator tube, in the test condition of simulated primary water chemistry in PWRs. The surface stress modification was applied by the electro-polishing and shot peening method. Shot peening process was applied using ceramic beads with different intensities through the variation of air pressure. The corrosion release tests performed at 330degC with LiOH 2 ppm and H 3 BO 4 1200 ppm, DH(dissolved hydrogen) 35 cc/kg (STP) and about 20 ppb of DO(dissolved oxygen) condition. The corrosion release rate was evaluated by a gravimetric analysis method and the surface analysed by SEM and optical microscope. The surface residual stress was measured by an X-ray diffractometer, and the distribution of stress state was evaluated by a micro-hardness tester. The metal ion release rate of alloy 690 was evaluated from the influence of the stress state on the metal surface. The oxide property and structure was affected by the residual stress in the oxide layer. (author)

  3. Practical application of fracture mechanics with consideration of multiaxiality of stress state to degraded nuclear piping

    International Nuclear Information System (INIS)

    Kussmaul, K.; Blind, D.; Herter, K.H.; Eisele, U.; Schuler, X.

    1995-01-01

    Within the scope of a research project nuclear piping components (T-branches and elbows) with dimensions like the primary coolant lines of PWR plants were investigated. In addition to the experimental full scale tests, extensive numerical calculations by means of the finite element method (FEM) as well as fracture mechanics analyses were performed. The applicability of these methods was verified by comparison with the experimental results. The calculation of fracture mechanics parameters as well as the calculated component stress enabled a statement on crack initiation. The failure behavior could be evaluated by means of the multiaxiality of stress state in the ligament (gradient of the quotient of the multiaxiality of stress state q). With respect to practical application on other pressurized components it is shown how to use the procedure (e.g. in a LBB analysis). A quantitative assessment with regard to crack initiation is possible by comparison of the effective crack initiation value J ieff with the calculated component stress. If the multiaxiality of stress state and the q gradient in the ligament of the fracture ligament of the fracture mechanics specimen and the pressurized component to be evaluated is comparable a quantitative assessment is possible as for crack extension and maximum load. If there is no comparability of the gradients a qualitative assessment is possible for the failure behavior

  4. Modeling of the stress-strain state of the ground mass contaminated with peracetic acid

    Directory of Open Access Journals (Sweden)

    Levenko Anna

    2017-01-01

    Full Text Available None of the methods described previously provides a solution to the problem that deals with the SSS evaluation of the ground mass which is under the influence of chemically active substances and, in particular, under the influence of peracetic acid. The stress-strain state of the ground mass contaminated with peracetic acid was estimated. Stresses occurring in the ground mass in the natural state were determined after the entry of acid into it and after the chemical fixation of it with sodium silicate. All the parameters of the stress-strain state of the ground mass were obtained under a number of physical and mechanical conditions. It was determined that following the work on the silicatization of the ground mass contaminated with peracetic acid the quantity of strain decreased by 26.11 to 48.9%. The comparison of the results of stress calculations indicates the stress reduction in the ground mass in 1.8 – 2.6 times after its fixing.

  5. The study of stress-strain state of stabilized layered soil foundations

    Directory of Open Access Journals (Sweden)

    Sokolov Mikhail V.

    2017-01-01

    Full Text Available Herein presented are the results of modeling and analysis of stress-strain state of layered inhomogeneous foundation soil when it is stabilised by injection to different depths. Produced qualitative and quantitative analysis of the components of the field of isolines of stresses, strains, stress concentration and the difference between the strain at the boundary of different elastic horizontal layers. Recommendations are given for the location of stabilised zones in relation to the border of different elastic layers. In particular, it found that stabilization of soil within the weak layer is inappropriate, since it practically provides no increase in the stability of the soil foundation, and when performing stabilisation of soil foundations, it is recommended to place the lower border of the stabilisation zone below the border of a stronger layer, at this the distribution of stresses and strains occurs more evenly, and load-bearing capacity of this layer is used to the maximum.

  6. Steady thermal stress and strain rates in a rotating circular cylinder under steady state temperature

    Directory of Open Access Journals (Sweden)

    Pankaj Thakur

    2014-01-01

    Full Text Available Thermal stress and strain rates in a thick walled rotating cylinder under steady state temperature has been derived by using Seth’s transition theory. For elastic-plastic stage, it is seen that with the increase of temperature, the cylinder having smaller radii ratios requires lesser angular velocity to become fully plastic as compared to cylinder having higher radii ratios The circumferential stress becomes larger and larger with the increase in temperature. With increase in thickness ratio stresses must be decrease. For the creep stage, it is seen that circumferential stresses for incompressible materials maximum at the internal surface as compared to compressible material, which increase with the increase in temperature and measure n.

  7. Finite element modelling of creep process - steady state stresses and strains

    Directory of Open Access Journals (Sweden)

    Sedmak Aleksandar S.

    2014-01-01

    Full Text Available Finite element modelling of steady state creep process has been described. Using an analogy of visco-plastic problem with a described procedure, the finite element method has been used to calculate steady state stresses and strains in 2D problems. An example of application of such a procedure have been presented, using real life problem - cylindrical pipe with longitudinal crack at high temperature, under internal pressure, and estimating its residual life, based on the C*integral evaluation.

  8. Water stress and social vulnerability in the southern United States, 2010-2040

    Science.gov (United States)

    cassandra Johnson-Gaither; John Schelhas; Wayne Zipperer; Ge Sun; Peter V. Caldwell; Neelam Poudyal

    2014-01-01

    Water scarcities are striking in semiarid, subregions of the Southern United States such as Oklahoma and western Texas (Glennon 2009, Sabo et al. 2010). In Texas, water stress has been a constant concern since the 1950s when the state experienced severe drought conditions (Moore 2005). The nearly 2000-mile Rio Grande River, which forms part of the Texas–Mexico border,...

  9. A review of creep analysis and design under multi-axial stress states

    International Nuclear Information System (INIS)

    Yao, H.-T.; Xuan Fuzhen; Wang Zhengdong; Tu Shantung

    2007-01-01

    The existence of multi-axial states of stress cannot be avoided in elevated temperature components. It is essential to understand the associated failure mechanisms and to predict the lifetime in practice. Although metal creep has been studied for about 100 years, many problems are still unsolved, in particular for those involving multi-axial stresses. In this work, a state-of-the-art review of creep analysis and engineering design is carried out, with particular emphasis on the effect of multi-axial stresses. The existing theories and creep design approaches are grouped into three categories, i.e., the classical plastic theory (CPT) based approach, the cavity growth mechanism (CGM) based approach and the continuum damage mechanics (CDM) based approach. Following above arrangements, the constitutive equations and design criteria are addressed. In the end, challenges on the precise description of the multi-axial creep behavior and then improving the strength criteria in engineering design are presented

  10. An Experimental and Numerical Study on Cracking Behavior of Brittle Sandstone Containing Two Non-coplanar Fissures Under Uniaxial Compression

    Science.gov (United States)

    Yang, Sheng-Qi; Tian, Wen-Ling; Huang, Yan-Hua; Ranjith, P. G.; Ju, Yang

    2016-04-01

    To understand the fracture mechanism in all kinds of rock engineering, it is important to investigate the fracture evolution behavior of pre-fissured rock. In this research, we conducted uniaxial compression experiments to evaluate the influence of ligament angle on the strength, deformability, and fracture coalescence behavior of rectangular prismatic specimens (80 × 160 × 30 mm) of brittle sandstone containing two non-coplanar fissures. The experimental results show that the peak strength of sandstone containing two non-coplanar fissures depends on the ligament angle, but the elastic modulus is not closely related to the ligament angle. With the increase of ligament angle, the peak strength decreased at a ligament angle of 60°, before increasing up to our maximum ligament angle of 120°. Crack initiation, propagation, and coalescence were all observed and characterized from the inner and outer tips of pre-existing non-coplanar fissures using photographic monitoring. Based on the results, the sequence of crack evolution in sandstone containing two non-coplanar fissures was analyzed in detail. In order to fully understand the crack evolution mechanism of brittle sandstone, numerical simulations using PFC2D were performed for specimens containing two non-coplanar fissures under uniaxial compression. The results are in good agreement with the experimental results. By analyzing the stress field, the crack evolution mechanism in brittle sandstone containing two non-coplanar fissures under uniaxial compression is revealed. These experimental and numerical results are expected to improve the understanding of the unstable fracture mechanism of fissured rock engineering structures.

  11. The study of the stress - strain state of the tank with bottom water drainage during operation

    Science.gov (United States)

    Shchipkova, Yu V.; Tokarev, V. V.

    2018-04-01

    Bottom drainage from tank is a current problem in modern tank usage. This article proposes the use of the bottom drainage system from the tank with the shape of the sloped cone to the centre of it. Changing the bottom design alters the stress - strain state to be analyzed in the Ansys. The analysis concluded that the proposed drainage system should be applied.

  12. Perceived Sources of Occupational Stress among Primary School Teachers in Delta State of Nigeria

    Science.gov (United States)

    Akpochafo, G. O.

    2012-01-01

    This study investigated the most prevalent sources of occupational stress and also the demographic variables of gender, age and length of service among primary school teachers in Delta State. Two research questions and three hypotheses guided the study. The study used a descriptive survey design. The population was the primary school teachers in…

  13. Sectoral contributions to surface water stress in the coterminous United States

    International Nuclear Information System (INIS)

    Averyt, K; Meldrum, J; Caldwell, P; Sun, G; McNulty, S; Huber-Lee, A; Madden, N

    2013-01-01

    Here, we assess current stress in the freshwater system based on the best available data in order to understand possible risks and vulnerabilities to regional water resources and the sectors dependent on freshwater. We present watershed-scale measures of surface water supply stress for the coterminous United States (US) using the water supply stress index (WaSSI) model which considers regional trends in both water supply and demand. A snapshot of contemporary annual water demand is compared against different water supply regimes, including current average supplies, current extreme-year supplies, and projected future average surface water flows under a changing climate. In addition, we investigate the contributions of different water demand sectors to current water stress. On average, water supplies are stressed, meaning that demands for water outstrip natural supplies in over 9% of the 2103 watersheds examined. These watersheds rely on reservoir storage, conveyance systems, and groundwater to meet current water demands. Overall, agriculture is the major demand-side driver of water stress in the US, whereas municipal stress is isolated to southern California. Water stress introduced by cooling water demands for power plants is punctuated across the US, indicating that a single power plant has the potential to stress water supplies at the watershed scale. On the supply side, watersheds in the western US are particularly sensitive to low flow events and projected long-term shifts in flow driven by climate change. The WaSSI results imply that not only are water resources in the southwest in particular at risk, but that there are also potential vulnerabilities to specific sectors, even in the ‘water-rich’ southeast. (letter)

  14. Stress state and movement potential of the Kar-e-Bas fault zone, Fars, Iran

    Science.gov (United States)

    Sarkarinejad, Khalil; Zafarmand, Bahareh

    2017-08-01

    The Kar-e-Bas or Mengharak basement-inverted fault is comprised of six segments in the Zagros foreland folded belt of Iran. In the Fars region, this fault zone associated with the Kazerun, Sabz-Pushan and Sarvestan faults serves as a lateral transfer zone that accommodates the change in shortening direction from the western central to the eastern Zagros. This study evaluates the recent tectonic stress regime of the Kar-e-Bas fault zone based on inversion of earthquake focal mechanism data, and quantifies the fault movement potential of this zone based on the relationship between fault geometric characteristics and recent tectonic stress regimes. The trend and plunge of σ 1 and σ 3 are S25°W/04°-N31°E/05° and S65°E/04°-N60°W/10°, respectively, with a stress ratio of Φ = 0.83. These results are consistent with the collision direction of the Afro-Arabian continent and the Iranian microcontinent. The near horizontal plunge of maximum and minimum principle stresses and the value of stress ratio Φ indicate that the state of stress is nearly strike-slip dominated with little relative difference between the value of two principal stresses, σ 1 and σ 2. The obliquity of the maximum compressional stress into the fault trend reveals a typical stress partitioning of thrust and strike-slip motion in the Kar-e-Bas fault zone. Analysis of the movement potential of this fault zone shows that its northern segment has a higher potential of fault activity (0.99). The negligible difference between the fault-plane dips of the segments indicates that their strike is a controlling factor in the changes in movement potential.

  15. Prospective Analysis of Risk Factors Related to Depression and Post Traumatic Stress Disorder in Deployed United States Navy Personnel

    Science.gov (United States)

    2011-03-28

    post traumatic stress disorder ( PTSD ) and depression (MDD) than...United States Several epidemiological studies have been conducted on the prevalence of post traumatic stress disorder ( PTSD ) and major depression in...forms contain the same 4-item screener for post - traumatic stress disorder ( PTSD ). This screener was developed by the National Center for PTSD and

  16. Stress state variations among the clay and limestone formations of the molasse basin of Northern Switzerland

    International Nuclear Information System (INIS)

    Vietor, Tim; Mueller, Herwig; Frieg, Bernd; Klee, Gerd

    2012-01-01

    Document available in extended abstract form only. Full text of publication follows: The design of geological repositories for radioactive waste responds to the requirements of technical feasibility and long-term safety in the context of a specific geological setting. An important aspect of the geological setting is the primary stress field. To a large extent the stress state controls repository induced effects such as the excavation damage zone and the associated potential changes in the waste isolation properties of the host rock. Therefore the measurement of the stress state receives some attention where the site selection for geological repositories focuses onto relatively weak host rocks such as clay-stones and marly shales that tend to develop a significant excavation damage zone. Measurements of the minimum stress magnitudes in a recently drilled geothermal well in the Molasse Basin of northern Switzerland have yielded a stress profile reaching from 592 m to 1455 m depth. It straddles several rock units and includes the top of the crystalline basement. The sedimentary sequence consists of Marine limestones, shales and marls unconformably covered by Tertiary rocks of the Molasse. In other parts of the basin the evaporitic rocks of the Triassic Muschelkalk formation at the base of the sedimentary layer served as a regional detachment and enabled thin skinned thrusting and the formation of the Jura Fold and Thrust Belt in the Late Miocene. The stress measurements have been performed in the open hole by Mini-frac tests. The method uses a double packer system to isolate a one meter long interval of the borehole that is then pressurized at high injection rates up to the breakdown of the formation. Repeated pressurization of the interval allows to determine the stress that acts on the newly created fracture. The total injected volume during such a test is in the range of a few litres and the size of the fracture that extends from the borehole normal to the minimum

  17. Evolution of microstructure and residual stress on L1{sub 0} ordering in FePt thin films with different initial stress states

    Energy Technology Data Exchange (ETDEWEB)

    Hsiao, S.N., E-mail: pmami.hsiao@gmail.com [Department of Materials Science and Engineering, Feng Chia University, Taichung 407, Taiwan (China); Yuan, F.T. [iSentek Ltd., Advanced Sensor Laboratory, New Taipei City 221, Taiwan (China); Chen, S.K. [Department of Materials Science and Engineering, Feng Chia University, Taichung 407, Taiwan (China); Sun, A.C. [Department of Chemical Engineering and Materials Science, Yuan Ze University, Jungli 320, Taiwan (China); Su, S.H.; Chiu, K.F. [Department of Materials Science and Engineering, Feng Chia University, Taichung 407, Taiwan (China)

    2016-01-15

    We have characterized the dependence of microstructure, and internal strain/stress on L1{sub 0} ordering in 40 nm thick FePt films with different initial stresses. The microstructural and crystallographic results indicate that defect annihilation and grain growth induced an increase in tensile stress of ~1 GPa before extensive L1{sub 0} ordering. The induced tensile stress can efficiently facilitate the nucleation of L1{sub 0} phase owing to that the volume expansion of L1{sub 0} ordering and atomic rearrangement neutralizes the tensile stress. If the as-deposited FePt film has a highly compressive state, the induced tensile stress will be canceled out and ordering is retarded, which results in a higher ordering temperature. - Highlights: • Microstructure-stress connection in FePt films was studied. • Initial stress alters microstructure and stress evolution during annealing. • Densification induces tensile stress of ~1 GPa before extensive L1{sub 0} ordering. • Induced tensile stress can efficiently facilitate the nucleation of L1{sub 0} phase. • Compressively initial stress results in a higher ordering temperature .

  18. Investigation of smooth specimen scc test procedures; variations in environment, specimen size, stressing frame, and stress state. [for high strength aluminum alloys

    Science.gov (United States)

    Lifka, B. W.; Sprowls, D. O.; Kelsey, R. A.

    1975-01-01

    The variables studied in the stress-corrosion cracking performance of high strength aluminum alloys were: (1) corrosiveness of the environment, (2) specimen size and stiffness of the stressing system, (3) interpretation of transgranular cracking, and (4) interaction of the state of stress and specimen orientation in a product with an anisotropic grain structure. It was shown that the probability of failure and time to fracture for a specimen loaded in direct tension are influenced by corrosion pattern, the stressing assembly stiffness, and the notch tensile strength of the alloy. Results demonstrate that the combination of a normal tension stress and a shear stress acting on the plane of maximum susceptibility in a product with a highly directional grain cause the greatest tendency for stress-corrosion cracking.

  19. Equation of limiting plasticity of the metal upon complex stress state

    International Nuclear Information System (INIS)

    Tin'gaev, A.K.

    2002-01-01

    A method for evaluation of the limiting plasticity of the metal in the zones of complex 3D stress state is presented. An analytic equation is derived for limiting plasticity. Parameters of the equation are expresses through the standard characteristics of the mechanical properties determined upon static tension of the smooth sample. Introduced into the obtained analytical equation is a universal fracture constant which indirectly characterizes the state of the material from the point of view of its capacity for elastic overstrain relaxation in the form of plastic flow or fracture. The new equation makes it possible to estimate the limiting plasticity of the metal in a state of complex stress on the basis of traditional characteristics of mechanical properties, which are not difficult to determine [ru

  20. Stress

    Science.gov (United States)

    ... taking care of an aging parent. With mental stress, the body pumps out hormones to no avail. Neither fighting ... with type 1 diabetes. This difference makes sense. Stress blocks the body from releasing insulin in people with type 2 ...

  1. A large-scale perspective on stress-induced alterations in resting-state networks

    Science.gov (United States)

    Maron-Katz, Adi; Vaisvaser, Sharon; Lin, Tamar; Hendler, Talma; Shamir, Ron

    2016-02-01

    Stress is known to induce large-scale neural modulations. However, its neural effect once the stressor is removed and how it relates to subjective experience are not fully understood. Here we used a statistically sound data-driven approach to investigate alterations in large-scale resting-state functional connectivity (rsFC) induced by acute social stress. We compared rsfMRI profiles of 57 healthy male subjects before and after stress induction. Using a parcellation-based univariate statistical analysis, we identified a large-scale rsFC change, involving 490 parcel-pairs. Aiming to characterize this change, we employed statistical enrichment analysis, identifying anatomic structures that were significantly interconnected by these pairs. This analysis revealed strengthening of thalamo-cortical connectivity and weakening of cross-hemispheral parieto-temporal connectivity. These alterations were further found to be associated with change in subjective stress reports. Integrating report-based information on stress sustainment 20 minutes post induction, revealed a single significant rsFC change between the right amygdala and the precuneus, which inversely correlated with the level of subjective recovery. Our study demonstrates the value of enrichment analysis for exploring large-scale network reorganization patterns, and provides new insight on stress-induced neural modulations and their relation to subjective experience.

  2. State-of-stress in magmatic rift zones: Predicting the role of surface and subsurface topography

    Science.gov (United States)

    Oliva, S. J. C.; Ebinger, C.; Rivalta, E.; Williams, C. A.

    2017-12-01

    Continental rift zones are segmented along their length by large fault systems that form in response to extensional stresses. Volcanoes and crustal magma chambers cause fundamental changes to the density structure, load the plates, and alter the state-of-stress within the crust, which then dictates fracture orientation. In this study, we develop geodynamic models scaled to a structure, petrologic and thermodynamic studies constrain material densities, and seismicity and structural analyses constrain active and time-averaged kinematics. This area is an ideal test area because a 60º stress rotation is observed in time-averaged fault and magma intrusion, and in local seismicity, and because this was the site of a large volume dike intrusion and seismic sequence in 2007. We use physics-based 2D and 3D models (analytical and finite elements) constrained by data from active rift zones to quantify the effects of loading on state-of-stress. By modeling varying geometric arrangements, and density contrasts of topographic and subsurface loads, and with reasonable regional extensional forces, the resulting state-of-stress reveals the favored orientation for new intrusions. Although our models are generalized, they allow us to evaluate whether a magmatic system (surface and subsurface) can explain the observed stress rotation, and enable new intrusions, new faults, or fault reactivation with orientations oblique to the main border faults. Our results will improve our understanding of the different factors at play in these extensional regimes, as well as contribute to a better assessment of the hazards in the area.

  3. Modelling of the in situ stress state at Olkiluoto Site, Western Finland

    International Nuclear Information System (INIS)

    Valli, J.; Kuula, H.; Hakala, M.

    2011-06-01

    In order to determine the interaction of in situ stress and geological features at Olkiluoto with the ONKALO area under more specific focus, stress modelling work was launched in 2009. This entailed updating a previously used model geometry to suit current needs whilst also updating interpreted brittle deformation zones according to the data provided by Posiva in the beginning of 2010. The previous model geometry was originally used for seismic and glacial load simulations. Brittle deformation zones were updated in the model according to a new selection criterion which added a number of brittle deformation zones. Changes in the geometry of certain brittle deformation zones were also necessary to better fit the early 2010 interpretations from Posiva. Modelling goals were to clarify the effect of joint parameters on stress magnitude and orientation and which of the major brittle deformation zones detected in the ONKALO region could have potential effects on local in situ stress states. Additional goals included modelling the effect of several optional thrust boundary conditions and an ice-age. Compression from the northwest-southeast was used as the default approach whilst north-south, east-west and northeast-southwest were optional conditions. A simplified glaciation cycle was also simulated. Results were clear in demonstrating the critical effect of joint cohesion and joint friction angle, i.e. shear strength, on stress-geology interaction, essentially in this order of importance. The case that utilised both drillhole core-logging and ONKALO tunnel mapping results did not exhibit much if any stress-geology interactions as BFZ strength parameters were too high in order to allow any interactions to occur. The geometry and orientation of brittle deformation zones was found to be of significant importance; deformation zones with a shallow dip roughly in the direction of applied compression were optimal for causing stress rotations and the increase of stress magnitude

  4. Structure/property relations of aluminum under varying rates and stress states

    Energy Technology Data Exchange (ETDEWEB)

    Tucker, Matthew T [Los Alamos National Laboratory; Horstemeyer, Mark F [MISSISSIPPI STATE UNIV; Whittington, Wilburn R [MISSISSIPPI STATE UNIV; Solanki, Kiran N [MISSISSIPPI STATE UNIV.

    2010-11-19

    In this work we analyze the plasticity, damage, and fracture characteristics of three different processed aluminum alloys (rolled 5083-H13, cast A356-T6, and extruded 6061-T6) under varying stress states (tension, compression, and torsion) and strain rates (0.001/, 1/s., and 1000/s). The stress state difference had more of a flow stress effect than the applied strain rates for those given in this study (0.001/sec up to 1000/sec). The stress state and strain rate also had a profound effect on the damage evolution of each aluminum alloy. Tension and torsional straining gave much greater damage nucleation rates than compression. Although the damage of all three alloys was found to be void nucleation dominated, the A356-T6 and 5083-H131 aluminum alloys incurred void damage via micron scale particles where the 6061-T6 aluminum alloy incurred void damage from two scales, micron-scale particles and nanoscale precipitates. Having two length scales of particles that participated in the damage evolution made the 6061-T6 incur a strain rate sensitive damage rate that was different than the other two aluminum alloys. Under tension, as the strain rate increased, the 6061-T6 aluminum alloy's void nucleation rate decreased, but the A356-T6 and 5083-H131 aluminum alloys void nucleation rate increased.

  5. Transactional stress and coping theory in accounting for psychological states measures

    Directory of Open Access Journals (Sweden)

    V. Buško

    2007-08-01

    Full Text Available The paper examines a relative predictive value of some stable individual attributes and the processes of cognitive appraisals and coping with stress in accounting for specific components of anxiety state measures. Self-report instruments for the measurement of selected psychological constructs, i.e. perceived incompetence, externality, stress intensity and duration, situation-specific coping strategies, and the two anxiety state components, were taken in a sample of 449 male military basics trainees, ranging in age from 18-27. Hierarchical multiple regression analyses showed that the set of predictors employed could account for statistically, as well as theoretically and practically a significant part of variance in cognitive anxiety component (45,5%, and in visceral-emotional component (32,2% of the anxiety state. The extent of anxiety reactions assessed by both scales could primarily be explained by general perception of personal incompetence, as a relatively stable dimension of general self-concept. Of the ways of coping examined, reinterpretation of stressful events was the only strategy contributing to low level, whereas passivization, wishful thinking, and seeking social support contributed to higher levels of anxiety measured by both scales. The results give partial support to the basic hypotheses on the mediating role of coping in the relationships among particular components of the stress and coping models.

  6. Mozart versus new age music: relaxation states, stress, and ABC relaxation theory.

    Science.gov (United States)

    Smith, Jonathan C; Joyce, Carol A

    2004-01-01

    Smith's (2001) Attentional Behavioral Cognitive (ABC) relaxation theory proposes that all approaches to relaxation (including music) have the potential for evoking one or more of 15 factor-analytically derived relaxation states, or "R-States" (Sleepiness, Disengagement, Rested / Refreshed, Energized, Physical Relaxation, At Ease/Peace, Joy, Mental Quiet, Childlike Innocence, Thankfulness and Love, Mystery, Awe and Wonder, Prayerfulness, Timeless/Boundless/Infinite, and Aware). The present study investigated R-States and stress symptom-patterns associated with listening to Mozart versus New Age music. Students (N = 63) were divided into three relaxation groups based on previously determined preferences. Fourteen listened to a 28-minute tape recording of Mozart's Eine Kleine Nachtmusik and 14 listened to a 28-minute tape of Steven Halpern's New Age Serenity Suite. Others (n = 35) did not want music and instead chose a set of popular recreational magazines. Participants engaged in their relaxation activity at home for three consecutive days for 28 minutes a session. Before and after each session, each person completed the Smith Relaxation States Inventory (Smith, 2001), a comprehensive questionnaire tapping 15 R-States as well as the stress states of somatic stress, worry, and negative emotion. Results revealed no differences at Session 1. At Session 2, those who listened to Mozart reported higher levels of At Ease/Peace and lower levels of Negative Emotion. Pronounced differences emerged at Session 3. Mozart listeners uniquely reported substantially higher levels of Mental Quiet, Awe and Wonder, and Mystery. Mozart listeners reported higher levels, and New Age listeners slightly elevated levels, of At Ease/Peace and Rested/Refreshed. Both Mozart and New Age listeners reported higher levels of Thankfulness and Love. In summary, those who listened to Mozart's Eine Kleine Nachtmusik reported more psychological relaxation and less stress than either those who listened to

  7. Mastering the biaxial stress state in nanometric thin films on flexible substrates

    Energy Technology Data Exchange (ETDEWEB)

    Faurie, D., E-mail: faurie@univ-paris13.fr [LSPM-CNRS, UPR3407, Université Paris 13, Villetaneuse (France); Renault, P.-O.; Le Bourhis, E. [Institut Pprime UPR3346, CNRS – Université de Poitiers, Futuroscope (France); Geandier, G. [Institut Jean Lamour, CNRS UMR7198, Université de Lorraine, Nancy Cedex (France); Goudeau, P. [Institut Pprime UPR3346, CNRS – Université de Poitiers, Futuroscope (France); Thiaudière, D. [SOLEIL Synchrotron, Saint-Aubin, Gif-Sur-Yvette (France)

    2014-07-01

    Biaxial stress state of thin films deposited on flexible substrate can be mastered thanks to a new biaxial device. This tensile machine allows applying in-plane loads F{sub x} and F{sub y} in the two principal directions x and y of a cruciform-shaped polymer substrate. The transmission of the deformation at film/substrate interface allows controlling the stress and strain field in the thin films. We show in this paper a few illustrations dealing with strain measurements in polycrystalline thin films deposited on flexible substrate. The potentialities of the biaxial device located at Soleil synchrotron are also discussed.

  8. Fabrication of imitative stress corrosion cracking specimens suitable for electromagnetic nondestructive evaluations using solid state bonding

    International Nuclear Information System (INIS)

    Yusa, Noritaka; Hashizume, Hidetoshi; Uchimoto, Tetsuya; Takagi, Toshiyuki

    2010-01-01

    This study proposes a method to fabricate artificial defects that is almost identical to stress corrosion cracking from the viewpoint of electromagnetic nondestructive evaluations. The key idea is to realize a region having electrical resistance embedded inside a conductive materials using solid state bonding. A rough region is introduced into the surface of the materials so that the region is partially bonded to realize electrical resistance. The validity of the method is demonstrated using type 316L austenitic stainless steels. Eddy current tests and subsequent destructive tests confirm that signals due to the fabricated specimens are very similar to those due to stress corrosion cracks. (author)

  9. Calculation of a steam generating tube stressed state under temperature oscillations in burnout zone

    International Nuclear Information System (INIS)

    Vorob'ev, V.A.; Loshchinin, V.M.; Remizov, O.V.

    1982-01-01

    The technique for evaluating the steam generating tube stressed state under the wall temperature oscillations in the burnout zone is described. The technique is based on analytical solutions for transfer functions connecting the amplitude of surface temperature oscillation with the amplitude and frequency of heat transfer coefficient oscillation and amplitude of thermoelastic stress oscillation with that of temperature oscillation. The results of calculations according to considered technique are compared with that of the problem numerical solution. The conclusion is made that the technique under consideration may be applied for evaluation of steam generator evaporating tube lifetime [ru

  10. Experimental Research of Reliability of Plant Stress State Detection by Laser-Induced Fluorescence Method

    Directory of Open Access Journals (Sweden)

    Yury Fedotov

    2016-01-01

    Full Text Available Experimental laboratory investigations of the laser-induced fluorescence spectra of watercress and lawn grass were conducted. The fluorescence spectra were excited by YAG:Nd laser emitting at 532 nm. It was established that the influence of stress caused by mechanical damage, overwatering, and soil pollution is manifested in changes of the spectra shapes. The mean values and confidence intervals for the ratio of two fluorescence maxima near 685 and 740 nm were estimated. It is presented that the fluorescence ratio could be considered a reliable characteristic of plant stress state.

  11. Shock Response of Commercial Purity Polycrystalline Magnesium Under Uniaxial Strain at Elevated Temperatures

    Science.gov (United States)

    Wang, Tianxue; Zuanetti, Bryan; Prakash, Vikas

    2017-12-01

    In the present paper, results of plate impact experiments designed to investigate the onset of incipient plasticity in commercial purity polycrystalline magnesium (99.9%) under weak uniaxial strain compression and elevated temperatures up to melt are presented. The dynamic stress at yield and post yield of magnesium, as inferred from the measured normal component of the particle velocity histories at the free (rear) surface of the target plate, are observed to decrease progressively with increasing test temperatures in the range from 23 to 500 °C. At (higher) test temperatures in the range 500-610 °C, the rate of decrease of dynamic stress with temperature at yield and post-yield in the sample is observed to weaken. At still higher test temperatures (617 and 630 °C), a dramatic increase in dynamic yield as well as flow stress is observed indicating a change in dominant mechanism of plastic deformation as the sample approaches the melt point of magnesium at strain rates of 105/s. In addition to these measurements at the wavefront, the plateau region of the free surface particle velocity profiles indicates that the longitudinal (plastic) impedance of the magnesium samples decreases continuously as the sample temperatures are increased from room to 610 °C, and then reverses trend (indicating increasing material longitudinal impedance/strength) as the sample temperatures are increased to 617 and 630 °C. Electron back scattered diffraction analysis of the as-received and annealed pre-test magnesium samples reveal grain coarsening as well as grain re-orientation to a different texture during the heating process of the samples.

  12. RESEARCH OF THE STRESS STATE OF A MODIFIED IN-SITU CONCRETE

    Directory of Open Access Journals (Sweden)

    D. V. Rudenko

    2016-12-01

    Full Text Available Purpose. The article focuses on investigation of the stress state of a modified in-situ concrete of natural hardening. Methodology. To achieve the aim, the research of the microstructure of the modified cement matrix of concrete, as well as the mechanism of structure formation of modified concrete with natural hardening was conducted; the methods for reliable evaluation of concrete strength were defined. Findings. The development of internal stresses affects the properties of concretedifferently. With an increase in temperature-shrinkage deformations in time and, thus, with increasing structural stresses in the cement sheath around the grains of the filler two opposite processes may develop: zone of plastic flow or cracking. Originality. It was established that the structural features complex of the modified concrete when the load transfer leads to the formation of extensive zones of prefracture which is able to absorb a significant amount of elastic strain energy that provides the design deformation properties of the concrete for special purposes. Ideas about the definition of the criteria of cracking modified concrete, hardening under natural conditions had further development. Practical value. The resulting equations allow to solve the problem about the minimum level of structural stress in monolithic concrete in a saturated large placeholder, as well as to assess the influence of structural stresses on the properties of concrete. In normal concrete with a relatively thin cement sheath at temperature-shrinkage deformations, high tangential and low radial tension occur. In vivo, this stress is higher as a result of higher values of Δε(τ, which is not observed in the modified concrete. In the modified concretes only tangential stresses are the greatest danger to structures. The change of shrinkage stress with time is straightforward. The total temperature-shrinkage deformations have a sawtooth graph. For modified concrete the amplitude is 48

  13. Study on Energy Absorption Capacity of Steel-Polyester Hybrid Fiber Reinforced Concrete Under Uni-axial Compression

    Science.gov (United States)

    Chella Gifta, C.; Prabavathy, S.

    2018-05-01

    This work presents the energy absorption capacity of hybrid fiber reinforced concrete made with hooked end steel fibers (0.5 and 0.75%) and straight polyester fibers (0.5, 0.8, 1.0 and 2.0%). Compressive toughness (energy absorption capacity) under uni-axial compression was evaluated on 100 × 200 mm size cylindrical specimens with varying steel and polyester fiber content. Efficiency of the hybrid fiber reinforcement is studied with respect to fiber type, size and volume fractions in this investigation. The vertical displacement under uni-axial compression was measured under the applied loads and the load-deformation curves were plotted. From these curves the toughness values were calculated and the results were compared with steel and polyester as individual fibers. The hybridization of 0.5% steel + 0.5% polyester performed well in post peak region due to the addition of polyester fibers with steel fibers and the energy absorption value was 23% greater than 0.5% steel FRC. Peak stress values were also higher in hybrid series than single fiber and based on the results it is concluded that hybrid fiber reinforcement improves the toughness characteristics of concrete without affecting workability.

  14. Magnetization reversal of in-plane uniaxial Co films and its dependence on epitaxial alignment

    Energy Technology Data Exchange (ETDEWEB)

    Idigoras, O., E-mail: o.idigoras@nanogune.eu; Suszka, A. K.; Berger, A. [CIC nanoGUNE Consolider, Tolosa Hiribidea 76, E-20018 Donostia-San Sebastian (Spain); Vavassori, P. [CIC nanoGUNE Consolider, Tolosa Hiribidea 76, E-20018 Donostia-San Sebastian (Spain); IKERBASQUE, The Basque Foundation for Science, E-48011 Bilbao (Spain); Obry, B.; Hillebrands, B. [Fachbereich Physik and Landesforschungzentrum OPTIMAS, Technische Universität Kaiserslautern, Erwin-Schrödinger-Straße 56, D-67663 Kaiserslautern (Germany); Landeros, P. [Departamento de Física, Universidad Técnica Federico Santa María, Avenida España 1680, 2390123 Valparaíso (Chile)

    2014-02-28

    This work studies the influence of crystallographic alignment onto magnetization reversal in partially epitaxial Co films. A reproducible growth sequence was devised that allows for the continuous tuning of grain orientation disorder in Co films with uniaxial in-plane anisotropy by the controlled partial suppression of epitaxy. While all stable or meta-stable magnetization states occurring during a magnetic field cycle exhibit a uniform magnetization for fully epitaxial samples, non-uniform states appear for samples with sufficiently high grain orientation disorder. Simultaneously with the occurrence of stable domain states during the magnetization reversal, we observe a qualitative change of the applied field angle dependence of the coercive field. Upon increasing the grain orientation disorder, we observe a disappearance of transient domain wall propagation as the dominating reversal process, which is characterized by an increase of the coercive field for applied field angles away from the easy axis for well-ordered epitaxial samples. Upon reaching a certain disorder threshold level, we also find an anomalous magnetization reversal, which is characterized by a non-monotonic behavior of the remanent magnetization and coercive field as a function of the applied field angle in the vicinity of the nominal hard axis. This anomaly is a collective reversal mode that is caused by disorder-induced frustration and it can be qualitatively and even quantitatively explained by means of a two Stoner-Wohlfarth particle model. Its predictions are furthermore corroborated by Kerr microscopy and by Brillouin light scattering measurements.

  15. Electrical resistivity of CeNiSn under uniaxial and hydrostatic pressures

    Science.gov (United States)

    Echizen, Y.; Umeo, K.; Igaue, T.; Takabatake, T.

    2002-05-01

    We present measurements of the electrical resistivity ρ(T) on high-quality single-crystalline CeNiSn under both hydrostatic pressure up to 1 GPa and uniaxial pressure up to 0.25 GPa. At ambient pressure, ρ(T) along the orthorhombic a-axis (b-axis) shows two maxima at TL = 12 K (14 K) and TH = 74 K (40 K), respectively, which arise from the Kondo scattering of conduction electrons by the crystal-field ground state and excited states. With increasing hydrostatic pressure, both TL and TH increase linearly, and for P≥0.8 GPa, the anisotropy in ρ(T) for I∥a and I∥b almost vanishes as a result of increased hybridization between the 4f electrons and the conduction electrons. Under P∥a, both TL and TH in ρ(I∥b) increase similarly to under hydrostatic pressure. Under P∥c, however, the depression of TL in ρ(I∥a) and ρ(I∥b) suggests that the c-f hybridization in the crystal-field ground state is weakened in the a-b plane of CeNiSn.

  16. Phonon dispersion evolution in uniaxially strained aluminum crystal

    Science.gov (United States)

    Parthasarathy, Ranganathan; Misra, Anil; Aryal, Sitaram; Ouyang, Lizhi

    2018-04-01

    The influence of loading upon the phonon dispersion of crystalline materials could be highly nonlinear with certain particular trends that depend upon the loading path. In this paper, we have calculated the influence of [100] uniaxial strain on the phonon dispersion and group velocities in fcc aluminum using second moments of position obtained from molecular dynamics (MD) simulation at 300 K. In contrast to nonlinear monotonic variation of both longitudinal and transverse phonon frequencies along the Δ , Λ and Σ lines of the first Brillouin zone under tension, transverse phonon branches along the Λ line show inflection at specific wavevectors when the compressive strain exceeds 5%. Further, the longitudinal group velocities along the high-symmetry Δ line vary non-monotonically with strain, reaching a minimum at 5% compressive strain. Throughout the strain range studied, the equilibrium positions of atoms displace in an affine manner preserving certain static structural symmetry. We attribute the anomalies in the phonon dispersion to the non-affine evolution of second moments of atomic position, and the associated plateauing of force constants under the applied strain path.

  17. Mechanical behavior of silicon carbide nanoparticles under uniaxial compression

    Energy Technology Data Exchange (ETDEWEB)

    He, Qiuxiang; Fei, Jing; Tang, Chao; Zhong, Jianxin; Meng, Lijun, E-mail: ljmeng@xtu.edu.cn [Xiangtan University, Hunan Key Laboratory for Micro-Nano Energy Materials and Devices, Faculty of School of Physics and Optoelectronics (China)

    2016-03-15

    The mechanical behavior of SiC nanoparticles under uniaxial compression was investigated using an atomic-level compression simulation technique. The results revealed that the mechanical deformation of SiC nanocrystals is highly dependent on compression orientation, particle size, and temperature. A structural transformation from the original zinc-blende to a rock-salt phase is identified for SiC nanoparticles compressed along the [001] direction at low temperature. However, the rock-salt phase is not observed for SiC nanoparticles compressed along the [110] and [111] directions irrespective of size and temperature. The high-pressure-generated rock-salt phase strongly affects the mechanical behavior of the nanoparticles, including their hardness and deformation process. The hardness of [001]-compressed nanoparticles decreases monotonically as their size increases, different from that of [110] and [111]-compressed nanoparticles, which reaches a maximal value at a critical size and then decreases. Additionally, a temperature-dependent mechanical response was observed for all simulated SiC nanoparticles regardless of compression orientation and size. Interestingly, the hardness of SiC nanocrystals with a diameter of 8 nm compressed in [001]-orientation undergoes a steep decrease at 0.1–200 K and then a gradual decline from 250 to 1500 K. This trend can be attributed to different deformation mechanisms related to phase transformation and dislocations. Our results will be useful for practical applications of SiC nanoparticles under high pressure.

  18. Uniaxial alignment of triisopropylsilylethynyl pentacene via zone-casting technique.

    Science.gov (United States)

    Su, Yajun; Gao, Xiang; Liu, Jiangang; Xing, Rubo; Han, Yanchun

    2013-09-14

    Uniaxially aligned triisopropylsilylethynyl pentacene (TIPS-pentacene) crystals over a large area were fabricated using zone-casting technique. The array of TIPS-pentacene displayed a high orientation degree with a dichroic ratio (DR) of 0.80. The crystals were arranged with c axis perpendicular to the substrate and the long axis of the ribbon corresponded to the a axis of TIPS-pentacene. The properties of the solutions and the processing parameters were shown to influence the formation of the oriented TIPS-pentacene crystalline array. Solvent with a low boiling point (such as chloroform) favoured the orientation of the ribbon-like crystals. The concentration of the solution should be appropriate, ensuring the crystallization velocity of TIPS-pentacene matching with the receding of the meniscus. Besides, we proved that the casting speed should be large enough to induce a sufficient concentration gradient. The orientation mechanism of TIPS-pentacene was attributed to a synergy of the ordered nuclei and a match between the crystallization velocity and the casting speed. Field effect transistors (FETs) based on the oriented TIPS-pentacene crystalline array showed a mobility of 0.67 cm(2) V(-1) s(-1).

  19. Study on infrasonic characteristics of coal samples in failure process under uniaxial loading

    Directory of Open Access Journals (Sweden)

    Bing Jia

    Full Text Available To study the precursory failure infrasonic characteristics of coal samples, coal rock stress loading system and infrasonic wave acquisition system were adopted, and infrasonic tests in uniaxial loading process were made for the coal samples in the studied area. Wavelet filtering, fast Fourier transform, and relative infrasonic energy methods were used to analyze the characteristics of the infrasonic waves in the loading process, including time domain characteristics, and relative energy. The analysis results demonstrated that the frequencies of the infrasonic signals in the loading process mainly distribute within 5–10 Hz, which are significantly different from noise signals. The changes of the infrasonic signals show clear periodic characters in time domain. Meanwhile, the relative energy changes of the infrasonic wave also show periodic characters, which are divided into two stages by the yield limit of coal samples, and are clear and easy to be recognized, so that they can be used as the precursory characteristics for recognizing coal sample failures. Moreover, the infrasonic waves generated by coal samples have low frequency and low attenuation, which can be collected without coupling and transmitted in long distance. This study provides an important support for the further in-situ prediction of coal rock failures. Keywords: Infrasound, Relative energy, Time-frequency analysis, Failure prediction, Identification feature

  20. Cyclic mechanical behavior of 316L: Uniaxial LCF and strain-controlled ratcheting tests

    International Nuclear Information System (INIS)

    Facheris, G.; Janssens, K.G.F.

    2013-01-01

    Highlights: ► Characterization of cyclic plastic deformation behavior of plate and tubular 316L. ► Strain-controlled ratcheting response between room temperature and 200 °C. ► Isotropic cyclic hardening is dependent on the yield criterion used. ► Ratcheting induced hardening mostly affects the kinematic hardening component. ► Ratcheting induced hardening is related to the mean strain and the ratcheting rate. -- Abstract: With the purpose of analyzing the fatigue behavior under loading conditions relevant for the primary cooling circuit of a light water nuclear reactor, a set of uniaxial low cycle fatigue and strain-controlled ratcheting tests (also named ‘cyclic tension tests’) has been performed at room temperature and at 200 °C on specimens manufactured from two different batches of stainless steel grade 316L. The experiments have been repeated varying strain amplitude, cyclic ratcheting rate and ratcheting direction in order to investigate the influence on the cyclic deformation behavior. In strain-controlled ratcheting tests, the stress response is found to be a superposition of two hardening mechanisms: the first one due to the zero mean strain cycling and the second one linked with the monotonic drifting of mean plastic strain. An approach is proposed to distinguish the effect of each mechanism and the influence of the test parameters on the hardening mechanisms is discussed

  1. Mechanical properties and fracture behaviour of defective phosphorene nanotubes under uniaxial tension

    Science.gov (United States)

    Liu, Ping; Pei, Qing-Xiang; Huang, Wei; Zhang, Yong-Wei

    2017-12-01

    The easy formation of vacancy defects and the asymmetry in the two sublayers of phosphorene nanotubes (PNTs) may result in brand new mechanical properties and failure behaviour. Herein, we investigate the mechanical properties and fracture behaviour of defective PNTs under uniaxial tension using molecular dynamics simulations. Our simulation results show that atomic vacancies cause local stress concentration and thus significantly reduce the fracture strength and fracture strain of PNTs. More specifically, a 1% defect concentration is able to reduce the fracture strength and fracture strain by as much as 50% and 66%, respectively. Interestingly, the reduction in the mechanical properties is found to depend on the defect location: a defect located in the outer sublayer has a stronger effect than one located in the inner layer, especially for PNTs with a small diameter. Temperature is also found to strongly influence the mechanical properties of both defect-free and defective PNTs. When the temperature is increased from 0 K to 400 K, the fracture strength and fracture strain of defective PNTs with a defect concentration of 1% are reduced further by 71% and 61%, respectively. These findings are of great importance for the structural design of PNTs as building blocks in nanodevices.

  2. Selective buckling via states of self-stress in topological metamaterials.

    Science.gov (United States)

    Paulose, Jayson; Meeussen, Anne S; Vitelli, Vincenzo

    2015-06-23

    States of self-stress--tensions and compressions of structural elements that result in zero net forces--play an important role in determining the load-bearing ability of structures ranging from bridges to metamaterials with tunable mechanical properties. We exploit a class of recently introduced states of self-stress analogous to topological quantum states to sculpt localized buckling regions in the interior of periodic cellular metamaterials. Although the topological states of self-stress arise in the linear response of an idealized mechanical frame of harmonic springs connected by freely hinged joints, they leave a distinct signature in the nonlinear buckling behavior of a cellular material built out of elastic beams with rigid joints. The salient feature of these localized buckling regions is that they are indistinguishable from their surroundings as far as material parameters or connectivity of their constituent elements are concerned. Furthermore, they are robust against a wide range of structural perturbations. We demonstrate the effectiveness of this topological design through analytical and numerical calculations as well as buckling experiments performed on two- and three-dimensional metamaterials built out of stacked kagome lattices.

  3. Recent state of stress change in the Walker Lane zone, western Basin and Range province, United States

    Science.gov (United States)

    Bellier, Olivier; Zoback, Mary Lou

    1995-06-01

    The NW to north-trending Walker Lane zone (WLZ) is located along the western boundary of the northern Basin and Range province with the Sierra Nevada. This zone is distinguished from the surrounding Basin and Range province on the basis of irregular topography and evidence for both normal and strike-slip Holocene faulting. Inversion of slip vectors from active faults, historic fault offsets, and earthquake focal mechanisms indicate two distinct Quaternary stress regimes within the WLZ, both of which are characterized by a consistent WNW σ3 axis; these are a normal faulting regime with a mean σ3 axis of N85°±9°W and a mean stress ratio (R value) (R=(σ2-σ1)/(σ3-σ1)) of 0.63-0.74 and a younger strike-slip faulting regime with a similar mean σ3 axis (N65° - 70°W) and R values ranging between ˜ 0.1 and 0.2. This younger regime is compatible with historic fault offsets and earthquake focal mechanisms. Both the extensional and strike-slip stress regimes reactivated inherited Mesozoic and Cenozoic structures and also produced new faults. The present-day strike-slip stress regime has produced strike-slip, normal oblique-slip, and normal dip-slip historic faulting. Previous workers have explained the complex interaction of active strike-slip, oblique, and normal faulting in the WLZ as a simple consequence of a single stress state with a consistent WNW σ3 axis and transitional between strike-slip and normal faulting (maximum horizontal stress approximately equal to vertical stress, or R ≈ 0 in both regimes) with minor local fluctuations. The slip data reported here support previous results from Owens Valley that suggest deformation within temporally distinct normal and strike-slip faulting stress regimes with a roughly constant WNW trending σ3 axis (Zoback, 1989). A recent change from a normal faulting to a strike-slip faulting stress regime is indicated by the crosscutting striae on faults in basalts the dominantly strike-slip earthquake focal mechanisms and

  4. The intersection of stress and reward: BNST modulation of aversive and appetitive states.

    Science.gov (United States)

    Ch'ng, Sarah; Fu, Jingjing; Brown, Robyn M; McDougall, Stuart J; Lawrence, Andrew J

    2018-01-09

    The bed nucleus of the stria terminalis (BNST) is widely acknowledged as a brain structure that regulates stress and anxiety states, as well as aversive and appetitive behaviours. The diverse roles of the BNST are afforded by its highly modular organisation, neurochemical heterogeneity, and complex intrinsic and extrinsic circuitry. There has been growing interest in the BNST in relation to psychopathologies such as anxiety and addiction. Although research on the human BNST is still in its infancy, there have been extensive preclinical studies examining the molecular signature and hodology of the BNST and their involvement in stress and reward seeking behaviour. This review examines the neurochemical phenotype and connectivity of the BNST, as well as electrophysiological correlates of plasticity in the BNST mediated by stress and/or drugs of abuse. Copyright © 2018 Elsevier Inc. All rights reserved.

  5. Cellular stress induces a protective sleep-like state in C. elegans.

    Science.gov (United States)

    Hill, Andrew J; Mansfield, Richard; Lopez, Jessie M N G; Raizen, David M; Van Buskirk, Cheryl

    2014-10-20

    Sleep is recognized to be ancient in origin, with vertebrates and invertebrates experiencing behaviorally quiescent states that are regulated by conserved genetic mechanisms. Despite its conservation throughout phylogeny, the function of sleep remains debated. Hypotheses for the purpose of sleep include nervous-system-specific functions such as modulation of synaptic strength and clearance of metabolites from the brain, as well as more generalized cellular functions such as energy conservation and macromolecule biosynthesis. These models are supported by the identification of synaptic and metabolic processes that are perturbed during prolonged wakefulness. It remains to be seen whether perturbations of cellular homeostasis in turn drive sleep. Here we show that under conditions of cellular stress, including noxious heat, cold, hypertonicity, and tissue damage, the nematode Caenorhabditis elegans engages a behavioral quiescence program. The stress-induced quiescent state displays properties of sleep and is dependent on the ALA neuron, which mediates the conserved soporific effect of epidermal growth factor (EGF) ligand overexpression. We characterize heat-induced quiescence in detail and show that it is indeed dependent on components of EGF signaling, providing physiological relevance to the behavioral effects of EGF family ligands. We find that after noxious heat exposure, quiescence-defective animals show elevated expression of cellular stress reporter genes and are impaired for survival, demonstrating the benefit of stress-induced behavioral quiescence. These data provide evidence that cellular stress can induce a protective sleep-like state in C. elegans and suggest that a deeply conserved function of sleep is to mitigate disruptions of cellular homeostasis. Copyright © 2014 Elsevier Ltd. All rights reserved.

  6. Probing stress state and phase content in ultra-thin Ta films

    International Nuclear Information System (INIS)

    Whitacre, J.F.; Yalisove, S.M.; Bilello, J.C.; Rek, Z.U.

    1998-01-01

    Ta films 25 angstrom to 200 angstrom in thickness were sputter-deposited using different sputter gas (Ar) pressures and cathode power settings. The average in-plane stresses were determined using double crystal diffraction topography (DCDT). X-ray analysis (using the grazing incidence x-ray scattering (GIXS) geometry) was performed using a synchrotron light source. To study microstructure and phase content, transmission electron microscopy (TEM) and transmission electron diffraction (TED) were used. Well resolved x-ray patterns were collected for all of the films. The DCDT stress data was found to be consistent with stress effects evidence in the GIXS data. In general, residual stress state was not strongly dependent upon Ar pressure. The strongest evidence of amorphous content was found in both x-ray and TED data taken from 25 angstrom thick films deposited using 2mTorr Ar pressure and 460 W cathode power. These results show that it is possible to create and study ultra-thin Ta films which possess a range of residual stresses and phase compositions

  7. Study of the stress-strain state of compressed concrete elements with composite reinforcement

    Directory of Open Access Journals (Sweden)

    Bondarenko Yurii

    2017-01-01

    Full Text Available The efficiency analysis of the application of glass composite reinforcement in compressed concrete elements as a load-carrying component has been performed. The results of experimental studies of the deformation-strength characteristics of this reinforcement on compression and compressed concrete cylinders reinforced by this reinforcement are presented. The results of tests and mechanisms of sample destruction have been analyzed. The numerical analysis of the stress-strain state has been performed for axial compression of concrete elements with glasscomposite reinforcement. The influence of the reinforcement percentage on the stressed state of a concrete compressed element with the noted reinforcement is estimated. On the basis of the obtained results, it is established that the glass-composite reinforcement has positive effect on the strength of the compressed concrete elements. That is, when calculating the load-bearing capacity of such structures, the function of composite reinforcement on compression should not be neglected.

  8. Investigation of mean spin orientation in the amorphous systems Fe/sub 81/B/sub 19/ under uniaxial extension conditions

    Energy Technology Data Exchange (ETDEWEB)

    Korsunskij, I L; Lomonosov, V V; Pazhin, Yu F; Sazonov, S B; Samarin, P F; Sedykh, V D; Serebryakov, A V; Suetin, V A

    1986-06-01

    The spin orientation averaged over the volume of an amorphous Fe/sub 81/B/sub 19/ band arising on uniaxial cyclic loading of the sample is investigated by NGR spectroscopy. It is found that in the unloaded state of the sample the hyperfine field at the Fe nucleus fluctuates depending on the prehistory of the loading procedure. A qualitative model is proposed which describes the behaviour of the averaged spin orientation.

  9. Stress-state monitoring of coal pillars during room and pillar extraction

    Czech Academy of Sciences Publication Activity Database

    Waclawik, Petr; Ptáček, Jiří; Koníček, Petr; Kukutsch, Radovan; Němčík, J.

    2016-01-01

    Roč. 15, č. 2 (2016), s. 49-56 ISSN 2300-3960 R&D Projects: GA MŠk(CZ) LO1406; GA MŠk ED2.1.00/03.0082 Institutional support: RVO:68145535 Keywords : stress-state monitoring * room and pillar * coal pillar Subject RIV: DH - Mining , incl. Coal Mining http://www.sciencedirect.com/science/article/pii/S2300396016300180

  10. Propagation of high-order circularly polarized Bessel beams and vortex generation in uniaxial crystals

    CSIR Research Space (South Africa)

    Belyi, VN

    2011-05-01

    Full Text Available The authors investigate the generation and transformation of Bessel beams through linear and nonlinear optical crystals. They outline the generation of high-order vortices due to propagation of Bessel beams along the optical axis of uniaxial...

  11. Mechanical properties of uniaxial natural fabric Grewia tilifolia reinforced epoxy based composites: Effects of chemical treatment

    CSIR Research Space (South Africa)

    Jayaramudu, J

    2014-07-01

    Full Text Available The effects of chemical treatment on the mechanical, morphological, and chemical resistance properties of uniaxial natural fabrics, Grewia tilifolia/epoxy composites, were studied. In order to enhance the interfacial bonding between the epoxy matrix...

  12. Profile of mood states and stress-related biochemical indices in long-term yoga practitioners

    Directory of Open Access Journals (Sweden)

    Sudo Nobuyuki

    2011-06-01

    Full Text Available Abstract Background Previous studies have shown the short-term or intermediate-term practice of yoga to be useful for ameliorating several mental disorders and psychosomatic disorders. However, little is known about the long-term influences of yoga on the mental state or stress-related biochemical indices. If yoga training has a stress-reduction effect and also improves an individual's mental states for a long time, long-term yoga practitioners may have a better mental state and lower stress-related biochemical indices in comparison to non-experienced participants. This study simultaneously examined the differences in mental states and urinary stress-related biochemical indices between long-term yoga practitioners and non-experienced participants. Methods The participants were 38 healthy females with more than 2 years of experience with yoga (long-term yoga group and 37 age-matched healthy females who had not participated in yoga (control group. Their mental states were assessed using the Profile of Mood States (POMS questionnaire. The level of cortisol, 8-hydroxydeoxyguanosine (8-OHdG and biopyrrin in urine were used as stress-related biochemical indices. Results The average self-rated mental disturbance, tension-anxiety, anger-hostility, and fatigue scores of the long-term yoga group were lower than those of the control group. There was a trend toward a higher vigor score in the long-term yoga group than that in the control group. There were no significant differences in the scores for depression and confusion in the POMS between the two groups. The urine 8-OHdG concentration showed a trend toward to being lower in the long-term yoga group in comparison to the control group. There were no significant differences in the levels of urine biopyrrin or cortisol. Conclusions The present findings suggest that long-term yoga training can reduce the scores related to mental health indicators such as self-rated anxiety, anger, and fatigue.

  13. FEA stress analysis considering cavity formation of metallic fuel pin under transient state

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Hyun-Woo; Oh, Young-Ryun; Kim, Yun-Jae [Korea University, Seoul (Korea, Republic of)

    2016-05-15

    The aim of this research is to study the stress state of the fuel and the cladding under transient state using the commercial finite element analysis software, ABAQUS v6.13. It is checked out that the gap distance between the fuel and the cladding is a major factor determining FCMI stress. In this regard, initial boundary condition of the fuel pin such as the initial gap distance should be set carefully when the stress analysis of the fuel pin under transient state is conducted. In case of simulating cavity formation, it is confirmed that the new cavity simulation model that elements in cavity region lose their stiffness is valid. There is a great deal of research into SFR, which is one of GEN IV reactors. When it comes to the accidents of SFR, there are two cases of accident process. One of them is In-pin process that molten fuel is discharged into upper plenum. The other is Ex-pin process that the molten fuel is discharged into coolant because of breakage of cladding.

  14. DEPRESSION, ANXIETY, STRESS, AND THEIR ASSOCIATED FACTORS AMONG CORPS MEMBERS SERVING IN KEBBI STATE.

    Science.gov (United States)

    Balami, Ahmed D

    2015-01-01

    Depression, anxiety and stress, are not only health problems by themselves, but also associated with other negative health consequences. The national youth service is usually characterized by a number of new challenges and experiences which may require life style adjustments by the corps member. However, no previous study on psychological factors has been conducted among corps members. This study was conducted to determine the prevalence of depression, anxiety and, stress and their associated factors among corps members serving in Kebbi state. A cross-sectional study was conducted among 264 corps members from four local government areas of the state. Selection of the local government areas and the individual participants was by simple random sampling. Data was collected from May to June 2014 using a self-administered questionnaire. Data analysis used chi-square test to identify the relationship between categorical variables and multivariate logistic regression to identify the independent factors for depression, anxiety and stress each. The response rate was 97%. Most of the respondents were males (63.6%), single (85.5%), and above 20 years of age (71.6%). The overall prevalences of depression, anxiety and stress among the respondents were 36.4%, 54.5% and 18.2% respectively. The independent factors for depression were; being from the North central (OR = 5.99; 95% CI: 2.194-16.354) or South-south; and the perception of earning enough income (OR = 2.987; 95% CI: 1.062-8.400). For anxiety, male gender (OR = 0.411; 95% CI: 0.169-0.999); and being from the North central were significant risk factors (OR = 3.731; 95% CI: 1.450-9.599). Being above 26 years of age was an independent risk factor for stress (OR = 0.083; 95% CI: 0.018-0.381). Also, those who had ever schooled outside their towns of residence were less likely to be stressed compared to those who had never (OR = 0.30; 95% CI: 0.110-0.855). All other factors did not show any significant association with any of

  15. In-situ stress analysis with X-Ray diffraction for yield locus characterization of sheet metals

    Energy Technology Data Exchange (ETDEWEB)

    Güner, A.; Tekkaya, A. E. [Institute of Forming Technology and Lightweight Construction, TU Dortmund University, Baroper Str. 301, 44227 Dortmund (Germany); Zillmann, B.; Lampke, T. [Institute of Materials Science and Engineering, Chemnitz University of Technology, Erfenschlager Strasse 73 D-09125 Chemnitz (Germany)

    2013-12-16

    A main problem in the field of sheet metal characterization is the inhomogeneous plastic deformation in the gauge regions of specimens which causes the analytically calculated stresses to differ from the sought state of stress acting in the middle of the gauge region. To overcome this problem, application of X-Ray diffraction is analyzed. For that purpose a mobile X-ray diffractometer and an optical strain measurement system are mounted on a universal tensile testing machine. This enables the recording of the whole strain and stress history of a material point. The method is applied to uniaxial tension tests, plane strain tension tests and shear tests to characterize the interstitial free steel alloy DC06. The applicability of the concepts of stress factors is verified by uniaxial tension tests. The experimentally obtained values are compared with the theoretical values calculated with crystal elasticity models utilizing the orientation distribution functions (ODF). The relaxation problem is addressed which shows itself as drops in the stress values with the strain kept at a constant level. This drop is analyzed with elasto-viscoplastic material models to correct the measured stresses. Results show that the XRD is applicable to measure the stresses in sheet metals with preferred orientation. The obtained yield locus is expressed with the Yld2000–2D material model and an industry oriented workpiece is analyzed numerically. The comparison of the strain distribution on the workpiece verifies the identified material parameters.

  16. Regional homogeneity and resting state functional connectivity: associations with exposure to early life stress.

    Science.gov (United States)

    Philip, Noah S; Kuras, Yuliya I; Valentine, Thomas R; Sweet, Lawrence H; Tyrka, Audrey R; Price, Lawrence H; Carpenter, Linda L

    2013-12-30

    Early life stress (ELS) confers risk for psychiatric illness. Previous literature suggests ELS is associated with decreased resting-state functional connectivity (rs-FC) in adulthood, but there are no studies of resting-state neuronal activity in this population. This study investigated whether ELS-exposed individuals demonstrate resting-state activity patterns similar to those found in PTSD. Twenty-seven adults (14 with at least moderate ELS), who were medication-free and without psychiatric or medical illness, underwent MRI scans during two 4-minute rest periods. Resting-state activity was examined using regional homogeneity (ReHo), which estimates regional activation patterns through indices of localized concordance. ReHo values were compared between groups, followed by rs-FC analyses utilizing ReHo-localized areas as seeds to identify other involved regions. Relative to controls, ELS subjects demonstrated diminished ReHo in the inferior parietal lobule (IPL) and superior temporal gyrus (STG). ReHo values were inversely correlated with ELS severity. Secondary analyses revealed decreased rs-FC between the IPL and right precuneus/posterior cingulate, left fusiform gyrus, cerebellum and caudate in ELS subjects. These findings indicate that ELS is associated with altered resting-state activity and connectivity in brain regions involved in trauma-related psychiatric disorders. Future studies are needed to evaluate whether these associations represent potential imaging biomarkers of stress exposure. Published by Elsevier Ireland Ltd.

  17. Experimental Studies on Strength Behaviour of Notched Glass/Epoxy Laminated Composites under Uni-axial and Bi-axial Loading

    Science.gov (United States)

    Guptha, V. L. Jagannatha; Sharma, Ramesh S.

    2017-11-01

    The use of FRP composite materials in aerospace, aviation, marine, automotive and civil engineering industry has increased rapidly in recent years due to their high specific strength and stiffness properties. The structural members contrived from such composite materials are generally subjected to complex loading conditions and leads to multi-axial stress conditions at critical surface localities. Presence of notches, much required for joining process of composites, makes it further significant. The current practice of using uni-axial test data alone to validate proposed material models is inadequate leading to evaluation and consideration of bi-axial test data. In order to correlate the bi-axial strengths with the uni-axial strengths of GFRP composite laminates in the presence of a circular notch, bi-axial tests using four servo-hydraulic actuators with four load cells were carried out. To determine the in-plane strength parameters, bi-axial cruciform test specimen model was considered. Three different fibre orientations, namely, 0°, 45°, and 90° are considered with a central circular notch of 10 mm diameter in the present investigation. From the results obtained, it is observed that there is a reduction in strength of 5.36, 2.41 and 13.92% in 0°, 45°, and 90° fibre orientation, respectively, under bi-axial loading condition as compared to that of uni-axial loading in laminated composite.

  18. Molecular dynamics modeling on the role of initial void geometry in a thin aluminum film under uniaxial tension

    International Nuclear Information System (INIS)

    Cui, Yi; Chen, Zengtao

    2015-01-01

    The effect of initial void geometry on damage progression in a thin aluminum film under uniaxial load is studied via molecular dynamics (MD) method. The embedded voids are with different initial geometries regarding shape, porosity and intervoid ligament distance (ILD). Major simulations are run upon twelve MD geometries with each containing 8–27 million atoms. The corresponding stress–strain relation is monitored during the microstructure evolution of the specimens. The critical stress to trigger the dislocation emission is found in line with the prediction of the Lubarda model. The simulation results reveal that the initial void geometry has substantial impact on the stress–strain relation especially for a specimen with larger initial porosity. (paper)

  19. Study of the temperature dependence of the uniaxial creep property of similar material of new soft rock

    Science.gov (United States)

    Wang, Y. Y.; Wu, Y.; Fan, X. Y.; Zhang, J. L.; Guo, P.; Li, J. G.

    2017-11-01

    Using the experimental method, the experimental research of creep properties were conducted under different temperature ranging from 10°C to 60°C. The similar material of new soft rock consists of paraffin, which can obtain that the deformation contains the instantaneous elastic deformation and creep deformation through the uniaxial creep experimental results. And thus the increase of temperature has great influence on the creep characteristics of similar soft rock according to the creep curve of similar soft rock at 10°C to 60°C. With the increase of temperature, the slope of the stress-strain curve of similar soft rock is increasing, while the average of the creep modulus is decreasing, which means that the capacity of resist deformation is reduced. Therefore, the creeps law of high-temperature and short-time can be shown the creep phenomenon of low-temperature and long-time, and further shorten the creep experimental cycle.

  20. Influence of water-soaking time on the acoustic emission characteristics and spatial fractal dimensions of coal under uniaxial compression

    Directory of Open Access Journals (Sweden)

    Jia Zheqiang

    2017-01-01

    Full Text Available The water-soaking time affects the physical and mechanical properties of coals, and the temporal and spatial evolution of acoustic emissions reflects the fracture damage process of rock. This study conducted uniaxial compression acoustic emissions tests of coal samples with different water-soaking times to investigate the influence of water-soaking time on the acoustic emissions characteristics and spatial fractal dimensions during the deformation and failure process of coals. The results demonstrate that the acoustic emissions characteristics decrease with increases in the water-soaking time. The acoustic emissions spatial fractal dimension changes from a single dimensionality reduction model to a fluctuation dimensionality reduction model, and the stress level of the initial descending point of the fractal dimension increases. With increases in the water-soaking time, the destruction of coal transitions from continuous intense failure throughout the process to a lower release of energy concentrated near the peak strength.

  1. Effects of single moor baths on physiological stress response and psychological state: a pilot study

    Science.gov (United States)

    Stier-Jarmer, M.; Frisch, D.; Oberhauser, C.; Immich, G.; Kirschneck, M.; Schuh, A.

    2017-11-01

    Moor mud applications in the form of packs and baths are widely used therapeutically as part of balneotherapy. They are commonly given as therapy for musculoskeletal disorders, with their thermo-physical effects being furthest studied. Moor baths are one of the key therapeutic elements in our recently developed and evaluated 3-week prevention program for subjects with high stress level and increased risk of developing a burnout syndrome. An embedded pilot study add-on to this core project was carried out to assess the relaxing effect of a single moor bath. During the prevention program, 78 participants received a total of seven moor applications, each consisting of a moor bath (42 °C, 20 min, given between 02:30 and 05:20 p.m.) followed by resting period (20 min). Before and after the first moor application in week 1, and the penultimate moor application in week 3, salivary cortisol was collected, blood pressure and heart rate were measured, and mood state (Multidimensional Mood State Questionnaire) was assessed. A Friedman test of differences among repeated measures was conducted. Post hoc analyses were performed using the Wilcoxon signed-rank test. A significant decrease in salivary cortisol concentration was seen between pre- and post-moor bath in week 1 ( Z = -3.355, p = 0.0008). A non-significant decrease was seen between pre- and post-moor bath in week 3. Mood state improved significantly after both moor baths. This pilot study has provided initial evidence on the stress-relieving effects of single moor baths, which can be a sensible and recommendable therapeutic element of multimodal stress-reducing prevention programs. The full potential of moor baths still needs to be validated. A randomized controlled trial should be conducted comparing this balneo-therapeutic approach against other types of stress reduction interventions.

  2. Experimental and numerical study of the failure process and energy mechanisms of rock-like materials containing cross un-persistent joints under uniaxial compression.

    Directory of Open Access Journals (Sweden)

    Rihong Cao

    Full Text Available Joints and fissures in natural rocks have a significant influence on the stability of the rock mass, and it is often necessary to evaluate strength failure and crack evolution behavior. In this paper, based on experimental tests and numerical simulation (PFC2D, the macro-mechanical behavior and energy mechanism of jointed rock-like specimens with cross non-persistent joints under uniaxial loading were investigated. The focus was to study the effect of joint dip angle α and intersection angle γ on the characteristic stress, the coalescence modes and the energy release of jointed rock-like specimens. For specimens with γ = 30° and 45°, the UCS (uniaxial compression strength, CIS (crack initiation stress and CDiS (critical dilatancy stress increase as α increases from 0° to 75°. When γ = 60° and 75°, the UCS, CIS and CDiS increase as α increases from 0° to 60° and decrease when α is over 60°. Both the inclination angle α and intersection angle γ have great influence on the failure pattern of pre-cracked specimens. With different α and γ, specimens exhibit 4 kinds of failure patterns. Both the experimental and numerical results show that the energy of a specimen has similar trends with characteristic stress as α increases.

  3. In-Situ Neutron Diffraction Under Tensile Loading of Powder-in-Tube Cu/Nb$_{3}$Sn Composite Wires Effect of Reaction Heat Treatment on Texture, Internal Stress State and Load Transfer

    CERN Document Server

    Scheuerlein, C; Thilly, L

    2007-01-01

    The strain induced degradation of Nb$_{3}$Sn superconductors can hamper the performance of high field magnets. We report elastic strain measurements in the different phases of entire non-heat treated and fully reacted Nb$_{3}$Sn composite strands as a function of uniaxial stress during in-situ deformation under neutron beam. After the reaction heat treatment the Cu matrix loses entirely its load carrying capability and the applied stress is transferred to the remaining Nb-Ta alloy and to the brittle (Nb-Ta)3Sn phase, which exhibits a preferential grain orientation parallel to the strand axis.

  4. Effect of different pneumoperitoneum pressure on stress state in patients underwent gynecological laparoscopy

    Directory of Open Access Journals (Sweden)

    Ai-Yun Shen

    2016-10-01

    Full Text Available Objective: To observe the effect of different CO2 pneumoperitoneum pressure on the stress state in patients underwent gynecological laparoscopy. Methods: A total of 90 patients who were admitted in our hospital from February, 2015 to October, 2015 for gynecological laparoscopy were included in the study and divided into groups A, B, and C according to different CO2 pneumoperitoneum pressure. The changes of HR, BP, and PetCO2 during the operation process in the three groups were recorded. The changes of stress indicators before operation (T0, 30 min during operation (T1, and 12 h after operation (T2 were compared. Results: The difference of HR, BP, and PetCO2 levels before operation among the three groups was not statistically significant (P>0.05. HR, BP, and PetCO2 levels 30 min after pneumoperitoneum were significantly elevated when compared with before operation (P0.05. PetCO2 level 30 min after pneumoperitoneum in group B was significantly higher than that in group A (P0.05. Conclusions: Low pneumoperitoneum pressure has a small effect on the stress state in patients underwent gynecological laparoscopy, will not affect the surgical operation, and can obtain a preferable muscular relaxation and vision field; therefore, it can be selected in preference.

  5. Application of nonlinear ultrasonic method for monitoring of stress state in concrete

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Gyu Jin; Kwak, Hyo Gyoung [Dept. of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Park, Sun Jong [Dept. of Structural System and Site Safety Evaluation, Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of)

    2016-04-15

    As the lifespan of concrete structures increases, their load carrying capacity decreases owing to cyclic loads and long-term effects such as creep and shrinkage. For these reasons, there is a necessity for stress state monitoring of concrete members. Particularly, it is necessary to evaluate the concrete structures for behavioral changes by using a technique that can overcome the measuring limitations of usual ultrasonic nondestructive evaluation methods. This paper proposes the use of a nonlinear ultrasonic method, namely, nonlinear resonant ultrasonic spectroscopy (NRUS) for the measurement of nonlinearity parameters for stress monitoring. An experiment compared the use of NRUS method and a linear ultrasonic method, namely, ultrasonic pulse velocity (UPV) to study the effects of continuously increasing loads and cyclic loads on the nonlinearity parameter. Both NRUS and UPV methods found a similar direct relationship between load level and that parameter. The NRUS method showed a higher sensitivity to micro-structural changes of concrete than UPV method. Thus, the experiment confirms the possibility of using the nonlinear ultrasonic method for stress state monitoring of concrete members.

  6. Seismicity and stress state in the South China Sea, Indochina and their vicinity

    Science.gov (United States)

    Zang, Shaoxian; Wu, Zhongliang; Li, Aibing

    1992-02-01

    The distribution of earthquakes from 1973 to 1982 in the South China Sea, Indochina and their vicinity was studied using the data from I. S. C. It was found that the earthquakes are mainly concentrated along the boundaries of plates. Beside, some of shallow eartqhuakes are distributed in west part of Burma and the boundary between Burma and China, a few of earthquakes occurred in South China Sea. The features of Benioff zone along the boundaries between India plate, Philippine Sea plate and Eurasia plate were studied. The plate do not coupled well under the Java trench and the Philippine trench. The subducted India plate under Burmese range, Andaman—Nicobar arc moves NNE. The fault plane solutions of earthquakes were studied using the first motions of P wave. The stress state on subduction zones and within the area were deduced from the fault plane solutions and the fault movement. It was found that the direction of principal compression axis of stress is in the NNE in west part of Burma, in S—N in south and middle part of Bruma and Thailand, and in NNE or S—N in the South China Sea. It was also found that the stress state has close relation with the interaction of plates.

  7. Application of nonlinear ultrasonic method for monitoring of stress state in concrete

    International Nuclear Information System (INIS)

    Kim, Gyu Jin; Kwak, Hyo Gyoung; Park, Sun Jong

    2016-01-01

    As the lifespan of concrete structures increases, their load carrying capacity decreases owing to cyclic loads and long-term effects such as creep and shrinkage. For these reasons, there is a necessity for stress state monitoring of concrete members. Particularly, it is necessary to evaluate the concrete structures for behavioral changes by using a technique that can overcome the measuring limitations of usual ultrasonic nondestructive evaluation methods. This paper proposes the use of a nonlinear ultrasonic method, namely, nonlinear resonant ultrasonic spectroscopy (NRUS) for the measurement of nonlinearity parameters for stress monitoring. An experiment compared the use of NRUS method and a linear ultrasonic method, namely, ultrasonic pulse velocity (UPV) to study the effects of continuously increasing loads and cyclic loads on the nonlinearity parameter. Both NRUS and UPV methods found a similar direct relationship between load level and that parameter. The NRUS method showed a higher sensitivity to micro-structural changes of concrete than UPV method. Thus, the experiment confirms the possibility of using the nonlinear ultrasonic method for stress state monitoring of concrete members

  8. Reliability assessment of stress concentration performance state for a perforated composite plate under traction

    Directory of Open Access Journals (Sweden)

    Jabbouri A.

    2012-07-01

    Full Text Available Considering a perforated sandwich plate made from two elastic homogenous and isotropic layers, and having a square hole, reliability assessment of stress concentration limit state for which the stress should not exceed a given threshold is performed in this work. Assuming that the plate dimensions and the applied loading are deterministic, focus is done on the square hole centre position and edge length considered to be random variables. The means and the standard deviations of these variables are assumed to be known, but no information is so far available about their densities of probabilities. To assess reliability of the performance state, reliability analysis known methods are applied to a response surface representation of the stress concentration factor of the perforated plate which is obtained through quadratic polynomial regression of finite element results. A parametric study is performed regarding the influence of the distributions of probabilities chosen to model the hole dimensions uncertainties. It is shown that the probability of failure depends largely on the selected densities of probabilities.

  9. Analysis of internal stress and anelasticity in the shock-compressed state from unloading wave data

    International Nuclear Information System (INIS)

    Johnson, J.N.; Lomdahl, P.S.; Wills, J.M.

    1991-01-01

    This paper reports on time resolved shock-wave measurements have often been used to infer microstructural behavior in crystalline solids. The authors apply this approach to an interpretation of the release-wave response of an aluminum alloy (6061-T6) as it is dynamically unloaded from a shock-compressed state of 20.7 GPa. The anelastic behavior in the initial portion of the unloading wave is attributed to the accumulation of internal stresses created by the shock process. Specific internal-stress models which are investigated are the double pile-up, the single pile-up, and single dislocation loops between pinning points. It is found that the essential characteristics of double and single pile-ups can be represented by a single dislocation between two pinned dislocations of like sing. Calculations of anelastic wave speeds at constant unloading strain rate are then compared with experimental data. The results suggest that the residual internal stress is due to pinned loops of density 10 15 M - 2 , and the viscous drag coefficient in the shock-compressed state is on the order of 10 - 7 MPa s (approximately two orders of magnitude greater than expected under ambient conditions)

  10. Assessment of Creep Deformation, Damage, and Rupture Life of 304HCu Austenitic Stainless Steel Under Multiaxial State of Stress

    Science.gov (United States)

    Sahoo, K. C.; Goyal, Sunil; Parameswaran, P.; Ravi, S.; Laha, K.

    2018-03-01

    The role of the multiaxial state of stress on creep deformation and rupture behavior of 304HCu austenitic stainless steel was assessed by performing creep rupture tests on both smooth and notched specimens of the steel. The multiaxial state of stress was introduced by incorporating circumferential U-notches of different root radii ranging from 0.25 to 5.00 mm on the smooth specimens of the steel. Creep tests were carried out at 973 K over the stress range of 140 to 220 MPa. In the presence of notch, the creep rupture strength of the steel was found to increase with the associated decrease in rupture ductility. Over the investigated stress range and notch sharpness, the strengthening was found to increase drastically with notch sharpness and tended toward saturation. The fractographic studies revealed the mixed mode of failure consisting of transgranular dimples and intergranular creep cavitation for shallow notches, whereas the failure was predominantly intergranular for relatively sharper notches. Detailed finite element analysis of stress distribution across the notch throat plane on creep exposure was carried out to assess the creep failure of the material in the presence of notch. The reduction in von-Mises stress across the notch throat plane, which was greater for sharper notches, increased the creep rupture strength of the material. The variation in fracture behavior of the material in the presence of notch was elucidated based on the von-Mises, maximum principal, and hydrostatic stresses. Electron backscatter diffraction analysis of creep strain distribution across the notch revealed localized creep straining at the notch root for sharper notches. A master curve for predicting creep rupture life under the multiaxial state of stress was generated considering the representative stress having contributions from both the von-Mises and principal stress components of the stress field in the notch throat plane. Rupture ductility was also predicted based on the

  11. Stress

    DEFF Research Database (Denmark)

    Keller, Hanne Dauer

    2015-01-01

    Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb.......Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb....

  12. Stress !!!

    OpenAIRE

    Fledderus, M.

    2012-01-01

    Twee op de vijf UT-studenten hebben last van ernstige studiestress, zo erg zelfs dat het ze in hun privéleven belemmert. Die cijfers komen overeen met het landelijk beeld van stress onder studenten. Samen met 14 andere universiteits- en hogeschoolbladen enquêteerde UT Nieuws bijna 5500 studenten. Opvallend is dat mannelijke studenten uit Twente zich veel minder druk lijken te maken over hun studie. Onder vrouwen ligt de stress juist erg hoog ten opzichte van het landelijk gemiddelde.

  13. Modeling assumptions influence on stress and strain state in 450 t cranes hoisting winch construction

    Directory of Open Access Journals (Sweden)

    Damian GĄSKA

    2011-01-01

    Full Text Available This work investigates the FEM simulation of stress and strain state of the selected trolley’s load-carrying structure with 450 tones hoisting capacity [1]. Computational loads were adopted as in standard PN-EN 13001-2. Model of trolley was built from several cooperating with each other (in contact parts. The influence of model assumptions (simplification in selected construction nodes to the value of maximum stress and strain with its area of occurrence was being analyzed. The aim of this study was to determine whether the simplification, which reduces the time required to prepare the model and perform calculations (e.g., rigid connection instead of contact are substantially changing the characteristics of the model.

  14. Experimental and Numerical Analysis of Microstructures and Stress States of Shot-Peened GH4169 Superalloys

    Science.gov (United States)

    Hu, Dianyin; Gao, Ye; Meng, Fanchao; Song, Jun; Wang, Rongqiao

    2018-04-01

    Combining experiments and finite element analysis (FEA), a systematic study was performed to analyze the microstructural evolution and stress states of shot-peened GH4169 superalloy over a variety of peening intensities and coverages. A dislocation density evolution model was integrated into the representative volume FEA model to quantitatively predict microstructural evolution in the surface layers and compared with experimental results. It was found that surface roughness and through-depth residual stress profile are more sensitive to shot-peening intensity compared to coverage due to the high kinetic energy involved. Moreover, a surface nanocrystallization layer was discovered in the top surface region of GH4169 for all shot-peening conditions. However, the grain refinement was more intensified under high shot-peening coverage, under which enough time was permitted for grain refinement. The grain size gradient predicted by the numerical framework showed good agreement with experimental observations.

  15. Stress and food deprivation: linking physiological state to migration success in a teleost fish

    DEFF Research Database (Denmark)

    Midwood, J.D.; Larsen, Martin Hage; Aarestrup, Kim

    2016-01-01

    for the cortisol treatment. Food availability and individual energetic state appear to dictate the future life-history strategy (migrate or remain resident) of juvenile salmonids while experimental elevation of the stress hormone cortisol caused impaired growth and reduced survival of both resident and migratory......Food deprivation (FD) is a naturally occurring stressor that is thought to influence the ultimate life-history strategy of individuals. Little is known about how FD interacts with other stressors to influence migration success. European populations of brown trout (Salmo trutta) exhibit partial...... of the glucocorticoid stress response in determining life-history strategy and survival of a migratory species. Using an experimental approach, the relative influences of short-term FD and experimental cortisol elevation (i.e., intra-coelomic injection of cortisol suspended in cocoa butter) on migratory status...

  16. Diffraction by a grating made of a uniaxial dielectric-magnetic medium exhibiting negative refraction

    Energy Technology Data Exchange (ETDEWEB)

    Depine, Ricardo A [Grupo de Electromagnetismo Aplicado, Departamento de FIsica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellon I, 1428 Buenos Aires (Argentina); Lakhtakia, Akhlesh [CATMAS-Computational and Theoretical Materials Sciences Group, Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, PA 16802-6812 (United States); Department of Physics, Imperial College, London SW7 2BZ (United Kingdom)

    2005-08-01

    Diffraction of linearly polarized plane electromagnetic waves at the periodically corrugated boundary of vacuum and a linear, homogeneous, uniaxial, dielectric-magnetic medium is formulated as a boundary-value problem and solved using the Rayleigh method. The focus is on situations where the diffracted fields maintain the same polarization state as the s- or p-polarized incident plane wave. Attention is paid to two classes of diffracting media: those with negative definite permittivity and permeability tensors, and those with indefinite permittivity and permeability tensors. For the situations investigated, whereas the dispersion equations in the diffracting medium turn out to be elliptic for the first class of diffracting media, they are hyperbolic for the second class. Examples are reported with the first class of diffracting media of instances when the grating acts either as a positively refracting interface or as a negatively refracting interface. For the second class of diffracting media, hyperbolic dispersion equations imply the possibility of an infinite number of refraction channels.

  17. Diffraction by a grating made of a uniaxial dielectric-magnetic medium exhibiting negative refraction

    International Nuclear Information System (INIS)

    Depine, Ricardo A; Lakhtakia, Akhlesh

    2005-01-01

    Diffraction of linearly polarized plane electromagnetic waves at the periodically corrugated boundary of vacuum and a linear, homogeneous, uniaxial, dielectric-magnetic medium is formulated as a boundary-value problem and solved using the Rayleigh method. The focus is on situations where the diffracted fields maintain the same polarization state as the s- or p-polarized incident plane wave. Attention is paid to two classes of diffracting media: those with negative definite permittivity and permeability tensors, and those with indefinite permittivity and permeability tensors. For the situations investigated, whereas the dispersion equations in the diffracting medium turn out to be elliptic for the first class of diffracting media, they are hyperbolic for the second class. Examples are reported with the first class of diffracting media of instances when the grating acts either as a positively refracting interface or as a negatively refracting interface. For the second class of diffracting media, hyperbolic dispersion equations imply the possibility of an infinite number of refraction channels

  18. Brittle Creep Failure, Critical Behavior, and Time-to-Failure Prediction of Concrete under Uniaxial Compression

    Directory of Open Access Journals (Sweden)

    Yingchong Wang

    2015-01-01

    Full Text Available Understanding the time-dependent brittle deformation behavior of concrete as a main building material is fundamental for the lifetime prediction and engineering design. Herein, we present the experimental measures of brittle creep failure, critical behavior, and the dependence of time-to-failure, on the secondary creep rate of concrete under sustained uniaxial compression. A complete evolution process of creep failure is achieved. Three typical creep stages are observed, including the primary (decelerating, secondary (steady state creep regime, and tertiary creep (accelerating creep stages. The time-to-failure shows sample-specificity although all samples exhibit a similar creep process. All specimens exhibit a critical power-law behavior with an exponent of −0.51 ± 0.06, approximately equal to the theoretical value of −1/2. All samples have a long-term secondary stage characterized by a constant strain rate that dominates the lifetime of a sample. The average creep rate expressed by the total creep strain over the lifetime (tf-t0 for each specimen shows a power-law dependence on the secondary creep rate with an exponent of −1. This could provide a clue to the prediction of the time-to-failure of concrete, based on the monitoring of the creep behavior at the steady stage.

  19. Characterization of degradation products of amorphous and polymorphic forms of clopidogrel bisulphate under solid state stress conditions

    DEFF Research Database (Denmark)

    Raijada, Dhara K; Prasad, Bhagwat; Paudel, Amrit

    2010-01-01

    The present study deals with the stress degradation studies on amorphous and polymorphic forms of clopidogrel bisulphate. The objective was to characterize the degradation products and postulate mechanism of decomposition of the drug under solid state stress conditions. For that, amorphous form, ...

  20. Relationships among Career and Life Stress, Negative Career thoughts, and Career Decision State: A Cognitive Information Processing Perspective

    Science.gov (United States)

    Bullock-Yowell, Emily; Peterson, Gary W.; Reardon, Robert C.; Leierer, Stephen J.; Reed, Corey A.

    2011-01-01

    According to cognitive information processing theory, career thoughts mediate the relationship between career and life stress and the ensuing career decision state. Using a sample of 232 college students and structural equation modeling, this study found that an increase in career and life stress was associated with an increase in negative career…

  1. Stress-free states of continuum dislocation fields : Rotations, grain boundaries, and the Nye dislocation density tensor

    NARCIS (Netherlands)

    Limkumnerd, Surachate; Sethna, James P.

    We derive general relations between grain boundaries, rotational deformations, and stress-free states for the mesoscale continuum Nye dislocation density tensor. Dislocations generally are associated with long-range stress fields. We provide the general form for dislocation density fields whose

  2. Flow stress anisotropy in aluminium

    DEFF Research Database (Denmark)

    Juul Jensen, D.; Hansen, N.

    1990-01-01

    The plastic anisotropy of cold-rolled high purity aluminum (99.996%) and commercially pure aluminum (99.6%) has been investigated. Sample parameters were the initial grain size and the degree of plastic strain (ϵ < 3.00). Flow stresses (0.2% offset) were measured at room temperature by uniaxial t...

  3. Applicability of initial stress measurement methods to Horonobe Siliceous rocks and initial stress state around Horonobe Underground Research Laboratory

    International Nuclear Information System (INIS)

    Sanada, Hiroyuki; Niunoya, Sumio; Matsui, Hiroya; Fujii, Yoshiaki

    2009-01-01

    Understanding initial stress condition in deep underground is important for such construction as rock cavern for geological disposal of HLW and underground power plant. Neogene sedimentary rock is widely distributed in Japan. There are only a few studies of initial stress measurement in Neogene sedimentary rock mass in Japan due to difficulty of measurement. Evaluation of initial stress condition around Horonobe Underground Research Laboratory Project was carried out in order to understand initial stress condition and applicability of AE, DSCA and hydraulic fracturing (HF) methods to Neogene sedimentary rock. Initial stress values obtained from AE method is smaller than overburden pressure due to time dependency of Kaizer effect. It would be difficult to use AE method as initial stress measurement method for Horonobe Siliceous rocks. Principal stress values by DSCA are similar to those by HF tests. Directions of maximum horizontal principal stresses are approximately in E-W and corresponded to HF results. In HF, rod type and wire-line type systems were compared. Workability of rod type was much better than wire-line type. However, re-opening pressure were not able to be precisely measured in case of rod type system due to the large compliance of the packers and rods. Horizontal maximum and minimum principal stresses increase linearly in HF results. Deviatoric stress is acting at shallow depth. Initial stress condition approaches hydrostatic condition with depth. Direction of maximum horizontal principal stress was in E-W direction which was similar to tectonic movement around Horonobe URL by triangular surveying. (author)

  4. Dry fracture method for simultaneous measurement of in-situ stress state and material properties

    International Nuclear Information System (INIS)

    Serata, S.; Oka, S.; Kikuchi, S.

    1996-01-01

    Based on the dry fracture principle, a computerized borehole probe has been developed to measure stress state and material properties, simultaneously. The probe is designed to obtain a series of measurements in a continuing sequence along a borehole length, without any interruptive measures, such as resetting packers, taking indentation of borehole wall, overcoming, etc. The new dry fracture probe for the single fracture method is designed to overcome the difficulties posed by its ancestor which was based on the double fracture method. The accuracy of the single fracture method is confirmed by a close agreement with the theory, FE modeling and laboratory testing

  5. Main results of BN-600 reactor stress-strain state investigations

    International Nuclear Information System (INIS)

    Panov, V.A.

    1983-01-01

    The development of BN-600 fast reactor plant needed the solution of a series of complex engineering problems including ones for confirming integrity of the most vital structural components. The particular attention was given to the main vessel since reactor availability end safe operation of the plant as a whole depend on vessel strength end integrity. The present report deals with the main results of theoretical and experimental investigations of the stress-strain state of BN-600 reactor vessel carried out during design, start-up and initial bringing the reactor to power

  6. Fabrication of imitative stress corrosion cracking specimens suitable for electromagnetic nondestructive evaluations using solid state bonding

    International Nuclear Information System (INIS)

    Yusa, Noritaka; Hashizume, Hidetoshi; Uchimoto, Tetsuya; Takagi, Toshiyuki

    2011-01-01

    This study proposes a method to fabricate an artificial defect that is almost identical to stress corrosion cracking from the viewpoint of electromagnetic nondestructive evaluations. The key idea is to realize a region having electrical resistance embedded inside a conductive materials using solid state bonding. A rough region is introduced into the surface of the materials to be bonded so that the region is partially bonded to realize electrical resistance. Experimental demonstrations are carried out using type 316L austenitic stainless steels. Eddy current tests and subsequent numerical evaluations are conducted to discuss the validity of the proposed method. (author)

  7. Determination of stress-strain state of the wooden church log walls with software package

    Directory of Open Access Journals (Sweden)

    Chulkova Anastasia

    2016-01-01

    Full Text Available The restoration of architectural monuments is going on all over the world today. The main aim of restoration is the renewal of stable functioning of building constructions in normal state. In this article, we have tried to figure out with special software the bearing capacity of log cabins of the Church of Transfiguration on Kizhi island. As shown in research results, determination of stress-strain stage with software package is necessary for the bearing capacity computation as well as field tests.

  8. Evaluation of the state of stress at the Forsmark site. Preliminary site investigation Forsmark area - version 1.2

    Energy Technology Data Exchange (ETDEWEB)

    Sjoeberg, Jonny; Lindfors, Ulf; Perman, Fredrik; Ask, Daniel [SwedPower AB, Stockholm (Sweden)

    2005-09-15

    This report presents an evaluation of the state of stress at the Forsmark site, based on all conducted stress measurements to date at the site, indirect stress estimates, geological and tectonic description of the site, and regional stress data from nearby locations. The work included (i) compilation of measurement results from Forsmark, as well as from nearby (regional) sites/locations, (ii) analysis of confidence intervals for each group of measurement, (iii) assessment of the stress state for the Forsmark site accounting for geological/tectonic evolution at the site, (iv) assessment of stress state for selected nearby (regional) sites/locations, and (v) comparison and combined interpretation of similarities and/or differences in stress state from a regional perspective. The combined assessment of the local (site-scale) and regional stress data for Forsmark showed that the major stress is orientated sub-horizontally and trending NW-SE; however, with significant local variation. A thrust faulting ({sigma}H > {sigma}h > {sigma}v) or possibly strike-slip faulting ({sigma}H > {sigma}v > {sigma}h) stress regime is evident at the Forsmark site. The maximum horizontal stress tends to be higher at the site compared to nearby sites and regional conditions. The site and regional data indicate that the vertical stress seems to be solely due to the overburden pressure. The lack of solid core discing for large portions of the boreholes at Forsmark was used to estimate an upper limit of the maximum horizontal stress magnitude. However, such an estimation is highly uncertain due to e.g. partly unknown mechanism for core discing failure, and unknown effects of the simplifying assumptions made in the analysis. The possible effects of shallow-dipping deformation zones on the stress state, could not be verified from the currently available data. However, the possibility of different stress regimes above and below deformation zones must be considered in future work. Slightly lower

  9. Evaluation of the state of stress at the Forsmark site. Preliminary site investigation Forsmark area - version 1.2

    International Nuclear Information System (INIS)

    Sjoeberg, Jonny; Lindfors, Ulf; Perman, Fredrik; Ask, Daniel

    2005-09-01

    This report presents an evaluation of the state of stress at the Forsmark site, based on all conducted stress measurements to date at the site, indirect stress estimates, geological and tectonic description of the site, and regional stress data from nearby locations. The work included (i) compilation of measurement results from Forsmark, as well as from nearby (regional) sites/locations, (ii) analysis of confidence intervals for each group of measurement, (iii) assessment of the stress state for the Forsmark site accounting for geological/tectonic evolution at the site, (iv) assessment of stress state for selected nearby (regional) sites/locations, and (v) comparison and combined interpretation of similarities and/or differences in stress state from a regional perspective. The combined assessment of the local (site-scale) and regional stress data for Forsmark showed that the major stress is orientated sub-horizontally and trending NW-SE; however, with significant local variation. A thrust faulting (σH > σh > σv) or possibly strike-slip faulting (σH > σv > σh) stress regime is evident at the Forsmark site. The maximum horizontal stress tends to be higher at the site compared to nearby sites and regional conditions. The site and regional data indicate that the vertical stress seems to be solely due to the overburden pressure. The lack of solid core discing for large portions of the boreholes at Forsmark was used to estimate an upper limit of the maximum horizontal stress magnitude. However, such an estimation is highly uncertain due to e.g. partly unknown mechanism for core discing failure, and unknown effects of the simplifying assumptions made in the analysis. The possible effects of shallow-dipping deformation zones on the stress state, could not be verified from the currently available data. However, the possibility of different stress regimes above and below deformation zones must be considered in future work. Slightly lower horizontal stress was found in

  10. Experimental study on infrared radiation temperature field of concrete under uniaxial compression

    Science.gov (United States)

    Lou, Quan; He, Xueqiu

    2018-05-01

    Infrared thermography, as a nondestructive, non-contact and real-time monitoring method, has great significance in assessing the stability of concrete structure and monitoring its failure. It is necessary to conduct in depth study on the mechanism and application of infrared radiation (IR) of concrete failure under loading. In this paper, the concrete specimens with size of 100 × 100 × 100 mm were adopted to carry out the uniaxial compressions for the IR tests. The distribution of IR temperatures (IRTs), surface topography of IRT field and the reconstructed IR images were studied. The results show that the IRT distribution follows the Gaussian distribution, and the R2 of Gaussian fitting changes along with the loading time. The abnormities of R2 and AE counts display the opposite variation trends. The surface topography of IRT field is similar to the hyperbolic paraboloid, which is related to the stress distribution in the sample. The R2 of hyperbolic paraboloid fitting presents an upward trend prior to the fracture which enables to change the IRT field significantly. This R2 has a sharp drop in response to this large destruction. The normalization images of IRT field, including the row and column normalization images, were proposed as auxiliary means to analyze the IRT field. The row and column normalization images respectively show the transverse and longitudinal distribution of the IRT field, and they have clear responses to the destruction occurring on the sample surface. In this paper, the new methods and quantitative index were proposed for the analysis of IRT field, which have some theoretical and instructive significance for the analysis of the characteristics of IRT field, as well as the monitoring of instability and failure for concrete structure.

  11. Cracking and Failure in Rock Specimen Containing Combined Flaw and Hole under Uniaxial Compression

    Directory of Open Access Journals (Sweden)

    Xiang Fan

    2018-01-01

    Full Text Available Flaw is a key factor influencing failure behavior of a fractured specimen. In the present study, rectangular-flawed specimens were prepared using sandstone to investigate the effect of flaw on failure behavior of rock. Open flaw and cylindrical hole were simultaneously precut within rock specimens using high-pressure water jet cutting technology. Five series of specimens including intact, single-hole-alone, two-hole-alone, single-hole and two-flaw, and two-hole and single-flaw blocks were prepared. Uniaxial compressive tests using a rigid servo control instrument were carried out to investigate the fracture processes of these flawed specimens. It is observed that during loading, internal stress always intensively distributed at both sidewalls of open hole, especially at midpoint of sidewalls, so rock crumb flaking was firstly observed among all sandstone specimens containing single hole or two holes. Cracking around open hole is associated with the flaw inclination angle which was observed in Series III and V. Crack easily initiated at the tips of flaw with inclination angles of 0°, 30°, and 60° but hard for 90° in Series III and V. Rock burst was the major failure mode among most tested specimens, which generally induced new cracks and finally created crater shape. Additionally, due to extrusion between blocks, new shear or tensile cracks were generated and the rock specimen surface spalled. Eventually, four typical failure processes including rock crumb flaking, crack initiation and propagation, rock burst, and second rupture, were summarized.

  12. Parenting stress as a mediator of parents' negative mood state and behavior problems in children with newly diagnosed cancer.

    Science.gov (United States)

    van der Geest, Ivana M; van den Heuvel-Eibrink, Marry M; Passchier, Jan; van den Hoed-Heerschop, Corry; Pieters, Rob; Darlington, Anne-Sophie E

    2014-07-01

    The aim was to investigate the influence of parents' negative mood state and parenting stress on behavior in children with newly diagnosed cancer. A total of 123 parents (n=58 fathers, n=65 mothers) of 67 children with newly diagnosed cancer completed three questionnaires separately at the same time measuring parents' negative mood state, parenting stress, and child behavior problems. Parents' negative mood state was weakly correlated to more child behavior problems (r=0.31, pparenting stress were strongly correlated to more child behavior problems (r=0.61, pparents' negative mood state and child behavior problems (c=0.29, p=0.02 (fathers); c=0.25, p=0.04 (mothers)) became non-significant after mediating for parenting stress (c'=0.003, p=0.98 (fathers); c'=0.10, p=0.42 (mothers)). The indirect effect of parents' negative mood state and child behavior problems was only significant for fathers (95% CI [0.12; 0.51]), indicating that parenting stress mediates the effect between fathers' negative mood state and child behavior problems. This is the first study to demonstrate the mediational role of parenting stress in fathers of a child with newly diagnosed cancer. Copyright © 2014 John Wiley & Sons, Ltd.

  13. Effect of Strength Coefficient of Bainite on Micromechanical Deformation and Failure Behaviors of Hot-Rolled 590FB Steel during Uniaxial Tension

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Eun-Young; Choi, Shi-Hoon [Sunchon National University, Suncheon (Korea, Republic of); Kim, Sung Il [POSCO Technical Research Laboratories, Gwangyang (Korea, Republic of)

    2016-11-15

    The effect of the strength coefficient (K{sub B}) of bainite on micromechanical deformation and failure behaviors of a hot-rolled 590MPa steel (590FB) during uniaxial tension was simulated using the elasto-plastic finite element method (FEM). The spatial distribution of the constituent phases was obtained using a phase identification technique based on optical microstructure. Empirical equations which depend on chemical composition were used to determine the stress-strain relationship of the constituent phases of the 590FB steel. The stress-strain partitioning and failure behavior were analyzed by increasing the K{sub B} of bainite. The elasto-plastic FEM results revealed that effective strain in the ferrite-bainite boundaries, and maximum principal stress in fibrous bainite, were enhanced as the K{sub B} increased. The elasto-plastic FEM results also demonstrated that the K{sub B} significantly affects the micromechanical deformation and failure behaviors of the hot-rolled 590FB steel during uniaxial tension.

  14. Effect of thermal exposure on the residual stress relaxation in a hardened cylindrical sample under creep conditions

    Science.gov (United States)

    Radchenko, V. P.; Saushkin, M. N.; Tsvetkov, V. V.

    2016-05-01

    This paper describes the effect of thermal exposure (high-temperature exposure) ( T = 675°C) on the residual creep stress relaxation in a surface hardened solid cylindrical sample made of ZhS6UVI alloy. The analysis is carried out with the use of experimental data for residual stresses after micro-shot peening and exposures to temperatures equal to T = 675°C during 50, 150, and 300 h. The paper presents the technique for solving the boundary-value creep problem for the hardened cylindrical sample with the initial stress-strain state under the condition of thermal exposure. The uniaxial experimental creep curves obtained under constant stresses of 500, 530, 570, and 600 MPa are used to construct the models describing the primary and secondary stages of creep. The calculated and experimental data for the longitudinal (axial) tensor components of residual stresses are compared, and their satisfactory agreement is determined.

  15. Study of stress-strain state of pipeline under permafrost conditions

    Science.gov (United States)

    Tarasenko, A. A.; Redutinskiy, M. N.; Chepur, P. V.; Gruchenkova, A. A.

    2018-05-01

    In this paper, the dependences of the stress-strain state and subsidence of pipelines on the dimensions of the subsidence zone are obtained for the sizes of pipes that have become most widespread during the construction of main oil pipelines (530x10, 820x12, 1020x12, 1020x14, 1020x16, 1220x14, 1220x16, 1220x18 mm). True values of stresses in the pipeline wall, as well as the exact location of maximum stresses for the interval of subsidence zones from 5 to 60 meters, are determined. For this purpose, the authors developed a finite element model of the pipeline that takes into account the actual interaction of the pipeline with the subgrade and allows calculating the SSS of the structure for a variable subsidence zone. Based on the obtained dependences for the underground laying of oil pipelines in permafrost areas, it is proposed to artificially limit the zone of possible subsidence by separation supports from the soil with higher building properties and physical-mechanical parameters. This technical solution would significantly reduce costs when constructing new oil pipelines in permafrost areas.

  16. Uniaxial Pressure Effect on the SdH Oscillations in Heavy-Fermion Semimetal CeRu4Sb12

    International Nuclear Information System (INIS)

    Saha, S. R.; Kobayashi, M.; Sugawara, H.; Namiki, T.; Abe, K.; Aoki, Y.; Sato, H.

    2003-01-01

    We report the first successful Shubnikov-de Haas (SdH) experiment under uniaxial pressure in the anomalous heavy-fermion semimetal CeRu 4 Sb 12 . The nature of the quantum oscillations in the magnetoresistance is found to be significantly sensitive to uniaxial pressure. The results reveal that the nearly spherical Fermi surface elongates along the direction of the uniaxial pressure. (author)

  17. Mechanical and electronic properties of monolayer and bilayer phosphorene under uniaxial and isotropic strains.

    Science.gov (United States)

    Hu, Ting; Han, Yang; Dong, Jinming

    2014-11-14

    The mechanical and electronic properties of both the monolayer and bilayer phosphorenes under either isotropic or uniaxial strain have been systematically investigated using first-principles calculations. It is interesting to find that: 1) Under a large enough isotropic tensile strain, the monolayer phosphorene would lose its pucker structure and transform into a flat hexagonal plane, while two inner sublayers of the bilayer phosphorene could be bonded due to its interlayer distance contraction. 2) Under the uniaxial tensile strain along a zigzag direction, the pucker distance of each layer in the bilayer phosphorene can exhibit a specific negative Poisson's ratio. 3) The electronic properties of both the monolayer and bilayer phosphorenes are sensitive to the magnitude and direction of the applied strains. Their band gaps decrease more rapidly under isotropic compressive strain than under uniaxial strain. Also, their direct-indirect band gap transitions happen at the larger isotropic tensile strains compared with that under uniaxial strain. 4) Under the isotropic compressive strain, the bilayer phosphorene exhibits a transition from a direct-gap semiconductor to a metal. In contrast, the monolayer phosphorene initially has the direct-indirect transition and then transitions to a metal. However, under isotropic tensile strain, both the bilayer and monolayer phosphorene show the direct-indirect transition and, finally, the transition to a metal. Our numerical results may open new potential applications of phosphorene in nanoelectronics and nanomechanical devices by external isotropic strain or uniaxial strain along different directions.

  18. Nutritional mitigation of winter thermal stress in gilthead seabream associated metabolic pathways and potential indicators of nutritional state

    DEFF Research Database (Denmark)

    Richard, Nadege; Silva, Tomé S.; Wulff, Tune

    2016-01-01

    and phenylalanine/tyrosine catabolism, and induced higher aerobic metabolism and gluconeogenesis. Results support the notion that WF diet had a positive effect on fish nutritional state by partially counteracting the effect of thermal stress and underlined the sensitivity of proteome data for nutritional....... A total of 404 protein spots, out of 1637 detected, were differentially expressed between the two groups of fish. Mass spectrometry analysis of selected spots suggested that WF diet improved oxidative stress defense, reduced endoplasmic reticulum stress, enhanced metabolic flux through methionine cycle...... and metabolic profiling purposes. Intragroup variability and co-measured information were also used to pinpoint which proteins displayed a stronger relation with fish nutritional state....

  19. Stress-strain state analysis and optimization of rod system under periodic pulse load

    Directory of Open Access Journals (Sweden)

    Grebenyuk Grigory

    2018-01-01

    Full Text Available The paper considers the problem of analysis and optimization of rod systems subjected to combined static and periodic pulse load. As a result of the study the analysis method was developed based on traditional approach to solving homogeneous matrix equations of state and a special algorithm for developing a particular solution. The influence of pulse parameters variations on stress-strain state of a rod system was analyzed. Algorithms for rod systems optimization were developed basing on strength recalculation and statement and solution of optimization problem as a problem of nonlinear mathematical programming. Recommendations are developed for efficient organization of process for optimization of rod systems under static and periodic pulse load.

  20. Stress !!!

    NARCIS (Netherlands)

    Fledderus, M.

    2012-01-01

    Twee op de vijf UT-studenten hebben last van ernstige studiestress, zo erg zelfs dat het ze in hun privéleven belemmert. Die cijfers komen overeen met het landelijk beeld van stress onder studenten. Samen met 14 andere universiteits- en hogeschoolbladen enquêteerde UT Nieuws bijna 5500 studenten.

  1. Strain Capacity of Reinforced Concrete Members Subjected to Uniaxial Tension

    DEFF Research Database (Denmark)

    Hagsten, Lars German; Rasmussen, Annette Beedholm; Fisker, Jakob

    2017-01-01

    The aim of this paper is to set up a method to determine the strain capacity of tension bars of reinforced concrete (RC) subjected to pure tension. Due to the interaction between reinforcement and concrete and due to the presence of cracks, the stresses in both reinforcement and concrete...... are varying along the length of the tension bar. The strain capacity of the tension bar is seen as the average strain in the reinforcement at the load level corresponding to the ultimate stress capacity of the reinforcement at the cracks. The result of the approach is in overall good agreement when comparing...

  2. Extracellular redox state: refining the definition of oxidative stress in aging.

    Science.gov (United States)

    Jones, Dean P

    2006-01-01

    Oxidative stress in aging can result from an imbalance of prooxidants and antioxidants with excessive, destructive free radical chemistry. Thiol systems are important in the control of these processes, both by protecting against damage and serving in redox signaling mechanisms to sense danger and repair the damage. Studies by a number of research groups in collaboration with the Emory Clinical Biomarkers Laboratory show that the redox state of the central tissue antioxidant, glutathione (GSH), can be measured in human plasma and provides a quantitative systemic indicator of oxidative stress. Plasma GSH/GSSG redox in humans becomes oxidized with age, in response to chemotherapy, as a consequence of cigarette smoking, and in association with common age-related diseases (e.g., type 2 diabetes, cardiovascular disease). However, the GSH/GSSG redox is not equilibrated with the larger plasma cysteine/cystine (Cys/CySS) pool, and the Cys/CySS redox varies with age in a pattern that is distinct from that of GSH/GSSG redox. Furthermore, in vitro studies show that variation in Cys/CySS redox over the range found in vivo affects signaling pathways, which control cell proliferation and oxidant-induced apoptosis. The results point to the conclusion that free radical scavenging antioxidants are of increased importance when thiol/disulfide redox states are oxidized. Because thiol/disulfide redox states, per se, function in redox signaling and control as well as antioxidant protection, GSH/GSSG and Cys/CySS redox states may provide central parameters to link environmental influences and progression of changes associated with aging.

  3. Oxidative stress markers in hypertensive states of pregnancy: preterm and term disease.

    Directory of Open Access Journals (Sweden)

    Lesia Olha Kurlak

    2014-08-01

    Full Text Available Discussion continues as to whether de novo hypertension in pregnancy with significant proteinuria (pre-eclampsia; PE and non-proteinuric new hypertension (gestational hypertension; GH are parts of the same disease spectrum or represent different conditions. Non-pregnant hypertension, pregnancy and PE are all associated with oxidative stress. We have established a 6 weeks post-partum clinic for women who experienced a hypertensive pregnancy. We hypothesized that PE and GH could be distinguished by markers of oxidative stress; thiobarbituric acid reactive substances (TBARS and antioxidants (ferric ion reducing ability of plasma; FRAP. Since the severity of PE and GH is greater pre-term, we also compared pre-term and term disease. Fifty-eight women had term PE, 23 pre-term PE, 60 had term GH and 6 pre-term GH, 11 pre-existing (essential hypertension (EH without PE. Limited data were available from normotensive pregnancies (n=7 and non-pregnant controls (n=14. There were no differences in postpartum TBARS or FRAP between hypertensive states; TBARS (P=0.001 and FRAP (P=0.009 were lower in plasma of non-pregnant controls compared to recently-pregnant women. Interestingly FRAP was higher in preterm than term GH (P=0.013. In PE and GH, TBARS correlated with low density lipoprotein (LDL-cholesterol (P=0.036; this association strengthened with inclusion of EH ((P=0.011. The 10 year Framingham index for cardiovascular risk was positively associated with TBARS (P=0.003.Oxidative stress profiles do not differ between hypertensive states but appear to distinguish between recently-pregnant and non-pregnant states. This suggests that pregnancy may alter vascular integrity with changes remaining 6 weeks postpartum. LDL-cholesterol is a known determinant of oxidative stress in cardiovascular disease and we have shown this association to be present in hypertensive pregnancy further emphasizing that such a pregnancy may be revealing a pre-existing cardiovascular

  4. Baseline and post-stress seasonal changes in immunocompetence and redox state maintenance in the fishing bat Myotis vivesi

    Science.gov (United States)

    Ibáñez-Contreras, Alejandra; Miranda-Labra, Roxana U.; Flores-Martínez, José Juan

    2018-01-01

    Little is known of how the stress response varies when animals confront seasonal life-history processes. Antioxidant defenses and damage caused by oxidative stress and their link with immunocompetence are powerful biomarkers to assess animal´s physiological stress response. The aim of this study was A) to determine redox state and variation in basal (pre-acute stress) immune function during summer, autumn and winter (spring was not assessed due to restrictions in collecting permit) in the fish-eating Myotis (Myotis vivesi; Chiroptera), and B) to determine the effect of acute stress on immunocompetence and redox state during each season. Acute stress was stimulated by restricting animal movement for 6 and 12 h. The magnitude of the cellular immune response was higher during winter whilst that of the humoral response was at its highest during summer. Humoral response increased after 6 h of movement restriction stress and returned to baseline levels after 12 h. Basal redox state was maintained throughout the year, with no significant changes in protein damage, and antioxidant activity was modulated mainly in relation to variation to environment cues, increasing during high temperatures and decreasing during windy nights. Antioxidant activity increased after the 6 h of stressful stimuli especially during summer and autumn, and to a lesser extent in early winter, but redox state did not vary. However, protein damage increased after 12 h of stress during summer. Prolonged stress when the bat is engaged in activities of high energy demand overcame its capacity to maintain homeostasis resulting in oxidative damage. PMID:29293551

  5. Obesity-Associated Oxidative Stress: Strategies Finalized to Improve Redox State

    Directory of Open Access Journals (Sweden)

    Valeria Gasperi

    2013-05-01

    Full Text Available Obesity represents a major risk factor for a plethora of severe diseases, including diabetes, cardiovascular disease, non-alcoholic fatty liver disease, and cancer. It is often accompanied by an increased risk of mortality and, in the case of non-fatal health problems, the quality of life is impaired because of associated conditions, including sleep apnea, respiratory problems, osteoarthritis, and infertility. Recent evidence suggests that oxidative stress may be the mechanistic link between obesity and related complications. In obese patients, antioxidant defenses are lower than normal weight counterparts and their levels inversely correlate with central adiposity; obesity is also characterized by enhanced levels of reactive oxygen or nitrogen species. Inadequacy of antioxidant defenses probably relies on different factors: obese individuals may have a lower intake of antioxidant- and phytochemical-rich foods, such as fruits, vegetables, and legumes; otherwise, consumption of antioxidant nutrients is normal, but obese individuals may have an increased utilization of these molecules, likewise to that reported in diabetic patients and smokers. Also inadequate physical activity may account for a decreased antioxidant state. In this review, we describe current concepts in the meaning of obesity as a state of chronic oxidative stress and the potential interventions to improve redox balance.

  6. Obesity-Associated Oxidative Stress: Strategies Finalized to Improve Redox State

    Science.gov (United States)

    Savini, Isabella; Catani, Maria Valeria; Evangelista, Daniela; Gasperi, Valeria; Avigliano, Luciana

    2013-01-01

    Obesity represents a major risk factor for a plethora of severe diseases, including diabetes, cardiovascular disease, non-alcoholic fatty liver disease, and cancer. It is often accompanied by an increased risk of mortality and, in the case of non-fatal health problems, the quality of life is impaired because of associated conditions, including sleep apnea, respiratory problems, osteoarthritis, and infertility. Recent evidence suggests that oxidative stress may be the mechanistic link between obesity and related complications. In obese patients, antioxidant defenses are lower than normal weight counterparts and their levels inversely correlate with central adiposity; obesity is also characterized by enhanced levels of reactive oxygen or nitrogen species. Inadequacy of antioxidant defenses probably relies on different factors: obese individuals may have a lower intake of antioxidant- and phytochemical-rich foods, such as fruits, vegetables, and legumes; otherwise, consumption of antioxidant nutrients is normal, but obese individuals may have an increased utilization of these molecules, likewise to that reported in diabetic patients and smokers. Also inadequate physical activity may account for a decreased antioxidant state. In this review, we describe current concepts in the meaning of obesity as a state of chronic oxidative stress and the potential interventions to improve redox balance. PMID:23698776

  7. The Autonomous Stress Indicator for Remotely Monitoring Power System State and Watching for Potential Instability

    Directory of Open Access Journals (Sweden)

    Geza Joos

    2009-02-01

    Full Text Available The proposed Autonomous Stress Indicator (ASI is a device that monitors the contents of the protection relays on a suspect weak power system bus and generates a performance level related to the degree of system performance degradation or instability. This gives the system operators some time (minutes to take corrective action. In a given operating area there would not likely be a need for an ASI on every bus. Note that the ASI does not trip any breakers; it is an INFORMATION ONLY device. An important feature is that the system operator can subsequently interrogate the ASI to determine the factor(s that led to the performance level that has been initially annunciated, thereby leading to a course of action. This paper traces the development of the ASI which is an ongoing project. The ASI could be also described as a stress-alert device whose function is to alert the System Operator of a stressful condition at its location. The characteristics (or essential qualities of this device are autonomy, selectivity, accuracy and intelligence. These will fulfill the requirements of the recommendation of the Canada –US Task Force in the August 2003 system collapse. Preliminary tests on the IEEE 39-bus model indicate that the concept has merit and development work is in progress. While the ASI can be applied to all power system operating conditions, its principal application is to the degraded state of the system where the System Operator must act to restore the system to the secure state before it migrates to a stage of collapse. The work of ASI actually begins with the Areas of Vulnerability and ends with the Predictive Module as described in detail in this paper. An application example of a degraded system using the IEEE 39-bus system is included.

  8. ANALYSIS OF STRESS STATE IN UPPER LAYER OF ROAD CONCRETE PAVEMENT WITH TEMPERATURE ACTION

    Directory of Open Access Journals (Sweden)

    M. K. Pshembaev

    2017-01-01

    Full Text Available While being operated auto-road pavements are subjected to intensive mechanical impacts, ultraviolet ray irradiation, freeze-thaw temperatures, freezing and thawing, drying and moistening. Due to these actions various types of pavement distresses appear on the road pavement. The most significant and dangerous type of distresses is micro-cracks on the road surface. One of the main reasons for their formation is an action of weather and climatic factors that initiate large changes in temperature of coating surface and occurrence of large temperature gradients in the upper layer. In this context while designing and operating auto-roads it is rather essential to investigate a stress state in road surface which is caused by temperature action. Purpose of the described investigations is to determine permissible temperature gradients for cement-concrete pavements that exclude formation of micro-cracks on their surface and thickness of damaged surface layer. Calculations of road pavement have been carried out at various laws for temperature distribution in its depth. A finite difference method realized in PARUS software has been used for studying a stress state of cement-concrete auto-roads. Regularities for distribution of stresses in cement-concrete pavement of auto-roads have been obtained at various surface temperatures. Permissible temperature gradients in the upper pavement layer have been determined and thickness of the layer where micro-cracks are formed has been assessed in the paper. Strength criterion based on the process of micro-crack formation and development in the concrete has been used for calculations. Risk of micro-crack formation on the auto-road pavement depends on material strength, conditions of plate fixing and temperature gradients.

  9. Evolution of regional stress state based on faulting and folding near the pit river, Shasta county, California

    Science.gov (United States)

    Austin, Lauren Jean

    We investigate the evolution of the regional stress state near the Pit River, northern California, in order to understand the faulting style in a tectonic transition zone and to inform the hazard analysis of Fault 3432 near the Pit 3 Dam. By analyzing faults and folds preserved in and adjacent to a diatomite mine north of the Pit River, we have determined principal stress directions preserved during the past million years. We find that the stress state has evolved from predominantly normal to strike slip and most recently to reverse, which is consistent with regional structures such as the extensional Hat Creek Fault to the south and the compressional folding of Mushroom Rock to the north. South of the Pit River, we still observe normal and strike slip faults, suggesting that changes in stress state are moving from north to south through time.

  10. Estimation of air void and aggregate spatial distributions in concrete under uniaxial compression using computer tomography scanning

    International Nuclear Information System (INIS)

    Wong, R.C.K.; Chau, K.T.

    2005-01-01

    Normal- and high-strength concrete cylinders (designed compressive strengths of 30 and 90 MPa at 28 days) were loaded uniaxially. Computer tomography (CT) scanning technique was used to examine the evolution of air voids inside the specimens at various loading states up to 85% of the ultimate compressive strength. The normal-strength concrete yielded a very different behaviour in changes of internal microstructure as compared to the high-strength concrete. There were significant instances of nucleation and growth in air voids in the normal-strength concrete specimen, while the increase in air voids in the high-strength concrete specimen was insignificant. In addition, CT images were used for mapping the aggregate spatial distributions within the specimens. No intrinsic anisotropy was detected from the fabric analysis

  11. THE STRESS STATE OF THE RADIALLY INHOMOGENEOUS HEMISPHERICAL SHELL UNDER LOCALLY DISTRIBUTED VERTICAL LOAD

    Directory of Open Access Journals (Sweden)

    Andreev Vladimir Igorevich

    2018-01-01

    Full Text Available Subject: one of the promising trends in the development of structural mechanics is the development of methods for solving problems in the theory of elasticity for bodies with continuous inhomogeneity of any deformation characteristics: these methods make it possible to use the strength of the material most fully. In this paper, we consider the two-dimensional problem for the case when a vertical, locally distributed load acts on the hemisphere and the inhomogeneity is caused by the influence of the temperature field. Research objectives: derive governing system of equations in spherical coordinates for determination of the stress state of the radially inhomogeneous hemispherical shell under locally distributed vertical load. Materials and methods: as a mechanical model, we chose a thick-walled reinforced concrete shell (hemisphere with inner and outer radii a and b, respectively, b > a. The shell’s parameters are a = 3.3 m, b = 4.5 m, Poisson’s ratio ν = 0.16; the load parameters are f = 10MPa - vertical localized load distributed over the outer face, θ0 = 30°, temperature on the internal surface of the shell Ta = 500 °C, temperature on the external surface of the shell Tb = 0 °C. The resulting boundary-value problem (a system of differential equations with variable coefficients is solved using the Maple software package. Results: maximal compressive stresses σr with allowance for material inhomogeneity are reduced by 10 % compared with the case when the inhomogeneity is ignored. But it is not so important compared with a 3-fold decrease in the tensile stress σθ on the inner surface and a 2-fold reduction in the tensile stress σθ on the outer surface of the hemisphere as concretes generally have a tensile strength substantially smaller than the compressive strength. Conclusions: the method presented in this article makes it possible to reduce the deformation characteristics of the material, i.e. it leads to a reduction in stresses

  12. Steady-state chlorophyll fluorescence (Fs) as a tool to monitor plant heat and drought stress

    Science.gov (United States)

    Cendrero Mateo, M.; Carmo-Silva, A.; Salvucci, M.; Moran, S. M.; Hernandez, M.

    2012-12-01

    Crop yield decreases when photosynthesis is limited by heat or drought conditions. Yet farmers do not monitor crop photosynthesis because it is difficult to measure at the field scale in real time. Steady-state chlorophyll fluorescence (Fs) can be used at the field level as an indirect measure of photosynthetic activity in both healthy and physiologically-perturbed vegetation. In addition, Fs can be measured by satellite-based sensors on a regular basis over large agricultural regions. In this study, plants of Camelina sativa grown under controlled conditions were subjected to heat and drought stress. Gas exchange and Fs were measured simultaneously with a portable photosynthesis system under light limiting and saturating conditions. Results showed that Fs was directly correlated with net CO2 assimilation (A) and inversely correlated with non-photochemical quenching (NPQ). Analysis of the relationship between Fs and Photosynthetically Active Radiation (PAR) revealed significant differences between control and stressed plants that could be used to track the status, resilience, and recovery of photochemical processes. In summary, the results provide evidence that Fs measurements, even without normalization, are an easy means to monitor changes in plant photosynthesis, and therefore, provide a rapid assessment of plant stress to guide farmers in resource applications. Figure1. Net CO2 assimilation rate (A) of Camelina sativa plants under control conditions and after heat stress exposure for 1 or 3 days (1d-HS and 3d-HS, respectively) (right) and control, drought and re-watering conditions (left). Conditions for infra-red gas analysis were: reference CO2 = 380 μmol mol-1, PPFD = 500 μmol m-2 s-1 and Tleaf set to 25°C (control, drought and re-water) or 35°C (HS). Different letters denote significant differences at the α=0.05 level. Values are means±SEM (n=10). Figure 2. Stable chlorophyll fluorescence (Fs) of Camelina sativa plants under control conditions and

  13. Quantum Monte Carlo simulation for S=1 Heisenberg model with uniaxial anisotropy

    International Nuclear Information System (INIS)

    Tsukamoto, Mitsuaki; Batista, Cristian; Kawashima, Naoki

    2007-01-01

    We perform quantum Monte Carlo simulations for S=1 Heisenberg model with an uniaxial anisotropy. The system exhibits a phase transition as we vary the anisotropy and a long range order appears at a finite temperature when the exchange interaction J is comparable to the uniaxial anisotropy D. We investigate quantum critical phenomena of this model and obtain the line of the phase transition which approaches a power-law with logarithmic corrections at low temperature. We derive the form of logarithmic corrections analytically and compare it to our simulation results

  14. The statitistical evaluation of the uniaxial compressive strength of the Ruskov andesite

    Directory of Open Access Journals (Sweden)

    Krepelka František

    2002-03-01

    Full Text Available The selection of a suitable model of the statistical distribution of the uniaxial compressive strength is discussed in the paper. The uniaxial compressive strength was studied on 180 specimens of the Ruskov andesite. The rate of loading was 1MPa.s-1. The experimental specimens had a prismatic form with a square base; the slightness ratio of specimens was 2:1. Three sets of specimens with a different length of the base edge were studied, namely 50, 30 and 10 mm. The result of the measurement were three sets with 60 values of the uniaxial compressive strength. The basic statistical parameters: the sample mean, the sample standard deviation, the variational interval, the minimum and maximum value, the sample obliqueness coefficient and the sharpness coefficient were evaluated for each collection. Two types of the distribution which can be joined with the real physical fundamentals of the desintegration of rocks ( the normal and the Weibull distribution were tested. The two-parametric Weibull distribution was tested. The basic characteristics of both distributions were evaluated for each set and the accordance of the model distribution with an experimental distribution was tested. The ÷2-test was used for testing. The two-parametric Weibull distribution was selected following the comparison of the test results of both model distributions as a suitable distribution model for the characterization of uniaxial compressive strength of the Ruskov andesite. The two-parametric Weibull distribution showed better results of the goodness-of-fit test. The normal distribution was suitable for two sets; one of the sets showed a negative result of the goodness-of-fit testing. At the uniaxial compressive strength of the Ruskov andesite, a scale effect was registered : the mean value of uniaxial compressive strength decreases with increasing the specimen base edge. This is another argument for using the Weibull distribution as a suitable statistical model of the

  15. Experimental study on uniaxial ratcheting deformation and failure behavior of 304 stainless steel

    International Nuclear Information System (INIS)

    Yang Xianjie; Gao Qing; Cai Lixun; Liu Yujie

    2004-01-01

    In the paper, the tests of cyclic strain ratcheting and low cycle fatigue for 304 stainless steel under uniaxial cyclic straining were carried out to systematically explore the deformation and failure behavior of the material. The experimental study shows that the cyclic strain ratcheting deformation behavior of the material is different from either the uniaxial monotonic tensile one or the cyclic deformation one under the symmetrical cyclic straining with the same strain amplitude, and the strain ratcheting deformation and failure behaviors depend on both the plastic strain amplitude and the strain increment at the cyclic maximum strain. Some significant results were observed

  16. Biaxial failure criteria and stress-strain response for concrete of containment structure

    International Nuclear Information System (INIS)

    Lee, S. K.; Woo, S. K.; Song, Y. C.; Kweon, Y. K.; Cho, C. H.

    2001-01-01

    Biaxial failure criteria and stress-strain response for plain concrete of containment structure on nuclear power plants are studied under uniaxial and biaxial stress(compression-compression, compression-tension, and tension-tension combined stress). The concrete specimens of a square plate type are used for uniaxial and biaxial loading. The experimental data indicate that the strength of concrete under biaxial compression, f 2 /f 1 =-1/-1, is 17 percent larger than under uniaxial compression and the poisson's ratio of concrete is 0.1745. On the base of the results, a biaxial failure envelope for plain concrete that the uniaxial strength is 5660 psi are provided, and the biaxial failure behaviors for three biaxial loading areas are plotted respectively. And, various analytical equations having the reliability are proposed for representations of the biaxial failure criteria and stress-strain response curves of concrete

  17. Mild Social Stress in Mice Produces Opioid-Mediated Analgesia in Visceral but Not Somatic Pain States.

    Science.gov (United States)

    Pitcher, Mark H; Gonzalez-Cano, Rafael; Vincent, Kathleen; Lehmann, Michael; Cobos, Enrique J; Coderre, Terence J; Baeyens, José M; Cervero, Fernando

    2017-06-01

    Visceral pain has a greater emotional component than somatic pain. To determine if the stress-induced analgesic response is differentially expressed in visceral versus somatic pain states, we studied the effects of a mild social stressor in either acute visceral or somatic pain states in mice. We show that the presence of an unfamiliar conspecific mouse (stranger) in an adjacent cubicle of a standard transparent observation box produced elevated plasma corticosterone levels compared with mice tested alone, suggesting that the mere presence of a stranger is stressful. We then observed noxious visceral or somatic stimulation-induced nociceptive behavior in mice tested alone or in mildly stressful conditions (ie, beside an unfamiliar stranger). Compared with mice tested alone, the presence of a stranger produced a dramatic opioid-dependent reduction in pain behavior associated with visceral but not somatic pain. This social stress-induced reduction of visceral pain behavior relied on visual but not auditory/olfactory cues. These findings suggest that visceral pain states may provoke heightened responsiveness to mild stressors, an effect that could interfere with testing outcomes during simultaneous behavioral testing of multiple rodents. In mice, mild social stress due to the presence of an unfamiliar conspecific mouse reduces pain behavior associated with noxious visceral but not somatic stimulation, suggesting that stress responsiveness may be enhanced in visceral pain versus somatic pain states. Published by Elsevier Inc.

  18. Characterization of mechanical behavior of a porcine pulmonary artery strip using a randomized uniaxial stretch and stretch-rate protocol

    Directory of Open Access Journals (Sweden)

    Criscione John C

    2008-01-01

    Full Text Available Abstract Background Much of the experimental work in soft tissue mechanics has been focused on fitting approximate relations for specific tissue types from aggregate data on multiple samples of the tissue. Such relations are needed for modeling applications and have reasonable predictability – especially given the natural variance in specimens. There is, however, much theoretical and experimental work to be done in determining constitutive behaviors for particular specimens and tissues. In so doing, it may be possible to exploit the natural variation in tissue ultrastructure – so to relate ultrastructure composition to tissue behavior. Thus, this study focuses on an experimental method for determining constitutive behaviors and illustrates the method with analysis of a porcine pulmonary artery strip. The method characterizes the elastic part of the response (implicitly in terms of stretch and the inelastic part in terms of short term stretch history (i.e., stretch-rate Ht2, longer term stretch history Ht1, and time since the start of testing T. Methods A uniaxial testing protocol with a random stretch and random stretch-rate was developed. The average stress at a particular stretch was chosen as the hyperelastic stress response, and deviation from the mean at this particular stretch is chosen as the inelastic deviation. Multivariable Linear Regression Analysis (MLRA was utilized to verify if Ht2, Ht1, and T are important factors for characterizing the inelastic deviation. For acquiring Ht2 and Ht1, an integral function type of stretch history was employed with time constants chosen from the relaxation spectrum of an identical size strip from the same tissue with the same orientation. Finally, statistical models that characterize the inelasticity were developed at various, nominal values of stretch, and their predictive capability was examined. Results Inelastic deviation from hyperelasticity was high (31% for low stretch and declined

  19. Superior colliculus resting state networks in post-traumatic stress disorder and its dissociative subtype.

    Science.gov (United States)

    Olivé, Isadora; Densmore, Maria; Harricharan, Sherain; Théberge, Jean; McKinnon, Margaret C; Lanius, Ruth

    2018-01-01

    The innate alarm system (IAS) models the neurocircuitry involved in threat processing in posttraumatic stress disorder (PTSD). Here, we investigate a primary subcortical structure of the IAS model, the superior colliculus (SC), where the SC is thought to contribute to the mechanisms underlying threat-detection in PTSD. Critically, the functional connectivity between the SC and other nodes of the IAS remains unexplored. We conducted a resting-state fMRI study to investigate the functional architecture of the IAS, focusing on connectivity of the SC in PTSD (n = 67), its dissociative subtype (n = 41), and healthy controls (n = 50) using region-of-interest seed-based analysis. We observed group-specific resting state functional connectivity between the SC for both PTSD and its dissociative subtype, indicative of dedicated IAS collicular pathways in each group of patients. When comparing PTSD to its dissociative subtype, we observed increased resting state functional connectivity between the left SC and the right dorsolateral prefrontal cortex (DLPFC) in PTSD. The DLPFC is involved in modulation of emotional processes associated with active defensive responses characterising PTSD. Moreover, when comparing PTSD to its dissociative subtype, increased resting state functional connectivity was observed between the right SC and the right temporoparietal junction in the dissociative subtype. The temporoparietal junction is involved in depersonalization responses associated with passive defensive responses typical of the dissociative subtype. Our findings suggest that unique resting state functional connectivity of the SC parallels the unique symptom profile and defensive responses observed in PTSD and its dissociative subtype. Hum Brain Mapp 39:563-574, 2018. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  20. Effect of cyclic block loading on character of deformation and strength of structural materials in plane stressed state

    International Nuclear Information System (INIS)

    Kul'chitskij, N.M.; Troshchenko, A.V.; Koval'chuk, B.I.; Khamaza, L.A.; Nikolaev, I.A.

    1982-01-01

    The paper is concerned with choice of conditions for preliminary cyclic block loading, determination of fatigue failure resistance characteristics for various structural materials under regular and selected block loading, investigation of the preliminary cyclic loading effect on regularities of elastoplastic deformation of materials concerned in the biaxial stressed state. Under selected conditions of cyclic block loading the character of damage accumulation is close to the linear law for the materials of high-srength doped steel, and VT6 alloys of concern. These materials in the initial state and after preliminary cyclic loading are anisotropic. Axial direction is characterized by a higher plastic strain resistance for steel and tangential direction - for VT6 alloy. The generalized strain curves for the materials in question are not invariant as to the stressed state type. It is stated that the effect of preliminary unsteady cyclic loading on resistance and general regularities of material deformation in the complex stressed state is insignificant. It is observed that stress-strain properties of the materials tend to vary in the following way: plastic strain resistance of the steel lowers and that of VT6 rises, anisotropy of the materials somehow decreases. The variation in the material anisotropy may be attributed to a decrease in residual stresses resulting from preliminary cyclic loading

  1. In-situ stress measurements in the earth's crust in the eastern United States

    International Nuclear Information System (INIS)

    Rundle, T.A.; Singh, M.M.; Baker, C.H.

    1987-04-01

    The US Nuclear Regulatory Commission requires that the design basis for vibratory ground motion should be determined through correlation of seismicity with tectonic structures or provinces (10CFR100, Appendix A). Such criteria are difficult to apply in the eastern United States, which experiences persistent low level seismicity, with occasional moderate to large earthquakes. This report presents the results of in-situ stress measurements conducted towards reducing this uncertainty at three (3) seismically active sites in the region, namely, near Moodus, Connecticut, around the Ramapo fault zone in New York and New Jersey, and in central Virginia. As far as possible, at each location one bore hole was drilled close to the ''apparent'' epicenter of the seismic activity and one outside the ''known'' seismic zone, so that the data obtained could be compared. The results obtained were very consistent both as to magnitude and direction. No attempt was made to correlate the in-situ stress measurements with the tectonic setting or seismic activity, since this was beyond the scope of this project. Extensive appendices report experimental data. 35 refs

  2. Finite Element Method Study on Stress State in Soil Induced by Agricultural Traffic

    Directory of Open Access Journals (Sweden)

    Adrian Molnar-Irimie

    2016-11-01

    Full Text Available In general, when a tyre is running on a deformable soil, the soil compaction will occur not only on surface layers, but also on soil profile, in deeper layers. This leads to a series of negative effects not only on physical and mechanical properties of soil, but also influences the crops growth and the crop yield. For these reasons, currently are needed solutions to reduce soil compaction, caused mainly by agricultural implements passing on the soil surface in order to aply the specific crop production technologies. From our simulation we can draw the following conclusions: the soil stresses decreased with depth; the soil displacements magnitude increased with soil water content due to lower friction forces between soil particles (water acts like a lubricant between soil particles; decreasing rate for soil displacement is influenced by load magnitude and tyre inflation pressure; the soil particles moved in vertical plain from the top to the bottom, but also in horizontal direction, from the center to the edge in cross section and in longitudinal direction; the dimensions of the geometric shape of the mentioned soil volume is influenced by load and tyre inflation pressure. In this paper the agricultural traffic and its influence on stress state in soil, it was used a software application based on Finite Element Method, that has been proved to be a useful tool for soil compaction assessment in order to find the right decisions for a proper field traffic management.

  3. Anisotropy effect of the clay soil masses on the stress-strain state of transport tunnels

    Directory of Open Access Journals (Sweden)

    Yushkov Boris Semenovich

    2014-09-01

    Full Text Available The article considers the kinds of clay soil mass anisotropy in the form of the spatial heterogeneity of properties of thawed and frozen soils, ambiguity of the frost heaving values and shrinkage in different directions. The questions of anisotropy of the clay soil properties at the positive temperatures are reported. The dependence of the heterogeneity of the physical and mechanical properties of frozen soils from the cryogenic texture, natural arrangement, different types of stratification and interbedding is considered. Indexes of the strength and strain anisotropy are noted. The accounting possibilities of the basic numerical indexes of heaving phenomena from the standpoint of anisotropy of the properties and processes inherent in the freezing through soil are analyzed by substitution in the heaving strain formula. The unevenness of thawed soil shrinkage in vertical and horizontal directions is noted during the freezing of the top layer. The unevenness of shrinkage in different directions is connected with kind of stress and cryogenic texture. Anisotropy of the frost heaving process is considered in the context of one-dimensional and non-one-dimensional problem depending on the amount of the freezing fronts and their direction. There is summarized the effect of anisotropy appearances on the stress-strain state of the transport tunnel. One can conclude that the resulting non-uniformity of heaving and shrinkage in conjunction with anisotropic properties of frozen soils, is a significant component in the complex of power factors determining the optimal design solution of a transport tunnel.

  4. The stem cell state in plant development and in response to stress

    Directory of Open Access Journals (Sweden)

    Gideon eGrafi

    2011-10-01

    Full Text Available Stem cells are commonly defined by their developmental capabilities, namely, self-renewal and multitype differentiation, yet the biology of stem cells and their inherent features both in plants and animals are only beginning to be elucidated. In this review article we highlight the stem cell state in plants (with reference to animals and the plastic nature of plant somatic cells (often referred to as totipotency as well as the essence of cellular dedifferentiation. Based on recent published data, we illustrate the picture of stem cells with emphasis on their open chromatin conformation. We discuss the process of dedifferentiation and highlight its transient nature, its distinction from reentry into the cell cycle and its activation following exposure to stress. We also discuss the potential hazard that can be brought about by stress-induced dedifferentiation and its major impact on the genome, which can undergo stochastic, abnormal reorganization leading to genetic variation by means of DNA transposition and/or DNA recombination.

  5. The effect of inertia, viscous damping, temperature and normal stress on chaotic behaviour of the rate and state friction model

    Science.gov (United States)

    Sinha, Nitish; Singh, Arun K.; Singh, Trilok N.

    2018-04-01

    A fundamental understanding of frictional sliding at rock surfaces is of practical importance for nucleation and propagation of earthquakes and rock slope stability. We investigate numerically the effect of different physical parameters such as inertia, viscous damping, temperature and normal stress on the chaotic behaviour of the two state variables rate and state friction (2sRSF) model. In general, a slight variation in any of inertia, viscous damping, temperature and effective normal stress reduces the chaotic behaviour of the sliding system. However, the present study has shown the appearance of chaos for the specific values of normal stress before it disappears again as the normal stress varies further. It is also observed that magnitude of system stiffness at which chaotic motion occurs, is less than the corresponding value of critical stiffness determined by using the linear stability analysis. These results explain the practical observation why chaotic nucleation of an earthquake is a rare phenomenon as reported in literature.

  6. STRESS-STRAIN STATE IN EMBEDMENT OF REINFORCEMENT IN CASE OF REPEATED LOADINGS

    Directory of Open Access Journals (Sweden)

    Mirsayapov Ilshat Talgatovich

    2016-05-01

    Full Text Available The author offer transforming the diagram of ideal elastic-plastic deformations for the description of the stress-strain state of embedment of reinforcement behind a critical inclined crack at repeatedly repeating loadings. The endurance limit of the adhesion between concrete and reinforcement and its corresponding displacements in case of repeated loadings are accepted as the main indicators. This adhesion law is the most appropriate for the description of physical and mechanical phenomena in the contact zone in case of cyclic loading, because it simply and reliably describes the adhesion mechanism and the nature of the deformation, and greatly simplifies the endurance calculations compared to the standard adhesion law. On the basis of this diagram the author obtained the equations for the description of the distribution of pressures and displacements after cyclic loading with account for the development of deformations of cyclic creep of the concrete under the studs of reinforcement.

  7. Seismicity, state of stress and induced seismicity in the molasse basin and Jura (N-Switzerland)

    Energy Technology Data Exchange (ETDEWEB)

    Deichmann, N. [Schweizerischer Erdbebendienst, ETH Zuerich, Zuerich (Switzerland); Burlini, L. [Institut of Geology, ETH Zuerich, Zuerich (Switzerland)

    2010-07-01

    This illustrated report for the Swiss Federal Office of Energy (SFOE) is one of a series of appendices dealing with the potential for geological sequestration of CO{sub 2} in Switzerland. This report takes a look at the seismicity, state of stress and induced seismicity in the molasse basin and Jura Mountains in northern Switzerland. Data collected since 1983 by the Swiss Earthquake Service and the National Cooperative for the Disposal of Radioactive Wastes NAGRA on the tectonics and seismic properties of North-western Switzerland is noted. The results are illustrated with a number of maps and graphical representations and are discussed in detail. Cases of induced seismicity as resulting from both natural and man-made causes are examined.

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

    DEFF Research Database (Denmark)

    Nielsen, Jens Henrik

    2016-01-01

    to the fragmentation process and some authors e.g. Barsom (J Am Ceram Soc 51(2):75, 1968), Gulati (Glass processing days, Tamglass Engineering Oy, Tampere, 1997), Warren (Fractography of glasses and ceramics IV, Alfred University, Alfred, 2001) and Tandon and Glass (Fracture mechanics of ceramics—active materials......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...

  9. Stressed and strained state for cermetic-rod-type fuel element

    International Nuclear Information System (INIS)

    Kulikov, I.S.

    1987-01-01

    Calculation technique for designing the stress-strained state of a cermetic rod-type fuel element has been proposed. The technique is based on the time-dependent step-by-step method and the solution of the deformation equilibrium equation for continuous and thick-wall long cylinders at every temporal step by the finite difference method. Additional strains, caused by thermal expansion and radiation swelling, have been taken into account. The transion from the non-contact model to the stiff-contact model has been provided in the case of cladding-fuel gap dissappearing in one or a number of cross-sections along the fuel element height. The method is supplemented by the formula for fuel cans stability estimation in the case of high coolant external pressure. The example of estimation of the cermetic-rod-type fuel elements are considered as an example

  10. The effect of multiaxial stress state on creep behavior and fracture mechanism of P92 steel

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Yuan; Xu, Hong, E-mail: xuhong@ncepu.edu.cn; Ni, Yongzhong; Lan, Xiang; Li, Hongyuan

    2015-06-11

    The creep experiments on plain and double U-typed notched specimens were conducted on P92 steel at 650 °C. The notch strengthening effect was found in the notched specimens. Fracture appearance observed by scanning electron microscopy revealed that dimpled fracture for relatively blunt notched specimen, and dimpled fracture doubled with intergranular brittle fracture for relatively sharp notched specimen, which meant that fracture mechanism of P92 steel altered due to the presence of the notch. Meanwhile, based on Norton–Bailey and Kachanov–Robotnov constitutive models, a modified model was proposed. Finite element simulations were carried out to investigate the effect of multiaxial stress state on the creep behavior, fracture mechanism and damage evolvement of P92 steel. The simulation results agreed well with the fracture behaviors observed experimentally.

  11. Thermal stress state of cryogenic HP vessels under freezing and pressurization

    International Nuclear Information System (INIS)

    Tsybenko, A.S.; Kuranov, B.A.; Chepurnoj, A.D.; Shaposhnikov, V.A.; Krishchuk, N.G.

    1986-01-01

    A mathematical model is developed for thermomechanical processes in cryogenic HP vessels under freezing either by liquid and (or) gaseous cryogen and under pressurization. Equations of nonlinear nonstationary thermal conductivity and nonisothermal thermoelastoplasticity are used for the case of the theory off low with isotropic hardening. Semiempiricaldependences of nonstationary heat exchange for gaseous medium, experimental curves of cryogenic liquid boiling, mass exchange relationships are allowed for when formulating boundary conditions. The mathematical modelis realized on the basi of the finite element method in the form of highly automated program complex TERSOD (heat resistanceof vessels), oriented for computer of the Unified System. Heat and stress-strained states for three constructions of vessels are thoroughly studied under different conditions of gaseous, liquid and combined freezing with subsequent pressurization

  12. Stress.

    Science.gov (United States)

    Chambers, David W

    2008-01-01

    We all experience stress as a regular, and sometimes damaging and sometimes useful, part of our daily lives. In our normal ups and downs, we have our share of exhaustion, despondency, and outrage--matched with their corresponding positive moods. But burnout and workaholism are different. They are chronic, dysfunctional, self-reinforcing, life-shortening habits. Dentists, nurses, teachers, ministers, social workers, and entertainers are especially susceptible to burnout; not because they are hard-working professionals (they tend to be), but because they are caring perfectionists who share control for the success of what they do with others and perform under the scrutiny of their colleagues (they tend to). Workaholics are also trapped in self-sealing cycles, but the elements are ever-receding visions of control and using constant activity as a barrier against facing reality. This essay explores the symptoms, mechanisms, causes, and successful coping strategies for burnout and workaholism. It also takes a look at the general stress response on the physiological level and at some of the damage American society inflicts on itself.

  13. Variations of electric resistance and H2 and Rn emissions of concrete blocks under increasing uniaxial compression

    Science.gov (United States)

    King, C.-Y.; Luo, G.

    1990-01-01

    Electric resistance and emissions of hydrogen and radon isotopes of concrete (which is somewhat similar to fault-zone materials) under increasing uniaxial compression were continuously monitored to check whether they show any pre- and post-failure changes that may correspond to similar changes reported for earthquakes. The results show that all these parameters generally begin to increase when the applied stresses reach 20% to 90% of the corresponding failure stresses, probably due to the occurrence and growth of dilatant microcracks in the specimens. The prefailure changes have different patterns for different specimens, probably because of differences in spatial and temporal distributions of the microcracks. The resistance shows large co-failure increases, and the gas emissions show large post-failure increases. The post-failure increase of radon persists longer and stays at a higher level than that of hydrogen, suggesting a difference in the emission mechanisms for these two kinds of gases. The H2 increase may be mainly due to chemical reaction at the crack surfaces while they are fresh, whereas the Rn increases may be mainly the result of the increased emanation area of such surfaces. The results suggest that monitoring of resistivity and gas emissions may be useful for predicting earthquakes and failures of concrete structures. ?? 1990 Birkha??user Verlag.

  14. Investigation of the Failure Mechanism of HTPB/AP/Al Propellant by In-situ Uniaxial Tensile Experimentation in SEM

    NARCIS (Netherlands)

    Ramshorst, M.C.J. van; Benedetto, G.L. di; Duvalois, W.; Hooijmeijer, P.A.; Heijden, A.E.D.M. van der

    2016-01-01

    The failure mechanism of a propellant consisting of hydroxyl terminated poly-butadiene filled with ammonium perchlorate and aluminum (HTPB/AP/Al) was determined by performing in-situ uniaxial tensile tests in a scanning electron microscope (SEM). The experimental test plan contained uniaxial tensile

  15. Evolution of the Fermi surface of the strongly correlated f electron system under hydrostatic and uniaxial pressures

    CERN Document Server

    Aoki, H; Endo, M; Nakayama, M; Takei, H; Kimura, N; Kunii, S; Terashima, T; Uji, S; Matsumoto, T

    2002-01-01

    We report our recent developments of experimental systems for measuring the de Haas-van Alphen (dHvA) effect under hydrostatic and uniaxial pressures. The dHvA effect of CeB sub 6 has been studied under both hydrostatic and uniaxial pressures and the effects of the pressures on the electronic structure are discussed.

  16. Strength Restoration of Cracked Sandstone and Coal under a Uniaxial Compression Test and Correlated Damage Source Location Based on Acoustic Emissions

    Science.gov (United States)

    Feng, Xiaowei; Zhang, Nong; Zheng, Xigui; Pan, Dongjiang

    2015-01-01

    Underground rock masses have shown a general trend of natural balance over billions of years of ground movement. Nonetheless, man-made underground constructions disturb this balance and cause rock stability failure. Fractured rock masses are frequently encountered in underground constructions, and this study aims to restore the strength of rock masses that have experienced considerable fracturing under uniaxial compression. Coal and sandstone from a deep-buried coal mine were chosen as experimental subjects; they were crushed by uniaxial compression and then carefully restored by a chemical adhesive called MEYCO 364 with an innovative self-made device. Finally, the restored specimens were crushed once again by uniaxial compression. Axial stress, axial strain, circumferential strain, and volumetric strain data for the entire process were fully captured and are discussed here. An acoustic emission (AE) testing system was adopted to cooperate with the uniaxial compression system to provide better definitions for crack closure thresholds, crack initiation thresholds, crack damage thresholds, and three-dimensional damage source locations in intact and restored specimens. Several remarkable findings were obtained. The restoration effects of coal are considerably better than those of sandstone because the strength recovery coefficient of the former is 1.20, whereas that of the latter is 0.33, which indicates that MEYCO 364 is particularly valid for fractured rocks whose initial intact peak stress is less than that of MEYCO 364. Secondary cracked traces of restored sandstone almost follow the cracked traces of the initial intact sandstone, and the final failure is mainly caused by decoupling between the adhesive and the rock mass. However, cracked traces of restored coal only partially follow the traces of intact coal, with the final failure of the restored coal being caused by both bonding interface decoupling and self-breakage in coal. Three-dimensional damage source

  17. Strength Restoration of Cracked Sandstone and Coal under a Uniaxial Compression Test and Correlated Damage Source Location Based on Acoustic Emissions.

    Directory of Open Access Journals (Sweden)

    Xiaowei Feng

    Full Text Available Underground rock masses have shown a general trend of natural balance over billions of years of ground movement. Nonetheless, man-made underground constructions disturb this balance and cause rock stability failure. Fractured rock masses are frequently encountered in underground constructions, and this study aims to restore the strength of rock masses that have experienced considerable fracturing under uniaxial compression. Coal and sandstone from a deep-buried coal mine were chosen as experimental subjects; they were crushed by uniaxial compression and then carefully restored by a chemical adhesive called MEYCO 364 with an innovative self-made device. Finally, the restored specimens were crushed once again by uniaxial compression. Axial stress, axial strain, circumferential strain, and volumetric strain data for the entire process were fully captured and are discussed here. An acoustic emission (AE testing system was adopted to cooperate with the uniaxial compression system to provide better definitions for crack closure thresholds, crack initiation thresholds, crack damage thresholds, and three-dimensional damage source locations in intact and restored specimens. Several remarkable findings were obtained. The restoration effects of coal are considerably better than those of sandstone because the strength recovery coefficient of the former is 1.20, whereas that of the latter is 0.33, which indicates that MEYCO 364 is particularly valid for fractured rocks whose initial intact peak stress is less than that of MEYCO 364. Secondary cracked traces of restored sandstone almost follow the cracked traces of the initial intact sandstone, and the final failure is mainly caused by decoupling between the adhesive and the rock mass. However, cracked traces of restored coal only partially follow the traces of intact coal, with the final failure of the restored coal being caused by both bonding interface decoupling and self-breakage in coal. Three

  18. STRESS-DEFORMED STATE OF A STRUT-FRAMED CRANE GIRDER

    Directory of Open Access Journals (Sweden)

    Kh. M. Muselemov

    2017-01-01

    Full Text Available Objectives. The aim of the present work is to study the influence of design parameters on the stress-deformed state of a sprengel crane girder; to compile the tables and corresponding graphs illustrating changes in internal force factors in the characteristic cross-sections of the system elements under consideration. The article describes the study of the stress-deformed state (SDS of a metal strut-framed crane girder.Methods. Numerical methods of analysis based on the use of the Green's function are used during solving this problem. A dimensionless parameter is introduced, depending on which the tables and graphs are constructed. According to the known algorithm, the calculations of internal force factors in the sections of the considered construction are performed.Results. Depending on the dimensionless parameter characterising the geometry and physical features of the system, tables of bending moments and transverse forces are compiled. According to these tables, the appropriate graphs are plotted in order to choose easily the optimal design parameters.Conclusion. The dependence of the moments and transverse forces on the dimensionless parameter k was found, the corresponding graphs were plotted and the metal costs for the girders were calculated. The minimum values of the moments and transverse forces are established to take place when the dimensionless parameter k values are close to zero. The most economical was a strut-framed crane girder having k = 0.0001. The most uneconomical had k = 0.05 and k =∞. Eventually, the sprengel girders were found to be more profitable as compared to conventional crane girders. In the examples considered in the article, the metal savings amounted up to 14%. The presented methodology allows the calculation and designing of strut-framed crane girders with two racks to be carried out. 

  19. Lithospheric Strength and Stress State: Persistent Challenges and New Directions in Geodynamics

    Science.gov (United States)

    Hirth, G.

    2017-12-01

    The strength of the lithosphere controls a broad array of geodynamic processes ranging from earthquakes, the formation and evolution of plate boundaries and the thermal evolution of the planet. A combination of laboratory, geologic and geophysical observations provides several independent constraints on the rheological properties of the lithosphere. However, several persistent challenges remain in the interpretation of these data. Problems related to extrapolation in both scale and time (rate) need to be addressed to apply laboratory data. Nonetheless, good agreement between extrapolation of flow laws and the interpretation of microstructures in viscously deformed lithospheric mantle rocks demonstrates a strong foundation to build on to explore the role of scale. Furthermore, agreement between the depth distribution of earthquakes and predictions based on extrapolation of high temperature friction relationships provides a basis to understand links between brittle deformation and stress state. In contrast, problems remain for rationalizing larger scale geodynamic processes with these same rheological constraints. For example, at face value the lab derived values for the activation energy for creep are too large to explain convective instabilities at the base of the lithosphere, but too low to explain the persistence of dangling slabs in the upper mantle. In this presentation, I will outline these problems (and successes) and provide thoughts on where new progress can be made to resolve remaining inconsistencies, including discussion of the role of the distribution of volatiles and alteration on the strength of the lithosphere, new data on the influence of pressure on friction and fracture strength, and links between the location of earthquakes, thermal structure, and stress state.

  20. Stress and food deprivation: linking physiological state to migration success in a teleost fish.

    Science.gov (United States)

    Midwood, Jonathan D; Larsen, Martin H; Aarestrup, Kim; Cooke, Steven J

    2016-12-01

    Food deprivation is a naturally occurring stressor that is thought to influence the ultimate life-history strategy of individuals. Little is known about how food deprivation interacts with other stressors to influence migration success. European populations of brown trout (Salmo trutta) exhibit partial migration, whereby a portion of the population smoltifies and migrates to the ocean, and the rest remain in their natal stream. This distinct, natural dichotomy of life-history strategies provides an excellent opportunity to explore the roles of energetic state (as affected by food deprivation) and activation of the glucocorticoid stress response in determining life-history strategy and survival of a migratory species. Using an experimental approach, the relative influences of short-term food deprivation and experimental cortisol elevation (i.e. intra-coelomic injection of cortisol suspended in cocoa butter) on migratory status, survival and growth of juvenile brown trout relative to a control were evaluated. Fewer fish migrated in both the food deprivation and cortisol treatments; however, migration of fish in cortisol and control treatments occurred at the same time while that of fish in the food deprivation treatment was delayed for approximately 1 week. A significantly greater proportion of trout in the food deprivation treatment remained in their natal stream, but unlike the cortisol treatment, there were no long-term negative effects of food deprivation on growth, relative to the control. Overall survival rates were comparable between the food deprivation and control treatments, but significantly lower for fish in the cortisol treatment. Food availability and individual energetic state appear to dictate the future life-history strategy (migrate or remain resident) of juvenile salmonids while experimental elevation of the stress hormone cortisol causes impaired growth and reduced survival of both resident and migratory individuals. © 2016. Published by The

  1. Symptoms of Psychological Distress and Post-Traumatic Stress Disorder in United States Air Force Drone Operators

    Science.gov (United States)

    2014-08-01

    Disorder in United States Air Force “ Drone ” Operators 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S...referred to as “ drones .” Participants were assessed for self-reported sources of occupational stress, levels of clinical distress using the Outcome...providers are discussed. 15. SUBJECT TERMS Stress, drone operator, PTSD, USAF 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT

  2. Elastic-plastic stresses in a thin rotating disk with shafthaving density variation parameter under steady-state temperature

    Directory of Open Access Journals (Sweden)

    Pankaj Thakur

    2014-01-01

    Full Text Available Steady thermal stresses in a rotating disc with shaft having density variation parameter subjected to thermal load have been derived by using Seth's transition theory. Neither the yields criterion nor the associated flow rule is assumed here. Results are depicted graphically. It has been seen that compressible material required higher percentage increased angular speed to become fully-plastic as compare to rotating disc made of incompressible material. Circumferential stresses are maximal at the outer surface of the rotating disc. With the introduction of thermal effect it decreases the value of radial and circumferential stresses at inner and outer surface for fully-plastic state.

  3. Parametric peak stress functions of 90o pipe bends with ovality under steady-state creep conditions

    International Nuclear Information System (INIS)

    Yaghi, A.H.; Hyde, T.H.; Becker, A.A.; Sun, W.

    2009-01-01

    Stress-based life prediction techniques are commonly used to estimate the failure life of pressurised pipe-related components, such as welds and bends, under creep conditions. Previous research has shown that reasonable life predictions can be obtained, based on the steady-state peak stresses, compared with the life predictions obtained from creep damage modelling. In this work, a series of parametric steady-state peak rupture stress functions of right-angled pipe bends with ovality are presented, which are based on the results obtained from finite element (FE) analyses, covering a number of material property and geometry parameters in practical ranges. Methods used to determine the stress functions are described. The FE analyses have been performed using axisymmetric models, subjected to internal pressure only, with a Norton creep law. Typical examples of parametric peak stress curve fitting are shown. In particular, the accuracy of the interpolation and extrapolation abilities of the stress functions is assessed. The results show that in most cases the interpolated and extrapolated peak stresses are accurate to within ±3% and ±5%, respectively.

  4. Stressed-deformed state of mountain rocks in elastic stage and between elasticity

    Directory of Open Access Journals (Sweden)

    Samedov A.M.

    2017-12-01

    Full Text Available The problems of the stress-strain state of rocks in the elastic stage and beyond the elastic limits, and the ways of schematizing the tension and compression diagrams were reviewed in the article. To simplify calculations outside the elastic range, the tension (compression diagrams are usually schematized, i.e. are replaced by curved smooth lines having a fairly simple mathematical expression and at the same time well coinciding with the experimentally obtained diagrams. When diagram is to be schematized, it is necessary to take a constant temperature of superheated water steam if a rock test is planned in a relaxed form. Note that when the diagram is schematizing, the difference between the limits of proportionality and fluidity is erased. This allows the limit of proportionality to be considered the limit of fluidity. Schematicization can be carried out in the area where the tensile strength (compression is planned to be destroyed with the established weakening of rocks by exposure to water steam or chemical reagents. Samples of rocks in natural form were tested and weakened by means of superheated water steam (220 °C and more and chemical reagents for tension and compression. The data are obtained, the diagrams of deformation are constructed and schematized in the elastic stage and beyond the elastic limit. Based on the schematic diagrams of deformation, the components of stress and strain were composed in the elastic stage and beyond the elastic limit. It is established in the publication that rocks under compression and stretching deform, both within the elastic stage, and beyond the limits of elasticity. This could be seen when the samples, both in natural and in weakened state, with superheated water steam (more than 220 °C or chemical reagents were tested. In their natural form, they are mainly deformed within the elastic stage and are destroyed as a brittle material, and in a weakened form they can deform beyond the elastic stage and

  5. Measuring the complex permittivity tensor of uniaxial biological materials with coplanar waveguide transmission line

    Science.gov (United States)

    A simple and accurate technique is described for measuring the uniaxial permittivity tensor of biological materials with a coplanar waveguide transmission-line configuration. Permittivity tensor results are presented for several chicken and beef fresh meat samples at 2.45 GHz....

  6. Molar mass of poly(ethylene terephthalate) (PET) during ultimate uniaxial drawing

    NARCIS (Netherlands)

    Göschel, U.; Cools, P.J.C.H.

    2000-01-01

    The changes of the average molar mass Mw, Mn, Mz, and molar mass distributions during multistep uniaxial drawing of poly(ethylene terephthalate) (PET) to achieve ultimate mechanical properties have been studied in detail by means of size exclusion chromatography (SEC) with triple detection:

  7. Molar-Mass of Poly(Ethylene-Terephthalate) (PET) During Ultimate Uniaxial Drawing

    NARCIS (Netherlands)

    Göschel, A.G.P.U.; Cools, P.J.C.H.

    2000-01-01

    The changes of the average molar mass Mw, Mn, Mz, and molar mass distributions during multistep uniaxial drawing of poly(ethylene terephthalate) (PET) to achieve ultimate mechanical properties have been studied in detail by means of size exclusion chromatography (SEC) with triple detection:

  8. Uniaxial Strain Induced Critical Current Degradation of Ag-Sheathed Bi-2212 Round Wire

    NARCIS (Netherlands)

    Dai, Chao; Qin, Jinggang; Liu, Bo; Liu, Peihang; Wu, Yu; Nijhuis, Arend; Zhou, Chao; Li, Chenshan; Hao, Qingbin; Liu, Sheng

    2018-01-01

    The critical current degradation of Bi-2212 Ag-sheathed round wire subjected to uniaxial strain was studied at 4.2 K in 14 T background field. The strains applied on the sample are both tension and compression. The additional tensile strain caused by the difference in thermal expansion between the

  9. The effects of different possible modes of uniaxial strain on the ...

    Indian Academy of Sciences (India)

    Dimple

    2017-06-19

    Jun 19, 2017 ... Ab-initio density functional theory; band gap; monolayer MoS2 nanosheet; strain. PACS Nos 31.15. ... drawn a surge in research interests. ..... Bader charge analysis of strain-free and uniaxially strained ML−MoS2 nanosheet.

  10. Viscosity overshoot in the start-up of uniaxial elongation of low density polyethylene melts

    DEFF Research Database (Denmark)

    Rasmussen, Henrik K.; Nielsen, Jens Kromann; Bach, Anders

    2005-01-01

    The transient uniaxial elongational viscosity of BASF Lupolen 1840D and 3020D melts has been measured on a filament stretch rheometer up to Hencky strains of 6-7. The elongational viscosity of both melts was measured at 130 degrees C within a broad range of elongational rates. At high elongation ...

  11. Mechanical stability of Ni and Ir under hydrostatic and uniaxial loading

    Czech Academy of Sciences Publication Activity Database

    Řehák, Petr; Černý, Miroslav; Šob, Mojmír

    2015-01-01

    Roč. 23, č. 5 (2015), art. n. 055010 ISSN 0965-0393 R&D Projects: GA ČR(CZ) GAP108/12/0311 Institutional support: RVO:68081723 Keywords : ab initio calculations * elastic stability * phonon instability * theoretical strength * hydrostatic loading * uniaxial loading Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.859, year: 2015

  12. Deformation response of gellan gum based bone scaffold subjected to uniaxial quasi-static loading

    Czech Academy of Sciences Publication Activity Database

    Kytýř, Daniel; Krčmářová, Nela; Šleichrt, Jan; Fíla, Tomáš; Koudelka_ml., Petr; Gantar, A.; Novak, S.

    2017-01-01

    Roč. 57, č. 1 (2017), s. 14-21 ISSN 1210-2709 EU Projects: European Commission(XE) ATCZ38 Institutional support: RVO:68378297 Keywords : gellan gum scaffold * reinforcement * uni-axial loading Subject RIV: JJ - Other Materials OBOR OECD: Materials engineering https://ojs.cvut.cz/ojs/index.php/ap/article/view/3885

  13. Hydrostatic-pressure and uniaxial-strain experiments for controlling the spin-Peierls transition

    International Nuclear Information System (INIS)

    Mito, Masaki; Deguchi, Hiroyuki; Fujita, Wataru; Kondo, Ryusuke; Kagoshima, Seiichi

    2010-01-01

    The spin-Peierls (SP) system is considered to be a quantum spin system strongly coupled with the lattice. We have succeeded in controlling SP transition by applying hydrostatic pressure and/or uniaxial strain. The observed phenomenon could be a typical example for understanding the SP transition based on the Hamiltonian. (author)

  14. Behaviour of S 355JO steel subjected to uniaxial stress at lowered ...

    Indian Academy of Sciences (India)

    Administrator

    curve determined by modeling procedure was compared with experimentally obtained ... All of experimental tests were performed using modern computer directed ... Josip Brnic et al ... alloy steel at elevated temperature is considered by Brnic.

  15. Smoothly varying in-plane stiffness heterogeneity evaluated under uniaxial tensile stress

    Science.gov (United States)

    J.M. Considine; F. Pierron; K.T. Turner; P. Lava; X. Tang

    2017-01-01

    Identification of spatially varying stiffness is a challenging, but important, research topic in the mechanics of materials and can provide the necessary information for material suitability, damage, and process control, especially for high‐value applications. One homogeneous and 3 heterogeneous virtual field method (VFM) formulations were used to create a methodology...

  16. Stress path dependent hydromechanical behaviour of heterogeneous carbonate rock

    Directory of Open Access Journals (Sweden)

    Dimanov A.

    2010-06-01

    Full Text Available The influence of stress paths, representative of reservoir conditions, on the hydromechanical behavior of a moderately heterogeneous carbonate has been investigated. Multiscale structural heterogeneities, common for instance in carbonate rocks, can strongly alter the mechanical response and significantly influence the evolution of flow properties with stress. Using a triaxial cell, the permeability evolutions during compression and the effects of brittle (fracture and plastic (pore collapse deformations at yield, were measured. A strong scattering was observed on the mechanical response both in term of compressibility and failure threshold. Using the porosity scaling predicted by an adapted effective medium theory (based on crack growth under Hertzian contact, we have rescaled the critical pressures by the normalized porosity deviation. This procedure reduces efficiently the scattering, revealing in the framework of proportional stress path loading, a linear relation between the critical pressures and the stress path parameter through all the deformation regimes. It leads to a new formulation for the critical state envelope in the 'mean stress, deviatoric stress' diagram. The attractive feature of this new yield envelope formulation relies on the fact that only the two most common different mechanical tests 'Uniaxial Compression' and 'Hydrostatic Compression', are needed to define entirely the yield envelope. Volumic strains and normalized permeabilities are finally mapped in the stresses diagram and correlated.

  17. Stress state and its anomaly observations in the vicinity of a fault in NanTroSEIZE Expedition 322

    Science.gov (United States)

    Wu, Hung-Yu; Saito, Saneatsu; Kinoshita, Masataka

    2015-12-01

    To better understand the stress state and geological properties within the shallow Shikoku Basin, southwest of Japan, two sites, C0011A and C0011B, were drilled in open-ocean sediments using Logging While Drilling (LWD) and coring, respectively. Resistivity image logging was performed at C0011A from sea floor to 950 m below sea floor (mbsf). At C0011B, the serial coring was obtained in order to determine physical properties from 340 to 880 mbsf. For the LWD images, a notable breakout anomaly was observed at a depth of 615 m. Using resistivity images and a stress polygon, the potential horizontal principal stress azimuth and its magnitude within the 500-750 mbsf section of the C0011A borehole were constrained. Borehole breakout azimuths were observed for the variation by the existence of a fault zone at a depth of 615 mbsf. Out of this fracture zone, the breakout azimuth was located at approximately 109° ± 12°, subparallel to the Nankai Trough convergence vector (300-315°). Our calculations describe a stress drop was determined based on the fracture geometry. A close 90° (73° ± 12°) rotation implied a 100% stress drop, defined as a maximum shear stress drop equal to 1 MPa. The magnitude of the horizontal principal stresses near the fracture stress anomaly ranged between 49 and 52 MPa, and the bearing to the vertical stress (Sv = 52 MPa) was found to be within the normal-faulting stress regime. Low rock strength and a low stress level are necessary to satisfy the observations.

  18. Stress induced reorientation of vanadium hydride

    International Nuclear Information System (INIS)

    Beardsley, M.B.

    1977-10-01

    The critical stress for the reorientation of vanadium hydride was determined for the temperature range 180 0 to 280 0 K using flat tensile samples containing 50 to 500 ppM hydrogen by weight. The critical stress was observed to vary from a half to a third of the macroscopic yield stress of pure vanadium over the temperature range. The vanadium hydride could not be stress induced to precipitate above its stress-free precipitation temperature by uniaxial tensile stresses or triaxial tensile stresses induced by a notch

  19. Hydrostatic and uniaxial pressure effect on Tc of YBa2Cu3Ox

    International Nuclear Information System (INIS)

    Ludwig, H.A.; Quenzel, R.; Schlachter, S.I.

    1996-01-01

    The variation of the transition temperature T c of YBa 2 Cu 3 O x with hydrostatic He-gas pressure depends on the oxygen content x. The pressure effect dT c /dp increases from small negative values at x=7 to dT c /dp=7.4 K/GPa at x=6.7. For oxygen contents below x=6.7 dT c /dp drops to 3 K/GPa and remains nearly constant. The charge transfer model cannot explain the drop at x=6.7. Thermal expansion measurements on YBa 2 Cu 3 O x indicated that the uniaxial pressure effects along the three crystal axes are different. To investigate the uniaxial pressure effects inductively an experimental setup was constructed. The T c -change of several YBa 2 Cu 3 O x single crystals with different oxygen contents has been investigated under pressure along the c-axis. To avoid oxygen ordering processes the samples were held below 105 K during the measurements. The results of uniaxial pressure measurements in c-axis direction fit to former uniaxial pressure data and are explained within the charge transfer model. Hydrostatic pressure data of overdoped samples fit to the same curve. However, this is not the case for under doped samples. From this the authors conclude that only a part of the hydrostatic pressure effect can be explained by charge transfer in the underdoped region. The remaining part can be ascribed to uniaxial pressure effects along the a- and b-axis

  20. Solid state dewetting and stress relaxation in a thin single crystalline Ni film on sapphire

    International Nuclear Information System (INIS)

    Rabkin, E.; Amram, D.; Alster, E.

    2014-01-01

    In this study, we deposited a 80 nm thick single crystalline Ni film on a sapphire substrate. Heat treatment of this film at 1000 °C followed by slow cooling resulted in the formation of faceted holes, star-like channel instabilities and faceted microwires. The ridges at the rims of faceted holes and channels exhibited a twinning orientation relationship with the rest of the film. A sub-nanometer-high hexagonal topography pattern on the surface of the unperturbed film was observed by atomic force microscopy. No such pattern was observed on the top facets of isolated Ni particles and hole ridges. We discuss the observed dewetting patterns in terms of the effects of Ni surface anisotropy and faceting on solid state dewetting. The hexagonal pattern on the surface of the unperturbed film was attributed to thermal stress relaxation in the film via dislocations glide. This work demonstrates that solid state dewetting of single crystalline metal films can be utilized for film patterning and for producing hierarchical surface topographies

  1. Stress state in the neighborhood of subways and pipe lines under the action of dynamic loads

    International Nuclear Information System (INIS)

    Alexeyeva, L.A.; Eskalieva, A.Z.; Shershnev, V.V.

    2001-01-01

    We consider the long underground constructions of deep and shallow types such as transport subways, mines, underground pipes etc. by the action of dynamic lads. Situated in areas of seismic activity, they are subjected to the influence of seismic waves during earthquakes and can be destroyed. Running loads inside constructions (transport for instance) affect upon toughness and stability of both subways and surrounding medium. If underground construction dispose near a day's surface, it acts also on nearby buildings. Evaluations of behavior of underground and pipes under dynamic influences in real conditions of usage are determined of stress state of constructions in the interaction with environment medium. Here underground constructions are simulated by infinitely long cylindrical cavities in utter ambience. As utter ambience the isotropic elastic medium and two-component medium of Biot are researched. Last one allows simulating saturated water oils. The elastic cylindrical shell simulates supporting of a tunnel (or pipeline). Both a tress state of construction and surrounding medium were investigated for a different contact conditions between support of tunnel and environment (rigid, slippery and viscous contacts). (author)

  2. Prevalence and predictors of posttraumatic stress disorder among victims of violence applying for state compensation.

    Science.gov (United States)

    Kunst, Maarten; Winkel, Frans Willem; Bogaerts, Stefan

    2010-09-01

    Many studies have focused on the predictive value of victims' emotions experienced shortly after violence exposure to identify those vulnerable for development of posttraumatic stress disorder (PTSD). However, many victims remain unidentified during the initial recovery phase, yet may still be highly in need of psychological help after substantial time since victimization has passed. Professionals involved in the settlement of civil damage claims filed by victims of violence may play an important role in referring victims with current psychological problems to appropriate treatment services, as they are likely to maintain relations with victims until all compensation possibilities have been exhausted. As an exploratory examination of this topic, the current study investigates the potential utility of file characteristics as predictors of chronic PTSD among 686 victims of violence who had applied for state compensation with the Dutch Victim Compensation Fund (DVCF) in 2006. Identification of significant predictors is preceded by estimating prevalence rates of PTSD. Results indicate that approximately 1 of 2 victims applying for state compensation in the Netherlands still have PTSD many years after victimization and claim settlement. Age, female sex, time since victimization, acquaintance with the perpetrator, violence-related hospitalization, and compensation for immaterial damage prove to be predictive of PTSD, although female sex and immaterial damage compensation fail to reach significance after adjusting for recalled peritraumatic distress severity. Implications for policy practice as well as strengths and limitations of the study are discussed.

  3. Geodynamics and Stress State of the Earth's Crust in the Greater and Lesser Caucasus (Azerbaijan) collision region

    Science.gov (United States)

    Babayev, Gulam; Akhmedova, Elnare; Babayev, Elvin

    2017-04-01

    The current study researches the present-day stress state of the Earth's crust within the territory of Azerbaijan by using the database of the international research project "World Stress Map" (WSM). The present stress state was also assessed by exploring the effects of the contemporary topographic properties of Caucasus in three-dimensional frame. Aiming to explore the relative roles of regional tectonic conditions in the definition of stress state of Greater and Lesser Caucasus, stress distribution model was developed by the earthquake data (1998-2016) and by the standard techniques of stress field calculation. The results show that the stress orientations are influenced also by the combination of topography and crust thickness distribution even at very large depth. Stress data and earthquake focal mechanisms indicate that the stress state of the Earth's crust of the Greater and Lesser Caucasus is characterized by the compression predominantly oriented across the regional strike. The model results suggest that the Lesser Caucasus and Kur depression are rotating coherently, with little or no internal deformation in a counter-clockwise rotation located near the north-eastern corner of the Black Sea. Orientation of stress axes well consistent with earthquake focal mechanisms revealed that within Upper and Lower Crusts, earthquakes are predominantly thrust-faulting with a number of normal-faulting and some strike-slip faulting. The map of the focal mechanisms and stress distribution suggests that the research area is characterized by the thrust of horizontal compression trending north-north-east in the western part of the southern Caucasus. In the western part of Azerbaijan, the compression takes place between the Main Caucasus Fault and the Kur depression, which strikes south along the northern margin of the mountain range. In addition, a clear transition from the left-lateral strike slip to the predominantly right-lateral strike slip is observed in the southern of

  4. Numerical analysis oriented biaxial stress-strain relation and failure criterion of plain concrete

    International Nuclear Information System (INIS)

    Link, J.

    1975-01-01

    A biaxial stress-strain relation and failure criterion is proposed, which is applicable to structural analysis methods. The formulation of material behavior of plain concrete in biaxial stress-state was developed. A nonlinear elastic, anisotropic stress-strain relation was derived with two moduli of elasticity, E 1 , E 2 and Poisson's ratios, ν 1 , ν 2 , which depend on the prevailing biaxial stress state. The stress-strain relation is valid in the whole biaxial stress field, that means with a smooth transition between the domains of tension/tension, tension/compression and compression/compression. The stress-dependent moduli E 1 , E 2 and the Poisson's ratios ν 1 , ν 2 are approximated by polynomials, trigonometrical and exponential functions. A failure criterion was defined by approximating the test results of the biaxial ultimate concrete strength with a 7th degree polynomial, which is also valid in the whole biaxial stress domain. The definition of the state of failure is given as a function of stresses as well as strains. Initial parameters of the formulation of the biaxial material behavior are the uniaxial cylindrical strength of concrete and the initial values of Young's modulus and Poisson's ratio. A simple expansion of this formulation makes it applicable not only to normal but also to light-weight concrete. Comparison of numerically calculated stress-strain curves up to the ultimate biaxial stresses which indicate the failure criteria with those obtained from tests show a very good agreement. It is shown, that the biaxial stress-strain relation can be extended for use in cases of triaxial tension/tension/compression stress state. Numerical examples of analysis of concrete slabs show the importance of incorporation of a realistic material behavior for better safety estimations

  5. Stressful life events are associated with insulin resistance among Chinese immigrant women in the United States

    Directory of Open Access Journals (Sweden)

    Carolyn Y. Fang

    2015-01-01

    Conclusions: This is one of the first studies to examine the associations between psychosocial stress and insulin resistance in Chinese immigrant women. These findings contribute to a growing body of literature on stress and diabetes risk in an immigrant population.

  6. Altered resting-state functional connectivity in post-traumatic stress disorder: a perfusion MRI study

    Science.gov (United States)

    Li, Baojuan; Liu, Jian; Liu, Yang; Lu, Hong-Bing; Yin, Hong

    2013-03-01

    The majority of studies on posttraumatic stress disorder (PTSD) so far have focused on delineating patterns of activations during cognitive processes. Recently, more and more researches have started to investigate functional connectivity in PTSD subjects using BOLD-fMRI. Functional connectivity analysis has been demonstrated as a powerful approach to identify biomarkers of different brain diseases. This study aimed to detect resting-state functional connectivity abnormities in patients with PTSD using arterial spin labeling (ASL) fMRI. As a completely non-invasive technique, ASL allows quantitative estimates of cerebral blood flow (CBF). Compared with BOLD-fMRI, ASL fMRI has many advantages, including less low-frequency signal drifts, superior functional localization, etc. In the current study, ASL images were collected from 10 survivors in mining disaster with recent onset PTSD and 10 survivors without PTSD. Decreased regional CBF in the right middle temporal gyrus, lingual gyrus, and postcentral gyrus was detected in the PTSD patients. Seed-based resting-state functional connectivity analysis was performed using an area in the right middle temporal gyrus as region of interest. Compared with the non-PTSD group, the PTSD subjects demonstrated increased functional connectivity between the right middle temporal gyrus and the right superior temporal gyrus, the left middle temporal gyrus. Meanwhile, decreased functional connectivity between the right middle temporal gyrus and the right postcentral gyrus, the right superior parietal lobule was also found in the PTSD patients. This is the first study which investigated resting-state functional connectivity in PTSD using ASL images. The results may provide new insight into the neural substrates of PTSD.

  7. Functional State of Rat’s Erythrocytes Under Different Stress Conditions

    Directory of Open Access Journals (Sweden)

    A.A. Martusevich

    2016-08-01

    Full Text Available Background: In our early publications was shown that electrophorhetic motility of erythrocytes (EPME is a high effective criteria of adaptation response. This correlation is based on parallel development of adaptation syndrome and activation of the main organism regulatory systems, such as sympatoadrenalic and hypotalamo-hypophosial-adrenal ones. Objective: study of the influence of physical exercises and adrenaline injections on electrophorhetic motility, membrahes phospholipids spectrum and oxidative metabolism of the rats’ erythrocytes. Methods: Rats were divided into three equal groups. First group of animals was control (n=10; without any manipulations. Rats of second group were subjected to physical load in the form of a sailing duration of 15 minutes with a cargo amounting to 10% of animal body weight (water temperature – 26-280C. Rats of third group were intraperitoneally injected with adrenaline hydrochloride (0.1 mg/kg. Blood sampling was made from the sublingual vein in 15, 30, 60, 120 minutes and 24 hours after exposure. We estimated the dynamics of the electrophorhetic motility of erythrocytes (EPME, the phospholipid spectrum of erythrocytes membranes, the concentration of malonic dialdehyde (MDA and the state of the glutathione system. Results and conclusions: The study suggests that red blood cell as a biological system is capable for realization of stress response may develop a special “alarm reaction” after action of the stress agent. This response initiates activation of free radical processes and phospholipids profile in erythrocyte membranes with reducing of its electronegativity. This stage enhances the activity of the antioxidant system, is limiting the development of lipid peroxidation processes, and leads to the development of "adaptation stage" of the cellular system, coupled with the restoration of the electronegativity of the membrane and the mobilization of reserves of low molecular antioxidants, particularly

  8. Relationship of perceived stress with depression: complete mediation by perceived control and anxiety in Iran and the United States.

    Science.gov (United States)

    Ghorbani, Nima; Krauss, Stephen W; Watson, P J; Lebreton, Daniel

    2008-12-01

    This study sought to clarify the importance and cross-cultural relevance of associations between generalized perceived stress and depression. Also tested was the hypothesis that perceived stress would correlate more strongly with anxiety than with depression, whereas control would be more predictive of depression than of anxiety. Relationships between perceived stress, anxiety, depression, and perceived control were examined in samples of Iranian (n = 191) and American (n = 197) undergraduates. Correlations among these variables were generally similar across the two societies. Perceived stress did predict anxiety better than depression, but perceptions of control predicted depression significantly better than anxiety only in the United States. Best fitting structural equation models revealed that anxiety and perceived control completely accounted for the linkage between perceived stress and depression in both societies. An equally acceptable and more parsimonious model described perceived stress as a consequence rather than as an antecedent of anxiety and perceived control. Structural equation models were essentially identical across the two cultures except that internal control displayed a significant negative relationship with anxiety only in Iran. This result seemed to disconfirm any possible suggestion that a supposedly individualistic process like internal control could have no noteworthy role within a presumably more collectivistic Muslim society like Iran. Overall, these data documented the importance of anxiety and perceived control in explaining the perceived stress-depression relationship cross-culturally and therefore questioned the usefulness of perceived stress in predicting depression. Whether this understanding of the stress-depression relationship deserves general acceptance will require additional studies that measure the frequency of stressful life events and that utilize a longitudinal design.

  9. Stress Coping Levels and Mental States of Police Vocational School of Higher Education Students

    Directory of Open Access Journals (Sweden)

    Arzu Yildirim

    2011-06-01

    Full Text Available SUMMARY AIM: This study was planned and carried out with the objective of determining stress coping levels and mental state of students attending Police Vocational Schools of Higher Education, in addition to factors effecting these. MATERIAL and METHOD: This desciptive and cross-sectional study consisted of 300 male students enrolled in the 2005-2006 academic year, at Police Vocational School of Higher Education, located in central Erzincan, Turkey. In this study, instead of random sampling, 281 (93.7% students who were present at the school at the time of the study and accepted to partipate in it were included. Data for this study was collected using a desciptive form created by the researchers, Rosenbaum’s Learned Resourcefulness Scale (RLRS and The Symptom Check List-90-R (SCL-90-R. During the data analysis, frequency distributions, Mann-Whitney U, Kruskal-Wallis and analysis of variance (one-way ANOVA were used; and for analysis of independent groups, t-test was used. RESULTS: Among the students, it was determined that 54.8% were 1. grade, 90.7% had their parents living together, 43.5% had a father and 60.5% had a mother who graduated from elementary school, fathers of 23.5% of students were retired, 93.6% of them had mothers who were home makers. In addition, it was found out that 78.6% of students chose their profession willingly, the average family income of 71.5% of students were at medium levels, 82.9% always believed in themselves and 63.3% of students did not smoke. Based on the results obtained, it was observed that second grade students, those with mothers who are highly educated and those who trusted themselved all the time had significantly high stress coping levels; students who chose their own profession, believed in themselves and did not smoke had significantly low levels of mental symptom indications. CONCLUSION: In this study, the students were determined to posess averge levels of stress coping skills and they were found

  10. Measuring Stress in Young Children Using Hair Cortisol: The State of the Science.

    Science.gov (United States)

    Bates, Randi; Salsberry, Pamela; Ford, Jodi

    2017-10-01

    Extensive literature suggests that adverse experiences in early childhood may deleteriously impact later health. These effects are thought to be related to the impact of persistent or chronic stress on various biological processes, mediated by dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, and ultimately irregularities in cortisol levels. Ameliorating persistent stress in young children requires accurately measuring the chronicity of physiologic stress, which is difficult in young children because of unreliable self-report and the burden and inaccuracy associated with using invasive acute-stress biomeasures. A better way to approximate persistent stress in young children is measuring hair cortisol concentration (HCC), as it only requires one noninvasive collection to measure months of HPA-axis activity or experienced stress. However, few studies measure HCC in young children despite wide use in adult stress research. This article reviews and synthesizes research that uses HCC to approximate persistent stress in healthy children, 12-60 months of age. Reviewed studies indicate that HCC is elevated in young children who are experiencing forms of persistent stress such as low socioeconomic status and maternal distress. Hair cortisol is thus a promising measure of early childhood persistent stress, but due to the limited use of HCC in this population, much research is still needed. Specifically, nurse researchers may need to measure several factors associated with early childhood persistent stress and HCC to identify which children are at risk for stress-related disease.

  11. Perceived Support as a Predictor of Acculturative Stress among International Students in the United States

    Science.gov (United States)

    Bai, Jieru

    2016-01-01

    A quantitative study was conducted to measure the acculturative stress of international students and investigate the predictors of acculturative stress. A total of 186 students participated in the survey. Results showed that 22.4% of the students in this study exceeded the normal stress level and might need counseling or psychological…

  12. REGULAR AND SPECIFIC FEATURES OF STRESSED AND DEFORMED STATE OF COMPOSITE MATERIAL WITH PIERCED OPENING

    Directory of Open Access Journals (Sweden)

    Yu. V. Vasilevich

    2007-01-01

    Full Text Available Mathematical model describing a dependence between deformations and stresses in the zone of prepreg piercing zone is given in the paper. Boundary conditions in the piercing zone in number of four functional dependences for prepregs can express either the given stresses or displacements, or describe boundary form, or express relations between stresses and displacements etc.

  13. Cognitive benefit and cost of acute stress is differentially modulated by individual brain state

    NARCIS (Netherlands)

    Kohn, N.; Hermans, E.J.; Fernandez, G.

    2017-01-01

    Acute stress is associated with beneficial as well as detrimental effects on cognition in different individuals. However, it is not yet known how stress can have such opposing effects. Stroop-like tasks typically show this dissociation: stress diminishes speed, but improves accuracy. We investigated

  14. Wearable physiological sensors reflect mental stress state in office-like situations

    NARCIS (Netherlands)

    Wijsman, J.L.P; Grundlehner, Bernard; Liu, Hao; Penders, Julien; Hermens, Hermanus J.

    Timely mental stress detection can help to prevent stress-related health problems. The aim of this study was to identify those physiological signals and features suitable for detecting mental stress in office-like situations. Electrocardiogram (ECG), respiration, skin conductance and surface

  15. Endoplasmic reticulum redox state is not perturbed by pharmacological or pathological endoplasmic reticulum stress in live pancreatic β-cells.

    Directory of Open Access Journals (Sweden)

    Irmgard Schuiki

    Full Text Available Accumulation of unfolded, misfolded and aggregated proteins in the endoplasmic reticulum (ER causes ER stress. ER stress can result from physiological situations such as acute increases in secretory protein biosynthesis or pathological conditions that perturb ER homeostasis such as alterations in the ER redox state. Here we monitored ER redox together with transcriptional output of the Unfolded Protein Response (UPR in INS-1 insulinoma cells stably expressing eroGFP (ER-redox-sensor and mCherry protein driven by a GRP78 promoter (UPR-sensor. Live cell imaging, flow cytometry and biochemical characterization were used to examine these parameters in response to various conditions known to induce ER stress. As expected, treatment of the cells with the reducing agent dithiothreitol caused a decrease in the oxidation state of the ER accompanied by an increase in XBP-1 splicing. Unexpectedly however, other treatments including tunicamycin, thapsigargin, DL-homocysteine, elevated free fatty acids or high glucose had essentially no influence on the ER redox state, despite inducing ER stress. Comparable results were obtained with dispersed rat islet cells expressing eroGFP. Thus, unlike in yeast cells, ER stress in pancreatic β-cells is not associated with a more reducing ER environment.

  16. On the determination of general plane stress states in orthotropic materials from ultrasonic velocity data in non symmetry planes

    International Nuclear Information System (INIS)

    Goncalves Filho, Orlando J.A.

    2015-01-01

    This work reports the progress in the development of a new experimental protocol for plane stress determination in orthotropic materials based on the ultrasonic velocity of bulk waves propagating in non symmetry planes with oblique incidence. The presence of stress-induced deformation introduces an acoustic anisotropy in the material in addition to that defined by its texture. Orthotropic materials under general plane stress states become acoustically monoclic and its orthotropic planes orthogonal to the stress plane become non symmetry planes. The inverse solution of the generalized Christoffel equation for ultrasonic bulk waves propagating in non symmetry planes of anisotropic bodies is known to be numerically unstable. The suggested protocol deals with this numerical instability without recourse to bulk wave propagation in the stress plane as proposed in the literature. Hence, it should be useful for plane stress analysis of thin wall pressure vessels where ultrasonic measurements in the direction of the wall plane are not possible. For the initial validation of the suggested protocol and verification of the stability of the inversion algorithm, computer simulation of stress determination have been performed from synthetic sets of velocity data obtained by the forward solution of the generalized Christoffel equation. Preliminary results for slightly orthotropic aluminium highlight the potential of the suggested protocol. (author)

  17. The association between high levels of cumulative life stress and aberrant resting state EEG dynamics in old age.

    Science.gov (United States)

    Marshall, Amanda C; Cooper, Nicholas R

    2017-07-01

    Cumulative experienced stress produces shortcomings in old adults' cognitive performance. These are reflected in electrophysiological changes tied to task execution. This study explored whether stress-related aberrations in older adults' electroencephalographic (EEG) activity were also apparent in the system at rest. To this effect, the amount of stressful life events experienced by 60 young and 60 elderly participants were assessed in conjunction with resting state power changes in the delta, theta, alpha, and beta frequencies during a resting EEG recording. Findings revealed elevated levels of delta power among elderly individuals reporting high levels of cumulative life stress. These differed significantly from young high and low stress individuals and old adults with low levels of stress. Increases of delta activity have been linked to the emergence of conditions such as Alzheimer's Disease and Mild Cognitive Impairment. Thus, a potential interpretation of our findings associates large amounts of cumulative stress with an increased risk of developing age-related cognitive pathologies in later life. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. On the impact of multi-axial stress states on trailing edge bondlines in wind turbine rotor blades

    Science.gov (United States)

    Noever Castelos, Pablo; Balzani, Claudio

    2016-09-01

    For a reliable design of wind turbine systems all of their components have to be designed to withstand the loads appearing in the turbine's lifetime. When performed in an integral manner this is called systems engineering, and is exceptionally important for components that have an impact on the entire wind turbine system, such as the rotor blade. Bondlines are crucial subcomponents of rotor blades, but they are not much recognized in the wind energy research community. However, a bondline failure can lead to the loss of a rotor blade, and potentially of the entire turbine, and is extraordinarily relevant to be treated with strong emphasis when designing a wind turbine. Modern wind turbine rotor blades with lengths of 80 m and more offer a degree of flexibility that has never been seen in wind energy technology before. Large deflections result in high strains in the adhesive connections, especially at the trailing edge. The latest edition of the DNV GL guideline from end of 2015 demands a three-dimensional stress analysis of bondlines, whereas before an isolated shear stress proof was sufficient. In order to quantify the lack of safety from older certification guidelines this paper studies the influence of multi-axial stress states on the ultimate and fatigue load resistance of trailing edge adhesive bonds. For this purpose, detailed finite element simulations of the IWES IWT-7.5-164 reference wind turbine blades are performed. Different yield criteria are evaluated for the prediction of failure and lifetime. The results show that the multi-axial stress state is governed by span-wise normal stresses. Those are evidently not captured in isolated shear stress proofs, yielding non-conservative estimates of lifetime and ultimate load resistance. This finding highlights the importance to include a three-dimensional stress state in the failure analysis of adhesive bonds in modern wind turbine rotor blades, and the necessity to perform a three-dimensional characterization

  19. The Stress-Strain State of Recent Structures in the Northeastern Sector of the Russian Arctic Region

    Science.gov (United States)

    Imaeva, L. P.; Imaev, V. S.; Mel'nikova, V. I.

    2018-03-01

    Complex research to determine the stress-strain state of the Earth's crust and the types of seismotectonic destruction for the northeastern sector of the Russian Arctic was conducted. The principles of regional ranking of neotectonic structures were developed according to the activity of geodynamic processes, and argumentation for their class differentiation is presented. The structural-tectonic position, the parameters of the deep structure, the system of active faults, and the tectonic stress fields, calculated on the basis of both tectonophysical analysis of discontinuous and folded late Cenozoic deformations and seismological data, were analyzed. This complex of investigations made it possible to determine the directions of the main axes of deformations of the stress-strain state of the Earth's crust and to reveal the regularity in the change of tectonic regimes.

  20. Development and validation of the Acculturative Stress Scale for Chinese College Students in the United States (ASSCS).

    Science.gov (United States)

    Bai, Jieru

    2016-04-01

    Chinese students are the biggest ethnic group of international students in the United States. This study aims to develop a reliable and valid scale to accurately measure their acculturative stress. A 72-item pool was sent online to Chinese students and a five-factor scale of 32 items was generated by exploratory factor analysis. The five factors included language insufficiency, social isolation, perceived discrimination, academic pressure, and guilt toward family. The Acculturative Stress Scale for Chinese Students demonstrated high reliability and initial validity by predicting depression and life satisfaction. It was the first Chinese scale of acculturative stress developed and validated among a Chinese student sample in the United States. In the future, the scale can be used as a diagnostic tool by mental health professionals and a self-assessment tool by Chinese students. (c) 2016 APA, all rights reserved.

  1. Uniaxial experimental study of the acoustic emission and deformation behavior of composite rock based on 3D digital image correlation (DIC)

    Science.gov (United States)

    Cheng, Jian-Long; Yang, Sheng-Qi; Chen, Kui; Ma, Dan; Li, Feng-Yuan; Wang, Li-Ming

    2017-12-01

    In this paper, uniaxial compression tests were carried out on a series of composite rock specimens with different dip angles, which were made from two types of rock-like material with different strength. The acoustic emission technique was used to monitor the acoustic signal characteristics of composite rock specimens during the entire loading process. At the same time, an optical non-contact 3D digital image correlation technique was used to study the evolution of axial strain field and the maximal strain field before and after the peak strength at different stress levels during the loading process. The effect of bedding plane inclination on the deformation and strength during uniaxial loading was analyzed. The methods of solving the elastic constants of hard and weak rock were described. The damage evolution process, deformation and failure mechanism, and failure mode during uniaxial loading were fully determined. The experimental results show that the θ = 0{°}-45{°} specimens had obvious plastic deformation during loading, and the brittleness of the θ = 60{°}-90{°} specimens gradually increased during the loading process. When the anisotropic angle θ increased from 0{°} to 90{°}, the peak strength, peak strain, and apparent elastic modulus all decreased initially and then increased. The failure mode of the composite rock specimen during uniaxial loading can be divided into three categories: tensile fracture across the discontinuities (θ = 0{°}-30{°}), sliding failure along the discontinuities (θ = 45{°}-75{°}), and tensile-split along the discontinuities (θ = 90{°}). The axial strain of the weak and hard rock layers in the composite rock specimen during the loading process was significantly different from that of the θ = 0{°}-45{°} specimens and was almost the same as that of the θ = 60{°}-90{°} specimens. As for the strain localization highlighted in the maximum principal strain field, the θ = 0{°}-30{°} specimens appeared in the rock

  2. Damage evolution under cyclic multiaxial stress state: A comparative analysis between glass/epoxy laminates and tubes

    DEFF Research Database (Denmark)

    Quaresimin, M.; Carraro, P.A.; Mikkelsen, Lars Pilgaard

    2014-01-01

    In this work an experimental investigation on damage initiation and evolution in laminates under cyclic loading is presented. The stacking sequence [0/θ2/0/-θ2]s has been adopted in order to investigate the influence of the local multiaxial stress state in the off-axis plies and the possible effect...

  3. Resting state functional connectivity of the anterior cingulate cortex in veterans with and without post-traumatic stress disorder

    NARCIS (Netherlands)

    Kennis, Mitzy; Rademaker, Arthur R.; van Rooij, Sanne J H; Kahn, René S.; Geuze, Elbert

    2015-01-01

    Post-traumatic stress disorder (PTSD) is an anxiety disorder that is associated with structural and functional alterations in several brain areas, including the anterior cingulate cortex (ACC). Here, we examine resting state functional connectivity of ACC subdivisions in PTSD, using a seed-based

  4. Self Efficacy and Some Demographic Variables as Predictors of Occupational Stress among Primary School Teachers in Delta State of Nigeria

    Science.gov (United States)

    Akpochafo, G. O.

    2014-01-01

    This study investigated self efficacy and some demographic variables as predictors of occupational stress among primary school teachers in Delta State. Three hypotheses were formulated to guide the study. The study adopted a descriptive survey design that utilized an expost-facto research type. A sample of one hundred and twenty primary school…

  5. Uniaxial-Strain-Orientation Dependence of the Competition between Mott and Charge Ordered Phases and their Corresponding Superconductivity of β-(BDA-TTP)2I3

    Science.gov (United States)

    Nuruzzaman, Md.; Yokogawa, Keiichi; Yoshino, Harukazu; Yoshimoto, Haruo; Kikuchi, Koichi; Kaihatsu, Takayuki; Yamada, Jun-ichi; Murata, Keizo

    2012-12-01

    We studied the electronic transport properties of the charge transfer salt β-(BDA-TTP)2I3 [BDA-TTP: 2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene] by applying uniaxial strains along the three crystallographic axes, and obtained three corresponding temperature-pressure phase diagrams. Three phase diagrams were quite dependent on the direction of compression. Following the preceding paper by Kikuchi et al., we speculate that the insulating states are of 1/2-filled Mott insulators for the a- and b-axes compressions, and of 1/4-filled charge ordered states for the c-axis compression as well as hydrostatic pressure. The superconducting phase under uniaxial strain was realized with Tc = 5 K at 1.9 GPa along the a-axis and with Tc = 5.6 K at 1.75 GPa along the b-axis. Superconductivity was also reproduced with a Tc of 9.5 K at 1.0 GPa for the c-axis compressions in the range of 0.85 to 1.53 GPa as previously reported. We studied tentative measurement on upper critical fields, Bc2's of these superconductivities and found that the extrapolated values, Bc2(0)'s, exceeded Pauli-limit by about 2--3 times. However, at least in terms of Bc2, the difference in superconductivity associated with two different insulating states was not clear.

  6. Uniaxial strain effects on transport properties of a supramolecular organic conductor theta-(DIETS) sub 2 [Au(CN) sub 4

    CERN Document Server

    Tajima, N; Kato, R; Nishio, Y; Kajita, K

    2003-01-01

    Pressure-controlled switching between an insulating state and a superconducting state has been successfully realized on a supramolecular organic conductor theta-(DIETS) sub 2 [Au(CN) sub 4] [DIETS = diiodo(ethylenedithio)diselenadithiafulvalene]. Strong contact between iodine on the donor (DIETS) molecule and nitrogen on the anion [Au(CN) sub 4] genetates characteristic uniaxial strain effects on transport properties. Under the ambient pressure, the present system undergoes a semiconductor-insulator transition at 226 K. The effect of strains parallel to the conduction plane (ab-plane) is very small. Even under uniaxial strains up to 20 kbar along the a- and b-axis directions, the transition is not suppressed. Surprisingly, however, the c-axis strain induces a superconducting state with T sub c of 8.6 K at 10 kbar. Band parameter calculation and the conductivity anisotropy ratio suggest that an increase in the bandwidth W associated with a c-axis strain transforms the system to the metallic and superconducting...

  7. Characterization of a 14Cr ODS steel by means of small punch and uniaxial testing with regard to creep and fatigue at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Bruchhausen, M., E-mail: matthias.bruchhausen@ec.europa.eu [European Commission, Joint Research Centre, Institute for Energy and Transport, P.O. Box 2, 1755 ZG Petten (Netherlands); Turba, K. [European Commission, Joint Research Centre, Institute for Energy and Transport, P.O. Box 2, 1755 ZG Petten (Netherlands); Lund University, Division of Materials Engineering, P.O. Box 118, SE-221 00 Lund (Sweden); Haan, F. de; Hähner, P.; Austin, T. [European Commission, Joint Research Centre, Institute for Energy and Transport, P.O. Box 2, 1755 ZG Petten (Netherlands); Carlan, Y. de [CEA, DEN, Service de Recherches Métallurgiques Appliquées, 91191 Gif-sur-Yvette (France)

    2014-01-15

    A 14Cr ODS steel was characterized at elevated temperatures with regard to its behavior in small punch and uniaxial creep tests and in low cycle fatigue tests. A comparison of small punch and uniaxial creep tests at 650 °C revealed a strong anisotropy of the material when strained parallel and perpendicular to the extrusion direction with rupture times being several orders of magnitude lower for the perpendicular direction. The stress-rupture and Larson–Miller plots show a very large scatter of the creep data. This scatter is strongly reduced when rupture time is plotted against minimum deflection rate or minimum creep rate (Monkman–Grant plot). Fatigue tests have been carried out at 650 °C and 750 °C. The alloy is cyclically very stable with practically no hardening/softening. Results from the tests at both temperatures can be described by a common power law. An increase in the test temperature has little influence on the fatigue ductility exponent. For a given total strain level, the fatigue life of the alloy is reduced with increasing temperature.

  8. State of stress in exhumed basins and implications for fluid flow: insights from the Illizi Basin, Algeria

    KAUST Repository

    English, Joseph M.

    2017-05-31

    The petroleum prospectivity of an exhumed basin is largely dependent on the ability of pre-existing traps to retain oil and gas volumes during and after the exhumation event. Although faults may act as lateral seals in petroleum traps, they may start to become hydraulically conductive again and enable fluid flow and hydrocarbon leakage during fault reactivation. We constrain the present day in situ stresses of the exhumed Illizi Basin in Algeria and demonstrate that the primary north–south and NW–SE (vertical strike-slip) fault systems in the study area are close to critical stress (i.e. an incipient state of shear failure). By contrast, the overpressured and unexhumed Berkine Basin and Hassi Messaoud areas to the north do not appear to be characterized by critical stress conditions. We present conceptual models of stress evolution and demonstrate that a sedimentary basin with benign in situ stresses at maximum burial may change to being characterized by critical stress conditions on existing fault systems during exhumation. These models are supportive of the idea that the breaching of a closed, overpressured system during exhumation of the Illizi Basin may have been a driving mechanism for the regional updip flow of high-salinity formation water within the Ordovician reservoirs during Eocene–Miocene time. This work also has implications for petroleum exploration in exhumed basins. Fault-bounded traps with faults oriented at a high angle to the maximum principal horizontal stress direction in strike-slip or normal faulting stress regimes are more likely to have retained hydrocarbons in exhumed basins than fault-bounded traps with faults that are more optimally oriented for shear failure and therefore have a greater propensity to become critically stressed during exhumation.

  9. An improved Corten-Dolan's model based on damage and stress state effects

    International Nuclear Information System (INIS)

    Gao, Huiying; Huang, Hong Zhong; Lv, Zhiqiang; Zuo, Fang Jun; Wang, Hai Kun

    2015-01-01

    The value of exponent d in Corten-Dolan's model is generally considered to be a constant. Nonetheless, the results predicted on the basis of this statement deviate significantly from the real values. In consideration of the effects of damage and stress state on fatigue life prediction, Corten-Dolan's model is improved by redefining the exponent d used in the traditional model. The improved model performs better than the traditional one with respect to the demonstration of a fatigue failure mechanism. Predictions of fatigue life on the basis of investigations into three metallic specimens indicate that the errors caused by the improved model are significantly smaller than those induced by the traditional model. Meanwhile, predictions derived according to the improved model fall into a narrower dispersion zone than those made as per Miner's rule and the traditional model. This finding suggests that the proposed model improves the life prediction accuracy of the other two models. The predictions obtained using the improved Corten-Dolan's model differ slightly from those derived according to a model proposed in previous literature; a few life predictions obtained on the basis of the former are more accurate than those derived according to the latter. Therefore, the improved model proposed in this paper is proven to be rational and reliable given the proven validity of the existing model. Therefore, the improved model can be feasibly and credibly applied to damage accumulation and fatigue life prediction to some extent.

  10. An improved Corten-Dolan's model based on damage and stress state effects

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Huiying; Huang, Hong Zhong; Lv, Zhiqiang; Zuo, Fang Jun; Wang, Hai Kun [University of Electronic Science and Technology of China, Chengdu (China)

    2015-08-15

    The value of exponent d in Corten-Dolan's model is generally considered to be a constant. Nonetheless, the results predicted on the basis of this statement deviate significantly from the real values. In consideration of the effects of damage and stress state on fatigue life prediction, Corten-Dolan's model is improved by redefining the exponent d used in the traditional model. The improved model performs better than the traditional one with respect to the demonstration of a fatigue failure mechanism. Predictions of fatigue life on the basis of investigations into three metallic specimens indicate that the errors caused by the improved model are significantly smaller than those induced by the traditional model. Meanwhile, predictions derived according to the improved model fall into a narrower dispersion zone than those made as per Miner's rule and the traditional model. This finding suggests that the proposed model improves the life prediction accuracy of the other two models. The predictions obtained using the improved Corten-Dolan's model differ slightly from those derived according to a model proposed in previous literature; a few life predictions obtained on the basis of the former are more accurate than those derived according to the latter. Therefore, the improved model proposed in this paper is proven to be rational and reliable given the proven validity of the existing model. Therefore, the improved model can be feasibly and credibly applied to damage accumulation and fatigue life prediction to some extent.

  11. Resting-State Neurophysiological Abnormalities in Posttraumatic Stress Disorder: A Magnetoencephalography Study

    Directory of Open Access Journals (Sweden)

    Amy S. Badura-Brack

    2017-04-01

    Full Text Available Posttraumatic stress disorder (PTSD is a debilitating psychiatric condition that is common in veterans returning from combat operations. While the symptoms of PTSD have been extensively characterized, the neural mechanisms that underlie PTSD are only vaguely understood. In this study, we examined the neurophysiology of PTSD using magnetoencephalography (MEG in a sample of veterans with and without PTSD. Our primary hypothesis was that veterans with PTSD would exhibit aberrant activity across multiple brain networks, especially those involving medial temporal and frontal regions. To this end, we examined a total of 51 USA combat veterans with a battery of clinical interviews and tests. Thirty-one of the combat veterans met diagnostic criteria for PTSD and the remaining 20 did not have PTSD. All participants then underwent high-density MEG during an eyes-closed resting-state task, and the resulting data were analyzed using a Bayesian image reconstruction method. Our results indicated that veterans with PTSD had significantly stronger neural activity in prefrontal, sensorimotor and temporal areas compared to those without PTSD. Veterans with PTSD also exhibited significantly stronger activity in the bilateral amygdalae, parahippocampal and hippocampal regions. Conversely, healthy veterans had stronger neural activity in the bilateral occipital cortices relative to veterans with PTSD. In conclusion, these data suggest that veterans with PTSD exhibit aberrant neural activation in multiple cortical areas, as well as medial temporal structures implicated in affective processing.

  12. A state of the art on primary side stress corrosion cracking in nuclear power plant

    Energy Technology Data Exchange (ETDEWEB)

    Kim, H. P.; Kim, J. S.; Han, J. H.; Lee, D. H.; Lim, Y. S.; Suh, J. H.; Hwang, S. S.; Hur, D. H

    1999-09-01

    A state of art on primary water stress corrosion cracking (PWSCC) of alloy 600 used as steam generator tubing of nuclear power plant and remedial action on the PWSCC were reviewed and analyzed. One of the major metallurgical factors which have effect on PWSCC is Cr carbide distribution. A semicontinuous intergranular Cr carbide distribution enhance PWSCC of alloy 600. PWSCC rate is reported to be reported to be proportional to exp(-50 cal/RT) {sigma}{sup 4}. PWSCC rate also increase with increase in hydrogen partial pressure from 0 to 150 ppm and then decreased with further increase in hydrogen partial pressure to 757 ppm. Development of PWSCC prediction technology which takes into account tubing material, fabrication process and operating history of steam generator is needed to manage PWSCC of domestic nuclear power plant. PWSCC has mainly occurred at expansion irregularities within tubesheet, expansion transitions, dented tube support plate intersections and transition and apex of U bend. Remedial actions to PWSCC are sleeving, plugging, temperature reduction, Ni plating, Ni sleeving, shot peening and steam generator replacement in worst case. Option to remedial actions depend on plant specific such as plant age, leak rate from primary to secondary, density and progression of PWSCC. Ni sleeving developed in Framatome seems to be a powerful method because it never subject to PWSCC. Remedial action should be developed and evaluated for possible PWSCC of domestic nuclear power plant. (author)

  13. Stress state reassessment of Romanian offshore structures taking into account corrosion influence

    Science.gov (United States)

    Joavină, R.; Zăgan, S.; Zăgan, R.; Popa, M.

    2017-08-01

    Progressive degradation analysis for extraction or exploration offshore structure, with appraisal of failure potential and the causes that can be correlated with the service age, depends on the various sources of uncertainty that require particular attention in design, construction and exploitation phases. Romanian self erecting platforms are spatial lattice structures consist of tubular steel joints, forming a continuous system with an infinite number of dynamic degrees of freedom. Reassessment of a structure at fixed intervals of time, recorrelation of initial design elements with the actual situation encountered in location and with structural behaviour represents a major asset in lowering vulnerabilities of offshore structure. This paper proposes a comparative reassessment of the stress state for an offshore structure Gloria type, when leaving the shipyard and at the end of that interval corresponding to capital revision, taking into account sectional changes due to marine environment corrosion. The calculation was done using Newmark integration method on a 3D model, asses of the dynamic loads was made through probabilistic spectral method.

  14. Thermal stress state of laminated shells of revolution made of isotropic and linearly orthotropic materials

    International Nuclear Information System (INIS)

    Savchenko, V.G.

    1995-01-01

    In this investigation, we will use a cylindrical coordinate system to study the stress state of laminated shells of revolution made of inelastically deforming isotropic materials and elastic materials with linear orthotropy. One of the principal directions of anisotropy coincides with the axis of revolution of the body. The shells will be subjected to nonaxisymmetric loading by body bar K (K Z , K r , K var-phi ) and surface bar t n (t nz , t nr , t nvar-phi ) forces and heating. The level of loading is such that the rheological properties of the materials of the layers are not a factor, although their thermomechanical characteristics depend on temperature. In addition, the loading and heating of the body occur in such a way that simple (or close to simple) deformation processes take place in its isotropic elements. These processes are accompanied by inelastic strains and the formation of unloading regions in which plastic strains having the sign opposite the initial strains develop. It is assumed that the layers of the body are secured to one another without interference and that conditions corresponding to ideal contact prevail at their interfaces

  15. Numerical simulation of stress-strain state of electrophoretic shell molds

    Science.gov (United States)

    Sviridov, A. V.; Odinokov, V. I.; Dmitriev, E. A.; Evstigneev, A. I.; Bashkov, O. V.

    2017-10-01

    In the foundry engineering, castings obtained in one-piece non-gas-generating high-refractory electrophoretic shell molds (ShM) by investment patterns (IP) have an increased rejects percentage associated with low deformation resistance and crack resistance of the SM at different stages of their formation and manufacturing. Crack resistance of the ShM based on IP depends mainly on their stress-strain state (SSS) at various stages of mold forming. SSS decrease significantly improves their crack resistance and decreases their rejects percentage of castings occurring due to clogging and surface defects. In addition, the known methods of decreasing the SSS are still poorly understood. Thus, current research trends are to determine SSS at each stage of ShM forming and develop the ways to decrease it. Theoretical predicting of crack formation in multiple-layer axisymmetric shell molds is given in the work [1], and SSS of multiple-layer axisymmetric shell molds is given in the work [2]. Monolayer electrophoretic ShM had a lack of concern in this field, thus it became an argument for the present workMathematical Model of ShM SSS

  16. Cognitive benefit and cost of acute stress is differentially modulated by individual brain state.

    Science.gov (United States)

    Kohn, Nils; Hermans, Erno J; Fernández, Guillén

    2017-07-01

    Acute stress is associated with beneficial as well as detrimental effects on cognition in different individuals. However, it is not yet known how stress can have such opposing effects. Stroop-like tasks typically show this dissociation: stress diminishes speed, but improves accuracy. We investigated accuracy and speed during a stroop-like task of 120 healthy male subjects after an experimental stress induction or control condition in a randomized, counter-balanced cross-over design; we assessed brain-behavior associations and determined the influence of individual brain connectivity patterns on these associations, which may moderate the effect and help identify stress resilience factors. In the mean, stress was associated to increase in accuracy, but decrease in speed. Accuracy was associated to brain activation in a distributed set of brain regions overlapping with the executive control network (ECN) and speed to temporo-parietal activation. In line with a stress-related large-scale network reconfiguration, individuals showing an upregulation of the salience and down-regulation of the executive-control network under stress displayed increased speed, but decreased performance. In contrast, individuals who upregulate their ECN under stress show improved performance. Our results indicate that the individual large-scale brain network balance under acute stress moderates cognitive consequences of threat. © The Author (2017). Published by Oxford University Press.

  17. Cognitive benefit and cost of acute stress is differentially modulated by individual brain state

    Science.gov (United States)

    Hermans, Erno J.; Fernández, Guillén

    2017-01-01

    Abstract Acute stress is associated with beneficial as well as detrimental effects on cognition in different individuals. However, it is not yet known how stress can have such opposing effects. Stroop-like tasks typically show this dissociation: stress diminishes speed, but improves accuracy. We investigated accuracy and speed during a stroop-like task of 120 healthy male subjects after an experimental stress induction or control condition in a randomized, counter-balanced cross-over design; we assessed brain–behavior associations and determined the influence of individual brain connectivity patterns on these associations, which may moderate the effect and help identify stress resilience factors. In the mean, stress was associated to increase in accuracy, but decrease in speed. Accuracy was associated to brain activation in a distributed set of brain regions overlapping with the executive control network (ECN) and speed to temporo-parietal activation. In line with a stress-related large-scale network reconfiguration, individuals showing an upregulation of the salience and down-regulation of the executive-control network under stress displayed increased speed, but decreased performance. In contrast, individuals who upregulate their ECN under stress show improved performance. Our results indicate that the individual large-scale brain network balance under acute stress moderates cognitive consequences of threat. PMID:28402480

  18. Specimen aspect ratio and progressive field strain development of sandstone under uniaxial compression by three-dimensional digital image correlation

    Directory of Open Access Journals (Sweden)

    H. Munoz

    2017-08-01

    Full Text Available The complete stress–strain characteristics of sandstone specimens were investigated in a series of quasi-static monotonic uniaxial compression tests. Strain patterns development during pre- and post-peak behaviours in specimens with different aspect ratios was also examined. Peak stress, post-peak portion of stress–strain, brittleness, characteristics of progressive localisation and field strain patterns development were affected at different extents by specimen aspect ratio. Strain patterns of the rocks were obtained by applying three-dimensional (3D digital image correlation (DIC technique. Unlike conventional strain measurement using strain gauges attached to specimen, 3D DIC allowed not only measuring large strains, but more importantly, mapping the development of field strain throughout the compression test, i.e. in pre- and post-peak regimes. Field strain development in the surface of rock specimen suggests that strain starts localising progressively and develops at a lower rate in pre-peak regime. However, in post-peak regime, strains increase at different rates as local deformations take place at different extents in the vicinity and outside the localised zone. The extent of localised strains together with the rate of strain localisation is associated with the increase in rate of strength degradation. Strain localisation and local inelastic unloading outside the localised zone both feature post-peak regime.

  19. The psychoemotional status and cardiovascular system functional state of the first-year students under the influence of examination stress

    Directory of Open Access Journals (Sweden)

    Liliana K. Tokaeva

    2012-12-01

    Full Text Available The aim of this research is to study of the influence of examination stress on psycho-emotional status and functional state of the cardiovascular system of the 1-st year students of pedagogical high school. Methods – The study involved 105 young men aged 17-18 enrolled in the specialty "Physical Education". The studies were conducted during the period in-between the exams and during the examination session. The psycho-emotional status was determined by the SAN test questionnaire and test and the CH.D. Spielberg test, adapted for Russia by Ju.L. Khanin. The state of CVS autonomic regulation was evaluated by heart rate, blood pressure, endurance ratio, Kerdo index and the adaptive capacities by P.M. Bayevsky. Results – In the absence of exposure to stress in the majority of young men the studied parameters are within normal limits, indicating sufficient adaptive capabilities. A clear correlation between the level of personal anxiety in students and the nature of their reactivity to examination stress was found: the higher the anxiety level in a student is, the more stress resistance decreases and more pronounced changes in the cardiovascular system autonomic regulation appear. The strain of adaptation mechanism was found in a stressful situation in the first-year students with a high level of personal anxiety and satisfactory adaptation – in young men with average and low personal anxiety.

  20. Acoustic emission under biaxial stresses in unflawed 21-6-9 and 304 stainless steel

    International Nuclear Information System (INIS)

    Hamstad, M.A.; Leon, E.M.; Mukherjee, A.K.

    1980-01-01

    Acoustic emission (AE) testing has been carried out with uniaxial and biaxial (2:1 stress ratio) stressing of smooth samples of 21-6-9 and 304 stainless steel (SS). Uniaxial testing was done with simple tensile and compression samples as well as with the special biaxial specimens. Biaxial tensile stressing was accomplished with a specially designed specimen, which had been used previously to characterize AE in 7075 aluminum under biaxial stressing. Results were obtained for air-melt and for vacuum-melt samples of 21-6-9 SS. The air-melt samples contain considerably more inclusion particles than the vacuum-melt samples. For the 304 SS, as received material was examined. To allow AE correlations with microstructure, extensive characterization of the 21-6-9 microstructure was carried out. Significant differences in AE occur in biaxially stressed specimens as compared to uniaxially stressed samples. 15 figures, 3 tables

  1. Saturation and oscillation of current in semiconductors subjected to uniaxial deformation

    International Nuclear Information System (INIS)

    Zdebskii, A.P.; Olikh, Yu.A.; Savchuk, A.U.

    1985-01-01

    The influence of an external uniaxial deformation on the saturation and oscillations of current in photosensitive CdS monocrystals is investigated. The specimens were subjected to uniaxial pressure up to 6 x 10 7 N/m 2 , the pressure being either parallel or perpendicular to the c axis in CdS. With application of external pressure, the shape of current oscillations and their amplitude changed. In the case where the pressure was perpendicular to the direction of current I, the amplitude of oscillations and the saturation depth of the volt-ampere characteristic, VAC, were increased. With pressure being parallel to the current direction, the reverse phenomenon was observed, i.e. the efficiency of the acousto-electronic interaction was reduced

  2. Giant valley drifts in uniaxially strained monolayer MoS{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Schwingenschloegl, Udo; Zhang, Qingyun; Cheng, Yingchun; Gan, Li-Yong [PSE Division, KAUST, Thuwal 23955 (Saudi Arabia)

    2016-07-01

    Using first-principles calculations, we study the electronic structure of monolayer MoS{sub 2} under uniaxial strain. We show that the energy valleys drift far off the corners of the Brillouin zone (K points), about 12 times the amount observed in graphene. Therefore, it is essential to take this effect into consideration for a correct identification of the band gap. The system remains a direct band gap semiconductor up to 4% uniaxial strain, while the size of the band gap decreases from 1.73 to 1.54 eV. We also demonstrate that the splitting of the valence bands due to inversion symmetry breaking and spin-orbit coupling is not sensitive to strain.

  3. Band Gap Changes Of Single Walled Carbon Nanotubes Under Uniaxial Strain

    International Nuclear Information System (INIS)

    Dereli, G.

    2010-01-01

    The study of the band gap variation with mechanical deformation is important in manipulations of Single Walled Carbon Nanotubes (SWCNT). In this study we investigated the electronic band structure and the mechanical properties of (12,0) and (13,0) SWCNTs under the effect of uniaxial strain. Electronic and mechanical properties are studied using a parallel, order N, tight-binding molecular dynamics (O(N) TBMD) simulation code designed by G. Dereli et. al. We showed the effect of uniaxial strain on the variations of band gaps and the total energy per atom of (12,0) and (13,0) SWCNTs. We calculated Young's modulus and the Poisson ratio of these SWCNTs. The research reported here was supported through the Yildiz Technical University Research Found Project No: 24-01-01-04. Simulations are performed in parallel environment at Carbon Nanotube Simulation Laboratory of Yildiz Technical University.

  4. Giant valley drifts in uniaxially strained monolayer MoS2

    KAUST Repository

    Zhang, Qingyun

    2013-12-30

    Using first-principles calculations, we study the electronic structure of monolayer MoS2 under uniaxial strain. We show that the energy valleys drift far off the corners of the Brillouin zone (K points), about 12 times the amount observed in graphene. Therefore, it is essential to take this effect into consideration for a correct identification of the band gap. The system remains a direct band gap semiconductor up to 4% uniaxial strain, while the size of the band gap decreases from 1.73 to 1.54 eV. We also demonstrate that the splitting of the valence bands due to inversion symmetry breaking and spin-orbit coupling is not sensitive to strain.

  5. Stable evaluation of Green's functions in cylindrically stratified regions with uniaxial anisotropic layers

    Science.gov (United States)

    Moon, H.; Donderici, B.; Teixeira, F. L.

    2016-11-01

    We present a robust algorithm for the computation of electromagnetic fields radiated by point sources (Hertzian dipoles) in cylindrically stratified media where each layer may exhibit material properties (permittivity, permeability, and conductivity) with uniaxial anisotropy. Analytical expressions are obtained based on the spectral representation of the tensor Green's function based on cylindrical Bessel and Hankel eigenfunctions, and extended for layered uniaxial media. Due to the poor scaling of these eigenfunctions for extreme arguments and/or orders, direct numerical evaluation of such expressions can produce numerical instability, i.e., underflow, overflow, and/or round-off errors under finite precision arithmetic. To circumvent these problems, we develop a numerically stable formulation through suitable rescaling of various expressions involved in the computational chain, to yield a robust algorithm for all parameter ranges. Numerical results are presented to illustrate the robustness of the formulation including cases of practical interest.

  6. The Landau-de Gennes theory of nematic liquid crystals: Uniaxiality versus Biaxiality

    KAUST Repository

    Majumdar, Apala

    2011-12-01

    We study small energy solutions within the Landau-de Gennes theory for nematic liquid crystals, subject to Dirichlet boundary conditions. We consider two-dimensional and three-dimensional domains separately. In the two-dimensional case, we establish the equivalence of the Landau-de Gennes and Ginzburg-Landau theory. In the three-dimensional case, we give a new definition of the defect set based on the normalized energy. In the threedimensional uniaxial case, we demonstrate the equivalence between the defect set and the isotropic set and prove the C 1,α-convergence of uniaxial small energy solutions to a limiting harmonic map, away from the defect set, for some 0 < a < 1, in the vanishing core limit. Generalizations for biaxial small energy solutions are also discussed, which include physically relevant estimates for the solution and its scalar order parameters. This work is motivated by the study of defects in liquid crystalline systems and their applications.

  7. Symmetry of Uniaxial Global Landau--de Gennes Minimizers in the Theory of Nematic Liquid Crystals

    KAUST Repository

    Henao, Duvan; Majumdar, Apala

    2012-01-01

    We extend the recent radial symmetry results by Pisante [J. Funct. Anal., 260 (2011), pp. 892-905] and Millot and Pisante [J. Eur. Math. Soc. (JEMS), 12 (2010), pp. 1069- 1096] (who show that the equivariant solutions are the only entire solutions of the three-dimensional Ginzburg-Landau equations in superconductivity theory) to the Landau-de Gennes framework in the theory of nematic liquid crystals. In the low temperature limit, we obtain a characterization of global Landau-de Gennes minimizers, in the restricted class of uniaxial tensors, in terms of the well-known radial-hedgehog solution. We use this characterization to prove that global Landau-de Gennes minimizers cannot be purely uniaxial for sufficiently low temperatures. Copyright © by SIAM.

  8. Mechanical properties of stanene under uniaxial and biaxial loading: A molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Mojumder, Satyajit [Department of Mechanical Engineering, Bangladesh University of Engineering and Technology, Dhaka 1000 (Bangladesh); Amin, Abdullah Al [Department of Mechanical and Aerospace Engineering, Case western Reverse University, Cleveland, Ohio 44106 (United States); Islam, Md Mahbubul, E-mail: mmi122@psu.edu [Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

    2015-09-28

    Stanene, a graphene like two dimensional honeycomb structure of tin has attractive features in electronics application. In this study, we performed molecular dynamics simulations using modified embedded atom method potential to investigate mechanical properties of stanene. We studied the effect of temperature and strain rate on mechanical properties of α-stanene for both uniaxial and biaxial loading conditions. Our study suggests that with the increasing temperature, both the fracture strength and strain of the stanene decrease. Uniaxial loading in zigzag direction shows higher fracture strength and strain compared to the armchair direction, while no noticeable variation in the mechanical properties is observed for biaxial loading. We also found at a higher loading rate, material exhibits higher fracture strength and strain. These results will aid further investigation of stanene as a potential nano-electronics substitute.

  9. Stable evaluation of Green's functions in cylindrically stratified regions with uniaxial anisotropic layers

    Energy Technology Data Exchange (ETDEWEB)

    Moon, H., E-mail: haksu.moon@gmail.com [ElectroScience Laboratory, The Ohio State University, Columbus, OH 43212 (United States); Donderici, B., E-mail: burkay.donderici@halliburton.com [Sensor Physics & Technology, Halliburton Energy Services, Houston, TX 77032 (United States); Teixeira, F.L., E-mail: teixeira@ece.osu.edu [ElectroScience Laboratory, The Ohio State University, Columbus, OH 43212 (United States)

    2016-11-15

    We present a robust algorithm for the computation of electromagnetic fields radiated by point sources (Hertzian dipoles) in cylindrically stratified media where each layer may exhibit material properties (permittivity, permeability, and conductivity) with uniaxial anisotropy. Analytical expressions are obtained based on the spectral representation of the tensor Green's function based on cylindrical Bessel and Hankel eigenfunctions, and extended for layered uniaxial media. Due to the poor scaling of these eigenfunctions for extreme arguments and/or orders, direct numerical evaluation of such expressions can produce numerical instability, i.e., underflow, overflow, and/or round-off errors under finite precision arithmetic. To circumvent these problems, we develop a numerically stable formulation through suitable rescaling of various expressions involved in the computational chain, to yield a robust algorithm for all parameter ranges. Numerical results are presented to illustrate the robustness of the formulation including cases of practical interest.

  10. Multi-purpose fatigue sensor. Part 1. Uniaxial and multiaxial fatigue

    Directory of Open Access Journals (Sweden)

    M.V. Karuskevich

    2016-10-01

    Full Text Available The paper describes the key principles and results of preliminary experiments aimed at the development of new technique for the fatigue life prediction under conditions of biaxial cyclic tension. The foundations of the method were developed early by the numerous tests with monitoring the process of surface deformation relief formation, which is proved to be an indicator of accumulated fatigue damage under uniaxial fatigue. The employed phenomenon was early applied for the development of a family of uniaxial loading fatigue sensors. The formation of strain induced relief has been recently taken into consideration as a part of damage accumulation criteria under biaxial fatigue as well. The home-made testing machine has been designed to implement combined bending and torsion loading that simulates loads experienced by an aircraft wing skin. The experimental evidences on formation and evolution of the deformation relief revealed under conditions of combined loading, supports the proposed concept of biaxial fatigue sensor

  11. Hierarchically mesoporous silica materials prepared from the uniaxially stretched polypropylene membrane and surfactant templates

    International Nuclear Information System (INIS)

    Wang Xiaocong; Ma Jin; Liu Jin; Zhou Chen; Zhao, Yan; Yi Shouzhi; Yang Zhenzhong

    2006-01-01

    Hierarchically mesoporous silica materials with a bimodal distribution were template-prepared from uniaxially stretched polypropylene membrane in the presence of a surfactant via a sol-gel process. Their regularity and morphologies were characterized by transmission electron microscopy (TEM), x-ray diffraction and Brunauer-Emmett-Teller (BET) surface area analysis. The larger channel pores formed by removing the microfibrils of uniaxially stretched polypropylene membrane have a broad pore size distribution, and their size is around 13 nm. In contrast, the smaller mesopores formed by surfactant templates have a narrow distribution; their size is about 3.9 nm. The size of the smaller pores could be tuned from 2 to 6 nm by selecting different surfactants and by changing the concentration of reactants

  12. Critical behaviour of nanocrystalline gadolinium: evidence for random uniaxial dipolar universality class

    International Nuclear Information System (INIS)

    Ferdinand, A; Probst, A-C; Birringer, R; Michels, A; Kaul, S N

    2014-01-01

    We report on how nanocrystal size affects the critical behaviour of the rare-earth metal Gd near the ferromagnetic-to-paramagnetic phase transition. The asymptotic critical behaviour of the coarse-grained polycrystalline sample (with an average crystallite size of L≅100 μm) is that of a (pure) uniaxial dipolar ferromagnet, as is the case with single crystal Gd, albeit the width of the asymptotic critical region (ACR) is reduced. As the grain size approaches ∼30 nm, the ACR is so narrow that it could not be accessed in the present experiments. Inaccessibly narrow ACR for L ∼ 30 nm and continuous increase in the width of the ACR as L decreases from 16 to 9.5 nm basically reflect a crossover to the random uniaxial dipolar fixed point caused by the quenched random exchange disorder prevalent at the internal interfaces (grain boundaries). (paper)

  13. Experimental and numerical study on mechanical properties of aluminum alloy under uniaxial tensile test

    Directory of Open Access Journals (Sweden)

    O. Daghfas

    2017-01-01

    Full Text Available The main objective is to model the behavior of 7075 aluminum alloy and built an experimental database to identify the model parameters. The first part of the paper presents an experimental database on 7075 aluminum alloy. Thus, uniaxial tensile tests are carried in three loading directions relative to the rolling direction, knowing that the fatigue of aircraft structures is traditionally managed based on the assumption of uniaxial loads. From experimental database, the mechanical properties are extracted, particularly the various fractures owing to pronounced anisotropy relating to material. In second part, plastic anisotropy is then modeled using the identification strategy which depends on yield criteria, hardening law and evolution law. In third part, a comparison with experimental data shows that behavior model can successfully describe the anisotropy of the Lankford coefficient.

  14. Changes in phase composition and stress state of surface layers of VK20 hard alloy after ion bombardment

    International Nuclear Information System (INIS)

    Platonov, G.L.; Leonov, E.Yu.; Anikin, V.N.; Anikeev, A.I.

    1988-01-01

    Titanium ion bombardment of the surface of the hard VK20 alloy is studied for its effect on variations in the phase and chemical composition of its surface layers. It is stated that ion treatment results in the appearance of the η-phase of Co 6 W 6 C composition in the surface layer of the VK20 alloy, in the increase of distortions and decrease of coherent scattering blocks of the hard alloy carbide phase. Such a bombardment is found to provoke a transition of the plane-stressed state of the hard alloy surface into the volume-stressed state. It is established that ion treatment does not cause an allotropic transition of the cobalt phase α-modification, formed during grinding of the hard alloy, into the β-modification

  15. State of residual stress in laser-deposited ceramic composite coatings on aluminum alloys

    OpenAIRE

    Kadolkar, P. B.; Watkins, T. R.; De Hosson, J. Th. M.; Kooi, B. J.; Dahotre, N. B.

    2007-01-01

    The nature and magnitude of the residual stresses within laser-deposited titanium carbide (TiC) coatings on 2024 and 6061 aluminum (Al) alloys were investigated. Macro- and micro-stresses within the coatings were determined using an X-ray diffraction method. Owing to increased debonding between the coating and the substrate, the macro-stresses were found to be compressive and to decrease in magnitude with increasing processing speed. The origin of the macro- and micro-stresses is discussed. T...

  16. The mutual influence of krypton implantation and pre-existing stress states in polycrystalline alpha titanium

    Energy Technology Data Exchange (ETDEWEB)

    Nsengiyumva, S. [Department of Physics, University of Cape Town, Rondebosch 7701 (South Africa); Department of Physics, Kigali Institute of Education, P.O. Box 5039 Kigali (Rwanda)], E-mail: schadrack.nsengiyumva@uct.ac.za; Ntsoane, T.P. [Nuclear Energy Corporation of South Africa (NECSA), P.O. Box 582 (South Africa); Raji, A.T. [Department of Physics, University of Cape Town, Rondebosch 7701 (South Africa); Topic, M. [iThemba LABS, Somerset West 7129 (South Africa); Kellermann, G. [Laboratorio Nacional de Luz Sincrotron (LNLS), Campinas (Brazil); Riviere, J.P. [Laboratoire de Physique des Materiaux UMR6630-CNRS, 86960 (France); Britton, D.T.; Haerting, M. [Department of Physics, University of Cape Town, Rondebosch 7701 (South Africa)

    2009-08-15

    The stress profile in polycrystalline titanium implanted with krypton ions at different fluences has been determined using synchrotron radiation diffraction. For each fluence, the krypton profile has been measured using Rutherford backscattering geometry. The results were compared to model calculations obtained from the SRIM 2008 computer code. A strong stress relaxation was found for high fluence implantation, whereas for low fluence implantation an additional source of tensile stress was introduced in the near surface region. The projected range of the implanted krypton was significantly reduced compared to the expected range. A possible cause of this discrepancy is the drift of implanted ions under the influence of the pre-existing stress gradient.

  17. The mutual influence of krypton implantation and pre-existing stress states in polycrystalline alpha titanium

    International Nuclear Information System (INIS)

    Nsengiyumva, S.; Ntsoane, T.P.; Raji, A.T.; Topic, M.; Kellermann, G.; Riviere, J.P.; Britton, D.T.; Haerting, M.

    2009-01-01

    The stress profile in polycrystalline titanium implanted with krypton ions at different fluences has been determined using synchrotron radiation diffraction. For each fluence, the krypton profile has been measured using Rutherford backscattering geometry. The results were compared to model calculations obtained from the SRIM 2008 computer code. A strong stress relaxation was found for high fluence implantation, whereas for low fluence implantation an additional source of tensile stress was introduced in the near surface region. The projected range of the implanted krypton was significantly reduced compared to the expected range. A possible cause of this discrepancy is the drift of implanted ions under the influence of the pre-existing stress gradient.

  18. Probing Stress States in Silicon Nanowires During Electrochemical Lithiation Using In Situ Synchrotron X-Ray Microdiffraction

    Directory of Open Access Journals (Sweden)

    Imran Ali

    2018-04-01

    Full Text Available Silicon is considered as a promising anode material for the next-generation lithium-ion battery (LIB due to its high capacity at nanoscale. However, silicon expands up to 300% during lithiation, which induces high stresses and leads to fractures. To design silicon nanostructures that could minimize fracture, it is important to understand and characterize stress states in the silicon nanostructures during lithiation. Synchrotron X-ray microdiffraction has proven to be effective in revealing insights of mechanical stress and other mechanics considerations in small-scale crystalline structures used in many important technological applications, such as microelectronics, nanotechnology, and energy systems. In the present study, an in situ synchrotron X-ray microdiffraction experiment was conducted to elucidate the mechanical stress states during the first electrochemical cycle of lithiation in single-crystalline silicon nanowires (SiNWs in an LIB test cell. Morphological changes in the SiNWs at different levels of lithiation were also studied using scanning electron microscope (SEM. It was found from SEM observation that lithiation commenced predominantly at the top surface of SiNWs followed by further progression toward the bottom of the SiNWs gradually. The hydrostatic stress of the crystalline core of the SiNWs at different levels of electrochemical lithiation was determined using the in situ synchrotron X-ray microdiffraction technique. We found that the crystalline core of the SiNWs became highly compressive (up to -325.5 MPa once lithiation started. This finding helps unravel insights about mechanical stress states in the SiNWs during the electrochemical lithiation, which could potentially pave the path toward the fracture-free design of silicon nanostructure anode materials in the next-generation LIB.

  19. Investigations into the Surface Strain/Stress State in a Single-Crystal Superalloy via XRD Characterization

    Directory of Open Access Journals (Sweden)

    Haodong Duan

    2018-05-01

    Full Text Available The present study was aimed at determining the surface strain/stress state in an Ni-based single-crystal (SC superalloy that was subjected to two different cooling rates from solid solution temperature through using the X-ray diffraction (XRD method. The normal stresses σ 11 s and σ 22 s were determined, then the Von Mises stresses ( σ V M s were derived from them. Field emission gun scanning electron microscope (FEG-SEM and transmission electron microscope (TEM micrographs were taken to illustrate the strain/stress state change. The precipitation of the secondary γ′ phases in the γ phase and the formation of the dislocation in the interphase upon a slower cooling rate caused the γ phase lattice distortion to increase, so a larger σ V M s of the γ phase was realized in comparison to the faster cooling sample. For both of the two cooling modes, we found that the σ V M s of the γ′ phase increased due to the growth of the γ′ phase during the aging process. Also, the aging process led to pronouncedly anisotropic lattice mismatches in the {331} and {004} planes. In addition, the surface strain/stress states of a cylinder sample and a tetragonal sample were also studied using a faster cooling rate, and σ 11 s and σ 22 s were analyzed to explain the influence of the shape factor on the stress anisotropy in the [001] and [ 1 1 ¯ 0 ] orientations. The strain in the [001] orientation of the γ phase is more sensitive to the shape change.

  20. [Emotional regulation in aspect of action vs. state orientation, stress and self - injurious behavior among people with borderline personality disorder].

    Science.gov (United States)

    Blasczyk-Schiep, Sybilla; Rabska, Ewelina; Jaworska-Andryszewska, Paulina; Laso, Agnieszka

    2015-06-01

    In the bordeline personality disorder a large role ascribe to biopsychosocial factors. Studies have shown that more than 70% patients BPD reported experiencing traumatic events in childhood. The findings are confirming that making self-harming is a frequent symptom of bordeline disorder and 70-75% patients show at least one act of self-harming. Selfharming can be a reaction to maladaptive emotional regulation. Moreover a lowered tolerance level is characteristic of them to the stress and determined course learning dysfunctional patterns of behavior. The aim of this study is to determine the level of emotional regulation through the variable action vs state orientation and to investigate their relation to stress, self-harming and suicidal behavior. In study participated 45 persons with emotionally unstable borderline personality diagnosis. In the group was 33 women and 12 men in age 19-43. A Polish adaptation of standardized questionnaires was used to measure stress and action vs state orientation (SSI-K), self-injurious behavior (SHI) and suicidal tendencies (RFL-I). By patients with borderline personality disorder the level of action control, reasons for living and stress are predictors of selfharming behavior. The mediation analyze showed, that stress and reasons for living are mediators between action vs. state control and the level of self-harming behavior. A high level of stress correlates positively with self-harming and negatively with action control in patients with borderline personality disorder, and a high level of reasons for living correlates positively with action control and negatively with self-harming in people with BPD. © 2015 MEDPRESS.